Bonding device and bonding method

Abstract

This bonding device bonds a first substrate and a second substrate. The bonding device comprises: a first holding unit for holding the first substrate; a second holding unit for holding the second substrate; a pushing unit for pushing down the first substrate on the first holding unit to bond the first substrate to the second substrate; and a gas supply mechanism for supplying gas between the first substrate and the second substrate. The gas supply mechanism includes a plurality of discharge units along the circumferential direction of the first substrate and the second substrate. The plurality of discharge units discharge the gas at mutually different discharge rates when the first substrate and the second substrate are bonded.

Description

Joining device and joining method

[0001] The present disclosure relates to a joining device and a joining method.

[0002] Patent Document 1 discloses a bonding device that includes a first holding unit (upper chuck) that adsorbs a first substrate (upper wafer) from above and a second holding unit (lower chuck) that adsorbs a second substrate (lower wafer) from below, and that bonds the first and second substrates to manufacture a bonded substrate. In manufacturing the bonded substrate, the bonding device presses down the center of the first substrate on the first holding unit to bring it into contact with the center of the second substrate on the second holding unit, bonds the centers of the two substrates together by intermolecular forces, and expands the bonded region from the center to the periphery.

[0003] Japanese Patent Application Laid-Open No. 2015-095579

[0004] The present disclosure provides a technique that can reduce distortion in bonded substrates.

[0005] According to one aspect of the present disclosure, there is provided a bonding device for bonding a first substrate and a second substrate, the bonding device including: a first holding portion that holds the first substrate; a second holding portion that holds the second substrate; a pushing portion that presses down the first substrate on the first holding portion to bond the first substrate to the second substrate; and a gas supply mechanism that supplies gas between the first substrate and the second substrate, the gas supply mechanism having a plurality of discharge portions along a circumferential direction of the first substrate and the second substrate, each of the plurality of discharge portions discharging the gas at a mutually different discharge amount when the first substrate and the second substrate are bonded.

[0006] According to one aspect, distortion of the bonded substrate can be reduced.

[0007] 9(A) is a plan view showing a bonding apparatus. FIG. 10(B) is a side view of the bonding apparatus of FIG. 1. FIG. 11 is a side view showing an example of a first substrate and a second substrate. FIG. 12 is a flowchart showing a bonding method. FIG. 13 is a plan view showing an example of a bonding module according to the first embodiment. FIG. 14 is a side view of the bonding module of FIG. 5. FIG. 15 is a cross-sectional view showing an example of an upper chuck and a lower chuck. FIG. 16 is a flowchart showing details of step S109 of FIG. 4. FIG. 17(A) is a side view showing an example of an operation in step S112 of FIG. 8. FIG. 18(B) is a side view showing an operation subsequent to FIG. 18(A). FIG. 19(C) is a side view showing an operation subsequent to FIG. 19(B). FIG. 10(A) is a cross-sectional view showing an example of an operation in step S113 of FIG. 8. FIG. 19(B) is a cross-sectional view showing an example of an operation in step S114 of FIG. 8. FIG. 19(C) is a cross-sectional view showing an operation subsequent to FIG. 19(B). FIG. 19(A ... a gas supply mechanism and an upper chuck according to the first embodiment. FIG. 20(A) is a cross-sectional view showing an enlarged view of an outer displacement sensor and a gas supply mechanism. FIG. 21(A) is a plan view showing a gas supply mechanism. FIG. 13(B) is a plan view illustrating the Young's modulus, Poisson's ratio, and shear modulus of the upper wafer. FIG. 15(A) is a graph illustrating the radial distortion of bonded wafers by the bonding method according to the first embodiment, including supply of a void reducing gas by a gas supply mechanism. FIG. 15(B) is a graph illustrating the radial distortion of bonded wafers by the bonding method according to a reference example. FIG. 16(A) is a diagram illustrating the operation of the bonding method of the gas supply mechanism according to the second embodiment. FIG. 16(B) is a diagram illustrating the operation of the bonding method of the gas supply mechanism according to the reference example. A flowchart illustrating the bonding method according to the second embodiment. A diagram illustrating the operation of the bonding method of the gas supply mechanism according to the third embodiment. A flowchart illustrating the bonding method according to the third embodiment. A plan view showing a gas supply mechanism according to a fourth embodiment.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted. Note that the X-axis, Y-axis, and Z-axis directions used in the following description are axes that intersect perpendicularly with each other, the X-axis and Y-axis directions are horizontal directions, and the Z-axis direction is vertical.

[0009] 1 and 2 , the bonding apparatus 1 bonds a first substrate W1 and a second substrate W2 to produce a bonded substrate T. At least one of the first substrate W1 and the second substrate W2 is a semiconductor substrate, such as a silicon wafer or a compound semiconductor wafer, on which multiple electronic circuits are formed. One of the first substrate W1 and the second substrate W2 may be a bare wafer on which no electronic circuits are formed. The compound semiconductor wafer is not particularly limited, but may be, for example, a GaAs wafer, a SiC wafer, a GaN wafer, or an InP wafer.

[0010] The first substrate W1 and the second substrate W2 are formed as circular plates of approximately the same shape (same diameter). As shown in FIG. 3 , the bonding apparatus 1 places the second substrate W2 on the negative Z-axis side (vertically below) of the first substrate W1, and bonds the first substrate W1 and the second substrate W2. Therefore, hereinafter, the first substrate W1 may be referred to as the "upper wafer W1," the second substrate W2 as the "lower wafer W2," and the bonded substrate T as the "bonded wafer T." Furthermore, hereinafter, the surface of the upper wafer W1 that is bonded to the lower wafer W2 will be referred to as the "bonding surface W1j," and the surface opposite the bonding surface W1j will be referred to as the "non-bonding surface W1n." Furthermore, the surface of the lower wafer W2 that is bonded to the upper wafer W1 will be referred to as the "bonding surface W2j," and the surface opposite the bonding surface W2j will be referred to as the "non-bonding surface W2n."

[0011] 1, the bonding apparatus 1 includes a loading / unloading station 2 and a processing station 3, which are arranged in this order in the positive direction of the X-axis. The loading / unloading station 2 and the processing station 3 are integrally connected.

[0012] The loading / unloading station 2 includes a mounting table 10 and a transfer area 20. The mounting table 10 has a plurality of mounting plates 11. Each mounting plate 11 is loaded with a cassette CS1, CS2, or CS3, which accommodates a plurality of substrates (e.g., 25 substrates) in a horizontal position. The cassette CS1 accommodates the upper wafer W1, the cassette CS2 accommodates the lower wafer W2, and the cassette CS3 accommodates the bonded wafer T. In the cassettes CS1 and CS2, the upper wafer W1 and the lower wafer W2 are accommodated with their respective bonding surfaces W1j and W2j facing upward and aligned in the same direction.

[0013] The transfer region 20 is disposed adjacent to the mounting table 10 on the positive side of the X-axis, and includes a transfer path 21 extending in the Y-axis direction, and a transfer device 22 movable along the transfer path 21. The transfer device 22 is movable also in the X-axis direction and rotatable about the Z-axis, and transfers the upper wafer W1, the lower wafer W2, and the bonded wafer T between the cassettes CS1 to CS3 placed on the mounting table 10 and a third processing block PB3 of the processing station 3, which will be described later.

[0014] The processing station 3 includes, for example, three processing blocks PB1, PB2, and PB3. The first processing block PB1 is provided on the rear side of the processing station 3 (the positive Y-axis side in FIG. 1 ). The second processing block PB2 is provided on the front side of the processing station 3 (the negative Y-axis side in FIG. 1 ). The third processing block PB3 is provided on the load / unload station 2 side of the processing station 3 (the negative X-axis side in FIG. 1 ).

[0015] Furthermore, the processing station 3 includes a transfer region 60 having a transfer device 61 in an area surrounded by the first processing block PB1 to the third processing block PB3. For example, the transfer device 61 has a transfer arm that is movable vertically, horizontally, and around a vertical axis. The transfer device 61 moves within the transfer region 60 to transfer the upper wafer W1, the lower wafer W2, and the bonded wafer T to devices in the first processing block PB1, the second processing block PB2, and the third processing block PB3 adjacent to the transfer region 60.

[0016] The first processing block PB1 includes, for example, a surface modification device 33 and a surface hydrophilization device 34. The surface modification device 33 modifies the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2. The surface hydrophilization device 34 hydrophilizes the modified bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2.

