Method for controlling frequency of narrow-band superconducting filter through dry etching

Abstract

The invention belongs to the technical field of superconducting filtering, and particularly relates to a method for controlling the frequency of a narrow-band superconducting filter through dry etching. The method comprises the following steps: partially covering a metal film of a narrow-band superconducting thin film substrate, covering an input / output port electrode and a surface-mounted original device bonding pad, and then carrying out dry etching; measuring the center frequency of the narrow-band superconducting thin film substrate according to the calibration temperature; when the error between the center frequency and the design frequency is not greater than + / -100kHz, the narrow-band superconducting filter reaches the standard; when the center frequency is too high, the dielectric constant is adjusted by simulation software to correct the center frequency; and when the center frequency is relatively low, repeating the steps until the error between the center frequency of the narrow-band superconducting thin film substrate and the design frequency is not greater than + / -100kHz. According to the invention, the dry etching process is adopted, the bombardment time of the ion beam on the superconducting thin film is regulated and controlled, the frequency adjustment of the resonator module of the narrow-band superconducting filter is realized, the adjustment of the center frequency is realized without adjusting the temperature, and the adjustment efficiency is high.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting filtering, and in particular relates to a method for controlling the frequency of a narrow-band superconducting filter by dry etching. Background Art

[0002] With the development of superconducting filtering technology, superconducting filtering technology has begun to gradually transition from single channel (single frequency) to multi-channel. However, when the multi-channel superconducting filter is integrated into the vacuum dewar, the frequency alignment problem often occurs. According to the traditional method, the only way is to adjust the simulation design and rebuild the superconducting filter, which will greatly increase the time and material costs of the project.

[0003] At present, the commonly used superconducting materials in the design and production of superconducting filters both at home and abroad are mainly yttrium barium copper oxide (YBCO) and TI series (TBCCO). Taking YBCO superconducting film as an example, after reaching the superconducting transition temperature, as the temperature decreases, the center frequency of the superconducting filter made of YBCO superconducting film will gradually increase. In actual production, multiple superconducting filters are usually integrated in a vacuum dewar to form a superconducting filter group, and the superconducting filter group is given a fixed temperature, which is usually called the calibration temperature. When multiple superconducting filters are integrated in a vacuum dewar, due to the different uniformity and position distribution of the superconducting materials, when the temperature reaches the calibration temperature, the center frequency of each single superconducting filter will not meet the indicators. Summary of the invention

[0004] The object of the present invention is to provide a method for controlling the frequency of a narrowband superconducting filter by dry etching. The method provided by the present invention can quickly fine-tune and match the center frequency of a single filter in a superconducting filter group.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for controlling the frequency of a narrow-band superconducting filter by dry etching, comprising the following steps:

[0007] (1) partially covering the metal film of the narrow-band superconducting thin film substrate to cover the input and output port electrodes and the surface mount device pads, and then performing dry etching; the dry etching time is 60 to 300 seconds;

[0008] (2) Measure the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency is no more than ±100 kHz, the narrow-band superconducting filter meets the standard; when the center frequency is too high, use simulation software to adjust the dielectric constant to correct the center frequency; when the center frequency is too low, repeat steps (1) to (2) until the error between the center frequency of the narrow-band superconducting thin film substrate and the design frequency is no more than ±100 kHz.

[0009] Preferably, the ion beam current of the dry etching is 57-63 mA.

[0010] Preferably, the dry engraving time is 100 to 200 seconds.

[0011] Preferably, the cathode current of the dry etching is 5-5.5A, and the anode current is 0.38-0.42A.

[0012] Preferably, the neutralization current of the dry etching is 70-75 mA.

[0013] Preferably, the anode voltage of the dry etching is 45-50V, and the acceleration voltage is 180V.

[0014] Preferably, the screen energy of the dry etching is 480 eV.

[0015] Preferably, the ratio of the total time of repeating steps (1) to (2) of dry engraving to the total time of dry engraving in step (1) is not greater than 1:4.

[0016] Preferably, the covering material used for the partial covering is a single-sided copper foil with adhesive; the thickness of the covering material is 0.01-1 mm.

[0017] Preferably, the resonator in the superconducting filter is in the form of a single spiral, with a line width of 20 to 40 μm and a dielectric constant of 9.73 to 9.80.

