Staggered Via Connections for Low-Capacitance Interconnects
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Solution Overview
Problem
Interconnect structures using low-k interlayer dielectrics and air gaps face challenges in integrating patternability and mechanical stability while maintaining reduced line-to-line capacitance, and the use of moderate-k etch stops to seal copper layers increases via resistance and reduces capacitance benefits.
Innovation Solution
Implementing staggered interconnect lines with air gaps and barrier-less or liner-less vias using alternative metals like Mo, Ru, W, and varied width vias with non-linear sidewalls to reduce via resistance and optimize performance without penalizing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional aligned via connections are used for interconnect lines, then manufacturing process is simpler, but interconnect density and signal integrity deteriorate due to crosstalk and congestion
Solution Approach 1:
The patent transitions from a two-dimensional aligned via connection layout to a three-dimensional staggered configuration. By offsetting vias in the lateral direction and creating overlapping patterns between adjacent interconnect layers, the design utilizes the third dimension (vertical stacking with lateral offset) to increase interconnect density without requiring additional via holes, thereby resolving the contradiction between density and structural complexity.
Solution Approach 2:
The staggered via connection structure implements a nested arrangement where vias from different interconnect layers are laterally offset and vertically stacked in an overlapping pattern. This nesting approach allows multiple interconnect lines to share common via regions, increasing the effective density of interconnections within the same physical footprint while maintaining manageable structural complexity through systematic overlap patterns.
2Quantity of substance
If staggered interconnect lines with offset vias are implemented, then interconnect density improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates preliminary alignment features including mandrels positioned adjacent to via holes and dummy via holes strategically placed to guide the via formation process. These pre-positioned structures serve as alignment references during manufacturing, ensuring that staggered vias are correctly positioned with appropriate lateral offsets and overlaps before the actual via holes are formed, thereby reducing the precision burden on subsequent lithography and etching steps.
Solution Approach 2:
The mandrels and dummy via holes act as intermediary alignment structures that mediate between the design specification for staggered via placement and the manufacturing process capabilities. These intermediary elements provide physical references that simplify the alignment process, allowing standard manufacturing equipment to achieve the required precision for complex staggered patterns without demanding ultra-precise direct via-to-via alignment.
3Reliability
If via holes are formed with lateral offsets for staggered interconnects, then signal integrity improves by reducing crosstalk, but via formation process complexity increases
Solution Approach 1:
The via formation process is segmented into distinct stages: first, mandrels are formed adjacent to where via holes will be positioned; second, via holes are etched through the mandrel regions; third, mandrels are removed; and fourth, conductive material is deposited. This segmentation allows each step to be optimized independently, with the lateral offsets between staggered vias being established during the mandrel formation stage rather than requiring complex single-step via alignment, thereby improving signal integrity while maintaining manufacturing ease.
Solution Approach 2:
Mandrels serve as intermediary structures that facilitate the formation of via holes with correct lateral offsets for staggered interconnects. The mandrels are positioned adjacent to the desired via locations, acting as temporary placeholders that define the spatial relationships between staggered vias. This intermediary approach transforms the complex task of directly forming offset vias into a simpler sequence of forming mandrels followed via hole etching, thereby achieving signal integrity improvements through proper staggering without significantly increasing via formation complexity.
Data Source
Figure 1~2C
Figure 3A
Figure 3B
AI summary
Via connections for staggered interconnect lines are disclosed. An interconnect structure includes a first plurality of interconnects and a second plurality of interconnects, wherein the first plurality of interconnects and the second plurality of interconnects are staggered such that individual interconnects of the second plurality of interconnects are laterally offset from individual interconnects of the first plurality of interconnects. The interconnect structure also includes a via coupling an individual interconnect of the first plurality of interconnects to an individual interconnect of the second plurality of interconnects.