GISAXS Overlay Measurement for Microelectronic Components
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Solution Overview
Problem
Existing methods for measuring overlay errors in microelectronic components using transmission X-ray scattering techniques are difficult to implement due to the need for high-intensity X-ray beams, which are not compatible with production line deployment, especially when components have a significant thickness like silicon substrates.
Innovation Solution
A method utilizing grazing-incidence small-angle X-ray scattering (GISAXS) that reflects X-rays off the surface of microelectronic components, enabling the use of less intense laboratory X-ray sources and allowing precise overlay measurements by reconstructing a reciprocal image and calculating overlay defects through spatial frequency differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission X-ray scattering technique is used to measure overlay, then overlay measurement can be performed, but high-intensity X-ray beam is required which is not compatible with production line deployment
Solution Approach 1:
The patent inverts the conventional transmission geometry by using reflection geometry for X-ray scattering. Instead of transmitting X-rays through the thick silicon substrate, the method measures scattering from the surface at grazing incidence angles, eliminating the need for high-intensity beams while maintaining measurement capability
Solution Approach 2:
The patent changes the key parameter of X-ray interaction geometry from transmission mode to reflection mode. By operating at grazing incidence angles and measuring scattered intensity at specific angles, the method achieves overlay measurement with conventional laboratory X-ray sources rather than requiring synchrotron-level intensity
2Measurement precision
If transmission X-ray scattering is used through thick silicon substrates, then overlay measurement is possible, but X-ray beam intensity must be very high
Solution Approach 1:
The patent inverts the conventional transmission geometry by using reflection geometry for X-ray scattering. Instead of transmitting X-rays through the thick silicon substrate, the method measures scattering from the surface at grazing incidence angles, eliminating the need for high-intensity beams while maintaining measurement capability
Solution Approach 2:
The patent transitions from measuring X-ray transmission through the bulk material (one-dimensional path) to measuring X-ray scattering at the surface interface (adding the angular dimension). By measuring scattered intensity as a function of scattering angle at grazing incidence, the method extracts overlay information without requiring deep penetration through the substrate
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
Enables precise overlay measurements compatible with production lines using laboratory X-ray sources, overcoming the limitations of transmission methods by reflecting X-rays and accounting for multi-reflection effects, resulting in accurate and efficient overlay defect determination.
Implementation Method 1
a method for measuring a covering defect affecting a pattern resulting from the superposition of a first network of lines carried by a first level of a microelectronic component and a second network of lines carried by a second level of the microelectronic component, an orthonormal reference frame x0y0z0 being associated with the microelectronic component, the lines of the first and second network of lines being oriented in the x0 direction, and the first and second network of lines being superimposed in the z0 direction, the measurement method implementing a small angle X-ray scattering technique by reflection - GI-SAXS making it possible to illuminate the pattern at an angle of incidence αi
Implementation Method 2
acquiring, by means of a detector placed in an observation plane, an orthonormal reference frame xyz being associated with the detector so that the z axis is parallel to the z0 axis and that the x axis, normal to the observation plane, coincides with the yo axis for a zero illumination angle, a plurality of intensity measurements of an X-ray beam scattered by the pattern carried by the component
Data Source
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AI summary
This GI-SAXS method (100) measures a defect affecting a pattern superimposing first and second line networks. It consists of: acquiring (110), in an observation plane, intensity measurements of the X-rays scattered by the pattern; reconstructing (120), from the intensity measurements, a reciprocal image; determining (130) a first position according to a first spatial frequency of a characteristic point on a first intensity curve corresponding to a section of the reciprocal image for a first value of a second spatial frequency, and a second position according to the first spatial frequency of the characteristic point on a second intensity curve corresponding to a section of the reciprocal image for a second value of the second spatial frequency; and, calculating (140) a defect from the difference between the first and second positions according to the first spatial frequency and the difference between the first and second values according to the second spatial frequency.