The Effect of Hydrogen Dilution on the Hot-Wire Deposition of Microcrystalline Silicon

1996 ◽  
Vol 420 ◽  
Author(s):  
H. N. Wanka ◽  
R. Zedlitz ◽  
M. Heintze ◽  
M. B. Schubert
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Interface Layer ◽  
Hot Wire ◽  
Nucleation Layer ◽  
Pronounced Increase ◽  
Hydrogen Dilution ◽  
20 Nm

AbstractThe growth of amorphous (a-Si:H) and microcrystalline (pc-Si) silicon by hot-wire chemical vapor deposition (HWCVD) has been studied by combining in-situ ellipsometry, atomic force microscopy (AFM), and Raman spectroscopy. Generally a dense nucleation layer is formed during a-Si:H HWCVD, containing nuclei about 0.8 nm high and 10 to 20 nm in diameter. The surface roughness gradually increases with film thickness and settles at a root mean square (RMS) value of 1.6 nm at about 200 nm thickness. For hydrogen dilution at gas flow ratios x=[H2]/[SiH4] of 15 to 120 microcrystalline material was obtained. The grain size and nucleation layer, however, are strongly dependent on x. Low H2 dilution enhances the formation of an amorphous-like interface layer from which the μc-Si:H growth eventually starts. Increasing x promotes the etching of amorphous regions and the surface diffusion of precursors, resulting in larger nuclei. X = 30 yields extended μc-Si nuclei (30 nm height, 90 nm diameter) and a pronounced increase in surface roughness for thicker films, but suppresses the formation of the amorphous-like nucleation layer. A further increase in x remarkably lowers the growth rate, but smoother surfaces at comparable film thickness and larger lateral dimensions of the grains occur. This is interpreted as incipient etching of the crystallites.

Characterization of Microcrystalline Transition from Amorphous Silicon as a Function of Hydrogen Dilution and Substrate Temperature of Hot-wire CVD

2002 ◽  
Vol 715 ◽  
Author(s):  
Keda Wang ◽  
Haoyue Zhang ◽  
Jian Zhang ◽  
Jessica M. Owens ◽  
Jennifer Weinberg-Wolf ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Sudden Change ◽  
Chemical Vapor ◽  
Threshold Value ◽  
Ir Absorption ◽  
Sudden Increase ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Integral Absorption ◽  
Two Peaks

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.

Structure and Optoelectronic Properties as a Function of Hydrogen Dilution of Micro-Crystalline Silicon Films Prepared by Hot Wire Chemical Vapor Deposition

1999 ◽  
Vol 557 ◽  
Author(s):  
Guozhen Yue ◽  
Jing Lin ◽  
Qi Wang ◽  
Daxing Han
Keyword(s):  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Peak Position ◽  
Initial Growth ◽  
Hot Wire ◽  
Dilution Ratio ◽  
Structure Transition ◽  
Transparent Substrate ◽  
Hydrogen Dilution ◽  
Substrate Side

AbstractFilms prepared by hot wire CVD using H dilution ratio, R=H 2/SiH4, from 1 to 20 were studied by X-ray, Raman, PL, and conductivity measurements. We found that (a) when the dilution ratio reached R=3, the structure transition from amorphous to microcrystalline growth occured; meanwhile, PL spectrum showed a dual-peak at 1.3 and 1.0 eV; (b) the total intensity, band width, and peak position of the low energy PL band decreased with increasing H dilution; (c) both the Raman and PL measured from the transparent substrate side showed that initial growth tends to be amorphous and a portion of μc-Si was formed when R ≥ 5; and (d) the conductivity activation energy first decreased from 0.68 to 0.15 eV when the film transition from a- to μc-Si; then increased slightly with increasing μc-Si fraction. The results demonstrate that the variation of the H-dilution ratio has significant effects on both the film structures and the optoelectric properties.

Advances in the Characterization of Compositionally-graded Layers in Amorphous Semiconductor Solar Cells by Real Time Spectroellipsometry

1996 ◽  
Vol 420 ◽  
Author(s):  
R. W. Collins ◽  
Sangbo Kim ◽  
Joohyun Koh ◽  
J. S. Burnham ◽  
Lihong Jiao ◽  
...  
Keyword(s):  
Solar Cells ◽  
Real Time ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Interface Layer ◽  
Open Circuit ◽  
Amorphous Semiconductor ◽  
Deposition Parameters ◽  
Gas Flow Ratio ◽  
Graded Layers

AbstractWe have developed a real time spectroellipsometry data analysis procedure that allows us to characterize compositionally- graded amorphous semiconductor alloy thin films prepared by plasma-enhanced chemical vapor deposition (PECVD). As an example, we have applied the analysis to obtain the depth-profile of the optical gap and alloy composition with ≤15 Å resolution for a hydrogenated amorphous silicon-carbon alloy (a-Si1−xCx:H) film prepared by continuously varying the gas flow ratio z=[CH4]/{[CH4]+[SiH4]} in the PECVD process. The graded layer has been incorporated at the p/i interface of widegap a-Si1−xCx:H (x∼0.05) p-i-n solar cells, and consistent improvements in open-circuit voltage have been demonstrated. The importance of the graded-layer characterization is the ability to relate improvements in device performance directly to the physical properties of the interface layer, rather to the deposition parameters with which they were prepared.

