Spatially Coded Grating Topography Measurement System
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Solution Overview
Problem
Conventional topography measurement systems in lithographic apparatuses face limitations in spatial resolution due to the size of the grating image, which affects the accuracy of substrate height mapping and pattern projection.
Innovation Solution
A topography measurement system utilizing a spatially coded grating that patterns a radiation beam, allowing for improved spatial resolution by decodifying the radiation beam reflected from the substrate, enabling the determination of substrate height without being limited by the size of the grating image, and using a processor to apply a decoding sequence or matrix to produce an output signal indicative of the substrate's height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional grating is used to measure substrate topography, then the measurement system is simple in structure, but the spatial resolution is limited by the size of the grating image
Solution Approach 1:
The grating is segmented into multiple zones with different spatial frequencies, allowing each zone to contribute to different spatial frequency components of the topography measurement. This segmentation enables the system to achieve high spatial resolution without requiring a proportionally large grating image size
Solution Approach 2:
The patent transitions from measuring only vertical height variations to also measuring lateral position variations of the grating image. By adding this lateral dimension measurement, the system can determine substrate topography with higher spatial resolution than the grating image size would conventionally allow
2Area of stationary object
If the grating image size is increased to improve measurement coverage, then the area measured increases, but the spatial resolution decreases
Solution Approach 1:
The grating is divided into multiple zones with progressively different spatial frequencies. This segmentation allows the system to maintain high spatial resolution across a large measurement area by using higher frequency zones for fine details and lower frequency zones for broader coverage
Solution Approach 2:
Different zones of the grating are assigned different local properties (spatial frequencies) optimized for different measurement needs. High-frequency zones provide fine spatial resolution for critical areas, while low-frequency zones provide broader coverage, creating a non-uniform but optimized measurement system
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
The system achieves enhanced spatial resolution, allowing for more accurate substrate topography measurement and pattern projection by decoupling the spatial resolution from the grating image size, thereby improving the precision of lithographic processes.
Implementation Method 1
a spatially coded grating configured to pattern a radiation beam and thereby provide a spatially coded radiation beam
Implementation Method 2
optics configured to form an image of the spatially coded grating at a target location on a substrate
Implementation Method 3
detection optics configured to receive radiation reflected from the target location of the substrate and form an image of the grating image at a second grating
Implementation Method 4
a detector configured to receive radiation transmitted through the second grating and produce an output signal
Data Source
AI summary
A topography measurement system comprising a radiation source configured to generate a radiation beam, a spatially coded grating configured to pattern the radiation beam and thereby provide a spatially coded radiation beam, optics configured to form an image of the spatially coded grating at a target location on a substrate, detection optics configured to receive radiation reflected from the target location of the substrate and form an image of the grating image at a second grating, and a detector configured to receive radiation transmitted through the second grating and produce an output signal.