JP2005191703A - Manufacturing method of surface acoustic wave element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a surface acoustic wave element capable of efficiently suppressing variations in center frequency on the same substrate. <P>SOLUTION: This method is provided with a mask forming process for forming on a metal film 11, a mask layer 13 having the pattern of the shape of interdigital electrodes 3 by applying resist 14 on the metal film 11 formed on a piezoelectric substrate 2, exposing the resist 14 to light for each unit region 2b comprising an element region 10, and developing the exposed resist 14; and an electrode forming process for forming the interdigital electrodes 3 by etching a part of the metal film 11 which is not covered with the mask layer 13. The center frequency of an element region 10 comprised in each unit region 2b is adjusted by exposing the resist 14 to light with an exposure determined for each unit region 2b, when the mask forming process is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a surface acoustic wave element.

  In recent years, surface acoustic wave elements such as surface acoustic wave filters and surface acoustic wave resonators in which comb-shaped electrodes are formed on a piezoelectric substrate are often used as components for high-frequency circuits incorporated in mobile phones and the like. The surface acoustic wave element can be reduced in size and has excellent electrical characteristics as compared with a dielectric filter or the like conventionally used.

  Generally, a surface acoustic wave element is manufactured as follows. First, a metal film is formed on a piezoelectric substrate. Next, a mask layer having a comb electrode shape pattern is formed on the metal film. And the part which is not covered with a mask layer among metal films is etched, and a comb-shaped electrode is formed. Finally, the piezoelectric substrate is divided to complete a plurality of surface acoustic wave elements.

Here, in the manufacturing stage of the surface acoustic wave element, the center frequency is adjusted according to the purpose of use. As a conventional method for adjusting the center frequency of the surface acoustic wave element, a method for selecting a material of the piezoelectric substrate, a method for adjusting the height of the comb-shaped electrode (for example, Patent Document 1), or the main surface of the piezoelectric substrate. Alternatively, there is a method of forming a polyimide film for adjusting the center frequency on the side surface (for example, Patent Documents 2 and 3).
JP 2003-179453 A JP 2000-278068 A JP 2002-353773 A

  However, for example, when the thickness of the metal film formed on the piezoelectric substrate is not uniform on the same substrate, the thickness of the comb-shaped electrode is not uniform on the same substrate. As a result, variations occur in the center frequencies of the plurality of surface acoustic wave elements manufactured from the same piezoelectric substrate. In each of the above-mentioned Patent Documents 1 to 3, only a method for individually adjusting the center frequency of the surface acoustic wave element after dividing the piezoelectric substrate is disclosed, and variations in the center frequency as described above on the same substrate are disclosed. It is difficult to efficiently suppress

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a surface acoustic wave device that can efficiently suppress variations in the center frequency on the same substrate.

  In order to solve the above-described problems, a first surface acoustic wave device manufacturing method according to the present invention forms a comb-shaped electrode in each of a plurality of element regions on a piezoelectric substrate, and provides piezoelectricity in units of a plurality of element regions. A method of manufacturing a surface acoustic wave device by dividing a substrate, wherein a resist is applied on a metal film formed on a piezoelectric substrate, and the resist is exposed for each unit region including the device region. A mask forming process for forming a mask layer having a comb electrode shape pattern on the metal film by developing the resist, and a comb electrode is formed by etching a portion of the metal film not covered by the mask layer And adjusting the center frequency of the element region included in each unit region by exposing the resist with an exposure amount determined for each unit region during the mask forming step. It is characterized in.

  In the surface acoustic wave device manufacturing method described above, the center frequency of the element region included in the unit region is adjusted by exposing the resist with the exposure amount determined for each unit region. That is, by changing the exposure amount, the pattern width of the mask layer is changed, thereby changing the width of the comb electrode. When the width of the comb electrode changes, the center frequency changes. Therefore, by determining a suitable exposure amount for each unit area, the center frequency can be arbitrarily changed for each unit area. According to this manufacturing method, the variation in the center frequency on the same piezoelectric substrate can be canceled by determining the exposure amount for each unit region, so that the variation in the center frequency on the same substrate can be efficiently suppressed. be able to.

