On-Wafer Waveguide Test Mechanism for Grating Fidelity
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Solution Overview
Problem
Current testing procedures for waveguides in head-worn displays are complex and time-consuming, requiring dicing of wafers and extensive metrology processes, which increases costs and inefficiency.
Innovation Solution
An on-wafer test mechanism that uses light sources, such as LEDs or laser diodes, to test the fidelity of waveguide gratings without dicing, by propagating light through the wafer and measuring diffraction efficiency using a conoscope, allowing for direct assessment of grating fidelity on the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dicing and metrology processes are used to test waveguide fidelity, then measurement precision is improved, but device complexity and loss of time increase
Solution Approach 1:
The patent extracts the testing function from the diced wafer context and performs it directly on the intact wafer. By using a light source to illuminate the wafer and detecting light transmission through the waveguide structures, the system obtains fidelity measurements without requiring physical separation or complex microscopy equipment, thus simplifying the testing procedure while maintaining measurement capability
Solution Approach 2:
The patent replaces mechanical/dicing-based metrology methods with an optical measurement system. Instead of physically cutting wafers and using microscopy equipment, the invention uses light propagation and detection to measure waveguide fidelity, substituting a simpler optical system for complex mechanical and metrological processes
2Measurement precision
If dicing and extensive metrology processes are used to test waveguides, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs measurements on the complete wafer before any dicing operations would be required. By establishing the testing methodology on intact wafers, the system eliminates subsequent time-consuming steps of physical separation and individual component testing, achieving measurements in advance of the traditional multi-step process
Solution Approach 2:
The optical measurement system replaces time-intensive mechanical dicing and microscopy procedures. Light-based detection provides rapid fidelity assessment without the sequential operations required by traditional methods, significantly reducing total testing time while maintaining measurement precision
3Measurement precision
If dicing and complex microscopy are used for testing, then measurement precision is improved, but ease of manufacture worsens
Solution Approach 1:
The patent extracts the essential measurement function from complex microscopy and dicing procedures, isolating the core capability to detect light transmission through waveguide structures. This extracted function can be implemented with simpler equipment and procedures, making the manufacturing process easier while preserving the ability to measure grating fidelity
Solution Approach 2:
The invention substitutes complex mechanical dicing and microscopy systems with a simpler optical transmission measurement system. This replacement reduces equipment complexity and procedural difficulty, improving ease of manufacture while maintaining the capability to assess grating fidelity through light-based detection
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 method reduces the time and cost associated with testing waveguide fidelity by eliminating the need for wafer dicing and complex microscopy, providing a more efficient and cost-effective means of evaluating grating integrity.
Implementation Method 1
uses light sources, such as LEDs or laser diodes, to test the fidelity of waveguide gratings without dicing, by propagating light through the wafer
Implementation Method 2
measuring diffraction efficiency using a conoscope
Data Source
AI summary
An on-wafer testing mechanism includes multiple waveguides and test structures disposed on a wafer. Light sources are coupled to the wafer and provide beams of light to the structures disposed on the wafer by propagating the light through the wafer. In response to receiving at least a portion of a beam of light, a test structure is configured to guide the light to an exit location on the test structure. As light exits a test structure, a conoscope determines the diffraction efficiency of the test structure based on a measurement taken of the light exiting the test structure.