WO2019153322A1

WO2019153322A1 - Infrared imaging device, fabrication method therefor, and simulation infrared spherical camera

Info

Publication number: WO2019153322A1
Application number: PCT/CN2018/076409
Authority: WO
Inventors: 徐云; 白霖; 陈华民; 宋国峰; 陈良惠
Original assignee: 中国科学院半导体研究所
Priority date: 2018-02-12
Filing date: 2018-02-12
Publication date: 2019-08-15

Abstract

Provided are an infrared imaging device having a flexible spherical structure, a fabrication method for said device, and a simulation infrared spherical camera. The infrared imaging device having a flexible spherical structure comprises: a substrate and an infrared detector array located on an inner surface of the substrate, wherein the substrate is a flexible spherical substrate. The infrared imaging device having a flexible spherical structure, the fabrication method for said device, and the simulation infrared spherical camera of the present disclosure allow for resilience to repeated bending and can be applied to the fields of wearable devices, bionic tissue, human-computer interaction and the like. The biological integration capability of infrared photoelectric imaging devices is substantially improved, the fabrication process is more mature, and the processing cost is low.

Description

Infrared imaging device and preparation method thereof, biomimetic infrared spherical camera

Technical field

The present disclosure relates to the field of flexible ductile electronics, semiconductor fabrication, and optoelectronic imaging technology, and more particularly to a flexible spherical structure infrared imaging device and a method of fabricating the same, and a biomimetic infrared spherical camera.

Background technique

The infrared detector is a device that converts an incident infrared radiation signal into an electrical signal, and can capture infrared light that is not perceived by the human eye and output it in the form of an electrical signal. Materials and devices for infrared detection mainly include pyroelectric detectors based on thermal effects, photodetectors based on photoelectric effects, and new material detectors based on graphene, carbon nanotubes, and quantum dots. At present, the technology of photodetector is the most mature. The infrared detector based on photoelectric technology can be prepared into a dense detector array, that is, the infrared focal plane. The focal plane is the core component of the infrared camera, and it is imaged in night vision. Astronomical observation, industrial control, medical, communication and many other fields have extremely wide applications.

The current infrared photodetectors are mainly made based on semiconductor photosensitive materials, and the materials and structures are rigid and non-deformable. With the imaging accuracy of the camera, the imaging details and other performance requirements continue to increase, the focal plane is developing in a more dense and large-scale direction. However, because the focal plane needs to be used in conjunction with the lens of the convex surface, the nature of the rigid plane of the focal plane damages the imaging effect to a certain extent, and the pixel of the edge has a certain degree of distortion, and the angle of the field of view is also affected. limit.

In nature, the animal's eyes are generally spherical, the front of the eyeball as a whole acts as a lens, the incident light is focused on the retina surface at the back of the eyeball, and finally the optic nerve transmits signals to the brain to obtain the perception of the image. The spherical structure has the advantages of large field of view angle, flexible rotation and small edge distortion, and is an important direction for further development and integration of imaging systems in the future. Analogous to an artificial imaging system, the photodetector array functions as the retina at the back of the eye. The flexibility and surface enhancement of the photodetector array is critical to such an imaging system that simulates a spherical design.

Summary of the invention

(1) Technical problems to be solved

In view of the above technical problems, the main object of the present disclosure is to provide a flexible spherical structure infrared imaging device and a preparation method thereof, and a bionic infrared spherical camera to solve the problem that the infrared detector array structure is fixed, edge distortion, and cannot be applied to bionic eyes. Technical problems in the preparation of the structure.

(2) Technical plan

In accordance with one aspect of the present disclosure, a flexible spherical structure infrared imaging device is provided comprising: a substrate and an array of infrared detectors on an inner surface of the substrate; wherein the substrate is a flexible spherical substrate.

In some embodiments, the infrared detector array is a rigid array of semiconductor infrared detectors, and the photosensitive material of each detector is an inorganic semiconductor material.

In some embodiments, the infrared detector array is distributed in an island structure on an inner surface of the substrate, forming a metal interconnection between the detectors, whereby the flexible spherical structure infrared imaging device Stress is concentrated on the interconnect between the detectors and the flexible spherical substrate during deformation to achieve strain isolation.

In some embodiments, the semiconductor infrared detector is a mesa-type InGaAs/InP short-wave infrared detector, and the epitaxial wafer structure comprises, in order from bottom to top, an InP substrate, an InGaAs sacrificial layer, an N-type doped InP contact layer, InGaAs absorber layer and InP cap layer.

