The use of high resolution haze for control of SOI surface roughness in a volume production environment.

It is well known that the final surface roughness of SOI wafers has to be controlled to a very tight tolerance in order to maintain transistor parameters required for today's advanced node semiconductor devices. The traditional method for this measurement is to use an atomic force microscope (AFM), but the tool's throughput and the area sampled by each measurement are very limited, and AFM repeatability is low. Such measurements can be used during process development, but are not practical during high-volume production. In this paper we will discuss the use of the haze signal from an industry-standard unpatterned wafer inspection system (KLA-Tencor's Surfscan® SP2) equipped with an optional metrology proxy and process signature module (SURFmonitor™), as a proxy for the SOI surface roughness. We will discuss its applicability to a high volume production environment, including the importance of maintaining haze matching across a fleet of inspection tools and practical methods to ensure matching.