1991 Volume 55 Issue 11 Pages 1249-1255
Characteristics of films used for X-ray mask membrane demand the tensile stress against Si substrate and the high optical transmittance over 70 or 80% at the 630 nm wave length of He-Ne laser using for the alignment between mask and wafer. It was difficult to obtain an amorphous BN (a-BN) film satisfied those requirements. We investigated the effect of addition of carbon to a-BN films and, as the result, obtained the conditions to produce a-BNC films suitable for mask membrane.
It was found that there were some optimum combinations of the deposition temperature and the gas flow ratio (CH3NH2/B2H6) . For example, with the gas flow ratios of 10 at 973 K, 0.53-1.6 at 1023 K and 0.53 at 1073 K, the films having the tensile stress of about 2×108 Pa and the optical transmittance of 70 or 80% were obtained.
Moreovere, the thermal stress and the thermal expansion coefficient αf of the films were calculated from the stress vs temperature curves of the substrates with films. The αf is proportional to the Boron (B) contents as follows: αf=1.38×10−7×B−5.6×10−6 (B: mol%).
