Alignment Sensor Vibration Compensation in Dual-Wafer-Stage Lithography
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Solution Overview
Problem
The dual-wafer-stage system in photolithography tools experiences increased vibration due to higher throughput requirements, leading to alignment errors and insufficient repeatability accuracy, which is challenging to control within the necessary 10 nm amplitude for accurate overlay positioning in semiconductor manufacturing.
Innovation Solution
An alignment system that includes a position acquisition module capable of collecting relative positional data from both the wafer stage and the alignment sensor, processing these data to zero out the vibration amplitude of the alignment sensor, allowing for precise alignment mark positioning independent of sensor vibration, utilizing optical signals and visible light beams to achieve higher alignment repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dual-wafer-stage system is employed to improve throughput, then productivity increases, but vibration of the alignment sensor increases leading to alignment errors
Solution Approach 1:
The system measures the vibration of the alignment sensor using a position acquisition module and feeds this information back to a signal processing device. The signal processing device then compensates for the measured vibration in real-time, allowing the system to maintain alignment accuracy despite the increased vibrations caused by higher throughput dual-wafer-stage operation.
Solution Approach 2:
The invention replaces direct mechanical stabilization of the alignment sensor with an optical measurement and signal processing system. Instead of mechanically isolating or stabilizing the sensor, the system uses optical position sensing and computational methods to measure and compensate for vibrations, substituting mechanical solutions with optical and information-processing approaches.
2Productivity
If greater accelerations are applied to increase throughput, then productivity improves, but impact on the alignment sensor increases causing greater alignment errors
Solution Approach 1:
The position acquisition module continuously monitors the alignment sensor position during wafer stage acceleration and measurement operations. This feedback information is processed to compensate for acceleration-induced impacts, allowing high-speed operation without sacrificing measurement precision of alignment marks.
Solution Approach 2:
The system performs preliminary measurement of the alignment sensor position and characteristics before actual alignment measurements are taken. This preliminary action allows the system to establish baseline data and compensation parameters that can be applied during subsequent high-speed operations, ensuring measurement precision is maintained despite acceleration impacts.
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 solution effectively reduces alignment errors by eliminating the impact of alignment sensor vibration, enhancing repeatability accuracy to meet the stringent requirements of overlay error performance, particularly for smaller characteristic dimensions in semiconductor manufacturing.
Implementation Method 1
an alignment sensor attached to the main frame and arranged above the alignment sensor, the alignment sensor being configured to output an optical signal
Implementation Method 2
a position acquisition module, configured to collect a relative positional data of the first wafer stage with respect to the alignment sensor
Data Source
AI summary
An alignment system, a dual-wafer-stage system and a measurement system are disclosed, the alignment system including a main frame (201, 301), a first wafer stage (205, 305), an alignment sensor (202, 302), a position acquisition module (208, 308) and a signal processing device (203, 303). The position acquisition module (208, 308) collects positional data from the first wafer stage (205, 305) and the reflector (204, 304) simultaneously. The reflector (204, 304) is arranged on the alignment sensor (202, 302). In other words, positional data of the alignment sensor (202, 302) and positional data of the first wafer stage (205, 305) are collected simultaneously. In addition, the data can be processed to indicate the relative position of the first wafer stage (205, 305) relative to the alignment sensor (202, 302) whose vibration has been zeroed. That is, a position where an alignment mark is aligned can be obtained with the relative vibration amplitude of the alignment sensor (202, 302) being zeroed. This can circumvent the impact of vibration of the alignment sensor (202, 302) and allow increased repeatability accuracy of alignment.