Silicon carbide semiconductor device and method for manufacturing the same
A silicon carbide semiconductor device includes: a silicon carbide layer, a reaction layer which is in contact with the silicon carbide layer, a conductive oxidation layer which is in contact with the reaction layer, and an electrode layer which is formed over the reaction layer with the conductive oxidation layer interposed therebetween. A thickness of the conductive oxidation layer falls within a range of 0.3 nm to 2.25 nm.
1. A silicon carbide semiconductor device comprising:
a silicon carbide layer;
a reaction layer and a conductive oxidation layer which is in contact with the reaction layer, the reaction layer and the conductive oxidation layer being formed by executing the steps in the following order: a conductive layer forming step where a conductive layer is formed on the silicon carbide layer; a heat treatment step where the silicon carbide layer and the conductive layer are made to react with each other thus forming the reaction layer which is in contact with the silicon carbide layer and a silicide layer which is present on the reaction layer; a first plasma ashing step where a carbon component which the silicide layer contains is removed; an etching step where at least a portion of the silicide layer is removed using an acid thus exposing at least a portion of a surface of the reaction layer; and a second plasma ashing step where a carbon component which remains on the reaction layer is removed and a conductive oxidation layer is formed on the reaction layer, and
an electrode layer which is formed over the reaction layer with the conductive oxidation layer interposed therebetween.
2. The silicon carbide semiconductor device according to claim 1 , wherein a thickness of the conductive oxidation layer falls within a range of 0.3 nm to 2.25 nm.
3. The silicon carbide semiconductor device according to claim 1 , wherein the acids are a hydrochloric acid, a nitric acid and a hydrofluoric acid.
4. A method for manufacturing a silicon carbide semiconductor device for manufacturing the silicon carbide semiconductor device; the method comprising the steps in the following order:
a conductive layer forming step where the conductive layer is formed on a silicon carbide
layer;
a heat treatment step where the silicon carbide layer and the conductive layer are made to react with each other thus forming a reaction layer which is in contact with the silicon carbide layer and a silicide layer which is present on the reaction layer;
a first plasma ashing step where a carbon component which the silicide layer contains is removed;
an etching step where at least a portion of the silicide layer is removed using an acid thus exposing at least a portion of a surface of the reaction layer;
a second plasma ashing step where a carbon component which remains on the reaction layer is removed and a conductive oxidation layer which is in contact with the reaction layer is formed on the reaction layer; and
an electrode layer forming step where an electrode layer is formed over the exposed reaction layer with the conductive oxidation layer interposed therebetween.
5. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein a thickness of the conductive oxidation layer falls within a range of 0.3 nm to 2.25 nm.
6. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein
an oxidation layer which includes the conductive oxidation layer is formed on the reaction layer in the second plasma ashing step, and
the method further comprises a second etching step where the oxidation layer formed in the second plasma ashing step is made thin so as to expose the conductive oxidation layer between the second plasma ashing step and the electrode layer forming step.
7. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein
an oxidation layer which includes the conductive oxidation layer is formed on the reaction layer in the second plasma ashing step, and
the method further comprises a cleaning step where the oxidation layer formed in the second plasma ashing step is made thin so as to expose the conductive oxidation layer between the second plasma ashing step and the electrode layer forming step.
8. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein an oxidation layer which is constituted of only the conductive oxidation layer is formed over the reaction layer in the second plasma ashing step.
9. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein the second plasma ashing step is carried out using any one of an oxygen gas and a mixed gas of an oxygen gas and a hydrogen gas.
10. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein the etching step is carried out using a hydrochloric acid, a nitric acid and a hydrofluoric acid.
11. The method for manufacturing a silicon carbide semiconductor device according to claim 10 , wherein the etching step is carried out using an etchant which contains a hydrochloric acid, a nitric acid and a hydrofluoric acid.
12. The method for manufacturing a silicon carbide semiconductor device according to claim 11 , wherein a content ratio among the hydrochloric acid, the nitric acid and the hydrofluoric acid which the etchant contains is set such that, assuming the content of the nitric acid as 100 mol, the content of the hydrochloric acid falls within a range of 300 mol to 500 mol, and the content of the hydrofluoric acid falls within a range of 0.1 mol to 5 mol.
13. The method for manufacturing a silicon carbide semiconductor device according to claim 10 , wherein
the etching step includes an etching step where an etchant A containing a hydrochloric acid is used and an etching step where an etchant B containing a nitric acid and a hydrofluoric acid is used.
14. The method for manufacturing a silicon carbide semiconductor device according to claim 13 , wherein
the content ratio between the nitric acid and the hydrofluoric acid which the etchant B contains is set such that, assuming the content of the nitric acid as 100 mol, the content of the hydrofluoric acid falls within a range of 0.1 mol to 5 mol.
15. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein
the first plasma ashing step is carried out using any one of an oxygen gas, a hydrogen gas and a mixed gas of an oxygen gas and a hydrogen gas.