Parallel Wafer Transfer Robots for Photolithography Cycle Time
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Solution Overview
Problem
Current photolithography tools face challenges in achieving high wafer transfer yields due to slow transfer rates, with manufacturers primarily focusing on enhancing robot motion properties rather than optimizing the wafer transfer system configuration.
Innovation Solution
A wafer transfer system design that eliminates direct wafer transfers between the dual-arm robot and the wafer stage, utilizing dual-arm, wafer-loading, and wafer-unloading linear robots to operate in parallel, allowing for efficient transfer of wafers across storage, pre-alignment, and buffer stages, accommodating various wafer sizes, and incorporating rubber suction cups for retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the robot directly transfers wafers with the wafer stage, then the device complexity is reduced, but the wafer transfer rate becomes slow and the transfer cycle time increases
Solution Approach 1:
The wafer transfer system is segmented into three independent robotic units: a dual-arm robot for storage apparatus operations, a wafer-loading linear robot for wafer stage operations, and a wafer-unloading linear robot for buffer stage operations. Each unit handles specific transfer tasks independently, eliminating the bottleneck of single-robot sequential operations and achieving parallel processing that increases overall transfer rate without excessive complexity.
Solution Approach 2:
The wafer-loading linear robot performs preliminary actions by pre-positioning wafers on the wafer stage before the dual-arm robot completes its cycle. The wafer-unloading linear robot simultaneously prepares the buffer stage for receiving wafers. These preliminary actions overlap with the dual-arm robot's operations, reducing idle time and accelerating the overall transfer cycle.
2Productivity
If the robot speed and acceleration are continuously improved, then the wafer transfer yield increases, but the system becomes less stable and more complex
Solution Approach 1:
By dividing the transfer system into three specialized robotic units, each operating at optimized speeds for its specific task, the system achieves high overall yield without requiring any single robot to operate at excessively high speeds. The segmentation allows each unit to maintain stable, controlled motion appropriate to its function.
Solution Approach 2:
The wafer-loading and wafer-unloading linear robots act as intermediaries between the dual-arm robot and the wafer stage/buffer stage. These intermediary units buffer the transfer process, allowing the dual-arm robot to operate at its optimal speed while the linear robots handle the slower, more stable transfer operations near the exposure chamber, thus decoupling speed requirements and maintaining stability.
3Loss of time
If the wafer transfer system is optimized with multiple linear robots operating in parallel, then the transfer cycle time is reduced, but the device complexity increases
Solution Approach 1:
The system segments transfer operations into three parallel streams handled by specialized robots, reducing overall cycle time through concurrent operations. While this increases component count, each robot is relatively simple in design, and the segmentation creates modular units that are easier to maintain and optimize individually.
Solution Approach 2:
The dual-arm robot is designed with universal capabilities to handle multiple tasks: transferring wafers to and from the storage apparatus, coordinating with both linear robots, and adapting to different wafer sizes. This multi-functionality reduces the need for additional specialized equipment, offsetting the complexity increase from having multiple robots.
4Device complexity
If the dual-arm robot handles all wafer transfers including direct stage transfer, then the device complexity is low, but the transfer burden on the robot increases and efficiency decreases
Solution Approach 1:
The workload is segmented across three robotic units based on their capabilities and optimal performance characteristics. The dual-arm robot focuses on storage apparatus operations where its multi-axis movement is most effective, while the linear robots handle the simpler, more repetitive tasks of loading and unloading the wafer stage and buffer stage, improving overall system efficiency.
Solution Approach 2:
The wafer-loading and wafer-unloading linear robots serve as intermediaries that offload the transfer burden from the dual-arm robot. These intermediary units handle the high-frequency, low-complexity transfer operations near the exposure chamber, allowing the dual-arm robot to focus on the more complex storage apparatus operations, thus improving the dual-arm robot's efficiency for its specialized tasks.
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 design significantly reduces the burden on the dual-arm robot, saves time in wafer transfers, and achieves higher yields by shortening the transfer cycle, enabling efficient handling of different wafer sizes and types, resulting in a 11.3s time savings and a theoretical yield of 248 WPH.
Implementation Method 1
incorporating rubber suction cups for retention
Data Source
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AI summary
A wafer transfer system for use in a photolithography system including a wafer storage apparatus (400), a pre-alignment apparatus (500), a buffer stage (700) and a wafer stage (600) is disclosed, which includes: a dual-arm robot (100), configured to take a wafer to be exposed from the wafer storage apparatus (400) and transfer it onto the pre-alignment apparatus (500) and further configured to remove an exposed wafer from the buffer stage (700) and place it back into the wafer storage apparatus (400); a wafer-loading linear robot (200), configured to transfer a pre-aligned wafer onto the wafer stage (600); and a wafer-unloading linear robot (300), configured to transfer the exposed wafer onto the buffer stage (700). The dual-arm robot (100), the wafer-loading linear robot (200) and the wafer-unloading linear robot (300) can operate in parallel so as to achieve time savings in the wafer transfers.