Semiconductor device and semiconductor device manufacturing method
A front surface element structure is formed on the front surface side of an n − -type semiconductor substrate. Then defects are formed throughout an n − -type semiconductor substrate to adjust a carrier lifetime. Hydrogen ions are ion-implanted from a rear surface side of the n − -type semiconductor substrate, and a hydrogen implanted region having a hydrogen concentration higher than a hydrogen concentration of a bulk substrate is formed in the surface layer of a rear surface side of the n − -type semiconductor substrate.
1. A semiconductor device in which a lifetime of carriers is locally controlled, comprising:
a first conductivity type semiconductor substrate having defects, the defects having dangling bonds generated by breaking of inter-atomic bonds of atoms constituting the semiconductor substrate, the semiconductor substrate having a rear surface side and a front surface side, the rear surface side being closer to a rear surface of the semiconductor substrate than is the front surface side, the semiconductor substrate including:
an upper region disposed in the semiconductor substrate closer to the front surface than is the rear surface,
a high hydrogen concentration region having hydrogen atoms and being formed in a lowermost portion of the rear surface side of the semiconductor substrate, the high hydrogen concentration region having a hydrogen concentration higher than a hydrogen concentration of the upper region,
wherein in the high hydrogen concentration region,
defects are fewer than defects in the upper region, based on hydrogen atoms in the high hydrogen concentration region being bonded with dangling bonds of the atoms constituting the semiconductor substrate,
a lifetime of carriers is longer than a lifetime of carriers in the upper region, and
a highest peak of a concentration of the hydrogen in the high hydrogen concentration region is located closer to the rear surface than is an interface between the high hydrogen concentration region and the upper region.
2. The semiconductor device according to claim 1 , wherein a carrier concentration in the high hydrogen concentration region is higher than a carrier concentration in the upper region.
3. The semiconductor device according to claim 2 , wherein an increase of the carrier concentration in the high hydrogen concentration region relative to the upper region is due to a hydrogen induced donor.
4. The semiconductor device according to claim 1 , wherein the dangling bonds are terminated by the hydrogen atoms in the high hydrogen concentration region.
5. The semiconductor device according to claim 1 , further comprising:
a second conductivity type layer formed on a surface layer of the upper region; and
a contact layer that is of the first conductivity type or the second conductivity type and formed on a surface layer of the rear surface side of the semiconductor substrate.
6. The semiconductor device according to claim 5 , wherein
the semiconductor device is a diode,
the contact layer is of the first conductivity type, and
the high hydrogen concentration region is a field stop layer of the diode.
7. The semiconductor device according to claim 5 , wherein
the semiconductor device is an insulated gate bipolar transistor that includes an insulated gate, constituted by a metal-oxide film-semiconductor, on the surface of the second conductivity type layer,
the contact layer is of the second conductivity type, and
the high hydrogen concentration region is a field stop layer of the insulated gate bipolar transistor.
8. The semiconductor device according to claim 7 , wherein the field stop layer includes a plurality of field stop layers, further wherein
a lifetime of carriers in the upper region is shorter than a lifetime of carriers in a portion of the rear surface side of the semiconductor substrate,
said portion is shallower than the field stop layers so that the field stop layers are located further away from the rear surface of the semiconductor substrate than is said portion.
9. The semiconductor device according to claim 1 , wherein the hydrogen concentration in the high hydrogen concentration region is higher than a hydrogen concentration of bulk single crystals of the substrate.
10. The semiconductor device of claim 1 , further comprising a low-carrier-lifetime region in the rear surface side of the semiconductor substrate,
wherein a lifetime of carriers in the low-carrier-lifetime region is shorter than in the high hydrogen concentration region.
11. The semiconductor device of claim 10 , wherein the low-carrier-lifetime region is closer to the rear surface of the semiconductor substrate than the high hydrogen concentration region.
12. The semiconductor device of claim 11 , wherein the low-carrier-lifetime region contains helium (He).
13. The semiconductor device of claim 1 , wherein the high hydrogen concentration region includes hydrogen induced donors, and a donor concentration of the hydrogen induced donors in the high hydrogen concentration region is greater than a donor concentration of the upper region.