Sub-Wavelength Alignment Key for 5 Nm Overlay Inspection
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Solution Overview
Problem
Existing post bonding inspection (PBI) keys have micron-scale structures that limit inspection precision as electronic components in semiconductor fabrication shrink, necessitating a new method for high-precision overlay inspection.
Innovation Solution
An alignment key is designed with first and second pattern layers of gratings arranged at sub-wavelength pitches, forming an optical interference pattern through incident light, and optionally incorporating a metastructure layer of nanostructures to enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micron-scale structures are used in existing PBI keys, then the device complexity is reduced and manufacturing is easier, but the measurement precision deteriorates due to the scale down of electronic components
Solution Approach 1:
The alignment key is divided into multiple pattern layers (first pattern layer with first gratings, second pattern layer with second gratings) disposed at different depths or positions. Each pattern layer contains multiple gratings with different pitches, allowing the system to achieve high measurement precision through the combined optical interference effects of all layers while distributing the structural complexity across separate, manageable components
Solution Approach 2:
The invention transitions from two-dimensional planar gratings to three-dimensional multi-layered grating structures with different pitches arranged in multiple pattern layers. This dimensional extension creates complex optical interference patterns that provide high-precision overlay measurement capability, effectively resolving the contradiction between measurement precision and device complexity by utilizing spatial arrangement rather than increasing individual grating complexity
2Measurement precision
If sub-wavelength pitch gratings are used in the alignment key, then the measurement precision is improved through optical interference patterns, but the manufacturing precision requirements worsen due to the sub-wavelength scale
Solution Approach 1:
The invention uses multiple gratings with different pitches (first pitch and second pitch) in separate pattern layers. By changing the pitch parameter across different layers rather than requiring ultra-precise single-pitch fabrication, the system achieves high measurement precision through optical interference while relaxing individual manufacturing precision requirements. The optical interference effect amplifies alignment errors into measurable moiré patterns, compensating for manufacturing tolerances
Solution Approach 2:
The alignment key employs a composite structure combining multiple pattern layers with different grating configurations. This composite approach allows each layer to be manufactured with standard precision tolerances, while the combined optical effect of all layers achieves superior measurement precision, effectively resolving the contradiction between measurement precision and manufacturing precision requirements
3Measurement precision
If multiple pattern layers with different pitches are used, then the measurement precision is enhanced through optical interference, but the device complexity increases due to additional layers and structures
Solution Approach 1:
Each pattern layer with different grating pitches serves multiple functions: (1) generating optical interference patterns for overlay measurement, (2) providing reference patterns for alignment, and (3) creating moiré patterns that amplify measurement signals. This multi-functionality allows the system to achieve high measurement precision without proportionally increasing device complexity, as each added layer provides multiple measurement capabilities simultaneously
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
The alignment key achieves precise overlay measurement with a resolution of about 5 nm, enabling accurate alignment of semiconductor components by amplifying alignment errors into measurable moiré patterns.
Implementation Method 1
a first pattern layer including a plurality of first gratings disposed on the first substrate, wherein the plurality of first gratings are regularly arranged at a first pitch that is less than a wavelength of the incident light; and a second pattern layer disposed to face the first pattern layer and including a plurality of second gratings, wherein the plurality of second gratings are regularly arranged at a second pitch that is different from the first pitch and less than the wavelength of the incident light
Implementation Method 2
configured to form an optical interference pattern by using incident light
Implementation Method 3
achieves precise overlay measurement with a resolution of about 5 nm, enabling accurate alignment of semiconductor components by amplifying alignment errors into measurable moiré patterns
Data Source
AI summary
An alignment key configured to form an optical interference pattern by using incident light, may include a first substrate, a first pattern layer including a plurality of first gratings disposed on the first substrate, the plurality of first gratings being regularly arranged at a first pitch that is less than a wavelength of the incident light, and a second pattern layer disposed to face the first pattern layer and including a plurality of second gratings. The plurality of second gratings may be regularly arranged at a second pitch that is different from the first pitch and less than the wavelength of the incident light, in the same arrangement direction as the plurality of first gratings.