Area array type pixel packaging uncooled infrared detector and preparation method thereof

Abstract

The invention relates to the technical field of uncooled infrared detectors, in particular to an area array type pixel packaging uncooled infrared detector and a preparation method thereof, and the preparation method comprises the steps: dividing a readout circuit substrate into a pixel region and a getter region, preparing a structural cavity, and manufacturing a first release hole and a second release hole in the structural cavity, releasing the sacrificial layer of the structural cavity; the first release hole is shielded, and only the second release hole is opened; a getter coating process is carried out on the structural cavity, and a getter material is deposited to a getter area through a second release hole in an area which is not shielded by the shielding baffle; after the getter of the structural cavity is deposited, the structural cavity shielding baffle is removed, and the first release hole is opened; and plating a hole sealing film on the structural cavity, completing the sealing of the vacuum cavity, and then activating the getter of the structural cavity. According to the invention, the vacuum degree of the detector cavity is ensured, and a powerful guarantee is provided for subsequent performance improvement of the detector.

Description

Technical Field

[0001] The present invention relates to the technical field of uncooled infrared detectors, and more specifically to a planar array pixel packaged uncooled infrared detector and a preparation method thereof. Background Art

[0002] Uncooled infrared focal plane detectors perform imaging by absorbing external infrared energy and converting it into electrical signals in an ultra-high vacuum environment. In the production process of uncooled infrared detectors, getters must be used and activated in the vacuum-sealed environment of the detector to remove residual gas to maintain a higher vacuum degree. If the vacuum degree decreases during the later use of the detector, the getter can be activated again to absorb the residual gas so that the detector can maintain a high vacuum environment again. At present, the packaging methods of uncooled infrared detectors mainly include metal, ceramic, wafer-level and pixel-level packaging. Among them, metal and ceramic packaging use columnar getters, which are welded to the tube shell leads by welding, and electrically activated or thermally activated getters are used before packaging to maintain a high vacuum degree. Wafer-level packaging uses thin film getters, which are integrated into the cap wafer. During bonding, the high temperature of bonding is used to activate the getter by thermal activation to avoid the influence of temperature on the getter during the MEMS process preparation of the chip. Pixel-level packaging is to integrate the cap wafer with the MEMS wafer on the basis of wafer-level packaging, and use a material to directly package the entire surface of the MEMS microstructure. Based on this packaging form, the getter needs to be integrated into the entire microcavity structure. In the existing technical solution, the getter is placed at the bottom of the infrared micro-bolometer, and the deposition of the getter is completed in the MEMS front-end process. However, the multiple high-temperature baking and organic solution cleaning processes involved in the conventional semiconductor process will affect the performance of the getter. At the same time, after the MEMS structure is completed, the sacrificial layer in the structure will be released and removed by 02 in a high-temperature environment. In this environment, the getter will be activated prematurely, resulting in the loss of air absorption ability, and the vacuum degree in the cavity cannot be guaranteed, which is manifested as a poor vacuum life of the detector. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention opens up a separate area for the getter and at the same time manufactures a second MEMS micro-bridge structure identical to the first MEMS micro-bridge structure in the area, and deposits the getter after the structural sacrificial layer is released, thereby avoiding the influence of high temperature and organic solution in the MEMS process on the getter performance. In addition, the getter activation method is diverse, which can be either electrically activated or thermally activated. The activation method is simple and easy to carry out mass production.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides a planar array pixel packaged uncooled infrared detector and a preparation method thereof. The planar array pixel packaged uncooled infrared detector comprises:

[0005] a readout circuit substrate;

[0006] The readout circuit substrate has a pixel region, and the pixel region is provided with a first MEMS micro-bridge structure electrically connected to the readout circuit substrate;

[0007] The readout circuit substrate also has a getter area, and the getter area is provided with a second MEMS micro-bridge structure supported on the readout circuit substrate and a getter located on the second MEMS micro-bridge structure;

[0008] A structural cavity is provided above the readout circuit substrate, a release hole is provided on the structural cavity, and the getter corresponds to the release hole located above the getter area.

[0009] As a preferred technical solution of the present invention, a sealing film for sealing the release hole is provided on the top of the structural cavity, and a vacuum cavity is formed between the readout circuit substrate, the structural cavity and the sealing film.

