Vacuum packaging structure body and packaging method thereof

Abstract

The invention relates to the field of vacuum packaging, and discloses a vacuum packaging structural body and a packaging method thereof.The vacuum packaging structural body comprises a substrate, a first packaging cap layer, a second packaging cap layer, an MEMS structure and a sealing layer, the first packaging cap layer is provided with a first opening, and the second packaging cap layer is provided with a second opening; the size of the second opening is smaller than that of the first opening; the first packaging cap layer is connected with the substrate and forms a first cavity with the substrate; the MEMS structure is located in the first cavity; the second packaging cap layer is connected with the surface, deviating from the first cavity, of the first packaging cap layer, and forms a second cavity with the first packaging cap layer; the second cavity is communicated with the first cavity through the first opening; the sealing layer is located on the surface of the second packaging cap layer and seals the second opening. According to the vacuum packaging structure body, the release efficiency of the sacrificial layer can be improved, the release effect can be improved, the sealing yield can be improved, and the problem of air leakage can be solved.

Description

Technical Field

[0001] The present application relates to the field of vacuum packaging, and particularly to a vacuum packaging structure and a packaging method thereof. Background Art

[0002] Vacuum packaging is an important link in the manufacturing of semiconductor devices, providing a vacuum environment for the MEMS (MicroElectro Mechanical Systems) structure in the packaging structure.

[0003] During the packaging process, a sacrificial layer is formed between the substrate and the packaging cap. A small hole is opened in the packaging cap, and the sacrificial layer is released through the small hole, and then the small hole is sealed. The size of the small hole in the packaging cap is related to the release efficiency of the sacrificial layer and the problem of release residue of the sacrificial layer. When the size of the small hole is relatively small, the release efficiency of the sacrificial layer will be very low, and it is easy to have release residues that are difficult to remove. When the size of the small hole is relatively large, although the release efficiency of the sacrificial layer can be improved, when making the sealing layer, the deposited coating particles will more easily affect the sealing yield, resulting in air leakage problems.

[0004] Therefore, how to solve the above technical problems should be the focus of attention of those skilled in the art. Summary of the Invention

[0005] The purpose of the present application is to provide a vacuum packaging structure and a packaging method thereof to improve the release efficiency of the sacrificial layer, reduce release residues, and improve the sealing yield.

[0006] To solve the above technical problems, the present application provides a vacuum packaging structure, including:

[0007] A substrate, a first packaging cap layer, a second packaging cap layer, a MEMS structure, and a sealing layer. The first packaging cap layer is provided with a first opening, and the second packaging cap layer is provided with a second opening; the size of the second opening is smaller than the size of the first opening;

[0008] The first packaging cap layer is connected to the substrate and forms a first cavity with the substrate; the MEMS structure is located in the first cavity;

[0009] The second packaging cap layer is connected to the surface of the first packaging cap layer facing away from the first cavity and forms a second cavity with the first packaging cap layer; the second cavity and the first cavity are communicated through the first opening;

[0010] The sealing layer is located on the surface of the second packaging cap layer and seals the second opening.

[0011] Optionally, the number of the first openings is at least one, and the projection of the second opening communicated with each first opening on the substrate is staggered from the projection of the first opening on the substrate.

[0012] Optionally, the number of the second openings communicated with each first opening is at least two, and the projection of the second opening on the substrate surrounds the projection of the first opening on the substrate.

[0013] Optionally, it further includes:

[0014] A support structure, located in the first cavity and between the first encapsulation cap layer and the substrate, for supporting the first encapsulation cap layer.

[0015] Optionally, the support structure includes support columns and a support tabletop, the support columns are located on the surface of the substrate, and the support tabletop is located on the surface of the support columns away from the substrate;

[0016] The area of the first encapsulation cap layer corresponding to the support tabletop is recessed into the first cavity, and the recessed area of the first encapsulation cap layer contacts the support tabletop;

[0017] The recessed area of the first encapsulation cap layer corresponds to at least the support tabletops of the support structures except those on both sides of the vacuum encapsulation structure.

[0018] Optionally, the projection of the first opening on the substrate is located between the projections of any two adjacent support structures on the substrate.

[0019] Optionally, it further includes:

[0020] A getter layer, located in the first cavity and on the surface of the substrate.

[0021] Optionally, the materials of the first encapsulation cap layer and the second encapsulation cap layer are the same.

[0022] Optionally, the number of the second encapsulation cap layers is equal to the number of the first openings, and the projection of one first opening on the substrate is located within the projection range of one second encapsulation cap layer on the substrate.

[0023] This application also provides a packaging method for a vacuum encapsulation structure, including:

[0024] Forming a first sacrificial layer on the surface of the substrate;

[0025] Fabricating a MEMS structure on the surface of the first sacrificial layer;

[0026] Forming a second sacrificial layer on the surface of the first sacrificial layer where the MEMS structure is distributed;

[0027] Etch the first sacrificial layer and the second sacrificial layer located in the edge region of the substrate, and fabricate a first encapsulation cap layer; the first encapsulation cap layer wraps the first sacrificial layer and the second sacrificial layer and is connected to the substrate;

[0028] Etch the first encapsulation cap layer to form a first opening;

[0029] Release the first sacrificial layer and the second sacrificial layer through the first opening to form a first cavity;

[0030] Fabricate a third sacrificial layer on the surface of the first encapsulation cap layer facing away from the first cavity;

[0031] Fabricate a second encapsulation cap layer on the surface of the third sacrificial layer; the second encapsulation cap layer wraps the third sacrificial layer and is connected to the first encapsulation cap layer;

[0032] Etch the second encapsulation cap layer to form a second opening; the size of the second opening is smaller than that of the first opening;

[0033] Release the third sacrificial layer through the second opening to form a second cavity; the second cavity and the first cavity communicate with each other through the first opening;

[0034] Fabricate a sealing layer on the surface of the second encapsulation cap layer, and the sealing layer seals the second opening.

