Silicon microstructuring method and microbattery

1. A method for processing a silicon wafer comprising the successive steps of:

performing a plasma etching of a surface of the wafer in conditions suitable to obtain a structure, and

performing two successive ion milling steps, one at an incidence in a range of 0 to 10°, the other at an incidence in a range of 40 to 60° relative to the normal to the wafer.

2. The method of claim 1 , wherein the plasma etching is a cryogenic etching, the wafer being maintained at a cryogenic temperature lower than −70° C.

3. The method of claim 2 , wherein the cryogenic temperature is in a range of −90 to −110° C.

4. The method of claim 2 , further comprising a prior calibration step during which a pitch between microtips is determined according to the cryogenic temperature of the wafer.

5. The method of claim 1 , wherein the different steps are adjusted so that the surface of the wafer comprises cone frustums having a height between 1 and 2 μm with a distance between cone bases in the range of 0 to 1 μm.

6. A method for forming a silicon wafer comprising:

performing a plasma etching of a surface of the wafer;

after performing the plasma etching, performing a first ion milling with ions impinging the wafer at a first incidence angle relative to the normal to the wafer; and

after performing the plasma etching and the first ion milling, performing a second ion milling with the ions impinging the wafer at a second incidence angle relative to the normal to the wafer, the second incidence angle being different from the first incidence angle.

7. The method of claim 6 , wherein the first incidence angle is in a range of 0 to 10°, the second incidence angle is in a range of 40 to 60°.

8. The method of claim 6 , wherein the plasma etching is a cryogenic etching, the wafer being maintained at a cryogenic temperature lower than −70° C.

9. The method of claim 8 , wherein the cryogenic temperature is in the range of −90 to −110° C.

10. The method of claim 8 , further comprising a prior calibration step during which a pitch between microtips is determined according to the cryogenic temperature of the wafer.

11. The method of claim 6 , wherein after performing the second ion milling, the wafer comprises cone frustums having a height between 1 μm and 2 μm.

12. The method of claim 6 , wherein a distance between bases of the cone frustums is in the range of 0 to 1 μm.

13. A method for forming a lithium battery, the method comprising:

performing a plasma etching of a surface of a lithium filled semiconductor wafer;

forming a plurality of cone frustums protruding from the semiconductor wafer by

after performing the plasma etching, performing a first ion milling with ions impinging the semiconductor wafer at a first incidence angle relative to the normal to the semiconductor wafer; and

after performing the plasma etching and the first ion milling, performing a second ion milling with the ions impinging the wafer at a second incidence angle relative to the normal to the semiconductor wafer, the second incidence angle being different from the first incidence angle.

14. The method of claim 13 , wherein the first incidence angle is in a range of 0 to 10°, the second incidence angle is in a range of 40 to 60°.

15. The method of claim 13 , wherein the plasma etching is a cryogenic etching, the wafer being maintained at a cryogenic temperature lower than −70° C.

16. The method of claim 15 , wherein the cryogenic temperature is in a range of −90 to −110° C.

17. The method of claim 15 , further comprising a prior calibration step during which a pitch between microtips is determined according to the cryogenic temperature of the wafer.

18. The method of claim 13 , wherein after performing the second ion milling, the cone frustums have a height between 1 μm and 2 μm.