Substrate bonding method and bonded substrate

Abstract

This substrate bonding method implements, in this order, (a) a step for providing two substrates including a plurality of wiring sections and a laminated section having a base layer and an upper layer that are provided between the plurality of wiring sections and have mutually different selection ratios in the thickness direction, (b) a step for forming planarized surfaces by the plurality of wiring sections and the upper layer, and (c) a step for forming planarized surfaces by leaving the base layer, (d) a step for forming an adhesive layer having a lower elastic modulus than the base layer by supplying an adhesive to at least the removed layer portion, (e) a step for forming a planarized bonding surface between the plurality of wiring portions and the adhesive layer, and (f) a step for causing the bonding surface of one of the two substrates to face the bonding surface of the other of the two substrates. And a step for bonding the two substrates via the adhesive layer.

Description

Technical Field

[0001] The present invention relates to a substrate bonding method and a bonded substrate. Background Art

[0002] Patent Document 1 discloses a technique for bonding two substrates together by placing the insulating films (Low-K dielectric layers) of the substrates facing each other. In this bonding method, if fine particles exist on the surface of the substrates, the bonding strength of the substrates decreases.

[0003] Furthermore, Patent Document 2 discloses a technique in which an interlayer insulating film provided between adjacent wiring portions is replaced with an adhesive and substrates are bonded together using the adhesive.

[0004] [Prior art literature]

[0005] [Patent Literature]

[0006] [Patent Document 1] U.S. Patent No. 6080640

[0007] [Patent Document 2] Japanese Patent Publication No. 2020-520562 Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] The present invention provides a technology for stably bonding two substrates.

[0010]

Methods to solve the problem

[0011] According to one embodiment of the present invention, there is provided a substrate bonding method for bonding two substrates, wherein the following steps are performed in sequence: (a) a step of providing the two substrates including a plurality of wiring portions and a stacked portion having a base layer and an upper layer which are provided between the plurality of wiring portions and are selected in a different ratio from each other along a thickness direction; (b) a step of forming the plurality of wiring portions and the upper layer into a flattened surface; (c) a step of leaving the base layer and removing the upper layer; (d) a step of supplying an adhesive to at least the removed layer portion to form an adhesive layer having an elastic modulus smaller than that of the base layer; (e) a step of forming the plurality of wiring portions and the adhesive layer into a flattened bonding surface; and (f) a step of bonding the two substrates via the adhesive layer by making the bonding surface of one of the two substrates face the bonding surface of the other of the two substrates.

[0012] [Effects of the invention]

[0013] According to one embodiment, two substrates can be stably bonded. BRIEF DESCRIPTION OF THE DRAWINGS

[0014]

Figure 1

[0015]

Figure 2

[0016]

Figure 3

[0017]

Figure 4

[0018]

Figure 5

[0019]

Figure 6

[0020]

Figure 7

[0021]

Figure 8

[0022] Hereinafter, the mode for implementing the present invention will be described with reference to the drawings. In each of the drawings, the same components are sometimes given the same reference numerals, and repeated descriptions are omitted.

[0023] [First embodiment]

[0024] A substrate bonding method according to a first embodiment of the present invention is as follows Figure 1 (A) and Figure 1 As shown in FIG. 1B , two substrates W are bonded together using the bonding apparatus 100 to produce a bonded substrate JW. In order to facilitate understanding of the substrate bonding method, the following first describes the structure of each substrate W before bonding in the bonding apparatus 100 and the structure of the bonded substrate JW after bonding.

[0025] Two substrates W (first substrate W1, second substrate W2) are formed into circular plates of substantially the same shape (same diameter). The two substrates W before bonding each have a base substrate 10 for forming a suitable semiconductor device in a silicon wafer, a compound semiconductor wafer, etc., and a block structure 20 in which a plurality of layers are stacked on the base substrate 10. As a silicon wafer, single crystal silicon, silicon carbide, SOI wafer, etc. can be used. As a compound semiconductor wafer, a GaAs wafer, a SiC wafer, a GaN wafer, an InP wafer, etc. can be used. There is no particular limitation on the device of the base substrate 10, and examples thereof include a transistor having a gate, a source, and a drain.

[0026] The block structure 20 of the substrate W is composed of a first insulating layer portion 21, a second insulating layer portion 22, and a conductive layer portion 23 stacked in sequence in the direction from the base substrate 10 side toward the surface (from the lower layer to the upper layer). In addition, the insulating layer portion of the block structure 20 is not limited to two layers (the first insulating layer portion 21 and the second insulating layer portion 22), and may be three or more layers or a single layer.

