JP2006258766A - Elastic wave sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the measuring precision of a measuring target in an elastic wave sensor. <P>SOLUTION: A measuring elastic wave element 12 and a reference elastic wave element 14 are formed on one main surface 10a of a common piezoelectric substrate 10. A measuring responsive film 16 showing adsorbabilities with respect to the measuring target is formed on the measuring elastic wave element 12 so as to be exposed with respect to the measuring target. A reference responsive film 18 similar to the measuring responsive film 16 in kind is formed to the reference elastic wave element 14 and a lid 32 for covering the reference responsive film 18 to hermetically seal the same is joined to one main surface 10a of the piezoelectric substrate 10. Since the reference responsive film 18 is sealed with respect to the measuring target by providing the lid 32, the reference elastic wave element 14 can be formed so as not to show the adsorbabilities with respect to the measuring target. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an elastic wave sensor using an elastic wave such as a surface acoustic wave (SAW) or a transverse wave elastic wave (STW), and in particular, an elastic wave for measurement in which a sensitive film showing adsorptivity to a measurement object is formed. The present invention relates to an acoustic wave sensor having an element and a reference acoustic wave element that does not exhibit adsorptivity to the object to be measured.

  In an elastic wave sensor using an elastic wave such as a surface acoustic wave (SAW) or a transverse wave elastic wave (STW), a sensitive film that exhibits adsorptivity to an object to be measured is formed. When the sensitive film adsorbs the object to be measured, the oscillation frequency of the acoustic wave element changes. Therefore, the concentration of the object to be measured can be detected by detecting the change in the oscillation frequency.

  Patent Documents 1 and 2 disclose conventional examples of acoustic wave sensors in which this sensitive film is formed. The elastic wave sensor of Patent Document 1 includes a measurement elastic wave element and a reference elastic wave element. In the acoustic wave element for measurement, a sensitive film that exhibits adsorptivity to the object to be measured is formed. On the other hand, the reference acoustic wave element does not show the adsorptivity to the object to be measured because the sensitive film is not formed. When the object to be measured exists in the vicinity of the sensor, the oscillation frequency of the acoustic wave element for measurement changes due to the sensitive film of the acoustic wave element for measurement adsorbing the object to be measured, whereas the elasticity for reference The wave element does not change the oscillation frequency without adsorbing the object to be measured. Using this property, the concentration of the object to be measured is detected by comparing the oscillation frequency of the measurement acoustic wave element with the oscillation frequency of the reference acoustic wave element. In Patent Document 1, the piezoelectric substrate used for the measurement acoustic wave element and the reference acoustic wave element is shared, so that the difference between the piezoelectric substrate is different between the measurement acoustic wave element and the reference acoustic wave element. This suppresses the deviation of oscillation characteristics due to.

  Further, in the elastic wave sensor disclosed in Patent Document 2, a sensitive film of a different type from the sensitive film of the measuring acoustic wave element is formed on the reference acoustic wave element, so that the sensitive film of the measuring acoustic wave element is adsorbed. Does not exhibit adsorptivity to the measured object. About another structure, it is the same as that of patent document 1. FIG.

  As other background art, a piezoelectric sensor using a crystal resonator disclosed in Patent Documents 3 to 5 is disclosed.

US Pat. No. 5,243,539 US Pat. No. 5,012,668 Japanese Patent Laid-Open No. 6-265459 Japanese Utility Model Publication No. 5-84847 Japanese Utility Model Publication No. 5-73560

  In Patent Document 1, a sensitive film is formed on the measurement acoustic wave element, whereas no sensitive film is formed on the reference acoustic wave element. Due to the effect of the presence or absence of the sensitive film, the change in the oscillation characteristics with respect to the change in the external environment such as temperature differs between the measurement acoustic wave element and the reference acoustic wave element. Therefore, in patent document 1, there exists a problem that the measurement precision of a to-be-measured object will fall.

  Further, in Patent Document 2, although a sensitive film is also formed on the reference acoustic wave element, since the type is different from the sensitive film of the measurement acoustic wave element, the temperature and the like are affected by the difference in the type of the sensitive film. The change in the oscillation characteristics with respect to the change in the external environment differs between the measurement acoustic wave element and the reference acoustic wave element. Therefore, Patent Document 2 also has a problem that the measurement accuracy of the object to be measured is lowered.

  An object of this invention is to provide the elastic wave sensor which can improve the measurement precision of a to-be-measured object.

