MPCVD制备金刚石中的光谱分析

Optical Emission Spectroscopy Analysis of Diamond Deposited by MPCVD

在微波等离子体化学气相沉积(MPCVD)多晶金刚石的过程中,利用发射光谱法(OES)诊断等离子体中活性基团的分布情况,研究了沉积气压、CH_4体积分数以及气体流量对等离子体中基团谱峰强度的影响,讨论了相关基团与金刚石沉积速率和质量之间的关系.结果表明:在微波功率800 W下,气压从12 k Pa增加到16 k Pa,等离子体中各基团浓度均显著增加,有利于提高金刚石的沉积速率.气压16 k Pa、功率800 W时,CH_4体积分数从2%增加到7%,C_2基团峰值强度从12 600 cps增加到24 800 cps,而氢原子峰值强度从60 000 cps变为61 000 cps,导致C_2基团与氢原子浓度比值从0.21增加到0.40,金刚石的沉积速率虽然提高,但沉积质量下降.当沉积气压和CH_4体积分数分别从16 k Pa、4%提高到18 k Pa、6%时,C_2基团峰值强度从28 000 cps增加到37 000 cps,同时保持了C_2基团与氢原子浓度比值约0.28不变,既保证了金刚石沉积质量又显著提高了金刚石的沉积速率.等离子体体系中基团浓度基本不受气体流量变化的影响.

The distribution of active species in plasma was diagnosed by the optical emission spectroscopy （OES） in the precess of the deposition of polycrystalline diamond by microwave plasma chemical vapor deposition（MPCVD）. The influences of the deposition pressure,the ratio of CH4 and the rate of gas flow on the intensity of active species in plasma were investigated,and the relationship between the active species with the deposition rate and the quality of diamond was discussed. The results show that at the microwave power of 800 W, the concentration of active species in plasma significantly increases with the increase of deposition pressure from 12 kPa to 16 kPa,which raises the deposition rate of diamond. At the deposition pressure of 16 kPa and microwave power of 800 W,the intensity of C2 group and hydrogen atom peak increase respectively from 12 600 cps and 60 000 cps to 24 800 cps and 61 000 cps when the CH4 volume fractions are from 2%to 7%,which lead to the increase of the concentration ratios of C2 group and hydrogen atom（from 0.21 to 0.40）,demonstrating that the deposition rate of diamond increases,but the quality of diamond decreases. The intensity of C2 group peak increases from 28 000 cps to 37 000 cps,and the ratio of C2 group and hydrogen atom keeps about 0.28,when the deposition pressure and CH4 volume fraction increase from 16 kPa and 4%to 18 kPa and 6%,respectively, which improves the deposition rate and the quality of diamond. We also find that the concentration of the groups in plasma system is not affected by the gas flow rate.