[0027] The first insulating layer portion 21 is a bulk insulating film covering the base substrate 10. For example, a silicon oxide film (SiO2 film) can be used on the first insulating layer portion 21. The SiO2 film can be formed by a known film forming method such as plasma CVD (chemical vapor deposition) method and thermal CVD method.

[0028] The second insulating layer portion 22 is formed of an insulating material having a higher dielectric constant than the first insulating layer portion 21. For example, a silicon nitride film (SiN film) can be used on the second insulating layer portion 22. The SiN film can also be formed by a known film forming method such as a plasma CVD method or a thermal CVD method.

[0029] The conductive layer portion 23 has a plurality of wiring portions 24 formed into a suitable conductive pattern according to the device of the base substrate 10 and an insulating laminate portion 25 formed between the plurality of wiring portions 24. In other words, the wiring portion 24 is formed by forming holes (contact holes) and grooves (trench) in the thickness direction of the insulating laminate portion 25 previously laminated on the second insulating layer portion 22, and burying the wiring portion 24 in the holes and grooves, respectively.

[0030] The plurality of wiring portions 24 are electrically connected to the device of the base substrate 10 and are formed at intervals along the surface direction of the conductive layer portion 23. A conductive metal material can be used for each wiring portion 24. Examples of the metal material include copper (Cu).

[0031] Furthermore, a barrier metal 24a for preventing the reaction between the wiring portion 24 and the insulating layer portion is formed between the second insulating layer portion 22 of each wiring portion 24 and between each wiring portion 24 and the insulating laminate portion 25. As the barrier metal 24a, for example, titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), etc. can be used.

[0032] The insulating laminated portion 25 forms an interlayer insulating film that insulates a plurality of adjacent wiring portions 24 spaced apart in the surface direction of the substrate W. Specifically, the insulating laminated portion 25 includes a base layer 26 laminated on the second insulating layer portion 22 and an adhesive layer 32 laminated on the base layer 26 .

[0033] The base layer 26 is formed first when the conductive layer 23 is formed on the surface of the second insulating layer 22, thereby constituting the lower layer (base layer) of the insulating laminated portion 25. The base layer 26 is preferably formed of an insulating material with a low dielectric constant. In addition, as will be described in detail later, the base layer 26 is formed in the process of forming the substrate W before bonding, and the upper layer 27 (see Figure 4 (A)) between the upper layer 27 and the lower layer 27, a material having a sufficient etching selectivity is selected. For example, when the upper layer 27 is formed of a SiO2 film, as the material of the base layer 26, a carbon-added silicon oxide film (SiOC film) having a lower dielectric constant than that of the SiO2 film and having resistance to the etching gas of the SiO2 film is preferably used.

[0034] The adhesive layer 32 is coated on the base layer 26 in the process of the substrate bonding method, thereby constituting a portion bonded to the facing substrate W when the bonding substrate JW is manufactured. The adhesive layer 32 uses, for example, an organic adhesive (organic film) having a high bonding force (surface free energy) at room temperature and a lower elastic modulus than each wiring portion 24 and the base layer 26. The type of organic adhesive is not particularly limited, and a suitable adhesive can be selected from thermoplastic resins, thermosetting resins, and elastomers in consideration of bonding force, elastic modulus, processability, etc.

[0035] The thickness T of the adhesive layer 32 before bonding is set to be thinner than the thickness of the base layer 26. For example, the thickness T of the adhesive layer 32 before bonding is preferably in the range of about 20nm to 150nm, and is set to 100nm in the present embodiment. When the thickness T of the adhesive layer 32 is smaller than 20nm, there is a possibility that the bonding force of the adhesive layer 32 is reduced. In addition, when the thickness T of the adhesive layer 32 is larger than 150nm, there is a possibility that the following inconveniences will occur: the wiring portion 24 is prone to collapse, and due to the difference in thermal expansion coefficient with the wiring portion 24, thermal contraction becomes larger, and damage such as cracks is likely to occur, and gas is easily generated from the adhesive layer 32, etc.

[0036] The adhesive layer 32 of each wiring portion 24 and the insulating laminate portion 25 forms an exposed surface (joining surface S) in each substrate W before joining. The joining surface S of the substrate W is formed into a continuous flat state on one surface by a flattening process in the substrate joining method. In this way, the conductive layer portion 23 of the substrate W constitutes a joining portion that can be joined to the facing substrate W.

[0037] like Figure 1 (A) and Figure 1 As shown in (B), the bonding substrate JW is made by making the bonding surfaces S of two substrates W face each other and bonding the conductive layer part 23. Therefore, the bonding substrate JW has an interface B in which the bonding surface S is integrated. For example, in the interface B, the wiring parts 24 facing each other are in close contact, and at the same time, the adhesive layers 32 facing each other are in close contact. The adhesive layers 32 are bonded to each other with a strong bonding strength, thereby the bonding substrate JW can be firmly fixed as a whole.

