CN111486973A - Full-flexible pyroelectric infrared detector - Google Patents

Abstract

The invention discloses a fully flexible pyroelectric infrared detector, which relates to the field of pyroelectric sensor structure design, including a flexible infrared radiation modulation mechanism and a flexible infrared sensitive unit; the flexible infrared radiation modulation mechanism is supported by single-end or double-end Metal film cantilever beam, by applying a voltage signal of a certain frequency between the cantilever beam and the upper electrode layer of the flexible infrared sensitive unit, the cantilever beam can move up and down within a certain range according to the corresponding frequency, so as to periodically interact with the upper surface of the flexible infrared sensitive unit. separation and contact, so as to realize modulation of infrared radiation; the invention solves the problem that the existing pyroelectric infrared detector adopts a mechanical chopper and is difficult to achieve integration and flexibility, so that the pyroelectric infrared detector can be applied to Wearable electronic devices such as flexible temperature sensors, flexible infrared cameras.

Description

A fully flexible pyroelectric infrared detector

technical field

The invention relates to the field of structural design of pyroelectric detectors, in particular to a fully flexible pyroelectric infrared detector.

Background technique

Pyroelectric infrared detector is a thermal infrared detector made of the effect of spontaneous polarization of pyroelectric materials changing with temperature. Traditional pyroelectric infrared detectors are made of rigid ferroelectric ceramics or Ferroelectric crystals, the existing flexible pyroelectric infrared detectors based on ferroelectric polymers have the advantages of light weight, flexibility, impact resistance, corrosion resistance, and easy processing. good application prospects.

However, the working principle of the pyroelectric infrared detector determines that it can only respond to changing temperature signals. Therefore, in order to detect static targets, a mechanical chopper must be added in front of the detector. The chopper rotates at a certain frequency to convert the static infrared Radiation modulation is dynamic infrared radiation that is periodically switched on and off. The appearance of the chopper makes it difficult to integrate, miniaturize, and even less flexible infrared detectors based on the pyroelectric effect, which greatly reduces the application prospects of pyroelectric infrared detectors in flexible electronics, portable devices, etc. It is necessary to develop a fully flexible pyroelectric infrared detector without mechanical chopper.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a fully flexible pyroelectric infrared detector, thereby laying a foundation for the application of pyroelectric infrared detectors in wearable portable devices, such as flexible temperature sensors, flexible infrared thermal imagers, and the like.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

A fully flexible pyroelectric infrared detector, comprising a flexible infrared radiation modulation mechanism and a flexible infrared pyroelectric sensitive unit, wherein the flexible infrared pyroelectric sensitive unit includes an insulating layer, an upper electrode layer, A pyroelectric sensitive film and a lower electrode layer; the flexible infrared radiation modulation mechanism is installed on the insulating layer, and the flexible infrared radiation modulation mechanism includes one or two support columns and a metal film, and the metal film is installed on the support column A single-ended or double-ended cantilever beam is formed; a voltage source is connected between the metal film of the cantilever beam and the upper electrode of the flexible infrared pyroelectric sensitive unit through a circuit switch, and the circuit switch can be controlled by a switch control circuit; A voltage signal of a certain frequency and amplitude is applied between the metal film and the upper electrode of the flexible infrared pyroelectric sensitive unit, and the metal film of the cantilever beam can move up and down within a certain range according to the corresponding frequency, so as to be compatible with the flexible infrared pyroelectric sensitive unit. The top insulating layer of the unit is periodically separated and contacted, so that the heat flow generated by the incident infrared radiation is periodically transferred to the pyroelectric sensitive film and causes its temperature to change periodically.

Further, the support column can be made of silicon oxide, silicon nitride, polysilicon inorganic materials, or polyimide, polydimethylsiloxane (PDMS) organic materials, or aluminum, nickel, chromium, copper, gold, Titanium common metal material preparation.

Further, the single-ended cantilever beam further includes a limiting structure mounted on the insulating layer, used to limit the upper intercept point of the upward movement of the metal film of the cantilever beam.

