Vibration device

Abstract

A vibration device suppresses degradation of electrical characteristics. A resonator device (1) includes: a resonator element (25); a base (10) connected to the vibrating element (25); and a cover body (20) joined to the base (10), in which the resonator element (25) is housed in a housing space (23) between the base (10) and the cover body (20), and at least one of the base (10) and the cover body (20) includes a P-type or N-type conductivity-type first semiconductor substrate (11) connected to a ground potential. The resonator element (25) has a resonator substrate (30), a first electrode (31a) disposed on the first semiconductor substrate (11) side of the resonator substrate (30), and a second electrode (31b) disposed on the opposite side of the resonator substrate (30) from the first semiconductor substrate (11) side. When the height of the housing space (23) is L1 [m], the length between the first semiconductor substrate (11) and the first electrode (31a) is d1 [m], the area of the first electrode (31a) is S1 [m2], and the dielectric constant of the housing space (23) is epsilon [F / m], L1 < = 0.2 * 10 <-3 > and d1 > = epsilon * S1 * 10 < 12 > are satisfied.

Description

Technical Field

[0001] The present invention relates to a vibrating device. Background Art

[0002] For example, Patent Document 1 discloses the following: In a vibration device in which a base and a cover are joined and a vibration element is housed in a space surrounded by the base and the cover, the base includes a P-type semiconductor or an N-type semiconductor, the cover is composed of a semiconductor of the same conductive type as the semiconductor of the base, and the semiconductor of the base and the semiconductor of the cover are connected to a ground potential.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-28095

[0004] However, when the vibration device described in Patent Document 1 is used to form an oscillator, the parasitic capacitance generated between the base or cover set to the ground potential and the electrode of the vibration element facing the base or cover becomes large, resulting in the problem of deterioration of electrical characteristics such as the starting characteristics of the oscillator and the output characteristics of the oscillation signal. Specifically, the electrical characteristics also include the narrowing of the variable frequency range and the fact that the oscillation start becomes unstable due to the insufficient negative resistance of the oscillation circuit. Summary of the invention

[0005] The vibration device includes: a vibration element; a base connected to the vibration element; and a cover body joined to the base, wherein the vibration element is accommodated in a storage space between the cover body and the base, at least one of the base and the cover body includes a first semiconductor substrate of P type or N type conductivity connected to a ground potential, and the vibration element has: a vibration substrate; a first electrode arranged on the first semiconductor substrate side of the vibration substrate; and a second electrode arranged on the side of the vibration substrate opposite to the first semiconductor substrate side, assuming that the height of the storage 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 ], when the dielectric constant of the storage space is ε[F / m], L1≤0.2×10 -3 And d1 ≥ ε × S1 × 10 12 . BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a perspective view showing a schematic structure of the vibration device according to the first embodiment.

[0007] Figure 2 It is a plan view showing a schematic structure of the vibration device according to the first embodiment.

[0008] Figure 3 yes Figure 2A1-A1 line section view.

[0009] Figure 4 1 is a diagram showing the relationship between the length d1 between the first semiconductor substrate and the first electrode and the capacitance C.

[0010] Figure 5 It is a plan view showing a schematic structure of a vibration device according to a second embodiment.

[0011] Figure 6 yes Figure 5 A2-A2 line section view.

[0012] Figure 7 It is a plan view showing a schematic structure of a vibration device according to a third embodiment.

[0013] Figure 8 yes Figure 7 A3-A3 line section view.

[0014] Description of symbols

[0015] 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: cover; 20a: third surface; 20b: fourth surface; 21: second semiconductor substrate; 22: recess; 23: storage 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 component; 50: circuit part; 51: oscillation circuit; d1, d2: length; L1: height; S1: area of ​​first electrode; S2: area of ​​second electrode; ε: dielectric constant. DETAILED DESCRIPTION

[0016] 1. First Implementation

[0017] First, as the vibration device 1 of the first embodiment, an oscillator having a vibration element 25 is cited as an example. Figure 1 to Figure 4 Provide explanation.

[0018] In addition, Figure 2In order to facilitate the explanation of the internal structure of the vibration device 1, the state in which the cover body 20 is removed is illustrated. In addition, for the convenience of explanation, in the subsequent stereoscopic views, top views and cross-sectional views, the X-axis, Y-axis and Z-axis are illustrated as three axes perpendicular to each other. In addition, 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". In addition, the arrow side of each axis is also called the "positive side", and the side opposite to the arrow is called the "negative side". In addition, the positive side of the Z direction is also called "up", and the negative side of the Z direction is called "down".

