Vibration device

Abstract

To provide a vibration device suppressed in deterioration of electrical characteristics.SOLUTION: A vibration device 1 includes a vibrator element 25, a base 10 to which the vibrator element 25 is coupled, and a lid 20 bonded to the base 10 and accommodating the vibrator element 25 in an accommodation space 23 between the base 10 and the lid. At least one of the base 10 and the lid 20 includes a first semiconductor substrate 11 connected to a ground potential and having a conductivity type of P-type or N-type. The vibrator element 25 includes a vibrator substrate 30, a first electrode 31a disposed on a side of the vibrator substrate 30 closer to the first semiconductor substrate 11, and a second electrode 31b disposed on a side of the vibrator substrate 30 opposite the first semiconductor substrate 11. When L1 [m] is the height of the accommodation space 23, and d1 [m] is the distance between the first semiconductor substrate 11 and the first electrode 31a, and when S1 [m2] is the area of the first electrode 31a, and ε [F / m] is the permittivity of the accommodation space 23, L1≤0.2×10-3 and d1≥ε×S1×1012 are satisfied.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vibration device. [Background technology]

[0002] For example, Patent Document 1 discloses that in a vibration device in which a base and a lid are joined and a vibration element is housed in a space surrounded by the base and the lid, the base includes a P-type semiconductor or an N-type semiconductor, the lid is made of a semiconductor of the same conductivity type as the semiconductor in the base, and the semiconductor in the base and the semiconductor in the lid are connected to a ground potential. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-28095 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when an oscillator is constructed using the vibration device described in Patent Document 1, the parasitic capacitance generated between the base or lid at ground potential and the electrode of the vibration element facing the base or lid becomes large, resulting in a problem that the electrical characteristics of the oscillator, such as the start-up characteristics and the output characteristics of the oscillation signal, deteriorate. Specifically, the electrical characteristics include a narrow frequency variable range and an insufficient negative resistance of the oscillation circuit, making the oscillation start unstable. [Means for solving the problem]

[0005] The vibration device includes a vibration element, a base to which the vibration element is connected, and a lid body joined to the base and accommodating the vibration element in an accommodating space between the base and the lid body, and at least one of the base and the lid body includes a first semiconductor substrate of a P-type or N-type conductivity type connected to a ground potential, and the vibration element has a vibration substrate, a first electrode disposed on the first semiconductor substrate side of the vibration substrate, and a second electrode disposed on the opposite side of the vibration substrate to the first semiconductor substrate side, and the height of the accommodating space is L1 [m], the length between the first semiconductor substrate and the first electrode is d1 [m], and the area of ​​the first electrode is S1 [m 2 ] and the dielectric constant of the storage space is ε [F / m], L1≦0.2×10 -3 and d1 ≥ ε × S1 × 10 12 Meet the following. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing a schematic structure of a vibration device according to a first embodiment. [Diagram 2] FIG. 1 is a plan view showing a schematic structure of a vibration device according to a first embodiment. [Diagram 3] Cross-sectional view taken along line A1-A1 in Figure 2. [Figure 4] 4 is a diagram showing the relationship between the length d1 between the first semiconductor substrate and the first electrode and the capacitance C. FIG. [Diagram 5] FIG. 11 is a plan view showing a schematic structure of a vibration device according to a second embodiment. [Figure 6] Cross-sectional view taken along line A2-A2 in Figure 5. [Figure 7] FIG. 11 is a plan view showing a schematic structure of a vibration device according to a third embodiment. [Figure 8] Cross-sectional view taken along line A3-A3 in Figure 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] 1. First embodiment First, an oscillator including a vibration element 25 will be taken as an example of the vibration device 1 according to the first embodiment and will be described with reference to FIGS. 1 to 4. FIG. In FIG. 2, for convenience of explanation of the internal configuration of the vibration device 1, the cover 20 is removed. For convenience of explanation, the following perspective views, plan views, and cross-sectional views show three mutually perpendicular axes, the X-axis, the Y-axis, and the Z-axis. The direction along the X-axis is called the "X-direction", the direction along the Y-axis is called the "Y-direction", and the direction along the Z-axis is called the "Z-direction". The arrow side of each axis is also called the "plus side", and the opposite side to the arrow is also called the "minus side". The plus side of the Z direction is also called the "upper", and the minus side of the Z direction is also called the "lower".

