JP6079280B2 - Vibration element, vibrator, electronic device, electronic device, and moving object - Google Patents

Description

  The present invention relates to a vibration element, a vibrator, an electronic device, an electronic apparatus, and a moving body that excite thickness shear vibration.

  The AT-cut quartz crystal resonator that excites thickness shear vibration as the main vibration mode is suitable for miniaturization and higher frequency, and exhibits a cubic curve with excellent frequency-temperature characteristics. It is used. In particular, in recent years, as the processing speed of transmission communication equipment and OA equipment has increased, or the capacity of communication data and processing volume has increased, the AT-cut crystal resonator used as the reference frequency signal source has a higher frequency. There is an increasing demand for conversion.

Patent Document 1 discloses an AT-cut crystal resonator having an inverted mesa structure in which a concave portion is formed in a part of a main surface to achieve high frequency. That is, in a crystal resonator that obtains a fundamental wave vibration of 300 MHz or higher, the ratio between the thickness of the crystal base plate and the film thickness obtained by converting the electrode film thickness into the crystal density is set to 7% to 13%. It is said that a good frequency temperature characteristic is obtained.
Further, Patent Document 2 discloses an AT-cut crystal resonator having an inverted mesa structure in which a concave portion is formed on a part of the main surface to increase the frequency as in Patent Document 1. That is, in a crystal resonator that obtains a fundamental wave vibration of 300 MHz or more, the ratio of the thickness of the crystal base plate to the electrode film thickness is 0.014 or 0.012 or less (the crystal substrate thickness and the electrode film thickness). Is 19.2% or 16.5% or less in terms of the ratio to the film thickness converted to the crystal density), it is said that the frequency change before and after reflow can be prevented and good frequency temperature characteristics can be obtained.

JP-A-11-284484 Japanese Patent Laid-Open No. 2005-203858

By the way, when trying to reduce the size and the frequency of a crystal resonator whose fundamental wave vibration vibrates at a resonance frequency of 200 MHz or higher, the crystal resonator having the above-described structure is a CI (crystal) required for an oscillation circuit.・ It has been found that there is a problem that the required specification of impedance = equivalent resistance of the crystal unit cannot be satisfied. In particular, when the frequency becomes a high frequency of 200 MHz or more, the film thickness of the excitation electrode and the lead electrode formed on the quartz resonator greatly affects the CI value of the main vibration. When trying to set only the main vibration of the crystal resonator to the confinement mode, it is necessary to make the electrode film thinner. When the electrode film becomes 100 nm or less as the electrode film becomes thinner, the sheet resistance increases rapidly. There is a problem that a large ohmic cross (resistance loss due to surface resistance) occurs in the excitation electrode portion and the lead electrode portion, resulting in an increase in the CI value of the crystal resonator.
In addition, if the film thickness is increased to prevent ohmic crossing of the electrode film, many in-harmonic mode vibrations are trapped in addition to the main vibration, and spurious are generated. Depending on the conditions, the main vibration is changed from the CI value of the main vibration. The CI value of the adjacent spurious becomes smaller, causing a problem that the oscillation circuit oscillates at the spurious resonance frequency.
Therefore, in the present invention, a problem in providing the vibration element is improvement of spurious due to the inharmonic mode.

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.
[Embodiment 1] A vibration element according to the present embodiment vibrates by thickness-shear vibration and is disposed on the first main surface and a substrate including a first main surface and a second main surface that are in a front-back relationship. A first excitation electrode, and a second excitation electrode disposed on the second main surface,
The first excitation electrode is disposed within an outer edge of the second excitation electrode in plan view;
The thickness of the substrate is ts, the total thickness of the first excitation electrode and the second excitation electrode is te, the thickness of the second excitation electrode is te2, and the thickness of the first excitation electrode is slipped. The length along the vibration direction of the vibration is hx, the density of the first excitation electrode and the second excitation electrode is ρe, the density of the substrate is ρx, the cutoff frequency of the substrate is fs, and the substrate The frequency excited by the substrate when the first excitation electrode and the second excitation electrode are arranged on the substrate is fe, the energy confinement coefficient of the substrate is M, the frequency reduction is Δ, and the frequency constant of the substrate is R, where K is the anisotropy constant of the substrate
M = K × (hx / (2 × ts)) × √Δ
Δ = (fs−fe) / fs
fs = R / [ts + te2 × (ρe / ρx)]
fe = R / [ts + te × (ρe / ρx)]
15.5 ≦ M ≦ 36.7
It is characterized by satisfying the relationship.
According to this embodiment, in a high-frequency vibration element excited in the thickness-shear vibration mode of the fundamental wave, the deterioration of the CI value due to the effect of ohmic cross accompanying the thinning of the excitation electrode and the lead electrode is reduced, and the dimensions of the excitation electrode and It is possible to reduce the excitation intensity of the in-harmonic mode spurious determined by the film thickness. As a result, the CI value of the main vibration is reduced, and there is an effect that a vibration element having a large ratio of CIs of adjacent spurious to the CIm value of the main vibration, that is, a CI value ratio (CIs / CIm) is obtained.
[Mode 2] The vibration element described in the above mode is characterized by satisfying a relationship of 17.1 ≦ M ≦ 35.7.
According to this embodiment, there is an effect that the excitation intensity of the spurious in the in-harmonic mode can be further reduced.
[Mode 3] In the resonator element according to the above mode, when the length along the direction orthogonal to the thickness-shear vibration direction of the first excitation electrode is hz,
1.25 ≦ hx / hz ≦ 1.31
It is characterized by satisfying the relationship.
According to this embodiment, when a substrate in which the displacement distribution in the displacement direction determined by the crystal anisotropy is different from the displacement distribution in the direction orthogonal thereto is used, the energy confinement efficiency of the main vibration can be increased. Furthermore, the capacitance ratio γ (= C0 / C1, where C0 is the capacitance and C1 is the series resonance capacitance) of the vibration element can be reduced.
Here, when the resonance frequency of the thickness-shear vibration is 200 MHz or more, the vibration element excited in the thickness-shear vibration mode is determined in inverse proportion to the thickness of the substrate. Since the plate thickness is as thin as 8.4 μm or less, the thickness of the excitation electrode to be formed needs to be very thin. Therefore, the effect of ohmic cross due to the thinning of the electrode becomes very large, and setting the energy confinement coefficient M in the above range can reduce these problems. Therefore, the CI value specification and spurious specification required by the oscillation circuit can be reduced. There is an effect that a satisfactory vibration element can be obtained.