[0017] For example, the surface modification device 33 may modify the SiO ２ This breaks the bond between the upper wafer W1 and the lower wafer W2, forming dangling bonds of Si, which enables subsequent hydrophilization. In the surface modification device 33, for example, oxygen gas, which is a processing gas, is excited to be turned into plasma and ionized in a reduced pressure atmosphere. The oxygen ions are then irradiated onto the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2, thereby subjecting the bonding surfaces W1j and W2j to plasma processing and modification. The processing gas is not limited to oxygen gas, and may be nitrogen gas or the like.

[0018] The surface hydrophilization device 34 hydrophilizes the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 using a hydrophilization treatment liquid such as pure water. The surface hydrophilization device 34 also serves to clean the bonding surfaces W1j and W2j. In the surface hydrophilization device 34, pure water is supplied onto the upper wafer W1 or the lower wafer W2 while rotating the upper wafer W1 or the lower wafer W2 held by, for example, a spin chuck. As a result, the pure water diffuses over the bonding surfaces W1j and W2j, attaching OH groups to dangling Si bonds and hydrophilizing the bonding surfaces W1j and W2j.

[0019] 2 , the second processing block PB2 includes, for example, a bonding module 41, a first temperature adjustment device 42, and a second temperature adjustment device 43. The bonding module 41 bonds a hydrophilized upper wafer W1 and a lower wafer W2 to produce a bonded wafer T. The first temperature adjustment device 42 adjusts the temperature distribution of the upper wafer W1 before producing the bonded wafer T. The second temperature adjustment device 43 adjusts the temperature distribution of the lower wafer W2 before producing the bonded wafer T. Note that in the embodiment, the first temperature adjustment device 42 and the second temperature adjustment device 43 are provided separately from the bonding module 41, but may also be provided as part of the bonding module 41.

[0020] The third processing block PB3 includes, for example, a first position adjustment device 51, a second position adjustment device 52, and transition devices 53 and 54, arranged in this order from top to bottom. The locations of the devices in the third processing block PB3 are not limited to those shown in FIG. 2 . The first position adjustment device 51 adjusts the horizontal orientation of the upper wafer W1 and also turns the upper wafer W1 upside down so that the bonding surface W1j of the upper wafer W1 faces downward. The second position adjustment device 52 adjusts the horizontal orientation of the lower wafer W2. The transition device 53 temporarily places the upper wafer W1 thereon. The transition device 54 temporarily places the lower wafer W2 and the bonded wafer T thereon.

[0021] Returning to FIG. 1 , the bonding apparatus 1 includes a control device (controller) 90 that controls each component. The control device 90 is a control computer having one or more processors 91, a memory 92, an input / output interface (not shown), and an electronic circuit. The one or more processors 91 are one or a combination of a central processing unit (CPU), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a circuit made up of multiple discrete semiconductors, and the like. The memory 92 includes non-volatile memory and volatile memory and forms a storage unit of the control device 90. In other words, in the present disclosure, the control device 90 is an electronic circuit having a CPU, a GPU, an ASIC, an FPGA, etc., and performs various control operations described in this specification by executing instruction codes stored in the memory 92 or by being designed as a circuit for a specific application.

[0022] Next, the joining method of the embodiment will be described with reference to Fig. 4. Steps S101 to S109 shown in Fig. 4 are performed under the control of the control device 90.

[0023] In the bonding method, an operator or a transport robot (not shown) places a cassette CS1 containing multiple upper wafers W1, a cassette CS2 containing multiple lower wafers W2, and an empty cassette CS3 on the loading / unloading station 2's loading table 10.

[0024] The bonding apparatus 1 uses the transfer device 22 to remove the upper wafer W1 from the cassette CS1 and transfer it to the transition device 53 in the third processing block PB3 of the processing station 3. Thereafter, the bonding apparatus 1 uses the transfer device 61 to remove the upper wafer W1 from the transition device 53 and transfer it to the surface modification device 33 in the first processing block PB1.

[0025] Next, the bonding apparatus 1 modifies the bonding surface W1j of the upper wafer W1 using the surface modification device 33 (step S101). The surface modification device 33 modifies the bonding surface W1j with the bonding surface W1j facing upward. Thereafter, the transfer device 61 removes the upper wafer W1 from the surface modification device 33 and transfers it to the surface hydrophilization device 34.

[0026] Then, the bonding apparatus 1 hydrophilizes the bonding surface W1j of the upper wafer W1 using the surface hydrophilization device 34 (step S102). The surface hydrophilization device 34 hydrophilizes the bonding surface W1j with the bonding surface W1j facing upward. Thereafter, the transfer device 61 removes the upper wafer W1 from the surface hydrophilization device 34 and transfers it to the first position adjustment device 51 in the third processing block PB3.

[0027] The bonding apparatus 1 adjusts the horizontal orientation of the upper wafer W1 using the first position adjustment device 51 and turns the upper wafer W1 upside down (step S103). As a result, the notch of the upper wafer W1 is oriented in a predetermined direction and the bonding surface W1j of the upper wafer W1 faces downward. Thereafter, the transfer device 61 removes the upper wafer W1 from the first position adjustment device 51 and transfers it to the first temperature adjustment device 42 in the second processing block PB2.

[0028] The bonding apparatus 1 adjusts the temperature of the upper wafer W1 using the first temperature adjustment device 42 (step S104). The temperature adjustment of the upper wafer W1 is performed with the bonding surface W1j of the upper wafer W1 facing downward. Thereafter, the transfer device 61 removes the upper wafer W1 from the first temperature adjustment device 42 and transfers it to the bonding module 41.

[0029] In parallel with the above-described processing of the upper wafer W1, the bonding apparatus 1 performs processing of the lower wafer W2. First, the bonding apparatus 1 causes the transfer device 22 to remove the lower wafer W2 from the cassette CS2 and transfer it to the transition device 54 in the third processing block PB3 of the processing station 3. Thereafter, the transfer device 61 removes the lower wafer W2 from the transition device 54 and transfers it to the surface modification device 33 in the first processing block PB1.

[0030] The bonding apparatus 1 modifies the bonding surface W2j of the lower wafer W2 using the surface modification device 33 (step S105). The surface modification device 33 modifies the bonding surface W2j with the bonding surface W2j facing upward. Thereafter, the transfer device 61 removes the lower wafer W2 from the surface modification device 33 and transfers it to the surface hydrophilization device 34.

[0031] The bonding apparatus 1 hydrophilizes the bonding surface W2j of the lower wafer W2 using the surface hydrophilization device 34 (step S106). The surface hydrophilization device 34 hydrophilizes the bonding surface W2j with the bonding surface W2j facing upward. Thereafter, the transfer device 61 removes the lower wafer W2 from the surface hydrophilization device 34 and transfers it to the second position adjustment device 52 in the third processing block PB3.

[0032] The bonding apparatus 1 adjusts the horizontal orientation of the lower wafer W2 using the second position adjustment device 52 (step S107). This orients the notch of the lower wafer W2 in a predetermined direction. Thereafter, the transfer device 61 removes the lower wafer W2 from the second position adjustment device 52 and transfers it to the second temperature adjustment device 43 in the second processing block PB2.

[0033] The bonding apparatus 1 adjusts the temperature of the lower wafer W2 by the second temperature adjustment device 43 (step S108). The temperature adjustment of the lower wafer W2 is performed with the bonding surface W2j of the lower wafer W2 facing upward. Thereafter, the transfer device 61 removes the lower wafer W2 from the second temperature adjustment device 43 and transfers it to the bonding module 41.

[0034] Then, in the bonding module 41, the bonding apparatus 1 bonds the upper wafer W1 and the lower wafer W2 to produce a bonded wafer T (step S109). After producing the bonded wafer T, the transfer device 61 removes the bonded wafer T from the bonding module 41 and transfers it to the transition device 54 in the third process block PB3.

[0035] Finally, in the bonding apparatus 1, the transfer device 22 removes the bonded wafer T from the transition device 54 and transfers it to the cassette CS3 on the mounting table 10. This completes the series of processes.

[0036] Next, an example of a bonding module 41 according to an embodiment will be described with reference to FIGS. 5 to 7. As shown in FIG. 5, the bonding module 41 has a processing vessel 210 whose interior can be sealed. A loading / unloading port 211 is formed on the side of the processing vessel 210 on the transfer region 60 side, and the loading / unloading port 211 is provided with an opening / closing shutter 212. The upper wafer W1, the lower wafer W2, and the bonded wafer T are loaded and unloaded through the loading / unloading port 211.

