Oxide Semiconductor Film Deposition for Low-Impurity Transistor Reliability
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Solution Overview
Problem
Transistors formed using oxide semiconductors often suffer from reliability issues due to impurities like hydrogen, nitrogen, and carbon, which can lead to shifts in threshold voltage and inhibit crystalline region formation, resulting in inferior performance compared to amorphous silicon transistors.
Innovation Solution
A method for forming an oxide semiconductor film with low impurity concentrations, specifically using a CAAC-OS film with aligned crystal regions and amorphous phases, and a deposition process that minimizes impurity entry through a high-purity gas environment and advanced vacuum pumping techniques, along with heat treatment to enhance crystallinity and reduce impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a sputtering method is used to form an oxide semiconductor film, then the film can be formed efficiently, but impurities such as hydrogen, nitrogen, and carbon may be incorporated into the film, leading to reduced reliability
Solution Approach 1:
The patent employs a sputtering method performed in a high-purity oxygen atmosphere with controlled impurity levels (hydrogen, nitrogen, carbon). By maintaining an inert-like oxygen environment during deposition, the method minimizes contamination while efficiently forming the oxide semiconductor film, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent optimizes sputtering parameters including oxygen flow rate, pressure, and power to control film quality. By adjusting these parameters, the method achieves both high deposition efficiency and low impurity incorporation, simultaneously improving productivity and transistor reliability
2Ease of manufacture
If hydrogen and nitrogen are present in the oxide semiconductor film, then the film formation process is simplified, but the threshold voltage shifts in the negative direction and reliability is reduced
Solution Approach 1:
The patent uses a high-purity oxygen atmosphere during sputtering to prevent hydrogen and nitrogen incorporation. This approach maintains manufacturing simplicity while ensuring transistor reliability by avoiding threshold voltage shifts caused by impurity-induced carrier generation
Solution Approach 2:
The patent implements monitoring and control of impurity levels during the sputtering process. By providing feedback on hydrogen, nitrogen, and carbon concentrations, the system adjusts process parameters to maintain reliability while keeping the manufacturing process straightforward
3Ease of manufacture
If nitrogen molecules and carbon dioxide molecules are present in the oxide semiconductor film, then the deposition process is easier, but crystalline region formation is inhibited
Solution Approach 1:
The patent employs a high-purity oxygen atmosphere that excludes nitrogen and carbon dioxide. This approach maintains easy deposition conditions while enabling proper crystalline region formation by preventing large-molecule impurities from disrupting the crystal lattice structure
Solution Approach 2:
The patent optimizes deposition parameters such as oxygen pressure and temperature to facilitate crystalline region formation. By adjusting these parameters, the method achieves both ease of manufacture and high manufacturing precision in terms of crystalline structure development
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 highly reliable transistor with stable threshold voltage and improved crystallinity, reducing the impact of impurities and enhancing semiconductor device performance.
Implementation Method 1
a sputtering method is considered the most suitable as a method for forming a film of the oxide semiconductor
Implementation Method 2
heat treatment to enhance crystallinity and reduce impurities
Implementation Method 3
a CAAC-OS film with aligned crystal regions and amorphous phases
Data Source
AI summary
The impurity concentration in the oxide semiconductor film is reduced, and a highly reliability can be obtained.