PVMaT cost reductions in the EFG high volume PV manufacturing line: Annual report, 5 August 1998--4 August 1999[PhotoVoltaic Manufacturing Technology, Edge-defined Film-fed Growth]

This report describes work performed by ASE Americas researchers during the first year of this Photovoltaic Manufacturing Technology 5A2 program. Significant accomplishments in each of three task are as follows. Task 1--Manufacturing Systems: Researchers completed key node analysis, started statistical process control (SPC) charting, carried out design-of-experiment (DoE) matrices on the cell line to optimize efficiencies, performed a capacity and bottleneck study, prepared a baseline chemical waste analysis report, and completed writing of more than 50% of documentation and statistical sections of ISO 9000 procedures. A highlight of this task is that cell efficiencies in manufacturing were increased by 0.4%--0.5% absolute, to an average in excess of 14.2%, with the help of DoE and SPC methods. Task 2--Low-Cost Processes: Researchers designed, constructed, and tested a 50-cm-diameter, edge-defined, film-fed growth (EFG) cylinder crystal growth system to successfully produce thin cylinders up to 1.2 meters in length; completed a model for heat transfer; successfully deployed new nozzle designs and used them with a laser wafer-cutting system with the potential to decrease cutting labor costs by 75% and capital costs by 2X; achieved laser-cutting speeds of up to 8X and evaluation of this system is proceeding in production; identified laser-cutting conditions that reduce damage for both Q-switched Nd:YAG and copper-vapor lasers with the help of a breakthrough in fundamental understanding of cutting with these short-pulse-length lasers; and found that bulk EFG material lifetimes are optimized when co-firing of silicon nitride and aluminum is carried out with rapid thermal processing (RTP). Task 3--Flexible Manufacturing: Researchers improved large-volume manufacturing of 10-cm {times} 15-cm EFG wafers by developing laser-cutting fixtures, adapting carriers and fabricating adjustable racks for etching and rinsing facilities, and installing a high-speed data collection net work; initiated fracture studies to develop methods to reduce wafer breakage; and started a module field studies program to collect data on field failures to help identify potential manufacturing problems. New encapsulants, which cure at room temperature, are being tested to improve flexibility and provide higher yields for thin wafers in lamination

PVMaT Cost Reductions in the EFG High-Volume PV Manufacturing Line: Annual Report, August 1998-December 2000

The PVMaT 5A2 program at ASE Americas is a three-year program that addresses topics in the development of manufacturing systems, low-cost processing approaches, and flexible manufacturing methods. The three-year objectives are as follows: (1) implementation of computer-aided manufacturing systems, including Statistical Process Control, to aid in electrical and mechanical yield improvements of 10%, (2) development and implementation of ISO 9000 and ISO 14000, (3) deployment of wafer production from large-diameter (up to 1 m) EFG cylinders and wafer thicknesses down to 95 microns, (4) development of low-damage, high-yield laser-cutting methods for thin wafers, (5) cell designs for >15% cell efficiencies on 100-micron-thick EFG wafers, (6) development of Rapid Thermal Anneal processing for thin high-efficiency EFG cells, and (7) deployment of flexible manufacturing methods for diversification in wafer size and module design. In the second year of this program, the significant accomplishments in each of three tasks that cover these areas are as follows: Task 4-Manufacturing systems, Task 5-Low-cost processes, and Task 6-Flexible manufacturing

Removal of Boron from Silicon by Solvent Refining Using Ferrosilicon Alloys

The distribution of boron between purified solid silicon and iron-silicon melt was evaluated to investigate the possibility of boron removal from silicon by solvent refining with iron-silicon alloys. The distribution coefficient, defined as the ratio of the mole fraction of boron in solid to that of liquid, was found to be strongly dependent on boron concentration. Solvent refining at lower temperatures resulted in smaller distribution coefficient values. The boron removal percentages for the lowest boron concentration examined in this study were, 70% (1583 K), 65% (1533 K), and 65% (1483 K). The values obtained for interaction parameter of boron on iron in solid silicon are as following: -813± 53 (1583 K), -830 ± 92 (1533 K), -863 ± 91 (1483 K). Lower temperature resulted in smaller distribution coefficient and higher silicon yield.This research is partly supported by Natural Sciences and Engineering Research Council of Canada (NSERC)