Photodiode array structure and method of manufacturing the same

Abstract

The present application provides a photodiode array structure and a manufacturing method thereof. The photodiode array structure comprises a plurality of photodiodes. Each photodiode comprises an active region, a first conductive type metal ring and a second conductive type metal ring. The first conductive type metal ring is arranged on the active region, and the second conductive type metal ring is arranged outside the active region. The second conductive type metal rings of adjacent photodiodes are arranged in close proximity to each other to be electrically connected in series as a common anode.

Description

Technical Field

[0001] This invention relates to a photodiode array structure and its manufacturing method, specifically, to a photodiode array structure with a common electrode and its manufacturing method. Background Technology

[0002] A photodiode is an electronic component that converts external light signals into electrical signals. Its core function is to absorb external light, detecting the light signal and converting it into a measurable current. This conversion is crucial for various applications, such as optical communication, optical measurement, and imaging.

[0003] The way photodiodes absorb external light is by utilizing the semiconductor material (such as a silicon substrate) inside the diode. When a photon enters the photodiode and is absorbed, the photon's energy causes electrons in the valence band to jump to the conduction band, thus generating electron-hole pairs. These photogenerated carriers separate under the influence of the diode's built-in electric field and generate current.

[0004] However, traditional photodiodes have two problems. First, to improve the photoresponse efficiency of traditional single-chip photodiodes, a common technique is to increase the chip size and the active area. However, increasing the chip size will simultaneously increase the junction capacitance (Cj), resulting in a slower charging and discharging speed of the photodiode. This makes the chip unsuitable for applications requiring high-frequency or optical communication applications with fast switching speeds. To overcome these problems, the industry urgently needs an innovative photodiode architecture that can improve the photoelectric efficiency of the photodiode while avoiding the increase in junction capacitance, which would affect the chip's response speed. Summary of the Invention

[0005] A primary objective of this invention is to provide an innovative photodiode array structure and its manufacturing method. Compared to traditional photodiodes, the photodiode array structure of this invention utilizes wafer transfer and bonding technology to transfer the epitaxial structure of the photodiode from a fragile epitaxial growth substrate to a high-strength transparent substrate. This strengthens the structural strength of the die body, thereby improving process yield and reducing production costs to meet the requirements of economical production. Specifically, this invention also utilizes laser sintering technology to incorporate laser-sintered sidewalls in the device structure. This effectively blocks external light interference from the device sidewalls, suppressing noise interference and improving the signal-to-noise ratio (SNR) and photocurrent gain of the device.

[0006] Another major objective of this invention is to provide an innovative photodiode array structure and its manufacturing method. Compared to photodiode array structures formed by connecting multiple individual chips in series, the photodiode array structure of this invention achieves the purpose of connecting multiple photodiode chips in series through a shared anode. This series-connected array structure not only has higher integration density, but more importantly, it can reduce the number of electrode pads on individual chips, thereby increasing the active area of ​​the photodiode and improving the photoresponse efficiency of a single photodiode, while still maintaining the characteristic of independent operation of each chip, thus avoiding a significant increase in junction capacitance that would affect the response speed of the photodiode chip.

[0007] To achieve the above objectives, the present invention provides a photodiode array structure comprising a plurality of photodiodes. Each of the plurality of photodiodes includes a transparent substrate, a mesa epitaxial layer, a second conductivity type epitaxial layer, a first conductivity type metal ring, and a second conductivity type metal ring. The mesa epitaxial layer has an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer, and a laser-sintered sidewall. The first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser-sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define the active region of each photodiode. The second conductivity type epitaxial layer is disposed on the transparent substrate, and the mesa epitaxial layer is disposed on the second conductivity type epitaxial layer. The first conductivity type metal ring is disposed around the surface of the first conductivity type in-situ doped epitaxial layer inside the laser-sintered sidewall. The second conductivity type metal ring is disposed adjacent to the sidewall of the mesa epitaxial layer and electrically connected to the second conductivity type epitaxial layer. The second conductivity type metal rings of adjacent photodiodes are disposed close to each other to be electrically connected in series as a common anode.

[0008] In the photodiode array structure of the embodiment of the present invention, the first conductivity type in-situ doped epitaxial layer is an N-type in-situ doped indium phosphide epitaxial layer, and the dopant is one of sulfur and silicon, with a doping concentration of 10. 17~19 cm -3 .

[0009] In the photodiode array structure of an embodiment of the present invention, each of the plurality of photodiodes further includes an optical bonding layer, which is disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

[0010] In the photodiode array structure of an embodiment of the present invention, the optical bonding layer is a distributed Bragg reflector layer.

