Compliant Micro Device Transfer Head for Height Variation Compensation
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Solution Overview
Problem
Integration and packaging of micro devices such as RF MEMS microswitches, LED display systems, and quartz-based oscillators face challenges due to limitations in traditional transfer technologies, which often require multiple bonding and de-bonding steps and involve the entire transfer wafer in the process, leading to inefficiencies and potential damage to devices.
Innovation Solution
A compliant monopolar micro device transfer head and array, featuring a patterned silicon layer with deflectable electrodes and a buried oxide layer, allows for improved contact and handling of micro devices by compensating for height variations and reducing compressive forces, enabling efficient transfer without the need for patterned metal electrodes, thus simplifying the processing sequence and reducing thermal processing constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wafer bonding or transfer printing is used, then micro devices can be transferred from donor to receiving substrate, but multiple bonding and de-bonding steps are required which increases process complexity and time
Solution Approach 1:
The invention extracts the active transfer function from the entire transfer wafer to individual transfer heads. Each transfer head is a独立的 transfer unit that can pick up and release devices independently, eliminating the need for wafer-level bonding and de-bonding operations. This extraction of the transfer function to the head level resolves the contradiction by simplifying the overall process while maintaining reliable device transfer.
Solution Approach 2:
The transfer wafer is segmented into multiple independent transfer heads, each capable of independent operation. This segmentation allows parallel processing where multiple devices can be transferred simultaneously by different heads, reducing the total number of bonding/de-bonding cycles required and simplifying the overall transfer process.
2Productivity
If the entire transfer wafer is involved in the transfer process, then array transfer is achieved, but the process is slow and inefficient for high-rate integration
Solution Approach 1:
The transfer system is divided into multiple independent transfer heads that operate in parallel. Each head can pick up and transfer devices independently, allowing simultaneous multi-device transfer operations. This parallelism dramatically increases the device transfer rate and reduces the total time required for integration compared to sequential wafer-level processing.
Solution Approach 2:
Transfer heads are pre-positioned and can be selectively activated to pick up devices before they are needed at the receiving substrate. This preliminary action allows for optimized transfer sequencing and reduces waiting time, enabling high-rate integration by preparing transfer operations in advance.
3Reliability
If rigid transfer heads are used, then structural stability is maintained, but height variations in devices cause poor contact and potential damage
Solution Approach 1:
The transfer heads incorporate compliant or flexible elements that allow dynamic adjustment of the contact point position and pressure distribution. This dynamic compliance enables the transfer head to adapt to height variations in different devices, maintaining reliable contact while distributing compressive forces to prevent device damage, thereby resolving the contradiction between structural stability and adaptive contact.
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
The compliant micro device transfer head effectively compensates for device height variations, ensures complete contact and pick-up of micro devices, and facilitates efficient transfer to receiving substrates with reduced risk of damage, enabling high transfer rates and integration into heterogeneous systems.
Implementation Method 1
a voltage is applied to the array of monopolar transfer heads to generate a grip pressure on the array of micro devices
Implementation Method 2
a voltage is applied to the array of monopolar transfer heads to generate a grip pressure on the array of micro devices
Data Source
AI summary
A compliant monopolar micro device transfer head array and method of forming a compliant monopolar micro device transfer array from an SOI substrate are described. In an embodiment, the micro device transfer head array including a base substrate and a patterned silicon layer over the base substrate. The patterned silicon layer may include a silicon interconnect and an array of silicon electrodes electrically connected with the silicon interconnect. Each silicon electrode includes a mesa structure protruding above the silicon interconnect, and each silicon electrode is deflectable into a cavity between the base substrate and the silicon electrode. A dielectric layer covers a top surface of each mesa structure.