Photodiode, preparation method thereof and optical module
By forming a reflectivity adjustment layer or an etching cutoff layer during the preparation of the photodiode, the problem of insufficient reliability of the photodiode is solved, the reliability of the device is improved and the cost is reduced.
Patent Information
- Application Number
- CN202510465377.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-05-13
- Estimated Expiration
- 2045-04-14
AI Technical Summary
The reliability of existing photodiodes needs to be improved.
During the preparation of the photodiode, a reflectivity adjustment layer or an etch cutoff layer covering the photosensitive surface is formed at least before the last first protective layer is formed, thereby avoiding etching damage to the photosensitive surface.
It effectively improves the reliability of the photodiode and reduces the process cost. At the same time, the reflectivity of light on the photosensitive surface is adjusted through the reflectivity adjustment layer.
Smart Images
Figure CN119997656A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor technology, and in particular to a photodiode and a preparation method thereof, and an optical module. Background Art
[0002] A photodiode is a semiconductor device that can convert light signals into electrical signals. Photodiodes have the characteristics of high sensitivity, fast response and low noise, and are widely used in photoelectric measurement, communication, automatic control and optical fiber transmission. In addition, photodiodes can also be used to make photoelectric sensors, photoelectric detectors, etc.
[0003] The reliability of existing photodiodes needs to be further improved. Summary of the invention
[0004] Based on this, the present application provides a photodiode and a preparation method thereof, and an optical module with effectively improved reliability.
[0005] A method for preparing a photodiode, comprising:
[0006] providing a substrate;
[0007] forming an epitaxial layer on the substrate, wherein the epitaxial layer includes a first conductive type semiconductor layer and a second conductive type semiconductor layer, wherein the first conductive type semiconductor layer is located on a side of the second conductive type semiconductor layer away from the substrate;
[0008] Etching the epitaxial layer to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer covering the previous structure, and forming a reflectivity adjustment layer covering at least the photosensitive surface before at least forming 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;
[0009] The first protective layer within the range where the photosensitive surface is located is etched until the reflectivity adjusting layer is exposed.
[0010] In one of the embodiments, the thickness of the reflectivity adjustment layer is an integer multiple of one quarter of the working wavelength.
[0011] In one embodiment, after etching the first protective layer within the range where the photosensitive surface is located until the reflectivity adjustment layer is exposed, the method further includes:
[0012] An adjustment and compensation layer is formed to cover the reflectivity adjustment layer and the first protective layer, wherein the sum of the thicknesses of the reflectivity adjustment layer and the adjustment and compensation layer is an integer multiple of one quarter of the working wavelength.
[0013] In one embodiment, the reflectivity adjusting layer is configured as a single-layer structure or a multi-layer stacked structure.
[0014] In one of the embodiments, when the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer is reused as an etching stop layer when etching the first protective layer.
[0015] In one embodiment, the material of the single-layer reflectivity adjustment layer includes SiO x , MgF2, Al2O3.
[0016] In one of the embodiments, 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 arranged on a side of the etching stop layer close to the photosensitive surface.
[0017] In one embodiment, the material of the etching stop layer includes SiO x , MgF2, Al2O3.
[0018] In one embodiment,
[0019] The epitaxial layer is etched to form at least one semiconductor step, and after each semiconductor step is formed, a first protective layer covering the previous structure is formed, and at least before the last first protective layer is formed, a reflectivity adjustment layer covering at least the photosensitive surface is formed, comprising:
[0020] forming the reflectivity adjustment layer on a side of the first conductive type semiconductor layer away from the substrate;
[0021] The reflectivity adjustment layer and the epitaxial layer are etched to form at least one semiconductor step, and after each semiconductor step is formed, a first protective layer covering the previous structure is formed.
[0022] In one embodiment,
[0023] The etching of 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, comprises:
[0024] Sequentially etching the reflectivity adjustment layer and the first conductive type semiconductor layer to form a first-stage semiconductor step;
[0025] forming a first protective layer covering the reflectivity adjusting layer, the sidewall of the first-step semiconductor step, and the second conductive type semiconductor layer outside the first-step semiconductor step;
[0026] Sequentially etching the first first protection layer and the second conductive type semiconductor layer outside the first-step semiconductor step to form a second-step semiconductor step;
[0027] A second first protection layer is formed to cover the first first protection layer, the sidewall of the second-step semiconductor step and the structure outside the second-step semiconductor step, and the second first protection layer is the last first protection layer.
[0028] A photodiode, comprising:
[0029] substrate;
[0030] an epitaxial layer, located on the substrate, and comprising a second conductive type semiconductor layer and a first conductive type semiconductor layer sequentially arranged on the substrate, wherein the epitaxial layer has at least a first-order semiconductor step formed by the first conductive type semiconductor layer, and a surface of the first conductive type semiconductor layer away from the substrate is a photosensitive surface;
[0031] a reflectivity adjustment layer, covering the photosensitive surface, wherein the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located;
[0032] The protective structure covers the epitaxial layer outside the photosensitive surface, and includes at least one first protective layer, which is arranged corresponding to the semiconductor step and at least covers the side wall and the bottom of the corresponding semiconductor step.
[0033] In one of the embodiments, the thickness of the reflectivity adjustment layer is an integer multiple of one quarter of the working wavelength.
[0034] In one embodiment, the photodiode further comprises:
[0035] The adjusting and compensating layer covers the reflectivity adjusting layer and the protective structure, and the sum of the thicknesses of the reflectivity adjusting layer and the adjusting and compensating layer is an integer multiple of one quarter of the working wavelength.
[0036] In one embodiment, the reflectivity adjusting layer is configured as a single-layer structure or a multi-layer stacked structure.
[0037] In one of the embodiments, when the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer and the first protective layer are made of different materials, 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, Al2O3.
[0039] In one of the embodiments, 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 arranged 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 SiO x , MgF2, Al2O3.
[0041] A method for preparing a photodiode, comprising:
[0042] providing a substrate;
[0043] forming an epitaxial layer on the substrate, wherein the epitaxial layer includes a first conductive type semiconductor layer and a second conductive type semiconductor layer, wherein the first conductive type semiconductor layer is located on a side of the second conductive type semiconductor layer away from the substrate;
[0044] forming an etching stop layer on a side of the first conductive 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 previous structure, wherein the first semiconductor step is formed by etching the first conductive type semiconductor layer, and the surface of the first semiconductor step away from the substrate is a photosensitive surface;
[0046] The first protection layer within the range where the photosensitive surface is located is etched to expose the etching stop layer.
[0047] In one embodiment, the thickness of the etching stop layer is an integer multiple of one quarter of the working wavelength.
[0048] In one embodiment,
[0049] Before forming the etching stop layer on the side of the first conductive type semiconductor layer away from the substrate, the method further comprises:
[0050] forming a first metal electrode on the first conductive type semiconductor layer;
[0051] A second protection layer is formed to cover the first metal electrode and the first conductive type semiconductor layer.
[0052] In one embodiment, the total thickness of the second protection layer and the etching stop layer is an integer multiple of one quarter of the working wavelength.
[0053] In one embodiment, it also includes:
[0054] The etching stop layer above the second protective layer is removed; wherein the thickness of the second protective layer is an integer multiple of one quarter of the working wavelength.
[0055] An optical module, comprising a light emitting component and a light receiving component, wherein the light receiving component comprises at least one photodiode as described above; or
[0056] The light receiving component includes at least one photodiode prepared by the above-mentioned method for preparing a photodiode; or
[0057] The light receiving component includes at least one photodiode prepared by the above-mentioned photodiode preparation method.
[0058] The above-mentioned photodiode and its preparation method, because at least before forming the last first protective layer, a reflectivity adjustment layer or an etching cut-off layer covering at least the photosensitive surface is formed. Therefore, when etching the first protective layer formed after the reflectivity adjustment layer or the etching cut-off layer is performed, no etching damage is caused to the photosensitive surface. Therefore, the present application effectively improves the reliability of the formed photodiode. BRIEF DESCRIPTION OF THE DRAWINGS
[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0060] Figure 1 is a flow chart of a method for preparing a photodiode provided in an embodiment;
[0061] Figures 2 to 6 is a schematic diagram of a cross-sectional structure of a structure obtained during the preparation process of a photodiode provided in an embodiment;
[0062] Figure 7 and Figure 8 In different embodiments, based on Figures 2 to 6 A schematic diagram of the cross-sectional structure of a photodiode formed by the preparation process;
[0063] Fig. 9 is a schematic diagram of a cross-sectional structure of a photodiode in another embodiment;
[0064] Fig.10 is a schematic diagram of a cross-sectional structure of a photodiode in yet another embodiment;
[0065] Figures 11 to 14is a schematic diagram of a cross-sectional structure of a structure obtained during the preparation process of a photodiode provided in an embodiment;
[0066] Figures 15 to 18 In different embodiments, based on Figures 11 to 14 Schematic diagram of the cross-sectional structure of a photodiode formed by the preparation process.
[0067] Description of reference numerals:
[0068] 100 - substrate, 200 - epitaxial layer, 210 - first conductive type semiconductor layer, 220 - second conductive type semiconductor layer, 300 - first protective layer, 400 - reflectivity adjustment layer, 410 - etching stop layer, 420 - adjustment layer, 500 - adjustment compensation layer, 600 - second protective layer. DETAILED DESCRIPTION
[0069] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided 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, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.
[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application 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" other elements or layers, it can be directly on other elements or layers, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can 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 the present application, the first element, component, region, layer, doping type or part discussed below can be represented as the second element, component, region, layer or part.
[0072] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an 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, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.
[0073] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, 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 relevant listed items.
[0074] In one embodiment, see Figure 1 , a method for preparing a photodiode is provided, comprising the following steps:
[0075] Step S10, see Figure 2 , providing a substrate 100;
[0076] Step S20, see Figure 2 , forming an epitaxial layer 200 on the substrate 100, wherein the epitaxial layer 200 includes a first conductive type semiconductor layer 210 and a second conductive type semiconductor layer 220, wherein the first conductive type semiconductor layer 210 is located on a side of the second conductive type semiconductor layer 220 away from the substrate 100;
[0077] Step S30, see Figures 3 to 6 , etching the epitaxial layer 200 to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer 300 covering the previous structure, and forming a reflectivity adjustment layer 400 covering at least the photosensitive surface at least before forming the last first protective layer 300; the reflectivity adjustment layer 400 is configured to adjust the reflectivity of light within the range where the photosensitive surface is located;
[0078] Step S40, see Figure 7, etching the first protective layer 300 within the range where the photosensitive surface is located to expose the reflectivity adjusting layer 400.
[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, refer to Figure 2 The substrate 100 may include but is not limited to a semiconductor substrate such as a gallium arsenide substrate, a silicon substrate, a gallium nitride substrate or a germanium substrate.
[0081] In step S20, refer to Figure 2 , the first conductivity type can be set to P type, and the second conductivity type can be set to N type. Alternatively, the first conductivity type can be set to N type, and the second conductivity type can be set to P type.
[0082] Epitaxial growth may be performed on the substrate 100 to form the epitaxial layer 200 .
[0083] For example, a buffer layer or the like may be formed on the substrate 100. Then, the second conductive type semiconductor layer 220 is epitaxially grown, and then the first conductive type semiconductor layer 210 is epitaxially grown. It is understood that the second conductive type semiconductor layer 220 and / or the first conductive type semiconductor layer 210 may include multiple film layers of different materials.
[0084] In step S30 , the first-step semiconductor step is the semiconductor step formed by etching first, and the last-step semiconductor step is the semiconductor step formed by etching last.
[0085] See also Figure 4 , the first conductive type semiconductor layer 210 is patterned and etched to form a plurality of first-stage semiconductor steps of the first conductive type that are spaced apart.
[0086] The surface of the first-stage semiconductor step away from the substrate 100 is a photosensitive surface, which can receive light, thereby generating a photocurrent in the photodiode.
[0087] For example, see Figure 5 After the first conductive type semiconductor layer 210 is patterned and etched, the second conductive type semiconductor layer 220 may be patterned and etched to form a plurality of second-order semiconductor steps of the second conductive type arranged at intervals. The second-order semiconductor steps are arranged one-to-one with the first-order semiconductor steps, so that a plurality of PN junction structures can be formed, and then a plurality of independent photodiode chip units can be formed. At this time, the last-order semiconductor step is a second-order semiconductor step.
[0088] Or, for example, see Fig.10After the first conductive type semiconductor layer 210 is patterned and etched, the second conductive type semiconductor layer 220 may no longer be etched. At this time, each first-stage semiconductor step can form a PN junction structure with the second conductive type semiconductor layer 220, thereby forming a plurality of chip units of photodiodes that share the second conductive type semiconductor layer 220. At this time, the first-stage semiconductor step is also the last-stage semiconductor step.
[0089] See also Figures 4 to 6 After forming each semiconductor step, a first protective layer 300 covering the previous structure is formed. The first protective layer 300 mainly plays a protective role in preventing water and oxygen from invading. The materials of the first protective layer 300 corresponding to each semiconductor step can be the same or different.
[0090] At the same time, the reflectivity adjustment layer 400 that at least covers the photosensitive surface is formed before at least forming the last first protective layer 300. That is, the reflectivity adjustment layer 400 can be formed before all the first protective layers 300 (see Figure 3 ), may also be formed before a portion of the first protective layer 300. It can be understood that, here, "a first protective layer 300" corresponds to a semiconductor step.
[0091] Meanwhile, the reflectivity adjustment layer 400 may 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 faster deposition speed and lower cost. At this time, the first protective layer 300 can be formed quickly to provide good protection for the structure under the first protective layer 300. At the same time, the precision 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, it is necessary to remove the first protective layer 300 covering the photosensitive surface so as to form an anti-reflection film layer with a precise thickness on the photosensitive surface to effectively reduce the reflection of the photosensitive surface.
[0093] In step S40, refer to Figure 7 , the first protective layer 300 formed after the reflectivity adjustment layer 400 can be patterned and etched to remove the portion covering the photosensitive surface and retain the portion outside the photosensitive surface. At this time, the reflectivity adjustment layer 400 can be not etched or can be partially etched.
[0094] In this embodiment, since the reflectivity adjustment layer 400 that at least covers the photosensitive surface is formed before at least forming the last first protective layer 300. Therefore, when etching the first protective layer 300 formed after the reflectivity adjustment layer 400, etching can be performed on the reflectivity adjustment layer 400, and etching can be performed without etching to the photosensitive surface, so that the photosensitive surface will not be damaged. 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, see Figure 7 The thickness of the reflectivity adjustment layer 400 is an integer multiple of one 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 anti-reflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.
[0097] In one embodiment, see Figure 8 , after step 40, further comprising:
[0098] Step S50 , forming an adjustment and 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 be used together as an anti-reflection film layer on the photosensitive surface to effectively reduce light reflection on the photosensitive surface.
[0100] The materials of the adjustment compensation layer 500 and the reflectivity adjustment layer 400 may be the same or different. For example, the adjustment compensation layer 500 may be deposited on the entire surface by a deposition process.
[0101] In one embodiment, see 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.
[0103] In one embodiment, see Fig. 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. Exemplarily, the material of the etching stop layer may include SiO x , MgF2, Al2O3.
[0104] The regulating layer 420 is disposed on a side of the etching stop layer 410 close to the photosensitive surface.
[0105] At this time, the etching stop layer 410 can be a material having a high selective etching ratio with the first protective layer 300, so that the etching in step S40 can effectively stop on the etching stop layer 410. The material of the adjustment layer 420 can be the same as the material of the first protective layer 300, or different from the material of the first protective layer 300, so as to facilitate flexible selection of materials.
[0106] In one embodiment, step S30 includes:
[0107] Step S32, see Figure 3 , forming a reflectivity adjustment layer 400 on a side of the first conductive type semiconductor layer 210 away from the substrate 100;
[0108] Step S33, see Figures 4 to 6 , the reflectivity adjustment layer 400 and the epitaxial layer 200 are etched to form at least one semiconductor step, and after each semiconductor step is formed, a first protective layer 300 covering the previous structure is formed.
[0109] That is, after the epitaxial layer 200 is formed and before the epitaxial layer 200 is etched, 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 covering the steps. Therefore, the thickness of the reflectivity adjustment layer 400 is easy to control, so as to better control the reflectivity of the photosensitive surface, thereby improving the performance of the photodiode. In the conventional technology, an anti-reflection film layer is usually deposited after forming each semiconductor step. At this time, the anti-reflection film layer is formed on the uneven surface with steps, and the thickness of the anti-reflection film layer on the photosensitive surface is not easy to control, thereby affecting the reflectivity control of the photosensitive surface.
[0111] In one embodiment, step S33 includes:
[0112] Step S331, see Figure 4 , sequentially etching the reflectivity adjustment layer 400 and the first conductive type semiconductor layer 210 to form a first-step semiconductor step;
[0113] Step S332, see Figure 4 , forming a first first protective layer covering the reflectivity adjustment layer 400, the sidewall of the first-step semiconductor step, and the second conductive type semiconductor layer 220 outside the first-step semiconductor step;
[0114] Step S333, see Figure 5 , sequentially etching the first protective layer 300 and the second conductive type semiconductor layer 220 outside the first-step semiconductor step to form a second-step semiconductor step;
[0115] Step S334, see Figure 6 , forming a second first protective layer covering the first first protective layer 300, the sidewall of the second-stage semiconductor step and the structure outside the second-stage semiconductor step, the second first protective layer is the last first protective layer.
[0116] In step S331, refer to Figure 4 The reflectivity adjustment layer 400 and the first conductive type semiconductor layer 210 may be pattern-etched in sequence by photolithography, etc. After etching, the first conductive type semiconductor layer 210 may form a plurality of first-stage semiconductor steps that are spaced apart.
[0117] After etching the first conductive type semiconductor layer 210 , a portion of the second conductive type semiconductor layer 220 may be exposed.
[0118] In step S332, refer to Figure 4 , the first protective layer can be deposited on the entire surface by a deposition method with a faster deposition speed and lower cost. The first protective layer can play a good protective role on the structure it covers.
[0119] In step S333, refer to Figure 5 , the first protective layer and the second conductive type semiconductor layer 220 can be patterned and etched in sequence by photolithography or the like. After etching, the second conductive type semiconductor layer 220 can form a plurality of second-order semiconductor steps arranged at intervals. The second-order semiconductor steps can be arranged in one-to-one correspondence with the first-order semiconductor steps, and the two can form a PN junction structure.
[0120] In step S334, refer to Figure 6 , a second first protective layer can be deposited on the entire surface by a deposition method with a faster deposition speed and lower cost. The second first protective layer can play a good protective role on 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 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 away in step S40, and thus both can be deposited using a more economical deposition method that does not require high precision.
[0122] Of course, in other embodiments, the formation method of the reflectivity adjustment layer 400 is not limited thereto.
[0123] For example, the reflectivity adjusting layer 400 may also be formed after forming the first-stage semiconductor step and before forming the first first protection layer.
[0124] For another example, the reflectivity adjustment layer 400 may be formed after forming the first first protective layer and before forming the second-order semiconductor step. Alternatively, the reflectivity adjustment layer 400 may be formed after forming the second-order semiconductor step and before forming the second first protective layer. In this case, both the first first protective layer and the reflectivity adjustment layer 400 may be used as components of the anti-reflection 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 accurately control the thickness of the film layer may be used for deposition.
[0125] For example, when a first protective layer is deposited by a deposition method that can more accurately control the thickness of the film layer, the first protective layer can be reused as the reflectivity adjustment layer 400. In this case, the second first protective layer and the first first protective layer can have different materials and deposition methods.
[0126] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple steps or multiple stages. These steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed in turn or alternately with other steps or at least part of the steps or stages in other steps.
[0127] In one embodiment, see Figure 7 , 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, a semiconductor substrate such as a gallium arsenide substrate, a silicon substrate, a gallium nitride substrate or a germanium substrate.
[0129] The epitaxial layer 200 is located on the substrate 100 , and includes a second conductive type semiconductor layer 220 and a first conductive type semiconductor layer 210 which are sequentially disposed on the substrate 100 .
[0130] The epitaxial layer 200 has at least a first-order semiconductor step formed by the first conductive type semiconductor layer 210 , and the surface of the first conductive type semiconductor layer 210 away from the substrate 100 is a photosensitive surface.
[0131] For example, the epitaxial layer 200 may have a first-step semiconductor step formed by the patterned first conductive type semiconductor layer 210 and a second-step semiconductor step formed by the patterned second conductive type semiconductor layer 220 .
[0132] Of course, see Fig.10 , the epitaxial layer 200 may also have only the first-order semiconductor steps.
[0133] The reflectivity adjustment layer 400 covers the photosensitive surface and is configured to adjust the reflectivity of light within the range where the photosensitive surface is located.
[0134] The protective structure covers the epitaxial layer 200 outside the photosensitive surface. The protective structure includes at least one first protective layer 300. The first protective layer 300 can be arranged corresponding to the semiconductor step. A first-order semiconductor step can correspond to one first protective layer 300.
[0135] The first protective layer 300 at least covers the sidewalls and bottom of the corresponding semiconductor step. For example, the first first protective layer 300 corresponding to the first-order semiconductor step covers the sidewalls and bottom of the first-order semiconductor step. The second first protective layer 300 corresponding to the second-order semiconductor step covers the sidewalls and bottom of the second-order semiconductor step, and covers the first first protective layer 300 located at the top of a portion of the second-order semiconductor step (the top of the portion of the second-order semiconductor step is the bottom of the first-order semiconductor step).
[0136] In this embodiment, the reflectivity adjustment layer 400 can protect the photosensitive surface during the preparation of the photodiode to prevent etching damage to the photosensitive surface when the first protection layer 300 covering the photosensitive surface is etched, thereby improving the reliability of the photodiode.
[0137] In one embodiment, see Figure 7 , the thickness of the reflectivity adjustment layer 400 is an integer multiple of one quarter of the working wavelength.
[0138] At this time, the reflectivity adjustment layer 400 can be used as an anti-reflection film layer on the photosensitive surface to effectively reduce the light reflection on the photosensitive surface.
[0139] In one embodiment, see Figure 8 The photodiode further includes an adjustment and compensation layer, which covers the reflectivity adjustment layer 400 and the protection structure.
[0140] The sum of the thickness of the reflectivity adjustment layer 400 and the adjustment compensation layer is an integral multiple of a quarter of the working wavelength. At this time, the reflectivity adjustment layer 400 and the adjustment compensation layer 500 can be used together as an anti-reflection film layer on the photosensitive surface to effectively reduce light reflection on the photosensitive surface.
[0141] In one embodiment, the reflectivity adjusting layer 400 is provided as a single layer structure or a multi-layer stacked structure.
[0142] In one embodiment, see Figure 7 The reflectivity adjustment layer 400 is a single-layer structure. The single-layer reflectivity adjustment layer 400 and the first protective layer are made of different materials, 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 SiO x , MgF2, Al2O3.