[0010] As a preferred technical solution of the present invention, the release hole includes a first release hole located above the pixel area and a second release hole located above the getter area, the second release hole is larger than the first release hole, and the getter corresponds to the second release hole in position and shape one by one.

[0011] As a preferred technical solution of the present invention, the getter area is located on one side of the pixel area, or the getter area is arranged around the pixel area.

[0012] As a preferred technical solution of the present invention, the second MEMS micro-bridge structure is electrically connected to the readout circuit substrate.

[0013] The preparation method of the area array pixel packaged uncooled infrared detector is realized by performing the following steps:

[0014] Step S1: dividing a pixel area and a getter area on a readout circuit substrate;

[0015] Step S2: preparing a first MEMS micro-bridge structure electrically connected to the readout circuit substrate in the pixel region of the readout circuit substrate, and preparing a second MEMS micro-bridge structure in the getter region of the readout circuit substrate;

[0016] Step S3: preparing a structural cavity covered on the readout circuit substrate through a sacrificial layer on the readout circuit substrate, making a first release hole located above the pixel area and a second release hole located above the getter area on the structural cavity, and completing the release of the sacrificial layer through the first release hole and the second release hole;

[0017] Step S4: blocking the first release hole above the pixel area and only opening the second release hole above the getter area;

[0018] Step S5: performing a getter coating process on the structural cavity manufactured in step S4, wherein the getter material is deposited to the getter area through the second release hole above the getter area and is located on the second MEMS micro-bridge structure to form a getter;

[0019] Step S6: after the getter deposition is completed, opening the first release hole located above the pixel area;

[0020] Step S7: plating a sealing film on the structural cavity to complete the sealing of the vacuum cavity, and then activating the getter.

[0021] As a preferred technical solution of the present invention, activating the getter comprises:

[0022] After the vacuum chamber is sealed, the packaged detector is placed in a high temperature environment, and when the getter material reaches the activation temperature of the getter, the thermal activation of the getter is completed.

[0023] As a preferred technical solution of the present invention, activating the getter further comprises:

[0024] The second MEMS microbridge structure is energized to generate Joule heat, which causes the temperature of the thermosensitive material on the second MEMS microbridge structure to rise. The heating process of the thermosensitive material locally heats the getter until the activation temperature of the getter is reached, thereby completing the activation of the getter.

[0025] As a preferred technical solution of the present invention, before performing the getter coating process, a shielding baffle is arranged on the top of the structural cavity to shield the first release hole located above the pixel area, and after the getter is deposited into the getter area through the second release hole located above the getter area, the shielding baffle is removed.

[0026] As a preferred technical solution of the present invention, the first MEMS micro-bridge structure and the second MEMS micro-bridge structure have the same structure and are manufactured at the same time.

[0027] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0028] The technical solution of the present invention opens up a separate area for the getter, and at the same time manufactures a second MEMS micro-bridge structure identical to the first MEMS micro-bridge structure in the area, and then deposits the getter after the structural sacrificial layer is released, thereby avoiding the influence of high temperature and organic solution in the MEMS process on the getter performance. In addition, the getter activation method is diverse, and can be either electrically activated or thermally activated. The activation method is simple and easy to carry out mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 It is a general schematic diagram of the planar array pixel packaged uncooled infrared detector of the present invention;

[0031] Figure 2 This is a schematic diagram of the structural cavity after the sacrificial layer is released in the present invention;

[0032] Figure 3 It is a schematic diagram of the shielding baffle and the structural cavity in the present invention;

[0033] Figure 4 A schematic diagram of the getter being deposited into the structure cavity through the release hole in the present invention;

[0034] Figure 5 is a schematic diagram of the getter deposited in the structural cavity in the present invention;

[0035] Figure 6 It is a schematic diagram of the plated sealing film and the structural cavity after sealing in the present invention;

[0036] In the figure, 1. readout circuit substrate; 2. first MEMS microbridge structure; 3. getter area; 4. structural cavity; 5. sealing film; 6. vacuum cavity; 7. shielding baffle; 31. getter; 32. second release hole; 33. second MEMS microbridge structure; 41. first release hole. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0039] When integrating a getter into an infrared microbolometer, existing technical solutions face the problems of impaired getter performance and failure to ensure vacuum due to high-temperature baking, organic solution cleaning, and sacrificial layer removal processes in the semiconductor process flow.

