Wafer bonding method

Abstract

The application relates to a wafer bonding method, which comprises the following steps: after providing a first wafer and a second wafer, a mixture of silicate and alcohol solvent is spin-coated on the bonding surfaces of the first wafer and the second wafer respectively by using a spin coating process; after the spin coating process, the first wafer and the second wafer are respectively subjected to static treatment, the mixture of silicate and alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer and a second silica sol layer on the bonding surface of the second wafer; the first silica sol layer and the second silica sol layer are respectively subjected to UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer; and the second silicon oxide layer of the second wafer is bonded to the first silicon oxide layer of the first wafer. The wafer bonding strength is improved by the method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a wafer bonding method. BACKGROUND

[0002] Wafer bonding technology is a key step in the field of microelectronics and microsystem technology. Through wafer bonding technology, two or more wafers or chips can be vertically stacked together to realize three-dimensional integrated circuits, greatly improving the integration level and enhancing the function, thereby improving the performance of the device.

[0003] The existing wafer bonding process generally includes surface treatment, alignment, pre-bonding, main bonding, and post-treatment. However, the bonding strength of the bonding structure formed by using the existing wafer bonding process still needs to be improved. SUMMARY

[0004] Therefore, the present application provides a wafer bonding method to improve the bonding strength of the wafer.

[0005] In a first aspect, the embodiments of the present application provide a wafer bonding method, including.

[0006] A first wafer and a second wafer are provided, and both the first wafer and the second wafer include a bonding surface;

[0007] A mixed solution including silicate and alcohol solvent is spin-coated on the bonding surface of the first wafer and the second wafer, respectively, by using a spin coating process;

[0008] After the spin coating process, the first wafer and the second wafer are respectively subjected to a standing treatment, and the mixed solution of silicate and alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer and a second silica sol layer on the bonding surface of the second wafer;

[0009] The first silica sol layer and the second silica sol layer are respectively subjected to UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer;

[0010] The second silicon oxide layer of the second wafer is bonded to the first silicon oxide layer of the first wafer.

[0011] In some embodiments of the present application, after the standing treatment and before the UV curing treatment, the method further includes: respectively performing alkaline solution treatment on the surfaces of the first silica sol layer and the second silica sol layer; and after the alkaline solution treatment, respectively performing UV curing treatment on the first silica sol layer and the second silica sol layer.

[0012] In some embodiments of the present application, the alkaline solution includes a sodium hydroxide solution or a potassium hydroxide solution.

[0013] In some embodiments of the present application, the time interval between the alkaline solution treatment and the standing treatment is greater than 20 minutes.

[0014] In some embodiments of the present application, the volume percentage of the silicate and the alcohol solvent in the mixed solution of the silicate and the alcohol solvent ranges from 1:10 to 1:20.

[0015] In some embodiments of the present application, the silicate includes methyl silicate or ethyl silicate, and the alcohol solvent includes an ethanol solution or an ethylene glycol solution.

[0016] In some embodiments of the present application, when the spin coating process is performed, the rotation speed of the first wafer and the second wafer is 200 revolutions per minute to 400 revolutions per minute, the flow rate of the mixed solution is 1.7 liters per minute to 1.9 liters per minute, and the temperature is 20 degrees Celsius to 25 degrees Celsius.

[0017] In some embodiments of the present application, when the UV curing treatment is performed, the wavelength of the UV light is 150 nanometers to 300 nanometers, the temperature is 150 degrees Celsius to 300 degrees Celsius, and the time is 5 seconds to 30 seconds.

[0018] In some embodiments of the present application, the bonding surface of the first wafer includes a scribe lane region, the scribe lane region has a recess, the first silica sol layer fills the recess, and the surface of the first silica sol layer away from the bonding surface of the first wafer is a flat surface.