[0035] Optionally, after forming the first sacrificial layer on the surface of the substrate, it further includes:

[0036] Etch the first sacrificial layer to form a first through-hole;

[0037] Fabricate a support structure at the first through-hole, and the support structure is located on the surface of the substrate and is used to support the first encapsulation cap layer;

[0038] After forming the second sacrificial layer on the surface of the first sacrificial layer where the MEMS structure is distributed, it further includes:

[0039] Etch the second sacrificial layer to form a second through-hole to expose the support structure.

[0040] Optionally, before forming the first sacrificial layer on the surface of the substrate, it further includes:

[0041] Fabricate a getter layer on the surface of the substrate.

[0042] Optionally, after fabricating the third sacrificial layer on the surface of the first encapsulation cap layer facing away from the first cavity, it further includes:

[0043] Etch the third sacrificial layer to form at least two patterned third sacrificial layers; the projection of one of the first openings on the substrate is within the projection of one of the third sacrificial layers on the substrate.

[0044] Fabricating a second encapsulation cap layer on the surface of the third sacrificial layer includes:

[0045] Simultaneously fabricate a second encapsulation cap layer on the surface of the patterned third sacrificial layer; the projection of one of the first openings on the substrate is within the projection of one of the second encapsulation cap layers on the substrate.

[0046] A vacuum encapsulation structure provided by the present application includes: a substrate, a first encapsulation cap layer, a second encapsulation cap layer, a MEMS structure, and a sealing layer. The first encapsulation cap layer is provided with a first opening, and the second encapsulation cap layer is provided with a second opening; the size of the second opening is smaller than the size of the first opening; the first encapsulation cap layer is connected to the substrate and forms a first cavity with the substrate; the MEMS structure is located in the first cavity; the second encapsulation cap layer is connected to the surface of the first encapsulation cap layer facing away from the first cavity and forms a second cavity with the first encapsulation cap layer; the second cavity and the first cavity communicate through the first opening; the sealing layer is located on the surface of the second encapsulation cap layer and seals the second opening.

[0047] It can be seen that in the vacuum encapsulation structure of the present application, the first encapsulation cap layer and the substrate form a first cavity for accommodating the MEMS structure. The first encapsulation cap layer is provided with a first opening, and the size of the first opening is relatively large, which can improve the release efficiency and release effect of the sacrificial layer in the space where the first cavity is located, reduce the release residue of the sacrificial layer in the first cavity, and further reduce the adverse effects of the release residue on the vacuum degree of the vacuum encapsulation structure and the thermal conductivity and heat capacity uniformity of the MEMS structure, thereby improving the performance of the vacuum encapsulation structure. A second encapsulation cap layer is provided on the first encapsulation cap layer, and a second opening is provided on the second encapsulation cap layer. The sealing layer seals the vacuum encapsulation structure by sealing the second opening. Since the size of the second opening is small, the influence of the sealing material particle defects during the fabrication of the sealing layer on the sealing yield can be reduced, thereby improving the sealing yield of the vacuum encapsulation structure and reducing the problem of air leakage. Therefore, the vacuum encapsulation structure in the present application can not only improve the release efficiency of the sacrificial layer and improve the release effect, but also improve the sealing yield and solve the problem of air leakage.

[0048] In addition, the present application also provides a packaging method having the above advantages. Description of the Drawings

[0049] To more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 A cross-sectional schematic diagram of a vacuum encapsulation structure provided by an embodiment of the present application;

[0051] Figure 2 A top view schematic diagram of a vacuum encapsulation structure provided by an embodiment of the present application;

[0052] Figure 3 A schematic diagram of the encapsulation process of a vacuum encapsulation structure provided by an embodiment of the present application;

[0053] Figures 4 to 15 A process flow diagram of the encapsulation process of a vacuum encapsulation structure provided by an embodiment of the present application;

[0054] In the figure: 1. Substrate, 2. First encapsulation cap layer, 3. Second encapsulation cap layer, 4. MEMS structure, 5. Sealing layer, 6. First opening, 7. Second opening, 8. First cavity, 9. Second cavity, 10. Getter layer, 11. Support structure, 111. Support column, 112. Support table, 12. First sacrificial layer, 13. Second sacrificial layer, 14. Third sacrificial layer, 15. Second through hole. Detailed implementation manners

[0055] In order to enable those skilled in the art to better understand the solution of the present application, the following will further elaborate on the present application in combination with the drawings and specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of them. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0056] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0057] As described in the background art section, in the prior art during vacuum encapsulation, if the size of the small holes for releasing the sacrificial layer is designed to be relatively small, problems such as low release efficiency of the sacrificial layer and easy occurrence of release residues are likely to occur. If the size of the small holes for releasing the sacrificial layer is designed to be relatively large, problems such as air leakage are likely to occur.

