Deposition Uniformity Control in a Commercial Scale HTO-CVD Reactor
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0989-A08-08
Deposition Uniformity Control in a Commercial Scale HTO-CVD Reactor Shigeru Sakai1, Masaaki Ogino1, Ryosuke Shimizu1, and Yukihiro Shimogaki2 1 Fujielectric Advanced Technology Co.,Ltd., 4-18-1,Tsukama,Matsumoto, Nagano, 390-0821, Japan 2 School of Engineering, University of Tokyo, 7-3-1,Hongo,Bunkyo-ku, Tokyo, 113-8656, Japan
ABSTRACT High-temperature silicon dioxide (HTO) chemical vapor deposition (CVD), using SiH2Cl2 and N2O, can realize dense and conformal oxide film, not only on large size silicon wafers, but even inside of microscopic silicon trenches, at high-temperature around 800∫C. In this work, we investigated the kinetics of HTO-CVD using a commercial scale low pressure (LP) CVD reactor, focusing on the correlation between deposition rate and surface-tovolume ratio (S/V ratio), which is a specific surface area of substrate wafer divided by the space volume between two adjacent wafers. We also investigated the deposition rate profile on wafers, and along the axial direction of the reactor near the region where one, two or three substrate wafers are extracted from the quartz holder. The deposition rate profiles on wafer characteristically change from skillet-like to pancake-like, according to the increase of wafer spacing. The influence of wafer spacing on the deposition rate spreads to ranges not only downstream, but also upstream in the gas flow. These experimental results strongly suggest that in the HTO-CVD gas-phase reactions through intermediate states of active species contribute to deposition reaction as well as direct deposition reaction of source gases on Si surface. INTRODUCTION HTO film is deposited on a higher temperature around 800∫C [1-3], compared with the deposition temperature, 350∫C of LTO (Low-temperature silicon dioxide) film, usually applied as passivation films of semiconductor devices. Because of high-temperature deposition, dense and conformal oxide film can be obtained even inside microscopic silicon trenches. HTO is promising as gate oxides of gallium nitride (GaN) MOSFET [4] and silicon trench-type MOSFET. We found that the deposition rate profile of HTO shows unique characteristics, greatly different from the profile of conventional films, such as poly-Si films obtained by commercial scale batch type reactors as in fig.1. From the background mentioned above, in this work, to improve the thickness uniformity, we investigated the kinetics of HTO-CVD using a commercial scale LPCVD reactor, through an analysis on deposition rate profiles both in the radial direction of 6inch silicon wafers and along the axial direction of the reactor. The deposition rate profile in the radius direction of the wafer gave us the insight of SiH2Cl2 (Dichlorosilane; DCS) and N2O based reaction chemistry. The experimental results of actual deposition behavior revealed the chemical species that controls the uniformity in HTO-CVD. Thus we could obtain the simple reaction model in a manufacturing scale reactor.
Heater Oute r tube
Figure.1 Schematic diagram of a longitudinal type CVD reacto
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