阅读说明：本技术 制造传感器装置的方法和传感器装置 (Method for producing a sensor device and sensor device ) 是由 仲村慎之介 福浦笃臣 胜田宏 于 2020-04-22 设计创作，主要内容包括：一种传感器装置,包括：基板,具有基板表面；第一IDT电极,设置在基板表面上；第二IDT电极,设置在基板表面上；波导；以及保护膜。波导设置在基板表面上并且在第一IDT电极与第二IDT电极之间。波导包括设置在基板表面上的第一固定层和设置在第一固定层上的第二固定层。当从平面图观察时,第二固定层设置在第一固定层的外边缘的内部。(A sensor device, comprising: a substrate having a substrate surface; a first IDT electrode disposed on the substrate surface; a second IDT electrode disposed on the substrate surface; a waveguide; and a protective film. The waveguide is disposed on the substrate surface and between the first IDT electrode and the second IDT electrode. The waveguide includes a first fixed layer disposed on a surface of the substrate and a second fixed layer disposed on the first fixed layer. The second fixing layer is disposed inside the outer edge of the first fixing layer when viewed in a plan view.)

1. A sensor device, comprising:

a substrate having a substrate surface;

a first IDT electrode disposed on the substrate surface;

a second IDT electrode disposed on the substrate surface; and

a waveguide disposed on the substrate surface and between the first IDT electrode and the second IDT electrode,

wherein the waveguide comprises a first fixed layer disposed on the substrate surface and a second fixed layer disposed on the first fixed layer, an

Wherein the second fixing layer is disposed inside an outer edge of the first fixing layer when viewed in a plan view.

2. The sensor device according to claim 1, wherein,

wherein the first fixing layer has a concave surface, an

Wherein the second fixing layer is disposed on the recess surface.

3. The sensor device according to claim 1 or 2, further comprising a protective film that covers the first IDT electrode, the second IDT electrode, and ends of the waveguide near the first IDT electrode and the second IDT electrode, respectively.

4. The sensor device according to claim 3, wherein,

wherein the waveguide comprises in an upper surface of the waveguide: a first region included in an upper surface of the first fixing layer and covered by the protective film; a second region including at least a portion of an upper surface of the second fixed layer; and a third region included in an upper surface of the first fixing layer and disposed between the first region and the second region, an

Wherein a height of the third region as viewed from the substrate surface is smaller than each of a height of the first region and a height of the second region.

5. The sensor device of any one of claims 1 to 3, further comprising:

a protective film covering the first IDT electrode and the second IDT electrode,

wherein ends of the first fixed layer adjacent to the first IDT electrode and the second IDT electrode, respectively, are covered with the protective film, and

wherein end portions of the second fixing layer respectively near the first IDT electrode and the second IDT electrode are disposed on an upper side of the protective film.

6. The sensor device of claim 5, further comprising:

a close contact layer disposed on the first fixing layer,

wherein the protective film is disposed on the close contact layer.

7. The sensor device of any one of claims 1 to 6, wherein the waveguide further comprises a third fixed layer disposed between the first and second fixed layers.

8. The sensor device of any one of claims 1-7, wherein the first fixed layer comprises the same material as the material of the first IDT electrode.

9. The sensor device of any one of claims 1-8, wherein the first fixed layer is connected to the first IDT electrode.

10. The sensor device of any one of claims 1-9, wherein the first fixed layer is connected to the second IDT electrode.

11. The sensor device of any one of claims 1 to 10, wherein the thickness of the second fixing layer is less than the thickness of the first fixing layer.

12. The sensor device of any one of claims 1 to 11, wherein the second fixing layer has a surface roughness that is less than a surface roughness of the first fixing layer.

13. The sensor device of any one of claims 1 to 12, wherein the second fixing layer comprises a material different from a material of the first fixing layer.

14. A method of manufacturing a sensor device, comprising:

a step of forming a metal layer on a substrate;

a step of removing a part of the metal layer to form a first IDT electrode, a second IDT electrode, and a first fixed layer disposed between the first IDT electrode and the second IDT electrode;

a step of forming a protective film covering the first IDT electrode, the second IDT electrode and the first fixed layer;

a step of removing a portion of the protective film to expose at least a portion of the first fixing layer; and

a step of forming a second anchor layer on at least a portion of the exposed surface of the first anchor layer.

Technical Field

The present disclosure relates to a method of manufacturing a sensor device and a sensor device.

Background

A known surface acoustic wave device has a configuration in which an electrode that generates a surface acoustic wave is covered with a film (see, for example, PTL 1).

Reference list

Patent document

PTL 1: japanese unexamined patent application publication No. 2017-28543.

Disclosure of Invention

A sensor device according to an embodiment of the present disclosure includes: a substrate having a substrate surface; a first IDT electrode disposed on the substrate surface; a second IDT electrode disposed on the substrate surface; a waveguide; and a protective film. The waveguide is disposed on the substrate surface and between the first IDT electrode and the second IDT electrode. The waveguide includes a first fixed layer disposed on a surface of the substrate and a second fixed layer disposed on the first fixed layer. The second fixing layer is disposed inside the outer edge of the first fixing layer when viewed in a plan view.

