Crystal resonator and preparation method thereof
By using precision micro-etching and coating processes to prepare quartz wafers, the problem of traditional processes being unable to process wafers with a thickness of 6μm has been solved, achieving a breakthrough in frequency and performance improvement for high-frequency small ultrathin crystal resonators.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING INST OF RADIO METROLOGY & MEASUREMENT
- Filing Date
- 2025-12-02
- Publication Date
- 2026-05-01
AI Technical Summary
Existing technologies cannot effectively process small, ultra-thin high-frequency crystal resonator wafers with a thickness of 6μm. Traditional grinding processes can only reach 30μm, and cannot process wafers with higher frequencies.
By employing precision micro-etching and coating processes, and through multiple precision micro-etching and gold-plated electrodes, a crystal resonator with a quartz wafer thickness of 5μm~7μm was fabricated, achieving a frequency of 800MHz.
This achievement breaks through traditional limitations in the frequency of small, ultra-thin high-frequency crystal resonators, reaching 800MHz, reducing jitter, and improving radiation resistance and single-event immunity.
Smart Images
Figure CN121966498A_ABST
Abstract
Description
A crystal resonator and its fabrication method Technical Field
[0001] This invention relates to the design and fabrication of crystal resonators and oscillators. More specifically, it relates to a crystal resonator and its fabrication method. Background Technology
[0002] Crystal oscillators are known as the "heart" of electronic devices, used to generate the frequency signals required by the system. Among them, miniaturized ultrathin high-frequency crystal resonators are key to manufacturing miniaturized, high-frequency crystal oscillators. Compared to traditional crystal resonators, the changes in miniaturized ultrathin high-frequency crystal resonators are mainly reflected in the following aspects: First, the output frequency of the product significantly breaks through the traditional crystal resonator's upper limit of 200MHz, extending to the near GHz level; second, the product achieves direct output of frequency signals, greatly reducing product jitter by an order of magnitude compared to traditional products; third, the product's resistance to total radiation dose and single-event immunity is significantly improved.
[0003] The thickness of a quartz resonator wafer is inversely proportional to its frequency. A small, ultra-thin, high-frequency crystal resonator wafer with a working area thickness of only 6 μm at 800 MHz is difficult to process effectively using existing wafer fabrication techniques. Traditional grinding processes can only achieve a wafer thickness of around 30 μm; at higher frequencies, the wafer thickness becomes too thin to be processed effectively. Summary of the Invention
[0004] The purpose of this invention is to provide a crystal resonator and its fabrication method to solve at least one of the problems existing in the prior art.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a crystal resonator, comprising: a quartz crystal wafer; a first electrode plated on the upper surface of the quartz crystal wafer and a second electrode plated on the lower surface of the quartz crystal wafer, wherein the first electrode and the second electrode are symmetrically arranged, and the first electrode and the second electrode form a resonant electrode; the frequency of the crystal resonator is less than or equal to 800MHz.
[0006] Optionally, the thickness of the quartz wafer ranges from 5 μm to 7 μm.
[0007] Optionally, both the first electrode and the second electrode are gold electrodes.
[0008] Optionally, the length of the gold electrode ranges from 1.3mm to 1.5mm; the width of the gold electrode ranges from 1.7mm to 1.9mm.
[0009] A second aspect of the present invention provides a method for fabricating a crystal resonator, comprising: cleaning a quartz wafer to be processed to obtain a cleaned quartz wafer; etching the cleaned quartz wafer at a preset temperature and a preset time to obtain an etched quartz wafer; measuring whether the frequency of the etched quartz wafer reaches a target frequency; if not, correcting the preset temperature and the preset time to obtain corrected preset temperature and corrected preset time, and etching the etched quartz wafer at the corrected preset temperature and the corrected preset time until the frequency of the etched quartz wafer reaches the target frequency.
[0010] Optionally, the length of the quartz wafer to be processed ranges from 3.4mm to 3.6mm; the width of the quartz wafer to be processed ranges from 1.7mm to 1.9mm.
[0011] Optionally, the preset temperature ranges from 24℃ to 25℃; the preset time ranges from 6 hours to 8 hours.
[0012] Optionally, the process of correcting the preset temperature and correcting the preset time to obtain the corrected preset temperature and corrected preset time includes: increasing the preset temperature and increasing the preset time.
[0013] Optionally, measuring whether the frequency of the etched quartz wafer reaches the target frequency includes: measuring the thickness of the etched quartz wafer using a step tester and obtaining the frequency of the etched quartz wafer according to the conversion formula between the thickness of the quartz wafer and the oscillation frequency.
