Pattern-Edge E-Beam Alignment for Dynamic Fin Overlay Correction
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Solution Overview
Problem
Electron beam lithography faces challenges in achieving precise overlay alignment due to positional errors between alignment mark and device pattern layers, leading to variations in chip-to-chip and wafer-to-wafer overlay errors, which compromise pattern exposure accuracy and yield.
Innovation Solution
An electron beam lithography method that includes executing a predefined scan over the pattern edge, generating signals from reflections, determining and applying offsets to achieve accurate alignment measurements, enabling dynamic fin overlay correction and addressing scale, rotation, and keystone errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment methods are used, then the alignment process is simple, but overlay precision deteriorates due to positional errors between alignment marks and device patterns
Solution Approach 1:
The patent replaces conventional optical alignment methods with electron beam-based measurement and correction. The Ebeam scanner scans alignment marks and device patterns to generate positional data, which is then processed to calculate correction values. This substitution of mechanical/optical alignment with electron beam measurement and computational correction enables sub-nanometer precision while managing complexity through automated processing.
Solution Approach 2:
The patent changes the measurement parameters by using electron beam scanning with specific beam currents, scan speeds, and detection thresholds to measure positions of alignment marks and device patterns. The system varies beam parameters dynamically during scanning to optimize measurement precision. Correction parameters are then applied to adjust the electron beam writing positions, achieving precise overlay alignment through parameter optimization.
2Manufacturing precision
If dynamic offset correction is applied to each chip, then alignment accuracy improves, but processing time increases
Solution Approach 1:
The patent performs preliminary measurement of all alignment marks and device patterns on the wafer before the actual electron beam writing process. Offset corrections for each chip are calculated in advance based on these measurements. This preliminary correction phase allows the subsequent writing process to proceed efficiently with pre-computed positional adjustments, minimizing real-time computation overhead and maintaining high throughput.
Solution Approach 2:
The system maintains continuous operation by overlapping the measurement and correction calculation processes with the preparation phases of electron beam writing. The Ebeam scanner continuously scans and collects positional data while the system prepares writing patterns. Correction values are continuously updated and applied without interrupting the overall manufacturing flow, ensuring continuous productive action throughout the process.
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 method allows for precise alignment with sub-nanometer accuracy, resulting in 100% device yield and increased throughput by over 70%, reducing wafer rework and enhancing pattern placement precision across multiple chips and wafers.
Implementation Method 1
generating a signal from reflections of the Ebeam scan off the pattern edge
Data Source
AI summary
An electron beam lithography (Ebeam) method for a wafer having alignment and device layers with a design alignment. The Ebeam method includes executing an Ebeam scan of predefined length and resolution based on the design alignment over a pattern edge of the device layer, generating a signal from reflections of the Ebeam scan off the pattern edge, determining an offset of the device layer relative to the alignment layer from a comparison of the signal and the design alignment and applying the offset to the design alignment to obtain an actual measurement of Ebeam alignment.