Micro-LED Bonded Wafer Failure Removal via Optical Mapping
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Solution Overview
Problem
The existing methods for producing bonded light-emitting device wafers face challenges due to protrusion-shaped bonding-failure portions, which lead to precision issues in device structure production, increased transfer failures during micro LED dice transfer, and difficulties in detecting and removing faulty portions.
Innovation Solution
A method involving bonding a light-emitting device structure to a transparent substrate via an adhesive that absorbs laser light, producing map data for removal by optically investigating failure portions, and using laser light to sublimate the adhesive and remove the failure portions, thereby producing a bonded light-emitting device wafer without mechanical intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods using BCB are used to bond wafers, then bonding is achieved, but bonding-failure portions in protrusion shape are generated due to surface conditions or foreign matters
Solution Approach 1:
The patent applies preliminary action by detecting bonding-failure portions before device production through optical inspection, and removing them in advance using laser irradiation. This prevents the protrusion-shaped failures from affecting subsequent photolithography and device fabrication processes, thereby maintaining manufacturing precision while preserving bonding reliability.
Solution Approach 2:
The patent extracts and removes the harmful bonding-failure portions from the wafer surface using laser irradiation that selectively vaporizes the adhesive at failure locations. This extraction eliminates the protrusion-shaped defects that would otherwise degrade shape and dimension precision during device production.
2Reliability
If protrusion-shaped bonding-failure portions are present on the wafer, then bonding structure is formed, but non-uniformity in applied pressure is generated during transfer, resulting in transfer failure
Solution Approach 1:
The patent performs preliminary removal of bonding-failure portions before the transfer process using laser irradiation. By eliminating the protrusion-shaped defects in advance, the wafer surface becomes uniform, ensuring even pressure distribution during subsequent transfer operations and preventing transfer failures.
Solution Approach 2:
The patent converts the harmful effect of bonding-failure portions into a beneficial detection opportunity by using optical inspection to identify their locations. This enables targeted laser removal of only the defective areas, transforming the presence of failures into a precise correction process that improves both transfer reliability and pressure uniformity.
3Ease of manufacture
If mechanical methods are used to remove bonding-failure portions, then removal is achieved, but the method is not capable of selectively removing only failure portions and requires batch transfer
Solution Approach 1:
The patent replaces mechanical removal methods with laser irradiation, which enables selective removal of bonding-failure portions based on optical detection data. The laser targets specific failure locations identified by optical inspection, vaporizing the adhesive precisely at those spots without affecting surrounding areas, thereby achieving both ease of manufacture and high selective removal precision.
Solution Approach 2:
The patent applies local quality by using laser irradiation to remove adhesive only at the specific locations where bonding-failure portions are detected through optical inspection. This localized treatment ensures that only defective areas are removed while preserving the integrity of successful bonding regions, achieving precise selective removal.
4Measurement precision
If optical detection is used to identify failure portions, then failure locations are detected, but mechanical pickup is impossible because failure portions are firmly bonded by BCB
Solution Approach 1:
The patent replaces mechanical pickup methods with laser irradiation for removing failure portions. The laser energy selectively vaporizes the BCB adhesive at detected failure locations, enabling easy removal of firmly bonded defective areas without requiring mechanical force that would affect surrounding bonded regions.
Solution Approach 2:
The patent changes the physical state of the BCB adhesive at failure portions by applying laser energy, which heats and vaporizes the adhesive locally. This parameter change from solid/bonded state to vapor state enables easy removal of failure portions while leaving the surrounding bonded areas intact.
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 allows for the selective and reliable removal of bonding-failure and device characteristics failure portions, improving the precision of device structure production and reducing transfer failures, while also preventing the transfer of faulty micro LEDs.
Implementation Method 1
irradiating a portion to be removed of the bonded wafer with laser light for removal from the to-be-bonded substrate, a portion of an adhesive included in the portion to be removed absorbs the laser light for removal
Implementation Method 2
causing the portion of the adhesive which is included in the failure portion to sublimate
Implementation Method 3
irradiating the failure portion of the bonded wafer with the laser light for removal from the to-be-bonded substrate
Implementation Method 4
removing the portion of the light-emitting device structure which is included in the failure portion
Data Source
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Figure 6~8
AI summary
The present invention is a method for producing a bonded light-emitting device wafer, in which a light-emitting device structure, to be a micro LED, and a to-be-bonded substrate are bonded with each other via an adhesive, the method includes the steps of bonding the light-emitting device structure to the to-be-bonded substrate via the adhesive to obtain a bonded wafer, producing a map data for removal by optically investigating a failure portion of the bonded wafer, and irradiating the failure portion of the bonded wafer with the laser light for removal from the to-be-bonded substrate based on the map data for removal, causing a portion of the adhesive which is included in the failure portion to absorb the laser light for removal and causing the portion of the adhesive which is included in the failure portion to sublimate, thereby removing the portion of the light-emitting device structure which is included in the failure portion to obtain the bonded light-emitting device wafer. This can provide the method for producing a bonded light-emitting device wafer capable of selectively removing the failure portion of the light-emitting device structure and producing the bonded light-emitting device wafer.