JP2007129788A - Elastic wave device - Google Patents

Abstract

Even if a side wall for preventing a solution to be processed from coming into contact with an electrode is provided on a substrate, the presence of the side wall suppresses attenuation of an elastic wave propagating on the surface of the substrate.
SOLUTION: The liquid dropped on the propagation path of the sensing elastic wave Ws does not contact the excitation electrode 14 and the reception electrode 16 so that the propagation path intersects the excitation electrode side and the reception electrode side on the propagation path. A side wall 20 is disposed on the wall. Tunnel portions 22a and 22b having such a size that the liquid on the propagation path does not pass to the electrode side are formed between the surface of the substrate 12 and the surface of the side wall 20 facing the excitation electrode and the reception electrode. In addition, the propagation path of the sensing elastic wave Ws from the excitation electrode 14 to the reception electrode 16 passes through the tunnel portions 22 a and 22 b formed by the surface of the substrate 12 and the side wall 20.
[Selection] Figure 1

Description

  The present invention utilizes the propagation of elastic waves generated on the surface of a substrate, performs sensing of the substance from changes in the propagation characteristics of the elastic wave caused by the substance on the propagation path of the elastic wave, or propagates the elastic wave. The present invention relates to an acoustic wave device that conveys a substance on a path.

  2. Description of the Related Art Conventionally, there are elastic wave devices that perform various treatments on a substance (especially liquid) on an elastic wave propagation path using elastic wave propagation, such as an elastic wave sensor or a carrier system using elastic waves. .

  As an elastic wave sensor, for example, there is a solution sensor 100 configured as shown in FIG. The solution sensor 100 has a configuration in which an excitation electrode 104 and a reception electrode 106 made of comb-like electrode fingers are formed on a piezoelectric substrate 102. When a high frequency signal is applied to the excitation electrode 104, an electric field is generated between the electrode fingers, and a surface acoustic wave (sensing acoustic wave) Ws is excited by the piezoelectric effect. In addition, the sensing region 108 between the excitation electrode 104 and the receiving electrode 106 is surrounded by, for example, a resin side wall 110 so that the solution to be measured dropped onto the sensing region 108 does not come into contact with both the electrodes 104 and 106. It is. When the solution to be measured is dropped onto the sensing region 108, the propagation characteristic (for example, propagation velocity) of the sensing elastic wave Ws propagating on the surface of the substrate 102 changes due to the presence of the solution. A change in the propagation characteristic of the elastic wave Ws is detected to sense the property of the solution to be measured.

  Further, the solution sensor as described above is provided with a transport system that transports the solution to be measured using propagation of elastic waves, and the solution to be measured is transported to the sensing region by the elastic waves and then sensed. There is also an elastic wave sensor configured (see FIG. 8).

  In the acoustic wave sensor 200 of FIG. 8, the substance to be measured is placed in the sensing region 210 between the excitation electrode 204 and the reception electrode 206 on the same surface of the substrate 202 as the surface on which the excitation electrode 204 and the reception electrode 206 are arranged. The electrode (transport electrode) 208 for exciting the transport elastic wave Wc for transporting the (solution) has a direction in which the transport elastic wave Wc is different from the sensing elastic wave Ws (in FIG. It is provided so as to propagate in a direction orthogonal to the propagation direction. That is, a transfer path (propagation path of the transfer elastic wave Wc) is formed from the transfer electrode 208 toward the sensing region 210 by the transfer elastic wave Wc. A dropping area 212 for dropping the solution onto the substrate is provided on the transfer path, and the solution is moved from the dropping area 212 toward the sensing region 210 by the propagation of the elastic wave Wc excited by the transfer electrode 208. It is designed to be transported. Then, when the solution is transported to the sensing region 210, the change is detected in the propagation characteristic of the sensing elastic wave Ws caused by the solution existing in the sensing region 210, and the solution is sensed as in the conventional acoustic wave sensor. It is like that. Here, in the acoustic wave sensor 200 of FIG. 8, the transport path including the sensing region 210 and the drip area 212 is prevented so that the substance to be measured (solution) does not contact the excitation electrode 204, the reception electrode 206, and the transport electrode 208. For example, it is surrounded by a side wall 214 made of resin.

