Air Gap Interconnects for Low Capacitance Semiconductor Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As device feature sizes decrease, interconnects in semiconductor devices face increased electrical resistivity and detrimental capacitance, necessitating the use of ultra low-k dielectric materials and air gaps to reduce capacitance effectively.
Innovation Solution
A method is described for fabricating air gaps in semiconductor devices by providing a substrate with raised metal features, filling the voids between them with a sacrificial fill material, depositing a cap layer with an overhang, removing the sacrificial material to form air gaps, and depositing a dielectric film, which facilitates the creation of low capacitance interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If device feature size is scaled down, then device density and integration are improved, but electrical resistivity increases and capacitance between adjacent features increases
Solution Approach 1:
The patent introduces air gaps (porous structures with k≈1) between adjacent metal interconnect lines to reduce parasitic capacitance. The air gaps are formed by depositing a porous dielectric material or by creating voids that are then filled with air, directly addressing the capacitance increase problem caused by feature size scaling.
Solution Approach 2:
The patent uses composite dielectric structures combining low-k dielectric materials with air gaps. The low-k dielectric material (with k<2.5) is deposited in regions where air gaps are not formed, while air gaps are created in critical areas, creating a composite structure that optimizes both capacitance reduction and mechanical support.
2Object-affected harmful factors
If air gaps are added to critical layers, then capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary patterning of the air gap regions before final metal deposition. Mask layers are formed and patterned to define where air gaps will be created, and these masks are used in subsequent etching or deposition steps to precisely locate the air gaps between specific metal lines, simplifying the overall manufacturing process.
Solution Approach 2:
The patent uses sacrificial materials as intermediaries to form air gaps. A sacrificial dielectric or organic material is deposited between metal lines, then removed through selective etching or thermal decomposition, leaving air gaps. This intermediary approach simplifies the direct formation of air gaps compared to attempting to deposit air or use complex self-aligned processes.
3Object-affected harmful factors
If ultra low-k dielectric materials are used, then capacitance is reduced, but manufacturing difficulty increases compared to air gaps
Solution Approach 1:
The patent applies different dielectric solutions in different locations: air gaps are created only in critical areas where capacitance reduction is most needed between specific metal interconnect lines, while other areas use standard or low-k dielectric materials. This local application optimizes capacitance reduction where necessary while maintaining ease of manufacture in other regions.
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 method effectively reduces capacitance between interconnects by forming air gaps, improving the performance of semiconductor devices by minimizing electrical resistivity and enhancing their operational efficiency.
Implementation Method 1
decomposing the sacrificial fill material into one or more gaseous decomposition products
Implementation Method 2
removing at least one of the one or more gaseous decomposition products by diffusion through the dielectric film
Implementation Method 3
depositing a cap layer on the top area of the raised metal features, where the cap layer has an overhang that extends past the sidewall
Implementation Method 4
depositing a dielectric film on the sacrificial fill material and the cap layer
Data Source
AI summary
A method of forming a semiconductor device with air gaps for low capacitance interconnects. The method includes providing a substrate containing raised metal features with a top area and a sidewall, and a void between the raised metal features, filling the void with a sacrificial fill material, and selectively depositing a blocking layer on the sacrificial fill material. The method further includes depositing a cap layer on the top area of the raised metal features, where the cap layer has an overhang that extends past the sidewall, removing the blocking layer and the sacrificial fill material between the raised metal features, and depositing a dielectric film, where the dielectric film forms an air gap between the raised metal features below the overhang.