  An elastic wave sensor according to the present invention includes a measurement elastic wave element on which a measurement sensitive film exhibiting adsorptivity to a measurement object is formed, and a reference elastic wave that does not exhibit adsorbability to the measurement object. A piezoelectric substrate used for the measurement acoustic wave element and the reference acoustic wave element is shared, and the reference acoustic wave element includes the measurement acoustic wave element. A reference sensitive film that is the same type as the sensitive film is formed, and a sealing means is provided that is bonded to the piezoelectric substrate and seals the reference sensitive film from the object to be measured. Is the gist.

  In the present invention, the reference sensitive film, which is the same type as the measuring sensitive film that exhibits the adsorptivity to the object to be measured, is formed on the reference acoustic wave element, thereby changing the external environment such as temperature. The change in the oscillation characteristic with respect to can be made almost equal between the measurement acoustic wave element and the reference acoustic wave element. In addition, since the reference sensitive film is sealed with respect to the object to be measured, the reference acoustic wave element can be prevented from exhibiting adsorptivity to the object to be measured. Therefore, according to the present invention, the measurement accuracy of the object to be measured can be improved.

  In the acoustic wave sensor according to the present invention, the piezoelectric substrate is flip-chip mounted on the package such that one main surface on which the reference acoustic wave element and the reference sensitive film are formed faces the mounting surface of the package. The sealing means surrounds the entire circumference of the reference sensitive film and is in close contact with the piezoelectric substrate and the package over the entire circumference, so that the reference sensitive film is covered with the covered film. It can also seal with respect to a measurement object. In this way, the reference sensitive film can be easily sealed.

  In the acoustic wave sensor according to the present invention, the measurement acoustic wave element and the measurement sensitive film may be formed on one main surface of the piezoelectric substrate. In the acoustic wave sensor according to this aspect of the present invention, an opening may be provided in a portion of the package that substantially faces the measurement sensitive film. In this way, the object to be measured can be reliably adsorbed to the measurement sensitive film.

  In the elastic wave sensor according to the present invention, the measurement acoustic wave element and the measurement sensitive film may be formed on the back surface of one main surface of the piezoelectric substrate. In the elastic wave sensor according to the present invention of this aspect, the measurement acoustic wave element and the measurement sensitive film are formed at a position substantially opposite to the formation position of the reference acoustic wave element and the reference sensitive film. It can also be. By so doing, it is possible to reduce the difference in oscillation characteristics between the measurement acoustic wave element and the reference acoustic wave element, thereby further improving the measurement accuracy of the object to be measured. Furthermore, the acoustic wave sensor can be downsized.

  In the acoustic wave sensor according to the present invention, the measurement acoustic wave element and the measurement sensitive film are formed on one main surface of the piezoelectric substrate, and the reference acoustic wave element and the reference sensitive film are The piezoelectric substrate may be formed on the back surface of one main surface of the piezoelectric substrate, and the piezoelectric substrate may be flip-chip mounted on the package such that the one main surface faces the mounting surface of the package.

  In the elastic wave sensor according to the present invention of this aspect, the measurement acoustic wave element and the measurement sensitive film are formed at a position substantially opposite to the formation position of the reference acoustic wave element and the reference sensitive film. It can also be. By so doing, it is possible to reduce the difference in oscillation characteristics between the measurement acoustic wave element and the reference acoustic wave element, thereby further improving the measurement accuracy of the object to be measured. Furthermore, the acoustic wave sensor can be downsized.

  In the acoustic wave sensor according to this aspect of the present invention, an opening may be provided in a portion of the package that substantially faces the measurement sensitive film. In this way, the object to be measured can be reliably adsorbed to the measurement sensitive film.

  The elastic wave sensor according to the present invention includes a measurement acoustic wave element on which a measurement sensitive film that exhibits adsorptivity to an object to be measured is formed, and a reference that does not exhibit adsorbability to the object to be measured. An acoustic wave sensor comprising: a piezoelectric substrate used in the measurement acoustic wave element and the reference acoustic wave element, and the measurement acoustic wave element and the measurement acoustic wave element. The sensitive film is formed on the back surface of the piezoelectric substrate on which the reference acoustic wave element is formed, and is formed at a position substantially on the back side of the reference acoustic wave element. The substrate is flip-chip mounted on the package such that the surface on which the measurement acoustic wave element and the measurement sensitive film are formed or the surface on which the reference acoustic wave element is formed faces the package mounting surface. With the gist being That.