[0019] In some embodiments of the present application, the spin coating process is performed by a spin coating device, the spin coating device includes a first liquid supply pipe, a second liquid supply pipe, a mixed solution tank, a liquid delivery pipe, and a nozzle, the first liquid supply pipe and the second liquid supply pipe are connected to the mixed solution tank, the first liquid supply pipe is used to supply the silicate to the mixed solution tank, the second liquid supply pipe is used to supply the alcohol solvent to the mixed solution tank, the silicate and the alcohol solvent are mixed in the mixed solution tank to form a mixed solution of the silicate and the alcohol solvent, the liquid delivery pipe is connected to the mixed solution tank and is used to deliver the mixed solution of the silicate and the alcohol solvent in the mixed solution tank to the nozzle, and when the spin coating process is performed, the mixed solution of the silicate and the alcohol solvent is sprayed to the bonding surfaces of the first wafer and the second wafer through the nozzle.

[0020] The embodiments of the present application can produce the following unexpected technical effects:

[0021] The wafer bonding method in the embodiment of the application provides a first wafer and a second wafer, then a mixed solution of silicate and alcohol solvent is spin-coated on the bonding surfaces of the first wafer and the second wafer respectively by using a spin-coating process; after the spin-coating process, the first wafer and the second wafer are respectively subjected to a standing treatment, the mixed solution of silicate and alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer and a second silica sol layer on the bonding surface of the second wafer; the first silica sol layer and the second silica sol layer are respectively subjected to a UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer; and the second silicon oxide layer of the second wafer is bonded to the first silicon oxide layer of the first wafer. The spin-coating process can make the mixed solution of silicate and alcohol solvent uniformly coated on the bonding surfaces of the first wafer and the second wafer, and after the spin-coating process, the first wafer and the second wafer are respectively subjected to a standing treatment, the mixed solution of silicate and alcohol solvent reacts (including hydrolysis reaction and condensation reaction) to form a first silica sol layer with a flat surface on the bonding surface of the first wafer and a second silica sol layer with a flat surface on the bonding surface of the second wafer, so that when the first silica sol layer and the second silica sol layer are respectively subjected to a UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer, the first silicon oxide layer and the second silicon oxide layer also have flat surfaces, and the flat surfaces can improve the bonding strength, so that the bonding strength of the first wafer and the second wafer bonded by the first silicon oxide layer and the second silicon oxide layer is improved.

[0022] In addition, the mixed solution of silicate and alcohol solvent used in the spin-coating process, the silicate in the mixed solution forms a silica sol (SiO2·nH2O) through hydrolysis reaction and condensation reaction, that is, the first silica sol layer formed on the bonding surface of the first wafer and the second silica sol layer formed on the bonding surface of the second wafer, and the alcohol solvent in the mixed solution is used to adjust the viscosity of the mixed solution and the uniformity of the distribution of silicate in the mixed solution, so that the mixed solution can be more uniformly coated on the bonding surfaces of the first wafer and the second wafer, and the first silica sol layer formed on the bonding surface of the first wafer and the second silica sol layer formed on the bonding surface of the second wafer have higher flatness.

[0023] On the other hand, the alcohol solvent as the solvent can also improve the coverage and filling capacity of the mixed solution, so that the mixed solution can better fill the recesses possibly existing on the bonding surfaces of the first wafer and the second wafer; and the alcohol solvent can also act as a catalyst to provide "-OH", part of the "-OH" participates in the hydrolysis reaction of the silicate, and part of the "-OH" can improve the coverage and hydrophilicity of the "-OH" on the surface of the first silicon oxide layer after the first silica sol layer is converted into the first silicon oxide layer, and improve the coverage and hydrophilicity of the "-OH" on the surface of the second silicon oxide layer after the second silica sol layer is converted into the second silicon oxide layer, and the improvement of the coverage and hydrophilicity of the "-OH" on the bonding surface can further improve the bonding strength of the first wafer and the second wafer;

[0024] On the other hand, the alcohol solvent can also reduce the temperature during the UV curing process (the temperature during the UV curing process ranges from 150°C to 300°C, and the temperature during the UV curing process is lower than the temperature during the existing annealing process (310°C-380°C)).

