JP2005101849A - Manufacturing method of piezoelectric substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of piezoelectric substrates for mass-producing the piezoelectric substrates with excellent yield by using a simple wet plating method to make a metallic thin film thick without the need for using a special photo resist so as to avoid pin-holes and cracks or the like and performing the photolithography and the etching. <P>SOLUTION: The manufacturing method of piezoelectric substrates includes: a first metallic thin film forming step of using a vacuum plating to form a first metallic thin film 2 to both sides of a piezoelectric substrate base metal 1; a second metallic thin film forming step of using a vacuum plating to form a second metallic thin film 3 on the first metallic thin film; a second metallic thick film forming step of forming the metallic film 4 of the same type of material as that of the second metallic thin film by wet plating to form a second metallic thick film 5 on the second metallic thin film; a photo resist coating step; a photo resist exposure / development step for selectively removing the photo resist film; a second metallic thick film - first metallic thin film etching step; a piezoelectric substrate etching step; and a photo resist film - second metallic thick film - first metallic thin film removing step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a piezoelectric substrate used for various applications such as a piezoelectric vibrator, and in particular, a yield which is a drawback when mass-producing piezoelectric substrate pieces by processing a piezoelectric substrate base material using a photolithography technique. The present invention relates to a method for manufacturing a piezoelectric substrate that can eliminate the deterioration of the substrate.

Small piezoelectric substrates used for piezoelectric vibrators, oscillators, SAW devices, various sensors, and the like are mass-produced by processing a large-area piezoelectric substrate base material using photolithography technology.
Conventionally, for example, a metal thin film (resistant film) made of chrome and gold is sequentially formed on both surfaces of a piezoelectric substrate base material by vacuum plating (vacuum deposition, ion plating, sputtering, etc.), and this metal thin film is formed by photolithography technology. A protective film is formed by processing into a required shape, and a piezoelectric substrate piece having a desired shape is obtained by etching using the protective film.
In Japanese Patent No. 3404293, a resist film having chemical durability is applied to a hydrofluoric acid solution at 70 ° C. or higher on a metal film (Cr—Au film) of a piezoelectric base plate having a metal film formed on the surface. Then, a mask having a desired shape is placed on the resist film, exposed and developed, and the exposed metal film is removed by etching, and the piezoelectric element plate on which the metal film and the resist film are formed is heated at 70 ° C. or higher. A method for manufacturing a piezoelectric element is disclosed in which a metal film and a resist film remaining on the surface of a piezoelectric element plate are removed by etching with an acid-based solution. According to the present invention, when a metal thin film is formed on the piezoelectric element plate by a vacuum deposition method, the hydrofluoric acid solution that has permeated the resist film is transferred to the piezoelectric element due to pinholes and cracks that are easily formed in the metal thin film. The problem of reaching the plate and etching up to the unnecessary portion of the surface of the base plate can be solved.
When a metal thin film is formed on the surface of a piezoelectric substrate by a vacuum plating method such as vacuum evaporation or sputtering, the adhesion state of the metal atoms constituting the metal thin film adhering to the surface of the piezoelectric substrate is not uniform and varies widely, so it is very fine. Gaps (pinholes and cracks) are easily formed. On the other hand, to prevent the formation of pinholes and the like, it is effective to increase the thickness of the metal thin film, but it is not economical to increase the film thickness by vacuum deposition or the like, which increases the processing time. . That is, in a vacuum plating method such as a vacuum deposition method, metal atoms from the source fly in the entire vacuum chamber without directivity, and deposition with a target focused on a specific substrate surface cannot be performed. However, it is scattered to the part off the substrate surface, and a source made of an expensive metal material such as gold is wasted. Nevertheless, if an attempt is made to form a thick film by this method, a great deal of time is required and the productivity is significantly reduced. For this reason, conventionally, a resist film has to be formed on a metal thin film having pinholes and the like.
In the invention described in the above publication, a resist film having a high durability against a hydrofluoric acid solution as an etchant is formed on a metal thin film to enhance the protection power.
However, since this conventional example uses a special photoresist, there is a drawback that the cost is increased.
Japanese Patent No. 3404293

