JP2012060417A - Surface acoustic wave device, electronic apparatus and sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SAW device for improving an electromechanical coupling coefficient and exhibiting a stable oscillation while maintaining excellent frequency temperature characteristics within an operational temperature range.SOLUTION: On a main surface of a crystal substrate 2 having Euler angles of (φ=0°,θ=123°,ψ), an SAW device 1 has: an IDT 3 for exciting an SAW of an upper limit mode of a stop band; and inter-electrode-finger grooves 8 recessed between electrode fingers 6a and 6b of the IDT 3. The depth G of the inter-electrode-finger grooves 8, the film thickness H of the electrode fingers 6a and 6b and the wave length λ of the SAW satisfy the following relation: 1≤G/λ≤4 and 1≤H/λ≤4. In addition to the above, a line occupancy ratio η and an Euler angle ψ of the IDT 3 are determined in such a manner that an electromechanical coupling coefficient is equal to 0.052% or more and further that the frequency temperature characteristics are equal to 20 ppm or less within an operational temperature range.

Description

  The present invention relates to a surface acoustic wave device such as a resonator and an oscillator using a surface acoustic wave (SAW), an electronic apparatus including the SAW device, and a sensor device.

  SAW devices include, for example, mobile phones, hard disks, personal computers, BS and CS broadcast reception tuners, coaxial cables or optical signal processing equipment that propagates in optical cables, and high-frequency, high-precision clocks (low jitter over a wide temperature range). , Low phase noise) is widely used in electronic devices such as server / network equipment, wireless communication equipment, and various sensor devices such as pressure sensors, acceleration sensors, and rotational speed sensors. In these devices and apparatuses, the influence of heat generation inside the apparatus is increasing with the recent increase in the frequency of the reference clock and the downsizing of the apparatus housing due to the speeding up of information communication. For this reason, electronic devices mounted inside the device are required to have a wide operating temperature range and high accuracy.For example, wireless base stations installed outdoors can be used for long periods of time in environments where temperature changes from low to high. Therefore, stable operation is required.

  In general, in a SAW device such as a SAW resonator, changes in frequency temperature characteristics include the SAW stop band, the cut angle of the quartz substrate used, and the form of the IDT (interdigital transducer) formed on the substrate. It has a big impact. For example, a reflection inversion SAW having an IDT in which unit sections composed of three electrode fingers per wavelength of SAW are repeatedly arranged on a piezoelectric substrate, and exciting each of the upper end mode and the lower end mode of the SAW stop band. A converter has been proposed (see, for example, Patent Document 1). If a SAW filter is constituted by this reflection inversion type SAW converter, it is said that a high attenuation can be realized in the high band side stop band near the pass band.

  Further, a reflection inversion SAW converter using a so-called ST-cut quartz substrate with Euler angles (φ, θ, ψ) = (0 °, 123 °, 0 °) is known (see, for example, Patent Document 2). ). The patent document describes that the resonance at the upper end of the stop band can be excited and the frequency temperature characteristic is improved as compared with the case of using the resonance at the lower end of the stop band. Furthermore, it has been reported that the upper end mode of the stop band in SAW has better frequency temperature characteristics than the lower end mode of the stop band (see, for example, Patent Documents 3 to 6).

  In particular, in Patent Documents 3 and 4, in order to obtain good frequency temperature characteristics in a SAW device using Rayleigh waves, the cut angle of the quartz substrate is adjusted and the normalized film thickness (H / λ) of the IDT electrode is set. It is described that the thickness is increased to about 0.1. The SAW resonator described in Patent Document 3 is formed on a quartz substrate with Euler angles (φ, θ, ψ) = (φ = 0 °, 0 ° ≦ θ ≦ 180 °, 0 ° <| ψ | <90 °). , A single type IDT electrode in which unit sections composed of two electrode fingers per wavelength of SAW are repeatedly arranged. Thereby, the Rayleigh wave is excited in the upper limit mode of the stop band, and it is possible to realize high frequency and good frequency temperature characteristics of the SAW resonator by using it.

In Patent Document 4, in the SAW device having the single-type IDT electrode, the quartz substrate is subjected to Euler angles (φ, θ, ψ) = (φ = 0 °, 110 ° ≦ θ ≦ 140 °, 38 ° ≦ | ψ | ≦ 44 °), the normalized electrode film thickness (H / H) defined by the IDT electrode thickness H, the electrode finger width d in the IDT electrode, the pitch P between the electrode fingers in the IDT electrode, and the SAW wavelength λ. λ) and the normalized electrode width η (= d / P),
H / λ ≧ 0.1796η ³ −0.4303η ² + 0.2071η + 0.0682
Is disclosed. As a result, the Rayleigh wave can be strongly excited in the upper limit mode of the stop band.

  In Patent Document 5, Euler angles (φ, θ, ψ) = (0 °, θ, 9 ° <| ψ | <46 °), preferably (0 °, 95 ° <θ <155 °, 33 ° < A SAW element is disclosed in which a single-type IDT electrode is disposed on a quartz substrate of | ψ | <46 °) and a standardized electrode film thickness (H / λ) is 0.045 ≦ H / λ ≦ 0.085. Yes. As a result, Rayleigh waves can be excited in the upper limit mode of the stop band, and good frequency temperature characteristics can be realized.

  In Patent Document 6, the single-type IDT electrode is arranged on an in-plane rotated ST-cut quartz substrate with Euler angles (φ, θ, ψ) = (0 ° 123 °, 43.2 °), and the standardized electrode A SAW element is disclosed in which the Rayleigh wave is excited in the upper limit mode of the stop band by setting the film thickness (H / λ) to H / λ = 0.06, so-called 6% λ. Further, the SAW element is configured by setting a standardized electrode width η (= Lt / Pt) defined by the electrode finger width Lt and the electrode finger pitch Pt of the IDT electrode to 0.5 ≦ η ≦ 0.7. A maximum frequency deviation of 830 ppm can be realized at room temperature (25 ° C.).

  On the other hand, a SAW resonator is known in which grooves or grooves are formed on the surface of a quartz substrate between electrode fingers constituting an IDT and between conductor strips constituting a reflector (see, for example, Patent Document 7 and Non-Patent Document 1). ). In Patent Document 7, an IDT and a reflector are formed of aluminum electrodes on an ST cut X propagation quartz substrate, and between electrode fingers constituting an IDT on the surface of the quartz substrate and between conductor strips (electrode fingers) constituting a reflector. It is disclosed that a SAW resonator having a high Q value and a low capacitance ratio and having a low resonance resistance can be realized by forming a groove in a corresponding region. Furthermore, the patent document describes a structure in which the groove of the IDT and the groove of the reflector are made the same depth, and a structure in which the groove of the reflector is deeper than the groove of the IDT.

  Non-Patent Document 1 describes the characteristics of a group-type SAW resonator using an ST cut quartz substrate. The frequency-temperature characteristic changes depending on the depth of the groove formed in the crystal surface not covered with the electrode of the SAW propagation substrate, and the apex temperature Tp of the upward convex quadratic curve becomes lower as the groove becomes deeper. It is reported to become.

  A method of adjusting the frequency by adjusting the effective film thickness by forming a groove in a piezoelectric substrate such as quartz is well known to those skilled in the art (see, for example, Patent Documents 8 to 11). In the SAW device described in Patent Document 8, the surface of the piezoelectric substrate on which the IDT is formed is etched under the condition that the etching rate of the piezoelectric substrate is larger than the etching rate of the IDT, and fine adjustment is performed so that the frequency is lowered. Similarly, in Patent Documents 9 to 11, the frequency of the SAW device is shifted to the low frequency side by dry etching using the IDT formed on the surface of the piezoelectric substrate as a mask.

  Furthermore, in a transversal SAW filter, it is known that the propagation speed is apparently reduced by etching a piezoelectric substrate surface between electrode fingers of an IDT electrode to form a groove (for example, see Patent Document 12). reference). As a result, the electrode finger pitch of the IDT electrode can be reduced without changing the basic design of the SAW filter, and the chip can be downsized.

  Further, in a SAW resonator that excites a slip wave called SSBW (Surface Skimming Bulk Wave), the rotation Y-cut, the cut angle of −43 ° to −52 °, and the slip wave propagation direction in the Z′-axis direction (Eulerian angle (φ, θT, ψ) = (0 °, 38 ≦ θ ≦ 47, 90 °)) and an IDT electrode having a normalized electrode film thickness (H / λ) of 2.0 ≦ H / λ ≦ 4.0% It is known that the frequency temperature characteristic of a cubic curve can be realized by forming aluminum with aluminum (see, for example, Patent Document 13). A slip wave (SH wave) confines its vibration energy directly under the electrode and propagates directly under the surface of the piezoelectric substrate. Therefore, compared with an ST-cut quartz SAW device in which SAW propagates along the substrate surface, There is a problem in that the reflection efficiency is poor and it is difficult to achieve miniaturization and a high Q value.

  In order to solve this problem, the surface of a rotated Y-cut quartz substrate with Euler angles (φ, θ, ψ) = (0 °, −64 ° <θ <−49.3 °, 85 ° ≦ ψ ≦ 95 °) A SAW device that forms an IDT and a grating reflector and excites SH waves has been proposed (for example, see Patent Document 14). This SAW device is small in size, high Q value and excellent frequency stability by setting the electrode film thickness H / λ normalized by the SAW wavelength λ to 0.04 <H / λ <0.12. Is realized.

