Piezoelectric Sputtering Target Grain Boundary Composition
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Solution Overview
Problem
Lead-free piezoelectric thin films experience leakage current issues due to fine defects, which existing methods struggle to adequately address, particularly in the context of miniaturized electronic components where high-quality, defect-free films are required.
Innovation Solution
A piezoelectric ceramic sputtering target with a perovskite type oxide composition, where the molar ratio of Nb, Ta, and Zr at grain boundaries exceeds that in the crystal grains by 30% or more, is used to suppress leakage current during sputtering deposition, ensuring high-quality lead-free piezoelectric thin films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric thin films are manufactured using conventional sputtering methods, then environmental concerns are addressed by eliminating lead, but leakage current occurs due to fine defects in the thin film
Solution Approach 1:
The patent applies local quality by creating a composition gradient where the grain boundary regions have a different chemical composition (higher Nb, Ta, or Zr content) compared to the grain interiors. This localized compositional modification at the grain boundaries suppresses defect formation and reduces leakage current, while maintaining the overall lead-free composition of the thin film.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing specific ratios of Nb, Ta, and Zr elements at grain boundaries. By controlling the molar ratios of these elements (where Nb+Ta+Zr ≥ 0.5 and Nb ≥ 0.2), the patent optimizes the electrical properties and suppresses leakage current while maintaining piezoelectric functionality.
2Productivity
If miniaturized piezoelectric components are developed, then higher performance and smaller size are achieved, but controlling thin film quality and suppressing defects becomes more difficult
Solution Approach 1:
The patent addresses miniaturization challenges by implementing local quality control through compositionally graded grain boundaries. This localized modification ensures high film quality and suppresses defects even in miniaturized components, maintaining manufacturing precision despite reduced component size.
Solution Approach 2:
The patent applies preliminary action by pre-engineering the grain boundary composition during the sputtering deposition process. By incorporating Nb, Ta, and Zr elements that preferentially segregate to grain boundaries during deposition, the patent prevents defect formation before they can occur, ensuring high quality thin films in miniaturized components.
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 approach effectively reduces leakage current occurrences in lead-free piezoelectric thin films, enhancing their reliability and performance, particularly in miniaturized components like sensors and actuators.
Implementation Method 1
Its mechanism is that a voltage is applied between a substrate (anode side) on which a thin film is to be deposited and a target (cathode side) made of material for thin film making which is opposite to the substrate in an inert gas atmosphere such as argon atmosphere, by which ionized rare gas atoms are forced to collide with the target which is a cathode material, and the constituent atoms of the target are knocked out by the energy, whereby a thin film is deposited on the opposite substrate.
Data Source
AI summary
A piezoelectric ceramic sputtering target containing a perovskite type oxide represented by chemical formula (I) of ABO3 as a main component, wherein the component A of the chemical formula (I) contains at least K (potassium) and/or Na (sodium), the component B of the chemical formula (I) contains at least one selected from the group consisting of Nb (niobium), Ta (tantalum) and Zr (zirconium) with Nb (niobium) as a necessity, the piezoelectric ceramic sputtering target is composed of a plurality of crystal grains and grain boundaries existing among the crystal grains, and in the grain boundary, the molar ratio of at least one of Nb (niobium), Ta (tantalum), and Zr (zirconium) in the B components is higher than the molar ratio in the interior of the crystal grains by 30% or more.