Terahertz superconducting dynamic inductance detector based on silicon nitride film and preparation method thereof

Abstract

The invention discloses a terahertz superconducting dynamic inductance detector based on silicon nitride films and a preparation method thereof, and the detector comprises a substrate which is a silicon substrate with the silicon nitride films on the upper surface and the lower surface; a terahertz superconducting dynamic inductance detector pixel array; the substrate hole digging array is arranged on the lower surface of the substrate by taking the terahertz superconducting dynamic inductance detector pixel array as a reference, and is obtained by removing a silicon substrate and a silicon nitride film on the lower surface of the silicon substrate; a silicon nitride film on the upper surface of the silicon substrate is arranged between the substrate hole digging array and the terahertz superconducting dynamic inductance detector pixel array. The resonant frequencies of the units of the terahertz superconducting dynamic inductance detector pixel array in the detector are different, reading is facilitated by adopting a frequency division multiplexing technology, a substrate hole digging array is realized below the position of a winding inductor of each unit of the terahertz superconducting dynamic inductance detector pixel array, the responsivity to photons can be improved, and the sensitivity of the terahertz superconducting dynamic inductance detector is improved. And the detection sensitivity is improved.

Description

Technical Field

[0001] The present invention relates to the field of detector technology, and in particular to a terahertz superconducting dynamic inductance detector based on silicon nitride film and a preparation method thereof. Background Art

[0002] The terahertz band is located between the microwave band and the visible light band, and the corresponding frequency range is generally defined between 0.1THz and 10THz. Since the peak of the cosmic microwave background (CMB) and a large part of the photon energy in the universe are in the terahertz band, the terahertz band contains rich astronomical information, which is of great significance for studying the evolution of the universe and the formation of stars and planets.

[0003] Lumped Element KID (LEKID) has made great progress in astronomical imaging and single photon detection due to its simple preparation process and the ability to use frequency division multiplexing readout technology for large array readout. However, existing superconducting dynamic inductance detectors generally have defects such as low detection sensitivity and high noise. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a terahertz superconducting dynamic inductance detector based on silicon nitride film that can improve detection sensitivity. Another purpose of the present invention is to provide a method for preparing the above-mentioned terahertz superconducting dynamic inductance detector.

[0005] Technical solution: The terahertz superconducting dynamic inductance detector based on silicon nitride film described in the present invention includes: a substrate, which is a silicon substrate with silicon nitride films on both the upper and lower surfaces; a terahertz superconducting dynamic inductance detector pixel array deposited on the upper surface of the substrate; and a substrate hole array, which is based on the terahertz superconducting dynamic inductance detector pixel array and is arranged on the lower surface of the substrate, and is obtained by removing the silicon substrate and the silicon nitride film on the lower surface of the silicon substrate, and the silicon nitride film on the upper surface of the silicon substrate is between the substrate hole array and the terahertz superconducting dynamic inductance detector pixel array.

[0006] Furthermore, each detector pixel unit of the terahertz superconducting dynamic inductance detector pixel array includes: a resonator circuit, which changes the resonant frequency by receiving incident light, thereby characterizing the detection of the incident light signal; and a coplanar waveguide feeder, which is composed of a center feeder and a ground plane, and is coupled to the resonator circuit to frequency-division multiplex the resonant frequency of the resonator circuit to an external frequency detection device, and the external frequency detection device detects the change in the resonant frequency, thereby characterizing the detection of the incident light signal by the resonator circuit.

[0007] Furthermore, the resonator circuit includes: a meander inductor, which receives incident light energy at a terahertz frequency, destroys Cooper pairs to generate quasiparticles, and thus produces a change in dynamic inductance; and a toe capacitor, which is connected to the meander inductor, and the two together form a resonator circuit, which is then coupled to a coplanar waveguide feeder. The change in the dynamic inductance of the resonator circuit causes the resonator frequency to change, and the information of the change in the resonant frequency is transmitted to an external frequency detection device through the coplanar waveguide feeder. Modifying the number of toe capacitors will change the resonant frequency of the resonator circuit.

[0008] Furthermore, the material used for the terahertz superconducting dynamic inductance detector pixel array is a superconducting metal, and the superconducting metal includes tantalum, aluminum or niobium.

[0009] Preferably, the material used for the meandering inductor part is aluminum, and the material used for the remaining part is tantalum.

[0010] Furthermore, the thickness of the silicon substrate is 300-500um; the thickness of the silicon nitride film is 100-300nm; the depth of the hole array in the silicon substrate is 300-500um; and the thickness of the pixel array of the terahertz superconducting dynamic inductance detector is 40-200nm.

