A Technical Perspective

Facilities operators and engineers in the semiconductor industry can reduce energy consumption by half, save water used in processing, and conserve expensive and hazardous chemicals by applying state-of-the-art resource-efficiency techniques and measures to their silicon production and semiconductor fabrication facilities.

Efficiency opportunities exist in all aspects of semiconductor manufacturing. Figure 1 shows that space conditioning typically consumes the most energy in fabrication facilities, followed by processing operations (EPA 1997). The most important areas for energy, resource, and cost savings are:

HVAC Systems and Plant
• Lower cleanroom make-up and exhaust airflow rates save energy and reduce costs. For example, a properly designed exhaust system eliminates exhaust fluctuations and allows the airflow rate to be reduced, saving 10% to 20% of the energy consumption in a fabrication facility (EPA 1997).
• Low face-velocity cooling coils have lower pressure drops and less energy loss through ducts and filters, saving 3% to 7% of cleanroom electricity usage (EPA 1998).
• Higher-performance air filters clean supply air more efficiently, reducing energy consumption in the process (EPA 1997).
• Variable-speed drives in recirculation, make-up, and exhaust fan motors use 15% to 30% less energy than constant-speed drives (Nadel et al. 1992).
• High-efficiency motors, fans, and pumps use less energy.
• Minimizing cleanroom volume reduces recirculation airflow requirements and the associated energy usage. Cleanroom mini-environments are designed to capture these savings.
• Lower water flow rates in cooling towers reduce chilled water piping pressure drops and pumping energy usage. This efficiency measure can reduce facility energy consumption by 3% to 7% (EPA 1998).
• Separating chiller loops for sensible and latent cooling functions, with correspondingly different supply temperatures and energy inputs, can save energy.

  Processing Tools and Supporting Utility Systems

• More efficient process tool components, such as motors, fans, pumps, compressors, and heat exchangers, use less energy directly in operation and indirectly in generating excess heat that must be removed from the cleanroom. Heat recovery systems that recapture heat released by process tools further reduce energy consumption.
• Stabilizing process tool exhaust reduces product contamination, thereby increasing production process efficiency. The exhaust airflow rate can then be reduced, decreasing the amount of energy used in moving the air.
• Using scroll compressors, rather than older types, can reduce the electricity used in vacuum systems by as much as 80%. Variable-speed drives in vacuum pumps can increase their efficiency by 30% to 40% (EPA 1997).
• Light guides and other efficient lighting systems produce lower cooling loads, have lower maintenance costs, reduce or eliminate the risk of lamp breakage, and reduce production interruptions for group relamping in cleanrooms.

  Silicon Production

• Increasing the thermal insulation surrounding the furnace in which silicon is melted maintains the required process temperature with lower energy input. It also reduces the release of heat from this unit and the associated cooling needs.
• Heat shields allow more rapid cooling of silicon crystals as they are pulled from the furnace, accelerating the production process.
• Redesigning the argon gas management system can conserve gas and reduce the energy needed to deliver it.
• Improving the power supplies that convert alternating current to direct current for furnace operation provides modest energy savings.

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This page last updated 3/24/00