  The method for manufacturing a surface acoustic wave element further includes a center frequency measuring step of measuring a center frequency of each of a plurality of element regions in the first piezoelectric substrate on which the comb-shaped electrode is formed, In the mask forming step, the exposure amount may be determined for each unit area based on the center frequency measured in the center frequency measuring step.

  For example, when the formation conditions when forming the comb-shaped electrode on the first piezoelectric substrate and the formation conditions when forming the comb-shaped electrode on the second piezoelectric substrate are the same conditions, The center frequency distribution in each of the first and second piezoelectric substrates tends to be similar to each other. Therefore, according to this manufacturing method, the exposure amount for each unit region when forming the mask layer on the second piezoelectric substrate is determined based on the center frequency distribution in the first piezoelectric substrate, thereby exposing the exposure. The amount can be suitably determined for each unit region, and variations in the center frequency on the same substrate can be effectively suppressed.

  In addition, in the method of manufacturing the surface acoustic wave element, when a positive resist is used as the resist in the mask forming process for the second piezoelectric substrate, the unit region having a large center frequency measured in the center frequency measuring process is used. In the case of using a negative resist as the resist, the exposure amount may be increased in a unit region having a larger center frequency measured in the center frequency measurement step.

  In the case where a positive resist is used in the mask formation process, if the exposure amount is relatively small, the width of the comb-shaped electrode can be increased and the center frequency can be decreased. In the case of using a negative resist, when the exposure amount is relatively large, the width of the comb-shaped electrode is widened and the center frequency can be decreased. Therefore, in a unit region with a higher center frequency, it is preferable to reduce the exposure amount when using a positive resist and to increase the exposure amount when using a negative resist, thereby favoring variations in the center frequency on the same substrate. Can be suppressed.

  The method for manufacturing a surface acoustic wave device further includes a film thickness measurement process for measuring a film thickness distribution of a metal film formed on the piezoelectric substrate, and is measured in the film thickness measurement process during the mask formation process. Further, the exposure amount may be determined for each unit area based on the thickness distribution of the metal film.

  For example, in a unit region where the metal film is thick on the piezoelectric substrate, the comb-shaped electrode formed by etching the metal film also becomes thick, and the center frequency becomes relatively small. Conversely, the center frequency is relatively large in a unit region where the metal film is relatively thin. Thus, the non-uniformity of the metal film thickness distribution causes variations in the center frequency. According to the manufacturing method described above, since the exposure amount for each unit region is determined based on the film thickness distribution of the metal film, the metal film thickness distribution is uneven (comb electrode thickness non-uniformity). The resulting variation in the center frequency can be offset by changing the width of the comb electrode for each unit region. Therefore, variations in the center frequency on the same substrate can be suitably suppressed.

  Further, in the method of manufacturing the surface acoustic wave device, when a positive resist is used as the resist in the mask forming process, the exposure amount is increased in the unit region where the thickness of the metal film measured in the film thickness measuring process is larger. When a negative resist is used as the resist, the exposure amount may be reduced in a unit region where the thickness of the metal film measured in the film thickness measurement step is larger.

  As described above, the center frequency tends to be smaller as the unit region is thicker. Therefore, by increasing the exposure amount when using a positive resist and reducing the exposure amount when using a negative resist, the unit region where the thickness of the metal film is thick (that is, the center frequency is small) Variations in the center frequency on the same substrate can be suitably suppressed.

  In the method for manufacturing the surface acoustic wave element described above, the piezoelectric substrate includes not only a substrate made of a piezoelectric material but also a substrate in which a layer of a piezoelectric material is formed on a substrate made of a non-piezoelectric material.

  According to the method for manufacturing a surface acoustic wave element according to the present invention, variations in the center frequency on the same substrate can be efficiently suppressed.

