Oxide Semiconductor Transistor Electrodes for Heat-Stable Operation
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Solution Overview
Problem
Transistors with oxide semiconductors face challenges in achieving stable electrical characteristics, low leakage current in the off state, high frequency characteristics, normally-off electrical characteristics, small subthreshold swing values, and high reliability due to issues with impurities and defects affecting the semiconductor material.
Innovation Solution
A semiconductor device is designed with conductors containing tungsten and elements like silicon, carbon, germanium, tin, aluminum, and nickel, which have a silicon concentration measured by Rutherford back scattering spectrometry between 5 atomic % and 70 atomic %, and include regions with silicon and oxygen on the surface, providing heat resistance and oxidation resistance to stabilize the transistor's electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment at high temperature is performed to reduce impurities in the oxide semiconductor transistor, then impurity content is reduced and electrical characteristics are improved, but the gate electrode, source electrode, or drain electrode may be damaged due to insufficient heat resistance and oxidation resistance
Solution Approach 1:
The patent employs composite conductor structures consisting of multiple layers with different materials (e.g., tungsten, molybdenum, titanium, aluminum, copper) to achieve both low resistance and high heat/oxidation resistance. This composite approach allows the conductor to withstand high-temperature heat treatment while maintaining electrical performance
Solution Approach 2:
The patent optimizes conductor material parameters by selecting specific materials with appropriate melting points, oxidation resistance, and electrical conductivity. The conductor materials are chosen to have higher heat resistance than the oxide semiconductor, enabling them to survive high-temperature processing without degradation
2Reliability
If conventional conductors are used in the transistor, then manufacturing is simpler, but the transistor cannot achieve stable electrical characteristics and high reliability due to damage during high-temperature processing
Solution Approach 1:
The patent applies different material properties to different parts of the conductor structure. The gate electrode uses materials optimized for heat resistance and adhesion to oxide semiconductor, while source and drain electrodes use materials optimized for low resistance and compatibility with contact regions. This localized optimization achieves both reliability and manufacturability
3Reliability
If the transistor structure is optimized for low leakage current and high frequency characteristics, then performance is improved, but the device complexity increases
Solution Approach 1:
The patent divides the conductor into multiple segmented layers, each with specific functions. The gate electrode is segmented into distinct layers for adhesion and conductivity, while source and drain electrodes are segmented to optimize contact with the oxide semiconductor channel. This segmentation enables performance optimization without excessive complexity
Data Source
AI summary
A transistor with favorable electrical characteristics is provided. One embodiment of the present invention is a semiconductor device including a semiconductor, a first insulator in contact with the semiconductor, a first conductor in contact with the first insulator and overlapping with the semiconductor with the first insulator positioned between the semiconductor and the first conductor, and a second conductor and a third conductor, which are in contact with the semiconductor. One or more of the first to third conductors include a region containing tungsten and one or more elements selected from silicon, carbon, germanium, tin, aluminum, and nickel.