A refrigerated infrared detector and its manufacturing method

Abstract

In a refrigerated infrared detector and its manufacturing method provided by the present invention, the manufacturing aspects include the following steps: providing a substrate with a superlattice composite layer formed thereon; performing a first cleaning and surface treatment process; forming a first passivation layer on the superlattice composite layer; forming a hard mask layer with an opening on the first passivation layer, using the hard mask layer as a mask, etching the first passivation layer and the superlattice composite layer in sequence to form trenches and mesa, and removing the hard mask layer; performing a second cleaning and surface treatment process; forming a second passivation layer on the first passivation layer, and the second passivation layer also covers the trenches and mesa; etching the first passivation layer and the second passivation layer to form an opening, and forming a metal electrode in the opening. By performing a cleaning and surface treatment process before forming each passivation layer, the present invention can reduce the surface leakage current of the device and improve the performance of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared detectors, and particularly to a refrigerated infrared detector and a preparation method thereof. Background Art

[0002] In the current research and manufacture of refrigerated infrared detectors, dark current is an important indicator for evaluating device performance. The smaller the dark current, the better the device performance.

[0003] Dark current mainly consists of internal dark current and surface leakage current in the device. Currently, surface leakage current is mainly optimized through passivation, such as SiO2 passivation, SI3N4 passivation, as well as sulfidation, hydrogenation, PI passivation, ALD passivation and other technologies to improve. However, the current mainstream passivation technologies are quite different from the theoretical values, and are affected by factors such as doping, device size, temperature, corrosion rate, passivation technology, etc. The detection rate of the long wavelength band of the devices prepared by the existing passivation processes is very unstable and cannot meet the design requirements. To improve the detection rate of the long wavelength band, the dark current of the device must be reduced. Summary of the Invention

[0004] The purpose of the present invention is to provide a refrigerated infrared detector and a preparation method thereof, which reduce the surface leakage current of the device to improve the performance of the device.

[0005] To solve the above technical problems, the present invention provides a preparation method of a refrigerated infrared detector, including the following steps:

[0006] Provide a substrate, on which a superlattice composite layer is formed;

[0007] Perform a first cleaning and surface treatment process on the surface of the substrate;

[0008] Form a first passivation layer on the superlattice composite layer;

[0009] Form a hard mask layer with an opening on the first passivation layer. Using the hard mask layer as a mask, etch the first passivation layer and the superlattice composite layer in sequence, and stop etching in the superlattice composite layer to form a trench and a mesa, and remove the hard mask layer;

[0010] Perform a second cleaning and surface treatment process on the surface of the substrate;

[0011] Form a second passivation layer on the first passivation layer, and the second passivation layer also covers the trench and the mesa;

[0012] Etch the first passivation layer and the second passivation layer to form an opening, and form a metal electrode in the opening.

[0013] Optionally, forming a first passivation layer on the superlattice composite layer includes:

[0014] The first passivation layer is grown and formed on the superlattice composite layer by electroplating, ALD, CVD or PVD.

[0015] Furthermore, the material of the first passivation layer grown by electroplating includes sulfide; the materials of the first passivation layer formed by ALD include aluminum nitride, aluminum oxide, hafnium oxide; the materials of the first passivation layer formed by PVD or CVD include silicon oxide, silicon nitride.

[0016] Furthermore, the thickness of the first passivation layer is 30 nm to 500 nm.

[0017] Optionally, forming a hard mask layer with an opening on the first passivation layer, using the hard mask layer as a mask, etching the first passivation layer and the superlattice composite layer in sequence, and stopping the etching in the superlattice composite layer to form a trench and a mesa. Removing the hard mask layer includes:

[0018] Forming a hard mask layer on the first passivation layer;

[0019] Forming a patterned photoresist layer on the hard mask layer, and using the patterned photoresist layer as a mask to etch the hard mask layer so that the hard mask layer has an opening, and the opening is used to form subsequent trenches and mesas;

[0020] Using the patterned photoresist layer and the hard mask layer as masks, etching the first passivation layer and the superlattice composite layer in sequence, and stopping the etching in the superlattice composite layer to form a trench and a mesa;

[0021] Removing the remaining photoresist layer and the hard mask layer.

[0022] Furthermore, performing a second cleaning and surface treatment process on the surface of the substrate includes:

[0023] In a vacuum reaction chamber, cleaning the surface of the substrate with hydrogen.

