Multi-Beam Sample Alignment Without Optical Calibration Drift
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Solution Overview
Problem
Current charged particle assessment systems face challenges in efficiently and accurately performing global alignment of samples with respect to electron beam paths, particularly due to the limitations of optical sensors and microscopes, which affect throughput and alignment accuracy.
Innovation Solution
A method and system that utilize a multi-beam of charged particles to align samples by directing the beam towards an alignment feature, detecting signal particles, and generating a dataset to determine global alignment, eliminating the need for optical sensors and microscopes by using an array of objective lenses and a detector array to control and process the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors or optical microscopes are used for global alignment, then alignment can be performed, but alignment accuracy varies and drifts with time, and calibration is required which affects throughput
Solution Approach 1:
The patent extracts the alignment measurement function from optical sensors and microscopes, and implements it directly using the charged particle beam system's own detectors. The detector array that is already present for assessing pattern defects is repurposed to detect alignment features, eliminating the need for separate optical alignment systems and their associated calibration procedures.
Solution Approach 2:
The patent makes the detector array multi-functional by using it for both pattern defect assessment and global alignment determination. The same detector array that detects secondary electrons for pattern inspection is also used to detect signal particles from alignment features, allowing one component to serve multiple purposes without requiring additional calibration.
2Productivity
If optical sensors or optical microscopes are used for global alignment, then alignment can be performed, but calibration is required which affects throughput
Solution Approach 1:
The patent removes the calibration step entirely by eliminating the interface between optical alignment systems and the charged particle beam system. By using the charged particle beam's own detector array for alignment, the system avoids the calibration that would otherwise be required to coordinate between optical and electron optics coordinate systems.
Solution Approach 2:
The detector array serves dual purposes: detecting signal particles for alignment determination and detecting secondary electrons for pattern assessment. This multi-functionality eliminates the need for separate calibration procedures that would be required if separate optical and electron optics alignment systems were used.
3Measurement precision
If a multi-beam of charged particles is used for alignment, then alignment accuracy and speed improve, but the system complexity increases
Solution Approach 1:
The charged particle assessment system performs its own global alignment function using its own multi-beam and detector array, without requiring external optical alignment systems. The system is self-sufficient, using its inherent capabilities to determine alignment before pattern assessment begins.
Solution Approach 2:
The alignment process is segmented into detecting signal particles from alignment features using the multi-beam, generating a dataset representative of the alignment feature, and determining global alignment from this dataset. This segmentation allows the alignment function to be integrated into the existing assessment workflow without overwhelming 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
This approach enables faster, more accurate, and cost-effective global alignment of samples, improving the overall efficiency and precision in semiconductor manufacturing by eliminating the need for optical calibration and reducing the risk of alignment errors.
Implementation Method 1
The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons.
Data Source
AI summary
Disclosed herein is a method of aligning a sample in a charged particle assessment system. The system comprises a support for supporting a sample, and is configured to project charged particles in a multi-beam towards a sample along a multi-beam path, the multi-beam comprising an arrangement of beamlets, and to detect signal particles emitted from the sample in response to a corresponding beamlet of the multi-beam. The method comprises: directing the multi-beam of charged particles along the multi-beam path towards an alignment feature of the sample, such that the field of view of the multi-beam of charged particles encompasses the alignment feature; detecting the signal particles emitted from the sample; generating a dataset representative of the alignment feature based on the detecting of the signal particles; and determining a global alignment of the sample with respect to the multi-beam path, using the dataset.