Slanted Grating Trench Depth Control via Mask Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing optical gratings with varied trench heights and widths are challenging, which affects the efficiency of optical components in augmented and virtual reality devices.
Innovation Solution
A method involving an optical grating layer on a substrate, with a patterned hardmask and a mask applied over portions, allowing for etching of trenches with varying depths and widths to form diffracted optical elements, enhancing grating characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct etching of angled trenches is used to form optical gratings, then the manufacturing process is simple, but it is challenging to achieve varied trench heights and widths across diffracting and viewing fields
Solution Approach 1:
The patent divides the masking process into multiple segments: first forming a base hardmask layer with initial patterning, then forming an additional mask layer that covers only specific regions. This segmented approach enables different trench depths in different regions (some areas have masks covering them throughout etching, others have masks removed mid-process), achieving varied trench heights and widths without requiring complete repatterning.
Solution Approach 2:
The patent performs preliminary patterning of the hardmask layer before the actual trench etching begins. The hardmask is patterned with the desired final trench geometry, then an additional mask layer is formed over it. During etching, the additional mask is selectively removed in stages, allowing the etch to progress to different depths in different regions. This preliminary action establishes the framework for achieving varied trench characteristics.
2Reliability
If uniform trench depth is used in optical gratings, then the manufacturing process is straightforward, but the optical efficiency for controlling diffraction of different wavelengths is reduced
Solution Approach 1:
The patent applies the principle of local quality by creating different trench depths in different spatial regions of the optical grating. The additional mask layer is positioned to cover specific regions during etching, causing those regions to have shallower trenches while other regions develop deeper trenches. This local variation in trench depth optimizes diffraction efficiency for different wavelengths and viewing angles across the grating surface.
Solution Approach 2:
The patent introduces dynamic control of the etching process by selectively removing the additional mask layer during etching. Rather than using a static mask configuration, the additional mask is removed in a controlled manner to expose different regions at different times, allowing the etch front to progress to different depths in different areas, creating the desired varied trench depth profile.
3Adaptability or versatility
If multiple different grating geometries are formed in different regions, then the diffraction control for different wavelengths is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functions into a single additional mask layer formation step. This additional mask simultaneously serves to: (1) protect regions where uniform trench depth is desired, (2) define the pattern for varied trench depths in other regions, and (3) enable selective etching progression. By combining these multiple masking functions into one layer formed in one step, the patent reduces the number of separate patterning operations needed.
Solution Approach 2:
The additional mask layer is designed to be multi-functional: it acts as a protective layer over the hardmask in regions where shallow trenches are desired, serves as a pattern definition layer for varied trench regions, and provides selective coverage during the etching process. This universal mask structure performs multiple roles that would otherwise require separate processing steps, simplifying the overall manufacturing approach while achieving complex grating geometries.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the optical efficiency and image quality by controlling diffraction of different wavelengths, increasing the clarity and quality of projected images in AR and VR devices.
Implementation Method 1
etching a plurality of trenches into the optical grating layer to form an optical grating
Implementation Method 2
micro-diffraction gratings have been utilized in holographic and augmented/virtual reality (AR and VR) devices
Data Source
AI summary
Methods of producing gratings with trenches having variable height and width are provided. In one example, a method includes providing an optical grating layer atop a substrate, and providing a patterned hardmask over the optical grating layer. The method may include forming a mask over just a portion of the optical grating layer and the patterned hardmask, and etching a plurality of trenches into the optical grating layer to form an optical grating. After trench formation, at least one of the following grating characteristics varies between one or more trenches of the plurality of trenches: a trench depth and a trench width.