A high-speed photodetector and a manufacturing method thereof

Abstract

The present application relates to the technical field of chip manufacturing, in particular to a high-speed photoelectric detector and a manufacturing method thereof, the antireflection film prepared based on the spraying process of the polymer has good antireflection effect on the communication waveband light signal, the external quantum efficiency of the photoelectric detector is increased, and the antireflection effect on the light signal is improved; meanwhile, the antireflection film prepared based on the spraying process of the polymer has good interface contact, the polymer releases thermal stress due to the periodic distribution of nano-pores when the temperature changes, the temperature influence on the photoelectric detector is reduced, and no defects are generated on the surface of the photoelectric detector, the influence of the degradation of the photoelectric detector is avoided, and the high-speed response characteristics of the photoelectric detector are ensured.

Description

Technical Field

[0001] This invention relates to the field of chip manufacturing technology, and in particular to a high-speed photodetector and its manufacturing method. Background Technology

[0002] Optical fiber communication uses photodetectors to convert optical signals in optical fibers into electrical signals for transmission. With the continuous development of communication technology and the explosive growth of data, optical communication requires higher transmission rates to improve information processing capabilities; therefore, increasing the transmission rate of photodetectors is crucial.

[0003] Currently, photodetectors suffer from performance degradation during long-term use, a problem stemming from poor compatibility of antireflection layer fabrication processes. Existing technologies often employ plasma-enhanced chemical vapor deposition (PECVD) or electron beam evaporation (EBSE) to prepare transparent silicon oxide (or silicon nitride) of a certain thickness, satisfying Fresnel's antireflection and anti-reflection formulas to match specific wavelengths in optical communication bands, thus constructing the antireflection layer for photodetectors.

[0004] To achieve patterning, reactive ion etching is required in certain areas to remove the antireflection film and expose the underlying material, facilitating the fabrication of patterned metal electrodes in subsequent processes. However, existing techniques suffer from interface mismatch between the antireflection layer and the epitaxial wafer: firstly, during annealing or infrared radiation, the photodetector heats up, causing a mismatch between the antireflection layer and the epitaxial wafer's lattice structure, resulting in significant thermal stress and affecting the photodetector's reliability; secondly, high-energy plasma clusters embed into the epitaxial wafer's lattice surface, disrupting its structure. The effects on the exposed surface of the photodetector scatter photogenerated carriers, reducing their mobility, and also trapping them, thus prolonging their migration time. In summary, during long-term use, the periodic thermal mismatch at the interface and the diffusion of cluster ions lead to performance degradation in the photodetector.

[0005] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to solve the problem of periodic thermal mismatch and diffusion of cluster ions on the light-receiving surface caused by the antireflection layer of traditional detectors during long-term use, which leads to the degradation of the performance of the photodetector.

[0007] The present invention adopts the following technical solution:

[0008] In a first aspect, a high-speed photodetector is provided, comprising: an epitaxial wafer 1, an antireflection film 2, a P electrode 3, and an N electrode 4; the antireflection film 2 is disposed on the light-receiving surface of the epitaxial wafer 1, and the P electrode 3 and the N electrode 4 are disposed on the epitaxial wafer 1;

[0009] The antireflection film 2 is prepared by polymer material on the light-receiving surface of the epitaxial wafer 1, and the antireflection film 2 has periodically distributed nanopores.

[0010] Preferably, the antireflective membrane 2 comprises a plurality of periodically distributed antireflective units, with nanopores between adjacent antireflective units.

[0011] Preferably, the epitaxial wafer 1 includes a substrate layer 10, a buffer layer 11, an absorption layer 12, a cap layer 13, and a contact layer 14 stacked sequentially.

[0012] The contact layer 14 covers a portion of the cap layer 13, and the antireflective film 2 is disposed on a portion of the cap layer 13.

[0013] Preferably, diffusion holes 15 are obtained by diffusion of a diffusion material on the cap layer 13, and the diffusion holes 15 are matched with the contact layer 14.

