All-silicon-based infrared polarized photoelectric detector and preparation method thereof

Abstract

The invention belongs to the technical field of optical sensing, and particularly relates to an all-silicon-based infrared photovoltaic polarized photoelectric detector and a preparation method thereof. According to the internal photoelectric emission process, the photo-thermal electronic effect is utilized, and a new mechanism that a light current is triggered by directional drifting of non-equilibrium hot carriers injected from the outside in the silicon nanowire is determined; structural parameters of a device are optimized through a finite difference time domain method, and an all-silicon-based infrared photovoltaic polarized photoelectric detector which has a high polarization ratio and has a photoelectric response rate in a short-wave infrared band is obtained through design. Comprising a substrate, a silicon nanowire, a metal antenna and two metal electrodes, the detector is divided into an active area and a passive area, the active area is provided with a metal antenna, and the passive area is not provided with a metal antenna. The detector disclosed by the invention has the advantages of working at room temperature, being tunable, high in polarization current ratio, high in response rate, zero in bias voltage, low in power consumption, compatible with a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) process and the like; the problems that a traditional polarization imaging system is large in size, heavy, high in cost and the like are solved, and wide application prospects are achieved in the polarization imaging field.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared polarization detection, and in particular relates to an infrared polarization photoelectric detector and a preparation method thereof. Background Art

[0002] Infrared polarization detection can accurately identify the contour information of objects under the interference of complex environments by extracting polarization information. Therefore, it has important applications in many fields such as national defense, medical treatment, and meteorological observation. Traditional infrared polarization detection technology usually uses polarizers integrated in the optical path of the infrared detection system to obtain polarization information. The main advantage is that the detector technology is mature and the system stability is good. However, it is large in size and high in cost, which makes it unable to meet the current demand for integration, intelligence, and miniaturization of polarization detection systems. Therefore, the current mainstream technical method is to integrate micro-polarizers on the infrared focal plane array chip, which has been widely used in commercial applications. However, this technology has a fatal flaw, that is, due to the presence of a layer of medium between the micro-polarizer and the detector, optical crosstalk will occur between different detection pixels, resulting in a relatively low overall polarization of the system and poor imaging quality. In recent years, another technical route has begun to be widely studied, that is, using the anisotropy of the material itself or the artificial metasurface and metamaterial to make the detector itself have an intrinsic polarization response. This method does not require the integration of micro-polarizers and avoids optical crosstalk. However, this detector has not been widely used so far. The main reason is that most of the current basic research and development is based on two-dimensional materials, which are incompatible with mainstream CMOS processes and chips.

[0003] In order to break through the above bottlenecks, there is an urgent need for an infrared polarization photodetector based on silicon-based materials, compatible with CMOS technology, and with intrinsic polarization response, so as to realize the popularization and widespread application of infrared polarization detection technology and open up new development directions for future intelligent sensing systems. Summary of the invention

[0004] The purpose of the present invention is to propose a high-performance all-silicon-based infrared polarization photodetector compatible with CMOS technology and a preparation method thereof, so as to solve the problems faced by the polarization photodetector mentioned in the above background technology.

[0005] The all-silicon-based infrared polarization photodetector provided by the present invention is based on the photothermoelectric effect; that is, according to the internal photoelectric emission process, the photothermoelectric effect is utilized to establish a new mechanism in which the directional drift of non-equilibrium hot carriers injected from the outside triggers the photocurrent in the silicon nanowire; the structural parameters of the device are optimized by the finite difference time domain method (FDTD), and a silicon-based photovoltaic detector with a high polarization ratio and a photoelectric response rate in the short-wave infrared band is designed. Specifically comprising: a substrate, a silicon nanowire, a metal antenna, and two metal electrodes. The detector is divided into an active area and a passive area, wherein a metal antenna exists in the active area, and no metal antenna exists in the passive area; wherein:

[0006] The substrate is a SiO2 / Si substrate;

[0007] The bottom surface of the silicon nanowire is located on the top surface of the substrate;

[0008] The metal antenna is a Ti / Au antenna; the metal antenna is divided into a top antenna and a bottom antenna; in the active area, the bottom surface of the top antenna is located on the top surface of the silicon nanowire; the bottom surface of the bottom antenna is located on the top surface of the substrate;

[0009] The two metal electrodes are respectively located at two ends of the silicon nanowire to form a Schottky contact;

[0010] The active region and the passive region form a non-uniform hot electron distribution under the irradiation of infrared light, and the hot electrons drift from the high-concentration region to the low-concentration region.

[0011] Further:

[0012] The silicon nanowires are periodically distributed on the substrate; the silicon nanowires are arc-shaped or straight-line-shaped. The straight-line silicon nanowires are silicon cubes with a certain length, width and height, such as Figure 1 As shown in ; the arc-shaped silicon nanowire is an arc-shaped silicon three-dimensional structure with a certain curvature, length, width and height, such as Figure 3 as shown in .

[0013] In the active region, the top antennas are periodically distributed on the silicon nanowires, and the bottom antennas are periodically distributed on the substrate between adjacent silicon nanowires.

[0014] The active region must exist.

[0015] The silicon-based infrared polarization photodetector operates in the near-infrared wavelength range of 1100-3000nm.

[0016] The method for preparing the all-silicon-based infrared polarization photoelectric detector provided by the present invention comprises the following specific steps:

[0017] S1, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0018] S2, importing the alignment mark pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0019] S3, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate Ti with a thickness of 5-15nm and Au with a thickness of 50-200nm, and peeling in an acetone solution to obtain a Ti / Au alignment mark.

[0020] S4, using a photoresist spin coating device to spin-coat PMMA photoresist on a silicon-on-insulator (SOI) substrate.

[0021] S5, importing the pre-drawn silicon nanowire pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing it using an electron beam lithography machine, and finally developing it in a mixed solution of MIBK and IPA, and fixing it in IPA.

[0022] S6, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate Cr with a thickness of 10-30 nm, and peeling in an acetone solution to obtain Cr nanowires.

[0023] S7, transferring the stripped sample to a reactive ion etching device, using the Cr nanowire as a mask, and using a mixed gas of SF6 and C4F8 to etch the silicon layer of the SOI device until the SiO2 layer is etched; then placing the etched sample in a chromium etchant to remove the Cr mask, thereby obtaining silicon nanowires.

[0024] S8, spin-coating ZEP520A photoresist on the sample surface using a photoresist spin coating device.

[0025] S9, importing the pre-drawn metal antenna pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing it using an electron beam lithography machine, and finally developing it in an oxylene solution and fixing it in water.

[0026] S10, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to successively evaporate Ti and Au, and then peeling in an acetone solution.

[0027] S11, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0028] S12, introducing the pre-drawn metal electrode pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0029] S13, transferring the fixed sample to an electron beam evaporation device, and then using the electron beam evaporation device to evaporate 5-15 nm Cr and 50-200 nm Au, and then peeling in an acetone solution.

[0030] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0031] (1) The polarization photodetector proposed in the present invention has an intrinsic polarization response and avoids optical crosstalk. It utilizes a new photodetection mechanism, that is, the directional photocurrent generated by externally injected hot carriers can realize self-powered photodetection.

[0032] (2) The polarization photodetector preparation method proposed in the present invention is compatible with the existing CMOS process and can be monolithically integrated with a CMOS chip compared to other types of non-silicon-based infrared photoelectric polarization photodetectors.

[0033] (3) The structural parameters of the polarization photodetector proposed in the present invention have a wide range for regulation, and this method can be used to achieve tunable polarization ratio and multi-band detection.

[0034] The detector of the present invention has the advantages of room temperature operation, tunable high polarization current ratio (i.e., using different geometric structures and polarization voltages to make the photocurrent ratio generated when different polarized light is incident adjustable), high response rate, zero bias, low power consumption, and compatibility with CMOS technology. The present invention solves the problems of bulky, heavy, and high cost of traditional polarization imaging systems, and has broad application prospects in the field of polarization imaging in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a diagrammatic representation of the structure of a linear silicon-based polarization photodetector in Example 1.

[0036] Figure 2 It is a photocurrent spectrum of the corresponding device of the linear silicon-based polarization photodetector in Example 1 as the polarization angle of the incident infrared light with a wavelength of 1.55 μm changes.

