Lithography Alignment Sensor Critical Dimension Measurement
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Solution Overview
Problem
Current lithographic techniques face challenges in accurately measuring small features, such as critical dimensions, due to the increasing difficulty and time consumption of measurements as patterns become smaller.
Innovation Solution
A system and method utilizing a light source with a Tm or Te polarized beam of light having a wavelength larger than the critical dimension, combined with a light sensor and processor to detect and calculate the critical dimension of patterned features on a substrate, which includes a super-wavelength grating and a sub-wavelength grating, allowing for the comparison of light intensities to determine feature sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used for small features, then measurement capability is maintained, but measurement time and difficulty increase significantly
Solution Approach 1:
The patent replaces conventional mechanical measurement systems with an optical measurement system using light reflection and diffraction. The alignment sensor uses optical principles to measure critical dimensions non-contactingly, eliminating time-consuming mechanical measurement processes while maintaining precision for small features.
Solution Approach 2:
The patent changes the measurement parameter from direct physical measurement to optical intensity detection. By measuring the intensity of reflected light from patterned structures with known grating parameters, the system calculates critical dimensions through computational analysis rather than direct measurement, significantly reducing measurement time.
2Measurement precision
If conventional measurement methods are used for small features, then measurement capability is maintained, but measurement complexity increases
Solution Approach 1:
The patent replaces complex mechanical measurement systems with a simplified optical detection system. The alignment sensor detects critical dimensions by measuring light intensity reflections from patterned structures, eliminating complex mechanical alignment and measurement procedures while maintaining high precision for small features.
Solution Approach 2:
The patent introduces light as an intermediary medium to transfer measurement information. Instead of directly measuring small features, the system uses light reflection and diffraction patterns as intermediaries to encode dimensional information, which is then decoded by the alignment sensor to determine critical dimensions.
3Measurement precision
If sub-wavelength gratings are used to measure small features, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent segments the grating structure into super-wavelength and sub-wavelength components. The super-wavelength grating provides the basic diffraction pattern, while the sub-wavelength grating modifies the pattern to enhance measurement precision for small features. This segmentation allows the system to achieve high precision without requiring entirely complex grating structures.
Solution Approach 2:
The patent embeds the sub-wavelength grating within or alongside the super-wavelength grating structure. The sub-wavelength features are nested within the larger super-wavelength periodic structure, allowing both grating types to work together synergistically. This nesting approach enables precise measurement of small features while keeping the overall device structure manageable.
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
Enables convenient and accurate measurement of critical dimensions in patterned substrates, improving the efficiency of lithographic processes by effectively measuring feature sizes and determining focus conditions within the lithographic apparatus.
Implementation Method 1
a light sensor configured to detect an intensity of light reflected from a patterned structure on the substrate
Implementation Method 2
The sub-wavelength grating is configured such that all the propagating diffraction orders of the incident light cease to exist except for the zero order
Data Source
AI summary
A system and method for determining parameters such as critical dimension of a patterned structure and best focus condition of a lithographic apparatus, based on measurement of the intensity of a non-zero order of light diffracted from an experimental structure. The experimental structure includes a first array of lines and partially filled spaces having a period longer than the wavelength of the diffracted light. The experimental structure also includes a second array of lines and spaces, where the second array of lines and spaces comprise the partially filled spaces.