Bonding strength evaluation method and bonding strength evaluation device

Abstract

To provide a joining method that can firmly join two objects.SOLUTION: A joining method of joining two boards W1 and W2 includes a joining step of joining two substrates W1 and W2, and a bonding strength evaluation step of evaluating the bonding strength between the two substrates W1 and W2 using a crack-and-opening method in an environment where the moisture content is less than a preset reference moisture content after the joining step.SELECTED DRAWING: Figure 14A

Description

[Technical field]

[0001] The present invention relates to a bonding method. [Background technology]

[0002] A bonding method has been proposed in which two substrates are bonded to each other by activating the bonding surfaces of each of the substrates by colliding particles having a preset kinetic energy with the bonding surfaces of the two substrates, and then bonding the two substrates by bringing the activated bonding surfaces into contact with each other (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-113633 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the bonding method described in Patent Document 1, when impurities are attached to the bonding surfaces of the two substrates, the impurities are removed by colliding with particles before activating the bonding surfaces. However, since there is variation in the adhesion strength of the impurities, it is difficult to set an appropriate time for irradiating the particles to remove the impurities, and if the bonding surfaces are irradiated with particles more than necessary, the bonding surfaces become rough, which may result in a decrease in the bonding strength when the two substrates are bonded together.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a joining method capable of firmly joining two objects to be joined. [Means for solving the problem]

[0006] In order to achieve the above object, the bonding method according to the present invention comprises the steps of: A method for joining two objects to be joined, comprising the steps of: a heat treatment step of heating at least one of the bonding surfaces of the two objects to be bonded to each other to a temperature higher than 60° C. in a reduced pressure atmosphere; an activation treatment step of activating the bonding surfaces of the two objects to be bonded while maintaining a reduced pressure atmosphere after the heat treatment step; The method includes a bonding step of bonding the two objects to be bonded in a state in which a reduced pressure atmosphere is maintained after the activation treatment step. Effect of the Invention

[0007] According to the present invention, in a state where the two objects to be bonded are spaced apart, a heat treatment step is performed in which the bonding surfaces of the two objects to be bonded are heated to a temperature higher than 60°C under a reduced pressure atmosphere, and then the two objects to be bonded are bonded under a reduced pressure atmosphere. By heating the bonding surfaces of the two objects to be bonded to a temperature higher than 60°C under a reduced pressure atmosphere, water or impurities present on the bonding surfaces of the objects to be bonded are vaporized and removed, or adhesion of water or impurities floating near the bonding surfaces of the objects to be bonded can be suppressed, so that the bonding surfaces of the objects to be bonded are easily activated or hydrophilized. Therefore, the bonding strength between the two objects to be bonded when the two objects to be bonded can be increased. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a bonding system according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic front view of a joining device according to a first embodiment. [Diagram 3] 3 is a schematic configuration diagram of a second transfer device, a bonding device, and a load lock unit according to the first embodiment. FIG. [Figure 4] FIG. 2 is a diagram showing a part of the joining device according to the first embodiment. [Diagram 5] 5A to 5C are explanatory views of the operation of the joining device according to the first embodiment. [Figure 6] 5A to 5C are explanatory views of the operation of the joining device according to the first embodiment. [Figure 7A]6 is a diagram showing a state in which a holding section of a second conveying device according to the first embodiment is disposed in a bonding device. FIG. [Figure 7B] 4 is a diagram showing a state in which a holder of a second transfer device according to the first embodiment is disposed in a load lock unit. FIG. [Figure 8] 4 is a flowchart showing the flow of a joining method according to the first embodiment. [Figure 9A] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the second transfer device receives a substrate from the load lock unit. [Figure 9B] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the second transfer device transfers a substrate to the bonding device. [Figure 10A] 4 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating a state in which a substrate has been transferred to the bonding device. FIG. [Figure 10B] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how a substrate is held by a head within the bonding device. [Figure 11A] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the second transfer device receives a substrate from the load lock unit. [Figure 11B] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the bonding device receives a substrate from the second transfer device. [Figure 12A] 4 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, and illustrates how a substrate is held on a stage within the bonding device. FIG. [Figure 12B] 4 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, and illustrates how a bonding process is performed in the bonding device. FIG. [Figure 13A] FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the second transfer device receives a substrate from the bonding device. [Figure 13B]FIG. 3 shows a second transfer device, a bonding device, and a load lock unit according to the first embodiment, illustrating how the second transfer device transfers a substrate from the bonding device to the load lock unit. [Figure 14A] FIG. 2 is a diagram for explaining a method for measuring the bonding strength (converted into surface energy) of substrates using a blade insertion method. [Figure 14B] 1A to 1C are diagrams for explaining a method for evaluating bonding strength according to an embodiment. [Figure 15] 5 is a diagram showing the relationship between the bonding strength between the substrates and the air pressure in the chamber during bonding in the first embodiment. FIG. [Figure 16] 10 is a flowchart showing the flow of a hydrophilic bonding method according to a second embodiment of the present invention. [Figure 17A] 1 is a photograph of two substrates bonded by a hydrophilic bonding method in which a heat treatment step is not performed before an activation treatment step according to a comparative example. [Figure 17B] 11 is a photograph of two substrates bonded by a hydrophilic bonding method according to the second embodiment. [Figure 18] FIG. 13 is a schematic configuration diagram of a bonding system according to a modified example. [Figure 19] FIG. 13 is a schematic configuration diagram of an activation treatment apparatus according to a modified example. [Figure 20] 13 is a flowchart showing the flow of a hydrophilic bonding method according to a modified example. [Figure 21] FIG. 13 is a diagram showing a part of a joining device according to a modified example. [Figure 22] FIG. 13 is a diagram showing a part of a joining device according to a modified example. [Figure 23] FIG. 13 is a diagram showing a part of a joining device according to a modified example. [Figure 24A] FIG. 13 is a diagram showing a part of a joining device according to a modified example. [Figure 24B] FIG. 13 is a diagram showing a part of a joining device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Embodiment 1) Hereinafter, a bonding apparatus according to a first embodiment of the present invention will be described with reference to the drawings. In the bonding apparatus according to this embodiment, in a chamber in a reduced pressure atmosphere, the bonding surfaces of two substrates are heated, and then an activation process is performed. Then, the substrates are brought into contact with each other and pressurized and heated to bond the two substrates. Here, the substrates W1 and W2 are objects to be bonded, such as a Si substrate, a glass substrate such as a SiO2 glass substrate, an oxide substrate (e.g., a silicon oxide (SiO2) substrate, an alumina substrate (Al2O3) including a sapphire substrate, a gallium oxide (Ga2O3), etc.), a nitride substrate (e.g., silicon nitride (SiN), aluminum nitride (AlN), gallium nitride (GaN)), a GaAs substrate, a silicon carbide (SiC) substrate, a lithium tantalate (Lt:LiTaO3) substrate, a lithium niobate substrate (Ln:LiNbO3), a diamond substrate, etc. Alternatively, the substrates W1 and W2 may be substrates having electrodes formed of metals such as Au, Cu, Al, and Ti on the bonding surfaces. In the activation process, the bonding surfaces of the two substrates to be bonded to each other are irradiated with a particle beam to activate the bonding surfaces of the substrates.

[0010] 1, the bonding system according to this embodiment includes introduction ports 811 and 812, an ejection port 813, a first transfer device 82, a cleaning device 3, a bonding device 1, a load lock unit 83, a second transfer device 84, and a control unit 9. The control unit 9 controls the first transfer device 82, the cleaning device 3, the bonding device 1, and the load lock unit 83. The first transfer device 82 and the cleaning device 3 are provided with HEPA (High Efficiency Particulate Air) filters (not shown). This creates an atmospheric pressure environment with extremely few particles inside the first transfer device 82 and the cleaning device 3.

[0011] The first transfer device 82 includes a transfer robot 821 having an arm with a holder 821a at its tip that holds a substrate. The transfer robot 821 is movable along the direction in which the introduction ports 811, 812 and the removal port 813 are arranged, and can rotate to change the orientation of the tip of the arm. The holder 821a has a vacuum chuck, an electrostatic chuck, or the like, and adsorbs and holds the side of the substrate opposite to the bonding surface.

[0012] The cleaning device 3 cleans the substrates while discharging water, cleaning liquid, or N2 gas toward the substrates. The cleaning device 3 has a stage (not shown) that supports the substrates, a rotary drive unit (not shown) that rotates the stage in a plane perpendicular to the vertical direction, and a cleaning nozzle (not shown) that discharges water, cleaning liquid, or N2 gas to which ultrasonic or megasonic vibrations have been applied. The cleaning device 3 cleans the entire bonding surfaces of the substrates W1 and W2 by rotating the stage while spraying water to which ultrasonic waves have been applied from the cleaning nozzle onto the bonding surfaces of the substrates while swinging the cleaning nozzle in the radial direction of the substrates W1 and W2. The cleaning device 3 spin-dries the substrates W1 and W2 by rotating the stage while stopping the discharge of water from the cleaning nozzle.

[0013] As shown in FIG. 2, the bonding apparatus 1 includes a chamber 120, a stage 141, a head 142, a stage driving unit 143, a head driving unit 144, substrate heating units 1411 and 1421, a positional deviation measuring unit 150, and particle beam sources 161 and 162. In the following description, the ±Z direction in FIG. 2 is appropriately defined as the up-down direction, and the XY direction is appropriately defined as the horizontal direction. The bonding apparatus 1 also includes covers 122A and 122B disposed in the chamber 120, and cover heating units 123A and 123B for heating the covers 122A and 122B. The covers 122A and 122B are disposed so as to include activation treatment areas in the activation treatment process around the stage 141 and the head 142. The cover heating units 123A and 123B are heaters fixed to the covers 122A and 122B on the opposite side to the particle beam sources 161 and 162, respectively. 3, the bonding apparatus 1 further includes a support mechanism 146 that is disposed near the stage 141 and receives the substrates W1, W2 transferred from the load lock unit 83 into the chamber 120. Returning to FIG. 2, the chamber 120 is connected to a vacuum pump 121a via an exhaust pipe 121b and an exhaust valve 121c. When the exhaust valve 121c is opened and the vacuum pump 121a is operated, the gas in the chamber 120 is exhausted to the outside of the chamber 120 through the exhaust pipe 121b, and the air pressure in the chamber 120 is reduced (decompressed). The air pressure in the chamber 120 is 10 -5 The pressure (degree of vacuum) within the chamber 120 can be adjusted by adjusting the amount of exhaust by varying the opening / closing amount of the exhaust valve 121c.

[0014] The stage 141 and the head 142 are disposed in the chamber 120 so as to face each other in the Z direction. The stage 141 supports the substrate W1 on its upper surface, and the head 142 supports the substrate W2 on its lower surface. The upper surface of the stage 141 and the lower surface of the head 142 may be roughened in consideration of the case where the contact surfaces of the substrates W1 and W2 with the stage 141 and the head 142 are mirror-finished and the substrates W1 and W2 are unlikely to peel off from the stage 141 and the head 142. The stage 141 and the head 142 each have a holding mechanism (not shown) for holding the substrates W1 and W2. The holding mechanism has an electrostatic chuck, a mechanical clamp, or the like. The stage 141 has a shape in which a step portion 141a is formed on the periphery. When the substrates W1 and W2 are placed on the stage 141, the periphery of the substrates W1 and W2 is disposed above the step portion 141a.

[0015] The stage driving unit 143 can move the stage 141 in the XY directions and rotate it around the Z axis. The head driving unit 144 has an elevation driving unit 1441 that raises and lowers the head 142 as shown by the arrow AR1, an XY direction driving unit 1442 that moves the head 142 in the XY directions, and a rotation driving unit 1443 that rotates the head 142 in a rotation direction around the Z axis. The head driving unit 144 also has a piezo actuator 1444 for adjusting the inclination of the head 142 with respect to the stage 141, and a pressure sensor 1445 for measuring the pressure applied to the head 142. The XY direction driving unit 1442 and the rotation driving unit 1443 move the head 142 relative to the stage 141 in the X direction, the Y direction, and the rotation direction around the Z axis, thereby enabling alignment between the substrate W1 held by the stage 141 and the substrate W2 held by the head 142. In addition, the stage driving unit 143 is not limited to a configuration in which it is arranged vertically below the stage 141. For example, a backup unit (not shown) that receives pressure vertically below the stage 141 may be provided, and the stage driving unit 143 may be arranged on the outer periphery of the stage 141 to drive the stage 141 from the side of the stage 141.

[0016] The lifting / lowering drive unit 1441 moves the head 142 vertically downward to bring the head 142 closer to the stage 141. The lifting / lowering drive unit 1441 also moves the head 142 vertically upward to move the head 142 away from the stage 141. When the lifting / lowering drive unit 1441 applies a driving force to the head 142 in a direction toward the stage 141 while the substrates W1 and W2 are in contact with each other, the substrate W2 is pressed against the substrate W1. The lifting / lowering drive unit 1441 is also provided with a pressure sensor 1441a that measures the driving force applied to the head 142 in a direction toward the stage 141. From the measured value by the pressure sensor 1441a, the pressure acting on the bonding surfaces of the substrates W1 and W2 when the substrate W2 is pressed against the substrate W1 by the lifting / lowering drive unit 1441 can be detected. The pressure sensor 1441a has, for example, a piezoelectric element.

[0017] A plurality of pairs of the piezo actuator 1444 and the pressure sensor 1445 are arranged between the head 142 and the XY direction drive unit 1442. The pressure sensor 1445 is interposed between the upper end of the piezo actuator 1444 and the lower side of the XY direction drive unit 1442. The piezo actuators 1444 can be individually expanded and contracted in the vertical direction, and by expanding and contracting, the tilt of the head 142 around the X axis and the Y axis and the vertical position of the head 142 are finely adjusted. In addition, the pressure sensor 1445 has, for example, a piezoelectric element and measures the pressure at a plurality of points on the lower surface of the head 142. Then, by driving each of the plurality of piezo actuators 411 so that the pressures measured by the plurality of pressure sensors 1445 are equal, the substrates W1 and W2 can be brought into contact with each other while maintaining the lower surface of the head 142 and the upper surface of the stage 141 parallel to each other.

[0018] The substrate heating units 1411 and 1421 are first bonded object heating units having electric heaters embedded in the back side of the holding mechanism when viewed from the surface side where the substrates W1 and W2 abut on the stage 141 and head 142 when the holding mechanism is an electrostatic chuck, for example. The substrate heating units 1411 and 1421 heat the substrates W1 and W2 by transferring heat to the substrates W1 and W2 supported by the stage 141 and head 142. The temperature of the substrates W1 and W2 or their bonding surfaces can be adjusted by adjusting the heat generation amount of the substrate heating units 1411 and 1421. The positional deviation amount measuring unit 150 measures the horizontal positional deviation amount of the substrate W1 with respect to the substrate W2 by recognizing the positions of alignment marks (alignment marks) provided on the substrates W1 and W2, respectively. The positional deviation amount measuring unit 150 recognizes the alignment marks of the substrates W1 and W2 by using light (for example, infrared light) that passes through the substrates W1 and W2, for example. The stage driving unit 143 performs an alignment operation between the substrates W1 and W2 by moving and rotating the stage 141 in the horizontal direction based on the amount of misalignment measured by the misalignment amount measuring unit 150. Both the measurement of the amount of misalignment by the misalignment amount measuring unit 150 and the alignment operation by the stage driving unit 143 are performed under the control of the control unit 9.