  Embodiments of a method for manufacturing a surface acoustic wave device according to the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  First, the intermediate product manufactured by the method for manufacturing the surface acoustic wave device according to the present embodiment will be described. FIG. 1 is a side sectional view showing an intermediate product 1 manufactured according to this embodiment. In addition, in FIG. 1, the center part (A in a figure) and peripheral part (B in a figure) of the intermediate product 1 are expanded and shown. Referring to FIG. 1, an intermediate product 1 includes a piezoelectric substrate 2, a plurality of interdigital transducers (IDTs) 3 formed on the piezoelectric substrate 2, a reflection electrode, an electrode pad, and a protection not shown. And a membrane.

The piezoelectric substrate 2 is a wafer-like substrate made of a piezoelectric material such as lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or quartz. The piezoelectric substrate 2 has a plurality of element regions 10 on the main surface, and a predetermined number of comb electrodes 3, reflection electrodes, and electrode pads are formed in each of the plurality of element regions 10. In the method of manufacturing a surface acoustic wave element described in detail later, a plurality of surface acoustic wave elements are manufactured by dividing the piezoelectric substrate 2 into 10 element regions.

  The plurality of comb-shaped electrodes 3 are made of, for example, a metal material mainly composed of Al, and are respectively formed in a comb shape on the piezoelectric substrate 2. The reflective electrode is made of, for example, the same material as the comb electrode 3 and is formed at a position sandwiching the comb electrode 3. The electrode pad is made of, for example, the same material as that of the comb-shaped electrode 3 and is electrically connected to the comb-shaped electrode 3 through a wiring pattern. The protective film is an insulating film that covers the piezoelectric substrate 2, the comb electrode 3, the reflective electrode, and the electrode pad.

  The thicknesses of the comb-shaped electrode 3 and the reflective electrode are not uniform on the piezoelectric substrate 2 and differ depending on the positions where the comb-shaped electrode 3 and the reflective electrode are formed. For example, in the present embodiment, as shown in FIG. 1, the thickness t1 of the comb-shaped electrode 3 on the element region 10 located in the central portion of the piezoelectric substrate 2 is the element region 10 located in the peripheral portion of the piezoelectric substrate 2. The upper comb-shaped electrode 3 is thinner than the thickness t2. As described above, the thicknesses of the comb-shaped electrode 3 and the reflective electrode are not uniform on the piezoelectric substrate 2 when the metal film for forming the comb-shaped electrode 3 and the reflective electrode is formed on the piezoelectric substrate 2. This is because it is difficult to make the thickness of the metal film strictly uniform.

  In the intermediate product 1, in order to adjust the variation between the center frequency regions of the element region 10 due to the nonuniform thickness of the comb electrode 3 and the reflective electrode, the comb electrode 3 And the width of the reflective electrode changes in the same substrate. For example, in the present embodiment, as shown in FIG. 1, the width W1 of the comb-shaped electrode 3 on the element region 10 located in the central portion of the piezoelectric substrate 2 is such that the element region 10 located in the peripheral portion of the piezoelectric substrate 2. The upper comb-shaped electrode 3 is wider than the width W2. That is, the width of the comb-shaped electrode 3 is wide in the portion where the thickness of the comb-shaped electrode 3 is relatively thin, and the width of the comb-shaped electrode 3 is narrowed in the portion where the thickness of the comb-shaped electrode 3 is relatively thick. In the intermediate product 1, the comb-shaped electrodes 3 are formed so that the cross-sectional areas of the plurality of comb-shaped electrodes 3 are close to each other in this manner, so that the variation in the center frequency of the element region 10 is adjusted within a specified range. ing.