[0018] The present invention provides a method for controlling the frequency of a narrowband superconducting filter by dry etching. The present invention adopts a dry etching process, and adjusts the bombardment time (dry etching time) of an ion beam on a superconducting film to achieve frequency adjustment of a resonator module of a narrowband superconducting filter, and adjusts the center frequency without adjusting the temperature, with high adjustment efficiency, greatly reducing the matching difficulty and matching time, and reducing the loss of the superconducting film, and is suitable for a narrowband multi-channel superconducting filter group. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a simulation result diagram of the narrow-band superconducting filter of Example 1 of the present invention;

[0021] Figure 2 This is a topographical diagram of the narrow-band superconducting thin film substrate of Example 1 of the present invention;

[0022] Figure 3This is a center frequency diagram of the narrow-band superconducting thin film substrate in step (2) of Example 1 of the present invention;

[0023] Figure 4 This is a center frequency diagram of the narrow-band superconducting thin film substrate in step (5) of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a method for controlling the frequency of a narrow-band superconducting filter by dry etching, comprising the following steps:

[0025] (1) partially covering the metal film of the narrow-band superconducting thin film substrate to cover the input and output port electrodes and the surface mount device pads, and then performing dry etching; the dry etching time is 60 to 300 seconds;

[0026] (2) Measure the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency is no more than ±100 kHz, the narrow-band superconducting filter meets the standard; when the center frequency is too high, use simulation software to adjust the dielectric constant to correct the center frequency; when the center frequency is too low, repeat steps (1) to (2) until the error between the center frequency of the narrow-band superconducting thin film substrate and the design frequency is no more than ±100 kHz.

[0027] The present invention partially covers the metal film of the narrowband superconducting thin film substrate, covers the input and output port electrodes and the surface mount original device pads, and then performs dry etching. In the present invention, the covering material used for the partial covering is preferably a single-sided copper foil with adhesive; the thickness of the covering material is preferably 0.01 to 1 mm, specifically 0.01 mm, 0.02 mm, 0.03 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.20 mm, 0.30 mm, 0.50 mm, 0.70 mm or 1 mm. The present invention prevents the narrowband superconducting thin film substrate from being broken down by the ion beam through the above-mentioned covering, and the covered area covers the input and output port electrodes and the surface mount original device (resistor, capacitor) pad range, avoiding damage to the input and output electrodes and the pads reserved for the surface mount components during the secondary dry etching process.

[0028] In the present invention, the cathode current of the dry etching is preferably 5-5.5A, specifically 5.2A, the anode current is preferably 0.38-0.42A, specifically 0.4A, the anode voltage is preferably 45-50V, specifically 47V, the acceleration voltage is preferably 180V, the neutralization current is preferably 70-75mA, specifically 72mA, the screen energy is preferably 480eV, the ion beam current is preferably 57-63mA, specifically 60mA, and the time is preferably 60-300s, specifically 60s, 80s, 100s, 120s, 150s, 200s, 250s or 300s.

[0029] The present invention measures the center frequency of a narrow-band superconducting thin film substrate according to a calibration temperature. In the present invention, the calibration temperature is preferably -203.15°C (70K).

[0030] In the present invention, the method for preparing the narrowband superconducting thin film substrate is preferably: designing a superconducting filter by simulation software, making a mask according to the simulation design, and photolithography and dry etching the superconducting thin film.

[0031] In the present invention, the form of the resonator in the superconducting filter is preferably a single spiral; the line width of the resonator is preferably 20 to 40 μm, specifically 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, and the dielectric constant is preferably 9.73 to 9.80. Through the above design, the present invention can accurately control the bandwidth and center frequency of the superconducting filter and control the center frequency at the calibration temperature.

[0032] In the present invention, the simulation software is preferably sonnet simulation software; the center frequency of the superconducting filter is preferably 0.1-1 GHz, specifically 0.1 GHz, 0.2 GHz, 0.3 GHz, 0.5 GHz, 0.7 GHz, 0.9 GHz or 1 GHz, and the bandwidth is preferably 0.1-1 MHz, specifically 0.1 MHz, 0.2 MHz, 0.3 MHz, 0.5 MHz, 0.7 MHz, 0.9 MHz or 1 MHz.

[0033] In the present invention, the photolithography is preferably: coating the superconducting thin film with glue, pre-baking, post-baking, exposing and developing in sequence.

[0034] In the present invention, the photoresist for coating is preferably BP212 photoresist; the coating rotation speed is preferably 900-2500rpm, specifically 900rpm, 1200rpm, 1500rpm, 1800rpm, 2100rpm, 2300rpm or 2500rpm; the coating time is preferably 6-30s, specifically 6s, 8s, 10s, 12s, 15s, 20s, 25s or 30s.

[0035] In the present invention, the pre-drying temperature is preferably 100° C., and the heat preservation and drying time is preferably 15 minutes.

[0036] In the present invention, the post-baking temperature is preferably 120° C., and the heat preservation and drying time is preferably 25 minutes.

[0037] In the present invention, the exposure intensity is preferably 20 mw, and the exposure time is preferably 5 s.

[0038] In the present invention, the development time is preferably 20 seconds.

[0039] In the present invention, the dry engraving time is preferably 60 minutes.

[0040] In the present invention, the device for measuring the center frequency of a narrow-band superconducting thin film substrate is preferably a low-temperature test platform; the low-temperature test platform is preferably equipped with a Force-Mann 4188 Stirling refrigerator and a vacuum dewar.

