Asymmetric Scatterometry Targets for Double Patterning Overlay
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Solution Overview
Problem
In the manufacturing of integrated circuits, double patterning techniques face challenges in accurately distinguishing and assessing features from two lithography steps due to their similarity, leading to difficulties in overlay error measurement and irregular pattern assessment, especially with existing SEM methods being too slow and inaccurate for high-volume manufacturing.
Innovation Solution
An inspection apparatus and method that introduce asymmetry between two populations of features on a substrate, allowing for the calculation of characteristics using radiation reflections from combined targets, enabling easier differentiation and measurement of overlay errors and pattern features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If angular resolved scatterometry is used to measure features from two lithography steps, then measurement capability is provided, but the features cannot be distinguished due to their similarity and regular pattern
Solution Approach 1:
The patent introduces asymmetry between the two feature populations by deliberately forming one population with different dimensions, shape, or orientation than the other. This asymmetric design creates distinct scattering signatures for each population, enabling angular resolved scatterometry to differentiate and measure each population's characteristics separately, thereby resolving the measurement difficulty caused by feature similarity
2Measurement precision
If SEM is used to assess features, then detailed measurement is possible, but the method is too slow for high-volume manufacturing
Solution Approach 1:
The patent replaces the mechanical scanning electron microscope (SEM) system with an optical scatterometry system. Scatterometry uses electromagnetic radiation (light) to measure features non-contactly and at high speed, while maintaining measurement precision. This substitution eliminates the slow scanning mechanism of SEM and enables high-volume manufacturing compatibility
3Manufacturing precision
If double patterning is used to generate detailed patterns, then pattern resolution is improved, but overlay errors and irregularities become difficult to detect
Solution Approach 1:
The patent applies asymmetry to the target structure design in double patterning by creating intentionally asymmetric features or asymmetric arrangements of the two patterned populations. This asymmetric configuration produces distinctive scattering patterns that encode overlay error information, making it possible to detect and measure overlay errors even in highly detailed double-patterned structures
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 enhances the ability to accurately assess and measure overlay errors and pattern features in double patterning techniques, improving manufacturing efficiency and accuracy by distinguishing between nominally identical features and detecting small irregularities.
Implementation Method 1
One form of specialized inspection tool is a scatterometer in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered or reflected beam are measured
Implementation Method 2
properties of the scattered or reflected beam are measured
Implementation Method 3
Spectroscopic scatterometers direct a broadband radiation beam onto the substrate and measure the spectrum (intensity as a function of wavelength) of the radiation scattered into a particular narrow angular range
Implementation Method 4
Angularly resolved scatterometers use a monochromatic radiation beam and measure the intensity of the scattered radiation as a function of angle
Data Source
AI summary
A plurality of targets including a second population superimposed on a first population are formed. In the first target the second population has an asymmetry with respect to the first population. In the second target the second population has a different asymmetry with respect to the first population. Reflected radiation is detected from both the targets and used to determine different characteristics of the underlying populations.