JPS6288408A - Piezoelectric vibrator and its manufacture - Google Patents

Abstract

PURPOSE:To increase the intensity and to improve the productivity while stabilizing the quality by sticking diaphragms made of constant elasticity thin metallic plates to a metallic base having holes in advance. CONSTITUTION:A piezoelectric vibrator utilizing the thickness vibration mode of the piezoelectric thin film 6 consists of a metallic plate 8, a diaphragm 9, the piezoelectric thin film 6 and an upper electrode 7. Plural holes 10 are made to the metallic plate 8. The holes 10 are made to make the vibrating part of the piezoelectric vibrator free. The diaphragm 9 is stuck to the surface of the metallic plate 8 by cold or hot rolling processing. The piezoelectric thin film 6 and the upper electrode 7 are formed to a position of the hole 10 at the rear face on the diaphragm by sputtering and vapor-deposition. Then single vibrators are obtained by cutting the base at each hole 10 in the direction of arrow A. The processes above are executed by the mechanical processing only to contribute to the productivity and sufficient strength is obtained by using the metal.

Description

Detailed Description of the Invention (81) Technical Field The present invention relates to a piezoelectric vibrator for high frequency use that utilizes the thickness vibration mode of a piezoelectric thin film such as zinc oxide ZnO, and a method for manufacturing the same.

(bl Conventional technology and its drawbacks) A diaphragm plate made of a constant elastic metal material such as Erinba.Secondly, a piezoelectric vibrator that uses a spreading vibration mode in which a piezoelectric thin film such as zinc oxide ZnO is formed has a frequency of up to about 5MHz. However, when used at high frequencies of several tens of MHz or higher, piezoelectric vibrators that utilize the thickness vibration mode of piezoelectric thin films are used.However, piezoelectric vibrators that utilize such thickness vibration modes are In order to increase the height of the vibration, the thickness of the vibrating part consisting of the diaphragm plate and piezoelectric thin film must be made sufficiently thin.For this reason, if you try to support the piezoelectric thin film only with the diaphragm plate, the plate thickness will become too thin and the rigidity will decrease. Because of this, it was necessary to support the periphery of the diaphragm plate with a holding frame.For this reason, conventional piezoelectric vibrators do not use a metal material such as a diaphragm, but instead rely on the anisotropy of the silicon substrate. Etching was used to integrally form a thin diaphragm plate and a holding frame that supported the periphery of the thin diaphragm plate.The manufacturing method of this conventional piezoelectric vibrator will be explained based on Fig. 3.First, the surface of the silicon substrate l A thin F'- film layer 2 is formed by doping boron (13) or the like, and an even thinner silicon oxide film layer 4 is formed on the - of this doped layer 2.Next, the back side of this silicon substrate l is A hole 3 is formed by etching from the bottom.Since this hole 3 makes use of the anisotropy of the silicon substrate 1, it is etched only in the depth direction, and 1Jty is etched in the vertical direction.
t tar is hardly etched, and since the etching rate of the doped layer 2 such as the boron 11 is at a boundary with that of the undoped silicon substrate 1, the etching rate is limited to 1 in this doped layer 2, and there is no etching between the doped layer 2 and the surface. A hole 3 is formed in which the thin plate-shaped silicon oxide film layer 4 and the doped If42 remain.

The silicon substrate l remaining around the hole 3 thus formed is used as a holding frame, and the thin silicon oxide film layer 4 between the bottom and surface of the hole 3 is used as a diaphragm plate. A lower electrode film 5 is formed on the top by sputtering or the like. Piezoelectric thin films 6 and -1 such as zinc oxide (ZnO)
By forming part of the electrode crotch 7, a piezoelectric vibrator is completed.

However, the conventional piezoelectric vibrator t configured as described above
It is because the thickness and surface condition of the doped layer 2 are not stable due to non-uniform doping depth and non-uniform etching amount.
The diaphragm plate composed of the doped layer 2 and the silicon oxide film layer 4 has poor uniformity, and not only lacks stability of vibration characteristics, but also the silicon oxide film layer 4 has a weak strength as a diaphragm plate over time. Moreover, there is a disadvantage that the number of work steps such as doping, formation of the silicon oxide film layer 4, and etching is increased, resulting in a lack of productivity.

fc1 Purpose of the invention This invention was made in view of the above circumstances, and by bonding a diaphragm plate made of a thin plate of a constant elastic metal material to a metal plate with holes provided in advance, quality can be stabilized and A piezoelectric vibrator with increased strength and production (11 directions) and its manufacturing method will be described as 1-1.

(d+ Structure and results of the invention) The piezoelectric vibrator of this invention has a hole on the back side for passing Vt or a hole on the back side at the - part of the flat surface.
8. A die phragm consisting of a thin plate of a constant elastic metal material closely fixed on the surface of the second metal plate, and a piezoelectric thin film 7 formed on the diaphragm plate at appropriate positions with holes on the back surface. The 45th feature is that it is composed of an electrode film.

When the piezoelectric vibrator of the present invention is configured as described in -1-, a diaphragm plate made of a constant elastic metal material formed in advance into a thin plate shape is used, so the thickness and surface condition are flat. Vibration characteristics are stabilized. Also, metal disc and constant bullet 1!
1 metal 42 (is used as the holding frame, the diaphragm, and the plate, respectively, so partial strength can be obtained.

