JP5850109B2 - Surface acoustic wave resonator, surface acoustic wave oscillator, and electronic device - Google Patents

Description

  The present invention relates to a surface acoustic wave resonator, and a surface acoustic wave oscillator and an electronic device on which the surface acoustic wave resonator is mounted, and more particularly to a surface acoustic wave resonator of a type in which a groove is provided on a substrate surface and About.

  In surface acoustic wave (SAW) devices (for example, SAW resonators), changes in frequency temperature characteristics include SAW stop band, cut angle of piezoelectric substrate (for example, quartz substrate), and IDT (interdigital transducer). The influence of the formation form etc. is great.

  For example, Patent Document 1 discloses a configuration that excites each of the upper end mode and the lower end mode of the SAW stop band, and the distribution of each standing wave in the upper end mode and the lower end mode of the stop band.

  Patent Documents 2 to 5 describe 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. In Patent Documents 2 and 3, 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 electrode is set. It is described that the thickness is increased to about 0.1.

  Patent Document 4 describes that in a SAW device using Rayleigh waves, the cut angle of the quartz substrate is adjusted and the standardized film thickness (H / λ) of the electrode is increased by about 0.045 or more. Yes.

  In addition, Patent Literature 5 uses a rotation Y-cut X-propagation quartz crystal substrate and uses the resonance at the upper end of the stop band to improve the frequency-temperature characteristics as compared with the case of using the resonance at the lower end of the stop band. Have been described.

In Patent Document 6 and Non-Patent Document 1, in a SAW device using an ST cut quartz substrate, a groove is provided between electrode fingers constituting the IDT and between conductor strips constituting the reflector. Have been described. Non-Patent Document 1 discloses that the apex temperature in the frequency-temperature characteristic of the quadratic curve changes with the depth of the groove, and that the secondary temperature coefficient is approximately −3.4 × 10 ⁻⁸ / ° C. ^2. Is described.

  Patent Document 7 describes a configuration for making a curve indicating frequency temperature characteristics a cubic curve in a SAW device using an LST cut quartz substrate, and in a SAW device using a Rayleigh wave. It is described that a substrate having a cut angle having a temperature characteristic as shown by a cubic curve could not be found.

  As described above, there are a variety of factors for improving the frequency temperature characteristics. In particular, in a SAW device using Rayleigh waves, increasing the film thickness of the electrode constituting the IDT is a factor contributing to the frequency temperature characteristics. It is considered one. However, the applicant of the present application has experimentally found that environmental resistance characteristics such as aging characteristics and temperature shock resistance characteristics deteriorate when the electrode thickness is increased. In addition, when the main purpose is to improve the frequency temperature characteristics, the electrode film thickness must be increased as described above, and this has inevitably deteriorates the aging characteristics and the temperature shock resistance characteristics. It was. This is also true for the Q value, and it has been difficult to achieve a high Q without increasing the electrode film thickness.

  In order to solve the above problem, Patent Document 8 discloses a configuration in which a groove is formed in a direction perpendicular to the propagation direction of the surface acoustic wave of a quartz substrate, and an electrode is formed on a convex portion formed by the groove. ing. As a result, environmental resistance characteristics such as aging characteristics and temperature shock resistance characteristics are improved, and a high Q value is realized. Patent Documents 9 and 10 disclose a structure in which a groove is formed between stripe-shaped metal films constituting reflectors arranged between IDT electrodes or on both sides of the IDT electrode in order to realize a high Q value. doing.

Further, in Patent Document 8, a systematic investigation is performed on the depth of the groove, the film thickness of the electrode formed on the groove, and the line occupation ratio of the electrode. When the surface acoustic wave resonator is excited in the stop band upper end mode, the secondary temperature coefficient of the surface acoustic wave is adjusted by adjusting the line occupancy for a given groove depth and electrode film thickness. The conditions for the absolute value to be 0.01 ppm / ° C. ² or less have been ascertained. As a result, the frequency-temperature characteristic of the surface acoustic wave becomes a cubic curve, and it is expected that the frequency deviation can be suppressed in the temperature range near the inflection point.

Japanese Patent Laid-Open No. 11-214958 JP 2006-148622 A JP 2007-208771 A JP 2007-267033 A JP 2002-100959 A Japanese Patent Laid-Open No. 57-5418 Japanese Patent No. 3851336 WO2010 / 098139 JP-A-61-220513 JP-A-61-252014 JP 2009-225420 A

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

  Further, Patent Document 11 discloses a configuration for reducing the frequency deviation in the operating temperature range of the surface acoustic wave resonator when the line width of the electrode fingers constituting the IDT electrode, that is, the line occupancy varies. However, in the surface acoustic wave resonators disclosed in Patent Documents 8 to 11, there is a strong demand to reduce the loss of the surface acoustic wave resonator, but no specific disclosure has been made about this. Currently.

  Accordingly, the present invention pays attention to the above-mentioned problems, and the surface acoustic wave resonator in which the frequency deviation of the surface acoustic wave is reduced and the loss of the surface acoustic wave resonator is reduced, the surface acoustic wave oscillator using the surface acoustic wave oscillator, and the electron The purpose is to provide equipment.

の関係を満たすことを特徴とする。
第２の形態に係る弾性表面波共振子は、第１の形態に係る弾性表面波共振子であって、前記実効ライン占有率ηｅｆｆが、

の関係を満たすことを特徴とする。
第３の形態に係る弾性表面波共振子は、第１の形態又は第２の形態のいずれか１の形態に係る弾性表面波共振子であって、前記電極指間溝の深さＧと前記電極膜厚Ｈとの和が、

の関係を満たすことを特徴とする。
第４の形態に係る弾性表面波共振子は、第１の形態乃至第４３の形態のいずれか１の形態に係る弾性表面波共振子であって、前記ψと前記θが、

の関係を満たすことを特徴とする。
第５の形態に係る弾性表面波共振子は、第１の形態乃至第４の形態のいずれか１の形態に係る弾性表面波共振子であって、前記ＩＤＴにおけるストップバンド上端モードの周波数をｆｔ２、前記ＩＤＴを弾性表面波の伝搬方向に挟み込むように配置される反射器におけるストップバンド下端モードの周波数をｆｒ１、前記反射器のストップバンド上端モードの周波数をｆｒ２としたとき、

の関係を満たすことを特徴とする。
第６の形態に係る弾性表面波共振子は、第５の形態の形態に係る弾性表面波共振子であって、前記反射器を構成する導体ストリップ間に位置する前記水晶基板の部分に導体ストリップ間溝を設け、前記電極指間溝よりも前記導体ストリップ間溝の深さの方が浅いことを特徴とする。
本形態に係る弾性表面波発振器は、第１の形態乃至第６の形態のいずれか１の形態に係る弾性表面波共振子と、前記ＩＤＴを駆動するための回路を備えたことを特徴とする。
本形態に係る電子機器は、第１の形態乃至第６の形態のいずれか１の形態に係る弾性表面波共振子を備えたことを特徴とする。
［適用例１］オイラー角（−１．５°≦φ≦１．５°，１１７°≦θ≦１４２°，４２．７９°≦｜ψ｜≦４９．５７°）の水晶基板と、前記水晶基板上に設けられ、複数の電極指を含み、ストップバンド上端モードの弾性表面波を励振するＩＤＴと、を備え、平面視で、前記電極指の間の位置に、前記水晶基板の窪である電極指間溝を配置し、前記電極指間溝の間に配置されている前記水晶基板の凸部のライン占有率をηｇ、前記凸部上に配置されている前記電極指のライン占有率をηｅとし、前記ＩＤＴの実効ライン占有率ηｅｆｆを前記ライン占有率ηｇと前記ライン占有率ηｅとの相加平均とした場合、下式の関係を満たすことを特徴とする弾性表面波共振子。

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
The surface acoustic wave resonator according to the first embodiment has an Euler angle (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °). And an IDT that is provided on the quartz substrate, includes a plurality of electrode fingers, and excites a stopband upper end mode surface acoustic wave; In plan view, a groove between the electrode fingers in the portion of the quartz substrate located between the electrode fingers, where the electrode film thickness of the IDT is H, and the wavelength of the surface acoustic wave is λ, and 0 <H ≦ 0.035λ is satisfied, ηg is the line occupancy ratio of the convex portions of the quartz crystal substrate disposed between the inter-electrode finger grooves, and the line occupancy ratio of the electrode fingers disposed on the convex portions Ηe, and the effective line occupancy ηeff of the IDT is As an arithmetic average of the line occupancy ηg and the line occupancy ηe,

It is characterized by satisfying the relationship.
The surface acoustic wave resonator according to the second embodiment is the surface acoustic wave resonator according to the first embodiment, and the effective line occupancy ηeff is

It is characterized by satisfying the relationship.
A surface acoustic wave resonator according to a third embodiment is a surface acoustic wave resonator according to any one of the first embodiment and the second embodiment, and the depth G of the inter-electrode finger groove The sum of the electrode thickness H is

It is characterized by satisfying the relationship.
A surface acoustic wave resonator according to a fourth embodiment is a surface acoustic wave resonator according to any one of the first to 43rd embodiments, wherein ψ and θ are

It is characterized by satisfying the relationship.
A surface acoustic wave resonator according to a fifth embodiment is a surface acoustic wave resonator according to any one of the first to fourth embodiments, wherein the frequency of the stopband upper end mode in the IDT is ft2. When the frequency of the stop band lower end mode of the reflector disposed so as to sandwich the IDT in the propagation direction of the surface acoustic wave is fr1, and the frequency of the stop band upper end mode of the reflector is fr2,

It is characterized by satisfying the relationship.
A surface acoustic wave resonator according to a sixth embodiment is a surface acoustic wave resonator according to a fifth embodiment, wherein a conductor strip is formed on a portion of the quartz substrate located between conductor strips constituting the reflector. An inter-groove is provided, and the groove between the conductor strips is shallower than the inter-electrode finger groove.
The surface acoustic wave oscillator according to the present embodiment includes the surface acoustic wave resonator according to any one of the first to sixth embodiments and a circuit for driving the IDT. .
An electronic apparatus according to this embodiment includes the surface acoustic wave resonator according to any one of the first to sixth embodiments.
Application Example 1 Quartz substrate with Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °) and the crystal An IDT that includes a plurality of electrode fingers and that excites a surface acoustic wave in a stop band upper end mode, and is a depression in the quartz substrate at a position between the electrode fingers in plan view. The inter-electrode finger grooves are arranged, the line occupancy rate of the convex portions of the quartz crystal substrate arranged between the inter-electrode finger grooves is ηg, and the line occupancy rate of the electrode fingers arranged on the convex portions is A surface acoustic wave resonator that satisfies the relationship of the following equation, where ηe is an arithmetic average of the line occupancy ηg and the line occupancy ηe: an effective line occupancy ηeff of the IDT.

  With the above configuration, it is possible to increase the excitation efficiency and reduce the loss of the surface acoustic wave resonator, and to suppress the variation in the primary temperature coefficient of the surface acoustic wave resonator, thereby suppressing the variation in the resonance frequency.

Application Example 2 In the surface acoustic wave resonator according to Application Example 1, the wavelength of the surface acoustic wave is λ, the depth of the inter-electrode finger groove is G, the electrode film thickness of the IDT is H, and the electrode When the plane coordinates based on the value G / λ obtained by dividing the inter-finger depth G by the wavelength λ of the surface acoustic wave and the effective line occupancy ηeff are (G / λ, ηeff), the plane coordinates (G / λ, ηeff) is
(1) In the case of 0.000λ <H ≦ 0.005λ,
(0.010, 0.710), (0.020, 0.710), (0.030, 0.710), (0.040, 0.710), (0.050, 0.710), (0.060, 0.710), (0.070, 0.710), (0.080, 0.710), (0.090, 0.710), (0.090, 0.420), (0.080, 0.570), (0.070, 0.590), (0.060, 0.615), (0.050, 0.630), (0.040, 0.635), (0.030, 0.650), (0.020, 0.670), a range surrounded by a line connecting in the order of (0.010, 0.710),
And (0.030, 0.590), (0.040, 0.580), (0.050, 0.550), (0.060, 0.520), (0.070, 0.480) ), (0.080, 0.450), (0.090, 0.400), (0.090, 0.180), (0.080, 0.340), (0.070, 0.410) ), (0.060, 0.460), (0.050, 0.490), (0.040, 0.520), (0.030, 0.550), (0.030, 0.590) ) In any of the bounded lines
(2) When 0.005λ <H ≦ 0.010λ,
(0.010, 0.770), (0.020, 0.740), (0.030, 0.715), (0.040, 0.730), (0.050, 0.740), (0.060, 0.730), (0.070, 0.730), (0.080, 0.730), (0.080, 0.500), (0.070, 0.570), (0.060, 0.610), (0.050, 0.630), (0.040, 0.635), (0.030, 0.655), (0.020, 0.680), A range surrounded by a line connecting (0.010, 0.760) and (0.010, 0.770) in order,
And (0.020, 0.650), (0.030, 0.610), (0.040, 0.570), (0.050, 0.550), (0.060, 0.520) ), (0.070, 0.470), (0.070, 0.370), (0.060, 0.440), (0.050, 0.480), (0.040, 0.520) ), (0.030, 0.550), (0.020, 0.590), (0.020, 0.650) included in any of the ranges surrounded by the line,
(3) When 0.010λ <H ≦ 0.015λ,
(0.010, 0.770), (0.020, 0.760), (0.030, 0.760), (0.040, 0.750), (0.050, 0.750), (0.060, 0.750), (0.070, 0.740), (0.080, 0.740), (0.080, 0.340), (0.070, 0.545), (0.060, 0.590), (0.050, 0.620), (0.040, 0.645), (0.030, 0.670), (0.020, 0.705), A range surrounded by a line connecting (0.010, 0.760) and (0.010, 0.770) in order,
And (0.010, 0.740), (0.020, 0.650), (0.030, 0.610), (0.040, 0.570), (0.050, 0.540) ), (0.060, 0.480), (0.070, 0.430), (0.070, 0.350), (0.060, 0.420), (0.050, 0.470) ), (0.040, 0.510), (0.030, 0.550), (0.020, 0.610), (0.010, 0.700), (0.010, 0.740) ) In any of the bounded lines
(4) When 0.015λ <H ≦ 0.020λ,
(0.010, 0.770), (0.020, 0.770), (0.030, 0.760), (0.040, 0.760), (0.050, 0.760), (0.060, 0.750), (0.070, 0.750), (0.070, 0.510), (0.060, 0.570), (0.050, 0.620), (0.040, 0.640), (0.030, 0.660), (0.020, 0.675), (0.010, 0.700), (0.010, 0.770) A range of lines connecting in order,
And (0.010, 0.690), (0.020, 0.640), (0.030, 0.590), (0.040, 0.550), (0.050, 0.510 ), (0.060, 0.470), (0.070, 0.415), (0.070, 0.280), (0.060, 0.380), (0.050, 0.470) ), (0.040, 0.510), (0.030, 0.550), (0.020, 0.610), (0.010, 0.680), (0.010, 0.690) ) In any of the bounded lines
(5) When 0.020λ <H ≦ 0.025λ,
(0.010, 0.770), (0.020, 0.770), (0.030, 0.760), (0.040, 0.760), (0.050, 0.760), (0.060, 0.760), (0.070, 0.760), (0.070, 0.550), (0.060, 0.545), (0.050, 0.590), (0.040, 0.620), (0.030, 0.645), (0.020, 0.680), (0.010, 0.700), (0.010, 0.770) A range surrounded by a line connecting in order,
And (0.010, 0.690), (0.020, 0.640), (0.030, 0.590), (0.040, 0.550), (0.050, 0.510 ), (0.060, 0.420), (0.070, 0.415), (0.070, 0.340), (0.060, 0.340), (0.050, 0.420) ), (0.040, 0.470), (0.030, 0.520), (0.020, 0.580), (0.010, 0.650), (0.010, 0.690) ) In any of the bounded lines
(6) When 0.025λ <H ≦ 0.030λ,
(0.010, 0.770), (0.020, 0.770), (0.030, 0.770), (0.040, 0.760), (0.050, 0.760), (0.060, 0.760), (0.070, 0.760), (0.070, 0.550), (0.060, 0.505), (0.050, 0.590), (0.040, 0.620), (0.030, 0.645), (0.020, 0.680), (0.010, 0.700), (0.010, 0.770) A range surrounded by a line connecting in order,
And (0.010, 0.670), (0.020, 0.605), (0.030, 0.560), (0.040, 0.520), (0.050, 0.470) ), (0.060, 0.395), (0.070, 0.500), (0.070, 0.490), (0.060, 0.270), (0.050, 0.410) ), (0.040, 0.470), (0.030, 0.520), (0.020, 0.580), (0.010, 0.620), (0.010, 0.670) ) In any of the bounded lines
(7) When 0.030λ <H ≦ 0.035λ,
(0.010, 0.770), (0.020, 0.770), (0.030, 0.770), (0.040, 0.760), (0.050, 0.760), (0.060, 0.760), (0.070, 0.760), (0.070, 0.550), (0.060, 0.500), (0.050, 0.545), (0.040, 0.590), (0.030, 0.625), (0.020, 0.650), (0.010, 0.680), (0.010, 0.770) A range surrounded by a line connecting in order,
And (0.010, 0.655), (0.020, 0.590), (0.030, 0.540), (0.040, 0.495), (0.050, 0.435) ), (0.060, 0.395), (0.070, 0.500), (0.070, 0.550), (0.060, 0.380), (0.050, 0.330) ), (0.040, 0.410), (0.030, 0.470), (0.020, 0.520), (0.010, 0.590), (0.010, 0.655) The surface acoustic wave resonator is included in any of the ranges surrounded by lines connecting in the order of