[0011] In the photodiode array structure of an embodiment of the present invention, each of the plurality of photodiodes further includes an optical filter layer. The optical filter layer is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of the external light other than the specific band from entering the active region.

[0012] In the photodiode array structure of the embodiments of the present invention, the optical filter layer further includes an anti-reflection layer to reduce the surface reflection loss of the optical filter layer.

[0013] To achieve the above objectives, the present invention provides a photodiode array structure comprising a plurality of photodiodes. Each of the plurality of photodiodes includes an active region, a first conductive metal ring, and a second conductive metal ring. The first conductive metal ring is disposed on the active region, and the second conductive metal ring is disposed outside the active region. Furthermore, the second conductive metal rings of adjacent photodiodes are arranged adjacent to each other and connected in series with a common electrical polarity to form a common anode.

[0014] In another embodiment of the photodiode array structure of the present invention, each of the plurality of photodiodes further includes a mesa epitaxial layer having an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer and a laser sintered sidewall, wherein the first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define each active region of each photodiode.

[0015] In another embodiment of the photodiode array structure of the present invention, each of the plurality of photodiodes further includes a second conductivity epitaxial layer, a mesa epitaxial layer is disposed on the second conductivity epitaxial layer, wherein each first conductivity metal ring is electrically connected to each first conductivity in-situ doped epitaxial layer, and each second conductivity metal ring is electrically connected to each second conductivity epitaxial layer.

[0016] In another embodiment of the photodiode array structure of the present invention, each of the plurality of photodiodes further includes an optical bonding layer and a transparent substrate, wherein the optical bonding layer is disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

[0017] In another embodiment of the photodiode array structure of the present invention, the optical bonding layer is a distributed Bragg reflector layer.

[0018] In another embodiment of the photodiode array structure of the present invention, each of the plurality of photodiodes further includes an optical filter layer, which is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of the external light other than the specific band from entering the active region.

[0019] In another embodiment of the photodiode array structure of the present invention, the optical filter layer further includes an anti-reflection layer to reduce surface reflection loss of the optical filter layer.

[0020] To achieve the above objectives, the present invention provides a method for manufacturing a photodiode array structure. The method includes the following steps: First, a transparent substrate is provided, on which a plurality of mesa epitaxial layers are provided; second, the transparent substrate is cut to form a plurality of photodiodes, wherein each of the plurality of photodiodes includes one of the plurality of mesa epitaxial layers, a first conductive metal ring and a second conductive metal ring, wherein the first conductive metal ring is disposed on the mesa epitaxial layer and the second conductive metal ring is disposed on the outer side of the mesa epitaxial layer, wherein the second conductive metal rings of adjacent photodiodes are arranged adjacent to each other to be connected in series with common electrical charge as a common anode.

[0021] In the manufacturing method of the photodiode array structure in the embodiment of the present invention, the mesa epitaxial layer has an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer and a laser sintered sidewall, wherein the first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define the active region of each photodiode.

[0022] In the manufacturing method of the photodiode array structure in an embodiment of the present invention, each of the plurality of photodiodes further includes a second conductivity epitaxial layer, a mesa epitaxial layer is disposed on the second conductivity epitaxial layer, wherein each first conductivity metal ring is electrically connected to each first conductivity in-situ doped epitaxial layer, and each second conductivity metal ring is electrically connected to each second conductivity epitaxial layer.

[0023] In the manufacturing method of the photodiode array structure in an embodiment of the present invention, each of the plurality of photodiodes further includes an optical bonding layer and a transparent substrate, wherein the optical bonding layer is disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

[0024] In the manufacturing method of the photodiode array structure in an embodiment of the present invention, each of the plurality of photodiodes further includes an optical filter layer. The optical filter layer is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of other bands in the external light from entering the active region.

[0025] In the manufacturing method of the photodiode array structure in the embodiments of the present invention, the optical filter layer further includes an anti-reflection layer to reduce the surface reflection loss of the optical filter layer.

[0026] Other objects of the present invention, as well as the technical means and embodiments of the present invention, will be understood by those skilled in the art upon referring to the accompanying drawings and the embodiments described below. Attached Figure Description

[0027] Figures 1 to 9 This diagram shows a cross-sectional view of the photodiode array structure manufactured in an embodiment of the present invention. Figure 10 A comparative schematic diagram of a photodiode array structure according to an embodiment of the present invention and a photodiode array structure not according to the present invention is shown; Figure 11 A schematic diagram of a packaged chip comprising two photodiode array structures is shown in an embodiment of the present invention; and Figure 12 A schematic diagram showing the process steps of the photodiode array structure in an embodiment of the present invention is provided. Detailed Implementation

[0028] The following embodiments will explain the content of this invention. These embodiments are not intended to limit the implementation of this invention to any specific environment, application, or special method described in the embodiments. Therefore, the descriptions of the embodiments are merely illustrative of the invention and not intended to limit it. It should be noted that in the following embodiments and drawings, elements not directly related to this invention have been omitted and are not drawn, and the dimensional relationships between the elements in the drawings are for ease of understanding only and are not intended to limit the actual scale.