[0038] Therefore, the bonding substrate JW has, in order from the first substrate W1 toward the second substrate W2, a base substrate 10, a first insulating layer portion 21, a second insulating layer portion 22, a conductive layer portion 23, a conductive layer portion 23, a second insulating layer portion 22, a first insulating layer portion 21, and a base substrate 10. Hereinafter, the two conductive layer portions 23 integrated by bonding in the bonding substrate JW are referred to as a conductive bonding layer portion 40.

[0039] The conductive bonding layer portion 40 includes a plurality of wiring portions 41 and an insulating laminate portion 42 provided between the plurality of wiring portions 41 along the planar direction (direction perpendicular to the thickness direction). The plurality of wiring portions 41 are formed by the wiring portions 24 of the first substrate W1 and the wiring portions 24 of the second substrate W2 being closely attached in the thickness direction. The insulating laminate portion 42 is formed by the insulating laminate portion 25 of the first substrate W1 and the insulating laminate portion 25 of the second substrate W2 being closely attached in the thickness direction.

[0040] Therefore, the insulating laminated portion 42 includes a pair of base layers 26 provided on both sides in the thickness direction and an adhesive layer 43 sandwiched between the pair of base layers 26. The adhesive layer 43 is a layer in which the adhesive layer 32 of the first substrate W1 and the adhesive layer 32 of the second substrate W2 are bonded and integrated.

[0041] Here, the conventional bonding substrate does not have an adhesive layer on the bonding surface of the two substrates, and has a wiring portion and an insulating layer (upper layer 27: see Figure 4 (A)) The bonding surfaces are bonded to each other. At this time, even if there are fewer fine particles on the bonding surface, the bonding strength between the insulating layers will be reduced. In addition, in the previous substrate bonding method, plasma treatment is performed to activate the insulating layer on the bonding surface before bonding. Due to the implementation of this plasma treatment, the following problems arise: the wiring part is deteriorated, the conductivity is reduced, and the leakage current increases due to metal sputtering and scattering of the wiring part. In addition, the previous substrate bonding method is bonded but with slight deviations, and even so there is the possibility of metal diffusion and poor insulation.

[0042] In this regard, the bonding substrate JW involved in this embodiment has an adhesive layer 43, so a strong bonding strength can be obtained without plasma treatment. Since no plasma treatment is performed, there is no diffusion of metal and no deterioration of the wiring portion 41, so the conductivity can be well ensured and the leakage current can be suppressed. In addition, even if it is assumed that there are some particles between the first substrate W1 and the second substrate W2, the elasticity of the adhesive layer 43 can suppress the reduction of the bonding strength. Furthermore, the bonding substrate JW has an adhesive layer 43 with diffusion resistance of metal (Cu), so even if there is a deviation in the bonding, the reliability of the insulation can be guaranteed.

[0043] In order to manufacture the above-mentioned bonded substrate JW, before bonding the two substrates W, it is necessary to form a substrate W having an adhesive layer 32 on the conductive layer portion 23 (see Figure 1 (A)). Therefore, in the substrate bonding method, Figure 2 As shown, a bonding system 1 composed of a plurality of devices is used to form two substrates W before bonding, and the two substrates W are bonded together. In addition, the bonding system 1 can be composed of a plurality of devices set at a single manufacturing location (such as a clean room in a factory), or a plurality of devices can be set at respective manufacturing locations.

[0044] Specifically, the bonding system 1 includes a flattening device 200, a removal device 300, and an adhesive coating device 400 as a device for forming a substrate W before bonding, and includes a bonding device 100 (see FIG. Figure 1 The planarizing device 200 is a device for planarizing the surface of the substrate W. The removing device 300 is a device for removing the upper layer 27 (see Figure 4(A)) The adhesive coating device 400 is a device for coating an adhesive on the surface of the substrate W.

[0045] In addition, the bonding system 1 includes a management device 900 that manages the operation status of each device, the state of the substrate in the process, etc. The management device 900 can be a computer, which has a processor, memory, input and output interface, and communication interface (not shown). Based on the control of the management device 900, the bonding system 1 links each device and a transport device (not shown) and the like, thereby forming an automated system for automatically manufacturing the bonding substrate JW.

[0046] In the substrate bonding method using each device of the bonding system 1, the following steps are performed in sequence: Figure 3 Specifically, the substrate bonding method sequentially implements the following steps: a substrate providing step (step S1), a first flattening step (step S2), an upper layer removing step (step S3), an adhesive coating step (step S4), a second flattening step (step S5), and a bonding step (step S6).

[0047] In the substrate providing process, Figure 4 As shown in (A), the operator of the bonding system 1 prepares a substrate W (hereinafter also referred to as a precursor substrate PW) before forming the adhesive layer 32. The precursor substrate PW includes a base substrate 10 and a block structure 20 in which a first insulating layer portion 21, a second insulating layer portion 22, and a conductive layer portion 23 are stacked.

[0048] The conductive layer portion 23 of the precursor substrate PW includes a plurality of wiring portions 24 and an insulating laminate portion 25 formed between the plurality of wiring portions 24. Here, the insulating laminate portion 25 is composed of a plurality of layers (base layer 26, upper layer 27) having different selectivities for etching along the thickness direction. The base layer 26 can be, for example, an insulating film having a lower dielectric constant than the upper layer 27, and a SiOC film is used as an example thereof.

[0049] The upper layer 27 also uses an insulating film for insulating the plurality of wiring portions 24 from each other, but in the substrate bonding method according to the present embodiment, it is removed in the upper layer removal step and then becomes a layer portion replaced by the adhesive layer 32. The material constituting the upper layer 27 is preferably a suitable material that can obtain a selectivity ratio with the base layer 26. In the present embodiment, a SiO2 film is used corresponding to the SiOC film of the base layer 26.

[0050] The conductive layer portion 23 of the precursor substrate PW is formed by, for example, Figure 5The conductive layer portion forming method shown in (A) is formed by sequentially performing each step. In the conductive layer portion forming method, first, the lower layer forming step S11 is performed to stack the base layer 26 on the second insulating layer portion 22. When a SiOC film is used as the base layer 26, for example, a plasma CVD method can be used to form the film by supplying a raw material gas containing organic siloxane while exciting plasma.

[0051] Next, in the conductive layer portion forming method, an upper layer forming step S12 is performed to stack an upper layer 27 on the formed base layer 26. When a SiO2 film is used as the upper layer 27, for example, a silicon-containing gas is supplied as a raw material gas, and oxygen or ozone gas is supplied as a reaction gas, and a plasma CVD method is used to form a film while exciting plasma.

[0052] Then, in the conductive layer forming method, a wiring portion embedding step (step S13) is implemented. In the wiring portion embedding step, holes and grooves are formed at designated positions of the previously formed base layer 26 and upper layer 27, and a Cu film is embedded in the formed holes and grooves by electroplating or the like. When the Cu film is embedded, a thin film of the barrier metal 24a is first formed on the exposed upper layer 27 and base layer 26, and a Cu film with a thickness is formed on the barrier metal 24a. By performing the above steps, the conductive layer forming method can be formed into the following form, in which the upper layer 27 and base layer 26 are entirely covered by forming a Cu film of each wiring portion 24.

[0053] The substrate bonding method performs a first planarization step ( Figure 3 In the first planarization step, the planarization device 200 of the bonding system 1 is used (see Figure 2 ) to flatten the surface of the precursor substrate PW (the surface covered by the Cu film).

[0054] For example, the planarization device 200 has, Figure 4 As shown in FIG. 2A , in a processing container (not shown), a chuck 201 holding a precursor substrate PW and a rotating body 202 capable of relative rotation and relative movement relative to the precursor substrate PW held by the chuck 201 are provided. A slurry 203 that contacts and polishes the Cu film during rotation is provided on the opposing portion of the rotating body 202 that faces the precursor substrate PW. The slurry 203 is composed of a material that can flatten the Cu constituting the wiring portion 24.

[0055] In addition, the planarization device 200 polishes the Cu film by appropriately setting the planarization conditions such as the contact pressure and the rotation speed of the slurry 203 relative to the precursor substrate PW. During the polishing, the Cu film (including the barrier metal 24a) covering the upper layer 27 is peeled off, thereby exposing the upper layer 27. Therefore, after the first planarization step is performed, the surface of the precursor substrate PW is in a state where the upper layer 27 is exposed between each wiring portion 24, and each wiring portion 24 and the upper layer 27 are continuous on one surface (planarized).

[0056] Then, the substrate bonding method is performed by performing an upper layer removal step ( Figure 3 In step S3), the base layer 26 is left among the multiple layers of the conductive layer portion 23, and the upper layer 27 is removed. There is no particular limitation on the means for removing the upper layer 27 of the precursor substrate PW, and examples thereof include dry etching, coating or immersion with a solvent for removal (e.g., hydrofluoric acid), and the like. Figure 4 In (B), a removal device 300 (etching device) that performs dry etching is exemplified.

