Floating Gate with Self-Assembled Nano-Crystals for Charge Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional non-volatile memory devices with floating gate electrodes face challenges in controlling charge storage capacity, data retention, and reliability due to defects in tunneling oxide films and high temperature heat treatment processes, which affect film quality and ion diffusion.
Innovation Solution
A floating gate structure with multiple charge storing layers is developed, using self-assembled metal nano-crystals and polyelectrolyte films to form a multi-layered charge trap layer without high temperature heat treatment, enhancing charge storage capacity and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional floating gate electrode structure is used, then the device structure is simple, but the charge storage capacity is limited and data retention is poor due to tunneling oxide film defects
Solution Approach 1:
The floating gate electrode is segmented into multiple charge storing layers (first charge storing layer with silicon oxide film and silicon nano-crystals, second charge storing layer with silicon oxide film and metal nano-crystals) instead of a single uniform layer. This segmentation allows each layer to contribute to charge storage capacity while providing redundancy against defects, thereby improving data retention without requiring a completely new device architecture
Solution Approach 2:
The charge storing layers use composite materials combining silicon oxide films with silicon nano-crystals and metal nano-crystals. The silicon oxide provides a matrix structure while the embedded nano-crystals provide additional charge trapping sites, enhancing the overall charge storage capacity and reliability without significantly increasing device complexity
2Quantity of substance
If high temperature heat treatment is applied to form nano-crystals, then the nano-crystal formation is effective, but film quality deteriorates and ion diffusion occurs
Solution Approach 1:
The patent changes the formation parameters of nano-crystals from high temperature heat treatment to low temperature formation methods using silane-containing precursors during CVD processes. This parameter change allows nano-crystals to form at temperatures that do not cause film quality deterioration or ion diffusion, while still achieving sufficient nano-crystal density for effective charge storage
Solution Approach 2:
The thermal energy-based nano-crystal formation (heat treatment) is replaced with a chemical vapor deposition process using silane-containing precursors. This substitution eliminates the need for high temperature processing while still achieving effective nano-crystal formation through chemical reactions at lower temperatures, thereby preserving film quality
3Productivity
If the tunneling oxide film is made thinner to increase tunneling probability, then charge injection efficiency improves, but defects in the film increase causing charge loss
Solution Approach 1:
The patent creates local quality variations by forming multiple charge storing layers with different compositions and properties at different locations within the floating gate structure. The silicon nano-crystals and metal nano-crystals provide localized charge trapping sites that compensate for defects in the tunneling oxide film, allowing thinner films to be used without proportionally increasing charge loss
Solution Approach 2:
The multiple charge storing layers act as a cushioning mechanism against charge loss through tunneling oxide defects. By providing alternative charge storage pathways through the nano-crystal-containing layers, the system preemptively compensates for potential charge loss through defects, maintaining charge retention even when the tunneling oxide is made thinner for improved injection efficiency
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 solution improves data retention and storage capacity by increasing the density of nano-crystals, reducing defects, and maintaining film quality, while preventing metallic diffusion and ion leakage, thus enhancing the memory characteristics of non-volatile memory devices.
Implementation Method 1
at least one charge trap layer of metal nano-crystals which are adsorbed on the upper surface of each stage of the polymer electrolytic film
Implementation Method 2
the tunneling oxide film through which charges pass has a high energy barrier in the band diagram. For this reason, a tunneling probability of charges reduces in the geometric series if thickness of the tunneling oxide film does not reduce
Data Source
AI summary
Provided is a floating gate having multiple charge storage layers, a non-volatile memory device using the same, and a method of fabricating the floating gate and the non-volatile memory device, in which the multiple charge storage layers using metallic/semiconducting nano-particles is formed to thereby enhance a charge storage capacity of the memory device. The floating gate includes a polymer electrolytic film which is deposited on a tunneling oxide film, and is formed of at least one stage in which at least one thin film is deposited on each stage, and at least one metal nano-particle layer which is self-assembled on the upper surface of each stage of the polymer electrolytic film and on which a number of nano-particles for trapping charges are formed. The floating gate is made by self-assembling the nano-particles on the polymer electrolytic film, and thus can be fabricated without undergoing a heat treatment process at high temperature.