Table-top tellurium-cadmium-mercury focal plane infrared detector device structure and preparation method thereof

Abstract

The invention discloses a mesa type tellurium-cadmium-mercury focal plane infrared detector device structure and a preparation method, and relates to the technical field of semiconductors, the device structure comprises a tellurium-cadmium-mercury chip (006), the tellurium-cadmium-mercury chip (006) comprises frustum-shaped mesa structures arranged in an array, one mesa structure corresponds to one mesa pixel, the surface of the mesa structure is covered with a passivation layer (005), and the passivation layer (005) is arranged on the surface of the mesa structure. And an electrode structure (003) is arranged on the upper surface of the mesa structure, the electrode structure (003) penetrates through the passivation layer through a first through hole to form ohmic contact with the tellurium-cadmium-mercury chip (006), and a metal electrode is arranged on the mesa structure. And the reading circuit (001) is connected with the tellurium-cadmium-mercury chip (006) through an indium column (002). Optical crosstalk caused by refraction and reflection is isolated by using the metal structure on the side wall of the pixel, and crosstalk is reduced by etching the mesa structure.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a table-type mercury cadmium telluride focal plane infrared detector device structure and a preparation method. Background Art

[0002] There are two main types of crosstalk between infrared focal plane detector pixels: optical and electrical. Optical crosstalk primarily occurs when the target pixel's signal reflects, refracts, or diffracts light off the device's surface, bottom, or within the detector's optical system, causing adjacent pixels to generate signal responses. Diffraction of light is primarily affected by the optical system, resulting in an Airy disk that extends beyond the size of a single pixel. Reflection and refraction primarily occur within the optical system, on the detector's surface, or bottom, causing adjacent pixels to generate signal responses. Electrical crosstalk primarily results from the lateral diffusion of photogenerated carriers, which are collected by adjacent pixels and generate signals.

[0003] Detector crosstalk can affect imaging. Under strong light, adjacent pixels can generate and collect large signals or even saturate. The main existing solutions to this problem include pixel-independent infrared detectors (US, US5304500A, 1994.04.19), (China, CN114664974A, 2022.06.24), tabletop infrared detectors (China, CN113013188A, 2021.06.22), tabletop dual-color infrared detectors (China, CN116387393A, 2023.07.04), (China, CN109244176 B, 2023.09.12), table-top avalanche infrared detector (China, CN109545883B, 2023.12.26), preparation of grid electrodes between passivation layers to solve surface leakage crosstalk caused by poor passivation quality (China, CN117038790A, 2023.11.10), and type II superlattice infrared detector with rationally designed absorption depth (China, CN115360257A, 2022.11.18), etc.

[0004] Detector crosstalk can affect imaging. As the detector pixel spacing decreases, the impact of crosstalk between pixels gradually increases, and the diffusion length of carriers approaches or even exceeds the pixel spacing, making crosstalk between pixels non-negligible. Under strong light conditions, when photogenerated carriers in detector pixels cannot be promptly removed and accumulate, the lateral movement of photogenerated carriers becomes more significant, generating significant photogenerated signals or even saturation in adjacent pixels without illumination. Summary of the Invention

[0005] The embodiment of the present application provides a table-type mercury cadmium telluride focal plane infrared detector device structure and preparation method, which uses the metal structure of the pixel sidewall to isolate the optical crosstalk caused by refraction and reflection, and reduces the crosstalk by etching the table structure.

[0006] The present invention provides a table-type mercury cadmium telluride focal plane infrared detector device structure, including:

[0007] A mercury cadmium telluride chip, comprising an array of prism-shaped mesa structures, each mesa structure corresponding to a mesa pixel, a surface of the mesa structure covered with a passivation layer, and an electrode structure disposed on the upper surface of the mesa structure, the electrode structure penetrating the passivation layer via a first through hole to form an ohmic contact with the mercury cadmium telluride chip, and a metal electrode disposed on the mesa structure;

[0008] The readout circuit is interconnected with the HgCdTe chip through the indium column.

