SiC Buried Implant Profiles for Uniform Deep Channel Doping
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Solution Overview
Problem
Silicon carbide (SiC) junction field effect transistors (JFETs) are normally-on devices, which can be a drawback, and achieving uniform doping profiles for channel regions is challenging, leading to variations in threshold voltage and on-state resistance, especially when using epitaxial doping or random implants.
Innovation Solution
The method involves forming a buried implanted region in a silicon carbide semiconductor layer using channeled implants along specific crystallographic axes, combining multiple implants to achieve a uniform doping profile with a de-channeled and channeled peak, reducing doping concentration variation and extending the channel depth while maintaining low on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxial doping or random implants are used to form channel regions, then doping can be applied, but uniform doping profiles are difficult to achieve, leading to variations in threshold voltage and on-state resistance
Solution Approach 1:
The patent divides the doping process into multiple sequential ion implantation steps, each targeting specific depth ranges. By segmenting the overall doping task into discrete implantation events with controlled energies and doses, the method achieves uniform doping profiles that eliminate threshold voltage variations while maintaining manufacturing precision.
2Length of stationary object
If ion implantation is used to form deep implanted regions, then channel depth can be extended, but doping concentration uniformity along the channel length becomes challenging
Solution Approach 1:
The patent systematically changes ion implantation parameters including energy, dose, and crystallographic axis orientation across multiple steps. By adjusting these parameters to create complementary doping profiles that overlap and merge, the method achieves uniform doping concentration along extended channel depths, resolving the contradiction between depth extension and uniformity maintenance.
3Manufacturing precision
If multiple ion implantation steps are performed to achieve uniform doping, then doping profile control improves, but manufacturing process complexity increases
Solution Approach 1:
The patent merges multiple ion implantation steps into an integrated process sequence where each step complements the others. By combining the steps to form a unified doping strategy with overlapping profiles that merge into a uniform distribution, the method achieves precise doping profile control while managing process complexity through systematic integration.
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 results in a substantially uniform doping profile along the channel length and across multiple devices, reducing threshold voltage variation and on-state resistance, enabling deeper channel regions with improved reliability and performance.
Implementation Method 1
implanting first dopant ions having a first conductivity type into the silicon carbide semiconductor layer along a first axis at a first dose and first implant energy to form a first channelized doping profile
Implementation Method 2
annealing the silicon carbide semiconductor layer after implanting the first and/or second dopant ions to activate the first and second dopant ions
Data Source
AI summary
A method of forming a buried implanted region in a silicon carbide semiconductor layer includes implanting first dopant ions into the silicon carbide semiconductor layer at a first dose and first implant energy to form a first channelized doping profile having a first de-channeled peak at a first depth in the silicon carbide semiconductor layer and a first channeled peak at a second depth that is greater than the first depth. Second dopant ions are implanted into the silicon carbide semiconductor layer at a second dose and second implant energy to form a second channelized doping profile. The second channelized doping profile has a second channeled peak at a third depth in the silicon carbide semiconductor layer that is between the first depth and the second depth. The first channelized doping profile and the second channelized doping profile form a combined doping profile that defines the buried implanted region.