[0037] 6, an upper chuck 230 and a lower chuck 231 are provided inside the processing vessel 210. The upper chuck 230 is a first holding part that releasably (displaceably) holds the upper wafer W1 from above with the bonding surface W1j of the upper wafer W1 facing downward. The lower chuck 231 is a second holding part that is provided below the upper chuck 230 and holds the lower wafer W2 from below with the bonding surface W2j of the lower wafer W2 facing upward. In other words, the upper chuck 230 and the lower chuck 231 are holding parts that releasably hold the upper wafer W1 and the lower wafer W2, which are substrates.

[0038] The upper chuck 230 is supported by a support member 220 provided on the ceiling surface of the processing vessel 210. On the other hand, the lower chuck 231 is supported by a first lower chuck moving part 291 provided below the lower chuck 231.

[0039] As will be described later, the first lower chuck moving unit 291 moves the lower chuck 231 in the horizontal direction (Y-axis direction). The first lower chuck moving unit 291 is configured to be able to move the lower chuck 231 vertically and rotate it around a vertical axis.

[0040] The first lower chuck moving part 291 is provided on the underside of the first lower chuck moving part 291 and is attached to a pair of rails 295 extending in the horizontal direction (Y-axis direction). The first lower chuck moving part 291 is configured to be movable along the rails 295. The rails 295 are provided on a second lower chuck moving part 296.

[0041] The second lower chuck moving part 296 is provided on the lower surface side of the second lower chuck moving part 296 and is attached to a pair of rails 297 extending in the horizontal direction (X-axis direction). The second lower chuck moving part 296 is configured to be movable along the rails 297. The pair of rails 297 is provided on a mounting part 298 provided on the bottom surface of the processing vessel 210.

[0042] The first lower chuck moving part 291 and the second lower chuck moving part 296 constitute a moving mechanism 290. The moving mechanism 290 moves the lower chuck 231 relative to the upper chuck 230. The moving mechanism 290 also moves the lower chuck 231 between a substrate transfer position and a joining position.

[0043] The substrate transfer position is a position where the upper chuck 230 receives the upper wafer W1 from the transfer device 61, the lower chuck 231 receives the lower wafer W2 from the transfer device 61, and the lower chuck 231 transfers the bonded wafer T to the transfer device 61. The substrate transfer position is a position where the bonded wafer T produced in the nth (n is a natural number greater than or equal to 1) bonding is successively transferred out and the upper wafer W1 and lower wafer W2 to be bonded in the n+1th bonding are continuously transferred in. The substrate transfer position is, for example, a position shown in FIGS.

[0044] The transfer device 61 enters directly below the upper chuck 230 when transferring the upper wafer W1 to the upper chuck 230. Furthermore, the transfer device 61 enters directly above the lower chuck 231 when receiving the bonded wafer T from the lower chuck 231 and transferring the lower wafer W2 to the lower chuck 231. To facilitate the transfer device 61's entry, the upper chuck 230 and the lower chuck 231 are shifted laterally, and the vertical distance between the upper chuck 230 and the lower chuck 231 is also large.

[0045] On the other hand, the bonding position is a position (opposing position) where the upper wafer W1 and the lower wafer W2 are faced to each other with a predetermined gap therebetween. The bonding position is, for example, the position shown in FIG. 7. At the bonding position, the gap between the upper wafer W1 and the lower wafer W2 in the vertical direction is narrower than at the substrate transfer position. Also, at the bonding position, unlike at the substrate transfer position, the upper wafer W1 and the lower wafer W2 overlap when viewed in the vertical direction.

[0046] The moving mechanism 290 moves the relative positions of the upper chuck 230 and the lower chuck 231 in the horizontal direction (both the X-axis direction and the Y-axis direction) and the vertical direction. In this embodiment, the moving mechanism 290 moves the lower chuck 231, but it may move either the lower chuck 231 or the upper chuck 230, or may move both. The moving mechanism 290 may also rotate the upper chuck 230 or the lower chuck 231 around a vertical axis.

[0047] 7, the upper chuck 230 is partitioned into a plurality of (e.g., three) regions 230a, 230b, and 230c along the radial direction of the upper chuck 230. These regions 230a, 230b, and 230c are provided in this order from the center toward the outer edge of the upper chuck 230. The region 230a is formed in a perfect circular shape in a plan view, and the regions 230b and 230c are formed in annular shapes in a plan view.

[0048] Suction pipes 240a, 240b, and 240c are independently provided in the respective regions 230a, 230b, and 230c. Different vacuum pumps 241a, 241b, and 241c are connected to the respective suction pipes 240a, 240b, and 240c. The upper chuck 230 can vacuum-suck the upper wafer W1 in each of the regions 230a, 230b, and 230c.

[0049] The upper chuck 230 has a plurality of radially and annularly extending ribs 230r (see FIG. 12), and the protruding ends of the ribs 230r form suction surfaces. The suction pipes 240a, 240b, and 240c communicate with the pipe installation bottom surfaces between the ribs 230r, and apply suction pressure to the spaces sandwiched between the upper wafer W1, the ribs 230r, and the pipe installation bottom surfaces, thereby suctioning the upper wafer W1.

[0050] The upper chuck 230 is provided with a plurality of holding pins 245 that can be raised and lowered in the vertical direction. The plurality of holding pins 245 are connected to a vacuum pump 246, and vacuum-suck the upper wafer W1 by operating the vacuum pump 246. The upper wafer W1 is vacuum-sucked to the lower ends of the plurality of holding pins 245. Ring-shaped suction pads may be used instead of the plurality of holding pins 245.

[0051] The plurality of holding pins 245 are lowered by a drive unit (not shown) to protrude from the suction surface of the upper chuck 230. In this state, the plurality of holding pins 245 vacuum-suck the upper wafer W1 and receive it from the transfer device 61. Thereafter, the plurality of holding pins 245 rise, and the upper wafer W1 comes into contact with the suction surface of the upper chuck 230. Next, the upper chuck 230 vacuum-sucks the upper wafer W1 horizontally in each of the regions 230a, 230b, and 230c by operation of the vacuum pumps 241a, 241b, and 241c.

[0052] The upper chuck 230 also has a through-hole 243 at its center that passes through the upper chuck 230 in the vertical direction. A pushing unit 250 is inserted into the through-hole 243. The pushing unit 250 pushes down the center of the upper wafer W1, which is disposed at a distance from the lower wafer W2, to bring the upper wafer W1 into contact with the lower wafer W2.

[0053] The pushing unit 250 has a pushing pin 251 and an outer cylinder 252 that serves as a lifting guide for the pushing pin 251. The pushing pin 251 is inserted into the through-hole 243 by, for example, a drive unit (not shown) having a built-in motor, protrudes from the suction surface of the upper chuck 230, and pushes down the center of the upper wafer W1.

[0054] The lower chuck 231 is also partitioned into a plurality of (for example, two) regions 231a and 231b along the radial direction of the lower chuck 231. These regions 231a and 231b are provided in this order from the center of the lower chuck 231 toward the outer edge. The region 231a is formed in a perfect circular shape in a plan view, and the region 231b is formed in an annular shape in a plan view. The region 231b may have a plurality of arc-shaped zones (small regions) along the circumferential direction.

[0055] Suction pipes 260a and 260b are provided independently for the respective regions 231a and 231b. Different vacuum pumps 261a and 261b are connected to the respective suction pipes 260a and 260b. This allows the lower chuck 231 to vacuum-suck the lower wafer W2 for each of the regions 231a and 231b.

[0056] A plurality of (e.g., three) holding pins 265 that can be raised and lowered in the vertical direction are provided on the lower chuck 231. The lower wafer W2 is placed on the upper ends of the plurality of holding pins 265. The lower wafer W2 may be vacuum-sucked to the upper ends of the plurality of holding pins 265.

[0057] As the multiple holding pins 265 rise, they protrude from the suction surface of the lower chuck 231. In this state, the multiple holding pins 265 receive the lower wafer W2 from the transfer device 61. Thereafter, the multiple holding pins 265 descend, causing the lower wafer W2 to come into contact with the suction surface of the lower chuck 231. Next, the lower chuck 231 horizontally vacuum-sucks the lower wafer W2 in multiple regions of the suction surface.

[0058] 8 to 10, the process of producing the bonded wafer T in step S109 of Fig. 4 will be described in detail. As shown in Fig. 8, the control device 90 causes the transfer device 61 to load the upper wafer W1 and the lower wafer W2 into the bonding module 41 (step S111). After the loading, the relative positions of the upper chuck 230 and the lower chuck 231 are the substrate transfer positions shown in Figs. 6 and 7.