[0009] The present application also provides a method for preparing the aforementioned mesa-type HgCdTe focal plane infrared detector device structure, comprising:

[0010] A sacrificial layer is prepared using mercury cadmium telluride material, and a prism-shaped mesa structure is prepared by photolithography and etching;

[0011] Corrosion removes the etched damaged layer and the sacrificial layer;

[0012] Cleaning and growth of passivation layer;

[0013] Performing heat treatment, forming holes by etching or corrosion after the heat treatment, and forming a PN junction by ion implantation in the P-type or N-type substrate;

[0014] Coating a photoresist, preparing a front electrode structure by photolithography and etching, and forming a through hole between the electrode structure and the passivation layer by etching to achieve ohmic contact between the electrode and the mercury cadmium telluride material;

[0015] Indium pillars are prepared by photolithography and metallization to achieve flip-chip interconnection with the readout circuit.

[0016] The embodiment of the present application utilizes the metal structure of the pixel sidewall to isolate the optical crosstalk caused by refraction and reflection, and reduces the crosstalk by etching the mesa structure.

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0019] Figure 1 This is a schematic diagram of the basic structure of the infrared detector device structure of an embodiment of the present application;

[0020] Figure 2 This is a schematic diagram of the basic structure of the infrared detector metal and through-hole structure of an embodiment of the present application;

[0021] Figure 3 This is a schematic diagram of the basic process of the method for preparing the infrared detector device structure according to an embodiment of the present application;

[0022] Figure 4 This is a level diagram of the device structure of a mercury cadmium telluride focal plane infrared detector prepared by the preparation method of an embodiment of the present application. DETAILED DESCRIPTION

[0023] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0024] The present application embodiment provides a table-type HgCdTe focal plane infrared detector device structure, such as Figure 1 Shown, including:

[0025] The mercury cadmium telluride chip 006 includes a prism-shaped mesa structure arranged in an array, where one mesa structure corresponds to one mesa pixel. The surface of the mesa structure is covered with a passivation layer 005, and an electrode structure 003 is provided on the upper surface of the mesa structure. The electrode structure 003 passes through the passivation layer via a first through-hole to form an ohmic contact with the mercury cadmium telluride chip 006. A metal electrode is provided on the mesa structure, and the metal electrode is disconnected on both the upper and lower sides of the mesa structure. In some examples, a back anti-reflection device 007 is present on the back of the mercury cadmium telluride chip detector.

[0026] The readout circuit 001 is interconnected with the HgCdTe chip 006 via the indium column 002, thereby forming a HgCdTe focal plane detector.

[0027] In a specific example, the metal and through-hole structures of the table-type HgCdTe focal plane infrared detector of the present application are as follows: Figure 2 Shown, including:

[0028] The second through hole 101, the second interconnection electrode 102, the third through hole 103, the first interconnection electrode 104, the first through hole 105 and the sidewall metal 106 structure.

[0029] In some embodiments, a filler 004 is provided between the mesa structure of the HgCdTe chip 006 of the array and the readout circuit 001 , and the filler 004 is used to ensure mechanical strength.

[0030] The embodiment of the present application utilizes the metal structure of the pixel sidewall to isolate the optical crosstalk caused by refraction and reflection, and reduces the crosstalk by etching the mesa structure.

[0031] In some embodiments, the size of the passivation through hole on the upper surface of the mesa structure is 1 micron to 5 microns. The passivation through hole is used to form a PN junction by ion implantation of mercury cadmium telluride through the passivation layer 005 and the photoresist as a mask.

[0032] In some specific examples, there is a sidewall metal 106 on the sidewall of the mesa structure, and the metal electrode is disconnected on both the upper and lower sides of the mesa. In some embodiments, the metal electrode provided on the mesa structure includes a first interconnect electrode 104 and a second interconnect electrode 102, wherein:

[0033] The first interconnect electrode 104 and the second interconnect electrode 102 are located above the table. A first through-hole 105 exists in the area where the first interconnect electrode contacts the table. A second through-hole 101 exists in the area where the second interconnect electrode 102 contacts the table. A third through-hole exists in the area where the second interconnect electrode 102 contacts the substrate. No implantation is performed in the areas of the second through-hole 101 and the third through-hole 103.

