Topical Reports Energy and Water Efficiency for Semiconductor Manufacturing

Introduction

Automobiles, Star Wars - The Phantom Menace, medical diagnostic devices. None of these appear to have anything in common. But, if you look a little bit deeper, at least one common element comes through: semiconductors. Semiconductors are the "building blocks" of computers, becoming an integral part of modern life much faster than those other "necessities" of the 20^th Century: radio, television, the automobile, and telephones. In fact, according to EPA's Design for the Environment (DfE) initiative, computers are the principal end use of semiconductors, constituting 40 percent of the market in 1992¹. Semiconductors are also used in many other products, including consumer electronics, telecommunications equipment, industrial machinery, transportation equipment, and military hardware. Typical functions of semiconductors in these products include information processing, information display, power handling, data storage, signal conditioning, and conversion between light and electrical energy sources.²

Although semiconductors have allowed for great advances in many diverse areas - everything from the research needed for the human genome project to making movies - they are not without costs. Manufacturing semiconductors requires an ultra-clean process, requiring a great deal of pure water and energy use. One speaker at the recent SEMICON West trade show (July 1999) noted the results of a study conducted by the European Union, which indicated that manufacturing a car generates less waste and uses fewer resources than manufacturing a laptop computer.³ Contrary to what some in the Northwest may think, these resources are not limitless. Water conservation and energy efficiency are fast becoming critical elements of the semiconductor manufacturing process.

The semiconductor industry is noted for its culture of innovation. Perhaps no other industry has such a pressing need to make changes continuously, keep up with research and development (R&D) in the field, and stay a step ahead of rivals in a furiously competitive business. It is this fast rate of change that provides the opportunity for the semiconductor industry to incorporate efficiencies into manufacturing systems. As efficient methods and processes are introduced to the marketplace, semiconductor manufacturers can put them in place when they retool for the next product cycle. The next product cycle is dictated by faster devices, smaller device geometry and larger wafers. These innovations require new tools that allow for the printing of small lines and the handling of larger wafers. As a result, the semiconductor industry can look to maximize their efficiencies every 3-5 years, as opposed to every 5, 10, or 20 years in other industries. Please note that this does not mean that the semiconductor facilities as a whole are replaced every 3-5 years. In fact, the buildings can be in use for 20 or more years; it is the processes and tools within the building that change.

Overview

The manufacture of any semiconductor requires an ultraclean environment, to ensure the purity of the semiconductor. This purity is vital; it helps ensure that the semiconductor can act as a circuit at practically the atomic level. In fact, with device lines for many semiconductors now 0.18 microns wide (a micron is one-thousandth of a millimeter), a particle as small as 0.5 microns can completely destroy a circuit. A "cleanroom" is required for the production process. Cleanrooms for semiconductors are maintained at various levels of cleanliness (dependent upon the semiconductors being made). Cleanrooms are rated using the U.S. Federal Standard 209E: the number of airborne particles 0.5 microns or larger in a standard cubic foot of air will be less than the number of the class.⁴ For example, a Class 1 clean room will have no more than one particle per cubic foot that is larger than 0.5 micron. Clean rooms are rated as class 1000, class 100 or class 10 or better.

The use of cleanrooms is not a new manufacturing technique introduced by the semiconductor industry. Cleanrooms date back to 19^th century surgical facilities. Nor is the semiconductor industry the only one using cleanrooms today. Cleanrooms are also used by manufacturers of optical devices, analytical instruments and pharmaceuticals.⁵ However, semiconductor manufacturers have the most stringent requirements for cleanliness, and, the cleaner the room requirements, the higher the demands (and costs) for energy and water consumption.

Economic Trends
For the past two decades, worldwide production of electronics (including computers) has grown faster than any other industrial sector. The American Electronics Association (AEA) notes that the electronics industry is the largest industry in the U.S.: 1996 domestic sales were $866 billion. The 1996 exports of $150 billion were also the largest of any industry (for single merchandise) in the U.S.⁶

The Pacific Northwest is not a newcomer to hosting semiconductor companies. Tektronix, an industry pioneer and leader in many different applications for semiconductors, has had its headquarters in Beaverton, Oregon, for more than 20 years. Intel, Oregon's largest employer and the world's largest producer of computer chips, designed and manufactured the 80286 chip at the company's Hillsboro, Oregon plant in 1982.^{7, 8} Micron Technology, Inc., a designer and manufacturer of semiconductors headquartered in Boise, Idaho, was started in 1978. Hewlett-Packard, another well-known player in the semiconductor field, has also kept a long-time presence in the Pacific Northwest, and has facilities in Corvallis, Oregon, and Everett, Washington.⁹

Employment in microelectronics surpasses employment in the Northwest's older mainstay industries of aerospace, forest products and agriculture. This growth has been fostered by the ready availability of clean water, low-cost electricity, a skilled labor force, and tax incentives from state and local governments. Some industry analysts believe that investments across the entire Northwest microelectronics sector may reach $20 billion between 1995 and 2004.¹⁰ Although the Northwest semiconductor industry is expected to continue growing in coming years, the industry as a whole suffered significantly from the recent Asian financial crisis. Production over-capacity caused several Northwest facilities to either reduce their workforces or shut down all together. It appears that the semiconductor industry has recently turned the corner, with the market and sales on the way back up again.

Resource Demands
The energy and water demands placed on natural resources in order to produce semiconductors are significant. As the complexity and size of the semiconductor facilities (known as fabs) have grown, so have these demands. New facilities can use 30 to 50 megawatts of peak electrical capacity,¹¹ enough to power a small city.

Energy is not the only commodity in high demand for semiconductor facilities. New wafer and integrated circuit manufacturing plants can consume millions of gallons of water every day, enough to supply several thousand households.¹² The growth will continue to have an impact on the resources of the Pacific Northwest. Industry projections for the next decade indicate an annual energy requirement of between 400-500 megawatts of additional electricity from Northwest power suppliers - an electricity demand approximately equivalent to two new natural gas-fired power plants,¹³ and up to 2 percent of the Northwest's current average annual electricity load.

Economic Costs of Semiconductor Manufacturing
The cost of building a fab is very high, due to complex production requirements. Over the past two decades, the building cost has increased to over $1 billion. The next generation of wafers (300mm, as opposed to the 200mm in use today) may cost up to twice that.¹⁴ These costs can, however, return great benefits. As noted at the recent SEMICON West 99 trade show (July 1999): one $60, eight inch diameter silicon wafer, plus $50 worth of ultrapure water (including water and sewer rates), and $140 worth of semiconductor chemicals and energy, produces about 360 chips. These chips can be valued from $20-$200 each, and retail for $7,200-$72,000 total.¹⁵

Energy and Water Use - Opportunities for Efficiency
Energy and water inputs should not be viewed separately for semiconductor manufacturing. Water use is inextricably linked to energy use. Water operations, from pumping water through the plant, to making the Ultra Pure Water (UPW) necessary for semiconductor manufacturing requires a great deal of energy.

