Surface modification method and surface modification apparatus

Abstract

A surface modification method of the present disclosure is used to modify a bonding surface of a substrate to be bonded to another substrate by processing a gas plasma, and includes an adjustment process and a modification process. In the adjustment process, the amount of moisture in a processing container capable of housing the substrate is adjusted by supplying a humidified gas into the processing container. In the modification process, a plasma of the processing gas is generated in the processing container in a state where the amount of moisture in the processing container has been adjusted, thereby modifying the bonding surface of the substrate.

Description

Technical Field

[0001] This disclosure relates to a surface modification method and a surface modification apparatus. Background Technology

[0002] Previously, as a method for bonding substrates such as semiconductor wafers together, one known method was to modify the bonding surfaces of the substrates to make the modified substrate surfaces hydrophilic, and then bond the hydrophilic substrates together through van der Waals forces and hydrogen bonds (intermolecular forces).

[0003] The surface modification of the substrate is performed using a surface modification apparatus. The surface modification apparatus contains the substrate within a processing container and modifies the surface of the contained substrate using plasma from a processing gas.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018 / 084285 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] This disclosure provides a technique for suppressing a decrease in the bonding strength between substrates being bonded.

[0009] Solution for solving the problem

[0010] One aspect of this disclosure is a surface modification method for modifying the bonding surface of a substrate to be bonded to other substrates using a plasma of a processing gas. The surface modification method includes an adjustment step and a modification step. In the adjustment step, the moisture content within a processing container is adjusted by supplying a humidified gas into the container capable of housing the substrate. In the modification step, with the moisture content within the processing container adjusted, a plasma of the processing gas is generated within the processing container, thereby modifying the bonding surface of the substrate.

[0011] The effects of the invention

[0012] According to this disclosure, the effect of suppressing the decrease in bonding strength between substrates being bonded is achieved. Attached Figure Description

[0013] Figure 1 This is a schematic top view illustrating the structure of the coupling system involved in the embodiment.

[0014] Figure 2 This is a schematic side view illustrating the structure of the coupling system involved in the embodiment.

[0015] Figure 3This is a schematic side view of the upper and lower wafers involved in the implementation method.

[0016] Figure 4 This is a schematic cross-sectional view showing the structure of the surface modification apparatus involved in the embodiment.

[0017] Figure 5 This is a schematic top view showing the structure of the coupling device involved in the embodiment.

[0018] Figure 6 This is a schematic side view illustrating the structure of the coupling device involved in the embodiment.

[0019] Figure 7 This is a schematic diagram illustrating the upper and lower holding plates involved in the embodiment.

[0020] Figure 8 This is a flowchart illustrating the process performed by the coupling system according to the embodiment.

[0021] Figure 9 This is a timing diagram showing the operation of each part when the bonding surface of the upper and lower wafers is modified in the bonding process involved in the embodiment.

[0022] Figure 10 This is an example diagram used to illustrate the measurement results of the moisture content in the treatment container.

[0023] Figure 11 This is an example diagram used to illustrate the measurement results of the moisture content in the treatment container.

[0024] Figure 12 This is another example of a diagram used to illustrate the measurement results of the moisture content in the treatment container.

[0025] Figure 13 This is a timing diagram showing the operation of each part when the bonding surface of the upper and lower wafers is modified in the bonding process involved in the modified example 1 of the embodiment.

[0026] Figure 14 This is a timing diagram showing the operation of each part when the bonding surface of the upper and lower wafers is modified in the bonding process involved in the modified example 2 of the embodiment.

[0027] Figure 15 This is a flowchart illustrating an example of the processing flow for determining whether the modification involved in Variation 3 of the implementation method can be performed. Detailed Implementation

[0028] The embodiments of the surface modification method and surface modification apparatus disclosed in this application will now be described in detail with reference to the accompanying drawings. Furthermore, the disclosed technology is not limited by the following embodiments. It should also be noted that the drawings are schematic, and the dimensional relationships and ratios of the elements may sometimes differ from reality. Additionally, the drawings may sometimes include portions with different dimensional relationships or ratios.

[0029] Furthermore, when the surface modification of a substrate is repeatedly performed within the processing container of the surface modification apparatus, the moisture content within the processing container gradually decreases due to factors such as vacuuming. As the moisture content decreases, the state of the plasma in the processing gas generated within the processing container changes, thus hindering sufficient surface modification of the substrate. Consequently, the bonding strength between the modified substrate and other substrates sometimes decreases. This decrease in bonding strength can lead to defects such as substrate peeling, which is undesirable. Therefore, a technique capable of suppressing the decrease in bonding strength between substrates being bonded is desired.

[0030] <Structure of the Joining System>

[0031] First, refer to Figures 1-3 The structure of the coupling system 1 involved in the implementation method will be explained. Figure 1 This is a schematic top view showing the structure of the coupling system 1 according to the embodiment. Figure 2 This is its schematic side view. Additionally, Figure 3 This is a schematic side view of the upper wafer W1 and the lower wafer W2 involved in the embodiment. Furthermore, in the figures referred to below, for ease of understanding, an orthogonal coordinate system with the vertically upward Z-axis as the positive direction is sometimes shown.

[0032] Figure 1 The bonding system 1 shown forms an overlapped wafer T by bonding a first substrate W1 to a second substrate W2.

[0033] The first substrate W1 is, for example, 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, for example, a bare wafer without electronic circuits. The first substrate W1 and the second substrate W2 have approximately the same diameter. Alternatively, electronic circuits may be formed on the second substrate W2.

[0034] Hereinafter, the first substrate W1 will be referred to as "upper wafer W1", and the second substrate W2 will be referred to as "lower wafer W2". That is, upper wafer W1 is an example of the first substrate, and lower wafer W2 is an example of the second substrate. In addition, when upper wafer W1 and lower wafer W2 are referred to collectively, they are sometimes referred to as "wafer W".

[0035] Additionally, below, as Figure 3 As shown, the side of the upper wafer W1 that is bonded to the lower wafer W2 is designated as "bonding surface W1j", and the side opposite to the bonding surface W1j is designated as "non-bonding surface W1n". Similarly, the side of the lower wafer W2 that is bonded to the upper wafer W1 is designated as "bonding surface W2j", and the side opposite to the bonding surface W2j is designated as "non-bonding surface W2n".

[0036] like Figure 1 As shown, the joining system 1 includes an inbound / outbound station 2 and a processing station 3. The inbound / outbound station 2 and the processing station 3 are arranged in the positive X-axis direction in the order of inbound / outbound station 2 and processing station 3. In addition, the inbound / outbound station 2 and the processing station 3 are connected as one unit.

[0037] The loading / unloading station 2 includes a loading stage 10 and a transport area 20. The loading stage 10 includes multiple loading plates 11. Each loading plate 11 holds boxes C1, C2, and C3 that horizontally house multiple (e.g., 25) substrates. For example, box C1 houses the upper wafer W1, box C2 houses the lower wafer W2, and box C3 houses the overlapping wafer T.

[0038] The transport area 20 is arranged adjacent to the positive X-axis side of the platform 10. The transport area 20 is provided with a transport path 21 extending along the Y-axis and a transport device 22 that can move along the transport path 21.

[0039] The conveying device 22 can move not only in the Y-axis direction but also in the X-axis direction and can rotate around the Z-axis. Moreover, the conveying device 22 conveys the upper wafer W1, the lower wafer W2 and the overlapping wafer T between the boxes C1 to C3 placed on the mounting plate 11 and the third processing block G3 of the processing station 3 described later.

[0040] Furthermore, the number of boxes C1 to C3 placed on the mounting plate 11 is not limited to the number shown in the figure. In addition to placing boxes C1, C2, and C3, the mounting plate 11 may also hold boxes for recycling substrates that have developed defects.

[0041] Processing station 3 is equipped with multiple processing blocks, such as processing blocks G1, G2, and G3, which are equipped with various devices. For example, on the front side of processing station 3 ( Figure 1 The first processing block G1 is provided on the negative Y-axis side of the processing station 3, on the back side of the processing station 3. Figure 1 A second processing block G2 is provided on the positive Y-axis side of the processing station 3. Additionally, on the side of the loading / unloading station 2 of the processing station 3... Figure 1 A third processing block G3 is provided on the negative X-axis side.

