Oxide Semiconductor Transistor Nitrogen Release Heat Treatment
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Solution Overview
Problem
Nitrogen contamination in oxide semiconductor films leads to increased carrier density and fluctuating electrical characteristics in transistors, particularly causing a negative shift in threshold voltage and instability over time or under bias-temperature stress tests.
Innovation Solution
A method involving the formation of a nitrogen-containing oxide insulating film over an oxide semiconductor film, followed by heat treatment to release nitrogen, reducing the nitrogen concentration to specific levels (≥1×10^18 atoms/cm^3 and ≤1×10^20 atoms/cm^3) to minimize defects and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen-containing oxide insulating film is formed to protect the oxide semiconductor film, then the oxide semiconductor film is protected from contamination, but nitrogen transfers to the oxide semiconductor film causing increased carrier density and threshold voltage shift
Solution Approach 1:
The patent removes nitrogen from the oxide insulating film through heat treatment to eliminate the harmful nitrogen transfer to the oxide semiconductor film, while retaining the protective function of the insulating film
Solution Approach 2:
The patent changes the nitrogen concentration parameter in the oxide insulating film from high to low levels through heat treatment, transforming it from a nitrogen-containing film that causes harm to a low-nitrogen film that provides protection without nitrogen transfer
2Object-generated harmful factors
If heat treatment is applied to release nitrogen from the oxide insulating film, then nitrogen concentration is reduced, but the process requires additional manufacturing steps and time
Solution Approach 1:
The patent performs heat treatment to release nitrogen from the oxide insulating film at an appropriate stage in the manufacturing process, preparing the film for subsequent use as a protective layer without nitrogen contamination
3Productivity
If plasma CVD method is used to form the oxide insulating film, then the film formation efficiency is high, but plasma damage is caused to the oxide semiconductor film creating oxygen vacancies
Solution Approach 1:
The patent removes oxygen vacancies from the oxide semiconductor film through heat treatment in an oxygen atmosphere, eliminating the damage caused by plasma CVD processing while maintaining the benefits of efficient film formation
4Ease of manufacture
If nitrogen is present in the oxide insulating film, then the film can be formed easily, but electrical characteristics fluctuate and reliability decreases under bias-temperature stress
Solution Approach 1:
The patent changes the nitrogen concentration parameter in the oxide insulating film through heat treatment, reducing it to levels that prevent electrical characteristic fluctuations while maintaining ease of manufacture
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 approach effectively suppresses changes in electrical characteristics and enhances the reliability of transistors by reducing nitrogen transfer to the oxide semiconductor film, stabilizing the threshold voltage and improving on-state current consistency across different drain voltages.
Implementation Method 1
a step of releasing nitrogen from the nitrogen-containing oxide insulating film by heat treatment
Data Source
AI summary
The amount of nitrogen that is transferred to an oxide semiconductor film of a transistor including the oxide semiconductor film is reduced. In addition, in a semiconductor device which includes a transistor including an oxide semiconductor film, change in electrical characteristics is suppressed and reliability is improved. After a nitrogen-containing oxide insulating film is formed over a transistor including an oxide semiconductor film where a channel region is formed, nitrogen is released from the nitrogen-containing oxide insulating film by heat treatment. Note that the nitrogen concentration which is obtained by secondary ion mass spectrometry (SIMS) is greater than or equal to the lower limit of detection by SIMS and less than 3×1020 atoms/cm3.