Characterization of hydrogenated amorphous silicon (a-Si:H) film stacks for deep submicron fuse link applications

Abstract

In the first part of the project, the characteristics of Plasma Enhanced Chemical Vapour Deposition (PECVD) ct-Si:H films deposited using pure Silane plasma and Silane plasma diluted with Argon under different deposition conditions were investigated in terms of the deposition rate, hydrogen content, refractive index and film morphology. Fourier transform infrared spectroscopy (FTIR) spectra showed that hydrogen was bonded to Si only in monohydride groups (SiH) in a-Si:H films deposited with argon dilution of the Silane plasma. Whereas for a monosilane glow discharge plasma, the spectra revealed the presence of SiH, S1H2 and (SiFk + SiHn) bonds. Results obtained through FTTR and spectroscopic ellipsometry (SE) showed a correlation between the hydrogen content and the RI. Films deposited at higher deposition temperatures had lower hydrogen content and higher RI values as compared to films deposited at lower temperature. These results were consistent with the higher hydrogen content observed in the FTTR spectra. This is mainly due to the decreasing Si densities of the films due to the formation of Si-H and SiHn (n>l) bonds in the films. Atomic force microscopy (AFM) was used to investigate the effect of deposition temperature on the film morphology and results showed that smaller grain sizes and tighter packing densities were characteristic of a-Si:H films deposited at higher temperature.