[0019] The particle beam sources 161 and 162 are, for example, fast atom beam (FAB) sources, and are activation processing units having a discharge chamber 1601, an electrode 1602 disposed in the discharge chamber 1601, a beam source driving unit 1603, and a gas supply unit 1604 for supplying argon gas into the discharge chamber 1601, as shown in FIG. 4. A FAB emission port 1601a for emitting neutral atoms is provided on the peripheral wall of the discharge chamber 1601. The discharge chamber 1601 is made of a carbon material. Here, the discharge chamber 1601 is in the shape of a long box, and a plurality of FAB emission ports 1601a are arranged in a straight line along the longitudinal direction. The beam source driving unit 1603 has a plasma generation unit (not shown) for generating plasma of argon gas in the discharge chamber 1601, and a DC power supply (not shown) for applying a DC voltage between the electrode 1602 and the peripheral wall of the discharge chamber 1601. The beam source driver 1603 applies a DC voltage between the peripheral wall of the discharge chamber 1601 and the electrode 1602 while generating a plasma of argon gas in the discharge chamber 1601. At this time, argon ions in the plasma are attracted to the peripheral wall of the discharge chamber 1601. At this time, the argon ions moving toward the FAB emission port 1601a receive electrons from the peripheral wall of the discharge chamber 1601, which is made of a carbon material and is located on the outer periphery of the FAB emission port 1601a, as they pass through the FAB emission port 1601a. ​​Then, these argon ions become electrically neutralized argon atoms and are emitted outside the discharge chamber 1601.

[0020] Here, as shown in FIG. 5, the particle beam sources 161 and 162 move as indicated by arrows AR22 while irradiating the bonding surfaces of the substrates W1 and W2 with particle beams as indicated by arrows AR21. Here, the particle beam sources 161 and 162 irradiate the particle beams to the regions including the covers 122A and 122B on the outer side of both ends of the substrate W1 in the moving direction of the particle beam sources 161 and 162, since the intensity of the particle beams varies in the moving direction in the projection plane of the particle beams alone, in order to reliably irradiate the entire substrates W1 and W2 with the particle beams. In addition, the intensity of the particle beams tends to decrease in the longitudinal direction of the discharge chamber 1601 of the particle beam source 161, that is, at both ends in the X-axis direction. Therefore, the length of the discharge chamber 1601 in the X-axis direction is set to cover the entire substrates W1 and W2 in the X-axis direction and to be longer than the length of the substrates W1 and W2 in the X-axis direction when the discharge chamber 1601 is arranged to overlap the substrates W1 and W2 in the Z-axis direction, as shown in FIG. 6, for example. Or, since the substrates W1 and W2 are circular in plan view, whereas the irradiation areas of the particle beam sources 161 and 162 are rectangular in plan view, areas other than the substrates W1 and W2 are irradiated. Here, the bonding apparatus 1 irradiates the bonding surfaces of the substrates W1 and W2 with the particle beam while moving the particle beam sources 161 and 162 in the +Y direction as indicated by the arrow AR22, for example, and then irradiates the bonding surfaces of the substrates W1 and W2 with the particle beam while moving the particle beam sources 161 and 162 in the -Y direction. The moving speed of the particle beam sources 161 and 162 is set to, for example, 1.2 to 14.0 mm / sec. The power supplied to the particle beam sources 161 and 162 is set to, for example, 1 kV and 100 mA. The flow rate of the argon gas introduced into the discharge chamber 1601 of each of the particle beam sources 161 and 162 is set to, for example, 50 sccm.

[0021] Returning to FIG. 3, the covers 122A and 122B are formed of, for example, metal, and are respectively disposed around the stage 141 and the head 142 in the chamber 120. The cover heating unit 123A has, for example, an electric heater, and is disposed adjacent to the cover 122A on the -Z direction side of the cover 122A. This cover 122A is fixed to the stage 141, and moves together with the stage 141. In addition, the cover heating unit 123B also has, for example, an electric heater, and is disposed adjacent to the cover 122B on the +Z direction side of the cover 122B. This cover 122B is fixed to the head 142, and moves together with the head 142.

[0022] The support mechanism 146 has a support member 1461 that supports the substrates W1 and W2, and a support member driving unit 1462 that raises and lowers the support member 1461. The support member 1462 has a substantially L-shape, and its tip portion extends to a step portion 141a formed on the periphery of the stage 141. In addition, for example, three support mechanisms 146 are provided, and in this case, the support members 1461 support three points on the periphery of the substrates W1 and W2, as shown in FIG. 7A, for example. In addition, a protrusion 1461a that supports the substrates W1 and W2 at its tip portion is disposed on the tip portion of the support member 1462. Then, the support mechanism 146 drives the support member 1462 in the +Z direction while the tip portion of the support member 1462 abuts against the periphery of the substrates W1 and W2 placed on the stage 141, as shown in FIG. 3, thereby lifting the substrates W1 and W2. The support mechanism 146 is fixed to the stage 141 and moves together with the stage 141 .

[0023] The load lock unit 83 includes a waiting chamber 831, an exhaust pipe 832b communicating with the waiting chamber 831, a vacuum pump 832a that exhausts gas from the waiting chamber 831 through the exhaust pipe 832b, and an exhaust valve 832c inserted in the exhaust pipe 832b. When the exhaust valve 832c is opened and the vacuum pump 832a is operated, the gas in the chamber 831 is exhausted to the outside of the chamber 831 through the exhaust pipe 832b, and the air pressure in the chamber 831 is reduced (decompressed). The air pressure in the chamber 831 is 10 -2Pa or less. The load lock unit 83 includes a gate 833a disposed on the first transfer device 82 side of the waiting chamber 831, a gate 833b disposed on the bonding device 1 side of the waiting chamber 831, and a gate driver 834 that drives the gates 833a and 833b to open and close separately. The load lock unit 83 also includes a substrate holding mechanism 836 that holds the substrates W1 and W2 transferred into the waiting chamber 831, and a substrate heating unit 835 that heats the substrates W1 and W2. The gates 833a and 833b are provided so as to cover an opening 831a that penetrates the waiting chamber 831 on the first transfer device 82 side and an opening 831b that penetrates the waiting chamber 831 on the bonding device 1 side, respectively. The substrate holding mechanism 836 includes a cassette 8361 for holding the substrates W1 and W2, a substrate heating unit 8363 for heating the substrates W1 and W2 held in the bottommost stage of the cassette 8361, and an elevation drive unit 8362 for raising and lowering the cassette 8361 as indicated by the arrow AR4. The cassette 8361 includes a plurality of slots SLT1, SLT2, and SLT3 (three in FIG. 3). The topmost slot SLT3 and the bottommost slot SLT1 hold the substrates W1 and W2 before bonding, respectively, and the second-highest slot, i.e., the central slot SLT2, holds the substrates W1 and W2 bonded to each other after the bonding process. This allows the substrate heating units 835 and 8363 to perform a heat treatment process on the substrates W1 and W2 in the load lock unit 83. Furthermore, since the cassette 8361 can hold the bonded substrates W1 and W2 in the slot SLT2 after the bonding process, the bonded substrates W1 and W2 after the bonding process in the bonding apparatus 1 can be returned to the central slot SLT2 of the cassette 8361, and then the substrates W1 and W2 held in the slots SLT1 and SLT3 can be transported from the standby chamber 831 to the bonding apparatus 1 to perform the bonding process in the bonding apparatus 1. As a result, while the bonding process is being performed in the bonding apparatus 1, the standby chamber 831 can be opened to the atmosphere, the bonded substrates W1 and W2 can be removed, and new substrates W1 and W2 can be transported into the standby chamber 831. This eliminates the need to open to the atmosphere multiple times in one cycle, and allows efficient replacement of one substrate during bonding, thereby shortening the processing time.Here, the substrate heating units 835 and 8363 are second object heating units having, for example, a lamp heater. The substrate heating unit 8363 may have, for example, an electric heater. The cassette 8361 has, for example, as shown in FIG. 7B, support pieces 8361a that support the peripheries of the substrates W1 and W2 from both sides of the substrates W1 and W2 in a direction perpendicular to the insertion direction of the substrates W1 and W2. In addition, a protrusion 8361b that supports the substrates W1 and W2 at its tip is provided at the tip of the support piece 8361a.

[0024] 3, the second transport device 84 has a long support rod 841 having a holding portion 845 for holding the substrates W1 and W2 at one end thereof, which is inserted into an opening 120a provided in the chamber 120 of the bonding device 1, a support 842 supporting the support rod 841 at the other end thereof, and a support drive portion 843 for driving the support 842. The second transport device 84 also has a bellows 844 interposed between the outer periphery of the opening 120a of the chamber 120 and the support 842 in order to maintain the degree of vacuum in the chamber 120. The support drive portion 843 has, for example, a rail (not shown) for supporting a slider (not shown) to which the support 842 is fixed so as to be slidable in the X-axis direction, and a ball screw mechanism (not shown) for driving the slide in the X-axis direction. The support driver 843 drives the support 842 in a direction in which the support rod 841 is inserted into and removed from the chamber 120, as shown by the arrow AR3, to transport the substrates W1 and W2 from either the load lock unit 83 or the bonding apparatus 1 to the other. Here, as shown in, for example, FIG. 7A and FIG. 7B, the holder 845 has a main part 8452 and two long support pieces 8451 extending in the same direction from the main part 8452. Protrusions 8453 for supporting the substrates W1 and W2 at their tips are provided at the center in the width direction of the main part 8452 and at the tips of the two support pieces 8451. The holder 845 has a size and shape that allows it to be inserted between the two support mechanisms 146 of the bonding apparatus 1 and between the pair of support pieces 8361a of the cassette 8361 of the load lock unit 83.

[0025] Returning to FIG. 1, the control unit 9 is, for example, a programmable logic controller. The control unit 9 calculates the pressure when the substrates W1 and W2 are pressed together and calculates the relative positional deviation of the substrates W1 and W2 based on the measurement signals input from the pressure sensor 148, the positional deviation measurement unit 150, etc. Furthermore, the control unit 9 controls the operations of the stage drive unit 143, the head drive unit 144, and the support mechanism 146 by outputting control signals to the stage drive unit 143, the head drive unit 144, and the support mechanism 146 based on the calculated pressure or positional deviation. Furthermore, the control unit 9 controls the operations of the substrate heating units 1411 and 1421, the particle beam sources 161 and 162, the second transport device 84, and the first transport device 82 by outputting control signals to these units.

[0026] Next, a bonding method for bonding substrates W1 and W2 together using the bonding system according to this embodiment will be described with reference to FIGS. 8 to 13. Here, the substrates W1 and W2 are assumed to be placed in the introduction ports 811 and 812 shown in FIG. 1 with their bonding surfaces facing vertically upward. The introduction port 811 is used to place the substrate W2 held by the head 142 in the bonding apparatus 1, for example, and the introduction port 812 is used to place the substrate W1 placed on the stage 141 in the bonding apparatus 1, for example. In addition, before carrying out the bonding method according to this embodiment, a chamber heating step is carried out in which the inner wall of the chamber 120 is heated in advance. Specifically, a heater jacket (not shown) is wrapped around the peripheral wall of the chamber 120, and the inner wall of the chamber 120 is heated (baked) at 150° C. for about 24 hours. As a result, the air pressure in the chamber 120 is increased to 100° C. -5Pa or less. When baking the chamber 120, a cover heating step of heating the covers 122A and 122B may be performed at the same time. Here, the length of the baking time for baking the chamber 120 in the chamber heating step may be equal to or longer than the length of the cover heating time for heating the covers 122A and 122B in the cover heating step, or may be shorter than the length of the cover heating time. This makes it possible to remove water or impurities attached to the covers 122A and 122B. In particular, when the chamber 120 is baked, the water or impurities desorbed from the chamber 120 are attached to the cover 122A, which has a relatively lower temperature than the chamber 120. In this case, when the activation process is performed, the water or impurities attached to the cover 122A are irradiated with a particle beam, and the water or impurities attached to the cover 122 float in the chamber 120 and are attached to the bonding surfaces of the substrates W1 and W2. For this reason, it is preferable to perform a cover heating step simultaneously with baking of the chamber 120, so that water or impurities that have been desorbed from the chamber 120 and adhered to the cover 122A are also removed.

[0027] 8, in the bonding method according to the present embodiment, first, the first transfer device 82 takes out the substrate W2 arranged in the introduction ports 811, 812 and transfers it to the cleaning device 3 (step S101). Here, after the transfer robot 821 takes out the substrates W1, W2 from the introduction ports 811, 812, it turns so that the tip of the arm 821a faces the cleaning device 3 while holding the substrates W1, W2. Next, when the cleaning device 3 opens the transfer entrance for the substrates W1, W2, the transfer robot 821 extends the arm 821a and inserts the tip of the arm 821a into the cleaning device 3. Then, the substrates W1, W2 are transferred from the tip of the arm 821a of the transfer robot 821 to the stage of the cleaning device 3.

[0028] Next, the cleaning device 3 executes a water cleaning process for cleaning the substrates W1 and W2 with water (step S102). Here, the cleaning device 3 cleans the entire bonding surfaces of the substrates W1 and W2 by rotating the stage on which the substrates W1 and W2 are placed while spraying ultrasonically charged water from the cleaning nozzle onto the bonding surfaces of the substrates W1 and W2. This removes foreign matter adhering to the bonding surfaces of the substrates W1 and W2. Next, the cleaning device 3 stops spraying water from the cleaning nozzle and then rotates the stage to spin-dry the substrates, thereby completing the water cleaning process. After that, the cleaning device 3 opens the entrance for the substrates W1 and W2 when this series of cleaning processes is completed.

[0029] Next, the first transfer device 82 transfers the substrates W1 and W2 for which the water cleaning process has been completed from the cleaning device 3 to the load lock unit 83 (step S103). Here, the transfer robot 821 of the first transfer device 82 extends the arm 821a with the transfer entrance for the substrates W1 and W2 of the cleaning device 3 open, inserts the tip of the arm 821a into the cleaning device 3, and receives the substrates W1 and W2 from the stage in the cleaning device 3. Next, the transfer robot 821 contracts the arm 821a to take out the substrates W1 and W2 from the cleaning device 3. Next, when the gate drive unit 834 of the load lock unit 83 opens the gate 833a on the first transfer device 82 side of the waiting chamber 831, the transfer robot 821 rotates while holding the substrates W1 and W2 so that the tip of the arm 821a faces the load lock unit 83 side. At this time, when the transport robot 821 receives the substrate W2 from the cleaning device 3, the arm 821a is inverted so that the bonding surface of the substrate W2 faces vertically downward, and the transport robot 821 turns while holding the substrate W2 in such a state that the bonding surface of the substrate W2 faces vertically downward. On the other hand, when the transport robot 821 receives the substrate W1 from the cleaning device 3, the transport robot 821 turns while maintaining the substrate W2 in such a state that the bonding surface faces vertically upward. After that, the transport robot 821 extends the arm 821a to insert the tip of the arm 821a into the waiting chamber 831. Then, the substrates W1 and W2 are transferred from the tip of the arm 821a to the cassette 8361 of the substrate holding mechanism 836 arranged in the waiting chamber 831. At this time, the substrates W1 and W2 are held in the top slot SLT3 and the bottom slot SLT1 of the cassette 8361, for example, as shown in FIG. 9A. Next, when the transfer robot 821 completes the transfer of the substrates W1 and W2 into the cassette 8361 of the substrate holding mechanism 836, the arm 821a is retracted. Then, the gate driver 834 closes the gate 833a of the waiting chamber 831.

[0030] 8, thereafter, in the waiting chamber 831 under reduced pressure, a heat treatment process is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded to each other are heated to a temperature higher than 60° C. (step S104).-2 Pa or less. Furthermore, the substrate heating section 835 of the load lock section 83 heats the substrate W2, and the substrate heating section 8363 heats the substrate W1. For example, the substrates W1 and W2 are heated by the substrate heating section 835 arranged above the waiting chamber 831 and the substrate heating section 8363 arranged below.

