Gate Contact Above Active Region Air Gap Spacer

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Solution Overview

Problem

In integrated circuits, the positioning of gate contacts above the active region is limited due to the presence of parasitic gate-to-contact capacitors, which delays switching speed and requires costly and complex air gap spacer formation, leading to reduced product yields.

Innovation Solution

A method involving gate contact etching to create a gate contact cavity above the active region, followed by forming a conductive gate contact and recessing the sidewall spacer to create an air gap between the new gate cap layer and the original spacer, allowing the gate contact to be positioned vertically above the active region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the gate contact is positioned above the active region, then parasitic capacitance is reduced and switching speed is improved, but complex air gap spacer formation is required which reduces manufacturing precision and product yields

Engineering Contradiction:

Improveswitching speedVSAvoidproduct yields

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The method performs preliminary actions by first forming the gate contact structure above the active region, then subsequently forming the air gap spacer in a controlled sequence. The gate contact cavity is etched and filled with conductive material before the air gap spacer formation process begins, ensuring proper positioning while maintaining manufacturing precision through staged fabrication steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The fabrication process is segmented into distinct stages: first forming the gate contact cavity and filling it with conductive material, then separately forming the air gap spacer structure. This segmentation allows each component to be optimized independently, reducing parasitic capacitance while maintaining manufacturing precision through controlled, separate fabrication steps

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If the gate contact is positioned above the active region, then space is conserved on the integrated circuit, but complex air gap spacer formation is required leading to reduced product yields

Engineering Contradiction:

Improvechip areaVSAvoidproduct yields

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The invention moves the gate contact from a lateral positioning approach to a vertical positioning approach above the active region. By utilizing the vertical dimension rather than lateral space, the method conserves valuable chip area while the air gap spacer provides electrical isolation, enabling this three-dimensional integration without compromising manufacturing precision

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The air gap spacer acts as an intermediary structure that enables the gate contact to be positioned above the active region. This intermediate element provides the necessary electrical isolation and mechanical support, allowing space conservation through vertical positioning while maintaining manufacturing precision through a well-defined fabrication process

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If air gap spacer formation is performed to enable gate contact positioning above the active region, then parasitic capacitance is reduced, but the process becomes costly and complex

Engineering Contradiction:

Improveparasitic capacitanceVSAvoidprocess complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The method extracts and removes the harmful parasitic capacitance by positioning the gate contact above the active region with the air gap spacer providing isolation. This extraction of the harmful effect is achieved through a systematic process that removes the capacitance problem while managing complexity through organized fabrication steps

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the spatial parameter of the gate contact position from lateral to vertical alignment above the active region. This parameter change reduces parasitic capacitance by increasing separation distance, while the air gap spacer formation process manages the associated complexity through controlled material deposition and etching steps

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10177241B2Methods of forming a gate contact for a transistor above the active region and an air gap adjacent the gate of the transistor

Publication Date: 2019.01.08 GLOBALFOUNDRIES US INC

AI summary

One illustrative method disclosed includes, among other things, removing a portion of an initial gate cap layer and a portion of an initial sidewall spacer so as to thereby define a gate contact cavity that exposes a portion of a gate structure, completely forming a conductive gate contact structure (CB) in a gate contact cavity, wherein the entire conductive gate contact structure (CB) is positioned vertically above the active region. The method also comprises removing the remaining portion of the initial gate cap layer and to recess a vertical height of exposed portions of the initial sidewall spacer to thereby define a recessed sidewall spacer and a gate cap cavity and forming a replacement gate cap layer in the gate cap cavity so as to define an air space between an upper surface of the recessed sidewall spacer and a lower surface of the replacement gate cap layer.