Photoelectric detector and preparation method thereof

Abstract

The photoelectric detector comprises a germanium thin film layer and a silicon dioxide dielectric layer which are arranged on an SOI (Silicon On Insulator) substrate, and the silicon dioxide dielectric layer covers the germanium thin film layer; the beryllium oxide interface passivation layer is arranged between the germanium thin film layer and the silicon dioxide dielectric layer, the germanium thin film layer in contact with the beryllium oxide interface passivation layer is provided with a germanium surface subjected to 850-950 DEG C high-temperature treatment, and the beryllium oxide interface passivation layer is formed at the low temperature of 188-212 DEG C; and the thin film layer which has a compact crystal structure of Be-O covalent bonds and is conformal with the surface of the germanium thin film layer and is 6-20nm in thickness after being subjected to medium-temperature treatment at 500-600 DEG C. The beryllium oxide interface passivation layer is arranged, so that the dark current of the photoelectric detector can be further reduced on the premise that the responsivity of the detector is not obviously influenced.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a photoelectric detection device and a preparation method thereof. Background Art

[0002] Germanium-based photodetectors are important active devices in silicon-based optoelectronic systems, responsible for the conversion of optical-electrical signals, and have extensive applications in fields such as optical communication, lidar, non-invasive blood glucose monitoring, quantum computing, and deep learning. Their key performance indicators include -3dB bandwidth, responsivity, and dark current. Different applications have different requirements for each performance of germanium-based photodetectors. For example, in non-invasive blood glucose monitoring and some applications combining free-space optical solutions, a lower dark current density is desired.

[0003] In germanium-based photodetectors, the sources of dark current mainly include three: 1) the diffusion current (intrinsic dark current) of the reverse-biased PIN junction; 2) the recombination leakage current caused by the generation of minority carriers in the depletion region; 3) the recombination leakage current caused by the generation of minority carriers on the surface of the germanium thin film. The first two of them belong to bulk dark current, and the latter belongs to surface dark current. Since the above source 1) belongs to intrinsic dark current and is a function of temperature and bias voltage, it cannot be optimized. The optimization direction of source 2) mainly lies in improving the growth process of germanium thin films and reducing the dislocation density. There has been rich and mature research in this regard, and the room for further optimization is limited; the optimization direction of source 3) lies in improving the quality of the germanium-silicon dioxide interface and reducing the interface state density. Considering that a typical germanium-based photodetector is a device with a relatively large perimeter / area ratio and a very large specific surface area, its dark current is mainly dominated by surface dark current. To sum up, the direction for further reducing the dark current of existing germanium-based photodetectors mainly lies in improving the quality of the germanium-silicon dioxide interface.

[0004] Some studies show that the reason for the poor quality of the germanium-silicon dioxide interface is that the oxidation of germanium surface by silicon dioxide is uncontrollable and unstable. In addition to generating germanium dioxide, germanium monoxide with volatility above about 550°C will also be generated, and germanium dioxide will also react with germanium to form oxygen vacancies that are easy to diffuse, resulting in more uncontrollable defects on the surface of the germanium thin film.

[0005] In the CMOS field, due to the interest in high-mobility germanium channels, there is relatively rich research on the germanium-oxide dielectric interface, and some interface passivation schemes have been developed: a) generating high-quality germanium dioxide through high-pressure oxidation / O2 annealing / O3 oxidation to inhibit the formation of germanium monoxide and oxygen vacancies; b) introducing thin oxygen diffusion barrier layers such as GeN, AlN, HfN; c) introducing some substances that can combine with germanium oxide (GeO x ) to form stable compounds, such as La2O3 and Y2O3.

[0006] However, the long-term reliability of the above-mentioned Scheme a) is relatively poor. Even for Schemes b) and c) with better reliability, they cannot be directly applied to germanium-based photodetectors because the optical properties of the interface also need to be considered. The germanium-silicon dioxide interface has always been the interface structure widely used in germanium-based photodetectors. In addition to the fact that the silicon dioxide window supports selective epitaxy of germanium on a silicon substrate, another important reason is that the refractive index of silicon dioxide at a wavelength of 1.55 μm is 1.44, which is much smaller than the refractive index of germanium of 4.28 in the same wavelength band. Its refractive index contrast is as high as 44%, and the critical angle of total reflection is small, making it very easy to confine the optical field in the germanium thin film, which is beneficial to light absorption, thus enabling the device to have a high responsivity. However, the refractive indices of the materials in Schemes b) and c) are significantly greater than that of silicon dioxide. For example, the refractive index of AlN is 2.12, and the refractive index of Y2O3 is 1.89. Their refractive index contrasts with germanium are relatively small, which will affect the optical field distribution in the device and thus significantly affect the responsivity of the device. Summary of the Invention

