Wafer Stage Lifting With Linear Actuators for Mask Alignment
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Solution Overview
Problem
Conventional spring-loading mechanisms in contact lithography systems suffer from limited accuracy, risk of damage, wear and tear, and lack of real-time feedback, leading to suboptimal wafer and photomask alignment and potential device yield and quality issues.
Innovation Solution
A wafer stage lifting system utilizing linear actuators and distance sensors, controlled by a controller, for precise alignment and real-time adjustments, minimizing damage and ensuring accurate contact between the wafer and photomask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a spring-loading mechanism is used to raise the wafer stage, then the system is simple and cost-effective, but the alignment accuracy between wafer and photomask is limited
Solution Approach 1:
The patent replaces the spring-loading mechanical system with a motor-driven lifting mechanism coupled with a feedback control system. The motor driver controls the lifting speed and position, while the feedback from distance sensors enables precise alignment, substituting passive mechanical force with active controlled motion to achieve both simplicity and high accuracy.
Solution Approach 2:
The patent introduces a feedback control mechanism where distance sensors continuously measure the position of the wafer stage and photomask stage, and the controller adjusts the motor-driven lifting mechanism based on this feedback to achieve precise alignment. This closed-loop control resolves the contradiction by enabling high precision without compromising system simplicity.
2Ease of manufacture
If a spring-loading mechanism is used to raise the wafer stage, then the system is simple and cost-effective, but the force exerted can damage the sensitive surfaces of wafer and photomask
Solution Approach 1:
The patent replaces the spring-loading mechanism with a motor-driven lifting system that provides controlled, gradual movement. This substitution eliminates the sudden force application characteristic of spring mechanisms, allowing the wafer stage to be raised smoothly and gently, thereby preventing damage to sensitive surfaces while maintaining system simplicity.
Solution Approach 2:
The patent employs a dynamic control approach where the motor driver regulates the lifting speed and force in real-time based on feedback from distance sensors. This dynamic adjustment allows the system to apply minimal necessary force, avoiding the excessive or sudden forces that could damage wafer or photomask surfaces, while keeping the overall system simple and cost-effective.
3Ease of manufacture
If conventional spring-loading mechanisms are used, then the system is simple, but mechanical components wear out over time requiring frequent maintenance
Solution Approach 1:
The patent replaces the spring-loading mechanism with a motor-driven lifting system. Motors and their control circuits have significantly longer service lives and require far less maintenance compared to mechanical springs that undergo repeated compression and expansion cycles. This substitution maintains system simplicity while dramatically improving reliability and reducing maintenance frequency.
4Ease of manufacture
If conventional spring-loading mechanisms are used, then the system is simple and cost-effective, but there is no real-time feedback mechanism for adjustments
Solution Approach 1:
The patent introduces distance sensors that continuously measure the positions of the wafer stage and photomask stage, providing real-time feedback to the controller. This feedback mechanism enables dynamic adjustments during the lifting process, allowing the system to adapt to variations in wafer thickness, stage positioning, or other parameters, while the overall system remains simple and cost-effective through the use of standard sensor and controller components.
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
Enhances alignment accuracy, reduces damage risk, and allows real-time adjustments, resulting in higher precision and repeatability in the lithography process.
Implementation Method 1
connected to a set of linear actuators for vertical movement
Implementation Method 2
a set of distance sensors positioned above the wafer stage. In one embodiment, the three distance sensors are configured to measure heights at three different points on the wafer surface
Data Source
AI summary
The present invention relates to a system and method for precisely aligning a wafer and a photomask in a semiconductor lithography process. The system includes a wafer stage, a photomask stage, multiple linear actuators and distance sensors, and a controller. The wafer stage is configured to carry a wafer; the photomask stage is configured to carry a photomask. The linear actuators are used to adjust the wafer stage, and the distance sensors measure the height of the wafer surface. The controller is configured to measure the height at multiple points on the wafer surface, adjust its level, calculate the distance between the wafer and the photomask, and raise the wafer stage so that the wafer contacts the 10 photomask. The present invention provides a semiconductor manufacturing method with improved accuracy, efficiency, and user control.