Application Example 1 A vibration element according to this application example is provided on the first main surface, the substrate including the first main surface and the second main surface that are vibrated by thickness shear vibration and have a front and back relationship. A first excitation electrode, and a second excitation electrode provided on the second main surface and larger than the first excitation electrode in plan view,
The first excitation electrode is within the outer edge of the second excitation electrode in a plan view;
M = K × (hx / 2 × ts) × √Δ
Δ = (fs−fe) / fs
fs = R / [ts + te2 × (ρe / ρx)]
fe = R / [ts + te × (ρe / ρx)]
15.5 ≦ M ≦ 36.7
It is characterized by satisfying the relationship.
Where M is the energy confinement coefficient, K is the anisotropy coefficient of the substrate, hx is the length along the thickness-shear vibration direction of the first excitation electrode, ts is the thickness of the substrate, Δ is the frequency reduction amount, fs Is the cut-off frequency of the substrate, fe is the frequency when the excitation electrode is disposed on the substrate, R is the frequency constant of the substrate, and te is the total thickness of the first excitation electrode and the second excitation electrode. , Te2 is the thickness of the second excitation electrode, ρe is the density of the excitation electrode, and ρx is the density of the substrate.

  According to this application example, in the high-frequency vibration element excited in the thickness-shear vibration mode of the fundamental wave, the deterioration of the CI value due to the effect of ohmic cross accompanying the thinning of the excitation electrode and the lead electrode is reduced, and the dimensions of the excitation electrode In addition, the excitation intensity of the in-harmonic mode spurious determined by the film thickness can be reduced. As a result, the CI value of the main vibration is reduced, and there is an effect that a vibration element having a large ratio of CIs of adjacent spurious to the CIm value of the main vibration, that is, a CI value ratio (CIs / CIm) is obtained.

  Application Example 2 In the resonator element described in the application example, 17.1 ≦ M ≦ 35.7 is satisfied.

  According to this application example, it is possible to further reduce the excitation intensity of the spurious in the inharmonic mode.

Application Example 3 In the resonator element according to the application example described above, when the length along the direction orthogonal to the thickness-shear vibration direction of the first excitation electrode is hz,
1.25 ≦ hx / hz ≦ 1.31
It is characterized by satisfying.

According to this application example, when a substrate in which the displacement distribution in the displacement direction determined by the crystal anisotropy is different from the displacement distribution in the direction orthogonal thereto is used, the energy confinement efficiency of the main vibration can be increased. Furthermore, the capacitance ratio γ (= C0 / C1, where C0 is the capacitance and C1 is the series resonance capacitance) of the vibration element can be reduced.
Here, when the resonance frequency of the thickness-shear vibration is 200 MHz or more, the vibration element excited in the thickness-shear vibration mode is determined in inverse proportion to the thickness of the substrate. Since the plate thickness is as thin as 8.4 μm or less, the thickness of the excitation electrode to be formed needs to be very thin. Therefore, the effect of ohmic cross due to the thinning of the electrode becomes very large, and setting the energy confinement coefficient M in the above range can reduce these problems. Therefore, the CI value specification and spurious specification required by the oscillation circuit can be reduced. There is an effect that a satisfactory vibration element can be obtained.

  Application Example 4 In the resonator element according to the application example, the substrate is a quartz substrate.

  According to this application example, the quartz substrate has an effect that a Q element is high and a vibration element having excellent temperature characteristics can be obtained.

  Application Example 5 In the resonator element according to the application example described above, the crystal substrate is an AT-cut crystal substrate.

  According to this application example, by using an AT-cut quartz crystal substrate having a cutting angle with excellent temperature characteristics as a substrate, it is possible to utilize experience and experience related to photolithography technology and etching technology, and vibration with small variation in characteristics. There is an effect that mass production of the element becomes possible.

  Application Example 6 A vibrator according to this application example includes the vibration element according to the application example described above and a package that accommodates the vibration element.

  According to this application example, a highly reliable vibrator can be obtained by housing the vibration element in the package. For example, since it is possible to prevent the influence of disturbance such as temperature change and humidity change and the influence of contamination, an oscillator having excellent frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics can be obtained. The

  Application Example 7 An electronic device according to this application example includes the vibration element according to the application example described above and an oscillation circuit that drives the vibration element.

According to this application example, when an electronic device is configured using a high-frequency vibration element excited by a fundamental wave, the capacitance ratio of the vibration element is small, so that the frequency variable width is widened, and a high-frequency with a good S / N ratio is obtained. The voltage controlled oscillator can be obtained.
In addition, an oscillator, a temperature compensated oscillator, and the like can be configured as an electronic device, and an oscillator excellent in frequency reproducibility, aging characteristics, and frequency temperature characteristics can be configured.

  Application Example 8 An electronic apparatus according to this application example includes the vibration element described in the application example.

According to this application example, by using the vibration element described in the application example described above for an electronic device, an electronic device including a reference frequency source having a high frequency and excellent frequency stability and a good S / N ratio can be configured. effective.
Application Example 9 A moving object according to this application example includes the vibration element described in the application example.
According to this application example, a highly reliable moving object is obtained.

