Charged-Particle Beam Position Calibration via Focus Deviation Correction
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Solution Overview
Problem
Current charged-particle beam systems face challenges in accurately measuring and correcting beam position deviations accompanying focus corrections, leading to residual aberrations and prolonged measurement times, especially in electron beam lithography systems where deflection field distortion is significant.
Innovation Solution
A method is developed to calibrate beam position deviations by determining focus correction voltages for arbitrary points within a deflection field, measuring beam position deviations, and adjusting deflection voltages to cancel out these deviations, thereby reducing deflection field distortion and improving measurement efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus correction is made using an electrostatic focus corrector, then focus accuracy is improved, but beam position deviation occurs
Solution Approach 1:
The patent applies preliminary anti-action by measuring the beam position deviation caused by focus correction in advance (during calibration) and then applying a corrective deflection signal to counteract this deviation before actual pattern writing. The computing unit calculates the corrective signal based on the measured deviation characteristics, thereby preventing the beam position error from affecting the final pattern accuracy.
Solution Approach 2:
The patent implements feedback by using the measured beam position deviation information to generate corrective deflection signals. The system measures the deviation characteristics during calibration, feeds this information back to the computing unit, which then generates appropriate corrective signals to compensate for the deviation during actual operation, creating a closed-loop control system.
2Manufacturing precision
If deflection field distortion is measured and corrected, then pattern writing precision is improved, but measurement time increases
Solution Approach 1:
The patent applies preliminary action by performing the beam position calibration and deviation measurement before actual pattern writing operations. The system pre-measures the beam position deviation characteristics at various deflection positions and stores this calibration data. During subsequent pattern writing, the pre-measured calibration information is used to generate corrective signals without requiring repeated measurements, thereby reducing measurement time while maintaining precision.
3Measurement precision
If beam position calibration is performed at multiple deflection positions, then correction accuracy is improved, but calibration time increases
Solution Approach 1:
The patent applies partial action by measuring beam position deviation at a selected number of representative deflection positions rather than attempting to measure at every possible position. The calibration process focuses on key positions that capture the essential deviation characteristics, and the computing unit interpolates or extrapolates the corrective signals for intermediate positions, thereby achieving sufficient correction accuracy with reduced calibration time.
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 accurate measurement and correction of beam position deviations, reducing deflection field distortion and shortening measurement time, enabling precise pattern writing in electron beam lithography systems.
Implementation Method 1
When a voltage is applied to the focus corrector 9 relative to a surrounding potential (normally zero potential), the potential distribution in the magnetic field produced by the first lens 1 varies, changing the velocity of electrons passing through the lens 1.
Implementation Method 2
Generally, electromagnetic lenses are used as the first lens 1 and second lens 4.
Implementation Method 3
An electrostatic deflector is used as the deflector 7 to provide high deflection speeds.
Implementation Method 4
As the beam is deflected by the deflector 7, deflection aberrations are produced.
Data Source
AI summary
A method of calibrating the beam position in a charged-particle beam system starts with finding a focus deviation on the material surface for each point within a deflection field. A focus correction voltage VF necessary to cancel out the focus deviation is determined. A beam position deviation fi per unit focus correction voltage is found. The deflection voltage is corrected so as to cancel out the product fi·VF. The deflection voltage is corrected so as to cancel out the sum of the product fi·VF and the measured deflection field distortion while correcting the focus based on the voltage VF.