Metal Oxide Wet Etching with High-Selectivity Acid Mixtures
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Solution Overview
Problem
Conventional methods for patterning and etching wafer stacks in electro-optic modulators and switches face challenges such as slow etch rates, non-selectivity to masks, and residue formation, particularly with materials like barium titanate (BTO) and strontium titanate (STO), leading to defects and performance deviations.
Innovation Solution
A wet etching method using a mixture of hydrofluoric acid and additional acids with higher acid dissociation constants, along with a diluent, is employed to etch metal oxide layers like BTO and STO, providing high selectivity to masks and rapid etch rates, reducing residue formation and improving process control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching methods are used on metal oxide layers, then the etching process can be performed, but the etch rate is slow and residue formation occurs
Solution Approach 1:
The patent changes the chemical parameters of the etching medium by combining hydrofluoric acid with additional acids having higher acid dissociation constants and a diluent. This parameter modification enables both rapid etching of metal oxide layers and prevention of residue formation, resolving the contradiction between etch rate and residue generation.
2Reliability
If conventional etching methods are used on metal oxide layers, then the etching process can be performed, but selectivity to masks is poor
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching medium to achieve high selectivity to masks while maintaining rapid etch rates. The specific combination of hydrofluoric acid, additional acids with higher dissociation constants, and diluent creates a chemically selective environment that differentiates between mask materials and metal oxide layers.
Solution Approach 2:
The etching medium functions as a composite chemical system combining multiple acid components with different properties. This composite approach enables simultaneous achievement of mask selectivity and high etch rate by leveraging the complementary characteristics of each acid component.
3Manufacturing precision
If conventional etching methods are used on metal oxide layers, then the etching process can be performed, but defects are generated leading to performance deviations
Solution Approach 1:
The patent optimizes the chemical parameters of the etching medium to achieve precise and defect-free etching of metal oxide layers. The controlled combination of acids and diluent creates optimal chemical conditions that prevent defect generation while maintaining high etching accuracy.
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
The method achieves faster etching with reduced defects, maintains stoichiometry, and enhances process integration, resulting in improved performance and efficiency of electro-optic components.
Implementation Method 1
etching the metal oxide layer using a wet etching medium containing hydrofluoric acid, one or more additional acids having an acid dissociation constant greater than that of the hydrofluoric acid, and a diluent
Data Source
AI summary
An etching method includes forming a metal oxide layer comprising a barium titanate layer or a strontium titanate layer over a substrate, forming a patterned masking layer over the metal oxide layer, and etching the metal oxide layer using a wet etching medium containing hydrofluoric acid, one or more additional acids having an acid dissociation constant greater than that of the hydrofluoric acid, and a diluent.