It is the schematic which showed the structure of the vibration element which concerns on one Embodiment of this invention, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing. The figure explaining the relationship between an AT cut quartz substrate and a crystal axis. The figure which shows resistance with respect to the film thickness of an electrode. The figure which shows the trial production conditions and measurement result of an AT cut crystal resonator element. The figure which shows CI value of the vibrator | oscillator with respect to the energy confinement factor M. The figure which shows CI value ratio of the main vibration CI value of a vibrator | oscillator with respect to the energy confinement factor M, and a spurious CI value. The figure which shows the trial production conditions and CI value of the AT cut quartz-crystal vibrating element which made the lead electrode and the pad electrode thick. It is the schematic which showed the structure of the vibrator | oscillator which concerns on one Embodiment of this invention, (a) is a top view, (b) is a longitudinal cross-sectional view. It is the schematic which showed the structure of the electronic device which concerns on one Embodiment of this invention, (a) is a top view, (b) is a longitudinal cross-sectional view. The perspective view which shows the structure of the mobile type (or notebook type) personal computer to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied. The perspective view which shows the structure of the mobile telephone (PHS is also included) to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied. The perspective view which shows the structure of the digital still camera to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied. The perspective view which shows roughly the motor vehicle as an example of the mobile body of this invention.

Hereinafter, a vibrating element, a vibrator, an electronic device, an electronic apparatus, and a moving body of the present invention will be described in detail based on preferred embodiments shown in the drawings.
1. First, the vibration element of the present invention will be described.
FIG. 1 is a schematic diagram illustrating a configuration of a vibration element according to an embodiment of the present invention. FIG. 1A is a plan view of the vibration element, and FIG. Sectional drawing and FIG.1 (c) are QQ sectional drawings of Fig.1 (a).
The vibration element 1 is integrated with the vibration part 12 and the vibration part 12, and includes a substrate 10 having a thick part 13 thicker than the vibration part 12, and both main surfaces of the vibration part 12 (front and back surfaces in the ± Y ′ direction). ) And the lead electrodes formed to extend from the excitation electrodes 25a and 25b toward the pad electrodes 29a and 29b provided in the thick portion, respectively. 27a, 27b.

The substrate 10 has a rectangular shape, a thin plate-shaped vibrating portion 12 that is thin, perpendicular to the Y ′ axis, and has a constant thickness, and a first integrated along three sides excluding one side of the vibrating portion 12. A thick portion 13 comprising a thick portion 14, a second thick portion 15, and a third thick portion 16 (also referred to as first, second and third thick portions 14, 15, 16). , And a slit 17 for preventing transmission of mount stress generated when the support is fixed to the vibration part 12.
The first thick body 14a, the second thick body 15a, and the third thick body 16a (also referred to as first, second, and third thick bodies 14a, 15a, 16a) are: A region where the thickness parallel to the Y ′ axis is constant.
The first inclined portion 14b, the second inclined portion 15b, and the third inclined portion 16b (also referred to as first, second, and third inclined portions 14b, 15b, and 16b) are the first and first An inclined surface generated between the second and third thick-walled main bodies 14a, 15a, and 16a and the vibrating portion 12.
One main surface of the vibration part 12 and one surface of each of the first, second and third thick parts 14, 15, 16 are on the same plane, that is, XZ of the coordinate axes shown in FIG. This surface (on the plane, the lower surface side in the −Y direction of FIG. 1B) is referred to as a flat surface (flat surface), and the opposite surface having the recess 11 (of FIG. 1B). The upper surface side in the + Y ′ direction is called a concave surface.

In the embodiment shown in FIG. 1, the excitation electrodes 25 a and 25 b have a rectangular shape, and are formed so as to overlap with both main surfaces (front surface and back surface) at substantially the center of the vibration unit 12 in plan view. The excitation electrode 25a as the first excitation electrode and the excitation electrode 25b as the second excitation electrode are different in size, and the excitation electrode 25b is larger than the excitation electrode 25a. The region actually excited in the vibration unit 12 is a region sandwiched between the excitation electrode 25a and the excitation electrode 25b. That is, in the excitation electrode 25b (second excitation electrode), a region that actually contributes to exciting the vibration unit 12 is a portion overlapping the excitation electrode 25a (first excitation electrode) in plan view. That is, the second excitation electrode is composed of an electrode that contributes to excitation and an electrode that does not contribute to excitation integrated with the outer edge of the electrode that contributes to the excitation.
The lead electrode 27a extends from the excitation electrode 25a formed on the concave surface, and passes through the third inclined portion 16b and the third thick main body 16a from above the vibration portion 12, and the second thick main body 15a. Is electrically connected to the pad electrode 29a formed on the concave surface of the. The lead electrode 27b extends from the excitation electrode 25b formed on the flat surface, and passes through the edge of the flat surface of the substrate 10 to be a pad electrode formed on the flat surface of the second thick body 15a. 29b is electrically connected.
The excitation electrodes 25a and 25b will be described in terms of the shape and area of the portion connected to the lead electrodes 27a and 27b, with an extension line (virtual line) along the outer edge (outer side) of the excitation electrode shape as a boundary.

The embodiment shown in FIG. 1A is an example of a lead-out structure of the lead electrodes 27a and 27b, and the lead electrode 27a may pass through another thick part. However, it is desirable that the length of the lead electrodes 27a and 27b is the shortest, and it is desirable to suppress an increase in capacitance by considering that the lead electrodes 27a and 27b do not cross each other with the substrate 10 interposed therebetween.
The excitation electrodes 25a and 25b, the lead electrodes 27a and 27b, and the pad electrodes 29a and 29b are formed by, for example, depositing nickel (Ni) as an underlayer by using a vapor deposition apparatus or a sputtering apparatus and the like. A gold (Au) layer is formed as a base layer. As the electrode material, chromium (Cr) may be used instead of nickel (Ni) for the base layer, and silver (Ag) or platinum (Pt) may be used instead of gold (Au) for the upper layer.

