CN119815942A - Photoelectric detector and method for manufacturing the same - Google Patents

Abstract

The embodiment of the present disclosure provides a photodetector and a manufacturing method thereof. A photodetector comprises: a substrate, 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; 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; the first direction is parallel to the surface of the substrate.

Description

Photoelectric detector and manufacturing method thereof

Technical Field

The embodiment of the disclosure relates to the technical field of photoelectric detectors, in particular to a photoelectric detector and a manufacturing method thereof.

Background

Modern optical fiber communication technology realizes long-distance and high-capacity ultra-high-speed transmission. The integration and miniaturization of optical modules have been a major trend in various network nodes of optical fiber communication systems. Meanwhile, the optical interconnection technology based on the silicon optical technology has the characteristics of low delay, low power consumption, large capacity and the like, and gradually becomes an alternative scheme of the traditional electrical interconnection technology in a large-scale data center and a high-performance computer. The silicon-based photoelectric detector can convert optical signals into electric signals, is one of core devices of silicon optical chips, and has wide application prospect.

Disclosure of Invention

In view of the foregoing, embodiments of the present disclosure provide a photodetector and a method for manufacturing the same.

In order to achieve the above purpose, the technical scheme of the present disclosure is realized as follows:

In a first aspect, embodiments of the present disclosure provide a photodetector, comprising:

The semiconductor device comprises a substrate, a first semiconductor layer, a second semiconductor layer, a first doping region and a second doping region, wherein the surface of the substrate is provided with the first semiconductor layer;

the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure;

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 two sides of the first direction, and the first direction is parallel to the surface of the substrate.

In some embodiments, the photodetector further comprises:

A second semiconductor layer covering at least a top surface of the germanium absorber layer, a dimension of the top surface of the germanium absorber layer in the first direction being smaller than a dimension of the second semiconductor layer in the first direction;

wherein the lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorber layer.

In some embodiments, the material of the second semiconductor layer comprises silicon nitride.

In some embodiments, the photodetector further comprises:

A first waveguide over the first doped region surface, the first waveguide having a first gap with the germanium absorber layer;

A second waveguide over the second doped region surface, the second waveguide having a second gap with the germanium absorber layer;

Wherein the first waveguide and the second waveguide are for coupling an optical signal received by the photodetector to the germanium absorption layer via the first gap and the second gap, respectively.

In some embodiments, the first waveguide increases in size in the first direction and the second waveguide decreases in size in the first direction along a second direction;

Wherein the second direction is parallel to the substrate surface and perpendicular to the first direction.

In some embodiments, the germanium absorber layer has a dimension along the first direction that is less than or equal to a first threshold value that is proportional to a transit time of carriers in the germanium absorber layer.

In a second aspect, embodiments of the present disclosure provide a method for manufacturing a photodetector, including:

Providing a substrate, wherein the surface of the substrate is a first semiconductor layer, and the first semiconductor layer comprises a groove, and a first doping region and a second doping region which are positioned at two sides of the groove along a first direction;

Forming a germanium absorption layer partially positioned in the groove, wherein the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure;

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 two sides of the first direction, and the first direction is parallel to the surface of the substrate.

In some embodiments, the forming a germanium absorber layer partially within the recess comprises:

forming an initial germanium absorber layer partially within the recess;

Respectively carrying out first light doping and second light doping on the side walls of the initial germanium absorption layer along the two sides of the first direction to form the germanium absorption layer;

The size of the germanium absorption layer along the first direction is smaller than or equal to a first threshold value, and the first threshold value is in direct proportion to the transit time of carriers in the germanium absorption layer.

In some embodiments, after forming the germanium absorber layer, the method further comprises:

Forming a second semiconductor layer covering at least a top surface of the germanium absorber layer, the top surface of the germanium absorber layer having a dimension in the first direction that is less than a dimension of the second semiconductor layer in the first direction;

wherein the lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorber layer.

In some embodiments, the method further comprises:

Forming a first waveguide over the surface of the first doped region with a first gap between the first waveguide and the germanium absorbing layer, and

Forming a second waveguide over the second doped region surface, the second waveguide having a second gap with the germanium absorber layer;

The size of the first waveguide along the first direction is gradually increased, and the size of the second waveguide along the first direction is gradually reduced in a second direction, wherein the second direction is parallel to the substrate surface and perpendicular to the first direction.

The embodiment of the disclosure provides a photoelectric detector and a manufacturing method thereof, wherein the photoelectric detector comprises a substrate, a first semiconductor layer, a first doping region, a second doping region and a germanium absorption layer, wherein the first semiconductor layer is arranged on the surface of the substrate, the first semiconductor layer comprises a groove, the first doping region and the second doping region are arranged on two sides of the groove along a first direction, the germanium absorption layer is partially arranged in the groove, the first doping region, the germanium absorption layer and the second doping region form a horizontal PIN structure, and the side walls of the germanium absorption layer along two sides of the first direction are respectively provided with doping of the same type as the first doping region and the second doping region. In addition, the side walls of the germanium absorption layer along the two sides of the first direction are respectively provided with doping of the same type as the first doping region and the second doping region, so that higher internal field intensity can be realized under lower bias voltage, and the response speed of the photoelectric detector in an L wave band is further effectively improved.