[0042] The first processing block G1 is equipped with a surface modification device 30 that modifies the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 using plasma with a processing gas. The surface modification device 30 forms dangling bonds on the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 by plasma irradiation, thereby modifying the bonding surfaces W1j and W2j to make them easier to hydrophilize later.

[0043] Furthermore, in the surface modification apparatus 30, a given processing gas is stimulated under a reduced pressure atmosphere to plasma-entrain it, thereby ionizing it. Moreover, the bonding surfaces W1j and W2j are modified by irradiating the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 with ions of elements contained in the processing gas. Details of this surface modification apparatus 30 will be described later.

[0044] The second processing block G2 is equipped with a surface hydrophilization device 40 and a bonding device 41. The surface hydrophilization device 40 hydrophilizes the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2, for example, by using pure water, and cleans the bonding surfaces W1j and W2j.

[0045] In the surface hydrophilization apparatus 40, for example, while rotating the upper wafer W1 or the lower wafer W2 held in a rotating chuck, pure water is supplied to the upper wafer W1 or the lower wafer W2. As a result, the pure water supplied to the upper wafer W1 or the lower wafer W2 diffuses on the bonding surfaces W1j and W2j of the upper wafer W1 or the lower wafer W2, thereby hydrophilizing the bonding surfaces W1j and W2j.

[0046] The bonding device 41 bonds the upper wafer W1 to the lower wafer W2. Details of the bonding device 41 will be described later.

[0047] like Figure 2 As shown, in the third processing block G3, the upper wafer W1, the lower wafer W2, and the transfer (TRS) devices 50 and 51 of the overlapping wafer T are arranged in two layers from bottom to top.

[0048] In addition, such as Figure 1 As shown, a transport area 60 is formed in the region surrounded by the first processing block G1, the second processing block G2, and the third processing block G3. A transport device 61 is disposed in the transport area 60. The transport device 61 has, for example, a transport arm that is movable in the vertical direction, the horizontal direction, and about the vertical axis.

[0049] The conveying device 61 moves within the conveying area 60 to convey the upper wafer W1, the lower wafer W2, and the overlapping wafer T to a given device in the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the conveying area 60.

[0050] Furthermore, the bonding system 1 includes a control device 4. The control device 4 controls the operation of the bonding system 1. This 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 that control various processes such as bonding processing. The control unit 5 controls the operation of the bonding system 1 by reading and executing the programs stored in the storage unit 6.

[0051] Furthermore, the program can 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 (HD), floppy disks (FD), optical disks (CD), magneto-optical disks (MO), and memory cards.

[0052] <Structure of the surface modification device>

[0053] Next, refer to Figure 4 The structure of the surface modification device 30 will be described. Figure 4 This is a schematic cross-sectional view showing the structure of the surface modification device 30 according to the embodiment.

[0054] like Figure 4 As shown, the surface modification apparatus 30 has a processing container 70 capable of sealing its interior. The processing container 70 is located in the conveying area 60 (see reference 60). Figure 1 The side of the upper wafer W1 or the lower wafer W2 is formed with a loading and unloading outlet 71, and a gate valve 72 is provided in the loading and unloading outlet 71.

[0055] A stage 80 is disposed inside the processing container 70. The stage 80 is, for example, a lower electrode, and is made of a conductive material such as aluminum. A pin-through hole (not shown) is formed in the stage 80, and a lifting pin (not shown) is received in the pin-through hole. The lifting pin is configured to be able to move up and down in the vertical direction by a lifting mechanism (not shown).

[0056] The upper surface of the stage 80, i.e. the facing surface opposite to the upper electrode 110, is a horizontal plane that appears circular when viewed from above 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 the mounting portion 91 of the stage cover 90.

[0057] An annular partition plate 103 with multiple baffle holes is disposed between the stage 80 and the inner wall of the processing container 70. The partition plate 103 is also referred to as an exhaust ring. The partition plate 103 divides the internal space of the processing container 70 vertically with the placement part 91 as the boundary. In addition, the partition plate 103 uniformly exhausts the atmosphere inside the processing container 70.

[0058] A power supply rod 104 formed of a conductor is connected to the lower surface of the stage 80. The power supply rod 104 is connected to a first high-frequency power supply 106, for example, via a matching device 105 consisting of a DC 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.

[0059] An upper electrode 110 is disposed inside the processing container 70. The upper surface of the stage 80 and the lower surface of the upper electrode 110 are arranged facing each other in a manner that is parallel to each other and spaced apart by a given interval.

[0060] The upper electrode 110 is grounded and connected to ground potential. By grounding the upper electrode 110 in this way, damage to the lower surface of the upper electrode 110 can be suppressed during plasma processing.

[0061] In this way, plasma is generated inside the processing container 70 by applying a high-frequency voltage from the first high-frequency power supply 106 to the stage 80, which serves as the lower electrode.

[0062] In this embodiment, the stage 80, power supply rod 104, matching device 105, first high-frequency power supply 106, and upper electrode 110 are an example of a plasma generation mechanism that generates plasma of the processing gas within the processing container 70. Furthermore, the first high-frequency power supply 106 is controlled by the control unit 5 of the aforementioned control device 4.

[0063] A hollow portion 120 is formed inside the upper electrode 110. A gas supply pipe 121 is connected to the hollow portion 120. The gas supply pipe 121 is connected to the processing gas supply mechanism 122, the inactive gas supply mechanism 123, and the humidifying gas supply mechanism 124.

[0064] The processing gas supply mechanism 122 supplies processing gas to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. Examples of processing gases used include oxygen, nitrogen, and argon. The processing gas supply mechanism 122 includes a processing gas supply source 122a, a flow regulator 122b, and a valve 122c. Furthermore, the processing gas supplied from the processing gas supply source 122a is flow-controlled by the flow 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 processing gas supply mechanism 122 is an example of a first gas supply unit.

[0065] The inactive gas supply mechanism 123 supplies inactive gas to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. Examples of inactive gases used are nitrogen and argon. The inactive gas supply mechanism 123 includes an inactive gas supply source 123a, a flow regulator 123b, and a valve 123c. Furthermore, the inactive gas supplied from the inactive gas supply source 123a has its flow rate controlled by the flow 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.

[0066] The humidifying gas supply mechanism 124 supplies humidified gas (hereinafter referred to as "humidifying gas") to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. Examples of humidifying gases used include humidified nitrogen and humidified argon. Alternatively, air with adjusted temperature and humidity can also be used. The humidifying gas supply mechanism 124 includes a humidifying gas supply source 124a, a flow regulator 124b, and a valve 124c. The humidifying gas supplied from the humidifying gas supply source 124a has its flow rate controlled by the flow regulator 124b and the valve 124c, and is supplied to the hollow portion 120 of the upper electrode 110 via the gas supply pipe 121. The humidifying gas supply mechanism 124 is an example of a second gas supply unit.

[0067] Inside the hollow section 120, a baffle 126 is provided to promote the uniform diffusion of the processing gas, inactive gas, and humidifying gas. Multiple small holes are provided in the baffle 126. Multiple gas outlets 125 are formed on the lower surface of the upper electrode 110 for ejecting the processing gas, inactive gas, and humidifying gas from the hollow section 120 into the interior of the processing container 70.

[0068] A suction port 130 is formed in the processing container 70. A suction pipe 132 is connected to the suction port 130, which is connected to a vacuum pump 131 for reducing the pressure inside the processing container 70 to a given vacuum level. An APC (Auto Pressure Controller) valve 133 is provided in the suction pipe 132. The opening of the APC valve 133 is adjusted by venting air from the processing container 70 by the vacuum pump 131, thereby maintaining the pressure inside the processing container 70 at a specified pressure.

[0069] A spectrophotometer 141 capable of measuring emission data at various wavelengths within the processing container 70 is installed in the processing container 70. Specifically, the spectrophotometer 141 is installed in the processing container 70 in a position positioned above the mounting section 91 and below the gas outlet 125. The spectrophotometer 141 is, for example, an OES (Optical Emission Spectroscopy) sensor used to measure the emission state of the plasma generated within the processing container 70. The spectrophotometer 141 may also be a self-biased OES sensor capable of generating plasma within its own chamber and measuring the emission state of the plasma. The spectrophotometer 141 outputs the measured emission data to the control unit 5 of the control device 4.

