Diffraction-Based Overlay Metrology for Critical Dimension Evaluation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for evaluating critical dimensions of semiconductor devices, such as CDSEM and OCD metrology, require expensive and specific equipment, limiting cost-effective quality control in semiconductor fabrication.
Innovation Solution
The implementation of diffraction-based overlay (DBO) metrology to determine critical dimension variations by using overlay markings on multiple layers, where a first set of diffraction gratings on a reference layer and a second set of diffraction grating clusters on a target layer with finer periods are used to measure diffraction parameters, allowing for the calculation of critical dimension variations without the need for expensive equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (CDSEM and OCD metrology) are used to evaluate critical dimensions, then measurement precision is improved, but device cost increases due to expensive equipment requirements
Solution Approach 1:
The patent makes the DBO system multi-functional by enabling it to perform both overlay measurement and critical dimension evaluation. The same diffraction-based measurement system is configured to measure multiple parameters (overlay and CD) using different marking structures, eliminating the need for separate expensive CDSEM or OCD equipment while maintaining measurement precision
Solution Approach 2:
The patent uses diffraction grating markings that replicate the critical dimension information in a measurable form. The periodic structures on the wafer layers create diffraction patterns that copy the dimensional information, allowing indirect but accurate CD measurement through the DBO system without requiring direct imaging equipment
2Ease of manufacture
If DBO system is used to evaluate critical dimensions, then device cost is reduced by avoiding expensive equipment, but measurement precision may be compromised
Solution Approach 1:
The patent changes the measurement parameters by using diffraction intensity ratios at different orders (e.g., +1 and -1 orders) to extract CD information. By measuring the ratio of diffraction intensities from the periodic structures, the system determines critical dimensions through parameter transformation rather than direct measurement, maintaining precision with lower-cost equipment
Solution Approach 2:
The patent replaces the mechanical/electronic imaging systems (CDSEM) or complex optical systems (OCD) with a simpler diffraction-based optical measurement approach. The DBO system uses light diffraction from periodic structures to obtain CD information, substituting complex measurement mechanics with a more straightforward optical diffraction method
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 cost-effective evaluation of critical dimensions on semiconductor devices by using existing DBO systems to measure diffraction parameters, reducing the reliance on expensive metrology tools like CDSEM and OCD, thereby improving quality control and reducing fabrication costs.
Implementation Method 1
receiving a plurality of diffraction parameters measured from corresponding overlay markings on the first and second layers
Data Source
AI summary
Systems and methods for evaluating critical dimensions of a semiconductor device are provided. The semiconductor device includes a first layer comprising a first set of overlay markings and a second layer comprising a second set of overlay markings. The second layer is higher than the first layer. The first set of overlay markings includes a plurality of diffraction gratings. Each of the plurality of diffraction gratings has a first period. The second set of overlay markings includes a plurality diffraction grating clusters. Each of the plurality of diffraction grating clusters has a plurality of diffraction grating units. The plurality of diffraction grating units in at least one of the plurality of diffraction grating clusters have the first period. At least one of the plurality of diffraction grating units includes a diffraction grating having a second period that is smaller than the first period.