CN107290067B - Uncooled infrared detector with low time constant - Google Patents

Uncooled infrared detector with low time constant Download PDF

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CN107290067B
CN107290067B CN201610205677.8A CN201610205677A CN107290067B CN 107290067 B CN107290067 B CN 107290067B CN 201610205677 A CN201610205677 A CN 201610205677A CN 107290067 B CN107290067 B CN 107290067B
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infrared detector
characteristic parameter
infrared
thermal
heat
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CN107290067A (en
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陈学枝
沈憧棐
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Shanghai Juge Technology Co ltd
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Shanghai Juge Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J2005/103—Absorbing heated plate or film and temperature detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J2005/106—Arrays

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  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

The invention discloses an uncooled infrared detector with a low time constant. The invention aims to provide an infrared detector which comprises a detector chip and a packaging structure, wherein the infrared detector chip comprises a reading circuit substrate and one or more micro-bridge structures positioned on the reading circuit substrate, each micro-bridge structure comprises a connecting column, a heat absorbing structure and a heat insulation beam for connecting the connecting column and the heat absorbing structure, the heat absorbing structure comprises a thin film, and the thin film comprises an infrared absorbing material, a heat sensitive material and an electrode material. The infrared detector is characterized in that the infrared detector comprises one or more characteristic quantities selected such that a thermal time constant of the infrared detector is smaller than a predetermined value. Compared with the prior art, the infrared detector greatly improves the effective frame rate of the infrared detector, does not trail when observing a high-speed moving object, ensures the imaging quality and improves the effect of the infrared detector.

Description

Uncooled infrared detector with low time constant
Technical Field
The invention relates to the technical field of infrared detectors, in particular to a non-refrigeration infrared detector with a low time constant.
Background
Uncooled infrared detectors have been widely used in the field of infrared thermal imaging. The detector chip absorbs infrared radiation to cause the temperature of the thermosensitive film of the detector to change, the temperature change causes the resistance of the thermosensitive film to change, and the change of the resistance is converted into an output signal through the reading circuit.
Fig. 1 shows a top view of a typical uncooled infrared detector chip structure including a heat absorbing structure 1, a heat insulating beam 2, and a support connection column 3. The heat absorption structure comprises a suspended film formed by an infrared absorption material, a thermosensitive material, an electrode material and the like, and functions of infrared heat absorption, thermoelectric conversion and the like are realized. The thermally insulating beam typically comprises a bent elongated beam connecting the heat sink structure to a connection post, which functions to thermally insulate the heat sink structure from the substrate and, together with the connection post, to electrically connect the heat sink structure to the substrate readout circuitry.
When the infrared detector works, the heat absorption structure receives infrared radiation to raise the temperature, so that the resistivity of the thermosensitive material in the heat absorption unit is changed, and the reading circuit applies bias current to the thermosensitive material, amplifies the bias current and outputs a response signal. The heat absorption structure absorbs infrared radiation and transmits heat to the substrate and the outside in modes of heat insulation beams, gas convection, heat radiation and the like, so that the heat absorption structure can achieve heat balance within a certain time, namely, the detector can output a stable signal corresponding to a target scene, and the heat balance time is generally measured by a thermal response time constant tau of the detector.
The time constant tau of the detector is determined by the heat capacity C of the heat absorption unit and the thermal conductance G between the heat absorption unit and the substrate and the outside: τ is C/G. Thermal conductance G except for the portion G contributed by thermal conduction of the insulating beamBeamAnd a portion G contributing to convection and conduction through the airQi (Qi)：G＝GBeam+GQi (Qi). In the prior art, due to the development of the infrared detector chip technology, in order to pursue the sensitivity of the chip, on one hand, the heat insulation performance of a heat absorption structure and the outside is continuously improved, which is mainly realized by increasing the thermal resistance of a heat insulation beam and a high vacuum degree packaging structure; on the other hand, since the heat absorbing structure is required to absorb the incident infrared radiation, a certain volume (corresponding to a certain heat capacity) of the heat absorbing structure is required. Under the condition that the thermal conductance is continuously reduced and the heat capacity cannot be reduced in proportion, the time constant tau of the detector is larger. The time constant of a typical infrared detector is about 10 milliseconds.