[0031] Next, the second transfer device 84 transfers the substrates W1 and W2 held in the cassette 8361 of the substrate holding mechanism 836 from the load lock unit 83 to the bonding device 1 (step S105). Here, the load lock unit 83 first reduces the pressure in the waiting chamber 831 to a vacuum level substantially equal to that of the chamber 120 of the bonding device 1. Next, the gate driver 834 opens the gate 833b of the waiting chamber 83 on the bonding device 1 side. Next, the lift driver 8362 of the load lock unit 83 moves the cassette 8361 to a position where the holder 845 of the second transfer device 84 can be inserted below the slot SLT3 holding the substrate W2, as shown in FIG. 9A. Thereafter, the second transfer device 84 moves the support rod 841 toward the load lock unit 83, as shown by the arrow AR31, to insert the holder 845 below the slot SLT3 holding the substrate W2 in the cassette 8361. Next, the lifting driver 8362 of the load lock unit 83 moves the cassette 8361 vertically downward as shown by the arrow AR41, so that the substrate W2 is transferred from the cassette 8361 to the holder 845. Here, the substrate W2 is held by the holder 845 in a position in which its bonding surface faces vertically downward, but as shown in, for example, FIG. 4A and FIG. 4B, the holder 845 holds the outer periphery of the bonding surface of the substrate W2 in point contact, so that there is no effect on the bonding of the substrates W1 and W2. Next, the second transport device 84 moves the support rod 841 in a direction away from the load lock unit 83 as shown by the arrow AR32 in FIG. 9B, so that the holder 845 is disposed in the chamber 120 of the bonding apparatus 1. After that, the gate driver 834 closes the gate 833b.

[0032] Next, as shown by an arrow AR51 in FIG. 10A, the support member driving unit 1462 of the support mechanism 146 raises the support member 1461 to lift the substrate W2. Then, the second transport device 84 moves the support rod 841 in a direction away from the load lock unit 83 while the substrate W2 is lifted by the support member 1461, thereby disposing the holder 845 at a preset standby position. Next, as shown by an arrow AR11 in FIG. 10B, the head driving unit 144 of the bonding device 1 moves the head 142 vertically downward, thereby bringing the head 142 into contact with the substrate W2 supported by the support member 1461, and then holding the substrate W2 on the head 142. Here, the load lock unit 83 moves the cassette 8361 to a position below the slot SLT1 that holds the substrate W1, as shown by an arrow AR42, where the holder 845 of the second transport device 84 can be inserted.

[0033] Thereafter, the head driver 144 raises the head 142 as shown by the arrow AR12 in FIG. 11A. At this time, the support member driver 1462 lowers the support member 1461 as shown by the arrow AR52. Next, the gate driver 834 opens the gate 833b on the bonding device 1 side of the waiting chamber 83 again. Next, the second transfer device 84 moves the support rod 841 toward the load lock unit 83 as shown by the arrow AR34, thereby inserting the holder 845 into the lower side of the slot SLT1 that holds the substrate W1 in the cassette 8361. Next, the lift driver 8362 of the load lock unit 83 moves the cassette 8361 vertically downward as shown by the arrow AR43, thereby transferring the substrate W1 from the cassette 8361 to the holder 845.

[0034] Next, the second transport device 84 moves the support rod 841 in a direction away from the load lock unit 83 as shown by an arrow AR35 in FIG. 11B, thereby disposing the holding unit 845 in the chamber 120 of the bonding apparatus 1. Thereafter, the gate driving unit 834 closes the gate 833b. Next, the support member driving unit 1462 of the support mechanism 146 lifts the substrate W1 by raising the support member 1461 as shown by an arrow AR53. Then, with the substrate W1 lifted by the support member 1461, the second transport device 84 moves the support rod 841 in a direction away from the load lock unit 83 as shown by an arrow AR36 in FIG. 12A, thereby disposing the holding unit 845 at a preset standby position. Next, the support member driving section 1462 of the support mechanism 146 lowers the support member 1461 as shown by the arrow AR54, whereby the substrate W1 is placed on the stage 141, and then the stage 141 is held by the substrate W1.

[0035] Returning to FIG. 8, next, a heat treatment process is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded to each other are heated to a temperature higher than 60° C. in a reduced pressure atmosphere (step S106). Here, the reduced pressure atmosphere refers to, for example, a pressure inside the chamber 120 of 10 -6 Pa or less. Furthermore, the substrate heating units 1411 and 1421 transfer heat to the substrates W1 and W2 supported by the stage 141 and head 142, respectively, to heat the substrates W1 and W2 to a temperature higher than 60° C. This removes foreign matter, mainly composed of water, adhering to the bonding surfaces of the substrates W1 and W2.

[0036] Next, an activation process is performed in which the bonding surfaces of the two substrates W1 and W2 are activated in a reduced pressure atmosphere (step S107). Here, the bonding apparatus 1 performs activation process on the bonding surfaces of the substrates W1 and W2 by irradiating the bonding surfaces of the substrates W1 and W2 with particle beams emitted from the particle beam sources 161 and 162, as shown by arrows AR21 in Fig. 5. Note that after the heat treatment process and before the activation process, a cooling process may be performed to cool the temperatures of the substrates W1 and W2 to 60°C or less.

[0037] Returning to FIG. 8, thereafter, a bonding step is performed to bond the substrates W1 and W2 together (step S108). Here, the head driving unit 144 of the bonding apparatus 1 first brings the head 142 supporting the substrate W2 closer to the stage 141 supporting the substrate W1, bringing the two substrates W1 and W2 closer to each other. Next, the head driving unit 144 performs an alignment operation for the two substrates W1 and W2 based on the positional deviation amount measured by the positional deviation amount measuring unit 150 while the two substrates W1 and W2 are in close proximity to each other. In this way, the head driving unit 144 performs an alignment operation after the activation process, thereby reducing the positional deviation of the substrates W1 and W2. Thereafter, the head driving unit 144 brings the head 142 closer to the stage 141 again, as shown by the arrow AR12 in FIG. 12B, to bring the two substrates W1 and W2 into contact with each other. Next, the head driving unit 144 applies pressure in a direction in which the two substrates W1 and W2 come into close contact with each other while the bonding surfaces of the substrates W1 and W2 are in contact with each other, thereby bonding the two substrates W1 and W2 together. Next, after the head 142 releases the substrate W2 from its holding, the head driving unit 144 raises the head 142 as shown by the arrow AR13 in FIG. 13A. At this time, the support member driving unit 1462 of the support mechanism 146 raises the support member 1461 as shown by the arrow AR55, thereby lifting the bonded substrates W1 and W2 together. In addition, the load lock unit 83 moves the cassette 8361 to the second stage from the top, that is, to a position above the central slot SLT2 where the holder 845 of the second transfer device 84 can be inserted, as shown by the arrow AR44.

[0038] Returning to FIG. 7, the second transfer device 84 then transfers the bonded substrates W1 and W2 from the bonding apparatus 1 to the load lock unit 83 (step S109). First, the second transfer device 84 moves the support rod 841 from the standby position toward the load lock unit 83 as shown by the arrow AR37 in FIG. 13A, thereby disposing the holder 845 below the substrates W1 and W2 in the chamber 120. Next, the gate driver 834 of the load lock unit 83 opens the gate 833b on the bonding apparatus 1 side in the standby chamber 831. Next, the support member driver 1462 of the support mechanism 146 lowers the support member 1461 as shown by the arrow AR56 in FIG. 13B, thereby transferring the bonded substrates W1 and W2 to the holder 845. Thereafter, the second transfer device 84 moves the support rod 841 from the standby position toward the load lock unit 83 as shown by arrow AR38, thereby inserting the holder 845 above the central slot SLT2 of the cassette 8361. Then, the lift drive unit 8362 of the load lock unit 83 lifts the cassette 8361 a preset distance as shown by arrow AR45, thereby transferring the substrates W1 and W2 from the holder 845 to the cassette 8361. Thereafter, the second transfer device 84 moves the support rod 841 to the standby position. Next, the gate drive unit 834 closes the gate 833b.

[0039] Returning to FIG. 8, the first transfer device 84 then transfers the bonded substrates W1 and W2 from the load lock unit 83 to the take-out port 813 (step S110). Here, the load lock unit 83 first opens the waiting chamber 831 to the atmosphere. Next, the gate driver 834 of the load lock unit 83 opens the gate 833a on the first transfer device 82 side in the waiting chamber 831, and the transfer robot 821 extends the arm 821a with the tip of the arm 821a facing the load lock unit 83 side to insert the tip of the arm 821a into the waiting chamber 831. Then, the bonded substrates W1 and W2 are transferred from the stage in the waiting chamber 831 to the tip of the arm 821a of the transfer robot 821. Next, the transfer robot 821 contracts the arm 821a to remove the bonded substrates W1 and W2 from the waiting chamber 831, and then the gate driver 834 of the load lock unit 83 closes the gate 833a. Next, the transfer robot 821 turns so that the tip of the arm 821a faces the removal port 813. Thereafter, while holding the bonded substrates W1 and W2, the transfer robot 821 extends the arm 821a to insert the tip of the arm 821a into the removal port 813, and places the bonded substrates W1 and W2 in the removal port 813.

[0040] Note that, before performing the above-mentioned bonding method, a step of heating the chamber 120 with the pressure inside the chamber 120 reduced, i.e., a cover heating step of heating the covers 122A and 122B by the cover heating units 123A and 123B may be performed after a step of baking the chamber 120. Alternatively, before performing the above-mentioned activation treatment step in which the substrates W1 and W2 are not yet placed in the chamber 120, a cover heating step of heating the cover with the pressure inside the chamber 120 reduced may be performed.

[0041] Next, the results of evaluating the bonding strength of 10 types of samples formed by bonding two substrates W1 and W2 using the bonding system according to this embodiment will be described. For each sample, the supply amount of argon gas to each of the particle beam sources 161 and 162 in the activation process was set to 50 sccm. The degree of vacuum in the chamber 120 immediately before the particle beam sources 161 and 162 irradiated the substrates W1 and W2 with particle beams was 2×10 -6 The pressure was set to 20,000 Pa. When the substrates W1 and W2 were bonded to each other, a pressure of 20,000 N was applied in the direction in which the two substrates W1 and W2 were in close contact with each other and maintained for 60 seconds. Both substrates W1 and W2 were Si substrates.

[0042] Table 1 below shows the stage (head) temperatures of the stage 141 and head 142 before the substrates W1 and W2 were held by them, the stage temperatures immediately after the substrates were transferred from the load lock unit 83 to the stage 141 of the bonding apparatus 1, the pre-contact temperatures in a separated state before the substrates W1 and W2 were brought into contact with each other, and the post-contact temperatures after the substrates W1 and W2 were brought into contact with each other, for each of the samples 1 to 7 out of the 10 types of samples. Note that for each of the samples 1 to 7, the time that the substrates W1 and W2 were left after being transferred from the load lock unit 83 to the stage 141 and head 142 of the bonding apparatus 1 and before the bonding process including the activation process was performed was 30 seconds. As for the samples 1 and 2, before the substrates W1 and W2 were held on the stage 141 and the head 142, the stage 141 and the head 142 were heated to 300°C, and then cooled to 25°C and 150°C, respectively, and the substrates W1 and W2 were then transported from the load lock unit 83 to the bonding device 1. As for the sample 7, after the activation process and the contacting step were completed, the substrates W1 and W2 that were in contact with each other were heated to 150°C. As for the sample 3, after the sample 3 was transported from the load lock unit 83 to the bonding device 1, the temperatures of the stage 141 and the head 142 were raised to 150°C with the opposing substrates spaced apart, and then the activation process was performed, and the substrates W1 and W2 were brought into contact with each other and bonded.

[0043] [Table 1]

[0044] Table 2 below shows the time that the substrates W1 and W2 were left after being transferred from the load lock unit 83 to the bonding apparatus 1 and before the bonding process was performed for each of the 10 types of samples, samples 6 and 8. For sample 8, the temperatures of the stage 141 and head 142 before the substrates W1 and W2 were set on the stage 141 and head 142 were 80° C., similar to sample 6. The temperature immediately after being transferred from the load lock unit 83 to the bonding apparatus 1 and the temperature at the time of bonding the substrates W1 and W2 were both 80° C., similar to sample 6.

[0045] [Table 2]

[0046] Furthermore, the following Table 3 shows whether or not the substrates W1 and W2 were heat-treated after being transported into the waiting chamber 831 for each of the 10 types of samples, Sample 9 and Sample 10. Here, "heat-treated" indicates that the substrates W1 and W2 were heated at 100°C for 10 minutes by the substrate heating unit 835 in the load lock unit 83. In addition, the time for leaving Sample 9 and Sample 10 after being transported from the load lock unit 83 to the bonding device 1 until the bonding process was performed was 30 seconds. Furthermore, for Sample 9 and Sample 10, the temperatures of the stage 141 and head 142 before the substrates W1 and W2 were set on the stage 141 and head 142, the temperature immediately after being transported from the load lock unit 83 to the bonding device 1, and the temperature at the time of bonding the substrates W1 and W2 were all 25°C. In addition, the degree of vacuum in the waiting chamber 831 of the load lock unit 83 was 10 -2 The temperature of the stage 141 and the head 142 of the bonding apparatus 1 before the substrates W1 and W2 are held on these stage (head) temperatures, the temperature immediately after the substrates are transferred from the load lock unit 83 to the bonding apparatus 1, and the pre-contact temperature and post-contact temperature described above were all set to room temperature, i.e., 25°C.

[0047] [Table 3]

[0048] The bond strength of the substrates W1 and W2 of the samples 1 to 10 was evaluated by measuring the bond strength (converted into surface energy) using a crack-and-open method in which a blade is inserted. In this crack-and-open method, first, as shown by the arrows in FIG. 14A, a blade BL, such as a razor blade, is inserted from the periphery of the two substrates W1 and W2 bonded to each other to the bonded portion, and the peel length L of the substrates W1 and W2 is measured. As the blade BL, for example, a blade with a thickness of 100 μm is used. Also, as shown in FIG. 14B, the blade BL is inserted into six places (Pos1, Pos2, Pos3, Pos4, Pos5, and Pos6) of the periphery of the two substrates W1 and W2 bonded to each other (see the arrows in FIG. 14B), and the peel length L from the blade contact point is measured. The bonding strength of the substrates W1 and W2 was evaluated by calculating the strength of the bonding interface between the substrates W1 and W2 in terms of surface energy per unit area from the peel length L for each of six locations on the periphery of the substrates W1 and W2. Note that when calculating the bonding strength (surface energy equivalent) Eb from the peel length L, the following relational expression (1) was used.

number

[0049] The evaluation results of the bonding strength of the substrates W1 and W2 for Samples 1 to 10 are shown in Table 4 below. In Table 4, the column "Sample name" corresponds to each of Samples 1 to 14 in Table 1 above. The value in the column "Peeling length" indicates the average value of the peeling length at six points ("Pos1" to "Pos6") on the periphery of the two substrates W1 and W2 shown in FIG. 14B. In addition, the value in the column "Bonding strength (surface energy conversion)" indicates the average value of the bonding strength (surface energy conversion) at six points ("Pos1" to "Pos6") on the periphery of the two substrates W1 and W2 shown in FIG. 14B, and when bulk fracture occurred at all six points on the periphery of the two substrates W1 and W2, it is described as "bulk fracture." The values ​​in parentheses in the "Bonding strength (surface energy equivalent)" column for samples 2, 3, 5, 6, 8, and 9 are theoretical values ​​calculated from the average peel length using formula (1), and are listed for reference only, although they do not actually exist. Furthermore, the values ​​in the "Number of bulk fracture locations" column indicate the number of locations where bulk fracture occurred among the six locations on the periphery of the two substrates W1 and W2.