Although the energy-water link is often overlooked when plant processes are examined, this is beginning to change. For example, Motorola's Austin, Texas facility has documented energy conservation gains it achieved through water use reduction.¹⁶ Motorola took into account the city of Austin's estimate that for each 1,000 gallons of water supplied to its customers, 5.11 kWh of energy has been consumed. This linkage illustrates the necessity of looking at water and energy efficiency together when trying to reduce resource consumption, as well as the economic costs incurred while producing semiconductors.

It is important to keep in mind, however, that the efficiency savings available represent a very small share of production costs. One industry representative indicated that the cost savings achieved for one year's worth of energy savings at a fab is equivalent to the total cost of one day of production.¹⁷ Put another way: energy accounts for about 1-2% of the cost of semiconductor production.¹⁸ Considering the amount of money at stake, it is easy to understand industry reluctance to invest in unfamiliar efficiency technologies, which could require costly production downtime. Nevertheless, the relative amount of resources that the semiconductor industry uses should be kept in perspective for efficiency changes. Although the cost savings may not be noteworthy for the facility usage, the water and energy resources used are often equivalent to those used by a small city or a number of towns. The overall impact on the local environment can be substantial, as can the efficiency changes made by the fabs. One small change or process improvement by a fab can equal what it may take all other industries in a city or town to implement. The impact on northwest salmon must also be considered. Water efficiency at fabs will keep more water in streams and aquifers, vital for salmon. Additionally, the efficiencies made in the production process will reduce the amount of resources spent on waste, and should create a facility that is more nimble and streamlined, better able to weather changes in the industry.

Primer: How semiconductors are made

Semiconductor manufacturing is complex, with multiple steps that can be repeated hundreds of times. For a text and an illustrated description of semiconductor fabrication go to http://www.intel.com/education/chips/fabrication.htm. The text below provides some additional details on how semiconductors are made.

Semiconductors are made of a solid crystalline material, usually silicon. The crystal is grown in the laboratory into large ingots, which are then cut and polished into wafer size silicon wafers. It is on this substrate that diodes and transistors are manufactured into integrated circuits. A simple diode or transistor is an individual circuit that performs a single function affecting the flow of electrical current. Integrated circuits combine two or more diodes or transistors. Up to 500 integrated circuits can be formed on a wafer and up to several thousand transistors and diodes can make up one integrated circuit. Also incorporated into a chip are capacitors (for storage) and resistors. Up to several thousand integrated circuits can be formed on the wafer, although 200-300 integrated circuits are usually formed. The area on the wafer occupied by integrated circuits is called a chip or die.¹⁹

The primary reason that semiconductors fail is contamination, particularly the presence of microscopic residue (including chemicals or dust) on the surface of the base material or circuit path. Cleaning operations precede and follow many of the manufacturing process steps. Wet processing, during which semiconductor devices are repeatedly dipped, immersed, or sprayed with solutions, is commonly used to minimize the risk of contamination.²⁰ An overview of semiconductors manufacturing is provided below; the steps noted are a simplification (by grouping) of the entire process.

Step One: Design
The circuit is designed using computer modeling techniques. Computer simulation is used to develop and test layouts of the circuit path. Then, patterning "masks," which are like stencils, are fabricated, manufacturing equipment is selected, and operating conditions are set. All of these steps occur prior to actually producing a semiconductor.²¹

Step Two: Crystal Processing
Silicon, in the form of ingots, is the primary crystalline material used in the production of 99 percent of all semiconductors. Silicon material is called semiconductor material because it can become a conductor when impurities are added to its crystal structure. Most semiconductor manufacturers obtain single crystal silicon ingots from outside suppliers. Ingots are sliced into round wafers approximately 0.76 mm (0.03 inches) thick and then rinsed. Wafers are the starting point of semiconductor production. A wafer's surface may be mechanically ground, smoothed, and polished, as well as chemically etched so that the surface is smooth and free of oxides and contaminants. Chemical etching removes organic contaminants using cleaning solvents, and removes damaged surfaces using acid solutions. Chemical etching is usually followed by a deionized water rinse and drying with nitrogen. In some cases, bare silicon wafers are cleaned using ultrasound techniques.²²

Step Three: Wafer Fabrication
Wafers are usually fabricated in batches. Wafer preparation begins with an oxidation step forming a thin oxide layer on the wafer. Next, patterns are imprinted onto a resist-coated substrate using photolithography (also referred to as lithography) and etching processes. Photolithography uses masks and ultraviolet light to create patterns. The etching process removes oxide within the developed pattern, and leaves bare silicon exposed. Photolithography is the most crucial step in semiconductor manufacturing because it sets a device's dimensions. Incorrect patterns alignments ruin or distort the electrical functions of the semiconductor. There can be up to 12 masking operation before the circuit is complete.

After photolithography, chemical developers are used to remove resist that was exposed to UV light on the substrate. The wafer is then etched in an acid solution to remove selected portions of the oxide layer to create depressions or patterns. After the etching operation, remaining photo resist is removed. The wafer is rinsed, typically by immersion in a stripping solution to remove unwanted photoresist, and then dried.

Because crystals of pure silicon are poor electrical conductors, controlled amounts of chemical impurities (dopants) are added during production of silicon ingots to enhance their semiconducting properties. Dopants eventually form the circuits that carry the flow of current. Antimony, arsenic, phosphorus, and boron compounds are the dopant materials most commonly used for silicon-based semiconductors.²³ Other materials used in the circuit manufacturing process, as thin films, include aluminum, gallium, gold, beryllium, germanium, magnesium, silicon, tin, and tellurium. These thin films can be doped with the materials above.²⁴

Dopants are applied to the patterned wafer surface typically using diffusion or ion implantation. Additional layers of silicon or silicon dioxide may also be applied to the wafer using deposition techniques. Many products require repeating steps two through three several times (in fact, up to 12 times in order to create the desired structure).²⁵ Once the wafer is patterned, the wafer surface is coated with thin layers of metal by a process called metallization. These metal layers perform circuit functions within the finished semiconductor, by making contact at any place where bare silicon exposes the circuit device. External connections to the silicon wafer are provided by evaporation of thin metal films onto areas of the semiconductor chip surface in a vacuum.

