Hafnium Oxide Ferroelectric Layers Using HfN to Cut Leakage
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Solution Overview
Problem
High thermal processing temperatures used in hafnium oxide (HfO2)-based ferroelectric random access memory (FeRAM) applications lead to increased leakage current and device degradation due to defect generation and film cracking, which degrades the ferroelectric properties of HfO2, making it unsuitable for commercialization.
Innovation Solution
The method involves depositing hafnium nitride (HfN) layers between or on top of HfO2 layers, followed by annealing and oxidation processes to form ferroelectric hafnium oxide, using techniques like atomic layer deposition (ALD) and rapid thermal annealing, and doping with silicon, aluminum, zirconium, or lanthanum to control ferroelectric properties and reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high thermal processing temperatures are used to form ferroelectric HfO2, then the ferroelectric phase formation is achieved, but leakage current increases and device degradation occurs due to defect generation and film cracking
Solution Approach 1:
A nitrogen-containing layer (such as silicon nitride or hafnium nitride) is introduced as an intermediary between the HfO2 ferroelectric layer and the electrode. This intermediary layer acts as a diffusion barrier that prevents metal atoms from the electrode from diffusing into the HfO2 layer during high-temperature annealing, thereby reducing defect generation and leakage current while allowing the ferroelectric phase to form at lower temperatures (700-900°C)
2Temperature
If high thermal processing temperatures are used to form ferroelectric HfO2, then the ferroelectric phase formation is achieved, but device degradation occurs due to film cracking
Solution Approach 1:
The nitrogen-containing intermediary layer serves as a stress-buffering interface that prevents film cracking during thermal processing. This layer accommodates thermal expansion differences between the HfO2 layer and substrate, maintaining film integrity during high-temperature annealing processes
Solution Approach 2:
The nitrogen-containing layer is deposited beforehand to establish a protective interface before high-temperature processing. This preliminary action prevents subsequent film cracking by creating a stable, crack-resistant structure that can withstand thermal stress
3Manufacturing precision
If conventional ferroelectric materials like PZT are used, then adequate switching window is achieved for thicker films, but they cannot be used for devices with feature sizes below 50 nm
Solution Approach 1:
The invention changes the material parameters by using HfO2 instead of conventional PZT, enabling thinner film thicknesses (below 50 nm) while maintaining ferroelectric properties. The nitrogen-containing layer modification allows HfO2 to achieve adequate switching windows at these reduced thicknesses, making it suitable for advanced nanoscale devices
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 effectively reduces leakage current and enhances the thermal stability of HfO2-based FeRAM by modifying the ferroelectric properties, allowing for the integration of HfO2 in 3D memory structures without degrading the device performance.
Implementation Method 1
Annealing the HfO2 layer and the HfN layer includes performing a rapid thermal annealing process at a temperature between 500 and 1100° C.
Implementation Method 2
Nitridating the HfO2 layer includes generating plasma using a nitrogen gas species.
Implementation Method 3
Performing the oxidation on the HfN layer includes performing the oxidation using at least one of molecular oxygen and ozone.
Data Source
AI summary
A method of forming ferroelectric hafnium oxide (HfO2) in a substrate processing system includes depositing an HfO2 layer on a substrate, depositing a hafnium nitride (HfN) layer on the HfO2 layer; and annealing the HfO2 layer and the HfN layer to form ferroelectric hafnium HfO2.