According to another aspect of the present disclosure, there is provided a bionic infrared spherical camera comprising the flexible spherical structure infrared imaging device, further comprising a lens and a readout circuit; wherein the lens is for focusing incident light in the The flexible spherical structure infrared imaging device is configured to convert an optical signal received by the infrared imaging device into an electrical signal; the readout circuit is configured to extract the flexible spherical structure infrared imaging The electrical signals of each detector in the detector array of the device are imaged.

According to another aspect of the present disclosure, there is provided a method of fabricating a flexible spherical structure infrared imaging device comprising the steps of: providing a flexible spherical substrate and stretching it to a flat state; and a substrate after stretching to a flat state The inner surface forms an array of infrared detectors and shrinks the substrate to a spherical surface, thereby completing the preparation of the flexible spherical structure infrared imaging device.

In some embodiments, the step of providing a flexible spherical substrate and stretching it to a flat state comprises: providing a malleable flexible substrate having a semi-spherical concave surface; and uniformly spreading the expandable flexible substrate circumferentially by a jig Stretching to a flat state; forming an infrared detector array on the inner surface of the substrate after stretching to a flat state, and shrinking the substrate to the spherical surface comprises: forming a plurality of mesa-type infrared detectors arranged in an array and forming an infrared a metal interconnection between the detectors; wherein the infrared detector is a rigid array of semiconductor infrared detectors, the photosensitive material of each detector is an inorganic semiconductor material; and the front side of the infrared detector array after the metal interconnection is formed Depressing on the flexible substrate stretched to a flat state and curing to complete bonding; removing the substrate and the sacrificial layer on the back side of the infrared detector array; and uniformly shrinking the substrate to a hemispherical concave shape.

In some embodiments, the step of forming each of the mesa-type semiconductor infrared detectors and forming the metal interconnection between the infrared detectors comprises: forming an epitaxial wafer of the semiconductor infrared detector; forming a first mesa and a portion on the epitaxial wafer Forming a passivation layer on the first mesa and the second mesa; forming a first opening on the passivation layer corresponding to the first mesa; and forming a second opening on the passivation layer corresponding to the second mesa; Forming a P-type ohmic contact metal at the first opening, forming an N-type ohmic contact metal at the second opening; forming a layer of flexible polymer material between the surface of the epitaxial wafer of the semiconductor infrared detector and the detector, and correspondingly Forming an opening at a position of the P-type ohmic contact metal and the N-type ohmic contact metal; forming a P-pole metal interconnection line and an N-electrode metal interconnection line between the detector arrays on the surface of the flexible polymer material layer; wherein The P-electrode interconnection and the N-electrode interconnection are respectively connected to the P-type ohmic contact metal and the N-type ohmic contact metal through openings.

In some embodiments, the forming the epitaxial wafer of the semiconductor infrared detector comprises: sequentially forming a sacrificial layer, a contact layer, an absorbing layer, and a cap layer on the substrate; wherein the first mesa is etched to the Contacting the surface of the layer, the second mesa is etched to the surface of the sacrificial layer, the first opening is formed on the cap layer, and the second opening is formed on the contact layer.

In some embodiments, the first mesa and the second mesa are formed by mask lithography, dry etching or wet etching techniques; the passivation layer is formed by chemical vapor deposition; the passivation layer The material is silicon dioxide, silicon nitride or polyimide; the ohmic contact metal and metal interconnection are formed by magnetron sputtering, electron beam evaporation or thermal evaporation; the ohmic contact metal is Au, Ti a single layer electrode of a Pt, Pd, Cr, Zn or AuGeNi alloy or a composite layer electrode thereof, the metal interconnect is made of Au; the flexible polymer material is polyimide; the ductile The flexible substrate is made of PDMS or Ecoflex; the P-electrode interconnection and the N-polar metal interconnection are straight conductors, curved serpentine conductors or solid space conductors, P-electrode interconnections and N-pole metal interconnections. The lines are distributed in two directions, horizontally and vertically.

