PZT Layer Etching with Acid-Fluorine Solution
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Solution Overview
Problem
Existing methods for processing epitaxially grown PZT layers in piezoelectric elements face challenges with etching rates being either too high or too low, leading to unstable pattern shapes and reduced productivity.
Innovation Solution
A method using an etching solution with hydrochloric acid and nitric acid in specific concentration ranges combined with fluorine compounds like ammonium fluoride and hydrogen fluoride, allowing for controlled etching of PZT layers at an appropriate rate, and the use of an SRO layer with non-(100) orientation to prevent etching of underlying electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching solutions containing strong acids are used to process PZT layers, then the etching rate increases, but the pattern shape becomes unstable and difficult to control
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentrations of hydrochloric acid (1-10 wt%) and nitric acid (1-10 wt%) in the etching solution. This specific concentration range optimizes the etching rate while maintaining pattern shape stability, resolving the contradiction between high productivity and manufacturing precision.
Solution Approach 2:
The patent uses a composite etching solution containing multiple acids (hydrochloric acid and nitric acid) in specific proportions. This composite formulation creates a balanced chemical environment that provides both sufficient etching power for productivity and controlled reaction characteristics for pattern stability.
2Ease of manufacture
If conventional etching solutions are used to process PZT layers, then the etching process is simple, but the etching rate is either very high or very low making it difficult to achieve appropriate processing
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by specifying precise concentration ranges for hydrochloric acid (1-10 wt%) and nitric acid (1-10 wt%). This parameter optimization enables appropriate etching rates while maintaining the simplicity of the wet etching process, avoiding complex alternative methods.
3Productivity
If the etching rate is increased to improve productivity, then more PZT layer is removed per unit time, but the pattern edge shape becomes unstable
Solution Approach 1:
The patent resolves this contradiction by optimizing the concentration parameters of the etching solution. The specific ranges of hydrochloric acid (1-10 wt%) and nitric acid (1-10 wt%) create a balanced etching environment that removes material at an appropriate rate while maintaining stable pattern edge shapes through controlled chemical reaction.
Solution Approach 2:
The composite etching solution containing multiple acids in specific proportions provides a balanced chemical environment. The combination of hydrochloric acid and nitric acid creates synergistic effects that enable both sufficient etching rate for productivity and stable pattern formation for shape stability.
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 precise control over the etching rate of PZT layers, maintaining pattern shape stability and enhancing productivity while preventing unwanted etching of second electrode layers.
Implementation Method 1
The fluorine compound functions as an etchant, by dissolving oxides
Implementation Method 2
the acid such as hydrochloric acid or the like has the function of ionizing metal after etching
Implementation Method 3
An SRO layer having an orientation plane other than a (100) plane hardly reacts with the etching solution used in the laminate processing step
Data Source
AI summary
A manufacturing method of the present invention comprises the step of epitaxially growing a PZT layer on a first electrode layer, and the step of processing the PZT layer to a desired shape using an etching solution after the growing step. The etching solution contains at least one acid from among hydrochloric acid and nitric acid in a concentration CHCl+3.3CHNO3 ranging from 1 wt % to 10 wt %, CHCl and CHNO3 denoting, respectively, a weight concentration of the hydrochloric acid and nitric acid relative to a weight of the etching solution; and at least one fluorine compound from among ammonium fluoride and hydrogen fluoride, such that a weight concentration of fluorine derived from ammonium fluoride and hydrogen fluoride ranges from 0.1 wt % to 1 wt % relative to the weight of the etching solution.