Characterization of minienvironments in a clean room: Design characteristics and environmental performance

A minienvironment is normally used to maintain a level of stringent cleanliness through controlling particle concentrations within a tightened volume of clean spaces. Because minienvironments are expected to locally achieve a higher level of cleanliness than their adjacent clean room, it is important to understand the characteristics of their design and operation and effectiveness in environmental control. This paper presents findings from an in-situ study on a group of minienvironments, with the focus on characterizing and evaluating environmental performance of the minienvironments as part of a large-scale of in-situ investigation into the total performance of the minienvironments operating in a clean room. In particular, this paper summarizes design and operating characteristics and presents measured environmental performance of five minienvironments and the clean room that housed them. The study discovers that pressure differentials as low as under 0.2 Pa can be sufficient for achieving a high level of air cleanliness to meet environmental control expectation and requirements. Comparisons with relevant industry standards show that existing standards or guidelines may have been suggesting thresholds that are higher than necessary at least in some minienvironment applications. The paper suggests potential benefits from identifying and optimizing the required range of pressure differentials, and likely opportunities and challenges in improving the system's total performance through further studies and refining relevant standards.