Preparation method of superconducting niobium nitride thermal electronic bolometer

Abstract

The invention discloses a preparation method of a superconducting niobium nitride thermal electronic bolometer. A silicon oxide / silicon double-layer substrate is adopted; the method comprises the following steps: growing a niobium nitride film on a silicon oxide surface of a substrate through radio frequency magnetron sputtering to serve as a buffer layer, and growing a niobium nitride film through direct current magnetron sputtering; drawing an external electrode through ultraviolet exposure of the double-layer photoresist, growing a titanium film and a gold film through magnetron sputtering, and preparing an electrode by lift-off stripping; drawing a planar helical antenna pattern through electron beam exposure, growing a titanium thin film and a gold thin film through magnetron sputtering, and preparing the antenna by utilizing lift-off stripping; defining a microbridge pattern through electron beam exposure, and transferring the microbridge pattern to the niobium nitride film through reactive ion etching; an area needing to be etched is defined on a substrate silicon surface through ultraviolet exposure, silicon is etched off through an FSE deep silicon etching machine, and a suspension bridge structure is prepared. According to the invention, the working temperature is increased to 9 K, and the sensitivity is still at a pw / Hz 1 / 2 magnitude.

Description

Technical Field

[0001] The invention relates to the field of terahertz (THz) detection, and in particular to a method for preparing a high-sensitivity superconducting niobium nitride thermal electron bolometer working in a liquid helium temperature region. Background Art

[0002] Terahertz waves refer to electromagnetic waves with a frequency of 0.1 to 10 THz (i.e., a wavelength of 30 μm to 3000 μm). The high frequency band of terahertz waves overlaps with far infrared, and the low frequency band overlaps with millimeter waves. We can use photonics to study the high frequency band, and microwaves to study the low frequency band. The terahertz band is at the intersection of the two, so compared with the more mature microwave and infrared technologies, terahertz technology is not yet perfect. The main reason is that there is a lack of effective technical means for the generation, regulation and detection of terahertz. Therefore, for a long time, the terahertz area has been called the "THz Gap".

[0003] Since 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 be used to effectively identify these molecules. It is widely used in drug component analysis, medical imaging, etc. In terms of alleviating the congestion of communication frequency bands, the frequency of the terahertz band is higher than that of microwaves, and it is a valuable frequency band resource for data communications.

[0004] Since terahertz waves have obvious propagation attenuation in the atmosphere, the development of highly sensitive terahertz detectors is one of the important development directions of terahertz technology. Among the many highly sensitive terahertz detectors, the superconducting thermal electron bolometer (HEB) is not limited by frequency due to its response mechanism. It has the advantages of wide spectrum response and high sensitivity, and is a highly competitive detector for applications above 1THz. In addition, the operating temperature of HEB is relatively high. Compared with transition edge sensors (TES) and microwave dynamic inductance detectors (MKID), although the sensitivity is often very high, the operating temperature is often limited to the sub-K level. At present, the operating temperature range of superconducting HEB is mostly around the liquid helium temperature (4.2K). Further increasing the working temperature of the detector can reduce the complexity of system construction, but it will also lead to a decrease in the sensitivity of the detector. Therefore, it is necessary to develop highly sensitive detectors that can operate at higher temperatures. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a highly sensitive superconducting thermal electron bolometer (HEB) operating above the temperature of liquid helium.

[0006] The technical solution to achieve the purpose of the present invention is: a method for preparing a superconducting niobium nitride thermal electron bolometer, using a double-layer substrate composed of silicon oxide and silicon, and the preparation includes the following steps:

[0007] A niobium hexanitride pentanitride film was grown on the silicon oxide surface of the substrate by radio frequency magnetron sputtering as a buffer layer, and a niobium nitride film was grown by direct current magnetron sputtering;

[0008] The external electrode pattern was drawn on the niobium nitride film by UV exposure of LOR 10B and AZ1500 double-layer photoresist, titanium film and gold film were grown by magnetron sputtering, and electrodes were prepared by lift-off.

