Back-side Process of RF Devices
The back side process creates the desired functionality of the back side of the wafer. After protecting the front side of the wafer with a protective coating the wafer is bonded with its front side to a carrier. After thinning the wafer to a thickness down to 100 µm, metal layers for subsequent chip bonding and thermal contacting are deposited.
For applications in the micro wave range short wires are often desirable, as they can enhance the high frequency properties and simplify the chip mounting. This is realized by means of through wafer vias that connect front side and back side electrically. These vias can be formed either by laser drilling or by plasma etching. After deposition of a conducting starting layer the vias are filled by means of galvanic metal deposition.
- Back-side processing up to 4" wafers
- Typical diameter of a via of 60 µm
- Via machining using plasma etching or laser ablation