Multi-Beam Charged Particle Scanning for Drift-Accurate Inspection
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Solution Overview
Problem
Existing charged particle beam inspection systems face challenges in maintaining high throughput and position accuracy due to thermal loads and drift issues, which affect the detection and identification of micro and nano-scale defects on semiconductor IC chips.
Innovation Solution
A method involving a multi-beam of sub-beams is used, where the sample is moved in a direction parallel to a first direction while the multi-beam is scanned relative to the sample in a direction parallel to a second direction, with displacement steps to process sections of elongate regions, allowing for improved scanning and reduced thermal impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charged particle beam is used to scan the sample surface, then detection precision is improved, but thermal load increases causing distortion and position errors
Solution Approach 1:
The patent divides the sample surface into multiple elongate regions that are processed sequentially. Each region is scanned by a sub-beam in a controlled manner, allowing the thermal load to be distributed and managed across different spatial and temporal segments rather than concentrating heat in one area. This segmentation approach maintains detection precision while reducing cumulative thermal distortion.
Solution Approach 2:
The patent implements periodic scanning patterns where the beam repeatedly scans the same elongate region multiple times. This periodic action allows for accumulation of signal data to improve detection precision while also providing intervals between scans that allow thermal dissipation, thereby managing thermal load. The repeated scanning at controlled intervals maintains measurement precision without causing excessive thermal distortion.
2Productivity
If the beam scanning speed is increased to improve throughput, then productivity is improved, but position accuracy deteriorates due to drift
Solution Approach 1:
The patent segments the scanning process into discrete elongate regions that are processed in sequence. Within each region, the beam scans at optimized speeds while the system maintains position accuracy through the structured approach of processing defined segments. This segmentation allows for higher overall throughput while maintaining position accuracy within each scanned region by limiting the cumulative drift effect.
Solution Approach 2:
The patent employs feedback mechanisms where the system continuously monitors and adjusts the beam position and scanning parameters. By implementing feedback control during the scanning process, the system can compensate for drift in real-time, maintaining position accuracy even at higher scanning speeds that improve throughput. The feedback loop ensures that position errors are corrected dynamically throughout the scanning process.
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 enhances throughput and maintains position accuracy by reducing thermal distortion and drift, enabling more efficient detection and identification of defects on semiconductor IC chips.
Implementation Method 1
The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause signal electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons.
Implementation Method 2
Exposing a sample to a beam of electrons can apply a thermal load to the sample. Such a thermal load may cause distortion in the sample resulting in position errors.
Data Source
AI summary
Methods of processing a sample and charged particle assessment systems are disclosed. In one arrangement, a sample is processed using a multi-beam of sub-beams of charged particles. At least a portion of a sub-beam processable area is processed with each sub-beam. The sub-beam processable area comprising an array of sections having rows of sections and columns of sections. Each row of sections defines an elongate region that is substantially equal to or smaller than a pitch at the sample surface of the sub-beams in the multi-beam. A plurality of the sections are processed.