Charged Particle Beam Optical Axis Deviation Correction
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Solution Overview
Problem
Conventional charged particle beam writing apparatuses face optical axis deviation issues due to high-frequency pulse applications, leading to decreased electron beam dose, pattern dimensional inaccuracies, and astigmatism, for which no effective solution has been established.
Innovation Solution
A charged particle beam writing apparatus and method that includes a deflector with electrodes and a control unit applying a two-step voltage to correct optical axis deviation by adjusting the position of the optical axis during beam ON/OFF cycles, using a Faraday cup to measure current and control the alignment coil to maximize current transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high-frequency pulse is applied to the blanker to enable high-speed beam ON/OFF operation, then productivity is improved, but optical axis deviation occurs leading to manufacturing precision deterioration
Solution Approach 1:
The patent applies preliminary anti-action by introducing a correction voltage that opposes the optical axis deviation caused by the blanker's high-frequency pulse. The correction voltage is applied in advance to the deflector to counteract the eddy current-induced magnetic field that would otherwise deflect the beam and cause optical axis deviation, thereby maintaining pattern dimensional accuracy during high-speed beam switching operations
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the voltage applied to the deflector based on the blanker's operating state. A correction voltage proportional to the blanker voltage is applied to the deflector, changing the deflector's electrical parameter to compensate for the optical axis deviation and maintain precise beam positioning during high-frequency pulse operation
2Reliability
If terminal resistors are connected to blanker electrodes to suppress reflected waves, then reliability is improved, but optical axis deviation increases due to concentrated surface current
Solution Approach 1:
The patent introduces an intermediary solution by using a deflector as a mediating component between the blanker and the beam path. The deflector, controlled by a correction voltage, acts as an intermediary mechanism that compensates for the optical axis deviation caused by the concentrated surface current on the blanker electrodes, thereby maintaining beam positioning accuracy while allowing the terminal resistors to suppress reflected waves
3Manufacturing precision
If the optical axis is adjusted for beam-ON state, then manufacturing precision is improved, but optical axis deviation occurs during beam switching cycles
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the deflector's voltage in response to the blanker's switching state. Before the beam switching occurs, the correction voltage is already applied to the deflector to prevent optical axis deviation, ensuring that the beam maintains accurate positioning throughout the entire beam-ON and beam-OFF cycle rather than requiring re-adjustment after deviation occurs
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 solution effectively corrects optical axis deviation, preventing electron beam cutting and ensuring accurate pattern formation by maintaining optimal beam alignment, thereby improving pattern dimensional accuracy and reducing astigmatism and distortion.
Implementation Method 1
a deflector having electrodes through which a current flows by applying a voltage and configured to deflect the charged particle beam passing between the electrodes onto the blocking unit by applying a predetermined voltage across the electrodes
Implementation Method 2
correcting an amount of optical axis deviation of the charged particle beam by adjusting a position of the optical axis while turning ON/OFF the beam by repeating two-step voltage application to the blanker
Data Source
AI summary
A charged particle beam writing apparatus includes a stage on which a target object is placed; an emitting unit configured to emit a charged particle beam to the stage side; a blocking unit arranged between the emitting unit and the stage and configured to block the charged particle beam emitted; a deflector having electrodes through which a current flows by applying a voltage and configured to deflect the charged particle beam passing between the electrodes onto the blocking unit by applying a predetermined voltage across the electrodes; an optical axis adjusting unit configured to correct optical axis deviation of the charged particle beam generated by continuously repeating irradiation (beam-ON) of the charged particle beam on a target object and blocking (beam-OFF) of the beam by applying a two-step voltage to the deflector; and a control unit configured to control the optical axis adjusting unit such that an amount of the optical axis deviation is corrected.