MIS Contact Structure With Conductive Metal Oxide for Thermal Stability
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Solution Overview
Problem
Metal-semiconductor contacts in integrated circuits degrade at high temperatures due to chemical reduction of the interfacial oxide layer, leading to increased contact resistivity, which is a challenge in maintaining low resistivity and thermal stability during semiconductor device manufacturing.
Innovation Solution
A metal-insulator-semiconductor (MIS) contact structure is developed using a conductive metal oxide layer and an interfacial dielectric layer, with a thickness of less than 4 nm, composed of materials like TiO2 or RuO2, which remains chemically stable up to 450°C, ensuring low contact resistivity and thermal stability by preventing chemical reactions that degrade the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional metal-semiconductor contact is used, then the contact resistivity is initially low, but the contact degrades at high temperatures due to chemical reduction of the interfacial oxide layer
Solution Approach 1:
The patent introduces an interfacial dielectric layer as an intermediary between the metal conductor and semiconductor. This dielectric layer prevents direct chemical interaction between the metal and semiconductor, thereby preventing chemical reduction of the interfacial oxide layer at high temperatures while maintaining low contact resistivity through its specific material properties and thickness control
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: a conductive metal oxide layer, an interfacial dielectric layer, and semiconductor material. This composite configuration combines the advantages of each material - the conductive metal oxide provides electrical conductivity, the dielectric layer provides thermal and chemical stability, and the semiconductor provides the desired electronic properties, achieving both low contact resistivity and high-temperature stability
2Reliability
If the interfacial dielectric layer is made thinner to reduce contact resistivity, then the contact resistivity decreases, but the thermal stability and chemical stability are compromised
Solution Approach 1:
The patent optimizes the thickness parameter of the interfacial dielectric layer to a specific range (0.5-5 nm) and controls the stoichiometry parameter of the metal oxide layer (ratio of metal to oxygen atoms). By precisely controlling these parameters, the patent achieves low contact resistivity while maintaining sufficient thermal and chemical stability, resolving the contradiction between thinness for conductivity and thickness for stability
3Reliability
If the metal oxide layer is made more conductive to lower contact resistivity, then the contact resistivity decreases, but the chemical stability at high temperatures is reduced
Solution Approach 1:
The patent controls the stoichiometry parameter of the metal oxide layer by adjusting the ratio of metal atoms to oxygen atoms. By optimizing this parameter, the patent achieves the desired electrical conductivity while maintaining chemical stability at high temperatures, as the controlled non-stoichiometry prevents excessive reactivity with the dielectric layer and semiconductor interface
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 MIS contact structure maintains low contact resistivity (less than 10−7 Ω-cm²) even after heating to 450°C, providing thermal stability and improving conductivity by preventing degradation of the interfacial layer, thus addressing the thermal budget constraints in IC manufacturing.
Implementation Method 1
a very thin, interfacial dielectric layer between the metal and semiconductor acts to reduce the Schottky barrier at the junction and at the same time has sufficient conductivity, despite being itself a dielectric with poor bulk electronic conduction, to provide a net improvement in the conductivity of the MIS junction
Implementation Method 2
the junction between the conductive metal oxide layer and the interfacial dielectric layer is chemically stable up to a temperature of 400° C. and more preferably, the junction between the conductive metal oxide layer and the interfacial dielectric layer is chemically stable up to a temperature of 450° C.
Data Source
AI summary
An electrical contact structure (an MIS contact) includes one or more conductors (M-Layer), a semiconductor (S-Layer), and an interfacial dielectric layer (I-Layer) of less than 4 nm thickness disposed between and in contact with both the M-Layer and the S-Layer. The I-Layer is an oxide of a metal or a semiconductor. The conductor of the M-Layer that is adjacent to and in direct contact with the I-Layer is a metal oxide that is electrically conductive, chemically stable and unreactive at its interface with the I-Layer at temperatures up to 450° C. The electrical contact structure has a specific contact resistivity of less than or equal to approximately 10−5-10−7 Ω-cm2 when the doping in the semiconductor adjacent the MIS contact is greater than approximately 2×1019 cm−3 and less than approximately 10−8 Ω-cm2 when the doping in the semiconductor adjacent the MIS contact is greater than approximately 1020 cm−3.