[0144] In one embodiment, see Fig. 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 etch stop layer 410 may be a material having a high selective etching ratio with the first protection layer 300. For example, the material of the etch stop layer may include SiO x , MgF2, Al2O3.
[0146] The adjustment layer 420 is disposed on a 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 protective layer, thereby facilitating flexible selection of materials.
[0147] In one embodiment, see Figures 2 to 7 , a method for preparing a photodiode is provided, comprising:
[0148] Step S10', providing a substrate 100;
[0149] Step S20', forming an epitaxial layer 200 on the substrate 100, wherein the epitaxial layer 200 includes a first conductive type semiconductor layer 210 and a second conductive type semiconductor layer 220, wherein the first conductive type semiconductor layer 210 is located on a side of the second conductive type semiconductor layer 220 away from the substrate;
[0150] Step S30', forming an etching stop layer 410 on a side of the first conductive type semiconductor layer 210 away from the substrate;
[0151] Step S40', etching the etching stop layer 410 and the epitaxial layer 200 to form at least one semiconductor step, and after forming each semiconductor step, forming a first protective layer 300 covering the front structure, wherein the first semiconductor step is formed by etching the first conductive type semiconductor layer 210, and the surface of the first semiconductor step away from the substrate is a photosensitive surface;
[0152] Step S50 ′, etching the first protection layer 300 within the area where the photosensitive surface is located to expose the etching stop layer 410 .
[0153] In step S10 ′ and step S20 ′, the substrate 100 and the epitaxial layer 200 may be understood by referring to the description in the embodiment of the aforementioned method for preparing a photodiode, and will not be described in detail here.
[0154] In step S30', the etching stop layer 410 may have a larger selective etching ratio with the first protective layer 300 formed subsequently. The material of the etching stop layer 410 may include but is not limited to SiO x , MgF2, Al2O3, etc.
[0155] In step S40', the etching stop layer 410 and the first conductive type semiconductor layer 210 may be etched in sequence to form a first-level semiconductor step. After that, the epitaxial layer 200 under the first conductive type semiconductor layer 210 may be further etched to form other semiconductor steps; or the epitaxial layer under the first conductive type semiconductor layer may not be etched.
[0156] And each time a step is formed, the first protection layer 300 is deposited once accordingly.
[0157] In step S50 ′, the first protective layer 300 within the region where the photosensitive surface is located may be subjected to dry etching or the like to remove the portion of the first protective layer 300 that blocks the photosensitive surface.
[0158] In this embodiment, before etching the epitaxial layer 200 to form the semiconductor step, an etching stop layer 410 is formed on the side of the first conductive 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 will stop on the etching stop layer 410 without damaging the photosensitive surface, thereby effectively improving the reliability of the device. At the same time, the etching 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 etching stop layer. And at this time, based on the etching stop layer 410, each first protective layer 300 corresponding to each semiconductor step can be removed. Therefore, each first protective layer 300 does not need to participate in the control of the reflectivity of the photosensitive surface, so each first protective layer 300 can be deposited using a more economical deposition method that does not require high thickness accuracy, thereby reducing process costs.
[0159] In one embodiment, the thickness of the etching stop layer 410 is an integer multiple of one quarter of the working wavelength.
[0160] At this time, by selecting a suitable optical material for the etching stop layer, the etching stop layer can be used as an anti-reflection film layer on the photosensitive surface.
[0161] Furthermore, the etching stop layer is formed before etching the epitaxial layer and can have a uniform thickness, thereby better controlling the reflectivity on the photosensitive surface.
[0162] In one embodiment, see Figures 11 to 15 , before step S30', further comprising:
[0163] Step S01, forming a first metal electrode (not shown) on the first conductive type semiconductor layer;
[0164] Step S02 : forming a second protection layer 600 covering the first metal electrode and the first conductive type semiconductor layer 210 .
[0165] In step S01, a first metal electrode is formed on a first conductive type semiconductor layer, so that it can be used as an electrode of a chip unit of a photodiode. When the first conductive type is P type, the first metal electrode can be an anode. When the first conductive type is N type, the first metal electrode can be a cathode.
[0166] In step S02 , the second protection layer covers the first metal electrode and the first conductive type semiconductor layer, thereby preventing water and oxygen from invading the first metal electrode and the first conductive type semiconductor layer.
[0167] In one embodiment, see Fig.15 The total thickness of the second protection layer 600 and the etching stop layer 410 is an integer multiple of one quarter of the working wavelength.
[0168] At this time, the second protective layer 600 and the etching stop layer 410 can be used together as an anti-reflection film layer on the photosensitive surface to reduce the reflectivity on the photosensitive surface.