Further, the metal thin film of the cantilever beam can be prepared from common and easy-to-process metal materials such as aluminum, nickel, chromium, copper, gold, and titanium.

Further, the insulating layer can be prepared using silicon oxide, silicon nitride, polysilicon inorganic materials, or polyimide, polydimethylsiloxane (PDMS) organic materials.

Further, the pyroelectric sensitive film can adopt flexible pyroelectric films of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, odd-numbered nylon, polyvinyl chloride or polypropylene. Polymer preparation, or a doping system with a flexible pyroelectric polymer as the main body, a doping system doped with barium strontium titanate and lead zirconate titanate inorganic ferroelectric ceramics.

Further, the circuit switch and the switch control circuit can be implemented by separate circuit modules, or can be implemented by an integrated circuit.

Further, the fully flexible pyroelectric infrared detector can be partially or completely realized by using a flexible film process and a micro-fabrication process from bottom to top as required.

The present invention also provides a method for preparing the above-mentioned fully flexible infrared pyroelectric detector without an external chopper, comprising the following steps:

Step 1: The flexible pyroelectric polymer is completely dissolved into a solution, and the solution is evenly coated on the flat substrate, and then baked in a constant temperature oven until the solution is completely volatilized, the flexible pyroelectric polymer forms a sensitive film, and then the The sensitive film is peeled off to obtain a pyroelectric sensitive film;

Step 2: preparing metal electrode layers of the same thickness on both the upper surface and the lower surface of the pyroelectric sensitive film by means of evaporation and sputtering to form upper and lower electrode layers;

Step 3: preparing an inorganic insulating layer of silicon oxide or silicon nitride on the upper electrode layer by chemical vapor deposition; or preparing an organic insulating layer of polyimide or PDMS by spin coating and casting;

Step 4: Prepare silicon oxide or silicon nitride inorganic insulating support pillars on the upper electrode layer or insulating layer by chemical vapor deposition, or prepare polyimide or polyimide on the upper electrode layer or insulating layer by spin coating and casting methods. PDMS organic insulating support column; or use evaporation, sputtering method to prepare metal support column on the insulating layer;

Step 5: prepare a sacrificial layer on the insulating layer with the same height as the support column, and then use evaporation and sputtering methods to prepare a metal film of a cantilever beam with low surface reflectivity, and then sacrifice the sacrificial layer to obtain a metal cantilever beam;

Step 6: The metal film of the cantilever beam and the upper electrode layer are connected to the driving circuit in two stages, and the upper electrode layer is grounded at the same time, and the signal of the flexible infrared pyroelectric sensitive unit can be drawn from the lower electrode to eliminate the influence of the cantilever beam driving voltage source on the signal .

The present invention has the following beneficial effects:

(1) The periodic modulation of the incident infrared radiation is realized by the up and down movement of the flexible metal film cantilever beam. Specifically, when the cantilever beam is suspended in the air and separated from the upper surface of the flexible infrared pyroelectric sensitive unit, the infrared radiation cannot be transmitted due to the existence of the air gap. to the flexible infrared pyroelectric sensitive unit, so the temperature of the flexible infrared pyroelectric sensitive unit remains unchanged; when the cantilever beam is in contact with the upper surface of the flexible infrared pyroelectric sensitive unit, because the metal film of the cantilever beam is very thin, the thermal resistance is extremely Small, the temperature rise of the cantilever beam caused by infrared radiation can be quickly transferred to the flexible infrared pyroelectric sensitive unit without loss, thereby causing the temperature of the flexible infrared pyroelectric sensitive unit to rise; when the cantilever beam is separated again, the flexible infrared pyroelectric sensitive unit The temperature drops back to the initial temperature.

(2) Combining the flexible infrared radiation modulation mechanism with the flexible pyroelectric infrared sensitive unit, the full flexibility and integration of the pyroelectric infrared detector is realized, and the pyroelectric infrared detection can be realized by further combining the micromachining technology Miniaturization and arraying of devices.

(3) Based on the idea of the present invention, it lays a foundation for the application of pyroelectric infrared detectors in wearable portable devices, such as flexible temperature sensors, flexible infrared thermal imagers, and the like.

