Photodetector and its formation method

Abstract

A photodetector and its formation method are disclosed. The photodetector includes: a substrate; a light transmission layer located on the substrate, the light transmission layer extending along the light propagation direction and perpendicular to the light propagation direction, the light transmission layer including a light absorption region; a light absorption layer located on the light transmission layer of the light absorption region; a first doped region located in the light transmission layer on the side of the light absorption region; and a second doped layer located on the light absorption layer, and on the side perpendicular to the light propagation direction, at least one side of the second doped layer protrudes outward relative to the light absorption layer, the doping type of the second doped layer being opposite to that of the first doped region. This invention is beneficial for improving the bandwidth and responsivity of the photodetector.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to a photodetector and a method for forming the same. Background Technology

[0002] With the rise of new businesses such as cloud services, artificial intelligence, and the Internet of Things, data transmission rates and capacities are facing unprecedented challenges, the key to which lies in the development of high-speed optoelectronic devices. In the past decade, silicon-based optoelectronics has developed rapidly, becoming a new mainstream technology in the field of integrated optoelectronics due to its outstanding advantages such as Complementary Metal-Oxide-Semiconductor (CMOS) compatibility and high integration.

[0003] As is well known, high-performance photodetectors are indispensable core components in almost all optical systems. In order to obtain higher sensitivity, photodetectors with higher gain have been developed, such as germanium-silicon photodetectors. Compared with traditional detectors, germanium-silicon photodetectors have the characteristics of high photoelectric conversion gain, faster response rate, and lower power consumption. Summary of the Invention

[0004] The problem solved by the embodiments of the present invention is to provide a photodetector and a method for forming the same, which is beneficial to improving the bandwidth and responsivity of the photodetector.

[0005] To address the aforementioned problems, embodiments of the present invention provide a photodetector, comprising: a substrate; a light transmission layer located on the substrate, the light transmission layer extending along the light propagation direction and perpendicular to the light propagation direction, the light transmission layer including a light absorption region; a light absorption layer located on the light transmission layer of the light absorption region; a first doped region located in the light transmission layer on the side of the light absorption region; and a second doped layer located on the light absorption layer, and in the direction perpendicular to the light propagation direction, at least one side of the second doped layer protrudes outward relative to the light absorption layer, the doping type of the second doped layer being opposite to that of the first doped region.

[0006] Optionally, the photodetector further includes: a first interconnect via structure located on and electrically connected to the first doped region; and a second interconnect via structure located on and electrically connected to the second doped layer protruding from the light-absorbing layer.

[0007] Optionally, in the direction perpendicular to the light propagation direction, both sides of the second doped layer protrude outward relative to the light absorption layer; a second interconnect via structure is formed on both sides of the second doped layer protruding from the light absorption layer.

[0008] Optionally, a first doped region is formed in the light transmission layer on both sides of the light absorption region; a first interconnect via structure is formed on the first doped region on both sides of the light absorption region.

[0009] Optionally, the optical transport layer has doped ions, and the optical transport layer has the same doping type as the first doped region.

[0010] Optionally, the length of the light-absorbing layer is 0.1 μm to 100 μm; the width of the light-absorbing layer is 0.1 μm to 5 μm; and the thickness of the light-absorbing layer above the light-transmitting layer is 0.1 μm to 5 μm.

[0011] Optionally, in the longitudinal direction, the light-absorbing layer extends into a portion of the transmission absorption layer.

[0012] Optionally, the depth to which the light absorption layer extends into the light transmission layer is less than or equal to 0.5 μm.

[0013] Optionally, the material of the light transport layer includes silicon or lithium niobate; the material of the light absorption layer includes germanium, group III-V compounds or group II-VI compounds.

[0014] Optionally, the material of the second doped layer includes silicon.

[0015] Accordingly, embodiments of the present invention also provide a method for forming a photodetector, comprising: providing a substrate, on which a light transmission layer is formed, the light transmission layer extending along the light propagation direction and perpendicular to the light propagation direction, the light transmission layer including a light absorption region, and a first doped region being formed in the light transmission layer on the side of the absorption region; forming a light absorption layer on the light transmission layer in the light absorption region; forming a second doped layer on the light absorption layer, wherein at least one side of the second doped layer protrudes outward relative to the light absorption layer in the direction perpendicular to the light propagation direction, and the doping type of the second doped layer is opposite to that of the first doped region.

[0016] Optionally, in the step of providing the substrate, a first dielectric layer covering the light transmission layer is further formed on the substrate; the step of forming the light absorption layer on the light transmission layer in the light absorption region includes: patterning the first dielectric layer to form an opening exposing the top of the light transmission layer in the light absorption region; and forming the light absorption layer in the opening.

[0017] Optionally, in the step of patterning the first dielectric layer to form an opening at the top of the light transmission layer that exposes the light absorption region, the light transmission layer with a portion of the thickness of the light absorption region is also patterned, and the opening extends longitudinally into the light transmission layer.

[0018] Optionally, the step of forming a light-absorbing layer in the opening includes: forming a light-absorbing material layer that fills the opening; planarizing the first dielectric layer and the light-absorbing material layer; removing a portion of the thickness of the first dielectric layer and the light-absorbing material layer; and retaining the remaining light-absorbing material layer as the light-absorbing layer.

[0019] Optionally, a chemical mechanical polishing process can be used to planarize the first dielectric layer and the light-absorbing material layer.

[0020] Optionally, an epitaxial growth process can be used to form a light-absorbing material layer that fills the opening.

[0021] Optionally, the step of forming a second doped layer on the light absorption layer includes: forming a doped material layer covering the first dielectric layer and the light absorption layer; patterning the doped material layer, and retaining the doped material layer located above the light absorption region as the second doped layer.

[0022] Optionally, after forming the second doped layer on the light-absorbing layer, the formation method further includes: forming a first interconnect via structure electrically connected thereto on the first doped region; and forming a second interconnect via structure electrically connected thereto on the second doped layer protruding from the light-absorbing layer.

