Semiconductor Device Multilayer Gate Insulating Film Structure
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Solution Overview
Problem
Conventional semiconductor devices experience fluctuations in impurity profiles of channel diffusion layers due to multiple thermal oxidation processes, leading to inconsistent transistor characteristics.
Innovation Solution
A semiconductor device with a multilayer gate insulating structure and reduced thermal oxidation processes, featuring silicon oxide films and high-k insulating films, which reduces the number of heat treatment steps and minimizes impurity diffusion, thereby stabilizing impurity profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple thermal oxidation processes are performed to form gate insulating films of different thicknesses, then the desired gate insulating film structure is achieved, but the impurity profiles of channel diffusion layers fluctuate and transistor characteristics become inconsistent
Solution Approach 1:
The gate insulating film formation process is segmented into two distinct stages: first forming a thick gate insulating film (5nm-20nm) to ensure adequate insulation and breakdown voltage, then forming a thin gate insulating film (1nm-3nm) to achieve low threshold voltage and high drive current. This segmentation allows each film to serve its specific function without compromising transistor characteristic consistency.
Solution Approach 2:
The channel diffusion layers are formed with predetermined impurity profiles and concentrations before the gate insulating film formation processes. By establishing the impurity distribution in advance, the subsequent thermal oxidation processes do not significantly alter the channel characteristics, ensuring consistent transistor performance across different devices.
2Reliability
If the number of thermal oxidation processes is reduced, then impurity diffusion is minimized and impurity profiles are stabilized, but the ability to form gate insulating films of different thicknesses is compromised
Solution Approach 1:
Different regions of the semiconductor device receive different gate insulating film thicknesses according to their specific functional requirements. High-voltage transistors receive thicker gate insulating films for breakdown protection, while low-voltage transistors receive thinner films for enhanced drive current. This local differentiation is achieved through selective area treatment rather than uniform processing.
Solution Approach 2:
The gate insulating film structure comprises a composite of two different oxide layers with distinct thicknesses and properties. The thick lower layer provides electrical isolation and breakdown voltage, while the thin upper layer enables low threshold voltage operation. This composite structure combines the advantages of both thickness regimes in a single integrated system.
3Strength
If thermal oxidation time is extended to form thicker gate insulating films, then adequate insulation is achieved, but impurity diffusion increases and transistor characteristics deteriorate
Solution Approach 1:
The gate insulating film thickness requirement is segmented into two components: the thick lower layer (5nm-20nm) formed by extended thermal oxidation provides the necessary insulation strength and breakdown voltage, while the thin upper layer (1nm-3nm) formed by brief thermal oxidation provides the interface quality needed for low threshold voltage without excessive impurity diffusion.
Solution Approach 2:
The channel diffusion layers are prepared with optimized impurity profiles before any thermal oxidation processes. This preliminary action ensures that even the extended oxidation required for the thick gate insulating film layer does not significantly degrade the channel characteristics, as the impurity distribution is already optimized for the final device performance.
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 approach effectively reduces fluctuations in impurity profiles, enabling the production of transistors with desired characteristics by shortening heat treatment times and minimizing impurity diffusion, thus improving transistor reliability and performance.
Implementation Method 1
first thermal oxidation for forming a gate insulating film is performed to provide a first film 103 for forming a silicon oxide film
Implementation Method 2
forming a first channel diffusion layer of a second conductivity type in an upper region of the first active region by first ion implantation
Data Source
AI summary
A semiconductor device includes a first, second, and third MIS transistors of a first conductivity type respectively including a first, second, and third gate electrodes on a first, second, and third active regions of a semiconductor substrate with a first, second, and third gate insulating films interposed therebetween. The first gate insulating film is formed of a first silicon oxide film and a first high-k insulating film on the first silicon oxide film. The second gate insulating film is formed of a second silicon oxide film and a second high-k insulating film on the second silicon oxide film. The third gate insulating film is formed of a third silicon oxide film and a third high-k insulating film on the third silicon oxide film. The second silicon oxide film has a same thickness as the first silicon oxide film, and a greater thickness than the third silicon oxide film.