  Next, the method for manufacturing the surface acoustic wave device according to the present embodiment will be described. FIG. 2 is a flowchart showing the method for manufacturing the surface acoustic wave device according to the present embodiment. 3 and 4 are cross-sectional views for explaining the method of manufacturing the surface acoustic wave device according to the present embodiment. 2 to 4, in this manufacturing method, first, a wafer-like piezoelectric substrate 2 made of a piezoelectric material is prepared (S101). Subsequently, the main surface 2a of the piezoelectric substrate 2 is cleaned, and a metal film 11 is formed on the cleaned main surface 2a (S102, FIG. 3A). When forming the metal film 11, for example, a metal material mainly composed of Al may be formed on the main surface 2a by sputtering or the like.

  Subsequently, the film thickness distribution of the metal film 11 is measured (film thickness measuring step, S103). That is, the film thickness distribution of the metal film 11 on the main surface 2a of the piezoelectric substrate 2 is measured using fluorescent X-rays or the like. Here, FIG. 5A and FIG. 5B are cross-sectional views showing typical examples of the film thickness distribution of the metal film 11. FIG. 5A shows a case where the thickness t3 of the metal film 11 in the central portion of the piezoelectric substrate 2 is thinner than the thickness t4 of the metal film 11 in the peripheral portion of the piezoelectric substrate 2. FIG. FIG. 5B shows a case where the thickness t3 of the metal film 11 in the central portion of the piezoelectric substrate 2 is thicker than the thickness t4 of the metal film 11 in the peripheral portion of the piezoelectric substrate 2. As in the example shown in FIGS. 5A and 5B, the thickness of the metal film 11 is often contrasted between the central portion and the peripheral portion of the piezoelectric substrate 2. The method for measuring the film thickness distribution is not limited to the method using fluorescent X-rays, and other methods may be used.

  Subsequently, one piezoelectric substrate 2 (trial substrate) is selected from the plurality of piezoelectric substrates 2, and a mask layer 13 is formed on the metal film 11 on the selected piezoelectric substrate 2 (first piezoelectric substrate). Mask forming step for the conductive substrate, S104). First, a resist 14 is applied on the metal film 11 (FIG. 3B). Then, the resist 14 is exposed to a predetermined pattern including each of a comb electrode shape, a reflective electrode shape, a pad electrode shape, and a wiring pattern shape (FIG. 3C). That is, when the resist 14 is a positive resist, the region 14b other than the region covering the region where the comb electrode is to be formed is irradiated with ultraviolet rays or the like to remove the region where the comb electrode is formed. A photosensitive portion is formed on the region. Then, by developing the resist 14, the photosensitive portion 14b of the resist 14 is removed, and the mask layer 13 is formed (FIG. 3D). Alternatively, when the resist 14 is a negative resist, the photosensitive portion is formed on the region where the comb electrode or the like is to be formed by irradiating ultraviolet rays or the like to the portion 14a of the resist 14 that covers the region where the comb electrode or the like is to be formed. It is formed. Then, by developing the resist 14, the portion 14 b other than the photosensitive portion of the resist 14 is removed and the mask layer 13 is formed (FIG. 3D).

  Here, FIG. 6 is a plan view of the wafer-like piezoelectric substrate 2. In the present embodiment, the exposure of the resist 14 in the mask formation step described above is performed for each unit region 2b shown in FIG. That is, using an exposure apparatus such as an i-line stepper, an exposure shot having a predetermined pattern including a comb electrode shape is irradiated for each unit region 2b. At this time, the exposure amount for each unit region 2b is individually determined. When the resist 14 is exposed, the area of the exposed portion in the resist 14 tends to increase as the exposure amount to the resist 14 increases. Accordingly, when the resist 14 is a positive type resist, the pattern width of the mask layer 13 becomes narrower as the exposure amount to the resist 14 is increased. When the resist 14 is a negative type resist, the exposure amount to the resist 14. The pattern width of the mask layer 13 is increased as the value is increased. In the present embodiment, the unit region 2b includes a predetermined number of element regions 10 (see FIG. 1).