[0070] In addition, a mass spectrometer 142 capable of analyzing the mass number of a specific substance in the atmosphere within the processing container 70 is installed in the processing container 70. Specifically, the mass spectrometer 142 is installed in the processing container 70 at a position lower than the partition plate 103. The mass spectrometer 142 is, for example, a quadrupole mass spectrometer (QMS), used to determine the analytical value obtained by measuring the mass number of a specific substance in the atmosphere within the processing container 70. The mass spectrometer 142 outputs the measured analytical value to the control unit 5 of the control device 4. By positioning the mass spectrometer 142 at a position lower than the partition plate 103, damage to the mass spectrometer 142 caused by plasma can be prevented.

[0071] <Structure of the Joining Device>

[0072] Next, refer to Figure 5 and Figure 6 To explain the structure of the coupling device 41. Figure 5 This is a schematic top view showing the structure of the coupling device 41 according to the embodiment. Figure 6 This is a schematic side view showing the structure of the coupling device 41 according to the embodiment.

[0073] like Figure 5 As shown, the bonding device 41 has a processing container 190 capable of sealing its interior. On the side of the processing container 190 near the transport area 60, there are loading and unloading outlets 191 for the upper wafer W1, the lower wafer W2, and the overlapping wafer T, and an opening and closing gate 192 is provided at the loading and unloading outlet 191.

[0074] The interior of the processing container 190 is divided into a transport area T1 and a processing area T2 by the inner wall 193. The aforementioned inlet and outlet 191 are formed on the side of the processing container 190 in the transport area T1. In addition, inlet and outlet 194 for the upper wafer W1, the lower wafer W2, and the overlapping wafer T are also formed on the inner wall 193.

[0075] In the transport area T1, the conveying unit 200, the substrate transport mechanism 201, the flipping mechanism 220, and the position adjustment mechanism 210 are arranged in the order described, for example, from the transport inlet / outlet 191 side.

[0076] The transport unit 200 temporarily holds the upper wafer W1, the lower wafer W2, and the overlapping wafer T. For example, the transport unit 200 is formed as two layers, capable of simultaneously holding any two of the upper wafer W1, the lower wafer W2, and the overlapping wafer T.

[0077] The substrate transport mechanism 201 has a transport arm that is movable in the vertical direction (Z-axis direction), the horizontal direction (Y-axis direction, X-axis direction), and about the vertical axis direction (θ direction). The substrate transport mechanism 201 can transport the upper wafer W1, the lower wafer W2, and the overlapping wafer T within the transport area T1 or between the transport area T1 and the processing area T2.

[0078] 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 includes: a base 211, which has a holding part (not shown) for holding and rotating the upper wafer W1 and the lower wafer W2; and a detection part 212 for detecting the position of the cut-out portions of the upper wafer W1 and the lower wafer W2. The position adjustment mechanism 210 rotates the upper wafer W1 and the lower wafer W2 held on the base 211 while using the detection part 212 to detect the position of the cut-out portions of the upper wafer W1 and the lower wafer W2, thereby adjusting the position of the cut-out portions. This adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2.

[0079] The flipping mechanism 220 flips the face and back sides of the upper wafer W1. Specifically, the flipping mechanism 220 has a holding arm 221 for holding the upper wafer W1. The holding arm 221 extends in the horizontal direction (X-axis direction). In addition, holding members 222 for holding the upper wafer W1 are provided at, for example, four positions on the holding arm 221.

[0080] The retaining arm 221 is supported by a drive unit 223, such as one equipped with a motor. The retaining arm 221 is rotatable about a horizontal axis via this drive unit 223. Furthermore, the retaining arm 221 is rotatable about the drive unit 223 and can move freely in the horizontal direction (X-axis direction). Below the drive unit 223, another drive unit (not shown), such as one equipped with a motor, is provided. This other drive unit allows the drive unit 223 to move vertically along a support column 224 extending vertically.

[0081] In this way, the upper wafer W1 held in the holding member 222 can rotate about a horizontal axis via the drive unit 223, and can move in both the vertical and horizontal directions. In addition, the upper wafer W1 held in the holding member 222 can rotate about the drive unit 223 and move between the position adjustment mechanism 210 and the upper holding disk 230 described later.

[0082] The processing area T2 includes: an upper holding disk 230, which holds the upper surface (non-bonding surface W1n) of the upper wafer W1 from above; and a lower holding disk 231, which holds the lower surface (non-bonding surface W2n) of the lower wafer W2 from below. The lower holding disk 231 is located below the upper holding disk 230 and is configured to face the upper holding disk 230. The upper holding disk 230 and the lower holding disk 231 are, for example, vacuum holding disks.

[0083] like Figure 6 As shown, the upper holding plate 230 is supported by a support member 270 disposed above the upper holding plate 230. The support member 270 is fixed to the top surface of the processing container 190, for example, via a plurality of support columns 271.

[0084] An upper camera unit 235 is provided on the side of the upper holding disk 230 to capture images of the upper surface (joint surface W2j) of the lower wafer W2 held on the lower holding disk 231. The upper camera unit 235 is, for example, a CCD camera.

[0085] The lower retaining plate 231 is supported by a first moving part 250 disposed below the lower retaining plate 231. The first moving part 250 moves the lower retaining plate 231 in the horizontal direction (X-axis direction) as described later. In addition, the first moving part 250 is configured to allow the lower retaining plate 231 to move freely in the vertical direction and to rotate about the vertical axis.

[0086] The first moving part 250 is provided with a lower imaging part 236 for capturing images of the lower surface (joint surface W1j) of the first substrate W1 held on the upper holding plate 230. The lower imaging part 236 is, for example, a CCD camera.

[0087] The first movable part 250 is mounted on a pair of guide rails 252, 252. The pair of guide rails 252, 252 are disposed on the lower surface side of the first movable part 250 and extend in the horizontal direction (X-axis direction). The first movable part 250 is configured to move freely along the guide rails 252.

[0088] A pair of guide rails 252, 252 are disposed on the second movable part 253. The second movable part 253 is mounted on a pair of guide rails 254, 254. The pair of guide rails 254, 254 are provided on the lower surface side of the second movable part 253 and extend in the horizontal direction (Y-axis direction). The second movable part 253 is configured to move freely in the horizontal direction (Y-axis direction) along the guide rails 254. In addition, the pair of guide rails 254, 254 are disposed on a mounting platform 255 provided on the bottom surface of the processing container 190.

[0089] The positioning alignment unit 256 is composed of a first moving part 250 and a second moving part 253, etc. The positioning alignment unit 256 performs horizontal positioning alignment between the upper wafer W1 held on the upper wafer 230 and the lower wafer W2 held on the lower wafer 231 by moving the lower holding disk 231 in the X-axis direction, the Y-axis direction, and the θ direction. Furthermore, the positioning alignment unit 256 performs vertical positioning alignment between the upper wafer W1 held on the upper wafer 230 and the lower wafer W2 held on the lower wafer 231 by moving the lower holding disk 231 in the Z-axis direction.

[0090] Furthermore, while the lower holding plate 231 is configured to move in the X-axis, Y-axis, and θ-axis directions, the positioning alignment unit 256 can also move the lower holding plate 231 in the X-axis and Y-axis directions, and move the upper holding plate 230 in the θ-axis direction. Additionally, while the lower holding plate 231 is configured to move in the Z-axis direction, the positioning alignment unit 256 can also move the upper holding plate 230 in the Z-axis direction.

[0091] Next, refer to Figure 7 To illustrate the structure of the upper holding plate 230 and the lower holding plate 231. Figure 7 This is a schematic diagram showing the upper holding plate 230 and the lower holding plate 231 involved in the embodiment.

[0092] like Figure 7 As shown, the upper holding disk 230 has a main body portion 260. The main body portion 260 is supported by a support member 270. A through hole 266 is formed in the support member 270 and the main body portion 260, penetrating through the support member 270 and the main body portion 260 in the vertical direction. The position of the through hole 266 corresponds to the center of the upper wafer W1 held in the upper holding disk 230. A pressing pin 281, through which a striking pin 280 passes, is inserted into the through hole 266.