[0040] In view of the above technical problems, the present invention proposes Figure 1-Figure 6 A planar array pixel packaged uncooled infrared detector and a preparation method thereof are shown, wherein the planar array pixel packaged uncooled infrared detector comprises:

[0041] The readout circuit substrate 1 has a pixel region, and the pixel region is provided with a first MEMS micro-bridge structure 2 electrically connected to the readout circuit substrate 1 . The first MEMS micro-bridge structure 2 is used to receive infrared radiation and convert it into an electrical signal.

[0042] The readout circuit substrate 1 also has an getter area 3, which is provided with a second MEMS micro-bridge structure 33 supported on the readout circuit substrate 1 and a getter 31 located on the second MEMS micro-bridge structure 33. The second MEMS micro-bridge structure 33 is used to support the getter 31 to raise the position of the getter 31 to facilitate the deposition of the getter 31; preferably, the second MEMS micro-bridge structure 33 is electrically connected to the readout circuit substrate 1 to facilitate the electrical activation of the getter 31.

[0043] A structural cavity 4 is provided on the readout circuit substrate 1 , and a release hole is provided on the structural cavity 4 . The getter 31 corresponds to the release hole located above the second MEMS micro-bridge structure 33 .

[0044] Specifically, a sealing film 5 for sealing the release hole is provided on the top of the structural cavity 4 , and a vacuum cavity 6 is formed between the readout circuit substrate 1 , the structural cavity 4 and the sealing film 5 . The sealing film 5 is preferably an infrared anti-reflection film.

[0045] Specifically, the release holes include a first release hole 41 located above the pixel area and a second release hole 32 located above the getter area 3 . The second release hole 32 is larger than the first release hole 41 . The positions and shapes of the getter 31 and the second release hole 32 correspond one to one.

[0046] Specifically, the getter area 3 is located on one side of the pixel area, or the getter area 3 is arranged around the pixel area. When the getter 31 is thermally activated, the getter area 3 is preferably located on one side of the pixel area. When the getter 31 is electrically activated, the getter area 3 can be located on one side of the pixel area or arranged around the pixel area.

[0047] The present invention also discloses a method for preparing a planar array pixel packaged uncooled infrared detector, which is implemented by executing the following steps:

[0048] Step S1: dividing a pixel region and a getter region 3 on a readout circuit substrate 1;

[0049] Step S2: preparing a first MEMS micro-bridge structure 2 electrically connected to the readout circuit substrate 1 in the pixel region of the readout circuit substrate 1, and preparing a second MEMS micro-bridge structure 33 in the getter region 3 of the readout circuit substrate 1;

[0050] Step S3: a structural cavity 4 is prepared on the readout circuit substrate 1 through a sacrificial layer, and a first release hole 41 located above the pixel area and a second release hole 32 located above the getter area 3 are made on the structural cavity 4, and the sacrificial layer is released through the first release hole 41 and the second release hole 32;

[0051] Step S4: blocking the first release hole 41 above the pixel area, and only opening the second release hole 32 above the getter area 3;

[0052] Step S5: performing a getter coating process on the structural cavity 4 manufactured in step S4, the getter material will be deposited to the getter area 3 through the second release hole 32 above the getter area 3 and located on the second MEMS micro-bridge structure 33 to form a getter 31;

[0053] Step S6: After the deposition of the getter 31 is completed, the first release hole 41 located above the pixel area is opened;

[0054] Step S7: a sealing film 5 is plated on the structural cavity 4 to complete the sealing of the vacuum cavity 6, and then the getter 31 is activated.

[0055] Through the coordination of the above steps, the planar array pixel packaged uncooled infrared detector was successfully designed and prepared, while ensuring the vacuum degree of the detector cavity, providing a strong guarantee for the subsequent performance improvement and long-term stability of the detector. The activation method is simple and easy to carry out mass production.

[0056] Further, activating the getter 31 comprises:

[0057] After the vacuum chamber 6 is sealed, the packaged detector is placed in a high temperature environment, and when the getter material reaches the activation temperature of the getter 31 , the thermal activation of the getter 31 is completed.

[0058] Specifically, thermal activation is a commonly used getter activation method. Its principle is to heat the getter material to a certain temperature (i.e., activation temperature). At this time, the surface or interior of the getter material will undergo physical or chemical changes to form an active surface or phase change product with strong adsorption capacity. The active surface or phase change product can efficiently adsorb residual gas molecules inside the detector, thereby maintaining a high vacuum inside the detector and improving its performance and stability. This activation method is simple and easy to mass produce.

