Tapered Backside Source/Drain Contacts with Air Structures
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Solution Overview
Problem
As semiconductor devices scale down, there is a need to reduce parasitic capacitance and ensure electrical stability between contacts while maintaining device performance and reliability, particularly in multi-gate transistors with 3D channels.
Innovation Solution
The semiconductor device incorporates a backside wiring line with fin-type patterns and air structures between source/drain patterns, featuring a tapered backside source/drain contact design to optimize electrical connections and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch size of semiconductor devices is decreased to increase density, then device density is improved, but parasitic capacitance between contacts increases and electrical stability deteriorates
Solution Approach 1:
The patent introduces air structures that extend in the vertical dimension between source/drain patterns, creating spatial separation that reduces parasitic capacitance. This vertical dimension approach allows maintaining high device density while reducing electrical interference through three-dimensional air gap formation.
Solution Approach 2:
Air structures serve as intermediary elements positioned between source/drain patterns and backside contacts. These air gaps act as dielectric mediators that reduce parasitic capacitance coupling while allowing the device to maintain high density through optimized contact configurations.
2Ease of manufacture
If conventional contact structures are used in scaled devices, then manufacturing is simpler, but parasitic capacitance increases and device performance deteriorates
Solution Approach 1:
The patent modifies the geometric parameters of backside contacts by introducing tapered portions with specific width ratios and height constraints. These parameter changes optimize the balance between manufacturing feasibility and performance, reducing parasitic capacitance while maintaining compatibility with existing fabrication processes.
3Reliability
If backside contacts are made larger to improve electrical connection, then electrical conductivity is improved, but parasitic capacitance with adjacent patterns increases
Solution Approach 1:
The backside contact structure employs local quality variations through tapered portions that have different widths at different heights. The upper portion has a narrower width to reduce parasitic capacitance, while the lower portion maintains sufficient width for good electrical connection, creating optimal local properties at different vertical positions.
Solution Approach 2:
The backside contact features asymmetric geometry with tapered portions that are narrower on one side. This asymmetric design allows the contact to achieve good electrical connection on the contact side while minimizing capacitance coupling with adjacent patterns on the other side.
Data Source
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AI summary
There is provided a semiconductor device including a backside source/drain contact formed at a backside thereof to be connected to a bottom surface of a first source/drain pattern, wherein a first portion of the backside contact has a tapering shape from a backside wiring line, a second portion of the backside contact has a constant width along a vertical direction, and a sacrificial epitaxial pattern is formed in an active pattern and connected to a bottom surface of a second source/drain pattern of which a top surface is connected to a frontside source/drain contact.