JPH06252677A - Manufacture of dual mode surface acoustic wave filter - Google Patents

Abstract

PURPOSE:To improve the characteristic even when the resistance is decreased and the operating frequency is high by forming a thin electrode and overlapping an electrode onto only a bus line electrode so as to increase a cross sectional area. CONSTITUTION:A resist 4 is coated onto a substrate 1 whose surface is made flat, a resist corresponding to each electrode is exfoliated and a bus line electrode 5, an IDT and a reflector 6 are formed. Then a resist 8 is coated as a 2nd resist, the resist is exfoliated only from a part of a bus line requiring a thick film thickness and the electrode film is formed in addition by the bus line electrode 5 requiring the thick film thickness by using the resist 8 as a mask. Moreover, when the resist is all exfoliated, the dual mode surface acoustic wave filter is manufactured with the bus line having a thick film thickness of the electrode and a low resistance and the IDT and the reflector requiring the thin electrode depending on their characteristics having a thin electrode thickness. Then the increase in the resistance of the bus line electrode caused at a high frequency is prevented. Thus, even when the operating frequency is higher, the characteristic is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a dual mode surface acoustic wave filter in which electrodes are formed on the surface of a substrate.

[0002]

2. Description of the Related Art Conventionally, a quartz substrate is coated with a resist,
The required electrode was formed on the substrate by peeling off the resist on the electrode portion, vapor-depositing the electrode, and peeling off all the resist.

[0003]

In the conventional dual-mode surface acoustic wave filter, the width of the bus line electrode must be narrowed when the pass band width is widened or the frequency used is increased. . Further, the film thickness of the bus line electrode becomes thinner as the electrode film thickness of the IDT or the reflector electrode becomes higher, so that the bus line electrode becomes thinner and the resistance of the bus line increases. As a result, there is a problem in that the pass band characteristic, the out-of-band attenuation characteristic, and the group delay characteristic are deteriorated in the lower frequency side as compared with the higher frequency side and the characteristics become significantly asymmetric.

[0004]

To solve the above problems, it is clear that the resistance of the bus line should be reduced. To reduce the resistance of the bus line, it is necessary to increase the cross-sectional area of the electrode of the bus line, but since it is not possible to increase the width of the bus line in order to maintain the characteristics, it is necessary to increase the thickness of the electrode I want to reduce the line resistance. As a method of increasing the electrode film thickness, at least thin electrode film thickness that can maintain the characteristics is formed on each electrode, and the electrode resistance of the electrode must be kept low. By forming the bus line electrode, the cross-sectional area of the bus line electrode is increased to reduce the resistance of the bus line electrode and solve the problem.

[0005]

2 to 5 are sectional views showing an embodiment of the present invention. As shown in FIG. 2, the resist 4 is applied on the substrate 1 having a flat surface, and the resist in the portions corresponding to the respective electrodes is peeled off. Next, as shown in FIG. 3, the bus line electrode 5
Then, the IDT and the reflector electrode 6 are formed by means of vapor deposition, scattering or the like. The film thickness in this case forms the thickness required for the IDT and the reflector. Next, as shown in FIG.
The resist 7 for the second time is applied, and the resist for the second time is peeled off only at the bus line portion that requires a large film thickness. Next, as shown in FIG. 5, using the second resist 8 as a mask,
An electrode film required for the bus line electrode 5 requiring a thick film thickness is additionally formed by using a technique such as vapor deposition or sputtering. Next, by peeling off all the resist, it is possible to manufacture a dual mode surface acoustic wave filter having a thin electrode for the IDT and the reflector portion which require a bus line having a large thickness of a target electrode and a low resistance and a thin electrode due to its characteristics. . FIG. 1 is a sectional view showing an electrode structure of a dual mode surface acoustic wave filter according to the manufacturing method of the present invention. In the dual mode surface acoustic wave filter of the present invention, since the film thickness of the electrode of the bus line is thicker than the film thickness of the electrode of the IDT or the reflector, the increase in the resistance value of the bus line electrode caused by the high frequency is prevented. I can. Note that the resist used in the manufacturing method of the present invention is usually a photosensitive resist used when forming an electrode, and a method of removing unnecessary resist by exposing after placing a photomask is used. The method may be a resist.

[0006]

In the dual mode surface acoustic wave filter using the quartz substrate, when the pass band is widened or the frequency is increased, the pass band characteristics and the band pass characteristics are increased due to the increase of the resistance of the bus line. There is a problem that the outer attenuation amount and the group delay characteristic are not sufficiently obtained in the lower frequency compared with those in the higher frequency. According to the invention I
The cross-sectional area of the bus line electrode can be increased by forming thin electrodes on each electrode that the DT and the reflector require in terms of characteristics, and then thickening only the bus line electrodes that require a thick film thickness by further stacking the electrodes. As a result, the resistance of the bus line electrode was lowered and the problem was solved, so a dual mode surface acoustic wave filter with good characteristics, even if the pass band width is widened or the operating frequency is increased, is easy and cheap. You can now make it.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a state in which an electrode of a bus line is thicker than an electrode of an IDT and a reflector of the present invention.

FIG. 2 is a partial cross-sectional view showing a state where each electrode portion of the resist applied on the substrate of the present invention is peeled off.

FIG. 3 is a partial cross-sectional view showing a state in which each electrode is formed with a thin thickness required for characteristics using the resist of the present invention as a mask.

FIG. 4 is a partial cross-sectional view showing a second resist state for thickening the electrode of the bus line of the present invention.

FIG. 5 is a partial cross-sectional view showing a state where a bus line electrode is thickened using the second resist of the present invention as a mask.

[Explanation of symbols]

 1 substrate 4 resist 5 bus line electrode 6 IDT and reflector electrode 8 second resist

Claims (1)

[Claims] 1. A method of manufacturing a dual-mode surface acoustic wave filter using a quartz substrate, comprising a step of applying a resist on at least the substrate, a step of peeling a resist corresponding to each electrode, and a step of removing each electrode. Step of forming, step of applying resist, step of removing the resist in the portion corresponding to the electrode of the bus line, step of forming the electrode film thickness required in the bus line, and step of removing all the resist A method of manufacturing a dual mode surface acoustic wave filter, comprising: