Stress-Temperature Behavior of O 3 -Teos Sub-Atmospheric CVD (SACVD) Oxide Films Deposited on Various Oxide Underlayers
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STRESS-TEMPERATURE BEHAVIOR OF 0 3 -TEOS SUB-ATMOSPHERIC CVD (SACVD) OXIDE FILMS DEPOSITED ON VARIOUS OXIDE UNDERLAYERS STUARDO A. ROBLES, ELLIE YIEH, MARIA GALIANO, KURT KWOK, AND BANG C. NGUYEN Applied Materials Inc., Santa Clara, CA 95054 ABSTRACT
A systematic evaluation of the stress-temperature behavior of 0 3 -TEOS SubAtmospheric CVD (SACVD) oxide films used in IMD applications was performed in order to elucidate the surface dependence and mechanical stability of these films when Silane-based, deposited on different oxide underlayers such as PECVD TEOS-based, and thermally grown oxides. SACVD films were deposited at 3600 C using different 0 3 :TEOS molar flow ratios. The results obtained in this study indicate that the stresstemperature behavior of SACVD films deposited on PECVD Silane-based and TEOSbased oxides using N2 0 as the oxidizing agent is similar to that of the SACVD films deposited on silicon. However, a large stress hysteresis is obtained when SACVD films are deposited on PECVD TEOS-0 2 and thermally grown oxide underlayers. This large stress hysteresis results from the surface dependence effects of the SACVD oxides on thermally grown and PECVD TEOS-0 2 oxide underlayers. Also, this stress hysteresis can be reduced or eliminated by treating the oxide underlayer surface with an in-situ Ar, He, or N2 plasma. Furthermore, it was also found that the SACVD oxides deposited using higher 0 3 :TEOS molar flow ratios are chemically and mechanically more stable. INTRODUCTION Silicon dioxide thin films deposited using 0 3 -TEOS CVD processes at high pressures (500-76OTorr) are promising candidates for inter-metal dielectric (IMD) films. Mechanical and chemical stability are required for IMD 0 3 -TEOS films in order to enhance device reliability and to preserve the integrity of the underlying
aluminum conductors. PECVD TEOS-0 2 oxides are typically used as underlayers for APCVD and SACVD oxides in order to avoid metal hillock formation. However, when PECVD TEOS-0 2 oxides are used as underlayers, the deposition rate, wet etch rate, and surface morphology of 0 3 -TEOS oxides are degraded. Other investigations on 0 3 -TEOS APCVD films have similarly shown that the film properties are dependent Control of mechanical stress of oxide films on the underlaying surface [1,2,3,4]. deposited by APCVD or SACVD is also necessary in order to prevent crystal defects in the underlayer substrate, cracking of deposited films, or voiding in the aluminum conductor lines. This work is part of an ongoing investigation of the stresstemperature behavior of oxides used for IMD applications [5,6]. A methodology on the use of stress-temperature analysis for IMD oxides is discussed. Furthermore, a systematic evaluation of the stress-temperature behavior of 0 3 -TEOS SACVD oxides is presented in order to elucidate the surface dependence and mechanical stability of SACVD films deposited at various 0 3 :TEOS ratios and on various types of oxide underlayers. EXPERIMENTAL All SACVD O3-TEOS oxide films (0.8-1.0im thick), PECVD oxide underl
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