A method of manufacturing a sensor device according to an embodiment of the present disclosure includes: and forming a metal layer on the substrate. The method comprises the following steps: a step of removing a portion of the metal layer to form a first IDT electrode, a second IDT electrode, and a first fixed layer disposed between the first IDT electrode and the second IDT electrode. The method comprises the following steps: and a step of forming a protective film covering the first IDT electrode, the second IDT electrode and the first fixed layer. The method comprises the following steps: a step of removing a portion of the protective film to expose at least a portion of the first fixing layer. The method comprises the following steps: a step of forming a second anchor layer on at least a portion of the exposed surface of the first anchor layer.

Drawings

Fig. 1 is a schematic diagram of a sensor device according to an embodiment.

Fig. 2 is a plan view of a sensor device according to an embodiment.

Fig. 3 is a sectional view taken along line a-a of fig. 2.

Fig. 4 is an enlarged view of an area surrounded by a two-dot chain line in fig. 3.

Fig. 5 is a cross-sectional view of a substrate on which a first step of the method of manufacturing a sensor device has been performed.

Fig. 6 is a plan view of a substrate on which a second step of the method of manufacturing a sensor device has been performed.

Fig. 7 is a sectional view taken along line B-B in fig. 6.

Fig. 8 is a cross-sectional view of a substrate on which a third step of the method of manufacturing a sensor device has been performed.

Fig. 9 is a plan view of a substrate on which a fourth step of the method of manufacturing a sensor device has been performed.

Fig. 10 is a sectional view taken along line C-C in fig. 9.

Fig. 11 is a sectional view showing an example of a configuration in which the second fixing layer is also positioned on the upper side of the protective film.

Fig. 12 is a sectional view taken along line D-D in fig. 11.

Fig. 13 is a sectional view showing an example of a configuration in which the waveguide includes a third fixed layer.

Fig. 14 is a sectional view showing an example of a configuration in which the first IDT electrode, the second IDT electrode and the waveguide are separated from each other.

Detailed Description

The surface acoustic wave device detects a change in state with respect to the waveguide by detecting a propagation state of the surface acoustic wave. There is a need to improve the accuracy of detecting changes with respect to the state of the waveguide.

The sensor device 1 (see fig. 1) and the method of manufacturing the sensor device 1 according to the embodiments of the present disclosure can improve the accuracy of detecting the surface state of the waveguide.

< function of SAW sensor >

As shown in fig. 1, a sensor device 1 according to the embodiment includes a substrate 10, a first IDT (interdigital transducer) electrode 11, a second IDT electrode 12, and a waveguide 20. The sensor device 1 functions as a SAW sensor, which can detect a change in the propagation characteristic of a Surface Acoustic Wave (SAW) 70. The sensor device 1 inputs an ac signal to the first IDT electrode 11. The first IDT electrode 11 generates a SAW70 along the surface of the substrate 10 based on an input electrical signal. The SAW70 propagates from the first IDT electrode 11 to the second IDT electrode 12. A propagation path from the first IDT electrode 11 to the second IDT electrode 12 includes a surface of the substrate 10 and a waveguide 20 provided on the surface of the substrate 10. That is, the SAW70 propagates from the first IDT electrode 11 to the second IDT electrode 12 via the substrate 10 and the waveguide 20. The second IDT electrode 12 outputs an electric signal based on the SAW70 propagated from the first IDT electrode 11. The electrical signal may comprise a voltage signal or a current signal. It can be said that the first IDT electrode 11 transmits the SAW70 toward the waveguide 20 and the second IDT electrode 12. It can be said that the second IDT electrode 12 receives the SAW70 from the first IDT electrode 11 and the waveguide 20.

SAW70 propagates with a predetermined propagation characteristic. The propagation characteristics of SAW70 are determined based on the state of the propagation path. The sensor device 1 can detect a change in the state of the propagation path by detecting a change in the propagation characteristic of the SAW 70. The propagation characteristics include, for example, propagation velocity. The sensor device 1 can detect a change in propagation velocity from a change in phase difference between the electric signal input to the first IDT electrode 11 and the electric signal output from the second IDT electrode 12. The electric signal input to the first IDT electrode 11 is also referred to as an "input signal". The electric signal output from the second IDT electrode 12 is also referred to as an "output signal". That is, the sensor device 1 can detect a change in the state of the propagation path based on a change in the phase difference between the input signal and the output signal.

In the sensor device 1 according to the present embodiment, the SAW70 propagates from the first IDT electrode 11 to the second IDT electrode 12 through the waveguide 20. Accordingly, the state of the propagation path of SAW70 is determined based on the state of waveguide 20.

The state of the waveguide 20 may be specified, for example, by parameters such as: the mass on or near the surface of the waveguide 20; or the density, viscosity, etc. of the substance present on or near the surface. Mass, density, viscosity, etc. may have an effect on the propagation characteristics of SAW 70.

When the sensor device 1 detects a change in the phase difference between the input signal and the output signal, the sensor device 1 can calculate a change in the state near the surface of the waveguide 20 based on the detection result. For example, when a change in mass near the surface of the waveguide 20 causes a change in the propagation characteristic of the SAW70 and a change in the phase difference between the input signal and the output signal, the sensor device 1 can calculate the change in mass near the surface of the waveguide 20. In this case, a calibration curve specifying the relationship between the amount of change in the phase difference and the amount of change in the mass near the surface of the waveguide 20 may be prepared in advance. The sensor device 1 can convert the amount of change in the phase difference into the amount of change in the mass near the surface of the waveguide 20 or the like based on the calibration curve.

