<title>Critical point drying and cleaning for MEMS technology</title>

Abstract

A critical step in surface micromachining of microelectromechanical systems (MEMS) is the process that releases, cleans, and dries the flexible structures that are crucial to MEMS functionality. Standard release methods employed today can leave residue particles and can cause sticking because of surface tension. Aggressive design requirements, liquid processing, packaging, handling, transportation, and device operation etc., can contribute to device failure due to stiction. The use of supercritical carbon dioxide has been proven in various industries to achieve ultra-clean surfaces. Recent critical research studies by academia, research laboratories and industry have shown that supercritical carbon dioxide can be successfully used to alleviate the stiction problem and provide a clean and dry surface. The absence of surface tension in the supercritical phase of a fluid provides an excellent means to overcome stiction. The advantages of supercritical carbon dioxide include its relatively low critical temperature and pressure, its high diffusivity, low surface tension, and environmentally friendly (non-ozone depleting, non- hazardous). This paper reviews the stiction problem for MEMS, and the application of critical point drying for MEMS technology.