JP2008283529A - Tuning fork oscillator and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning fork oscillator which is extremely small, provides a resonance frequency, for example, of a band of several tens of kHz, and has a large electromechanical coupling coefficient. <P>SOLUTION: The tuning fork oscillator 100 includes: a base body having a substrate, an oxide layer formed over the substrate, and a semiconductor layer formed over the oxide layer; a tuning fork type oscillating part 10 formed by working the semiconductor layer and the oxide layer and made of the semiconductor layer; and driving parts 20a to 20d for generating bending oscillations of the oscillating part 10. The oscillating part 10 has a support part 12, two beam parts 14a and 14b formed in the form of a cantilever with the support part 12 as a base end, the driving parts 20a to 20d are formed over the two beam parts 14a and 14b by one set each, one driving part has a first electrode layer, a second piezoelectric body layer formed over the first electrode layer and a second electrode layer formed over the piezoelectric body layer, and when the thickness of the beam parts 14a and 14b is defined as T0, and the thickness of the piezoelectric body layer is defined as T1, T0/T1≤1 is satisfied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tuning fork vibrator for driving a tuning fork type vibration portion formed on a base such as an SOI substrate by vibration of a piezoelectric layer, and an electronic apparatus including the tuning fork vibrator.

  In general, information devices such as clocks and microcomputers are becoming smaller and more power-saving. For this reason, clock modules are required to be smaller and power-saving. Among them, as a vibrator used in the oscillator part of the clock module, a 32 kHz tuning fork vibrator is still used to take advantage of conventional design assets and power saving. This tuning fork vibrator has a structure that can be driven by sandwiching a piezoelectric material such as quartz processed into a tuning fork shape with electrodes, and has advantages such as good temperature characteristics and excellent power saving. Yes. However, in the case of such a 32 kHz tuning fork vibrator, the arm length of the tuning fork becomes several mm, and the total length including packaging becomes close to 10 mm.

  Recently, vibrators using a piezoelectric thin film formed on a silicon substrate instead of quartz have been developed. Such a vibrator has a laminated structure in which a piezoelectric thin film is sandwiched between upper and lower electrodes on a silicon substrate, and drives bending vibration by in-plane expansion and contraction. As a structure of such a vibrator, there are known a beam-shaped structure (FIG. 1 of Patent Document 1) and a structure in which a tuning fork vibrator is formed from two beams (FIG. 1 of Patent Document 2). Yes. Among them, the tuning fork vibrator structure is superior in that the vibration portion of the vibrator is not in direct contact with the substrate and vibration energy does not leak to the substrate.

By the way, even in a vibrator using a piezoelectric thin film formed on such a silicon substrate, the thickness of the silicon substrate can only be reduced to about 100 μm at most. Therefore, the sound velocity of bending vibration is reduced only to about several hundreds m / s. However, in order to obtain a resonance frequency in the several tens of kHz band, the arm length of the beam needs to be several mm or more, and there is a problem that it is difficult to reduce the size of the clock module.
JP 2005-291858 A JP 2005-249395 A

  The present invention solves the above-mentioned problems, and its object is to provide a tuning fork vibrator that is extremely small, can obtain a resonance frequency of, for example, several tens of kHz, and has a large electromechanical coupling coefficient. It is in.

The tuning fork vibrator according to the present invention is
A substrate having a substrate, an oxide layer formed above the substrate, and a semiconductor layer formed above the oxide layer;
A tuning fork type vibration part made of a semiconductor layer formed by processing the semiconductor layer and the oxide layer;
A drive unit for generating flexural vibration of the vibration unit;
Including
The vibrating portion includes a support portion and two beam portions formed in a cantilever shape with the support portion as a base end,
A pair of the driving units are formed above the two beam units, and one driving unit includes a first electrode layer, a piezoelectric layer formed above the first electrode layer, and the piezoelectric layer. A second electrode layer formed above the body layer,
When the thickness of the beam portion is T0 and the thickness of the piezoelectric layer is T1, T0 / T1 ≦ 1.

  According to the tuning fork vibrator of the present invention, since the thickness of the beam portion and the piezoelectric layer has the above relationship, the load of the driving force applied to the piezoelectric layer can be reduced, and the electromechanical coupling coefficient can be increased.