[0014] Optionally, the conversion formula between the thickness of the quartz wafer and the oscillation frequency is as follows:
[0015] In the formula, The oscillation frequency; The number of overtones; It is a frequency constant; The thickness of the quartz wafer.
[0016] The beneficial effects of the present invention are as follows: The technical solution of the present invention proposes a small ultra-thin high-frequency crystal resonator, which meets the requirements of miniaturization and high frequency of quartz resonators, and overcomes the problem that the wafer thickness processed by traditional grinding process can only reach about 30μm. At higher frequencies, the wafer thickness is too thin to process. Attached Figure Description
[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0018] Figure 1 shows a schematic diagram of a crystal resonator provided in an embodiment of the present invention.
[0019] Figure 2 shows a physical diagram of the crystal resonator provided in an embodiment of the present invention.
[0020] Figure 3 shows a schematic diagram of a high-precision stepper measuring the thickness of a quartz wafer in the crystal resonator fabrication method provided in an embodiment of the present invention.
[0021] Figure 4 shows a schematic diagram of the testing of a small, ultra-thin, high-frequency wafer in the crystal resonator fabrication method provided in an embodiment of the present invention.
[0022] Figure 5 shows a flowchart of the small ultrathin high-frequency wafer testing process in the crystal resonator fabrication method provided in the embodiment of the present invention. Detailed Implementation
[0023] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.
[0024] Crystal oscillators are known as the "heart" of electronic devices, used to generate the frequency signals required by the system. Among them, miniaturized ultrathin high-frequency crystal resonators are key to manufacturing miniaturized, high-frequency crystal oscillators. Compared to traditional crystal resonators, the changes in miniaturized ultrathin high-frequency crystal resonators are mainly reflected in the following aspects: First, the output frequency of the product significantly breaks through the traditional crystal resonator's upper limit of 200MHz, extending to the near GHz level; second, the product achieves direct output of frequency signals, greatly reducing product jitter by an order of magnitude compared to traditional products; third, the product's resistance to total radiation dose and single-event immunity is significantly improved.
[0025] The thickness of a quartz resonator wafer is inversely proportional to its frequency. A small, ultra-thin, high-frequency crystal resonator wafer with a working area thickness of only 6 μm at 800 MHz is difficult to process effectively using existing wafer fabrication techniques. Traditional grinding processes can only achieve a wafer thickness of around 30 μm; at higher frequencies, the wafer thickness becomes too thin to be processed effectively.
[0026] In view of this, one embodiment of the present invention provides a crystal resonator, comprising: a quartz crystal wafer; a first electrode plated on the upper surface of the quartz crystal wafer and a second electrode plated on the lower surface of the quartz crystal wafer, wherein the first electrode and the second electrode are symmetrically arranged, and the first electrode and the second electrode form a resonant electrode; the frequency of the crystal resonator is less than or equal to 800MHz.
[0027] This embodiment proposes a small, ultrathin, high-frequency crystal resonator that meets the requirements of miniaturization and high frequency of quartz resonators. It overcomes the problem that the wafer thickness processed by traditional grinding processes can only reach about 30μm, and the wafer thickness is too thin to process at higher frequencies.
[0028] In one possible implementation, the thickness of the quartz wafer ranges from 5 μm to 7 μm.
[0029] In one possible implementation, both the first electrode and the second electrode are gold electrodes.
[0030] In one possible implementation, the length of the gold electrode ranges from 1.3 mm to 1.5 mm, and the width of the gold electrode ranges from 1.7 mm to 1.9 mm.
[0031] In a specific example, as shown in Figures 1 and 2, the miniature ultrathin high-frequency crystal resonator includes a miniature ultrathin high-frequency quartz wafer 101 and a gold electrode 102.
[0032] In a specific example, a small, ultra-thin, high-frequency quartz wafer 101 undergoes multiple precision micro-etching processes on an SMD wafer. This process precisely micro-etches an AT-cut 200MHz fundamental frequency quartz wafer, with dimensions of 3.5mm x 1.8mm. The etching process achieves a wafer thickness of 6μm, enabling a resonator frequency of 800MHz.
[0033] In a specific example, gold electrodes 102 are deposited on the surface of a small, ultrathin, high-frequency quartz wafer 101 using a deposition mask. The SMD wafer is then deposited with gold electrodes through a deposition process, forming symmetrical resonant electrodes on the front and back sides. The gold electrodes have a length * width of 1.4 mm * 0.9 mm. After electrode deposition, the frequency of the quartz resonator can reach 800 MHz. This leads to the development and fabrication of a small, ultrathin, high-frequency SMD crystal resonator with a frequency up to 800 MHz.
