MIM Structure Ferroelectric Stack for Capacitance Density and Leakage
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Solution Overview
Problem
Conventional metal insulator metal (MIM) structures face challenges in enhancing capacitance density due to high leakage caused by direct tunneling and small bandgap issues in high-k dielectric materials, which are exacerbated by the thinning of dielectric layers.
Innovation Solution
A ferroelectric/dielectric heterostructure stack is introduced between the electrode layers, leveraging the polarization coupling effect to increase capacitance density without significantly increasing the overall thickness of the MIM structure, using a combination of high-k dielectric and ferroelectric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-k dielectric materials are used to enhance capacitance density, then capacitance density is improved, but leakage increases due to direct tunneling and small bandgap
Solution Approach 1:
The patent divides the single high-k dielectric layer into a stacked structure consisting of a first dielectric layer and a second dielectric layer with different dielectric constants. The first dielectric layer (with higher k-value) provides high capacitance density, while the second dielectric layer (with lower k-value) acts as a barrier to reduce direct tunneling leakage. This segmentation allows the system to achieve both high capacitance and low leakage by combining materials with complementary properties.
Solution Approach 2:
The patent employs a composite dielectric structure where two different dielectric materials are stacked together. Each layer is made of materials with specific dielectric constants tailored for its function: the first layer uses high-k material (e.g., HfO2, SrTiO3) for capacitance enhancement, while the second layer uses lower-k material (e.g., SiO2, Al2O3) for leakage suppression. This composite approach leverages the strengths of each material to resolve the contradiction between high capacitance and low leakage.
2Quantity of substance
If dielectric layer thickness is reduced to increase capacitance density, then capacitance density is improved, but leakage due to direct tunneling increases
Solution Approach 1:
The patent segments the thin dielectric structure into two distinct layers: a first thin layer with high-k material that provides the necessary capacitance density, and a second layer with lower-k material that serves as a tunneling barrier. This segmentation enables the structure to maintain thin overall thickness for high capacitance while incorporating a specific layer designed to block direct tunneling leakage.
Solution Approach 2:
The second dielectric layer with lower dielectric constant acts as an intermediary barrier between the electrode and the high-k dielectric layer. This intermediate layer with appropriate thickness and material properties (lower k-value) reduces the direct tunneling probability while still allowing the overall structure to achieve high capacitance density through the high-k first layer.
3Quantity of substance
If high-k dielectric materials with small bandgap are used, then capacitance density is improved, but leakage increases
Solution Approach 1:
The patent segments the dielectric structure into two layers with different bandgap characteristics. The first dielectric layer uses high-k material with smaller bandgap for high capacitance, while the second dielectric layer uses material with larger bandgap to serve as a leakage barrier. This segmentation allows exploitation of the small bandgap advantage for capacitance while using the large bandgap property for leakage suppression.
Solution Approach 2:
The patent creates a composite dielectric structure combining materials with different bandgap energies. The first layer employs high-k material (e.g., HfO2, SrTiO3) with smaller bandgap for high capacitance density, while the second layer uses lower-k material (e.g., SiO2, Al2O3) with larger bandgap to act as an energy barrier against leakage currents, thereby resolving the contradiction between capacitance enhancement and leakage reduction.
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 boosts the total capacitance value beyond that of structures using only dielectric or ferroelectric materials, while minimizing leakage issues associated with high-k dielectric materials, thereby enhancing the capacitance density of the MIM structure.
Implementation Method 1
leveraging the polarization coupling effect to increase capacitance density
Data Source
AI summary
A MIM structure and manufacturing method thereof are provided. The MIM structure includes a substrate and a metallization structure over the substrate. The metallization structure includes a bottom electrode layer, a dielectric layer on the bottom electrode layer, a ferroelectric layer on the dielectric layer, a top electrode layer on the ferroelectric layer, a first contact electrically coupled to the top electrode layer, and a second contact penetrating the dielectric layer and the ferroelectric layer, electrically coupled to a base portion of the bottom electrode layer. The bottom electrode layer includes the base portion and a plurality of protrusions, each of the protrusions is protruding from the base portion and leveled with a lower surface of the dielectric layer, each portion of the dielectric layer over the bottom electrode layer substantially have identical thicknesses.