Cap structure for infrared detector and method of forming the same

Abstract

The application provides a cap structure for an infrared detector and a forming method thereof. In the cap structure and the forming method thereof, a first recess is formed on a front surface of a substrate, the first recess defines a plurality of first signal receiving columns distributed at intervals, a second recess is formed on a back surface of the substrate, the second recess corresponds to the first recess in position, and the second recess defines a plurality of second signal receiving columns distributed at intervals, and a side wall structure surrounding the first recess is formed on the front surface of the substrate. The cap structure of the application uses the plurality of first signal receiving columns and the plurality of second signal receiving columns formed on the front surface and the back surface of the substrate to replace a traditional infrared window film, and directly forms the side wall structure on the front surface of the substrate, so that the manufacturing difficulty of the cap structure is reduced and the product yield is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to a cap structure for an infrared detector and a method for forming the same. Background Technology

[0002] An infrared detector is a device that converts absorbed infrared signals into electrical signals. Based on their working principle, infrared detectors can be divided into two main categories: quantum and uncooled. Quantum infrared detectors have high sensitivity but generally require cooling and are therefore more expensive. Uncooled infrared detectors have slightly lower sensitivity, do not require cooling, and offer better value for money. To achieve high performance, uncooled infrared detectors require vacuum packaging.

[0003] Traditional vacuum packaging involves dicing the chip, transferring it to another substrate, and then encapsulating it. Traditional vacuum packaging is divided into metal-cased packaging and ceramic packaging, both of which involve numerous process steps and are costly. Wafer-level vacuum packaging, or chip-level packaging, involves vacuum packaging the entire wafer before dicing it, resulting in higher packaging efficiency. Furthermore, compared to traditional vacuum packaging, device size is reduced, easily meeting the requirements of high integration and miniaturization. The process is also simpler, which helps reduce packaging costs and improve device yield.

[0004] In chip-level packaging, the upper substrate, or cap structure (CAP), is typically integrated onto the lower substrate, which includes infrared devices, via bonding to form a complete package structure. Currently, the method for forming the cap structure involves depositing an infrared window film on the surface of a substrate and then bonding the substrate to a wall sheet to form the cap structure. However, due to the small end-face area of ​​the wall sheet and the small bonding surface between the substrate and the wall sheet, the process of forming the cap structure is difficult and results in low yield. Summary of the Invention

[0005] One of the objectives of this invention is to provide a cap structure for an infrared detector and a method for forming the same, which can reduce the manufacturing difficulty of the cap structure and improve product yield.

[0006] To achieve the above objectives, the present invention provides a method for forming a cap structure for an infrared detector. The method includes:

[0007] A substrate is provided, the substrate having opposing front and back sides;

[0008] The front side of the substrate is etched to form a first groove, which defines a plurality of first signal receiving posts spaced apart.

[0009] A first material layer is formed on the front side of the substrate;

[0010] A second groove is formed by etching the back side of the substrate. The second groove corresponds to the position of the first groove, and the second groove defines a plurality of spaced-apart second signal receiving posts.

[0011] A portion of the first material layer is removed, and the remaining first material layer serves as a sidewall structure, which surrounds the first groove.

[0012] Optionally, the step of forming a first material layer on the front side of the substrate includes: bonding the first material layer to the front side of the substrate.

[0013] Optionally, a silicon oxide bonding layer is formed between the first material layer and the substrate.

[0014] Optionally, the step of forming a first material layer on the front side of the substrate includes: forming the first material layer on the front side of the substrate by a selective epitaxial process.

[0015] Optionally, the selective epitaxial growth of the first material layer on the front side of the substrate includes: selectively epitaxially growing the first material layer on the front side of the substrate surrounding the first groove and on the top surface of the plurality of first signal receiving pillars.

[0016] Optionally, after the cap structure is bonded to the lower substrate including the infrared detector, the sidewall structure is connected to the lower substrate, and a cavity is formed between the cap structure and the lower substrate. The thickness of the first material layer is set according to the height requirement of the cavity.

[0017] The present invention also provides a cap structure for an infrared detector. The cap structure includes a substrate and a sidewall structure formed on the front side of the substrate. The substrate has opposing front and back sides; a first groove is formed on the front side of the substrate, defining a plurality of spaced-apart first signal receiving posts; a second groove is formed on the back side of the substrate, the second groove corresponding to the first groove in position, and the second groove defining a plurality of spaced-apart second signal receiving posts.

[0018] Optionally, the plurality of first signal receiving posts and the plurality of second signal receiving posts are staggered in the vertical direction of the substrate thickness.

[0019] Optionally, the cross-sectional shape of the first signal receiving post includes a circle, a hexagon, or a trapezoid; the cross-sectional shape of the second signal receiving post includes a circle, a hexagon, or a trapezoid.

[0020] Optionally, the height of the sidewall structure is greater than 100 micrometers.

[0021] Compared with the prior art, the cap structure for infrared detectors and its formation method of the present invention have the following advantages: (1) In the prior art, infrared signals are received by depositing an infrared window film on the substrate surface. Usually, the infrared window film includes multiple material layers, and the thickness of each material layer is relatively thin, so the process of forming the infrared window film is complicated and difficult. The present invention forms multiple first signal receiving pillars and multiple second signal receiving pillars for receiving infrared signals on the front and back sides of the substrate by etching process, which is simple and easy, and is conducive to improving product yield. (2) In the prior art, the substrate with infrared window film deposited on the surface is combined with the wall sheet to form a cap structure. Since the end face area of ​​the wall sheet is small, the bonding surface between the substrate and the wall sheet is small, which makes the process of forming the cap structure difficult. The present invention directly etches the first material layer on the front side of the substrate to form the sidewall structure. That is to say, the substrate and the sidewall structure are an integral structure, avoiding the process of bonding the formed sidewall structure to the substrate surface, which helps to further reduce the manufacturing difficulty of the cap structure and improve the product yield. Attached Figure Description

[0022] Figure 1 This is a cross-sectional schematic diagram of a cap structure according to an embodiment of the present invention.

[0023] Figure 2 This is a flowchart of a method for forming a cap structure for an infrared detector according to an embodiment of the present invention.

[0024] Figures 3 to 5 This is a cross-sectional schematic diagram of the cap structure formation process in one embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 10-Substrate; 101-First groove; 102-First signal receiving post; 103-Second groove; 104-Second signal receiving post; 20-First material layer; 201-Sidewall structure. Detailed Implementation

[0027] The cap structure for an infrared detector and its formation method proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0028] To reduce the manufacturing difficulty of the cap structure and improve the product yield, this invention proposes a cap structure. Figure 1 This is a cross-sectional schematic diagram of a cap structure according to an embodiment of the present invention. Figure 1As shown, the cap structure (also referred to as the "upper substrate") includes a substrate 10 and a sidewall structure 201 formed on the front side of the substrate 10.

[0029] Specifically, the substrate 10 has a front side and a back side. A first groove 101 is formed on the front side of the substrate 10, defining a plurality of spaced-apart first signal receiving posts 102. A second groove 103 is formed on the back side of the substrate 10, corresponding to the position of the first groove 101, and defining a plurality of spaced-apart second signal receiving posts 104.

[0030] In this embodiment, in the vertical direction of the thickness direction of the substrate 10, that is... Figure 1 In the horizontal direction, the plurality of first signal receiving posts 102 and the plurality of second signal receiving posts 104 can be arranged in a staggered manner, but are not limited thereto. In other embodiments, the arrangement positions of the first signal receiving posts 102 and the second signal receiving posts 104 can be adjusted according to the actual situation of the infrared signals to be received.

[0031] The cross-sectional shape of the first signal receiving post 102 may include a circle, a hexagon, or a trapezoid, and the cross-sectional shape of the second signal receiving post 104 may include a circle, a hexagon, or a trapezoid, but is not limited thereto. The cross-sectional shapes of the first signal receiving post 102 and the second signal receiving post 104 can be designed according to the actual situation of the infrared signals to be received.

[0032] like Figure 1 As shown, the sidewall structure 201 is formed on the front side of the substrate 10, and the sidewall structure 201 surrounds the first groove 101. That is to say, in this embodiment, the sidewall structure 201 and the substrate 10 are integral structures, avoiding the process of bonding the formed sidewall structure to the substrate surface, which helps to reduce the manufacturing difficulty of the cap structure and improve the product yield.

[0033] The cap structure is a cover type. When the cap structure is bonded to the lower substrate (not shown in the figure) including the infrared detector, the sidewall structure 201 is connected to the lower substrate, and a cavity is formed between the cap structure and the lower substrate. The height of the cavity is determined by the height of the sidewall structure 201. The height of the sidewall structure 201, that is, the height of the sidewall structure 201 at... Figure 1 The vertical dimension is, for example, 100 micrometers or more.

[0034] This application also provides a method for forming a cap structure for an infrared detector. Figure 2 This is a flowchart illustrating a method for forming a cap structure for an infrared detector according to an embodiment of the present invention. Figure 2 As shown, the method for forming the cap structure for the infrared detector includes:

[0035] S1, providing a substrate having opposing front and back sides;

[0036] S2, etching the front side of the substrate to form a first groove, the first groove defining a plurality of first signal receiving posts spaced apart;

[0037] S3, a first material layer is formed on the front side of the substrate;

[0038] S4, etching the back side of the substrate to form a second groove, the second groove corresponding to the position of the first groove, and the second groove defining a plurality of spaced-apart second signal receiving posts; and

[0039] S5, remove part of the first material layer, and retain the first material layer as a sidewall structure, the sidewall structure surrounding the first groove.