Step Four: Final Layering and Cleaning
Passivation (making the surface less chemically reactive) is used to apply a final layer of oxide over the wafer surface to provide a protective seal over the circuit. This coating protects the semiconductor from external influences and may range in thickness from a single layer of silicon dioxide to a relatively thick deposit of special glass. It also insulates the chip from unwanted contact with other external metal contacts. After all layers have been applied to the wafer, the wafer is typically rinsed in deionized water. The back of the wafer is then mechanically ground (also called lapping or backgrinding) to remove unnecessary material. Testing is conducted to ensure that each chip is performing the operation for which it was designed. The wafer is cleaned again after testing, using solvents such as deionized water, isopropyl alcohol, acetone, and methanol.²⁶

Step Five: Assembly
Semiconductors are assembled by mounting chips onto a metal frame, connecting the chips to metal strips (leads), and enclosing the device to protect against mechanical shock and the external environment. Plastic semiconductor packages comprised more than 90 percent of the market in 1990. Each package contains five parts: the die (e.g., chip), the lead frame of the package, the die-attach pad, the wire bonds, and the plastic housing. All semiconductor packages, whether plastic, metal or ceramic, share the same basic parts and are assembled using the same general processes.²⁷

The lead frame consists of a rectangular metal frame connected to metal strips called "leads." Plastic package lead frames are fabricated from sheets of metal, either punched or etched. The lead frame and leads provide the connections for the electronic components. The chip is then mounted to an "attach pad," with a substance such as an epoxy material (thermoset plastic). Once mounted, the chips are inspected. The chip parts are bonded to the leads of the package with tiny gold or aluminum wires. A package may have between 2 and 48 wire bonds. The assembly is cleaned and inspected again. The combined components are then placed into a molding press, which encases the chip, wire bonds, and portions of the leads in plastic. After the molding compound cures and cools around the package, the package is heated again to ensure that the plastic is completely cured. The final steps in package fabrication include trimming and forming the leads.²⁸

Final computer tests are conducted to evaluate whether the product meets specifications. Even though the chips are produced using the same process, some may work better (e.g., they meet the specifications for which they were designed) than others. As a result, packages are separated into low-and high-quality circuits. Often, low-quality circuits can still be sold. The finished product is then packaged, labeled, and shipped according to customer specifications.²⁹

Energy Demands for Semiconductor Manufacturing

As noted above, semiconductor fabs require a significant amount of energy. To help the reader understand energy terminology, and energy use in fabs, a brief overview is provided below.

Energy -- what the units mean
Energy use, or "power," is generally measured as the amount of electricity needed to run machinery, lighting, air conditioning, and many other services over a period of time. A watt measures instantaneous energy demand, while a watt-hour measures energy use over time. A more useful scale is kilowatts (kW) and kilowatt-hours (kWh). The kWh is standard for industrial and residential measures of energy use - for example, your refrigerator energy use per year is measured in kWh. One kW equals 1,000 watts, and one kilowatt-hour (kWh) is one hour of using electricity at a rate of 1,000 watts of instantaneous demand.³⁰ To provide an idea of the amount of energy required for semiconductor manufacturing, consider that 800 kWh of electrical energy is used to manufacture one 200 mm semiconductor wafer.³¹ More than one-third of this energy is used in the fab.³² This is equal to the amount of energy used in a typical household for one month. As another comparison, a typical major fab uses the electrical power equivalent of 7,500 or more houses.³³

Energy use in a fab
Fab plants are built very quickly to capitalize on known semiconductor technology. Typically, plant construction takes only 12-18 months from design to completion, although it can be longer with larger fabs. More often than not, facility designs are "copycatted" from existing facilities which may not be efficient. The duplication of designs occurs primarily because there is a perceived lessening of risk (of reliability or production slowdowns) by using a known design.^{34, 35}

As noted above, even though the electricity demands for semiconductor manufacturing are a small percentage of production costs, the energy use is still fairly significant. For the whole semiconductor industry in the U.S., cleanroom electricity demand is estimated at 3500 megawatts and consumption at over 15,000 gigawatt-hours per year,³⁶ about 1.5 percent of total industrial electricity use, for all industry sectors in 1998.³⁷ For many plants, electricity costs are the single greatest facility operating cost, greater than both labor and materials. In fact, for large fabs, it is not uncommon to have electric bills that are greater than $1 million per month.³⁸

The electricity use per square foot in fab can be up to 100 times the energy demands of a modern office.³⁹ Much of the energy use in fabs is attributed to production equipment (also known as tools) which account for the majority of energy use. These tools include support utilities such as making deionized water; and vacuum, exhaust, and compressed air, systems.⁴⁰ However, the tool manufacturers have generally not focused on energy efficiency when designing the tools.⁴¹ Typically, the purchase cost is minimized first, to make tools more appealing to the semiconductor manufacturers. Life cycle costs are usually not considered, by either the tool or semiconductor manufacturer.⁴²

In the fab itself, there are two main production areas that use the majority of the electricity at the facility. The Heating, Ventilation, Air Conditioning (HVAC) system (including chillers) uses approximately 50% of the total energy at a fab, and process tools another 30-40%. The rest of the facility accounts for 10-20% of the remaining use.^{43, 44} One of the reasons the HVAC system uses so much energy is the need to maintain the necessary cleanroom environment. HVAC energy intensities are 10-100 times higher than ordinary buildings.⁴⁵

Fans and filters used to maintain ultra-clean air are an integral part of a fab's HVAC system. Class 100 clean rooms require ceilings filters covering 100% of the ceiling. The air is changed within these areas 26 to 66 times per hour. There can be hundreds of fans, also known as recirculation air handlers (RAHs), in use, running 24 hours a day, 7 days a week.⁴⁶ Neither the fans nor the filters are always built with energy efficiency in mind. It is important to note that it is not always possible to switch to a more energy-efficient fan or air circulation system, and that there has been an ongoing debate in the industry over the best way to circulate air: using a small number of large fans or a large number of small fans. One area that has to be looked at is the possible contamination that can result in a cleanroom with a switch in fans. However, one way to increase energy efficiency, regardless of the type of fan in use, is to avoid using compressors to heat or cool air - a highly inefficient use of this tool.

Energy Efficiency at Semiconductor Fabs

The Northwest has long enjoyed the benefits of electricity rates that are generally the lowest in the nation. The majority of this energy (with the exception of Alaska) is produced by hydroelectric facilities (ranging from 55 to 75 percent, depending on water supply⁴⁷); the remainder is generated by facilities that run on coal, gas, biomass, one nuclear facility, and two wind plants. However, with the listing of numerous Columbia and Snake River salmon and steelhead runs as threatened or endangered species, and an ever-growing awareness of effects of global climate change, it is becoming apparent that efficiently using energy is critical throughout the region and nation, regardless of how the power is generated. The semiconductor industry, with its projected rapid growth in the region, can have a significant impact on reducing its energy use by implementing efficiency methods.

Why look for energy efficiency?
In many industries, including microelectronics, energy costs have not been separated from general operating costs, making it harder to track both the costs and benefits of becoming more energy efficient. For the semiconductor industry, it has been estimated that at least half the energy used is wasted. This waste could be converted into a profit with returns exceeding 30% return on investment (ROI). As an interesting savings/investment comparison, the risk of energy efficiency investments is slightly less than the risk involved in investing in long-term Treasury bonds.⁴⁸

What does saving energy return to a facility? There are many benefits, beyond saving money on electric bills. In many cases, saving electricity will increase product yield, through time savings and improved productivity.^{49, 50} Energy efficiency can also provide a fab with more flexibility than competitors who do not address efficiency issues, since they are less susceptible to price changes in resources. The bottom line is healthier, making the plant more stable in times when industry has downturned; overhead is lower; and there is a lower overall demand for natural resources, making them more desired in communities.⁵¹

