Linearity estimation of high accurate energy detector for excimer laser

High accurate pulse energy detection for excimer laser is one of the most important technologies in deep ultra violet (DUV) lithography machine for precise dose control. In order to estimate the linearity of the SIOM proprietary energy detector (ED), a modified correlation method and the corresponding system have been developed. In the proposed method, an identical home-made ED was used as reference in the experimental system showing benefit as pulse energy fluctuation elimination. Secondly, this method provides a solution of high accurate measurement with a reference detector which is the same as the tested detector. The linearity estimation system contains an excimer laser, a beam expander, an adjustable diaphragm, a beam splitter, a reference ED (R-ED), a set of attenuators and a tested ED (T-ED). Experimental results show that, with linear least-squares fitting, the measured nonlinearity factor of the ED is 0.617% in a dynamic range of about 1–10 nJ per pulse, and the combined uncertainty is 1.140%. It is proved that the SIOM proprietary ED can be used in high accurate pulse energy measurement of excimer lasers.