Micro-Transfer Printing With Tether Fracture for Reliable Chiplet Pickup

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Solution Overview

Problem

Existing micro-transfer printing methods face challenges in achieving high reliability and ease of use for transferring small, active components with excellent pick-up-and-print yields, particularly due to the design limitations of stamp structures.

Innovation Solution

A method involving a visco-elastic stamp with controlled horizontal and vertical movements, including rotations, is used to detach micro-components from a source wafer by fracturing or separating the tether, utilizing a motion-control platform for precise alignment and stress concentration on the tether to facilitate detachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a viscoelastic stamp is pressed against chiplets on a native source wafer to adhere each chiplet to an individual stamp post, then chiplet pickup is achieved, but the force required for detachment may damage the chiplets or reduce yield

Engineering Contradiction:

Improvechiplet pickup reliabilityVSAvoiddetachment force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The stamp is divided into multiple individual stamp posts, each independently contacting a single chiplet. This segmentation allows localized force application and detachment, reducing the risk of damage to individual chiplets while maintaining overall pickup reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stamp material's viscoelastic properties are utilized to change the mechanical parameters of the stamp-post system. The viscoelasticity allows the stamp to conform to chiplet surfaces during pickup and to reduce detachment force through controlled deformation, preventing chiplet damage.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If the distal end of each stamp post is made flat for simple manufacturing, then ease of manufacture is improved, but chiplet pickup and printing yield may be reduced

Engineering Contradiction:

Improvestamp post fabricationVSAvoidpick-up-and-print yield

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The distal end of each stamp post is formed with a spherical or curved geometry rather than a flat surface. This curvature improves contact with the chiplet surface, enhancing pickup reliability and printing yield while maintaining manufacturing feasibility through standard fabrication techniques.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If micro-tips in a three-dimensional relief pattern are used on the stamp, then chiplet pickup and printing yield are improved, but device complexity increases

Engineering Contradiction:

Improvepick-up-and-print yieldVSAvoidstamp structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The three-dimensional relief pattern creates localized variations in stamp post geometry, with each post having optimized dimensions and shapes tailored to specific chiplet types. This local quality enhancement improves pickup and printing yield for diverse components while managing overall device complexity through modular design.

Inventive Principle:

Principle #3Local quality

4Force

If horizontal movement is used to detach the micro-component by fracturing the tether, then the force required for detachment is reduced, but precision in placement may be compromised

Engineering Contradiction:

Improvedetachment forceVSAvoidcomponent placement precision

Core Design Contradiction:

ForceVSManufacturing precision

Solution Approach 1:

The stamp is positioned and aligned with the target substrate before detachment occurs. The horizontal movement that fractures the tether is executed after precise positioning, ensuring that even though the detachment mechanism uses lateral force, the component is already correctly positioned for high-precision placement.

Inventive Principle:

Principle #10Preliminary action

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

Enhances the reliability and efficiency of micro-component transfer by reducing the force required for detachment, improving yield and robustness under varying conditions, and enabling precise placement on target substrates.

Implementation Method 1

providing a stamp (e.g., a visco-elastic stamp comprising PDMS)

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Implementation Method 2

utilizing a motion-control platform for precise alignment and stress concentration on the tether to facilitate detachment

Methodology Applied

Scientific EffectStress concentration: Fracture Mechanics

Data Source

PatentUS20250210399A1Micro-transfer printing methods

Publication Date: 2025.06.26 X CELEPRINT LIMITED

AI summary

A method of micro-transfer printing includes providing a stamp controlled by a motion-control platform and a micro-component source wafer comprising a micro-component disposed over a cavity in a surface of the micro-component source wafer and connected to the micro-component source wafer with a tether. The stamp can contact the micro-component to adhere the micro-component to the stamp. The stamp and the micro-component can be removed from the micro-component source wafer by moving the stamp in a vertical direction orthogonal to the surface and in a horizontal direction parallel to the surface.