Photosensitive diode and method for manufacturing the same

Abstract

The application relates to the technical field of semiconductor manufacturing, in particular to a photosensitive diode which comprises an intrinsic layer, an N-type doped layer, a P-type doped layer, a cutoff ring, a dielectric layer, an oxidation layer and an anti-reflection layer, the intrinsic layer has opposite lower and upper ends, the N-type doped layer is arranged at the lower end of the intrinsic layer, the P-type doped layer is arranged at the upper end of the intrinsic layer, the cutoff ring is arranged at the upper end of the intrinsic layer, the intrinsic layer exists between the cutoff ring and the P-type doped layer, the dielectric layer is arranged above the P-type doped layer, the oxidation layer is arranged above the intrinsic layer between the P-type doped layer and the cutoff ring, the anti-reflection layer covers the dielectric layer and the oxidation layer, and the dielectric layer is doped with P-type ions. The photosensitive diode arranged in the structure can effectively improve the short-wave response capability of the photosensitive diode, and the production cost is relatively low.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a photodiode and its fabrication method. Background Technology

[0002] In the optocoupler (or optocoupler, opto-isolator) product series, the photodiode (also known as a photodiode) is mainly used to receive light signals and is a photodetector that converts light into current or voltage signals depending on the application. Photodiodes have a specific spectral response range. In recent years, with the expansion of application areas for optocoupler products, the requirements for the short-wavelength response of photodiodes have gradually increased.

[0003] In the process of developing this invention, the inventors discovered at least the following problems in the prior art: Currently, the main method for improving the short-wavelength (mainly referring to the range of blue-green light wavelengths) response in photodiodes is through shallow junction diffusion. However, the breakdown voltage of the photodiode decreases due to the shallow junction and fused wire bonding, which limits the efficiency of improving the short-wavelength response of the photodiode. Furthermore, the effect of surface recombination also limits the ability to improve the short-wavelength response in photodiodes.

[0004] Therefore, improving the short-wavelength response capability of photodiodes has become one of the technical challenges that urgently need to be addressed by engineers in this field.

[0005] It should be noted that the information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The present invention provides a photodiode, which includes an intrinsic layer, an N-type doped layer, a P-type doped layer, a cutoff ring, a dielectric layer, an oxide layer and an antireflection layer.

[0007] The intrinsic layer has a lower end and an upper end. An N-type doped layer is disposed at the lower end of the intrinsic layer, a P-type doped layer is disposed at the upper end of the intrinsic layer, a cutoff ring is disposed at the upper end of the intrinsic layer, and an intrinsic layer exists between the cutoff ring and the P-type doped layer. A dielectric layer is disposed on top of the P-type doped layer, an oxide layer is disposed on top of the intrinsic layer located between the P-type doped layer and the cutoff ring, and an antireflection layer covers the dielectric layer and the oxide layer. The dielectric layer is doped with P-type ions.

[0008] In some embodiments, the material of the dielectric layer includes at least one selected from the group consisting of SiN, SiO2, SiON, and Al2O3.

[0009] In some embodiments, the P-type ions doped in the dielectric layer are boron ions.

[0010] In some embodiments, the concentration of boron ions doped in the dielectric layer ranges from 1E19cm⁻³ to 1E21cm⁻³.

[0011] In some embodiments, the thickness of the dielectric layer ranges from 1 to 100 nm.

[0012] In some embodiments, the thickness of the antireflection layer located above the dielectric layer ranges from 30 to 130 nm.

[0013] In some embodiments, the sum of the optical thicknesses of the antireflection layer and the dielectric layer is equal to n / 4 of the desired absorption wavelength, where n is a positive odd number.

[0014] In some embodiments, the concentration of P-type ions doped in the surface layer of the P-type doped layer near the dielectric layer is greater than the concentration of P-type ions doped in the non-surface layer of the P-type doped layer away from the dielectric layer.

[0015] In some embodiments, the photodiode further includes an N-type electrode, a P-type electrode, and an ohmic contact hole. The ohmic contact hole penetrates the antireflection layer and the dielectric layer to expose the P-type doped layer. The P-type electrode is disposed on the antireflection layer and connected to the P-type doped layer through the ohmic contact hole. The N-type electrode is connected to the N-type doped layer.

[0016] In some embodiments, the upper surface of the cutoff ring, the upper surface of the intrinsic layer, and the upper surface of the P-type doped layer are all located in the same plane.

[0017] The present invention also provides a method for fabricating a photodiode, comprising the following steps: providing a substrate and forming an oxide layer on the substrate; removing a portion of the oxide layer to expose a predetermined P-type doped layer region within the substrate; growing a dielectric layer on the surface of the substrate, wherein the dielectric layer is doped with P-type ions; growing an antireflection layer on the dielectric layer and the oxide layer; removing a portion of the dielectric layer, the oxide layer, and the antireflection layer to expose a predetermined cutoff ring region within the substrate; and performing high-temperature diffusion in a phosphorus-containing atmosphere to form a P-type doped layer, an N-type doped layer, and a cutoff ring.

[0018] In some embodiments, after forming the P-type doped layer, the N-type doped layer, and the stop ring, the method further includes the following steps: photolithographically etching the dielectric layer and the antireflection layer to form an ohmic contact hole, the ohmic contact hole penetrating the antireflection layer and the dielectric layer to expose the P-type doped layer; forming a P-type electrode on the surface of the antireflection layer, the P-type electrode being connected to the P-type doped layer through the ohmic contact hole; and forming an N-type electrode on the back side of the N-type doped layer.

[0019] An embodiment of the present invention provides a photodiode and its fabrication method. By doping P-type ions in a dielectric layer covering a P-type doped layer, a high concentration of P-type doped layer can be controlled to form on the surface through only one high-temperature oxidation process, thereby reducing surface carrier recombination and improving short-wavelength response performance. At the same time, P-type doped layer and N-type doped layer can be formed simultaneously by relying on only one high-temperature oxidation process, simplifying the process and reducing production costs.

[0020] Other features and advantages of the present invention will be set forth in the following description, and some of the technical features and advantages may be apparent from the description or learned by practicing the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a photodiode provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic flowchart of a photodiode fabrication method provided in an embodiment of the present invention;

[0024] Figures 3 to 11 This is a schematic diagram of the structure of a photodiode at each stage of the manufacturing process according to an embodiment of the present invention.

[0025] Figure label:

[0026] 12 - Intrinsic layer; 14 - N-type doped layer; 16 - P-type doped layer; 18 - Cut-off ring; 20 - Dielectric layer; 22 - Oxide layer; 24 - Antireflection layer; 26 - N-type electrode; 28 - P-type electrode; 30 - Ohmic contact hole; 40 - Photosensitive area. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be understood that the terms "center," "lateral," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Additionally, the term "comprising" and any variations thereof mean "at least comprising."

[0029] Please see Figure 1 , Figure 1 This is a schematic diagram of a photodiode provided in an embodiment of the present invention. To achieve at least one or more of the aforementioned advantages, an embodiment of the present invention provides a photodiode. As shown in the figure, the photodiode may include an intrinsic layer 12, an N-type doped layer 14, a P-type doped layer 16, a cutoff ring 18, a dielectric layer 20, an oxide layer 22, and an antireflection layer 24.

[0030] Intrinsic layer 12 has a lower end and a higher end. Intrinsic layer 12 refers to an unintentionally doped layer, also known as the I layer. N-type doped layer 14 is disposed at the lower end of intrinsic layer 12. P-type doped layer 16 is disposed at the upper end of intrinsic layer 12, thereby forming a PIN structure in the vertical direction (from top to bottom).

[0031] A stop ring 18 is disposed at the upper end of the intrinsic layer 12. The stop ring 18 is doped with N-type ions and can be used to block leakage current caused by defects in the sidewall of the dicing channel. The stop ring 18 and the P-type doped layer 16 are spaced apart. Specifically, the intrinsic layer 12 exists between the stop ring 18 and the P-type doped layer 16, that is, the intrinsic layer 12 separates the stop ring 18 and the P-type doped layer 16. The upper surfaces of the stop ring 18, the intrinsic layer 12, and the P-type doped layer 16 are all located in the same plane.

[0032] The dielectric layer 20 is disposed on top of the p-type doped layer 16. The dielectric layer 20 is doped with p-type ions. Compared with the traditional p-type doped layer 16, which is formed by depositing and diffusing a p-type dopant source (boron source) into the silicon wafer at high temperature, the silicon wafer surface is accompanied by an oxidation process during the process, which forms an oxide layer 22 on the silicon wafer surface. The oxide layer 22 has a boron-absorbing effect, which causes the boron ions on the silicon wafer surface (in the p-type doped layer 16) to be absorbed away, thereby reducing the boron concentration on the silicon wafer surface and thus reducing the short-wavelength response of the device. This invention, by doping P-type ions into the dielectric layer 20 covering the P-type doped layer 16, achieves a high concentration of P-type doped layer 16 on the surface through a single high-temperature oxidation process. (Since the dielectric layer 20 is doped with P-type ions, an oxide layer 22 with boron-absorbing properties is not formed, and the dielectric layer 20 itself does not have boron-absorbing properties). This effectively reduces the surface defect state density, decreases surface carrier recombination, and improves short-wavelength response performance. Furthermore, a single high-temperature oxidation process can simultaneously form both the P-type doped layer 16 and the N-type doped layer 14, simplifying the process and reducing production costs. Experiments conducted by the inventors show that photodiodes using this structure exhibit an approximately 16% improvement in response efficiency for the 525nm short-wavelength spectrum.

[0033] In some embodiments, the material of the dielectric layer 20 includes at least one selected from the group consisting of SiN, SiO2, SiON, and Al2O3. The p-type ions doped in the dielectric layer 20 are preferably boron ions. For example, the dielectric layer 20 may be SiO2 doped with boron ions, SiON doped with boron ions, etc.

[0034] An oxide layer 22 is disposed on the intrinsic layer 12 located between the p-type doped layer 16 and the stop ring 18. The material of the oxide layer 22 may include SiO2. Since the oxide layer 22 is disposed on the intrinsic layer 12, it can isolate leakage problems caused by contamination.

[0035] The antireflection layer 24 covers the dielectric layer 20 and the oxide layer 22. The antireflection layer 24 is mainly used to improve the light transmission effect, thereby improving the spectral response speed of the photodiode. The antireflection layer 24 can be made of at least one or a combination of silicon nitride and titanium oxide.

[0036] In some embodiments, considering that sufficient boron ions can be provided to the p-type doped layer 16, preferably, the concentration of boron ions doped in the dielectric layer 20 is in the range of 1E19cm⁻¹. -3 ~1E21cm -3 This allows for the formation of a high doping concentration on the surface of the doped layer 16 through high-temperature propulsion, thereby reducing surface recombination of charge carriers. If the boron ion concentration is too low, it will not provide sufficient boron ions for the P-type doped layer 16; if it is too high, it will affect the quality of the photodiode.

[0037] In some embodiments, considering that a sufficient number of boron ions can be propelled to form a doped layer 16 of a certain depth to match the subsequent metallization process, the thickness of the dielectric layer 20 is preferably in the range of 1 to 100 nm.

[0038] In some embodiments, considering that it can effectively block phosphorus diffusion in subsequent processes while having good transmission effect on the target absorption band, the thickness range of the antireflection layer 24 located on the dielectric layer 20 is preferably 30 to 130 nm.

[0039] In some embodiments, the sum of the optical thicknesses of the antireflective layer 24 and the dielectric layer 20 is equal to n / 4 of the desired absorption wavelength, where n is a positive odd number. This reduces the reflectivity of the antireflective layer 24 and the dielectric layer 20 in the photosensitive region 40, thereby improving the performance of the photodiode. Generally, the desired absorption wavelength is denoted by λ, and the sum of the optical thicknesses of the antireflective layer 24 and the dielectric layer 20 can be 1 / 4λ, 3 / 4λ, 5 / 4λ, 7 / 4λ, etc. The desired absorption wavelength refers to the device detection wavelength of the photodiode.

[0040] In some embodiments, the P-type doped layer 16 includes a surface layer and a non-surface layer. The concentration of P-type ions in the surface layer is greater than that in the non-surface layer. This is because, by doping P-type ions into the dielectric layer 20 covering the P-type doped layer 16, the present invention can control the formation of a high-concentration P-type doped layer 16 on the surface through only one high-temperature oxidation process, thereby reducing surface carrier recombination and improving short-wavelength response performance. The surface layer refers to the portion of the P-type doped layer 16 close to the dielectric layer 20, and preferably has a thickness ranging from 1 to 20 nm. The concentration of P-type ions in the surface layer is preferably greater than 1E18 cm⁻¹. -3 Non-surface layer refers to the portion of the P-type doped layer 16 that is far from the dielectric layer 20. In some cases, non-surface layer refers to all layers in the P-type doped layer 16 except for the surface layer.

[0041] In some embodiments, the photodiode may further include an N-type electrode 26, a P-type electrode 28, and an ohmic contact hole 30. The ohmic contact hole 30 penetrates the antireflection layer 24 and the dielectric layer 20 to expose the P-type doped layer 16. The P-type electrode 28 is disposed on the antireflection layer 24 and connected to the P-type doped layer 16 through the ohmic contact hole 30, forming a good ohmic contact between the P-type electrode 28 and the P-type doped layer 16. The N-type electrode 26 is connected to the N-type doped layer 14, forming a good ohmic contact between the N-type electrode 26 and the N-type doped layer 14. The N-type electrode 26 and the P-type electrode 28 may be made of metal materials, such as Al, Pt, Au, etc.

[0042] Please see Figures 2 to 11 , Figure 2This is a schematic flowchart of a photodiode fabrication method according to an embodiment of the present invention. Figures 3 to 11 This is a schematic diagram of the structure of a photodiode at various stages of its manufacturing process according to an embodiment of the present invention. The present invention provides a method for fabricating a photodiode, as shown in the figure. The method for fabricating a photodiode includes the following steps:

[0043] S100: A substrate is provided, and an oxide layer 22 is formed on the substrate. The undoped portion of the substrate is the intrinsic layer 12. Therefore, in Figure 3 The wafers and substrates in the subsequent illustrations are indicated by the number 12. Figure 3 As shown, the mask oxide layer 22 can be generated on the high-resistivity silicon wafer 12 (substrate) by high-temperature oxidation.

[0044] S200: Remove part of the oxide layer 22 to expose the pre-defined P-type doped layer 16 region within the substrate. For example... Figure 4 As shown, the oxide layer 22 grown at high temperature in step S100 is photolithographically and etched to open the photosensitive region 40, which serves as the light-receiving area of ​​the photodiode to receive light.

[0045] S300: A dielectric layer 20 is grown on the surface of substrate 12, and the dielectric layer 20 is doped with P-type ions. For example... Figure 5 As shown, in step S200, a dielectric layer 20 is grown on the surface of the silicon wafer 12. The dielectric layer 20 is composed of boron-containing materials such as SiN, SiO2, SiON, and Al2O3.

[0046] S400: An antireflective layer 24 is grown on the dielectric layer 20 and the oxide layer 22. For example... Figure 6 As shown, an antireflection layer 24 is grown on a boron-containing dielectric layer 20 and an oxide layer 22. The material of the antireflection layer 24 can be SiNx, TiOx, NiOx, etc.

[0047] S500: Part of the dielectric layer 20, oxide layer 22, and antireflective layer 24 are removed to expose the predetermined stop ring 18 region within the substrate 12. For example... Figure 7 As shown, the surfaces of the grown oxide layer 22, dielectric layer 20 and antireflection layer are photolithographically and etched to open up the cutoff ring 18 region.

[0048] S600: High-temperature diffusion is performed in a phosphorus-containing atmosphere to form a P-type doped layer 16, an N-type doped layer 14, and a stop ring 18. For example... Figure 8 As shown, the silicon wafer 12 in S500 undergoes high-temperature diffusion in an atmosphere containing a phosphorus source, ultimately forming a P-type doped layer 16, an N-type doped layer 14, and a cutoff ring 18.

[0049] Following the steps of forming the P-type doped layer 16, the N-type doped layer 14, and the cutoff ring 18, the following steps are also included:

[0050] S700: Photolithographic etching is performed on the dielectric layer 20 and the antireflection layer 24 to form the ohmic contact hole 30. For example... Figure 9 As shown, photolithography is performed on the dielectric layer 20 and the antireflection layer 24 in the photosensitive region 40 to obtain the ohmic contact hole 30. The ohmic contact hole 30 penetrates the antireflection layer 24 and the dielectric layer 20 to expose the P-type doped layer 16.

[0051] S800: A P-type electrode 28 is formed on the surface of the antireflection layer 24. The P-type electrode 28 is connected to the P-type doped layer 16 through an ohmic contact hole 30. For example... Figure 10 As shown, a metal thin film can be sputtered onto the structural surface obtained in step S700, and then a photolithography etching process can be performed to retain the metal layer on the ohmic metal hole, and annealing can be performed to form the front P-type electrode 28.

