Semiconductor Wafer Slicing
Wafer slicing transforms cylindrical silicon ingots into thin disc-shaped wafers that will become the starting substrates for semiconductor devices. This step uses precision diamond wire saws to slice ingots into wafers only a fraction of a millimeter thick. Controlling stress, bowing, and microcracks during slicing is essential, as defects at this stage reduce wafer yield and reliability downstream.
Slicing Process
- Diamond Wire Saws: High-speed wire embedded with diamond particles cuts through ingots with micrometer precision.
- Wafer Thickness: Standard ~775 µm for 300 mm wafers; thinner wafers are being explored to reduce material use.
- Kerf Loss: The silicon lost as sawdust during slicing; a significant cost factor in wafer production.
- Stress Control: Minimized by optimized sawing parameters and coolant flow.
Wafer Slicing Mapping
| Parameter | Typical Value | Impact |
|---|---|---|
| Thickness (300 mm wafer) | ~775 µm | Balance between mechanical strength and material cost |
| Kerf Loss | ~150 µm per cut | Silicon waste; cost driver in slicing efficiency |
| Bow / Warp | <30 µm typical | Critical for downstream polishing and lithography |
Key Considerations
- Material Efficiency: Diamond wire technology reduces kerf loss compared to slurry-based saws.
- Defect Control: Microcracks and dislocations introduced here are difficult to remove later.
- Scaling Trends: Larger-diameter wafers (300 mm+) require improved sawing stability.
FAQs
- What happens to the sawdust? – Kerf waste is often recycled back into polysilicon refining.
- Can wafers be sliced thinner? – Yes, but handling and breakage risks rise dramatically.
- Why use diamond wire? – Higher precision, lower kerf loss, and smoother surfaces than slurry saws.
