Doped Polar Capacitor Stack for Low-Voltage Nonvolatile Memory
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Solution Overview
Problem
Conventional semiconductor memory technologies face challenges in achieving high remnant polarization and low coercive voltage for ultra-low voltage operation, particularly in advanced technology nodes, where maintaining nonvolatility and high cycling endurance is essential.
Innovation Solution
A semiconductor device with a capacitor comprising a polar layer doped with a metal element that differs from the base polar material, featuring crystalline conductive oxide electrodes and barrier metal layers, engineered to achieve a ferroelectric switching voltage and remnant polarization suitable for nonvolatile memory applications, with a ferroelectric oxide layer undergoing a transition at a voltage lower than 600 mV and having a remnant polarization greater than 10 μC/cm2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric materials are used in DRAM capacitors, then the device can operate with simple structure, but the leakage current is high and data is lost when powered off
Solution Approach 1:
The patent changes the fundamental parameter of the dielectric material from conventional materials to ferroelectric materials, which exhibit spontaneous polarization and hysteresis loops. This parameter change enables nonvolatile data storage while reducing leakage current, as the ferroelectric material maintains its polarization state without continuous power supply.
Solution Approach 2:
The patent employs composite material structures including ferroelectric capacitor stacks with multiple layers (electrode layers, ferroelectric layers, and optional tunnel barrier layers) integrated with transistor structures. This composite approach combines the nonvolatile properties of ferroelectric materials with the operational characteristics of conventional semiconductor devices.
2Reliability
If ferroelectric materials are used to achieve nonvolatility, then data retention is improved, but the switching voltage becomes too high for ultra-low voltage operation
Solution Approach 1:
The patent applies local quality by creating spatially varying compositions within the ferroelectric layer, such as gradient doping profiles or compositional gradients in mixed ferroelectric materials. This allows different regions of the ferroelectric layer to have optimized properties, with the overall structure achieving both low switching voltage and high remnant polarization.
Solution Approach 2:
The patent modifies the chemical composition parameters of the ferroelectric material, such as adjusting the ratio of elements in lead zinc niobate-lead titanate (PZN-PST) or lead magnesium niobate-lead titanate (PMN-PT) solid solutions. By changing compositional parameters, the Curie temperature and coercive field are tuned to achieve ultra-low voltage switching while maintaining nonvolatile properties.
3Productivity
If the device footprint is scaled down with advancing technology nodes, then integration density is improved, but the dielectric constant must be increased while reducing leakage current
Solution Approach 1:
The patent transitions from planar capacitor structures to vertically stacked three-dimensional capacitor structures. This dimensional change increases the effective capacitor area within the same footprint, thereby improving integration density while maintaining or enhancing dielectric performance through the use of high-k ferroelectric materials in the vertical dimension.
Solution Approach 2:
The patent uses composite material systems such as lead zinc niobate-lead titanate (PZN-PST) and lead magnesium niobate-lead titanate (PMN-PT) with high dielectric constants and low leakage currents. These composite ferroelectric materials provide the necessary dielectric performance for scaled devices while enabling higher integration densities.
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 solution enables fast and low-voltage switching with high remnant polarization, enhancing nonvolatility and cycling endurance, addressing the limitations of conventional technologies by optimizing the polar layer's composition and electrode structure.
Implementation Method 1
the ferroelectric oxide layer undergoes a transition at a voltage lower than 600 mV and having a remnant polarization greater than 10 μC/cm2
Data Source
AI summary
The disclosed technology generally relates to ferroelectric materials and semiconductor devices, and more particularly to semiconductor memory devices incorporating doped polar materials. In one aspect, a semiconductor device comprises a capacitor which in turn comprises a polar layer comprising a base polar material doped with a dopant. The base polar material includes one or more metal elements and one or both of oxygen or nitrogen. The dopant comprises a metal element that is different from the one or more metal elements and is present at a concentration such that a ferroelectric switching voltage of the capacitor is different from that of the capacitor having the base polar material without being doped with the dopant by more than about 100 mV. The capacitor stack additionally comprises first and second crystalline conductive oxide electrodes on opposing sides of the polar layer. The capacitor stack further comprises first and second barrier metal layers on respective ones of the first and second crystalline conductive oxide electrodes on opposing sides of the polar layer.