  In the present invention, since the difference in oscillation characteristics between the measurement acoustic wave element and the reference acoustic wave element can be reduced, the measurement accuracy of the object to be measured can be improved. Furthermore, the acoustic wave sensor can be downsized.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

“Embodiment 1”
1A and 1B are diagrams showing an outline of a configuration of an elastic wave sensor according to Embodiment 1 of the present invention. FIG. 1A shows an outline of a side sectional view, and FIG. 1B shows an outline of a top view. Indicates. The acoustic wave sensor according to the present embodiment includes a measurement acoustic wave element 12 and a reference acoustic wave element 14 described below, and is mounted on a package PKG.

  The measurement acoustic wave element 12 is configured by forming an input comb-shaped electrode 12a and an output comb-shaped electrode 12b on one main surface 10a of the piezoelectric substrate 10 at a predetermined interval. Similarly, the reference acoustic wave element 14 is configured by forming the input comb-shaped electrode 14a and the output comb-shaped electrode 14b on the main surface 10a of the piezoelectric substrate 10 at a predetermined interval. As described above, in the present embodiment, the comb electrodes 12a and 12b of the measurement acoustic wave element 12 and the comb electrodes 14a and 14b of the reference acoustic wave element 14 are formed on the common piezoelectric substrate 10. The piezoelectric substrate 10 used for the measurement acoustic wave element 12 and the reference acoustic wave element 14 is shared. As shown in FIG. 1, the comb-shaped electrodes 12a and 12b of the measurement acoustic wave element 12 and the comb-shaped electrodes 14a and 14b of the reference acoustic wave element 14 are arranged so that the acoustic wave propagation directions are substantially parallel to each other. In addition, the elastic wave excited by the measurement elastic wave element 12 and the elastic wave excited by the reference elastic wave element 14 do not interfere with each other, and are arranged at a predetermined distance with respect to the elastic wave propagation direction and the substantially vertical direction. Has been. In FIG. 1A, illustration of the comb electrodes 12a, 12b, 14a, and 14b is omitted.

  The measurement acoustic wave element 12 is formed with a measurement sensitive film 16 that is adsorbable to the object to be measured and is composed of, for example, a protein. The measurement sensitive film 16 is exposed to the object to be measured. ing. Here, to give an example of a combination of the measurement object and the measurement sensitive film 16 that adsorbs the measurement object, the measurement object is a C-reactive protein (CRP) antigen, and the measurement sensitive film 16 is Anti-CRP monoclonal antibody.

  In the present embodiment, the reference sensitive film 18 of the same type as the measurement sensitive film 16 is also formed on the reference acoustic wave element 14. Further, a lid 32 that covers and seals the reference sensitive film 18 is joined to one main surface 10 a of the piezoelectric substrate 10. By providing the lid 32, the reference sensitive film 18 can be sealed from the object to be measured. Accordingly, the reference sensitive film 18 is formed on the reference acoustic wave element 14 even though the reference sensitive film 18 is formed on the reference acoustic wave element 14 and has an adsorptivity to the measurement object to which the measurement sensitive film 16 adsorbs. The measurement object can be prevented from being adsorbed, and the reference acoustic wave element 14 can be prevented from exhibiting adsorbability with respect to the object to be measured. As described above, in this embodiment, the reference sensitive film 18 that is the same type as the measurement sensitive film 16 is formed on the reference acoustic wave element 14, and the reference sensitive film 18 is sealed against the object to be measured. As a result, the measurement acoustic wave element 12 and the reference acoustic wave element 14 change in oscillation characteristics with respect to changes in the external environment such as temperature depending on the presence or absence of the sensitive film and the type of the sensitive film. Is suppressed. In FIG. 1B, the illustration of the lid 32 is omitted for the most part and the reference acoustic wave element 14 appears, but in actuality, the reference acoustic wave element 14 is sealed by the lid 32. ing. Moreover, as a material of the lid | cover 32, resin is used, for example.

  Here, as the acoustic wave elements 12 and 14, for example, SAW elements using SAW (Rayleigh waves) propagating on the surface of the piezoelectric substrate 10 can be used. Alternatively, STW elements using STW (bulk waves) that propagate near the surface of the piezoelectric substrate 10 can be used as the acoustic wave elements 12 and 14. When STW elements are used as the elastic wave elements 12 and 14, the propagation loss of elastic waves (STW) due to the formation of the sensitive films 16 and 18 on the elastic wave propagation path can be reduced. The sensitive films 16 and 18 can also be formed on the acoustic wave elements 12 and 14 with a gold film (not shown) interposed therebetween.

