Surface modification method and surface modification device

Abstract

This surface modification method modifies, by means of plasma of a treatment gas, a joining surface of a substrate at which the substrate joins to another substrate, the surface modification method including an adjustment step and a modification step. In the adjustment step, the water content in a treatment container that can accommodate the substrate is adjusted by supplying a humidified gas to the inside of the treatment container. In the modification step, the joining surface of the substrate is modified by generating plasma of the treatment gas in the treatment container in a state in which the water content inside the treatment container has been adjusted.

Description

[Technical Field]

[0001] The present disclosure relates to a surface modification method and a surface modification apparatus. [Background technology]

[0002] Conventionally, a known method for bonding substrates such as semiconductor wafers together 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).

[0003] The surface modification of the substrate is performed using a surface modification apparatus, which accommodates the substrate in a processing chamber and modifies the surface of the accommodated substrate with plasma of a processing gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 084285 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can suppress a decrease in the bonding strength between bonded substrates. [Means for solving the problem]

[0006] A surface modification method according to one aspect of the present disclosure is a surface modification method for modifying a bonding surface of a substrate to be bonded to another substrate by using plasma of a processing gas, and includes an adjusting step and a modifying step. The adjusting step adjusts the moisture content in the processing vessel by supplying a humidified gas into a processing vessel capable of accommodating the substrate. The modifying step modifies the bonding surface of the substrate by generating plasma of the processing gas in the processing vessel with the moisture content adjusted in the processing vessel. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to suppress a decrease in the bonding strength between the bonded substrates. [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 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 timing chart showing the operation of each part when modifying the bonding surfaces of the upper wafer and the lower wafer in the bonding process according to the embodiment. [Figure 10] FIG. 10 is a diagram for explaining an example of a measurement result of the amount of water in the processing container. [Figure 11] FIG. 11 is a diagram for explaining an example of a measurement result of the amount of water in the processing container. [Figure 12] FIG. 12 is a diagram for explaining another example of the measurement results of the water amount in the processing container. [Figure 13] FIG. 13 is a timing chart showing the operation of each part when modifying the bonding surfaces of the upper wafer and the lower wafer in the bonding process according to the first modification of the embodiment. [Figure 14] FIG. 14 is a timing chart showing the operation of each part when modifying the bonding surfaces of the upper wafer and the lower wafer in the bonding process according to the second modification of the embodiment. [Figure 15] FIG. 15 is a flowchart showing an example of the process flow of a reforming execution possibility determination method according to the third modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the surface modification method and surface modification device disclosed herein will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to the following embodiments. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Furthermore, the drawings may include parts with different dimensional relationships and ratios.

[0010] 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 other processes. 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, resulting in insufficient surface modification of the substrate. 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 is undesirable because it can cause problems such as substrate peeling. Therefore, a technology that can suppress the decrease in bonding strength between bonded substrates is desired.

[0011] <Configuration of the joining system> First, the configuration of a bonding system 1 according to an embodiment will be described with reference to FIGS. 1 to 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. Note that, for ease of understanding, the drawings referred to below may show an orthogonal coordinate system in which the vertically upward direction is the positive direction of the Z axis.

[0012] 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.

[0013] 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.

[0014] 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."

[0015] 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."

[0016] 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.

[0017] 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 an overlapped wafer T.

[0018] 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.

[0019] 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 overlapping wafer T between the cassettes C1 to C3 placed on the mounting plate 11 and a third processing block G3 of the processing station 3, which will be described later.

[0020] 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.

[0021] 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).

[0022] 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 with plasma of a processing gas. The surface modification device 30 forms dangling bonds on the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2 by irradiating them with plasma, thereby modifying the bonding surfaces W1j, W2j so that they are more likely to be subsequently hydrophilized.

[0023] In the surface modification apparatus 30, for example, a given process gas is excited to generate plasma and ionized in a reduced pressure atmosphere. Then, ions of elements contained in the process 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. Details of the surface modification apparatus 30 will be described later.

[0024] The second processing block G2 is provided with a surface hydrophilization device 40 and a bonding device 41. The surface hydrophilization 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.

[0025] 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 being 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The transfer device 61 moves within the transfer region 60 and transfers the upper wafer W1, the lower wafer W2, and the overlapping 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.

[0030] 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.

[0031] 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.

[0032] <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.

[0033] 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 facing the transfer region 60 (see FIG. 1), and a gate valve 72 is provided at the loading / unloading port 71.

[0034] 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).

[0035] 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 that 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.

[0036] 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.

[0037] A power feed rod 104 made of a conductor is connected to the underside of the stage 80. A first high-frequency power supply 106 is connected to the power feed rod 104 via a matching box 105, which may be a blocking capacitor or the like. During plasma processing, a given high-frequency voltage is applied to the stage 80 from the first high-frequency power supply 106.

[0038] 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.

[0039] 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.

[0040] In this manner, a high frequency voltage is applied from the first high frequency power supply 106 to the stage 80 serving as the lower electrode, thereby generating plasma inside the processing chamber 70 .

