Multi-Beam Charged Particle Scanning With Aberration-Controlled Beamlets
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Solution Overview
Problem
Single-beam scanning electron microscopes (SEMs) face throughput limitations when inspecting semiconductor wafers due to the time-consuming process of scanning large areas at high resolution, necessitating the development of multi-beam systems for increased efficiency.
Innovation Solution
A charged particle beam device utilizing multiple beamlets that pass through a deflector and scanner to form an array of focal spots, allowing for simultaneous inspection across multiple locations, with the ability to operate in both centered and beamlet-displaced configurations to minimize aberrations and maintain high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-beam scanning electron microscope is used to inspect large wafer areas at high resolution, then measurement precision is improved, but productivity deteriorates due to time-consuming scanning
Solution Approach 1:
The patent divides a single electron beam into multiple beamlets using an aperture plate with multiple openings. Each beamlet can be independently focused and directed to different locations on the wafer, enabling parallel inspection of multiple areas simultaneously. This segmentation of the beam increases throughput while maintaining high resolution at each focal spot.
2Productivity
If multiple beamlets are used to inspect multiple locations simultaneously, then productivity is improved, but device complexity worsens due to additional control requirements
Solution Approach 1:
The patent employs a single scanner that controls all multiple beamlets simultaneously, rather than requiring separate scanners for each beamlet. This multi-functional approach allows one scanner to deflect multiple beams in parallel, reducing device complexity while maintaining high productivity. The scanner performs the same deflection function for all beamlets at once.
Solution Approach 2:
The patent combines multiple beam control functions into unified optical elements. A single objective lens focuses all beamlets, and a single scanner deflects all beamlets, merging what could have been separate control systems into integrated components. This reduces the overall complexity of the multi-beam system.
3Productivity
If beamlets are deflected to scan large areas, then productivity is improved, but measurement precision deteriorates due to aberrations
Solution Approach 1:
The patent uses a deflector positioned before the scanner to pre-deflect beamlets toward coma-free points on a virtual plane. This preliminary action compensates for aberrations that would otherwise occur during scanning, ensuring that even when beamlets are deflected to scan large areas, they maintain high focal spot quality and measurement precision throughout the scan.
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
Enhances inspection speed and throughput by enabling simultaneous inspection of multiple locations on a wafer while maintaining high resolution, overcoming the limitations of single-beam SEMs.
Implementation Method 1
Each of the beamlets is focused with an objective lens on a sample to form a plurality of focal spots, forming an array
Implementation Method 2
each of the plurality of beamlets is directed by the deflector toward a coma free point on a virtual plane perpendicular to an optical axis
Implementation Method 3
the scanner is scanned
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A method of operating a charged particle beam device is disclosed, including passing each of a plurality of beamlets through a deflector (6) and a scanner (12), in that order. Each of the beamlets is focused with an objective lens on a sample to form a plurality of focal spots, forming an array. A first beamlet (4A) is focused on a first spot (40A) and a second beamlet (4D) is focused on a second spot (40D). In a centered configuration of the device, each of the plurality of beamlets is directed by the deflector toward a coma free point (100). In a beamlet-displaced configuration of the device, the scanner is scanned such that the first beamlet passes through an acceptable aberrations point (105), the first beamlet scanning a displaced first field of view; and the first spot is displaced from the regular first focal spot to a displaced first focal spot (45A).