  In addition, as a system which conveys a substance using propagation of an elastic wave, there exists a thing of the following patent document 1, for example. This apparatus has a configuration including a piezoelectric substrate made of a piezoelectric material that generates a Rayleigh mode elastic wave and a cut surface, and an input electrode that excites the Rayleigh mode elastic wave on the surface of the piezoelectric substrate. Then, when liquid is supplied to the propagation path through which the surface acoustic wave from the input electrode propagates and an electric signal is applied to the input electrode to excite the elastic wave (Rayleigh wave) from the piezoelectric substrate, it propagates on the substrate. Since the elastic wave entering the liquid radiates a longitudinal wave in the liquid while propagating through the interface between the propagation surface and the liquid, the liquid that has received the radiation flows in the traveling direction of the elastic wave by the radiant energy. Based on such a principle, in the apparatus described in Patent Document 1 below, it is possible to transport, for example, a liquid as a material to be transported using elastic waves.

JP-A-10-327590

  In the acoustic wave sensor configured as described above, the sensing acoustic wave excited from the excitation electrode propagates under the measured substance (solution) in the sensing region after propagating under the side wall on the excitation electrode side, and further receiving the electrode. It propagates under the side wall and reaches the receiving electrode. However, in this case, since the side wall is formed in contact with the substrate surface, the sensing elastic wave is attenuated when propagating under the side wall. Therefore, the presence of the side wall for preventing the solution from coming into contact with the excitation electrode and the reception electrode has hindered high sensitivity of sensing.

  In addition, the elastic wave for conveyance excited from the conveyance electrode reaches the solution that is the material to be conveyed in the dropping area after propagating under the side wall, but part of the energy of the elastic wave when passing under the side wall. Will be attenuated. The amount of attenuation when passing under this side wall is larger than the amount of attenuation of the elastic wave due to the energy being radiated into the solution that is the material to be transported. Therefore, the side wall for preventing the solution from contacting the transport electrode The presence of hindered the transport of this solution.

  The main object of the present invention is to provide an elastic wave device that prevents the attenuation of an elastic wave due to the presence of a side wall in view of the above-described problems of the prior art.

  In order to achieve the above object, the acoustic wave device of the present invention propagates so that an electrode that excites an acoustic wave on the substrate surface and a liquid dropped on the propagation path of the acoustic wave from the electrode do not contact the electrode. A side wall disposed on the surface of the substrate so as to cross the path, and the side wall includes a tunnel portion having a size such that liquid on the propagation path does not pass to the electrode side. It is formed and provided on the substrate surface so that the propagation path of the elastic wave from the electrode passes through the tunnel portion.

  The acoustic wave device of the present invention also receives an excitation electrode for exciting a sensing acoustic wave for sensing a liquid to be measured on the substrate surface, and a sensing acoustic wave propagating near the substrate surface and the surface. A measurement electrode using a change in the propagation characteristics of the sensing acoustic wave caused by the liquid existing on the propagation path of the sensing acoustic wave connecting the excitation electrode and the reception electrode. In an acoustic wave device that performs liquid sensing, a propagation path is provided on the excitation electrode side and the reception electrode side on the propagation path so that liquid dropped on the sensing acoustic wave propagation path does not contact the excitation electrode and the reception electrode. The side walls are arranged so as to intersect, and the side walls arranged on the excitation electrode side and the reception electrode side on the propagation path are between the substrate surface and the liquid on the propagation path is electrically charged. A tunnel part with a size that does not pass to the side is formed, and it is provided on the substrate surface so that the propagation path of the elastic wave for sensing from the excitation electrode to the reception electrode passes through the tunnel part. It is characterized by.