  With the above configuration, the absolute value of the secondary temperature coefficient of the surface acoustic wave resonator can be suppressed to 0.01 ppm / ° C. or less in correspondence with the thickness of H.

の関係を満たすことを特徴とする弾性表面波共振子。 Application Example 3 In the surface acoustic wave resonator according to claim 1, the depth G of the inter-electrode finger groove and the effective line occupancy ηeff are

A surface acoustic wave resonator characterized by satisfying the following relationship:

With the above configuration, the absolute value of the secondary temperature coefficient of the surface acoustic wave resonator can be suppressed to 0.01 ppm / ° C. ² or less.

の関係を満たすことを特徴とする弾性表面波共振子。 [Application Example 4] The surface acoustic wave resonator according to Application Example 3,
The electrode thickness H of the IDT is

A surface acoustic wave resonator characterized by satisfying the following relationship:

  According to the surface acoustic wave resonator having such a feature, it is possible to realize good frequency temperature characteristics within the operating temperature range. Moreover, according to having such a characteristic, it becomes possible to suppress degradation of the environmental resistance characteristics accompanying the increase in the electrode film thickness.

の関係を満たすことを特徴とする弾性表面波共振子。 Application Example 5 The surface acoustic wave resonator according to Application Example 4,
The effective line occupancy ηeff is

A surface acoustic wave resonator characterized by satisfying the following relationship:

By defining ηeff so as to satisfy the above formula within the range of the electrode film thickness in Application Example 4, it is possible to keep the absolute value of the secondary temperature coefficient within 0.01 ppm / ° C. ² or less.

の関係を満たすことを特徴とする弾性表面波共振子。
電極指間溝の深さGと電極膜厚Hとの和を上式のように定めることで、従来の弾性表面波共振子よりも高いＱ値を得ることができる。 [Application Example 6] The surface acoustic wave resonator according to any one of Application Example 2, Application Example 4, and Application Example 5, wherein a depth G between the electrode finger grooves and an electrode film thickness H are The sum is

A surface acoustic wave resonator characterized by satisfying the following relationship:
By determining the sum of the inter-electrode finger groove depth G and the electrode film thickness H as in the above equation, a higher Q value than that of a conventional surface acoustic wave resonator can be obtained.

の関係を満たすことを特徴とする弾性表面波共振子。 Application Example 7 The surface acoustic wave resonator according to any one of Application Examples 1 to 6, wherein ψ and θ are

A surface acoustic wave resonator characterized by satisfying the following relationship:

  By manufacturing a surface acoustic wave resonator using a quartz crystal substrate cut with a cut angle having such characteristics, a surface acoustic wave resonator exhibiting good frequency temperature characteristics in a wide range can be obtained.

の関係を満たすことを特徴とする弾性表面波共振子。 [Application Example 8] The surface acoustic wave resonator according to any one of Application Examples 1 to 7,
The frequency of the stop band upper end mode in the IDT is ft2, the frequency of the stop band lower end mode in the reflector arranged so as to sandwich the IDT in the propagation direction of the surface acoustic wave is fr1, and the frequency of the stop band upper end mode of the reflector. Is fr2,

A surface acoustic wave resonator characterized by satisfying the following relationship:

  By having such a feature, the reflection coefficient | Γ | of the reflector increases at the frequency ft2 of the IDT stopband upper end mode, and the stopband upper end mode surface acoustic wave excited from the IDT is generated in the reflector. Therefore, it is reflected to the IDT side with a high reflection coefficient. And the energy confinement of the surface acoustic wave of the stop band upper end mode becomes strong, and a surface acoustic wave resonator having a low loss can be realized.

  [Application Example 9] The surface acoustic wave resonator according to any one of Application Examples 1 to 8, wherein a groove between conductor strips is provided between conductor strips constituting the reflector, and the gap between the electrode fingers 2. A surface acoustic wave resonator according to claim 1, wherein the groove between the conductor strips is shallower than the groove.

  By having such a feature, the stop band of the reflector can be frequency-shifted to a higher frequency side than the stop band of the IDT. For this reason, the relationship of Formula 9 can be realized.

  [Application Example 10] A surface acoustic wave oscillator comprising the surface acoustic wave resonator according to any one of Application Examples 1 to 9 and a circuit for driving the IDT.

  Application Example 11 An electronic apparatus comprising the surface acoustic wave resonator according to any one of Application Examples 1 to 9.

It is a figure which shows the structure of the SAW device of 1st Embodiment, Comprising: (A) is a figure which shows a plane structure, (B) is a figure which shows the partial expanded cross section in a side surface, (C) is (B). FIG. 4D is a partially enlarged view for explaining details in FIG. 2D, and FIG. 4D is a partially enlarged view in FIG. 2C, and a groove portion that can be assumed when the SAW resonator is manufactured by using a photolithography technique and an etching technique. It is a figure which shows no cross-sectional shape. It is a figure which shows an example of the direction of the wafer used as the base material of the crystal substrate used by this invention. It is a figure which shows the structural example of the SAW device at the time of employ | adopting inclination type IDT as a modification of 1st Embodiment, (A) is an example of the form which inclined the electrode finger and made it orthogonal to the X ″ axis. (B) is an example of a SAW device having an IDT in which a bus bar connecting electrode fingers is inclined. It is a figure which shows the relationship between stopband upper end mode and lower end mode. It is a graph which shows the relationship between the depth of an electrode finger groove | channel, and the amount of frequency fluctuations in an operating temperature range. It is a figure which shows the temperature characteristic in a ST cut quartz substrate. It is a graph which shows the difference of the change of the secondary temperature coefficient with the change of the line occupation rate (eta) in the resonance point of a stop band upper end mode, and the resonance point of a stop band lower end mode, (A) is groove depth G 2% (lambda). 7B is a graph showing the displacement of the secondary temperature coefficient β in the stop band upper end mode when the groove depth G is set, and (B) is the displacement of the secondary temperature coefficient β in the stop band lower end mode when the groove depth G is 2% λ. (C) is a graph showing the displacement of the secondary temperature coefficient β in the stop band upper end mode when the groove depth G is 4% λ, and (D) is a graph showing the groove depth G of 4%. It is a graph which shows the displacement of the secondary temperature coefficient (beta) of the stop band lower end mode when it is set to% (lambda). It is a graph which shows the relationship between the line occupation rate (eta) and the secondary temperature coefficient (beta) at the time of changing the depth of an electrode finger groove | channel by making electrode film thickness 0, (A) is groove depth G 1% (lambda), (B) is the groove depth G of 1.25% λ, (C) is the groove depth G of 1.5% λ, (D) is the groove depth G of 2% λ, and (E) is the groove depth. G is 3% λ, (F) is the groove depth G is 4% λ, (G) is the groove depth G is 5% λ, (H) is the groove depth G is 6% λ, and (I) is the groove. It is a graph in case the depth G is 8% λ. It is a graph which shows the relationship between the depth of the electrode finger groove | channel where a secondary temperature coefficient becomes 0 when an electrode film thickness is set to 0, and line occupation rate (eta). It is a graph which shows the relationship between line occupation rate (eta) and frequency variation | change_quantity (DELTA) F when the electrode film thickness is set to 0 and the depth of a groove | channel between electrode fingers is changed, (A) is groove depth G 1% (lambda), ( B) has a groove depth G of 1.25% λ, (C) has a groove depth G of 1.5% λ, (D) has a groove depth G of 2% λ, and (E) has a groove depth G. (F) is 4% λ, (G) is 5% λ, (H) is 6% λ, and (I) is the groove depth. It is a graph when the thickness G is 8% λ. It is a graph which shows the relationship between the depth of an electrode finger groove, and the amount of frequency fluctuations when the depth of the electrode finger groove is shifted by ± 0.001λ. It is a graph which shows the relationship between the depth of the electrode finger groove | channel where the secondary temperature coefficient becomes 0 when changing an electrode film thickness, and line occupation rate (eta), (A) is electrode film thickness 1% (lambda), ( (B) is the electrode film thickness of 1.5% λ, (C) is the electrode film thickness of 2% λ, (D) is the electrode film thickness of 2.5% λ, and (E) is the electrode film thickness of 3% λ. (F) is a graph when the electrode film thickness is 3.5% λ. A diagram that graphically summarizes the relationship between the depth of the secondary temperature coefficient ^{β ≒ 0 (ppm / ℃ 2} ) to become η1 and inter-electrode-finger groove at each electrode thickness, (A) is the electrode thickness 1% The relationship between the groove depth G and η1 when changing from λ to 3.5% λ is shown, and (B) shows a region where | β | ≦ 0.01 (ppm / ° C. ² ) It is a figure explaining being in the polygon formed by connecting H. It is the figure which showed the relationship between the electrode finger-groove depth from the electrode film thickness H≈0 to H = 0.035λ and the line occupancy η by an approximate curve. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) in the case where the electrode film thickness is 0.01 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, (B) Groove depth G 1% λ, (C) Groove depth G 2% λ, (D) Groove depth G 3% λ, (E) Groove depth G 4%. λ and (F) are graphs when the groove depth G is 5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) in the case where the electrode film thickness is 0.015λ and the depth of the inter-electrode finger groove is changed. (B) is the groove depth G of 1% λ, (C) is the groove depth G of 1.5% λ, (D) is the groove depth G of 2.5% λ, and (E) is the groove depth. G is 3.5% λ, and (F) is a graph when the groove depth G is 4.5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) at the time of changing the depth of an electrode finger groove | channel by making electrode film thickness 0.02 (lambda), (A) is groove depth G 0, (B) Groove depth G 1% λ, (C) Groove depth G 2% λ, (D) Groove depth G 3% λ, (E) Groove depth G 4%. λ and (F) are graphs when the groove depth G is 5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) at the time of changing electrode electrode groove | channel depth with the electrode film thickness of 0.025 (lambda), (A) is groove depth G 0, (B) is the groove depth G of 1% λ, (C) is the groove depth G of 1.5% λ, (D) is the groove depth G of 2.5% λ, and (E) is the groove depth. G is 3.5% λ, and (F) is a graph when the groove depth G is 4.5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) in the case where the electrode film thickness is 0.03λ and the depth of the inter-electrode finger groove is changed, and (A) shows the groove depth G as 0, (B) Groove depth G 1% λ, (C) Groove depth G 2% λ, (D) Groove depth G 3% λ, (E) Groove depth G 4%. λ and (F) are graphs when the groove depth G is 5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and secondary temperature coefficient (beta) at the time of changing electrode electrode groove | channel thickness to 0.035 (lambda), and the groove depth G is 0, (A). (B) Groove depth G 1% λ, (C) Groove depth G 2% λ, (D) Groove depth G 3% λ, (E) Groove depth G 4%. λ and (F) are graphs when the groove depth G is 5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and frequency variation | change_quantity (DELTA) F when the electrode film thickness is 0.01 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, ( B) Groove depth G is 1% λ, (C) Groove depth G is 2% λ, (D) Groove depth G is 3% λ, and (E) Groove depth G is 4% λ. (F) is a graph when the groove depth G is 5% λ. It is a graph which shows the relationship between the line occupation rate (eta) and frequency variation | change_quantity (DELTA) F when the electrode film thickness is 0.015 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, ( (B) is the groove depth G of 1% λ, (C) is the groove depth G of 1.5% λ, (D) is the groove depth G of 2.5% λ, and (E) is the groove depth G. Is a graph when the groove depth G is 4.5% λ. It is a graph which shows the relationship between line occupation rate (eta) and frequency variation (DELTA) F when the electrode film thickness is 0.02 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, ( B) Groove depth G is 1% λ, (C) Groove depth G is 2% λ, (D) Groove depth G is 3% λ, and (E) Groove depth G is 4% λ. (F) is a graph when the groove depth G is 5% λ. It is a graph which shows the relationship between line occupation rate (eta) and frequency variation (DELTA) F at the time of changing electrode groove depth with an electrode film thickness of 0.025 (lambda), (A) is groove depth G 0, ( (B) is the groove depth G of 1% λ, (C) is the groove depth G of 1.5% λ, (D) is the groove depth G of 2.5% λ, and (E) is the groove depth G. Is a graph when the groove depth G is 4.5% λ. It is a graph which shows the relationship between line occupation rate (eta) and frequency variation (DELTA) F when the electrode film thickness is 0.03 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, ( B) Groove depth G is 1% λ, (C) Groove depth G is 2% λ, (D) Groove depth G is 3% λ, and (E) Groove depth G is 4% λ. (F) is a graph when the groove depth G is 5% λ. It is a graph which shows the relationship between line occupation rate (eta) and frequency variation (DELTA) F when the electrode film thickness is 0.035 (lambda) and the depth of an electrode finger groove | channel is changed, (A) is groove depth G 0, ( B) Groove depth G is 1% λ, (C) Groove depth G is 2% λ, (D) Groove depth G is 3% λ, and (E) Groove depth G is 4% λ. (F) is a graph when the groove depth G is 5% λ. A graph showing a range in which | β | ≦ 0.01 (ppm / ° C. ² ) by a graph showing the relationship between the line occupation ratio η and the groove depth G when the electrode film thickness H is 0 ≦ H <0.005λ. (A) shows the case of η1, and (B) shows the case of η2. A range in which | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupation ratio η and the groove depth G when the electrode film thickness H is 0.005λ ≦ H <0.010λ. (A) shows the case of η1, and (B) shows the case of η2. A range in which | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupancy η and the groove depth G when the electrode film thickness H is 0.010λ ≦ H <0.015λ. (A) shows the case of η1, and (B) shows the case of η2. A range in which | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupation ratio η and the groove depth G when the electrode film thickness H is 0.015λ ≦ H <0.020λ. (A) shows the case of η1, and (B) shows the case of η2. A range where | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupancy η and the groove depth G when the electrode film thickness H is 0.020λ ≦ H <0.025λ. (A) shows the case of η1, and (B) shows the case of η2. A range in which | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupancy η and the groove depth G when the electrode film thickness H is 0.025λ ≦ H <0.030λ. (A) shows the case of η1, and (B) shows the case of η2. A range where | β | ≦ 0.01 (ppm / ° C. ² ) is obtained by a graph showing the relationship between the line occupancy η and the groove depth G when the electrode film thickness H is 0.030λ ≦ H <0.035λ. (A) shows the case of η1, and (B) shows the case of η2. 6 is a graph showing the relationship between the electrode finger groove depth and Euler angle ψ when the electrode film thickness and line occupation ratio η (η1: solid line, η2: broken line) are determined. % Λ, (B) is the electrode thickness of 1.5% λ, (C) is the electrode thickness of 2% λ, (D) is the electrode thickness of 2.5% λ, and (E) is the electrode thickness. Is a graph when the electrode film thickness is 3.5% λ. It is the figure which put together the relationship between the depth G of the electrode finger groove | channel in each electrode film thickness H, and Euler angle (psi) in the graph. Is a graph showing the secondary temperature coefficient β is -0.01 (ppm / ℃ ²⁾ and comprising a depth of the inter-electrode-finger groove and the relationship between Euler angle [psi. The secondary temperature coefficient β is a graph showing the relationship between +0.01 (ppm / ℃ ²⁾ and comprising a depth of the inter-electrode-finger groove and the Euler angle [psi. When the range of the electrode film thickness H is 0 <H ≦ 0.005λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ). (B) are graphs each showing a region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.005λ <H ≦ 0.010λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.010λ <H ≦ 0.015λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.015λ <H ≦ 0.020λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.020λ <H ≦ 0.025λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.025λ <H ≦ 0.030λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. When the range of the electrode film thickness H is 0.030λ <H ≦ 0.035λ, it is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ), (A) Are the maximum and minimum values of ψ, and (B) is a graph showing the region of ψ that satisfies the requirement of β. It is a graph which shows the relationship between Euler angle (theta) and secondary temperature coefficient (beta) in electrode film thickness 0.02 (lambda) and depth of electrode finger groove | channel 0.04 (lambda). It is a graph which shows the relationship between Euler angle (phi) and secondary temperature coefficient (beta). It is a graph which shows the relationship between Euler angle (theta) and Euler angle (psi) from which a frequency temperature characteristic becomes favorable. It is a figure which shows the example of the frequency temperature characteristic data in four test pieces on the conditions where the frequency temperature characteristic became the best. It is a graph which shows the relationship between the level | step difference which is the sum of the depth of an electrode finger groove | channel, and an electrode film thickness, and CI value. It is a table | surface which shows the example of the equivalent circuit constant and static characteristic in the SAW resonator which concerns on this embodiment. It is impedance curve data in the SAW resonator according to the present embodiment. It is a graph for comparing the relationship between the step and the Q value in the conventional SAW resonator and the relationship between the SAW resonator step and the Q value according to the present embodiment. It is a figure which shows SAW reflection characteristic of IDT and a reflector. It is a graph which shows the relationship between the electrode film thickness H and the frequency fluctuation | variation in a heat cycle test. It is a figure which shows the structure of the SAW oscillator which concerns on embodiment. 2 is a graph showing frequency temperature characteristics of a SAW resonator, (A) is a graph showing frequency temperature characteristics of a SAW resonator disclosed in Japanese Patent Laid-Open No. 2006-203408, and (B) is in a substantial operating temperature range. It is a graph which shows the range of the frequency temperature characteristic in. It is a graph which shows the change of the frequency fluctuation amount in the operating range in the SAW resonator which coat | covered the IDT and the reflector as the protective film with the alumina. It is a graph which shows the change of the amount of frequency fluctuations in the operating range in the SAW resonator which coat | covered SiO2 as a protective film in IDT and a reflector. FIG. 59A is a plan view of the SAW resonator according to the second embodiment, FIG. 59B is a partially enlarged sectional view, and FIG. 59C is a SAW resonator according to the second embodiment. FIG. 59 (D) is an enlarged view for explaining details in FIG. 5 (B), and FIG. 59 (D) is a partially enlarged view of FIG. 59 (C). The SAW resonator according to the present invention is used by photolithography technique and etching technique. It is a figure for demonstrating the identification method of effective line occupation rate (eta) eff of an IDT electrode finger when it is a cross-sectional shape which can be assumed at the time of manufacture, and cross-sectional shape became trapezoid shape instead of the rectangle. It is a figure which shows the frequency temperature characteristic of type 1 and type 2 in Example 1. It is a figure which shows the frequency temperature characteristic of Type 1 and Type 2 in Example 2. It is a figure which shows the change of the variation | change_quantity of the primary temperature coefficient when changing the line occupation rate (eta) of type 1. FIG. It is a figure which shows the change of the variation | change_quantity of a primary temperature coefficient when the effective line occupation rate (eta) eff of type 2 is changed.