The sensor device 1 shown in fig. 1 includes a first channel including a pair of first and second IDT electrodes 11-1 and 12-1 and a waveguide 20-1. The sensor device 1 shown in fig. 1 includes a second channel including a pair of first and second IDT electrodes 11-2 and 12-2 and a waveguide 20-2. The number of channels of the sensor device 1 is not limited to two, and may be one or three or more.

The sensor device 1 detects a phase difference between an input signal and an output signal in each of the first channel and the second channel. The phase differences detected in the first channel and the second channel will be referred to as "first phase difference" and "second phase difference", respectively. The phase difference between the input signal and the output signal is based on the propagation velocity of the SAW70 and the distance from the first IDT electrode 11 to the second IDT electrode 12. The first phase difference is equal to the second phase difference if the speed of propagation of SAW70 in the first and second channels is the same. If the propagation speeds of the SAW70 in the first channel and the second channel are different, the first phase difference and the second phase difference are different from each other unless the propagation time of the SAW70 coincides with an integral multiple of the period of the SAW 70.

The waveguide 20-2 of the second channel includes an antibody on its surface. The antibody reacts with the specific antigen 61 to be detected. The antibody that has not reacted with the antigen 61 is referred to as "unreacted antibody 51". The antibody that has reacted with the antigen 61 is referred to as "reacted antibody 52". It is assumed that the waveguide 20 of the second channel includes an unreacted antibody 51 and a reacted antibody 52 on its surface. The reacted antibodies 52 of the waveguide 20 of the second channel may be generated by a reaction between unreacted antibodies 51 originally present on the surface of the waveguide 20 and antigens 61 included in the sample 60 introduced into the waveguide 20. On the other hand, it is assumed that the waveguide 20-1 of the first channel does not include an antigen on its surface.

The reacted antibody 52 has bound to the antigen 61. Because the reacted antibody 52 has bound the antigen 61, the mass near the surface of the waveguide 20 is greater than the mass of the unreacted antibody 51 by the amount of the antigen 61 that has reacted with the reacted antibody 52. Therefore, since the ratio of the reacted antibody 52 to the antibody included in the waveguide 20-2 is increased, the mass near the surface of the waveguide 20-2 of the second channel is increased. That is, the state of the propagation path of the second channel changes according to the change in the proportion of the reacted antibody 52.

The antibody may be replaced with an aptamer. Aptamers include nucleic acid molecules, peptides, etc., that specifically bind to a particular molecule to be detected. When the waveguide 20 includes an aptamer on its surface, the mass near the surface of the waveguide 20 increases as the aptamer binds to a particular molecule. The antibody may be replaced with an enzyme. The mass increases because the enzyme forms a complex with a specific molecule. Instead of these examples, the antibody may not be replaced with another component (element) that can react with or bind to the substance to be detected. The waveguide 20 having a component (e.g., an antibody) that can react or bind with a detection target substance is also referred to as a "reaction unit".

The first channel of sensor apparatus 1 allows SAW70 to propagate through waveguide 20 and detect a first phase difference. The first phase difference is used as a reference value for the phase difference detected by the sensor device 1. The second channel of the sensor device 1 allows the SAW70 to propagate through the waveguide 20 including the unreacted antibody 51 or the reacted antibody 52 and detect the second phase difference. The second phase difference is determined by the ratio of reacted antibody 52 to the antibody comprised in the waveguide 20. The sensor device 1 can correct the result of detection of the second phase difference by using the first phase difference as a reference value. The sensor device 1 may calculate the amount of the antigen 61 bound by the antibody of the waveguide 20-2 of the second channel based on the result of the detection of the second phase difference. A calibration curve specifying the relationship between the amount of change in the second phase difference and the amount of the antigen 61 may be prepared in advance. The sensor device 1 can convert the amount of change in the second phase difference into the amount, concentration, density, and the like of the antigen 61 based on the calibration curve. Thus, the sensor device 1 can detect the detection target included in the sample 60.

The sample 60 may include, for example, human blood, urine, saliva, etc. The sample 60 is not so limited and may comprise any suitable chemical. The sample 60 may be pre-treated before introducing the sample 60 into the channel of the sensor device 1.

The reaction in which the unreacted antibody 51 binds to the antigen 61 to become the reacted antibody 52 proceeds at a predetermined reaction rate. Therefore, the ratio of the reacted antibody 52 to the antibody included in the waveguide 20 increases according to the time elapsed after the sample 60 is introduced into the channel, and the ratio of the antigen concentration can be gradually approached. Therefore, the phase difference detected by the sensor device 1 in the channel changes according to the elapsed time, and can gradually approach the predetermined phase difference. When the reaction between the antigen 61 and the unreacted antibody 51 is almost completed, the amount of the reacted antibody 52 in the antibodies included in the waveguide 20 may be saturated. The sensor device 1 may calculate the amount of the antigen 61 based on the phase difference detected after a sufficiently long time has elapsed since the introduction of the sample 60 into the channel.

The sensor device 1 can detect a period from input of an electric signal to the first IDT electrode 11 to detection of the electric signal by the second IDT electrode 12. The sensor device 1 can detect a change in the state near the surface of the waveguide 20 by detecting a change in the propagation speed by calculating the propagation speed based on the time period from the input of the electric signal to the detection of the electric signal and the distance between the electrodes. It is to be noted that the sensor device 1 can detect a change in the amplitude or a plurality of characteristics of the SAW70 as a propagation characteristic.

