Bonding system and surface modification method

Abstract

To provide a technique capable of improving a joint quality of a polymerization substrate.SOLUTION: A joint system comprises a surface modification device and a joint device. The surface modification device modifies a joint surface of a substrate to be jointed with the other substrate by plasma of a processing gas. The joint device joints the two substrates modified by the surface modification device by an intermolecular force. Further, the surface modification device comprises: a processing container which can house the substrate; a processing gas supply part that supplies a processing gas containing water into the processing container; and a plasma generation part that generates the plasma of the processing gas containing water.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to bonding systems and surface modification 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 aspect of the present disclosure includes a surface modification device and a bonding device. The surface modification device modifies a bonding surface of a substrate to be bonded to another substrate using plasma of a processing gas. The bonding device bonds the two substrates modified by the surface modification device using intermolecular forces. The surface modification device also includes a processing vessel capable of accommodating the substrates, a processing gas supply unit that supplies a processing gas containing moisture into the processing vessel, and a plasma generation unit that generates plasma of the processing gas containing moisture. [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 bonding system according to an embodiment. [Figure 2] FIG. 2 is a schematic side view showing the configuration of the joint system according to the embodiment. [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 apparatus according to an embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of the configuration of a processing gas supply source according to this embodiment. [Figure 6] FIG. 6 is a diagram illustrating another example of the configuration of the processing gas supply source according to this embodiment. [Figure 7] FIG. 7 is a schematic plan view showing the configuration of the bonding device according to the embodiment. [Figure 8] FIG. 8 is a schematic side view showing the configuration of the joining device according to the embodiment. [Figure 9] FIG. 9 is a schematic diagram showing an upper chuck and a lower chuck according to the embodiment. [Figure 10] FIG. 10 is a flowchart illustrating a procedure of a process executed by the joint system according to the embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of a procedure for the surface modification treatment according to the embodiment. [Figure 12] FIG. 12 is a graph showing the measurement results of the emission intensity of OH radicals and H radicals in water vapor plasma. [Figure 13] FIG. 13 is a graph showing the measurement results of the emission intensity of OH radicals and H radicals in water vapor plasma. [Figure 14]FIG. 14 is a timing chart showing the operation of each part in the surface modification process according to the embodiment. [Figure 15] FIG. 15 is a timing chart showing the operation of each part in the surface modification process according to the modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of a bonding system and a surface modification method (hereinafter referred to as an "embodiment") for carrying out the disclosed embodiment. Note that the present disclosure is not limited to the embodiment. Furthermore, each embodiment and modified example can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same parts in each of the following embodiments and modified examples are given the same reference numerals, and duplicated 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] On the other hand, when metal wiring is provided on the bonding surfaces of the substrates, the metal wiring may be damaged by the plasma in a surface modification process using plasma of a processing gas. If the bonding quality of the laminated substrate deteriorates due to the deterioration of the bonding surface, the yield of elements formed in the laminated substrate may decrease.

[0015] Therefore, there is a need for a technology that can overcome the above-mentioned problems and improve the bonding quality of laminated substrates.

[0016] The surface modification of the substrate is performed using a surface modification device, which accommodates the substrate in a processing chamber and modifies the surface of the accommodated substrate with plasma of a processing gas.

[0017] Here, when surface modification of substrates is repeatedly performed in a processing chamber of a surface modification device, the amount of moisture in the processing chamber gradually decreases due to evacuation or the like. When the amount of moisture in the processing chamber decreases, the state of the plasma of the processing gas generated in the processing chamber changes, and the surface modification of the substrate is not performed sufficiently. As a result, the bonding strength between the substrates obtained when bonding a modified substrate to another substrate may decrease. This decrease in bonding strength may cause problems such as peeling of the substrates. For this reason, there is a need for technology that can improve the bonding quality of laminated substrates.

[0018] <Configuration of the joining system> First, the configuration of a bonding system 1 according to an 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 an 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 an embodiment.

[0019] 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.

[0020] The first substrate W1 is a semiconductor substrate such as a silicon wafer or a compound semiconductor wafer on which multiple electronic circuits are formed. The second substrate W2 is a bare wafer on which no electronic circuits are formed. The first substrate W1 and the second substrate W2 have approximately the same diameter. The second substrate W2 may have electronic circuits formed thereon.

[0021] 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."

[0022] 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."

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] 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 subjecting the bonding surfaces W1j, W2j to plasma processing and modification.

[0030] 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 modify the bonding surfaces W1j and W2j so that they are more likely to be hydrophilized thereafter.

[0031] On the other hand, the surface modification apparatus 30 according to the embodiment generates plasma using a gas containing moisture (for example, water vapor) as the processing gas. When the processing gas containing moisture is converted into plasma, OH radicals and H radicals are generated. The surface modification apparatus 30 can form dangling bonds on the bonding surfaces W1j and W2j using the OH radicals and terminate the dangling bonds with OH groups. Furthermore, the surface modification apparatus 30 according to the embodiment can remove metal oxides formed on the surfaces of metals (for example, Cu wiring) exposed on the bonding surfaces W1j and W2j using the reducing power of the H radicals. The surface modification apparatus 30 will be described in detail later.

[0032] The second processing block G2 is provided with a surface hydrophilizing device 40 and a bonding device 41. The surface hydrophilizing device 40 hydrophilizes the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2, for example, by using pure water, and cleans the bonding surfaces W1j, W2j.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] <Configuration of the surface modification device> Next, the configuration of the surface modification apparatus 30 will be described with reference to Fig. 4. Fig. 4 is a schematic cross-sectional view showing the configuration of the surface modification apparatus 30 according to the embodiment.

[0041] 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.

[0042] 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).

[0043] 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.

