Preparation method of superconducting niobium nitride hot electron bolometer

Abstract

This invention discloses a method for fabricating a superconducting niobium nitride thermionic radiometric calorimeter, employing a silicon oxide / silicon bilayer substrate. A hexanitrogen-niobium-1,6-niobium thin film is grown on the silicon oxide surface of the substrate using radio frequency magnetron sputtering as a buffer layer, followed by DC magnetron sputtering to grow a niobium nitride thin film. External electrodes are patterned using ultraviolet light exposure with a double-layer photoresist, and titanium and gold thin films are grown by magnetron sputtering, followed by lift-off stripping to fabricate the electrodes. A planar helical antenna pattern is patterned using electron beam exposure, and titanium and gold thin films are grown by magnetron sputtering, followed by lift-off stripping to fabricate the antenna. A microbridge pattern is defined using electron beam exposure, and the pattern is transferred to the niobium nitride thin film using reactive ion etching. The area to be etched is defined on the silicon surface of the substrate using ultraviolet light exposure, and silicon is etched away using an FSE deep silicon etching machine to fabricate the levitation bridge structure. This invention maintains the sensitivity at pw / Hz while increasing the operating temperature to 9 K. 1 / 2 Magnitude.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of terahertz (THz) detection, and in particular to a preparation method of a high-sensitivity superconducting niobium nitride hot electron bolometer operating in the liquid helium temperature range. BACKGROUND

[0002] Terahertz waves refer to electromagnetic waves with a frequency of 0.1-10 THz (i.e., a wavelength of 30-3000 μm). The high-frequency band of terahertz waves coincides with the far infrared, and the low-frequency band coincides with the millimeter wave. The high-frequency band can be studied by photonic methods, and the low-frequency band can be studied by microwave methods. The terahertz band is in the intersection of the two bands, and therefore, compared with the relatively mature microwave technology and infrared technology, the terahertz technology is not very perfect. The main reason is that there is a lack of effective technical means for the generation, regulation, and detection of terahertz waves. Therefore, for a long time, the terahertz region has been referred to as the "THz Gap".

[0003] Because the frequencies corresponding to the rotational or vibrational energy levels of most molecules are in the terahertz band, the unique spectral characteristics of terahertz technology can effectively identify these molecules. Terahertz technology has a wide range of applications in pharmaceutical ingredient analysis, medical imaging, and other fields. In terms of alleviating communication frequency congestion, the frequency of the terahertz band is higher than that of the microwave, and is a valuable frequency band resource for data communication.

[0004] Because the terahertz wave has a significant propagation attenuation in the atmosphere, the development of a high-sensitivity terahertz detector is one of the important development directions of terahertz technology. Among the many high-sensitivity terahertz detectors, the superconducting hot electron bolometer (HEB) has the advantages of wide spectral response and high sensitivity because of its response mechanism, and is a highly competitive detector for applications above 1 THz. Moreover, the working temperature of the HEB is relatively high, and compared with the transition edge sensor (TES) and the microwave kinetic inductance detector (MKID), although the sensitivity is often very high, the working temperature is often limited to the sub-K level. At present, the working temperature range of the superconducting HEB is mostly near the liquid helium temperature (4.2 K). Further increasing the working temperature of the detector can reduce the complexity of the system, but will also lead to a decrease in the sensitivity of the detector. Therefore, it is necessary to develop a high-sensitivity detector that can work at a higher temperature. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a high-sensitivity superconducting hot electron bolometer (HEB) operating above the liquid helium temperature.

[0006] The technical solution for achieving the purpose of the present application is: a preparation method of a superconducting niobium nitride hot electron bolometer, which adopts a double-layer substrate composed of silicon oxide and silicon, and comprises the following steps:

[0007] Six nitrogen five niobium film is grown on the substrate silicon oxide surface as a buffer layer by radio frequency magnetron sputtering, and the niobium nitride film is grown by direct current magnetron sputtering;

[0008] The pattern of the external electrode is drawn on the niobium nitride film by the way of ultraviolet exposure of LOR 10B and AZ1500 double-layer photoresist, the titanium film and the gold film are grown by magnetron sputtering, and the electrode is prepared by the way of lift-off;

[0009] The planar spiral antenna pattern is drawn by the way of electron beam exposure of PMMA A4 electron beam glue, the titanium film and the gold film are grown by magnetron sputtering, and the antenna is prepared by the way of lift-off;

[0010] The micro-bridge pattern is defined by the way of electron beam exposure of HSQ electron beam glue, and the micro-bridge pattern is transferred to the niobium nitride film by the way of reactive ion etching;

[0011] The area to be etched is defined by the way of ultraviolet exposure of AZ4620 photoresist on the substrate silicon surface, and the silicon is etched by FSE deep silicon etching machine to prepare a suspended bridge structure.

