Beam Shaping Slit for T-SAXS Spot Size Control
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Solution Overview
Problem
Current x-ray metrology systems face challenges in accurately measuring complex, high-aspect ratio structures due to finite source size limitations, which result in beam divergence issues and reduced measurement precision, especially when dealing with opaque materials and small feature sizes.
Innovation Solution
The solution involves locating a beam shaping slit in close proximity to the specimen, with a slender profile that does not interfere with wafer stage components, even at large angles of incidence, and using multiple independently actuated slits to minimize beam divergence effects and achieve a sharply defined beam spot with minimal shadow zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the beam shaping slit is located far from the specimen, then the beam divergence effects are reduced, but the beam spot size increases and measurement precision deteriorates
Solution Approach 1:
The beam shaping slit is made movable relative to the specimen through a positioning mechanism, allowing dynamic adjustment of the slit-specimen distance. This enables optimization of beam spot size at the specimen location while maintaining system flexibility for different measurement configurations
Solution Approach 2:
The system changes the physical parameter of slit position distance to optimize beam characteristics. By adjusting the distance parameter between the beam shaping slit and specimen, the system achieves optimal balance between beam divergence control and spot size minimization
2Adaptability or versatility
If the beam shaping slit has a large profile, then it can accommodate beam divergence, but it interferes with wafer stage components at large angles of incidence
Solution Approach 1:
The beam shaping slit is divided into multiple independently controllable slit elements or segments. Each segment can be positioned and shaped independently, allowing the system to accommodate beam divergence while maintaining a compact overall profile that avoids interference with wafer stage components
Solution Approach 2:
The system addresses beam divergence accommodation not by increasing the slit profile in the horizontal plane, but by utilizing the vertical dimension and angular positioning. The slit is positioned at an angle and configured to work with the beam geometry in three-dimensional space, allowing divergence accommodation without horizontal interference
3Measurement precision
If the beam shaping slit is positioned close to the specimen, then beam spot size is reduced, but beam divergence effects increase
Solution Approach 1:
The system dynamically adjusts the slit position and opening characteristics in real-time to compensate for beam divergence. The movable slit mechanism allows continuous optimization of beam quality close to the specimen while maintaining stable measurement conditions through active compensation
4Measurement precision
If multiple independently actuated slits are used, then beam spot definition is improved, but device complexity increases
Solution Approach 1:
The multiple slit elements serve multiple functions: they define beam shape, control beam size, manage beam divergence, and accommodate different measurement configurations. This multi-functionality justifies the increased device complexity by providing versatile control over beam characteristics for various measurement applications
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 enhances measurement accuracy and precision by reducing beam spot size to less than 50 micrometers, allowing for effective characterization of high-aspect ratio structures and improving the ability to penetrate opaque materials, while maintaining sufficient photon flux for effective metrology.
Implementation Method 1
The beam shaping slit is located in close proximity to the specimen under measurement to reduce the effect of finite source size on illumination beam spot size
Implementation Method 2
By locating the beam shaping slit in close proximity to the specimen, the effect of beam divergence on beam spot size is minimized
Data Source
AI summary
Methods and systems for reducing the effect of finite source size on illumination beam spot size for Transmission, Small-Angle X-ray Scatterometry (T-SAXS) measurements are described herein. A beam shaping slit having a slender profile is located in close proximity to the specimen under measurement and does not interfere with wafer stage components over the full range of angles of beam incidence. In one embodiment, four independently actuated beam shaping slits are employed to effectively block a portion of an incoming x-ray beam and generate an output beam having a box shaped illumination cross-section. In one aspect, each of the beam shaping slits is located at a different distance from the specimen in a direction aligned with the beam axis. In another aspect, the beam shaping slits are configured to rotate about the beam axis in coordination with the orientation of the specimen.