Semiconductor device, method for manufacturing the same, and power conversion system
An anode electrode and a cathode electrode formed on a silicon semiconductor substrate, p-type layer formed next to the anode electrode, an n-type layer formed next to the cathode electrode by a V-group element being diffused, an n − layer formed between the p-type layer and the n-type layer, and an n-buffer layer formed between the n − layer and the n-type layer and containing oxygen are provided and an oxygen concentration in an area of a width of at least 30 μm from a surface on a side of the n-type layer of the cathode electrode toward the anode electrode is set to 1×10 17 cm −3 or more and also the oxygen concentration of the n − layer in a position in contact with the p-type layer is set to less than 3×10 17 cm −3 .
1. A semiconductor device comprising:
an anode electrode formed on one side of a silicon semiconductor substrate;
a cathode electrode formed on the other side of the silicon semiconductor substrate;
a p-type layer formed next to the anode electrode;
an n-type layer formed next to the cathode electrode by a V-group element being diffused;
an n − layer formed between the p-type layer and the n-type layer; and
an n-buffer layer formed between the n − layer and the n-type layer and containing oxygen, wherein
an oxygen concentration in an area of a width of at least 30 μm from a surface on a side of the n-type layer of the cathode electrode toward the anode electrode is 1×10 17 cm −3 or more and
the oxygen concentration of the n − layer in a position in contact with the p-type layer is less than 3×10 17 cm −3 .
2. The semiconductor device according to claim 1 , wherein
a thickness of the n-type layer is 50 μm or more and the oxygen concentration in the area of the width of at least 30 μm from the surface on the side of the n-type layer of the cathode electrode toward the anode electrode is 3×10 17 cm −3 or more and less than 1×10 18 cm −3 .
3. The semiconductor device according to claim 1 , further comprising:
a second n-buffer layer between the n-type layer and the n-buffer layer formed by the V-group element being diffused, wherein
the oxygen concentration of the second n-buffer layer is higher than an n-type carrier concentration of the second n-buffer layer,
a thermal donor concentration of the second n-buffer layer is higher than that of the n − layer, and
the thermal donor concentration of the second n-buffer layer is lower than the n-type carrier concentration of the V-group element of the second n-buffer layer.
4. The semiconductor device according to claim 1 , wherein
the n-buffer layer contains oxygen continuously throughout the area of a thickness of 30 μm.
5. The semiconductor device according to claim 4 , wherein
the n-buffer layer has an oxygen concentration decreasing area in which the oxygen concentration decreases toward a cathode side throughout the area of at least 10 μm and
the oxygen concentration in the oxygen concentration decreasing area is 5×10 17 cm −3 or more and 1×10 18 cm −3 or less.
6. The semiconductor device according to claim 4 , wherein
the oxygen concentration of the n-buffer layer in a position 30 μm away from the n-type layer is higher than that of the n-type layer.
7. The semiconductor device according to claim 4 , further comprising:
a second n-buffer layer between the n-type layer and the n-buffer layer formed by the V-group element being diffused.
8. The semiconductor device according to claim 7 , wherein
a maximum value of an n-type carrier concentration of the n-type layer is higher than the oxygen concentration of the n-type layer,
the maximum value of the n-type carrier concentration of the second n-buffer layer is lower than the oxygen concentration of the n-type layer,
the maximum value of the n-type carrier concentration of the n-buffer layer is lower than the maximum value of the n-type carrier concentration of the second n-buffer layer, and
the maximum value of the n-type carrier concentration of the n − layer is lower than the maximum value of the n-type carrier concentration of the n-buffer layer.
9. The semiconductor device according to claim 4 , wherein
the thickness of the n-type layer is 50 μm or more.
10. A method for manufacturing a semiconductor device including:
an anode electrode formed on one side of a silicon semiconductor substrate;
a cathode electrode formed on the other side of the silicon semiconductor substrate;
a p-type layer formed next to the anode electrode;
an n-type layer formed next to the cathode electrode by a V-group element being diffused;
an n − layer formed between the p-type layer and the n-type layer; and
an n-buffer layer formed between the n − layer and the n-type layer and containing oxygen throughout an area of a thickness of 30 μm or more, wherein
an n-type carrier concentration of the n-buffer layer is higher than that of the n − layer and is 1×10 15 cm −3 ,
an oxygen concentration in the area of a width of at least 30 μm from a surface on a side of the n-type layer of the cathode electrode toward the anode electrode is 1×10 17 cm −3 or more and 1×10 18 cm −3 or less, and
the oxygen concentration of the n − layer in a position in contact with the p-type layer is less than 3×10 17 cm −3 , the method comprising:
removing an oxygen thermal donor by heat treatment at 800° C. or higher;
forming the anode electrode; and
generating the oxygen thermal donor by the heat treatment at 400° C. or higher.
11. The method for manufacturing a semiconductor device according to claim 10 , wherein
a layer containing the V-group element is formed, the layer is thermally treated in an atmosphere containing oxygen, the V-group element and the oxygen are diffused simultaneously, and then one side thereof is removed.
12. A power conversion system including:
a first semiconductor switching element and a second semiconductor switching element connected in series; and
diodes, each of which connected in anti-parallel with the first semiconductor switching element or the second semiconductor switching element, wherein
the diodes are semiconductor devices according to claim 1 .