Method for manufacturing a power semiconductor device
View Patent ↗An exemplary method is disclosed for manufacturing a power semiconductor device which has a first electrical contact on a first main side and a second electrical contact on a second main side opposite the first main side and at least a two-layer structure with layers of different conductivity types, and includes providing an n-doped wafer and creating a surface layer of palladium particles on the first main side. The wafer is irradiated on the first main side with ions. Afterwards, the palladium particles are diffused into the wafer at a temperature of not more than 750° C., by which diffusion a first p-doped layer is created. Then, the first and second electrical contacts are created. At least the irradiation with ions is performed through a mask.
1. A method for manufacturing a power semiconductor device, which comprises a first electrical contact on a first main side and a second electrical contact on a second main side opposite the first main side and at least a two-layer structure with layers of different conductivity types, the method comprising:
providing an n-doped wafer;
creating a surface layer of palladium particles on the first main side of the n-doped wafer;
irradiating the wafer on the first main side with ions;
after irradiating the wafer with ions, diffusing the palladium particles into the wafer at a temperature of not more than 750° C., by which diffusion a first p-doped layer is created; and
after diffusing the palladium particles, creating the first and second electrical contacts,
wherein during at least the irradiating step, the irradiation ions enter the wafer through an opening in a first mask, or at least one of radiation ion energy and intensity of the irradiation ions is lowered by at least one of the surface layer and the first mask.
2. The method according to claim 1 , wherein parts of the wafer with doping form a base layer, the method comprising:
creating a second p-doped layer on the first main side before the creation of the surface layer and before irradiating; and
diffusing particles for the creation of the first layer into the wafer into a depth below the second p-doped layer.
3. The method according to claim 1 , wherein the surface layer is created before the irradiating is performed.
4. The method according to claim 1 , wherein the thickness of the surface layer is between 1 nm and 10 μm.
5. The method according to claim 1 , wherein the irradiating step is performed with at least one of protons, helium ions, other inert gas ions and electrons.
6. The method according to claim 1 , wherein the irradiating step is performed with protons and a dose in a range between 1*10 11 and 1*10 14 cm −2 .
7. The method according to claim 1 , wherein the diffusing step is performed at least one of a temperature of at least 400° C., and with a diffusion time between 5 and 60 min.
8. The method according to claim 1 , comprising at least one of: removing the surface layer after diffusion; and retaining the surface layer as part of the first electrical contact.
9. The method according to claim 1 , wherein the semiconductor power device is one of a diode, transistor, thyristor and a MOSFET.
10. The method according to claim 1 , wherein the surface layer is used as a second mask for the irradiating step.
11. The method according to claim 10 , wherein the thickness of the surface layer is constant.
12. The method according to claim 1 , wherein the first mask has a varying thickness.
13. The method according to claim 1 , wherein first layers are created on the first main side and on the second main side.
14. The method according to claim 1 , the irradiating step is performed before creation of the surface layer.
15. The method according to claim 1 , wherein the irradiating step is performed with at least one of helium ions, and other insert gas ions, and with a dose in a range between 1*10 10 and 1*10 13 cm −2 .
16. The method according to claim 1 , wherein the irradiating step is performed with electrons and a dose in a range between 1*10 13 and 1*10 17 cm −2 .
17. The method according to claim 1 , wherein the diffusion step is performed at least one of a temperature of between 600 and 650° C., and with a diffusion time between 5 and 60 min.
18. The method according to claim 1 , wherein the diffusion step is performed at least one of a temperature of between 600 and 700° C., and a diffusion time between 5 and 60 min.
19. The method according to claim 11 , wherein the thickness of the surface layer is up to 150 μm.
20. The method according to claim 10 , wherein the first mask has a varying thickness.
21. The method according to claim 5 , wherein the surface layer is used as a second mask for the irradiating step.
22. The method according to claim 6 , wherein the surface layer is used as a second mask for the irradiating step.
23. The method according to claim 15 , wherein the surface layer is used as a second mask for the irradiating step.
24. The method according to claim 16 , wherein the surface layer is used as a second mask for the irradiating step.