[0012] Further, six nitrogen five niobium film is grown on the substrate silicon oxide surface as a buffer layer by radio frequency magnetron sputtering, and the specific conditions are as follows:

[0013] Background vacuum: better than 2×10 -5 Pa;

[0014] Gas: Ar, N2;

[0015] Target material: Nb;

[0016] Sputtering pressure: 12 mTorr;

[0017] N2: Ar flow ratio: 30 sccm: 10 sccm;

[0018] Sputtering power: 400 W constant power radio frequency sputtering;

[0019] Deposition rate: 20 nm / min.

[0020] Further, the niobium nitride film is grown by direct current magnetron sputtering, and the specific conditions are as follows:

[0021] Background vacuum: better than 2×10 -5 Pa;

[0022] Gas: Ar, N2;

[0023] Target material: Nb;

[0024] Sputtering pressure: 2 mTorr;

[0025] N2: Ar flow ratio: 10 sccm: 85 sccm;

[0026] Sputtering current: 1.85 A constant current direct current sputtering;

[0027] Deposition rate: 70 nm / min.

[0028] Further, the pattern of the external electrode was drawn on the niobium nitride film by the way of ultraviolet exposure of LOR 10B and AZ1500 double-layer photoresist, and the specific conditions were as follows:

[0029] (1) Photoresist 1

[0030] Photoresist 1: LOR 10B;

[0031] Precoating: 600 r / min, 6 s;

[0032] Main coating: 4000 r / min, 40 s;

[0033] Pre-baking: 150°C, 1.5 min;

[0034] (2) Photoresist 2

[0035] Photoresist 2: AZ1500

[0036] Precoating: 600 r / min, 6 s;

[0037] Main coating: 4000 r / min, 40 s;

[0038] Pre-baking: 90°C, 1.5 min;

[0039] Post-baking: 110°C, 1.5 min;

[0040] Exposure time: 7 s;

[0041] Developing time: 17 s.

[0042] Further, titanium film and gold film were grown by magnetron sputtering, and the specific conditions were as follows:

[0043] (1) Ti film growth conditions

[0044] Background vacuum: better than 2 x 10 -5 Pa;

[0045] Gas: Ar;

[0046] Target material: Ti;

[0047] Sputtering pressure: 4 mTorr;

[0048] Sputtering current: 0.4 A constant current direct current sputtering;

[0049] (2) Growth Au thin film conditions

[0050] Background vacuum: better than 2 x 10 -5 Pa;

[0051] Gas: Ar;

[0052] Target material: Au;

[0053] Sputtering pressure: 4 mTorr;

[0054] Sputtering current: 80 W constant power direct current sputtering.

[0055] Further, the planar spiral antenna pattern is drawn by the way of electron beam exposure of PMMA A4 electron beam glue, and the specific conditions are as follows:

[0056] Photoresist type: PMMA A4;

[0057] Pre-coating: 600 r / min, 6 s;

[0058] Main coating: 3000 r / min, 60 s;

[0059] Pre-baking: 180℃, 4 min;

[0060] Exposure dose: 800 μA / cm 2 .

[0061] Further, the micro-bridge pattern is defined by the way of electron beam exposure of HSQ electron beam glue, and the specific conditions are as follows:

[0062] Photoresist type: HSQ 002;

[0063] Pre-coating: 500 r / min, 5 s;

[0064] Main coating: 5000 r / min, 60 s;

[0065] Pre-baking: 80℃, 2 min;

[0066] Exposure dose: 2500 μA / cm 2 .

[0067] Further, the micro-bridge pattern is transferred to the niobium nitride thin film by the way of reactive ion etching, and the specific conditions are as follows:

[0068] Etching material: NbN;

[0069] Reaction gas: CF4;

[0070] Flow rate: 30 sccm;

[0071] Pressure: 1.2 Pa;

[0072] Power: 50W;

[0073] Time: 1min.

[0074] Further, the area to be etched is defined by the way of exposing AZ4620 photoresist on the substrate silicon surface, and the specific conditions are as follows:

[0075] Photoresist: AZ4620;

[0076] Precoating: 600r / min, 6s;

[0077] Main coating: 3000r / min, 40s;

[0078] Pre-baking: 100℃, 30min;

[0079] Exposure time: 23.5s;

[0080] Developing time: 240s.

