JP3432983B2 - Quartz crystal resonator and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a crystal unit whose outer shape is formed by etching and a crystal unit in which the diffusion of Cr is prevented.

[0002]

2. Description of the Related Art Conventionally, the structure of a protect film used for etching a quartz plate, which is an outer shape of a quartz plate by etching, has a C on the surface of the quartz to be left.
A method of vapor-depositing an r (chrome) layer, vapor-depositing an Au (gold) layer thereon, immersing it in an etching solution (hydrofluoric acid mixed solution), and etching and removing a portion without a protective film by photolithography. Was taken. Further, an electrode for depositing an Au layer on a Cr layer has been used as an excitation electrode of a crystal unit.

[0003]

However, when the thickness of the crystal plate to be processed becomes thick, the etching time becomes long, the protect film cannot withstand the time, and when the protect film is damaged, the part where the protect film is damaged is damaged. The crystal, that is, the necessary portion of the crystal plate, is etched. Moreover, Cr is diffused into the Au layer only with the Cr layer and the Au layer in the excitation electrode. As a result, the elastic constant apparently changes, and the frequency changes with time.

FIG. 3 shows a conventional example. It suffices to increase the thickness of the protect film on the crystal plate 1. The Au layer 3 is vapor-deposited on the underlayer of the Cr layer 2 of the protect film.
When the Au layer is vapor-deposited thickly, the Au particles become huge and gaps are generated between the particles to make the vapor deposition surface less dense. Therefore, even if the protective film of the Au layer is thickened, the protective effect cannot be improved. . Therefore, in a case where the protect film is damaged, there is a problem that the time-consuming work such as having to stop the etching, reattach the protect film, and continue the etching increases.

[0005]

In order to solve this problem, in order to improve the protection effect in proportion to the thickness of the protection film, the protection film can be thickened while maintaining a dense state. An Au layer is vapor-deposited on the underlayer of the Cr layer of the protect film, a Cr layer is vapor-deposited on the Au layer, and an Au layer is further vapor-deposited thereon. Thus, the problem was solved by stacking the Au layers while sandwiching the Cr layer. Also,
It was possible to prevent the diffusion of Cr into Au by vapor-depositing an Au layer on the Cr layer and further depositing an Au layer on the Ni layer or the NiCr layer in the excitation electrode.

[0006]

[Background and Action] Generally, when a thin quartz plate (for example, a plate up to about t = 0.2 mm) is etched, a protective film formed by vapor deposition of a Cr layer and an Au layer is sufficient. . However, in recent years, the necessity of etching a thick crystal plate (for example, a plate having a thickness of about t = 0.2 to 0.6 mm) has increased, and it is necessary to say that the etching surface is etched as vertically as possible from the surface of the crystal plate. The nature has increased.

The fact that the etching surface is perpendicular to the surface of the crystal plate means that the crystal is an anisotropic crystal and therefore the etching rate differs depending on the axial direction of the crystal. In the case of a quartz plate having a flat surface), the etching cross section on the X axis is etched from both sides of the quartz plate, so that the center in the thickness direction of the plate tends to be convex. The central projection in the thickness direction of this plate is related to the axial direction of the crystal, −
The cross section in the X direction has a small convex in the center of the plate in the thickness direction,
In the cross section in the + X direction, the central projection in the thickness direction of the plate is large.

The central protrusion in the thickness direction of the crystal plate becomes a factor of deteriorating the characteristics of the crystal unit because of the cause of imbalance of the arm. Therefore, we want to eliminate the central protrusion in the thickness direction of the crystal plate.

In general, in order to reduce the central projection of the crystal plate in the thickness direction, it is realized by prolonging the etching time (etching more deeply than just removing the crystal plate). it can. Etching is performed until the projection of the largest central projection in the thickness direction of the crystal plate is reduced to a satisfactory degree or disappeared, so that the etching time naturally increases.

This is the background to the need for a protective film that can withstand etching for a long time. Incidentally, the reason why the protect film using the Au layer, which should not be originally attacked by the etching solution, is attacked is due to the diffusion of Cr. Due to its good diffusibility, Cr diffuses into other substances (eg, quartz, Au, etc.). Due to this diffusion, the adhesiveness is good, and it is used for bonding the quartz layer and the Au layer. However, if Cr diffuses into Au and spreads to the surface of the Au layer, during etching,
The Cr portion is attacked by an etching solution (for example, a hydrofluoric acid mixed solution) to open a hole in the protect film, and the quartz plate in the hole portion is attacked. After the outer shape is formed, the protect film is removed and the excitation electrode is formed on the crystal piece. In the excitation electrode, the apparent elastic constant fluctuates due to the progress of diffusion of Cr into Au, and the frequency gradually changes.