[0040] It should be noted that, although Figure 2 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 2 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0041] Figures 3 to 5 This is a cross-sectional schematic diagram showing the formation process of the cap structure in one embodiment of the present invention. The following structure... Figure 1 , Figure 2 , Figures 3 to 5 The method for forming the cap structure of the present invention will be described.

[0042] like Figure 3 As shown, a substrate 10 is provided, having a front side and a back side facing each other. The material of the substrate 10 can be silicon, germanium, silicon-germanium, or other semiconductor materials.

[0043] Next, a first groove 101 is formed on the front side of the substrate 10 by etching, the first groove 101 defining a plurality of first signal receiving posts 102 spaced apart.

[0044] Specifically, the method of forming the first groove 101 may include: forming a patterned first mask layer (not shown in the figure) on the front side of the substrate 10, using the patterned first mask layer as a mask, etching the substrate 10 and stopping the formation of the first groove 101 in the substrate 10, the first groove 101 defining a plurality of first signal receiving posts 102.

[0045] It should be noted that the gaps around the multiple first signal receiving posts 102 are interconnected, or in other words, the multiple first signal receiving posts 102 stand within the first groove 101. In practical applications, multiple first grooves 101 are formed in the substrate 10.

[0046] After forming a plurality of first signal receiving pillars 102, a first material layer is formed on the front side of the substrate 10.

[0047] In some embodiments, to simplify the process and protect the already formed first signal receiving post 102, such as Figure 4 As shown, the method for forming a first material layer 20 on the front side of the substrate 10 includes bonding the first material layer 20 to the front side of the substrate 10. In this case, the first material layer 20 can be a polished substrate. The material of the first material layer 20 can be silicon, germanium, silicon-germanium, or other semiconductor materials.

[0048] A silicon oxide bonding layer (not shown in the figure) is formed between the front side of the substrate 10 and the first material layer 20. Specifically, a silicon oxide bonding layer can be formed on the surface of the first material layer 20 facing the substrate 10, and then the first material layer 20 can be bonded to the substrate 10.

[0049] In some embodiments, the method of forming a first material layer 20 on the front side of the substrate 10 includes forming the first material layer 20 on the front side of the substrate 10 by a selective epitaxial process. Specifically, the first material layer 20 can be selectively epitaxially grown on the front side of the substrate surrounding the first groove 101 and on the top surface of the first signal receiving post 102. Subsequently, the first material layer 20 on the top surface of the first signal receiving post 102 is etched away, and at least a portion of the first material layer surrounding the first groove 101 is retained as a sidewall structure.

[0050] As an example, selective silicon epitaxial growth can be performed using a mixture of silicon source gas and hydrogen halide; wherein the silicon source gas is at least one of monochlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane or silane; and the hydrogen halide gas is hydrogen chloride or hydrogen fluoride.

[0051] The following description will continue to illustrate the method for forming the cap structure of the present invention by taking the bonding of the first material layer 20 to the front side of the substrate 10 as an example.

[0052] like Figure 5As shown, a second groove 103 is formed by etching the back side of the substrate 10. The second groove 103 corresponds to the position of the first groove 101, and the second groove 103 defines a plurality of second signal receiving posts 104 that are spaced apart.

[0053] To facilitate the formation of the second groove 103, a flipping process can be performed before etching the back side of the substrate 10, so that the back side of the substrate 10 faces upward.

[0054] The method of etching the back side of the substrate 10 to form a second groove 103 may include: forming a patterned second mask layer (not shown) on the back side of the substrate 10, using the patterned second mask layer as a mask, etching the back side of the substrate 10 and stopping the formation of the second groove 103 in the substrate 10, the second groove 103 defining a plurality of second signal receiving posts 104.

[0055] It should be noted that the gaps around the multiple second signal receiving posts 104 are interconnected, or in other words, the multiple second signal receiving posts 104 stand within the second groove 103. Multiple second grooves 103 can be formed in the substrate 10, with each second groove 103 corresponding to a first groove 101.

[0056] After forming multiple second signal receiving columns 104, refer to Figure 1 A portion of the first material layer 20 is removed, and the remaining first material layer 20 serves as a sidewall structure 201, which surrounds the first groove 101.

[0057] Specifically, the method of removing part of the first material layer 20 to form the sidewall structure 201 may include: performing a flipping process such that the first material layer 20 is located above the substrate 10 to facilitate etching of the first material layer 20; forming a patterned third mask layer (not shown in the figure) on the surface of the first material layer 20 away from the substrate 10; using the patterned third mask layer as a mask, etching the first material layer 20 and stopping on the front side of the substrate 10, with the remaining first material layer 20 serving as the sidewall structure 201.