However, since the response rate of the infrared detector to the infrared scene is determined by the thermal response time constant τ of the detector, when the time constant τ is increased, the response rate of the detector is decreased, and the output effective frame rate f (roughly, the effective frame rate f ≈ 1/(3 × τ)) is also decreased, where the effective frame rate refers to the maximum frame rate that ensures that the image does not generate obvious blur or "tail", so that the effect of the infrared detector is not good.
Disclosure of Invention
The invention aims to provide an infrared detector.
According to an aspect of the present invention, there is provided an infrared detector comprising a detector chip, a package structure, wherein the infrared detector chip comprises a readout circuit substrate and one or more micro-bridge structures on the readout circuit substrate, the micro-bridge structures comprising connection posts, a heat absorbing structure, and heat insulating beams connecting the connection posts and the heat absorbing structure, wherein the heat absorbing structure comprises a thin film comprising an infrared absorbing material, a heat sensitive material, and an electrode material. The infrared detector is characterized in that the infrared detector comprises one or more characteristic quantities selected such that a thermal time constant of the infrared detector is smaller than a predetermined value.
Preferably, the predetermined value is 5 milliseconds.
Preferably, the characteristic parameter includes at least any one of:
-a thermal capacity corresponding to the membrane of the microbridge structure;
-thermal conductance corresponding to the insulating beams of the micro-bridge structure;
-a thermal conductance corresponding to a gas within the encapsulation structure.
More preferably, the heat capacity is less than 1 e-10J/K.
More preferably, the sum of the thermal conductance corresponding to the thermal insulation beam of the micro-bridge structure and the thermal conductance corresponding to the gas in the package structure is greater than 2e-8W/K。
Preferably, when the characteristic parameter includes a heat capacity corresponding to a thin film of the microbridge structure, the characteristic parameter further includes a thin film characteristic parameter corresponding to the thin film, where the thin film characteristic parameter includes at least any one of a specific heat capacity, a volume, and a density of the thin film.
More preferably, when the characteristic parameter of the thin film is the volume of the thin film, the thin film comprises one or more hollowed-out pores.
More preferably, the projection length of the hollow small hole in at least one direction is less than one half of the wavelength of incident infrared radiation, wherein the projection length refers to the length of the hollow small hole vertically projected to the direction by taking any direction on the film plane where the hollow small hole is located as an axis.
More preferably, the projection length of the hollow small holes in any direction is less than half of the wavelength of incident infrared radiation, so that the absorption of the incident infrared rays is not reduced or is reduced less.
Preferably, when the characteristic parameter includes thermal conductivity corresponding to the heat-insulating beam of the micro-bridge structure, the characteristic parameter further includes a heat-insulating beam characteristic parameter corresponding to the heat-insulating beam, where the heat-insulating beam characteristic parameter includes at least any one of thermal conductivity, cross-sectional area, and length corresponding to the heat-insulating beam.
More preferably, when the characteristic parameter of the insulating beam is the cross-sectional area corresponding to the insulating beam, the characteristic parameter further includes at least one connection characteristic parameter corresponding to the insulating beam and the connecting column connected to the substrate in the micro-bridge structure, wherein the connection characteristic parameter includes a connection mode and/or the number of the connected insulating beams and connecting columns.
More preferably, the connection means comprises an electrical connection to the substrate readout circuitry or a mechanical connection but electrical isolation to the substrate.
More preferably, said number comprises at least 2, such as 3 or 4.
More preferably, when the characteristic parameter of the heat insulation beam is the thermal conductivity corresponding to the heat insulation beam, the heat insulation beam comprises a material with the thermal conductivity larger than 4W/m.K.
More preferably, the material having a thermal conductivity greater than 4W/m.k is a metal or silicon nitride.
More preferably, the characteristic quantities also include the area of the insulating beam occupied by the material when the insulating beam is covered with a material having a thermal conductivity greater than 10W/m.k and/or the thickness of the material when the insulating beam is covered with a material having a thermal conductivity greater than 10W/m.k.
More preferably, when the characteristic parameter of the heat insulation beam comprises a cross-sectional area and a length corresponding to the heat insulation beam, the ratio of the cross-sectional area to the length is greater than 0.05 micrometer. The cross-sectional area comprises the sum of the cross-sectional areas of the insulating beams of the microbridge structure.
Preferably, when the characteristic parameter includes a thermal conductance corresponding to a gas of the package structure, the characteristic parameter further includes a gas pressure and/or a gas type within the package structure.
More preferably, the gas pressure is greater than 1 Pa.
More preferably, the gas type comprises a macromolecular inert gas.
According to another aspect of the present invention, there is also provided a focal plane array, wherein the focal plane array comprises an array formed by microbridge structures of an infrared detector as described above.
According to another aspect of the present invention, there is also provided an infrared imager, wherein the infrared imager comprises the infrared detector as described above.
Compared with the prior art, the invention provides the infrared detector which comprises one or more selected characteristic parameters, so that the thermal time constant of the infrared detector is smaller than a preset value, the effective frame rate of the infrared detector is greatly improved, trailing is avoided when a high-speed moving object is observed, the imaging quality is ensured, and the effect of the infrared detector is improved.
Moreover, the invention can also select specific characteristic parameters, such as a mode that one or more hollow holes are included in the film, and the projection length of the hollow holes in at least one direction is less than one half of the wavelength of the incident infrared radiation, so that the absorption of the film on the incident infrared rays is not influenced or is less influenced, and the thermal time constant of the infrared detector is smaller than a preset value, therefore, the heat capacity can be reduced, the effective frame rate of the infrared detector is improved, the sensitivity of the detector is not influenced, the imaging quality of the infrared detector is further ensured, and the effect of the infrared detector is improved.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:
FIG. 1 shows a top view of a prior art infrared detector chip structure;
FIG. 2 shows a top view of a microbridge structure of an infrared detector chip according to a preferred embodiment of the present invention;
FIG. 3 shows a top view of a microbridge structure of an infrared detector chip according to another preferred embodiment of the present invention;
fig. 4 shows a top view of a microbridge structure of an infrared detector chip according to another preferred embodiment of the present invention.
The same or similar reference numbers in the drawings identify the same or similar elements.
Detailed Description
The present invention is described in further detail below with reference to the attached drawing figures.
The infrared detector comprises an infrared detector chip and a packaging structure. The infrared detector chip comprises a readout circuit substrate and one or more micro-bridge structures located on the readout circuit substrate. The micro-bridge structure comprises a connecting column, a heat absorbing structure and a heat insulation beam for connecting the connecting column and the heat absorbing structure, wherein the heat absorbing structure comprises a film, and the film comprises an infrared absorbing material, a heat sensitive material and an electrode material. The infrared detector is characterized in that the infrared detector comprises one or more characteristic quantities selected such that a thermal time constant of the infrared detector is smaller than a predetermined value.
The characteristic variables include parameter classes, parameter values, etc. Here, it should be understood by those skilled in the art that after the parameter type of the characteristic parameter is selected, due to the corresponding proportional relationship (such as linear relationship, exponential relationship, etc.) between the characteristic parameter and the thermal time constant, those skilled in the art can determine the parameter value corresponding to the characteristic parameter based on a limited number of adjustments to achieve low heat capacity or high thermal conductivity so that the thermal time constant is smaller than a predetermined value.
Preferably, the microbridge structures are arranged in an array on the readout circuitry substrate.
Preferably, the predetermined value is 5 milliseconds, i.e., the thermal time constant of the infrared detector is less than 5 milliseconds. Based on a simple calculation of the effective frame rate, i.e., f ≈ 1/(3 × τ), the effective frame rate is about 67.
More preferably, the predetermined value may be 2 milliseconds or 3 milliseconds, i.e., the thermal time constant of the infrared detector is less than 2 milliseconds or 3 milliseconds. Based on a simple calculation of the effective frame rate, i.e., f ≈ 1/(3 × τ), when the predetermined value is 2 ms, the effective frame rate is about 167, and when the predetermined value is 3 ms, the effective frame rate is about 111.
Preferably, the characteristic parameter includes at least any one of:
-a thermal capacity corresponding to the membrane of the microbridge structure;
-thermal conductance corresponding to the insulating beams of the micro-bridge structure;
-a thermal conductance corresponding to a gas within the encapsulation structure.