[0041] In the embodiment, the stage 80, the power feed rod 104, the matching box 105, the first high frequency power supply 106, and the upper electrode 110 are an example of a plasma generation mechanism that generates plasma of the processing gas in the processing chamber 70. The first high frequency power supply 106 is controlled by the control unit 5 of the control device 4 described above.

[0042] 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 mechanism 122, an inert gas supply mechanism 123, and a humidified gas supply mechanism 124 are connected to the gas supply pipe 121.

[0043] The process gas supply mechanism 122 supplies a process gas to the hollow portion 120 of the upper electrode 110 via a gas supply pipe 121. Examples of the process gas include oxygen gas, nitrogen gas, and argon gas. The process gas supply mechanism 122 includes a process gas supply source 122a, a flow rate regulator 122b, and a valve 122c. The process gas supplied from the process gas supply source 122a has its flow rate controlled by the flow rate regulator 122b and the valve 122c, and is supplied to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. The process gas supply mechanism 122 is an example of a first gas supply unit.

[0044] The inert gas supply mechanism 123 supplies an inert gas to the hollow portion 120 of the upper electrode 110 via a gas supply pipe 121. Examples of inert gases that can be used include nitrogen gas and argon gas. The inert gas supply mechanism 123 includes an inert gas supply source 123a, a flow rate regulator 123b, and a valve 123c. The inert gas supplied from the inert gas supply source 123a has its flow rate controlled by the flow rate regulator 123b and the valve 123c, and is supplied to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121.

[0045] The humidified gas supply mechanism 124 supplies humidified gas (hereinafter referred to as "humidified gas") to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. For example, humidified nitrogen gas or humidified argon gas is used as the humidified gas. Note that temperature- and humidity-adjusted air may also be used as the humidified gas. The humidified gas supply mechanism 124 includes a humidified gas supply source 124a, a flow rate regulator 124b, and a valve 124c. The flow rate of the humidified gas supplied from the humidified gas supply source 124a is controlled by the flow rate regulator 124b and the valve 124c, and the humidified gas is supplied to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. The humidified gas supply mechanism 124 is an example of a second gas supply unit.

[0046] A baffle plate 126 is provided inside the hollow portion 120 to promote uniform diffusion of the process gas, inert gas, and humidified gas. 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, inert gas, and humidified gas from the hollow portion 120 into the process vessel 70.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] <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.

[0051] 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 overlapping wafer T is formed on the side surface 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.

[0052] 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 a 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 overlapping wafer T are also formed in the inner wall 193.

[0053] 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.

[0054] The transition 200 temporarily holds the upper wafer W1, the lower wafer W2, and the overlapping 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 overlapping wafer T can be held thereon at the same time.

[0055] 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 overlapping wafer T within the transfer region T1 or between the transfer region T1 and the processing region T2.

[0056] 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 notch portions of the upper wafer W1 and the lower wafer W2. The position adjustment mechanism 210 adjusts the positions of the notch portions by detecting the positions of the notch portions 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.

[0057] 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). In addition, the holding arm 221 is provided with holding members 222 that hold the upper wafer W1 at, for example, four locations.

[0058] 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.

[0059] 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 be rotated around the driving unit 223 and moved between the position adjustment mechanism 210 and the upper chuck 230, which will be described later.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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 align the upper wafer W1 held by the upper chuck 230 with the lower wafer W2 held by the lower chuck 231 in the horizontal direction. In addition, the alignment unit 256 moves the lower chuck 231 in the Z-axis direction to align the upper wafer W1 held by the upper chuck 230 with the lower wafer W2 held by the lower chuck 231 in the vertical direction.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The actuator unit 282 generates a constant pressure in a certain direction (vertically downward in this case) by using air supplied from, for example, an electropneumatic regulator (not shown). The actuator unit 282 can control the pressure load applied to the center of the upper wafer W1 by contacting the center of the upper wafer W1 using the air supplied from the electropneumatic regulator. Pressing pin 281 The tip of the is inserted through a through hole 266 and can be raised and lowered vertically by air from an electropneumatic regulator.

[0073] 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.

[0074] 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.

[0075] 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 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 261 are evenly arranged at intervals of, for example, 2 mm.

[0076] The upper chuck 230 includes a plurality of suction portions for suctioning 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 for suctioning 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.

[0077] The plurality of outer suction portions 391 are arranged on the outer periphery of the main body portion 260. The plurality of 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.

[0078] 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 the center of the upper wafer W1 by vacuuming.

[0079] 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.

[0080] The upper surface of the main body 290 is connected to the lower surface (non-bonding surface) of the lower wafer W2. W2n) are provided. The pins 291 have a diameter of, for example, 0.1 mm to 1 mm and a height of, for example, several tens of μm to several hundreds of μm. The pins 291 are evenly spaced, for example, at intervals of 2 mm.

[0081] 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.

[0082] 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).

[0083] 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 suction-held by the lower chuck 231.

[0084] 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 of the lower wafer W2 is released.

[0085] <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.

[0086] 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 loading / unloading station 2. Thereafter, the upper wafer W1 in the cassette C1 is removed by the transfer device 22 and transferred to the transition device 50 arranged in the third processing block G3.

