SiC MOSFET Channel Formation Without Ion Implantation
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Solution Overview
Problem
Silicon carbide (SiC) MOSFETs face a challenge with lower carrier mobility compared to silicon-based MOSFETs, primarily due to disruptions in crystallinity and increased scattering from ion implantation-induced defects and surface roughness.
Innovation Solution
A semiconductor device structure is developed with a SiC layer featuring a channel region formed in the front surface region where no impurity ions are implanted, reducing crystallinity disruption and scattering, and including specific impurity concentrations and layer configurations to enhance carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is performed to form the channel region in SiC MOSFET, then the channel can be formed, but carrier mobility decreases due to crystallinity disruption and scattering
Solution Approach 1:
The patent extracts the harmful effect of ion implantation by forming the channel region in the front surface region where no impurity ions are implanted. The channel formation is achieved through selective removal of the gate insulating film in the front surface region, exposing the SiC substrate directly to form the channel without ion implantation damage.
Solution Approach 2:
The patent applies different processing conditions to different regions of the SiC substrate. The front surface region (where the channel forms) receives no ion implantation, while other regions may receive ion implantation for different purposes. This local differentiation preserves carrier mobility in the channel region while allowing other regions to be optimized for their specific functions.
2Quantity of substance
If impurity ions are implanted in the front surface region, then doping can be achieved, but surface roughness increases causing increased scattering
Solution Approach 1:
The patent removes the gate insulating film selectively in the front surface region to expose the SiC substrate, allowing direct channel formation without ion implantation. This extraction of the insulating film in the critical channel region eliminates the source of surface roughness and scattering that would result from ion implantation in this area.
Solution Approach 2:
The patent segments the device into distinct regions with different structures: the front surface region with direct SiC channel formation (no gate insulating film), and other regions with gate insulating film coverage. This segmentation allows optimal processing for each region, preventing surface roughness in the channel area while maintaining necessary insulation elsewhere.
3Reliability
If ion implantation is used to form the channel, then channel region can be created, but crystallinity is disrupted reducing carrier mobility
Solution Approach 1:
The patent extracts the gate insulating film selectively in the front surface region to allow direct channel formation on the SiC substrate. By removing the insulating film in this specific region, the channel can form through natural silicon diffusion without requiring ion implantation, thereby preserving the crystalline structure and high carrier mobility.
Data Source
AI summary
A semiconductor device according to an embodiment includes a SiC layer having a first plane and a second plane, a gate insulating film provided on the first plane, a gate electrode provided on the gate insulating film, a first SiC region of a first conductivity type provided in the SiC layer, a second SiC region of a second conductivity type provided in the first SiC region, a third SiC region of the first conductivity type provided in the second SiC region, and a fourth SiC region of the first conductivity type provided between the second SiC region and the gate insulating film, the fourth SiC region interposed between the second SiC regions, and the fourth SiC region provided between the first SiC region and the third SiC region.