Joining system and joining method

Abstract

To provide a technique capable of improving the bonding quality of a polymerized substrate.SOLUTION: A junction system includes a surface modification unit, a joining unit, and a control unit. The surface modification unit performs surface modification treatment to modify an insulating film out of the insulating film and a metal wiring located on the surface of the substrate by plasma of processing gas. The joining unit performs a series of joining processing to join two substrates whose insulating film has been modified by surface modification treatment by intermolecular force. The control unit acquires a piece of information about the thickness of the metal oxide film on the surface of the substrate before the surface modification treatment and determines the treatment conditions for the surface modification treatment based on the acquired information.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present disclosure relates to bonding systems and methods. [Background technology]

[0002] To meet the demand for higher integration of semiconductor devices, 3D integration technology has been proposed, which stacks semiconductor devices in three dimensions. A bonding system that bonds substrates such as semiconductor wafers together is known as a semiconductor manufacturing device used in this 3D integration technology.

[0003] Patent Document 1 discloses a bonding system in which the surfaces of substrates to be bonded are modified, the modified surfaces of the substrates are made hydrophilic, and the hydrophilized substrates are bonded together by van der Waals forces and hydrogen bonds (intermolecular forces). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-073455 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can improve the bonding quality of laminated substrates. [Means for solving the problem]

[0006] A bonding system according to one embodiment of the present disclosure includes a surface modification device, a bonding device, and a control unit. The surface modification device performs a surface modification process to modify the insulating film of the insulating film and metal wiring located on the surface of a substrate using plasma of a processing gas. The bonding device performs a bonding process to bond two substrates whose insulating films have been modified by the surface modification process using intermolecular forces. The control unit acquires information about the thickness of the metal oxide film on the surface of the substrate before the surface modification process, and determines processing conditions for the surface modification process based on the acquired information. [Effects of the Invention]

[0007] According to the present disclosure, the bonding quality of laminated substrates can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic plan view showing the configuration of a joining system according to a first embodiment. [Figure 2] FIG. 2 is a schematic side view of the same. [Figure 3] FIG. 3 is a schematic side view of the upper wafer and the lower wafer according to the embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the configuration of a surface modification device. [Figure 5] FIG. 5 is a schematic plan view showing the configuration of the bonding device according to the embodiment. [Figure 6] FIG. 6 is a schematic side view showing the configuration of the joining device according to the embodiment. [Figure 7] FIG. 7 is a schematic diagram showing an upper chuck and a lower chuck according to the embodiment. [Figure 8] FIG. 8 is a flowchart showing the procedure of the process executed by the joint system according to the embodiment. [Figure 9] FIG. 9 is a graph showing an example of the relationship between the treatment time of the surface modification treatment and the bonding strength. [Figure 10] FIG. 10 is a graph showing an example of the relationship between the processing time of the surface modification processing and the thickness of the metal oxide film when the power applied from the high frequency power supply to the stage is relatively low. [Figure 11] FIG. 11 is a graph showing an example of the relationship between the processing time of the surface modification processing and the thickness of the metal oxide film when the power applied from the high frequency power supply to the stage is relatively high. [Figure 12] FIG. 12 is a graph showing an example of a process window for a surface modification process taking into consideration both the modification threshold and the film thickness threshold. [Figure 13] FIG. 13 is a flowchart showing an example of a procedure for determining processing conditions for a surface modification process. [Figure 14] FIG. 14 is a flowchart illustrating an example of a procedure for determining whether or not joining processing is executable. [Figure 15] FIG. 15 is a diagram showing another example of the configuration of the processing station included in the bonding system. [Figure 16] FIG. 16 is a diagram showing another example of the configuration of the joining system. [Figure 17] FIG. 17 is a schematic plan view showing the configuration of a joint system according to the second embodiment. [Figure 18] FIG. 18 is a schematic diagram showing the configuration of a removal device according to the second embodiment. [Figure 19] FIG. 19 is a graph showing the relationship between the plasma power applied in the plasma treatment and the proportion of metal oxide films and metal nitride films present on the Cu substrate after the plasma treatment. [Figure 20] FIG. 20 is a graph showing the relationship between the plasma irradiation time in the plasma treatment and the proportion of metal oxide films and metal nitride films present on the Cu substrate after the plasma treatment. [Figure 21] FIG. 21 is a graph showing the relationship between the plasma applied power and the proportion of metal nitride film present after plasma treatment on a Cu substrate having a metal oxide film on its surface. [Figure 22] FIG. 22 is a graph showing the relationship between the plasma applied power and the proportion of metal nitride film present after plasma treatment on a Cu substrate on the surface of which no metal oxide film exists. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a detailed description will be given of a bonding system and a bonding method according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments are given the same reference numerals, and redundant explanations will be omitted.

[0010] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0011] In addition, for ease of understanding, the drawings referred to below may show an orthogonal coordinate system in which the X-axis, Y-axis, and Z-axis directions are defined as being orthogonal to each other, with the positive Z-axis direction being the vertically upward direction. Also, the direction of rotation around the vertical axis may be referred to as the θ direction.

[0012] It should be noted that the drawings are schematic and that the dimensional relationships and ratios of each element may differ from reality. Furthermore, there may be parts in which the dimensional relationships and ratios of each element differ from those of the drawings.

[0013] Conventionally, a known method for bonding substrates such as semiconductor wafers involves modifying the surfaces of the substrates to be bonded, making the modified surfaces of the substrates hydrophilic, and bonding the hydrophilized substrates together using van der Waals forces and hydrogen bonds (intermolecular forces).

[0014] The surface modification process of a substrate is a process of modifying the surface of the substrate by plasma of a processing gas. Specifically, the surface modification process is a process of activating an insulating film located on the surface of the substrate by plasma.

[0015] Here, there are cases where not only an insulating film but also metal wiring is located on the surface of the substrate. When a surface modification treatment is performed on a substrate with an insulating film and metal wiring on its surface, the native oxide film on the metal wiring (hereinafter referred to as "metal oxide film") is removed by the plasma and then re-deposited on the metal wiring. In other words, the thickness of the metal oxide film on the metal wiring is once thinned by the surface modification treatment and then thickened again. Note that this phenomenon does not always occur, and it is known to occur more easily when plasma is generated with relatively high power. On the other hand, it is also known that when plasma is generated with relatively low power, the metal oxide film itself is not removed (or is hardly removed at all).

[0016] If the thickness of the metal oxide film on the metal wiring of the substrate after the surface modification treatment is too thick, there is a risk of poor bonding between the metal wiring of one substrate and the metal wiring of the other substrate when the substrates are bonded together.

[0017] The thickness of the metal oxide film formed on the metal wiring varies from substrate to substrate due to factors such as the manufacturing process and environment. Therefore, if a surface modification process is performed under fixed processing conditions (applied power, processing time, etc.), the thickness of the metal oxide film may not be appropriately controlled. For example, if a surface modification process is performed on a substrate with a thick metal oxide film using low-power plasma, the metal oxide film may not be removed, and the metal oxide film may proceed to the bonding process while remaining thicker than the critical thickness. Furthermore, if a surface modification process is performed on a substrate with a thick metal oxide film using high-power plasma, the metal oxide film may be removed by the plasma, but depending on the processing time, the metal oxide film may re-deposit and become thicker than the critical thickness. The critical thickness is a predetermined thickness that prevents poor bonding between metal wirings.

[0018] Therefore, it is hoped that a technology that can overcome the above-mentioned problems and improve the bonding quality of laminated substrates will be realized. Specifically, it is hoped that a technology that can improve the bonding quality of laminated substrates will be realized by suppressing the thickness of the metal oxide film on the metal wiring below the critical film thickness while achieving the activation of the insulating film in the surface modification treatment.

[0019] (First embodiment) <Configuration of the joining system> First, the configuration of a bonding system 1 according to the first embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a schematic plan view showing the configuration of the bonding system 1 according to the first embodiment, and Fig. 2 is a schematic side view of the same. Also, Fig. 3 is a schematic side view of an upper wafer W1 and a lower wafer W2 according to the first embodiment.

[0020] The bonding system 1 shown in FIG. 1 forms a laminated wafer T by bonding a first substrate W1 and a second substrate W2 together.

[0021] The first substrate W1 and the second substrate W2 are semiconductor substrates such as silicon wafers, compound semiconductor wafers, etc. The first substrate W1 and the second substrate W2 have approximately the same diameter.

[0022] Hereinafter, the first substrate W1 will be referred to as the "upper wafer W1," and the second substrate W2 will be referred to as the "lower wafer W2." That is, the upper wafer W1 is an example of the first substrate, and the lower wafer W2 is an example of the second substrate. Furthermore, the upper wafer W1 and the lower wafer W2 may be collectively referred to as "wafer W."