[0050] [Table 4]

[0051] As shown in Table 4, the bonding strength (surface energy equivalent) of samples 2 and 3 was 2.5 J / m 2All six points reached the bulk fracture strength, whereas the bonding strength (surface energy equivalent) of samples 1 and 7 was 2.5 J / m 2 The results of Sample 3, on the other hand, showed that even if the temperatures of the substrates W1 and W2 before they are held by the stage 141 and the head 142 are kept at room temperature, i.e., about 25°C, the bonding strength between the substrates W1 and W2 is greatly increased by increasing the temperature immediately after they are transferred from the load lock unit 83 to the bonding device 1 and the temperature before contact to 150°C. From these results, it was found that increasing the temperature of the substrates W1 and W2 to 300°C before they are held by the stage 141 and the head 142 and baking them does not contribute to improving the bonding strength between the substrates W1 and W2. It was also found that heating the substrates W1 and W2 to 150°C after they are brought into contact with each other does not contribute to improving the bonding strength between the substrates W1 and W2. In other words, it was found that increasing the temperature immediately after they are transferred from the load lock unit 83 to the bonding device 1 and the temperature before contact between the substrates W1 and W2 contributes to improving the bonding strength between the substrates W1 and W2. In other words, it was found that performing the heat treatment step immediately before performing the activation treatment step is important in order to increase the bonding strength between the substrates W1 and W2.

[0052] The bonding strength (surface energy equivalent) of sample 4 was 2.5 J / m 2 The bonding strength (surface energy equivalent) of samples 3, 5, and 6 was less than 2.5 J / m 2 The results were as above. In particular, in samples 3 and 5, all six points reached the bulk fracture strength. From these results, it was found that the bonding strength between the substrates W1 and W2 is increased by increasing the temperature immediately after the substrates are transferred from the load lock unit 83 to the bonding apparatus 1, i.e., the temperature immediately before and during bonding of the substrates W1 and W2, to a temperature higher than 60°C, and in particular, the bonding strength between the substrates W1 and W2 is significantly increased by increasing the temperature immediately before bonding of the substrates W1 and W2 to a temperature of 100°C or higher.

[0053] Furthermore, while sample 6 had two locations where its bulk fracture strength was reached, sample 8 had four locations where its bulk fracture strength was reached. From these results, it was found that when the temperature of substrates W1, W2 before they are held on stage 141 and head 142, i.e., the temperature immediately before bonding of substrates W1, W2, is 80° C., the bonding strength between substrates W1, W2 is improved by extending the time that substrates W1, W2 are left after being transported from load lock unit 83 to bonding apparatus 1 and before the bonding process is performed.

[0054] In addition, the bonding strength (surface energy equivalent) of sample 10 was 2.5 J / m 2 The bonding strength (surface energy equivalent) of sample 9 is less than 2.5 J / m 2 As a result, the bulk fracture strength was reached at two points. From this, it was found that heating the substrates W1 and W2 in the load lock unit 83 also contributes to improving the bonding strength between the substrates W1 and W2. -2 It was also found that the pressure should be less than 10 Pa. The bonding strength of sample 9 is lower than that of sample 5. For this reason, the pressure in the heat treatment step should be less than 10 -5 It was found that a pressure of 10 Pa or less is more preferable. This is thought to reflect the fact that a large amount of impurities, mainly composed of water molecules, attached to the surfaces of the substrates W1 and W2 were removed, and re-adhesion was prevented. -2 Pa is about 10 -5 This is also thought to be due to the fact that the atmosphere contains more moisture and impurities than the atmosphere below 10 Pa.

[0055] The principle of direct bonding by this activation process is that the impurities on the surface are removed by the Ar particle beam, and the dangling bonds that become the bonds are exposed by breaking the molecular bonds, and if there are no other molecules that become impurities floating in the environment, the dangling bonds of the other substrate can be directly bonded at room temperature. Therefore, in a vacuum where impurities float, the dangling bonds are terminated by the impurities, and bonding is not possible.

[0056] The bond strength (surface energy equivalent) of the substrates W1 and W2 exhibits a dependency on the air pressure in the chamber 120 in the activation process, for example, as shown in FIG. 15. The results shown in FIG. 15 are for the case where both the substrates W1 and W2 are Si substrates. From the results shown in FIG. 15, it can be seen that the air pressure in the chamber 120 in the activation process is 10 -5 The intensity increases rapidly from below 10 Pa. -5 In order to achieve a pressure of 10 Pa or less, a heater jacket (not shown) is wrapped around the periphery of the chamber 120 and the inside of the chamber 120 is heat-treated (baked) at 150° C. for about 24 hours to remove impurities, mainly moisture, from the chamber 120. The reason why the results shown in FIG. 15 were obtained was that the pressure in the chamber 120 was 10 -5 If the pressure is below 1 Pa, it is considered that impurities mainly composed of moisture floating in the chamber 120 are removed in the heat treatment process, and do not adhere to the substrates W1 and W2, thereby indicating that the bonding strength between the substrates W1 and W2 is improved. However, since the substrates W1 and W2 themselves are brought in from the atmosphere, impurities mainly composed of moisture adhere to the surfaces, and it is preferable to remove the impurities before bonding. From this, it is possible to understand the reason why the bonding strength between the substrates W1 and W2 is further improved by similarly subjecting the substrates W1 and W2 themselves to a heat treatment before bonding the substrates W1 and W2 to remove impurities mainly composed of moisture.

[0057] In addition, in the samples 1 to 10, Si substrates are used as the substrates W1 and W2, but the substrates W1 and W2 may be glass substrates such as SiO2 glass substrates, oxide substrates (e.g., silicon oxide (SiO2) substrates, alumina substrates (Al2O3) including sapphire substrates, gallium oxide (Ga2O3), etc.), nitride substrates (e.g., silicon nitride (SiN), aluminum nitride (AlN), gallium nitride (GaN)), GaAs substrates, silicon carbide (SiC) substrates, lithium tantalate (Lt:LiTaO3) substrates, lithium niobate (Ln:LiNbO3) substrates, diamond substrates, etc. In addition, even if various substrates having electrodes made of metals such as Au, Cu, Al, Ti, etc. on the bonding surfaces of the substrates W1 and W2 are used, it is considered that the effect of removing impurities mainly composed of water molecules attached to the surfaces of the substrates W1 and W2 in the heat treatment process as described above can be obtained.

[0058] We also evaluated the case where substrates W1 and W2 made of materials with different linear expansion coefficients were bonded together. A Si substrate was used as substrate W1, and a lithium tantalate (Lt:LiTaO3) substrate or a lithium niobate (Ln:LiNbO3) substrate was used as substrate W2, and the bonding method described above was carried out. Here, when substrates W1 and W2 were heat-treated at 100°C and then bonded together while maintaining the temperature of substrates W1 and W2 at 100°C, the bonding strength (surface energy equivalent) between substrates W1 and W2 was 1.0 J / m 2 On the other hand, when the substrates W1 and W2 are heat-treated at 100° C., and then the temperature of the substrates W1 and W2 is cooled to 60° C., and then the substrates W1 and W2 are bonded together, the bonding strength (converted into surface energy) between the substrates W1 and W2 is 1.6 J / m 2The bond strength between the substrates W1 and W2 was improved when the substrates W1 and W2 were bonded together after the temperature of the substrates W1 and W2 had dropped to a temperature lower than the temperature during the heat treatment. This indicates that if the substrates W1 and W2 were bonded together while the substrates W1 and W2 were maintained at a relatively high temperature during the heat treatment, the degree of expansion of the substrates W1 and W2 due to the thermal expansion would differ due to the difference in the linear expansion coefficients of the substrates W1 and W2, and a force would be applied to the substrates W1 and W2 in the direction in which the substrate W1 would peel off from the substrate W2, causing the substrates W1 and W2 to warp or crack, and not only that, but also reducing the bond strength between the substrates W1 and W2. Therefore, when bonding two substrates W1 and W2 made of materials with different linear expansion coefficients, it is preferable to bond the substrates W1 and W2 together after cooling the substrates W1 and W2 after the heat treatment process.

[0059] In addition, after the substrates W1 and W2 were washed with water in the washing device 3 and the water adhering to the bonding surfaces of the substrates W1 and W2 was removed by the spin dry method, the substrates W1 and W2 were immediately transferred to the load lock unit 83, and then the substrates W1 and W2 were bonded together without a heat treatment process. In this case, the bonding strength between the substrates W1 and W2 (converted into surface energy) was 0.5 J / m 2 In contrast, when the substrates W1 and W2 were washed with water in the washing device 3 and the water adhering to the bonding surfaces of the substrates W1 and W2 were removed by the spin dry method, the substrates were transferred to the load lock unit 83, and a heat treatment process was performed in the load lock unit 83 or the bonding device 1 at 100° C. for 30 seconds. The bonding strength (surface energy equivalent) between the substrates W1 and W2 was 2.5 J / m 2It was larger than that. That is, even if water cleaning was performed before the bonding process, the bonding strength between the substrates W1 and W2 could be improved. This is because water is removed by the spin dry method after water cleaning in the cleaning device 3, but if the heat treatment process of the substrates W1 and W2 is not performed, water molecules remain as a thin layer on the bonding surface of the substrates W1 and W2, and it is considered that this causes the bonding strength between the substrates W1 and W2 to be lower than the bonding strength between the substrates W1 and W2 when water cleaning is not performed. On the other hand, it is considered that the bonding strength between the substrates W1 and W2 is improved by removing almost all of the water remaining on the bonding surface of the substrates W1 and W2 by performing the heat treatment process of the substrates W1 and W2. It is also clear from this result that if water remains on the bonding surface of the substrates W1 and W2, the water remaining on the substrates W1 and W2 cannot be completely removed by simply leaving the substrates W1 and W in a vacuum atmosphere. This result shows that water remains on the bonding surfaces of the substrates W1 and W2 even in a vacuum atmosphere, and that heating the substrates W1 and W2 in a vacuum atmosphere is effective in completely removing this water.

[0060] Furthermore, using Si substrates as substrates W1 and W2, the bonding surfaces of substrates W1 and W2 were irradiated with a particle beam and then substrates W1 and W2 were bonded together. The change in bonding strength over time was compared between the case where the above-mentioned heat treatment process was performed and the case where the heat treatment process was not performed. Note that the number of times of irradiation with the particle beam was reduced in order to lower the bonding strength between substrates W1 and W2 to some extent and make it easier to confirm the change in bonding strength between substrates W1 and W2 over time. As a result, the bonding strength between substrates W1 and W2 when the heat treatment process was performed was more than twice as high as that when the heat treatment process was not performed.

[0061] As described above, in the bonding system according to the present embodiment, the bonding apparatus 1 performs a heat treatment process in which the bonding surfaces of the two substrates W1 and W2 are heated to a temperature higher than 60° C. in a reduced pressure atmosphere while the two substrates W1 and W2 are spaced apart, and then performs an activation process to activate the bonding surfaces of the substrates W1 and W2. The bonding apparatus 1 then bonds the two substrates W1 and W2 in a reduced pressure atmosphere. As a result, by heating the bonding surfaces of the two substrates W1 and W2 to a temperature higher than 60° C. in a reduced pressure atmosphere, water or impurities present on the bonding surfaces of the substrates W1 and W2 are vaporized and removed, so that the bonding surfaces of the substrates W1 and W2 are easily activated by the activation process. Therefore, the bonding strength between the two substrates W1 and W2 when the two substrates W1 and W2 are bonded after the activation process can be increased.

[0062] One method for removing impurities attached to the bonding surfaces of the substrates W1 and W2 is to irradiate them with a particle beam. In this case, the DC voltage applied between the electrode 1602 of the particle beam sources 161 and 162 and the peripheral wall of the discharge chamber 1601 is set to 1 kV, the current value flowing between the electrode 1602 and the peripheral wall of the discharge chamber 1601 is set to 100 mA, and the flow rate of Ar gas introduced into the discharge chamber 1601 is set to 50 sccm, and the particle beam is continuously irradiated onto the bonding surfaces of the substrates W1 and W2. However, in this method, it is necessary to irradiate the bonding surfaces of the substrates W1 and W2 with an extra particle beam in order to remove the impurities, which increases the irradiation time of the particle beam. For example, when impurities with a thickness of about several nm are attached to the bonding surfaces of the substrates W1 and W2, the irradiation time of the particle beam is extended by about 5 min. In addition, since the thickness or adhesion strength of the impurities attached to the bonding surfaces of the substrates W1 and W2 varies, it is difficult to set the irradiation time of the particle beam required to remove the impurities. As a result, the particle beam may be irradiated onto the bonding surfaces of the substrates W1 and W2 more than necessary. In this case, the substrates W1 and W2 may be scraped by the particle beam, compromising the flatness of the bonding surfaces, and as a result, the bonding strength between the substrates W1 and W2 may be reduced.

[0063] In contrast, in the bonding method according to the present embodiment, the bonding surfaces of the two substrates W1 and W2 are heated to a temperature higher than 60° C. before the activation process, thereby removing impurities present on the bonding surfaces of the substrates W1 and W2. As a result, by simply irradiating the particle beam for about 2 to 3 minutes in the activation process, the bonding surfaces of the substrates W1 and W2 are etched by about 1 nm, that is, by a thickness equivalent to one atomic layer exposed on the bonding surfaces of the substrates W1 and W2, and dangling bonds necessary for improving the bonding between the substrates W1 and W2 can be exposed while maintaining the flatness of the bonding surfaces of the substrates W1 and W2. This makes it possible to increase the bonding strength between the substrates W1 and W2.

[0064] Since the substrates W1 and W2 are inserted from the atmosphere, moisture and impurities are attached to the bonding surfaces of the substrates W1 and W2. Therefore, it is considered that impurities mainly composed of water molecules are attached to the surfaces of the substrates W1 and W2. In contrast, in the bonding method according to the present embodiment, the substrates W1 and W2 are heated before the activation process, so that if impurities mainly composed of water molecules are attached to the substrates W1 and W2, these can be effectively removed. In particular, since water crystallizes in a reduced pressure atmosphere, it can be easily removed by vaporizing (sublimating) the substrates W1 and W2 by heating them. From the experimental results, it is considered that the impurities are mainly composed of moisture, since they are removed at around 100°C. In other words, it is preferable to remove impurities mainly composed of water molecules by heating in a reduced pressure atmosphere rather than by etching, such as irradiation with a particle beam, which may damage the bonding surfaces of the substrates W1 and W2.

[0065] In addition, in the conventional bonding method, cleaning with water immediately before bonding the substrates W1 and W2 together may cause a decrease in the bonding strength between the substrates W1 and W2, so cleaning is difficult. Therefore, it is difficult to avoid the generation of voids due to particles attached to the bonding surfaces of the substrates W1 and W2. In contrast, in the bonding system according to the present embodiment, the substrates W1 and W2 are washed in the cleaning device 3 and then put into the bonding device 1. Many water molecules are attached to the bonding surfaces of the substrates W1 and W2 during cleaning in the cleaning device 3, but they can be removed by performing a heat treatment process in the bonding device 1. Therefore, the cleaning process of removing particles from the bonding surfaces of the substrates W1 and W2 with water can be performed before the bonding process, which is also preferable from the viewpoint of suppressing voids generated in the bonded substrates W1 and W2.

