Permanent Magnet Electron Lens for Low-Energy Overlay Resolution
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Solution Overview
Problem
Existing electrostatic lens designs for electron beam systems fail to meet resolution requirements at low landing energies, limiting the detection of buried defects in semiconductor devices with shrinking critical dimensions.
Innovation Solution
Integration of a permanent magnetic lens with electrostatic elements and a positive wafer bias to enhance electron beam systems, enabling high landing energies and improved resolution for defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrostatic lens designs are used for electron beam systems, then the system structure is simple, but the resolution requirement is not met at low landing energies
Solution Approach 1:
The patent combines permanent magnetic lens elements with electrostatic lens elements into a hybrid lens system. The permanent magnetic lens provides strong focusing capability at low landing energies, while the electrostatic elements fine-tune the focusing. This merging of magnetic and electrostatic principles resolves the contradiction by achieving high resolution without requiring a completely complex system redesign.
Solution Approach 2:
The lens system uses composite magnetic materials with specific remanence and coercivity properties to create the permanent magnetic lens. These composite material properties enable the lens to provide sufficient focusing strength at low energies while maintaining a compact structure, thus improving resolution without proportionally increasing device complexity.
2Measurement precision
If low landing energy is used for electron beam detection, then the detection sensitivity for surface defects is improved, but the resolution requirement is not met
Solution Approach 1:
The patent changes the magnetic field parameters of the permanent magnetic lens to optimize focusing at low landing energies. By adjusting the magnetic flux density distribution and lens geometry, the system achieves both high detection sensitivity and acceptable resolution at low energies, resolving the contradiction between these two parameters.
3Reliability
If high landing energy is used for electron beam detection, then the detection capability for buried defects is improved, but the resolution deteriorates
Solution Approach 1:
The patent creates a dynamic lens system where the permanent magnetic lens provides strong focusing that can be supplemented or adjusted by electrostatic elements. This dynamic configuration allows the system to maintain high resolution while operating at high landing energies, enabling detection of buried defects without sacrificing resolution.
4Productivity
If the field of view is increased to at least 70 μm for efficient yield management, then the productivity is improved, but the resolution may be compromised
Solution Approach 1:
The patent employs a segmented lens design where the permanent magnetic lens and electrostatic elements work in conjunction to provide both wide field of view and high resolution. The segmented approach to focusing allows different regions of the beam to be optimized for different requirements, achieving both large field of view for productivity and sufficient resolution for precision measurement.
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
The system achieves high resolution and detection of buried defects with a field of view of at least 70 μm, supporting efficient yield management in semiconductor manufacturing.
Implementation Method 1
a magnetic objective lens disposed in the path of the electron beam
Implementation Method 2
combining permanent magnetic lenses with other electrostatic elements can meet these requirements
Implementation Method 3
combining permanent magnetic lenses with other electrostatic elements
Implementation Method 4
a backscattered electron detector disposed in the path of the electron beam between the focus element and the magnetic objective lens
Implementation Method 5
an electron source that generates an electron beam
Data Source
AI summary
A system includes an electron source that generates an electron beam, a stage that holds a workpiece in a path of the electron beam, a magnetic objective lens disposed in a path of the electron beam, a focus element disposed in the path of the electron beam between the magnetic objective lens and the stage, and a backscattered electron detector disposed in the path of the electron beam between the focus element and the magnetic objective lens. Backscattered electrons, secondary electrons, and x-rays are emitted from the workpiece. The backscattered electrons are measured with the backscattered electron detector.