Structural and electrical studies of radio frequency sputtered hydrogenated amorphous silicon carbide films

The structural and electrical properties of radio frequency (rf) sputtered hydrogenated amorphous silicon carbide films are presented in this paper. Films were prepared with sputtering pressure P-S varied from 0.8 to 3 Pa, or with substrate temperature T-S varied from 100 to 300 degrees C. For films deposited with an argon plus hydrogen ambient, the deposition rate was found to increase with increase in P-S and decrease with an increase in T-S. For films prepared with an argon ambient only, the deposition rate increased slightly with an increase in P-S or T-S. The deposition rate was also approximately two to eight times higher when sputtering was carried out in an argon plus hydrogen ambient than in argon only. Infrared (IR), x-ray photoelectron (XPS), and Raman spectroscopies were employed in the structural analysis. The IR results showed that the Si-C bond gave the most prominent absorption peak and was affected by changes in P-S. The Si-H and SiHn stretching modes were observed in all films, and the amount of Si-H bonds N-Si-H were found to increase as P-S or T-S was increased. The C-Hn stretching mode was absent in all films, and this was attributed to the low carbon content in these films. The Si-N stretching mode was suggested to contribute to the extra features between 800 to 1100 cm(-1) in the IR spectra for films prepared at a higher P-S (3 Pa) or T-S (300 degrees C). The stoichiometry of silicon carbide and the film composition were determined by the XPS method. The carbon content of silicon carbide was found to be similar to the target composition and varied only slightly with changes in P-S or T-S. The Raman spectra showed that only the C-C bond can be detected in all of the films. From the electrical measurements, the film's conductivity was found to reduce from 4.21X10(-9) to 4.35X10(-11) Ohm(-1) cm(-1) as P-S was increased from 0.8 to 3 Pa; and decreased from 3.81X10(-9) to 1.31X10(-8) Ohm(-1) cm(-1) when T-S was raised from 150 to 300 degrees C. The conductivity was found to be related to N-Si-H, With higher N-Si-H resulting in lower conductivity. A comparison with data published in the literature suggested that rf sputtering technique was not effective in varying the carbon content in amorphous silicon carbide film. This technique, however, can be used to vary N-Si-H and thus change the structural and electrical properties of the sputtered films. (C) 1995 American Institute of Physics.