Semiconductor Wiring with Protective Layers to Suppress Diffusion
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Solution Overview
Problem
The use of low-resistance materials like copper, aluminum, and silver in semiconductor wiring is challenging due to processing difficulties and impurity diffusion into the semiconductor layer, leading to poor electrical characteristics and increased threshold voltage variability.
Innovation Solution
A semiconductor device structure with a stacked-layer configuration of electrodes, including a conductive layer with protective layers to prevent diffusion of low-resistance material elements into the semiconductor layer, formed through specific etching steps and anisotropic etching processes, ensuring high reliability and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low-resistance materials such as copper, aluminum, gold, or silver are used for wiring, then wiring delay is reduced, but the constituent elements are diffused into the semiconductor layer causing poor electrical characteristics
Solution Approach 1:
The electrode is divided into multiple functional layers: a conductive layer containing the low-resistance material (copper, aluminum, gold, or silver) and protective layers made of different materials (first protective layer in contact with semiconductor, second protective layer on top, third protective layer on side surfaces). This segmentation allows each layer to perform its specific function - conductivity or diffusion prevention - resolving the contradiction between achieving low wiring delay and preventing impurity diffusion.
Solution Approach 2:
Protective layers act as intermediary barrier layers between the low-resistance conductive material and the semiconductor layer. These intermediary layers prevent direct contact and diffusion of constituent elements while allowing the conductive layer to maintain its low-resistance property for reducing wiring delay.
2Quantity of substance
If low-resistance materials are used in wiring, then resistance is reduced, but entry of impurities into the semiconductor layer increases threshold voltage variation
Solution Approach 1:
The electrode structure is segmented into conductive layers and protective layers, where protective layers specifically prevent impurity entry into the semiconductor layer during processing. This segmentation enables the use of low-resistance materials while maintaining precise control over threshold voltage variation.
Solution Approach 2:
Protective layers are formed beforehand to prevent the harmful action of impurity diffusion into the semiconductor layer. By establishing this protective barrier before processing, the invention preemptively counteracts the potential for threshold voltage variation caused by impurity entry.
3Reliability
If protective layers are added to prevent diffusion, then reliability is improved, but device complexity increases
Solution Approach 1:
Multiple protective layers with different functions are merged into a unified electrode structure. The first protective layer, second protective layer, and third protective layer work together as an integrated system to prevent diffusion from different directions, achieving comprehensive protection without requiring separate processing systems.
Solution Approach 2:
The stacked-layer electrode structure serves multiple functions simultaneously: the conductive layers provide low resistance for signal transmission, while the protective layers prevent diffusion and serve as masks during processing. This multi-functionality reduces the need for additional separate components or processes.
4Reliability
If multiple protective layers are formed, then diffusion prevention is enhanced, but manufacturing process becomes more complex
Solution Approach 1:
The protective layers are designed to serve as self-aligned masks during etching processes. The second protective layer on the top surface and the third protective layer on the side surfaces automatically define the etching boundaries without requiring additional mask layers, allowing the structure to guide its own fabrication process.
Solution Approach 2:
The protective layers are positioned in different spatial dimensions - the first protective layer at the bottom interface, the second protective layer on the top surface, and the third protective layer on the side surfaces. This three-dimensional arrangement provides comprehensive diffusion prevention while enabling self-aligned processing that simplifies manufacturing.
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 solution effectively suppresses impurity diffusion and wiring delay, enhancing the reliability and stability of semiconductor devices by maintaining the electrical characteristics and reducing the variation in threshold voltage.
Implementation Method 1
The side surface of the conductive layer is covered with a third protective layer. With this structure, entry or diffusion of the constituent element of the pair of conductive layers containing a low-resistance material into the semiconductor layer is suppressed.
Implementation Method 2
the first and third protective layers can be formed in a self-aligned manner by anisotropic etching using the second protective layer as an etching protective film
Data Source
AI summary
To improve the reliability of a semiconductor device including a low-resistance material such as copper, aluminum, gold, or silver as a wiring. Provided is a semiconductor device including a pair of electrodes electrically connected to a semiconductor layer which has a stacked-layer structure including a first protective layer in contact with the semiconductor layer and a conductive layer containing the low-resistance material and being over and in contact with the first protective layer. The top surface of the conductive layer is covered with a second protective layer functioning as a mask for processing the conductive layer. The side surface of the conductive layer is covered with a third protective layer. With this structure, entry or diffusion of the constituent element of the pair of conductive layers containing the low-resistance material into the semiconductor layer is suppressed.