[0059] Further, activating the getter 31 further comprises:

[0060] The second MEMS microbridge structure 33 is energized to generate Joule heat, which heats up the thermosensitive material on the second MEMS microbridge structure 33 . The heating process of the thermosensitive material locally heats the getter 31 until the activation temperature of the getter 31 is reached, thereby completing the activation of the getter 31 .

[0061] Specifically, local Joule heat activation is a method of heating using the heat generated when current passes through a conductor. In the MEMS microbridge structure, an embedded electric heating element such as a metal wire or a thin film heater can be designed. The electric heating element is in close contact with or adjacent to the getter material. When current is passed through the electric heating element, the Joule heat generated when the current passes through will heat up the electric heating element and the surrounding materials. If the position and size of the electric heating element are properly designed, it can ensure that the getter material is locally heated to its activation temperature without causing excessive thermal impact on the surrounding structural cavity or readout circuit. This method has the advantages of fast heating speed, low energy consumption, and little impact on the surrounding environment. The activation method is simple and easy to mass produce.

[0062] Furthermore, before performing the getter coating process, a shielding baffle 7 is set on the top of the structural cavity 4 to shield the first release hole 41 located above the pixel area. After the getter 31 is deposited into the getter area 3 through the second release hole 32 located above the getter area 3, the shielding baffle 7 is removed.

[0063] Specifically, the shielding baffle 7 is provided to conveniently block the first release hole 41, so that the getter 31 is conveniently deposited through the second release hole 32, and the positioning of the getter 31 is completed. Among them, the physical vapor deposition technology refers to the technology of vaporizing the surface of the material source into gaseous atoms or molecules, or partially ionizing into ions, and depositing a thin film on the surface of the substrate through a low-pressure gas or plasma process under vacuum conditions. Physical vapor deposition is one of the main surface treatment technologies.

[0064] Furthermore, the first MEMS micro-bridge structure 2 and the second MEMS micro-bridge structure 33 have the same structure and are manufactured at the same time.

[0065] Specifically, the shielding baffle 7 completes the positioning deposition of the getter 31 after temporary bonding, so that the shielding baffle 7 can be removed and the sealing film 5 can be used for coating to complete the sealing of the vacuum chamber 6. Among them, the electron beam evaporation coating process is adopted. Different from the traditional evaporation method, the electron beam evaporation can accurately realize the use of high-energy electrons to bombard the target material in the crucible with the cooperation of the electromagnetic field, so that it melts and then deposits on the substrate. The electron beam evaporation can plate a high-purity and high-precision film, thereby ensuring that the sealing film 5 has a good effect.

[0066] One of the main functions of the MEMS microbridge structure in the getter area is to provide support, and it also has the function of electrical conduction. That is, the MEMS microbridge structure cavity can also be used as part of the circuit to allow current to pass through. During the getter activation process, if electrical activation is used, the microbridge structure can directly serve as a current path to transfer electrical energy to the getter material, thereby generating Joule heat for heating and activation.

[0067] After the sacrificial layer of the structural cavity 4 is released, a temporary bonding process is performed with the wafer through the shielding baffle 4, and only the second MEMS micro-bridge structure 33 is opened. Through the coating process, the getter is deposited into the vacuum cavity. After the deposition of the getter 31 is completed, the sealing film shielding baffle 7 is removed, and the first release hole 41 located above the first MEMS micro-bridge structure 2 of the sealing film is opened. Finally, the sealing film 5 is plated on the sealing film structural cavity 4 to complete the sealing of the vacuum cavity 6, and then the getter 31 is activated. Among them, the activation method of the getter 31 can be either electrical activation or thermal activation.

[0068] In summary, by opening up a separate area for the getter and making a second MEMS microbridge structure identical to the first MEMS microbridge structure in this area, the getter is deposited after the structural sacrificial layer is released, thereby avoiding the influence of high temperature and organic solution in the MEMS process on the getter performance. In addition, the getter activation method is diverse, and it can be activated by both electrical activation and thermal activation. The activation method is simple and easy to carry out mass production.