[0058] In view of this, the present application provides a vacuum encapsulation structure. Please refer to Figures 1 to 2 , which may include:

[0059] A substrate 1, a first encapsulation cap layer 2, a second encapsulation cap layer 3, a MEMS structure 4, and a sealing layer 5. The first encapsulation cap layer 2 is provided with a first opening 6, and the second encapsulation cap layer 3 is provided with a second opening 7; the size of the second opening 7 is smaller than the size of the first opening 6;

[0060] The first encapsulation cap layer 2 is connected to the substrate 1 and forms a first cavity 8 with the substrate 1; the MEMS structure 4 is located in the first cavity 8;

[0061] The second encapsulation cap layer 3 is connected to the surface of the first encapsulation cap layer 2 facing away from the first cavity 8 and forms a second cavity 9 with the first encapsulation cap layer 2; the second cavity 9 and the first cavity 8 communicate through the first opening 6;

[0062] The sealing layer 5 is located on the surface of the second encapsulation cap layer 3 and seals the second opening 7.

[0063] The vacuum encapsulation structure in the present application can be applied to various vacuum MEMS structures 4. For example, the vacuum encapsulation structure can be an infrared detector, etc. When the vacuum encapsulation structure is an infrared detector, the MEMS structure 4 can be a microbolometer.

[0064] The microbolometer includes a support layer, a thermosensitive layer, an electrode layer, and a passivation layer. Among them, the support layer and the passivation layer can be a laminate of any one or any several of silicon nitride, silicon oxide, and silicon oxynitride; the thermosensitive layer is a material with thermosensitive properties such as vanadium oxide, amorphous silicon, titanium oxide, etc.; the electrode layer is Ti or other alloy materials.

[0065] It should be noted that in this embodiment, the number of MEMS structures 4 in the first cavity 8 is not limited and depends on the situation.

[0066] As an implementable manner, the number of MEMS structures 4 in the first cavity 8 can be one. In this case, the vacuum encapsulation structure is to individually encapsulate a single MEMS structure 4.

[0067] As an implementable manner, the number of MEMS structures 4 in the first cavity 8 can be at least two. In this case, the vacuum encapsulation structure is to jointly encapsulate two or more MEMS structures 4.

[0068] The surface of the substrate 1 is provided with electrodes and a passivation layer. The MEMS structure 4 is electrically connected to the electrodes on the substrate 1. The passivation layer can protect the metal on the surface of the substrate 1 and prevent the metal on the surface of the substrate 1 from contacting the air.

[0069] It should be noted that in this embodiment, the material of the first encapsulation cap layer 2 is not limited and can be set by oneself. For example, the material of the first encapsulation cap layer 2 can be a material with a high transmittance to infrared radiation, such as silicon nitride, amorphous silicon, etc.

[0070] It should also be noted that in this embodiment, the thickness of the first encapsulation cap layer 2 is not limited and can be set by oneself. For example, the thickness of the first encapsulation cap layer 2 can be 0.5 μm to 2 μm. During the manufacturing process, a third sacrificial layer needs to be fabricated on the surface of the first encapsulation cap layer 2. If the thickness of the first encapsulation cap layer 2 is too thin, the mechanical strength is insufficient and it is prone to collapse; if the thickness of the first encapsulation cap layer 2 is too thick, raw materials will be wasted, the cost will increase, and at the same time, the manufacturing difficulty of the first opening 6 will also increase.

[0071] It should be noted that in this embodiment, the material of the second encapsulation cap layer 3 is not limited and can be set by oneself. For example, the material of the second encapsulation cap layer 3 can be a material with a high transmittance to infrared radiation, such as silicon nitride, amorphous silicon, etc.

[0072] It should also be noted that in this embodiment, the thickness of the second encapsulation cap layer 3 is not limited and can be set by oneself. For example, the thickness of the second encapsulation cap layer 3 can be 0.5 μm to 2 μm to ensure that the second encapsulation cap layer 3 has sufficient mechanical strength while avoiding material waste.

[0073] In order to prevent the problem of mismatch in the coefficient of thermal expansion between the first encapsulation cap layer 2 and the second encapsulation cap layer 3, as an implementable manner, the materials of the first encapsulation cap layer 2 and the second encapsulation cap layer 3 are the same.

[0074] The sealing layer 5 can fill the second opening 7. The material of the sealing layer 5 is not limited in this embodiment and can be set by oneself. For example, it can be any one or several of materials with a high transmittance to infrared radiation, such as germanium, zinc sulfide, etc. The thickness of the sealing layer 5 can be 1 μm to 5 μm.

[0075] The number of the first openings 6 is at least one. The specific number of the first openings 6 is not limited in this embodiment and can be determined according to the size of the vacuum encapsulation structure. Generally, the number of the first openings 6 is at least two and can be distributed in an array form.

[0076] The projection of the first opening 6 on the substrate 1 is located between the projections of any two adjacent support structures 11 on the substrate 1, as Figure 2 shown, Figure 2 only the case where the first opening 6 is located between the projections of the middle two columns of support structures 11 on the substrate 1 is shown.

[0077] In the vacuum encapsulation structure of the present application, since the sealing is performed on the second opening 7 and the sealing of the first opening 6 does not need to be considered, the size of the first opening 6 can be set larger. The first cavity 8 is formed by releasing the first sacrificial layer and the second sacrificial layer within the range of the first cavity 8 through the first opening 6. In this embodiment, making the size of the first opening 6 larger can quickly release the first sacrificial layer and the second sacrificial layer, while reducing the release residue.

[0078] The shape of the first opening 6 includes, but is not limited to, rectangle, square, circle, ellipse, and hexagon.