[0044] A ring-shaped partition plate 103 with multiple baffle holes is disposed between the stage 80 and the inner wall of the processing vessel 70. The partition plate 103 is also called an exhaust ring. The partition plate 103 separates the interior space of the processing vessel 70 into upper and lower sections, with the mounting portion 91 as the boundary. The partition plate 103 also allows the atmosphere inside the processing vessel 70 to be uniformly exhausted from inside the processing vessel 70.

[0045] 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 voltage is applied to the stage 80 from the high-frequency power supply 106.

[0046] 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 therebetween.

[0047] 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.

[0048] In this manner, a high frequency voltage is applied from the high frequency power supply 106 to the stage 80 serving as the lower electrode, thereby generating plasma inside the processing chamber 70 .

[0049] In the embodiment, the stage 80, the power feed rod 104, the matching box 105, the high-frequency power supply 106, and the upper electrode 110 are an example of a plasma generating unit 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.

[0050] A hollow portion 120 is formed inside the upper electrode 110. A gas supply pipe 121 is connected to the hollow portion 120. A process gas supply unit 122, an inert gas supply unit 123, and a purge gas supply unit 124 are connected to the gas supply pipe 121.

[0051] The process gas supply unit 122 supplies a process gas containing moisture (HO) to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. The process gas containing moisture is, for example, water vapor. The process gas containing moisture may also contain a carrier gas in addition to moisture. Examples of the carrier gas that can be used include an inert gas such as nitrogen gas, argon gas, or helium gas.

[0052] The process gas supply unit 122 includes a process gas supply source 122a, a process gas supply path 122b, a flow rate regulator 122c, and an on-off valve 122d. The process gas supply source 122a supplies a process gas containing moisture (hereinafter, sometimes simply referred to as "process gas"). The process gas supply path 122b is a process gas supply path and connects the process gas supply source 122a to the gas supply pipe 121. The flow rate regulator 122c and the on-off valve 122d are provided in the middle of the process gas supply path 122b. Of these, the flow rate regulator 122c regulates the flow rate of the process gas flowing through the process gas supply path 122b. The on-off valve 122d opens and closes the process gas supply path 122b.

[0053] The processing gas supplied from the processing gas supply source 122 a to the processing gas supply line 122 b is flow-controlled by the flow rate regulator 122 c and the on-off valve 122 d and is supplied to the hollow portion 120 of the upper electrode 110 through the gas supply pipe 121 .

[0054] Here, a configuration example of the processing gas supply source 122a will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a diagram showing an example of the configuration of the processing gas supply source 122a according to an embodiment. Fig. 6 is a diagram showing another example of the configuration of the processing gas supply source 122a according to an embodiment.

[0055] As shown in FIG. 5, the process gas supply source 122a includes a storage section 1221, a carrier gas supply source 1222, and a carrier gas supply path 1223. The storage section 1221 stores water. A process gas supply path 122b is connected to the storage section 1221. The process gas supply path 122b is provided at a position higher than the water surface in the storage section 1221. The storage section 1221 is, for example, a sealed container. The carrier gas supply path 1223 connects the carrier gas supply source 1222 and the storage section 1221. A tip end of the carrier gas supply path 1223 (corresponding to a carrier gas outlet) is provided at a position lower than the water surface in the storage section 1221.

[0056] The process gas supply source 122a configured as described above bubbles the water stored in the storage unit 1221 using the carrier gas supplied from the carrier gas supply source 1222 to the storage unit 1221 via the carrier gas supply path 1223. As a result, a process gas containing moisture and components of the carrier gas is generated inside the storage unit 1221. The process gas generated inside the storage unit 1221 is supplied into the processing vessel 70 via the process gas supply path 122b.

[0057] As shown in FIG. 6, the process gas supply source 122a may include a water supply source 1224, a water supply channel 1225, and a liquid material vaporizer 1226. The water supply source 1224 supplies water. The water supply channel 1225 connects the water supply source 1224 and the liquid material vaporizer 1226. The liquid material vaporizer 1226 directly vaporizes water supplied from the water supply source 1224 via the water supply channel 1225. For example, the liquid material vaporizer 1226 can vaporize water by applying heat to the water supplied from the water supply source 1224 via the water supply channel 1225. Any known technology may be used for the liquid material vaporizer 1226. The process gas supply channel 122b is connected to the liquid material vaporizer 1226.

[0058] The process gas supply source 122a configured as described above directly vaporizes water supplied from the water supply source 1224 via the water supply path 1225 using the liquid material vaporizer 1226. This generates a process gas containing moisture but not carrier gas, and the generated process gas is supplied into the process vessel 70 via the process gas supply path 122b.

[0059] Returning to Fig. 4, the inert gas supply unit 123 supplies an inert gas to the hollow space 120 of the upper electrode 110 via the gas supply pipe 121. As the inert gas, for example, helium gas, argon gas, nitrogen gas, or the like can be used.

[0060] The inert gas supply unit 123 includes an inert gas supply source 123a, an inert gas supply path 123b, a flow rate regulator 123c, and an on-off valve 123d. The inert gas supply source 123a supplies an inert gas. The inert gas supply path 123b is an inert gas supply path that connects the inert gas supply source 123a to the gas supply pipe 121. The flow rate regulator 123c and the on-off valve 123d are provided midway along the inert gas supply path 123b. Of these, the flow rate regulator 123c regulates the flow rate of the inert gas flowing through the inert gas supply path 123b. The on-off valve 123d opens and closes the inert gas supply path 123b.

[0061] The purge gas supply unit 124 supplies a purge gas to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. As the purge gas, for example, an inert gas such as nitrogen gas, helium gas, or argon gas can be used.

[0062] It is preferable that the inert gas (first inert gas) supplied from the inert gas supply unit 123 has a mass smaller than that of the inert gas (second inert gas) supplied from the purge gas supply unit 124. This will be described later. Here, helium gas is used as the first inert gas, and nitrogen gas is used as the second inert gas.