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

[0010] The micro-bridge pattern was defined by electron beam exposure of HSQ electron beam glue, and the micro-bridge pattern was transferred onto the niobium nitride film by reactive ion etching.

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

[0012] Furthermore, a hexanitrogen pentaniobium film is grown on the silicon oxide surface of the substrate by radio frequency magnetron sputtering as a buffer layer, and the specific conditions are:

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

[0014] Gas: Ar, N2;

[0015] Target material: Nb;

[0016] Sputtering gas pressure: 12mTorr;

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

[0018] Sputtering power: 400W constant power RF sputtering;

[0019] Deposition rate: 20nm / min.

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

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

[0022] Gas: Ar, N2;

[0023] Target material: Nb;

[0024] Sputtering gas pressure: 2mTorr;

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

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

[0027] Deposition rate: 70nm / min.

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

[0029] (1) Photoresist 1

[0030] Photoresist 1: LOR 10B;

[0031] Pre-coating: 600r / min, 6s;

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

[0033] Pre-baking: 150℃, 1.5min;

[0034] (2) Photoresist 2

[0035] Photoresist 2: AZ1500

[0036] Pre-coating: 600r / min, 6s;

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

[0038] Pre-baking: 90℃, 1.5min;

[0039] Post-baking: 110℃, 1.5min;

[0040] Exposure time: 7s;

[0041] Development time: 17s.

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

[0043] (1) Ti film growth conditions

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

[0045] Gas: Ar;

[0046] Target material: Ti;

[0047] Sputtering gas pressure: 4mTorr;

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

[0049] (2) Au film growth conditions

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

[0051] Gas: Ar;

[0052] Target material: Au;

[0053] Sputtering gas pressure: 4mTorr;

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

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

[0056] Photoresist type: PMMA A4;

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

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

[0059] Pre-baking: 180℃, 4min;

[0060] Exposure dose: 800μA / cm 2 .

[0061] Furthermore, the microbridge pattern is defined by electron beam exposure of HSQ electron beam glue, and the specific conditions are:

[0062] Photoresist type: HSQ 002;

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

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

[0065] Pre-baking: 80℃, 2min;

[0066] Exposure dose: 2500μA / cm 2 .

[0067] Furthermore, the pattern of the microbridge is transferred onto the niobium nitride film by reactive ion etching, and the specific conditions are as follows:

[0068] Etching material: NbN;

[0069] Reaction gas: CF4;

[0070] Flow rate: 30sccm;

[0071] Pressure: 1.2Pa;

[0072] Power: 50W;

[0073] Time: 1min.

[0074] Furthermore, the area to be etched is defined on the silicon surface of the substrate by ultraviolet exposure of AZ4620 photoresist, and the specific conditions are:

[0075] Photoresist: AZ4620;

[0076] Pre-coating: 600r / min, 6s;

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

[0078] Pre-baking: 100℃, 30min;

[0079] Exposure time: 23.5s;

[0080] Development time: 240s.

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

[0082] Etching material: Si;

[0083] Reaction gas 1: C4F8;

[0084] Reaction gas 1 flow rate: 100 sccm;

[0085] Reactive gas 2: SF6;

[0086] Reaction gas 2 flow rate: 200 sccm;

[0087] Pressure: 2.7Pa;

[0088] Power: 1800W;

[0089] Time: 45 minutes.

[0090] Compared with the prior art, the present invention has the following significant advantages: 1) the working temperature of the HEB detector is increased by adding a buffer layer, and on this basis, a suspended bridge structure is prepared to improve the sensitivity of the device; 2) the HEB prepared has both a suspended bridge structure and a buffer layer, which increases the working temperature to 9K while ensuring that the NEP is still within pw / Hz. 1 / 2 The best NEP at 5K is 0.42pw / Hz 1 / 2 , compared with ordinary devices, NEP is improved by an order of magnitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 is an optical microscope image of the device.

