JPH07142951A - Manufacture of surface acoustic wave device - Google Patents

Abstract

PURPOSE:To manufacture a surface acoustic wave device capable of forming a highly precise pattern and small in the fluctuation of characteristic with high yield by using a negative photoresist, forming a film by a vapor deposition method and forming the pattern by lift-off. CONSTITUTION:The negative photoresist 2 is applied on the piezoelectric substrate 1 made of LiNbO3 and the like as shown in a figure (a). The pattern is formed in exposure/development as shown in a figure (b). A metallic layer, an Al film 3, for example, is formed on the substrate 1 and a photoresist pattern 2 by using a vapor deposition method as shown in a figure (c). Then, the photoresist 2 and the Al film 3 on the resist are lifted off by the resist peeling liquid of an organic system and an Al electrode pattern in a figure (d) is formed. A chip thus obtained is mounted on a package. An Al particle is vertically made incident on the substrate 1 from above the resist 2 of a reverse trapezoid. Thus, the Al film 3 is prevented from infiltrating to the side of the photoresist.

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 surface acoustic wave device used in a mobile phone or the like.

[0002]

2. Description of the Related Art In recent years, along with the use of higher frequency bands in surface acoustic wave devices, the miniaturization of metal electrodes in surface acoustic wave devices has become remarkable. Therefore, minute unevenness at the end of the electrode pattern, which has not been a problem in the past, may cause an electrode short circuit defect, or a slight variation in the electrode width may affect the characteristics. Therefore, in the industrial world, more advanced pattern forming technology is desired.

A conventional method of manufacturing a surface acoustic wave device will be described with reference to FIG. First, a metal film such as A1 is formed on the piezoelectric substrate by using the sputtering technique.
(a). Next, apply a positive photoresist (201) (b),
A pattern is formed by exposure and development (c). After that, a metal electrode pattern is formed by using a wet or dry etching method (d). Then, the unnecessary resist (201) is removed (e).

The surface acoustic wave device can be obtained by mounting the element thus produced in a package. In the above process,
Since the metal film is patterned by etching, the number of steps is large and the manufacturing cost is high. Also, with wet etching, the line width became narrower due to side etching, and etching residue was left. Therefore, there was a remarkable tendency that the difference between the characteristics was large and the yield was low. Further, since the device in the high frequency band has a fine pattern, it is difficult to form it. With dry etching, after-corrosion may occur, which raises questions about yield and reliability. Therefore, it was not possible to form a fine pattern with high accuracy and high yield.

[0005]

As described above, in the conventional method of manufacturing a surface acoustic wave device, there are problems that the difference in characteristics of individual devices is large and a fine pattern cannot be formed. The present invention has been made in order to solve these problems, by forming a metal film by vapor deposition using a negative resist and patterning by lift-off, high-definition device with less variation in characteristics with high yield. It is an object of the present invention to provide a method of manufacturing a surface acoustic wave device that can be obtained.

[0006]

According to the present invention, a step of forming a pattern on a piezoelectric substrate using a negative photoresist, and a metal layer is formed on the piezoelectric substrate and the photoresist by a vapor deposition method. A method of manufacturing a surface acoustic wave device, comprising at least a step and then a step of patterning this metal layer on an electrode structure by a lift-off method.

[0007]

First, by using the method of the present invention, a negative photoresist is used, and the resist cross section after pattern formation becomes an inverted trapezoid as shown in FIG. 3 (b). As a result, the pattern is formed with the positive resist as shown in FIG.
Since the metal film is less likely to adhere to the side surface of the resist, the resist stripper is more likely to penetrate, the resist strippability is improved, and lift-off is facilitated. When a positive resist is used, even if a film is formed in the vertical direction by a vapor deposition method,
As shown in (c), the metal film adheres to the side surface and is difficult to peel off.

Secondly, by forming the metal film by the vapor deposition method, the metal particles are incident on the substrate in a direction perpendicular to the substrate as shown in FIG. The part is cut cleanly, the line width becomes constant, and lift-off becomes easy. When a metal film is formed by the sputtering method, the metal film adheres to the side surface and is difficult to peel off even if a negative resist is used as shown in FIG. 3 (a).

Thirdly, by patterning the metal electrode by the lift-off method, the number of steps can be reduced and the manufacturing cost can be suppressed as compared with the etching process. Also, since there is no concern about side etching or after-corrosion as in etching, line width control is easy and yield /
Reliability is also improved.

As a result, it is possible to form a high-definition pattern which is difficult to form by the conventional manufacturing method, and it is possible to obtain an elastic surface device with a small difference in the characteristics of individual elements with a high yield.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. First, as shown in Fig. 1 (a), LiNb
A negative photoresist (2) is coated on a piezoelectric substrate (1) such as O ₃ and exposed and developed to form a pattern as shown in FIG. 1 (b).

Next, as shown in FIG. 1C, a metal layer such as an A1 film (3) is formed on the substrate (1) and the photoresist pattern (2) by using a vapor deposition method. Next, the photoresist (2) and the A1 film on the resist are lifted off by an organic resist stripping solution to form an A1 electrode as shown in FIG. 1 (d). A schematic pattern of the obtained A1 electrode is shown in FIGS. 2 (a) and 2 (b).
The chip thus obtained is mounted on a package to obtain a surface acoustic wave device.

Using the above process, A1 particles are vertically incident on the substrate (1) from above the inverted trapezoidal resist (2).
Therefore, since the A1 film does not wrap around the side surface of the photoresist, the resist stripping solution easily penetrates during lift-off, and the stripping property is good. In addition, the A1 film pattern after lift-off is also clean because the film (3) is cut off by the resist (2) during film formation, so that there are no irregularities at the edges. Furthermore, since there is no thin film-forming portion behind the resist (2), a predetermined film thickness is uniformly formed, the line width is constant, and variations in characteristics are reduced. The film forming method is not limited to the vapor deposition method, and similar effects can be obtained as long as directional metal particles are incident on the substrate.

[0014]

According to the present invention, by using a negative photoresist, the resist cross section becomes an inverted trapezoid, the resist releasability is improved, and lift-off is facilitated. Further, since the film is formed by the vapor deposition method, the metal film does not wrap around the side surface of the resist, so that the line width is constant and lift-off becomes easy. Further, since the pattern is formed by lift-off, the number of steps can be reduced and the cost can be suppressed. Also, since there is no concern about side etching or after-corrosion, line width control is easy and yield and reliability are improved.

As a result, it becomes possible to form a high-definition pattern which is difficult to form by the conventional manufacturing method, and it is possible to obtain a surface acoustic wave device with a small variation in characteristics with a high yield.

[Brief description of drawings]

FIG. 1 is a simplified sectional view showing an embodiment of the present invention.

FIG. 2 is a simplified cross-sectional view showing a device pattern manufactured according to an embodiment of the present invention.

FIG. 3 is a simplified cross-sectional view for explaining the effect of the present invention.

FIG. 4 is a simplified cross-sectional view for explaining a conventional technique.

[Explanation of symbols]

 (1)… Piezoelectric substrate (2)… Negative photoresist (201)… Positive photoresist (3)… Metal electrode (Al film)

Claims (1)

[Claims] 1. A step of forming a pattern on a piezoelectric substrate using a negative photoresist, a step of forming a metal layer on the piezoelectric substrate and the photoresist by an evaporation method, and then a lift-off method. And a step of patterning a metal layer on the electrode structure.