Interconnect Spacer Structure for Low-RC Semiconductor Wiring
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Solution Overview
Problem
As device dimensions shrink, increased line resistance and parasitic capacitance lead to slower chip speeds and higher power consumption, and the use of air gaps between interconnect lines is hindered by structural deformation and reduced mechanical strength.
Innovation Solution
A method involving the formation of spacers on the sidewalls of metal interconnections within a semiconductor device, using a low-k dielectric material and air gaps to reduce RC signal delay, while maintaining structural integrity through the use of asymmetrical spacers and a multi-layer dielectric structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If air gaps are used 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 low-k dielectric material and air gaps. The low-k dielectric material fills the spaces between interconnect lines while air gaps are strategically positioned to further reduce the effective dielectric constant. This composite approach achieves lower RC delay and power consumption while the low-k material provides mechanical support to prevent structural deformation.
Solution Approach 2:
The patent applies different dielectric properties to different regions: low-k dielectric material is used in areas requiring mechanical strength, while air gaps are introduced in regions where maximum capacitance reduction is needed. This localized application of different dielectric characteristics optimizes both electrical performance and mechanical integrity.
2Productivity
If spacing between conducting lines is reduced to increase packing density, then chip performance is improved, but parasitic capacitance increases
Solution Approach 1:
The patent changes the dielectric parameter (dielectric constant) by introducing air gaps with k≈1 between closely spaced interconnect lines. This parameter change allows lines to be placed closer together (increasing packing density) while the low-k air gaps reduce the parasitic capacitance that would normally increase with reduced spacing.
Solution Approach 2:
The patent creates a composite dielectric structure where air gaps (k≈1) and low-k dielectric material are combined between closely spaced interconnect lines. This composite structure enables high packing density while minimizing parasitic capacitance through the low effective dielectric constant of the combined structure.
3Ease of manufacture
If conventional oxide etching techniques are used for high-aspect-ratio contacts, then manufacturing is simplified, but dielectric constant cannot be reduced below 4.1-4.5
Solution Approach 1:
The patent changes the dielectric constant parameter by transitioning from conventional oxide (k=4.1-4.5) to low-k dielectric materials (k<4.1) and air gaps (k≈1). This parameter change is achieved through modified deposition and etching processes that are extensions of conventional techniques, maintaining ease of manufacture while dramatically reducing the dielectric constant.
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 while enhancing the mechanical strength of the semiconductor device by using spacers to prevent excessive protrusion and leakage during metal interconnect formation.
Implementation Method 1
The line capacitance, C, is directly proportional to the dielectric constant, or k-value of a dielectric material. A low-k dielectric reduces the total interconnect capacitance of the chip
Implementation Method 2
Another method being proposed to lower the dielectric constant even further is to form air gaps between the interconnect lines. While silicon dioxide has a dielectric constant of about 4 and greater, the dielectric constant of air is about 1.
Data Source
AI summary
A method for fabricating semiconductor device includes the steps of: forming a first inter-metal dielectric (IMD) layer on a substrate; forming a first metal interconnection in the first IMD layer; removing part of the first IMD layer; forming a spacer adjacent to the first metal interconnection; forming a second IMD layer on the spacer and the first metal interconnection; and forming a second metal interconnection in the second IMD layer and on the spacer and the first metal interconnection.