JPH05283965A - Manufacturing of saw device - Google Patents

Abstract

PURPOSE:To improve yield by restraining the dispersion of a characteristic by preparing chip groups where pitchs of an input/output comb type electrode part are changed in steps when many chip shaped SAW devices are arranged. CONSTITUTION:Plural pieces of pattern 2 for chip shaped SAW device composed of an input/output comb type electrode part 3 and a pad electrode part 4 are arrayed in a grid-shape on the upper surface of a pattern main body 1 by taking a pattern 2 as one unit. The width dimension of the electrode part 3 is made 1/4 of a pitch (a) Figure is divided into two blocks of a center part A and an outer peripheral part B by defining the location surrounded by a thick solid line as a boundary, and the pitch dimension (a) of the electrode part 3 of the pattern 2 arranged on the A part and the pitch dimension (a) of the electrode part 3 of the pattern 2 arranged on the outer peripheral part B are different from each other. When the pitch (a) of the electrode part 3 of the center part A is made 1.0, that of the outer peripheral part B side is made 1.0006 so that the pitch (a) of the electrode part 3 of the outer peripheral part B may be larger than that of the part A. Further, respective chip groups have a frequency difference of 200kHz in advance.

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 SAW device used for communication equipment and the like.

[0002]

2. Description of the Related Art A conventional SAW device manufacturing method will be described below.

FIG. 5 shows a conventional method for manufacturing a SAW device. As shown in FIG. 5, a metal such as aluminum is formed on one surface of a piezoelectric substrate by an electron beam method, a resistance heating method, a sputtering method or the like. And a metal thin film forming step of vapor-depositing the metal thin film formed by a photolithography method, a dry etching method, or the like.
A patterning step of forming a pattern in which a plurality of AW devices are arranged in a grid pattern on a piezoelectric substrate, and a chip which is cut into a plurality of chips at a portion where the input / output comb-shaped electrode portion and the pad electrode portion are not formed Dividing process, die-bonding process for adhesively fixing each divided chip to the stem that is the base, wire bonding process for electrically connecting the adhesively fixed chip and stem, and electrically connecting the chips by adhesive fixing After the sealing step of sealing the formed stem with a can and the characteristic test step of measuring the electrical characteristics of the SAW device produced in this series of steps, the chip is manufactured by the method of determining the quality and completing. To obtain a SAW device in the shape of a circle.

[0004]

However, in the above-mentioned conventional method for manufacturing a SAW device, the crystal orientation of the piezoelectric substrate is set, the metal thin film is set according to the crystal orientation, and the metal thin film is set according to the setting of the metal thin film. In order to set the pitch of the comb-shaped electrode parts for input and output so as to have the desired frequency characteristics, the mask pattern used in the patterning process is composed of a plurality of grids arranged corresponding to the set metal thin film. All the chips were formed uniformly.

However, the metal thin film forming step of vapor deposition by the electron beam method, the resistance heating method, the sputtering method or the like does not always obtain a uniform thickness, but rather the film thickness distribution of about several percent on the piezoelectric substrate. The frequency characteristics, which are generally the electrical characteristics of SAW devices, are determined by the propagation velocity of the surface acoustic wave propagating on the piezoelectric substrate. The propagation velocity of this surface acoustic wave is the piezoelectric substrate. It is determined by the crystal orientation of the piezoelectric element and the pitch and thickness of the input / output comb-shaped electrode portions. Therefore, each chip formed on the piezoelectric substrate in a grid pattern has an input / output comb-shaped electrode portion. Due to the thickness of the metal thin film, a product having a desired frequency characteristic is manufactured, resulting in a defective product and a reduction in manufacturing yield.

Such a state is shown in FIG. 4, which is a distribution diagram showing the frequency characteristics of the SAW device obtained at the position of the piezoelectric substrate. The frequency characteristics are shown in the center of the piezoelectric substrate. It is shown that the frequency characteristics are low, and the frequency characteristics increase as the distance to the outer peripheral portion increases.

The present invention solves the above problems.
Prevents cost increase and suppresses characteristic variations due to locations on the piezoelectric substrate without adding manufacturing steps,
It is an object of the present invention to provide a method for manufacturing a SAW device capable of improving the manufacturing yield.

[0008]

In order to solve this problem, a method of manufacturing a SAW device according to the present invention is a method of forming a mask pattern for photolithography for patterning a metal thin film formed on a piezoelectric substrate in a comb shape. A chip-shaped pattern consisting of an electrode part and a pad electrode part is set as one unit,
A plurality of the chips are arranged in a grid pattern, and the pitch of the comb-shaped electrode portions is larger in the peripheral portion than in the central portion. After performing patterning using this same pattern, the plurality of chip groups are cut and divided, and the divided individual chips are adhesively fixed to a stem serving as a base, and this adhesive fixation is performed. This is a manufacturing method in which a chip and a stem are electrically connected by wire bonding and sealing is performed.