[0007] The object of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a photodetector device and a preparation method thereof.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] The present invention provides a photodetector device, including:

[0010] A germanium thin film layer and a silicon dioxide dielectric layer provided on an SOI substrate, and the silicon dioxide dielectric layer covers the germanium thin film layer;

[0011] A beryllium oxide interface passivation layer provided at the interface between the germanium thin film layer and the silicon dioxide dielectric layer. The germanium thin film layer in contact with the beryllium oxide interface passivation layer has a germanium surface after being heat-treated at a high temperature of 850 - 950 °C. The beryllium oxide interface passivation layer is a 6 - 20 nm thick thin film layer formed at a low temperature of 188 - 212 °C and having a dense crystal structure with Be - O covalent bonds after being heat-treated at a medium temperature of 500 - 600 °C and conformal to the surface of the germanium thin film layer.

[0012] Furthermore, the beryllium oxide interface passivation layer is used to inhibit the oxidation of the surface of the germanium thin film layer at the interface with the silicon dioxide dielectric layer, block the diffusion of oxygen vacancies, and inhibit the phonon scattering of carriers, thereby improving the interface quality between the germanium thin film layer and the silicon dioxide dielectric layer, reducing the interface state density, and inhibiting the generation of surface recombination leakage current.

[0013] Further, the germanium thin film layer includes an intrinsic germanium region, a first doped region of a first conduction type and a second doped region of a second conduction type are respectively disposed at two opposite ends of the intrinsic germanium region, and the germanium thin film layer further includes the first doped region or the second doped region.

[0014] Further, a first contact region is disposed on the first doped region, a second contact region is disposed on the second doped region, a first electrode is connected to the first contact region, a second electrode is connected to the second contact region, and the first electrode and the second electrode are led out from the surface of the silicon dioxide dielectric layer; and / or, the photodetector device is connected to a waveguide disposed on the SOI substrate through one of the first doped region and the second doped region.

[0015] Further, the photodetector device includes a vertical PIN type photodetector device or a horizontal PIN type photodetector device formed on the SOI substrate and covered by the silicon dioxide dielectric layer. The vertical PIN type photodetector device or the horizontal PIN type photodetector device is provided with a P-type doped region, an I intrinsic region, and an N-type doped region. The first doped region is one of the P-type doped region and the N-type doped region, the second doped region is the other of the P-type doped region and the N-type doped region, and the intrinsic germanium region is the I intrinsic region.

[0016] The present invention also provides a method for manufacturing a photodetector device, including:

[0017] Providing an SOI substrate;

[0018] Forming a germanium thin film layer and a silicon dioxide dielectric layer on the SOI substrate, covering the germanium thin film layer with the silicon dioxide dielectric layer, and forming a beryllium oxide interface passivation layer at the interface between the germanium thin film layer and the silicon dioxide dielectric layer;

[0019] Wherein, before forming the beryllium oxide interface passivation layer, the surface of the germanium thin film layer in contact with the beryllium oxide interface passivation layer is subjected to a high-temperature treatment at 850-950 °C to form a germanium surface. When forming the beryllium oxide interface passivation layer, a beryllium oxide thin film layer is first formed at a low temperature of 188-212 °C, and then subjected to a medium-temperature treatment at 500-600 °C to form a dense crystal structure with Be-O covalent bonds and a 6-20 nm thick beryllium oxide interface passivation layer conformal to the surface of the germanium thin film layer.

[0020] Further, before forming the beryllium oxide interface passivation layer, hydrogen is used to perform a high-temperature annealing treatment on the surface of the germanium thin film layer in contact with the beryllium oxide interface passivation layer at 850-950 °C to remove the natural oxide layer of germanium on the surface of the germanium thin film layer and form a germanium surface. When forming the beryllium oxide interface passivation layer, a low-temperature atomic layer deposition process at 188-212 °C using beryllium dimethyl and water as reactants is adopted. First, a beryllium oxide thin film layer is formed, and then a medium-temperature annealing treatment at 500-600 °C is performed to form the beryllium oxide interface passivation layer with a thickness of 6-20 nm.

[0021] Further, the methods for forming the germanium thin film layer, the beryllium oxide interface passivation layer, and the silicon dioxide dielectric layer specifically include:

[0022] Form a flat area on the SOI substrate;

[0023] Form a first doped area on the surface of the flat area;

[0024] Form a sacrificial dielectric layer on the surface of the SOI substrate, form a window on the surface of the sacrificial dielectric layer, and stop the bottom of the window at the surface of the flat area at the first doped area;

[0025] Form the germanium thin film layer in the window, and form a second doped area on the top of the germanium thin film layer, so as to form an intrinsic germanium area in the germanium thin film layer below the second doped area;

[0026] Remove the sacrificial dielectric layer, form the beryllium oxide interface passivation layer on the surface of the SOI substrate, and cover the surface of the germanium thin film layer;

[0027] Form the silicon dioxide dielectric layer on the surface of the SOI substrate to cover the germanium thin film layer and the beryllium oxide interface passivation layer, and make the beryllium oxide interface passivation layer formed at the interface between the germanium thin film layer and the silicon dioxide dielectric layer.

