Gate Air Gap Structure for Low-RC Semiconductor Interconnects
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Solution Overview
Problem
The use of air gaps in integrated circuit fabrication is hindered by reduced mechanical strength and structural deformation, which affects the performance and reliability of semiconductor devices.
Innovation Solution
A method is developed to form an air gap around the gate structure by selectively removing the interlayer dielectric layer using etching processes, exposing the contact etch stop layer, and sealing it with an additional intermetal dielectric layer to maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If air gaps are formed between interconnect lines to reduce dielectric constant, then RC signal delay and power consumption are reduced, but mechanical strength is reduced and structural deformation occurs
Solution Approach 1:
The patent uses a composite structure combining air gaps with dielectric material bridges. The air gaps provide low dielectric constant (k≈1) for reduced RC delay, while the dielectric bridges (formed from remaining ILD or IMD layers) provide mechanical strength and prevent structural collapse. This composite approach allows simultaneous achievement of low power consumption and adequate mechanical strength.
Solution Approach 2:
The air gap structure is segmented into discrete regions separated by dielectric bridges rather than forming continuous gaps. This segmentation maintains mechanical integrity by dividing the air gap into manageable sections supported by dielectric structures, preventing overall structural deformation while still achieving capacitance reduction in each gap region.
2Loss of time
If air gaps are formed between interconnect lines to reduce dielectric constant, then RC signal delay is reduced, but structural deformation and weakened structure occur
Solution Approach 1:
The composite structure of air gaps with dielectric bridges provides both low signal delay (through air gap capacitance reduction) and high structural reliability (through dielectric bridge support). The dielectric bridges act as structural reinforcement that prevents the air gap structure from deforming during subsequent fabrication processes and device operation.
Solution Approach 2:
The dielectric bridges serve as intermediary structures between the air gaps and the surrounding device architecture. These bridges transfer mechanical loads and provide structural support to the air gap regions, ensuring that the air gaps do not cause structural deformation or reliability issues while maintaining their electrical function for reduced signal delay.
3Ease of manufacture
If conventional oxide etching techniques are used for high-aspect-ratio contacts and via holes, then manufacturing is simplified, but dielectric constant reduction is limited
Solution Approach 1:
The low-k dielectric material (air gaps) is formed preliminarily during the interconnect fabrication process by selectively removing ILD/IMD layers, before final contact and via hole formation. This preliminary creation of air gaps allows subsequent conventional etching processes to proceed unchanged, maintaining ease of manufacture while achieving dielectric constant reduction for lower power consumption.
Solution Approach 2:
Air gaps are created locally in specific regions between interconnect lines where capacitance reduction is needed, while leaving other regions (such as contact and via hole areas) with conventional dielectric structures. This local application of air gaps allows use of conventional etching techniques for high-aspect-ratio structures while achieving power consumption reduction in the interconnect 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
The method enhances chip performance by reducing RC signal delay and power consumption while maintaining device strength and reliability.
Implementation Method 1
removing the first stop layer and the ILD layer around the gate structure to form an air gap exposing the CESL
Data Source
AI summary
A method for fabricating a semiconductor device includes the steps of forming a gate structure on a substrate, forming a contact etch stop layer (CESL) on the gate structure, forming an interlayer dielectric (ILD) layer on the CESL, forming a contact plug in the ILD layer and adjacent to the gate structure, forming a first stop layer on the ILD layer, and removing the first stop layer and the ILD layer around the gate structure to form an air gap exposing the CESL.