[0024] Furthermore, in the second cleaning and surface treatment process, the flow rate of hydrogen is greater than 10 sccm, and the process time is greater than 200 seconds.

[0025] Furthermore, etching the first passivation layer and the second passivation layer to form an opening, and forming a metal electrode in the opening includes:

[0026] Etching the first passivation layer and the second passivation layer to expose the superlattice composite layer to form an opening;

[0027] After forming the opening, an annealing process is performed on the substrate; alternatively, a third cleaning and surface treatment process is performed on the surface of the substrate;

[0028] A metal electrode is formed in the opening.

[0029] On the other hand, the present invention also provides a refrigerated infrared detector prepared by the above-described preparation method.

[0030] Optionally, it includes a substrate and a superlattice composite layer formed on the substrate. Grooves and mesa are formed in the superlattice composite layer. Both the grooves and the mesa expose a part of the depth of the superlattice composite layer. A first passivation layer and a second passivation layer are sequentially formed on the superlattice composite layer outside the grooves. The first passivation layer and the second passivation layer have a first opening, and a first metal electrode is formed in the first opening; the grooves and the mesa are covered with the second passivation layer, and the second passivation layer in the grooves and the mesa has a second opening, and a second metal electrode is formed in the second opening.

[0031] Compared with the prior art, in a refrigerated infrared detector and its preparation method provided by the present invention, the preparation aspect includes the following steps: providing a substrate on which a superlattice composite layer is formed; performing a first cleaning and surface treatment process on the surface of the substrate; forming a first passivation layer on the superlattice composite layer; forming a hard mask layer with an opening on the first passivation layer, using the hard mask layer as a mask, sequentially etching the first passivation layer and the superlattice composite layer, and stopping the etching in the superlattice composite layer to form grooves and mesa, and removing the hard mask layer; performing a second cleaning and surface treatment process on the surface of the substrate; forming a second passivation layer on the first passivation layer, and the second passivation layer also covers the grooves and mesa; etching the first passivation layer and the second passivation layer to form openings, and forming metal electrodes in the openings. By performing a cleaning and surface treatment process before forming each passivation layer, the present invention enables the passivation layer to have good adhesion when formed, and forming the first passivation layer and the second passivation layer can reduce the surface leakage current of the device and improve the performance of the device.

[0032] Further, after forming the opening, an annealing process is performed on the substrate; alternatively, a third cleaning and surface treatment process is performed on the surface of the substrate to increase the surface adhesion of the exposed superlattice composite layer, improve the surface states of the device, and enhance the ohmic contact. Description of the Drawings

[0033] Figure 1a-1g Structural schematic diagrams of the steps of a preparation method of a refrigerated infrared detector;

[0034] Figure 2Flow chart of a preparation method of a refrigerated infrared detector according to an embodiment of the present invention;

[0035] Figure 3a-3e Structural schematic diagrams of the steps of a preparation method of a refrigerated infrared detector according to an embodiment of the present invention.

[0036] Explanation of reference numerals:

[0037] Figure 1a-1g Among them:

[0038] 10 - Substrate; 11 - Superlattice composite layer; 12 - Hard mask layer; 21 - Trench; 22 - Mesa; 30 - Passivation film layer; 31 - Opening; 40 - Metal electrode;

[0039] Figure 3a-3e Among them:

[0040] 1 - Substrate; 100 - Compound substrate; 110 - Buffer layer; 120 - Superlattice composite layer; 121 - p - type heavily doped superlattice structure; 122 - p - type lightly doped superlattice structure; 123 - n - type lightly doped superlattice structure; 124 - n - type heavily doped superlattice structure; 131 - Trench; 132 - Mesa;

[0041] 210 - First passivation layer; 220 - Second passivation layer;

[0042] 300 - Metal electrode; 310 - First metal electrode; 320 - Second metal electrode. Detailed implementation manners

[0043] The current preparation method of a refrigerated infrared detector includes the following steps:

[0044] As Figure 1a shown, step S11: Provide a substrate 10, and a superlattice composite layer 11 and a hard mask layer 12 are sequentially formed on the substrate 10;

[0045] As Figure 1b shown, step S12: Etch the hard mask layer 12 to expose a part of the surface of the superlattice composite layer 11;