More preferably, when the characteristic parameter is a heat capacity corresponding to the thin film of the microbridge structure, the heat capacity is less than 1e-10J/K。
More preferably, when the characteristic parameter is thermal conductance corresponding to the thermal insulation beam of the micro-bridge structure or thermal conductance corresponding to the gas in the package structure, the sum of the thermal conductance corresponding to the thermal insulation beam of the micro-bridge structure and the thermal conductance corresponding to the gas in the package structure is greater than 2e-8W/K。
Therefore, the infrared detector can greatly improve the effective frame rate of the infrared detector, reduce the tailing when a high-speed moving object is observed, ensure the imaging quality and improve the effect of the infrared detector.
Fig. 2, 3 and 4 respectively show top views of microbridge structures of an infrared detector chip according to a preferred embodiment of the present invention. In the above-described view, the micro-bridge structure includes a heat absorbing structure 1, a heat insulating beam 2, and a support connection column 3.
The heat absorption structure 1 includes a thin film made of an infrared absorption material, a thermosensitive material, an electrode material, and the like, and realizes functions of infrared heat absorption, thermoelectric conversion, and the like.
The heat-sensitive material can be made of amorphous silicon, amorphous silicon germanium, vanadium oxide and other materials. The infrared absorption material can be composed of insulating materials of silicon nitride (SiN) and silicon oxide (SiO 2); or from a conductive material such as titanium silicon oxide (Ti), titanium nitride (TiN), tantalum nitride (TaN), in which case the infrared absorbing material also serves as the electrode material to form the bias electrode of the read circuit, and the thermally sensitive material applies a bias current.
The insulating beam 2 generally comprises a bent elongated beam connecting the heat sink structure to the connection post, and functions to thermally insulate the heat sink structure from the substrate and to electrically connect the heat sink structure to the substrate readout circuitry together with the connection post.
Fig. 2, 3, 4 each include one or more different characteristic parameters selected to cause a thermal time constant of the infrared detector to be less than a predetermined value. Which are described separately below in connection with the accompanying drawings.
In the present invention, when the characteristic parameter includes a heat capacity corresponding to a thin film of the microbridge structure, the characteristic parameter further includes a thin film characteristic parameter corresponding to the thin film, where the thin film characteristic parameter includes at least any one of a specific heat capacity, a volume, and a density of the thin film.
Wherein the volume comprises the area or thickness of the membrane, i.e. volume-area-thickness. It will be understood by those skilled in the art that the heat capacity is the specific heat capacity, and the mass is the volume, i.e. any parameters such as specific heat capacity, mass, volume, density, area, thickness, etc. corresponding to the film can be selected so that the thermal time constant of the infrared detector is less than a predetermined value.
For example, the heat capacity may be reduced by reducing the area of the film and/or reducing the thickness of the film, reducing the specific heat capacity of the film, or reducing the mass of the film.
In the microbridge structure shown in FIG. 2, the characteristic parameter of the film is the volume of the film, and the film includes one or more hollow-out small holes.
The openings shown in fig. 2 are square and arranged in an array, however, those skilled in the art should understand that the shapes, positions, arrangement, etc. of the openings are not limited to the example shown in fig. 2. For example, the shape of the hollow-out pores can be rectangular, circular, triangular, irregular polygonal or other arbitrary shapes; the positions of the hollow holes can be any positions on the film, such as the middle or the edge of the film; the hollow small holes can be closed small holes or non-closed small holes (such as when the hollow small holes are positioned at the edges of the film); the arrangement mode of the hollow holes can be array arrangement as shown in fig. 2, or other array arrangement or non-array arrangement and the like.
Preferably, the film forming the heat absorption structure is provided with a plurality of hollowed-out holes, and the projection length of the hollowed-out holes in at least one direction is less than one half of the wavelength of incident infrared radiation, wherein the projection length refers to the length of the hollowed-out holes vertically projected to the direction by taking any direction on the film plane where the hollowed-out holes are located as an axis.
More preferably, the projection length of the hollow small holes in any direction is less than one half of the wavelength of incident infrared radiation, and the absorption of the incident infrared rays is kept unchanged or slightly changed.
For example, if the small hollow holes are irregular, a straight line is formed in any direction of the small hollow holes on the film plane to serve as an axis, and the axis can penetrate through the small hollow holes, namely, intersects with the small hollow holes, or does not intersect with the small hollow holes; then, vertically projecting the shape of the hollow small hole on the axis, wherein the small hole with the irregular shape can be projected to form a line segment, and the length of the line segment is the length of the hollow small hole projected to the direction; along different directions, the hollowed-out small holes can have one or more projection lengths, and at least one projection length in the one or more projection lengths is smaller than one half of the wavelength of incident infrared radiation. Generally, the infrared radiation wavelength is about 7.5-14 um.
