Improving Front Side Process Uniformity by Back-Side Metallization

Plasma processes are an integral and important part of semiconductor device fabrication. The applications include the dry etching of metals, dielectrics, and semiconductors; chemical vapor deposition of thin films and oxygen plasma descum for organics removal. While each of these processes plays a critical role in the performance of the device, process uniformity across the wafer is crucial for consistent probe yield. If the plasmaprocess condition varies drastically from the center of the wafer to the edge, device performance will change and probe yield will be affected. The critical parameters in a plasma process include temperature, gas flow, gas chemistries, pressure, and effective power. Each of these parameters modifies the etching or deposition-process characteristics. This paper demonstrates that overall process uniformity can be enhanced by metalizing the backside of the wafer. GaAs devices are fabricated on semi-insulating substrates with a bulk resistivity on the order of 1E