Vacuum packaging structure for optical device

Abstract

Provided in the present invention is a vacuum packaging structure for an optical device. The vacuum packaging structure comprises a window piece, a chip and a transition ring, wherein the transition ring is disposed on the upper surface of the chip, and the transition ring and the chip form a packaging cavity which is open at the top; and the window piece is connected to the transition ring in an embedded manner, and seals the opening of the packaging cavity. In the present invention, by means of providing the transition ring between the window piece and the chip, the distance between the window piece and the chip is increased, reducing the influence of foreign matter, and improving the yield; moreover, the window piece is embedded in the transition ring, and the periphery of the window piece is protected by means of an inner ring wall of the transition ring, thereby reducing the risk of damage to the window piece during a packaging process, and reducing the manufacturing cost of a packaging structure.

Description

Optical device vacuum packaging structure TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor packaging, and particularly relates to an optical device vacuum packaging structure. BACKGROUND

[0002] MEMS (microelectromechanical system) devices generally need to be hermetically packaged to ensure the stability of the MEMS structure and the reliability of the function due to the fragile structure. In particular, special devices such as MEMS infrared devices, MEMS accelerometers, MEMS gyroscopes and the like need to be packaged by introducing protective gas or even vacuum packaging. In order to further reduce the packaging cost, the mainstream packaging method is wafer-level packaging, which bonds the chip and the window sheet in a whole piece and then gets a single chip by dicing. However, the upper window sheet of the conventional wafer-level packaging is limited by the etching process, and the etching depth of the cavity inside the window sheet is limited, resulting in a small distance between the window sheet and the chip, which cannot meet the requirements of high performance while reducing the cost.

[0003] A typical single chip structure of an optical device after wafer-level packaging is shown in FIG. 1. The upper window sheet 1 and the bottom chip 4 are hermetically welded by a solder layer 2. The distance between the window sheet 1 and the chip 3 is limited by the etching depth of the cavity on the lower surface of the window sheet 1, and the spacing is small, so that the imaging effect is easily affected by the surface defects of the window sheet 1, causing the finished product to be defective. Moreover, the four edges of the window sheet 1 are exposed without protection, which has the risk of being damaged during the packaging process. At the same time, the window sheet 1 has a large area and high cost, and the selection space of the window sheet material for wafer-level packaging is limited, which cannot meet the requirements of high-performance chips. SUMMARY

[0004] The purpose of the present application is to provide an optical device vacuum packaging structure, which can at least solve some of the defects in the prior art.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0006] An optical device vacuum packaging structure, comprising a window sheet, 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 enclose a packaging cavity with an open top, the window sheet is embedded and connected to the transition ring, and the window sheet seals the opening of the packaging cavity.

[0007] Further, an adsorbent is arranged in the packaging cavity, and an isolation structure for blocking the heat radiation of the adsorbent to the sensitive area of the chip is arranged between the adsorbent and the sensitive area of the chip.

[0008] Further, the isolation structure is an isolation chamber arranged in the wall of the transition ring, the isolation chamber is in communication with the packaging cavity, and the adsorbent is arranged in the isolation chamber.

[0009] Further, the isolation chamber is a reverse U-shaped structure enclosed by a first vertical section, a first horizontal section and a second vertical section, and the bottom of the second vertical section is connected with the chip.

[0010] Further, the top of the window sheet is not higher than the top of the transition ring.

[0011] Further, the side wall of the transition ring where the window sheet is connected is in an L-shaped structure, and the window sheet is arranged on the horizontal section of the L-shaped structure.

[0012] Further, the optical device vacuum packaging structure further comprises a conducting element for electrically activating the getter, one end of the conducting element extends through the transition ring 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.

[0013] Further, the optical device vacuum packaging structure further comprises a conducting element for electrically activating the getter, and the inner and outer surfaces of the transition ring corresponding to the mounting position of the conducting element are respectively provided with an inner cavity metal gasket and a surface metal plating layer, the end of the conducting element is welded to the surface metal plating layer, the getter is welded to the inner cavity metal gasket, and the inner cavity metal gasket and the surface metal plating layer are electrically connected.

[0014] Further, the inner side wall of the transition ring is provided with a light extinction structure.

[0015] Further, the light extinction structure is at least one of a light-absorbing film layer, a rough surface structure layer or a stepped structure.

