MIS Transistor Nonvolatile Memory via Hot Carrier Injection
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Solution Overview
Problem
Nonvolatile semiconductor memory devices, such as flash EEPROMs, FeRAMs, and MRAMs, require special structures and materials, leading to increased manufacturing costs due to the need for floating gates, ferroelectric, or ferromagnetic materials, whereas MIS transistors can store data using a hot-carrier effect without these requirements, but existing methods for programming, recalling, and erasing data are inefficient and irreversible.
Innovation Solution
A nonvolatile memory device utilizing a pair of MIS transistors where one is programmed using a hot carrier effect to store data, and a control unit manages the recall and erase operations, ensuring efficient data storage and retrieval by swapping source and drain roles and applying specific voltage settings to trap and remove electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If special structures (floating gate) or special materials (ferroelectric, ferromagnetic) are used to achieve nonvolatile storage, then data retention capability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The invention extracts the nonvolatile storage function from the transistor structure itself by utilizing the hot-carrier effect to trap electrons in the oxide film, eliminating the need for separate floating gate structures or special materials. The standard MIS transistor structure is sufficient, and the storage capability is achieved through controlled electron trapping in the existing oxide layer.
Solution Approach 2:
The invention uses a standard MIS transistor with ordinary materials instead of expensive special structures or materials. The oxide film in the MIS transistor serves as the storage medium, which is a byproduct of the transistor fabrication process, thereby eliminating the need for additional floating gate structures or special material deposits.
2Device complexity
If hot-carrier effect is used to program MIS transistors for data storage, then device simplicity is improved, but data erasure capability deteriorates due to irreversibility
Solution Approach 1:
The invention inverts the approach to erasing trapped electrons instead of trying to remove them directly. By applying a negative voltage to the gate, the invention creates a strong electric field that accelerates holes toward the oxide film, where they neutralize trapped electrons. This indirect erasure mechanism enables complete and reversible data erasure while maintaining the simple MIS transistor structure.
Solution Approach 2:
The invention introduces holes as an intermediary to erase trapped electrons. Instead of directly removing electrons from the oxide film, the erasure process uses holes generated in the channel by applying negative gate voltage. These holes migrate to the oxide film and neutralize the trapped electrons, achieving erasure through this intermediary mechanism.
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 enables efficient and reversible data storage in MIS transistors, reducing manufacturing costs by avoiding special materials and structures, while maintaining nonvolatile data retention through controlled hot-carrier operations.
Implementation Method 1
The hot-carrier effect refers to the injection of electrons into the insulating film (i.e., oxide film) and/or sidewalls of the transistor
Data Source
AI summary
A nonvolatile memory device includes a pair of MIS transistors one of which is placed in a programmed state by a first program operation utilizing a hot carrier effect to store one-bit data in the pair of MIS transistors, and a control unit configured to recall the one-bit data from the pair of MIS transistors in a recall operation, to cause an unprogrammed one of the MIS transistors to be placed in a programmed state by a second program operation utilizing a hot carrier effect in response to the one-bit data recalled from the pair of MIS transistors, and to erase the programmed states of both of the MIS transistors in an erase operation.