Fabricating of diffraction grating by ion beam etching

1. A method for fabricating a diffraction grating, the method comprising:

generating an ionized gas;

passing the ionized gas through a gating structure to selectively direct the ionized gas toward a substrate;

injecting an etchant gas into the directed gas, the etchant gas different from the directed gas; and

exposing a surface of the substrate to the directed gas and the injected etchant gas to form grating structures on the surface of the substrate.

2. The method of claim 1 , wherein the substrate is tilted at a predetermined angle relative to the path of the directed gas to form the grating structures on the substrate.

3. The method of claim 1 , wherein the ionized gas is accelerated in the gating structure into the directed gas.

4. The method of claim 1 , further comprising neutralizing the directed gas using neutralizing gas ionized with polarity opposite to the directed gas.

5. The method of claim 1 , wherein the gating platform comprises a first grid and a second grid through which the ionized gas pass sequentially, a voltage difference applied across the first grid and the second grid to accelerate the ionized gas into the directed gas.

6. The method of claim 5 , wherein the voltage difference is applied across portions of the first grid and portions of the second grid.

7. The method of claim 1 , wherein the gating structure comprises a first plate with a first aperture and a second plate with a second aperture aligned with the first aperture, a voltage difference applied across the first plate and the second plate.

8. The method of claim 7 , further comprising sequentially causing relative movements between the gating structure and the substrate to form different portions of the grating structure.

9. The method of claim 1 , wherein the ionized gas is ionized Argon gas, and the etchant gas is at least one of Cl 2 , CF 4 , SF 6 , NF 3 , O 2 , CH 3 OH, and C 2 H 5 OH.