Abstract: New methods of weakening the bonds between a bonded pair of wafers or substrates are provided. The substrates are preferably bonded at their outer peripheries. When it is desired to separate the substrates, they are contacted with a solvent system suitable for weakening, softening, and/or dissolving the bonding composition at their outer peripheries. Megasonic energy is simultaneously directed at the substrates (and preferably the bonding composition itself), so as to increase solvent penetration into the composition, thus decreasing the time needed for substrate separation and increasing throughput.