STATISTICAL CONTROL OF VLSI FABRICATION PROCESSES

Random fluctuations in Very Large Scale Integrated Circuit (VLSIC) fabrication processes cause the parametric production yield to fall below acceptable levels, causing the lines to be counter-profitable, which results in a loss of competitive edge. We propose a profit-based framework for an integrated Computer Aided Design-Computer Aided Manufacturing (CAD-CAM) system that will enable the design, fabrication, control, and diagnosis of present and future VLSIC's profitably. The inefficiencies of present-day CAM systems are due to the lack of appropriate methodologies for process monitoring and statistical techniques to analyze the in-process and end-of-process data. Methodologies for monitoring lots in fabrication lines, using in situ measurements, and for controlling lots, using the multivariate distribution of observable in-process parameters, are developed at the Carnegie Mellon University; these methodologies attempt to eliminate the pitfalls of the previous statistical process control algorithms. The software system which implements the new algorithms has shown encouraging results when applied to industrial fabrication lines. © 1990 IEEE