  A piezoelectric material such as quartz belongs to the trigonal system and has crystal axes X, Y, and Z orthogonal to each other as shown in FIG. The X axis, the Y axis, and the Z axis are referred to as an electric axis, a mechanical axis, and an optical axis, respectively. As the quartz substrate, a “rotated Y-cut quartz substrate” cut out from the quartz along a plane obtained by rotating the XZ plane around the X axis by a predetermined angle θ is used as the substrate 10. For example, in the case of an AT-cut quartz substrate, the angle θ is approximately 35 ° 15 ′. Note that the Y-axis and the Z-axis are also rotated by θ around the X-axis to become the Y′-axis and the Z′-axis, respectively. Therefore, the AT-cut quartz substrate has crystal axes X, Y ′, and Z ′ that are orthogonal to each other. The AT-cut quartz substrate has a Y 'axis in the thickness direction, and an XZ ′ plane (plane including the X axis and Z ′ axis) orthogonal to the Y ′ axis is the main surface, and thickness shear vibration is excited as the main vibration. Is done.

That is, as shown in FIG. 2, the substrate 10 has an X-axis of an orthogonal coordinate system composed of an X-axis (electric axis), a Y-axis (mechanical axis), and a Z-axis (optical axis) as a rotation axis, The axis tilted so that the + Z side rotates in the −Y direction of the Y axis is the Z ′ axis, the axis tilted so that the + Y side rotates in the + Z direction of the Z axis is the Y ′ axis, and the X axis And a “rotating Y-cut quartz substrate” having a surface including the Z ′ axis as a main surface and a thickness along the direction along the Y ′ axis.
The substrate 10 according to the present embodiment is not limited to the AT cut having an angle θ of about 35 ° 15 ′, and can be widely applied to a substrate such as a BT cut that excites thickness shear vibration.
Furthermore, although it demonstrated using the example which provided the thick part along the outer edge of the vibration part 12, it is not restricted to this, The board | substrate and thick part which provided the thick part along the outer edge perimeter of the vibration part 12 The present invention can be widely applied to a plate-like substrate in which no is provided.

Generally, in the thickness-shear vibration mode, when a partial electrode is formed on a substrate or a thickness difference is provided, vibration energy can be confined in the vicinity of the portion, and a stable resonance frequency can be obtained. The resonance frequency of the confinement mode in this case is expressed as a function of the energy confinement coefficient M determined by the thickness ts of the substrate, the film thickness te of the excitation electrode, and the dimension hx.
The energy confinement factor M is expressed by the following formula (1).
M = K × (hx / ( 2 × ts ) ) × √Δ (1)
Here, K is the anisotropy coefficient of the substrate (1.538 in the case of an AT cut substrate), hx is the dimension along the displacement direction of the thickness-slip vibration of the excitation electrode, ts is the thickness of the substrate, and Δ is the amount of frequency reduction It is. Note that hx takes the maximum value of the length along the displacement direction of the thickness-shear vibration mode when the excitation electrode is not a rectangle such as a circle or an ellipse.
Further, the frequency decrease amount Δ is expressed by the following formula (2).
Δ = (fs−fe) / fs (2)
Here, fs is a cutoff frequency of the substrate, and fe is a frequency when the excitation electrode is formed on the entire surface of the substrate.
When the shape and area of the front and back excitation electrodes are the same, the cut-off frequency fs of the substrate is expressed by the following formula (3), and the frequency fe when the excitation electrode is formed on the entire surface of the substrate is expressed by the following formula (4). Is done.
fs = R / ts (3)
fe = R / [ts + te × (ρe / ρx)] (4)
Here, R is the frequency constant of the substrate, ts is the thickness of the substrate, te is the total thickness of the front and back excitation electrodes, ρe is the density of the excitation electrodes, and ρx is the density of the substrate.
When the shape and area of the front and back excitation electrodes are different, the cut-off frequency fs of the substrate is expressed by the following formula (5), and the frequency fe when the excitation electrode is formed on the entire surface of the substrate is expressed by the following formula (6). The
fs = R / [ts + te2 × (ρe / ρx)] (5)
fe = R / [ts + te × (ρe / ρx)] (6)
Here, R is the frequency constant of the substrate, ts is the thickness of the substrate, te2 is the thickness of the excitation electrode with the larger area, te is the total thickness of the excitation electrodes on the front and back sides, ρe is the density of the excitation electrode, and ρx is the density of the substrate Density. In the formula (1), hx is a dimension along the displacement direction of the thickness-shear vibration of the excitation electrode having the smaller area.

From the formulas (1) to (6), when the shape and area of the front and back excitation electrodes are different, the thickness ts of the substrate, the thickness te of the excitation electrode, the dimension hx, etc. Compared to the case where the shape and the area are the same, the thickness of the excitation electrode having the larger area is added to the thickness of the substrate. As a result, the substrate becomes thicker, and thus the cut-off frequency fs of the substrate is lowered. It becomes. For this reason, since the frequency drop amount Δ becomes small, the energy confinement coefficient M becomes small, and it becomes easy to reduce spurious in the inharmonic mode.
Further, when the energy confinement coefficient M is the same, the film thickness te of the excitation electrode can be made thicker than when the shape and area of the excitation electrode on the front and back sides are the same.

