面向化学气相沉积生长单晶金刚石的高导热嵌入型基片托盘设计及其高质量生长工艺研究

Study on the Synthesis of High Quality Single Crystal Diamond by Chemical Vapor Deposition Using the Embeded Type of Substrate Holder with Highly Thermal Conductivity

针对高功率密度微波等离子体化学气相沉积法生长单晶金刚石过程中,金刚石籽晶表面温度容易发生漂移的问题,提出了一种新的基片托盘结构设计方法。基片托盘中间采用通孔结构,以避免籽晶底部与钼托盘的直接接触,在基片托盘与水冷台之间、籽晶和水冷台之间添加高导热材料氮化铝片,以保证外延沉积金刚石所需的均匀温度场环境。实验结果显示,利用新型基片托盘可以连续工作48 h,并获得生长厚度达1.66 mm的单晶金刚石,经过多次反复生长可实现厚度3 mm的高质量单晶金刚石制备。新型基片托盘能有效地抑制生长过程中石墨等大颗粒煤烟沉积引起的温度漂移现象,满足不同条件下金刚石单晶的同质外延生长,抑制籽晶边沿处多晶金刚石的生成,从而保证金刚石单晶在高功率密度下长时间稳定生长,获得高质量、大尺寸的化学气相沉积单晶金刚石。

In this paper, a new structure was designed and tested for the substrate holder of crystal diamond seeds to solve the problems of inhomogeneously distributed temperature. A through-hole was drilled on the substrate holder, and the Al N sheets were added to the contacted areas where the diamond epitaxial growth process was carrying out. With such a substrate holder structure, direct contact between diamond seeds and substrate can be avoided, so as to ensure the essentially homogeneous temperature distributions simutaneously. Effect of the proposed substrate holder was verified by several experiments. The experiments related to single diamonds were carried out on the traditional and the proposed substrate holders respectively. The experimental results show that the single diamond with the thickness of 1.66 mm is obtained by continually growing of 48 h, and achieved the high quality single diamond of 3 mm by repeating the growth on the proposed substrate holder. The proposed substrate holder can restrain the occurrence of temperature drifting of large grains during the deposited process and provide a suitable environment for diamond homoepitaxial growth. The polycrystalline diamonds around diamond seeds can be suppressed and high purity chemical vapor deposition single diamonds with thickness of larger than 3 mm can be successfully fabricated by the proposed substrate holder and high power density microwave plasma chemical vapor deposition method.