[0081] Further, the silicon is etched by FSE deep silicon etching machine to prepare the suspended bridge structure, and the specific conditions are as follows:

[0082] Etching material: Si;

[0083] Reaction gas 1: C4F8;

[0084] Reaction gas 1 flow: 100sccm;

[0085] Reaction gas 2: SF6;

[0086] Reaction gas 2 flow: 200sccm;

[0087] Pressure: 2.7Pa;

[0088] Power: 1800W;

[0089] Time: 45min.

[0090] Compared with the prior art, the present application has the following advantages: 1) the working temperature of the HEB detector is improved by adding a buffer layer, and the suspended bridge structure is prepared to improve the sensitivity of the device; 2) the HEB prepared at the same time has the suspended bridge structure and the buffer layer, which improves the working temperature to 9K while ensuring that the NEP is still in the order of pw / Hz 1 / 2 The best NEP at 5K is 0.42pw / Hz 1 / 2 , which is an order of magnitude higher than that of the ordinary device. BRIEF DESCRIPTION OF DRAWINGS

[0091] Figure 1is an optical microscope image of the device.

[0092] Figure 2 is a characterization result of the device NEP, wherein Type A is a common NbN device; Type B is a NbN device with a suspended bridge structure; Type C is a NbN device with a Nb5N6 buffer layer; Type D is a NbN device with both a suspended bridge structure and a Nb5N6 buffer layer, and the noise equivalent power (NEP) is the most important parameter for measuring the sensitivity of a detector, which refers to the lowest incident power required for the detector to produce a response signal with a signal-to-noise ratio of 1 when the test bandwidth is 1 Hz.

[0093] Figure 3 is a device process flow chart provided by the application. DETAILED DESCRIPTION

[0094] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0095] A preparation method of a high-sensitivity superconducting niobium nitride hot electron bolometer (NbN HEB) working above liquid helium temperature, wherein a substrate is a double-layer substrate composed of 270 nm thick silicon oxide and 360 μm thick silicon, and the preparation method comprises the following steps:

[0096] Step 1, the substrate is sent into a magnetron sputtering system auxiliary chamber with the silicon oxide facing upward, and Ar + ion milling, the purpose of which is to remove molecular-level impurities on the surface of the substrate and make the thin film more easily combined with the substrate, and the conditions are shown in Table 1.

[0097] Table 1 Ion milling conditions

[0098]

[0099]

[0100] Step 2, the substrate after ion milling is sent into a main chamber, and a Nb5N6 thin film is grown by radio frequency magnetron sputtering, and the sputtering parameters are shown in Table 2.

[0101] Table 2 Conditions for growing a Nb5N6 thin film by radio frequency sputtering

[0102] Background vacuum Better than 2 x 10 -5 Pa <!-- 4 -->]]> Gas Ar (99.999%), N2 (99.999%) Target material Nb (purity 99.999%) Sputtering gas pressure 12 mTorr N2:Ar flow ratio 30 sccm: 10 sccm Sputtering power 400 W constant power RF sputtering Deposition rate 20 nm / min

[0103] Step 3, after the thin film is grown, a niobium nitride thin film is magnetron sputtered in situ in a vacuum chamber, and the sputtering parameters are shown in Table 3.

[0104] Table 3 DC sputtering growth conditions of NbN thin film

[0105] Background vacuum Better than 2 x 10 -5 Pa]] Gas Ar (99.999%), N2 (99.999%) Target material Nb (purity 99.999%) Sputtering gas pressure 2 mTorr N2:Ar flow ratio 10 sccm: 85 sccm Sputtering current 1.85 A constant current DC sputtering Deposition rate 70 nm / min

[0106] Step 4, after taking out the sample from the magnetron sputtering system chamber, spin-coat LOR 10B, AZ1500 photoresist on the surface of the sample in turn, then use ultraviolet exposure machine to photoetch the sample, put it into positive photoresist developer to develop for 17s, then put it into deionized water to fix for 1min, transfer the external electrode pattern of the photoetch mask to the surface of the sample, the photoetching conditions are shown in Table 4.

[0107] Table 4 Ultraviolet photoetching conditions

[0108]

[0109]

[0110] Step 5, put the sample into the magnetron sputtering system, use the magnetron sputtering to in-situ grow 10nm thick Ti thin film and 100nm thick Au thin film, the growth conditions are shown in Table 5 and Table 6.

