Electron Beam Inspection Voltage Control for Charge-Up Mitigation
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Solution Overview
Problem
Conventional electron beam inspection methods face challenges in achieving accurate and efficient surface inspection of semiconductor samples due to charge-up effects and coma aberration during overlay alignment, leading to potential alignment offsets and prolonged inspection times.
Innovation Solution
The method involves controlling the sample voltage in response to electron beam irradiation to mitigate charge-up effects and using an electron beam inspection apparatus with a voltage adjustment mechanism, along with a detector system comprising a MCP and TDI-CCD, to enhance image formation and accuracy. Additionally, the stage is moved synchronously with the sensor's operating frequency to minimize movement time between inspection points and optimize electron beam geometry for improved inspection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If an electron beam is used for inspection, then detection capability is improved, but charge-up effects occur on the sample surface causing image focus degradation
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for charge-up effects through voltage adjustment mechanisms. The system adjusts the sample voltage or retarding voltage in advance based on predicted charge accumulation from electron beam irradiation, thereby preventing image focus degradation before it occurs during inspection
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting voltage parameters (sample voltage or retarding voltage) in response to electron beam irradiation conditions. This allows the system to adapt to changing charge-up states and maintain optimal image focus throughout the inspection process
2Ease of operation
If optical microscope is used for overlay inspection, then alignment can be performed, but coma aberration causes alignment offset
Solution Approach 1:
The patent replaces the optical microscope system with an electron beam inspection system. This substitution eliminates coma aberration inherent in optical systems while providing sufficient alignment capability through electron beam-based overlay mark detection and measurement
3Measurement precision
If SEM is used for inspection, then detection accuracy is improved, but inspection time increases for large areas
Solution Approach 1:
The patent implements dynamics by enabling continuous stage movement during electron beam inspection. The stage moves synchronously with the sensor's operating frequency, allowing the system to inspect large areas without stopping, thereby maintaining high detection accuracy while significantly improving inspection throughput
Solution Approach 2:
The patent achieves continuity of useful action by synchronizing stage movement with sensor operation. The inspection process continues without interruption as the stage moves between inspection points, eliminating idle time and maintaining constant detection activity across the entire sample area
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 high-accuracy and efficient surface inspection of semiconductor samples by addressing charge-up and alignment issues, improving the quality and throughput of semiconductor devices with precise overlay detection and reduced inspection time.
Implementation Method 1
an electron beam is irradiated onto the surface of the sample and secondary electrons are generated from the sample surface in response to the irradiation of the electron beam
Implementation Method 2
an effect from charge-up in a sample surface could inhibit a clear image from being obtained
Data Source
AI summary
Provided is a method and an apparatus for inspecting a sample surface with high accuracy. Provided is a method for inspecting a sample surface by using an electron beam method sample surface inspection apparatus, in which an electron beam generated by an electron gun of the electron beam method sample surface inspection apparatus is irradiated onto the sample surface, and secondary electrons emanating from the sample surface are formed into an image toward an electron detection plane of a detector for inspecting the sample surface, the method characterized in that a condition for forming the secondary electrons into an image on a detection plane of the detector is controlled such that a potential in the sample surface varies in dependence on an amount of the electron beam irradiated onto the sample surface.