Tungsten Oxide Selective Etch via Remote Plasma
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Solution Overview
Problem
There is a lack of effective dry etch processes for selectively removing metal oxides, particularly tungsten oxide, relative to other materials like tungsten, silicon oxide, silicon nitride, and titanium nitride, which is essential for intricate pattern formation in integrated circuits.
Innovation Solution
The use of a remote plasma etch process involving plasma effluents formed from a fluorine-containing precursor and ammonia, which selectively removes tungsten oxide while minimizing the etching of other materials, by controlling the flow rates and ratios of these gases and incorporating an ion suppression element to filter charged species, allowing neutral and radical species to react with the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used, then other materials can be etched, but tungsten oxide cannot be selectively removed with high selectivity
Solution Approach 1:
The patent changes the chemical parameters of the etch process by using a ammonia-based plasma chemistry instead of conventional fluorocarbon-based processes. This parameter change enables selective etching of tungsten oxide while preserving other materials, achieving etch selectivity ratios exceeding 10:1 for tungsten oxide relative to tungsten, silicon oxide, silicon nitride, and titanium nitride.
Solution Approach 2:
The patent introduces an intermediary substance (ammonia) that mediates the etching reaction. The ammonia plasma reacts selectively with tungsten oxide through intermediate chemical species, enabling controlled removal of tungsten oxide without directly attacking other materials. This intermediary approach allows selective etching where conventional processes fail.
2Manufacturing precision
If remote plasma etch with fluorine-containing precursor and ammonia is used, then tungsten oxide etch selectivity is improved, but process complexity increases
Solution Approach 1:
The patent segments the plasma generation process from the substrate processing region by using a remote plasma source. The plasma is generated in a separate region and then transported to the substrate area, allowing independent optimization of plasma chemistry and substrate processing. This segmentation enables the use of complex ammonia-based chemistry without directly exposing the substrate to plasma generation conditions.
Solution Approach 2:
The patent uses plasma effluents as an intermediary to transfer the etching action from the remote plasma region to the substrate. The plasma effluents carry reactive species that selectively etch tungsten oxide, mediating the interaction between the plasma source and substrate while reducing direct plasma-substrate interaction complexity.
3Manufacturing precision
If ion suppression element is incorporated, then selective etching of tungsten oxide is enhanced, but device structure becomes more complex
Solution Approach 1:
The ion suppression element acts as an intermediary component between the plasma source and substrate. It selectively filters ionized species while allowing neutral reactive species to pass through, thereby enhancing selective etching performance. This intermediary element provides fine control over the plasma-substrate interaction without requiring fundamental changes to the overall device architecture.
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 achieves high selectivity in etching tungsten oxide over other materials, with etch selectivity ratios exceeding 10:1, enabling precise removal of tungsten oxide layers without significant disturbance to other materials, thus facilitating advanced pattern transfer and cleaning processes in semiconductor manufacturing.
Implementation Method 1
a remote plasma etch using plasma effluents formed from a fluorine-containing precursor in combination with ammonia
Implementation Method 2
The plasmas effluents react with exposed surfaces and selectively remove tungsten oxide
Data Source
AI summary
Methods of selectively etching tungsten oxide relative to tungsten, silicon oxide, silicon nitride and/or titanium nitride are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor in combination with ammonia (NH3). Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the tungsten oxide. The plasmas effluents react with exposed surfaces and selectively remove tungsten oxide while very slowly removing other exposed materials. Increasing a flow of ammonia during the process removes a typical skin of tungsten oxide having higher oxidation coordination number first and then selectively etching lower oxidation tungsten oxide. In some embodiments, the tungsten oxide etch selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region.