[0029] Please refer to the combined reference. Figures 1 to 9 , Figures 1 to 9This diagram illustrates a cross-sectional view of a photodiode array structure fabricated in an embodiment of the present invention. Specifically, the photodiode array structure is a compound semiconductor photodiode array structure. In this embodiment, the steps for fabricating the photodiode array structure 10 include first epitaxially growing an ohmic contact epitaxial layer 110 on an epitaxial growth substrate 100, which serves to form an ohmic contact with the metal layer in subsequent metal interconnect processes. Specifically, the epitaxial growth substrate 100 may be, but is not limited to, an indium phosphide (InP) substrate. The ohmic contact epitaxial layer 110 may be, but is not limited to, an indium gallium arsenide (InGaAs) epitaxial layer.

[0030] Next, as Figure 1 As shown, a first conductivity type in-situ doped epitaxial layer 120 and an intrinsic epitaxial layer 130 are sequentially epitaxially grown on the ohmic contact epitaxial layer 110. Specifically, the first conductivity type in-situ doped epitaxial layer 120 is an N-type doped epitaxial layer formed by metal-organic chemical vapor deposition (MOCVD). For example, doping is performed simultaneously during the epitaxial growth of the indium phosphide (InP) epitaxial layer, for example, but not limited to, using sulfur (S) or silicon (Si) as a dopant, with a doping concentration of approximately 10. 17~19 cm -3 This establishes a suitable built-in electric field to drive electron drift. Furthermore, the intrinsic epitaxial layer 130 can be an indium gallium arsenide (InGaAs) epitaxial layer disposed on the first conductivity type in-situ doped epitaxial layer 120. The intrinsic epitaxial layer 130 has a low doping concentration of approximately 10⁻⁶. 14~ 15 cm -3 This ensures a long carrier drift distance, prevents carrier recombination within the intrinsic epitaxial layer, effectively separates and drifts electrons and holes, and improves photoresponse efficiency. It should be noted that, because the first conductivity type in-situ doped epitaxial layer 120 of this invention has a uniform doping distribution formed by an "in-situ doping" process, compared to known doping distributions formed by ion doping and diffusion processes, the ion doping distribution in the first conductivity type in-situ doped epitaxial layer 120 of this invention is more uniform, thus improving the photoresponse efficiency and gain current of the photodiode.

[0031] Please refer to Figure 2 Next, a second conductivity epitaxial layer 140 is epitaxially grown on the intrinsic epitaxial layer 130. Specifically, the second conductivity epitaxial layer 140 can be, but is not limited to, a p-type indium phosphide (InP) epitaxial layer. This p-type indium phosphide epitaxial layer can be grown using a conventional ion doping combined with diffusion process, or, similarly, using an in-situ doping process to dope one of zinc (Zn), magnesium (Mg), or beryllium (Be), with a doping concentration of 10⁻⁶.17~19 cm -3 .

[0032] Next, as Figure 3 As shown, an optical bonding layer 150 is grown on the second conductive epitaxial layer 140 for subsequent wafer transfer and bonding. Specifically, this optical bonding layer 150 can also serve as an optical reflective layer. For example, it can be, but is not limited to, a distributed Bragg reflector (DBR) layer. This DBR layer is a reflective thin film constructed using silicon oxide and titanium oxide, consisting of multiple alternating layers of high and low refractive indices. It exhibits strong reflection of light of a specific wavelength due to interference effects between the multilayer interfaces. Therefore, the reason this invention specifically utilizes a DBR thin film as the optical bonding layer 150 is to effectively isolate noise from the underlying layer of the device and improve the response capability of the photodiode through its optical reflection effect.

[0033] Secondly, please refer to Figure 4 As shown, a transparent substrate 160 is then provided. The transparent substrate 160 may be, for example, but not limited to, a sapphire substrate. The transparent substrate 160 has a passivation layer 170. Specifically, the passivation layer 170 is selected from the group consisting of silicon oxide and titanium oxide, or a combination of silicon oxide and titanium oxide, and is used in conjunction with the optical bonding layer 150 for wafer transfer and bonding between the epitaxial growth substrate 100 and the transparent substrate 160, so that the passivation layer 170 of the transparent substrate 160 is bonded to the optical bonding layer 150 on the epitaxial growth substrate 100. For example, the optical bonding layer 150 and the passivation layer 170 can be surface-treated using a chemical solution to form floating bonds on their surfaces, and then the two wafers can be bonded together by high temperature and high pressure and the application of van der Waals forces. After the optical bonding layer 150 and the passivation layer 170 are bonded, the indium phosphide epitaxial growth substrate 100 is removed by chemical selective etching, and the etching is stopped at the indium gallium arsenide (InGaAs) ohmic contact epitaxial layer 110.

[0034] Secondly, such as Figure 5 As shown, after forming a first conductive metal ring 180 on the ohmic contact epitaxial layer 110 using a lift-off forming vapor deposition process, the first conductive metal ring 180 is then used as a patterned protective layer to etch away the portion of the ohmic contact epitaxial layer 110 exposed outside the first conductive metal ring 180. Then, the first conductive metal ring 180 and the patterned ohmic contact epitaxial layer 110 below it are formed on the surface (e.g., the upper surface) of the first conductive in-situ doped epitaxial layer 120. Specifically, the first conductive metal ring 180 is an N-type metal material, which can be, but is not limited to, one of chromium (Cr), palladium (Pd), gold (Au), titanium (Ti), aluminum (Al), and silver (Ag), or a combination of their alloys.

[0035] Next, please refer to Figure 6 To avoid the problem of low signal-to-noise ratio caused by external light affecting the photodiode, this invention specifically provides a first laser at the outer edge of the photodiode array structure 10, and forms a first laser-sintered sidewall 190 using a laser sintering method, such as... Figure 6 As shown, a first laser-sintered sidewall 190 is disposed on the outer edge of the first conductive in-situ doped epitaxial layer 120 to define the active region and block external light from entering the first conductive in-situ doped epitaxial layer 120. Specifically, the first laser-sintered sidewall 190 is disposed on the inner side of the device sidewall, and a first conductive metal ring 180 is disposed around the upper inner edge of the first laser-sintered sidewall 190. The first laser-sintered sidewall 190 blocks unwanted external light from entering the active region of the device through the device sidewall, preventing subsequent malfunctions. Specifically, a green laser or an ultraviolet (UV) laser can be used to form a laser-sintered sidewall with a length of not less than 1 micrometer (µm) on the outer edge of the first conductive in-situ doped epitaxial layer 120 to block external light from entering the active region of the first conductive in-situ doped epitaxial layer 120. The length of the first laser-sintered sidewall 190 can be adjusted according to the differences in device specifications of the actual photodiode array structure. Preferably, the first laser sintering sidewall 190 can also be disposed in the intrinsic epitaxial layer to ensure that unexpected external light enters the active region inside the diode element through the element sidewall, erroneously causing noise, and at the same time increase the electrostatic protection capability of the photodiode array structure.

[0036] It should be further explained that, in conventional photodiode devices, the epitaxial layer within the active region uses diffusion to define the doped area in older processes. The doping uniformity is not as good as the conductive in-situ doped epitaxial layer in the active region of the device of this invention. This means that in conventional diffusion processes, only the diffused areas can form P-type, intrinsic (I), and N-type PIN structures, thus generating an internal electric field and photocurrent. Areas not diffused, such as the outer edges of the active region, cannot generate photocurrent due to the lack of an electric field. In contrast, because the active region of the photodiode device of this invention uses an in-situ doped epitaxial structure, its doping concentration is uniform. An internal electric field can still be formed at the outer edges of the active region to generate photocurrent. Therefore, a first laser-sintered sidewall is needed to effectively isolate the doped epitaxial layer areas of the active and inactive regions of the device, preventing the generation of an electric field in the inactive areas and thus avoiding unnecessary noise. In other words, as... Figure 6 As shown, the first laser sintering sidewall 190 in the element of the present invention must penetrate into the intrinsic epitaxial layer 130 and have the function of blocking environmental noise.

[0037] Secondly, a mesa etching process is performed. For example... Figure 7As shown, a portion of the first conductivity type in-situ doped epitaxial layer 120 and a portion of the intrinsic epitaxial layer 130 are removed using dry etching or wet etching to form a mesa epitaxial layer in a horizontal device structure, thereby exposing a portion of the surface of the second conductivity type epitaxial layer 140 to serve as the location of the metal ring for the second conductivity type common electrode. Next, a metallization process is performed to form a second conductivity type metal ring 200 on the exposed surface of the second conductivity type epitaxial layer 140 outside the sidewall of the mesa epitaxial layer, and the second conductivity type metal ring 200 is electrically connected to the second conductivity type epitaxial layer 140. Specifically, the second conductivity type metal ring 200 is a P-type metal material, which may be, but is not limited to, one of platinum (Pt), palladium (Pd), gold (Au), or a combination of alloys thereof. It should be noted that, for the needs of the subsequent photodiode array structure, when patterning the mesa epitaxial layer of the photodiode, it is necessary to increase the area of ​​the mesa epitaxial layer as much as possible to increase the active area of ​​the photodiode. For example, the cross-sectional dimensions of the second conductive metal ring 200 on the left and right sides of the mesa epitaxial layer can be different. Specifically, such as... Figure 7 As shown in the figure, the right side of the diagram represents the physical link and electrical connection used for the subsequent two adjacent photodiode structures, with the size of the second conductive metal ring on the right being minimized as much as possible. On the other hand, the left side of the diagram is used for external electrical connection, while the size of the second conductive metal ring on the left remains at a normal specification, thereby increasing the overall active area of ​​the grain.

[0038] Please refer to the combined reference. Figure 8 , Figure 8 The diagram shows photodiode chips identical to those described above on both the left and right sides. The central dashed area represents a corresponding number of identical photodiodes arranged according to actual needs, serving as an embodiment of the photodiode array structure of the present invention. Based on the foregoing, the following is performed... Figure 7 During the mesa etching process of adjacent grains, the second conductive metal rings 200 on adjacent sides of adjacent grains are closely connected and electrically connected in series, achieving the purpose of forming internal metal interconnects in the array structure by interconnecting the second conductive metal rings 200 of adjacent grains. It should be particularly noted that the photodiodes in the array structure of this invention, when subjected to processes such as... Figure 4 After the wafer bonding process shown, the original... Figure 3The first conductivity type in-situ doped epitaxial layer 120 is disposed above the epitaxial growth (InP) substrate 100 and the ohmic contact epitaxial layer 110. After wafer bonding is completed and the epitaxial growth substrate 100 is removed, the overall structure of the device will be reversed from the traditional top-down PIN structure to a top-down NIP structure, making the polarity of the device electrodes exactly opposite to the original structure. Therefore, the first conductivity type metal ring 180 electrically connected to the first conductivity type in-situ doped epitaxial layer 120 will become an N-type electrode. Conversely, the second conductivity type metal ring 200 electrically connected to the second conductivity type epitaxial layer 140 will become a P-type electrode, so that the second conductivity type metal rings 200 of adjacent grains are connected in series to form a common anode.

[0039] On the other hand, to control the wavelength range of light entering the photodiode, this invention uses special optical materials to replace the traditional protective layer, thus providing both electrical isolation and filtering functions. For example... Figure 8 As shown, Figure 8 The optical filter layer 210 covers the surface (e.g., the upper surface) and sidewalls of the mesa epitaxial layer, and partially covers the portions of the first conductive metal ring 180 and the second conductive metal ring 200 between adjacent sides of two grains, thus exposing portions of the first conductive metal ring 180 and the second conductive metal ring 200 on the outer sides of the two grains. Specifically, the optical filter layer 210 covers the exposed surface (e.g., the upper surface) of the first conductive in-situ doped epitaxial layer 120 and the exposed sidewalls of the first conductive in-situ doped epitaxial layer 120 and the intrinsic epitaxial layer 130, to precisely control the entry of external light with a specific wavelength into the mesa epitaxial layer while blocking other light of different wavelengths from entering the active regions of each photodiode, thereby shielding against unintended external noise interference.

[0040] Specifically, in this embodiment, the optical filter layer 210 is a multi-band bandpass filter layer that covers the surface (e.g., the upper surface) and sidewalls of the mesa epitaxial layer. In specific applications, the composition of the multi-band bandpass filter layer can be adjusted according to the actual filtering band requirements. The optical filter layer 210 can be, for example, but is not limited to, using a dielectric material, including silicon oxide (SiO2). x Titanium oxide (TiO) x ), tantalum oxide (Ta2O3), etc. In a preferred embodiment, the optical filter layer 210 further includes an anti-reflection layer to enhance the transmission of light with that specific wavelength and reduce the surface reflection loss of the optical filter layer 210.

[0041] Finally, please continue to refer to Figure 9The sapphire substrate is diced for component cutting. In practical applications, the outermost sidewall of the array structure formed by multiple photodiodes can be cut according to the array structure design requirements, so that the array structure can contain multiple independently operating and electrically connected photodiodes. Specifically, a second laser is provided, and laser cutting is performed on the outermost sidewall of the array structure to form second laser-sintered sidewalls 240 on the sidewalls surrounding the transparent substrate 160, passivation layer 170, optical bonding layer 150, second conductive epitaxial layer 140, and second conductive metal ring 200, thereby forming a photodiode array structure 10. At the same time, the second laser-sintered sidewall 240 can also block external light from entering the device through the component sidewall and causing interference. Figure 9 As shown, in the photodiode array structure of the present invention, each photodiode has its own independent first conductivity type pad to provide the characteristic of individual operation of each photodiode. However, in order to maximize the active area of ​​the array structure, the second conductivity type metal rings 200 between adjacent grains in the array structure are electrically connected in series to form a common anode, thereby saving the configuration of multiple pads connected to the external electrode in the array structure and increasing the active area. In other words, the common electrode design of the present invention allows the photodiode array structure to select only one photodiode grain in the array structure and set one pad for electrical connection between the array structure and the external electrode in that grain. In this way, by reducing the number of pads, the overall active area of ​​the array structure is increased, and the integration between the grains of the array structure is improved at the same time.

