Alternating Recessed Interconnects for Low-Capacitance Dense Routing
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Solution Overview
Problem
As microprocessors become faster and smaller, the line-to-line capacitance between neighboring interconnect lines increases, limiting the pitch reduction, and precise alignment of contact masks is required, which conventional lithography processes may not achieve, leading to structural integrity issues and misaligned connections.
Innovation Solution
The formation of interconnect lines with alternating recessed trenches using separate etching processes and dielectric materials with high selectivity allows for increased effective distance between lines, reducing line-to-line capacitance and enabling more forgiving mask alignment, utilizing low-k dielectric materials and air gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch of interconnect lines is decreased to increase density, then the quantity of interconnect lines per area increases, but the line-to-line capacitance between neighboring interconnect lines increases
Solution Approach 1:
The patent introduces vertical dimensionality by creating alternating recessed and non-recessed interconnect lines at different depths within the interlayer dielectric. This three-dimensional arrangement increases the effective distance between neighboring lines, thereby reducing line-to-line capacitance while maintaining high horizontal density. The recessed lines are positioned deeper in the dielectric, creating a stepped configuration that reduces capacitive coupling.
Solution Approach 2:
Different regions of the interconnect structure are given different depths (local quality variations). Specifically, first interconnect lines are recessed deeper into the interlayer dielectric while second interconnect lines remain at a higher level. This local differentiation in depth creates varying capacitance characteristics across the structure, reducing overall line-to-line capacitance while maintaining high density.
2Quantity of substance
If the pitch of interconnect lines is decreased to increase density, then the quantity of interconnect lines per area increases, but the structural integrity and alignment precision deteriorate
Solution Approach 1:
By utilizing the vertical dimension to create alternating recessed and non-recessed lines, the patent provides a larger effective target area for contact formation. The mask can be positioned at different depths to selectively contact specific interconnect lines, providing greater tolerance for lateral misalignment while maintaining precise electrical connections.
Solution Approach 2:
The recessed interconnect lines are formed in advance before final contact formation. This preliminary recessing creates a pre-defined depth structure that guides subsequent mask and etch processes, allowing for more forgiving alignment tolerances during contact formation since the depth variation provides an additional degree of freedom for alignment compensation.
3Ease of manufacture
If conventional lithography processes are used for contact mask alignment, then the manufacturing process remains simple, but the alignment precision and manufacturing capability are insufficient
Solution Approach 1:
The patent changes the depth parameter of interconnect lines to create alternating recessed and non-recessed structures. This parameter variation provides additional alignment margins for contact formation, allowing conventional lithography processes to achieve the required precision without needing more advanced (and complex) lithography techniques. The depth difference creates a larger effective target zone for acceptable alignment.
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 line-to-line capacitance and enhances the misalignment tolerance in mask openings, improving the structural integrity and connectivity of semiconductor devices without relying solely on dielectric constant improvements.
Implementation Method 1
separate etching processes and dielectric materials with high selectivity
Implementation Method 2
utilizing low-k dielectric materials and air gaps
Implementation Method 3
utilizing low-k dielectric materials and air gaps
Data Source
AI summary
Embodiments of the invention describe low capacitance interconnect structures for semiconductor devices and methods for manufacturing such devices. According to an embodiment of the invention, a low capacitance interconnect structure comprises an interlayer dielectric (ILD). First and second interconnect lines are disposed in the ILD in an alternating pattern. The top surfaces of the first interconnect lines may be recessed below the top surfaces of the second interconnect lines. Increases in the recess of the first interconnect lines decreases the line-to-line capacitance between neighboring interconnects. Further embodiments include utilizing different dielectric materials as etching caps above the first and second interconnect lines. The different materials may have a high selectivity over each other during an etching process. Accordingly, the alignment budget for contacts to individual interconnect lines is increased.