Looking at energy efficiency at the design/build stage and when retrofitting a fab
Energy efficiency opportunities for fabs differ depending on whether the fab is being built from the ground up, or whether there is an existing fab being retrofitted. In many cases, the biggest savings opportunities are efficient HVAC systems. Since the HVAC system can have a typical life-span of 10-20 years, as opposed to process tools that may change every 3-5 years, designing or retrofitting an efficient HVAC system can have a lasting impact on energy use. The Northwest Power Planning Council sponsored a workshop identifying areas where an efficient design could reduce at least 70% of total HVAC energy use, although this total depends on plant-specific examples and theoretical improvements. Capital costs were also reduced up to one-third.⁵²

It is important to keep in mind that energy costs are not the only reason to design for efficiency. Generally, using an energy efficient design for fabs and process tools results in a more reliable facility. With less wear on filters, pumps and motors, maintenance and operating costs are reduced. Perhaps most importantly, an energy efficient design has lower pressures and slower airflow, which improves filtration efficiency for these systems. The end result is reduced particle contamination on the semiconductor, generating improved product yields and product quality.⁵³

Fab processes can be made more efficient whether the construction is new or a retrofit. Opportunities exist in numerous systems, including deionized water, vacuum, exhaust, and compressed air. Efficiencies are available in different parts of these systems, including better design, equipment and controls, recycling, and heat recovery. For existing factories, the opportunities of retrofitting are not as dramatic as in new construction. However, the savings can be substantial, with some factories getting energy savings of 30 - 60 percent in HVAC systems.⁵⁴

Possible obstacles to energy efficiency
Although the benefits to energy efficient fabs are many, there are still obstacles to be aware of when investigating the opportunities. Some of the barriers are common to many industries and include:

Lack of awareness of the available options.

Unavailability/existence of success stories using the efficiency options.

Risk-averse company culture which prohibits consideration of innovation that is not completely proven.55

Companies not budgeting for fab, equipment and process upgrading.

Lack of production downtime to make efficiency changes.

For semiconductor manufacturers in particular, there are additional barriers:
- Energy

Utility deregulation and restructuring has created an uncertain environment that led to a reduction or elimination of energy efficiency programs for industry.

- Design

The design-build-operate cycle is very short, reducing opportunities to try something new and (relatively) unknown.56

Efficiency information is lacking for facility process modelers, and in design criteria for fabs and tools.

Building code/fire code requirements for ventilation of cleanrooms may require much more exhaust air than what is required to operate the production tools.57

Reliability concerns may result in sticking with familiar designs that may have inefficient rules of thumb.

- Facility

Tool suppliers may have operating requirements that ignore energy efficiency opportunities or options.58

Tool manufacturers put guarantee restrictions on equipment, which leads to tool over-design and resulting in inefficiency.59

- Information

Fab managers are uncertain about equipment performance, in particular vendor efficiency and durability claims. There has also been a lack of quantifiable successes, and corresponding data, to back up various claims.60

Lack of measurement/metering for energy, both for current processes and if a change is to be made. Without this information, it is difficult to justify a change to energy efficient processes to managers concerned about uncertainties. It also prevents managers from distinguishing true costs from apparent costs.61

The information available for energy efficiency is not presented to designers in time to evaluate design tradeoffs.62

- Culture

In general, process engineers resist trying unfamiliar technologies.63

There is a justification process within the culture, taking into account issues such as return on investment (ROI), and a lack of time and knowledge to make changes.64

For many managers, the perceived low payback (hidden in overhead costs)of energy efficiency changes does not justify the risks and time involved in making those changes.65

- Production

Above all else, the product output schedule dominates. If energy efficiency will delay the schedule, the measures are much less likely to be implemented.66

There are many production impacts associated with a possible shutdown if a process does not work correctly.67

With the short product cycles needed for semiconductors, there is a belief that there is not sufficient time to look for and/or implement energy efficiency.68

Opportunities for energy efficiency
The semiconductor industry rapidly changes its production methods, especially when compared to other industries such as automobile manufacturing and paper processing. A well-known representation of this rapid change is Moore's Law: the number of transistors on a memory chip will double every 18-24 months.⁶⁹

With each new generation of chips comes the need for new production tools and (usually) new fabrication facilities. As a result, the semiconductor industry is positioned to implement energy efficiency options with each new chip generation. Even if there is a slowdown in growth or new construction, efficiency opportunities can be more closely studied and implemented, since there may be more flexibility in time frames for product lines.⁷⁰

The are numerous areas in a fab where implementing energy efficiency options can result in significant resource and cost savings. As Motorola noted in a 1998 presentation, an efficient cleanroom can achieve annual savings of over 5.4 million kW-h, and the optimized cleanroom can achieve an additional savings of 3.6 million kW-h.⁷¹ In addition to the energy savings, the most efficient cleanrooms can also be more reliable, smaller, and cleaner than standard cleanrooms.⁷² Keep in mind, the best way to determine the efficiency opportunities of an existing plant is to determine how the system is currently operating, through monitoring data. This information can provide efficiency opportunities, bench marking information (to compare to other facilities or over time to itself) and increased reliability.

Some of the highest impact efficiency options include:
- Design

Specifying optimal efficiency components, including high efficiency motors, fans, and pumps.73

Using any available industry benchmarks that may exist for energy efficiency.74

Integrating HVAC, tools, and facilities in the initial design.75

- HVAC systems and plant.

Lower cleanroom make-up and exhaust airflow rates.76

Low face-velocity cooling coils. These have lower pressure drops and less energy loss through ducts and filters, saving 3-7% of cleanroom electricity usage.77 Another opportunity is to lower the recirculation velocity.78

Air filters. Higher-performance air filters clean supply air more efficiently, resulting in a reduction of energy consumption.79

Variable-speed drives. When used in air recirculation, make-up, and exhaust fan motors, these drives use 15-30% less energy than constant-speed drives.80

Use high-efficiency motors, fans, and pumps.81

Minimize cleanroom volume. Doing this reduces recirculation airflow requirements and the associated energy usage. Cleanroom mini-environments are designed to capture these savings. (Mini-environments are discussed in more detail below.)82

Lower water flow rates. When used in cooling towers, the lower flow rates reduce chilled water piping pressure drops and pumping energy usage, reducing facility energy consumption by 3-7%.83

Separate chiller loops, based on the functions, with correspondingly different supply temperatures and energy inputs.84

Variable outside air/recirculated air proportion. This reduces the need for mechanical chilling, by taking advantage of free cooling.85

Possibly, reduce the horsepower size of the recirculation fans. With the potential for a fab to have as many as 150-300 recirculation fan units circulating 20,000 cubic feet per minute, reducing the motor size from 15 horsepower to 5 horsepower would result in a large drop.86 However, the 5 horsepower fan must be able to produce the same level of cleanliness for the cleanroom as the 15 horsepower fan.