[0008] 1, 2, and 3, the vibration device 1 includes a vibration element 25, a base 10 to which the vibration element 25 is connected, and a lid body 20 joined to the base 10 and accommodating the vibration element 25 in an accommodating space 23 between the base 10 and the lid body 20. The base 10 and the lid body 20 together form a package 2 that accommodates the vibration element 25.

[0009] The base 10 includes a first semiconductor substrate 11 of a P-type or N-type conductivity connected to a ground potential, and a circuit section 50 arranged on the opposite side of the first semiconductor substrate 11 to the vibration element 25. The base 10 is a rectangular flat plate in a plan view from the Z direction, and has a first surface 10a and a second surface 10b that are in a front-back relationship, with an internal terminal 12 provided on the first surface 10a and an external terminal 13 provided on the second surface 10b. The base 10 is provided with a through electrode (not shown) that penetrates the first surface 10a and the second surface 10b, and electrically connects the internal terminal 12 and the circuit section 50. The circuit section 50 has an oscillation circuit 51 electrically connected to the vibration element 25.

[0010] The lid body 20 includes a second semiconductor substrate 21 of the same conductivity type as the first semiconductor substrate 11 connected to the ground potential. The lid body 20 is rectangular in plan view from the Z direction, has a third surface 20a and a fourth surface 20b which are opposite surfaces, and has a recess 22 which opens to the base 10 side. The third surface 20a of the lid body 20 is directly bonded to the first surface 10a of the base 10, and together with the base 10, defines an accommodation space 23 which accommodates the vibration element 25. The height L1 of the accommodation space 23 is 0.2×10-3 [m] or less, that is, 200 [μm] or less. By setting the height L1 of the accommodation space 23 to 200 [μm] or less, it is possible to reduce the height of the vibration device 1 while accommodating the vibration element 25. The accommodation space 23 is in any one of a vacuum atmosphere, a nitrogen atmosphere, and a helium atmosphere. Examples of the main material of the first semiconductor substrate 11 of the base 10 and the second semiconductor substrate 21 of the lid 20 include various semiconductor materials such as silicon, germanium, silicon oxide, gallium nitride, and indium gallium arsenide. Of these, it is preferable that the first semiconductor substrate 11 and the second semiconductor substrate 21 are made mainly of silicon. This is because silicon is easy to obtain and process as a semiconductor material, and is inexpensive.

[0011] The direct bonding between the base 10 and the lid 20 may be any type of bonding that does not require an intermediate material between two bonding surfaces made of the same material. The bonding method is not limited to this, and may be a bonding method using glass frit or the like, a metal eutectic bonding method in which metal films formed on the first surface 10a of the base 10 and the third surface 20a of the lid 20 are bonded to each other, or an activation bonding method in which the surface of the first surface 10a of the base 10 and the surface of a metal film such as Au formed on the third surface 20a of the lid 20 are activated by plasma irradiation to bond them.

[0012] The vibration element 25 has a vibration substrate 30, a first electrode 31a arranged on the first semiconductor substrate 11 side, which is the base 10 side of the vibration substrate 30, and a second electrode 31b arranged on the cover 20 side, which is the opposite side of the first semiconductor substrate 11 side of the vibration substrate 30. The first electrode 31a and the second electrode 31b have an excitation electrode 32 that vibrates the vibration substrate 30, a pad electrode 34 that outputs a vibration signal to the outside and fixes the vibration element 25 to the base 10, and a lead electrode 33 that electrically connects the excitation electrode 32 and the pad electrode 34. The second electrode 31b further has a side electrode 35 that electrically connects the lead electrode 33 formed on the vibration substrate 30 and the pad electrode 34 formed under the vibration substrate 30. The area of ​​the excitation electrode 32 of the first electrode 31a and the area of ​​the excitation electrode 32 of the second electrode 31b are the same, and are arranged to overlap each other in a plan view from the Z direction.

