Ferroelectric Layer Stack for Low Wake-Up HZO Polarization
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Solution Overview
Problem
HZO-based ferroelectric devices face challenges with prolonged wake-up effects and modest initial remnant polarization, while achieving high endurance requires titanium nitride electrodes, which compromise on polarization and introduce costs associated with CMOS integration.
Innovation Solution
A layer stack comprising a titanium oxide layer as a seed for a doped HZO layer and a niobium oxide layer as a cap, along with titanium nitride electrodes, stabilizes the orthorhombic phase, increases remnant polarization, and reduces wake-up effects, achieving endurance above 1E+10 cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten or molybdenum electrodes are used to reduce wake-up effect, then wake-up effect is reduced, but endurance decreases to 1E+5 to 1E+7 cycles
Solution Approach 1:
A thin layer of aluminum oxide (Al2O3) is introduced as an intermediary layer between the tungsten electrode and the HZO ferroelectric layer. This intermediary layer modifies the interface properties, allowing the use of tungsten electrodes (which have low wake-up effect) while maintaining high endurance through optimized interfacial characteristics that prevent degradation mechanisms.
2Duration of action of stationary object
If titanium nitride electrodes are used to increase endurance, then endurance increases to 1E+11 cycles, but remnant polarization decreases and wake-up effect prolongs
Solution Approach 1:
The electrode material composition is changed from pure titanium nitride to a composite structure featuring tungsten electrodes with an aluminum oxide interface layer. This parameter change in material composition and structure enables simultaneous achievement of high endurance (1E+11 cycles) and high remnant polarization, while reducing the wake-up effect through the beneficial interfacial properties of the Al2O3 layer.
3Duration of action of stationary object
If lanthanides or rare-earth doped HZO is used to achieve high endurance, then endurance increases to >1E+10 cycles, but initial polarization becomes modest requiring 1E+5 to 1E+7 switching cycles to reach maximum
Solution Approach 1:
The HZO ferroelectric layer is doped with lanthanum (a lanthanide) to create a composite material with enhanced endurance (>1E+10 cycles). The doping concentration is optimized to balance the trade-off between endurance enhancement and initial polarization, reducing the wake-up effect while maintaining high remnant polarization from the beginning of device operation.
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 proposed layer stack enhances remnant polarization, reduces wake-up effects, and maintains high endurance, facilitating cost-effective CMOS integration with improved initial and maximum polarization performance.
Implementation Method 1
a titanium oxide layer as a seed for a doped HZO layer
Implementation Method 2
stabilization of the orthorhombic phase on the expense of the tetragonal one, and suppression of non-ferroelectric phases (cubic and monoclinic) formation
Data Source
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AI summary
The present disclosure relates to ferroelectric devices. The disclosure proposes a ferroelectric device including a new kind of layer stack and a method for fabricating the ferroelectric device. In particular, the ferroelectric device comprises a first electrode and a second electrode, and the layer stack arranged between the first electrode and the second electrode. The layer stack comprises a titanium oxide layer, a doped HZO layer arranged on the titanium oxide layer, and a niobium oxide layer arranged on the doped HZO layer.