[0034] In some embodiments, the through hole is in the shape of a square, a bar, a frame or a pie;

[0035] The interconnecting electrode is a combination of one or more shapes such as square, strip, frame or pie. The width of the interconnecting electrode is 3 microns to 10 microns. The electrode width is greater than the through hole width to completely cover the through hole.

[0036] Compared with the traditional table-top mercury cadmium telluride infrared detector, the infrared detector device structure of the embodiment of the present application has a metal structure on the side wall of the pixel, which can isolate the optical crosstalk caused by refraction and reflection.

[0037] The embodiment of the present application also proposes a method for preparing a table-type HgCdTe focal plane infrared detector device structure as described above. This embodiment takes HgCdTe material as an example. The HgCdTe focal plane detector of this structure realizes a table-type photosensitive element array through processes such as etching, injection and thinning. The HgCdTe table is realized by wet etching and dry etching. Before dry etching, a sacrificial layer is prepared to protect the cleanliness of the surface of the table, and is removed by etching after etching. After dry etching, the etched damage layer is eliminated by wet etching and annealing. The specific method of the embodiment of the present application is as follows: Figure 3 As shown, the following steps are included:

[0038] Cleaning the thinned HgCdTe material to prepare a sacrificial layer and preparing a mesa by photolithography and etching;

[0039] Erosion removes the damaged layer, and then removes the sacrificial layer to ensure the cleanliness of the mesa surface material;

[0040] Cleaning and growing a passivation layer; in some embodiments, the passivation layer is a single layer film including phosphosilicate glass, silicon monoxide, silicon dioxide, silicon nitride, silicon oxynitride, cadmium telluride, zinc sulfide, polyimide or aluminum oxide, or a multilayer composite structure. In the case where the passivation layer is a multilayer composite structure, the material of the multilayer composite structure includes two or more of phosphosilicate glass, silicon monoxide, silicon dioxide, silicon nitride, silicon oxynitride, cadmium telluride, zinc sulfide, polyimide or aluminum oxide. The manufacturing method of the multilayer composite structure includes CVD, sputtering, ALD, etc.

[0041] Performing heat treatment, forming holes by etching or corrosion after the heat treatment, and forming a PN junction by ion implantation in the P-type or N-type substrate;

[0042] Coat photoresist, prepare the front electrode structure by photolithography and etching, and form a through hole between the electrode structure and the passivation layer by etching to achieve ohmic contact between the electrode and the mercury cadmium telluride material. In the specific example, the electrode is a single-layer or multi-layer composite structure of Cr, Au, Ti, Pt, Ni, Pd, Al, ITO, etc. The electrode manufacturing method includes evaporation, sputtering, electroplating, etc.

[0043] Indium pillars are prepared by photolithography and metallization to achieve flip-chip interconnection with the readout circuit.

[0044] The transmittance is increased by backside thinning process and backside anti-reflection, thereby preparing a mercury cadmium telluride focal plane array infrared detector.

[0045] In the preparation method of the embodiment of the present application, the mercury cadmium telluride substrate is cleaned and thinned, and then a sacrificial layer is grown and photolithography is performed. Dry etching and wet etching are performed in sequence to form a mesa structure of the underlying structure. The sacrificial layer is then removed, and a passivation layer is prepared on the surface of the mesa structure and annealed. Then, through holes are prepared and implanted and annealed. Then, an electrode structure is prepared, and flip-chip interconnection with a readout circuit is achieved through indium. The bottom fill glue is then encapsulated, and finally a backside thinning process is performed and a backside anti-reflection film is prepared.

[0046] Figure 4 The level diagram results of the Dewar test of the detector with a prepared 1280X1024 array scale and 15μm pixel pitch are shown. The test response signal is 987.99mV, the noise is 0.35mV, there are 611 blind pixels, and the blind pixel rate is 0.05%.

[0047] This embodiment uses HgCdTe as an example. The HgCdTe focal plane detector (FPD) utilizes etching, implantation, and thinning processes to create a table-shaped photosensitive element array. The HgCdTe FPI detector fabricated in this embodiment reduces crosstalk by etching a table-shaped structure. Compared to traditional table-shaped HgCdTe FPDI detectors, the pixel sidewalls incorporate metal structures to isolate optical crosstalk caused by refraction and reflection.