[0069] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0071] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A planar array pixel packaged uncooled infrared detector, characterized in that: include: A readout circuit substrate (1); The readout circuit substrate (1) has a pixel region, and the pixel region is provided with a first MEMS micro-bridge structure (2) electrically connected to the readout circuit substrate (1); The readout circuit substrate (1) also has a getter area (3), and the getter area (3) is provided with a second MEMS micro-bridge structure (33) supported on the readout circuit substrate (1) and a getter (31) located on the second MEMS micro-bridge structure (33); A structural cavity (4) is provided above the readout circuit substrate (1), a release hole is provided on the structural cavity (4), and the getter (31) corresponds to the release hole located above the second MEMS micro-bridge structure (33).

2. The area array pixel packaged uncooled infrared detector according to claim 1, characterized in that: A sealing film (5) for sealing the release hole is provided on the top of the structural cavity (4), and a vacuum cavity (6) is formed between the readout circuit substrate (1), the structural cavity (4) and the sealing film (5).

3. The area array pixel packaged uncooled infrared detector according to claim 1, characterized in that: The release holes include a first release hole (41) located above the pixel area and a second release hole (32) located above the getter area (3), the second release hole (32) being larger than the first release hole (41), and the getter (31) and the second release hole (32) corresponding in position and shape to each other.

4. The area array pixel packaged uncooled infrared detector according to claim 1, characterized in that: The getter region (3) is located on one side of the pixel region, or the getter region (3) is arranged around the pixel region.

5. The area array pixel packaged uncooled infrared detector according to claim 1, characterized in that: The second MEMS micro-bridge structure (33) is electrically connected to the readout circuit substrate (1).

6. A method for preparing a planar array pixel packaged uncooled infrared detector, characterized in that: The preparation method comprises: Step S1: dividing a pixel region and a getter region (3) on a readout circuit substrate (1); Step S2: preparing a first MEMS micro-bridge structure (2) electrically connected to the readout circuit substrate (1) in the pixel region of the readout circuit substrate (1), and preparing a second MEMS micro-bridge structure (33) in the getter region (3) of the readout circuit substrate (1); Step S3: preparing a structural cavity (4) covering the readout circuit substrate (1) through a sacrificial layer on the readout circuit substrate (1), making a first release hole (41) located above the pixel area and a second release hole (32) located above the getter area (3) on the structural cavity (4), and completing the release of the sacrificial layer through the first release hole (41) and the second release hole (32); Step S4: blocking the first release hole (41) above the pixel area and only opening the second release hole (32) above the getter area (3); Step S5: performing a getter coating process on the structural cavity (4) manufactured in step S4, wherein the getter material is deposited on the getter area (3) through the second release hole (32) above the getter area (3) and is located on the second MEMS micro-bridge structure (33), thereby forming a getter (31); Step S6: after the deposition of the getter (31) is completed, opening the first release hole (41) located above the pixel area; Step S7: Plating a sealing film (5) on the structural cavity (4) to complete the sealing of the vacuum cavity (6), and then activating the getter (31).

7. The method for preparing the area array pixel packaged uncooled infrared detector according to claim 6, characterized in that: Activating the getter (31) comprises: After the vacuum chamber (6) is sealed, the packaged detector is placed in a high-temperature environment, and when the getter material reaches the activation temperature of the getter (31), thermal activation of the getter (31) is completed.

8. The method for preparing the area array pixel packaged uncooled infrared detector according to claim 6, characterized in that: Activating the getter (31) further comprises: The second MEMS micro-bridge structure (33) is energized to generate Joule heat, which causes the temperature of the thermosensitive material on the second MEMS micro-bridge structure (33) to rise. The process of heating the thermosensitive material locally heats the getter (31) until the activation temperature of the getter (31) is reached, thereby completing the activation of the getter (31).

9. The method for preparing the area array pixel packaged uncooled infrared detector according to claim 6, characterized in that: Before performing a getter coating process, a shielding baffle (7) is arranged on the top of the structural cavity (4) to shield the first release hole (41) located above the pixel area, and after the getter (31) is deposited into the getter area (3) through a second release hole (32) located above the getter area (3), the shielding baffle (7) is removed.

10. The method for preparing the area array pixel packaged uncooled infrared detector according to claim 6, characterized in that: The first MEMS micro-bridge structure (2) and the second MEMS micro-bridge structure (33) have the same structure and are manufactured at the same time.

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