Temporary bonding and de-bonding method, preparation method of composite substrate and manufacturing method of wafer

Abstract

The invention belongs to the field of semiconductor processing and manufacturing, and provides a temporary bonding and de-bonding method, a composite substrate preparation method and a wafer manufacturing method.The temporary bonding and de-bonding method comprises the steps that silicon oxide layers are formed on two silicon substrates; the silicon oxide layer is subjected to ion implantation, hydrofluoric acid treatment and plasma activation, temporary bonding of the two silicon substrates is realized through hydrophilic bonding, and a temporary bonding interface is cracked through de-bonding annealing, so that de-bonding is realized. According to the method, a bonding medium does not need to be used, the thermal properties of the two substrates can be kept consistent, and warping and breaking are effectively avoided; temporary bonding is high in strength and good in stability, the functional substrate can be greatly thinned through the method, and therefore the composite substrate is prepared or the method is further used for manufacturing a multi-layer wafer bonding structure.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor processing and manufacturing, and relates to a temporary bonding and debonding method, a composite substrate preparation method and a wafer manufacturing method. Background Art

[0002] Temporary bonding is a key technology in semiconductor manufacturing and advanced packaging processes. It is mainly used to solve the "holding" and "support" problems in ultra-thin wafer processing. The implementation of this technology usually requires a thicker supporting substrate and a thinner functional substrate supported (held) by it. By temporarily bonding the functional substrate to the supporting substrate, the strength of the functional substrate can be improved to ensure that it is not damaged in subsequent process steps (such as thinning). At the end of the process, the supporting substrate will be removed, and this removal process is called debonding.

[0003] The existing temporary bonding and debonding methods are mainly the following:

[0004] First, thermal compression bonding. This method heats the support substrate and the functional substrate to a specific temperature, and bonds the two together with a certain pressure. The temporary bonding interface is coated with a bonding medium (usually glue). When debonding, the bonding medium is softened by heating, losing its adhesion, and thus separating the support substrate from the functional substrate.

[0005] The second method is thermal slip debonding. This method also uses a bonding medium to adhere the support substrate and the functional substrate together. When debonding, the bonding medium is first heated to soften and lose its adhesion, and then a slip force in opposite directions is applied to the support substrate and the functional substrate to separate the two.

[0006] Third, laser debonding. It is still to first adhere the support substrate and the functional substrate through the bonding medium. During debonding, the bonding medium layer is ablated by laser to soften it and lose its adhesion ability, thereby separating the support substrate from the functional substrate.

[0007] In summary, in the existing temporary bonding methods, a bonding medium for bonding, generally a bonding glue, is provided on the temporary bonding surfaces of the support substrate and the functional substrate.

[0008] However, bonding glue has the following problems in temporary bonding:

[0009] First, the thermal stability is poor. The maximum heat resistance of bonding adhesive is about 300°C. This limitation makes it impossible for functional substrates to be processed in high-temperature processes.

[0010] Secondly, the thickness of the bonding adhesive layer in the existing process is generally around 100μm, and it is often spin-coated on the substrate surface using a spin coating process. It is difficult to form an atomically flat adhesive surface on the substrate surface, resulting in poor parallelism of the functional substrate relative to the supporting substrate, and poor rigidity of the bonding adhesive layer, which ultimately leads to poor support strength for the functional substrate. These problems make it impossible to effectively thin the functional substrate to the extreme, making it difficult to obtain an ultra-thin functional substrate, and thus making it impossible to reduce the thickness of the subsequent prepared device. At the same time, the inability to reduce the thickness will also affect the performance of the device, for example, increasing the length of the conductive medium between the stacked layers, thereby affecting the heat dissipation and working efficiency of the device.

[0011] Third, the decomposition and volatilization of the bonding adhesive will introduce impurities onto the surface of the functional substrate, and the remaining adhesive requires additional processes for cleaning and removal, which increases the cost and complexity of the process.

[0012] In order to avoid the disadvantages brought by bonding adhesive, the existing technology also studies the use of metal as bonding medium to achieve temporary bonding. Correspondingly, when debonding, laser needs to be used to ablate the metal medium through the supporting substrate to achieve debonding. Although this technology can be used to perform high-temperature processes on functional substrates due to the high temperature resistance of metals, the following problems still exist:

[0013] When laser debonding is used, in order to prevent the laser from damaging the functional substrate, the laser needs to pass through the supporting substrate from the supporting substrate side, and then focus on the bonding medium layer to ablate the metal bonding medium layer. In order to allow the laser to pass through the supporting substrate and effectively focus on the bonding medium layer, glass with high light transmittance is often used as the supporting substrate. The functional substrate is generally a silicon substrate. When the glass supporting substrate and the silicon functional substrate are temporarily bonded and subjected to a high-temperature process, due to the difference in the thermal expansion coefficient of the materials, a large stress will be introduced, causing the thinner functional substrate to warp or break. If silicon material is used as the supporting substrate, although the adverse factors caused by the difference in thermal expansion coefficient can be avoided, the laser transmittance is low and the metal dielectric layer cannot be effectively ablated, which leads to failure of successful debonding.

[0014] From the above, it can be seen that there is currently a lack of a solution that can avoid the influence of the bonding medium or even effectively achieve temporary bonding and debonding without using a bonding medium. Summary of the invention

[0015] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for temporary bonding and debonding, a method for preparing a composite substrate and a method for manufacturing a wafer, wherein the method for temporary bonding and debonding comprises forming a silicon oxide layer on two silicon substrates, ion implanting, hydrofluoric acid treating and plasma activating the silicon oxide layer, achieving temporary bonding of the two silicon substrates by hydrophilic bonding, and then cracking the temporary bonding interface by debonding annealing to achieve debonding. The method does not require the use of a bonding medium, and can keep the thermal properties of the two substrates consistent, effectively avoiding warping and breakage; the temporary bonding has high strength and good stability, and can withstand and adapt to other processing techniques that require high temperature treatment of 350~1250℃. The method can achieve substantial thinning of the functional substrate, thereby preparing a composite substrate or further using it to manufacture a multi-layer wafer bonding structure.

