Method for manufacturing a grid
A grid is manufactured with a combination of ion implant and epitaxy growth. The grid structure is made in a SiC semiconductor material with the steps of a) providing a substrate comprising a doped semiconductor SiC material, said substrate comprising a first layer (n 1 ), b) by epitaxial growth adding at least one doped semiconductor SiC material to form separated second regions (p 2 ) on the first layer (n 1 ), if necessary with aid of removing parts of the added semiconductor material to form separated second regions (p 2 ) on the first layer (n 1 ), and c) by ion implantation at least once at a stage selected from the group consisting of directly after step a), and directly after step b); implanting ions in the first layer (n 1 ) to form first regions (p 1 ). It is possible to manufacture a grid with rounded corners as well as an upper part with a high doping level. It is possible to manufacture a component with efficient voltage blocking, high current conduction, low total resistance, high surge current capability, and fast switching.
1. A method for the manufacture of a grid structure in a silicon carbide (SiC) semiconductor material, the method comprising:
providing a substrate comprising a doped semiconductor SiC material, the substrate comprising a first layer of a first conductivity type;
epitaxial growth growing at least one doped semiconductor SiC material of a second conductivity type opposite to the first conductivity type on the first layer;
removing parts of the epitaxial growth grown semiconductor SiC material to form separated second regions; and
implanting ions in the first layer to form first regions of a second conductivity type opposite to the first conductivity type such that each of the separated second regions is in contact with one of the first regions,
wherein the first regions have a lower doping concentration than the separated second regions.
2. The method of claim 1 , wherein:
the first regions have a first doping concentration in an interval of 1e18 cm−3 to 1e19 cm−3; and
the separated second regions have a second doping concentration in an interval of 5e19 cm−3 to 3e20 cm−3.
3. The method of claim 1 , further comprising:
epitaxial growth growing a second layer on the separated second regions and on the first layer.
4. The method of claim 3 , wherein the second layer is epitaxial growth grown such that a thickness of the second layer is in the interval 0.5 μm to 3 μm.
5. The method of claim 3 , further comprising:
performing a surface planarization of the second layer.
6. The method of claim 3 , further comprising:
making a Schottky contact on at least a part of the second layer.
7. The method of claim 1 , further comprising:
epitaxial growth growing a second layer on the first layer; and
etching through portions of the second layer,
wherein the separated second regions are formed within the etched portions.
8. The method of claim 1 , wherein:
a fraction of the first regions have a portion of the separated second regions on top;
all of the first regions have a portion of the separated second regions on top; or
a lower surface of the separated second regions in contact with the first regions is smaller than an upper surface of the first regions.
9. The method of claim 1 , wherein the separated second regions have a thickness in an interval 0.1 μm to 3.0 μm.
10. The method of claim 1 , wherein the epitaxial growth grown doped semiconductor SiC material has a doping gradient with a higher doping concentration furthest away from the first regions.
11. The method of claim 1 , wherein the parts of the at least one doped semiconductor material are removed by dry etching.
12. The method of claim 1 , wherein:
the ion implantation is performed before forming the separated second regions;
the method comprises simultaneously annealing the implanted ions in the first regions and epitaxial growth growing the at least one doped semiconductor SiC material on the first layer to form the separated second regions.
13. The method of claim 1 , wherein:
the first regions have a thickness in an interval 0.2 μm to 2.0 μm; or
the first regions have a doping gradient with a higher doping concentration towards the second regions.
14. The method of claim 1 , wherein:
Al or B is utilized for doping of the first regions;
Al is utilized for doping of the separated second regions and B is utilized for doping of the first regions; or
B is utilized for doping of the first regions and the ion implantation is followed by diffusion.
15. The method of claim 1 , further comprising:
making an Ohmic contact directly on top of at least one of the separated second regions.
16. The method of claim 15 , wherein making the Ohmic contact directly on top of the at least one of the separated second regions comprises removing at least a portion of a second layer to expose the at least one of the separated second regions.
17. The method of claim 1 , wherein, for all spaces between any two of the separated second regions, a ratio between a thickness of the separated second regions to a spacing between the two separated second regions is below 1.
18. The method of claim 1 , wherein an edge termination of a device is integrated into at least one of the first regions.
19. A grid structure in a semiconductor material manufactured according to the method of claim 1 .
20. A device manufactured according to the method of claim 1 .