High precision electron optical system for absolute and CD-measurements on large substrates

For measurement and inspection purposes in semiconductor fabrication a high precision electron optical tool has been developed. It is characterized by a high performance electron optics with unique specifications at low beam energies. At an energy of 1 keV a spatial resolution of 3 nm is obtained which provides excellent image quality. The reasons lie in the high probe current of more than 50 pA and the high detector efficiency. The optics is combined with a high precision x, y stage. An accuracy of 10 nm can be obtained within a travel range up to 12 in. Maximum travel speed is 100 mm/s. With these specifications the instrument is applicable for absolute as well as critical dimension measurements, for process inspection and for the review of defects.