[0023] 3, of the surfaces of the upper wafer W1, the surface that is bonded to the lower wafer W2 will be referred to as a "bonding surface W1j," and the surface opposite the bonding surface W1j will be referred to as a "non-bonding surface W1n." Also, of the surfaces of the lower wafer W2, the surface that is bonded to the upper wafer W1 will be referred to as a "bonding surface W2j," and the surface opposite the bonding surface W2j will be referred to as a "non-bonding surface W2n."

[0024] 3, an insulating film WL and metal wiring WM are located on the bonding surface W1j of the first substrate W1 and the bonding surface W2j of the second substrate W2. The insulating film WL is, for example, a SiO2 (silicon dioxide) film or a SiCN (silicon carbonitride) film. The metal wiring WM is, for example, a Cu (copper) wiring.

[0025] 1, the bonding system 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are arranged in the positive direction of the X-axis in this order. The loading / unloading station 2 and the processing station 3 are also integrally connected.

[0026] The loading / unloading station 2 includes a mounting table 10 and a transfer area 20. The mounting table 10 includes a plurality of mounting plates 11. Each mounting plate 11 is loaded with a cassette C1, C2, or C3, which stores a plurality of substrates (e.g., 25 substrates) in a horizontal position. For example, the cassette C1 stores an upper wafer W1, the cassette C2 stores a lower wafer W2, and the cassette C3 stores a laminated wafer T.

[0027] The transport area 20 is disposed adjacent to the mounting table 10 on the positive side of the X-axis. The transport area 20 is provided with a transport path 21 extending in the Y-axis direction and a transport device 22 movable along the transport path 21.

[0028] The transfer device 22 is movable not only in the Y-axis direction but also in the X-axis direction and rotatable around the Z-axis. The transfer device 22 transfers the upper wafer W1, the lower wafer W2, and the overlapped wafer T between the cassettes C1 to C3 placed on the mounting plate 11 and the third processing block G3 of the processing station 3, which will be described later.

[0029] The number of cassettes C1 to C3 placed on the placement plate 11 is not limited to that shown in the figure. In addition to the cassettes C1, C2, and C3, the placement plate 11 may also be placed with a cassette for recovering defective substrates.

[0030] Processing station 3 is provided with multiple processing blocks equipped with various devices, for example, three processing blocks G1, G2, and G3. For example, a first processing block G1 is provided on the front side of processing station 3 (the negative Y-axis side in FIG. 1), and a second processing block G2 is provided on the back side of processing station 3 (the positive Y-axis side in FIG. 1). Furthermore, a third processing block G3 is provided on the loading / unloading station 2 side of processing station 3 (the negative X-axis side in FIG. 1).

[0031] The first processing block G1 is provided with a surface modification device 30 that modifies the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2 using plasma of a processing gas. In the surface modification device 30, for example, a given processing gas is excited to be converted into plasma and then ionized or radicalized in a reduced pressure atmosphere. Then, the ions (radicals) of elements contained in the processing gas are irradiated onto the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2, thereby activating the insulating films WL located on the bonding surfaces W1j, W2j.

[0032] For example, when nitrogen gas is used as the processing gas, the surface modification apparatus 30 can form dangling bonds on the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 by plasma irradiation. In this case, the surface modification apparatus 30 can activate the insulating films WL located on the bonding surfaces W1j and W2j so that they are easily hydrophilized thereafter.

[0033] The first processing block G1 also includes a surface hydrophilization device 40. The surface hydrophilization device 40 hydrophilizes the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2 using, for example, pure water, and cleans the bonding surfaces W1j, W2j.

[0034] In the surface hydrophilization device 40, pure water is supplied onto the upper wafer W1 or the lower wafer W2 while the upper wafer W1 or the lower wafer W2 held by, for example, a spin chuck is rotated. As a result, the pure water supplied onto the upper wafer W1 or the lower wafer W2 spreads over the bonding surfaces W1j, W2j of the upper wafer W1 or the lower wafer W2, thereby making the bonding surfaces W1j, W2j hydrophilic.

[0035] A film thickness measuring device 35 is disposed in the second processing block G2. The film thickness measuring device 35 measures the film thickness of the metal oxide film on the metal wiring WM located on the bonding surface W1j of the upper wafer W1. Similarly, the film thickness measuring device 35 measures the film thickness of the metal oxide film on the metal wiring WM located on the bonding surface W2j of the lower wafer W2. The film thickness measuring device 35 may be, for example, an ellipsometer or an optical interferometer (e.g., a UV interferometer).

[0036] The optical axis of the film thickness measuring instrument 35 is preferably perpendicular to the bonding surfaces W1j and W2j, which are the surfaces to be measured. With this configuration, the area illuminated by the incident light can be narrowed compared to when the optical axis is oblique to the bonding surfaces W1j and W2j. Therefore, even if the pattern of the metal wiring WM is fine, it is easy to illuminate only the metal wiring WM with the incident light, and it is possible to eliminate the influence of anything other than the metal wiring WM (i.e., the insulating film WL) on the measurement results. In other words, the measurement accuracy of the film thickness of the metal oxide film can be improved.

[0037] The optical axis of the film thickness measuring instrument 35 does not necessarily have to be perpendicular to the bonding surfaces W1j and W2j, but may be oblique to the bonding surfaces W1j and W2j.

[0038] The second processing block G2 also includes a bonding device 41. The bonding device 41 bonds the upper wafer W1 and the lower wafer W2 together. Details of the bonding device 41 will be described later.

[0039] As shown in FIG. 2, in the third processing block G3, transition (TRS) devices 50 and 51 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T are provided in two stages in this order from the bottom.

[0040] 1, a transfer region 60 is formed in an area surrounded by the first processing block G1, the second processing block G2, and the third processing block G3. A transfer device 61 is disposed in the transfer region 60. The transfer device 61 has a transfer arm that is movable, for example, vertically, horizontally, and around a vertical axis.

[0041] The transfer device 61 moves within the transfer region 60 and transfers the upper wafer W1, the lower wafer W2, and the overlapped wafer T to given devices within the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the transfer region 60.

[0042] The bonding system 1 also includes a control device 4. The control device 4 controls the operation of the bonding system 1. The control device 4 is, for example, a computer, and includes a control unit 5 and a storage unit 6. The storage unit 6 stores programs for controlling various processes such as the bonding process. The control unit 5 controls the operation of the bonding system 1 by reading and executing the programs stored in the storage unit 6.

[0043] Such a program may be recorded on a computer-readable recording medium and installed from that recording medium into the storage unit 6 of the control device 4. Examples of computer-readable recording media include hard disks (HDs), flexible disks (FDs), compact disks (CDs), magnetic optical disks (MOs), and memory cards.

[0044] <Configuration of the surface modification device> Next, the configuration of the surface modification device 30 will be described with reference to Fig. 4. Fig. 4 is a schematic cross-sectional view showing the configuration of the surface modification device 30.

[0045] 4, the surface modification apparatus 30 has a processing vessel 70 whose interior can be sealed. A loading / unloading port 71 for the upper wafer W1 or the lower wafer W2 is formed on the side of the processing vessel 70 on the transfer region 60 (see FIG. 1) side, and a gate valve 72 is provided at the loading / unloading port 71.

[0046] A stage 80 is disposed inside the processing vessel 70. The stage 80 is, for example, a lower electrode and is made of a conductive material such as aluminum. Pin through holes (not shown) are formed in the stage 80, and lifter pins (not shown) are housed in the pin through holes. The lifter pins are configured to be able to move up and down by a lifting mechanism (not shown).

[0047] An exhaust ring 103 having a plurality of baffle holes is disposed between the stage 80 and the inner wall of the processing vessel 70. The exhaust ring 103 allows the atmosphere in the processing vessel 70 to be uniformly exhausted from the processing vessel 70.

[0048] A power feed rod 104 made of a conductor is connected to the underside of the stage 80. A high-frequency power supply 106 is connected to the power feed rod 104 via a matching box 105, which may be a blocking capacitor, for example. During plasma processing, a given high-frequency power is applied to the stage 80 from the high-frequency power supply 106.

[0049] An upper electrode 110 is disposed inside the processing vessel 70. The upper surface of the stage 80 and the lower surface of the upper electrode 110 are disposed parallel to each other and facing each other with a given gap between them. The gap between the upper surface of the stage 80 and the lower surface of the upper electrode 110 is adjusted by a lifting mechanism (not shown).

[0050] The upper electrode 110 is grounded and connected to the ground potential. Since the upper electrode 110 is grounded in this manner, damage to the lower surface of the upper electrode 110 can be suppressed during plasma processing.

[0051] In this manner, plasma is generated inside the processing chamber 70 by applying high frequency power from the high frequency power supply 106 to the stage 80 which is the lower electrode.