  Furthermore, in such a SAW device, in order to solve the problem that the Q value and the frequency stability are deteriorated due to the stress migration caused by the thick electrode film thickness, the crystal between the electrode fingers of the IDT is solved. It has been proposed to form a groove in a substrate (see, for example, Patent Document 15). When the depth of the groove is Hp and the film thickness of the IDT metal film is Hm, the electrode film thickness H / λ normalized by the SAW wavelength λ is 0.04 <H / λ <0.12. Since the apparent film thickness of the metal film can be reduced by setting the range of H = Hp + Hm), the SAW device suppresses frequency fluctuation due to stress migration during energization, has a high Q value, and has excellent frequency stability. Can be realized.

  In the mass production process of SAW devices, when the electrode finger of the IDT is formed on the surface of the quartz substrate by etching, if the electrode finger is thick, the line occupancy (line space ratio) η of the IDT is caused by side etching resulting from the etching. Variations are likely to occur. As a result, if the fluctuation amount of the frequency due to the temperature change of the SAW device occurs, the reliability and quality of the product are impaired. In order to solve this problem, an in-plane rotation ST-cut quartz substrate with Euler angles (φ, θ, ψ) = (0 °, 95 ° ≦ θ ≦ 155 °, 33 ° ≦ | ψ | ≦ 46 °) is employed. In addition, a SAW device is known in which a SAW stopband upper limit mode is excited to form a groove between electrode fingers on the surface of a quartz substrate between IDT electrode fingers (see, for example, Patent Document 16).

  Further, when the frequency temperature characteristic of the SAW device is a quadratic curve in the operating temperature range, it is difficult to minimize the frequency fluctuation range and to realize the inflection point. Therefore, in order to obtain a frequency temperature characteristic of a cubic curve, a SAW device has been proposed in which an IDT electrode is formed on an LST-cut quartz crystal substrate via a gap layer and a dielectric film to excite a leaky SAW. (For example, see Patent Document 17). The patent document describes that in a SAW device using Rayleigh waves, a quartz substrate having a cut angle that realizes frequency temperature characteristics as indicated by a cubic curve could not be found.

  Furthermore, in an ST-cut quartz SAW resonator or the like, an IDT and a reflector are placed on the surface of the quartz substrate with respect to the direction of the SAW phase velocity in order to increase the Q value without deteriorating the excellent frequency temperature characteristics. Inclined IDTs are known that are arranged along the direction of power flow angle PFA ± 3 ° (see, for example, Patent Documents 18 and 19). Since the SAW device composed of this tilted IDT can efficiently reflect the SAW with the reflector by arranging the IDT and the reflector so as to cover the traveling direction of the SAW phase and the traveling direction of the vibration energy, It is possible to efficiently confine energy and further increase the Q value.

Japanese Patent No. 326684 JP 2002-100959 A JP 2006-148622 A JP 2007-208771 A JP 2007-267033 A JP 2007-300287 A Japanese Patent Publication No. 2-7207 (Japanese Patent Laid-Open No. 57-5418) Japanese Patent Laid-Open No. 2-189011 JP-A-5-90865 Japanese Patent Laid-Open No. 1-231412 JP-A-61-92011 Japanese Patent Laid-Open No. 10-270974 Japanese Patent Publication No. 1-334411 Republished WO2005 / 099089A1 JP 2006-203408 A JP 2009-225420 A Japanese Patent No. 3851336 Japanese Patent No. 3216137 JP-A-2005-204275

Manufacturing conditions and characteristics of groove-type SAW resonators (Electrotechnical Society Technical Report MW82-59 (1982))

  As described above, many factors are related to the frequency temperature characteristics of the SAW device, and various devices have been devised to improve the frequency temperature characteristics. In particular, in a SAW device using Rayleigh waves, it is considered that increasing the film thickness of the electrode fingers constituting the IDT contributes to the improvement of frequency temperature characteristics. Simply increasing the electrode film thickness of the IDT causes problems such as stress migration during energization and frequency stability degradation due to line occupancy fluctuations due to side etching during IDT formation. As a countermeasure, it is effective to form a groove between IDT electrode fingers on the surface of the quartz substrate so as to reduce the frequency variation by increasing the effective film thickness while reducing the electrode film thickness.

  However, all of the above-described SAW devices, except for the SAW device of Patent Document 13 that excites a leaky SAW, show the frequency temperature characteristics in the operating temperature range as a quadratic curve, so the frequency fluctuation range is made sufficiently small. The inflection point has not been realized. For this reason, it is not possible to sufficiently meet the demands such as expansion of the operating temperature range and high accuracy for recent SAW devices and long-term operation stability in an environment where temperature changes are severe.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and its purpose is to exhibit excellent frequency-temperature characteristics in which the amount of frequency fluctuation is extremely small in the operating temperature range, so that the temperature fluctuates greatly. An object of the present invention is to provide a SAW device such as a resonator or an oscillator having excellent environmental resistance characteristics that stably operate even under an environment and capable of realizing a high Q value.

  In order to achieve the above object, the inventor of the present application employs an in-plane rotated ST-cut quartz substrate, forms an IDT for exciting SAW in the upper end mode of the stop band on the surface, and between the electrode fingers constituting the IDT In the SAW resonator in which the surface of the quartz substrate is recessed to form grooves, parameters such as SAW wavelength λ, groove depth G, IDT electrode film thickness H, line occupancy η of the electrode fingers, and frequency temperature The relationship with characteristics was verified. As a result, a novel SAW resonator has been devised that can achieve a minimum frequency fluctuation range and an inflection point in the operating temperature range.

…（１）、及び

…（２）
の関係を満たすことを特徴とする。 The SAW resonator according to the novel embodiment (hereinafter referred to as the SAW resonator according to the present embodiment) has a Euler angle (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ) in the first mode. ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °), and a quartz crystal positioned between the electrode fingers constituting the IDT and exciting the SAW in the stop band upper end mode. It has a groove between electrode fingers with a recessed substrate,
When the wavelength of the SAW is λ and the depth of the inter-electrode finger groove is G, the relationship of 0.01λ ≦ G is satisfied,
When the IDT line occupancy is η, the inter-electrode finger groove depth G and the line occupancy η

... (1) and

... (2)
It is characterized by satisfying the relationship.

  The SAW resonator according to this embodiment is characterized in that, in the second mode, in addition to the first mode, the depth G of the inter-electrode finger groove satisfies a relationship of 0.01λ ≦ G ≦ 0.0695λ. And By setting the depth G of the inter-electrode finger groove within this range, the amount of frequency fluctuation within the operating temperature range (for example, −40 ° C. to + 85 ° C.) can be suppressed to be small, and the depth between the inter-electrode fingers is manufactured. Even if the above variation occurs, the shift amount of the resonance frequency between the individual SAW resonators can be suppressed within a correctable range.

  Furthermore, the SAW resonator of the present embodiment has a relationship of 0 <H ≦ 0.035λ in the third aspect, in addition to the first or second aspect, where the electrode film thickness of the IDT is H. It is characterized by satisfying. As a result, good frequency temperature characteristics are realized within the operating temperature range, and deterioration of environmental resistance characteristics that can occur when the electrode film thickness is increased is prevented in advance.

…（３）
の関係を満たすことを特徴とする。これにより、周波数温度特性の二次温度係数を小さく抑制することができる。 Further, the SAW resonator of the present embodiment has a line occupation ratio η in the fourth aspect, in addition to the third aspect,

... (3)
It is characterized by satisfying the relationship. Thereby, the secondary temperature coefficient of a frequency temperature characteristic can be suppressed small.

  Furthermore, in the fifth aspect, the SAW resonator according to the present embodiment has a sum of the inter-electrode finger groove depth G and the electrode film thickness H of 0. 5 in addition to the third or fourth aspect. 0407λ ≦ G + H is satisfied. Thereby, a Q value higher than the conventional case using resonance in the lower end mode of the stop band without providing a groove between the electrode fingers can be obtained.

  FIG. 1 shows a typical example of the SAW resonator of this embodiment. As shown in FIG. 1A, a SAW resonator 1 of this embodiment includes a rectangular quartz substrate 2, an IDT 3 formed on the main surface of the quartz substrate, and a pair of reflectors 4 and 4, respectively. Have.

  The quartz substrate 2 has an in-plane represented by Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °). A rotating ST-cut quartz substrate is used. Here, the Euler angle will be described. A substrate represented by Euler angles (0 °, 0 °, 0 °) is a Z-cut substrate having a main surface perpendicular to the Z-axis. Here, φ of Euler angles (φ, θ, ψ) relates to the first rotation of the Z-cut substrate, and the positive rotation angle is the direction rotating from the + X axis to the + Y axis side with the Z axis as the rotation axis. The first rotation angle. Euler's angle θ is related to the second rotation performed after the first rotation of the Z-cut substrate. The X-axis after the first rotation is the rotation axis, and the rotation from the + Y axis after the first rotation to the + Z-axis is performed. This is a second rotation angle in which the direction to perform is a positive rotation angle. The cut surface of the piezoelectric substrate is determined by the first rotation angle φ and the second rotation angle θ. The Euler angle ψ relates to the third rotation performed after the second rotation of the Z-cut substrate. The Z axis after the second rotation is used as the rotation axis, and the second rotation from the + X axis after the second rotation. This is a third rotation angle in which the direction of rotation toward the + Y-axis side after rotation is a positive rotation angle. The propagation direction of SAW is represented by a third rotation angle ψ with respect to the X axis after the second rotation.

