Low-impedance quartz tuning fork resonator and preparation method thereof

Abstract

According to the low-impedance quartz tuning fork resonator and the preparation method thereof, grooves are formed in the front face and the back face of a tuning fork arm, the intensity of an excitation electric field of an electrode on the tuning fork arm can be effectively improved, the equivalent impedance value of a device is effectively reduced, the quality factor of the device is improved, and through grooves are formed in the ends, close to a base, of the grooves, so that the quality factor of the device is improved. According to the quartz tuning fork structure, the mechanical inertia moment of the quartz tuning fork structure can be effectively reduced, so that the tuning fork arm is easier to vibrate under the condition of the same driving force, the equivalent impedance value of the device can be further reduced, and a high-quality low-impedance device is obtained.

Description

Technical Field

[0001] The invention relates to a low-impedance quartz tuning fork resonator and a preparation method thereof, and belongs to the field of piezoelectric devices. Background Art

[0002] Quartz crystal tuning forks have become a valuable basic component in frequency measurement due to their good stability, high precision, and low power consumption. Quartz crystals have piezoelectric effect and anisotropy. Quartz crystals with different cutting directions have different field bias effects. By exciting the resonance of quartz piezoelectric elastomers to achieve a stable resonant frequency, it can be used as a standard frequency source, or by frequency offset to detect different physical quantities in the external environment.

[0003] In recent years, quartz tuning fork resonators have been widely used in different fields. First of all, they are most commonly used as the frequency source of electronic clocks, with a nominal frequency of 32.768kHz. With the continuous miniaturization and low power consumption of electronic equipment, quartz tuning forks will inevitably develop in the direction of miniaturization and low power consumption. Therefore, a low-impedance quartz tuning fork resonator is urgently needed. Summary of the invention

[0004] The invention provides a low-impedance quartz tuning fork resonator and a preparation method thereof, which solves the problem disclosed in the background technology.

[0005] According to one aspect of the present disclosure, a low-impedance quartz tuning fork resonator is provided, including a base and a tuning fork arm connected to the base, grooves along the length direction are provided on the front and back sides of the tuning fork arm, a through groove connecting the front groove and the back groove is provided at the end of the groove close to the base, electrodes are provided in the groove and the through groove, the electrode in the front groove is connected to the front electrode of the tuning fork arm, the electrode in the back groove is connected to the back electrode of the tuning fork arm, and the electrode in the through groove connects the electrode in the front groove with the electrode in the back groove.

[0006] In some embodiments of the present disclosure, the length of the through-slot is smaller than the length of the groove, and the width of the through-slot is consistent with that of the groove.

[0007] In some embodiments of the present disclosure, the depth of the groove ranges from (T-10) / 2 to T / 2, wherein T is the thickness of the wafer external to the resonator.

[0008] In some embodiments of the present disclosure, a connection portion for externally connecting to a wafer is provided at one end of the base away from the tuning fork arm, and an electrode on the base extends to a connection point between the connection portion and the wafer.

[0009] In some embodiments of the present disclosure, a counterweight is connected to one end of the tuning fork arm away from the base, an electrode is provided on the counterweight, the electrode on the counterweight is connected to the side electrode of the tuning fork arm, and the counterweight provided with the electrode is plated with a counterweight metal.

[0010] In some embodiments of the present disclosure, the counterweight metal is different from the outermost metal of the electrode.

[0011] According to another aspect of the present disclosure, a method for preparing a low-impedance quartz tuning fork resonator is provided, wherein the resonator is the above-mentioned resonator, and the method comprises: Carve out the shape of the quartz tuning fork resonator and the through groove on the quartz crystal plate; A groove is carved into the shape of a quartz tuning fork resonator with a through slot; Electrodes are engraved on a quartz tuning fork resonator shape with through slots and grooves.

[0012] In some embodiments of the present disclosure, if the resonator is configured with a weight plated with a weight metal, after the electrodes are engraved, the weight metal is bombarded until the resonant frequency of the resonator is adjusted to a desired value.