[0016] Compared with the prior art, the beneficial effects of the present application are:

[0017] (1) The present application increases the distance between the window sheet and the chip by arranging a transition ring between the window sheet and the chip, reduces the influence of excess material, and improves the yield; at the same time, the window sheet is embedded in the transition ring, and the inner ring wall of the transition ring forms protection around the window sheet, thereby reducing the risk of damage to the window sheet during packaging and reducing the manufacturing cost of the packaging structure.

[0018] (2) The present application isolates the getter by arranging an isolation chamber, and locally heats and activates the getter by using an electric activation method, thereby reducing the influence of heat on the sensitive area of the chip and improving the performance of the chip.

[0019] (3) The present application designs a light extinction structure on 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 the imaging of the chip and further improving the product quality.

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

[0021] Fig. 1 is a schematic diagram of a single chip structure after wafer level packaging in the prior art;

[0022] Fig. 2 is a schematic diagram of a vacuum packaging structure of an optical device in the present application, in which a lead pin electrode is used as a lead-through element;

[0023] Fig. 3 is a schematic diagram of a vacuum packaging structure of an optical device in the present application, in which a solder pad electrode is used as a lead-through element;

[0024] Fig. 4 is a schematic diagram of a connection between a lead-through element and a transition ring in the present application, in which (a) a lead pin electrode is used as a lead-through element, and (b) a solder pad electrode is used as a lead-through element;

[0025] Fig. 5 is a schematic diagram of a connection between a lead-through element and a transition ring in the present application, in which (a) a lead pin electrode is used as a lead-through element, and (b) a solder pad electrode is used as a lead-through element;

[0026] Fig. 6 is a schematic diagram of a window structure in a vacuum packaging structure of an optical device in the present application;

[0027] Fig. 7 is a schematic diagram of a chip structure in a vacuum packaging structure of an optical device in the present application;

[0028] Fig. 8 is a schematic diagram of an inner wall light absorption treatment of a transition ring in a vacuum packaging structure of an optical device in the present application, in which (a) the inner wall surface of the transition ring is a stepped 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 absorption film layer.

[0029] Reference signs: 1, window; 2, solder layer; 3, chip; 4, transition ring; 5, packaging cavity; 6, getter; 7, isolation chamber; 8, lead-through 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 coating layer; 16, light transmission area; 17, window soldering area; 18, chip soldering area; 19, sensitive area; 20, cavity metal gasket. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0031] In the description of the present application, it needs to be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0032] In the description of the present application, it needs to be understood that the terms "installation", "connection", "connection" should be understood broadly, for example, it can be fixed connection, it can also be detachable connection, it can also be in contact connection or integral connection; for those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] The terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features; in the description of the present application, unless otherwise stated, the meaning of "multiple" is two or more.

[0034] As shown in FIGS. 2 and 3, the present embodiment provides an optical device vacuum packaging structure, which comprises a window sheet 1, a chip 3 and a transition ring 4, the transition ring 4 is arranged on the upper surface of the chip 3, and the transition ring 4 and the chip 3 form a top-opened packaging cavity 5, the window sheet 1 is embeddedly connected to the transition ring 4, and the window sheet 1 seals the opening of the packaging cavity 5. In the present embodiment, by arranging the transition ring 4 between the window sheet 1 and the chip 3, the protective gas packaging / vacuum packaging of the optical device is realized, the spacing between the window sheet 1 and the chip 3 is increased, the imaging abnormal problem caused by the defects on the surface of the window sheet 1 on the chip is reduced, and the product yield is improved; at the same time, the window sheet 1 is embedded on the transition ring 4, that is, the side wall of the window sheet 1 is at least partially inlaid in the wall body of the transition ring 4, so that the wall body of the transition ring 4 can be used to envelope and protect the window sheet 1 around, the area of the window sheet 1 is reduced, and the damage risk of the window sheet 1 in the packaging process is also reduced, thereby reducing the manufacturing cost of the packaging structure.

[0035] The lower surface of the transition ring 4 is connected to the chip 3 by a solder layer 2, and the transition ring 4 is connected to the window sheet 1 by a solder layer 2. The material of the solder layer 2 can be selected from, but is not limited to, gold-tin solder, indium-silver solder, and tin-silver-copper solder. The window sheet 1, the transition ring 4, and the chip 3 form a three-layer bonding structure, the bonding stress is relatively small, and the problems of large bonding stress of the traditional two-layer bonding structure of the window sheet 1 and the chip 3, chip 3 warping, and difficult bonding are effectively avoided.