Generally, in the thickness-shear vibration mode of an AT-cut quartz substrate, the condition for confining a single fundamental wave mode is said to be an energy confinement factor M = 2.8 or less.
For example, an AT-cut quartz crystal resonator that resonates at a resonance frequency of 491 MHz band has an excitation electrode film thickness of about 1 nm with an energy confinement factor M = 2.8 when the excitation electrode size hx = 0.30 mm. Even if it is realized, the CI value becomes very large due to the effect of ohmic cross due to the electrode thinning, and the oscillation circuit cannot oscillate.
Therefore, when the film is formed so as to avoid ohmic cross of the electrode film thickness (thickness is increased) at high frequencies, the energy confinement coefficient M = 2.8, which confines only the main vibration, is greatly increased. It is inevitable that low-order inharmonic mode spurious will be trapped. However, if the CI value ratio between the minimum CI value of the confined spurious and the main vibration CI value is 1.8 or more, it can be said that there is theoretically no oscillation with spurious in the inharmonic mode. Therefore, the inventor of the present application reduced the main vibration CI value to 20Ω or less, and set the CI value ratio between the main vibration CI value and the spurious CI value to 2.0 or more in consideration of manufacturing variation. I came to realize that the circuit could meet the required specifications of the circuit and oscillate, making it practical.

  FIG. 3 shows the thickness and sheet resistance value of a gold (Au) layer as an upper layer with nickel (Ni) as a base layer. It is a measurement result of sheet resistance when the thickness of the nickel (Ni) layer of the underlayer is constant at 7 nm and the thickness of gold (Au) is changed from 45 nm to 150 nm. 3 that the sheet resistance increases rapidly when the thickness is 90 nm or less. Therefore, in order to prevent the CI value of the main vibration from increasing due to the effect of ohmic cross, other than the excitation electrode film thickness that determines the energy confinement factor M, the film thicknesses of the lead electrodes 27a and 27b and the pad electrodes 29a and 29b are increased. There is a need to. In particular, since the lead electrode portion is thinner and longer than the pad portion, the influence of ohmic cross is large. For example, assuming that the length of the lead electrode portion is 10 □ (the length in which 10 squares are connected), in order to set the resistance value of the lead electrode portion to 2Ω or less, the sheet resistance is 0.2Ω from FIG. The thickness of the electrode that becomes / □ needs to be 150 nm or more.

  In the embodiment shown in FIG. 1A, the planar shape of the excitation electrode 25a on the concave surface side (the front surface side in FIG. 1B) is the excitation on the flat surface side (the back surface side in FIG. 1B). The size is set to fit within the outer edge of the outer shape of the electrode 25b. That is, the excitation electrode 25a is formed in a smaller shape than the excitation electrode 25b. This is because the energy confinement factor M due to the mass load effect of the excitation electrode is not increased more than necessary. That is, by enlarging the excitation electrode 25b on the back surface side (lower surface side), the amount of frequency decrease Δ depends only on the mass load effect of the excitation electrode 25a on the front surface side (upper surface side). Cut in half. Therefore, the in-harmonic mode spurious to be confined can be reduced.

For example, when the excitation electrodes 25a and 25b have the same shape and area on the front and back, and the electrode film thickness is 60 nm, the energy confinement coefficient M is the same on the front and back when the front and back shapes and areas of the excitation electrodes 25a and 25b are different. In order to make it equal to the case of the shape and area, the electrode film thicknesses on the front and back sides are each 120 nm. When the resistance value of the excitation electrode portion at each electrode film thickness is calculated, it can be seen from FIG. 3 that the sheet resistance of the electrode film thickness of 60 nm is 1.2Ω / □ in the case of the same shape and area on the front and back surfaces. The resistance value at the electrode portion is about 2.4Ω. On the other hand, when the shape and area of the front and back sides are different, the sheet resistance with an electrode film thickness of 120 nm is 0.3Ω / □, and the resistance value at the excitation electrode portions on the front and back sides is about 0.6Ω. Therefore, when designing a vibration element having the same energy confinement factor M, the design of the excitation electrode with different shapes and areas of the front and back surfaces can reduce the CI value because the influence of ohmic cross can be reduced to about 1/4. is there.

FIG. 4 shows prototype conditions and measurement results of an AT-cut quartz-crystal vibrating element that vibrates at a resonance frequency in the 246 MHz to 491 MHz band that was prototyped in the embodiment of FIG.
In the excitation electrodes 25a and 25b on the front and back sides, the thickness of a nickel (Ni) layer as a base layer is constant at 7 nm, and the thickness of a gold (Au) layer as an upper layer is 45 nm to 120 nm. The dimensions of the excitation electrode 25a are hx 0.14 mm to 0.70 mm and hz 0.11 mm so that 1.25 ≦ hx / hz ≦ 1.31 is satisfied with hx / hz = 1.28 as the center. It is set to -0.56 mm. Note that hz is a dimension (length) along the direction orthogonal to the thickness-shear vibration direction of the excitation electrode 25a.
In addition, the lead electrodes 27a and 27b on the front and back sides and the pad electrodes 29a and 29b are laminated with a layer of nickel (Ni) having a thickness of 7 nm on the upper layer portion having a thickness equivalent to that of the excitation electrode in order to avoid the influence of ohmic cross. On top of that, a gold (Au) layer having a thickness of 200 nm is laminated.
Here, the trial production conditions shown in FIG. 4 satisfy the above-described formulas (1), (2), (5), and (6).
M = K × (hx / ( 2 × ts ) ) × √Δ (1)
Δ = (fs−fe) / fs (2)
fs = R / [ts + te2 × (ρe / ρx)] (5)
fe = R / [ts + te × (ρe / ρx)] (6)
Each parameter is as follows.
K = 1.538
R = 1.67 (MHz · mm)
ρx = 2.649 (g / cm 3)
ρ _Au (gold density) = 19.3 (g / cm ³ )
ρ _Ni (Nickel density) = 8.9 (g / cm ³ )
The density ρe of the excitation electrode having a two-layer structure is calculated as follows.
ρe = (ρ _Au × t _Au + ρ _Ni × t _Ni ) / (t _Au + t _Ni )
Here, t _Au is the thickness of the upper layer gold (Au) layer, and t _Ni is the thickness of the lower layer nickel (Ni) layer.
fs is a cut-off frequency of the vibration part 12, and fe is a frequency when the excitation electrode is arranged on the vibration part 12.
FIG. 4 shows that when the energy confinement coefficient M is 15.5 ≦ M ≦ 36.7, the CI value of the main vibration can be reduced to 20 (Ω) or less.