[0057] The removal device 300 includes a chuck 301 for holding a precursor substrate PW in a processing container (not shown) and a shower head 302 for supplying an etching gas to the precursor substrate PW held by the chuck 301. The etching gas can be a suitable gas based on the type of the film of the upper layer 27 to be removed. For example, when the upper layer 27 is a SiO2 film, a fluorine-containing gas such as a CF-based gas can be supplied.

[0058] In addition, the removal device 300 removes the upper layer 27 in the following manner: by supplying high-frequency power to the shower head 302 or other electrodes not shown, plasma is excited in the plasma processing space PPS between the shower head 302 and the precursor substrate PW. The plasmatized CF-based gas thus collides with the upper layer 27 of the precursor substrate PW, that is, the interlayer insulating film can be etched. During this etching, the base layer 26 having a different selectivity from the upper layer 27 remains and is not removed by the removal device 300. In this way, by removing the upper layer 27, the precursor substrate PW is in the following state, the base layer 26 is exposed, and each wiring portion 24 slightly protrudes from the base layer 26. The precursor substrate PW can prevent the collapse and peeling of each wiring portion 24 through the base layer 26.

[0059] After the upper layer removal step, the substrate bonding method is performed by applying an adhesive ( Figure 3 In step S4), an adhesive layer (hereinafter referred to as the precursor adhesive layer 31) is formed by covering the entire surface of the precursor substrate PW with an adhesive. In the adhesive coating step, an adhesive coating device 400 (see Figure 2 ) supplies adhesive to the surface of the precursor substrate PW.

[0060] For example, the adhesive coating device 400 is Figure 6As shown in (A), there is a chuck 401 for holding a precursor substrate PW in a processing container not shown in the figure, and a nozzle part 402 for discharging an adhesive to the precursor substrate PW held by the chuck 401. In addition, the chuck 401 has the following function, which is to rotate the precursor substrate PW with the center of the chuck 401 as a base point through a rotating mechanism not shown in the figure. The nozzle part 402 supplies liquid adhesive from the upper side in the vertical direction of the center of the chuck 401. Thus, the adhesive coating device 400 can use the centrifugal force during rotation to guide the adhesive to the entire surface of the precursor substrate PW. The supply of adhesive is carried out until all the wiring parts 24 and the base layer 26 of the precursor substrate PW are covered with the adhesive.

[0061] In addition, in the adhesive coating process, after the adhesive is supplied, the precursor adhesive layer 31 may be heated to cure it. Figure 5 As shown in (B), the adhesive coating process includes an adhesive supplying step (step S41) of supplying the adhesive through the above-mentioned adhesive coating device 400 and an annealing step (step S42) of heating the adhesive. In the annealing step, the precursor substrate PW having the precursor adhesive layer 31 is accommodated in a heating device not shown in the figure and heated to a target temperature (for example, a suitable temperature in the range of 200°C to 400°C). As a result, the precursor adhesive layer 31 has an elastic modulus greater than the elastic modulus after the adhesive supplying step, and the processing in the second planarizing step is easy. Here, since the precursor adhesive layer 31 after the annealing step is an organic film, it has an elastic modulus lower than the elastic modulus of the wiring portion 24 and the elastic modulus of the base layer 26.

[0062] After the adhesive coating step, the substrate bonding method is performed by performing a second planarization step ( Figure 3 In step S5), the surface of the precursor substrate PW having the precursor adhesive layer 31 is polished to form a bonding surface S having the wiring portion 24 and the adhesive layer 32. In the second planarization step, the planarization device 200 (see FIG. 2 ) can be used in the same manner as the first planarization step. Figure 2 ) is flattened. In addition, it is apparent that the bonding system 1 can use a flattening device different from the flattening device 200 used in the first flattening process in the second flattening process.

[0063] The object of polishing by the planarization device 200 in the second planarization step is the precursor adhesive layer 31. Figure 6 As shown in (B), a slurry 210 different from the slurry 203 of the first planarization process is used. The slurry 210 can be made of Cu (metal material) that can reduce the adhesive but cannot reduce the wiring portion 24. In addition, the planarization device 200 polishes the precursor adhesive layer 31 by setting the planarization conditions such as the contact pressure of the slurry 210 with respect to the precursor substrate PW and the rotation speed differently from the planarization conditions of the first planarization process.

[0064] For example, at least one of the contact pressure and the rotation speed of the slurry 210 in the second planarization process is set to be lower than the contact pressure or the rotation speed of the slurry 203 in the first planarization process. Obviously, the contact pressure and the rotation speed in the second planarization process can be set lower than the contact pressure and the rotation speed in the first planarization process. As a result, the wiring portions 24 are not damaged in the second planarization process, and the (planarized) adhesive layer 32 on the same surface as the wiring portions 24 can be well formed.

