Refrigerated infrared detector and method of manufacturing the same

Abstract

The application provides a refrigeration infrared detector and a preparation method thereof, and the preparation method comprises the following steps: providing a mercury cadmium telluride substrate, the surface of the mercury cadmium telluride substrate is covered with a lattice transition layer, an insulating protective layer and a sacrifice layer are formed on the lattice transition layer in sequence; an ion implantation process is performed by using a patterned mask layer to form an ion implantation area in the mercury cadmium telluride substrate; the patterned mask layer and the sacrifice layer are removed; a metal electrode is formed above the ion implantation area, the metal electrode penetrates through the insulating protective layer and the lattice transition layer, and the metal electrode is electrically connected to the ion implantation area. In the application, the initial interface state of the surface of the mercury cadmium telluride substrate is protected by using the lattice transition layer, the adverse effect of the ion implantation process on the mercury cadmium telluride substrate is reduced by using the sacrifice layer, the lattice transition layer is protected by using the insulating protective layer in the subsequent process, the manufacturing yield is improved, and the risk of electric leakage caused by the contamination or damage of the interface state of the mercury cadmium telluride substrate is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a refrigeration infrared detector and a preparation method thereof. BACKGROUND

[0002] With the continuous popularization and development of infrared application, advanced infrared detection technology requires the detector to have higher spatial resolution and better target recognition capability. The infrared detector is an optoelectronic device that converts infrared radiation into electronic signals. The photoelectric reaction only occurs on the photosensitive element, and the subsequent signal processing process only involves electronic technology. Therefore, the infrared detection chip is the core element of the infrared detector.

[0003] Taking the formation of a mercury cadmium telluride (MCT) infrared detection chip on a mercury cadmium telluride substrate as an example, the existing mercury cadmium telluride infrared detection chip has a low yield and is prone to leakage problems. SUMMARY

[0004] The present application aims to provide a refrigeration infrared detector and a preparation method thereof, so as to improve the manufacturing yield of the refrigeration infrared detector and reduce the risk of leakage.

[0005] To solve the above technical problems, the preparation method of the refrigeration infrared detector provided by the present application comprises the following steps: providing a mercury cadmium telluride substrate, the surface of the mercury cadmium telluride substrate is covered with a lattice transition layer, the lattice transition layer is matched with the lattice of the mercury cadmium telluride substrate or the stress is matched; forming an insulating protective layer and a sacrificial layer on the lattice transition layer in sequence; forming a patterned mask layer on the sacrificial layer, and performing an ion implantation process by using the patterned mask layer to form an ion implantation region in the mercury cadmium telluride substrate; removing the patterned mask layer and the sacrificial layer; forming a metal electrode above the ion implantation region, the metal electrode penetrates through the insulating protective layer and the lattice transition layer, and the metal electrode electrically leads out the ion implantation region.

[0006] Optionally, the material of the lattice transition layer comprises zinc sulfide and / or cadmium telluride.

[0007] Optionally, the relative dielectric constant of the insulating protective layer is greater than 3.9.

[0008] Optionally, the material of the insulating protective layer comprises aluminum nitride, silicon nitride or silicon carbide.

[0009] Optionally, the material of the sacrificial layer comprises one or a combination of at least two of polysilicon, amorphous silicon, silicon oxide or germanium silicon.

[0010] Optionally, the process temperature for forming the insulating protective layer and forming the sacrificial layer is less than 150 DEG C.

[0011] Optionally, the step of forming the metal electrode comprises: forming an opening in the insulating protective layer and the lattice transition layer, the opening exposing the ion implantation region; performing a plasma pretreatment process and / or a wet cleaning process on the opening, and forming a metal barrier layer covering the inner wall of the opening; forming the metal electrode to fill the opening, and the metal electrode protruding out of the opening.

[0012] Optionally, a cross section of the opening along a direction perpendicular to the HgCdTe substrate is in a reverse trapezoidal shape.

[0013] Optionally, a top surface of the metal electrode is concave.

[0014] Based on another aspect of the present application, a refrigeration infrared detector is also provided, which is prepared by the preparation method of the refrigeration infrared detector as described above.

