An Intelligent Polarimetric System for High-Throughput and High-Sensitivity Quality Assessment of Commercial Semiconductor Wafers

An intelligent polarimetric system has been developed for high-throughput quality assessment of commercial semiconductor wafers by measuring a small amount of residual strains while scanning the wafer at high speed. Residual strain is an important quality measure in semiconductor wafers and computer-controlled polarimetric system is widely used to characterize its distribution. In order to handle the novel semiconductors such as silicon carbide (SiC) and gallium nitride (GaN), more high-throughput and high-sensitivity characterization is expected, but it was difficult due to the limitation of the conventional system both in sensitivity and scanning speed. In order to achieve both high sensitivity and fast scanning, the developed system adopted a small-scale SoC including a control law accelerator (CLA) with ultra-low interrupt latency. A special firmware of distributed processing was originally developed where the CLA performed fast polarization control and its synchronized photometry, while the CPU covered overall processes and communication to the host. The developed system exhibited 5 times faster scanning speed and 10 times higher photometric sensitivity compared with the scanning-type conventional system, which revealed the potential for the world class performance in the quality assessment of the commercial semiconductor wafers and implied the applicability for further study on advanced strain analysis based on measurement informatics.