[0013] The vibration element 25 is disposed on the first surface 10a side of the base 10, and is fixed to the internal terminal 12 of the base 10 at the portion of the pad electrode 34 via a conductive bonding member 41 such as a conductive adhesive or a gold bump. Therefore, the excitation electrode 32 of the vibration element 25 is electrically connected to the oscillation circuit 51 via the conductive bonding member 41 and the internal terminal 12, and the vibration substrate 30 can be vibrated. Note that an AT-cut quartz substrate, an SC-cut quartz substrate, a BT-cut quartz substrate, or the like is used as the vibration substrate 30.

[0014] Since the base 10 and the lid 20 are the first semiconductor substrate 11 and the second semiconductor substrate 21 of the same conductivity type connected to the ground potential, it is possible to block external electromagnetic noise that overlaps with the first electrode 31a and the second electrode 31b of the vibration element 25 and causes problems such as abnormal oscillation and deterioration of the quality of the output signal. Therefore, it is possible to obtain a vibration device 1 that is less susceptible to the influence of external electromagnetic noise and has excellent oscillation characteristics.

[0015] However, because the base 10 and the lid 20 are the first semiconductor substrate 11 and the second semiconductor substrate 21 of the same conductivity type connected to the ground potential, parasitic capacitance is likely to occur between the first semiconductor substrate 11 and the first electrode 31a, or between the second semiconductor substrate 21 and the second electrode 31b. Therefore, an investigation was conducted on the capacitance C that occurs between the semiconductor substrates 11, 21 and the electrodes 31a, 31b.

[0016] Generally, the capacitance C of a parallel plate capacitor is expressed by the following formula (1). C=ε×(S / d) (1) Here, C is capacitance [F], ε is dielectric constant [F / m], and S is area [m 2 ], and d is the distance between the opposing conductive plates [m]. FIG. 4 shows the results of simulating the capacitance C when the length d1 between the first semiconductor substrate 11 and the first electrode 31a is changed using equation (1). In the simulation, the storage space 23 is in a vacuum atmosphere, and the dielectric constant of the vacuum is ε=8.85419×10 -12 [F / m], area S1 of the first electrode 31a = 2.0 × 10 -10 [m 2 The simulation was performed by changing d1. The area S1 of the first electrode 31a is the total area of ​​the excitation electrode 32, the lead electrode 33, and the pad electrode 34 that face the first semiconductor substrate 11. Fig. 4 shows the simulation result of the capacitance C versus the length d1 using an approximation curve.

[0017] The approximation curve shown in FIG. 4 indicates that the capacitance C decreases exponentially as the length d1 increases, and tends to converge to approximately 0.01 pF when the length d1 is 1.4 μm or greater.

[0018] 4, the capacitance C is 1.0 pF when the length d1 is 1.8 μm, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be set to 1.0 pF or less by setting the length d1 to 1.8 μm or more. In other words, d1≧ε×S1×10 12By satisfying this condition, the capacitance C can be set to 1.0 pF or less.

[0019] 4, the capacitance C is 0.5 pF when the length d1 is 3.6 μm, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be set to 0.5 pF or less by setting the length d1 to 3.6 μm or more. In other words, d1≧2×ε×S1×10 12 By satisfying this condition, the capacitance C can be kept below 0.5 pF.