[0065] The substrate bonding method proceeds to the second flattening step, and a substrate W is obtained in which each wiring portion 24 and the adhesive layer 32 are continuous on the same surface in the bonding surface S. The adhesive layer 32 of the substrate W has a thickness T (for example, 100 nm) corresponding to the thickness of the original upper layer 27. The final bonding step ( Figure 3 In step S6), the two substrates W formed in the above steps are transported to the bonding device 100 (see Figure 2 ) and a bonding substrate JW is produced by a bonding device 100.

[0066] like Figure 1 As shown in FIG. 1A , the bonding apparatus 100 includes a lower chuck 101 for holding a first substrate W1 at a lower side in a vertical direction and an upper chuck 102 for holding a second substrate W2 at an upper side in a vertical direction in a processing container (not shown). In addition, the bonding apparatus 100 includes an impact mechanism 103 for pressing down the second substrate W2 at the center of the upper chuck 102.

[0067] In the bonding apparatus 100, the first substrate W1 and the second substrate W2 are placed facing each other in the vertical direction, and the second substrate W2 is pressed down by the impact mechanism 103 of the upper chuck 102, thereby causing the second substrate W2 to fall relative to the first substrate W1. Thus, the first substrate W1 and the second substrate W2 are bonded from the center to the outer edge. Through this bonding process, Figure 1 As shown in (B), the adhesive layers 32 facing each other between the wiring portions 24 are bonded to each other, thereby forming a bonded substrate JW in which the first substrate W1 and the second substrate W2 are bonded together.

[0068] As described above, the substrate bonding method involved in this embodiment can bond two substrates W to each other with a greater bonding strength by having an adhesive layer 32 between each wiring portion 24. In particular, the adhesive layer 32 is formed thinner by being stacked on the base layer 26. Therefore, each substrate W and the bonded substrate JW can avoid the collapse of each wiring portion 24, and at the same time, the residual gas contained in the adhesive can be reduced as much as possible. In addition, each substrate W and the bonded substrate JW have a thin adhesive layer 32, which greatly reduces the thermal shrinkage of the adhesive layer 32, and can suppress the occurrence of damage such as cracks.

[0069] In addition, the substrate bonding method and the bonded substrate JW involved in this embodiment are not limited to the above-mentioned embodiment, and various modifications are possible. For example, in the substrate bonding method, the upper layer 27 may not be completely removed in the upper layer removal step, and the upper layer 27 may remain on the base layer 26. In this case, the remaining upper layer 27 is covered by the adhesive layer 32 formed in the subsequent adhesive coating step and the second flattening step, so that a flat bonding surface S can be obtained.

[0070] [Second embodiment]

[0071] Figure 7 (A)~ Figure 7 (D) Figure 8 (A) and Figure 8 In the substrate bonding method according to the second embodiment shown in (B), the laminated structure of the insulating laminated portion 25A of the substrate W before bonding is different from the laminated structure of the insulating laminated portion 25 according to the first embodiment. Figure 7 As shown in (A), in the precursor substrate PW, the insulating laminated portion 25A is formed into a three-layer structure in which two base layers 26 (a first base layer 261 and a second base layer 262) and one upper layer 27 are laminated.

[0072] The first base layer 261 constitutes a base portion of the insulating laminated portion 25A (interlayer insulating film). As the first base layer 261, for example, a SiO2 film or a SiOC film can be used.

[0073] The second base layer 262 is, for example, a layer formed in such a way that the insulating laminated portion 25A has a low dielectric constant, and is a so-called Low-K layer. A silicon carbon nitride film (SiCN film) can be used as the second base layer 262. In addition, in the substrate W (precursor substrate PW), a SiCN film can also be used for the second insulating layer portion 22.

[0074] The upper layer 27 is a layer portion replaced by the adhesive layer 32, and can be made of an appropriate film that can obtain an etching selectivity ratio with the second base layer 262. For example, the upper layer 27 can be made of a SiO2 film or the like as in the first embodiment.

[0075] Even with the precursor substrate PW having such an insulating laminated portion 25A, by performing the same steps as the substrate bonding method according to the first embodiment, a bonded substrate JW in which two substrates W are firmly bonded to each other can be obtained. That is, in the substrate bonding method according to the second embodiment, the following steps are also performed in sequence: Figure 3 As shown, there are a substrate providing step (step S1), a first planarizing step (step S2), an upper layer removing step (step S3), an adhesive coating step (step S4), a second planarizing step (step S5), and a bonding step (step S6).

