Capacitor Electrode Material for Low Leakage Current
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Solution Overview
Problem
Conventional DRAM capacitor cells face challenges in achieving low leakage current and high permittivity due to limitations in existing dielectric and electrode materials, particularly with titanium oxide having a rutile structure, which is difficult to form at normal semiconductor manufacturing temperatures and when using ruthenium as an electrode material.
Innovation Solution
A capacitor design incorporating a lower electrode with a combination of platinum group metals and ruthenium or iridium, where the titanium oxide dielectric layer is formed using atomic layer deposition at a temperature equal to or less than 400°C, allowing for the formation of a rutile structured titanium oxide with high permittivity and reduced leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ruthenium is used as electrode material to form rutile structured titanium oxide, then the dielectric layer can be formed at high temperature, but the leakage current increases due to lower work function
Solution Approach 1:
The patent employs a composite electrode structure consisting of multiple metal layers (e.g., Ru/Ir alloy, Pt/Ru alloy, or stacked layers) to combine the benefits of different materials. The composite structure enables rutile TiO2 formation at high temperature while the presence of higher work function metals (Pt, Ir) suppresses leakage current, resolving the contradiction between temperature capability and electrical performance.
Solution Approach 2:
The patent modifies the work function parameter of the electrode material by adjusting composition ratios, doping concentrations, or layer thicknesses in the composite structure. By changing these parameters, the electrode achieves both high-temperature processing capability and low leakage current, as the effective work function is optimized through material composition control.
2Device complexity
If conventional dielectric materials are used, then the manufacturing process is simple, but the permittivity is insufficient for next generation DRAM
Solution Approach 1:
The patent changes the chemical composition parameter of the dielectric material from conventional options (SiO2, Al2O3) to titanium oxide-based materials with inherently higher permittivity. This parameter change enables next-generation DRAM performance requirements to be met while the deposition process remains relatively straightforward using existing ALD or CVD techniques.
Solution Approach 2:
The patent uses composite dielectric structures including titanium oxide combined with other oxides (e.g., SiO2, Al2O3, HfO2) to achieve high permittivity. The composite structure leverages the high-k properties of titanium oxide while maintaining process compatibility and electrical performance, resolving the contradiction between simplicity and performance.
3Stability of the object's composition
If high temperature processing is applied to form rutile titanium oxide, then the dielectric layer achieves stable structure, but the capacitor electrode deteriorates
Solution Approach 1:
The patent uses composite electrode materials (e.g., Pt/Ir, Ru/Ir alloys, or multi-layer structures) that maintain structural integrity at high temperatures. These composite materials have higher thermal stability and resistance to oxidation compared to conventional single-metal electrodes, allowing them to withstand the high-temperature processing required for rutile TiO2 formation without deterioration.
Solution Approach 2:
The patent changes the thermal stability parameter of the electrode material by selecting metals or alloys with higher melting points and oxidation resistance (e.g., Pt, Ir, Ru). This parameter change enables the electrode to survive high-temperature processing conditions while maintaining its structural integrity and electrical properties.
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 enables the formation of a titanium oxide dielectric layer with a rutile structure at a relatively low temperature, preventing deterioration of memory elements, achieving high permittivity, and reducing leakage current by increasing the work function, while avoiding damage to the capacitor electrode during heat-treating processes.
Implementation Method 1
A dielectric layer including titanium oxide is formed on the lower electrode. An upper electrode is formed on the dielectric layer. The lower electrode includes a first metal and a second metal... titanium oxide of the dielectric layer has a rutile structure
Implementation Method 2
ruthenium has a relatively high work function... However, a work function of Ru is about 4.8 eV, which is lower than other precious metals such as Ir (5.1 ̃5.4 eV), Pt (5.1 ̃5.8 eV). Thus, when Ru is used for a capacitor electrode, a capacitor may have a high leakage current
Data Source
AI summary
A capacitor for a semiconductor memory element includes a lower electrode, a dielectric layer disposed on the lower electrode and including titanium oxide, and an upper electrode disposed on the dielectric layer. The lower electrode includes a first metal and a second metal, the first metal including at least one selected from the group consisting of platinum (Pt), osmium (Os), rhodium (Rh) and palladium (Pd), the second metal including at least one selected from the group consisting of ruthenium (Ru) and iridium (Ir).