  In the tuning fork vibrator of the present invention, 0.3 ≦ T0 / T1 ≦ 1.0 may be satisfied.

  In the tuning fork vibrator of the present invention, when the width of the drive unit is W1 and the width of the beam unit is W0, 0.2 ≦ W1 / W0 ≦ 0.4 can be satisfied.

  In the tuning fork vibrator of the present invention, the piezoelectric layer may be made of lead zirconate titanate or lead zirconate titanate solid solution.

  In the tuning fork vibrator of the present invention, the piezoelectric layer can be made of aluminum nitride or aluminum nitride solid solution.

  In the tuning fork vibrator of the present invention, the base may be an SOI (Silicon On Insulator) substrate.

  In the tuning fork vibrator of the present invention, an underlayer may be provided between the vibrating portion and the first electrode layer of the driving portion.

  An electronic apparatus according to the present invention includes the tuning fork vibrator of the present invention.

  In the present invention, when a specific B member (hereinafter referred to as “B member”) provided above a specific A member (hereinafter referred to as “A member”), the B member is directly on the A member. The meaning includes the case where it is provided and the case where the B member is provided on the A member via another member.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1. Tuning Fork Vibrator FIG. 1 is a plan view schematically showing the structure of a tuning fork vibrator 100 of this embodiment, and FIG. 2 is a cross-sectional view schematically showing the structure along the line AA in FIG. is there.

  As shown in FIG. 1, the tuning fork vibrator 100 includes an SOI substrate 1 as a base, a tuning fork type vibration unit 10 formed on the SOI substrate 1, and a drive for generating bending vibration of the vibration unit 10. Part 20 (20a-20d). The base body can include a substrate, an oxide layer formed above the substrate, and a semiconductor layer formed above the oxide layer.

  As shown in FIG. 2, the SOI substrate 1 has an oxide layer (silicon oxide layer) 3 and a semiconductor layer (silicon layer) 4 sequentially stacked on a silicon substrate 2. The thickness of the semiconductor layer 4 is desirably 20 μm or less in order to reduce the size of the tuning fork vibrator 100. Since the SOI substrate 1 can also be used as a semiconductor substrate and various semiconductor circuits can be formed in the SOI substrate 1, the tuning fork vibrator 100 and the semiconductor integrated circuit can be integrated. Among these, using a silicon substrate is advantageous in that a general semiconductor manufacturing technique can be used.

  As shown in FIG. 1, the vibration part 10 has a tuning fork shape in plan view. As shown in FIG. 2, the vibration part 10 is formed on the first opening 3 a formed by removing the oxide layer 3 of the SOI substrate 1. Is formed. A second opening 4 a that allows vibration of the vibrating portion 10 is formed around the vibrating portion 10. The first opening 3a and the second opening 4a are continuous. The vibrating portion 10 is formed by a part of the semiconductor layer 4 and includes a support portion 12 and two beam portions 14a and 14b formed in a cantilever shape with the support portion 12 as a base end. . The two first beam portions 14a and the second beam portion 14b are arranged in parallel with each other in the longitudinal direction at a predetermined interval.

  The support portion 12 includes a first support portion 12a that is continuous with the semiconductor layer 4, and a second support portion 12b that is wider than the first support portion 12a. The 2nd support part 12b has a function which supports the 1st beam part 14a and the 2nd beam part 14b, and a function which does not propagate vibration of these beam parts 14a and 14b to the 1st support part 12a. Since the second support portion 12b has such a function, for example, as shown in FIG. 1, the side portion thereof can have an uneven shape.

  The drive units 20 are formed in pairs on the first beam unit 14a and the second beam unit 14b, respectively. That is, on the first beam portion 14a, the first drive portion 20a and the second drive portion 20b are formed in parallel along the longitudinal direction of the first beam portion 14a. Similarly, a third drive unit 20c and a fourth drive unit 20d are formed in parallel along the longitudinal direction of the second beam unit 14b on the second beam unit 14b. And the 1st drive part 20a arrange | positioned on the outer side of the 1st beam part 14a and the 3rd drive part 20c arrange | positioned on the outer side of the 2nd beam part 14b are electrically connected by the wiring which is not shown in figure. Yes. In addition, the second drive unit 20b disposed inside the first beam unit 14a and the fourth drive unit 20d disposed inside the second beam unit 14b are electrically connected by a wiring (not shown). Yes. Therefore, when an AC electric field is applied to these wirings, the first beam 14a and the second beam portion 14b can bend and vibrate in mirror symmetry, thereby realizing tuning fork vibration.

