Ruthenium CMP Slurry Chemistry for High-Rate Smooth Planarization
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Solution Overview
Problem
Conventional ruthenium etch and chemical-mechanical polishing (CMP) processes face challenges with surface corrosion, material removal rates, and post-etch surface roughness due to the nobility of ruthenium and the use of strong oxidizers, which can lead to pitting and contamination hazards.
Innovation Solution
A new ruthenium CMP slurry chemistry utilizing halogenation to form ruthenium halide or oxyhalide surface intermediates, followed by ligand-assisted reactive dissolution, which controls pitting and enhances material removal rates while improving surface smoothness by adjusting the kinetics of halogenation and dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong oxidizers are used to etch ruthenium, then material removal rate is improved, but surface pitting and contamination increase
Solution Approach 1:
The invention changes the chemical mechanism from oxidation-based etching to halogenation-based etching. Specifically, it uses halogenating agents (such as I2, Br2, ICl, or Iodixanol) to form volatile ruthenium halide species (RuX4) that can be removed without causing surface pitting. This parameter change in the chemical reaction pathway resolves the contradiction by achieving high material removal rates through volatile product formation while maintaining surface smoothness through controlled halogenation kinetics.
Solution Approach 2:
The invention introduces halogenating agents as intermediary substances that facilitate ruthenium removal through a different chemical pathway. These agents (I2, Br2, ICl, or Iodixanol) act as mediators that form intermediate ruthenium halide compounds which are volatile and can be easily removed. This intermediary approach allows high etch rates without the harmful side effects of strong oxidizers, thus resolving the contradiction between productivity and manufacturing precision.
2Productivity
If strong oxidizers are used to create soluble ruthenium compounds, then etching efficiency is improved, but metal contamination hazard increases
Solution Approach 1:
The invention employs volatile ruthenium halide species (RuX4) as short-lived intermediate products that evaporate completely during the etching process. These volatile compounds serve as disposable intermediaries that carry ruthenium away from the substrate without leaving residual contamination. The volatile nature ensures complete removal, eliminating metal contamination hazards while maintaining high etching efficiency.
Solution Approach 2:
Halogenating agents serve as intermediary substances that enable efficient ruthenium etching through formation of volatile halide species. These intermediaries (ruthenium halides) provide a clean etching pathway that avoids the contamination issues associated with strong oxidizers, thus resolving the contradiction between etching efficiency and contamination control.
3Productivity
If conventional oxidizer-based CMP slurry is used, then material removal rate is maintained, but surface pitting occurs
Solution Approach 1:
The invention fundamentally changes the chemical parameter of the CMP slurry from oxidizer-based to halogenation-based chemistry. By using halogenating agents instead of oxidizers, the process achieves material removal through formation of volatile ruthenium halides rather than soluble oxides. This parameter change eliminates surface pitting while maintaining high material removal rates, as the volatile products can be easily removed without mechanical stress that causes pitting.
4Speed
If ruthenium grain boundaries are etched preferentially, then etching speed is improved, but post-etch surface roughness increases
Solution Approach 1:
Halogenating agents act as intermediaries that enable uniform etching across different ruthenium surface regions. The halogenation reaction proceeds through volatile intermediate species that can access and react with ruthenium atoms uniformly, regardless of whether they are at grain boundaries or grain surfaces. This intermediary mechanism eliminates preferential grain boundary etching while maintaining high overall etching speed, thus resolving the contradiction between speed and surface roughness.
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 provides a self-limiting etch process that reduces pitting and enhances material removal rates, resulting in a smoother post-etch surface and higher throughput in semiconductor manufacturing.
Implementation Method 1
a halogenation agent that halogenates a ruthenium surface to form a halogenated ruthenium surface
Implementation Method 2
a ligand that reacts with the halogenated ruthenium surface to dissolve the halogenated ruthenium surface
Data Source
AI summary
The present disclosure provides a new corrosion control chemistry for use in ruthenium (Ru) chemical-mechanical polishing (CMP) processes. More specifically, the present disclosure provides an improved CMP slurry chemistry and CMP process for planarizing a ruthenium surface. In the CMP process disclosed herein, a ruthenium surface (e.g., a post-etch ruthenium surface) is exposed to a CMP slurry containing a halogenation reagent, which reacts with the ruthenium surface to create a halogenated ruthenium surface, and a ligand for ligand-assisted reactive dissolution of the halogenated ruthenium surface. Relative amounts of the halogenation agent and the ligand can be controlled in the CMP slurry, so as to provide a diffusion-limited etch process that improves pos-etch surface morphology, while providing high material removal rates.