JP4918758B2 - Temperature calibration method for spherical surface acoustic wave device - Google Patents

Description

  The present invention relates to a spherical surface acoustic wave device used in a method for measuring a physicochemical property of an object to be measured in a sample, and a surface acoustic wave excitation method necessary for temperature calibration thereof.

  Usually, the electrode of the surface acoustic wave element formed on the piezoelectric material substrate is formed by photolithography using a flat mask.

  Patent Document 1 discloses a surface acoustic wave device having a plurality of frequencies. In the case of a planar type surface acoustic wave element, an element is generally used in which surface acoustic waves of each frequency pass through different paths. In addition, the patent literature includes an element that propagates surface acoustic waves having a plurality of frequencies in one waveguide. In this case, the surface acoustic waves having a plurality of frequencies are converged by disposing the comb-shaped electrodes having protrusions alternately protruding from both sides of the annular surface acoustic wave path.

Patent documents are as follows.
Japanese Patent Laid-Open No. 11-340772 Japanese Patent Laid-Open No. 7-50548

  When a comb-shaped electrode is formed on the surface using a photolithographic technique in a spherical surface acoustic wave device, it is ideally desirable to use an optical system that focuses light along a spherical spherical surface. It becomes a complicated optical system and the cost becomes high. On the other hand, as shown in FIG. 2, when a spherical surface is exposed using a flat mask as in the case of forming an electrode pattern on a flat substrate, the cost can be reduced, but the peripheral portion is more spherical on the periphery due to the influence of the curved surface. As a result, the pattern is exposed greatly, and the image is blurred due to out of focus. Here, 1 is a plane mask, 2 is a pattern on the plane mask, 5 is a material ball, and 4 is a photosensitive material film formed on the surface of the material ball. Obviously, this effect becomes more prominent as the electrode pattern to be exposed becomes larger.

  In the spherical surface acoustic wave element, since the frequency used is about 10 MHz to 100 GHz, the attenuation characteristic of the surface acoustic wave is an important factor. One of the causes for attenuating the surface acoustic wave is an electrode for exciting the surface acoustic wave. In order to excite the surface acoustic wave, an electrode is required on the surface, but the electrode also attenuates the surface acoustic wave. Therefore, in order to suppress attenuation due to this effect, it is preferable to reduce the number of electrodes. However, a large number of electrodes are required for strong excitation.

In the spherical surface acoustic wave element, the temperature can be calibrated by using surface acoustic waves having a plurality of frequencies. However, in order to do this, it is necessary to form an electrode structure that can excite surface acoustic waves of a plurality of frequencies. At this time, if a plurality of surface acoustic waves can be excited in one path, variation in characteristics may be suppressed. In the spherical surface acoustic wave element, the technique as in Patent Document 2 cannot be used. This is because, in a spherical surface acoustic wave element, one path makes a round circle around the surface of the sphere, and this surface acoustic wave needs to be excited on this path, so that an electrode cannot be disposed in a concave shape. One way to solve this is to arrange two electrodes with different frequencies side by side in the circuit path. However, in this case, since electrodes having two frequencies are formed separately, the electrode pattern to be exposed becomes large, and the electrode pattern is eventually distorted accordingly.

In order to solve the above problem, in the invention according to claim 1, the first electrode and the second electrode are arranged on the annular surface acoustic wave path on the piezoelectric crystal sphere or the sphere formed with the piezoelectric material film on the surface. a protrusion provided alternately from and the circle sensitive film provided on the annular surface acoustic wave paths, and a third electrode between the projecting portion and the projecting portion of the second electrode of each first electrode A method of temperature calibration of a spherical surface acoustic wave element provided with a first electrode and a second electrode, and the first electrode and the second electrode connected to each other, and a first method The surface sensitive wave is detected by exciting a surface acoustic wave of a plurality of frequencies by applying an electrical signal between the electrodes of the three electrodes, detecting the surface acoustic wave signal, and performing temperature calibration using the surface acoustic wave signal of the plurality of frequencies. spherical surface acoustic wave device characterized by calibrating the signal due to factors other than There is provided a temperature correction method.

In the invention according to claim 2 in order to solve the problem, in the spherical surface acoustic wave element, and characterized in that the third electrode is continuous between the first electrode and the second electrode A temperature calibration method for a spherical surface acoustic wave device according to claim 1 is provided.

  Specifically, for example, as shown in FIG. 1, the first electrode and the second electrode, which are simple saddle-shaped electrodes in which protruding portions alternately protrude from both sides of the annular surface acoustic wave path, are connected to each other. A third electrode is used that passes in a zigzag so as to sew between the first electrode and the second electrode. This eliminates the need to provide a new counter electrode corresponding to the third electrode by utilizing the existing first electrode and second electrode, and can reduce the exposure area, thereby minimizing distortion. It has become possible.

  Here, the invention will be described with a simple example. A set of saddle-shaped electrodes having four pairs of protrusions for exciting surface acoustic waves of frequency f and a pair of saddle-shaped electrodes having eight pairs of protrusions for exciting surface acoustic waves of frequency 2 × f When the electrodes are formed on the element surface, if two pairs of electrodes are simply formed, a total of 12 pairs and 24 protrusions are required, which is equivalent to two saddle-shaped electrodes for exciting surface acoustic waves of frequency f. A surface area is required.

