US 2020/0271850 A1 · VARIABLE-ETCH-DEPTH GRATINGS

Abstract

Disclosed herein are techniques for fabricating straight or slanted variable-etch-depth gratings. A photoresist material for fabricating a variable-etch-depth grating in a substrate is sensitive to light with a wavelength shorter than 300 nm and has an etch rate comparable to the etch rate of the substrate. A depth of an exposed portion of a photoresist material layer including the photoresist material correlates with the exposure dose. After exposure using a gray-scale mask and development, the photoresist material layer has a non-uniform thickness. The photoresist material layer with the non-uniform thickness and the underlying substrate are etched using a straight etching or slanted etching process to form the straight or slanted variable-etch-depth grating in the substrate. The variable-etch-depth grating is characterized by a non-uniform depth profile corresponding to the non-uniform thickness of the photoresist material layer before etching.

Claims25

Dependent claims

A method comprising:

forming a patterned etch mask on a substrate;
depositing a photoresist material layer on the patterned etch mask, the photoresist material layer sensitive to ultra-violet (UV) light;
exposing the photoresist material layer to UV light through a variable transparency photomask;
developing the photoresist material layer exposed to the UV light to form a patterned photoresist layer having a non-uniform thickness;
etching the patterned photoresist layer and the substrate to obtain a grating having a non-uniform etch depth in the substrate, wherein the patterned photoresist layer is characterized by an etch rate comparable to an etch rate of the substrate;
and
removing the patterned photoresist layer and the patterned etch mask from the substrate.

4 more elements

Dependencies are inferred from the claim text.

Variable-etch-depth gratings

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Variable-etch-depth gratings

Life of this patent

Abstract

Claims25