  In addition, the acoustic wave device of the present invention is configured so that the electrode that excites the acoustic wave for conveyance for conveying the liquid and the liquid dropped on the propagation path of the acoustic wave for conveyance from the electrode do not contact the electrode. A side wall disposed on the substrate surface so as to intersect the propagation path of the elastic wave for conveyance, and the side wall is so large that the liquid on the propagation path does not pass to the electrode side between the side wall and the substrate surface. Is formed on the substrate surface so that the propagation path of the elastic wave for conveyance from the electrode passes through the tunnel portion.

  Here, in the above acoustic wave device, it is preferable that the region on the electrode side of the opening on the substrate surface is a non-affinity region having non-affinity with respect to the liquid.

  According to the elastic wave device of the present invention, even if a side wall is provided on the substrate to prevent the solution to be processed from coming into contact with the electrode that excites the elastic wave on the substrate surface, It can suppress that the elastic wave which propagates is attenuate | damped.

First, an acoustic wave device according to an embodiment of the present invention will be described with reference to FIG. As in FIG. 7, the acoustic wave device 10 of FIG. 1 includes an excitation electrode 14 that excites a sensing acoustic wave Ws such as a transverse acoustic wave (STW) on the surface of the substrate 12, and an excitation electrode. 14 and a receiving electrode 16 for receiving the sensing elastic wave Ws propagated from 14. The excitation electrode 14 in the acoustic wave device 10 of FIG. 1 is connected to a drive circuit (not shown) that generates a high-frequency signal, and excites the sensing elastic wave Ws by the input of the high-frequency signal from this drive circuit. In addition, the sensing region 18 between the excitation electrode 14 and the receiving electrode 16 is surrounded by, for example, a resin side wall 20 so that the solution to be measured dropped onto the sensing region 18 does not come into contact with the electrodes 14 and 16. It is. Then, a solution to be measured is dropped onto the sensing region 18, and then the sensing elastic wave Ws is propagated from the excitation electrode 14 to the receiving electrode 16, and the propagation characteristic of the sensing elastic wave Ws generated by the presence of the solution (for example, , Sensing the property of the solution to be measured. As the substrate 12, for example, a quartz substrate, a piezoelectric substrate (for example, a LiNbO ₃ substrate or a LiTaO ₃ substrate), or a substrate having a piezoelectric thin film (for example, ZnO or AlN) on the surface of a substrate such as glass or silicon is used. Yes.

  In addition, on the side wall 20 of the acoustic wave device 10 in the present embodiment, the propagation path of the sensing acoustic wave Ws that connects the excitation electrode 14 and the reception electrode 16 (between the dotted line that connects the excitation electrode 14 and the reception electrode 16 in FIG. 1). Two portions intersecting with each other are tunnel portions 22a and 22b opened in a tunnel shape as shown in FIG. That is, at the portion of the side wall 20 facing the excitation electrode 14 and the reception electrode 16, the elastic wave for sensing Ws propagating from the excitation electrode 14 on the propagation path passes through the tunnel portions 22a and 22b opened as shown in FIG. It reaches the receiving electrode 16. In this embodiment, the tunnel portions 22a and 22b are about the same length as the height H from the substrate surface (propagation path) of about 2 μm and the width L as long as the width of the electrode (about 1000 μm). Is set.

  Here, such a side wall 20 is produced by the following procedure, for example. 3 and 4 are diagrams illustrating a process in which the side wall 20 of the acoustic wave device having the tunnel portions 22a and 22b according to the present embodiment is manufactured.

  First, the sacrificial layer 30 is formed on the substrate 12 at positions where the tunnel portions 22a and 22b are to be formed (see FIG. 3). In this embodiment, the tunnel portions 22a and 22b are formed at two locations on the excitation electrode 14 side and the reception electrode 16 side, so that the propagation path intersects the propagation path at two locations on the propagation path connecting the excitation electrode 14 and the reception electrode 16. Thus, the sacrificial layer 30 is formed.