[0025] The details of one or more embodiments of the present application are presented in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The flowchart of the wafer bonding method provided in some embodiments of the present application;

[0028] Figure 2 The structure diagram for forming the mixed solution of silicate and alcohol solvent on the bonding surface of the first wafer by using the spin coating process;

[0029] Figure 3 The structure diagram for forming the mixed solution of silicate and alcohol solvent on the bonding surface of the second wafer by using the spin coating process;

[0030] Figure 4 The structure diagram for Figure 2 The structure diagram for forming the first silica sol on the cross-sectional structure obtained along the cutting line AA1 in the first wafer;

[0031] Figure 5 The structure diagram for Figure 3 The structure diagram for forming the second silica sol on the cross-sectional structure obtained along the cutting line BB1 in the second wafer;

[0032] Figure 6 Structure diagram after forming the first silicon oxide layer on the bonding surface of the first wafer by UV curing treatment on the first silica sol layer;

[0033] Figure 7 Structure diagram after forming the second silicon oxide layer on the bonding surface of the second wafer by UV curing treatment on the second silica sol layer respectively;

[0034] Figure 8 Structure diagram after bonding the second silicon oxide layer of the second wafer to the first silicon oxide layer of the first wafer.

[0035] Explanation of reference signs:

[0036] 201 - first wafer; 202 - second wafer; 203 - first silica sol layer; 204 - second silica sol layer; 205 - first silicon oxide layer; 206 - second silicon oxide layer; 301 - nozzle; 302 - liquid delivery pipe; 21 - mixed liquid; 22 - UV curing treatment. DETAILED DESCRIPTION

[0037] For the purpose of facilitating the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the present application. Rather, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0038] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0039] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element or layer, there are no intervening elements or layers present. It will also be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application.

[0040] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can also be oriented in the other direction, and the spatially relative terms used herein can be interpreted accordingly.

[0041] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", or the like, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

[0042] The structures of embodiments of the present application should not be limited to the specific shapes shown in the drawings accompanying the specification, but include deviations in shape due to, for example, manufacturing techniques.

[0043] It can be understood that in the drawings of the present application, some adjacent film layers of the same film layer material are drawn as being connected to each other so as to be similar to the actual structure.

[0044] In the existing wafer bonding process, a silicon oxide material is generally used as a bonding layer. The general process for forming the bonding layer includes: forming a silicon oxide bonding layer on the wafer bonding surface by a deposition process; and performing planarization on the surface of the silicon oxide bonding layer by a chemical mechanical polishing process. In order to make the surface of the final bonding layer flat enough, multiple deposition processes and chemical mechanical polishing processes are generally required, which increases the cost of the process. In addition, since the wafer generally includes a scribe lane region, the scribe lane region has a groove. When the surface of the silicon oxide bonding layer is planarized by the chemical mechanical polishing process after the silicon oxide bonding layer is formed on the wafer bonding surface, the existence of the groove is easy to cause the surface of the silicon oxide bonding layer to have a butterfly-shaped depression, which affects the flatness of the surface of the silicon oxide bonding layer and thus affects the bonding strength.

[0045] Therefore, the embodiments of the present application provide a wafer bonding method. Figure 1 A flowchart of the wafer bonding method provided in some embodiments of the present application is shown in FIG. 1. Figures 2-8 Structural diagrams of various stages in the wafer bonding method provided in some embodiments of the present application are shown in FIGS. 2-5.

[0046] Reference Figure 1 In some embodiments of the present application, a wafer bonding method is provided, which includes the following steps:

[0047] In step S101, a first wafer and a second wafer are provided, and both the first wafer and the second wafer include a bonding surface.

[0048] In step S102, a mixed solution including silicate and an alcohol solvent is spin-coated on the bonding surface of the first wafer and the bonding surface of the second wafer by a spin coating process.

[0049] In step S103, after the spin coating process, the first wafer and the second wafer are respectively subjected to a static treatment. The mixed solution of the silicate and the alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer and a second silica sol layer on the bonding surface of the second wafer.

[0050] In step S104, the first silica sol layer and the second silica sol layer are respectively subjected to a UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer.

[0051] In step S105, the second silicon oxide layer of the second wafer is bonded to the first silicon oxide layer of the first wafer.

[0052] The following will be described in detail with reference to the drawings. Figures 2-8The detailed process of the foregoing wafer bonding method is described in detail.

[0053] First, referring to Figure 1 and in conjunction with the reference Figure 2 and Figure 3 , a step S101 is performed to provide a first wafer 201 and a second wafer 202, both of which include a bonding surface.

