硅锗等离子体起辉的瞬态不稳定性研究

INVESTIGATION ON THE INITIAL TRANSIENT INSTABILITY OF THE PLASMA IGNITION FROM SILANE/GERMANE/HYDROGEN

利用光发射谱(OES)监测技术对氢气(H_2)、硅烷(SiH_4)、锗烷(GeH_4)等离子体的起辉稳定时间进行瞬态在线原位监测,探索功率及压强对等离子体起辉稳定时间的影响规律。结果表明,功率对等离子体的起辉稳定性影响较大,即相比于较小功率,在较大功率下起辉时,等离子体需要长很多的时间才能达到稳定状态。但随着功率的增大,气压对起辉稳定性的影响逐渐变得明显。分析认为这种等离子体的起辉不稳定性主要是由硅烷(SiH_4)、锗烷(GeH_4)等气体的反扩散所造成,并进一步发现通过增加氢气流量,可有效降低SiH_4等气体的反扩散程度,缩短硅锗等离子体达稳定状态所需的时间。

The transient instability of H2, SiH4 and GeH4 plasma ignition was investigated by using optical emission spectroscopy （OES） monitoring technology. The influence of the deposition power and pressure on the time for the plasma to be stable was studied. The results show that the effect of the deposition power on the plasma stability is greater than that of the deposition pressure. When the power is high, a long time is needed for the plasma to stabilize, And the effect of the pressure on the plasma stability becomes obviously when the power increases. The transient instability of the plasma ignition can be attributed to the gas back diffusion of SiH4 and GeH4 from the chamber into the electrode space. Further, it is found that such gas back diffusion and instability can be improved greatly by increasing the flow rate of H2 while keeping the good performance of the deposited a-SiGe ： H film.