Method of separating surface layer of semiconductor crystal using a laser beam perpendicular to the separating plane
This invention provides two variations of methods of separating a surface layer of the semiconductor crystal. In the second variation of the method, pulse laser emission is generated; a focused laser beam is directed onto the crystal in such a way that focus is placed in the layer separation plane perpendicular the axis of the beam, a laser beam is moved in such a way that focus is moved in the layer separation plane with forming the non-overlapping local regions with a disturbed topology of the crystal structure and with reduced interatomic bonds, wherein the local regions is distributed over the whole plane, an external action disturbing the reduced interatomic bonds is applied to the separable layer. The invention allows separating flat lateral surface layers from semiconductor crystals, and thin semiconductor washes from cylindrical semiconductor boules.
1. A method of separating a surface layer of a monolithic semiconductor crystal or crystal boule, the monolithic semiconductor crystal or crystal boule having a top surface and a bottom surface, the method comprising:
generating a pulsed laser beam having a wavelength λ in a range of 2πch/E g , ≤λ≤c/v 0 , wherein E g , is a forbidden gap for the monolithic semiconductor crystal or crystal boule, v 0 is a frequency of an optical phonon for the monolithic semiconductor crystal or crystal boule, c is a velocity of light and h is a Plank constant;
directing the pulsed laser beam onto the top surface the monolithic semiconductor crystal or crystal boule and focusing the pulsed laser beam such that a focus of the pulsed laser beam is placed in a separation plane perpendicular to an axis of the pulsed laser beam, the separation plane located intermediate the top surface and the bottom surface;
moving the pulsed laser beam such that the focus of the pulsed laser beam is moved along an entirety of the separation plane while forming non-overlapping local regions in which structure of chemical bonds is disturbed, chemical interaction between atoms is reduced, and mechanical strength is decreased wherein the surface layer of the monolithic semiconductor crystal or crystal boule extends from the separation plane to the top surface;
applying an external action to the surface layer, the external action destroying the reduced chemical interaction between atoms of the non-overlapping local regions, wherein the destroying causes complete separation of the surface layer of the monolithic semiconductor crystal or crystal boule along the separation plane.
2. The method according to claim 1 , wherein the external action is a mechanical action.
3. The method according to claim 2 , wherein the mechanical action is a mechanical stress applied to the surface layer in relation to the monolithic semiconductor crystal or crystal boule.
4. The method according to claim 1 , wherein a distance between the centers of the non-overlapping local regions is 3%-30% of a thickness of the surface layer.
5. The method according to claim 1 , wherein the surface layer of the monolithic semiconductor crystal or crystal boule contains grown in layered semiconductor device structure.