Photoelectric detector and manufacturing method thereof

Abstract

The embodiment of the invention provides a photoelectric detector and a manufacturing method thereof. The photoelectric detector comprises a substrate, wherein the surface of the substrate is a first semiconductor layer; the first semiconductor layer comprises a groove, and a first doped region and a second doped region which are positioned on two sides of the groove along a first direction; the germanium absorption layer is partially positioned in the groove; the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure; wherein the germanium absorption layer is provided with doping of the same type as the first doping region and the second doping region along the side walls of the two sides of the first direction respectively; the first direction is parallel to the surface of the substrate.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of photoelectric detectors, and in particular, to a photoelectric detector and a method for manufacturing the same. Background Art

[0002] Modern fiber-optic communication technology has achieved ultra-high-speed transmission over long distances and with large capacity. In each network node of the fiber-optic communication system, the integration and miniaturization of optical modules has become a major trend. At the same time, optical interconnection technology based on silicon photonics has the characteristics of low latency, low power consumption, and large capacity, and has gradually become an alternative to traditional electrical interconnection technology in large data centers and high-performance computers. Silicon-based photodetectors can convert optical signals into electrical signals and are one of the core components of silicon photonic chips, with broad application prospects. Summary of the invention

[0003] In view of this, an embodiment of the present disclosure provides a photodetector and a method for manufacturing the same.

[0004] To achieve the above objectives, the technical solution of the present disclosure is implemented as follows:

[0005] In a first aspect, an embodiment of the present disclosure provides a photodetector, the photodetector comprising:

[0006] A substrate, wherein the surface of the substrate is a first semiconductor layer; the first semiconductor layer comprises a groove, and a first doping region and a second doping region located on both sides of the groove along a first direction;

[0007] a germanium absorption layer partially located in the groove; the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure;

[0008] The side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region; and the first direction is parallel to the substrate surface.

[0009] In some embodiments, the photodetector further comprises:

[0010] A second semiconductor layer at least covering the top surface of the germanium absorption layer; the size of the top surface of the germanium absorption layer in the first direction is smaller than the size of the second semiconductor layer in the first direction;

[0011] The lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorption layer.

[0012] In some embodiments, a material of the second semiconductor layer includes silicon nitride.

[0013] In some embodiments, the photodetector further comprises:

[0014] a first waveguide located above the surface of the first doped region, with a first gap between the first waveguide and the germanium absorption layer;

[0015] a second waveguide located above the surface of the second doped region, with a second gap between the second waveguide and the germanium absorption layer;

[0016] The first waveguide and the second waveguide are used to couple the optical signal received by the photodetector to the germanium absorption layer via the first gap and the second gap, respectively.

[0017] In some embodiments, along the second direction, the size of the first waveguide in the first direction gradually increases, and the size of the second waveguide in the first direction gradually decreases;

[0018] The second direction is parallel to the substrate surface and perpendicular to the first direction.

[0019] In some embodiments, a size of the germanium absorption layer along the first direction is less than or equal to a first threshold; and the first threshold is proportional to a transit time of carriers in the germanium absorption layer.

[0020] In a second aspect, an embodiment of the present disclosure provides a method for manufacturing a photodetector, comprising:

[0021] A substrate is provided, wherein the surface of the substrate is a first semiconductor layer; the first semiconductor layer comprises a groove, and a first doping region and a second doping region located on both sides of the groove along a first direction;

[0022] forming a germanium absorption layer partially located in the groove; the first doped region, the germanium absorption layer and the second doped region constitute a horizontal PIN structure;

[0023] The side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region; and the first direction is parallel to the substrate surface.

[0024] In some embodiments, forming a germanium absorption layer partially located in the groove includes:

[0025] forming an initial germanium absorption layer partially located in the groove;

[0026] Performing first light doping and second light doping on the sidewalls of the initial germanium absorption layer at both sides along the first direction, respectively, to form the germanium absorption layer;

[0027] The size of the germanium absorption layer along the first direction is less than or equal to a first threshold; and the first threshold is proportional to the transit time of carriers in the germanium absorption layer.

[0028] In some embodiments, after forming the germanium absorption layer, the method further comprises:

[0029] forming a second semiconductor layer at least covering the top surface of the germanium absorption layer; wherein the size of the top surface of the germanium absorption layer in the first direction is smaller than the size of the second semiconductor layer in the first direction;

[0030] The lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorption layer.

[0031] In some embodiments, the method further comprises:

[0032] forming a first waveguide located above the surface of the first doped region, with a first gap between the first waveguide and the germanium absorption layer; and,

[0033] forming a second waveguide located above the surface of the second doped region, with a second gap between the second waveguide and the germanium absorption layer;

[0034] Wherein, in the second direction, the size of the first waveguide along the first direction gradually increases, and the size of the second waveguide along the first direction gradually decreases; the second direction is parallel to the substrate surface and perpendicular to the first direction.

