Method of laser separation of the epitaxial film or of the epitaxial film layer from the growth substrate of the epitaxial semiconductor structure (variations)

Abstract

The present invention proposes variations of the laser separation method allowing separating homoepitaxial films from the substrates made from the same crystalline material as the epitaxial film. This new method of laser separation is based on using the selective doping of the substrate and epitaxial film with fine donor and acceptor impurities. In selective doping, concentration of free carries in the epitaxial film and substrate may essentially differ and this can lead to strong difference between the light absorption factors in the infrared region near the residual beams region where free carriers and phonon-plasmon interaction of the optical phonons with free carriers make an essential contribution to infrared absorption of the optical phonons. With the appropriate selection of the doping levels and frequency of infrared laser radiation it is possible to achieve that laser radiation is absorbed in general in the region of strong doping near the interface substrate-homoepitaxial film. When scanning the interface substrate-homoepitaxial film with the focused laser beam of sufficient power, thermal decomposition of the semiconductor crystal takes place with subsequent separation of the homoepitaxial film. The advantage of the proposed variations of the method for laser separation of epitaxial films in comparison with the known ones is in that it allows to separate homoepitaxial films from the substrates, i.e., homoepitaxial films having the same width of the forbidden gap as the initial semiconductor substrate has. The proposed variations of the method can be used for separation of the epitaxial films. Besides, the proposed method allows using the high-effective and inexpensive infrared gas silicon dioxide COor silicon oxide CO lasers for separation of the epitaxial films.