FIG. 5 is a graph plotting CI values with respect to the energy confinement factor M of the AT-cut quartz resonator shown in FIG. The CI value tends to decrease as the energy confinement factor M increases, and the influence of ohmic cross decreases as the electrode film thickness increases, and the excitation charge increases and the resistance decreases as the electrode area increases. This is probably because of this.
Therefore, as shown in FIG. 5, when the energy confinement coefficient M is 17.1 or more, the CI value specification (CI ≦ 20Ω) required by the oscillation circuit can be satisfied.

FIG. 6 shows the CI value ratio (CIs / CIm) between the CI value (CIm) of the main vibration and the CI value (CIs) of the spurious relative to the energy confinement factor M of the AT-cut quartz crystal resonator element shown in FIG. is there. This is because the CI value ratio (CIs / CIm) tends to decrease as the energy confinement factor M increases, and the in-harmonic mode spurious is confined strongly by increasing the film thickness and area of the excitation electrode. .
As shown in FIG. 6, when the energy confinement coefficient M is 35.7 or less, the spurious specifications (CIs / CIm ≧ 2.0) required by the oscillation circuit can be satisfied.

  From the above results, when the shapes and areas of the front and back surfaces of the excitation electrodes 25a and 25b are different, the CI value specification (CI ≦ 20Ω) and the spurious specification (CIs / CIm ≧ 2.0) required by the oscillation circuit are simultaneously obtained. It has been found that the energy confinement factor M satisfies 17.1 ≦ M ≦ 35.7.

In the embodiment shown in FIG. 1, the excitation electrodes 25a and 25b are shown as square, that is, square or rectangular (the long side is the X-axis direction), but it is not necessary to limit to this. The excitation electrode 25a on the front surface side may be circular or elliptical, and the excitation electrode 25b on the back surface side may be a rectangle, circle, or ellipse that is sufficiently larger than the excitation electrode 25a.
Furthermore, in the thickness-shear vibration mode using an AT-cut quartz substrate, the displacement distribution in the displacement direction determined by the crystal anisotropy differs from the displacement in the direction orthogonal thereto, and the electrode dimension ratio (hx / hz) is Since about 1.28 is said to be the most efficient, the elliptical or rectangular excitation electrode shape of the ratio is the capacitance ratio γ (= C0 / C1, where C0 is the electrostatic capacitance) , C1 can minimize the series resonance capacity).

Next, FIG. 7 shows an experimental result in which the lead electrodes 27a and 27b on the front and back sides and the pad electrodes 29a and 29b are thickened in order to avoid the influence of ohmic cross. To increase the film thickness, a nickel (Ni) film thickness of 7 nm is laminated on the upper layer part having a film thickness equivalent to that of the excitation electrodes 25a and 25b, and gold (Au) is laminated thereon to a thickness of 200 nm. FIG. 7 shows the CI value with respect to the lead electrode film thickness of the AT-cut quartz-crystal vibrating element that vibrates at the resonance frequency in the 491 MHz band, which was prototyped in the embodiment of FIG.
As shown in FIG. 7, the CI value can be reduced from 25.1Ω to 13.2Ω by increasing the film thickness of the lead electrodes 27a and 27b and the pad electrodes 29a and 29b. Therefore, increasing the film thickness of the lead electrodes 27 a and 27 b and the pad electrodes 29 a and 29 b is effective for reducing the CI of the vibration element 1. In particular, the lead electrodes 27a and 27b that need to be thin and long have a great effect of reducing the CI by reducing the film thickness.

2. Next, a vibrator (the vibrator of the present invention) to which the above-described vibration element 1 is applied will be described.
8A and 8B are diagrams showing the configuration of the vibrator according to the embodiment of the present invention. FIG. 8A is a plan view in which the lid member is omitted, and FIG. 8B is a longitudinal sectional view. The vibrator 2 includes a vibration element 1, a package body 40 formed in a rectangular box shape for housing the vibration element 1, and a lid member 49 made of metal, ceramic, glass, or the like. .
As shown in FIG. 8, the package body 40 is formed by stacking a first substrate 41, a second substrate 42, a third substrate 43, a seal ring 44, and mounting terminals 45. Yes. A plurality of mounting terminals 45 are formed on the outer bottom surface of the first substrate 41. The third substrate 43 is an annular body from which the central portion is removed, and a seal ring 44 such as Kovar is formed on the upper peripheral edge of the third substrate 43.
The third substrate 43 and the second substrate 42 form a recess (cavity) that houses the vibration element 1. A plurality of element mounting pads 47 that are electrically connected to the mounting terminals 45 by conductors 46 are provided at predetermined positions on the upper surface of the second substrate 42. The element mounting pad 47 is disposed so as to correspond to the pad electrode 29a formed on the second thick body 15a when the vibration element 1 is mounted.

  When fixing the vibration element 1, first, the vibration element 1 is inverted (turned over) and the pad electrode 29 a is placed on the element mounting pad 47 coated with the conductive adhesive 30 and a load is applied. The conductive adhesive 30 uses a polyimide adhesive with little degassing in consideration of aging.

