JP2003318695A - Piezoelectric thin-film resonator and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for a piezoelectric thin-film resonator and a manufacturing method thereof by, which especially, a gap below a resonance thin-film can be easily formed, processings such as cleaning or drying of a wafer can be easily performed, a piezoelectric thin-film resonator can be manufactured with a simple structure, and yield is improved. <P>SOLUTION: The method of manufacturing a piezoelectric thin-film resonator includes a step of forming grooves on the surface of a substrate by a mechanical means, a step of forming a resonator supporting film on the surface after providing a sacrifice layer on the grooves, a step of forming a lower electrode, a resonating film and an upper electrode on the resonator supporting film, a step of etching the resonator supporting film into a prescribed shape, a step of removing the sacrifice film from the grooves, and a step of dividing the substrate into respective resonators. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a manufacturing method of a piezoelectric thin film resonator, and in particular, it is easy to manufacture a void under a vibrator supporting film, and moreover, a process such as cleaning and drying of a substrate during processing can be performed. It has an easy structure.

[0002]

2. Description of the Related Art Resonant frequencies of conventional resonators and filters are restricted by physical dimensions such as length, width or thickness of vibrating parts. However, piezoelectric substrates such as ceramics and crystals have a limit in thickness reduction in order to miniaturize and increase the frequency of components. Therefore, semiconductor manufacturing technology can be used,
A piezoelectric thin film resonator has been studied as a microminiature resonator that can be used in a high frequency band.

The structure of the piezoelectric thin film resonator can be downsized because it utilizes a vibration mode having a relatively large electromechanical coupling coefficient such as thickness longitudinal vibration or thickness sliding vibration, and a wide band characteristic can be easily realized in the filter. Since the vibrating portion can be formed by combining materials having different temperature coefficients of elastic stiffness, a resonator having good temperature characteristics can be obtained. There are advantages such as.

Conventionally, as a method of forming a void under a thin film in a piezoelectric thin film resonator, a silicon nitride film 31 is formed on the surface of (a) as shown in FIGS. 4 (a), (b) and (c), respectively. Silicon substrate 32
A method of forming a recess by anisotropic etching so that the diaphragm is formed from the back surface to the central portion. (b) After forming the sacrificial layer 34 on the surface of the silicon substrate 32 and forming the electrodes and the vibration film 33, the sacrificial layer 34 is removed to form voids. On the silicon nitride film where the void is formed,
A method of forming a piezoelectric thin film in which electrodes are sandwiched between the top and bottom. And (c) the substrate 32 is cut from the surface to form a number of holes 35, the holes are provided with a sacrificial layer 34, the sacrificial layer is covered with a silicon nitride film 31, and the vibrating film 33 is formed on the surface. There is a method to remove 34 and make a void.

However, in the method (a), a back surface alignment device is required for manufacturing, and there is a problem that a device for adsorbing the back surface after etching is difficult to use. In the method of (b), since the step difference on the surface due to the sacrificial layer becomes large, the problem that the mask floats in a later step and the processing accuracy deteriorates, and cracks are caused by the influence of stress because a film is formed at the step difference. There are problems such as easy occurrence. Since the method (c) has almost no unevenness on both sides, it is easy to process in the subsequent steps and the influence of stress is relatively small. However, as shown in FIG. 5, the conventional voids are obtained by individual holes provided in the silicon substrate, so that there is a problem that it is difficult to wash or dry after formation. Further, although an etching process is performed to form a hole, there is a problem in that the side surface of the wafer is etched and even a small scratch is etched.

[0006]

The present invention is based on the above-mentioned (c).
The present invention is intended to solve the problems in the method of manufacturing a piezoelectric thin film resonator. By using a method of shaving the substrate from the surface of the substrate, the voids are formed into a shape that facilitates cleaning and drying of the wafer, and shaving is performed by a mechanical method without using etching.

[0007]