[0063] The purge gas supply unit 124 includes a purge gas supply source 124a, a purge gas supply path 124b, a flow rate regulator 124c, and an on-off valve 124d. The purge gas supply source 124a supplies purge gas. The purge gas supply path 124b is a purge gas supply path that connects the purge gas supply source 124a to the gas supply pipe 121. The flow rate regulator 124c and the on-off valve 124d are provided in the middle of the purge gas supply path 124b. Of these, the flow rate regulator 124c regulates the flow rate of the purge gas flowing through the purge gas supply path 124b. The on-off valve 124d opens and closes the purge gas supply path 124b.

[0064] The inert gas supplied from the inert gas supply source 123 a to the inert gas supply path 123 b is flow-controlled by the flow regulator 123 c and the on-off valve 123 d and is supplied to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121 .

[0065] A baffle plate 126 for promoting uniform diffusion of the process gas and the inert gas is provided inside the hollow portion 120. A number of small holes are provided in the baffle plate 126. A number of gas outlets 125 are formed on the lower surface of the upper electrode 110 to eject the process gas and the inert gas from the hollow portion 120 into the process vessel 70.

[0066] The processing vessel 70 is formed with an intake port 130. The intake port 130 is connected to an intake pipe 132 that communicates with a vacuum pump 131 that reduces the atmosphere inside the processing vessel 70 to a given vacuum level. An APC (Auto Pressure Controller) valve 133 is provided on the intake pipe 132. The inside of the processing vessel 70 is evacuated by the vacuum pump 131, and the pressure inside the processing vessel 70 is maintained at a given pressure by adjusting the opening of the APC valve 133.

[0067] A spectrophotometer 141 capable of measuring light emission data of each wavelength within the processing vessel 70 is attached to the processing vessel 70. Specifically, the spectrophotometer 141 is attached to the processing vessel 70, positioned above the mounting portion 91 and below the gas outlet 125. The spectrophotometer 141 is, for example, an OES (Optical Emission Spectroscopy) sensor, and measures the light emission state of plasma generated within the processing vessel 70. The spectrophotometer 141 may be a self-biased OES sensor that generates plasma within its own chamber and measures the light emission state of the plasma. The spectrophotometer 141 outputs the measured light emission data to the control unit 5 of the control device 4.

[0068] Furthermore, a mass spectrometer 142 capable of analyzing the atmosphere in the processing vessel 70 with respect to the mass number of a specific substance is attached to the processing vessel 70. Specifically, the mass spectrometer 142 is attached to the processing vessel 70 and disposed below the partition plate 103. The mass spectrometer 142 is, for example, a quadrupole mass spectrometer (QMS), and measures an analytical value obtained by analyzing the atmosphere in the processing vessel 70 with respect to the mass number of a specific substance. The mass spectrometer 142 outputs the measured analytical value to the control unit 5 of the control device 4. By disposing the mass spectrometer 142 below the partition plate 103, it is possible to prevent the mass spectrometer 142 from being damaged by plasma.

[0069] <Configuration of the joining device> Next, the configuration of the joining device 41 will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a schematic plan view showing the configuration of the joining device 41 according to the embodiment, and Fig. 8 is a schematic side view showing the configuration of the joining device 41 according to the embodiment.

[0070] 7, 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 8, 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] Next, the configuration of the upper chuck 230 and the lower chuck 231 will be described with reference to Fig. 9. Fig. 9 is a schematic diagram showing the upper chuck 230 and the lower chuck 231 according to the embodiment.

[0089] 9, 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] A plurality of pins 291 that come into contact with the lower surface (non-bonding surface Wn2) 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.

[0100] 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.

[0101] 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).

[0102] 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.

[0103] 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.

[0104] <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. 10. Fig. 10 is a flowchart showing the procedure of processing executed by the bonding system 1 according to the embodiment. The various processing shown in Fig. 10 is executed based on the control by the control unit 5 of the control device 4.

[0105] 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.

[0106] Next, the upper wafer W1 is transferred to the surface modification device 30 in the first processing block G1 by the transfer device 61. In the surface modification device 30, the bonding surface W1j of the upper wafer W1 is subjected to surface modification (step S101). This will be described later.

[0107] 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 S102).

[0108] 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 S103).

[0109] 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 S104). Specifically, the bonding surface W1j of the upper wafer W1 faces downward.

[0110] 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 S105).

[0111] The processing of the lower wafer W2 overlaps with the processing of steps S101 to S105 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.

[0112] 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 S106), as will be described later.

[0113] 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 S107).

[0114] 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 S108).

[0115] 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 S109).

[0116] 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 S110).

[0117] 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 S111). 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.

[0118] Next, after the suction and holding of the upper wafer W1 by the multiple inner suction portions 392 is released (step S112), the pressing pin 281 of the striker 280 is lowered to press down the center of the upper wafer W1 (step S113).

[0119] 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.

[0120] 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 portions 391 (step S114). This causes the outer periphery of the upper wafer W1, which had been suction-held by the outer suction portions 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.

[0121] 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.

[0122] Next, the surface modification process in steps S101 and S106 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of the procedure of the surface modification process according to the embodiment.

[0123] As shown in FIG. 11, in the embodiment, the surface modification apparatus 30 executes a carry-in step (step S201), an activation step (step S202), a reduction step (step S203), an unloading step (step S204), and a waiting step (step S205) in this order.

[0124] The loading step (step S201) is a step of loading the wafer W into the surface modification apparatus 30. The activation step is a step mainly for modifying the bonding surfaces W1j, W2j of the wafer W. The reduction step is a step mainly for removing metal oxide formed on the surface of metal (for example, metal wiring such as Cu wiring) when the metal is exposed on the bonding surfaces W1j, W2j. The unloading step is a step of unloading the wafer W from the surface modification apparatus 30. The waiting step is a step performed during the waiting time after unloading the wafer W from the surface modification apparatus 30 until the loading step for the next wafer W into the surface modification apparatus 30 begins.

