Lithography Stage Thrust Control via Z-Position Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor exposure apparatuses face challenges in accurately driving fine moving stages at high acceleration and accuracy, particularly when the electromagnet and magnetic material face each other in the z direction, leading to incorrect thrust calculation and reduced driving accuracy in the x and y directions, which impedes throughput.
Innovation Solution
A stage apparatus with an electromagnetic actuator and a controller that corrects the thrust command value based on the relative position of the fine moving stage to the coarse moving stage in the z direction, using a magnetic flux command value correction method to maintain accurate thrust control across different z positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the fine moving stage is driven in the z direction to change the opposing area between electromagnet and magnetic material, then the position adjustment capability is improved, but the thrust calculation accuracy in x and y directions deteriorates
Solution Approach 1:
The controller pre-stores the relationship between z-direction positions and opposing areas in a lookup table. Before driving the fine moving stage in x or y directions, the system determines the current z-position and retrieves the corresponding opposing area value, ensuring accurate thrust calculation is prepared in advance without needing real-time measurements that would slow down operation.
Solution Approach 2:
The system changes the parameter used for thrust calculation from a fixed opposing area value to a variable opposing area value that depends on the z-direction position. By retrieving the appropriate opposing area from storage based on the current z-position, the system adapts the calculation parameters to match the actual physical configuration, resolving the contradiction between position flexibility and calculation accuracy.
2Measurement precision
If the opposing area between electromagnet and magnetic material is kept fixed, then the thrust calculation accuracy is improved, but the ability to adjust fine moving stage position in z direction is restricted
Solution Approach 1:
The system transitions from using a fixed opposing area value to using a dynamic opposing area value that automatically adjusts based on the z-direction position of the fine moving stage. The controller continuously updates the opposing area parameter according to the current z-position, allowing the system to maintain calculation accuracy while adapting to different positional configurations.
Solution Approach 2:
The controller acts as an intermediary that manages the relationship between z-position and opposing area. Instead of directly measuring opposing area during operation, the controller uses the z-position as an intermediate parameter to retrieve the appropriate opposing area value from stored data, enabling accurate thrust calculation without requiring direct measurement of the opposing area itself.
3Productivity
If high acceleration is applied to the fine moving stage in x and y directions, then the productivity is improved, but the driving accuracy deteriorates when opposing area changes in z direction
Solution Approach 1:
The system implements feedback by continuously monitoring the z-direction position of the fine moving stage and using this information to adjust the opposing area parameter for thrust calculation. The controller retrieves the current z-position, determines the corresponding opposing area from stored data, and uses this corrected value to calculate the required coil current for achieving the desired thrust, ensuring accurate control even at high acceleration levels.
Solution Approach 2:
The system performs preliminary action by pre-calculating and storing the relationship between z-positions and opposing areas before actual operation. During high-speed operation in x and y directions, the system simply retrieves the pre-computed opposing area value based on the current z-position, avoiding any delay in thrust calculation and maintaining both high acceleration and high accuracy.
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
Enables precise and independent driving of the fine moving stage in all directions, enhancing the accuracy and throughput of the exposure apparatus by compensating for changes in the opposing area between the electromagnet and magnetic material.
Implementation Method 1
an electromagnetic actuator using the principle of an electromagnet, which is used as the actuator of a fine moving stage
Implementation Method 2
An attraction force generated by a magnetic force becomes the thrust of the electromagnetic actuator
Implementation Method 3
a magnetic flux generated in an electromagnet is detected by a coil, and feedback control is performed
Data Source
AI summary
A stage apparatus includes: a coarse moving stage; a fine moving stage located at an interval from the coarse moving stage in a first direction; an electromagnetic actuator including a first core located on one of the coarse moving stage and the fine moving stage and a second core located on the other of the coarse moving stage and the fine moving stage and configured to accelerate or decelerate the fine moving stage in a second direction perpendicular to the first direction; and a controller configured to correct a command value of a thrust of the electromagnetic actuator in the second direction in accordance with a relative position of the fine moving stage with respect to the coarse moving stage in the first direction.