Patent ID: 8021959

Claim:
A method for forming a plurality of thin layers from a microtechnological donor substrate, the method comprising cycles including: forming a buried weakened layer by ion implantation below a free face of the donor substrate, the material thickness contained between the free face and the buried weakened layer defining a thickness of a thin layer; placing the donor substrate in intimate contact with a handle substrate by molecular adhesion between the free face of the donor substrate and a free face of the handle substrate; inducing a fracture along the buried weakened layer so as to release the thin layer from a remainder of the donor substrate, while exposing respective faces of the thin layer and the remainder of the donor substrate; treating the exposed face of the remainder of the donor substrate such that the remainder constitutes a new donor substrate, wherein treating the exposed face comprises planarizing the exposed face of the remainder of the donor substrate by placing the exposed face in a bath and applying ultrasound at a frequency of between 10 kHz and 80 kHz, and under bath conditions suitable for causing cavitation along the exposed face and for a time duration that eliminates residual non-transferred zones on the exposed face after inducing the fracture and without substantially degrading the exposed face, so as to form a planarized exposed face.