[0052] In the embodiment, the stage 80, the power feed rod 104, the matching box 105, the high-frequency power supply 106, the upper electrode 110, and the matching box are an example of a plasma generation mechanism that generates plasma of the processing gas in the processing chamber 70. The high-frequency power supply 106 is controlled by the control unit 5 of the control device 4 described above.

[0053] A hollow portion 120 is formed inside the upper electrode 110. A gas supply pipe 121 is connected to the hollow portion 120. The gas supply pipe 121 is connected to a gas supply source 122 that stores a processing gas and a static elimination gas therein. The gas supply pipe 121 is also provided with a supply device group 123 that includes valves and flow rate regulators that control the flow of the processing gas and the static elimination gas.

[0054] The processing gas and static elimination gas supplied from the gas supply source 122 are flow-controlled by a supply device group 123 and introduced into the hollow portion 120 of the upper electrode 110 via a gas supply pipe 121. For example, oxygen gas, nitrogen gas, argon gas, etc. are used as the processing gas. For example, inert gas such as nitrogen gas or argon gas is used as the static elimination gas.

[0055] A baffle plate 124 for promoting uniform diffusion of the processing gas and the static elimination gas is provided inside the hollow portion 120. A large number of small holes are provided in the baffle plate 124. A large number of gas outlets 125 are formed on the lower surface of the upper electrode 110 to eject the processing gas and the static elimination gas from the hollow portion 120 into the processing vessel 70.

[0056] An intake port 130 is formed in the processing vessel 70. An intake pipe 132 communicating with a vacuum pump 131 that reduces the atmosphere inside the processing vessel 70 to a given vacuum level is connected to the intake port 130.

[0057] The upper surface of the stage 80, i.e., the surface facing the upper electrode 110, is a horizontal surface that is circular in plan view and has a diameter larger than those of the upper wafer W1 and the lower wafer W2. A stage cover 90 is placed on the upper surface of the stage 80, and the upper wafer W1 or the lower wafer W2 is placed on a placement portion 91 of the stage cover 90.

[0058] <Configuration of the joining device> Next, the configuration of the joining device 41 will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a schematic plan view showing the configuration of the joining device 41 according to the embodiment, and Fig. 6 is a schematic side view showing the configuration of the joining device 41 according to the embodiment.

[0059] 5, the bonding apparatus 41 has a processing container 190 whose interior can be sealed. A loading / unloading port 191 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T is formed on the side of the processing container 190 on the transfer region 60 side, and an opening / closing shutter 192 is provided at the loading / unloading port 191.

[0060] The interior of the processing vessel 190 is divided into a transfer region T1 and a processing region T2 by an inner wall 193. The above-mentioned loading / unloading port 191 is formed on the side surface of the processing vessel 190 in the transfer region T1. In addition, loading / unloading ports 194 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T are also formed in the inner wall 193.

[0061] In the transfer region T1, a transition 200, a substrate transfer mechanism 201, a reversing mechanism 220, and a position adjustment mechanism 210 are arranged, for example, from the loading / unloading port 191 side in this order.

[0062] The transition 200 temporarily holds the upper wafer W1, the lower wafer W2, and the overlapped wafer T. The transition 200 is formed, for example, in two stages, and any two of the upper wafer W1, the lower wafer W2, and the overlapped wafer T can be held thereon at the same time.

[0063] The substrate transfer mechanism 201 has a transfer arm that is movable, for example, in the vertical direction (Z-axis direction), horizontal directions (Y-axis direction, X-axis direction), and directions around the vertical axis (θ direction). The substrate transfer mechanism 201 can transfer the upper wafer W1, the lower wafer W2, and the overlapped wafer T within the transfer region T1 or between the transfer region T1 and the processing region T2.

[0064] The position adjustment mechanism 210 adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2. Specifically, the position adjustment mechanism 210 has a base 211 equipped with a holder (not shown) that holds and rotates the upper wafer W1 and the lower wafer W2, and a detector 212 that detects the positions of the notches of the upper wafer W1 and the lower wafer W2. The position adjustment mechanism 210 adjusts the positions of the notches by detecting the positions of the notches of the upper wafer W1 and the lower wafer W2 using the detector 212 while rotating the upper wafer W1 and the lower wafer W2 held on the base 211. This adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2.

[0065] The reversing mechanism 220 reverses the upper wafer W1 upside down. Specifically, the reversing mechanism 220 has a holding arm 221 that holds the upper wafer W1. The holding arm 221 extends in the horizontal direction (X-axis direction). The holding arm 221 is provided with holding members 222 that hold the upper wafer W1 at, for example, four locations.

[0066] The holding arm 221 is supported by a drive unit 223 equipped with, for example, a motor. The holding arm 221 is rotatable about a horizontal axis by the drive unit 223. The holding arm 221 is rotatable about the drive unit 223 and is also movable in the horizontal direction (X-axis direction). Below the drive unit 223, another drive unit (not shown) equipped with, for example, a motor is provided. This other drive unit allows the drive unit 223 to move in the vertical direction along a support column 224 extending in the vertical direction.

[0067] In this way, the upper wafer W1 held by the holding member 222 can be rotated around the horizontal axis and moved in the vertical and horizontal directions by the driving unit 223. Furthermore, the upper wafer W1 held by the holding member 222 can rotate around the driving unit 223 and move between the position adjustment mechanism 210 and the upper chuck 230, which will be described later.

[0068] The processing region T2 is provided with an upper chuck 230 that suction-holds the upper surface (non-bonding surface W1n) of the upper wafer W1 from above, and a lower chuck 231 that suction-holds the lower surface (non-bonding surface W2n) of the lower wafer W2 from below. The lower chuck 231 is provided below the upper chuck 230 and is configured to be able to be arranged opposite the upper chuck 230. The upper chuck 230 and the lower chuck 231 are, for example, vacuum chucks.

[0069] 6, the upper chuck 230 is supported by a support member 270 provided above the upper chuck 230. The support member 270 is fixed to the ceiling surface of the processing vessel 190 via a plurality of support columns 271, for example.

[0070] An upper imaging unit 235 is provided on the side of the upper chuck 230 to capture an image of the upper surface (bonding surface W2j) of the lower wafer W2 held by the lower chuck 231. The upper imaging unit 235 may be, for example, a CCD camera.

[0071] The lower chuck 231 is supported by a first moving unit 250 provided below the lower chuck 231. The first moving unit 250 moves the lower chuck 231 in the horizontal direction (X-axis direction), as will be described later. The first moving unit 250 is configured to be able to move the lower chuck 231 vertically and to rotate it around a vertical axis.

[0072] The first moving section 250 is provided with a lower imaging section 236 that captures an image of the lower surface (bonding surface W1j) of the first substrate W1 held by the upper chuck 230. The lower imaging section 236 may be, for example, a CCD camera.

[0073] The first moving section 250 is attached to a pair of rails 252, 252. The pair of rails 252, 252 are provided on the underside of the first moving section 250 and extend in the horizontal direction (X-axis direction). The first moving section 250 is configured to be movable along the rails 252.

[0074] The pair of rails 252, 252 are disposed on a second moving section 253. The second moving section 253 is attached to a pair of rails 254, 254. The pair of rails 254, 254 are disposed on the lower surface of the second moving section 253 and extend in the horizontal direction (Y-axis direction). The second moving section 253 is configured to be movable in the horizontal direction (Y-axis direction) along the rails 254. The pair of rails 254, 254 are disposed on a mounting table 255 provided on the bottom surface of the processing vessel 190.

[0075] The first moving unit 250, the second moving unit 253, etc. constitute an alignment unit 256. The alignment unit 256 moves the lower chuck 231 in the X-axis direction, the Y-axis direction, and the θ direction to horizontally align the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231. The alignment unit 256 also moves the lower chuck 231 in the Z-axis direction to vertically align the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231.

[0076] Although the lower chuck 231 is moved in the X-axis direction, the Y-axis direction, and the θ-direction here, the alignment unit 256 may, for example, move the lower chuck 231 in the X-axis direction and the Y-axis direction, and move the upper chuck 230 in the θ-direction. Also, although the lower chuck 231 is moved in the Z-axis direction here, the alignment unit 256 may, for example, move the upper chuck 230 in the Z-axis direction.

[0077] Next, the configuration of the upper chuck 230 and the lower chuck 231 will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing the upper chuck 230 and the lower chuck 231 according to the embodiment.

[0078] 7, the upper chuck 230 has a main body 260. The main body 260 is supported by a support member 270. A through-hole 266 is formed in the support member 270 and the main body 260, passing through the support member 270 and the main body 260 in the vertical direction. The position of the through-hole 266 corresponds to the center of the upper wafer W1 held by suction on the upper chuck 230. A pressing pin 281 of a striker 280 is inserted into the through-hole 266.

