Letter 41010

Au-sn peel off  

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We have e-beam deposited Au-sn (80-20) on the back of the wafer and we are mounting it on an adhesive tape for sawing. But this tape,(which is least adhesive available in the market), is peeling off the Au-Sn layer. Is it possible to elminate this problem by sintering, heating etc? I appreciate your reply.

Regards,
Deepa

Deepasree Konduparthi
Semiconductor electronics - Westford, Massachusetts

You could use a coating of wax on the backside before using adhesive tape, after dicing and removal of tape you can dissolve the wax.

What is your substrate? Are you depositing Au/Sn on top of any adhesion layer (say Cr/Au)? Au/Sn will not adher if you deposit directly without a seed layer.

Annealing (@ 200 - 250'C for several hours ) might help reduce the stress in ebeam deposited Au/Sn (280'c is the melting point). Stress can cause the film to peel, it depends on the thickness, your deposition parameters etc.

Without more information, it is difficult to give the right fix.

Good luck ..

Karthik Thambidurai
- Austin, TX

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