[0125] As a result of extensive research, the inventors of the present invention have found that the ratio of OH radicals to H radicals in plasma can be controlled by changing the conditions for generating plasma using a processing gas containing moisture.

[0126] 12 and 13 are graphs showing the measurement results of the emission intensity of OH radicals and H radicals in water vapor plasma. Each of these graphs shows emission data measured by the spectrophotometer 141 when water vapor plasma is generated in the processing vessel 70. In the graphs shown in FIGS. 12 and 13, the peaks observed near 310 nm indicate the emission intensity due to OH radicals, and the peaks observed near 650 nm indicate the emission intensity due to H radicals.

[0127] 12 shows the measurement results of the emission intensity of OH radicals and H radicals when the flow rate of the processing gas (water vapor) among the water vapor plasma generation conditions is changed. Specifically, of the two graphs shown in FIG. 12, the upper graph shows the measurement results when water vapor plasma is generated under the generation conditions of the power of the high-frequency power supply 106 of "100 W," the internal pressure of the processing vessel 70 of "10 Pa," and the flow rate of the processing gas (water vapor) of "50 sccm." Also, of the two graphs shown in FIG. 12, the lower graph shows the measurement results when water vapor plasma is generated under the generation conditions of the power of the high-frequency power supply 106 of "100 W," the internal pressure of the processing vessel 70 of "10 Pa," and the flow rate of the processing gas (water vapor) of "400 sccm." The internal pressure of the processing vessel 70 can be controlled by the APC valve 133 (see FIG. 4).

[0128] As shown in Figure 12, when water vapor plasma was generated under low flow conditions (top panel of Figure 12), the ratio of H radicals to OH radicals was found to be higher compared to when water vapor plasma was generated under high flow conditions (bottom panel of Figure 12).One reason for this is thought to be that, for example, gas molecules stay for a longer time under low flow conditions compared to high flow conditions, which increases the opportunities for electron collisions (ionization) of OH radicals, promoting the dissociation of OH radicals and resulting in a relative increase in the emission intensity of H radicals.

[0129] Fig. 13 shows measurement results of the emission intensity of OH radicals and H radicals when the internal pressure of the processing vessel 70, which is one of the water vapor plasma generation conditions, is changed. Specifically, of the two graphs shown in Fig. 13, the upper graph shows measurement results when water vapor plasma is generated under the following generation conditions: power of the high frequency power supply 106: "100 W," internal pressure of the processing vessel 70: "10 Pa," and flow rate of the processing gas (water vapor): "200 sccm." Also, of the two graphs shown in Fig. 13, the lower graph shows measurement results when water vapor plasma is generated under the following generation conditions: power of the high frequency power supply 106: "100 W," internal pressure of the processing vessel 70: "52 Pa," and flow rate of the processing gas (water vapor): "200 sccm.

[0130] As shown in Figure 13, when water vapor plasma is generated under low pressure conditions (top panel of Figure 13), the ratio of H radicals to OH radicals is found to be higher compared to when water vapor plasma is generated under high pressure conditions (bottom panel of Figure 13).One reason for this is thought to be that, for example, under low pressure conditions, the residence time of gas molecules is longer than under high flow rate conditions, which increases the opportunities for electron collisions (ionization) of OH radicals, promoting the dissociation of OH radicals and resulting in a relative increase in the emission intensity of H radicals.

[0131] In this way, the ratio of OH radicals to H radicals in the water vapor plasma can be changed by changing the conditions for generating the water vapor plasma. Specifically, the ratio of H radicals to OH radicals can be increased by relatively decreasing the flow rate of the processing gas (water vapor) or relatively decreasing the internal pressure of the processing vessel 70.

[0132] The inventors of the present application also measured the emission intensity of OH radicals and H radicals when the power of the high-frequency power supply 106, one of the conditions for generating water vapor plasma, was changed. The results showed that the ratio of H radicals to OH radicals was higher when water vapor plasma was generated under high-power conditions (800 W) than when water vapor plasma was generated under low-power conditions (100 W). One possible reason for this is that, for example, electrons store more energy under high-power conditions than under low-power conditions, which promotes dissociation of OH radicals, resulting in a relative increase in the emission intensity of H radicals. Thus, the ratio of H radicals to OH radicals can also be increased by relatively increasing the power of the high-frequency power supply 106.

[0133] FIG. 14 is a timing chart showing the operation of each part in the surface modification process according to the embodiment.

[0134] 14, in a standby step before the start of the loading step, the controller 5 opens the on-off valve 124d of the purge gas supply unit 124 to supply a purge gas (here, nitrogen gas) into the processing vessel 70. In addition, in the standby step, the controller 5 opens the APC valve 133 to exhaust the purge gas, which has been supplied from the purge gas supply unit 124 to the processing vessel 70, from the processing vessel 70. At this time, the controller 5 adjusts the internal pressure of the processing vessel 70 to a predetermined pressure (first pressure) by adjusting the aperture of the APC valve 133 to a first aperture.

[0135] Next, in the loading step, the controller 5 first raises the lifter pins (not shown in FIG. 4 ) from the stage 80 at time T11, and then opens the gate valve 72 at time T12, a predetermined time after time T11. The controller 5 then advances the transfer arm of the transfer device 61 into the processing chamber 70 and transfers the upper wafer W1 held on the transfer arm to the lifter pins. The controller 5 then closes the gate valve 72 and lowers the lifter pins to place the wafer W on the stage 80 at time T13, when the transfer arm of the transfer device 61 retracts from the processing chamber 70. The controller 5 then adjusts the aperture of the APC valve 133 from the initial first aperture to the fully open position at time T14, a predetermined time after time T13, thereby evacuating the processing chamber 70. This adjusts the internal pressure of the processing chamber 70 from the initial first pressure to a pressure lower than the first pressure.

[0136] Next, the control unit 5 performs an activation step. First, as a pre-treatment for the activation step, at time T15, which is a predetermined time after time T14, the control unit 5 stops the supply of purge gas from the purge gas supply unit 124 and starts the supply of process gas from the process gas supply unit 122. As a result, the atmosphere inside the process container 70 is switched from the purge gas (here, nitrogen gas) to a process gas containing moisture (here, water vapor).

[0137] At this time, the control unit 5 supplies the processing gas at a first flow rate into the processing chamber 70. As an example, the first flow rate is equal to or greater than 300 sccm and equal to or less than 500 sccm.

[0138] At time T16, a predetermined time after time T15, the controller 5 adjusts the aperture of the APC valve 133 from fully open to a second aperture smaller than the first aperture. This adjusts the internal pressure of the processing vessel 70 to the second pressure higher than the first pressure. For example, the second pressure is 20 Pa or more and 40 Pa or less.

[0139] Next, the control unit 5 performs the main activation process. Specifically, at time T17, which is a predetermined time after time T16, the control unit 5 controls the high-frequency power supply 106 to apply a high-frequency voltage to the stage 80, thereby generating plasma of the moisture-containing processing gas (here, water vapor) inside the processing vessel 70.

[0140] In the main activation step, the flow rate of the processing gas (water vapor) is set higher than in the main reduction step described below. Also, in the main activation step, the internal pressure of the processing vessel 70 is set higher than in the main reduction step.

[0141] By generating water vapor plasma under these conditions, the ratio of H radicals to OH radicals is smaller in the main activation step than in the main reduction step; in other words, the amount of OH radicals generated is greater. As a result, in the activation step, oxidation of silicon by OH radicals and Si-OH are promoted at the bonding surfaces W1j and W2j of the wafers W. That is, dangling bonds are formed by removing terminating groups at the bonding surfaces W1j and W2j, and the dangling bonds can be terminated with OH groups.

[0142] Next, as a pretreatment for the reduction step, the control unit 5 stops the application of the high-frequency voltage at time T18, a predetermined time after time T17. At time T18, the control unit 5 also changes the flow rate of the process gas (water vapor) from the first flow rate to a second flow rate that is lower than the first flow rate. For example, the second flow rate is 10 sccm or more and 100 sccm or less. The control unit 5 also changes the aperture of the APC valve 133 from the second aperture to a third aperture that is higher than the first and second apertures. By changing the aperture of the APC valve 133 to the third aperture, the internal pressure of the process chamber 70 is adjusted from the second pressure to a third pressure that is lower than the second pressure. For example, the third pressure is 5 Pa or more and 15 Pa or less.

[0143] In this way, in the reduction step, water vapor plasma is generated under lower flow rate and pressure conditions than in the activation step, resulting in a greater amount of H radicals being generated in the reduction step than in the activation step.

[0144] Furthermore, at time T18, the control unit 5 starts supplying an inert gas (here, helium gas) from the inert gas supply unit 123 into the processing vessel 70. The flow rate of the inert gas is a third flow rate that is lower than the first flow rate and the second flow rate. As an example, the third flow rate is equal to or greater than 5 sccm and equal to or less than 20 sccm.

[0145] In this way, in the reduction step, by supplying a type of gas (helium gas in this case) different from the water vapor processing gas into the processing vessel 70, the ionization of OH radicals is promoted by the Penning effect, and as a result, more H radicals can be generated. In addition, by using helium gas, which has a relatively small mass, as the inert gas to be mixed with the water vapor, damage to the wafer W can be minimized.

[0146] Next, the control unit 5 performs the main process of the reduction step. Specifically, at time T19, which is a predetermined time after time T18, the control unit 5 controls the high-frequency power supply 106 to apply a high-frequency voltage to the stage 80, thereby generating water vapor plasma inside the processing vessel 70.

[0147] In the activation step described above, a relatively large number of OH radicals are generated, which easily oxidizes metal (e.g., Cu wiring) exposed on the bonding surfaces W1j and W2j of the wafers W. When the upper wafer W1 with the deteriorated condition of the bonding surface W1j is bonded to the lower wafer W2 with the deteriorated condition of the bonding surface W2j, the bonding quality of the overlapped wafer T may deteriorate.

[0148] In contrast, in the main treatment of the reduction step, the ratio of H radicals to OH radicals in the water vapor plasma is higher than in the main treatment of the activation step. Therefore, in the reduction step, the reduction of metal oxides formed on the metal surfaces exposed at the bonding surfaces W1j, W2j by H radicals is promoted. That is, in the reduction step, metal oxides can be removed from the metal surfaces exposed at the bonding surfaces W1j, W2j, and by removing the metal oxides, the bonding quality of the laminated wafer T can be improved.

[0149] Next, after completing the main processing of the reduction step, the control unit 5 performs the unloading step. Specifically, the control unit 5 stops the application of the high-frequency voltage at time T20, a predetermined time after time T19. Also, at time T20, the control unit 5 stops the supply of the inert gas and the process gas and starts the supply of the purge gas. Also, the control unit 5 raises the lifter pin from the stage 80 and adjusts the aperture of the APC valve 133 from the third aperture to fully open.

[0150] Next, at time T21, a predetermined time after time T20, the control unit 5 opens the gate valve 72, and at time T22, a predetermined time after time T21, adjusts the aperture of the APC valve 133 from fully open to the first aperture, thereby returning the pressure inside the processing vessel 70 to the initial pressure. In this state, the control unit 5 advances the transfer arm of the transfer device 61 into the processing vessel 70 and hands over the modified wafer W placed above the stage 80 to the transfer arm. Thereafter, the control unit 5 transfers the modified wafer W to the surface hydrophilization device 40 using the transfer device 61.

