Patent ID: 10755933

Abstract:
Laser light of a short-wavelength laser is irradiated from a rear surface of an n−-type semiconductor substrate, activating a p+-type collector region and an n+-type cathode region. At this time, a surface layer at the rear surface of the n−-type semiconductor substrate is melted and recrystallized, eliminating amorphous parts. Thereafter, laser light of a long-wavelength laser is irradiated from the rear surface of the n−-type semiconductor substrate and an n-type FS region is activated. Substantially no amorphous parts exist in the surface layer at the rear surface of the n−-type semiconductor substrate. Therefore, decreases in the absorption rate and increases in the reflection rate of the laser light of the long-wavelength laser are suppressed and heat from the laser light of the long-wavelength laser is transmitted to the n-type FS region, enabling the n-type FS region to be assuredly activated by laser annealing using lower energy.