气体进出方式对MPCVD大面积金刚石膜均匀性的影响
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摘要
使用自行研制的MPCVD装置,在功率为8 k W条件下、气体由四种方式进出反应腔体时,在直径65 mm的Si基片上制备了金刚石膜。分别利用数字千分尺和Raman光谱对金刚石膜的厚度和品质均匀性进行了表征。使用Comsol软件模拟了不同进出气方式下腔体内部气体流场的分布,并分析了气体进出方式与所制备金刚石膜均匀性之间的关系。研究表明,反应气体进出位置的改变对等离子体的状态没有明显的影响,但对膜的厚度和品质均匀性有影响较大。气体由中间腔体侧壁上的进气孔进入时,容易造成膜厚度和品质的不均匀性。气体由耦合天线的圆盘中心的进气孔进入时,膜厚度和品质的均匀性明显提高,而由锥形反射体底平面上的出气孔排出时均匀性最优。反应气体流场分布的不均匀性和等离子体区域流速的差异是导致金刚石膜厚度和品质不均匀性的主要原因。
The diamond films were deposited on 65 mm diameter Si substrates by a self-designed microwave plasma chemical vapor deposition( MPCVD) system with input power of 8 k W. The effect of the gas inlet and outlet location on the film thickness and quality uniformity was investigated. The thickness and the quality of the diamond films were characterized by digital micrometer and Raman spectrometer,respectively. Comsol software was adopted to simulate the gas flow field in the cavity with different gas inlets and outlets. The results indicated that the gas-inlet and gas-outlet locations did not impact the plasma state,but would cause serious thickness and quality problems of diamond films. Whenthe gas was introduced into the cavity from the gas inlet embed in the wall of the middle chamber,both the thickness and quality of the diamond films are non-uniform. Nevertheless, when the gas was introduced from the coaxial inner conductor center,the uniformity of both was improved. Moreover,when the gas was departed from the bottom of the cone-shaped reflector,the best uniformity could be obtained.The non-uniformity of the gas flow field and the different flow rate at the plasma region are the main reason for the thickness and quality non-uniformity of the diamond films.
The diamond films were deposited on 65 mm diameter Si substrates by a self-designed microwave plasma chemical vapor deposition( MPCVD) system with input power of 8 k W. The effect of the gas inlet and outlet location on the film thickness and quality uniformity was investigated. The thickness and the quality of the diamond films were characterized by digital micrometer and Raman spectrometer,respectively. Comsol software was adopted to simulate the gas flow field in the cavity with different gas inlets and outlets. The results indicated that the gas-inlet and gas-outlet locations did not impact the plasma state,but would cause serious thickness and quality problems of diamond films. Whenthe gas was introduced into the cavity from the gas inlet embed in the wall of the middle chamber,both the thickness and quality of the diamond films are non-uniform. Nevertheless, when the gas was introduced from the coaxial inner conductor center,the uniformity of both was improved. Moreover,when the gas was departed from the bottom of the cone-shaped reflector,the best uniformity could be obtained.The non-uniformity of the gas flow field and the different flow rate at the plasma region are the main reason for the thickness and quality non-uniformity of the diamond films.
引文
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[2]Gu C Z,Jing Z S.The characteristics and Applications of Diamond Film and the Researching Status[J].Journal of Functional Materials,1997,28(3):232-236.
[3]Thumn M.MPCVD-Diamond Windows for High-power and Long-pulse Millimeter Wave Transmission[J].Diamond and Related Materials,2001,10(9-10):1692-1699.
[4]Hemawan K W,Grotjohn T A,Reinhard D K,et al.Improved Microwave Plasma Cavity Reactor for Diamond Synthesis at High-pressure and High Power Density[J].Diamond and Related Materials,2010,19(12):1446-1452.
[5]Yu S W,Liu Y Q,Tang W Z,et al.Effects of Process Parameters on the Preferred Orientation of Diamond Films Deposited by MPCVD[J].Journal of Synthetic Crystals,2012,41(4):868-871.
[6]An K,Liu X P,Li X J,et al.Numerical Simulation and Experimental Study of a Novel High-power Microwave Plasma CVD Reactor for Diamond Films Deposition[J].Journal of Synthetic Crystals,2015,44(6):1544-1550.
[7]K.An,S.W.Yu,X.J Li,et al.Microwave Plasma Reactor with Conical-reflector for Diamond Deposition[J].Vacuum,2015,117:112-120.
[8]Yu S W,Li X J,Zhang S K,et al.Deposition of Polycrystalline Diamond Films by a New Type MPCVD Reactor at High Power Density[J].Journal of Functional Materials,2011,9(42):1722-1726.
[9]Li Y F.Design of High Power MPCVD Reactors and Synthesis of High Quality Diamond Films[D].Beijing:Doctoral Dissertation of University of Science and Technology Beijing,2014.
[10]H Yamada,A Chayahara,Y Mokuno,et al.Numerical Analyses of a Microwave Plasma Chemical Vapor Deposition Reactor for Thick Diamond Syntheses[J].Diamond and Related Materials,2006,15:1389-1394.
[11]H Yamada,A Chayahara,Y Mokuno,et al.Simulation of Temperature and Gas Flow Distributions in Region Close to A Diamond Substrate with Finite Thickness[J].Diamond and Related Materials,2006,15:1738-1742.
[12]Ralchenko V,Sychov I,Vlasov I,et al.Quality of Diamond Wafers Grown by Microwave Plasma CVD:Effects of Gas Flow Rate[J].Diamond and Related Materials,1999,8(2):189-193.
[13]于盛旺.高功率微波等离子体法高品质金刚石膜沉积技术研究[D].北京:北京科技大学博士学位论文,2012.