Heated Sulfuric Acid Etching for TiN-W Selectivity
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Solution Overview
Problem
Existing techniques face challenges in achieving high selectivity when etching one material out of two kinds, such as wiring material and diffusion prevention film, on semiconductor wafers, as the desired selectivity is often difficult to obtain.
Innovation Solution
A substrate treatment method involving a temperature-raising step for concentrated sulfuric acid and a liquid supply step where the heated sulfuric acid is applied to the substrate, promoting specific chemical reactions to selectively etch titanium nitride over tungsten with improved selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching techniques are used to selectively remove one material from two kinds of materials on a substrate, then etching can be performed, but high selectivity between the two materials is difficult to achieve
Solution Approach 1:
The patent applies parameter changes by heating the concentrated sulfuric acid to elevated temperatures (e.g., 80°C to 150°C) before supplying it to the substrate. This temperature parameter change modifies the chemical reactivity of the sulfuric acid, enabling high-selective etching of titanium nitride while minimizing etching of tungsten. The temperature control is a critical parameter that resolves the contradiction between achieving high selectivity and maintaining reliable etching performance.
Solution Approach 2:
The patent utilizes concentrated sulfuric acid as a strong oxidizing agent to achieve selective etching. The sulfuric acid selectively oxidizes and removes titanium nitride while leaving tungsten substantially unaffected. This chemical principle enables high etching selectivity (e.g., 10:1 or higher) by exploiting the different chemical reactivities of the two materials toward the oxidizing agent.
2Manufacturing precision
If temperature of concentrated sulfuric acid is raised to improve etching selectivity, then etching performance is enhanced, but energy consumption and safety risks increase
Solution Approach 1:
The patent optimizes the temperature parameter within a specific range (80°C to 150°C) to balance etching selectivity improvement against energy consumption. The temperature is raised sufficiently to achieve high selectivity but not excessively to minimize energy waste. This optimized parameter selection resolves the contradiction between enhanced etching performance and increased energy use.
Solution Approach 2:
The patent employs a circulation system where the concentrated sulfuric acid is continuously heated and circulated over the substrate surface. This continuous process maintains optimal temperature and etching conditions throughout the treatment, improving energy efficiency compared to batch heating methods while sustaining high etching selectivity throughout the processing period.
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 method allows for the high-selective etching of titanium nitride relative to tungsten, enhancing the etching process by controlling the temperature and concentration of the sulfuric acid, thereby improving the etching selectivity and efficiency.
Implementation Method 1
a temperature raising step of raising a temperature of concentrated sulfuric acid, and a liquid supply step of supplying the concentrated sulfuric acid having the raised temperature to a substrate placed on a substrate processing part
Data Source
AI summary
A substrate treatment method according to an embodiment of the present disclosure includes a temperature raising step of raising a temperature of a concentrated sulfuric acid, and a liquid supply step of supplying the concentrated sulfuric acid having the raised temperature to a substrate placed on a substrate processing part.