System and Etching Method for Fabricating Photonic Device Elements

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This patent describes a novel method and system for fabricating high aspect ratio nanostructures on semiconductor substrates, primarily for use as elements in photonic devices. The key innovation is a metal-assisted chemical etching process that uses a continuous metal mesh patterned on the substrate, a stabilizing metal-semiconductor alloy catalyst, and a simple combination of air (as the oxidant) and vapor-phase hydrofluoric acid (as the etchant). This method enables the creation of extremely deep, narrow structures with high precision, without the need for hazardous oxidizing gases or external electrical biases, and works in a gas-phase environment that avoids issues like nanostructure sticking and complex post-processing.

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

• Manufacturing of X-ray diffractive gratings for medical and industrial imaging systems.
• Fabrication of nanostructures for photonic devices, such as laser diodes, LEDs, solar cells, and optical amplifiers.
• Production of high aspect ratio nanowires and gratings for use in advanced sensors and MEMS devices.
• Creation of micro- and nanostructured elements for optical displays and information-processing devices.
• Development of nanostructured materials for enhanced photovoltaics, thermoelectrics, and energy storage.
• Manufacturing microfluidic channels and biocompatible scaffolds in bioengineering applications.

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• Enables extremely high aspect ratio etching (up to 10000:1) with nanometer-scale precision.
• Employs normal air as an oxidant, eliminating the need for dangerous gases like O2 or unstable chemicals like H2O2.
• No requirement for external electrical bias or magnetic fields, simplifying apparatus and increasing reliability.
• Operates in a gas-phase environment, reducing issues such as nanostructure agglomeration (stiction) and need for complex drying steps.
• Compatible with large-area and high-throughput manufacturing processes.
• Robust to high concentrations of etchant and works with various semiconductor materials (Si, Ge, III-Vs) and metal catalysts.
• Minimizes porosity and defects in etched structures, improving optical properties and device performance.
• Reduces production cost and complexity compared to conventional nanoscale etching methods like reactive ion etching.

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Patent Abstract

The present disclosure provides a method to fabricate high aspect ratio patterns in a semiconductor substrate that are elements of photonic devices by using a continuous metal mesh and etching in presence of air in a continuous flow and an etchant. In one approach, a stabilizing catalyst that involves the formation of a stable metal-semiconductor alloy allows to etch the substrate in vertical direction even in conditions of very low oxidant concentration (e.g. the oxidizer species being present in the air) without any external bias or magnetic field so to realize very high aspect ratio structures in the semiconductor substrate. The metal layer on the semiconductor substrate reacts with the oxidant contained in the air and catalyzes the semiconductor etching by the etchant. In one approach, the etchant is supplied by evaporating a water diluted HF solution. Air in continuous flow in proximity of the metal layer allows to maintain constant the oxidant concentration in proximity of the metal layer. This favors the mass transport of the reactant species and the etching by-products, thereby the process can continue for long time in order to form very high aspect ratio structures. Once the etched semiconductor structure is formed, the continuous air flow supports the reactant species diffusing through the etched semiconductor structure so to maintain a uniform etching rate of high aspect ratio structure. The continuous air flow supports the diffusion of the reaction by-products so to avoid the poisoning of the etching reaction. Structures with aspect ratios in the order of 10000:1 can be obtained with this method. The method has excellent capability of pattern transfer at the nanometer scale. Since the oxidant can be provided by the normal air, the system has particular advantage for implementation as it does not require any handling of hazardous and inflammable gases such as O2 gas or instable chemicals, such as H2O2.