Properties Of A-Si: H Prepared By RF-PECVD & DBD-PECVD And Their Compare

In this essay, the apply of amorphous silicon in the field of solar energy is introduced and the methods of preparing amorphous silicon are listed, among which we introduce the RF-PECVD and DBD-PECVD in details. We discussed how parameters affect the properties of a-Si:H film in both preparing methods by experiments, and compared these two methods' advantages. Then we analyzed the mechanics of a-Si:H deposition in DBD-PECVD, which is just in its initial stages.There are lots of properties affecting parameters in PECVD. Experimental results suggested: in RF-PECVD, the increase of silicane concentration, deposition power and deposition temperature raised the deposition rate of a-Si:H. The highest deposition rate reached 0.39nm/s. High deposition power leaded to film desquamating. The configurations shifted from SiH to SiH₂ and photon energy of film broadened when the silicon concentration and deposition power were increased. Disposition rate decreased when deposition temperature over 350℃ and configurations shifted from SiH to SiH₂ when deposition temperature below 150 ℃ . Between these two temperature, photon energy of film broadened with temperature increasing. Vapor nucleation occurred under high silicon concentration and high deposition power.B doping of a-Si:H by RF-PECVD leaded to crystallize of the film and size of grains increased with increasing of B doping ratio. Room temperature conductivity of film increased when deposition temperature raised and reached its peak at 280℃. It also increased with B doping ratio and trended to saturate after doping ratio higher than 0.01. The peak room temperature conductivity is 7.76×10^-5Ω^-1cm^-1. B doping ratio also resulted in rapidly decreasing of photo/dark conductivity ratio when doping ratio higher than 0.002, photo/dark conductivity ratio showed stabilized and the value was approximate to 20.The configurations of a-Si:H prepared by DBD-PECVD were mainly SiH₂ and SiH₃. Increasing of deposition voltage and silicane concentration conduced higher deposition rate which peak at 0.44nm/s. Film's configurations shifted from SiH₂ toSiH3 when silicane concentration increased. We all agree that much higher silicane concentration will induce SiH configuration and grow high quality a-Si:H film. Like RF-PECVD high silicon concentration and high deposition power leaded to Vapor nucleate. In DBD-PECVD, no crystallines were founded when parameters changed.Compare these two method and results shows: Under same silicane concentration, deposition rate of DBD-PECVD is 2.5 times faster than that of RF-PECVD. Film prepared by RF-PECVD configuration is mainly SiH and photon energy is 1.8eV, while the configuration is mainly Sit^ and photon energy is 2.0eV in DBD-PECVD preparation. The vapor nucleation is more obviously in DBD-PECVD.From above, we concluded that: High power densities induced by high deposition voltage in DBD-PECVD is partly used to increase the amounts of SiHn clusters. The most of the energy is used to raise up the energy of SiHn clusters, which is the most important support of probability that a-Si:H could be deposited in room temperature by DBD-PECVD. Though DBD-PECVD could decompose silicane fully, the deposition rate still limited by amount of SiHn clusters which are restricted by silicane concentration. The occurring of configurations of SiH2 and SiH3 was also due to exhaust of silicane. The etch of hydrogen is also strengthened in DBD-PECVD. So we agree that: increase silicane concentration, decrease hydrogen concentration, heated up substract somewhat, may deposit high quality a-Si:H rapidly.