Patent ID: 7205211

Claim:
Method for making a thin layer starting from a wafer comprising a front face divided into surface elements and with a given relief, and a back face, comprising steps consisting of: a) obtaining a support handle with a face acting as a bonding face; b) preparing the front face of the wafer, this preparation including incomplete planarisation of the front face of the wafer, to obtain a bonding energy E 0 with the bonding face of the support handle, between a first value corresponding to the minimum bonding energy compatible with the later thinning step, and a second value corresponding to the maximum bonding energy compatible with the subsequent desolidarisation operation, the bonding energy E 0 being such that E 0 =α.E, where E is the bonding energy that would be obtained if the front face of the wafer was completely planarised, α is the ratio between the incompletely planarised surface of the front face of the wafer and the surface of the front face of the wafer if it were completely planarised; c) solidarising the front face of the wafer on the bonding face of the support handle, by direct bonding; d) thinning the wafer starting from its back face until the thin layer is obtained; e) transferring the surface elements from the thin layer onto a usage support, involving separation from the support handle.