Microfluidic MEMS for semiconductor processing

The advent of MEMS (microelectromechanical system) will enable dramatic changes in semiconductor processing. MEMS-based devices offer opportunities to achieve higher functionality, at lower cost, with decreased size and increased reliability. In this work, we describe the achievement of several important devices for use in the semiconductor equipment industry. They include a low-flow mass flow controller, a high-precision pressure regulator, and an integrated gas panel. Compared to current technology, the devices are ultra-small in size, thus minimizing dead volumes and gas contact surface areas. With wettable surfaces comprised of ceramic and silicon (or, silicon coated with Si3N4 or Sic), they are resistant to corrosion, and generate virtually no particles. The devices are created fiom modular components. The science and technology of these components wiU be detailed. The modules examined are: normally-open proportional valves; normally-closed, low leak-rate shut-off valves; critical orifices (to extract information of flow rate); flow models (to extract flow rate fiom pressure and temperature information); silicon-based pressure sensors; and, the precision ceramic-based packages which integrate these modules into useful devices for semiconductor processing. The work finishes with a detailed description of the low-flow mass flow controller. List of Symbols and Variables Volumetric change and initial volume of Fluorinert Temperature coefficient of expansion of Fluorinert liquid Mean and fiU temperatures of Fluorinert liquid Membrane stroke (or, membrane-to-NO-orifice gap) and radius Membrane, cavity thickness Pressure differential across the membrane Young's modulus (190,000 m a) and Poisson's ratio (0.09) for silicon Membrane stress Mass flow (typically in sccm, normalized to the STP flow at 273 IS) Inlet, outlet, intermediate (pressure sensor) pressures Flow velocity, loss coefficient Ratio of specific heats, cp / c,-/H l +