  As shown in FIG. 2, the drive unit 20 (20a to 20d) includes a first electrode layer 22 formed on the underlayer 5, a piezoelectric layer 24 formed above the first electrode layer 22, And a second electrode layer 26 formed above the piezoelectric layer 24.

The underlayer 5 is an insulating film such as a silicon oxide layer (SiO ₂ ) or a silicon nitride layer (Si ₃ N ₄ ), and may be composed of two or more composite layers. Arbitrary electrode materials can be used for the 1st electrode layer 22, for example, platinum etc. can be illustrated. The thickness of the first electrode layer 22 may be 10 nm or more and 5 μm or less as long as a sufficiently low electric resistance value is obtained.

  Any piezoelectric material can be used for the piezoelectric layer 24, and examples thereof include lead zirconate titanate or aluminum nitride.

  Any electrode material can be used for the second electrode layer 26, and platinum or the like can be exemplified. The thickness of the second electrode layer 26 may be 10 nm or more and 5 μm or less as long as a sufficiently low electric resistance value is obtained.

  The thickness of the piezoelectric layer 24 has a specific relationship with the thickness of the beam portions 14a and 14b as described below. That is, T0 / T1 ≦ 1 when the thickness of the beam portions 14a and 14b is T0 and the thickness of the piezoelectric layer 24 is T1. In the present embodiment, it is further preferable that 0.3 ≦ T0 / T1 ≦ 1.0 as is clear from the result of mode analysis described later. Therefore, for example, when the thickness of the beam portions 14a and 14b is 0.3 μm to 4.0 μm, the thickness of the piezoelectric layer 24 can be 1.0 μm or more and 4.0 μm or less. When the thicknesses of the beam portions 14a and 14b and the piezoelectric layer 24 have the above relationship, the driving force applied to the piezoelectric layer is small, and the electromechanical coupling coefficient can be increased. As a result, the tuning fork vibrator 100 can be reduced in size and efficiency.

  FIG. 3 shows the analysis performed on the relationship between the thickness T0 of the beam portions 14a and 14b and the thickness T1 of the piezoelectric layer 24 and the results thereof. FIG. 3 shows the ratio (T0 / T1) between the thickness of the beam portion and the thickness of the piezoelectric layer on the horizontal axis, and the electromechanical coupling coefficient (k2) on the vertical axis.

  Specifically, mode analysis is performed on the tuning fork vibrator 100 using the finite element method, the resonance frequency and the anti-resonance frequency in the first-order bending vibration mode are calculated, and the electromechanical coupling coefficient is calculated from the difference. did.

In the mode analysis, the material constant of silicon constituting the beam portion is set to a density of 2.33 g / cm ³ , and the elastic constants are set to Y ₁₁ = 167 GPa and Y ₄₄ = 80 GPa. The material constant of PZT constituting the piezoelectric layer is a density of 7.50 g / cm ³ , a dielectric constant is ε ₁₁ = 804.6, ε ₃₃ = 659.7, and a piezoelectric constant is e ₃₁ = −4.1 C. / M ² , e ₃₃ = 14.1 C / m ² , e ₁₅ = 10.5 C / m ^2, and elastic constants are Y ₁₁ = 132 GPa, Y ₃₃ = 115 GPa, and Y ₄₄ = 30 GPa. The length of the beam part is 500 μm, the width W0 is 6 μm, the distance between the beam parts is 6 μm, and the thickness T1 of the piezoelectric layer is 1 μm.

  Then, when the electromechanical coupling coefficient when the thickness T0 of the beam portion was changed while the thickness T1 of the piezoelectric layer was kept constant, the result shown in FIG. 3 was obtained. As shown in FIG. 3, in the region of T0 / T1 ≦ 1, preferably 0.3 ≦ T0 / T1 ≦ 1.0, the electromechanical coupling coefficient increases remarkably as the beam portion thickness T0 decreases.

