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Advancements in Lithographic Positioning Control

New control method improves positioning accuracy in lithographic systems for semiconductors.

― 5 min read


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Table of Contents

The semiconductor industry is growing rapidly, and with it comes the need for more precise and efficient equipment. One important piece of equipment is the lithographic system used to produce integrated circuits. This system requires high levels of accuracy in positioning, which can be challenging due to the flexible dynamics of the machinery. This paper discusses a new control approach that helps to manage these flexible dynamics, improving positioning accuracy in high-precision systems.

The Challenge of Positioning

Lithographic systems project extreme ultraviolet light to create patterns on silicon wafers. As the industry demands higher outputs and better accuracy, these systems must handle fast motion profiles. However, moving quickly can introduce errors in positioning due to the flexibility of the machine's components. This flexibility leads to difficulties in maintaining accurate position tracking.

The Solution: Active Compensation

To counteract these issues, a new control method has been developed. This approach actively manages the flexible dynamics of the system instead of only focusing on the rigid body movements. By using a traditional control structure and extending it to incorporate flexible dynamics, the new method can better track positions even when the machine is moving aggressively.

Real-Time Implementation

Real-time implementation of this control approach is crucial. To make it work efficiently, the method uses position-dependent weighting functions. These functions help process the information quickly, ensuring that the control system responds in real-time to changing positions of the machine.

Experimental Validation

To test the effectiveness of the new method, experiments were conducted using a state-of-the-art extreme ultraviolet wafer stage. This advanced piece of equipment is designed to operate with high precision, making it an ideal candidate for validating the new control approach.

Understanding the Mechanics

The wafer stage uses a combination of long and short stroke mechanisms. The long-stroke function allows for broader movements, while the short stroke enables fine-tuning at a smaller scale. Both mechanisms work together to ensure that the silicon wafer is positioned perfectly under the projection optics.

Complications in Measurement

One of the challenges faced is the need for accurate relative position measurements of the moving-body. These measurements are critical for controlling the system effectively. Position-dependent transformations are used to connect control points on the moving body with actual measurement points, which is essential for maintaining accuracy.

The Innovative Approach

The proposed control method integrates a flexible mode control loop. This loop consists of several components: an output-based modal state observer that helps reconstruct the flexible dynamics and a state feedback design that actively controls resonance modes. By combining these elements with a traditional control setup, the new method can address flexibility issues more effectively.

Key Contributions

The main contributions of this approach include the integration of flexible mode control and the development of the modal observer. Together, these components lead to improved performance in tracking positions, allowing the lithographic equipment to operate more efficiently.

Addressing Position-Dependent Dynamics

Position-dependent effects are common in high-precision motion systems. These effects arise from the way the equipment measures position and can lead to inaccuracies. To tackle these, the new approach uses a linear-parameter-varying representation. This representation allows the system to account for different behaviors at various positions, leading to more accurate control.

Designing the Control System

In designing the new control system, the flexible dynamics are considered to ensure that the control loop can manage the influences of these dynamics effectively. The system's design incorporates a feedback loop to continuously adjust and improve the control process.

Experimental Setup

The experiments utilize a cutting-edge EUV wafer stage, which includes a dual-stroke mechanism and advanced control capabilities. This system provides a practical application for testing the new control methods, as it embodies the challenges faced in today's semiconductor production.

Results of Implementation

The results from the experiments showed that the proposed active damping method significantly improved position tracking performance. By actively dampening the first resonance mode, the control approach managed to reduce Tracking Errors effectively.

Improving Performance Metrics

To measure the success of the new control system, specific performance metrics were evaluated. These included analyzing the moving position errors during the operation of the equipment. Results indicated a clear advantage in using the new approach compared to traditional systems.

Cumulative Power Analysis

The cumulative power spectral density of the tracking errors was assessed, showing that the new method led to a noticeable reduction in errors. By addressing the flexible dynamics directly, the control system was able to function more smoothly during critical operation periods.

Conclusion

This study presents a promising approach to managing flexible dynamics in high-precision motion systems. By actively compensating for these dynamics, the control method enhances position tracking performance, which is vital for the semiconductor industry. The experimental validation on advanced wafer stage systems reinforces the effectiveness of the proposed solutions.

Future Directions

There is a continuing need for improvements in lithographic systems to meet the stringent demands of the semiconductor industry. The insights gained from this research will contribute to developing even more advanced control methods that enhance performance and accuracy in high-precision applications. As technology evolves, ongoing innovation will be crucial to maintaining competitiveness within this dynamic field.

Original Source

Title: Active Compensation of Position Dependent Flexible Dynamics in High-Precision Mechatronics

Abstract: Growing demands in the semiconductor industry necessitate increasingly stringent requirements on throughput and positioning accuracy of lithographic equipment. Meeting these demands involves employing highly aggressive motion profiles, which introduce position-dependent flexible dynamics, thus compromising achievable position tracking performance. This paper introduces a control approach enabling active compensation of position-dependent flexible dynamics by extending the conventional rigid-body control structure to include active control of flexible dynamics. To facilitate real-time implementation of the control algorithm, appropriate position-dependent weighting functions are introduced, ensuring computationally efficient execution of the proposed approach. The efficacy of the proposed control design approach is demonstrated through experiments conducted on a state-of-the-art extreme ultraviolet (EUV) wafer stage.

Authors: Yorick Broens, Hans Butler, Ramidin Kamidi, Koen Verkerk, Siep Weiland

Last Update: 2024-08-07 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2408.03642

Source PDF: https://arxiv.org/pdf/2408.03642

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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