[0020] 4, the capacitance C is 0.2 pF when the length d1 is 9.0 μm, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be set to 0.2 pF or less by setting the length d1 to 9.0 μm or more. In other words, d1≧5×ε×S1×10 12 By satisfying this condition, the capacitance C can be kept below 0.2 pF.

[0021] Next, the relationship between the length d2 between the second semiconductor substrate 21 and the second electrode 31b and the capacitance C is also determined in the same manner as the relationship between the length d1 between the first semiconductor substrate 11 and the first electrode 31a described above and the capacitance C, assuming that the accommodation space 23 is a vacuum atmosphere and the dielectric constant of the vacuum is ε=8.85419×10 -12 [F / m], area of ​​second electrode 31b S2=2.0×10 -10 [m 2 ] and simulating by changing d2, the same results as the approximation curve in Figure 4 were obtained. Therefore, d2 ≥ ε × S2 × 10 12 By satisfying this condition, the capacitance C between the second semiconductor substrate 21 and the second electrode 31b can be set to 1.0 [pF] or less.

[0022] Also, d2 ≥ 2 × ε × S2 × 10 12 By satisfying this condition, the capacitance C between the second semiconductor substrate 21 and the second electrode 31b can be set to 0.5 pF or less.

[0023] Also, d2 ≥ 5 × ε × S2 × 10 12By satisfying this condition, the capacitance C between the second semiconductor substrate 21 and the second electrode 31b can be set to 0.2 [pF] or less.

[0024] Here, the storage space 23 was simulated as a vacuum atmosphere, but the simulation was also performed in a nitrogen atmosphere and a helium atmosphere. The result was that the dielectric constant of nitrogen is ε=8.85955×10 -12 [F / m], and the dielectric constant of helium ε = 8.85484 × 10 -12 [F / m] is the dielectric constant of a vacuum ε = 8.85419 × 10 -12 [F / m] is very close to the capacitance C, so the approximation curve of the capacitance C is approximately consistent with the approximation curve of FIG. 4. Therefore, even when the accommodation space 23 is a nitrogen atmosphere or a helium atmosphere, the capacitance C can be made 1.0 [pF] or less by making the length d1 between the first semiconductor substrate 11 and the first electrode 31a 1.8 [μm] or more. Furthermore, the capacitance C can be made 0.5 [pF] or less by making the length d1 between the first semiconductor substrate 11 and the first electrode 31a 3.6 [μm] or more. Furthermore, the capacitance C can be made 0.2 [pF] or less by making the length d1 between the first semiconductor substrate 11 and the first electrode 31a 9.0 [μm] or more. Therefore, the accommodation space 23 may be any of a vacuum atmosphere, a nitrogen atmosphere, and a helium atmosphere. Furthermore, the accommodation space 23 may be an inert gas atmosphere other than a nitrogen atmosphere or a helium atmosphere as long as the inert gas atmosphere has a dielectric constant approximately equal to that of a vacuum.

[0025] The area S1 of the first electrode 31a is 3.1684×10 -12 [m 2 ]≦S1≦4.45556×10 -8 [m 2 By ensuring such an electrode area, it is possible to increase vibration efficiency and maintain the CI value while reducing the parasitic capacitance to 1.0 pF or less.

[0026] In this embodiment, the first semiconductor substrate 11 and the second semiconductor substrate 21 of the same conductivity type connected to a ground potential are used for the base 10 and the lid 20, but the present invention is not limited to this, and a non-conductive substrate such as glass may be used for either the base 10 or the lid 20. When a non-conductive substrate is used for the base 10, the second semiconductor substrate 21 in this embodiment corresponds to the first semiconductor substrate 11, the second electrode 31b corresponds to the first electrode 31a, and the length d2 between the second semiconductor substrate 21 and the second electrode 31b corresponds to d1.

