X-Ray Substrate Alignment Through Thick Silicon Layers
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Solution Overview
Problem
Conventional optical alignment methods struggle to precisely align semiconductor substrates due to the opacity of thick silicon and metallized copper layers, leading to systematic shift errors and exceeding acceptable tolerances in 3D integration processes.
Innovation Solution
X-ray methods and systems, including X-ray Talbot-Lau interferometry and X-ray fluorescence, are integrated with Moiré fringe-based alignment techniques to measure misalignment between substrates, providing high-precision overlay and sensitive misalignment measurements in D2D and D2W bonding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical alignment methods are used, then the alignment process is simple and cost-effective, but alignment precision deteriorates due to opacity of thick silicon and metallized copper layers
Solution Approach 1:
The patent replaces traditional optical alignment methods with X-ray based alignment methods. X-rays have penetrating capability that allows them to pass through thick silicon substrates and metallized copper layers that are opaque to visible light, enabling precise alignment measurements in 3D integration processes where optical methods fail.
Solution Approach 2:
The patent changes the wavelength parameter of the alignment radiation from visible/optical range to X-ray range. This parameter change fundamentally alters the interaction with the substrate materials, allowing penetration through layers that are opaque to optical wavelengths, thereby achieving the required alignment precision through thick and metallized layers.
2Measurement precision
If X-ray methods are used to achieve high alignment precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent segments the alignment measurement process into two independent modes: X-ray fluorescence mode for measuring misalignment of alignment marks, and X-ray Talbot-Lau interferometry mode for measuring overlay of transparent objects. Each mode uses specialized alignment marks optimized for that specific measurement type, allowing the system to achieve high precision in each mode without requiring a single complex universal solution.
Solution Approach 2:
The patent introduces Moiré fringe-based alignment techniques as an intermediary method that works in conjunction with X-ray methods. The Moiré fringes provide enhanced sensitivity and precision for detecting misalignment, acting as a mediator that amplifies the alignment signal and improves measurement precision while working within the X-ray measurement framework.
3Measurement precision
If dual-mode X-ray measurement is implemented, then alignment accuracy improves, but measurement time increases
Solution Approach 1:
The patent performs preliminary alignment using one X-ray mode (e.g., fluorescence mode for misalignment measurement) before performing the final precision alignment using the second mode (e.g., Talbot-Lau interferometry for overlay measurement). This preliminary action reduces the initial misalignment to within a range where the second mode can achieve high precision, thereby reducing the number of iterative adjustments needed and minimizing total measurement time.
Solution Approach 2:
The patent applies each measurement mode selectively based on the specific alignment requirement rather than using both modes for all measurements. For misalignment of alignment marks, only fluorescence mode is used; for overlay of transparent objects, only Talbot-Lau interferometry is used. This partial application of measurement modes optimizes the measurement process by avoiding unnecessary measurements and reducing total measurement time.
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 X-ray methods achieve alignment accuracy of at least 20 nm with 10% precision and 99% linearity, reducing reference errors and re-focus adjustments, and enabling precise alignment through thick and highly doped silicon substrates.
Implementation Method 1
detecting fluorescent X-rays emitted from the first alignment mark and from the second alignment mark
Implementation Method 2
detecting at least some of the X-rays transmitted through the first substrate and through the second substrate using X-ray Talbot-Lau interferometry
Implementation Method 3
X-ray methods and systems, including X-ray Talbot-Lau interferometry and X-ray fluorescence, are integrated with Moiré fringe-based alignment techniques
Data Source
AI summary
X-rays are directed to a first substrate and to a second substrate in a bonding configuration for bonding together. The X-rays are directed to first and third alignment marks in the first substrate and to second and fourth alignment marks in the second substrate. Fluorescent X-rays are detected upon emission from the first alignment mark and the second alignment mark to measure a first misalignment of the first substrate with respect to the second substrate based on a first detected misalignment of the first and second alignment marks. X-rays transmitted through the first and second substrates using X-ray Talbot-Lau interferometry to measure a second misalignment of the first and second substrates based on a second detected misalignment of the third and fourth alignment marks.