In-situ Optical Verification for Micro Device Transfer Accuracy
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Solution Overview
Problem
Current micro device transfer technologies face challenges such as failure to pick or place micro devices, positional offsets, and interference from particles, leading to errors in the integration of micro devices like RF MEMS, LEDs, and quartz-based oscillators, which hinder their commercialization due to inefficiencies in transfer processes.
Innovation Solution
The implementation of a mass transfer system with in-situ optical verification methods using a micro pick-up array (MPA) that illuminates and inspects micro devices during transfer, employing image capture and analysis to verify the presence, absence, and global offset of micro devices, allowing for real-time correction and minimal disruption to the transfer workflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional transfer printing technologies are used, then micro devices can be transferred from donor substrate to receiving substrate, but the process suffers from errors such as failure to pick or place devices, positional offsets, and particle interference
Solution Approach 1:
The patent performs optical verification of micro device presence on the transfer wafer before the actual transfer process. This preliminary inspection allows the system to identify missing devices, positional offsets, or particles that could cause transfer errors, enabling corrective actions to be taken before the transfer begins, thereby improving both reliability and manufacturing precision
Solution Approach 2:
The patent implements a feedback mechanism where optical verification results are obtained during or after the transfer process, and this information is used to identify and correct errors such as failed pickups, misplaced devices, or contamination. This closed-loop feedback system continuously improves transfer accuracy and reduces defects in subsequent transfers
2Measurement precision
If optical verification is performed during transfer, then real-time detection of micro device presence and position is achieved, but the system complexity increases due to additional illumination and imaging components
Solution Approach 1:
The patent designs the optical verification system to serve multiple functions: it not only detects the presence of micro devices but also determines their positional accuracy, identifies particles or contaminants, and provides feedback for process correction. This multi-functionality reduces the need for separate inspection systems, thereby limiting the increase in overall system complexity while maintaining high measurement precision
Solution Approach 2:
The patent uses light as an intermediary to indirectly observe and verify micro device characteristics without physically contacting or disturbing the devices during transfer. This optical mediation enables high-precision measurement while keeping the physical interaction minimal, thus balancing measurement precision with system complexity
3Productivity
If the entire transfer wafer is involved in the transfer process, then batch transfer efficiency is improved, but the de-bonding process becomes more complex and time-consuming
Solution Approach 1:
The patent performs optical verification before the de-bonding step to identify any issues with device attachment or positioning on the transfer wafer. By detecting problems early, the system can address them before committing to the time-consuming de-bonding process, thereby reducing unnecessary de-bonding time while maintaining batch transfer efficiency
Solution Approach 2:
The patent replaces physical inspection methods with optical verification to assess transfer wafer status. This substitution eliminates the need for manual or mechanical inspection during de-bonding, reducing the time and complexity of the de-bonding process while maintaining batch processing efficiency
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 ensures high accuracy and efficiency in micro device transfer by enabling real-time detection and correction of errors, reducing the need for halting the transfer process for inspection and minimizing errors, thus improving the integration and packaging of micro devices.
Implementation Method 1
the wavelength of light is selected to create a known contrast ratio between the wavelength of light reflective from an MPA layer and micro device layers on the array of micro devices
Data Source
AI summary
An optical verification method and mass transfer system described. In an embodiments, a mass transfer sequence may be accompanied by optical imaging and inspection to detect pick and place errors. The optical imaging and inspection techniques may be performed in-situ.