  Next, the side wall 20 is formed in a predetermined shape using, for example, resin. Specifically, the resin side wall 20 is formed in a predetermined shape by applying a resin with a dispenser or the like and curing the resin. At this time, in a portion facing the excitation electrode 14 and the reception electrode 16, the applied resin is in a state of straddling the sacrificial layer 30 (see FIG. 4).

  After the resin-shaped side wall 20 having a predetermined shape is thus formed, sacrificial layer etching is performed. Thereby, since only the sacrificial layer 30 is removed, tunnel portions 22a and 22b as shown in FIG. 2 are formed at locations on the side wall 20 facing the excitation electrode 14 and the reception electrode 16.

  In this embodiment, a photosensitive resin (for example, a chemically amplified resist or a permanent resist) is used as the resin for forming the sidewall 20, and the curing temperature of the chemically amplified resist or the permanent resist is used for the sacrificial layer 30. The resist is resistant to heat and can be removed by an organic solvent. In particular, the reason why the resist that can be removed by the organic solvent is used as the sacrificial layer 30 is as follows. In an acoustic wave device, it is common to use an electrode made of aluminum. However, if the etching solution is made acidic or alkaline, it reacts with the aluminum electrode during the sacrificial layer etching. The frequency characteristics of this will change. Therefore, particularly when the side wall 20 is formed after the electrode is formed on the substrate surface, a resist that can be removed by an organic solvent is used for the sacrificial layer 30 in order to avoid a reaction with the electrode, and an organic solvent is used. It is preferable to perform etching.

  According to the structure of the side wall 20 as described above, since the height H of the tunnel portions 22a and 22b is about 2 μm, displacement of the substrate surface by the elastic wave (displacement in the normal direction of the substrate surface) is several angstroms. Therefore, the elastic wave can pass through the tunnel portions 22 a and 22 b without touching the side wall 20.

  Further, since the height H of the tunnel portions 22a and 22b is about 2 μm, the solution permeates into the tunnel portions 22a and 22b by capillary action, but passes through the tunnel portions 22a and 22b from the sensing region 18. It does not flow out to the electrodes 14 and 16 side, and the function of preventing the solution from contacting the electrodes 14 and 16 is maintained. At this time, the tunnel portions 22a and 22b are filled with the solution.

  In the acoustic wave device 10, the sensing acoustic wave Ws passes through the tunnel portion 22 a on the excitation electrode side from the excitation electrode 14 (more specifically, below the solution in the tunnel portion 22 a on the excitation electrode side). It enters the region 18, propagates under the solution in the sensing region 18, and further passes through the tunnel portion 22 b on the receiving electrode side (more specifically, below the solution in the tunnel portion 22 b on the receiving electrode side) to enter the sensing region 18. And reaches the receiving electrode 16. That is, instead of passing under the side wall in the prior art, the acoustic wave device 10 in FIG. 1 passes under the solution in the tunnel portions 22a and 22b.

  Here, for example, a propagation loss (propagation attenuation) in an STW (surface transverse wave) element is about 0.75 dB per wavelength when passing under the side wall, but when passing under water. Since it is about 0.026 dB per wavelength, it is much more exciting for the excitation electrode 14 to pass under the solution in the tunnel portions 22a and 22b as in the present embodiment than to pass under the side wall as in the prior art. The propagation loss (propagation attenuation) of the elastic wave propagating from the electrode to the receiving electrode 16 is small. Further, in the elastic wave device 10 of FIG. 1, since the substance existing on the propagation path of the elastic wave from the excitation electrode 14 to the receiving electrode 16 is only the solution, the propagation characteristic of the elastic wave depends on the property of the solution. It becomes.

  Therefore, according to the acoustic wave device 10 of the present embodiment, there is no large propagation loss (propagation attenuation) that occurs when the acoustic wave propagates under the side wall as in the conventional case, and high sensitivity of the sensing can be realized.

  In addition, you may make it the area | region (excitation electrode side and receiving electrode side) outside the tunnel parts 22a and 22b in the side wall 20 be the non-affinity area | region 24 which has non-affinity with respect to a solution (refer FIG. 5). . Here, the non-affinity region 24 may be formed by using a film made of a substance having non-affinity with respect to the solution, or the surface of the substrate 12 is surface-modified by non-affinity by surface treatment. May be formed.

