Proton-Assisted Plasma Etching for Clean Metal Thin Film Patterning
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Solution Overview
Problem
Conventional dry etching processes face challenges in preventing undesirable deposition of etching by-products on chamber surfaces and substrates, particularly at low vacuum and temperature conditions, which hinders clean etching of metallic, oxide, and nitride layers.
Innovation Solution
The method involves using activated proton assist plasma etching by injecting hydrogen ions (protons) generated during plasma etching to facilitate secondary chemical reactions, generating vaporizable etching by-products, which are gaseous, under low vacuum and temperature conditions, utilizing high plasma electron temperature sources and controlling substrate temperature and bias voltage to prevent deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching is performed at low vacuum (50 mTorr or less) and low substrate temperature (100°C or less), then etching precision and fine line width control are improved, but etching by-products cannot be vaporized and deposit on chamber surfaces and substrates
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from conventional halogen gases (CF4, SF6, CCl4) to hydrogen halide gases (HCl, HBr, HI). This parameter change enables the etching by-products to be vaporized at low temperatures and low vacuum conditions, resolving the contradiction between maintaining etching precision and preventing by-product deposition.
Solution Approach 2:
The patent utilizes phase transition by selecting etching reactions that produce gaseous by-products (metal halides) that can vaporize and be removed from the chamber. The reaction products transition from solid/liquid deposits to gaseous state, allowing them to be evacuated without depositing on surfaces, thus solving the deposition problem while maintaining low temperature operation.
2Ease of manufacture
If wet etching is used for metal wiring formation, then ease of manufacturing is improved, but fine line width etching capability deteriorates
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based dry etching using hydrogen halide gases. This substitution maintains the chemical etching mechanism's ease of use while achieving dry etching's precision benefits, eliminating the need for photoresist stripping steps and enabling fine line width control.
3Productivity
If conventional halogen gas etching is used on copper, nickel, or similar metals, then etching capability is improved, but high boiling point by-products cause chamber and pump contamination
Solution Approach 1:
The patent changes the etching chemistry from conventional halogen gases to hydrogen halide gases, which produce metal halide by-products with lower boiling points. This parameter change in gas composition enables the by-products to remain in gaseous state and be evacuated without contaminating the chamber and pump system.
Solution Approach 2:
The patent converts the previously harmful high boiling point by-products into beneficial low boiling point gaseous products. The hydrogen halide etching reactions produce volatile metal halides that can be easily removed, transforming the contamination problem into an effective etching solution.
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 effectively prevents undesirable deposition of etching by-products within the process chamber, ensuring clean etching and maintaining process stability by generating gaseous by-products, thus minimizing process delays and device failures.
Implementation Method 1
etching the etching target layer by generating plasma, wherein, in the etching, protons having a same molar ratio as halogen ions are generated as the halogenated hydrogen is ionized by the plasma
Implementation Method 2
the generated protons assist a secondary chemical reaction in which a second etching by-product, which is gaseous, is synthesized under a process condition of the etching from a first etching by-product synthesized through a primary chemical reaction
Implementation Method 3
utilizing high plasma electron temperature sources
Data Source
AI summary
A method for a thin film process including activated proton assist plasma etching includes positioning, in a process chamber, a substrate having, on the top surface, at least one layer to be etched from among a metallic layer, a metallic oxide layer and a metallic nitride layer; supplying, into the chamber, a halogenated hydrogen gas as a source gas; and generating plasma to etch the layer to be etched, wherein, in the etching, protons with the same molar ratio as a halogen ion are generated while the halogenated hydrogen is ionized by the plasma, and the generated protons can assist a secondary chemical reaction in which a gaseous second etching by-product is synthesized, under process conditions of the etching, from a first etching by-product synthesized through a primary chemical reaction between a metal atom forming the layer to be etched and a halogenated hydrogen radical or the halogen ion.