Etching process for micromachining materials and devices fabricated thereby
View Patent ↗The present invention provides an optical microbench having intersecting structures etched into a substrate. In particular, microbenches in accordance with the present invention include structures having a planar surfaces formed along selected crystallographic planes of a single crystal substrate. Two of the structures provided are an etch-stop pit and an anisotropically etched feature disposed adjacent the etch-stop pit. At the point of intersection between the etch-stop pit and the anisotropically etched feature the orientation of the crystallographic planes is maintained. The present invention also provides a method for micromachining a substrate to form an optical microbench. The method comprises the steps of forming an etch-stop pit and forming an anisotropically etched feature adjacent the etch-stop pit. The method may also comprise coating the surfaces of the etch-stop pit with an etch-stop layer.
1. A method for micromachining <100> silicon, comprising:
(a) defining three areas of a substrate: an unetched area, a dry etch area, and a wet etch area, wherein the dry etch area and the wet etch area are adjacent;
(b) forming an SiO 2 layer over the unetched and wet etch areas of a substrate, forming silicon nitride on the SiO 2 in the wet etch area, wherein the dry etch area is uncovered;
(c) dry etching the dry etch area to form a dry-etched pit;
(d) oxidizing the substrate to form a SiO 2 layer in the dry-etched pit;
(e) removing the silicon nitride and thinning the SiO 2 to expose the wet etch area; and
(f) wet etching the wet etch area.
2. The method of claim 1 , further comprising removing SiO 2 after (f).
3. A method for micromachining <100> silicon, comprising:
(a) defining three areas of a substrate: an unetched area, a dry etch area, and a wet etch area, wherein the dry etch area and the wet etch area are adjacent;
(b) forming a silicon nitride/SiO 2 layer over the unetched area, with the SiO 2 on top, forming an SiO 2 layer over the wet etch area, wherein the dry etch area is uncovered;
(c) dry etching the dry etch area to form a dry-etched pit;
(d) conformally coating the substrate with a hard mask material to form a hard mask layer in the dry-etched pit;
(e) removing the SiO 2 from the substrate so that the wet etch area is exposed; and
(f) wet etching the wet etch area.
4. The method of claim 3 , further comprising removing hard mask material after (f).
5. The method of claim 3 , wherein the hard mask material is chemical vapor deposited nitride.
6. A method for micromachining <100> silicon, comprising:
(a) defining three areas of a substrate: an unetched area, a dry etch area, and a wet etch area, wherein the dry etch area and the wet etch area are adjacent;
(b) forming a photoresist layer over the unetched area, forming a hard mask layer over the wet etch area, wherein the dry etch area is uncovered;
(c) dry etching the dry etch area to form a dry-etched pit;
(d) removing the photoresist;
(e) oxidizing the substrate to form a SiO 2 layer in the dry-etched pit;
(f) removing the hard mask to expose the wet etch area; and
(g) wet etching the wet etch area.
7. The method of claim 6 , wherein the hard mask material comprises silicon nitride.
8. The method of claim 6 , further comprising removing SiO 2 after (g).