Ti Diffusion Barrier for Faster Ru CMP and Lower RuO2 Contamination
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Solution Overview
Problem
The existing chemical mechanical polishing (CMP) process for ruthenium (Ru) in semiconductor interconnect structures is inefficient due to low removal rates and the formation of insoluble ruthenium dioxide (RuO2) by-products, leading to dishing of conductive metal and defects on patterned surfaces.
Innovation Solution
Incorporating a titanium (Ti)-containing diffusion barrier layer allows for the use of a mild oxidizing agent like hydrogen peroxide in the CMP slurry, which oxidizes titanium to titanium hydroperoxide, a stronger oxidizing agent that can convert RuO2 into water-soluble high valence ruthenium compounds, facilitating their removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional CMP process is used for ruthenium, then the polishing can be performed, but the removal rate is low and insoluble RuO2 by-products form causing dishing and defects
Solution Approach 1:
A titanium-containing layer is introduced as an intermediary between the ruthenium layer and the CMP slurry. The titanium reacts with hydrogen peroxide to form titanium hydroperoxide, which then oxidizes ruthenium to water-soluble high-valence ruthenium compounds, preventing insoluble RuO2 formation and enabling efficient removal without dishing
Solution Approach 2:
The oxidation state of ruthenium is changed from +4 (insoluble RuO2) to +6 or +7 (water-soluble compounds) through the titanium-mediated oxidation process. This parameter change in oxidation state transforms the harmful insoluble by-product into a removable water-soluble compound
2Productivity
If a strong oxidizing agent is used to increase Ru removal rate, then productivity improves, but harmful by-products increase and surface quality deteriorates
Solution Approach 1:
Titanium acts as a mediator that enables the use of mild oxidizing agents (hydrogen peroxide) to achieve effective ruthenium removal. The titanium hydroperoxide formed intermediate provides controlled oxidation that produces water-soluble ruthenium compounds without the harsh conditions that cause dishing and surface defects
Solution Approach 2:
While hydrogen peroxide itself is a mild oxidant, the in-situ generated titanium hydroperoxide acts as a strong oxidizing agent that selectively oxidizes ruthenium to high-valence water-soluble compounds, achieving fast removal rates without the side effects of conventional strong oxidants
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 CMP removal rate of Ru and reduces contamination from RuO2 by-products, thereby improving the reliability and quality of semiconductor interconnect structures.
Implementation Method 1
oxidizes titanium to titanium hydroperoxide, a stronger oxidizing agent that can convert RuO2 into water-soluble high valence ruthenium compounds
Data Source
AI summary
A semiconductor device is provided. The semiconductor device includes a dielectric layer over a substrate and a contact structure embedded in the dielectric layer. The contact structure includes a diffusion barrier contacting the dielectric layer, the diffusion barrier including a titanium (Ti)-containing alloy. The contact structure further includes a liner on the diffusion barrier, the liner including a noble metal. The contact structure further includes a conductive plug on the liner.