Bipolar junction field effect transistor and manufacturing method therefor

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Solution Overview

Problem

The voltage-bearing capacity of the termination area in conventional superjunction IGBTs is limited due to the constraints of the conventional fabrication process, leading to inconsistent device performance and low yield in mass production.

Innovation Solution

A bipolar junction field effect transistor design with vertically extended pillar regions of a second doping type in the drift region, where the pillar regions in the termination area are directly connected to a field oxide layer, allowing for a higher P-type superjunction region and drift region, enhancing the voltage-bearing capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional fabrication process is used for superjunction IGBT, then manufacturing process is simple, but voltage-bearing capacity of termination area is limited

Engineering Contradiction:

Improvevoltage-bearing capacityVSAvoidstructure complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The device is divided into cell area and termination area with different structures. The termination area uses a simplified structure without second epitaxy layer, while the cell area maintains the full superjunction structure with staggered P-N junctions. This segmentation allows optimization of voltage-bearing capacity in the termination area without compromising the switching performance in the cell area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are given different structural characteristics suited to their functional requirements. The termination area has a higher P-type superjunction region directly contacting the field oxide layer for enhanced voltage bearing, while the cell area has the complete superjunction structure for optimal switching. This local differentiation resolves the contradiction between simplicity and voltage-bearing capacity.

Inventive Principle:

Principle #3Local quality

2Reliability

If conventional superjunction structure is used, then manufacturing process is established, but device performance consistency is poor

Engineering Contradiction:

Improvedevice performance consistencyVSAvoidstructure consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The second epitaxy layer is extracted or removed from the termination area, leaving only the P-type superjunction region and drift region. This simplification reduces process complexity and variability in the termination area, leading to more consistent device performance across mass production while maintaining the essential voltage-bearing function.

Inventive Principle:

Principle #2Taking out (Extraction)

3Strength

If higher P-type superjunction region is formed in termination area, then voltage-bearing capacity increases, but conventional process constraints prevent this

Engineering Contradiction:

Improvebreakdown voltageVSAvoidfabrication process flexibility

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Instead of trying to form a higher P-type superjunction region within the constraints of the conventional second epitaxy structure, the approach is inverted by removing the second epitaxy layer entirely from the termination area. This allows the P-type superjunction region to extend higher and directly contact the field oxide layer, achieving enhanced breakdown voltage without process constraints.

Inventive Principle:

Principle #13The other way round (Inversion)

4Length of stationary object

If second epitaxy layer is present in termination area, then conventional structure is maintained, but pillar region height is limited

Engineering Contradiction:

Improvepillar region heightVSAvoidstructure complexity

Core Design Contradiction:

Length of stationary objectVSDevice complexity

Solution Approach 1:

The second epitaxy layer is extracted from the termination area, allowing the P-type superjunction pillar region to extend to the surface and contact the field oxide layer directly. This increases the effective height of the pillar region in the termination area, improving voltage-bearing capacity while simplifying the overall structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS20250220939A1Bipolar junction field effect transistor and manufacturing method therefor

Publication Date: 2025.07.03 SUZHOU WATECH ELECTRONICS CO LTD

AI summary

A bipolar junction field effect transistor includes a drift region of a first doping type, formed in a cell area and a termination area of the bipolar junction field effect transistor; a plurality of pillar regions of a second doping type, extended in a vertical direction, spaced out in a lateral direction, and arranged in a drift region of a first doping type; a first doping type region and a well region of the second doping type formed inversely, successively arranged on the top of the pillar region in the cell area from near to far; and in the termination area, a field oxide layer provided above the drift region of the first doping type, where the pillar region in the termination area is in contact with the field oxide layer.