Description of drawings

FIG. 1 is a working schematic diagram of the fully flexible pyroelectric infrared detector of the single-ended cantilever beam of the present invention (the circuit switch is in an off state).

FIG. 2 is a working schematic diagram of the fully flexible pyroelectric infrared detector of the single-ended cantilever beam of the present invention (the circuit switch is in a connected state).

FIG. 3 is a schematic working diagram of the fully flexible pyroelectric infrared detector of the cantilever beam at both ends of the present invention (the circuit switch is in an off state).

FIG. 4 is a working schematic diagram of the fully flexible pyroelectric infrared detector of the cantilever beam at both ends of the present invention (the circuit switch is in a connected state).

FIG. 5 is a schematic diagram of the processing process of Embodiment 2 of the present invention.

FIG. 6 is a schematic diagram of the processing process of Embodiment 3 of the present invention.

FIG. 7 is a schematic diagram of the processing process of Example 4 of the present invention.

Marked in the figure: 11, pyroelectric sensitive film; 12, upper electrode layer; 13, lower electrode layer; 20, insulating layer; 31, support column; 32, metal film; 33, limit structure; 41, voltage source; 42, circuit switch; 43, switch control circuit; 51, base; 52, sacrificial layer; 53, cantilever beam sacrificial layer.

Among them, the large arrows in Figures 1 to 4 represent the incident infrared radiation, and the small arrows represent the heat flow from the metal film to the flexible pyroelectric sensitive film by thermal conduction.

Detailed ways

Example 1

As shown in FIGS. 1 to 4 , a fully flexible pyroelectric infrared detector provided in this embodiment includes a flexible infrared radiation modulation mechanism and a flexible infrared pyroelectric sensitive unit, and the flexible infrared pyroelectric sensitive unit includes a The insulating layer 20, the upper electrode layer 12, the pyroelectric sensitive film 11 and the lower electrode layer 13 are arranged in sequence from top to bottom; the insulating layer 20 is installed with the flexible infrared radiation modulation mechanism, and the flexible infrared radiation modulation mechanism includes 1 or 2 support columns 31 and metal films 32, the metal films 32 are installed on the support columns 31 to form a single-ended or double-ended cantilever beam; on the metal film 32 of the cantilever beam and the flexible infrared pyroelectric sensitive unit The electrodes are connected to a voltage source 41 through a circuit switch 42, which can be controlled by a switch control circuit 43; a certain frequency and amplitude are applied between the metal film 32 of the cantilever beam and the upper electrode layer 12 of the flexible infrared pyroelectric sensitive unit. The metal film 32 of the cantilever beam can move up and down within a certain range according to the corresponding frequency, so as to periodically separate and contact the top insulating layer 20 of the flexible infrared pyroelectric sensitive unit, so that the incident infrared radiation generates The heat flow is periodically transferred to the pyroelectric sensitive film 11 and causes its temperature to change periodically.

The support column 31 can be made of inorganic materials of silicon oxide, silicon nitride, polysilicon, or organic materials of polyimide and polydimethylsiloxane (PDMS), or common materials of aluminum, nickel, chromium, copper, gold, and titanium. Preparation of metal materials.

The metal thin film 32 of the cantilever beam can be prepared from common and easy-to-process metal materials such as aluminum, nickel, chromium, copper, gold, and titanium.

The insulating layer 20 can be made of inorganic materials of silicon oxide, silicon nitride, polysilicon, or organic materials of polyimide and polydimethylsiloxane (PDMS).

The pyroelectric sensitive film 11 can be a flexible pyroelectric polymer of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, odd-numbered nylon, polyvinyl chloride or polypropylene. Preparation, or a doping system with a flexible pyroelectric polymer as the main body, a doping system doped with barium strontium titanate and lead zirconate titanate inorganic ferroelectric ceramics.

The circuit switch 42 and the switch control circuit 43 may be implemented by separate circuit modules, or may be implemented by an integrated circuit.

The fully flexible pyroelectric infrared detector can be partially or completely realized by using a flexible film process and a micro-fabrication process from bottom to top as required.