[0027] As described above, in the vibration device 1 of the present embodiment, the height L1 of the accommodation space 23 is ≦0.2×10 -3 [m] and the length d1 between the first semiconductor substrate 11 and the first electrode 31a ≧ ε × S1 × 10 12 Since the above requirement is satisfied, the resonator device 1 can be made low-profile, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be set to 1.0 pF or less. Therefore, the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a is reduced, and deterioration of electrical characteristics such as the start-up characteristics of the oscillator and the output characteristics of the oscillation signal can be suppressed. Specifically, the electrical characteristics include a narrow frequency variable range and an insufficient negative resistance of the oscillation circuit 51, which makes the oscillation start unstable.

[0028] In addition, the height L1 of the storage space 23 is 0.2×10 -3 [m] and the length d1 between the first semiconductor substrate 11 and the first electrode 31a ≧2×ε×S1×10 12 Since the above requirement is satisfied, the resonator device 1 can be made low-profile, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made 0.5 pF or less. Therefore, the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a is smaller, so that the deterioration of electrical characteristics such as the start-up characteristics of the oscillator and the output characteristics of the oscillation signal can be further suppressed.

[0029] In addition, the height L1 of the storage space 23 is 0.2×10 -3[m] and the length d1 between the first semiconductor substrate 11 and the first electrode 31a ≧5×ε×S1×10 12 Since the above requirement is satisfied, the resonator device 1 can be made low-profile, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made 0.2 pF or less. Therefore, the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a is further reduced, and deterioration of electrical characteristics such as the start-up characteristics of the oscillator and the output characteristics of the oscillation signal can be further suppressed.

[0030] 2. Second embodiment Next, a vibration device 1a according to a second embodiment will be described with reference to FIGS. In FIG. 5, for the sake of convenience in explaining the internal configuration of the vibration device 1a, the cover 20 is removed.

[0031] The resonator device 1a of this embodiment is similar to the resonator device 1 of the first embodiment, except that the arrangement of the circuit section 50a of the base 10c is different from that of the resonator device 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment, and similar items will be denoted by the same reference numerals and their description will be omitted.

[0032] 5 and 6, the vibration device 1a includes a vibration element 25, a base 10c, and a lid 20. The base 10c and the lid 20 form a package 2a that houses the vibration element 25.

[0033] The base 10c has a circuit section 50a disposed on the first surface 10a side, which is the vibration element 25 side, of the first semiconductor substrate 11. The circuit section 50a has an oscillation circuit 51 electrically connected to the vibration element 25.

[0034] With this configuration, by setting the height L1 of the accommodating space 23 to a predetermined value or less and setting the length d1 between the first semiconductor substrate 11 and the first electrode 31a to a predetermined value or less, it is possible to obtain the same effect as in the first embodiment.

[0035] 3. Third embodiment Next, a vibration device 1b according to a third embodiment will be described with reference to FIGS. In addition, in FIG. 7, for the sake of convenience in explaining the internal configuration of the vibration device 1b, a state in which the lid 20 is removed is illustrated.

[0036] The resonator device 1b of this embodiment is similar to the resonator device 1 of the first embodiment, except that the structure of the resonator element 25b is different from that of the resonator device 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment, and similar items will be denoted by the same reference numerals and their description will be omitted.

[0037] 7 and 8, the vibration device 1b includes a vibration element 25b, a base 10, and a lid 20. The base 10 and the lid 20 form a package 2 that houses the vibration element 25b.

[0038] The vibration element 25b has a recess 36 formed in the center of the vibration substrate 30b, the recess 36 opening toward the base 10. The excitation electrode 32 of the first electrode 31a is provided on the inner bottom surface of the recess 36. Therefore, the length d2 between the second semiconductor substrate 21 and the second electrode 31b is smaller than the length d1 between the first semiconductor substrate 11 and the first electrode 31a, and therefore the parasitic capacitance is determined by the length d2.

