Industrial-Grade Differential Interference Contrast Inspection System for Unpatterned Wafers

In the field of optical inspection for unpatterned wafer surfaces, this paper presents a novel inspection system designed to meet the semiconductor industry’s growing demand for high efficiency and cost-effectiveness. The system is built around the principles of simplicity, stability, speed, and low cost. Its core is a low-speed stepping rotary line-scan architecture. This architecture is integrated with a two-step phase-shifting algorithm. The combination leverages line-scan differential interference contrast (DIC) technology. This aims to transform DIC technology—traditionally used for detailed observation—into an industrialized solution capable of rapid, accurate quantitative measurement. Experimental validation on an equivalent platform confirms strong performance. The system achieves an imaging uniformity exceeding 85% across dual channels. Its Modulation Transfer Function (MTF) value is greater than 0.55 at 71.8 lp/mm. The vertical detection clearly resolves 3 nm standard height steps. Additionally, the throughput exceeds 80 wafers per hour. The proposed line-scan DIC system achieves both high inspection accuracy and industrial-grade scanning speed, delivering robust performance and reliable operation.