Charged Particle Beam Probe Current and Divergence Control
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Solution Overview
Problem
The existing charged particle beam inspection techniques for semiconductor manufacturing face challenges in maintaining a balance between focal depth and resolution due to variations in the objective aperture diameter, leading to performance imbalances and reduced defect detection rates.
Innovation Solution
A charged particle beam apparatus is designed with a controller that independently controls the probe current and objective divergence angle, using a system of condenser lenses and a memory device to adjust settings based on the objective aperture diameter, ensuring a stable probe current and optimal focal depth for high-resolution defect inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the objective aperture diameter varies, then the objective divergence angle changes, but the balance between focal depth and resolution deteriorates
Solution Approach 1:
The patent changes the parameters of the condenser lens (excitation current, focal length) to compensate for variations in objective aperture diameter. By adjusting the condenser lens parameters, the system maintains a stable objective divergence angle and preserves the balance between focal depth and resolution despite aperture variations.
Solution Approach 2:
The patent implements a feedback control mechanism where the actual objective aperture diameter is measured, and based on this measurement, the condenser lens parameters are automatically adjusted. This closed-loop control ensures that the objective divergence angle remains stable, maintaining consistent focal depth and resolution performance.
2Device complexity
If the objective aperture diameter is not controlled, then device complexity is reduced, but performance consistency deteriorates
Solution Approach 1:
The system measures the actual objective aperture diameter and uses this information to adjust condenser lens parameters, creating a feedback loop that compensates for aperture variations without requiring complex mechanical aperture control mechanisms.
Solution Approach 2:
Instead of controlling the aperture diameter directly, the system changes the parameters of the condenser lens to compensate for aperture variations, achieving performance consistency through parameter adjustment rather than physical aperture control.
3Measurement precision
If the probe current is not independently controlled, then device complexity is reduced, but defect detection accuracy deteriorates
Solution Approach 1:
The system independently controls the probe current by adjusting the condenser lens excitation current, allowing precise control of the electron beam parameters to optimize defect detection accuracy without requiring additional complex control mechanisms.
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 solution allows for precise adjustment of the objective divergence angle and probe current, enabling the detection of fine defects with high accuracy and consistency, even with variations in the objective aperture diameter, thereby ensuring a high defect detection rate.
Implementation Method 1
a first condenser lens that focuses the primary charged particle beam on the sample; a second condenser lens disposed closer to the sample than the first condenser lens
Implementation Method 2
an objective aperture disposed between the first and second condenser lenses
Implementation Method 3
scanning the sample with the primary electron beam by using a scanning deflector
Implementation Method 4
detecting secondary signals generated from the sample by the irradiation of the primary electron beam
Data Source
AI summary
Disclosed herewith is a charged particle beam apparatus capable of controlling each of the probe current and the objective divergence angle to obtain a desired probe current and a desired objective divergence angle in accordance with the diameter of the subject objective aperture. The apparatus is configured to include an objective aperture between first and second condenser lenses to calculate and set a control value of a first condenser lens in accordance with the diameter of the hole of the objective aperture so as to obtain a desired probe current and calculate a control value of a second condenser lens setting device in accordance with the diameter of the hole of the objective divergence angle and the control value of the second condenser lens setting device, thereby setting the calculated control value for the second condenser lens setting device to control the objective divergence angle.