[0023] Optionally, in the step of forming a second doped layer on the light-absorbing layer, both sides of the second doped layer protrude outward relative to the light-absorbing layer in a direction perpendicular to the light propagation direction; in the step of forming a second interconnect via structure electrically connected to the second doped layer protruding from the light-absorbing layer, a second interconnect via structure is formed on both sides of the second doped layer protruding from the light-absorbing layer.

[0024] Optionally, in the step of providing the substrate, a first doped region is formed in the light transmission layer on both sides of the light absorption region; in the step of forming a first interconnect via structure electrically connected to the first doped region, a first interconnect via structure is formed in the first doped region on both sides of the light absorption region.

[0025] Compared with the prior art, the technical solution of the embodiments of the present invention has the following advantages:

[0026] In the photodetector provided in this embodiment of the invention, the light absorption layer is located on the light transmission layer of the light absorption region, the first doped region is located in the light transmission layer on the side of the light absorption region, and the second doped layer is located on the light absorption layer. At least one side of the second doped layer protrudes outward relative to the light absorption layer in the direction perpendicular to the light propagation direction. The doping type of the second doped layer is opposite to that of the first doped region. In this embodiment, since at least one side of the second doped layer protrudes outward relative to the light absorption layer in the direction perpendicular to the light propagation direction, electrical connection with the outside can be achieved through the second doped layer protruding from the light absorption layer. That is, an electrical interconnect structure can be formed above the side of the light absorption layer, avoiding the situation where the electrical interconnect structure is directly above the light absorption layer. This allows the size of the light absorption layer to be unaffected by the formation of the electrical interconnect structure, thus allowing for flexible adjustment of the size of the light absorption layer. For example, a light absorption layer with a smaller width along the direction perpendicular to the light propagation direction can be formed, which helps to reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light absorption layer, which helps to alleviate the light absorption of the electrical interconnect structure, thereby improving the light absorption rate of the light absorption layer and thus improving the responsivity of the photodetector.

[0027] In the formation method provided by this embodiment of the invention, the light transport layer includes a light absorption region, and a first doped region is formed in the light transport layer on the side of the absorption region. A light absorption layer is formed on the light transport layer in the light absorption region, and a second doped layer is formed on the light absorption layer. At least one side of the second doped layer protrudes outward relative to the light absorption layer in a direction perpendicular to the light propagation direction. The doping type of the second doped layer is opposite to that of the first doped region. In this embodiment of the invention, since at least one side of the second doped layer protrudes outward relative to the light absorption layer in a direction perpendicular to the light propagation direction, electrical connection with the outside can be achieved through the second doped layer protruding from the light absorption layer. In other words, an electrical interconnect structure can be formed above the side of the light absorption layer, avoiding the situation where the electrical interconnect structure is located directly above the light absorption layer. This allows the size of the light absorption layer to be unaffected by the formation of the electrical interconnect structure, thus enabling flexible adjustment of the size of the light absorption layer. For example, a light absorption layer with a narrow width perpendicular to the light propagation direction can be formed, which helps to reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light absorption layer, which helps to alleviate the light absorption of the electrical interconnect structure, thereby improving the light absorption rate of the light absorption layer and thus improving the responsivity of the photodetector. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a photodetector.

[0029] Figures 2 to 3 This is a schematic diagram of the structure of one embodiment of the photodetector of the present invention;

[0030] Figures 4 to 15 This is a schematic diagram of the structure corresponding to each step in one embodiment of the method for forming the photodetector of the present invention. Detailed Implementation

[0031] Currently, it is difficult to improve the bandwidth and responsivity of photodetectors. This paper analyzes the reasons why it is difficult to improve the bandwidth and responsivity using a specific photodetector as an example.

[0032] Figure 1 This is a schematic diagram of the structure of a photodetector.

[0033] refer to Figure 1 The photodetector includes: a substrate 10; a light transmission layer 20, on which a first doped region 21 is formed; a light absorption layer 31 located on the light transmission layer 20, on which a second doped region 41 is formed, the doping type of the second doped region 41 being opposite to that of the first doped region 21; a first interconnect via structure 18 located on and electrically connected to the first doped region 21; and a second interconnect via structure 19 located on and electrically connected to the second doped region 41.

[0034] The second doped region 41 is electrically connected to the outside through the second interconnect via structure 19, and the first doped region 21 is electrically connected to the outside through the first interconnect via structure 18, realizing the longitudinal movement of charge carriers to shorten the carrier transit time. However, the formation of the second doped region 41 at the top of the light absorption layer 31 requires thermal activation of the doping of the light absorption layer 31, resulting in a high thermal budget for the process. Moreover, the second interconnect via structure 19 needs to be formed at the top of the second doped region 41, which requires the size of the second doped region 41 to be large, which can easily lead to a large junction capacitance of the device and affect the bandwidth. At the same time, the second interconnect via structure 19 is formed at the top of the second doped region 41. During operation, the second interconnect via structure 19 easily absorbs light, which reduces the light absorption rate of the light absorption layer 31, thereby reducing the responsivity of the photodetector.

[0035] To address the aforementioned technical problems, embodiments of the present invention provide a photodetector, comprising: a substrate; a light transmission layer located on the substrate, the light transmission layer extending along the light propagation direction and perpendicular to the light propagation direction, the light transmission layer including a light absorption region; a light absorption layer located on the light transmission layer of the light absorption region; a first doped region located in the light transmission layer on the side of the light absorption region; and a second doped layer located on the light absorption layer, and at least one side of the second doped layer protruding outward relative to the light absorption layer in the direction perpendicular to the light propagation direction, the doping type of the second doped layer being opposite to that of the first doped region.

