AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS1+TF-ThM

Paper PS1+TF-ThM10
Surface Reactions during Ammonia-Plasma-Assisted Atomic Layer Deposition of Silicon Nitride

Thursday, November 13, 2014, 11:00 am, Room 305

Session: Plasma Deposition and Plasma Assisted ALD
Presenter: Dennis Hausmann, Lam Research Corporation
Authors: D. Hausmann, Lam Research Corporation
R. Ovanesyan, Colorado School of Mines
S. Agarwal, Colorado School of Mines
Correspondent: Click to Email
The advent of FinFETs with high-aspect-ratio 3-D geometries increases demands on conformality of the SiNx films. These stringent requirements on conformality and low thermal budget can be simultaneously met using atomic layer deposition (ALD). While there are a few reports in the literature that show that SiNx can be conformally deposited via ALD at <400 °C, these films are not sufficiently dense to serve as moisture or oxidation barriers. Hence, improvements in this area are needed via a fundamental understanding of the surface reaction processes. Recently, we have developed a novel ALD processes for the growth of Si3N4 thin films using trisilylamine (Si(NH3)3, TSA) and silane precursors, and an NH3 plasma. This ALD process with TSA provides dense films with a conformal coverage over aspect ratios typical for the applications; 10:1. To understand the underlying film growth mechanism, the specific surface reactions involved during each half-reaction cycle of this ALD process were monitored with in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. ZnSe internal reflection crystals were used as substrates since ZnSe is transparent in the infrared up to 700 cm-1. This spectral range, combined with the high sensitivity achieved with ATR-FTIR spectroscopy, allows us to identify and monitor in real time the different surface species generated and consumed due to sequential exposure of the growth surface to Si-containing precursors and an NH3 plasma. The vibrational modes that were monitored include the surface SiHx and NHx stretching modes in the 2100 and 3400 cm-1 region, respectively, and Si3N4 phonon modes, which appear in the 800-900 cm-1 region. The corresponding surface reaction products were monitored using quadrupole mass spectrometry. Further, these films were extensively characterized using a suite of ex situ diagnostic tools.