Compliant Monopolar Micro Device Transfer Head with Silicon Electrodes
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Solution Overview
Problem
Traditional micro device transfer technologies face challenges in efficiently transferring micro devices like RF MEMS, LED display systems, and quartz-based oscillators due to integration and packaging issues, particularly in handling variations in device height and surface contamination, which can lead to incomplete pick-up processes and damage to the devices.
Innovation Solution
A compliant monopolar micro device transfer head with deflectable silicon electrodes and a mesa structure is developed, allowing for improved contact with micro devices of varying heights and reduced compressive forces, enabling efficient pick-up and transfer without the need for patterned metal electrodes, and incorporating a processing sequence that minimizes thermal processing constraints and reduces the number of processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional transfer wafer technologies are used, then device transfer can be achieved, but handling variations in device height and surface contamination lead to incomplete pick-up processes and device damage
Solution Approach 1:
The transfer head employs a flexible membrane structure that can deform to accommodate variations in device height. The membrane acts as a compliant interface between the rigid transfer head body and the micro devices, allowing uniform grip pressure to be applied across devices of different heights without causing damage or incomplete pick-up.
Solution Approach 2:
The patent utilizes electrostatic actuation to change the physical state of the membrane from relaxed to actuated position. By applying voltage, the membrane deflects to make contact with devices, and by removing voltage, it returns to its original position, enabling controlled pick-up and release cycles.
2Adaptability or versatility
If deflectable silicon electrodes with mesa structure are used, then contact with varying device heights is improved, but device complexity increases
Solution Approach 1:
The electrode system is segmented into multiple independent deflectable electrodes arranged in an array. Each electrode can independently deflect to contact devices at different positions and heights, providing adaptability while maintaining a modular structure that simplifies manufacturing through repetitive patterning.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with electrostatic actuation. Instead of using mechanical springs, levers, or actuators to achieve deflection, the system uses electric fields to deform the membrane and electrodes, significantly reducing mechanical complexity.
3Ease of manufacture
If patterned metal electrodes are avoided, then processing steps are reduced, but achieving uniform grip pressure becomes more challenging
Solution Approach 1:
The membrane is designed as a homogeneous continuous structure that distributes applied forces uniformly across its surface. When actuated, the entire membrane deflects together, ensuring that all electrodes experience the same grip pressure, which simplifies manufacturing compared to individually addressing each electrode.
Solution Approach 2:
The membrane serves multiple functions simultaneously: it acts as a structural support, an actuator, a force distributor, and a positioning element. This multi-functionality eliminates the need for separate components to achieve uniform grip pressure, reducing processing steps while maintaining manufacturing precision.
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 height variations, ensures complete pick-up of micro devices, and protects their physical integrity by applying uniform grip pressure, while simplifying the processing sequence and reducing thermal constraints.
Implementation Method 1
Each silicon electrode is deflectable into a cavity between the base substrate and the silicon electrode
Implementation Method 2
A voltage applied to the array of silicon electrodes creates a grip pressure on an 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.