Gate Air-Gap Interconnect Structure for Lower RC Delay
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Solution Overview
Problem
As device dimensions shrink, increased line resistance and parasitic capacitance lead to RC signal delay, which is exacerbated by the use of conventional dielectric materials like silicon dioxide, necessitating the introduction of air gaps to reduce capacitance, but existing methods face challenges in maintaining structural integrity.
Innovation Solution
A method for fabricating semiconductor devices with an air gap around the gate structure, involving the formation of a contact etch stop layer, interlayer dielectric layer, and inter-metal dielectric layer, with air gaps created by selective etching to expose the contact etch stop layer and metal interconnections, using materials like silicon oxide and ultra low-k dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air gaps are introduced to reduce parasitic capacitance and RC signal delay, then chip performance and speed are improved, but the mechanical strength and structural integrity of the device are reduced
Solution Approach 1:
The patent employs a composite dielectric structure combining ultra-low-k dielectric material (with k-value of 2.5 or less) and air gaps. The ultra-low-k material provides mechanical support and structural integrity, while the air gaps provide the low-dielectric constant necessary for reducing parasitic capacitance. This composite approach allows simultaneous achievement of high chip speed and adequate mechanical strength.
Solution Approach 2:
The air gaps are selectively formed only in specific regions where parasitic capacitance reduction is most critical, rather than throughout the entire device. The ultra-low-k dielectric material is used in regions requiring mechanical support. This localized application optimizes the balance between performance improvement and structural integrity.
2Stability of the object's composition
If conventional dielectric materials like silicon dioxide are used to fill gaps between metal lines, then structural stability is maintained, but RC signal delay increases due to higher dielectric constant
Solution Approach 1:
The patent changes the dielectric constant parameter from conventional materials (k=4.1 to 4.5 for silicon dioxide) to ultra-low-k material (k≤2.5) and air (k≈1). This parameter change directly reduces parasitic capacitance and RC signal delay while the ultra-low-k material maintains sufficient structural stability through its mechanical properties and bonding characteristics.
Solution Approach 2:
The patent replaces expensive, heavy conventional dielectric materials with lighter, lower-dielectric constant materials. The ultra-low-k dielectric and air gap combination provides the necessary electrical performance with reduced mass and improved signal propagation characteristics.
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 effectively reduces RC signal delay and power consumption by incorporating air gaps, enhancing mechanical strength and structural integrity of the semiconductor device.
Implementation Method 1
The line capacitance, C, is directly proportional to the dielectric constant, or k-value of a dielectric material. Although air is the best dielectric material for lowering the RC value, the dielectric constant of air is about 1, while silicon dioxide has a dielectric constant of about 4 and greater.
Implementation Method 2
a method of forming air gap around gate structure
Data Source
AI summary
A semiconductor device includes a gate structure on a substrate, a contact etch stop layer (CESL) on the gate structure, an interlayer dielectric (ILD) layer on the CESL, a first contact plug in the ILD layer and adjacent to the gate structure, a first stop layer on the ILD layer, an inter-metal dielectric (IMD) layer on the first stop layer, a first metal interconnection in the IMD layer, and an air gap around the gate structure and exposing the CESL and the first metal interconnection.