CN110095185A - A kind of THz wave detection micro-bridge structure of integrated sub-wavelength metal ring absorbing structure and preparation method thereof - Google Patents

Abstract

The invention discloses a terahertz wave detection microbridge structure integrated with a subwavelength metal ring absorption structure and a preparation method thereof, including a microbridge, a subwavelength absorption structure layer is arranged on the bridge surface of the microbridge, and the subwavelength A metal disc and a concentric metal ring surrounding the metal disc are etched on the absorbing structure layer, and the micro-bridge includes a substrate, a drive circuit arranged on the substrate, a circuit interface arranged on the drive circuit, a circuit interface arranged on the drive circuit and The sacrificial layer on the substrate, the support layer with bridge surface and bridge legs arranged on the sacrificial layer in sequence from bottom to top, the electrode lead layer connected to the circuit interface, the dielectric layer that can expose the electrode lead interface, and the electrode The vanadium oxide layer connected to the lead interface and the passivation layer covering the vanadium oxide film, the sub-wavelength absorption structure layer is arranged on the passivation layer, the microbridge structure of the present invention can realize the detection and imaging of the terahertz band, and has multiple It has the advantages of high frequency absorption, high absorption rate, and polarization insensitivity.

Description

A microbridge structure for terahertz wave detection integrated with subwavelength metal ring absorbing structure and its preparation method

technical field

The invention relates to the technical field of terahertz detection and imaging, in particular to a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure and a preparation method thereof.

Background technique

Terahertz (THz) waves refer to electromagnetic radiation with a frequency ranging from 0.1 to 10 THz (wavelength 3 mm to 30 μm), and its electromagnetic spectrum lies between the microwave and infrared bands. Therefore, terahertz systems take advantage of both electronics and optics. For a long time, due to the lack of effective terahertz radiation generation and detection methods, people's understanding of the properties of electromagnetic radiation in this band is very limited, so that this band is called the terahertz gap in the electromagnetic spectrum. This band is also the last frequency window in the electromagnetic spectrum to be fully studied. Compared with electromagnetic waves in other bands, terahertz electromagnetic waves have the following unique properties: ①Transient: the typical pulse width of terahertz pulses is on the order of picoseconds; ②broadband: terahertz pulse sources usually only contain several cycles Electromagnetic oscillation, the frequency band of a single pulse can cover the range from GHz to tens of THz; ③ coherence: the coherent measurement technology of terahertz time-domain spectroscopy technology can directly measure the amplitude and phase of the terahertz electric field, and can easily extract the refractive index of the sample , absorption coefficient; ④ low energy: the energy of terahertz photons is only millielectron volts, and will not destroy the detected substance due to ionization, so that biomedical detection and diagnosis can be safely performed; ⑤ Penetration: terahertz radiation is for Many non-polar insulating substances, such as cardboard, plastics, textiles and other packaging materials have high penetration characteristics, which can be used to detect hidden objects. These characteristics of terahertz waves make them have great scientific value and broad application prospects in object imaging, environmental monitoring, medical diagnosis, radio astronomy, broadband mobile communication, especially in satellite communication and military radar. In recent years, due to the development of free electron laser and ultrafast laser technology, a stable and reliable excitation light source has been provided for the generation of terahertz pulses, and the research on the generation mechanism, detection technology and application technology of terahertz radiation has been vigorously developed.

Terahertz detectors are key devices for the application of terahertz technology. In the development and application of terahertz detectors, detecting terahertz radiation signals is of great significance. The traditional uncooled infrared focal plane array structure can theoretically be used for detection and imaging in the terahertz band. According to the 1/4 wavelength theory, taking the radiation frequency of 3 THz as an example, in order to fully absorb the terahertz radiation, the height of the optical resonator of the uncooled infrared focal plane array should be 25 μm (1/4 wavelength of the incident radiation). However, such a resonant cavity height is difficult to achieve in device fabrication (the resonant cavity height of a traditional uncooled infrared focal plane array is about 1.5-3 μm). If the height of the resonant cavity is not changed, the absorption of terahertz radiation by its film structure is extremely low, making signal detection more difficult. In the literature (F.Simoens, etc, "Terahertz imaging with a quantum cascade laser and amorphous-silicon microbolometer array", Proceedings of SPIE, vol.7485, pp.74850M-1–74850M-9, 2009), will be based on amorphous The uncooled infrared focal plane array of silicon is used for terahertz imaging. After simulation and experimental measurement, the terahertz radiation absorption rate of the detection unit is only 0.16-0.17%. Therefore, the commonly used solution at present is: keep the resonant cavity height of the uncooled infrared focal plane array unchanged, and add a special terahertz radiation absorbing layer on the top layer of the film structure to realize the detection and imaging of terahertz radiation . Alan W.M.Lee et al. reported real-time, continuous terahertz wave imaging using a 160×120 uncooled infrared focal plane array. The sensitive material is a vanadium oxide layer on a silicon nitride microbridge. They proposed that in order to improve the signal-to-noise ratio and spatial resolution, the design of the focal plane array needs to be improved, and the main work is to optimize the terahertz radiation absorbing material (Alan W.M.Lee, etc, “Real-time, continuous-wave terahertz imaging by use of a microbolometer focal-plane array”, Optics Letters, vol. 30, pp. 2563–2565, 2005).

