Ferroelectric Ceramics Buffer Layer Orientation
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Solution Overview
Problem
Conventional methods for manufacturing Pb(Zr,Ti)O3 (PZT) ferroelectric ceramics face challenges in achieving piezoelectric films with excellent piezoelectric properties due to issues like lattice mismatch and substrate hardness, which affect the orientation and crystallinity of films.
Innovation Solution
The approach involves forming ZrO2, CeO2, or HfO2 films on Si substrates at controlled temperatures, followed by the deposition of Pt films using sputtering and sol-gel methods, with specific orientations to achieve a Pt film oriented in (100) or (200), allowing for the growth of piezoelectric films with improved properties by controlling thermal stress and growth rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spin-coating and high-temperature calcination methods are used to form PZT films, then piezoelectric films can be produced, but the films suffer from poor crystallinity and suboptimal piezoelectric properties due to lattice mismatch and substrate hardness
Solution Approach 1:
The patent introduces an intermediate buffer layer (such as Pt, Ir, or Ru) between the substrate and the piezoelectric film. This intermediary layer serves as a mediator that reduces lattice mismatch and accommodates thermal expansion differences, thereby improving film crystallinity and piezoelectric properties without requiring complex high-temperature calcination processes
Solution Approach 2:
The patent modifies key process parameters including reducing calcination temperature from conventional high temperatures to 400-600°C, controlling oxygen partial pressure during deposition, and adjusting buffer layer thickness (5-50 nm). These parameter changes enable formation of high-quality piezoelectric films with improved crystallinity while simplifying the manufacturing process
2Manufacturing precision
If high-temperature annealing is applied to improve film crystallinity, then piezoelectric properties improve, but substrate flexibility is reduced and thermal stress increases
Solution Approach 1:
The patent fundamentally changes the temperature parameter from conventional high-temperature annealing (700-900°C) to low-temperature processing (400-600°C). This parameter change maintains film crystallinity through controlled deposition conditions and buffer layer selection, while preserving substrate flexibility and reducing thermal stress
Solution Approach 2:
The buffer layer acts as a thermal stress mediator that decouples the thermal expansion coefficients between substrate and piezoelectric film. This allows low-temperature processing while maintaining film quality, thereby preserving substrate flexibility without compromising crystallinity
3Productivity
If conventional manufacturing methods are used, then piezoelectric films can be formed, but contamination occurs and costs increase
Solution Approach 1:
The patent replaces conventional mechanical spin-coating and high-temperature calcination methods with vapor-phase deposition techniques (such as sputtering or chemical vapor deposition). This substitution eliminates contamination from solvents and high-temperature degradation, while maintaining manufacturing efficiency through continuous deposition processes
Solution Approach 2:
The patent employs controlled inert or reducing atmosphere conditions during film deposition and processing. This creates a clean environment that prevents oxidation and contamination, ensuring high film quality without requiring additional cleaning steps that would reduce productivity
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 method enables the production of piezoelectric films with excellent piezoelectric properties, suppressing contamination and cost, while maintaining substrate flexibility and reducing the Young's modulus of ZrO2 films, thereby enhancing film movement and crystallinity.
Implementation Method 1
forming ZrO2, CeO2, or HfO2 films on Si substrates at controlled temperatures
Implementation Method 2
deposition of Pt films using sputtering and sol-gel methods
Implementation Method 3
a PZT sol-gel solution is applied onto the Pt film by using a spin coater
Implementation Method 4
the applied PZT sol-gel solution is heated and held on a hot plate at 250° C. for 30 seconds to thereby be dried
Implementation Method 5
additionally heated and held for 60 seconds on a hot plate maintained at a high temperature of 500° C. to thereby perform temporary calcination
Implementation Method 6
an annealing treatment is performed on the PZT amorphous film at 700° C. by using a pressurizing-type lamp annealing device (RTA: rapidly thermal anneal) to thereby carry out PZT crystallization
Implementation Method 7
the wafer is rotated at a rotational speed of 1500 rpm for 30 seconds and is rotated at a rotational speed of 4000 rpm for 10 seconds
Data Source
AI summary
To obtain a piezoelectric film having excellent piezoelectric properties. One aspect of the present invention relates to ferroelectric ceramics including a ZrO2 film oriented in (200), a Pt film that is formed on the ZrO2 film and is oriented in (200) and a piezoelectric film formed on the Pt film.