Charged Particle Beam Calibration Reference Pattern
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Solution Overview
Problem
Conventional tuning and calibration methods for charged particle beam apparatuses, such as scanning electron microscopes, face inefficiencies, robustness issues, and risk of sample damage due to poor repeatability and limited range, especially in multi-beam inspection systems where synchronizing multiple beams and achieving high precision is challenging.
Innovation Solution
A reference pattern comprising an arrangement of dots and grids on a substrate with varying sizes and spacings is used to calibrate and tune the charged particle beam apparatus, allowing for robust calibration and minimizing the need for frequent re-tuning by analyzing images at multiple coarseness levels and adjusting parameters based on measured characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional tuning methods use large features for initial calibration, then coordinate baseline can be established easily, but location repeatability is poor
Solution Approach 1:
The reference specimen is divided into multiple regions containing objects of different sizes and densities. Large unique objects are used for initial coordinate establishment, while dense regions with many small objects provide high repeatability for fine calibration. This segmentation allows the system to leverage the advantages of both large and small features without requiring physical movement between regions.
Solution Approach 2:
A single reference specimen design serves multiple calibration functions simultaneously. The specimen contains both large unique objects for coarse alignment and dense patterns of small objects for fine precision calibration, eliminating the need for multiple separate reference specimens or sequential positioning operations.
2Measurement precision
If conventional calibration moves to regions with densely arranged objects, then repeatability improves, but the process becomes less efficient and more complex
Solution Approach 1:
Multiple calibration functions are merged into a single field of view. The reference specimen contains large unique objects and dense small objects in the same region, allowing the imaging system to perform both coarse and fine calibration simultaneously without moving the stage or changing magnification, thereby improving efficiency while maintaining high repeatability.
3Measurement precision
If excessive scanning is performed for calibration, then calibration accuracy may improve, but sample damage increases
Solution Approach 1:
The patent uses partial action by selecting only the necessary objects within the reference specimen for calibration. Instead of scanning the entire specimen or performing exhaustive searches, the system identifies and uses specific large unique objects for initial alignment and specific dense regions for fine calibration, reducing the total scanning area and electron dose while maintaining calibration accuracy.
4Measurement precision
If conventional methods are used for multi-beam synchronization, then individual beam calibration may be achieved, but coordination among multiple beams becomes difficult and time-consuming
Solution Approach 1:
The reference specimen design enables universal calibration for multiple beams simultaneously. All beamlets can observe the same unique large objects and the same dense patterns of small objects, providing a common reference framework that simplifies synchronization and coordination among multiple beams while maintaining individual calibration precision.
Data Source
AI summary
Systems and methods for tuning and/or calibrating a charged particle beam apparatus are disclosed. According to certain embodiments, a reference specimen comprises a substrate having a plurality of first objects at a first pitch, and a plurality of second objects at a second pitch. Regions containing the first and second objects may overlap. A method of tuning and/or calibrating may comprise analyzing an image of a sample at a plurality of coarseness levels, determining whether a parameter of the image satisfies a criteria based on measured characteristics of the image at the coarseness levels, and adjusting the parameter.