Drawings

Fig. 1 is a schematic structural diagram of a photodetector according to an embodiment of the disclosure;

fig. 2 is a schematic structural diagram of a photodetector according to an embodiment of the disclosure;

fig. 3 is a schematic structural diagram of a photodetector according to an embodiment of the disclosure;

FIG. 4 is a flow chart of a method of fabricating a photodetector provided by an embodiment of the present disclosure;

fig. 5A to 5E are step diagrams of a method for manufacturing a photodetector according to an embodiment of the present disclosure.

Detailed Description

The following description of the embodiments of the present disclosure will be made clearly and fully with reference to the embodiments of the present disclosure and the accompanying drawings, it being apparent that the described embodiments are only some, but not all, of the embodiments of the present disclosure. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure are intended to be within the scope of this disclosure.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that the present disclosure may be practiced without one or more of these details. In other instances, well-known functions and constructions are not described in detail to avoid obscuring the present disclosure, i.e., not all features of an actual embodiment are described herein.

In the drawings, the size of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on," "adjacent," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure. When a second element, component, region, layer or section is discussed, it does not necessarily mean that the first element, component, region, layer or section is present in the present disclosure.

Spatial relationship terms such as "under", "above", "over" and the like may be used herein for convenience of description to describe one element or feature as illustrated in the figures in relation to another element or feature. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under" and "under" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

For a thorough understanding of the present disclosure, detailed steps and detailed structures will be presented in the following description in order to illustrate the technical aspects of the present disclosure. Preferred embodiments of the present disclosure are described in detail below, however, the present disclosure may have other implementations in addition to these detailed descriptions.

Silicon-based photodetectors for high-speed integration are mainly two types, one is a germanium-silicon photodetector compatible with CMOS technology, and the other is a heterogeneous integrated III-V photodetector. Due to the development of silicon-based germanium material epitaxy technology, germanium-silicon photodetectors are used in silicon light integration, and waveguide-type PIN-structured germanium-silicon photodetectors have become the mainstream structure.

Aiming at the requirement of developing mass data of the optical interconnection service of the data center, aiming at the ultra-high speed, large capacity and large bandwidth, how to realize the ultra-high-speed germanium-silicon photoelectric detector covering higher wave bands in the application of a coherent optical communication receiver becomes a problem to be solved urgently.

In the silicon germanium photodetector, the material of the light absorbing layer for absorbing light is germanium, and hereinafter, the light absorbing layer is collectively referred to as a germanium absorbing layer. Since germanium is an indirect bandgap semiconductor material, its absorption of light in the wavelength band above 1550nm is significantly reduced. Thus, the responsivity of the germanium-silicon photoelectric detector in the L-band (wavelength 1565 nm-1625 nm) is sharply reduced. In order to improve the responsivity of the germanium-silicon photoelectric detector, the germanium-silicon photoelectric detector covering the C+L wave band can be realized by adopting the following solutions.

The method comprises the following steps:

1. the absorption efficiency of germanium in the long wavelength direction is improved by utilizing the-Kerr effect (Franz-KELDYSH EFFECT, FK effect) of the Frlan generated by the germanium material under high electric field intensity, so that the responsivity of the germanium-silicon photoelectric detector is improved. Here, the Fries-Kerr effect means an effect in which the light absorption of a semiconductor changes when an electric field is applied.

In an example, a high concentration differential doped region may be formed inside the germanium absorber layer such that a higher internal field strength of the germanium absorber layer may be achieved even at lower bias voltages. This solution requires a doping design of the germanium absorber layer.

2. The surface of the germanium absorber layer is given a tensile stress (TENSILE STRAIN) that can red shift (shift in the long wavelength direction) the optical absorption boundary of germanium. Therefore, the absorption efficiency of germanium in the L wave band can be improved, and the responsivity of the germanium-silicon photoelectric detector is further improved.

In one example, a material having a higher lattice density may be deposited on the surface of the germanium absorber layer, for example, a layer of silicon nitride may be deposited on the surface of the germanium absorber layer. Because of the different lattice densities of the two materials, the silicon nitride deposited on the germanium absorption layer can generate a certain tensile stress on the surface of the germanium absorption layer, so that the optical absorption boundary of germanium is red shifted, and the responsivity of the germanium-silicon photoelectric detector is improved.

In addition, the germanium-silicon photoelectric detector needs to increase the 3dB bandwidth of the detector to realize ultra-high speed detection. In other words, by increasing the 3dB bandwidth of the silicon germanium photodetector, an increase in the response speed of the silicon germanium photodetector can be achieved. The method comprises the following steps:

by utilizing a space charge regulation technology, the silicon nitride waveguides are coupled on two sides of the germanium absorption layer to regulate the light field distribution in the germanium absorption layer, so that the aggregation effect of photo-generated carriers at the front end of the germanium absorption layer is reduced, namely, the space charge effect (SPACE CHARGE EFFECT) is avoided, and the bandwidth of the detector is improved.

