An interferometric method is presented that has been successfully used to measure the alignment precision of different mask patterns superimposed on a silicon wafer in the lithographic process. Based on an extremely precise electrooptical phase measurement technique this method is capable of measuring the relative pattern displacement with precision in the nanometer region. The principle of the measurement technique is described. Results of experiments are discussed including suggestions for improving the measurement precision.
© 1984 Optical Society of AmericaFull Article | PDF Article