[0087] 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, nitrogen gas, which is a processing gas, is excited to plasma and ionized in a predetermined reduced-pressure atmosphere. The nitrogen ions are irradiated onto the bonding surface W1j of the upper wafer W1, and the bonding surface W1j is plasma-processed. This modifies the bonding surface W1j of the upper wafer W1 (step S101). Here, in the surface modification device 30 of this embodiment, the amount of moisture in the processing chamber 70 is adjusted by supplying a humidifying gas, and with the amount of moisture in the processing chamber 70 adjusted, plasma of the processing gas is generated in the processing chamber 70, thereby modifying the bonding surface W1j of the upper wafer W1.

[0088] In this way, by modifying the bonding surface W1j of the upper wafer W1 with the moisture content adjusted in the processing container 70, it is possible to suppress a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 that would be obtained when the upper wafer W1 and the lower wafer W2 are bonded together. The factors that suppress a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 will be explained after the explanation of the various processes in the bonding system 1 is finished.

[0089] Next, the upper wafer W1 is transferred to the first transfer unit 61. 2 Processing Block G 2 The upper wafer W1 is then transferred to the surface hydrophilization device 40. 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).

[0090] Next, the upper wafer W1 is transferred to the bonding device 41 in the second processing block G2 by the transfer device 61. The upper wafer W1 transferred into the bonding device 41 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).

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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). Note that step S106 is the same process as step S101 described above, and is performed in a state where the amount of moisture in the processing container 70 is adjusted.

[0095] 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).

[0096] 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).

[0097] 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).

[0098] 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).

[0099] 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.

[0100] Next, after the suction 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).

[0101] 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.

[0102] 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 units 391 (step S114). This causes the outer periphery of the upper wafer W1, which had been suction-held by the outer suction units 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 an overlapped wafer T.

[0103] 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.

[0104] 9 is a timing chart showing the operation of each part when modifying the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 in the bonding process according to the embodiment. Note that Fig. 9 shows the timing chart from the point when the upper wafer W1 starts to be transferred to the surface modification device 30 before the above-mentioned step S101 (modification of the bonding surface W1j of the upper wafer W1) is started.

[0105] 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 and W2j of the upper wafer W1 and the lower wafer W2. Therefore, in the surface modification apparatus 30 according to the embodiment, the amount of moisture in the processing vessel 70 is adjusted by supplying humidified gas into the processing vessel 70 prior to the surface modification of the upper wafer W1.

[0106] The control unit 5 operates the inert gas supply mechanism 123 to supply the inert gas into the processing chamber 70 from time T10 when the transfer of the upper wafer W1 to the surface modification device 30 starts.

[0107] Furthermore, from time T10, the control unit 5 operates the humidified gas supply mechanism 124 to supply the humidified gas into the processing chamber 70 together with the inert gas.

[0108] 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 the spectrophotometer 141 or the mass spectrometer 142. In this case, the control unit 5 may control the flow rate or moisture content of the humidified gas based on the measured value indicating the amount of moisture in the processing vessel 70.

[0109] 10 and 11 are diagrams illustrating an example of measurement results of the amount of moisture in the processing vessel 70. FIG. 10 shows optical emission data at each wavelength in the processing vessel 70 immediately after the processing vessel 70 is opened to the atmosphere during maintenance. FIG. 10 also shows optical emission data measured by the spectrophotometer 141 when plasma of nitrogen gas, which is the processing gas, is generated in the processing vessel 70. The nitrogen gas plasma contains nitrogen ions at a first excitation level (1st POS) and nitrogen ions at a second excitation level (2nd POS), which have higher activity than the nitrogen ions at the first excitation level. The wavelength of the nitrogen ions at the first excitation level is in the range of approximately 530 nm to 800 nm, and the wavelength of the nitrogen ions at the second excitation level is in the range of approximately 280 nm to 440 nm. The optical emission data shown in FIG. 10 indicates that when the processing vessel 70 is opened to the atmosphere during maintenance, almost no nitrogen ions at the first excitation level are generated. This is thought to be because the amount of moisture in the processing vessel 70 increases due to exposure to the atmosphere, and the energy of the nitrogen ions at the first excitation level is transferred to the moisture (H2O) present in the processing vessel 70, causing the nitrogen ions at the first excitation level to disappear from the processing vessel 70.

[0110] 11 shows optical emission data at each wavelength in the processing vessel 70 after surface modification of the upper wafer W1 has been repeated a predetermined number of times. FIG. 11 also shows optical emission data measured by the spectrophotometer 141 when plasma of nitrogen gas, which is the processing gas, is generated in the processing vessel 70. The optical emission data shown in FIG. 11 indicates that the amount of nitrogen ions at the first excitation level increases when surface modification of the upper wafer W1 is repeatedly performed in the processing vessel 70. This is thought to be because, when surface modification is repeatedly performed, the amount of moisture in the processing vessel 70 decreases due to evacuation or the like, making it difficult for the energy of the nitrogen ions at the first excitation level to be transferred to moisture (HO), and the remaining nitrogen ions at the first excitation level increase.