[0019] like Figure 1 , Figure 2 and Figure 3 As shown, the vibration device 1 includes: a vibration element 25; a base 10 connected to the vibration element 25; and a cover 20 joined to the base 10 to accommodate the vibration element 25 in a storage space 23 between the base 10 and the cover 20. The base 10 and the cover 20 constitute a package 2 for accommodating the vibration element 25.

[0020] The base 10 includes: a first semiconductor substrate 11 of P-type or N-type conductivity connected to the ground potential; and a circuit unit 50 arranged on the side of the first semiconductor substrate 11 opposite to the vibration element 25. In addition, when viewed from the Z direction, the base 10 is a rectangular flat plate, having a first surface 10a and a second surface 10b in a front-back relationship, and an internal terminal 12 is provided on the first surface 10a, and an external terminal 13 is provided on the second surface 10b. A through electrode (not shown) penetrating the first surface 10a and the second surface 10b is provided on the base 10, and the internal terminal 12 is electrically connected to the circuit unit 50. In addition, the circuit unit 50 has an oscillation circuit 51 electrically connected to the vibration element 25.

[0021] The cover 20 includes a second semiconductor substrate 21 of the same conductivity type as the first semiconductor substrate 11 connected to the ground potential. In addition, when viewed from the Z direction, the cover 20 is rectangular in shape and has a third surface 20a and a fourth surface 20b in a positive and negative relationship, and a recess 22 is formed that opens toward the base 10. The third surface 20a of the cover 20 is directly bonded to the first surface 10a of the base 10, and the cover 20 and the base 10 together form a storage space 23 for storing the vibration element 25. In addition, the height L1 of the storage space 23 is 0.2×10 -3 By setting the height L1 of the storage space 23 to 200 [μm] or less, the vibration device 1 can be made thinner while accommodating the vibration element 25. The storage space 23 is any one of a vacuum atmosphere, a nitrogen atmosphere, and a helium atmosphere.

[0022] As the main material of the first semiconductor substrate 11 of the base 10 and the second semiconductor substrate 21 of the cover 20, various semiconductor materials such as silicon, germanium, silicon oxide, gallium nitride, and indium gallium arsenide can be listed. Among them, the first semiconductor substrate 11 and the second semiconductor substrate 21 are preferably made of silicon as the main material. This is because silicon is easy to obtain and process as a semiconductor material and is cheap.

[0023] The direct bonding between the base 10 and the cover 20 may be any bonding method as long as no intervening object is required between two bonding surfaces of the same material. In addition, the bonding method is not limited thereto, and may be a bonding method via glass frit or the like, a metal eutectic bonding method in which a metal film formed on the first surface 10a of the base 10 and the third surface 20a of the cover 20 are bonded to each other, or an activation bonding method in which a metal film such as Au formed on the surface of the first surface 10a of the base 10 and the third surface 20a of the cover 20 is activated by plasma irradiation to bond.

[0024] The vibration element 25 includes a vibration substrate 30, a first electrode 31a disposed on the base 10 side of the vibration substrate 30, that is, the first semiconductor substrate 11 side, and a second electrode 31b disposed on the side of the vibration substrate 30 opposite to the first semiconductor substrate 11 side, that is, the cover 20 side. The first electrode 31a and the second electrode 31b include 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. In addition, the second electrode 31b also includes a side electrode 35 that electrically connects the lead electrode 33 formed on the upper side of the vibration substrate 30 and the pad electrode 34 formed on the lower side of the vibration substrate 30. In addition, the area of ​​the excitation electrode 32 of the first electrode 31a is the same as the area of ​​the excitation electrode 32 of the second electrode 31b, and they are overlapped when viewed from the Z direction.

[0025] The vibration element 25 is arranged on the first surface 10a side of the base 10, and is fixed to the internal terminal 12 of the base 10 via a conductive bonding member 41 such as a conductive adhesive or a gold bump at the portion of the pad electrode 34. 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. In addition, as the vibration substrate 30, an AT-cut quartz substrate, an SC-cut quartz substrate, a BT-cut quartz substrate, or the like is used.

