On-Chip Waveguide Facet Angle Measurement
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Solution Overview
Problem
Conventional methods for determining the facet angle of photonic chip facets, such as scanning electron microscopic techniques, face limitations in accuracy and throughput, and often require destructive processing steps, making them inadequate for wafer-scale measurements.
Innovation Solution
A test system comprising a photonic chip with a waveguide that directs test light towards the facet, a detector to measure the reflected or transmitted test light, and a processor to determine surface characteristics like facet angle, curvature, and roughness using empirical models and optical components like Michelson interferometers and grating structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscopic techniques are used to determine facet angle, then measurement capability is provided, but measurement precision and throughput are inadequate
Solution Approach 1:
The patent replaces mechanical/physical SEM imaging systems with an optical measurement system that uses light propagation through waveguides to determine facet angle. The waveguide-based optical system measures facet characteristics non-contactly and non-destructively, achieving both high precision and high throughput by eliminating the need for complex SEM imaging processing and enabling parallel measurement of multiple facets.
Solution Approach 2:
The measurement system uses the waveguide structure itself as both the component under test and the measurement tool. The waveguide's light propagation characteristics automatically reveal facet angle information without requiring external probing or additional measurement apparatus, enabling self-measurement that improves both precision and throughput.
2Measurement precision
If cross-sectional SEM images are used to determine facet angle, then measurement accuracy is improved, but additional and destructive processing steps are required
Solution Approach 1:
The patent replaces destructive physical sectioning and SEM imaging with non-destructive optical measurement. Light transmitted through the waveguide provides facet angle information without requiring physical access to cross-sections, eliminating all associated processing steps and preserving the complete chip structure.
Solution Approach 2:
The patent introduces light as an intermediary medium to probe facet characteristics. Instead of physically accessing the facet through cross-sectioning, light propagates through the waveguide and its transmission properties serve as an indirect but accurate indicator of facet angle, avoiding all destructive processing.
3Measurement precision
If conventional measurement techniques are used, then facet angle can be determined, but the method is inadequate for wafer scale measurements
Solution Approach 1:
The patent divides the wafer into multiple independently measurable segments (individual chips or chip regions), each with its own waveguide structure. This segmentation allows parallel measurement of multiple facets simultaneously, achieving wafer-scale throughput while maintaining precise measurement of each individual facet through its dedicated waveguide.
Solution Approach 2:
The waveguide structure serves multiple functions: it acts as both the photonic component to be tested and the measurement probe itself. This multi-functionality enables a single integrated system to measure numerous facets across a wafer without requiring separate measurement apparatus for each location, achieving both precision and scale.
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
Enables accurate and efficient determination of surface characteristics at the wafer scale without destructive processing, improving measurement sensitivity and throughput while allowing for precise facet angle determination.
Implementation Method 1
a waveguide configured to direct test light towards the facet
Implementation Method 2
a detector configured to measure an amount of a portion of the test light reflected by the facet
Implementation Method 3
a detector configured to measure an amount of a portion of the test light transmitted by the facet
Implementation Method 4
optical components like Michelson interferometers
Data Source
AI summary
A test system for determining a surface characteristic of a chip facet includes an on-chip waveguide, a detector, and a processor. The on-chip waveguide is configured to direct test light towards the facet, where a portion of the test light is reflected and a portion of the test light is transmitted. The detector is configured to measure an amount of the reflected portion or the transmitted portion, and the processor is configured to determine a surface characteristic of the facet, such as a facet angle, a facet curvature, and/or a facet roughness, on the basis of the measured amount.