Semiconductor device and manufacturing method thereof
View Patent ↗An object is to provide a transistor in which the state of an interface between an oxide semiconductor layer and an insulating film (gate insulating layer) in contact with the oxide semiconductor layer is favorable; and a method for manufacturing the transistor. In order to obtain the transistor, nitrogen is added to a region of the oxide semiconductor layer in the vicinity of the interface with the gate insulating layer. Specifically, a concentration gradient of nitrogen is formed in the oxide semiconductor layer, and a region containing much nitrogen is provided at the interface with the gate insulating layer. By the addition of nitrogen, a region with high crystallinity can be formed in the region of the oxide semiconductor layer in the vicinity of the interface with the gate insulating layer, so that a stable interface state can be obtained.
1. A semiconductor device comprising:
a substrate;
a base insulating layer over the substrate;
an oxide semiconductor layer over the base insulating layer;
a gate insulating layer over the oxide semiconductor layer; and
a gate electrode layer over the gate insulating layer;
wherein the oxide semiconductor layer has a concentration gradient of nitrogen, which becomes higher as closer to the gate insulating layer, and has a concentration gradient of oxygen, which becomes higher as closer to the base insulating layer.
2. The semiconductor device according to claim 1 , wherein the oxide semiconductor layer is non-single-crystalline.
3. The semiconductor device according to claim 1 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer has higher crystallinity than other regions of the oxide semiconductor layer.
4. The semiconductor device according to claim 1 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer has a wurtzite crystal structure.
5. The semiconductor device according to claim 1 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer is higher than or equal to 1×10 20 /cm 3 and lower than 7 atomic %.
6. The semiconductor device according to claim 1 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the base insulating layer is higher than or equal to 1×10 17 /cm 3 and lower than 5×10 19 /cm 3 .
7. A semiconductor device comprising:
a substrate;
a gate electrode layer over the substrate;
a first insulating layer in contact with the gate electrode layer;
an oxide semiconductor layer in contact with the first insulating layer; and
a second insulating layer in contact with the oxide semiconductor layer,
wherein the oxide semiconductor layer has a concentration gradient of nitrogen, which becomes higher as closer to the first insulating layer, and has a concentration gradient of oxygen, which becomes higher, as closer to the second insulating layer.
8. The semiconductor device according to claim 7 , wherein the oxide semiconductor layer is non-single-crystalline.
9. The semiconductor device according to claim 7 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the first insulating layer has higher crystallinity than other regions of the oxide semiconductor layer.
10. The semiconductor device according to claim 7 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the first insulating layer has a wurtzite crystal structure.
11. The semiconductor device according to claim 7 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the first insulating layer is higher than or equal to 1×10 20 /cm 3 and lower than 7 atomic %.
12. The semiconductor device according to claim 7 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the second insulating layer is higher than or equal to 1×10 17 /cm 3 and lower than 5×10 19 /cm 3 .
13. A semiconductor device comprising:
a substrate;
a gate electrode layer over the substrate;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer over the gate insulating layer; and
a protective insulating layer over the oxide semiconductor layer;
wherein the oxide semiconductor layer has a concentration gradient of nitrogen, which becomes higher as closer to the gate insulating layer, and has a concentration gradient of oxygen, which becomes higher as closer to the protective insulating layer.
14. The semiconductor device according to claim 13 , wherein the oxide semiconductor layer is non-single-crystalline.
15. The semiconductor device according to claim 13 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer has higher crystallinity than other regions of the oxide semiconductor layer.
16. The semiconductor device according to claim 13 , wherein a region of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer has a wurtzite crystal structure.
17. The semiconductor device according to claim 13 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the gate insulating layer is higher than or equal to 1×10 20 /cm 3 and lower than 7 atomic %.
18. The semiconductor device according to claim 13 , wherein a nitrogen concentration of the oxide semiconductor layer in a vicinity of an interface with the protective insulating layer is higher than or equal to 1×10 17 /cm 3 and lower than 5×10 19 /cm 3 .
19. The semiconductor device according to claim 13 , wherein a thickness of the protective insulating layer is greater than or equal to 50 nm.
20. The semiconductor device according to claim 13 , further comprising a layer containing nitrogen between the gate electrode layer and the gate insulating layer,
wherein the layer containing nitrogen is in contact with the gate insulating layer.