Package structure integrating optical element and photosensitive device, and manufacturing method therefor

Abstract

The present application provides a package structure integrating an optical element and a photosensitive device, and a manufacturing method therefor. The package structure comprises a photosensitive device and an optical element. The photosensitive device has a first surface. The optical element has a fourth surface, the fourth surface being disposed face-to-face with the first surface of the photosensitive device. The first surface of the photosensitive device is bonded to the fourth surface of the optical element by means of a transient liquid phase bonding layer.

Description

Packaging structure and fabrication method of integrated optical components and photosensitive devices Technical Field

[0001] This application relates to the field of infrared imaging technology, and in particular to a packaging structure and manufacturing method of an integrated optical element and photosensitive device. Background Technology

[0002] Infrared detectors are widely used in fields such as medicine and industrial monitoring. As the sensitivity and resolution of infrared detectors improve, the requirements for their packaging structure also become more stringent.

[0003] To further improve the optical performance of infrared detectors, integrated microlens technology has gradually become an important means to improve the focusing ability of light signals and improve the field of view. Summary of the Invention

[0004] A first aspect of this application provides a packaging structure integrating an optical element and a photosensitive device. The packaging structure includes: a photosensitive device having a first surface; an optical element having a fourth surface, the fourth surface being disposed face-to-face with the first surface of the photosensitive device; and a transient liquid phase bonding layer, wherein the first surface of the photosensitive device is bonded to the fourth surface of the optical element through the transient liquid phase bonding layer.

[0005] In some embodiments, the encapsulation structure further includes a gasket, the gasket being annular and having a first end and a second end opposite to and far apart from each other, the first end being adjacent to a fourth surface of the optical element and the second end being adjacent to a first surface of the photosensitive device; wherein the transient liquid phase bonding layer is located between the gasket and the photosensitive device, and between the gasket and the optical element; wherein the photosensitive device, the optical element, and the gasket enclose a cavity.

[0006] In some embodiments, the transient liquid phase bonding layer includes a low-melting-point metal layer and a high-melting-point metal layer, wherein the low-melting-point metal layer is made of indium and / or tin, and the high-melting-point metal layer is made of gold, copper, and / or nickel.

[0007] In some embodiments, the transient liquid phase bonding layer further includes an interface promoting layer, wherein the transient liquid phase bonding layer satisfies at least one of the following: when the transient liquid phase bonding layer is pre-formed on a first end of the pad, the interface promoting layer is disposed between the first end of the pad and the high melting point metal layer; when the transient liquid phase bonding layer is pre-formed on a second end of the pad, the interface promoting layer is disposed between the second end of the pad and the high melting point metal layer; when the transient liquid phase bonding layer is pre-formed on a fourth surface of the optical element, the interface promoting layer is disposed between the fourth surface of the optical element and the high melting point metal layer; when the transient liquid phase bonding layer is pre-formed on a first surface of the photosensitive device, the interface promoting layer is disposed between the first surface of the photosensitive device and the high melting point metal layer; the material of the interface promoting layer includes titanium, chromium and / or nickel.

[0008] In some embodiments, the transient liquid phase bonding layer further includes a liquid phase protective layer, wherein the liquid phase protective layer covers the low-melting-point metal layer, and the transient liquid phase bonding layer satisfies at least one of the following: when the transient liquid phase bonding layer is pre-formed on a first end of the pad, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the first end of the pad; when the transient liquid phase bonding layer is pre-formed on a second end of the pad, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the second end of the pad; when the transient liquid phase bonding layer is pre-formed on a fourth surface of the optical element, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the fourth surface of the optical element; when the transient liquid phase bonding layer is pre-formed on a first surface of the photosensitive device, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the first surface of the photosensitive device; the material of the liquid phase protective layer includes an inert metal.

[0009] In some embodiments, the transient liquid phase bonding layer further includes a diffusion barrier layer, wherein the diffusion barrier layer is disposed between the low melting point metal layer and the low melting point metal layer, the material of the diffusion barrier layer includes titanium, chromium and / or nickel, and the melting point of the diffusion barrier layer is higher than the melting point of the low melting point metal layer.

[0010] In some embodiments, the optical element is a microlens array structure, the optical element includes a base and a lens portion, wherein a first end of the spacer is bonded to an edge region of the base, and the lens portion is integrally formed in the middle region of the base.

[0011] In some embodiments, the gasket is made of silicon, silicon oxide, or silicon nitride; a getter is disposed within the cavity; the photosensitive device includes an infrared detector; and a photosensitive material layer is disposed on the first surface of the photosensitive device.

[0012] A second aspect of this application provides a method for fabricating a package structure integrating an optical element and a photosensitive device. The method includes: providing a photosensitive device and an optical element, wherein the photosensitive device has a first surface and the optical element has a fourth surface; and using a transient liquid phase bonding process to bond the first surface of the photosensitive device to the fourth surface of the optical element through a transient liquid phase bonding layer, wherein the fourth surface of the optical element and the first surface of the photosensitive device are disposed face-to-face.

[0013] In some embodiments, the manufacturing method further includes: providing a spacer, the spacer being annular and having a first end and a second end that are opposite to and far apart from each other; wherein, bonding the photosensitive device to the optical element via a transient liquid phase bonding layer using a transient liquid phase bonding process includes: bonding the first end of the spacer to the optical element via a first transient liquid phase bonding layer using a first transient liquid phase bonding process; and bonding the second end of the spacer to the photosensitive device via a second transient liquid phase bonding layer using a second transient liquid phase bonding process; wherein the photosensitive device, the optical element, and the spacer together form a cavity.

