Problems of Power Feeding in Large Area PECVD of Amorphous Silicon

AbstractThe production of amorphous silicon, e.g. for solar cells, requires large area, high-deposition rate plasma reactors. Increasing the radio frequency from the conventional 13.56MHz up to VHF has demonstrated higher deposition and etch rates and lower particle generation, a reduced ion bombardement and lower breakdown, process and bias voltages.But otherwise the use of VHF leads to some problems. The non-uniformity of deposition rate increase due to the generation of standing waves (TEM wave) and evanescent waveguide modes (TE waves) at the electrode surface.Increasing the frequency and/or the deposition area the plasma impedance, the capacitic stray impedance of the RF electrode and other parasitic capacitive impedances decrease. Increasing the frequency and/or the RF power, the phase angle of the discharge and of the impedance at every point at the lines between the RF matching network an the RF electrode tends more and more towards -90°. This results in increasing currents and standing waves with extremly high local current maximas. Increasing resistances of lines and contacts due to the skin effect and loss-caused heating up of the lines the power losses increase extremely, up to 90% and more. In spite of the increasing of the coupled power, the plasma power does not increase. Thermal destructions of the lines due to extreme expansion or melting are possible.Some solutions to reduce the non-uniformity of the deposition rate like multipower feeding, central backside power feeding, electrode segmentation, use of load impedances, published in former publications, will be discussed in connection with several reactor types (coaxial, large area, long plasma source) in view of the efficiency of power coupling and the practical realization. Solutions to minimize the power losses at the lines will be presented.

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VHF Large Area Plasma Processing on Moving Substrats

MRS Proceedings ◽

10.1557/proc-664-a5.5 ◽

2001 ◽

Vol 664 ◽

Cited By ~ 1

Author(s):

J. Kuske ◽

U. Stephan ◽

R. Terasa ◽

H. Brechtel ◽

A. Kottwitz

Keyword(s):

Deposition Rate ◽

Optical Emission ◽

Plasma Source ◽

Deposition Process ◽

Small Scale ◽

High Deposition Rate ◽

Plasma Reactors ◽

Large Area ◽

Particle Generation ◽

Deposition Parameters

ABSTRACTThe production of amorphous and microcrystalline silicon, e.g. for solar cells, requires large area, high-deposition rate plasma reactors. Increasing the frequency from the conventional 13.56MHz up to VHF has demonstrated higher deposition and etch rates and lower particle generation, a reduced ion bombardement and lower breakdown, process and bias voltages. But the use of VHF for large area systems leads to some problems. The non-uniformity of deposition rate increases due to the generation of standing waves and evanescent waveguide modes at the electrode surface. One possibility to process large area substrates is the use of a one-dimensional extended, homogeneous plasma source in combination with a moving substrate. The requirements, which result from the deposition process and from the RF-engineering, corresponds with the developed plasma source, using deposition frequencies in the VHF-range (50-100 MHz), almost perfectly.Using a source of 550mm length experiments were done with 81.36MHz at RF power densities of 70-180mW/cm2, silane/ hydrogen pressures of 5-30Pa and flow rates of 10-300sccm. The measured potential distribution error was ±2%. Optical emission spectroscopy delivered discharge intensity errors of ±3-10%. Deposition rates up to 20µm/h for amorphous silicon (60Å/s) and film thickness inhomogenities less than ±5% were achieved (with an area of the moved substrate of 30cm–30cm). Experimental results of the film properties will be discussed in relation to the deposition parameters and compared with complementary experiments, carried out on a small scale equipment with excitation frequencies up to 165 MHz.

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High deposition rate nanocrystalline and amorphous silicon thin film production via surface wave plasma source

Surface and Coatings Technology ◽

10.1016/j.surfcoat.2017.05.074 ◽

2017 ◽

Vol 325 ◽

pp. 370-376 ◽

Cited By ~ 5

Author(s):

Jason A. Peck ◽

Piyum Zonooz ◽

Davide Curreli ◽

Gianluca A. Panici ◽

Brian E. Jurczyk ◽

...

Keyword(s):

Thin Film ◽

Surface Wave ◽

Amorphous Silicon ◽

Deposition Rate ◽

Plasma Source ◽

High Deposition Rate ◽

Film Production ◽

Silicon Thin Film ◽

Nanocrystalline And Amorphous ◽

Thin Film Production

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Deposition Conditions for Large Area PECVD of Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-467-591 ◽

1997 ◽

Vol 467 ◽

Cited By ~ 8

Author(s):

J. Kuske ◽

U. Stephan ◽

W. Nowak ◽

S. Röhlecke ◽

A. Kottwitz

Keyword(s):

Film Thickness ◽

Amorphous Silicon ◽

Deposition Rate ◽

Excitation Frequency ◽

Input Power ◽

High Deposition Rate ◽

Large Area ◽

Deposition Parameters ◽

Plate Size ◽

Area Deposition

ABSTRACTThe production of amorphous silicon devices usually requires large area, high-deposition-rate plasma reactors. Non-uniformity of the film thickness at high power and deposition rate is found to be an important factor for large area deposition.Increasing the radio frequency from the conventional 13.56 MHz up to VHF has demonstrated advantages for the deposition of a-Si:H films, including higher deposition rates and lower particle generation. The use of VHF for large area deposition leads to the generation of standing waves and evanescent waveguide modes at the electrode surface and on the power feeding lines. Thereby increasing the non-uniformity of the film thickness. The uniformity of the film thickness for an excitation frequency strongly depends on the deposition parameters e.g. pressure, input power, silane flow and the value of load impedances. With increasing exciting frequencies the range of deposition parameters for obtaining uniform films narrows.Subsequently it is shown that for a large-area plasma-box reactor (500 × 600 mm2 plate size) with a double-sided RF electrode, the non-uniformity of the film decreases due to a homoge-neization of the electrode voltage distribution by using multiple power supplies and load impedances on the end of the RF electrode. The uniformity errors decrease from ±20% to ±2.4% (27.12MHz) and from ±40% to ±5.9% (54.24MHz). Experimental results of the film uniformity will be discussed in dependence on excitation frequencies and the deposition parameters.

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