[0058] The cap structure is a cover type. When the cap structure is bonded to the lower substrate (not shown in the figure) including the infrared detector, the sidewall structure 201 is connected to the lower substrate, and a cavity is formed between the cap structure and the lower substrate. The height of the cavity is determined by the height of the sidewall structure 201. The height of the sidewall structure 201, that is, the height of the sidewall structure 201 at... Figure 1 The vertical dimension is determined by the thickness of the first material layer 20. In order to meet the bonding vacuum requirements between the cap structure and the lower substrate, the thickness of the first material layer 20 is set according to the height requirements of the cavity.

[0059] Compared with the prior art, the cap structure for infrared detectors and its formation method of the present invention have the following advantages: (1) In the prior art, infrared signals are received by depositing an infrared window film on the substrate surface. Usually, the infrared window film includes multiple material layers, and the thickness of each material layer is relatively thin, so the process of forming the infrared window film is complex and difficult. The present invention forms multiple first signal receiving pillars 102 and multiple second signal receiving pillars 104 for receiving infrared signals on the front and back sides of the substrate 10 by etching process, which is simple and easy, and has advantages. To improve product yield; (2) In the prior art, a substrate with an infrared window film deposited on its surface is combined with a wall sheet to form a cap structure. Since the end face area of ​​the wall sheet is small, the bonding surface between the substrate and the wall sheet is small, which makes the process of forming the cap structure difficult. In this invention, the first material layer 20 is directly etched on the front side of the substrate 10 to form the side wall structure 201. That is to say, the substrate 10 and the side wall structure 201 are an integral structure, avoiding the process of bonding the formed side wall structure to the substrate surface, which helps to further reduce the manufacturing difficulty of the cap structure and improve product yield.

[0060] It should be noted that this instruction manual uses a progressive approach. The formation method of the cap structure described later focuses on the differences from the cap structure described earlier. For the same or similar parts, please refer to each other.

[0061] The phrases "some embodiments" or "this embodiment" used throughout this specification indicate that a particular component, structure, or feature described with the embodiments is included in at least one embodiment. Therefore, the phrases "some embodiments" or "this embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiments. Furthermore, in one or more embodiments, specific components, structures, or features may be combined in any suitable manner.

[0062] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for forming a cap structure for an infrared detector, characterized in that, include: A substrate is provided, the substrate having opposing front and back sides; The front side of the substrate is etched to form a first groove, which defines a plurality of first signal receiving posts spaced apart. A first material layer is formed on the front side of the substrate; The back side of the substrate is etched to form a second groove, the second groove being located corresponding to the first groove, and the second groove defining a plurality of second signal receiving posts spaced apart; as well as A portion of the first material layer is removed, and the remaining first material layer serves as a sidewall structure, which surrounds the first groove. The cap structure is bonded to the lower substrate including the infrared detector, the sidewall structure is connected to the lower substrate, and a cavity is formed between the cap structure and the lower substrate.

2. The forming method as described in claim 1, characterized in that, The provision of a first material layer on the front side of the substrate includes: The first material layer is bonded to the front side of the substrate.

3. The forming method as described in claim 2, characterized in that, A silicon oxide bonding layer is formed between the first material layer and the substrate.

4. The forming method as described in claim 1, characterized in that, The provision of a first material layer on the front side of the substrate includes: The first material layer is formed on the front side of the substrate using a selective epitaxial process.

5. The forming method as described in claim 4, characterized in that, The formation of the first material layer on the front side of the substrate by selective epitaxy includes: The first material layer is selectively epitaxially grown on the front side of the substrate surrounding the first groove and on the top surface of the plurality of first signal receiving pillars.

6. The forming method as described in claim 1, characterized in that, The thickness of the first material layer is set according to the height requirement of the cavity.

7. A cap structure for an infrared detector, characterized in that, include: A substrate having opposing front and back sides; A first groove is formed on the front side of the substrate, which defines a plurality of first signal receiving posts spaced apart; a second groove is formed on the back side of the substrate, which corresponds to the position of the first groove and defines a plurality of second signal receiving posts spaced apart. as well as A sidewall structure formed on the front side of the substrate, the sidewall structure surrounding the first groove; The cap structure is bonded to the lower substrate including the infrared detector, the sidewall structure is connected to the lower substrate, and a cavity is formed between the cap structure and the lower substrate.

8. The cap structure as described in claim 7, characterized in that, In the vertical direction of the substrate thickness, the plurality of first signal receiving posts and the plurality of second signal receiving posts are arranged in a staggered manner.

9. The cap structure as described in claim 7, characterized in that, The cross-sectional shape of the first signal receiving post includes a circle, a hexagon, or a trapezoid; the cross-sectional shape of the second signal receiving post includes a circle, a hexagon, or a trapezoid.

10. The cap structure as described in claim 7, characterized in that, The height of the sidewall structure is greater than 100 micrometers.

Images