  As shown in FIG. 2, the in-plane rotation ST-cut quartz substrate has three crystal axes that are orthogonal to each other, that is, an electric axis, a mechanical axis, and an optical axis expressed by an X axis, a Y axis, and a Z axis, respectively. The XZ plane 5a perpendicular to the axis is rotated by an angle θ ′ (°) from the + Z axis to the −Y axis direction about the X axis as the rotation axis, and is perpendicular to the Y ′ axis of the coordinate axes (X, Y ′, Z ′). Cut out from the wafer 5 having the XZ 'plane. The quartz substrate 2 is further moved to a new coordinate axis (X ′, Y ′, Z ″) rotated by an angle + ψ (or −ψ) (°) with the Y ′ axis as the rotation axis and the + Z ′ axis direction as the positive direction. Then, the crystal substrate 2 is cut out from the wafer 5 and separated into individual pieces.At this time, the long side (or short side) of the quartz crystal substrate 2 may be arranged along either the X′-axis direction or the Z ″ -axis direction. The angle θ ′ and the Euler angle θ have a relationship of θ ′ = θ−90 °.

  The IDT 3 includes a pair of comb-like electrodes 3a and 3b each composed of a plurality of electrode fingers 6a and 6b and having their base ends connected by bus bars 7a and 7b. The electrode fingers 6a and 6b are arranged in such a direction that the extension direction thereof is orthogonal to the SAW propagation direction X ′ excited by the IDT. The electrode fingers 6a of the one comb-like electrode 3a and the electrode fingers 6b of the other comb-like electrode 3b are arranged at a constant pitch alternately and at a predetermined interval. As shown in FIG. 1 (B), the surface of the quartz substrate 2 exposed between the electrode fingers 6a and 6b has concave grooves 8 between the electrode fingers each having a certain depth by removing the surface by etching or the like. It is installed.

  The pair of reflectors 4 and 4 are arranged outside the IDT 3 along the SAW propagation direction X ′ so as to sandwich the IDT from both sides. Each reflector 4 includes a plurality of conductor strips 4a and 4a arranged at a constant pitch in the SAW propagation direction X ′. Each conductor strip is arranged in a direction in which the extension direction thereof is orthogonal to the SAW propagation direction X ′, like the electrode fingers of the IDT 3. As shown in FIG. 1B, a groove 9 between the conductor strips having a certain depth is formed on the surface of the quartz substrate 2 exposed between the conductor strips 4a and 4a by removing the surface by etching or the like. It is installed.

  In the present embodiment, the electrode fingers 6a and 6b and the conductor strips 4a and 4a are formed to have the same film thickness H by a metal film using, for example, Al or an alloy mainly composed of Al. The electrode finger groove 8 and the conductor strip groove 9 are formed at the same depth G. The surface of the quartz substrate is similarly removed between the outermost electrode finger 6a (or 6b) of the IDT 3 and the conductor strips of the reflectors 4 and 4 adjacent to the electrode finger 6a (or 6b). The groove is recessed.

  The SAW resonator 1 configured as described above excites a Rayleigh-type SAW having vibration displacement components in both the X′-axis direction and the Y′-axis direction of the quartz crystal substrate 2. Since the Euler angle quartz crystal substrate 2 described above has a SAW propagation direction deviated from the X axis, which is the crystal axis of the quartz crystal, it is possible to excite SAW in the stop band upper end mode.

The Euler angles (φ, θ, ψ) of the quartz substrate 2 described above were selected as follows. In general, the frequency temperature characteristic of a SAW resonator is expressed by the following equation.
Δf = α × (T−T0) + β × (T−T0) ²
Where Δf is the amount of frequency change (ppm) between temperature T and apex temperature T0, α is the primary temperature coefficient (ppm / ° C.), β is the secondary temperature coefficient (ppm / ° C. 2), T is the temperature, T 0 Is the temperature at which the frequency is maximum (apex temperature). The absolute value of the secondary temperature coefficient β is set to a minimum, preferably 0.01 (ppm / ° C. ² ) or less, and more preferably substantially zero, so that the frequency temperature characteristic shows a cubic curve. For example, high frequency stability can be obtained by reducing the frequency fluctuation amount even in a wide operating temperature range.

First, the Euler angles of the quartz substrate 2 are set to (0 °, 123 °, ψ), and the Euler angles ψ and the distance between the electrode fingers when a line occupancy η satisfying β = ± 0.01 (ppm / ° C. ² ) is obtained. The relationship with the groove depth G was simulated. Here, the Euler angle ψ was appropriately selected so that the absolute value of the secondary temperature coefficient β was 0.01 (ppm / ° C. ² ). As a result, the range of Euler angles ψ where the secondary temperature coefficient β can be set to −0.01 ≦ β ≦ + 0.01 under the above conditions could be determined as 43 ° <ψ <45 °.

  The line occupation ratio η of IDT 3 is a value obtained by dividing the electrode finger width L by the electrode finger pitch λ / 2 (= L + S) as shown in FIG. FIG. 1D shows the IDT 3 line in a trapezoidal cross section that would be formed when the electrode fingers 6 a and 6 b and the inter-electrode finger groove 8 of the IDT 3 were manufactured by a photolithography technique and an etching technique. This is for explaining a method of specifying the occupation ratio η. In this case, the line occupancy η is an electrode measured from the bottom of the electrode finger groove 8 at a height that is ½ of the total value (G + H) of the depth G of the electrode finger groove and the electrode film thickness H. Calculation is based on the finger width L and the inter-electrode finger groove width S.

Next, the crystal substrate 2 is set to (0, θ, ψ) in terms of the cut angle and SAW propagation direction in terms of Euler angle, the inter-electrode finger groove depth G is 0.04λ, and the electrode finger film thickness H is 0.02λ. The change of the secondary temperature coefficient β with respect to the Euler angle θ was simulated by setting the line occupation ratio η to 0.6383 according to the above equation (3). Here, the Euler angle ψ was appropriately selected within the above-mentioned range of 43 ° <ψ <45 ° so as to minimize the absolute value of the secondary temperature coefficient β based on the set angle of the angle θ. As a result, if the Euler angle θ is within the range of 117 ° ≦ θ ≦ 142 °, the secondary can be obtained even if the electrode finger film thickness H, the electrode finger groove depth G, and the line occupancy η are changed. It was confirmed that the absolute value of the temperature coefficient β was in the range of 0.01 (ppm / ° C. ² ).

Next, the quartz substrate 2 is set to Euler angle display (φ, 123 °, 43.77 °), the inter-electrode finger groove depth G is 0.04λ, the electrode finger film thickness H is 0.02λ, and the line occupation The change of the secondary temperature coefficient β with respect to the Euler angle φ was simulated by setting the rate η to 0.65. As a result, if the Euler angle φ is in the range of −1.5 ° ≦ φ ≦ + 1.5 °, the absolute value of the secondary temperature coefficient β is in the range of 0.01 (ppm / ° C. ² ). It was confirmed.

Furthermore, a highly desirable relationship between Euler angles θ and ψ that minimizes the amount of frequency fluctuation in the operating temperature range (−40 ° C. to + 85 ° C.) was obtained by simulation. Also in this case, the depth G between the electrode fingers and the film thickness H of the electrode fingers were set to G = 0.04λ and H = 0.02λ, respectively. As a result, the Euler angle ψ increased so as to draw a cubic curve in the range of the Euler angle θ described above. This relationship can be approximated by the following equation.

  Thus, the Euler angle ψ becomes ψ = 42.79 ° when the lower limit value θ = 117 ° of the Euler angle θ, and becomes ψ = 49.57 ° when the upper limit value θ = 142 °. Therefore, the Euler angle ψ can be set to 42.79 ° ≦ ψ ≦ 49.57 ° within a range of 117 ° ≦ θ ≦ 142 °.

By setting the Euler angle of the quartz substrate 2 in this way, the SAW resonator 1 of the present embodiment has excellent frequency temperature characteristics in which the absolute value of the secondary temperature coefficient β is 0.01 (ppm / ° C. ² ) or less. Can be realized.

For the SAW resonator 1 of the present embodiment, frequency temperature characteristics were simulated under the following conditions.
-Basic data H of the SAW resonator 1 of this embodiment: 0.02λ
G: Change IDT line occupancy η: 0.6
Reflector line occupancy ηr: 0.8
Euler angles: (0 °, 123 °, 43.5 °)
IDT logarithm: 120
Electrode finger crossing width: 40λ (λ = 10 μm)
Number of reflectors (per one side): 60
Electrode finger tilt angle: None

  The simulation result is shown in FIG. As can be seen from the figure, the frequency-temperature characteristic shows a substantially cubic curve in the operating temperature range (−40 to + 85 ° C.), and the frequency fluctuation range can be suppressed to an extremely small fluctuation amount of 20 ppm or less.

ここで、Ｆは周波数、ＱはＱ値、γは容量比、ＣＩはＣＩ（クリスタルインピーダンス：Crystal Impedance）値、Ｍは性能指数（フィギュアオブメリット：Figure of Merit）である。 Table 1 below summarizes the frequency, equivalent circuit constants, and static characteristics of the SAW resonator 1 showing the frequency temperature characteristics of FIG.

Here, F is a frequency, Q is a Q value, γ is a capacitance ratio, CI is a CI (Crystal Impedance) value, and M is a figure of merit (Figure of Merit).

  The SAW resonator 1 is set so that the frequency ft2 at the upper end of the stop band of the IDT 3, the frequency fr1 at the lower end of the stop band of the reflector 4 and the frequency fr2 at the upper end of the stop band satisfy the relationship fr1 <ft2 <fr2. Is preferred. FIG. 4 shows the SAW reflection characteristics of the IDT 3 and the reflector 4 with respect to frequency. As shown in the figure, when the frequency ft2 is set between the frequency fr1 and the frequency fr2, the reflection coefficient of the reflector 4 becomes larger than the reflection coefficient of the IDT 3 at the frequency ft2. As a result, the stopband upper end mode SAW excited from the IDT 3 is reflected from the reflector 4 to the IDT 3 side with a high reflection coefficient. Therefore, the SAW vibration energy can be efficiently confined, and the low-loss SAW resonator 1 can be realized.

