Remote Plasma Tungsten Etch Selectivity
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Solution Overview
Problem
Current dry etch processes lack effective methods for selectively removing metals and their native oxidation from semiconductor substrates without causing physical disturbance or damage to miniature structures.
Innovation Solution
The use of a remote plasma etch process formed from a fluorine-containing precursor and/or hydrogen, which selectively removes tungsten relative to silicon-containing films and tungsten oxide by flowing plasma effluents into a substrate processing region, while minimizing the etch rate of other materials through the use of an ion suppressor to control ionic species and enhance radical and neutral species reaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used to remove tungsten, then material removal can be achieved, but selectivity against silicon-containing films and tungsten oxide is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the etch process by using a fluorine-containing precursor in remote plasma configuration. This creates a chemically reactive environment that specifically targets tungsten through fluorine-tungsten reactions, achieving high selectivity (greater than 10:1, greater than 20:1, greater than 50:1, or greater than 100:1) against silicon-containing films and tungsten oxide while maintaining effective tungsten removal capability
Solution Approach 2:
The patent introduces fluorine-containing species as an intermediary chemical agent that mediates the selective removal of tungsten. The fluorine from the precursor forms intermediate compounds with tungsten (such as WF6) that facilitate selective etching, while the remote plasma configuration allows these reactive species to reach the substrate without direct ion bombardment that would compromise selectivity
2Manufacturing precision
If remote plasma etch with fluorine-containing precursor is used, then high selectivity for tungsten removal is achieved, but process complexity increases
Solution Approach 1:
The patent segments the plasma generation region from the substrate processing region by using remote plasma configuration. The fluorine-containing precursor is activated in a separate remote plasma source, and the activated species are then transported to the substrate region. This spatial segmentation allows independent optimization of plasma generation and substrate processing, achieving high selectivity while managing process complexity through modular configuration
3Productivity
If conventional plasma etching is used, then material removal speed can be increased, but physical disturbance and damage to miniature structures occurs
Solution Approach 1:
The patent replaces the mechanical/physical sputtering mechanism of conventional plasma etching with a chemical reaction mechanism. By using fluorine-containing precursors in remote plasma, the etching proceeds through chemical reactions between fluorine species and tungsten, forming volatile compounds that are removed from the surface. This chemical mechanism eliminates ion bombardment and physical disturbance, achieving rapid tungsten removal without damage to miniature structures
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 and rapid removal of tungsten compared to other materials, such as silicon and tungsten oxide, with reduced plasma damage and surface distortion, suitable for intricate patterned substrates.
Implementation Method 1
The methods include a remote plasma etch formed from a fluorine-containing precursor and/or hydrogen (H2). Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the tungsten.
Implementation Method 2
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers or thinning lateral dimensions of features already present on the surface.
Implementation Method 3
The use of an ion suppressor to control ionic species and enhance radical and neutral species reaction
Implementation Method 4
The plasma effluents react with exposed surfaces and selectively remove tungsten while very slowly removing other exposed materials.
Data Source
AI summary
Methods of selectively etching tungsten relative to silicon-containing films (e.g. silicon oxide, silicon carbon nitride and (poly)silicon) as well as tungsten oxide are described. The methods include a remote plasma etch formed from a fluorine-containing precursor and/or hydrogen (H2). Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the tungsten. The plasma effluents react with exposed surfaces and selectively remove tungsten while very slowly removing other exposed materials. Sequential and simultaneous methods are included to remove thin tungsten oxide which may, for example, result from exposure to the atmosphere.