Thin metal or metal composite films can absorb terahertz radiation, and the film thickness below 50nm has little effect on the heat capacity of the detector, which is conducive to the production of high response rate detection units, and is often used as the absorption of terahertz microarray detectors Floor. N.Oda et al. used 320×240 and 640×480 uncooled infrared focal plane arrays based on vanadium oxide thermosensitive thin films to detect terahertz radiation. Because the absorption rate of the original film structure to the terahertz radiation is only 2.6-4%. Therefore, they added a metal film with appropriate sheet resistance on the top layer of the film structure as a terahertz radiation absorbing layer, reducing the noise equivalent power to 40pW when the incident radiation frequency is 3THz (N.Oda, etc, " Detection of terahertz radiation from quantum cascade laser using vanadium oxide microbolometer focal plane arrays”, Proceedings of SPIE, vol.6940, pp.69402Y-1–69402Y-12, 2008). The use of metal thin films as THz radiation absorbing layers has also been reported in the literature (L. Marchese, etc, "A microbolometer-based THz imager", Proceedings of SPIE, vol.7671, pp. 76710Z-1–76710Z-8, 2010) , the terahertz radiation absorption can be maximized by optimizing the thickness of the metal absorbing layer. In the patent 201310124924.8, an infrared-terahertz dual-band array detector microbridge structure and its preparation method are disclosed. The top layer of the microbridge structure is a double-layer vanadium oxide layer, and the lower layer of vanadium oxide layer has a high temperature coefficient of resistance (TCR). The non-phase-change vanadium oxide layer is used as a sensitive layer in the infrared and terahertz bands. The upper vanadium oxide layer has a lower phase transition temperature, and a reversible phase transition from semiconductor phase to metal phase can occur. When the semiconductor phase is in the same state as the lower vanadium oxide layer The layers work together as an infrared absorbing layer, and after a phase change to a metallic phase, act as a terahertz radiation absorbing layer. However, the absorption rate of the metal film is limited. Ideally, the absorption rate of the terahertz radiation of the unsupported metal film is only 50%, and the absorption rate of the metal film integrated into the microbridge structure is lower. The absorption efficiency of the bridge structure can theoretically reach 100%. At the same time, the microbridge structures in the above methods all use an additional layer of material as a terahertz radiation absorbing layer alone.

The research team disclosed a helical antenna coupling microbridge structure and its preparation method in patent 201510409891.0, which solves the problem that the metal thin film has a low absorption rate in the prior art and can only be used as a terahertz radiation absorbing layer alone. The invention uses the helical antenna layer (metal thin film) as the light absorbing layer and the electrode lead layer at the same time, and uses the small-sized vanadium oxide layer located at the feeding point of the helical antenna layer as the heat-sensitive layer. The helical antenna layer has high absorption rate, tunable, Polarization detection and other characteristics; the helical antenna layer is also used as the electrode lead, which can simplify the process and facilitate integration; the vanadium oxide layer has a small heat-sensitive film area and has high detection sensitivity; by adjusting the antenna structure parameters, infrared and terahertz can be realized. Band Detection and Imaging. However, in this method, since the helical antenna layer is also used as an electrode lead, the antenna type and structural parameters are poorly adjustable due to the limitation of the structure and width of the electrode lead.

In the patent 201610314140.5, our research team disclosed a bridge leg separation antenna coupling micro-bridge structure and its preparation method. The bridge leg separation antenna layer is prepared on the top layer of the detection unit of the micro bridge structure. The invention comprises a substrate, a driving circuit arranged on the substrate, a circuit interface arranged on the driving circuit, a sacrificial layer arranged on the driving circuit and the substrate, and a bridge surface arranged on the sacrificial layer sequentially from bottom to top The support layer and the bridge leg, the electrode lead layer connected with the circuit interface, the passivation layer that can expose the electrode lead interface, the vanadium oxide heat sensitive layer connected with the electrode lead interface, and the antenna layer whose feeding point is located at the vanadium oxide. The antenna layer is composed of a bridge deck antenna and a bridge leg antenna. The structure and parameters of the bridge deck antenna can be adjusted within the range of the passivation layer. The shape of the bridge leg antenna is consistent with the bridge leg, and the width can be adjusted within the range of the bridge leg. The bridge leg separated antenna coupled micro-bridge structure has the characteristics of independent adjustable antenna, multi-frequency absorption, high absorption rate, polarization detection, etc., and is used for infrared and terahertz band detection and imaging. However, in this method, due to the limitation of the width of the bridge leg, the adjustment range of the bridge leg antenna is limited, and the structure has polarization selectivity.