[0009]

With this manufacturing method, a mask pattern, which is prepared in advance by gradually changing the pitch of the comb-shaped electrode portions for input and output so as to have different frequencies, has a film thickness distribution of about several percent on the piezoelectric substrate. Corresponding to the respective thicknesses of the formed metal thin films, almost all chips having desired frequency characteristics can be manufactured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Since the manufacturing process is the same as the manufacturing process described with reference to FIG. 5 in the conventional example, detailed description will be omitted.

In the present embodiment, when the resistance heating method is adopted in the forming method of the metal thin film forming step of FIG. 5, the thickness of the metal thin film on the piezoelectric substrate is thick in the central portion and thin in the peripheral portion. is there. Therefore, when a chip-shaped SAW device is manufactured using the conventional photolithography mask pattern, the frequency characteristic is low in the central portion as shown in the graph of FIG.
The peripheral area becomes high. If the variation of this frequency characteristic is 400 kHz, the required variation accuracy is 2
If it was 00 kHz, the manufacturing yield would be about 50%, and a method of solving this variation in frequency characteristics with a mask pattern for photolithography will be described in detail.

FIG. 1 is a plan view showing a photolithographic mask pattern according to this embodiment.
A chip-shaped SAW device pattern 2 composed of input / output comb-shaped electrode portions 3 and pad electrode portions 4 is set as one unit on the upper surface of the above, and a plurality of the SAW device patterns 2 are arranged in a grid pattern. The pattern body 1 is configured.

Further, the pattern 2 for each SAW device
2 is composed of an input / output comb-shaped electrode portion 3 and a pad electrode portion 4 as shown in FIG. 2, and the width dimension of the comb-shaped electrode portion 3 is the same as that of the comb-shaped electrode portion 3 in this embodiment. 1 of pitch dimension a
It was formed to be / 4.

In the structure shown in FIG. 1 in which a plurality of individual SAW device patterns 2 thus formed are arranged in a grid pattern, the central portion A and the outer peripheral portion are bordered by the positions surrounded by thick solid lines in FIG. It is divided into two blocks of B and this central part A
The pitch dimension a of the comb-shaped electrode portion 3 of the SAW device pattern 2 arranged on the outer peripheral portion B and the pitch dimension a of the comb-shaped electrode portion 3 of the SAW device pattern 2 arranged on the outer peripheral portion B are changed. In the embodiment, when the same pitch dimension a of the central portion A is 1.0, the same pitch dimension a of the outer peripheral portion B is 1.0.
The outer peripheral portion B side is enlarged so as to have a ratio of 006, and each chip group is configured to have a frequency difference of 200 kHz in advance.

The frequency characteristics of the SAW device manufactured by the manufacturing method described in the above-mentioned conventional example using the mask pattern for photolithography manufactured in this way are shown in a distribution chart in FIG. As is clear from the figure, by using a photolithography mask pattern formed in advance with a frequency difference corresponding to the variation of the metal thin film formed on the upper surface of the piezoelectric substrate, The frequency characteristics of the chips of the group A and the chips of the peripheral portion B are suppressed from varying and can be kept within a range of 200 kHz as desired, and the frequency characteristics are almost 100.
% Manufacturing yield can be secured.

In the above embodiment, the pattern body 1 is divided into two blocks, the central portion A and the outer peripheral portion B, in order to correct the frequency difference of 200 kHz.
Even when the accuracy of variation is further improved like the frequency of z and 50 kHz, the pitch of the comb-shaped electrode portion of the input and output is changed by subdividing the mask pattern for one photolithography into a plurality of stages. It goes without saying that it is possible to easily deal with this by arranging a chip group.

[0018]

As described above, in the method for manufacturing a SAW device according to the present invention, when the mask pattern for photolithography is manufactured, the chip group in which the pitch of the comb-shaped electrode portions for input and output is changed stepwise is manufactured. As a result, it is possible to deal with the SAW device manufacturing process without adding any special process, and it is possible to suppress the variation in the frequency characteristics of each SAW device, dramatically improve the manufacturing yield, and reduce the cost. It is possible.

[Brief description of drawings]

FIG. 1 is a plan view of a mask pattern for photolithography according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part showing the same pattern of a SAW device according to the same embodiment.

FIG. 3 is a frequency characteristic diagram of a SAW device obtained in the same example.

FIG. 4 is a frequency characteristic diagram of a conventional SAW device.

FIG. 5 is a manufacturing process diagram showing a method for manufacturing a SAW device according to the related art and the present invention.

[Explanation of symbols]

 1 Pattern body 2 SAW device pattern 3 Comb type electrode part 4 Pat electrode part

Claims (1)

[Claims] 1. A metal thin film is formed on a piezoelectric substrate, and the pitch of the comb-shaped electrode portions of a chip-shaped SAW device consisting of the comb-shaped electrode portion and the pad electrode portion is arranged in the center portion of the metal thin film. After performing patterning with a photolithographic mask pattern arranged in a lattice so that the chips arranged in the outer peripheral portion are larger than the chips, the plurality of chip groups are cut and divided, A method for manufacturing a SAW device, in which the divided individual chips are adhesively fixed to a stem serving as a base, and the adhesively fixed chip and the stem are electrically connected by wire bonding for sealing.