On the quality of hydrogenated amorphous silicon deposited by sputtering

Amorphous hydrogenated silicon (a-Si:H) is well-known material in the global semiconductor industry. The quality of the a-Si:H films is generally decided by silicon and hydrogen bonding configuration (Si–Hx, x=1,2) and hydrogen concentration (CH). These quality aspects are correlated with the plasma parameters like ion density (Ni) and electron temperature (Te) of DC, Pulsed DC (PDC) and RF plasmas during the sputter-deposition of a-Si:H thin films. It was found that the Ni and Te play a major role in deciding Si–Hx bonding configuration and the CH value in a-Si:H films. We observed a trend in the variation of Si–H and Si–H2 bonding configurations, and CH in the films deposited by DC, Pulsed DC and RF reactive sputtering techniques. Ion density and electron energy are higher in RF plasma followed by PDC and DC plasma. Electrons with two different energies were observed in all the plasmas. At a particular hydrogen partial pressure, RF deposited films have higher CH followed by PDC and then DC deposited films. The maximum energy that can be acquired by the ions was found to be higher in RF plasma. Floating potential (Vf) is more negative in DC plasma, whereas, plasma potential (Vp) is found to be more positive in RF plasma.