Photodiode, method for manufacturing the same, and optical module

Abstract

The present application relates to a photodiode, a preparation method thereof, and an optical module. The preparation method of the photodiode includes: providing a substrate; forming an epitaxial layer on the substrate, the epitaxial layer including a first-conductivity-type semiconductor layer and a second-conductivity-type semiconductor layer, the first-conductivity-type semiconductor layer being located on the side of the second-conductivity-type semiconductor layer away from the substrate; etching the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the front structure, and forming a reflectivity adjustment layer covering at least the photosensitive surface before forming at least the last first protective layer; the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located; etching the first protective layer within the range where the photosensitive surface is located until the reflectivity adjustment layer is exposed. The present application can effectively improve the reliability of the photodiode.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and particularly to a photodiode, a preparation method thereof, and an optical module. Background Art

[0002] A photodiode is a semiconductor device that can convert an optical signal into an electrical signal. The photodiode has characteristics such as high sensitivity, fast response, and low noise, and is widely used in fields such as optical measurement, communication, automatic control, and optical fiber transmission. In addition, the photodiode can also be used to manufacture optical sensors, photodetectors, etc.

[0003] The reliability of existing photodiodes still needs to be further improved. Summary of the Invention

[0004] Based on this, the present application provides a photodiode, a preparation method thereof, and an optical module with effectively improved reliability.

[0005] A preparation method of a photodiode includes:

[0006] Providing a substrate;

[0007] Forming an epitaxial layer on the substrate, the epitaxial layer including a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, and the first conductivity type semiconductor layer is located on a side of the second conductivity type semiconductor layer away from the substrate;

[0008] Etching the epitaxial layer to form at least one-order semiconductor step, and after forming each order of semiconductor step, forming a first protection layer covering the front structure, and forming a reflectivity adjustment layer covering at least the photosensitive surface before forming at least the last first protection layer; the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located;

[0009] Etching the first protection layer within the range where the photosensitive surface is located until the reflectivity adjustment layer is exposed.

[0010] In one embodiment, the thickness of the reflectivity adjustment layer is an integer multiple of a quarter of the working wavelength.

[0011] In one embodiment, after etching the first protection layer within the range where the photosensitive surface is located until the reflectivity adjustment layer is exposed, it further includes:

[0012] Forming an adjustment compensation layer covering the reflectivity adjustment layer and the first protection layer, and the sum of the thicknesses of the reflectivity adjustment layer and the adjustment compensation layer is an integer multiple of a quarter of the working wavelength.

[0013] In one embodiment, the reflectivity adjustment layer is provided as a single-layer structure or a multi-layer stacked structure.

[0014] In one embodiment, when the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer is reused as an etch stop layer when etching the first protective layer.

[0015] In one embodiment, the material of the single-layer reflectivity adjustment layer includes any one of SiO x , MgF2, and Al2O3.

[0016] In one embodiment, when the reflectivity adjustment layer is a multi-layer stacked structure, the multi-layer stacked structure includes an etch stop layer and at least one adjustment layer; the adjustment layer is disposed on a side of the etch stop layer close to the photosensitive surface.

[0017] In one embodiment, the material of the etch stop layer includes any one of SiO x , MgF2, and Al2O3.

[0018] In one embodiment,

[0019] Etching the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the front structure, and forming a reflectivity adjustment layer covering at least the photosensitive surface before forming at least the last first protective layer, includes:

[0020] Forming the reflectivity adjustment layer on a side of the first-conductive-type semiconductor layer away from the substrate;

[0021] Etching the reflectivity adjustment layer and the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the front structure.

[0022] In one embodiment,

[0023] The etching the reflectivity adjustment layer and the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the front structure, includes:

[0024] Sequentially etching the reflectivity adjustment layer and the first-conductive-type semiconductor layer to form a first semiconductor step;

[0025] Forming a first first protective layer covering the reflectivity adjustment layer, sidewalls of the first semiconductor step, and a second-conductive-type semiconductor layer outside the first semiconductor step;

[0026] Etch the first first protective layer and the second-conductivity-type semiconductor layer outside the first-order semiconductor step in sequence to form a second-order semiconductor step;

[0027] Form a second first protective layer covering the first first protective layer, the sidewall of the second-order semiconductor step, and the structure outside the second-order semiconductor step. The second first protective layer is the last first protective layer.

[0028] A photodiode, comprising:

[0029] A substrate;

[0030] An epitaxial layer located on the substrate and including a second-conductivity-type semiconductor layer and a first-conductivity-type semiconductor layer sequentially provided on the substrate. The epitaxial layer has at least a first-order semiconductor step formed by the first-conductivity-type semiconductor layer, and the surface of the first-conductivity-type semiconductor layer away from the substrate is a photosensitive surface;

[0031] A reflectivity adjustment layer covering the photosensitive surface, and the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located;

[0032] A protection structure covering the epitaxial layer outside the photosensitive surface, including at least one first protective layer. The first protective layer is correspondingly arranged with the semiconductor step and covers at least the sidewall and the bottom of the corresponding semiconductor step.

[0033] In one embodiment, the thickness of the reflectivity adjustment layer is an integer multiple of a quarter of the working wavelength.

[0034] In one embodiment, the photodiode further includes:

[0035] An adjustment compensation layer covering the reflectivity adjustment layer and the protection structure, and the sum of the thicknesses of the reflectivity adjustment layer and the adjustment compensation layer is an integer multiple of a quarter of the working wavelength.

