Bulk Material Processing

(Wafer Production)

The bulk material processing capabilities of the SiC lab result in SiC wafers ready for use in device fabrication or for use as seed crystals for bulk growth research. After a single crystalline ingot is grown in the bulk growth lab, it comes here and an X-Ray Diffractometer is used to determine the crystallographic orientation of the ingot. The ingot is then reoriented to the desired orientation and the unwanted polycrystalline edges are ground away using the custom built grinder. The result is a smooth cylinder, usually 50.8mm or 2 inches in diameter.

After grinding, the cylindrical ingot is sliced using a superabrasive wiresaw. The lab has two wiresaws, one is a commercial model made by Laser Technology West and the other is a custom built system that was designed in house to create high quality as-cut wafer surfaces. Both saws use diamond impregnated steel wire that is also manufactured here in the lab. At the end of slicing, the ingots have now been separated into multiple wafers. These wafers then move to the lapping and polishing facilities to remove the surface damage left behind by the saw.

The lapping process begins using boron carbide powder with large grain sizes and continues until the wafer has a flat and uniform finish. When the wafer is flat, it moves through successive polishing stages of finer diamond powders until the desired surface quality is achieved. The wafers are now ready for use and usually go to the epitaxial growth facilities before device fabrication.

Laser Tech Wiresaw

The wiresaw was manufactured by Laser Technology West and produces multiple wafers from a single ingot using high speed diamond abrasive wire. USC has also developed wiresaw technologies including a manufacturing process for diamond impregnated wire as well as our own wiresaw design. Patent applications have been submitted.

Polishing Machines

These polishing machines are manufactured by Lapmaster and use diamond or boron carbide powders for removal of material. Pressure is applied to wafers as they counter rotate over a rotating polishing pad. Different machines are used for different diamond particle sizes and they are never mixed, otherwise scratches will occur.

Double Sided Polishing Machine

The double sided polishing machine is also made by Lapmaster and functions in the same manner as the other machines. The difference is throughput. This machine polishes both sides of the wafer in a single step.