Method of fabricating molds for forming eyepieces with integrated spacers
Methods are disclosed for fabricating molds for forming eyepieces having waveguides with integrated spacers. The molds are formed by etching deep holes (e.g., 5 μm to 1000 μm deep) into a substrate using a wet etch or dry etch. The etch masks for defining the holes may be formed with a thick metal layer and/or multiple layers of different metals. A resist layer may be disposed over the etch mask. The resist layer may be patterned to form a pattern of holes, the pattern may be transferred to the etch mask, and the etch mask may be used to transfer the pattern into the underlying substrate. The patterned substrate may be utilized as a mold onto which a flowable polymer may be introduced and allowed to harden. Hardened polymer in the holes may form integrated spacers. The hardened polymer may be removed from the mold to form a waveguide with integrated spacers.
1 . A method for forming a mold, comprising:
providing a substrate;
depositing an etch mask layer over a top surface of the substrate;
depositing an etch resistant layer on a bottom surface of the substrate;
defining openings in the etch mask layer by subjecting the etch mask layer to a directional etch to expose the substrate; and
etching the substrate through the etch mask layer to define openings in the substrate, wherein etching the substrate comprises subjecting the substrate to an isotropic etch, wherein the openings in the substrate have a depth between 5 μm and 1000 μm, wherein the depth is less than a thickness of the substrate, and wherein the etch resistant layer is exposed to etch species from underneath the substrate during etching the substrate.
2 . The method of claim 1 , further comprising:
depositing a photoresist layer over the etch mask layer; and
lithographically defining openings in the photoresist layer,
wherein defining openings in the etch mask layer comprises extending the openings in the photoresist layer into the etch mask layer.
3 . The method of claim 1 , further comprising depositing an adhesion layer over the substrate before depositing the etch mask.
4 . The method of claim 1 , further comprising augmenting the etch mask layer after stopping depositing the etch mask.
5 . The method of claim 4 , wherein augmenting the etch mask layer comprises depositing additional etch mask material directly on the etch mask layer.
6 . The method of claim 5 , wherein depositing the additional etch mask material comprises a vapor deposition.
7 . The method of claim 5 , wherein depositing the additional etch mask material comprises electroplating.
8 . The method of claim 5 , wherein the additional etch mask material is a same material as the material deposited during depositing the etch mask layer.
9 . The method of claim 1 , wherein etch mask layer has a thickness of 10 nm to 200 nm.
10 . The method of claim 1 , wherein etching the substrate through the etch mask layer comprises a wet etch.
11 . The method of claim 1 , wherein etching the substrate through the etch mask layer comprises a dry etch.
12 . The method of claim 1 , wherein the substrate is formed of an optically transparent material.
13 . The method of claim 12 , wherein the optically transparent material is chosen from the group consisting of glass, quartz, and fused silica.
14 . The method of claim 1 , wherein the etch mask layer is formed of metal.
15 . The method of claim 1 , wherein the openings are disposed in a periphery of the substrate, further comprising defining interior openings in an interior region of the substrate, wherein a ratio of the heights of the interior openings and the openings in the substrate is 500:1 or greater.
16 . The method of claim 15 , wherein the ratio is 100000:1 or less.
17 . The method of claim 15 , wherein the interior openings have a size and periodicity corresponding to diffractive gratings for diffracting visible light.
18 . The method of claim 1 , further comprising removing the etch mask layer.
19 . The method of claim 14 , wherein the etch resistant layer is formed of metal, wherein the metal forming the etch resistant layer is different from the metal forming the etch mask layer.
20 . The method of claim 19 , wherein the metal forming the etch resistant layer has a higher resistance to etch species for etching the substrate than the metal forming the etch mask layer.