Anti-radiation silicon-based single photon detector surface array and preparation method

Abstract

The application relates to the technical field of photoelectric detection, in particular to an anti-radiation silicon-based single-photon detector surface array and a preparation method thereof, which comprises a single-photon detection array chip, a passivation layer plated on the upper surface of the single-photon detection array chip and a micro-nano structure array formed on the upper surface of the passivation layer; the passivation layer comprises a SiO2 film and a Si3N4 film located above the SiO2 film; and the micro-nano structure array is obtained by etching the Si3N4 film. The preparation method of the anti-radiation silicon-based single-photon detector is also disclosed. By longitudinally integrating the micro-nano structure array and the single-photon detector array, the surface defect state density of the active layer is reduced, the optical transmittance in a wide waveband range is enhanced, and the photoelectric detection performance and the anti-radiation level of the single-photon detector are improved. The application has the advantages of high optical transmittance, high photoelectric detection performance and high anti-radiation performance, and can be applied to the fields of laser radar, quantum information, fluorescence measurement and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detection, in particular to an anti-radiation silicon-based single-photon detector array and a preparation method thereof. BACKGROUND

[0002] A single-photon detector is a core device of an extremely weak light detection system, which can convert a weak light signal carrying object characteristics into an electrical signal through photoelectric conversion and electrical signal processing, and has the advantages of low dark count, high detection efficiency, compact structure and the like. Compared with a traditional photoelectric detector, the single-photon detector has a photon energy detection limit of 10 -19 W, can realize detection of a weak target signal in a complex background noise, and has important research value and broad application prospects in many fields of national major needs and national economic development. However, a conventional single-photon detector is easily affected by radiation damage, resulting in serious decline in device reliability, stability and anti-interference capability, and is difficult to meet the working needs of spacecrafts, satellites and other devices. In a complex radiation environment in space, it is currently the primary technical problem to improve the anti-radiation capability of the single-photon detector.

[0003] At present, the anti-radiation reinforcement of the single-photon detector can be achieved by using a dielectric material with a high dielectric constant on the surface of the device, reducing the number of holes generated by radiation by reducing the electric field strength in the dielectric, or reducing the thickness of the oxide layer to reduce the charge accumulation amount of the holes generated by radiation in the oxide layer, or pre-doping or injecting impurities such as nitrogen, phosphorus, fluorine, aluminum and arsenic in the oxide layer to actively introduce electron traps to compensate for hole traps, so as to reduce the number of holes and thus reduce the influence of radiation on the single-photon detector.

[0004] In summary, although the above methods can achieve the effect of radiation reinforcement of the single-photon detector, these methods usually reduce the performance of the device, and it is difficult to balance the photoelectric detection performance and the anti-radiation performance of the device. SUMMARY

[0005] The purpose of the present application is to provide an anti-radiation silicon-based single-photon detector array and a preparation method thereof, which can reduce the surface defect state density of the active layer by longitudinally integrating a micro-nano structure array and a single-photon detector array, enhance the optical transmittance in a wide wavelength range, and thus improve the photoelectric detection performance and the anti-radiation level of the single-photon detector.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides an anti-radiation silicon-based single-photon detector array, comprising a single-photon detection array chip, a passivation layer plated on the upper surface of the single-photon detection array chip, and a micro-nano structure array formed on the upper surface of the passivation layer; the passivation layer comprises a SiO2 film and a Si3N4 film located above the SiO2 film; the micro-nano structure array is obtained by etching the Si3N4 film.

[0008] Further, the size and period of the micro-nano structure array range from 1 μm to 10 μm, and the thickness ranges from 50 nm to 200 nm.

[0009] Further, the thickness of the SiO2 film in the passivation layer ranges from 5 nm to 30 nm, and the thickness of the Si3N4 film ranges from 20 nm to 1000 nm.

[0010] Further, the micro-nano structure array is rectangular, circular, triangular, cross-shaped or circular hole-shaped in the transverse direction of the device.

[0011] Further, the single-photon detection array chip comprises, from bottom to top, a readout circuit, a metal mirror, an N + contact layer, an avalanche layer, an absorption layer, a P + contact layer.

