Nitride Transistor Threshold Voltage Control via Ion Doping
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Solution Overview
Problem
Conventional nitride semiconductor transistors face challenges in achieving a high threshold voltage necessary for normally-off operation due to the introduction of positive charges in the gate dielectric, which reduces the transistor's ability to function as a normally-off device.
Innovation Solution
Introducing negatively charged ions or electronegative chemical species into the gate dielectric to counteract positive charges, increasing the threshold voltage and enabling the transistor to operate in enhancement mode by modulating the concentration and distribution of these ions within the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitride semiconductor transistors are fabricated with gate dielectric, then the device structure is formed, but positive charges in the gate dielectric reduce the threshold voltage preventing normally-off operation
Solution Approach 1:
The patent converts the harmful positive charges in the gate dielectric into a beneficial effect by introducing negatively charged ions that neutralize these positive charges. This transforms the harmful charge accumulation into a useful threshold voltage enhancement mechanism, enabling normally-off operation while utilizing the existing dielectric structure.
Solution Approach 2:
The patent changes the electrical parameters of the gate dielectric by controlling the concentration and distribution of negatively charged ions within the dielectric layer. By adjusting ion concentration, the threshold voltage can be precisely tuned to achieve the desired normally-off operation characteristics.
2Reliability
If negatively charged ions are introduced into the gate dielectric to increase threshold voltage, then normally-off operation is achieved, but the device structure and fabrication process become more complex
Solution Approach 1:
The gate dielectric serves multiple functions: it provides electrical insulation between the gate electrode and semiconductor channel, and simultaneously acts as a medium for containing negatively charged ions that control the threshold voltage. This multi-functionality eliminates the need for separate threshold control structures, reducing overall device complexity.
Solution Approach 2:
The negatively charged ions act as an intermediary mechanism within the gate dielectric, mediating between the fixed dielectric structure and the variable threshold voltage requirement. This intermediary approach allows flexible threshold voltage control without modifying the fundamental device architecture.
3Reliability
If high concentration of negatively charged ions is used to ensure normally-off operation, then threshold voltage is sufficiently high, but manufacturing precision requirements increase
Solution Approach 1:
The negatively charged ions are introduced into the gate dielectric during the dielectric formation process itself, before subsequent device fabrication steps. This preliminary action ensures uniform ion distribution and eliminates the need for precise post-fabrication ion implantation, reducing manufacturing precision requirements.
Solution Approach 2:
The gate dielectric material itself provides the mechanism for threshold voltage control through inherent charge trapping or ion incorporation during standard deposition processes. The dielectric structure serves its own threshold control function without requiring external control mechanisms, reducing manufacturing complexity and precision requirements.
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 introduction of negatively charged ions effectively increases the threshold voltage of nitride transistors to values suitable for normally-off operation, enhancing the reliability and design simplicity of power electronics by ensuring the transistors are off in the absence of a gate voltage.
Implementation Method 1
At least a portion of the dielectric region comprises a chemical species to neutralize positive charges of the dielectric region. The chemical species includes negatively charged ions and/or electronegative chemical species.
Implementation Method 2
A concentration of the chemical species in the at least a portion of the dielectric region increases along a line from the first surface to the second surface or is uniform between the first surface and the second surface.
Data Source
AI summary
A field effect transistor that has a source, a drain, a gate, a semiconductor region, and a dielectric region. The dielectric region is located between the semiconductor region and the gate. Negatively charged ions are located within the dielectric layer underneath the gate.