Flash Memory Sector Erase Shared Transistor
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Solution Overview
Problem
Conventional flash memory devices require separate dedicated sector select transistors for each sector, consuming valuable die area and risking erase disturbances due to hot hole operations.
Innovation Solution
Implementing a shared common sector selection transistor and P-well for all sectors, allowing sectors to share voltages for erasure without dedicated transistors, using a channel erase operation with Fowler-Nordheim tunneling to prevent disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate dedicated sector select transistors are used for each sector, then sector selection and erasure control is achieved, but die area is consumed and erase disturbances may occur
Solution Approach 1:
Multiple sector select transistors are merged into a single shared sector select transistor. The transistor is configured with multiple word line connections to different sectors, allowing one transistor to control selection across multiple sectors through different word lines, thereby reducing die area while maintaining sector selection capability
Solution Approach 2:
The sector select transistor is designed with multi-functional capability to serve multiple sectors. It can be selectively connected to different word lines corresponding to different sectors through control signals, enabling a single transistor to perform the selection function for multiple sectors rather than requiring dedicated transistors for each sector
2Productivity
If hot hole erase operation is used, then sector erasure is achieved, but erase disturbances occur in adjacent sectors
Solution Approach 1:
The patent converts the harmful hot hole mechanism into a beneficial effect by using Fowler-Nordheim tunneling with electron injection. Instead of relying on hot hole generation that causes disturbances, the invention uses controlled electron tunneling through the oxide layer to achieve erasure, transforming the potential harm of high-energy particle generation into a precise and localized erasure mechanism that does not disturb adjacent sectors
3Area of stationary object
If a single common sector select transistor is shared by all sectors, then die area is conserved, but voltage sharing and selection control becomes complex
Solution Approach 1:
The control of the shared sector select transistor is segmented through multiple word line connections. Each word line is independently controllable and corresponds to specific sectors, allowing the single transistor to be selectively activated for different sector groups. This segmentation of control signals simplifies the management of voltage sharing compared to a fully integrated control approach
Solution Approach 2:
Word lines serve as intermediaries between the control logic and the shared sector select transistor. The control signals are routed through specific word lines to activate the transistor for desired sectors, providing a structured mediation layer that manages the complexity of voltage control and sector selection without requiring direct complex control circuitry for each sector
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 conserves die area and prevents erase disturbances by allowing multiple sectors to share a single sector select transistor, enabling efficient sector erasure without dedicated transistors, while maintaining stable operation.
Implementation Method 1
using a channel erase operation with Fowler-Nordheim tunneling to prevent disturbances
Data Source
AI summary
A memory device is provided which includes a substrate, a common P-well isolated from the substrate, a plurality of sectors, and a common sector selection transistor configured to select one of the sectors for erasure. Each of the sectors share the same common sector select transistor, and the common P-well. The selected sector is configured to be erased by applying appropriate voltages to the selected sector.