[0079] In this embodiment, the size of the first opening 6 is not limited and can be set by oneself. Exemplarily, when the shape of the first opening 6 is a rectangle, the length can be 2 μm to 5 μm, and the width can be 1 μm to 3 μm.

[0080] The shape of the second opening 7 includes, but is not limited to, rectangle, square, circle, ellipse, and hexagon.

[0081] The second cavity 9 is formed by releasing the third sacrificial layer within the range of the second cavity 9 through the second opening 7. The size of the second opening 7 will affect the release effect of the third sacrificial layer and will also significantly affect the sealing yield of the vacuum encapsulation structure. Therefore, the size of the second opening 7 should not be too large or too small. In this embodiment, the specific size of the second opening 7 is not limited, as long as it is smaller than the size of the first opening 6.

[0082] Exemplarily, when the shape of the second opening 7 is a rectangle, the length can be 1 μm to 2 μm, and the width can be 0.3 μm to 0.5 μm.

[0083] In this embodiment, the positional relationship between the second opening 7 and the first opening 6 is not limited and can be set by oneself.

[0084] As an implementable manner, the projection of the second opening 7 on the substrate 1 can be located within the projection range of the first opening 6 on the substrate 1.

[0085] As another implementable manner, as Figure 1 and Figure 2As shown, the number of the first openings 6 is at least one, and the projection of the second opening 7 communicated with each first opening 6 on the substrate 1 is staggered from the projection of the first opening 6 on the substrate 1, wherein the first opening 6 and the second opening 7 are communicated through the second cavity 9. On the one hand, when releasing the third sacrificial layer, the plasma can enter the first cavity 8 later, so as to minimize the contact time between the MEMS structure 4 in the first cavity 8 and the plasma and prevent the MEMS structure 4 from being damaged by the plasma; on the other hand, when manufacturing the sealing layer 5, the sealing material particles can be prevented from vertically falling into the first cavity 8, so as to prevent the sealing material from affecting the MEMS structure 4.

[0086] In an embodiment of the present application, the number of the second openings 7 communicated with each first opening 6 is at least two, and the projection of the second opening 7 on the substrate 1 surrounds the projection of the first opening 6 on the substrate 1. The release efficiency of the third sacrificial layer can be improved, the second cavity 9 can be formed faster, and the release residue can be reduced at the same time.

[0087] Exemplarily, as Figure 1 and Figure 2 shown, the number of the projections of the second openings 7 around the projection of each first opening 6 is four.

[0088] In order to ensure the vacuum degree inside the vacuum encapsulation structure, the vacuum encapsulation structure may further include:

[0089] A getter layer 10, which is located in the first cavity 8 and on the surface of the substrate 1.

[0090] The material of the getter layer 10 includes but is not limited to any one or any several alloys formed by zirconium, titanium, vanadium, aluminum, and rare metals.

[0091] The thickness of the getter layer 10 is 0.5 μm to 1 μm.

[0092] In addition, when the MEMS structure 4 is a microbolometer, the getter layer 10 can also be used as a reflective layer of the microbolometer to improve the absorption rate of the microbolometer to infrared radiation.

[0093] In the vacuum encapsulation structure of this embodiment, a first encapsulation cap layer 2 and a substrate 1 form a first cavity 8 for accommodating the MEMS structure 4. A first opening 6 is provided on the first encapsulation cap layer 2. The size of the first opening 6 is relatively large, which can improve the release efficiency and release effect of the sacrificial layer in the space where the first cavity 8 is located, reduce the release residue of the sacrificial layer in the first cavity 8, and further reduce the adverse effects of the release residue on the vacuum degree of the vacuum encapsulation structure and the thermal conductivity and heat capacity uniformity of the MEMS structure 4, thereby improving the performance of the vacuum encapsulation structure. A second encapsulation cap layer 3 is provided on the first encapsulation cap layer 2, and a second opening 7 is provided on the second encapsulation cap layer 3. The sealing layer 5 seals the vacuum encapsulation structure by sealing the second opening 7. Since the size of the second opening 7 is small, the influence of sealing material particle defects on the sealing yield during the production of the sealing layer 5 can be reduced, thereby improving the sealing yield of the vacuum encapsulation structure and reducing the problem of air leakage. Therefore, the vacuum encapsulation structure in this embodiment can not only improve the release efficiency of the sacrificial layer and improve the release effect, but also improve the sealing yield and solve the problem of air leakage.

[0094] Based on the above embodiment, in an embodiment of the present application, the vacuum encapsulation structure may further include:

[0095] A support structure 11, located in the first cavity 8 and between the first encapsulation cap layer 2 and the substrate 1, for supporting the first encapsulation cap layer 2.

[0096] By providing the support structure 11 to support the first encapsulation cap layer 2, the mechanical strength of the first encapsulation cap layer 2 can be improved.

[0097] In this embodiment, the support structure 11 is not specifically limited and can be determined according to the situation.

[0098] As an implementable manner, as Figure 1 shown, the support structure 11 includes support columns 111 and a support table 112. The support columns 111 are located on the surface of the substrate 1, and the support table 112 is located on the surface of the support columns 111 away from the substrate 1; the area of the first encapsulation cap layer 2 corresponding to the support table 112 is recessed into the first cavity 8, and the recessed area of the first encapsulation cap layer contacts the support table 112;

[0099] The recessed area of the first encapsulation cap layer 2 corresponds to at least the support tables 112 of the support structures 11 except for those located on both sides of the vacuum encapsulation structure.

[0100] The sunken area of the first encapsulation cap layer 2 can only sink towards the support table surfaces 112 of the support structures 11 except for those located on both sides of the vacuum encapsulation structure body. Since the side walls of the first encapsulation cap layer 2 on both sides of the vacuum encapsulation structure body have a certain supporting effect, the areas closest to both sides do not need to sink towards the support table surfaces 112; alternatively, it can also sink towards the support table surfaces 112 of all the support structures 11, which is not limited in this application.

[0101] For example Figure 1 As shown, the sunken area of the first encapsulation cap layer 2 only sinks towards the support table surfaces 112 of the support structures 11 except for those located on both sides of the vacuum encapsulation structure body (i.e., Figure 1 the middle two support table surfaces 112 in

[0102] The support table surface 112 can include a support layer, an electrode layer, and a passivation layer, and the size can be 1μm - 3μm. The materials of the support layer, the electrode layer, and the passivation layer can be the same as those in the microbolometer.

[0103] The support table surface 112 is in direct contact with the first encapsulation cap layer 2 to support the first encapsulation cap layer 2. In addition, the MEMS structure 4 and the support column 111 can be electrically connected through the support table surface 112, so that the MEMS structure 4 is electrically connected to the electrode on the substrate 1. All the support table surfaces 112 and support columns 111 in the vacuum encapsulation structure body play the role of electrical connection.

[0104] Based on any of the above embodiments, in an embodiment of the present application, as Figure 1 and Figure 2 shown, the number of the second encapsulation cap layers 3 is equal to the number of the first openings 6, and the projection of one first opening 6 on the substrate 1 is within the projection range of one second encapsulation cap layer 3 on the substrate 1.

[0105] When the number of the first openings 6 is at least two, compared with the case of arranging one second encapsulation cap layer 3 on the first encapsulation cap layer 2 and covering all the first openings 6 with this one second encapsulation cap layer 3, in this embodiment, multiple second encapsulation cap layers 3 are arranged, and one second encapsulation cap layer 3 is arranged above each first opening 6. This can not only make the supporting effect of the first encapsulation cap layer 2 on the second encapsulation cap layer 3 better, but also, there is less third sacrificial layer in the space of each second cavity 9, which is more conducive to the release of the third sacrificial layer.

[0106] In summary, the vacuum encapsulation structure body in this application has the following advantages:

[0107] 1. Higher yield can be obtained: By reducing the size of the second opening to be sealed, the adverse effect of coating particles during the deposition of the sealing layer on the sealing yield is reduced, so as to obtain a higher sealing yield;

[0108] 2. Better device performance can be obtained: By increasing the size of the first opening used for the release in the area where the MEMS structure is located, the release efficiency is improved and the release effect is enhanced, thereby reducing the release residue in the first cavity, and further reducing the adverse effects of the release residue on the vacuum degree of the packaging structure and the uniformity of the thermal conductivity and heat capacity of the MEMS structure, and improving the device performance.

[0109] This application also provides a packaging method for a vacuum packaging structure. Please refer to Figure 3 , and this method may include:

[0110] Step S101: Form a first sacrificial layer on the surface of the substrate.

[0111] The first sacrificial layer can be fabricated and cured on the surface of the substrate by spin coating or spraying. The material of the first sacrificial layer can be materials such as PI (Polyimide) or PSG (Phosphosilicate Glass).

[0112] The thickness of the first sacrificial layer can be 1.5 μm to 2.5 μm. The first sacrificial layer is used to fabricate the suspended MEMS structure.

[0113] In an embodiment of this application, before forming the first sacrificial layer on the surface of the substrate, it may further include:

[0114] Fabricate a getter layer on the surface of the substrate to ensure the vacuum degree of the vacuum packaging structure.

[0115] Use the LIFT OFF (lift-off) process or the photolithography etching process to fabricate a patterned getter layer. The getter layer can be deposited by methods such as PVD, magnetron sputtering, or thermal evaporation.

[0116] Step S102: Fabricate a MEMS structure on the surface of the first sacrificial layer.

[0117] The MEMS structure can be fabricated according to specific types, and the specific fabrication process will not be elaborated here in detail.

[0118] For example, when the MEMS structure is a microbolometer, it can be formed by processes such as photolithography and RIE (reactive ion etching).

[0119] The microbolometer includes a support layer, a thermosensitive layer, an electrode layer, and a passivation layer. Among them, the support layer and the passivation layer can be formed by PECVD (Plasma Enhanced Chemical Vapor Deposition), PVD (Physical Vapor Deposition), etc.; the thermosensitive layer can be formed by processes such as CVD (Chemical Vapor Deposition), PVD, etc.; the electrode layer can be formed by processes such as PVD.

[0120] Step S103: Form a second sacrificial layer on the surface of the first sacrificial layer where the MEMS structure is distributed.

[0121] The second sacrificial layer can be fabricated and cured by spin coating or spraying. The material of the second sacrificial layer can be materials such as PI (Polyimide), PSG (phosphosilicate glass), etc., which is the same as the material of the first sacrificial layer.

[0122] The thickness of the second sacrificial layer can be 1 μm to 2 μm.

[0123] Step S104: Etch the first sacrificial layer and the second sacrificial layer located in the edge region of the substrate, and fabricate a first encapsulation cap layer;

[0124] Among them, the first encapsulation cap layer wraps the first sacrificial layer and the second sacrificial layer and is connected to the substrate.