The embodiment of the disclosure provides a photoelectric detector, which is an ultra-high-speed photoelectric detector with higher responsivity in an L wave band.

Before describing the photodetector and the manufacturing method thereof provided in the embodiments of the present disclosure, various directions that may be involved in the embodiments of the present disclosure are defined. The direction perpendicular to the plane of the substrate is defined as the Z direction, and the intersecting X direction and Y direction are defined in the plane of the substrate. In the embodiment of the disclosure, the first direction is defined as an X direction, the second direction is defined as a Y direction, the third direction is defined as a Z direction, wherein the transmission direction of the optical signal is defined as the Y direction, and the X direction is perpendicular to the Y direction.

Fig. 1 is a schematic structural diagram of a photodetector according to an embodiment of the disclosure. As shown in fig. 1, an embodiment of the disclosure provides a photodetector 100, where the photodetector 100 includes a substrate 110, a first semiconductor layer 111 is formed on a surface of the substrate 110, the first semiconductor layer 111 includes a recess 111a, a first doped region 111b and a second doped region 111c located at two sides of the recess 111a along an X direction, a germanium absorbing layer 120 partially located in the recess 111a, and the first doped region 111b, the germanium absorbing layer 120 and the second doped region 111c form a horizontal PIN structure, where side walls of the germanium absorbing layer 120 along two sides of the X direction have the same type of doping as the first doped region 111b and the second doped region 111c, respectively.

In some embodiments of the present disclosure, the substrate 110 may be a silicon-on-insulator (Silicon On Insulator, SOI) substrate, or may also be a substrate comprising a silicon substrate, or the like. Referring to fig. 1, a substrate 110 includes a first semiconductor layer 111, and the first semiconductor layer 111 is located on a surface of the substrate 110, wherein a material of the first semiconductor layer 111 includes silicon. The first semiconductor layer 111 includes a recess 111a, and a first doped region 111b and a second doped region 111c located at both sides of the recess 111a in the X direction, wherein ion doping (e.g., undoped silicon) is not performed in a bottom region 111d located in the recess 111 a. In addition, the doping types of the first doped region 111b and the second doped region 111c are opposite, for example, the first doped region 111b may be a P-type doped region, the second doped region 111c may be an N-type doped region, the doping elements of the P-type doped region include group III elements such as boron and gallium, and the doping elements of the N-type doped region include group V elements such as phosphorus and arsenic.

In the embodiment of the disclosure, referring to fig. 1, the substrate 110 further includes a stacked silicon substrate layer 112 and an oxygen-buried layer 113, and the first semiconductor layer 111 covers the surface of the oxygen-buried layer 113. Wherein the material of the silicon substrate layer 112 comprises silicon and the material of the buried oxide layer 113 comprises silicon dioxide (SiO ₂).

In the embodiment of the disclosure, please continue to refer to fig. 1, when the portion of the germanium absorbing layer 120 is located in the recess 111a, it means that the rest of the germanium absorbing layer 120 may extend to the outside of the recess 111a along the direction away from the substrate 110 (Z direction) when the bottom of the germanium absorbing layer 120 is located in the recess 111 a. Here, the size of the germanium absorbing layer in the X direction may be designed according to the size of the groove 111a in the X direction, so that the germanium absorbing layer may have an ultra-small size in the X direction. Here, the material of the germanium absorption layer 120 includes elemental germanium.

Further, referring to fig. 1, in the germanium absorption layer 120, a side wall of the side wall contacting the first doped region 111b has a first light doping to form a first light doped region 121 on the side wall, a side wall of the side wall contacting the second doped region 111c has a second light doping to form a second light doped region 122 on the side wall, and the remaining undoped region forms an intrinsic region 123. The first doped region 111b and the first lightly doped region 121 may be doped with P-type dopants, and the second doped region 111c and the second lightly doped region 122 may be doped with N-type dopants.

In this way, in the first aspect, since the germanium absorbing layer 120 has the first lightly doped region 121 and the second lightly doped region 122 on two sides along the X direction, in the case that the total size of the germanium absorbing layer 120 is unchanged, on one hand, the size of the intrinsic region 123 along the X direction can be designed according to the thicknesses (i.e., the ion doping depths) of the first lightly doped region 121 and the second lightly doped region 122, so that the size of the intrinsic region 123 along the X direction can be adjusted, and further the transit time of carriers can be reduced, so as to improve the 3dB bandwidth of the photodetector 100, and in the second aspect, after the side wall of the germanium absorbing layer 120 is doped, a doped region with a high concentration difference can be formed inside the germanium absorbing layer 120, so that the local field intensity of the germanium absorbing layer 120 can be improved, and further the FK effect can be realized under the low voltage condition, so that the absorption efficiency of the germanium absorbing layer 120 in the L band can be improved. In the third aspect, the germanium absorbing layer 120 is partially embedded in the first semiconductor layer 111, so that 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, which is beneficial to control of an electric field, so that not only the equivalent distance of the PIN junction can be reduced, but also the bandwidth can be increased, and the external voltage required by the FK effect can be reduced.

