JP2000349578A - Manufacture of crystal vibration chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contribute to cost reduction of a manufacturing method of a crystal vibration chip by reducing a consumed quantity of a metallic material (especially Au) used for a pattern mask. SOLUTION: In the manufacturing method of the crystal vibration chip that has a pattern mask forming process where pattern masks 2, 3 are formed on a crystal substrate 1 and an etching process where a liquid containing fluoric acid is used to etch the crystal substrate 1 on which the pattern masks are formed in this order, a metallic thin film is formed by sputtering under a condition of a gas pressure of 0.45 Pa or below in a metallic thin film forming process conducted in the pattern mask forming process.

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 resonator element used for an ultra-small crystal resonator such as a tuning-fork type crystal resonator and an AT-cut type crystal resonator.

[0002]

2. Description of the Related Art FIG. 2 is a view for explaining a method of manufacturing a crystal resonator element used for a conventional tuning-fork type crystal resonator. This manufacturing method is described, for example, in Japanese Patent Application Laid-Open No. 57-99012.
No. 6,009,045.

According to this method for manufacturing a crystal resonator element, first, a metal thin film including a Cr film 5 and an Au film 6 is formed on a quartz substrate 1 by sputtering (FIG. 2A). The gas pressure during sputtering at this time is usually 0.5 Pa
A pressure of about 2 Pa is used, and the thickness of each of the Cr film and the Au film is usually 50 nm to 200 nm.

Then, a photosensitive resin 7 is coated on the metal thin film, and is patterned into a predetermined shape by a photolithography technique (FIG. 2B).

Thereafter, the quartz substrate 1 is etched using the patterned metal thin film as a pattern mask (FIG. 2C), and the Cr film 5, the Au film 6 and the photosensitive resin 7 are etched.
Is obtained by removing the crystal resonator.

As an etching solution, a solution containing hydrofluoric acid such as hydrofluoric acid or buffered hydrofluoric acid (a mixed solution of hydrofluoric acid and an aqueous solution of ammonium fluoride) is used from the viewpoint of speedy and inexpensive etching of quartz. ing.

A Cr film 5 as a metal thin film of a pattern mask
The reason why the two-layer film of Au and the Au film 6 is used is that corrosion resistance to an etching solution is high, adhesion to a quartz substrate is good, and film formation is easy. The Au thin film acts as a complete corrosion resistant film against hydrofluoric acid or buffered hydrofluoric acid, and the Cr thin film
It works as a film that adheres the thin film and the quartz substrate.

[0008]

However, these materials are destined to be dissolved in an etching solution or a stripping solution, that is, disposable in the final step of the photolithography process. Since these materials, particularly Au, are expensive materials, they are a major factor in increasing the cost in the method of manufacturing a crystal resonator element.

Accordingly, an object of the present invention is to reduce the amount of a metal material (particularly, Au) used as a pattern mask, thereby contributing to a reduction in the cost of a method for manufacturing a crystal resonator element.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing a crystal resonator element, comprising the steps of: forming a pattern mask on a quartz substrate; and forming the pattern mask using a solution containing hydrofluoric acid. In the method for manufacturing a crystal resonator element having an etching step of etching the quartz substrate, and the pattern mask forming step, in this order,
The method is characterized by comprising a metal thin film forming step of forming a metal thin film by performing sputtering under a condition that the gas pressure is 0.45 Pa or less.

As described above, by performing sputtering under the condition that the gas pressure is 0.45 Pa or less, the number of gas molecules that are hindered during the process in which particles to be sputtered reach the quartz substrate is reduced. Therefore, the speed of the particles when colliding with the quartz substrate is increased, and the particles are strongly pushed into the thin film during film formation. As a result, the formed thin film becomes denser than the conventional thin film, and the etching resistance can be improved. Therefore, even if the film thickness is made thinner than before, the etching resistance is secured, so that the film thickness can be made thinner, and the amount of the metal material (particularly Au) used as the mask is reduced, and the crystal unit Cost of the manufacturing method can be reduced.

According to a second aspect of the present invention, there is provided a method of manufacturing a quartz oscillator piece according to the first aspect, wherein the metal thin film formed in the metal thin film forming step is a Cr film and an A thin film.
a two-layer film consisting of a Cr film and A
A feature is that both the u films are formed by performing sputtering under the condition that the gas pressure is 0.45 Pa or less.

As described above, since the metal thin film as the pattern mask is a two-layer film composed of the Cr film and the Au film,
It has high corrosion resistance to an etchant, good adhesion to a quartz substrate, and facilitates film formation. Further, since both the Cr film and the Au film are subjected to sputtering under the condition that the gas pressure is 0.45 Pa or less, a denser two-layer film can be obtained than the conventional two-layer film, so that the etching resistance is improved. In addition, the thickness can be reduced, and the amount of metal materials (Cr and Au) used as a mask can be reduced.
It is possible to reduce the cost of the method of manufacturing the crystal resonator piece.

In the method of manufacturing a quartz oscillator piece according to the present invention, both the Cr film and the Au film may be formed by performing sputtering under a gas pressure of 0.01 to 0.2 Pa. Preferred (claim 3).