< configuration of SAW sensor >

Each element of the sensor device 1 will be described in more detail with reference to fig. 2, 3 and 4. As described above, the sensor device 1 includes the substrate 10, the first IDT electrode 11, the second IDT electrode 12, and the waveguide 20. The sensor device 1 further comprises a protective film 30.

The substrate 10 has a substrate surface 10 a. The substrate 10 is assumed to be a quartz substrate. However, the substrate 10 is not limited thereto, and may be made of another material such as piezoelectric ceramics that causes a piezoelectric phenomenon.

The first IDT electrode 11 and the second IDT electrode 12 are provided on the substrate surface 10 a. The first IDT electrode 11 and the second IDT electrode 12 may be made of metal such as gold (Au) or aluminum (Al). Instead of gold (Au) or aluminum (Al), the first IDT electrode 11 and the second IDT electrode 12 may be made of any other suitable material such as an alloy of aluminum (Al) and copper (Cu) (AlCu).

The first IDT electrode 11 and the second IDT electrode 12 may have a substrate-side close contact layer 15 between the first IDT electrode 11 and the second IDT electrode 12 and the substrate surface 10 a. The first IDT electrode 11 and the second IDT electrode 12 may have a protective film side close contact layer 17 between the protective film 30 and the surfaces of the first IDT electrode 11 and the second IDT electrode 12 on the side opposite to the side facing the substrate surface 10 a. The substrate-side close contact layer 15 and the protective film-side close contact layer 17 may be made of, for example, titanium (Ti), chromium (Cr), or the like, and may be made of any other suitable material in place of these materials. The substrate-side close contact layer 15 and the protective film-side close contact layer 17 may be made of different materials.

The first IDT electrode 11 includes a first reference electrode 11G and a first signal electrode 11A to which a voltage is to be applied. The sensor device 1 generates the SAW70 in the first IDT electrode 11 by applying a voltage signal between the first reference electrode 11G and the first signal electrode 11A. The first reference electrode 11G may be connected to a ground point. The SAW70 is generated between the first reference electrode 11G and the first signal electrode 11A. The distance between the first reference electrode 11G and the first signal electrode 11A is denoted by W1. In the range of lengths represented by W1, SAW70 has higher energy than in other ranges.

The second IDT electrode 12 includes a second reference electrode 12G and a second signal electrode 12A to which a voltage is to be applied. Sensor device 1 detects the electrical signal generated by propagating SAW70 by using second reference electrode 12G and second signal electrode 12A. The second reference electrode 12G may be connected to a ground point. SAW70 propagates between second reference electrode 12G and second signal electrode 12A. The distance between the second reference electrode 12G and the second signal electrode 12A is denoted by W2. The electric signal generated in the second IDT electrode 12 by the SAW70 propagated to the range of the length denoted by W2 is larger than the electric signals generated by the SAWs 70 propagated to other ranges. That is, the second IDT electrode 12 can efficiently detect the SAW70 in the range indicated by W2.

The waveguide 20 is disposed on the substrate surface 10a and between the first IDT electrode 11 and the second IDT electrode 12. The waveguide 20 comprises a first fixed layer 21 and a second fixed layer 22.

The first fixed layer 21 is provided on the substrate surface 10 a. The first fixed layer 21, the first reference electrode 11G, and the second reference electrode 12G are considered to be integrally formed, but they are separated in fig. 2 and 3 for convenience of description. In the other drawings below, it is considered that the first fixed layer 21, the first reference electrode 11G, and the second reference electrode 12G are integrally formed even if they are described below as if they are separated. For convenience of description, the first fixed layer 21, the first reference electrode 11G, and the second reference electrode 12G may be regarded as independent elements, but they are not separated in the description thereof. When the first fixed layer 21 is integrally formed with the first reference electrode 11G and the second reference electrode 12G, the first fixed layer 21 is made of the same material as that of the first reference electrode 11G and the second reference electrode 12G. The first fixing layer 21 may be made of, for example, gold (Au). The waveguide 20 is brought into contact with the sample 60. Instead of gold (Au), the first fixing layer 21 may be made of another material having oxidation resistance and corrosion resistance to contact with the specimen 60. When the first fixed layer 21 is integrally formed with the first reference electrode 11G and the second reference electrode 12G, the waveguide 20 has the same potential as the first reference electrode 11G and the second reference electrode 12G.

The first fixed layer 21 may be formed as an independent member separated from the first reference electrode 11G and the second reference electrode 12G by a predetermined distance. When the first fixed layer 21 is formed as a separate member from the first reference electrode 11G and the second reference electrode 12G, the first fixed layer 21 may be made of the same material as or a different material from that of the first reference electrode 11G and the second reference electrode 12G. The first fixing layer 21 may be made of, for example, gold (Au) or another material having oxidation and corrosion resistance to contact with the specimen 60. When the first fixed layer 21 is integrally formed with the first reference electrode 11G and the second reference electrode 12G, the potential of the waveguide 20 may be the same as the potential of at least one of the first reference electrode 11G and the second reference electrode 12G. The potential of the waveguide 20 may be a floating potential.

The first pinned layer 21 may have a substrate-side close contact layer 15 between the first pinned layer 21 and the substrate surface 10 a. The substrate-side close contact layer 15 of the first fixed layer 21 may be integrally formed with or separated from the substrate-side close contact layers 15 of the first IDT electrode 11 and the second IDT electrode 12.