  Further, in the tuning fork vibrator 100 of the present embodiment, as shown in FIG. 1, when the width of the drive unit 20 (20a to 20d) is W1, and the width of the beam units 14a and 14b is W0, 0.2 ≦ It is preferable that W1 / W0 ≦ 0.4. Since the width W1 of the drive unit 20 and the width W0 of the beam portions 14a and 14b have the above relationship, the effect of increasing the electromechanical coupling coefficient when the area of the drive portion increases and the drive portion at the center portion of the width However, since the effect of preventing vibration is balanced, the electromechanical coupling coefficient can be increased. As a result, the tuning fork vibrator 100 can be reduced in size and efficiency.

  FIG. 4 shows the analysis performed on the relationship between the width W1 of the drive unit 20 and the width W0 of the beam portions 14a and 14b and the results thereof. In FIG. 4, the horizontal axis represents the ratio between the width of the drive section and the width of the beam section (W1 / W0), and the vertical axis represents the electromechanical coupling coefficient (k2). The analysis method is the same as the mode analysis described above. In this mode analysis, the change of the electromechanical coupling coefficient when the width W1 of the drive unit was changed while the width W0 of the beam unit was kept constant was obtained, and the result shown in FIG. 4 was obtained. As shown in FIG. 4, the electromechanical coupling coefficient increases almost linearly with the increase of the width W1 of the beam portion, and the ratio (W1 / W0) becomes a maximum in the vicinity of 0.33. It starts to decrease. From the above, it is desirable from the viewpoint of the electromechanical coupling coefficient that the relationship of 0.2 ≦ W1 / W0 ≦ 0.4 is satisfied.

  In the present embodiment, in the drive unit 20, only the piezoelectric layer 26 exists between the first electrode layer 22 and the second electrode layer 26, but other than the piezoelectric layer 24 described above between the electrode layers 22 and 26. You may have a layer of. In this case, the film thickness of the piezoelectric layer 24 may be appropriately changed according to the resonance condition.

  Next, a configuration example of the tuning fork vibrator 100 of the present embodiment will be described.

Tuning fork vibrator 100, is 1 [mu] m, thickness 0.1μm of the first electrode layer 22, the thickness T1 of the piezoelectric layer 24 is 1 [mu] m, the thickness of the second electrode layer 26 thickness of the underlying layer (SiO ₂ layer) Is 0.1 μm, the overall thickness of the drive unit 20 is 1.2 μm, the width W1 of the drive unit 20 is 2 μm, the thickness T0 of the beam portions 14a and 14b is 1 μm, the length is 250 μm, and the width W0 is 6 μm. It is. In this configuration example, T0 / T1 = 1.0 and W1 / W0 = 0.33. The width W1 of the drive unit 20 is specifically the width of the piezoelectric layer 24. The length of the second support portion 12b is 125 μm, and the width (maximum width) is 18 μm. The vibration part 10 is housed in the second opening 4a having a long side of 950 μm and a short side of 350 μm. When the tuning fork vibrator 100 having such a structure is simulated by solving the equation of motion by the finite element method, the resonance frequency of the bending vibration is 32 kHz.

  According to the tuning fork vibrator 100 of the present embodiment, since the vibration part 10 is configured by the semiconductor layer 4 of the SOI substrate 1, the thickness of the vibration part 10 is reduced and the lengths of the beam parts 14a and 14b are reduced. can do. For example, in this embodiment, the thickness of the vibration part 10 can be 4 μm or less, and the length of the vibration part 10 can be 500 μm or less. The tuning fork vibrator 100 of the present embodiment can be a package having a length of 1 mm or less when using a frequency of 32 kHz band.

  Further, according to the tuning fork vibrator 100 of the present embodiment, the ratio (T0 / T1) between the thickness of the beam portion and the thickness of the piezoelectric layer is in a specific range, and further, the width of the drive portion and the width of the beam portion. When the ratio of (W1 / W0) is in a specific range, a high electromechanical coupling coefficient can be obtained.

  Furthermore, according to the present embodiment, the tuning fork vibrator 100 can be formed on the SOI substrate 1, so that the oscillation circuit and the tuning fork vibrator can be integrally formed on the SOI substrate 1. As a result, it is possible to realize an ultra-low power consumption one-chip tuning fork vibrator module by taking advantage of the low operating voltage characteristics of the device using the SOI substrate 1.