[0035] The disclosed embodiment provides a photodetector and a method for manufacturing the same; wherein the photodetector comprises: a substrate, the surface of the substrate being a first semiconductor layer; the first semiconductor layer comprising a groove, and a first doping region and a second doping region located on both sides of the groove along a first direction; a germanium absorption layer partially located in the groove; the first doping region, the germanium absorption layer and the second doping region constitute a horizontal PIN structure; wherein the side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region. In the disclosed embodiment, the germanium absorption layer is partially formed in the groove, which helps to improve the coupling efficiency of the optical signal, thereby effectively improving the responsiveness of the photodetector; in addition, the side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region, so that a higher internal field strength can be achieved under a lower bias voltage, thereby effectively improving the response speed of the photodetector in the L band. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The structure of the photodetector provided in the embodiment of the present disclosure is shown in FIG. Figure 1 ;

[0037] Figure 2 The structure of the photodetector provided in the embodiment of the present disclosure is shown in FIG. Figure 2 ;

[0038] Figure 3 The structure of the photodetector provided in the embodiment of the present disclosure is shown in FIG. Figure 3 ;

[0039] Figure 4 A flow chart of a method for manufacturing a photodetector provided in an embodiment of the present disclosure;

[0040] FIG. 5A to FIG. 5E A step diagram of a method for manufacturing a photodetector provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present disclosure and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0042] In the following description, a large number of specific details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0043] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0044] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present disclosure necessarily has the first element, component, region, layer or part.

[0045] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0046] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0047] In order to thoroughly understand the present disclosure, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present disclosure. The preferred embodiments of the present disclosure are described in detail below, but in addition to these detailed descriptions, the present disclosure may also have other implementations.

[0048] There are two main types of silicon-based photodetectors used for high-speed integration: one is the germanium-silicon photodetector that is compatible with CMOS technology, and the other is the III-V group photodetector that uses heterogeneous integration. Thanks to the development of silicon-based germanium material epitaxial technology, germanium-silicon photodetectors are widely used in silicon photonic integration, and waveguide-type PIN-structured germanium-silicon photodetectors have become their mainstream structure.

[0049] In response to the demand for massive data in the development of optical interconnection services in data centers, with the goals of ultra-high speed, large capacity and large bandwidth, in the application of coherent optical communication receivers, how to achieve ultra-high-speed germanium silicon photodetectors covering higher bands has become an urgent problem to be solved.

[0050] In the germanium silicon photodetector, the material of the light absorption layer used to absorb light is germanium. Hereinafter, the light absorption layer will be collectively referred to as the germanium absorption layer. Since germanium is an indirect bandgap semiconductor material, its absorption of light in the wavelength band above 1550nm will be significantly reduced. As a result, the responsivity of the germanium silicon photodetector in the L band (wavelength 1565nm~1625nm) is sharply reduced. In order to improve the responsivity of the germanium silicon photodetector and realize a germanium silicon photodetector covering the C+L band, the following solutions can be adopted.

[0051] The details are as follows:

[0052] 1. Use the Franz-Keldysh effect (FK effect) produced by germanium materials under high electric field strength to improve the absorption efficiency of germanium in the long wavelength direction, thereby improving the responsivity of germanium silicon photodetectors. Here, the Franz-Keldysh effect refers to the effect that the light absorption of semiconductors changes when an electric field is applied.

[0053] In one example, a doping region with a high concentration difference can be formed inside the germanium absorption layer, so that a higher internal field strength of the germanium absorption layer can be achieved even at a lower bias voltage. This solution requires doping design of the germanium absorption layer.

[0054] 2. Adding tensile strain to the surface of the germanium absorption layer can red-shift the optical absorption edge of germanium (move toward the long wavelength direction). In this way, the absorption efficiency of germanium in the L band can be improved, thereby improving the responsivity of the germanium silicon photodetector.

[0055] In one example, a material with a higher lattice density can be deposited on the surface of the germanium absorption layer, for example, a layer of silicon nitride can be deposited on the surface of the germanium absorption layer. Due to the different lattice densities of the two materials, the silicon nitride deposited on the germanium absorption layer can cause a certain tensile stress to be generated on the surface of the germanium absorption layer, thereby red-shifting the optical absorption edge of germanium, thereby improving the responsivity of the germanium silicon photodetector.

[0056] In addition, if the germanium silicon photodetector wants to achieve ultra-high-speed detection, it needs to improve its own 3dB bandwidth. In other words, by improving the 3dB bandwidth of the germanium silicon photodetector, the response speed of the germanium silicon photodetector can be improved. The details are as follows:

[0057] By using space charge control technology, the silicon nitride waveguide is coupled to both sides of the germanium absorption layer to control the light field distribution in the germanium absorption layer, reducing the aggregation effect of photogenerated carriers at the front end of the germanium absorption layer, that is, avoiding the space charge effect, thereby improving the detector bandwidth.

[0058] An embodiment of the present disclosure provides a photodetector, which is an ultra-high-speed photodetector with high responsivity in the L band.

[0059] Before introducing the photodetector and its manufacturing method provided by the embodiment of the present disclosure, various directions that may be involved in the embodiment of the present disclosure are first defined. The direction perpendicular to the plane where the substrate is located is defined as the Z direction, and the intersecting X direction and Y direction are defined in the plane where the substrate is located. In the embodiment of the present disclosure, the first direction is defined as the X direction, the second direction is defined as the Y direction, and the third direction is defined as the Z direction; wherein the transmission direction of the optical signal is the Y direction, and the X direction is perpendicular to the Y direction.

