Wafer broken

[Chong Xie]

Dear CMP users,

The CMP broke most of my wafers (3 out of 4) last time I use it. Chucking was all right, but the wafers were broken during polishing. I was just using the normal setting: 

Platen: 50RPM
Head1: 30RPM
Head2: 60RPM

Polishing pressure: 200gm/cm2
Retainer pressure: 300gm/cm2

My wafers have 2 um deep trenches on them. I thought that might be the reason, but the same conditions worked for me all right before. 
I was wondering whether I could tune any of these parameters. Dose anyone have similar problems before?
Any input is appreciated, and thanks in advance.


chong