[0066] In the activation process according to the present embodiment, in order to reliably irradiate the entire substrate W1 with the particle beam, the particle beams emitted from the particle beam sources 161 and 162 are irradiated to an area including the covers 122A and 122B on the outer side of both ends of the substrates W1 and W2 in the moving direction of the particle beam sources 161 and 162. In addition, the particle beam sources 161 and 162 tend to significantly reduce the intensity of the particle beams at both ends in the longitudinal direction of the long discharge chamber 1601. Therefore, the length of the particle beam sources 161 and 162 is set to be longer than the longitudinal length of the particle beam sources 161 and 162 on the substrates W1 and W2, as shown in FIG. 6. Therefore, the particle beams emitted from the particle beam sources 161 and 162 are irradiated to an area including the covers 122A and 122B on the outer side of both ends of the substrates W1 and W2 in the longitudinal direction of the particle beam sources 161 and 162. Therefore, if impurities are attached to the surfaces of the covers 122A, 122B, when the activation process is performed, the impurities attached to the surfaces of the covers 122A, 122B may be repelled by the particle beam irradiated to the covers 122A, 122B and may end up adhering to the bonding surfaces of the substrates W1, W2.

[0067] In contrast, in the bonding method according to the present embodiment, impurities attached to the surfaces of the covers 122A and 122B are removed by heating the covers 122A and 122B before the activation process is performed. This makes it possible to suppress adhesion of impurities to the bonding surfaces of the substrates W1 and W2 caused by the impurities attached to the surfaces of the covers 122A and 122B being blown away by the particle beam during the activation process.

[0068] Furthermore, in the bonding method according to the present embodiment, after the heat treatment step is performed in the load lock unit 83, a heat treatment step is also performed immediately before the activation treatment step. As a result, impurities mainly composed of moisture are removed to a certain extent in advance in the load lock unit 83, and then impurities mainly composed of moisture are further removed in the heat treatment step in the bonding apparatus 1, so that the time required for the heat treatment step in the bonding apparatus 1 can be shortened. Therefore, the time required for the entire treatment performed on the substrates W1 and W2 in the bonding apparatus 1 can be shortened, and the processing efficiency can be increased accordingly.

[0069] However, if the heat treatment step is performed only in the load lock unit 83 and not in the bonding apparatus 1, the bonding strength between the substrates W1 and W2 is reduced compared to the case where the heat treatment step is performed in the bonding apparatus 1. Therefore, it is preferable to perform the heat treatment step in the load lock unit 83 and then in the bonding apparatus 1. Since the substrates W1 and W2 are transported from the atmosphere into the load lock unit 83, impurities mainly composed of moisture are attached to the bonding surfaces of the substrates W1 and W2. For this reason, it is preferable to perform the heat treatment step primarily in a reduced pressure atmosphere of 10-2 Pa in the load lock unit 83, and then perform the heat treatment step in a reduced pressure atmosphere of 10-5 Pa in the bonding apparatus 1. This makes it possible to almost completely remove the impurities attached to the bonding surfaces of the substrates W1 and W2, thereby improving the bonding strength between the substrates W1 and W2. Furthermore, the sample 8 was subjected to a heat treatment for 10 min in the load lock unit 83, but one cycle of the bonding system according to this embodiment is about 15 min. In this manner, in the bonding system according to the present embodiment, the heat treatment can be performed for 10 minutes in the load lock unit 83 without reducing the cycle time of one cycle.

[0070] In order to investigate the effect of moisture contained in the environment in which the bonding strength between the substrates W1 and W2 is evaluated, the bonding strength between the substrates W1 and W2 made of SiN is evaluated in air, N2 atmosphere, and vacuum (1×10 -3 The results of the evaluation using the crack and opening method described above at a pressure of 1×10 Pa will be explained. Here, the N2 atmosphere contains less moisture than the air, and in order to further reduce the moisture content in the environment, a pressure of 1×10 -3 The bonding strength was 1.1 J / m 2 In N2 atmosphere, it was 1.5 J / m 2 , 2.5 J / m in vacuum 2That's all. This is thought to indicate that when moisture is present in the environment in which the bond strength is evaluated, the moisture diffuses to the bond interface between the substrates W1 and W2, causing stress corrosion at the bond interface to progress and reducing the bond strength. For this reason, it is thought that by performing the above-mentioned heat treatment, moisture attached to the bond interface between the substrates W1 and W2 is removed, thereby suppressing stress corrosion in the area that is easily affected by moisture at the bond interface, and improving the bond strength between the substrates W1 and W2. However, this is merely an example of a factor that improves the bond strength due to the above-mentioned heat treatment, and the effect of improving the bond strength is not limited to this factor.

[0071] (Embodiment 2) The bonding system according to this embodiment differs from that of embodiment 1 in that it bonds the substrates W1 and W2 together through so-called hydrophilic bonding. The bonding system according to this embodiment performs an activation treatment step for activating the bonding surfaces of the substrates W1 and W2, and then performs a water cleaning step for cleaning the bonding surfaces of the substrates W1 and W2 with water.

[0072] The configuration of the bonding system according to this embodiment is similar to that of the bonding system described in embodiment 1. Hereinafter, configurations similar to those of embodiment 1 will be described using the same reference numerals as those shown in Figs. 1 to 3. The air pressure in the chamber 120 of the bonding apparatus 1 can be set within a range of 1 Pa or more and 1000 Pa or less.

[0073] Next, a hydrophilic bonding method in which the bonding system according to the present embodiment bonds the substrates W1 and W2 together by so-called hydrophilic bonding will be described with reference to FIG. 16. Here, the substrates W1 and W2 are arranged in the introduction ports 811 and 812 shown in FIG. 1 with their bonding surfaces facing vertically upward. In the introduction port 811, for example, the substrate W2 held by the head 142 in the bonding apparatus 1 is arranged, and in the introduction port 812, for example, the substrate W1 placed on the stage 141 in the bonding apparatus 1 is arranged. First, the first transfer device 82 takes out the substrate W2 arranged in the introduction ports 811 and 812 and transfers it to the load lock unit 83 (step S201). Here, the transfer robot 821 takes out the substrates W1 and W2 from the introduction ports 811 and 812. Then, when the gate driver 834 of the load lock unit 83 opens the gate 833a on the first transfer device 82 side of the waiting chamber 831, the transfer robot 821 turns so that the tip of the arm 821a faces the load lock unit 83 side while holding the substrates W1 and W2. At this time, when the transfer robot 821 takes out the substrate W2 from the introduction port 812, the arm 821a is inverted so that the joining surface side of the substrate W2 faces vertically downward, thereby turning while holding the substrate W2 in a position where the joining surface side of the substrate W2 faces vertically downward. On the other hand, when the transfer robot 821 takes out the substrate W1 from the introduction port 811, the transfer robot 821 turns while maintaining the position of the substrate W2 in a position where the joining surface side faces vertically upward. Thereafter, the transfer robot 821 extends the arm 821a to insert the tip of the arm 821a into the waiting chamber 831. Then, the substrates W1 and W2 are transferred from the tip of the arm 821a to a cassette 8361 of the substrate holding mechanism 836 arranged in the waiting chamber 831. Next, when the transfer robot 821 completes the transfer of the substrates W1 and W2 to the cassette 8361 of the substrate holding mechanism 836, the transfer robot 821 retracts the arm 821a. Then, the gate driver 834 closes the gate 833a of the waiting chamber 831.

[0074] Thereafter, the second transfer device 84 transfers the substrates W1 and W2 held in the cassette 8361 of the substrate holding mechanism 836 from the load lock unit 83 to the bonding apparatus 1 (step S202). Note that the operation in step S202 is similar to the operation in step S105 described in the embodiment.

[0075] Next, an activation process is performed in which the bonding surfaces of the two substrates W1 and W2 are activated in a reduced pressure atmosphere (step S203). Note that the operation in step S203 is similar to the operation in step S107 described in the embodiment.

[0076] Next, the second transfer device 84 transfers the substrates W1 and W2 from the bonding device 1 to the load lock unit 83 (step S204). Here, the second transfer device 84 transfers, for example, the substrates W1 and W2 to the bottom slot SLT1 and the top slot SLT3 of the cassette 8361, respectively. Thereafter, the transfer robot 821 transfers the substrates W1 and W2 to the cleaning device 3 (step S205). Here, when the gate drive unit 834 of the load lock unit 83 opens the gate 833a on the first transfer device 82 side of the waiting chamber 831, the transfer robot 821 takes out the substrates W1 and W2 from the cassette 8361 in the waiting chamber 831. Then, when the cleaning device 3 opens the transfer entrance for the substrates W1 and W2, the transfer robot 821 rotates while holding the substrates W1 and W2 so that the tip of the arm 821a faces the cleaning device 3 side. Next, the transfer robot 821 extends the arm 821a and inserts the tip of the arm 821a into the cleaning apparatus 3. Then, the substrates W1 and W2 are transferred from the tip of the arm 821a of the transfer robot 821 to the stage of the cleaning apparatus 3.

[0077] Next, the cleaning device 3 performs a water cleaning process for cleaning the substrates W1 and W2 with water (step S206). This water cleaning process corresponds to a hydrophilization process for hydrophilizing the bonding surfaces of the substrates W1 and W2. The cleaning device 3 corresponds to a hydrophilization treatment device for hydrophilizing the substrates using water. After that, the first transfer device 82 transfers the substrates W1 and W2 for which the water cleaning process has been completed from the cleaning device 3 to the load lock unit 83 (step S207). Next, in the waiting chamber 831 with a reduced pressure atmosphere, a heat treatment process is performed for heating the bonding surfaces of the two substrates W1 and W2 to a temperature higher than 60° C. (step S208). Next, the second transfer device 84 transfers the substrates W1 and W2 held in the cassette 8361 of the substrate holding mechanism 836 from the load lock unit 83 to the bonding device 1 (step S209). Next, a heat treatment process is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded to each other are heated to a temperature higher than 60° C. in a reduced pressure atmosphere (step S210). Here, the inside of the chamber 120 is maintained at a reduced pressure of 10,000 Pa or less to reduce voids caused by entrapment of air. By performing this heat treatment process, only excess water molecules attached to the bonding surfaces of the substrates W1 and W2 are removed, and the bonding surfaces of the substrates W1 and W2 are left with many OH groups that contribute to bonding the substrates W1 and W2. However, if the inside of the chamber 120 is evacuated from a state in which it is open to the atmosphere to a reduced pressure of 10,000 Pa, the chamber 120 contains a lot of moisture, so that the water molecules cannot be sufficiently removed by the heat treatment of the substrates W1 and W2. Therefore, the degree of vacuum in the chamber 120 is preferably 1,000 Pa or less, more preferably 1 Pa or less, and more preferably 10 Pa or less. -2 It is more preferable to reduce the pressure in the chamber 120 to 10,000 Pa or less. Also, as in this embodiment, it is preferable to provide a load lock unit 83 and introduce a moisture-free gas such as nitrogen into the chamber 120 of the bonding apparatus 1 to reduce the pressure in the chamber 120 to 10,000 Pa or less. Note that the operations in steps S207 to S210 are the same as the operations in steps S103 to S106 described in the embodiment. Thereafter, a bonding step is performed to bond the substrates W1 and W2 together (step S211).

[0078] Next, the second transfer device 84 transfers the bonded substrates W1, W2 from the bonding device 1 to the load lock unit 83 (step S212). Then, the first transfer device 84 transfers the bonded substrates W1, W2 from the load lock unit 83 to the take-out port 813 (step S213). Note that the operations in steps S212 and S213 are similar to the operations in steps S109 and S110 described in the embodiment.

[0079] However, in the conventional hydrophilic bonding method under reduced pressure, it was not possible to suppress the generation of voids caused by air being drawn between the substrates W1 and W2 when the hydrophilic bonding method was performed in the atmosphere. In addition, in the conventional hydrophilic bonding method, although particles that cause voids can be removed in the water cleaning process, excess water adheres to the bonding surfaces of the substrates W1 and W2, and may cause microvoids in the annealing process performed after the substrates W1 and W2 are bonded together. In contrast, in the hydrophilic bonding method according to the present embodiment, the pressure in the chamber 120 is set to 1000 Pa or less to avoid air being drawn between the substrates W1 and W2, and the substrates W1 and W2 are bonded together. As a result, the excess water that causes microvoids and adheres to the bonding surfaces of the substrates W1 and W2 can be blown off by the heat treatment process performed before the substrates W1 and W2 are brought into contact with each other in the chamber 120. In addition, since the OH groups formed on the bonding surfaces of the substrates W1 and W2 come into direct contact with each other when the substrates W1 and W2 are bonded together, the processing temperature and processing time can be reduced in the process of performing an annealing process to remove excess water attached to the bonding surfaces of the substrates W1 and W2 after bonding the substrates W1 and W2 together. For example, the processing temperature in the annealing process can be reduced from 350°C to 150°C. Therefore, the substrates W1 and W2 can be bonded together at a relatively low temperature and in a short time. In addition, by performing an activation process to generate a sufficient amount of OH groups on the bonding surfaces of the substrates W1 and W2 before bonding the substrates W1 and W2 together, water and impurities present between the substrates W1 and W2 can be almost eliminated, and the OH groups formed on the bonding surfaces of the substrates W1 and W2 are directly bonded to each other, an increase in the bonding strength between the substrates W1 and W2 can be expected.

[0080] Here, the results of a comparison of the appearance and bonding strength (converted to surface energy) of the bonded substrates W1 and W2 between cases where a heat treatment step was performed before the bonding step and cases where a heat treatment step was not performed in the hydrophilic bonding method according to this embodiment will be described. First, in the case where a heat treatment step was not performed before the bonding step, the occurrence of microvoids was confirmed as shown in FIG. 17A. Then, the bonding strength (converted to surface energy) between the substrates W1 and W2 was 1.9 mJ / m 2 In contrast, when the activation treatment step was performed after the heat treatment step as in the hydrophilic bonding method according to the present embodiment, the generation of microvoids was not confirmed as shown in FIG. 17B. Furthermore, the bonding strength (converted into surface energy) between the substrates W1 and W2 was 2.5 mJ / m 2 This shows that by performing the heat treatment step before the bonding step, the generation of microvoids at the bonding interface between the bonded substrates W1 and W2 is suppressed, and the bonding strength between the substrates W1 and W2 is increased accordingly.

[0081] The bonding method according to the present embodiment was also evaluated in the case where substrates W1 and W2 made of materials with different linear expansion coefficients were bonded together. As in the first embodiment, a Si substrate was used as the substrate W1, and a lithium tantalate (Lt:LiTaO3) substrate or a lithium niobate (Ln:LiNbO3) substrate was used as the substrate W2, and the bonding method was performed. As a result, as in the first embodiment, warping or cracking of the substrates W1 and W2 was prevented, and the bonding strength between the substrates W1 and W2 was improved when the substrates W1 and W2 were bonded together after the temperature of the substrates W1 and W2 had decreased to a temperature lower than that during the heat treatment process after the heat treatment process.

[0082] In addition, if excess moisture remains at the bonding interface between the substrates W1 and W2, there is a risk that the diffusion of the moisture will cause stress corrosion at the bonding interface, and the effect of improving the bonding strength by the heat treatment will not last. For this reason, it is preferable to perform a heat treatment process on the substrates W1 and W2 to remove the moisture attached to the bonding surfaces of the substrates W1 and W2, so that excess moisture does not remain at the bonding interface between the substrates W1 and W2. This is also true for hydrophilic bonding, and good results were obtained by removing excess moisture by heat treatment before bonding. For example, after the hydrophilic treatment process, at least one of the bonding surfaces of the two bonded objects to be bonded to each other may be heated to a temperature higher than 60°C in a reduced pressure atmosphere, and then the two bonded objects may be bonded while maintaining the reduced pressure atmosphere.