[0014] In some embodiments, bonding the first end of the pad to the fourth surface of the optical element using the first transient liquid phase bonding process via the first transient liquid phase bonding layer includes: disposing the first transient liquid phase bonding layer on the first end of the pad and / or the fourth surface of the optical element; aligning the optical element with the pad; heating to a first temperature in a vacuum or inert gas environment to melt the first transient liquid phase bonding layer into a liquid phase and diffuse to form an intermetallic compound; and completing the bonding after cooling and solidification, wherein the first temperature is between 200°C and 40°C. The bonding process involves: bonding the pad to the first surface of the photosensitive device using the second transient liquid phase bonding layer at a temperature between 0°C and 400°C; and / or using the second transient liquid phase bonding process to bond the pad to the first surface of the photosensitive device and / or the second end of the pad using the second transient liquid phase bonding layer; aligning the photosensitive device with the pad; heating to a second temperature in a vacuum or inert gas environment to melt the second transient liquid phase bonding layer into a liquid phase and diffuse to form an intermetallic compound; and completing the bonding process after cooling and solidification.

[0015] In some embodiments, the first transient liquid phase bonding layer and / or the second transient liquid phase bonding layer are prepared using a thin film deposition process.

[0016] In some embodiments, the first transient liquid phase bonding layer and the second transient liquid phase bonding layer each include a low-melting-point metal layer and a high-melting-point metal layer, wherein the material of the low-melting-point metal layer includes indium and / or tin, and the material of the high-melting-point metal layer includes gold, copper and / or nickel.

[0017] In some embodiments, the first transient liquid phase bonding layer and the second transient liquid phase bonding layer each further include an interface promoting layer, wherein when the first transient liquid phase bonding layer is pre-formed at the first end of the pad, the interface promoting layer is disposed between the first end of the pad and the high melting point metal layer, and / or when the first transient liquid phase bonding layer is pre-formed on the fourth surface of the optical element, the interface promoting layer is disposed between the fourth surface of the optical element and the high melting point metal layer; and / or, wherein when the second transient liquid phase bonding layer is pre-formed on the first surface of the photosensitive device, the interface promoting layer is disposed between the first surface of the photosensitive device and the high melting point metal layer, and / or when the second transient liquid phase bonding layer is pre-formed on the second end of the pad, the interface promoting layer is disposed between the second end of the pad and the high melting point metal layer; the material of the interface promoting layer includes titanium, chromium and / or nickel.

[0018] In some embodiments, the first transient liquid phase bonding layer and the second transient liquid phase bonding layer each further include a liquid phase protective layer, wherein the liquid phase protective layer covers the low-melting-point metal layer, wherein when the first transient liquid phase bonding layer is pre-formed at the first end of the pad, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the first end of the pad, and / or when the first transient liquid phase bonding layer is pre-formed on the fourth surface of the optical element, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the fourth surface of the optical element, and the material of the liquid phase protective layer includes an inert metal; and / or, wherein when the second transient liquid phase bonding layer is pre-formed on the first surface of the photosensitive device, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the first surface of the photosensitive device, and / or when the second transient liquid phase bonding layer is pre-formed on the second end of the pad, the liquid phase protective layer is disposed on the side of the low-melting-point metal layer away from the second end of the pad, and the material of the liquid phase protective layer includes an inert metal.

[0019] In some embodiments, the first transient liquid phase bonding layer and the second transient liquid phase bonding layer each further include a diffusion barrier layer, the diffusion barrier layer being disposed between the low-melting-point metal layer and the high-melting-point metal layer, the diffusion barrier layer being made of titanium, chromium, and / or nickel, and the melting point of the diffusion barrier layer being higher than that of the low-melting-point metal layer. In some embodiments, a getter is disposed within the cavity; the first temperature required for bonding heating in the first transient liquid phase bonding process is different from the second temperature required for bonding heating in the second transient liquid phase bonding process; in the first and second transient liquid phase bonding processes, the transient liquid phase bonding process with the lower required temperature is executed first to avoid activating the getter; then, the other transient liquid phase bonding process with the higher required temperature is executed, and the getter is activated.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0022] Figure 1 is a schematic diagram of a packaging structure provided in an embodiment of this application.

[0023] Figure 2 is a schematic diagram of the structure of a first transient liquid phase bonding layer or a second transient liquid phase bonding layer provided in an embodiment of this application.

[0024] Figure 3 is a flowchart illustrating a method for manufacturing an encapsulation structure according to an embodiment of this application. Detailed Implementation

[0025] The technical solutions in the embodiments (or "implementations") of this application will be clearly and completely described herein with reference to the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0026] If the embodiments of this application contain terms relating to directional indications or positional relationships (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationships and movement of the components in a specific posture; if the specific posture changes, the directional indications or positional relationships will also change accordingly. Furthermore, the terms "first" and "second" used in the embodiments of this application are only for descriptive convenience and should not be construed as indicating or implying relative importance.

[0027] Current infrared detector packaging technologies often suffer from poor material thermal matching, insufficient hermeticity, and complex manufacturing processes, especially in uncooled infrared detectors integrated with MEMS (Micro-electromechanical Systems). To further improve the optical performance of infrared detectors, integrated microlens technology has gradually become an important means to improve the focusing ability of light signals and improve the field of view. However, integrating microlenses into the packaging structure of infrared detectors usually involves complex optical alignment and packaging processes, and the mechanical strength, hermeticity, and thermal matching of the packaging also pose challenges. The inventors discovered that transient liquid phase bonding (TLP) is a process in which a low-melting-point metal layer forms a transient liquid phase at a specific temperature, which diffuses with adjacent materials and eventually solidifies into a strong bonding layer. Transient liquid phase bonding has good material compatibility, hermeticity, and high mechanical strength, making it very suitable for the packaging of high-precision electronic devices such as infrared detectors.

[0028] In view of this, embodiments of this application provide a packaging structure 100 integrating optical elements and photosensitive devices, as shown in FIG1. ​​The packaging structure 100 includes a photosensitive device 20 and an optical element 30. One surface of the photosensitive device 20 is bonded to one surface of the optical element 30 through a transient liquid phase bonding layer.