[0079] Striker 280 is disposed on the upper surface of support member 270, and includes a pressing pin 281, an actuator unit 282, and a linear motion mechanism 283. Pressing pin 281 is a cylindrical member extending along the vertical direction, and is supported by actuator unit 282.

[0080] The actuator unit 282 generates a constant pressure in a certain direction (vertically downward in this case) using air supplied from, for example, an electropneumatic regulator (not shown). The actuator unit 282 contacts the center of the upper wafer W1 using air supplied from the electropneumatic regulator, and is able to control the pressure load applied to the center of the upper wafer W1. In addition, the tip of the actuator unit 282 is movable up and down in the vertical direction through the through-hole 266 using air from the electropneumatic regulator.

[0081] The actuator section 282 is supported by a linear motion mechanism 283. The linear motion mechanism 283 moves the actuator section 282 in the vertical direction by means of a drive section incorporating a motor, for example.

[0082] The striker 280 is configured as described above, and controls the movement of the actuator unit 282 by the linear motion mechanism 283, and controls the pressing load on the upper wafer W1 by the pressing pin 281 by the actuator unit 282. As a result, the striker 280 presses the center of the upper wafer W1, which is held by suction on the upper chuck 230, to bring it into contact with the lower wafer W2.

[0083] A plurality of pins 261 that come into contact with the upper surface (non-bonding surface W1n) of the upper wafer W1 are provided on the lower surface of the main body 260. The pins 261 each have a diameter of 0.1 mm to 1 mm and a height of several tens to several hundreds of μm. The pins 261 are evenly spaced, for example, at intervals of 2 mm.

[0084] The upper chuck 230 has a plurality of suction portions that suction-hold the upper wafer W1 in a portion of the region where the plurality of pins 261 are provided. Specifically, a plurality of outer suction portions 391 and a plurality of inner suction portions 392 that suction-hold the upper wafer W1 by vacuum suction are provided on the lower surface of the main body 260 of the upper chuck 230. The plurality of outer suction portions 391 and the plurality of inner suction portions 392 have suction regions that are arc-shaped in plan view. The plurality of outer suction portions 391 and the plurality of inner suction portions 392 have the same height as the pins 261.

[0085] The outer suction portions 391 are arranged on the outer periphery of the main body 260. The outer suction portions 391 are connected to a suction device (not shown) such as a vacuum pump, and suck the outer periphery of the upper wafer W1 by vacuuming.

[0086] The multiple inner suction portions 392 are arranged side by side along the circumferential direction, radially inward of the main body portion 260 from the multiple outer suction portions 391. The multiple inner suction portions 392 are connected to a suction device (not shown), such as a vacuum pump, and suck the region between the outer periphery and center of the upper wafer W1 by vacuuming.

[0087] The lower chuck 231 has a main body 290 having a diameter equal to or larger than that of the lower wafer W2. Here, the lower chuck 231 having a diameter larger than that of the lower wafer W2 is shown. The upper surface of the main body 290 is an opposing surface that faces the lower surface (non-bonding surface W2n) of the lower wafer W2.

[0088] A plurality of pins 291 that come into contact with the lower surface (non-bonding surface W2n) of the lower wafer W2 are provided on the upper surface of the main body 290. The pins 291 each have a diameter of, for example, 0.1 mm to 1 mm and a height of several tens of μm to several hundreds of μm. The pins 291 are evenly spaced, for example, at intervals of 2 mm.

[0089] Furthermore, a lower rib 292 is provided in an annular shape on the upper surface of the main body 290, outside the plurality of pins 291. The lower rib 292 is formed in an annular shape, and supports the outer periphery of the lower wafer W2 over the entire periphery.

[0090] The main body 290 also has a plurality of lower suction ports 293. The plurality of lower suction ports 293 are provided in a suction region surrounded by the lower ribs 292. The plurality of lower suction ports 293 are connected to a suction device (not shown), such as a vacuum pump, via a suction pipe (not shown).

[0091] The lower chuck 231 reduces the pressure in the suction region surrounded by the lower ribs 292 by vacuuming the suction region through the plurality of lower suction ports 293. As a result, the lower wafer W2 placed in the suction region is held by suction on the lower chuck 231.

[0092] Because the lower ribs 292 support the entire outer periphery of the lower surface of the lower wafer W2, the lower wafer W2 is properly vacuumed up to the outer periphery. This allows the entire surface of the lower wafer W2 to be suction-held. Furthermore, because the lower surface of the lower wafer W2 is supported by the multiple pins 291, the lower wafer W2 is easily peeled off from the lower chuck 231 when the vacuum suction of the lower wafer W2 is released.

[0093] <Specific operation of the joining system> Next, a specific operation of the bonding system 1 according to the embodiment will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the procedure of processing executed by the bonding system 1 according to the embodiment. The various processing shown in Fig. 8 is executed based on the control by the control unit 5 of the control device 4.

[0094] First, a cassette C1 containing a plurality of upper wafers W1, a cassette C2 containing a plurality of lower wafers W2, and an empty cassette C3 are placed on a predetermined loading plate 11 in the load / unload station 2. Then, the upper wafer W1 is removed from the cassette C1 by the transfer device 22 and transferred to the transition device 50 arranged in the third processing block G3.

[0095] Next, the upper wafer W1 is transferred by the transfer device 61 to the film thickness measuring device 35. The film thickness measuring device 35 measures the film thickness of the upper wafer W1 (step S101). Specifically, the film thickness measuring device 35 measures the film thickness of the metal oxide film on the metal wiring WM located on the bonding surface W1j of the upper wafer W1. The measurement results by the film thickness measuring device 35 are input to the control unit 5.

[0096] Next, the upper wafer W1 is transferred by the transfer device 61 to the surface modification device 30 in the first processing block G1. In the surface modification device 30, the bonding surface W1j of the upper wafer W1 is surface modified (step S102). Specifically, dangling bonds are formed by removing terminal groups in the insulating film WL located on the bonding surface W1j of the upper wafer W1, and the dangling bonds are terminated with OH groups.

[0097] Next, the upper wafer W1 is transferred by the transfer device 61 to the surface hydrophilization device 40 in the first processing block G1. In the surface hydrophilization device 40, pure water is supplied onto the upper wafer W1 while the upper wafer W1 held by the spin chuck is being rotated. This makes the bonding surface W1j of the upper wafer W1 hydrophilic. The bonding surface W1j of the upper wafer W1 is also cleaned with the pure water (step S103).

[0098] Next, the upper wafer W1 is transferred to the bonding device 41 in the second processing block G2 by the transfer device 61. After being transferred into the bonding device 41, the upper wafer W1 is transferred to the position adjustment mechanism 210 via the transition 200, and its horizontal orientation is adjusted by the position adjustment mechanism 210 (step S104).

[0099] Thereafter, the upper wafer W1 is transferred from the position adjusting mechanism 210 to the reversing mechanism 220, and the upper wafer W1 is reversed upside down by the reversing mechanism 220 (step S105). Specifically, the bonding surface W1j of the upper wafer W1 faces downward.

[0100] Subsequently, the upper wafer W1 is transferred from the reversing mechanism 220 to the upper chuck 230, and the upper wafer W1 is held by suction by the upper chuck 230 (step S106).

[0101] The processing of the lower wafer W2 overlaps with the processing of steps S101 to S106 for the upper wafer W1. First, the transfer device 22 removes the lower wafer W2 from the cassette C2 and transfers it to the transition device 50 arranged in the third processing block G3.

[0102] Next, the lower wafer W2 is transferred by the transfer device 61 to the film thickness measuring device 35. The film thickness measuring device 35 measures the film thickness of the lower wafer W2 (step S107). Specifically, the film thickness measuring device 35 measures the film thickness of the metal oxide film on the metal wiring WM located on the bonding surface W2j of the lower wafer W2. The measurement results by the film thickness measuring device 35 are input to the control unit 5.

[0103] Next, the lower wafer W2 is transferred by the transfer device 61 to the surface modification device 30, where the bonding surface W2j of the lower wafer W2 is modified (step S108).

[0104] Thereafter, the lower wafer W2 is transferred by the transfer device 61 to the surface hydrophilization device 40, where the bonding surface W2j of the lower wafer W2 is hydrophilized and cleaned (step S109).

[0105] Thereafter, the lower wafer W2 is transferred to the bonding device 41 by the transfer device 61. The lower wafer W2 transferred into the bonding device 41 is transferred to the position adjustment mechanism 210 via the transition 200. Then, the horizontal orientation of the lower wafer W2 is adjusted by the position adjustment mechanism 210 (step S110).

[0106] Thereafter, the lower wafer W2 is transferred to the lower chuck 231 and is held by suction on the lower chuck 231 with the notch facing in a predetermined direction (step S111).

[0107] Next, the horizontal positions of the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231 are adjusted (step S112).

[0108] Next, the vertical positions of the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231 are adjusted (step S113). Specifically, the first moving part 250 moves the lower chuck 231 vertically upward, thereby bringing the lower wafer W2 closer to the upper wafer W1.

[0109] Next, after the suction and holding of the upper wafer W1 by the multiple inner suction portions 392 is released (step S114), the pressing pin 281 of the striker 280 is lowered to press down the center of the upper wafer W1 (step S115).

[0110] When the center of the upper wafer W1 contacts the center of the lower wafer W2 and the striker 280 presses the centers of the upper wafer W1 and the lower wafer W2 together with a predetermined force, bonding begins between the pressed centers of the upper wafer W1 and the lower wafer W2. That is, because the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 are modified, van der Waals forces (intermolecular forces) are first generated between the bonding surfaces W1j and W2j, bonding the bonding surfaces W1j and W2j together. Furthermore, because the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 are hydrophilized, the hydrophilic groups between the bonding surfaces W1j and W2j form hydrogen bonds, firmly bonding the bonding surfaces W1j and W2j together. In this manner, a bonded region is formed.

[0111] Thereafter, a bonding wave is generated between the upper wafer W1 and the lower wafer W2, expanding the bonding region from the center of the upper wafer W1 and the lower wafer W2 toward their outer peripheries. Then, the upper wafer W1 is released from suction and hold by the outer suction members 391 (step S116). This causes the outer periphery of the upper wafer W1, which had been suction-held by the outer suction members 391, to fall. As a result, the entire bonding surface W1j of the upper wafer W1 and the entire bonding surface W2j of the lower wafer W2 come into contact with each other, forming the overlapped wafer T.

[0112] Thereafter, the pressing pins 281 are raised to the upper chuck 230, and the lower wafer W2 is released from suction and holding by the lower chuck 231. Thereafter, the overlapped wafer T is carried out of the bonding device 41 by the transfer device 61. In this way, a series of bonding processes is completed.

[0113] Next, the surface modification treatment in steps S102 and S108 will be described. First, the relationship between the processing time of the surface modification treatment and the bonding strength will be described with reference to Fig. 9. Fig. 9 is a graph showing an example of the relationship between the processing time of the surface modification treatment and the bonding strength.

[0114] As shown in Figure 9, there is a correlation between the processing time of the surface modification treatment and the bond strength. Specifically, the longer the processing time of the surface modification treatment, the higher the bond strength tends to be. In order to obtain the desired bond strength, in other words, to obtain a bond strength equal to or greater than the modification threshold, a processing time of at least time t0 is required. Although not shown in Figure 9, it is known that if the processing time of the surface modification treatment is too long, the bond strength will actually decrease.

[0115] Next, the relationship between the processing time of the surface modification process and the thickness of the metal oxide film on the metal wiring WM (hereinafter referred to as "metal oxide film thickness") will be described with reference to Figures 10 and 11. Figure 10 is a graph showing an example of the relationship between the processing time of the surface modification process and the thickness of the metal oxide film when the power applied from the high-frequency power supply 106 to the stage 80 is relatively low (e.g., 30 W). Figure 11 is a graph showing an example of the relationship between the processing time of the surface modification process and the thickness of the metal oxide film when the power applied from the high-frequency power supply 106 to the stage 80 is relatively high (e.g., 150 W).

[0116] As shown in Figure 10, metal oxide films are not removed (or are removed almost completely) by plasma generated with a relatively low applied power. Therefore, for example, if the metal oxide film thickness is T1, which is equal to or less than the film thickness threshold (the upper limit of the film thickness at which bonding failure does not occur, or the critical film thickness), there is no problem. However, if the film thickness T2 exceeds the film thickness threshold, there is a risk of bonding failure occurring because the film thickness does not change even after surface modification treatment.

[0117] Note that "almost no abrasion" means that the amount of abrasion of the metal oxide film is negligibly small when a reasonable processing time for the surface modification process is taken into account. Also, "relatively low applied power" means an applied power (equivalent to an example of the first power) for generating plasma that does not (or hardly) abrade the metal oxide film.

[0118] On the other hand, as shown in Figure 11, when plasma is generated with a relatively high applied power, the metal oxide film is eroded by the plasma. That is, the metal oxide film thickness becomes thinner as the processing time of the surface modification process elapses. Therefore, for example, when the metal oxide film thickness is T2, when the processing time of the surface modification process exceeds t1, the metal oxide film thickness becomes equal to or less than the film thickness threshold at which bonding failure does not occur.

[0119] However, when plasma is generated with a relatively high applied power, the metal oxide film is once removed and then begins to deposit again on the metal wiring WM. For example, if the metal oxide film thickness is T2, the metal oxide film will exceed the film thickness threshold if the surface modification treatment time exceeds t3. Also, even if the metal oxide film thickness is originally T1, which is below the film thickness threshold, the metal oxide film will exceed the film thickness threshold if the surface modification treatment time exceeds t2.

[0120] The "relatively high applied power" means the applied power (corresponding to an example of the second power) for generating plasma that scrapes off the metal oxide film.

[0121] FIG. 12 is a graph showing an example of a process window for a surface modification process taking into consideration both the modification threshold and the film thickness threshold.

[0122] As described above, in order to obtain a bonding strength equal to or greater than the modification threshold, the processing time of the surface modification treatment must be set to t0 or greater. Furthermore, when the metal oxide film thickness is T1, in order to keep the metal oxide film thickness equal to or less than the film thickness threshold, the processing time of the surface modification treatment must be set to t2 or less. Furthermore, when the metal oxide film thickness is T2, in order to keep the metal oxide film thickness equal to or less than the film thickness threshold, the processing time of the surface modification treatment must be set to t1 or greater and t3 or less.

[0123] Therefore, considering both the modification threshold and the film thickness threshold, the processing time of the surface modification process needs to be set within the range of t0 to t2 (range P1 shown in FIG. 12) when the metal oxide film thickness is T1. Also, the processing time of the surface modification process needs to be set within the range of t1 to t3 (range P2 shown in FIG. 12) when the metal oxide film thickness is T2.

[0124] In the bonding system 1 according to the first embodiment, before performing the surface modification treatment, the control unit 5 acquires the measurement results from the film thickness measuring instrument 35. Then, based on the acquired measurement results, the control unit 5 determines the treatment conditions for the surface modification treatment so as to satisfy both the modification threshold and the film thickness threshold.

[0125] 13 is a flowchart showing an example of the procedure for determining processing conditions for the surface modification processing. The processing condition determination processing shown in FIG. 13 is executed between step S101 and step S102 or between step S107 and step S108 shown in FIG.

[0126] 13, the control unit 5 first acquires the measurement result of the metal oxide film thickness by the film thickness measuring instrument 35 (step S201). Next, the control unit 5 determines whether the metal oxide film thickness is equal to or less than the film thickness threshold (step S202).

[0127] In step S202, if the metal oxide film thickness is equal to or less than the film thickness threshold (step S202, Yes), the control unit 5 determines the power to be applied from the high frequency power supply 106 to the stage 80 to be the first power (step S203). As described above, the first power is a power that is preset as the power to be applied to generate plasma that does not (or hardly does) remove the metal oxide film.

[0128] Furthermore, the control unit 5 determines the processing time as a first processing time (step S204). Specifically, when the applied power is determined to be the first power, the control unit 5 determines, as the first processing time, a time that is predetermined as the processing time for the surface modification processing at which the bonding strength becomes equal to or greater than the modification threshold value.

[0129] On the other hand, if the metal oxide film thickness exceeds the film thickness threshold in step S202 (No in step S202), the control unit 5 determines the power to be applied from the high frequency power supply 106 to the stage 80 to be the second power (step S205). As described above, the second power is a power that is preset as the power to be applied to generate plasma that removes the metal oxide film.

[0130] Furthermore, the control unit 5 determines the processing time as the second processing time (step S206). Specifically, when the applied power is determined to be the second power, the control unit 5 determines the processing time of the surface modification process at which the bonding strength becomes equal to or greater than the modification threshold and the metal oxide film thickness becomes equal to or less than the film thickness threshold as the second processing time.

[0131] Here, the "processing time of the surface modification process at which the metal oxide film thickness becomes equal to or less than the film thickness threshold" may be determined, for example, based on information (hereinafter referred to as "film thickness change information") previously stored in the memory unit 6 as information indicating the relationship between the metal oxide film thickness and the processing time of the surface modification process.

[0132] The film thickness change information may be stored in the storage unit 6 for each of a plurality of second powers. For example, the storage unit 6 may store film thickness change information when the second power is 100 W, film thickness change information when the second power is 120 W, and film thickness change information when the second power is 150 W. In this case, the control unit 5 can determine the processing time of the surface modification process for making the metal oxide film thickness equal to or less than the film thickness threshold, using the film thickness change information corresponding to the second power determined in step S205 and the metal oxide film thickness acquired in step S201.

