Etching Process for Metal Mixed Oxides

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This patent describes a selective chemical etching process for metal mixed oxides, which are materials composed of at least two different metals and oxygen. The process uses a specially chosen etching agent that alters the oxidation state of one metal in the compound, making it easier to dissolve and remove without affecting other layers or materials such as photoresists used in lithography. The etching agent’s redox potential is tightly controlled to ensure the process is sufficiently aggressive for practical applications, but still selective and safe for other components in electronic device fabrication.

Use CasesContent extracted from patent full text and abstract with AI.

• Microfabrication of electronic devices, enabling precise patterning of metal mixed oxide layers (such as electrodes and functional structures) on semiconductor wafers.
• Manufacturing of perovskite oxides and other complex oxide-based functional devices for sensors, memory, or catalysis.
• Production of free-standing epitaxial oxide structures by underetching support layers.
• Selective removal or patterning of challenging materials like SrRuO3, (La,Sr)MnO3, and related oxides during chip or MEMS manufacturing.
• Selective recycling of valuable metals like ruthenium from catalyst materials or electronic waste through targeted dissolution.
• Surface preparation and termination control for heteroepitaxial growth in research or industrial processes.
• Surface cleaning or chemical-mechanical polishing (CMP) of mixed oxide thin films.

BenefitsContent extracted from patent full text and abstract with AI.

• Highly selective etching that targets only the metal mixed oxide, sparing photoresists and other materials, thus improving process precision in lithography.
• Allows processing of previously very difficult-to-etch materials (e.g., SrRuO3, (La,Sr)MnO3) with safer, more controllable chemicals than ozone or hydrofluoric acid.
• Improves the quality and fidelity of device structures thanks to gentler chemical action compared to plasma or ion beam methods, preserving crystal structure and thin film integrity.
• Flexible control over etch rate and selectivity by tuning redox potential, pH, and the type of etching agent, enabling compatibility with various substrate materials and fabrication needs.
• Utilizes safer, easier-to-handle chemicals (such as ascorbic acid or glucose), reducing hazards in lab or manufacturing environments.
• Enables new fabrication techniques and device architectures by making a broad class of oxides patternable with standard lithographic processes.
• Potentially improves yields and reliability in advanced microelectronics due to better process integration and reduced damage to sensitive materials.

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Inventors & Applicants

Patent Abstract

Within the scope of the invention, a method for etching a metal mixed oxide has been developed. A metal mixed oxide is understood to be a compound of at least two different metals and oxygen. According to the invention, an etching agent is chosen that brings at least one of the metals in the mixed oxide to another oxidation stage in which said metal is bonded more weakly and/or in a less directed manner. The etching agent has a redox potential of below + 2 V and contains either a reducing agent that lowers the redox potential thereof by at least 0.15 V or an oxidising agent that raises the redox potential thereof by at least 0.05 V. The change of the oxidation stage and the redox potential in the claimed range co-operate synergistically, such that the etching agent overall is just as aggressive as is necessary in order to etch the metal mixed oxide at a rate that is of interest for technical applications. The etching process is thus selective and does not affect any other materials that are not intended to be etched, such as the photoresist used for lithographic structuring.