Tunable Voltage Margin Access Diodes Using MIEC Layers
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Solution Overview
Problem
Current access devices in high-density memory technologies face challenges with low-quality single-crystal silicon p-n and Schottky diodes, particularly in 3D applications, due to low mobility and reliability issues, and solid electrolyte diodes require slow erase steps and low endurance during high-current programming.
Innovation Solution
The use of mixed ionic-electronic conduction (MIEC) layers, specifically MoS2, with conductive defect dopants to form access diodes with tunable voltage margins, allowing for adjustable bandgap and effective mass, enabling high current densities and reliable operation compatible with standard BEOL processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte diodes are used to provide high ON state currents, then the ON/OFF ratio is improved, but the erase step becomes slow and reliability deteriorates during high current programming
Solution Approach 1:
The patent changes the material parameter from solid electrolyte to MIEC material, which fundamentally alters the conduction mechanism. The MIEC material enables high ON/OFF ratios through its unique mixed conduction properties without requiring slow erase steps, as the conductive filaments can be rapidly switched through ionic and electronic conduction mechanisms that respond faster to voltage changes.
Solution Approach 2:
The patent uses composite MIEC materials that combine ionic and electronic conduction capabilities in a single layer. This composite structure allows the material to exhibit both high ON state current (through electronic conduction) and fast switching (through ionic conduction), resolving the contradiction between high ON/OFF ratio and fast erase speed.
2Ease of manufacture
If single-crystal silicon p-n and Schottky diodes are used, then the manufacturing process is simplified, but the mobility is low and reliability is poor in 3D applications
Solution Approach 1:
The patent changes the material class from single-crystal silicon to MIEC materials, which can be deposited as thin films using standard BEOL processing techniques. This maintains ease of manufacture in 3D applications while providing superior reliability through the MIEC material's inherent properties of high mobility and robustness in vertical current flow.
3Power
If access diodes are designed for high current density operation, then the memory element performance is improved, but the voltage margin becomes insufficient
Solution Approach 1:
The patent introduces tunability into the access diode design by varying the MIEC layer thickness. This dynamic parameter adjustment allows optimization of the voltage margin while maintaining high current density operation. By making the voltage margin可调 (tunable), the system can be adapted to different operating conditions without sacrificing either high current capability or sufficient voltage margin.
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 MIEC-based access diodes provide high ON/OFF ratios, ultra-low leakage, and tunable voltage margins, enabling large arrays and high-performance RRAM operation while maintaining compatibility with standard processing temperatures.
Implementation Method 1
a mixed ionic-electronic conduction (MIEC) layer on a substrate
Implementation Method 2
doping the MIEC layer with a conductive defect dopant; adjusting defect energy and effective mass of the access diode by doping the MIEC material with a conductive defect dopant
Data Source
AI summary
The present invention relates generally to high current density access devices (ADs), and more particularly, to a structure and method of forming tunable voltage margin access diodes in phase change memory (PCM) blocks using layers of copper-containing mixed ionic-electronic conduction (MIEC) materials. Embodiments of the present invention may use layers MIEC material to form an access device that can supply high current-densities and operate reliably while being fabricated at temperatures that are compatible with standard BEOL processing. By varying the deposition technique and amount of MIEC material used, the voltage margin (i.e. the voltage at which the device turns on and the current is above the noise floor) of the access device may be tuned to specific operating conditions of different memory devices.