[0133] After completing step S204 or step S206, the control unit 5 completes the process condition determination process for the surface modification process. Thereafter, the control unit 5 proceeds to step S102 or step S108, and performs the surface modification process under the process conditions determined in the process condition determination process.

[0134] (First modified example of the first embodiment) In the first embodiment described above, an example has been described in which thickness measurement of a metal oxide film is performed before a surface modification process. However, the bonding system 1 according to the first embodiment may also perform thickness measurement of a metal oxide film after a surface modification process. This example will be described with reference to FIG. 14. FIG. 14 is a flowchart showing an example of the procedure for a bonding process execution feasibility determination process. The bonding process execution feasibility determination process shown in FIG. 14 is performed after a surface modification process is performed on a wafer W and before a surface hydrophilization process is performed.

[0135] 14, the control unit 5 carries the wafer W after the surface modification process into the film thickness measuring device 35 (step S301), and performs a process of measuring the metal oxide film thickness in the film thickness measuring device 35 (step S302). Then, the control unit 5 acquires the measurement result of the metal oxide film thickness by the film thickness measuring device 35 (step S303).

[0136] Next, the control unit 5 determines whether the metal oxide film thickness is equal to or less than the film thickness threshold based on the measurement result acquired in step S303 (step S304).

[0137] In step S304, if the metal oxide film thickness is equal to or less than the film thickness threshold (step S304, Yes), the control unit 5 permits the execution of the bonding process (step S305). Specifically, if the wafer is the upper wafer W1, the control unit 5 proceeds with the process from step S103 shown in FIG. 8, and if the wafer is the lower wafer W2, the control unit 5 proceeds with the process from step S109 shown in FIG. 8.

[0138] On the other hand, in step S304, if the metal oxide film thickness exceeds the film thickness threshold (step S304, No), the control unit 5 prohibits the execution of the bonding process (step S306). That is, if the wafer is the upper wafer W1, the control unit 5 does not perform the process from step S103 onwards shown in Fig. 8, and if the wafer is the lower wafer W2, the control unit 5 does not perform the process from step S109 onwards shown in Fig. 8.

[0139] Furthermore, the control unit 5 executes an abnormality handling process for wafers W whose metal oxide film thickness exceeds the threshold (step S307).

[0140] For example, as an abnormality handling process, the control unit 5 may perform a process of returning the wafer W, whose metal oxide film thickness exceeds the threshold, to the carry-in / out station 2 (an example of a carry-in / out unit) in order to carry it out of the bonding system 1. In this case, a cassette (not shown) for recovering the defective wafer may be placed on the mounting table 10. The control unit 5 may control the transfer device 61 and the transfer device 22 to remove the wafer W, whose metal oxide film thickness exceeds the threshold, from the film thickness measuring device 35 and store it in the recovery cassette.

[0141] Furthermore, as an abnormality handling process, the control unit 5 may load a wafer W having a metal oxide film thickness exceeding a threshold into the surface modification apparatus 30 and perform the surface modification process again in the surface modification apparatus 30. In this case, the control unit 5 may set different processing conditions for the first surface modification process and the second surface modification process. For example, if the first surface modification process is performed at a first power, the control unit 5 may perform the second surface modification process at a second power. Furthermore, if the first surface modification process and the second surface modification process are performed at a second power, the control unit 5 may set the processing time for the second surface modification process to be shorter than the processing time for the first surface modification process. Note that when the surface modification process is to be performed again in step S307, the control unit 5 may return the process to step S301 and perform the process from step S301 again.

[0142] When the process of step S306 or step S307 is completed, the control unit 5 ends the joining process execution possibility determination process.

[0143] In this way, the bonding system 1 according to the first embodiment may measure the thickness of the metal oxide film after the surface modification treatment.

[0144] (Second Modification) 15 is a diagram showing another example of the configuration of the processing station 3 included in the bonding system 1. In the first embodiment described above, an example in which the film thickness measuring device 35 is arranged in the second processing block G2 of the processing station 3 has been described, but the arrangement of the film thickness measuring device 35 is not limited to this example.

[0145] 15, the film thickness measuring device 35 may be built into the surface modification device 30. This configuration can shorten the time required for a series of processes in the bonding system 1. In addition, the increase in the footprint of the bonding system 1 due to the incorporation of the film thickness measuring device 35 can be suppressed.

[0146] (Third Modification) 16 is a diagram showing another example of the configuration of the bonding system 1. As shown in FIG. 16, the film thickness measuring device 35 may be provided separately from the bonding system 1. That is, the bonding system 1 does not necessarily need to include the film thickness measuring device 35. In this case, the control device 4 may acquire information about the metal oxide film thickness from the film thickness measuring device 35 via a network such as a LAN (Local Area Network). In this case, the wafer W whose film thickness has been measured by the film thickness measuring device 35 is carried into the bonding system 1.

[0147] As described above, the bonding system according to the first embodiment (for example, the bonding system 1) includes a surface modification device (for example, the surface modification device 30), a bonding device (for example, the bonding device 41), and a control unit (for example, the control unit 5). The surface modification device performs a surface modification process to modify the insulating film of the insulating film (for example, the insulating film WL) and the metal wiring (for example, the metal wiring WM) located on the surfaces of the substrates (for example, the upper wafer W1 and the lower wafer W2) using plasma of a processing gas. The bonding device performs a bonding process to bond, by intermolecular forces, two substrates whose insulating films have been modified by the surface modification process. The control unit acquires information about the thickness of the metal oxide film on the surfaces of the substrates before the surface modification process and determines the processing conditions for the surface modification process based on the acquired information.

[0148] This bonding system can achieve activation of the insulating film while suppressing bonding defects caused by the metal oxide film. Therefore, the bonding system according to the first embodiment can improve the bonding quality of the laminated substrates.

[0149] Furthermore, the bonding system according to the first embodiment (for example, bonding system 1) includes a surface modification device (for example, surface modification device 30), a bonding device (for example, bonding device 41), and a control unit (for example, control unit 5). The surface modification device performs a surface modification process to modify the insulating film of the insulating film (for example, insulating film WL) and the metal wiring (for example, metal wiring WM) located on the surfaces of substrates (for example, upper wafer W1 and lower wafer W2) using plasma of a processing gas. The bonding device performs a bonding process to bond two substrates whose insulating films have been modified by the surface modification process using intermolecular forces. The control unit acquires information about the thickness of the metal oxide film on the surfaces of the substrates after the surface modification process, and determines whether or not to perform a bonding process on the substrates after the surface modification process based on the acquired information.

[0150] In this way, by determining whether or not the bonding process can be performed before the bonding process based on information about the film thickness of the metal oxide film, the bonding quality of the laminated substrates can be improved.

[0151] For example, the bonding system according to the first embodiment can suppress yield by prohibiting the execution of the bonding process when the thickness of the metal oxide film is thicker than the critical thickness. In other words, two substrates bonded by the bonding process cannot be separated and then bonded again. In contrast, if the substrate is before the bonding process, it can be salvaged as a product substrate by, for example, temporarily removing it from the bonding system, subjecting it to CMP (chemical mechanical polishing) processing, and then loading it back into the bonding system.

[0152] (Second embodiment) The bonding system may perform a process of removing the metal oxide film from the substrate before measuring the thickness of the metal oxide film. Therefore, in the second embodiment, an example will be described in which the thickness measurement process of the metal oxide film is performed after at least a part of the metal oxide film on the substrate is removed using a removal device.

[0153] 17 is a schematic plan view showing the configuration of a joint system 1A according to the second embodiment. In the following description, parts that are similar to parts that have already been described are given the same reference numerals as those already described, and duplicated description will be omitted.

[0154] 17, the bonding system 1A according to the second embodiment differs from the bonding system 1 according to the first embodiment in that a removal apparatus 300 is disposed in the second processing block G2. The removal apparatus 300 removes at least a portion of the metal oxide film on the metal wiring WM located on the bonding surface W1j of the upper wafer W1. Similarly, the removal apparatus 300 removes at least a portion of the metal oxide film on the metal wiring WM located on the bonding surface W2j of the lower wafer W2.

[0155] An example of the configuration of such a removal device 300 will be described with reference to Fig. 18. Fig. 18 is a schematic diagram showing the configuration of a removal device 300 according to the second embodiment.

[0156] As shown in FIG. 18, the removal apparatus 300 includes a chamber 320, a substrate holding mechanism 330, a liquid supply unit 340, and a collection cup 350.

[0157] The chamber 320 accommodates a substrate holding mechanism 330, a liquid supply unit 340, and a collection cup 350. An FFU (Fan Filter Unit) 321 is provided on the ceiling of the chamber 320. The FFU 321 forms a downflow within the chamber 320.

