Multi-Beam Wafer Inspection Control for Stage Drift Compensation
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Solution Overview
Problem
Multi-beam charged particle inspection systems face challenges in maintaining high precision, high resolution, and high throughput due to issues like stage movement errors, drifts, and dynamic aberrations, which affect image quality and reliability during wafer inspection.
Innovation Solution
The system employs a method of predicting and compensating error amplitudes by analyzing sensor data to adjust the primary and secondary beam paths, and stage movement, using a control unit to compute and apply control signals to deflection systems, ensuring accurate positioning and focus maintenance across image patches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer stage moves quickly between image patches to increase throughput, then productivity improves, but manufacturing precision deteriorates due to stage movement errors and drifts
Solution Approach 1:
The system continuously monitors the actual positions of primary and secondary beam spots using sensor data, compares them with reference positions, and generates feedback signals to adjust deflection system parameters. This closed-loop feedback mechanism compensates for stage movement errors and drifts in real-time, maintaining positioning accuracy despite fast stage movement between image patches.
Solution Approach 2:
The patent replaces mechanical positioning precision requirements with electromagnetic field control. Instead of relying solely on mechanical stage stability, the system uses electric and magnetic fields in the deflection systems to dynamically adjust beam paths and compensate for mechanical errors, substituting mechanical precision requirements with field control capabilities.
2Manufacturing precision
If the deflection system parameters are dynamically adjusted to compensate for drifts and errors, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The control unit serves multiple functions: it processes sensor data, calculates position deviations, determines parameter adjustments, and generates control signals for the deflection systems. This multi-functional integration reduces the need for separate dedicated components for each control function, managing complexity through consolidation while maintaining precise beam spot positioning capability.
Solution Approach 2:
The system performs self-calibration and self-correction by continuously monitoring its own beam spot positions and automatically adjusting deflection parameters to maintain accuracy. The control unit uses reference positions and actual position data to autonomously determine and apply corrections without external intervention, enabling the system to maintain precision while managing complexity through autonomous operation.
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 the system's ability to achieve high precision and high-resolution image acquisition with high throughput, reducing errors and maintaining image quality across sequential image patches.
Implementation Method 1
interaction products, e.g. secondary electrons, originate from the plurality of intersection points formed by the focus points of the primary charged particle beamlets
Implementation Method 2
The plurality of primary charged particle beamlets is focused by a common objective lens
Implementation Method 3
A sequence of electrostatic and magnetic elements is provided in the charged particle beam path
Data Source
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Figure 2
Figure 3a
AI summary
A multi-beam charged particle inspection system and a method of operating a multi-beam charged particle inspection system for wafer inspection with high throughput and with high resolution and high reliability is provided. The method and the multi-beam charged particle beam inspection system are configured to extract from a plurality of sensor data a set of control signals to control the multi- beam charged particle beam inspection system and thereby maintain the imaging specifications including a movement of a wafer stage during the wafer inspection task. In particular, the system is operated such that a time interval Tr overlaps with a time interval Ts1 and/or Ts2 for image acquisition.