[0014] Preferably, the doping concentration of the buffer layer 11 is 1×10⁻⁶. 17 cm -3 ~1.5×10 17 cm -3 The thickness of the buffer layer 11 is 1.0 μm to 2.0 μm;

[0015] The doping concentration of the absorption layer 12 is less than 5 × 10⁻⁶. 15 cm -3 The thickness of the absorption layer 12 is 1.0 μm to 3.5 μm;

[0016] The doping concentration of the cap layer 13 is less than 5 × 10⁻⁶. 15 cm -3 The thickness of the cap layer 13 is 0.5 μm to 1.5 μm;

[0017] The doping concentration of the contact layer 14 is greater than 1×10⁻⁶. 19 cm -3 The thickness of the contact layer 14 is 0.05μm to 0.2μm.

[0018] Secondly, a method for manufacturing a high-speed photodetector is provided. This method is used to manufacture the high-speed photodetector as described in the first aspect, and includes:

[0019] Fabricate the epitaxial wafer 1;

[0020] A spray solution made of polymer material is sprayed onto the light-receiving surface of the epitaxial wafer 1 to fabricate the antireflection film 2 based on the spray solution; wherein the antireflection film 2 has periodically distributed nanopores;

[0021] The P electrode 3 and the N electrode 4 are fabricated on the epitaxial wafer 1 to obtain the high-speed photodetector.

[0022] Preferably, the polymer material includes a first polymer and a second polymer; the step of spraying a spray solution made of the polymer material onto the light-receiving surface of the epitaxial wafer 1 to form the antireflection film 2 based on the spray solution includes:

[0023] The first polymer and the second polymer are mixed in a preset ratio, and the mixed polymer is dissolved in a good solvent to obtain the spraying solution;

[0024] The spraying solution is sprayed onto the light-receiving surface of the epitaxial wafer 1 to form a polymer film 5;

[0025] The polymer film 5 is subjected to a thermosetting operation to allow the residual spraying solution in the polymer film 5 to fully evaporate, so that the first polymer is cured into an antireflection unit and the second polymer is cured into a spacer unit. The antireflection unit and the spacer unit are periodically distributed and are alternately arranged.

[0026] The antireflection membrane 2 is fabricated by removing part of the spacer unit using a selective solvent while retaining the antireflection unit.

[0027] Preferably, the solubility of the first polymer in the good solvent is less than the solubility of the second polymer in the good solvent.

[0028] Preferably, the thermosetting operation of the polymer film 5 includes: thermosetting the polymer film 5 at a temperature of 60°C to 90°C for 3 min to 15 min.

[0029] Preferably, the first polymer is polymethyl methacrylate, the second polymer is polystyrene, the good solvent is tetrahydrofuran, and the selective solvent is cyclohexane. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The antireflection film prepared by the polymer-based spraying process of this invention has a good antireflection effect on optical signals in the communication band, increases the external quantum efficiency of the photodetector, and thus improves the antireflection effect on optical signals. At the same time, the antireflection film prepared by the polymer-based spraying process has good interfacial contact. When the temperature changes, the polymer can release thermal stress through the periodically distributed nanopores on the antireflection film, reducing the temperature influence on the photodetector, and will not generate defects on the surface of the photodetector, avoiding the effects of photodetector degradation and ensuring the high-speed response characteristics of the photodetector. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of a high-speed photodetector provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the specific structure of a high-speed photodetector provided in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram illustrating the effect of different types of antireflection films on photodetectors according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic flowchart of a method for manufacturing a high-speed photodetector provided in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of an epitaxial wafer provided in an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of another structure of an epitaxial wafer provided in an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of a diffusion hole structure provided in an embodiment of the present invention;

[0039] Figure 8 This is a schematic flowchart of a method for manufacturing an antireflective membrane according to an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of a structure in which photoresist is disposed on an epitaxial wafer according to an embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram of the structure of a polymer film provided in an embodiment of the present invention;

[0042] Figure 11 This is a schematic diagram of the microscopic arrangement of two polymers provided in an embodiment of the present invention;

[0043] Figure 12 This is a schematic diagram of the structure of an antireflection membrane provided in an embodiment of the present invention;

[0044] Figure 13 This is a schematic diagram of the microscopic arrangement of two polymers on an antireflection membrane provided in an embodiment of the present invention;

[0045] Figure 14 This is a schematic diagram of the structure of a high-speed photodetector provided in an embodiment of the present invention;

[0046] Figure 15 This is a design and optical simulation diagram of a polymer antireflection film provided in an embodiment of the present invention.

