TRANSITION OF PARTICLE GROWTH REGION IN SIH4 RF DISCHARGES

The growth region of particles in SiH4 RF discharges is investigated w ith the parameters of pressure, SiH4 concentration and RF power. When the diffusion time tau(D) of SiH2 radicals (key species for fast parti cle nucleation) through their production region is longer than their r eaction time tau(R) with SiH4 and sufficient SiH2 radicals are supplie d, particles grow at, a high growth rate of greater than or similar to 10's nm/s localized only around the plasma/sheath (P/S) boundary near the RF electrode where the radicals are produced. Under this conditio n, neutral clusters (resulting from the polymerization reactions) reac t with each other many times before they diffuse out of the radical pr oduction region. Since the diffusion time of clusters through the radi cal production region increases with cluster size, large clusters tend to be localized there and grow further to sizes on the order of nm. W ith tau(R) > tau(D) and/or insufficient supply of SiH2 radicals, parti cles grow at a low rate of 1 nm/s and exist in the plasma bulk as well as around the P/S boundary. Such low growth rates suggest that negati vely charged clusters are indispensable in order for particles to grow to above several nm in size.