[0013] The beneficial effects achieved by the present invention are as follows: the present invention arranges grooves on both the front and back sides of the tuning fork arm, which can effectively increase the excitation electric field strength of the electrode on the tuning fork arm, thereby effectively reducing the equivalent impedance value of the device and improving its quality factor, and a through groove is provided at the end of the groove close to the base, which can effectively reduce the mechanical inertia moment of the quartz tuning fork structure, so that under the condition of the same driving force, the tuning fork arm is more likely to vibrate, so that the equivalent impedance value of the device can be further reduced, so as to achieve a high-quality low-impedance device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of a low impedance quartz tuning fork resonator; Figure 2 It is an enlarged view of the through-slot part in the low-impedance quartz tuning fork resonator; Figure 3 is a cross-sectional view of a tuning fork arm portion of a low impedance quartz tuning fork resonator; Figure 4 This is an enlarged view of the weight part of the low-impedance quartz tuning fork resonator; Figure 5 Flow chart of the method for preparing a low impedance quartz tuning fork resonator. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0016] Unless otherwise specified, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0017] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0018] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0019] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0020] It should be noted that similar symbols and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

[0021] In order to solve the problem of lack of low-impedance quartz tuning fork resonator, the present disclosure proposes a low-impedance quartz tuning fork resonator and a preparation method thereof, specifically, two-stage groove structures are provided on the front and back sides of the tuning fork arm, and low impedance is achieved through the two-stage grooves.

[0022] Figure 1 This is a schematic diagram of an embodiment of a low-impedance quartz tuning fork resonator disclosed in the present invention. Similar to the existing quartz tuning fork resonator, the quartz tuning fork resonator disclosed in the present invention also includes a base 1, two opposite tuning fork arms 2 connected to the base 1, and electrodes covering the base 1 and the tuning fork arms 2.

[0023] It should be noted that the part of the base 1 covering the electrode mainly includes the front side, back side and side surface of the base 1. The first side of the front side of the base 1 covers the first electrode, and the second side of the front side of the base 1 covers the second electrode. Similarly, the first side of the back side of the base 1 covers the first electrode, and the second side of the back side of the base covers the second electrode. The first electrode on the front side of the base 1 is connected to the first electrode on the back side of the base 1 through the first side electrode of the base 1, and the second electrode on the front side of the base 1 is connected to the second electrode on the back side of the base 1 through the second side electrode of the base 1.

[0024] In the embodiment, the structures of the two tuning fork arms 2 are similar. Taking one of the tuning fork arms 2 as an example, grooves 3 are provided along the length direction on the front and back sides of the tuning fork arm 2, and a through groove 4 connecting the front groove 3 and the back groove 3 is provided at the end of the groove 3 close to the base 1. Electrodes are provided in the groove 3 and the through groove 4. The electrode in the front groove 3 is connected to the front electrode of the tuning fork arm 2, and the electrode in the back groove 3 is connected to the back electrode of the tuning fork arm 2. The electrode in the through groove 4 connects the electrode in the front groove 3 with the electrode in the back groove 3.

[0025] The grooves 3 are arranged on both sides of the tuning fork arm 2, which can effectively increase the excitation electric field strength of the electrode on the tuning fork arm 2, thereby effectively reducing the equivalent impedance value of the device (i.e., the quartz tuning fork resonator) and improving its quality factor. In addition, a through groove 4 is provided at the end of the groove 3 close to the base 1. The through groove 4 can effectively connect the electrodes on both sides of the tuning fork arm 2 to avoid disconnection during the manufacturing process, and can effectively reduce the mechanical inertia moment of the quartz tuning fork structure, so that under the condition of the same driving force, the tuning fork arm 2 is more likely to vibrate, so that the equivalent impedance value of the device can be further reduced, so as to achieve a high-quality low-impedance device, thereby realizing its low power consumption characteristics after integration.

[0026] The arrangement of the tuning fork electrode can make the device vibrate in anti-phase along the width direction of the tuning fork arm 2 when resonating, so as to keep the device balanced after packaging and ensure the stability of the device.

