A micromachined sensor for in-situ polymer buildup monitoring in reactive ion etching systems

This paper reports a micromachined sensor for the direct measurement of polymer buildup in reactive ion etching systems. The sensor is based on an electrothermal oscillator that measures mass change as polymer builds up on a stress-compensated dielectric window containing metal film heating and sensing resistors. The device operates with a typical cooling time of 2.7 msec and has a measurement resolution of <1 nm. The dielectric windows are 0.5 mm on a side; the overall die size is 3.5 mm×7.5mm. A chevron-based support structure allows the device to be held in wafer form after micromachining for testing and high-yield die separation. The device is flush-mounted in the chamber wall and is protected by a thin film of iridium against damage by the plasma