[0036] In one embodiment, the reflectivity adjustment layer is set as a single-layer structure or a multi-layer stacked structure.

[0037] In one embodiment, when the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer is made of a different material from the first protective layer so that the reflectivity adjustment layer is reused as an etching stop layer.

[0038] In one embodiment, the material of the single-layer reflectivity adjustment layer includes SiO x , MgF2, or Al2O3.

[0039] In one embodiment, when the reflectivity adjustment layer is a multi-layer stacked structure, the multi-layer stacked structure includes an etching stop layer and at least one adjustment layer; the adjustment layer is disposed on a side of the etching stop layer close to the photosensitive surface.

[0040] In one embodiment, the material of the etching stop layer includes any one of SiO x , MgF2, and Al2O3.

[0041] A method for manufacturing a photodiode includes:

[0042] Providing a substrate;

[0043] Forming an epitaxial layer on the substrate, the epitaxial layer including a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, the first conductivity type semiconductor layer being located on a side of the second conductivity type semiconductor layer away from the substrate;

[0044] Forming an etching stop layer on a side of the first conductivity type semiconductor layer away from the substrate;

[0045] Etching the etching stop layer and the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the front structure, wherein the first semiconductor step is formed by etching the first conductivity type semiconductor layer, and a surface of the first semiconductor step away from the substrate is a photosensitive surface;

[0046] Etching the first protective layer within a range where the photosensitive surface is located to expose the etching stop layer.

[0047] In one embodiment, the thickness of the etching stop layer is an integer multiple of a quarter of the working wavelength.

[0048] In one embodiment,

[0049] Before forming the etching stop layer on a side of the first conductivity type semiconductor layer away from the substrate, further including:

[0050] Forming a first metal electrode on the first conductivity type semiconductor layer;

[0051] Forming a second protective layer covering the first metal electrode and the first conductivity type semiconductor layer.

[0052] In one embodiment, the total thickness of the second protective layer and the etching stop layer is an integer multiple of a quarter of the working wavelength.

[0053] In one embodiment, further including:

[0054] Remove the etch stop layer above the second protective layer; wherein, the thickness of the second protective layer is an integer multiple of a quarter of the working wavelength.

[0055] An optical module includes an optical transmitting component and an optical receiving component, wherein the optical receiving component includes at least one photodiode as described above; or

[0056] The optical receiving component includes at least one photodiode prepared by using the preparation method of the photodiode as described above; or

[0057] The optical receiving component includes at least one photodiode prepared by using the preparation method of the photodiode as described above.

[0058] For the above-mentioned photodiode and its preparation method, since at least a reflectivity adjustment layer or an etch stop layer covering at least the photosensitive surface is formed before forming the last first protective layer. Therefore, when etching the first protective layer formed after the reflectivity adjustment layer or the etch stop layer, the photosensitive surface will not be etched and damaged. Therefore, the reliability of the formed photodiode is effectively improved in this application. Description of the Drawings

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0060] Figure 1 It is a flowchart of the preparation method of the photodiode provided in an embodiment;

[0061] Figures 2 to 6 It is a cross-sectional structure schematic diagram of the structure obtained during the preparation of the photodiode provided in an embodiment;

[0062] Figure 7 And Figure 8 For Figures 2 to 6 It is a cross-sectional structure schematic diagram of the photodiode formed based on the preparation process in different embodiments;

[0063] Figure 9 It is a cross-sectional structure schematic diagram of the photodiode in another embodiment;

[0064] Figure 10 It is a cross-sectional structure schematic diagram of the photodiode in yet another embodiment;

[0065] Figures 11 to 14Schematic cross-sectional structure diagram of the structure obtained during the preparation process of a photodiode provided in an embodiment;

[0066] Figures 15 to 18 Schematic cross-sectional structure diagrams of photodiodes formed based on the preparation process of Figures 11 to 14 in different embodiments.

[0067] Explanation of reference numerals:

[0068] 100 - Substrate, 200 - Epitaxial layer, 210 - Semiconductor layer of the first conductivity type, 220 - Semiconductor layer of the second conductivity type, 300 - First protective layer, 400 - Reflectivity adjustment layer, 410 - Etching stop layer, 420 - Adjustment layer, 500 - Adjustment compensation layer, 600 - Second protective layer. Detailed implementation manners

[0069] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and comprehensive.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0071] It should be understood that when an element or layer is referred to as "on...", "adjacent to...", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on...", "directly adjacent to...", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of this application, the first element, component, region, layer, doping type or part discussed below may be referred to as the second element, component, region, layer or part.

[0072] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. may be used herein to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, an element or feature described as "under" or "beneath" or "underneath" other elements or features will be oriented "over" the other elements or features. Thus, the exemplary terms "under" and "underneath" can include both an upper and a lower orientation. Additionally, the device may also include additional orientations (such as, rotated 90 degrees or other orientations), and the spatial descriptors used herein are to be interpreted accordingly.

[0073] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / comprising" or "has / having" etc. specify the presence of the stated features, integers, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the related listed items.