- Process tools and supporting utility systems

Use more efficient process tool components. Tool components, such as motors, fans, pumps, compressors, and heat exchangers that are designed efficiently use less energy when in operation. They also generate less excess heat that must be removed from the cleanroom, further increasing their efficiency impact.87

Stabilize process tool exhaust. Doing this reduces product contamination, which then increases production process efficiency. A corresponding result is that the exhaust airflow rate can be reduced, decreasing the amount of energy used in that part of the HVAC system.88

Lighting. Light guides and other efficient lighting systems have lower cooling loads, and maintenance costs. They can reduce or eliminate the risk of lamp breakage, and reduce production interruptions for group relamping in cleanrooms.89

Vacuum pumps that support process tools should be placed as close to the tool as possible. This saves pump down-time, which requires less maintenance and fewer oil changes for the pump.

- Other efficiency opportunities

Recover wasted heat. One example includes recovering heat from the exhaust air by using recuperation and reverse cycle heat pumps.90

Minimize air humidification in the fab.91

Reduce air flow rate outside production hours.92

Use an automatic control system. Such a system can be used for the management of a building system, and will make overall management easier.

"Re-balance" the air in the fab to its designed specification. Over a period of time the fab can become unbalanced due to the addition of tools, heat load and added exhaust.

Mini-environments
Mini-environments are being increasingly used as a replacement for large, extensive cleanrooms. Rather than having a large room with all the process tools and transportation systems within it, a mini-environment allows the fab to be designed with "pieces" of cleanrooms. The surrounding areas need not be kept at the Class 1 or Class 10 level (for example) that the mini-environment is kept at. Thus, the amount of space that must be kept ultraclean is significantly reduced, without any corresponding reduction in the quality of the space where the semiconductor is manufactured.

Mini-environments are chosen over conventional cleanrooms for a number of reasons. These include:

Possible reduction in the first costs of the facility.

Reduction in operating costs, primarily due to lower airflow and space requirements.

An upgrade of an existing facility - rather than building a brand new facility.93

Water Demands for Semiconductor Manufacturing

Water use at semiconductor manufacturing facilities is intensive. A large amount of water is used to rinse and clean the semiconductors, and a great deal of this water is ultra pure water (UPW). In general, 1,400-1,600 gallons of city water is needed to produce 1,000 gallons of UPW.⁹⁴ More than 2,000 gallons of UPW can be used in the production of one eight inch wafer. As a point of reference, a typical 200mm wafer fab processes 40,000 wafers per month.⁹⁵ A large facility can use up to 3 million gallons of UPW per day.⁹⁶ An approximate breakdown of UPW use:

wet cleans: 60%;

acid processes (etch): 20%;

solvent processes: 10%; and

tool cleaning processes: 10%.97

Even though UPW is costly to make, only 50-75% of the produced UPW is used for the wafer processing.⁹⁸ The remaining UPW, as well as deionized and raw and/or potable water, is used in other processes at the facility, including:

cooling towers;

irrigation and landscaping; and

kitchens, restrooms, drinking faucets.

The water demands for semiconductors are expected to continue growing. The next generation of chips (300mm, as opposed to 200mm) are estimated to require at least 1.5 times more water than 200 mm fabs, and as much water as needed annually by a city of 60,000 people.^{99, 100}

Water Efficiency at Semiconductor Fabs

Even though parts of the Pacific Northwest appear to be blessed with an abundance of water (especially between October and May), water efficiency is an important issue for the region. Water demand peaks in summer, when precipitation is at its lowest. Storage capacity is limited. Furthermore, high water use degrades habitat for salmon and steelhead on the threatened and endangered species list. As a result, water must be used efficiently, and the semiconductor industry is one that can have a direct impact on the region's water resources.

Why look for water efficiency?
As noted above, making UPW is one of the most energy and water intensive uses of water at fabs. The efficient use of UPW can be viewed as a critical feature of semiconductor manufacturing. One reason to look for water efficiencies is the cost of producing and managing UPW: for every dollar a fab spends on utility-supplied water, $20 is spent to treat it to ultrapure quality, and another $10 is spent to treat to National Pollutant Discharge Elimination System (NPDES), state, and/or local discharge levels.¹⁰¹ Another reason is the cost of energy it takes to produce UPW. Approximately 46 kWh can be saved for every thousand gallons of UPW conserved. For a facility using 3 million gallons of UPW daily, reducing UPW by only 10% can result in an annual savings of 5 million kWh, or about $225,000 at an energy purchase cost of 4.5 cents per kWh, in addition to savings on per-kW demand charges.¹⁰²

Another reason to look for water use reductions: municipalities are facing an increased demand to provide both adequate water supply and wastewater treatment facilities, and often have difficult times meeting these demands. Facilities that want to expand existing facilities and increase levels of wastewater discharge can encounter expensive permit upgrades and/or a local Publicly Owned Treatment Works (POTW) that cannot accept additional wastewater discharges. These restrictions force facilities to limit the discharge volume through efficiency, reclaim/recycle water, or subsidize an expansion of the POTW treatment capacity.¹⁰³

There are additional benefits when incorporating water efficiency into the fab beyond the water costs reductions. SEMATECH, a research consortium for the semiconductor industry, has done research on recycling UPW, and has discovered that the maintenance required for UPW systems is reduced when recycling. Recycling reduces chemical costs of regeneration, cleaning time/down time, and lowers the amount of wastewater produced, while increasing the water quality at the point of use. The recycling systems have a payback period of approximately 30 months.¹⁰⁴

Possible obstacles to water efficiency
One of the difficulties in establishing a water efficiency program in a fab is that there is usually not one person/department accountable for water use. Water use is often a part of environmental, facilities and accounting responsibilities, but efficiency may not be addressed by any of them.¹⁰⁵ There are also specific difficulties associated with water recycling systems in Fab-Fab recycling (taking water from one process and into another specific for semiconductor manufacturing). If the system fails for any reason - either due to design or operation - the fab can shut down and lose literally millions of dollars of product.¹⁰⁶ As a result, the personnel who are responsible for keeping the fab up and running must be convinced that the rewards associated with recycling not only outweigh the risks¹⁰⁷ but that the risks are minimized to begin with. There are risks beyond the introduction of impurities to the system that should be considered when implementing a water-recycling process:

Organic compounds that are difficult to test for quickly may get through the recycling system;

Buildup of recalcitrant compounds;

Possibility of a new, unwanted chemical interaction in the system; and

Introduction of process-generated compounds into the system which can't be removed using current purification methods.108

Opportunities for water efficiency
There are a number of ways that water use can be reduced at a fab. The primary methods include recycling, reuse/reclamation and reduction.¹⁰⁹ Recycling can include Fab into Scrubbing and Fab Cascading, which are less risky than Fab-Fab recycling. Cooling water efficiency is also a prime area of reducing water use, especially since cooling water is about 20% of total water flow in a fab. Also important are conservation methods, including such items and processes as "night mode" switches and flow verification after each startup - which ensures that the flow remains at the level recommended by the manufacturer and does not increase after each startup.¹¹⁰

Upgrading a deionized water reverse osmosis (DI/RO) unit can also reduce water use. Analog Devices, in Santa Clara, California, changed their RO unit from cellulose acetate membranes to thin-film composite membranes. As a result, the total dissolved solids (TDS) present in the product stream had a direct effect on regeneration frequencies of ion exchange columns and chemical use. Overall, Analog reduced water and chemical use approximately 80%.