[0012] Further, the thickness of the metal mirror ranges from 100 nm to 300 nm, and the material is a dense metal material selected from Au, Ag, Cu and Al.

[0013] In a second aspect, the present application provides a preparation method of an anti-radiation silicon-based single-photon detector array, comprising the following steps:

[0014] S1, depositing a SiO2 film on the upper surface of a single-photon detection array chip;

[0015] S2, depositing a Si3N4 film on the upper surface of the SiO2 film;

[0016] S3, spin-coating photoresist on the upper surface of the Si3N4 film, exposing and developing by electron beam lithography technology to obtain a micro-nano structure reverse photoresist pattern;

[0017] S4, sputtering metal on the micro-nano structure reverse photoresist pattern, and obtaining a metal mask pattern same as the micro-nano structure after liquid phase stripping;

[0018] S5, removing the photoresist and processing the Si3N4 film by reactive ion etching to form a micro-nano structure array with Si3N4 as the material;

[0019] S6, removing the metal mask to obtain the above-mentioned anti-radiation silicon-based single-photon detector array.

[0020] The beneficial effects of the present application are as follows:

[0021] 1、The passivation layer comprises a SiO2 film and a Si3N4 film located above the SiO2 film, compared with a pure SiO2 film, the Si-N bond at the Si3N4 / SiO2 interface in the composite film replaces the radiation-sensitive Si-O stress bond, compensates the compressive stress in the SiO2 transition zone close to the SiO2 / Si interface, reduces the space occupied by the Si-O stress bond which is easy to be broken by gamma radiation, and releases the interface stress to a certain extent. At the same time, since the Si-N bond replaces the Si-O bond, the generation of SiO2 / Si interface states is inhibited, and the radiation resistance of the composite material is improved. Moreover, the interface state density of the Si3N4 / SiO2 composite film as the passivation layer is high, which can be used as a stress relief layer, solves the problem that the lattice mismatch rate of the pure SiO2 film passivation layer as the natural oxide layer of Si is extremely low, inhibits the generation of SiO2 / Si interface states, and has stronger charge storage capacity and radiation resistance than the pure SiO2 film.

[0022] 2、The micro-nano structure array is micro-nano processed on the surface of the Si3N4 film, a specific size of micro-nano structure based on the Si3N4 film is designed according to the application scene and waveband requirement, so as to excite Mie resonance at the micro-nano structure and produce a strong local electromagnetic field to enhance the transmittance of the required waveband. It should be noted that the micro-nano structure array pattern size and period parameters are not unique and can be adaptively designed within a certain range. Moreover, the size and period parameters of the Si3N4 micro-nano structure array are accurately controlled by adjusting the preparation process parameters, and the light wave band that needs to be enhanced is accurately controlled, so as to enhance the light energy utilization rate of the detected target photons, and improve the device photoelectric response performance without reducing the device radiation resistance. By vertically integrating the micro-nano structure array and the single-photon detector array, the surface defect state density of the active layer is reduced, the optical transmittance is enhanced in a wide waveband range, and the photoelectric detection performance and radiation resistance level of the single-photon detector are improved.

[0023] 3、The anti-radiation silicon-based single-photon detector array adopts a bottom-up processing method, and the preparation method of the Si3N4 / SiO2 composite film, i.e., the passivation layer and the Si3N4 micro-nano structure array, is compatible with standard film plating process and photolithography process, which has the obvious advantages of simple processing process and batch production.

[0024] 4、The anti-radiation silicon-based single-photon detector array can simultaneously improve the device photoelectric response and radiation resistance, has good stability, high signal-to-noise ratio, can be processed in a large area, selectively enhances detection, and has a wide application prospect in the fields of laser radar, quantum information, fluorescence measurement, etc. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a cross-sectional view of the anti-radiation silicon-based single photon detector array chip in the embodiment of the present application.

[0026] Figure 2 The figure is a three-dimensional view of the anti-radiation silicon-based single photon detector array chip in the embodiment of the present application.

[0027] Figure 3 The figure is a schematic view of the micro-nano structure array in the cross direction of the device, a is rectangular, b is disc-shaped, c is triangular, and d is cross-shaped.

