Charged Particle Beam Trajectory Adjustment via Brightness Area Feedback
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Solution Overview
Problem
Existing charged particle beam apparatuses, such as mirror electron microscopes, face challenges in maintaining high reproducibility and sensitivity in defect identification due to the difficulty in accurately adjusting the trajectory of the irradiation electron beam to be parallel to the wafer surface normal, especially when dealing with varying charge amounts and defect types, as the existing methods lack a reliable means for evaluating beam parallelism.
Innovation Solution
A charged particle beam apparatus is designed with an irradiation optical system, an imaging optical system, and a control apparatus that evaluates and adjusts the lens conditions based on the size of a specific brightness area, using a negative voltage application power supply to control the trajectory of the charged particle beams and ensure they are parallel to the wafer surface normal, allowing for quantitative and reproducible trajectory adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron beam trajectory is adjusted to be parallel to the wafer surface normal using tabulated apparatus conditions, then the beam parallelism is improved to some extent, but high reproducibility is required for the power supply that controls the lens and extremely high parallelism is difficult to achieve and maintain
Solution Approach 1:
The patent implements a feedback mechanism by detecting the actual electron beam trajectory using a detector and comparing it with the desired parallel trajectory. The system automatically adjusts the condenser lens conditions based on this feedback to maintain beam parallelism, eliminating the need for manual tabulated adjustments and improving reproducibility.
Solution Approach 2:
The patent replaces the manual mechanical adjustment system (tabulated lens conditions requiring experienced operators) with an automated detection and control system. The detector automatically measures beam trajectory and the control system adjusts lens parameters, substituting human expertise with an automated measurement and control mechanism.
2Measurement precision
If manual adjustment of electron beam trajectory is performed based on adjuster experience, then some degree of beam parallelism can be achieved, but it is difficult to maintain high reproducibility and quantitative evaluation is lacking
Solution Approach 1:
The system performs self-adjustment by automatically detecting its own beam trajectory and correcting lens conditions without requiring external expert intervention. The detector and control system enable the apparatus to self-evaluate and self-correct, eliminating dependence on operator experience and skill.
Solution Approach 2:
The patent replaces the human expert adjustment process with an automated detection and control system. The detector quantitatively measures beam trajectory and the control system automatically adjusts lens parameters, substituting manual mechanical adjustment based on experience with an automated measurement and control mechanism.
3Ease of operation
If the irradiation electron beam trajectory is not parallel to the wafer surface normal, then the apparatus is easier to adjust without precise measurement, but different contrasts appear in the mirror electron image even for defects with the same charge amount
Solution Approach 1:
The system uses feedback from the detector to automatically adjust the electron beam trajectory to be parallel with the wafer surface normal. This feedback mechanism ensures consistent image contrast by maintaining proper beam alignment, eliminating the need to choose between ease of adjustment and image quality.
Solution Approach 2:
The patent automatically adjusts the lens parameters (current, voltage) to change the electron beam trajectory, ensuring it remains parallel to the wafer surface normal. This dynamic parameter adjustment maintains consistent image contrast across different operating conditions without requiring manual intervention.
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 configuration enables proper evaluation and adjustment of the charged particle beam trajectory, enhancing the reproducibility and sensitivity of defect identification, ensuring stable performance in defect inspection.
Implementation Method 1
a negative voltage application power supply configured to apply a negative voltage to the sample
Implementation Method 2
an irradiation optical system including a lens which is configured to converge charged particle beams emitted from a charged particle source
Implementation Method 3
an imaging optical system which is configured to image charged particles obtained by irradiating a sample with the charged particle beams on an imaging element
Data Source
AI summary
A purpose of the present invention is to provide a charged particle beam apparatus that performs apparatus adjustment based on a proper evaluation of a beam. To achieve the abovementioned purpose, with the present invention, proposed is a charged particle beam apparatus comprising: an irradiation optical system including a lens for converging charged particle beams emitted from a charged particle source; and an imaging optical system for imaging the charged particles obtained by irradiating the charged particle beams toward a sample on an imaging element, wherein the charged particle beam apparatus comprises a control apparatus for controlling the lens, and the control apparatus evaluates for each lens condition the size of a specific brightness area obtained by the charged particle beam being made to reach the sample, and selects the lens condition for which the size information fulfills a designated condition.