Contents of the invention

The purpose of the present invention is to provide a terahertz wave detection microbridge structure integrating a sub-wavelength metal ring absorption structure and its preparation method. High, polarization insensitive and other advantages.

The technical scheme that the present invention adopts is as follows:

In order to achieve the above object, the present invention provides a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure, including a microbridge, a subwavelength absorption structure layer is arranged on the bridge surface of the microbridge, and the subwavelength A metal disc and concentric metal rings surrounding the metal disc are etched on the absorbing structure layer.

Preferably, the microbridge includes a substrate, a driver circuit arranged on the substrate, a circuit interface arranged on the driver circuit, a sacrificial layer arranged on the driver circuit and the substrate, and arranged on the sacrificial layer sequentially from bottom to top The support layer with bridge deck and bridge legs, the electrode lead layer connected to the circuit interface, the dielectric layer that can expose the electrode lead interface, the vanadium oxide layer connected to the electrode lead interface and the passivation layer covering the vanadium oxide film , the sub-wavelength absorption structure layer is disposed on the passivation layer.

Preferably, the sub-wavelength absorbing structure layer is made of aluminum, tungsten, titanium, platinum, nickel, chromium or any alloy thereof, and its thickness is 50-500 nm.

Preferably, the metal disc is located at the center of the bridge deck of the micro-bridge, and has a diameter of 5 μm-160 μm.

Preferably, the number of the metal rings is 1-10, the outer diameter of the metal rings is 10 μm-180 μm, the width is 1 μm-30 μm, and the pitch is 1 μm-100 μm.

Preferably, the microbridge structure is used as a unit structure of a terahertz microbolometer detection array, and its area is (20 μm×20 μm)˜(200 μm×200 μm).

Preferably, the material of the sacrificial layer is any one of polyimide, silicon dioxide, oxidized porous silicon and phosphosilicate glass; the supporting layer is composed of a single-layer film or a multilayer film, and the material is two Silicon oxide or silicon nitride, the supporting layer has a thickness of 0.1-1 μm; the electrode lead layer is made of aluminum, tungsten, titanium, platinum, nickel, chromium or any alloy thereof, and the thickness is 10-200 nm. The material of the layer is silicon dioxide or silicon nitride, with a thickness of 50-300nm; the temperature coefficient of resistance of the vanadium oxide layer is -2%/K--6%/K, and the thickness is 30-300nm; the passivation The material of the layer is silicon nitride, and the thickness is 50-300nm.

The present invention also provides a method for preparing the terahertz wave detection microbridge structure integrated with the sub-wavelength metal ring absorption structure, including the following preparation steps:

(1) Integrate the driving circuit on the substrate, and then prepare and pattern a sacrificial layer on the substrate with the driving circuit, exposing the circuit interface of the driving circuit;

(2) preparing a supporting layer on the sacrificial layer, patterning the supporting layer, and partially covering the circuit interface;

(3) Prepare an electrode lead layer on the support layer, and connect the electrode lead layer to the circuit interface of the drive circuit, pattern the electrode lead layer to obtain an electrode lead layer with an electrode lead interface;

(4) Prepare a dielectric layer on the electrode lead layer, and expose the electrode lead interface after patterning the dielectric layer;

(5) preparing a vanadium oxide layer on the dielectric layer, and patterning the vanadium oxide layer so that it covers and connects with the electrode lead interface;

(6) preparing a passivation layer on the vanadium oxide layer, and patterning the passivation layer so that it covers the vanadium oxide layer;

(7) Prepare a subwavelength absorption structure layer on the passivation layer, and pattern the subwavelength absorption structure layer as a metal disc and metal ring structure;

(8) The sacrificial layer is released to form a terahertz wave detection microbridge structure integrated with a subwavelength metal ring absorption structure, and then packaged to form a detection device.

Preferably, the patterned support layer, dielectric layer, and passivation layer in the steps (2), (4), and (6) are completed using photolithography and reactive ion etching processes, and the reactive ion etching gas is A mixed gas of fluorine-based gas and O ₂ , the flow ratio of the fluorine-based gas and O ₂ is (10:20)-(90:10), the radio frequency power is 100-500W, and the reaction chamber pressure is 2-10Pa.