  Hereinafter, embodiments of a surface acoustic wave resonator and a surface acoustic wave oscillator according to the present invention will be described in detail with reference to the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

First, a first embodiment of a surface acoustic wave (SAW) resonator according to the present invention will be described with reference to FIG. 1A is a plan view of a SAW resonator, FIG. 1B is a partially enlarged sectional view, and FIG. 1C is an enlarged view for explaining details in FIG. 1B. FIG. 1D is a cross-sectional shape that can be assumed when the SAW resonator according to the present invention is manufactured using a photolithographic technique and an etching technique with respect to a partially enlarged view of FIG. It is a figure for demonstrating the identification method of line occupation rate (eta) of an IDT electrode finger in case a cross-sectional shape becomes trapezoid shape instead of a rectangle. The line occupancy η is a convexity at a height that is ½ of (G + H), which is a value obtained by adding the depth (pedestal height) G of the groove 32 and the electrode film thickness H from the bottom of the groove 32. The ratio of the width L to the value obtained by adding the width L of the portion and the width S of the groove 32 (L + S) is appropriate.
The SAW resonator 10 according to the present embodiment is configured based on a quartz substrate 30, an IDT 12, and a reflector 20.

  FIG. 2 is a diagram showing an example of the orientation of the wafer 1 that is the base material of the quartz crystal substrate 30 used in the present invention. In FIG. 2, the X axis is an electric axis of quartz, the Y axis is a mechanical axis of quartz, and the Z axis is an optical axis of quartz. As described later, the wafer 1 has a cut surface with the Z ′ axis as a normal line, and has an X ″ axis and a Y ″ ″ axis perpendicular to the X ″ axis in the cut surface. Further, the IDT 12 and the reflector 20 constituting the SAW resonator 10 are arranged along the X ″ axis in consideration of the SAW propagation direction as described later. The quartz crystal substrate 30 constituting the SAW resonator 10 is cut out from the wafer 1 and separated into pieces. The shape of the quartz substrate 30 in plan view is not particularly limited, but may be a rectangle having a long side in the direction parallel to the X ″ axis and a short side in the direction parallel to the Y ″ ″ axis.

  In this embodiment, the quartz substrate 30 is represented by Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °). An in-plane rotating ST-cut quartz substrate was adopted. Here, the Euler angle will be described with reference to FIG. A substrate represented by Euler angles (0 °, 0 °, 0 °) is a Z-cut substrate 3 having a main surface perpendicular to the Z-axis.

  Here, φ of Euler angles (φ, θ, ψ) is related to the first rotation of the Z-cut substrate 3, and the Z axis is the rotation axis, and the direction rotating from the + X axis to the + Y axis is positive rotation. The first rotation angle is an angle. The X axis and the Y axis after the first rotation are taken as an X ′ axis and a Y ′ axis, respectively. In FIG. 2, as a description of the Euler angle, a case where the Euler angle φ is 0 ° is illustrated. Therefore, in FIG. 2, the X ′ axis overlaps the X axis, and the Y ′ axis overlaps the Y axis.

  The Euler angle θ relates to the second rotation performed after the first rotation of the Z-cut substrate 3, and after the first rotation, the X axis after the first rotation (that is, the X ′ axis) is the rotation axis. This is a second rotation angle in which the direction of rotation from the + Y axis (that is, the + Y ′ axis) to the + Z axis is a positive rotation angle. The cut surface of the piezoelectric substrate, that is, the cut surface of the wafer 1 described above is determined by the first rotation angle φ and the second rotation angle θ. In other words, when the Y axis after the second rotation is the Y ″ axis and the Z axis after the second rotation is the Z ′ axis, the plane parallel to both the X ′ axis and the Y ″ axis is the cut of the piezoelectric substrate. And the Z ′ axis is the normal of this cut surface.

  Euler angle ψ relates to the third rotation performed after the second rotation of the Z-cut substrate 3, and the Z ′ axis, which is the Z axis after the second rotation, is used as the rotation axis, and + This is a third rotation angle in which the direction of rotation from the X axis (that is, + X ′ axis) to the + Y axis (that is, + Y ″ axis) after the second rotation is a positive rotation angle. The propagation direction of the SAW is represented by a third rotation angle ψ with respect to the X axis (that is, the X ′ axis) after the second rotation. That is, if the X axis after the third rotation is the X ″ axis and the Y axis after the third rotation is the Y ″ axis, the plane is parallel to both the X ″ axis and the Y ″ axis. Becomes the cut surface of the piezoelectric substrate, and its normal is the Z ′ axis. Since the normal line does not change even when the third rotation is performed in this way, the cut surface of the piezoelectric substrate also becomes the cut surface of the wafer 1 described above. The direction parallel to the X ″ axis is the SAW propagation direction.

  The SAW phase velocity direction is parallel to the X ″ axis direction. The phenomenon called SAW power flow is a phenomenon in which a shift occurs between the direction in which the SAW phase advances (phase velocity direction) and the direction in which the SAW energy advances (group velocity direction). The angle formed by the phase velocity direction and the group velocity direction is called a power flow angle (see FIG. 3).

  The IDT 12 includes a pair of comb-like electrodes 14a and 14b in which the base ends of the plurality of electrode fingers 18a and 18b are respectively connected by bus bars 16a and 16b, and the electrode fingers 18a constituting one comb-like electrode 14a; The electrode fingers 18b constituting the other comb-like electrode 14b are alternately arranged at a predetermined interval. Further, as shown in FIG. 1A, the electrode fingers 18a and 18b are arranged so that the extending direction of the electrode fingers is orthogonal to the X ″ axis, which is the propagation direction of the surface acoustic wave. The SAW excited by the SAW resonator 10 configured as described above is a Rayleigh type (Rayleigh type) SAW, and has vibration displacement components on both the X ″ axis and the Z ′ axis. Thus, by shifting the SAW propagation direction from the X axis, which is the crystal axis of the quartz crystal, it is possible to excite the SAW in the stop band upper end mode.

  Furthermore, the SAW resonator 10 according to the modification of the first embodiment can be configured as shown in FIG. That is, as shown in FIG. 3, even when an IDT inclined by a power flow angle (hereinafter referred to as PFA) δ from the X ″ axis is applied, high Q can be achieved by satisfying the following requirements. it can. FIG. 3A is a plan view showing an embodiment of the tilted IDT 12a. The X ″ axis, which is the SAW propagation direction determined by the Euler angle, and the extending direction of the electrode fingers 18a and 18b of the tilted IDT 12a are shown in FIG. Are inclined so that the electrode fingers 18a and 18b are arranged in the inclined IDT 12a.

  FIG. 3B is a plan view showing another embodiment of the tilted IDT 12a. In this example, the bus bars 16a and 16b that connect the electrode fingers 18a and 18b to each other are inclined so that the electrode finger arrangement direction is inclined with respect to the X ″ axis. FIG. Similarly, the X ″ axis and the extending direction of the electrode fingers 18a and 18b are orthogonal to each other.

  Regardless of which tilted IDT is used, by arranging the electrode fingers so that the direction perpendicular to the X ″ axis is the extension direction of the electrode fingers as in these embodiment examples, it is possible to obtain good results in the present invention. A low-loss SAW resonator can be realized while maintaining temperature characteristics.

  Here, the relationship between the stop band upper end mode SAW and the lower end mode SAW will be described. FIG. 4 is a diagram showing the distribution of standing waves in the stopband upper end mode and lower end mode in the normal type IDT 12. In the stop band lower end mode and the upper end mode SAW formed by the regular IDT 12 as shown in FIG. 4 (the electrode finger 18 constituting the IDT 12 is shown in FIG. 4), each standing wave is an antinode (or The positions of the nodes are shifted from each other by π / 2 (ie, λ / 4).

  According to FIG. 4, as described above, the standing wave in the stop band lower end mode indicated by the solid line has an antinode at the center position of the electrode finger 18, that is, the reflection center position, and the stop band upper end mode indicated by the alternate long and short dash line. The standing wave has a node at the reflection center position. In such a mode in which a node exists at the center position between the electrode fingers, the SAW vibration cannot be efficiently converted into electric charges by the electrode fingers 18 (18a, 18b), and the mode is excited as an electric signal, or In many cases, it cannot be received. However, according to the method described in the present application, the standing wave in the stopband upper end mode is changed to a solid line in FIG. 4 by making ψ at the Euler angle not zero and shifting the SAW propagation direction from the X axis that is the crystal axis of the crystal. That is, the antinode of the standing wave of the mode can be shifted to the center position of the electrode finger 18, and the SAW in the stop band upper end mode can be excited.