  When detecting the concentration of the object to be measured using the acoustic wave sensor according to this embodiment, as shown in FIG. 2, the input side of the amplifier AMP1 is connected to the output comb electrode 12b, and the output side of the amplifier AMP1 is connected to the output side. By connecting to the input comb electrode 12a, the oscillation loop 20 including the measurement acoustic wave element 12 and the amplifier AMP1 is formed. Similarly, by connecting the input side of the amplifier AMP2 to the output comb electrode 14b and connecting the output side of the amplifier AMP2 to the input comb electrode 14a, an oscillation loop 22 including the reference acoustic wave element 14 and the amplifier AMP2 is formed. . Here, the electrical connection to the comb-shaped electrodes 14a and 14b can be realized by pulling out the electrode pad outside the lid 32, and the sealing performance of the lid 32 can be ensured. In FIG. 2, the lid 32 and the package PKG are not shown.

  When the measurement sensitive film 16 adsorbs the object to be measured, the oscillation frequency of the measurement acoustic wave element 12 changes, and the frequency of the oscillation signal circulating in the oscillation loop 20 changes. On the other hand, since the reference sensitive film 18 is sealed by the lid 32 and does not adsorb the object to be measured, the oscillation frequency of the reference acoustic wave element 14 remains substantially constant, and oscillation that circulates through the oscillation loop 22. The signal frequency also remains substantially constant. Therefore, by comparing the frequency of the oscillation signal circulating in the oscillation loop 20 and the frequency of the oscillation signal circulating in the oscillation loop 22 by the frequency comparison circuit 24, the concentration of the object to be measured can be detected. Thus, in the elastic wave sensor according to the present embodiment, the oscillation frequency of the measurement acoustic wave element 12 (frequency of the oscillation signal circulating in the oscillation loop 20) and the oscillation frequency of the reference acoustic wave element 14 (oscillation loop 22). The concentration of the object to be measured is detected by comparing the frequency of the oscillation signal circulating through

  As described above, in this embodiment, the reference sensitive film 18 that is the same type as the measurement sensitive film 16 of the measurement acoustic wave element 12 is formed on the reference acoustic wave element 14, and the reference sensitive film 18 is formed. The film 18 is sealed with respect to the object to be measured by being covered with the lid 32. Thus, since the types of the sensitive films 16 and 18 formed in the measurement acoustic wave element 12 and the reference acoustic wave element 14 are the same, depending on the presence or absence of the sensitive film and the type of the sensitive film, It is possible to suppress changes in the oscillation characteristics with respect to changes in the external environment such as temperature. In addition, since the reference sensitive film 18 of the reference acoustic wave element 14 is sealed by being covered with the lid 32, the reference sensitive film 18 can be prevented from adsorbing an object to be measured. The oscillation frequency of the acoustic wave element 14 is not affected by the presence of the object to be measured. Therefore, according to this embodiment, the measurement accuracy of the object to be measured can be improved. Furthermore, since the types of the sensitive films 16 and 18 formed in the measurement acoustic wave element 12 and the reference acoustic wave element 14 are the same, the sensitive films 16 and 18 can be formed in the same process, The sensitive films 16 and 18 can be easily formed.

  In the present embodiment, the piezoelectric substrate 10 used for the measurement acoustic wave element 12 and the reference acoustic wave element 14 is shared, so that the measurement acoustic wave element 12 and the reference acoustic wave element 14 are It is possible to prevent the oscillation characteristics from being different depending on the substrate. Therefore, the measurement accuracy of the object to be measured can be further improved. Further, when the acoustic wave elements 12 and 14 are manufactured, the comb-shaped electrodes 12a, 12b, 14a and 14b and the sensitive films 16 and 18 can be easily formed.

“Embodiment 2”
3A and 3B are diagrams showing an outline of the configuration of the elastic wave sensor according to the second embodiment of the present invention. FIG. 3A shows an outline of a side sectional view, and FIG. 3B shows an outline of a bottom view. Indicates. However, in FIG. 3A, illustration of the comb-shaped electrodes 12a, 12b, 14a, and 14b is omitted, and in FIG. 3B, the illustration of the package PKG is largely omitted, and the measurement acoustic wave element 12 is omitted. In addition, the reference acoustic wave element 14 is shown.