[0076] like Figure 7 As shown in (A), in the first planarization step, the plurality of wiring portions 24 and the upper layer 27 on the surface of the precursor substrate PW are planarized. Figure 7 As shown in (B), in the upper layer removal step, the second base layer 262 of the precursor substrate PW is left and the upper layer 27 is removed. Figure 7 As shown in (C), in the adhesive coating step, an adhesive is coated on the surface of the precursor substrate PW to form a precursor adhesive layer 31. Figure 7 As shown in FIG. 2D , in the second planarization step, the precursor adhesive layer 31 is polished to form a planarized bonding surface S between each wiring portion 24 and the adhesive layer 32 . Thus, the substrate bonding method can obtain a substrate W having the adhesive layer 32 on the second base layer 262 .

[0077] Therefore, if Figure 8 As shown in (A), in the bonding process, the bonding surface S of the first substrate W1 and the bonding surface S of the second substrate W2 are made to face each other, and the second substrate W2 is dropped, thereby forming a bonded substrate JW in which the first substrate W1 and the second substrate W2 are bonded. The adhesive layer 32 of each substrate W can bond the two substrates W to each other with a large bonding strength.

[0078] In particular, the conductive bonding layer portion 40 of the bonding substrate JW is bonded by the adhesive layer 32 on the two-layer base layer 26, thereby insulating the wiring portions 24 with a sufficiently low dielectric constant and bonding the substrates W. The adhesive layer 32 is formed thinner by the two-layer base layer 26, thereby further promoting the avoidance of the collapse of the wiring portion 24, the suppression of the gas in the adhesive layer 32, the reduction of thermal shrinkage, etc.

[0079] The technical ideas and effects of the present invention described in the above embodiments are described below.

[0080] The first mode of the present invention is a substrate bonding method for bonding two substrates W to each other, wherein the following steps are performed in sequence: (a) a step of providing two substrates W including a plurality of wiring portions 24 and a laminated portion (insulating laminated portion 25) having a base layer 26 and an upper layer 27 which are arranged between the plurality of wiring portions 24 and have different selection ratios in the thickness direction; (b) a step of forming a flattened surface between the plurality of wiring portions 24 and the upper layer 27; (c) a step of leaving the base layer 26 and removing the upper layer 27; (d) a step of supplying an adhesive to at least the removed layer portion to form an adhesive layer (precursor adhesive layer 31) having an elastic modulus smaller than that of the base layer 26; (e) a step of forming a flattened bonding surface S between the plurality of wiring portions 24 and the adhesive layer 32; and (f) a step of bonding the two substrates via the adhesive layer 32 by making the bonding surface S of one of the two substrates W face the bonding surface S of the other of the two substrates W.

[0081] According to the above, the substrate bonding method is obtained, in the stacking part (insulating stacking part 25) between multiple wiring parts 24, the substrate W with the adhesive layer 32 stacked on the base layer 26 can stably bond two substrates W to each other. That is, the adhesive layer 32 avoids the reduction of the conductivity of each wiring part 24 and the diffusion of metal by removing the plasma treatment during bonding. Furthermore, due to the low elastic modulus, the adhesive layer 32 can absorb particles to some extent, so that each wiring part 24 is closely attached to each other. In particular, the stacking part prevents the collapse of each wiring part 24 by leaving the base layer 26 when the upper layer 27 is removed, and at the same time, the generation of gas and the damage of the adhesive layer 32 itself are reduced by thinning the adhesive layer 32. Therefore, the substrate bonding method can make each wiring part 24 and the adhesive layer 32 more stably closely attached.

[0082] Furthermore, the thickness of the adhesive layer 32 formed in the step (e) is thinner than the thickness of the base layer 26. Thus, the substrate bonding method can make the adhesive layer 32 sufficiently thin, and the effect of the thin adhesive layer 32 can be further enhanced.

[0083] The thickness of the adhesive layer 32 formed in step (e) is in the range of 20 nm to 150 nm. Thus, the substrate bonding method can ensure the bonding strength provided by the adhesive layer 32 while making the adhesive layer 32 as thin as possible.

[0084] In addition, in step (d), after supplying the adhesive, the adhesive is heated to increase the elastic modulus of the adhesive. Thus, the substrate bonding method can flatten the adhesive layer (precursor adhesive layer 31) in a state of high elastic modulus in step (e), thereby improving the processability of flattening the adhesive layer 32.

