Backside Wraparound Contact Structure for Low-Capacitance S/D Trenches

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Solution Overview

Problem

Existing semiconductor devices face challenges in increasing the contact area between source/drain trench structures and backside contacts without significantly increasing backside source/drain contact-to-gate capacitance.

Innovation Solution

A semiconductor device is designed with a backside wrap around contact structure that physically contacts and wraps around the lower portion of the source/drain trench structure, increasing the contact area while maintaining minimal capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the contact area between backside contact and source/drain trench structure is increased, then the electrical connection is improved, but the backside source/drain contact-to-gate capacitance increases

Engineering Contradiction:

Improveelectrical connectionVSAvoidbackside source/drain contact-to-gate capacitance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The contact structure transitions from a planar configuration to a three-dimensional wraparound configuration. The backside contact structure extends laterally along the sidewalls of the source/drain trench structure, utilizing the vertical dimension to increase contact area while maintaining horizontal separation from the gate structure, thereby reducing capacitance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The backside contact structure is divided into multiple segments: a bottom surface contact portion and lateral contact portions that wrap around the sidewalls. This segmentation allows the contact to achieve extensive surface area contact with the source/drain trench structure while maintaining spatial separation from the gate structure through the dielectric layer.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the backside contact structure is positioned closer to the gate structure to increase contact area, then the electrical connection is improved, but the capacitance between contact and gate increases

Engineering Contradiction:

Improveelectrical connectionVSAvoidcontact-to-gate capacitance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The dielectric layer serves as an intermediary between the backside contact structure and the gate structure. This intermediate layer provides electrical isolation, allowing the contact structure to be positioned in close proximity to the gate structure for improved electrical connection while preventing direct capacitive coupling through the insulating dielectric material.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250294806A1Backside wrap around contact structure

Publication Date: 2025.09.18 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A semiconductor device is provided that includes a transistor located on a frontside of a dielectric layer, the transistor includes a source/drain region located on a first side of a gate structure and a source/drain trench structure located on a second side of the gate structure. The source/drain trench structure extends through the dielectric layer and has an upper portion located on the frontside of the dielectric layer and a lower portion located on the backside of the dielectric layer. A backside wrap around contact structure is present that physically contacts, and wraps around, the lower portion of the source/drain trench structure.