[0060] Figure 1 The structure of the photodetector provided in the embodiment of the present disclosure is shown in FIG. Figure 1 .like Figure 1 As shown, an embodiment of the present disclosure provides a photodetector 100, which includes: a substrate 110, a surface of the substrate 110 is a first semiconductor layer 111; the first semiconductor layer 111 includes a groove 111a, and a first doping region 111b and a second doping region 111c located on both sides of the groove 111a along the X direction; a germanium absorption layer 120 is partially located in the groove 111a; the first doping region 111b, the germanium absorption layer 120 and the second doping region 111c constitute a horizontal PIN structure; wherein the side walls of the germanium absorption layer 120 on both sides along the X direction have the same type of doping as the first doping region 111b and the second doping region 111c.

[0061] In some embodiments of the present disclosure, the substrate 110 may be a silicon on insulator (SOI) substrate, or may be a substrate including a silicon substrate, etc. Figure 1 , the substrate 110 includes a first semiconductor layer 111, and the first semiconductor layer 111 is located on the surface of the substrate 110; wherein the material of the first semiconductor layer 111 includes silicon. The first semiconductor layer 111 includes a groove 111a, and a first doping region 111b and a second doping region 111c located on both sides of the groove 111a along the X direction; wherein, ion doping (for example, undoped silicon) is not performed in the bottom area 111d located in the groove 111a. In addition, the doping types of the first doping region 111b and the second doping region 111c are opposite, for example, the first doping region 111b can be a P-type doping region, and the second doping region 111c can be an N-type doping region; the doping elements of the P-type doping region include III-group elements such as boron and gallium, and the doping elements of the N-type doping region include V-group elements such as phosphorus and arsenic.

[0062] In this disclosure, please continue to refer to Figure 1 The substrate 110 further includes a stacked silicon substrate layer 112 and a buried oxide layer 113, and the first semiconductor layer 111 covers the surface of the buried oxide layer 113. The material of the silicon substrate layer 112 includes silicon, and the material of the buried oxide layer 113 includes silicon dioxide (SiO2).

[0063] In this disclosure, please continue to refer to Figure 1 , part of the germanium absorption layer 120 is located in the groove 111a means that when the bottom of the germanium absorption layer 120 is located in the groove 111a, the rest of the germanium absorption layer 120 can extend to the outside of the groove 111a in a direction away from the substrate 110 (Z direction). Here, the size of the germanium absorption layer in the X direction can be designed according to the size of the groove 111a in the X direction, so that the germanium absorption layer can have an ultra-small size in the X direction. Here, the material of the germanium absorption layer 120 includes a single germanium substance.

[0064] For further information, please refer to Figure 1 In the germanium absorption layer 120, the sidewall on the side in contact with the first doping region 111b has a first light doping to form a first light doping region 121 on the sidewall; the sidewall on the side in contact with the second doping region 111c has a second light doping to form a second light doping region 122 on the sidewall; the remaining undoped region constitutes an intrinsic region 123. The first doping region 111b and the first light doping region 121 have the same doping type, for example, both can be P-type doping; the second doping region 111c and the second light doping region 122 have the same doping type, for example, both can be N-type doping.

[0065] Thus, on the one hand, since the germanium absorption layer 120 has the first lightly doped region 121 and the second lightly doped region 122 on both sides along the X direction, when the total size of the germanium absorption layer 120 remains unchanged, on the one hand, the size of the intrinsic region 123 along the X direction can be designed according to the thickness of the first lightly doped region 121 and the second lightly doped region 122 (i.e., the depth of ion doping), so that the size of the intrinsic region 123 in the X direction can be adjusted, thereby reducing the transit time of carriers to improve the 3dB bandwidth of the photodetector 100; on the other hand, after the sidewalls of the germanium absorption layer 120 are doped, a doping region with a high concentration difference can be formed inside the germanium absorption layer 120, thereby improving the local field strength of the germanium absorption layer 120, thereby realizing the FK effect under low voltage conditions, and improving the absorption efficiency of the germanium absorption layer 120 in the L band. Thirdly, since the germanium absorption layer 120 is partially embedded in the first semiconductor layer 111, the first doped region 111b is connected to the first lightly doped region 121, and the second doped region 111c is connected to the second lightly doped region 122. This is beneficial to the control of the electric field, which can not only reduce the equivalent distance of the PIN junction and improve the bandwidth, but also reduce the external voltage required for the FK effect.

[0066] In this disclosure, please continue to refer to Figure 1 , the first doped region 111b, the germanium absorption layer 120 and the second doped region 111c together constitute a horizontal PIN structure, which means that: the first doped region 111b and the first lightly doped region 121 can constitute a P region in the PIN structure, the intrinsic region 123 can constitute an I region in the PIN structure, and the second lightly doped region 122 and the second doped region 111c can constitute an N region in the PIN structure. In other embodiments, when the first doped region 111b and the first lightly doped region 121 are N-type doped, they can constitute an N region in the PIN structure; when the second lightly doped region 122 and the second doped region 111c are P-type doped, they can constitute a P region in the PIN structure.

[0067] In some embodiments, please refer to Figure 1 The photodetector 100 further includes: a second semiconductor layer 130 at least covering the top surface of the germanium absorption layer 120; a size of the top surface of the germanium absorption layer 120 in the X direction is smaller than a size of the second semiconductor layer 130 in the X direction; wherein the lattice density of the second semiconductor layer 130 is greater than the lattice density of the germanium absorption layer 120.

[0068] In the embodiment of the present disclosure, since the lattice density of the second semiconductor layer 130 is greater than the lattice density of the germanium absorption layer 120, a lattice mismatch phenomenon occurs at the contact interface between the second semiconductor layer 130 and the germanium absorption layer 120. This lattice mismatch will form tensile stress at the contact interface between the two, which is beneficial to the red shift of the absorption optical boundary of germanium and improves the responsiveness of the photodetector 100 in the L band.

[0069] In some embodiments, the material of the second semiconductor layer 130 includes silicon nitride.

[0070] In the embodiment of the present disclosure, silicon nitride can be deposited on the top surface of the germanium absorption layer 120 by a process method such as plasma enhanced chemical vapor deposition (PECVD) to generate tensile strain on the surface of the germanium absorption layer 120; thus, the band gap of the germanium absorption layer 120 can be reduced, and the detection range can be extended to more than 1550nm. In addition, please continue to refer to Figure 1 The second semiconductor layer 130 (ie, silicon nitride) may also be formed on a portion of the sidewall of the germanium absorption layer 120 .

[0071] It should be noted that, in one example, the optical signal of the waveguide-type silicon-based germanium photodetector is input from one end of the waveguide layer along the Y direction (i.e., the optical input end of the waveguide layer) and then coupled to the germanium absorption layer. However, in the photodetector of this structure, most of the light absorption is concentrated in the region of the germanium absorption zone in the first few microns near the input end of the waveguide layer. Therefore, under the action of high input light power, it is easy to cause uneven distribution of the light field in the germanium absorption layer. In addition, due to the existence of the space charge effect, a large number of photogenerated carriers generated in the local area of ​​the germanium absorption layer will break its built-in electric field distribution, affecting the timely transport of the photogenerated carriers, resulting in a serious decrease in the response speed of the photodetector.

[0072] Here, the space charge effect refers to the fact that the photogenerated carriers in the germanium absorption layer quickly separate and form drift motion under the action of the external electric field. Due to the different mobility of electrons and holes in the germanium absorption layer, there is a natural difference in the carrier movement speed in the intrinsic region, which leads to charge imbalance inside the intrinsic region, thus affecting the distribution of the external electric field.

[0073] Figure 2 The structure of the photodetector provided in the embodiment of the present disclosure is shown in FIG. Figure 2 It should be noted that Figure 2 The schematic diagram shown is not the actual structure diagram of the photodetector, it is only to illustrate the relative position relationship between the first waveguide, the second waveguide and the germanium absorption layer. The specific structure of the photodetector can be referred to Figure 1 , Figure 1 Corresponds to Figure 2 Cross-sectional structure diagram of the photodetector along section AA.

[0074] In some embodiments, the photodetector 100 further includes: a first waveguide 141 located above the surface of the first doped region 111b, with a first gap A between the first waveguide 141 and the germanium absorption layer 120; a second waveguide 142 located above the surface of the second doped region 111c, with a second gap B between the second waveguide 142 and the germanium absorption layer 120; wherein the first waveguide 141 and the second waveguide 142 are used to couple the optical signal received by the photodetector 100 to the germanium absorption layer 120 via the first gap A and the second gap B, respectively.

[0075] Combination Figure 1 and Figure 2 As shown, in the embodiment of the present disclosure, a first waveguide 141 is arranged on one side of the germanium absorption layer 120 along the X direction, and a second waveguide 142 is arranged on the other side of the germanium absorption layer 120 along the X direction, and the first waveguide 141 and the second waveguide 142 are respectively used to couple the optical signal received by the photodetector 100 to the germanium absorption layer 120 via the first gap A and the second gap B.

[0076] It should be noted that if the size of the first gap A and the second gap B along the X direction is too large, the light field will be incompletely absorbed by the germanium absorption layer 120, thereby increasing the absorption length, causing the entire photodetector 100 to be too long and affecting the bandwidth; if the size of the first gap A and the second gap B along the X direction is too small, the light signal will be coupled too quickly and the effect of space charge regulation will not be achieved. Among them, the appropriate gap size can be selected by simulation or preparation of detectors with gaps of different sizes; for example, the size of the first gap A and the second gap B along the X direction can be 150nm.

[0077] In the disclosed embodiments, please refer to Figure 2 , the optical signal from the outside can be provided to the photodetector 100 through the two output ends 220 of the optical beam splitter 210, respectively. And the two output ends 220 of the optical beam splitter 210 are respectively connected to the first waveguide 141 and the second waveguide 142. Specifically, the first waveguide 141 has a first end 141a and a second end 141b opposite to each other along the Y direction, and the second waveguide 142 has a first end 142a and a second end 142b opposite to each other along the Y direction. The first end 141a of the first waveguide 141 and the second end 142b of the second waveguide 142 can be respectively connected to the two output ends 220 of the optical beam splitter 210. Alternatively, the second end 141b of the first waveguide 141 and the first end 142a of the second waveguide 142 can be respectively connected to the two output ends 220 of the optical beam splitter 210.

[0078] In some embodiments, along the Y direction, the size of the first waveguide 141 in the X direction gradually increases, and the size of the second waveguide 142 in the X direction gradually decreases.

[0079] In the disclosed embodiments, please refer to Figure 1 and Figure 3 , the top view of the first waveguide 141 and the second waveguide 142 may be conical; along the Y direction, the size of the first waveguide 141 in the X direction may increase from the second size L2 to the first size L1, and the size of the second waveguide 142 in the X direction may decrease from the first size L1 to the second size L2; wherein the optical signal (as shown in the direction of the arrow) is input from the end with a larger size (i.e., the first size L1). In some embodiments, along the Y direction, the size of the first waveguide 141 in the X direction may gradually decrease, and the size of the second waveguide 142 in the X direction may gradually increase. The materials of the first waveguide 141 and the second waveguide 142 may both be silicon nitride (Si3N4).

[0080] In summary, the embodiment of the present disclosure couples the first waveguide 141 and the second waveguide 142 on both sides of the germanium absorption layer 120 so that the optical signal can be simultaneously coupled to the germanium absorption layer 120 from both sides of the germanium absorption layer 120 along the X direction, thereby regulating the light field distribution in the germanium absorption layer to make the light field distribution more uniform, balance the spatial distribution of photogenerated carriers, reduce the aggregation effect of photogenerated carriers at the front end of the germanium absorption layer, that is, avoid the space charge effect, and thus improve the detector bandwidth.

[0081] It should be noted that Figure 3 The corresponding Figure 2 The first waveguide, the second waveguide and the germanium absorption layer.

[0082] In some embodiments, the size of the germanium absorption layer 120 along the X direction is less than or equal to a first threshold; the first threshold is proportional to the transit time of carriers in the germanium absorption layer.

[0083] In the embodiment of the present disclosure, the smaller the first threshold, the shorter the transit time of the carriers in the germanium absorption layer, and the faster the response speed of the photodetector 100; conversely, the larger the first threshold, the slower the transit time of the carriers in the germanium absorption layer, and the slower the response speed of the photodetector 100; here, the first threshold may be 500nm. In addition, the germanium absorption layer 120 is less than or equal to the second threshold along the Z-axis direction; wherein the second threshold may be, for example, 400nm or other suitable dimensions. That is, the germanium absorption layer 120 has an ultra-small size, which can further improve the bandwidth of the photodetector 100, so that the photodetector 100 can be an ultra-high-speed germanium silicon photodetector 100. It can be understood that in the process of manufacturing the photodetector 100, the size of the germanium absorption layer 120 in the X direction and the Z direction can be further reduced on the basis of the first threshold and the second threshold, respectively, at which time, the bandwidth of the photodetector 100 can be further increased, and the response speed of the photodetector 100 is also improved accordingly.

[0084] In this disclosure, please continue to refer to Figure 1In the manufacturing process of the photodetector 100, after the PIN structure is formed, a metal electrode for realizing the electrical connection between the PIN structure and the external circuit needs to be prepared. The metal electrode includes a first metal electrode 151 located on the first doping region 111b, and a second metal electrode 152 located on the second doping region 111c. The first metal electrode 151 and the second metal electrode 152 are respectively located on opposite sides of the germanium absorption layer 120 in the X direction. It should be noted that, with the current technology node of the industry, the size of the first metal electrode 151 and the second metal electrode 152 in the X direction can be 400nm, and the size of the first metal electrode 151 and the second metal electrode 152 in the X direction is difficult to be made smaller. In the embodiment of the present disclosure, since the PIN structure is horizontal, the size of the germanium absorption layer 120 in any direction will not affect the connection between the PIN structure and the metal electrode 118. In this way, it is beneficial to reduce the size of the germanium absorption layer 120 in the X direction, effectively avoiding the problem that it is difficult to lead out the electrode when the size of the germanium absorption layer 120 in the X direction is small, thereby facilitating the improvement of the 3dB bandwidth of the photodetector 100.

[0085] In this disclosure, please continue to refer to Figure 1 The surface of the first doping region 111b and the surface of the second doping region 111c are both provided with metal silicide 160, and the metal silicide 160 includes cobalt silicide (Cobal-Silicide), nickel silicide (Nickel-Silicide), etc. Since the metal silicide has a lower resistance value, the contact resistance between the metal electrode and the doping region can be reduced.

[0086] In this disclosure, please continue to refer to Figure 1 The photodetector 100 further includes: a dielectric layer 170, which is filled between the structures; the material of the isolation layer 170 can be silicon oxide, silicon nitride or silicon oxynitride.

[0087] Figure 4 Flow chart of the method for manufacturing a photodetector provided in an embodiment of the present disclosure. Figure 4 As shown, the present disclosure provides a method for manufacturing a photodetector, the manufacturing method comprising:

[0088] Step S401: providing a substrate, wherein the surface of the substrate is a first semiconductor layer; the first semiconductor layer comprises a groove, and a first doping region and a second doping region located on both sides of the groove along the X direction;

[0089] Step S402: forming a germanium absorption layer partially located in the groove; the first doped region, the germanium absorption layer and the second doped region constitute a horizontal PIN structure; wherein the sidewalls of the germanium absorption layer on both sides along the X direction have the same type of doping as the first doped region and the second doped region.

[0090] FIG. 5A to FIG. 5E A step diagram of a method for manufacturing a photodetector provided in an embodiment of the present disclosure.

[0091] First, execute step S401; Figure 5A As shown, the substrate 110 can be prepared by a multi-step deposition process and an etching process. Specifically, a buried oxide layer 113 and an initial first semiconductor layer (not shown) can be formed on a silicon substrate layer 112 in sequence; then, the initial first semiconductor layer is ion-doped to form a first doping region 111b and a second doping region 111c; thereafter, a first dielectric layer 171 is formed on the surface of the substrate 110, and the first dielectric layer 171 and the doped initial first semiconductor layer are sequentially etched by any suitable etching process, and a groove 111a is formed in the undoped region between the first doping region 111b and the second doping region 111c; wherein, ion doping (for example, undoped silicon) is not performed in the bottom region 111d of the groove 111a. In other embodiments, the substrate can also be prepared by other methods, for example, it can be prepared based on an SOI substrate, and its preparation method is similar to the above-mentioned embodiment, which will not be described in detail here.

[0092] In the embodiment of the present disclosure, the size of the formed groove 111a along the X direction is less than or equal to the first threshold; the first threshold may be 500nm, so that the size of the subsequently formed germanium absorption layer along the X-axis direction can be designed according to the size of the groove 111a along the X direction.

[0093] In some embodiments, please refer to Figure 5A The first dielectric layer 171 includes a first sub-dielectric layer and a second sub-dielectric layer sequentially located on the surface of the substrate 110; before forming the groove 111a, the method for manufacturing the photodetector also includes: forming a first waveguide 141 located above the surface of the first doping region 111b, and forming a second waveguide 142 located above the surface of the second doping region 111c.

[0094] Specifically, first, a first sub-dielectric layer is formed on the surface of the substrate 110, and the first sub-dielectric layer is etched by any suitable etching process to form a first etched groove (not shown) located above the surface of the first doping region 111b, and a second etched groove (not shown) located above the surface of the second doping region 111c; next, a first waveguide 141 and a second waveguide 142 are formed in the first etched groove and the second etched groove, respectively; finally, a second sub-dielectric layer is formed on the surfaces of the first sub-dielectric layer, the first waveguide 141, and the second waveguide 142.

[0095] There is a first gap A between the first waveguide 141 and the extension line inside the first doping region 111b, and there is a second gap B between the second waveguide 142 and the extension line inside the second doping region 111c. In this way, there can be a first gap A between the first waveguide 141 and the subsequently formed germanium absorption layer, and there can be a second gap B between the second waveguide 142 and the subsequently formed germanium absorption layer.

[0096] In addition, in the Y direction, the size of the first waveguide 141 along the X direction gradually increases, and the size of the second waveguide 142 along the X direction gradually decreases (refer to Figure 3 ). The materials of the first waveguide 141 and the second waveguide 142 may both be silicon nitride.

[0097] In the embodiment of the present disclosure, the first waveguide 141 and the second waveguide 142 can be coupled on both sides of the subsequently formed germanium absorption layer, so that the light field distribution in the germanium absorption layer can be regulated to make the light field distribution more uniform, balance the spatial distribution of photogenerated carriers, and reduce the aggregation effect of photogenerated carriers at the front end of the germanium absorption layer, that is, avoid the space charge effect, thereby improving the detector bandwidth.

[0098] In the embodiment of the present disclosure, after forming the groove 111a, the manufacturing method of the photodetector also includes: smoothing the surface exposed by the groove 111a; for example, using tetramethylammonium hydroxide (TMAH) and hydrofluoric acid (HF) for surface treatment to make the surface exposed by the groove 111a smooth and have hanging bonds with good consistency.

[0099] Next, execute step S402; please refer to Figure 5A and Figure 5B , forming a germanium absorption layer 120 partially located in the groove 111a, including: forming an initial germanium absorption layer 120a partially located in the groove 111a; performing a first light doping and a second light doping on the sidewalls of both sides of the initial germanium absorption layer 120a along the X direction, respectively, to form the germanium absorption layer 120.

[0100] Specifically, please refer to Figure 5A , an initial germanium absorption layer 120a may be formed in the groove 111a by an epitaxial growth process, and the material of the initial germanium absorption layer 120a includes a single germanium substance. In the embodiment of the present disclosure, the surface of the initial germanium absorption layer 120a may be flush with the surface of the first dielectric layer 171, or the height of the surface of the initial germanium absorption layer 120a in the Z direction is lower than the height of the surface of the first dielectric layer 171 in the Z direction. Figure 5A Since the germanium single substance grows from the bottom of the groove 111a in a direction away from the substrate 110, there may be a gap between the initial germanium absorption layer 120a and the sidewall of the groove 111a (ie, the top of the initial germanium absorption layer 120a is arc-shaped).