[0074] In one embodiment, refer to Figure 1 , a method for preparing a photodiode is provided, including the following steps:

[0075] Step S10, refer to Figure 2 , provide a substrate 100;

[0076] Step S20, refer to Figure 2 , form an epitaxial layer 200 on the substrate 100, the epitaxial layer 200 includes a first conductivity type semiconductor layer 210 and a second conductivity type semiconductor layer 220, and the first conductivity type semiconductor layer 210 is located on the side of the second conductivity type semiconductor layer 220 away from the substrate 100;

[0077] Step S30, refer to Figures 3 to 6 , etch the epitaxial layer 200 to form at least one semiconductor step, and after forming each semiconductor step, form a first protective layer 300 covering the front structure, and form a reflectivity adjusting layer 400 covering at least the photosensitive surface before forming at least the last first protective layer 300; the reflectivity adjusting layer 400 is configured to adjust the reflectivity of light in the range where the photosensitive surface is located;

[0078] Step S40, refer to Figure 7, etch the first protective layer 300 within the range where the photosensitive surface is located until the reflectivity adjustment layer 400 is exposed.

[0079] The "range where the photosensitive surface is located" can be understood as the device area where the photosensitive surface is located.

[0080] In step S10, please refer to Figure 2 , the substrate 100 may include, but is not limited to, semiconductor substrates such as gallium arsenide substrates, silicon substrates, gallium nitride substrates, or germanium substrates, etc.

[0081] In step S20, please refer to Figure 2 , the first conduction type can be set as P-type and the second conduction type can be set as N-type. Alternatively, the first conduction type can also be set as N-type and the second conduction type can be set as P-type.

[0082] Epitaxial growth can be performed on the substrate 100 to form an epitaxial layer 200.

[0083] Exemplarily, a buffer layer or the like can be formed on the substrate 100. Then, a semiconductor layer 220 of the second conduction type is epitaxially grown, and then a semiconductor layer 210 of the first conduction type is epitaxially grown. It can be understood that the semiconductor layer 220 of the second conduction type and / or the semiconductor layer 210 of the first conduction type may include multiple different material film layers.

[0084] In step S30, the first-order semiconductor step is the semiconductor step etched first, and the last-order semiconductor step is the semiconductor step etched last.

[0085] Please refer to Figure 4 , perform patterned etching on the semiconductor layer 210 of the first conduction type to form multiple spaced-apart first-order semiconductor steps of the first conduction type.

[0086] The surface of the first-order semiconductor step away from the substrate 100 is the photosensitive surface. The photosensitive surface can receive light, thereby generating a photocurrent within the photodiode.

[0087] Exemplarily, please refer to Figure 5 , after performing patterned etching on the semiconductor layer 210 of the first conduction type, patterned etching can also be performed on the semiconductor layer 220 of the second conduction type to form multiple spaced-apart second-order semiconductor steps of the second conduction type. The second-order semiconductor steps are arranged in one-to-one correspondence with the first-order semiconductor steps, so that multiple PN junction structures can be formed, and then multiple chip units of independent photodiodes can be formed. At this time, the last-order semiconductor step is the second-order semiconductor step.

[0088] Or, exemplarily, please refer to Figure 10, after patterning and etching the first-conductivity-type semiconductor layer 210, the second-conductivity-type semiconductor layer 220 may not be etched any further. At this time, each first-order semiconductor step can form a PN junction structure with the second-conductivity-type semiconductor layer 220, so that chip units of a plurality of photodiodes sharing the second-conductivity-type semiconductor layer 220 can be formed. At this time, the first-order semiconductor step is also the last-order semiconductor step.

[0089] Please refer to Figures 4 to 6 , after forming each semiconductor step, a first protective layer 300 covering the front structure is formed. The main function of the first protective layer 300 is to prevent the intrusion of water and oxygen and other protective effects. The materials of the first protective layers 300 corresponding to each semiconductor step can be the same or different.

[0090] At the same time, at least before forming the last first protective layer 300, a reflectivity adjustment layer 400 covering at least the photosensitive surface is formed. That is, the reflectivity adjustment layer 400 can be formed before all the first protective layers 300 (please refer to Figure 3 ), or can be formed before some of the first protective layers 300. It can be understood that here, "one first protective layer 300" corresponds to one semiconductor step.

[0091] At the same time, the reflectivity adjustment layer 400 can be a single-layer structure or a multi-layer stacked structure.

[0092] After forming the reflectivity adjustment layer 400, when forming the first protective layer 300, it can be deposited by a deposition method with a relatively fast deposition rate and low cost. At this time, the first protective layer 300 can be quickly formed to provide good protection for the structure under the first protective layer 300. At the same time, the accuracy of the first protective layer 300 deposited by this deposition method may be relatively low. Based on this, after forming the first protective layer 300, the first protective layer 300 covering the photosensitive surface needs to be removed in order to form an antireflection film layer with an accurate thickness on the photosensitive surface to effectively reduce the reflection of the photosensitive surface.

[0093] In step S40, please refer to Figure 7 , the first protective layer 300 formed after the reflectivity adjustment layer 400 can be pattern-etched to remove the part covering the photosensitive surface while retaining the part outside the photosensitive surface. At this time, the reflectivity adjustment layer 400 may not be etched or may be partially etched.

[0094] In this embodiment, since the reflectivity adjustment layer 400 covering at least the photosensitive surface is formed at least before forming the last first protection layer 300. Therefore, when etching the first protection layer 300 formed after the reflectivity adjustment layer 400, it can be etched onto the reflectivity adjustment layer 400 and not etched onto the photosensitive surface, so as not to damage the photosensitive surface. Therefore, this embodiment can effectively improve the reliability of the formed photodiode. At the same time, the reflectivity adjustment layer 400 is configured to adjust the reflectivity of light within the range where the photosensitive surface is located, and can participate in the control of the reflectivity of the photosensitive surface, thereby reducing the process cost.

[0095] In one embodiment, please refer to Figure 7 , the thickness of the reflectivity adjustment layer 400 is an integer multiple of a quarter of the working wavelength. It can be understood that the working wavelength is the working wavelength of the photodiode.

[0096] At this time, the reflectivity adjustment layer 400 can be used as an antireflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.

[0097] In one embodiment, please refer to Figure 8 , after step 40, it further includes:

[0098] Step S50, forming an adjustment compensation layer 500 covering the reflectivity adjustment layer 400 and the first protection layer 300.

[0099] The sum of the thicknesses of the reflectivity adjustment layer 400 and the adjustment compensation layer 500 is an integer multiple of a quarter of the working wavelength. Therefore, the reflectivity adjustment layer 400 and the adjustment compensation layer 500 can jointly serve as an antireflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.

[0100] The materials of the adjustment compensation layer 500 and the reflectivity adjustment layer 400 can be the same or different. Exemplarily, the adjustment compensation layer 500 can be deposited over the entire surface by a deposition process.

[0101] In one embodiment, please refer to Figure 7 or Figure 8 , the reflectivity adjustment layer 400 is a single-layer structure. The single-layer reflectivity adjustment layer 400 is reused as an etching stop layer when etching the first protection layer in step S40, so that the etching in step S40 can effectively stop on the reflectivity adjustment layer 400.

[0102] Exemplarily, the material of the single-layer reflectivity adjustment layer 400 includes SiO x , MgF2, Al2O3, any one of them.

[0103] In one embodiment, please refer to Figure 9, the reflectivity adjustment layer 400 has a multi-layer stacked structure. The multi-layer stacked structure includes an etch stop layer 410 and at least one adjustment layer 420. Exemplarily, the material of the etch stop layer may include any one of SiO x , MgF2, and Al2O3.

[0104] The adjustment layer 420 is disposed on the side of the etch stop layer 410 close to the photosensitive surface.

[0105] At this time, the etch stop layer 410 can be a material with a high selective etch ratio with the first protective layer 300, so that the etching in step S40 can effectively stop on the etch stop layer 410. And the material of the adjustment layer 420 can be the same as or different from the material of the first protective layer 300, which facilitates the flexible selection of materials.

[0106] In one embodiment, step S30 includes:

[0107] Step S32, please refer to Figure 3 , form a reflectivity adjustment layer 400 on the side of the first conductive type semiconductor layer 210 away from the substrate 100;

[0108] Step S33, please refer to Figures 4 to 6 , etch the reflectivity adjustment layer 400 and the epitaxial layer 200 to form at least one semiconductor step, and after forming each semiconductor step, form a first protective layer 300 covering the front structure.

[0109] That is, after forming the epitaxial layer 200 and before etching the epitaxial layer 200, the reflectivity adjustment layer 400 is formed.

[0110] At this time, the reflectivity adjustment layer 400 is deposited before the epitaxial layer 200 is patterned and etched. Therefore, the reflectivity adjustment layer 400 can be formed on a flat surface without the need to cover the steps. Therefore, the thickness of the reflectivity adjustment layer 400 is easy to control, which facilitates better control of the reflectivity of the photosensitive surface, thereby improving the performance of the photodiode. In the traditional technology, usually after forming each semiconductor step, an antireflection film layer is deposited. At this time, the antireflection film layer is formed on an uneven surface with steps, and the thickness of the antireflection film layer on the photosensitive surface is not easy to control, thus affecting the reflectivity control of the photosensitive surface.

[0111] In one embodiment, step S33 includes:

[0112] Step S331, please refer to Figure 4 , sequentially etch the reflectivity adjustment layer 400 and the first conductive type semiconductor layer 210 to form the first semiconductor step;

[0113] Step S332, refer to Figure 4 to form a first first protective layer covering the reflectivity adjustment layer 400, the sidewalls of the first-order semiconductor steps, and the second-conductivity-type semiconductor layer 220 outside the first-order semiconductor steps;

[0114] Step S333, refer to Figure 5 to etch the first first protective layer 300 and the second-conductivity-type semiconductor layer 220 outside the first-order semiconductor steps in sequence to form second-order semiconductor steps;

[0115] Step S334, refer to Figure 6 to form a second first protective layer covering the first first protective layer 300, the sidewalls of the second-order semiconductor steps, and the structure outside the second-order semiconductor steps. The second first protective layer is the last first protective layer.

[0116] In step S331, refer to Figure 4 to perform patterning etching on the reflectivity adjustment layer 400 and the first-conductivity-type semiconductor layer 210 in sequence through a photolithography process or the like. The etched first-conductivity-type semiconductor layer 210 can form a plurality of first-order semiconductor steps arranged at intervals.

[0117] And after etching the first-conductivity-type semiconductor layer 210, a part of the second-conductivity-type semiconductor layer 220 can be exposed.

[0118] In step S332, refer to Figure 4 to deposit the first first protective layer over the entire surface through a deposition method with a relatively fast deposition rate and low cost. The first first protective layer can play a good protective role for the structure it covers.

[0119] In step S333, refer to Figure 5 to perform patterning etching on the first first protective layer and the second-conductivity-type semiconductor layer 220 in sequence through a photolithography process or the like. The etched second-conductivity-type semiconductor layer 220 can form a plurality of second-order semiconductor steps arranged at intervals. The second-order semiconductor steps and the first-order semiconductor steps can be arranged in one-to-one correspondence, and the two can form a PN junction structure.

[0120] In step S334, refer to Figure 6 to deposit the second first protective layer over the entire surface through a deposition method with a relatively fast deposition rate and low cost. The second first protective layer can play a good protective role for the structure it covers.

[0121] In this embodiment, the reflectivity adjustment layer 400 is formed before the semiconductor step is formed, and thus is formed before all the first protective layers 300 (the first first protective layer and the second first protective layer). Therefore, both the first first protective layer and the second first protective layer can be etched and removed in step S40, and thus both can be deposited by a relatively economical deposition method with low precision requirements.

[0122] Of course, in other embodiments, the formation method of the reflectivity adjustment layer 400 is not limited to this.

[0123] For example, the reflectivity adjustment layer 400 can also be formed after the first-order semiconductor step is formed and before the first first protective layer is formed.

[0124] For another example, the reflectivity adjustment layer 400 can also be formed after the first first protective layer is formed and before the second-order semiconductor step is formed. Or, the reflectivity adjustment layer 400 can also be formed after the second-order semiconductor step is formed and before the second first protective layer is formed. At this time, both the first first protective layer and the reflectivity adjustment layer 400 can be used as components of the antireflection film layer and participate in the control of the reflectivity of the photosensitive surface. When forming the first first protective layer, a deposition method that can more precisely control the deposition thickness of the film layer can be used for deposition.

[0125] For another example, when the first first protective layer is deposited by a deposition method that can more precisely control the deposition thickness of the film layer, the first first protective layer can be reused as the reflectivity adjustment layer 400. At this time, the materials and deposition methods of the second first protective layer and the first first protective layer can be different.

[0126] It should be understood that although Figure 1 the steps in the flowchart of Figure 1 are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise clearly stated in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover,

[0127] In one embodiment, please refer to Figure 7 , and a photodiode is also provided. The photodiode includes a substrate 100, an epitaxial layer 200, a reflectivity adjustment layer 400, and a protection structure.

[0128] The substrate 100 may include, but is not limited to, semiconductor substrates such as gallium arsenide substrates, silicon substrates, gallium nitride substrates, or germanium substrates.

[0129] The epitaxial layer 200 is located on the substrate 100 and includes a second-conductivity-type semiconductor layer 220 and a first-conductivity-type semiconductor layer 210 sequentially disposed on the substrate 100.

[0130] The epitaxial layer 200 has at least a first-order semiconductor step formed by the first-conductivity-type semiconductor layer 210, and the surface of the first-conductivity-type semiconductor layer 210 away from the substrate 100 is a photosensitive surface.

[0131] Exemplarily, the epitaxial layer 200 may have a first-order semiconductor step and a second-order semiconductor step. The first-order semiconductor step is formed by the patterned first-conductivity-type semiconductor layer 210, and the second-order semiconductor step is formed by the patterned second-conductivity-type semiconductor layer 220.

[0132] Of course, please refer to Figure 10 , the epitaxial layer 200 may also have only the first-order semiconductor step.

[0133] The reflectivity adjustment layer 400 covers the photosensitive surface. The reflectivity adjustment layer 400 is configured to adjust the reflectivity of light within the range where the photosensitive surface is located.

[0134] The protection structure covers the epitaxial layer 200 outside the photosensitive surface. The protection structure includes at least one first protection layer 300. The first protection layer 300 may be correspondingly disposed with the semiconductor step. The first-order semiconductor step may correspond to one first protection layer 300.

[0135] The first protection layer 300 covers at least the sidewall and the bottom of the corresponding semiconductor step. For example, the first first protection layer 300 corresponding to the first-order semiconductor step covers the sidewall and the bottom of the first-order semiconductor step. The second first protection layer 300 corresponding to the second-order semiconductor step covers the sidewall and the bottom of the second-order semiconductor step, and covers the first first protection layer 300 located on the top of a part of the second-order semiconductor step (the top of this part of the second-order semiconductor step is the bottom of the first-order semiconductor step).

[0136] In this embodiment, during the preparation process of the photodiode, the reflectivity adjustment layer 400 can protect the photosensitive surface and prevent etching damage to the photosensitive surface when etching the first protection layer 300 covering the photosensitive surface, thereby improving the reliability of the photodiode.

[0137] In one embodiment, please refer to Figure 7 , the thickness of the reflectivity adjustment layer 400 is an integer multiple of a quarter of the working wavelength.

[0138] At this time, the reflectivity adjustment layer 400 can serve as an antireflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.

[0139] In one embodiment, referring to Figure 8 , the photodiode further includes an adjustment compensation layer. The adjustment compensation layer covers the reflectivity adjustment layer 400 and the protection structure.

[0140] The sum of the thicknesses of the reflectivity adjustment layer 400 and the adjustment compensation layer is an integer multiple of a quarter of the working wavelength. At this time, the reflectivity adjustment layer 400 and the adjustment compensation layer 500 can jointly serve as an antireflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.

[0141] In one embodiment, the reflectivity adjustment layer 400 is provided as a single-layer structure or a multi-layer stacked structure.

[0142] In one embodiment, referring to Figure 7 , the reflectivity adjustment layer 400 is a single-layer structure. And the single-layer reflectivity adjustment layer 400 is made of a different material from that of the first protection layer, so that the reflectivity adjustment layer 400 is reused as an etching stop layer.

[0143] Exemplarily, the material of the single-layer reflectivity adjustment layer 400 includes any one of SiO x , MgF2, and Al2O3.

[0144] In one embodiment, referring to Figure 9 , the reflectivity adjustment layer 400 is a multi-layer stacked structure. The multi-layer stacked structure includes an etching stop layer 410 and at least one adjustment layer 420.

[0145] The etching stop layer 410 can be a material having a high selective etching ratio with the first protection layer 300. Exemplarily, the material of the etching stop layer can include any one of SiO x , MgF2, and Al2O3.

[0146] The adjustment layer 420 is disposed on the side of the etching stop layer 410 close to the photosensitive surface. The material of the adjustment layer can be the same as or different from that of the first protection layer, thus facilitating the flexible selection of materials.

[0147] In one embodiment, referring to Figures 2 to 7 , a method for manufacturing a photodiode is provided, including:

[0148] Step S10’, providing a substrate 100;

[0149] Step S20', an epitaxial layer 200 is formed on the substrate 100. The epitaxial layer 200 includes a first-conductivity-type semiconductor layer 210 and a second-conductivity-type semiconductor layer 220. The first-conductivity-type semiconductor layer 210 is located on the side of the second-conductivity-type semiconductor layer 220 away from the substrate.

[0150] Step S30', an etch stop layer 410 is formed on the side of the first-conductivity-type semiconductor layer 210 away from the substrate.

[0151] Step S40', the etch stop layer 410 and the epitaxial layer 200 are etched to form at least one semiconductor step. And after forming each semiconductor step, a first protective layer 300 covering the front structure is formed. Among them, the first semiconductor step is formed by etching the first-conductivity-type semiconductor layer 210, and the surface of the first semiconductor step away from the substrate is a photosensitive surface.

[0152] Step S50', the first protective layer 300 within the range where the photosensitive surface is located is etched to expose the etch stop layer 410.

[0153] In steps S10' and S20', the understanding of the substrate 100 and the epitaxial layer 200 can refer to the description in the embodiments in the foregoing method for manufacturing a photodiode, and will not be elaborated here.

[0154] In step S30', the etch stop layer 410 can have a large etch selectivity ratio with respect to the first protective layer 300 formed subsequently. The material of the etch stop layer 410 can include but is not limited to SiO x , MgF2, Al2O3, etc.

[0155] In step S40', the etch stop layer 410 and the first-conductivity-type semiconductor layer 210 can be etched sequentially first to form the first semiconductor step. After that, the epitaxial layer 200 under the first-conductivity-type semiconductor layer 210 can be continuously etched to form other semiconductor steps; or the epitaxial layer under the first-conductivity-type semiconductor layer can no longer be etched.

[0156] And for each formed step, the first protective layer 300 is deposited correspondingly once.

[0157] In step S50', the first protective layer 300 within the range where the photosensitive surface is located can be subjected to dry etching treatment, etc., to remove the part of the first protective layer 300 that blocks the photosensitive surface.

[0158] In this embodiment, before etching the epitaxial layer 200 to form a semiconductor step, an etch stop layer 410 is formed on the side of the first-conductivity-type semiconductor layer 210 away from the substrate. Therefore, when etching the first protective layer 300 within the range where the photosensitive surface is located, the etching stops on the etch stop layer 410 without damaging the photosensitive surface, thereby effectively improving the device reliability. At the same time, the etch stop layer 410 is formed before etching the epitaxial layer 200, so that it can be formed on a flat surface, thereby improving the uniformity of the etch stop layer. And at this time, based on the etch stop layer 410, each of the first protective layers 300 corresponding to each semiconductor step can be removed. Therefore, each of the first protective layers 300 does not need to participate in controlling the reflectivity of the photosensitive surface, so each of the first protective layers 300 can be deposited by a relatively economical deposition method with low requirements for thickness accuracy, thereby reducing the process cost.

[0159] In one embodiment, the thickness of the etch stop layer 410 is an integer multiple of a quarter of the working wavelength.

[0160] At this time, by selecting a suitable optical material for the etch stop layer, the etch stop layer can be used as an antireflection film layer on the photosensitive surface.

[0161] Moreover, since the etch stop layer is formed before etching the epitaxial layer, it can have a uniform thickness, thereby better controlling the reflectivity on the photosensitive surface.

[0162] In one embodiment, please refer to Figures 11 to 15 , before step S30', it further includes:

[0163] Step S01, forming a first metal electrode (not shown) on the first-conductivity-type semiconductor layer;

[0164] Step S02, forming a second protective layer 600 covering the first metal electrode and the first-conductivity-type semiconductor layer 210.

[0165] In step S01, the first metal electrode is formed on the first-conductivity-type semiconductor layer, and thus can serve as an electrode of the chip unit of the photodiode. When the first conductivity type is P-type, the first metal electrode can be an anode. When the first conductivity type is N-type, the first metal electrode can be a cathode.

[0166] In step S02, the second protective layer covers the first metal electrode and the first-conductivity-type semiconductor layer, thereby preventing water and oxygen from invading the first metal electrode and the first-conductivity-type semiconductor layer.

[0167] In one embodiment, please refer to Figure 15 , the total thickness of the second protective layer 600 and the etch stop layer 410 is an integer multiple of a quarter of the working wavelength.

[0168] At this time, the second protective layer 600 and the etching stop layer 410 can jointly serve as an antireflection film layer on the photosensitive surface to reduce the reflectivity of the photosensitive surface.

[0169] In one embodiment, please refer to Figure 16 , the total thickness of the second protective layer 600 and the etching stop layer 410 is less than an integer multiple of a quarter of the working wavelength. Then, after step S50', the following steps may further be included:

[0170] Step S60', forming an adjustment and compensation layer 500 covering the first protective layer 300 and the etching stop layer 410.

[0171] The total thickness of the adjustment and compensation layer 500, the second protective layer 600, and the etching stop layer 410 is an integer multiple of a quarter of the working wavelength.

[0172] In one embodiment, please refer to Figure 17 , after step S50', the following steps may further be included:

[0173] Step S70', removing the etching stop layer above the second protective layer 600; wherein, the thickness of the second protective layer 600 is an integer multiple of a quarter of the working wavelength.

[0174] There may be a large etch selectivity between the second protective layer 600 and the etching stop layer 400. When removing the etching stop layer 400 covering the photosensitive surface through an etching process, the etching process can stop on the second protective layer 600, so that the photosensitive surface will not be damaged during the process of removing the etching stop layer 400.

[0175] At this time, the material of the etching stop layer 410 can be any material that has a large etch selectivity with both the second protective layer 600 and the first protective layer 300.

[0176] In this case, the thickness of the second protective layer 600 is an integer multiple of a quarter of the working wavelength. At this time, the second protective layer 600 can be directly used as the antireflection film layer on the photosensitive surface.

[0177] Or, please refer to Figure 18 , it is also possible to set the thickness of the second protective layer 600 to be less than an integer multiple of a quarter of the working wavelength. After removing the etching stop layer 400 in step S60, the following steps may further be included:

[0178] Step S70, forming an adjustment and compensation layer 500 covering at least the second protective layer 600.

[0179] The materials of the second protective layer 600 and the adjustment and compensation layer 500 may be the same or different.

[0180] At this time, the sum of the thicknesses of the second protective layer 600 and the adjustment compensation layer 500 can be an integer multiple of a quarter of the working wavelength, so that the second protective layer 600 and the adjustment compensation layer 500 can jointly form an antireflection film layer on the photosensitive surface.

[0181] The thickness of the second protective layer 600 can be specifically set according to actual requirements.

[0182] In one embodiment, an optical module is further provided. The optical module includes an optical transmitting component and an optical receiving component. Among them, the optical receiving component includes at least one photodiode as described in any of the above embodiments. Alternatively, the optical receiving component includes at least one photodiode prepared by using the preparation method of the photodiode in any of the above embodiments.

[0183] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. mean that the specific features, structures, materials or features described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0184] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0185] The above-described embodiments only represent several implementation manners of the present application. The descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for preparing a photodiode, characterized in that, Comprising: Providing a substrate; Forming an epitaxial layer on the substrate, the epitaxial layer including a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, the first conductivity type semiconductor layer being located on a side of the second conductivity type semiconductor layer away from the substrate; Etching the epitaxial layer to form at least one order of semiconductor steps, and after forming each order of semiconductor steps, forming a first protective layer covering the front structure, and forming a reflectivity adjusting layer covering at least the photosensitive surface before forming at least the last first protective layer; the reflectivity adjusting layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located; wherein, the surface of the first order of semiconductor steps away from the substrate is the photosensitive surface, Etching the first protective layer within the range where the photosensitive surface is located until the reflectivity adjusting layer is exposed; Etching the epitaxial layer to form at least one order of semiconductor steps, and after forming each order of semiconductor steps, forming a first protective layer covering the front structure, and forming a reflectivity adjusting layer covering at least the photosensitive surface before forming at least the last first protective layer, including: Forming the reflectivity adjusting layer on a side of the first conductivity type semiconductor layer away from the substrate; Etching the reflectivity adjusting layer and the epitaxial layer to form at least one order of semiconductor steps, and after forming each order of semiconductor steps, forming a first protective layer covering the front structure.

2. The manufacturing method of the photodiode according to claim 1, characterized in that, The thickness of the reflectivity adjusting layer is an integer multiple of a quarter of the working wavelength.

3. The manufacturing method of the photodiode according to claim 1, characterized in that, After etching the first protective layer within the range where the photosensitive surface is located until the reflectivity adjusting layer is exposed, further including: Forming an adjustment compensation layer covering the reflectivity adjusting layer and the first protective layer, the sum of the thicknesses of the reflectivity adjusting layer and the adjustment compensation layer being an integer multiple of a quarter of the working wavelength.

4. The method for preparing a photodiode according to claim 1, wherein, The reflectivity adjusting layer is provided as a single-layer structure or a multi-layer stacked structure.

5. The manufacturing method of the photodiode according to claim 4, wherein, When the reflectivity adjusting layer is a single-layer structure, the single-layer reflectivity adjusting layer is reused as an etching stop layer when etching the first protective layer.

6. The manufacturing method of the photodiode according to claim 5, characterized in that, The material of the single-layer reflectivity adjustment layer includes SiO x , any one of MgF2, and Al2O3.

7. The manufacturing method of the photodiode according to claim 4, characterized in that, When the reflectivity adjusting layer is a multi-layer stacked structure, the multi-layer stacked structure includes an etching stop layer and at least one adjusting layer; the adjusting layer is disposed on a side of the etching stop layer close to the photosensitive surface.

8. The manufacturing method of the photodiode according to claim 7, wherein The material of the etching stop layer includes SiO x , any one of MgF2 and Al2O3.

9. The method for manufacturing a photodiode according to claim 1, wherein, The etching of the reflectivity adjusting layer and the epitaxial layer to form at least one order of semiconductor steps, and after forming each order of semiconductor steps, forming a first protective layer covering the front structure, includes: Sequentially etching the reflectivity adjusting layer and the first conductivity type semiconductor layer to form a first order of semiconductor steps; Forming a first first protective layer covering the reflectivity adjusting layer, the sidewall of the first order of semiconductor steps, and the second conductivity type semiconductor layer outside the first order of semiconductor steps; Sequentially etching the first first protective layer and the second conductivity type semiconductor layer outside the first order of semiconductor steps to form a second order of semiconductor steps; Form a second first protective layer that covers the first first protective layer, the sidewalls of the second-order semiconductor step, and the structure outside the second-order semiconductor step. The second first protective layer is the last first protective layer.

10. A photodiode, characterized in that, Prepared and formed according to the method described in any one of claims 1-9, and includes: A substrate; An epitaxial layer located on the substrate, and including a second-conductivity-type semiconductor layer and a first-conductivity-type semiconductor layer sequentially arranged on the substrate, and the epitaxial layer has at least a first-order semiconductor step formed by the first-conductivity-type semiconductor layer. The surface of the first-conductivity-type semiconductor layer away from the substrate is a photosensitive surface; A reflectivity adjustment layer covering the photosensitive surface, and the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located; A protection structure covering the epitaxial layer outside the photosensitive surface and the sidewalls of the reflectivity adjustment layer, including at least one first protective layer. The first protective layer is correspondingly arranged with the semiconductor step and at least covers the sidewalls and the bottom of the corresponding semiconductor step.

11. The photodiode according to claim 10, characterized in that, The thickness of the reflectivity adjustment layer is an integer multiple of a quarter of the working wavelength.

12. The photodiode according to claim 10, wherein The photodiode further includes: An adjustment compensation layer covering the reflectivity adjustment layer and the protection structure, and the sum of the thicknesses of the reflectivity adjustment layer and the adjustment compensation layer is an integer multiple of a quarter of the working wavelength.

13. The photodiode according to claim 11, wherein The reflectivity adjustment layer is provided as a single-layer structure or a multi-layer stacked structure.

14. The photodiode according to claim 13, wherein, When the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer is made of a different material from the first protective layer, so that the reflectivity adjustment layer is reused as an etching stop layer.

15. The photodiode according to claim 14, wherein, The material of the single-layer reflectivity adjustment layer includes SiO x , any one of MgF2 and Al2O3.

16. The photodiode according to claim 13, wherein, When the reflectivity adjustment layer is a multi-layer stacked structure, the multi-layer stacked structure includes an etching stop layer and at least one adjustment layer; the adjustment layer is provided on the side of the etching stop layer close to the photosensitive surface.

17. The photodiode according to claim 16, wherein The material of the etching stop layer includes SiO x , any one of MgF2 and Al2O3.

18. A method for preparing a photodiode, characterized in that, Includes: Provide a substrate; Form an epitaxial layer on the substrate, the epitaxial layer includes a first-conductivity-type semiconductor layer and a second-conductivity-type semiconductor layer, and the first-conductivity-type semiconductor layer is located on the side of the second-conductivity-type semiconductor layer away from the substrate; Form an etching stop layer on the side of the first-conductivity-type semiconductor layer away from the substrate; Etch the etching stop layer and the epitaxial layer to form at least one-order semiconductor step, and after forming each-order semiconductor step, form a first protective layer covering the previous structure. Among them, the first-order semiconductor step is formed by etching the first-conductivity-type semiconductor layer, and the surface of the first-order semiconductor step away from the substrate is a photosensitive surface; Etch the first protective layer within the range where the photosensitive surface is located to expose the etching stop layer.

19. The method for manufacturing a photodiode according to claim 18, characterized in that, The thickness of the etching stop layer is an integer multiple of a quarter of the working wavelength.

20. The method for manufacturing a photodiode according to claim 18, wherein Before forming the etching stop layer on the side of the first-conductivity-type semiconductor layer away from the substrate, it further includes: Form a first metal electrode on the first-conductivity-type semiconductor layer; Form a second protective layer covering the first metal electrode and the first conductivity type semiconductor layer.

21. The method for manufacturing a photodiode according to claim 20, wherein, The total thickness of the second protective layer and the etching stop layer is an integer multiple of a quarter of the working wavelength.

22. The method for preparing a photodiode according to claim 20, wherein Further comprising: Remove the etching stop layer above the second protective layer; wherein, the thickness of the second protective layer is an integer multiple of a quarter of the working wavelength.

23. An optical module includes an optical transmitting component and an optical receiving component, wherein, The optical receiving component includes at least one photodiode according to any one of claims 10-17; or The optical receiving component includes at least one photodiode prepared by using the preparation method of the photodiode according to any one of claims 1-9; or The optical receiving component includes at least one photodiode prepared by using the preparation method of the photodiode according to any one of claims 18-22.

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