[0026] The base 10 and the cover 20 are the first semiconductor substrate 11 and the second semiconductor substrate 21 of the same conductivity type connected to the ground potential, so that it is possible to cut off the external electromagnetic noise that overlaps with the first electrode 31a or the second electrode 31b of the vibration element 25 and becomes the main cause of the generation of abnormal oscillation or the deterioration of the quality of the output signal. Therefore, it is not easy to be affected by the electromagnetic noise from the outside, and it is possible to obtain the vibration device 1 with excellent oscillation characteristics.

[0027] However, since the base 10 and the cover 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 easily generated between the first semiconductor substrate 11 and the first electrode 31a, or between the second semiconductor substrate 21 and the second electrode 31b. Therefore, the capacitance C generated between the semiconductor substrates 11, 21 and the electrodes 31a, 31b was investigated.

[0028] Generally, the capacitance C of a parallel plate capacitor is expressed by the following equation (1).

[0029] C=ε×(S / d).......(1)

[0030] Here, C is capacitance [F], ε is dielectric constant [F / m], and S is area [m 2 ], d is the distance between the opposing conductive plates [m].

[0031] Figure 4 The following is a simulation result of the capacitance C when the length d1 between the first semiconductor substrate 11 and the first electrode 31 a is changed using the equation (1).

[0032] In the simulation, the storage space 23 was set to a vacuum atmosphere, and the dielectric constant of vacuum is ε=8.85419×10 -12 [F / m], the area S1 of the first electrode 31a = 2.0 × 10 -10 [m 2 ], and d1 is varied to perform simulation. In addition, the area S1 of the first electrode 31a is a value obtained by adding the areas of the excitation electrode 32, the lead electrode 33, and the pad electrode 34 facing the first semiconductor substrate 11. In addition, Figure 4 The result of simulating the capacitance C with respect to the length d1 is represented by an approximate curve.

[0033] Figure 4 The approximate curve shown shows a tendency that the capacitance C decreases exponentially as the length d1 increases, and converges to approximately 0.01 [pF] when the length d1 is 1.4 [μm] or more.

[0034] Therefore, according to Figure 4, the capacitance C is 1.0 [pF] when the length d1 is 1.8 [μm]. By making the length d1 greater than 1.8 [μm], the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 1.0 [pF]. That is, by satisfying d1 ≥ ε × S1 × 10 12 , the capacitance C can be made less than 1.0 [pF].

[0035] In addition, according to Figure 4 , the capacitance C is 0.5 [pF] when the length d1 is 3.6 [μm]. By making the length d1 greater than 3.6 [μm], the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 0.5 [pF]. That is, by satisfying d1 ≥ 2 × ε × S1 × 10 12 , the capacitance C can be reduced to 0.5 [pF] or less.

[0036] In addition, according to Figure 4 , the capacitance C is 0.2 [pF] when the length d1 is 9.0 [μm]. By making the length d1 greater than 9.0 [μm], the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 0.2 [pF]. That is, by satisfying d1 ≥ 5 × ε × S1 × 10 12 , the capacitance C can be reduced to 0.2 [pF] or less.

[0037] Next, the relationship between the length d2 between the second semiconductor substrate 21 and the second electrode 31b and the capacitance C is similar to the relationship between the length d1 between the first semiconductor substrate 11 and the first electrode 31a and the capacitance C. The storage space 23 is set to a vacuum atmosphere, and the dielectric constant of the vacuum is set to ε=8.85419×10 -12 [F / m], the area S2 of the second electrode 31b = 2.0×10 -10 [m 2 ], and simulated by changing d2, and obtained the same Figure 4 The same result is obtained for the approximate curve. Therefore, by satisfying d2≥ε×S2×10 12 , the capacitance C between the second semiconductor substrate 21 and the second electrode 31 b can be made less than or equal to 1.0 [pF].

[0038] In addition, by satisfying d2≥2×ε×S2×10 12 , the capacitance C between the second semiconductor substrate 21 and the second electrode 31 b can be made 0.5 [pF] or less.

[0039] In addition, by satisfying d2≥5×ε×S2×10 12 , the capacitance C between the second semiconductor substrate 21 and the second electrode 31 b can be reduced to 0.2 [pF] or less.

