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Title: Laser annealing of ion implanted CZ silicon for solar cell junction formation

Abstract

Results on a contract to evaluate the merits of large spot size pulsed laser annealing of ion implanted silicon wafers for junction formation of solar cells are presented. Three inch diameter cells were fabricated for reference by furnace annealing of the ion implanted wafers. Conversion efficiencies on these cells ranged from 12.3% to 14.3%, with and without a BSF. Scaled-up size cells, from 2 x 2 cm to 2 x 4 cm, were fabricated using a two-step 25% overlap pulsed laser annealing process. Conversion efficiencies up to 15.4% were achieved. Pulsed laser annealing of textured surface wafers proved unacceptable based on the subpar electrical performances of fabricated 2 x 2 cm and 2 x 4 cm cells. Further laser annealing work using textured surfaces has been discontinued. SIMS profiling of /sup 11/B and/or /sup 49/BF/sub 2/ ion implanted species for back surface field followed by pulse annealing, both by electron beam and laser, revealed that additional work is required for optimization. The process verification phase of the contract was initiated for small (2 x 2 cm) and large (3 in. dia) cells using the surviving processing candidates showing best promise. A high throughput laser system was conceptualized which will accommodatemore » three (3) inch diameter wafers at a rate of one per second.« less

Authors:
Publication Date:
Research Org.:
Lockheed Missiles and Space Co., Sunnyvale, CA (USA)
OSTI Identifier:
6736037
Alternate Identifier(s):
OSTI ID: 6736037
Report Number(s):
DOE/JPL/955696-80/3
DOE Contract Number:
NAS-7-100-955696
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; SILICON; ANNEALING; SILICON SOLAR CELLS; CRYSTAL DEFECTS; CZOCHRALSKI METHOD; EFFICIENCY; FABRICATION; ION IMPLANTATION; LASER-RADIATION HEATING; LASERS; MONOCRYSTALS; PERFORMANCE; PHYSICAL RADIATION EFFECTS; SEMICONDUCTOR JUNCTIONS; CRYSTAL GROWTH METHODS; CRYSTAL STRUCTURE; CRYSTALS; DIRECT ENERGY CONVERTERS; ELEMENTS; EQUIPMENT; HEAT TREATMENTS; HEATING; JUNCTIONS; PHOTOELECTRIC CELLS; PHOTOVOLTAIC CELLS; PLASMA HEATING; RADIATION EFFECTS; SEMIMETALS; SOLAR CELLS; SOLAR EQUIPMENT 140501* -- Solar Energy Conversion-- Photovoltaic Conversion; 360605 -- Materials-- Radiation Effects

Citation Formats

Katzeff, J. S.. Laser annealing of ion implanted CZ silicon for solar cell junction formation. United States: N. p., 1981. Web. doi:10.2172/6736037.
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Katzeff, J. S.. Laser annealing of ion implanted CZ silicon for solar cell junction formation. United States. doi:10.2172/6736037.
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Katzeff, J. S.. Thu . "Laser annealing of ion implanted CZ silicon for solar cell junction formation". United States. doi:10.2172/6736037. https://www.osti.gov/servlets/purl/6736037.
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@article{osti_6736037,
title = {Laser annealing of ion implanted CZ silicon for solar cell junction formation},
author = {Katzeff, J. S.},
abstractNote = {Results on a contract to evaluate the merits of large spot size pulsed laser annealing of ion implanted silicon wafers for junction formation of solar cells are presented. Three inch diameter cells were fabricated for reference by furnace annealing of the ion implanted wafers. Conversion efficiencies on these cells ranged from 12.3% to 14.3%, with and without a BSF. Scaled-up size cells, from 2 x 2 cm to 2 x 4 cm, were fabricated using a two-step 25% overlap pulsed laser annealing process. Conversion efficiencies up to 15.4% were achieved. Pulsed laser annealing of textured surface wafers proved unacceptable based on the subpar electrical performances of fabricated 2 x 2 cm and 2 x 4 cm cells. Further laser annealing work using textured surfaces has been discontinued. SIMS profiling of /sup 11/B and/or /sup 49/BF/sub 2/ ion implanted species for back surface field followed by pulse annealing, both by electron beam and laser, revealed that additional work is required for optimization. The process verification phase of the contract was initiated for small (2 x 2 cm) and large (3 in. dia) cells using the surviving processing candidates showing best promise. A high throughput laser system was conceptualized which will accommodate three (3) inch diameter wafers at a rate of one per second.},
doi = {10.2172/6736037},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 1981},
month = {Thu Jan 01 00:00:00 EST 1981}
}
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Technical Report:
View Technical Report (2.05 MB)
DOI:  10.2172/6736037
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  • An investigation was conducted which evaluated the merits of large spot size pulsed laser annealing of phosphorus implanted, Czochralski grown silicon for junction formation of solar cells. The feasibility and requirements were also determined to scale-up a laser system to anneal 7.62 cm diameter wafers at a rate of 1 wafer/second. Laser parameters were developed for optimized performance as substantiated by surface analysis. Functional cells with AM1 conversion efficiencies up to 15.4% for 2 x 2 cm and 2 x 4 cm sizes were attained, and conversion efficiencies ranged up to 14.5% for cells of 7.62 cm diameter. Texture etchedmore » surfaces are found incompatible with pulsed laser anneaing due to surface melting. Laser annealed cells are generally found to exhibit conversion efficiencies equal to or better than those of furnace annealed cells. (LEW)« less