[0029] Because transient liquid phase bonding achieves the connection through diffusion between metals, the joint has high strength and toughness, thus ensuring high mechanical strength of the packaging structure. Furthermore, the transient liquid phase bonding process ensures that the joint is free of defects such as cracks and pores, thereby guaranteeing high reliability and high hermeticity of the packaging structure.

[0030] In some embodiments, the encapsulation structure 100 may further include a gasket 40, and the transient liquid phase bonding layer may include a first transient liquid phase bonding layer 50 and a second transient liquid phase bonding layer 60. The gasket 40 may be annular in a horizontal cross-section perpendicular to the second direction Z. The gasket 40 may have a first end 41 and a second end 43 that are opposite to and far apart from each other.

[0031] The photosensitive device 20 may have a first surface 21 and a second surface 23. Both the first surface 21 and the second surface 23 may extend a certain length in a first direction X. The first surface 21 and the second surface 23 may be arranged at different heights in a second direction Z.

[0032] The photosensitive device 20 may be or includes an infrared detector. The infrared detector is the core component of the packaging structure 100, responsible for converting infrared light signals into electrical signals. The first surface 21 of the photosensitive device 20 may be provided with a photosensitive material layer 70, capable of efficiently absorbing infrared light of a certain wavelength. The substrate material of the photosensitive device 20 may be silicon (Si), germanium (Ge), etc. Silicon and germanium are commonly used materials in manufacturing processes, and their coefficients of thermal expansion are suitable for high-temperature packaging processes.

[0033] The optical element 30 has a third surface 35 and a fourth surface 37. Both the third surface 35 and the fourth surface 37 extend a certain length along a first direction X. The third surface 35 and the fourth surface 37 can be arranged at different heights along a second direction Z. The fourth surface 37 of the optical element 30 is positioned face-to-face with the first surface 21 of the photosensitive device 20.

[0034] The optical element 30 may be or includes a microlens array structure. The microlens array is primarily used to focus infrared light entering the infrared detector, enhancing signal strength and improving the detector's FOV (Field of View) and sensitivity. The design of the microlens array not only considers the optical focal length but also ensures precise correspondence between each lens and its corresponding detector element to avoid focus shift or signal loss.

[0035] The optical element 30 may include a base 32 and a lens portion 34. The first end 41 of the spacer 40 may be bonded to the edge region 323 of the base 32. The lens portion 34 may be integrally formed in the middle region 325 of the base 32.

[0036] The optical element 30 can be made of materials with high infrared transmittance and good thermal stability. Materials for the optical element 30 include silicon and germanium. These materials, combined with an antireflective coating, exhibit good infrared transmittance, particularly in the long-wave infrared (LWIR) range of 8 to 14 micrometers.

[0037] The lens portion 34 can adopt a spherical or aspherical geometry. The lens portion 34 can effectively focus infrared light, reduce light scattering, and enhance the collection efficiency of the light signal. The diameter and radius of curvature of the lens can be customized according to the specific requirements of the infrared detector to optimize optical performance.

[0038] The first end 41 of the spacer 40 may be adjacent to the fourth surface 37 of the optical element 30. The second end 43 of the spacer 40 may be adjacent to the first surface 21 of the photosensitive device 20. In an infrared detector, the spacer 40 can be used to adjust the distance between the lens portion 34 and the photosensitive material layer 70, so as to facilitate the photosensitive material layer 70 to better receive or focus light from the lens portion 34. The length of the spacer 40 in the second direction Z can be adjusted according to the focal length requirement of the lens portion 34. The length of the spacer 40 in the second direction Z can be adjusted by grinding, etching, or other methods.

[0039] The gasket 40 can be made of silicon, silicon oxide, silicon oxynitride, or other materials compatible with the process. The cross-sectional shape of the gasket 40 can be a circular through-hole ring, and the diameter of the circle can be set as needed.

[0040] The first end 41 of the gasket 40 can be bonded to the fourth surface 37 of the optical element 30 via the first transient liquid phase bonding layer 50. The second end 43 of the gasket 40 can be bonded to the first surface 21 of the photosensitive device 20 via the second transient liquid phase bonding layer 60. After bonding, the photosensitive device 20, the optical element 30, and the gasket 40 form a cavity 12. A getter 80 can be provided in the cavity 12 to ensure a vacuum and low-gas environment within the cavity 12. The getter 80 can be provided on the fourth surface 37 of the optical element 30. Since air and moisture can reduce the thermal insulation of sensor elements, including the photosensitive material layer 70, their sensitivity will decrease. In particular, high-sensitivity image sensors used in thermal imagers and thermal imaging cameras require very high vacuum levels. Therefore, the provision of the getter 80 and the vacuum environment within the cavity 12 are beneficial to improving the sensitivity of the photosensitive material layer 70.

[0041] Traditional bonding processes require higher temperatures, which can prematurely activate the getter 80. Before bonding is complete and the cavity 12 is isolated from the external environment, prematurely activated getter 80 cannot reduce the air volume or vacuum level within the cavity 12. In contrast, transient liquid-phase bonding processes require lower heating temperatures, typically avoiding premature activation of the getter 80. This ensures a vacuum environment within the cavity 12 after bonding is complete, thereby improving the sensitivity of the photosensitive material layer 70.

[0042] The first transient liquid phase bonding layer 50 and the second transient liquid phase bonding layer 60 are used to achieve transient liquid phase bonding. During the transient liquid phase bonding process, the low-melting-point metal material forms a transient liquid phase at high temperature, and forms intermetallic compounds (IMCs) through diffusion and solidification, thus forming a stable multilayer bonding structure.

[0043] Prior to bonding, a first transient liquid phase bonding layer 50 may be pre-formed at the first end 41 of the pad 40. Prior to bonding, the first transient liquid phase bonding layer 50 may also be pre-formed on the fourth surface 37 of the optical element 30.

