Copper Wiring Barrier Layer for Oxide Semiconductor Stability
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Solution Overview
Problem
Oxygen vacancies in oxide semiconductor films used in transistors lead to adverse effects on electrical characteristics, such as shifts in threshold voltage, and impurities like hydrogen can cause carrier supply issues, affecting the reliability and performance of semiconductor devices.
Innovation Solution
A semiconductor device structure is implemented with a stacked-layer structure of oxide conductive films and conductive films, where excess oxygen is added to reduce oxygen vacancies and prevent impurity diffusion, using copper conductive films with metal oxide barrier layers to maintain transistor integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as wiring material to reduce resistance, then conductivity is improved, but copper diffusion into semiconductor film occurs which impairs transistor characteristics
Solution Approach 1:
A barrier layer is introduced as an intermediary between the copper wiring and the oxide semiconductor film. This barrier layer prevents copper atoms from diffusing into the semiconductor film while also preventing impurities from the semiconductor film from contaminating the copper wiring, thus resolving the harmful interaction between copper and the semiconductor film.
Solution Approach 2:
The barrier layer is formed using a composite structure of metal oxide materials (such as tungsten oxide, molybdenum oxide, or titanium oxide) which combine the properties of copper diffusion prevention and impurity blocking, enabling simultaneous protection of both the copper wiring and the oxide semiconductor film.
2Reliability
If oxygen vacancy is present in oxide semiconductor film, then carrier supply increases, but threshold voltage shifts and electrical characteristics change
Solution Approach 1:
Oxygen is supplied to the oxide semiconductor film in advance through heat treatment in an oxygen atmosphere or plasma treatment. This preliminary oxygen supply fills oxygen vacancies before the transistor operation begins, preventing threshold voltage shifts and maintaining stable electrical characteristics during device operation.
Solution Approach 2:
Plasma treatment using oxygen plasma or heat treatment in an oxygen-rich atmosphere is applied to the oxide semiconductor film. This accelerated oxidation process efficiently replenishes oxygen in the film, reducing oxygen vacancies and stabilizing the electrical characteristics without requiring complex additional structures.
3Reliability
If hydrogen diffuses into oxide semiconductor film, then carrier supply source is generated, but effective channel length shortens and transistor performance degrades
Solution Approach 1:
The barrier layer serves as a mediator that blocks hydrogen diffusion from the oxide semiconductor film to the copper wiring and prevents hydrogen from reaching the channel region. This intermediary layer maintains the effective channel length and prevents performance degradation caused by hydrogen-induced carrier supply sources.
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
This configuration enhances the reliability and stability of transistor electrical characteristics by reducing oxygen vacancies and impurity effects, improving the integration density and reducing power consumption in semiconductor devices.
Implementation Method 1
a barrier layer that prevents copper in the copper wiring from diffusing into a semiconductor film
Implementation Method 2
it is necessary to reduce oxygen vacancy by effectively supplying oxygen to the channel region of the oxide semiconductor film
Data Source
AI summary
A gate electrode, a first insulating film thereover, an oxide semiconductor film thereover, a source electrode and a drain electrode thereover, and a second insulating film thereover are included. The source and the drain electrodes 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 includes copper. The first and the third conductive films each include an oxide conductive film. An end portion of the first conductive film includes a region located outward from an end portion of the second conductive film. The third conductive film covers a top surface and a side surface of the second conductive film and includes a region in contact with the first conductive film.