Dual-NA Optical Subsystem for Lithography Substrate Grid Correction
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Solution Overview
Problem
In lithographic processes, particularly at low k1 regimes, achieving accurate pattern reproduction on substrates is challenging due to the limitations of current technologies in measuring and correcting for substrate deformation and asymmetry, which affects feature size and alignment precision.
Innovation Solution
A method and apparatus for determining a substrate grid by obtaining position and asymmetry data from features on the substrate, using a combination of low and high numerical aperture optical systems, to correct for substrate deformation and improve alignment accuracy before exposure, thereby enhancing the precision of feature fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single numerical aperture optical systems are used for substrate measurement, then device complexity is reduced, but measurement precision of substrate deformation and asymmetry is insufficient
Solution Approach 1:
The optical system is segmented into two distinct numerical aperture systems: a first optical system with first numerical aperture for measuring substrate position, and a second optical system with second numerical aperture for measuring substrate asymmetry. This segmentation allows each system to be optimized for its specific measurement function, achieving high measurement precision for both substrate deformation and asymmetry without requiring a single overly complex system to handle all measurements.
Solution Approach 2:
The measurement apparatus integrates multiple functions into a unified system that can perform both position measurement and asymmetry measurement on the substrate. The system uses both optical systems to obtain comprehensive measurement data including substrate deformation information and asymmetry information, which are then combined to generate corrected substrate grid data for the lithographic apparatus.
2Manufacturing precision
If only position data is used for substrate grid determination, then measurement process is simplified, but manufacturing precision of feature fabrication is insufficient
Solution Approach 1:
The system performs preliminary measurements of both substrate position and substrate asymmetry before the lithographic exposure process. By obtaining asymmetry data in advance and using it to generate corrected substrate grid data, the system prepares compensation information that will be applied during feature fabrication, thereby improving manufacturing precision without adding complexity to the actual exposure process.
Solution Approach 2:
The measurement apparatus provides feedback to the lithographic apparatus by transmitting both substrate grid data and asymmetry data. This feedback enables the lithographic apparatus to adjust its exposure process based on measured substrate characteristics, improving feature fabrication precision through closed-loop control that incorporates both position and asymmetry information.
3Measurement precision
If high numerical aperture optical system is used for asymmetry measurement, then measurement precision is improved, but measurement speed decreases
Solution Approach 1:
The measurement system is divided into two parallel optical paths: one optimized for position measurement and another optimized for asymmetry measurement. This segmentation allows both measurements to be performed simultaneously or in rapid succession, maintaining high measurement speed while achieving high precision asymmetry measurements through the second optical system with appropriate numerical aperture.
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 approach allows for more accurate substrate alignment and deformation correction, leading to improved feature size control and reduced substrate-to-substrate variations, thereby enhancing the overall precision and consistency of lithographic processes.
Implementation Method 1
an optical system configured to obtain position data for a plurality of first features and/or a plurality of second features on the substrate, wherein the optical system is further configured to obtain asymmetry data for at least a feature of the plurality of first features and/or the plurality of second features
Data Source
AI summary
A measurement apparatus and method for determining a substrate grid describing a deformation of a substrate prior to exposure of the substrate in a lithographic apparatus configured to fabricate one or more features on the substrate. Position data for a plurality of first features and/or a plurality of second features on the substrate is obtained. Asymmetry data for at least a feature of the plurality of first features and/or the plurality of second features is obtained. The substrate grid based on the position data and the asymmetry data is determined. The substrate grid and asymmetry data are passed to the lithographic apparatus for controlling at least part of an exposure process to fabricate one or more features on the substrate.