Variable Rate Scanning Electron Microscopy for Semiconductor Wafer Inspection
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Solution Overview
Problem
Current methods for imaging semiconductor wafers using electron beams are inefficient as they require scanning the entire surface at high speeds, compromising resolution and increasing imaging time.
Innovation Solution
Classifying surface regions into high and low interest areas and adjusting scan rates accordingly, allowing for high resolution imaging of critical regions while using faster scan rates for less critical areas, thereby reducing overall imaging time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electron beam scan rate is increased to reduce imaging time, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies local quality by differentiating scan rates based on region importance. High interest regions (containing critical features) are scanned at low speeds to maintain high resolution, while low interest regions are scanned at high speeds to reduce overall imaging time. This resolves the contradiction by making the scan rate adaptive to local image quality requirements rather than uniform across the entire field of view.
Solution Approach 2:
The patent segments the field of view into multiple regions of interest with different importance levels. By dividing the imaging area into high interest and low interest regions, the system can apply different scan rates to different segments, thereby achieving both high resolution where needed and fast imaging where not needed, resolving the speed-resolution tradeoff.
2Measurement precision
If the electron beam scan rate is decreased to improve image resolution, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The system applies local quality by assigning different scan rates to different regions based on their importance. Only high interest regions containing critical features are scanned at low speeds to achieve high resolution, while low interest regions are scanned at high speeds. This resolves the contradiction by limiting slow scanning to only where high resolution is actually needed.
Solution Approach 2:
The patent applies partial action by scanning only the necessary portions of the field of view at high resolution. Instead of uniformly scanning the entire area at low speed for maximum resolution, the system performs partial high-resolution scanning only on high interest regions, accepting lower resolution in low interest regions to maintain overall productivity.
3Measurement precision
If the entire surface is scanned at high resolution, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies local quality by differentiating scan rates based on region importance. High interest regions (containing critical features) are scanned at low speeds to maintain high resolution, while low interest regions are scanned at high speeds to reduce overall imaging time. This resolves the contradiction by making the scan rate adaptive to local image quality requirements rather than uniform across the entire field of view.
Solution Approach 2:
The patent applies partial action by scanning only the necessary portions of the field of view at high resolution. Instead of uniformly scanning the entire area at low speed for maximum resolution, the system performs partial high-resolution scanning only on high interest regions, accepting lower resolution in low interest regions to maintain overall productivity.
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 efficient imaging of semiconductor wafers by prioritizing high resolution in key areas while maintaining acceptable resolution in less critical regions, significantly decreasing the time required to image the entire surface.
Implementation Method 1
Secondary electrons from the surface are collected, and may be used to form an image of the irradiated surface
Data Source
AI summary
A method for imaging a surface, including scanning a first region of the surface with a primary charged particle beam at a first scan rate so as to generate a first secondary charged particle beam from the first region, and scanning a second region of the surface with the primary charged particle beam at a second scan rate faster than the first scan rate so as to generate a second secondary charged particle beam from the second region. The method also includes receiving the first secondary charged particle beam and the second secondary charged particle beam at a detector configured to generate a signal in response to the beams, and forming an image of the first and the second regions in response to the signal.