Changes in chemical composition and nanostructure of SiC thin films prepared by PECVD during thermal annealing

Abstract

Silicon carbide (SiC) thin films were deposited on silicon (Si) using plasma enhanced chemical vapor deposition (PECVD). Annealing was done in a rapid thermal annealing furnace at a temperature of 1300 °C. As-deposited and annealed Si-rich and stoichiometric SiC thin films were investigated by analytical transmission electron microscopy (AEM). TEM-energy-dispersive X-ray spectroscopy was used to quantify the chemical composition of the SiC thin films with high accuracy. The chemical composition of the near stoichiometric SiC thin film changed during annealing from Si0.4C0.6 to Si0.5C0.5 due to diffusion of Si from the Si substrate into the film. The Si-rich Si1-xCx film had the identical chemical composition of Si0.8C0.2 before and after annealing. As-deposited films show nanoporosity within the bulk film. During annealing, v-shaped defect structures were formed at the interface of the stoichiometric SiC thin film to the Si substrate. Diffraction patterns revealed that as-deposited films were amorphous. During annealing the crystallization of 3C-SiC occurred in near-stoichiometric SiC thin films, whereas in Si-rich Si1-xCx thin films two phases, namely Si and 3C-SiC, crystallized. Low-loss and core-loss electron energy loss spectroscopy (EELS) verified the diffraction results. In the low-loss spectra of the near stoichiometric SiC thin film, a plasmon peak located at 20.2 eV before and at 22.3 eV after annealing was detected. The low-loss spectra of the Si-rich Si1-xCx thin film showed an asymmetric plasmon peak with two maxima located at 18.5 and 25.0 eV in the as-deposited film and 18.6 and 24.3 eV in the annealed Si-rich Si1-xCx film. The 18.5 eV plasmon peaks is assigned to Si and the 25 eV plasmon peak is attributed to the SiC phase

Electron tomography analysis of 3D interfacial nanostructures appearing in annealed Si rich SiC films

“…26 The observation of 3C-SiC NPs in the annealed SRSC films was also reported in previous studies. 14 Fig. 1e indicates that the phase separation of Si and SiC starts after 15 minutes of annealing and continues by the crystallization of separated Si and SiC phases resulting in the coexistence of c-Si and 3C-SiC NPs during the first 15 minutes of annealing.…”

“…In the plasmonic spectrum in the electron energy loss spectrum (EELS) in the TEM, of SRSC films, the Si, amorphous SiC (a-SiC), and crystalline SiC (3C-SiC) plasmon peaks have clearly distinct positions 14 and can therefore be used to distinguish the presence of the different constituents of the materials systems. In addition, when the different parts of the system change their phase or crystallographic structure, this also leads to shifts in plasmon energy and makes such phase changes detectable.…”

Effect of RF power and gas flow ratio on the growth and morphology of the PECVD SiC thin film s for MEMS applications

“…This process causes diffusion of Si from the substrate into the thin film there by causing the formation of Si nanocrystallites and SiC crystallites. 17 It was also explained by Kim et al, 18 that the annealing of the films cause the breaking of the Si-H and C-Hn bonds there by reducing the H2 content in the thin films which improves the optical properties of the thin films. Awad et al 19 mentioned that the roughness of the SiC thins films can be reduced to ∼1nm due to film densification when the samples were annealed.…”

“…It was also reported that by annealing the thin films the residual stress can be reduced. 17 The stoichiometry of the thin films changed when the samples were annealed at 1300 • C in an Ar atmosphere for 30 minutes. This process causes diffusion of Si from the substrate into the thin film there by causing the formation of Si nanocrystallites and SiC crystallites.…”