Metrology Tool Detector Array for Scattered Radiation Dose Measurement
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Solution Overview
Problem
Existing metrology tools face challenges in efficiently measuring parameters of interest on substrates, particularly in lithographic processes, due to the need for multiple sequential measurements with different wavelengths and the limitations of neutral density filters, which affect throughput and practicality.
Innovation Solution
A metrology tool comprising projection and detection optics, a detector array with multiple detector elements, and a controller that configures each detector element to determine a dose of scattered radiation over multiple discrete time intervals, allowing for a single image to be read out and processed efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sequential measurements with different wavelengths are performed using neutral density filters, then measurement precision is improved, but productivity deteriorates due to increased measurement time and throughput limitations
Solution Approach 1:
The patent combines multiple sequential measurements with different wavelengths into a single simultaneous measurement using a detector array that captures multiple exposure images at once. This merging eliminates the need for sequential measurements with neutral density filters, thereby improving throughput while maintaining measurement precision through parallel data collection.
Solution Approach 2:
The patent transitions from temporal sequencing (measuring one wavelength at a time in sequence) to spatial parallelization (measuring multiple wavelengths simultaneously across different detector elements). This dimensional change from time to space enables concurrent measurements, resolving the contradiction between precision and productivity.
2Measurement precision
If neutral density filters are used to control radiation intensity, then measurement precision is improved, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The patent removes the neutral density filter component from the system entirely. Instead of using filters to control radiation intensity, the invention employs a detector array with multiple detector elements that directly capture multiple wavelengths simultaneously, eliminating the need for mechanical filter components and simplifying the overall device structure.
Solution Approach 2:
The patent replaces the mechanical neutral density filter system with an electronic/detector-based solution. Rather than physically blocking radiation with mechanical filters, the system uses detector elements to selectively detect and record radiation at different wavelengths, substituting mechanical intensity control with electronic detection and processing.
3Measurement precision
If multiple sequential measurements are performed, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent enables continuous simultaneous measurement of multiple wavelengths across all detector elements in parallel, eliminating the interruptions and sequential steps inherent in traditional methods. This continuous parallel action completes all measurements in a single exposure event, dramatically reducing processing time while maintaining precision through comprehensive data collection.
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 better averaging of system-induced dynamic effects, such as vibrations, and prevents wavelength changes, resulting in improved measurement accuracy and significantly quicker processing times compared to traditional multiple exposure methods.
Implementation Method 1
a detector array comprising a plurality of detector elements, each of the plurality of detector elements being operable to determine a dose of received scattered radiation
Implementation Method 2
projection optics arranged to project radiation onto the structure
Implementation Method 3
detection optics arranged to receive at least a portion of radiation scattered by the structure
Data Source
Figure 1
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Figure 4
AI summary
A metrology tool for inspection of a structure on an object comprises: projection optics; detection optics; a detector array; and a controller. The projection optics is arranged to project radiation onto the structure and the detection optics is arranged to receive radiation scattered by the structure. The detector array comprises a plurality of detector elements. The controller is operable to: control the detector array so as to determine at least one image; and determine one or more parameters of interest in dependence on the at least one determined image. The controller is configurable such that each pixel of at least one determined image is indicative of a total dose of radiation received by one of detector elements in a plurality of discrete time intervals during a measurement time interval, the pixel value being read out from the corresponding detector element at the end of the measurement time interval.