Pt Lower Electrode Crystallinity and Ti Precipitation in Piezoelectric Devices
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Solution Overview
Problem
Conventional methods struggle to simultaneously achieve improved piezoelectric properties of thin films by Ti precipitation and crystallinity of the lower electrode, as excessive Ti precipitation inhibits crystal growth of the lower electrode, leading to a tradeoff between the two effects.
Innovation Solution
A piezoelectric device with a Pt lower electrode having a crystal grain size of 75 nm to 150 nm, where Ti is precipitated from the bonding layer onto the lower electrode, allowing Ti to serve as crystal nuclei for the piezoelectric thin film while maintaining appropriate crystallinity, thereby enhancing both Ti precipitation and lower electrode crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ti is deposited in large amount on the lower electrode to improve piezoelectric properties, then the piezoelectric properties of the thin film are improved, but the crystallinity of the lower electrode deteriorates due to inhibition of crystal growth
Solution Approach 1:
The patent applies parameter changes by precisely controlling the substrate temperature during Pt deposition to fall within 100°C to 400°C. This temperature parameter control enables Ti atoms to precipitate as seeds on the Pt surface without excessive Ti accumulation that would inhibit Pt crystal growth. The controlled temperature ensures both Ti seed formation for piezoelectric property improvement and maintenance of Pt electrode crystallinity
Solution Approach 2:
The patent applies local quality by creating localized Ti seed regions on the Pt electrode surface rather than uniform Ti distribution. The Ti atoms precipitate as discrete seeds that provide localized nucleation sites for PZT film growth, improving piezoelectric properties without creating continuous Ti layers that would inhibit Pt crystal growth throughout the electrode
2Productivity
If the deposition time is shortened to achieve 1.5% atom ratio of Ti to Pt, then the productivity is improved, but the uniformity of the deposited film deteriorates
Solution Approach 1:
The patent applies self-service by utilizing the Pt electrode itself as the source of heating during deposition. The Pt layer absorbs deposition energy and maintains the substrate temperature within the optimal 100°C to 400°C range, enabling Ti atoms to automatically precipitate as uniform seeds across the Pt surface during the deposition process without requiring external heating or extended deposition time
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 effectively improves the piezoelectric properties of the thin film and the crystallinity of the lower electrode, achieving a balance between the two effects and enabling efficient inkjet head operation with improved ink ejection characteristics.
Implementation Method 1
Ti is precipitated from the bonding layer onto the lower electrode
Implementation Method 2
the Ti islands can serve as crystal nuclei to control the orientation of PZT during the deposition of the PZT film
Implementation Method 3
A lower electrode including Pt is formed on the bonding layer
Implementation Method 4
the Ti islands can serve as crystal nuclei to control the orientation of PZT during the deposition of the PZT film
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An actuator as a piezoelectric device has a bonding layer (24) including titanium (Ti), a lower electrode (25) including platinum (Pt), a piezoelectric thin film (26), and an upper electrode formed in this order on a substrate. Ti particles (24a) precipitate from the bonding layer (24) onto the lower electrode (25). Pt that forms the lower electrode (25) has a crystal grain size of 75 nm to 150 nm.