	Prior to RO upgrade	After RO upgrade
Regenerations/week	4	0.8
Water used	40,000 gal	8,000 gal
Sodium hydroxide	400 gal	80 gal
Sulfuric acid	240 gal	48 gal
TDS	65 ppm	13 ppm 111

To confirm that any of these methods have been successful, monitoring of the water use is necessary. Water use monitoring provides an opportunity to accurately measure results of efficiency measures taken and determine the cost-effectiveness of the methods implemented. For example, water meters should be placed on individual pieces of water-using equipment to provide a complete overview of water use at the facility.¹¹²

When instituting water recycling, the water goes back to the same application in which it was originally used.¹¹³ There are essentially two approaches to recycling fab wastewater: use only the cleanest streams to recycle, or collect and treat all wastewater for recycle. By selecting only the cleanest streams, the least amount of pre-treatment is necessary. Also, this option can produce enough water to make up as much as 40-50% of the UPW usage. The second approach would maximize the amount of water recycled, but the cost per gallon for pre-treatment is much greater, and it is more difficult to address all the contaminants found in the wastewater. The facility managers may also decide to take an intermediate approach, which can increase the recycled water above the first option, at a fairly reasonable cost.¹¹⁴ Keep in mind that a recycling system can be retrofitted at a facility at a cost of $250,000 - $1 million worth of additional plumbing. The price is at the low end of the range if a rinsewater collection system exists. The biggest challenge in retrofitting is in finding space for the additional plumbing.¹¹⁵

In a water reuse system, wastewater from one process goes to a different process. These other processes can be anything from cooling towers, to process exhaust scrubbers, to irrigation ponds.¹¹⁶ Finally, water reduction is an opportunity to optimize processes; modify processes to reduce water use - (e.g., convert from continuous flow to periodic water use); modify equipment; and replace/install equipment.¹¹⁷

Other opportunities for recycling, reuse and reduction are provided below.
- Rinsing

Evaluate the number of rinses and their duration. Eliminate those that are unnecessary.118

Use counter-current rinsing. This improves the efficiency of tank rinsing.119 However, this may require additional hood space, tanks and piping.120

Use spray rinsing, which is even more efficient than counter-current rinsing. As much as 60% water use reduction has been claimed in comparison to immersion rinses.121

End the rinse based on the level of contamination present in the effluent from the rinse tank. The wafer is then rinsed until clean, but not over-rinsed.122

Modify the flow of UPW and automatic dumps in rinsing operations, based upon contaminant measurements. Potential exists to reduce the wet bench UPW idle flows from several gallons per minute (gpm), to less than one gpm, and autodumps could go from once per hour to once per day. These actions can save millions of gallons per year in UPW use. As an example, a Motorola fab in Austin, TX reduced its UPW usage by 29 % (over $472,000 per year) by implementing wet bench UPW idle flow reduction and autodump elimination.123

Switching from continuous flow to on-demand rinsing in the fabrication operations.124

Use conductivity controls to measure TDS concentration in rinses and to control electrically-operated flow control valves.125

Reduce the rate of "trickle flows" maintained through process rinse baths, during periods when processing is not taking place.126 The same method can be done for any piece of machinery that is inactive: install "sleep mode" switches that reduce flow to a trickle.127

Install automatic, timer-controlled shut-off or flow-reducing devices for process rinse lines that are not in constant use.128 This is analogous to motion-sensor light switches for office buildings.

Eliminate plenum flushes where not necessary.129

- Water reclamation & materials recovery

Apply membrane technologies (microfiltration, ultrafiltration, reverse osmosis & electrodialysis) to recycling and recovery of process wastewater.130

Recover materials in spent process flows, such as chromium and copper, which can then be recycled, reused, or sold.131

Remove suspended and settleable materials by filtration.132

If possible, return the final portion of rinsewater flows to the circulating deionized (DI) water return loop. It may be feasible to re-treat this water at the DI water generating plant less expensively than incoming municipal water. Keep in mind that the design and operation of the system must prevent inadvertent contamination of the DI return supply by discharges of concentrated chemicals to the wet bench drain.133

- Water use changes

Meter the amount of DI water delivered to the various departments and work groups in the plant, and bill them for actual DI water use.134

- Process-related

Use better operating procedures for drag-in and drag-out, minimizing the contamination from the drag-out.135

Install flow meters, manually-operated flow control valves, or flow reducers.136 This provides operating flexibility and the ability to respond to changes in water supply pressure.

- Fume scrubbers
In most wet scrubbers, a supply of recirculating water is supplemented by a stream of makeup water, and a portion of the circulating scrubber water is discharged to the sewer. Wet fume scrubbers often use considerable volumes of water, and make-up flow rates between 5-10 gallons per minute are not unusual.¹³⁷

Make sure you know what the flow rates to the fume scrubbers are, and limit water flows to no more than necessary.138

Install flow meters. The flows should be limited to the rate specified by the scrubber manufacturer for proper operation.139

Identify opportunities for reuse of non-potable water in the scrubbers.140

- Cooling systems
There are three main categories of cooling systems: cooling towers, evaporative coolers, and once-through cooling. Opportunities for all three are provided below.
    Cooling towers

Verify that the original design conditions still apply to the cooling needs. This will ensure that the tower is operating within its original design parameters, and remain energy and water efficient.

Inventory each cooling tower, its cooling capacity, and equipment/processes it serves. Meter and record amounts of make-up water added and bleed-off water discharged ("blowdown"), in order to quantify water use.141

Reduce the amount of bleed-off discharged from the system to the minimum level for good operating practice.142

Make sure the purpose and action of each chemical used for treating the recirculating cooling tower water is known.143

If using conventional water treatment, increase cycles of concentration (by working with the chemical vendor) to decrease the amount of water bled off.144 The cycle of concentration can have a significant impact on water use. For example, increasing the cycles of concentration (the number of times water is used before being bled off) from 2 to 4 for a 500-ton cooling tower operating at 60% capacity for 350 days per year, will save 2.4 million gallons per year, providing a savings of as much as $9,000 per year in water and sewer costs.145

Make sure the chemicals used are compatible with each other (do not neutralize one another), and are effective at the tower pH.

Consider incorporating sulfuric acid in the treatment program. This would help decrease carbonate scale and achieve significantly higher cycles of concentration.146 However, before introducing sulfuric acid, make sure that all materials that the sulfuric acid will be in contact with are compatible at the low concentrations used.