[0169] In one embodiment, see Fig.16 , the total thickness of the second protective layer 600 and the etching stop layer 410 is less than an integral multiple of a quarter of the working wavelength. Then after step S50', the following may also be included:
[0170] Step S60 ′, forming an adjusting and compensating layer 500 covering the first protection layer 300 and the etching stop layer 410 .
[0171] The total thickness of the adjustment compensation layer 500 , the second protection layer 600 and the etching stop layer 410 is an integer multiple of a quarter of the working wavelength.
[0172] In one embodiment, see Fig.17 , after step S50', further comprising:
[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 one quarter of the working wavelength.
[0174] The second protective layer 600 may have a large selective etching ratio with the etching stop layer 400. When the etching stop layer 400 covering the photosensitive surface is removed by an etching process, the etching process may stop on the second protective layer 600, so that the photosensitive surface will not be damaged during the removal of the etching stop layer 400.
[0175] At this time, the material of the etching stop layer 410 can be any material that has a relatively large selective etching ratio with both the second protection layer 600 and the first protection layer 300 .
[0176] In this case, the thickness of the second protective layer 600 is an integral multiple of a quarter of the working wavelength. In this case, the second protective layer 600 can be directly used as an anti-reflection film layer on the photosensitive surface.
[0177] Alternatively, see Fig.18 , the thickness of the second protective layer 600 may also be set to be less than an integral multiple of a quarter of the working wavelength. After removing the etching stop layer 400 in step S60, the method may further include:
[0178] Step S70 , forming an adjustment and compensation layer 500 that at least covers the second protection layer 600 .
[0179] The second protection layer 600 and the adjustment compensation layer 500 may be made of the same material or different materials.
[0180] At this time, the sum of the thicknesses of the second protective layer 600 and the adjustment compensation layer 500 may be an integer multiple of one quarter of the working wavelength, so that the second protective layer 600 and the adjustment compensation layer 500 may jointly form an anti-reflection film layer on the photosensitive surface.
[0181] The thickness of the second protective layer 600 can be set according to actual needs.
[0182] In one embodiment, an optical module is also provided. The optical module includes an optical emitting component and an optical receiving component. The optical receiving component includes at least one photodiode as in any of the above embodiments. Alternatively, the optical receiving component includes at least one photodiode prepared by the method for preparing a photodiode in any of the above embodiments.
[0183] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction 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-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features of the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0185] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.
Claims
1. A method for preparing a photodiode, characterized in that: include: providing a substrate; forming an epitaxial layer on the substrate, wherein the epitaxial layer includes a first conductive type semiconductor layer and a second conductive type semiconductor layer, wherein the first conductive type semiconductor layer is located on a side of the second conductive 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 previous structure, and forming a reflectivity adjustment layer covering at least the photosensitive surface before at least forming 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; The first protective layer within the range where the photosensitive surface is located is etched until the reflectivity adjusting layer is exposed.
2. The method for preparing a photodiode according to claim 1, characterized in that: The thickness of the reflectivity adjustment layer is an integer multiple of one quarter of the working wavelength.
3. The method for preparing a 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 adjustment layer is exposed, the method further includes: An adjustment and compensation layer is formed to cover the reflectivity adjustment layer and the first protective layer, and the sum of the thicknesses of the reflectivity adjustment layer and the adjustment and compensation layer is an integer multiple of one quarter of the working wavelength.
4. The method for preparing a photodiode according to claim 1, characterized in that: The reflectivity adjustment layer is provided as a single-layer structure or a multi-layer stacked structure.
5. The method for preparing a photodiode according to claim 4, characterized in that: When the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer is reused as an etching stop layer when etching the first protective layer.
6. The method for preparing a photodiode according to claim 5, characterized in that: The material of the single-layer reflectivity adjustment layer includes SiO x , MgF2, Al2O3.
7. The method for preparing a photodiode according to claim 4, characterized in that: 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 arranged on a side of the etching stop layer close to the photosensitive surface.
8. The method for preparing a photodiode according to claim 7, characterized in that: The material of the etching stop layer includes SiO x , MgF2, Al2O3.
9. The method for preparing a photodiode according to any one of claims 1 to 8, characterized in that: The epitaxial layer is etched to form at least one semiconductor step, and after each semiconductor step is formed, a first protective layer covering the previous structure is formed, and at least before the last first protective layer is formed, a reflectivity adjustment layer covering at least the photosensitive surface is formed, comprising: forming the reflectivity adjustment layer on a side of the first conductive type semiconductor layer away from the substrate; The reflectivity adjustment layer and the epitaxial layer are etched to form at least one semiconductor step, and after each semiconductor step is formed, a first protective layer covering the previous structure is formed.