In the embodiment of the disclosure, please continue to refer to fig. 1, in which the first doped region 111b, the germanium absorbing layer 120 and the second doped region 111c together form a horizontal PIN structure, that is, the first doped region 111b and the first lightly doped region 121 may form a P region in the PIN structure, the intrinsic region 123 may form an I region in the PIN structure, and the second lightly doped region 122 and the second doped region 111c may form an N region in the PIN structure. In other embodiments, the first doped region 111b and the first lightly doped region 121 may constitute an N region in the PIN structure when they are N-type doped, and the second lightly doped region 122 and the second doped region 111c may constitute a P region in the PIN structure when they are P-type doped.

In some embodiments, referring to FIG. 1, the photodetector 100 further comprises a second semiconductor layer 130 covering at least the top surface of the germanium absorber layer 120, the top surface of the germanium absorber layer 120 having a dimension in the X direction that is less than the dimension of the second semiconductor layer 130 in the X direction, wherein the second semiconductor layer 130 has a lattice density that is greater than the lattice density of the germanium absorber layer 120.

In the embodiment of the disclosure, since the lattice density of the second semiconductor layer 130 is greater than that of the germanium absorption layer 120, a lattice mismatch phenomenon is generated at the contact interface between the second semiconductor layer 130 and the germanium absorption layer 120, and the lattice mismatch forms tensile stress at the contact interface between the two, so that the absorption optical boundary of germanium is red shifted, and the responsivity of the photodetector 100 in the L-band is improved.

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

In the embodiment of the disclosure, silicon nitride may be deposited on the top surface of the germanium absorption layer 120 by a process such as Plasma Enhanced Chemical Vapor Deposition (PECVD) to generate tensile strain on the surface of the germanium absorption layer 120, so that the band gap of the germanium absorption layer 120 may be reduced, and the detection range may be extended to 1550nm or more. In addition, referring to fig. 1, a second semiconductor layer 130 (i.e., silicon nitride) may also be formed on a portion of the sidewall of the germanium absorber layer 120.

It should be noted that, in an example, the optical signal of the waveguide-type silicon-based germanium photodetector is input from one end of the waveguide layer in 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 region of the first few microns near the input end of the waveguide layer. Therefore, under high input optical power, the optical field distribution in the germanium absorption layer is easily caused to be uneven. In addition, due to the existence of space charge effect, a large number of photo-generated carriers generated in the local area of the germanium absorption layer break the built-in electric field distribution of the photo-generated carriers, so that the timely transportation of the photo-generated carriers is affected, and the response speed of the photoelectric detector is seriously reduced.

The space charge effect means that photo-generated carriers in the germanium absorption layer are rapidly separated and form drifting motion under the action of an external electric field. The mobility of electrons and holes in the germanium absorption layer are different, so that the difference of the movement speeds of carriers in the intrinsic region naturally occurs, and further, the charge imbalance exists in the intrinsic region, so that the distribution effect of an external electric field is influenced.

Fig. 2 is a schematic structural diagram of a photodetector according to an embodiment of the disclosure. It should be noted that the schematic diagram shown in fig. 2 is not a real structural diagram of the photodetector, but is merely for illustrating the relative positional relationship among the first waveguide, the second waveguide, and the germanium absorption layer. The specific structure of the photodetector may be referred to fig. 1, and fig. 1 corresponds to a cross-sectional structure diagram of the photodetector along the AA section in fig. 2.

In some embodiments, the photodetector 100 further comprises a first waveguide 141 positioned over the surface of the first doped region 111B with a first gap A between the first waveguide 141 and the germanium absorbing layer 120, and a second waveguide 142 positioned over the surface of the second doped region 111c with a second gap B between the second waveguide 142 and the germanium absorbing layer 120, wherein the first waveguide 141 and the second waveguide 142 are configured to couple optical signals received by the photodetector 100 to the germanium absorbing layer 120 via the first gap A and the second gap B, respectively.

As shown in conjunction with fig. 1 and 2, in the embodiment of the present disclosure, a first waveguide 141 is disposed on one side of the germanium absorption layer 120 along the X direction, a second waveguide 142 is disposed 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 used to couple the optical signal received by the photodetector 100 to the germanium absorption layer 120 via a first gap a and a second gap B, respectively.

It should be noted that, the excessive size of the first gap a and the second gap B along the X direction may cause the incomplete absorption of the optical field by the germanium absorption layer 120, thereby increasing the absorption length and resulting in too long effect bandwidth of the whole photodetector 100, and the too small size of the first gap a and the second gap B along the X direction may cause the optical signal coupling to be too fast and may not achieve the effect of space charge regulation. The suitable gap size can be selected by simulation or by preparing 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.

In the embodiment of the disclosure, referring to fig. 2, optical signals from outside may be provided to the photodetector 100 through two output ends 220 of the optical beam splitter 210, respectively. And two output ends 220 of the optical splitter 210 are connected to the first waveguide 141 and the second waveguide 142, respectively. Specifically, the first waveguide 141 has a first end 141a and a second end 141b opposite in the Y direction, and the second waveguide 142 has a first end 142a and a second end 142b opposite in the Y direction. The first end 141a of the first waveguide 141 and the second end 142b of the second waveguide 142 may be connected to two output ends 220 of the optical splitter 210, respectively. Or the second end 141b of the first waveguide 141 and the first end 142a of the second waveguide 142 may be connected to two output ends 220 of the optical splitter 210, respectively.

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

In the embodiment of the disclosure, referring to fig. 1 and 3, the top views of the first waveguide 141 and the second waveguide 142 may be tapered, the dimension of the first waveguide 141 in the X direction may be increased from the second dimension L2 to the first dimension L1 along the Y direction, and the dimension of the second waveguide 142 in the X direction may be decreased from the first dimension L1 to the second dimension L2, wherein the optical signal (as indicated by the arrow direction) is input from one end with a larger dimension (i.e., the first dimension L1). In some embodiments, the first waveguide 141 may gradually decrease in size in the X direction and the second waveguide 142 may gradually increase in size in the X direction along the Y direction. The material of the first waveguide 141 and the second waveguide 142 may be silicon nitride (Si ₃N₄).

In summary, in the embodiment of the disclosure, the first waveguide 141 and the second waveguide 142 are coupled to two sides of the germanium absorption layer 120, so that optical signals can be respectively coupled to the germanium absorption layer 120 from two sides of the germanium absorption layer 120 along the X direction at the same time, so that the optical field distribution in the germanium absorption layer can be regulated and controlled, the optical field distribution is more uniform, the spatial distribution of photo-generated carriers is balanced, the aggregation effect of the photo-generated carriers at the front end of the germanium absorption layer is reduced, that is, the space charge effect is avoided, and the detector bandwidth is improved.

Note that, fig. 3 shows the first waveguide, the second waveguide, and the germanium absorption layer in fig. 2.

In some embodiments, the dimension of the germanium absorber layer 120 along the X-direction is less than or equal to a first threshold value, which is proportional to the transit time of carriers in the germanium absorber layer.

In the embodiment of the disclosure, the smaller the first threshold value is, the smaller the transit time of the carrier in the germanium absorption layer is, the faster the response speed of the photodetector 100 is, whereas the larger the first threshold value is, the slower the transit time of the carrier in the germanium absorption layer is, the slower the response speed of the photodetector 100 is, where the first threshold value may be 500nm. In addition, the germanium absorption layer 120 is less than or equal to a second threshold along the Z-axis, where the second threshold may be 400nm or other suitable dimension, for example. I.e., the germanium absorber layer 120 has an ultra-small size, which may further increase the bandwidth of the photodetector 100 such that the photodetector 100 may be an ultra-high speed silicon germanium photodetector 100. It will be appreciated that during the process of manufacturing the photodetector 100, the dimensions of the germanium absorbing layer 120 in the X-direction and the Z-direction may be further reduced based on the first threshold and the second threshold, respectively, and that the bandwidth of the photodetector 100 may be further increased, thereby increasing the response speed of the photodetector 100.

In the embodiments of the present disclosure, with continued reference to fig. 1, during the fabrication process of the photodetector 100, after forming the PIN structure, it is necessary to prepare a metal electrode for electrically connecting the PIN structure and the external circuit. The metal electrode includes a first metal electrode 151 located on the first doped region 111b, and a second metal electrode 152 located on the second doped region 111 c. Wherein the first metal electrode 151 and the second metal electrode 152 are respectively located at opposite sides of the germanium absorption layer 120 in the X direction. It should be noted that, in the current technical node of the industry, the dimensions of the first metal electrode 151 and the second metal electrode 152 in the X direction may be 400nm, and the dimensions of the first metal electrode 151 and the second metal electrode 152 in the X direction may be 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. Thus, the size of the germanium absorption layer 120 in the X direction is reduced, and the problem that the electrode is difficult to be led out when the size of the germanium absorption layer 120 in the X direction is smaller is effectively avoided, so that the 3dB bandwidth of the photodetector 100 is improved.

In the embodiment of the disclosure, please continue to refer to fig. 1, a metal silicide 160 is disposed on the surface of the first doped region 111b and the surface of the second doped region 111c, and the metal silicide 160 includes cobalt silicide (Cobal-Silicide), nickel silicide (Nickel-Silicide), and the like. Since the metal silicide has a low resistance, the contact resistance between the metal electrode and the doped region can be reduced.

In the embodiment of the disclosure, please continue to refer to fig. 1, the photodetector 100 further includes a dielectric layer 170, wherein the dielectric layer 170 is filled between the structures, and the material of the isolation layer 170 may be silicon oxide, silicon nitride, silicon oxynitride, or the like.

Fig. 4 is a flowchart of a method for manufacturing a photodetector according to an embodiment of the present disclosure. As shown in fig. 4, an embodiment of the present disclosure provides a method for manufacturing a photodetector, the method comprising:

Step S401, providing a substrate, wherein the surface of the substrate is a first semiconductor layer, and the first semiconductor layer comprises a groove, and a first doping region and a second doping region which are positioned at two sides of the groove along the X direction;

step S402, forming a germanium absorption layer partially positioned in the groove, wherein the first doping region, the germanium absorption layer and the second doping region form a horizontal PIN structure, and the side walls of the germanium absorption layer along the two sides of the X direction are respectively provided with doping of the same type as the first doping region and the second doping region.

Fig. 5A to 5E are step diagrams of a method for manufacturing a photodetector according to an embodiment of the present disclosure.

First, step S401 is performed, and as shown in fig. 5A, the substrate 110 may be prepared through a multi-step deposition process and an etching process. Specifically, the first doped region 111b and the second doped region 111c may be formed by sequentially forming the buried oxide layer 113 and an initial first semiconductor layer (not shown) on the silicon substrate layer 112, then ion-doping the initial first semiconductor layer, then forming the first dielectric layer 171 on the surface of the substrate 110, sequentially etching the first dielectric layer 171 and the doped initial first semiconductor layer by any suitable etching process, and forming the recess 111a in an undoped region between the first doped region 111b and the second doped region 111c, wherein ion doping (e.g., undoped silicon) is not performed in a bottom region 111d located in the recess 111 a. In other embodiments, the substrate may be prepared in other ways, for example, may be prepared based on an SOI substrate, and the preparation method is similar to that of the above embodiments, and will not be described herein.

In the embodiment of the disclosure, the size of the formed groove 111a along the X direction is less than or equal to a first threshold, and the first threshold may be 500nm, so that the size of the subsequently formed germanium absorption layer along the X axis direction may be designed by the size of the groove 111a along the X direction.

In some embodiments, referring to FIG. 5A, the first dielectric layer 171 comprises a first sub-dielectric layer and a second sub-dielectric layer sequentially on the surface of the substrate 110, and the method of fabricating the photodetector further comprises forming a first waveguide 141 over the surface of the first doped region 111b and forming a second waveguide 142 over the surface of the second doped region 111c prior to forming the recess 111 a.

Specifically, first, a first sub-dielectric layer is formed on the surface of the substrate 110, the first sub-dielectric layer is etched by any suitable etching process, a first etched recess (not shown) above the surface of the first doped region 111b and a second etched recess (not shown) above the surface of the second doped region 111c are formed, next, a first waveguide 141 and a second waveguide 142 are formed in the first etched recess and the second etched recess, respectively, and 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.

Wherein, a first gap a is provided between the first waveguide 141 and the extension line inside the first doped region 111B, and a second gap B is provided between the second waveguide 142 and the extension line inside the second doped region 111 c. In this way, a first gap a may be provided between the first waveguide 141 and the subsequently formed germanium absorption layer, and a second gap B may be provided between the second waveguide 142 and the subsequently formed germanium absorption layer.

In addition, in 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 (refer to fig. 3). The materials of the first waveguide 141 and the second waveguide 142 may be silicon nitride.

In the embodiment of the disclosure, the first waveguide 141 and the second waveguide 142 may be coupled to two sides of the subsequently formed germanium absorption layer, so that optical field distribution in the germanium absorption layer may be regulated and controlled, so that the optical field distribution is more uniform, the spatial distribution of photo-generated carriers is balanced, the aggregation effect of the photo-generated carriers at the front end of the germanium absorption layer is reduced, that is, the space charge effect is avoided, and the detector bandwidth is improved.

In an embodiment of the present disclosure, after forming the recess 111a, the method of manufacturing the photodetector further includes smoothing the exposed surface of the recess 111a, for example, using tetramethylammonium hydroxide (TMAH) and hydrofluoric acid (HF) to smooth the exposed surface of the recess 111a and have a well-consistent dangling bond.

Next, step S402 is performed, referring to fig. 5A and 5B, forming a germanium absorbing layer 120 partially located in the recess 111a includes forming an initial germanium absorbing layer 120a partially located in the recess 111a, and performing a first light doping and a second light doping on sidewalls of the initial germanium absorbing layer 120a along two sides of the X direction, respectively, to form the germanium absorbing layer 120.

Specifically, referring to fig. 5A, an initial germanium absorption layer 120a may be formed in the recess 111a by using an epitaxial growth process, and a material of the initial germanium absorption layer 120a includes elemental germanium. 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 surface of the initial germanium absorption layer 120a may have a lower height in the Z direction than the surface of the first dielectric layer 171. Referring to fig. 5A, since elemental germanium is grown from the bottom of the recess 111a in a direction away from the substrate 110, a gap may exist between the initial germanium absorption layer 120a and the sidewalls of the recess 111a (i.e., the top of the initial germanium absorption layer 120a is arc-shaped).