[0046] As Figure 1c shown, step S13: Using the hard mask layer 12 as a mask, etch the superlattice composite layer 11 to a certain depth to form a trench 21 and a mesa 22;

[0047] As Figure 1d shown, step S14: Remove the remaining hard mask layer 12;

[0048] As Figure 1eAs shown, step S15: A passivation film layer 30 is formed on the surface of the superlattice composite layer 11 at one time, and the passivation film layer 30 covers the inner wall of the trench 21 and the surface of the mesa 22;

[0049] As Figure 1f shown, step S16: The passivation film layer 30 is etched to form an opening 31, and the opening 31 exposes the surface 11 of the superlattice composite layer;

[0050] As Figure 1g shown, step S17: A metal electrode 40 is formed in the opening 31.

[0051] The surface leakage current of the refrigerated infrared detector formed by the above process steps is relatively large, resulting in poor performance of the refrigerated infrared detector. Therefore, to solve the above problems, the present invention provides a refrigerated infrared detector and a preparation method thereof. By performing a cleaning and surface treatment process before each formation of the passivation layer, the passivation layer has good adhesion ability when formed, and the formation of the first passivation layer and the second passivation layer can reduce the surface leakage current of the device and improve the performance of the device.

[0052] Next, a refrigerated infrared detector and a preparation method thereof according to the present invention will be described in more detail with reference to the schematic diagrams. The preferred embodiments of the present invention are shown, and it should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a broad guidance for those skilled in the art and not as a limitation to the present invention.

[0053] For clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not described in detail because they would obscure the present invention with unnecessary details. It should be considered that in the development of any actual embodiment, a large number of implementation details must be made to achieve the specific goals of the developer, such as changing from one embodiment to another according to the relevant system or commercial limitations. Additionally, it should be considered that such development work may be complex and time-consuming, but it is only routine work for those skilled in the art.

[0054] In the following paragraphs, the present invention will be described more specifically by way of example with reference to the accompanying drawings. The advantages and features of the present invention will be clearer according to the following description and the claims. It should be noted that the drawings are all in a very simplified form and use non-precise scales, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0055] Figure 2 is a flowchart of a preparation method of a refrigerated infrared detector according to an embodiment of the present invention. As Figure 2As shown, this embodiment provides a method for manufacturing a refrigerated infrared detector, including the following steps:

[0056] Step S21: Provide a substrate on which a superlattice composite layer is formed.

[0057] Step S22: Perform a first cleaning and surface treatment process on the surface of the substrate.

[0058] Step S23: Form a first passivation layer on the superlattice composite layer.

[0059] Step S24: Form a hard mask layer with an opening on the first passivation layer. Using the hard mask layer as a mask, etch the first passivation layer and the superlattice composite layer in sequence, and stop etching in the superlattice composite layer to form a trench and a mesa, and remove the hard mask layer.

[0060] Step S25: Perform a second cleaning and surface treatment process on the surface of the substrate.

[0061] Step S26: Form a second passivation layer on the first passivation layer, and the second passivation layer also covers the trench and the mesa.

[0062] Step S27: Etch the first passivation layer and the second passivation layer to form an opening, and form a metal electrode in the opening.

[0063] The following Figure 2 to Figure 3e Specifically illustrate a method for manufacturing a refrigerated infrared detector.

[0064] Figure 3a is a schematic structural diagram of the substrate provided in this embodiment. As Figure 3a shown, first, perform step S1 to provide a substrate 1 on which a superlattice composite layer 120 is formed.

[0065] The substrate 1 includes a compound substrate 100 and a buffer layer 110. In this embodiment, the materials of the compound substrate 100 and the buffer layer 110 both include indium phosphide (InP) for example. The buffer layer 110 can be a buffer layer doped with impurities or a buffer layer not doped with impurities. In other embodiments, the material of the compound substrate includes gallium arsenide (GaAs) for example, and the material of the buffer layer includes gallium antimonide (GaSb) for example.

[0066] The superlattice composite layer 120 includes a p-type superlattice structure layer and an n-type superlattice structure layer formed in sequence on the substrate 1. In this embodiment, the p-type superlattice structure includes a p-type heavily doped superlattice structure 121 and a p-type lightly doped superlattice structure 122 formed in sequence on the substrate 1, and the n-type superlattice structure layer includes an n-type lightly doped superlattice structure 123 and an n-type heavily doped superlattice structure 124 formed in sequence on the p-type superlattice structure layer. In other embodiments, the p-type superlattice structure includes a p-type heavily doped superlattice structure and a p-type lightly doped superlattice structure formed in sequence on the substrate, and the n-type superlattice structure layer includes an n-type heavily doped superlattice structure.

