Damascene Structure Planarization via Sacrificial Layer
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Solution Overview
Problem
The existing CMP process for manufacturing damascene structures faces issues such as dishing of metal lines, leading to increased interconnect resistance and lifetime decrease, along with challenges in removing copper residues and barrier corrosion, particularly with low-dishing slurries and ALCVD-deposited WCN barriers.
Innovation Solution
A method involving the deposition of a sacrificial layer and a barrier layer, where the sacrificial layer reacts electrochemically with the barrier or damascene structure during planarization, using materials like TaN, TiN, W, or Al, to reduce dishing and copper residues, and provide galvanic protection, while the barrier layer is formed using ALCVD for improved conformality and barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP process uses low-dishing slurry, then dishing performance is improved, but copper residues remain on wafer surface and are difficult to remove
Solution Approach 1:
A sacrificial layer is introduced as an intermediary between the barrier layer and the copper damascene structure. This sacrificial layer undergoes electrochemical reaction with the barrier material during CMP, controlling the copper removal rate and preventing both dishing and excessive copper residues. The sacrificial layer mediates the interaction between barrier and copper, enabling selective removal.
Solution Approach 2:
The invention changes the chemical composition parameters of the multi-layer structure by introducing a sacrificial layer with specific electrochemical properties. This alters the removal rate parameters during CMP, creating a controlled electrochemical environment that prevents dishing while allowing complete copper removal. The parameter change transforms the CMP process from purely mechanical to electrochemical-mechanical hybrid.
2Reliability
If barrier layer prevents copper diffusion, then adhesion and barrier properties are improved, but barrier corrosion is promoted during CMP
Solution Approach 1:
The sacrificial layer serves as a protective intermediary between the barrier layer and CMP slurry. It undergoes preferential electrochemical reaction with the barrier material, forming a galvanic couple that protects the barrier from direct slurry exposure and corrosion. The sacrificial layer absorbs the corrosive attack, preserving barrier integrity.
Solution Approach 2:
The sacrificial layer provides beforehand cushioning protection to the barrier layer against CMP-induced corrosion. By being positioned between the barrier and slurry, it anticipates and absorbs the corrosive effects before they can reach the barrier, ensuring barrier survival through the CMP process.
3Manufacturing precision
If ALCVD deposits conformal barrier layers, then barrier conformality and thinness are improved, but WCN etches faster than copper during CMP causing copper protrusion
Solution Approach 1:
The sacrificial layer acts as an intermediary that modifies the relative etch rates between barrier and copper during CMP. Through electrochemical interaction, it reduces the barrier removal rate to match or exceed the copper removal rate, preventing copper protrusion while preserving the conformal ALCVD barrier structure.
Solution Approach 2:
The invention changes the electrochemical parameters of the CMP process by introducing the sacrificial layer, which alters the effective removal rate parameters of the barrier material. This parameter change transforms the etch rate relationship from barrier-faster-than-copper to barrier-slower-or-equal-to-copper, eliminating protrusion.
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 minimizes dishing and copper residue issues, reduces barrier corrosion, and enhances the planarization process, leading to improved damascene structure quality and reduced metal protrusion, thereby addressing the limitations of conventional CMP methods.
Implementation Method 1
the materials of the sacrificial layer and the barrier layer being chosen so that during planarising the sacrificial layer reacts electrochemically with the barrier layer or with the damascene structure
Implementation Method 2
When both copper and the barrier material are exposed to the polishing solution (at the end of the copper CMP process), they form a galvanic couple in which copper is the cathode. This stops the corrosion of copper and therefore protects the damascene copper structure from dishing.
Implementation Method 3
A CMP process comprises moving a sample surface to be planarised or polished against a polishing pad that is used to provide support against the sample surface and to carry slurry between the sample surface and the polishing pad to affect polishing which leads to planarisation.
Data Source
AI summary
Manufacturing a damascene structure involves: forming a sacrificial layer (20) on a substrate (10) to protect an area around a recess (30) for the damascene structure, forming a barrier layer (40) in the recess, and in electrical contact with the sacrificial layer, forming the damascene structure (50) in the recess, and planarizing. During the planarizing the sacrificial layer reacts electrochemically with the barrier layer or with the damascene structure. This can alter a relative rate of removal of the damascene structure and the sacrificial layer so as to reduce dishing or protrusion of the damascene structure, and reduce copper residues, and reduce barrier corrosion. The barrier layer can be formed by ALCVD. The barrier material being one or more of WCN and TaN. The sacrificial layer can be TaN, TiN or W.