[0027] It should be noted that, in the tuning fork arm 2, in addition to the front electrode and the back electrode of the tuning fork arm 2, the side electrode is also covered on the side of the tuning fork arm 2. Figure 2, the side electrodes of the tuning fork arm 2 are disconnected from the front electrode and the back electrode of the base 1 itself. Assume that the two tuning fork arms 2 are defined as the first tuning fork arm and the second tuning fork arm respectively, the first tuning fork arm is located on the first side of the base 1, and the second tuning fork arm is located on the second side of the base 1, the side electrodes of the first tuning fork arm are disconnected from the front electrode and the back electrode of the first tuning fork arm, and the side electrodes of the second tuning fork arm are disconnected from the front electrode and the back electrode of the second tuning fork arm, but the front electrode and the back electrode of the first tuning fork arm are connected to the second side electrode of the base 1 through the electrode in the through groove 4, and similarly, the front electrode and the back electrode of the second tuning fork arm are connected to the first side electrode of the base 1 through the electrode in the through groove 4.

[0028] In some embodiments, the length of the through slot 4 of the tuning fork arm 2 is less than the length of the groove 3, and the width of the through slot 4 is consistent with the groove 3, so that the two grooves are connected to form two sections of grooves. This design can effectively reduce the moment of inertia of the device. The depth range of the groove 3 is (T-10) / 2 ~ T / 2, T is the thickness of the wafer connected to the resonator, generally between 150um and 300um, see Figure 3 .

[0029] It should be noted that in order to facilitate the connection of the quartz tuning fork resonator to the wafer, in some embodiments, the end of the base 1 away from the tuning fork arm 2 is connected to the connecting part 5 of the external wafer, and the electrode on the base 1 extends to the connection between the connecting part 5 and the wafer. The device can be tested by directly contacting the electrode of the wafer, avoiding the risk of damaging the device.

[0030] It should be noted that see Figure 4 In order to achieve controllable resonant frequency of the device, a counterweight 7 is connected to the end of each tuning fork arm 2 away from the base 1, and the counterweight 7 is covered with an electrode. The electrode on the counterweight 7 is connected to the side electrode of the tuning fork arm 2, and the electrode on the counterweight 7 is not connected to the electrodes on the front and back sides of the tuning fork arm 2. The counterweight 7 covering the electrode is plated with a counterweight metal. By arranging the counterweight 7 at the end of the tuning fork arm 2, the plating area of ​​the counterweight metal can be effectively increased, so that the resonant frequency of the tuning fork can be better controlled.

[0031] It should be noted that the counterweight 7 is generally configured to be a structure that is larger in volume than the tuning fork arm 2, which can be a hammer head structure or a column as shown in the figure, which can provide more space for adjustment in the subsequent frequency modulation process, thereby ensuring higher quality.

[0032] In some embodiments, the counterweight metal is different from the outermost metal of the electrode. For example, the electrode generally has two layers of metal, such as a chromium layer and a gold layer. The chromium layer is plated first. The chromium serves as an adhesion layer between the gold layer and the quartz, and the thickness is generally 20nm~50nm. Then the gold layer is plated. The thickness of the gold layer is generally 80nm~500nm. In this case, the counterweight metal can be chromium, and its thickness should be greater than the thickness of the metal layer of the electrode, which is convenient for adjusting the resonant frequency. In addition, the use of different metals can effectively distinguish the areas.

[0033] Figure 3 This is a schematic diagram of an embodiment of a method for preparing a low-impedance quartz tuning fork resonator disclosed in the present invention, which may include the following steps: Step 1: Carve out a quartz tuning fork resonator shape and a through groove 4 on a quartz wafer.

[0034] It should be noted that the quartz wafer can be first cleaned with a mixed solution of concentrated sulfuric acid and hydrogen peroxide to remove impurities on the quartz wafer, and then sputter-coated or evaporated (i.e., chromium, gold film) in sequence as a protective film for subsequent corrosion, and then spin-coated with photoresist and photolithographed out the device shape and through-groove 4 pattern, and finally wet-etched.

[0035] Step 2: Carve a groove 3 on the quartz tuning fork resonator with a through groove 4.