[0044] The first transient liquid phase bonding layer 50, as shown in Figures 1 and 2, may include a first low-melting-point metal layer 54 and a first high-melting-point metal layer 52. The first low-melting-point metal layer 54 and the first high-melting-point metal layer 52 are the main components of the first transient liquid phase bonding layer 50. The first low-melting-point metal layer 54 is primarily made of low-melting-point metals, such as indium (In) and / or tin (Sn). The first high-melting-point metal layer 52 is primarily made of gold (Au) and / or copper (Cu) and / or nickel (Ni). The melting point of the first high-melting-point metal layer 52 is higher than that of the first low-melting-point metal layer 54. These low-melting-point metals can form a liquid phase at relatively low temperatures, interdiffused with the high-melting-point metals, and rapidly solidify into a stable high-melting-point solid structure upon cooling.

[0045] The first transient liquid phase bonding layer 50 may further include a first interface promoting layer 51. The first interface promoting layer 51 is disposed between the solder (including the first low-melting-point metal layer 54 and the first high-melting-point metal layer 52, etc.) and the substrate, serving as an adhesion layer. When the first transient liquid phase bonding layer 50 is pre-formed at the first end 41 of the gasket 40, the first interface promoting layer 51 may be disposed between the first end 41 of the gasket 40 and the first high-melting-point metal layer 52. When the first transient liquid phase bonding layer 50 is pre-formed on the fourth surface 37 of the optical element 30, the first interface promoting layer 51 may be disposed between the fourth surface 37 of the optical element 30 and the first high-melting-point metal layer 52. In some embodiments, a first transient liquid phase bonding layer 50 is pre-configured on the first end 41 of the gasket 40, and another first transient liquid phase bonding layer 50 is pre-configured on the fourth surface 37 of the optical element 30. In this case, a first interface promoting layer 51 is disposed between the first end 41 of the gasket 40 and the first high-melting-point metal layer 52 on the gasket 40, and between the fourth surface 37 of the optical element 30 and the first high-melting-point metal layer 52 on the optical element 30. The material of the first interface promoting layer 51 may include titanium (Ti), chromium (Cr), nickel (Ni), etc.

[0046] The first transient liquid phase bonding layer 50 may further include a first liquid phase protective layer 55. The first liquid phase protective layer 55 is used to prevent oxidation of the first low-melting-point metal layer 54. Oxidation will cause a decrease in the bonding performance of the metal and affect the subsequent diffusion effect. The first liquid phase protective layer 55 may cover the first low-melting-point metal layer 54.

[0047] When a first transient liquid phase bonding layer 50 is pre-formed on the first end 41 of the gasket 40, the first liquid phase protective layer 55 may be disposed on the side of the first low-melting-point metal layer 54 away from the first end 41 of the gasket 40. When a first transient liquid phase bonding layer 50 is pre-formed on the fourth surface 37 of the optical element 30, the first liquid phase protective layer 55 may be disposed on the side of the first low-melting-point metal layer 54 away from the fourth surface 37 of the optical element 30. In some embodiments, a first transient liquid phase bonding layer 50 is pre-configured on the first end 41 of the gasket 40, and another first transient liquid phase bonding layer 50 is pre-configured on the fourth surface 37 of the optical element 30. In this case, the first liquid phase protective layer 55 may be disposed on the side of the first low-melting-point metal layer 54 on the gasket 40 away from the first end 41 of the gasket 40, and on the side of the first low-melting-point metal layer 54 on the optical element 30 away from the fourth surface 37 of the optical element 30. The first liquid phase protective layer 55 may be made of an inert metal such as gold (Au) or platinum (Pt). The first liquid phase protective layer 55 effectively isolates oxygen from the air, preventing oxidation of the bonded metals.

[0048] The first liquid phase protective layer 55 can be deposited on the surface of the first low-melting-point metal layer 54 by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), or sputtering. In the above deposition process, the thickness of the first liquid phase protective layer 55 can be controlled at the nanometer level, thereby ensuring sufficient protection for the first low-melting-point metal layer 54 without affecting the bonding performance.

[0049] The first transient liquid phase bonding layer 50 may further include a first diffusion barrier layer 53. The function of the first diffusion barrier layer 53 is to prevent the first low-melting-point metal layer 54 from diffusing prematurely during heating, ensuring the controllability of the bonding process. Premature diffusion can lead to uneven bonding and may impair the alignment of the optical element 30 with the photosensitive device 20. The first diffusion barrier layer 53 may be disposed between the first low-melting-point metal layer 54 and the first high-melting-point metal layer 52. The material of the first diffusion barrier layer 53 may include titanium (Ti), chromium (Cr), and / or nickel (Ni). The melting point of the first diffusion barrier layer 53 is higher than that of the first low-melting-point metal layer 54, allowing the first diffusion barrier layer 53 to remain stable in a solid state at high temperatures, preventing the first low-melting-point metal layer 54 from diffusing prematurely to the high-melting-point metal to form an IMC during heating. The first diffusion barrier layer 53 may be deposited using processes such as physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0050] Prior to bonding, a second transient liquid phase bonding layer 60 may be pre-formed on the first surface 21 of the photosensitive device 20. Prior to bonding, the second transient liquid phase bonding layer 60 may also be pre-formed on the second end 43 of the pad 40.

[0051] As shown in Figures 1 and 2, the second transient liquid phase bonding layer 60 may include a second low-melting-point metal layer 64 and a second high-melting-point metal layer 62. The second low-melting-point metal layer 64 and the second high-melting-point metal layer 62 are the main components of the second transient liquid phase bonding layer 60. The material of the second low-melting-point metal layer 64 is mainly a low-melting-point metal, such as indium (In) or tin (Sn). The melting point of the second high-melting-point metal layer 62 is higher than that of the second low-melting-point metal layer 64. These low-melting-point metals can form a liquid phase at relatively low temperatures, forming interdiffusion with the high-melting-point metal and rapidly solidifying into a stable high-melting-point solid structure upon cooling.

[0052] The second transient liquid phase bonding layer 60 may further include a second interface promoting layer 61. The second interface promoting layer 61 is positioned between the solder and the substrate, acting as an adhesion layer. When the second transient liquid phase bonding layer 60 is pre-formed on the first surface 21 of the photosensitive device 20, the second interface promoting layer 61 may be disposed between the first surface 21 of the photosensitive device 20 and the second high-melting-point metal layer 62. When the second transient liquid phase bonding layer 60 is pre-formed on the second end 43 of the spacer 40, the second interface promoting layer 61 may be disposed between the second end 43 of the spacer 40 and the second high-melting-point metal layer 62. In some embodiments, a first transient liquid phase bonding layer 60 is pre-configured on the second end 43 of the gasket 40, and another second transient liquid phase bonding layer 60 is pre-configured on the first surface 21 of the photosensitive device 20. In this case, the second interface promoting layer 61 may be disposed between the second end 43 of the gasket 40 and the second high melting point metal layer 62 on the gasket, and between the first surface 21 of the photosensitive device 20 and the second high melting point metal layer 62 on the photosensitive device.

[0053] The material of the second interface promoting layer 61 may include titanium (Ti), chromium (Cr), nickel (Ni), etc.

[0054] The second transient liquid phase bonding layer 60 may further include a second liquid phase protective layer 65. The second liquid phase protective layer 65 is used to prevent oxidation of the second low-melting-point metal layer 64. Oxidation will cause a decrease in the bonding performance of the metal and affect the subsequent diffusion effect. The second liquid phase protective layer 65 may cover the second low-melting-point metal layer 64.

[0055] When the second transient liquid phase bonding layer 60 is pre-formed on the first surface 21 of the photosensitive device 20, the second liquid phase protective layer 66 may be disposed on the side of the second low-melting-point metal layer 64 away from the first surface 21 of the photosensitive device 20. When the second transient liquid phase bonding layer 60 is pre-formed on the second end 43 of the pad 40, the second liquid phase protective layer 65 may be disposed on... In some embodiments, the second end 43 of the pad 40 is pre-configured with a first transient liquid phase bonding layer 60, and the first surface 21 of the photosensitive device 20 is pre-configured with another second transient liquid phase bonding layer 60. In this case, the second liquid phase protective layer 66 may be disposed on the side of the second low-melting-point metal layer 64 on the pad 40 away from the second end 43 of the pad 40, and on the side of the second low-melting-point metal layer 64 on the photosensitive device 20 away from the first surface 21 of the photosensitive device 20. The material of the second liquid phase protective layer 65 may include inert metals such as gold (Au) and platinum (Pt). The second liquid phase protective layer 65 can effectively isolate oxygen in the air and prevent the bonding metal from oxidizing.

[0056] The second liquid phase protective layer 65 can be deposited on the surface of the second low-melting-point metal layer 64 by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), or sputtering. In the above deposition processes, the thickness of the second liquid phase protective layer 65 can be controlled at the nanometer level, thereby ensuring sufficient protection for the second low-melting-point metal layer 64 without affecting the bonding performance.

[0057] The second transient liquid-phase bonding layer 60 may further include a second diffusion barrier layer 63. The function of the second diffusion barrier layer 63 is to prevent the second low-melting-point metal layer 64 from diffusing prematurely during heating, ensuring the controllability of the bonding process. Premature diffusion can lead to uneven bonding and may impair the alignment of the optical element 30 with the photosensitive device 20. The second diffusion barrier layer 63 may be disposed between the second low-melting-point metal layer 64 and the second high-melting-point metal layer 62. The material of the second diffusion barrier layer 63 may include titanium (Ti), chromium (Cr), and / or nickel (Ni). The melting point of the second diffusion barrier layer 63 is higher than that of the second low-melting-point metal layer 64, allowing the second diffusion barrier layer 63 to remain stable in a solid state at high temperatures, preventing the second low-melting-point metal layer 64 from diffusing prematurely to the second high-melting-point metal layer 62 during heating. The second diffusion barrier layer 63 can be deposited using processes such as physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0058] In the above packaging structure, by adding a gasket, a three-layer bonding packaging structure of optical element-gasket-photosensitive device is formed. This structure can improve the sealing of the bonding area and the reliability of the device.

[0059] The first transient liquid phase bonding layer uses a low-temperature transient liquid phase bonding process (e.g., Au-In 200℃) to avoid premature activation of the getter; at the same time, the bonded IMC (intermetallic compound) has a high melting point, which can improve the sealing and stability of the bonding area; the second transient liquid phase bonding uses a relatively high-temperature transient liquid phase bonding process (e.g., Au-Sn 280℃) to activate the getter and complete vacuum bonding.

[0060] In addition, by preparing the first transient liquid phase bonding layer and the second transient liquid phase bonding layer through thin film deposition process, the thickness of the solder layer can be significantly reduced and the consistency improved, the deviation in the vertical direction (i.e., the second direction Z in Figure 1) after bonding can be reduced, and the optical alignment accuracy can be improved.

[0061] Furthermore, by introducing a diffusion barrier layer and a liquid phase protective layer, the transient liquid phase bonded metal structure can be further optimized, thereby improving the bonding quality.

[0062] By integrating optical elements into the aforementioned packaging structure of the photosensitive device, the integration and wafer-level packaging of microlens arrays on infrared uncooled detectors can be achieved. This method is also applicable to three-layer wafer-level packaging (WLP) to meet the needs of industrial mass production and low-cost process manufacturing.

[0063] This application also provides a method for fabricating a package structure integrating optical elements and photosensitive devices. The fabrication method can be used to fabricate the package structure 100 as described above. As shown in Figures 1 and 3, the fabrication method includes steps S20 to S40.

[0064] Step S20: Provide a photosensitive device 20, an optical element 30, and a spacer 40. The photosensitive device 20 has a first surface 21, the optical element 30 has a fourth surface 37, and the spacer 40 is annular with a first end 41 and a second end 43 that are opposite to and far apart from each other.