[0151] Next, at time T23, when a predetermined time has elapsed since time T22, the control unit 5 closes the gate valve 72 and lowers the lifter pins. After that, at time T24, the control unit 5 transitions from the carry-out step to the standby step.

[0152] However, when nitrogen gas is used as the processing gas, for example, increasing the power (high frequency voltage) of the high frequency power supply tends to decrease the bonding strength. Thus, in conventional surface modification devices that use nitrogen gas as the processing gas, the relatively narrow process window (optimum range) of the high frequency voltage has been an issue in improving the bonding quality of the polymerized wafer T.

[0153] In response to this, the present inventors have discovered that when a surface modification process is performed using a moisture-containing process gas (water vapor), the bonding strength is less likely to decrease even when the high-frequency voltage is increased, compared to when nitrogen gas is used. That is, the present inventors have discovered that performing a surface modification process using a moisture-containing process gas (water vapor) widens the process window (optimal range) of the high-frequency voltage. In this way, using a moisture-containing process gas (water vapor) improves the ease of control of the surface modification process compared to when nitrogen gas is used, thereby stabilizing the bonding quality of the polymerized wafer T. In other words, the bonding quality of the polymerized wafer T can be improved.

[0154] Furthermore, by performing the surface modification process using a process gas containing moisture (water vapor), OH groups can be formed even on wafers that do not have O on the bonding surfaces W1j and W2j, for example, wafers that have silicon carbonitride layers (SiCN layers) on the bonding surfaces W1j and W2j.

[0155] (Variation) 15 is a timing chart showing the operation of each part in the surface modification process according to the modified example. As shown in FIG. 15, the control unit 5 may perform a humidity adjustment step of adjusting the amount of moisture inside the process container 70 before starting the activation step and the reduction step.

[0156] As a result of extensive research, the inventors of the present application have found that adjusting the amount of moisture in the processing vessel 70 of the surface modification apparatus 30 promotes the formation of dangling bonds on the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2. Therefore, the control unit 5 may adjust the amount of moisture in the processing vessel 70 by supplying a processing gas containing moisture (water vapor) as a humidified gas into the processing vessel 70 instead of a purge gas during the waiting step and the loading step.

[0157] In the example shown in Figure 15, water vapor is supplied at a constant flow rate (fourth flow rate) in the humidity adjustment step, but the control unit 5 may also change the flow rate of water vapor as a humidifying gas depending on the amount of moisture in the processing container 70.

[0158] Specifically, when supplying the humidified gas into the processing vessel 70, the control unit 5 can measure a value indicating the amount of moisture in the processing vessel 70 using, for example, the mass spectrometer 142. In this case, the control unit 5 may control the flow rate or moisture content of the water vapor as the humidified gas based on the measured value indicating the amount of moisture in the processing vessel 70.

[0159] For example, when the surface modification of the wafers W is repeatedly performed a predetermined number of times in the processing chamber 70, the amount of moisture in the processing chamber 70 gradually decreases due to evacuation.

[0160] The controller 5 measures the analysis value measured by the mass spectrometer 142 as a value indicating the amount of moisture in the processing vessel 70. The controller 5 then controls the flow rate or moisture content of the humidified gas based on the measured analysis value. As the amount of moisture in the processing vessel 70 decreases, the analysis value of the mass spectrometer 142 decreases. For example, the controller 5 determines whether the amount of moisture in the processing vessel 70 has fallen below a specified lower limit by determining whether the measured analysis value is equal to or less than a predetermined threshold. If the controller 5 determines that the amount of moisture in the processing vessel 70 has fallen below the specified lower limit, the controller 5 controls the processing gas supply unit 122 to increase the flow rate or moisture content of the humidified gas. This allows the controller 5 to appropriately adjust the amount of moisture in the processing vessel 70.

[0161] Below, we will explain why modifying the bonding surfaces W1j, W2j of the wafers W while the moisture content in the processing container 70 is adjusted suppresses a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 to be bonded.

[0162] That is, in this embodiment, prior to modifying the upper wafer W1, a humidified gas is supplied into the processing vessel 70 capable of accommodating the upper wafer W1, thereby adjusting the moisture content within the processing vessel 70. This increases the moisture content within the processing vessel 70, creating a state in which a large amount of moisture (H2O) exists near the bonding surface W1j of the upper wafer W1.

[0163] In this state, the upper wafer W1 is subjected to a surface modification process using plasma of nitrogen gas, which is a process gas. During this process, the energy of the nitrogen ions of the first excitation level, which have a relatively low activity level, is transferred to water (HO) present near the bonding surface W1j.

[0164] As a result, nitrogen ions of the first excitation level disappear from the processing vessel 70, while the proportion of nitrogen ions of the second excitation level, which have higher activity than nitrogen ions of the first excitation level, increases. As a result, while suppressing nitridation by nitrogen ions of the first excitation level, nitrogen ions of the second excitation level, which have relatively higher activity, can be irradiated onto the bonding surface W1j, thereby promoting the formation of dangling bonds of silicon atoms on the outermost surface of the bonding surface W1j. On the other hand, since nitridation by nitrogen ions of the first excitation level is suppressed on the outermost surface of the bonding surface W1j, the generation of nitrided portions is reduced.

[0165] In this state, when the upper wafer W1 is carried out from the surface modification apparatus 30 and exposed to the air atmosphere, the dangling bonds of the silicon atoms are terminated with OH groups due to moisture (H2O) in the air.

[0166] Here, since the generation of nitrided portions is reduced on the outermost surface of the joining surface W1j, the formation of OH groups is not inhibited by such nitrided portions.