  In addition, regarding the Q value of the SAW resonator 1, the relationship between the height of the electrode fingers 6a and 6b, that is, the film thickness H, and the size of the step formed by the depth G of the inter-electrode finger groove 8 (G + H) is simulated. It verified by. For comparison, a relationship between the Q value and the height of the electrode finger, that is, the film thickness was simulated under the following conditions for a conventional SAW resonator that does not provide a groove between the electrode fingers and uses resonance in the stop band upper end mode.

-Basic data H of conventional SAW resonator H: Change G: Zero (none)
IDT line occupancy η: 0.4
Reflector line occupancy ηr: 0.3
Euler angles (0 °, 123 °, 43.5 °)
IDT logarithm: 120
Electrode finger crossing width: 40λ (λ = 10 μm)
Number of reflectors (per one side): 60
Electrode finger tilt angle: None

  The simulation result is shown in FIG. In the figure, a thick line indicates the SAW resonator 1 of the present embodiment, and a thin line indicates a conventional SAW resonator. As can be seen from the figure, the SAW resonator 1 of the present embodiment obtains a higher Q value than the conventional SAW resonator in the region where the step (G + H) is 0.0407λ (4.07% λ) or more. Can do.

However, as described above, the SAW resonator having the IDT structure provided with the inter-electrode finger groove may deteriorate the electromechanical coupling coefficient k ² as compared with the IDT structure SAW resonator not provided with the inter-electrode finger groove. is there. As shown in FIG. 6A, the SAW resonator 1 in FIG. 1 has an electric field E generated between adjacent electrode fingers 6a and 6b, where V = the voltage applied to the IDT 3, and E = V / (2G + S ). On the other hand, as shown in FIG. 6B, in the case of the SAW resonator 1 ′ having the IDT structure without the inter-electrode finger groove, the electric field E ′ generated between the adjacent electrode fingers 6a ′ and 6b ′ is E ′ = V / S. When the same voltage V is applied to the IDT, the electric field E is smaller than the electric field E ′ by the distance between the adjacent electrode fingers 6a and 6b being twice as long as the depth G of the inter-electrode finger groove 8. .

When an electric field generated between the electrode fingers decreases, the applied conversion efficiency from electrical energy to the surface wave energy, that is, the electromechanical coupling coefficient k ² deteriorates. Electromechanical coupling coefficient k ^2, the capacitance ratio gamma, the following relationship between the equivalent series resistance (CI value).
k ² ∝ 1 / γ ∝ 1 / CI
Degradation of the electromechanical coupling coefficient k ^2, since increasing the capacitance ratio γ and the CI value of the SAW resonator, if this is applied to a voltage controlled SAW oscillator (VCSO), variable width of frequency narrows There is a risk that stable and excellent oscillation characteristics cannot be obtained.

Therefore, in an SAW device with an IDT structure provided with an inter-electrode finger groove, while maintaining excellent frequency temperature characteristics in the operating temperature range, when used in an oscillator, it can exhibit stable and excellent oscillation characteristics. it is desirable to improve the electromechanical coupling coefficient k ^2. Considering practical use conditions as an oscillator such as VCSO in particular, an electromechanical coupling coefficient k ^{2 of} 0.052% or more while suppressing the frequency fluctuation amount Δf to 20 ppm or less in a temperature range of −40 to 85 ° C., for example. It is desirable to realize.

Therefore, the inventors of the present invention, with respect to the SAW resonator 1 of the present embodiment shown in FIG. 1, the depth G of the inter-electrode finger groove 8, the electrode film thickness H and the line occupancy η of the IDT 3, As a parameter, the relationship with the electromechanical coupling coefficient k ² was verified. As a result, by appropriately setting the Euler angle of the quartz substrate 2, the depth G of the inter-electrode finger groove, and the electrode film thickness H of the IDT, excellent frequency temperature characteristics and improvement of the electromechanical coupling coefficient k ² can be achieved. We found that it can be realized at the same time.

Further, as practical use conditions of the oscillator, the above-described frequency fluctuation amount Δf ≦ 20 ppm and the electromechanical coupling coefficient k ² ≧ 0.052% were set as target values, and the verification was advanced. In particular, with respect to the SAW resonator 1 of the present embodiment, the Euler angles φ and θ of the quartz substrate 2 are fixed to φ = 0 ° and θ = 123 °, which are excellent in frequency temperature characteristics, respectively, and the above-described parameters and electromechanical coupling to verify the relationship between the coefficient k ^2. As a result, it has been found that the target value can be achieved by appropriately setting the Euler angle ψ and the line occupation ratio η of the IDT in addition to the electrode finger groove depth G and the IDT electrode film thickness H. It was. The present inventors have conceived the present invention based on these findings.

The SAW device of the present invention comprises a quartz substrate with Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 122 ° ≦ θ ≦ 126 °, ψ),
An IDT comprising a plurality of electrode fingers provided on the principal surface of the quartz substrate and exciting a surface acoustic wave in a stop band upper end mode;
A plurality of inter-electrode finger grooves recessed in the surface of the quartz substrate between adjacent electrode fingers of the IDT;
When the SAW wavelength is λ, the inter-electrode finger groove depth G and the electrode finger film thickness H are 1% ≦ G / λ ≦ 4% and 1% ≦ H / λ ≦ 4%, respectively. It is characterized by satisfaction.

  In this way, by setting the Euler angle of the quartz substrate to be used, the depth G of the interelectrode finger groove of the IDT, and the film thickness H of the electrode finger, while maintaining excellent frequency temperature characteristics in the operating temperature range, It is possible to realize a SAW device having an excellent oscillation stability by improving the mechanical coupling coefficient as compared with the prior art and suppressing the capacitance ratio and the CI value. Furthermore, by applying this SAW device, the frequency variable width of the VCSO can be expanded as compared with the conventional case.

  In some embodiments, the line occupancy η of the IDT can be determined such that the electromechanical coupling factor is 0.052% or more within the operating temperature range, thereby practically reducing the capacitance ratio and CI value. Since it can be suppressed low, more excellent oscillation stability can be obtained.

Furthermore, in one embodiment, the line occupancy η of the IDT is in an orthogonal coordinate with the line occupancy η (%) as the vertical axis and the electrode finger groove depth G (% λ) as the horizontal axis.
When the electrode finger film thickness H is 1.0 to 1.5% λ, each point (1.0, 0.757), (2.0, 0.703), (3.0, 0.679), (4.0, 0.650), (4.0, 0.642), (3.0, 0.659), (2.0, 0.686), (1.0, 0.754), (1.0, 0.757) within the range enclosed by the polygon,
When the electrode finger film thickness H is 1.5 to 2.0% λ, each point (1.0, 0.749), (2.0, 0.690), (3.0, 0.676), (4.0, 0.650), (4.0, 0.637), (3.0, 0.657), (2.0, 0.684), (1.0, 0.748), (1.0, 0.749) is within the range surrounded by the polygon connecting,
When the electrode finger film thickness H is 2.0 to 2.5% λ, each point (1.0, 0.732), (2.0, 0.691), (3.0, 0.670), (4.0, 0.641), (4.0, 0.629), (3.0, 0.651), (2.0, 0.680), (1.0, 0.730), (1.0, 0.732) is within the range enclosed by the polygon,
When the electrode finger film thickness H is 2.5 to 3.0% λ, each point (1.0, 0.732), (2.0, 0.669), (3.0, 0.658), It is within the range surrounded by the polygon connecting (3.0, 0.642), (2.0, 0.667), (1.0, 0.710), (1.0, 0.732) ,
When the electrode finger film thickness H is 3.0 to 3.5% λ, each point (1.0, 0.692), (2.0, 0.669), (3.0, 0.640), It is within the range surrounded by the polygon connecting (3.0, 0.629), (2.0, 0.655), (1.0, 0.690), (1.0, 0.692) ,
When the electrode finger film thickness H is 3.5 to 4.0% λ, each point (1.0, 0.679), (2.0, 0.663), (3.0, 0.620), It is within the range surrounded by the polygon connecting (3.0, 0.615), (2.0, 0.642), (1.0, 0.672), (1.0, 0.679) ,And,
The Euler angle ψ of the quartz substrate is an orthogonal coordinate having the Euler angle ψ (°) as the vertical axis and the electrode finger groove depth G (% λ) as the horizontal axis.
When the electrode finger film thickness H is 1.0 to 1.5% λ, each point (1.0, 43.63), (2.0, 43.68), (3.0, 43.72), (4.0, 43.78), (4.0, 43.71), (3.0, 43.67), (2.0, 43.66), (1.0, 43.62), (1.0, 43.63) is within the range enclosed by the polygon,
When the electrode finger film thickness H is 1.5 to 2.0% λ, each point (1.0, 43.58), (2.0, 43.62), (3.0, 43.69), (4.0, 43.78), (4.0, 43.72), (3.0, 43.64), (2.0, 43.60), (1.0, 43.57), (1.0, 43.58) is within a range surrounded by a polygon connecting,
When the electrode finger film thickness H is 2.0 to 2.5% λ, each point (1.0, 43.56), (2.0, 43.60), (3.0, 43.68), (4.0, 43.78), (4.0, 43.76), (3.0, 43.64), (2.0, 43.57), (1.0, 43.54), (1.0, 43.56) is within the range surrounded by the polygon connecting,
When the electrode finger film thickness H is 2.5 to 3.0% λ, each point (1.0, 43.50), (2.0, 43.58), (3.0, 43.68), It is within the range surrounded by the polygon connecting (3.0, 43.66), (2.0, 43.55), (1.0, 43.49), (1.0, 43.50) ,
When the electrode finger film thickness H is 3.0 to 3.5% λ, each point (1.0, 43.49), (2.0, 43.58), (3.0, 43.70), Within the range represented by the polygon connecting (3.0, 43.69), (2.0, 43.54), (1.0, 43.45), (1.0, 43.49) Yes,
When the electrode finger film thickness H is 3.5 to 4.0% λ, each point (1.0, 43.42), (2.0, 43.55), (3.0, 43.73), It is within the range surrounded by the polygon connecting (3.0, 43.72), (2.0, 43.55), (1.0, 43.42), (1.0, 43.49). It is characterized by that.