[0015] In summary, the present application forms a lattice transition layer, an insulating protective layer and a sacrificial layer on the surface of a HgCdTe substrate, uses the lattice transition layer to protect the initial interface state of the surface of the HgCdTe substrate, uses the sacrificial layer as a first layer for ion implantation and removes the sacrificial layer after the ionization implantation process, thereby reducing the adverse effects of the ion implantation process on the HgCdTe substrate, and the lattice transition layer and the insulating protective layer are not removed in subsequent process manufacturing, and the insulating protective layer is used to protect the lattice transition layer, thereby preventing the surface of the HgCdTe substrate from being contaminated or damaged to protect the initial interface state, thereby improving the manufacturing yield of the refrigeration infrared detector and reducing the risk of electric leakage caused by contamination or damage of the interface state of the HgCdTe substrate. BRIEF DESCRIPTION OF DRAWINGS

[0016] Those skilled in the art will understand that the drawings provided are for a better understanding of the present application, and do not constitute any limitation on the scope of the present application.

[0017] Figure 1 A flowchart of the preparation method of the refrigeration infrared detector provided in the present embodiment is provided;

[0018] Figures 2 to 8 A structure schematic diagram corresponding to the respective steps of the preparation method of the refrigeration infrared detector provided in the present embodiment is provided.

[0019] In the drawings:

[0020] 10 - substrate; 11 - ion implantation region; 21 - lattice transition layer; 22 - insulating protective layer; 23 - sacrificial layer; 24 - patterned mask layer; 25 - first opening;

[0021] 26 - second opening; 31 - metal barrier layer; 32 - patterned photoresist layer; 33 - third opening; 34 - metal electrode. DETAILED DESCRIPTION

[0022] In order to make the objects, advantages and features of the present application more clearly, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that all the drawings are very simplified and not drawn according to scale, and are only used to facilitate and clearly assist the purpose of describing the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis shown in each drawing is different, and sometimes different scales are used.

[0023] As used in the present application, the singular forms "a", "an" and "the" include plural referents, the term "or" is generally used in the sense of "and / or", the term "several" is generally used in the sense of "at least one", the term "at least two" is generally used in the sense of "two or more", and in addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third" can explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0024] Figure 1 A flowchart of the preparation method of the refrigeration infrared detector provided in the present embodiment is shown.

[0025] As shown in Figure 1 The preparation method of the refrigeration infrared detector provided in the present embodiment comprises:

[0026] S01: providing a mercury cadmium telluride substrate, a lattice transition layer is covered on the surface of the mercury cadmium telluride substrate, and the lattice transition layer is matched with the lattice of the mercury cadmium telluride substrate or stress matched;

[0027] S02: sequentially forming an insulating protective layer and a sacrificial layer on the lattice transition layer;

[0028] S03: forming a patterned mask layer on the sacrificial layer, performing an ion implantation process by using the patterned mask layer, and forming an ion implantation region in the mercury cadmium telluride substrate;

[0029] S04: removing the patterned mask layer and the sacrificial layer;

[0030] S05: forming a metal electrode, the metal electrode penetrates through the insulating protective layer and the lattice transition layer, and the metal electrode electrically leads out the ion implantation region.

[0031] Figures 2 to 8 is the structure schematic diagram corresponding to the corresponding step of the preparation method of the refrigeration infrared detector provided in the present application. Next, the preparation method of the refrigeration infrared detector provided in the present embodiment will be described in combination with Figures 2 to 8The method for manufacturing the refrigeration infrared detector is described in detail.

[0032] Firstly, referring to Figure 2 , step S01 is performed to provide a mercury cadmium telluride substrate 10, and a lattice transition layer 21 is formed on the surface of the mercury cadmium telluride substrate 10, and the lattice transition layer 21 is matched with the lattice of the mercury cadmium telluride substrate 10 or is stress matched with the mercury cadmium telluride substrate 10.

[0033] The mercury cadmium telluride substrate 10 can be a substrate formed of mercury cadmium telluride material or a substrate covered with mercury cadmium telluride material with a certain thickness, and the conductivity type of the mercury cadmium telluride substrate 10 can be N type or P type and has any suitable doping concentration.

[0034] The lattice transition layer 21 is formed on the mercury cadmium telluride material of the mercury cadmium telluride substrate 10 and is matched with the lattice of the mercury cadmium telluride material as much as possible (for example, the lattice parameters are matched), so as to protect the initial interface state of the surface of the mercury cadmium telluride substrate 10 (the mercury cadmium telluride material), and the material of the lattice transition layer 21 can be cadmium telluride, for example. In another embodiment, the lattice transition layer 21 can also be a material matched with the stress of the mercury cadmium telluride substrate 10 (matched with the Young's modulus), such as zinc sulfide. The thickness of the lattice transition layer 21 can be 500 angstroms to 5000 angstroms, and in the process of forming the lattice transition layer 21, the process temperature can be lower than 150°C, for example, so as to reduce the stress of the lattice transition layer 21 and ensure better adhesion of the lattice transition layer 21 to the mercury cadmium telluride substrate 10. In a preferred embodiment, the lattice transition layer 21 can also be a double-layer structure of a cadmium telluride layer and a zinc sulfide layer to improve the protection effect, wherein the cadmium telluride layer can be formed in situ to cover the mercury cadmium telluride substrate 10, and then the zinc sulfide layer is formed to cover the cadmium telluride layer.

[0035] Next, referring to Figure 2 , the insulating protective layer 22 and the sacrificial layer 23 are sequentially formed on the lattice transition layer 21, the insulating protective layer 22 covers the lattice transition layer 21, and the sacrificial layer 23 covers the insulating protective layer 22.

[0036] The materials of the insulating protective layer 22 and the sacrificial layer 23 are different. The insulating protective layer 22 can be a material with better electrical insulation performance and better physical and chemical protection performance, which is used to protect the lattice transition layer 21 and the mercury cadmium telluride substrate 10 in subsequent processes such as ion implantation and etching, and the sacrificial layer 23 can be a material that is easier to remove, which is used as a barrier layer for subsequent ion implantation. The thickness of the insulating protective layer 22 can be 300 angstroms to 2000 angstroms, and the thickness of the sacrificial layer 23 can be 500 angstroms to 5000 angstroms. In a specific embodiment, the thickness of the lattice transition layer 21 can be 2000 angstroms, the thickness of the insulating protective layer 22 can be 800 angstroms, and the thickness of the sacrificial layer 23 can be 1000 angstroms.

[0037] Further, the insulating protective layer 22 can be a dielectric layer with a high dielectric constant, which can be greater than 3.9 (the dielectric constant of silicon dioxide is 3.9), and the material of the insulating protective layer 22 can be, for example, aluminum nitride, silicon carbide, or silicon nitride, so that the insulating protective layer 22 has better electrical insulation performance and physical and chemical stability. The material of the sacrificial layer 23 can be, for example, one of polysilicon, amorphous silicon, silicon oxide, or germanium silicon, or a combination of at least two of them.

[0038] Further, the insulating protective layer 22 and the sacrificial layer 23 can be formed by a low-temperature process to reduce the stress of the insulating protective layer 22, so that it has better adhesion, and at the same time, prevent the thermal budget from affecting other film layers. The low-temperature process for forming the insulating protective layer 22 and the sacrificial layer 23 can be, for example, a PECVD process with a process temperature lower than 150°C.

[0039] Next, referring to Figure 3 A patterned mask layer 24 is formed on the sacrificial layer 23, and an ion implantation process is performed using the patterned mask layer 24 to form an ion implantation region 11 in the tellurium cadmium mercury substrate 10.

[0040] Specifically, the patterned mask layer 24 can be a patterned photoresist layer 32, which has a first opening 25, and an ion implantation process is performed on the tellurium cadmium mercury substrate 10 using the first opening 25 to form an ion implantation region 11 in the tellurium cadmium mercury substrate 10, which has a conductivity type opposite to that of the tellurium cadmium mercury substrate 10, and thus forms a PN structure in the tellurium cadmium mercury substrate 10 as a sensitive (detection) element of the refrigeration infrared detector. The energy and depth of ion implantation can be determined according to the material and thickness of the lattice transition layer 21, the insulating protective layer 22, and the sacrificial layer 23, and combined with the design requirements of the sensitive element. Of course, the thickness of the patterned mask layer 24 matches the energy of ion implantation, that is, the greater the energy of ion implantation, the thicker the thickness of the patterned mask layer 24. In addition, in the first opening 25, ion implantation is performed through the sacrificial layer 23 and the insulating protective layer 22, which is beneficial to reduce the channeling effect of ion implantation, and can minimize the damage of ion implantation to the ion implantation region 11 in the tellurium cadmium mercury substrate 10. It should be understood that the sacrificial layer 23 and the insulating protective layer 22 as the first layer and the second layer of ion implantation can absorb more energy in the ion implantation process, so as to reduce the damage of the ion implantation process to the tellurium cadmium mercury substrate 10.

[0041] In one embodiment, the thickness of the lattice transition layer 21 can be 2000 angstroms, the thickness of the insulating protective layer 22 can be 800 angstroms, the thickness of the sacrificial layer 23 can be 1000 angstroms, the thickness of the patterned photoresist layer 32 can be 1-6 microns, and preferably 1.8 microns.