Next, in order to cure the conductive adhesive 30 of the vibration element 1 mounted on the package body 40, it is placed in a high temperature furnace at a predetermined temperature for a predetermined time. After the conductive adhesive 30 is cured, the pad electrode 29b that is inverted and turned to the upper surface side and the electrode terminal 48 of the package body 40 are electrically connected by the bonding wire BW. As shown in FIG. 8B, since the vibration element 1 is supported / fixed to the package body 40 at one place (one point), the magnitude of the mount stress generated by the support fixation can be reduced. Become.
After the annealing treatment, the frequency is adjusted by adding mass to the excitation electrode 25b or reducing the mass. Thereafter, the lid member 49 is placed on the seal ring 44 formed on the upper surface of the package body 40, and the lid member 49 is sealed by seam welding in a reduced pressure atmosphere or an atmosphere of nitrogen gas. Complete. Alternatively, there is a method in which the lid member 49 is placed on the low-melting glass applied on the upper surface of the third substrate 43 of the package body 40 and melted and adhered. Also in this case, the inside of the cavity of the package is made into a reduced pressure atmosphere or filled with an inert gas such as nitrogen gas to complete the vibrator 2.

The vibration element 1 formed by separating the pad electrodes 29a and 29b in the Z′-axis direction may be configured. In this case as well, the vibrator can be configured similarly to the vibrator 2 described with reference to FIG. Moreover, you may comprise the vibration element 1 which formed the pad electrodes 29a and 29b on the same surface at intervals. In this case, the vibration element 1 has a structure in which the conductive adhesive 30 is applied at two locations (two points) so as to be conductive, supported, and fixed. Although the structure is suitable for reducing the height, the mounting stress due to the conductive adhesive 30 may be slightly increased.
In the above-described embodiment of the vibrator 2, an example in which a laminated plate is used for the package body 40 has been described. However, vibration is performed using a cap that uses a single-layer ceramic plate for the package body 40 and has a drawing process for the lid. You may comprise a child.

  As shown in FIG. 8, the portion that supports the vibration element 1 is one point, and the mounting stress caused by the conductive adhesive 30 is provided by providing the slit 17 between the thick portion 13 and the vibration portion 12. Therefore, it is possible to obtain the vibrator 2 having excellent frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics.

3. Next, an oscillator (an electronic device of the present invention) to which the vibration element of the present invention is applied will be described.
9A and 9B are diagrams showing a configuration of an electronic device according to an embodiment of the present invention. FIG. 9A is a plan view in which a lid member is omitted, and FIG. 9B is a longitudinal sectional view. . The electronic device 3 includes a package body 50, a lid member 49, the vibration element 1, an IC component 51 on which an oscillation circuit for exciting the vibration element 1 is mounted, a variable capacitance element whose capacitance varies with voltage, and a resistance higher than temperature. And at least one electronic component 52 such as a changing thermistor or inductor.

As shown in FIG. 9, the package body 50 is formed by stacking a first substrate 61, a second substrate 62, and a third substrate 63. A plurality of mounting terminals 45 are formed on the outer bottom surface of the first substrate 61. The 2nd board | substrate 62 and the 3rd board | substrate 63 are formed with the annular body from which the center part was removed.
The first substrate 61, the second substrate 62, and the third substrate 63 form a recess (cavity) that accommodates the vibration element 1, the IC component 51, the electronic component 52, and the like. A plurality of element mounting pads 47 that are electrically connected to the mounting terminals 45 by conductors 46 are provided at predetermined positions on the upper surface of the second substrate 62. The element mounting pad 47 is disposed so as to correspond to the pad electrode 29a formed on the second thick body 15a when the vibration element 1 is mounted.

The pad electrode 29a of the inverted vibration element 1 is placed on the element mounting pad 47 of the package body 50 to which the conductive adhesive (polyimide) 30 is applied, and conduction between the pad electrode 29a and the element mounting pad 47 is achieved. One electrode of the IC component 51 is connected through a conductor formed between the substrates of the package body 50 by connecting the pad electrode 29b which is inverted to the upper surface side and the electrode terminal 48 of the package body 50 by a bonding wire BW. Conduction with the terminal 55 is intended. The IC component 51 is fixed at a predetermined position of the package body 50, and the terminal of the IC component 51 and the electrode terminal 55 of the package body 50 are connected by the bonding wire BW. Further, the electronic component 52 is placed at a predetermined position of the package body 50 and connected to the conductor 46 using a metal bump or the like. The package body 50 is filled with an inert gas such as vacuum or nitrogen, and the package body 50 is sealed with a lid member 49 to complete the electronic device 3.
In the method of connecting the pad electrode 29b and the electrode terminal 48 of the package body 50 with the bonding wire BW, the portion supporting the vibration element 1 is one place (one point), and the mount stress caused by the conductive adhesive 30 Make it smaller. Further, since the vibrating element 1 is inverted and the larger excitation electrode 25b is placed on the upper surface when housed in the package body 50, the frequency adjustment of the electronic device 3 is facilitated.

As shown in FIG. 9, since the high-frequency vibrating element 1 excited by the fundamental wave is used by configuring the electronic device 3, the capacitance ratio is small, the frequency variable width is widened, and the S / N ratio is increased. There is an effect that a good voltage controlled oscillator can be obtained.
In addition, an oscillator, a temperature compensated oscillator, and the like can be configured as the electronic device 3, and an oscillator excellent in frequency reproducibility, aging characteristics, and frequency temperature characteristics can be configured.

4). Electronic Device Next, an electronic device (electronic device of the present invention) to which the vibration element according to an embodiment of the present invention is applied will be described in detail with reference to FIGS.
FIG. 10 is a perspective view illustrating a configuration of a mobile (or notebook) personal computer as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, a personal computer 1100 includes a main body portion 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display portion 100. The display unit 1106 is rotated with respect to the main body portion 1104 via a hinge structure portion. It is supported movably. Such a personal computer 1100 incorporates a vibration element 1 that functions as a filter, a resonator, a reference clock, and the like.

  FIG. 11 is a perspective view illustrating a configuration of a mobile phone (including PHS) as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and the display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a cellular phone 1200 incorporates the vibration element 1 that functions as a filter, a resonator, or the like.