[0036] It should be noted that the photoresist can be first spin-coated or spray-coated and the groove 3 pattern of the device can be photoetched, and then the gold and chromium films can be developed and etched to produce the required groove 3 pattern on the quartz wafer, and finally wet etching can be performed.

[0037] It should be noted that the solution of the wet etching process is a fluorine-based solution, which is a saturated ammonium bifluoride solution or a mixed solution of ammonium fluoride and hydrofluoric acid. The etching morphology and etching effect of the device are completed and optimized by controlling the solution concentration, ratio, temperature and etching time.

[0038] Step 3: Carve out electrodes on the quartz tuning fork resonator shape with through slots 4 and grooves 3.

[0039] It should be noted that the film is sputtered or evaporated in sequence, then the photoresist is spin-coated or sprayed and the electrode pattern of the device is photoetched, and finally the gold and chromium films are developed and etched to produce the required electrode pattern on the quartz wafer.

[0040] The above process can prepare a quartz tuning fork resonator without a counterweight 7. If it is necessary to further prepare the device configured with the counterweight 7, the above method also includes step 4, bombarding the counterweight metal after engraving the electrode until the resonant frequency of the resonator is adjusted to the expected value.

[0041] It should be noted that the process of tuning the resonant frequency can be: first, sputter coating or evaporation coating is performed, and then the counterweight metal is bombarded with a laser to adjust the frequency to the expected frequency target.

[0042] The above method is based on MEMS technology, involving the steps of cleaning, coating, photolithography, wet etching, and frequency modulation. Compared with the traditional process, it has great advantages in terms of cost, accuracy, and consumption. At the same time, the structure produced by this process can also be extended to other cantilever beam structures with grooves 3, such as quartz accelerometers, quartz gyroscopes and other inertial devices.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low impedance quartz tuning fork resonator, comprising a base and a tuning fork arm connected to the base, characterized in that: Grooves along the length direction are provided on the front and back sides of the tuning fork arm, and a through groove connecting the front groove and the back groove is provided at the end of the groove close to the base. Electrodes are provided in the groove and the through groove. The electrode in the front groove is connected to the front electrode of the tuning fork arm, and the electrode in the back groove is connected to the back electrode of the tuning fork arm. The electrode in the through groove connects the electrode in the front groove with the electrode in the back groove.

2. The low impedance quartz tuning fork resonator according to claim 1, characterized in that: The length of the through slot is smaller than the length of the groove, and the width of the through slot is consistent with that of the groove.

3. The low impedance quartz tuning fork resonator according to claim 1 or 2, characterized in that: The depth of the groove ranges from (T-10) / 2 to T / 2, where T is the thickness of the wafer external to the resonator.

4. The low impedance quartz tuning fork resonator according to claim 1, characterized in that: A connecting portion for externally connecting to the wafer is arranged at one end of the base away from the tuning fork arm, and an electrode on the base extends to the connection between the connecting portion and the wafer.

5. The low impedance quartz tuning fork resonator according to claim 1, characterized in that: One end of the tuning fork arm away from the base is connected with a counterweight, an electrode is arranged on the counterweight, the electrode on the counterweight is connected to the side electrode of the tuning fork arm, and the counterweight with the electrode is plated with a counterweight metal.

6. The low impedance quartz tuning fork resonator according to claim 5, characterized in that: The counterweight metal is different from the outermost metal of the electrode.

7. A method for preparing a low impedance quartz tuning fork resonator, characterized in that: The resonator is the resonator according to any one of claims 1 to 6, and the method comprises: Carve out the shape of the quartz tuning fork resonator and the through groove on the quartz crystal plate; A groove is carved into the shape of a quartz tuning fork resonator with a through slot; Electrodes are engraved on a quartz tuning fork resonator shape with through slots and grooves.

8. The method for preparing a low impedance quartz tuning fork resonator according to claim 7, characterized in that: If the resonator is equipped with a weight plated with a weight metal, after the electrodes are carved out, the weight metal is bombarded until the resonant frequency of the resonator is adjusted to a desired value.

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