Micro-Substrate Posts and Indentations for Reliable Die Transfer
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Solution Overview
Problem
Existing methods fail to reliably transfer small integrated circuits, particularly those formed on sapphire substrates, without damage during micro-transfer printing, and there is a need for efficient methods to connect these circuits to destination substrates with improved accuracy and reduced costs.
Innovation Solution
The development of micro-substrate structures with spatially separated indentations and posts that allow for micro-devices to be precisely positioned and easily detached from a support substrate, enabling accurate micro-transfer printing and electrical connection to a target substrate, using a release layer and etching processes to minimize physical contact and stiction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pick-and-place or vacuum tools are used to handle small integrated circuit dies, then the dies can be transferred to destination substrates, but the handling process becomes difficult and results in loss or damage of the dies
Solution Approach 1:
A handle substrate is introduced as an intermediary carrier that temporarily holds the integrated circuits during processing. The handle substrate provides a stable platform for handling multiple dies simultaneously, eliminating the need for delicate individual manipulation with vacuum tools while preventing die loss or damage through secure adhesion.
Solution Approach 2:
The handle substrate is divided into multiple discrete handle regions, each corresponding to a specific integrated circuit location. This segmentation allows individual die handling and placement while maintaining the overall structural integrity of the handle substrate, enabling precise positioning without complex tooling.
2Reliability
If integrated circuits are formed on sapphire substrates, then crystal lattice mismatch is reduced, but the substrates cannot be reliably undercut for micro-transfer printing without damaging the circuits
Solution Approach 1:
A release layer is deposited on the sapphire substrate before forming the integrated circuits. This preliminary action creates a sacrificial layer that can be selectively removed later through chemical etching, enabling substrate undercutting without direct mechanical contact that would damage the fragile circuits. The release layer protects the circuits during the substrate removal process.
Solution Approach 2:
The mechanical undercutting process is replaced with a chemical etching process. Instead of mechanically removing the sapphire substrate beneath the circuits (which would cause damage), a chemical etchant selectively removes the release layer and then the sapphire substrate, allowing the circuits to be released and transferred intact to the destination substrate.
3Productivity
If multiple integrated circuits are transferred using a single stamp, then productivity is improved, but alignment precision between circuits and destination substrate becomes more difficult to achieve
Solution Approach 1:
Alignment marks are integrated directly into the handle substrate structure, allowing the handle substrate to self-align with the destination substrate during the transfer process. The alignment marks provide reference features that guide the positioning of multiple circuits simultaneously, enabling high-throughput transfer while maintaining precise alignment without requiring complex external alignment systems.
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 facilitates the reliable transfer and connection of micro-devices, such as micro-LEDs, with enhanced alignment and reduced manufacturing costs, allowing for precise electrical and optical connections on destination substrates.
Implementation Method 1
using a release layer and etching processes to minimize physical contact and stiction
Data Source
AI summary
A micro-device substrate structure includes a support substrate having a support-substrate surface, spatially separated indentations extending into the support substrate, and a micro-device comprising a micro-device body and micro-device posts. The micro-device posts extend from the micro-device body into the support substrate and each of the posts is disposed at least partly in a different indentation. A release layer can be disposed between the micro-device posts and the support substrate. When the release layer is etched, the micro-device can be completely disconnected from the source substrate, removed from the indentations and source substrate, and micro-transfer printed to a target substrate.