[0054] The first wafer 201 includes a first semiconductor substrate, and the material of the first semiconductor substrate in the first wafer 201 can include silicon (Si), germanium (Ge), or silicon germanium (GeSi), silicon carbide (SiC); can also be silicon-on-insulator (SOI), germanium-on-insulator (GOI); or can further include other materials, such as group III-V compound of gallium arsenide, etc., and the bonding surface of the first wafer 201 can be a surface of the first semiconductor substrate. In some other embodiments, the first wafer 201 can include a first semiconductor substrate and a first dielectric layer located on the first semiconductor substrate, and the bonding surface of the first wafer 201 can be a surface of the first dielectric layer away from the first semiconductor substrate.

[0055] In some embodiments, the first wafer 201 includes a plurality of die regions and a plurality of scribe regions between the die regions, each die region can form an integrated circuit with a specific function, and after the first wafer 201 and the second wafer 202 are bonded, the bonded structure can be segmented along the scribe regions to form a plurality of discrete semiconductor functional structures.

[0056] In some embodiments, the integrated circuit of a certain function in each die region of the first wafer 201 can include a first semiconductor device and a first wiring layer electrically connected with the first semiconductor device, the first semiconductor device can be formed on an active surface of a first semiconductor substrate of the first wafer 201 (the first semiconductor substrate can include an active surface and a back surface opposite to each other), the first semiconductor device can include one or more of a transistor, a sensor (e.g., an image sensor), a memory cell of a memory, a passive device (e.g., a capacitor, an inductor, a resistor), the first wiring layer is located on the active surface of the first semiconductor substrate of the first wafer 201, the first wiring layer can include a first dielectric layer covering the first semiconductor device and a first metal wiring located in the first dielectric layer, the first metal wiring is electrically connected with the first semiconductor device, the first dielectric layer also covers a street region of the first wafer 201. In some embodiments, the first dielectric layer includes a single layer or a multi-layer stack structure. In some embodiments, the material of the first dielectric layer includes silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride, FSG (fluorine-doped silicon dioxide), BSG (boron-doped silicon dioxide), PSG (phosphorus-doped silicon dioxide), or BPSG (boron-phosphorus-doped silicon dioxide), a low dielectric constant (K less than 2.5) material, or a combination thereof, the metal wiring includes one or more of a metal layer, a connection plug, a through-silicon via (TSV), a via connection structure, a redistribution layer (RDL), and the material of the metal wiring includes one or more of aluminum, copper, nickel, tin, titanium, tungsten, platinum, chromium, tantalum, gold, silver. In some embodiments, the surface of the first dielectric layer away from the first semiconductor substrate of the first wafer 201 is the bonding surface of the first wafer 201. In some embodiments, the surface of the first interlayer dielectric layer of the street region of the first wafer 201 has a depression, the depression is a butterfly-shaped depression, i.e., the bonding surface of the first wafer 201 has a depression, the position of the depression corresponds to the position of the street, when a mixture including silicate and alcohol solvent is spin-coated on the bonding surface of the first wafer, the mixture can better fill the depression during spin-coating, the mixture after spin-coating has a flat surface, so that the first wafer is placed for treatment, the mixture of silicate and alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer, and the surface of the first silica sol layer away from the bonding surface of the first wafer is also a flat surface.

[0057] The second wafer 202 includes a second semiconductor substrate, and the material of the second semiconductor substrate can include silicon (Si), germanium (Ge), or silicon germanium (GeSi), silicon carbide (SiC), silicon-on-insulator (SOI), germanium-on-insulator (GOI), or other materials such as group III-V compound of gallium arsenide, etc. The bonding surface of the second wafer 202 is one surface of the second semiconductor substrate. In some other embodiments, the second wafer 202 can include a second semiconductor substrate and a second dielectric layer located on one surface of the second semiconductor substrate, and the bonding surface of the second wafer 202 is the surface of the second dielectric layer away from the second semiconductor substrate. In some embodiments, the material of the second dielectric layer includes silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride, FSG (fluorine-doped silicon dioxide), BSG (boron-doped silicon dioxide), PSG (phosphorus-doped silicon dioxide), or BPSG (boron-phosphorus-doped silicon dioxide), low dielectric constant (K less than 2.5) material, or a combination thereof.

[0058] In some embodiments, the material of the second semiconductor substrate in the second wafer 202 can be the same as or different from the material of the first semiconductor substrate in the first wafer 201, so that when the first wafer 201 and the second wafer 202 are bonded, the bonding of homogenous wafers or the bonding of heterogeneous wafers can be achieved to meet the process and device performance requirements.

[0059] In some embodiments, no semiconductor device such as a second semiconductor device is formed in the second semiconductor substrate of the second wafer 202 before the second wafer 202 is bonded with the first wafer 201. After the first wafer 201 and the second wafer 202 are bonded, a second semiconductor device and a second wiring layer electrically connected to the second semiconductor device can be formed on the surface of the second semiconductor substrate away from the first wafer 201 (or the first semiconductor substrate), and a via connection structure can be formed through the first wafer 201 (or the first semiconductor substrate) and the bonding layer between the first wafer 201 and the second wafer 202. The corresponding structure (such as the first wiring layer and / or the first semiconductor device) in the first wafer 201 and the corresponding structure (such as the second wiring layer and / or the second semiconductor device) in the second wafer 202 can be electrically connected through the via connection structure. In some embodiments, the second semiconductor substrate and the second wiring layer electrically connected to the second semiconductor device can be formed on the surface of the second wafer 202 away from the bonding surface of the second wafer 202 before the second wafer 202 is bonded with the first wafer 201.

[0060] Next, with reference to Figure 1 and with reference to Figures 2-5 (wherein, Figure 4 is Figure 2A schematic diagram of the structure after forming the first silica sol on the cross-sectional structure obtained by cutting along the cutting line AA1 direction; Figure 5 To Figure 3 A schematic diagram of the structure after forming the second silica sol on the cross-sectional structure obtained by cutting along the cutting line BB1 direction), step S102 is performed to spin-coat the mixed solution 21 including the silicate and the alcohol solvent on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using a spin-coating process; and step S103 is performed to, after the spin-coating process, respectively place the first wafer 201 and the second wafer 202 for processing, so that the mixed solution of the silicate and the alcohol solvent reacts to form a first silica sol layer 203 on the bonding surface of the first wafer 201 and a second silica sol layer 204 on the bonding surface of the second wafer 202.

[0061] The spin-coating process is performed by using a spin-coating device. In some embodiments, the spin-coating device includes a first liquid supply pipe (not shown in the figure), a second liquid supply pipe (not shown in the figure), a mixed solution tank (not shown in the figure), a liquid delivery pipe 302, and a nozzle 301. The first liquid supply pipe and the second liquid supply pipe are connected to the mixed solution tank. The first liquid supply pipe is used to supply the silicate into the mixed solution tank, and the second liquid supply pipe is used to supply the alcohol solvent into the mixed solution tank. The silicate and the alcohol solvent are mixed in the mixed solution tank to form the mixed solution 21 of the silicate and the alcohol solvent. The liquid delivery pipe 302 is connected to the mixed solution tank and is used to deliver the mixed solution 21 of the silicate and the alcohol solvent in the mixed solution tank to the nozzle 301. During the spin-coating process, the mixed solution 21 of the silicate and the alcohol solvent is sprayed onto the bonding surfaces of the first wafer 201 and the second wafer 202 respectively through the nozzle 301. In some embodiments, the first liquid supply pipe is provided with a first control switch for controlling the on-off of the silicate in the first liquid supply pipe, the second liquid supply pipe is provided with a second control switch for controlling the on-off of the alcohol solvent in the second liquid supply pipe, and the liquid delivery pipe 302 is provided with a third control switch for controlling the on-off of the mixed solution 21 of the silicate and the alcohol solvent in the liquid delivery pipe 302. Figure 2 Or Figure 3 In some embodiments, when the mixed solution 21 of the silicate and the alcohol solvent is formed on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process in the same spin-coating device, the mixed solution 21 of the silicate and the alcohol solvent is sequentially formed on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process in the same spin-coating cavity of the spin-coating device, or the mixed solution 21 of the silicate and the alcohol solvent is formed on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process in different spin-coating cavities of the spin-coating device.

[0062] The formation of the mixed solution 21 of the silicate and the alcohol solvent on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process can be performed in the same spin-coating device or in different spin-coating devices. In some embodiments, when the formation of the mixed solution 21 of the silicate and the alcohol solvent on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process is performed in the same spin-coating device, the mixed solution 21 of the silicate and the alcohol solvent is sequentially formed on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process in the same spin-coating cavity of the spin-coating device, or the mixed solution 21 of the silicate and the alcohol solvent is formed on the bonding surfaces of the first wafer 201 and the second wafer 202 respectively by using the spin-coating process in different spin-coating cavities of the spin-coating device.

[0063] The present application has the following unexpected technical effects: in the present application, the mixed solution 21 of silicate and alcohol solvent can be uniformly coated on the bonding surfaces of the first wafer 201 and the second wafer 202 through the spin coating process. After the spin coating process, the first wafer 201 and the second wafer 202 are respectively treated by standing. The mixed solution of silicate and alcohol solvent reacts (including hydrolysis reaction and condensation reaction), and a first silica sol layer 203 with a flat surface is formed on the bonding surface of the first wafer 201, and a second silica sol layer 204 with a flat surface is formed on the bonding surface of the second wafer 202. Therefore, the first silica sol layer 203 and the second silica sol layer 204 are respectively subjected to UV curing treatment, a first silicon oxide layer 205 (refer to Figure 6 ) is formed on the bonding surface of the first wafer 201, and a second silicon oxide layer 206 (refer to Figure 7 ) is formed on the bonding surface of the second wafer 202. The first silicon oxide layer 205 and the second silicon oxide layer 206 formed have flat surfaces, which can improve the bonding strength. Therefore, the bonding strength of the first wafer 201 and the second wafer 202 bonded through the first silicon oxide layer 205 and the second silicon oxide layer 206 is improved.

[0064] In addition, the mixed solution 21 of silicate and alcohol solvent is used in the spin coating process. The silicate in the mixed solution 21 forms silica sol (SiO2·nH2O) through hydrolysis reaction and condensation reaction, that is, the first silica sol layer 203 formed on the bonding surface of the first wafer 201 and the second silica sol layer 204 formed on the bonding surface of the second wafer 202. The alcohol solvent in the mixed solution 21 is used to adjust the viscosity of the mixed solution 21 and the uniformity of the distribution of silicate in the mixed solution, so that the mixed solution 21 can be more uniformly coated on the bonding surfaces of the first wafer 201 and the second wafer 202, and the first silica sol layer 203 formed on the bonding surface of the first wafer 201 and the second silica sol layer 204 formed on the bonding surface of the second wafer 202 have higher flatness.

[0065] On the other hand, the alcohol solvent as the solvent can also improve the coverage and filling capacity of the mixed solution 21, so that the mixed solution can better fill the recesses possibly existing on the bonding surfaces of the first wafer 201 and the second wafer 202; and the alcohol solvent can also act as a catalyst to provide "-OH", part of the "-OH" participates in the hydrolysis reaction of the silicate, and part of the "-OH" can improve the coverage and hydrophilicity of the "-OH" on the surface of the first silicon oxide layer after the first silica sol layer 203 is converted into the first silicon oxide layer, and improve the coverage and hydrophilicity of the "-OH" on the surface of the second silicon oxide layer after the second silica sol layer 204 is converted into the second silicon oxide layer. The improvement of the coverage and hydrophilicity of the "-OH" on the bonding surface can further improve the bonding strength of the first wafer 201 and the second wafer 202.

[0066] On the other hand, the alcohol solvent can also reduce the temperature during subsequent UV curing treatment (the temperature during subsequent UV curing treatment ranges from 150°C to 300°C, and the temperature during UV curing treatment is lower than the temperature during existing annealing (310°C-380°C)).

[0067] In some embodiments, in the mixed solution 21 of the silicate and the alcohol solvent, the volume percentage of the silicate and the alcohol solvent ranges from 1:10 to 1:20, and can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20. At this specific ratio, the viscosity of the mixed solution 21 is better, and the silicate in the mixed solution 21 is more uniformly distributed, so that the mixed solution 21 of the silicate and the alcohol solvent can be more uniformly and easily coated on the bonding surfaces of the first wafer 201 and the second wafer 202, thereby further improving the surface flatness of the first silica sol layer 203 formed on the bonding surface of the first wafer 201 and the second silica sol layer 204 formed on the bonding surface of the second wafer 202.

