THE FORMATION AND STABILITY OF SUBMICRON CLUSTERS IN SILANE AND ARGON PLASMAS

We have studied the formation of small silicon clusters in the plasma of a capacitively coupled RF-glow discharge deposition system used for the preparation of a-Si:H. These particles were detected by light scattering and are found to grow from SiH4 in the gas phase only if the temperature during deposition is substantially lower than in plasmas normally used for the deposition of device-quality films. We find that the particles are confined to the inner plasma region. This is explained by the fact that the particles become negatively charged due to the higher mobility of electrons vs. the positive ions. On account of their charge the particles are confined to the positive plasma region. The influence of the negative charge on the defect density of the a-Si:H forming the small particles is discussed.