  A pair of reflectors 20 are provided so as to sandwich the IDT 12 in the SAW propagation direction. As a specific configuration example, both ends of a plurality of conductor strips 22 provided in parallel with the electrode fingers 18 constituting the IDT 12 are connected.

  Here, in another embodiment, only one end of each of the plurality of conductor strips 22 can be connected. In still another embodiment, the plurality of conductor strips 22 can be connected at locations other than both ends (for example, the center of the conductor strip 22 in the extending direction).

It should be noted that end face reflection type SAW resonators that actively use the reflected wave from the end face of the quartz substrate in the SAW propagation direction, and that the IDT itself excites SAW standing waves by increasing the number of electrode finger pairs of the IDT. In the anti-IDT type SAW resonator, the reflector is not always necessary.
As the material of the electrode film constituting the IDT 12 and the reflector 20 thus configured, aluminum (Al) or an alloy mainly composed of Al can be used.

  By minimizing the thickness of the electrodes of the electrode films constituting the IDT 12 and the reflector 20, the influence of the temperature characteristics of the electrodes is minimized. Furthermore, a good frequency temperature characteristic is derived by taking a large depth of the groove of the quartz substrate portion and utilizing the good temperature characteristic of the quartz according to the performance of the groove of the quartz substrate portion. As a result, the influence of the temperature characteristics of the electrode on the temperature characteristics of the SAW resonator can be reduced, and good temperature characteristics can be maintained if the mass of the electrode varies within 10%.

  When an alloy is used as the electrode film material for the above reason, the metal other than Al as the main component may be 10% or less, preferably 3% or less by weight. Thereby, the temperature characteristics and other electrical characteristics can be made equivalent to each other when pure Al is used and when an Al alloy is used.

  When an electrode mainly composed of a metal other than Al is used, the thickness of the electrode may be adjusted so that the mass of the electrode is within ± 10% of the case where Al is used. In this way, good temperature characteristics equivalent to those obtained when Al is used can be obtained.

  The quartz crystal substrate 30 in the SAW resonator 10 having the above basic configuration is provided with grooves (interelectrode finger grooves) 32 between the electrode fingers of the IDT 12 and between the conductor strips of the reflector 20.

とすると良い。なお溝深さＧについて上限値を定める場合には、図５を参照することで読み取れるように、

の範囲とすると良い。溝深さＧをこのような範囲で定めることにより、動作温度範囲内（−４０℃〜＋８５℃）における周波数変動量を、詳細を後述する目標値としての２５ｐｐｍ以下とすることができるからである。また、溝深さＧについて望ましくは、

の範囲とすると良い。溝深さＧをこのような範囲で定めることにより、溝深さＧに製造上のばらつきが生じた場合であっても、ＳＡＷ共振子１０個体間における共振周波数のシフト量を補正範囲内に抑えることができる。 The groove 32 provided in the quartz substrate 30 has the SAW wavelength in the stop band upper end mode as λ and the groove depth as G.

And good. When the upper limit value is determined for the groove depth G, as can be read by referring to FIG.

The range is good. This is because by defining the groove depth G in such a range, the amount of frequency fluctuation within the operating temperature range (−40 ° C. to + 85 ° C.) can be set to 25 ppm or less as a target value to be described in detail later. . Desirably, the groove depth G is:

The range is good. By determining the groove depth G in such a range, even if manufacturing variations occur in the groove depth G, the shift amount of the resonance frequency among the 10 SAW resonators is suppressed within the correction range. be able to.

ここで本実施形態に係るＳＡＷ共振子１０は、ライン占有率ηを式（５）、（６）を満たすような範囲で定めると良い。なお、数（５）、（６）からも解るようにηは溝３２の深さＧを定めることにより導き出すことができる。

In addition, as shown in FIG. 1C and FIG. 1D, the line occupancy η is the line width of the electrode finger 18 (in the case of only the crystal convex portion, it means the width of the convex portion) L. The value divided by the pitch λ / 2 between 18 (= L + S). Therefore, the line occupancy η can be expressed by Equation (4).

Here, in the SAW resonator 10 according to the present embodiment, the line occupancy η may be determined in a range that satisfies the expressions (5) and (6). As can be seen from the equations (5) and (6), η can be derived by determining the depth G of the groove 32.

の範囲とすることが望ましい。 Further, the film thickness of the electrode film material (IDT 12, reflector 20, etc.) in the SAW resonator 10 according to the present embodiment is as follows:

It is desirable to be in the range.

Furthermore, when the thickness of the electrode film shown in the equation (7) is taken into consideration for the line occupancy η, η can be obtained by the equation (8).

As the electrode film thickness increases, the variation in electrical characteristics (especially resonance frequency) increases as the electrode film thickness increases, and the electrode film thickness H is within ± 0.04 within the range of equations (5) and (6). When H> 0.035λ, there is a high possibility that a manufacturing variation greater than ± 0.04 will occur. However, if the electrode film thickness H is within the range of the formulas (5) and (6) and the variation of the line occupancy η is within ± 0.04, the SAW device having a small absolute value of the secondary temperature coefficient β. Can be realized. That is, the line occupancy η can be allowed up to the range of the formula (9) obtained by adding a tolerance of ± 0.04 to the formula (8).

In the SAW resonator 10 according to the present embodiment having the above-described configuration, the secondary temperature coefficient β is set within ± 0.01 (ppm / ° C. ² ), and preferably the SAW operating temperature range is −40 ° C. to + 85 ° C. In this case, the object is to improve the frequency temperature characteristic to such an extent that the frequency fluctuation amount ΔF within the operating temperature range can be 25 ppm or less.

By the way, the temperature characteristic of a surface acoustic wave resonator is generally expressed by the following equation.
Δf = α × (T−T ₀ ) + β × (T−T ₀ ) ²
Where Δf is the amount of frequency change (ppm) between temperature T and apex temperature T ₀ , α is the primary temperature coefficient (ppm / ° C.), β is the secondary temperature coefficient (ppm / ° C. ² ), T is the temperature, T ₀ means the temperature (apex temperature) at which the frequency is maximum.

For example, when the piezoelectric substrate is formed of a quartz plate having a so-called ST cut (Euler angles (φ, θ, ψ) = (0 °, 120 ° to 130 °, 0 °)), the primary temperature coefficient α = 0. 0 (ppm / ° C.) and secondary temperature coefficient β = −0.034 (ppm / ° C. ² ), which are shown in FIG. In FIG. 6, the temperature characteristic has an upwardly convex parabola (secondary curve).

  The SAW resonator as shown in FIG. 6 has a very large frequency fluctuation amount with respect to a temperature change, and it is necessary to suppress the frequency change amount Δf with respect to the temperature change. Accordingly, the elastic surface is adjusted so that the secondary temperature coefficient β shown in FIG. 6 is closer to 0 and the frequency change Δf with respect to the change in temperature (operating temperature) when the SAW resonator is actually used approaches 0. It is necessary to realize a wave resonator based on new knowledge.

  Accordingly, one of the objects of the present invention is to solve the above-mentioned problems, to make the surface temperature wave device have excellent frequency-temperature characteristics, and to operate with a stable frequency even if the temperature changes. It is to realize the device.

  If the SAW device having the above-described technical idea (technical element) is used, it is possible to achieve the above-described problem. That is, the present inventor repeats the simulation and the experiment. Whether or not the inventor has come up with the knowledge of the present invention will be described and proved in detail below.

In the SAW resonator in which the propagation direction is the crystal X-axis direction using the above-described quartz substrate called ST cut, the frequency variation ΔF within the operating temperature range is about 133 (ppm) when the operating temperature range is the same. ) And the secondary temperature coefficient β is about −0.034 (ppm / ° C. ² ). In addition, a stop band in a SAW resonator using an in-plane rotating ST-cut quartz substrate in which the cut angle and SAW propagation direction of the quartz substrate are expressed as Euler angles (0, 123 °, 45 °) and the operating temperature range is the same. When the lower end mode excitation is used, the frequency variation ΔF is about 63 ppm, and the secondary temperature coefficient β is about −0.016 (ppm / ° C. ² ).

All of these SAW resonators using ST-cut quartz substrates and in-plane rotating ST-cut quartz substrates use surface acoustic waves called Rayleigh waves, compared to surface acoustic waves called leaky waves of LST-cut quartz substrates. Since the variation of the frequency and frequency temperature characteristics with respect to the processing accuracy of the quartz substrate and the electrode is extremely small, it is excellent in mass productivity and is used in various SAW devices. However, SAW resonators using ST-cut quartz substrates and in-plane rotated ST-cut quartz substrates that have been used in the past have secondary temperature characteristics in which the curve indicating the frequency temperature characteristics is a quadratic curve as described above. Furthermore, since the absolute value of the secondary temperature coefficient of the secondary temperature characteristic is large, the amount of frequency fluctuation in the operating temperature range is large, and a resonator used in a wired communication device or a wireless communication device that seeks frequency stability, It has been difficult to use for SAW devices such as oscillators. For example, the secondary temperature coefficient β corresponding to an improvement of 1/3 or less of the secondary temperature coefficient β of the ST cut quartz substrate and 37% or more of the secondary temperature coefficient β of the in-plane rotated ST cut quartz substrate is ± 0.01. If a frequency temperature characteristic having a secondary temperature characteristic of (ppm / ° C. ² ) or less is obtained, an apparatus for obtaining such frequency stability can be realized. Furthermore, if the secondary temperature coefficient β is almost zero and a tertiary temperature characteristic having a cubic curve representing the frequency temperature characteristic can be obtained, the frequency stability is more improved in the operating temperature range, which is more desirable. With such third-order temperature characteristics, even within a wide operating temperature range of −40 ° C. to + 85 ° C., an extremely high frequency stability of ± 25 ppm or less, which could not be realized with a conventional SAW device, is obtained.

  As described above, the change in the frequency temperature characteristic of the SAW resonator 10 is related to the line occupancy η, the electrode film thickness H, the groove depth G, and the like of the electrode fingers 18 in the IDT 12. It was clarified by the knowledge based on the simulation and experiment conducted. The SAW resonator 10 according to the present embodiment uses stopband upper end mode excitation.

  FIG. 7 shows a crystal substrate 30 in FIG. 1C in which the electrode film thickness H is zero (H = 0% λ), that is, in the state where grooves 32 made of uneven crystals are formed on the surface of the crystal substrate 30. It is a graph which shows the change of the secondary temperature coefficient (beta) with respect to the change of the line occupation rate (eta) when SAW is excited and propagated on the surface of this. 7A shows the secondary temperature coefficient β in the resonance of the stop band upper end mode when the groove depth G is 0.02λ, and FIG. 7B shows the groove depth G of 0.02λ. The secondary temperature coefficient β in the resonance of the stop band lower end mode is shown. 7C shows the secondary temperature coefficient β in resonance in the stop band upper end mode when the groove depth G is 0.04λ, and FIG. 7D shows the groove depth G of 0. The secondary temperature coefficient β in the resonance of the stop band lower end mode when .04λ is set is shown. The simulation shown in FIG. 7 shows an example in which SAW is propagated in some form to the quartz crystal substrate 30 not provided with an electrode film in order to reduce the factor that fluctuates the frequency temperature characteristic. The cut angle of the quartz substrate 30 was Euler angles (0 °, 123 °, ψ). For ψ, a value that minimizes the absolute value of the secondary temperature coefficient β is appropriately selected.

  From FIG. 7, it can be read that the secondary temperature coefficient β greatly changes when the line occupancy η is 0.6 to 0.7 in both the stop band upper end mode and the lower end mode. it can. When the change in the secondary temperature coefficient β in the stop band upper end mode is compared with the change in the secondary temperature coefficient β in the stop band lower end mode, the following can be read. That is, the characteristic of the change in the secondary temperature coefficient β in the stop band lower end mode is deteriorated by changing from the minus side to the minus side (the absolute value of the secondary temperature coefficient β is increased). On the other hand, the change in the secondary temperature coefficient β in the stop band upper end mode is improved by changing from the minus side to the plus side (there is a point where the absolute value of the secondary temperature coefficient β becomes small). It is that).

  From this, it has been clarified that it is desirable to use the vibration in the stop band upper end mode in order to obtain good frequency temperature characteristics in the SAW device.

  Next, the inventor examined the relationship between the line occupancy η and the secondary temperature coefficient β when the stop band upper end mode SAW was propagated in the quartz substrate with various groove depths G.

  8A to 8I, similarly to FIG. 7, the electrode film thickness H is set to zero (H = 0% λ), and the groove depth G is changed from 0.01λ (1% λ) to 0.08λ ( It is a graph which shows the evaluation result when simulating the relationship between the line occupation rate (eta) and the secondary temperature coefficient (beta) when changing to 8% (lambda). From the evaluation results, the point where β = 0 is obtained when the groove depth G is set to 0.0125λ (1.25% λ) as shown in FIG. 8B, that is, the approximate curve indicating the frequency temperature characteristic is a cubic curve. It can be seen that the points shown are beginning to appear. From FIG. 8, there are two η at which β = 0 (point (η1) where β = 0 when η is larger, and point (η2) where β = 0 when η is smaller)). It was also found to exist. Furthermore, it can be read from the evaluation results shown in FIG. 8 that the variation amount of the line occupancy η with respect to the change in the groove depth G is larger in η2 than in η1.

  About this point, the understanding can be deepened by referring to FIG. FIG. 9 is a graph plotting η1 and η2 at which the secondary temperature coefficient β becomes 0 when the groove depth G is changed. FIG. 9 shows that η1 and η2 become smaller with each other as the groove depth G becomes larger. However, η2 is a groove depth in the graph showing the scale of the vertical axis η in the range of 0.5λ to 0.9λ. It can be read that the amount of variation increases as the scale-out occurs when G = 0.04λ. That is, it can be said that η2 has a large fluctuation amount with respect to the change of the groove depth G.

  10 (A) to 10 (I) show frequency fluctuations in which the electrode film thickness H is zero (H = 0% λ) and the vertical axis in FIG. It is the graph shown as quantity (DELTA) F. Naturally, it can be seen from FIG. 10 that the frequency variation ΔF decreases at two points (η1, η2) where β = 0. Further, from FIG. 10, it can be read that at two points where β = 0, the frequency fluctuation amount ΔF is suppressed smaller at the point corresponding to η1 in any graph where the groove depth G is changed. be able to.