  Moreover, the structure of the side wall 20 having the tunnel portions 22a and 22b as described above includes a transport system that transports a substance using propagation of elastic waves, and the substance (for example, a solution or the like) to be measured up to the sensing region by the elastic waves. In the acoustic wave sensor as shown in FIG. 8 having a configuration in which the liquid is transported and then sensed, it may be applied to the side wall facing the transport electrode.

  FIG. 6 is a diagram showing a configuration of an elastic wave sensor to which the structure having the tunnel portion as described above is applied at a portion facing the transport electrode on the side wall. In the acoustic wave sensor 40 of FIG. 6, the sensing region 50 and the drip area 52 are arranged so that the substance to be measured (for example, a liquid such as a solution) does not contact each of the excitation electrode 44, the reception electrode 46, and the transport electrode 48 on the substrate 42. A conveyance path (propagation path of the elastic wave for conveyance Wc) is surrounded by a side wall 54 made of resin, for example. Here, as in FIGS. 1 and 2, the two portions intersecting the propagation path of the sensing elastic wave Ws connecting the excitation electrode 44 and the reception electrode 46 on the side wall 54 are tunnel portions each opened in a tunnel shape. 56a and 56b. That is, at a position facing the excitation electrode 44 and the reception electrode 46, the sensing elastic wave Ws propagating from the excitation electrode 44 on the propagation path passes through the tunnel portions 56a and 56b and reaches the reception electrode 46. It has become.

  Further, in the acoustic wave sensor 40 of FIG. 6, a portion of the side wall 54 facing the carrier electrode 48 and a propagation path through which the carrier acoustic wave Wc from the carrier electrode 48 propagates (from the carrier electrode 48 to the sensing region 50 in FIG. 6). A portion where the crossing line (between the dotted lines extending in the direction) intersects opens in a tunnel shape as in FIG. In other words, the side wall facing the transport electrode 48 has a structure in which the elastic wave for transport Wc propagating from the transport electrode 48 on the propagation path passes through the tunnel portion 56c and reaches the solution in the dropping area 52. ing. Here, regarding the size of the tunnel portions 56a to 56c, the height H from the substrate surface (propagation path) is set to about 2 μm, and the width L is set to the same length as the electrode width (about 1000 μm). ing. Moreover, such a side wall 54 is produced through the process similar to FIG.3 and FIG.4, for example.

  According to the structure of the side wall 54 as described above, since the height H of the tunnel portions 56a to 56c is about 2 μm, the displacement of the substrate surface by the elastic wave (the displacement of the substrate surface in the normal direction) is several angstroms. Therefore, the elastic wave can pass through the tunnel portions 56a to 56c without touching the side wall.

  Further, since the height H of the tunnel portions 56a to 56c is about 2 μm, the solution does not flow out from the tunnel portions 56a to 56c to the respective electrode sides, and the solution contacts the electrodes 44, 46, and 48. The function to prevent this is maintained.

  In the acoustic wave device 40, the acoustic wave for conveyance Wc excited from the conveyance electrode 48 passes through the tunnel portion 56c from the conveyance electrode 48 and reaches the solution in the dropping area 52, and conveys this solution. Therefore, unlike the conventional method, a part of the energy of the elastic wave is not attenuated when passing under the side wall, and the presence of the side wall 54 for preventing the solution from coming into contact with the transporting electrode 48 is present. There is no hindrance to the transport of the measurement substance.

  Also in this embodiment, the region outside the tunnel portion 56c (on the transport electrode side) on the side wall 54 may be a non-affinity region having non-affinity with respect to the solution as in FIG. Here, the non-affinity region may be formed by using a film made of a substance having non-affinity for the solution, or formed by surface modification of the substrate surface to non-affinity by surface treatment. May be.

