Semiconductor device and method for producing semiconductor device
Hydrogen atoms and crystal defects are introduced into an n− semiconductor substrate by proton implantation. The crystal defects are generated in the n− semiconductor substrate by electron beam irradiation before or after the proton implantation. Then, a heat treatment for generating donors is performed. The amount of crystal defects is appropriately controlled during the heat treatment for generating donors to increase a donor generation rate. In addition, when the heat treatment for generating donors ends, the crystal defects formed by the electron beam irradiation and the proton implantation are recovered and controlled to an appropriate amount of crystal defects. Therefore, for example, it is possible to improve a breakdown voltage and reduce a leakage current.
1. A semiconductor device comprising:
a first-conduction-type semiconductor substrate including a first-conduction-type drift layer;
a first second-conduction-type semiconductor layer that is provided in one main surface of the semiconductor substrate and is adjacent to the drift layer;
a second first-conduction-type or second-conduction-type semiconductor layer that is provided in the other main surface of the semiconductor substrate;
one or more first-conduction-type high-concentration layer that are provided between the drift layer and the second semiconductor layer and have a higher impurity concentration than the drift layer;
a first crystal defect region including the drift layer; and
a second crystal defect region that includes the high-concentration layer, is provided adjacent to the first crystal defect region, and has a lower defect concentration than the first crystal defect region.
2. The semiconductor device according to claim 1 , wherein the high-concentration layer has a hydrogen-induced donor.
3. The semiconductor device according to claim 1 , wherein a carrier lifetime of the second crystal defect region is longer than a carrier lifetime of the first crystal defect region.
4. The semiconductor device according to claim 1 , wherein a carrier lifetime of the second crystal defect region increases from one main surface to the other main surface of the semiconductor substrate.
5. The semiconductor device according to claim 1 , wherein the first crystal defect region includes a vacancy and a divacancy as the main crystal defects.
6. The semiconductor device according to claim 1 , wherein the second crystal defect region includes a composite defect of a vacancy, oxygen, and hydrogen as the main crystal defect.
7. The semiconductor device according to claim 1 , wherein the second crystal defect region has a dangling bond which is terminated by hydrogen.
8. The semiconductor device according to claim 1 , wherein the distance of the high-concentration layer adjacent to the drift layer from the other main surface of the semiconductor substrate is at least 15 μm.
9. The semiconductor device according to claim 1 , wherein, when q is an elementary charge, N d is the average concentration of the drift layer, ε S is the permittivity of the semiconductor substrate, V rate is a rated voltage, J F is rated current density, and v sat is a saturated velocity in which a carrier speed is saturated with predetermined electric field intensity, a distance index L is represented by the following Expression (1):
L
=
q
ɛ
S
V
rate
(
J
F
qv
sat
+
N
d
)
[
Expression
(
1
)
]
when the depth of a position, where the carrier concentration of the high-concentration layer which is adjacent to the first semiconductor layer with the drift layer interposed therebetween is the maximum, from the other main surface of the semiconductor substrate is X and the thickness of the semiconductor substrate is W0, X=W0−γL is established and γ is in the range of 0.7 to 1.6.
10. The semiconductor device according to claim 1 , wherein a carrier lifetime of the first crystal defect region is uniform in a depth direction.