[0093] Figure 2 It is the characterization result of the device NEP, where Type A is an ordinary 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. The noise equivalent power (NEP) is the most important parameter for measuring the sensitivity of the detector. It refers to the minimum incident power required for the detector to generate a response signal with a signal-to-noise ratio of 1 when the test bandwidth is 1Hz.

[0094] Figure 3 It is a flow chart of the device process preparation proposed by the present invention. DETAILED DESCRIPTION

[0095] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0096] A method for preparing a high-sensitivity superconducting niobium nitride hot electron bolometer (NbN HEB) operating above liquid helium temperature, wherein the substrate used is a double-layer substrate consisting of 270nm thick silicon oxide and 360μm thick silicon, and the preparation method comprises the following steps:

[0097] Step 1: Place the substrate with silicon oxide facing upward into the sub-chamber of the magnetron sputtering system for Ar + The purpose of milling is to remove molecular-level impurities on the surface of the substrate and make it easier for the film to combine with the substrate. The conditions are shown in Table 1.

[0098] Table 1 Ion milling conditions

[0099]

[0100]

[0101] Step 2, the ion-milled substrate is sent into the main chamber, and the Nb5N6 film is grown by radio frequency magnetron sputtering. The sputtering parameters are shown in Table 2.

[0102] Table 2 RF sputtering growth conditions of Nb5N6 thin films

[0103] Background vacuum <![CDATA[Better than 2×10 -5 Pa]]> gas <![CDATA[Ar(99.999%),N2(99.999%)]]> Target Nb (purity 99.999%) Sputtering pressure 12mTorr N2:Ar flow ratio 30sccm:10sccm Sputtering power 400W constant power RF sputtering Deposition rate 20nm / min

[0104] Step 3: After the film growth is completed, the niobium nitride film is in-situ magnetron sputtered in a vacuum chamber, and the sputtering parameters are shown in Table 3.

[0105] Table 3 DC sputtering growth conditions of NbN thin films

[0106] Background vacuum <![CDATA[Better than 2×10 -5 Pa]]> gas <![CDATA[Ar(99.999%),N2(99.999%)]]> Target Nb (purity 99.999%) Sputtering pressure 2mTorr N2:Ar flow ratio 10sccm:85sccm Sputtering current 1.85A constant current DC sputtering Deposition rate 70nm / min

[0107] Step 4, take out the sample from the chamber of the magnetron sputtering system, and then spin-coat LOR 10B and AZ1500 photoresists on the sample surface in turn, and then use a UV exposure machine to photolithography the sample, put it into a positive photoresist developer for 17 seconds, and then put it into deionized water for fixing for 1 minute, and transfer the external electrode pattern of the photolithography mask to the sample surface. The photolithography conditions are shown in Table 4.

[0108] Table 4 UV lithography conditions

[0109]

[0110]

[0111] Step 5, sending the sample into a magnetron sputtering system, using magnetron sputtering to in-situ grow a 10 nm thick Ti film and a 100 nm thick Au film, the growth conditions are shown in Tables 5 and 6.

[0112] Table 5 DC sputtering growth conditions of Ti films

[0113] Background vacuum <![CDATA[Superior to 2×10 -5 Pa]]> gas Ar(99.999％) Target Ti (purity 99.999%) Sputtering pressure 4mTorr Sputtering current 0.4A constant current DC sputtering

[0114] Table 6 DC sputtering growth conditions of Au thin films

[0115] Background vacuum <![CDATA[Better than 2×10 -5 Pa]]> gas Ar(99.999％) Target Au (purity 99.999%) Sputtering pressure 4mTorr Sputtering current 80W constant power DC sputtering

[0116] Step 6, after taking out the sample, soak it in acetone for about 5 minutes, then put it in an ultrasonic cleaner for cleaning for 20 seconds, then put it in deionized water for further cleaning, and finally soak it in positive photoresist developer for about 10 seconds, and finally put it in water for cleaning to complete the lift-off process and prepare the gold electrode.

