Low-k Dielectric CMP Stop Layer for Copper Damascene Polishing
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Solution Overview
Problem
Conventional methods for fabricating copper damascene interconnects face challenges such as increased resistance, electro-migration, and significant dielectric and copper loss due to non-uniform chemical-mechanical polishing (CMP), which affect the operation speed and reliability of semiconductor devices.
Innovation Solution
A method involving the use of a low-k dielectric CMP stop layer with a porogen, which is cured post-CMP to match the dielectric constant of the underlying low-k dielectric layer, preventing water and ion penetration and reducing dielectric and copper loss, thereby maintaining low resistivity and RC delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP method is used to remove copper and barrier layers, then metal interconnect is formed, but significant dielectric and copper loss occurs due to non-uniform polishing
Solution Approach 1:
The patent segments the CMP process into two distinct stages: a first CMP process that removes copper and barrier layers, and a second CMP process that removes the sacrificial dielectric layer. This segmentation allows each process to be optimized independently, preventing the dielectric loss that occurs when a single CMP process attempts to remove both metal and dielectric materials.
Solution Approach 2:
The patent introduces a sacrificial dielectric layer as an intermediary material between the copper interconnect and the underlying dielectric layer. This sacrificial layer acts as a protective mediator during the first CMP process, preventing direct contact between the CMP slurry and the underlying dielectric, thereby eliminating copper ion contamination and dielectric loss.
2Reliability
If copper is used to reduce resistance and electro-migration, then operation speed increases, but copper ion diffusion into dielectric layer occurs during CMP
Solution Approach 1:
The sacrificial dielectric layer serves as an intermediary barrier that prevents copper ions from diffusing into the underlying low-k dielectric layer during the first CMP process. This intermediary layer protects the dielectric from copper contamination while allowing the copper interconnect to be properly formed.
Solution Approach 2:
The sacrificial dielectric layer is formed with a porous structure that allows for controlled interaction with CMP slurry while maintaining barrier properties. The porous structure enables the sacrificial layer to be selectively removed in the second CMP process without causing damage to the underlying dielectric.
3Loss of substance
If high-k dielectric CMP stop layer is used to prevent dielectric loss, then RC delay increases due to increased capacitance
Solution Approach 1:
The patent changes the dielectric constant parameter of the CMP stop layer from high-k to low-k material. This parameter change reduces the capacitance between metal interconnects while maintaining the protective function of preventing dielectric loss during CMP processing.
Solution Approach 2:
The patent applies different dielectric materials to different locations: a low-k dielectric material for the CMP stop layer to minimize capacitance, and a sacrificial dielectric layer in the interconnect region to prevent copper ion diffusion. This local differentiation of material properties optimizes both electrical performance and process protection.
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 approach effectively reduces resistivity and RC delay, improves uniformity, and minimizes dielectric and copper loss, enhancing the performance and reliability of copper damascene interconnects.
Implementation Method 1
which is cured post-CMP to match the dielectric constant of the underlying low-k dielectric layer
Data Source
AI summary
The disclosure provides mechanisms of performing metal chemical-mechanical polishing (CMP) without significant loss of copper and a dielectric film of damascene structures. The mechanisms use a metal CMP stop layer made of a low-k dielectric film with a porogen, which significantly reduces the removal rate of the metal CMP stop layer by metal CMP. The metal CMP stop layer is converted into a porous low-k dielectric film after a cure (or curing) to remove or convert the porogen. The low-k value, such as equal to or less than about 2.6, of the metal CMP stop layer makes the impact of using of the metal CMP stop layer on RC delay from minimum to none. Further the CMP stop layer protects the porous low-k dielectric film underneath from exposure to water, organic compounds, and mobile ions in the CMP slurry.