On-site SiH4 generator using hydrogen plasma generated in slit-type narrow gap

We have been developing an on-site silane (SiH4) generator based on use of the chemical etching reaction between solid silicon (Si) and the high-density H atoms that are generated in high-pressure H-2 plasma. In this study, we have developed a slit-type plasma source for high-efficiency SiH4 generation. High-density H-2 plasma was generated in a narrow slit-type discharge gap using a 2.45 GHz microwave power supply. The plasma's optical emission intensity distribution along the slit was measured and the resulting distribution was reflected by both the electric power distribution and the hydrogen gas flow. Because the Si etching rate strongly affects the SiH4 generation rate, the Si etching behavior was investigated with respect to variations in the experimental parameters. The weight etch rate increased monotonically with increasing input microwave power. However, the weight etch rate decreased with increasing H-2 pressure and an increasing plasma gap. This reduction in the etch rale appears to be related to shrinkage of the plasma generation area because increased input power is required to maintain a constant plasma area with increasing H-2 pressure and the increasing plasma gap. Additionally, the weight etch rate also increases with increasing H-2 flow rate. The SiH4 generation rate of the slit-type plasma source was also evaluated using gas-phase Fourier transform infrared absorption spectroscopy and the material utilization efficiencies of both Si and the H-2 gas for SiH4 gas formation were discussed. The main etch product was determined to be SiH4 and the developed plasma source achieved a SiH4 generation rate of 10 seem (standard cubic centimeters per minute) at an input power of 900 W. In addition, the Si utilization efficiency exceeded 60%.