[0039] With this configuration, by setting the height L1 of the accommodating space 23 to a predetermined value or less and setting the length d2 between the second semiconductor substrate 21 and the second electrode 31b to a predetermined value or less, it is possible to obtain the same effect as in the first embodiment. [Explanation of symbols]

[0040] 1,1a,1b...vibration device, 2...package, 10...base, 10a...first surface, 10b...second surface, 11...first semiconductor substrate, 12...internal terminal, 13...external terminal, 20...lid, 20a...third surface, 20b...fourth surface, 21...second semiconductor substrate, 22...recess, 23...accommodation space, 25...vibration element, 30...vibration substrate, 31a...first electrode, 31b...second electrode, 32...excitation electrode, 33...lead electrode, 34...pad electrode, 35...side electrode, 41...conductive bonding member, 50...circuit portion, 51...oscillating circuit, d1,d2...length, L1...height, S1...area of ​​first electrode, S2...area of ​​second electrode, ε...dielectric constant.

Claims

1. A vibration element; A base to which the vibration element is connected; a lid body joined to the base and accommodating the vibration element in an accommodating space between the lid body and the base; Including, At least one of the base and the lid includes a first semiconductor substrate of a P-type or N-type conductivity type connected to a ground potential; the vibration element includes a vibration substrate, a first electrode disposed on a side of the vibration substrate facing the first semiconductor substrate, and a second electrode disposed on a side of the vibration substrate facing away from the first semiconductor substrate; The height of the storage space is L1 [m], The length between the first semiconductor substrate and the first electrode is d1 [m], The area of ​​the first electrode is S1 [m 2 ]year, When the dielectric constant of the storage space is ε [F / m], L1≦0.2×10 -3 and d1 ≧ ε × S1 × 10 12 Fulfilling Vibration devices.

2. The d1, the ε, and the S1 are d1 ≧ 2 × ε × S1 × 10 12 Fulfilling The vibration device according to claim 1 .

3. The d1, the ε, and the S1 are d1 ≧ 5 × ε × S1 × 10 12 Fulfilling The vibration device according to claim 1 .

4. the first electrode is disposed on the base side of the vibration substrate, the second electrode is disposed on the lid side of the vibration substrate, the base includes the first semiconductor substrate; the lid body includes a second semiconductor substrate of the conductivity type connected to the ground potential, The length between the second semiconductor substrate and the second electrode is d2 [m], The area of ​​the second electrode is S2 [m 2 ], d1 ≧ ε × S1 × 10 12 and d2 ≧ ε × S2 × 10 12 Fulfilling The vibration device according to claim 1 .

5. The d1, the ε, the S1, the d2, and the S2 are d1 ≧ 2 × ε × S1 × 10 12 and d2 ≧ 2 × ε × S2 × 10 12 Fulfilling The vibration device according to claim 4 .

6. The d1, the ε, the S1, the d2, and the S2 are d1 ≧ 5 × ε × S1 × 10 12 and d2 ≧ 5 × ε × S2 × 10 12 Fulfilling The vibration device according to claim 4 .

7. the base includes a circuit portion disposed on a side of the first semiconductor substrate opposite to the vibration element, The circuit unit has an oscillator circuit electrically connected to the vibration element. The vibration device according to claim 4 .

8. the base includes a circuit portion disposed on a side of the first semiconductor substrate facing the vibration element, The circuit unit has an oscillator circuit electrically connected to the vibration element. The vibration device according to claim 4 .

9. The S1 is 3. 1684 x ​​10 -12 ≦S1≦4.45556×10 -8 Fulfilling A vibration device according to any one of claims 1 to 8.

10. The storage space is in a vacuum atmosphere, a nitrogen atmosphere, or a helium atmosphere. A vibration device according to any one of claims 1 to 8.

11. The S1 is 3. 1684 x ​​10 -12 ≦S1≦4.45556×10 -8 Fulfilling The storage space is in a vacuum atmosphere, a nitrogen atmosphere, or a helium atmosphere. A vibration device according to any one of claims 1 to 8.

Images