  In the mask formation process of the present embodiment, the exposure amount for each unit region 2b is determined based on the film thickness distribution of the metal film 11 measured in the film thickness measurement process (S103). That is, in the unit region (unit region 2c in FIG. 3C) in which the metal film 11 is relatively thick on the piezoelectric substrate 2, the thickness of the comb-shaped electrode formed from the metal film 11 in the subsequent process is also large. Relatively thick. Since the center frequency of the element region included in the unit region 2c tends to be smaller as the comb electrode is thicker, in this embodiment, the width of the comb electrode is larger in the unit region 2c where the metal film 11 is relatively thick. The mask layer 13 is formed so that the width of the comb-shaped electrode is wide in the unit region where the film thickness of the metal film 11 is relatively thin (unit region 2d in FIG. 3C). Form. That is, in the unit region 2c where the film thickness of the metal film 11 is relatively large, the exposure amount is relatively large when a positive resist is used, and the exposure amount is relatively small when a negative resist is used. In this way, the center frequency of the element region 10 included in each unit region 2b is adjusted within the specified region.

  Subsequently, a portion of the metal film 11 that is not covered with the mask layer 13 is removed by etching, whereby the comb-shaped electrode 3, the input / output electrode 5 serving as a base portion of the electrode pad, a reflection electrode and a wiring pattern (not shown), (Electrode forming step, S105, FIG. 3E). Then, after forming the comb-shaped electrode 3 and the like, the mask layer 13 is removed. In the present embodiment, the metal film 11 may be etched by dry etching such as ICP (Inductive Coupling Plasma) etching.

  Subsequently, the center frequency distribution on the piezoelectric substrate 2 is measured (center frequency measuring step, S106). That is, the center frequency characteristics of each of the plurality of element regions 10 on the trial substrate are measured using, for example, a wafer prober, and the center frequency distribution is obtained in consideration of the position of each element region.

  Subsequently, the mask layer 13 is formed on the piezoelectric substrate 2 (mass production substrate) other than the trial substrate selected in the above-described step S104 (mask forming step for the second piezoelectric substrate, S107). This step S107 is the same as step S104 described above except for the condition for determining the exposure amount for the resist. That is, in step S107, the exposure amount for each unit region 2b is determined based on the center frequency distribution measured in step S106 and the film thickness distribution of the metal film 11 measured in step S103.

  Here, FIG. 7 is a graph showing the correlation between the exposure amount for the positive resist 14 and the center frequency of the element region 10 having the comb-shaped electrode formed by the exposure amount. Referring to FIG. 7, the exposure amount for the positive resist 14 and the center frequency of the element region 10 are substantially proportional, and the center frequency increases as the exposure amount increases. This is because the width of the comb-shaped electrode 3 is reduced when the exposure amount for the positive resist 14 is increased. That is, when a positive resist is used as the resist 14, the exposure amount is preferably decreased for the unit region 2 b having a larger center frequency. When a negative resist is used as the resist 14, the exposure amount is preferably increased in the unit region 2b having a larger center frequency. In this way, the center frequency of the element region 10 included in each unit region 2b can be adjusted within a specified range. The exposure amount to each unit region 2b for realizing a desired center frequency in the mass production substrate is determined by using the inclination of the graph in FIG. 7 and the center frequency in the trial substrate measured in step S106 and each of the trial substrate. It is calculated based on the exposure amount to the unit area 2b.

  In step S107, the exposure amount for each unit region 2b of the mass production substrate is determined based on the relationship between the exposure amount and the center frequency as described above. Further, in step S107, the exposure amount for each unit region 2b is determined based on the film thickness distribution of the metal film 11 as in step S104 described above.

  Subsequently, a portion of the metal film 11 on the mass production substrate that is not covered with the mask layer 13 is removed by etching to form the comb-shaped electrode 3 and the input / output electrodes 5 on the mass production substrate (electrode formation step, S108). FIG. 3 (e)). Then, after forming the comb-shaped electrode 3 and the like, the mask layer 13 is removed. When forming the comb electrodes 3 and the input / output electrodes 5 on the mass production substrate, it is preferable that the etching conditions are the same as those for the trial substrate.