[0059] Next, the control device 90 causes the moving mechanism 290 to move the relative positions of the upper chuck 230 and the lower chuck 231 from the substrate transfer position to the bonding position shown in Fig. 7 (step S112). In this step S112, the control device 90 aligns the upper wafer W1 and the lower wafer W2 using the first camera S1 and the second camera S2 as shown in Fig. 9.

[0060] The first camera S1 is fixed to the upper chuck 230 and captures an image of the lower wafer W2 held by the lower chuck 231. A plurality of reference points P21 to P23 are formed in advance on the bonding surface W2j of the lower wafer W2. The reference points P21 to P23 are formed by using patterns of electronic circuits or the like. The number of reference points can be set arbitrarily.

[0061] On the other hand, the second camera S2 is fixed to the lower chuck 231 and captures an image of the upper wafer W1 held by the upper chuck 230. A plurality of reference points P11 to P13 are formed in advance on the bonding surface W1j of the upper wafer W1. The reference points P11 to P13 are formed by using patterns of electronic circuits or the like. The number of reference points can be set arbitrarily.

[0062] 9A , the joining module 41 adjusts the relative horizontal positions of the first camera S1 and the second camera S2 using the movement mechanism 290. Specifically, the movement mechanism 290 moves the lower chuck 231 horizontally so that the second camera S2 is positioned approximately directly below the first camera S1. Then, the movement mechanism 290 finely adjusts the horizontal position of the second camera S2 so that the first camera S1 and the second camera S2 capture images of a common target X and the horizontal positions of the first camera S1 and the second camera S2 match.

[0063] Next, as shown in Fig. 9(B), the moving mechanism 290 moves the lower chuck 231 vertically upward to adjust the horizontal positions of the upper chuck 230 and the lower chuck 231. Specifically, while the moving mechanism 290 moves the lower chuck 231 horizontally, the first camera S1 sequentially images the reference points P21 to P23 of the lower wafer W2, and the second camera S2 sequentially images the reference points P11 to P13 of the upper wafer W1. Note that Fig. 9(B) shows how the first camera S1 images the reference point P21 of the lower wafer W2, and the second camera S2 images the reference point P11 of the upper wafer W1.

[0064] The first camera S1 and the second camera S2 transmit the captured image data to the control device 90. The control device 90 controls the moving mechanism 290 based on the image data captured by the first camera S1 and the image data captured by the second camera S2, and adjusts the horizontal position of the lower chuck 231 so that the reference points P11 to P13 of the upper wafer W1 and the reference points P21 to P23 of the lower wafer W2 coincide with each other when viewed in the vertical direction.

[0065] 9C, the moving mechanism 290 moves the lower chuck 231 vertically upward. As a result, the gap G (see FIG. 7) between the bonding surface W2j of the lower wafer W2 and the bonding surface W1j of the upper wafer W1 becomes a predetermined distance, for example, 80 μm to 200 μm. The gap G is adjusted using the first displacement gauge S3 and the second displacement gauge S4.

[0066] The first displacement meter S3, like the first camera S1, is fixed to the upper chuck 230 and measures the thickness of the lower wafer W2 held by the lower chuck 231. The first displacement meter S3, for example, irradiates the lower wafer W2 with light and receives light reflected from both the upper and lower surfaces of the lower wafer W2 to measure the thickness of the lower wafer W2. This thickness measurement is performed, for example, when the moving mechanism 290 moves the lower chuck 231 in the horizontal direction. The measurement method of the first displacement meter S3 is, for example, a confocal method, a spectral interference method, a triangulation method, or the like. The light source of the first displacement meter S3 is an LED or a laser.

[0067] On the other hand, the second displacement meter S4, like the second camera S2, is fixed to the lower chuck 231 and measures the thickness of the upper wafer W1 held by the upper chuck 230. The second displacement meter S4, for example, irradiates light onto the upper wafer W1 and receives light reflected from both the upper and lower surfaces of the upper wafer W1 to measure the thickness of the upper wafer W1. This thickness measurement is performed, for example, when the moving mechanism 290 moves the lower chuck 231 in the horizontal direction. The measurement method of the second displacement meter S4 is, for example, a confocal method, a spectral interference method, a triangulation method, or the like. The light source of the second displacement meter S4 is an LED or a laser.

[0068] The first displacement meter S3 and the second displacement meter S4 transmit the measured data to the control device 90. The control device 90 controls the moving mechanism 290 based on the data measured by the first displacement meter S3 and the data measured by the second displacement meter S4, and adjusts the vertical position of the lower chuck 231 so that the gap G becomes a set value.

[0069] Next, the operation of the vacuum pump 241a is stopped, and the vacuum suction of the upper wafer W1 in the region 230a is released, as shown in FIG. 10A. Thereafter, the pushing pin 251 of the pushing unit 250 descends to push down the center of the upper wafer W1, thereby bringing the upper wafer W1 into contact with the lower wafer W2 (step S113). As a result, the centers of the upper wafer W1 and the lower wafer W2 are bonded together.

[0070] Since the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 have been modified, van der Waals forces (intermolecular forces) are generated between the bonding surfaces W1j and W2j, bonding the bonding surfaces W1j and W2j together. Furthermore, since the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 have been hydrophilized, hydrophilic groups (e.g., OH groups) form hydrogen bonds, firmly bonding the bonding surfaces W1j and W2j together.

[0071] Next, the control device 90 stops the operation of the vacuum pump 241b, and releases the vacuum suction of the upper wafer W1 in the region 230b as shown in Fig. 10(B). Subsequently, the control device 90 stops the operation of the vacuum pump 241c, and releases the vacuum suction of the upper wafer W1 in the region 230c as shown in Fig. 10(C).

[0072] In this manner, the vacuum suction of the upper wafer W1 is gradually released from the center toward the periphery of the upper wafer W1, and the upper wafer W1 gradually drops and contacts the lower wafer W2. Then, bonding of the upper wafer W1 and the lower wafer W2 proceeds sequentially from the center toward the periphery (step S114). As a result, the bonding surface W1j of the upper wafer W1 and the bonding surface W2j of the lower wafer W2 come into contact over their entire surfaces, the upper wafer W1 and the lower wafer W2 are bonded, and a bonded wafer T is obtained. Thereafter, the bonding apparatus 1 raises the pushing pin 251 to its original position.

[0073] After the bonded wafer T is formed, the control device 90 causes the moving mechanism 290 to move the relative positions of the upper chuck 230 and the lower chuck 231 from the bonding position shown in Fig. 7 to the substrate transfer position shown in Fig. 5 and Fig. 6 (step S115). For example, the moving mechanism 290 first lowers the lower chuck 231 to widen the vertical gap between the lower chuck 231 and the upper chuck 230. Next, the moving mechanism 290 moves the lower chuck 231 laterally to laterally shift the lower chuck 231 and the upper chuck 230.

[0074] Thereafter, the control device 90 causes the transfer device 61 to transfer the bonded wafer T out of the bonding module 41 (step S116). Specifically, first, the lower chuck 231 releases the bonded wafer T. Next, the multiple holding pins 265 rise and transfer the bonded wafer T to the transfer device 61. Then, the multiple holding pins 265 descend to their original positions.

[0075] 11 , the above-described bonding apparatus 1 includes a plurality of displacement sensors 270 for measuring the height position of the upper wafer W1 in the upper chuck 230 in order to monitor the progress of bonding between the upper wafer W1 and the lower wafer W2. The bonding apparatus 1 also includes a gas supply mechanism 280 around the upper chuck 230 for supplying a void-reducing gas near the outer edges of the upper wafer W1 and the lower wafer W2 during bonding.

[0076] The plurality of displacement sensors 270 are arranged, for example, at three different radial positions radially outward from the center of the upper chuck 230, and are arranged at equal intervals along the circumferential direction at the same radial positions. As an example, three displacement sensors 270 at different radial positions are provided in each of regions 230a, 230b, and 230c set in the upper chuck 230. Hereinafter, the displacement sensor 270 located in the region 230a will also be referred to as an inner displacement sensor 270a, the displacement sensor 270 located in the region 230b will also be referred to as an intermediate displacement sensor 270b, and the displacement sensor 270 located in the region 230c will also be referred to as an outer displacement sensor 270c.