[0047] In all the accompanying drawings, the same reference numerals denote the same structure, wherein:

[0048] Epitaxial wafer 1, substrate layer 10, buffer layer 11, absorber layer 12, cap layer 13, contact layer 14, diffusion hole 15, antireflection film 2, P electrode 3, N electrode 4, polymer film 5. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0051] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0052] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0053] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0054] Example 1:

[0055] Existing antireflection layers in photodetectors are ineffective, leading to performance degradation over prolonged use. To address this issue, this embodiment provides a photodetector whose antireflection film achieves good interfacial contact with the epitaxial wafer. Furthermore, the antireflection film possesses periodically distributed nanopores to release thermal stress and reduce the temperature-related impact on the photodetector. The structure of this photodetector is described below with reference to the accompanying drawings. It is worth noting that, for ease of illustration, all structural drawings in this embodiment are presented as front sectional views.

[0056] To address the problems existing in the prior art, in one embodiment, such as Figure 1 As shown, this embodiment proposes a high-speed photodetector, including: an epitaxial wafer 1, an antireflection film 2, a P electrode 3, and an N electrode 4; the antireflection film 2 is disposed on the light-receiving surface of the epitaxial wafer 1, and the P electrode 3 and N electrode 4 are disposed on the epitaxial wafer 1; wherein, the antireflection film 2 is prepared from a polymer material on the light-receiving surface of the epitaxial wafer 1, and the antireflection film 2 has periodically distributed nanopores (e.g., ... Figure 11 and Figure 13 (As shown). The antireflection film 2 achieves both the enhancement of light transmission and the protection of the epitaxial wafer 1 through its nanopores.

[0057] The main innovation of this embodiment is that an antireflection film 2 is made on the light-receiving surface of the epitaxial wafer 1 using a polymer material. The antireflection film 2 includes a plurality of periodically distributed antireflection units, and there are nanopores between adjacent antireflection units.

[0058] In one embodiment, the antireflection film 2 can be prepared by a spray coating process. Polymer materials typically have a low coefficient of thermal expansion and a certain degree of flexibility. The antireflection film 2 made of polymer materials can better match the epitaxial wafer 1 when the temperature changes, and can undergo moderate deformation with the thermal expansion and contraction of the epitaxial wafer 1, reducing thermal stress generated at the light-receiving surface due to thermal mismatch. Compared with antireflection films made of traditional inorganic antireflection materials, polymer materials have significant advantages in mitigating thermal mismatch. Specifically, the periodically distributed antireflection units formed on the surface of the antireflection film 2, and the nanopores between adjacent antireflection units, can effectively release thermal stress and reduce the temperature impact on the photodetector. The method for fabricating the antireflection film 2 will be specifically described in the following embodiments.

[0059] The epitaxial wafer 1 is the core component of the photodetector, and its main function is to convert the received optical signal into an electrical signal. When light shines on the epitaxial wafer 1, the photon interacts with the electrons in the epitaxial wafer 1, causing a change in the energy state of the electrons. For example, in the semiconductor epitaxial wafer 1, when the photon energy is greater than or equal to the band gap energy of the material, electrons in the valence band are excited to the conduction band, thereby generating electron-hole pairs. The movement of electron-hole pairs forms an electric current, thus realizing the conversion from optical signal to electrical signal.

[0060] In one embodiment, such as Figure 2 As shown, the epitaxial wafer 1 in this embodiment uses a PIN structure as an example, but other structures can be used instead in other embodiments. The epitaxial wafer 1 includes a substrate layer 10, a buffer layer 11, an absorption layer 12, a cap layer 13, and a contact layer 14 stacked sequentially; the contact layer 14 covers a portion of the cap layer 13, and the antireflection film 2 is disposed on a portion of the cap layer 13.

[0061] The substrate layer 10 is typically a stable semiconductor material, providing support for the entire structure. The buffer layer 11 is located above the substrate layer 10. The buffer layer 11 can be an N-type InP buffer layer with a doping concentration of 1 × 10⁻⁶. 17 cm -3 ~1.5×10 17 cm -3 The thickness is 1.0 μm to 2.0 μm. The doping concentration of the N-type InP buffer layer can be 1 × 10⁻⁶. 17 cm -3 It can also be 1.5 × 10 17 cm -3 It can also be 1×10 17 cm -3 ~1.5×10 17 cm -3For any doping concentration between 1.0µm and 2.0µm, the thickness of the N-type InP buffer layer can be 1.0µm or 2.0µm, or any thickness value between 1.0µm and 2.0µm. This rule applies to the following text and will not be elaborated further in this embodiment.

[0062] The absorption layer 12 is a key light absorption region of the photodetector, typically having a small band gap to effectively absorb light signals. It is usually composed of heavily doped semiconductor materials to improve light absorption efficiency. The absorption layer 12 can be a type I InGaAs absorption layer, with a doping concentration of less than 5 × 10⁻⁶. 15 cm -3 The thickness ranges from 1.0 μm to 3.5 μm.

[0063] The cap layer 13 is located above the absorption layer 12. The function of the cap layer 13 is to protect the absorption layer 12 from environmental factors and also to provide passivation, reducing surface defects. The cap layer 13 can be a P-type InP cap layer with a doping concentration of less than 5 × 10⁻⁶. 15 cm -3 The thickness is 0.5μm to 1.5μm;

[0064] The contact layer 14 is located above the cap layer 13 and is used to provide electrical contact with external circuits. The contact layer 14 can be a P+ type InGaAs contact layer with a doping concentration greater than 1×10⁻⁶. 19 cm -3 The thickness is 0.05μm to 0.2μm.

[0065] In one embodiment, the contact layer 14 can be designed as a P+ type InGaAs contact ring. InGaAs is a III-V group semiconductor material, an alloy of indium (In) and gallium (Ga), commonly used in optoelectronic and photodetector applications. P+ indicates that the doping level in the material is sufficient to generate free holes, which can act as charge carriers to transmit signals in the photodetector. The contact ring design allows light to enter the photodetector and be absorbed by the absorption layer 12, while providing a region to contact the P-electrode 3 to collect the electrical signal generated by photogenerated charge carriers (electrons and holes). The presence of the P+ type InGaAs contact ring ensures efficient hole collection, thereby achieving efficient photoelectric conversion.

[0066] In one embodiment, to obtain the P electrode 3 and the N electrode 4, continue referring to... Figure 2A diffusion hole 15 is formed on the cap layer 13 by diffusion through a diffusion material, and the diffusion hole 15 matches the contact layer 14. The P electrode 3 is disposed on the contact layer 14 and part of the antireflection film 2, and the N electrode 4 is disposed at the bottom of the substrate layer 10.

[0067] The matching of the diffusion hole 15 and the contact layer 14 means that the contact layer 14 is disposed on the diffusion hole 15 and covers part of the diffusion hole 15.

[0068] In one embodiment, the materials of the P electrode 3 and the N electrode 4 can be one or more of Ti, Pt, and Au. For example, both the P electrode 3 and the N electrode 4 are made of... Ti、 Pt and Au was obtained by alternating growth.

[0069] In one embodiment, the P electrode 3 is fabricated by depositing a P metal contact layer on the contact layer 14, typically achieved through methods such as physical vapor deposition or chemical vapor deposition. In one embodiment, the material of the P metal contact layer can be... Ti、 Pt and The P-metal contact layer, contact layer 14, and diffusion hole 15 are alternately grown to form an ohmic contact. This contact method is also to ensure good conductivity and stability. Through the above steps, an ohmic contact is formed between the P-metal contact layer on the diffusion hole 15 and the semiconductor material, thus obtaining the P-electrode 3. The P-electrode 3 is used to collect holes generated by photogenerated carriers in the absorption layer 12.

[0070] The P-electrode 3 and N-electrode 4 are used to collect the electrical signal formed by electron-hole pairs generated on the epitaxial wafer 1 under light irradiation. In the semiconductor epitaxial wafer 1, the P-type region and N-type region provide conductive channels for holes and electrons, respectively. When photogenerated carriers (electrons and holes) are generated, they move towards the P-electrode 3 and N-electrode 4 under the influence of the electric field. For example, photogenerated electrons generated near the PN junction move towards the N-electrode 4, and photogenerated holes move towards the P-electrode 3, thus being collected by the electrodes. After collecting the electrical signal, the P-electrode 3 and N-electrode 4 transmit the electrical signal to the external circuit. They act as a bridge connecting the photodetector and the subsequent signal processing circuit, enabling the electrical signal output by the photodetector to be further amplified, processed, and analyzed for various practical applications, such as signal decoding in optical communication and physical quantity measurement in fiber optic sensing.

[0071] To further illustrate the advantages of using polymer materials to fabricate the antireflection membrane 2 in this embodiment, such as... Figure 3As shown, the bandwidths of bare devices, photodetectors based on traditional antireflection films, and photodetectors based on polymer antireflection films were compared experimentally. Figure 3 As can be seen, traditional antireflective coatings degrade the bandwidth of photodetectors, while the fabrication process of polymer-based antireflective coatings does not damage the photodetector and can maintain the high-speed response detection characteristics of the photodetector.

[0072] The antireflection film 2 prepared by the polymer-based spraying process in this embodiment has a good antireflection effect on optical signals in the communication band, increases the external quantum efficiency of the photodetector, and thus improves the antireflection effect on optical signals. At the same time, the antireflection film 2 prepared by the polymer-based spraying process has good interfacial contact. When the temperature changes, the polymer benefits from the release of thermal stress through the periodically distributed nanopores, reducing the temperature influence on the photodetector, and will not generate defects on the surface of the photodetector, avoiding the effects of photodetector degradation and ensuring the high-speed response characteristics of the photodetector.

[0073] Example 2:

[0074] In Example 1, a high-speed photodetector was proposed. This example will describe the fabrication process of the high-speed photodetector. In one embodiment, such as... Figure 4 As shown, the manufacturing method includes:

[0075] Step 101: Fabricate the epitaxial wafer 1.

[0076] Among them, such as Figure 5 As shown, step 101 specifically includes: sequentially growing a buffer layer 11, an absorber layer 12, a cap layer 13, and a contact material (as shown in Figure a) on the substrate layer 10; as shown in Figure a. Figure 6 As shown, a portion of the contact material is removed to obtain the contact layer 14, thereby obtaining the epitaxial wafer 1.

[0077] The buffer layer 11, grown on the substrate layer 10, primarily addresses the lattice mismatch issue between the substrate layer 10 and subsequent functional layers. Different materials often have different lattice constants; directly growing the absorption layer 12 on the substrate layer 10 could lead to numerous crystal defects, affecting the photodetector's performance. The buffer layer 11, by gradually adjusting the lattice structure, achieves a smooth transition from the substrate layer 10 to the absorption layer 12, reducing lattice defects and laying the foundation for high-quality epitaxial growth. Furthermore, the buffer layer 11 also acts to block the diffusion of impurities from the substrate layer 10, preventing impurities from affecting the photoelectric performance of subsequent functional layers.

[0078] The absorption layer 12 is the core functional layer of the photodetector. Its function is to efficiently absorb incident light signals and convert photon energy into electron-hole pairs, achieving photoelectric conversion. Growing a high-quality absorption layer 12 is crucial for improving the detector's sensitivity and responsivity. The material selection for the absorption layer 12 is typically determined based on the desired wavelength range of the light to be detected, ensuring maximum absorption of the target light signal. Simultaneously, controlling the growth process is also critical, ensuring uniform thickness and good crystal quality of the absorption layer 12 to reduce carrier recombination losses and improve photoelectric conversion efficiency.

[0079] The cap layer 13 primarily serves to protect the absorption layer 12. During the fabrication and use of the photodetector, the absorption layer 12 is susceptible to external environmental factors, such as moisture, oxygen, and dust in the air. These factors can lead to a decline in the performance of the absorption layer 12 or even damage. As a protective layer, the cap layer 13 effectively isolates the absorption layer 12 from the external environment, preventing contamination and corrosion. The cap layer 13 also provides suitable surface conditions for the subsequent growth of the contact layer 14. It can adjust the surface's chemical properties and roughness, allowing the contact layer 14 to adhere better and achieve good electrical contact.

[0080] The growth of the contact material facilitates the subsequent formation of a good contact between the electrode and the epitaxial wafer 1. A good contact reduces contact resistance and improves the collection efficiency of photogenerated carriers, thereby enhancing detector performance. The selection of the contact material typically considers its electrical compatibility and chemical stability with the materials of each layer of the epitaxial wafer 1. After the contact material is grown, a portion of the contact material is removed using specific processing techniques to form the contact layer 14. This process may involve techniques such as photolithography and etching. For example, a specific pattern is formed on the surface of the contact material using photoresist, and then the portion of the contact material not protected by the photoresist is removed by chemical or physical etching. The precision and uniformity of the etching are crucial to the quality of the contact layer 14. Uneven etching may lead to uneven contact resistance, affecting the performance stability of the detector. In one embodiment, referring to... Figure 6 By using photolithography and chemical etching processes, annular P+ type InGaAs contact layers with an outer diameter of 10μm to 30μm and a width of 1μm to 2μm were fabricated.

[0081] like Figure 7 As shown, diffusion holes 15 are formed in the cap layer 13. The diffusion holes 15 can be formed by photolithography and Zn diffusion processes.

[0082] Step 102: Spray a coating solution made of polymer material onto the light-receiving surface of the epitaxial wafer 1 to form the antireflection film 2 based on the coating solution.

[0083] The antireflection film 2 has periodically distributed nanopores, and the polymer material includes a first polymer and a second polymer. Before performing step 102, the epitaxial wafer 1 needs to be pretreated. The pretreatment operations include: Figure 9 As shown, a layer of photoresist is coated onto the contact layer 14 using a photolithography process. Figure 9 (As shown in b).

[0084] like Figure 8 As shown, step 102 specifically includes:

[0085] Step 1021: Mix the first polymer and the second polymer in a preset ratio, and dissolve the mixed polymer in a good solvent to obtain the spraying solution.

[0086] In one embodiment, the mixing ratio of the two polymers affects the uniformity of their distribution in the solvent. Poor uniformity can prevent the two polymers from being discretely distributed in the polymer film 5, resulting in the inability to form the desired porous structure. That is, the preset ratio affects the porosity of the antireflection membrane 2. Therefore, the preset ratio can be changed to change the porosity of the antireflection membrane 2, thereby changing the refractive index and thus altering the antireflection effect of the antireflection membrane 2.

[0087] In one embodiment, the first polymer and the second polymer are mixed in a preset ratio, and the resulting mixture is dissolved in a good solvent. The good solvent can dissolve both polymers without affecting the photoresist. The first polymer can be polymethyl methacrylate (PMMA), and the second polymer can be polystyrene (PS). The good solvent is tetrahydrofuran (THF), which can dissolve both polymers. THF cannot dissolve commonly used photoresists.

[0088] In one embodiment, an excessively high or low content of the second polymer can affect the uniformity of the distribution of the two polymers in the solvent. Therefore, the proportion of the second polymer in the total polymer is set to 40% to 70% (i.e., a preset proportion), and the mass ratio of solute to solvent is controlled at 1:40 to 1:60 to obtain the spraying solution.

[0089] Step 1022: Spray the coating solution onto the light-receiving surface of the epitaxial wafer 1 to form a polymer film 5.

[0090] like Figure 10 As shown, the spraying solution obtained in step 1021 is sprayed onto... Figure 9 The light-receiving surface is shown, thereby forming a polymer film 5 on the light-receiving surface. The spraying process enables large-area production, and the thickness of the polymer film 5 can be changed by varying the spraying flow rate and time.

[0091] In one embodiment, the required thickness can be calculated using the Fresnel diffraction theorem to achieve high light transmission enhancement. The specific calculation method will not be explained in detail in this embodiment.

[0092] Step 1023: Perform a thermosetting operation on the polymer film 5 to allow the residual spray solution in the polymer film 5 to fully evaporate, so that the first polymer is cured into an anti-reflection unit and the second polymer is cured into a spacer unit. The anti-reflection unit and the spacer unit are periodically distributed and are alternately arranged.

[0093] In one embodiment, the thermosetting operation of the polymer film 5 includes: thermosetting the polymer film 5 at a temperature of 60°C to 90°C for 3 min to 15 min, so that the solvent remaining in the polymer film 5 can be fully evaporated, thereby increasing the adhesion and mechanical strength of the polymer film 5 to the substrate (i.e., capping layer 13).