[0041] When the center frequency is too high, the dielectric constant is adjusted by using simulation software to correct the center frequency. In the present invention, the simulation software is preferably sonnet simulation software.

[0042] When the center frequency is low, repeat steps (1) to (2) until the center frequency of the narrowband superconducting thin film substrate has an error of no more than ±100kHz with respect to the design frequency. In the present invention, the ratio of the total time of the repeated dry engraving steps (1) to (2) to the total time of the dry engraving in step (1) is preferably no more than 1:4, and can specifically be 1:4, 1:5, 1:6, 1:8, 1:10, 1:12, 1:15 or 1:20. The present invention measures the center frequency of the superconducting thin film substrate according to the calibration temperature, and the center frequency will rise. When the center frequency has an error of no more than ±100kHz with respect to the design frequency, the narrowband superconducting filter meets the standard.

[0043] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0044] Example 1

[0045] (1) Using the sonnet simulation software, a superconducting filter with a center frequency of 198 MHz and a bandwidth of 0.6 MHz is designed. The resonator is designed in the form of a single spiral. The line width of the resonator is 40 μm and the dielectric constant is 9.73. Figure 1 shown.

[0046] (2) A mask was made according to the simulation design, and a narrow-band superconducting thin film substrate was prepared according to the photolithography and dry etching parameters in Table 1. The morphology is as follows: Figure 2 shown.

[0047] Table 1 Parameters of photolithography and dry etching in Example 1

[0048]

[0049]

[0050] Through the same low temperature test platform equipped with Li Han 4188 Stirling refrigerator + vacuum dewar, calibrate the 70K temperature test and record the center frequency. The center frequency test results are as follows Figure 3As shown: the center frequency is 196.007MHz, which is about 2MHz lower than the design frequency of 198MHz.

[0051] (3) Partially cover the narrow-band superconducting thin film substrate with a 20 μm metal film (copper foil, aluminum foil), and the covered area covers the input and output port electrodes and the pads of the surface-mounted components (resistors, capacitors).

[0052] (4) Dry etching is performed on the narrow-band superconducting thin film substrate after partial masking. The specific parameters are as follows: cathode current 5-5.5A, anode current 0.38-0.42A, anode voltage 45-50V, acceleration voltage 180V, neutralization current 70-75mA, screen grid energy 480eV, ion beam current 57-63mA, and time control is 180s.

[0053] (5) Re-measure the center frequency of the narrow-band superconducting thin film substrate according to step (2). The center frequency test result is as follows: Figure 4 As shown: the center frequency is 197.988MHz, the error is no more than ±100kHz, it has been corrected and completed.

[0054] It can be seen from the above embodiments that the method provided by the present invention can quickly fine-tune and match the center frequency of a single filter in a superconducting filter group.

[0055] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for controlling the frequency of a narrowband superconducting filter by dry etching, characterized in that: The following steps are involved: (1) partially covering the metal film of the narrow-band superconducting thin film substrate to cover the input and output port electrodes and the surface mount device pads, and then performing dry etching; the dry etching time is 60 to 300 seconds; (2) Measure the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency is no more than ±100 kHz, the narrow-band superconducting filter meets the standard; when the center frequency is too high, use simulation software to adjust the dielectric constant to correct the center frequency; when the center frequency is too low, repeat steps (1) to (2) until the error between the center frequency of the narrow-band superconducting thin film substrate and the design frequency is no more than ±100 kHz.

2. The method according to claim 1, characterized in that The ion beam current of the dry etching in step (1) is 57-63 mA.

3. The method according to claim 1 or 2, characterized in that: The dry engraving time in step (1) is 100 to 200 seconds.

4. The method according to claim 1, characterized in that: The cathode current of the dry etching in step (1) is 5 to 5.5A, and the anode current is 0.38 to 0.42A.

5. The method according to claim 1 or 4, characterized in that: The neutralization current of the dry etching in step (1) is 70-75 mA.

6. The method according to claim 1 or 2, characterized in that: The anode voltage of the dry etching in step (1) is 45-50V, and the acceleration voltage is 180V.

7. The method according to claim 1 or 2, characterized in that: The screen energy of the dry etching in step (1) is 480 eV.

8. The method according to claim 1, characterized in that The ratio of the total time of repeating steps (1) to (2) to the total time of dry engraving in step (1) is not greater than 1:

4.

9. The method according to claim 1, characterized in that: The covering material used for the partial covering is a single-sided copper foil with adhesive; the thickness of the covering material is 0.01-1 mm.

10. The method according to claim 1 or 9, characterized in that: The resonator in the superconducting filter is in the form of a single spiral, with a line width of 20 to 40 μm and a dielectric constant of 9.73 to 9.80.

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