Growth of particles in cluster-size range in low pressure and low power SiH4 rf discharges

Growth processes of particles in a cluster-size range below a few nm in siz e in low pressure and low power SiH4 rf discharges are studied using the ne w method, in which the threshold photoemission method is coupled with the m icrowave interferometry, for measurements of their size and density. The de nsity of particles is above 10(10) cm(-3) and much exceeds that of positive ions, the result of which shows that most of them are neutral. The particl es grow mainly around the plasma/sheath boundary near the powered electrode and their size growth rate is 3.4-4.4 nm/s, being much higher than a film growth rate of 0.064-0.12 nm/s. These features strongly indicate that their growth is due to deposition of polymerized species, originated from short lifetime SiH2 radicals, on them, while coagulation between particles become s appreciable after a time when their density reaches about 10(11) cm(-3). Moreover, the pulse modulation of rf discharge is found to be effective in reducing the density of cluster-size particles. The reduction can be explai ned by a model taking account of diffusion of the polymerized species throu gh the radical production region, where the particles nucleate and grow. (C ) 1999 American Institute of Physics. [S0021-8979(99)06419-1].