[0111] The controller 5 controls the spectrophotometer 141 and the process gas supply mechanism 122 to acquire optical emission data supplied into the process vessel 70 and measures the value of a peak occurring at a wavelength corresponding to nitrogen ions at the first excitation level in the optical emission data as a value indicating the moisture content in the process vessel 70. The controller 5 then controls the flow rate or moisture content of the humidifying gas based on the measured value of the peak occurring at a wavelength corresponding to nitrogen ions at the first excitation level. As the moisture content in the process vessel 70 decreases, the value of the peak occurring at a wavelength corresponding to nitrogen ions at the first excitation level in the optical emission data of the spectrophotometer 141 increases. Therefore, it is possible to determine whether the moisture content in the process vessel 70 has decreased and fallen below a specified lower limit from the value of the peak occurring at a wavelength corresponding to nitrogen ions at the first excitation level. For example, the controller 5 determines whether the moisture content in the process vessel 70 has fallen below a specified lower limit by determining whether the measured peak value is equal to or greater than a predetermined threshold. When the control unit 5 determines that the amount of moisture in the processing vessel 70 is below a predetermined lower limit, the control unit 5 controls the humidified gas supply mechanism 124 to increase the flow rate or moisture content of the humidified gas. This allows the control unit 5 to appropriately adjust the amount of moisture in the processing vessel 70.

[0112] Fig. 12 is a diagram illustrating another example of the measurement results of the amount of moisture in the processing vessel 70. Fig. 12 shows analytical value data obtained by analyzing the atmosphere in the processing vessel 70 with respect to the mass number (m / z=18) of water (H2O) when the processing vessel 70 is opened to the atmosphere and then evacuated. Fig. 12 also shows analytical value data measured by the mass spectrometer 142. The analytical value data shown in Fig. 12 indicates that when the surface modification of the upper wafer W1 is repeated a predetermined number of times in the processing vessel 70, the amount of moisture in the processing vessel 70 gradually decreases due to the evacuation.

[0113] 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 humidified gas supply mechanism 124 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.

[0114] Returning to the description of FIG. 9 , the control unit 5 raises the lifter pins from the stage 80 at time T11, a predetermined time elapsed from time T10, and opens the gate valve 72 at time T12, a predetermined time elapsed from time T11. The control unit 5 advances the transfer arm of the transfer device 61 into the processing vessel 70 at time T13, a predetermined time elapsed from time T12, and transfers the upper wafer W1 held on the transfer arm to the lifter pins. The control unit 5 closes the gate valve 72 at time T14, when the transfer arm of the transfer device 61 retracts from the processing vessel 70. Then, the control unit 5 stops the inert gas supply mechanism 123 at time T15, a predetermined time elapsed from time T14, to complete the loading of the upper wafer W1 into the processing vessel 70. The period from time T10 to time T15 is referred to as a “standby period.”

[0115] At time T15, the controller 5 stops the humidified gas supply mechanism 124. That is, during the standby period, the controller 5 supplies the humidified gas into the processing vessel 70 to adjust the moisture content inside the processing vessel 70. The moisture content inside the processing vessel 70 is adjusted to within a range of 1000 ppm to 5000 ppm, for example.

[0116] Furthermore, from time T15, which is the end of the waiting period, the control unit 5 adjusts the aperture of the APC valve 133 from the first aperture, which is the initial value, to the fully open position, thereby evacuating the processing vessel 70. Then, at time T16, which is a predetermined time after time T15, the control unit 5 lowers the lifter pins toward the stage 80, thereby placing the upper wafer W1 on the stage 80.

[0117] From time T17, a predetermined time after time T16, the control unit 5 adjusts the opening of the APC valve 133 from full open to a second opening greater than the first opening, thereby setting the pressure inside the processing vessel 70 to the process pressure used for the surface modification processing.

[0118] After the pressure in the processing chamber 70 reaches the process pressure, the control unit 5 operates the processing gas supply mechanism 122 from time T18 to supply nitrogen gas as the processing gas into the processing chamber 70. Then, at time T19, which is a predetermined time after time T18, the control unit 5 controls the first high frequency power supply 106 to supply high frequency power to the stage 80. Voltage By applying the voltage, a plasma of nitrogen gas is generated in the processing chamber 70.

[0119] The nitrogen ions in the plasma thus generated are irradiated onto the bonding surface W1j of the upper wafer W1, thereby modifying the bonding surface W1j, thereby forming dangling bonds of silicon atoms on the outermost surface of the bonding surface W1j.

[0120] At time T20, a predetermined time after time T19, the control unit 5 stops the first high frequency power supply 106 and adjusts the aperture of the APC valve 133 from the second aperture to the first aperture, thereby reducing the pressure inside the processing vessel 70 to the initial pressure. Then, at time T21, when the pressure inside the processing vessel 70 reaches the initial pressure, the control unit 5 raises the lifter pins from the stage 80 to place the modified upper wafer W1 above the stage 80. Then, at time T22, a predetermined time after time T21, the control unit 5 stops the processing gas supply mechanism 122.