Preferably, the patterned electrode lead layer, vanadium oxide layer, and subwavelength absorption structure layer in the steps (3), (5), and (7) are completed by photolithography and reactive ion etching processes, and the reactive ion The etching gas is a mixed gas of BCl ₃ , Cl ₂ and neutral gas, the neutral gas is any one of N ₂ and CH ₄ or a mixture of both, and the flow ratio of BCl ₃ and Cl ₂ is (10:30)-(90:10), the flow rate of the neutral gas is 0-90sccm, the radio frequency power is 100-500W, and the pressure of the reaction chamber is 2-10Pa.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

1. The present invention integrates the sub-wavelength absorption structure into the micro-bridge structure, and the sub-wavelength absorption structure layer is etched with a metal disc and a concentric metal ring surrounding the metal disc, so that the size of the metal disc can be adjusted according to actual needs, The number and size of metal rings are used to adjust the number, position and size of resonance absorption peaks, so that the microbridge structure has the characteristics of multi-frequency absorption, high absorption rate, and adjustable absorption characteristics.

2. The metal disk and the concentric metal ring surrounding the metal disk are etched on the sub-wavelength absorption structure layer of the present invention. Due to the symmetry of the metal disk and metal ring structure, the microbridge structure of the present invention has polarization insensitive Advantages, it has a high absorption rate for both TE wave and TM wave.

3. The sub-wavelength absorbing structure layer of the present invention can be prepared by etching a ring pattern in a metal thin film. The preparation process is simple and compatible with the preparation process of the microbridge structure, which is beneficial to the integrated preparation of the terahertz wave detection microbridge array.

Description of drawings

The invention will be illustrated by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a structural sectional view of the present invention, wherein, a is a sectional view of a substrate with a drive circuit, b is a sectional view of a substrate with a sacrificial layer prepared, c is a sectional view of a substrate with a support layer prepared, and d is a sectional view of a prepared substrate The sectional view of the substrate of the electrode lead layer, e is the sectional view of the substrate with the dielectric layer prepared, f is the sectional view of the substrate with the vanadium oxide layer prepared, g is the sectional view of the substrate with the passivation layer prepared, h is A cross-sectional view of the substrate of the prepared subwavelength metal ring absorption structure, i is a cross-sectional view of the device structure after releasing the sacrificial layer;

Fig. 2 is a top view of the structure of the present invention, wherein, a is a top view of a substrate prepared with a sacrificial layer and a support layer, b is a top view of a substrate with an electrode lead layer prepared, c is a top view of a substrate with a dielectric layer prepared, d is the top view of the substrate with the vanadium oxide layer prepared, e is the top view of the substrate with the passivation layer prepared, and f is the top view of the microbridge structure with the subwavelength metal ring absorption structure prepared;

Fig. 3 is the terahertz radiation absorption curve diagram of the present invention in embodiment 1;

FIG. 4 is a terahertz radiation absorption curve of the present invention in Example 2. FIG.

Marked in the figure: 10-substrate, 20-drive circuit, 21-circuit interface, 30-sacrifice layer, 40-support layer, 41-bridge deck, 42-bridge leg, 50-electrode lead layer, 51-electrode lead Interface, 60-dielectric layer, 70-vanadium oxide layer, 80-passivation layer, 90-subwavelength metal ring absorption structure layer, 91-metal disc, 92-metal ring, 100-micro bridge.

Detailed ways

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

A terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure, including a microbridge 100, a subwavelength absorption structure layer 90 is arranged on the bridge surface of the microbridge 100, and on the subwavelength absorption structure layer 90 A metal disc 91 and a concentric metal ring 92 surrounding the metal disc 91 are etched.

The microbridge 100 includes a substrate 10, a driver circuit 20 arranged on the substrate 10, a circuit interface 21 arranged on the driver circuit 20, a sacrificial layer 30 arranged on the driver circuit 20 and the substrate 10, bottom-up The support layer 40 with the bridge surface 41 and the bridge leg 42 arranged on the sacrificial layer 30 in sequence, the electrode lead layer 50 connected to the circuit interface 21, the dielectric layer 60 that can expose the electrode lead interface 51, and the electrode lead interface 51 The connected vanadium oxide layer 70 and the passivation layer 80 covering the vanadium oxide film, the sub-wavelength absorption structure layer 90 is arranged on the passivation layer 80 .

The microbridge structure is used as the detection unit of the terahertz microarray detector, and the area of the microbridge structure unit of the array detector is 35 μm×35 μm.

