Frequently Asked Questions
Check here to find answers to questions received from customers about KRYSTAL’s products and original technologies.
What types of unique features does single crystal PZT have?
In terms of piezoelectric characteristics, single crystal PZT maintains performance that is similar to polycrystal PZT, but with less than half of the dielectric constant. This makes it possible to reduce power consumption in actuator applications, and to increase the signal-to-noise (S/N) ratio in sensor applications.
Because there are few crystal domain walls, loss is reduced in applications that use resonance, and for the same reason, the transmission rate increases in optical applications.
Also, because the crystals are extremely stable, characteristics are not significantly influenced by environmental temperatures, and the single crystal PZT demonstrates high linearity in displacement as voltage changes.
Keep in mind that these are only examples. We can offer optimum solutions to suit your applications.
It seems that KRYSTAL has single crystal PZT for sensor applications and for actuator applications,
but how do they differ?
Both are PZT materials, but we have tuned each type to suit the applications by changing the component ratio of Zr/Ti and adjusting the recipe during film formation.
For example, PZT for actuator applications is designed to minimize power consumption and heat volumes. As a result, consumption current has been reduced to around 25% compared to polycrystal PZT, which means that the PZT can be used effectively in the miniaturization of drive ICs and other products.
In the case of sensor applications, improvements in the S/N ratio can be achieved by increasing the output electrical charge. This contributes to the development of more compact sensors or sensors with even higher sensitivity.
These two examples refer only to standard specifications. In response to requests from customers, we can tune the PZT by applying the various properties of single crystal piezoelectric film.
Do you have any single crystal piezoelectric film products that are not PZT?
Yes, we do. These are the materials that KRYSTAL currently offers in single crystal form:
〇 Metal materials: Pt, Ru, Ta, Ag, Cu
〇 Oxide film electrode material: SRO, SRTO, STO
〇 Piezoelectric film: PZT, BT, BFO, BLT, LT/LN, AlN, KNN, Ta2O5
KRYSTAL’s slogan is “All materials in single crystal thin film,” and in keeping with that slogan, we will provide a variety of single crystal film products to meet your needs.
Can you form films on any substrate?
Up to now, we have formed film on both Si and SOI substrates.
Basically, if the substrate has an exposed Si surface, then film forming is possible. We can accommodate standard substrate sizes of 4”, 6”, and 8”. If you need film forming on substrates of other sizes, please let us know.
When forming film on SOI substrates, fine adjustments to film forming conditions may be required depending on BOX layer specifications and whether there is an oxide film on the back surface, so please provide the relevant specifications. Also, if you are not able to supply the SOI substrates, we can provide those as well. Just include that request in your inquiry.
If you require film forming on substrates with oxide film or other specialized substrates, do not hesitate to ask. Our staff will be pleased to accommodate you.
We would like to purchase only the substrate with bottom electrode films, and then form the single crystal piezoelectric film ourselves. Will that work?
KRYSTAL sells the Si substrate with bottom electrode films alone as well.
Up to now, we have not been successful in creating single crystals for all materials, but many of our customers have reported success with the creation of single crystal film using our substrates with bottom electrode layers. Single crystal film formation has been confirmed in the case of non-lead-based piezoelectric materials such as AlN and KNN.
We would need you to provide basic information, but if you would like, we can offer advice regarding process conditions. All customer information is managed with the utmost care, including the completion of NDAs, so please feel free to contact our staff with any requests or concerns.
What other services do you offer, aside from film forming services and the sale of completed film products?
For example, can you help us with MEMS processes?
KRYSTAL has many engineers with extensive experience and expertise in MEMS design and process flow. By leveraging these strengths, we offer services that include design and process flow subcontracting, depending on your requirements.
In some cases, our engineers may need some time to respond, but please feel free to contact us. We also offer consulting services, leveraging our extensive experience in this field. We can provide the advice that you need, based on a rich store of knowledge that could only be gained through first-hand experience.
Please allow us to support you in ensuring the success of your project.
What should we keep in mind when using KRYSTAL’s PZT film in MEMS processes?
Single crystals are known to demonstrate orientation dependence in the etching rate. For this reason, when using wet etching, the etching is nearly perpendicular. As a result, improved performance can be expected in sensor applications and resonating devices, but there is a risk of reduced reliability in actuator applications, because stress is concentrated at the edges, and this can lead to damage originating at the edges.
Also, perchloric acid can cause SRO to dissolve, so when using Cr etching, please check the etchant components carefully.
You will also need to be careful when forming the top electrode layer on the PZT layer at high temperatures (300°C or more), because performance could deteriorate due to oxygen defects or other factors. These defects can likely be prevented by forming an oxidized electrode layer between the PZT layer and the top electrode layer. Even if performance does deteriorate temporarily, it can be recovered through an annealing process. Feel free to contact us about detailed process conditions.
I have heard that single crystal layers of lead-free piezoelectric materials are currently
in development. When do you expect that they will be ready for practical applications?
We are currently undertaking development aiming for the first practical applications during 2021. If you would like to have a sample, we can provide one even now.
There are many different types of lead-free piezoelectric materials available, and many different applications as well, so deciding which materials to give priority in development is a challenge. If you have any specific requirements, we would be pleased to work with you in preparing for the development process.
Could you give us some examples of actual devices that were created using KRYSTAL’s PZT film?
Unfortunately, none of these devices have been released to the market yet. Our customers are currently in the process of developing devices for a variety of applications, and evaluations are also underway. To give you just a couple of examples, some customers are evaluating speakers, microphones for smartphones, and ultrasonic devices. We also designed an inkjet head at the request of another customer. We have completed the prototype, and we have confirmed the ink discharge performance. Studies are underway in preparation for the startup of volume production.
Has PZT been used in any applications that apply physical properties other than piezoelectric characteristics?
There have been studies of applications as optical elements, for example in optical switches and communication filters. PZT for sensor applications in particular is being considered as a promising material for expanding the range of RF filters. There has also been a focus on PZT’s pyroelectric characteristics, and there have been studies regarding the development of devices using these characteristics.
To give you one example of a less successful case, when PZT was considered for memory applications, the conclusion was reached that these materials would not be suitable because one characteristic of single crystals is their resistance to polarization reversal.
We will continue our search for new possibilities in these materials, never deterred by a fear of failure. We look forward to receiving your various proposals and inquiries.