Sidewall Angle Metrology via Scatterometry
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Solution Overview
Problem
Existing methods for measuring sidewall angles (SWAs) of structures in thick resist layers are either destructive, require accurate height information, or are not non-invasive, limiting their accuracy and throughput.
Innovation Solution
A method using a scatterometer-based metrology tool to determine angular information of structures by illuminating a surface with a small illumination beam spot size and measuring radiation scattering, where the degree of asymmetry in the pupil signal is used to derive the sidewall angle without destructive methods or accurate height information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive measurement methods are used to measure sidewall angles, then measurement accuracy can be achieved, but the resist or sample is damaged
Solution Approach 1:
The patent replaces destructive mechanical or chemical measurement methods with non-destructive optical scattering measurement. A radiation beam is directed at the structure surface, and the scattered radiation pattern is analyzed to determine sidewall angle, eliminating physical contact or chemical etching that could damage the resist or sample
Solution Approach 2:
The patent utilizes changes in the optical scattering characteristics (analogous to color changes in spectral analysis) of the radiation beam scattered from the structure surface. By analyzing the angular distribution and intensity of scattered radiation at different angles, the sidewall angle can be determined through optical property variations rather than physical destruction
2Productivity
If traditional scatterometry with large spot size is used, then measurement speed is improved, but measurement accuracy of small features deteriorates
Solution Approach 1:
The patent applies local quality by using a small spot size illumination beam that is specifically tailored to the dimensions of the feature being measured. The spot size is configured to be smaller than the pitch of the grating structure, allowing precise local measurement of sidewall angles without averaging effects that would occur with larger spot sizes, thereby maintaining both speed and accuracy
3Measurement precision
If accurate height information is required for sidewall angle measurement, then measurement accuracy is improved, but process complexity and time increase
Solution Approach 1:
The patent implements self-service by designing the scattering-based measurement system to automatically determine sidewall angle from the scattered radiation pattern itself, without requiring external height measurement inputs. The asymmetry in the scattering pattern inherently contains the sidewall angle information, allowing the system to self-determine the parameter without additional complex height measurement equipment or processes
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 allows for non-destructive, fast, and accurate measurement of sidewall angles, improving system throughput and avoiding damage to the resist or deformation of the sample.
Implementation Method 1
illuminating a first surface portion of said one or more structures with an illumination beam and measuring radiation scattered therefrom
Data Source
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Figure 3~4
Figure 5(a)~5(d)
AI summary
There is provided a method for determining angular information of one or more structures comprising: illuminating a first surface portion of said one or more structures with an illumination beam and measuring radiation scattered therefrom to determine a first signal; determining a first asymmetry metric value describing degree of asymmetry of the first signal; and determining the angular information based on at least the first asymmetry metric value, wherein the illumination beam comprises a spot size smaller in at least one dimension of a smallest element of the first surface portion.