[0093] The striking pin 280 is disposed on the upper surface of the support member 270 and includes a pressing pin 281, an actuator part 282, and a linear motion mechanism 283. The pressing pin 281 is a cylindrical member extending in the vertical direction and is supported by the actuator part 282.

[0094] The actuator section 282 generates a fixed pressure in a fixed direction (here, vertically downward) by air supplied from an electro-pneumatic regulator (not shown). The actuator section 282 can control the pressing load applied to the center of the upper wafer W1 by contacting it with the air supplied from the electro-pneumatic regulator. Furthermore, the front end of the pressing pin 281 is inserted into the through-hole 266 by air from the electro-pneumatic regulator and can move freely up and down in the vertical direction.

[0095] The actuator section 282 is supported by the linear motion mechanism 283. The linear motion mechanism 283 moves the actuator section 282 in the vertical direction via a drive section, for example, with a built-in motor.

[0096] The striking pin 280 is configured as described above. The movement of the actuator section 282 is controlled by the linear motion mechanism 283, and the pressing load of the pressing pin 281 on the upper wafer W1 is controlled by the actuator section 282. As a result, the striking pin 280 presses and is held at the center of the upper wafer W1 on the upper holding disk 230, so that it contacts the lower wafer W2.

[0097] A plurality of pins 261 are provided on the lower surface of the main body 260 to contact the upper surface (non-bonding surface W1n) of the upper wafer W1. The plurality of pins 261 have, for example, a diameter of 0.1 mm to 1 mm and a height of tens of μm to hundreds of μm. The plurality of pins 261 are arranged evenly at intervals of 2 mm, for example.

[0098] The upper holding disk 230 has a plurality of adsorption portions for adsorbing the upper wafer W1 in a portion of the area where the plurality of pins 261 are provided. Specifically, a plurality of outer adsorption portions 391 and a plurality of inner adsorption portions 392 are provided on the lower surface of the main body portion 260 of the upper holding disk 230 for adsorbing the upper wafer W1 by evacuating the vacuum. The plurality of outer adsorption portions 391 and the plurality of inner adsorption portions 392 have adsorption areas that are arc-shaped when viewed from above. The plurality of outer adsorption portions 391 and the plurality of inner adsorption portions 392 have the same height as the pins 261.

[0099] Multiple outer adsorption portions 391 are disposed on the outer periphery of the main body 260. The multiple outer adsorption portions 391 are connected to an attraction device (not shown) such as a vacuum pump, and adsorb the outer periphery of the wafer W1 by drawing a vacuum.

[0100] Multiple inner adsorption portions 392 are arranged circumferentially at a position radially inward of the main body 260 compared to the multiple outer adsorption portions 391. The multiple inner adsorption portions 392 are connected to an attraction device (not shown) such as a vacuum pump, and adsorb the region between the outer periphery and the center of the upper wafer W1 by drawing a vacuum.

[0101] The lower holding disk 231 has a main body portion 290, which has the same diameter as or a larger diameter than the lower wafer W2. Here, a lower holding disk 231 with a diameter larger than the lower wafer W2 is shown. The upper surface of the main body portion 290 is an opposing surface facing the lower surface (non-bonding surface W2n) of the lower wafer W2.

[0102] A plurality of pins 291 are provided on the upper surface of the main body 290, which contact the lower surface (non-bonding surface W2n) of the lower wafer W2. The plurality of pins 291 have, for example, a diameter of 0.1 mm to 1 mm and a height of tens of μm to hundreds of μm. The plurality of pins 291 are arranged evenly at intervals of 2 mm, for example.

[0103] Additionally, on the upper surface of the main body 290, lower side ribs 292 are provided in a ring shape on the outer side of a plurality of pins 291. The lower side ribs 292 are formed in a ring shape and support the outer periphery of the lower wafer W2 throughout the entire circumference.

[0104] In addition, the main body 290 has a plurality of lower suction ports 293. Multiple lower suction ports 293 are provided in the adsorption area surrounded by 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 tube (not shown).

[0105] The lower holding disk 231 depressurizes the adsorption region surrounded by the lower ribs 292 by evacuating the adsorption region through multiple lower suction ports 293. As a result, the lower wafer W2 placed in the adsorption region is adsorbed and held in the lower holding disk 231.

[0106] Since the lower rib 292 supports the outer periphery of the lower surface of the lower wafer W2 throughout its entire circumference, the lower wafer W2 is properly evacuated up to its outer periphery. This allows the entire surface of the lower wafer W2 to be held in place. Furthermore, since the lower surface of the lower wafer W2 is supported by multiple pins 291, the lower wafer W2 can be easily detached from the lower holding disk 231 when the evacuation of the lower wafer W2 is released.

[0107] <Specific Operations of the Joining System>

[0108] Next, refer to Figure 8 To explain the specific operation of the coupling system 1 involved in the implementation method. Figure 8 This is a flowchart illustrating the process performed by the coupling system 1 according to the embodiment. Figure 8 The various processes shown are executed under the control of the control unit 5 of the control device 4.

[0109] First, a box C1 containing multiple upper wafers W1, a box C2 containing multiple lower wafers W2, and an empty box C3 are placed on a designated mounting plate 11 in the loading / unloading station 2. Then, the upper wafers W1 in box C1 are removed by the conveying device 22 and transported to the conveying device 50 configured in the third processing block G3.

[0110] Next, the upper wafer W1 is transported to the surface modification apparatus 30 of the first processing block G1 via the conveying device 61. In the surface modification apparatus 30, nitrogen gas, used as a processing gas, is excited under a predetermined reduced pressure atmosphere to plasmaize and ionize. This nitrogen ion is then irradiated onto the bonding surface W1j of the upper wafer W1 to perform plasma treatment on the bonding surface W1j. This modifies the bonding surface W1j of the upper wafer W1 (step S101). Here, in the surface modification apparatus 30 of this embodiment, the moisture content within the processing container 70 is adjusted by supplying a humidifying gas. With the moisture content in the processing container 70 adjusted, plasma of the processing gas is generated within the processing container 70, thereby modifying the bonding surface W1j of the upper wafer W1.

[0111] In this way, by modifying the bonding surface W1j of the upper wafer W1 while adjusting the moisture content within the processing container 70, it is possible to suppress the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 when bonding the upper wafer W1 and the lower wafer W2. The reason for suppressing the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 will be explained after the description of the various processes in the bonding system 1.

[0112] Next, the upper wafer W1 is transported to the surface hydrophilization apparatus 40 of the second processing block G2 via the conveying device 61. In the surface hydrophilization apparatus 40, while the upper wafer W1, held on a rotating holding disk, is rotated, pure water is supplied to the upper wafer W1. This hydrophilizes the bonding surface W1j of the upper wafer W1. Furthermore, the bonding surface W1j of the upper wafer W1 is cleaned with this pure water (step S102).

[0113] Next, the upper wafer W1 is transported to the bonding device 41 of the second processing block G2 via the transport device 61. The upper wafer W1, which has been transported into the bonding device 41, is then transported to the position adjustment mechanism 210 via the transport unit 200, and the horizontal orientation is adjusted by the position adjustment mechanism 210 (step S103).

[0114] Next, the upper wafer W1 is transferred from the position adjustment mechanism 210 to the flipping mechanism 220, and the surface and back of the upper wafer W1 are flipped by the flipping mechanism 220 (step S104). Specifically, the mating surface W1j of the upper wafer W1 is made to face downward.

[0115] Next, the upper wafer W1 is transferred from the flipping mechanism 220 to the upper holding disk 230, and the upper holding disk 230 is used to hold the upper wafer W1 (step S105).

[0116] The processing of the lower wafer W2 is repeated in steps S101 to S105 for the upper wafer W1. First, the lower wafer W2 is taken out of the box C2 by the transfer device 22 and transferred to the transfer device 50 arranged in the third processing block G3.

[0117] Next, the lower wafer W2 is transferred to the surface modification apparatus 30 via the conveying device 61, and the bonding surface W2j of the lower wafer W2 is modified (step S106). Furthermore, step S106 is the same process as step S101 described above, and is performed with the moisture content in the processing container 70 adjusted.

