Detecting Defects over the Whole Surface of Wafer by Non-destructive and Non-contact Pulse Photoconductivity Method (PPCM)

J. Ndagijimana, Y. Soh, H. Kubota, K. Kobayashi
Kumamoto University, JP

Keywords: TDDB, PPCM, non-destructive and non-contact measurement method, inline process


With the miniaturization of CMOS, the gate insulator has extremely become thin until reaching the EOT (equivalent oxide thickness) of less than 1nm in order to keep maintaining high-speed performances of devices and low electric energy consumption. Since the gate insulator is so thin, leakage current increases and the gate dielectric breakdown can easily occur. This affects the reliability of semiconductor devices. To make good devices, it is necessary to use technologies for the evaluation of the gate insulator reliability. TDDB (Time Dependent Dielectric Breakdown) has been one of the main methods for this evaluation. In this case, a wafer is destroyed in order to be evaluated, which makes this method inappropriate for inline processes. Moreover, it takes time to evaluate a sample. This study proposes a new technique for the evaluation of the gate insulator which is a non-destructive and non-contact measurement method. The method is called Pulse Photoconductive Method (PPCM).The purpose of this study is to inspect the condition of the gate insulator over the whole surface of a 4-inch Silicon wafer using this method.