[0016] To achieve this object, the present invention adopts the following technical solutions:

[0017] In a first aspect, the present invention provides a method for temporary bonding and debonding, comprising the following steps:

[0018] A1. Providing two silicon substrates, forming a silicon oxide layer on one side of the silicon substrate;

[0019] A2. Sequentially ion implanting the silicon oxide layer, treating with hydrofluoric acid and plasma activation to form a temporary bonding surface;

[0020] A3. The temporary bonding surfaces are contacted to perform hydrophilic bonding, and then annealed to form a temporary bonding body between the two silicon substrates to complete the temporary bonding;

[0021] A4. Performing debonding annealing on the temporary bonded body to separate the silicon oxide layers of the two silicon substrates at the temporary bonding interface, thereby completing debonding.

[0022] In the temporary bonding and debonding method of the present invention, the two substrates used for temporary bonding (respectively referred to as the supporting substrate and the functional substrate) are selected as silicon substrates. Both of them are made of silicon material, which can effectively avoid the warping or breakage problems caused by the difference in thermal expansion coefficient. The supporting substrate and the functional substrate made of silicon material have high consistency in thermal properties, and the degree of thermal expansion and contraction under various temperature conditions is relatively close, thereby greatly reducing the risk of damage to the bonding structure due to different thermal expansion coefficients.

[0023] The principle of temporary bonding and debonding of the present invention includes: generating sufficient hanging hydroxyl groups and active sites on the surface of the silicon oxide layer (temporary bonding surface) through plasma activation, thereby realizing hydrophilic bonding by using two activated silicon oxide layers, and further enhancing the bonding strength (>2J / m 2), to ensure the strength and stability of the temporary bonding. Before the hydrophilic bonding, the present invention performs ion implantation and hydrofluoric acid treatment on the silicon oxide layer, wherein the ion implantation forms an ion implantation layer inside the silicon oxide layer, and then the hydrofluoric acid treatment is performed so that the hydrofluoric acid component reacts with the silicon oxide layer to destroy the ring structure formed by the silicon-oxygen bond, and a channel is created in the oxide layer for the ion elements to flow, and the high-temperature treatment of the debonding annealing is performed to promote the movement of the ion elements between the crystal lattices of the silicon oxide layer and to precipitate from the channel to the temporary bonding interface, thereby cracking the temporary bonding interface, so that the two temporarily bonded silicon oxide layers are cracked and separated, and debonding is achieved.

[0024] It can be seen that in the temporary bonding and debonding method described in the present invention, the temporary bonding interface between the support substrate and the functional substrate does not need to introduce a bonding medium. The advantage of this design is that, first, it can avoid the problem of high-temperature process limitations caused by the bonding medium. For example, in some cases, the bonding medium may soften in a high temperature environment, thereby affecting the reliability of the entire temporary bonding structure. Second, due to the absence of the traditional coated organic chemical bonding medium, the flatness of the temporary bonding surface, the temperature tolerance and the strength of the temporary bonding interface are greatly improved, and the subsequent processing of the functional substrate is easy to operate and control, for example, it can greatly reduce the difficulty of thinning the functional substrate and realize the manufacture of ultra-thin functional substrates. Third, impurity contamination and cleaning problems caused by the use of bonding media can be avoided. The bonding medium may introduce impurities, which will not only affect the bonding quality, but also have an adverse effect on product performance in subsequent processes, and removing these impurities also requires additional time and resources.

[0025] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0026] As a preferred technical solution of the present invention, in step A1, the method of forming the silicon oxide layer includes thermal oxygen oxidation.

[0027] Preferably, the thickness of the silicon oxide layer is 1 to 1000 nm, for example, 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 25 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm.

[0028] As a preferred technical solution of the present invention, in step A2, before the ion implantation, the surface of the silicon oxide layer is first planarized so that the surface roughness is ≤1nm, for example, 1nm, 0.95nm, 0.9nm, 0.85nm, 0.8nm, 0.75nm, 0.7nm, 0.65nm, 0.6nm, 0.55nm, 0.5nm, 0.45nm, 0.4nm, 0.35nm, 0.3nm, 0.25nm, 0.2nm, 0.15nm, 0.1nm or 0.05nm, etc.

[0029] Preferably, in step A2, the ion elements of the ion implantation include hydrogen ions.

[0030] The ion elements of the ion implantation of the present invention are preferably hydrogen ions. During the debonding annealing, hydrogen atoms move between the crystal lattices of the silicon oxide layer, flow through the channels formed by the hydrofluoric acid treatment and precipitate onto the temporary bonding interface, and form hydrogen gas through recombination and form uniform bubbles on the temporary bonding interface, so that the temporary bonding interface is cracked and the debonding is completed.

[0031] Preferably, the ion implantation energy is 1-80 keV, such as 1 keV, 3 keV, 5 keV, 8 keV, 10 keV, 15 keV, 20 keV, 25 keV, 30 keV, 35 keV, 40 keV, 45 keV, 50 keV, 55 keV, 60 keV, 65 keV, 70 keV, 75 keV or 80 keV, etc.; the implantation dose is 1×10 13 ~8×10 16 ions / cm 2 , for example 1×10 13 ions / cm 2 , 3×10 13 ions / cm 2 , 5×10 13 ions / cm 2 , 8×10 13 ions / cm 2 , 1×10 14 ions / cm 2 , 3×10 14 ions / cm 2 , 5×10 14 ions / cm 2 , 8×10 14 ions / cm 2 , 1×10 15 ions / cm 2 , 3×10 15 ions / cm 2 , 5×10 15ions / cm 2 , 8×10 15 ions / cm 2 , 1×10 16 ions / cm 2 , 3×10 16 ions / cm 2 , 5×10 16 ions / cm 2 or 8×10 16 ions / cm 2 etc.; the implantation depth is 0.1~1000nm, for example, 0.1nm, 0.3nm, 0.5nm, 0.8nm, 1nm, 3nm, 5nm, 8nm, 10nm, 25nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm, etc.