(3) Beneficial effects

It can be seen from the above technical solutions that the flexible spherical structure infrared imaging device, the preparation method thereof and the bionic infrared spherical camera of the present disclosure have at least one of the following beneficial effects:

(1) The flexible spherical structure infrared imaging device of the present disclosure has repeated bending recoverability, and the final shape can be flexibly adjusted by the shape of the flexible substrate, and can be applied to the fields of wearable devices, bionic tissues, human-computer interaction, etc., and can be greatly improved. The bio-integration capabilities of infrared optoelectronic imaging devices provide more design freedom for optoelectronic imaging devices.

(2) Flexible Spherical Structure The photosensitive material of the infrared imaging device is a conventional inorganic semiconductor material, which itself does not have bendability and ductility. The present disclosure utilizes a substrate removal method to transfer a rigid detector array onto a flexible substrate. Forming an island-like structure, the stress is mainly concentrated on the flexible substrate and the interconnecting line between the island-like structures during stretching and bending deformation, thereby achieving flexibility and ductility while ensuring that the detector array is under bending conditions. Performance stability.

(3) Compared with the conventional rigid planar semiconductor infrared imaging device, the flexible spherical structure infrared imaging device provided by the present disclosure is closer to the animal's eyeball structure, and has the advantages of large field of view angle and small image edge distortion. Compared with infrared detectors based on new materials, such as graphene, carbon nanotubes, etc., the imaging array photosensitive materials provided by the present disclosure are conventional semiconductor materials, the overall preparation process is more mature, the processing cost is low, and the performance and The stability is much higher than the new material and can be put into practical use.

DRAWINGS

The drawings are intended to provide a further understanding of the disclosure, and are in the In the drawing:

1 is a schematic view of a flexible spherical structure infrared imaging device in an embodiment of the present disclosure.

2 is a flow chart of a method for preparing a flexible spherical structure infrared imaging device according to an embodiment of the present disclosure.

3 is a schematic structural view of an epitaxial wafer of a semiconductor infrared detector according to an embodiment of the present disclosure.

4 is a schematic cross-sectional view showing a process of preparing a mesa-type upper and lower electrode detector from an epitaxial wafer in an embodiment of the present disclosure.

Figure 5 is a top plan view of the detector structure on the surface of the epitaxial wafer after the planar semiconductor process is completed in the embodiment of the present disclosure.

6 is a schematic cross-sectional view showing the planar semiconductor process after the planar semiconductor process is completed, the surface of the package is bonded to the pre-stretched flexible substrate with a ductile flexible material, and the substrate and the sacrificial layer are finally removed.

FIG. 7 is a three-dimensional schematic diagram of the surface of a semiconductor device after the planar semiconductor process is completed, bonded to the pre-stretched flexible substrate with a ductile flexible material, and finally the substrate and the sacrificial layer are removed.

Symbol Description

1-P contact layer and cap layer, 2-light absorbing layer, 3-N type contact layer, 4-sacrificial layer, 5-substrate, 6-passivation layer, 7-N type ohmic contact metal, 8-P type Ohmic contact metal, 9-flexible polymer material polyimide, 10-N metal interconnect, 11-P metal interconnect, 12-protective bonding layer, 13-substrate, 14-semiconductor infrared detector Array.

Detailed ways

The present disclosure will be further described in detail below with reference to the specific embodiments thereof and the accompanying drawings.

It should be noted that in the drawings or the description of the specification, the same reference numerals are used for similar or identical parts. Implementations not shown or described in the figures are in the form known to those of ordinary skill in the art. Additionally, although an example of a parameter containing a particular value may be provided herein, it should be understood that the parameter need not be exactly equal to the corresponding value, but rather may approximate the corresponding value within an acceptable tolerance or design constraint. The directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only referring to the directions of the drawings. Therefore, the directional terminology used is intended to be illustrative of the scope of the disclosure.

The primary structure of the flexible spherical structure infrared imaging device of the present disclosure includes a flexible spherical substrate and an array of infrared detectors that are transferred to its interior surface. The infrared detector is a semiconductor infrared detector comprising a rigid photodiode having a mesa structure; the electrodes are interconnected by a curved metal wire; and the stress is used to concentrate the metal between the detectors when the whole bending is performed. On the wire and on the flexible substrate. The overall structure of the imaging device prepared by the present disclosure is a hemispherical surface, and the specific size and bending radius thereof can be adjusted as needed, thereby solving the defects of imaging distortion of the edge of the planar detector array and small field of view. Moreover, the infrared imaging device based on the preparation method conforms to the bionic design, and is beneficial to applications in the fields of wearable devices, bionic tissues, human-computer interaction, etc., and provides higher imaging quality and more design freedom for imaging system design.