[0034] Another embodiment of the present invention provides a method for fabricating a crystal resonator, comprising: cleaning a quartz wafer to be processed to obtain a cleaned quartz wafer; etching the cleaned quartz wafer at a preset temperature and a preset time to obtain an etched quartz wafer; measuring whether the frequency of the etched quartz wafer reaches a target frequency; if not, correcting the preset temperature and the preset time to obtain corrected preset temperature and the corrected preset time, and etching the etched quartz wafer at the corrected preset temperature and the corrected preset time until the frequency of the etched quartz wafer reaches the target frequency.
[0035] In a specific example, to overcome the various difficulties in the fabrication of small, ultra-thin, high-frequency crystal resonators, a multi-stage precision micro-etching process was employed to precisely micro-etch the smaller SMD wafer, achieving a wafer thickness of 6μm and a resonator frequency of 800MHz. Then, gold electrodes were deposited onto the SMD wafer using a coating process, resulting in a small, ultra-thin, high-frequency SMD crystal resonator with a frequency as high as 800MHz. This meets the requirements for miniaturization and high-frequency operation of quartz resonators and solves the problem of fabricating small, ultra-thin, high-frequency crystal resonators that are difficult to achieve with traditional quartz resonators.
[0036] In one possible implementation, the length of the quartz wafer to be processed ranges from 3.4 mm to 3.6 mm; the width of the quartz wafer to be processed ranges from 1.7 mm to 1.9 mm.
[0037] In one possible implementation, the preset temperature ranges from 24°C to 25°C; the preset time ranges from 6 hours to 8 hours.
[0038] In one possible implementation, the process of correcting the preset temperature and correcting the preset time to obtain the corrected preset temperature and corrected preset time includes: increasing the preset temperature and increasing the preset time.
[0039] In a specific example, the corrected preset temperature is 26℃ and the corrected preset time is 7 to 9 hours.
[0040] In one possible implementation, measuring whether the frequency of the etched quartz wafer reaches the target frequency includes: measuring the thickness of the etched quartz wafer using a step tester and obtaining the frequency of the etched quartz wafer according to the conversion formula between the thickness of the quartz wafer and the oscillation frequency.
[0041] In a specific example, small, ultra-thin, high-frequency quartz wafers to be processed are placed in a crystallizing dish and cleaned using a wafer cleaning process to reduce the impact of contaminants on their flatness. The cleaned wafers are then sorted at intervals less than 1 / 4 of the etching frequency tolerance. Two wafers are selected and placed in an etching basket, which is then placed in an etching tank containing etching solution. The etching tank is placed in a constant-temperature water bath, typically set at 25°C, to ensure a constant etching rate. The etching rate and time are controlled through multiple precision etching processes.
[0042] In a specific example, after multiple precision micro-etching processes, the selected small, ultra-thin, high-frequency quartz wafers are placed in an etching basket and then into an etching tank containing etching solution. After a predetermined time, they are removed together and placed in a crystallizing dish. The wafer frequency is then tested to see if it reaches the desired frequency. If the frequency does not meet the design requirements, the etching rate and etching time are adjusted until the wafer frequency reaches the desired frequency.
[0043] In a specific example, the thickness of a small, ultra-thin, high-frequency quartz wafer to be processed is tested using a step tester. The frequency of the quartz wafer is then calculated using the AT-cut quartz wafer thickness-frequency conversion formula until the wafer frequency reaches the target frequency.
[0044] In a specific example, after etching, the thickness of the small, ultra-thin, high-frequency quartz wafer to be processed reaches 6μm, and the resonator frequency can reach 800MHz.
[0045] In a specific example, to address the challenge of fabricating high-frequency ultrathin quartz resonators, a multi-stage precision etching method can effectively achieve batch processing of high-frequency ultrathin wafers. By using chemical etching to treat the crystal surface, the wafer surface becomes relatively smooth, and the wafer is protected from damage, achieving ideal results in terms of dimensions and other indicators.
[0046] In a specific example, since the frequency, resistance, Q value, flatness, and dimensional error of the original quartz wafer are the basic conditions for the performance parameters of the etched quartz wafer, high Q value quartz wafers with good frequency consistency are selected before processing. The wafers are inspected with a 10x to 30x microscope to ensure that they are free from abnormal morphologies such as broken edges, chipped edges, serrated edges, and cracks. The wafer frequency sorting machine can be used to sort the wafer frequency to ensure the consistency of the wafer frequency before etching.
