Investigating the role of hydrogen in silicon deposition using an energy-resolved mass spectrometer and a Langmuir probe in an Ar/H 2 radio frequency magnetron discharge


The plasma parameters and ion energy distributions (IED) of the dominant species in an Ar-H 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 n+, SiH n+, SiH n fragments (with n 1, 2, 3) together with Ar + and ArH + species are detected in the discharge. The most important species for the film deposition is SiH n (with n 0, 1, 2). H fragments affect the hydrogen content in the material. The flux of Ar + decreases and the flux of ArH + increases when the hydrogen flow rate is increased; however, both fluxes saturate at hydrogen flow rates above 15 sccm. Electron density, n e, electron energy, T e, and ion density, n i, are estimated from the Langmuir probe data. T e is below 1.2 eV at hydrogen flow rates below 8 sccm, and about 2 eV at flow rates above 8 sccm. n e and n i decrease with increased hydrogen flow but the ratio of n i to n e increases. The formation of H + 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. © 2012 American Institute of Physics.

Publication Title

Physics of Plasmas