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KRYSTAL,lnc. > Why do customers choose KRYSTAL?

The evolution of materials leads to breakthroughs

素材の進化が限界突破へ導く

KRYSTAL has long been involved in the MEMS film forming business. MEMS is already used in many products and applications, including automotive and telecommunications devices. Piezoelectric MEMS, which incorporates piezoelectric thin film, enables even more compact sizes and more advanced applications than conventional MEMS, and so can be used in an even broader range of applications.
In addition to the film forming technologies cultivated up to now, the adoption of single crystal piezoelectric thin film has made it possible to develop and manufacture high voltage piezoelectric MEMS devices that are even better suited to general-purpose applications.
Single crystal technologies contribute to resolving the customers’ issues, realizing functionality that had been considered impossible to achieve in the past.

KRYSTAL’s single crystals

KRYSTALの単結晶

The most distinctive feature of KRYSTAL’s single crystal technologies is the broad process margin, which is made possible by unique buffer layer technologies. The buffer layer changes its shape to fill in gaps between the substrate and the crystal lattice of the piezoelectric thin film, creating a single crystal structure with minimal residual stress.
Furthermore, advanced plasma control enables fine-tuning of material characteristics in keeping with the application, with no change in the material composition.
Piezoelectric materials manufactured using basic film structures have the following characteristics:

  • ① They maintain continuous single crystal structures from the silicon (Si) substrate, and reflect single crystal structures without being influenced by the thickness of the piezoelectric thin film
  • ② They have a “ Cube on Cube” structure; that is, a crystal structure somewhat like dice stacked up so they will not roll
  • ③ There are few crystal flaws in piezoelectric thin film on strontium ruthenate (SRO), enabling reliable operation even with sub-micron thickness

These characteristics can be applied not only to PZT (lead zirconate titanate), which is well known as a piezoelectric material, but also to barium titanate (BTO) and numerous other materials as well. Silicon based substrates with a regular (100) orientation are used as a standard, but other orientations have the following characteristics:

  • ④ When the silicon substrate orientation of <(110) or (111)> is changed, the film orientation can be carried over from the upper layer, providing an optimum combination of materials.

KRYSTAL offers these platforms and proposes ideal combinations to meet the customers’ needs.

MEMS

MEMS

MEMS, which are minute in size and have 3D structures,are already used extensively throughout the world,and these applications continue to expand. In the past, electrostatic MEMS were the mainstream, but in recent years, there has been a growing trend toward the adoption of piezoelectric MEMS devices, which use piezoelectric thin film to achieve even more advanced characteristics. Piezoelectric thin film dramatically affects the characteristics of piezoelectric MEMS. The use of single crystals in this piezoelectric thin film further draws out these exceptional device characteristics.

PZT created by KRYSTAL’s single crystals technology

KRYSTALの作る単結晶PZT

Lead zirconate titanate (PZT) thin film is one of the platforms offered by KRYSTAL Inc. PZT has drawn attention as a material that demonstrates the highest performance of any piezoelectric thin film type, and which can be applied in a wide range of application fields. Although it has been the subject of research reports targeting single crystal technologies, KRYSTAL is the only company that has achieved commercialization of PZT thin film (as of May 2020), demonstrating both productivity and stability. KRYSTAL’s product lineup also features varying characteristics in keeping with the application requirements. We offer optimum solutions to support customers’ piezoelectric MEMS applications.

Unique features of KRYSTAL’s single crystal
KRYSTALの単結晶PZTの特長

Following are the most notable features of PZT thin film produced by KRYSTAL:

  • ① Single crystal thin film
  • ② Initial polarization from immediately after film forming
     is maintained
  • ③ High heat resistance, with no depolarization even at reflow
     temperatures (450℃)
  • ④ Dielectric constant is less than half compared to
     polycrystalline materials with similar displacement

By leveraging these unique features, KRYSTAL offers two types of standard films with differing characteristics:

  1. 1.Sensor specifications
    These thin films have strong c-axis orientation, so the dielectric constant is reduced to 140 or less, which in turn increases the electric charge generated by distortion.
    The films are designed to match applications using piezoelectric effects.
  2. 2.Actuator specifications
    These thin films have a high d-constant and withstand voltage, and a low dielectric constant.
    The films are designed to match applications using inverse piezoelectric effects.

KRYSTAL’s strength is in its ability to customize film characteristics using plasma control. We provide customers with optimum PZT solutions based on their evaluation of these standard films.

KRYSTAL’s thin film technologies

The synthesis of single crystal PZT was considered extremely dif ficult in the past, but KRYSTAL has established a manufacturing method by combining the plasma control and inorganic crystal control technologies that it cultivated through many years of experience in the formation of DLC film.
Single crystal PZT can be applied in a wide range of semiconductor processes, and demonstrates outstanding characteristics in comparison to existing polycrystalline materials.

Mechanisms of single crystal technologies

The key to KRYSTAL’s single crystal technologies is in the buffer layer, and the shape of zirconia in particular. A minute pyramid (nano-pyramid) structure grows regularly on the interface surface of platinum or zirconia.
This is thought to be because in the case of zirconia, which has a tetragonal structure, the space group has a P4₂/nmc Ditetragonal-dipyramidal structure, so the crystal grows as the pyramid structure is formed.
This nano-pyramid structure is a “variable pyramid” depending on the crystal lattice of the piezoelectric material, and it has been proven that structures actually change when different films are formed using different piezoelectric materials. It is possible to automatically control the orientation by changing the upper and lower film in the buffer layer itself, rather than the buffer layer for regular lattice adjustment. In this way, it becomes possible to secure a broad process margin, and to form single crystals using a wide range of materials.

Advanced Material Technologies

Advanced Material Technologies

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