Trench MOS Net Doping Profile for Breakdown Voltage
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Solution Overview
Problem
TrenchMOS semiconductor devices face challenges in reducing electric fields and improving breakdown voltage and long-term reliability due to uniform doping concentrations, which can lead to device breakdown and reduced performance.
Innovation Solution
A semiconductor device with a layer of doped silicon where the net doping concentration is tailored by compensating donor and acceptor ions, creating a minimum concentration beneath the body region, achieved through ion implantation, allowing for reduced electric fields and enhanced breakdown voltage and on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform doping concentration is used in the epitaxial layer, then the manufacturing process is simple, but the electric fields within the device are high leading to device breakdown and reduced reliability
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration profile where the net doping concentration varies with depth, specifically having a minimum in the region immediately beneath the body region. This is achieved by compensating donor ions (from epitaxial growth) with acceptor ions (from ion implantation) to create a tailored doping profile that reduces electric fields in critical regions while maintaining uniformity in other areas, thus improving reliability without excessive complexity
Solution Approach 2:
The patent changes the doping concentration parameter by varying the net doping concentration as a function of depth through ion implantation. The donor concentration from epitaxial growth is compensated by implanting acceptor ions at specific doses and energies, transforming the uniform doping parameter into a depth-dependent parameter that optimizes electric field distribution and device performance
2Reliability
If graded doping concentration is used to reduce electric fields, then the breakdown voltage and reliability improve, but the epitaxial growth process becomes more complex
Solution Approach 1:
The patent segments the doping process into two distinct stages: (1) epitaxial growth that provides a uniform donor-doped foundation layer, and (2) ion implantation that adds acceptor ions to create the desired non-uniform net doping profile. This segmentation allows each process to be optimized independently, simplifying manufacturing compared to attempting to create graded doping directly during epitaxial growth
Solution Approach 2:
The patent performs preliminary action by first growing the epitaxial layer with uniform donor doping, then subsequently implanting acceptor ions to modify the doping profile. This preliminary establishment of a uniform base layer simplifies the overall process compared to attempting to create the complex graded profile directly during the epitaxial growth phase
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 tailored net doping concentration reduces electric fields near junctions and gate dielectric, increasing breakdown voltage and improving long-term reliability, while allowing for precise control over doping profiles and device performance.
Implementation Method 1
the layer of doped silicon in a region located beneath the body region includes donor ions and acceptor ions forming a net doping concentration within said region by compensation
Implementation Method 2
implanting ions into the layer of silicon, wherein the ions are of a type for doping the layer of silicon to have a second conductivity type, wherein the implanted ions produce a non-constant net doping concentration within the layer of silicon as a function of depth by compensation
Data Source
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AI summary
A semiconductor device and a method of making a semiconductor device. The device includes a semiconductor substrate having a first conductivity type, a layer of doped silicon located on the substrate, a trench extending into the layer of silicon, and a gate electrode and gate dielectric located in the trench. The device also includes a drain region, a body region having a second conductivity type located adjacent the trench and above the drain region, and a source region having the first conductivity type located adjacent the trench and above the body region. The layer of doped silicon in a region located beneath the body region includes donor ions and acceptor ions forming a net doping concentration within said region by compensation. The net doping concentration of the layer of doped silicon as a function of depth has a minimum in a region located immediately beneath the body region.