A method for preparing a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure, comprising the following preparation steps:

(1) First prepare the driving circuit 20 on the substrate 10, and prepare the circuit interface 21 on the driving circuit 20, as shown in a in FIG. 1;

(2) Clean the surface of the substrate 10 with the drive circuit 20 to remove surface contamination, and bake the substrate 10 with the drive circuit 20 at 200° C. to remove the moisture on the surface and enhance the bonding performance. Coating the photosensitive polyimide on the glue coating track, that is, preparing the sacrificial layer 30, by controlling the rotation speed to be 3000rpm when coating the glue, and baking the coated photosensitive polyimide at 120°C to remove part of the glue in the glue. Solvent, which is beneficial to the neatness of the exposure lines, adopts the NIKON photolithography machine to carry out the exposure process to the photosensitive polyimide, and the substrate 10 (prepared photosensitive polyimide) with the driving circuit 20 after exposure is sent to the automatic development track for gluing The developer is a standard positive photoresist developer TMAH, and the photosensitive polyimide after development presents an inverted trapezoidal pattern, as shown in b in Figure 1, and then the belt that is prepared with the photosensitive polyimide film is driven The substrate 10 of the circuit 20 is placed in an annealing oven protected by an inert gas for imidization treatment, the imidization temperature is set to rise in stages, the highest temperature is 350°C, and the constant temperature time is 90min. After imidization, the photosensitive polyamide The imine thickness is 2 μm, and the sacrificial layer 30 partially covers the substrate 10;

(3) Use PECVD equipment and frequency mixing sputtering technology to make low-stress silicon nitride, that is, the support layer 40, and prepare the support layer 40 with a thickness range of 0.4 μm, then carry out photolithography and etching to the support layer 40, etch Out of the graphics of the supporting layer 40, the supporting layer 40 partially covers the circuit interface pattern, as shown in c in Figure 1;

(4) Using sputtering equipment to prepare a layer of metal aluminum thin film as the electrode lead layer 50, the thickness is 50nm, and then adopt photolithography and reactive ion etching process to complete the patterning of the electrode lead layer 50, and the reactive ion etching gas is BCl _3. Cl ₂ and N ₂ , set the flow ratio of BCl ₃ , Cl ₂ and N ₂ to 20 sccm: 20 sccm: 5 sccm, the radio frequency power to 300W, the reaction chamber pressure to 4Pa, and the electrode width after patterning to be 1 μm, as shown in Figure 1 as shown in d;

(5) Using PECVD equipment and frequency mixing sputtering technology to produce low-stress silicon nitride, that is, the dielectric layer 60, the thickness of the prepared dielectric layer 60 is 50nm, and the passivation layer 60 dielectric film is completed by photolithography and reactive ion etching technology patterning, the etching gas is a mixed gas of CHF ₃ and O ₂ , the flow ratio of CHF ₃ and O ₂ is set to 20sccm: 3sccm, the RF power is 400W, and the reaction chamber pressure is 4Pa; after etching the dielectric layer 60, the support A rectangular through-hole pattern is formed on the layer to expose the electrode lead interface 51, as shown in e in FIG. 1 ;

(6) The vanadium oxide layer 70 is prepared by magnetron sputtering equipment, the sputtering power is controlled to be 300W during sputtering, the oxygen partial pressure is 3%, the sputtering time is 10min, and the annealing temperature is 300°C; the pattern of the vanadium oxide layer 70 The photolithography and reactive ion etching process are used to complete the process. The reactive ion etching gas is BCl ₃ , Cl ₂ and N ₂ . The flow ratio of BCl ₃ , Cl ₂ and N ₂ is set to 40sccm: 20sccm: 5sccm, and the radio frequency power is 300W. , the reaction chamber pressure is 4Pa; the patterned vanadium oxide layer 70 is a rectangular pattern, covering the electrode lead interface 51, as shown in f in Figure 1;

(7) Using PECVD equipment and frequency mixing sputtering technology to produce low-stress silicon nitride, that is, the passivation layer 80, the thickness of the prepared passivation layer 80 is 50nm, and the passivation layer 80 is completed by photolithography and reactive ion etching technology. For the patterning of the dielectric film, the etching gas is a mixed gas of CHF ₃ and O ₂ , the flow ratio of CHF ₃ and O ₂ is set to 20sccm: 3sccm, the radio frequency power is 400W, and the reaction chamber pressure is 40Pa; the etching passivation layer is 80 After forming a rectangular pattern to cover the vanadium oxide layer 70, as shown in g in FIG. 1;

(8) Using sputtering equipment to prepare a layer of metal aluminum film as the subwavelength absorption structure layer 90, the thickness is 100nm, and then adopt photolithography and reactive ion etching process to complete the patterning of the subwavelength absorption structure layer 90, and reactive ion etching The etching gas is BCl ₃ , Cl ₂ and N ₂ , the flow ratio of BCl ₃ , Cl ₂ and N ₂ is set to 20sccm: 20sccm: 5sccm, the radio frequency power is 250W, and the reaction chamber pressure is 4Pa; the patterned subwavelength absorption structure layer is The metal disc 91 and the metal ring 92 are shown as h in FIG. 1 . The diameter of the metal disc is 16 μm, the number of metal rings is 2, the outer diameter of the inner metal ring is 26 μm, the outer diameter of the outer metal ring is 33 μm, the width of the inner metal ring is 4 μm, and the width of the outer metal ring is 2.5 μm;