[0083] However, when the substrates W1 and W2 are bonded together in the atmosphere, air or excess water is trapped between the bonding surfaces of the substrates W1 and W2, which causes the generation of voids. In contrast, according to the hydrophilic bonding method of the present embodiment, the substrates W1 and W2 are bonded together in a reduced pressure atmosphere with little air or moisture, so that the generation of voids as described above is suppressed. Furthermore, according to the hydrophilic bonding method of the present embodiment, before the bonding step, a heat treatment step is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded together are heated to a temperature higher than 60° C. in a reduced pressure atmosphere. This removes excess water molecules attached to the bonding surfaces of the substrates W1 and W2, and the bonding surfaces of the substrates W1 and W2 are made to have a state in which only a large number of OH groups that contribute to the bonding of the substrates W1 and W2 are present. Therefore, the substrates W1 and W2 can be firmly bonded together.

[0084] Furthermore, according to the hydrophilic bonding method of the present embodiment, the substrates W1 and W2 are bonded together under hydrophilic conditions using a bonding system equipped with a load lock unit 83. This eliminates the need to open the chamber 120 of the bonding apparatus 1 to the atmosphere, thereby shortening the processing time accordingly.

[0085] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations of the above-mentioned embodiments. For example, the bonding system may include introduction ports 811 and 812, an extraction port 813, a first transfer device 82, a cleaning device 3, a bonding device 1, a load lock unit 83, a second transfer device 84, an activation treatment device 2002, and a control unit 9, as shown in Fig. 18. In Fig. 18, the same components as those in the embodiments are denoted by the same reference numerals as those in Fig. 1.

[0086] The activation processing device 2002 performs activation processing on the bonding surfaces of the substrates W1 and W2 by performing at least one of reactive ion etching using nitrogen gas and irradiation with nitrogen radicals. The activation processing is performed on the bonding surfaces of the substrates. The activation processing device 2002 is a device that generates inductively coupled plasma (ICP), and as shown in FIG. 19, includes a stage 210, a chamber 212, a plasma chamber 213, an induction coil 215 wound around the outside of the plasma chamber 213, and a high-frequency power source 216 that supplies high-frequency current to the induction coil 215. The activation processing device 2 may be, for example, a type that generates plasma in the upper part of the chamber and allows only radicals contained in the plasma to flow down through holes formed in an ion trap plate. The plasma generation source may be a parallel plate type plasma generation source or a plasma generation source using microwaves. The plasma chamber 213 is formed of, for example, quartz glass. The activation treatment device 2002 also includes a nitrogen gas supply unit 220A and an oxygen gas supply unit 220B. The nitrogen gas supply unit 220A includes a nitrogen gas storage unit 221A, a supply valve 222A, and a supply pipe 223A. The oxygen gas supply unit 220B includes an oxygen gas storage unit 221B, a supply valve 222B, and a supply pipe 223B. The substrates W1 and W2 are placed on the stage 210. The stage 210 also includes a substrate heating unit 210a for heating the substrates W1 and W2. The chamber 212 communicates with the inside of the plasma chamber 213. The chamber 212 is connected to a vacuum pump 201a via an exhaust pipe 201b and an exhaust valve 201c. When the exhaust valve 201c is opened and the vacuum pump 201a is operated, the gas in the chamber 212 is exhausted to the outside of the chamber 212 through the exhaust pipe 201b, and the air pressure in the chamber 212 is reduced (decompressed). -2 It can be made to be less than Pa.

[0087] The high frequency power supply 216 may be one that supplies a high frequency current of, for example, 27 MHz to the induction coil 215. When a high frequency current is supplied to the induction coil 215 in a state where N2 gas is introduced into the plasma chamber 213, a plasma PLM is formed in the plasma chamber 213. Here, since ions contained in the plasma are trapped in the plasma chamber 213 by the induction coil 215, a configuration without a trap plate may be used in a portion between the plasma chamber 213 and the chamber 212. The bias application unit 217 is a high frequency power supply that applies a high frequency bias to the substrates W1 and W2 supported by the stage 210. For example, a bias application unit that generates a high frequency bias of 13.56 MHz may be used as the bias application unit 217. In this way, by applying a high frequency bias to the substrates W1 and W2 by the bias application unit 217, a sheath region is generated near the bonding surface of the substrates W1 and W2 where ions having kinetic energy repeatedly collide with the substrates W1 and W2. The bonding surface of the substrates W1 and W2 is etched by the ions having kinetic energy present in this sheath region.

[0088] Here, a hydrophilic bonding method in which the bonding system according to this modified example bonds the substrates W1 and W2 together through so-called hydrophilic bonding will be described with reference to Fig. 20. Here, it is assumed that the substrates W1 and W2 are placed in the introduction ports 811 and 812 shown in Fig. 1 with their bonding surfaces facing vertically upward. Note that, for example, the substrate W2 held by the head 142 in the bonding apparatus 1 is placed in the introduction port 811, and, for example, the substrate W1 placed on the stage 141 in the bonding apparatus 1 is placed in the introduction port 812.

[0089] First, the first transfer device 82 takes out the substrate W2 arranged in the introduction ports 811 and 812 and transfers it to the activation treatment device 2002 (step S301). Here, the transfer robot 821 takes out the substrates W1 and W2 from the introduction ports 811 and 812. Then, when the introduction port of the activation treatment device 2002 is opened, the transfer robot 821 turns so that the tip of the arm 821a faces the activation treatment device 2002 while holding the substrates W1 and W2. At this time, the transfer robot 821 turns while maintaining the substrates W1 and W2 taken out from the introduction ports 811 and 812 in a position in which the bonding surface side faces vertically upward. Thereafter, the transfer robot 821 extends the arm 821a to insert the tip of the arm 821a into the chamber 212. Then, the substrates W1 and W2 are transferred from the tip of the arm 821a to the stage 210 in the chamber 212. Next, when the transfer of the substrates W1 and W2 onto the stage 210 is completed, the transfer robot 821 retracts the arm 821a.

[0090] Next, after reducing the pressure inside the chamber 212 of the activation processing device 2002, the substrate heating unit 210a heats the substrates W1 and W2 while they are placed on the stage 210. Then, an activation process is performed to activate the bonding surfaces of the substrates W1 and W2 in a reduced pressure atmosphere (step S302). Here, the reduced pressure atmosphere refers to, for example, a pressure inside the chamber 212 of 1×10 -2Pa or less. The activation processing device 2002 introduces N2 gas from the nitrogen gas storage unit 221A through the supply pipe 223A into the chamber 212 by opening the supply valve 222A shown in FIG. 16, for example. Next, the activation processing device 2002 applies a high-frequency bias to the substrates W1 and W2 placed on the stage 210 by the bias application unit 217 while stopping the supply of high-frequency current from the high-frequency power source 216 to the induction coil 215. This causes reactive ion etching (RIE) using N2 gas to be performed on the bonding surface of the substrate W1. Next, the activation processing device 2002 starts the supply of high-frequency current from the high-frequency power source 216 to the induction coil 215 to generate plasma with the N2 gas. At this time, the activation processing device 2002 stops the application of the high-frequency bias to the substrate W1 by the bias application unit 217. In this manner, N2 radicals are irradiated onto the bonding surface of the substrate W1.

[0091] On the other hand, when activating the bonding surface of the substrate W2, i.e., the Si or nitride substrate, the activation processing device 2002 first introduces O2 gas from the oxygen gas storage unit 221B through the supply pipe 223B into the chamber 212 by opening the supply valve 222B. Next, the activation processing device 2002 applies a high-frequency bias to the substrate W2 placed on the stage 210 by the bias application unit 217 while stopping the supply of high-frequency current from the high-frequency power source 216 to the induction coil 215. This causes reactive ion etching (RIE) using O2 gas to be performed on the bonding surface of the substrate W2. Next, the activation processing device 2002 closes the supply valve 622B to stop the supply of O2 gas from the O2 gas storage unit 621B into the chamber 612, thereby exhausting the O2 gas from the chamber 612. Thereafter, the activation processing device 2002 introduces N2 gas from the nitrogen gas storage unit 221A through the supply pipe 223A into the chamber 212 by opening the supply valve 222A. Thereafter, the activation processing device 2002 starts supplying a high-frequency current from the high-frequency power source 216 to the induction coil 215 to generate plasma with the N2 gas. At this time, the activation processing device 2002 stops applying a high-frequency bias to the substrate W2 by the bias application unit 217. In this manner, the bonding surface of the substrate W2 is irradiated with N2 radicals. Note that a cover heating step may be performed simultaneously with or before the activation processing step, in which a cover (not shown) arranged in the chamber 212 in a manner including the activation processing area around the substrates W1 and W2 to be activated is heated.

[0092] Thereafter, the transport robot 821 transports the substrates W1 and W2 to the cleaning apparatus 3 (step S303). Here, when the inlet of the activation processing apparatus 2002 is opened, the transport robot 821 takes out the substrates W1 and W2 placed on the stage 210 in the chamber 212 of the activation processing apparatus 2002. Then, when the cleaning apparatus 3 opens the transfer entrance for the substrates W1 and W2, the transport robot 821 rotates while holding the substrates W1 and W2 so that the tip of the arm 821a faces the cleaning apparatus 3. Next, the transport robot 821 extends the arm 821a to insert the tip of the arm 821a into the cleaning apparatus 3. Then, the substrates W1 and W2 are transferred from the tip of the arm 821a of the transport robot 821 to the stage of the cleaning apparatus 3.

[0093] Next, the cleaning device 3 executes a water cleaning process for cleaning the substrates W1 and W2 with water (step S304). After that, the first transfer device 82 transfers the substrates W1 and W2 for which the water cleaning process has been completed from the cleaning device 3 to the load lock unit 83 (step S305). Here, when the transfer robot 821 receives the substrate W2 from the cleaning device 3, it inverts the arm 821a so that the bonding surface side of the substrate W2 faces vertically downward, and then rotates while holding the substrate W2 in a posture in which the bonding surface of the substrate W2 faces vertically downward, and then transfers the substrate W2 to the load lock unit 83. Next, in the waiting chamber 831 with a reduced pressure atmosphere, a heat treatment process is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded to each other are heated to a temperature higher than 60° C. (step S306). Next, the second transfer device 84 transfers the substrates W1 and W2 held in the cassette 8361 of the substrate holding mechanism 836 from the load lock unit 83 to the bonding device 1 (step S307). After that, a heat treatment process is performed in which the bonding surfaces of the two substrates W1 and W2 to be bonded to each other are heated to a temperature higher than 60° C. in a reduced pressure atmosphere (step S308). Next, a bonding process is performed in which the substrates W1 and W2 are bonded to each other (step S309).

[0094] Thereafter, the second transfer device 84 transfers the bonded substrates W1, W2 from the bonding device 1 to the load lock unit 83 (step S310). Next, the first transfer device 84 transfers the bonded substrates W1, W2 from the load lock unit 83 to the take-out port 813 (step S311). Note that the operations in steps S310 and S311 are similar to the operations in steps S109 and S110 described in the embodiment.

[0095] According to this configuration, the number of steps can be reduced when bonding the substrates W1 and W2 together through so-called hydrophilic bonding, and therefore the time required to bond the substrates W1 and W2 together can be shortened.

[0096] In the embodiment, an example has been described in which, after the activation process, in the bonding process, the head driving unit 144 performs an alignment operation of both substrates W1 and W2 based on the misalignment amount measured by the misalignment amount measuring unit 150 while the substrates W1 and W2 are in close proximity to each other. However, this is not limiting, and for example, the head driving unit 144 may perform the alignment operation of the substrates W1 and W2 before performing the activation process. In this case, the bonding process can be performed immediately after the activation process, so that the substrates W1 and W2 can be bonded to each other in a state in which their bonding surfaces are activated.

[0097] In the embodiment, an example has been described in which covers 122A and 122B are arranged around stage 141 and head 142 in chamber 120, respectively, but this is not limited thereto, and covers 122A and 122B may be arranged only around cover 122A or head 142 in chamber 120, for example.

[0098] In the bonding method shown in FIG. 8 according to the embodiment, the heat treatment step in step S104 or the heat treatment step in step S106 may be omitted. -2 In contrast, the heat treatment in step S106 is performed in a reduced pressure atmosphere of about 10 Pa. -6The heat treatment is performed in a reduced pressure atmosphere of about Pa. Here, as shown in FIG. 15, the bonding strength between the substrates W1 and W2 is 10 -6 Since the temperature rises significantly in a reduced pressure atmosphere of 10 Pa, from the viewpoint of firmly bonding the substrates W1 and W2 to each other, it is preferable to omit the heat treatment step in step S104 rather than omitting the heat treatment step in step S106.

[0099] 16 to 20, the load lock unit 83 may be omitted. In the modified example of the hydrophilic bonding method described above, the pressure in the chamber 120 of the bonding apparatus 1 only needs to be set within a range of 1 Pa to 1000 Pa, so that the processing time is not excessively long even if the substrates W1 and W2 are transported into the chamber 120 while the chamber 120 is open to the atmosphere. For this reason, the load lock unit 83 can be omitted in the modified example of the hydrophilic bonding method described above.

[0100] In the second embodiment, an example has been described in which the substrates W1 and W2 are bonded together after the activation process and the water cleaning process, but the present invention is not limited to this. For example, in the activation process, the bonding surfaces of the substrates W1 and W2 may be chemically treated using a wet process to generate OH groups on the bonding surfaces of the substrates W1 and W2, and then the substrates W1 and W2 may be bonded together. Alternatively, the activation process may be omitted and only the water cleaning process may be performed, and then the substrates W1 and W2 may be bonded together.

[0101] In each embodiment, the method of heat treating the covers 122A, 122B may be performed simultaneously when baking the chamber 120, or may be performed simultaneously when performing the heat treatment process for the substrates W1, W2 before performing the activation process.

[0102] In each embodiment, an example in which a particle beam is irradiated onto the bonding surfaces of the substrates W1 and W2 in the activation process has been described, but the present invention is not limited to this, and for example, an ion gun may be used to irradiate the ion beam onto the bonding surfaces of the substrates W1 and W2. Also, in each embodiment, the particle beam sources 161 and 162 may irradiate the bonding surfaces of the substrates W1 and W2 with Si particles together with argon. Furthermore, in the first embodiment, a plasma generation source may be adopted instead of the particle beam sources 161 and 162.

[0103] In each embodiment, the heat treatment step may be performed only in the bonding apparatus 1 without performing the heat treatment step in the load lock unit 83 .

[0104] In each embodiment, a Si particle deposition step may be performed in which Si particles are deposited on at least one of the bonding surfaces of the two substrates W1 and W2. In this case, for example, two particle beam sources 161 and 162 may be used to irradiate the bonding surfaces of the substrates W1 and W2 with Si particles. In this case, for example, as shown in FIG. 21, a target material TA made of Si is fixed to a side surface of the particle beam source 161, and the particle beam source 162 irradiates a particle beam toward the target material TA fixed to the particle beam source 161 as shown by an arrow AR41, thereby sputtering the target material TA. At this time, the target material TA fixed to the particle beam source 161 is sputtered by the particle beam incident from the particle beam source 162, and Si particles are irradiated from the target material TA to the bonding surface of the substrate W1 as shown by an arrow AR42. Here, the two particle beam sources 161 and 162 to which the target material TA is fixed correspond to the Si particle irradiation unit. Then, by moving the two particle beam sources 161 and 162 as shown by the arrow AR43, a Si layer is formed on the bonding surface of the substrate W1. Also, for example, as shown in FIG. 22, a target material TA made of Si is fixed to the side of the particle beam source 162, and the particle beam source 161 irradiates the particle beam toward the target material TA fixed to the particle beam source 162 as shown by the arrow AR44, thereby sputtering the target material TA. At this time, the target material TA fixed to the particle beam source 162 is sputtered by the particle beam incident from the particle beam source 161, and Si particles are irradiated from the target material TA to the bonding surface of the substrate W2 as shown by the arrow AR45. Then, by moving the two particle beam sources 161 and 162 as shown by the arrow AR44, a Si layer is formed on the bonding surface of the substrate W2. Note that after forming a Si layer on the substrates W1 and W2, the Si layer may be etched by irradiating the particle beam to the Si layer.