[0067] This step includes: growing the superlattice composite layer 120 on the substrate 1 by methods such as MOCVD (Metal-organic Chemical Vapor Deposition) or MBE (Molecular Beam Epitaxy).

[0068] Please continue to refer to FIG. 1, and then execute step S22 to perform a first cleaning and surface treatment process on the surface of the substrate 1 to remove damage on the surface of the substrate 1, as well as charge accumulation and dangling bonds on the surface of the substrate 1.

[0069] In this step, the first cleaning and surface treatment process is performed on the surface of the substrate 1 in a PECVD (Plasma Enhanced Chemical Vapor Deposition) or ALD (Atomic Layer Deposition) device. The first cleaning and surface treatment process is, for example, to clean the surface of the substrate 1 with a plasma gas. Specifically, the surface of the substrate 1 is cleaned with a plasma of hydrogen (H2) or other inert gases to increase the adhesion ability of the surface of the superlattice composite layer 120. In this embodiment, for example, a plasma gas containing hydrogen is introduced, and the flow rate of hydrogen is greater than 10 sccm, specifically, for example, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, etc., and the process time is, for example, greater than 200 seconds (S), specifically, for example, 200 S, 500 S, 550 S, 600 S, 650 S, 700 S, etc.

[0070] Figure 3b It is a schematic structural diagram after forming the first passivation layer in this embodiment. As Figure 3bAs shown, step S23 is then executed to form a first passivation layer 210 on the superlattice composite layer 120. Specifically, the first passivation layer 210 is grown on the superlattice composite layer 120 by means of electroplating (i.e., sulfidation), ALD, CVD, PVD, etc. In this step, the material of the first passivation layer 210 grown by electroplating is elemental sulfur; the material of the first passivation layer 210 grown by ALD is sulfide (zinc sulfide), aluminum nitride, aluminum oxide, hafnium oxide, etc.; the material of the first passivation layer 210 grown by CVD or PVD is a high dielectric material such as silicon oxide, silicon nitride (Si3N4). It can be seen that a surface passivation protection layer (the first passivation layer 210) is first grown on the superlattice composite layer 120, which serves as a protection layer for the device (cooling infrared detector) to prevent the surface of the device from being damaged in subsequent processes, which is conducive to better implementation of subsequent processes. For example, the surface of the device will not be contaminated or damaged in subsequent processes. Among them, the thickness of the first passivation layer 210 is 30 nm to 300 nm. In other embodiments, the material of the first passivation layer 210 can also be a metal material, so that the charges and damages generated in subsequent processes are concentrated on the first passivation (protection) layer and the interface. After the process is completed, all damages, contaminations or attachments are removed together with the metal.

[0071] Figure 3c This is a schematic structural diagram of the trench and mesa formed in this embodiment. As Figure 3c shown, step S24 is then executed to form a hard mask layer with an opening (not shown in the figure) on the first passivation layer 210. Using the hard mask layer as a mask, the first passivation layer 210 and the superlattice composite layer 120 are etched in sequence, and the etching stops in the superlattice composite layer 120 to form a trench 131 and a mesa 132, and the remaining hard mask layer is removed. The first passivation layer 210 can be used as a barrier layer during the etching process of the hard mask layer to protect the surface of the structure (substrate) below the first passivation layer 210 from being over-etched and damaged.

[0072] This step specifically includes the following steps:

[0073] First, a hard mask layer is formed on the first passivation layer 210. Specifically, a hard mask layer is generated on the first passivation layer 210 by PECVD or ICPCVD (inductively coupled plasma chemical vapor deposition equipment). The material of the hard mask layer is, for example, silicon oxide, and the thickness of the hard mask layer is 0.5 μm to 1.5 μm.

[0074] Next, a patterned photoresist layer is formed on the hard mask layer, and the hard mask layer is etched using the patterned photoresist layer as a mask, such that the hard mask layer has openings for forming subsequent trenches 131 and mesa 132. In this step, the first passivation layer 210 can serve as a barrier layer during the etching of the hard mask layer, protecting the structures below the first passivation layer 210 from over-etching and damage. In this step, the first passivation layer 210 can be removed (for example, when the first passivation layer is made of a high-k dielectric material); it can also not be removed. In this embodiment, the first passivation layer 210 is not removed to reduce the etching time and steps.

