Manufacturing method for controlling carrier lifetimes in semiconductor substrates that includes injection and annealing
A semiconductor device comprises: an n-type semiconductor substrate; a p-type anode region formed in the semiconductor substrate on its front surface side; an n-type field stop region formed in the semiconductor substrate on its rear surface side with protons as a donor; and an n-type cathode region formed in the semiconductor substrate to be closer to its rear surface than the field stop region is, wherein a concentration distribution of the donor in the field stop region in its depth direction has a first peak, and a second peak that is closer to the rear surface of the semiconductor substrate than the first peak is, and has a concentration lower than that of the first peak, and a carrier lifetime in at least a partial region between the anode region and the cathode region is longer than carrier lifetimes in the anode region.
1. A manufacturing method of manufacturing a semiconductor device having:
an n-type semiconductor substrate;
a p-type anode region formed in the semiconductor substrate on its front surface side;
an n-type field stop region formed in the semiconductor substrate on its rear surface side with protons as a donor; and
an n-type cathode region formed in the semiconductor substrate to be closer to its rear surface than the field stop region is, the method comprising:
injecting protons from the rear surface side of the semiconductor substrate such that a concentration distribution of the donor in the field stop region in its depth direction has a plurality of peaks including a first peak, and a second peak that is closer to the rear surface of the semiconductor substrate than the first peak is, and has a concentration lower than that of the first peak; and
annealing the semiconductor substrate to diffuse the protons so that a carrier lifetime in at least a partial region including the first peak becomes longer than a carrier lifetime in the anode region, wherein
the first peak is a peak closest to the front surface of the semiconductor substrate among the plurality of peaks,
in the annealing, a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is made longer than the carrier lifetime in the anode region, and
in the annealing, the region that has a carrier lifetime longer than that in the anode region is caused to extend toward the front surface side of the semiconductor substrate past a position at which the concentration distribution of the donor exhibits the first peak.
2. The manufacturing method according to claim 1 , further comprising irradiating the semiconductor substrate with a lifetime killer that shortens a carrier lifetime of the entire semiconductor substrate, wherein
the protons are diffused in the annealing to recover the carrier lifetime in a region where the protons are diffused.
3. The manufacturing method according to claim 2 , further comprising, between the injecting and the irradiating, annealing the semiconductor substrate.
4. The manufacturing method according to claim 2 , wherein in the irradiating, the semiconductor substrate is irradiated with an electron ray.
5. The manufacturing method according to claim 1 , wherein a position of the first peak is adjusted according to a withstand voltage class of the semiconductor device.
6. The manufacturing method according to claim 1 , wherein in the annealing, the carrier lifetime in at least a partial region between the anode region and the cathode region is made longer than a carrier lifetime in the cathode region.
7. The manufacturing method according to claim 1 , further comprising irradiating the rear surface side of the semiconductor substrate with a local lifetime killer that shortens the carrier lifetime.
8. The manufacturing method according to claim 1 , further comprising irradiating, with a local lifetime killer that shortens the carrier lifetime, the region that: extends toward the front surface side of the semiconductor substrate past a position at which the concentration distribution of the donor exhibits the first peak; and has a carrier lifetime longer than that of the anode region.