  Further, the present invention can be applied to a side wall for preventing a solution to be processed from coming into contact with an electrode in an acoustic wave device using a solution. Therefore, the application range of the present invention is not limited to the elastic wave sensor as in the above-described embodiment or the conveyance system using the elastic wave.

It is a figure which shows the structure of the elastic wave device (solution sensor) in embodiment of this invention. It is the sectional view on the AA line in the elastic wave device of FIG. FIGS. 3A and 3B are diagrams illustrating a process of manufacturing the sidewall of the acoustic wave device of FIG. 1, FIG. 3A is a diagram illustrating a state in which a sacrificial layer is formed on a substrate, and FIG. FIG. 4A and 4B are diagrams illustrating a process of manufacturing the side wall of the acoustic wave device of FIG. 1, in which FIG. 4A illustrates a state in which the side wall is formed by applying a resin on the sacrificial layer, and FIG. C line sectional drawing and FIG.4 (c) are DD line sectional drawings. It is a figure which shows the example of application of the elastic wave device of FIG. It is a figure which shows the structure of the elastic wave device (elastic wave sensor with a conveyance system) in other embodiment of this invention. It is a figure which shows the structure of the conventional elastic wave device (solution sensor). It is a figure which shows the structure of the conventional elastic wave device (elastic wave sensor with a conveyance system).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Elastic wave device, 12 Board | substrate, 14 Excitation electrode, 16 Reception electrode, 18 Sensing area | region, 20 Side wall, 22a, 22b Tunnel part, 24 Non-affinity area | region, 30 Sacrificial layer, 40 Elastic wave device (elastic wave sensor), 42 Substrate, 44 excitation electrode, 46 receiving electrode, 48 carrier electrode, 50 sensing area, 52 dropping area, 54 side wall, 56a to 56c tunnel, Ws sensing elastic wave, Wc carrying elastic wave.

Claims (4)

An electrode for exciting an elastic wave on the substrate surface;
Side walls arranged to cross the propagation path so that the liquid dropped on the propagation path of the elastic wave from the electrode does not contact the electrode;
On the substrate surface,
The side wall forms a tunnel portion having a size that prevents the liquid on the propagation path from passing through the electrode side between the substrate surface and the propagation path of the elastic wave from the electrode through the tunnel portion. Provided on the substrate surface,
An elastic wave device characterized by that. An excitation electrode for exciting a sensing acoustic wave for sensing a liquid to be measured and a receiving electrode for receiving a sensing acoustic wave propagating on the substrate surface and in the vicinity of the surface are arranged on the substrate surface and excited. In the acoustic wave device that senses the liquid to be measured using the change in the propagation characteristics of the sensing acoustic wave caused by the liquid existing on the sensing acoustic wave propagation path connecting the electrode and the receiving electrode,
Side walls are arranged to cross the propagation path on the excitation electrode side and the reception electrode side on the propagation path so that the liquid dropped on the sensing elastic wave propagation path does not contact the excitation electrode and the reception electrode,
Each side wall disposed on the excitation electrode side and the reception electrode side on the propagation path forms a tunnel portion having a size such that liquid on the propagation path does not pass to the electrode side between the substrate surface and Provided on the substrate surface so that the propagation path of the elastic wave for sensing from the excitation electrode to the reception electrode passes through the tunnel portion.
An elastic wave device characterized by that. An electrode for exciting an elastic wave for conveyance for conveying a liquid;
Side walls arranged so as to intersect the propagation path of the elastic wave for conveyance so that the liquid dropped on the propagation path of the elastic wave for conveyance from the electrode does not contact the electrode;
On the substrate surface,
The side wall forms a tunnel part with a size that prevents the liquid on the propagation path from passing through the electrode side, and the propagation path of the elastic wave for transport from the electrode passes through the tunnel part. Is provided on the surface of the substrate,
An elastic wave device characterized by that. In the elastic wave device according to any one of claims 1 to 3,
The region on the electrode surface side of the opening on the substrate surface was a non-affinity region having non-affinity for the liquid,
An elastic wave device characterized by that.

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