[0028] Further, when forming the first doped area, it further includes: forming first contact areas on the surfaces of the flat areas on both sides of the first doped area; when forming the second doped area, forming second contact areas on the surface of the second doped area; after forming the silicon dioxide dielectric layer, it further includes: forming through holes on the surface of the silicon dioxide dielectric layer with the bottoms respectively connected to the first contact area and the second contact area, and filling the through holes to form a first electrode connected to the first contact area and a second electrode connected to the second contact area.

[0029] Further, when forming the flat area in the active area, a waveguide with a size-graded structure connected to the flat area is also formed on the SOI substrate at the same time.

[0030] As can be seen from the above technical solutions, in the present invention, a beryllium oxide interface passivation layer is formed between the germanium thin film layer and the silicon dioxide dielectric layer of the optoelectronic detection device. By utilizing the strong Be-O covalent bond and dense crystal structure of beryllium oxide crystals, the generation of germanium oxide on the surface of the germanium thin film layer and the diffusion of oxygen vacancies can be inhibited, resulting in a decrease in the interface state density on the surface of the germanium thin film compared to the germanium-silicon dioxide interface. Therefore, the surface leakage current can be reduced. At the same time, by utilizing the relatively low phonon frequency of beryllium oxide crystals, the surface recombination leakage current can be further inhibited. Moreover, the refractive index of beryllium oxide at a certain wavelength is relatively close to that of silicon dioxide, and the optical field can be well confined within the germanium thin film as well, without significantly affecting the light absorption of the device, and thus the responsivity of the device will not be significantly reduced. Therefore, by setting the beryllium oxide interface passivation layer, the dark current of the optoelectronic detection device is further reduced without significantly affecting the responsivity of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural cross-sectional view of an optoelectronic detection device according to a preferred embodiment of the present invention.

[0032] Figure 2 It is a structural perspective view of an optoelectronic detection device according to a preferred embodiment of the present invention.

[0033] Figures 3 - 15 It is a schematic diagram of the process steps of a method for manufacturing an optoelectronic detection device according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art in the field to which the present invention pertains. The words such as "including" used herein mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0035] The present invention aims to solve the problem that there is currently no germanium-silicon dioxide interface passivation solution applicable to optoelectronic detection devices, and provides a novel optoelectronic detection device and a manufacturing method thereof.

[0036] By forming a unique beryllium oxide interface passivation layer at the interface between the germanium thin film layer and the silicon dioxide dielectric layer, the present invention can passivate the interface between the germanium thin film layer and the silicon dioxide dielectric layer, and can further reduce the dark current of the device without significantly affecting the device responsivity.

[0037] The following further elaborates on the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0038] Reference Figure 1 . A photodetector device of the present invention includes: a germanium thin film layer 19 provided on an SOI substrate (i.e., the top silicon layer of the SOI substrate) 10, a silicon dioxide dielectric layer 11 covering the germanium thin film layer 19, and a beryllium oxide interface passivation layer 12 provided at the interface between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11.

[0039] Among them, the surface 191 of the germanium thin film layer 19 in contact with the beryllium oxide interface passivation layer 12, that is, the surface 191 of the germanium thin film layer 19 at the interface with the silicon dioxide dielectric layer 11, is a pure germanium surface after being treated at a high temperature of 850 - 950 °C. And the beryllium oxide interface passivation layer 12 is a 6 - 20 nm thick thin film layer formed at a low temperature of 188 - 212 °C, having a dense crystal structure with Be - O covalent bonds after being treated at a medium temperature of 500 - 600 °C, and conformal with the surface of the germanium thin film layer 19.

[0040] The beryllium oxide interface passivation layer 12 provided by the present invention is used to inhibit the oxidation of the surface 191 of the germanium thin film layer 19 at the interface with the silicon dioxide dielectric layer 11 (i.e., the surface 191 of the germanium thin film layer 19 in contact with the beryllium oxide interface passivation layer 12), block the diffusion of oxygen vacancies, and inhibit the phonon scattering of carriers, thereby improving the interface quality between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11, reducing the interface state density, and inhibiting the generation of surface recombination leakage current.

[0041] Reference Figure 1 . The germanium thin film layer 19 protrudes from the upper surface of the SOI substrate 10. The silicon dioxide dielectric layer 11 is provided on the upper surface of the SOI substrate 10 and completely covers the germanium thin film layer 19, thereby forming an interface between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11 at the junction between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11. The beryllium oxide interface passivation layer 12 is provided at the interface between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11. In other words, the beryllium oxide interface passivation layer 12 is provided between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11 and is closely attached to the germanium thin film layer 19 and the silicon dioxide dielectric layer 11.

[0042] In some embodiments, the germanium thin film layer 19 includes an intrinsic germanium region 16; a first doped region of the first conductivity type and a second doped region of the second conductivity type are provided at the upper and lower opposite ends of the intrinsic germanium region 16, and the germanium thin film layer 19 also includes the first doped region or the second doped region.

[0043] The first conductivity type may be one of N-type and P-type, and the second conductivity type may be the other of N-type and P-type. The N-type may be formed by injecting an N-type dopant (such as P, As, etc.) into a semiconductor material. The P-type may be formed by injecting a P-type dopant (such as B, etc.) into a semiconductor material.

[0044] In the following embodiments of the present invention, the first doping region 20 is disposed on the lower end of the intrinsic germanium region 16, the second doping region 17 is disposed on the upper end of the intrinsic germanium region 16, and the first doping region 20 is an N-type doping region, and the second doping region 17 is a P-type doping region. It is described in detail as an example, but it can be understood that it is only used to illustrate the embodiments of the present invention, rather than limiting the specific implementation methods of the present invention.

[0045] refer to Figure 1 In some embodiments, the first doped region 20 is located in the SOI substrate 10 and exposed on the upper surface of the SOI substrate 10 ; the germanium thin film layer 19 is connected to the upper surface of the SOI substrate 10 at its lower end surface, so that the first doped region 20 is disposed on the lower end surface of the intrinsic germanium region 16 .

[0046] The second doping region 17 is disposed on the upper end of the intrinsic germanium region 16, that is, the germanium thin film layer 19 includes the intrinsic germanium region 16 and the second doping region 17, and the second doping region 17 is formed by performing P-type doping on the upper end of the germanium thin film layer 19, thereby forming the intrinsic germanium region 16 in the germanium thin film layer 19 below the second doping region 17. In other words, the beryllium oxide interface passivation layer 12 covers the second doping region 17.

[0047] The properties of beryllium oxide crystals are as follows: the atomic number of beryllium oxide is 4, its 2p orbital is unoccupied, the atomic radius is very small, the Be-O bond length is very short, and a strong covalent bond can be formed. It is difficult for Ge (germanium) to capture oxygen atoms from it to form GeO. The crystal structure of beryllium oxide is dense and the interstitial space is small, which can block the perturbation of the interface by the diffusion of oxygen vacancies. At the same time, the strong Be-O bond makes it have a relatively low phonon frequency, which can suppress the phonon scattering of carriers, thereby suppressing the surface recombination leakage current.

[0048] Taking the above-mentioned germanium-based photodetector with a typical vertical PIN structure as an example, by introducing a beryllium oxide crystal layer as the interface passivation layer 12 on the sidewalls and the top of the germanium thin film layer 19, the strong Be-O covalent bond and the dense crystal structure of the beryllium oxide crystal can be utilized to inhibit the formation of germanium oxide and the diffusion of oxygen vacancies, so that the interface state density on the surface of the germanium thin film layer 19 is decreased compared with that of the germanium-silicon dioxide interface, and the surface leakage current is reduced.

[0049] Meanwhile, the beryllium oxide crystal has a relatively low phonon frequency, which can further inhibit the surface recombination leakage current. Therefore, by setting the beryllium oxide crystal as the interface passivation layer 12, the interface quality can be improved, the interface state density can be reduced, and thus the dark current of the germanium-based photodetector device is reduced. Moreover, the refractive index of beryllium oxide at a wavelength of 1.55 μm is 1.7016, which is relatively close to the refractive index of the silicon dioxide dielectric layer 11, and the refractive index contrast with germanium reaches 42%, which is equivalent to the refractive index contrast of the germanium-silicon dioxide interface. By introducing the interface passivation layer 12 of the beryllium oxide crystal, the optical field can also be confined in the germanium thin film layer 19 relatively well, and there is no significant impact on the light absorption of the device, so that the responsivity of the device will not be significantly reduced, that is, the impact on the responsivity of the device is small. Therefore, by introducing the beryllium oxide crystal as the interface passivation layer 12 in the present invention, the dark current of the device is further reduced on the premise of not significantly affecting the responsivity of the device.

[0050] Reference Figure 1 . In some embodiments, a first contact region 15 is provided on the first doped region 20, and a second contact region 18 is provided on the second doped region 17. A first electrode 14 is connected to the first contact region 15, and a second electrode 13 is connected to the second contact region 18; the first electrode 14 and the second electrode 13 are led out from the surface of the silicon dioxide dielectric layer 11.

[0051] Among them, the first contact region 15 is respectively disposed on the SOI substrate 10 on both sides of the first doped region 20, and enters the SOI substrate 10 downward from the upper surface of the SOI substrate 10 and is respectively connected to the first doped region 20. The second contact region 18 is formed on the second doped region 17 and enters the second doped region 17 downward from the upper end surface of the germanium thin film layer 19.

[0052] Part of the region in the second doped region 17 can be directly used as the second contact region 18.

[0053] The lower end of the second electrode 13 needs to pass through the beryllium oxide interface passivation layer 12 covering the upper end surface of the germanium thin film layer 19 to form a connection with the second contact region 18 below.

[0054] Reference Figure 2 And in combination with reference Figure 1。In some embodiments, a flat plate region 101 is provided in the active region of the optoelectronic detection device. The flat plate region 101 is formed by patterning the upper surface of the SOI substrate 10 to form the boundary of the flat plate region 101. The first doping region 20 and the first contact region 15 are located in the flat plate region 101, and the germanium thin film layer 19 is located in the region within the flat plate region 101 and is connected to the first doping region 20 below. The beryllium oxide interface passivation layer 12 covers the germanium thin film layer 19 and conformally and completely coats the exposed surface (top surface and side surfaces) of the germanium thin film layer 19.

[0055] In some embodiments, the beryllium oxide interface passivation layer 12 can extend from the upper surfaces of the flat plate region 101 on both sides of the germanium thin film layer 19 to the two side boundaries of the flat plate region 101. When the beryllium oxide interface passivation layer 12 covers the entire upper surface of the flat plate region 101 and the germanium thin film layer 19, the lower ends of the first electrode 14 and the second electrode 13 both need to pass through the corresponding beryllium oxide interface passivation layer 12 to be correspondingly connected to the first contact region 15 and the second contact region 18 below. Figure 2 The silicon dioxide dielectric layer 11 is omitted.

[0056] In some embodiments, a waveguide 102 is further provided on the SOI substrate 10. The waveguide 102 is formed by patterning the upper surface of the SOI substrate 10. The waveguide 102 is connected to the flat plate region 101 through a size gradient structure 1021 provided, and is connected to the position below the germanium thin film layer 19 between the two first contact regions 15.

[0057] The above Figure 1 and Figure 2 The optoelectronic detection device shown forms a vertical PIN type optoelectronic detection device. The vertical PIN type optoelectronic detection device is formed on the SOI substrate 10 and is covered by the silicon dioxide dielectric layer 11. The vertical PIN type optoelectronic detection device is provided with a P-type doping region, an I intrinsic region, and an N-type doping region. The first doping region 20 is an N-type doping region, the second doping region 17 is a P-type doping region, and the intrinsic germanium region 16 is an I intrinsic region.

[0058] In some other embodiments, the optoelectronic detection device of the present invention can also be a horizontal PIN type optoelectronic detection device formed on an SOI substrate and covered by a silicon dioxide dielectric layer. The horizontal PIN type optoelectronic detection device is provided with a P-type doping region, an I intrinsic region, and an N-type doping region. The first doping region is one of a P-type doping region and an N-type doping region, the second doping region is the other of a P-type doping region and an N-type doping region, and the intrinsic germanium region is an I intrinsic region. It can be understood by referring to the above embodiments and will not be elaborated here.

[0059] The following further elaborates in detail on a method for manufacturing an optoelectronic detection device of the present invention through specific embodiments and in combination with the drawings.

[0060] Refer toFigures 3 - 15 。A method for preparing an optoelectronic detection device according to the present invention can be used to prepare an optoelectronic detection device of the present invention as described above, for example Figure 1 shown. An optoelectronic detection device of the present invention is a vertical PIN type optoelectronic detection device, and the method includes the following steps:

[0061] Step S1: Provide an SOI substrate.

[0062] An SOI substrate is used to form a vertical PIN type optoelectronic detection device of the present invention on a silicon substrate.

[0063] As Figure 3 shown, first, a photolithography and etching process is performed on the SOI substrate (i.e., the top silicon layer of the SOI substrate) 10 to obtain Figure 1 the active region silicon flat region 101 structure shown in

[0064] A photolithography and etching process can also be performed on the SOI substrate 10 to simultaneously obtain Figure 2 the silicon waveguide 102 with a size-graded structure 1021 and the active region silicon flat region 101 structure shown in

[0065] Step S2: Form a germanium thin film layer 19 on the SOI substrate 10, and a first doping region 20 of a first conductivity type and a second doping region 17 of a second conductivity type disposed at two opposite ends of the germanium thin film layer 19.

[0066] As Figure 4 shown, an ion implantation process is used to perform N-type doping on the surface of the entire flat region 101 to form the first doping region 20; and an ion implantation process is used to perform N-type heavy doping on the regions to be contacted on both sides of the flat region 101, and rapid thermal annealing is performed to activate the impurity ions. Thus, the first doping region 20 is formed on the surface of the flat region 101 of the SOI substrate 10, and two first contact regions 15 connected to both sides of the first doping region 20 are formed.

[0067] As Figure 5 shown, then, a sacrificial dielectric layer 21 is formed on the surface of the SOI substrate 10. In this embodiment, a chemical vapor deposition process is used to form a silicon dioxide sacrificial dielectric layer 21 with a thickness of 400 - 500 nm on the surface of the SOI substrate 10.

[0068] As Figure 6 shown, then, a photolithography and etching process is used to form a window 22 for epitaxy on the surface of the sacrificial dielectric layer 21, and the bottom of the window 22 stops at the surface of the flat region 101 at the first doping region 20.

[0069] As Figure 7As shown, next, an epitaxial process is used to form a germanium thin film layer 19 in the window 22. In this embodiment, selective epitaxy of germanium is used to grow germanium material 192 with a thickness of 550 - 650 nm in the window 22. Subsequently, a chemical mechanical polishing process is used to planarize the top of the germanium material 192, obtaining a germanium thin film layer 19 whose surface in the window 22 is flush with the surface of the sacrificial dielectric layer 21, as Figure 8 shown. The lower end of the germanium thin film layer 19 is connected to the first doping region 20 on the lower flat region 101 through the opening at the bottom of the window 22. The thickness of the remaining germanium material 192 (i.e., the thickness of the germanium thin film layer 19) is approximately 400 nm.

[0070] As Figure 9 shown, then, an ion implantation process is used to perform P-type doping on the top region of the germanium thin film layer 19, and the impurities are activated by rapid thermal annealing. Thus, a second doping region 17 is formed on the top of the germanium thin film layer 19, and the surface of the formed second doping region 17 is directly used as the surface of the second contact region 18 in contact with the electrode. Thus, an intrinsic germanium region 16 is formed in the germanium thin film layer 19 below the second doping region 17.

[0071] As Figure 10 shown, after that, a wet etching process is used, and a diluted hydrofluoric acid etching solution is used to remove the remaining silicon dioxide sacrificial dielectric layer 21.

[0072] After the above steps, a germanium thin film layer 19 is formed on the SOI substrate 10, and an N-type first doping region 20 and a P-type second doping region 17 are respectively provided on the upper and lower two opposite ends of the germanium thin film layer 19. That is, a first doping region 20 and a second doping region 17 are respectively formed on the upper and lower two opposite ends of the intrinsic germanium region 16.

[0073] Step S3: Form a silicon dioxide dielectric layer 11 on the SOI substrate 10 to cover the germanium thin film layer 19, and form a beryllium oxide interface passivation layer 12 between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11.

[0074] Since germanium material is prone to natural oxidation, which affects the interface quality with silicon dioxide, therefore, after removing the remaining silicon dioxide sacrificial dielectric layer 21, it is necessary to further remove the natural oxide layer of germanium on the surface of the germanium thin film layer 19.

[0075] As Figure 10 shown, in this embodiment, hydrogen gas is used to perform a high-temperature annealing treatment on the surface of the germanium thin film layer 19 in contact with the beryllium oxide interface passivation layer 12 at a temperature of 850 - 950 °C. Preferably, the high-temperature annealing treatment temperature is, for example, 901 °C, 893 °C, 897 °C, 905 °C, to remove the natural oxide layer of germanium on the surface of the germanium thin film layer 19 and form a pure germanium surface 191.

[0076] As shown in Figure 11 , next, a deposition process can be adopted to form a beryllium oxide interface passivation layer 12 between the germanium-silicon dioxide interfaces. In this embodiment, an atomic layer deposition process is used, and dimethyl beryllium and water are used as reactants, and a low-temperature atomic layer deposition process is carried out at 188-212 °C. Preferably, the process temperature is, for example, 197 °C, 195 °C, 204 °C. First, a beryllium oxide thin film layer covering the surface of the germanium thin film layer 19 is formed on the surface of the SOI substrate 10. Subsequently, a medium-temperature annealing treatment is carried out at 500-600 °C. Preferably, the medium-temperature annealing treatment temperature is, for example, 550 °C, 504 °C, 500 °C. Thus, a 6-20 nm thick beryllium oxide interface passivation layer 12 that conformally wraps the top and sidewall surfaces of the germanium thin film layer 19 is formed on the surface of the SOI substrate 10. Preferably, the thickness of the beryllium oxide interface passivation layer 12 is 9.6 nm, 10.1 nm, 10.7 nm.