[0032] It should be noted that, in order to ensure that the ion implantation does not damage the silicon substrate, the depth of the ion implantation should preferably be smaller than the thickness of the silicon oxide layer.

[0033] Preferably, after the ion implantation and before the hydrofluoric acid treatment, the silicon substrate is first cleaned to remove surface impurities; the first cleaning method includes first using a mixed solution of ammonia water, hydrogen peroxide and deionized water for tank cleaning, and then using a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water for tank cleaning.

[0034] As a preferred technical solution of the present invention, in step A2, the hydrofluoric acid treatment method includes immersion in a hydrofluoric acid solution, and the mass percentage concentration of the hydrofluoric acid solution is 0.1% to 30%, for example, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28% or 30%, etc.

[0035] Preferably, the temperature of the hydrofluoric acid treatment is 10-50°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C, and the time is 1-100s, for example, 1s, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s, 95s or 100s, etc.

[0036] Preferably, after the hydrofluoric acid treatment and before the plasma activation, the silicon substrate is subjected to a second cleaning and then spin-dried to remove residual solution on the surface; the second cleaning method includes cleaning with deionized water.

[0037] In the present invention, the purpose of the hydrofluoric acid treatment is to form a channel for the ion implantation element to flow. If the treatment degree is too large, the surface roughness will increase due to corrosion. During temporary bonding, voids will easily exist at the temporary bonding interface, resulting in a decrease in temporary bonding strength and even lattice damage in the silicon substrate. Therefore, the concentration of the hydrofluoric acid solution used for the hydrofluoric acid treatment, as well as the temperature and time of the hydrofluoric acid treatment should be reasonably adjusted and selected.

[0038] As a preferred technical solution of the present invention, in step A2, the gas for plasma activation to generate plasma includes N 2 , O 2 , Ar or He.

[0039] Preferably, after the plasma activation and before the hydrophilic bonding, the silicon substrate is subjected to a third cleaning to remove surface particles.

[0040] As a preferred technical solution of the present invention, in step A3, the hydrophilic bonding method includes a center point pressure method or a plane pressure method.

[0041] Preferably, the pressurization pressure of the hydrophilic bond is 1-1000N, such as 1N, 5N, 8N, 10N, 30N, 50N, 80N, 100N, 200N, 300N, 400N, 500N, 600N, 700N, 800N, 900N or 1000N, etc., and the pressurization holding time is 1-200s, such as 1s, 3s, 5s, 8s, 10s, 30s, 50s, 80s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s or 200s, etc., so that the bonding strength is ≥2J / m 2 .

[0042] Preferably, the temperature of the hydrophilic bonding is 15-35°C, for example, 15°C, 18°C, 20°C, 23°C, 25°C, 28°C, 30°C, 32°C or 35°C.

[0043] Preferably, the temperature of the strengthening annealing is 100-350°C, for example, 100°C, 120°C, 150°C, 180°C, 200°C, 230°C, 250°C, 280°C, 300°C, 330°C or 350°C, and the time is ≥10min, for example, 10min, 12min, 15min, 18min, 20min, 23min, 25min, 28min or 30min, etc.

[0044] As a preferred technical solution of the present invention, in step A4, the temperature of the debonding annealing is 350~1250°C, for example, 350°C, 380°C, 400°C, 420°C, 450°C, 470°C, 500°C, 530°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 730°C, 750°C, 775°C, 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, 1200°C, 1225°C or 1250°C, etc.

[0045] In a second aspect, the present invention provides a method for preparing a composite substrate, the method comprising the following steps:

[0046] B1. Providing two silicon substrates, respectively, as a support substrate and a functional substrate, and completing temporary bonding according to the temporary bonding and debonding method of the first aspect to obtain a temporary bonded body;

[0047] B2. Thinning the functional substrate in the resulting temporary bond;

[0048] B3 provides a target substrate, the thinned functional substrate in the temporary bonding body is permanently bonded to the target substrate to obtain a bonding intermediate;

[0049] B4. Debonding is completed by the temporary bonding and debonding method according to the first aspect, removing the supporting substrate to obtain a bonded body;

[0050] B5. Remove the silicon oxide layer on the functional substrate in the obtained bonded body to obtain a composite substrate.

[0051] Based on the advantages of the temporary bonding and debonding method described in the present invention, it is convenient to process the functional substrate in the temporary bonding body, especially to thin the functional substrate to an extreme extent (such as up to 1 micron level, which can be measured by a finished film thickness meter), and then the ultra-thin functional substrate (film) can be transferred to the target substrate through permanent bonding through the preparation method of the composite substrate, and then the temporary bonding is released, so as to prepare a composite substrate with a thin film. In the prior art, a composite substrate with a thin film can also be prepared by ion implantation stripping and permanent bonding technology. This method is: ion implantation is started directly on one side of the permanent bonding surface of the functional substrate, with an implantation depth of about 1 micron, and then the ion-implanted functional substrate is permanently bonded to the target substrate, and then the ion implantation layer is cracked by high temperature treatment, so as to transfer the functional substrate of about 1 micron to the target substrate to form a composite substrate, but the problem is that ion implantation will cause direct damage and loss to the functional substrate (film layer) to be transferred. However, the preparation method of the composite substrate of the present invention does not have this problem, and there are no lattice defects caused by ion implantation in the functional substrate, and the crystal quality of the obtained "film" layer is higher.

[0052] As a preferred technical solution of the present invention, in step B2, the thinning method includes grinding thinning and / or ion implantation peeling.

[0053] Preferably, the grinding and thinning method includes polishing.

[0054] Preferably, the ion implantation stripping method includes implanting hydrogen ions on a side of the functional substrate away from the temporary bonding interface to form a damaged layer, performing high-temperature stripping to crack the damaged layer, removing the portion stripped from the functional substrate, and then polishing the surface of the functional substrate to complete thinning and obtain a thinned functional substrate.

