JP3221166B2 - Manufacturing method of piezoelectric resonator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is based on the principle that PbTiO _3-
The present invention relates to a method for manufacturing a piezoelectric resonator having a piezoelectric substrate made of PbZrO ₃ .

[0002]

2. Description of the Related Art Conventionally, the main component is PbTiO ₃ -PbZr.
In a piezoelectric resonator having a piezoelectric substrate made of O ₃ , after polishing the outer surface of the piezoelectric substrate, an adhesive metal layer (Ta, Mo, Cr, Ti) + conductive metal layer is formed on the front and back surfaces of the piezoelectric substrate by vapor deposition. (Cu, Ag, Au, Pd, etc.) + Corrosion prevention metal layer (Ag, Au, Pd, etc.)
Next, a resist coating is performed to form an electrode pattern, and then an electrode is formed by wet etching with a strong alkali or strong acid etching solution.

[0003]

In the above-mentioned conventional configuration,
Distortion occurred during polishing of the piezoelectric substrate, and surface defects occurred due to scratching by abrasive grains, and during wet etching, the surface of the piezoelectric substrate was eluted with an etchant, resulting in a rough surface state. . As a result, there is a problem that the elastic wave is attenuated and the dynamic range represented by (Equation 1) is reduced.

[0004]

(Equation 1)

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a piezoelectric resonator having a large dynamic range by preventing distortion of a piezoelectric substrate and roughness of a surface state, thereby preventing elastic wave attenuation. It is the purpose.

[0006]

Means for Solving the Problems In order to achieve this object, the present invention provides a composition comprising PbTiO ₃ -PbZrO ₃ as a main component.
And at least one of Sr, Ba, and Ca
Polishing the outer surface of a piezoelectric substrate containing two types of compounds
Step 1 and then 50 to 2 from the sintering temperature of the piezoelectric substrate.
A second step of heat treatment at a temperature lower by 00 ° C .;
Aluminum film by vapor phase plating on the front and back of the piezoelectric substrate
Forming a third step, and thereafter, on this aluminum film
Resist coating to form an electrode pattern on the fourth
And then the aluminum film is treated with phosphoric acid , nitric acid and acetic acid.
Wet etching with an etching solution consisting of water and water
And a fifth step of forming an electrode by
You.

[0007]

According to the above method , the piezoelectric substrate is heated at a temperature lower than the sintering temperature.
Heat treatment at a temperature lower by 50 to 200 ° C.
Repairs defects and internal distortions generated in the piezoelectric substrate during the polishing process
be able to. The aluminum film used as an electrode, the adhesion metal layer is not required since Ru create a strong bond with oxide ceramic. Further since the aluminum film stabilized oxidized non-operating <br/> body coating formed on the surface, the corrosion preventing layer is not required.

In addition, in a phosphoric acid-nitric acid-acetic acid-based etchant, the elution rate of the piezoelectric substrate is extremely low, and the thickness of the aluminum film causes almost no surface defects on the piezoelectric substrate.

Therefore, the method of manufacturing a piezoelectric resonator according to the present invention can provide a piezoelectric resonator having a large dynamic range while preventing attenuation of elastic waves.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a piezoelectric resonator according to one embodiment of the present invention.

First, PbO, TiO_Two, ZrO_Two, SrCO
_Three, BaCO_Three, CaCO_Three, MnO_Two, Cr_TwoO_Three, Co
O, Fe_TwoO_Three, NiO, Al_TwoO_Three, Nb_TwoO_Five, Ta
_TwoO_Five, La _TwoO_Five, Sb_TwoO_Three(Table 1) and (Table 2)
The components were weighed and wet-mixed to obtain the composition shown.

[0012]

[Table 1]

[0013]

[Table 2]

After calcination at about 850 ° C. for 2 hours, an organic binder is added to the pulverized product, and the resulting mixture is granulated.
0mm, 1mm thick disk-shaped, 110mm in closed furnace
The resultant was baked at 0 to 1300 ° C. for about 1 hour to form the piezoelectric substrate 1.

A vibrating electrode 2 having a diameter of 2 mm was formed on the front and back surfaces of the piezoelectric substrate 1 by the following two methods. In addition, the sample No. of (Table 1). Using the second method only for 5, 6
The first method was applied to the remaining samples.

