Wafer-Level Optical Device Testing via Direct Light Injection
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Solution Overview
Problem
Current methods for testing optical devices on wafers require individual testing of each device after separation, which is time-consuming and costly, and do not allow for identification of defective wafers before separation.
Innovation Solution
A system where optical devices on a wafer include waveguides terminating at testing ports that can inject or extract light directly from a light source without reflecting surfaces, enabling wafer-level testing before device separation, reducing fabrication costs and allowing for identification of defective wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual device testing is performed after separation from wafer, then testing accuracy is improved, but testing time and cost increase significantly
Solution Approach 1:
Multiple optical devices on a wafer are tested simultaneously by merging their testing processes into a single wafer-level operation. The waveguides are configured to allow light injection at the wafer level, enabling parallel testing of multiple devices rather than sequential individual testing after separation.
Solution Approach 2:
Testing is performed before the devices are separated from the wafer. The waveguides are designed with facets that allow light injection while still attached to the wafer, enabling preliminary testing to identify defective devices or wafers before separation occurs, thus avoiding unnecessary individual testing of defective devices.
2Ease of operation
If waveguides terminate at intradevice testing ports, then light injection is enabled, but fabrication complexity increases
Solution Approach 1:
The testing port functionality is extracted from the main device structure. Waveguides terminate at dedicated testing ports that are separate from the functional device components, allowing light injection for testing without interfering with the device's operational structure. This separation enables testing capability while maintaining relatively simple device fabrication.
3Productivity
If multiple devices are fabricated on the same wafer, then production efficiency is improved, but defect identification capability deteriorates
Solution Approach 1:
While multiple devices are fabricated on the same wafer for production efficiency, each device's waveguide is segmented to terminate at its own dedicated testing port. This segmentation allows individual device testing through the respective testing ports while maintaining the benefits of wafer-level fabrication, thus preserving both production efficiency and defect identification capability.
Solution Approach 2:
Testing ports serve as intermediary structures between the external light source and the waveguides of multiple devices on the wafer. These intermediary testing ports enable individual device testing and defect identification while allowing multiple devices to coexist on the same wafer for efficient production.
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 efficient testing of optical devices on wafers before separation, reducing costs and time associated with device fabrication by identifying defective wafers and components like optical modulators, and allowing for the reuse of testing ports as functional components post-testing.
Implementation Method 1
The light source generates light that travels directly from the light source to the facet at an angle greater than or equal to 1° and less than or equal to 40° where the angle is measured between a direction the light exits from the light source and a longitudinal axis of the waveguide at the facet
Data Source
AI summary
A wafer includes multiple optical devices. One of the devices includes a waveguide that terminates at a facet that is included in a testing port. Light is injected from a light source into the waveguide through the facet without being reflected between exiting from the light source and entering the facet. The devices are separated from the wafer after the light is injected into the waveguide.