[0117] Step 7, spin-coat PMMA A4 electron beam resist on the surface of the sample, and then use a RAITH EBPG5200 exposure machine to perform electron beam writing on the electron beam resist to form a spiral antenna pattern. The photolithography conditions are shown in Table 7.

[0118] Table 7 Electron beam lithography conditions

[0119]

[0120]

[0121] Step 8, same as step (6), in situ grow 10 nm Ti and 100 nm Au, then put the sample into N-methylpyrrolidone, and then put it into a water bath and heat it at 80°C for 4-6 hours. Finally, take out the sample and put it into acetone, alcohol, and deionized water for ultrasonic peeling to prepare the gold antenna.

[0122] Step 9, spin-coat HSQ electron beam resist on the sample surface, and then use electron beam exposure to write to form a microbridge pattern on the electron beam resist. The photolithography conditions are shown in Table 7.

[0123] Step 10: Next, the sample after electron beam exposure is etched by reactive ion etching to form a microbridge. The submicron microbridge is etched by a Samco RIE-10, the etching gas is CF4, and the specific etching parameters are shown in Table 8.

[0124] Table 8 Reactive ion etching conditions

[0125] Etching materials Reaction gas Flow rate / sccm Pressure / Pa Power / W Time / min Nb <![CDATA[CF4]]> 30 1.2 50 1

[0126] Step 11, AZ4620 photoresist is then spin-coated on both the front and back sides of the sample. Then, a UV photolithography machine is used for back overlay, and the photolithography conditions are shown in Table 4. Then, the positive photoresist is placed in a developer for 240 s, and then fixed in deionized water for 1 min to form a pattern of the area to be etched designed by the mask on the photoresist, and the photolithography conditions are shown in Table 4.

[0127] Step 12, use an HSE deep silicon etcher to etch from the back of the sample to prepare a suspended structure. The etching conditions are shown in Table 9.

[0128] Table 9 Deep silicon etching conditions

[0129]

[0130] In summary, the present invention can increase the operating temperature of the device by adding a buffer layer, and can increase the sensitivity of the device by adding a suspension structure. By combining the two control methods, the sensitivity of the device can be comparable to that of ordinary devices while the operating temperature is increased by nearly double. Example

[0131] In order to verify the effectiveness of the scheme of the present invention, the following experiment was carried out.

[0132] (A) Sputtering

[0133] In the laboratory DE500 magnetron sputtering system, Nb5N6 thin films were grown on the silicon oxide surface of the substrate by radio frequency magnetron reactive sputtering. The substrate was ultrasonically cleaned with acetone, alcohol, and deionized water for 5 minutes each, and then sent to the sub-chamber through the sample delivery chamber. The sub-chamber was decontaminated by ion milling, and then the substrate was sent to the main chamber by the push rod. When the background vacuum was better than 2.0×10 -5 When the temperature is 0.0457°C, the gas flow meter is used to adjust N2:Ar=3:1. The gate valve of the main chamber is controlled to make the sputtering gas pressure 12mTorr. The RF power of the RF source is set to 400W. A 30nm Nb5N6 film is sputtered on the substrate. During the entire sputtering process, the chassis is cooled by circulating water (T~300K). After the film is sputtered, a certain amount of nitrogen (30sccm) is filled into the main chamber again to fully nitride it. Next, the NbN film is magnetron sputtered in situ. Ar and N2 in a ratio of 8.5:1 are filled into the sputtering chamber. A 4nm NbN film is sputtered on the Nb5N6 film at a constant current of 1.85A. Figure 3 (a) shown.

