Schottky Selector Memory Cell Layout for Low-Leakage Writing
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Solution Overview
Problem
Conventional non-volatile memory devices using bi-directional MOS devices as selectors face challenges in size reduction, limited conduction current, and increased leakage current, making them less efficient in terms of area and current per unit area.
Innovation Solution
The use of Schottky diodes as selectors in non-volatile memory devices, which are formed with a cathode in a monocrystalline semiconductor layer, allowing for one-way conduction, reducing device size and increasing current density, and providing better insulation to minimize leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bi-directional MOS devices are used as selectors, then the device can operate bidirectionally, but the device size becomes larger and leakage current increases
Solution Approach 1:
The patent extracts the bidirectional selection function from a single MOS device and implements it using two unidirectional Schottky diodes connected in opposite directions. This allows each diode to be simpler and smaller while collectively providing the bidirectional functionality, thus reducing overall device size while maintaining adaptability.
Solution Approach 2:
The bidirectional selector is segmented into two separate unidirectional Schottky diodes, each handling one direction of current flow. This segmentation allows for more compact individual components compared to a single bidirectional MOS device, reducing the total area occupied by the selector.
2Adaptability or versatility
If bi-directional MOS devices are used as selectors, then the device can operate bidirectionally, but the leakage current increases
Solution Approach 1:
The patent separates the bidirectional selection into two independent unidirectional Schottky diodes. Each diode only conducts in one direction and blocks in the other, providing superior off-state leakage characteristics compared to MOS devices. This extraction of directional functionality eliminates the leakage issues inherent in bidirectional MOS operation.
Solution Approach 2:
The patent changes the electrical parameters by using Schottky diodes with their characteristic low forward voltage drop and low reverse leakage current. This parameter change from MOS device characteristics to Schottky diode characteristics fundamentally reduces the harmful leakage effect while maintaining bidirectional operation capability.
3Area of stationary object
If Schottky diodes are used as selectors, then the device size is reduced and current density is increased, but the conduction current is limited compared to MOS devices
Solution Approach 1:
The patent transitions from planar MOS device geometry to vertically stacked Schottky diode structure. This dimensional change allows for higher current density in a smaller footprint, as the current flows through the vertical Schottky junction rather than laterally through a MOS channel, effectively packing more current capability into less area.
Solution Approach 2:
The patent exploits the Schottky diode's ability to support high current density despite smaller size by changing the conduction mechanism from MOS field-effect to Schottky barrier conduction. The Schottky diode's exponential I-V characteristic allows it to deliver sufficient conduction current in a compact form factor, resolving the apparent contradiction between size and current capability.
4Use of energy by moving object
If Schottky diodes are used as selectors, then the operation voltage is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent replaces the mechanically complex gate control structure of MOS devices with the simpler Schottky barrier junction formation. This substitution eliminates the need for precise gate oxide thickness control and gate electrode alignment, replacing them with more robust metallization processes that are better suited for high-volume manufacturing with consistent precision.
Solution Approach 2:
The patent changes the critical manufacturing parameters from MOS gate oxide thickness (requiring atomic-layer precision) to Schottky metal-semiconductor interface properties (tolerant of broader process variations). This parameter change enables lower operation voltage while maintaining manufacturability, as Schottky junctions can be formed with less stringent precision requirements than MOS gates.
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 Schottky diode-based selectors enable smaller device size, higher current density, reduced leakage current, and lower operation voltage, enhancing the application range and performance of non-volatile memory devices.
Implementation Method 1
a first Schottky diode (43), which is formed on the insulation layer (42), wherein a cathode of the first Schottky is formed in a monocrystalline semiconductor layer
Implementation Method 2
providing better insulation to minimize leakage current
Data Source
AI summary
A non-volatile memory device includes: an insulation layer; a Schottky diode, which is formed on the insulation layer; a writing wire which is conductive and is electrically connected to a first end of the Schottky diode; a memory unit on the Schottky diode, the memory unit being electrically connected to a second end of the Schottky diode; and a selection wire on the memory unit, the selection wire being electrically connected to the memory unit; wherein when the non-volatile memory device is selected for a data to be written into, a first current flows through the Schottky diode to write the data into the memory unit.