The first fixed layer 21 has an upper surface on the side opposite to the side facing the substrate surface 10 a. The upper surface of the first fixing layer 21 may include a tapered surface 21a, a recessed surface 21b, and a capping surface 21 c. The first fixing layer 21 may have a protective film side close contact layer 17 between the cover surface 21c and the protective film 30. The height of the recessed surface 21b is less than or equal to the height of the covering surface 21c as viewed from the substrate surface 10 a. The tapered surface 21a is disposed between the recessed surface 21b and the covering surface 21c, and is inclined at a predetermined angle with respect to the substrate surface 10 a.

The second fixing layer 22 has an upper surface 22a, and is disposed on the upper surface of the first fixing layer 21. The second pinned layer 22 may be disposed inside an outer edge of the upper surface of the first pinned layer 21 in a plan view of the substrate 10. The second fixing layer 22 may have a contact surface 22b on the side facing the substrate surface 10 a. The contact surface 22b may be in direct contact with a portion of the upper surface of the first fixed layer 21. As described below, when the third fixed layer 23 is disposed between the first fixed layer 21 and the second fixed layer 22, the contact surface 22b may be in contact with a portion of the upper surface of the first fixed layer 21 via the third fixed layer 23. In other words, the contact surface 22b may face a portion of the upper surface of the first fixed layer 21 via the third fixed layer 23 while being in contact with the third fixed layer 23. The contact surface 22b may be disposed inside an outer edge of the upper surface of the first fixing layer 21 in a plan view of the substrate 10. The second fixing layer 22 may be disposed within the range of the recess surface 21 b. That is, the second fixing layer 22 may be disposed not to overlap with the tapered surface 21 a. A portion of the second fixing layer 22 may be disposed on the tapered surface 21 a. The second fixing layer 22 may be disposed to cover half or more of the upper surface of the first fixing layer 21. As described below, the waveguide 20 may include a third fixed layer 23 between the first fixed layer 21 and the second fixed layer 22 (see fig. 13). When the waveguide 20 does not include the third fixed layer 23, the first fixed layer 21 and the second fixed layer 22 may be distinguished from each other by using any suitable analysis method. As the analysis method, for example, a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), or the like may be used, or another method may be used.

The second fixing layer 22 may be made of, for example, gold (Au). Instead of gold (Au), the second fixing layer 22 may be made of another material having oxidation resistance and corrosion resistance to contact with the specimen 60. The second fixing layer 22 may be made of the same material as that of the first fixing layer 21 or a material different from that of the first fixing layer 21. The surface roughness of the upper surface 22a of the second fixed layer 22 may be different from the surface roughness of the upper surface of the first fixed layer 21. The surface roughness of the upper surface 22a of the second fixed layer 22 may be less than the surface roughness of the upper surface of the first fixed layer 21. The thickness of the second fixing layer 22 may be different from that of the first fixing layer 21. The thickness of the second fixing layer 22 may be smaller than that of the first fixing layer 21.

The protective film 30 covers the substrate surface 10a, the first IDT electrode 11, the second IDT electrode 12, and the cover surface 21c of the first fixed layer 21. The protective film 30 covers the cover surfaces 21c disposed close to the first IDT electrode 11 and the second IDT electrode 12, respectively. That is, the protective film 30 covers the end portions of the waveguide 20 near the first IDT electrode 11 and the second IDT electrode 12, respectively.

The protective film 30 may be a TEOS oxide film. The TEOS oxide film is a silicon oxide film formed by using a plasma Chemical Vapor Deposition (CVD) method using tetraethyl orthosilicate as a material gas. The protective film 30 is not limited to the TEOS oxide film and may be made of another insulating material. The protective film 30 includes a sidewall 30a intersecting the substrate surface 10 a. The sidewall 30a defines an opening of the protective film 30. The tapered surface 21a and the recessed surface 21b of the first fixing layer 21 and the second fixing layer 22 are disposed in the opening of the protective film 30. That is, the protective film 30 does not cover the tapered surface 21a and the recessed surface 21b of the first fixed layer 21 and the upper surface 22a of the second fixed layer 22.

The sensor device 1 includes an unreacted antibody 51 on the upper surface 22a of the second fixing layer 22 to detect an antigen 61. The sensor device 1 may include another component, such as an aptamer or an enzyme, which may react with or may bind to the detection target substance, on the upper surface 22a of the second immobilization layer 22.

The sensor device 1 is required to detect the change of the state near the upper surface 22a of the second fixed layer 22 with high accuracy. SAW70 propagates in a region including the vicinity of upper surface 22a of second fixed layer 22. Since a large amount of energy of the SAW70 propagating in the second fixed layer 22 is distributed in the vicinity of the upper surface 22a, the correlation between the propagation characteristic of the SAW70 and the change of the state in the vicinity of the upper surface 22a of the second fixed layer 22 becomes stronger.

As shown in fig. 4, the waveguide 20 includes, in its upper surface, a covered surface 21c of the first fixed layer 21 covered with the protective film 30. The area including at least a part of the cover surface 21c of the first fixing layer 21 is also referred to as "first area" and is denoted by a 1. The waveguide 20 includes, in its upper surface, an upper surface 22a of the second fixed layer 22 not covered with the protective film 30. The region including at least a portion of the upper surface 22a of the second fixed layer 22 is also referred to as "second region" and is denoted by a 2. The waveguide 20 includes, in its upper surface, a tapered surface 21a of the first fixed layer 21 and a recessed surface 21b where the second fixed layer 22 is not provided. The region including at least a part of the tapered surface 21a of the first fixing layer 21 and at least a part of the recessed surface 21b where the second fixing layer 22 is not provided is also referred to as "third region" and is denoted by a 3.