[0042] Please refer to Figure 10 , Figure 10 A comparative schematic diagram is shown, illustrating a photodiode array structure according to an embodiment of the present invention and a photodiode array structure without the present invention. The upper half of the figure shows the photodiode array structure according to the present invention. Specifically, Figure 10The upper part shows three photodiode chips, and a top view of a (1×3) strip array structure composed of the first photodiode chip A1, the second photodiode chip A2, and the third photodiode chip A3. It is clear that in this photodiode array structure, three square-shaped first conductive metal rings 180 are respectively disposed in the first photodiode chip A1, the second photodiode chip A2, and the third photodiode chip A3. However, only one square-shaped second conductive metal ring 200 is disposed in the first photodiode chip A1. The other two second photodiode chips A2 and the third photodiode chip A3 do not have square-shaped second conductive metal rings 200. Instead, they are connected in series with each other through the second conductive metal rings 200 between adjacent chips. This achieves the purpose of three chips having a common anode and maintaining the independent operation of each chip, so as to avoid increasing the junction capacitance and affecting the device switching speed.

[0043] In comparison, such as Figure 10 The lower half of the diagram shows a photodiode array structure not according to the present invention. The structural features of the three photodiode chips—a fourth photodiode chip A4, a fifth photodiode chip A5, and a sixth photodiode chip A6—are the same as those of the first photodiode chip A1 in the upper half. Each chip contains a complete square-shaped first conductive metal ring 180 and a square-shaped second conductive metal ring 200. Furthermore, with… Figure 10 The array structure of the present invention shown in the upper part differs from that shown in the upper part, in Figure 10 In the lower part, in the (1×3) array structure not according to the present invention, which is composed of three identical grains, the second conductive metal rings 200 between adjacent grains are not physically linked or electrically connected. Furthermore, in practical applications, the fourth photodiode grain A4, the fifth photodiode grain A5, and the sixth photodiode grain A6 cannot be placed close together; an empty space must be reserved between the die-bonding positions of each grain to prevent the grains from being squeezed and broken. Through comparison... Figure 10 The upper and lower halves of the array structure clearly demonstrate that the photodiode array structure according to the present invention significantly increases the active area by saving the area that would otherwise be required to set up two square-shaped second conductive metal rings 200, while still maintaining the advantage of individual die operation. On the other hand, because adjacent dies in the upper half share the common anode formed by the shared second conductive metal rings 200, the length of the photodiode array structure according to the present invention is significantly shorter than the length of the lower half photodiode array structure without the present invention. Therefore, the integration density of the photodiode array structure of the present invention is significantly increased, which is beneficial for further miniaturization of the packaged chip according to the present invention.

[0044] It should be noted that if increasing the active area is considered simply by enlarging the active area of ​​a single device, for example, by merging three small chips into a single large chip, while the active area can be enlarged in the same way, the junction capacitance of the active region in the single large chip will increase significantly, thus severely affecting the switching speed of photodiodes used in high-frequency devices. In summary, the design of this invention combines the advantages of increasing the active area while maintaining the characteristics of single-chip operation and a junction capacitance level similar to that of a single chip, thus conforming to the characteristics of high-frequency device operation, and also possessing high integration, which is beneficial to the trend of chip miniaturization.

[0045] Please refer to Figure 11 , Figure 11 This diagram illustrates a packaged chip comprising two photodiode array structures according to an embodiment of the present invention. The packaged chip has two array structures according to the present invention, each array structure arranged side-by-side to form a long strip-shaped chip. Each array structure has eight photodiode chips arranged in a (1×8) long strip-shaped matrix structure, and the entire packaged chip has a total of 16 photodiode chips. As shown in Table 1 below, the 16 photodiode chips in this packaged chip have a total of 18 pins, of which 16 pins serve as cathodes, distributed at pins P1 to P5, pins P7 to P8, and pins P9 and P10 respectively. 12 Pin P 14 To pin P 18 On the other hand, the 16 photodiode chips in this package only have two common pins as anodes, distributed at pin P6 and pin P7 respectively. 13 Clearly, the number of pins in the packaged chip according to the present invention can also be significantly reduced by setting a common anode, giving the chip the advantages of high integration and miniaturization.

[0046] Table 1

[0047] Please refer to Figure 12 , Figure 12 This diagram illustrates the process steps of the photodiode array structure in an embodiment of the present invention. First, in step S01, a transparent substrate is provided, wherein the transparent substrate has multiple mesa epitaxial layers. Second, in step S02, the transparent substrate is cut to form multiple photodiodes, wherein each photodiode has a mesa epitaxial layer, a first conductive metal ring, and a second conductive metal ring. Each first conductive metal ring is disposed above each mesa epitaxial layer, and each second conductive metal ring is disposed outside each mesa epitaxial layer. The second conductive metal rings of adjacent photodiodes are arranged adjacent to each other and connected in series with a common anode. The descriptions of the relevant components are as described above and will not be repeated here.

[0048] In summary, the photodiode array structure 10 of the present invention has the following advantages: (1) By using wafer transfer bonding technology, the main body of the photodiode element is transferred to a high-strength sapphire transparent substrate, which improves the fragility of the indium phosphide substrate used in traditional SWIR (short-wave infrared) photodiodes, enhances the structural strength of the element, thereby improving the process yield and reducing the manufacturing cost to meet the requirements of economical mass production; (2) The photodiode array structure of the present invention further blocks external noise interference through various designs, improves the signal-to-noise ratio of the element, improves the light response efficiency of the element, and increases the current gain. For example, the optical bonding layer provided above the transparent substrate at the bottom of the element has a mirror structure to reflect external light from the bottom of the element, preventing it from entering the element and causing noise interference. In addition, for the sidewalls of the element, the present invention provides two laser-sintered sidewalls, namely a first laser-sintered sidewall to prevent noise from entering the active area from the sidewall and a second laser-sintered sidewall on the outermost side. Both laser-sintered sidewalls can effectively block noise interference from the sidewalls of the element. For the top of the component, a multi-band bandpass filter layer is used to control the passage of only light with a specific band of light in the external light while blocking light of other bands. In addition, with the addition of an anti-reflection layer, the passage of light of that specific band of light can be enhanced and the reflection loss of the surface of the optical filter layer can be reduced. Therefore, the photodiode array structure of the present invention has a design that avoids noise interference in all directions, which can significantly improve the signal-to-noise ratio of the component and increase the photocurrent gain; (3) the photodiode array structure of the present invention has a design of shared electrodes between adjacent chips, thereby improving the integration of the packaged chip; and (4) through the design of shared electrodes, the area of ​​the active region in the array structure can be increased, improving the photoresponse efficiency, while still maintaining the characteristics of single crystal junction capacitance, meeting the requirements of high-frequency components for fast switching speed.

[0049] The above embodiments are merely illustrative of the present invention and to explain its technical features, and are not intended to limit the scope of protection of the present invention. Any changes or equivalent arrangements that can be easily made by those skilled in the art are within the scope of protection of the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims.

[0050] [Symbol Explanation] 10 photodiode array structure 100 epitaxial growth substrate 110-ohm contact epitaxial layer 120 First conductivity type in-situ doped epitaxial layer 130 intrinsic epitaxial layers 140 Second Conductivity Type Epitaxial Layer 150 optical bonding layers 160 transparent substrate 170 passivation layer 180 First conductive metal ring 190 First Laser Sintered Sidewall 200 Second Conductive Metal Ring 210 optical filter layer 240 Second Laser Sintering Sidewall A1 First Photodiode Chip A2 Second Photodiode Chip A3 Third Photodiode Chip A4 fourth photodiode chip A5 Fifth Photodiode Chip A6 sixth photodiode chip P1 pin P6 pin P9 pin P 10 pin P 13 pin P 18 Pin.

Claims

1. A photodiode array structure, the photodiode array structure comprising a plurality of photodiodes, each of the plurality of photodiodes comprising: Transparent substrate; The mesa epitaxial layer has an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer, and a laser sintered sidewall, wherein the first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define the active region of each photodiode. A second conductive epitaxial layer is disposed on the transparent substrate, and the mesa epitaxial layer is disposed on the second conductive epitaxial layer; A first conductive metal ring is disposed on the surface of the first conductive in-situ doped epitaxial layer, inside the laser sintering sidewall; and A second conductive metal ring is disposed adjacent to the sidewall of the mesa epitaxial layer and electrically connected to the second conductive epitaxial layer. In this configuration, the second conductivity type metal rings of each adjacent photodiode are arranged close to each other and connected in series with a common electrical charge to form a common anode.

2. The photodiode array structure as described in claim 1, wherein, The first conductive in-situ doped epitaxial layer is an N-type in-situ doped indium phosphide epitaxial layer, with the dopant being either sulfur or silicon, and the doping concentration being 10. 17~19 cm -3 .

