High-accuracy aerial image measurement for electron-beam projection lithography

A direct means of measuring an image blur of electron beam projection lithography (EPL) tools is described. An aerial image sensor used for the image blur measurement was fabricated and evaluated. The signal to noise ratio (SNR) was very high and the signal contrast was 97%. The measured image blur, defined as the distance between 12% and 88% of the beam edge profile, under the optimum condition was 13 nm and the measurement repeatability was 3 nm (e sigma). The measurement error due to the sensor was extremely small, and a quantitative measurement of the image blur can be realized using this technique. The application of this technique to a system calibration is demonstrated. Focus and astigmatism were measured and the optimum settings of focus coils and stigmators were determined with an excellent repeatability. The potential for this technique to provide an automated self-calibration system on the EPL tools is clearly shown.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.