Minienvironment Case Study

LBNL's initial minienvironment research involves a collaboration with ASYST Technologies, Inc. to instrument and evaluate the energy performance of a minienvironment used to conduct research on the 300mm silicon wafer process. The current focus is on the operation of the air system associated with a minienvironment space, as distinct from tools or equipment within the minienvironment used to run the manufacturing process.

The dimensions of the first minienvironment studied are approximately 2'x4'x7.5', and it is located inside a traditional ballroom cleanroom. Once-through airflow is provided to the mini-environment by four 1'x2' fan filter units. Preliminary results are shown in the diagram. The positive pressure is maintained to control airflows and prevent contamination from the surrounding environment. In general, a lower air system EPI value indicates better minienvironment air system energy efficiency. Defining energy metrics such as this is not straight forward, e.g. W/ft2 versus, total facility energy, versus a production metric such as energy per cm2 of wafer produced. Processes vary widely, and thus so do the appropriate metrics.

As seen in the chart, the air-system's EPI (W/CFM) falls in the more efficient part of the range of those benchmarked in normal cleanrooms by LBNL (ISO Class 4 or Class 5), which suggests a significant overall energy savings potential due to the vastly smaller volumes of air that must be moved, conditioned, and filtered thanks to the smaller volume of minienvironments compared to that of full-scale cleanrooms.