Why Wafer Back Grinding?
Before assembly, the backside of the wafer is ground to the proper wafer thickness in a process
called wafer back grind. This step will help to reduce wafer thickness and allow stacking & high-density packaging of integrated circuits (IC).
Wafer thinning is another name for it. Prostech provides temporary bonding and debonding for this process.
Wafer Back Grinding Process
The wafer back grinding process will basically combine 8 steps:
1. Spin coat adhesive
2. Laminate support glass
3. UV cure adhesive: from liquid stage to solid stage and create the crosslinked film
4. Back grinding process
5. Attach dicing tape and frame
6. Raster laser across the wafer
7. Lift the glass of the wafer
8. Peel off the adhesive
During this process, there will be two steps involving adhesive technology: bonding & debonding
Bonding the semiconductor wafer and glass carrier customer supplied (with light-to-heat-conversion release coating) by liquid UV-curable adhesive.
Debonding the wafer de-taping tape and semiconductor wafer
Challenges
When choosing an adhesive for easy bonding and debonding process, there are 3 main challenges manufacturers have to face:
- The back grind process can easily cause warpage, cracking, edge chipping, and low yields on thin/delicate wafer
- The conventional adhesive is used to form small voids which can potentially lead to delamination under high vacuum or during high-temperature processing.
- The debonding step needs to apply a mechanical force to debond the glass off wafer which can cause damage as well as take a long time.
Solutions
Then how PROSTECH can overcome these difficulties:
UV-curable adhesive
- minimizes stress, less warpage, higher yields, and less waste;
- low out-gassing, high mechanical strength, fast curing, curing according to the user’s request
- easy to peel off, leaves no residue
Light-to-Heat coating (LTHC)
- room temperature cure
- low stress
- solvent-free
De-taping tape
- low-stress
- simple peeling off
- good holding power
- transparent