Consider ozone as an alternative for cooling water treatment.147

Establish a performance-based specification for the cooling towers and have vendors make proposals for the facility's cooling tower water treatment. As part of the proposal, require vendors to commit to a predetermined minimum level of water efficiency, and have the vendors show projected annual water and chemical consumption costs.148

    Evaporative coolers

Make sure there are pumps in the coolers to recirculate the water. This will also improve efficiency by keeping the water as cool as possible.149

Check to make sure you are not bleeding off an excessive amount of water. For a typical small cooler, anything more than a few gallons per hour may be excessive.150

    Once-through cooling
      This is the most water-intensive cooling method in use.¹⁵¹

Eliminate all uses of water for once-through or "single-pass" cooling. Air-cooled models can replace many types of water-cooled equipment.152 Connect to a recirculating cooling water loop (such as a chilled water system, if present) instead of using once-through cooling.153

- Non-process water efficiency options
    Restrooms

Consider replacing existing toilets and urinals with ultra-low flush (ULF) models.154

Consider installing automatic sensor controls for toilets and urinals.155

For older toilets & urinals equipped with flush valves that flush more than 3.5 gallons: retrofit them with insert orifices or valve replacement kits to reduce the volume of water per flush. Or, for older tank-type toilets that flush more than 3.5 gallons, insert dams or water-filled plastic containers to reduce volume of water used per flush.156

As a third alternative for toilets, adjust the flush valves to use less water.157

Do twice-yearly dye-tablet test to check all tank toilets for leaks.158

Retrofit faucets with aerators to add air to flow stream, or insert a flow-restricting orifice in each faucet.159

Change to alternative faucets, including metering faucets, self-closing faucets, and/or automatic sensor-controlled faucets.160

Make regular inspections of plumbing faucets for leaks. A faucet with a slow drip can waste 10 gallons or more per day.161

Conduct a monthly water audit of metered water consumption for early leak detection.162

Install a pressure reducing valve to reduce pressures to 60 psi.163

Collect rainwater to use for toilet flushing.

    Landscaping

Use water-efficient plants, and plants that are native to the area.

Use trees and shrubs in planters, rather than turf. Planting beds should have a layer of wood, mulch or rock to help retain water.164

Make sure irrigation systems are designed to avoid unnecessary sprinklers and blockage of the spray stream by obstacles.165

Install timers or moisture sensors to activate system before sunrise or after sunset to reduce evaporation losses.166

Do not mix low and high water use plants. Keep turfed areas separate from planters, trees, and shrubs.167

Inspect sprinkler heads regularly; replace damaged, worn or broken heads.168 Clean sprinkler heads regularly to remove mineral deposits and maintain hydraulic efficiency.

Inspect the sprinkler system for leaks in pipes, couplings and faucets.169

Adjust sprinkling timing cycles seasonally. Consider letting turf go dormant in summer. Water large turf areas according to evapotranspiration rate.170

Plant higher water use plants in low areas to intercept runoff and decrease the need for supplemental water.171

Keep turf cut to proper height172; use grasscycling.

Aerate and dethatch turf every spring or summer.173

Consider installing a drip irrigation system that slowly and steadily applies water onto the ground at each needy plant. Bubblers work best for trees and shrubs.174

Inspect exterior faucets for leaks.175

Consider using gray water - either from the non-process waste water facilities, or the semiconductor process - for landscaping.

Other turf tips are available at the City of Seattle webpage, "6 Steps to Natural Lawn Care," http://www.ci.seattle.wa.us/util/rescons/n_6step.htm.

List of resources
The resource listing that follows provides information that should be helpful for facility managers, technical assistance providers, and anyone else interested in energy and water issues for the semiconductor industry. The topics covered:

Energy Efficiency

Resource Listing	Description and Comments	Contact (if applicable)
http://www.infinitepower.com/watts.html	Worksheet, "What's a Watt?" From Renewable Energy, the Infinite Power of Texas, Sponsored by the Texas General Services Commission's State Energy Conservation Office. November 1, 1997.    Provides some comparative examples that help make some of the language used in energy understandable for those who do not work with it everyday.
http://www.ci.portland.or.us/energy/ 1997bestwinners.html	1997 BEST Business Award Winners from the City of Portland. Specific awards for semiconductor and semiconductor-related companies: Oki Semiconductor - Water Conservation Intel Oregon - Winners for Overall Success Wacker Siltronic - Winners for Overall Success	City of Portland Energy Office 1211 SW Fifth Ave, Suite 1170 Portland, OR 97204 Tel: 503-823-7222 pdxenergy@ci.portland.or.us
"Energy Conservation Through Water Usage Reduction in the Semiconductor Industry," L. Mendicino, K. McCormack, S. Gibson, B. Patton, D. Lyon, J. Covington. Motorola. Austin, TX	An excellent summary of what Motorola's Austin, TX plant has done to increase energy efficiency and decrease water consumption. A number of good ideas that are applicable to many facilities in the semiconductor sector are provided.    This paper has been presented and published at the following conferences: 20th National Industrial Energy Technology Conference, April 1998 Semiconductor Manufacturing Energy-Efficiency Opportunities Workshop, October 1998 195th Meeting of the Electrochemical Society, May 1999
http://www.nwppc.org/welcome.htm	Website for the Northwest Power Planning Council. As noted on the "About the Council" page: The Northwest Power Planning Council is a four-state compact formed by Idaho, Montana, Oregon and Washington to oversee electric power system planning and fish and wildlife recovery in the Columbia River Basin. The Council was initiated by Congress through approval of the Northwest Power Act of 1980 (Public Law 96-501).    One of the documents available at the website (as an Adobe Acrobat file: http://www.nwppc.org/enr_issu.htm#micro): "Opportunities for Efficiency: The Northwest Microelectronics Industry." This report is one of the products that resulted from a study of efficiency opportunities in the microelectronics industry. It was produced through the collaborative efforts of The Northwest Power Planning Council, The Oregon Office of Energy and The Bonneville Power Administration.	Northwest Power Planning Council 851 SW 6th Avenue, Suite 1100 (Central Office) Portland, OR 97204-1348 Tel: 800-222-3355 Fax: 503-795-3370
http://www.semi.org/882565b10062217a/ ad09cecebf092f71882565e60016fc57/ 5ef74c448632375c882565e2006306b9? OpenDocument	Found on the http://www.semi.org/ website: Article "Pollution Prevention and Profitability Go Hand In Hand." This article includes an overview of Wacker Siltronics a silicon wafer manufacturer in Oregon, with a different example than the BEST program above. Identifies more details on water savings. The article also describes forming partnerships to get P2 programs and energy efficiency program paid for and implemented.
Oregon State University Industrial Assessment Center	The OSU Industrial Assessment Center provides energy efficiency and pollution prevention assessments at no direct cost to Northwest manufacturers (OR, WA, ID, MT).	Greg Wheeler 344 Batcheller Hall Oregon State University Corvallis OR 97331-2405 Tel: 541-737-2515 Fax: 541-737-5035 greg.wheeler@orst.edu
http://www.obd.com/oki/otr/ html/nf/otr-160-12.html	Article, Matsuki, M., Tanaka, N., "Energy Saving System for Air Conditioning of Clean Room for Semiconductor Factory (Estimation of FMU System)," from Oki Technical Review, Number 160, Volume 63, January 1998.    Describes savings that Oki achieved in their AC unit, which takes up 43% of energy consumption for semiconductor plants.    Note: this can also be downloaded as an Adobe Acrobat file.
http://www.psychologie.uni-kiel.de/ nordlicht/sme/c2.htm	From Interdisciplinary Analysis of Successful Implementation of Energy Efficiency in the industrial, commercial and service sector, Final Report, Volume III, Documentation of Company Case Studies, "2. Case Study - A Producer Of Electronic Semiconductors (D)." Copenhagen, Karlsruhe, Kiel, Vienna, Wuppertal, February 1998.    Looks at the psychology involved in decision making process, specifically for an energy efficiency project. Provides an interesting perspective on how company cultures and business drivers influence decisions on energy efficiency projects.
http://www.nwalliance.org/ projects/current/micro.html	Information from the Northwest Energy Efficiency Alliance (http://www.nwalliance.org/). Brief overview of the Alliance's work in energy conservation for the microelectronics industry, as well as providing some information about non-energy benefits of energy efficiency, including productivity, product quality, and product cycle times.	Alliance contact: Blair Collins Tel: 503-827-8416 x 233 bcollins@nwalliance.org Chris Robertson and Associates Chris Robertson Tel: 503-287-5477 crobertson@igc.org
http://www.rmi.org/newsletters/ 98spnl/nexttrick.htm	Spring 1998 Article from Rocky Mountain Institute, "And For Our Next Trick...".    Provides a brief, good overview of issues that create energy consumption in semiconductor manufacturing, and why efficiency is important.	Rocky Mountain Institute 1739 Snowmass Creek Road Snowmass, CO 81654-9199 Tel: 970-927-3851 Fax: 970-927-3420 emalia@rmi.org.