[0037] Figure 3 This is a diagram of the arc-shaped silicon-based polarization photodetector structure in Example 2.

[0038] Figure 4 It is a photovoltage spectrum of the device corresponding to the arc-shaped silicon-based polarization photodetector in Example 2 as the polarization angle of the incident infrared light with a wavelength of 1.55 μm changes.

[0039] Figure 5 It is a detailed structural diagram of the active region silicon nanowires and metal antenna of the linear silicon-based polarization photodetector in the embodiment. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the embodiments. Any simple changes to the calculation parameters in the embodiments fall within the protection scope of the present invention.

[0041] Example 1: A linear silicon-based polarization photodetector, see Figure 1 and 5 The specific size is W Si =205nm,P Si =500nm,W Au =50nm,P Au =100nm. The height of the silicon nanowire is 200nm, and the metal antenna is composed of 5nm Ti and 25nm Au. The implementation method is:

[0042] S1, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0043] S2, importing the alignment mark pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0044] S3, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 15nm Ti and 200nm Au, and peeling in an acetone solution to obtain a Ti / Au alignment mark.

[0045] S4, using a photoresist spin coating device to spin-coat PMMA photoresist on a silicon-on-insulator (SOI) substrate.

[0046] S5, introducing the silicon nanowire pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of MIBK and IPA, and fixing in IPA.

[0047] S6, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 30 nm Cr, and peeling in an acetone solution to obtain Cr nanowires.

[0048] S7, transferring the stripped sample to a reactive ion etching device, using the Cr nanowire as a mask and using a mixed gas of SF6 and C4F8 to etch the silicon layer of the SOI device until the SiO2 layer is etched. Then, the etched sample is placed in a chromium etchant to remove the Cr mask, thereby obtaining a silicon nanowire.

[0049] S8, spin-coating ZEP520A photoresist on the sample surface using a photoresist spin coating device.

[0050] S9, importing the metal antenna pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing it using an electron beam lithography machine, and finally developing it in an oxylene solution and fixing it in water.

[0051] S10, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to successively evaporate Ti and Au, and then peeling in an acetone solution.

[0052] S11, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0053] S12, introducing the metal electrode pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0054] S13, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 15nm Cr and 200nm Au, and then stripping in an acetone solution.

[0055] The prepared photodetector was subjected to photoelectric testing, and the polarization-dependent photocurrent spectrum under infrared light with a wavelength of 1.55 μm was obtained, showing that the prepared detector has a photocurrent polarization ratio of up to 576 without an external voltage, and the corresponding response rate can reach 22 mA / W, which is significantly better than similar devices, see Figure 2 .

[0056] Example 2: An arc-shaped silicon-based polarization photodetector, see Figure 3 As shown; the specific size is, W Si =205nm, P Si =500nm, the arc of the silicon arc is 90°, the innermost ring radius is 30μm, and the outermost ring radius is 60μm. The gold antenna is distributed radially periodically, W Au =50nm,θ=0.19°, and the implementation method is:

[0057] S1, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0058] S2, importing the alignment mark pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0059] S3, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 15nm Ti and 200nm Au, and peeling in an acetone solution to obtain a Ti / Au alignment mark.

[0060] S4, using a photoresist spin coating device to spin-coat PMMA photoresist on a silicon-on-insulator (SOI) substrate.

[0061] S5, introducing the silicon nanowire pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of MIBK and IPA, and fixing in IPA.

[0062] S6, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 30 nm Cr, and peeling in an acetone solution to obtain Cr nanowires.

[0063] S7, transferring the stripped sample to a reactive ion etching device, using the Cr nanowire as a mask and using a mixed gas of SF6 and C4F8 to etch the silicon layer of the SOI device until the SiO2 layer is etched. Then, the etched sample is placed in a chromium etchant to remove the Cr mask, thereby obtaining a silicon nanowire.

[0064] S8, spin-coating ZEP520A photoresist on the sample surface using a photoresist spin coating device.

[0065] S9, importing the metal antenna pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing it using an electron beam lithography machine, and finally developing it in an oxylene solution and fixing it in water.

[0066] S10, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to successively evaporate Ti and Au, and then peeling in an acetone solution.