  According to the above tendency, for mass-produced products that are likely to cause an error during manufacturing, it is desirable to adopt η1 that has a smaller amount of frequency fluctuation at the point where β = 0 with respect to fluctuation of the groove depth G. FIG. 5 is a graph showing the relationship between the frequency variation ΔF and the groove depth G at the point (η1) at which the secondary temperature coefficient β is minimum at each groove depth G. According to FIG. 5, the lower limit value of the groove depth G at which the frequency fluctuation amount ΔF is 25 ppm or less, which is the target value, is 0.01λ, and the range of the groove depth G is more than that, that is, 0. 01 ≦ G.

  In FIG. 5, an example in which the groove depth G is 0.08 or more is also added by simulation. According to this simulation, when the groove depth G is 0.01λ or more, the frequency variation ΔF is 25 ppm or less, and thereafter, as the groove depth G increases, the frequency variation ΔF decreases. However, when the groove depth G is about 0.9λ or more, the frequency variation ΔF increases again, and when it exceeds 0.094λ, the frequency variation ΔF exceeds 25 ppm.

と示すことができる。 The graph shown in FIG. 5 is a simulation in a state where the electrode film such as the IDT 12 and the reflector 20 is not formed on the quartz substrate 30. As will be understood with reference to FIGS. The SAW resonator 10 is considered to be able to reduce the frequency fluctuation amount ΔF when the electrode film is provided. Accordingly, if the upper limit value of the groove depth G is determined, the maximum value in a state where the electrode film is not formed, that is, G ≦ 0.94λ may be set, and the groove depth G suitable for achieving the target is set. As a range,

Can be shown.

  In the mass production process, the groove depth G has a maximum variation of about ± 0.001λ. Accordingly, FIG. 11 shows individual frequency fluctuation amounts Δf of the SAW resonator 10 when the groove depth G is shifted by ± 0.001λ when the line occupation ratio η is constant. According to FIG. 11, when G = 0.04λ, when the groove depth G is shifted by ± 0.001λ, that is, when the groove depth is 0.039λ ≦ G ≦ 0.041λ, It can be read that Δf is about ± 500 ppm.

  Here, if the frequency fluctuation amount Δf is less than ± 1000 ppm, the frequency can be adjusted by various frequency fine adjustment means. However, when the frequency fluctuation amount Δf becomes ± 1000 ppm or more, the frequency adjustment affects static characteristics such as Q value and CI (crystal impedance) value and long-term reliability. This leads to a decrease in the yield rate.

When an approximate expression showing the relationship between the frequency fluctuation amount Δf [ppm] and the groove depth G is derived for the straight line connecting the plots shown in FIG. 11, Expression (10) can be obtained.

とすることが望ましいということができる。 Here, when a value of G satisfying Δf <1000 ppm is obtained, G ≦ 0.0695λ. Therefore, preferably as the range of the groove depth G according to the present embodiment,

It can be said that it is desirable.

  Next, in FIGS. 12A to 12F, evaluation results obtained by simulating the relationship between η at which the secondary temperature coefficient β = 0, that is, the line occupancy η indicating the tertiary temperature characteristic and the groove depth G are simulated. The graph of is shown. The quartz substrate 30 has Euler angles (0 °, 123 °, ψ). Here, for ψ, an angle at which the frequency temperature characteristic shows a tendency of a cubic curve, that is, an angle at which the secondary temperature coefficient β = 0 is appropriately selected. FIG. 34 shows the relationship between Euler angle ψ and groove depth G when η where β = 0 is obtained under the same conditions as in FIG. In the graph of electrode film thickness H = 0.02λ in FIG. 34 (FIG. 34C), a plot of ψ <42 ° is not displayed, but the plot of η2 in this graph is ψ at G = 0.03λ. = 41.9 °. With respect to the relationship between the groove depth G and the line occupancy η for each electrode film thickness, plots are obtained based on FIGS.

From the evaluation results shown in FIGS. 12A to 12F, it can be read that at any film thickness, as described above, η1 is less fluctuated due to changes in the groove depth G than η2. it can. Therefore, η1 is extracted from the graph showing the relationship between the groove depth G of each film thickness and the line occupancy η in FIG. 12, and the points where β≈0 are plotted and summarized in FIG. On the other hand, when the region satisfying | β | ≦ 0.01 (ppm / ° C. ² ) is evaluated even though β≈0, the polygonal area indicated by the solid line as shown in FIG. It is clear that η1 is concentrated in the area.

Table 1 shows the coordinates of the points a to h in FIG.

式（１１）、（１２）、（１３）より、図１３（Ｂ）において実線で囲った範囲において、ライン占有率ηは、式（５）と式（６）の両方を満たす範囲として特定することができるといえる。

In FIG. 13B, as long as it is within a polygon surrounded by points a to h, | β | ≦ 0.01 (ppm / ° C. ² ) is guaranteed regardless of the thickness of the electrode film thickness H, which is good. It shows that frequency temperature characteristics can be obtained. The range in which this favorable frequency-temperature characteristic is obtained is a range that satisfies both the following formulas (11), (12), and (13).

From the expressions (11), (12), and (13), the line occupancy η is specified as a range that satisfies both the expressions (5) and (6) in the range surrounded by the solid line in FIG. It can be said that it is possible.

Here, when the secondary temperature coefficient β is allowed to be within ± 0.01 (ppm / ° C. ² ), in 0.0100λ ≦ G ≦ 0.0500λ, both the expressions (3) and (5) are satisfied, In the case of 0.0500λ <G ≦ 0.0695λ, the second-order temperature coefficient β should be within ± 0.01 (ppm / ° C. ² ) if both the expressions (3) and (6) are satisfied. It was confirmed.

The values of secondary temperature coefficient β (ppm / ° C. ² ) of each electrode film thickness H at points a to h are shown in Table 2 below. From Table 2, it can be confirmed that | β | ≦ 0.01 (ppm / ° C. ² ) at all points.

  Further, the SAW resonator 10 having electrode thicknesses H≈0, 0.01λ, 0.02λ, and 0.03λ based on the equations (11) to (13) and the equations (5) and (6) derived thereby. FIG. 14 shows the relationship between the groove depth G at which β = 0 and the line occupancy η as approximate lines. In addition, the relationship between the groove depth G and the line occupation ratio η in the quartz crystal substrate 30 without the electrode film is as shown in FIG.

ここで、Ｇ、Ｈの単位はλである。
但し、この式（８）は、電極膜厚Ｈが、０＜Ｈ≦０．０３０λの範囲において成立するものである。 When the electrode film thickness H is changed to 3.0% λ (0.030λ) or less, β = 0, that is, a frequency-temperature characteristic of a cubic curve is obtained. At this time, a relational expression between G and η that provides good frequency-temperature characteristics can be expressed by Expression (8).

Here, the unit of G and H is λ.
However, this equation (8) is established when the electrode film thickness H is in the range of 0 <H ≦ 0.030λ.

As the electrode film thickness increases, the variation in electrical characteristics (especially resonance frequency) increases as the electrode film thickness increases, and the electrode film thickness H is within ± 0.04 within the range of equations (5) and (6). When H> 0.035λ, there is a high possibility that a manufacturing variation greater than ± 0.04 will occur. However, if the electrode film thickness H is in the range of the formulas (5) and (6) and the variation in the line occupancy η is within ± 0.04, a SAW device having a small secondary temperature coefficient β can be realized. . That is, when the secondary temperature coefficient β is set within ± 0.01 ppm / ° C. ² in consideration of manufacturing variation of the line occupancy, the line occupancy η adds ± 0.04 tolerance to the equation (8). The range of the formula (9) is acceptable.

  15 to 20, the electrode film thicknesses are 0.01λ (1% λ), 0.015λ (1.5% λ), 0.02λ (2% λ), and 0.025λ (2.5% λ, respectively). ), 0.03λ (3% λ), 0.035λ (3.5% λ), and the relationship between the line occupancy η and the secondary temperature coefficient β when the groove depth G is changed. A graph is shown.

  21 to 26 are graphs showing the relationship between the line occupancy η and the frequency variation ΔF in the SAW resonator 10 corresponding to FIGS. 15 to 20 respectively. Note that all quartz substrates have Euler angles (0 °, 123 °, ψ), and an angle that minimizes ΔF is appropriately selected for ψ.

  Here, FIGS. 15A to 15F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.01λ, and FIG. (F) to (F) are diagrams showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.01λ.

  FIGS. 16A to 16F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.015λ, and FIGS. (F) is a diagram showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.015λ.

  FIGS. 17A to 17F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.02λ, and FIGS. (F) is a diagram showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.02λ.

  18A to 18F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.025λ, and FIGS. (F) is a diagram showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.025λ.

  FIGS. 19A to 19F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.03λ, and FIGS. (F) is a diagram showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.03λ.

  20A to 20F are diagrams showing the relationship between the line occupancy η and the secondary temperature coefficient β when the electrode film thickness H is 0.035λ, and FIGS. (F) is a diagram showing the relationship between the line occupancy η and the frequency variation ΔF when the electrode film thickness H is 0.035λ.

In these figures (FIGS. 15 to 26), although there is a slight difference in any of the graphs, the line occupancy η, the secondary temperature coefficient β, and the line occupancy of only the quartz substrate 30 are related to the change tendency. It can be seen that the graph is similar to FIGS. 8 and 10 which are graphs showing the relationship between the rate η and the frequency variation ΔF.
That is, it can be said that the effect according to the present embodiment can also be achieved in the propagation of the surface acoustic wave in the crystal substrate 30 alone excluding the electrode film.

For each of the two points η1 and η2 at which the secondary temperature coefficient β is 0, the range of η1 and η2 when the range of β is expanded to | β | ≦ 0.01 (ppm / ° C. ² ), A simulation was performed for each of the cases where the groove depth G was changed by defining the range of the electrode film thickness H. Incidentally, .eta.1, respectively η2, | β | ≦ 0.01 ( ppm / ℃ 2) to become larger the η η1, | β | ≦ 0.01 and becomes smaller the η (ppm / ℃ ²⁾ η2 is set. In addition, all quartz substrates have Euler angles (0 °, 123 °, ψ), and an angle that minimizes ΔF is appropriately selected for ψ.

FIG. 27A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.000λ <H ≦ 0.005λ. Table 3 FIG. 28 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 27A and the value of β at the measurement points.

  From FIG. 27A and Table 3, when the electrode film thickness H is within the above range for η1, the measurement point a-r is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.09λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 27B is a graph showing the relationship between η2 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.000λ <H ≦ 0.005λ. Table 4 28 is a table showing the coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 27B and the value of β at the measurement points.

  From FIG. 27B and Table 4, when the electrode film thickness H is within the above range at η2, the measurement point an is the apex in the range where the groove depth G is 0.03λ ≦ G ≦ 0.09λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 28A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.005λ <H ≦ 0.010λ. Table 5 FIG. 29 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 28A and the value of β at the measurement points.

  From FIG. 28A and Table 5, when the electrode film thickness H is within the above range at η1, the measurement point ap is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.08λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 28B is a graph showing the relationship between η2 that satisfies the above range of β and the groove depth G when the electrode film thickness H is 0.005λ <H ≦ 0.010λ. FIG. 29 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 28B and the value of β at the measurement points.

  From FIG. 28B and Table 6, when the electrode film thickness H is within the above range at η2, the measurement point a-1 is the apex in the range where the groove depth G is 0.02λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 29A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.010λ <H ≦ 0.015λ. Table 7 30 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 29A and the value of β at the measurement points.

  29A and Table 7, from η1, when the electrode film thickness H is within the above range, the measurement point ap is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.08λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 29B is a graph showing the relationship between η2 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.010λ <H ≦ 0.015λ. Table 8 30 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 29B and the value of β at the measurement points.

  From FIG. 29B and Table 8, when the electrode film thickness H is within the above range at η2, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 30A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.015λ <H ≦ 0.020λ. Table 9 FIG. 31 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 30A and the value of β at the measurement points.

  30A and Table 9, from η1, when the electrode film thickness H is within the above range, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 30B is a graph showing the relationship between η2 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.015λ <H ≦ 0.020λ. Table 10 FIG. 31 is a table showing coordinates (G / λ, η) of main measurement points for defining the range shown in FIG. 30B and the value of β at the measurement points.

  From FIG. 30B and Table 10, when the electrode film thickness H is within the above range at η2, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 31A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.020λ <H ≦ 0.025λ. Table 11 FIG. 32 is a table showing coordinates (G / λ, η) of main measurement points for defining the range shown in FIG. 31A and the value of β at the measurement points.

  From FIG. 31A and Table 11, when the electrode film thickness H is within the above range at η1, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 31B is a graph showing the relationship between η2 that satisfies the range of β and the groove depth G when the electrode film thickness H is 0.020λ <H ≦ 0.025λ. Table 12 FIG. 32 is a table showing the coordinates (G / λ, η) of main measurement points for defining the range shown in FIG. 31B and the value of β at the measurement points.

  From FIG. 31B and Table 12, when the electrode film thickness H is within the above range at η2, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 32A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.025λ <H ≦ 0.030λ. Table 13 FIG. 33 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 32A and the value of β at the measurement points.

  From FIG. 32A and Table 13, when the electrode film thickness H is within the above range at η1, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 32B is a graph showing the relationship between η2 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.025λ <H ≦ 0.030λ. Table 14 FIG. 33 is a table showing coordinates (G / λ, η) of main measurement points for determining the range shown in FIG. 32B and the value of β at the measurement points.

  From FIG. 32 (B) and Table 14, when the electrode film thickness H is within the above range at η2, the measurement point an is defined as the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 33A is a graph showing the relationship between η1 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.030λ <H ≦ 0.035λ. Table 15 It is a table | surface which shows the coordinate (G / (lambda), (eta)) of the main measurement points for defining the range shown to FIG. 33 (A), and the value of (beta) in the said measurement point.

  From FIG. 33A and Table 15, when the electrode film thickness H is within the above range at η1, the measurement point an is defined as the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

FIG. 33 (B) is a graph showing the relationship between η2 satisfying the range of β and the groove depth G when the electrode film thickness H is 0.030λ <H ≦ 0.035λ. FIG. 34 is a table showing coordinates (G / λ, η) of main measurement points for defining the range shown in FIG. 33B and the value of β at the measurement points.

  From FIG. 33 (B) and Table 16, when the electrode film thickness H is within the above range at η2, the measurement point an is the apex in the range where the groove depth G is 0.01λ ≦ G ≦ 0.07λ. It can be read that β satisfies the above requirement in the region surrounded by the polygons.

  FIG. 35 summarizes the relationship between ψ obtained by η1 and the groove depth G in the graph shown in FIG. The reason for selecting η1 is as described above. As shown in FIG. 35, even when the film thickness of the electrode film changes, there is almost no difference in the angle of ψ, and the optimum angle of ψ may change according to the variation of the groove depth G. I understand. This can also be said to support that the ratio of the change in the secondary temperature coefficient β is high due to the form of the crystal substrate 30.