[0111] Table 5 DC sputtering growth conditions of Ti thin film

[0112] Background vacuum Better than 2 x 10 -5 Pa]] Gas Ar(99.999％) Target material Ti (purity 99.999%) Sputtering gas pressure 4 mTorr Sputtering current 0.4 A constant current DC sputtering

[0113] Table 6 DC sputtering growth conditions of Au thin film

[0114] Background vacuum Better than 2 x 10 -5 Pa]] Gas Ar(99.999％) Target material Au (purity 99.999%) Sputtering gas pressure 4 mTorr Sputtering current 80 W constant power DC sputtering

[0115] Step 6, after taking out the sample, put it into acetone to soak for about 5 minutes, then put it into the ultrasonic cleaning machine to clean for 20s, then put it into deionized water to further clean, finally put it into positive photoresist developer to soak for about 10s, and finally put it into water to clean, complete the lift-off process, and prepare the gold electrode.

[0116] Step 7, spin-coat PMMA A4 electron beam resist on the surface of the sample, then use RAITH EBPG5200 exposure machine to perform electron beam writing on the electron beam resist, form a spiral antenna pattern, the photoetching conditions are shown in Table 7.

[0117] Table 7 Electron beam photoetching conditions

[0118]

[0119]

[0120] Step 8, synchronously with step (6), 10 nm Ti and 100 nm Au are grown in situ, then the sample is put into N-methyl pyrrolidone and then into a water bath at 80℃ for 4-6 hours, and finally the sample is taken out and put into acetone, alcohol and deionized water in sequence for ultrasonic peeling to prepare the gold antenna.

[0121] Step 9, HSQ electron beam resist is spin-coated on the surface of the sample, then the sample is exposed to electron beam to form a micro-bridge pattern on the electron beam resist, and the photolithography conditions are shown in Table 7.

[0122] Step 10, then, the sample after electron beam exposure is etched by reactive ion etching to form a micro-bridge, and the etching machine used is Samco RIE-10, the etching gas is CF4, and the specific etching parameters are shown in Table 8.

[0123] Table 8 Reactive ion etching conditions

[0124] Etching material Reaction gas Flow / sccm Pressure / Pa Power / W Time / min NbN CF4 30 1.2 50 1

[0125] Step 11, then, AZ4620 photoresist is spin-coated on the front and back surfaces of the sample, then backside overlay is performed by using a UV photolithography machine, the photolithography conditions are shown in Table 4, then the sample is developed in a positive photoresist developer for 240 s, and then fixed in deionized water for 1 min to form a mask pattern of the designed etching area on the photoresist, and the photolithography conditions are shown in Table 4.

[0126] Step 12, the sample is etched from the back surface by using a HSE deep silicon etching machine to prepare a suspended structure, and the etching conditions are shown in Table 9.

[0127] Table 9 Deep silicon etching conditions

[0128]

[0129] In summary, the working temperature of the device can be improved by adding a buffer layer, the sensitivity of the device can be improved by adding a suspended structure, and the sensitivity of the device can be comparable to that of an ordinary device while the working temperature is doubled by combining the two methods. Embodiment

[0130] In order to verify the effectiveness of the scheme of the present application, the following experiments are performed.

[0131] (A) Sputtering

[0132] Nb5N6 thin films were grown on SiO2 substrates by RF magnetron reactive sputtering in a lab-built DE500 magnetron sputtering system. The substrates were cleaned by ultrasonic cleaning in acetone, alcohol and deionized water for 5 minutes, respectively, and then were sent into the sub-chamber by the sample holder. The substrates were cleaned by ion milling in the sub-chamber, and then were sent into the main chamber by the push rod. When the background pressure was better than 2.0 x 10 -5 -4 Pa, the N2:Ar ratio was adjusted to 3:1 by the gas flow meter, the sputtering pressure was adjusted to 12 mTorr by controlling the main chamber valve, the RF power of the RF source was set to 400 W, and 30 nm of Nb5N6 thin film was sputtered on the substrate. During the sputtering process, the base plate was water-cooled (T ~ 300 K) by circulating water. After the sputtering of the thin film, a certain amount of nitrogen gas (30 sccm) was filled into the main chamber to fully nitride the thin film. Next, NbN thin film was in-situ sputtered on the Nb5N6 thin film. Ar and N2 were filled into the sputtering chamber at a ratio of 8.5:1, and 4 nm of NbN thin film was sputtered on the Nb5N6 thin film at a constant current of 1.85 A, as shown in (a). Figure 3