[0077] The beryllium oxide thin film on the surface of the flat region 101 other than the top and sidewall surfaces of the germanium thin film layer 19 can be retained or removed. In this embodiment, a process method of retaining the beryllium oxide thin film on the surface of the flat region 101 other than the top and sidewall surfaces of the germanium thin film layer 19 is adopted.

[0078] As shown in Figure 12 , next, a deposition process is adopted to form a silicon dioxide dielectric layer 11 on the surface of the SOI substrate 10, covering the germanium thin film layer 19 and the beryllium oxide interface passivation layer 12, so that the beryllium oxide interface passivation layer 12 is formed at the interface between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11. In this embodiment, a chemical vapor deposition process is used to deposit a 650-750 nm thick silicon dioxide thin film on the surface of the SOI substrate 10. And a chemical mechanical polishing process is adopted to planarize the surface of the silicon dioxide thin film, and a required thickness distance is maintained between the planarized surface of the silicon dioxide thin film and the top surface of the germanium thin film layer 19, so as to form a silicon dioxide dielectric layer 11 covering the germanium thin film layer 19 and the beryllium oxide crystal beryllium oxide interface passivation layer 12, as shown in Figure 13 . In this way, a required beryllium oxide crystal beryllium oxide interface passivation layer 12 is formed at the interface between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11.

[0079] As shown in Figure 14 , then, a photolithography and etching process is adopted to form vias 23 at the bottom of which are respectively connected to the first contact region 15 and the second contact region 18 on the surface of the silicon dioxide dielectric layer 11. It is necessary to etch through the beryllium oxide thin film to expose the surfaces of the silicon flat region 101 and the germanium thin film layer 19.

[0080] As shown in Figure 15As shown in the figure, finally, a deposition process is adopted to fill each through hole 23 with an electrode material, forming a first electrode 14 connecting the first contact region 15 and a second electrode 13 connecting the second contact region 18. In this embodiment, a chemical vapor deposition process is used to deposit a tungsten thin film on the surface of the silicon dioxide dielectric layer 11 to fill the through holes 23; and after the through holes 23 are filled, a chemical mechanical polishing process is used to planarize and remove the excess tungsten thin film on the surface of the silicon dioxide dielectric layer 11 to obtain a flat surface of the silicon dioxide dielectric layer 11. Thus, the germanium-based photodetector device of the present invention is obtained.

[0081] In summary, in the present invention, by forming a beryllium oxide interface passivation layer 12 between the germanium thin film layer 19 and the silicon dioxide dielectric layer 11 of the photodetector device, the strong Be-O covalent bond and the dense crystal structure of the beryllium oxide crystal can be utilized to inhibit the generation of germanium oxide on the surface of the germanium thin film layer 19 and the diffusion of oxygen vacancies, so that the interface state density on the surface of the germanium thin film is decreased compared with that of the germanium-silicon dioxide interface, and thus the surface leakage current can be reduced; at the same time, the relatively low phonon frequency of the beryllium oxide crystal can be utilized to further inhibit the surface recombination leakage current; and, the refractive index of beryllium oxide at a certain wavelength is relatively close to that of silicon dioxide, and the optical field can also be confined in the germanium thin film relatively well, without significantly affecting the light absorption of the device, and thus the responsivity of the device will not be significantly reduced. Therefore, in the present invention, by setting the beryllium oxide interface passivation layer 12, the dark current of the photodetector device is further reduced without significantly affecting the responsivity of the device.

[0082] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. An optoelectronic detection device, characterized in that Comprising: A germanium thin film layer and a silicon dioxide dielectric layer provided on an SOI substrate, and the silicon dioxide dielectric layer covers the germanium thin film layer; A beryllium oxide interface passivation layer provided at the interface between the germanium thin film layer and the silicon dioxide dielectric layer, and the germanium thin film layer at the contact with the beryllium oxide interface passivation layer has a germanium surface after being heat-treated at a high temperature of 850 - 950 °C. The beryllium oxide interface passivation layer is a dense crystal structure with Be-O covalent bonds formed at a low temperature of 188 - 212 °C and having a thickness of 6 - 20 nm that is conformal to the surface of the germanium thin film layer after being heat-treated at a medium temperature of 500 - 600 °C.

2. The optoelectronic detection device according to claim 1, characterized in that, The beryllium oxide interface passivation layer is used to inhibit the oxidation of the surface of the germanium thin film layer at the interface with the silicon dioxide dielectric layer, block the diffusion of oxygen vacancies, and inhibit the phonon scattering of carriers, thereby improving the interface quality between the germanium thin film layer and the silicon dioxide dielectric layer, reducing the interface state density, and inhibiting the generation of surface recombination leakage current.