[0121] At time T23, a predetermined time after time T22, the control unit 5 operates the inert gas supply mechanism 123 to supply inert gas into the processing vessel 70. As a result, the control unit 5 replaces the nitrogen gas remaining in the processing vessel 70 with the inert gas. Then, at time T24, a predetermined time after time T23, the control unit 5 completely replaces the nitrogen gas remaining in the processing vessel 70 with the inert gas, thereby completing the modification of the bonding surface W1j of the upper wafer W1. Hereinafter, the period from time T15, which is the end of the waiting period, to time T24 will be referred to as the "first process period" as appropriate.

[0122] Furthermore, the control unit 5 opens the gate valve 72 at time T24, which is the end of the first process period. At time T25, a predetermined time after time T24, the control unit 5 causes the transfer arm of the transfer device 61 to advance into the processing chamber 70 and transfers the modified upper wafer W1, which is placed above the stage 80, to the transfer arm. Thereafter, the control unit 5 causes the transfer device 61 to transfer the modified upper wafer W1 to the surface hydrophilization device 40.

[0123] When the modified upper wafer W1 is transported to the surface hydrophilization device 40, the unmodified lower wafer W1 is transported to the surface modification device 30. 2 That is, the control unit 5 controls the transfer arm of the transfer device 61 to transfer the lower wafer W. 2After holding the lower wafer W on the transfer arm, the transfer device 61 is moved to the surface modification device 30. Then, at time T26 when the transfer device 61 reaches the surface modification device 30, the control unit 5 advances the transfer arm of the transfer device 61 into the processing chamber 70, and transfers the lower wafer W held on the transfer arm. 2 The control unit 5 then transfers the modified upper wafer W1 to the lifter pin. At time T27 when the transfer arm of the transfer device 61 exits the processing chamber 70, the control unit 5 closes the gate valve 72. The control unit 5 then waits until time T28, a predetermined time after time T27. In this manner, during the period from time T24 to time T28, the unmodified lower wafer W2 is loaded into the processing chamber 70 in place of the modified upper wafer W1. Hereinafter, the period from time T24 to time T28, which is the end of the first process period, will be referred to as the "wafer replacement period" as appropriate. Then, after time T28, which is the end of the wafer replacement period, the lower wafer W2 is processed in the same manner as the upper wafer W1 was processed during the first process period. As a result, the bonding surface W of the lower wafer W2 is 2 j is modified. Hereinafter, the period from time T28, which is the end of the wafer replacement period, to the time when the modification of the bonding surface W2j of the lower wafer W2 is completed will be referred to as the "second process period" as appropriate. When the second process period ends, the control unit 5 can remove the modified lower wafer W2 from the surface modification device 30 using the transfer device 61.

[0124] Thus, in the embodiment, by modifying the bonding surface W1j of the upper wafer W1 while the moisture content in the processing vessel 70 is adjusted, it is possible to suppress a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 to be bonded.

[0125] <Reason for preventing a decrease in bonding strength between wafers> Below, we will explain why modifying the bonding surface W1j of the upper wafer W1 while the moisture content in the processing container 70 is adjusted suppresses a decrease in the bonding strength between the bonded upper wafer W1 and lower wafer W2.

[0126] 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.

[0127] 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.

[0128] 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 W1, 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.

[0129] 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.

[0130] 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.

[0131] Next, the upper wafer W1 and the lower wafer W2 carried out from the surface modification device 30 undergo hydrophilization treatment of the bonding surfaces W1j and W2j in the surface hydrophilization device 40, and are then bonded in the bonding device 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.

[0132] In this embodiment, the generation of nitrided portions on the outermost surface of the bonding surface W1j is reduced, so that the above-described 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.

[0133] <Variation 1> Next, various modified examples of the embodiment will be described with reference to Fig. 13 to Fig. 15. Fig. 13 is a timing chart showing the operation of each part when modifying the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 in the bonding process according to Modification 1 of the embodiment. Note that Fig. 13 shows the timing chart from the point when the upper wafer W1 starts to be transferred to the surface modification device 30 before the above-mentioned step S101 (modification of the bonding surface W1j of the upper wafer W1) is started.

[0134] The control unit 5 operates the inert gas supply mechanism 123 to supply the inert gas into the processing chamber 70 from time T10 when the transfer of the upper wafer W1 to the surface modification device 30 starts.

[0135] Furthermore, from time T10, the control unit 5 operates the humidified gas supply mechanism 124 to supply the humidified gas into the processing chamber 70 together with the inert gas.

[0136] The control unit 5 raises the lifter pins from the stage 80 at time T11, a predetermined time after time T10, and opens the gate valve 72 at time T12, a predetermined time after time T11. At time T13, a predetermined time after time T12, the control unit 5 advances the transfer arm of the transfer device 61 into the processing vessel 70 and transfers the upper wafer W1 held on the transfer arm to the lifter pins. At time T14, when the transfer arm of the transfer device 61 retracts from the processing vessel 70, the control unit 5 closes the gate valve 72. Then, at time T15, a predetermined time after time T14, the control unit 5 stops the inert gas supply mechanism 123, completing the loading of the upper wafer W1 into the processing vessel 70.

