Transfer-Printable Micro-Device Testing via Separated Tethers
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Solution Overview
Problem
Existing methods for testing and transferring micro-devices on substrates are limited by the use of electrically conductive breakable tethers, which restrict material and connection options, leading to inefficiencies in identifying and removing faulty devices before transfer printing.
Innovation Solution
A method involving a source wafer with sacrificial portions and anchors, where micro-devices are connected via test connections that can be removed to define tethers, allowing for testing and removal of faulty devices before transferring only functional ones to a destination substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrically conductive breakable tethers are used to connect micro-devices to anchors, then the micro-devices can be tested and selectively removed before transfer printing, but the material and connection options are restricted
Solution Approach 1:
The patent extracts the testing and connection functions from the tether structure itself. Test connections are provided separately from the release tether, allowing the tether to be made of simple releaseable material while test signals are routed through separate conductive paths to test contact pads on the substrate.
Solution Approach 2:
The patent segments the connection system into distinct functional components: release tethers for mechanical attachment and release, and separate test connections for electrical testing. This segmentation allows each component to be optimized independently for its specific function.
2Reliability
If comprehensive testing is performed on micro-devices before transfer printing, then faulty devices can be identified and removed, but the testing process becomes more complex and time-consuming
Solution Approach 1:
The patent combines multiple testing capabilities into a unified test contact pad structure. Multiple test connections can be routed to shared test pads, allowing comprehensive testing of multiple micro-devices through a common interface rather than requiring separate test structures for each device.
Solution Approach 2:
The substrate serves as an intermediary platform that provides test contact pads and routing infrastructure. This mediator enables comprehensive testing without requiring complex test equipment to be integrated with each micro-device, simplifying the overall testing architecture.
3Reliability
If test connections are maintained during transfer printing, then continuous monitoring is possible, but the transfer printing process is hindered and faulty devices cannot be selectively removed
Solution Approach 1:
The patent extracts the test connection function from the mechanical tether structure. Test connections are provided through separate paths that can be independently managed, allowing the tether to be cleanly released during transfer printing while test functionality is preserved through the substrate's test contact infrastructure.
Data Source
AI summary
A method of making and testing transfer-printable micro-devices on a source wafer includes providing a source wafer comprising a plurality of sacrificial portions spatially separated by anchors, the source wafer comprising one or more test contact pads, providing a micro-device entirely over each of the plurality of sacrificial portions, each micro-device physically connected to at least one anchor with one or more tethers, providing one or more electrical test connections from each micro-device to a corresponding test contact pad, testing the micro-devices through the test connections to determine functional micro-devices and faulty micro-devices, and removing at least a portion of the one or more test connections.