[0133] (B) Peeling off the electrode

[0134] Gold was selected as the antenna material and the electrode material. LOR10B and AZ1500 double-layer glue were spin-coated on the NbN thin film at a rotation speed of 4000 RPM, and then exposed for 7 s using the ABM photoetching machine. After the photoetching, the sample was developed for 17 s. After the sample was developed by the positive glue developer after the pattern exposure, 10 nm of titanium and 100 nm of gold were sputtered using the DE magnetron sputtering system. Acetone, alcohol and water were used for ultrasonic cleaning at a power of 40 W, and finally the gold electrode was developed for 10 s by the positive glue developer and peeled off, as shown in (b). Figure 3

[0135] (C) Peeling off the antenna

[0136] The EBPG5200 high-performance electron beam nanolithography system of Raith Company in Germany was used to write the antenna pattern. The electron beam acceleration voltage was 100 kV, the beam current was 0.2 nA, the exposure dose was 800 μA / cm 2 , and the exposure dose was obtained by comparison test. After the photoetching, the sample was developed in MIBK developer for 90 s, fixed in isopropyl alcohol (IPA) for 60 s, cleaned in deionized water, and finally dried by N2 gas gun. Then, about 10 nm of Ti was sputtered as an adhesion buffer layer using the DE magnetron sputtering system, and then about 100 nm of Au thin film was sputtered.

[0137] ​​Then the sample is immersed in a beaker containing N-methyl pyrrolidone solvent, and then the beaker is placed in a constant temperature water bath at 80℃ for about 4-6 hours, the activity of the glue is increased, and the peeling effect is observed during the cleaning. After the peeling is completed, it is immersed in acetone, and finally it is cleaned with alcohol and water in sequence. The antenna preparation is completed. For example Figure 3 (c) as shown.

[0138] (D) Preparation of micro-bridge

[0139] The micro-bridge pattern is etched by electron beam. The method of exposing HSQ 002 glue to electron beam is used to cover the two inner contact electrode areas with HSQ 002 glue mask layer, and the exposure dose is 2500 μA / cm 2 . After the HSQ 002 glue is exposed, SiO2 mask is formed by developing, and the NbN film not covered is etched away by reactive ion etching. The model of the reactive ion etching machine used is Samco RIE-10, CF4 gas is introduced, the flow rate is 30 sccm, the power is 50 W, the gas pressure is 1.2 Pa, and the etching time is 60 s, as shown in Figure 3 (d) as shown.

[0140] (E) Backside etching

[0141] First, spin-coat AZ4620 photoresist on the substrate silicon side at a speed of 3000 RPM to protect the sample, then spin-coat AZ4620 photoresist on the substrate silicon side at a speed of 3000 RPM, then expose the sample backside to the required etching area by SUSS ultraviolet photolithography machine for 23.5 s, and develop the positive resist for 240 s.

[0142] (F) Backside etching

[0143] The HSE deep silicon etching machine is used to etch the sample backside, C4F8 and SF6 gases are introduced, the power is 1800 W, the gas pressure is 2.7 Pa, and the etching time is 45 min, to prepare the suspended bridge structure. As shown in Figure 3 (e) as shown.

[0144] The technical features of the above embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combination of the technical features does not exist, it should be considered as the scope of the present disclosure.

[0145] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific manner, but should not be construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for preparing a superconducting niobium nitride thermionic radiometric calorimeter, characterized in that, A double-layer substrate composed of silicon oxide and silicon is used to prepare a device, including the following steps: A six-nitrogen five-niobium film is grown on the silicon oxide surface of the substrate as a buffer layer by radio frequency magnetron sputtering, and a niobium nitride film is grown by direct current magnetron sputtering; The pattern of an external electrode is drawn on the niobium nitride film by ultraviolet exposure of LOR 10B and AZ1500 double-layer photoresist, and a titanium film and a gold film are grown by magnetron sputtering to prepare the electrode by lift-off; A planar spiral antenna pattern is drawn by electron beam exposure of PMMA A4 electron beam resist, a titanium film and a gold film are grown by magnetron sputtering, and the antenna is prepared by lift-off; A micro-bridge pattern is defined by electron beam exposure of HSQ electron beam resist, and the micro-bridge pattern is transferred to the niobium nitride film by reactive ion etching; The region to be etched is defined by ultraviolet exposure of AZ4620 photoresist on the silicon surface of the substrate, and the silicon is etched by a FSE deep silicon etching machine to prepare a suspended bridge structure.