In the embodiment of the disclosure, since the initial germanium absorption layer 120a is formed in the recess 111a by an epitaxial process, the dimension of the initial germanium absorption layer 120a in the X direction may be designed according to the dimension of the recess 111a in the X direction, so that the subsequently formed germanium absorption layer may have an ultra-small dimension in the X direction.

Next, please continue to refer to fig. 5B, in the initial germanium absorption layer 120a, a side wall on a side contacting the first doped region 111B is lightly doped to form a first lightly doped region 121 on the side wall, a side wall on a side contacting the second doped region 111c is lightly doped to form a second lightly doped region 122 on the side wall, the remaining undoped region forms an intrinsic region 123, and the first lightly doped region 121, the intrinsic region 123 and the second doped region 111c form the germanium absorption layer 120. The first doped region 111b and the first lightly doped region 121 may be doped with P-type dopants, and the second doped region 111c and the second lightly doped region 122 may be doped with N-type dopants.

In the embodiment of the disclosure, on one hand, the size of the intrinsic region 123 along the X direction may be designed according to the thicknesses (i.e., the ion doping depths) of the first lightly doped region 121 and the second lightly doped region 122, so that the size of the intrinsic region 123 along the X direction may be adjusted, and further the transit time of carriers may be reduced, so as to improve the 3dB bandwidth of the photodetector 100, and on the other hand, after the side wall of the germanium absorption layer 120 is doped, a doped region with a high concentration difference may be formed inside the germanium absorption layer 120, so that the local field strength of the germanium absorption layer 120 may be improved, and further the FK effect may be realized under a low voltage condition, so as to improve 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 is helpful to improve coupling efficiency of optical signals, thereby effectively improving responsivity of the photodetector.

In some embodiments, referring to fig. 5C and 5D, after forming the germanium absorbing layer 120, the method further includes forming a second semiconductor layer 130 covering at least a top surface of the germanium absorbing layer 120, wherein a dimension of the top surface of the germanium absorbing layer 120 in an X-direction is smaller than a dimension of the second semiconductor layer 130 in the X-direction, and wherein a lattice density of the second semiconductor layer 130 is greater than a lattice density of the germanium absorbing layer 120.

Specifically, referring to fig. 5C, an initial second semiconductor layer 130a may be formed by depositing an initial second semiconductor layer 130a on the exposed surfaces of the germanium absorber layer 120 and the first dielectric layer 171 by a Plasma Enhanced Chemical Vapor Deposition (PECVD) or the like. Next, referring to fig. 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 forms the second semiconductor layer 130, so that not only the local stress of the second semiconductor layer 130 in the active region 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, and the responsivity of the detector can be further improved.

It should be noted that, since a gap may exist between the germanium absorption layer 120 and the sidewall of the recess 111a (i.e., 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.

In the embodiment of the disclosure, since the lattice density of the second semiconductor layer 130 is greater than that of the germanium absorption layer 120, a lattice mismatch phenomenon is generated at the contact interface between the second semiconductor layer 130 and the germanium absorption layer 120, and the lattice mismatch forms tensile stress at the contact interface between the two, so that the absorption optical boundary of germanium is red shifted, and the responsivity of the photodetector 100 in the L-band is improved.

Further, 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, so that the band gap of the germanium absorption layer 120 can be reduced, and the detection range can be extended to 1550nm or more.

In the embodiment of the present disclosure, after the second semiconductor layer 130 is formed, a metal electrode for realizing electrical connection of the PIN structure and the external circuit may be formed, as shown in fig. 5E. Specifically, a second dielectric layer 172 covering exposed surfaces of the first dielectric layer 171 and the second semiconductor layer 130 may be first formed, wherein the first dielectric layer 171 and the second dielectric layer 172 constitute the dielectric layer 170, and a material of the second dielectric layer 172 may be the same as that of the first dielectric layer 171. Thereafter, the dielectric layer 170 may be etched by any suitable etching process to form a plurality of metal filling holes extending to the surfaces of the first and second doped regions 111b and 111c, respectively. The metal filling holes may be filled with a metal material simultaneously to form a plurality of first metal electrodes 151 on the first doped region 111b and a plurality of second metal electrodes 152 on the second doped region 111 c. Wherein the first metal electrode 151 and the second metal electrode 152 are respectively located at opposite sides of the germanium absorption layer 403 in the X direction.

In some embodiments, as shown in fig. 5E, before forming the metal electrode, a metal silicide 160 may be formed at positions where the surfaces of the first doped region 111b and the second doped region 111c are respectively used to contact the metal electrode, thereby reducing contact resistance between each doped region and the metal electrode. The metal silicide 160 includes cobalt silicide (Cobal-Silicide), nickel silicide (Nickel-Silicide), and the like.

