CD Sensitivity to Process Parameters in Photomask Fabrication Using a LASER Pattern Generator

The control of critical dimension is very important for photomask fabrication. This paper describes the critical dimension (CD) variability for fabricating photomasks using wet etching process when masks were written using 413 nm wavelength LASER pattern generator. The photomask fabrication involves three fundamental processes-exposure using LASER beam, development and etching. Experiments were conducted to observe how CD is affected by process parameters. The critical parameters are exposure energy, development time and etching time. For 2 µ CD [line width (LW)], the CD sensitivity to exposure energy was observed as 8.3 nm/mW for BF patterns and 5.6 nm/mW for DF patterns. The CD sensitivity for development time was 5 nm/s for both BF and DF patterns. The CD sensitivity to etch time was 8.3 nm/s for BF patterns and 5.6 nm/s for DF patterns.