Transforming a single crystal ingot or a squared poly-crystalline slab of silicon into individual wafers is termed “wafering”. The newest process for wafering is “diamond wire sawing”. Diamond wire sawing uses a machine similar to a slurry saw. The difference between the two types of saws are that the slurry saw uses a brass coated wire and an abrasive slurry (silicon carbide) to perform the cutting while a diamond wire saw uses a diamond coated wire and specialized coolants/lubricants to perform the cutting.
The advantages of using a diamond coated wire and coolant in place of a brass coated wire and abrasive slurry are:
- Increased cutting rate (2X)
- Thinner kerf
- Easier cleaning of wafers post sawing
- Lower costs associated with slurry make-up, maintenance and disposal
- Easier retrieval of silicon swarf for recycling
Post-sawn wafers are more easily rinsed on the beam and more easily cleaned afterwards in both pre-cleaning and final cleaning processes. Properly developed low-foaming, non-staining easily filtered coolants can be recycled in a properly designed filtration system for use over a long period of time. Properly designed coolant will not be carried off with the silicon swarf or on the wafers so maintenance of the coolant concentration is easy.