In the same manner as described above, the relationship between the groove temperature G and ψ with a secondary temperature coefficient β = −0.01 (ppm / ° C. ² ) and ψ with β = + 0.01 (ppm / ° C. ² ) is obtained. 36 and FIG. 37. When the angle of ψ that can satisfy −0.01 ≦ β ≦ + 0.01 is obtained from these graphs (FIGS. 35 to 37), the preferable angle range of ψ under the above conditions is 43 ° <ψ <45. It can be defined as °, more preferably 43.2 ° ≦ ψ ≦ 44.2.

When the electrode film thickness H was changed, a simulation was performed for a range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the groove depth G was changed. The simulation results are shown in FIGS. In addition, all quartz substrates have Euler angles (0 °, 123 °, ψ), and an angle that minimizes ΔF is appropriately selected for ψ.

FIG. 38A is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0 <H ≦ 0.005λ. is there. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695, and the range of the solid line and the broken line shown in FIG. 38 (A) is approximated by a polygonal shape, it can be shown as FIG. 38 (B), It can be said that β satisfies the above condition in the range corresponding to the inside of the polygon indicated by the solid line in FIG. When the polygonal range shown in FIG. 38B is expressed by an approximate expression, it can be expressed by expressions (14) and (15).

FIG. 39A shows the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.005λ <H ≦ 0.010λ. It is a graph. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695, and the range of the solid line and the broken line shown in FIG. 39 (A) is approximated by a polygonal shape, it can be shown as FIG. 29 (B), It can be said that β satisfies the above condition in the range corresponding to the inside of the polygon indicated by the solid line in FIG. When the polygonal range shown in FIG. 39B is expressed by an approximate expression, it can be expressed by expressions (16) and (17).

FIG. 40A shows the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.010 <H ≦ 0.015λ. It is a graph. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695 and the range of the solid line and the broken line shown in FIG. 40 (A) is approximated by a polygonal shape, it can be shown as FIG. 40 (B), In the range corresponding to the inside of the polygon indicated by the solid line in FIG. When the polygonal range shown in FIG. 40B is expressed by an approximate expression, it can be expressed by expressions (18) and (19).

FIG. 41A shows the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.015 <H ≦ 0.020λ. It is a graph. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695 and the range of the solid line and the broken line shown in FIG. 41 (A) is approximated by a polygonal shape, it can be shown in FIG. 41 (B), In the range corresponding to the inside of the polygon indicated by the solid line in FIG. 41B, it can be said that β satisfies the above condition. When the polygonal range shown in FIG. 41B is expressed by an approximate expression, it can be expressed by expressions (20) and (21).

FIG. 42 is a graph showing the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.020 <H ≦ 0.025λ. . Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695, and the range of the solid line and the broken line shown in FIG. 42 is approximated by a polygonal shape, it can be shown as FIG. In the range corresponding to the inside of the polygon indicated by the solid line in B), it can be said that β satisfies the above condition. When the polygonal range shown in FIG. 42B is expressed by an approximate expression, it can be expressed by expressions (22) to (24).

FIG. 43A shows the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.025 <H ≦ 0.030λ. It is a graph. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

図４４（Ａ）は、電極膜厚Ｈの範囲を０．０３０＜Ｈ≦０．０３５λとした場合において、｜β｜≦０．０１（ｐｐｍ／℃^２）の要件を満たすψの範囲を示すグラフである。ここで、ψの最大値を示すプロットを結ぶ直線と、ψの最小値を示すプロットを結ぶ破線とで挟まれた範囲が、上記条件を満たす範囲である。 When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695 and the range of the solid line and the broken line shown in FIG. 43 (A) is approximated by a polygonal shape, it can be shown in FIG. 43 (B), It can be said that β satisfies the above condition in the range corresponding to the inside of the polygon indicated by the solid line in FIG. When the polygonal range shown in FIG. 43B is represented by an approximate expression, it can be represented by expressions (25) to (27).

FIG. 44A shows the range of ψ that satisfies the requirement of | β | ≦ 0.01 (ppm / ° C. ² ) when the range of the electrode film thickness H is 0.030 <H ≦ 0.035λ. It is a graph. Here, a range sandwiched between a straight line connecting plots indicating the maximum value of ψ and a broken line connecting plots indicating the minimum value of ψ is a range satisfying the above condition.

When the groove depth G is in the range of 0.01λ ≦ G ≦ 0.0695 and the range of the solid line and the broken line shown in FIG. 44 (A) is approximated by a polygonal shape, it can be shown in FIG. 44 (B), It can be said that β satisfies the above condition in the range corresponding to the inside of the polygon indicated by the solid line in FIG. When the polygonal range shown in FIG. 44B is expressed by an approximate expression, it can be expressed by expressions (28) to (30).

  Next, FIG. 45 shows a change in the secondary temperature coefficient β when the angle θ is changed, that is, the relationship between θ and the secondary temperature coefficient β. Here, the SAW device used for the simulation is a quartz substrate in which the cut angle and the SAW propagation direction are represented by Euler angles (0, θ, ψ) and the groove depth G is 0.04λ, and the electrode thickness H Is 0.02λ. Regarding ψ, a value that minimizes the absolute value of the secondary temperature coefficient β was appropriately selected within the above-described angle range based on the set angle of θ. Further, η was set to 0.6383 according to the above formula (8).

From FIG. 45 showing the relationship between θ and the secondary temperature coefficient β under such conditions, the absolute value of the secondary temperature coefficient β is 0.00 when the θ is in the range of 117 ° to 142 °. It can be read that it is within the range of 01 (ppm / ° C. ² ). Therefore, it can be said that the SAW resonator 10 having good frequency temperature characteristics can be configured by setting θ within the range of 117 ° ≦ θ ≦ 142 ° in the above set values.

Tables 17 to 19 are shown as simulation data supporting the relationship between θ and the secondary temperature coefficient β.

Table 17 is a table showing the relationship between θ and the secondary temperature coefficient β when the electrode film thickness H is changed. When the electrode film thickness H is 0.01% λ, the electrode film thickness H is 3%. The value of the secondary temperature coefficient β at the critical value of θ (117 °, 142 °) in the case of .50% λ is shown. Note that the groove depth G in this simulation is 4% λ. From Table 17, when the thickness of the electrode film thickness H is changed within the range of 117 ° ≦ θ ≦ 142 ° (0≈0.01% λ and 3.5% λ defined as the critical value of the electrode film thickness). Even so, it can be read that | β | ≦ 0.01 (ppm / ° C. ² ) is satisfied without depending on the thickness.

表１８は、溝深さＧを変えた場合におけるθと二次温度係数βとの関係を示す表であり、溝深さＧを１．００％λと６．９５％λとした場合におけるθの臨界値（１１７°、１４２°）での二次温度係数βの値を示す。なお、このシミュレーションにおける電極膜厚Ｈは、いずれも２．００％λである。表１８からは、１１７°≦θ≦１４２°の範囲では、溝深さＧを変えた場合（溝深さＧの臨界値として規定した１．００％λと６．９５％λ）であっても、その深さに依存する事無く｜β｜≦０．０１（ｐｐｍ／℃^２）を満足するということを読み取ることができる。

Table 18 is a table showing the relationship between θ and the secondary temperature coefficient β when the groove depth G is changed, and θ when the groove depth G is 1.00% λ and 6.95% λ. The values of the secondary temperature coefficient β at the critical values (117 °, 142 °) are shown. Note that the electrode film thickness H in this simulation is 2.00% λ. From Table 18, in the range of 117 ° ≦ θ ≦ 142 °, the groove depth G is changed (1.00% λ and 6.95% λ defined as the critical value of the groove depth G). However, it can be read that | β | ≦ 0.01 (ppm / ° C. ² ) is satisfied without depending on the depth.

表１９は、ライン占有率ηを変えた場合におけるθと二次温度係数βとの関係を示す表であり、ライン占有率ηを０．６２と０．７６とした場合におけるθの臨界値（１１７°、１４２°）での二次温度係数βの値を示す。なお、このシミュレーションにおける電極膜厚Ｈは、いずれも２．００％λであり、溝深さＧは、いずれも４．００％λである。表１９からは、１１７°≦θ≦１４２°の範囲では、ライン占有率ηを変えた場合（η＝０．６２、０．７６は、電極膜厚Ｈを０．０２０λ〜０．０２５の範囲としてライン占有率η（η１）と溝深さＧの関係を示した図３１（Ａ）において、溝深さを４％λとした場合におけるηの最小値と最大値）であっても、その値に依存する事無く｜β｜≦０．０１（ｐｐｍ／℃^２）を満足するということを読み取ることができる。

Table 19 is a table showing the relationship between θ and the secondary temperature coefficient β when the line occupancy η is changed. The critical value of θ when the line occupancy η is 0.62 and 0.76 ( The values of the secondary temperature coefficient β at 117 °, 142 °) are shown. In this simulation, the electrode film thickness H is 2.00% λ, and the groove depth G is 4.00% λ. From Table 19, when the line occupancy η is changed in the range of 117 ° ≦ θ ≦ 142 ° (η = 0.62, 0.76, the electrode film thickness H is in the range of 0.020λ to 0.025. In FIG. 31A showing the relationship between the line occupancy η (η1) and the groove depth G, the minimum and maximum values of η when the groove depth is 4% λ It can be read that | β | ≦ 0.01 (ppm / ° C. ² ) is satisfied without depending on the value.

  In FIG. 46, a crystal substrate 30 of Euler angle display (φ, 123 °, 43.77 °) is used, the groove depth G is 0.04λ, the electrode film thickness H is 0.02λ, and the line occupancy η is It is a graph which shows the relationship between the angle of (phi), and secondary temperature coefficient (beta), when it is set to 0.65.

From FIG. 46, when φ is −2 ° and + 2 °, the secondary temperature coefficient β is lower than −0.01 (ppm / ° C. ² ), but φ is −1.5. It can be reliably read that the absolute value of the secondary temperature coefficient β is within the range of 0.01 (ppm / ° C. ² ) within the range of from ° to + 1.5 °. Therefore, by setting φ within the range of −1.5 ° ≦ φ ≦ + 1.5 °, preferably −1 ° ≦ φ ≦ + 1 ° at the set values as described above, good frequency temperature characteristics can be obtained. The SAW resonator 10 can be configured.

In the above description, φ, θ, and ψ each derive an optimum value range in relation to the groove depth G under certain conditions. On the other hand, FIG. 47 shows a highly desirable relationship between θ and ψ that minimizes the amount of frequency fluctuation from −40 ° C. to + 85 ° C., and an approximate expression is obtained. According to FIG. 47, the angle of ψ changes as the angle of θ increases, and rises to draw a cubic curve. In the example of FIG. 47, ψ when θ = 117 ° is 42.79 °, and ψ when θ = 142 ° is 49.57 °. When these plots are shown as approximate curves, they become curves shown by broken lines in FIG. 47, and can be expressed by equation (31) as an approximate expression.

  From this, ψ can be determined by defining θ, and the range of ψ when the range of θ is 117 ° ≦ θ ≦ 142 ° is 42.79 ° ≦ ψ ≦ 49.57 °. it can. In the simulation, the groove depth G and the electrode film thickness H were G = 0.04λ and H = 0.02λ, respectively.

  For the reasons described above, by configuring the SAW resonator 10 under various conditions in the present embodiment, a SAW resonator capable of realizing a good frequency temperature characteristic satisfying the target value can be obtained.

  Further, in the SAW resonator 10 according to the present embodiment, as shown in the equation (7) and FIGS. 15 to 26, the frequency H is set with the electrode film thickness H in the range of 0 <H ≦ 0.035λ. The temperature characteristics are improved. This is to improve the frequency temperature characteristics while maintaining the environmental resistance characteristics, unlike the conventional technique in which the film thickness H is extremely increased to improve the frequency temperature characteristics. FIG. 54 shows the relationship between the electrode film thickness (Al electrode film thickness) and the frequency fluctuation in the heat cycle test. The results of the heat cycle test shown in FIG. 54 are as follows: the SAW resonator was exposed to a −55 ° C. atmosphere for 30 minutes, then the ambient temperature was raised to + 125 ° C. and then exposed for 30 minutes, and the cycle was continued 8 times. Is. From FIG. 54, compared with the case where the electrode film thickness H is set to 0.06λ and no inter-electrode finger groove is provided, in the range of the electrode film thickness H of the SAW resonator 10 according to the present embodiment, the frequency variation (F variation). ) Can be read as 1/3 or less. In FIG. 54, H + G = 0.06λ is set for all plots.

  In addition, when a high temperature storage test was performed for a SAW resonator manufactured under the same conditions as in FIG. 54 for 1000 hours in a 125 ° C. atmosphere, it was compared with a conventional SAW resonator (H = 0.06λ and G = 0). The SAW resonator according to this embodiment (H = 0.03λ and G = 0.03λ, H = 0.02λ and G = 0.04λ, H = 0.015λ, G = 0.045λ, H = 0. It was confirmed that the amount of frequency fluctuation before and after the test (4 conditions of 01λ and G = 0.05λ) was 1/3 or less.

  Under the above conditions, H + G = 0.067λ (aluminum film thickness 2000 mm, groove depth 4700 mm), IDT line occupancy ηi = 0.6, reflector line occupancy ηr = 0.8, Euler angle (0 °, 123 °, 43.5 °), 120 pairs of IDTs, intersection width 40λ (λ = 10 μm), 72 reflectors (per side) (36 pairs), no inclination angle of electrode fingers (electrodes 48. The SAW resonator 10 manufactured under the condition that the finger arrangement direction and the SAW phase velocity direction match) exhibits frequency-temperature characteristics as shown in FIG.

  FIG. 48 is a plot of frequency temperature characteristics with the number of test pieces n = 4. According to FIG. 48, it can be read that the frequency fluctuation amount ΔF in the operating temperature range by these test pieces is suppressed to about 20 ppm or less.

  In the present embodiment, the influence of the groove depth G and the electrode film thickness H on the frequency temperature characteristics has been described. However, the depth (step) obtained by combining the groove depth G and the electrode film thickness H also affects the static characteristics such as equivalent circuit constants and CI values, and the Q value. For example, FIG. 49 is a graph showing the relationship between the step and the CI value when the step is changed from 0.062λ to 0.071λ. According to FIG. 49, it can be read that the CI value converges when the step is set to 0.067λ, and does not improve (is not lowered) even when the step is further increased.

  FIG. 50 summarizes the frequencies, equivalent circuit constants, and static characteristics of the SAW resonator 10 exhibiting frequency temperature characteristics as shown in 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).

  FIG. 52 shows a graph for comparing the relationship between the step and the Q value in the conventional SAW resonator and the SAW resonator 10 according to the present embodiment. In FIG. 52, the graph indicated by the bold line shows the characteristics of the SAW resonator 10 according to the present embodiment, and a groove is provided between the electrode fingers and the resonance in the stop band upper end mode is used. . A graph indicated by a thin line shows the characteristics of a conventional SAW resonator, and uses a stop band upper end mode resonance without providing a groove between electrode fingers. As is apparent from FIG. 52, when a groove is provided between the electrode fingers and the resonance in the stop band upper end mode is used, the gap between the electrode fingers is in a region where the step (G + H) is 0.0407λ (4.07% λ) or more. Thus, a higher Q value can be obtained than in the case of using the stop-band lower-end mode resonance without providing a groove.

