JPS62122405A - Manufacture of surface wave element - Google Patents

Abstract

PURPOSE:To prevent the width of an electrode element at the outermost part of a comb-line electrode after the photolithography processing from being made thin by forming a mask pattern of the electrode element of the outermost part of the comb-line electrode wider than the mask pattern of the electrode element of then other part. CONSTITUTION:The mask pattern of the electrode element at the outermost part having a largest diffraction of light is formed widely from a mask pattern 10 due to the interference of light at exposure among electrode elements 6A, 6B, 7A, 7B of comb-line electrodes 3, 4 of the surface wave element 1. Thus, much light is diffracted from the peripheral side of the mask pattern of the wider electrode element at the outermost part at the exposure of the photolithography processing. Thus, the electrode element of the outermost part is formed nearly the same width to that of the electrode elements other than the outermost part finally and the surface wave element having the comb-line electrodes where the width of all the electrode elements is equal is obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a so-called surface acoustic wave device or a method for manufacturing a surface wave device, and in particular, to a surface acoustic wave device that improves the process of forming a comb-shaped electrode pattern by photolithography. The present invention relates to a method of manufacturing an element.

[Summary of the invention]

In the present invention, when forming a comb-shaped electrode pattern consisting of a plurality of tBil elements, which becomes an electrode of a surface wave element, by photolithography, the mask pattern of the outermost electrode element of the comb-shaped electrode is replaced with that of other parts. By forming the electrode element to be wider than the mask pattern, the outermost electrode element of the comb-shaped electrode is prevented from becoming narrow after photolithography processing.

[Conventional technology]

Generally, a surface acoustic wave element or a surface wave element has a structure as shown in FIG. 10, for example. In the surface acoustic wave device or surface wave device l shown in FIG. 1θ, LiN
An input electrode 3 and an output electrode 4 are formed on a substrate 2 made of a piezoelectric material such as bO3, LiTa01, PbZrOs, etc., and these electrodes 3.4 are used in a so-called comb-like shape such as an interdigital transducer. It is formed in a (blind or interdigitated) pattern. That is, the input electrode 3 (same as the output electrode 4) has electrode elements 6Δ and 7A arranged alternately corresponding to each tooth portion (or finger-like portion) of a pair of comb-like electrode patterns 6.7. These electrode elements 6A and 7A are connected in common at their respective ends to connecting portions 6B and 7B for connecting lead wires and the like. An input signal is supplied between each electrode pattern 6.7 via these connecting portions 6B and 7B, and an output signal is taken out from between each electrode pattern 6.7 of the output electrode 4. That is, the input electrode 3 of such a surface wave element 1 constitutes an input transducer, and the output electrode 4 constitutes an output transducer, and the input signal is supplied to the electrode pattern 6.7 of the input electrode 3 and It is converted into an elastic wave, propagates on the surface of the substrate 2, and is converted into an electrical signal and taken out by an output electrode 4, which is an output transducer, separated by a distance corresponding to a predetermined delay time. Furthermore, the comb-shaped input/output electrodes 3.4 are themselves bandpass filters, and filters with various transfer characteristics can be designed depending on the structure.

Here, each width of the electrode elements 6A and 7A of the electrode of the surface wave element 1, that is, the input electrode 3 or the output electrode 4 is defined as W(1
, the distance between adjacent electrode elements 6A and 7A is d
.

[Problem that the invention seeks to solve]

By the way, in manufacturing such a surface wave element 1,
When a metal thin film for electrodes is deposited on a piezoelectric material substrate and the electrode pattern described above is formed by photolithography processing, light wraparound and light interference from around the photomask pattern during exposure occur. For example, the first
As shown in Figure 1, m-toothed (input/output) electrodes 3 or 4
The outermost electrode elements 6A+, 7A, and the other electrode elements 6Az~6An, 7A1~? It is formed narrower than A. This is the electrode element 6A2-6A4.7
A1~? The amount of light that wraps around A3 due to light interference through the mask pattern is the electrode element 6A+, ? A
, between ~6 Aa,? The outermost electrode element 6A1.7A4 is regulated by the spacing d0 between A4, whereas the outermost electrode element 6A1.7A4 is regulated by the outermost peripheral side, that is, the electrode element 6A in FIG.
There is no restriction on the amount of light that wraps around from the left side of + and the right side of electrode element 7A4, and these electrode elements 6AI
, the amount of light that wraps around from the outermost peripheral side of IAa increases, and the electrode element 6A+, ? after pattern etching increases. Aa
This is because the electrode width becomes narrower than the predetermined width W.

