Lithographic Alignment Metrology With Multi-Order Intensity Detection
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Solution Overview
Problem
Existing lithographic processes face challenges in accurately aligning and measuring features on substrates, leading to reduced quality and yield in fabricated devices due to misalignment errors.
Innovation Solution
A metrology system that utilizes a radiation source to generate beams of different diffraction orders, with an optical element to direct and block specific scattered beams, allowing an imaging detector to determine intensity signals and generate detection signals for precise structure property determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional alignment measurement methods are used, then the alignment process is simpler, but the measurement precision and accuracy of feature placement are reduced
Solution Approach 1:
The patent segments the scattered radiation beam into multiple diffraction orders (first, second, third orders, etc.) and directs each order to separate detection channels. This segmentation allows independent measurement of intensity ratios for each diffraction order, thereby improving alignment measurement precision while managing system complexity through modular detection architecture
Solution Approach 2:
The patent introduces an intermediary optical system including beam splitters, mirrors, and diffraction grating that mediates between the scattered beam from the alignment mark and the detectors. This intermediary system enables precise separation and measurement of different diffraction orders, improving measurement accuracy while maintaining manageable device complexity through established optical components
2Measurement precision
If multiple scattered beams are measured simultaneously, then the measurement comprehensiveness is improved, but the device complexity increases
Solution Approach 1:
The optical system segments the scattered beam into multiple diffraction orders using a diffraction grating, with each order directed to separate detection channels. This allows simultaneous measurement of multiple intensity values (I1, I2, I3, etc.) while maintaining organized, manageable system complexity through spatial separation of measurement channels
Solution Approach 2:
The patent employs universal optical components such as beam splitters and mirrors that can direct different diffraction orders to multiple detectors simultaneously. These multi-functional components enable comprehensive intensity measurement across multiple channels while avoiding the need for separate specialized components for each measurement, thereby controlling device complexity
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
Enhances the accuracy of feature placement on substrates, improving the quality and yield of fabricated devices by providing more precise alignment and measurement capabilities.
Implementation Method 1
receive a first scattered beam and a second scattered beam of radiation from the target structure
Implementation Method 2
the first scattered beam comprises a first non-zero diffraction order and the second scattered beam comprises a second non-zero diffraction order
Data Source
AI summary
A metrology system includes a radiation source, an adjustable diffractive element, an optical system, an optical element, and a processor. The radiation source generates radiation. The adjustable diffractive element diffracts the radiation to generate first and second beams of radiation. The first and second beams have first and second different non-zero diffraction orders, respectively. The optical system directs the first and second beams toward a target structure such that first and second scattered beams of radiation are generated based on the first and second beams, respectively. The metrology system adjusts a phase difference of the first and second scattered beams. The optical element interferes the first and second scattered beams at an imaging detector that generates a detection signal. The processor receives and analyzes the detection signal to determine a property of the target structure based on the adjusted phase difference.