Airgap Single Diffusion Break for Low-Capacitance Isolation
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Solution Overview
Problem
Conventional single diffusion breaks (SDBs) in semiconductor structures can cause capacitance issues between neighboring source/drain regions, which affects the electrical isolation and performance of transistors.
Innovation Solution
A semiconductor structure is developed that includes a single diffusion break (SDB) containing an airgap, where the airgap has an upper region with a first width and a lower region with a second width less than the first width, pinched off on the backside in proximity to a backside interconnect structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single diffusion break (SDB) is used to electrically isolate neighboring transistors, then electrical isolation is achieved, but capacitance between neighboring source/drain regions increases
Solution Approach 1:
The patent introduces an airgap (a porous/void structure) within the single diffusion break region. This airgap reduces the dielectric material volume between neighboring source/drain regions, thereby minimizing parasitic capacitance while preserving the electrical isolation function of the SDB.
Solution Approach 2:
The SDB structure is formed as a composite consisting of dielectric material and an airgap region. This composite structure combines the isolation properties of the dielectric with the low-capacitance properties of the airgap, achieving both electrical isolation and reduced capacitance.
2Loss of energy
If the airgap width is reduced to minimize capacitance, then capacitance decreases, but leakage between source/drain regions may increase
Solution Approach 1:
The airgap is designed with non-uniform width along its length, creating different local properties: a narrower upper portion for minimizing capacitance and a wider lower portion for preventing leakage. This local quality variation allows the structure to simultaneously address both capacitance reduction and leakage prevention requirements.
Solution Approach 2:
Instead of uniformly reducing the airgap width in one dimension, the patent varies the airgap width along its vertical extent (another dimension). This dimensional variation allows optimization of both capacitance (through reduced average width) and leakage (through maintained minimum width at critical regions).
Data Source
AI summary
A semiconductor structure including a single diffusion break (SDB) containing an airgap located between neighboring source/drain regions is provided. The airgap has an upper region that has a first width and a lower region that has a second width that is less than the first width. The airgap is pinched off on the backside of the structure in a region that is in close proximity to a backside interconnect structure. The presence of the airgap containing SDB can minimize capacitance as well as leakage of the structure.