[0077] Each displacement sensor 270 (inner displacement sensor 270a, middle displacement sensor 270b, and outer displacement sensor 270c) is installed to face the upper wafer W1 held by the upper chuck 230. The upper chuck 230 has a placement portion 275 for placing each displacement sensor 270. The placement portion 275 includes a recess 276 that accommodates part or all of the displacement sensor 270, a fixing portion 277 that fixes the displacement sensor 270, and an aperture 278 that connects the recess 276 to a space on the chucking surface side of the upper chuck 230. Each fixing portion 277 fixes each displacement sensor 270 so that the tips (lower ends) of the displacement sensors 270 are at the same height. The aperture 278 is formed through the bottom of the recess 276 and tapers toward the chucking surface, thereby narrowing the range of the measurement light of the displacement sensor 270.

[0078] Each displacement sensor 270 arranged in each arrangement portion 275 is an optical sensor that irradiates measurement light onto the upper wafer W1 and receives reflected light from the upper wafer W1 to obtain measurement information. Each displacement sensor 270 measures the distance to the surface (non-bonding surface W1n) of the upper wafer W1 facing it through the space from its tip to the upper wafer W1. Each displacement sensor 270 is also connected to the control device 90 so as to be able to communicate information with it, and transmits acquired information to the control device 90 under command of the control device 90 or automatically.

[0079] For example, a white light confocal sensor that emits white (multicolor) measurement light toward the upper wafer W1 and measures distance using information about the light reflected from the surface (non-bonding surface W1 n) of the upper wafer W1 can be applied to this displacement sensor 270. However, the displacement sensor 270 is not limited to a confocal sensor, and various optical sensors such as a spectral interference sensor or a triangulation sensor can be applied.

[0080] First Embodiment Next, a gas supply mechanism 280 according to a first embodiment will be described with reference to FIGS. 11 to 15B. The gas supply mechanism 280 installed in the bonding apparatus 1 (bonding module 41) discharges a void-reducing gas onto the outer periphery between the upper wafer W1 and the lower wafer W2 to reduce voids (particularly edge voids) that are defects at the bonding interface. For this reason, as shown in FIG. 11 , the gas supply mechanism 280 includes a discharge structure 281 and a supply unit 285 connected to the discharge structure 281 to supply the void-reducing gas.

[0081] 12 , the discharge structure 281 is fixed to the upper chuck 230 of the bonding module 41 or the processing vessel 210. The discharge structure 281 has an inclined surface between its inner circumferential surface and its lower surface, and this inclined surface has a plurality of discharge ports 281 a. Each discharge port 281 a communicates with the internal space of the discharge structure 281 and discharges the void-reducing gas supplied to this internal space between the upper wafer W1 and the lower wafer W2 and near the outer edges thereof.

[0082] 13A , the discharge structure 281 is formed, for example, in a ring shape that surrounds the side of the side peripheral surface of the upper chuck 230. The discharge structure 281 also has a plurality of partition walls 283 that divide the internal space along the circumferential direction, thereby dividing the ring-shaped discharge structure 281 into a plurality of discharge sections 282. The discharge structure 281 according to the embodiment has eight discharge sections 282. A port 284 that can allow the inflow of void-reducing gas is connected to each of the plurality of discharge sections 282. Therefore, eight ports 284 are provided, one for each discharge section 282.

[0083] Each of the discharge units 282 has one or more discharge ports 281 a (four in FIG. 13A ) for discharging the void-reducing gas. When the void-reducing gas is supplied from the supply unit 285 to each of the discharge units 282 via each port 284, the void-reducing gas is diffused within each discharge unit 282 and discharged from each discharge port 281 a of the respective discharge unit 282.

[0084] The supply unit 285 includes a supply path 286 connected to the discharge structure 281, and a gas source 287 provided at the upstream end of the supply path 286 and storing a void-reducing gas. The void-reducing gas of the gas source 287 may be, for example, a noble gas such as helium (He) gas, neon (Ne) gas, or argon (Ar) gas, or hydrogen (H ２ ) gas, etc. Alternatively, the void-reducing gas may be a combination of these types of gases. These gases have smaller molecular sizes than nitrogen gas and oxygen gas, have a high Joule-Thomson effect, and are highly effective in suppressing condensation, so they can be said to be gases that can reduce voids. The void-reducing gas is also a low-humidity gas that does not contain moisture (or has moisture reduced as much as possible). The supply unit 285 according to the embodiment supplies He gas as the void-reducing gas to the discharge structure 281.

[0085] The supply path 286 has a plurality of branch paths (a first branch path 286a, a second branch path 286b) that connect to the above-described plurality of discharge portions 282. The first branch path 286a further branches into four paths, which are connected to the four discharge portions 282 of the discharge structure 281 via four ports 284. The four discharge portions 282 connected to the first branch path 286a are a pair of discharge portions 282 that overlap on the X-axis (first axis) and a pair of discharge portions 282 that overlap on the Y-axis (second axis) that is perpendicular to the X-axis. Hereinafter, the discharge portions 282 in the X-axis and Y-axis directions will be referred to as axial discharge portions 282x and 282y.

[0086] The second branch path 286b also branches into four, which are connected to the four discharge portions 282 of the discharge structure 281 via four ports 284. The four discharge portions 282 connected to the second branch path 286b are four diagonal direction discharge portions 282d in the diagonal direction, which are circumferentially midway between the X axis and the Y axis. Hereinafter, the diagonal direction discharge portions 282 are referred to as diagonal direction discharge portions 282d.

[0087] The first branch path 286a includes an on-off valve 288 that opens and closes the flow path, a flow rate regulator 289 that adjusts the gas flow rate, and the like, in a common path before it branches into four. Similarly, the second branch path 286b also includes an on-off valve 288 that opens and closes the flow path, a flow rate regulator 289 that adjusts the gas flow rate, and the like, in a common path before it branches into four. Each on-off valve 288 and each flow rate regulator 289 is connected to and operates under the control of the control device 90. This allows the supply unit 285 to change the discharge amount, discharge timing, and the like of the void-reducing gas in each of the first branch path 286a and the second branch path 286b.

[0088] The gas supply mechanism 280 described above can discharge different amounts of void-reducing gas from the axial discharge ports 282x, 282y and the diagonal discharge port 282d. The void-reducing gas is discharged between the upper wafer W1 and the lower wafer W2 during bonding of the upper wafer W1 and the lower wafer W2, thereby affecting the bonding speed (progress of bonding). For example, when the discharge rate of the void-reducing gas is low (including when the discharge rate is zero), there is little (or no) void-reducing gas between the upper wafer W1 and the lower wafer W2, which increases the bonding speed of the upper wafer W1 and the lower wafer W2. Conversely, when the discharge rate of the void-reducing gas is high, there is a large amount of void-reducing gas between the upper wafer W1 and the lower wafer W2, which decreases the bonding speed of the upper wafer W1 and the lower wafer W2.

[0089] The in-plane misalignment (in-plane distortion) between the upper wafer W1 and the lower wafer W2 in the bonded wafer T is affected by the bonding speed during bonding. In an environment where no void-reducing gas is supplied between the upper wafer W1 and the lower wafer W2, the bonding speed is affected by the Young's modulus, Poisson's ratio, shear modulus (modulus of rigidity), etc. of the wafers, or the anisotropy of the wafer's crystal orientation (arrangement of atoms in the crystal structure). However, the wafer's Young's modulus, Poisson's ratio, shear modulus, or crystal orientation also varies depending on the shape, position, number, etc. of devices formed on the wafer.

[0090] For example, as shown in FIG. 13B , the upper wafer W1 exhibits a Young's modulus Wy that is large in the axial (X-axis, Y-axis) directions but small in the diagonal directions. The upper wafer W1 also exhibits a significantly small Poisson's ratio in the axial directions but a significantly large Poisson's ratio in the diagonal directions. Furthermore, the upper wafer W1 exhibits a slightly small shear modulus in the axial directions but a large shear modulus in the diagonal directions. The shear modulus is a physical property (shear modulus, shear modulus, transverse modulus) that indicates the resistance to deformation due to shear force, and can be defined as the ratio of shear stress to shear strain. Because the shear modulus is directly related to the deformation of the upper wafer W1 in the thickness direction, the magnitude of the shear modulus will be used as an example for the following explanation.

