Selective Ru/Cu Etching Composition to Suppress RuO4 Vapor
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Solution Overview
Problem
Existing methods for etching ruthenium and/or copper in microelectronic devices are inefficient and unsafe, particularly in the case of copper in microelectronic devices, and the use of alkaline aqueous compositions in the case of ruthenium, which leads to the formation of toxic and volatile RuO4 vapor, limiting the pH range for safe etching to ≥9, and preferably to ≥10, in order to form only non-volatile oxyanions of ruthenium.
Innovation Solution
A composition comprising one or more heptavalent iodine oxoacids, such as orthoperiodic acid (H5IO6) or metaperiodic acid (HIO4) or salts thereof; (ii) an alkylammonium hydroxide compound or an alkylphosphonium hydroxide compound; (iii) a carbonate/bicarbonate buffering compound; (iii) a carbonate/bicarbonate buffering compound; wherein said composition has a pH of about 9 to about 12.5. In the compositions of the invention, an alkylammonium hydroxide compound or an alkylphosphonium hydroxide compound; (iv) a carbonate/bicarbonate buffering compound; wherein said composition has a pH of about 9 to about 12.5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong oxidants are used to etch ruthenium and RuO2, then etching capability is improved, but toxic and volatile RuO4 vapor is generated
Solution Approach 1:
The patent changes the pH parameter to a high alkaline range (pH 10-12.5) and uses periodic acid instead of traditional strong oxidants. This parameter change allows etching ruthenium and copper at similar rates while forming non-volatile ruthenium hydroxide species instead of volatile RuO4, thereby maintaining productivity while eliminating the harmful effect.
Solution Approach 2:
The patent converts the harmful volatile RuO4 formation into a beneficial non-volatile ruthenium hydroxide formation by using periodic acid in high pH conditions. The periodic acid oxidizes ruthenium to form ruthenium hydroxide species that remain in solution rather than volatilizing, thus converting a harmful process into a safe one.
2Reliability
If pH is increased to ≥10 to form non-volatile oxyanions of ruthenium, then safety is improved, but etching rate is reduced
Solution Approach 1:
The patent uses periodic acid (H5IO6 or HIO4) instead of traditional oxidants in combination with high pH (10-12.5). This specific chemical parameter change enables maintaining high etching rates (>20 Å/min for both Cu and Ru) while ensuring safety by forming non-volatile ruthenium species, thus resolving the contradiction between safety and productivity.
3Productivity
If traditional etching methods are used for copper, then copper etching is achieved, but etching selectivity and safety are compromised
Solution Approach 1:
The patent employs a universal etching composition based on periodic acid and high pH that can etch both ruthenium and copper at similar rates (>20 Å/min). This multi-functional composition eliminates the need for separate etching processes for different metals, improving productivity while maintaining selectivity and safety by forming non-volatile products.
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 composition effectively etches Cu and Ru at similar rates, minimizing etch rates of dielectrics, and avoids the formation of toxic and volatile RuO4 vapor, allowing safe etching at pH levels between 9 and 12.5, thereby enhancing the efficiency and safety of the etching process.
Implementation Method 1
Periodic acid exists in two main forms, orthoperiodic acid (H5IO6) and metaperiodic acid (HIO4) and both forms are contemplated for use as component (i) above. In the compositions of the invention, periodic acid is utilized as an oxidant.
Implementation Method 2
Its etching requires strong oxidants, which however tend to convert Ru and RuO2 into the volatile and toxic oxide RuO4. The RuO4 vapor so formed reacts with organic materials and generates RuO2 particles. These characteristics limit the range of pH in which ruthenium can be etched safely to ≥9, and preferably to ≥10, in order to form only non-volatile oxyanions of ruthenium.
Implementation Method 3
a carbonate/bicarbonate buffering compound; wherein said composition has a pH of about 9 to about 12.5
Data Source
Figure 1
AI summary
The invention provides compositions useful for selectively etching ruthenium and/or copper. The compositions comprise certain periodate compounds, alkylammonium or alkylphosphonium hydroxides, carbonate or bicarbonate buffers, and water, wherein the pH of the composition is about 9 to about 12.5. The compositions of the invention are effectively utilized in the method of the invention and have been found to be capable of etching Cu and Ru at similar rates, i.e., >20 /min, while minimizing etch rates of dielectrics (<2 /min).