Thus, by specifying the IDT line occupancy η and the Euler angle ψ of the quartz substrate, the frequency variation Δf ≦ 20 ppm and the electromechanical coupling coefficient k ² ≧ 0.052% can be achieved. Thus, a SAW device capable of sufficiently suppressing the capacitance ratio and the CI value and exhibiting excellent oscillation stability can be obtained.

を満足することにより、周波数温度特性の二次温度係数をより小さく抑制できるので、周波数変動量をより小さくしかつより優れた三次曲線の周波数温度特性が得られる。 In another embodiment, the IDT line occupancy η is

By satisfying the above, the secondary temperature coefficient of the frequency temperature characteristic can be further reduced, so that the frequency fluctuation characteristic can be further reduced and a more excellent cubic temperature frequency temperature characteristic can be obtained.

  In another embodiment, it is preferable that the sum of the inter-electrode finger groove depth G and the electrode finger film thickness H satisfies 0.0407λ ≦ G + H. Thereby, the present invention using the resonance in the stop band upper end mode can obtain a higher Q value than the conventional SAW resonator using the resonance in the stop band lower end mode without providing a groove between the electrode fingers of the IDT.

  In still another embodiment, the angle formed between the first direction orthogonal to the electrode fingers and the conductor strip and the electric axis of the quartz substrate is the Euler angle ψ of the quartz substrate, and at least a part of the IDT and the reflector is The Q value can be further improved by arranging in the second direction that intersects the direction 1 with an angle δ and the angle δ is within the range of the power flow angle ± 1 ° of the quartz substrate.

  In another embodiment, by further including an oscillation circuit for driving the IDT, a SAW oscillator having an extremely small frequency variation, a low CI value and excellent oscillation stability in a wide operating temperature range is obtained. be able to.

(A) is a plan view showing the configuration of the SAW resonator of this embodiment, (B) is a partially enlarged longitudinal sectional view, (C) is a partially enlarged view of (B), and (D) is a diagram. The partial expanded sectional view similar to FIG. (C) which shows the shape of the groove | channel between electrode fingers formed by photolithography and an etching technique. Explanatory drawing which shows typically the quartz substrate of this embodiment. The diagram which shows the frequency temperature characteristic of this embodiment. The diagram which shows the SAW reflection characteristic of IDT of this embodiment, and a reflector. The diagram which shows the relationship between the level | step difference between electrode fingers of this embodiment, and Q value. FIGS. 4A and 4B are partial enlarged cross-sectional views respectively showing an electric field generated between adjacent electrode fingers of the SAW resonator of the present embodiment and a SAW resonator having no inter-electrode finger groove. The diagram which shows the relationship between the depth of the electrode finger groove | channel of the SAW resonator of 1st Example by this invention, and an electromechanical coupling coefficient. The diagram which shows the relationship between the line occupation rate of IDT of 1st Example, and an electromechanical coupling coefficient. FIGS. 5A and 5B are diagrams respectively showing frequency temperature characteristics at the depth G / λ = 1% and 2% of the inter-electrode finger groove of the first embodiment. (C) and (D) are diagrams respectively showing frequency temperature characteristics at the depth G / λ = 3% of the inter-electrode finger groove of the first embodiment, and 4%. (A), (B) are the electrode finger film thickness H / λ = 1.0 to 1.5% of the first embodiment, the Euler angle ψ, and the line occupancy ratio of IDT. The diagram which shows each relationship. (A), (B) shows the electrode finger thickness H / λ = 1.5 to 2.0% of the first embodiment, the Euler angle ψ, and the line occupancy ratio of IDT. The diagram which shows each relationship. (A) and (B) are the electrode finger film thickness H / λ = 2.0 to 2.5% of the first embodiment SAW resonator, and the line occupancy of the electrode finger groove depth and Euler angles ψ and IDT. The diagram which shows the relationship with a rate, respectively. (A), (B) is the figure of electrode finger film thickness H / λ = 2.5-3.0% of the first embodiment, Euler angle ψ, IDT line occupancy The diagram which shows each relationship. (A), (B) are the electrode finger film thickness H / λ = 3.0 to 3.5% of the first embodiment, the Euler angle ψ, and the line occupancy ratio of IDT. The diagram which shows each relationship. (A), (B) are the electrode finger film thickness H / λ = 3.5 to 4.0% of the first embodiment, the Euler angle ψ, and the line occupancy ratio of IDT. The diagram which shows each relationship. (A), (B) figure is a diagram which respectively shows the amount of frequency fluctuations regarding the Euler angle (theta) of Table 9, and the change of an electromechanical coupling coefficient. (A), (B) is a top view which shows the SAW resonator of 2nd Example of this invention which has inclination type IDT of a respectively different structure. (A) is a plan view showing a SAW oscillator according to the present invention, and (B) is a longitudinal sectional view taken along line BB.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same or similar reference numerals.

  Since the basic configuration of the first embodiment of the SAW resonator according to the present invention is the same as that of the SAW resonator 1 shown in FIG. 1, it will be described with reference to FIG. That is, the SAW resonator 1 according to the first embodiment includes a rectangular quartz substrate 2, an IDT 3 formed on the main surface of the quartz substrate, and a pair of reflectors 4 and 4. As the quartz substrate 2, a quartz substrate having Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 122 ° ≦ θ ≦ 126 °, ψ) is used.

  The IDT 3 includes a pair of comb-like electrodes 3a and 3b each composed of a plurality of electrode fingers 6a and 6b and having their base ends connected by bus bars 7a and 7b. The electrode fingers 6a and 6b are arranged such that their extending directions are orthogonal to the SAW propagation direction excited by the IDT. The electrode fingers 6a of the one comb-like electrode 3a and the electrode fingers 6b of the other comb-like electrode 3b are arranged at a constant pitch alternately and at a predetermined interval. On the surface of the quartz crystal substrate 2 exposed between the electrode fingers 6a and 6b, a groove 8 between the electrode fingers having a fixed depth is formed by removing the surface by etching or the like.

  The pair of reflectors 4 and 4 are arranged outside the IDT 3 along the SAW propagation direction so as to sandwich the IDT from both sides. Each reflector 4 has a plurality of conductor strips (electrode fingers) 4a and 4a arranged at a constant pitch in the SAW propagation direction. The conductor strips are arranged such that the extending direction thereof is orthogonal to the SAW propagation direction. On the surface of the quartz crystal substrate 2 exposed between the conductor strips 4a, 4a, a groove 9 between conductor strips having a predetermined depth is formed by removing the surface by etching or the like.

  The electrode fingers and the conductor strips are formed with the same film thickness H, for example, using a metal film made of Al or an alloy mainly composed of Al. The electrode finger grooves and the conductor strip grooves are formed at the same depth G. Similarly, between the innermost conductor strip of each of the reflectors 4 and 4 and the outermost electrode finger 6a (or 6b) of the IDT 3 adjacent thereto, the quartz substrate surface is deleted, A groove of the same depth is recessed.

  By configuring in this way, the SAW resonator 1 excites a Rayleigh type (Rayleigh type) SAW having vibration displacement components in both the X′-axis direction and the Y′-axis direction of the quartz crystal substrate 2. By using the Euler angle quartz crystal substrate 2 described above, the SAW propagation direction is deviated from the X axis, which is the crystal axis of the quartz crystal, so that the SAW in the stop band upper end mode can be excited.

In this embodiment, when the depth G of the inter-electrode finger groove 8 and the film thickness H of the electrode fingers 6a, 6b are λ, the wavelength of the SAW excited by the IDT 3 is 1% ≦ G / λ ≦ 4% and 1% ≦ H / λ ≦ 4% (4)
Are set to satisfy each. Within this setting range of H / λ, G / λ was changed within the setting range, and the electromechanical coupling coefficient of the SAW resonator 1 of this example was calculated by simulation. In this example, the Euler angles φ and θ of the quartz substrate 2 were fixed to φ = 0 ° and θ = 123 °.

In FIG. 7, seven film thickness conditions are set for every 0.5% of the electrode finger film thickness in the range of H / λ = 1% to 4%, and the depth of the inter-electrode finger groove G is set for each film thickness condition. / λ = 1% ~4% of varied for each 1.0% range, shows the result of calculating the electromechanical coupling coefficient k ² by simulation. As can be seen from the figure, in all of the film thickness conditions, the electromechanical coupling coefficient k ² is represented by the curve of the convex upward within the setting range of G / lambda.

This is because, when the above-described conditional expression (4) is satisfied, the electromechanical coupling coefficient k ² has a maximum value within the set range of G / λ, and the electromechanical coupling coefficient before and after the maximum value. It shows that the range of high k ² is present. In particular, when applied as an oscillator for VCSO such, practically are preferred to exhibit stable oscillation properties, it can be seen that can realize the electromechanical coupling coefficient k ² of more than 0.052%.