More preferably, in at least one projection direction, the projection length of the hollow small hole is 0.5-2 um; more preferably, the size of the space between the hollowed-out small holes is 1-5 um.
The above structure has the advantages that the area of the film is reduced by adding the hollowed-out small holes on the film, so that the volume of the heat absorbing structure is reduced, namely the heat capacity of the heat absorbing structure is reduced, the thermal response time constant is reduced, and further, the existence of the small holes does not influence the heat absorbing efficiency of the heat absorbing structure because the size of the small holes is obviously smaller than the wavelength of infrared radiation.
In the present invention, when the characteristic parameter includes thermal conductivity corresponding to the heat insulating beam of the micro-bridge structure, the characteristic parameter further includes a heat insulating beam characteristic parameter corresponding to the heat insulating beam, where the heat insulating beam characteristic parameter includes at least any one of thermal conductivity, cross-sectional area, and length corresponding to the heat insulating beam.
Wherein the thermal conductivity, the cross-sectional area and the length can be used as separate parameters, for example, increasing the cross-sectional area of the insulating beam or decreasing the length of the insulating beam to increase the thermal conductivity; furthermore, the thermal conductivity, the cross-sectional area and the length may be combined as parameters, for example, a ratio (a/L) of the cross-sectional area to the length may be used as a parameter. For example, since thermal conductance is proportional to A/L, the ratio of A/L may be selected to adjust the thermal conductance of the infrared detector such that the thermal time constant of the infrared detector is less than a predetermined value. Preferably, the ratio of the cross-sectional area to the length is greater than 0.05 microns.
Preferably, when the characteristic parameter of the heat insulation beam includes a length corresponding to the heat insulation beam, the length is less than 10 micrometers.
Preferably, when the characteristic parameter of the insulating beam is the cross-sectional area corresponding to the insulating beam, the characteristic parameter further includes at least one connection characteristic parameter corresponding to the insulating beam and the connecting column connected to the substrate in the micro-bridge structure, wherein the connection characteristic parameter includes a connection mode and/or the number of the connected insulating beams and connecting columns.
If the infrared detector chip comprises a plurality of heat insulation beams, the cross section area corresponding to the heat insulation beams comprises the sum of the cross section areas of the heat insulation beams.
More preferably, the connection means comprises an electrical connection to the substrate readout circuitry or a mechanical connection but electrical isolation to the substrate. Generally, the thermal conductivity in the electrical connection system is better.
More preferably, the number includes at least 2, that is, by increasing the number of the adiabatic beams, the area of the adiabatic beams is increased, thereby improving thermal conduction and reducing thermal resistance.
More preferably, the number is 3 or 4.
Fig. 3 shows a top view of a microbridge structure of an infrared detector chip according to another preferred embodiment of the present invention. In the schematic diagram, one connecting column 3 is respectively arranged at 4 corners of the micro-bridge structure of the infrared detector, namely 4 connecting columns are included; 2 of the connecting posts form electrode channels connected with a substrate reading circuit, and the other 2 connecting posts are electrically insulated from the substrate and only connected as mechanical supports. The multiple support columns increase the thermal conductivity of the insulating beam, reduce the time constant of the detector, and increase the mechanical stability of the structure.
In the present invention, when the characteristic parameter of the heat insulation beam is the thermal conductivity corresponding to the heat insulation beam, the heat insulation beam comprises a material having a thermal conductivity of more than 4W/m.k, that is, the heat insulation beam comprises a material having a high thermal conductivity.
Preferably, the material having a thermal conductivity greater than 4W/m.k is a metal or silicon nitride. In the prior art, silica with poor thermal conductivity is generally used to increase thermal resistance.
It will be understood by those skilled in the art that when the above-mentioned material having a thermal conductivity of more than 4W/m.k is used, it means that the material of the adiabatic beam is the material having the above-mentioned thermal conductivity.
