Trench Transistor Structure with Planarized ESD Protection

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Solution Overview

Problem

Current trench MOSFET structures face issues with undesired metal bridging due to height differences between the trench MOSFET device and the ESD protection device, leading to reduced device reliability and product yield, especially when the planarization of subsequent dielectric layers is inadequate.

Innovation Solution

The trench transistor structure incorporates both the transistor device and ESD protection device as trench structures, with the ESD protection device having a main body layer in a second trench that is planarized and isolated from the substrate, allowing for improved planarization of dielectric layers by ensuring the electrode and main body layer are formed by the same material and have specific conductive types, thereby reducing height differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the ESD protection device is formed on the substrate as a separate structure, then the ESD protection function is provided, but a height difference is created between the trench MOSFET device and the ESD protection device leading to metal bridging

Engineering Contradiction:

ImproveESD protection functionVSAvoidplanarization of dielectric layer

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The ESD protection device is merged with the trench MOSFET device by forming both structures within the same substrate and using the same trench formation process. The ESD protection device shares the trench structure with the MOSFET, eliminating the height difference between separate devices and enabling better planarization of subsequent dielectric layers.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The ESD protection device is integrated into the vertical dimension of the trench structure rather than being formed as a separate planar structure on the substrate surface. By utilizing the trench depth dimension, both the MOSFET and ESD device achieve similar elevation levels, resolving the height difference issue.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If the ESD protection device is formed separately on the substrate, then ESD protection is provided, but product yield is reduced due to metal bridging in interconnect process

Engineering Contradiction:

ImproveESD protection functionVSAvoidproduct yield

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The ESD protection device is integrated with the trench MOSFET device structure, ensuring both devices have similar heights and enabling proper planarization of dielectric layers. This eliminates metal bridging defects in the interconnect process, thereby improving product yield while maintaining ESD protection functionality.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11289470B2Method of manufacturing trench transistor structure

Publication Date: 2022.03.29 POWERCHIP SEMICON MFG CORP

AI summary

A method of manufacturing a trench transistor structure including the following steps is provided. A substrate structure is provided. A first region and a second region are defined in the substrate structure. The substrate structure has a first trench located in the first region and a second trench located in the second region. A transistor device is formed in the first region. The transistor device includes an electrode located in the first trench. The electrode and the substrate structure are isolated from each other. An electrostatic discharge (ESD) protection device is formed in the second region. The ESD protection device includes a main body layer located in the second trench. The main body layer has a planarized top surface. PN junctions are located in the main body layer. The main body layer and the substrate structure are isolated from each other.