Method for manufacturing a contact on a silicon carbide semiconductor substrate, and silicon carbide semiconductor device
The present disclosure generally relates to a method of manufacturing a contact on a silicon carbide semiconductor substrate wherein the method comprises providing a 4H—SiC semiconductor substrate, irradiating a surface area of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam, thereby generating a phase separation of the surface area comprising at least a 3C—SiC layer, and depositing a contact material onto the 3C—SiC layer to form a contact layer on the semiconductor substrate. The disclosure further relates to a silicon carbide semiconductor device with an Ohmic contact comprising a 4H—SiC semiconductor substrate, a 3C—SiC layer, and a contact layer directly in contact with the 3C—SiC layer at the semiconductor surface.
1 . A method for manufacturing a contact on a silicon carbide semiconductor substrate, the method comprising:
providing a 4H—SiC semiconductor substrate;
directly irradiating a surface area, having a crystalline structure, of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam to generate a phase separation of the surface area comprising at least a 3C—SiC layer; and
depositing a contact material onto the 3C—SiC layer to form a contact layer on the 4H—SiC semiconductor substrate.
2 . The method of claim 1 , wherein before irradiation with the first thermal annealing laser beam:
no further layer is applied to the 4H—SiC semiconductor substrate.
3 . The method of claim 1 , wherein before irradiation with the first thermal annealing laser beam, a second layer applied to the 4H—SiC semiconductor substrate has a maximum absorption of 10%.
4 . The method of claim 3 , wherein the second layer is at least one of a heat-trapping layer or an antireflective layer.
5 . The method of claim 1 , wherein the irradiation with the first laser thermal annealing laser beam is a double shot annealing.
6 . The method of claim 1 , wherein the contact material comprises at least one of a metal, metal silicide, metal carbide, or ternary silicide and carbide.
7 . The method of claim 1 , wherein the contact material has a work-function smaller than 4.1 eV.
8 . The method of claim 1 , wherein the contact material is titanium or nickel silicide.
9 . The method of claim 1 , wherein the 4H—SiC semiconductor substrate has a surface roughness Rq of less than 80 nm.
10 . The method of claim 1 , wherein before irradiation, the 4H—SiC semiconductor substrate is roughened with grinding to induce crystal damages in the 4H—SiC semiconductor substrate.
11 . The method of claim 1 , wherein the contact layer is irradiated by a second laser thermal annealing pulse on the contact material contacting the 3C—SiC layer.
12 . The method of claim 1 , wherein a second metal layer is deposited on the contact layer.
13 . The method of claim 1 , wherein the crystalline structure of the surface area is a monocrystalline structure.
14 . The method of claim 1 , wherein the 3C—SiC layer has a polycrystalline structure.
15 . A method for manufacturing a contact on a silicon carbide semiconductor substrate, the method comprising:
providing a 4H—SiC semiconductor substrate;
directly irradiating a surface area, having a crystalline structure, of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam to generate a phase separation of the surface area comprising at least a 3C—SiC layer comprising a silicon portion and a carbon portion;
removing at least some of the silicon portion;
removing at least some of the carbon portion; and
depositing a contact material onto the 3C—SiC layer to form a contact layer on the 4H—SiC semiconductor substrate.
16 . The method of claim 15 , wherein the removing at least some of the carbon portion is performed via an oxygen plasma etching treatment.
17 . The method of claim 15 , wherein the removing at least some of the silicon portion is performed via an oxidizing treatment.
18 . A silicon carbide semiconductor device, comprising
a 4H—SiC semiconductor substrate;
a 3C—SiC layer; and
a contact layer in contact with the 3C—SiC layer at a surface of the 4H—SiC semiconductor substrate, wherein the contact layer is a backside contact.
19 . The silicon carbide semiconductor device of claim 18 , wherein a second metal layer is deposited above the contact layer.
20 . The silicon carbide semiconductor device of claim 18 , wherein the 4H—SiC semiconductor substrate comprises a plurality of device structures at a frontside surface.