[0167] Next, the upper wafer W1 and the lower wafer W2 carried out from the surface modification apparatus 30 undergo hydrophilization treatment of the bonding surfaces W1j, W2j in the surface hydrophilization apparatus 40, and are then bonded in the bonding apparatus 41. In this bonding treatment, bonding is formed from the center of the wafer W toward the edge by hydrogen bonding between the OH groups on the bonding surface W1j and the OH groups on the bonding surface W2j.

[0168] In this embodiment, the generation of nitrided portions on the outermost surface of the bonding surface W1j is reduced, so that the above-mentioned bonding due to OH groups is not hindered by such nitrided portions. That is, in this embodiment, the generation of nitrided portions that hinder the formation of Si-O-Si bonds originating from OH groups can be suppressed by adjusting the amount of moisture in the processing vessel 70. Therefore, according to this embodiment, it is possible to suppress a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 to be bonded.

[0169] In the above-described embodiment, an example in which the activation step and the reduction step are performed in this order has been described, but the control unit 5 may reverse the order of the activation step and the reduction step. That is, the control unit 5 may perform the reduction step and the activation step in this order.

[0170] Although the above-described embodiment describes an example in which both the activation step and the reduction step are performed, the control unit 5 may perform only one of the activation step and the reduction step. For example, for a wafer W in which no metal is exposed on the bonding surfaces W1j, W2j, only the activation step may be performed without performing the reduction step.

[0171] In the above-described embodiment, an example has been described in which the surface modification treatment is performed in the surface modification apparatus 30, and then the surface hydrophilization treatment is performed in the surface hydrophilization apparatus 40. However, according to the surface modification apparatus 30 according to the embodiment, OH groups can be formed on the bonding surfaces W1j, W2j in the activation step. Therefore, the control unit 5 may omit the surface hydrophilization treatment depending on the type of wafer W, for example.

[0172] In the above-described embodiment, an example in which water vapor is used as the moisture-containing process gas has been described, but the moisture-containing process gas is not limited to water vapor and may be, for example, ammonia gas, hydrogen gas, etc. However, from the viewpoint of ease of management and cost, it is preferable that the moisture-containing process gas be water vapor.

[0173] In the above-described embodiment, an example in which a process gas containing moisture is used in both the activation step and the reduction step has been described. However, the present invention is not limited to this. For example, the control unit 5 may use a process gas other than the process gas containing moisture (for example, an inert gas such as nitrogen gas) in the activation step, and may use a process gas containing moisture in the reduction step.

[0174] In the above-described embodiment, the method for controlling the generation ratio of OH radicals and H radicals includes changing the flow rate of the processing gas, changing the internal pressure of the processing vessel, and supplying an inert gas. However, the present invention is not limited to this, and the control unit 5 may perform at least one of changing the flow rate of the processing gas, changing the internal pressure of the processing vessel, and supplying an inert gas.

[0175] <Effects> As described above, the bonding system according to the embodiment includes a surface modification device (for example, the surface modification device 30) and a bonding device (for example, the bonding device 41). The surface modification device modifies bonding surfaces (for example, bonding surfaces W1j and W2j) of substrates (for example, the upper wafer W1 and the lower wafer W2) to be bonded to other substrates (for example, the upper wafer W1 and the lower wafer W2) using plasma of a processing gas. The bonding device bonds the two substrates modified by the surface modification device using intermolecular forces. The surface modification device also includes a processing vessel (for example, the processing vessel 70) capable of accommodating the substrates, a processing gas supply unit (for example, the processing gas supply unit 122) that supplies a processing gas containing moisture (for example, water vapor) into the processing vessel, and a plasma generation unit (for example, the stage 80, the power feed rod 104, the matching box 105, the high-frequency power supply 106, and the upper electrode 110) that generates plasma of the processing gas containing moisture.

[0176] As a result, by supplying a processing gas containing moisture into the processing vessel, a decrease in the amount of moisture inside the processing vessel is suppressed. This makes it possible to suppress a decrease in bonding strength that would otherwise be caused by a decrease in the amount of moisture. Therefore, the bonding system according to the embodiment can improve the bonding quality of the laminated substrates.

[0177] The plasma generating unit generates OH radicals and H radicals by converting a moisture-containing processing gas into plasma. For example, if a metal (such as Cu wiring) is exposed on the bonding surface, the metal oxide formed on the surface of the metal can be removed by the reducing power of the H radicals. This improves the condition of the bonding surfaces W1j and W2j, thereby improving the bonding quality of the laminated substrates. Furthermore, the OH radicals can promote the oxidation of silicon and Si-OH formation.

[0178] The surface modification apparatus includes an inert gas supply unit (for example, inert gas supply unit 123) that supplies an inert gas into the inside of the processing vessel, and an on-off valve (for example, on-off valve 123d) provided in a supply path (for example, inert gas supply path 123b) of the inert gas from the inert gas supply unit to the inside of the processing vessel. This makes it possible, for example, to supply the inert gas together with the processing gas containing moisture into the inside of the processing vessel during the surface modification process, or to stop the supply of the inert gas and supply only the processing gas containing moisture into the inside of the processing vessel.

[0179] The bonding system according to the embodiment includes a control unit (for example, a control unit 5) that controls the surface modification apparatus. The control unit causes the surface modification apparatus to perform an activation step in which a moisture-containing processing gas is supplied into a processing vessel and a substrate is processed using plasma of the moisture-containing processing gas, and a reduction step in which a moisture-containing processing gas and an inert gas are supplied into the processing vessel and a substrate is processed using plasma of the moisture-containing processing gas and the inert gas. As a result, for example, in the activation step, oxidation of silicon and Si—OH by OH radicals can be promoted, and in the reduction step, metal oxide formed on the surface of the metal exposed to the bonding surface can be removed by H radicals.