[0158] The FFU 321 is connected to a downflow gas supply source 323 via a valve 322. The FFU 321 discharges a downflow gas (for example, dry air) supplied from the downflow gas supply source 323 into the chamber 320.

[0159] The substrate holding mechanism 330 includes a rotary holder 331, a support column 332, and a drive unit 333. The rotary holder 331 is provided approximately in the center of the chamber 320. A holding member 311 that holds the wafer W from the side is provided on the upper surface of the rotary holder 331. The wafer W is held horizontally by the holding member 311 at a slight distance from the upper surface of the rotary holder 331.

[0160] The support column 332 is a member extending in the vertical direction, and has a base end rotatably supported by the drive section 333, and a tip end that horizontally supports the rotation holder 331. The drive section 333 rotates the support column 332 around the vertical axis.

[0161] The substrate holding mechanism 330 rotates the support column 332 using the drive unit 333, thereby rotating the rotary holder 331 supported by the support column 332, thereby rotating the wafer W held by the rotary holder 331.

[0162] The liquid supply unit 340 supplies various processing liquids to the wafer W held by the substrate holding mechanism 330. The liquid supply unit 340 includes a nozzle 341, an arm 342 that horizontally supports the nozzle 341, and a pivoting and lifting mechanism 343 that pivots and raises and lowers the arm 342.

[0163] Nozzle 341 is connected to citric acid supply source 345a via valve 344a. Nozzle 341 is also connected to rinse liquid supply source 345b via valve 344b. Citric acid supply source 345a supplies citric acid (citric acid aqueous solution) to nozzle 341 via valve 344a. Rinse liquid supply source 345b supplies rinse liquid to nozzle 341 via valve 344b. The rinse liquid is, for example, pure water (deionized water) at room temperature (approximately 23 to 25 degrees). FIG. 18 shows an example in which liquid supply unit 340 has one nozzle 341, but liquid supply unit 340 may also have a total of two nozzles: one for supplying citric acid and one for supplying rinse liquid.

[0164] The liquid supply unit 340 is configured as described above and supplies the citric acid aqueous solution or the rinse liquid to the wafer W.

[0165] Citric acid is an example of a removal processing liquid that removes at least a portion of a metal oxide film from the surface of the wafer W. Note that, instead of citric acid, for example, oxalic acid or sulfuric acid may be used as the removal processing liquid. The rinse liquid is a processing liquid for washing away citric acid remaining on the wafer W.

[0166] The collection cup 350 is disposed to surround the rotary holder 331, and collects the processing liquid scattered from the wafer W by the rotation of the rotary holder 331. A drain port 351 is formed in the bottom of the collection cup 350, and the processing liquid collected by the collection cup 350 is discharged from the drain port 351 to the outside of the removal apparatus 300. In addition, an exhaust port 352 is formed in the bottom of the collection cup 350, which discharges the downflow gas supplied from the FFU 321 to the outside of the removal apparatus 300.

[0167] Next, a specific operation of the removal apparatus 300 according to the second embodiment will be described. The processing by the removal apparatus 300 may be performed, for example, before the thickness measurement of the metal oxide film in the first embodiment. In this case, the processing by the removal apparatus 300 may be performed on the upper wafer W1 and the lower wafer W2, respectively, before steps S101 and S107 in FIG. 8. Hereinafter, the upper wafer W1 and the lower wafer W2 will be collectively referred to as "wafer W." Similarly, hereinafter, the bonding surfaces W1j and W2j will be collectively referred to as "bonding surfaces."

[0168] First, a substrate loading process is performed in the removal apparatus 300. In this substrate loading process, the wafer W loaded into the chamber 320 by the substrate transfer device is held by the holding member 311 of the substrate holding mechanism 330. At this time, the wafer W is held by the holding member 311 with the bonding surface facing upward. Thereafter, the rotating holder 331 is rotated by the driving unit 333. As a result, the wafer W rotates together with the rotating holder 331 while being held horizontally by the rotating holder 331.

[0169] Next, in the removal device 300, a metal oxide film removal process is performed. In this metal oxide film removal process, the nozzle 341 of the liquid supply unit 340 is positioned above the center of the wafer W. Then, citric acid, which is a metal oxide film removal process liquid, is supplied to the bonding surface of the wafer W. The citric acid supplied to the wafer W spreads over the bonding surface of the wafer W due to centrifugal force caused by the rotation of the wafer W. This removes at least a portion of the metal oxide film on the bonding surface of the wafer W. For example, the removal device 300 may remove almost all of the metal oxide film on the bonding surface of the wafer W using citric acid. The removal rate of the metal oxide film can be controlled, for example, by the concentration of citric acid, the supply time of citric acid, the supply flow rate, etc.

[0170] Subsequently, a rinsing process is performed in the removal unit 300. In the rinsing process, a rinsing liquid is supplied to the rotating wafer W, so that the bonding surface of the wafer W is cleaned.

[0171] Next, a drying process is performed in the removal apparatus 300. In this drying process, for example, the rotation speed of the wafer W is increased for a predetermined time to shake off the rinse liquid remaining on the surface of the wafer W and dry the wafer W. Thereafter, the rotation of the wafer W is stopped.

[0172] The drying process may be a process of reducing the humidity inside the chamber 320 by using a downflow gas supplied from the FFU 321.

[0173] Next, a substrate unloading process is performed in the removal apparatus 300. In this substrate unloading process, the transfer device 61 (see FIG. 1) removes the wafer W from the chamber 320 of the removal apparatus 300. Thereafter, the wafer W is transferred to the film thickness measuring device 35 by the transfer device 61. When this substrate unloading process is completed, the metal oxide film removal process for one wafer W is completed.

[0174] Here, the inventors of the present invention have found through experiments that when a plasma treatment is performed on a substrate having a metal oxide film on its surface, a metal nitride film is formed on the surface of the substrate.

[0175] The details of the experiment are as follows. First, the inventors prepared a number of Cu substrates on the surfaces of which metal oxide films (CuO) were formed, and irradiated these Cu substrates with plasma generated by applying different powers. Specifically, plasma was irradiated on four Cu substrates at applied powers of 50 W, 100 W, 200 W, and 400 W, respectively. Then, the inventors examined the metal oxide films (CuO) and metal nitride films (CuO) on the four Cu substrates that had been subjected to plasma treatment and the Cu substrate that had not been subjected to plasma treatment (i.e., the Cu substrate with an applied power of 0 W), for a total of five Cu substrates. x O y The abundance of N) was investigated, and the results are shown in Figure 19.

[0176] FIG. 19 shows the relationship between the applied plasma power during plasma processing and the metal oxide film (CuO) and metal nitride film (Cu x O y 19 is a graph showing the relationship between the abundance ratio of a metal nitride film (CuN) and the Cu substrate that was not subjected to plasma treatment (Cu substrate with an applied power of 0 W). x O y In contrast, no metal nitride film (Cu N) was detected on the four plasma-treated Cu substrates. x O y N) was detected. Also, a metal nitride film (Cu x O y The abundance ratio of N) tended to be higher for Cu substrates that had been plasma-treated with higher applied power, i.e., Cu substrates from which a larger amount of metal oxide film (Cu2O) had been removed.

[0177] The inventors of the present invention also irradiated plasma generated by the same applied power to a plurality of Cu substrates having metal oxide films formed on their surfaces for different irradiation times. Then, the inventors measured the metal oxide film (CuO) and metal nitride film (CuO) of each Cu substrate that had been subjected to plasma treatment and a Cu substrate that had not been subjected to plasma treatment (i.e., a Cu substrate with an irradiation time of 0 seconds). x O y The abundance of N was investigated, and the results are shown in Figure 20.

[0178] FIG. 20 shows the relationship between the plasma irradiation time in the plasma treatment and the metal oxide film (CuO) and metal nitride film (Cu x O y 1 is a graph showing the relationship between the abundance ratio of α- and β-blocking agents and the abundance ratio of β- and β-blocking agents.

[0179] As shown in Figure 20, the metal nitride film (Cu x O y The abundance ratio of N tended to be higher for Cu substrates with longer plasma exposure times, i.e., Cu substrates with a larger amount of metal oxide film (Cu2O) removed.

[0180] From the results shown in FIGS. 19 and 20, when a substrate having a metal oxide film (CuO) is subjected to plasma treatment, a metal nitride film (CuO) is formed on the substrate. x O y N) is generated.

[0181] The mechanism by which a metal nitride film is produced by plasma processing is, for example, that nitrogen used in the plasma processing combines with a metal oxide film (CuO) during the plasma processing to form a metal nitride film (Cu x O y N) is likely to be generated.

