PROCESS INNOVATIONS
NorSun has a
roadmap for cost reductions through process innovation in the crystal pulling, ingot shaping and wafer slicing portion of the monocrystalline high efficiency solar energy segment.
ROADMAP
A set of well-defined initiatives aimed at reducing cost per wafer by 40 - 50 % by 2012:
EXAMPLE OF PROJECTS
An example from crystal pulling
Replenishing crucible to increase batch size:
- Increase batch size to make longer crystals (Additional charging)
- Replenish melt to produce multiple crystals from each cycle (Recharging)
- Reduce cycle time in batch process (e.g., increase crystal growth rate)
- Reduce cost through lower consumption of consumables per kg ingot
- Increase yield through reduced waste
Status:
- Additional charging tool developed internally;implemented in regular production
- Recharging tool developed with engineering partner; in test production
An example from wafer
slicing
Wafer slicing with diamond coated steel wires:
- Capex reduction due to more efficient slicing (fewer saws)
- Avoidance of costly silicon carbide grits and polyethylene glycol
- Improved wafer quality due to lower subsurface damage, surface roughness and TTV
- Reuse of wire (normal steel wire is only used once)
- Recycling of polysilicon kerf for PV application expected
- Reduced electricity consumption
Status:
- Stable and low cost industrial process for wafer sawing with diamond wire developed and
implemented in commercial production
- 100 % productivity increase per saw demonstrated
- Wafers perform well in high efficiency customers' cell processes
- Complete production switched from slurry based slicing to diamond wire