Micro-Device Etch Hole Layout for Faster Sacrificial Release
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Solution Overview
Problem
Existing micro-device transfer methods face challenges with slow etching rates and anisotropic etching in crystalline wafers, leading to etching damage and reduced manufacturing throughput, compromising the integrity of micro-devices and transfer structures.
Innovation Solution
The introduction of micro-device structures with etch holes that expose sacrificial portions through the micro-device, allowing for faster and more controlled etching, reducing damage by orienting etch holes and tethers to minimize undercutting and facilitate efficient release from the source wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sacrificial layer etching is used to release micro-devices from source wafer, then micro-device release is achieved, but etching time is excessive and etching damage occurs to micro-device and transfer structures
Solution Approach 1:
The patent introduces etch holes that segment the sacrificial layer into isolated regions beneath the micro-device. This segmentation allows etchant to access and remove sacrificial material from multiple locations simultaneously, dramatically reducing etching time while preventing etchant contact with the micro-device and transfer structures from above.
Solution Approach 2:
The etch holes serve as intermediary pathways that enable indirect access to the sacrificial layer. By creating controlled openings through the micro-device structure, the etchant can reach the sacrificial material without directly contacting sensitive components, thus reducing damage while accelerating release.
2Reliability
If slow etching is used to prevent damage, then etching damage is reduced, but manufacturing throughput decreases
Solution Approach 1:
By segmenting the sacrificial layer through etch holes, the patent enables parallel etching of multiple sacrificial regions simultaneously. This increases the effective etching rate without increasing etchant exposure time for sensitive structures, thereby improving manufacturing throughput while maintaining reliability.
Solution Approach 2:
The patent transitions from top-down etching to side-access etching by introducing vertical etch holes. This dimensional change allows etchant to approach the sacrificial layer from a different direction, enabling faster removal of sacrificial material without increasing horizontal exposure distance and thus improving throughput without compromising structure integrity.
3Productivity
If anisotropic etching is used in crystalline wafers, then etching speed varies by direction, but this causes incomplete undercutting and partial release failure
Solution Approach 1:
The patent intentionally introduces asymmetric etch hole patterns that compensate for anisotropic etching characteristics. By strategically positioning etch holes at specific locations and orientations, the design ensures that faster-etching directions are balanced by additional hole placements, achieving uniform and complete undercutting despite directional etching rate variations.
Solution Approach 2:
By dividing the sacrificial layer into multiple segments accessible through separately positioned etch holes, the patent ensures that each segment can be completely removed regardless of anisotropic etching preferences. This segmentation approach guarantees complete release by addressing each region independently.
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 approach enables rapid and damage-reduced release of micro-devices, enhancing manufacturing efficiency and reducing etching-related failures, thus improving the integrity and throughput of micro-device transfer processes.
Implementation Method 1
a sacrificial portion of the source wafer can etch more rapidly in one direction than another so that a micro-device or tether disposed over the sacrificial portion is only partially undercut and are partially unetched
Data Source
AI summary
A micro-device structure comprises a source substrate having a sacrificial layer comprising a sacrificial portion adjacent to an anchor portion, a micro-device disposed completely over the sacrificial portion, the micro-device having a top side opposite the sacrificial portion and a bottom side adjacent to the sacrificial portion and comprising an etch hole that extends through the micro-device from the top side to the bottom side, and a tether that physically connects the micro-device to the anchor portion. A micro-device structure comprises a micro-device disposed on a target substrate. Micro-devices can be any one or more of an antenna, a micro-heater, a power device, a MEMs device, and a micro-fluidic reservoir.