[0091] In areas where the upper wafer W1 has a large shear modulus (small Young's modulus or large Poisson's ratio), high stress is generated in the deformed shape during bonding, resulting in elastic recovery, and the bonding speed tends to be faster. In other words, the bonding progresses more quickly in the diagonal direction of the upper wafer W1. Conversely, in areas where the upper wafer W1 has a small shear modulus (large Young's modulus or small Poisson's ratio), low stress is generated in the deformed shape during bonding, resulting in elastic recovery, and the bonding speed tends to be slower. In other words, the bonding progresses more slowly in the axial direction of the upper wafer W1. This difference in bonding speed affects the in-plane distortion of the bonded wafer T.

[0092] Therefore, the bonding apparatus 1 according to the embodiment adjusts the bonding speed by changing the discharge amount of the void-reducing gas in the axial direction and the diagonal direction. Specifically, the axial direction discharge units 282x, 282y discharge a small amount of void-reducing gas because they face the axial direction in which low stress occurs in the upper wafer W1. The diagonal direction discharge unit 282d discharges a large amount of void-reducing gas because they face the diagonal direction in which high stress occurs in the upper wafer W1. This allows the bonding apparatus 1 to bond the upper wafer W1 and the lower wafer W2 at approximately the same bonding speed, thereby suppressing in-plane distortion between the upper wafer W1 and the lower wafer W2.

[0093] The bonding apparatus 1 according to the embodiment is basically configured as described above, and its operation (the bonding method according to the first embodiment, including the supply of void-reducing gas by the gas supply mechanism 280) will be described below with reference to FIG. 14.

[0094] 14 during bonding of the upper wafer W1 and the lower wafer W2. The control device 90 acquires information on the shear modulus of the upper wafer W1 calculated using an appropriate analysis device before the upper wafer W1 is carried into the bonding apparatus 1. Furthermore, in adjusting the attitude of the upper wafer W1, the control device 90 appropriately adjusts the orientations of the X-axis and Y-axis of the upper wafer W1 based on the acquired shear modulus, and holds the upper wafer W1 in this state on the upper chuck 230.

[0095] Specifically, with the upper wafer W1 and the lower wafer W2 facing each other, the control device 90 controls the pushing unit 250 to push down the upper wafer W1 (step S121). This step S121 is the same process flow control as step S113 in the flowchart of Fig. 8. That is, the pushing unit 250 pushes down the center of the upper wafer W1 with the pushing pin 251, bringing the upper wafer W1 into contact with the lower wafer W2.

[0096] Then, under the control of the control device 90, the gas supply mechanism 280 supplies different amounts of void-reducing gas to the axial direction dischargers 282x, 282y and the diagonal direction discharger 282d (step S122). Specifically, the gas supply mechanism 280 increases the discharge rate of the void-reducing gas from the diagonal direction discharger 282d, which faces the area with a large shear modulus. Meanwhile, the gas supply mechanism 280 decreases the discharge rate of the void-reducing gas from the axial direction dischargers 282x, 282y, which face the area with a small shear modulus. This allows the bonding apparatus 1 to slow down the progress of bonding the upper wafer W1 in the diagonal direction (to match the progress of bonding the upper wafer W1 in the axial direction). The timing of supplying the void-reducing gas is not limited to after the upper wafer W1 is pushed down, but may be simultaneous with or before the upper wafer W1 is pushed down.

[0097] During bonding of the upper wafer W1 and the lower wafer W2, the control device 90 monitors the progress of bonding by detecting the height position of the upper wafer W1 with each displacement sensor 270 (step S123). The control device 90 may adjust the discharge rate of the void-reducing gas according to the height position of the upper wafer W1 detected by each displacement sensor 270.

[0098] For example, if it is determined based on the height position of the upper wafer W1 that the diagonal bonding speed is faster than the axial bonding speed, the amount of void-reducing gas discharged from the diagonal direction discharge unit 282d is increased during the bonding process, thereby slowing down the diagonal bonding speed. Alternatively, the amount of void-reducing gas discharged from the axial direction discharge units 282x, 282y may be reduced during the bonding process to increase the axial bonding speed.

[0099] Conversely, if it is determined based on the height position of the upper wafer W1 that the diagonal bonding speed is slower than the axial bonding speed, the amount of void-reducing gas discharged from the diagonal direction discharge unit 282d is controlled to be reduced during the bonding process, thereby increasing the diagonal bonding speed. Alternatively, the amount of void-reducing gas discharged from the axial direction discharge units 282x, 282y may be increased during the bonding process to slow the axial bonding speed.

[0100] Furthermore, during bonding of the upper wafer W1 and the lower wafer W2, the bonding apparatus 1 determines whether or not the bonding is completed based on the detection information of the outer displacement sensor 270c (step S124). If the bonding is not completed (step S124: NO), the bonding apparatus 1 continues monitoring using the displacement sensor 270. On the other hand, if the bonding is completed (step S124: YES), the process proceeds to step S125.

[0101] In step S125, the gas supply mechanism 280 stops the discharge of the void-reducing gas between the upper wafer W1 and the lower wafer W2 by closing the on-off valves 288 of the supply path 286 (the first branch path 286 a and the second branch path 286 b). This allows the bonding apparatus 1 to reduce the generation of voids at the bonding interface between the upper wafer W1 and the lower wafer W2 while suppressing in-plane distortion of the upper wafer W1 and the lower wafer W2.

[0102] 15A is a graph illustrating the radial distortion of the bonded wafer T obtained by the bonding method according to the first embodiment. FIG. 15B is a graph illustrating the radial distortion of the bonded wafer T obtained by the bonding method according to a reference example. The dashed-dotted lines in FIG. 15 indicate reference values ​​for the positions of the upper wafer W1 and the lower wafer W2 when no distortion occurs. The closer each radial position of the bonded wafer is to this reference value, the more suppressed the distortion. Conversely, the further away from the reference value the position is from the reference value, the greater the distortion.

[0103] In the bonding method according to the reference example, the same discharge rate (e.g., 3 L / min) of void-reducing gas is discharged from the entire circumferential direction of the discharge structure of the gas supply mechanism. As shown in FIG. 15B, the bonded wafers bonded by the bonding method according to the reference example exhibit a greater deviation from the reference value from the reference wafer center toward the outer edge. It can be seen that significant distortion occurs particularly near the outer edge of the bonded wafer. In other words, the gas supply mechanism according to the reference example discharges the same discharge rate of void-reducing gas from the axial discharge portion and the diagonal region, resulting in significant in-plane distortion between the upper wafer W1 and the lower wafer W2.

[0104] In contrast, in the bonding method according to the embodiment, different discharge rates of the void-reducing gas are discharged from each of the circumferential discharge portions 282 (axial discharge portions 282x, 282y, diagonal discharge portion 282d). For example, the discharge rates of the axial discharge portions 282x, 282y are set to 1 L / min (or 0 L / min), and the discharge rate of the diagonal discharge portion 282d is set to 4 L / min (or 3 L / min).

[0105] 15A , the bonded wafer T bonded by the bonding method according to the embodiment exhibits distortion from the center toward the outer edge, but the magnitude of the distortion is suppressed compared to the reference example. In particular, the distortion near the outer edge of the bonded wafer T is sufficiently smaller than the distortion near the outer edge in the reference example. Therefore, it can be said that the gas supply mechanism 280 according to the embodiment can suppress in-plane distortion between the upper wafer W1 and the lower wafer W2 by discharging different amounts of void-reducing gas from the axial direction discharge portion and the diagonal direction region.

[0106] As described above, the bonding apparatus 1 can suppress in-plane distortion (misalignment) of the upper wafer W1 and the lower wafer W2 by varying the amount of void-reducing gas discharged from the discharge structure 281 in the circumferential direction of the discharge structure 281. In particular, the bonding apparatus 1 can appropriately adjust the bonding speed and reduce in-plane distortion occurring near the outer edge of the bonded wafer T by adjusting the amount of void-reducing gas discharged based on the magnitude of the shear modulus (or Young's modulus, Poisson's ratio) of the wafers.

[0107] Furthermore, the bonding apparatus 1 can uniformly reduce in-plane distortion around the entire circumference of the bonded wafer T by discharging the void-reducing gas from multiple discharge portions 282 arranged circumferentially in the ring-shaped discharge structure 281. Furthermore, the gas supply mechanism 280 includes the axial discharge portions 282x, 282y and the diagonal discharge portion 282d, which makes it possible to adjust the discharge amount of the void-reducing gas according to the shear modulus, which tends to change at 45° intervals in the circumferential direction. Therefore, the bonding apparatus 1 can easily suppress in-plane distortion of the bonded wafer T.

