Backside Metal Gate Cut for Isolating Nanostructure Gate Electrodes

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Solution Overview

Problem

Forming gate terminals with desired characteristics in nanostructure transistors is challenging, leading to difficulties in reducing parasitic capacitance and achieving improved switching speed and reduced power consumption in integrated circuits.

Innovation Solution

A backside gate cutting process is employed to selectively remove portions of the gate cap metal between adjacent gate electrodes, electrically isolating some gate electrodes and reducing parasitic capacitance by minimizing the amount of gate metal between them.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gate terminals are formed in nanostructure transistors, then transistor functionality is achieved, but parasitic capacitance increases

Engineering Contradiction:

Improvetransistor functionalityVSAvoidparasitic capacitance

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes portions of the gate cap metal between adjacent gate electrodes through a backside gate cutting process. This extraction reduces the amount of conductive material present, thereby reducing parasitic capacitance while maintaining the necessary gate terminal functionality for transistor operation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The continuous gate cap metal layer is segmented into discrete portions by removing sections between adjacent gate electrodes. This segmentation isolates the gate terminals electrically, reducing capacitive coupling between them while preserving individual gate functionality for controlling respective nanostructure channels.

Inventive Principle:

Principle #1Segmentation

2Object-generated harmful factors

If gate metal is reduced between adjacent gate electrodes, then parasitic capacitance decreases, but manufacturing complexity increases

Engineering Contradiction:

Improveparasitic capacitanceVSAvoidmanufacturing process

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

Instead of performing gate cutting from the front side where gate terminals are accessible, the patent inverts the approach by accessing and cutting the gate cap metal from the backside of the substrate. This inversion simplifies the manufacturing process by allowing gate electrode isolation to be performed after substrate thinning, avoiding complex front-side patterning operations.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The substrate is thinned to expose the backside surface before performing the gate cutting operation. This preliminary action of substrate thinning prepares the structure for subsequent gate electrode isolation by providing access to the gate cap metal from the backside, simplifying the overall manufacturing sequence.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250366158A1Integrated circuit with backside metal gate cut for reduced coupling capacitance

Publication Date: 2025.11.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An integrated circuit includes a first nanostructure transistor and a second nanostructure transistor. The first and second nanostructure each include gate electrodes. A backside trench separates the first gate electrode from the second gate electrode. A bulk dielectric material fills the backside trench. A gate cap metal electrically connects the first gate electrode to the second gate electrode.