[0036] In this embodiment of the invention, at least one side of the second doped layer protrudes outward relative to the light-absorbing layer in a direction perpendicular to the light propagation direction. This allows for electrical connection to the outside through the second doped layer protruding from the light-absorbing layer. In other words, an electrical interconnect structure can be formed above the side of the light-absorbing layer, avoiding the situation where the electrical interconnect structure is directly above the light-absorbing layer. This allows the size of the light-absorbing layer to be unaffected by the formation of the electrical interconnect structure, thus enabling flexible adjustment of the light-absorbing layer size. For example, a light-absorbing layer with a narrow width along the direction perpendicular to the light propagation direction can be formed, which helps reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light-absorbing layer, which helps alleviate light absorption by the electrical interconnect structure, thereby improving the light absorption rate of the light-absorbing layer and ultimately improving the photodetector responsivity. In this embodiment of the invention, at least one side of the second doped layer protrudes outward relative to the light absorption layer in a direction perpendicular to the light propagation direction. This allows for electrical connection to the outside through the second doped layer protruding from the light absorption layer. In other words, an electrical interconnect structure can be formed above the side of the light absorption layer, avoiding the situation where the electrical interconnect structure is directly above the light absorption layer. This allows the size of the light absorption layer to be unaffected by the formation of the electrical interconnect structure, thus enabling flexible adjustment of the light absorption layer size. For example, a light absorption layer with a narrow width along the direction perpendicular to the light propagation direction can be formed, which helps reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light absorption layer, which helps alleviate light absorption by the electrical interconnect structure, thereby improving the light absorption rate of the light absorption layer and ultimately improving the photodetector responsivity.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Figures 2 to 3 This is a schematic diagram of the structure of one embodiment of the photodetector of the present invention.

[0039] Reference Figures 2 to 3 , Figure 3 for Figure 2 A partial top view of the structure shows that the photodetector includes: a substrate 100; and a light transmission layer 200 located on the substrate 100, with the light transmission layer 200 positioned along the light propagation direction (e.g., ...). Figure 2 Extending in the Y direction (as shown in the image), and along a direction perpendicular to the light propagation direction (e.g., ...). Figure 2(As shown in the X direction), the light transmission layer 200 includes a light absorption region 100a; a light absorption layer 310 located on the light transmission layer 200 in the light absorption region 100a; a first doped region 210 located in the light transmission layer 200 on the side of the light absorption region 100a; and a second doped layer 410 located on the light absorption layer 310, and at least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in a direction perpendicular to the light propagation direction, and the doping type of the second doped layer 410 is opposite to that of the first doped region 210.

[0040] Substrate 100 provides the basis for the fabrication process of the photodetector.

[0041] In this embodiment, the substrate 100 includes a substrate 110 and an isolation layer 120 covering the substrate 110.

[0042] Specifically, in the photodetector manufacturing process, a silicon-on-insulator (SOI) substrate is used as substrate 100. The substrate 110 is a base silicon, which is usually thick and serves as a mechanical support. The isolation layer 120 is an insulating layer (Buried Oxide, BOX). Between the top silicon and the base silicon, there is usually a thin layer of silicon oxide (SiO2) which serves as an electrical isolation layer. The light transmission layer 200 is formed from the top silicon (Device Layer), which is the silicon layer used to form semiconductor devices.

[0043] The light transmission layer 200 is used as a channel for light propagation, wherein the light absorption region 100a is the main region for light absorption.

[0044] Specifically, in this embodiment, the light absorption region 100a extends along the light propagation direction.

[0045] In this embodiment, the material of the light transmission layer 200 includes silicon or lithium niobate. The lithium niobate is a thin-film lithium niobate.

[0046] As an example, in this embodiment, the material of the optical transmission layer 200 is silicon.

[0047] Using silicon as the optical transmission layer 200 helps to reduce optical transmission loss.

[0048] In this embodiment, the optical transmission layer 200 has doped ions.

[0049] The light doping of the optical transport layer 200 is beneficial for effectively controlling the carrier concentration of the optical transport layer 200, thereby reducing the dark current. It can also serve as a carrier transport channel, which helps to ensure that photogenerated carriers can be collected efficiently.

[0050] As an example, in this embodiment, the optical transport layer 200 has lightly doped P-type ions.

[0051] In this embodiment, the thickness of the optical transmission layer 200 is 0.1 μm to 0.5 μm, which helps to ensure a faster transmission rate of charge carriers and a better bandwidth of the device.

[0052] The light-absorbing layer 310 is used to absorb photons.

[0053] Specifically, in this embodiment, when photons are absorbed by the light-absorbing layer 310, electron-hole pairs are generated. Under the action of an applied electric field, these charge carriers drift and form a current, thereby converting the optical signal into an electrical signal.

[0054] In this embodiment, the length l of the light absorption layer 310 is from 0.1 μm to 100 μm, so that the dark current of the light absorption layer 310 is not too large, and the light absorption layer 310 enables the device to obtain a large responsivity.

[0055] In this embodiment, the width w of the light absorption layer 310 is 0.1 μm to 5 μm, which ensures the basic function of the light absorption layer 310 in absorbing photons, while making the capacitance of the light absorption layer 310 small, thereby maintaining a large bandwidth.

[0056] In this embodiment, the thickness h2 of the light absorption layer 310 above the light transmission layer 200 is 0.1 μm to 5 μm, so that the thickness h2 of the light absorption layer 310 is not too large and will reduce the bandwidth. This is beneficial to shortening the transit time of the longitudinal movement of charge carriers, thereby increasing the bandwidth.

[0057] In this embodiment, the light absorption layer 310 extends into the light transmission layer 200, which has a partial thickness.

[0058] The light absorption layer 310 extends into the partial thickness of the light transmission layer 200, combining evanescent wave coupling and docking coupling, thereby improving light absorption efficiency and device responsivity.

[0059] In this embodiment, the depth h1 into the light transmission layer 200 of the light absorption layer 310 is less than or equal to 0.5 μm, so that the light absorption layer 310 will not be embedded too deep or too shallow in the light transmission layer 200, which would cause a decrease in light absorption rate, thereby ensuring that the light absorption rate is in a high range.

[0060] In this embodiment, the material of the light absorption layer 310 includes germanium, a group III-V compound, or a group II-VI compound.