[0011] The method for preparing the terahertz superconducting dynamic inductance detector based on silicon nitride film comprises the following steps:

[0012] (1) growing a superconducting metal film on the surface of a substrate using a magnetron sputtering device, and preparing a terahertz superconducting dynamic inductance detector pixel array by laser direct writing technology, reactive ion etching technology, electron beam exposure process and stripping process for the obtained superconducting metal film layer;

[0013] (2) By using laser direct writing technology and reactive ion etching technology, the silicon nitride film at the position corresponding to the pixel array of the terahertz superconducting dynamic inductance detector on the lower surface of the substrate is removed; then, the position of the silicon substrate exposed on the silicon nitride film on the lower surface of the substrate is chemically etched by potassium hydroxide solution to realize the substrate hole digging process, obtain the substrate hole digging array, and finally prepare the terahertz superconducting dynamic inductance detector based on silicon nitride film.

[0014] Furthermore, the reactive ion etching process further includes a process of: cleaning the residual photoresist with an organic solvent; the organic solvent is N-methylpyrrolidone, isopropanol, acetone and anhydrous ethanol.

[0015] Principle of the invention: The superconducting dynamic inductance detector is composed of a microwave resonator made of a superconducting film. Its working mechanism is related to the complex impedance change of the superconducting film. The present invention uses the resonator to read the complex impedance change of the superconducting film. When the incident photon energy is higher than twice the superconducting energy gap, the absorbed photon will break up the Cooper pairs into quasiparticles, and the increase in the number of quasiparticles in the superconducting film will change the surface impedance of the superconducting film, thereby causing the resonant frequency of the microwave resonator to shift to a low frequency and reduce the quality factor (Q value). The detection of the incident photon signal can be achieved by detecting the phase shift of the microwave resonance signal.

[0016] When photons incident on the superconducting film destroy Cooper pairs and generate quasiparticles, phonons are also released, which carry a portion of energy. If the silicon substrate is directly below the superconducting film, the phonons will be dissipated into the silicon substrate, and the energy carried by the phonons will be lost. In the present invention, the area used to sense photons is the meandering inductor part composed of aluminum metal on the pixel array of the terahertz superconducting dynamic inductance detector. The present invention removes the silicon substrate directly below the meandering inductor through a substrate hole array, and only retains a layer of silicon nitride film. In this way, most of the phonons generated by the meandering inductor part cannot be dissipated into the silicon substrate, and this part of the energy is retained, further improving the device's responsiveness to photons, thereby improving the device's sensitivity.

[0017] In the present invention, the pixel array of the terahertz superconducting dynamic inductance detector is composed of a number of resonator circuits with different resonant frequencies, and the resonant frequency is achieved by modifying the number of toe capacitors of the resonator circuit. The meandering inductance part of the resonator circuit adopts the same periodic structure and is designed for detecting the same terahertz frequency. The resonator circuit is composed of toe capacitors and meandering inductance based on a lumped structure. The meandering inductance part is composed of a unit periodic structure, and the appearance contour is roughly a rectangular area of ​​80um*90um. The terahertz superconducting dynamic inductance detector has high sensitivity when detecting terahertz band signals, and adopts frequency division multiplexing technology for easy readout.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The resonant frequencies of various units of the terahertz superconducting dynamic inductance detector pixel array are different, which is convenient for readout using frequency division multiplexing technology; (2) A silicon substrate hole structure is implemented below the location of the meandering inductance of each unit of the terahertz superconducting dynamic inductance detector pixel array, which can improve the responsiveness of the superconducting dynamic inductance detector to photons, thereby improving its detection sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional schematic diagram of a novel terahertz superconducting dynamic inductance detector based on silicon nitride film in Example 1;

[0020] Figure 2 is a flow chart of a method for preparing a novel terahertz superconducting dynamic inductance detector based on silicon nitride film in Example 1;

[0021] Figure 3 is a schematic diagram of the array structure of the novel terahertz superconducting dynamic inductance detector based on silicon nitride film in Example 1;

[0022] Figure 4 yes Figure 3 A magnified view of a single unit 13 of the detector pixel array;

[0023] Figure 5 yes Figure 4 An enlarged view of the meandering inductor portion 24 of the resonator circuit;

[0024] Figure 6 These are actual images of the detector taken under an optical microscope at different magnifications. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments and drawings.

[0026] Example 1: Figure 1 As shown, the novel terahertz superconducting dynamic inductance detector based on silicon nitride film provided in this embodiment includes a substrate, a terahertz superconducting dynamic inductance detector pixel array deposited on the upper surface of the substrate, and a substrate hole array 6, wherein the substrate includes, from top to bottom, an upper silicon nitride film 1 arranged on the upper surface of a silicon substrate 2, a silicon substrate 2, and a lower silicon nitride film 3 arranged on the lower surface of the silicon substrate 2; the terahertz superconducting dynamic inductance detector pixel array includes a tantalum metal film 4 and an aluminum metal film 5, and between the substrate hole array 6 and the terahertz superconducting dynamic inductance detector pixel array is an upper silicon nitride film 1 on the upper surface of the silicon substrate.