[0075] Next, using the patterned photoresist layer and hard mask layer as masks, the first passivation layer 210 and the superlattice composite layer 120 are etched in sequence, and the etching is stopped within the superlattice composite layer 120 to form trenches 131 and mesa 132. In this embodiment, the etching of both the trenches 131 and mesa 132 is stopped within the p-type heavily doped superlattice structure. Since the substrate 1 includes multiple arrayed cooled infrared detection chips, adjacent chips are separated by scribing channels, and each chip includes at least one trench 131 and one mesa 132. The trench 131 has a bottom wall and closed sidewalls, such that the cross-sectional shape of the trench is U-shaped, and the mesa 132 has a bottom wall and non-closed sidewalls, such that the cross-sectional shape of the mesa is L-shaped, that is, the side of the mesa 132 adjacent to the scribing channel is without a sidewall. It should be noted that for ease of illustration, this embodiment only includes one cooled infrared detection chip, and this chip includes one trench and one mesa.

[0076] Next, the remaining photoresist layer and hard mask layer are removed. Specifically, the photoresist layer is removed by ashing; the hard mask layer can be removed by a dry etching process, specifically a plasma etching process. When the material of the first passivation layer is a metal material, this passivation layer needs to be removed after removing the hard mask layer to completely remove the accumulated charges, defects, and attachments on the surface of the first passivation layer. Please continue to refer to Figure 3c , and then step S25 is executed to perform a second cleaning and surface treatment process on the surface of the substrate 1.

[0077] In this step, a second cleaning and surface treatment process is performed on the surface of the substrate 1 in a PECVD (Plasma Enhanced Chemical Vapor Deposition) or ALD (Atomic Layer Deposition) device. The second cleaning and surface treatment process is, for example, cleaning the surface of the substrate 1 with a plasma gas. Specifically, the surface of the substrate 1 is cleaned with a plasma of hydrogen (H2) or other inert gases to increase the adhesion ability of the surface of the superlattice composite layer 120, while reducing the dangling bonds on the surface of the superlattice composite layer 120, improving the interface state of the device, and at the same time increasing the adhesion ability of the subsequently formed first passivation layer, reducing the surface leakage current, and improving the performance of the device. The second cleaning and surface treatment process is, for example, carried out in a vacuum reaction chamber, and a plasma gas of hydrogen or other inert gases is introduced into the reaction chamber. The specific flow rate and process time of the introduced plasma are determined according to the specific process. In this embodiment, for example, a plasma gas of hydrogen is introduced, and the flow rate of hydrogen is greater than 10 sccm, specifically, for example, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, etc., and the process time is, for example, greater than 400 seconds (S), specifically, for example, 400 S, 500 S, 550 S, 600 S, 650 S, 700 S, etc.

[0078] Figure 3d This is a schematic structural diagram after forming the second passivation layer in this embodiment. As Figure 3d shown, then step S26 is executed to form a second passivation layer 220 on the first passivation layer 210, and the second passivation layer 220 also covers the trench 131 and the mesa 132. At this time, a first passivation layer 210 and a second passivation layer 220 are formed on the refrigerated infrared detector chip, forming a double passivation layer, which further reduces the surface leakage current. The thickness of the second passivation layer 220 includes but is not limited to 200 nm to 5000 nm. In this embodiment, the second passivation layer 220 is deposited and formed on the first passivation layer 210 by an ALD process in an ALD device. The second passivation layer 220, for example, includes passivation materials such as aluminum nitride, aluminum oxide, and hafnium oxide. In other embodiments, the second passivation layer can be formed by other several conventional passivation methods such as sulfidation, and its materials are silicon dioxide, silicon nitride, HfO, SU8, PI, etc. In other embodiments, the first passivation layer is removed, and a third passivation layer can be formed before the second passivation layer is formed, and the passivation effect of this passivation layer is better than that of the first passivation layer.

[0079] In this embodiment, a cleaning and surface treatment process is performed before forming the passivation layer each time, so that the passivation layer has good adhesion ability when formed.

