Multi-Drain Power MOS Device with Elliptical Column Regions

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Solution Overview

Problem

Multi-drain power MOS devices face challenges in achieving low output resistance and high breakdown voltage due to variations in epitaxial layer thickness and dopant concentration, leading to increased manufacturing costs and reduced productive yield.

Innovation Solution

The process involves forming P column regions with elliptical portions through selective implantation and diffusion steps on a semiconductor substrate, ensuring charge balance and reducing lateral extension, which allows for reduced epitaxial layer thickness and increased number of layers, thereby achieving low output resistance and high breakdown voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the epitaxial layer thickness is reduced to achieve lower output resistance, then the output resistance decreases, but the breakdown voltage control becomes difficult and manufacturing precision deteriorates

Engineering Contradiction:

Improveoutput resistanceVSAvoidbreakdown voltage control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces column regions with different dopant concentrations at specific locations within the epitaxial layer. These localized doped regions create vertical electric field modulation that enables independent control of output resistance and breakdown voltage, resolving the trade-off between low output resistance and high breakdown voltage by making the dopant concentration non-uniform in the vertical direction

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the dopant concentration parameter locally by forming column regions with higher dopant concentration compared to the surrounding epitaxial layer. This parameter change in specific regions allows the device to achieve low output resistance through enhanced carrier concentration in column regions while maintaining high breakdown voltage through the overall epitaxial layer structure

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple epitaxial layers are formed to reduce output resistance, then the output resistance decreases, but the manufacturing process complexity increases

Engineering Contradiction:

Improveoutput resistanceVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the dopant distribution by forming discrete column regions within the epitaxial layer rather than using a uniformly doped structure. This segmentation allows the device to achieve low output resistance through multiple localized conductive paths while maintaining a single epitaxial layer, thereby reducing manufacturing process complexity compared to forming multiple separate epitaxial layers

Inventive Principle:

Principle #1Segmentation

3Reliability

If the dopant concentration in the epitaxial layer is increased to reduce output resistance, then the output resistance decreases, but the breakdown voltage decreases

Engineering Contradiction:

Improveoutput resistanceVSAvoidbreakdown voltage

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by creating column regions with high dopant concentration only in specific vertical columns rather than uniformly throughout the epitaxial layer. This localized doping provides low output resistance through enhanced conductivity in column regions while the surrounding lower-doped regions maintain the breakdown voltage characteristic, thus resolving the contradiction between low output resistance and high breakdown voltage

Inventive Principle:

Principle #3Local quality

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 enhances charge balance control, reduces manufacturing costs, and improves the scalability of power devices by forming column regions with elliptical shapes, achieving lower output resistance and maintaining high breakdown voltage.

Implementation Method 1

selective implantation and diffusion steps

Methodology Applied

Scientific EffectIon Implantation: Ion Implantation

Implementation Method 2

selective implantation and diffusion steps

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8012832B2Process for manufacturing a multi-drain electronic power device integrated in semiconductor substrate and corresponding device

Publication Date: 2011.09.06 STMICROELECTRONICS SRL

AI summary

A process manufactures a multi-drain power electronic device integrated on a semiconductor substrate of a first type of conductivity whereon a drain semiconductor layer is formed. The process includes: forming a first semiconductor epitaxial layer of the first type of conductivity of a first value of resistivity forming the drain epitaxial layer on the semiconductor substrate, forming first sub-regions of a second type of conductivity by a first selective implant step with a first implant dose, forming second sub-regions of the first type of conductivity by a second implant step with a second implant dose, and forming a surface semiconductor layer. The process also includes forming body regions of the second type of conductivity aligned with the first sub-regions, and carrying out a thermal diffusion process so that the first sub-regions form a single electrically continuous column region aligned and in electric contact with the body regions.