MOS Junction Diode Program Selector for Resistive Memory
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Solution Overview
Problem
Conventional programmable resistive memory cells, such as those using NMOS or bipolar transistors, require large device sizes and complex fabrication processes, leading to increased costs and inefficiencies in programming and reading operations.
Innovation Solution
The use of junction diodes as program selectors in standard CMOS logic processes, allowing for the reduction of cell size and cost by leveraging existing P+/N well diodes, which can be fabricated without additional processing steps, and incorporating heat sinks or generators to assist in programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional NMOS or bipolar transistors are used as program selectors, then reliable programming of resistive states can be achieved, but device size increases and fabrication complexity increases
Solution Approach 1:
The patent replaces complex, expensive bipolar transistors with simpler, cheaper diodes that can be fabricated using standard CMOS processes. The diode serves as a disposable program selector that achieves sufficient reliability for OTP applications without requiring complex fabrication steps, thereby reducing both device complexity and manufacturing cost while maintaining programming reliability.
Solution Approach 2:
The patent changes the device type from active transistors (NMOS/bipolar) to passive diodes, fundamentally altering the selection mechanism. This parameter change enables the use of standard CMOS fabrication processes instead of complex bipolar processes, reducing fabrication complexity while the diode's inherent simplicity maintains sufficient programming reliability for resistive state selection.
2Reliability
If conventional NMOS or bipolar transistors are used as program selectors, then reliable programming of resistive states can be achieved, but cell size increases
Solution Approach 1:
The patent replaces large-area bipolar transistors with compact diodes fabricated in standard CMOS. The diode's simpler structure requires fewer fabrication steps and occupies less area, achieving the same program selector function with reduced cell size while maintaining sufficient reliability for resistive state programming through its diode junction characteristics.
Solution Approach 2:
The patent merges the program selector function with standard CMOS diode structures that are already present in the fabrication process. By utilizing existing P+/N well diodes or other CMOS-compatible diode structures, the patent eliminates the need for separate large-area bipolar transistor fabrication, thereby reducing cell size while maintaining programming reliability through the diode's inherent selection capability.
3Ease of manufacture
If standard CMOS logic processes are used with junction diodes, then fabrication costs decrease and cell size reduces, but additional processing steps are required
Solution Approach 1:
The patent makes the junction diode serve multiple functions: it acts as both the program selector and utilizes existing CMOS fabrication structures (P+/N well diodes, contact structures, interconnect layers). This multi-functionality allows the diode to be integrated into standard CMOS processes without requiring entirely new fabrication equipment or processes, reducing overall fabrication costs while minimizing additional processing steps by leveraging existing universal CMOS structures.
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 approach enables the creation of smaller, more cost-effective programmable resistive device cells with improved programming reliability and efficiency, utilizing standard CMOS processes to reduce cell size and enhance programming control.
Implementation Method 1
turning on the program selector causes a current to flow through the resistive device
Implementation Method 2
incorporating heat sinks or heat generators to assist in programming
Implementation Method 3
incorporating heat sinks or heat generators to assist in programming
Data Source
AI summary
A programmable resistive device cell using at least one MOS device as selector can be programmed or read by turning on a source junction diode of the MOS or a channel of the MOS. A programmable resistive device cell can include at least one programmable resistive element and at least one MOS device. The programmable resistive element can be coupled to a first supply voltage line. The MOS can have a source coupled to the programmable resistive element, a bulk coupled to a drain, a drain coupled to a second supply voltage line, and a gate coupled to a third supply voltage line. The programmable resistive element can be configured to be programmable or readable by applying voltages to the first, second, and/or third supply voltage lines to turn on the source junction of the MOS and/or to turn on the channel of the MOS.