Micro-electro-mechanical charge sensing devices

In recent years, it has been reported that plasma non uniformity across the wafer due to non-uniformities in RF current flow, electron current flow, and ion current flow can cause significant charging of surfaces, which can severely degrade or destroy devices, especially MOS gate dielectrics. This work reports, a device which can non-invasively measure this charging in-situ, in real time, in the plasma reactor, as opposed to the conventional method of inferring the charge from later measurement of device degradation. The charging is measured in-situ by measuring the deflection of micro-cantilevers. The device can be used to measure charging in reactors without optical ports, and to quickly map charging non-uniformities across a wafer surface. In addition to being useful as a charge sensing device for plasma processing, the device may be useful for general purpose sensing of surface charge.