SAW70 propagates near the upper surface of waveguide 20. The height of the third region is smaller than the height of the first region as viewed from the substrate surface 10 a.

The propagation characteristics of the SAW70 in the waveguide 20 are based on the propagation characteristics of the first fixed layer 21 and the propagation characteristics of the second fixed layer 22. As the thickness of the first fixed layer 21 and the second fixed layer 22 becomes larger, the first fixed layer 21 and the second fixed layer 22 exert a larger influence on the propagation characteristics of the SAW70 in the waveguide 20. That is, the sensitivity of the sensor device 1 can be controlled by controlling the above thickness. The height of the third region is smaller than the height of the second region as viewed from the substrate surface 10 a.

The energy of SAW70 may be concentrated near the surface of second pinned layer 22. The dimension of the second fixed layer 22 in the direction intersecting the propagation direction of the SAW70 is denoted by W3 in fig. 2. The length of W3 is greater than or equal to W1 and W2. If W3 is shorter than W1 and W2, the proportion of the energy of SAW70 propagating to the outside of the second fixed layer 22 among the energy of SAW70 propagating from the first IDT electrode 11 to the second IDT electrode 12 increases. Since the proportion of the energy of the SAW70 propagating to the outside of the second fixed layer 22 increases, the sensitivity of detecting the change in the state near the surface of the second fixed layer 22 decreases. When the length of W3 is greater than or equal to W1 and W2, the proportion of energy of SAW70 propagating to the outside of second pinned layer 22 can be reduced. In this case, the sensitivity of detecting the change in the state near the surface of the second fixed layer 22 can be improved. When the length of W3 is greater than or equal to W1 and W2, the SAW70 can efficiently propagate from the first IDT electrode 11 to the second fixed layer 22.

The first reference electrode 11G and the first signal electrode 11A of the first IDT electrode 11 are both comb-shaped in plan view. In the sensor device 1 shown in fig. 2, the first reference electrode 11G and the first signal electrode 11A each include two comb teeth. However, the electrode 11G and the electrode 11A may each include one comb tooth or three or more comb teeth. The first reference electrodes 11G and the first signal electrodes 11A are alternately arranged in a direction from the waveguide 20 toward the first IDT electrodes 11. Pairs each composed of one first reference electrode 11G and one first signal electrode 11A are arranged at a first pitch. As described above, the first IDT electrode 11 generates the SAW70 along the surface of the substrate 10 based on the electric signals input to the first reference electrode 11G and the first signal electrode 11A. The wavelength of the SAW70 generated by the first IDT electrode 11 corresponds to the first pitch.

The second reference electrode 12G and the second signal electrode 12A of the second IDT electrode 12 are each comb-shaped in plan view. In the sensor device 1 shown in fig. 2, the second reference electrode 12G and the second signal electrode 12A each include two comb teeth. However, each of the electrodes 12G and 12A may include one comb tooth or three or more comb teeth. The second reference electrodes 12G and the second signal electrodes 12A are alternately arranged in a direction from the waveguide 20 toward the second IDT electrode 12. Pairs each composed of one second reference electrode 12G and one second signal electrode 12A are arranged at the second pitch. As described above, the second IDT electrode 12 outputs an electric signal to the second reference electrode 12G and the second signal electrode 12A based on the SAW70 propagating from the first IDT electrode 11 through the waveguide 20. As the wavelength of the SAW70 becomes closer to the second pitch, the efficiency of converting the SAW70 into an electrical signal by the second IDT electrode 12 increases. In other words, as the difference between the first pitch and the second pitch becomes smaller, the efficiency of conversion of the SAW70 into an electrical signal by the second IDT electrode 12 increases. In the present embodiment, the sensor device 1 is configured such that the first pitch and the second pitch coincide.

< method of manufacturing SAW sensor >

A method of manufacturing the sensor device 1 will be described with reference to fig. 2 to 10.

In the first step, the substrate-side close contact layer 15, the metal layer 16, and the protective-film-side close contact layer 17 are formed on the substrate surface 10a of the substrate 10. As a result of performing the first step, the substrate 10 is configured as shown in fig. 5. It is assumed that the substrate-side close contact layer 15 and the protective film-side close contact layer 17 are made of titanium (Ti). It is assumed that the metal layer 16 is made of gold (Au).

In the second step, the first reference electrode 11G and the first signal electrode 11A, the second reference electrode 12G and the second signal electrode 12A, and the first fixed layer 21 constituting the waveguide 20 are formed. The first reference electrode 11G and the first signal electrode 11A constitute a first IDT electrode 11. The second reference electrode 12G and the second signal electrode 12A constitute a second IDT electrode 12. As a result of performing the second step, the substrate 10 is configured as shown in fig. 6 and 7.

The first reference electrode 11G, the first signal electrode 11A, the second reference electrode 12G, the second signal electrode 12A, and the first fixed layer 21 may be formed by using any suitable processing technique. For example, an etch based on a mask having a desired pattern may be used. The mask may be formed, for example, by photolithography. A resist resin or the like may be used as a mask. The etching may include wet etching or dry etching. Wet etching may include the step of dissolving the material in an acid solution, an alkali solution, or the like. Dry etching may include a step of removing a material by using plasma (e.g., Reactive Ion Etching (RIE) or sputter etching).

