Mechanism of High Rate a-Si:H Deposition in a VHF Plasma

1993 ◽  
Vol 297 ◽  
Author(s):  
M. Heintze ◽  
R. Zedlitz ◽  
G.H. Bauer
Keyword(s):  
Optical Emission ◽  
Impedance Analysis ◽  
High Energy ◽  
High Rate ◽  
Growth Surface ◽  
Very High Frequency ◽  
Ion Energy ◽  
Glow Discharges ◽  
Radical Generation ◽  
Very High

Very high frequency (VHF) glow discharges are employed for high rate a-Si:H deposition while maintaining good optoelectronic materials properties. A more efficient radical generation, either due to higher electron densities or an enhanced high energy electron tail is generally assumed as the mechanism. We have investigated a VHF a-Si:H deposition plasma between 40 and 250MHz by optical emission spectroscopy (OES), mass spectroscopy (MS), ion energy measurements and electrical impedance analysis. The present study shows that the increase of the deposition rate with frequency is essentially due to an enhanced ion flux to the growth surface.

High Rate Deposition of a-SiNxH by VHF PECVD

1997 ◽  
Vol 467 ◽  
Author(s):  
T. Takagi ◽  
Y. Nakagawa ◽  
Y. Watabe ◽  
K. Takechi ◽  
S. Nishida
Keyword(s):  
Amorphous Silicon ◽  
Deposition Rate ◽  
Excitation Frequency ◽  
Chemical Vapour ◽  
Optical Emission ◽  
High Rate ◽  
Very High Frequency ◽  
Silicon Nitride Films ◽  
Very High

ABSTRACTVery High Frequency (VHF) has been applied to the plasma enhanced chemical vapour deposition (PECVD) of hydrogenated amorphous silicon nitride films (a-SiNx:H) to fabricate amorphous silicon (a-Si:H) thin film transistors (TFTs). Especially, the effect of the excitation frequency on the deposition rate and the film quality of a-SiNx.H deposited in a SiH4/NH3/N2 plasma has been investigated. The films were prepared by VHF (40 MHz and 60 MHz) and HF (13.56 MHz) plasma enhanced CVD.The optical bandgap, the hydrogen content, the Si-H/N-H ratio and TFT mobility for films deposited in VHF plasma did not change significantly with the increase in deposition rate up to 300 nm/min. Internal stress could be constrained to acceptable levels at very high deposition rates. In contrast, the film quality deteriorated with an increase of the deposition rate in HF plasma. There seems to be a parallel relation between the optical emission intensity and the deposition rate which depends on the excitation frequency.

Influence of Pressure and Plasma Potential on High Growth Rate Microcrystalline Silicon Grown by Vhf Pecvd

2005 ◽  
Vol 862 ◽  
Author(s):  
A. Gordijn ◽  
J. Francke ◽  
L. Hodakova ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Solar Cells ◽  
High Pressures ◽  
Defect Density ◽  
Plasma Potential ◽  
High Rate ◽  
Growth Surface ◽  
Microcrystalline Silicon ◽  
Ion Energy ◽  
Single Junction ◽  
External Power Source

AbstractMicrocrystalline silicon (μc-Si) based single junction solar cells are deposited by VHF PECVD using a showerhead cathode at high pressures in depletion conditions. At a deposition rate of 4.5 nm/s, a stabilized conversion efficiency of 6.7 % is obtained for a single junction solar cell with a μc-Si i-layer of 1 μm. The i-layer is made near the transition from amorphous to crystalline. In order to control the material properties in the growth direction, the hydrogen dilution of silane in the gas phase is graded following different profiles with a parabolic shape. It is observed that the performance of solar cells deposited at high rate improves under light soaking conditions at 50 °C, which we attribute to post deposition equilibration of a fast deposited transition material.The performance is lower at higher rates due to poorer i-layer quality (higher defect density), which may be attributed to smaller relaxation times for growth precursors at the growth surface and the higher energy ion bombardment at higher plasma power. High process pressures can be used to reduce the ion energy by decreasing the mean free path. We have introduced an additional method to limit the ion energy by controlling the DC self bias voltage using an external power source. In this way the quality of the μc-Si layers and the performance of the solar cells is further improved.

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