Multi-Beam Electron Source Conversion for Wafer Inspection
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Solution Overview
Problem
Conventional single-electron beam apparatuses in semiconductor manufacturing struggle with high throughput and detection sensitivity for inspecting defects and particles on wafers/masks, particularly due to the limitations of spatial resolution and Coulomb Effect, which are exacerbated by the shrinking critical dimensions of semiconductor features.
Innovation Solution
A multi-beam apparatus employing a new source-conversion unit to form a slant virtual multi-source array with oblique illumination, using a primary projection imaging system to create multiple probe spots on the sample surface, and a beam separator to separate and detect dark-field or bright-field signal electron beams, enhancing image contrast and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single electron beam with large current is used to increase throughput, then productivity improves, but spatial resolution deteriorates due to Coulomb Effect
Solution Approach 1:
The invention divides a single high-current electron beam into multiple low-current electron beams. Each beam operates at low current to avoid Coulomb Effect and maintain spatial resolution, while the collective array of multiple beams achieves high throughput by simultaneously scanning multiple regions of the sample surface.
2Ease of operation
If conventional optical beam tools are used, then ease of operation is maintained, but measurement precision deteriorates due to diffraction effect
Solution Approach 1:
The invention replaces conventional optical beam systems with an electron beam system. Electron beams have much shorter wavelengths than optical beams, eliminating diffraction effects and enabling superior spatial resolution while maintaining operational simplicity through automated scanning and detection systems.
3Ease of manufacture
If beam interval between adjacent beams is increased to 30-50 mm for multi-column apparatus, then ease of manufacture improves, but area of observed object is reduced
Solution Approach 1:
The invention arranges multiple electron beams in a two-dimensional array pattern rather than simple linear spacing. This allows beams to cover a larger observed area by utilizing both horizontal and vertical dimensions, increasing the effective inspection area while maintaining manageable beam intervals and system complexity.
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 multi-beam apparatus achieves high detection efficiency and throughput for inspecting defects and particles on wafers/masks with improved spatial resolution and image contrast, effectively addressing the limitations of single-electron beam systems.
Implementation Method 1
a source-conversion unit for forming a virtual source array being slant to a surface being observed and from a plurality of beamlets of the single charged particle beam
Implementation Method 2
The electrons of each probe spot generate secondary electrons from the sample surface where they land on
Implementation Method 3
A primary projection imaging system for projecting the multi-source array onto the surface with the plurality of beamlets obliquely landing on the surface
Implementation Method 4
a beam separator to separate and detect dark-field or bright-field signal electron beams
Data Source
AI summary
A multi-beam apparatus for observing a sample with oblique illumination is proposed. In the apparatus, a new source-conversion unit changes a single electron source into a slant virtual multi-source array, a primary projection imaging system projects the array to form plural probe spots on the sample with oblique illumination, and a condenser lens adjusts the currents of the plural probe spots. In the source-conversion unit, the image-forming means not only forms the slant virtual multi-source array, but also compensates the off-axis aberrations of the plurality of probe spots. The apparatus can provide dark-field images and/or bright-field images of the sample.