[0137] Furthermore, even after time T15, which is the end of the waiting time, the controller 5 continues to supply the humidified gas into the processing vessel 70 without stopping the humidified gas supply mechanism 124. That is, in the first modification, the controller 5 continues to supply the humidified gas into the processing vessel 70 even after the waiting period has elapsed.

[0138] From time T15, which is the end of the waiting period, the control unit 5 adjusts the aperture of the APC valve 133 from the first aperture, which is the initial value, to the fully open position, thereby evacuating the processing vessel 70. Then, at time T16, which is a predetermined time after time T15, the control unit 5 lowers the lifter pins toward the stage 80, thereby placing the upper wafer W1 on the stage 80.

[0139] From time T17, a predetermined time after time T16, the control unit 5 adjusts the opening of the APC valve 133 from full open to a second opening greater than the first opening, thereby setting the pressure inside the processing vessel 70 to the process pressure used for the surface modification processing.

[0140] After the pressure in the processing chamber 70 reaches the process pressure, the control unit 5 operates the processing gas supply mechanism 122 from time T18 to supply nitrogen gas as the processing gas into the processing chamber 70. Then, at time T19, which is a predetermined time after time T18, the control unit 5 controls the first high frequency power supply 106 to supply high frequency power to the stage 80. Voltage By applying the voltage, a plasma of nitrogen gas is generated in the processing chamber 70.

[0141] The nitrogen ions in the plasma thus generated are irradiated onto the bonding surface W1j of the upper wafer W1, thereby modifying the bonding surface W1j, thereby forming dangling bonds of silicon atoms on the outermost surface of the bonding surface W1j.

[0142] At time T20, a predetermined time after time T19, the control unit 5 stops the first high frequency power supply 106 and adjusts the aperture of the APC valve 133 from the second aperture to the first aperture, thereby reducing the pressure inside the processing vessel 70 to the initial pressure. Then, at time T21, when the pressure inside the processing vessel 70 reaches the initial pressure, the control unit 5 raises the lifter pins from the stage 80 to place the modified upper wafer W1 above the stage 80. Then, at time T22, a predetermined time after time T21, the control unit 5 stops the processing gas supply mechanism 122.

[0143] At time T23, a predetermined time after time T22, the control unit 5 operates the inert gas supply mechanism 123 to supply inert gas into the processing vessel 70. As a result, the control unit 5 replaces the nitrogen gas remaining in the processing vessel 70 with the inert gas. Then, at time T24, a predetermined time after time T23, the control unit 5 completely replaces the nitrogen gas remaining in the processing vessel 70 with the inert gas, thereby completing the modification of the bonding surface W1j of the upper wafer W1.

[0144] Furthermore, the control unit 5 stops the humidified gas supply mechanism 124 at time T24 when the modification of the bonding surface W1j of the upper wafer W1 is completed.

[0145] That is, in the first modification, the control unit 5 continues to supply humidified gas into the processing vessel 70 during the first process period from time T15, which is the end of the waiting period, to time T24, when the modification of the bonding surface W1j of the upper wafer W1 is completed.

[0146] This allows the control unit 5 to continuously adjust the amount of moisture in the processing vessel 70 during the first process period after the standby period. Therefore, according to Modification 1, it is possible to more efficiently reduce the generation of nitrided portions that inhibit bonding due to OH groups on the outermost surface of the bonding surface W1j, and therefore it is possible to more efficiently prevent a decrease in the bonding strength between the upper wafer W1 and the lower wafer W2 to be bonded.

[0147] Then, at time T24, which is the end of the first process period, the control unit 5 opens the gate valve 72. The subsequent processing is the same as in the embodiment, and therefore a detailed description thereof will be omitted.

[0148] <Variation 2> Modification 2 differs from Modification 1 in that after time T28, which is the end of the wafer replacement period, humidified gas is further supplied into the processing vessel 70. Since other points are the same as Modification 1, detailed description thereof will be omitted.

[0149] 14 is a timing chart showing the operation of each part when modifying the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 in the bonding process according to Modification 2 of the embodiment. Note that Fig. 14 shows the timing chart from the point when the upper wafer W1 starts to be transported to the surface modification device 30 before the above-mentioned step S101 (modification of the bonding surface W1j of the upper wafer W1) is started.

[0150] The control unit 5 operates the humidified gas supply mechanism 124 from time T28, which is the end of the wafer replacement period, to supply humidified gas into the processing chamber 70. Then, the control unit 5 stops the humidified gas supply mechanism 124 when the modification of the bonding surface W2j of the lower wafer W2 is completed.

[0151] That is, in the second modification, humidified gas is further supplied into the processing chamber 70 during a second process period from time T28, which is the end of the wafer replacement period, to the time when modification of the bonding surface W2j of the lower wafer W2 is completed.

[0152] This allows the control unit 5 to further adjust the amount of moisture in the processing vessel 70 during the second process period after the wafer replacement period. Therefore, according to Modification 2, the generation of nitrided portions that inhibit bonding due to OH groups on the outermost surface of the bonding surface W2j can be more efficiently reduced, and therefore, the reduction in the bonding strength between the upper wafer W1 and the lower wafer W2 to be bonded can be more efficiently suppressed.