8, in the case of satisfying the above-mentioned conditional expression (4) shows the change in electromechanical coupling coefficient k ² relates η line occupying ratio of the IDT 3. As can be seen, practically there is preferably 0.052% or more high electromechanical coupling coefficient k ² ranges, in the range, the electromechanical coupling coefficient k ² is generally in the gentle curve of the upwardly convex It is represented.

  Next, for the SAW resonator 1 of the present example satisfying the conditional expression (4), the operating temperature range was set to −40 ° C. to + 85 ° C., and the frequency temperature characteristics were calculated by simulation. The results are shown in FIGS. 9-1 (A) and (B) and FIGS. 9-2 (C) and (D). FIG. 9-1 (A) shows the electrode finger film thickness every 0.5% within the range of H / λ = 1% to 4% when the depth of the inter-electrode finger groove is G / λ = 1%. The results of calculating the frequency deviation (frequency fluctuation amount) ΔF by simulation for the seven film thickness conditions changed in FIG. FIGS. 9-1 (B) and FIGS. 9-2 (C) and (D) show the case where the depth of the inter-electrode finger groove is set to G / λ = 2%, 3% and 4%, respectively. Similarly to -1 (A), the results of calculating the frequency deviation (frequency fluctuation amount) ΔF by simulation for seven film thickness conditions of H / λ are shown. As can be seen from these measurement results, in any case, the frequency variation ΔF is suppressed within a small range of 20 ppm, and the SAW resonator 1 of the present example maintains excellent frequency temperature characteristics.

Therefore, as a practically preferable use condition when applied as an oscillator such as a VCSO, an electromechanical coupling coefficient k ² ≧ 0.052% and a frequency variation ΔF ≦ 20 ppm are set. For the SAW resonator 1 of this example, the range of the Euler angle ψ of the quartz crystal substrate 2 and the IDT 3 line occupancy ratio that satisfies this use condition was evaluated.

First, when H / λ = 1.0% and 1.5%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / λ (%)), Euler angle ψ (°), and IDT line occupancy η (%) were calculated. The calculation results are shown in Table 2 below.

FIG. 10A is a plot of each point in Table 2 on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. Each point (1.0, 43.63), (2.0, 43.68), (3.0, 43.72), (4.0, 43) plotted in the orthogonal coordinate system of FIG. .78), (4.0, 43.71), (3.0, 43.67), (2.0, 43.66), (1.0, 43.62), (1.0, 43 .63) in the order of polygons connecting in order satisfies the above-mentioned use conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm.

FIG. 10B is a plot of each point in Table 2 on orthogonal coordinates with the line occupancy η (%) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. . Each point (1.0, 0.757), (2.0, 0.703), (3.0, 0.679), (4.0, 0) plotted in the orthogonal coordinate system of FIG. .650), (4.0, 0.642), (3.0, 0.659), (2.0, 0.686), (1.0, 0.754), (1.0, 0 .757) in the order of the polygons connected in order satisfies the use condition. Accordingly, the SAW resonator 1 of this embodiment is defined by polygons shown in FIGS. 10A and 10B when the electrode finger film thickness H / λ = 1.0 to 1.5%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

Next, when H / λ = 1.5% and 2.0%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / Λ (%)), Euler angle ψ (°), and IDT line occupancy η (%). The calculation results are as shown in Table 3 below.

FIG. 11A is a graph in which each point of Table 3 is plotted on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. is there. Each point (1.0, 43.58), (2.0, 43.62), (3.0, 43.69), (4.0, 43) plotted in the orthogonal coordinate system of FIG. .78), (4.0, 43.72), (3.0, 43.64), (2.0, 43.60), (1.0, 43.57), (1.0, 43 .58) in the order of the polygons connecting in order satisfies k ² ≧ 0.052% and ΔF ≦ 20 ppm of the use conditions.

FIG. 11B is a plot of each point in Table 3 on orthogonal coordinates with the line occupancy η (%) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. . Each point (1.0, 0.749), (2.0, 0.690), (3.0, 0.676), (4.0, 0) plotted in the orthogonal coordinate system of FIG. .650), (4.0, 0.637), (3.0, 0.657), (2.0, 0.684), (1.0, 0.748), (1.0, 0 .749) in the order of the polygons connecting in order satisfies the use conditions. Therefore, the SAW resonator 1 of the present embodiment is defined by polygons shown in FIGS. 11A and 11B when the electrode finger film thickness H / λ = 1.5 to 2.0%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

When H / λ = 2.0% and 2.5%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / λ ( %)), Euler angle ψ (°), and IDT line occupancy η (%). The calculation results are shown in Table 4 below.

Similarly, FIG. 12A plots the points in Table 4 on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. is there. Each point (1.0, 43.56), (2.0, 43.60), (3.0, 43.68), (4.0, 43) plotted in the orthogonal coordinate system of FIG. .78), (4.0, 43.76), (3.0, 43.64), (2.0, 43.57), (1.0, 43.54), (1.0, 43 .56) in the order of polygons connecting in order satisfies the above-mentioned use conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm.

FIG. 12B is a plot of each point in Table 4 on orthogonal coordinates with the line occupancy η (%) on the vertical axis and the inter-electrode finger groove depth G (% λ) on the horizontal axis. . Each point (1.0, 0.732), (2.0, 0.691), (3.0, 0.670), (4.0, 0) plotted in the orthogonal coordinate system of FIG. .641), (4.0, 0.629), (3.0, 0.651), (2.0, 0.680), (1.0, 0.730), (1.0, 0 .732) in the order of the polygons connected in order satisfies the use condition. Therefore, the SAW resonator 1 of this embodiment is defined by polygons shown in FIGS. 12A and 12B when the electrode finger film thickness H / λ = 2.0 to 2.5%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

When H / λ = 2.5% and 3.0%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / λ ( %)), Euler angle ψ (°), and IDT line occupancy η (%). The calculation results are shown in Table 5 below.

FIG. 13A is a graph in which each point in Table 5 is plotted on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. is there. Each point (1.0, 43.50), (2.0, 43.58), (3.0, 43.68), (3.0, 43) plotted in the orthogonal coordinate system of FIG. .66), (2.0, 43.55), (1.0, 43.49), and (1.0, 43.50), the range surrounded by the polygon in order is k ^{2 of the} use condition. ≧ 0.052% and ΔF ≦ 20 ppm are satisfied.

FIG. 13B is a plot of each point in Table 5 on orthogonal coordinates with the line occupancy η (%) on the vertical axis and the inter-electrode finger groove depth G (% λ) on the horizontal axis. . Each point (1.0, 0.732), (2.0, 0.669), (3.0, 0.658), (3.0, 0) plotted in the orthogonal coordinate system of FIG. .642), (2.0, 0.667), (1.0, 0.710), and (1.0, 0.732) in a range enclosed by a polygon satisfy the use conditions. . Therefore, the SAW resonator 1 of this embodiment is defined by polygons shown in FIGS. 13A and 13B when the electrode finger film thickness H / λ = 2.5 to 3.0%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

When H / λ = 3.0% and 3.5%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / λ ( %)), Euler angle ψ (°), and IDT line occupancy η (%). The calculation results are shown in Table 6 below.

FIG. 14A is a graph in which the points in Table 6 are plotted on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. is there. Each point (1.0, 43.49), (2.0, 43.58), (3.0, 43.70), (3.0, 43) plotted in the orthogonal coordinate system of FIG. .69), (2.0,43.54), (1.0,43.45), area surrounded by a polygon connecting sequentially the (1.0,43.49) is of the use conditions ^{k 2} ≧ 0.052% and ΔF ≦ 20 ppm are satisfied.

FIG. 14B is a plot of each point in Table 6 on orthogonal coordinates with the line occupancy η (%) on the vertical axis and the inter-electrode finger groove depth G (% λ) on the horizontal axis. . Each point (1.0, 0.692), (2.0, 0.669), (3.0, 0.640), (3.0, 0) plotted in the orthogonal coordinate system of FIG. .629), (2.0, 0.655), (1.0, 0.690), and a range surrounded by a polygon connecting (1.0, 0.692) in order, satisfies the use condition. . Therefore, the SAW resonator 1 of this example is defined by polygons shown in FIGS. 14A and 14B when the electrode finger film thickness H / λ = 3.0 to 3.5%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

Further, when H / λ = 3.5% and 4.0%, the depth of the inter-electrode finger groove 8 where G / λ and the angle ψ are k ² = 0.052% and ΔF = 20 ppm (G / λ (%)), Euler angle ψ (°), and IDT line occupancy η (%) were calculated. The calculation results are as shown in Table 7 below.

FIG. 15A is a graph in which each point in Table 7 is plotted on orthogonal coordinates with the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. is there. Each point (1.0, 43.42), (2.0, 43.55), (3.0, 43.72), (3.0, 43) plotted in the orthogonal coordinate system of FIG. .73), (2.0,43.59), (1.0,43.49), area surrounded by a polygon connecting sequentially the (1.0,43.42) is of the use conditions ^{k 2} ≧ 0.052% and ΔF ≦ 20 ppm are satisfied.