  In the acoustic wave sensor according to the present embodiment, the bump electrode 26 is joined to the electrode pad connected to the comb electrodes 12a, 12b, 14a, 14b. The piezoelectric substrate 10 on which the measurement acoustic wave element 12, the measurement sensitive film 16, the reference acoustic wave element 14, and the reference sensitive film 18 are formed on one principal surface 10a has the one principal surface 10a packaged. It is flip-chip mounted on the package PKG so as to face the mounting surface 8 of the PKG. Here, electrical bonding between the piezoelectric substrate 10 side and the package PKG side is performed via the bump electrode 26, and a gap is formed between the sensitive films 16 and 18 and the mounting surface 8 of the package PKG. As described above, the height of the bump electrode 26 is set. As a result, since the measurement sensitive film 16 is exposed to the object to be measured, the measurement sensitive film 16 can adsorb the object to be measured, and the measurement acoustic wave element 12 has an adsorptivity to the object to be measured. Indicates.

  Further, in the present embodiment, there is provided a molding material 34 that surrounds the entire circumference of the reference sensitive film 18 and is joined in close contact with the piezoelectric substrate 10 and the package PKG over the entire circumference. The molding material 34 can seal the reference sensitive film 18 against the object to be measured. Therefore, it is possible to prevent the reference sensitive film 18 from adsorbing the object to be measured, and it is possible to prevent the reference acoustic wave element 14 from exhibiting adsorbability to the object to be measured. As a material of the molding material 34, for example, a resin is used.

  Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Also in the present embodiment, when detecting the concentration of the object to be measured, the oscillation loop 20 including the measurement acoustic wave element 12 and the oscillation loop 22 including the reference acoustic wave element 14 are detected as in the first embodiment. Form each one. When the measurement sensitive film 16 adsorbs the object to be measured, the oscillation frequency of the measurement acoustic wave element 12 changes, and the frequency of the oscillation signal circulating in the oscillation loop 20 changes. On the other hand, since the reference sensitive film 18 is sealed by the molding material 34 and does not adsorb the object to be measured, the oscillation frequency of the reference acoustic wave element 14 remains substantially constant and circulates through the oscillation loop 22. The frequency of the oscillation signal also remains substantially constant. Therefore, as in the first embodiment, the frequency of the oscillation signal circulating through the oscillation loop 20 (the oscillation frequency of the measurement acoustic wave element 12) and the frequency of the oscillation signal circulating through the oscillation loop 22 (of the reference acoustic wave element 14) The frequency of the measured object can be detected by comparing the oscillation frequency) with the frequency comparison circuit 24.

  Also in this embodiment, since the types of the sensitive films 16 and 18 formed in the measurement acoustic wave element 12 and the reference acoustic wave element 14 are the same, the presence or absence of the sensitive film and the difference in the type of the sensitive film are different. Therefore, it is possible to prevent the change in the oscillation characteristics from changing due to a change in the external environment such as temperature. Therefore, the measurement accuracy of the object to be measured can be improved. Furthermore, in the present embodiment, the principal surface 10a of the piezoelectric substrate 10 on which the reference sensitive film 18 is formed is opposed to the mounting surface 8 of the package PKG and is flip-chip mounted face-down so that the reference sensitive film is mounted. The film 18 can be easily sealed.

  In the present embodiment, as shown in FIG. 4, an opening 36 may be provided in a portion of the package PKG substantially facing the measurement sensitive film 16. The molding material 34 surrounds not only the entire circumference of the reference sensitive film 18 but also the entire circumference of the measurement sensitive film 16 and is bonded to the piezoelectric substrate 10 and the package PKG so as to be in close contact with each other. Yes. Here, FIG. 4A shows an outline of a side sectional view, and FIG. 4B shows an outline of a bottom view. However, in FIG. 4A, illustration of the comb-shaped electrodes 12a, 12b, 14a, and 14b is omitted, and in FIG. 4B, the illustration of the package PKG is largely omitted, and the reference acoustic wave element 14 is used. It is shown in the state where appears.

  In the configuration shown in FIG. 4, the object to be measured can be reliably adsorbed to the measurement sensitive film 16 by providing the opening 36 in a portion of the package PKG substantially facing the measurement sensitive film 16.

“Embodiment 3”
5A and 5B are diagrams showing an outline of the configuration of an elastic wave sensor according to Embodiment 3 of the present invention. FIG. 5A shows an outline of a side sectional view, and FIG. 5B shows an outline of a bottom view. Indicates. However, in FIG. 5A, illustration of the comb-shaped electrodes 12a, 12b, 14a, 14b is omitted, and in FIG. 5B, the illustration of the package PKG is largely omitted, and the reference acoustic wave element 14 is used. It is shown in the state where appears.