[0028] Figure 4 The figure is a flow chart of the preparation method of the anti-radiation silicon-based single photon detector array chip in the embodiment of the present application.

[0029] Figure 5 The figure is a flow chart of the preparation method of the single photon detector array chip in the embodiment of the present application.

[0030] Figure 6 The figure is a SEM image of the micro-nano structure array in the embodiment of the present application.

[0031] Figure 7 The figure is a reflectivity curve of the bare chip Si, nano-pore array, and single-layer Si3N4 film under different period conditions.

[0032] Figure 8 The figure is a transmittance curve of the anti-radiation silicon-based single photon detector array chip in the embodiment of the present application.

[0033] Figure 9 The figure is a schematic view of the noise size comparison of the single photon detector before and after radiation reinforcement.

[0034] In the figure, 1 is a single photon detector array chip, 11 is a readout circuit, 12 is a metal mirror, 13 is a nano-pore array, 14 is an avalanche layer, 15 is an absorption layer, 16 is a P + contact layer, 14 is an avalanche layer, 15 is an absorption layer, 16 is a P + contact layer, 2 is a passivation layer, and 3 is a micro-nano structure array. DETAILED DESCRIPTION

[0035] The embodiments of the present application will be described below with reference to the accompanying drawings and preferred embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the contents disclosed in the present specification. The present application can also be implemented or applied by means of other different specific embodiments, and each detail in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for the purpose of illustrating the present application, and are not intended to limit the protection scope of the present application.

[0036] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concepts of the present application in a schematic manner, and only show the components related to the present application in the diagrams, not drawn according to the number, shape and size of the components in actual implementation. The shape, number and proportion of each component in actual implementation can be a random change, and the component layout pattern can be more complex.

[0037] Embodiment one, referring to Figure 1 and Figure 2 , an anti-radiation silicon-based single-photon detector surface array includes a single-photon detection array chip 1, a passivation layer 2 plated on the upper surface of the single-photon detection array chip 1, and a micro-nano structure array 3 formed on the upper surface of the passivation layer 2. The passivation layer 2 includes a SiO2 film and a Si3N4 film located above the SiO2 film, the thickness of the SiO2 film is 5-30 nm, and the thickness of the Si3N4 film is 20-1000 nm; the micro-nano structure array 3 is obtained by etching the Si3N4 film.

[0038] Compared with a pure SiO2 film, the Si-N bond at the Si3N4 / SiO2 interface in the composite film of the passivation layer 2 replaces the Si-O stress bond sensitive to radiation, compensates the compression stress in the transition zone near the SiO2 / Si interface in SiO2, reduces the space occupied by the Si-O stress bond prone to be broken by γ radiation, and releases the interface stress to a certain extent. At the same time, since the Si-N bond replaces the Si-O bond, the generation of the SiO2 / Si interface state is inhibited, and the anti-radiation capability of the composite material is improved. Moreover, the interface state density of the passivation layer, i.e. the Si3N4 / SiO2 composite film, is high, which can serve as a stress relief layer, solves the problem of extremely low lattice mismatch rate of the SiO2 film passivation layer as the natural oxide layer of Si, inhibits the generation of the SiO2 / Si interface state, and has stronger charge storage capability and anti-radiation capability than the pure SiO2 film.

[0039] The micro-nano structure array 3 is micro-nano processed on the surface of the Si3N4 film. According to the application scenario and waveband requirement, a specific size of micro-nano structure based on the Si3N4 film is designed, so as to excite Mie resonance at the micro-nano structure and generate a strong local electromagnetic field, thereby enhancing the transmittance of the required waveband light. Further, by controlling the period and structure size of the micro-nano structure array 3, the excitation frequency of the local electromagnetic field can be adjusted, so as to selectively enhance the transmittance of a specific wavelength light or the transmittance of a wide waveband.

