## 3 Results and Discussion
### Characteristics of SiN\({}_{\mathrm{x}}\) Thin Films  
AFM was used to analyze the roughness of the SiN\({}_{\mathrm{x}}\) thin film. Figure 3 shows AFM images of SiN\({}_{\mathrm{x}}\) thin film deposited at 250 \({}^{\circ}\)C, 350 \({}^{\circ}\)C, and 500 \({}^{\circ}\)C, respectively. Figure 3a has an RMS (route mean square) value of 0.077 nm, if SiN\({}_{\mathrm{x}}\) thin film was deposited at 500 \({}^{\circ}\)C, the value of the SiN\({}_{\mathrm{x}}\) film is 0.058 nm. Compared with the SiN\({}_{\mathrm{x}}\) thin film deposited at low temperature, the roughness was slightly decreased as the process temperature increased. However, the width of the increase is so small that all thin films seem to have high surface quality. Even though the thin film is processed by various temperature conditions, good uniformity in the film can be observed. To investigate the chemical compositions of the SiN\({}_{\mathrm{x}}\) thin films, depth profiles were measured by AES, as shown in Figure 4. According to the AES analysis, there was an absolute decrease in carbon content with deposition temperature, which means that sufficient thermal energy was contributed to the reaction. Also, the films deposited at low temperature were vulnerable to oxidation due to low film density. SiN\({}_{\mathrm{x}}\) thin films deposited below 250 \({}^{\circ}\)C contain a considerable amount of oxygen, which was reduced with increasing deposition temperature to 500 \({}^{\circ}\)C and measured to be less than 2%. The constant N and Si atomic contents indicate a uniform film stoichiometry throughout the entire film thickness. The ratio of N to Si was 1.34, which is nearly a stoichiometric Si\({}_{\mathrm{3}}\)N\({}_{\mathrm{4}}\) film. Figure 2: Effect of growth rate and refractive index as a function of deposition temperature at a plasma power of 100 W.  
The chemical binding states in each film were investigated using XPS analysis. With the XPS scans of Si 2p and N 1s peaks, we obtained information regarding the bonding behavior of SiN\({}_{x}\), as shown in Figure 5 (N 1s peak not shown). The XPS spectrum corresponding to the Si 2p with peak at 101.82 eV is the signature of the Si-N bond. The spectra corresponding to the N 1s content with peaks centered at 397.72 eV are the signature of the N-Si bond. The Si 2p spectra showed that all the samples had peaks at 101.82 eV. In the N 1s spectra, all the samples exhibited a peak at 397.72 eV [16]. In other words, the deposited samples were nearly stoichiometric Si\({}_{3}\)N\({}_{4}\) and no difference in binding energy state was shown when the deposition temperature increased from 250 to 500 \({}^{\circ}\)C. As shown in Figure 5, the Si 2p peak deconvolution was performed with the Si-N binding energy corresponding to 101.82 eV and the Si-O binding energy corresponding to 103.27 eV. References to XPS and AES data confirmed that the oxygen content decreased sharply as the deposition temperature increased [16]. Figure 4: Auger electron spectroscopy (AES) depth profiles of RPALD SiN\({}_{x}\) film deposited at (a) 250 \({}^{\circ}\)C, (b) 350 \({}^{\circ}\)C, and (c) 500 \({}^{\circ}\)C.  
Figure 5: Si 2p peak deconvolution of X-ray photoelectron spectroscopy (XPS) spectra for RPALD SiN\({}_{x}\) film deposited at (a) 250 \({}^{\circ}\)C, (b) 350 \({}^{\circ}\)C, and (c) 500 \({}^{\circ}\)C.  
Figure 3: Atomic force microscopy (AFM) images (5 \(\times\) 5 \(\mu\)m) of RPALD SiN\({}_{x}\) film deposited at (a) 250 \({}^{\circ}\)C, (b) 350 \({}^{\circ}\)C, and (c) 500 \({}^{\circ}\)C.  
The step coverage of SiN\({}_{\rm x}\) thin film was investigated using trench-patterned wafers, as shown in Figure 6. The aspect ratio of the trench patterned wafer is 2.7 with a top trench width of 31.2 nm in a narrow pattern. SiN\({}_{\rm x}\) thin film thickness was measured at the top, side, and bottom of the trench with film conformality. The step coverage of the films improved with increasing deposition temperature.