Transistor with buried p-field termination region
In one aspect, a method of fabricating a transistor includes depositing a first epitaxial layer, depositing a second epitaxial layer on the first epitaxial layer, implanting the second epitaxial layer to form a p-field termination region, depositing a third epitaxial layer on the p-field termination layer and forming trenches in the third epitaxial layer. The trenches include a trench gate of the transistor and a termination trench.
1. A method of fabricating a transistor, comprising:
depositing a first epitaxial layer having a n-type doping onto a doped substrate having a p+-type doping, wherein the doped substrate is a collector of the transistor;
depositing a second epitaxial layer having n-type doping on the first epitaxial layer;
implanting the second epitaxial layer to form a p-field termination region;
depositing a third epitaxial layer having n-type doping directly on the p-field termination region; and
forming trenches in the third epitaxial layer, wherein the trenches comprise a trench gate of the transistor and a termination trench.
2. The method of claim 1 , further comprising, after depositing the third epitaxial layer, implanting the third epitaxial layer to form a base region.
3. The method of claim 2 , wherein implanting the third epitaxial layer comprises implanting the third epitaxial layer with boron.
4. The method of claim 3 , further comprising heating the base region to drive the boron further in to the third epitaxial layer.
5. The method of claim 4 , wherein heating the base region comprises heating the base region to 1150° C. for more than 5 hours.
6. The method of claim 1 , wherein implanting the second epitaxial layer to form the p-field termination region comprises implanting the second epitaxial layer with boron.
7. The method of claim 1 , further comprising:
after depositing the second epitaxial layer, growing a silicon dioxide on the second epitaxial layer; and
implanting boron through the silicon dioxide into the second epitaxial layer.
8. The method of claim 7 , further comprising:
after depositing the third epitaxial layer, growing a silicon dioxide on the second epitaxial layer; and
implanting boron through the silicon dioxide into the third epitaxial layer.
9. The method of claim 1 , wherein the termination trench extends through the third epitaxial layer and into and ends in the p-field termination region.
10. The method of claim 1 , wherein the second epitaxial layer has a thickness greater than a thickness of the first epitaxial layer.
11. The method of claim 10 , wherein the thickness of the second epitaxial layer is at least twice the thickness of the first epitaxial layer.