Example 2

As shown in FIG. 5 , a method for manufacturing a fully flexible pyroelectric infrared detector provided in this embodiment includes the following steps:

Step 1: Sputtering a Ni-Cr alloy film with a thickness of 1 μm on the base 51 prepared by using a silicon wafer as the sacrificial layer 52 .

Step 2: The flexible pyroelectric polymer is completely dissolved into a solution, and then the solution is evenly coated on the sacrificial layer 52 of the base 51, and then placed in an incubator and baked until the solvent is completely volatilized, and the flexible pyroelectric polymer is formed. Pyroelectric sensitive film 11 .

Step 3: Using the sputtering method to prepare 100 nm metal aluminum on the upper surface of the pyroelectric sensitive film 11 as the upper electrode layer 12 of the flexible infrared pyroelectric sensitive unit.

Step 4: A 200 nm silicon nitride dielectric film is prepared on the surface of the upper electrode layer 12 by chemical vapor deposition as the insulating layer 20 .

Step 5 : deposit a 1 μm metal titanium film with appropriate tensile stress on the surface of the 200 nm silicon nitride insulating layer 20 , and prepare the support column 31 of the cantilever beam by combining photolithography and etching processes.

Step 6: A metal cantilever sacrificial layer 53 with a thickness of 1 μm is prepared on the insulating layer 20 by using photosensitive polyimide.

Step 7: A metal titanium film with a thickness of 200-300 nm is deposited on the metal cantilever sacrificial layer 53 by the sputtering method as the metal film 32 of the cantilever beam.

Step 8: The sacrificial layer 52 above the base 11 is etched with a TFN nickel-chromium etching solution, and the flexible infrared pyroelectric sensitive unit is peeled off from the base 51 .

Step 9: Prepare 100 nm metal aluminum on the lower surface of the flexible pyroelectric sensitive film 11 by sputtering as the lower electrode layer 13 of the flexible infrared pyroelectric sensitive unit.

Step 10: Using oxygen plasma to release photosensitive polyimide to prepare metal cantilever sacrificial layer 53 to obtain a final fully flexible infrared detector.

Example 3

As shown in FIG. 4 , this embodiment provides a method for manufacturing a fully flexible pyroelectric infrared detector, which includes the following steps:

Step 1: Sputtering a Ni-Cr alloy film with a thickness of 1 μm on the base 51 prepared by using a silicon wafer as the sacrificial layer 52 .

Step 2: The flexible pyroelectric polymer is completely dissolved into a solution, and then the solution is evenly coated on the sacrificial layer 52 of the base 51, and then placed in an incubator and baked until the solvent is completely volatilized, and the flexible pyroelectric polymer is formed. Pyroelectric sensitive film 11 .

Step 3: Using the sputtering method to prepare 100 nm metal aluminum on the upper surface of the pyroelectric sensitive film 11 as the upper electrode layer 12 of the flexible infrared pyroelectric sensitive unit.

Step 4: A 200 nm silicon nitride dielectric film is prepared on the surface of the upper electrode layer 12 by chemical vapor deposition as the insulating layer 20 .

Step 5: The support column 31 of the cantilever beam and the lower part of the limiting structure 33 of the cantilever beam are prepared on the surface of the 200nm silicon nitride insulating layer 20 by chemical vapor deposition method of 1μm silicon oxide, combined with photolithography and etching process.

Step 6: Use photosensitive polyimide to prepare a metal cantilever sacrificial layer 52 with a thickness of 1 μm on the insulating layer 20; use a sputtering method to deposit a metal titanium film with an appropriate tensile stress of 200-300 nm as the metal film 32 of the cantilever beam.

Step 7: A chemical vapor deposition method is used to prepare 1 μm silicon oxide on the lower part of the limiting structure 33 of the cantilever beam, and the middle part of the limiting structure 33 of the cantilever beam is prepared by combining photolithography and etching processes.

Step 8: Use photosensitive polyimide to prepare a second sacrificial layer with a thickness of 1 μm on the metal film 32 of the cantilever beam, and use chemical vapor deposition method in the middle of the limiting structure 33 of the cantilever beam. 1 μm silicon oxide, combined with photolithography and etching processes Control the top of the cantilever beam limit structure 33 .

