On-Chip Sensor for Wafer Overlay Measurement
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Solution Overview
Problem
Current lithographic sensor systems face challenges in accurately measuring overlay errors and on-process accuracy errors due to process variations, which limit their ability to form precise features on substrates, especially with extreme ultraviolet radiation, and require larger footprints and less scalability.
Innovation Solution
A compact sensor apparatus with integrated optic configurations, including photonic crystal fibers and waveguides, and a microelectromechanical system-based actuator, is used to transmit and focus illumination beams onto diffraction targets, generating signal beams for simultaneous measurement of overlay errors across multiple alignment marks on a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensor systems are used for overlay measurement, then measurement capability is provided, but the sensor footprint is large and scalability is limited
Solution Approach 1:
The patent integrates multiple optical components including illumination sources, optical fibers, waveguides, mirrors, lenses, and detectors into a single compact sensor chip. This merging of components enables overlay measurement functionality while dramatically reducing the sensor footprint from conventional large-scale systems to a miniaturized chip format, directly resolving the contradiction between measurement capability and compact size
Solution Approach 2:
The patent implements a nested structure where optical components are integrated within hierarchical layers on the sensor chip. The illumination system, optical pathways, and detection elements are arranged in nested configurations that maximize functionality within minimal space, enabling compact footprint while maintaining measurement precision
2Measurement precision
If conventional sensor systems are used, then overlay measurement is possible, but the system is not scalable and cost efficiency is reduced
Solution Approach 1:
The patent designs a universal sensor chip platform that can measure multiple characteristics of alignment marks including overlay errors, on-process accuracy errors, and other metrological parameters. The integrated optical system serves multiple measurement functions simultaneously, enabling scalability across different measurement applications and reducing costs through multi-functionality
Solution Approach 2:
The patent divides the sensor system into modular functional units including separate illumination systems, optical pathways, and detection elements that can be independently optimized and scaled. This segmentation allows the sensor design to be replicated and scaled across multiple chips or systems while maintaining measurement precision, thereby improving scalability and cost efficiency
3Measurement precision
If multiple alignment marks are measured sequentially, then measurement completeness is achieved, but measurement time increases and productivity decreases
Solution Approach 1:
The patent implements preliminary action by having multiple alignment marks illuminated and measured simultaneously in parallel rather than sequentially. The optical system is configured to illuminate multiple marks at once and detect their characteristics concurrently, completing all measurements in a single operation rather than requiring sequential processing, thereby dramatically improving productivity while maintaining measurement completeness
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 solution enables precise, scalable, and cost-effective measurement of overlay errors, improving the accuracy and efficiency of lithographic processes while reducing the sensor's footprint, allowing for real-time correction of processing errors and enhanced long-term stability.
Implementation Method 1
The illumination system can include a photonic crystal fiber disposed on the sensor chip and coupled to the first optical system
Implementation Method 2
an optical fiber disposed on the sensor chip and coupled to the first optical system
Implementation Method 3
the first integrated optic configuration includes a mirror and an integrated waveguide disposed on the first side of the sensor chip. For example, the integrated waveguide can include a photonic crystal waveguide
Implementation Method 4
the mirror includes a microelectromechanical system-based actuator configured to focus the illumination beam onto the diffraction target
Implementation Method 5
generate a signal beam including diffraction order sub-beams generated from the diffraction target
Implementation Method 6
the second optical system is coupled to the sensor chip and includes a second integrated optic configuration to collect and transmit the signal beam from the first side to the second side of the sensor chip
Implementation Method 7
The detector system is configured to measure a characteristic of the diffraction target based on the signal beam transmitted by the second optical system
Data Source
AI summary
A sensor apparatus includes a sensor chip, an illumination system, a first optical system, a second optical system, and a detector system. The illumination system is coupled to the sensor chip and transmits an illumination beam along an illumination path. The first optical system is coupled to the sensor chip and includes a first integrated optic to configure and transmit the illumination beam toward a diffraction target on a substrate, disposed adjacent to the sensor chip, and generate a signal beam including diffraction order sub-beams generated from the diffraction target. The second optical system is coupled to the sensor chip and includes a second integrated optic to collect and transmit the signal beam from a first side to a second side of the sensor chip. The detector system is configured to measure a characteristic of the diffraction target based on the signal beam transmitted by the second optical system.