  The reference acoustic wave element 14 is configured by forming an input comb electrode 14a and an output comb electrode 14b on one main surface 10a of the piezoelectric substrate 10 at a predetermined interval. On the other hand, the measurement acoustic wave element 12 is configured by forming the input comb-shaped electrode 12a and the output comb-shaped electrode 12b on the back surface 10b of the one main surface 10a of the piezoelectric substrate 10 at a predetermined interval. As described above, in the present embodiment, the piezoelectric substrate 10 used for the measurement acoustic wave element 12 and the reference acoustic wave element 14 is shared, but the measurement acoustic wave element 12 and the reference acoustic wave element are used. 14 are formed on opposite surfaces of the piezoelectric substrate 10. Since the elastic wave propagates almost on the surface of the piezoelectric substrate 10, the elastic wave excited by the measurement elastic wave element 12 and the elastic wave excited by the reference elastic wave element 14 do not interfere with each other.

  The measurement acoustic wave element 12 is formed with a measurement sensitive film 16 that is adsorbable to an object to be measured and is made of, for example, a protein. Further, the reference sensitive film 18 of the same type as the measurement sensitive film 16 is also formed on the reference acoustic wave element 14. In addition, the measurement acoustic wave element 12 and the measurement sensitive film 16 are formed at a position substantially on the back side of the formation position of the reference acoustic wave element 14 and the reference sensitive film 18.

  In the present embodiment, the bump electrode 26 is bonded to the electrode pad connected to the comb electrodes 14 a and 14 b of the reference acoustic wave element 14. The piezoelectric substrate 10 is flip-chip mounted on the package PKG so that one main surface 10a on which the reference acoustic wave element 14 and the reference sensitive film 18 are formed faces the mounting surface 8 of the package PKG. . Here, the electrical bonding between the piezoelectric substrate 10 side and the package PKG side is performed via the bump electrode 26, and a gap is formed between the reference sensitive film 18 and the mounting surface 8 of the package PKG. As described above, the height of the bump electrode 26 is set.

  Further, in the present embodiment as well, as in the second embodiment, the molding material surrounds the entire circumference of the reference sensitive film 18 and is joined in close contact with the piezoelectric substrate 10 and the package PKG. 34 is provided. The molding material 34 can seal the reference sensitive film 18 against the object to be measured. Therefore, it is possible to prevent the reference sensitive film 18 from adsorbing the object to be measured, and it is possible to prevent the reference acoustic wave element 14 from exhibiting adsorbability to the object to be measured. On the other hand, since the measurement sensitive film 16 is exposed to the object to be measured, the measurement sensitive film 16 can adsorb the object to be measured, and the elastic wave element 12 for measurement adsorbs to the object to be measured. Showing gender. In addition, as the material of the molding material 34, for example, a resin is used.

  Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Also in this embodiment, since the types of the sensitive films 16 and 18 formed in the measurement acoustic wave element 12 and the reference acoustic wave element 14 are the same, the presence or absence of the sensitive film and the difference in the type of the sensitive film are different. Therefore, it is possible to prevent the change in the oscillation characteristics from changing due to a change in the external environment such as temperature. Therefore, the measurement accuracy of the object to be measured can be improved. Then, the main surface 10a of the piezoelectric substrate 10 on which the reference sensitive film 18 is formed faces the mounting surface 8 of the package PKG and is flip-chip mounted face down so that the reference sensitive film 18 is sealed. It becomes easy. Further, in the present embodiment, the measurement acoustic wave element 12 and the measurement sensitive film 16 are formed at a position almost on the back side of the formation position of the reference acoustic wave element 14 and the reference sensitive film 18. The distance between the acoustic wave element for use 12 and the reference acoustic wave element can be reduced. Therefore, since the difference in oscillation characteristics between the measurement acoustic wave element 12 and the reference acoustic wave element 14 can be further reduced, the measurement accuracy of the object to be measured can be further improved. Furthermore, the piezoelectric substrate 10 can be reduced in size, and the elastic wave sensor can be reduced in size.

“Embodiment 4”
6A and 6B are diagrams showing an outline of a configuration of an acoustic wave sensor according to Embodiment 4 of the present invention. FIG. 6A shows an outline of a side sectional view, and FIG. 6B shows an outline of a top view. Indicates. However, in FIG. 6A, illustration of the comb-shaped electrodes 12a, 12b, 14a, and 14b is omitted.

