RRAM Device With Embedded Bipolar Transistor Selector
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Solution Overview
Problem
The scaling of flash memory devices is hindered by challenges such as program/erase voltages, access speed, reliability, and the number of charges stored per floating gate, necessitating the development of more efficient non-volatile memory solutions like RRAM devices with variable resistance materials.
Innovation Solution
A compact RRAM device with an embedded bipolar junction transistor selector structure is developed, featuring sidewall spacers and variable resistance material regions, allowing for efficient switching between low- and high-resistance states using a conductive word line electrode and dedicated bit line contacts, enabling operation in both unipolar and bipolar modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If flash memory devices are scaled down to reduce size, then integration density improves, but program/erase voltage control, access speed, and reliability deteriorate
Solution Approach 1:
The patent changes the fundamental operating parameter from charge storage (flash memory) to resistance state storage (RRAM). This allows scaling to smaller dimensions while maintaining reliable operation through resistance switching mechanisms that are less sensitive to dimensional scaling effects than charge storage mechanisms.
Solution Approach 2:
The patent replaces the mechanical/electrical charge storage system of flash memory with an electrical resistance switching system. The RRAM device uses variable resistance material layers that switch between high and low resistance states through electrical pulses, eliminating the need for complex charge trapping and tunneling mechanisms required in scaled flash memory.
2Area of moving object
If flash memory devices are scaled down, then integration density improves, but access speed deteriorates
Solution Approach 1:
The patent changes the operating mechanism from charge-based to resistance-based, enabling faster switching speeds. The RRAM device can transition between resistance states in nanoseconds, providing superior access speed compared to scaled flash memory devices that suffer from increased program/erase times at smaller dimensions.
3Device complexity
If conventional RRAM devices are used without selector structures, then device complexity is reduced, but data storage reliability deteriorates
Solution Approach 1:
The patent segments the RRAM device into distinct functional regions: variable resistance material layers for data storage and bipolar junction transistor selector structures for reliable selection. This segmentation allows independent optimization of storage and selection functions, improving overall data storage reliability while maintaining manageable device complexity.
Solution Approach 2:
The patent introduces bipolar junction transistor selector structures as intermediary elements between the variable resistance material layers and the external circuitry. These selector structures act as controlled switches that enable reliable data storage and retrieval by precisely controlling current flow through the RRAM cells, preventing leakage and ensuring data integrity.
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 RRAM device achieves efficient data storage with reduced footprint, improved reliability, and enhanced integration capabilities by utilizing a bipolar transistor selector structure, enabling incremental changes in resistance states for data storage and retrieval.
Implementation Method 1
an embedded bipolar junction transistor selector structure
Implementation Method 2
The resistance of the variable resistance material layer may be varied or changed based upon the polarity and/or amplitude of an applied electric pulse. The electric field strength or electric current density from the pulse, or pulses, is sufficient to switch the physical state of the materials so as to modify the properties of the material and establish a highly localized conductive filament (CF) in the variable resistance material.
Implementation Method 3
first and second sidewall spacers positioned above a semiconducting substrate
Data Source
AI summary
One device disclosed herein includes first and second sidewall spacers positioned above a semiconducting substrate, wherein the first and second sidewall spacers are comprised of at least a conductive material, a conductive word line electrode positioned between the first and second sidewall spacers and first and second regions of variable resistance material positioned between the conductive word line electrode and the conductive material of the first and second sidewall spacers, respectively. This example also includes a base region of a bipolar transistor in the substrate below the word line electrode, an emitter region formed below the base region and first and second collector regions formed in the substrate within the base region, wherein the first collector region is positioned at least partially under the first region of variable resistance material and the second collector region is positioned at least partially under the second region of variable resistance material.