Multi-Beam Particle Microscope Raster Shifting for Faster Wafer Inspection
Solution Overview
Problem
Existing multi-beam electron microscopes are not sufficiently fast for area-wise inspection of semiconductor samples, as the pitch of individual particle beams is often much larger than the field of view required for defect recognition.
Innovation Solution
The method involves adjusting the raster arrangement of individual particle beams to optimize area inspection, using a collective scan deflector and individual deflectors to achieve targeted scanning without the need for radiofrequency signals in the vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a multi-beam electron microscope uses a standard raster arrangement with large pitch between individual particle beams, then the field of view covers a larger area, but the inspection speed is insufficient and throughput is low
Solution Approach 1:
The patent applies dynamic adjustment of the raster arrangement by individually deflecting particle beams based on detected defect positions. The system transitions from a static, uniform raster pattern to a dynamic, adaptive pattern that concentrates scanning resources on areas of interest, thereby increasing inspection speed and throughput without sacrificing detection accuracy
Solution Approach 2:
The patent implements local quality by assigning different scanning behaviors to different regions of the sample. Areas with detected defects receive intensified, targeted scanning with adjusted raster parameters, while areas without defects maintain standard scanning. This localized adaptation optimizes the balance between inspection speed and detection sensitivity
2Speed
If the pitch between individual particle beams is reduced to increase inspection speed, then the field of view becomes too small for effective area-wise inspection, but larger pitch reduces scanning resolution
Solution Approach 1:
The patent uses preliminary optical inspection to detect defect positions before particle beam scanning. This preliminary action provides advance information about where defects are located, allowing the particle beam system to pre-position its raster arrangement and focus scanning efforts on relevant areas, thereby achieving both speed and precision
Solution Approach 2:
The system implements feedback by using detection results from optical inspection to continuously adjust the particle beam raster arrangement. The feedback loop ensures that the scanning pattern adapts to actual defect locations, maintaining measurement precision while optimizing scanning speed through intelligent resource allocation
3Measurement precision
If individual particle beams are deflected to achieve targeted scanning of defect areas, then inspection accuracy improves, but the system complexity increases due to radiofrequency signal management in vacuum
Solution Approach 1:
The patent extracts and removes the radiofrequency deflection system from the vacuum environment. By taking out the complex signal management infrastructure and replacing it with simpler magnetic or electrostatic deflection mechanisms that operate directly within the vacuum, the system achieves targeted scanning without the burden of radiofrequency signal management complexity
Solution Approach 2:
The patent substitutes complex radiofrequency electromagnetic systems with simpler magnetic or electrostatic field-based deflection mechanisms. This mechanical/electrical substitution eliminates the need for sophisticated radiofrequency signal generation and management, reducing device complexity while maintaining the ability to individually deflect particle beams for precise defect targeting
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 approach allows for faster area-wise inspection of semiconductor samples by reducing the scanning area to only what is necessary, thereby increasing throughput and accuracy while avoiding the complexities of radiofrequency signal management in the vacuum.
Implementation Method 1
a collective scan deflector arranged between the beam switch and the sample surface and configured to collectively scan the sample surface using the plurality of charged first particle beams
Implementation Method 2
an individual deflector arrangement arranged between the multi-beam particle generator and the collective scan deflector and configured to in each case deflect the first individual particle beams individually
Implementation Method 3
a magnetic and/or electrostatic objective lens, through which both the first and the second individual particle beams pass
Implementation Method 4
During the illumination of the wafer surface with the charged primary individual particle beams, interaction products, for example secondary electrons or backscattered electrons, can emanate from the surface of the wafer
Data Source
AI summary
A method includes: providing position data for a plurality of areas on the sample which are to be inspected; providing a first raster arrangement of the plurality of individual particle beams, with a single field of view on the sample assigned to each individual particle beam; defining the position of a nominal scanning area in each single field of view in relation to the first raster arrangement, with the dimensions of the nominal scanning area smaller than the complete single field of view; determining an individual position deviation between a nominal scanning area and the area to be inspected for the at least one individual particle beam; changing the first raster arrangement based on the determined individual position deviation to produce a second raster arrangement of the plurality of individual particle beams; and area-wise scanning the sample using the plurality of individual particle beams in the second raster arrangement.