[0011]

【Example】

(Embodiment related to claim 1) FIG.
FIG. 3 is a sectional view showing a detailed example regarding the above. The Cr layer 2 is vapor-deposited on the crystal plate 1, and the Au layer 3 is vapor-deposited thereon. A Cr layer 4 is vapor-deposited thereon, and an Au layer 5 is vapor-deposited thereon. This means that two sets of Cr layer and Au layer films were vapor deposited. A Cr layer 6 is vapor-deposited thereon, and an Au layer 7 is vapor-deposited thereon.
This means that three sets of Cr layer and Au layer films were deposited.

The Cr layer is 50 ± 10% nm, and the Au layer is 20.
An example of the relationship between the number of vapor deposition layers of the protect film and the protect time when the etchant is 0 ± 10% nm and is used as an etching solution (for example, a hydrofluoric acid-based etchant) is as follows.

[0013] Number of vapor deposition groups Protect time 1 group → 60 minutes 2 pairs → 180 minutes 3 groups → 300 to 360 minutes

When the Cr layer and the Au layer are overlapped, the protect time of the protect film becomes longer as the protect layer increases, as described above. The number is about 3 times and about 6 times that of the set.

(Embodiment relating to Claim 2) FIG. 2 is a sectional view showing a detailed embodiment relating to Claim 2 of the present invention. The Cr layer 2 is vapor-deposited on the crystal plate 1, and the Au layer 3 is vapor-deposited thereon. A Ni or NiCr layer 8 is vapor-deposited thereon, and an Au layer 9 is vapor-deposited thereon. This prevents the Ni layer from spreading Cr to the surface of the Au layer film.

Cr layer 50 ± 10% nm, Au layer 190 ±
10% nm, Ni or NiCr layer 30 ± 10% nm, A
When the u layer is 200 ± 10% nm and an etching solution (for example, a hydrofluoric acid-based etching agent) is used, an example of the protect time of the protect film is about 400 minutes.

(Embodiment relating to claim 3) FIG. 2 shows a sectional view of an embodiment relating to claim 3 of the present invention. The excitation electrode has the same structure as in claim 2 described above. Cr on the crystal plate
Although diffusion occurs between the layer 2 and the Au layer 3, a Ni or Ni or NiCr layer 8 is further formed on the Au layer 3, and an Au layer 9 is further formed.
Of Cr diffused in the Au layer 3 by vapor deposition of
Is blocked by the Ni or NiCr layer 8 and can no longer diffuse. The Au layer 9 on the Ni or NiCr layer 8 is for preventing the Ni or NiCr layer 8 from being oxidized.

[0018]

According to the present invention, since a protect film having a long protect time against an etching solution can be realized, not only is it possible to etch a thick crystal plate by forming the protect film once. , The etching surface perpendicular to the crystal surface can be easily made, and therefore, the effect of being able to realize the processing of the crystal plate with a good outer shape balance accuracy can be achieved. We were able to reduce costs through improvements. Also, C is used as the excitation electrode.
By vapor-depositing r, Au, Ni or NiCr, Au, the diffusion of Cr into Au was reduced, and the change with time of the crystal unit was extremely reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the structure of a protect film of the present invention.

FIG. 2 is a cross-sectional view showing an example of a structure of a protect film and an excitation electrode of the present invention.

FIG. 3 is a cross-sectional view showing an example of a structure of a protect film and a structure of an excitation electrode film of a conventional technique.

[Explanation of symbols]

1 Crystal plate 2, 4, 6 Cr layer 8 Ni or NiCr layer 3, 5, 7, 9 Au layer

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03H 9/00-9/24 H03H 3/02

Claims (3)

(57) [Claims] 1. A method for manufacturing a crystal resonator, wherein an outer shape is formed by etching , wherein a Cr layer is formed on a crystal plate.
Forming, forming an Au layer on the Cr layer, and forming on the Au layer
In addition, a layered film consisting of a Cr layer and an Au layer,
A protective film with multiple layers stacked so that
A method for manufacturing a crystal unit, which is characterized by being used. 2. A method of manufacturing a crystal unit, wherein an outer shape is formed by etching , wherein a Cr layer is provided on a crystal plate.
Forming, forming an Au layer on the Cr layer, and forming on the Au layer
Ni or NiCr layer is formed on the
Use a protect film with a Au layer formed on top
A method of manufacturing a crystal unit, comprising: 3. A crystal resonator having an excitation electrode formed on a crystal plate, wherein a layer structure of the excitation electrode formed on the crystal plate is
First, the layer formed on the quartz plate is a Cr layer, and the Cr layer is
The upper layer is an Au layer, and the layer above the Au layer is a Ni layer or an N layer.
The iCr layer is used, and the layer above the Ni layer or the NiCr layer is Au.
A crystal unit having a four-layer structure including layers.