Backside Power Rail Air Gaps for Parasitic Leakage Reduction
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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 sizes shrink, necessitating an improved device structure to address these issues.
Innovation Solution
The introduction of power rails at the backside of the semiconductor device structure with conductive features enclosed by air gaps, which effectively reduce leakage current by minimizing capacitive coupling between conductive features and channel regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device size is shrunk to increase device density, then productivity 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 and the channel region. This air gap acts as a mediator that reduces the capacitive coupling between these two structures, thereby reducing parasitic electrical leakage while maintaining the shrunk device dimensions for high device density.
Solution Approach 2:
The air gap is selectively positioned only in specific locations where capacitive coupling occurs between conductive features and channel regions. This localized approach reduces parasitic leakage at critical interfaces without affecting the overall device density or requiring global structural changes.
2Reliability
If air gaps are introduced to reduce parasitic capacitance, then reliability is improved, but device complexity increases
Solution Approach 1:
The air gap is formed by removing material (vacuuming out a sacrificial layer) rather than adding complex structures. This extraction approach creates the necessary isolation space while maintaining a relatively simple overall device architecture, thus improving reliability without proportionally increasing complexity.
Solution Approach 2:
The sacrificial layer is deposited and patterned in advance before the final device assembly. This preliminary action allows the air gap to be easily formed by simple removal of the sacrificial material, avoiding the need for complex post-assembly structuring and thereby limiting the increase in device complexity.
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
This solution enhances the performance of semiconductor devices by reducing parasitic capacitance and leakage currents, thereby improving reliability and timing accuracy.
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, a first source/drain feature and a second source/drain feature disposed in opposing sides of the gate stack, wherein each first source/drain feature and second source/drain feature comprises a first side and a second side, and the second side of the first source/drain feature and the back side of the substrate are at different elevations. The semiconductor device structure also includes a conductive feature in contact with the second side of the first source/drain feature, wherein a portion of the back side of the substrate is exposed to air.