Multi-layer Source Drain Electrodes for Oxide Semiconductor Transistors
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Solution Overview
Problem
Current semiconductor technologies face challenges in miniaturization and achieving highly reliable semiconductor devices with favorable electrical characteristics, particularly when using oxide semiconductors for transistors in electronic devices.
Innovation Solution
A semiconductor device design featuring an island-shaped oxide semiconductor layer with specific electrode structures, including first and second conductive layers with different thicknesses, and a gate insulating layer, optimized for miniaturization and improved electrical performance. The manufacturing method involves precise etching and layer formation using techniques like electron beam exposure and extreme ultraviolet light to create a configuration where the second conductive layers are positioned between the first conductive layers, enhancing coverage and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer source/drain electrode is used, then the manufacturing process is simple, but the electrical characteristics and coverage are insufficient
Solution Approach 1:
The source/drain electrode is divided into multiple layers (first conductive layer and second conductive layer) with different functions. The first conductive layer provides mechanical support and basic conductivity, while the second conductive layer enhances electrical characteristics and reduces off-state leakage current. This segmentation allows each layer to be optimized for its specific function, improving overall device performance without requiring complete redesign of the electrode system.
Solution Approach 2:
Different regions of the electrode structure are assigned different materials and thicknesses to achieve local optimization. The first conductive layer uses a thicker structure for mechanical stability, while the second conductive layer uses a thinner structure with specific materials (such as titanium nitride or tungsten) to reduce resistance and improve electrical characteristics in critical areas. This local quality approach allows the electrode to simultaneously achieve mechanical strength and superior electrical performance.
2Area of moving object
If the transistor size is reduced for miniaturization, then the integration density increases, but the manufacturing precision and electrical performance deteriorate
Solution Approach 1:
Instead of further reducing the planar dimensions of the transistor, the invention improves performance by adding a vertical dimension through multi-layer electrodes. The stacked conductive layers provide additional degrees of freedom for optimizing electrical characteristics without compromising the miniaturized footprint. This dimensional transition allows continued scaling while maintaining manufacturing precision and electrical performance.
Solution Approach 2:
The electrode structure employs composite materials with different properties in each layer. The first conductive layer may use materials optimized for adhesion and mechanical strength, while the second conductive layer uses materials with superior electrical conductivity and low resistance. This composite approach enables the miniaturized transistor to achieve the required electrical performance without sacrificing manufacturing feasibility.
3Adaptability or versatility
If oxide semiconductors are used for transistors, then alternative material benefits are achieved, but the off-state leakage current increases
Solution Approach 1:
The second conductive layer acts as an intermediary between the oxide semiconductor channel and the metal contact, preventing direct interaction that causes high off-state leakage. This intermediate layer with specific material composition (such as titanium nitride or tungsten) serves as a barrier that suppresses leakage current while maintaining good electrical contact, effectively decoupling the benefits of oxide semiconductors from their harmful leakage characteristics.
Solution Approach 2:
The invention changes the electrical parameters of the source/drain electrode by introducing a multi-layer structure with controlled thicknesses and materials. By adjusting the thickness and composition of the second conductive layer, the electrode resistance and contact properties are optimized to reduce off-state leakage current. This parameter optimization allows oxide semiconductor transistors to achieve low leakage performance comparable to or better than conventional semiconductors.
Data Source
AI summary
A semiconductor device for miniaturization is provided. The semiconductor device includes a semiconductor layer; a first electrode and a second electrode that are on the semiconductor layer and apart from each other over the semiconductor layer; a gate electrode over the semiconductor layer; and a gate insulating layer between the semiconductor layer and the gate electrode. The first and second electrodes comprise first conductive layers and second conductive layers. In a region overlapping with the semiconductor layer, the second conductive layers are positioned between the first conductive layers, and side surfaces of the second conductive layers are in contact with side surfaces of the first conductive layers. The second conductive layers have smaller thicknesses than those of the first conductive layers, and the top surface levels of the second conductive layers are lower than those of the first conductive layers.