The basic data of the SAW resonator according to the simulation is as follows.
Basic data H of the SAW resonator 10 according to the present embodiment: 0.02λ
G: Change IDT line occupancy ηi: 0.6
Reflector line occupancy ηr: 0.8
Euler angles (0 °, 123 °, 43.5 °)
Logarithm: 120
Crossing width: 40λ (λ = 10μm)
Number of reflectors (per one side): 60
No inclination angle of electrode fingers Basic data of conventional SAW resonator H: Change G: Zero IDT line occupancy ηi: 0.4
Reflector line occupancy ηr: 0.3
Euler angles (0 °, 123 °, 43.5 °)
Logarithm: 120
Crossing width: 40λ (λ = 10μm)
Number of reflectors (per one side): 60
No electrode finger tilt angle

  Referring to FIG. 50 and FIG. 52 for comparing the characteristics of these SAW resonators, it can be understood how the QW of the SAW resonator 10 according to the present embodiment is increased. Such a high Q is considered to be due to an improvement in the energy confinement effect, for the following reason.

の関係を満たすように設定すれば良い。これにより、ＩＤＴ１２のストップバンド上端の周波数ｆｔ２において、反射器２０の反射係数Γが大きくなり、ＩＤＴ１２から励振されたストップバンド上端モードのＳＡＷが、反射器２０にて高い反射係数でＩＤＴ１２側に反射されるようになる。そしてストップバンド上端モードのＳＡＷのエネルギー閉じ込めが強くなり、低損失な共振子を実現することができる。 In order to efficiently confine energy of the surface acoustic wave excited in the upper end mode of the stop band, the frequency ft2 at the upper end of the stop band of the IDT 12 and the frequency fr1 at the lower end of the stop band of the reflector 20 and the reflector as shown in FIG. What is necessary is just to set between the frequency fr2 of 20 stopband upper ends. That is,

It may be set so as to satisfy the relationship. As a result, the reflection coefficient Γ of the reflector 20 becomes large at the frequency ft2 at the upper end of the stop band of the IDT 12, and the SAW in the stop band upper end mode excited from the IDT 12 is reflected by the reflector 20 toward the IDT 12 with a high reflection coefficient. Will come to be. And the energy confinement of the SAW in the stop band upper end mode becomes stronger, and a low-loss resonator can be realized.

  On the other hand, the relationship between the frequency ft2 at the upper end of the stop band of the IDT 12, the frequency fr1 at the lower end of the stop band of the reflector 20, and the frequency fr2 at the upper end of the stop band of the reflector 20 is set to a state of ft2 <fr1 or fr2 <ft2. If set, the reflection coefficient Γ of the reflector 20 becomes small at the stop band upper end frequency ft2 of the IDT 12, and it becomes difficult to realize a strong energy confinement state.

  Here, in order to realize the state of Expression (32), it is necessary to shift the frequency of the stop band of the reflector 20 to a higher frequency side than the stop band of the IDT 12. Specifically, this can be realized by making the arrangement period of the conductor strips 22 of the reflector 20 smaller than the arrangement period of the electrode fingers 18 of the IDT 12. As another method, the film thickness of the electrode film formed as the conductor strip 22 of the reflector 20 is made thinner than the film thickness of the electrode film formed as the electrode finger 18 of the IDT 12, or between the electrode fingers of the IDT 12 This can be realized by making the depth of the groove between the conductor strips of the reflector 20 shallower than the depth of the groove. Also, a combination of these methods may be applied.

  According to FIG. 50, it can be said that a high figure of merit M can be obtained in addition to high Q. FIG. 51 is a graph showing the relationship between impedance Z and frequency in the SAW resonator obtained in FIG. From FIG. 51, it can be read that there is no useless spurious near the resonance point.

  As described above, the SAW resonator according to the present invention has an inflection point in the operating temperature range (operating temperature range: −40 ° C. to + 85 ° C.) as shown in FIG. Alternatively, a frequency temperature characteristic of about 20 ppm or less with a very small frequency fluctuation amount close to a cubic curve could be realized.

  FIG. 56 (A) is a graph showing the frequency temperature characteristics of the SAW resonator disclosed in Japanese Patent Laid-Open No. 2006-203408. Although the frequency temperature characteristic shows a cubic curve, as shown, the inflection point exists in a region exceeding the operating temperature range (operating temperature range: −40 ° C. to + 85 ° C.). As shown in (B), a quadratic curve having an upwardly convex vertex is obtained. For this reason, the frequency fluctuation amount is an extremely large value of 100 (ppm).

  On the other hand, the SAW resonator according to the present invention achieves a cubic curve or a frequency fluctuation amount close to the cubic curve within the operating temperature range, thereby realizing a drastic reduction in the frequency fluctuation amount. FIG. 57 and FIG. 58 show changes in the frequency fluctuation amount within the operating range in the SAW resonator in which the IDT and the reflector are covered with the protective film.

The example shown in FIG. 57 is a diagram showing the amount of frequency fluctuation within the operating temperature range when alumina as a protective film is coated on the electrode. According to FIG. 57, it can be read that the amount of frequency fluctuation within the operating temperature range can be 10 (ppm) or less.
・ Basic data H (material: aluminum) of the SAW resonator according to the example shown in FIG. 57: 2000 (Å)
G: 4700 (Å)
(H + G = 0.067λ)
IDT line occupancy ηi: 0.6
Reflector line occupancy ηr: 0.8
In-plane rotation of Euler angles (0 °, 123 °, 43.5 °) ST-cut substrate pair: 120
Crossing width: 40λ (λ = 10 (μm))
Number of reflectors (per side): 36
Protective film (alumina) film thickness 400 (Å) without electrode finger tilt angle
Secondary temperature coefficient β = + 0.0007 (ppm / ° C. ² )

Example shown in FIG. 58 is a diagram showing a frequency variation in the operating temperature range in the case where the film of SiO ₂ as a protective film against the electrodes. According to FIG. 58, it can be read that the frequency fluctuation amount within the operating temperature range can be 20 (ppm) or less.
・ Basic data H (material: aluminum) of the SAW resonator according to the example shown in FIG. 58: 2000 (Å)
G: 4700 (Å)
(H + G = 0.067λ)
IDT line occupancy ηi: 0.6
Reflector line occupancy ηr: 0.8
In-plane rotation of Euler angles (0 °, 123 °, 43.5 °) ST-cut substrate pair: 120
Crossing width: 40λ (λ = 10 (μm))
Number of reflectors (per side): 36
Thickness 400 (ＳｉＯ) of protective film (SiO ₂ ) without electrode finger tilt angle
Secondary temperature coefficient β = + 0.0039 (ppm / ° C. ² )

The inventor of the present application can adjust the absolute value of the secondary temperature coefficient β to 0.01 ppm / ° C. ² or less by adjusting the line occupation ratio η with respect to G and H designed as described above. I mentioned a certain point. On the other hand, the inventors of the present application have found that the frequency temperature characteristics of the surface acoustic wave fluctuate when the line occupancy η fluctuates when excited in the upper end mode of the stop band. When manufacturing multiple surface acoustic wave resonators, it is difficult to match all the surface acoustic wave resonators to the desired design line occupancy, and products with a line occupancy different from the design line occupancy are manufactured. May be. At this time, the fluctuation amount of the line occupancy from the design line occupancy is not constant, and the line occupancy varies. Therefore, when a plurality of surface acoustic wave resonators are manufactured, the frequency temperature characteristics of the surface acoustic wave vary. Therefore, the inventors of the present application have found that these causes cause variations in the frequency deviation in the operating temperature range of the surface acoustic wave element, thereby reducing the yield of the surface acoustic wave resonator.

Further, as described above, the line occupancy η when the variation in the primary temperature coefficient when the line occupancy η varies and the secondary temperature coefficient β are minimum (−0.01 ≦ β The inventor of the present application has also found that the values of the line occupation ratio η satisfying ≦ 0.01) do not coincide with each other.
Therefore, in the second embodiment, the value of the secondary temperature coefficient β is suppressed to the above range, and the fluctuation amount of the primary temperature coefficient that acts predominantly in the frequency temperature characteristic of the operating temperature range can be minimized. A simple SAW device will be described.

  FIG. 59 shows a schematic diagram of a SAW resonator according to the second embodiment. In FIG. 59, FIG. 59 (A) is a plan view of the SAW resonator of the second embodiment, FIG. 59 (B) is a partially enlarged sectional view, and FIG. 59 (C) shows the details in FIG. 59 (B). 59 (D) is an enlarged view for explanation, and FIG. 59 (D) is a partially enlarged view of FIG. 59 (C), and is a cross-section that can be assumed when the SAW resonator according to the present invention is manufactured using a photolithography technique and an etching technique. It is a figure for demonstrating the identification method of effective line occupation rate (eta) eff of an IDT electrode finger in case a shape and cross-sectional shape became trapezoid shape instead of the rectangle.

  The basic configuration of the SAW resonator of the second embodiment is similar to that of the SAW resonator 10 of the first embodiment. That is, the SAW resonator 110 is configured to include the quartz substrate 30, the IDT 112 formed on the quartz substrate, and the reflectors 120 formed on both sides of the IDT 112. The IDT 112 is formed by comb-like electrodes 114a and 114b extending in a direction perpendicular to the direction in which the surface acoustic wave (wavelength λ) propagates and intersecting each other. The comb-like electrode 114a includes a plurality of electrode fingers 118a arranged at equal intervals (λ) in the propagation direction of the surface acoustic wave, and a bus bar 116a that connects the plurality of electrode fingers 118a in parallel. Similarly, the comb-like electrode 114b includes a plurality of electrode fingers 118b arranged at equal intervals (λ) in the propagation direction of the surface acoustic wave, and a bus bar 116b that connects the plurality of electrode fingers 118b in parallel. Therefore, the electrode fingers 118a and 118b are alternately arranged at equal intervals (λ / 2) in the propagation direction of the surface acoustic wave. The reflector 120 has conductor strips 122 arranged at equal intervals (λ / 2) in the propagation direction of the surface acoustic wave. The SAW resonator 110 excites the surface acoustic wave in the stop band upper end mode.

  In the first embodiment, the widths in the propagation directions of the surface acoustic waves of the convex portions 34 formed by the inter-electrode finger grooves 32 and the electrode fingers 18a and 18b are the same. However, in the present embodiment, the width in the propagation direction of the surface acoustic waves of the electrode fingers 118a and 118b on the projections 134 formed by the interelectrode finger grooves 132 is larger than the width of the projections in the propagation direction of the surface acoustic waves. It differs in that it is narrower. Then, both ends of the electrode fingers 118a and 118b in the propagation direction of the surface acoustic wave are arranged on the inner side of the both ends of the projection 134 in the propagation direction of the surface acoustic wave in plan view. Therefore, both ends of the convex portion 134 in the propagation direction of the surface acoustic wave are exposed without being covered with the electrode fingers 118a and 118b. A similar configuration is also formed in the reflectors 120 disposed at both ends of the IDT 112.

となる。これにより、第１実施形態と比較して、電極指１１８ａ、１１８ｂから発散される電気力線を凸部１３４が取りこむ量（立体角）が増えるので、弾性表面波の励振効率を向上させ、ＳＡＷ共振子１１０の損失を低減させることができる。 In FIG. 59C, if the width of the convex portion 134 in the propagation direction of the surface acoustic wave is Lg and the width of the electrode fingers 118a and 118b in the propagation direction of the surface acoustic wave is Le,

It becomes. Thereby, compared with the first embodiment, the amount (solid angle) that the convex portion 134 takes in the electric lines of force that diverge from the electrode fingers 118a and 118b increases, so that the surface acoustic wave excitation efficiency is improved and the SAW is improved. Loss of the resonator 110 can be reduced.

  By the way, in the SAW resonator 10 of 1st Embodiment, a surface acoustic wave reflects in the part which the level | step difference of the thickness (G) direction of the both ends of the convex part 34 (refer FIG. 1) of width L rises. Since the line occupancy η is adjusted by adjusting L, the secondary temperature coefficient β can be minimized by adjusting the reflection position of the surface acoustic wave. Further, since the fluctuation amount of the primary temperature coefficient depends on the line occupancy η of the convex portion 34, the fluctuation amount of the primary temperature coefficient can be minimized by adjusting this value. However, since the width of the convex portion 134 corresponding to the line occupancy η is also L, in the configuration of the first embodiment, the line occupancy η that minimizes the secondary temperature coefficient β and the fluctuation amount of the primary temperature coefficient It is difficult to simultaneously specify the line occupation ratio η that minimizes.

を実効幅とし、その両端位置で弾性表面波を反射するものと考えることができる。よってこのときの実効ライン占有率ηｅｆｆは、凸部１３４のライン占有率をηｇ（＝Ｌｇ／Ｐ）、電極指１１８ａ、１１８ｂのライン占有率をηｅ（＝Ｌｅ／Ｐ）とすると、

となる。このとき、

となる。よって、このηｅｆｆを調整することにより二次温度係数を調整することができる。一方、一次温度係数の変動量は、ηｇにより調整することができる。したがって、ηｅｆｆを調整することにより二次温度係数を調整し、ηｇを調整することにより一次温度係数の変動量を調整することができる。 On the other hand, in the SAW resonator 110 according to the second embodiment, the thickness (G) in the thickness (G) direction at both ends of the convex portion 134 having the width Lg and the thickness (H) at both ends of the electrode fingers 118a and 118b having the width Le are as follows. The surface acoustic wave is reflected at the rising part. Therefore, in the second embodiment, the electrode fingers 118a and 118b are

Can be considered to reflect surface acoustic waves at both end positions. Therefore, the effective line occupancy ηeff at this time is defined as ηg (= Lg / P) for the line occupancy of the convex portion 134 and ηe (= Le / P) for the line occupancy of the electrode fingers 118a and 118b.

It becomes. At this time,

It becomes. Therefore, the secondary temperature coefficient can be adjusted by adjusting this ηeff. On the other hand, the fluctuation amount of the primary temperature coefficient can be adjusted by ηg. Therefore, the secondary temperature coefficient can be adjusted by adjusting ηeff, and the fluctuation amount of the primary temperature coefficient can be adjusted by adjusting ηg.

である。このとき、Ｌｅ、Ｌｇは、

と定義する。 In addition, as shown in FIG. 59D, when the electrode fingers 119 and both side surfaces in the width direction of the convex portion 135 are inclined and the cross section has a trapezoidal shape, the width of the lower end in the thickness direction of the electrode fingers 119 Is Leb and the width of the upper end is Let. And the width | variety of the lower end of the thickness direction of the convex part 135 is set to Lgb, and the width | variety of an upper end is set to Lgt. At this time,

It is. At this time, Le and Lg are

It is defined as

  The inventor of the present application has a case where the width Le of the electrode finger and the width Lg of the convex portion coincide with each other as in the first embodiment (type 1) and a case where Lg> Le as in the second embodiment (type 2). The variation in frequency deviation, CI value, and primary temperature coefficient were investigated.