A piezoelectric thin film resonator according to the present invention comprises a thin film oscillator support film formed on the surface of a substrate through a void and a piezoelectric film disposed and formed on the oscillator support film in the void. A piezoelectric thin film resonator including a thin film and an electrode for exciting the piezoelectric thin film is characterized in that the gap is formed of a groove formed in a substrate and facing a side surface facing the substrate.
A method of manufacturing a piezoelectric thin film resonator according to the present invention comprises a step of forming a groove on a surface of a substrate by a mechanical means, a step of forming a vibrator supporting film on the surface provided with the groove, and a step of forming the vibrator supporting film on the vibrator supporting film. The method is characterized by including a step of forming a lower electrode, a piezoelectric thin film, and an upper electrode. Another method of manufacturing a piezoelectric thin film resonator according to the present invention is a step of forming a groove on the surface of a substrate by mechanical means, and forming a vibrator supporting film on the surface of the substrate after providing a sacrificial layer in the groove. A step, a step of forming a lower electrode, a piezoelectric thin film and an upper electrode on the oscillator supporting film, a step of etching the oscillator supporting film into a predetermined shape, a step of removing the sacrificial layer from the groove, and each resonator. It is characterized by including a step of dividing into.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A piezoelectric thin film resonator according to the present invention comprises a vibrator supporting film made of a silicon nitride thin film formed on a surface of a silicon substrate or a glass substrate through a void and a vibrator supporting film in the void. This is a piezoelectric thin film resonator provided with a piezoelectric thin film such as aluminum nitride and an electrode for exciting the piezoelectric thin film, and the voids are grooves formed by mechanical means in a silicon substrate or a glass substrate. Grooves open across the resonator substrate on opposite sides thereof. A method of manufacturing a piezoelectric thin film resonator according to the present invention includes a step of forming a groove on a surface of a substrate by a mechanical means such as a dicer, and a wafer such as silicon nitride is attached to the surface of the groove and polished to support the vibrator. It includes a step of forming a film and a step of forming a lower electrode, a piezoelectric thin film and an upper electrode on the oscillator supporting film in the groove portion. Further, the method for manufacturing a piezoelectric thin film resonator of the present invention comprises a step of forming a groove on the surface of a silicon substrate or a glass substrate by a mechanical means such as a dicer, and after providing a sacrificial layer in the groove, nitriding the surface of the substrate. A step of forming a thin vibrator supporting film such as silicon by CVD, and a step of forming a lower electrode, a vibrating film made of a piezoelectric material such as aluminum nitride, and an upper electrode on the vibrator supporting film in the groove portion,
It includes a step of etching the oscillator support film into a predetermined shape, a step of removing the sacrificial layer from the groove, and a step of dicing to separate each resonator.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In the piezoelectric thin film resonator of the present invention, as shown in FIG. 1, a groove 2 is formed on a surface of a substrate 1, a silicon nitride thin film is formed as a vibrator supporting film 3 so as to cover the groove 2, and the groove 2 is formed on the groove. A piezoelectric thin film 4 made of aluminum nitride or the like disposed on the vibrator supporting film 3, and a lower electrode 5 for exciting the piezoelectric thin film 4.
And an upper electrode 6. The groove 2 is the substrate 1 of the resonator
Across each of the opposite sides to open.

The piezoelectric thin film resonator of the present invention is manufactured by the following steps shown in FIGS. (A) of the drawing
Is a plan view, and (b) is a cross-sectional view showing a groove portion to be a void. As the substrate, for example, a silicon single crystal substrate 21 is used. The substrate of the piezoelectric thin film resonator is, for example, a silicon wafer 21, and the groove 22 is formed by processing the silicon wafer from the surface with a dicer. (2-1) Plural grooves are provided on the wafer in parallel at a predetermined interval. Its depth is about 4 microns.

Then, zinc oxide (ZnO) and phosphor conversion glass (PSG) were formed on the surface of the silicon wafer having grooves by the sputtering method.
A sacrificial film 27 is applied to fill the groove. The surface of the wafer is polished to remove unnecessary sacrificial film, and then processed into a flat surface. (2-2) A silicon nitride film (Si
₃ N ₄ ) or the like is formed as the oscillator support film 23. Surface Si
The thickness of the ₃ N ₄ film varies depending on the type of piezoelectric thin film formed on it. (2-3)

A lower electrode 25 is formed on the formed oscillator support film 23.
The Au / Cr film is formed by vapor deposition or sputtering. Lower electrode 2
A film of AlN, ZNO, PZT or the like is formed as a piezoelectric thin film 24 on 5 and an Al film is further formed thereon as an upper electrode 26 by vapor deposition or sputtering. (2-4), (2-5) (2-6)

Next, Si on the silicon single crystal wafer
_An etching pattern is formed so that the portion of the ₃ N ₄ film to be the oscillator supporting film remains. The Si ₃ N ₄ film is etched to expose a part of the groove 22 while leaving a part to be a diaphragm. (2-7) The sacrifice layer 27 is removed by etching from the exposed groove 22, the void is dug in the silicon single crystal wafer 21 from the surface of the substrate to form a diaphragm, and a vibrator is obtained. (2-8)