This photolithography reduces the width of the outermost electrode element and causes variations in the width of each electrode element, which is a big problem especially when manufacturing interdigital transducers with fine electrode patterns. Such variations in the width of the electrode elements cause adverse effects such as an increase in loss and a shift in the frequency characteristic P1.

The present invention has been made in order to solve the above-mentioned problems, and the present invention has been made to solve the above-mentioned problems. The purpose is to provide a method for manufacturing elements.

[Means for solving problems]

In the method for manufacturing a surface wave device according to the present invention, when forming a comb-shaped electrode consisting of a plurality of electrode elements on a substrate by photolithography, the outermost electrode element of the comb-shaped electrode is formed. The above-mentioned problem is solved by performing exposure using a mask pattern that is wider than the mask pattern of electrode elements other than the outermost electrode elements.

[For production]

Among the electrode elements of the comb-shaped electrode of the surface wave element, the mask pattern of the outermost electrode element, where light from the mask pattern is largely reflected due to light interference during exposure, is formed to have a wide mask pattern. Therefore, during exposure in the photolithography process, a lot of light wraps around from the outer periphery of the mask pattern of the wide outermost electrode element, and eventually the outermost electrode element is also referred to as an electrode element other than the outermost electrode element. Patterned to the same width, all electrode elements have equal width 1ii
It becomes possible to manufacture a surface wave element having i-toothed electrodes.

〔Example〕

FIG. 1 is a schematic diagram showing a mask pattern 10 used in a method of manufacturing a surface wave device according to an embodiment of the present invention, and is a schematic diagram showing a mask pattern 10 used in a method for manufacturing a surface wave device according to an embodiment of the present invention. This figure shows a mask pattern 10 for forming, by photolithography, a comb-shaped electrode that can be applied to a surface wave device for users, especially a comb-shaped electrode in which the width of the electrode element is around 1 μm or in the submicron range. .

In FIG. 1, the comb-shaped electrode mask pattern 10 consists of a pair of comb-shaped mask patterns 11.12.
Electrode element patterns 11Al, 1 corresponding to each tooth portion of
1Ai, 11Az, 11A, and 12A+, 12A
! , 12Ai, 12A are arranged alternately, and
One end of each of the electrode element patterns IIA, ~1IAn is connected in common and connected to the connection part pattern IIB, and the other ends of each of the electrode element patterns 12A1 to 12A are connected in common and connected to the connection part pattern 12B. has been done.

Here, the alternating arrangement order of the electrode element patterns 11A+ to 11A4 and 12A, to 128 of the comb-shaped electrode mask pattern IO is llAl, 12A1.1IA2 from the cloth in the figure.
．． 12A2..., the outermost electrode element patterns are llAl and 12A. These outermost electrode element patterns IIA and 12Aa have the pattern width W of the other electrode element patterns 12A and 11A4. ,
The pattern width W2 is wider than the width of the outermost electrode element after the pattern etching process by photolithography. For example, W, /W, = 1.05 to 1.5 so that it is equal to the width of the element.
It is set in the range of 0. That is, when the comb-shaped electrode mask pattern 10 is used as a photomask for exposure, light interference causes light to wrap around the outermost electrode element pattern, and the outermost electrode after pattern etching processing is caused by light interference. Considering that the elements are formed to be thinner than the width of the outermost electrode element patterns 11 Al and 12A4 of the mask pattern 10, the reduction in electrode width due to the wraparound of this light is added in advance to the mask pattern width. That's why there is. In addition, the mask pattern 10 for comb-shaped electrodes
Electrode element pattern lIA+ ~11Aa, 12A, ~
Of course, the number of 12A4's and the pattern shape are not limited to the example shown in FIG.

Next, as a specific example, a 128° Y-cut LiNb0. In the case of manufacturing a surface acoustic wave (SAW) filter with a center frequency of 830 MHz using a piezoelectric crystal wafer, we will explain the process of forming comb-shaped electrodes that will become an interdigital transducer (IDT) by photolithography. . The width of each important element of the tooth-shaped electrode III at this time is approximately 1.2 μm, but if the width of the portion of the mask pattern corresponding to all electrode elements is 1.2 μm, then the outermost electrode element described above In this case, by setting the mask width corresponding to the outermost electrode element to 1.4μ, the width of the outermost electrode element after the photolithography process can be reduced. About 1 above
．． It can be made into a 2μ cocoon. Therefore, the widths of all the electrode elements of the comb-like electrodes constituting the interdigital transducer (IDT) can be made equal to each other, approximately 1.2 μm, thereby obtaining the desired frequency characteristics and reducing the increase in loss. Prevention is possible.

