Charged Particle Beam Imaging Using Stored Focus Corrections
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Solution Overview
Problem
Current charged particle beam apparatuses, such as scanning electron microscopes, face challenges in efficiently measuring overlay errors between layers of semiconductor devices with high accuracy and speed, particularly due to increasing measurement points and time demands in semiconductor manufacturing processes.
Innovation Solution
A charged particle beam apparatus that stores a correction value table and uses a computer system to adjust imaging conditions based on previous measurement results, allowing for optimized measurement procedures across multiple points on different samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of measurement points per wafer is increased to improve measurement accuracy, then measurement precision is improved, but measurement time increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by acquiring the height distribution of the wafer in advance using an optical height detector before the charged particle beam measurement. This pre-acquired height information is then used to predict the focusing height at each measurement point, allowing the system to skip time-consuming autofocus operations and directly perform measurements with pre-calculated focus settings, thereby reducing measurement time while maintaining accuracy across increased measurement points
2Measurement precision
If autofocus is performed at each measurement point to ensure measurement quality, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The system performs preliminary action by acquiring the overall height distribution of the wafer before measurement using an optical height detector. Based on this pre-acquired height information, the focusing height at each measurement point is predicted in advance, eliminating the need for time-consuming autofocus operations at each individual measurement point while still achieving accurate focus
Solution Approach 2:
The patent introduces an intermediary approach by using optical height detection as a preliminary step to bridge the gap between rough wafer topography and precise measurement requirements. The optical height detector provides initial height information that serves as a foundation for predicting focus heights, acting as an intermediary that reduces the burden of autofocus operations during the actual charged particle beam measurement
Data Source
AI summary
The present disclosure makes it possible to shorten the time required for measurement of a sample and to measure the sample with high throughput. A charged particle beam apparatus includes a storage device that stores a correction value table corresponding to a recipe and a computer system that executes measurement on a plurality of measurement points of a sample according to a measurement order determined in the recipe. The computer system stores, when executing the recipe on a first sample, an adjustment result of one or more imaging conditions in the correction value table at each of a plurality of measurement points of the first sample, and adjusts, when executing the recipe on a second sample different from the first sample, the imaging condition based on the adjustment result of the one or more imaging conditions stored in the correction value table at each of the plurality of measurement points.