3. The optoelectronic detection device according to claim 1, characterized in that, The germanium thin film layer includes an intrinsic germanium region, and a first doping region of a first conduction type and a second doping region of a second conduction type are respectively provided at two opposite ends of the intrinsic germanium region. The germanium thin film layer further includes the first doping region or the second doping region.

4. The optoelectronic detection device according to claim 3, wherein A first contact region is provided on the first doping region, a second contact region is provided on the second doping region, a first electrode is connected to the first contact region, a second electrode is connected to the second contact region, and the first electrode and the second electrode are led out from the surface of the silicon dioxide dielectric layer; and / or, the photodetector is connected to a waveguide provided on the SOI substrate through one of the first doping region and the second doping region.

5. The optoelectronic detection device according to claim 3, characterized in that The photodetector includes a vertical PIN type photodetector or a horizontal PIN type photodetector formed on the SOI substrate and covered by the silicon dioxide dielectric layer. The vertical PIN type photodetector or the horizontal PIN type photodetector is provided with a P-type doping region, an I intrinsic region, and an N-type doping region. The first doping region is one of the P-type doping region and the N-type doping region, the second doping region is the other of the P-type doping region and the N-type doping region, and the intrinsic germanium region is the I intrinsic region.

6. A method for preparing an optoelectronic detection device, characterized in that, Comprising: Providing an SOI substrate; Forming a germanium thin film layer and a silicon dioxide dielectric layer on the SOI substrate, covering the germanium thin film layer with the silicon dioxide dielectric layer, and forming a beryllium oxide interface passivation layer at the interface between the germanium thin film layer and the silicon dioxide dielectric layer; Wherein, before forming the beryllium oxide interface passivation layer, the surface of the germanium thin film layer in contact with the beryllium oxide interface passivation layer is heat-treated at a high temperature of 850 - 950 °C to form a germanium surface, and when forming the beryllium oxide interface passivation layer, a beryllium oxide thin film layer is first formed at a low temperature of 188 - 212 °C, and then heat-treated at a medium temperature of 500 - 600 °C to form the beryllium oxide interface passivation layer with a thickness of 6 - 20 nm that has a dense crystal structure with Be-O covalent bonds and is conformal to the surface of the germanium thin film layer.

7. The method for manufacturing an optoelectronic detection device according to claim 6, wherein Before forming the beryllium oxide interface passivation layer, hydrogen is used to perform a high-temperature annealing treatment on the surface of the germanium thin film layer in contact with the beryllium oxide interface passivation layer at 850-950 °C to remove the natural oxide layer of germanium on the surface of the germanium thin film layer and form a germanium surface; when forming the beryllium oxide interface passivation layer, a low-temperature atomic layer deposition process at 188-212 °C using beryllium dimethyl and water as reactants is adopted. First, a beryllium oxide thin film layer is formed, and then a medium-temperature annealing treatment at 500-600 °C is performed to form the beryllium oxide interface passivation layer with a thickness of 6-20 nm.

8. The method for manufacturing an optoelectronic detection device according to claim 6, wherein The method for forming the germanium thin film layer, the beryllium oxide interface passivation layer, and the silicon dioxide dielectric layer specifically includes: Form a flat area on the SOI substrate; Form a first doped area on the surface of the flat area; Form a sacrificial dielectric layer on the surface of the SOI substrate, form a window on the surface of the sacrificial dielectric layer, and stop the bottom of the window at the surface of the flat area at the first doped area; Form the germanium thin film layer in the window, and form a second doped area on the top of the germanium thin film layer, so as to form an intrinsic germanium area in the germanium thin film layer below the second doped area; Remove the sacrificial dielectric layer, form the beryllium oxide interface passivation layer on the surface of the SOI substrate, and cover the surface of the germanium thin film layer; Form the silicon dioxide dielectric layer on the surface of the SOI substrate, cover the germanium thin film layer and the beryllium oxide interface passivation layer, and make the beryllium oxide interface passivation layer formed at the interface between the germanium thin film layer and the silicon dioxide dielectric layer.

9. The method for manufacturing an optoelectronic detection device according to claim 8, wherein When forming the first doped area, it further includes: forming first contact areas on the surfaces of the flat areas on both sides of the first doped area; when forming the second doped area, forming second contact areas on the surface of the second doped area; after forming the silicon dioxide dielectric layer, it further includes: forming through holes with bottoms respectively connected to the first contact area and the second contact area on the surface of the silicon dioxide dielectric layer, and filling the through holes to form a first electrode connected to the first contact area and a second electrode connected to the second contact area.

10. The method for manufacturing an optoelectronic detection device according to claim 8, characterized in that, When forming the flat area in the active area, a waveguide with a size-graded structure connected to the flat area is also formed on the SOI substrate at the same time.

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