(9) The microbridge structure of the subwavelength absorption structure layer 90 is completed by bombarding with oxygen plasma, and the photosensitive polyimide (sacrifice layer) that has been imidized is removed to form a detection unit with a support layer structure. The cross-sectional schematic diagram of Fig. 1 is shown in i.

The terahertz radiation absorption curve of the microbridge structure obtained by CST software simulation is shown in Fig. 3 . It can be seen that the terahertz wave detection microbridge structure with integrated sub-wavelength metal ring absorption structure designed with the above parameters has the characteristics of multi-frequency absorption, with absorption peaks at 2.3THz, 3.4THz and other frequencies, and the absorption rate at 2.25THz reaches 98%, and the absorption rate at 3.35THz reaches 76%, which can be used for multi-band terahertz wave detection and imaging.

Example 2

A terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure, including a microbridge 100, a subwavelength absorption structure layer 90 is arranged on the bridge surface of the microbridge 100, and on the subwavelength absorption structure layer 90 A metal disc 91 and a concentric metal ring 92 surrounding the metal disc 91 are etched.

The microbridge 100 includes a substrate 10, a driver circuit 20 arranged on the substrate 10, a circuit interface 21 arranged on the driver circuit 20, a sacrificial layer 30 arranged on the driver circuit 20 and the substrate 10, bottom-up The support layer 40 with the bridge surface 41 and the bridge leg 42 arranged on the sacrificial layer 30 in sequence, the electrode lead layer 50 connected to the circuit interface 21, the dielectric layer 60 that can expose the electrode lead interface 51, and the electrode lead interface 51 The connected vanadium oxide layer 70 and the passivation layer 80 covering the vanadium oxide film, the sub-wavelength absorption structure layer 90 is arranged on the passivation layer 80 .

The microbridge structure serves as the detection unit of the terahertz microarray detector. The area of the microbridge structural unit of the array detector is 50 μm × 50 μm.

A method for preparing a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure, comprising the following preparation steps:

(1) First prepare the driving circuit 20 on the substrate 10, and prepare the circuit interface 21 on the driving circuit 20, as shown in a in FIG. 1;

(2) Clean the surface of the substrate 10 with the drive circuit 20 to remove surface contamination, and bake the substrate 10 with the drive circuit 20 at 200° C. to remove the moisture on the surface and enhance the bonding performance. Coating the photosensitive polyimide on the glue coating track, that is, preparing the sacrificial layer 30, by controlling the rotation speed to be 3000rpm when coating the glue, and baking the coated photosensitive polyimide at 120°C to remove part of the glue in the glue. Solvent, which is beneficial to the neatness of the exposure lines, adopts the NIKON photolithography machine to carry out the exposure process to the photosensitive polyimide, and the substrate 10 (prepared photosensitive polyimide) with the driving circuit 20 after exposure is sent to the automatic development track for gluing The developer is a standard positive photoresist developer TMAH, and the photosensitive polyimide after development presents an inverted trapezoidal pattern, as shown in b in Figure 1, and then the belt that is prepared with the photosensitive polyimide film is driven The substrate 10 of the circuit 20 is placed in an annealing oven protected by an inert gas for imidization treatment, the imidization temperature is set to rise in stages, the highest temperature is 350°C, and the constant temperature time is 90min. After imidization, the photosensitive polyamide The imine thickness is 2 μm, and the sacrificial layer 30 partially covers the substrate 10;

(3) Using PECVD equipment and frequency mixing sputtering technology to make low-stress silicon nitride, that is, the support layer 40, the thickness of the prepared support layer 40 is 0.4 μm, and then photolithography and etching are performed on the support layer 40 to etch out The pattern of the support layer 40, the support layer 40 partially covers the circuit interface pattern, as shown in c in Figure 1;

(4) Using sputtering equipment to prepare a layer of metal aluminum thin film as the electrode lead layer 50, the thickness is 50nm, and then adopt photolithography and reactive ion etching process to complete the patterning of the electrode lead layer 50, and the reactive ion etching gas is BCl _3. Cl ₂ and N ₂ , set the flow ratio of BCl ₃ , Cl ₂ and N ₂ to 20 sccm: 20 sccm: 5 sccm, the radio frequency power to 300W, the reaction chamber pressure to 4Pa, and the electrode width after patterning to be 1 μm, as shown in Figure 1 as shown in d;