[0105] When the substrates W1 and W2 are made of SiO2, the bonding strength between the substrates W1 and W2 is further improved when the substrates W1 and W2 are bonded together after forming a Si layer on the bonding surfaces of the substrates W1 and W2. However, when simultaneously forming a Si layer by depositing Si particles on the substrates W1 and W2 and etching the Si layer by irradiating a particle beam containing Ar, it is difficult to adjust the balance between the amount of deposited Si particles and the amount of etched Si layer. In contrast, in a method of etching a Si layer by irradiating a particle beam onto the Si layer after forming a Si layer on the substrates W1 and W2, the time for sputtering the target TA by the particle beam source 161 and the time for irradiating the substrates W1 and W2 with the particle beam are controlled, and the balance between the thickness of the Si layer formed by sputtering and the amount of etching by the particle beam is appropriately adjusted as described above, so that a Si layer of optimal thickness or an island-shaped region formed from Si can be formed. For example, even in a structure in which electrodes are exposed on the substrates W1 and W2, by forming a Si layer of an optimal thickness or an island-shaped region made of Si, the electrodes can be prevented from becoming conductive to each other and the bonding strength between the substrates W1 and W2 can be increased.

[0106] 15 in the first embodiment, when the substrates W1 and W2 are Si substrates, the strength is rapidly improved by removing impurities mainly composed of moisture floating in the chamber 120 by increasing the degree of vacuum. Based on this result, in this modification, particularly when the substrates W1 and W2 are made of a material other than Si, the bonding strength between the substrates W1 and W2 bonded by a bonding method in which a heat treatment process is performed on the substrates W1 and W2 can be improved by irradiating the bonding surfaces of the substrates W1 and W2 with Si particles to form a Si layer.

[0107] Here, the results of comparing the bonding strength when the substrates W1 and W2 are bonded to each other when the substrates W1 and W2 are made of SiO2 and when a Si layer is formed on the bonding surface of the substrates W1 and W2 and when no Si layer is formed on the bonding surface of the substrates W1 and W2 are bonded to each other will be described. Here, four samples 11 to 14 were fabricated and their bonding strengths were evaluated. In addition, the samples 11 to 14 were fabricated under conditions that lower the bonding strength compared to the conditions described in the embodiment in order to make it easier to confirm the change over time in the bonding strength between the substrates W1 and W2. The sample 11 was fabricated by forming a Si layer on the bonding surface of the substrates W1 and W2 by scanning the two particle beam sources 161 and 162 set in the posture shown in FIG. 22 multiple times on each of the substrates W1 and W2, and then scanning the particle beam sources 161 and 162 once on the substrates W1 and W2 in a posture in which the particle beams are irradiated to the substrates W1 and W2. The sample 12 was fabricated by performing the same process as the sample 11, and then performing a heat treatment on the substrates W1 and W2 at 150° C. for 10 min. Sample 13 was fabricated by forming a Si layer on the bonding surfaces of substrates W1 and W2 by scanning two particle beam sources 161 and 162, which were set in the posture shown in FIG. 22, over substrates W1 and W2 multiple times, and then scanning the particle beam sources 161 and 162 multiple times over substrates W1 and W2 in a posture for irradiating the substrates W1 and W2 with particle beams. Sample 14 was fabricated by carrying out the same process as sample 13, and then carrying out a heat treatment on substrates W1 and W2 at 150° C. for 10 minutes. Here, the Si layers of samples 11 and 12 were thinner than those of samples 13 and 14. Specifically, the Si layers of samples 11 and 12 were less than 3 nm, and the Si layers of samples 13 and 14 were 3 nm or more.

[0108] The bonding strength of Samples 11 to 14 was evaluated immediately after bonding the substrates W1 and W2 together and one to four weeks after bonding the substrates W1 and W2 together using the crack and opening method described in the first embodiment. As a result, the bonding strength of Sample 12 (0.48 mJ / m 2 ) is the bonding strength of sample 11 (0.25 mJ / m 2 ), which is larger than the bonding strength of sample 14 (1.1 mJ / m 2) is the bonding strength of sample 13 (0.7 mJ / m 2 However, after 1 week to 4 weeks had passed since the substrates W1 and W2 were bonded, the bonding strength of the samples 11 and 12 was 0.5 mJ / m 2 On the other hand, the bonding strength of sample 14 (1.49 mJ / m 2 ) is the bonding strength of sample 13 (1.15 mJ / m 2) was larger than that of the sample 11. This shows that when the Si layer is relatively thin, the effect of improving the bonding strength between the substrates W1 and W2 by the heat treatment does not last, but when the Si layer becomes thicker to a certain extent, the effect of improving the bonding strength between the substrates W1 and W2 by the heat treatment lasts. This is because, in the case of samples 11 and 12, the Si layer is relatively thin, so that moisture remaining at the bonding interface between the substrates W1 and W2 is likely to form an SiO2 region at the bonding interface between the substrates W1 and W2. It is considered that the moisture remaining at the bonding interface between the substrates W1 and W2 diffuses over time through the SiO2 region, which causes stress corrosion at the bonding interface, and the effect of improving the bonding strength between the substrates W1 and W2 by the heat treatment is offset by the decrease in bonding strength due to stress corrosion. On the other hand, in the case of samples 13 and 14, the Si layer is relatively thick, so that Si-Si bonds are dominant at the bonding interface between the substrates W1 and W2, and therefore an SiO2 region is unlikely to form at the bonding interface between the substrates W1 and W2. Therefore, the diffusion of moisture remaining at the bonding interface between the substrates W1 and W2 is suppressed, and the stress corrosion at the bonding interface caused by this is suppressed, and as a result, it is considered that the effect of improving the bonding strength between the substrates W1 and W2 by the heat treatment is sustained. In other words, when the SiO2 region is dominant at the bonding interface between the substrates W1 and W2, stress corrosion at the bonding interface caused by the diffusion of moisture remaining at the bonding interface between the substrates W1 and W2 occurs, and it can be said that the effect of improving the bonding strength by the heat treatment does not last. Note that similar results were obtained when the substrates W1 and W2 are made of SiN. From this, it can be said that when SiN is dominant at the bonding interface between the substrates W1 and W2, stress corrosion at the bonding interface caused by the diffusion of moisture remaining at the bonding interface between the substrates W1 and W2 occurs, and the effect of improving the bonding strength by the heat treatment does not last. In other words, in hydrophilic bonding, if the bonding interface is dominated by a region that is easily affected by moisture, such as an oxide region such as a SiO2 region or a nitride region, stress corrosion occurs over time due to the diffusion of moisture remaining at the bonding interface, and the strength of the bond between the substrates W1 and W2 decreases. In contrast, the above-mentioned heat treatment reduces the moisture remaining at the bonding interface between the substrates W1 and W2, suppressing stress corrosion in the region that is easily affected by moisture at the bonding interface, and improving the bonding strength between the substrates W1 and W2. This principle can be derived from the evaluation results of the above-mentioned samples 11 to 14.However, this evaluation result shows only one example of the factor of the effect of improving the bonding strength by the above-mentioned heat treatment, and the effect of improving the bonding strength is not limited to this factor.

[0109] In addition, in the case where the substrates W1 and W2 are sapphire substrates, the results of comparing the bonding strength when the bonding surfaces of the substrates W1 and W2 are irradiated with a particle beam containing carbon and with a particle beam containing Si particles will be described. Here, four samples 15 to 18 were prepared and their bonding strengths were evaluated. In addition, the samples 15 to 18 were prepared under conditions that reduce the bonding strength compared to the conditions described in the embodiment in order to make it easier to confirm the change over time in the bonding strength between the substrates W1 and W2. The sample 15 was prepared by performing an activation process in which the particle beam sources 161 and 162 irradiate the substrates W1 and W2 with a particle beam containing carbon. The sample 16 was subjected to the same process as the sample 15, and then the substrates W1 and W2 were subjected to a heat treatment at 110° C. for 10 minutes. The sample 17 was prepared by performing an activation process in which the particle beam sources 161 and 162 irradiate the substrates W1 and W2 with a particle beam containing Si particles. For sample 18, the same treatment as for sample 17 was carried out, and then the substrates W1 and W2 were subjected to a heat treatment at 110° C. for 10 minutes.

[0110] The bonding strength of Samples 15 to 18 was evaluated using the crack and opening method described above immediately after bonding the substrates W1 and W2 together and one to four weeks after bonding the substrates W1 and W2 together. As a result, the bonding strength of Sample 16 (2.4 mJ / m 2 ) is the bonding strength of sample 15 (2.0 mJ / m 2 ), and the bonding strength of sample 18 was 1.8 mJ / m 2 However, after 1 week to 4 weeks had passed since the substrates W1 and W2 were bonded together, the bonding strength of samples 15 and 16 was 0.9 mJ / m 2 The bonding strength of samples 17 and 18 was also approximately equal, ranging from 0.6 to 0.7 mJ / m 2From this, it is considered that when the substrates W1 and W2 are sapphire substrates, the influence of moisture remaining at the bonding interface between the substrates W1 and W2 on the bonding strength is small.

[0111] From the above results, the bonding method including the Si particle deposition step according to this modified example is effective when the substrates W1 and W2 are made of SiO2.

[0112] In this modification, the method of irradiating the bonding surfaces of the substrates W1 and W2 with Si particles is not limited to the above-mentioned Si particle irradiation method, and for example, the bonding surfaces of the substrates W1 and W2 may be irradiated with Si particles in a film forming apparatus other than the bonding apparatus 1. In this way, forming a Si layer on the bonding surfaces of the substrates W1 and W2 by irradiating the bonding surfaces of the substrates W1 and W2 with Si particles is effective not only in the case of directly bonding the substrates W1 and W2 as described in the first embodiment, but also in the case of hydrophilically bonding the substrates W1 and W2 as described in the second embodiment, because OH groups are generated in the implanted Si, the strength is further increased.

[0113] Apart from the modified examples described with reference to Figs. 21 and 22, for example, in the activation process of the first embodiment, Si particles may be irradiated to at least one of the bonding surfaces of the substrates W1 and W2 together with the particle beam as shown by the arrow AR51 in Fig. 23. Here, if a part or all of the inner wall of the discharge chamber 1601 of the particle beam sources 161 and 162 described with reference to Fig. 5 is formed from Si, for example, Si particles can be emitted from the particle beam sources 161 and 162 simultaneously with the Ar beam. In this way, Si particles are implanted into the bonding surfaces of the substrates W1 and W2 by irradiating the bonding surfaces of the substrates W1 and W2 with Si particles at the same time as irradiating the bonding surfaces with the particle beam. The Si particles implanted into the bonding surfaces of the substrates W1 and W2 are etched by the particle beam containing Ar or N2, so that the Si particles do not accumulate to form a Si layer, and the bonding surfaces can be modified to have a Si-rich surface.

[0114] 15 in the first embodiment, when the bonding surfaces of the substrates W1 and W2 are made of Si, the strength is rapidly improved by removing impurities mainly composed of moisture floating in the chamber 120 by increasing the degree of vacuum. Based on this result, in this modification, particularly when the substrates W1 and W2 are made of a material other than Si, Si particles are implanted into the bonding surfaces of the substrates W1 and W2 to improve the bonding strength between the substrates W1 and W2 bonded by a bonding method in which a heat treatment process is performed on the substrates W1 and W2.

[0115] In this modified example, the heat treatment step is preferably performed after implanting Si particles into the bonding surfaces of the substrates W1 and W2. Furthermore, after the heat treatment step is performed on the substrates W1 and W2, it is preferable to perform an activation treatment step while implanting Si particles into the bonding surfaces of the substrates W1 and W2 while maintaining the temperature of the substrates W1 and W2 at a temperature close to the treatment temperature in the heat treatment step without cooling the substrates W1 and W2 to 60°C, and then to contact the substrates W1 and W2 with each other at a temperature close to the treatment temperature in the heat treatment step. This makes it possible to remove impurities mainly composed of moisture attached to the bonding surfaces of the substrates W1 and W2 from the bonding surfaces of the substrates W1 and W2, thereby improving the bonding strength between the substrates W1 and W2. For example, when the substrates W1 and W2 are a lithium tantalate (Lt:LiTaO3) substrate and a Si substrate, respectively, when the substrates W1 and W2 are bonded without implanting Si particles into the bonding surfaces of the substrates W1 and W2, the bonding strength between the substrates W1 and W2 is 1.6 mJ / m 2 In contrast, when the substrates W1 and W2 are bonded to each other after Si particles are implanted into the bonding surfaces of the substrates W1 and W2 as in this modified example, the bonding strength between the substrates W1 and W2 is 2.5 J / m 2 or more (14.3J / m 2 ) and there were four bulk fractures. In other words, the bonding strength between the substrates W1 and W2 was improved. Note that when the heat treatment process for the substrates W1 and W2 was not performed, the bonding strength between the substrates W1 and W2 was 1.3 J / m 2 From these findings, it was found that by implanting Si particles into the bonding surfaces of the substrates W1 and W2 in the activation treatment step as in this modified example, the bonding strength between the substrates W1 and W2 was 1 J / m2 to 1.3 J / m 2 Furthermore, by subjecting the substrates W1 and W2 to a heat treatment process, the bonding strength is improved to 14.3 J / m 2 In other words, the bonding strength between the substrates W1 and W2 is improved to 0.3 J / m by simply implanting Si particles into the bonding surfaces of the substrates W1 and W2. 2 However, by subjecting the substrates W1 and W2 to a heat treatment process, the bonding strength between the substrates W1 and W2 increased to 13.3 J / m 2 It was found to be a great improvement.

[0116] Furthermore, in this modification, when Si particles are implanted into the bonding surfaces of the substrates W1 and W2 in the activation process, no Si layer is formed on the bonding surfaces of the substrates W1 and W2, which has the advantage that the electrodes are not electrically short-circuited even when electrodes and insulating layers are mixed on the bonding surfaces of the substrates W1 and W2.

[0117] However, insulating films made of oxide films, nitride films, etc. are ion crystalline, and cannot be bonded by so-called direct bonding, which involves an activation process using a particle beam. Also, the bonding strength between the substrates W1 and W2 cannot be achieved by simply implanting Si particles into the bonding surfaces of the substrates W1 and W2. In contrast, in this modified example, Si particles are implanted into the bonding surfaces of the substrates W1 and W2, and the substrates W1 and W2 are subjected to a heat treatment process, so that the insulating films made of oxide films, nitride films, etc. can be bonded together. Therefore, it is possible to firmly bond oxide films made of lithium tantalate (Lt:LiTaO3) and lithium niobate substrates (Ln:LiNbO3) used in SAW filters, for example, so that the performance of the SAW filter can be improved. In addition, it is possible to realize so-called hybrid bonding, which bonds bonding surfaces where metal electrodes made of Cu, Au, etc. and insulating films made of oxide films, nitride films, etc. are mixed on approximately the same surface, without causing a short circuit between the metal electrodes.

[0118] The method of implanting Si particles into the bonding surfaces of the substrates W1 and W2 in the activation process as in this modification can improve the bonding strength between the substrates W1 and W2 not only in the case of directly bonding the substrates W1 and W2 described in the first embodiment, but also in the case of hydrophilic bonding using the substrates W1 and W2 whose bonding surfaces have been implanted with Si particles by this method. In this case, by subjecting the bonding surfaces of the substrates W1 and W2 to hydrophilic treatment, OH groups are attached to the Si particles implanted into the bonding surfaces of the substrates W1 and W2, and the amount of OH groups present on the bonding surfaces of the substrates W1 and W2 increases. This improves the bonding strength between the substrates W1 and W2.

