On-line measurement of profile parameters of rectangular holographic photoresist gratings during development

Abstract

This paper presents a method for on-line measuring photoresist grating profiles during the development process by detecting the diffraction efficiencies of surface-relief photoresist gratings on transparent substrates. A He-Ne laser of 594.1 nm wavelength is employed as the monitoring light source. Firstly, the groove depth of a grating is determined from the minimum value of the monitoring curve of the 0 th -order transmission intensity. Then, with the groove depth known, the duty cycle of the grating is measured from the -1 st -order transmission intensity. The feasibility of our method has been demonstrated through fabrication of many rectangular photoresist gratings of 1200, 2200, and 3000 lines/mm on glass substrates. Good agreement between the on-line, real-time measured results and the scanning electron microscopy results is obtained.