Oxide Semiconductor Transistor Electrodes With Copper Diffusion Barriers
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Solution Overview
Problem
The use of copper (Cu) in transistor electrodes for oxide semiconductor devices leads to diffusion issues, causing deterioration of electrical characteristics and reliability, particularly at the back-channel side, and increases manufacturing costs.
Innovation Solution
Incorporating copper and silicon compounds in the end portions of source and drain electrodes, along with conductive films that inhibit copper diffusion, to stabilize the transistor structure and enhance electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used in transistor electrodes for oxide semiconductor devices, then electrical conductivity is improved, but copper diffusion into the semiconductor film causes deterioration of electrical characteristics and reliability
Solution Approach 1:
A barrier film comprising a first barrier metal layer and a second barrier metal layer is introduced between the copper-containing electrode and the oxide semiconductor film. The first barrier metal layer (e.g., tungsten, molybdenum, or their oxides/nitrides) provides primary diffusion prevention, while the second barrier metal layer (e.g., titanium, tantalum, or their oxides/nitrides) enhances the barrier effect. This intermediary structure effectively blocks copper diffusion into the semiconductor film while maintaining electrical conductivity.
Solution Approach 2:
The barrier film is constructed as a composite structure with two different barrier metal layers, each having distinct properties. The first layer uses metals with high diffusion barrier performance (tungsten, molybdenum), while the second layer uses metals with good adhesion and additional barrier properties (titanium, tantalum). This composite approach synergistically addresses both diffusion prevention and electrical performance requirements.
2Ease of manufacture
If copper is used in transistor electrodes, then manufacturing costs are reduced, but adhesion to the base film is poor
Solution Approach 1:
The barrier film serves as an intermediary layer between the copper electrode and the oxide semiconductor film, providing both adhesion promotion and diffusion prevention. The specific barrier metal materials (tungsten, molybdenum, titanium, tantalum) and their compounds are selected for their ability to bond effectively with both copper and the oxide semiconductor, thereby improving interfacial adhesion.
Solution Approach 2:
The barrier film is strategically positioned only at critical interfaces where copper diffusion and adhesion issues occur (between the electrode and semiconductor film, and between the electrode and insulating film), while allowing copper to be used in the bulk electrode material for cost-effectiveness and conductivity.
3Reliability
If copper diffusion is prevented using barrier films, then electrical characteristics are maintained, but device complexity increases
Solution Approach 1:
The barrier film is segmented into two distinct layers with different material compositions and functions. The first layer focuses on primary diffusion blocking, while the second layer enhances adhesion and provides secondary barrier protection. This segmentation allows each layer to be optimized for its specific function, achieving effective copper prevention with controlled complexity.
Solution Approach 2:
The thickness and material composition of each barrier layer are precisely controlled within specific ranges. The first barrier metal layer has a thickness of 1-10 nm, and the second barrier metal layer has a thickness of 1-5 nm. By controlling these parameters, the barrier film provides effective copper diffusion prevention while minimizing the increase in device complexity and manufacturing steps.
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 provides a semiconductor device with improved electrical characteristics, reliability, and reduced manufacturing costs, while maintaining high productivity.
Implementation Method 1
an end portion of the source electrode and an end portion of the drain electrode each include a region containing copper and silicon
Data Source
AI summary
A semiconductor device including an oxide semiconductor film that includes a transistor with excellent electrical characteristics is provided. It is a semiconductor device including a transistor. The transistor includes a gate electrode, a first insulating film, an oxide semiconductor film, a source electrode, a drain electrode, and a second insulating film. The source electrode and the drain electrode each include a first conductive film, a second conductive film over and in contact with the first conductive film, and a third conductive film over and in contact with the second conductive film. The second conductive film contains copper, the first conductive film and the third conductive film include a material that inhibits diffusion of copper, and an end portion of the second conductive film includes a region containing copper and silicon.