Plasma enhanced chemical vapor deposition systems are massively deployed to grow numerous thin film coatings including hydrogenated amorphous silicon. A new deposition chamber was designed, procured, and constructed to investigate the plasma properties of a 100% silane (SiH4) glow discharge with varying chamber pressure and inter-electrode spacing. A Hiden EQP1000 ion mass spectrometer sampled the plasma from the substrates point of view. Ion energy distributions were obtained using four different excitation sources +DC, –DC, radio frequency (at 13.56 MHz), and the DC Saddle Field (DCSF) in the tetrode configuration.
The shape of the ion energy distributions was constant for the capacitively coupled +DC, –DC, and rf (at higher pressures of 75 and 160 mTorr) glow discharges. The shape of the ion energy distributions for the DCSF plasma exhibited a double peak or saddle structure analogous to radio frequency plasmas. The width between the peaks (peak separation) was controlled by the pressure and the semi-transparent cathode to semi-transparent anode distance. Ion energy distributions from the DCSF plasma concurred with rf and +DC ion energy distributions at specific pressures and inter-electrode distances. This result demonstrates the versatility of the DCSF glow discharge system. Moreover, control of the peak separation is modeled to be
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equivalent to controlling the critical ratio (ion transit time in the sheath to the electron oscillating period), and/or the inferred electron oscillating sheath potential.
The DCSF possesses a fusion of rf and +DC methods. The long high energy tail or constant background are indicative of a +DC high voltage sheath in which there is an increasing fraction of collisionless ions as the anode-cathode distance increases. These collisionless ions are provided by the oscillating electrons (or rf nature) of the DCSF method. Higher order silane (silicon containing) ions increase in relative intensity with increasing inter-electrode spacing for the +DC, –DC, and rf plasmas. These higher order silane ions are also detected in the DCSF plasma, and can be reduced at either lower pressure or lower cathode to anode or cathode to substrate distances.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/43637 |
| Date | 10 January 2014 |
| Creators | Leong, Keith R. |
| Contributors | Zukotynski, Stefan, Kherani, Nazir P. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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