[0125] Etching the first sacrificial layer and the second sacrificial layer in the edge region is to make the first encapsulation cap layer in contact connection with the substrate.

[0126] The first encapsulation cap layer can be deposited and formed by CVD.

[0127] Step S105: Etch the first encapsulation cap layer to form a first opening.

[0128] The area of the second sacrificial layer corresponding to the first opening is exposed.

[0129] Step S106: Release the first sacrificial layer and the second sacrificial layer through the first opening to form a first cavity.

[0130] The first sacrificial layer and the second sacrificial layer can be released by an oxygen plasma etching process to form a suspended MEMS structure and a first cavity.

[0131] Step S107: Fabricate a third sacrificial layer on the surface of the first encapsulation cap layer facing away from the first cavity.

[0132] The third sacrificial layer can be fabricated and cured by spin coating.

[0133] To prevent a large amount of the third sacrificial layer from entering the first cavity through the first opening during the fabrication of the third sacrificial layer, the material of the third sacrificial layer is preferably an organic sacrificial layer material with a relatively high viscosity, such as a special high-viscosity PI, etc.

[0134] Step S108: Fabricate a second encapsulation cap layer on the surface of the third sacrificial layer; the second encapsulation cap layer wraps the third sacrificial layer and is connected to the first encapsulation cap layer.

[0135] The second encapsulation cap layer can be deposited by CVD.

[0136] Step S109: Etch the second encapsulation cap layer to form a second opening; the size of the second opening is smaller than that of the first opening.

[0137] The area of the third sacrificial layer corresponding to the second opening is exposed.

[0138] Step S110: Release the third sacrificial layer through the second opening to form a second cavity; the second cavity and the first cavity communicate through the first opening.

[0139] The third sacrificial layer can be released by an oxygen plasma etching process to form a second cavity.

[0140] Step S111: Fabricate a sealing layer on the surface of the second encapsulation cap layer, and the sealing layer seals the second opening.

[0141] The sealing layer can be deposited by a high-vacuum PVD process to achieve vacuum sealing.

[0142] In the vacuum encapsulation structure obtained by the encapsulation method of this embodiment, the first encapsulation cap layer and the substrate form a first cavity for accommodating the MEMS structure. The first encapsulation cap layer is provided with a first opening, and the size of the first opening is relatively large, which can improve the release efficiency and release effect of the sacrificial layer in the space where the first cavity is located, reduce the release residue of the sacrificial layer in the first cavity, and further reduce the adverse effects of the release residue on the vacuum degree of the vacuum encapsulation structure and the thermal conductivity and heat capacity uniformity of the MEMS structure, thereby improving the performance of the vacuum encapsulation structure. A second encapsulation cap layer is provided on the first encapsulation cap layer, and a second opening is provided on the second encapsulation cap layer. The sealing layer seals the second opening to seal the vacuum encapsulation structure. Since the size of the second opening is small, the influence of the sealing material particles on the sealing yield during the fabrication of the sealing layer can be reduced, thereby improving the sealing yield of the vacuum encapsulation structure and reducing the problem of air leakage. Therefore, the vacuum encapsulation structure in this embodiment can not only improve the release efficiency of the sacrificial layer and improve the release effect, but also improve the sealing yield and solve the problem of air leakage.

[0143] Based on the above embodiments, in an embodiment of the present application, after forming a first sacrificial layer on the surface of the substrate, the method further includes:

[0144] Etching the first sacrificial layer to form a first through hole;

[0145] Fabricating a support structure at the first through hole, the support structure being located on the surface of the substrate and used for supporting the first encapsulation cap layer;

[0146] After forming a second sacrificial layer on the surface of the first sacrificial layer where the MEMS structure is distributed, the method further includes:

[0147] Etching the second sacrificial layer to form a second through hole to expose the support structure.

[0148] In this embodiment, by providing the support structure to support the first encapsulation cap layer, the mechanical strength of the first encapsulation cap layer can be improved.

[0149] The support structure may include support pillars and a support tabletop. The support pillars are fabricated in the first through hole, and the support tabletop is located on the surface of the first sacrificial layer. The support tabletop can be formed simultaneously with the MEMS structure by lithography, RIE, etc. in the process.

[0150] The second through hole is correspondingly located above the support tabletop. Subsequently, when fabricating the first encapsulation cap layer, the first encapsulation cap layer is recessed at the second through hole and contacts the support tabletop, thereby supporting the first encapsulation cap layer. In addition, the MEMS structure and the support pillars can be electrically connected through the support tabletop, and further the MEMS structure is electrically connected to the electrode on the substrate.

[0151] Based on any of the above embodiments, in an embodiment of the present application, the encapsulation method of the vacuum encapsulation structure may include:

[0152] Step S201: Form a patterned getter layer on the surface of the substrate.

[0153] As Figure 4 shown, the getter layer 10 is located on the upper surface of the substrate 1.

[0154] Step S202: Form a first sacrificial layer on the surface of the substrate having the getter layer.

[0155] As Figure 5 shown, the first sacrificial layer 12 is located on the upper surface of the substrate 1 and covers the getter layer 10.

[0156] Step S203: Etch the first sacrificial layer to form a first through hole.

[0157] Step S204: Fabricate a support structure at the first through-hole. The support structure is located on the surface of the substrate and is used to support the first encapsulation cap layer.

[0158] As Figure 6 shown, the support structure 11 may include support pillars 111 and a support table 112. The support pillars 111 are located at the first through-hole.