Since the gas pressure is 0.2 Pa or less, sufficient densification can be achieved. Further, the gas pressure is set to 0.01 Pa
As described above, a sufficient film forming speed can be obtained.

In the method for manufacturing a crystal resonator element according to a third aspect, it is preferable that the thickness of the Au film is in a range of 5 to 15 nm.

Thus, according to the condition of claim 3, A
Even if the thickness of the u film is in the range of 5 to 15 nm, sufficient etching resistance can be obtained, which can greatly contribute to the cost reduction of the method for manufacturing a crystal resonator element.

[0018]

Embodiments of the present invention will be described below based on examples.

(Embodiment 1) FIG. 1 is an explanatory view of a method of manufacturing a quartz oscillator piece of Embodiment 1. (A) to
(C).

First, a quartz plate is cut out from a rough quartz at a predetermined angle, and further polished to obtain a quartz substrate 1. The thickness of the quartz substrate 1 is 30 to 200 microns.

Then, Cr on both sides of the quartz substrate 1
A metal thin film composed of the thin film 2 and the Au thin film 3 is formed (FIG. 1).
(A)). The metal thin film is formed by a sputtering method. Ar is used as a gas at the time of sputtering, the gas pressure is 0.05 Pa, the thickness is Cr film: 10 nm, and Au is
Film: 10 nm.

Thereafter, a photosensitive resin is formed on the entire surface by a spin coating method, exposed and developed using a predetermined photomask, and the photosensitive resin 4 is patterned. The metal thin film is patterned into a predetermined shape by a photo-etching technique of etching the Cr thin film 2 and the Au thin film 3 using as an etching mask (FIG. 1B). Here, an iodine-based aqueous solution is used for etching the Au thin film 3, and a mixed solution of ceric ammonium nitrate and perchloric acid is used for etching the Cr thin film 2.

Thereafter, the quartz substrate 1 is etched using the Cr thin film 2, the Au thin film 3, and the photosensitive resin 4 as an etching mask (FIG. 1C). As the etching solution, a mixture of 47% by weight of hydrofluoric acid and a 40% by weight aqueous solution of ammonium fluoride in a volume ratio of 1: 1 is used.

When a quartz oscillator piece was manufactured by the method of Example 1, the quartz substrate 1 under the Cr thin film 2 was formed although the Au thin film was as thin as 10 nm.
No etching damage was observed, and it was confirmed that the Au thin film 3 completely functions as an etching mask material.

Example 2 A quartz oscillator piece was manufactured under the same conditions as in Example 1 except that the gas pressure during sputtering was set to 0.1 Pa. As a result, similarly to Embodiment 1, Au
Despite the very thin film thickness of 10 nm, the quartz substrate 1 under the Cr thin film 2 is not damaged by any etching, and the Au thin film 3 completely functions as an etching mask material. It was confirmed that it was fulfilled.

Comparative Example 1 A quartz oscillator piece was manufactured under the same conditions as in Example 1 except that the gas pressure during sputtering was changed to 1.0 Pa. As a result, it was confirmed that the quartz substrate 1 under the Cr thin film 2 was damaged by etching, and the Au thin film 3 did not completely function as an etching mask material.

Comparative Example 2 A quartz oscillator piece was manufactured under the same conditions as in Comparative Example 1 except that the thickness of each of the Cr thin film 2 and the Au thin film was 100 nm. As a result, the Cr thin film 2
The quartz substrate 1 underneath was not damaged at all by the etching, and it was confirmed that the Au thin film 3 completely functions as an etching mask material. However, it requires about 10 times as much Au material as the first and second embodiments, which is an obstacle to cost reduction.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for manufacturing a crystal resonator element according to a first embodiment.

FIG. 2 is an explanatory diagram of a conventional method for manufacturing a crystal resonator element.

[Explanation of symbols]

 1. Crystal substrate 2. 2. Cr thin film Au thin film Photosensitive resin 5. Conventional Cr thin film Conventional Au thin film

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Sunagawa 3-3-5 Yamato, Suwa-shi, Nagano F-term (reference) in Seiko Epson Corporation 5J108 MM08

Claims (4)

[Claims] 1. A quartz crystal having a pattern mask forming step of forming a pattern mask on a quartz substrate and an etching step of etching the quartz substrate on which the pattern mask is formed using a solution containing hydrofluoric acid in this order. In the method for manufacturing a vibrator piece, in the pattern mask forming step, the gas pressure is 0.45 P
a. A method for manufacturing a crystal resonator element, comprising a metal thin film forming step of forming a metal thin film by sputtering under the following conditions. 2. The method according to claim 1, wherein the metal thin film formed in the metal thin film forming step is a two-layer film made of a Cr film and an Au film. A method for manufacturing a crystal resonator element, characterized in that both the Au film and the Au film are formed by performing sputtering under a gas pressure of 0.45 Pa or less. 3. The method of manufacturing a quartz resonator element according to claim 2, wherein the Cr film and the Au film have a gas pressure of 0.01.
A method for manufacturing a crystal resonator element, wherein the method is performed by performing sputtering under a condition of about 0.2 Pa. 4. The method for manufacturing a crystal resonator element according to claim 3, wherein the thickness of the Au film is in a range of 5 to 15 nm.