Oxide Semiconductor Film Oxygen Vacancy Reduction via Bias Sputtering
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Solution Overview
Problem
Transistors using oxide semiconductors face poor electric characteristics due to hydrogen and oxygen vacancies, leading to shifted threshold voltage and increased resistance, making it difficult to reduce oxygen vacancies in the manufacturing process.
Innovation Solution
A semiconductor device is developed with an oxide semiconductor film formed using a sputtering method in an oxygen atmosphere with bias power applied to the substrate, generating self-bias voltage to increase oxygen ion uptake and subsequent heat treatment to remove impurities, thereby reducing oxygen vacancies and hydrogen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sputtering is performed in an oxygen atmosphere with bias power supplied to the substrate, then oxygen content in the oxide semiconductor film is increased and oxygen vacancies are reduced, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the bias power supplied to the substrate during sputtering, adjusting the self-bias voltage to specific ranges (e.g., -100V to -500V) to optimize oxygen ion incorporation. This quantitative parameter control enables precise regulation of oxygen content in the film without requiring complex additional process steps
Solution Approach 2:
The substrate is supplied with bias power to generate self-bias voltage, which automatically attracts oxygen ions during sputtering. This self-service mechanism allows the substrate to actively participate in its own oxygenation process, reducing the need for external oxygen supply systems or complex post-processing steps
2Reliability
If heat treatment is performed to remove impurities from the oxide semiconductor film, then hydrogen content is reduced and electric characteristics improve, but the manufacturing time and energy consumption increase
Solution Approach 1:
The patent performs heat treatment at relatively low temperatures (e.g., 100°C to 550°C) for short durations to remove hydrogen and other impurities from the oxide semiconductor film. This preliminary action is performed immediately after sputtering while the film is still in a favorable state, preventing impurity accumulation and reducing the need for extended high-temperature processing later
Solution Approach 2:
The heat treatment parameters are optimized by controlling temperature, atmosphere (oxygen or inert gas), and duration to achieve effective impurity removal. By adjusting these parameters, the patent achieves good electric characteristics with reduced processing time and energy consumption compared to conventional high-temperature long-duration annealing
3Productivity
If oxygen vacancies are reduced in the oxide semiconductor film, then field-effect mobility increases and leakage current decreases, but the manufacturing process becomes more difficult
Solution Approach 1:
The patent replaces mechanical or chemical oxygen supply methods with a field-based approach by applying bias power to the substrate. This generates an electric field that actively attracts oxygen ions during sputtering, achieving effective oxygen incorporation without complex mechanical oxygen delivery systems or chemical oxygen plasma treatments
Solution Approach 2:
The patent supplies oxygen ions in excess during sputtering by controlling bias power to create strong self-bias voltage. This partial or excessive oxygen supply ensures that even with some oxygen loss during subsequent processing steps, the final film maintains sufficient oxygen content and low vacancy concentration to achieve high field-effect mobility
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 approach results in a transistor with reduced off-state current, increased on-state current, and improved field-effect mobility, achieving favorable electric characteristics by minimizing oxygen vacancies and hydrogen presence in the oxide semiconductor film.
Implementation Method 1
a sputtering method in an oxygen atmosphere with bias power applied to the substrate
Implementation Method 2
bias power applied to the substrate, generating self-bias voltage to increase oxygen ion uptake
Implementation Method 3
subsequent heat treatment to remove impurities
Data Source
AI summary
One embodiment of the present invention is a semiconductor device at least including an oxide semiconductor film, a gate insulating film in contact with the oxide semiconductor film, and a gate electrode overlapping with the oxide semiconductor film with the gate insulating film therebetween. The oxide semiconductor film has a spin density lower than 9.3×1016 spins/cm3 and a carrier density lower than 1×1015/cm3. The spin density is calculated from a peak of a signal detected at a g value (g) of around 1.93 by electron spin resonance spectroscopy. The oxide semiconductor film is formed by a sputtering method while bias power is supplied to the substrate side and self-bias voltage is controlled, and then subjected to heat treatment.