Charged Particle Beam Inclination Correction via Reflector Plate Feedback
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Solution Overview
Problem
Scanning electron microscopes face challenges in observing patterns with deep grooves and deep holes due to inclined electron beam incidence, leading to uneven observations and precision measurement failures, as mechanical tolerances cause electron lenses to be non-concentric, resulting in non-perpendicular beam incidence.
Innovation Solution
A charged particle beam inclination correction method using a reflector plate between the charged particle source and objective lens, where the deflector adjusts the beam to pass through the objective lens center and be perpendicular to the sample by monitoring secondary electron trajectories and adjusting the deflection vectors of the upper and lower deflectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical axis adjustment techniques are used, then the electron beam can be aligned with the objective lens center, but the beam still incidents with inclination due to mechanical tolerance in lens arrangement
Solution Approach 1:
The patent replaces mechanical alignment methods with an optical feedback system. A reflector plate is positioned at the objective lens focal point to reflect secondary electrons back through the lens system to the detector. By detecting the position of reflected electron signals and adjusting the condenser lens position accordingly, the system achieves precise beam alignment without relying on mechanical concentricity of lenses. This substitutes mechanical alignment with optical detection and feedback control.
2Ease of operation
If the electron beam is emitted through the center of the objective lens, then the beam path is simplified, but the beam incidents with inclination on the sample due to non-concentric lens arrangement
Solution Approach 1:
The patent implements a feedback mechanism using the reflector plate and detector system. The reflector plate at the focal point reflects secondary electrons back through the lens system. The detector measures the position of these reflected electrons, providing feedback information about beam alignment status. Based on this feedback, the condenser lens position is adjusted to achieve perpendicular beam incidence on the sample, ensuring both ease of operation and manufacturing precision.
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 method allows for high-precision correction of microscopic inclination angles, ensuring the electron beam is incident perpendicularly to the sample, even with mechanical deviations, thereby improving measurement accuracy for patterns with deep features.
Implementation Method 1
a reflector plate is arranged between a charged particle source and an objective lens to focus the charged particle beam
Implementation Method 2
an objective lens to focus the charged particle beam
Data Source
AI summary
With conventional optical axis adjustment, a charged particle beam will not be perpendicularly incident to a sample, affecting the measurements of a pattern being observed. Highly precise measurement and correction of a microscopic inclination angle are difficult. Therefore, in the present invention, in a state where a charged particle beam is irradiated toward a sample, a correction of the inclination of the charged particle beam toward the sample is performed on the basis of secondary electron scanning image information from a reflector plate. From the secondary electron scanning image information, a deviation vector for charged particle beam deflectors is adjusted, causing the charged particle beam to be perpendicularly incident to the sample. At least two stages of charged particle beam deflectors are provided.