  The present invention has been made in view of the above, and after forming a metal thin film as a resistant film on the piezoelectric substrate surface by vacuum plating methods such as vacuum deposition and ion plating, forming a protective film by photolithography, In a manufacturing method for mass production of a piezoelectric substrate having a desired shape by sequentially performing the etching used, pinholes are obtained by thickening a metal thin film using a simple wet plating method without using a special photoresist. An object of the present invention is to provide a method of manufacturing a piezoelectric substrate that can mass-produce piezoelectric substrates with high yield by eliminating photolithography and the like and then performing photolithography and etching.

In order to achieve the above object, the first aspect of the present invention includes a first metal thin film forming step of forming a first metal thin film on both surfaces of a piezoelectric substrate base material by vacuum plating, and a first metal thin film on the first metal thin film. A second metal thin film forming step of forming a second metal thin film by vacuum plating; and a metal film of the same material as the second metal thin film is formed on the second metal thin film by wet plating. A second metal thick film forming step for forming a second metal thick film on the first metal thin film, a photoresist coating step for applying a photoresist film on the second metal thick film, and a photoresist film on the photoresist film. A photoresist exposure / development process that selectively removes the photoresist film by arranging and exposing a mask, and a second metal thick film and a first metal thin film using the remaining photoresist film as a mask. Second metal thick film removed by etching 1 metal thin film etching step, and the remaining photoresist film, the second metal thick film, and the first metal thin film are used as a mask to remove the exposed portion of the piezoelectric substrate base material by etching and process it into a piece size Etching process, photoresist film, second metal thick film, and first metal thin film laminated on both sides of piezoelectric substrate piece by etching, photoresist film-second metal thick film-first metal And a thin film removing step.
The invention of claim 2 is characterized in that, in claim 1, the metal constituting the first metal thin film is chrome, and the metal constituting the second metal thick film is gold.
According to a third aspect of the present invention, in the first or second aspect, the piezoelectric substrate is a quartz substrate.

  According to the present invention, pinholes, cracks, etc. are eliminated by thickening the metal thin film using a simple wet plating method without using a special photoresist, and then photolithography and etching are performed. Thus, the piezoelectric substrate can be mass-produced with a high yield.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIG. 1 is a process diagram showing an example of a method for manufacturing a piezoelectric substrate according to the present invention.
In this embodiment, an example using a quartz substrate as a piezoelectric substrate is shown, but this is only an example, and the present invention can be applied to general piezoelectric materials.
First, FIG. 1A shows a quartz substrate base material 1 used as a piezoelectric substrate base material in the present invention, and a chrome thin film forming step (first metal thin film forming step) shown in FIG. ), A chrome thin film 2 as a first metal thin film is formed on both surfaces of the quartz substrate base material 1 by a dry film forming method (vacuum plating method) such as vacuum deposition, ion plating, or sputtering, and the like. In the gold thin film forming step 1 (c) (second metal thin film forming step), a gold thin film 3 as a second metal thin film is formed on the chrome thin film 2 by a vacuum plating method such as vapor deposition.
In this embodiment, a metal film composed of the chrome thin film 2 and the gold thin film 3 is used as the resistant film. However, this is only an example, and any material can be used as long as it can be plated.
Next, FIG. 1D is a second gold thick film plating process which is a characteristic process of the present invention. A gold film 4 as a third layer is wet-plated (electroless plating, Alternatively, a second thick gold film (second thick metal film) 5 having a desired thickness is formed by film formation by electroplating. In this step, the minute gaps (pinholes and cracks) formed in the chrome thin film 2 and the gold thin film 3 are filled with the gold film 4 and closed. Therefore, it is not necessary to select a material having a strong resistance to a hydrofluoric acid solution or the like as the photoresist film laminated on the second gold thick film 5. Further, when the gold film 4 is formed by wet plating, only the pattern portion can be selectively thickened even after the Au—Cr film is patterned by photolithography.