[0068] In some embodiments, the silicate includes methyl silicate or ethyl silicate, and the alcohol solvent includes an ethanol solution or an ethylene glycol solution.

[0069] In some embodiments, when the spin coating process is performed, the rotation speed of the first wafer and the second wafer is 200-400 rpm, specifically, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, the flow rate of the mixture is 1.7-1.9 L / min, specifically, 1.7 L / min, 1.75 L / min, 1.8 L / min, 1.85 L / min, 1.9 L / min, and the temperature is 20-25°C, specifically, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C. Under the specific spin coating process parameters, the mixture of silicate and alcohol solvent 21 can be more uniformly and easily coated on the bonding surfaces of the first wafer 201 and the second wafer 202, so as to further improve the surface flatness of the first silica sol layer 203 formed on the bonding surface of the first wafer 201 and the second silica sol layer 204 formed on the bonding surface of the second wafer 202.

[0070] In some embodiments, after the static treatment, before the UV curing treatment, further comprising: respectively performing alkaline solution treatment on the surfaces of the first silica sol layer 203 and the second silica sol layer 204; after the alkaline solution treatment, subsequently performing UV curing treatment on the first silica sol layer 203 and the second silica sol layer 204, respectively. The purpose of respectively performing alkaline solution treatment on the surfaces of the first silica sol layer 203 and the second silica sol layer 204 is to further improve the coverage and hydrophilicity of the "-OH" on the surfaces of the first silica sol layer 203 and the second silica sol layer 204, so as to further improve the coverage and hydrophilicity of the "-OH" on the surfaces of the first silica layer 205 (refer to Figure 6 ) and the second silica layer 206 (refer to Figure 7 ) after the first silica sol layer 203 and the second silica sol layer 204 are correspondingly converted into the first silica layer 205 and the second silica layer 206, so as to further improve the bonding strength when the first wafer 201 and the second wafer 202 are bonded subsequently.

[0071] In some embodiments, the alkaline solution comprises sodium hydroxide solution or potassium hydroxide solution; the time interval between the alkaline solution treatment and the static treatment is greater than 20 minutes, so that the mixture of silicate and alcohol solvent after spin coating on the bonding surfaces of the first wafer 201 and the second wafer 202 is fully reacted to form the first silica sol layer 203 and the second silica sol layer 204 with better quality and uniformity.

[0072] Next, with continued reference to Figure 1 , and in combination with reference to Figure 6 and Figure 7 , the step S104 is performed on the first silica sol layer 203 (refer to Figure 4) and the second silica sol layer 204 (reference) Figure 5 ) are subjected to UV curing treatment 22, and a first silicon oxide layer 205 is formed on the bonding surface of the first wafer 201 (reference) Figure 6 A second silicon oxide layer 206 is formed on the bonding surface of the second wafer 202 (reference). Figure 7 ).

[0073] The purpose of UV (Ultraviolet) curing treatment 22 is to transform the first silica sol layer 203 into the first silica oxide layer 205 and the second silica sol layer 204 into the second silica oxide layer 206. Specifically, during UV curing treatment 22, the solvent and water in the first silica sol layer 203 and the second silica sol layer 204 evaporate. Furthermore, during UV curing treatment 22, the first silica sol layer 203 and the second silica sol layer 204 absorb UV light energy and decompose into free radicals / cations. These free radicals / cations undergo polymerization reactions with monomers or oligomers in the silica sol to form a cross-linked network structure, causing the first silica sol layer 203 and the second silica sol layer 204 to rapidly transform from a liquid state into a solid state, namely the first silica oxide layer 205 and the second silica oxide layer 206.

[0074] In some embodiments, the wavelength of the UV light during UV curing is 150 nm to 300 nm, the temperature is 150 °C to 300 °C, and the time is 5 to 30 seconds, which improves the conversion efficiency while maintaining a low thermal budget.

[0075] Finally, continue to refer to Figure 1 and in conjunction with references Figure 8 In step S105, the second silicon oxide layer 206 of the second wafer 202 is bonded to the first silicon oxide layer 205 of the first wafer 201 to form a bonding structure.