10. The method for preparing a photodiode according to claim 9, characterized in that: The etching of 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, comprises: Sequentially etching the reflectivity adjustment layer and the first conductive type semiconductor layer to form a first-stage semiconductor step; forming a first protective layer covering the reflectivity adjusting layer, the sidewall of the first-step semiconductor step, and the second conductive type semiconductor layer outside the first-step semiconductor step; Sequentially etching the first first protection layer and the second conductive type semiconductor layer outside the first-step semiconductor step to form a second-step semiconductor step; A second first protection layer is formed to cover the first first protection layer, the sidewall of the second-step semiconductor step and the structure outside the second-step semiconductor step, and the second first protection layer is the last first protection layer.
11. A photodiode, characterized in that: include: substrate; an epitaxial layer, located on the substrate, and comprising a second conductive type semiconductor layer and a first conductive type semiconductor layer sequentially arranged on the substrate, wherein the epitaxial layer has at least a first-order semiconductor step formed by the first conductive type semiconductor layer, and a surface of the first conductive type semiconductor layer away from the substrate is a photosensitive surface; a reflectivity adjustment layer, covering the photosensitive surface, wherein the reflectivity adjustment layer is configured to adjust the reflectivity of light within the range where the photosensitive surface is located; The protective structure covers the epitaxial layer outside the photosensitive surface, and includes at least one first protective layer, which is arranged corresponding to the semiconductor step and at least covers the side wall and the bottom of the corresponding semiconductor step.
12. The photodiode according to claim 11, characterized in that: The thickness of the reflectivity adjustment layer is an integer multiple of one quarter of the working wavelength.
13. The photodiode according to claim 11, characterized in that: The photodiode further comprises: The adjusting and compensating layer covers the reflectivity adjusting layer and the protective structure, and the sum of the thicknesses of the reflectivity adjusting layer and the adjusting and compensating layer is an integer multiple of one quarter of the working wavelength.
14. The photodiode according to claim 11, characterized in that: The reflectivity adjustment layer is provided as a single-layer structure or a multi-layer stacked structure.
15. The photodiode according to claim 14, characterized in that When the reflectivity adjustment layer is a single-layer structure, the single-layer reflectivity adjustment layer and the first protective layer are made of different materials, so that the reflectivity adjustment layer is reused as an etching stop layer.
16. The photodiode according to claim 15, characterized in that The material of the single-layer reflectivity adjustment layer includes SiO x , MgF2, Al2O3.
17. The photodiode according to claim 14, characterized in that 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 arranged on a side of the etching stop layer close to the photosensitive surface.
18. The photodiode according to claim 17, characterized in that The material of the etching stop layer includes SiO x , MgF2, Al2O3.
19. A method for preparing a photodiode, characterized in that: include: providing a substrate; forming an epitaxial layer on the substrate, wherein the epitaxial layer includes a first conductive type semiconductor layer and a second conductive type semiconductor layer, wherein the first conductive type semiconductor layer is located on a side of the second conductive type semiconductor layer away from the substrate; forming an etching stop layer on a side of the first conductive type semiconductor layer away from the substrate; 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 previous structure, wherein the first semiconductor step is formed by etching the first conductive type semiconductor layer, and the surface of the first semiconductor step away from the substrate is a photosensitive surface; The first protection layer within the range where the photosensitive surface is located is etched to expose the etching stop layer.
20. The method for preparing a photodiode according to claim 19, characterized in that: The thickness of the etching cut-off layer is an integral multiple of one quarter of the working wavelength.
21. The method for preparing a photodiode according to claim 19, characterized in that: Before forming the etching stop layer on the side of the first conductive type semiconductor layer away from the substrate, the method further comprises: forming a first metal electrode on the first conductive type semiconductor layer; A second protection layer is formed to cover the first metal electrode and the first conductive type semiconductor layer.
22. The method for preparing a photodiode according to claim 21, characterized in that: The total thickness of the second protection layer and the etching stop layer is an integer multiple of one quarter of the working wavelength.
23. The method for preparing a photodiode according to claim 21, characterized in that: Also includes: The etching stop layer above the second protective layer is removed; wherein the thickness of the second protective layer is an integer multiple of one quarter of the working wavelength.
24. An optical module, comprising an optical transmitting component and an optical receiving component, wherein: The light receiving component comprises at least one photodiode according to any one of claims 11 to 18; or The light receiving component comprises at least one photodiode prepared by the method for preparing a photodiode according to any one of claims 1 to 10; or The light receiving component includes at least one photodiode prepared by the method for preparing a photodiode as described in any one of claims 19 to 23.
Citation Information
Patent Citations
Mesa-type photodetectors with lateral diffusion junctions
CN101350378A
Method for fabricating semiconductor device
JP2001094087A
METHOD FOR MANUFACTURING pin-TYPE PHOTODIODE
JP2008066329A