[0085] In addition, at least one of the contact pressure and the rotation speed of the slurry 210 for planarizing the adhesive layer 32 in the step (e) is set to be lower than the contact pressure or the rotation speed of the slurry 203 for planarizing the plurality of wiring portions 24 and the upper layer 27 in the step (b). Thus, when the planarization is performed in the step (f) of the substrate bonding method, damage to the wiring portion 24 can be suppressed, and the adhesive layer 32 can be planarized easily.

[0086] In addition, the base layer 26 is a SiOC film, and the upper layer 27 is a SiO2 film. Thus, in the substrate bonding method, the base layer 26 can be left and the upper layer 27 can be removed stably in the step (c).

[0087] In addition, the base layer 26 is formed of a plurality of layers. Thus, the substrate bonding method can obtain an interlayer insulating film having various characteristics and improve the bonding strength between two substrates by the thin adhesive layer 32 .

[0088] In addition, the plurality of layers of the base layer 26 contain SiCN films. Thus, the substrate bonding method can form an interlayer insulating film having a low dielectric constant in the base layer 26.

[0089] In the bonding substrate JW for bonding two substrates W to each other, the portion for bonding the two substrates W includes a plurality of wiring portions 41 and a laminated portion (insulating laminated portion 42) provided between the plurality of wiring portions 41 and composed of a plurality of layers in the thickness direction, the laminated portion includes a pair of base layers 26 provided on both sides in the thickness direction and an adhesive layer 43 sandwiched between the pair of base layers 26 and having a smaller elastic modulus than the base layers 26, and the two substrates W are bonded by the adhesive layer 43. In this case, the bonding substrate JW can bond the two substrates W to each other stably.

[0090] The substrate bonding method and bonding substrate JW involved in the embodiments disclosed this time are only examples and not limitations in all aspects. The embodiments can be deformed and improved in various forms without departing from the attached claims and their main purpose. The matters recorded in the above multiple embodiments can take other configurations within the scope of non-contradiction, and can also be combined within the scope of non-contradiction.

[0091] This application claims the benefit of priority based on basic application No. 2022-149457 filed on September 20, 2022 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0092] [Reference Signs]

[0093] 24 Wiring Department

[0094] 25 Insulation laminated part

[0095] 26 Basal layer

[0096] 27 Upper

[0097] 31 Precursor bonding layer

[0098] 32 Adhesive layer

[0099] S joint surface

[0100] W substrate

[0101] JW bonded substrate

Claims

1. A substrate bonding method, which comprises bonding two substrates to each other, wherein: Carry out the following steps in sequence: (a) step, providing the two substrates including a plurality of wiring portions and a laminated portion, wherein the laminated portion has a base layer and an upper layer provided between the plurality of wiring portions and having different selectivity in the thickness direction, (b) step of forming a flat surface of the plurality of wiring portions and the upper layer, (c) step, leaving the base layer and removing the upper layer, (d) step of supplying an adhesive to at least the removed layer portion to form an adhesive layer having a smaller elastic modulus than that of the base layer, (e) step of forming a planarized bonding surface between the plurality of wiring portions and the adhesive layer, and (f) The step of bonding the two substrates via the adhesive layer so that the bonding surface of one of the two substrates faces the bonding surface of the other of the two substrates. 2 . The substrate bonding method according to claim 1 , wherein the thickness of the adhesive layer formed in the step (e) is thinner than the thickness of the base layer. 3 . The substrate bonding method according to claim 2 , wherein the thickness of the adhesive layer formed in the step (e) is in the range of 20 nm to 150 nm. 4 . The substrate bonding method according to claim 1 , wherein in the step (d), after supplying the adhesive, a treatment is performed to heat the adhesive to increase the elastic modulus of the adhesive.

5. The substrate bonding method according to any one of claims 1 to 3, wherein at least one of a contact pressure and a rotation speed of a slurry used to flatten the adhesive layer in the step (e) is set to be lower than a contact pressure or a rotation speed of a slurry used to flatten the plurality of wiring portions and the upper layer in the step (b).

6. The substrate bonding method according to any one of claims 1 to 3, wherein the base layer is a SiOC film, The upper layer is a SiO2 film. 7 . The substrate bonding method according to claim 1 , wherein the base layer is formed of a plurality of layers. The substrate bonding method according to claim 7 , wherein the plurality of layers of the base layer include a SiCN film.

9. A bonding substrate, wherein two substrates are bonded to each other, The portion where the two substrates are joined includes a plurality of wiring portions and a stacking portion. The stacked portion is provided between the plurality of wiring portions and is composed of a plurality of layers along the thickness direction. The laminated portion includes a pair of base layers provided on both sides in the thickness direction, and an adhesive layer interposed between the pair of base layers and having a smaller elastic modulus than the base layers, and the two substrates are bonded together via the adhesive layer.

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