HfO2 Ferroelectric Capacitor Structure With Al2O3 Stress Interlayer
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Solution Overview
Problem
Conventional ferroelectric materials face challenges such as complex chemical composition, difficulty in integration with CMOS processes, small forbidden band width, and environmental concerns, limiting their application in advanced non-volatile semiconductor memories like FeRAM.
Innovation Solution
A HfO2-based ferroelectric capacitor structure is developed, incorporating a substrate layer, bottom and top electrodes, a dielectric layer of HfO2 doped with Zr, and an Al2O3 intercalation layer to provide tensile stress during annealing, enhancing the o-phase component and remanent polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ferroelectric materials with perovskite structure are used, then ferroelectricity can be achieved, but the chemical composition becomes complex and compatibility with CMOS process deteriorates
Solution Approach 1:
The patent replaces complex conventional ferroelectric materials with a simpler HfO2-based system that can be deposited using standard ALD equipment already present in CMOS fabs. The HfO2 material system is easier to manufacture and integrate, sacrificing some material complexity to gain manufacturing simplicity and CMOS compatibility.
Solution Approach 2:
The patent creates a composite structure by doping HfO2 with Zr to form HZO (Hf1-xZrxO2) and further incorporating Si doping. This composite material approach allows tuning of ferroelectric properties while maintaining compatibility with standard semiconductor processing. The multi-element composition enables optimization of both ferroelectric performance and manufacturability.
2Reliability
If conventional ferroelectric materials are used, then ferroelectricity can be achieved, but the forbidden band width becomes small making film thickness reduction difficult
Solution Approach 1:
The patent changes the material composition parameters by doping HfO2 with Zr and Si, which increases the forbidden band width compared to conventional ferroelectric materials. This parameter change enables the film thickness to be reduced to approximately 5 nm while maintaining adequate electrical performance and preventing excessive leakage current, thus resolving the contradiction between achieving ferroelectricity and reducing film thickness.
3Reliability
If PZT material is used, then ferroelectricity can be achieved, but toxicity issues arise leading to bans in some countries
Solution Approach 1:
The patent replaces toxic PZT (lead zirconium titanate) with a lead-free HfO2-based ferroelectric material system. This substitution eliminates the harmful lead content while maintaining ferroelectric functionality, allowing the material to be used in commercial products without environmental or health restrictions. The HfO2-based material serves as a safe, non-toxic alternative that preserves the desired electrical properties.
4Reliability
If Al2O3 intercalation layer is inserted to increase o-phase ratio, then remanent polarization and memory window improve, but device structure becomes more complex
Solution Approach 1:
The patent introduces an Al2O3 intercalation layer as an intermediary between the HZO dielectric layer and the top electrode. This intermediate layer serves multiple functions: it provides tensile stress during annealing to increase the o-phase ratio, improves interfacial quality, and enhances remanent polarization. The thin Al2O3 layer (deposited via ALD) adds minimal structural complexity while delivering significant performance improvements in memory window and reliability.
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 structure increases the memory window and reliability of the ferroelectric memory by improving the ratio of the o-phase component and remanent polarization, preventing data misreading and enhancing integration capabilities.
Implementation Method 1
During the annealing and crystallization process, the material is subjected to asymmetric stress, so a transition from the m-phase to the o-phase occurs
Implementation Method 2
the Al2O3 intercalation layer with a thermal expansion coefficient smaller than TiN is inserted between the dielectric layer and the top electrode (TiN) of the ferroelectric capacitor to provide larger tensile stress during annealing
Implementation Method 3
The ferroelectric capacitor is configured to store data and includes top and bottom electrodes and a dielectric layer in a sandwich structure. The dielectric layer is ferroelectric and has a polarization hysteresis curve. The polarization direction of the ferroelectric domain represents stored data of binary '0' and '1'
Implementation Method 4
The polarization direction of the ferroelectric domain represents stored data of binary '0' and '1'
Implementation Method 5
depositing an Al2O3 intercalation layer on the dielectric layer
Data Source
AI summary
A HfO2-based ferroelectric capacitor and a preparation method therefor, and a HfO2-based ferroelectric memory, relating to the technical field of microelectronics. The purpose of enlarging the memory window of the ferroelectric memory is achieved by inserting an Al2O3 intercalation layer having a coefficient of thermal expansion smaller than TiN between a dielectric layer and an upper electrode (TiN) of the ferroelectric capacitor. The HfO2-based ferroelectric capacitor comprises a substrate layer, a lower electrode, a dielectric layer, an Al2O3 intercalation layer, an upper electrode and a metal protection layer from bottom to top. The memory window can be increased, information misreading is effectively prevented, and therefore, the reliability of the memory is improved.