[0159] Step S205: Fabricate a MEMS structure on the surface of the first sacrificial layer.

[0160] As Figure 6 shown, the MEMS structure 4 is located on the upper surface of the first sacrificial layer.

[0161] Step S206: Form a second sacrificial layer on the surface of the first sacrificial layer where the MEMS structure is distributed.

[0162] As Figure 7 shown, the second sacrificial layer 13 is located on the upper surface of the first sacrificial layer 12 and covers the MEMS structure 4 and the support table 112.

[0163] Step S207: Etch the second sacrificial layer to form a second through-hole to expose the support structure.

[0164] As Figure 8 shown, the second through-hole 15 corresponds to the support table 112 to expose the support table 112.

[0165] Step S208: Etch the first sacrificial layer and the second sacrificial layer in the edge region of the substrate and fabricate a first encapsulation cap layer; the first encapsulation cap layer wraps the first sacrificial layer and the second sacrificial layer and is connected to the substrate.

[0166] As Figure 8 and Figure 9 shown, the edge region of the substrate 1 is exposed to be connected to the subsequently fabricated first encapsulation cap layer 2. Due to the existence of the second through-hole 15, the first encapsulation cap layer 2 is recessed downward in the region of the second through-hole 15 and contacts the support table 112.

[0167] Step S209: Etch the first encapsulation cap layer to form a first opening.

[0168] As Figure 10 shown, the first opening 6 may be located at a position between two second through-holes.

[0169] Exemplarily, when the shape of the first opening is rectangular, the length may be 2 μm to 5 μm and the width may be 1 μm to 3 μm.

[0170] Step S210: Release the first sacrificial layer and the second sacrificial layer through the first opening to form a first cavity.

[0171] As Figure 11 shown, the first sacrificial layer and the second sacrificial layer are removed to form a first cavity 8 and a suspended MEMS structure 4.

[0172] Step S211: Fabricate a third sacrificial layer on the surface of the first encapsulation cap layer facing away from the first cavity.

[0173] Step S212: Etch the third sacrificial layer to form at least two patterned third sacrificial layers; the projection of one of the first openings on the substrate is within the projection of one of the third sacrificial layers on the substrate;

[0174] As Figure 12 shown, after the third sacrificial layer 14 is etched, only the third sacrificial layer 14 around the first opening 6 is retained. The thickness of the third sacrificial layer 14 can be 1 μm to 2 μm.

[0175] The size of the third sacrificial layer 14 is larger than the size of the first opening 6. The length of the third sacrificial layer 14 is 1 μm to 1.5 μm longer than the first opening 6, and the width is 1 μm to 1.5 μm wider than the first opening 6.

[0176] Step S213: Simultaneously fabricate a second encapsulation cap layer on the surface of the patterned third sacrificial layer; the projection of one of the first openings on the substrate is within the projection of one of the second encapsulation cap layers on the substrate; the second encapsulation cap layer wraps the third sacrificial layer and is connected to the first encapsulation cap layer.

[0177] As Figure 13 shown, the second encapsulation cap layer 3 can be deposited and formed by CVD. Each third sacrificial layer 14 is wrapped by a second encapsulation cap layer 3. All the second encapsulation cap layers 3 are fabricated at one time.

[0178] In this embodiment, multiple second encapsulation cap layers are provided, and one second encapsulation cap layer is provided above each first opening, which can not only make the support effect of the first encapsulation cap layer on the second encapsulation cap layer better, but also, there are fewer third sacrificial layers in the space where each second cavity is located, which is more conducive to the release of the third sacrificial layer.

[0179] Step S214: Etch the second encapsulation cap layer to form a second opening; the size of the second opening is smaller than the first opening.

[0180] As Figure 14 and Figure 2 shown, the second opening 7 is etched and formed, and the area of the third sacrificial layer 14 corresponding to the second opening 7 is exposed.

[0181] Step S215: Release the third sacrificial layer through the second opening to form a second cavity; the second cavity and the first cavity communicate with each other through the first opening.

[0182] As Figure 15 shown, the third sacrificial layer is removed to form a second cavity 9.

[0183] Step S216: Fabricate a sealing layer on the surface of the second encapsulation cap layer, and the sealing layer seals the second opening.

[0184] As Figure 1 shown, the sealing layer 5 seals the second opening 7, thereby achieving the sealing of the entire vacuum encapsulation structure. The sealing layer 5 can be located on the surfaces of the first encapsulation cap layer 2 and the second encapsulation cap layer 3.

[0185] Among them, Figures 4 to 10 is Figure 2 a schematic diagram of the BB cross-section in the figure shown, Figure 1 、 Figures 11 to 15 is Figure 2 a schematic diagram of the AA cross-section in the figure shown.

[0186] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0187] The vacuum encapsulation structure and its encapsulation method provided in this application have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the solution and core idea of this application. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of this application, several improvements and modifications can still be made to this application, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A vacuum packaging structure, characterized in that: include: A substrate (1), a first packaging cap layer (2), a second packaging cap layer (3), a MEMS structure (4) and a sealing layer (5), wherein the first packaging cap layer (2) is provided with a first opening (6), and the second packaging cap layer (3) is provided with a second opening (7); the size of the second opening (7) is smaller than the size of the first opening (6); The first packaging cap layer (2) is connected to the substrate (1) and forms a first cavity (8) with the substrate (1); the MEMS structure (4) is located in the first cavity (8); The second encapsulation cap layer (3) is connected to a surface of the first encapsulation cap layer (2) facing away from the first cavity (8), and forms a second cavity (9) with the first encapsulation cap layer (2); the second cavity (9) and the first cavity (8) are connected via the first opening (6); The sealing layer (5) is located on the surface of the second packaging cap layer (3) and seals the second opening (7).