2. Next, an example of a method for manufacturing the tuning fork vibrator 100 according to the present embodiment will be described with reference to FIGS.

  (1) As shown in FIG. 5, the base layer 5, the first electrode layer 22, the piezoelectric layer 24, and the second electrode layer 26 are sequentially formed on the SOI substrate 1. The SOI substrate 1 is obtained by sequentially forming an oxide layer (silicon oxide layer) 3 and a semiconductor layer 4 on a silicon substrate 2.

  The underlayer 5 can be formed by a thermal oxidation method, a CVD method, a sputtering method, or the like. The underlayer 5 is formed to be patterned to have a desired shape. This patterning can be performed by ordinary photolithography and etching techniques.

  The first electrode layer 22 can be formed on the underlayer 5 using a vapor deposition method, a sputtering method, or the like. The first electrode layer 22 is patterned to have a desired shape. This patterning can be performed by ordinary photolithography and etching techniques.

The piezoelectric layer 24 can be formed by various methods such as a solution method such as a sol-gel method, a vapor deposition method, a sputtering method, a laser ablation method, and a CVD method. For example, when a lead zirconate titanate layer is formed using a laser ablation method, a laser beam is used as a target for lead zirconate titanate, for example, a target of Pb _1.05 Zr _0.52 Ti _0.48 NbO ₃ . Irradiate. Then, lead atoms, zirconium atoms, titanium atoms, and oxygen atoms are released from the target by ablation, a plume is generated by laser energy, and the plume is irradiated toward the SOI substrate 1. In this way, the piezoelectric layer 24 made of lead zirconate titanate is formed on the first electrode layers 22 and 32. The piezoelectric layer 24 is patterned and formed to have a desired shape. This patterning can be performed by ordinary photolithography and etching techniques.

  The second electrode layer 26 can be formed by vapor deposition, sputtering, CVD, or the like. The second electrode layer 26 is patterned to have a desired shape. This patterning can be performed by ordinary photolithography and etching techniques.

  Patterning of the underlayer 5, the first electrode layer 22, the piezoelectric layer 24, and the second electrode layer 26 can be performed for each layer, or a plurality of layers can be performed in a lump.

  (2) As shown in FIG. 6, the semiconductor layer 4 of the SOI substrate 1 is patterned into a desired shape. Specifically, as shown in FIG. 1, in the semiconductor layer 4, a vibrating portion 10 having a desired planar shape is formed in the second opening 4 a. The patterning of the semiconductor layer 4 can be performed by known photolithography and etching techniques. Etching can be dry etching or wet etching. In this patterning step, the oxide layer 3 of the SOI substrate 1 can be used as an etching stopper layer.

  (3) As shown in FIG. 7, the oxide layer 3 of the SOI substrate 1 is etched to form a first opening 3 a under the vibration part 10. As the etching, for example, wet etching using hydrogen fluoride can be used as an etchant of silicon oxide. The first opening 3a can use the silicon substrate 2 and the semiconductor layer 4 as an etching stopper layer. By providing the second opening 4a and the first opening 3a described above, the mechanical restraining force of the tuning fork type vibrator 10 is reduced, and the vibration part 10 can freely vibrate.

  Through the above steps, the tuning fork vibrator 100 shown in FIGS. 1 and 2 can be formed. According to the manufacturing method of this embodiment, a tuning fork vibrator can be easily manufactured using a known MEMS technique.

3. Examples of electronic equipment to which tuning fork vibrator is applied 3.1. Oscillator An oscillator having the tuning fork vibrator 100 described above will be described.

  FIG. 8 is a circuit diagram showing a basic configuration of an oscillator 500 having the tuning fork vibrator 100 described above. The oscillator 500 can include this circuit (oscillation circuit). The oscillation circuit includes an amplifier 401 that amplifies an electric signal, and a feedback circuit 410 connected between the input and output of the amplifier 401. The amplifier 401 is composed of, for example, a CMOS inverter. The feedback circuit 410 includes, for example, the tuning fork vibrator 100, a resistor 403, and two capacitors 404 and 405. A voltage E is applied to the amplifier 401 from a DC power supply. When the power supply voltage E is increased and the oscillation start voltage is reached, the current I increases rapidly and oscillation starts. When the power supply voltage E is further increased, the current I increases almost proportionally while maintaining the oscillation state.