In embodiments of the present disclosure, deposition processes for forming layers in a photodetector include, but are not limited to, chemical vapor deposition (Chemical Vapor Deposition, CVD), physical vapor deposition (Physical Vapor Deposition, PVD), or atomic layer deposition (Atomic Layer Deposition, ALD).

The resulting photodetector 100 of the embodiments of the present disclosure is a high-speed silicon germanium photodetector capable of operating in the c+l band. The germanium-silicon photoelectric detector with the waveguide structure is suitable for being used in a large-scale optical path, thereby being beneficial to being applied to next-generation (800G) coherent optical communication.

Similar to the photodetector provided in the above embodiment, the photodetector formed by the method for manufacturing a photodetector provided in the embodiment of the present disclosure has technical features that are not fully disclosed in the embodiment of the present disclosure, and will be understood with reference to the above embodiment, which is not repeated here.

In several embodiments provided by the present disclosure, it should be understood that the disclosed structures and methods may be implemented in a non-targeted manner. The structural embodiments described above are merely illustrative, e.g., the division of elements is merely a logical functional division, and there may be additional divisions in actual implementation, e.g., multiple elements or components may be combined or integrated into another system, or some features may be omitted, or not implemented. In addition, the components shown or discussed are coupled to each other or directly.

Features disclosed in the several method or structure embodiments provided in the present disclosure may be arbitrarily combined without any conflict to obtain new method embodiments or structure embodiments.

The above is merely some embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present disclosure, and should be covered in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (10)

1. A photoelectric detector, which comprises a light source, a light source and a light receiving element, characterized by comprising the following steps:

The semiconductor device comprises a substrate, a first semiconductor layer, a second semiconductor layer, a first doping region and a second doping region, wherein the surface of the substrate is provided with the first semiconductor layer;

the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure;

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 two sides of the first direction, and the first direction is parallel to the surface of the substrate.

2. The photodetector of claim 1, wherein the photodetector further comprises:

A second semiconductor layer covering at least a top surface of the germanium absorber layer, a dimension of the top surface of the germanium absorber layer in the first direction being smaller than a dimension of the second semiconductor layer in the first direction;

wherein the lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorber layer.

3. The photodetector of claim 2 wherein the material of said second semiconductor layer comprises silicon nitride.

4. A photodetector according to any one of claims 1 to 3, further comprising:

A first waveguide over the first doped region surface, the first waveguide having a first gap with the germanium absorber layer;

A second waveguide over the second doped region surface, the second waveguide having a second gap with the germanium absorber layer;

Wherein the first waveguide and the second waveguide are for coupling an optical signal received by the photodetector to the germanium absorption layer via the first gap and the second gap, respectively.

5. The photodetector of claim 4 wherein the light source is a photodetector,

The size of the first waveguide in the first direction is gradually increased, and the size of the second waveguide in the first direction is gradually decreased along the second direction;

Wherein the second direction is parallel to the substrate surface and perpendicular to the first direction.

6. The photodetector of claim 1 wherein a dimension of said germanium absorber layer along said first direction is less than or equal to a first threshold value, said first threshold value being proportional to a transit time of carriers in said germanium absorber layer.

7. A method of manufacturing a photodetector, comprising:

Providing a substrate, wherein the surface of the substrate is a first semiconductor layer, and the first semiconductor layer comprises a groove, and a first doping region and a second doping region which are positioned at two sides of the groove along a first direction;

Forming a germanium absorption layer partially positioned in the groove, wherein the first doped region, the germanium absorption layer and the second doped region form a horizontal PIN structure;

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 two sides of the first direction, and the first direction is parallel to the surface of the substrate.

8. The method of manufacturing of claim 7, wherein forming a germanium absorber layer partially within the recess comprises:

forming an initial germanium absorber layer partially within the recess;

Respectively carrying out first light doping and second light doping on the side walls of the initial germanium absorption layer along the two sides of the first direction to form the germanium absorption layer;

The size of the germanium absorption layer along the first direction is smaller than or equal to a first threshold value, and the first threshold value is in direct proportion to the transit time of carriers in the germanium absorption layer.

9. The method of manufacturing of claim 8, wherein after forming the germanium absorber layer, the method further comprises:

Forming a second semiconductor layer covering at least a top surface of the germanium absorber layer, the top surface of the germanium absorber layer having a dimension in the first direction that is less than a dimension of the second semiconductor layer in the first direction;

wherein the lattice density of the second semiconductor layer is greater than the lattice density of the germanium absorber 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 over the surface of the first doped region with a first gap between the first waveguide and the germanium absorbing layer, and

Forming a second waveguide over the second doped region surface, the second waveguide having a second gap with the germanium absorber layer;

The size of the first waveguide along the first direction is gradually increased, and the size of the second waveguide along the first direction is gradually reduced in a second direction, wherein the second direction is parallel to the substrate surface and perpendicular to the first direction.