Cavity ring down study of the densities and kinetics of Si and SiH in a remote Ar-H-2-SiH4 plasma

Cavity ring down absorption spectroscopy is applied for the detection of Si and SiH radicals in a remote Ar-H-2-SiH4 plasma used for high rate deposit ion of device quality hydrogenated amorphous silicon (a-Si:H). The formatio n and loss mechanisms of SiH in the plasma are investigated and the relevan t plasma chemistry is discussed using a simple one-dimensional model. From the rotational temperature of SiH typical gas temperatures of similar to 15 00 K are deduced for the plasma, whereas total ground state densities in th e range of 10(15)-10(16) m(-3) for Si and 10(16)-10(17) m(-3) for SiH are o bserved. It is demonstrated that both Si and SiH have only a minor contribu tion to a-Si:H film growth of similar to0.2% and similar to2%, respectively . From the reaction mechanisms in combination with optical emission spectro scopy data, it is concluded that Si and SiH radicals initiate the formation of hydrogen deficient polysilane radicals. In this respect, Si and SiH can still have an important effect on the a-Si:H film quality under certain ci rcumstances. (C) 2001 American Institute of Physics.