Chromatic Aberration Alignment Optics for Single-Capture Overlay
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Solution Overview
Problem
Existing semiconductor device manufacturing metrology tools face challenges in efficiently performing overlay measurements due to the need for focusing on alignment marks at different vertical levels, which requires switching between different wavelengths and results in significant time consumption.
Innovation Solution
A dual focus optical measurement tool equipped with a chromatic aberration enhancement component allows for simultaneous optical detection of alignment marks at different vertical levels using two different wavelengths, enabling a single capture process instead of the traditional double capture process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional optical measurement tools use single wavelength focusing for overlay measurements, then the optical system remains simple, but significant time is consumed due to switching between different wavelengths for alignment marks at different vertical levels
Solution Approach 1:
The patent introduces a chromatic aberration enhancement component that deliberately modifies the wavelength parameter of the radiation beam to create different focal depths. By using a broadband radiation source with multiple peak wavelengths and introducing controlled chromatic aberration, the system achieves dual focus capability without mechanical wavelength switching, thereby reducing measurement time while managing optical complexity through a dedicated component.
Solution Approach 2:
The chromatic aberration enhancement component acts as an intermediary element between the radiation source and the alignment marks. This component introduces controlled chromatic aberration to separate the focal points for different wavelengths, enabling simultaneous imaging of alignment marks at different vertical levels without requiring the optical system to physically switch configurations.
2Measurement precision
If dual focus capability is achieved through wavelength switching, then alignment marks at different vertical levels can be measured, but the measurement process becomes time-consuming due to sequential capture
Solution Approach 1:
The patent merges the imaging of alignment marks at different vertical levels into a single capture process. By using a broadband radiation source with multiple peak wavelengths and a chromatic aberration enhancement component, both underlying and overlying alignment marks are simultaneously focused and captured in one exposure, eliminating the need for sequential wavelength switching and thereby improving productivity while maintaining measurement precision.
Solution Approach 2:
The system enables continuous imaging of multiple focal planes simultaneously through the chromatic aberration enhancement component. Instead of interrupting the measurement process to switch wavelengths, the broadband radiation source with controlled chromatic aberration allows continuous capture of both deep and shallow focal planes in an uninterrupted single shot, thereby enhancing process throughput.
3Loss of time
If chromatic aberration enhancement component is introduced, then simultaneous dual wavelength focusing is achieved, but the optical system complexity increases
Solution Approach 1:
Rather than adding complex mechanical switching mechanisms or multiple independent optical paths, the patent modifies the optical parameters by introducing a chromatic aberration enhancement component that works with a broadband radiation source. This approach achieves dual focus capability through controlled chromatic dispersion, reducing the need for additional complex components while minimizing capture process 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
This approach significantly reduces the time required for overlay measurements, improving process throughput by allowing simultaneous focus on both underlying and overlying alignment marks, thus addressing the inefficiencies of traditional methods.
Implementation Method 1
a chromatic aberration enhancement component which increases a chromatic aberration of the emitted radiation beam
Data Source
AI summary
An optical alignment method includes providing an emitted radiation beam which includes a first peak wavelength and a second peak wavelength to a chromatic aberration enhancement component which increases a chromatic aberration of the emitted radiation beam, providing a first incident radiation beam having the first peak wavelength and a second incident radiation beam having the second peak wavelength which is shorter than the first peak wavelength to respective first and second alignment marks located at different vertical levels in a device under test, detecting reflected radiation from the first and second alignment marks, and using the detected reflected radiation for optical alignment of layers in the device under test.