Relationship between wafer fracture reduction and controlling during the edge manufacturing process

Abstract

Given the trend towards wafers of a larger diameter, microelectronics circuits are driven by modern IC manufacturing technology. Silicon wafer breakage has become a major concern of all semiconductor fabrication lines because silicon wafer is brittle and high stresses are induced in the manufacturing process. Additionally, the production cost is increasing. Even a breakage loss of a few per cent drives up device costs significantly if wafers are broken near completion, but wafer breakage even near the beginning of the process is significant. In this paper, we first point out the approach for the characterization of silicon wafer failure strength empolying a simple drop test, thereby providing a better understanding of the stress accumulated in wafer bulk before failure. This study also presents a brand new method using a charge coupled device (CCD) to capture the cross-section image of the wafer at the wafer edge; the data measured at the edge can be used to diagnose overall wafer strength. Analysis of the image of the wafer edge is used to characterize silicon strength and a simple drop test is conducted to elucidate wafer failure, improving our understanding of the accumulation of stress in wafer bulk before failure. This work presents an approach for characterizing silicon wafer failure strength using a simple drop test, to improve our understanding of the stress accumulated in wafer bulk before failure. However, this work will describe many of the improvements that have resulted in the virtual elimination of wafer breakage due to unknown reasons. According to an analysis based on the material mechanical theory for the bevel lengths (A1, A2), the edge length and the bevel angle ( θ) are optimized to design the edge profile of the produced wafer, to prevent wafer breakage. Restated, when proper material and process control techniques are utilized, silicon wafer breakage should be prevented. This work is the first to demonstrate the importance of understanding wafer strength using a simple mechanical approach.