MECHANICAL-PROPERTIES OF SILICON-CARBIDE FILMS FOR X-RAY-LITHOGRAPHY APPLICATION

Hydrogenated amorphous silicon carbide a-SixC1-x:H films of various co mpositions (0.4 less-than-or-equal-to x less-than-or-equal-to 0.7) wer e deposited using a plasma-enhanced chemical vapour deposition techniq ue. The as-deposited films are under high compressive stress (1 GPa). The control of the stress relaxation is an important stage in the X-ra y mask technology. The stress of the a-Si(x)C1-x:H films is measured b y the wafer bow technique, whereas the resonance frequency and the bul ge techniques are used to measure the stress of the a-Si(x)C1-x:H free -standing membranes. These three methods give similar results and it i s pointed out that the wafer bow technique can be used with confidence to determine the stress of a-Si(x)C1-x:H films intended to X-ray memb rane processing. From the bulge method, the biaxial Young's modulus E/ (1 - v) of the a-SixC1-x:H membranes is also deduced. Values of 200 +/ - 25 GPa are obtained for a-Si(x)C1-x:H films at x = 0.4 and 0.5 film compositions. At x = 0.67, E/(1 - v) is reduced by a factor of about t wo. The structure and composition of the a-Si(x)C1-x:H films were inve stigated by means of elastic recoil detection, X-ray diffraction, and Fourier transform infrared absorption techniques. It is shown that the biaxial Young's modulus increases with the Si-C bond density in the f ilm.