[0118] Then, the lower wafer W2 is transported to the surface hydrophilization device 40 by the conveying device 61 to hydrophilize the bonding surface W2j of the lower wafer W2, and the bonding surface W2j is cleaned (step S107).

[0119] Next, the lower wafer W2 is transported to the bonding unit 41 via the transport device 61. The lower wafer W2, which has been transported into the bonding unit 41, is then transported to the position adjustment mechanism 210 via the transfer unit 200. Then, the horizontal orientation of the lower wafer W2 is adjusted by the position adjustment mechanism 210 (step S108).

[0120] Next, the lower wafer W2 is transferred to the lower holding disk 231 and held in the lower holding disk 231 with the cut portion facing a predetermined direction (step S109).

[0121] Next, the horizontal position of the upper wafer W1 held on the upper holding disk 230 and the lower wafer W2 held on the lower holding disk 231 is adjusted (step S110).

[0122] Next, the vertical position of the upper wafer W1 held on the upper holding disk 230 and the lower wafer W2 held on the lower holding disk 231 is adjusted (step S111). Specifically, the first moving part 250 moves the lower holding disk 231 vertically upward, thereby bringing the lower wafer W2 closer to the upper wafer W1.

[0123] Next, after releasing the adsorption and retention of the upper wafer W1 by the multiple inner adsorption parts 392 (step S112), the center of the upper wafer W1 is pressed by lowering the pressing pin 281 of the impact pin 280 (step S113).

[0124] When the center portion of the upper wafer W1 contacts the center portion of the lower wafer W2 and is pressed down by the pin 280 with a predetermined force, bonding begins between the pressed center portions of the upper wafer W1 and the lower wafer W2. That is, since the bonding surfaces W1j of the upper wafer W1 and W2j of the lower wafer W2 have been modified, van der Waals forces (intermolecular forces) are first generated between the bonding surfaces W1j and W2j, causing them to bond together. Furthermore, since the bonding surfaces W1j of the upper wafer W1 and W2j of the lower wafer W2 have been hydrophilized, hydrogen bonding occurs between the hydrophilic groups of the bonding surfaces W1j and W2j, firmly bonding them together. In this way, a bonding region is formed.

[0125] Subsequently, a bonding region is generated between the upper wafer W1 and the lower wafer W2, with a bonding wave expanding from the center of both wafers outwards. Then, the adhesion of the multiple outer adsorption portions 391 to the upper wafer W1 is released (step S114). As a result, the outer periphery of the upper wafer W1, held by the outer adsorption portions 391, falls off. Consequently, the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 abut against each other across their entire surfaces, forming an overlapping wafer T.

[0126] Next, the pressing pin 281 is raised to the upper holding plate 230, and the lower holding plate 231 releases its hold on the lower wafer W2. Then, the overlapping wafer T is removed from the bonding device 41 via the transfer device 61. This completes the series of bonding processes.

[0127] Figure 9 This is a timing diagram showing the operation of each part when the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 are modified in the bonding process involved in the embodiment. Furthermore, Figure 9 The diagram shows a timing diagram starting from the point in time when the upper wafer W1 is transported to the surface modification apparatus 30 before the start of the above-described step S101 (modification of the bonding surface W1j of the upper wafer W1).

[0128] After in-depth research, the inventors of this application discovered that by adjusting the moisture content within the processing container 70 of the surface modification apparatus 30, it is possible to promote the formation of dangling bonds at the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2. Therefore, in the surface modification apparatus 30 of the embodiment, the moisture content within the processing container 70 is adjusted by supplying a humidifying gas into the processing container 70 before performing surface modification on the upper wafer W1.

[0129] The control unit 5 starts operating the inactive gas supply mechanism 123 from the time T10 when the wafer W1 is transferred to the surface modification device 30 to supply inactive gas into the processing container 70.

[0130] In addition, the control unit 5 starts the humidifying gas supply mechanism 124 from time T10 to supply the humidifying gas and the inactive gas into the processing container 70 together.

[0131] Furthermore, when supplying humidifying gas into the processing container 70, the control unit 5 can use a spectrophotometer 141 or a mass spectrometer 142 to measure the value indicating the moisture content within the processing container 70. In this case, the control unit 5 can control the flow rate or water content of the humidifying gas based on the measured value indicating the moisture content within the processing container 70.

[0132] Figure 10 and Figure 11 This is a diagram illustrating an example of the measurement results of the moisture content within the treatment container 70. Figure 10 The image shows emission data for each wavelength within the processing container 70 immediately after it was opened to the atmosphere during maintenance. Figure 10 The image shows luminescence data measured by spectrophotometer 141 when a nitrogen plasma, which is generated as a process gas, is produced within the processing container 70. The nitrogen plasma includes nitrogen ions at a first excitation energy level (1st POS) and nitrogen ions at a second excitation energy level (2nd POS) with higher reactivity than the nitrogen ions at the first excitation energy level. The wavelengths of the nitrogen ions at the first excitation energy level are in the range of approximately 530 nm to 800 nm, and the wavelengths of the nitrogen ions at the second excitation energy level are in the range of approximately 280 nm to 440 nm. Figure 10 The emission data shown indicates that almost no nitrogen ions at the first excitation energy level were generated when the treatment container 70 was opened to the atmosphere during maintenance. This is believed to be because, by opening to the atmosphere, the water content inside the treatment container 70 increases, and the energy of the nitrogen ions at the first excitation energy level is transferred to the water (H2O) present in the treatment container 70, thereby causing the nitrogen ions at the first excitation energy level to disappear from the treatment container 70.

[0133] Figure 11 The image shows emission data for each wavelength within the processing container 70 after the surface modification of the upper wafer W1 has been repeated a specified number of times. Figure 11 The image shows luminescence data measured by spectrophotometer 141 when a plasma of nitrogen gas, which is generated as a process gas, is produced within the processing container 70. Figure 11 The luminescence data shown indicates an increase in the amount of nitrogen ions in the first excitation energy level when the surface modification of the upper wafer W1 is repeatedly performed within the processing container 70. This is believed to be because: when the surface modification is repeatedly performed, the moisture content within the processing container 70 decreases due to processes such as vacuuming, making it difficult for the energy of the nitrogen ions in the first excitation energy level to be transferred to the water (H2O), resulting in an increase in the amount of nitrogen ions remaining in the first excitation energy level.

[0134] The control unit 5 controls the spectrophotometer 141 and the processing gas supply mechanism 122 to acquire luminescence data supplied to the processing container 70, and measures the value of the peak generated in the luminescence data at the wavelength corresponding to the nitrogen ions of the first excitation energy level as a value representing the water content in the processing container 70. Furthermore, the control unit 5 controls the flow rate or water content of the humidifying gas based on the measured peak value at the wavelength corresponding to the nitrogen ions of the first excitation energy level. The value of the peak generated in the luminescence data of the spectrophotometer 141 at the wavelength corresponding to the nitrogen ions of the first excitation energy level increases as the water content in the processing container 70 decreases. Therefore, it is possible to determine whether the water content in the processing container 70 has decreased and fallen below a predetermined lower limit based on the value of the peak generated at the wavelength corresponding to the nitrogen ions of the first excitation energy level. For example, the control unit 5 determines whether the measured peak value is above or below a predetermined threshold, thereby determining whether the water content in the processing container 70 is below a predetermined lower limit. Furthermore, when the control unit 5 determines that the moisture content in the treatment container 70 is below a predetermined lower limit, it controls the humidifying gas supply mechanism 124 to increase the flow rate or moisture content of the humidifying gas. Thus, the control unit 5 can appropriately adjust the moisture content in the treatment container 70.

[0135] Figure 12 These are other examples of figures used to illustrate the results of moisture content measurements within the treatment container 70. Figure 12 The data shown are analytical values ​​obtained by analyzing the mass number (m / z = 18) of water (H2O) in the atmosphere inside the processing container 70 after it was opened to the atmosphere, under conditions where a vacuum had been applied inside the processing container 70. Figure 12 The data for the analytical values ​​measured by mass spectrometer 142 are shown in the figure. Figure 12 The analytical values ​​shown indicate that the moisture content inside the processing container 70 gradually decreases due to vacuuming when the surface modification of the upper wafer W1 is repeated a specified number of times within the processing container 70.

