Positive ions as growth precursors in plasma enhanced chemical vapor deposition of hydrogenated amorphous silicon

We present a straightforward method to determine the contribution of ions t o the growth rate in capacitively coupled plasma deposition systems. Ions a nd radicals from the plasma can be spatially separated by a small aperture in front of the substrate. Separation is caused by the different angular di stribution of the velocity of these types of particles. From measured thick ness profiles of deposited hydrogenated amorphous silicon, we deduce a surf ace reaction probability of the radicals of 0.30. It is concluded that the ions contribute about 10% of the silicon atoms to the growth process under typical deposition conditions. (C) 1999 American Institute of Physics. [S00 03-6951(99)00431-3].