Silicon carbide device with trench gate structure and method of manufacturing
A silicon carbide device includes a silicon carbide body having a hexagonal crystal lattice with a c-plane and with further main planes. The further main planes include a-planes and m-planes. A mean surface plane of the silicon carbide body is tilted to the c-plane by an off-axis angle. The silicon carbide body includes a columnar portion with column sidewalls. At least three of the column sidewalls are oriented along a respective one of the further main planes. A trench gate structure is in contact with the at least three of the column sidewalls.
1. A silicon carbide device, comprising:
a silicon carbide body having a hexagonal crystal lattice with a c-plane and further main planes, wherein the further main planes comprise a-planes and m-planes, wherein a lateral mean surface plane of the silicon carbide body is tilted to the c-plane by an off-axis angle, wherein the silicon carbide body comprises a columnar portion with column sidewalls, wherein at least three of the column sidewalls are oriented along a respective one of the further main planes; and
a trench gate structure in contact with the at least three of the column sidewalls.
2. The silicon carbide device of claim 1 ,
wherein for each of the at least three of the column sidewalls, the c-plane and the column sidewall form a respective first intersection line and the c-plane and the further main plane that is oriented to the column sidewall form a respective second intersection line, and
wherein an absolute value of an in-plane tilt angle between the first intersection line and the second intersection line is in a range from 0 degrees to 2 degrees.
3. The silicon carbide device of claim 1 , wherein for each of the at least three of the column sidewalls, an absolute value of a vertical tilt angle between the column sidewall and the further main plane that is oriented to the column sidewall is in a range from 0 degrees to the degree of the off-axis angle.
4. The silicon carbide device of claim 3 , wherein the absolute values of the vertical tilt angles are in a range from 0 degrees to half of the degree of the off-axis angle.
5. The silicon carbide device of claim 1 , wherein the at least three column sidewalls neighbor each other.
6. The silicon carbide device of claim 1 ,
wherein at least four of the column sidewalls are oriented along a respective one of the further main planes, and
wherein the gate structure is in contact with the at least four of the column sidewalls.
7. The silicon carbide device of claim 1 , wherein a cross-section of the columnar portion in the c-plane forms a hexagon.
8. The silicon carbide device of claim 1 , wherein the gate structure forms a grid laterally separating neighboring columnar portions.
9. The silicon carbide device of claim 1 ,
wherein the columnar portion comprises a source region of a first conductivity type and a body region of a second conductivity type,
wherein the source region is formed between a first surface of the silicon carbide body and the body region, and
wherein the source region is in contact with the at least three of the column sidewalls.
10. The silicon carbide device of claim 9 ,
wherein the silicon carbide body further comprises a voltage sustaining layer, and
wherein the columnar portion is formed between the first surface and the voltage sustaining layer.
11. The silicon carbide device of claim 10 , further comprising:
a deep shielding region of the second conductivity type and extending from a side oriented to the body region into the voltage sustaining layer,
wherein the deep shielding region is at a lateral distance to the gate structure, and
wherein a distance between the first surface and a local dopant maximum in the deep shielding region is greater than a vertical extension of the gate structure.
12. The silicon carbide device of claim 10 , further comprising:
a shielding connection region of the second conductivity type and extending from the first surface to the deep shielding region, and
wherein the shielding connection region is at a lateral distance to the gate structure.
13. The silicon carbide device of claim 10 , further comprising:
a groove contact structure extending from the first surface to or into the deep shielding region.
14. The silicon carbide device of claim 13 ,
wherein the body region comprises a heavily doped body contact region, and
wherein the body contact region is in contact with the groove contact structure.
15. The silicon carbide device of claim 13 ,
wherein the voltage sustaining layer and the groove contact structure form a Schottky contact, and
wherein the Schottky contact is located between the body region and the deep shielding region.
16. A method of manufacturing a silicon carbide device, the method comprising:
providing a silicon carbide body having a hexagonal crystal lattice with a c-plane and further main planes, wherein the further main planes comprise a-planes and m-planes, wherein a mean surface plane of the silicon carbide body is tilted to the c-plane by an off-axis angle;
forming a trench extending from a first surface into the silicon carbide body, wherein the trench laterally exposes column sidewalls of a columnar portion of the silicon carbide body, and wherein at least three of the column sidewalls are oriented along the further main planes; and
forming a trench gate structure in the trench, wherein the gate structure is in contact with the at least three of the column sidewalls.
17. The method of claim 16 , wherein forming the trench comprises a directed etch process with an axis of an etch beam oriented parallel to the <0001> lattice direction.
18. The method of claim 16 , wherein forming the trench comprises a directed etch process with an axis of an etch beam oriented vertical to the first surface and, after etching, a heat treatment in an atmosphere containing hydrogen gas.