Vertical ESD Protection Device Trench Isolation

Solution Overview

Problem

Conventional lateral diodes for electrostatic discharge (ESD) protection in integrated circuits are inadequate for handling large currents and high voltage strikes, as they have limited current-carrying capacity and large footprints.

Innovation Solution

The development of trench isolated vertical bidirectional ESD protection devices, which involve a multi-layer n-type epitaxial layer structure with a first n-type epitaxial layer having a peak doping level at least double that of a second n-type epitaxial layer, and a p+ layer, along with trench isolation and metal contact formation to enhance ESD protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional lateral diodes are used for ESD protection, then the device structure is simple, but the current-carrying capacity is limited and the footprint is large

Engineering Contradiction:

ImproveESD protection capabilityVSAvoidfootprint

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The patent transitions from a conventional lateral diode structure to a vertical ESD protection device. This dimensional change allows the current flow path to extend vertically through multiple epitaxial layers rather than laterally across the surface, significantly increasing current-carrying capacity while reducing the device footprint to a compact vertical column structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The n-type epitaxial layer is divided into multiple segments with different doping levels (first n-type layer with peak doping level at least double that of the second n-type layer). This segmentation creates optimized regions for different functions: the highly doped first layer provides low resistance current path, while the lightly doped second layer enables voltage breakdown control and snap-back-free operation.

Inventive Principle:

Principle #1Segmentation

2Reliability

If conventional lateral diodes are used for ESD protection, then the device structure is simple, but the current-carrying capacity is limited

Engineering Contradiction:

Improvecurrent-carrying capacityVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from a conventional lateral diode structure to a vertical ESD protection device. This dimensional change allows the current flow path to extend vertically through multiple epitaxial layers rather than laterally across the surface, significantly increasing current-carrying capacity while reducing the device footprint to a compact vertical column structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The device employs a composite structure with multiple n-type epitaxial layers having different doping levels, combined with a p-type substrate and p+ layer. This composite material approach creates optimized regions for different functions: the highly doped first n-type layer provides low resistance current path, while the lightly doped second n-type layer enables voltage breakdown control.

Inventive Principle:

Principle #40Composite materials

3Reliability

If a multi-layer n-type epitaxial layer structure is used, then ESD protection capability is improved, but the manufacturing process complexity increases

Engineering Contradiction:

ImproveESD protection capabilityVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The n-type epitaxial layer is divided into multiple segments with different doping levels (first n-type layer with peak doping level at least double that of the second n-type layer). This segmentation creates optimized regions for different functions: the highly doped first layer provides low resistance current path, while the lightly doped second layer enables voltage breakdown control and snap-back-free operation.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8664080B2Vertical ESD protection device

Publication Date: 2014.03.04 TEXAS INSTRUMENTS INC

AI summary

A method for forming a vertical electrostatic discharge (ESD) protection device includes depositing a multi-layer n-type epitaxial layer on a substrate having p-type surface including first epitaxial depositing to form a first n-type epitaxial layer on the p-type surface, and second epitaxial depositing to form a second n-type epitaxial layer formed on the first n-type epitaxial layer. The first type epitaxial layer has a peak doping level which is at least double that of the second n-type epitaxial layer. A p+ layer is formed on the second n-type epitaxial layer. An etch step etches through the p+ layer and multi-layer n-type epitaxial layer to reach the substrate to form a trench. The trench is filled with a filler material to form a trench isolation region. A metal contact is formed on the p+ layer for providing contact to the p+ layer.