Spiral Electrostatic Lens for Electron Beam Field of View
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Solution Overview
Problem
The existing multiple electron beam inspection apparatus faces challenges in maintaining accurate pattern inspection due to differences in electron beam spot diameter caused by curvature of field, which limits the field of view and inspection accuracy for ultrafine patterns on semiconductor wafers.
Innovation Solution
The apparatus incorporates an electromagnetic lens and an electrostatic lens with spiral-shaped through-holes and electrodes, allowing multiple electron beams to pass through, enabling improved beam alignment and irradiation accuracy by adjusting the voltage applied to each electron beam based on its distance from the central axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple electron beams are separated away from the optical axis to increase field of view, then field of view is enlarged, but spot diameter difference occurs due to curvature of field
Solution Approach 1:
The patent applies local quality by providing different voltages to individual electrostatic lenses corresponding to different through-holes. Each electrostatic lens is locally adjusted to compensate for the curvature of field at its specific position, maintaining uniform spot diameter across the entire field of view while allowing electron beams to be separated from the optical axis.
Solution Approach 2:
The patent changes the voltage parameter of each electrostatic lens individually to compensate for position-dependent curvature of field. By adjusting the voltage applied to each lens based on its distance from the central axis, the system maintains consistent spot diameter across the expanded field of view.
2Device complexity
If conventional electrostatic lens with straight through-holes is used, then structure is simple, but curvature of field causes spot diameter difference
Solution Approach 1:
The patent applies curvature by forming through-holes with spiral or curved shapes instead of straight cylindrical holes. This curved geometry allows electron beams to pass through while being subjected to controlled electrostatic fields that compensate for curvature of field, improving beam irradiation accuracy without significantly increasing structural complexity.
Solution Approach 2:
The spiral shape and voltage application are tailored to the local position of each through-hole. Electrodes are provided on the wall surfaces of spiral through-holes, and voltages are adjusted locally to match the specific curvature requirements at each position, maintaining beam accuracy across the field of view.
3Area of stationary object
If electron beams are irradiated at positions far from optical axis, then field of view is expanded, but inspection accuracy decreases due to spot diameter variation
Solution Approach 1:
The patent changes the voltage parameter of electrostatic lenses based on the position of electron beams relative to the optical axis. By increasing voltage for beams farther from the center, the system compensates for curvature of field effects, maintaining consistent spot diameter and inspection accuracy across the expanded field of view.
Solution Approach 2:
The system incorporates feedback by measuring the actual spot diameter or beam position and adjusting the voltage applied to electrostatic lenses accordingly. This closed-loop control ensures that inspection accuracy is maintained across the entire field of view by dynamically compensating for curvature of field.
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 enhances the irradiation accuracy of multiple electron beams, allowing for a larger field of view and improved detection of pattern defects on semiconductor wafers, thereby increasing the yield in LSI manufacturing.
Implementation Method 1
an electromagnetic lens provided between the irradiation source and the stage, the electromagnetic lens generating a lens magnetic field, the multiple electron beams being capable of passing through the lens magnetic field
Implementation Method 2
an electrostatic lens provided in the lens magnetic field, the electrostatic lens including a plurality of through-holes and a plurality of electrodes, the plurality of through-holes having wall surfaces respectively, each of the multiple electron beams being capable of passing through the corresponding each of the plurality of through-holes, each of the plurality of electrodes provided on each of the wall surfaces of the plurality of through-holes
Data Source
AI summary
Provided is a multiple electron beam inspection apparatus including: an irradiation source irradiating a substrate with multiple electron beams; a stage on which is cable of mounting the substrate; an electromagnetic lens provided between the irradiation source and the stage, the electromagnetic lens generating a lens magnetic field, the multiple electron beams being capable of passing through the lens magnetic field; an electrostatic lens provided in the lens magnetic field, the electrostatic lens including a plurality of through-holes and a plurality of electrodes, the plurality of through-holes having wall surfaces respectively, each of the multiple electron beams being capable of passing through the corresponding each of the plurality of through-holes, each of the plurality of electrodes provided on each of the wall surfaces of the plurality of through-holes, at least one of the through-holes provided apart from a central axis of trajectory of the multiple electron beams having a spiral shape; and a power source connected to the electrodes.