[0094] In one embodiment, the solubility of the first polymer in the good solvent is less than the solubility of the second polymer in the good solvent, so that the degree of collapse of the antireflection unit formed by curing the first polymer is less than the degree of collapse of the spacer unit formed by curing the second polymer. Figure 11 As shown, the solubility of polymers PS and PMMA in solvents is not the same, resulting in different degrees of collapse between the two polymers. PS (black area in the figure) has a higher solubility in THF than PMMA (white area in the figure), and therefore collapses more severely.

[0095] Step 1024: Use a selective solvent to remove part of the spacer unit, retaining the antireflection unit, to produce the antireflection membrane 2.

[0096] In one embodiment, to obtain the desired nanopores in the antireflective membrane, a discretely distributed polymer is removed using a selective solvent.

[0097] In practice, the selectivity of selective solvents that can simultaneously dissolve one polymer and photoresist without dissolving the other polymer is limited. In this embodiment, the selective solvent can be cyclohexane.

[0098] In practical applications, both the anti-reflective elements and the spacer elements have anti-reflective effects. Theoretically, one can choose to remove the spacer elements formed by PS and retain the anti-reflective elements formed by PMMA; similarly, one can also choose to remove the anti-reflective elements formed by PMMA and retain the spacer elements formed by PS. From the perspective of ease of operation, it is generally preferable to remove the spacer elements because the spacer elements collapse more severely and are easier to remove.

[0099] In one embodiment, the structural component treated in step 1023 is immersed in a cyclohexane solution and dissolved at a high temperature of 70°C to 90°C for 1 to 10 minutes to remove PS and photoresist, leaving a PMMA-based antireflection film 2. The device structure is as follows. Figure 12 As shown, the microscopic schematic diagram of the thin film is as follows: Figure 13 As shown.

[0100] In practice, PS cannot be completely removed, so the PS content will be slightly greater than the porosity. If the volume ratio of PS in the raw material is A0, and the porosity after removing PS is A, then the amount of PS remaining is A0-A. The refractive index n can be derived as follows:

[0101]

[0102] Therefore, the values ​​of A0 and A can be adjusted to make the refractive index of the antireflective film meet the requirements.

[0103] Step 103: Fabricate the P electrode 3 and the N electrode 4 on the epitaxial wafer 1 to obtain the high-speed photodetector.

[0104] In one embodiment, a diffusion hole 15 is obtained by diffusion of a diffusion material in the cap layer 13, and the diffusion hole 15 matches the contact layer 14; the P electrode 3 is fabricated on the contact layer 14 and part of the antireflection film 2, and the N electrode 4 is disposed at the bottom of the substrate layer 10.

[0105] For ease of operation, such as Figure 7 As shown, after completing step 101 above, diffusion holes 15 can be fabricated in the cap layer 13. The diffusion holes 15 can be formed by photolithography and Zn diffusion processes.

[0106] like Figure 14 As shown, the P electrode 3 is fabricated on the annular P+ type InGaAs contact layer 14 using photolithography, thermal evaporation, and lift-off processes. The specific thickness can be [missing information]. Ti / Pt / Au; The epitaxial wafer 1 is thinned and polished to 150µm ± 20µm using a chemical mechanical polishing (CMP) process, and the N-electrode 4 is fabricated at the bottom of the substrate layer 10 using thermal evaporation technology. The thickness of the N-electrode 4 can be... Ti / Pt / Au. Finally, after rapid annealing of epitaxial wafer 1, the annealed epitaxial wafer 1 is cleaved along the crystal direction to obtain the high-speed photodetector.

[0107] In one embodiment, the refractive index of the polymer-based antireflective film 2 is closely related to its structure. In this embodiment, the refractive index of the antireflective film 2 is related to PMMA, PS, and the porosity left after removing PS (e.g., ...). Figure 13 The refractive index of the resulting antireflective coating 2 is related to the ratio of PMMA to PS (as shown in the mesopores). Changing the ratio of PMMA to PS can alter the refractive index of the resulting antireflective coating 2. Figure 15 As shown, this figure simulates the light signal transmittance variation of polymer-based antireflection films 2 with different refractive indices and thicknesses in the c-band, where d is the thickness of the antireflection film and n2 is the refractive index.

[0108] In one embodiment, based on Figure 15 The simulation results were used to adjust the corresponding spraying process (including spraying flow rate and time) to obtain the optimal solution where the light signal transmittance tends to 100%, so as to produce an antireflection film with the best antireflection effect.