[0065] Step S40: Using a first transient liquid phase bonding process, the first end 41 of the pad 40 is bonded to the fourth surface 37 of the optical element 30 through a first transient liquid phase bonding layer 50. Using a second transient liquid phase bonding process, the second end 43 of the pad 40 is bonded to the first surface 21 of the photosensitive device 20 through a second transient liquid phase bonding layer 60. The fourth surface 37 and the first surface 21 of the photosensitive device 20 are arranged face to face. The photosensitive device 20, the optical element 30 and the pad 40 enclose a cavity 12.

[0066] Optical element 30 can be fabricated or provided using microfabrication processes such as photolithography and etching. The main material of optical element 30 can be silicon.

[0067] The gasket 40 can be fabricated using microfabrication processes such as photolithography, etching, and grinding. Silicon can be used as the main material for the gasket 40.

[0068] Before bonding begins, the surfaces of the photosensitive device 20 and the optical element 30 should be cleaned to ensure they are free of contaminants. Additionally, a precise alignment device can be used to align the photosensitive device 20 and the optical element 30 to ensure accurate focusing of the infrared light. The alignment accuracy of the microlens array and the infrared detector is one of the key aspects of the packaging design. Precise alignment ensures that the focal point of the lens falls precisely within the photosensitive area of ​​the infrared detector, improving the collection efficiency of the infrared light signal. Simultaneously, the thickness of the spacer can be precisely controlled to achieve the optimal focal length.

[0069] In some embodiments, the first end 41 of the pad 40 is bonded to the fourth surface 37 of the optical element 30 via a first transient liquid phase bonding layer 50 using a first transient liquid phase bonding process, including: disposing the first transient liquid phase bonding layer 50 on the first end 41 of the pad 40 and / or the fourth surface 37 of the optical element 30; aligning the optical element 30 with the pad 40; heating to a first temperature in a vacuum or inert gas environment (such as a nitrogen environment) to melt the first transient liquid phase bonding layer 50 into a liquid phase and diffuse to form an intermetallic compound; and completing the bonding after cooling and solidification. The first temperature is the melting temperature of the first low-melting-point metal layer 54, etc., which is typically between 200°C and 400°C.

[0070] The first transient liquid phase bonding layer 50 can be prepared using a thin film deposition process. This thin film deposition process may include physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering, or electroplating. This process allows for control of the thickness of the first transient liquid phase bonding layer 50 within the micrometer range, ensuring a suitable liquid phase thickness is formed during bonding.

[0071] In some embodiments, the second end 43 of the pad 40 is bonded to the first surface 21 of the photosensitive device 20 via the second transient liquid phase bonding layer 60 using a second transient liquid phase bonding process, including: disposing the second transient liquid phase bonding layer 60 on the first surface 21 of the photosensitive device 20 and / or the second end 43 of the pad 40; aligning the photosensitive device 20 with the pad 40; heating to a second temperature in a vacuum or inert gas environment (such as a nitrogen environment) to melt the second transient liquid phase bonding layer 60 into a liquid phase and diffuse to form an intermetallic compound; and completing the bonding after cooling and solidification. The second temperature is the melting temperature of the second low-melting-point metal layer 64, etc., which is typically between 200°C and 400°C.

[0072] The second transient liquid phase bonding layer 60 can be prepared using a thin film deposition process. This thin film deposition process may include physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering, or electroplating. This process allows for control of the thickness of the second transient liquid phase bonding layer 60 at the micrometer level, ensuring a suitable liquid phase thickness is formed during bonding.

[0073] In both of the above bonding processes, when the bonding material is heated or reaches a predetermined temperature, pressure can be applied to make the bonding tighter. Applying pressure during the bonding process can also improve the quality of thin-layer solder bonding.

[0074] During the bonding process, as the bonding time increases, the solder metal gradually diffuses at the interface with the substrate, forming a stable bond structure. After diffusion ends, the temperature gradually decreases, and the liquid metal re-solidifies, thus forming a solid bond layer with high mechanical strength, airtightness, and temperature resistance.

[0075] To further enhance the strength and long-term stability of the encapsulation structure, the first transient liquid phase bonding layer 50 and / or the second transient liquid phase bonding layer 60 can adopt a multilayer design. That is, both the first transient liquid phase bonding layer 50 and the second transient liquid phase bonding layer 60 can include multiple low-melting-point metal layers, each with a different melting point. Since the multiple low-melting-point metal layers are stacked sequentially and gradually solidify after each heating diffusion, a multilayer bonding structure can be formed, thereby enhancing mechanical strength and improving thermal compatibility.

[0076] To avoid premature activation of the getter, the first temperature required for bonding heating in the first transient liquid phase bonding process and the second temperature required for bonding heating in the second transient liquid phase bonding process may be different. Throughout the process, a transient liquid phase bonding process with a lower required temperature can be performed first to prevent premature activation of the getter. Then, another transient liquid phase bonding process with a higher required temperature is performed, and this higher temperature will simultaneously activate the getter. In some embodiments, in the first transient liquid phase bonding process corresponding to the first transient liquid phase bonding layer 50, the first temperature required for bonding heating is relatively low (e.g., Au-In 200°C), which can prevent premature activation of the getter. In the second transient liquid phase bonding process corresponding to the second transient liquid phase bonding layer 60, the second temperature required for bonding heating is relatively high (e.g., Au-Sn 280°C), which can activate the getter. Correspondingly, the first transient liquid phase bonding process can be performed first, followed by the second transient liquid phase bonding process.

[0077] In the packaging structures and manufacturing methods of the above embodiments, the entire packaging structure consists of multiple layers, including a photosensitive device, optical elements, and spacers. This multi-layer bonding structure not only improves integration but also ensures the matching of thermal expansion coefficients between different materials, reducing stress caused by temperature changes.