[0042] Next, referring to Figure 4 , the patterned mask layer 24 and the sacrificial layer 23 are removed.

[0043] Specifically, any suitable process can be used to remove the patterned mask layer 24 and the sacrificial layer 23, such as a wet process or a dry process. During the removal of the patterned mask layer 24, the sacrificial layer 23 can be used to protect the insulating protective layer 22 and the layers below from the removal process. During the removal of the sacrificial layer 23, the sacrificial layer 23 can be used to protect the lattice transition layer 21 and the mercury cadmium telluride substrate 10 from the removal process due to the sacrificial layer 23's easy removal and the insulating protective layer 22's blocking.

[0044] Next, a metal electrode 34 is formed, which penetrates the insulating protective layer 22 and the lattice transition layer 21, and the metal electrode 34 electrically connects to the ion implantation region 11 of the mercury cadmium telluride substrate 10.

[0045] The specific formation steps can be, for example, as follows: First, referring to Figure 5A second opening 25 is formed in the insulation protective layer 22 and the lattice transition layer 21, and the second opening 25 exposes the ion implantation region 11 of the tellurium cadmium mercury substrate 10. Preferably, the cross-sectional shape (in the depth direction of the second opening 25) of the second opening 25 can be an inverted trapezoid, which is beneficial for the subsequent filling of the material (e.g. the metal barrier layer and the metal electrode) in the second opening 25, guarantees the step coverage, and on the other hand, can prevent the under cut and reduce the risk of electric leakage. The above-mentioned inverted trapezoidal second opening 25 can be formed by utilizing the material difference between the insulation protective layer 22 and the lattice transition layer 21, and the characteristics of the dry etching process and the wet etching process. For example, the wet etching process is first used to form an opening in the insulation protective layer 22 to improve the efficiency of forming the opening, and then the dry etching process is used to remove the lattice transition layer 21 under the opening, and the anisotropy of the dry etching process is utilized to form the inverted trapezoidal second opening 25. It can be understood that even if the under cut phenomenon occurs during the wet etching of the insulation protective layer 22, the morphology of the sidewall can be corrected by the subsequent ion bombardment of the dry etching process, and the under cut phenomenon will not occur during the dry etching of the lattice transition layer 21.

[0046] Next, please refer to Figure 6 The plasma pretreatment process and / or the wet cleaning process are performed on the second opening 25 to remove the contaminants caused in the above-mentioned process, and then the metal barrier layer 31 is formed in the second opening 25, the metal barrier layer 31 covers the inner wall of the second opening 25 and forms an electrical connection with the ion implantation region 11. The plasma pretreatment process can use one or more of oxygen, hydrogen, nitrogen, nitrogen or argon plasma; and the cleaning solution used in the wet cleaning process can be hydrochloric acid or ammonia. In practice, the metal barrier layer 31 can also extend to cover the surface of the insulation protective layer 22 around the second opening 25 to increase the contact area. The metal barrier layer 31 is used to block the electromigration of the metal electrode 34 into the insulation protective layer 22 and the lattice transition layer 21, and the material of the metal barrier layer 31 can be metal, alloy metal or metal nitride. In a preferred embodiment, the step of forming the metal barrier layer 31 on the inner wall of the second opening 25 includes: first forming a patterned photoresist layer (e.g. lift-off photoresist) to cover the surface of the insulation protective layer, the opening of the patterned photoresist layer exposes the region of the insulation protective layer where the metal barrier layer is to be formed, then forming a metal barrier material layer to cover the patterned photoresist layer and the region where the metal barrier layer is to be formed, and then removing the patterned photoresist layer, which can also remove the metal barrier material layer on the patterned photoresist layer, and the remaining metal barrier material layer is used as the metal barrier layer 31.

[0047] Next, please refer to Figure 7The insulating protective layer 22 and the metal barrier layer 31 partially on the insulating protective layer 22 are covered by forming a patterned photoresist layer 32 (for example, a lift-off photoresist layer), the second opening 25 is covered by the patterned photoresist layer 32, and the third opening 33 is formed by the opening of the patterned photoresist layer 32, the third opening 33 is above the second opening 25, and the cross-sectional shape of the third opening 33 is a trapezoidal shape with a narrow top and a wide bottom, facilitating the peeling of the patterned photoresist layer 32.

