Metal Impurities and Gettering in Crystalline Silicon

2019 ◽  
pp. 1-46
Author(s):  
Eugene B. Yakimov
Keyword(s):  
Crystalline Silicon ◽  
Metal Impurities

Flame Synthesis Of High Purity, Nanosized Crystalline Silicon Carbide Powder

1995 ◽  
Vol 410 ◽  
Author(s):  
D. G. Keil ◽  
H. F. Calcote ◽  
R. J Gill
Keyword(s):  
Silicon Carbide ◽  
Crystalline Silicon ◽  
Flame Synthesis ◽  
Carbide Powder ◽  
Air Exposure ◽  
Precise Control ◽  
Metal Impurities ◽  
High Yields ◽  
Silicon Carbide Powder

ABSTRACTSelf-propagating flames in pure silane-acetylene mixtures produce silicon carbide (SiC) powder and hydrogen as main products. Through precise control of the stoichiometry of the reactant gas mixture, it has been possible to produce white SiC at high yields. Characterization of such powders by TEM has shown that the nascent powder consists of polycrystalline hexagonal plates with a narrow size distribution (40 ± 7 nm diameter). Infrared spectroscopy of powders indicate microcrystalline SiC and little bound hydrogen. Chemical analysis by the ANSI method showed the powder to be >96 wt % SiC with an impurity of silica (3.9 weight %) due to air exposure of the powder. Traces (0.1 to 0.2 weight %) of both free carbon and free silicon were found. Metal impurities detected by SIMS were typically low: less than 10 ppba for aluminum, sodium, titanium and vanadium. Boron was observed at 10 ppma. Like the oxygen, the boron impurities are probably associated with exposure of the powders to the atmosphere.

Identification of metal impurities in crystalline silicon wafers

2012 ◽  
Author(s):  
Bijaya Paudyal ◽  
Yo Han Yoon ◽  
David Cornwell ◽  
Phil Shaw ◽  
Francisco Machuca
Keyword(s):  
Crystalline Silicon ◽  
Silicon Wafers ◽  
Metal Impurities

‘Just-Clean-Enough’: Optimization of Wet Chemical Cleaning Processes for Crystalline Silicon Solar Cells

2016 ◽  
Vol 255 ◽  
pp. 344-347 ◽  
Author(s):  
Michael Haslinger ◽  
M. Soha ◽  
S. Robert ◽  
M. Claes ◽  
Paul W. Mertens ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Crystalline Silicon ◽  
Silicon Solar Cells ◽  
Semiconductor Surface ◽  
Cleaning Process ◽  
Chemical Cleaning ◽  
Crystalline Silicon Solar Cells ◽  
Metal Impurities ◽  
Wet Chemical

Advanced concepts for photovoltaic silicon solar cells, especially high-efficiency n-type solar cells, requires appropriate wet cleaning treatment in order to remove metallic contamination prior to high temperature processes like diffusion and passivation [1]. The cost of the cleaning process should be as low as possible that requires an optimized usage of the chemicals by increasing process tank lifetimes and developing dedicated feed and bleed recipes. The just clean enough concept has been developed to fulfil the needs of PV industry to minimize the consumption of chemicals. When the dominant contamination metal is identified in quality and quantity, a dedicated wet chemical cleaning process can be applied to remove the metal concentration from the semiconductor surface under a specified limit with the minimum volume on cleaning solution. The paper describes how to optimize a dedicated wet cleaning process for prominent metal impurities like Fe, Cu, Cr, Ti, Co and Zn. For each metal an exchange volume is determined to develop a feed and bleed recipe. The accumulation of the metal impurities in the process tank is calculated and process tank lifetimes are predicted.