3. The photodiode array structure as described in claim 1, wherein, Each of the plurality of photodiodes further includes an optical bonding layer disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

4. The photodiode array structure as described in claim 3, wherein, The optical bonding layer is a distributed Bragg reflector layer.

5. The photodiode array structure as described in claim 1, wherein, Each of the plurality of photodiodes further includes an optical filtering layer, which is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of the external light other than the specific band from entering the active region.

6. The photodiode array structure as described in claim 5, wherein, The optical filter layer also includes an anti-reflection layer to reduce surface reflection loss of the optical filter layer.

7. A photodiode array structure, the photodiode array structure comprising: A plurality of photodiodes, wherein each of the plurality of photodiodes includes an active region, a first conductive metal ring, and a second conductive metal ring, wherein the first conductive metal ring is disposed on the active region, and the second conductive metal ring is disposed outside the active region. In this configuration, the second conductivity type metal rings of each adjacent photodiode are arranged close to each other and connected in series with a common electrical charge to form a common anode.

8. The photodiode array structure as described in claim 7, wherein, Each of the plurality of photodiodes further includes a mesa epitaxial layer having an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer, and a laser-sintered sidewall, wherein the first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser-sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define each active region of each photodiode.

9. The photodiode array structure as described in claim 8, wherein, Each of the plurality of photodiodes further includes a second conductivity epitaxial layer, the mesa epitaxial layer being disposed on the second conductivity epitaxial layer, wherein each first conductivity metal ring is electrically connected to each first conductivity in-situ doped epitaxial layer, and each second conductivity metal ring is electrically connected to each second conductivity epitaxial layer.

10. The photodiode array structure as described in claim 9, wherein, Each of the plurality of photodiodes further includes an optical bonding layer and a transparent substrate, wherein the optical bonding layer is disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

11. The photodiode array structure as described in claim 10, wherein, The optical bonding layer is a distributed Bragg reflector layer.

12. The photodiode array structure as described in claim 8, wherein, Each of the plurality of photodiodes further includes an optical filtering layer, which is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of the external light other than the specific band from entering the active region.

13. The photodiode array structure as described in claim 12, wherein, The optical filter layer also includes an anti-reflection layer to reduce surface reflection loss of the optical filter layer.

14. A method for manufacturing a photodiode array structure, the method comprising: A transparent substrate is provided, wherein the transparent substrate has a plurality of mesa epitaxial layers; as well as The transparent substrate is diced to form a plurality of photodiodes, wherein each of the plurality of photodiodes includes one of the plurality of mesa epitaxial layers, a first conductive metal ring, and a second conductive metal ring, wherein the first conductive metal ring is disposed on the mesa epitaxial layer, and the second conductive metal ring is disposed outside the mesa epitaxial layer. In this configuration, the second conductivity type metal rings of each adjacent photodiode are arranged close to each other and connected in series with a common electrical charge to form a common anode.

15. The method for manufacturing a photodiode array structure as described in claim 14, wherein, The mesa epitaxial layer has an intrinsic epitaxial layer, a first conductivity type in-situ doped epitaxial layer, and a laser sintered sidewall. The first conductivity type in-situ doped epitaxial layer is disposed on the intrinsic epitaxial layer, and the laser sintered sidewall is disposed on the outer edge of the first conductivity type in-situ doped epitaxial layer to define the active region of each photodiode.

16. The method for manufacturing a photodiode array structure as described in claim 15, wherein, Each of the plurality of photodiodes further includes a second conductivity epitaxial layer, the mesa epitaxial layer being disposed on the second conductivity epitaxial layer, wherein each first conductivity metal ring is electrically connected to each first conductivity in-situ doped epitaxial layer, and each second conductivity metal ring is electrically connected to each second conductivity epitaxial layer.

17. The method for manufacturing a photodiode array structure as described in claim 16, wherein, Each of the plurality of photodiodes further includes an optical bonding layer and a transparent substrate, wherein the optical bonding layer is disposed between the transparent substrate and the second conductive epitaxial layer to block external light from entering the second conductive epitaxial layer through the transparent substrate.

18. The method for manufacturing a photodiode array structure as described in claim 15, wherein, Each of the plurality of photodiodes further includes an optical filtering layer, which is a multi-band bandpass filter layer and covers the surface and sidewalls of the mesa epitaxial layer to allow light of a specific band in the external light to pass through while blocking other light of the external light other than the specific band from entering the active region.

19. The method for manufacturing a photodiode array structure as described in claim 18, wherein, The optical filter layer also includes an anti-reflection layer to reduce surface reflection loss of the optical filter layer.

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