Roughness, impurities and strain in low-temperature epitaxial silicon films grown by tantalum filament hot-wire chemical vapor deposition

2006 ◽  
Vol 910 ◽  
Author(s):  
Charles W. Teplin ◽  
Matthew Page ◽  
Eugene Iwaniczko ◽  
Kim M. Jones ◽  
Robert M. Ready ◽  
...  
Keyword(s):  
Growth Rate ◽  
Surface Roughness ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Epitaxial Films ◽  
Silicon Films ◽  
Epitaxial Silicon ◽  
Hot Wire ◽  
Film Interface

AbstractWe grow epitaxial silicon films onto (100) silicon wafers from pure silane by hot-wire chemical vapor deposition (HWCVD). The films grow epitaxially for a thickness hepi before a Si:H cones nucleate and expand. We study the dependence of hepi on growth rate and the differences between Ta and W filaments. The surface morphology of thin but completely epitaxial films are studied in order to correlate the surface roughness during growth with the eventual epitaxial breakdown thickness. Surface roughness, strain and H at the wafer/film interface are not likely to cause the observed breakdown.

Increase of Hydrogen-Radical Density and Improvement of The Crystalline Volume Fraction of Microcrystalline Silicon Films Prepared by Hot-Wire Assisted Pecvd Method

2000 ◽  
Vol 609 ◽  
Author(s):  
Norimitsu Yoshida ◽  
Takashi Itoh ◽  
Hiroki Inouchi ◽  
Hidekuni Harada ◽  
Katsuhiko Inagaki ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
Hot Wire ◽  
Dilution Ratio ◽  
Microcrystalline Silicon ◽  
Hydrogen Dilution ◽  
Hydrogen Radical ◽  
Hydrogen Radicals ◽  
Hydrogenated Amorphous

ABSTRACTHigher crystalline Si volume fractions in hydrogenated microcrystalline silicon ( µc-Si:H) films have been achieved by the hot-wire assisted plasma enhanced chemical vapor deposition (HWA-PECVD) method compared with those in films by conventional PECVD. µc-Si:H films can also be prepared by HWA-PECVD under typical conditions used for preparing hydrogenated amorphous silicon (a-Si:H) films by PECVD, in which the hydrogen-dilution ratio (H2 / SiH4) is ∼ 10. The hot wire seems to produce hydrogen radicals. As a result, the HWA- PECVD method can control hydrogen-radical densities in the RF plasma, and this method can also control the ratio of hydrogen coverage at the surface of the film.

Thin Film a-Si/poly-Si Multibandgap Tandem Solar Cells With Both Absorber Layers Deposited by Hot Wire Cvd

2001 ◽  
Vol 664 ◽  
Author(s):  
R.E.I. Schropp ◽  
C.H.M. Van Der Werf ◽  
M.K. Van Veen ◽  
P.A.T.T. Van Veenendaal ◽  
R. Jimenez Zambrano ◽  
...  
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Band Gap ◽  
Steel Substrate ◽  
Light Trapping ◽  
Chemical Vapor ◽  
Hot Wire ◽  
Tandem Solar Cells ◽  
Hydrogen Dilution ◽  
P Type

ABSTRACTThe first competitive a-Si/poly-Si multibandgap tandem cells have been made in which the two intrinsic absorber layers are deposited by Hot Wire Chemical Vapor Deposition (HWCVD). These cells consist of two stacked n-i-p type solar cells on a plain stainless steel substrate using plasma deposited n- and p-type doped layers and Hot-Wire deposited intrinsic (i) layers, where the i-layer is either amorphous (band gap 1.8 eV) or polycrystalline (band gap 1.1 eV). In this tandem configuration, all doped layers are microcrystalline and the two intrinsic layers are made by decomposing mixtures of silane and hydrogen at hot filaments in the vicinity of the substrate. For the two layers we used individually optimized parameters, such as gas pressure, hydrogen dilution ratio, substrate temperature, filament temperature, and filament material. The solar cells do not comprise an enhanced back reflector, but feature a natural mechanism for light trapping, due to the texture of the (220) oriented poly-Si absorber layer and the fact that all subsequent layers are deposited conformally. The deposition rate for the throughput limiting step, the poly-Si i-layer, is ≍ 5-6 Å/s. This layer also determines the highest substrate temperature required during the preparation of these tandem cells (500 °C). The initial efficiency obtained for these tandem cells is 8.1 %. The total thickness of the silicon nip/nip structure is only 1.1 µm.

Microstructural Characterization of Platinum Films Grown by Mocvd

1995 ◽  
Vol 403 ◽  
Author(s):  
M. Vellaikal ◽  
S. K. Streiffer ◽  
R. R. Woolcott ◽  
A. I. Kingon
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Side Wall ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Si Substrates ◽  
Wall Film ◽  
Conformal Coverage ◽  
Formation Resistivity ◽  
Pt Films

AbstractPlatinum thin films were deposited on SiO2/Si(100) by metalorganic chemical vapor deposition using Pt(acetylacetonate) and Pt(hexaflouroacetylacetonate) as precursors. The films were characterized in terms of orientation, surface roughness and morphology. As expected, Pt(111) was the preferred orientation. Higher substrate temperatures led to higher growth rates and increased surface roughness. The presence of oxygen during deposition decreased the minimum substrate temperature required for platinum deposition, indicating that oxygen played a role in the decomposition of these metalorganic compounds. Annealing platinum films at 550°C in an oxygen ambient resulted in hillock formation. Resistivity measurements showed that films deposited without oxygen were more resistive. Conformal coverage of platinum on patterned SiO2/Si substrates was investigated, and a side wall film thickness to top film thickness ratio of 0.6 for growth at 400°C was obtained. These Pt films produced by MOCVD displayed greater surface roughnesses than films grown by evaporation or sputtering.

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