[0153] <Variation 3> In the above embodiment, an example was described in which, when adjusting the moisture content in the processing vessel 70, a value indicating the moisture content in the processing vessel 70 was measured, and the flow rate or moisture content of the humidified gas was controlled based on the measurement result. Alternatively, after adjusting the moisture content in the processing vessel 70, a value indicating the moisture content in the processing vessel 70 may be measured, and based on the measurement result, it may be determined whether or not to modify the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2. Therefore, in Modification 3, an example will be described in which, after adjusting the moisture content in the processing vessel 70, a value indicating the moisture content in the processing vessel 70 is measured, and based on the measurement result, it is determined whether or not to modify the bonding surfaces W1j, W2j of the upper wafer W1 and the lower wafer W2.

[0154] Fig. 15 is a flowchart showing an example of the process flow of the modification execution possibility determination method according to Modification 3 of the embodiment. Note that Fig. 15 shows the flowchart from the point in time when the process (adjustment of the water content in the processing vessel 70) at time T15 shown in Fig. 9 is completed.

[0155] When the humidified gas supply mechanism 24 is stopped to finish adjusting the moisture content in the processing vessel 70 (step S201), the controller 5 measures a value indicating the moisture content in the processing vessel 70 (step S202). The value indicating the moisture content in the processing vessel 70 is, for example, a peak value occurring at a wavelength corresponding to nitrogen ions at the first excitation level in the emission data measured by the spectrophotometer 141. Alternatively, the value indicating the moisture content in the processing vessel 70 may be an analytical value measured by the mass spectrometer 142, i.e., an analytical value obtained by analyzing the atmosphere in the processing vessel 70 with respect to the mass number (m / z=18) of water (HO).

[0156] Next, the control unit 5 determines whether modification of the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 (i.e., surface modification processing) of the upper wafer W1 and the lower wafer W2 is possible based on the measured value indicating the amount of moisture in the processing vessel 70 (step S203). For example, assume that the value indicating the amount of moisture in the processing vessel 70 is a peak value occurring at a wavelength corresponding to nitrogen ions at the first excitation level. For example, if the measured peak value is equal to or greater than a predetermined threshold, the control unit 5 determines that the amount of moisture in the processing vessel 70 is below a specified lower limit and therefore determines that the surface modification processing is impossible. On the other hand, if the measured peak value is smaller than the predetermined threshold, the control unit 5 determines that the amount of moisture in the processing vessel 70 is not below a specified lower limit and therefore determines that the surface modification processing is possible.

[0157] When the control unit 5 determines that the surface modification process cannot be performed (step S204; No), it stops the execution of the surface modification process (step S205) and ends the process.

[0158] On the other hand, when the control unit 5 determines that the surface modification process can be performed (step S205; Yes), the process proceeds to the process after time T15 shown in Fig. 9, and plasma of the processing gas is generated in the processing vessel 70 (step S206). As a result, the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 are modified.

[0159] Therefore, according to variant example 3, it is possible to appropriately determine whether or not the surface modification process can be performed based on the value indicating the amount of moisture in the processing vessel 70 measured after adjusting the amount of moisture in the processing vessel 70.

[0160] <Effects> The surface modification method according to the embodiment is a surface modification method for modifying a bonding surface (e.g., bonding surface W1j) of a substrate (e.g., upper wafer W1) to be bonded to another substrate (e.g., lower wafer W2) by plasma of a processing gas, and includes an adjusting step and a modifying step. The adjusting step adjusts the amount of moisture in a processing vessel (e.g., processing vessel 70) capable of accommodating a substrate by supplying humidified gas into the processing vessel. The modifying step modifies the bonding surfaces of the substrates by generating plasma of the processing gas in the processing vessel with the amount of moisture adjusted in the processing vessel. This makes it possible to suppress a decrease in the bonding strength between the bonded substrates.

[0161] Furthermore, the adjusting step may supply humidified gas into the processing vessel during a first period (e.g., a waiting period) from when the substrate starts to be transported into the processing vessel until the substrate is loaded into the processing vessel. This reduces the occurrence of chemically reacted portions (e.g., nitrided portions) that inhibit bonding due to OH groups on the outermost surfaces of the bonding surfaces during the surface modification process, thereby efficiently suppressing a decrease in bonding strength.

[0162] Furthermore, the adjustment step may continue to supply the humidified gas during a second period (e.g., a first process period) from the end of the first period until the modification of the bonding surfaces of the substrates is completed. This makes it possible to more efficiently reduce the occurrence of chemically reacted portions (e.g., nitrided portions) that inhibit bonding due to OH groups on the outermost surfaces of the bonding surfaces during the surface modification process, thereby more efficiently suppressing a decrease in bonding strength.

