Charged Particle Beam Resolution Measurement Using Composite Waveform Fitting
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Solution Overview
Problem
Current charged particle beam resolution measurement methods face inaccuracies due to deviations in beam intensity distribution from the error function waveform, primarily caused by scattering and mark shape irregularities, limiting the measurable range and increasing beam resolution values.
Innovation Solution
A method and apparatus that utilize an approximation equation defined by a prespecified mark shape function and error function to fit the waveform of reflection signals from a scanned charged particle beam, allowing for improved fitting accuracy and removal of mark shape dependency, thereby measuring beam resolution with increased precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional beam intensity distribution measurement is used, then measurement process is simple, but measurement precision deteriorates due to deviation from error function waveform
Solution Approach 1:
The patent changes the parameter of waveform fitting by introducing an approximation equation that combines mark shape function and error function. This transforms the measurement approach from direct error function fitting to a more accurate composite function fitting, improving beam resolution measurement precision while managing the increased computational complexity through a structured mathematical model.
2Measurement precision
If scattering and mark shape irregularities are present, then measurement process is easier to implement, but measurement precision deteriorates due to waveform deviation
Solution Approach 1:
The patent extracts the mark shape function as a separate component from the beam intensity distribution. By isolating and characterizing the mark shape function independently, the method removes the confounding effect of mark shape irregularities and scattering, allowing the error function component to be fitted more accurately for beam resolution measurement.
Solution Approach 2:
The approximation equation serves as an intermediary model that bridges the measured waveform (affected by scattering and mark shape) and the underlying error function (representing true beam intensity). This intermediary model separates the harmful effects from the useful information, enabling accurate beam resolution extraction despite presence of scattering and irregularities.
3Measurement precision
If mark shape dependency is included in measurement, then measurement process reflects actual conditions, but measurement precision deteriorates due to unwanted variations
Solution Approach 1:
The patent extracts and separates the mark shape function from the beam intensity distribution measurement. By identifying and removing the mark shape dependency as a distinct component, the method eliminates unwanted variations caused by different mark shapes while retaining the essential beam intensity information through the error function fitting.
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 enables the accurate measurement of beam resolution by improving fitting accuracy, aligning the measured waveform with the error function, and excluding mark shape dependency, resulting in highly precise beam resolution determination.
Implementation Method 1
an instrumentation unit which performs instrumentation of a reflection signal from a mark that is obtained by scanning the mark while irradiating the charged particle beam onto the mark
Data Source
AI summary
A charged particle beam apparatus in accordance with one preferred form of this invention includes an irradiation unit for irradiating a charged particle beam, an instrumentation unit which performs instrumentation of a reflection signal from a mark as obtained by scanning the mark while irradiating the charged particle beam onto the mark, and a measurement unit which uses an approximation equation defined by use of a prespecified mark shape function and an error function to perform the fitting of a waveform obtained based on the reflection signal and which measures beam resolution which becomes a parameter of the error function from the waveform obtained based on the reflection signal.