[0180] The control unit supplies the moisture-containing process gas at a first flow rate in the activation step, and supplies the moisture-containing process gas at a second flow rate lower than the first flow rate and the inert gas at a third flow rate lower than the first flow rate in the reduction step. This makes it possible to reduce the ratio of H radicals to OH radicals in the activation step compared to the same ratio in the reduction step. That is, the amount of OH radicals generated can be increased in the activation step, and the amount of H radicals generated can be increased in the reduction step.

[0181] A bonding system according to an embodiment includes a control unit for controlling a surface modification apparatus. The control unit controls the surface modification apparatus to perform an activation step in which a moisture-containing process gas is supplied into a process chamber at a first flow rate and a substrate is processed using plasma of the moisture-containing process gas, and a reduction step in which a moisture-containing process gas is supplied into the process chamber at a second flow rate lower than the first flow rate and a substrate is processed using plasma of the moisture-containing process gas. This allows, for example, the activation step to promote oxidation of silicon and Si—OH by OH radicals, and the reduction step to remove metal oxide formed on the surface of the metal exposed to the bonding surface by H radicals.

[0182] The control unit causes the reduction step to be performed after the activation step, thereby making it possible to remove metal oxide formed on the surface of the metal exposed to the joining surface in the activation step in the reduction step, for example.

[0183] The inert gas is helium gas, which minimizes damage to the substrate.

[0184] The control unit controls the surface modification device to perform a humidity control step of adjusting the moisture content inside the processing vessel by supplying a moisture-containing processing gas into the processing vessel before starting the activation step and the reduction step, thereby preventing the plasma state in the activation step and the reduction step from varying depending on the moisture content inside the processing vessel.

[0185] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0186] For example, in the above embodiment, examples have been shown in which the plasma P of the processing gas is generated using an SWP type, an ICP type, and an ECR type plasma generation apparatus. However, the plasma generation apparatus according to the embodiment is not limited to these types, and any type of plasma generation apparatus may be used as long as it can generate the plasma P of the processing gas using microwaves M.

[0187] 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]

[0188] 1; Joint system 2. Loading / unloading station 3. Processing station 4. Control device 5; Control unit 6;Memory section 30: Surface modification equipment 40;Surface hydrophilization device 41;Joining equipment 50;Transition device 70; Processing container 72; Gate valve 80;Stage 106;High frequency power supply 110;Top electrode 120;Hollow part 121: Gas supply pipe 122: Processing gas supply unit 123: Inert gas supply unit 124: Purge gas supply unit 133;APC valve 141;Spectrophotometer 142;Mass spectrometer 230; Upper chuck 231; Lower chuck 280;Striker 1221; Storage section 1222: Carrier gas supply source 1223: Carrier gas supply line 1224; water supply source 1225;Water supply channel 1226: Liquid material vaporizer

Claims

1. a surface modification device that modifies a bonding surface of a substrate to be bonded to another substrate by plasma of a processing gas; a bonding device that bonds the two substrates modified by the surface modification device together by intermolecular forces; a control unit for controlling the surface modification device; Equipped with The surface modification device includes: a processing vessel capable of accommodating the substrate; a processing gas supply unit that supplies a processing gas containing moisture into the processing vessel; a plasma generating unit that generates plasma of the processing gas containing moisture; an inert gas supply unit that supplies an inert gas into the processing chamber; an on-off valve provided on a supply path of the inert gas from the inert gas supply unit to the inside of the processing vessel; Equipped with The control unit a surface modification device that performs an activation step of supplying the moisture-containing processing gas into the processing vessel and processing the substrate using plasma of the moisture-containing processing gas, and a reduction step of supplying the moisture-containing processing gas and the inert gas into the processing vessel and processing the substrate using plasma of the moisture-containing processing gas and the inert gas, wherein in the activation step, the moisture-containing processing gas is supplied at a first flow rate, and in the reduction step, the moisture-containing processing gas is supplied at a second flow rate that is lower than the first flow rate, and the inert gas is supplied at a third flow rate that is lower than the first flow rate.

2. The bonding system according to claim 1 , wherein the plasma generating unit generates OH radicals and H radicals by converting the processing gas containing moisture into plasma.

3. The bonding system according to claim 1 or 2, wherein the control unit causes the reduction step to be performed after the activation step.

4. 4. The bonding system according to claim 1, wherein the inert gas is helium gas.

5. The control unit The bonding system according to any one of claims 1 to 4, wherein, before starting the activation step and the reduction step, the surface modification device executes a humidity control step of adjusting the amount of moisture inside the processing vessel by supplying a processing gas containing the moisture into the processing vessel.

6. A surface modification method for modifying a bonding surface of a substrate to be bonded to another substrate, comprising the steps of: a supply step of supplying a processing gas containing moisture into the processing vessel containing the substrate; a generating step of generating plasma of the moisture-containing processing gas inside the processing vessel; Including, The generating step includes: an activation step of supplying the moisture-containing processing gas into the processing chamber and processing the substrate using plasma of the moisture-containing processing gas; a reduction step of supplying the moisture-containing processing gas and an inert gas into the processing chamber and processing the substrate using plasma of the moisture-containing processing gas and the inert gas; Including, the activation step includes supplying the moisture-containing processing gas at a first flow rate, and the reduction step includes supplying the moisture-containing processing gas at a second flow rate that is less than the first flow rate and supplying the inert gas at a third flow rate that is less than the first flow rate.

7. 7. The surface modification method according to claim 6, wherein the generating step generates OH radicals and H radicals by converting the processing gas containing moisture into plasma.

8. The generating step includes: The surface modification method according to claim 6 or 7, wherein the reduction step is carried out after the activation step.

9. 9. The surface modification method according to claim 6, wherein the inert gas is helium gas.

10. a humidity control step of adjusting the amount of moisture inside the processing vessel by supplying the processing gas containing the moisture into the processing vessel before the generation step; The surface modification method according to any one of claims 6 to 9, comprising:

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