Instrument for Rapid Quantitative and Nondestructive Wafer Microroughness/Surface Quality Evaluation for In-Process Control

A new approach to an optical scanning heterodyne microscope is proposed. The system will employ a resolution enhancement technique that will provide rapid quantitative submicron surface deposit and surface roughness measurements on semiconductor wafers. The system will be capable of resolving vertical heights and lateral widths less than 100 Angstroms and have a working distance greater than 10 cm in air or vacuum. In addition, the system will be able to provide and identification "signature" for different materials deposited on the wafer surface. The scanned image of the wafer will provide sharp delineation between surface steps, scratches, and particles whether insulating or metallic. With the rapid response and long working distance, the system can be used for in-process wafer evaluations. Coupled with the systems capability to identify deposits on the wafer surface, the electronically enhanced optical data can lead to analyses through SPA to directly control the processing of silicon wafers in production environments.