Micro Device Transfer Head with Electrostatic Grip
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Solution Overview
Problem
Integration and packaging issues, such as transfer wafer de-bonding and surface tension forces, hinder the commercialization of micro devices like RF MEMS microswitches, LED display systems, and quartz-based oscillators in traditional transfer printing technologies.
Innovation Solution
A micro device transfer head with a mesa structure and dielectric layer is used to apply voltage and create a grip pressure on micro devices, allowing for selective bonding and de-bonding during transfer, using a phase change in the bonding layer to facilitate pick-up and release onto a receiving substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional transfer printing technologies are used, then micro devices can be transferred from donor wafer to receiving wafer, but surface tension forces and de-bonding issues occur during the transfer process
Solution Approach 1:
The patent replaces traditional mechanical bonding and de-bonding processes with electrostatic forces. An electrostatic gripper assembly applies voltage to electrodes that generate electrostatic attraction to hold the micro device during transfer, eliminating the need for adhesive bonding and subsequent de-bonding steps that cause surface tension issues.
Solution Approach 2:
The patent changes the physical state of the bonding layer through phase change (e.g., from solid to liquid or vice versa) to facilitate device release. By controlling temperature or other parameters, the bonding layer transitions between bonded and released states, enabling reliable transfer without traditional de-bonding challenges.
2Productivity
If the entire transfer wafer with array of devices is involved in the transfer process, then batch transfer is achieved, but selective bonding and de-bonding becomes difficult
Solution Approach 1:
The patent divides the transfer wafer into individual transferable units or regions that can be independently controlled. The electrostatic gripper can selectively activate specific electrodes or electrode regions to pick up and transfer individual devices or subsets of devices from the array, enabling selective operation while maintaining batch processing capability.
Solution Approach 2:
The patent introduces dynamic control of electrostatic fields to enable selective bonding and de-bonding during the transfer process. By dynamically adjusting voltage application to different electrode regions, the system can selectively hold or release specific devices in the array, providing operational flexibility during batch transfer.
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 transfer of micro devices with high precision and control, overcoming surface tension and other forces holding them to the carrier substrate, and allows for the integration of micro devices into heterogeneous systems with high transfer rates.
Implementation Method 1
at least one is electrode formed over the mesa structure... a voltage is applied to an electrode in the transfer head to create a grip pressure on the micro device
Implementation Method 2
using a phase change in the bonding layer to facilitate pick-up and release onto a receiving substrate
Data Source
AI summary
A method of transferring a micro device and an array of micro devices are disclosed. A carrier substrate carrying a micro device connected to a bonding layer is heated to a temperature below a liquidus temperature of the bonding layer, and a transfer head is heated to a temperature above the liquidus temperature of the bonding layer. Upon contacting the micro device with the transfer head, the heat from the transfer head transfers into the bonding layer to at least partially melt the bonding layer. A voltage applied to the transfer head creates a grip force which picks up the micro device from the carrier substrate.