[0027] Each detector pixel unit of the above-mentioned terahertz superconducting dynamic inductance detector pixel array includes: a resonator circuit, which changes the resonant frequency by receiving incident light, thereby characterizing the detection of the incident light signal; and a coplanar waveguide feeder, which is composed of a center feeder and a ground plane. The coplanar waveguide feeder is coupled to the resonator circuit, and the resonant frequency of the resonator circuit is frequency-division multiplexed to an external frequency detection device. The external frequency detection device detects the change in the resonant frequency, thereby characterizing the detection of the incident light signal by the resonator circuit.

[0028] The resonator circuit includes: a meander inductor, which receives incident light energy at a terahertz frequency, destroys Cooper pairs to generate quasiparticles, and then produces a change in dynamic inductance; and a toe capacitor, which is connected to the meander inductor, and the two together form a resonator circuit, which is then coupled to a coplanar waveguide feeder. The change in the dynamic inductance of the resonator circuit causes the resonator frequency to change, and the information of the change in the resonant frequency is transmitted to an external frequency detection device through the coplanar waveguide feeder. Modifying the number of toe capacitors will change the resonant frequency of the resonator circuit.

[0029] like Figure 2 As shown, the preparation method of the novel terahertz superconducting dynamic inductance detector based on silicon nitride film is as follows:

[0030] (a) cleaning an original silicon wafer having a silicon substrate thickness of 300-500 μm and a silicon nitride film thickness of 100-300 nm on the upper and lower surfaces of the silicon substrate with N-methylpyrrolidone and isopropanol to remove impurities on the surface of the original silicon wafer;

[0031] (b) growing a tantalum metal with a thickness of 100-200 nm on the surface of the silicon nitride film on the upper surface of the silicon substrate by magnetron sputtering;

[0032] (c) coating photoresist uniformly on the surface of the silicon nitride film on the lower surface of the silicon substrate, leaving a corresponding pattern on the silicon nitride film on the lower surface of the silicon substrate by using laser direct writing technology and development technology, and removing the silicon nitride film in the corresponding area by using reactive ion etching technology to expose the silicon substrate;

[0033] (d) uniformly coating photoresist on the surface of the tantalum metal film, and using photolithography, development and reactive ion etching techniques to leave a pattern of a terahertz superconducting dynamic inductance detector pixel array on the tantalum metal film. The pattern structure is as follows: Figure 3 and Figure 4 As shown, Figure 3 1 is a schematic diagram of the array structure of a new type of terahertz superconducting dynamic inductance detector based on silicon nitride film, 11 is the coplanar waveguide feed line of the terahertz superconducting dynamic inductance detector pixel array, 12 is the square mark on the layout, 13 is a single unit of the detector pixel array, Figure 4 is an enlarged view of a single unit 13 of the detector pixel array, in which 21 is the ground plane of the terahertz superconducting dynamic inductance detector pixel array, 22 is the toe capacitance part of the resonator circuit, 23 is the center feed line of the coplanar waveguide feed line, 24 is the meandering inductance part of the resonator circuit, 25 is the position of the silicon substrate hole array unit relative to the terahertz superconducting dynamic inductance detector pixel array unit, and the structure of a single detector pixel unit is as shown in FIG. Figure 4 As shown in 21, 22, and 23, at this time Figure 4 The structures 24 and 25 do not actually exist; Figure 423 in the middle is the central feed line of the coplanar waveguide, with a width of 16um; Figure 4 21 in the middle is the ground plane, and the gap between the center feed line and the ground planes on both sides is 10um. Figure 4 22 is the fork-toe capacitor part of the resonator circuit, the thin fork-toe capacitors distributed longitudinally on both sides thereof have a length of 1000um and a width of 4um, and are spaced 10um apart from each other, and the width of the remaining fork-toe capacitors is 10um;

[0034] (e) The silicon wafer that has been subjected to reactive ion etching in the previous step is cleaned with N-methylpyrrolidone and isopropyl alcohol, and an electron beam exposure photoresist is evenly coated on the surface of the tantalum metal film. The small-size pattern of the meander inductor is left by electron beam exposure. After the development operation is completed, an aluminum metal film of 40nm-50nm is grown by electron beam evaporation technology. The excess aluminum metal film is removed by a stripping process, leaving only the meander inductor part, such as Figure 5 As shown in 32 ( Figure 5 31 is the connection part between the toe capacitor and the meander inductor of the resonator circuit, 32 is the meander inductor, 33 and 34 are partial structures of the toe capacitor of the resonator circuit), wherein the width of the meander inductor aluminum line is 90-110nm, Figure 5 31 shows the connection part between the toe capacitor and the meander inductor, and the size is 2um*4um;

[0035] (f) Finally, the exposed silicon on the silicon nitride film on the lower surface of the silicon substrate is etched cleanly with potassium hydroxide solution to obtain the final new terahertz superconducting dynamic inductance detector based on silicon nitride film. It is placed under an optical microscope and photographed with bottom lighting. The pictures taken at different magnifications are as follows: Figure 6 As shown, the red squares in the figure are the locations of the hole array in the silicon substrate, the silicon nitride film is light-transmissive, and the aluminum metal meander inductor on the front is not made.