Preferably, the characteristic quantities also include the area of the insulating beam occupied by the material when the insulating beam is covered with a material having a thermal conductivity greater than 10W/m.k and/or the thickness of the material when the insulating beam is covered with a material having a thermal conductivity greater than 10W/m.k.
It will be understood by those skilled in the art that when a material having a thermal conductivity greater than 10W/m.k is used, it means at least partial coverage with a material having a thermal conductivity greater than 10W/m.k.
By increasing the area or decreasing the thickness, thermal conductance is improved so that the thermal time constant of the infrared detector is less than a predetermined value.
Fig. 4 shows a top view of a microbridge structure of an infrared detector chip according to another preferred embodiment of the present invention. In fig. 4, the insulating beam 2 comprises a metal layer with good thermal conductivity. This metal layer is commonly used in existing probe structures to form anchor posts that connect to the substrate. According to the invention, the metal layer is arranged on the heat insulation beam, so that the heat conductivity of the heat insulation beam is improved, the thermal response time constant of the detector is reduced, and the mechanical stability of the structure is improved by the metal layer on the heat insulation beam on the premise of not changing the complexity of the structure and the process of the detector. By adjusting the length, width or/and thickness of the metal layer covering the insulating beam, the thermal response time constant can be freely adjusted.
In the present invention, when the characteristic parameter includes a thermal conductance corresponding to a gas of the package structure, the characteristic parameter further includes a gas pressure and/or a gas type in the package structure.
The air pressure of the packaged detector chip is controlled by selecting the air pressure and/or the type of air in the packaging structure, so that the thermal conduction generated between the micro-bridge structure of the detector and the substrate through air is adjusted.
Preferably, the pressure is greater than 1Pa, and generally, in the present invention, there is no excessive limit to the upper limit of the pressure, such as 100Pa or 1000 Pa. As can be understood by those skilled in the art, in the vacuum package of the detector chip, the vacuum pressure is controlled according to the requirement of the thermal time constant, for example, the pressure is controlled to be 1-1000 Pa, the larger the pressure is, the larger the thermal conductance of the detector due to the convection and conduction of the gas is, and the smaller the time constant is. By controlling the vacuum pressure of the package, the detector chip with the same structure can be packaged into a detector with any time constant and practical value. The low thermal time constant realized by the method has the advantages that the random regulation and control of the thermal time constant can be realized directly through packaging under the condition that the structure, the layout and the process of the infrared detector chip are not changed, and the production efficiency of the detector is improved.
Preferably, the gas type includes a macro inert gas, wherein the macro inert gas means an inert gas having a molecular weight of 18 (argon) or more, for example, argon (Ar), krypton (Kr), xenon (Xe), or the like.
Under the same vacuum degree, the heat conductance of the macromolecular gas is smaller than that of the micromolecular gas. And the higher the vacuum degree is, the greater the packaging difficulty is. The use of macromolecular gases has the advantage that the encapsulation can be accomplished at very low atmospheric or vacuum levels and with low time constants. It will be appreciated by those skilled in the art that while the use of macromolecules actually reduces thermal conductance, it is contemplated that one approach of this patent is to relax the vacuum requirements, and that further use of macromolecules may further relax the vacuum requirements, thereby further reducing the difficulty of encapsulation. Therefore, the matching of the macromolecule inert gas and the packaging gas pressure is utilized to realize the random regulation and control of the thermal time constant by selecting the related parameters of the packaging.
In the present invention, a focal plane array is also included, which includes an array formed by the microbridge structures of the infrared detector as described in any of the above embodiments. Here, the arrangement of the array is not limited.
In the present invention, the present invention further includes an infrared imager, and the infrared imager includes the infrared detector according to any one of the above embodiments.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A plurality of units or means recited in the apparatus claims may also be implemented by one unit or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims (19)

1. An infrared detector comprises an infrared detector chip and a packaging structure, wherein the infrared detector chip comprises a reading circuit substrate and one or more micro-bridge structures positioned on the reading circuit substrate, each micro-bridge structure comprises a connecting column, a heat absorbing structure and a heat insulation beam for connecting the connecting column and the heat absorbing structure, the heat absorbing structure comprises a thin film, and the thin film comprises an infrared absorbing material, a thermosensitive material and an electrode material; said infrared detector being characterized in that said infrared detector includes one or more characteristic quantities selected such that a thermal time constant of said infrared detector is less than a predetermined value;
when the characteristic parameter comprises the thermal conductance corresponding to the gas of the packaging structure, the characteristic parameter also comprises the gas pressure and/or the type of the gas in the packaging structure; the gas pressure and/or the gas type in the packaging structure are/is selected, and the gas pressure packaged by the infrared detector chip is controlled to adjust the thermal conductance generated by the gas; the gas type comprises macromolecular inert gas, so that the requirement on the vacuum degree is relaxed, the packaging difficulty is further reduced, and the matching of the macromolecular inert gas and the packaging gas pressure is utilized, so that the random regulation and control of the thermal time constant are realized by selecting the related parameters of the packaging.
