Selective Metal Nitride Etching via Oxidation and Halide
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Solution Overview
Problem
The semiconductor industry faces challenges in selectively etching metal nitride films, such as TaN and TiN, which are crucial for advanced integration schemes, as existing methods struggle to control the thickness and oxidation of these films, affecting device performance and work function.
Innovation Solution
A method involving exposing the metal nitride films to an oxidizing agent to form a metal oxynitride layer, followed by a metal halide etchant, allows for selective etching of TaN or TiN films without affecting the other, enabling controlled thickness removal and maintaining the integrity of the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing etching methods are used on metal nitride films, then the etching process can be performed, but the selectivity between different metal nitride films (TaN and TiN) is insufficient and the etch rate control is poor
Solution Approach 1:
The patent applies preliminary oxidation to the metal nitride film surface before etching. By exposing the film to an oxidizing environment first, a thin oxide layer is formed on the surface, which then enables selective and controlled etching in subsequent steps. This preliminary action transforms the surface chemistry to achieve the desired selectivity and control without complicating the overall process
Solution Approach 2:
The patent changes the chemical state of the metal nitride film surface by controlling the oxidation process. By adjusting oxidation parameters (time, temperature, atmosphere composition), the surface is transformed into a more etchable state while maintaining bulk film integrity. This parameter change enables precise control over etch rate and selectivity between TaN and TiN films
2Manufacturing precision
If the metal nitride film thickness is reduced to achieve better device performance, then the work function control is improved, but the film becomes more susceptible to oxidation and degradation
Solution Approach 1:
The patent performs preliminary oxidation under controlled conditions to create a stable surface layer on thin metal nitride films. This pre-oxidation treatment protects the thin film from uncontrolled oxidation during subsequent processing steps, maintaining film stability while preserving the desired thin-film properties for work function control
Solution Approach 2:
The patent employs inert or controlled atmosphere environments during film deposition and processing to prevent uncontrolled oxidation. By maintaining an inert environment until the film is ready for its intended function, the thin metal nitride films remain stable and resistant to degradation, even at reduced thicknesses
3Productivity
If high aspect ratio trenches are filled with metal nitride films, then the device integration density is improved, but the seam formation and incomplete filling occur due to pinch-off effects
Solution Approach 1:
The patent applies preliminary oxidation to the trench walls and deposited film before attempting to fill seams. This oxidation creates a more etchable surface that facilitates subsequent seam removal processes, enabling complete trench filling without permanent seam formation
Solution Approach 2:
The patent uses oxidation as an intermediary process between film deposition and seam removal. The oxidation step transforms the deposited metal nitride into a more reactive state that can be selectively removed, serving as a mediator that enables seam elimination without affecting the overall trench fill quality
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 provides selective etching with high selectivity and controlled etch rates, allowing for precise removal of metal nitride films, improving the filling of high aspect ratio trenches and maintaining the quality of metal nitride layers, thus enhancing the semiconductor device performance.
Implementation Method 1
exposing the metal nitride film to an oxidizing agent to form a layer of metal oxynitride on a surface of the metal nitride film
Implementation Method 2
etching the metal oxynitride layer from the surface of the metal nitride film by exposing the substrate to a metal halide etchant
Data Source
AI summary
Processing methods comprising oxidizing a metal nitride film to form a metal oxynitride layer and etching the metal oxynitride layer with a metal halide etchant. The metal halide etchant can be, for example, WCl5, WOCl4 or TaCl5. Methods of filling a trench with a seam-free gapfill are also described. A metal nitride film is deposited in the trench to form a seam and pinch-off an opening of the trench. The pinched-off opening is subjected to a directional oxidizing plasma and a metal halide etchant to open the pinched-off top and allow access to the seam.