[0136] The control unit 5 measures the analytical value obtained by the mass spectrometer 142 as a value representing the moisture content within the processing container 70. Furthermore, the control unit 5 controls the flow rate or moisture content of the humidifying gas based on the measured analytical value. As the moisture content within the processing container 70 decreases, the analytical value obtained by the mass spectrometer 142 decreases. For example, the control unit 5 determines whether the measured analytical value falls below a predetermined threshold, thereby determining whether the moisture content within the processing container 70 is below a predetermined lower limit. Moreover, if the control unit 5 determines that the moisture content within the processing container 70 is below the predetermined lower limit, it controls the humidifying gas supply mechanism 124 to increase the flow rate or moisture content of the humidifying gas. Thus, the control unit 5 can appropriately adjust the moisture content within the processing container 70.

[0137] Return to Figure 9The control unit 5 raises the lifting pin from the platform 80 at time T11, a predetermined time elapsed from time T10. At time T12, a predetermined time elapsed from time T11, the gate valve 72 is opened. At time T13, a predetermined time elapsed from time T12, the control unit 5 causes the conveying arm of the conveying device 61 to enter the processing container 70, transferring the upper wafer W1 held on the conveying arm to the lifting pin. At time T14, when the conveying arm of the conveying device 61 withdraws from the processing container 70, the control unit 5 closes the gate valve 72. Furthermore, at time T15, a predetermined time elapsed from time T14, the control unit 5 stops the inactive gas supply mechanism 123, thus ending the transfer of the upper wafer W1 into the processing container 70. The period from time T10 to time T15 is referred to as the "standby period".

[0138] The control unit 5 stops the humidifying gas supply mechanism 124 at time T15. That is, during standby, the control unit 5 adjusts the water content in the processing container 70 by supplying humidifying gas into the processing container 70. The water content in the processing container 70 is adjusted to, for example, within the range of 1000 ppm to 5000 ppm.

[0139] Furthermore, starting from the last time T15 of the standby period, the control unit 5 adjusts the opening of the APC valve 133 from the initial first opening to full opening, thereby evacuating the processing container 70. Moreover, at time T16, after a predetermined time has elapsed from time T15, the control unit 5 lowers the lifting pin toward the stage 80 to place the upper wafer W1 onto the stage 80.

[0140] Starting from time T17, after a predetermined time has elapsed since time T16, the control unit 5 adjusts the opening of the APC valve 133 from fully open to a second opening that is larger than the first opening, thereby setting the pressure inside the processing container 70 to the process pressure used in the surface modification process.

[0141] After the pressure inside the processing container 70 reaches the process pressure, the control unit 5 starts operating the processing gas supply mechanism 122 from time T18 to supply nitrogen gas as the processing gas into the processing container 70. Moreover, at time T19, after a predetermined time has elapsed from time T18, the control unit 5 controls the first high-frequency power supply 106 to apply a high-frequency voltage to the stage 80, thereby generating nitrogen plasma inside the processing container 70.

[0142] The bonding surface W1j of the upper wafer W1 is modified by irradiating it with nitrogen ions from the plasma generated in this way. As a result, dangling bonds of silicon atoms are formed on the outermost surface of the bonding surface W1j.

[0143] At time T20, after a predetermined time has elapsed since time T19, control unit 5 stops the first high-frequency power supply 106 and adjusts the opening of APC valve 133 from the second opening to the first opening, thereby reducing the pressure inside processing container 70 to the initial pressure. Furthermore, at time T21, when the pressure inside processing container 70 reaches the initial pressure, control unit 5 raises the lifting pin from stage 80 to position the modified upper wafer W1 above stage 80. Finally, at time T22, after a predetermined time has elapsed since time T21, control unit 5 stops the processing gas supply mechanism 122.

[0144] At time T23, after a predetermined time has elapsed since time T22, control unit 5 activates inactive gas supply mechanism 123 to supply inactive gas into processing container 70. This replaces the nitrogen remaining in processing container 70 with inactive gas. Furthermore, at time T24, after a predetermined time has elapsed since time T23, control unit 5 completely replaces the nitrogen remaining in processing container 70 with inactive gas, thereby completing the modification of the bonding surface W1j of upper wafer W1. Hereinafter, the period from time T15, the last time of the standby period, to time T24 will be appropriately referred to as the "first process period".

[0145] Additionally, at time T24, the final time of the first process, control unit 5 opens gate valve 72. At time T25, after a predetermined time has elapsed since time T24, control unit 5 causes the transfer arm of transfer device 61 to enter the processing container 70, transferring the modified upper wafer W1, positioned above the stage 80, to the transfer arm. Afterwards, control unit 5 uses transfer device 61 to transfer the modified upper wafer W1 to the surface hydrophilization device 40.

[0146] When the modified upper wafer W1 is transferred to the surface hydrophilization apparatus 40, the unmodified lower wafer W2 is transferred to the surface modification apparatus 30. Specifically, after the control unit 5 holds the lower wafer W2 on the transfer arm of the transfer device 61, it moves the transfer device 61 towards the surface modification apparatus 30. Furthermore, at time T26 when the transfer device 61 reaches the surface modification apparatus 30, the control unit 5 causes the transfer arm of the transfer device 61 to enter the processing container 70, transferring the lower wafer W2 held on the transfer arm to the lifting pin. At time T27 when the transfer arm of the transfer device 61 withdraws from the processing container 70, the control unit 5 closes the gate valve 72. Afterward, the control unit 5 waits until time T28, a predetermined time has elapsed since time T27. In this way, during the period from time T24 to time T28, the unmodified lower wafer W2 is transferred into the processing container 70 to replace the modified upper wafer W1. The period from time T24, the last time of the first process period, to time T28, will be appropriately referred to as the "wafer replacement period". Furthermore, from time T28, the last time of the wafer replacement period, the lower wafer W2 is processed in the same manner as the upper wafer W1 in the first process period. As a result, the bonding surface W2j of the lower wafer W2 is modified. The period from time T28, the last time 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 appropriately referred to as the "second process period". When the second process period ends, the control unit 5 can remove the modified lower wafer W2 from the surface modification device 30 via the conveying device 61.

[0147] In this way, in the embodiment, by modifying the bonding surface W1j of the upper wafer W1 while adjusting the amount of moisture in the processing container 70, it is possible to suppress the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 that are being bonded.

[0148] Reasons for suppressing the decrease in bonding strength between wafers

[0149] The following explains the reasoning for suppressing the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 by modifying the bonding surface W1j of the upper wafer W1 under the condition of adjusting the moisture content in the processing container 70.

[0150] That is, in this embodiment, before modifying the upper wafer W1, the moisture content in the processing container 70 is adjusted by supplying humidifying gas into the processing container 70 that can house the upper wafer W1. As a result, the moisture content in the processing container 70 increases, resulting in a state where a large amount of moisture (H2O) exists near the bonding surface W1j of the upper wafer W1.

[0151] In this state, the upper wafer W1 is surface modified using a nitrogen plasma as the processing gas. At this time, the energy of nitrogen ions in the first excitation energy level and the nitrogen ions in the second excitation energy level, which have relatively low activity, are transferred to the water (H2O) present near the junction surface W1j.

[0152] As a result, nitrogen ions from the first excitation energy level disappear from the processing container 70, while the ratio of nitrogen ions from the second excitation energy level, which have higher reactivity than those from the first excitation energy level, increases. Consequently, nitriding caused by nitrogen ions from the first excitation energy level can be suppressed, and nitrogen ions from the relatively more reactive second excitation energy level can be irradiated onto the junction surface W1, thereby promoting the formation of dangling bonds of silicon atoms on the outermost surface of the junction surface W1j. Furthermore, since nitriding caused by nitrogen ions from the first excitation energy level is suppressed on the outermost surface of the junction surface W1j, the formation of nitrided portions is reduced.

[0153] In this state, when the upper wafer W1 is removed from the surface modification device 30 and exposed to the atmospheric atmosphere, the dangling bonds of silicon atoms are capped by OH groups due to the moisture (H2O) in the atmosphere.

[0154] Here, since the generation of nitrided portions at the outermost position of the bonding surface W1j is reduced, the formation of OH groups is not hindered by these nitrided portions.

