Air-Gap Spacers for Reduced Stray Capacitance in Semiconductors
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Summary
Problems
As semiconductor technology advances to smaller geometries, stray capacitance between the gate structure and source/drain contacts in field effect transistors increases, hindering device switching speed, power consumption, and coupling noise performance, despite the use of low-k materials.
Innovation solutions
The introduction of air-gap spacers interposed between the gate structure and source/drain contacts, replacing conventional solid dielectric spacers, to reduce relative permittivity and stray capacitance, achieved through a method involving sacrificial spacer layers, etching processes, and sealing air gaps with dielectric layers.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If conventional solid dielectric spacers are used between gate structure and source/drain contacts, then structural integrity and manufacturing simplicity are maintained, but stray capacitance remains large due to higher relative permittivity
Why choose this principle:
The patent introduces air-gap spacers containing voids or porous regions between the gate structure and source/drain contacts. These porous structures have significantly lower effective permittivity compared to solid dielectric materials, thereby reducing stray capacitance. The air gaps are formed by removing sacrificial materials or by direct deposition of porous dielectric layers, creating a structure that maintains mechanical integrity while minimizing capacitive coupling.
Principle concept:
If conventional solid dielectric spacers are used between gate structure and source/drain contacts, then structural integrity and manufacturing simplicity are maintained, but stray capacitance remains large due to higher relative permittivity
Why choose this principle:
The air-gap spacer structure combines multiple materials including porous dielectric materials, air voids, and potentially low-k materials to create a composite spacer system. This composite approach allows optimization of both electrical properties (low permittivity) and mechanical properties (structural support), resolving the contradiction between reducing stray capacitance and maintaining device integrity.
Application Domain
Data Source
AI summary:
The introduction of air-gap spacers interposed between the gate structure and source/drain contacts, replacing conventional solid dielectric spacers, to reduce relative permittivity and stray capacitance, achieved through a method involving sacrificial spacer layers, etching processes, and sealing air gaps with dielectric layers.
Abstract
A method includes forming a gate structure on a substrate, forming a seal spacer covering a sidewall of the gate structure, forming a sacrificial spacer covering a sidewall of the seal spacer, forming source/drain regions sandwiching a channel region that is under the gate structure, and depositing a contact etch stop layer covering a sidewall of the sacrificial spacer. The method further includes removing the sacrificial spacer to form a trench, wherein the trench exposes a sidewall of the contact etch stop layer and the sidewall of the seal spacer, and depositing an inter-layer dielectric layer, wherein the inter-layer dielectric layer caps the trench, thereby defining an air gap inside the trench.