[0101] In the embodiment of the present disclosure, since the initial germanium absorption layer 120a is formed in the groove 111a by an epitaxial process, the size of the initial germanium absorption layer 120a along the X direction can be designed according to the size of the groove 111a along the X direction, so that the subsequently formed germanium absorption layer can have an ultra-small size in the X direction.

[0102] Next, please continue to refer to Figure 5B In the initial germanium absorption layer 120a, the side wall on the side in contact with the first doping region 111b is first lightly doped to form a first lightly doped region 121 on the side wall; the side wall on the side in contact with the second doping region 111c is second lightly doped to form a second lightly doped region 122 on the side wall; the remaining undoped area constitutes an intrinsic region 123; the first lightly doped region 121, the intrinsic region 123 and the second doping region 111c constitute the germanium absorption layer 120. The first doping region 111b and the first lightly doped region 121 have the same doping type, for example, both can be P-type doping; the second doping region 111c and the second lightly doped region 122 have the same doping type, for example, both can be N-type doping.

[0103] In the disclosed embodiment, on the one hand, the size of the intrinsic region 123 along the X direction can be designed according to the thickness of the first lightly doped region 121 and the second lightly doped region 122 (i.e., the depth of ion doping), so that the size of the intrinsic region 123 in the X direction can be adjusted, thereby reducing the transit time of carriers to improve the 3dB bandwidth of the photodetector 100; on the other hand, after the sidewall of the germanium absorption layer 120 is doped, a doping region with a high concentration difference can be formed inside the germanium absorption layer 120, thereby improving the local field strength of the germanium absorption layer 120, thereby realizing the FK effect under low voltage conditions and improving the absorption efficiency of the germanium absorption layer 120 in the L band. In addition, since the germanium absorption layer 120 is partially embedded in the first semiconductor layer 111, it helps to improve the coupling efficiency of the optical signal, thereby effectively improving the responsivity of the photodetector.

[0104] In some embodiments, please refer to Figure 5C and Figure 5D After forming the germanium absorption layer 120, the manufacturing method of the photodetector further includes: forming a second semiconductor layer 130 that at least covers the top surface of the germanium absorption layer 120; the size of the top surface of the germanium absorption layer 120 in the X direction is smaller than the size of the second semiconductor layer 130 in the X direction; wherein the lattice density of the second semiconductor layer 130 is greater than the lattice density of the germanium absorption layer 120.

[0105] Specifically, please refer to Figure 5CThe initial second semiconductor layer 130a can be deposited on the exposed surface of the germanium absorption layer 120 and the first dielectric layer 171 by a process method such as plasma enhanced chemical vapor deposition (PECVD). Figure 5D The initial second semiconductor layer 130a located on the top surface of the first dielectric layer 171 is removed by any suitable etching process, and the remaining initial second semiconductor layer 130a constitutes the second semiconductor layer 130; in this way, not only the local stress of the second semiconductor layer 130 in the active area can be released, but also the optical coupling effect between the first waveguide 141 and the second waveguide 142 and the second semiconductor layer 130 can be reduced, thereby further improving the responsiveness of the detector.

[0106] It should be noted that, since there may be a gap between the germanium absorption layer 120 and the sidewall of the groove 111 a (ie, the top of the germanium absorption layer 120 is arc-shaped), the second semiconductor layer 130 also covers the sidewall of the germanium absorption layer 120 .

[0107] In the embodiment of the present disclosure, since the lattice density of the second semiconductor layer 130 is greater than the lattice density of the germanium absorption layer 120, a lattice mismatch phenomenon occurs at the contact interface between the second semiconductor layer 130 and the germanium absorption layer 120. This lattice mismatch will form tensile stress at the contact interface between the two, which is beneficial to the red shift of the absorption optical boundary of germanium and improves the responsiveness of the photodetector 100 in the L band.

[0108] Furthermore, the material of the second semiconductor layer 130 includes silicon nitride. The second semiconductor layer 130 can generate tensile strain on the surface of the germanium absorption layer 120, thereby reducing the band gap of the germanium absorption layer 120 and extending the detection range to above 1550nm.

[0109] In the embodiment of the present disclosure, after forming the second semiconductor layer 130, a metal electrode for realizing electrical connection between the PIN structure and an external circuit may be formed, such as Figure 5E As shown. Specifically, a second dielectric layer 172 covering the exposed surface of the first dielectric layer 171 and the second semiconductor layer 130 may be formed first; wherein the first dielectric layer 171 and the second dielectric layer 172 constitute the dielectric layer 170, and the material of the second dielectric layer 172 may be the same as that of the first dielectric layer 171. Afterwards, the dielectric layer 170 may be etched by any suitable etching process to form a plurality of metal-filled holes extending to the surfaces of the first doping region 111b and the second doping region 111c, respectively. Metal material may be filled into the plurality of metal-filled holes at the same time to form a first metal electrode 151 located on the first doping region 111b, and a second metal electrode 152 located on the second doping region 111c. The first metal electrode 151 and the second metal electrode 152 are located on opposite sides of the germanium absorption layer 403 in the X direction, respectively.