Claims

1. A terahertz superconducting dynamic inductance detector based on silicon nitride film, characterized in that: include: A substrate, wherein the substrate is a silicon substrate having a silicon nitride film on both the upper and lower surfaces; A terahertz superconducting dynamic inductance detector pixel array deposited on the upper surface of the substrate; and a substrate hole array, wherein the substrate hole array is based on the terahertz superconducting dynamic inductance detector pixel array, is arranged on the lower surface of the substrate, and is obtained by removing the silicon substrate and the silicon nitride film on the lower surface of the silicon substrate, and the silicon nitride film on the upper surface of the silicon substrate is between the substrate hole array and the terahertz superconducting dynamic inductance detector pixel array.

2. The terahertz superconducting dynamic inductance detector according to claim 1, characterized in that: Each detector pixel unit of the terahertz superconducting dynamic inductance detector pixel array comprises: A resonator circuit, wherein the resonator circuit changes the resonant frequency by receiving incident light, thereby representing the detection of the incident light signal; and a coplanar waveguide feeder, wherein the coplanar waveguide feeder is composed of a center feeder and a ground plane, and the coplanar waveguide feeder is coupled to the resonator circuit, and the resonant frequency of the resonator circuit is frequency-division multiplexed to an external frequency detection device, and the external frequency detection device detects the change of the resonant frequency, thereby characterizing the detection of the incident optical signal by the resonator circuit.

3. The terahertz superconducting dynamic inductance detector according to claim 2, characterized in that: The resonator circuit comprises: A meander inductor receives incident light energy at a terahertz frequency, destroys Cooper pairs to generate quasiparticles, and thus generates a change in dynamic inductance; and a toe capacitor, wherein the toe capacitor is connected to the meandering inductor, and the two together constitute a resonator circuit, which is further coupled to the coplanar waveguide feeder. The change of the dynamic inductance of the resonator circuit causes the resonator frequency to change, and the information of the resonant frequency change is transmitted to an external frequency detection device through the coplanar waveguide feeder, wherein modifying the number of toe capacitors will change the resonant frequency of the resonator circuit.

4. The terahertz superconducting dynamic inductance detector according to claim 3, characterized in that: The material used for the terahertz superconducting dynamic inductance detector pixel array is a superconducting metal, and the superconducting metal includes tantalum, aluminum or niobium.

5. The terahertz superconducting dynamic inductance detector according to claim 3, characterized in that: The material used for the meandering inductor part is aluminum, and the material used for the remaining part is tantalum.

6. The terahertz superconducting dynamic inductance detector according to claim 1, characterized in that: The thickness of the terahertz superconducting dynamic inductance detector pixel array is 40-200nm.

7. The terahertz superconducting dynamic inductance detector according to claim 1, characterized in that: The thickness of the silicon nitride film is 100-300 nm, and the depth of the hole array in the silicon substrate is 300-500 um.

8. The terahertz superconducting dynamic inductance detector according to claim 7, characterized in that: The thickness of the silicon substrate is 300-500um.

9. A method for preparing a terahertz superconducting dynamic inductance detector based on silicon nitride film according to claim 1, characterized in that: The following steps are involved: (1) growing a superconducting metal film on the surface of a substrate using a magnetron sputtering device, and preparing a terahertz superconducting dynamic inductance detector pixel array by laser direct writing technology, reactive ion etching technology, electron beam exposure process and stripping process for the obtained superconducting metal film layer; (2) removing the silicon nitride film at a position corresponding to the pixel array of the terahertz superconducting dynamic inductance detector on the lower surface of the substrate by using laser direct writing technology and reactive ion etching technology; The silicon substrate is then exposed by chemically etching the silicon nitride film on the lower surface of the substrate with a potassium hydroxide solution to implement a substrate hole digging process to obtain a substrate hole array, and finally a terahertz superconducting dynamic inductance detector based on silicon nitride film is prepared.

10. The preparation method according to claim 9, characterized in that: The reactive ion etching process also includes a cleaning process after the treatment, in which an organic solvent is used to clean the residual photoresist; the organic solvent is N-methyl pyrrolidone, isopropanol, acetone and anhydrous ethanol.

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