  The measurement acoustic wave element 12 is configured by forming an input comb-shaped electrode 12a and an output comb-shaped electrode 12b on one main surface 10a of the piezoelectric substrate 10 at a predetermined interval. On the other hand, the reference acoustic wave element 14 is configured by forming the input comb-shaped electrode 14a and the output comb-shaped electrode 14b on the back surface 10b of the one main surface 10a of the piezoelectric substrate 10 at a predetermined interval. As described above, in the present embodiment, the piezoelectric substrate 10 used for the measurement acoustic wave element 12 and the reference acoustic wave element 14 is shared, but the measurement acoustic wave element 12 and the reference acoustic wave element are used. 14 are formed on opposite surfaces of the piezoelectric substrate 10. Since the elastic wave propagates almost on the surface of the piezoelectric substrate 10, the elastic wave excited by the measurement elastic wave element 12 and the elastic wave excited by the reference elastic wave element 14 are mutually similar to the third embodiment. There is no interference.

  The measurement acoustic wave element 12 is formed with a measurement sensitive film 16 that is adsorbable to an object to be measured and is made of, for example, a protein. Further, the reference sensitive film 18 of the same type as the measurement sensitive film 16 is also formed on the reference acoustic wave element 14. In addition, the measurement acoustic wave element 12 and the measurement sensitive film 16 are formed at a position substantially on the back side of the formation position of the reference acoustic wave element 14 and the reference sensitive film 18.

  In the present embodiment, the bump electrode 26 is bonded to the electrode pad connected to the comb-shaped electrodes 12 a and 12 b of the measurement acoustic wave element 12. The piezoelectric substrate 10 is flip-chip mounted on the package PKG so that one main surface 10a on which the measurement acoustic wave element 12 and the measurement sensitive film 16 are formed faces the mounting surface 8 of the package PKG. . Here, electrical bonding between the piezoelectric substrate 10 side and the package PKG side is performed via the bump electrode 26, and a gap is formed between the measurement sensitive film 16 and the mounting surface 8 of the package PKG. As described above, the height of the bump electrode 26 is set. As a result, since the measurement sensitive film 16 is exposed to the object to be measured, the measurement sensitive film 16 can adsorb the object to be measured, and the measurement acoustic wave element 12 has an adsorptivity to the object to be measured. Indicates.

  Furthermore, in the present embodiment, a lid 32 that covers and seals the reference sensitive film 18 is joined to the back surface 10b of the one main surface 10a of the piezoelectric substrate 10. By providing the lid 32, the reference sensitive film 18 can be sealed from the object to be measured. Therefore, it is possible to prevent the reference sensitive film 18 from adsorbing the object to be measured, and it is possible to prevent the reference acoustic wave element 14 from exhibiting adsorbability to the object to be measured. In FIG. 6B, illustration of the lid 32 is omitted for the most part and the reference acoustic wave element 14 appears, but in actuality, the reference acoustic wave element 14 is sealed by the lid 32. ing. Moreover, as a material of the lid | cover 32, resin is used, for example.

  Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Also in this embodiment, since the types of the sensitive films 16 and 18 formed in the measurement acoustic wave element 12 and the reference acoustic wave element 14 are the same, the presence or absence of the sensitive film and the difference in the type of the sensitive film are different. Therefore, it is possible to prevent the change in the oscillation characteristics from changing due to a change in the external environment such as temperature. Therefore, the measurement accuracy of the object to be measured can be improved. In the present embodiment, the measurement acoustic wave element 12 and the measurement sensitive film 16 are formed at positions substantially opposite to the positions where the reference acoustic wave element 14 and the reference sensitive film 18 are formed. The distance between the acoustic wave element for use 12 and the reference acoustic wave element can be reduced. Therefore, since the difference in oscillation characteristics between the measurement acoustic wave element 12 and the reference acoustic wave element 14 can be further reduced, the measurement accuracy of the object to be measured can be further improved. Furthermore, the piezoelectric substrate 10 can be reduced in size, and the elastic wave sensor can be reduced in size.

  In the present embodiment, as shown in FIG. 7, an opening 36 may be provided in a portion of the package PKG substantially facing the measurement sensitive film 16. The molding material 34 surrounds the entire circumference of the measurement sensitive film 16 and is bonded to the piezoelectric substrate 10 and the package PKG in close contact with each other. Here, FIG. 7A shows an outline of a side sectional view, and FIG. 7B shows an outline of a bottom view. However, in FIG. 7A, illustration of the comb-shaped electrodes 12a, 12b, 14a, and 14b is omitted, and in FIG. 7B, illustration of the package PKG is partially omitted. As a material of the molding material 34, for example, a resin is used.

  In the configuration shown in FIG. 7, the object to be measured can be surely adsorbed to the measurement sensitive film 16 by providing the opening 36 in a portion of the package PKG substantially facing the measurement sensitive film 16.

