Methods for fabrication of high aspect ratio micropillars and nanopillars

1. A method for fabricating high aspect ratio pillars comprising:

providing a substrate;

coating the substrate by a resist;

defining the high aspect ratio pillars by patterning and exposing the resist;

developing the resist to remove portions of the resist on the substrate, to expose portions of the substrate;

depositing an etch mask on the resist and the exposed portions of the substrate;

placing the resist in a chemical bath to dissolve the resist and the etch mask on the resist, such that the etch mask on the substrate remain undissolved;

etching sections of the substrate exposed as a consequence of dissolving the resist and the etch mask on the resist, the etching being performed with an SF 6 /O 2 cryogenic etch to fabricate high aspect ratio micropillars and a Pseudo Bosch etch to fabricate high aspect ratio nanopillars; and

removing a remainder of the etch mask to form the high aspect ratio pillars.

2. The method of claim 1 , wherein the substrate is a silicon substrate.

3. The method of claim 2 , wherein the etch mask is an alumina etch mask.

4. The method of claim 3 , wherein the alumina is sputtered on the substrate.

5. The method of claim 4 , wherein a 99.995% aluminum target is used to produce the etch mask and a 5:1 mixture of argon to oxygen is used as a process gas to sputter the alumina.

6. The method of claim 5 , wherein the alumina is sputtered using a 400 watts DC power.

7. The method of claim 3 , wherein the etching is a plasma etching.

8. The method of claim 3 , wherein a remainder of the alumina etch mask is removed using either buffered hydrofluoric acid or ammonium hydroxide mixed with hydrogen peroxide.

9. The method of claim 1 , wherein a 10 to 1 ratio of SF 6 to O 2 is employed for the SF 6 /O 2 cryogenic etch.

10. The method of claim 1 , wherein an ICP power of 900 W combined with a RIE power of 3 to 9 is employed to fabricate micropillars and an ICP power of 1200 W combined with a RIE power of 20 W is used to generate nanopillars.

11. The method of claim 1 , wherein the high aspect ratio pillars are micropillars of diameters ranging from 5 to 50 micron with aspect ratios greater than 25.

12. The method of claim 11 , wherein the micropillars are controllably placed at a distance of 5 micron or more from one another.

13. The method of claim 1 , wherein the high aspect ratio pillars are nanopillars of diameters ranging from 30 to 50 nm with aspect ratios greater than 25.

14. The method of claim 13 , wherein the nanopillars are controllably placed at a distance of 50 nm or more from one another.