Boosting Capacitor for Resistive Memory Voltage Scaling
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Solution Overview
Problem
Non-volatile resistive memory devices require higher voltages for electroforming and switching operations, which can overstress the transistor gate oxide, exceeding the supply voltage and gate oxide breakdown voltage limits.
Innovation Solution
Incorporating a boosting capacitor connected between the transistor source/drain and the resistive memory element, with a specific biasing scheme that allows up to 2x higher voltage on the memory element without overstressing the transistor gate oxide, using a dielectric material matching the resistive memory structure, and configuring the form lines and word lines in separate layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a higher voltage is applied to the resistive memory element for electroforming and switching operations, then the memory element can be properly formed and switched, but the transistor gate oxide may be overstressed and exceed breakdown voltage limits
Solution Approach 1:
A boosting capacitor is introduced as an intermediary component between the voltage supply and the resistive memory element. This capacitor temporarily stores and releases voltage energy, enabling the application of high forming voltages (e.g., 2x higher than supply voltage) to the memory element while isolating the transistor gate oxide from direct exposure to these excessive voltage levels, thus preventing gate oxide breakdown
Solution Approach 2:
The patent employs dynamic voltage control through a specific biasing scheme that applies different voltages to different terminals of the resistive memory element at different times. By dynamically switching voltage polarity and magnitude during electroforming and switching operations, the system achieves proper memory element formation and operation while keeping the transistor gate voltage within safe operational limits throughout the process
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
Enables electroforming and switching operations within safe voltage limits for the transistor gate oxide, allowing higher voltage application to the resistive memory structure, enhancing the scalability and reliability of non-volatile resistive memory devices.
Implementation Method 1
an additional capacitance is added to the cell, namely the boosting capacitor
Implementation Method 2
a thin HfO2 dielectric film... exhibits resistive switching properties... The bipolar operation of HfO2, requiring voltages of opposite polarity to switch on/off the cell, is believed to be due to the formation of conductive paths (filaments) associated with presence of oxygen vacancies (Vo), which can be ruptured/restored through oxygen/Vo migration under electric field
Data Source
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AI summary
Non-volatile resistive memory device comprising memory cells and bit, word, source and form lines for addressing and biasing the memory cells, a memory controller for applying voltages to said lines, each of the memory cells comprising a cell selecting transistor, a resistive memory structure serially connected to a drain-source path of the cell selecting transistor, the resistive memory structure and the cell selecting transistor together forming a conductive path between the bit lines and the source lines and the gate of the cell selecting transistor being connected to the word lines and a boosting capacitor connected between the form lines and an internal node of the memory cell at a connection between the resistive memory structure and the cell selecting transistor, said boosting capacitor being configured for boosting a voltage on said internal node. The invention also relates to a method for biasing such resistive memory device.