The first method is an embodiment of the present invention, in which the GC
Lapping the outer surface of the piezoelectric substrate 1 with # 2000 abrasive grains,
The thickness of the piezoelectric substrate 1 was reduced to 0.3 mm, and then a heat treatment was performed at the temperatures shown in (Table 1) and (Table 2).
Next, an aluminum electrode film is formed on the entire front and back surfaces of the piezoelectric substrate 1 by vacuum deposition, then the piezoelectric substrate 1 is polarized using the front and back electrode films, and then a resist coat is formed on the electrode film. A vibration electrode pattern was formed by photolithography, and after etching, the resin on the vibration electrode 2 was removed.

In the second method, thick-film Ag electrodes are baked on both surfaces of the piezoelectric substrate 1 by a conventional method, and after polarization, both surfaces are lapped and polished with GC # 2000 abrasive grains so as to have a thickness of 0.3 mm. Then, the vibrating electrode 2 shown in FIG. 1 was formed by mask evaporation.

The etching solutions used are (Table 3) and (Table 4)
Shown in

[0019]

[Table 3]

[0020]

[Table 4]

In Tables 3 and 4, the vibration mode is a thickness longitudinal vibration mode of the piezoelectric resonator. This depends on the Poisson's ratio of the piezoelectric substrate and is selected from a fundamental wave or a harmonic that can confine the vibration energy.

The dynamic range was determined by (Equation 2).

[0023]

(Equation 2)

FIG. 2 shows a sample N formed using the second method.
o. 5 is a schematic SEM photograph of a porcelain surface of the piezoelectric resonator of No. 5. FIG. 3 is a schematic SEM photograph of a porcelain surface of a piezoelectric resonator produced by a method according to an embodiment of the present invention. As can be seen by comparing these two figures, the piezoelectric resonator made by the manufacturing method of the present invention has no change in the surface of the porcelain, whereas the piezoelectric resonator made by the conventional manufacturing method has a porcelain with elution of grain boundaries. The crystal grains on the surface can be clearly distinguished. Sample No. It is considered that this is why the dynamic range of the piezoelectric resonators 5 and 6 is smaller than that of the other piezoelectric resonators.

FIG. 4 is a graph showing the yield rate of the piezoelectric resonator with respect to time at a temperature of 60 ° C. and a humidity of 95%. The non-defective piezoelectric resonator ratio was defined as the number ratio of the piezoelectric resonator having a dynamic range of 90% or more of the initial value. Sample No. 1 is 1
No dynamic range has decreased after 000 hours. Sample No. In Nos. 5 and 6, the dynamic range is reduced by 10% or more after 200 hours or more, and it can be seen that the non-defective rate decreases with time.

Sample No. 4,8,10,12,1
4,16,18,20,22,24,26,28,3
Nos. 0, 32 and 34 have not been subjected to heat treatment after polishing the surface of the piezoelectric substrate. When the dynamic range is compared with that of a piezoelectric substrate having the same composition and subjected to heat treatment, the dynamic range is lower by 5 dB or more.

[0027]

As described above, according to the present invention, the surface defects and internal strains caused by the polishing of the piezoelectric substrate are reduced by 50 to 50 °
It is repaired by heat treatment at a temperature lower by 200 ° C. The electrode is a single-layer thin film of aluminum, and elution of the surface is prevented by using a phosphoric acid-nitric acid-acetic acid-based etchant having low reactivity with the piezoelectric substrate in forming the electrode.

As a result, it is possible to obtain a piezoelectric resonator having a large dynamic range while preventing attenuation of elastic waves of the piezoelectric resonator.

[Brief description of the drawings]

FIG. 1 is a perspective view of a piezoelectric vibrator according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a surface SEM photograph of a piezoelectric substrate of a piezoelectric resonator created by a conventional manufacturing method.

FIG. 3 is a diagram schematically illustrating a surface SEM photograph of a piezoelectric substrate of a piezoelectric resonator according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a defective product rate of the piezoelectric resonator over time.

[Explanation of symbols]

 1 piezoelectric substrate 2 vibrating electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 3/00-3/04 H01L 41/22-41/26

Claims (1)

(57) [Claims] 1. PbTiO ₃ —PbZrO ₃ as a main component
And at least one of Sr, Ba, and Ca
Polishing the outer surface of a piezoelectric substrate containing two types of compounds
Step 1 and then 50 to 2 from the sintering temperature of the piezoelectric substrate.
A second step of heat treatment at a temperature lower by 00 ° C .;
Aluminum film by vapor phase plating on the front and back of the piezoelectric substrate
Forming a third step, and thereafter, on this aluminum film
Resist coating to form an electrode pattern on the substrate
And then the aluminum film is treated with phosphoric acid , nitric acid and acetic acid.
Wet etching with an etching solution consisting of water and water
And a fifth step of forming an electrode according to (1) .