Row Calibration for Dose Inhomogeneity in Particle Lithography
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Solution Overview
Problem
Existing charged-particle multi-beam lithography systems face challenges in maintaining a uniform dose distribution across the substrate due to inhomogeneities in the illumination system and aperture sizes, leading to variations in the current density, which cannot be effectively compensated by static methods.
Innovation Solution
A method is developed to compute a compensated exposure pattern by using a current dose map to adjust individual beam dose assignments in real-time, incorporating row-wise corrections and oversampling techniques to ensure homogeneous dose delivery across the substrate, even with varying current densities and aperture sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If static compensation methods are used for dose distribution, then device complexity is reduced, but manufacturing precision deteriorates due to inability to compensate for time-dependent variations and inhomogeneities
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing a current dose map that characterizes the inhomogeneous dose distribution of the particle beam across different aperture positions. This pre-computed compensation data is then applied during pattern writing to correct for dose variations, eliminating the need for complex real-time measurement and adjustment systems while maintaining high manufacturing precision.
Solution Approach 2:
The patent changes the parameter approach from dynamic real-time adjustment to static pre-characterization. By transforming the complex time-dependent compensation problem into a spatial parameter map (current dose map) that correlates aperture positions with dose values, the system achieves precise dose distribution control without requiring complex active control mechanisms.
2Manufacturing precision
If individual beam dose assignments are adjusted in real-time, then manufacturing precision is improved, but productivity decreases due to additional computation time
Solution Approach 1:
The patent performs the computationally intensive dose compensation calculations in advance, before pattern writing begins. The current dose map is pre-computed and stored, allowing rapid lookup and application of compensation factors during actual pattern writing. This separates the heavy computational burden from the production process, maintaining both high precision and productivity.
Solution Approach 2:
The patent creates a computational model (current dose map) that replicates the physical beam dose distribution characteristics. This virtual copy of the dose distribution allows for rapid mathematical corrections to be applied to pattern data without requiring physical adjustments or real-time measurements, significantly speeding up the compensation process while maintaining accuracy.
3Manufacturing precision
If row-wise corrections with calibration factors are applied, then manufacturing precision is improved, but device complexity increases due to additional calibration measurements
Solution Approach 1:
The patent segments the aperture array into rows and applies row-specific calibration factors to compensate for systematic dose variations within each row. This segmentation approach simplifies the calibration process by reducing the number of independent correction parameters needed, as all apertures in a given row share the same calibration factor, thereby improving dose homogeneity without proportionally increasing system complexity.
Data Source
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AI summary
An exposure pattern is computed which is used for exposing a desired pattern on a target by means of a particle beam and a blanking aperture array in a particle-optical lithography apparatus, taking into account a non-uniform current dose distribution as generated by the beam over the positions of the apertures of the blanking aperture array: From the desired pattern a nominal exposure pattern is calculated as a raster graphics comprising nominal dose values for the pixels of the raster graphics; based on a map of the current dose distribution, which correlates each aperture with a current factor describing the current dose of the beam at the location of the aperture, a compensated dose value is calculated for each pixel, by dividing its nominal dose value by a row compensation factor (qm) which is uniform within each row (rm) of apertures parallel to a scanning direction (sd); and for each pixel, a discrete value is determined by selecting a value from a discrete gray scale so as to approximate the compensated dose value.