Electrostatic Lens Substrate Bias for Electron Beam Focus Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multiple electron beam irradiation systems face challenges in accurately correcting focus, magnification, and rotation changes due to substrate unevenness, making it difficult to control these factors individually and efficiently.
Innovation Solution
A multiple electron beam irradiation apparatus with a stage, a first electromagnetic lens, and a first electrostatic lens that uses the substrate as a bias electrode, generating an electrostatic field to dynamically focus electron beams based on substrate height changes, with a control electrode and ground electrode configuration to optimize adjustments and simplify control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If three or more electrostatic lenses are used to correct focus, magnification, and rotation changes, then the correction capability is improved, but the control system becomes enlarged and more complex
Solution Approach 1:
The patent makes the substrate serve multiple functions: it acts as both the object to be inspected and as an electrostatic lens (bias electrode) for beam focusing. By applying negative potential to the substrate, it generates electrostatic fields that enable dynamic focusing correction without requiring separate electrostatic lenses, thereby simplifying the control system while maintaining correction capability for focus, magnification, and rotation changes.
2Measurement precision
If the height position of the substrate surface changes due to unevenness, then the focus position must be corrected, but this causes magnification change and rotation change that are difficult to control individually
Solution Approach 1:
The substrate serves itself as an electrostatic lens by having negative potential applied to it. This self-service approach allows the substrate to generate the electrostatic fields needed for beam focusing and correction, eliminating the need for external electrostatic lenses and their complex control systems, thereby enabling easier individual control of focus, magnification, and rotation corrections.
3Manufacturing precision
If multiple electrostatic lenses are used to correct focus changes, then the focusing accuracy is improved, but the control system becomes enlarged
Solution Approach 1:
The substrate is made to serve dual purposes: as the inspection target and as the electrostatic lens (bias electrode). By applying negative potential to the substrate, it generates the electrostatic fields necessary for dynamic focusing, eliminating the need for separate electrostatic lenses and thereby simplifying the device structure while maintaining focusing accuracy.
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 allows for simultaneous correction of focus, magnification, and rotation changes, enhancing the precision and ease of control in multiple electron beam irradiation systems, improving the accuracy of pattern inspection on semiconductor wafers and masks.
Implementation Method 1
a first electrostatic lens, configured using the substrate used as a bias electrode by being applied with a negative potential, a control electrode to which a control potential is applied and a ground electrode to which a ground potential is applied, the first electrostatic lens configured to provide dynamic focusing of the multiple electron beams onto the substrate, in accordance with change of the height position of the surface of the substrate, by generating an electrostatic field
Implementation Method 2
a first electromagnetic lens, disposed such that a center of a lens magnetic field is located at a height position of a surface of the substrate, configured to focus the multiple electron beams onto the substrate
Implementation Method 3
an inspection apparatus that acquires a pattern image by scanning the inspection substrate with electron beams and detecting secondary electrons emitted from the inspection substrate by the irradiation with the electron beams
Data Source
AI summary
A multiple-electron-beam irradiation apparatus includes a first electrostatic lens, configured using the substrate used as a bias electrode by being applied with a negative potential, a control electrode to which a control potential is applied and a ground electrode to which a ground potential is applied, configured to provide dynamic focusing of the multiple electron beams onto the substrate, in accordance with change of the height position of the surface of the substrate, by generating an electrostatic field, wherein the control electrode is disposed on an upstream side of a maximum magnetic field of the lens magnetic field of the first electromagnetic lens with respect to a direction of a trajectory central axis of the multiple electron beams, and a ground electrode is disposed on an upstream side of the control electrode with respect to the direction of the trajectory central axis.