  FIG. 9 is a plan view schematically showing the oscillator 500 according to the present embodiment, and FIG. 10 is a cross-sectional view schematically showing the oscillator 500. 10 is a cross-sectional view taken along the line XX of FIG. 9 and 10, the tuning fork vibrator 100 is simplified for convenience.

  The oscillator 500 is sealed with a sealing material 502. The IC (integrated circuit) 503 is connected to the external terminal 570 by a bonding wire 504 such as a gold wire. The external terminal 570 is electrically connected to the mounting terminal 541 via the lead frame 505 and the bonding material 506. The mounting terminal 541 is electrically connected to each electrode of the tuning fork vibrator 100 by wiring (not shown). The tuning fork vibrator 100 is sealed with a lid member 539, a seal member 540, and the like.

  FIG. 11 is a diagram schematically showing a manufacturing process example of the oscillator 500 according to the present embodiment.

  First, tape attachment and dicing are performed on the IC wafer. Next, the chip of the IC 503 is mounted on the lead frame 505. Next, wire bonding is performed on the IC 503 using the bonding wires 504.

  Next, the mounting fork vibrator 100 is mounted by bonding the mounting terminal 541 of the tuning fork vibrator 100 to the lead frame 505 using a bonding material 506 such as solder. Next, the tuning fork vibrator 100 and the IC 503 are resin-sealed using a sealing material (molding material) 502. After that, characteristic inspection and marking are performed, taping, packing, and shipment.

  Although not shown, for example, an IC that is planarly adjacent to the tuning fork vibrator 100 is formed on the base 1 (see FIG. 2) on which the tuning fork vibrator 100 is formed by using a semiconductor process. An oscillator according to the above can also be formed. Thereby, the package can be omitted, and a one-chip type oscillator can be formed.

3.2. Real-Time Clock Next, a real-time clock having the tuning fork vibrator 100 described above will be described.

  FIG. 12 is a circuit block diagram schematically showing a real-time clock 600 having the oscillator (OSC) 500 described above. The integrated circuit portion of the real-time clock 600 is integrated on a single substrate 601 and connected to a microprocessor (not shown).

  A clock pulse of high frequency (for example, 32 kHz) is output from the oscillator 500 connected to the timing connection terminals 602 and 603. The clock pulse is frequency-divided by the frequency dividing circuit 605, and a time measuring pulse of 1 Hz is input to the time counting counter 606. The clock counter 606 includes, for example, a second clock bit s, a minute clock bit m, a clock clock bit h, a day clock bit d, a daily clock bit D, a monthly clock bit M, and an annual clock bit Y. Has been. When a predetermined number of timing pulses are input to the timing counter 606, each timing bit can be incremented. Connected to the time counter 606 is a control unit 620 that rewrites and reads time bits. For example, the control unit 620 can include a command decoder 612 and shift registers 609 and 610.

  When rewriting the clock bit of the clock counter 606, first, a select signal is supplied from the microprocessor to the select input terminal 607. Next, external information composed of a data bit representing information to be rewritten, an address bit representing the address of the timekeeping bit, and an operation bit representing a write operation to the timekeeping counter 606 is input from the microprocessor to the data input terminal 608. Supply. As a result, the external information is stored in the shift registers 609 and 610 connected in series. Then, the command decoder 612 sends a write enable signal to the time counter 606 based on the operation bit and address bit stored in the shift register 610 and outputs an address signal designating the time bit. As a result, the data bits stored in the shift register 609 are written into the timekeeping bits of the timekeeping counter 606, and real-time data is rewritten.

  When real-time data is read from the time counter 606, external information having an operation bit indicating a read operation is transmitted from the microprocessor. Then, the command decoder 612 sets the write enable signal to the time counter 606 to an inactive state. As a result, the inverter 613 supplies the write enable signal in the active state to the shift register 609, the shift register 609 becomes ready for reading, and the contents of the time counter 606 are read to the shift register 609. The real-time data read to the shift register 609 is transferred to the data output terminal 615 in synchronization with the clock signal applied to the clock input terminal 614, and is sent to, for example, a microprocessor register.

