Composite Oxide Memory Channels for Mobility and Leakage Control
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Solution Overview
Problem
Existing three-dimensional memory devices face issues with insufficient charge carrier mobility, high leakage current, and bias instability in metal oxide semiconductor channels, particularly in indium gallium zinc oxide (IGZO), which affect device performance and reliability.
Innovation Solution
The use of composite metal oxide semiconductor channels with varying compositions between inner and outer portions, specifically employing indium tin zinc oxide (ITZO) and indium gallium tin zinc oxide (IGTZO) layers, to enhance charge carrier mobility, reduce leakage current, and improve on-current and subthreshold slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If metal oxide semiconductor channels (e.g., IGZO) are used in three-dimensional memory devices, then device integration is achieved, but charge carrier mobility is insufficient
Solution Approach 1:
The patent employs composite metal oxide semiconductor channels combining multiple metal oxides (e.g., IGZO, ITZO, IGTZO) with different compositions and properties. This composite structure enables optimization of charge carrier mobility while maintaining device reliability, as different metal oxide components contribute different beneficial properties to the overall channel material system.
Solution Approach 2:
The patent implements radial composition gradients within the semiconductor channel, where the metal oxide composition varies from the center to the outer regions. This local quality variation allows different regions of the channel to have optimized properties for their specific functional requirements, improving overall charge carrier mobility while maintaining structural integrity.
2Reliability
If metal oxide semiconductor channels are used, then device structure is formed, but leakage current is high
Solution Approach 1:
The patent modifies the compositional parameters of the metal oxide semiconductor channel by varying metal ratios (In, Ga, Zn, Sn) and oxidation states. These parameter changes enable precise control over the material's electrical properties, reducing leakage current while maintaining acceptable device reliability through optimized band structure and defect management.
3Ease of operation
If metal oxide semiconductor channels are used, then device is operational, but bias instability occurs
Solution Approach 1:
The composite metal oxide structure provides multiple mechanisms for stabilizing bias characteristics. Different metal oxide phases and compositions within the channel resist degradation under electrical stress, maintaining stable device operation over time through synergistic effects that prevent composition drift and electrical breakdown.
Data Source
AI summary
A memory die includes an alternating stack of insulating layers and electrically conductive layers, a memory opening vertically extending through the alternating stack, and a memory opening fill structure located in the memory opening and including a memory film and a vertical composite metal oxide semiconductor channel having a different composition between its inner and outer portions.