Split-Gate Memory Charge Storage Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In split-gate memory arrays, charge stored in nanocrystals migrates over time, reducing the memory array's performance due to lack of effective charge storage isolation, as traditional methods use continuous charge storage layers that allow charge diffusion between neighboring nanocrystals.
Innovation Solution
The implementation of isolated charge storage regions using split-gate memory arrays with multiple control and select gate electrodes, where each electrode is electrically isolated from others via layers, and source/drain regions are isolated from both control and select gates, preventing charge migration through the use of specific deposition and etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If continuous charge storage layers are used, then manufacturing is simpler, but charge migration occurs between neighboring nanocrystals
Solution Approach 1:
The continuous charge storage layer is divided into isolated nanocrystal regions separated by insulating materials. This segmentation prevents charge migration between neighboring storage regions while maintaining manufacturing feasibility through controlled deposition and etching processes.
Solution Approach 2:
Insulating materials are introduced as intermediary layers between adjacent charge storage regions. These intermediary insulating layers act as barriers that prevent charge diffusion while allowing the overall structure to be fabricated using standard semiconductor manufacturing techniques.
2Reliability
If charge storage isolation is implemented, then charge migration is prevented, but device complexity increases
Solution Approach 1:
The memory array structure is segmented into discrete bit cells with isolated charge storage regions. Each bit cell contains nanocrystals confined within insulating barriers, creating a modular structure that prevents charge migration while maintaining organizational simplicity at the array level.
Solution Approach 2:
Insulating materials are selectively placed in specific locations between charge storage regions rather than uniformly throughout the structure. This local quality approach provides necessary isolation where needed while minimizing overall structural complexity and maintaining ease of fabrication.
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 approach effectively reduces or eliminates charge migration, allowing the memory array to maintain sufficient charge storage capacity over time, enabling better performance and scalability of memory arrays.
Implementation Method 1
electrically isolated from one another by bit line isolation regions
Implementation Method 2
charge stored in nanocrystals migrates over time
Data Source
AI summary
Forming a memory structure includes forming a charge storage layer over a substrate; forming a first control gate layer; patterning the first control gate layer to form an opening in the first control gate layer and the charge storage layer, wherein the opening extends into the substrate; filling the opening with an insulating material; forming a second control gate layer over the patterned first control gate layer and the insulating material; patterning the second control gate layer to form a first control gate electrode and a second control gate electrode, wherein the first control gate electrode comprises a first portion of each of the first and second control gate layers and the second control gate electrode comprises a second portion of each of the first and second control gate layers, and the insulating material is between the control gate electrodes; and forming select gate electrodes adjacent the control gate electrodes.