Methylamine Growth of SiCN Films Using ECR-CVD
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115 Mat. Res. Soc. Symp. Proc. Vol. 606 © 2000 Materials Research Society
EXPERIMENTAL The silicon carbon nitride films were deposited using an ECR-CVD reactor. Detailed description of the ECR-CVD used in this work has been reported in our recent work [9]. Substrate cleaning process includes standard HF acid deoxidization, acetone and methanol degrease, and distilled water cleaning followed by H2 plasma etching of surface impurities. A mixture of semiconductor grade gases, H 2, N 2, CH 3NH 2, and 10% SiH 4 diluted in N 2, were used as reaction gas sources. In order to characterize the role of methylamine for the growth of SiCN films, various CH 3NH2/SiH 4 ratios and substrate temperatures at a constant pressure of 3.2 mTorr and a microwave power of 1200 W were used for the film growth. The quantitative composition analysis was performed by Rutherford backscattering spectrometry (RBS) using 3.5 MeV 4He ion. The non-RBS cross-section of 4He ion from C and N [12,13] were linked to RUMP2 program for quantitative analysis. A Perkin Elmer Phi 1600 ESCA system was used to study the chemical bonding state of the films, in which Mg Koa radiation of 1253.6 eV was used as the xray source with a linewidth of 0.7 eV. The analysis area for XPS measurement was 800 ýtm in diameter and the pass energy for the chemical state analysis was 11.75eV. Scanning electron microscope (SEM) was employed to get the surface morphology of the SiCN films. HRTEM investigation of the films was performed on a JEOL-4000EX microscope at an operating voltage of 400 kV. The band edge of the direct band to band transition was measured by PzR method, in which the basic principle is detecting the strain-induced changes of the interband transitions [14,15]. RESULTS AND DISCUSSION A summary of the film compositions determined by RBS measurement for various CH 3NH 2 gas flow and substrate temperature is listed in Table I. To examine the process-composition interrelationship, the adjusted parameters were divided into two groups. The first group is for different CH3 NH2 flow while keeping constant substrate temperature, and the second group is different substrate temperatures under a constant reaction gas flow ratio. The C/Si ratio in the SiCN films increases with increasing [CH 3NH 2]/[SiH 4] ratio and decreases at higher substrate temperature. The amount of the carbon content incorporated in the films depends on the various active carbon species in the gas phase and gas-surface interactions at different substrate temperature. The possible reactions of CH 3NH 2 and SiH 4 in the gas phase are listed in Table II. Assuming that the reactions take place not far way from the substrates and the reaction temperatures are close to Table I
The process parameters in the ECR CVD reactors and the results of compositions and growth rates of the SiCN films. Experimental results Composition Growth rate
Process parameters Gas flow rate (sccm) Substrate Temperature
No. N2
H2
CH 3NH2
SiH 4
(OC)
C
Si
N
C/Si
(nm/h)
1
2.5
2.5
1.0
0.5
700
12.8
32.1
55.1
0.4
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