[0040] Here, the simulation was performed with the storage space 23 set to a vacuum atmosphere, but simulations were also performed with a nitrogen atmosphere and a helium atmosphere. As a result, the dielectric constant ε of nitrogen is 8.85955×10 -12 [F / m] and the dielectric constant of helium ε=8.85484×10 -12 [F / m] is very close to the dielectric constant of vacuum, ε = 8.85419 × 10 -12 [F / m], so the approximate curve of capacitance C is Figure 4 The approximate curves are roughly consistent. Therefore, even when the storage space 23 is a nitrogen atmosphere or a helium atmosphere, by setting the length d1 between the first semiconductor substrate 11 and the first electrode 31a to be greater than 1.8 [μm], the capacitance C can be less than 1.0 [pF]. In addition, by setting the length d1 between the first semiconductor substrate 11 and the first electrode 31a to be greater than 3.6 [μm], the capacitance C can be less than 0.5 [pF]. In addition, by setting the length d1 between the first semiconductor substrate 11 and the first electrode 31a to be greater than 9.0 [μm], the capacitance C can be less than 0.2 [pF]. Therefore, the storage space 23 can be any one of a vacuum atmosphere, a nitrogen atmosphere, and a helium atmosphere. In addition, the storage space 23 can be an inert gas atmosphere having a dielectric constant substantially the same as that of a vacuum, and an inert gas atmosphere other than a nitrogen atmosphere and a helium atmosphere can also be applied.

[0041] The area S1 of the first electrode 31a satisfies 3.1684×10 -12 [m 2 ]≤S1≤4.45556×10 -8 [m]. By ensuring such an electrode area, the vibration efficiency can be improved while maintaining the CI value and the parasitic capacitance can be reduced to 1.0 [pF] or less.

[0042] In the present embodiment, the base 10 and the cover 20 use the first semiconductor substrate 11 and the second semiconductor substrate 21 of the same conductivity type connected to the ground potential, but the present invention is not limited thereto, and either the base 10 or the cover 20 may use a non-conductive substrate such as glass. In addition, when the base 10 uses a non-conductive substrate, the second semiconductor substrate 21 in the present embodiment is equivalent to the first semiconductor substrate 11, the second electrode 31b is equivalent to the first electrode 31a, and the length d2 between the second semiconductor substrate 21 and the second electrode 31b is equivalent to d1.

[0043] As described above, the vibration device 1 of the present embodiment satisfies the height L1 of the storage space 23 ≤ 0.2×10 -3 [m] and the length d1 between the first semiconductor substrate 11 and the first electrode 31a ≥ ε×S1×10 12Therefore, the vibration device 1 can be made thinner, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 1.0 [pF]. Therefore, since the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a is reduced, the degradation of electrical characteristics such as the starting characteristics of the oscillator and the output characteristics of the oscillation signal can be suppressed. In addition, specifically, the electrical characteristics also include the narrowing of the frequency variable range and the insufficient negative resistance of the oscillation circuit 51, which makes the oscillation start unstable.

[0044] In addition, since the height L1 of the storage space 23 is less than or equal to 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 Therefore, the vibration device 1 can be made thinner, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 0.5 [pF]. Therefore, since the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a becomes smaller, the degradation of the electrical characteristics such as the starting characteristics of the oscillator and the output characteristics of the oscillation signal can be further suppressed.

[0045] In addition, since the height L1 of the storage space 23 is less than or equal to 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 Therefore, the vibration device 1 can be made thinner, and the capacitance C between the first semiconductor substrate 11 and the first electrode 31a can be made less than 0.2 [pF]. Therefore, since the parasitic capacitance between the first semiconductor substrate 11 and the first electrode 31a is further reduced, the degradation of the electrical characteristics such as the starting characteristics of the oscillator and the output characteristics of the oscillation signal can be further suppressed.

[0046] 2. Second Implementation

[0047] Next, refer to Figure 5 and Figure 6 A resonator device 1 a according to the second embodiment will be described.

[0048] In addition, Figure 5 In order to facilitate the description of the internal structure of the vibration device 1a, the state in which the cover body 20 is removed is shown.

[0049] The vibration device 1a of this embodiment is the same as the vibration device 1 of the first embodiment except that the configuration of the circuit part 50a of the base 10c is different from that of the vibration device 1 of the first embodiment. In addition, the description will be centered on the differences from the above-mentioned first embodiment, and the same items are marked with the same reference numerals and their descriptions are omitted.

[0050] like Figure 5 and Figure 6 As shown, the vibration device 1a includes a vibration element 25, a base 10c, and a cover 20. The base 10c and the cover 20 constitute a package 2a that houses the vibration element 25.

[0051] The base 10c has a circuit unit 50a disposed on the first surface 10a side, that is, on the vibration element 25 side of the first semiconductor substrate 11. The circuit unit 50a has an oscillation circuit 51 electrically connected to the vibration element 25.

