Automatic testing and analysis of misregistrations found in semiconductor processing

Abstract

For advantage to be taken of advanced lithographic techniques it is necessary to be able to measure and understand the causes of misregistrations found in semiconductor lithographic processes. A device for making such measurements is described which is simple, versatile, compatible with standard processes, and has sufficient accuracy for expected requirements. Devices made using this technique can be automatically tested using standard equipment. Analysis is carried out using computer programs and a brief account of the various outputs is given. Results are discussed which show how misregistrations between masks in a set have been measured and errors in the lead screw of an optical step-and-repeat camera quantified. Misregistrations due to distortion of silicon slices have so far been found to be very small and masked by other effects.