[0134] (B) Stripping electrode

[0135] Gold was selected as the antenna material and electrode material. First, a double layer of LOR10B and AZ1500 was spin-coated on the NbN film at a speed of 4000RPM, and then an ABM photolithography machine was used to expose for 7s, and then developed for 17s after photolithography. After the sample after pattern exposure was developed with a positive photoresist developer, a 10nm thick titanium and a 100nm thick gold layer were sputtered using a DE magnetron sputtering system, and acetone, alcohol, and water were used in turn with a 40W power ultrasound, and finally developed with a positive photoresist developer for 10s to peel off the gold electrode. Figure 3 (b) as shown.

[0136] (C) Peel off the antenna

[0137] The antenna pattern was written using the EBPG5200 high-performance electron beam nanolithography system from Raith, Germany. The electron beam acceleration voltage was 100 kV, the beam current was 0.2 nA, and the exposure dose was 800 μA / cm 2 The exposure dose is obtained by comparative test. After photolithography, it is developed in MIBK developer for 90s, fixed in isopropyl alcohol (IPA) for 60s, cleaned with deionized water, and finally dried with N2 air gun. Then, a DE magnetron sputtering system is used to sputter Ti with a thickness of about 10nm as an adhesion buffer layer, followed by sputtering of an Au film with a thickness of about 100nm.

[0138] Then immerse the sample in a beaker containing N-methylpyrrolidone solvent, and then place the beaker in a constant temperature water bath at 80°C for about 4-6 hours to increase the activity of the glue, and use 40W ultrasonic cleaning, while observing the peeling effect while cleaning. After the peeling is completed, immerse it in acetone, and finally use alcohol and water ultrasonic cleaning in turn. The antenna preparation is completed. Figure 3 (c) as shown.

[0139] (D) Preparation of microbridge

[0140] The microbridge pattern is engraved using an electron beam. The HSQ 002 photoresist is exposed by an electron beam, and the HSQ 002 photoresist mask layer covers the two inner contact electrode areas. The exposure dose is 2500μA / cm 2 After HSQ 002 photoresist is exposed and developed to form a SiO2 mask, the uncovered NbN film is then etched away by reactive ion etching. The reactive ion etcher used is Samco RIE-10, CF4 gas is introduced, and etching is performed for 60 seconds at a flow rate of 30 sccm, a power of 50 W, and a gas pressure of 1.2 Pa. Figure 3 (d) as shown.

[0141] (E) Back engraving

[0142] First, AZ4620 photoresist was spin-coated on the silicon oxide surface of the substrate at a speed of 3000RPM to protect the sample, and then AZ4620 photoresist was spin-coated on the silicon surface of the substrate at a speed of 3000RPM. Then, a SUSS UV photolithography machine was used to expose the sample for 23.5s. After developing the sample with a positive photoresist developer for 240s, the area to be etched was determined on the back of the sample.

[0143] (F) Backside etching

[0144] The HSE deep silicon etcher was used to etch the sample from the back, with C4F8 and SF6 gases introduced, and the etching time was 45 minutes under the conditions of power 1800W and gas pressure 2.7Pa to prepare the suspended bridge structure. Figure 3 (e) as shown.

[0145] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations 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 shall be subject to the attached claims.

Claims

1. A method for preparing a superconducting niobium nitride thermal electron bolometer, characterized in that: A double-layer substrate composed of silicon oxide and silicon is prepared by the following steps: A niobium hexanitride pentanitride film was grown on the silicon oxide surface of the substrate by radio frequency magnetron sputtering as a buffer layer, and a niobium nitride film was grown by direct current magnetron sputtering; The external electrode pattern was drawn on the niobium nitride film by UV exposure of LOR 10B and AZ1500 double-layer photoresist, titanium film and gold film were grown by magnetron sputtering, and electrodes were prepared by lift-off. The planar spiral antenna pattern was drawn by electron beam exposure of PMMA A4 electron beam glue, titanium film and gold film were grown by magnetron sputtering, and the antenna was prepared by lift-off. The micro-bridge pattern was defined by electron beam exposure of HSQ electron beam glue, and the micro-bridge pattern was transferred onto the niobium nitride film by reactive ion etching. The area to be etched is defined on the silicon surface of the substrate by ultraviolet exposure of AZ4620 photoresist, and the silicon is etched away by FSE deep silicon etcher to prepare the suspended bridge structure.

2. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: A niobium hexanitride pentaoxide film was grown as a buffer layer on the silicon oxide surface of the substrate by radio frequency magnetron sputtering. The specific conditions were: Background vacuum: better than 2×10 -5 Pa; Gas: Ar, N2; Target material: Nb; Sputtering gas pressure: 12mTorr; N2:Ar flow ratio: 30sccm:10sccm; Sputtering power: 400W constant power RF sputtering; Deposition rate: 20nm / min.

3. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The niobium nitride film was grown by DC magnetron sputtering. The specific conditions were: Background vacuum: better than 2×10 -5 Pa; Gas: Ar, N2; Target material: Nb; Sputtering gas pressure: 2mTorr; N2:Ar flow ratio: 10sccm:85sccm; Sputtering current: 1.85A constant current DC sputtering; Deposition rate: 70nm / min.

4. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The external electrode pattern was drawn on the niobium nitride film by UV exposure of LOR 10B and AZ1500 double-layer photoresist. The specific conditions were: (1) Photoresist 1 Photoresist 1: LOR 10B; Pre-coating: 600r / min, 6s; Main coating: 4000r / min, 40s; Pre-baking: 150℃, 1.5min; (2) Photoresist 2 Photoresist 2: AZ1500 Pre-coating: 600r / min, 6s; Main coating: 4000r / min, 40s; Pre-baking: 90℃, 1.5min; Post-baking: 110℃, 1.5min; Exposure time: 7s; Development time: 17s.

5. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: Titanium and gold films were grown by magnetron sputtering under the following conditions: (1) Ti film growth conditions Background vacuum: better than 2×10 -5 Pa; Gas: Ar; Target material: Ti; Sputtering gas pressure: 4mTorr; Sputtering current: 0.4A constant current DC sputtering; (2) Au film growth conditions Background vacuum: better than 2×10 -5 Pa; Gas: Ar; Target material: Au; Sputtering gas pressure: 4mTorr; Sputtering current: 80W constant power DC sputtering.

6. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The planar spiral antenna pattern was drawn by electron beam exposure of PMMA A4 electron beam glue. The specific conditions were: Photoresist type: PMMA A4; Pre-coating: 600r / min, 6s; Main coating: 3000r / min, 60s; Pre-baking: 180℃, 4min; Exposure dose: 800μA / cm 2 .

7. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The microbridge pattern is defined by electron beam exposure of HSQ electron beam gel, and the specific conditions are: Photoresist type: HSQ 002; Pre-coating: 500r / min, 5s; Main coating: 5000r / min, 60s; Pre-baking: 80℃, 2min; Exposure dose: 2500μA / cm 2 .

8. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The microbridge pattern was transferred onto the niobium nitride film by reactive ion etching. The specific conditions were: Etching material: NbN; Reaction gas: CF4; Flow rate: 30sccm; Pressure: 1.2Pa; Power: 50W; Time: 1min.

9. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The area to be etched is defined by UV exposure of AZ4620 photoresist on the silicon surface of the substrate. The specific conditions are: Photoresist: AZ4620; Pre-coating: 600r / min, 6s; Main coating: 3000r / min, 40s; Pre-baking: 100℃, 30min; Exposure time: 23.5s; Development time: 240s.

10. The method for preparing a superconducting niobium nitride thermal electron bolometer according to claim 1, characterized in that: The silicon is etched away by the FSE deep silicon etcher to prepare the suspended bridge structure. The specific conditions are: Etching material: Si; Reaction gas 1: C4F8; Reaction gas 1 flow rate: 100 sccm; Reactive gas 2: SF6; Reaction gas 2 flow rate: 200 sccm; Pressure: 2.7Pa; Power: 1800W; Time: 45 minutes.

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