[0109] For the specific structure of the high-speed photodetector, please refer to Embodiment 1, which will not be repeated in this embodiment.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed photodetector, characterized in that, include: Epitaxial wafer (1), antireflection film (2), P electrode (3) and N electrode (4); the antireflection film (2) is disposed on the light-receiving surface of the epitaxial wafer (1), and the P electrode (3) and N electrode (4) are disposed on the epitaxial wafer (1); The antireflective film (2) is prepared by polymer material on the light-receiving surface of the epitaxial wafer (1), and the antireflective film (2) has periodically distributed nanopores.

2. The high-speed photodetector according to claim 1, characterized in that, The antireflective membrane (2) comprises a plurality of periodically distributed antireflective units, with nanopores between adjacent antireflective units.

3. The high-speed photodetector according to claim 1, characterized in that, The epitaxial wafer (1) includes a substrate layer (10), a buffer layer (11), an absorption layer (12), a cap layer (13), and a contact layer (14) stacked sequentially. The contact layer (14) covers a portion of the cap layer (13), and the antireflective film (2) is disposed on a portion of the cap layer (13).

4. The high-speed photodetector according to claim 3, characterized in that, A diffusion hole (15) is obtained by diffusion of a diffusion material on the cap layer (13), and the diffusion hole (15) matches the contact layer (14).

5. The high-speed photodetector according to claim 3, characterized in that, The doping concentration of the buffer layer (11) is 1×10⁻⁶. 17 cm -3 ~1.5×10 17 cm -3 The thickness of the buffer layer (11) is 1.0 μm to 2.0 μm; The doping concentration of the absorption layer (12) is less than 5 × 10⁻⁶. 15 cm -3 The thickness of the absorption layer (12) is 1.0 μm to 3.5 μm; The doping concentration of the cap layer (13) is less than 5 × 10⁻⁶. 15 cm -3 The thickness of the cap layer (13) is 0.5 μm to 1.5 μm; The doping concentration of the contact layer (14) is greater than 1×10⁻⁶. 19 cm -3 The thickness of the contact layer (14) is 0.05μm to 0.2μm.

6. A method for fabricating a high-speed photodetector, characterized in that, The manufacturing method is used to manufacture the high-speed photodetector as described in any one of claims 1-5, and the manufacturing method includes: Fabricate the epitaxial wafer (1); A spray solution made of polymer material is sprayed onto the light-receiving surface of the epitaxial wafer (1) to form the antireflection film (2) based on the spray solution; wherein the antireflection film (2) has periodically distributed nanopores; The P electrode (3) and the N electrode (4) are fabricated on the epitaxial wafer (1) to obtain the high-speed photodetector.

7. The method for fabricating a high-speed photodetector according to claim 6, characterized in that, The polymer material includes a first polymer and a second polymer; the process of spraying a spray solution made of the polymer material onto the light-receiving surface of the epitaxial wafer (1) to form the antireflection film (2) based on the spray solution includes: The first polymer and the second polymer are mixed in a preset ratio, and the mixed polymer is dissolved in a good solvent to obtain the spraying solution; The spraying solution is sprayed onto the light-receiving surface of the epitaxial wafer (1) to form a polymer film (5); The polymer film (5) is subjected to a thermosetting operation to allow the residual spray solution in the polymer film (5) to fully evaporate, so that the first polymer is cured into an anti-reflection unit and the second polymer is cured into a spacer unit. The anti-reflection unit and the spacer unit are periodically distributed and are alternately arranged. The antireflection membrane (2) is fabricated by removing part of the spacer unit with a selective solvent while retaining the antireflection unit.

8. The method for manufacturing a high-speed photodetector according to claim 7, characterized in that, The solubility of the first polymer in the good solvent is less than that of the second polymer in the good solvent.

9. The method for manufacturing a high-speed photodetector according to claim 7, characterized in that, Thermosetting the polymer film (5) includes: The polymer film (5) is thermocured for 3 min to 15 min at a temperature of 60℃ to 90℃.

10. The method for fabricating a high-speed photodetector according to claim 7, characterized in that, The first polymer is polymethyl methacrylate, the second polymer is polystyrene, the good solvent is tetrahydrofuran, and the selective solvent is cyclohexane.

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