Planarized Crystalline Films for Low-Roughness Diffractive Optics
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Solution Overview
Problem
Optical devices often have a root-mean-square (RMS) surface roughness greater than 2.2 microinches, which reduces their functionality.
Innovation Solution
Forming optical device films using crystalline or nano-crystalline materials with a refractive index greater than 2.0 and a RMS surface roughness less than 2.2 microinches, achieved through deposition and etching processes that match the etch rates of the optical device layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical device structures are formed, then manufacturing is easier, but surface roughness increases above 2.2 microinches reducing functionality
Solution Approach 1:
A planarization layer is deposited over the optical device layer before final processing. This preliminary action creates a planar surface that will later be etched away, ensuring the optical device layer achieves the required surface roughness specification without requiring complex in-situ planarization processes
Solution Approach 2:
The planarization layer serves as an intermediary element between the deposition process and the final optical device structure. It enables surface planarization through simple deposition followed by selective removal, avoiding the need for complex real-time surface control during deposition
2Reliability
If surface roughness is reduced below 2.2 microinches, then optical functionality improves, but manufacturing complexity increases
Solution Approach 1:
The planarization layer is deposited in advance to establish a planar surface before final device formation. This preliminary planarization simplifies subsequent processing steps while ensuring the optical layer meets surface roughness requirements for reliable optical functionality
Solution Approach 2:
The process utilizes etch rate matching between the planarization layer and optical device layer as a key parameter. By controlling deposition and etching parameters, the planarization layer can be selectively removed without affecting the optical layer, achieving low surface roughness through parameter optimization rather than complex process equipment
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
The solution results in optical devices with improved functionality by reducing surface roughness and maintaining high refractive index, enhancing performance in augmented, virtual, and mixed reality applications.
Implementation Method 1
depositing an optical device layer on a substrate
Implementation Method 2
depositing a planar coating on the optical device layer
Implementation Method 3
performing one or more of an etch process, an ion or neutral beam shaping process, or a chemical mechanical polishing (CMP) process
Implementation Method 4
performing one or more of an etch process, an ion or neutral beam shaping process, or a chemical mechanical polishing (CMP) process
Implementation Method 5
performing one or more of an etch process, an ion or neutral beam shaping process, or a chemical mechanical polishing (CMP) process
Data Source
AI summary
Optical device films and methods of forming optical device films having a RMS surface roughness less than about 2.2 μin and a refractive index greater than 2.0 are provided. In one embodiment, an optical device film is provided and includes a crystalline or nano-crystalline material having a refractive index greater than 2.0. A top surface of the optical device film has a root-mean-square (RMS) surface roughness less than about 2.2 microinches (μin).