  In each embodiment, the case where the sensitive films | membranes 16 and 18 were formed on the input comb electrode of the elastic wave elements 12 and 14, an output comb electrode, and the elastic wave propagation path was demonstrated. However, in each embodiment, the sensitive films 16 and 18 may be formed on at least one of the input comb electrodes of the acoustic wave elements 12 and 14, the output comb electrodes, and the acoustic wave propagation path.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 1 of this invention. It is a figure explaining an example of the circuit structure in the case of measuring a to-be-measured object using the elastic wave sensor which concerns on embodiment of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 2 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 2 of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 3 of this invention. It is a figure which shows the outline of a structure of the elastic wave sensor which concerns on Embodiment 4 of this invention. It is a figure which shows the outline of the other structure of the elastic wave sensor which concerns on Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate, 12 Measurement acoustic wave element, 14 Reference acoustic wave element, 16 Measurement sensitive film, 18 Reference sensitive film, 20, 22 Oscillation loop, 24 Frequency comparison circuit, 26 Bump electrode, 32 Lid, 34 Resin for molding, 36 openings, AMP1, AMP2 amplifier, PKG package.

Claims (10)

An elastic wave sensor having a measurement acoustic wave element on which a measurement sensitive film showing adsorptivity to an object to be measured is formed, and a reference acoustic wave element not showing adsorbability to the object to be measured There,
Piezoelectric substrates used for the measurement acoustic wave element and the reference acoustic wave element are shared,
In the reference acoustic wave element, a reference sensitive film that is the same type as the measurement sensitive film is formed,
An elastic wave sensor comprising: a sealing unit that is bonded to the piezoelectric substrate and seals the reference sensitive film from the object to be measured. The elastic wave sensor according to claim 1,
The piezoelectric substrate is flip-chip mounted on the package such that one main surface on which the reference acoustic wave element and the reference sensitive film are formed faces the package mounting surface.
The sealing means surrounds the entire circumference of the reference sensitive film and is in close contact with the piezoelectric substrate and the package over the entire circumference, so that the reference sensitive film is attached to the object to be measured. An elastic wave sensor characterized by sealing. The elastic wave sensor according to claim 2,
The acoustic wave sensor, wherein the measurement acoustic wave element and the measurement sensitive film are formed on one main surface of the piezoelectric substrate. The elastic wave sensor according to claim 3,
The elastic wave sensor according to claim 1, wherein an opening is provided in a portion of the package facing the measurement sensitive film. The elastic wave sensor according to claim 2,
The acoustic wave sensor, wherein the measurement acoustic wave element and the measurement sensitive film are formed on a back surface of one main surface of the piezoelectric substrate. The elastic wave sensor according to claim 5,
The elastic wave sensor according to claim 1, wherein the measurement acoustic wave element and the measurement sensitive film are formed at a position substantially opposite to a position where the reference acoustic wave element and the reference sensitive film are formed. The elastic wave sensor according to claim 1,
The measurement acoustic wave element and the measurement sensitive film are formed on one main surface of the piezoelectric substrate,
The reference acoustic wave element and the reference sensitive film are formed on the back surface of one main surface of the piezoelectric substrate,
The acoustic wave sensor according to claim 1, wherein the piezoelectric substrate is flip-chip mounted on the package such that the one main surface faces the mounting surface of the package. The elastic wave sensor according to claim 7,
The elastic wave sensor according to claim 1, wherein the measurement acoustic wave element and the measurement sensitive film are formed at a position substantially opposite to a position where the reference acoustic wave element and the reference sensitive film are formed. The elastic wave sensor according to claim 7 or 8,
The elastic wave sensor according to claim 1, wherein an opening is provided in a portion of the package facing the measurement sensitive film. An elastic wave sensor having a measurement acoustic wave element on which a measurement sensitive film showing adsorptivity to an object to be measured is formed, and a reference acoustic wave element not showing adsorbability to the object to be measured There,
Piezoelectric substrates used for the measurement acoustic wave element and the reference acoustic wave element are shared,
The measurement acoustic wave element and the measurement sensitive film are formed on a back surface of the surface of the piezoelectric substrate on which the reference acoustic wave element is formed, and substantially on the back side of the formation position of the reference acoustic wave element. Formed in position,
The piezoelectric substrate is mounted on the package such that the surface on which the measurement acoustic wave element and the measurement sensitive film are formed, or the surface on which the reference acoustic wave element is formed faces the mounting surface of the package. An elastic wave sensor, which is flip-chip mounted.

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