Deep Si etch with ICP cryo-RIE

11/01/1996

Deep Si etch with ICP cryo-RIE

Plasmalab System 100 Cryo Etch, a high-performance RIE instrument for MEMS applications, has a sample plate temperature control system that allows the temperature of the sample to be controlled between ambient and -150?C. This system permits high etch rates, high selectivity to the chosen mask material, high aspect ratio capability, and good uniformity. These results are achieved by thermodynamic suppression of lateral etching, keeping etched surfaces clean and smooth using nontoxic fluorine-based chemistry. Such low-temperature plasma etching of silicon does not suffer from the rough sidewalls associated with room-temperature pulse processing. The high gas conductance design of the process chamber ensures effective delivery of etchant species to the wafer surface and efficient removal of etch by-products. This configuration maintains a high aspect ratio capability at high etch rate without the need for positioning the electrode inside the ICP cavity. Typical process results are: etch rate up to 3.0 ?m/min; mask selectivities - resist >100:1, oxide >200:1, metal >500:1; uniformity x-wafer <+3% for 100-mm wafers; aspect ratio >20:1; and vertical sidewalls, controllable for negative and positive wall angle. Oxford Instruments Plasma Technology, Yatton, UK; ph 44/1934/833851, fax 44/1934/834918.