Role of metal impurities in the growth of chains of crystalline-silicon nanospheres

2001 ◽  
Vol 308-310 ◽  
pp. 1097-1099 ◽  
Author(s):  
H. Kohno ◽  
T. Iwasaki ◽  
Y. Mita ◽  
M. Kobayashi ◽  
S. Endo ◽  
...  
Keyword(s):  
Crystalline Silicon ◽  
Metal Impurities

Comparison of Efficiency and Kinetics of Phosphorus-Diffusion and Aluminum Gettering of Metal Impurities in Silicon: a Simulation study

2009 ◽  
Vol 156-158 ◽  
pp. 229-234 ◽  
Author(s):  
M.A. Falkenberg ◽  
D. Abdelbarey ◽  
Vitaly V. Kveder ◽  
Michael Seibt
Keyword(s):  
Crystalline Silicon ◽  
Limiting Factor ◽  
Dissolved Metals ◽  
Metal Impurity ◽  
Phosphorus Diffusion ◽  
Metal Impurities ◽  
Precipitate Dissolution ◽  
Silicon Materials ◽  
Further Development ◽  
Kinetics Of

The efficiency of solar cells produced from crystalline silicon materials is considerably affected by the presence of metal impurities. In order to reduce the concentration of metal impurities, gettering processes as phosphorus diffusion gettering (PDG) and aluminum gettering (AlG) are routinely included in solar cell processing. Further development and optimization of gettering schemes has to ground on physics-based simulations of gettering processes. In this contribution we use quantitative simulations to compare the efficiency and kinetics of PDG and AlG in the presence of precipitates for interstitially dissolved metals, like iron, at different gettering conditions. Recently measured segregation coefficients of iron in liquid AlSi with respect to crystalline silicon are used in order to compare with PDG under typical conditions. It is shown that kinetics of both, PDG and AlG, can be separated into two regimes: (i) at low temperatures kinetics are limited by precipitate dissolution, and (ii) at high temperatures kinetics of AlG is mainly limited by metal impurity diffusion while phosphorus in-diffusion is the limiting factor of PDG.

Diffusion gettering of metal impurities in crystalline silicon

2012 ◽  
Author(s):  
Hele Savin ◽  
Ville Vahanissi ◽  
Marko Yli-Koski ◽  
Heli Talvitie ◽  
Antti Haarahiltunen
Keyword(s):  
Crystalline Silicon ◽  
Metal Impurities

Experiment Research on Purifying Metallurgical Grade Silicon and Crystal Growth in Directional Solidification

2009 ◽  
Vol 79-82 ◽  
pp. 1213-1216 ◽  
Author(s):  
Xiang Yang Mei ◽  
Wen Hui Ma ◽  
Kui Xian Wei ◽  
Yong Nian Dai
Keyword(s):  
Crystal Growth ◽  
Directional Solidification ◽  
Crystalline Silicon ◽  
Acid Leaching ◽  
Raw Material ◽  
Metallurgical Grade Silicon ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Segregation Effect ◽  
Grade Silicon

The main raw material of solar energy is multi-crystalline silicon. Directional solidification technique is one important technological process of metallurgy purification technology for multi-crystalline silicon. It can purify metallurgical grade silicon by removing metal impurities and control crystal growth at the same time. In experiment, metallurgical grade silicon by acid leaching pre-treatment, was purified by our self-assembled directional solidification furnace. The sample was analyzed by electron-prode micro analysis (EPMA). According to the results, the removal efficiency of Fe and Al is 96.3% and 96.7%, respectively. The removing mechanism of metal impurities and the difference between theory value and experiment value were also discussed. The segregation effect in directional solidification is the reason of removing Fe, but analgesic effects of the segregation effect combined with vacuum volatilization are that of removing Al. When the silicon ingot was cooled down, lengthways section of silicon ingot was cut and etched, crystal growth was studied. The results indicate that columnar crystal growth shows diverging tendency from the bottom to the top of silicon ingots, and solidification interface shape is convex. The reasons may be the nucleation of new crystals on crucible sidewall is very serious and the pulling rate is too high.

Sign in / Sign up

Export Citation Format

Share Document