[0110] In some embodiments, Figure 5E As shown, before forming the metal electrode, metal silicide 160 can be formed at the positions on the surfaces of the first doping region 111b and the second doping region 111c respectively for contacting with the metal electrode, thereby reducing the contact resistance between each doping region and the metal electrode. The metal silicide 160 includes cobalt silicide (Cobal-Silicide), nickel silicide (Nickel-Silicide), etc.

[0111] In the embodiments of the present disclosure, the deposition process for forming each layer in the photodetector includes but is not limited to chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD).

[0112] The photodetector 100 formed in the embodiment of the present disclosure is a high-speed SiGe photodetector capable of operating in the C+L band. The SiGe photodetector with a waveguide structure is suitable for use in large-scale optical paths, thus being applicable to the next generation (800G) coherent optical communications.

[0113] The photodetector formed by the method for manufacturing the photodetector provided in the embodiment of the present disclosure is similar to the photodetector provided in the above embodiment. For the technical features not fully disclosed in the embodiment of the present disclosure, please refer to the above embodiment for understanding, and no further details will be given here.

[0114] In the several embodiments provided in the present disclosure, it should be understood that the disclosed structures and methods can be implemented in a non-targeted manner. The structural embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the components shown or discussed are coupled or directly coupled to each other.

[0115] The features disclosed in several method or structural embodiments provided in the present disclosure may be arbitrarily combined without conflict to obtain new method embodiments or structural embodiments.

[0116] The above are only some embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A photoelectric detector, characterized in that: include: A substrate, wherein a surface of the substrate is a first semiconductor layer; The first semiconductor layer comprises a groove, and a first doping region and a second doping region located at two sides of the groove along a first direction; a germanium absorption layer partially located in the groove; the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure; The side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region; and the first direction is parallel to the substrate surface.

2. The photodetector according to claim 1, characterized in that: The photodetector further comprises: A second semiconductor layer at least covering the top surface of the germanium absorption layer; the size of the top surface of the germanium absorption layer in the first direction is smaller than the size of the second semiconductor layer in the first direction; The lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorption layer.

3. The photodetector according to claim 2, characterized in that: The material of the second semiconductor layer includes silicon nitride.

4. The photodetector according to any one of claims 1 to 3, characterized in that: The photodetector further comprises: a first waveguide located above the surface of the first doped region, with a first gap between the first waveguide and the germanium absorption layer; a second waveguide located above the surface of the second doped region, with a second gap between the second waveguide and the germanium absorption layer; The first waveguide and the second waveguide are used to couple the optical signal received by the photodetector to the germanium absorption layer via the first gap and the second gap, respectively.

5. The photodetector according to claim 4, characterized in that: Along the second direction, the size of the first waveguide in the first direction gradually increases, and the size of the second waveguide in the first direction gradually decreases; The second direction is parallel to the substrate surface and perpendicular to the first direction.

6. The photodetector according to claim 1, characterized in that: The size of the germanium absorption layer along the first direction is less than or equal to a first threshold; the first threshold is proportional to the transit time of carriers in the germanium absorption layer.

7. A method for manufacturing a photodetector, characterized in that: include: Providing a substrate, wherein a surface of the substrate is a first semiconductor layer; The first semiconductor layer comprises a groove, and a first doping region and a second doping region located at two sides of the groove along a first direction; forming a germanium absorption layer partially located in the groove; the first doped region, the germanium absorption layer and the second doped region constitute a horizontal PIN structure; The side walls of the germanium absorption layer on both sides along the first direction respectively have the same type of doping as the first doping region and the second doping region; and the first direction is parallel to the substrate surface.

8. The manufacturing method according to claim 7, characterized in that: The step of forming a germanium absorption layer partially located in the groove comprises: forming an initial germanium absorption layer partially located in the groove; Performing first light doping and second light doping on the sidewalls of the initial germanium absorption layer at both sides along the first direction, respectively, to form the germanium absorption layer; The size of the germanium absorption layer along the first direction is less than or equal to a first threshold; and the first threshold is proportional to the transit time of carriers in the germanium absorption layer.

9. The manufacturing method according to claim 8, characterized in that: After forming the germanium absorption layer, the method further comprises: forming a second semiconductor layer at least covering the top surface of the germanium absorption layer; wherein the size of the top surface of the germanium absorption layer in the first direction is smaller than the size of the second semiconductor layer in the first direction; The lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorption layer.

10. The manufacturing method according to any one of claims 7 to 9, characterized in that: The method further comprises: forming a first waveguide located above the surface of the first doped region, with a first gap between the first waveguide and the germanium absorption layer; and, forming a second waveguide located above the surface of the second doped region, with a second gap between the second waveguide and the germanium absorption layer; Wherein, in the second direction, the size of the first waveguide along the first direction gradually increases, and the size of the second waveguide along the first direction gradually decreases; the second direction is parallel to the substrate surface and perpendicular to the first direction.

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