[0119] The bonding system may also include, for example, an ion implantation device that implants ions into one of the two objects to be bonded, a first heat treatment device that heats the bonding surfaces of the two objects to be bonded to each other under a reduced pressure atmosphere, an activation treatment device that activates the bonding surfaces of at least one of the two objects to be bonded, a bonding device, and a control unit that controls the operation of the first heat treatment device, the driving unit, and the second heat treatment device. At least one of the two objects to be bonded may be a lithium tantalate (Lt:LiTaO3) substrate or a lithium niobate (Ln:LiNbO3) substrate. Alternatively, the two bonded objects may be an acoustic wave device or an optical modulator. At least one of the two objects to be bonded has been implanted with ions in advance. Also, both of the two objects to be bonded may be implanted with ions. Usually, the ion implantation device is often provided separately from the above-mentioned bonding system.

[0120] The bonding apparatus may have, for example, a chamber, a stage disposed in the chamber and supporting one of the two objects to be bonded, a head disposed in the chamber facing the stage and supporting the other of the two objects to be bonded, and a drive unit for moving at least one of the stage and the head in a first direction in which the stage and the head approach each other or a second direction in which the stage and the head move away from each other. The control unit may control a first heat treatment device to heat the bonding surfaces of the two objects to be bonded to a temperature of 60°C or more and less than 150°C in a reduced pressure atmosphere, then control an activation treatment device to activate the bonding surfaces of the two objects to be bonded to each other while maintaining the reduced pressure atmosphere, and then control the drive unit to move at least one of the stage and the head in the first direction to bond the two objects to be bonded to each other while maintaining the reduced pressure atmosphere, and then control a second heat treatment device to heat the two objects to be bonded to each other to a temperature of 210°C or more and less than 300°C. The first heat treatment device may be one in which a heater is provided on at least one of the head and the stage, and may also be one that is used as the above-mentioned second heat treatment device.

[0121] The bonding system according to this modification may include a transport device that transports the two bonded objects between any two of the first heat treatment device, the activation treatment device, the bonding device, and the second heat treatment device during the period from when at least one of the two bonded objects is heat-treated in the first heat treatment device to when the two bonded objects are heat-treated in the second heat treatment device. In this case, the transport device may maintain the two bonded objects at a temperature of 50° C. or higher when transporting the two bonded objects.

[0122] Incidentally, in an acoustic wave device such as a SAW filter manufactured by bonding a lithium tantalate (Lt:LiTaO3) substrate or a lithium niobate (Ln:LiNbO3) substrate to a Si substrate, a SiO2 substrate, a sapphire substrate, or the like, it is necessary to thin the thickness of the lithium tantalate (Lt:LiTaO3) substrate or the lithium niobate (Ln:LiNbO3) substrate to about several μm in order to improve the frequency characteristics. On the other hand, due to the difference in the linear expansion coefficient between the lithium tantalate (Lt:LiTaO3) substrate or the lithium niobate (Ln:LiNbO3) substrate and the Si substrate, the SiO2 substrate, the sapphire substrate, or the like, when these bonded objects are bonded at a temperature of 150°C or higher, warping or cracking occurs when the temperature returns to normal after bonding. Therefore, in the past, the bonding surfaces of the objects to be bonded were activated by irradiating them with a particle beam in an ultra-high vacuum environment, and then the objects were bonded at room temperature. After bonding, the lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate was polished to a thin thickness. However, in this case, the thickness of the lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate is limited to about 50 μm, and the frequency characteristics cannot be sufficiently improved. In order to improve the frequency characteristics, especially in the high frequency range, the thickness of the lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate must be at least 10 μm.

[0123] Also, an optical modulator using the lithium niobate (Ln:LiNbO3) substrate as an optical waveguide may be fabricated by bonding the lithium niobate (Ln:LiNbO3) substrate to a Si substrate or the like. In this case, the lithium niobate (Ln:LiNbO3) substrate needs to be thinned according to the wavelength of light passing through the optical waveguide, and the thickness needs to be within 10 μm to improve the optical modulation characteristics in the high frequency range. Note that an optical modulator using the lithium tantalate (Lt:LiTaO3) substrate as an optical waveguide may be fabricated by bonding a lithium tantalate (Lt:LiTaO3) substrate to a Si substrate or the like instead of the lithium niobate (Ln:LiNbO3) substrate.

[0124] Incidentally, Smart Cut technology has been used as a manufacturing technology for SOI (Silicon on Insulator) substrates. This Smart Cut technology is a microfabrication technology in which hydrogen atoms are implanted into a single crystal Si substrate to a depth of several μm using ion implantation, and then the single crystal Si substrate is heat-treated at a temperature of 200°C or higher to break the bonds between the Si atoms in the single crystal Si, and peel off the entire surface of the single crystal Si substrate by a thickness of several μm. Applications of this technology to the production of SOI elements and single crystal Si thin films for next-generation solar cells are being promoted.

[0125] However, when attempting to apply this Smart Cut technology to a lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate bonded to a Si substrate, etc., heat treatment at a temperature of 200°C or higher is required after bonding, which causes warping or cracking of the lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate. For this reason, Smart Cut technology could not be applied to such applications.

[0126] In contrast, the bonding method according to this modification is a method developed to meet these applications, and by using the above-mentioned heat treatment method, ions are implanted into the material on the side to be thinned in advance, and heat treatment is performed at a temperature of 60°C or more and less than 150°C, followed by activation treatment before bonding. Then, heat treatment is performed to heat the bonded objects to a temperature of 200°C or more while maintaining the temperature at which cracks or warping do not occur, without lowering the temperature to a temperature at which cracks or warping occurs. This allows the objects to be peeled off at a depth of about several μm where the ions are implanted without causing cracks or warping, so that a thin lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate can be easily manufactured. In addition, since a method of performing heat treatment before the bonding process is used, it is possible to increase the bonding strength between the lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate and a so-called support substrate such as a Si substrate, which is a new method that was not possible with conventional room temperature bonding.

[0127] Here, if the temperature of the heat treatment is too high, it will crack due to the difference in linear expansion when it returns to room temperature. For this reason, the temperature in the heat treatment is preferably 60°C or more and less than 150°C. Similarly, the difference between the temperature at the time of bonding after the heat treatment and the temperature at the time of performing the additional heat treatment for smart cut is also preferably 210°C or more and less than 300°C, since warping or cracking will occur if it is not less than 150°C. Note that when the heat treatment temperature is 60°C, smart cut can be performed by heating to 210°C, and when it is 150°C, smart cut can be performed by heating to 300°C. As a result, a lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate with a thickness of several μm is firmly bonded to the support substrate. Also, the remaining lithium tantalate (Lt:LiTaO3) substrate or lithium niobate (Ln:LiNbO3) substrate peeled off by smart cut may be separated in the additional heat treatment process, and the bonded substrate and the remaining substrate may be discharged separately. Alternatively, the peeling may be performed after the film is discharged from the second heat treatment device. Furthermore, the film peeled off to a thickness of several μm is extremely thinner than the support substrate even if there is a difference in the linear expansion coefficient between the support substrate and the film, so warping or cracking is unlikely to occur, and there are often no problems even if the film is cooled to room temperature after the heat treatment.

[0128] The above-mentioned heat treatment and the additional heat treatment can be performed in the same heat treatment device, but since it takes time to raise and lower the temperature, it is preferable to perform the two heat treatments in different heat treatment devices from the viewpoint of improving mass productivity. However, since the temperature of the bonded objects drops when they are transported, it is preferable to heat the bonded objects when transporting them. Furthermore, by maintaining the temperature at 50°C or higher after the above-mentioned heat treatment and before the additional heat treatment, the occurrence of warping or cracking during the additional heat treatment can be suppressed.

[0129] In each embodiment, an example has been described in which the objects to be bonded are substrates W1 and W2, but the present invention is not limited to this. For example, the objects to be bonded may be a chip and a substrate.

[0130] In each embodiment, an example in which water is sprayed onto the bonding surfaces of the substrates W1 and W2 for cleaning in the water cleaning step has been described, but the present invention is not limited to this, and the water cleaning may be performed by a so-called wet processing method in which the substrates W1 and W2 are immersed in water. Alternatively, the water cleaning process may be performed after the bonding surfaces of the substrates W1 and W2 are treated with hydrofluoric acid or other acids, organic solvents, or the like. In other words, the method of the water cleaning process is not particularly limited as long as particles and other deposits attached to the bonding surfaces of the substrates W1 and W2 can be removed by cleaning with at least water.

[0131] In each embodiment, the substrates W1 and W2 are subjected to a heat treatment process, a cooling process, a hydrophilization process, a cleaning process, a process of implanting Si on the bonding surface, and a Si particle deposition process of depositing Si particles on the bonding surface, but the method is not necessarily limited to a method in which all of these steps are performed on both substrates W1 and W2. For example, all of the above-mentioned steps may be performed on only one of the substrates W1 and W2.

[0132] In each embodiment, an example has been described in which the cover heating parts 123A and 123B are heaters fixed to the side of the covers 122A and 122B opposite to the particle beam sources 161 and 162. However, this is not limited thereto, and for example, as shown in FIG. 24A, the covers 5122A and 5122B may be formed in a plate shape from glass and arranged in a form including an activation treatment area in an activation treatment step around the stage 141 and the head 142, and the cover heating parts 5123A and 5123B may be heaters made of a conductor pattern embedded in the covers 5122A and 5122B. Here, the cover heating parts 5123A and 5123B are made of a conductor pattern laid so as to cover the entire covers 5122A and 5122B as shown in FIG. 24B.

[0133] In this modification, a cover heating step is performed to heat the covers 5122A and 5122B at the same time as baking the chamber 120. At this time, the cover heating parts 5123A and 5123B are embedded in the covers 5122A and 5122B, so that the covers 5122A and 5122B are uniformly and efficiently heated. The cover heating parts 5123A and 5123B heat the entire covers 5122A and 5122B to a temperature higher than the temperature of the chamber 120.

[0134] Incidentally, as described in the embodiment, when the chamber 120 is baked in advance before the step of bonding the substrates W1 and W2, if the temperature of the covers 122A and 122B is lower than the temperature of the chamber 120, water or impurities adhering to the chamber 120 may be detached from the chamber 120 and adhere to the covers 122A and 122B. In this case, when the activation process is performed with a particle beam, the impurities adhering to the covers 122A and 122B are sputtered by the particle beam and float in the chamber 120. Then, the water or impurities floating in the chamber 120 may adhere to the bonding surfaces of the substrates W1 and W2, which may reduce the strength of the bond between the substrates W1 and W2. In response to this, after baking the chamber 120, a process is performed in which a particle beam is irradiated onto the dummy substrate and the covers 122A and 122B while a dummy substrate is held on the stage 141 and the head 142, so-called blank irradiation is performed to remove water or impurities adhering to the covers 122A and 122B. However, this blank irradiation process takes about one to four hours, resulting in a loss of processing time. In addition, the discharge chamber 1601 made of a carbon material is worn down by the amount of the particle beams 161 and 162 used for blank irradiation.

[0135] In contrast, in this modification, when the chamber 120 is baked, a cover heating step is performed in which the cover heating units 5123A and 5123B heat the entire covers 5122A and 5122B to a temperature higher than the temperature of the chamber 120. This makes it possible to suppress adhesion of water or impurities desorbed from the chamber 120 to the covers 5122A and 5122B. Also, similar to the effect of the heat treatment step described in the embodiment, water or impurities adhering to the bonding surfaces of the substrates W1 and W2 can be removed. Therefore, even if the time for performing the so-called blank firing step described above is shortened or omitted, the strength of the bond between the substrates W1 and W2 can be ensured.

[0136] In each embodiment, after the bonding process, the -3 A bonding strength evaluation step may be performed in an environment of 100 MPa (or less) Pa, in which the bonding strength between the substrates W1 and W2 is evaluated using the crack-and-opening method described above. However, if moisture is present in the environment in which the bonding strength is evaluated, the moisture causes stress corrosion at the bonding interface, resulting in a bonding strength that is lower than the actual bonding strength. In contrast, according to the present configuration, the effect of moisture in the environment on the bonding strength can be suppressed, so that the bonding strength between the substrates W1 and W2 can be evaluated with high accuracy.

[0137] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto are considered to be within the scope of the present invention.

[0138] This application is based on Japanese Patent Application No. 2021-008275 filed on January 21, 2021, Japanese Patent Application No. 2021-162509 filed on October 1, 2021, and International Application No. PCT / JP2022 / 001970 filed on January 20, 2022. The entire specification, claims and drawings of Japanese Patent Application No. 2021-008275, the entire specification, claims and drawings of Japanese Patent Application No. 2021-162509, and the entire specification, claims and drawings of International Application No. PCT / JP2022 / 001970 are incorporated herein by reference. [Industrial Applicability]

[0139] The present invention is suitable for the manufacture of, for example, CMOS (Complementary MOS) image sensors, memories, computing elements, and MEMS (Micro Electro Mechanical Systems). [Explanation of symbols]

[0140] 1: bonding device, 3: cleaning device, 9: control unit, 82: first transfer device, 83: load lock unit, 84: second transfer device, 120, 212: chamber, 120a, 831a, 831b: opening, 121a, 201a, 832a: vacuum pump, 121b, 201b, 832b: exhaust pipe, 121c, 201c, 832c: exhaust valve, 122A, 122B, 5122A, 5122B: cover, 123A, 123B, 5123A, 512 3B: cover heating unit, 141, 210: stage, 142: head, 143: stage driving unit, 144: head driving unit, 146: support mechanism, 150: position deviation amount measuring unit, 161, 162: particle beam source, 210a, 1411, 1421, 835, 8363: substrate heating unit, 213: plasma chamber, 215: induction coil, 216: high frequency power supply, 217: bias application unit, 220A: nitrogen gas supply unit, 220B: oxygen Gas supply unit, 221A: nitrogen gas storage unit, 221B: oxygen gas storage unit, 222A, 222B: supply valve, 223A, 223B: supply pipe, 811, 812: introduction port, 813: removal port, 821: transfer robot, 821a: arm, 831: waiting chamber, 833a, 833b: gate, 834: gate drive unit, 836: substrate holding mechanism, 841: support rod, 842: support, 843: support drive unit, 844: tongue 845: holder, 1441, 8362: lifting drive, 1441a, 1445: pressure sensor, 1442: XY direction drive, 1443: rotation drive, 1444: piezo actuator, 1461, 1462: support member, 1461a, 8361b: protrusion, 2002: activation processing device, 8361: cassette, 8361a, 8451: support piece, 8452: main part, PLM: plasma, TA: target material, W1, W2: substrate

Claims

1. A method for evaluating the bonding strength between two objects bonded to each other using a crack and opening method in an environment in which the moisture content is less than a predetermined moisture content in the atmosphere. Bond strength evaluation method.

2. The bonding strength between two objects bonded to each other is evaluated using a crack and opening method in an environment in which the moisture content is adjusted to a predetermined moisture content. Bond strength evaluation method.

3. The environment is a N 2 atmosphere or a vacuum. The bonding strength evaluation method according to claim 1 or 2.

4. For two objects to be joined together, the bonding strength between the two objects to be joined is evaluated using a crack and opening method in an environment in which the moisture content is less than a predetermined moisture content in the atmosphere. Bond strength evaluation device.

5. The bonding strength between two objects bonded to each other is evaluated using a crack and opening method in an environment in which the moisture content is adjusted to a predetermined moisture content. Bond strength evaluation device.

6. The environment is a N 2 atmosphere or a vacuum. The bonding strength evaluation device according to claim 4 or 5.

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