As shown in FIG. 1, the flexible spherical structure infrared imaging device of the present disclosure includes a substrate 13 and an infrared detector array 14 on an inner surface of the substrate 13; wherein the substrate 13 is a flexible spherical substrate. Compared with the conventional rigid planar infrared imaging device, the flexible spherical structure infrared imaging device provided by the present disclosure is closer to the animal's eyeball structure, and has the advantages of large field of view angle and small image edge distortion.

Wherein, the infrared detector array is a rigid semiconductor infrared detector array, and the photosensitive material of each detector is a conventional inorganic semiconductor material, which itself does not have bendability and ductility, and the present disclosure utilizes substrate removal means to be rigid. The semiconductor infrared detector array is transferred onto the flexible substrate to form an island-like structure, and metal interconnections are formed between the detectors (ie, between the island structures), thereby being deformed (eg, stretched, bent) When the stress is concentrated, the stress is mainly concentrated on the flexible substrate and the interconnection line between the island structures, thereby achieving strain isolation. This achieves both bendability and ductility while maintaining the performance stability of the detector array under bending conditions. Compared with infrared detectors based on new materials, such as graphene, carbon nanotubes, etc., the imaging array photosensitive materials provided by the present disclosure are conventional semiconductor materials, the overall preparation process is more mature, the processing cost is low, and the performance and The stability is much higher than the new material and can be put into practical use.

The present disclosure also provides a biomimetic infrared spherical camera comprising the flexible spherical structure infrared imaging device, further comprising a lens and a readout circuit. Wherein the lens is for focusing incident light on a detector array of the flexible spherical structure infrared imaging device; the flexible spherical structure infrared imaging device is configured to convert an optical signal received thereby into an electrical signal; An output circuit is used to extract an electrical signal from each detector in the detector array of the flexible spherical structure infrared imaging device for imaging.

In addition, the present disclosure further provides a method for preparing a flexible spherical structure infrared imaging device. As shown in FIG. 2, the method for preparing the flexible spherical structure infrared imaging device includes:

Providing a flexible spherical substrate and stretching it to a flat state;

The infrared detector array is formed on the inner surface of the substrate after being stretched to a flat state, and the substrate is shrunk to a spherical surface, thereby completing the preparation of the flexible spherical structure infrared imaging device.

More specifically, the method for preparing the flexible spherical structure infrared imaging device includes:

Step 1: Growth of an epitaxial wafer by metal organic chemical vapor deposition MOCVD or molecular beam epitaxy MBE apparatus: a sacrificial layer, a contact layer, an absorption layer, and a cap layer are sequentially formed on the substrate. In contrast to prior art epitaxial wafers, the present disclosure incorporates a sacrificial layer having a high corrosion selectivity to adjacent layers under the epitaxial layer of the detector in epitaxial wafer growth of the semiconductor infrared detector.

Step 2: Using a semiconductor fabrication process such as photolithography etching, metal growth, and passivation film growth, an array-type mesa-type detector is prepared. The upper mesa (also referred to as the first mesa) is etched to the surface of the lower contact layer of the detector, and the lower mesa (also referred to as the second mesa) is etched to the surface of the sacrificial layer. The device grows the surface P, N electrodes and forms an ohmic contact.

Step 3: Spin-coating the flexible polymer material on the surface of the device, patterning the P and N electrode openings, and forming a metal interconnect shape between the devices. This layer of flexible polymer material is used to protect subsequent metal interconnects.

Step 4: The metal is grown and patterned to form a metal interconnect between the detector arrays, and the metal interconnects are grown on the surface of the flexible polymeric material of step 3. The metal interconnect is a single layer, which is routed in both directions, and finally realizes the signal output of a single detector in a manner similar to word lines and bit lines. The metal interconnects of the detector are ultimately led out to form an interface on the outside of the array.

Step 5: Spin coating the uncured, ductile flexible material on the surface of the device to protect the front side of the detector and the metal interconnects between the devices and for bonding to the flexible substrate.

Step 6: A malleable flexible material substrate having a semi-spherical concave surface is provided, which is uniformly stretched to a flat state in a circumferential distribution using a jig.

Step 7: The detector array is buckled down on the flexible substrate stretched to a flat state and cured to complete the bonding.

Step 8: Thoroughly remove the substrate and sacrificial layer on the back side of the detector array with a selective etching solution so that only the device array remains on the flexible material substrate.

