BEOL Interconnect Via Alignment and Dielectric Constant Reduction
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Solution Overview
Problem
As BEoL interconnect structures are miniaturized, precise alignment of vias with conductive lines becomes challenging, leading to misalignment issues and increased dielectric constants, which result in reduced yields and reliability.
Innovation Solution
The method involves forming a conductive line, a capping layer, and a low-k layer, with techniques like atomic layer deposition and conformal diffusion barrier layers to isolate vias and conductive lines from dielectric layers, allowing for narrower vias and reduced dielectric constants, thereby improving alignment precision and dielectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conductive lines are made narrower to increase device density, then device performance improves, but alignment precision between vias and conductive lines deteriorates
Solution Approach 1:
A capping layer is introduced as an intermediary element between the conductive line and the via. This capping layer extends beyond the conductive line edges, creating an intermediate structure that facilitates via formation even when alignment is imperfect. The capping layer acts as a mediator that bridges the gap between the shrinking conductive line dimensions and the via alignment requirements.
Solution Approach 2:
The capping layer is formed in advance before via formation, preliminarily establishing a structure that compensates for potential alignment issues. By pre-forming the capping layer with edges extending beyond the conductive line, the system proactively addresses the alignment precision problem before the via formation step occurs.
2Ease of manufacture
If conventional dielectric layers are used in BEoL interconnect structures, then manufacturing simplicity is maintained, but overall dielectric constant increases
Solution Approach 1:
Different dielectric layers are assigned different dielectric constant characteristics based on their local function within the interconnect structure. Low-k dielectric layers are strategically positioned in specific regions where signal integrity is most critical, while other dielectric layers may use different materials optimized for their specific functions such as mechanical support or stress management.
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 enhances the alignment of vias with conductive lines, reduces the overall dielectric constant, and increases the tolerance for misalignment, leading to higher yields and greater reliability in BEoL interconnect structures.
Implementation Method 1
forming the first diffusion barrier layer can include atomic layer deposition of ruthenium or tantalum
Implementation Method 2
forming a low-k layer over the first capping layer... reducing the overall dielectric constant
Data Source
AI summary
Back-End of Line (BEoL) interconnect structures, and methods for their manufacture, are provided. The structures are characterized by narrower conductive lines and reduced overall dielectric constant values. Conformal diffusion barrier layers, and selectively formed capping layers, are used to isolate the conductive lines and vias from surrounding dielectric layers in the interconnect structures. The methods of the invention employ techniques to narrow the openings in photoresist masks in order to define narrower vias. More narrow vias increase the amount of misalignment that can be tolerated between the vias and the conductive lines.