BORIDING OF CHROMIUM PHOTOMASKS FOR INCREASED ABRASION RESISTANCE

In the photolithographic processing of semiconductor material, 700-1000 Å of chromium on soda-lime or borosilicate glass is the most commonly used masking material. During contact printing the chromium surface may become scratched or abraded so that the opaque regions lose the ability to block actinic radiation. The gas phase diffusion of boron into chromium is used to increase the hardness of the photomask surface and to improve the wear resistance. The boronizing process confers great resistance both to sliding wear and to abrasive wear. Boriding at elevated temperatures on a graphite substrate decreases the warpage of the photomask blank and improves the overall quality of the photomask without introducing defects or without affecting the plasma etching characteristics of the chromium. Thus the standard photomask fabrication techniques of resist application, patterning and etching may still be applied after boriding treatment to produce a longer life photomask. © 1979.