[0078] Through transient liquid phase bonding technology, the packaging structure can achieve high airtightness, which can effectively prevent external contaminants such as water vapor and dust from entering the packaging cavity, ensuring the reliability of photosensitive devices in long-term use.

[0079] It should be noted that the technical solutions or features described in the above embodiments can be combined or complemented by each other without conflict. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the accompanying drawings; all modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A packaging structure integrating optical elements and photosensitive devices, comprising: A photosensitive device (20) has a first surface (21); An optical element (30) has a fourth surface (37) which is disposed face-to-face with the first surface (21) of the photosensitive device (20); A transient liquid phase bonding layer is provided, wherein the first surface (21) of the photosensitive device (20) is bonded to the fourth surface (37) of the optical element (30) through the transient liquid phase bonding layer.

2. The packaging structure as described in claim 1, wherein, The packaging structure (100) further includes: A gasket (40) is annular and has a first end (41) and a second end (43) that are opposite to each other and far apart. The first end (41) is adjacent to the fourth surface (37) of the optical element (30), and the second end (43) is adjacent to the first surface (21) of the photosensitive device (20). The transient liquid phase bonding layer is located between the pad (40) and the photosensitive device (20), and between the pad (40) and the optical element (30); The photosensitive device (20), the optical element (30), and the gasket (40) together form a cavity (12).

3. The packaging structure as described in claim 2, wherein, The transient liquid-phase bonding layers (50, 60) include low-melting-point metal layers (54, 64) and high-melting-point metal layers (52, 62). The low-melting-point metal layer (54, 64) is made of indium and / or tin. The high-melting-point metal layers (52, 62) are made of gold, copper and / or nickel.

4. The packaging structure as described in claim 3, wherein, The transient liquid-phase bonding layers (50, 60) further include interface promoting layers (51, 61). Wherein, the transient liquid phase bonding layer (50, 60) satisfies at least one of the following: When the transient liquid phase bonding layer (50, 60) is pre-formed on the first end (41) of the gasket (40), the interface promoting layer (51, 61) is disposed between the first end (41) of the gasket (40) and the high melting point metal layer (52, 62). When the transient liquid phase bonding layer (50, 60) is pre-formed on the second end (43) of the gasket (40), the interface promoting layer (51, 61) is disposed between the second end (43) of the gasket (40) and the high melting point metal layer (52, 62); when the transient liquid phase bonding layer (50, 60) is pre-formed on the fourth surface (37) of the optical element (30), the interface promoting layer (51, 61) is disposed between the fourth surface (37) of the optical element (30) and the high melting point metal layer (52, 62); When the transient liquid bonding layer (50, 60) is pre-formed on the first surface (21) of the photosensitive device (20), the interface promoting layer (51, 61) is disposed between the first surface (21) of the photosensitive device (20) and the high melting point metal layer (52, 62). The interface promoting layer (51, 61) is made of materials including titanium, chromium and / or nickel.

5. The packaging structure as described in claim 3, wherein, The transient liquid phase bonding layers (50, 60) further include liquid phase protective layers (55, 65). The liquid phase protective layer (55, 65) covers the low melting point metal layer (54, 64). The transient liquid-phase bonded layers (50, 60) satisfy at least one of the following: When the transient liquid phase bonding layer (50) is pre-formed on the first end (41) of the gasket (40), the liquid phase protective layer (55, 65) is disposed on the side of the low melting point metal layer (54, 64) away from the first end (41) of the gasket (40); When the transient liquid phase bonding layer (50) is pre-formed on the second end (43) of the gasket (40), the liquid phase protective layer (55, 65) is disposed on the side of the low melting point metal layer (54, 64) away from the second end (43) of the gasket (40); when the transient liquid phase bonding layer (50, 60) is pre-formed on the fourth surface (37) of the optical element (30), the liquid phase protective layer (55, 65) is disposed on the side of the low melting point metal layer (54, 64) away from the fourth surface (37) of the optical element (30); When the transient liquid phase bonding layer (50, 60) is pre-formed on the first surface (21) of the photosensitive device (20), the liquid phase protective layer (55, 65) is disposed on the side of the low melting point metal layer (54, 64) away from the first surface (21) of the photosensitive device (20); The liquid phase protective layer (55, 65) is made of inert metal.

6. The packaging structure as described in claim 5, wherein, The transient liquid-phase bonding layers (50, 60) further include diffusion barrier layers (53, 63). The diffusion barrier layer (53, 63) is disposed between the low-melting-point metal layer (54, 64) and the low-melting-point metal layer (54, 64). The diffusion barrier layers (53, 63) are made of materials including titanium, chromium, and / or nickel. The melting point of the diffusion barrier layer (53, 63) is higher than that of the low melting point metal layer (54, 64).

7. The packaging structure as described in claim 2, wherein, The optical element (30) is a microlens array structure, and the optical element (30) includes a base (32) and a lens portion (34). The first end (41) of the gasket (40) is bonded to the edge region (323) of the base (32), and the lens portion (34) is integrally formed in the middle region (325) of the base (32).

8. The packaging structure as described in claim 2, wherein, The material of the gasket (40) includes silicon, silicon oxide or silicon nitride; A getter (80) is provided inside the cavity (12); The photosensitive device (20) includes an infrared detector; The first surface (21) of the photosensitive device (20) is provided with a photosensitive material layer (70).

9. A method for fabricating a packaging structure integrating optical elements and photosensitive devices, comprising: A photosensitive device (20) and an optical element (30) are provided, the photosensitive device (20) having a first surface (21) and the optical element (30) having a fourth surface (37); The first surface (21) of the photosensitive device (20) is bonded to the fourth surface (37) of the optical element (30) through a transient liquid phase bonding process, wherein the fourth surface (37) of the optical element (30) and the first surface (21) of the photosensitive device (20) are arranged face to face.

