Transition Metal Oxide Floating Gate for Nonvolatile Memory
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Solution Overview
Problem
Conventional semiconductor memory devices face challenges in increasing integration density without reducing yield, as existing methods for enhancing trap site density are limited by non-uniformity and inefficiency in particle size and distribution, particularly in flash memory applications.
Innovation Solution
A nonvolatile memory device is developed with a semiconductor substrate, a tunneling oxide film, a floating gate made of transition metal oxide (TMO), a blocking oxide film, and a gate electrode, which increases trap site density by using TMO to trap electrons more efficiently, allowing for higher storage capacity and faster signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods (scattering or depositing Si-nano particles) are used to increase trap site density, then trap site density can be increased to some extent, but non-uniformity of particle size and particle distribution occurs, limiting further increase in density
Solution Approach 1:
The patent changes the material parameter from silicon-nitride or Si-nano particles to transition metal oxide (TMO) floating gate material. This material substitution enables significantly higher trap site density while maintaining uniformity, as TMO can be deposited as a homogeneous thin film rather than relying on particle scattering or deposition processes
Solution Approach 2:
The patent uses a composite structure consisting of tunneling oxide film, TMO floating gate, and blocking oxide film. This multi-layer composite architecture integrates the advantages of different materials: oxide films provide excellent insulation and interface quality, while TMO provides high trap site density with uniform distribution, resolving the contradiction between density and uniformity
2Quantity of substance
If integration density is increased by reducing element volumes, then integration density improves, but process margins for photolithography and etching are significantly reduced, requiring more precise processes and reducing yield
Solution Approach 1:
The patent changes the data storing mechanism from conventional capacitor-based charge storage to TMO-based electron trapping. This parameter change in the storage mechanism allows for smaller cell size (higher integration density) without requiring extremely precise photolithography and etching processes, thereby maintaining yield while increasing density
Solution Approach 2:
The patent applies local quality by creating a highly functional TMO floating gate layer with specific trap site characteristics within the gate stack. This localized functional enhancement allows the transistor volume to be reduced for higher integration density while the TMO region maintains reliable electron trapping, decoupling the relationship between size reduction and process precision requirements
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
The use of TMO in the floating gate enhances electron trapping efficiency, enabling higher integration density and larger memory capacity without yield reduction, as demonstrated by improved capacitance-voltage and current-voltage characteristics.
Implementation Method 1
the nitride film 18b has a trap site having predetermined density. Therefore, when a predetermined voltage is applied to the gate electrode 18d, electrons passed through the tunneling oxide film 18a are trapped in the trap site of the nitride film 18b
Implementation Method 2
electrons passed through the tunneling oxide film 18a are trapped in the trap site
Implementation Method 3
The blocking oxide film 18c blocks the migration of electrons to the gate electrode 18d while the electrons are trapped
Data Source
AI summary
The nonvolatile memory device includes a semiconductor substrate on which a source, a drain, and a channel region are formed, a tunneling oxide film formed on the channel region, a floating gate formed of a transition metal oxide (TMO) on the tunneling oxide, a blocking oxide film formed on the floating gate, a gate electrode formed on the blocking oxide film.