Oxide Semiconductor Transistor Insulating Stack for Leakage Current Control
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Solution Overview
Problem
Semiconductor devices with oxide semiconductor films face reliability issues due to water and hydrogen contamination, leading to increased leakage current and contact resistance, particularly because of oxygen vacancies and the slow etching of aluminum oxide barrier films which generates etching residues.
Innovation Solution
A manufacturing method involving a stacked-layer insulating film structure with a first insulating film that releases oxygen by heating and a second insulating film with high gas barrier properties, where the films are subjected to argon plasma or reverse sputtering to reduce etching residues and improve contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed to reduce water and hydrogen in the base film, then oxygen can be supplied to the oxide semiconductor film, but oxygen is also released together with water and hydrogen
Solution Approach 1:
An aluminum oxide barrier film is introduced as an intermediary layer between the base film and the oxide semiconductor film. This barrier film prevents oxygen released during heat treatment from escaping, while still allowing oxygen to be supplied to the oxide semiconductor film when needed. The barrier film acts as a mediator that controls oxygen movement in both directions.
Solution Approach 2:
The aluminum oxide barrier film is formed in advance before heat treatment. This preliminary action ensures that when heat treatment is subsequently performed to reduce water and hydrogen, the oxygen released is retained by the barrier film rather than being lost, thus maintaining oxygen supply to the oxide semiconductor film.
2Reliability
If an aluminum oxide film is provided as a barrier film to prevent oxygen release, then oxygen can be retained, but it takes a long time to etch the aluminum oxide film
Solution Approach 1:
The insulating film structure is designed with different layers having different etchability characteristics. The first insulating film is made of material that is easily etched, while the aluminum oxide barrier film is positioned strategically to provide protection where needed. This local differentiation allows selective etching without requiring the entire structure to be difficult to process.
Solution Approach 2:
The insulating film is segmented into multiple layers with different functions: a first insulating film for easy etching and opening formation, and an aluminum oxide barrier film for oxygen retention. This segmentation allows each layer to optimize its specific function without compromising the other.
3Ease of manufacture
If the insulating film is etched to form opening portions, then contact holes can be formed, but many etching residues are generated in the opening portion
Solution Approach 1:
The aluminum oxide barrier film, which has poor chemical reactivity and is difficult to etch, is converted from a manufacturing obstacle into a beneficial element. By positioning it as the second insulating film, it provides a protective function that prevents oxygen loss during heat treatment, transforming its etching difficulty into an advantage for oxygen retention.
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 method results in semiconductor devices with reduced leakage current and low contact resistance, enhancing the reliability and performance of oxide semiconductor transistors by minimizing water and hydrogen content and optimizing the etching process.
Implementation Method 1
the first insulating film is an insulating film in which part of oxygen is released by heating
Implementation Method 2
exposing the opening portion of the first insulating film and the second insulating film to argon plasma
Implementation Method 3
subjecting the opening portion of the first insulating film and the second insulating film to reverse sputtering
Data Source
AI summary
A first insulating film in contact with an oxide semiconductor film and a second insulating film are stacked in this order over an electrode film of a transistor including the oxide semiconductor film, an etching mask is formed over the second insulating film, an opening portion exposing the electrode film is formed by etching a portion of the first insulating film and a portion of the second insulating film, the opening portion exposing the electrode film is exposed to argon plasma, the etching mask is removed, and a conductive film is formed in the opening portion exposing the electrode film. The first insulating film is an insulating film whose oxygen is partly released by heating. The second insulating film is less easily etched than the first insulating film and has a lower gas-permeability than the first insulating film.