Laser-Enhanced Electron Tunneling for Deep Feature Defect Detection
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Solution Overview
Problem
Conventional electron beam inspection (EBI) tools are unable to detect under-etch defects in lower-stack substrates due to the presence of sacrificial layers that block electron passage, making it difficult to monitor defects in 3D NAND memory manufacturing processes.
Innovation Solution
A laser-enhanced electron beam inspection method is employed, where a laser beam induces electron tunneling through the sacrificial protection layer, allowing for the differentiation between normal and under-etch defects by capturing bright and dark voltage contrast signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electron beam inspection is used, then the inspection process is simple, but under-etch defects cannot be detected due to electron blocking by sacrificial layers
Solution Approach 1:
A laser beam is introduced as an intermediary to interact with the sacrificial protection layer and induce electron tunneling. The laser acts as a mediator that enables electron passage through the previously blocking layer, allowing defect detection without removing the sacrificial layer.
Solution Approach 2:
The inspection method changes the energy state of electrons by using laser irradiation. The laser provides energy that enables electrons to tunnel through the sacrificial protection layer, fundamentally changing the electron transport mechanism from blocked to transmitted through quantum tunneling.
2Measurement precision
If sacrificial layers are removed to enable defect detection, then under-etch defects become detectable, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The sacrificial protection layer is designed to be inherently present from the manufacturing process. The laser-enhanced tunneling method utilizes this pre-existing layer rather than requiring its removal, performing the detection function while the protective layer remains in place.
Solution Approach 2:
The laser beam serves as an intermediary that enables detection through the intact sacrificial layer, eliminating the need for time-consuming removal steps while maintaining defect detection capability.
3Measurement precision
If laser-enhanced electron tunneling is used, then under-etch defects can be detected through sacrificial layers, but energy consumption increases
Solution Approach 1:
The method changes the energy delivery mechanism by using focused laser irradiation at specific locations rather than bulk heating. The laser energy is concentrated only where electron tunneling is needed, minimizing overall energy consumption while enabling detection through the sacrificial layer.
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 enables effective in-line detection of under-etch defects in deep features like channel holes and via holes, providing real-time monitoring with high accuracy and non-destructive inspection without the need to remove the sacrificial oxide layer.
Implementation Method 1
The substrate is subjected to a laser-enhanced electron beam inspection process. The substrate is scanned by an electron beam and illuminated by a laser beam. The laser beam induces electron tunneling through the sacrificial protection layer during the laser-enhanced electron beam inspection process
Data Source
AI summary
A method for detecting defects in deep features like channel holes, via holes or trenches based on laser-enhanced electron tunneling effect. A substrate having thereon a film stack is provided. First and second deep features are formed in the film stack. The first deep feature has a sacrificial oxide layer disposed at its bottom. The second deep feature comprises an under-etch defect. The sacrificial oxide layer has a thickness of less than 50 angstroms. The substrate is subjected to a laser-enhanced electron beam inspection process. The substrate is scanned by an electron beam and illuminated by a laser beam. The laser beam induces electron tunneling across the sacrificial protection layer, thereby capturing a bright voltage contrast (BVC) signal corresponding to the first deep feature, and detecting a dark voltage contrast (DVC) signal corresponding to the second deep feature.