[0076] In some embodiments, the process of bonding the second silicon oxide layer 206 of the second wafer 202 to the first silicon oxide layer 205 of the first wafer 201 includes: first fixing the first wafer 201 on a stage in the bonding chamber of a bonding apparatus; aligning the second wafer 202 with the first wafer 201; then placing the second wafer 202 onto the first wafer 201, so that the second silicon oxide layer 206 on the bonding surface of the second wafer 202 contacts and bonds with the first silicon oxide layer 205 on the bonding surface of the first wafer 201. During the bonding process, a moving pressure can be applied to the surface of the second wafer 202 away from the second silicon oxide layer 206, and a certain bonding temperature can be maintained in the bonding chamber. During bonding, the "-OH" groups on the surfaces of the first silicon oxide layer 205 and the second silicon oxide layer 206 participate in the bonding process to improve the bonding strength.

[0077] In the description of the specification, the description of the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are contained in at least one embodiment or example of the present application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0078] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features of the above-described embodiments are described, however, as long as the combination of the technical features does not result in a contradiction, it should be considered within the scope of the present disclosure.

[0079] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A wafer bonding method, characterized in that, include: A first wafer and a second wafer are provided, both of which include a bonding surface; A mixture comprising silicate ester and alcohol solvent is spin-coated onto the bonding surfaces of the first and second wafers respectively using a spin-coating process. After the spin coating process, the first wafer and the second wafer are left to stand for treatment. The mixture of silicate ester and alcohol solvent reacts to form a first silica sol layer on the bonding surface of the first wafer and a second silica sol layer on the bonding surface of the second wafer. The surfaces of the first silica sol layer and the second silica sol layer were treated with an alkaline solution, respectively. The first silica sol layer and the second silica sol layer are respectively subjected to UV curing treatment to form a first silicon oxide layer on the bonding surface of the first wafer and a second silicon oxide layer on the bonding surface of the second wafer. The second silicon oxide layer of the second wafer is bonded to the first silicon oxide layer of the first wafer; The bonding surface of the first wafer includes a dicing region with a recess, the first silica sol layer fills the recess, and the surface of the first silica sol layer away from the bonding surface of the first wafer is a flat surface.

2. The wafer bonding method according to claim 1, characterized in that, The alkaline solution includes sodium hydroxide solution or potassium hydroxide solution.

3. The wafer bonding method according to claim 1, characterized in that, The time interval between the alkaline solution treatment and the standing treatment is greater than 20 minutes.

4. The wafer bonding method according to claim 1, characterized in that, In the mixture of silicate ester and alcohol solvent, the volume percentage of silicate ester and alcohol solvent ranges from 1:10 to 1:

20.

5. The wafer bonding method according to claim 4, characterized in that, The silicate ester includes methyl silicate or ethyl silicate, and the alcohol solvent includes an ethanol solution or an ethylene glycol solution.

6. The wafer bonding method according to claim 4, characterized in that, During the spin coating process, the rotation speed of the first wafer and the second wafer is 200 rpm to 400 rpm, the flow rate of the mixture is 1.7 L / min to 1.9 L / min, and the temperature is 20°C to 25°C.

7. The wafer bonding method according to claim 6, characterized in that, The UV light used in the UV curing process has a wavelength of 150 nm to 300 nm, a temperature of 150 °C to 300 °C, and a duration of 5 to 30 seconds.

8. The wafer bonding method according to claim 1, characterized in that, The spin coating process is performed using a spin coating device, which includes a first supply pipe, a second supply pipe, a mixing tank, a delivery pipe, and a nozzle. The first and second supply pipes are connected to the mixing tank. The first supply pipe supplies silicate ester to the mixing tank, and the second supply pipe supplies alcohol solvent to the mixing tank. The silicate ester and the alcohol solvent are mixed in the mixing tank to form a mixture of silicate ester and alcohol solvent. The delivery pipe is connected to the mixing tank and is used to deliver the mixture of silicate ester and alcohol solvent in the mixing tank to the nozzle. During the spin coating process, the mixture of silicate ester and alcohol solvent is sprayed onto the bonding surfaces of the first and second wafers through the nozzle.

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