[0155] Next, the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2, which are removed from the surface modification device 30, are hydrophilized using the surface hydrophilization device 40, and then bonded using the bonding device 41. In this bonding process, a bond is formed from the center of the wafer W towards its ends through hydrogen bonding between the OH groups of bonding surfaces W1j and W2j.

[0156] In this embodiment, since the generation of nitrided portions at the outermost surface of the bonding surface W1j is reduced, the bonding caused by the OH groups is not hindered by these nitrided portions. That is, in this embodiment, the generation of nitrided portions that would hinder the formation of Si-O-Si bonds originating from OH groups can be suppressed by adjusting the water content within the processing container 70. Therefore, according to this embodiment, the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 being bonded can be suppressed.

[0157] <Variation Example 1>

[0158] Next, refer to Figures 13-15 Various variations of the implementation method will be described. Figure 13This is a timing diagram showing the operation of each part when the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 are modified in the bonding process involved in the modified example 1 of the embodiment. Furthermore, Figure 13 The diagram shows the timing from the point when the upper wafer W1 is moved to the surface modification apparatus 30 before the start of the above-described step S101 (modification of the bonding surface W1j of the upper wafer W1).

[0159] The control unit 5 starts operating the inactive gas supply mechanism 123 from the time T10 when the wafer W1 is transferred to the surface modification device 30, to supply inactive gas into the processing container 70.

[0160] In addition, the control unit 5 starts the humidifying gas supply mechanism 124 from time T10 to supply the humidifying gas and the inactive gas into the processing container 70 together.

[0161] At time T11, after a predetermined time has elapsed since time T10, control unit 5 raises the lifting pin from the platform 80. At time T12, after a predetermined time has elapsed since time T11, control unit 5 opens the gate valve 72. At time T13, after a predetermined time has elapsed since time T12, control unit 5 causes the conveying arm of the conveying device 61 to enter the processing container 70 and transfers the upper wafer W1 held on the conveying arm to the lifting pin. At time T14, when the conveying arm of the conveying device 61 withdraws from the processing container 70, control unit 5 closes the gate valve 72. Furthermore, at time T15, after a predetermined time has elapsed since time T14, control unit 5 stops the inactive gas supply mechanism 123, ending the transfer of the upper wafer W1 into the processing container 70.

[0162] Furthermore, even after the last time T15 of the standby period, the control unit 5 does not stop the humidifying gas supply mechanism 124, but continues to supply humidifying gas into the processing container 70. That is, in Modification 1, even after the standby period has elapsed, the control unit 5 continues to supply humidifying gas into the processing container 70.

[0163] Starting from the last time T15 of the standby period, the control unit 5 adjusts the opening of the APC valve 133 from the initial first opening to full opening, thereby evacuating the processing container 70. Furthermore, at time T16, after a predetermined time has elapsed from time T15, the control unit 5 lowers the lifting pin toward the stage 80 to place the upper wafer W1 onto the stage 80.

[0164] Starting from time T17, after a predetermined time has elapsed since time T16, the control unit 5 adjusts the opening of the APC valve 133 from fully open to a second opening that is larger than the first opening, thereby setting the pressure inside the processing container 70 to the process pressure used in the surface modification process.

[0165] After the pressure inside the processing container 70 reaches the process pressure, the control unit 5 starts operating the processing gas supply mechanism 122 from time T18 to supply nitrogen gas as the processing gas into the processing container 70. Moreover, at time T19, after a predetermined time has elapsed from time T18, the control unit 5 controls the first high-frequency power supply 106 to apply a high-frequency voltage to the stage 80, thereby generating nitrogen plasma inside the processing container 70.

[0166] The bonding surface W1j of the upper wafer W1 is modified by irradiating it with nitrogen ions from the plasma generated in this way. As a result, dangling bonds of silicon atoms are formed on the outermost surface of the bonding surface W1j.

[0167] At time T20, after a predetermined time has elapsed since time T19, control unit 5 stops the first high-frequency power supply 106 and adjusts the opening of APC valve 133 from the second opening to the first opening, thereby reducing the pressure inside processing container 70 to the initial pressure. Furthermore, at time T21, when the pressure inside processing container 70 reaches the initial pressure, control unit 5 raises the lifting pin from stage 80 to position the modified upper wafer W1 above stage 80. Finally, at time T22, after a predetermined time has elapsed since time T21, control unit 5 stops the processing gas supply mechanism 122.

[0168] At time T23, after a predetermined time has elapsed since time T22, control unit 5 activates the inactive gas supply mechanism 123 to supply inactive gas into processing container 70. As a result, control unit 5 replaces the nitrogen gas remaining in processing container 70 with inactive gas. Furthermore, at time T24, after a predetermined time has elapsed since time T23, control unit 5 completely replaces the nitrogen gas remaining in processing container 70 with inactive gas, thereby completing the modification of the bonding surface W1j of upper wafer W1.

[0169] Additionally, at time T24 when the modification of the bonding surface W1j of the upper wafer W1 is completed, the control unit 5 stops the humidifying gas supply mechanism 124.

[0170] That is, in Modified Example 1, during the first process period from the last time T15, which is the standby period, to the time T24, when the modification of the bonding surface W1j of the upper wafer W1 is completed, the control unit 5 continuously supplies humidifying gas into the processing container 70.

[0171] Therefore, the control unit 5 can continuously adjust the water content in the processing container 70 during the first process period after the standby period. Thus, according to Modification 1, the generation of nitrided portions that would hinder bonding due to OH groups at the outermost surface of the bonding surface W1j can be reduced more efficiently, thereby more efficiently suppressing the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 that are being bonded.

[0172] Furthermore, at the final time T24 during the first process, the control unit 5 opens the gate valve 72. Since the following processing is the same as in the embodiment, detailed descriptions are omitted.

[0173] <Variation Example 2>

[0174] The difference between Modified Example 2 and Modified Example 1 is that, after time T28, which is the last time during the wafer replacement, humidifying gas is further supplied into the processing container 70. Since other aspects are the same as Modified Example 1, detailed description is omitted.

[0175] Figure 14 This is a timing diagram showing the operation of each part when the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 are modified in the bonding process involved in the modified example 2 of the embodiment. Furthermore, in Figure 14 The diagram shows the timing from the point when the upper wafer W1 is moved to the surface modification apparatus 30 before the start of the above-described step S101 (modification of the bonding surface W1j of the upper wafer W1).

[0176] The control unit 5 starts operating the humidifying gas supply mechanism 124 from the last time T28 during the wafer replacement period to supply humidifying gas into the processing container 70. Moreover, when the modification of the bonding surface W2j of the lower wafer W2 is completed, the control unit 5 stops the humidifying gas supply mechanism 124.

[0177] That is, in Modification 2, during the second process from the last time T28, which is the wafer replacement period, to the time when the modification of the bonding surface W2j of the lower wafer W2 is completed, humidifying gas is further supplied into the processing container 70.

[0178] Therefore, the control unit 5 can further adjust the moisture content in the processing container 70 during the second process after the wafer replacement. Thus, according to Modification 2, the formation of nitrided portions that hinder bonding due to OH groups at the outermost position of the bonding surface W2j can be reduced more efficiently, thereby more effectively suppressing the decrease in bonding strength between the upper wafer W1 and the lower wafer W2 during bonding.

[0179] <Variation Example 3>

[0180] In the above embodiments, an example is shown where the value representing the water content in the processing container 70 is measured when adjusting the water content in the processing container 70, and the flow rate or water content of the humidifying gas is controlled based on the measurement result. Conversely, the value representing the water content in the processing container 70 can also be measured after adjusting the water content in the processing container 70, and the modification of the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 can be determined based on the measurement result. Therefore, in Modification Example 3, the following example is described: the value representing the water content in the processing container 70 is measured after adjusting the water content in the processing container 70, and the modification of the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 can be determined based on the measurement result.

[0181] Figure 15 This is a flowchart illustrating an example of the process for determining whether the modification involved in Modification 3 of the embodiment can be performed. Furthermore, in Figure 15 The text shows from Figure 9 The flowchart shows the time point from the end of the treatment (adjustment of moisture content in treatment container 70) at time T15.

