XeF2 Etching of Titanium Nitride Films
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Solution Overview
Problem
Current methods for removing titanium nitride (TiN) films from silicon dioxide (SiO2) and silicon nitride (SiN) surfaces in semiconductor deposition chambers and equipment are inefficient, as conventional fluorine-based etchants often damage these surfaces, and xenon difluoride (XeF2) is expensive, unstable, and difficult to handle.
Innovation Solution
The use of xenon difluoride (XeF2) as an etchant, either preformed or in situ generated by reacting xenon with a fluorine-containing chemical in a remote plasma, to selectively convert TiN films to volatile species without affecting SiO2 and SiN surfaces, along with the activation of perfluoro etching agents in a remote plasma to enhance etching selectivity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fluorine-based etchants are used to remove TiN films, then etching capability is improved, but SiO2 and SiN surfaces are damaged
Solution Approach 1:
The patent uses a remote plasma source as an intermediary to generate reactive fluorine species that selectively etch TiN without directly contacting and damaging SiO2/SiN surfaces. The plasma acts as a mediator that delivers etching capability while protecting sensitive surfaces from harmful direct exposure to aggressive etchants.
Solution Approach 2:
The patent changes the physical state and reactivity parameters of fluorine-based etchants by generating them in a remote plasma environment rather than using them in conventional liquid or gas form. This parameter change enables selective etching of TiN while preserving SiO2 and SiN surfaces through controlled reactivity.
2Manufacturing precision
If preformed XeF2 is used as etchant, then selective etching of TiN is improved, but cost and handling difficulty increase
Solution Approach 1:
The system generates XeF2 in situ within the reaction chamber using xenon gas and a fluorine-containing chemical compound as precursors. This self-service approach eliminates the need for external XeF2 handling, storage, and delivery infrastructure, reducing both cost and operational complexity while maintaining high etching selectivity.
Solution Approach 2:
The patent replaces expensive, unstable preformed XeF2 with inexpensive, stable precursor gases (xenon and fluorine-containing compounds) that are mixed and reacted in situ. These precursors are much easier to handle and store, and their reactive form is generated only when needed, effectively replacing a valuable but problematic material with cheaper, more manageable alternatives.
3Ease of manufacture
If in situ generation of XeF2 is used, then cost and safety are improved, but formation of hazardous byproducts like XeF4 may occur
Solution Approach 1:
The patent employs periodic or controlled introduction of fluorine-containing chemicals and xenon gas into the reaction chamber, allowing precise control over the formation and consumption of XeF2. This periodic action prevents excessive accumulation of XeF2 that could lead to hazardous byproduct formation, while maintaining efficient TiN etching rates.
Solution Approach 2:
The system incorporates monitoring and control mechanisms to regulate the in situ generation of XeF2, ensuring optimal conditions for TiN etching while preventing the formation of hazardous byproducts like XeF4. Feedback control adjusts precursor gas flows and reaction conditions to maintain safe operating parameters.
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 allows for the selective and efficient removal of TiN films from SiO2 and SiN surfaces at modest temperatures, reducing maintenance costs and improving productivity by using high vapor pressure gases, while minimizing the formation of hazardous byproducts like XeF4.
Implementation Method 1
forming the xenon difluoride by reacting xenon with the fluorine containing chemical in the chamber
Implementation Method 2
activation of perfluoro etching agents in a remote plasma to enhance etching selectivity and efficiency
Implementation Method 3
selectively convert TiN films to volatile species
Data Source
AI summary
This invention relates to a process for selective removal of materials, such as: silicon, molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, tantalum, niobium, boron, phosphorus, germanium, arsenic, and mixtures thereof, from silicon dioxide, silicon nitride, nickel, aluminum, TiNi alloy, photoresist, phosphosilicate glass, boron phosphosilicate glass, polyimides, gold, copper, platinum, chromium, aluminum oxide, silicon carbide and mixtures thereof. The process is related to the important applications in the cleaning or etching process for semiconductor deposition chambers and semiconductor tools, devices in a micro electro mechanical system (MEMS), and ion implantation systems. Methods of forming XeF2 by reacting Xe with a fluorine containing chemical are also provided, where the fluorine containing chemical is selected from the group consisting of F2, NF3, C2F6, CF4, C3F8, SF6, a plasma containing F atoms generated from an upstream plasma generator and mixtures thereof.