  On the other hand, in the case of the pattern as shown in FIG. 1, if the distance between the first electrode and the second electrode corresponds to the frequency f from the relationship between the sound speed and the wavelength, the first electrode and the second electrode By applying an electric signal having a frequency f between them, a surface acoustic wave having a frequency f can be excited. Further, when an electric signal having a frequency of 2 × f is applied between the electrode connecting the first electrode and the second electrode and the third electrode, a surface acoustic wave having a frequency of 2 × f can be excited. In this case, the protrusions on the 16 annular surface acoustic wave paths, that is, the electrodes that excite the surface acoustic waves having the frequency f by using the two-thirds of the protrusions are equivalent to the surface acoustic waves. One area can be formed.

  Thus, by using the first electrode and the second electrode, which are a pair of comb-shaped electrodes, and the third electrode passing through between them, a hook-shaped electrode is formed as a whole, and the number of electrodes is reduced. In addition, the area necessary for forming the electrode can be reduced.

According to the present invention, it is possible to form an electrode of a spherical surface acoustic wave device using a plurality of frequencies with an area smaller than the conventional area. Thereby, it can form easily using normal planar photolithography. Thereby, surface acoustic waves having a plurality of frequencies can be excited in one path. Furthermore, by reducing the number of electrodes as a whole, attenuation due to the electrodes can be suppressed, and since the exposure area has become smaller, distortion can be minimized and the performance as a spherical surface acoustic wave device is improved. It has become possible.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiment.

  FIG. 1 is a schematic diagram of electrodes of a spherical surface acoustic wave device according to Embodiment n of the present invention. Reference numerals 6, 7, and 8 denote formed electrodes. When an electric signal having a frequency f is applied between the first electrode 6 and the second electrode 7, a surface acoustic wave 9 having a frequency f is excited as shown in FIG. At this time, the third electrode 8 may be in an electrically floating state.

  When an electric signal having a frequency of 2 × f is applied between the first electrode 6 and the second electrode 7 connected to each other and the third electrode 8, the surface elasticity of 2 × f is obtained as shown in FIG. Wave 9 is excited.

The excited surface acoustic wave circulates around the spherical surface and outputs an electrical signal from the comb-shaped electrode every time it returns to the excited electrode after one round. By forming a sensitive film on the spherical surface and observing the surface acoustic wave signal, it can be used as a highly sensitive sensor. Further, by causing the surface acoustic waves of a plurality of frequencies to circulate, it is possible to calibrate signals due to factors other than the sensitive film such as temperature.

  FIG. 5 is a diagram showing the surface acoustic wave circulation phenomenon of the spherical surface acoustic wave device of the present invention. A and B respectively connect the first electrode 6 and the second electrode 7 when an electric signal having a frequency of 30 MHz is applied between the first electrode 6 and the second electrode 7 in the schematic diagram of FIG. 3 shows an output signal indicating that a surface acoustic wave circulates on a sphere when an electrical signal of 60 MHz is applied between the electrode and the third electrode 8. It can be seen that a plurality of frequencies can be excited by changing the connection of the electrodes and the frequency of the input signal.

  The present invention relates to an electrode pattern in a spherical surface acoustic wave device and an electrode pattern in a surface acoustic wave device that can be used for a temperature calibration technique.

Plan view of electrode pattern capable of exciting multiple frequencies according to the present invention Explanatory cross-sectional view of exposure on a spherical surface using a planar mask FIG. 3 is an explanatory diagram of a surface acoustic wave output from a state where the frequency of f is excited using the electrode pattern of FIG. 1. FIG. 2 is an explanatory diagram of surface acoustic waves output from a state where a frequency of 2 × f is excited using the electrode pattern of FIG. 1. FIG. 2 is an explanatory diagram of surface acoustic waves output from a state where f and 2 × f frequencies are excited using the electrode pattern of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plane mask 2 ... Pattern 4 on plane mask ... Photosensitive material film 5 coated on material sphere surface ... Material sphere 7 ... First electrode (electrode for exciting frequency of f and 2xf)
8 ... 2nd electrode (electrode for exciting the frequency of f and 2xf)
9 ... 3rd electrode (electrode for exciting the frequency of 2xf)

Claims (2)

Protruding portions are alternately provided from the first electrode and the second electrode on the annular surface acoustic wave path on the surface of the piezoelectric crystal sphere or the sphere formed with the piezoelectric material film , and
Providing a sensitive film on the annular surface acoustic wave path; and
A method for temperature calibration of a spherical surface acoustic wave element in which a third electrode is provided between a protruding portion of each first electrode and a protruding portion of a second electrode ,
By applying an electric signal between the first electrode and the second electrode, and between the first electrode and the second electrode connected to each other and the third electrode, surface acoustic waves having a plurality of frequencies are generated. A temperature calibration of a spherical surface acoustic wave device , wherein the surface acoustic wave signal is excited, the surface acoustic wave signal is detected, a temperature calibration is performed with the surface acoustic wave signals of the plurality of frequencies, and a signal due to a factor other than the sensitive film is calibrated Way . In the spherical surface acoustic wave device, temperature correction method of the spherical surface acoustic wave device according to claim 1, wherein the third electrode, characterized in that continuous between the first electrode and the second electrode.

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