[0182] When the humidifying gas supply mechanism 24 is stopped to end the adjustment of the moisture content in the treatment container 70 (step S201), the control unit 5 measures the value indicating the moisture content in the treatment container 70 (step S202). The value indicating the moisture content in the treatment container 70 is, for example, the value of the peak generated at the wavelength corresponding to the nitrogen ion of the first excitation energy level in the luminescence data measured by the spectrophotometer 141. Alternatively, the value indicating the moisture content in the treatment container 70 can also be an analytical value measured by the mass spectrometer 142, that is, an analytical value obtained by analyzing the mass number (m / z = 18) of water (H2O) in the atmosphere inside the treatment container 70.

[0183] Next, the control unit 5 determines whether the modification (i.e., surface modification treatment) of the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 can be performed based on the measured value indicating the amount of water in the processing container 70 (step S203). For example, it is assumed that the value indicating the amount of water in the processing container 70 is the value of the peak generated at the wavelength corresponding to the nitrogen ions of the first excitation energy level. For example, if the measured peak value is above a predetermined threshold, the control unit 5 estimates that the amount of water in the processing container 70 is below a predetermined lower limit value, and therefore determines that the surface modification treatment cannot be performed. On the other hand, if the measured peak value is below the predetermined threshold value, the control unit 5 estimates that the amount of water in the processing container 70 is not below the predetermined lower limit value, and therefore determines that the surface modification treatment can be performed.

[0184] If 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.

[0185] On the other hand, if the control unit 5 determines that a surface modification process can be performed (step S205; "Yes"), it proceeds to... Figure 9 The process shown, starting from time T15, generates plasma of the processing gas within the processing container 70 (step S206). As a result, the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2 are modified.

[0186] Therefore, according to Modification 3, it is possible to appropriately determine whether surface modification treatment can be performed based on the value representing the amount of water in the treatment container 70 after adjusting the amount of water in the treatment container 70.

[0187] <Effect>

[0188] The surface modification method described in this embodiment is a surface modification method that modifies the bonding surface (e.g., bonding surface W1j) of a substrate (e.g., upper wafer W1) bonded to another substrate (e.g., lower wafer W2) using plasma of a processing gas. This surface modification method includes an adjustment step and a modification step. In the adjustment step, the moisture content within a processing container (e.g., processing container 70) that can house the substrate is adjusted by supplying humidified gas into the processing container. In the modification step, with the moisture content within the processing container adjusted, plasma of the processing gas is generated within the processing container, thereby modifying the bonding surface of the substrate. This suppresses the decrease in bonding strength between the bonded substrates.

[0189] Alternatively, during the adjustment process, humidified gas can be supplied to the processing container during the first period from the start of transporting the substrate into the processing container until the substrate is placed into the processing container (e.g., standby period). This reduces the amount of chemical reaction portions (e.g., nitriding portions) that would hinder bonding due to OH groups at the outermost surface of the bonding surface during surface modification treatment, thus effectively suppressing the decrease in bonding strength.

[0190] Alternatively, during the adjustment process, humidified gas can be continuously supplied during a second period (e.g., the first process period) from the end of the first period until the modification of the bonding surface of the substrate is completed. This allows for a more efficient reduction in the formation of chemical reaction portions (e.g., nitriding portions) on the outermost surface of the bonding surface during surface modification treatment that would hinder bonding due to OH groups, thus more effectively suppressing the decrease in bonding strength.

[0191] Alternatively, during the adjustment process, in a third period (e.g., during the second process) from the point where unmodified substrates are moved into the processing container to replace the modified substrates until the modification of the bonding surfaces of the other substrates is completed, humidified gas can be further supplied into the processing container. This can more effectively reduce the formation of chemical reaction portions (e.g., nitriding portions) at the outermost surface of the bonding surface during surface modification treatment that would hinder bonding due to OH groups, thus more effectively suppressing the decrease in bonding strength.

[0192] Furthermore, the surface modification method described in the embodiments may also include a measurement step. In the measurement step, a value indicating the amount of moisture in the treatment container can be measured during the adjustment step. Moreover, in the adjustment step, the flow rate or moisture content of the humidified gas can be controlled based on the value indicating the amount of moisture in the treatment container measured in the measurement step. Thus, the amount of moisture in the treatment container can be appropriately adjusted.

[0193] Furthermore, the surface modification method according to the embodiments may also include a measurement step and a determination step. In the measurement step, a value indicating the amount of water in the processing container can be measured after the adjustment step. In the determination step, it can be determined whether the modification step can be performed based on the value indicating the amount of water in the processing container measured in the measurement step. Moreover, in the modification step, if it is determined by the determination step that the modification step can be performed, plasma of the processing gas can be generated in the processing container. Thus, it is possible to appropriately determine whether the surface modification treatment can be performed based on the value indicating the amount of water in the processing container measured after adjusting the amount of water in the processing container.

[0194] Furthermore, the processing gas can be at least one of oxygen, nitrogen, and argon. Therefore, even when the bonding surfaces of the substrates are modified using various processing gases, the decrease in bonding strength between the substrates being bonded can be suppressed.

[0195] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, and modified in various ways without departing from the appended claims and their spirit.

[0196] For example, in the above embodiment, the case of supplying humidifying gas to the processing container 70 by activating the humidifying gas supply mechanism 124 has been described as an example, but the disclosed technology is not limited to this. For example, a gas containing moisture from the atmosphere can be supplied to the processing container 70 as a humidifying gas by opening the processing container 70 to the atmosphere. Alternatively, opening the processing container 70 to the atmosphere can also be performed during wafer replacement.

[0197] Explanation of reference numerals in the attached figures

[0198] 1: Bonding system; 5: Control unit; 30: Surface modification device; 41: Bonding device; 70: Processing container; 122: Processing gas supply mechanism; 123: Inactive gas supply mechanism; 124: Humidifying gas supply mechanism; 141: Spectrophotometer; 142: Mass spectrometer; W1: Upper wafer; W2: Lower wafer.

Claims

1. A surface modification method for modifying the bonding surface of a substrate to be bonded to other substrates by means of plasma of a processing gas, the surface modification method comprising; The adjustment process involves supplying humidified gas into a processing container capable of housing the substrate to adjust the moisture content within the processing container; and In the modification process, with the moisture content in the processing container adjusted, plasma of the processing gas is generated in the processing container, thereby modifying the bonding surface of the substrate.

2. The surface modification method according to claim 1, characterized in that, In the adjustment process, during the first period from the start of conveying the substrate into the processing container until the substrate is moved into the processing container, the humidified gas is supplied into the processing container.

3. The surface modification method according to claim 2, characterized in that, In the adjustment process, the humidified gas is continuously supplied during the second period from the end of the first period until the modification of the bonding surface of the substrate is completed.

4. The surface modification method according to any one of claims 1 to 3, characterized in that, In the adjustment process, during the third period from when other unmodified substrates are moved into the processing container to replace the modified substrates until the modification of the bonding surfaces of the other substrates is completed, the humidified gas is further supplied into the processing container.

5. The surface modification method according to any one of claims 1 to 3, characterized in that, The surface modification method further includes a measurement step, in which a value representing the water content within the treatment container is measured during the execution of the adjustment step. In the adjustment process, the flow rate or water content of the humidified gas is controlled based on the value representing the water content in the processing container measured in the measurement process.

6. The surface modification method according to any one of claims 1 to 3, characterized in that, Also includes: The measurement process involves measuring a value representing the amount of water in the treatment container after the adjustment process. as well as The determination process determines whether the modification process can be performed based on the value representing the water content in the treatment container measured in the measurement process.

7. The surface modification method according to any one of claims 1 to 3, characterized in that, The processing gas is at least one of oxygen, nitrogen, and argon.

8. A surface modification apparatus for modifying the bonding surface of a substrate to other substrates by using plasma of a processing gas, the surface modification apparatus comprising: A processing container capable of containing the substrate; A first gas supply unit is used to supply the processing gas into the processing container; a second gas supply portion for supplying a humidified gas into the processing vessel; as well as Control Department in, The control unit causes each part to perform a surface modification method, the surface modification method including: The adjustment process involves supplying the humidified gas into the processing container to adjust the water content within the container. as well as In the modification process, with the moisture content in the processing container adjusted, plasma of the processing gas is generated in the processing container, thereby modifying the bonding surface of the substrate.

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