Step 9: Slowly and uniformly shrink the semi-spherical concave flexible substrate to the original state, thereby completing the preparation of the infrared spherical imaging device of the flexible spherical structure.

Wherein, the epitaxial wafer of the semiconductor infrared detector is an indium-phosphorus or gallium-arsenide-based epitaxial wafer, and an epitaxial wafer of an infrared detector epitaxially having a p-i-n structure.

The sacrificial layer having a high etching selectivity ratio with the adjacent layer has a high degree of lattice matching with the substrate, does not seriously affect the growth quality of the upper layer during growth, and corrodes the layer in the wet etching of the semiconductor device preparation process. At the same time, the epitaxial layer has little corrosive effect on adjacent layers. The indium gallium arsenide material can serve as a sacrificial layer for indium phosphorus based devices.

The technique for preparing and forming the mesa is mask lithography, dry etching or wet etching in a semiconductor processing and fabrication process.

The passivation layer material is a passivation film of silicon dioxide, silicon nitride or polyimide, and the passivation layer growth technique is chemical vapor deposition.

The ohmic contact metal of the device is a single layer electrode of Au, Ti, Pt, Pd, Cr, Zn or AuGeNi alloy or a composite layer electrode of the combination thereof, and the metal interconnection (interconnect metal) is made of Au. The metal growth technique is magnetron sputtering or electron beam evaporation or thermal evaporation. The metal interconnect is a straight wire, a curved serpentine wire or a solid space wire.

The flexible polymeric material is polyimide.

In the above step 8, the selective etching solution is determined according to the material to be corroded, and the etching solution of the citric acid and hydrogen peroxide ratio can selectively remove the sacrificial layer composed of indium gallium arsenide from the indium phosphorus.

In the

above steps

5 and 6, the ductile flexible material is a silica gel having good ductility and mechanical properties, specifically PDMS or Ecoflex. Wherein, the uncured silica gel is used in the above step 5, and the cured solidified silica gel produced by the mold is used in the above step 6.

The flexible spherical structure infrared imaging device of the present disclosure and a method of fabricating the same are described in detail below with reference to FIGS. 3-7. 3 is a schematic structural view of a semiconductor infrared detector epitaxial wafer. As shown in FIG. 3, the semiconductor infrared detector epitaxial wafer includes: a P contact layer and a cap layer 1, a light absorbing layer 2, an N contact layer 3, a sacrificial layer 4, and a substrate. 5. Taking an InGaAs/InP short-wave infrared detector as an example, the epitaxial wafer includes an InP cap layer, an InGaAs absorber layer, an N-type doped InP contact layer, an InGaAs sacrificial layer, and an InP substrate. The epitaxial wafers were grown using metal organic chemical vapor deposition MOCVD or molecular beam epitaxy MBE equipment.

4 is a schematic cross-sectional view showing a process of preparing a mesa-type upper and lower electrode detector from an epitaxial wafer. First, as shown in (1) to (2) of FIG. 4, etching of the first mesa is performed using a photolithography mask process, and the surface of the InP contact layer is stopped. Then, as shown in (3) of FIG. 4, the etching of the second mesa is continued using the photolithography mask process, and the surface of the sacrificial layer of InGaAs is stopped. Next, a SiNx passivation layer 6 is grown on the mesa of the device as shown in (4) of FIG. 4, and holes are formed in the photosensitive surface and the N contact layer. As shown in (5) of FIG. 4, annular metal electrodes are grown in the upper and lower mesa openings of the device: an N-type ohmic contact metal 7 of AuGeNi/Au and a P-type ohmic contact metal 8 of Ti/Pt/Au, respectively, after completion Thermal annealing to form an ohmic contact. Finally, a flexible polymer material polyimide 9 is spin-coated between the surface of the device and the device as shown in (6) of FIG. 4, and openings are formed at the P and N electrodes of the device for interconnection contact, and mutual devices are formed. Wire the pattern to carry and protect the metal wires. Metal is grown thereon and patterned to form interconnecting wires.

Figure 5 is a top plan view of a completed single photodetector structure. The mesas are protected by polyimide 9 and supported under the interconnects. The N-electrode interconnection 10 and the P-electrode interconnection 11 are respectively routed in the horizontal and vertical directions on the detector, and the interconnection and the ohmic contact metal together constitute a line connecting the devices. The P and N interconnects are electrically isolated using SiNx on the device surface.

