两段成长法改善微波电浆辅助化学气相沉积多晶金刚石之品质(英文)

Improved quality of polycrystalline diamond grown by two-stage growth in microwave plasma chemical vapor deposition

以化学气相沉积法成长多晶金刚石薄膜时,薄膜的品质会受到成长时间、成长压力、反应气体比例、偏压与否及成核的机制等因素影响。研究采用微波电浆辅助化学气相沉积(MPECVD)法,以甲烷(CH4)和氢气(H2)作为反应气体原料,在p型(111)硅基板沉积多晶金刚石薄膜。典型沉积多晶金刚石薄膜的制程可分为四个阶段:抛蚀表面阶段、渗碳阶段、偏压增强成核(BEN)阶段及成长阶段。研究将成长阶段划分为两个阶段,第一阶段压力较低(成长I阶段),第二阶段压力较高(成长II阶段)。结果表明:第一阶段可大大改善金刚石薄膜的品质,所获多晶金刚石薄膜的晶粒具有明确的颗粒边界、较低的碳化物或缺陷,电导率急剧降低,显现出本徵金刚石半绝缘的性质。可以认为金刚石薄膜品质的改善完全为低压成长所致。实验发现在成长I阶段或成长II阶段施加偏压时,只会降低多晶金刚石薄膜的品质。

The quality of polycrystalline diamond films grown by chemical vapor deposition is dependent on the growth time, pressure, carbon-to-hydrogen ratio, bias, and nucleation mechanism involved. In this study, reaction gases, methane （ CH4 ） and hydrogen （ H2 ）, were used to grow polycrystalline diamond on a p-type （ 111 ） silicon substrate with a microwave plasma-enhanced chemical vapor deposition system. In addition to the conventional etching, bias-enhanced nucleation, and growth steps, the growth step was further divided into two stages. The first stage （ growth I） was carried out at low pressure and the second （ growth II） was carried out at high pressure. Results clearly indicate that the use of the growth I stage can considerably improve the quality of the diamond film. In the growth I stage, well-faceted grains with lower contents of graphite and carbide, and fewer defects are obtained. Therefore, the conductivity is drasti- cally decreased by nearly two orders of magnitude and the diamond film exhibits the semi-insulating characteristics of intrinsic diamond. The improvement is caused solely by the addition of the low-pressure growth I stage. Application of bias in the growth I and/or growth II stages can only degrade the synthesized polycrystalline diamond film.