[0036] In some embodiments, the structure of the window sheet 1 is shown in FIG. 6, which includes a light transmission area 16 and a window sheet welding area 17 arranged on the periphery of the light transmission area 16. The base material of the window sheet 1 can be selected from silicon, germanium, sapphire, calcium fluoride, etc. The window sheet welding area 17 is a metal plating layer for welding with the transition ring 4, which can be plated with Ni / Au. The light transmission area 16 is used for transmitting light to irradiate the sensitive area of the chip 3. The light transmission area 16 can be coated with ZnS, AlF3, MgF2, etc. for antireflection treatment, or can be etched with a microstructure for increasing the transmission capacity of the window sheet. The structure of the chip 3 is shown in FIG. 7, which includes a chip welding area 18 and a sensitive area 19. The sensitive area 19 is used for receiving light projected from the window sheet 1 and converting the optical signal into an electrical signal. The chip welding area 18 is plated with metal for fusion sealing with the transition ring 4. The metal plating material of the chip welding area 18 can be selected from, but is not limited to, Ni / Au.

[0037] In an optimized embodiment, an air adsorber 6 is arranged in the packaging cavity 5 to absorb the air inside the packaging cavity 5, so that the packaging cavity 5 reaches a vacuum packaging state. An isolation structure is arranged between the air adsorber 6 and the sensitive area of the chip to block the heat radiation of the air adsorber to the sensitive area of the chip, thereby preventing the air adsorber 6 from activating heat release to interfere with the sensitive area 19 of the chip 3 and improving the performance of the chip. The air adsorber 6 can be selected from barium aluminum alloy, zirconium vanadium iron, and zirconium aluminum, etc.

[0038] In some embodiments, the isolation structure can be designed as an isolation chamber 7 arranged in the wall of the transition ring 4. The isolation chamber 7 is in communication with the packaging cavity 5, and the air adsorber 6 is arranged in the isolation chamber 7. Specifically, the isolation chamber 7 can be designed as a reverse U-shaped structure enclosed by a first vertical section 10, a first horizontal section 9, and a second vertical section 12. The second vertical section 12 simultaneously serves as a 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 arranged on the transition ring 4, which effectively isolates the air adsorber 6 without affecting the structure of the window sheet 1 and the chip 3.

[0039] Preferably, the top of the window sheet 1 is designed to be not higher than the top of the transition ring 4, so that the wall of the transition ring 4 can completely envelop the side wall of the window sheet 1, and the window sheet 1 is better protected.

[0040] Further, the side wall of the transition ring 4 connected with the window sheet 1 can be designed as an L-shaped structure, the window sheet 1 is placed on the horizontal section of the L-shaped structure, and the window sheet 1 is supported by the horizontal section, and the window sheet 1 and the horizontal section can be connected by a solder layer airtight bonding; preferably, the vertical section of the L-shaped structure is designed to have a height 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 into the packaging cavity 5 can be connected to the end of the first vertical section 10, 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 machined by cutting, milling and other machining processes, and the base material of the transition ring 4 can be selected from, but not limited to, Kovar alloy material and ceramic material.

[0041] In a preferred embodiment, the getter 6 is electrically activated, and therefore the above-mentioned optical device vacuum packaging structure further comprises a conducting element 8 for electrically activating the getter 6; and for the connection mode of the conducting element 8 and the getter 6, in some embodiments, as shown in FIG. 4, one end of the conducting element 8 extends into the packaging cavity 5 through the transition ring 4, the getter 6 is welded to the end of the conducting element 8, and the conducting element 8 and the transition ring 4 are filled with an insulating material layer 13. The conducting element 8 can be a lead pin electrode, and can also be a pad electrode, the pad electrode has a large contact area, which is convenient for contacting and activating the getter 6, and the specific structure of the conducting element 8 can be selected according to actual needs; a metal gasket 14 is connected to the end of the conducting element 8 extending into the packaging cavity 5, so as to facilitate welding of the getter 6, the metal gasket 14 can be made of Kovar metal such as 4j42 or 4j29, and the surface is plated with Ni / Au; the insulating material layer 13 can be made of ceramic material.