The first step and the second step may be replaced with a step of forming the first IDT electrode 11, the second IDT electrode 12 and the first fixed layer 21 on the substrate surface 10a in a patterned state. The step of forming these in a patterned state may be achieved, for example, by: the substrate-side close contact layer 15, the metal layer 16, and the protective film-side close contact layer 17 are formed in a state of being covered with a hard mask made of metal, a resist resin mask, or the like.

In the first step and the second step, the first IDT electrode 11, the second IDT electrode 12 and the first fixed layer 21 are simultaneously formed. The step of forming the first IDT electrode 11 and the second IDT electrode 12 and the step of forming the first fixed layer 21 may be divided into separate steps. When the steps are separated, any one of the steps may be performed first. When the first IDT electrode 11, the second IDT electrode 12 and the first fixed layer 21 are simultaneously formed, the position of the first fixed layer 21 with respect to the first IDT electrode 11 and the second IDT electrode 12 can be controlled with high accuracy. When the SAW70 is propagated from the first IDT electrode 11 to the second IDT electrode 12 via the waveguide 20, the distance from the first IDT electrode 11 and the second IDT electrode 12 to the first fixed layer 21 is important. With this step, since the position of the first fixed layer 21 with respect to the first IDT electrode 11 and the second IDT electrode 12 is controlled with high accuracy, it is possible to improve the accuracy of the distance and to improve the measurement accuracy.

In the third step, a protective film 30 for covering the elements formed on the substrate surface 10a is formed. As a result of performing the third step, the substrate 10 is configured as shown in fig. 8. It is assumed that the protective film 30 is a TEOS oxide film.

In the fourth step, a part of the protective film 30 is removed. As a result of performing the fourth step, the substrate 10 is configured as shown in fig. 9 and 10. The protective film 30 is removed to expose at least a portion of the first fixed layer 21 while the first IDT electrode 11 and the second IDT electrode 12 are covered. Since a part of the protective film 30 is removed, an opening surrounded by the sidewall 30a is formed in the protective film 30. The first fixing layer 21 can be said to be exposed in the opening. The protective film 30 may be removed, for example, by etching based on a mask having an opening pattern. The etching may be performed by using any suitable method.

It is assumed that the opening in the protective film 30 is formed by etching such as dry etching or wet etching. In the present embodiment, it is assumed that the opening is formed by, for example, dry etching (e.g., RIE) including sputtering. The sputtering may form the tapered surface 21a and the recessed surface 21b of the first fixed layer 21 while forming the opening of the protective film 30. The tapered surface 21a and the recessed surface 21b of the first pinned layer 21 are referred to as "exposed surfaces" of the first pinned layer 21.

In the fifth step, the second fixed layer 22 is formed. As a result of performing the fifth step, the substrate 10 is configured as shown in fig. 2 and 3. The second fixed layer 22 may be formed in a desired pattern formed by, for example, being covered with a hard mask. In the case where the second fixed layer 22 is patterned in a state covered with a mask, it becomes easier to keep the state of the second fixed layer 22 after being patterned the same as the state immediately after being formed, compared to the case where the fixed layer is patterned by etching. That is, the patterning performed by forming the layers in a masked state is less likely to exert an influence on the second fixed layer 22 than the patterning performed by etching. That is, the surface of the second immobilization layer 22 is more regular than the surface of the first immobilization layer 21, and the antibody is more easily immobilized on the surface of the second immobilization layer 22 than on the surface of the first immobilization layer 21.

Since the thickness of the second fixed layer 22 increases, the thickness of the waveguide 20 including the first fixed layer 21 and the second fixed layer 22 increases. The thickness of the waveguide 20 exerts an influence on the sensitivity of the sensor device 1. By forming the second fixed layer 22 in a step different from the step of forming the first fixed layer 21, it becomes easier to control the thickness of the waveguide 20. Therefore, it becomes easier to control the sensitivity of the sensor device 1.

In the sixth step, a substance such as an antibody, an aptamer, or an enzyme that reacts with the detection target is immobilized on the upper surface 22a of the second immobilization layer 22. In the present embodiment, it is assumed that the unreacted antibody 51 (see fig. 1) is immobilized on the upper surface 22a of the second immobilization layer 22. That is, the unreacted antibody 51 is fixed on the upper surface of the waveguide 20. When the second fixing layer 22 is made of gold (Au), an antibody may be formed on the surface of the second fixing layer 22, for example, based on a gold thiol bond (gold thiol bond) which is a bond between gold (Au) and divalent sulfur (S). In this case, a polymer film is formed on the surface of the second fixing layer 22, and the antibody may be bound to the polymer by amine coupling using an appropriate condensing agent (e.g., EDC/NHS reagent) in the polymer film. The antibody may be immobilized on the second immobilization layer 22 by binding to a polymer film. The state of the upper surface 22a of the second fixing layer 22 may exert an influence on the fixation of the antibody. For example, the surface state such as the composition and surface roughness of the upper surface 22a may exert an influence on whether the antibody can be easily immobilized on the upper surface 22 a.

The state of the second fixing layer 22 may exert an influence on the fixing of the antibody to the upper surface. In order to control the sensitivity of the sensor device 1 with high accuracy, it is necessary to control the state of the second fixing layer 22 to which the unreacted antibody 51 is to be fixed.

