SiC MOSFET Channel Length Reduction via Barrier Layer
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Solution Overview
Problem
The manufacturing of silicon carbide (SiC) MOSFETs faces challenges in reducing cell size and increasing current density due to the low diffusion coefficient of SiC, which limits the use of standard self-aligned processes, and requires separate masks for forming P+ contact regions, increasing costs.
Innovation Solution
A method involving a self-aligned process with a patterned deposition layer and thermal oxidation to form a barrier layer, followed by ion implantation for source and contact regions, and a high-temperature annealing process to activate impurities, allowing for the formation of SiC MOSFETs with reduced channel length and optimized doping profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If standard self-aligned process is used, then manufacturing simplicity is maintained, but channel length cannot be reduced below 0.5 um due to lithography accuracy limits
Solution Approach 1:
The patent applies preliminary action by forming the barrier layer patterned deposition layer before the actual channel formation process. This preliminary structure serves as a self-aligned mask that defines the channel region boundaries, enabling precise channel length control without relying solely on lithography resolution. The barrier layer is formed and patterned in advance to guide subsequent ion implantation and material deposition steps, ensuring that the channel length can be reduced below conventional lithography limits while maintaining manufacturing precision.
2Manufacturing precision
If separate masks are used for forming P+ contact regions, then doping precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the functions of multiple masks into a single integrated barrier layer structure. The barrier layer patterned deposition layer simultaneously serves as the mask for forming both the channel region and the P+ contact regions. By combining these functions into one structure, the patent eliminates the need for separate masks while maintaining precise doping control. The merged structure is formed through a unified process sequence that defines multiple regions of interest without requiring additional masking steps.
Solution Approach 2:
The barrier layer patterned deposition layer performs multiple functions: it acts as a mask for channel formation, defines the P+ contact region boundaries, and serves as a protective layer during subsequent processing steps. This multi-functional structure replaces what would traditionally require multiple specialized masks, each designed for a specific purpose. The universal nature of this single structure simplifies the manufacturing process while maintaining the precision needed for different doping regions.
3Productivity
If channel length is reduced to increase current density, then device performance is improved, but manufacturing difficulty increases due to low diffusion coefficient of SiC
Solution Approach 1:
The patent replaces the diffusion-based material introduction process with ion implantation. Instead of relying on thermal diffusion, which is inefficient in SiC due to its low diffusion coefficient, the patent uses directed ion implantation to introduce dopants into the channel region. This substitution of the material introduction mechanism allows for precise dopant placement in ultra-short channels without being constrained by diffusion length limitations. The ion implantation process can achieve the required doping profiles in channels shorter than what would be possible with conventional diffusion methods.
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 enables the production of SiC MOSFETs with shorter channel lengths and higher current densities, reducing manufacturing costs and improving device performance by allowing for precise control of doping and region formation without the need for additional masks.
Implementation Method 1
forming a patterned first barrier layer on a first surface of the substrate; the first barrier layer includes a first portion and a second portion
Implementation Method 2
forming a source region with a first doping type in the substrate; forming a base region with a second doping type and a contact region with a second doping type
Implementation Method 3
a high-temperature annealing process to activate impurities
Data Source
AI summary
A method of making a silicon carbide MOSFET device can include: providing a substrate with a first doping type; forming a patterned first barrier layer on a first surface of the substrate; forming a source region with a first doping type in the substrate; forming a base region with a second doping type and a contact region with a second doping type in the substrate, and forming a gate structure. The first barrier layer can include a first portion and a second portion, the first portion can include a semiconductor layer and a removable layer different from the semiconductor layer, and the second portion can only include the removable layer.