Therefore, the piezoelectric vibrator of the present invention can stabilize the quality of the product.

11. A method for manufacturing a piezoelectric vibrator according to the present invention is to make a hole in a part of the flat surface of a metal plate that penetrates the back surface or does not penetrate the back surface, and then a constant elastic metal is formed on the surface of the metal plate. The method is characterized in that a diaphragm plate made of thin plates of material is bonded together by cold rolling or hot rolling, and furthermore, a piezoelectric thin film and an electrode film are appropriately formed on the diaphragm plate at positions with holes on the back surface.

When the method for manufacturing a piezoelectric vibrator of the present invention is configured as described above, the diaphragm plate and holding frame portion of the piezoelectric vibrator whose quality is stable and improved can be formed by machining, so that the piezoelectric vibrator can be manufactured at low cost. be able to. Therefore, the piezoelectric vibrator manufacturing method of the present invention can improve the productivity of piezoelectric vibrators with stable and improved quality.

(Ql Embodiment FIG. 1 is a perspective view of a metal plate and a diaphragm plate of a piezoelectric vibrator used in an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of the same piezoelectric vibrator.

The piezoelectric vibrator of this embodiment is composed of a metal plate 8, a diaphragm plate 9, a piezoelectric thin film 6, and a partial electrode 7. Metal plate 30: l, constant bullet 1?1 metal) IA'it''It is a flat plate on both sides with sufficient thickness compared to a diaphragm plate made of other rollable metal materials, and at the manufacturing stage Since a plurality of piezoelectric vibrations 1) are applied all at once, a large number of holes 10 are formed as shown in FIG. 1. In this embodiment, the holes 10 are through holes.
Since it is for freeing the vibrating part of the piezoelectric vibration r-, it may be a type that does not penetrate the back side of the metal plate 8. The diaphragm plate 9 is a thin plate made of a constant elastic metal material such as Erimba in the form of a foil, and is closely fixed to cover the surface -I- of the metal plate F. The piezoelectric thin film 6 is a thin film of zinc oxide formed by sputtering on the surface -1= of this ditophragm plate 9.The upper electrode 7 also serves as the piezoelectric thin film 61-. It is a thin film of aluminum formed by vapor deposition with open ends.

The piezoelectric vibrator of this example is 1. If you configure it as shown below,
Since a constant elastic metal material processed into a foil shape in advance is used as the diaphragm plate 9, the thickness can be kept constant and the surface state can be made flat, thereby stabilizing the vibration characteristics of the piezoelectric thin film 6 formed thereon. I can do it. Further, since metal is used for the diaphragm plate 9 and the holding frame, the rigidity is higher than that of a silicon oxide film layer or a silicon substrate, and sufficient strength can be obtained. Furthermore, since the diaphragm plate 9 is also used as the lower electrode, the step of forming the lower electrode film can be omitted.

A method of manufacturing the piezoelectric vibrator of this example will be explained. first,
A plurality of holes 3 are made in a metal plate 8 by punching. Next, a diaphragm plate 9 is bonded onto the surface of this metal plate 8 by cold rolling. Such bonding of metal plates can be carried out reliably and firmly even between dissimilar metals by the manufacturing method of Kuraso I' material. In addition,
This bonding can also be performed by hot rolling. The piezoelectric Fi film 6 and the upper electrode 7 are formed by sputtering and vapor deposition at the positions of the holes 10 on the back surface of the diaphragm plate 9 bonded to the metal plate 8 in this manner. Finally, the metal plate 8 and diaphragm plate 9 on which the piezoelectric thin film 6 and two-part electrode 7 have been formed are cut at each hole 10 at the point indicated by arrow A in FIG. 2, and packaged as a single piezoelectric vibrator. will be stored in.

When the method for manufacturing the piezoelectric vibrator of this embodiment is configured as described in -, the holes 1o in the metal plate 8 are formed by punching, and the diaphragm plate 9 is cold-rolled or hot-rolled.
Since the metal plate 8 is bonded to the surface of the metal plate 8, these steps are performed only with machine oil T, which contributes to improved productivity. Incidentally, the crank 1 material made by bonding dissimilar metals together in this way is applied to bimetals, etc., and has gained sufficient technical reliability.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a metal plate and a diaphragm plate of a piezoelectric vibrator used in an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of the same piezoelectric vibrator, and FIG. 3 is a vertical cross-section of a conventional piezoelectric vibrator. It is a diagram. 6-piezoelectric thin film, 7-" partial electrode, 8-metal plate, 9-diaphragm plate, 10-hole.

Claims (2)

[Claims] (1) A metal plate in which a hole that penetrates or does not penetrate the back surface is provided in a part of the flat surface, and a diaphragm plate made of a thin plate of a constant elastic metal material that is closely fixed to the surface of the metal plate. A piezoelectric vibrator comprising a piezoelectric thin film and an electrode film appropriately formed on the diaphragm plate at positions with holes on the back surface. (2) A hole is drilled in a part of the flat surface of the metal plate, and then a diaphragm plate made of a thin plate of a constant-modulus metal material is cooled on the surface of the metal plate. A method for manufacturing a piezoelectric vibrator, which comprises bonding the diaphragm plates together by rolling or hot rolling, and further forming a piezoelectric thin film and an electrode film on the diaphragm plate at positions where holes are provided on the back surface.