  Subsequently, the center frequency distribution on the mass production substrate is measured (center frequency measurement step, S109). That is, the center frequency characteristics of each of the plurality of element regions 10 on the mass production substrate are measured using, for example, a wafer prober, and it is confirmed that the center frequency of each element region 10 is within a specified range.

  Subsequently, a raised electrode is formed on the input / output electrode 5 (S110). First, a barrier layer 12 made of Cr or the like is formed so as to cover the piezoelectric substrate 2, the comb electrode 3, the input / output electrode 5 and the reflective electrode (FIG. 4A). The barrier layer 12 covering the piezoelectric substrate 2, the comb electrode 3, and the reflective electrode is removed when the mask 17 is removed. Next, a metal film 15 made of, for example, Al or a material containing an alloy containing Al as a main component is formed so as to cover the piezoelectric substrate 2, the comb-shaped electrode 3, the input / output electrode 5, and the reflective electrode (see FIG. 4 (b)). Next, a resist is applied on the metal film 15, and exposure and development are performed so that the resist remains at a position corresponding to the input / output electrode 5 on the metal film 15. As a result, a mask 17 is formed on the metal film 15 at a position corresponding to the input / output electrode 5 as shown in FIG. Then, as shown in FIG. 4D, the raised electrode 7 is formed on the input / output electrode 5 by etching the portion of the metal film 15 that is not covered with the mask 17. Thus, the electrode pad 8 including the input / output electrode 5 and the raised electrode 7 is formed.

  Subsequently, a protective film 9 is formed to cover the piezoelectric substrate 2, the comb electrode 3, the electrode pad 8, the reflective electrode, and the like (S111, FIG. 4E). Through the above steps, the intermediate product 1 shown in FIG. 1 is formed. Then, by dividing the intermediate product 1 into each element region (S112), a plurality of surface acoustic wave elements are completed.

  The method for manufacturing the surface acoustic wave device according to the present embodiment described above has the following effects. That is, in the method for manufacturing the surface acoustic wave device according to the present embodiment, the center frequency of the element region 10 included in the unit region 2b is adjusted by exposing the resist 14 with the exposure amount determined for each of the plurality of unit regions 2b. doing. According to this manufacturing method, the variation in the center frequency on the same piezoelectric substrate 2 can be canceled by selecting the exposure amount for each unit region 2a, so that the variation in the center frequency on the same substrate can be efficiently performed. It can be suppressed well.

  In the method for manufacturing the surface acoustic wave device according to the present embodiment, when the mask layer 13 is formed on the mass production substrate, the exposure amount is determined for each unit region 2b based on the center frequency measured on the trial substrate. Yes. As in this embodiment, when the formation conditions when forming the comb-shaped electrode 3 on the trial substrate and the formation conditions when forming the comb-shaped electrode 3 on the mass production substrate are substantially the same conditions, The center frequency distributions on the respective substrates tend to be similar to each other. Therefore, according to this manufacturing method, since the exposure amount with respect to the resist 14 on the mass production substrate can be suitably determined for each unit region 2b, variation in the center frequency on the same substrate can be effectively suppressed.

  Further, in the method of manufacturing the surface acoustic wave device according to the present embodiment, when a positive resist is used as the resist 14 in the mask forming process for the mass production substrate, the exposure amount of the unit region 2b having a larger center frequency on the trial substrate Is made smaller. When a negative resist is used as the resist 14, the exposure amount is increased in the unit region 2b having a larger center frequency on the trial substrate. In the case where a positive resist is used in the mask formation process, when the exposure amount is reduced, the width of the comb-shaped electrode 3 is increased and the center frequency is decreased. In the case of using a negative resist, when the exposure amount is increased, the width of the comb electrode is increased and the center frequency is decreased. Accordingly, the unit area 2b having a larger center frequency reduces the exposure amount when using a positive resist, and increases the exposure amount when using a negative resist, thereby causing variations in the center frequency on the same substrate. It can suppress suitably.

