Air-Gap Interconnect Structure for Lower Metal-Line Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increase in capacitance between adjacent metal lines in semiconductor integrated circuits due to shrinking pitch degrades device performance and requires new processing and manufacturing developments to address this issue without excessive cost increases.
Innovation Solution
The formation of air gaps between adjacent metal lines in semiconductor devices, combined with the use of protecting layers on sidewall surfaces and controlled etching processes, reduces capacitance by 10% to 20% through a method involving sacrificial layers and chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pitch is shrunk to increase functional density, then productivity and manufacturing efficiency are improved, but capacitance between adjacent metal lines increases degrading device speed
Solution Approach 1:
An air gap is introduced as an intermediary material between adjacent metal lines. This air gap acts as a mediator that reduces the capacitance coupling between metal lines while maintaining the shrunk pitch for high functional density. The air gap's low dielectric constant (k≈1) provides electrical isolation that prevents signal interference and maintains device speed despite reduced pitch.
Solution Approach 2:
The dielectric constant parameter of the material between metal lines is changed from conventional dielectric materials (k>2.0) to air (k≈1). This parameter change significantly reduces the capacitance between adjacent metal lines, allowing pitch shrinkage to proceed without degrading device speed. The capacitance reduction enables maintaining high functional density while preserving signal integrity and device performance.
2Speed
If air gaps are formed between metal lines to reduce capacitance, then device speed is improved, but manufacturing complexity increases
Solution Approach 1:
A sacrificial layer is deposited and patterned beforehand to define the locations where air gaps will eventually form. This preliminary structure serves as a template that guides subsequent processing steps. The sacrificial layer is removed after metal line formation, leaving precisely defined air gaps without requiring complex direct air gap formation processes.
Solution Approach 2:
The sacrificial layer is temporarily introduced and then completely removed from the structure after serving its purpose of defining air gap locations. This extraction approach simplifies the overall process by using a temporary material that can be easily deposited, patterned, and removed, avoiding the need for complex direct air gap formation techniques.
3Object-affected harmful factors
If protecting layers are deposited on sidewall surfaces to enable air gap formation, then capacitance reduction is achieved, but manufacturing steps increase
Solution Approach 1:
The sacrificial layer serves multiple functions: it defines the air gap locations, provides a pattern transfer mask for metal line formation, and acts as a placeholder during subsequent processing. This multi-functionality consolidates several process steps into one, reducing overall manufacturing complexity despite the additional deposition and pattern steps required.
Solution Approach 2:
The protecting layer on sidewalls acts as an intermediary structure that enables precise air gap formation. It protects the metal lines during sacrificial layer removal while defining the exact boundaries of the air gaps. This intermediary approach simplifies the air gap formation process compared to direct methods, as it provides a controlled and reproducible way to create the air gaps.
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 approach effectively reduces capacitance, enhancing device performance by improving electrical isolation and maintaining manufacturing efficiency.
Implementation Method 1
removing second portions of the sacrificial material layer to form gaps between the line features
Implementation Method 2
forming dielectric features in the gaps, the dielectric features enclosing an air gap
Data Source
AI summary
In one example aspect, the present disclosure is directed to a method. The method includes receiving a workpiece having a conductive feature over a semiconductor substrate, forming a sacrificial material layer over the conductive feature, removing first portions of the sacrificial material layer to form line trenches and to expose a top surface of the conductive feature in one of the line trenches; forming line features in the line trenches, removing second portions of the sacrificial material layer to form gaps between the line features, and forming dielectric features in the gaps, the dielectric features enclosing an air gap.