Oxide Semiconductor Channel Processing for Oxygen Vacancy Control
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Solution Overview
Problem
Oxygen vacancies in the channel region of oxide semiconductor films lead to unstable electric characteristics and normally-on characteristics in transistors, which are exacerbated by gate bias-temperature stress and light irradiation, leading to reliability issues and high power consumption.
Innovation Solution
A method involving the formation of an insulating film over an oxide semiconductor film, followed by adding oxygen to a buffer film and conductive film, and using these as masks to introduce impurity elements, thereby reducing oxygen vacancies and stabilizing the transistor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen vacancies are present in the channel region of oxide semiconductor film, then the transistor exhibits normally-on characteristics and low resistance, but the electric characteristics become unstable and reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by forming an insulating film containing oxygen (such as silicon oxide or aluminum oxide) over the oxide semiconductor film before subsequent processing steps. This insulating film serves as an oxygen source that can compensate for oxygen vacancies in the channel region during heat treatment, thereby preventing the formation of harmful oxygen vacancies and ensuring stable transistor characteristics from the outset
Solution Approach 2:
The patent utilizes parameter changes by controlling the oxygen partial pressure and temperature during heat treatment processes. By adjusting these parameters, oxygen is supplied from the insulating film to the oxide semiconductor film, filling oxygen vacancies in the channel region and transforming the material properties to achieve stable electric characteristics and reliable transistor operation
2Reliability
If impurity elements are added to reduce oxygen vacancies, then electric characteristics stabilize, but the manufacturing process complexity increases
Solution Approach 1:
The patent employs an insulating film containing oxygen as an intermediary substance between the oxide semiconductor film and the external environment. This intermediary film serves dual purposes: it acts as a barrier to prevent oxygen escape during manufacturing processes and as an oxygen source to fill vacancies, thereby stabilizing electric characteristics without requiring complex impurity addition processes
Solution Approach 2:
The patent applies the discarding and recovering principle by utilizing the oxygen already present in the insulating film (such as silicon oxide or aluminum oxide layers) that would otherwise be wasted. During heat treatment, this oxygen is recovered and supplied to the oxide semiconductor film to fill oxygen vacancies, achieving stabilization of electric characteristics while avoiding the need for additional complex processing 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 method results in a semiconductor device with stable electric characteristics, improved reliability, and reduced power consumption by minimizing oxygen vacancies and hydrogen concentration, ensuring positive threshold voltage and low off-state current.
Implementation Method 1
oxygen is added to the buffer film and the insulating film
Implementation Method 2
an impurity element is added to the oxide semiconductor film using the conductive film as a mask
Data Source
AI summary
Provided is a method for manufacturing a semiconductor device whose electric characteristics are prevented from being varied and whose reliability is improved. In the method, an insulating film is formed over an oxide semiconductor film, a buffer film is formed over the insulating film, oxygen is added to the buffer film and the insulating film, a conductive film is formed over the buffer film to which oxygen is added, and an impurity element is added to the oxide semiconductor film using the conductive film as a mask. An insulating film containing hydrogen and overlapping with the oxide semiconductor film may be formed after the impurity element is added to the oxide semiconductor film.