In addition, as another specific example, 128” Y-cut LiN
b0. When producing a surface acoustic wave filter with a center frequency of 1.6 GHz using a piezoelectric crystal wafer, the width of the electrode element of the comb-shaped electrode that becomes the interdigital transducer is approximately 0.6 μm. . In this case, by setting the mask width corresponding to the outermost electrode element to 0.9 μm steel, the width of all the electrode elements after the photolithography process can be set to the above-mentioned approximately 0.6 μm.

The electro-scratch pattern formation by photolithography as described above is performed simultaneously on a plurality of surface wave element forming regions allocated on the piezoelectric material wafer. For example,
As shown in Figure 2, 112° Y cut and 1 Taos
A single crystal wafer 20 is prepared, and this LiTaO3 wafer 2
As shown in FIG. 3, an electrode metal layer 21 is deposited on the electrode metal layer 21, and a resist 11922 for photolithography is deposited on the electrode metal layer 21, as shown in FIG. Form.

The resist film 22 is exposed to light through a photomask in which the width of the mask pattern corresponding to the outermost electrode element as described above is wider than the width of the other electrode elements, and
After processing steps such as development, etching, and resist removal,
For example, a wafer 20 on which electrode patterns of a plurality of surface acoustic wave elements 1 as shown in FIG. 5 are formed is obtained. Of course, each electrode element of this electrode pattern is formed to have the same width. Next, the wafer 20 on which the electrode pattern has been formed is cut and separated along the boundary line of each surface wave element 1 as shown in FIG. 6, and a plurality of surface wave elements (chips) 1 are obtained.

Incidentally, the process of cutting and separating the wafer 20 into chips into a plurality of surface wave elements 1 is generally performed by dicing, etc., and conventionally, the cut and separated chips are processed as they are without any processing. Available for assembly. For this reason, defects (or crack sources) 25 such as minute chips and cracks exist around the chip as shown in FIG. 7, and during heat cycle tests,
When placed in an environment with large temperature differences or when subjected to shock, the chip may crack and lose its function as a surface acoustic wave element.

Therefore, as shown in Figure 8, diamond paste (
The corners around the chip of the surface acoustic wave element 1 are polished using a grain size of about 2 .mu.m to make them rounded, and the defects such as the minute chips and cranks are removed. Alternatively, as shown in FIG. 9, the defective portions may be removed by polishing the chip end faces A, B, etc. of the surface acoustic wave element 1.

In this way, by polishing and removing minute chips and defective parts such as cranks on the peripheral corners of the chip (crank sources), chips will not crack during heat cycle tests, etc., and the reliability of surface wave devices will be improved. performance is significantly improved.

In addition, as the polishing agent used in the polishing step, in addition to diamond paste, cerium oxide, chromium oxide, or various abrasive papers can be used.

〔Effect of the invention〕

As is clear from the above explanation, since the photomask pattern of the outermost electrode element of the comb-shaped electrode is formed wider than the mask pattern of the t-shaped elements in other parts, the comb pattern after the photolithography process is Since the outermost electrode element of the tooth-like electrode is prevented from becoming narrow and all electrode elements are formed to have the same width, a surface wave element with desired frequency characteristics can be obtained, and an increase in loss can also be avoided. Can be effectively prevented. This is particularly effective when applied to interdigital transducers with comb-like electrodes where the electrode element width is around l1w or in the submicron range, so that light interference during exposure cannot be ignored.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing one embodiment of the present invention, FIGS. 2 to 6 are diagrams for explaining the manufacturing process of a surface wave device, and FIGS. 2 to 4 are schematic diagrams. Perspective view, 5th
6 and 6 are partially cutaway schematic plan views, FIGS. 7 to 9 are partially cutaway schematic perspective views showing the peripheral area of the surface wave element chip, and FIG. 10 is a schematic plan view of the surface wave element. FIG. 11 is a schematic plan view showing a comb-shaped electrode patterned by a conventional manufacturing method. l...Surface wave element 3.4...Comb-shaped (input/output) electrodes 6A1 to 6A4, ? A1~? A,...electrode element 10.
...Mask patterns for comb-shaped electrodes 11A, to 11A4.
12AI, 12A4...fi element pattern resist II! ! '! ? i7f table trouble 1191
1 (Resistance chart Figure 4 Den Ishi pattern? IS A f & Notsu L Ha's Suedaida bJ
P side view Fig. 5 Fig. 6 Width for 1000 mm after wafer cl'JrMr - Fig. 7 Fig. 10 Fig. 11

Claims (1)

[Claims] When forming a comb-shaped electrode consisting of a plurality of electrode elements on a piezoelectric substrate by photolithography, the mask pattern for forming the outermost electrode element of the comb-shaped electrode is different from the mask pattern for the electrode elements other than the outermost one. 1. A method of manufacturing a surface wave device, characterized in that exposure is performed using a mask formed with a wide width.