  For example, data such as calculation results can be stored in a random access memory (RAM) 616.

  FIG. 13 is a top perspective view schematically showing the real-time clock 600 according to the present embodiment, and FIG. 14 is a side perspective view schematically showing the real-time clock 600. 14 is a view seen in the direction of arrow XIV in FIG.

  An IC chip 651 having an oscillation circuit or the like is bonded and fixed to the island portion 653 of the lead frame 652 with a conductive adhesive or the like. Each electrode pad 654 provided on the upper surface of the IC chip 651 is electrically connected to an input / output lead terminal 656 disposed on the outer periphery of the package by a bonding wire 655. In plan view, a vibrator housing 657 in which the tuning fork vibrator 100 is housed is disposed next to the IC chip 651. In the vibrator housing 657, for example, the tuning fork vibrator 100 shown in FIGS. 1 and 2 is sealed in an airtight state. Leads 658 that are electrically connected to the respective electrodes of the tuning fork vibrator 100 protrude outward from the vibrator housing 657. The lead 658 is bonded and fixed to the connection pad 659 of the lead frame 652 with a conductive adhesive or the like. The IC chip 651, the lead frame 652, and the vibrator housing 657 are integrally molded with a resin 660 and packaged.

  Although not shown, for example, an IC that is planarly adjacent to the tuning fork vibrator 100 is formed on the base 1 (see FIG. 2) on which the tuning fork vibrator 100 is formed by using a semiconductor process. It is also possible to form a real-time clock according to the above. As a result, the package can be omitted, and a one-chip real-time clock can be formed.

3.3. Next, a radio clock receiver module having the tuning fork vibrator 100 described above will be described.

  FIG. 15 is a circuit block diagram schematically showing the radio clock receiver module 800 according to the present embodiment.

  The radio clock receiver module 800 includes a receiver 801, a frequency filter 805, a peripheral circuit 810, and the above-described real time clock (RTC) 600. The frequency filter 805 includes, for example, the tuning fork vibrator 100 (100A, 100B) shown in FIGS. The peripheral circuit 810 can include, for example, a detection / rectification circuit 806, a waveform shaping circuit 807, and a central processing unit (CPU) 808.

  The radio timepiece is a timepiece having a function of receiving a standard radio wave including time information and automatically correcting and displaying the correct time. In Japan, there are transmitting stations that transmit standard radio waves to Fukushima Prefecture (40 kHz) and Saga Prefecture (60 kHz).

  A receiving unit (for example, an antenna) 801 receives a long standard wave of 40 kHz or 60 kHz. The standard radio wave is obtained by applying time modulation (AM) to a carrier wave of 40 kHz or 60 kHz and carrying time information (time code).

  The received electrical signal is amplified by an amplifier 802 and filtered and tuned by a frequency filter 805 having tuning fork vibrators 100A and 100B having the same resonance frequency as the carrier frequency. From the filtered electrical signal, the peripheral circuit 810 can read the time code. Specifically, first, a filtered signal having a predetermined frequency is detected and demodulated by a detection / rectification circuit 806. Then, the time code is taken out via the waveform shaping circuit 807 and counted by the CPU 808. The CPU 808 reads information such as the current year, accumulated date, day of the week, and time, for example. The read information is reflected on the RTC 600, and accurate time information is displayed.

  Since the carrier wave is 40 kHz or 60 kHz, the tuning fork vibrator 100A, 100B of the frequency filter 805 is suitable for the tuning fork vibrator according to the present invention.

  Although not shown, for example, an IC that is planarly adjacent to the tuning fork vibrator 100 is formed on the base 1 (see FIG. 2) on which the tuning fork vibrator 100 is formed by using a semiconductor process. It is also possible to form a radio clock receiver module according to the above. As a result, the package can be omitted, and a one-chip radio timepiece receiving module can be formed.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