FIG. 15B is a graph in which each point in Table 7 is plotted on orthogonal coordinates with the line occupancy η (%) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis. . Each point (1.0, 0.679), (2.0, 0.663), (3.0, 0.620), (3.0, 0) plotted in the orthogonal coordinate system of FIG. .615), (2.0, 0.642), (1.0, 0.672), and (1.0, 0.679) in a range surrounded by a polygon satisfying the use condition. . Accordingly, the SAW resonator 1 of this embodiment is defined by polygons shown in FIGS. 15A and 15B when the electrode finger film thickness H / λ = 3.5 to 4.0%. By setting the Euler angle ψ and the line occupancy η of the IDT within the ranges, the above usage conditions of k ² ≧ 0.052% and ΔF ≦ 20 ppm are always satisfied.

As described above, by specifying the line occupancy η of the IDT and the Euler angle ψ of the quartz substrate within the range of the Euler angles φ = 0 °, θ = 123 ° and the conditional expression (4), the frequency variation ΔF ≦ Use conditions of 20 ppm and an electromechanical coupling coefficient k ² ≧ 0.052% can be achieved. Therefore, even when applied to an oscillator, it is possible to obtain a SAW device that can sufficiently suppress the capacitance ratio and the CI value and exhibit excellent oscillation stability. In particular, when used in a VCSO, the frequency variable width can be expanded as compared with the conventional case.

を満足するように設定することが好ましい。これにより、周波数温度特性の二次温度係数をより小さく抑制できるので、周波数変動量をより小さくし、より優れた三次曲線の周波数温度特性が得られる。 Also for the SAW resonator of this example, the line occupancy η of the IDT 3 is further reduced, as in the SAW resonator of this embodiment.

It is preferable to set so as to satisfy the above. Thereby, since the secondary temperature coefficient of the frequency temperature characteristic can be suppressed to be smaller, the frequency fluctuation amount can be further reduced, and a more excellent cubic temperature frequency temperature characteristic can be obtained.

Furthermore, the inventor of the present application uses the electrode finger film thickness H, the electrode finger groove depth G, and the Euler angle θ as parameters, and has excellent frequency temperature characteristics of a cubic curve with a small amount of frequency variation and a frequency variation amount ΔF ≦ 20 ppm. The IDT line occupancy η and the Euler angle ψ that can realize the use condition of the electromechanical coupling coefficient k ² ≧ 0.052%, and the k ² value and ΔF value obtained in that case were calculated by simulation. The calculation results are shown in Table 8 below.

In general, the electromechanical coupling coefficient k ² is substantially determined by the confinement effect of SAW energy. In other words, the k ² value is determined by the reflection efficiency of the reflector, that is, the reflector structure (number of reflectors, effective film thickness, conductor strip line width, density, etc.). Therefore, even if the cut angle of the quartz substrate, for example, the Euler angle θ, changes slightly, the k ² value should be hardly affected.

In Table 8 above, the Euler angle θ was changed to 121 °, 122 °, 126 °, and 127 ° within an angle range in which excellent frequency temperature characteristics were obtained as described above. From the table, the boundary condition of the angle range, that is, Euler angle θ = 121 ° (including θ <122 °) and θ = 127 ° (including θ> 126 °) is not exceeded 122 ° ≦ θ In the angle range of ≦ 126 °, it can be seen that the frequency variation ΔF ≦ 20 ppm and the electromechanical coupling coefficient k ² ≧ 0.052% in all cases. Accordingly, it was confirmed that the influence of the change of the Euler angle θ on the k ² value and the ΔF value was small.

Further, in the simulation of Table 8 above, the electrode finger film thickness H = 1% λ and the electrode finger groove depth G = 2% λ are fixed, and the Euler angle θ (= 121 ° to 127 °) is used as a parameter. Similarly, an IDT line occupancy η capable of realizing an excellent frequency temperature characteristic of a cubic curve with a small amount of frequency fluctuation and a use condition of a frequency fluctuation ΔF ≦ 20 ppm and an electromechanical coupling coefficient k ² ≧ 0.052% Euler angle ψ, k ² value and ΔF value obtained in that case were calculated. The calculation results are shown in Table 9 below.

FIGS. 16A and 16B show changes in the frequency fluctuation amount ΔF and the electromechanical coupling coefficient k ² with respect to the Euler angle θ based on the results in Table 9, respectively. From the figure and Table 9, it was confirmed that the use conditions of ΔF ≦ 20 ppm and k ² ≧ 0.052% were satisfied in all cases in the range of Euler angles θ122 ° ≦ θ ≦ 126 °.

In general, one of the factors determining the reflection efficiency of the reflector is the density of the reflector. In the case where the reflector has a groove between conductor strips as in the SAW resonator of the present embodiment, the density of the reflector is determined by the step formed by the groove between conductor strips, that is, the thickness of the crystal portion constituting the effective film thickness. The ratio between (G) and the film thickness (H) of the conductor strip (electrode finger) is greatly affected. In this example, the difference in specific gravity between the electrode material aluminum and quartz is small, so even if the ratio of the effective film thickness changes, it is considered that the influence on the reflection efficiency is small. Table 9 also shows that this idea is correct because the electromechanical coupling coefficient k ² does not vary with the effective film thickness (G: H) ratio.

Thus, in the SAW device of the present invention, the electrode finger film thickness H, the electrode finger groove depth G, and the Euler angle θ are 1% ≦ G / λ ≦ 4%, 1% ≦ H / λ ≦ 4. % And 122 ° ≦ θ ≦ 126 ° are satisfied, so that it is possible to dramatically improve the k ² value without being affected by various conditions other than the IDT line occupation ratio η. It was. Further, if the Euler angle φ is in the range of −1.5 ° ≦ φ ≦ + 1.5 °, the frequency fluctuation amount ΔF ≦ 20 ppm and the electromechanical coupling coefficient k ² ≧ 0.052% may be satisfied. confirmed.

  Further, in the SAW resonator of the present example, similarly to the SAW resonator of the present embodiment, the sum of the depth G of the inter-electrode finger groove 8 and the film thickness H of the electrode fingers 6a and 6b is 0.0407λ ≦ It is preferable to set so as to satisfy G + H. As a result, in the present embodiment using the resonance in the stop band upper end mode, a higher Q value is obtained than in the conventional SAW resonator using the resonance in the stop band lower end mode without providing a groove between the electrode fingers of the IDT.

FIGS. 17A and 17B show a second embodiment of the SAW resonator according to the present invention having a tilted IDT, respectively. SAW resonator 21 ₁ in FIG. 17 (A) similarly to the first embodiment Euler angles (-1.5 ° ≦ φ ≦ 1.5 ° , 122 ° ≦ θ ≦ 126 °, 43.49 ° ≦ | An inclined IDT 23 ₁ and a pair of reflectors 24 ₁ and 24 ₁ are provided on the main surface of the quartz substrate 22 ₁ represented by ψ | ≦ 43.78 °. Quartz substrate 22 ₁ has its longitudinal direction, inclined by the power flow angle (PFA) δ ° is the direction of propagation of energy to the X 'axis is the propagation direction of the phase velocity of the SAW excited by the IDT 23 ₁ orientation Is oriented along.

The IDT 23 ₁ includes a pair of comb-like electrodes 23a ₁ and 23b ₁ each composed of a plurality of electrode fingers 25a ₁ and 25b ₁ and having their base ends connected by bus bars 26a ₁ and 26b ₁ . Reflectors ₂₄ 1, 24 ₁ of a pair are arranged so as to sandwich the IDT on both sides of the IDT 23 ₁ along the propagation direction of the SAW, a plurality of conductor strips _24a 1 arranged in the SAW propagation direction, respectively, 24a ₁ The electrode fingers 25a ₁ and 25b ₁ and the conductor strip 24a ₁ are arranged in a direction orthogonal to the X ′ axis whose extension direction is inclined by a power flow angle (PFA) δ °.

The surface exposed between the quartz crystal substrate 22 _first electrode fingers 25a _1, 25b _1, the inter-electrode-finger groove as in the first embodiment are recessed. Also quartz substrate 22 _first surface between conductor strips _24a 1, 24a _1, likewise between the conductive strip grooves are recessed.

Thus the IDT and the reflectors of at least a part, by being arranged in a direction intersecting with a X 'axis direction and the power flow angle [delta], with the SAW device 21 ₁ the same effects as the first embodiment The Q value can be further increased. As a result, a SAW resonator with lower loss is realized.

SAW resonator 21 ₂ shown in FIG. 17 (B) has the main surface of the quartz crystal substrate 22 ₂ and reflectors ₂₄ 2, 24 ₂ of the inclined IDT 23 ₂ and a pair of different configuration from that of FIG. 17 (A). The longitudinal direction of the quartz substrate 22 ₂ is oriented along the X ′ axis, which is the propagation direction of the SAW phase velocity excited by the IDT 23 ₂ .

IDT 23 ₂ has a plurality of electrode fingers _25a 2, 25b consists of _two and comb-shaped electrodes _23a 2 of the pair of connecting their base ends in the bus bar _26a 2, 26b _2, 23b _2. 1 reflector ₂₄ 2, 24 ₂ of the pair are arranged so as to sandwich the IDT on both sides of the IDT 23 ₂ along the propagation direction of the SAW, a plurality of conductor strips _24a 2 arranged in the SAW propagation direction, respectively, 24a ₂ The electrode fingers 25a ₂ and 25b ₂ and the conductor strip 24a ₂ are arranged so that their extending directions are orthogonal to the X ′ axis, and the bus bars 26a ₂ and 26b ₂ are connected to the power flow angle (PFA) δ from the X ′ axis. Oriented in a tilted direction.

The surface exposed to the quartz crystal substrate 22 _{and second} electrode fingers 25a _2, 25b between _2, the inter-electrode-finger groove as in the first embodiment are recessed. Also quartz substrate 22 _second surface between the conductor strip _24a 2, 24a _2, likewise between conductor strips groove is recessed.