  In the method for manufacturing the surface acoustic wave element according to the present embodiment, the exposure amount is determined for each unit region based on the film thickness distribution of the metal film 11 during the mask formation process. In the unit region 2b where the metal film 11 is thick on the piezoelectric substrate 2, the comb electrode 3 is also thick, and the center frequency is relatively small. Conversely, in the unit region 2b where the metal film 11 is relatively thin, the center frequency is relatively large. According to the method for manufacturing a surface acoustic wave element according to the present embodiment, the exposure amount for each unit region 2b is determined based on the film thickness distribution of the metal film 11, so that the film thickness distribution of the metal film 11 is not uniform. Variations in the center frequency caused by (non-uniform thickness of the comb electrode 3) can be offset by changing the width of the comb electrode 3 for each unit region 2b. Therefore, variations in the center frequency on the same substrate can be suitably suppressed.

  Further, in the method of manufacturing the surface acoustic wave device according to the present embodiment, when a positive resist is used as the resist 14 in the mask forming process, the exposure amount is increased as the unit region 2b having a thicker metal film 11 is formed. However, when a negative resist is used as the resist 14, the exposure amount is reduced as the unit region 2b where the metal film 11 is thicker. As a result, variations in the center frequency on the same substrate can be suitably suppressed.

  8 and 9 are diagrams showing examples of the method for manufacturing the surface acoustic wave device according to the above-described embodiment. FIG. 8 is a diagram showing a measurement result of the center frequency distribution of the intermediate product 1 in the manufacturing method described above. FIG. 9 is a histogram showing the frequency of the center frequency in the center frequency distribution shown in FIG. FIG. 10 and FIG. 11 are diagrams showing an example in which the center frequency is not adjusted as a comparative example. FIG. 10 is a diagram illustrating a measurement result of the center frequency distribution of the intermediate product in the comparative example. FIG. 11 is a histogram showing the frequency of the center frequency in the center frequency distribution shown in FIG. In FIG. 8 and FIG. 10, the grid-like lines indicate the boundary lines of the unit areas.

  Referring to FIG. 10, in the intermediate product produced by the manufacturing method without adjusting the center frequency, the center frequency is greatly different between the unit regions, and the center frequency in the central portion of the piezoelectric substrate is larger than the center frequency in the peripheral portion. I understand that. This is considered to be because when the metal film was formed on the piezoelectric substrate, the film thickness distribution of the metal film was relatively thin in the central portion of the substrate and relatively thick in the peripheral portion of the substrate (see FIG. 5 (a)). Also, referring to the histogram of FIG. 11, it can be seen that there are many element regions having a center frequency outside the specified range R, and the center frequency varies on the same substrate.

  On the other hand, referring to FIG. 8, in the intermediate product 1 produced by the manufacturing method of the above embodiment, it can be seen that the center frequency of each unit region is substantially uniform on the substrate. Note that the film thickness distribution of the metal film 11 in this embodiment is the same as the film thickness distribution of the metal film in the comparative example shown in FIG. Further, referring to the histogram of FIG. 9, it can be seen that there is almost no element region having a center frequency outside the specified range R, and the center frequency is adjusted within the specified range on the same substrate. As described above, according to the method for manufacturing the surface acoustic wave device according to the above-described embodiment, it is possible to suitably suppress variation in the center frequency on the same substrate.

  The method for manufacturing a surface acoustic wave device according to the present invention is not limited to the above-described embodiments, and various other modifications are possible. For example, in the above-described embodiment, the film thickness measurement process is performed only on the metal film on the trial substrate, but the film thickness measurement process may be further performed on the metal film on the mass production substrate. Thereby, the adjustment precision of the center frequency on a mass-production board | substrate can be improved more.