[0061] As an example, in this embodiment, the material of the light-absorbing layer 310 is germanium.

[0062] In this embodiment, in the detector, the optical signal is converted into a measurable electrical signal by the generation, separation and collection of photogenerated carriers between the optical transmission layer 200 and the optical absorption layer 310 in the longitudinal direction.

[0063] It should be noted that in this embodiment, the silicon phototransmission layer 200 is used, which is based on a silicon platform and is compatible with CMOS technology, which is beneficial for the integration of photodetectors with other optoelectronic devices.

[0064] The first doped region 210 is used to form a low-resistance ohmic contact on the optical transmission layer 200.

[0065] It should be noted that in this embodiment, the first doped region 210 is located in the light transmission layer 200 on the side of the light absorption region 100a. The side of the light absorption region 100a refers to the side of the light absorption region 100a along the direction perpendicular to the light propagation direction.

[0066] Specifically, in this embodiment, the first doped region 210 is a heavily doped region. The impurity concentration in the heavily doped region is high, so the carrier concentration is also high, and the conductivity is significantly increased. Thus, the first doped region 210 is used to form a low-resistance ohmic contact.

[0067] In this embodiment, the optical transmission layer 200 and the first doped region 210 have the same doping type, thus realizing the basic function of forming a PIN-type photodetector.

[0068] Accordingly, as an example, in this embodiment, the first doped region 210 is a heavily doped P-type layer.

[0069] In this embodiment, a first doped region 210 is formed in the light transmission layer 200 on both sides of the light absorption region 100a.

[0070] If a first doped region 210 is formed in both sides of the light transmission layer 200 along the light propagation direction perpendicular to the light absorption region 100a, then the light transmission layer 200 can be electrically connected through the first doped regions 210 on both sides.

[0071] It should be noted that, in this embodiment, the two sides of the light absorption region 100a refer to the two sides of the light absorption region 100a along the direction perpendicular to the light propagation direction.

[0072] The second doped layer 410 is used to form a low-resistance ohmic contact on the light-absorbing layer 310.

[0073] It should be noted that in this embodiment, at least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in the direction perpendicular to the light propagation direction. Protruding outward means protruding outward relative to the inside of the light absorption layer 310.

[0074] Specifically, in this embodiment, the second doped layer 410 is a heavily doped region. The impurity concentration in the heavily doped region is high, so the carrier concentration is also high, and the conductivity is significantly increased. Thus, the second doped layer 410 is used to form a low-resistance ohmic contact.

[0075] In this embodiment, the second doped layer 410 has the opposite doping type to the first doped region 210, forming a PIN-type photodetector.

[0076] Accordingly, as an example, in this embodiment, the second doped layer 410 is an N-type heavily doped layer.

[0077] In this embodiment, at least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in the direction perpendicular to the light propagation direction. This allows for electrical connection to the outside through the second doped layer 410 protruding from the light absorption layer 310. In other words, an electrical interconnect structure can be formed above the side of the light absorption layer 310, avoiding the situation where the electrical interconnect structure is directly above the light absorption layer 310. This allows the size of the light absorption layer 310 to be unaffected by the formation of the electrical interconnect structure, thus enabling flexible adjustment of the size of the light absorption layer 310. For example, a light absorption layer 310 with a narrow width along the direction perpendicular to the light propagation direction can be formed, which helps reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light absorption layer 310, which helps alleviate light absorption by the electrical interconnect structure, thereby improving the light absorption rate of the light absorption layer 310 and thus improving the photodetector responsivity.

[0078] In this embodiment, both sides of the second doped layer 410 protrude outward relative to the light absorption layer 310 in a direction perpendicular to the light propagation direction.

[0079] Both sides of the second doped layer 410 protrude outward relative to the light absorption layer 310, so that the light absorption layer 310 can be electrically connected through the second doped layer 410 on both sides.

[0080] In this embodiment, the material of the second doped layer 410 includes silicon.

[0081] Using silicon with doped ions as the second doped layer 410 is beneficial to reduce the light absorption of the second doped layer 410 and improve the light absorption rate of the light absorption layer 310.

[0082] It should be noted that in this embodiment, a second doped layer 410 is formed above the light absorption layer 310. It is not necessary to perform ion doping on the top of the light absorption layer 310 to form a second doped layer 410 in the light absorption layer 310. This avoids the step of thermally activating doping of the light absorption layer 310, thereby helping to reduce the thermal budget of the process.

[0083] In this embodiment, the photodetector further includes a first interconnect via structure 180, which is located on and electrically connected to the first doped region 210.

[0084] The first interconnect via structure 180 is used to realize the electrical connection between the first doped region 210 and the outside.

[0085] In this embodiment, the material of the first interconnect via structure 180 includes a metallic material. As an example, in this embodiment, the material of the first interconnect via structure 180 is tungsten.

[0086] Accordingly, in this embodiment, first interconnect via structures 180 are formed on the first doped regions 210 on both sides of the light absorption region 100a.

[0087] Circuit conduction is achieved through the first interconnect via structure 180 on both sides of the optical transmission layer 200, which helps to reduce the aggregation effect, increase the carrier transmission rate, and thus improve the bandwidth.

[0088] In this embodiment, a first electrode 181 electrically connected to the first interconnect via structure 180 is also formed thereon for loading an electrical signal onto the first doped region 210.

[0089] In this embodiment, the photodetector further includes a second interconnect via structure 190, which is located on and electrically connected to the second doped layer 410 protruding from the light absorption layer 310.

[0090] The second interconnect via structure 190 is used to realize the electrical connection between the second doped layer 410 and the outside.

[0091] It should be noted that in this embodiment, the second interconnect via structure 190 is formed above the side of the light absorption layer 310, which is beneficial to make the second interconnect via structure 190 far away from the light absorption layer 310, so as to avoid the light absorption of the second interconnect via structure 190 as much as possible, thereby improving the light absorption rate and the responsivity of the photodetector.

[0092] In this embodiment, the material of the second interconnect via structure 190 includes a metallic material. As an example, in this embodiment, the material of the second interconnect via structure 190 is tungsten.

[0093] Accordingly, in this embodiment, a second interconnect via structure 190 is formed on the second doped layer 410 protruding from both sides of the light absorption layer 310.

[0094] Circuit conduction is achieved through the second interconnect via structure 190 above both sides of the light absorption layer 310, which helps to reduce the aggregation effect, increase the carrier transport rate, and thus improve the bandwidth.

[0095] In this embodiment, a second electrode 191 electrically connected to the second interconnect via structure 190 is also formed thereon for loading electrical signals onto the second doped layer 410.

[0096] In this embodiment, the photodetector further includes a dielectric layer 600, which is located on the substrate 100 and covers the light transmission layer 200 and the light absorption layer 310.

[0097] The dielectric layer 600 is used to provide a process operation platform for the formation of the photodetector part structure.

[0098] In this embodiment, the material of the dielectric layer 600 includes silicon oxide.

[0099] Figures 4 to 15 This is a schematic diagram of the structure corresponding to each step in one embodiment of the method for forming the photodetector of the present invention.

[0100] Reference Figures 4 to 5 , Figure 5 for Figure 4 A partial top view of the structure shows a substrate 100 on which a light transmission layer 200 is formed. The light transmission layer 200 is positioned along the direction of light propagation (e.g., ...). Figure 4 Extending along the Y-direction (as shown in the middle), along a direction perpendicular to the light propagation direction (such as...). Figure 4 (As shown in the X direction), the light transmission layer 200 includes a light absorption region 100a, and a first doped region 210 is formed in the light transmission layer 200 on the side of the light absorption region 100a.

[0101] Substrate 100 provides the basis for the fabrication process of the photodetector.

[0102] In this embodiment, the substrate 100 includes a substrate 110 and an isolation layer 120 covering the substrate 110.

[0103] Specifically, in the photodetector manufacturing process, a silicon-on-insulator (SOI) substrate is used as substrate 100. The substrate 110 is a base silicon, which is usually thick and serves as a mechanical support. The isolation layer 120 is an insulating layer (Buried Oxide, BOX). Between the top silicon and the base silicon, there is usually a thin layer of silicon oxide (SiO2) which serves as an electrical isolation layer. The light transmission layer 200 is formed from the top silicon (Device Layer), which is the silicon layer used to form semiconductor devices.

[0104] The light transmission layer 200 is used as a channel for light propagation, wherein the light absorption region 100a is the main region for light absorption.

[0105] Specifically, in this embodiment, the light absorption region 100a extends along the light propagation direction.

[0106] In this embodiment, the material of the optical transmission layer 200 includes silicon.

[0107] Using silicon as the optical transmission layer 200 helps to reduce optical transmission loss.

[0108] In this embodiment, the optical transmission layer 200 has doped ions.

[0109] The light doping of the optical transport layer 200 is beneficial for effectively controlling the carrier concentration of the optical transport layer 200, thereby reducing the dark current. It can also serve as a carrier transport channel, which helps to ensure that photogenerated carriers can be collected efficiently.

[0110] As an example, in this embodiment, the optical transport layer 200 has lightly doped P-type ions.

[0111] In this embodiment, during the step of providing the substrate 100, the thickness of the optical transmission layer 200 is 0.1 μm to 0.5 μm, which helps to ensure a faster carrier transmission rate and a better bandwidth for the device.

[0112] The first doped region 210 is used to form a low-resistance ohmic contact on the optical transmission layer 200.

[0113] It should be noted that in this embodiment, the first doped region 210 is located in the light transmission layer 200 on the side of the light absorption region 100a. The side of the light absorption region 100a refers to the side of the light absorption region 100a along the direction perpendicular to the light propagation direction.

[0114] Specifically, in this embodiment, the first doped region 210 is a heavily doped region. The impurity concentration in the heavily doped region is high, so the carrier concentration is also high, and the conductivity is significantly increased. Thus, the first doped region 210 is used to form a low-resistance ohmic contact.

[0115] In this embodiment, the optical transmission layer 200 and the first doped region 210 have the same doping type, thus realizing the basic function of forming a PIN-type photodetector.

[0116] Accordingly, as an example, in this embodiment, the first doped region 210 is a heavily doped P-type layer.

[0117] In this embodiment, during the step of providing the substrate, a first doped region 210 is formed in the light transmission layer 200 on both sides of the light absorption region 100a.

[0118] If a first doped region 210 is formed in both sides of the light transmission layer 200 along the light propagation direction perpendicular to the light absorption region 100a, then the light transmission layer 200 can be electrically connected through the first doped regions 210 on both sides.

[0119] It should be noted that, in this embodiment, the two sides of the light absorption region 100a refer to the two sides of the light absorption region 100a along the direction perpendicular to the light propagation direction.

[0120] In this embodiment, during the step of providing the substrate 100, a first dielectric layer 130 covering the optical transmission layer 200 is also formed on the substrate 100.

[0121] The first dielectric layer 130 is used to provide a process operation platform for subsequent processes.

[0122] In this embodiment, the material of the first dielectric layer 130 includes silicon oxide.

[0123] Reference Figures 6 to 10 A light absorption layer 310 is formed on the light transmission layer 200 in the light absorption region 100a.

[0124] The light-absorbing layer 310 is used to absorb photons.

[0125] Specifically, in this embodiment, when photons are absorbed by the light-absorbing layer 310, electron-hole pairs are generated. Under the action of an applied electric field, these charge carriers drift and form a current, thereby converting the optical signal into an electrical signal.

[0126] In this embodiment, in the step of forming the light absorption layer 310, the length l of the light absorption layer 310 is 0.1 μm to 100 μm, so that the dark current of the light absorption layer 310 is not too large, and the light absorption layer 310 enables the device to obtain a large responsivity.

[0127] In this embodiment, in the step of forming the light absorption layer 310, the width w of the light absorption layer 310 is 0.1μm to 5μm, which ensures the basic function of the light absorption layer 310 in absorbing photons, while making the capacitance of the light absorption layer 310 small, thereby maintaining a large bandwidth.

[0128] In this embodiment, in the step of forming the light absorption layer 310, the thickness h2 of the light absorption layer 310 above the light transmission layer 200 is 0.1 μm to 5 μm, so that the thickness h2 of the light absorption layer 310 will not be too large and thus reduce the bandwidth. This is beneficial to shortening the transit time of the longitudinal movement of the charge carriers, thereby increasing the bandwidth.

[0129] In this embodiment, during the step of forming the light absorption layer 310, the light absorption layer 310 extends into the light transmission layer 200 of a certain thickness.

[0130] The light absorption layer 310 extends into the partial thickness of the light transmission layer 200, combining evanescent wave coupling and docking coupling, thereby improving light absorption efficiency and device responsivity.

[0131] In this embodiment, in the step of forming the light absorption layer 310, the depth h1 of the light absorption layer 310 extending into the light transmission layer 200 is less than or equal to 0.5 μm, so that the light absorption layer 310 will not be embedded too deep or too shallow in the light transmission layer 200, which would cause the light absorption rate to decrease, thereby ensuring that the light absorption rate is in a high range.

[0132] In this embodiment, the material of the light absorption layer 310 includes germanium.

[0133] In this embodiment, in the detector, the optical signal is converted into a measurable electrical signal by the generation, separation and collection of photogenerated carriers between the optical transmission layer 200 and the optical absorption layer 310 in the longitudinal direction.

[0134] It should be noted that in this embodiment, the silicon phototransmission layer 200 is used, which is based on a silicon platform and is compatible with CMOS technology, which is beneficial for the integration of photodetectors with other optoelectronic devices.

[0135] Specifically, in conjunction with reference Figures 6 to 7 , Figure 7 for Figure 6 The partial top view of the structure shows that the step of forming a light absorption layer 310 on the light transmission layer 200 of the light absorption region 100a includes: patterning a first dielectric layer 130 to form an opening 140 that exposes the top of the light transmission layer 200 of the light absorption region 100a.

[0136] The opening 140 is used to provide a spatial location for the formation of the light-absorbing layer 310.

[0137] In this embodiment, in the step of patterning the first dielectric layer 130 to form an opening 140 that exposes the top of the light transmission layer 200 of the light absorption region 100a, the light transmission layer 200 with a partial thickness of the light absorption region 100a is also patterned, and the opening 140 extends longitudinally into the light transmission layer 200.

[0138] The opening 140 extends longitudinally into the light transmission layer 200, such that the light absorption layer 310 formed in the opening 140 extends into the light transmission layer 200.

[0139] Reference Figures 8 to 10 A light-absorbing layer 310 is formed in the opening 140.

[0140] Specifically, refer to Figure 8 The step of forming a light-absorbing layer 310 in the opening 140 includes: forming a light-absorbing material layer 300 that fills the opening 140.

[0141] The light-absorbing material layer 300 is used to form the light-absorbing layer 310.

[0142] Accordingly, in this embodiment, in the step of forming the light-absorbing material layer 300 that fills the opening 140, the light-absorbing material layer 300 also protrudes from the top of the opening 140 and covers part of the top surface of the first dielectric layer 130.

[0143] In this embodiment, an epitaxial growth process is used to form a light-absorbing material layer 300 that fills the opening 140.

[0144] The epitaxial growth process can easily obtain a light-absorbing material layer 300 with good film quality. Since the material of the light transmission layer 200 is silicon and the material of the light-absorbing material layer 300 is germanium, the light-absorbing material layer 300 can be obtained by growing it on the light transmission layer 200 using the epitaxial growth process.

[0145] It should be noted that in this embodiment, during the growth of germanium, germanium does not nucleate on the first dielectric layer 130 on the sidewall of the opening 140. Therefore, the upward extension process of dislocations formed by germanium growth within the opening 140 is blocked by the sidewall of the first dielectric layer 130, which also helps to reduce the dislocation density of grown germanium, thereby helping to obtain a light-absorbing material layer 300 with better film quality.

[0146] Reference Figures 9 to 10 , Figure 10 for Figure 9 In the partial top view of the structure, the first dielectric layer 130 and the light-absorbing material layer 300 are planarized, and a portion of the thickness of the first dielectric layer 130 and the light-absorbing material layer 300 is removed, leaving the remaining light-absorbing material layer 300 as the light-absorbing layer 310.

[0147] The first dielectric layer 130 and the light-absorbing material layer 300 are planarized to provide a process platform with high flatness for subsequent processes. A portion of the thickness of the first dielectric layer 130 and the light-absorbing material layer 300 is removed to obtain a light-absorbing layer 310 of the target thickness.

[0148] In this embodiment, a chemical mechanical polishing (CMP) process is used to planarize the first dielectric layer 130 and the light-absorbing material layer 300.

[0149] Reference Figures 11 to 13 A second doped layer 410 is formed on the light absorption layer 310. At least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in a direction perpendicular to the light propagation direction. The doping type of the second doped layer 410 is opposite to that of the first doped region 210.

[0150] The second doped layer 410 is used to form a low-resistance ohmic contact on the light-absorbing layer 310.

[0151] It should be noted that in this embodiment, at least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in the direction perpendicular to the light propagation direction. Protruding outward means protruding outward relative to the inside of the light absorption layer 310.

[0152] Specifically, in this embodiment, the second doped layer 410 is a heavily doped region. The impurity concentration in the heavily doped region is high, so the carrier concentration is also high, and the conductivity is significantly increased. Thus, the second doped layer 410 is used to form a low-resistance ohmic contact.

[0153] In this embodiment, the second doped layer 410 has the opposite doping type to the first doped region 210, forming a PIN-type photodetector.

[0154] Accordingly, as an example, in this embodiment, the second doped layer 410 is an N-type heavily doped layer.

[0155] In this embodiment, at least one side of the second doped layer 410 protrudes outward relative to the light absorption layer 310 in the direction perpendicular to the light propagation direction. This allows for electrical connection to the outside through the second doped layer 410 protruding from the light absorption layer 310. In other words, an electrical interconnect structure can be formed above the side of the light absorption layer 310, avoiding the situation where the electrical interconnect structure is directly above the light absorption layer 310. This allows the size of the light absorption layer 310 to be unaffected by the formation of the electrical interconnect structure, thus enabling flexible adjustment of the size of the light absorption layer 310. For example, a light absorption layer 310 with a narrow width along the direction perpendicular to the light propagation direction can be formed, which helps reduce capacitance and increase bandwidth. Furthermore, it allows the electrical interconnect structure to be located away from the light absorption layer 310, which helps alleviate light absorption by the electrical interconnect structure, thereby improving the light absorption rate of the light absorption layer 310 and thus improving the photodetector responsivity.

[0156] In this embodiment, during the step of forming the second doped layer 410 on the light absorption layer 310, both sides of the second doped layer 410 protrude outward relative to the light absorption layer 310 in the direction perpendicular to the light propagation direction.

[0157] Both sides of the second doped layer 410 protrude outward relative to the light absorption layer 310, so that the light absorption layer 310 can be electrically connected through the second doped layer 410 on both sides.

[0158] In this embodiment, the material of the second doped layer 410 includes silicon.

[0159] Using silicon with doped ions as the second doped layer 410 is beneficial to reduce the light absorption of the second doped layer 410 and improve the light absorption rate of the light absorption layer 310.

[0160] It should be noted that in this embodiment, a second doped layer 410 is formed above the light absorption layer 310. It is not necessary to perform ion doping on the top of the light absorption layer 310 to form a second doped layer 410 in the light absorption layer 310. This avoids the step of thermally activating doping of the light absorption layer 310, thereby helping to reduce the thermal budget of the process.

[0161] Specifically, refer to Figure 11 The step of forming a second doped layer 410 on the light absorption layer 310 includes forming a doped material layer 400 covering the first dielectric layer 130 and the light absorption layer 310.

[0162] The doped material layer 400 is used to form the second doped layer 410.

[0163] In this embodiment, a doped material layer 400 covering the first dielectric layer 130 and the light absorption layer 310 is formed by low-pressure chemical vapor deposition (LP-CVD).

[0164] Reference Figures 12 to 13 , Figure 13 for Figure 12 A top view of a partial structure, showing a patterned doped material layer 400, with the doped material layer 400 above the light absorption region 100a retained as a second doped layer 410.

[0165] Correspondingly, a doped material layer 400 is retained above the light absorption region 100a, covering the light absorption layer 310, and protruding from both sides of the light absorption layer 310 along the direction perpendicular to the light propagation as a second doped layer 410.

[0166] Reference Figures 14 to 15 After forming the second doped layer 410 on the light absorption layer 310, the formation method further includes: forming a first interconnect via structure 180 electrically connected thereto on the first doped region 210; and forming a second interconnect via structure 190 electrically connected thereto on the second doped layer 410 protruding from the light absorption layer 310.

[0167] The first interconnect via structure 180 is used to realize the electrical connection between the first doped region 210 and the outside.

[0168] In this embodiment, the material of the first interconnect via structure 180 includes a metallic material. As an example, in this embodiment, the material of the first interconnect via structure 180 is tungsten.

[0169] Accordingly, in this embodiment, in the step of forming a first interconnect via structure 180 electrically connected to the first doped region 210, a first interconnect via structure 180 is formed on both sides of the first doped region 210 of the light absorption region 100a.

[0170] Circuit conduction is achieved through the first interconnect via structure 180 on both sides of the optical transmission layer 200, which helps to reduce the aggregation effect, increase the carrier transmission rate, and thus improve the bandwidth.

[0171] The second interconnect via structure 190 is used to realize the electrical connection between the second doped layer 410 and the outside.

[0172] It should be noted that in this embodiment, the second interconnect via structure 190 is formed above the side of the light absorption layer 310, which is beneficial to make the second interconnect via structure 190 far away from the light absorption layer 310, so as to avoid the light absorption of the second interconnect via structure 190 as much as possible, thereby improving the light absorption rate and the responsivity of the photodetector.

[0173] In this embodiment, the material of the second interconnect via structure 190 includes a metallic material. As an example, in this embodiment, the material of the second interconnect via structure 190 is tungsten.

[0174] Accordingly, in this embodiment, in the step of forming a second interconnect via structure 190 electrically connected to the second doped layer 410 protruding from the light absorption layer 310, a second interconnect via structure 190 is formed on both sides of the second doped layer 410 protruding from the light absorption layer 310.

[0175] Circuit conduction is achieved through the second interconnect via structure 190 above both sides of the light absorption layer 310, which helps to reduce the aggregation effect, increase the carrier transport rate, and thus improve the bandwidth.

[0176] Specifically, refer to Figure 14 The steps of forming a first interconnect via structure 180 electrically connected thereto on the first doped region 210 and forming a second interconnect via structure 190 electrically connected thereto on the second doped layer 410 protruding from the sidewall of the light absorption layer 310 include: forming a second dielectric layer 150 covering the first dielectric layer 130 and the second doped layer 410.

[0177] The second dielectric layer 150 provides a process operation platform for forming the first interconnect via structure 180 and the second interconnect via structure 190.

[0178] As an example, in this embodiment, the material of the second dielectric layer 150 includes silicon oxide.

[0179] Continue to refer to Figure 14 The second dielectric layer 150 and the first dielectric layer 130 are patterned to form a first via 160 located on the first doped region 210 and exposing the top surface of the first doped region 210, and a second via 170 located on the second doped layer 410 and exposing the top surface of the second doped layer 410.

[0180] The first through hole 160 is used to provide a spatial location for forming the first interconnect through hole structure 180, and the second through hole 170 is used to provide a spatial location for forming the second interconnect through hole structure 190.