SAW resonator 21 ₂ of the present embodiment also, thus the IDT and the reflectors of at least a part, by being arranged in a direction intersecting with a X 'axis direction and the power flow angle [delta], and good frequency temperature characteristic While exhibiting the effect of realizing a high Q value, the Q value can be further increased. As a result, a SAW resonator with lower loss is realized.

  18A and 18B show the configuration of the SAW oscillator according to the present invention. The SAW oscillator 31 of the present embodiment includes a SAW resonator 32 according to the present invention, an IC (integrated circuit) 33 that drives and controls the SAW resonator, and a package 34 that accommodates these. The SAW resonator 32 and the IC 33 are surface-mounted on the bottom plate 34 a of the package 34.

  The SAW resonator 32 has the same configuration as that of the SAW resonator 11 of the first embodiment, and a quartz substrate 35 displayed at the same Euler angle as that of the first embodiment and a pair of combs formed on the surface thereof. It has an IDT composed of tooth-like electrodes 36a and 36b and a pair of reflectors 37 and 37. Electrode pads 38 a to 38 f are provided on the upper surface of the IC 33. Electrode patterns 39 a to 39 g are formed on the bottom plate 34 a of the package 34. The comb-like electrodes 36a and 36b of the SAW resonator 32 and the electrode pads 38a to 38f of the IC 33 are electrically connected to the corresponding electrode patterns 39a to 39g by bonding wires 40 and 41, respectively. Thus, the package 34 on which the SAW resonator 32 and the IC 33 are mounted is hermetically sealed by the lid 42 bonded to the upper part thereof.

  By providing the SAW resonator of the present invention, the SAW oscillator 31 of the present embodiment has an excellent frequency temperature characteristic in which the frequency fluctuation amount is extremely small over a wide operating temperature range, and also improves the electromechanical coupling coefficient compared to the conventional one. In addition, since the capacitance ratio and the CI value are suppressed, stable oscillation operation is possible, and further reduction of power consumption can be realized by reducing impedance. As a result, in response to the recent demand for higher frequency and higher accuracy based on higher speed of information communication, excellent environmental resistance characteristics that operate stably for a long time even in environments where the temperature fluctuates greatly from low temperature to high temperature Is obtained.

  The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, the present invention can also be applied to SAW devices other than the above-described SAW resonator and SAW oscillator. In addition, the SAW resonator of the first embodiment has a configuration having reflectors on both sides of the IDT, but the present invention can be similarly applied to a SAW device having a configuration having no reflector. Regarding the electrode structure of the IDT, various known configurations can be adopted in addition to the above-described embodiments.

  Further, the SAW device of the present invention includes, for example, a mobile phone, a hard disk, a personal computer, a reception tuner for BS and CS broadcasting, various processing devices for high-frequency signals and optical signals propagating in coaxial cables and optical cables, and a wide temperature range. Various electronic devices such as server / network equipment and wireless communication equipment that require high frequency and high precision clocks (low jitter and low phase noise), various module devices, pressure sensors, acceleration sensors, rotational speed sensors, etc. It can be widely applied to various sensor devices.

1, 21 _{1, 21} 2, 32 ... SAW _resonator, 2,22 1, ₂₂ 2, 35 ... a quartz _{substrate, 3,23 1, 23 2 ... IDT} , 3a, 3b, 23a 1, 23b 1, 23a 2, 23b _2, 36a, 36b ... comb-shaped electrodes _4, 24 1, ₂₄ 2, 37 ... reflector, 4a, 4a, _24a 1, 24a 2 _... conductor strips, 5 ... wafer, 5a ... surface, 6a, 6b, 25a ₁ , 25b ₁ , 25a ₂ , 25b ₂ ... electrode fingers, 7a, 7b, 26a ₁ , 26b ₁ , 26a ₂ , 26b ₂ ... bus bars, 8 ... grooves between electrode fingers, 9 ... grooves between conductor strips, 31 ... SAW Oscillator 33 ... IC 34 ... package 34a ... bottom plate 38a-38f ... electrode pad 39a-39g electrode pattern 40, 41 ... bonding wire 42 ... lid

Claims (7)

A quartz substrate with Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, θ = 123 °, ψ),
An IDT comprising a plurality of electrode fingers provided on the principal surface of the quartz substrate and exciting a surface acoustic wave in a stop band upper end mode;
A plurality of inter-electrode finger grooves recessed in the surface of the quartz substrate between the electrode fingers adjacent to the IDT;
The depth G between the electrode fingers and the thickness H of the electrode fingers are 1% ≦ G / λ ≦ 4% and 1% ≦ H / λ ≦ 4, where λ is the wavelength of the surface acoustic wave. % Surface acoustic wave device satisfying each of the following relationships:   2. The surface acoustic wave device according to claim 1, wherein the line occupation ratio η of the IDT is determined so that an electromechanical coupling coefficient is 0.052% or more within an operating temperature range. The line occupancy η of the IDT is an orthogonal coordinate having the line occupancy η (%) as a vertical axis and the electrode finger groove depth G (% λ) as a horizontal axis.
When the electrode finger film thickness H is 1.0 to 1.5% λ, each point (1.0, 0.757), (2.0, 0.703), (3.0, 0.679) , (4.0, 0.650), (4.0, 0.642), (3.0, 0.659), (2.0, 0.686), (1.0, 0.754) , (1.0, 0.757) within a range surrounded by a polygon,
When the electrode finger film thickness H is 1.5 to 2.0% λ, each point (1.0, 0.749), (2.0, 0.690), (3.0, 0.676) , (4.0, 0.650), (4.0, 0.637), (3.0, 0.657), (2.0, 0.684), (1.0, 0.748) , (1.0, 0.749) within a range surrounded by a polygon,
When the electrode finger film thickness H is 2.0 to 2.5% λ, each point (1.0, 0.732), (2.0, 0.691), (3.0, 0.670) , (4.0, 0.641), (4.0, 0.629), (3.0, 0.651), (2.0, 0.680), (1.0, 0.730) , (1.0, 0.732) within the range surrounded by the polygon,
When the electrode finger film thickness H is 2.5 to 3.0% λ, each point (1.0, 0.732), (2.0, 0.669), (3.0, 0.658) , (3.0, 0.642), (2.0, 0.667), (1.0, 0.710), (1.0, 0.732) Yes,
When the electrode finger film thickness H is 3.0 to 3.5% λ, each point (1.0, 0.692), (2.0, 0.669), (3.0, 0.640) , (3.0, 0.629), (2.0, 0.655), (1.0, 0.690), (1.0, 0.692). Yes,
When the electrode finger film thickness H is 3.5 to 4.0% λ, each point (1.0, 0.679), (2.0, 0.663), (3.0, 0.620) , (3.0, 0.615), (2.0, 0.642), (1.0, 0.672), (1.0, 0.679). Yes, and
The Euler angle ψ of the quartz substrate is an orthogonal coordinate having the Euler angle ψ (°) as the vertical axis and the inter-electrode finger groove depth G (% λ) as the horizontal axis,
When the electrode finger film thickness H is 1.0 to 1.5% λ, each point (1.0, 43.63), (2.0, 43.68), (3.0, 43.72) , (4.0, 43.78), (4.0, 43.71), (3.0, 43.67), (2.0, 43.66), (1.0, 43.62) , (1.0, 43.63) is within the range surrounded by the polygon,
When the electrode finger film thickness H is 1.5 to 2.0% λ, each point (1.0, 43.58), (2.0, 43.62), (3.0, 43.69) , (4.0, 43.78), (4.0, 43.72), (3.0, 43.64), (2.0, 43.60), (1.0, 43.57) , (1.0, 43.58) are within the range enclosed by the polygon,
When the electrode finger film thickness H is 2.0 to 2.5% λ, each point (1.0, 43.56), (2.0, 43.60), (3.0, 43.68) , (4.0, 43.78), (4.0, 43.76), (3.0, 43.64), (2.0, 43.57), (1.0, 43.54) , (1.0, 43.56) within a range surrounded by a polygon connecting,
When the electrode finger film thickness H is 2.5 to 3.0% λ, each point (1.0, 43.50), (2.0, 43.58), (3.0, 43.68) , (3.0, 43.66), (2.0, 43.55), (1.0, 43.49), (1.0, 43.50). Yes,
When the electrode finger film thickness H is 3.0 to 3.5% λ, each point (1.0, 43.49), (2.0, 43.58), (3.0, 43.70) , (3.0, 43.69), (2.0, 43.54), (1.0, 43.45), within a range represented by a polygon connecting (1.0, 43.49) And
When the electrode finger film thickness H is 3.5 to 4.0% λ, each point (1.0, 43.42), (2.0, 43.55), (3.0, 43.72) , (3.0, 43.73), (2.0, 43.59), (1.0, 43.49), (1.0, 43.42). The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is provided. The line occupancy η of the IDT is

The surface acoustic wave device according to any one of claims 1 to 3, wherein:   5. The surface acoustic wave device according to claim 1, wherein a sum of a depth G of the inter-electrode finger groove and a film thickness H of the electrode finger satisfies 0.0407λ ≦ G + H. The angle formed by the first direction perpendicular to the electrode fingers and the conductor strip and the electrical axis of the quartz substrate is the Euler angle ψ.
At least a portion of the IDT and reflector is disposed in a second direction that intersects the first direction at an angle δ;
6. The surface acoustic wave device according to claim 1, wherein the angle δ is within a range of a power flow angle ± 1 ° of the quartz substrate.   7. The surface acoustic wave device according to claim 1, further comprising an oscillation circuit for driving the IDT.

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