Wafer back side inspection applications for yield protection and enhancement

Semiconductor manufacturers employ various techniques and tools to detect and identify the physical defects that limit product and process yields. Most of these techniques focus on measuring the front side of the semiconductor wafer where the devices are manufactured. Attention to defectivity on the wafer backside has been minimal. Two possible reasons are the lack of suitable equipment and methods, and a lack of awareness of how backside defectivity can affect a manufacturing line. This paper presents four case studies which describe how back side defectivity can affect yield, scrap and production costs. New technology, which facilitates backside inspection, has recently been developed. Key improvements include the ability to non-destructively scan wafer backsides and improved coordinate accuracy, which allows adder calculations and SEM review. This paper describes how this new technology was applied in these case studies, thereby improving yield and reducing scrap and production costs.