  The SAW devices used in this study are Euler angles (φ = 0 °, θ = 123 °, ψ = 44 °), G = 0.046λ, H = 0.021λ for both Type 1 and Type 2, and IDT The number of electrode pairs was 210, and the number of reflectors at both ends of the IDT electrode was 94 per side.

  First, as Example 1, in Type 1, the line occupancy ηe of the electrode fingers is 0.64, the line occupancy ηg of the convex portion 34 (see FIG. 1) is 0.64, and thereby the line occupancy η is 0.64. It was. In Type 2, ηe was 0.57, ηg was 0.71, and the effective line occupancy ηeff was 0.64.

  Next, as Example 2, in Type 1, the line occupancy ηe of the electrode fingers 118a and 118b is 0.66, the line occupancy ηg of the convex portion 134 is 0.66, and thereby the line occupancy η is 0.66. did. In Type 2, ηe was 0.59, ηg was 0.73, and the effective line occupancy ηeff was 0.66. That is, in any example, ηeff of type 2 is adjusted to satisfy ηg> ηe while maintaining the value of η of type 1. For the CI value, a large number (1784) of each type of sample was prepared, and the average value was calculated.

  FIG. 60 shows the frequency temperature characteristics of Type 1 and Type 2 in Example 1, and FIG. 61 shows the frequency temperature characteristics of Type 1 and Type 2 in Example 2. As shown in FIG. 60, in Example 1, a cubic function-like curve is drawn in which the temperature (reference temperature) serving as an inflection point is approximately 25 ° C. for both Type 1 and Type 2. As shown in FIG. 61, in Example 2, a cubic function-like curve is drawn in which the temperature (reference temperature) serving as the inflection point is about 40 ° C. in both Type 1 and Type 2. Therefore, in Examples 1 and 2, it can be seen that Type 1 and Type 2 both have a very small secondary temperature coefficient β.

  As shown in FIG. 60, in Example 1, both Type 1 and Type 2 have a frequency deviation at −40 ° to + 85 ° of 12 ppm and have the same curved shape. As shown in FIG. 61, in Example 2, the frequency deviation of type 1 is 18 ppm, and the frequency deviation of type 2 is 16 ppm. Therefore, it can be seen that even if the type 1 is changed to the type 2, as long as the ηeff of the type 2 maintains the value of η (ηg) of the type 1, the type 2 maintains the frequency temperature characteristic of the type 1.

  Furthermore, in Example 1, the CI value of Type 1 was 23.8Ω, but in Type 2, it was improved to 20.1Ω. In Example 2, the CI value of Type 1 was 22.4Ω, but in Type 2 it was improved to 19.2Ω, and a low-loss SAW resonator was realized in Type 2 of Examples 1 and 2. As described above, it is considered that the solid angle at which the convex portion looks at the electric lines of force generated from the electrode fingers is larger in Type 2 than in Type 1 and the excitation efficiency is increased.

  Next, the change of the fluctuation amount of the primary temperature coefficient of type 1 and type 2 was investigated. FIG. 62 shows changes in the amount of fluctuation of the primary temperature coefficient when the type 1 line occupancy η is changed by 0.01, and FIG. 63 shows the results when the type 2 effective line occupancy ηeff is changed by 0.01. The change of the fluctuation | variation amount of a primary temperature coefficient is shown. The SAW devices used in this investigation were Euler angles (φ = 0 °, θ = 123 °, ψ = 44 °), G = 0.045λ, and H = 0.02λ in both types 1 and 2.

  As shown in FIG. 62, in Type 1, when η (or ηg) is increased from 0.60, it decreases monotonically, becomes the minimum value of the fluctuation of the primary temperature coefficient at 0.70, and increases monotonously at 0.70 or more. It becomes.

  On the other hand, as shown in FIG. 63, in Type 2, when ηeff is increased from 0.53, the fluctuation amount of the primary temperature coefficient decreases monotonously, reaches a minimum value at 0.63, and increases monotonously at 0.63 or more. .

とすることにより、一次温度係数の変動量を０．６ｐｐｍ／℃以下に抑制することができることがわかる。 As described above, Type 1 and Type 2 of Example 1 have a good frequency deviation of 12 ppm as shown in FIG. However, in Type 1, as shown in FIG. 62, when η (or ηg) is 0.64, the fluctuation amount of the primary temperature coefficient is 0.6 ppm / ° C. Therefore, the variation in the primary temperature coefficient (that is, the variation in the frequency temperature characteristic) due to the variation in the line occupancy η (ηg) becomes significant. On the other hand, in Type 2, if an approximate curve is generated from the plot of FIG. 63 and ηeff = 0.64 on the approximate curve is extracted, the fluctuation amount of the primary temperature coefficient is about 0.2. Recognize. Furthermore, from FIG.

It can be seen that the fluctuation amount of the primary temperature coefficient can be suppressed to 0.6 ppm / ° C. or less.

  In addition, a large number (1784) of type 1 and type 2 samples of Example 1 were prepared, and the variation of the primary temperature coefficient and the variation of the resonance frequency at 25 ° C. were investigated. Then, when the magnitude of variation in the primary temperature coefficient of type 1 is 1, the magnitude of variation in the primary temperature coefficient of type 2 is improved to 0.2. As described above, in type 1, the line occupancy ηg of the convex portion 34 (see FIG. 1) is 0.64, and the fluctuation amount of the primary temperature coefficient is 0.6 ppm / ° C. according to FIG. On the other hand, in type 2, if the line occupancy ηg of the convex portion 134 is 0.71, an approximate curve is generated from the plot of FIG. 62 and ηg = 0.71 on the approximate curve is extracted. Can be confirmed to be about 0.1 ppm / ° C. Since the variation of the primary temperature coefficient is proportional to the amount of fluctuation of the primary temperature coefficient, it is considered that such an improvement was observed. Also, the variation in resonance frequency at 25 ° C. is improved to 0.5 in Type 2 when the magnitude is 1 in Type 1.

Further, from the above, type 2 maintains the frequency temperature characteristic of type 1 having η that matches the value of ηeff. Therefore, η can be replaced with ηeff in all the drawings in which the horizontal axis is η. Therefore, ηeff is included in the range of the formula (39) and is surrounded by a line that is connected in alphabetical order in FIG. 13B, that is, the above formulas (3), (5), and ( 6) By designing to a range satisfying 6), the fluctuation amount of the primary temperature coefficient is suppressed to suppress the variation of the frequency deviation in the operating temperature range of the SAW resonator 110, and the absolute value of the secondary temperature coefficient β is set to 0. It can be suppressed to 01 (ppm / ° C. ² ) or less.

Further, ηeff is included in the range of the equation (39), and FIG. 27A (0 <H ≦ 0.005λ), FIG. 28A (0.005λ <H ≦ 0.010λ), and FIG. ) (0.010λ <H ≦ 0.015λ), FIG. 30A (0.015λ <H ≦ 0.020λ), FIG. 31A (0.020λ <H ≦ 0.025λ), FIG. A) (0.025λ <H ≦ 0.030λ), FIG. 33 (A) (0.030λ <H ≦ 0.035λ), each point indicated by the plane coordinates (G / λ, ηeff) in the figure Are set to ranges included in a range surrounded by a line that connects in alphabetical order. Thereby, the fluctuation amount of the primary temperature coefficient is suppressed, and the variation of the frequency temperature characteristic, that is, the variation of the frequency deviation in the operating range of the SAW resonator 110 is suppressed. The absolute value of the next temperature coefficient β can be suppressed to 0.01 (ppm / ° C. ² ) or less.

  In the above-described embodiment, the IDT 12 constituting the SAW resonator 10 and the IDT 112 constituting the SAW resonator 110 are shown such that all electrode fingers cross each other alternately. However, the SAW resonator 10 and the SAW resonator 110 according to the present invention can achieve a considerable effect only by the quartz substrate. Therefore, even when the electrode fingers 18 in the IDT 12 and the electrode fingers 118a and 118b in the IDT 112 are thinned out, the same effect can be obtained.

  In the first embodiment, the grooves 32 may be partially provided between the electrode fingers 18 or between the conductor strips 22 of the reflector 20. In particular, since the central portion of the IDT 12 having a high vibration displacement has a dominant influence on the frequency temperature characteristics, the groove 32 may be provided only in that portion. Even with such a structure, the SAW resonator 10 having good frequency-temperature characteristics can be obtained.

Moreover, in the said embodiment, it described that the alloy which has Al or Al as a main component was used as an electrode film. However, the electrode film may be configured using other metal materials as long as the metal can achieve the same effect as the above embodiment. Further, a protective film such as SiO ₂ or alumina may be provided on the electrode film.

  The above embodiment is a one-terminal-pair SAW resonator provided with only one IDT, but the present invention can also be applied to a two-terminal-pair SAW resonator provided with a plurality of IDTs. The present invention is also applicable to other types of dual mode SAW filters and multimode SAW filters.

  Next, a SAW oscillator according to the present invention will be described with reference to FIG. As shown in FIG. 55, the SAW oscillator according to the present invention is driven and controlled by applying a voltage to the above-described SAW resonator 10 (SAW resonator 110) and the IDT 12 of the SAW resonator 10 (SAW resonator 110). It consists of an IC (integrated circuit) 50 serving as a circuit and a package for housing them. In FIG. 55, FIG. 55 (A) is a plan view excluding the lid, and FIG. 55 (B) is a cross-sectional view taken along the line AA in FIG. 55 (A).

  In the SAW oscillator 100 according to the embodiment, the SAW resonator 10 and the IC 50 are accommodated in the same package 56, the electrode patterns 54 a to 54 g formed on the bottom plate 56 a of the package 56, and the comb-like electrode 14 a of the SAW resonator 10. 14b and the pads 52a to 52f of the IC 50 are connected by a metal wire 60. The cavity of the package 56 containing the SAW resonator 10 (SAW resonator 110) and the IC 50 is hermetically sealed with a lid 58. With such a configuration, the IDT 12 (see FIG. 1), the IC 50, and an external mounting electrode (not shown) formed on the bottom surface of the package 56 can be electrically connected.

  Therefore, in addition to the recent increase in frequency of the reference clock due to higher speeds of information communication, the influence of internal heat generation has increased with the downsizing of chassis such as blade servers, which is required for electronic devices mounted inside. In the market where the operation temperature range needs to be expanded and the accuracy needs to be improved, and further, a stable operation is required over a long period of time in a low to high temperature environment such as a radio base station installed outdoors. Such a SAW oscillator is suitable because it has a very good frequency temperature characteristic in which the frequency fluctuation amount is about 20 (ppm) or less in the operating temperature range (operating temperature range: −40 ° C. to + 85 ° C.).

  Furthermore, since the SAW resonator according to the present invention or the SAW oscillator including the SAW resonator realizes a significant improvement in frequency temperature characteristics, for example, mobile phones, hard disks, personal computers, BSs and CS broadcasts can be used. Receiving tuners, equipment that processes high-frequency signals propagating in coaxial cables or optical signals propagating in optical cables, servers that require high-frequency and high-accuracy clocks (low jitter and low phase noise) over a wide temperature range In electronic devices such as network devices and wireless communication devices, it greatly contributes to the realization of products with excellent frequency temperature characteristics, as well as excellent jitter and phase noise characteristics, and further improves system reliability and quality. Needless to say, it contributes greatly.

DESCRIPTION OF SYMBOLS 10 ..... Surface acoustic wave resonator (SAW resonator), 12 ..... IDT, 14a, 14b .... Comb-like electrode, 16a, 16b ..... Bus bar, 18a, 18b ..... Electrode finger, 20 ......... Reflector, 22 ......... Conductor strip, 30 ......... Quartz substrate, 32 ......... Groove, 34 ......... Protrusion, 110 ......... Surface acoustic wave resonator (SAW resonator), 112 ... ... IDT, 114a, 114b ... ... Comb-like electrodes, 116a, 16b ... ... Busbar, 118a, 118b ... ... Electrode fingers, 119 ... ... Electrode fingers, 120 ... ... Reflectors, 122 ... ... Conductor strip, 132... Groove, 134... Convex, 135.

Claims (8)

A quartz substrate with Euler angles (−1.5 ° ≦ φ ≦ 1.5 °, 117 ° ≦ θ ≦ 142 °, 42.79 ° ≦ | ψ | ≦ 49.57 °);
An IDT that is made of aluminum or an alloy containing aluminum as a main component, is provided on the quartz substrate, includes a plurality of electrode fingers, and excites a surface acoustic wave of a stop band upper end mode;
A groove between the electrode fingers in a portion of the quartz substrate located between the electrode fingers in plan view,
The electrode thickness of the IDT is H, the wavelength of the surface acoustic wave is λ, and the relationship 0 <H ≦ 0.035λ is satisfied,
The line occupation rate of the convex part of the quartz crystal substrate arranged between the groove between the electrode fingers is ηg, the line occupation rate of the electrode finger arranged on the convex part is ηe,
The effective line occupancy ηeff of the IDT is an arithmetic average of the line occupancy ηg and the line occupancy ηe,

A surface acoustic wave resonator characterized by satisfying the following relationship: The surface acoustic wave resonator according to claim 1,
The effective line occupancy ηeff is

A surface acoustic wave resonator characterized by satisfying the following relationship: The surface acoustic wave resonator according to claim 1 or 2 ,
The sum of the inter-electrode finger groove depth G and the electrode film thickness H is:

A surface acoustic wave resonator characterized by satisfying the following relationship: The surface acoustic wave resonator according to any one of claims 1 to 3 , wherein the ψ and the θ are

A surface acoustic wave resonator characterized by satisfying the following relationship: The surface acoustic wave resonator according to any one of claims 1 to 4 ,
The frequency of the stop band upper end mode in the IDT is ft2, the frequency of the stop band lower end mode in the reflector arranged so as to sandwich the IDT in the propagation direction of the surface acoustic wave is fr1, and the frequency of the stop band upper end mode of the reflector. Is fr2,

A surface acoustic wave resonator characterized by satisfying the following relationship: The surface acoustic wave resonator according to claim 5 ,
Providing a groove between conductor strips in a portion of the quartz substrate located between conductor strips constituting the reflector;
2. A surface acoustic wave resonator according to claim 1, wherein the groove between the conductor strips is shallower than the groove between the electrode fingers. It claims 1 to surface acoustic wave resonator according to any one of claims 6, a surface acoustic wave oscillator comprising the circuit for driving the IDT. An electronic apparatus comprising the surface acoustic wave resonator according to any one of claims 1 to claim 6.

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