[0108] The bonding apparatus 1 of the present disclosure is not limited to the above embodiment and may take various modified forms. For example, the bonding apparatus 1 is configured to discharge the void-reducing gas by dividing it into eight sections, namely, the axial direction discharge sections 282x, 282y and the diagonal direction discharge section 282d. However, the number of discharge sections 282 is not particularly limited as long as it is possible to suppress misalignment between the upper wafer W1 and the lower wafer W2.

[0109] In the embodiment, the axial discharge ports 282x, 282y and the diagonal discharge port 282d are configured to have different discharge rates of the void-reducing gas, but the targets for which the different discharge rates of the void-reducing gas are to be used are not particularly limited. For example, in order to adjust the discharge rate of the void-reducing gas for each of the plurality of discharge ports 282, the supply unit 285 is configured such that each discharge port 282 is individually connected to a gas source 287 via a respective supply path 286, and each supply path 286 is equipped with an on-off valve 288 and a flow rate regulator 289. This makes it possible to individually adjust the discharge rate of the void-reducing gas for each of the plurality of discharge ports 282.

[0110] As described above, the position and magnitude of Young's modulus, Poisson's ratio, shear modulus, and the like of a wafer vary depending on the shape, position, number, or crystal orientation of semiconductor devices formed on the surface. As an example, a pair of axial discharge portions 282x may have a small shear modulus, while the other discharge portions 282 (the axial discharge portion 282y and the diagonal discharge portion 282d) have a large shear modulus. In this case, the bonding apparatus 1 may increase the discharge rate of the void-reducing gas from the other discharge portions 282 and decrease the discharge rate of the void-reducing gas from the pair of axial discharge portions 282x in accordance with the small (or large) shear modulus of only one discharge portion 282 of the discharge structure 281. Of course, even if the shear modulus of only one discharge portion 282 of the discharge structure 281 is small (or large), the discharge rate may be adjusted to correspond to the small (or large) shear modulus.

[0111] Furthermore, if the amount of void-reducing gas discharged from each of the plurality of discharge ports 282 is adjustable, the amount of void-reducing gas discharged may be adjusted in three or more stages, such as high, low, medium, etc.

[0112] Second Embodiment Next, a gas supply mechanism 280 and a bonding method of a bonding apparatus 1 according to a second embodiment will be described with reference to FIGS. 16A to 17. The gas supply mechanism 280 according to the second embodiment differs from the gas supply mechanism 280 according to the first embodiment in that the gas supply mechanism 280 stops discharging the void-reducing gas at the start of bonding the upper wafer W1 and the lower wafer W2 and starts discharging the void-reducing gas midway through bonding the upper wafer W1 and the lower wafer W2. The structure of the gas supply mechanism 280 according to the second embodiment is the same as that of the first embodiment.

[0113] For example, the control device 90 of the bonding apparatus 1 determines the timing of ejection of the void-reducing gas from the gas supply mechanism 280 based on detection information from the middle displacement sensor 270b of the multiple displacement sensors 270. The control device 90 stores a threshold value Th for comparison with the height position of the upper wafer W1 at the installation position of the middle displacement sensor 270b. If the height position of the upper wafer W1 during bonding is equal to or greater than the threshold value Th, the control device 90 continues to stop supplying the void-reducing gas, and starts supplying the void-reducing gas when the height position of the upper wafer W1 during bonding becomes less than the threshold value Th.

[0114] 16(B) , the gas supply mechanism 280′ according to the reference example starts supplying a void-reducing gas (He gas) at the start of bonding the upper wafer W1 and the lower wafer W2, and continues supplying the void-reducing gas until bonding of the upper wafer W1 and the lower wafer W2 is completed. In this case, the amount of void-reducing gas discharged increases throughout the entire bonding period, which increases the manufacturing cost of the bonded wafer T.

[0115] In contrast, in the bonding method according to the second embodiment, the supply of the void-reducing gas is started immediately before bonding the outer edges of the upper wafer W1 and the lower wafer W2. This significantly reduces the amount of void-reducing gas discharged during the entire bonding period, thereby reducing the manufacturing cost of the bonded wafer T. As shown in Figures 15A and 15B, the positional misalignment between the upper wafer W1 and the lower wafer W2 becomes large near the outer edges of the bonded wafer T, and voids are also likely to occur near the outer edges of the bonded wafer. Therefore, if the void-reducing gas is supplied at the timing of bonding the outer edges, it is possible to obtain a bonded wafer T with sufficiently small in-plane distortion and suppressed voids.

[0116] The gas supply mechanism 280 may control the delay of the ejection timing of the void-reducing gas for all of the ejection units 282 or for only some of the ejection units 282. For example, if the axial ejection units 282x and 282y eject the void-reducing gas at a rate of 1 L / min and the diagonal ejection unit 282d ejects the void-reducing gas at a rate of 4 L / min, the gas supply mechanism 280 may delay the ejection timing of the void-reducing gas for all of the ejection units 282. For example, if the axial ejection units 282x and 282y eject the void-reducing gas at a rate of 0 L / min and the diagonal ejection unit 282d ejects the void-reducing gas at a rate of 3 L / min, the gas supply mechanism 280 may delay the ejection timing of the void-reducing gas for only the diagonal ejection unit 282d. Alternatively, if the discharge rate of the void-reducing gas from the axial discharge sections 282x and 282y is 1 L / min and the discharge rate of the void-reducing gas from the diagonal discharge section 282d is 4 L / min, only the discharge timing of the void-reducing gas from the axial discharge sections 282x and 282y may be delayed.

[0117] A bonding method including a method for supplying a void-reducing gas by the gas supply mechanism 280 according to the second embodiment is, for example, as shown in the flowchart of Fig. 17. Note that step S131 in Fig. 17 is the same as step S113 in Fig. 8 and step S121 in Fig. 14.

[0118] In step S132, the control device 90 allows the bonding of the upper wafer W1 and the lower wafer W2 to proceed while stopping the discharge of the void reducing gas by the gas supply mechanism 280. Then, the control device 90 monitors the progress of the bonding by detecting the height position of the upper wafer W1 with each displacement sensor 270 (step S133).

[0119] The control device 90 compares the height position of the upper wafer W1 detected by the intermediate displacement sensor 270b with a stored threshold value Th to determine the timing of ejection of the void-reducing gas (step S134). If the height position of the upper wafer W1 is equal to or greater than the threshold value Th (step S134: NO), the control device 90 continues to stop ejection of the void-reducing gas. On the other hand, if the height position of the upper wafer W1 falls below the threshold value Th (step S134: YES), the control device 90 proceeds to step S135.

[0120] In step S135, the control device 90 controls the gas supply mechanism 280 to start supplying the void-reducing gas, so that the upper wafer W1 is bonded to the lower wafer W2 near the outer edge at a bonding speed adjusted to the bonding speed of each discharge part 282.

[0121] Thereafter, the bonding apparatus 1 releases the suction of the upper wafer W1 in the region 230c, thereby bonding the upper wafer W1 and the lower wafer W2 together (step S136). Note that the timing of step S136 may be the same as that of step S135.

[0122] Furthermore, the control device 90 determines whether or not the bonding is completed based on the detection information of the outer displacement sensor 270c (step S137), and when the bonding is completed, stops the discharge of the void-reducing gas by the gas supply mechanism 280 (step S138). Steps S137 and S138 are the same as steps S124 and S125 according to the first embodiment.

[0123] As described above, in the second embodiment, it is possible to reduce the generation of voids at the bonding interface between the upper wafer W1 and the lower wafer W2 while suppressing in-plane distortion of the upper wafer W1 and the lower wafer W2. Moreover, the bonding apparatus 1 can significantly reduce the discharge amount of the void-reducing gas, thereby promoting lower manufacturing costs.

[0124] Third Embodiment Next, a gas supply mechanism 280 and a bonding method of a bonding apparatus 1 according to a third embodiment will be described with reference to FIGS. 18 and 19 . The gas supply mechanism 280 according to the third embodiment differs from the first and second embodiments in that, during bonding of the upper wafer W1 and the lower wafer W2, an inexpensive void-reducing gas is first supplied, and then an expensive void-reducing gas is supplied. Although not specifically shown in the drawings, the gas supply mechanism 280 according to the third embodiment includes multiple gas sources 287 and supply paths 286 to supply multiple types of void-reducing gas (an inexpensive void-reducing gas and an expensive void-reducing gas).

