Micro-Device Tether Structure for Low-Particle Transfer Printing
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Solution Overview
Problem
Existing methods for heterogeneous micro-device assembly struggle to reliably and repeatedly transfer micro-devices from source wafers to destination substrates without generating contaminating particles.
Innovation Solution
The proposed solution involves a wafer structure with a patterned sacrificial layer and a patterned device layer, where devices are anchored to the sacrificial layer via a tether structure. This tether structure is designed to fracture predictably during micro-transfer printing, minimizing particle generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional pick-and-place technologies are used for heterogeneous micro-device assembly, then a wide variety of devices can be assembled, but the device size is limited to packages with lateral dimensions larger than about 400 microns
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary between the micro-device and the source wafer. This sacrificial layer enables the micro-device to be released from the source wafer and transferred to the destination substrate through a controlled release process, allowing assembly of devices with lateral dimensions smaller than 400 microns while maintaining assembly reliability
Solution Approach 2:
The patent segments the connection between the micro-device and source wafer into two distinct functional layers: a sacrificial layer for controlled release and a tether structure for mechanical support. This segmentation enables precise control over the release process and allows reliable assembly of microscopic devices
2Productivity
If micro-transfer printing is used to transfer micro-devices from source wafers, then microscopic devices can be assembled, but contaminating particles are generated during the transfer process
Solution Approach 1:
The sacrificial layer acts as a mediator that enables controlled release of micro-devices from the source wafer. By dissolving or removing this sacrificial layer, the micro-devices are released in a controlled manner that minimizes particle generation, allowing efficient micro-device assembly without contaminating particle generation
Solution Approach 2:
The patent performs preliminary actions by forming the sacrificial layer and tether structure before the transfer process. The sacrificial layer is positioned and configured in advance to enable controlled release, preventing particle generation during the actual transfer operation and enabling efficient micro-device assembly
3Reliability
If tethers are used to connect micro-devices to the source wafer during transfer, then devices can be held in place, but particle generation occurs when tethers fracture
Solution Approach 1:
The connection structure is segmented into a tether portion that provides mechanical support and a sacrificial layer portion that enables controlled release. This segmentation allows the tether to hold the device in place during positioning while the sacrificial layer dissolves to release the device without fracturing the tether and generating particles
Solution Approach 2:
The patent replaces the mechanical fracture of tethers with a chemical dissolution process of the sacrificial layer. Instead of mechanically breaking the tether connection, the sacrificial layer is dissolved chemically, allowing the tether to maintain device positioning accuracy while releasing the device without particle generation
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 approach enables reliable and repeatable micro-transfer printing, reducing particulate generation and contamination, and allowing for the efficient assembly of micro-devices with microscopic sizes.
Implementation Method 1
a tether connecting the tether device portion to the tether anchor portion
Data Source
AI summary
An exemplary wafer structure comprises a source wafer having a patterned sacrificial layer defining anchor portions separating sacrificial portions. A patterned device layer is disposed on or over the patterned sacrificial layer, forming a device anchor on each of the anchor portions. One or more devices are disposed in the patterned device layer, each device disposed entirely over a corresponding one of the one or more sacrificial portions and spatially separated from the one or more device anchors. A tether structure connects each device to a device anchor. The tether structure comprises a tether device portion disposed on or over the device, a tether anchor portion disposed on or over the device anchor, and a tether connecting the tether device portion to the tether anchor portion. The tether is disposed at least partly in the patterned device layer between the device and the device anchor.