Windowless Wide Area Vuv Lamp for Energy Assisted CVD

1988 ◽  
Vol 129 ◽  
Author(s):  
Z. Yu ◽  
T. Y. Sheng ◽  
H. Zarnani ◽  
G. J. Collins
Keyword(s):  
Vacuum Ultraviolet ◽  
Hydrogenated Amorphous Silicon ◽  
Electron Gun ◽  
Large Area ◽  
Deposition Rates ◽  
Surface Mobility ◽  
Excited Species ◽  
Hydrogenated Amorphous ◽  
Deposited Films ◽  
Excited Radical

ABSTRACTA ring shaped cold cathode electron gun provides a large area disc shaped vacuum ultraviolet (VUV) light source up to 20 cm in diameter. The windowless disc plasma is also a source of radical and excited atomic gas species. VUV photons, excited species, and radicals can all assist dissociation of CVD feedstock reactants via volume photo-absorption and sensitized atom-molecule collisions, respectively. In addition, the excited radical flux and VUV impingement on the film may also assist heterogeneous surface reactions and increase surface mobility of absorbed species. Thin films of aluminum nitride, Si3N4, and hydrogenated amorphous silicon have been deposited at temperatures between 100°C - 400°C. The deposited films show significant improvement over other photoassisted CVD processes in the film quality achieved, the substrate temperature required and the maximum deposition rates.

Phosphorus and Boron Doping of a-Si:H Effects of Deposition Temperature

1987 ◽  
Vol 95 ◽  
Author(s):  
M. J. M. Pruppers ◽  
K. H. M. Maessen ◽  
J. Bezemer ◽  
F. H. P. M. Habraken ◽  
W. F. van der Weg
Keyword(s):  
Deposition Temperature ◽  
Room Temperature ◽  
Hydrogenated Amorphous Silicon ◽  
Boron Doping ◽  
Dark Conductivity ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Deposited Films

AbstractHeavily phosphorus and boron doped hydrogenated amorphous silicon films were deposited in the temperature range 50 to 300 °C. Concentrations of P, B and H, IR spectra and room temperature conductivity have been measured. When the deposition temperature is raised from 50 to 300 °C the concentration of P increases, while the concentration of B decreases. The dark conductivity of both P and B doped films decreases dramatically when the deposition temperature is lowered. We interpret these results on the basis of assumptions concerning the microstructure of the deposited films, and especially the variation of this structure with deposition temperature.

A Particular Photo-CVD Apparatus for Hydrogenated Amorphous Silicon Deposition

1992 ◽  
Vol 258 ◽  
Author(s):  
C. Manfredotti ◽  
F. Fizzotti ◽  
C. Osenga ◽  
M. Boero ◽  
V. Rigato ◽  
...  
Keyword(s):  
Thin Films ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Deposition Chamber ◽  
Amorphous Thin Films ◽  
Lock Chamber ◽  
Hydrogenated Amorphous ◽  
Deposited Films

ABSTRACTA new PHOTO-CVD apparatus has been built in order to deposit a – Si : H films and other kinds of amorphous thin films by a technique which is both simple and versatile. This apparatus is composed of three chambers connected together: a load-lock chamber, a process chamber and a third chamber for in-situ analysis of deposited films. A peculiarity of the lamp, a dielectric discharge lamp which can work with noble gases like Xe or Kr, is that it can be completely dismounted without breaking the vacuum in order to clean the optical MgF2 window. By this method, the deposition chamber can be kept in very clean conditions. In this apparatus, we started to deposit a – SixC1−x: H of very good quality, taking their thickness into account. These films have been completely characterized by chemical (RBS, ERDA) and optical (PDS) methods. Their quality can be compared with quality of a – Si : H samples of the same thickness obtained by PECVD.

Higher Crystalline Volume Yields from Excimer Laser Crystallization of Amorphous Silicon with an Asymmetrical Peak Pulse Profile

2007 ◽  
Vol 31 ◽  
pp. 185-188 ◽  
Author(s):  
A.A.D.T. Adikaari ◽  
N.K. Mudugamuwa ◽  
S.R.P. Silva
Keyword(s):  
Surface Roughness ◽  
Amorphous Silicon ◽  
Laser Energy ◽  
Hydrogenated Amorphous Silicon ◽  
Leading Edge ◽  
Gaussian Pulse ◽  
Large Area ◽  
Pulse Profile ◽  
Beam Shape ◽  
Hydrogenated Amorphous

Excimer lasers have been utilized for the crystallization of hydrogenated amorphous silicon for electronic applications. These lasers typically operate in the ultraviolet and hence photons are absorbed by the silicon thin films within a few nanometres of the surface, melting and solidifying the silicon on a nanosecond timescale, often without affecting the underlying substrate. This technique enables the use of inexpensive substrates, such as glass, which are highly preferable for low cost, large-area electronic devices. The depth of crystallization becomes important for applications such as photovoltaics, which depends on a number of factors; with laser beam shape one of the most significant. A Gaussian beam profile has been reported to be best suited for controlled evolution of hydrogen during crystallization with minimum surface damage. Previous reports show the typical energy densities of crystallization, comparing the crystalline volume and surface roughness of the resultant films for different film thicknesses. We report significant reductions of laser energy densities for crystallization by modifying the Gaussian pulse profile, while retaining the controlled evolution of hydrogen from hydrogenated amorphous silicon films. An asymmetrical, shorter pulse profile retains the desirable gradual leading edge of the Gaussian pulse for controlled evaporation of hydrogen, while increasing the peak energy. The resultant films show increased surface roughness along with higher crystalline volumes, which may be beneficial for photovoltaics.

Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD at Deposition Rates up to 1 µm/minute

2000 ◽  
Vol 609 ◽  
Author(s):  
Brent P. Nelson ◽  
Yueqin Xu ◽  
A. Harv Mahan ◽  
D.L. Williamson ◽  
R.S. Crandal
Keyword(s):  
Amorphous Silicon ◽  
Deposition Rate ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Conductivity Ratio ◽  
Hot Wire ◽  
Single Filament ◽  
Deposition Rates ◽  
X Ray ◽  
Hydrogenated Amorphous

ABSTRACTWe grow hydrogenated amorphous-silicon (a-Si:H) by the hot-wire chemical vapor deposition (HWCVD) technique. In our standard tube-reactor we use a single filament, centered 5 cm below the substrate and obtain deposition rates up to 20 Å/s. However, by adding a second filament, and decreasing the filament-to-substrate distance, we are able to grow a-Si:H at deposition rates exceeding 167 Å/s (1 µm/min). We find the deposition rate increases with increasing deposition pressure, silane flow rate, and filament current and decreasing filament-tosubstrate distance. There are significant interactions among these parameters that require optimization to grow films of optimal quality for a desired deposition rate. Using our best conditions, we are able to maintain an AM1.5 photoconductivity-to-dark-conductivity ratio of 105 at deposition rates up to 130 Å/s, beyond which the conductivity ratio decreases. Other electronic properties decrease more rapidly with increasing deposition rate, including the ambipolar diffusion length, Urbach energy, and the as-grown defect density. Measurements of void density by small-angle X-ray scattering (SAXS) reveal an increase by well over an order of magnitude when going from one to two filaments. However, both Raman and X-ray diffraction (XRD) measurements show no change in film structure with increasing deposition rates up to 144 Å/s, and atomic force microscopy (AFM) reveals little change in topology.

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