After forming the bumps 28 for connection from both electrodes, the elements are diced and divided along the dotted line for each element to form a groove opening on the back surface of the vibrator supporting film and 250 to 300 μm.
A 2 mm square piezoelectric thin film resonator element with square diaphragm was obtained. (2-9)

Another embodiment of the present invention is the same as the above-mentioned embodiment (2-
No sacrificial film is formed unlike 2). A silicon nitride (Si ₃ N ₄ ) wafer is directly attached to the entire surface of the silicon wafer 21 which is processed from the surface by a dicer and formed with a large number of grooves 22 in parallel at a predetermined interval without forming a sacrificial film. . The wafer is flat-polished to form a vibrator supporting film 23 having a predetermined thickness. A lower electrode, a piezoelectric thin film and an upper electrode are formed on the oscillator supporting film in the groove portion.
Electrodes for connection are derived from the upper and lower electrodes, and each element is diced and divided, and a piezoelectric thin film resonator element having a groove on the back side of the oscillator support film and a groove opening on the opposite side surface of the substrate is formed. Obtained. In this embodiment, since the sacrificial film is not formed under the vibrator supporting film, the sacrificial layer 27 is etched and removed (2
-8) It is not necessary to do it.

An example in which a silicon single crystal wafer is used as the substrate of the piezoelectric thin film resonator has been described above.
A glass substrate such as tempered glass may be used as the substrate.

[0017]

According to the present invention, in the manufacture of the piezoelectric thin film resonator, the groove of the substrate is manufactured by the mechanical working method in forming the void under the vibrator supporting film, so that the void can be easily manufactured. Moreover, the groove has a structure that facilitates processing such as cleaning and drying of the wafer. The groove can be manufactured by a mechanical method, and in this case, there is no problem such as the etching from the side surface of the wafer as in the conventional case, or the etching from a small scratch. Since the etching reaches the composite diaphragm consisting of the non-piezoelectric thin film, the piezoelectric thin film and the electrode, and the resonance characteristics are deteriorated, the yield is deteriorated with a simple structure. Will be easier.

[Brief description of drawings]

FIG. 1 is an explanatory view of a piezoelectric thin film resonator of the present invention.

FIG. 2 is a process explanatory view showing a method for manufacturing a piezoelectric thin film resonator of the present invention.

FIG. 3 is a diagram showing a method of manufacturing the piezoelectric thin film resonator of the present invention.
Illustration of the process following

FIG. 4 is an explanatory view of a conventional method for manufacturing a piezoelectric thin film resonator.

FIG. 5 is an explanatory view of a conventional method for manufacturing a piezoelectric thin film resonator.

[Explanation of symbols]

1, 21 board 2,22 groove 3, 23 Transducer support film 4, 24 Piezoelectric thin film 5, 25 lower electrode 6, 26 Upper electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroko Onoda             Toko, 18 Gomigaya, Oji, Tsurugashima City, Saitama Prefecture             Saitama Office Co., Ltd. F-term (reference) 5J108 BB07 CC04 CC09 CC11 EE13                       KK01 MM11

Claims (5)

[Claims] 1. A thin-film vibrator supporting film formed on a surface of a substrate with a space therebetween, a piezoelectric thin film arranged and formed on the vibrator supporting film in the space, and an electrode for exciting the piezoelectric thin film. In the provided piezoelectric thin film resonator, the piezoelectric thin film resonator characterized in that the void is formed of a groove formed in a side surface of the substrate facing the substrate. 2. A step of forming a groove on the surface of a substrate by a mechanical means, a step of forming an oscillator supporting film on the surface provided with the groove, and a lower electrode, a piezoelectric thin film and a piezoelectric thin film on the oscillator supporting film. A method for manufacturing a piezoelectric thin film resonator, comprising the step of forming an upper electrode. 3. A step of forming a groove on the surface of a substrate by a mechanical means, a step of forming a sacrificial layer in the groove and then forming a vibrator supporting film on the surface of the substrate, and a step of forming a vibrator supporting film on the vibrator supporting film. It includes a step of forming a lower electrode, a piezoelectric thin film, and an upper electrode, a step of etching the oscillator supporting film into a predetermined shape, a step of removing a sacrificial layer from the groove, and a step of dividing each resonator. A method of manufacturing a piezoelectric thin film resonator, comprising: 4. A method of manufacturing a piezoelectric thin film resonator according to claim 2, wherein a groove is formed on the surface of the silicon substrate by mechanical means. 5. A method of manufacturing a piezoelectric thin film resonator according to claim 2, wherein grooves are formed on the surface of the glass substrate by mechanical means.