[0042] In some other embodiments, as shown in Fig. 5, the inner and outer surfaces of the transition ring 4 corresponding to the installation position of the conductive element 8 can also be respectively provided with a cavity inner metal pad 20 and a surface metal plating layer 15, the end of the conductive element 8 is welded to the surface metal plating layer 15, and the getter 6 is welded to the cavity inner metal pad 20. The cavity inner metal pad 20 and the surface metal plating layer 15 can be electrically connected through the internal wiring of the transition ring 4, so that the conductive element 8 is in electrical connection with the inner and outer surfaces of the cavity inner metal pad 20, and the getter 6 is electrically activated. In this embodiment, the conductive element 8 can also be a pin electrode or a pad electrode, and the materials of the cavity inner metal pad 20 and the surface metal plating layer 15 can be selected from Ni / Au.

[0043] In order to reduce the influence of the reflected light generated by the incident light irradiated to the inner side wall of the transition ring 4 on the sensitive area of the chip 3 after the transition ring 4 is added between the window sheet 1 and the chip 3, the inner side of the transition ring 4 can be subjected to low reflection extinction treatment. For example, the inner side of the transition ring 4 can be processed to have an extinction structure, so that the reflectivity of the inner side wall of the transition ring 4 is reduced, thereby reducing the influence of stray light on the imaging of the chip. In some embodiments, the inner side wall surface of the transition ring 4 can be designed to have a stepped structure, as shown in Fig. 8(a). The light irradiated to the inner side wall of the transition ring 4 from the window sheet 1 is reflected to the horizontal stepped surface, thereby eliminating the influence of the reflected light generated by the incident light irradiated to the inner side wall on the sensitive area of the chip 3. The inner surface of the transition ring 4 can also be subjected to roughening treatment to form a rough surface structure, as shown in Fig. 8(b). The irregularity of the inner side 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. The inner side wall surface of the transition ring 4 can also be coated with a light-absorbing film layer, as shown in Fig. 8(c). The light-absorbing film layer absorbs the light to reduce the adverse effects caused by the incident light irradiated to the inner side wall of the transition ring 4. The light-absorbing film layer can be an ultrablack nanometer film layer or a vacuum-deposited black light-absorbing film layer. The darker the material, the wider the light absorption range. The ultrablack film layer can absorb the light, including ultraviolet light, visible light, near-infrared light, and mid-far infrared light, irradiated to the surface of the material.

[0044] The above examples are only illustrative of the present application and do not constitute a limitation on the protection scope of the present application. Any design identical or similar to the present application falls within the protection scope of the present application.

Claims

1. An optical device vacuum package structure, characterized by: The package includes a window sheet, 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 enclose a top-opened package cavity, the window sheet is embeddedly connected to the transition ring, and the window sheet seals the opening of the package cavity.

2. The optical device vacuum packaging structure according to claim 1, wherein: An adsorber is arranged in the package cavity, and an isolation structure for blocking heat radiation of the adsorber to a sensitive area of the chip is arranged between the adsorber and the sensitive area of the chip.

3. The optical device vacuum encapsulation structure of claim 2, wherein: The isolation structure is an isolation chamber arranged in the wall of the transition ring, the isolation chamber is in communication with the package cavity, and the adsorber is arranged in the isolation chamber.

4. The optical device vacuum packaging structure according to claim 3, wherein: The isolation chamber is a reverse 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, wherein: The top of the window sheet is not higher than the top of the transition ring.

6. The optical device vacuum packaging structure according to claim 1, wherein: The sidewall of the transition ring connected to the window sheet is an L-shaped structure, and the window sheet is arranged on the horizontal section of the L-shaped structure.

7. The optical device vacuum packaging structure according to claim 2, wherein: A conducting element for electrically activating the adsorber is further included, one end of the conducting element extends through the transition ring into the package cavity, the adsorber 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, wherein: A conducting element for electrically activating the adsorber is further included, inner and outer surfaces of the transition ring corresponding to the mounting position of the conducting element are respectively provided with an inner cavity metal gasket and a surface metal plating layer, the end of the conducting element is welded to the surface metal plating layer, the adsorber is welded to the inner cavity metal gasket, and the inner cavity metal gasket and the surface metal plating layer are electrically connected.

9. The optical device vacuum packaging structure according to claim 1, wherein: An extinction structure is arranged on the inner sidewall of the transition ring.

10. The optical device vacuum packaging structure according to claim 9, wherein: The extinction structure is at least one of a light-absorbing film layer, a rough surface structure layer or a stepped structure.

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