Bonding of Hydrogen and Deuterium in Silicon Nitride Films Prepared by Remote Plasma Enhanced Chemical Vapor Deposition
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Mat. Res. Soc. Symp. Proc. Vol. 377 01995 Materials Research Society
2. EXPERIMENTAL The amorphous silicon nitride samples were deposited by a helium RPECVD process in an ultrahigh multi-chamber vacuum system. Prior to deposition, the N-type (100) infrared wafer substrates were H-terminated by a rinse in 1:30 dilute HF for 30 seconds, following a UV-ozone exposure of 8 minutes. The substrate was then loaded into the load lock of the RPECVD system and transferred6 under high vacuum to the deposition chamber, which has a base pressure of approx. 2x10 - Torr. In the RPECVD chamber, silane, SiH(D)4, and ammonia, NH(D)3, source gases were fed downstream through gas dispersal rings in the proximity of the deposition surface to promote film growth by CVD. The upstream He gas, and H2 gas for the hydrogen assisted depositions, underwent direct plasma excitation remote from the deposition region [1]. Prior to deposition, the RPECVD chamber was coated with amorphous silicon for 15 minutes at 300 'C in order to reduce the amount of contamination from previous runs. The silicon nitride films were deposited with an R.F. power of 60W, a chamber pressure of 300 mTorr, a substrate temperature of 300 'C, and an upstream flow of 200 sccm He. The deposition times for the samples were approximately two hours. The remaining gas flows are listed for the various samples studied: Table I: Gas Flow Ratios for Film Deposition Sample GD1 GD5 GD6 GD4 GD2 GD3 GH27
Gas Ring I SiH(D)4: Flow (sccm), (% in He) SiD4:10 (2%) SiH4: 2 (10%) SiHl4:2 (10%) SiD4:10 (2%) SiD4: 10 (2%) SiD4:10 (2%) SiH4: 10 (10%)
Gas Ring 2 NH(D)3: Flow (sccm), (% in He) ND3:2 (20%) ND3: 2 (20%) ND3:2 (20%) ND3:2 (20%) ND3: 2 (20%) ND3:2 (20%) NH3: 2 (pure)
Plasma Tube H2 Flow (sccm) 0 2 3.5 5 10 15 0
Following deposition, the samples were examined using Infrared Absorption Spectroscopy (FTIR). The film thicknesses of 500-1000 A gave adequate signal amplitude for the FTIR measurements. A Nicolet, Magna-IR-750, FTIR spectrometer running under OMINC 1.20 software and spectral resolution of 1.9 cm-1 collected and displayed the spectra. The gas species present during the film depositions were detected by a quadrupole mass spectrometer, VG model SXP-300 Elite, running under SXP Elite 6.2 software, and examined in Postsoft software. The mass spectrometer was mounted in the deposition chamber in a line of sight configuration with the deposition surface to monitor the gas phase conditions during film formation. A metal plate with an orifice of 127 [tm reduced the pressure between the deposition chamber and the mass spectrometer. Prior to the mass spectrometry studies, the RPECVD chamber was baked at 450 'C in order to diminish the diffusion of contaminants from the chamber during data acquisition. In this study, we examined both neutral and plasma ionized gas species close to the deposition surface. Some of the instrument parameter settings are listed in following table. Table II. Mass Spectromter Settings emission (mA) 0.5
electron energy (eV) 70
source
focus
pole bias
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