Vacuum packaging structure of optical device

Abstract

The invention provides an optical device vacuum packaging structure, which comprises a window sheet, a chip and a transition ring, and is characterized in that the transition ring is arranged on the upper surface of the chip, the transition ring and the chip are enclosed to form a packaging cavity with a top opening, the window sheet is connected to the transition ring in an embedded manner, and the window sheet seals the opening of the packaging cavity. According to the invention, the transition ring is arranged between the window and the chip, so that the distance between the window and the chip is increased, the influence of redundant materials is reduced, and the yield is improved; meanwhile, the window sheet is embedded in the transition ring, and the inner ring wall body of the transition ring is used for protecting the periphery of the window sheet, so that the damage risk of the window sheet in the packaging process is reduced, and the manufacturing cost of the packaging structure is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor packaging, and in particular relates to a vacuum packaging structure of an optical device. Background Art

[0002] MEMS (micro-electromechanical) devices are generally required to be hermetically packaged due to their fragile structure to ensure the stability of the MEMS structure and reliable functions. In particular, special devices, such as MEMS infrared devices, MEMS accelerometers, MEMS gyroscopes, etc., need to be packaged with protective gas or even vacuum packaged. In order to further reduce the packaging cost, the mainstream packaging method is wafer-level packaging, which is to bond the chip to the window piece as a whole and then slice it to obtain a single chip. However, the upper window piece of conventional wafer-level packaging is limited by the etching process, and the etching depth of the cavity inside the window piece is limited, resulting in a small cavity distance between the window piece and the chip, which cannot meet the requirements of high performance at low cost.

[0003] Typical single chip structure after wafer-level packaging of optical devices is as follows: Figure 1 As shown, the upper window piece 1 and the bottom chip 4 are airtightly welded through the solder layer 2; the distance between the window piece 1 and the chip 3 is limited by the cavity etching depth of the lower surface of the window piece 1, and the spacing is small, so the imaging effect is easily affected by the surface defects of the window piece 1, resulting in poor finished products; and the four sides of the window piece 1 are exposed and unprotected, and there is a risk of being easily damaged during the packaging process; at the same time, the window piece 1 has a large area and a high cost, and the optional space for wafer-level packaging window material is limited, which cannot meet the requirements of high-performance chips. Summary of the invention

[0004] The purpose of the present invention is to provide a vacuum packaging structure for optical devices, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A vacuum packaging structure for an optical device comprises a window piece, a chip and a transition ring, wherein the transition ring is arranged on the upper surface of the chip, and the transition ring and the chip enclose a packaging cavity with a top opening, the window piece is embedded and connected to the transition ring, and the window piece seals the opening of the packaging cavity.

[0007] Furthermore, a getter is provided in the packaging cavity, and an isolation structure for blocking heat radiation of the getter to the sensitive area of ​​the chip is provided between the getter and the sensitive area of ​​the chip.

[0008] Furthermore, the isolation structure is an isolation chamber arranged in the transition ring wall body, the isolation chamber is communicated with the packaging cavity, and the getter is placed in the isolation chamber.

[0009] Furthermore, the isolation chamber is an inverted U-shaped structure formed by a first vertical section, a first horizontal section and a second vertical section, and the bottom of the second vertical section is connected to the chip.

[0010] Furthermore, the top of the window piece is not higher than the top of the transition ring.

[0011] Furthermore, the side wall of the transition ring connected to the window piece is an L-shaped structure, and the window piece is placed in the horizontal section of the L-shaped structure.

[0012] Furthermore, the above-mentioned optical device vacuum packaging structure also includes a conductive element for electrically activating the desiccant, one end of the conductive element passes through the transition ring and extends into the packaging cavity, the desiccant is welded to the end of the conductive element, and an insulating material layer is filled between the conductive element and the transition ring.

[0013] Furthermore, the above-mentioned vacuum packaging structure of the optical device also includes a conductive element for electrically activating the desiccant, and the inner and outer surfaces of the transition ring corresponding to the installation position of the conductive element are respectively provided with an intra-cavity metal gasket and a surface metal coating, the end of the conductive element is welded to the surface metal coating, the desiccant is welded to the intra-cavity metal gasket, and the intra-cavity metal gasket and the surface metal coating are electrically connected.

[0014] Furthermore, a matte structure is provided on the inner side wall of the transition ring.

[0015] Furthermore, the matt structural component is at least one of a light-absorbing film layer, a rough surface structural layer or a step structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention increases the distance between the window and the chip by setting a transition ring between the window and the chip, reduces the influence of superfluous materials, and improves the yield; at the same time, the window is embedded in the transition ring, and the inner ring wall of the transition ring is used to protect the window around, thereby reducing the risk of damage to the window during the packaging process and reducing the manufacturing cost of the packaging structure.

