FEA Thermal Investigation of Wafer Thinning by Plasma Etching

In this work, finite element analysis (FEA) was used to predict transient heating and temperature distribution on the wafer surface during plasma etching process as backgrind (BG) tape degradation after plasma stress relief was observed. The wafer surface temperature during plasma process was measured using temperature indicator strips and used as input temperature for FEA analysis. Parametric studies were performed to analyse the effect of temperature on different Silicon thickness and different wafer contact on electro static chuck (ESC) to understand the temperature distribution during the plasma process. The thermal behaviour of BG tape was also characterised using differential scanning calorimetry (DSC). Perfect wafer contact on ESC predicted 99.1degC after 0.1 s. With presence of air gaps, temperature increases to 105degC and based on DSC analysis, melting is likely to occur. We have demonstrated the application of FEA and DSC methods can be applied to BG tape selection.