SiC Schottky Device Junction Termination Structure

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Solution Overview

Problem

Conventional silicon carbide semiconductor devices face challenges in reducing the size of the breakdown voltage structure portion while maintaining a large active region, leading to increased die size and costs due to variations in etching during fabrication.

Innovation Solution

A silicon carbide semiconductor device with a junction termination structure is fabricated by depositing a wide band gap semiconductor layer with a lower impurity concentration, forming a Schottky junction, and positioning the end portions of the metal films within a narrower p+ type region, allowing for a smaller breakdown voltage structure portion and a larger active region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional fabrication process with thick electrode pad is used, then the electrode pad provides sufficient mechanical strength and electrical conductivity, but the etching variation causes the breakdown voltage structure portion to extend further, increasing die size

Engineering Contradiction:

Improveelectrode pad mechanical strength and electrical conductivityVSAvoidbreakdown voltage structure portion area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The electrode pad structure is segmented into multiple layers with different functions: a thick bottom layer (Al-Si alloy, 5μm) providing mechanical strength and electrical conductivity, and a thin top layer (Ti, 0.2μm) forming the Schottky junction. This segmentation allows each layer to be optimized independently, enabling the top layer to be positioned precisely within the narrower p+ region while the bottom layer provides the required mechanical support.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the electrode structure have different thicknesses and materials tailored to local requirements. The Schottky electrode layer is thin (0.2μm) where it forms the junction with the semiconductor, while the electrode pad layer is thick (5μm) where mechanical strength is needed. The p+ region is concentrated in specific areas to provide local field termination without extending the overall breakdown voltage structure portion area.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If the breakdown voltage structure portion is reduced in size, then the active region can be enlarged, but the etching variation in conventional processes makes precise positioning difficult

Engineering Contradiction:

Improveactive region areaVSAvoidpositioning precision of metal films

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent changes the material parameters of the electrode layers to achieve different etching rates. The Ti layer etches much faster than the Al-Si layer in the mixture liquid, creating a self-aligned structure where the Ti ends are exposed beyond the Al-Si ends. This parameter change enables precise positioning of the Schottky junction within the narrower p+ region despite variations in etching conditions.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If a narrower p+ type region is used, then the breakdown voltage structure portion size is reduced, but positioning the metal film end portions becomes more critical

Engineering Contradiction:

Improvebreakdown voltage structure portion areaVSAvoidfabrication process complexity

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The Ti layer is deposited first to define the Schottky junction position, followed by the Al-Si layer that is patterned to extend beyond the Ti layer. This preliminary action of depositing the Ti layer first establishes the critical positioning reference before adding the thicker support layer, simplifying the overall fabrication process despite the narrow p+ region requirements.

Inventive Principle:

Principle #10Preliminary action

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 a smaller breakdown voltage structure region and a larger active region, reducing die size and fabrication complexity while maintaining high-voltage performance.

Implementation Method 1

forming a first metal film forming Schottky junction with the first-conductivity-type wide band gap semiconductor deposition layer

Methodology Applied

Scientific EffectSchottky junction:

Implementation Method 2

a first-conductivity-type wide band gap semiconductor deposition layer is deposited with an impurity concentration lower than the first-conductivity-type wide band gap semiconductor substrate

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS9799732B2Silicon carbide semiconductor device and fabrication method of silicon carbide semiconductor device

Publication Date: 2017.10.24 FUJI ELECTRIC CO LTD

AI summary

A P+ type region, a p-type region, and a P− type region are disposed in a surface layer of a silicon carbide substrate base and are disposed in a breakdown voltage structure portion surrounding an active region to make up an element structure of Schottky junction. The p− type region surrounds the P+ type region and the p-type region to form a junction termination structure. A Schottky electrode forms a Schottky junction with an n-type silicon carbide epitaxial layer. The Schottky electrode and an electrode pad have end portions positioned on the P+ type region and the end portion of the Schottky electrode is exposed from the end portion of the electrode pad. As a result, the region of the breakdown voltage structure portion can be made smaller while the active region can be made larger, and a semiconductor device is easily fabricated.