Nitrogen-Rich Dielectric Interfaces for Low-Resistance IC Vias
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Solution Overview
Problem
As integrated circuit (IC) transistor density increases, interconnect parasitics, particularly the resistance-capacitance (RC) delay, become a significant challenge due to the scaling of interconnect dimensions, leading to higher interconnect resistances from liner materials with higher electrical resistance than fill metals.
Innovation Solution
Introduce nitrogen into the surface of dielectric materials to enhance adhesion with metals, eliminating the need for a liner by incorporating nitrogen-enriched regions through techniques like plasma exposure or thermal processes, ensuring direct contact between metals and dielectric materials with low nitrogen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a liner material is used to improve adhesion between metal fill and dielectric material, then adhesion is improved, but electrical resistance increases
Solution Approach 1:
The patent applies nitrogen enrichment only at the interface region between the dielectric material and metal fill, rather than uniformly throughout the entire dielectric material. This localized modification creates a nitrogen-rich adhesion layer precisely where adhesion is needed, while maintaining low nitrogen content in the bulk dielectric material to preserve low electrical resistance and low relative permittivity properties.
Solution Approach 2:
The patent changes the nitrogen concentration parameter of the dielectric material as a function of depth from the surface. The nitrogen content is increased at the interface region to enhance adhesion, then gradually decreases toward the bulk material to maintain optimal electrical properties. This gradient approach resolves the contradiction between adhesion strength and electrical resistance.
2Productivity
If the aspect ratio of via opening is increased due to scaling, then transistor density increases, but adhesion problems worsen
Solution Approach 1:
The patent addresses adhesion in high aspect ratio vias by locally enriching nitrogen at the dielectric-metal interface within the via opening. This localized nitrogen enrichment creates strong adhesion bonds precisely where the metal fill contacts the dielectric, ensuring reliable adhesion even when the via depth increases due to scaling for higher transistor density.
3Strength
If nitrogen content is increased throughout the dielectric material to improve adhesion, then adhesion improves, but relative permittivity increases
Solution Approach 1:
The patent resolves this contradiction by confining nitrogen enrichment to only the interface region between dielectric and metal, rather than distributing nitrogen uniformly throughout the entire dielectric material. This localized approach provides sufficient nitrogen for adhesion while maintaining low bulk nitrogen content to preserve low relative permittivity, which is critical for high-speed signal transmission.
Solution Approach 2:
The patent segments the dielectric material into two functional regions: a nitrogen-rich interface layer for adhesion and a nitrogen-poor bulk region for low permittivity. This segmentation allows each region to optimize its nitrogen content for its specific function, resolving the contradiction between adhesion and permittivity requirements.
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 reduces interconnect resistance by improving adhesion and conductivity, maintaining low relative permittivity and avoiding the use of high-resistance liners, thus enhancing the performance of ICs.
Implementation Method 1
exposing the surface of the dielectric material to nitrogen species activated by plasma
Implementation Method 2
exposing the surface of the dielectric material to nitrogen species activated by a transient thermal process in the presence of a source gas comprising nitrogen
Data Source
AI summary
Integrated circuit structures including an interconnect feature without a higher-resistance liner material. In absence of a liner, metal of low resistance directly contacts an adjacent dielectric material, enabling lower resistance interconnect. Even for low-k dielectric compositions, adhesion of the metal to the dielectric material is improved through the incorporation of nitrogen proximal to the interface. Prior to deposition of the metal upon a surface of the dielectric, the surface is exposed to nitrogen species to form a nitrogen-rich compound at the surface. The metal deposited upon the surface may then be nitrogen-lean, for example a substantially pure elemental metal or metal alloy.