[0048] Next, refer to Figure 8 The electrode material layer is formed to cover the surface of the patterned photoresist layer 32 and fill the second opening 25 and the third opening 33, and then the patterned photoresist layer 32 is removed, that is, the electrode material layer on the patterned photoresist layer 32 is removed together, so that the remaining electrode material layer serves as a metal electrode 34, and the ion implantation region 11 is electrically led out by the metal electrode 34. The metal electrode 34 protrudes from the insulating protective layer 22, the shape of the metal electrode 34 is the superposition of the shapes of the second opening 25 and the third opening 33, and the top surface of the metal electrode 34 is concave downward (concave), which is beneficial to subsequent flip-chip bonding. Preferably, the material of the electrode material layer can be metal indium, and the formed metal electrode 34 is an indium column.

[0049] It should be noted that when the metal electrode is formed to electrically lead out the ion implantation region, other metal electrodes can also be formed synchronously to electrically lead out the mercury cadmium telluride substrate, and the forming process of the metal electrodes can be similar to that of the metal electrode, which will not be described here.

[0050] The embodiment also provides a refrigeration infrared detector prepared by the preparation method of the refrigeration infrared detector.

[0051] In summary, the present application forms a lattice transition layer, an insulating protective layer and a sacrificial layer on the surface of the mercury cadmium telluride substrate, uses the lattice transition layer to protect the initial interface state of the surface of the mercury cadmium telluride substrate, uses the sacrificial layer as the first layer of ion implantation and removes the sacrificial layer after the ionization implantation process, thereby reducing the adverse effects of the ion implantation process on the mercury cadmium telluride substrate, and the lattice transition layer and the insulating protective layer are not removed in subsequent process manufacturing, and the insulating protective layer is used to protect the lattice transition layer, thereby preventing the surface of the mercury cadmium telluride substrate from being contaminated or damaged to protect the initial interface state, thereby improving the manufacturing yield of the refrigeration infrared detector and reducing the risk of electric leakage caused by the contamination or damage of the interface state of the mercury cadmium telluride substrate.

[0052] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way, and any modification or modification of the present application by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A method of fabricating a cryogenic infrared detector, comprising: The application relates to a preparation method of a refrigeration infrared detector. ​ A tellurium-cadmium-mercury substrate is provided, a surface of the tellurium-cadmium-mercury substrate is covered with a lattice transition layer which is matched with the lattice of the tellurium-cadmium-mercury substrate or stress matched; An insulating protective layer and a sacrifice layer are sequentially formed on the lattice transition layer, the insulating protective layer covers the lattice transition layer, the sacrifice layer covers the insulating protective layer, and the process temperature for forming the insulating protective layer is less than 150 DEG C; A patterned mask layer is formed on the sacrifice layer, an ion implantation process is performed by using the patterned mask layer to form an ion implantation region in the tellurium-cadmium-mercury substrate; The patterned mask layer and the sacrifice layer are removed; A metal electrode is formed above the ion implantation region, the metal electrode penetrates through the insulating protective layer and the lattice transition layer, and the metal electrode is electrically connected to the ion implantation region.

2. The method of claim 1, wherein the method further comprises: The material of the lattice transition layer comprises zinc sulfide and / or cadmium telluride.

3. The method of claim 1, wherein the method further comprises: The relative dielectric constant of the insulating protective layer is greater than 3.

9.

4. The method of claim 3, wherein the method further comprises: The material of the insulating protective layer comprises aluminum nitride, silicon nitride or silicon carbide.

5. The method of claim 1, wherein the method further comprises: The material of the sacrifice layer comprises one or a combination of two or more of polysilicon, amorphous silicon, silicon oxide and germanium silicon.

6. The method of claim 1, wherein the method further comprises: The process temperature for forming the sacrifice layer is less than 150 DEG C.

7. The method of claim 1, wherein the method further comprises: The step of forming the metal electrode comprises: An opening is formed in the insulating protective layer and the lattice transition layer, the opening exposes the ion implantation region; An ion implantation region is formed in the tellurium-cadmium-mercury substrate by using a patterned mask layer, and an ion implantation process is performed by using the patterned mask layer; The opening is subjected to a plasma pretreatment process and / or a wet cleaning process, and a metal barrier layer is formed to cover the inner wall of the opening; 8. The method of claim 7, wherein the method further comprises: The metal electrode fills the opening and protrudes from the opening.

9. The method of claim 7, wherein the method further comprises: The cross section of the opening along the direction perpendicular to the tellurium-cadmium-mercury substrate is in an inverted trapezoidal shape.

10. A refrigerated infrared detector, characterized by The top surface of the metal electrode is concave. The refrigeration infrared detector is prepared by using the preparation method of any one of claims 1 to 9.

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