[0047] In a specific example, a high-precision profilometer is used to accurately measure the thickness of a quartz wafer, achieving a measurement accuracy of 1 nm. This allows for the measurement and calculation of high-frequency quartz wafers with a fundamental frequency up to 1550 MHz (corresponding to a quartz wafer thickness of approximately 1 μm). This method can accurately measure the thickness of quartz wafers within a range of 10 angstroms to 0.5 millimeters, with a measurement accuracy of 1 nm, and can calculate high-frequency quartz wafers with a fundamental frequency up to 1550 MHz (corresponding to a quartz wafer thickness of approximately 1 μm).
[0048] In one possible implementation, the formula for converting the thickness of the quartz wafer to the oscillation frequency is:
[0049] In the formula, The oscillation frequency; For the number of overtones, ; It is a frequency constant, typically 1670 kHz·mm; The thickness (mm) of the quartz wafer.
[0050] In a specific example, for an AT-cut fundamental frequency quartz wafer, when its length and width are much greater than its thickness, its wafer thickness can be calculated using the frequency equation.
[0051] In a specific example, a high-precision step tester is set up to accurately measure the thickness of a quartz wafer, as shown in Figure 3. Figure 3 includes the step tester control computer, the step tester, the probe station and probes, the wafer under test, the wafer stage, the step tester base, and the control software.
[0052] In a specific example, during testing, the computer controls the step tester to adjust the step tester, causing the probe station and probes to move from the initial probe measurement position to the final probe measurement position, as shown in Figure 4. This allows for the measurement of the thickness d of the wafer under test. As shown in Figure 4, the distance from the initial probe measurement position to the final probe measurement position is a+b.
[0053] In a specific example, the contact test steps for the fundamental frequency quartz crystal are shown in Figure 5. The steps include: 1. Placing the crystal; 2. Placing the stage; 3. Adjusting the step meter; 4. Measuring the crystal thickness; 5. Calculating the average thickness after multiple measurements; 6. Converting the quartz crystal frequency; 7. Removing the stage and the crystal.
[0054] In a specific example, through tackling key challenges, the accurate measurement of the thickness of ultrathin quartz wafers was achieved, with a measurement range of 10 angstroms to 0.5 millimeters and a measurement accuracy of 1 nm. This enabled nanometer-level consistency control of the surface finish, improved the Q value of the resonator, and significantly enhanced the product performance indicators.
[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A crystal resonator, characterized in that, include: Quartz wafer; A first electrode is plated on the upper surface of the quartz wafer and a second electrode is plated on the lower surface of the quartz wafer. The first electrode and the second electrode are symmetrically arranged and form a resonant electrode. The frequency of the crystal resonator is less than or equal to 800MHz.
2. The crystal resonator according to claim 1, characterized in that, The thickness of the quartz wafer ranges from 5 μm to 7 μm.
3. The crystal resonator according to claim 2, characterized in that, Both the first electrode and the second electrode are gold electrodes.
4. The crystal resonator according to claim 3, characterized in that, The length of the gold electrode ranges from 1.3mm to 1.5mm; the width of the gold electrode ranges from 1.7mm to 1.9mm.
5. A method for fabricating a crystal resonator as described in any one of claims 1 to 4, characterized in that, include: The quartz wafer to be processed is cleaned to obtain a cleaned quartz wafer; the cleaned quartz wafer is etched at a preset temperature and time to obtain an etched quartz wafer; the frequency of the etched quartz wafer is measured to see if it reaches the target frequency. If not, the preset temperature and preset time are corrected to obtain the corrected preset temperature and preset time. The etched quartz wafer is then etched according to the corrected preset temperature and preset time until the frequency of the etched quartz wafer reaches the target frequency.
6. The preparation method according to claim 5, characterized in that, The length of the quartz wafer to be processed ranges from 3.4mm to 3.6mm; the width of the quartz wafer to be processed ranges from 1.7mm to 1.9mm.
7. The preparation method according to claim 6, characterized in that, The preset temperature ranges from 24℃ to 25℃; the preset time ranges from 6 hours to 8 hours.
8. The preparation method according to claim 7, characterized in that, The process of correcting the preset temperature and time to obtain the corrected preset temperature and time includes: increasing the preset temperature and increasing the preset time.
9. The preparation method according to claim 8, characterized in that, The measurement of whether the frequency of the etched quartz wafer reaches the target frequency includes: measuring the thickness of the etched quartz wafer using a step tester and obtaining the frequency of the etched quartz wafer according to the conversion formula between the thickness of the quartz wafer and the oscillation frequency.
10. The preparation method according to claim 9, characterized in that, The formula for converting the thickness of the quartz wafer to the oscillation frequency is as follows: In the formula, The oscillation frequency; For the number of overtones, It is an odd number; It is a frequency constant; The thickness of the quartz wafer.