[0018] (2) The present invention isolates the getter by setting up an isolation chamber and uses electric activation to locally heat and activate the getter, thereby reducing the impact of heat on the sensitive area of ​​the chip and improving the chip performance.

[0019] (3) The present invention designs a matte structure for the inner side wall of the transition ring to reduce the reflectivity of the inner side wall of the transition ring, thereby reducing the influence of stray light on chip imaging and further improving product quality.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a single chip after existing wafer-level packaging;

[0022] Figure 2 It is a schematic diagram of the vacuum packaging structure of an optical device in which the conducting element adopts a lead-in electrode in the present invention;

[0023] Figure 3 It is a schematic diagram of the vacuum packaging structure of an optical device in which the conducting element adopts a pad electrode in the present invention;

[0024] Figure 4 Schematic diagram of the connection mode between the transition ring and the conducting element when the transition ring is made of kovar metal material in the present invention, wherein (a) the conducting element is a lead-in electrode, and (b) the conducting element is a pad electrode;

[0025] Figure 5 Schematic diagram of the connection mode between the transition ring and the conductive element when the transition ring is made of ceramic material in the present invention, wherein (a) the conductive element is a lead-in electrode, and (b) the conductive element is a pad electrode;

[0026] Figure 6 It is a schematic diagram of the window structure in the vacuum packaging structure of the optical device of the present invention;

[0027] Figure 7 It is a schematic diagram of the chip structure in the vacuum packaging structure of the optical device of the present invention;

[0028] Figure 8 It is a schematic diagram of the matting treatment of the inner wall of the transition ring in the vacuum packaging structure of the optical device of the present invention; wherein, (a) the inner wall surface of the transition ring is a step structure, (b) the inner wall surface of the transition ring is a rough surface structure, and (c) the inner wall surface of the transition ring is coated with a light-absorbing film layer.

[0029] Explanation of the reference numerals in the accompanying drawings: 1. Window; 2. Solder layer; 3. Chip; 4. Transition ring; 5. Packaging cavity; 6. Getter; 7. Isolation chamber; 8. Conductive element; 9. First horizontal section; 10. First vertical section; 11. Second horizontal section; 12. Second vertical section; 13. Insulating material layer; 14. Metal gasket; 15. Surface metal plating; 16. Light-transmitting area; 17. Window welding area; 18. Chip welding area; 19. Sensitive area; 20. Metal gasket in the cavity. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0034] like Figure 2 and Figure 3 As shown, this embodiment provides a vacuum packaging structure for an optical device, including a window 1, a chip 3 and a transition ring 4, wherein the transition ring 4 is arranged on the upper surface of the chip 3, and the transition ring 4 and the chip 3 enclose a packaging cavity 5 with an opening at the top, and the window 1 is embedded and connected to the transition ring 4, and the window 1 seals the opening of the packaging cavity 5. In this embodiment, by arranging the transition ring 4 between the window 1 and the chip 3, the protective gas packaging / vacuum packaging of the optical device is realized, the spacing between the window 1 and the chip 3 is increased, the imaging abnormality problem caused by the defects on the surface of the window 1 on the chip is reduced, and the product yield is improved; at the same time, the window 1 is embedded in the transition ring 4, that is, the side wall of the window 1 is at least partially embedded in the wall of the transition ring 4, so that the wall of the transition ring 4 can be used to envelop and protect the window 1, which reduces the area of ​​the window 1 and reduces the risk of damage to the window 1 during the packaging process, thereby reducing the manufacturing cost of the packaging structure.

[0035] Among them, the lower surface of the transition ring 4 is airtightly bonded to the chip 3 through the solder layer 2, and the transition ring 4 and the window piece 1 are airtightly bonded through the solder layer 2. The material of the solder layer 2 can be selected but not limited to gold-tin solder, indium-silver solder, tin-silver-copper solder; the three-layer bonding structure is formed by the window piece 1, the transition ring 4, and the chip 3, and the bonding stress is relatively small, which effectively avoids the problem of large bonding stress of the two-layer bonding of the traditional window piece 1 and the chip 3, which easily causes the chip 3 to warp and has great bonding difficulty.