Step 9: The nickel-chromium sacrificial layer 52 above the base 51 is etched with TFN nickel-chromium etching solution, and the flexible infrared pyroelectric sensitive unit is peeled off from the base 51; A 100-nm metal aluminum was prepared by the radiation method as the lower electrode layer 13 of the flexible infrared pyroelectric sensitive unit.

Step 10: Using oxygen plasma to release photosensitive polyimide to prepare metal cantilever sacrificial layer 53 to obtain a final fully flexible infrared detector.

Example 4

As shown in FIG. 5 , this embodiment provides a method for manufacturing a fully flexible pyroelectric infrared detector, including the following steps:

Step 1: Sputtering a Ni-Cr alloy film with a thickness of 1 μm on the base 51 prepared by using a silicon wafer as the sacrificial layer 52 .

Step 2: The flexible pyroelectric polymer is completely dissolved into a solution, and then the solution is evenly coated on the sacrificial layer 52 of the base 51, and then placed in an incubator and baked until the solvent is completely volatilized, and the flexible pyroelectric polymer is formed. Pyroelectric sensitive film 11 .

Step 3: Prepare 100 nm metal aluminum on the upper surface of the pyroelectric sensitive film 11 by sputtering as the upper electrode layer 12 of the flexible infrared pyroelectric sensitive unit.

Step 4: A 200 nm silicon nitride dielectric film is prepared on the surface of the upper electrode layer 12 by chemical vapor deposition as the insulating layer 20 .

Step 5 : deposit a 1 μm metal titanium film with appropriate tensile stress on the surface of the 200 nm silicon nitride insulating layer 20 , and prepare the cantilever beam support column 31 by combining photolithography and etching processes.

Step 6: Using photosensitive polyimide to prepare a metal cantilever sacrificial layer 53 with a thickness of 1 μm.

Step 7: A metal titanium film with a thickness of 200-300 nm is deposited by sputtering as the metal film 32 of the cantilever beam.

Step 8 : Etching the Ni-Cr sacrificial layer 52 above the base 51 with TFN Ni-Cr etching solution, and peeling the flexible infrared pyroelectric sensitive unit from the base 51 .

Step 9: Using the sputtering method to prepare 100 nm metal aluminum on the lower surface of the pyroelectric sensitive film 11 as the lower electrode layer 13 of the flexible infrared pyroelectric sensitive unit.

Step 10: Using oxygen plasma to release photosensitive polyimide to prepare metal cantilever sacrificial layer 52 to obtain a final fully flexible infrared detector.

Among the three fully flexible infrared detector structures prepared in Examples 2 to 4, the single-ended support structure in Example 2 has a simple process and is suitable for occasions where the device deformation is small; when the deformation is large, the cantilever beam may be far away from the upper surface of the detector. It cannot be driven normally. Therefore, the cantilever beam limiting structure 33 is added in the third embodiment, and there are many process steps, so that the detector can work in the situation of large deformation; The same, but due to the double-end support, the detector can also work in large deformation occasions.

The above are only the preferred embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any modification and replacement based on the technical solutions and inventive concepts provided by the present invention should be covered by the protection scope of the present invention. Inside.

Claims (9)