Water Efficiency

Resource Listing	Description and Comments	Contact (if applicable)
"Energy Conservation Through Water Usage Reduction in the Semiconductor Industry," L. Mendicino, K. McCormack, S. Gibson, B. Patton, D. Lyon, J. Covington. Motorola. Austin, TX	An excellent summary of what Motorola's Austin, TX plant has done to increase energy efficiency and decrease water consumption. A number of good ideas that are applicable to many facilities in the semiconductor sector are provided.    This paper has been presented and published at the following conferences: 20th National Industrial Energy Technology Conference, April 1998 Semiconductor Manufacturing Energy-Efficiency Opportunities Workshop, October 1998 195th Meeting of the Electrochemical Society, May 1999
http://www.epa.gov/docs/ watrhome/you/recirc.html	Brief case study from EPA Office of Water, "Recirculating Cooling Water." Provides overview of what International Microelectronic Products did to reduce water use, as well as their overall, annual savings.
http://www.semiconductor.net/ semiconductor/archive/Jul99/ docs/web_feature8.html	Semiconductor International, February 1999, Web Exclusive. P.T. Brown, J. Covington, V. Ladigo, K. McCormack, J. McDonald, L. Mendicino, K. Rhodes. "Environmental Impacts and COO of Two Wet Clean Tools."    Analysis of a plug flow system (PFS), which the vendor claimed had significant reductions in chemical usage, UPW usage, and air emissions compared to the wet benches (WTB) used in most fabs.
http://www.sematech.org/public/ docubase/abstract/3599aeng.htm	Found on the Sematech site: Donovan, R. P.; Morrison, D. J.; Timon, R. P., "Design of Recycling System for Spent Rinse Water in Sandia's Microelectronics Development Laboratory," Nov 30, 1998, Sematech document ID number 98113599A-ENG. From the abstract: This report describes a project to design, install, and operate a system to recycle rinse waters discharged from wet benches. Using a single-tank system, representative properties--particularly total oxidizable carbon (TOC), nonvolatile residue (NVR), and dissolved silica--of the water collected for recycling were measured. Response times of the analyzers that measured these properties were correlated with transit times between fab wet benches and the collection tank. The quality of weekend rinse water, overnight water, and production-time water was also compared. The system was not in place, as of November 1998, but this report provides a comprehensive overview of what Sandia looked at to get the system in place. Available as an Adobe Acrobat file.
http://www.future-fab.com/futurefab/ docs/ff5/docs/5_6_1.html	Weber, T. L., Joiner, J. A., DeGenova, J. "Deionized Water Recycling Results and Benefits from a Case Study At Texas Instruments' DMOS 5 Facility," Future Fab Issue 5.    Case study from Texas Instruments, and how they have reduced water use at their Dallas, TX facility.	Jeffrey A. Joiner, P.E. Texas Instruments, Inc. 13353 Floyd Road, MS 377 Dallas, TX 75243 Tel: 972-927-3122 Fax: 972-995-0978 j-joiner2@ti.com
http://www.obd.com/oki/otr /html/nf/otr-160-11.html	Article by Wakamatsu, H., Kikka, Y., Tanaka, N., "Introduction of Ultra Pure Water Close System into Semiconductor Plant," from Oki Technical Review, Number 160, Volume 63, January 1998. From the abstract: ... installed an ultra pure water closed system in Oki's semiconductor plants. This pure water supply equipment supplies ultra pure water with a 95% or higher pure water recovery percentage. The waste water collection equipment has a low pressure evaporation condenser, which saved energy, resources and space. Waste water treatment equipment can recycle high purity calcium fluoride (fluorite) using a hydrofluoric acid recycling unit with a high efficiency substitution reaction, which allows hydrofluoric acid material to be recycled. The running costs are about double that of a semi-closed system, which has a recovery percentage of 80%    Note: this can also be downloaded as an Adobe Acrobat file.
http://www.mntap.umn.edu/ P2/AIR&WA/wa-a4.htm	"Low-Tech Ideas: Water Conservation Idea File," MnTAP SOURCE, Spring 1997 Issue, Volume 12, Number 2.    May provide some assistance for those getting started with water efficiency.
http://www.aceee.org/ p2/p2cases.htm#sandia	"Sandia National Laboratories Microelectronics Development Laboratory    Water-Use and Wastewater Reduction," 1997 case study from the American Council for an Energy-Efficient Economy (ACEEE) report, "Making Business Sense of Energy Efficiency and Pollution Prevention."	John Jewell Sandia National Laboratories PO Box 5800 Mailstop 1074 New Mexico Albuquerque, NM 87185-1074 Tel: 505-845-8334 Fax: 505-844-7210 JEWELLJR@sandia.gov http://www.sandia.gov/
http://www.svtc.org/larachart.htm	Information compiled by the Silicon Valley Toxics Coalition, "Did You Know?: Water Use and other Materials and Wastes Associated with Semiconductor Production."	Silicon Valley Toxics Coalition 760 N. First Street San Jose, CA 95112 Tel: 408-287-6707 Fax: 408-287-6771 svtc@igc.apc.org
State of California, Department of Water Resources, "Water Efficiency Guide for Business Managers and Facility Engineers," October 1994.	Companion volume to the American Water Works Association's "Helping Business Manage Water Use - A Guide for Water Utilities."    An excellent resource for those who are interested in reducing water throughout their facility. Cuts across many different types of industries.    PPRC library resource	Department of Water Resources Bulletins & Reports P. O. Box 942836 Sacramento, CA 94236-0001 Tel: 916-653-1097

Semiconductor Research

Trade Associations

General Resources

The information provided in this report is current as of February 2000.

Resources used to compile information about the semiconductor industry include: