Market-Driven EFG Modules: Annual Subcontract Report, 14 December 1996 - 13 February 1998

This report summarizes the progress made at ASE Americas Inc. during Phase II of this subcontract. Accomplishments under Task 4: Wafers include optimization of edge-defined film-fed growth (EFG) crystal growth variables, leading to reduced crystal stresses and improved wafer flatness; increased die run length due to improvements in the design of furnace components; construction and testing of EFGgrowth furnace enclosure; reduction of EFG wafer thickness from 300 ..mu..m for 50% of all standard production material; implementation of new equipment to reduce costs of silicon feedstock sorting prior to EFG crystal growth with a 3% increase in silicon feedstock utilization; and development work demonstrating the laser cutting of EFG wafers at higher speeds and with reduced silicon damage.Accomplishments under Task 5: Cells include characterization of cells after diffusion as preliminary work toward improving diffusion conditions and improving cell efficiency; demonstration of a continuous process to remove phosphorous glass from diffused wafers, reducing chemical consumption and hazardous waste by 98%; development of statistical process control methods to improve cell productionprocess control; the use of design of experiments to study interactions between processing at various steps in cell manufacturing, and to develop strategies for productivity improvements; improvements in EFG cell efficiency due to the reduction in average wafer thickness; design and construction of equipment for producing cells with an improved grid design; and demonstration of averageefficiencies over 14.1% on production lots of EFG cells. Accomplishments under Task 6: Modules include production and successful testing of prototypes of a lower-cost module diode housing; successful demonstration of a module design that greatly improves collection of light from space between cells in modules; testing of new encapsulants and lamination processes to demonstrate reduced laminationtime, improved yield and enhanced durability; and completion of options study for lower-cost module frames, and development of a frameless module design using mounting clamps.