FIG. 12 is a perspective view illustrating a configuration of a digital still camera as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, connection with an external device is also simply shown. Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an image sensor such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.
A display unit 100 is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to perform display based on an imaging signal from the CCD. The display unit 100 displays a subject as an electronic image. Functions as a viewfinder. A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side (the back side in the drawing) of the case 1302.
When the photographer confirms the subject image displayed on the display unit 100 and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory 1308. In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation. Such a digital still camera 1300 incorporates a vibration element 1 that functions as a filter, a resonator, or the like.

  Note that the electronic apparatus including the vibration element according to the embodiment of the present invention includes, for example, an inkjet in addition to the personal computer (mobile personal computer) in FIG. 10, the mobile phone in FIG. 11, and the digital still camera in FIG. Dispenser (for example, ink jet printer), laptop personal computer, TV, video camera, video tape recorder, car navigation device, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game machine, word processor , Workstations, videophones, crime prevention TV monitors, electronic binoculars, POS terminals, medical equipment (eg, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic devices, electronic endoscopes), fish detectors, Various measuring instruments and instruments (example If, gages for vehicles, aircraft, and ships), can be applied to a flight simulator or the like.

5). Next, a moving body (moving body of the present invention) to which the vibrator of the present invention is applied will be described.
FIG. 13 is a perspective view schematically showing an automobile as an example of the moving object of the present invention. The automobile 1500 is equipped with a vibrator 2 (vibration element 1). The vibrator 2 includes keyless entry, immobilizer, car navigation system, car air conditioner, anti-lock brake system (ABS), air bag, tire pressure monitoring system (TPMS), engine control, hybrid car, The present invention can be widely applied to an electronic control unit (ECU) 1510 such as an electric vehicle battery monitor and a body posture control system.

  As described above, the resonator element, the vibrator, the oscillator, the electronic device, and the moving body of the present invention have been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is the same. It can be replaced with any configuration having the above function. In addition, any other component may be added to the present invention. Moreover, you may combine each embodiment mentioned above suitably.

  DESCRIPTION OF SYMBOLS 1 ... Vibration element, 2 ... Vibrator, 3 ... Electronic device, 10 ... Board | substrate, 11 ... Recessed part, 12 ... Vibrating part, 13 ... Thick part, 14 ... 1st thick part, 14a ... 1st thickness Meat body, 14b ... 1st inclined part, 15 ... 2nd thick part, 15a ... 2nd thick body, 15b ... 2nd inclined part, 16 ... 3rd thick part, 16a ... 3rd 16b ... the third inclined part, 17 ... slit, 25a, 25b ... excitation electrode, 27a, 27b ... lead electrode, 29a, 29b ... pad electrode, 30 ... conductive adhesive, 40 ... package body, DESCRIPTION OF SYMBOLS 41 ... 1st board | substrate, 42 ... 2nd board | substrate, 43 ... 3rd board | substrate, 44 ... Seal ring, 45 ... Mounting terminal, 46 ... Conductor, 47 ... Element mounting pad, 48 ... Electrode terminal, 49 ... Lid member 50 ... Package body, 51 ... IC component, 52 ... Electronic component, 55 ... Electrode terminal, 61 ... 1 substrate 62 62 second substrate 63 third substrate 100 display unit 1100 personal computer 1102 keyboard 1104 main body 1106 display unit 1200 mobile phone 1202 operation Button 1204 ... Earpiece, 1206 ... Mouthpiece, 1300 ... Digital still camera, 1302 ... Case, 1304 ... Light receiving unit, 1306 ... Shutter button, 1308 ... Memory, 1312 ... Video signal output terminal, 1314 ... Input / output terminal, 1430 ... TV monitor, 1440 ... personal computer, 1500 ... automobile, 1510 ... electronic control unit.

Claims (9)

A substrate including a first main surface and a second main surface which are vibrated by thickness-shear vibration and have a front-back relationship;
A first excitation electrode disposed on the first main surface;
A second excitation electrode arranged on the second main surface,
Including
It said first excitation electrodes, in a plan view, is disposed within the outer edge than the second excitation electrode,
The thickness of the substrate is ts, the total thickness of the first excitation electrode and the second excitation electrode is te, the thickness of the second excitation electrode is te2, and the thickness of the first excitation electrode is slipped. The length along the vibration direction of the vibration is hx, the density of the first excitation electrode and the second excitation electrode is ρe, the density of the substrate is ρx, the cutoff frequency of the substrate is fs, and the substrate The frequency excited by the substrate when the first excitation electrode and the second excitation electrode are arranged on the substrate is fe, the energy confinement coefficient of the substrate is M, the frequency reduction is Δ, and the frequency constant of the substrate is R, where K is the anisotropy constant of the substrate, M = K × (hx / ( 2 × ts ) ) × √Δ
Δ = (fs−fe) / fs
fs = R / [ts + te2 × (ρe / ρx)]
fe = R / [ts + te × (ρe / ρx)]
15.5 ≦ M ≦ 36.7
Transducer elements and satisfies the relationship. In claim 1,
17.1 ≦ M ≦ 35.7
A vibration element characterized by satisfying the relationship: In claim 1 or 2,
When the length along the direction orthogonal to the thickness shear vibration direction of the first excitation electrode is hz,
1.25 ≦ hx / hz ≦ 1.31
A vibration element characterized by satisfying the relationship: In any one of Claims 1 thru | or 3,
The vibration element, wherein the substrate is a quartz substrate. In claim 4,
A vibrating element, wherein the quartz substrate is an AT cut quartz substrate. The vibration element according to any one of claims 1 to 5,
A package containing the vibration element;
A vibrator characterized by comprising: The vibration element according to any one of claims 1 to 5,
An oscillation circuit for driving the vibration element;
An electronic device comprising:   An electronic apparatus comprising the vibration element according to claim 1.   A moving body comprising the vibration element according to claim 1.

Images