[0040] Referring to Figure 3 a、 Figure 3 b、 Figure 3 c and Figure 3As shown in d, the micro-nano structure array is rectangular, circular, triangular or cross-shaped in the transverse direction of the device. The micro-nano structure array has a size and a period ranging from 1 μm to 10 μm and a thickness ranging from 50 nm to 200 nm. It should be noted that the size and period parameters of the micro-nano structure array are not unique and can be adaptively designed within a certain range. Moreover, the size and period parameters of the Si3N4 micro-nano structure array are accurately controlled by adjusting the preparation process parameters, and the light wave band requiring the antireflection is accurately controlled, so as to enhance the light energy utilization rate of the detected target photons and improve the photoelectric response performance of the device without reducing the anti-radiation capability of the device.

[0041] In the embodiment, referring to Figure 1 and Figure 2 , the single-photon detection array chip 1 comprises, from bottom to top, a readout circuit 11, a metal mirror 12, an N + contact layer 13, an avalanche layer 14, an absorption layer 15, a P + contact layer 16.

[0042] The thickness of the metal mirror 12 is 100 nm to 300 nm, and the material is a dense metal material selected from Au, Ag, Cu and Al. The metal mirror 12 forms a total reflection structure, so that the device works in a back-illumination mode and improves the equivalent optical path of the device. The duty cycle of the photosensitive area is large, and the different absorption depths of short-wave photons and long-wave photons can be considered to enhance the quantum efficiency of the device. Generally, increasing the length of the depletion region of the single-photon detection array chip is required to increase the quantum efficiency, but increasing the length of the depletion region will reduce the avalanche probability under the same over-bias condition, which is in conflict with each other. Therefore, the present application adopts the scheme of appropriately reducing the thickness of the absorption layer + back metal mirror. The characteristics of the scheme are that the depletion region of the single-photon detection array chip is thinned to meet the requirement of high avalanche probability, and a dielectric film and a metal electrode are made on the back of the single-photon detection array chip to form a back mirror, so that the equivalent optical path of the device is doubled to meet the requirement of high quantum efficiency.

[0043] In the embodiment, referring to Figure 4 , a preparation method of an anti-radiation silicon-based single-photon detector array is provided, which comprises the following steps:

[0044] S1, a layer of SiO2 film is plated on the upper surface of the single-photon detection array chip by atomic layer deposition, magnetron sputtering, vacuum evaporation and the like.

[0045] S2, a layer of Si3N4 film is deposited on the upper surface of the SiO2 film.

[0046] S3, photoresist is spin-coated on the upper surface of the Si3N4 film, and a micro-nano structure reverse photoresist pattern is obtained by electron beam lithography technology exposure and development.

[0047] S4, sputtering metal on the micro-nano structure inverse structure photoresist pattern, and obtaining the same metal mask pattern as the micro-nano structure after liquid phase stripping.

[0048] S5, removing the photoresist, and processing the Si3N4 film by reactive ion etching to form the micro-nano structure array with Si3N4 as the material.

[0049] S6, removing the metal mask to obtain the anti-radiation silicon-based single photon detector array as described in the first embodiment.

[0050] In the embodiment, the preparation of the single photon detector array chip comprises the following steps:

[0051] Step one, preparing a metal mirror,

[0052] Step two, preparing an N + contact layer,

[0053] Step three, preparing an avalanche layer,

[0054] Step four, preparing an absorption layer,

[0055] Step five, preparing a P + contact layer.

[0056] The anti-radiation silicon-based single photon detector array of the application adopts a bottom-up processing mode, and the preparation method of the Si3N4 / SiO2 composite film, i.e., the passivation layer and the Si3N4 micro-nano structure array, is compatible with standard film plating and photolithography processes, and has obvious advantages of simple processing technology and batch production.

[0057] The application adopts a micro-nano optical composite film structure to improve the anti-radiation capability. If only SiO2 is used as the passivation layer, under the action of space radiation, the surface positive charge density increases, causing defects on the surface of the detector material and greatly reducing the performance of the device. Compared with using only SiO2 as the passivation layer, the application introduces a high dielectric constant material, i.e., silicon nitride Si3N4, to form a composite film. Compared with SiO2, the high dielectric constant material is not sensitive to ionizing radiation, has stronger charge storage capacity and anti-radiation capability. In addition, the composite film has high interface state density and can be used as a stress relief layer to solve the problem of low lattice mismatch rate of pure SiO2 as the natural oxide layer of Si, inhibit the generation of SiO2 / Si interface states, and improve the anti-radiation capability of the composite material.