[0052] By configuring in this way and setting the height L1 of the storage space 23 to a predetermined value or less and the length d1 between the first semiconductor substrate 11 and the first electrode 31 a to a predetermined value or less, the same effects as those of the first embodiment can be obtained.

[0053] 3. Third Implementation

[0054] Next, refer to Figure 7 and Figure 8 A resonator device 1 b according to the third embodiment will be described.

[0055] In addition, Figure 7 In order to facilitate the description of the internal structure of the vibration device 1b, the state in which the cover body 20 is removed is shown.

[0056] The vibration device 1b of this embodiment is the same as the vibration device 1 of the first embodiment except that the structure of the vibration element 25b is different from that of the vibration device 1 of the first embodiment. The description will focus on the differences from the first embodiment, and the same items are denoted by the same reference numerals and their descriptions will be omitted.

[0057] like Figure 7 and Figure 8 As shown, the vibration device 1b includes a vibration element 25b, a base 10, and a cover 20. The base 10 and the cover 20 constitute a package 2 that accommodates the vibration element 25b.

[0058] The vibration element 25b has a recess 36 opened toward the base 10 formed at the center of the vibration substrate 30b. The excitation electrode 32 of the first electrode 31a is provided on the inner bottom surface of the recess 36. Therefore, since 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, the parasitic capacitance is determined by the length d2.

[0059] By configuring in this way and setting the height L1 of the storage space 23 to a predetermined value or less and the length d2 between the second semiconductor substrate 21 and the second electrode 31 b to a predetermined value or less, the same effects as those of the first embodiment can be obtained.

Claims

1. A vibration device, comprising: Vibrating elements; a base connected to the vibration element; and a cover body, which is engaged with the base, and the vibration element is accommodated in the accommodation space between the cover body and the base, At least one of the base and the cover includes a first semiconductor substrate of P-type or N-type conductivity connected to a ground potential. The vibration element includes: a vibration substrate; a first electrode disposed on the first semiconductor substrate side of the vibration substrate; and a second electrode disposed on the side of the vibration substrate opposite to the first semiconductor substrate side. Assuming that the height of the storage 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 ], when the dielectric constant of the storage space is ε[F / m], Satisfy L1≤0.2×10 -3 And d1 ≥ ε × S1 × 10 12 .

2. The vibration device according to claim 1, wherein: The d1, the ε and the S1 satisfy d1≥2×ε×S1×10 12 .

3. The vibration device according to claim 1, wherein The d1, the ε and the S1 satisfy d1≥5×ε×S1×10 12 .

4. The vibration device according to claim 1, wherein The first electrode is arranged on the base side of the vibration substrate, The second electrode is arranged on the cover side of the vibration substrate, The base includes the first semiconductor substrate, The cover includes a second semiconductor substrate of the conductive type connected to the ground potential. Assuming that the length between the second semiconductor substrate and the second electrode is d2 [m], and the area of ​​the second electrode is S2 [m 2 ]hour, Satisfies d1≥ε×S1×10 12 And d2 ≥ ε × S2 × 10 12 .

5. The vibration device according to claim 4, wherein: The d1, the ε, the S1, the d2 and the S2 satisfy d1≥2×ε×S1×10 12 And d2 ≥ 2 × ε × S2 × 10 12 .

6. The vibration device according to claim 4, wherein: The d1, the ε, the S1, the d2 and the S2 satisfy d1≥5×ε×S1×10 12 And d2 ≥ 5 × ε × S2 × 10 12 .

7. The vibration device according to claim 4, wherein: The base includes a circuit portion, the circuit portion being arranged on a side of the first semiconductor substrate opposite to the vibration element. The circuit unit includes an oscillation circuit electrically connected to the vibration element.

8. The vibration device according to claim 4, wherein: The base includes a circuit portion, the circuit portion being arranged on the vibration element side of the first semiconductor substrate, The circuit unit includes an oscillation circuit electrically connected to the vibration element.

9. The vibration device according to any one of claims 1 to 8, wherein: The S1 satisfies 3.1684×10 -12 ≤S1≤4.45556×10 -8 .

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

11. The vibration device according to any one of claims 1 to 8, wherein: The S1 satisfies 3.1684×10 -12 ≤S1≤4.45556×10 -8 , The storage space is a vacuum atmosphere, a nitrogen atmosphere, or a helium atmosphere.

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