Spatially Resolved Ellipsometry for Semiconductor Process Control: Application to GaInAs MIS Structures

A new assessment technique, a spectroscopic ellipsometry system with high lateral resolution (10× 10 μm spot), is introduced. Its high surface sensitivity is used at each step of a typical technological process, the fabrication of GaInAs metal-insulator-semiconductor structures, namely oxide removal, etching, and dielectric deposition. The measured non-uniformity of the Si₃N₄/GaInAs interface quality over the wafer is directly correlated to the electrical characteristics of the devices. This is a direct proof of the influence of the native oxide at this interface upon the electrical drift of MIS structures.