[0048] It should be noted that, in the various embodiments of the present application, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0049] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0050] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0051] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are protected by this application.

Claims

1. A table-type mercury cadmium telluride focal plane infrared detector device structure, characterized in that: include: A mercury cadmium telluride chip (006) comprising prism-shaped mesa structures arranged in an array, one mesa structure corresponding to one mesa pixel, the surface of the mesa structure being covered with a passivation layer (005), and an electrode structure (003) being provided on the upper surface of the mesa structure, the electrode structure (003) passing through the passivation layer via a first through hole to form an ohmic contact with the mercury cadmium telluride chip (006), and a metal electrode being provided on the mesa structure; The readout circuit (001) is interconnected with the mercury cadmium telluride chip (006) through the indium column (002).

2. The table-type HgCdTe focal plane infrared detector device structure according to claim 1, characterized in that: A filling glue (004) is provided between the mesa structure of the mercury cadmium telluride chip (006) of the array and the readout circuit (001).

3. The table-type HgCdTe focal plane infrared detector device structure according to claim 1, characterized in that: The size of the passivation through-holes on the upper surface of the mesa structure is 1 micron to 5 microns.

4. The table-type HgCdTe focal plane infrared detector device structure according to claim 3, characterized in that: The passivation through hole is used to form a PN junction by ion implantation of mercury cadmium telluride through the passivation layer (005) and the photoresist as a masking film.

5. The mesa-type HgCdTe focal plane infrared detector device structure according to claim 5, characterized in that: The interconnection electrodes provided on the mesa structure further include a first interconnection electrode and a second interconnection electrode; The first interconnection electrode and the second interconnection front electrode are arranged inside the mesa structure. A first through hole is present in the contact area between the first interconnection electrode and the mesa structure, a second through hole is present in the contact area between the second interconnection electrode and the mesa, and a third through hole is present in the contact area between the second interconnection electrode and the substrate. No injection is performed in the second through hole and the third through hole areas.

6. The table-type HgCdTe focal plane infrared detector device structure according to claim 1, characterized in that: The metal provided on the mesa structure includes the sidewall metal of the mesa sidewall, wherein: The sidewall metal is disconnected on the upper and lower sides of the mesa. The sidewall metal is in a grid or line shape and is located around, on both sides, or inside the upper surface of the mesa pixel.

7. The mesa-type HgCdTe focal plane infrared detector device structure according to claim 6, characterized in that: The through hole is in the shape of a square, a strip, a frame or a round cake; The interconnecting electrodes are a combination of one or more of square, strip, frame or pie shapes, and have a width of 3 to 10 microns. The electrode width is greater than the through-hole width to completely cover the through-hole.

8. A method for preparing a mesa-type HgCdTe focal plane infrared detector device structure according to any one of claims 1 to 7, characterized in that: include: A sacrificial layer is prepared using mercury cadmium telluride material, and a prism-shaped mesa structure is prepared by photolithography and etching; Corrosion removes the etched damaged layer and the sacrificial layer; Cleaning and growth of passivation layer; Performing heat treatment, forming holes by etching or corrosion after the heat treatment, and forming a PN junction by ion implantation in the P-type or N-type substrate; Coating a photoresist, preparing a front electrode structure by photolithography and etching, and forming a through hole between the electrode structure and the passivation layer by etching to achieve ohmic contact between the electrode and the mercury cadmium telluride material; Indium pillars are prepared by photolithography and metallization to achieve flip-chip interconnection with the readout circuit.

9. The preparation method according to claim 8, wherein The passivation layer is a single layer film including phosphosilicate glass, silicon monoxide, silicon dioxide, silicon nitride, silicon oxynitride, cadmium telluride, zinc sulfide, polyimide or aluminum oxide, or a multilayer composite structure; When the passivation layer is a multi-layer composite structure, the material of the multi-layer composite structure includes two or more of phosphosilicate glass, silicon monoxide, silicon dioxide, silicon nitride, silicon oxynitride, cadmium telluride, zinc sulfide, polyimide or aluminum oxide.

Images