[0052] S900: An N-type electrode 26 is formed on the back side of the N-type doped layer 14. For example... Figure 11 As shown, a metal thin film is sputtered onto the back side of a high-resistivity silicon wafer 12 and then annealed to form an N-type electrode 26 on the back side. Individual photodiode chips can then be obtained by dicing.

[0053] An embodiment of the present invention provides a photodiode and its fabrication method. By doping P-type ions into the dielectric layer 20 covering the P-type doped layer 16, a high concentration of P-type doped layer 16 can be controlled to form on the surface through only one high-temperature oxidation process, thereby reducing surface carrier recombination and improving short-wavelength response performance. At the same time, the P-type doped layer 16 and the N-type doped layer 14 can be formed simultaneously by relying on only one high-temperature oxidation process, which simplifies the process and reduces production costs.

[0054] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photodiode, characterized in that: The photodiode includes: The intrinsic layer has a relative lower end and an upper end; An N-type doped layer is disposed at the lower end of the intrinsic layer; A p-type doped layer is disposed at the upper end of the intrinsic layer; A cutoff ring is disposed at the upper end of the intrinsic layer, and the intrinsic layer exists between the cutoff ring and the P-type doped layer; A dielectric layer is disposed on the p-type doped layer; An oxide layer is disposed on the intrinsic layer located between the p-type doped layer and the stop ring; An anti-reflective layer covers the dielectric layer and the oxide layer; The dielectric layer is doped with p-type ions; the material of the dielectric layer includes at least one selected from the group consisting of SiN, SiO2, SiON, and Al2O3; and the p-type ions doped in the dielectric layer are boron ions.

2. The photodiode according to claim 1, characterized in that: The concentration range of boron ions doped in the dielectric layer is 1E19cm⁻¹. -3 ~1E21cm -3 .

3. The photodiode according to claim 1, characterized in that: The thickness of the dielectric layer ranges from 1 to 100 nm.

4. The photodiode according to claim 1, characterized in that: The thickness of the antireflection layer located above the dielectric layer ranges from 30 to 130 nm.

5. The photodiode according to claim 1, characterized in that: The sum of the optical thicknesses of the antireflection layer and the dielectric layer is equal to n / 4 of the desired absorption wavelength, where n is a positive odd number.

6. The photodiode according to claim 1, characterized in that: The concentration of P-type ions in the surface layer of the P-type doped layer near the dielectric layer is greater than the concentration of P-type ions in the non-surface layer of the P-type doped layer away from the dielectric layer.

7. The photodiode according to claim 1, characterized in that: The photodiode further includes an N-type electrode, a P-type electrode, and an ohmic contact hole. The ohmic contact hole penetrates the antireflection layer and the dielectric layer to expose the P-type doped layer. The P-type electrode is disposed on the antireflection layer and connected to the P-type doped layer through the ohmic contact hole. The N-type electrode is connected to the N-type doped layer.

8. The photodiode according to claim 1, characterized in that: The upper surface of the cutoff ring, the upper surface of the intrinsic layer, and the upper surface of the P-type doped layer are all located in the same plane.

9. A method for fabricating a photodiode, characterized in that: The method for fabricating the photodiode includes the following steps: A substrate is provided, and an oxide layer is formed on the substrate; Remove part of the oxide layer to expose a predetermined P-type doped layer region within the substrate; A dielectric layer is grown on the surface of the substrate, and the dielectric layer is doped with P-type ions; An antireflection layer is grown on the dielectric layer and the oxide layer; Part of the dielectric layer, the oxide layer, and the antireflection layer are removed to expose a predetermined cutoff ring region within the substrate; High-temperature diffusion is carried out in a phosphorus-containing atmosphere to form a P-type doped layer, an N-type doped layer, and a cutoff ring; The material of the dielectric layer includes at least one selected from the group consisting of SiN, SiO2, SiON, and Al2O3; the p-type ions doped in the dielectric layer are boron ions.

10. The method for fabricating a photodiode according to claim 9, characterized in that: Following the steps of forming the P-type doped layer, the N-type doped layer, and the cutoff ring, the following steps are also included: Photolithographic etching is performed on the dielectric layer and the antireflection layer to form an ohmic contact hole, which penetrates the antireflection layer and the dielectric layer to expose the P-type doped layer; A P-type electrode is formed on the surface of the antireflection layer, and the P-type electrode is connected to the P-type doped layer through the ohmic contact hole; An N-type electrode is formed on the back side of the N-type doped layer.

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