[0182] The inventors of the present application prepared Cu substrates with and without a metal oxide film on their surfaces, and performed plasma treatment on each Cu substrate at applied powers of 100 W and 400 W. After the plasma treatment, the inventors measured the metal oxide film (CuO) and metal nitride film (CuO) on each Cu substrate. x O y The abundance of N was investigated, and the results are shown in Figures 21 and 22.

[0183] FIG. 21 shows the relationship between the plasma power applied to a Cu substrate with a metal oxide film on its surface and the metal nitride film (Cu x O y 22 is a graph showing the relationship between the applied power of plasma and the proportion of a metal nitride film (CuN) present on the surface of a Cu substrate on which no metal oxide film exists. x O y 1 is a graph showing the relationship between the abundance ratio of α- and β-blocking agents and the abundance ratio of β- and β-blocking agents.

[0184] As shown in FIG. 21, when a plasma treatment is performed on a Cu substrate having a metal oxide film (CuO) on its surface, a metal nitride film (Cu x O y On the other hand, as shown in FIG. 22, when a plasma treatment is performed on a Cu substrate having a metal oxide film (CuO) on its surface, a metal nitride film (Cu x O y These results show that removing the metal oxide film from the surface of the Cu substrate suppresses the formation of a metal nitride film due to plasma treatment (surface modification treatment).

[0185] Because metal nitride films are relatively difficult to reduce, the presence of a metal nitride film on a substrate may have adverse effects, such as a decrease in bonding strength, in the subsequent bonding process. In contrast, in the second embodiment, a process for removing the metal oxide film on the substrate is performed before measuring the thickness of the metal oxide film, specifically before the surface modification process, thereby preventing the formation of a metal nitride film on the substrate during the surface modification process. Therefore, the bonding system 1A according to the second embodiment can prevent the metal nitride film on the substrate from adversely affecting the bonding process.

[0186] (Modification of the second embodiment) In the second embodiment described above, the metal oxide film removal process is performed using citric acid, but the metal oxide film removal process is not limited to wet processing using a processing liquid and may be dry processing. For example, the metal oxide film may be removed by supplying hydrogen (H2) gas to the bonding surface of the wafer W. The hydrogen gas reduces and removes the metal oxide film. The hydrogen gas may be heated to a high temperature to promote a chemical reaction. The hydrogen gas may also be converted into plasma to promote a chemical reaction.

[0187] As described above, in the bonding system 1A according to the second embodiment, a process for removing at least a portion of the metal oxide film is performed before measuring the thickness of the metal oxide film. As described above, in the flowchart of FIG. 8 according to the first embodiment, the metal oxide film removal process is performed on each of the upper wafer W1 and the lower wafer W2 before steps S101 and S107. The control unit 5 then determines the process conditions for the surface modification process based on information about the thickness of the metal oxide film after the removal process. This process reduces the thickness of the metal oxide film, so the answer to step S202 in FIG. 13 described in the first embodiment is Yes, and the surface modification process can be performed using plasma generated by applying a relatively low power.

[0188] When the metal oxide film removal process is performed in the first modified example of the first embodiment, the removal process is performed on each of the upper wafer W1 and the lower wafer W2, for example, before step S301 in the flowchart of Fig. 14, specifically, before the surface modification process. Thereafter, the surface modification process is performed on the wafer W, and the process of step S301 is started.

[0189] According to this metal oxide film removal process, the thickness of the metal oxide film is reduced, so that the surface modification process can be performed using plasma generated by applying a relatively low power. Furthermore, according to this metal oxide film removal process, the thickness of the metal oxide film is reduced, so that the answer in step S304 becomes Yes and the bonding process is performed. In other words, in the first modification, by performing the metal oxide film removal process, it is possible to reduce the number of substrates that are subject to abnormality response processing.

[0190] Furthermore, as shown in FIG. 12 described in the first embodiment, the metal oxide film has a small thickness, so that the processing time for the surface modification process can be shortened.

[0191] Furthermore, by performing the metal oxide film removal process, it is possible to suppress the generation of a metal nitride film on the metal wiring due to the surface modification process, and to suppress adverse effects on the subsequent bonding process.

[0192] Therefore, according to the bonding system 1A according to the second embodiment, the surface modification process can be performed more efficiently, and the occurrence of bonding defects due to the metal oxide film can be suppressed.

[0193] (Other embodiments) The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0194] 1. Joint System 2 Loading / unloading station 3 Processing Stations 4. Control device 5. Control section 6 Memory section 10. Mounting table 30 Surface modification equipment 35 Film Thickness Measuring Instrument 40 Surface hydrophilization device 41 Joining equipment 80 stages 106 High frequency power supply 110 Upper electrode 230 Upper chuck 231 Lower chuck 280 Striker T Polymerized Wafer W1 upper wafer W2 lower wafer WL insulating film WM metal wiring

Claims

1. a surface modification device for performing a surface modification process to modify the insulating film of the insulating film and the metal wiring located on the surface of the substrate by plasma of a processing gas; a bonding apparatus for performing a bonding process by which the two substrates, the insulating films of which have been modified by the surface modification process, are bonded together by intermolecular forces; a control unit that acquires information about the thickness of the metal oxide film on the surface of the substrate before the surface modification treatment, and determines treatment conditions for the surface modification treatment based on the acquired information; A joining system comprising:

2. The bonding system according to claim 1 , further comprising a film thickness measuring device for measuring the film thickness of the metal oxide film on the surface of the substrate.

3. The bonding system according to claim 2 , wherein the surface modification device includes the film thickness measuring device.

4. The bonding system of claim 2 , wherein the optical axis of the film thickness gauge is perpendicular to the surface of the substrate.

5. 2. The bonding system according to claim 1, wherein the control unit generates plasma at a first power when a thickness of the metal oxide film is equal to or less than a threshold value, and generates plasma at a second power greater than the first power when the thickness of the metal oxide film exceeds the threshold value.

6. The bonding system according to claim 5 , wherein the control unit changes the processing time of the surface modification treatment depending on whether the thickness of the metal oxide film is equal to or less than the threshold value or whether the thickness of the metal oxide film is greater than the threshold value.

7. 7. The bonding system according to claim 6, wherein the control unit determines a processing time for the surface modification treatment within a predetermined range as a processing time range in which the thickness of the metal oxide film does not exceed the threshold value when the thickness of the metal oxide film exceeds the threshold value.

8. a removal device for performing a removal process to remove at least a part of the metal oxide film from the surface of the substrate before the surface modification process; Equipped with The bonding system according to claim 1 , wherein the control unit acquires information about a thickness of the metal oxide film after the removal process.

9. a surface modification device for performing a surface modification process to modify the insulating film of the insulating film and the metal wiring located on the surface of the substrate by plasma of a processing gas; a bonding apparatus for performing a bonding process by which the two substrates, the insulating films of which have been modified by the surface modification process, are bonded together by intermolecular forces; a control unit that acquires information about the thickness of a metal oxide film on the surface of the substrate after the surface modification treatment, and determines whether or not to perform the bonding treatment on the substrate after the surface modification treatment based on the acquired information; A joining system comprising:

10. 10. The bonding system according to claim 9, wherein the control unit permits the execution of the bonding process on the substrate after the surface modification process when the thickness of the metal oxide film is equal to or less than a threshold value, and prohibits the execution of the bonding process on the substrate after the surface modification process when the thickness of the metal oxide film exceeds the threshold value.

11. a loading / unloading section where the substrate is loaded into and unloaded from the bonding system; Equipped with The bonding system according to claim 10 , wherein the control unit returns the substrate for which the execution of the bonding process has been prohibited to the carry-in / out unit.

12. The bonding system according to claim 10 , wherein the control unit carries the substrate for which the execution of the bonding process has been prohibited into the surface modification device, and performs the surface modification process on the substrate again.

13. a removal device for performing a removal process to remove at least a part of the metal oxide film from the surface of the substrate before the surface modification process; Equipped with The bonding system according to claim 9 , wherein the control unit acquires information about a thickness of the metal oxide film after the removal process.

14. a step of performing a surface modification process in which the insulating film and the metal wiring located on the surface of the substrate are modified by plasma of a processing gas; a step of performing a bonding process of bonding the two substrates, the insulating films of which have been modified by the surface modification process, by intermolecular forces; acquiring information about the thickness of the metal oxide film on the surface of the substrate before the surface modification treatment, and determining treatment conditions for the surface modification treatment based on the acquired information; A bonding method comprising:

15. a step of performing a surface modification process in which the insulating film and the metal wiring located on the surface of the substrate are modified by plasma of a processing gas; a step of performing a bonding process of bonding the two substrates, the insulating films of which have been modified by the surface modification process, by intermolecular forces; acquiring information about the thickness of the metal oxide film on the surface of the substrate after the surface modification treatment, and determining whether or not to perform the bonding treatment on the substrate after the surface modification treatment based on the acquired information; A bonding method comprising:

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