[0125] An inexpensive void-reducing gas is, for example, nitrogen gas (N ２ gas), carbon dioxide gas (CO ２ On the other hand, an expensive void reducing gas is, for example, He gas. ２ 1 shows an example in which a gas is first supplied to the upper wafer W1 and a gas is then supplied to the lower wafer W2, and then expensive He gas is supplied. The gas supply mechanism 280 can selectively supply these gases between the upper wafer W1 and the lower wafer W2 under the control of the control device 90.

[0126] The gas supply mechanism 280 may change the type of void reducing gas for all of the discharge parts 282 or for only some of the discharge parts 282. For example, the gas supply mechanism 280 may change the type of void reducing gas for the axial discharge parts 282x, 282y and the diagonal discharge part 282d by controlling N ２ For example, the gas supply mechanism 280 supplies N gas to the discharge part 282 (for example, the diagonal direction discharge part 282d) that discharges a large amount of void reducing gas. ２Alternatively, the gas supply mechanism 280 may supply N gas and He gas in sequence while continuing to supply He gas to the discharge parts 282 (e.g., axial discharge parts 282x, 282y) that discharge a small amount of void-reducing gas. ２ While supplying gas and He gas in sequence, the timing of ejection of the ejection part 282 that ejects a small amount of void reducing gas may be delayed to supply He gas only near the outer edge.

[0127] A bonding method including a method for supplying a void-reducing gas by the gas supply mechanism 280 according to the third embodiment is, for example, as shown in the flowchart of Fig. 19. Note that step S141 in Fig. 19 is the same as step S113 in Fig. 8 and step S121 in Fig. 14.

[0128] In step S142, the gas supply mechanism 280 first ２ At this time, the axial direction discharge portions 282x and 282y discharge N ２ The diagonal direction discharge portion 282d increases the amount of N2 gas discharged, and the diagonal direction discharge portion 282d decreases the amount of N2 gas discharged.

[0129] The control device 90 then monitors the progress of bonding by detecting the height position of the upper wafer W1 using each displacement sensor 270 (step S143). At this time, the control device 90 compares the height position of the upper wafer W1 detected by the intermediate displacement sensor 270b with a stored threshold value Th to determine the timing for switching the void-reducing gas (step S144). For example, if the height position of the upper wafer W1 is equal to or greater than the threshold value (step S144: NO), the control device 90 ２ On the other hand, if the height position of the upper wafer W1 has reached a level below the threshold (step S144: YES), the control device 90 proceeds to step S145.

[0130] In step S145, the control device 90 controls the gas supply mechanism 280 to supply N ２The gas is switched to He gas, and the He gas is discharged between the upper wafer W1 and the lower wafer W2. This makes it possible to reliably reduce the generation of voids near the outer edges of the upper wafer W1 and the lower wafer W2 by the He gas. Note that the subsequent steps S146 to S148 are the same as steps S136 to S138 in FIG. 17.

[0131] As described above, in the third embodiment, it is possible to reduce the generation of voids at the bonding interface between the upper wafer W1 and the lower wafer W2 while suppressing in-plane distortion of the upper wafer W1 and the lower wafer W2. ２ The bonding speed can be adjusted by supplying gas, so that it is possible to further suppress misalignment between the upper wafer W1 and the lower wafer W2 while achieving cost reduction.

[0132] Fourth Embodiment Next, a gas supply mechanism 280A of a bonding apparatus 1 according to a fourth embodiment will be described with reference to Fig. 20. The gas supply mechanism 280A according to the fourth embodiment differs from the first to third embodiments in that the void-reducing gas discharged from each discharge port 282 is more directional and less likely to spread.

[0133] Specifically, the gas supply mechanism 280A includes a plurality of partition walls 281b corresponding to each discharge portion 282 along the circumferential direction of the discharge structure 281. The installation position of each partition wall 281b in the circumferential direction of the discharge structure 281 coincides with the installation position of the partition wall 283. Each partition wall 281b protrudes from the inner circumferential surface and the lower surface of the discharge structure 281, and is adjacent to the space between the upper chuck 230 and the lower chuck 231.

[0134] Each partition wall 281b installed as described above prevents the void-reducing gas discharged from each discharge part 282 from spreading in the circumferential direction. This allows the void-reducing gas discharged from each discharge part 282 to move smoothly into the space between the upper wafer W1 and the lower wafer W2 while maintaining the directionality of the discharge during bonding of the upper wafer W1 and the lower wafer W2. In other words, the gas supply mechanism 280 can more reliably supply a target amount of void-reducing gas to a region where a slower bonding speed is desired (or a region where a faster bonding speed is desired).

[0135] The joining device 1 and joining method according to the presently disclosed embodiments are illustrative in all respects and are not limiting. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above-described embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0136] This application claims priority from Japanese Patent Application No. 2024-120298, filed on July 25, 2024, with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0137] 1 Bonding device 230 Upper chuck 231 Lower chuck 250 Pushing unit 280 Gas supply mechanism 282 Discharge unit W1 Upper wafer W2 Lower wafer

Claims

1. A bonding device for bonding a first substrate and a second substrate, comprising: a first holding section that holds the first substrate; a second holding section that holds the second substrate; a pushing section that presses down on the first substrate on the first holding section to bond the first substrate to the second substrate; and a gas supply mechanism that supplies gas between the first substrate and the second substrate, wherein the gas supply mechanism has a plurality of discharge sections along the circumferential direction of the first substrate and the second substrate, and each of the plurality of discharge sections discharges the gas at a different discharge rate from one another when the first substrate and the second substrate are bonded.

2. The bonding device according to claim 1, wherein the first substrate has a shear modulus that varies in magnitude in the circumferential direction, and the plurality of discharge sections increase the amount of gas discharged from the discharge section facing the area with a large shear modulus and decrease the amount of gas discharged from the discharge section facing the area with a small shear modulus.

3. The bonding apparatus according to claim 2, wherein the shear modulus of the first substrate is set by at least one of the shape, position, and number of devices formed on the first substrate, and the crystal orientation of the first substrate.

4. The joining device described in claim 2, wherein the first substrate is set so that it has a small shear modulus in the axial direction including a first axis and a second axis perpendicular to the first axis, while it has a large shear modulus in the diagonal direction that is circumferentially midway between the first axis and the second axis, and the discharge amount of the multiple discharge portions facing each other in the diagonal direction is made greater than the discharge amount of the multiple discharge portions facing each other in the axial direction.

5. A bonding device according to any one of claims 1 to 4, wherein the gas supply mechanism comprises a ring-shaped discharge structure in which the plurality of discharge parts are arranged in the circumferential direction, and each of the plurality of discharge parts is formed in an arc shape with a plurality of discharge ports on the inside.

6. A bonding device according to any one of claims 1 to 4, wherein the gas supply mechanism stops discharging the gas when bonding of the first substrate and the second substrate begins, and starts discharging the gas midway through bonding of the first substrate and the second substrate.

7. A bonding device as described in claim 6, comprising: a displacement sensor that detects the height position of the first substrate; and a control device that controls the timing of gas ejection by the gas supply mechanism based on detection information from the displacement sensor, wherein the control device determines whether the height position of the first substrate detected by the displacement sensor is below a threshold value, and stops ejecting the gas when the height position of the first substrate is equal to or greater than the threshold value, while starting ejection of the gas when the height position of the first substrate falls below the threshold value.

8. The bonding device according to any one of claims 1 to 4, wherein the gas supply mechanism discharges an inexpensive gas as the gas from the plurality of discharge ports, and then discharges an expensive gas that can reduce voids between the first substrate and the second substrate.

9. A bonding apparatus as described in claim 8, comprising: a displacement sensor that detects the height position of the first substrate; and a control device that controls the timing of gas ejection by the gas supply mechanism based on detection information from the displacement sensor, wherein the control device determines whether the height position of the first substrate detected by the displacement sensor is below a threshold value or not, and ejects the inexpensive gas when the height position of the first substrate is equal to or greater than the threshold value, while switching to ejecting the expensive gas when the height position of the first substrate falls below the threshold value.

10. The joining device according to any one of claims 1 to 4, further comprising a partition wall separating the adjacent discharge sections.

11. A bonding method for a bonding device that bonds a first substrate and a second substrate, the bonding device including: a first holding section that holds the first substrate; a second holding section that holds the second substrate; a pushing section that presses down on the first substrate on the first holding section to bond the first substrate to the second substrate; and a gas supply mechanism that supplies gas between the first substrate and the second substrate, the bonding method comprising: when bonding the first substrate and the second substrate, ejecting the gas at mutually different ejection rates from each of a plurality of ejection sections of the gas supply mechanism that are provided along the circumferential directions of the first substrate and the second substrate.

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