If the second fixing layer 22 is not formed, the unreacted antibody 51 is fixed on the recess surface 21b of the first fixing layer 21. The state of the depression surface 21b is changed due to the etching of the protective film 30. Etching includes many uncertain factors. Therefore, it is difficult to control the change in the state of the surface due to etching. For example, the surface roughness of the depression surface 21b changes due to etching. However, it is difficult to control the surface roughness.

On the other hand, in the present embodiment, the second fixed layer 22 is formed. The state of the upper surface 22a of the second pinned layer 22 may be more easily controlled than the state of the recess surface 21b of the first pinned layer 21. For example, the surface roughness of the upper surface 22a can be controlled by controlling the film formation conditions of the second fixed layer 22. In general, it is easier to control the surface roughness by film formation than by etching. Therefore, it becomes easier to immobilize the unreacted antibody 51 on the upper surface 22a of the second immobilization layer 22. Therefore, it becomes easier to control the sensitivity of the sensor device 1.

The sensor device 1 according to the present embodiment can be manufactured by performing each of the above-described steps. The above steps are all examples. Any suitable steps may be added. Some steps may be omitted.

As shown in fig. 11 and 12, the second fixing layer 22 may be disposed on the sidewall 30a of the protective film 30. The second fixing layer 22 may be disposed further outside when viewed from the opening formed with the side wall 30 a. That is, the ends of the second fixed layer 22 near the first IDT electrode 11 and the second IDT electrode 12, respectively, are disposed on the upper side of the protective film 30.

The protective film 30 covers the cover surface 21c, and the cover surface 21c is disposed adjacent to the first IDT electrode 11 and the second IDT electrode 12, respectively. That is, the protective film 30 covers the end portions of the first fixed layer 21 near the first IDT electrode 11 and the second IDT electrode 12, respectively.

As shown in fig. 13, the waveguide 20 may further include a third fixed layer 23 between the concave surface 21b of the first fixed layer 21 and the second fixed layer 22. The third fixing layer 23 may improve the tightness of the contact between the second fixing layer 22 and the first fixing layer 21. The third fixed layer 23 may be made of, for example, titanium (Ti), chromium (Cr), or the like. The material of the third fixing layer 23 is not limited to these, and may be a material that allows contact between the first fixing layer 21 and the second fixing layer 22 to have high compactness. When the tightness of the contact between the first pinned layer 21 and the second pinned layer 22 is increased, the reliability of the sensor device 1 can be improved.

As shown in fig. 14, when the first and second IDT electrodes 11 and 12 and the waveguide 20 are formed as separate members, the protective film 30 does not need to cover the waveguide 20, but the protective film 30 covers the first and second IDT electrodes 11 and 12. That is, the side wall 30a of the protective film 30 may be disposed between the first and second IDT electrodes 11 and 12 and the waveguide 20. The waveguide 20 comprises a first fixed layer 21 and a second fixed layer 22. The first fixing layer 21 has an upper surface 21 d. The second fixing layer 22 has an upper surface 22a and is disposed on the upper surface 21d of the first fixing layer 21. The second fixing layer 22 has a contact surface 22b on the side facing the substrate surface 10 a. The contact surface 22b is in contact with a part of the upper surface 21d of the first fixed layer 21. The second fixing layer 22 may be disposed to cover half or more of the upper surface 21d of the first fixing layer 21. The waveguide 20 may include a third fixed layer 23 between the first fixed layer 21 and the second fixed layer 22 (see fig. 13). In these cases, the second fixed layer 22 may be formed in a step different from the step of forming the first fixed layer 21. By forming the second fixed layer 22 in a step different from the step of forming the first fixed layer 21, it becomes easier to control the thickness of the waveguide 20. Therefore, it becomes easier to control the sensitivity of the sensor device 1.

The drawings showing embodiments in accordance with the disclosure are diagrammatic.

So far, embodiments of the present disclosure have been described based on the drawings and examples. It is to be noted that various modifications and corrections can be easily performed by those skilled in the art based on the present disclosure. Accordingly, it is noted that such modifications and corrections are included within the scope of the present disclosure. For example, functions and the like included in each element may be rearranged without allowing a logical contradiction, and a plurality of elements may be combined or split, and the like.

In the present embodiment, ordinals such as "first" and "second" are identifiers used to distinguish between elements. In the present disclosure, for elements distinguished by ordinals such as "first" and "second", the ordinals may be replaced with each other. For example, the identifiers "first" and "second" of the first phosphor and the second phosphor may be substituted for each other. The replacement of the identifiers is performed simultaneously. The elements may be distinguished even after the identifier is replaced. The identifier may be omitted. Elements with omitted identifiers are distinguished by reference numerals. In this disclosure, the identifiers "first", "second", etc. should not be used to interpret the order of the elements based on the presence of identifiers having smaller numbers.

List of reference numerals

1 sensor device

10 base plate

10a substrate surface

11 first IDT electrode

11A first signal electrode

11G first reference electrode

12 second IDT electrode

12A second signal electrode

12G second reference electrode

15 substrate side close contact layer

16 metal layer

17 protective film side close contact layer

20 waveguide

21 first fixing layer

21a tapered surface

21b concave surface

21c cover surface

21d upper surface

22 second anchoring layer

22a upper surface

22b contact surface

23 third fixed layer

30 protective film

30a side wall

51 unreacted antibody

52 reacted antibody

60 sample

61 antigen

70 SAW。