JPH10233641A - Manufacturing method of surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an electrode pattern as designed and to provide excellent characteristics by providing an antireflection film on the back surface of a piezoelectric substrate and suppressing light transmitted through the piezoelectric substrate from being reflected from the back surface and reflected to a surface at the time of an exposure processing. SOLUTION: The resist film 2 of the organic high polymer of thickness 0.4-2.0μm is provided on the surface side of the piezoelectric substrate 1, the antireflection film 3 containing dye provided with absorptivity to the ultraviolet light of a wavelength 365nm is provided on the substrate of the organic high polymer of the thickness 0.1-1.0μm and a conductive film 4 is provided on it further on a back surface side. At the time of radiating the light through the opening part 6 of a photo mask 5 installed above the piezoelectric substrate 1 and performing the exposure processing, the light transmitted through the piezoelectric substrate 1 and made to reach the back surface is substantially absorbed by the antireflection film 3 and the light reflected to the surface side is drastically reduced. Thus, the electrode pattern is formed in the almost same shape as the opening part 6 of the photo mask 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a surface acoustic wave device such as a SAW filter.

[0002]

2. Description of the Related Art In a conventional method of manufacturing a surface acoustic wave device of this type, first, a resist is provided on the surface of a piezoelectric substrate, and then a photomask is provided above the surface of the piezoelectric substrate, and the surface resist is exposed to light. Then, it is manufactured by forming electrodes on the surface of the piezoelectric substrate.

[0003]

However, the surface acoustic wave device manufactured as described above has a problem that the characteristics as designed cannot be obtained. That is, in the above-described conventional manufacturing method, in the exposure processing performed by providing a photomask above the front surface of the piezoelectric substrate, light that has passed through the resist film through the photomask and travels straight is reflected on the back surface side of the piezoelectric substrate, and After returning to the above, a portion where light is not transmitted is originally provided by providing a photomask, and as a result, the resist film has a shape different from that of the photomask due to a subsequent development process.
As a result, the electrode formed by the remaining resist film does not become as originally designed as the photomask, and the characteristics cannot be obtained.

Accordingly, an object of the present invention is to provide a method of manufacturing a surface acoustic wave device capable of obtaining characteristics as designed.

[0005]

According to the present invention, a resist film is provided on the surface of a piezoelectric substrate, an antireflection film is provided on the back surface, and a photomask is provided above the surface of the piezoelectric substrate. Then, a resist film on the surface is exposed to light, an electrode film is formed on the surface of the piezoelectric substrate, and then the resist film on the surface is removed.

The provision of the anti-reflection film as described above suppresses the reflected light. As a result, the resist pattern remaining on the surface of the piezoelectric substrate has the same shape as the photomask. Then, the characteristics as designed can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that a resist film is provided on the front surface of a piezoelectric substrate, an antireflection film is provided on the back surface, and a photomask is provided above the front surface of the piezoelectric substrate. This is a method of manufacturing a surface acoustic wave device in which a resist film is exposed to light, then an electrode film is formed on the surface of the piezoelectric substrate, and then the resist film on the surface is removed. Is applied, the proportion of light that has entered the piezoelectric substrate through the resist film during exposure and is reflected from the back surface of the piezoelectric substrate toward the front surface can be significantly suppressed. As a result, the surface of the piezoelectric substrate The remaining resist pattern is formed in the same shape as the photomask, and as a result, the characteristics as designed can be obtained when electrodes are formed later.

According to a second aspect of the present invention, a conductive film is provided on the antireflection film on the back surface of the piezoelectric substrate, and at least a part of the conductive film is brought into contact with the piezoelectric substrate. By providing the conductive film and at least part of the conductive film being in contact with the piezoelectric substrate in this manner, the charge generated by the temperature fluctuation of the piezoelectric substrate is released through the conductive film. This makes it possible to avoid the difficulty in the process that the position of the piezoelectric substrate cannot be accurately set because the stage supporting the substrate sticks due to the electric charge accumulated in the piezoelectric substrate.

An embodiment of the present invention will be described below with reference to FIGS. Figure 1 is 100-900μ thick
2 shows a piezoelectric substrate 1 made of lithium tantalate, lithium niobate, quartz or the like having a thickness of 0.4 to 2.0 μm as shown in FIG. Is provided. On the back side, an organic polymer having a thickness of 0.1 to 1.0 μm is used as a base material,
An antireflection film 3 containing a dye having absorptivity to ultraviolet light having a wavelength of 365 nm is provided. Further, a conductive film 4 made of an electrically conductive material such as aluminum is provided on the antireflection film 3, and a part of the conductive film 4 is in contact with a side surface of the piezoelectric substrate 1.

In this state, as shown in FIG.
A light-shielding film made of chromium or the like is placed on a light-transmitting plate such as quartz glass above the surface of the substrate, and the patterned photomask 5 is set apart from the piezoelectric substrate 1 by a predetermined distance. Then, light is irradiated through the opening 6 of the photomask 5, and thereafter, a developing process is performed. Then, a resist pattern concave portion 2a having the same shape as the opening 6 of the photomask 5 is formed on the surface of the piezoelectric substrate 1 as shown in FIG.