[0080] Figure 3e It is a schematic structural diagram after forming the second passivation layer in this embodiment. As Figure 3e shown, then step S27 is performed, etching the first passivation layer 210 and the second passivation layer 220 to form an opening, and forming a metal electrode 300 in the opening.

[0081] This step specifically includes the following steps:

[0082] First, etch the first passivation layer 210 and the second passivation layer 220, and expose the superlattice composite layer 120 to form an opening. In this embodiment, through a dry etching process or a wet etching process, the second passivation layer 220 and the first passivation layer 210 are etched in sequence, and a part of the surface of the n-type heavily doped superlattice structure 124 is exposed to form a first opening; the second passivation layer 220 is etched to expose a part of the surface of the p-type heavily doped superlattice structure 121 in the trench 131 and the mesa 132 to form a second opening. The first opening is used to form a first metal electrode, and the second opening is used to form a second metal electrode.

[0083] Optionally, after forming the opening, an annealing process is performed on the substrate 1; or, a third cleaning and surface treatment process is performed on the surface of the substrate 1 to increase the surface adhesion ability of the exposed superlattice composite layer 120, improve the surface state of the device, and enhance the ohmic contact. Specifically, when performing the annealing process on the surface of the substrate 1, the annealing temperature is 150°C to 350°C. Or, a third cleaning and surface treatment process is performed on the surface of the substrate 1. The third cleaning and surface treatment process is, for example, carried out in a vacuum reaction chamber, and a plasma of hydrogen or other inert gas is introduced into the reaction chamber. The specific flow rate of the introduced plasma and the process time are determined according to the specific process. In this embodiment, a plasma gas of hydrogen is introduced, and the flow rate of hydrogen is greater than 10 sccm, specifically, for example, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, etc., and the process time is, for example, greater than 400 seconds (S), specifically, for example, 400 S, 500 S, 550 S, 600 S, 650 S, 700 S, etc.

[0084] Then, a metal electrode 300 is formed in the opening. A first metal electrode is formed at the first opening, and a second metal electrode 320 is formed at the second opening. The metal electrode has good contact with the superlattice composite layer 120, reduces the surface leakage current, and improves the performance of the device.

[0085] A method for manufacturing a cooled infrared detector according to this embodiment increases the adhesion ability of the device surface, reduces the surface leakage current, and improves the device performance by forming a double passivation layer, performing a cleaning and surface treatment process before forming each passivation layer, and performing a cleaning and surface treatment process or an annealing process after forming the opening.

[0086] As Figure 3e shown, this embodiment further provides a cooled infrared detector, including a substrate 1 and a superlattice composite layer 120 formed on the substrate 1. Grooves 131 and mesa 132 are formed in the superlattice composite layer 120, and both the grooves 131 and the mesa 132 expose a part of the depth of the superlattice composite layer 120. A first passivation layer 210 and a second passivation layer 220 are sequentially formed on the superlattice composite layer 120 outside the grooves. A first opening is formed in the first passivation layer 210 and the second passivation layer 220, and a first metal electrode 310 is formed in the first opening; the grooves 131 and the mesa 132 are covered with the second passivation layer 220, and a second opening is formed in the second passivation layer 220 in the grooves 131 and the mesa 132, and a second metal electrode 320 is formed in the second opening.

[0087] In summary, in a cooled infrared detector and a method for manufacturing the same provided by the present invention, the manufacturing aspect includes the following steps: providing a substrate on which a superlattice composite layer is formed; performing a first cleaning and surface treatment process on the surface of the substrate; forming a first passivation layer on the superlattice composite layer; forming a hard mask layer with an opening on the first passivation layer, using the hard mask layer as a mask, etching the first passivation layer and the superlattice composite layer in sequence, and stopping the etching in the superlattice composite layer to form grooves and mesa, and removing the hard mask layer; performing a second cleaning and surface treatment process on the surface of the substrate; forming a second passivation layer on the first passivation layer, and the second passivation layer also covers the grooves and mesa; etching the first passivation layer and the second passivation layer to form openings, and forming metal electrodes in the openings. By performing a cleaning and surface treatment process before forming each passivation layer, on the one hand, the surface charges and attachments brought by other process steps are removed, the accumulation of defects and charges is reduced, the interface states are optimized, thereby reducing the dangling bonds and the tunneling current caused by defects. On the other hand, the passivation layer has good adhesion ability and compactness when formed, and forming the first passivation layer and the second passivation layer can reduce the surface leakage current of the device and improve the device performance.