[0055] It should be emphasized that, based on the temporary bonding achieved in the present invention, ion implantation stripping is used to thin the functional substrate, and the portion that is stripped and removed is the portion that has been ion implanted, that is, the damaged portion. After this portion is removed, the thinned functional substrate in the temporary bonding body is undamaged, and a high-quality ultra-thin functional substrate can be formed after polishing.

[0056] Preferably, the stripping temperature of the high temperature stripping is 700-1150°C, for example, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1120°C or 1150°C.

[0057] Preferably, the stripping temperature of the ion implantation stripping is lower than the temperature of the debonding annealing.

[0058] It should be noted that in order to avoid the stripping temperature of ion implantation stripping and the debonding annealing temperature range of the present invention for debonding overlapping, which may have an adverse effect on the completed temporary bonding. Therefore, temperature matching is required to make the debonding temperature higher than the stripping temperature of high-temperature stripping to ensure that the stripped part is detached, while the thinned functional substrate is still temporarily bonded to the supporting substrate. Specifically, the stripping temperature of ion implantation stripping and / or the debonding annealing temperature of temporary bonding can be changed by adjusting the ion implantation dose and implantation depth to change the temperature required for ion precipitation from the silicon oxide layer. Similarly, if after temporary bonding, the functional substrate needs to undergo other processing techniques that require high-temperature treatment, then it is only necessary to ensure that the temperature of these high-temperature treatments is less than the debonding temperature.

[0059] As a preferred technical solution of the present invention, in step B3, the material of the target substrate includes at least one of diamond, gallium nitride or silicon carbide.

[0060] As a preferred technical solution of the present invention, in step B3, the permanent bonding method includes any one of hydrophilic bonding, room temperature bonding or hot pressing bonding.

[0061] As a preferred technical solution of the present invention, in step B3, if hydrophilic bonding is selected as the permanent bonding method, after permanent bonding, annealing is required to increase the strength of the permanent bonding, and the annealing temperature is 100-300°C, for example, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 280°C or 300°C, etc., and the time is ≥10min, for example, 10min, 13min, 15min, 18min, 20min, 23min, 25min, 28min or 30min, etc.

[0062] It should be noted that the purpose of step B3 of the method for preparing the composite substrate of the present invention is to achieve permanent bonding between the target substrate and the functional substrate. Therefore, all permanent bonding methods in the art are suitable for performing the permanent bonding. According to the selection of the specific method of permanent bonding, it is possible to consider adding annealing to enhance the effect of permanent bonding. Generally speaking, for room temperature bonding and hot pressing bonding, subsequent annealing may not be required. Technicians in the art can make reasonable adjustments and selections based on actual conditions.

[0063] In a third aspect, a composite substrate is obtained according to the method for preparing the composite substrate in the second aspect.

[0064] In a fourth aspect, the present invention provides a method for manufacturing a wafer, the method comprising the following steps:

[0065] C1. Providing two silicon substrates, respectively serving as a support substrate and a functional substrate, and completing temporary bonding according to the temporary bonding and debonding method of the first aspect to obtain a temporary bonded body;

[0066] C2. The non-temporary bonding surface of the functional substrate has a circuit structure, or the non-temporary bonding surface of the functional substrate is thinned and processed to form a functional wafer;

[0067] C3 provides a target wafer, the functional wafer in the temporary bonding body is permanently bonded to the target wafer to obtain a bonding intermediate;

[0068] C4. According to the temporary bonding and debonding method of the first aspect, the bonded intermediate is debonded, the supporting substrate is removed, and a bonded body is obtained;

[0069] C5. Removing the silicon oxide layer on the functional wafer in the resulting bonded body to obtain a composite wafer.

[0070] Based on the advantages of the temporary bonding and debonding method described in the present invention, it is convenient to extremely thin the functional substrate in the temporary bonding body and implement other processing techniques, and then the circuit structure can be processed in the thinned functional substrate by the wafer manufacturing method to form a functional wafer, and permanent bonding is performed on the functional wafer to obtain a composite wafer. Of course, the functional substrate can have an original circuit structure before temporary bonding, so there is no need to process the circuit structure after temporary bonding. At this time, the functional substrate with the original circuit structure has been transformed into the functional wafer when it is temporarily bonded to form a temporary bonding body, or after being temporarily bonded to form a temporary bonding body, it can be transformed into a functional wafer by only thinning.

[0071] It can be understood that the non-temporary bonding surface refers to the other side surface opposite to the temporary bonding surface.

[0072] As a preferred technical solution of the present invention, in step C3, the target wafer has or does not have a circuit structure.

[0073] Preferably, the target wafer further has an RDL layer disposed on the circuit structure.

[0074] In the present invention, the target wafer includes the following three situations: first, there is no circuit structure on the target wafer, and its function is only to dissipate heat, and it is permanently bonded to the functional wafer with the circuit structure; second, there is a circuit structure on the target wafer, and it is permanently bonded to the functional wafer with the circuit structure; third, the target wafer has a circuit structure, and the circuit structure has an RDL layer, and then it is permanently bonded to the functional wafer.

[0075] Preferably, the manufacturing method also includes step C6, preparing an RDL layer on the functional wafer of the obtained composite wafer, and then using the composite wafer provided with the RDL layer as the target wafer, repeating steps C1 to C5 to perform stacking bonding until the target number of layers is reached, thereby obtaining a multi-layer composite wafer.

[0076] Preferably, the step C6 further comprises, before preparing the RDL layer on the functional wafer, thinning the functional wafer to remove part of the silicon layer to expose the circuit structure in the functional wafer.

[0077] Preferably, the method for preparing the RDL layer includes forming a dielectric layer on the functional wafer, then making a through hole in the dielectric layer, and then filling the through hole with a conductive medium to form a metal wiring so that the through hole has an electrical connection function; using the obtained composite wafer as the target wafer, repeating steps C1 to C5, and performing the permanent bonding on one side of the RDL layer.