10. The manufacturing method as described in claim 9, further comprising: A gasket (40) is provided, wherein the gasket (40) is annular and has a first end (41) and a second end (43) that are opposite to and far apart from each other; The process of bonding the first surface (21) of the photosensitive device (20) to the fourth surface (37) of the optical element (30) using the transient liquid phase bonding process includes: The first end (41) of the gasket (40) is bonded to the fourth surface (37) of the optical element (30) through the first transient liquid phase bonding layer (50) using the first transient liquid phase bonding process; The second end (43) of the pad (40) is bonded to the first surface (21) of the photosensitive device (20) through the second transient liquid phase bonding layer (60) using the second transient liquid phase bonding process; The photosensitive device (20), the optical element (30), and the gasket (40) together form a cavity (12).

11. The manufacturing method as described in claim 10, wherein, Using the first transient liquid phase bonding process, the first end (41) of the gasket (40) is bonded to the fourth surface (37) of the optical element (30) through the first transient liquid phase bonding layer (50), including: The first transient liquid phase bonding layer (50) is disposed on the first end (41) of the pad (40) and / or the fourth surface (37) of the optical element (30); the optical element (30) is aligned with the pad (40); in a vacuum or inert gas environment, it is heated to a first temperature to melt the first transient liquid phase bonding layer (50) into a liquid phase and diffuse to form an intermetallic compound, and the bonding is completed after cooling and solidification, wherein the first temperature is between 200°C and 400°C; and / or The second transient liquid phase bonding process is used to bond the pad (40) to the first surface (21) of the photosensitive device (20) through the second transient liquid phase bonding layer (60), including: The second transient liquid phase bonding layer (60) is disposed on the first surface (21) of the photosensitive device (20) and / or the second end (43) of the gasket (40); Align the photosensitive device (20) with the pad (40); In a vacuum or inert gas environment, the second transient liquid phase bonding layer (60) is heated to a second temperature, causing it to melt into a liquid phase and diffuse to form an intermetallic compound. After cooling and solidification, the bonding is completed. The second temperature is between 200°C and 400°C.

12. The manufacturing method as described in claim 11, wherein, The first transient liquid phase bonding layer (50) and / or the second transient liquid phase bonding layer (60) are prepared by thin film deposition process.

13. The manufacturing method as described in claim 11, wherein, The first transient liquid phase bonding layer (50) and the second transient liquid phase bonding layer (60) each include a low-melting-point metal layer (54, 64) and a high-melting-point metal layer (52, 62). The low-melting-point metal layer (54, 64) is made of indium and / or tin. The high-melting-point metal layers (52, 62) are made of gold, copper and / or nickel.

14. The manufacturing method as described in claim 13, wherein, The first transient liquid phase bonding layer (50) and the second transient liquid phase bonding layer (60) each further include interface promoting layers (51, 61). in, When the first transient liquid phase bonding layer (50) is pre-formed at the first end (41) of the gasket (40), the interface promoting layer (51) is disposed between the first end (41) of the gasket (40) and the high melting point metal layer (52), and / or When the first transient liquid bonding layer (50) is pre-formed on the fourth surface (37) of the optical element (30), the interface promoting layer (51) is disposed between the fourth surface (37) of the optical element (30) and the high melting point metal layer (52); and / or in, When the second transient liquid phase bonding layer (60) is pre-formed on the first surface (21) of the photosensitive device (20), the interface promoting layer (61) is disposed between the first surface (21) of the photosensitive device (20) and the high melting point metal layer (62), and / or When the second transient liquid phase bonding layer (60) is pre-formed on the second end (43) of the gasket (40), the interface promoting layer (61) is disposed between the second end (43) of the gasket (40) and the high melting point metal layer (62); The interface promoting layer (51, 61) is made of materials including titanium, chromium and / or nickel.

15. The manufacturing method as described in claim 13, wherein, The first transient liquid phase bonding layer (50) and the second transient liquid phase bonding layer (60) each further include a liquid phase protective layer (55, 65). The liquid phase protective layer (55, 65) covers the low melting point metal layer (54, 64). in, When the first transient liquid phase bonding layer (50) is pre-formed at the first end (41) of the gasket (40), the liquid phase protective layer (55) is disposed on the side of the low melting point metal layer (54) away from the first end (41) of the gasket (40), and / or When the first transient liquid phase bonding layer (50) is pre-formed on the fourth surface (37) of the optical element (30), the liquid phase protective layer (55) is disposed on the side of the low melting point metal layer (54) away from the fourth surface (37) of the optical element (30), and the material of the liquid phase protective layer (55) includes an inert metal; and / or in, When the second transient liquid phase bonding layer (60) is pre-formed on the first surface (21) of the photosensitive device (20), the liquid phase protective layer (65) is disposed on the side of the low melting point metal layer (64) away from the first surface (21) of the photosensitive device (20), and / or When the second transient liquid phase bonding layer (60) is pre-formed on the second end (43) of the gasket (40), the liquid phase protective layer (65) is disposed on the side of the low melting point metal layer (64) away from the second end (43) of the gasket (40), and the material of the liquid phase protective layer (65) includes an inert metal.

16. The manufacturing method as described in claim 15, wherein, The first transient liquid phase bonding layer (50) and the second transient liquid phase bonding layer (60) each further include diffusion barrier layers (53, 63). The diffusion barrier layer (53, 63) is disposed between the low-melting-point metal layer (54, 64) and the high-melting-point metal layer (52, 62). The diffusion barrier layers (53, 63) are made of materials including titanium, chromium, and / or nickel. The melting point of the diffusion barrier layer (53, 63) is higher than that of the low melting point metal layer (54, 64).

17. The manufacturing method as described in claim 10, wherein, A getter is provided inside the cavity; The first temperature required for bonding heating in the first transient liquid phase bonding process is different from the second temperature required for bonding heating in the second transient liquid phase bonding process; In the first transient liquid phase bonding process and the second transient liquid phase bonding process, the transient liquid phase bonding process with a lower required temperature is executed first to avoid activating the getter; then the other transient liquid phase bonding process with a higher required temperature is executed to activate the getter.

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