Thinning to Either an Etch or Polish Stop

As illustrated in Fig. 15.11, wafers can be bonded face-to-face, the handle of the SOI wafer can be thinned to stop on the buried oxide layer, rebonded to another handle wafer, thinned again to stop on the bonding layer, and then tested. Lu et al. have used this approach to demonstrate process compatibility on passive structures [85], Gutmann et al. have used this method to demonstrate process compatibility using active electrical structures [49], and 

FIGURE 15.11 Process flow for thinning to a hurried oxide etch stop, rebonding, and repeating to allow electrical testing of the original structures (from Ref. 49). 

Pozder et al. have employed this approaeh to demonstrate paekaging compatibility of dielectric adhesive 3D with active electrical structures [50]. 

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