[0067] S11, spin-coating UV5 chemically amplified photoresist on a silicon-on-insulator (SOI) substrate using a photoresist spin coating device.

[0068] S12, introducing the metal electrode pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water.

[0069] S13, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate 15nm Cr and 200nm Au, and then stripping in an acetone solution.

[0070] The prepared photodetector was subjected to photoelectric testing, and the polarization-dependent photovoltage spectrum under infrared light with a wavelength of 1.55 μm was obtained, showing that the photovoltage polarization ratio of the prepared detector was -1 when there was no external voltage applied, see Figure 4 .

Claims

1. An all-silicon-based infrared polarization photodetector, characterized in that: That is, according to the internal photoemission process, using the photothermal electron effect, a new mechanism of photocurrent induced by the directional drift of non-equilibrium hot carriers injected from the outside in silicon nanowires is established; the structural parameters of the device are optimized by the finite difference time domain method; specifically, it includes a substrate, a silicon nanowire, a metal antenna, and two metal electrodes; the detector is divided into an active area and a passive area, a metal antenna exists in the active area, and no metal antenna exists in the passive area; wherein: The substrate is a SiO2 / Si substrate; The bottom surface of the silicon nanowire is located on the top surface of the substrate; The metal antenna is a Ti / Au antenna; the metal antenna is divided into a top antenna and a bottom antenna; in the active area, the bottom surface of the top antenna is located on the top surface of the silicon nanowire; the bottom surface of the bottom antenna is located on the top surface of the substrate; The two metal electrodes are respectively located at two ends of the silicon nanowire; The active region and the passive region form a non-uniform hot electron distribution under the irradiation of infrared light, and the hot electrons drift from the high-concentration region to the low-concentration region.

2. The silicon-based infrared polarization photodetector according to claim 1, characterized in that: The silicon nanowires are distributed periodically on the substrate; the silicon nanowires are arc-shaped or straight-line-shaped.

3. The silicon-based infrared polarization photodetector according to claim 1, characterized in that: In the active region, the top antennas are periodically distributed on the silicon nanowires, and the bottom antennas are periodically distributed on the substrate between adjacent silicon nanowires.

4. The silicon-based infrared polarization photodetector according to claim 1, characterized in that: The operating range of near infrared wavelength is 1100-3000nm.

5. The method for preparing a silicon-based infrared polarization photodetector according to any one of claims 1 to 4, characterized in that: The specific steps are: S1, spin coating UV5 chemically amplified photoresist on a silicon-on-insulator substrate using a photoresist spin coating device; S2, introducing the alignment mark pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water; S3, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate Ti with a thickness of 5-15 nm and Au with a thickness of 50-200 nm, and peeling in an acetone solution to obtain a Ti / Au alignment mark; S4, spin coating PMMA photoresist on the silicon-on-insulator substrate using a photoresist spin coating device; S5, introducing the pre-drawn silicon nanowire pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of MIBK and IPA, and fixing in IPA; S6, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate Cr with a thickness of 10-30 nm, and peeling in an acetone solution to obtain Cr nanowires; S7, transferring the stripped sample to a reactive ion etching device, using the Cr nanowire as a mask, and using a mixed gas of SF6 and C4F8 to etch the silicon layer of the SOI device until the SiO2 layer is etched; then placing the etched sample in a chromium etchant to remove the Cr mask, thereby obtaining silicon nanowires; S8, using a photoresist spin coating device to spin coat ZEP520A photoresist on the sample surface; S9, importing the pre-drawn metal antenna pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in an oxylene solution and fixing in water; S10, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to successively evaporate Ti and Au, and then peeling in an acetone solution; S11, spin coating UV5 chemically amplified photoresist on the silicon-on-insulator substrate using a photoresist spin coating device; S12, introducing the pre-drawn metal electrode pattern into an electron beam lithography machine, adjusting the exposure dose according to the shape of the pattern and the thickness of the photoresist, then exposing using the electron beam lithography machine, and finally developing in a mixed solution of TMAH and water, and fixing in water; S13, transferring the fixed sample to an electron beam evaporation device, then using the electron beam evaporation device to evaporate Cr with a thickness of 5-15 nm and Au with a thickness of 50-200 nm, and then peeling in an acetone solution.

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