SiC MOSFET Gate Electrode Work Function Adjustment
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Solution Overview
Problem
There is a need to reduce the specific on-resistance of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) without significantly affecting the threshold voltage, as existing methods either decrease the on-resistance at the cost of altering the threshold voltage or fail to effectively lower the on-resistance.
Innovation Solution
The solution involves reducing the implantation dose of dopant atoms in the body region and adjusting the work function of the gate electrode to counteract the reduction in threshold voltage, achieved by forming a gate dielectric and a gate electrode with a first electrode layer, implanting work function adjusting atoms, and a second electrode layer on top, ensuring the work function is greater than 4.1 electron volts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the implantation dose of dopant atoms in the body region is reduced, then the on-resistance decreases, but the threshold voltage is significantly reduced
Solution Approach 1:
The patent changes the work function parameter of the gate electrode by implanting work function adjusting atoms (such as nitrogen or fluorine) into the gate electrode. This parameter change allows the threshold voltage to be maintained at the desired level even when the dopant implantation dose in the body region is reduced, thereby achieving lower on-resistance without sacrificing threshold voltage stability
Solution Approach 2:
The patent employs a composite gate electrode structure with at least two distinct layers having different material compositions and functions. The first electrode layer provides work function adjustment capabilities, while the second electrode layer contributes to the overall gate performance, enabling independent optimization of threshold voltage and on-resistance parameters
2Loss of energy
If the implantation dose of dopant atoms in the body region is reduced, then the on-resistance decreases, but the voltage blocking capability is compromised
Solution Approach 1:
By adjusting the work function of the gate electrode through implantation of work function adjusting atoms, the patent maintains the threshold voltage at the required level. This parameter adjustment ensures that the voltage blocking capability is preserved even when the dopant implantation dose in the body region is reduced to lower the on-resistance
Solution Approach 2:
The patent performs preliminary adjustment of the gate electrode's work function during the fabrication process, before the device is put into operation. This preliminary action ensures that the threshold voltage is set correctly from the outset, allowing the device to maintain both low on-resistance and adequate voltage blocking capability without requiring post-fabrication adjustments
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 reduces the on-resistance of SiC MOSFETs while maintaining the threshold voltage, thereby improving the device's performance without requiring redesign of drive circuits or compromising voltage blocking capabilities.
Implementation Method 1
a work function of the gate electrode is greater than 4.1 electron volts (eV)
Implementation Method 2
implanting work function adjusting atoms into the first electrode layer
Data Source
AI summary
A silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) and a method for forming a SiC MOSFET are disclosed. In an example, the method includes forming a gate dielectric that adjoins a body region arranged in a semiconductor body, and forming a gate electrode on the gate dielectric. Forming the gate electrode includes forming a first electrode layer, implanting work function adjusting atoms into the first electrode layer, and forming a second electrode layer on the first electrode layer.