Power coupling and utilization efficiencies of silicon-depositing plasmas in mixtures of H2, SiH4, Si2H6, and Si3H8
Mark A. Sobolewski
Adding Si2H6 or Si3H8 additives to SiH4/H2 discharges increases the growth rates for thin films of microcrystalline and amorphous silicon, but the reasons for this increase are not well understood. To better distinguish the chemical and physical from electrical effects of these additives, a comprehensive electrical study was performed for mixtures of H2, SiH4, Si2H6, and Si3H8. The power coupling efficiency, power utilization efficiency, voltage, current, impedance, and phase were measured as a function of total pressure, electrode gap, gas mixture, rf power, and time. When the pressure and gap are appropriately chosen, the power coupling efficiency is quite high and insensitive to gas mixture. Variations in mixture do affect the impedance of the plasma and its sheaths, and, in turn, the power utilization efficiency, but the changes in this efficiency and the predicted changes in growth rates from it alone were rather small. These results suggest that, for well-designed processes and equipment, chemical or physical effects on growth rates should predominate over electrical effects. In addition, electrical signals were identified that can be used to detect a transient in the gas-phase density of silicon-containing molecules during deposition as well as other transient phenomena. The signals show promise for use in process monitoring and control.
Power coupling and utilization efficiencies of silicon-depositing plasmas in mixtures of H2, SiH4, Si2H6, and Si3H8, Journal of Vacuum Science and Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914651
(Accessed November 29, 2023)