As shown in FIG. 6 and FIG. 7, after the planar semiconductor process is completed, the interconnected detector arrays are formed on the epitaxial wafer. Next, the main component of the silica gel PDMS (polydimethylsiloxane, DOW CORNING, USA) and the curing agent were uniformly mixed at a mass ratio of 10:1, then uniformly stirred for 20 minutes, then vacuum degassed to no bubbles, and the mixture was well mixed. The PDMS is spin coated on the surface of the detector array to form a protective bonding layer 12 for protecting the front side of the detector and the metal interconnects between the devices, as well as for bonding to the flexible substrate.

Prepare a hemispherical ductile flexible substrate: mix the main component of the silica gel PDMS (polydimethylsiloxane, DOW CORNING, USA) with the curing agent in a mass ratio of 10:1, then uniformly stir for 20 minutes, then vacuum degas. Until there are no bubbles. Then, it was placed in a curing mold of a ready shape, and baked in an oven at 80 ° C for 2 hours to be cured into a hemispherical flexible substrate 13 . Here, the size and radius of the hemispherical flexible substrate can be designed according to the needs of the actual device, and can be adjusted by changing the shape of the mold.

The hemispherical flexible substrate was uniformly stretched to a flat shape in the circumferential direction (i.e., stretched from a hemispherical surface to a plane), and then placed under ultraviolet ozone for 3 minutes to enhance the adhesion of the surface.

The epitaxial wafer was closely inverted on a flexible material substrate stretched to a flat state, and then heat-cured at 80 ° C for 2 hours to make the epitaxial wafer adhere well to the flexible material substrate. The substrate and the sacrificial layer are then removed, and the InP substrate is removed using an etching solution of hydrochloric acid and phosphoric acid having a high etching selectivity to InP/InGaAs, and then a citric acid: hydrogen peroxide ratio having a high etching selectivity to InGaAs/InP is used. The etching solution etches away the sacrificial layer of InGaAs, at which point only the detector array and interconnect lines are left on the flexible material substrate.

Finally, the hemispherical flexible substrate is slowly shrunk to its original shape, and the infrared imaging device of the flexible spherical structure is prepared. Subsequent interconnections that are reserved outside the detector array can be connected to the back-end drive and readout circuits through the leads, and combined with the lens system, the mechanical system is put into practical use.

Heretofore, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the flexible spherical structure infrared imaging device of the present disclosure, the preparation method thereof, and the bionic infrared spherical camera.

It should be noted that the implementations that are not shown or described in the drawings or the text of the specification are all known to those of ordinary skill in the art and are not described in detail. In addition, the above definitions of the various elements and methods are not limited to the specific structures, shapes or manners mentioned in the embodiments, and those skilled in the art can simply modify or replace them.

In the description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, Figure, or a description of it. However, the method disclosed is not to be interpreted as reflecting the intention that the claimed invention requires more features than those recited in the claims. Rather, as disclosed in the following claims, the disclosed aspects are less than all features of the single embodiments disclosed herein. Therefore, the claims following the specific embodiments are hereby explicitly incorporated into the specific embodiments, and each of the claims as a separate embodiment of the present disclosure.

The specific embodiments of the present invention have been described in detail with reference to the specific embodiments of the present disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the present disclosure are intended to be included within the scope of the present disclosure.

Claims

A flexible spherical structure infrared imaging device comprising: a substrate and an array of infrared detectors on an inner surface of the substrate; wherein the substrate is a flexible spherical substrate.
The flexible spherical structure infrared imaging device according to claim 1, wherein the infrared detector array is a rigid semiconductor infrared detector array, and the photosensitive material of each detector is an inorganic semiconductor material.
The flexible spherical structure infrared imaging device according to claim 1 or 2, wherein the infrared detector array is distributed in an island structure on an inner surface of the substrate, and metal interconnection lines are formed between the detectors, Thereby, stress is concentrated on the interconnect line between the detectors and the flexible spherical substrate when the flexible spherical structure infrared imaging device is deformed, thereby achieving strain isolation.
The flexible spherical structure infrared imaging device according to claim 2, wherein the semiconductor infrared detector is a mesa-type InGaAs/InP short-wave infrared detector, and the epitaxial wafer structure comprises, in order from bottom to top, an InP substrate, an InGaAs sacrifice. Layer, N-type doped InP contact layer, InGaAs absorber layer, and InP cap layer.
A bionic infrared spherical camera comprising the flexible spherical structure infrared imaging device according to any one of claims 1 to 4, further comprising a lens and a readout circuit;