[0163] Furthermore, in the adjusting step, a humidified gas may be further supplied into the processing vessel during a third period (e.g., a second process period) from when an unmodified substrate is loaded into the processing vessel in place of the modified substrate until the modification of the bonding surface of the unmodified substrate is completed. This can more efficiently reduce the occurrence of chemically reacted portions (e.g., nitrided portions) that inhibit bonding due to OH groups on the outermost surfaces of the bonding surfaces during the surface modification process, thereby more efficiently suppressing a decrease in bonding strength.

[0164] The surface modification method according to the embodiment may further include a measuring step. The measuring step may measure a value indicating the amount of moisture in the processing vessel during the adjusting step. The adjusting step may then control the flow rate or moisture content of the humidified gas based on the value indicating the amount of moisture in the processing vessel measured in the measuring step. This allows the amount of moisture in the processing vessel to be appropriately adjusted.

[0165] Furthermore, the surface modification method according to the embodiment may further include a measuring step and a determining step. The measuring step may measure a value indicating the amount of moisture in the processing vessel after the adjusting step. The determining step may determine whether or not the modification step can be performed based on the value indicating the amount of moisture in the processing vessel measured in the measuring step. Then, the modifying step may generate plasma of the processing gas in the processing vessel when it is determined in the determining step that the modification step can be performed. This makes it possible to appropriately determine whether or not the surface modification process can be performed based on the value indicating the amount of moisture in the processing vessel measured after adjusting the amount of moisture in the processing vessel.

[0166] The processing gas may be at least one of oxygen gas, nitrogen gas, and argon gas, which can prevent a decrease in the bonding strength between the substrates even when the bonding surfaces of the substrates are modified by plasma of various processing gases.

[0167] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0168] For example, in the above embodiment, the humidified gas supply mechanism 124 is operated to supply humidified gas into the processing vessel 70, but the disclosed technology is not limited to this. For example, the processing vessel 70 may be opened to the atmosphere, so that gas containing moisture in the atmosphere can be supplied as humidified gas into the processing vessel 70. Furthermore, the processing vessel 70 may be opened to the atmosphere during a wafer replacement period. [Explanation of symbols]

[0169] 1. Joint System 5. Control section 30 Surface modification equipment 41 Joining equipment 70 Processing vessel 122 Processing gas supply mechanism 123 Inert gas supply mechanism 124 Humidified gas supply mechanism 141 Spectrophotometer 142 Mass spectrometer W1 upper wafer W2 lower wafer

Claims

1. A surface modification method for modifying a bonding surface of a substrate to be bonded to another substrate by plasma of a processing gas, comprising: an adjusting step of adjusting the moisture content in a processing vessel by supplying a humidified gas into the processing vessel capable of accommodating the substrate; a modifying step of modifying the bonding surface of the substrate by generating plasma of the processing gas in the processing vessel while the moisture content in the processing vessel is adjusted; a measuring step of measuring a value indicating the amount of moisture in the processing container during the adjusting step; Including, the measuring step includes acquiring light emission data of the processing gas supplied into the processing vessel, and measuring a peak value occurring at a specific wavelength of the light emission data as a value indicating the moisture content in the processing vessel; A surface modification method in which the adjustment process increases the flow rate or moisture content of the humidified gas when the value of a peak occurring at a specific wavelength of the light emission data measured in the measurement process becomes equal to or greater than a predetermined threshold.

2. 2. The surface modification method according to claim 1, wherein the adjustment step supplies the humidified gas into the processing vessel during a first period from when the substrate starts to be transported into the processing vessel until the substrate is loaded into the processing vessel.

3. 3. The surface modification method according to claim 2, wherein the adjusting step continues supplying the humidified gas during a second period from the end of the first period until modification of the bonding surface of the substrate is completed.

4. The surface modification method according to any one of claims 1 to 3, wherein the adjustment step further supplies the humidified gas into the processing vessel during a third period from when an unmodified other substrate is loaded into the processing vessel in place of the modified substrate until modification of the bonding surface of the other substrate is completed.

5. 5. The surface modification method according to claim 1, wherein the processing gas is at least one of oxygen gas, nitrogen gas, and argon gas.

6. A surface modification device that modifies a bonding surface of a substrate to be bonded to another substrate by plasma of a processing gas, comprising: a processing vessel capable of accommodating the substrate; a first gas supply unit for supplying the processing gas into the processing vessel; a second gas supply unit for supplying a humidified gas into the processing vessel; a measuring unit that measures a value indicating the amount of moisture in the treatment container; Control unit and Equipped with The control unit an adjusting step of adjusting the moisture content in the processing vessel by supplying the humidified gas into the processing vessel; a modifying step of modifying the bonding surface of the substrate by generating plasma of the processing gas in the processing container while the moisture content in the processing container is adjusted; a measuring step of measuring a value indicating the amount of moisture in the processing container during the adjusting step; A surface modification method including the steps of: the measuring step includes acquiring light emission data of the processing gas supplied into the processing vessel, and measuring a peak value occurring at a specific wavelength of the light emission data as a value indicating the moisture content in the processing vessel; The adjustment process increases the flow rate or moisture content of the humidified gas when the value of the peak occurring at a specific wavelength of the light emission data measured in the measurement process becomes equal to or greater than a predetermined threshold.

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