Reactivity enhancement in ion beam etcher

1. A method of fabricating a slanted surface-relief structure in a material layer, the method comprising:

injecting a first reactive gas into an reactive ion source generator;

generating a plasma using the first reactive gas in the reactive ion source generator, the plasma including reactive ions of the first reactive gas that are configured to react with the material layer to generate volatile materials;

extracting at least some of the reactive ions from the plasma to form a collimated reactive ion beam towards the material layer; and

injecting a second reactive gas onto the material layer, the second reactive gas configured to react with the material layer,

wherein the collimated reactive ion beam and the second reactive gas etch the material layer both physically and chemically to form the slanted surface-relief structure in the material layer.

2. The method of claim 1 , further comprising:

rotating the material layer based on a desired slant angle of the slanted surface-relief structure.

3. The method of claim 1 , wherein the first reactive gas comprises at least one of CF 4 , CHF 3 , N 2 , O 2 , SF 6 , Cl 2 , BCl 3 , HBr, H 2 , Ar, He, or Ne.

4. The method of claim 1 , wherein the material layer includes a semiconductor substrate, a SiO 2 layer, a Si 3 N 4 material layer, a titanium oxide layer, an alumina layer, a SiC layer, a SiO x N y layer, an amorphous silicon layer, a spin on carbon (SOC) layer, an amorphous carbon layer (ACL), a diamond like carbon (DLC) layer, a TiO x layer, an AlO x layer, a TaO x layer, or a HFO x layer.

5. The method of claim 1 , wherein generating the plasma in the reactive ion source generator comprises:

applying an RF signal to an inductively coupled plasma generator of the reactive ion source generator.

6. The method of claim 1 , wherein extracting at least some of the reactive ions from the plasma to form the collimated reactive ion beam comprises:

applying an extraction voltage on an extraction grid adjacent to the reactive ion source generator; and

applying an acceleration voltage on an acceleration grid to extract and accelerate at least some of the reactive ions,

wherein the extraction grid and the acceleration grid are aligned; and

wherein the acceleration voltage is lower than the extraction voltage.

7. The method of claim 1 , wherein injecting the second reactive gas comprises:

injecting the second reactive gas onto the material layer using a gas ring.

8. The method of claim 1 , wherein the second reactive gas comprises at least one of CF 4 , CHF 3 , N 2 , O 2 , SF 6 , Cl 2 , BCl 3 , or HBr.

9. The method of claim 1 , further comprising:

neutralizing the collimated reactive ion beam before etching the material layer using the collimated reactive ion beam and the second reactive gas.

10. The method of claim 9 , wherein neutralizing the collimated reactive ion beam comprises:

injecting an electron beam into the collimated reactive ion beam.

11. The method of claim 1 , wherein:

the slanted surface-relief structure comprises a slanted surface-relief optical grating.

12. The method of claim 11 , wherein:

the slanted surface-relief optical grating comprises a plurality of ridges; and

a leading edge of each ridge is parallel to a trailing edge of the ridge.

13. The method of claim 12 , wherein:

a slant angle of the leading edge and a slant angle of the trailing edge are greater than 30 degrees with respect to a surface normal of the material layer.

14. The method of claim 11 , wherein:

a depth of the slanted surface-relief optical grating is greater than 100 nm.

15. The method of claim 11 , wherein:

a duty cycle of the slanted surface-relief optical grating is greater than 60%.