[0036] In some embodiments, the structure of the window sheet 1 is as follows: Figure 6 As shown, it includes a light-transmitting area 16 and a window welding area 17 arranged outside the light-transmitting area 16. The base material of the window 1 can be selected from silicon, germanium, sapphire, calcium fluoride, etc. The window welding area 17 is a metal coating for welding with the transition ring 4, which can be plated with Ni / Au. The light-transmitting area 16 is used to transmit light so that the light can irradiate the sensitive area of ​​the chip 3. The light-transmitting area 16 can be coated with ZnS, AlF3, MgF2 and other materials for anti-reflection treatment, and can also be etched with microstructures to increase the transmittance of the window. The structure of the chip 3 is as shown in FIG. Figure 7 As shown, it includes a chip welding area 18 and a sensitive area 19, wherein the sensitive area 19 is used to receive the light projected from the window 1 and convert the optical signal into an electrical signal; the metal plating of the chip welding area 18 is used for sealing and welding with the transition ring 4, and the metal plating material of the chip welding area 18 can be selected but not limited to Ni / Au.

[0037] In an optimized implementation, a getter 6 is provided in the packaging cavity 5 to absorb the air inside the packaging cavity 5, so that the packaging cavity 5 is vacuum packaged, and an isolation structure is provided between the getter 6 and the sensitive area of ​​the chip to block the heat radiation of the getter to the sensitive area of ​​the chip, thereby preventing the getter 6 from activating and releasing heat to interfere with the sensitive area 19 of the chip 3, thereby improving the chip performance. The getter 6 can be made of getter materials such as barium aluminum alloy, zirconium vanadium iron and zirconium aluminum.

[0038] In some embodiments, the isolation structure can be designed as an isolation chamber 7 disposed in the wall of the transition ring 4, the isolation chamber 7 is connected to the packaging cavity 5, and the getter 6 is placed in the isolation chamber 7. Specifically, the isolation chamber 7 can be designed as an inverted U-shaped structure formed by the first vertical section 10, the first horizontal section 9 and the second vertical section 12, the second vertical section 12 also serves as the side wall of the packaging cavity 5, the bottom of the second vertical section 12 is connected to the chip 3, and the projection of the isolation chamber 7 on the chip 3 is located outside the sensitive area 19 of the chip 3. In this embodiment, the isolation chamber 7 is disposed on the transition ring 4, and on the basis of effectively isolating the getter 6, the window 1 and the chip 3 structure will not be affected.

[0039] Preferably, the top of the window sheet 1 is designed not to be higher than the top of the transition ring 4 , so that the wall of the transition ring 4 can completely wrap around the side wall of the window sheet 1 , thereby providing better protection for the window sheet 1 .

[0040] Furthermore, the side wall of the transition ring 4 connected to the window sheet 1 can be designed as an L-shaped structure, and the window sheet 1 is placed in the horizontal section of the L-shaped structure to support the window sheet 1, and the window sheet 1 and the horizontal section can be connected by airtight bonding through a solder layer; preferably, the height of the vertical section of the L-shaped structure is not less than the thickness of the window sheet 1, and the vertical section of the L-shaped structure is used to envelop and protect the window sheet 1. Specifically, for the L-shaped structure design of the side wall of the transition ring 4 at the isolation chamber, a second horizontal section 11 extending horizontally toward the inside of the packaging cavity 5 can be connected to the end of the first vertical section 10, and the window sheet 1 is placed on the second horizontal section 11, and the height of the first vertical section 10 is not less than the thickness of the window sheet 1. In this embodiment, the transition ring 4 can be formed by machining processes such as cutting and milling, and the base material of the transition ring 4 can be selected but not limited to Kovar alloy material and ceramic material.

[0041] In a preferred embodiment, the getter 6 is electrically activated, so the optical device vacuum packaging structure further includes a conductive element 8 for electrically activating the getter 6; and as for the connection between the conductive element 8 and the getter 6, in some embodiments, such as Figure 4 As shown, one end of the conductive element 8 can be extended through the transition ring 4 to the package cavity 5, the getter 6 is welded to the end of the conductive element 8, and the insulating material layer 13 is filled between the conductive element 8 and the transition ring 4. The conductive element 8 can be a lead pin electrode or a pad electrode. The pad electrode has a large contact area, which is convenient for contacting and conducting to activate the getter 6. The specific structure of the conductive element 8 can be selected according to actual needs; the end of the conductive element 8 extending into the package cavity 5 is connected with a metal gasket 14 to facilitate welding of the getter 6. The material of the metal gasket 14 can be selected from kovar metal, such as 4j42 or 4j29, with Ni / Au plated on the surface; the insulating material layer 13 can be selected from ceramic material.