[0078] Preferably, the material of the dielectric layer includes SiO 2 , SiN or SiCN.

[0079] The purpose of step C6 of the wafer manufacturing method described in the present invention is to continue to stack more functional wafers on the functional wafer that has been permanently bonded to the target wafer, that is, to use the temporary bonding and debonding method described in the present invention to "hold" and "grab" the new functional wafer and permanently bond it to the existing functional wafer in the composite wafer, thereby achieving stacked bonding. Therefore, the target number of layers can be adjusted according to actual design and needs until a multi-layer composite wafer (multi-layer wafer bonding structure) is obtained. That is, the multi-layer composite wafer refers to a functional wafer with at least two layers stacked on the initial target wafer.

[0080] It should be noted that before the two functional wafers are permanently bonded, an RDL layer (rewiring layer) is needed to achieve circuit connection between the two functional wafers. Therefore, the bonded functional wafers in the composite wafer need to be thinned to remove part of the silicon layer to expose the circuit wiring in the functional wafer, and then the RDL layer is prepared on it to achieve the extension and connection of the circuit structure and prepare for the bonding of the new functional wafer.

[0081] The composite wafer and multi-layer composite wafer obtained by the wafer manufacturing method of the present invention have obvious advantages, that is, in 2.5D and 3D packaging, the stacking of multi-layer circuits can be achieved by stacking bonding, and the interconnection between multi-layer circuits is preferably interconnected by through-holes. When the functional wafer is prepared very thin, the length of the through-hole will be shortened, which will greatly reduce the transmission time of the signal and reduce the heat generation, thereby improving the performance of the device or chip. The thinning of the functional wafer can also reduce the volume of the subsequent prepared device or chip, adapting to the development trend of device miniaturization.

[0082] As a preferred technical solution of the present invention, the functional wafer and the target wafer are also provided with corresponding bonding alignment marks respectively.

[0083] As a preferred technical solution of the present invention, before the functional wafer is permanently bonded to the target wafer, the functional wafer is first cut to form functional chips, and defective functional chips are removed. Then, the remaining qualified functional chips are permanently bonded to the target wafer to obtain the bonding intermediate.

[0084] As a preferred technical solution of the present invention, in step C3, the method for manufacturing the initial target wafer includes providing a silicon substrate, processing a circuit structure on the silicon substrate, and forming the initial target wafer; the method for processing the circuit structure includes photolithography.

[0085] It should be noted that the method for thinning the functional substrate in step C2 may be the same as step B2 of the method for preparing a composite substrate described in the second aspect of the present invention. The specific scheme has been recorded in the second aspect and will not be repeated here.

[0086] It should be noted that the permanent bonding method in step C3 may be the same as step B3 of the method for preparing a composite substrate described in the second aspect of the present invention. The specific scheme has been described in the second aspect and will not be repeated here.

[0087] In a fifth aspect, the present invention provides a wafer comprising at least two stacked wafer layers, obtained according to the manufacturing method described in the fourth aspect.

[0088] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0089] The substrates of the temporary bonding and debonding methods described in the present invention are all silicon substrates. Being made of silicon, they can effectively avoid warping or breakage problems caused by differences in thermal expansion coefficients, greatly reducing the risk of damage to the temporary bonding structure due to differences in thermal expansion coefficients. The present invention does not require the introduction of a bonding medium, thus avoiding the problem of high-temperature process limitations caused by the bonding medium. The flatness and temperature tolerance of the temporary bonding surface and the strength of the temporary bonding interface are greatly improved, and impurity contamination and cleaning problems caused by the bonding medium can also be avoided.

[0090] The temporary bonding and debonding method described in the present invention facilitates the advantage of greatly thinning the functional substrate, and then the ultra-thin functional substrate (film) with a thickness of up to 1 micron can be transferred to the target substrate through the composite substrate preparation method, thereby preparing a composite substrate with a thin film. The lattice defects caused by ion implantation are avoided, and the crystal quality of the obtained "film" layer is higher.

[0091] Furthermore, the wafer manufacturing method can realize the manufacture of multi-layer composite wafers in a stacked bonding manner and process, and the ultra-thin functional wafer is conducive to greatly reducing the transmission time of signals and reducing the generation of heat, thereby improving the performance of devices or chips. The thinning of functional wafers can also reduce the volume of subsequent prepared devices or chips, thereby adapting to the development trend of device miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 It is a schematic flow chart of a temporary bonding and debonding method in Example 1.

[0093] Figure 2 It is a schematic flow chart of a method for preparing a composite substrate in Application Example 1.

[0094] Figure 3 It is a flow chart of a method for manufacturing a wafer in Application Example 3.

[0095] In the figure: 10-silicon substrate, 11-support substrate, 12-functional substrate, 13-functional wafer, 20-silicon oxide layer, 30-temporary bonding interface, 40-temporary bonding body, 50-target substrate, 51-target wafer, 60-composite substrate, 61-composite wafer, 62-multi-layer composite wafer, 70-RDL layer, 71-dielectric layer, 72-through hole, 73-conductive medium. DETAILED DESCRIPTION

[0096] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0097] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0098] Example 1

[0099] This embodiment provides a temporary bonding and debonding method, such as Figure 1 As shown, the following steps are included:

[0100] A1. Preparing two silicon substrates 10, respectively, on the two silicon substrates 10, a silicon oxide layer 20 is prepared by thermal oxidation, the thickness of the silicon oxide layer 20 is 800nm;

[0101] A2. The surface of the silicon oxide layer 20 is planarized to a surface roughness of less than 1 nm, and then hydrogen ions are implanted into the silicon oxide layers 20 of the two silicon substrates 10 by ion implantation, with an implantation energy of 40 keV and an implantation dose of 5×10 15 ions / cm 2 , the implantation depth is 460nm, and an ion implantation layer is formed in the silicon oxide layer 20;

[0102] The silicon substrate 10 after ion implantation is first cleaned by sequentially using a mixed solution of ammonia, hydrogen peroxide and deionized water for tank cleaning, and then using a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water for tank cleaning to remove surface impurities;

[0103] The silicon substrate 10 after the first cleaning is treated with hydrofluoric acid using a hydrofluoric acid solution with a mass percentage concentration of 20%, the treatment temperature is 35° C., and the treatment time is 57 seconds. The surface of the silicon substrate 10 is then cleaned for a second time with deionized water to remove the residual solution on the surface, and then dried at a high speed.

[0104] After the second cleaning, the temporary bonding surfaces of the two silicon substrates 10, that is, the surfaces of the silicon oxide layer 20, are plasma activated by plasma activation technology to generate hanging hydroxyl groups and active sites on the temporary bonding surfaces, and the activation gas is Ar gas;

[0105] The silicon substrate 10 after plasma activation is cleaned for the third time with deionized water to remove particles on the surface of the silicon substrate 10 and reduce voids formed by particles at the subsequent temporary bonding interface 30;

[0106] A3. After the third cleaning, the two silicon substrates 10 are temporarily bonded to the surface in contact, and a planar pressure method is adopted at room temperature for hydrophilic bonding, the pressure is 420N, maintained for 80s, to form a temporary bond body 40,

[0107] The temporary bonding body 40 is placed at 280°C for strengthening annealing for 25 minutes to increase the temporary bonding strength. After annealing, the temporary bonding is completed, and the temporary bonding strength is greater than 2J / m 2 ;

[0108] A4. During debonding, the temporary bonded body 40 after temporary bonding is placed at 730° C. for debonding annealing to complete the debonding.

[0109] Example 2

[0110] This embodiment provides a temporary bonding and debonding method. In the method, in step (A2), the implantation dose is adjusted to 1×10 15 ions / cm 2 , the implantation depth is 600nm, and the temperature of the debonding annealing in step A4 is adjusted from 730°C to 1000°C. Except for the above, other conditions are exactly the same as those in Example 1.

[0111] Comparative Example 1

[0112] This comparative example provides a temporary bonding and debonding method, in which no hydrofluoric acid treatment is performed in step A2, that is, the silicon substrate 10 after the first cleaning is directly subjected to plasma activation. Except for the above, other conditions are exactly the same as those in Example 1.

[0113] Comparative Example 2

[0114] The comparative example provides a temporary bonding and debonding method, wherein in step A2, hydrofluoric acid treatment is first performed, and then ion implantation is performed, that is, a hydrofluoric acid solution with a mass percentage concentration of 20% is used to perform hydrofluoric acid treatment on one side of the silicon oxide layer 20 of the two silicon substrates 10 obtained in step A1, the treatment temperature is 35° C., and the treatment time is 57 s, and then the surface of the silicon substrate 10 is secondly cleaned with deionized water to remove the residual solution on the surface, and then dried at a high speed; and then hydrogen ions are respectively implanted into the silicon oxide layer 20 of the two silicon substrates 10 that have undergone the second cleaning by ion implantation, and the implantation energy is 40 keV, and the implantation dose is 5×10 15 ions / cm 2 , the implantation depth is 460nm, and an ion implantation layer is formed in the silicon oxide layer 20; the silicon substrate 10 after ion implantation is first cleaned, and the first cleaning method is to use a mixed solution of ammonia water, hydrogen peroxide and deionized water for tank cleaning in sequence, and then use a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water for tank cleaning to remove surface impurities; then the two silicon substrates 10 after the first cleaning are plasma activated. Except for the above, other conditions are exactly the same as those in Example 1.

[0115] The temporary bonding and debonding methods in Examples 1 and 2 of the present invention can not only ensure the strength and stability of the temporary bonding, but also enable the hydrogen atoms to move between the lattices of the silicon oxide layer 20 during the debonding annealing, and flow through the channels formed by the ion implantation layer through the hydrofluoric acid treatment and precipitate onto the temporary bonding interface 30, and form hydrogen gas through the compound and form uniform bubbles at the temporary bonding interface 30, so that the temporary bonding interface 30 is cracked, so that the silicon oxide layers 20 of the two silicon substrates 10 are completely and effectively separated at the temporary bonding interface 30. When debonding is performed in Comparative Examples 1 and 2, as the temperature rises, the ion implantation layer in the silicon oxide layer 20 cracks in situ, and the cracking force is uneven, resulting in the thinned functional substrate 12 attached thereto being broken. Therefore, the temporary bonding and debonding methods of Examples 1 and 2 are used in subsequent applications.

[0116] Application Example 1

[0117] This application example provides a method for preparing a composite substrate. Figure 2 As shown, the preparation method comprises the following steps:

[0118] B1. Providing two silicon substrates 10, respectively serving as a support substrate 11 and a functional substrate 12, and completing temporary bonding according to the temporary bonding and debonding method described in Example 1 to obtain a temporary bonding body 40;

[0119] B2. The functional substrate 12 in the obtained temporary bond body 40 is ground and thinned using chemical mechanical polishing until the thickness reaches 1 μm;

[0120] B3 provides a target substrate 50, the target substrate 50 is made of diamond, the thinned functional substrate 12 in the temporary bonding body 40 is bonded to the target substrate 50 at room temperature to complete permanent bonding to obtain a bonding intermediate;

[0121] B4. Debonding is completed by the temporary bonding and debonding method according to Example 1, and the support substrate 11 is removed to obtain a bonded body;

[0122] B5. The silicon oxide layer 20 on the functional substrate 12 in the obtained bonded body is removed to obtain a composite substrate 60.

[0123] Application Example 2

[0124] This application example provides a method for preparing a composite substrate. In steps B1 and B4 of the preparation method, temporary bonding and debonding are respectively completed according to the temporary bonding and debonding methods described in Example 2, and in step B2, ion implantation stripping is used instead of the chemical mechanical polishing method.