[0088] Further, after forming the opening, an annealing process is performed on the substrate; or, a third cleaning and surface treatment process is performed on the surface of the substrate to increase the surface adhesion ability of the exposed superlattice composite layer, while improving the surface states of the device and enhancing the ohmic contact.

[0089] In addition, it should be noted that unless otherwise specified or indicated, the descriptions of the terms "first", "second", and "third" in the specification are only used to distinguish between various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship between various components, elements, steps, etc.

[0090] It can be understood that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or it can be modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a refrigerated infrared detector, characterized in that, It includes the following steps: Provide a substrate, on which a superlattice composite layer is formed; Perform a first cleaning and surface treatment process on the surface of the substrate through a plasma gas in a PECVD device or an ALD device; Form a first passivation layer on the superlattice composite layer; Form a hard mask layer with an opening on the first passivation layer. Using the hard mask layer as a mask, etch the first passivation layer and the superlattice composite layer in sequence, and stop etching in the superlattice composite layer to form trenches and mesa, and remove the hard mask layer; Perform a second cleaning and surface treatment process on the surface of the substrate through a plasma gas in a PECVD device or an ALD device; Form a second passivation layer on the first passivation layer, and the second passivation layer also covers the trenches and mesa; Etch the first passivation layer and the second passivation layer to form an opening, and form a metal electrode in the opening; 2. The preparation method according to claim 1, wherein Forming a first passivation layer on the superlattice composite layer includes: The first passivation layer is grown on the superlattice composite layer by electroplating, ALD, CVD or PVD.

3. The preparation method according to claim 2, characterized in that, The materials of the first passivation layer grown by electroplating include sulfides and fluorides; the materials of the first passivation layer grown by ALD include aluminum nitride, aluminum oxide, and hafnium oxide; the materials of the first passivation layer grown by PVD or CVD include silicon oxide and silicon nitride.

4. The preparation method according to claim 3, wherein, The thickness of the first passivation layer is 30nm to 500nm.

5. The preparation method according to claim 1, characterized in that, Form a hard mask layer with an opening on the first passivation layer. Using the hard mask layer as a mask, etch the first passivation layer and the superlattice composite layer in sequence, and stop etching in the superlattice composite layer to form trenches and mesa, and remove the hard mask layer includes: Form a hard mask layer on the first passivation layer; Form a patterned photoresist layer on the hard mask layer, and using the patterned photoresist layer as a mask, etch the hard mask layer so that the hard mask layer has an opening, and the opening is used to form subsequent trenches and mesa; Using the patterned photoresist layer and the hard mask layer as a mask, etch the first passivation layer and the superlattice composite layer in sequence, and stop etching in the superlattice composite layer to form trenches and mesa; Remove the remaining photoresist layer and the hard mask layer.

6. The preparation method according to claim 1, wherein Performing a second cleaning and surface treatment process on the surface of the substrate includes: In a vacuum reaction chamber, clean and pre-treat the surface of the substrate with hydrogen.

7. The preparation method according to claim 6, characterized in that, In the second cleaning and surface treatment process, the flow rate of hydrogen is greater than 10sccm, and the process time is greater than 200 seconds.

8. The preparation method according to claim 1, characterized in that, Etch the first passivation layer and the second passivation layer to form an opening, and form a metal electrode in the opening includes: Etch the first passivation layer and the second passivation layer to expose the superlattice composite layer to form an opening; After forming the opening, perform an annealing process on the substrate; or, perform a third cleaning and surface treatment process on the surface of the substrate; Form a metal electrode in the opening.

9. A refrigerated infrared detector, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. The refrigerated infrared detector according to claim 9, characterized in that, It includes a substrate and a superlattice composite layer formed on the substrate. Grooves and mesa are formed in the superlattice composite layer, and both the grooves and the mesa expose a part of the depth of the superlattice composite layer. A first passivation layer and a second passivation layer are sequentially formed on the superlattice composite layer outside the grooves. The first passivation layer and the second passivation layer have a first opening, and a first metal electrode is formed in the first opening; The grooves and the mesa are covered with a second passivation layer. The second passivation layer in the grooves and the mesa has a second opening, and a second metal electrode is formed in the second opening.

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