Vertical Trigger SCR Structure for Faster SOI ESD Protection

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Solution Overview

Problem

Existing semiconductor structures face challenges with high power dissipation, lower switching speed, and poor voltage scaling due to the Darlington effect in bulk string diodes used for RF-switches, which also result in inadequate electrostatic discharge (ESD) protection levels.

Innovation Solution

A trigger silicon controlled rectifier (SCR) circuit is integrated in a semiconductor-on-insulator (SOI) substrate with a single crystalline semiconductor trigger element between the anode and cathode of the SCR, eliminating the Darlington effect through vertical integration and using polysilicon trigger diodes stacked on top, thereby reducing area requirements and maintaining efficient ESD protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If a separate trigger diode is used in bulk region, then the SCR can be triggered, but the area usage increases and power dissipation increases due to Darlington effect

Engineering Contradiction:

Improvearea usageVSAvoidpower dissipation

Core Design Contradiction:

Area of moving objectVSLoss of energy

Solution Approach 1:

The trigger diode and SCR are merged into a single vertically integrated structure where the trigger diode is formed within the SOI layer above the SCR. This eliminates the need for separate lateral connections and reduces the overall device area while eliminating the Darlington effect that causes excessive power dissipation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The structure transitions from a lateral configuration to a vertical configuration by forming the trigger diode within the SOI layer above the SCR. This vertical integration reduces the footprint area and improves current flow efficiency by eliminating lateral current paths that contribute to the Darlington effect.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Speed

If trigger diode is laterally connected with SCR in bulk region, then triggering function is achieved, but switching speed decreases

Engineering Contradiction:

Improveswitching speedVSAvoidconnection structure

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The lateral connection between trigger diode and SCR is replaced by a vertical integration where the trigger diode is formed within the SOI layer directly above the SCR. This vertical arrangement shortens the current path and eliminates the complex lateral interconnections, thereby improving switching speed.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If bulk string diode is used for ESD protection, then protection function is provided, but voltage scaling deteriorates and harmonics distortion increases

Engineering Contradiction:

ImproveESD protection levelVSAvoidharmonics distortion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The device utilizes a composite structure combining SOI material for the trigger diode and bulk silicon for the SCR. This composite architecture provides effective ESD protection while maintaining good voltage scaling characteristics and reducing harmonics distortion through the optimized vertical current flow path.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20240096874A1Trigger silicon controlled rectifier

Publication Date: 2024.03.21 GLOBALFOUNDRIES US INC

AI summary

The present disclosure relates to a structure including a trigger element within a semiconductor-on-insulator (SOI) substrate, and a silicon controlled rectifier (SCR) under a buried insulator layer of the SOI substrate. The trigger element is between an anode and a cathode of the SCR.