Etching Metal Oxide Layers Using Hydrogen Bromide and Chlorine
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Solution Overview
Problem
Conventional methods for etching wafer stacks in electro-optic devices, such as phase shifters and switches, face limitations in patterning and removing metal oxide layers like barium titanate and strontium titanate, leading to defects and inefficiencies due to non-volatile by-products and lack of selectivity in plasma etching processes.
Innovation Solution
The method involves forming a metal oxide layer over a substrate, followed by a patterned masking layer, and performing a combination of anisotropic dry etching processes with higher ion bombardment and isotropic wet etching to effectively remove residual materials and form a patterned metal oxide layer, using a gas mixture of hydrogen bromide and chlorine to create volatile by-products that desorb easily, and employing hard masks like SiO2 or Si3N4 for selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional plasma etching is used to etch metal oxide layers, then the etching process is simple, but non-volatile by-products are formed and selectivity is poor
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a specific gas mixture (hydrogen bromide and chlorine) instead of conventional plasma etching gases. This chemical parameter change enables volatile by-product formation and improves selectivity while maintaining process feasibility
Solution Approach 2:
The patent replaces the mechanical/physical plasma etching mechanism with a chemical etching mechanism that forms volatile compounds. This substitution eliminates non-volatile by-products and improves selectivity by utilizing chemical reactions specific to the metal oxide composition
2Productivity
If conventional plasma etching is used to remove metal oxide materials, then the process is fast, but residual materials remain due to non-volatile by-products
Solution Approach 1:
The patent changes the chemical reactivity parameters by selecting etchants that form volatile compounds with metal oxide materials. This enables complete material removal through vaporization of by-products, eliminating residues while maintaining high etching rates
Solution Approach 2:
The patent converts the typically problematic non-volatile by-products into volatile by-products that easily desorb. This transformation turns the harmful residue problem into a beneficial complete removal advantage, achieving both speed and completeness
3Manufacturing precision
If higher ion bombardment is applied to remove residual materials, then material removal improves, but mask damage increases
Solution Approach 1:
The patent introduces a soft mask layer as an intermediary between the pattern definition and the metal oxide etching. This soft mask is specifically designed to withstand the etching conditions and enables selective removal of residual materials without damaging the underlying pattern structure
Solution Approach 2:
The patent changes the ion bombardment parameters by applying higher ion energy specifically in the second etching step after the soft mask is in place. This parameter change enables effective residual removal while the soft mask protects critical pattern areas from damage
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 enhances etch rate, reduces defects, and improves selectivity and control over the etching process, resulting in higher fidelity and shorter processing times for wafer patterning in electro-optic devices.
Implementation Method 1
performing an anisotropic dry etching process to etch the metal oxide layer in regions not covered by the patterned masking layer
Implementation Method 2
using a gas mixture of hydrogen bromide and chlorine to create volatile by-products that desorb easily
Implementation Method 3
performing an isotropic wet etching process to remove residual materials not removed by the anisotropic dry etching process
Implementation Method 4
employing hard masks like SiO2 or Si3N4 for selective etching
Data Source
AI summary
An etching method includes forming a metal oxide layer including a barium titanate layer or a strontium titanate layer over a substrate, forming a patterned masking layer over the metal oxide layer, performing an anisotropic dry etching process to etch the metal oxide layer in regions not covered by the patterned masking layer, and performing an isotropic wet etching process to remove residual materials not removed by the anisotropic dry etching process and to form a patterned metal oxide layer.