2. The vacuum packaging structure according to claim 1, characterized in that: The number of the first opening (6) is at least one, and the projection of the second opening (7) connected to each of the first openings (6) on the substrate (1) is staggered from the projection of the first opening (6) on the substrate (1).

3. The vacuum packaging structure according to claim 2, characterized in that: The number of the second openings (7) connected to each of the first openings (6) is at least two, and the projection of the second openings (7) on the substrate (1) surrounds the projection of the first openings (6) on the substrate (1).

4. The vacuum packaging structure according to claim 1, characterized in that: Also includes: A support structure (11) is located in the first cavity (8) and between the first packaging cap layer (2) and the substrate (1), and is used to support the first packaging cap layer (2).

5. The vacuum packaging structure according to claim 4, characterized in that: The support structure (11) comprises a support column (111) and a support table (112), wherein the support column (111) is located on a surface of the substrate (1), and the support table (112) is located on a surface of the support column (111) away from the substrate (1); An area of ​​the first packaging cap layer (2) corresponding to the support table (112) is recessed into the first cavity (8), and the recessed area of ​​the first packaging cap layer (2) is in contact with the support table (112); The recessed area of ​​the first packaging cap layer (2) at least corresponds to the support table (112) of the support structure (11) except for the two sides of the vacuum packaging structure.

6. The vacuum packaging structure according to claim 4, characterized in that: The projection of the first opening (6) on the substrate (1) is located between the projections of any two adjacent support structures (11) on the substrate (1).

7. The vacuum packaging structure according to claim 1, characterized in that: Also includes: A getter layer (10) is located in the first cavity (8) and on the surface of the substrate (1).

8. The vacuum packaging structure according to claim 1, characterized in that: The first packaging cap layer (2) and the second packaging cap layer (3) are made of the same material.

9. The vacuum packaging structure according to any one of claims 1 to 8, characterized in that: The number of the second encapsulation cap layers (3) is equal to the number of the first openings (6), and the projection of one of the first openings (6) on the substrate (1) is located within the range of the projection of one of the second encapsulation cap layers (3) on the substrate (1).

10. A packaging method for a vacuum packaging structure, characterized in that: include: forming a first sacrificial layer (12) on the surface of the substrate (1); Fabricating a MEMS structure (4) on the surface of the first sacrificial layer (12); forming a second sacrificial layer (13) on the surface of the first sacrificial layer (12) on which the MEMS structure (4) is distributed; Etching the first sacrificial layer (12) and the second sacrificial layer (13) located in the edge region of the substrate (1), and manufacturing a first packaging cap layer (2); the first packaging cap layer (2) wraps the first sacrificial layer (12) and the second sacrificial layer (13) and is connected to the substrate (1); Etching the first packaging cap layer (2) to form a first opening (6); releasing the first sacrificial layer (12) and the second sacrificial layer (13) through the first opening (6) to form a first cavity (8); Making a third sacrificial layer (14) on a surface of the first packaging cap layer (2) facing away from the first cavity (8); A second encapsulation cap layer (3) is fabricated on the surface of the third sacrificial layer (14); the second encapsulation cap layer (3) wraps the third sacrificial layer (14) and is connected to the first encapsulation cap layer (2); Etching the second packaging cap layer (3) to form a second opening (7); the second opening (7) is smaller in size than the first opening (6); The third sacrificial layer (14) is released through the second opening (7) to form a second cavity (9); the second cavity (9) and the first cavity (8) are connected through the first opening (6); A sealing layer (5) is made on the surface of the second packaging cap layer (3), and the sealing layer (5) seals the second opening (7).

11. The packaging method of the vacuum packaging structure according to claim 10, characterized in that: After forming a first sacrificial layer (12) on the surface of the substrate (1), the method further comprises: Etching the first sacrificial layer (12) to form a first through hole; Making a support structure (11) at the first through hole, wherein the support structure (11) is located on the surface of the substrate (1) and is used to support the first packaging cap layer (2); After forming a second sacrificial layer (13) on the surface of the first sacrificial layer (12) on which the MEMS structure (4) is distributed, the method further comprises: The second sacrificial layer (13) is etched to form a second through hole (15) to expose the support structure (11).

12. The packaging method of the vacuum packaging structure according to claim 10, characterized in that: Before forming the first sacrificial layer (12) on the surface of the substrate (1), the method further comprises: A getter layer (10) is produced on the surface of the substrate (1).

13. The packaging method of the vacuum packaging structure according to any one of claims 10 to 12, characterized in that: After a third sacrificial layer (14) is formed on a surface of the first packaging cap layer (2) facing away from the first cavity (8), the method further comprises: Etching the third sacrificial layer (14) to form at least two patterned third sacrificial layers (14); a projection of one of the first openings (6) on the substrate (1) is located within the range of a projection of one of the third sacrificial layers (14) on the substrate (1); Producing a second encapsulation cap layer (3) on the surface of the third sacrificial layer (14) comprises: A second encapsulation cap layer (3) is simultaneously produced on the surface of the patterned third sacrificial layer (14); a projection of one of the first openings (6) on the substrate (1) is located within the range of a projection of one of the second encapsulation cap layer (3) on the substrate (1).

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