Electron Beam Mark Detection Using Background Waveform Removal
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Solution Overview
Problem
The challenge in electron beam writing for semiconductor devices is the low signal-to-noise ratio (SN ratio) due to low electron yield from fine alignment marks, leading to difficulty in mark detection, and the contamination risk from high-dose electron beams used to enhance contrast.
Innovation Solution
A method involving scanning a target object at multiple regions near line patterns, determining and removing background waveforms, and calculating mark positions to improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the dose of electron beam is increased to obtain contrast, then the contrast is improved, but the resist is scattered to contaminate the inside of the chamber
Solution Approach 1:
The patent segments the waveform signal into background components and mark components by acquiring waveforms from multiple regions (with and without marks) and performing differential processing. This allows extraction of mark-specific signals without increasing electron beam dose, thus improving contrast measurement while avoiding resist scattering contamination.
2Measurement precision
If background waveform is acquired by scanning position with no mark, then the background component is obtained, but it is difficult to judge whether it is a background component or not due to substrate arrangement deviation
Solution Approach 1:
The patent applies local quality by acquiring waveforms from multiple specific regions around the mark (both with and without marks) rather than assuming a generic background region. By performing differential processing between these locally-acquired waveforms, the system accurately identifies background components while accounting for substrate arrangement deviations and inclination.
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
Enhances the accuracy of mark position detection and reduces contamination by effectively distinguishing background waveforms from mark waveforms, improving the SN ratio and alignment precision.
Implementation Method 1
when a mark is irradiated with an electron beam, the electron yield is too small to achieve good contrast
Data Source
AI summary
According to one aspect of the present invention, a background waveform acquisition method includes scanning a target object with an electron beam, at a plurality of regions which are in a vicinity of a line pattern on the target object where a mark using the line pattern is formed, and are arranged in a direction not parallel to an extending direction of the line pattern, and determining a waveform of a background which is not the mark, in a plurality of measured waveforms measured by the scanning at the plurality of regions, and outputting the waveform of the background.