(5) Using PECVD equipment and frequency mixing sputtering technology to produce low-stress silicon nitride, that is, the dielectric layer 60, the thickness of the prepared dielectric layer 60 is 50nm, and the passivation layer 60 dielectric film is completed by photolithography and reactive ion etching technology patterning, the etching gas is a mixed gas of CHF ₃ and O ₂ , the flow ratio of CHF ₃ and O ₂ is set to 20sccm: 3sccm, the RF power is 400W, and the reaction chamber pressure is 4Pa; after etching the dielectric layer 60, the support A rectangular through-hole pattern is formed on the layer to expose the electrode lead interface 51, as shown in e in FIG. 1 ;

(6) The vanadium oxide layer 70 is prepared by magnetron sputtering equipment, the sputtering power is controlled to be 300W during sputtering, the oxygen partial pressure is 3%, the sputtering time is 10min, and the annealing temperature is 300°C; the pattern of the vanadium oxide layer 70 The photolithography and reactive ion etching process are used to complete the process. The reactive ion etching gas is BCl ₃ , Cl ₂ and N ₂ . The flow ratio of BCl ₃ , Cl ₂ and N ₂ is set to 40sccm: 20sccm: 5sccm, and the radio frequency power is 300W. , the reaction chamber pressure is 4Pa; the patterned vanadium oxide layer 70 is a rectangular pattern, covering the electrode lead interface 51, as shown in f in Figure 1;

(7) Using PECVD equipment and frequency mixing sputtering technology to produce low-stress silicon nitride, that is, the passivation layer 80, the thickness of the prepared passivation layer 80 is 50nm, and the passivation layer 80 is completed by photolithography and reactive ion etching technology. For the patterning of the dielectric film, the etching gas is a mixed gas of CHF ₃ and O ₂ , the flow ratio of CHF ₃ and O ₂ is set to 20sccm: 3sccm, the radio frequency power is 400W, and the reaction chamber pressure is 40Pa; the etching passivation layer is 80 Finally, a rectangular pattern is formed to cover the vanadium oxide layer 70, as shown in g in FIG. 1 ;

(8) Using sputtering equipment to prepare a layer of metal aluminum film as the subwavelength absorption structure layer 90, the thickness is 100nm, and then adopt photolithography and reactive ion etching process to complete the patterning of the subwavelength absorption structure layer 90, and reactive ion etching The etching gas is BCl ₃ , Cl ₂ and N ₂ , the flow ratio of BCl ₃ , Cl ₂ and N ₂ is set to 20sccm: 20sccm: 5sccm, the radio frequency power is 250W, and the reaction chamber pressure is 4Pa; the patterned subwavelength absorption structure layer is The metal disc 91 and the metal ring 92 are shown as h in FIG. 1 . The diameter of the metal disc is 16 μm, the number of metal rings is 2, the outer diameter of the inner metal ring is 30 μm, the outer diameter of the outer metal ring is 44 μm, the width of the inner metal ring is 6 μm, and the width of the outer metal ring is 6 μm;

(9) The microbridge structure of the subwavelength absorption structure layer 90 is completed by bombarding with oxygen plasma, and the photosensitive polyimide (sacrifice layer) that has been imidized is removed to form a detection unit with a support layer structure. The cross-sectional schematic diagram of Fig. 1 is shown in i.

The terahertz radiation absorption curve of the microbridge structure obtained by CST software simulation is shown in Fig. 4 . It can be seen that the terahertz wave detection microbridge structure with integrated sub-wavelength metal ring absorption structure designed with the above parameters also has the characteristics of multi-frequency absorption, and has absorption peaks at frequencies such as 2.1THz and 3.2THz, and can be used for multi-band terahertz detection. Hertzian wave detection and imaging.

Claims (10)

