Manufacturing a semiconductor device using electrochemical etching, semiconductor device and super junction semiconductor device
A trench is formed in a semiconductor substrate between mesas of a first conductivity type. The trench extends from a process surface down to a bottom plane. A semiconductor layer of a second, complementary conductivity type is formed on sidewalls of the trench. At least in the mesas a vertical impurity concentration profile vertical to the process surface is non-constant between the process surface and the bottom plane. A portion of the semiconductor layer in the trench is removed by electrochemical etching. Thereafter, the thickness of the recessed semiconductor layer images the vertical impurity concentration profile in the mesa.
1. A method of manufacturing a semiconductor device, the method comprising:
forming a trench in a semiconductor substrate between mesas of a first conductivity type, the trench extending from a process surface down to a bottom plane;
forming a semiconductor layer of a second, complementary conductivity type on sidewalls of the trench, wherein at least in the mesas a vertical impurity concentration profile vertical to the process surface is non-constant between the process surface and the bottom plane; and thereafter
removing a portion of the semiconductor layer in the trench by electrochemical etching.
2. The method of claim 1 , further comprising:
implanting impurities into at least one of the semiconductor substrate and the semiconductor layer before the electrochemical etching to define the non-constant vertical impurity concentration profile.
3. The method of claim 1 , further comprising:
implanting protons into at least one of the semiconductor substrate and the semiconductor layer; and
electrically activating the implanted protons as donors by thermal processing before the electrochemical etching to define the non-constant vertical impurity concentration profile.
4. The method of claim 3 , further comprising:
thermal processing the semiconductor substrate and the semiconductor layer after the electrochemical etching to deactivate the proton-induced donors as donors.
5. The method of claim 3 , wherein
implanting protons comprises a plurality of implant processes at different implant energies.
6. The method of claim 5 , wherein
the implant processes are carried out at different implant doses.
7. The method of claim 1 , wherein
between the process surface and the bottom plane a maximum net impurity concentration exceeds at least two times a minimum net impurity concentration.
8. The method of claim 1 , further comprising:
filling the trench with at least one of an intrinsic or a lightly doped semiconductor material, a dielectric material and a passivation material.
9. The method of claim 1 , further comprising:
closing the trench with an epitaxial layer grown by epitaxy.
10. The method of claim 1 , wherein
the electrochemical etching comprises bringing an etching solution into contact with the semiconductor layer while applying a blocking voltage between the etching solution and the semiconductor substrate.
11. The method of claim 10 , further comprising:
introducing impurities of the second conductivity type before the electrochemical etching to form a heavily doped region of the second conductivity type in the semiconductor layer or the semiconductor substrate outside the trench, wherein the etching solution is in direct contact with the heavily doped region during the electrochemical etching.
12. A semiconductor device, comprising:
semiconductor mesas of a first conductivity type extending between a first surface and a bottom plane of a semiconductor portion; and
a semiconductor structure of a second, complementary conductivity type extending along sidewalls of the semiconductor mesas,
wherein a thickness of the semiconductor structure has a local maximum value at a first distance to both the first surface and the bottom plane, and a vertical impurity concentration profile in the semiconductor portion has a local maximum at the first distance to the first surface.
13. The semiconductor device of claim 12 , wherein
the thickness of the semiconductor structure has more than one local maximum along the respective sidewall of the semiconductor mesas.
14. The semiconductor device of claim 12 , wherein
two semiconductor structures extend on opposite sidewalls of neighboring semiconductor mesas.
15. The semiconductor device of claim 12 , wherein
the sidewalls of the semiconductor mesas are vertical to the first surface.
16. A super junction semiconductor device, comprising:
a semiconductor portion comprising a subsurface structure extending from a first surface of the semiconductor portion between mesas down to a bottom plane,
wherein the mesas have a first conductivity type and the subsurface structure comprises semiconductor structures of a second, complementary conductivity type extending along sidewalls of the mesas,
wherein a thickness of the semiconductor structures has a local maximum at a first distance to the first surface, the first distance being smaller than a main distance between the first surface and the bottom plane, and
wherein the super junction semiconductor device is a vertical insulated gate field effect transistor including a first load electrode and a control terminal at a first side of the semiconductor portion and a second load electrode at a second side of the semiconductor portion opposite to the first side.
17. The super junction semiconductor device of claim 16 ,
wherein the subsurface structure includes a fill structure of a filling material separating the semiconductor structures of the subsurface structure, the filling material being at least one of an intrinsic and a lightly doped semiconductor material and a dielectric material.
18. The super junction semiconductor device of claim 16 , wherein the subsurface structure comprises a void.