Wafer probe mark area estimation via digital image processing approach

Abstract

This article presents a digital image processing approach applied to estimate the probe mark area on semiconductor wafer pads. The value of mark area can be used to judge the acceptance of the wafer. Before wire bonding to the wafer, a probing needle contacts each pad to test the electrical characteristics of the chip. However, this contact leaves probe marks on the pad. A large probe mark area results in poor adhesion forces at the bond ball of the pad, thus leading to undesirable products. Traditionally, given the difficulty of calculating the area of the irregular probe mark, probe mark area calculations were substituted by calculating the area of the oval that is manually drawn to cover the probe mark area. Nevertheless, this method is inaccurate, and the results varied from person to person. In this article, we present an imaging processing approach to calculate the probe mark area utilizing high-magnification microscopes to capture probe mark images. Our approach is faster and more accurate compared to the traditional method.