Characterization of a-SiC:H films produced in a standard plasma enhanced chemical vapor deposition system for x-ray mask application

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Abstract
Hydrogenated amorphous a‐SixC1−x:H films with various compositions (0.2≤x≤0.8) were prepared by a radio frequency (rf 100 kHz) glow discharge decomposition of a silane and methane mixture diluted in argon. The deposition system used was a commercially available plasma enhanced chemical vapor deposition reactor allowing a high throughput (22 wafers of 4 in. diameter each run). The properties of the films such as thickness, density, and stress were investigated. The composition, including hydrogen content and Si/C ratio, and the structure of the films were systematically examined by means of several diagnostics including electron recoil detection, x‐ray photoelectron spectroscopy, and infrared (IR) absorption analysis. Thickness and density of the films were dependent on the film composition, while the stress of the films was highly compressive (3×109–1×1010 dynes/cm2). Density was about 2.4 g/cm3 for nearly stoichiometric SiC films. The hydrogen content of the films was practically constant at 27 at. % over the whole investigated composition range. The IR analyses suggested that the structure of the silicon carbide films is inorganic‐like over the whole range of compositions. From stoichiometric to carbon‐rich films, the structure mainly consists of a tetrahedral network where silicon atoms are randomly replaced by carbon atoms and one hydrogen atom is bonded to silicon (SiH group). However, the presence of SiH2 groups and microvoids was observed in the structure of Si‐rich silicon carbide films. Finally, the development of SiC membranes for x‐ray lithography was presented including the control of film stress by means of rapid thermal annealing. Silicon carbide membranes of relatively high surface area (32×32 mm2) and showing high optical transparency (80%) were successfully fabricated.

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