1. A terahertz wave detection microbridge structure of an integrated subwavelength metal ring absorption structure, including a microbridge (100), is characterized in that, the bridge surface of the microbridge (100) is provided with a subwavelength absorption structure layer ( 90), the sub-wavelength absorption structure layer (90) is etched with a metal disc (91) and a concentric metal ring (92) surrounding the metal disc (91). 2. A kind of terahertz wave detection micro-bridge structure integrating a sub-wavelength metal ring absorbing structure according to claim 1, characterized in that, the micro-bridge (100) comprises a substrate (10), arranged on the substrate ( 10) on the drive circuit (20), the circuit interface (21) set on the drive circuit (20), the sacrificial layer (30) set on the drive circuit (20) and the substrate (10), from bottom to top A support layer (40) with a bridge surface (41) and bridge legs (42) arranged on the sacrificial layer (30), an electrode lead layer (50) connected to the circuit interface (21), and an exposed electrode lead interface The dielectric layer (60) of (51), the vanadium oxide layer (70) connected with the electrode lead interface (51) and the passivation layer (80) covering the vanadium oxide film, the subwavelength absorption structure layer (90) is set on the passivation layer (80). 3. The terahertz wave detection microbridge structure of a kind of integrated subwavelength metal ring absorbing structure according to claim 1, is characterized in that, described subwavelength absorbing structure layer (90) is aluminum, tungsten, titanium, platinum, Nickel, chromium or any one of their alloys has a thickness of 50-500nm. 4. A terahertz wave detection microbridge structure integrating a sub-wavelength metal ring absorption structure according to claim 1, wherein the metal disc (91) is located at the center of the bridge deck of the microbridge (100), And the diameter is 5 μm to 160 μm. 5. A terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure according to claim 1, characterized in that, the number of the metal rings (92) is 1 to 10, and the metal rings (92) The outer diameter of the ring (92) is 10 μm-180 μm, the width is 1 μm-30 μm, and the pitch is 1 μm-100 μm. 6. A terahertz wave detection microbridge structure integrating a subwavelength metal ring absorption structure according to claim 1, characterized in that the microbridge structure is used as a unit structure of a terahertz microbolometer detection array, and its The area is (20 μm×20 μm) to (200 μm×200 μm). 7. The terahertz wave detection microbridge structure integrating a sub-wavelength metal ring absorption structure according to claim 1, characterized in that, the material of the sacrificial layer (30) is polyimide, silicon dioxide, Any one of oxidized porous silicon and phosphosilicate glass; the support layer (40) is made of a single-layer film or a multi-layer film, and the material is silicon dioxide or silicon nitride, and the thickness of the support layer (40) is 0.1 ~1 μm; the electrode lead layer (50) is aluminum, tungsten, titanium, platinum, nickel, chromium or any alloy thereof, with a thickness of 10-200nm; the material of the dielectric layer (60) is silicon dioxide or silicon nitride, with a thickness of 50-300nm; the temperature coefficient of resistance of the vanadium oxide layer (70) is -2%/K to -6%/K, and a thickness of 30-300nm; the passivation layer (80) The material is silicon nitride, and the thickness is 50-300nm. 8. A method for preparing a terahertz wave detection microbridge structure integrating a sub-wavelength metal ring absorption structure according to any one of claims 1 to 7, characterized in that it comprises the following preparation steps: (1) Integrate the driving circuit on the substrate, and then prepare and pattern a sacrificial layer on the substrate with the driving circuit, exposing the circuit interface of the driving circuit; (2) preparing a supporting layer on the sacrificial layer, patterning the supporting layer, and partially covering the circuit interface; (3) Prepare an electrode lead layer on the support layer, and connect the electrode lead layer to the circuit interface of the drive circuit, pattern the electrode lead layer to obtain an electrode lead layer with an electrode lead interface; (4) Prepare a dielectric layer on the electrode lead layer, and expose the electrode lead interface after patterning the dielectric layer; (5) preparing a vanadium oxide layer on the dielectric layer, and patterning the vanadium oxide layer so that it covers and connects with the electrode lead interface; (6) preparing a passivation layer on the vanadium oxide layer, and patterning the passivation layer so that it covers the vanadium oxide layer; (7) Prepare a subwavelength absorption structure layer on the passivation layer, and pattern the subwavelength absorption structure layer as a metal disc and metal ring structure; (8) The sacrificial layer is released to form a terahertz wave detection microbridge structure integrated with a subwavelength metal ring absorption structure, and then packaged to form a detection device. 9. The preparation method of a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorbing structure according to claim 8, characterized in that, in the steps (2), (4), and (6) The patterned support layer, dielectric layer and passivation layer are completed by photolithography and reactive ion etching process. The reactive ion etching gas is a mixed gas of fluorine-based gas and _O2 , and the mixture of fluorine-based gas and _O2 The flow ratio is (10:20)~(90:10), the radio frequency power is 100~500W, and the reaction chamber pressure is 2~10Pa. 10. The preparation method of a terahertz wave detection microbridge structure integrating a subwavelength metal ring absorbing structure according to claim 8, characterized in that, in the steps (3), (5), and (7) The patterned electrode lead layer, vanadium oxide layer, and subwavelength absorption structure layer are completed by photolithography and reactive ion etching. The reactive ion etching gas is a mixed gas of BCl ₃ , Cl ₂ and neutral gas. The neutral gas is any one of N ₂ , CH ₄ or a mixture of both, the flow ratio of BCl ₃ and Cl ₂ is (10:30) to (90:10), the flow rate of the neutral gas 0-90sccm, RF power 100-500W, reaction chamber pressure 2-10Pa.