Lithography Optical Calibration Using Spot-Width Fitting
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Solution Overview
Problem
Conventional photolithography systems face challenges in achieving fast and precise optical calibration, particularly in direct-writing SP super diffraction photolithography, due to the narrow exposure latitude and the need for complex and time-consuming atomic force microscopy (AFM) measurements for determining exposure parameters.
Innovation Solution
A method and apparatus for fast precise optical calibration using a fitting relationship based on field strength distribution at the exit plane of a bowtie nano-aperture structure, combined with optical microscopy, to determine exposure parameters quickly and accurately, reducing the time required from hours to minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If atomic force microscopy (AFM) is used to measure spot width for calibration, then measurement precision is improved, but time consumption increases significantly
Solution Approach 1:
The patent creates an optical copy of the spot-mapping pattern using optical microscopy, which can be obtained rapidly without the time-consuming AFM measurement process. The optical image serves as a surrogate for direct physical measurement, enabling fast calibration while maintaining sufficient precision for determining exposure parameters.
Solution Approach 2:
The patent replaces the mechanical AFM measurement system with an optical microscopy system. This substitution eliminates the need for physical contact and slow scanning measurements, allowing rapid acquisition of spot width data through optical imaging and image processing techniques.
2Manufacturing precision
If exposure latitude is narrowed to achieve higher resolution, then manufacturing precision is improved, but system stability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the spot-mapping pattern is measured and used to determine the exposure dose parameter. This feedback loop allows real-time adjustment of exposure parameters to compensate for system variations, maintaining stability even when operating with narrow exposure latitude for high resolution.
Solution Approach 2:
The patent changes the exposure dose parameter based on the measured spot-mapping pattern to optimize both resolution and stability. By dynamically adjusting exposure parameters rather than fixing them, the system can maintain high precision while compensating for the reduced exposure latitude.
3Measurement precision
If conventional calibration methods are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential calibration information from the spot-mapping pattern using optical microscopy and image processing, eliminating the need for complex AFM measurement systems and procedures. This extraction approach simplifies the overall calibration process while retaining the necessary precision for exposure parameter determination.
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
The method enables rapid and accurate determination of exposure parameters, improving the calibration process efficiency and reducing time consumption, while maintaining high precision and fidelity of exposure patterns.
Implementation Method 1
Surface plasmon (SP) super diffraction photolithography is a type of maskless near-field nano-level photolithography, and is advantageous in circumventing the diffraction limit
Implementation Method 2
determining a first spot-width dataset for the point light source based on an optical microscopic image of a spot-mapping pattern on a surface of the photoresist
Data Source
AI summary
A method for fast precise optical calibration on a photolithography system, including: determining a fitting relationship for a spot width corresponding to a point light source based on distribution of field strength generated by the point light source at an exit plane of a focusing element; determining, based on the fitting relationship, a first correspondence between the spot width and a parameter for exposing a photoresist, where the spot width in the first correspondence is for optical microscopy; determining a first spot-width dataset for the point light source based on an optical microscopic image of a spot-mapping pattern on a surface of the photoresist; determining, based on the first spot-width dataset, a second correspondence between the spot width and the parameter; and determining the first correspondence as a means for determining the parameter, when the first correspondence and the second correspondence meet a preset condition.