Antifuse Memory Cell Design Reducing Read Transistor Stress
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Solution Overview
Problem
Conventional nonvolatile memory cells with antifuse components and read transistors are prone to damage during programming due to high voltages that can lead to charge trapping and gate dielectric degradation, resulting in reduced lifetime and failure of memory cells.
Innovation Solution
A nonvolatile memory cell design incorporating an antifuse component in the form of a capacitor, an access transistor, and a read transistor, where the antifuse component is formed over the channel region, utilizing a double polysilicon process to reduce cell size and tailor the physical design for existing process flows, with the antifuse dielectric layer breaking down during programming to allow current flow, thereby reducing stress on the read transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage is applied during programming of conventional nonvolatile memory cells, then the antifuse component can be programmed, but the read transistor suffers damage due to charge trapping and gate dielectric degradation
Solution Approach 1:
The gate member is segmented into two separate gate members, with each gate member controlling a different transistor (access transistor and read transistor). This segmentation allows the programming voltage to be applied to the access transistor's gate without directly exposing the read transistor's gate dielectric to the full stress, thereby reducing damage while maintaining programming functionality.
Solution Approach 2:
The antifuse component acts as an intermediary element between the access transistor and the read transistor. During programming, the antifuse breaks down and creates a conductive path that bypasses the need for high voltage to pass through the read transistor's gate dielectric, thus protecting the read transistor while still achieving the desired programming state.
2Area of moving object
If the antifuse component is integrated over the channel region, then cell size is reduced, but the physical design must be tailored for existing process flows
Solution Approach 1:
The antifuse component is merged with the capacitor structure, where the antifuse dielectric layer is integrated into the capacitor's dielectric stack. This merging allows the antifuse functionality to be achieved without adding separate process steps, making the design compatible with existing capacitor fabrication processes while reducing the overall cell area.
Solution Approach 2:
The gate member structure is designed to serve multiple functions: it acts as the control electrode for the transistor, forms part of the capacitor structure, and provides the antifuse breakdown path. This multi-functionality eliminates the need for separate antifuse structures and allows the design to be implemented using standard process flows without requiring significant modifications.
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 design minimizes damage to the read transistor during programming, extends the memory cell's lifetime by reducing exposure to high voltages, and allows for a binary distribution of I-V characteristics between programmed and unprogrammed states, enhancing the reliability of the memory cell.
Implementation Method 1
the antifuse dielectric layer breaking down during programming to allow current flow
Data Source
AI summary
An electronic device can include a nonvolatile memory cell, wherein the nonvolatile memory cell can include an access transistor, a read transistor, and an antifuse component coupled to the access transistor and the read transistor. In an embodiment, the read transistor can include a gate electrode, and the antifuse component can include a first electrode and a second electrode overlying the first electrode. The gate electrode and the first electrode can be parts of the same gate member. In another embodiment, the access transistor can include a gate electrode, and the antifuse component can include a first electrode, an antifuse dielectric layer, and a second electrode. The electronic device can further include a conductive member overlying the antifuse dielectric layer and the gate electrode of the access transistor, wherein the conductive member is configured to electrically float. Processes for making the same are also disclosed.