FIG. 1 is a side sectional view showing an intermediate product. FIG. 2 is a flowchart showing a method for manufacturing the surface acoustic wave element. FIG. 3A to FIG. 3E are cross-sectional views for explaining a method for manufacturing a surface acoustic wave element. FIG. 4A to FIG. 4E are cross-sectional views for explaining a method for manufacturing a surface acoustic wave element. FIGS. 5A and 5B are cross-sectional views showing typical examples of the film thickness distribution of the metal film. FIG. 6 is a plan view of a wafer-like piezoelectric substrate. FIG. 7 is a graph showing the correlation between the exposure amount for the positive resist and the center frequency of the element region having the comb-shaped electrode formed by the exposure amount. FIG. 8 is an example of the method for manufacturing the surface acoustic wave device according to the above-described embodiment, and is a diagram illustrating the measurement result of the center frequency distribution of the intermediate product. FIG. 9 is an example of the method for manufacturing the surface acoustic wave device according to the above-described embodiment, and is a histogram showing the frequency of the center frequency in the center frequency distribution shown in FIG. FIG. 10 is an example of the case where the exposure amount is not adjusted, and is a diagram showing the measurement result of the center frequency distribution of the intermediate product. FIG. 11 is an example when the exposure amount is not adjusted, and is a histogram showing the frequency of the center frequency in the center frequency distribution shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Intermediate product, 2a ... Main surface, 2b-2d ... Unit area | region, 2 ... Piezoelectric substrate, 3 ... Comb-shaped electrode, 5 ... Input / output electrode, 7 ... Raised electrode, 8 ... Electrode pad, 9 ... Protective film, DESCRIPTION OF SYMBOLS 10 ... Element area | region, 11 ... Metal film, 12 ... Barrier layer, 13 ... Mask layer, 14 ... Resist, 15 ... Metal film, 17 ... Mask

Claims (5)

A method of manufacturing a surface acoustic wave element by forming a comb-shaped electrode in each of a plurality of element regions on a piezoelectric substrate and dividing the piezoelectric substrate into a plurality of element region units,
The shape of the comb-shaped electrode is obtained by applying a resist on a metal film formed on the piezoelectric substrate, exposing the resist for each unit region including the element region, and developing the exposed resist. A mask forming step of forming a mask layer having a pattern on the metal film;
An electrode forming step of forming the comb-shaped electrode by etching a portion of the metal film not covered with the mask layer, and
An elastic surface characterized by adjusting the center frequency of the element region included in each unit region by exposing the resist with an exposure amount determined for each unit region during the mask forming step. Manufacturing method of wave element. A center frequency measuring step of measuring a center frequency of each of the plurality of element regions in the first piezoelectric substrate on which the comb electrode is formed;
The exposure amount is determined for each of the unit regions based on the center frequency measured in the center frequency measurement step during the mask formation step on the second piezoelectric substrate. Item 2. A method for manufacturing a surface acoustic wave device according to Item 1.   In the case of using a positive resist as the resist in the mask forming step for the second piezoelectric substrate, the exposure amount is set to the unit region having a larger center frequency measured in the center frequency measuring step. 3. The exposure amount according to claim 2, wherein when the negative resist is used as the resist, the exposure amount is increased in the unit region having the larger center frequency measured in the center frequency measuring step. Manufacturing method of the surface acoustic wave element. A film thickness measurement step for measuring a film thickness distribution of the metal film formed on the piezoelectric substrate;
4. The exposure amount is determined for each unit region based on the film thickness distribution of the metal film measured in the film thickness measurement process during the mask formation process. The manufacturing method of the surface acoustic wave element as described in any one of these.   When a positive resist is used as the resist in the mask forming step, the exposure amount is increased in the unit region where the thickness of the metal film measured in the film thickness measuring step is larger. 5. The elasticity according to claim 4, wherein, when a negative resist is used, the exposure amount is decreased in the unit region where the thickness of the metal film measured in the film thickness measurement step is larger. A method for manufacturing a surface acoustic wave device.

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