Phase-Modulated Scanning Metrology for Precise Lithography Alignment
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Solution Overview
Problem
Existing lithographic systems 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 and optical systems to split and modulate phase differences between beams, interfering them at an imaging detector to analyze target structures for accurate property determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment methods are used, then the alignment process is simple, but the measurement precision and manufacturing precision deteriorate due to misalignment errors
Solution Approach 1:
The radiation beam is split into multiple beams (first beam and second beam) that travel along different optical paths and are reflected from different alignment marks. This segmentation allows simultaneous measurement of multiple alignment parameters, improving measurement precision while distributing the measurement task across separate beam paths
Solution Approach 2:
The patent introduces phase modulators as intermediary components that modulate the phase of individual beams before recombination. These intermediaries enable precise control and differentiation of beam paths, allowing the system to extract detailed alignment information from the interference pattern without requiring direct mechanical contact or complex positioning mechanisms
2Manufacturing precision
If phase modulation is applied to enhance measurement accuracy, then the manufacturing precision improves, but the device complexity increases due to additional optical components
Solution Approach 1:
Phase modulators are used to apply periodic phase modulation to the beams at different frequencies. This periodic action creates distinct interference patterns that can be decoded to extract precise alignment measurements. The modulation frequencies are chosen to be distinguishable, allowing the system to separate and analyze different measurement signals simultaneously
Solution Approach 2:
The system dynamically modulates the phase of beams during measurement, transforming a static optical path into a dynamic measurement process. This allows the system to encode multiple measurement parameters into the time-varying interference pattern, improving manufacturing precision through enhanced signal discrimination
3Measurement precision
If multiple beams are used for measurement, then the measurement precision improves through interference patterns, but the loss of time increases due to complex optical path management
Solution Approach 1:
The system continuously modulates and recombines multiple beams simultaneously to generate interference patterns that encode alignment information. This continuous multi-beam interference process eliminates the need for sequential measurements, maintaining high measurement precision while reducing the overall measurement cycle time through parallel information acquisition
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 and measurement in lithographic processes, improving device quality and yield by reducing misalignment errors.
Implementation Method 1
a first optical system configured to split the radiation into first and second beams of radiation and impart one or more phase differences between the first and second beams
Implementation Method 2
impart one or more phase differences between the first and second beams
Implementation Method 3
a second optical system configured to direct the first and second beams toward a target structure to produce first and second scattered beams
Implementation Method 4
a third optical system configured to interfere the first and second scattered beams at an imaging detector
Implementation Method 5
The imaging detector is configured to generate a detection signal based on the interfered first and second scattered beams
Data Source
AI summary
A metrology system includes a radiation source, first, second, and third optical systems, and a processor. The first optical system splits the radiation into first and second beams of radiation and impart one or more phase differences between the first and second beams. The second optical system directs the first and second beams toward a target structure to produce first and second scattered beams of radiation. The third optical system interferes the first and second scattered beams at an imaging detector. The imaging detector generates a detection signal based on the interfered first and second scattered beams. The metrology system modulates one or more phase differences of the first and second scattered beams based on the imparted one or more phase differences. The processor analyzes the detection signal to determine a property of the target structure based on at least the modulated one or more phase differences.