Off-Line Quality Control in Integrated Circuit Fabrication Using Experimental Design

In this paper we describe the off-line quality control method and its application in optimizing the process for forming contact windows in 3.5-μm complementary metal-oxide semiconductor circuits. The offline quality control method is a systematic method of optimizing production processes and product designs. It is widely used in Japan to produce high-quality products at low cost. The key steps of off-line quality control are: (i) Identify important process factors that can be manipulated and their potential working levels; (ii) perform fractional factorial experiments on the process using orthogonal array designs; (iii) analyze the resulting data to determine the optimum operating levels of the factors (both the process mean and the process variance are considered in this analysis; (iv) conduct an additional experiment to verify that the new factor levels indeed improve the quality control.