Substrate Holder Feedback Control for Reliable Wafer Release
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Solution Overview
Problem
Existing substrate transfer devices face challenges in separating substrates from pads due to stickiness, leading to issues like substrates jumping off during transfer or remaining on the transfer arm without delivery.
Innovation Solution
A substrate holder with a stage that can be raised and lowered, a measurer to measure weight, pressure, or displacement, and a controller to predict the state of the transfer arm based on measurement results, allowing for proper evaluation of substrate separatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum suction is used to hold the substrate on the transfer arm, then the substrate can be securely held during transfer, but the substrate may stick to the pads and fail to separate properly
Solution Approach 1:
The system uses a load cell to continuously monitor the weight of the substrate on the transfer arm and provides feedback to the controller. The controller adjusts the vacuum suction force based on this feedback, reducing it when the substrate is near the destination to facilitate separation, while maintaining high suction during transfer to ensure secure holding.
Solution Approach 2:
The vacuum suction force is made dynamic rather than static. The system transitions between different suction levels: high suction during transfer to secure the substrate, and reduced suction near the destination to enable easy separation. This dynamic adjustment resolves the contradiction between secure holding and easy release.
2Manufacturing precision
If the substrate is held firmly during transfer, then transfer accuracy is improved, but substrate separation from pads becomes difficult
Solution Approach 1:
The vacuum suction force is dynamically adjusted based on the transfer arm's position and the substrate's proximity to the destination. High suction is applied during the transfer motion to ensure accuracy, then gradually reduced as the substrate approaches the target location to facilitate clean separation without affecting transfer precision.
Solution Approach 2:
The load cell provides real-time weight feedback that indicates the substrate's attachment status. The controller uses this feedback to determine when to reduce vacuum suction, ensuring that transfer accuracy is maintained during the critical transfer phase while enabling separation when the substrate reaches the destination.
3Reliability
If vacuum suction force is increased to prevent substrate drop, then substrate holding is more reliable, but substrate separation becomes more difficult
Solution Approach 1:
The vacuum suction force is made dynamic, transitioning from high force during transfer to low force during separation. The system maintains high suction when the substrate is on the transfer arm to prevent drops, then reduces suction when near the destination to minimize the force needed for separation, resolving the contradiction between holding reliability and separation ease.
Solution Approach 2:
The vacuum suction is applied periodically with different intensity levels: high intensity during the transfer phase and low intensity during the separation phase. This periodic variation in suction force allows the system to achieve both reliable holding and easy separation at different stages of the transfer process.
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 solution effectively evaluates and improves the separatability of substrates from transfer pads, preventing transfer issues and ensuring reliable substrate delivery.
Implementation Method 1
a load cell 220 that supports the wafer holder 200 and that measures a weight of the wafer holder 200
Implementation Method 2
a laser displacement meter 230 that measures a position of the wafer holder 200
Data Source
AI summary
A substrate holder for receiving a substrate from a transfer arm and holding the substrate, includes: a stage configured to be raised and lowered in a vertical direction and configured to place the substrate thereon; a measurer configured to measure at least one of a weight, a pressure, and a displacement of the stage; and a controller configured to predict a state of the transfer arm based on measurement results of the measurer.