The top view which shows typically the structure of the tuning fork vibrator of embodiment. Sectional drawing cut | disconnected along the AA line of FIG. The graph which shows the result of having calculated the electromechanical coupling coefficient of the tuning fork vibrator. The graph which shows the result of having calculated the electromechanical coupling coefficient of the tuning fork vibrator. Sectional drawing which shows typically the manufacturing method of the tuning fork vibrator of embodiment. Sectional drawing which shows typically the manufacturing method of the tuning fork vibrator of embodiment. Sectional drawing which shows typically the manufacturing method of the tuning fork vibrator of embodiment. FIG. 3 is a circuit diagram showing a basic configuration of an oscillator to which the tuning fork vibrator of the present embodiment is applied. FIG. 2 is a plan view schematically showing an oscillator to which the tuning fork vibrator of the present embodiment is applied. FIG. 3 is a cross-sectional view schematically showing an oscillator to which the tuning fork vibrator of the present embodiment is applied. The figure which shows schematically the example of a manufacturing process of the oscillator to which the tuning fork vibrator of this embodiment is applied. The circuit block diagram which shows roughly the real-time clock to which the tuning fork vibrator of this embodiment is applied. FIG. 3 is a top perspective view schematically showing a real-time clock to which the tuning fork vibrator of the present embodiment is applied. FIG. 5 is a side perspective view schematically showing a real-time clock to which the tuning fork vibrator of the present embodiment is applied. 1 is a circuit block diagram schematically showing a radio clock receiver module to which a tuning fork vibrator according to an embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... SOI substrate, 2 ... Silicon substrate, 3 ... Oxide layer, 3a, 4a ... Opening part, 4 ... Semiconductor layer (silicon layer), 5 ... Underlayer, 10 ... Vibration part, 12 ... Support part, 14a ... 1st 1 beam part, 14b ... 2nd beam part, 20 ... drive part, 22 ... 1st electrode layer, 24 ... piezoelectric material layer, 26 ... 2nd electrode layer, 100 ... tuning fork vibrator, 401 amplifier, 403 resistance, 404, 405 capacitor, 410 feedback circuit, 500 oscillator, 502 sealing material, 503 IC, 504 bonding wire, 505 lead frame, 506 bonding material, 539 lid member, 540 seal member, 541 mounting terminal, 570 external terminal, 600 real time clock, 601 board, 602, 603 timing connection terminal, 605 frequency divider, 606 timing counter, 607 select input terminal, 608 Input terminal, 609, 610 shift register, 612 command decoder, 613 inverter, 614 clock input terminal, 615 data output terminal, 620 control unit, 651 IC chip, 652 lead frame, 653 island unit, 654 electrode pad, 655 bonding wire , 656 I / O lead terminal, 657 vibrator housing, 658 lead, 659 connection pad, 660 resin, 800 radio clock receiver module, 801 receiver, 802 amplifier, 805 frequency filter, 806 detector / rectifier circuit, 807 waveform Shaping circuit, 808 CPU, 810 peripheral circuit

Claims (8)

A substrate having a substrate, an oxide layer formed above the substrate, and a semiconductor layer formed above the oxide layer;
A tuning fork type vibration part made of a semiconductor layer formed by processing the semiconductor layer and the oxide layer;
A drive unit for generating flexural vibration of the vibration unit;
Including
The vibrating portion includes a support portion and two beam portions formed in a cantilever shape with the support portion as a base end,
A pair of the driving units are formed above the two beam units, and one driving unit includes a first electrode layer, a piezoelectric layer formed above the first electrode layer, and the piezoelectric layer. A second electrode layer formed above the body layer,
A tuning fork vibrator in which T0 / T1 ≦ 1 when T0 is the thickness of the beam portion and T1 is the thickness of the piezoelectric layer. In claim 1,
A tuning fork vibrator in which 0.3 ≦ T0 / T1 ≦ 1.0. In claim 1 or 2,
A tuning fork vibrator in which 0.2 ≦ W1 / W0 ≦ 0.4, where W1 is the width of the driving unit and W0 is the width of the beam unit. In any one of Claims 1 thru | or 3,
The piezoelectric layer is a tuning fork vibrator made of lead zirconate titanate or lead zirconate titanate solid solution. In any one of Claims 1 thru | or 3,
The piezoelectric layer is a tuning fork vibrator made of aluminum nitride or aluminum nitride solid solution. In any of claims 1 to 5,
A tuning fork vibrator, wherein the base is an SOI substrate. In any one of Claims 1 thru | or 6.
A tuning fork vibrator having a foundation layer between the vibrating section and the first electrode layer of the driving section.   An electronic apparatus comprising the tuning fork vibrator according to claim 1.

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