Shear Release Posts for Micro Device Transfer
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Solution Overview
Problem
Integration and packaging issues, particularly in transferring micro devices such as RF MEMS microswitches and LED display systems, are hindered by traditional transfer methods that require multiple bonding and de-bonding steps and involve the entire transfer wafer, limiting efficiency and precision.
Innovation Solution
A stabilization structure with a carrier substrate featuring an array of staging cavities and shear release posts allows for the secure attachment and transfer of micro devices, enabling their pick-up and placement on a receiving substrate with reduced pressure and contact area, utilizing a sacrificial release layer and a stabilization layer formed from materials like benzocyclobutene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional wafer bonding transfer methods are used, then devices can be transferred from transfer wafer to receiving wafer, but multiple bonding and de-bonding steps are required and the entire transfer wafer must be involved, reducing efficiency
Solution Approach 1:
The invention segments the transfer wafer into individual device-level units by introducing isolation trenches between adjacent devices. This segmentation allows devices to be transferred independently or in smaller groups rather than requiring the entire transfer wafer to be processed as one unit, thereby reducing the complexity of bonding and de-bonding operations while improving transfer efficiency
Solution Approach 2:
The invention extracts the bonding interface from the entire transfer wafer by creating localized bonding regions at each device level. The isolation trenches remove unnecessary material between devices, enabling selective bonding of only the required devices to the receiving wafer, thus eliminating the need to process the entire transfer wafer and reducing the number of bonding/de-bonding steps
2Productivity
If the entire transfer wafer is involved in the transfer process, then all devices can be transferred, but the process becomes less efficient and scalable
Solution Approach 1:
The transfer wafer is segmented into discrete device regions separated by isolation trenches. This segmentation enables the transfer process to focus only on the necessary device areas rather than involving the entire transfer wafer substrate, thereby improving productivity by reducing the quantity of material that must be handled and processed during each transfer operation
3Reliability
If micro devices are transferred without isolation structures, then the process is simpler, but adjacent devices cannot be properly separated and stabilized during transfer
Solution Approach 1:
Isolation trenches act as intermediary structures between adjacent micro devices during the transfer process. These trenches provide mechanical separation and stabilization, preventing devices from shifting or interfering with each other during bonding and transfer operations. The trenches serve as a mediating element that enables reliable device handling without requiring complex active control mechanisms
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 method enhances the transfer process by reducing the required pick-up pressure, allowing for more precise alignment and handling of micro devices, and simplifies the transfer process, potentially increasing the density of devices on the carrier substrate and reducing manufacturing costs.
Implementation Method 1
etching the sacrificial release layer to expose side surface portions of the array of micro devices
Implementation Method 2
the stabilization layer is formed of a thermoset material such as, but not limited to, benzocyclobutene (BCB)
Implementation Method 3
Each micro device is laterally attached to a shear release post laterally extending from a sidewall of a corresponding staging cavity
Data Source
AI summary
A stabilization structure includes a stabilization layer on a carrier substrate. The stabilization layer includes an array of staging cavities. An array of micro devices are within the array of staging cavities. Each micro device is laterally attached to a shear release post laterally extending from a sidewall of a staging cavity. A pressure is applied to the array of micro devices from the array of transfer heads to shear the array of micro devices off the shear release posts. The sheared off micro devices are picked up from the carrier substrate using the array of transfer heads.