[0058] The embodiment adopts a Si3N4 / SiO2 composite film structure based on a nano-pore array, the Si3N4 film has a thickness of 90 nm, and the nano-pore has a diameter of 360 nm. The SEM image of the nano-pore array prepared is shown in Figure 6 .

[0059] Figure 7 The reflectivity of bare Si, single layer Si3N4 film and Si3N4 / SiO2 composite film when the period increases from 400 nm to 1100 nm. It can be seen from the figure that Figure 7 It can be seen that the reflectivity of bare Si surface to incident light is strong, about 30% of the incident light is reflected; single layer Si3N4 antireflection film can effectively reduce the reflection of incident light, the average reflectivity is less than 15%; the Si3N4 / SiO2 composite film structure based on nano-pore array can also effectively reduce the reflectivity of light, and the average reflectivity is less than 10%. It can be seen that the antireflection effect of nano-pore array film is better than that of single layer antireflection film.

[0060] Figure 8 The transmittance curve of micro-nano optical composite structure, the Si3N4 / SiO2 composite film structure based on nano-pore array is selected as the antireflection film of single photon detector, which can reduce the light reflection of the surface of the device and improve the light energy utilization rate of the device.

[0061] Figure 9 The noise size of single photon detector array before and after irradiation hardening, after irradiation hardening, the Si3N4 / SiO2 composite film and the micro-nano structure array formed by micro-nano processing on the surface of Si3N4 film are used, which can effectively reduce the noise level of single photon detector.

[0062] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above examples, those skilled in the art should understand that the examples and examples are only considered to be exemplary, and various changes can be made in form and details, the true scope and spirit of the present application are defined by the claims.

Claims

1. A radiation-hardened silicon-based single-photon detector area array, characterized by: The single-photon detection array chip (1), a passivation layer (2) plated on the upper surface of the single-photon detection array chip (1), and a micro-nano structure array (3) formed on the upper surface of the passivation layer; the micro-nano structure array (3) has a size and a period ranging from 1 μm to 10 μm and a thickness ranging from 50 nm to 200 nm, and the micro-nano structure array (3) is in the shape of a rectangle, a circle, a triangle, a cross or a circular hole in the transverse direction of the device; The passivation layer (2) comprises a SiO2 film and a Si3N4 film located above the SiO2 film; the thickness of the SiO2 film in the passivation layer (2) ranges from 5 nm to 30 nm, and the thickness of the Si3N4 film ranges from 20 nm to 1000 nm; The micro-nano structure array (3) is obtained by etching the Si3N4 film.

2. The radiation-hardened silicon-based single-photon detector area array of claim 1, wherein: The single-photon detection array chip (1) comprises, from bottom to top, a readout circuit (11), a metal mirror (12), N + a contact layer (13), an avalanche layer (14), an absorption layer (15) and a P + contact layer (16).

3. The radiation-hardened silicon-based single-photon detector area array of claim 2, wherein: The metal mirror (12) has a thickness ranging from 100 nm to 300 nm and is made of a dense metal material selected from Au, Ag, Cu or Al.

4. A method for preparing an anti-radiation silicon-based single-photon detector area array, characterized in that, The method comprises the following steps: S1, depositing a SiO2 film on the upper surface of the single-photon detection array chip (1); S2, depositing a Si3N4 film on the upper surface of the SiO2 film; S3, spin-coating photoresist on the upper surface of the Si3N4 film, exposing and developing to obtain a micro-nano structure reverse-structure photoresist pattern; S4, sputtering metal on the micro-nano structure reverse-structure photoresist pattern, and obtaining a metal mask pattern identical to the micro-nano structure after liquid-phase stripping; S5, removing the photoresist and processing the Si3N4 film by reactive ion etching to form the micro-nano structure array (3) made of Si3N4; S6, removing the metal mask to obtain the anti-radiation silicon-based single-photon detector array of any one of claims 1 to 3.

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