Investigating the role of hydrogen in silicon deposition using an energy-resolved mass spectrometer and a Langmuir probe in an Ar/H{sub 2} radio frequency magnetron discharge
The plasma parameters and ion energy distributions (IED) of the dominant species in an Ar-H{sub 2} discharge are investigated with an energy resolved mass spectrometer and a Langmuir probe. The plasmas are generated in a conventional magnetron chamber powered at 150 W, 13.56 MHz at hydrogen flow rates ranging from 0 to 25 sccm with a fixed argon gas flow rate of 15 sccm. Various H{sub n}{sup +}, SiH{sub n}{sup +}, SiH{sub n} fragments (with n = 1, 2, 3) together with Ar{sup +} and ArH{sup +} species are detected in the discharge. The most important species for the film deposition is SiH{sub n} (with n = 0, 1, 2). H fragments affect the hydrogen content in the material. The flux of Ar{sup +} decreases and the flux of ArH{sup +} increases when the hydrogen flow rate is increased; however, both fluxes saturate at hydrogen flow rates above 15 sccm. Electron density, n{sub e}, electron energy, T{sub e}, and ion density, n{sub i}, are estimated from the Langmuir probe data. T{sub e} is below 1.2 eV at hydrogen flow rates below 8 sccm, and about 2 eV at flow rates above 8 sccm. n{sub e} and n{sub i} decrease with increased hydrogen flow but the ratio of n{sub i} to n{sub e} increases. The formation of H{sup +} ions with energies above 36 eV and electrons with energies greater than 2 eV contributes to the decrease in hydrogen content at hydrogen flow rates above 8 sccm. Analysis of the IEDs indicates an inter-dependence of the species and their contribution to the thin film growth and properties.