Objective Lens Hysteresis Estimation for Electron Beam Throughput
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Solution Overview
Problem
The frequent lens reset operations in charged particle beam devices, such as scanning electron microscopes, lead to a significant reduction in throughput due to the delay in magnetic field response caused by overcurrent generation in the magnetic circuit of the objective lens, which is influenced by magnetic hysteresis and requires a constant magnetized state.
Innovation Solution
A charged particle beam device equipped with an electron source, an objective lens, a control unit, a hysteresis characteristic storage unit, and an estimation unit that reduces the frequency of lens resetting by storing hysteresis characteristic information and history data to estimate the magnetic field generated by the objective lens, allowing for accurate adjustment of the coil current without the need for frequent lens resets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lens reset operation is performed frequently to maintain constant magnetized state, then the relation between coil current and magnetic field is kept unique, but the throughput is significantly lowered due to current changes and magnetic field response delay
Solution Approach 1:
The patent applies feedback by storing hysteresis characteristic information and history information about coil current changes, then using this stored data to estimate the magnetic field value. This feedback mechanism allows the system to predict and compensate for magnetic field variations without requiring frequent lens reset operations, thus maintaining reliability while improving throughput
Solution Approach 2:
The patent performs preliminary action by pre-storing hysteresis characteristic information and history information in memory before actual measurement or imaging operations. This preliminary preparation enables the estimation unit to quickly estimate magnetic field values without requiring time-consuming lens reset operations, thereby improving throughput while maintaining accurate magnetic field relationships
2Reliability
If lens reset operation is performed to avoid deflection magnification and image rotation, then the magnetized state is kept constant, but the response delay of magnetic field increases due to overcurrent generation
Solution Approach 1:
The estimation unit uses stored hysteresis characteristic information and history information to estimate the current magnetic field value, providing feedback that allows the system to maintain constant magnetized state without requiring lens reset operations. This eliminates the response delay caused by overcurrent generation while preserving the constancy of the magnetized state
Solution Approach 2:
The patent creates a computational model (copy) of the magnetic field behavior by storing hysteresis characteristic information and history information. This model allows the system to predict magnetic field values and maintain constant magnetized state through calculation rather than physical lens reset operations, thereby eliminating response delay
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 reduces the frequency of lens resetting, thereby improving the throughput of the device by accurately estimating the magnetic field and adjusting the capturing conditions, minimizing errors in image reproducibility and length measurement.
Implementation Method 1
an electron beam discharged from an electron source is emitted and converged on a sample by a magnetic field which is generated by an objective lens
Implementation Method 2
The relation between the coil current and the magnetic field generated by the objective lens is not uniquely set due to an influence of a magnetic hysteresis
Data Source
AI summary
A charged particle beam device includes an electron source which generates an electron beam, an objective lens which is applied with a coil current to converge the electron beam on a sample, a control unit which controls the current to be applied to the objective lens, a hysteresis characteristic storage unit which stores hysteresis characteristic information of the objective lens, a history information storage unit which stores history information related to the coil current, and an estimation unit which estimates a magnetic field generated by the objective lens on the basis of the coil current, the history information, and the hysteresis characteristic information.