[0181] refer to Figure 15 The first through hole 160 is filled to form the first interconnect through hole structure 180, and the second through hole 170 is filled to form the second interconnect through hole structure 190.

[0182] Continue to refer to Figure 15 The forming method further includes: forming a first electrode 181 electrically connected thereto on the first interconnect via structure 180, and forming a second electrode 191 electrically connected thereto on the second interconnect via structure 190.

[0183] The first electrode 181 is used to apply an electrical signal to the first doped region 210, and the second electrode 191 is used to apply an electrical signal to the second doped layer 410.

[0184] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A photodetector, comprising: The photodetector comprises: a substrate; a light transmission layer on the substrate, the light transmission layer extending along a light propagation direction and along a direction perpendicular to the light propagation direction, the light transmission layer comprising a light absorption region; a light absorption layer on the light transmission layer of the light absorption region; a first doped region in the light transmission layer on a side of the light absorption region; a second doped layer on the light absorption layer and protruding outwardly from the light absorption layer on at least one side of the second doped layer in the direction perpendicular to the light propagation direction, the second doped layer being opposite in doping type to the first doped region.

2. The photodetector of claim 1, wherein, The photodetector further comprises: a first interconnection via structure on and electrically connected to the first doped region; 3. The photodetector of claim 2, wherein, a second interconnection via structure on and electrically connected to the second doped layer protruding from the light absorption layer. Both sides of the second doped layer protrude outwardly from the light absorption layer in the direction perpendicular to the light propagation direction; 4. The photodetector of claim 2, wherein, The second interconnection via structure is formed on both sides of the second doped layer protruding from the light absorption layer. The first doped region is formed in the light transmission layer on both sides of the light absorption region; 5. The photodetector of claim 1, wherein, The first interconnection via structure is formed on both sides of the first doped region.

6. The photodetector of claim 1, wherein, The light transmission layer has a doping ion, and the doping type of the light transmission layer is the same as that of the first doped region. The length of the light absorption layer is 0.1 μm to 100 μm; The width of the light absorption layer is 0.1 μm to 5 μm; 7. The photodetector of claim 1, wherein, The thickness of the light absorption layer above the light transmission layer is 0.1 μm to 5 μm.

8. The photodetector of claim 7, wherein, In a longitudinal direction, the light absorption layer extends into the light transmission layer to a partial thickness.

9. The photodetector of claim 1, wherein, The depth to which the light absorption layer extends into the light transmission layer is less than or equal to 0.5 μm. The material of the light transmission layer comprises silicon or lithium niobate; 10. The photodetector of claim 1, wherein, The material of the light absorption layer comprises germanium, a III-V compound or a II-VI compound.

11. A method of forming a photodetector, the method comprising: The material of the second doped layer comprises silicon. The photodetector comprises: providing a substrate, the substrate having a light transmission layer formed thereon, the light transmission layer extending along a light propagation direction and along a direction perpendicular to the light propagation direction, the light transmission layer comprising a light absorption region, and the light transmission layer on a side of the light absorption region having a first doped region formed therein; forming a light absorption layer on the light transmission layer of the light absorption region; 12. The method of forming a photodetector of claim 11, wherein, forming a second doped layer on the light absorption layer, at least one side of the second doped layer protruding outwardly from the light absorption layer in the direction perpendicular to the light propagation direction, the second doped layer being opposite in doping type to the first doped region. In the step of providing the substrate, the substrate further has a first dielectric layer formed thereon, the first dielectric layer covering the light transmission layer; In the step of forming the light absorption layer on the light transmission layer of the light absorption region, the step comprises patterning the first dielectric layer to form an opening exposing a top portion of the light transmission layer of the light absorption region; 13. The method of forming a photodetector of claim 12, wherein, forming the light absorption layer in the opening. In the step of patterning the first dielectric layer to form an opening exposing a top portion of the light transmission of the light absorption region, the step further comprises patterning the light transmission layer to a partial thickness of the light absorption region, the opening extending into the light transmission layer in a longitudinal direction.

14. The method of forming a photodetector of claim 12, wherein, The step of forming the light-absorbing layer in the opening comprises: forming a layer of light-absorbing material filling the opening; The first dielectric layer and the layer of light-absorbing material are planarized to remove part of the thickness of the first dielectric layer and the layer of light-absorbing material, and the remaining layer of light-absorbing material is reserved as the light-absorbing layer.

15. The method of forming a photodetector of claim 14, wherein, The first dielectric layer and the layer of light-absorbing material are planarized by a chemical mechanical polishing process.

16. The method of forming a photodetector of claim 14, wherein, The layer of light-absorbing material filling the opening is formed by an epitaxial growth process.

17. The method of forming a photodetector of claim 12, wherein, The step of forming a second doped layer on the light-absorbing layer comprises: forming a layer of doped material covering the first dielectric layer and the light-absorbing layer; The layer of doped material is patterned to reserve the layer of doped material above the light-absorbing region as the second doped layer.

18. The method of forming a photodetector of claim 11, wherein, After the second doped layer is formed on the light-absorbing layer, the forming method further comprises: forming a first interconnection via structure electrically connected to the first doped region on the first doped region; A second interconnection via structure is formed on the second doped layer protruding from the light-absorbing layer and electrically connected thereto.

19. The method of forming a photodetector of claim 18, wherein, In the step of forming a second doped layer on the light-absorbing layer, in a direction perpendicular to the light propagation direction, both sides of the second doped layer protrude outward compared to the light-absorbing layer; In the step of forming a second interconnection via structure on the second doped layer protruding from the light-absorbing layer and electrically connected thereto, the second interconnection via structure is formed on both sides of the second doped layer protruding from the light-absorbing layer.

20. The method of forming a photodetector of claim 18, wherein, In the step of providing the substrate, the first doped region is formed in the light transmission layer on both sides of the light-absorbing region; In the step of forming a first interconnection via structure electrically connected to the first doped region on the first doped region, the first interconnection via structure is formed on both sides of the first doped region on the light-absorbing region.

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