MPCVD高功率外延生长单晶金刚石均匀性研究

Homogeneity of Single Crystal Diamond under Epitaxial Growth by MPCVD High Power

目的 为了优化单晶金刚石大批量生长的等离子体环境,开展了高功率微波等离子体环境对单晶金刚石外延生长研究。方法 利用实验室自主研发的915 MHz-MPCVD装置,在15~37 kW的高功率微波馈入的条件下,研究了在高功率微波等离子体环境中CVD单晶金刚石的均匀生长条件,利用光学显微镜及激光拉曼光谱对所生长的单晶金刚石进行了形貌质量表征,利用等离子体发射光谱对高功率微波等离子体环境进行了诊断。结果 在保持甲烷体积分数为5%时,当微波功率为15k W时,等离子体球的尺寸较小,并不能完全覆盖直径150 mm的基片台;将微波功率从28 kW提高到37 kW,肉眼所见的等离子体尺寸变化并不明显,但等离子体的能量分布范围有一定的扩大,这意味着在一定的范围内活性基团的能量分布更均匀。在较高的微波功率下,分布于基片台不同区域的单晶金刚石片均能获得较好的层状生长台阶。随着微波功率的提高以及基片温度的增加,分布于基片台不同区域的微波电磁场强度都有所增强,提高了单晶金刚石的生长速率和质量。结论 在高功率等离子体环境中,通过大幅度的提高微波功率,可以有效地活化含碳基团,在等离子体中产生有利于单晶金刚石高质量高速生长的活性基团。在微波功率为37k W、甲烷体积分数为5%的情况下,将基片温度控制在950℃附近,可以有效地抑制多晶杂质的生成,实现了57片单晶金刚石的批量生长。

Chemical vapor deposition(CVD)single crystal diamond possess lots of excellent physical and chemical properties,and the large production of the CVD single crystal diamond is a hot issue in the growth and the industrial production of CVD single crystal diamond.The work aims to study the homoepitaxial growth of single crystal diamond in high power microwave plasma environment,in order to optimize the plasma environment for the growth of single crystal diamond in bulk.The 915 MHz-MPCVD device independently developed by the laboratory was adopted to study the uniform growth of CVD single crystal diamond in the high power microwave plasma environment with 15-37 kW microwave.The morphology and quality of the grown single crystal diamond were characterized by optical microscope and Raman spectroscopy.The high power microwave plasma environment was diagnosed by plasma emission spectrum.The results indicated that when the methane concentration was 5% and the microwave power was 15 kW,the size of the plasma ball was too small to cover the substrate platform with the diameter of 150 mm completely.When the microwave power was increased to 37 kW from 28 kW and the methane concentration was also kept at 5%,the energy distribution range of plasma was enlarged to some extent although the scale of the plasma size could not be observed by naked eyes.The substrate platform with the diameter of 150 mm was entirely immersed in the plasma ball which was confirmed by the results of the plasma emission spectrum.Meanwhile,the plasma emission spectrum recorded from the center to the edge regions in the plasma also indicated that increase of the microwave power led to more uniform energy distribution of activated groups within a certain range and also implied that the intensity of microwave electromagnetic field distributed in the different areas of the substrate platform was enhanced with the increase of the microwave power and the substrate temperature.When the microwave power was increased from 28 kW to 37 kW,the better step growth condition could be easier obtained for the grown single crystal diamond distributed in different regions of the substrate.Besides,the increase of the microwave power not only increased the substrate temperature and decreased the variation of the temperature among the single crystal diamond substrates,but also increased the growth rate of the single crystal diamond located at different regions of the substrate platform.In the high microwave power plasma environment,the quality of the grown single crystal diamond is improved obviously,which is attributable to the increase of the activated groups generated in the plasma,because these groups are beneficial to the improving of the quality and growth rate of the single crystal diamond,such as C2 and [H].Based on the results,the batch growth of 57 single crystal diamond is realized under the condition of the microwave power of 35 kW,the methane concentration of 5% and the substrate temperature of about 950 ℃ and the formation of polycrystalline impurities can also be effectively inhibited in this plasma environment.