[0125] The ion implantation stripping method includes implanting hydrogen ions on a side of the functional substrate 12 away from the temporary bonding interface 30 to form a damaged layer, performing high-temperature stripping at 900° C. to crack the damaged layer, removing the portion stripped from the functional substrate 12, and then polishing the surface of the functional substrate 12 to complete thinning, thereby obtaining a thinned functional substrate 12 with a thickness of 1 μm;

[0126] Except for the above, other conditions are exactly the same as those in Application Example 1.

[0127] Application Example 3

[0128] This application example provides a method for manufacturing a wafer, such as Figure 3 As shown, the wafer manufacturing method includes the following steps:

[0129] C1. Providing two silicon substrates 10, respectively serving as a supporting substrate 11 and a functional substrate 12, and completing temporary bonding according to the temporary bonding and debonding method of Example 1 to obtain a temporary bonding body 40;

[0130] C2. The non-temporary bonding surface of the functional substrate 12 in the obtained temporary bonding body 40 is thinned and the circuit structure and bonding alignment marks are processed to form a functional wafer 13; the functional wafer 13 is cut to remove defective parts;

[0131] C3. Providing another silicon substrate 10, processing a circuit structure and bonding alignment marks on the silicon substrate 10 by photolithography to form an initial target wafer 51; hydrophilically bonding the functional wafer 13 in the temporary bonding body 40 to the target wafer 51 to complete permanent bonding, and then annealing at 260° C. for 15 minutes to obtain a bonding intermediate;

[0132] C4. According to the temporary bonding and debonding method of embodiment 1, the bonded intermediate is debonded, the support substrate 11 is removed, and a bonded body is obtained;

[0133] C5. The silicon oxide layer 20 on the functional wafer 13 in the resulting bonded body is removed to obtain a composite wafer 61;

[0134] C6. In the composite wafer 61, an RDL layer 70 is prepared on the surface of the functional wafer 13 that is farthest from the initial target wafer 51. Specifically, the functional wafer 13 is first thinned to remove part of the silicon layer to expose the circuit structure in the functional wafer 13, and then a dielectric layer 71 is formed on the functional wafer 13. The material of the dielectric layer 71 is SiN. Then, a through hole 72 is made in the dielectric layer 71, and then a conductive medium 73 is filled in the through hole 72 to form a metal wiring so that the through hole 72 has an electrical connection function. Then, the obtained composite wafer 61 is used as the target wafer 51, and steps C1 to C5 are repeated to perform the permanent bonding on one side of the RDL layer 70 until a multi-layer composite wafer 62 with a target number of layers is obtained.

[0135] Application Example 4

[0136] This application example provides a method for manufacturing a wafer, wherein:

[0137] C1. Providing two silicon substrates 10, respectively serving as a support substrate 11 and a functional substrate 12, and completing temporary bonding according to the temporary bonding and debonding method of Example 1 to obtain a temporary bonding body 40;

[0138] C2. The functional substrate 12 in the obtained temporary bonding body 40 has an original circuit structure; the original circuit structure is formed by processing the circuit structure and bonding alignment marks on the silicon substrate 10 by photolithography before temporary bonding, and the initial functional substrate 12 is formed. At this time, the functional substrate 12 in the obtained temporary bonding body 40 is a functional wafer 13;

[0139] C3. Providing another silicon substrate 10 without a circuit structure as an initial target wafer 51; hydrophilically bonding the functional wafer 13 in the temporary bonding body 40 to the target wafer 51 to complete permanent bonding, and then annealing at 260° C. for 15 min to obtain a bonding intermediate;

[0140] C4. According to the temporary bonding and debonding method of embodiment 1, the bonded intermediate is debonded, the support substrate 11 is removed, and a bonded body is obtained;

[0141] C5. The silicon oxide layer 20 on the functional wafer 13 in the resulting bonded body is removed to obtain a composite wafer 61;

[0142] C6. In the composite wafer 61, an RDL layer 70 is prepared on the surface of the functional wafer 13 that is farthest from the initial target wafer 51. Specifically, the functional wafer 13 is first thinned to remove part of the silicon layer to expose the circuit structure in the functional wafer 13, and then a dielectric layer 71 is formed on the functional wafer 13. The material of the dielectric layer 71 is SiN. Then, a through hole 72 is made in the dielectric layer 71, and then a conductive medium 73 is filled in the through hole 72 to form a metal wiring so that the through hole 72 has an electrical connection function. Then, the obtained composite wafer 61 is used as the target wafer 51, and steps C1 to C5 are repeated to perform the permanent bonding on one side of the RDL layer 70 until a multi-layer composite wafer 62 with a target number of layers is obtained.

[0143] From the above, it can be seen that in the temporary bonding and debonding method of the present invention, on the one hand, both substrates are made of silicon material (homogeneous material), which can effectively avoid the warping or breakage caused by the difference in thermal expansion coefficient. The support substrate and the functional substrate made of silicon material have high consistency in thermal properties, and the degree of thermal expansion and contraction under various temperature conditions is relatively close, thereby greatly reducing the risk of damage to the bonding structure due to different thermal expansion coefficients.

[0144] On the other hand, the bonding interface between the support substrate and the functional substrate does not require the introduction of a bonding medium. The advantages of this design are that, first, it can avoid the problem of high-temperature process limitations caused by the use of a bonding medium. Secondly, it can solve the problem of difficulty in reducing the thickness of the functional substrate. Since there is no bonding medium, it is easier to operate and control when thinning the functional substrate. Finally, it can also avoid impurity contamination and cleaning problems caused by the bonding medium, as well as the problem of adverse effects on product performance in subsequent processes.

[0145] On the other hand, based on the advantages and characteristics of the temporary bonding and debonding method, the functional substrate can be made very thin, and the composite substrate preparation method can be used to obtain a composite substrate with an ultra-thin functional substrate (film). Furthermore, through the wafer manufacturing method, the multi-layer bonded wafer obtained by repeatedly performing multi-layer bonding can greatly reduce the thickness of the finished device, which can meet the needs of device miniaturization and multi-function.

[0146] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0147] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0148] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A temporary bonding and debonding method, characterized in that: The steps include: A1. Providing two silicon substrates, forming a silicon oxide layer on one side of the silicon substrate; A2. Sequentially ion implanting the silicon oxide layer, treating with hydrofluoric acid and plasma activation to form a temporary bonding surface; A3. The temporary bonding surfaces are contacted to perform hydrophilic bonding, and then annealed to form a temporary bonding body between the two silicon substrates to complete the temporary bonding; A4. Performing debonding annealing on the temporary bonded body to separate the silicon oxide layers of the two silicon substrates at the temporary bonding interface, thereby completing debonding.

2. The temporary bonding and debonding method according to claim 1, characterized in that: In step A1, the method for forming the silicon oxide layer includes thermal oxidation; the thickness of the silicon oxide layer is 1-1000 nm.

3. The temporary bonding and debonding method according to claim 1, characterized in that: In step A2, before the ion implantation, the surface of the silicon oxide layer is planarized to make the surface roughness ≤1nm; the ion elements of the ion implantation include hydrogen ions; the implantation energy of the ion implantation is 1-80keV, and the implantation dose is 1×10 13 ~8×10 16 ions / cm 2 , the injection depth is 0.1~1000nm.

4. The temporary bonding and debonding method according to claim 1, characterized in that: In step A2, the hydrofluoric acid treatment method includes immersion in a hydrofluoric acid solution, wherein the mass percentage concentration of the hydrofluoric acid solution is 0.1% to 30%; the temperature of the hydrofluoric acid treatment is 10 to 50° C., and the time is 1 to 100 seconds.

5. The temporary bonding and debonding method according to claim 1, characterized in that: In step A2, the gas used to generate plasma during the plasma activation includes at least one of N2, O2, Ar or He.

6. The temporary bonding and debonding method according to claim 1, characterized in that: In step A3, the hydrophilic bonding method includes a center point pressurization method or a plane pressurization method; the pressurization pressure of the hydrophilic bonding is 1~1000N, and the pressurization holding time is 1~200s; the temperature of the hydrophilic bonding is 15~35℃.

7. The temporary bonding and debonding method according to claim 1, characterized in that: In step A3, the strengthening annealing temperature is 100-350°C and the time is ≥10min; In step A4, the temperature of the debonding annealing is 350-1250°C.

8. A method for preparing a composite substrate, characterized in that: The preparation method comprises the following steps: B1. Providing two silicon substrates, respectively, as a support substrate and a functional substrate, and completing temporary bonding according to any one of claims 1 to 7 and the method for temporarily bonding and debonding to obtain a temporary bonded body; B2. Thinning the functional substrate in the resulting temporary bond; B3 provides a target substrate, the thinned functional substrate in the temporary bonding body is permanently bonded to the target substrate to obtain a bonding intermediate; B4. Debonding is completed by the temporary bonding and debonding method according to any one of claims 1 to 7, removing the supporting substrate to obtain a bonded body; B5. Remove the silicon oxide layer on the functional substrate in the obtained bonded body to obtain a composite substrate.

9. The method for preparing a composite substrate according to claim 8, characterized in that: In step B2, the thinning method includes grinding thinning and / or ion implantation stripping; the stripping temperature of the ion implantation stripping is lower than the temperature of the debonding annealing; In step B3, the material of the target substrate includes at least one of diamond, gallium nitride or silicon carbide.

10. A composite substrate, characterized in that: Obtained according to the method for preparing the composite substrate according to claim 8 or 9.

11. A method for manufacturing a wafer, characterized in that: The wafer manufacturing method comprises the following steps: C1. Providing two silicon substrates, respectively as a support substrate and a functional substrate, and completing temporary bonding according to the temporary bonding and debonding method according to any one of claims 1 to 7 to obtain a temporary bonded body; C2. The non-temporary bonding surface of the functional substrate has an original circuit structure, or the non-temporary bonding surface of the functional substrate is thinned and processed to form a functional wafer; C3 provides a target wafer, the functional wafer in the temporary bonding body is permanently bonded to the target wafer to obtain a bonding intermediate; C4. The temporary bonding and debonding method according to any one of claims 1 to 7, wherein the bonded intermediate is debonded, the support substrate is removed, and a bonded body is obtained; C5. Removing the silicon oxide layer on the functional wafer in the resulting bonded body to obtain a composite wafer.

12. The method for manufacturing a wafer according to claim 11, characterized in that: In step C3, the target wafer has a circuit structure; the target wafer also has an RDL layer arranged on the circuit structure.

13. The method for manufacturing a wafer according to claim 12, characterized in that: The manufacturing method further comprises step C6, preparing an RDL layer on the functional wafer of the obtained composite wafer, and then using the composite wafer provided with the RDL layer as the target wafer, repeating steps C1 to C5 to perform stacking bonding until the target number of layers is reached, thereby obtaining a multi-layer composite wafer; Before preparing the RDL layer on the functional wafer, the functional wafer is thinned to remove part of the silicon layer so as to expose the circuit structure in the functional wafer.

14. The method for manufacturing a wafer according to claim 12 or 13, characterized in that: The method for preparing the RDL layer includes forming a dielectric layer on the functional wafer, then making a through hole in the dielectric layer, and then filling the through hole with a conductive medium to form a metal wiring so that the through hole has an electrical connection function; using the obtained composite wafer as the target wafer, repeating steps C1 to C5, and performing the permanent bonding on one side of the RDL layer; The material of the dielectric layer includes at least one of SiO2, SiN or SiCN.

15. The method for manufacturing a wafer according to claim 11, characterized in that: The functional wafer and the target wafer are also provided with corresponding bonding alignment marks respectively.

16. The method for manufacturing a wafer according to claim 11, characterized in that: Before the functional wafer is permanently bonded to the target wafer, the functional wafer is first cut to form functional chips, and defective functional chips are removed. Then, the remaining qualified functional chips are permanently bonded to the target wafer one by one to obtain the bonding intermediate.

17. A wafer, characterized in that: Comprising at least two stacked wafer layers, obtained according to the manufacturing method according to any one of claims 11-16.

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