  • Results on a contract to evaluate the merits of large spot size pulsed laser annealing of ion implanted silicon wafers for junction formation in solar cells are reported. Investigations on homogenization of the laser beam were continued. In addition to the 30 mm diameter fused silica rod with a 90/sup 0/ bend configuration, quartz tubes were obtained and briefly tried. Best results were obtained with the rod homogenizer. Laser annealing experimentation resulted in complete recrystallization of ion implanted silicon substrates as confirmed by TEM and RBS analysis. Single pulse laser annealed, functional cells (2 x 2cm) were fabricated using varyingmore » process conditions, yielding conversion efficiencies predominantly in the 13% to slightly less than 15%.« less

  • A project to evaluate the merits of large spot size pulsed laser annealing of ion implanted silicon wafers for junction formation on solar cells is described. A Q-switched Nd:Glass laser system is used operating in the 1064 (regular) and 532 (with frequency doubler) nm wavelengths. The laser output is in excess of 30 joules with a 20 to 50 ns pulse duration. Material used in this investigation is 3-inch diameter CZ silicon, P-type 0.014 inches thick, 10..cap omega..-cm resistivity, <100> orientation. Three wafer surface conditions are being evaluated in this pulse annealing investigation: chem-polished, texture etched, and flash etched. Annealingmore » was performed with and without beam homogenization. Both modes showed excellent lattice recovery from the implant-induced damage as analyzed using Rutherford backscattering techniques. Homogenization of the beam was performed using a fused silica rod configured with a 90/sup 0/ bend. The unhomogenized annealing was performed using a plano-concave lens. Fabrication of laser annealed cells using both modes is forthcoming.« less

  • Liquid diffusion masks and liquid dopants to replace the more expensive CVD SiO2 mask and gaseous diffusion processes were investigated. Silicon pellets were prepared in the silicon shot tower and solar cells were fabricated using web grown where the pellets were used as a replenishment material. Verification runs were made using the boron dopant and liquid diffusion mask materials. The average of cells produced in these runs was 13%. The relationship of sheet resistivity, temperature, gas flows, and gas composition for the diffusion of the P-8 liquid phosphorus solution was investigated. Solar cells processed from web grown from Si shotmore » material were evaluated, and results qualified the use of the material produced in the shot tower for web furnace feed stock.« less

  • Liquid diffusion masks and liquid applied dopants to replace the CVD Silox masking and gaseous diffusion operations specified for forming junctions in the Westinghouse baseline process sequence for producing solar cells from dendritic web silicon were investigated. The baseline diffusion masking and drive processes were compared with those involving direct liquid applications to the dendritic web silicon strips. Attempts were made to control the number of variables by subjecting dendritic web strips cut from a single web crystal to both types of operations. Data generated reinforced earlier conclusions that efficiency levels at least as high as those achieved with themore » baseline back junction formation process can be achieved using liquid diffusion masks and liquid dopants. The deliveries of dendritic web sheet material and solar cells specified by the current contract were made as scheduled.« less