Next, in FIG. 1E, a photoresist coating process for coating a photoresist film 6 on the second thick gold film 5 is performed. In FIGS. 1F and 1G, the photoresist film 6 is applied. A photoresist exposure / development process for selectively removing the photoresist film 6 is performed by sequentially performing exposure, development, washing, and baking after arranging a mask 7 having a predetermined opening shape thereon. As a result, a portion of the photoresist film 6a corresponding to the mask 7 remains.
In FIG. 1H, the remaining portion of the second thick gold film 5 and the chrome thin film 2 (the portion located in the opening of the photoresist film 6a) is removed by etching using the remaining photoresist film 6a as a mask. The metal thick film-first metal thin film etching step is performed. At this time, an iodine-based solution is used as an etchant. By this etching, only the metal film portion covered with the photoresist film 6a remains, and the crystal substrate surface is exposed between the remaining metal films.
Next, in FIG. 1 (i), the exposed portion of the quartz substrate base material 1 is removed by etching using the remaining second thick gold film 5, chrome thin film 2 and photoresist film 6a as a mask, and processed into individual pieces. A quartz substrate (piezoelectric substrate) etching process is performed. The etchant used is a hydrofluoric acid solution.
In FIG. 1 (j), the photoresist film 6a, the second gold thick film 5 and the chrome thin film 2 laminated on both surfaces of the piezoelectric substrate piece 1a are removed by etching-second metal thick film-second. By performing the metal thin film removing step 1, the piezoelectric substrate piece 1 a can be obtained.
As described above, in the present invention, it is possible to fill a minute gap existing in the second metal thin film or the like by thickening the second metal thin film by wet plating. For this reason, when the quartz substrate is etched using the hydrofluoric acid solution, the quartz portion covered with the resistant film is not eroded by the hydrofluoric acid solution, and the yield is low and the yield is high. Piezoelectric substrates can be mass-produced.

Process drawing for demonstrating the manufacturing method which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Crystal substrate base material (piezoelectric substrate base material), 1a Piezoelectric substrate (piece | piece), 2 Chrome thin film (1st metal thin film), 3 Gold thin film (2nd metal thin film), 4 Gold film, 5 Gold thick film (Second metal thin film), 6 photoresist film.

Claims (3)

A first metal thin film forming step of forming a first metal thin film on both surfaces of the piezoelectric substrate base material by vacuum plating;
A second metal thin film deposition step of depositing a second metal thin film on the first metal thin film by vacuum plating;
Forming a second metal thick film by forming a metal film of the same material as the second metal thin film on the second metal thin film by wet plating to form a second metal thick film on the first metal thin film Process,
A photoresist coating step of coating a photoresist film on the second metal thick film;
A photoresist exposure / development step that selectively removes the photoresist film by placing a mask on the photoresist film and exposing and developing;
A second metal thick film-first metal thin film etching step of removing the second metal thick film and the first metal thin film by etching using the remaining photoresist film as a mask;
A piezoelectric substrate etching step in which the exposed portion of the piezoelectric substrate base material is removed by etching using the remaining photoresist film, the second metal thick film and the first metal thin film as a mask, and processed into individual pieces;
A photoresist film, a second metal thick film, and a first metal thin film removing step for removing the photoresist film, the second metal thick film, and the first metal thin film laminated on both surfaces of the piezoelectric substrate piece by etching; ,
A method for manufacturing a piezoelectric substrate, comprising: The metal constituting the first metal thin film is chrome,
2. The method for manufacturing a piezoelectric substrate according to claim 1, wherein the metal constituting the second thick metal film is gold.   The method for manufacturing a piezoelectric substrate according to claim 1, wherein the piezoelectric substrate is a quartz substrate.

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