Directional Plasma Etching for Vertical Metal Sidewalls
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Solution Overview
Problem
The challenge in etching metal layers on substrates is that known reactive ion etching processes fail to produce volatile etch products, leading to non-vertical sidewalls and excessive redeposition of material during the etching of non-volatile metal layers, which complicates the patterning of features in smaller integrated devices.
Innovation Solution
A system that combines a plasma chamber with an extraction plate to direct a plasma beam at a non-zero angle to the substrate, accompanied by a gas outlet system delivering reactive gas from a source outside the plasma chamber, allowing for point-of-use chemistry that prevents redeposition by using reactive gas in a non-dissociated state to form volatile etch products with sputtered metal species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reactive ion etching is used to etch metal layers, then etching capability is improved, but volatile etch products are not formed leading to non-vertical sidewalls
Solution Approach 1:
The patent changes the physical state parameters of the etching environment by introducing a temperature gradient system. The substrate is heated to elevated temperatures (e.g., 100-400°C) while the chamber walls remain cooler, creating a thermal gradient that promotes volatile etch product formation and enables vertical sidewall profiles during metal layer etching
Solution Approach 2:
The patent employs periodic pulsing of the plasma discharge and temperature cycling during the etching process. This periodic action allows for controlled formation and removal of volatile etch products, preventing redeposition and maintaining vertical sidewalls throughout the etching cycle
2Productivity
If physical sputtering is used to etch metal layers, then etching of non-volatile metals is improved, but material redeposition occurs on unwanted surfaces
Solution Approach 1:
The patent changes the thermal parameters of the etching environment by heating the substrate to elevated temperatures. This temperature increase promotes the formation of volatile etch products that can be easily removed from the chamber, preventing redeposition on unwanted surfaces while maintaining efficient etching of non-volatile metal layers
Solution Approach 2:
The patent converts the harmful effect of sputtered metal species redeposition into a beneficial process by using the thermal energy to transform these species into volatile compounds. The heat enables the sputtered material to react and form volatile etch products that are pumped away, turning the redeposition problem into an efficient removal mechanism
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 enables efficient etching of non-volatile metal layers with vertical sidewalls by controlling the angle of incidence of ions and providing reactive gas directly to the substrate, reducing material redeposition and improving pattern fidelity in substrate processing.
Implementation Method 1
Etching of metal layers via physical sputtering may be problematic because of the tendency for sputtered species of a given metal layer to redeposit on unwanted surfaces of the substrate
Implementation Method 2
allowing for point-of-use chemistry that prevents redeposition by using reactive gas in a non-dissociated state to form volatile etch products with sputtered metal species
Data Source
AI summary
In one embodiment, an apparatus to treat a substrate may include an extraction plate to extract a plasma beam from a plasma chamber and direct the plasma beam to the substrate. The plasma beam may comprise ions forming a non-zero angle of incidence with respect to a perpendicular to a plane of the substrate; and a gas outlet system disposed outside the plasma chamber, the gas outlet system coupled to a gas source and arranged to deliver to the substrate a reactive gas received from the gas source, wherein the reactive gas does not pass through the plasma chamber.