[0042] In other embodiments, Figure 5As shown, the inner and outer surfaces of the transition ring 4 corresponding to the installation position of the conductive element 8 can also be provided with an intracavity metal gasket 20 and a surface metal coating 15, respectively. The end of the conductive element 8 is welded to the surface metal coating 15, and the getter 6 is welded to the intracavity metal gasket 20. The intracavity metal gasket 20 and the surface metal coating 15 can be electrically connected through the internal wiring of the transition ring 4, so that the conductive element 8 and the intracavity metal gasket 20 are electrically connected inside and outside, and the getter 6 is electrically activated. In this embodiment, the conductive element 8 can also use a lead pin electrode or a pad electrode, and the material of the intracavity metal gasket 20 and the surface metal coating 15 can be selected from Ni / Au.

[0043] In order to reduce the impact of incident light on the sensitive area of ​​the chip caused by reflected light generated by the inner wall of the transition ring 4 after the transition ring 4 is added between the window 1 and the chip 3, the inner side of the transition ring 4 can be subjected to low reflection extinction treatment. For example, an extinction structure can be processed on the inner side of the transition ring 4 to reduce the reflectivity of the inner wall of the transition ring 4, thereby reducing the impact of stray light on chip imaging. In some embodiments, the inner wall surface of the transition ring 4 can be designed as a step structure, such as Figure 8 As shown in Figure (a), the light irradiated from the window 1 to the inner wall of the transition ring 4 is reflected by the side wall to the horizontal step surface, thereby eliminating the influence of the reflected light generated by the incident light irradiating the side wall on the sensitive area of ​​the chip 3; the inner surface of the transition ring 4 can also be roughened to form a rough surface structure, such as Figure 8 As shown in Figure (b), the irregularity of the inner wall surface of the transition ring 4 causes the incident light to be diffusely reflected or scattered, thereby reducing the intensity of the reflected light; a light-absorbing film layer can also be added to the inner wall surface of the transition ring 4, such as Figure 8 As shown in Figure (c), the absorption effect of the light-absorbing film layer on light is used to reduce the adverse effects caused by the incident light irradiating the inner wall of the transition ring 4. The light-absorbing film layer can be an ultra-black nano-film layer or a vacuum-deposited black light-absorbing film layer. The darker the material, the wider the light absorption range. The ultra-black film layer can absorb light incident on the surface of the material, including ultraviolet light, visible light, near-infrared light, and light in the mid- and far-infrared bands.

[0044] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. An optical device vacuum packaging structure, characterized in that: It includes a window piece, a chip and a transition ring. The transition ring is arranged on the upper surface of the chip, and the transition ring and the chip are combined to form a packaging cavity with a top opening. The window piece is embedded and connected to the transition ring, and the window piece seals the opening of the packaging cavity.

2. The optical device vacuum packaging structure according to claim 1, characterized in that: A getter is arranged in the packaging cavity, and an isolation structure for blocking heat radiation of the getter to the sensitive area of ​​the chip is arranged between the getter and the sensitive area of ​​the chip.

3. The optical device vacuum packaging structure according to claim 2, characterized in that: The isolation structure is an isolation chamber arranged in the transition ring wall body, the isolation chamber is communicated with the packaging cavity, and the getter is placed in the isolation chamber.

4. The optical device vacuum packaging structure according to claim 3, characterized in that: The isolation chamber is an inverted U-shaped structure formed by a first vertical section, a first horizontal section and a second vertical section, and the bottom of the second vertical section is connected to the chip.

5. The optical device vacuum packaging structure according to claim 1, characterized in that: The top of the window piece is not higher than the top of the transition ring.

6. The optical device vacuum packaging structure according to claim 1, characterized in that: The side wall of the transition ring connected to the window piece is an L-shaped structure, and the window piece is placed in a horizontal section of the L-shaped structure.

7. The optical device vacuum packaging structure according to claim 2, characterized in that: It also includes a conducting element for electrically activating the getter, one end of the conducting element passes through the transition ring and extends into the packaging cavity, the getter is welded to the end of the conducting element, and an insulating material layer is filled between the conducting element and the transition ring.

8. The optical device vacuum packaging structure according to claim 2, characterized in that: It also includes a conductive element for electrically activating the getter, and the inner and outer surfaces of the transition ring corresponding to the installation position of the conductive element are respectively provided with an intra-cavity metal gasket and a surface metal coating, the end of the conductive element is welded to the surface metal coating, the getter is welded to the intra-cavity metal gasket, and the intra-cavity metal gasket and the surface metal coating are electrically connected.

9. The optical device vacuum packaging structure according to claim 1, characterized in that: A matte structural part is provided on the inner side wall of the transition ring.

10. The optical device vacuum packaging structure according to claim 9, characterized in that: The matt structure is at least one of a light-absorbing film layer, a rough surface structure layer or a step structure.

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