MIM Capacitor Noble Metal Liner for Low Leakage Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing MIM capacitors in DRAM devices face issues with high leakage currents due to the energy difference between the conduction band of the dielectric and the work function of the metal electrode, leading to unwanted electron injection and oxygen scavenging, which increases trap density.
Innovation Solution
A method of fabricating MIM capacitors with a thin noble metal liner sandwiched between the electrode and the insulator, using a thickness of 0.5 to 5 nm, formed from materials like iridium, ruthenium, or platinum, to act as a scavenging barrier and alter the effective work function, reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-k dielectric materials are used to increase the dielectric constant, then the capacitance is improved, but the conduction band offset decreases leading to increased leakage current
Solution Approach 1:
A noble metal liner (iridium, ruthenium, or platinum) is introduced as an intermediary layer between the metal electrode and the high-k dielectric material. This liner acts as a mediator that prevents direct interaction between the electrode and dielectric, thereby reducing electron injection and oxygen scavenging while maintaining the high capacitance benefits of high-k materials.
Solution Approach 2:
The electrode structure is transformed from a simple metal layer to a composite structure consisting of metal electrode plus noble metal liner. This composite configuration combines the high conductivity of the metal electrode with the protective properties of the noble metal liner, achieving both high capacitance and low leakage current.
2Speed
If the work function of the metal electrode is reduced to increase conductivity, then the device speed is improved, but the energy difference with the conduction band decreases leading to increased electron injection
Solution Approach 1:
The noble metal liner serves as an intermediary that decouples the relationship between electrode work function and dielectric conduction band. This allows the use of low work function metals for high speed operation while the liner prevents excessive electron injection into the dielectric.
Solution Approach 2:
The noble metal liner is applied locally at the critical electrode-dielectric interface where electron injection occurs, while the bulk electrode material can be optimized for conductivity. This localized intervention addresses the electron injection problem without compromising overall device speed.
3Reliability
If the electrode material is changed to achieve desired work function, then the conductivity is improved, but oxygen scavenging increases leading to higher trap density
Solution Approach 1:
The noble metal liner acts as a protective intermediary between the electrode and dielectric, preventing the electrode material from scavenging oxygen from the dielectric. This is particularly important when using electrode materials with optimized work functions that may have higher oxygen affinity.
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 use of a noble metal liner effectively reduces leakage currents by minimizing oxygen scavenging and trap density, while also lowering costs and requiring minimal process modifications, thus enhancing the performance and efficiency of MIM capacitors.
Implementation Method 1
by scavenging oxygen from the dielectric materials, which generates oxygen vacancies and, thus, increases the trap density
Implementation Method 2
depositing a layer of a noble metal over the electrode layer
Data Source
AI summary
A noble metal liner and a metal-insulator-metal (MIM) capacitor (MIMCAP) are described along with the methods of manufacture or fabrication. The MIM capacitor includes a liner formed of a thin layer or film of a noble metal, which is only a few nanometers thick, e.g., a thickness in the range of about 0.5 nm to about 5 nm or more. In a finished device such as a MIM capacitor, the noble metal liner is sandwiched between a thicker electrode and the insulator, e.g., a layer or thin film of high or ultra high-k material, thereby providing a cap for the electrode to limit leakage currents in the device.