X-ray Scatterometry Asymmetry Correction for High Aspect Ratio Features
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Solution Overview
Problem
X-ray scatterometry techniques face challenges in accurately measuring high aspect ratio features in semiconductor devices due to undesired reflections from sidewalls, causing asymmetry in the measured X-ray intensity distribution, which degrades measurement quality.
Innovation Solution
The method involves correcting the X-ray distribution by averaging intensities on either side of the reference axis or selecting the orientation with the lowest asymmetry, and applying an asymmetric correcting function to reduce asymmetry, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional X-ray scatterometry is used to measure high aspect ratio features, then measurement capability is provided, but asymmetry in intensity distribution degrades measurement precision
Solution Approach 1:
The patent converts the harmful asymmetry caused by sidewall reflections into a beneficial measurement signal. By intentionally introducing a known asymmetric element (beam stopper) and measuring its effect, the system transforms the problematic asymmetry into a useful reference for calibration and correction, thereby improving measurement precision of high aspect ratio features
Solution Approach 2:
The patent changes the parameter of beam intensity distribution by introducing a beam stopper that creates a controlled asymmetric attenuation. This parameter change allows the system to characterize and correct the asymmetry in the scattering pattern, leading to improved measurement accuracy
2Measurement precision
If beam stopper is introduced to correct asymmetry, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The beam stopper is a simple, inexpensive component that can be easily positioned and removed. Rather than implementing a complex real-time correction system, the patent uses this simple disposable-like element to correct asymmetry, minimizing device complexity while improving measurement accuracy
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 accurate measurement of high aspect ratio features by reducing asymmetry caused by undesired reflections, leading to precise determination of geometrical parameters such as feature dimensions and distances.
Implementation Method 1
receiving a first distribution of an X-ray beam scattered from a sample
Data Source
AI summary
A method for X-ray scatterometry includes receiving a first distribution of an X-ray beam scattered from a sample. The first distribution exhibits asymmetry with respect to a reference axis. A correction is applied to the first distribution, so as to produce a second distribution in which a level of the asymmetry is reduced relative to the first distribution. One or more parameters of the sample are estimated based on the second distribution.