2. The method of claim 1, wherein the Nb-doped titanium nitride is formed by a process comprising: depositing a titanium nitride layer on a substrate; and annealing the titanium nitride layer in a nitrogen atmosphere at a temperature of 600- 1000 °C. A six-nitrogen five-niobium film is grown on the silicon oxide surface of the substrate as a buffer layer by radio frequency magnetron sputtering, and a niobium nitride film is grown by direct current magnetron sputtering; Background vacuum: better than 2 x 10 -5 Pa; Gas: Ar, N2; Target material: Nb; Sputtering gas pressure: 12 mTorr; N2: Ar flow ratio: 30 sccm: 10 sccm; Sputtering power: 400 W constant power radio frequency sputtering; Deposition rate: 20 nm / min.

3. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, A niobium nitride film is grown by direct current magnetron sputtering, and the specific conditions are as follows: Background vacuum: better than 2 x 10 -5 Pa; Gas: Ar, N2; Target material: Nb; Sputtering gas pressure: 2 mTorr; N2: Ar flow ratio: 10 sccm: 85 sccm; Sputtering current: 1.85 A constant current direct current sputtering; Deposition rate: 70 nm / min.

4. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, The pattern of an external electrode is drawn on the niobium nitride film by ultraviolet exposure of LOR 10B and AZ1500 double-layer photoresist, and the specific conditions are as follows: (1) Photoresist 1 Photoresist 1: LOR 10B; Precoating: 600 r / min, 6 s; Main coating: 4000 r / min, 40 s; Pre-baking: 150℃, 1.5 min; (2) Photoresist 2 Photoresist 2: AZ1500 Precoating: 600 r / min, 6 s; Main coating: 4000 r / min, 40 s; Pre-baking: 90℃, 1.5 min; Post-baking: 110℃, 1.5 min; Exposure time: 7 s; Developing time: 17 s.

5. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, A titanium film and a gold film are grown by magnetron sputtering, and the specific conditions are as follows: (1) Ti film growth conditions Background vacuum: better than 2 x 10 -5 Pa; Gas: Ar; Target material: Ti; Sputtering gas pressure: 4 mTorr; Sputtering current: 0.4 A constant current direct current sputtering; (2) Au film growth conditions Background vacuum: better than 2 x 10 -5 Pa; Gas: Ar; Target material: Au; Sputtering gas pressure: 4 mTorr; Sputtering current: 80 W constant power direct current sputtering.

6. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, A planar spiral antenna pattern is drawn by electron beam exposure of PMMA A4 electron beam resist, and the specific conditions are as follows: Photoresist type: PMMA A4; Precoating: 600 r / min, 6 s; Main coating: 3000 r / min, 60 s; Pre-baking: 180℃, 4 min; Exposure dose: 800 μA / cm2 2 .

7. The method of claim 1, wherein the NbN superconducting hot electron bolometer is prepared by a process comprising: depositing a first layer of NbN on a substrate; depositing a second layer of NbN on the first layer of NbN; and depositing a third layer of NbN on the second layer of NbN. The micro-bridge pattern is defined by electron beam exposure of HSQ electron beam glue, and the specific conditions are as follows: Photoresist type: HSQ 002; Precoating: 500 r / min, 5 s; Main coating: 5000 r / min, 60 s; Pre-baking: 80°C, 2 min; Exposure dose: 2500 μA / cm 2 .

8. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, The micro-bridge pattern is transferred to the NbN film by reactive ion etching, and the specific conditions are as follows: Etching material: NbN; Reaction gas: CF4; Flow rate: 30 sccm; Pressure: 1.2 Pa; Power: 50 W; Time: 1 min.

9. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, The area to be etched is defined by UV exposure of AZ4620 photoresist on the substrate silicon surface, and the specific conditions are as follows: Photoresist: AZ4620; Precoating: 600 r / min, 6 s; Main coating: 3000 r / min, 40 s; Pre-baking: 100°C, 30 min; Exposure time: 23.5 s; Developing time: 240 s.

10. The method for preparing a superconducting niobium nitride thermionic radiometric calorimeter according to claim 1, characterized in that, The suspended bridge structure is prepared by etching away the silicon using the FSE deep silicon etching machine, and the specific conditions are as follows: Etching material: Si; Reaction gas 1: C4F8; Reaction gas 1 flow rate: 100 sccm; Reaction gas 2: SF6; Reaction gas 2 flow rate: 200 sccm; Pressure: 2.7 Pa; Power: 1800 W; Time: 45 min.

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