The lens is for focusing incident light on a detector array of the flexible spherical structure infrared imaging device;

The flexible spherical structure infrared imaging device is configured to convert an optical signal received thereby into an electrical signal;

The readout circuit is configured to extract an electrical signal of each detector in the detector array of the flexible spherical structure infrared imaging device for imaging.
A method for preparing a flexible spherical structure infrared imaging device comprises the following steps:

Providing a flexible spherical substrate and stretching it to a flat state;

The infrared detector array is formed on the inner surface of the substrate after being stretched to a flat state, and the substrate is shrunk to a spherical surface, thereby completing the preparation of the flexible spherical structure infrared imaging device.
The method of fabricating a flexible spherical structure infrared imaging device according to claim 6, wherein

The step of providing a flexible spherical substrate and stretching it to a flat state comprises:

a malleable flexible substrate providing a semi-spherical concave surface;

The ductile flexible substrate is uniformly stretched to a flat state by a circumferential distribution using a jig;

The step of forming an infrared detector array on the inner surface of the substrate after stretching to a flat state and shrinking the substrate to the spherical surface includes:

Forming a plurality of mesa-type infrared detectors arranged in an array and forming a metal interconnection between the infrared detectors; wherein the infrared detector is a rigid array of semiconductor infrared detectors, and the photosensitive material of each detector is an inorganic semiconductor material;

Forming the front surface of the infrared detector array after forming the metal interconnection line on the flexible substrate stretched to a flat state, and curing to complete the bonding;

Removing the substrate and sacrificial layer on the back side of the infrared detector array;

The substrate is uniformly shrunk to a hemispherical concave shape.
The method of fabricating a flexible spherical structure infrared imaging device according to claim 7, wherein the step of forming each mesa-type semiconductor infrared detector and forming a metal interconnection between the infrared detectors comprises:

Forming an epitaxial wafer of a semiconductor infrared detector;

Forming a first mesa and a second mesa on the epitaxial wafer;

Forming a passivation layer on the first mesa and the second mesa, and forming a first opening on the passivation layer corresponding to the first mesa, and forming a second opening on the passivation layer corresponding to the second mesa;

Forming a P-type ohmic contact metal at the first opening and forming an N-type ohmic contact metal at the second opening;

Forming a layer of flexible polymer material between the surface of the epitaxial wafer of the semiconductor infrared detector and the detector, and forming an opening at a position corresponding to the P-type ohmic contact metal and the N-type ohmic contact metal;

Forming a P-pole metal interconnect line and an N-electrode metal interconnect line between the detector arrays on the surface of the flexible polymer material layer; wherein the P-pole metal interconnect line and the N-pole metal interconnect line are respectively opened The hole is connected to the P-type ohmic contact metal and the N-type ohmic contact metal.
The method of fabricating a flexible spherical structure infrared imaging device according to claim 8, wherein the step of forming an epitaxial wafer of the semiconductor infrared detector comprises sequentially forming a sacrificial layer, a contact layer, an absorbing layer, and a cap layer on the substrate. ;among them,

The first mesa is etched to the surface of the contact layer, the second mesa is etched to the surface of the sacrificial layer, the first opening is formed on the cap layer, and the second opening is formed in the second opening On the contact layer.
The method of manufacturing a flexible spherical structure infrared imaging device according to claim 8, wherein

Forming the first mesa and the second mesa by mask lithography, dry etching or wet etching;

Forming the passivation layer by a chemical vapor deposition technique; the passivation layer is made of silicon dioxide, silicon nitride or polyimide;

Forming the ohmic contact metal and metal interconnect by magnetron sputtering, electron beam evaporation or thermal evaporation techniques; the ohmic contact metal is a single layer electrode of Au, Ti, Pt, Pd, Cr, Zn or AuGeNi alloy or a combined layer electrode of the combination, the metal interconnect is made of Au;

The flexible polymer material is polyimide;

The ductile flexible substrate is made of PDMS or Ecoflex;

The P-electrode interconnection and the N-electrode interconnection are straight conductors, curved serpentine conductors or three-dimensional space conductors, and the P-electrode interconnections and the N-electrode interconnections are respectively oriented in the horizontal and vertical directions. distributed.