Stress Relief

The process of wafer backgrinding induces process marks and damage that propagates into the bulk of the wafer causing it to weaken. This weakening effect of the wafer can be repaired by PVA TePla’s plasma stress relief process. Backgrinding tape protects the active side of the wafer during the thinning process (grinding from 725 µm down to a target thickness of e.g. 30 µm). After this, the stress relief by remote plasma treatment is applied to the wafer backside in order to eliminate the 3 µm zone of damaged silicon left behind after thinning. Downstream cold plasma is a pure, dry, isotropic chemical etch process containing no free ions or electrons that could potentially charge the surface of the wafer. The back-grinding tape is protected by limiting the process temperature to about 70°C, avoiding any damage to the back-grinding tape. Stress Relief can be applied in-situ with Passivation and Wafer Thinning.