ELTRAN/sup (R)/ by water-jet splitting in stress-controlled porous Si

The ELTRAN/sup (R)/ SOI wafer process (Yonehara et al, 1994) has effectively used porous Si in the epitaxial and etching processes. In addition, porous Si again plays the other significant role in cost reduction. If the bonded pairs are split at the porous Si layers and the wasted starting materials (device wafers) are reused for the next device wafers, the manufacturing cost can be dramatically reduced. The splitting technique was developed and demonstrated using double layered porous Si in conjunction with water jets. The mechanism of splitting was investigated from the viewpoint of the stress in porous Si. The dynamic stress configuration was observed and controlled for the splitting of double porous Si layers. By reusing the device wafers, three-cycled ELTRAN/sup (R)/ wafers were successfully fabricated from one device wafer. SOI quality was found not to be degraded by the device wafer reuse and to be comparable to that of the conventional process.