1. a fully flexible pyroelectric infrared detector, it is characterized in that: comprise flexible infrared radiation modulation mechanism and flexible infrared pyroelectric sensitive unit, described flexible infrared pyroelectric sensitive unit comprises insulation that is arranged sequentially from top to bottom layer, an upper electrode layer, a pyroelectric sensitive film and a lower electrode layer; the flexible infrared radiation modulation mechanism is installed on the insulating layer, and the flexible infrared radiation modulation mechanism includes one or two supporting columns and a metal film, and the metal The film is installed on the support column to form a single-ended or double-ended cantilever beam; a voltage source is connected between the metal film of the cantilever beam and the upper electrode layer of the flexible infrared pyroelectric sensitive unit through a circuit switch, and the circuit switch can control the circuit through the switch control; a voltage signal of a certain frequency and amplitude is applied between the metal film of the cantilever beam and the upper electrode layer of the flexible infrared pyroelectric sensitive unit, and the metal film of the cantilever beam can move up and down within a certain range according to the corresponding frequency, Therefore, it is periodically separated and contacted with the insulating layer of the flexible infrared pyroelectric sensitive unit, so that the heat flow generated by the incident infrared radiation is periodically transferred to the pyroelectric sensitive film and causes its temperature to change periodically. 2 . The fully flexible pyroelectric infrared detector according to claim 1 , wherein the support column can be made of silicon oxide, silicon nitride, polysilicon inorganic materials, or polyimide, polydimethylformaldehyde, etc. 3 . Siloxane (PDMS) organic materials, or aluminum, nickel, chromium, copper, gold, titanium common metal materials. 3. A fully flexible pyroelectric infrared detector according to claim 1 or 2, characterized in that: the single-ended cantilever beam further comprises a limit structure installed on the insulating layer, for limiting the cantilever beam The upper intercept point of the upward movement of the metal film. 4. The fully flexible pyroelectric infrared detector according to claim 1, wherein the metal film of the cantilever beam can be made of common and easy-to-process metal materials such as aluminum, nickel, chromium, copper, gold, and titanium. preparation. 5 . The fully flexible pyroelectric infrared detector according to claim 1 , wherein the insulating layer can be made of inorganic materials of silicon oxide, silicon nitride, polysilicon, or polyimide, polydimethylformaldehyde, etc. 6 . Preparation of siloxane (PDMS) organic materials. 6. A fully flexible pyroelectric infrared detector according to claim 1, wherein the pyroelectric sensitive film can be made of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride Preparation of flexible pyroelectric polymers of vinyl fluoride-trifluoroethylene, odd-numbered nylon, polyvinyl chloride or polypropylene, or doping systems based on flexible pyroelectric polymers, doped with barium strontium titanate, zirconium titanium Doping systems for lead-acid inorganic ferroelectric ceramics. 7 . The fully flexible pyroelectric infrared detector according to claim 1 , wherein the circuit switch and the switch control circuit can be realized by separate circuit modules or by integrated circuits. 8 . 8 . The fully flexible pyroelectric infrared detector according to claim 1 , wherein the fully flexible pyroelectric infrared detector can partially or completely adopt flexible film technology and Micro-machining process is realized. 9. a method for preparing the fully flexible infrared pyroelectric detector without external chopper according to claim 1, is characterized in that comprising the steps: Step 1: The flexible pyroelectric polymer is completely dissolved into a solution, and the solution is evenly coated on the flat substrate, and then baked in a constant temperature oven until the solution is completely volatilized, the flexible pyroelectric polymer forms a sensitive film, and then the The sensitive film is peeled off to obtain a pyroelectric sensitive film; Step 2: preparing metal electrode layers of the same thickness on both the upper surface and the lower surface of the pyroelectric sensitive film by means of evaporation and sputtering to form upper and lower electrode layers; Step 3: preparing an inorganic insulating layer of silicon oxide or silicon nitride on the upper electrode layer by chemical vapor deposition; or preparing an organic insulating layer of polyimide or PDMS by spin coating and casting; Step 4: Prepare silicon oxide or silicon nitride inorganic insulating support pillars on the upper electrode layer or insulating layer by chemical vapor deposition, or prepare polyimide or polyimide on the upper electrode layer or insulating layer by spin coating and casting methods. PDMS organic insulating support column; or use evaporation, sputtering method to prepare metal support column on the insulating layer; Step 5: prepare a sacrificial layer on the insulating layer with the same height as the support column, and then use evaporation and sputtering methods to prepare a metal film of the cantilever beam with low surface reflectivity, and then remove the sacrificial layer to obtain a metal cantilever beam; Step 6: The metal film of the cantilever beam and the upper electrode layer are connected to the driving circuit in two stages, and the upper electrode layer is grounded at the same time, and the signal of the flexible infrared pyroelectric sensitive unit can be drawn from the lower electrode to eliminate the influence of the cantilever beam driving voltage source on the signal .

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