2. The infrared detector as set forth in claim 1, wherein the predetermined value is 5 milliseconds.
3. An infrared detector according to claim 1 or 2, wherein said characteristic parameter comprises at least any one of:
-a thermal capacity corresponding to the membrane of the microbridge structure;
-thermal conductance corresponding to the insulating beams of the micro-bridge structure.
4. The infrared detector of claim 3, wherein the heat capacity is less than 1 e-10J/K.
5. The infrared detector of claim 3, wherein a sum of a thermal conductance corresponding to the insulating beams of the microbridge structure and a thermal conductance corresponding to the gas within the package structure is greater than 2 e-8W/K.
6. The infrared detector according to claim 3, wherein when the characteristic parameter includes a heat capacity corresponding to a thin film of the microbridge structure, the characteristic parameter further includes a thin film characteristic parameter corresponding to the thin film, wherein the thin film characteristic parameter includes at least any one of a specific heat capacity, a volume, and a density of the thin film.
7. The infrared detector as set forth in claim 6, wherein said film includes one or more pierced holes when said film characteristic parameter is a volume of said film.
8. The infrared detector according to claim 7, wherein a projection length of the pierced hole in at least one direction is less than one half of an incident infrared radiation wavelength, wherein the projection length refers to a length of the pierced hole vertically projected to the direction based on an arbitrary direction on a film plane where the pierced hole is located.
9. The infrared detector according to claim 3, wherein when the characteristic parameter includes thermal conductivity corresponding to an adiabatic beam of the microbridge structure, the characteristic parameter further includes an adiabatic beam characteristic parameter corresponding to the adiabatic beam, wherein the adiabatic beam characteristic parameter includes at least any one of thermal conductivity, cross-sectional area, and length corresponding to the adiabatic beam.
10. The infrared detector as set forth in claim 9, wherein when said adiabatic beam characteristic parameter includes a cross-sectional area and a length corresponding to said adiabatic beam, a ratio of said cross-sectional area to said length is greater than 0.05 μm.
11. The infrared detector according to claim 9, wherein when the characteristic parameter of the adiabatic beam is a cross-sectional area corresponding to the adiabatic beam, the characteristic parameter further includes at least one connection characteristic parameter corresponding to the adiabatic beam and the connection column connected to the substrate in the microbridge structure, wherein the connection characteristic parameter includes a connection mode and/or a number of the adiabatic beams and the connection columns connected.
12. The infrared detector as set forth in claim 11, wherein said connection means includes electrical connection to a substrate readout circuitry or mechanical connection to but electrical isolation from the substrate.
13. The infrared detector as set forth in claim 11, wherein the number includes at least 2.
14. The infrared detector of claim 9, wherein the insulating beam comprises a material having a thermal conductivity greater than 4W/m-K when the insulating beam characteristic parameter is a thermal conductivity corresponding to the insulating beam.
15. The infrared detector as set forth in claim 14, wherein the material having a thermal conductivity of greater than 4W/m-K is a metal or silicon nitride.
16. The infrared detector according to claim 9, wherein said characteristic parameters further include an area of said insulating beam occupied by said material when said insulating beam is covered with a material having a thermal conductivity greater than 10W/m-K and/or a thickness of said material when said insulating beam is covered with a material having a thermal conductivity greater than 10W/m-K.
17. The infrared detector of claim 1, wherein said air pressure is greater than 1 Pa.
18. A focal plane array, wherein the focal plane array comprises an array of microbridge structures of the infrared detector as claimed in any one of claims 1 to 16.
19. An infrared imager, wherein said infrared imager comprises an infrared detector as claimed in any one of claims 1 to 17.
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