Lithographic Alignment Mark Deformation Characterization
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Solution Overview
Problem
In lithographic processes, alignment mark deformations and substrate deformations lead to inaccuracies in overlay measurements, causing errors in the alignment of subsequent layers, which can result in malfunctioning integrated circuits due to misalignment of patterns.
Innovation Solution
A method involving the measurement of alignment marks using multiple parameters, followed by Principal Component Analysis to decompose positional deviations into mark deformation and substrate deformation components, allowing for accurate alignment and overlay assessment by separating these effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are measured using a single measurement parameter, then the measurement process is simple and fast, but the measurement precision is reduced due to inability to distinguish mark deformation from substrate deformation
Solution Approach 1:
The patent segments the measurement process by using multiple measurement parameters (e.g., different wavelengths, polarizations, or beam angles) to separately characterize mark deformation and substrate deformation. This allows the complex deformation problem to be divided into independent components that can be measured and corrected separately, thereby improving measurement precision without requiring an overly complex single-measurement system.
Solution Approach 2:
The patent introduces additional measurement dimensions by employing multiple measurement parameters beyond the single conventional parameter. This dimensional expansion enables the system to distinguish between mark deformation and substrate deformation, transforming a single-point measurement into a multi-dimensional analysis that resolves the ambiguity and improves precision.
2Measurement precision
If multiple alignment measurement parameters are used to characterize deformations, then measurement precision is improved, but the measurement time and processing complexity increase
Solution Approach 1:
The patent performs preliminary characterization of mark and substrate deformations using multiple measurement parameters before the actual overlay measurement. By pre-computing the deformation models and storing them for rapid application during overlay measurement, the system avoids the time-consuming real-time decomposition process, thus improving precision while minimizing measurement time.
Solution Approach 2:
The patent implements a feedback mechanism where the deformation characterization results are used to correct subsequent overlay measurements. The system continuously refines the deformation models based on measurement data and uses these updated models to improve future measurements, thereby achieving high precision without requiring excessive measurement time for each individual measurement.
3Manufacturing precision
If alignment mark deformations are not accounted for, then the measurement process is straightforward, but manufacturing precision deteriorates due to erroneous overlay determination
Solution Approach 1:
The patent introduces deformation models as intermediary components that mediate between the raw measurement data and the final overlay determination. These models act as translators that convert the complex interaction between mark and substrate deformations into correctable parameters, allowing the system to achieve high manufacturing precision by accounting for deformations through mathematical models rather than complex physical corrections.
4Reliability
If a single alignment mark position is measured, then the process is simple, but the reliability is reduced due to inability to distinguish between mark deformation and substrate deformation effects
Solution Approach 1:
The patent makes the measurement system universal by using the same multiple-parameter measurement approach for both mark deformation characterization and substrate deformation characterization. This multi-functional measurement system can handle different types of deformations and measurement scenarios with a unified approach, thereby improving reliability without requiring separate specialized systems for each measurement task.
Data Source
AI summary
A method of characterizing a deformation of a plurality of substrates is described. The method includes: measuring, for a plurality of n different alignment measurement parameters λ and for a plurality of substrates, a position of the alignment marks; determining a positional deviation as the difference between the n alignment mark position measurements and a nominal alignment mark position; grouping the positional deviations into data sets; determining an average data set; subtracting the average data set from the data sets to obtain a plurality of variable data sets; performing a blind source separation method on the variable data sets, thereby decomposing the variable data sets into a set of eigenwafers representing principal components of the variable data sets; and subdividing the set of eigenwafers into a set of mark deformation eigenwafers and a set of substrate deformation eigenwafers.