Semiconductor Air-Gap Isolation for Backside Power Rail Leakage
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Solution Overview
Problem
In semiconductor integrated circuits, parasitic electrical leakage due to capacitive coupling between input wires and neighboring components leads to logic failures and timing degradation as device size shrinks, necessitating an improved device structure to mitigate these issues.
Innovation Solution
The implementation of power rails at the backside of the semiconductor device structure with conductive features enclosed by air gaps to reduce leakage current, effectively isolating the conductive features from channel regions and enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device size is shrunk to increase device density, then device density is improved, but parasitic electrical leakage increases due to capacitive coupling
Solution Approach 1:
An air gap is introduced as an intermediary layer between the conductive feature (power rail) and the channel region. This air gap acts as a mediator that reduces the capacitive coupling effect, thereby reducing parasitic leakage current while allowing the device to maintain high density through backside contact architecture.
Solution Approach 2:
The device structure is segmented into front-side active region and backside contact region. The power rail is divided into portions, with the first portion extending to the backside surface where it forms a backside contact, separated from the channel region by an air gap. This segmentation allows electrical connection while minimizing parasitic coupling.
2Reliability
If power rails are positioned close to channel regions to reduce resistance, then electrical connection is improved, but capacitive coupling increases causing leakage current
Solution Approach 1:
The air gap serves as an intermediary that physically separates the power rail from the channel region while maintaining electrical connectivity through the backside contact architecture. This intermediary structure reduces the harmful capacitive coupling effect without compromising the electrical connection quality.
Solution Approach 2:
The power rail connection is moved from the front-side planar dimension to the backside vertical dimension. By extending the power rail to the backside surface and forming contacts there, the design reduces in-plane capacitive coupling while maintaining low-resistance electrical paths through the vertical dimension.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The air gap enclosure significantly reduces parasitic capacitance and leakage current, thereby improving the performance and reliability of semiconductor devices by minimizing capacitive coupling effects.
Implementation Method 1
parasitic electrical leakage may appear in the device due to capacitive coupling formed between an input wire and neighboring components
Data Source
AI summary
A semiconductor device structure, along with methods of forming such, are described. In one embodiment, a semiconductor device structure is provided. The semiconductor device structure includes a substrate having a front side and a back side opposing the front side, a gate stack disposed on the front side of the substrate, and a first source/drain feature and a second source/drain feature disposed in opposing sides of the gate stack. Each first source/drain feature and second source/drain feature comprises a first side and a second side, and a portion of the back side of the substrate is exposed to an air gap.