SEM Moiré Overlay Measurement for Nanometer Lithography Alignment
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Solution Overview
Problem
The challenge in semiconductor manufacturing is accurately determining overlay errors between two layers in lithography operations, particularly at nanometer technology process nodes, where existing optical methods face resolution limits.
Innovation Solution
An electron beam-based overlay measurement method using scanning electron microscopy (SEM) with specific periodic patterns and phase shifts to generate Moiré fringe patterns, allowing precise calculation of overlay errors through curve fitting and pattern matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical methods are used for overlay measurement, then the measurement process is simple and fast, but the measurement precision deteriorates due to resolution limits at nanometer technology process nodes
Solution Approach 1:
The patent introduces an intermediary structure (the overlay measurement pattern with Moiré fringe generation capability) that mediates between the optical measurement system and the nanometer-scale overlay error. By using the Moiré effect as an intermediary phenomenon, the system can measure sub-pixel displacements with high precision without requiring the measurement system itself to have nanometer-scale resolution
Solution Approach 2:
The patent changes the measurement parameter from direct optical imaging of the overlay pattern to detection of Moiré fringe patterns. This parameter change allows the system to convert nanometer-scale displacement into measurable fringe phase shifts, thereby improving measurement precision while maintaining optical method simplicity
2Manufacturing precision
If conventional overlay measurement methods are used, then the process is straightforward, but the manufacturing precision deteriorates due to insufficient accuracy at nanometer nodes
Solution Approach 1:
The patent transitions from measuring overlay error in the direct spatial domain to measuring it in the frequency domain through Moiré fringe patterns. This dimensional change in the measurement space allows for enhanced precision by exploiting the phase information of the fringes, which provides more sensitive detection of small displacements
3Measurement precision
If higher resolution optical systems are used to overcome resolution limits, then measurement precision improves, but the device complexity and cost increase significantly
Solution Approach 1:
The patent creates a Moiré fringe pattern that copies and amplifies the overlay displacement information into a visually detectable form. Instead of directly resolving the nanometer-scale overlay error, the system creates a magnified representation through the Moiré effect that can be measured with standard optical resolution
Solution Approach 2:
The patent changes the measurable parameter from direct spatial position to fringe phase angle. This parameter transformation converts the measurement problem into one that can be solved with conventional optical systems, avoiding the need for high-resolution nanometer-scale imaging while maintaining high measurement precision
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
Enhances the accuracy and speed of overlay error measurement by leveraging SEM to analyze Moiré fringe patterns, improving precision and efficiency in semiconductor manufacturing processes.
Implementation Method 1
A Moiré fringe pattern of the lower layer pattern and the upper layer pattern is obtained by using an electron beam
Data Source
AI summary
According to an aspect of the present disclosure, in a method of manufacturing a semiconductor device, a lower layer pattern including first periodic patterns having a first pitch is formed, and an upper layer pattern including second periodic patterns having a second pitch different from the first pitch is formed. The first periodic patterns at least partially overlaps the second periodic patterns in plan view. A Moiré fringe pattern of the lower layer pattern and the upper layer pattern is obtained by using an electron beam, and an overlay error between the lower layer pattern and the upper layer pattern is obtained from the Moiré fringe pattern.