At this time, when light is applied to the piezoelectric substrate 1 through the opening 6 of the photomask 5 as shown in FIG. 3, most of this light passes through the resist film 2 and further passes through the piezoelectric substrate 1. After reaching the back surface of the piezoelectric substrate 1, the light is greatly absorbed by the antireflection film 3 provided on the back surface side of the piezoelectric substrate 1, and as a result, the light reflected on the front surface side Will decrease dramatically. Therefore, as shown in FIG. 4, the resist pattern concave portion 2a formed on the piezoelectric substrate 1 has substantially the same shape as that of the opening 6 of the photomask 5.

In this state, as shown in FIG.
0.5 μm aluminum, or aluminum-copper alloy, or aluminum-scandium-copper alloy,
Alternatively, after the electrode film 7 having a multilayer structure composed of aluminum and copper is formed by a vapor deposition method or a sputtering method, the remaining resist pattern 2b is peeled off to remove the electrode pattern as designed as shown in FIG. 7a can be formed.

Further, after that, the antireflection film 3 and the conductive film 4
It is preferable that the device is finally formed with the configuration as shown in FIG. 7 in view of the characteristics of the surface acoustic wave element. However, for simplification of the process, the antireflection film 3 and the conductive film 4 are removed. Step may be omitted.

The reason why the antireflection film 3 is provided on the back surface of the piezoelectric substrate 1 instead of the front surface will be described below. Assuming that the antireflection film 3 is provided on the front surface side of the piezoelectric substrate 1, after patterning the resist film 2,
Alternatively, it is necessary to pattern the antireflection film 3 at the same time. Here, the resist film 2 has photosensitivity, whereas the antireflection film 3 does not have photosensitivity. Therefore, only the resist pattern reflects the pattern of the photomask 5 as a matter of course. Therefore, the final electrode pattern is
It is necessary to depend not on the pattern of the anti-reflection film 3 but on the resist pattern. For this purpose, at least the line width of the anti-reflection film 3 below the resist line width is formed relatively thin. There is a need to.

More specifically, since the antireflection film 3 has alkali solubility, the antireflection film 3 can be formed utilizing the isotropic etching action of an alkaline developer. Therefore,
As the thickness of the anti-reflection film 3 is increased to reduce the reflected light, the amount of side etching of the anti-reflection film 3 with reference to the resist line width increases. Problems such as pattern collapse easily occur. The above means that when the antireflection film 3 is provided on the surface side of the piezoelectric substrate 1, the effect of suppressing the reflected light is limited.

On the other hand, if the anti-reflection film 3 is provided on the back side of the piezoelectric substrate 1, the above-mentioned problem can be avoided. That is, since the thickness of the antireflection film 3 is not limited, the reflection light can be largely suppressed by providing the antireflection film 3 thick enough to sufficiently suppress the reflected light. For the above reasons, the antireflection film 3 is formed on the piezoelectric substrate 1.
Should be provided on the back side of the.

[0017]

As described above, according to the present invention, a resist film is provided on the front surface of a piezoelectric substrate, and an anti-reflection film is provided on the back surface. Next, a photomask is provided above the front surface of the piezoelectric substrate, and the resist film is exposed to light. Thereafter, an electrode film is formed on the surface of the piezoelectric substrate, and then the resist pattern on the surface is removed.

Therefore, according to the above manufacturing method, the reflected light from the back surface of the piezoelectric substrate can be suppressed. As a result, the resist pattern remaining on the piezoelectric substrate has the same shape as that of the photomask. When the electrodes are formed, the characteristics as designed can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a piezoelectric substrate showing a method of manufacturing a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a front view showing the manufacturing method.

FIG. 3 is a front view showing the manufacturing method.

FIG. 4 is a front view showing the manufacturing method.

FIG. 5 is a front view showing the manufacturing method.

FIG. 6 is a front view showing the manufacturing method.

FIG. 7 is a front view showing a surface acoustic wave device manufactured by the same manufacturing method.

[Explanation of symbols]

 Reference Signs List 1 piezoelectric substrate 2 resist film 2a resist pattern concave portion 2b resist pattern 3 antireflection film 4 conductive film 5 photomask 6 opening of photomask 7 electrode film 7a electrode pattern

Continuation of front page (72) Inventor Ryoichi Takayama 1006 Ojidoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A resist film is provided on a front surface of a piezoelectric substrate, and an antireflection film is provided on a back surface. Next, a photomask is provided above the front surface of the piezoelectric substrate, and the resist film is exposed to light. A method of manufacturing a surface acoustic wave device in which an electrode film is formed and then a resist film on the surface is removed. 2. The method of manufacturing a surface acoustic wave device according to claim 1, wherein a conductive film is provided on the antireflection film on the back surface of the piezoelectric substrate, and at least a part of the conductive film is brought into contact with the piezoelectric substrate.