Substrate processing device and method for mounting substrate

Abstract

A substrate processing device according to the present invention includes a holding unit having, on a suction surface for suctioning a substrate, a circular central region and an annular outer region arranged outside the central region. A plurality of zones are set on the suction surface, the plurality of zones being in the central region and in regions obtained by dividing the outer region in the circumferential direction. The substrate processing device includes a pressure generation unit which generates pressure in each of the plurality of zones. In a state in which the substrate is mounted on the suction surface and in which negative pressure is applied to at least one of the plurality of zones, the pressure generation unit applies positive pressure to at least one of the plurality of zones to which negative pressure is not applied.

Description

Substrate processing apparatus and substrate mounting method

[0001] The present disclosure relates to a substrate processing apparatus and a substrate mounting method.

[0002] Patent Document 1 discloses a substrate processing apparatus (bonding apparatus) that includes an upper chuck that adsorbs an upper substrate from above and a lower chuck that adsorbs a lower substrate from below, and bonds two substrates face to face. In bonding the substrates, the bonding apparatus presses down the center of the substrate on the upper chuck to bring it into contact with the center of the substrate on the lower chuck, bonds the centers of the two substrates together by intermolecular forces, and expands the bonding area from the center toward the outer edges.

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

[0004] The present disclosure provides a technique that can improve the bonding accuracy of substrates.

[0005] According to one aspect of the present disclosure, there is provided a substrate processing apparatus including a holding unit having an adsorption surface that adsorbs a substrate, the holding unit having a circular central region and an annular outer region located outside the central region, wherein the adsorption surface has a region that divides the outer region circumferentially and a plurality of zones in the central region, and the substrate processing apparatus is provided with a pressure generating unit that generates pressure in each of the plurality of zones, and wherein the pressure generating unit applies positive pressure to at least one of the plurality of zones to which the negative pressure is not applied when the substrate is placed on the adsorption surface and negative pressure is applied to at least one of the plurality of zones.

[0006] According to one aspect, the bonding accuracy of the substrates can be improved.

[0007] 1 is a plan view showing a bonding apparatus according to an embodiment of the present disclosure; FIG. 2 is a side view of the bonding apparatus of FIG. 1; FIG. 3 is a side view showing an example of a first substrate and a second substrate; FIG. 4 is a flowchart showing a bonding method of the bonding apparatus; FIG. 5 is a side view of the bonding module of FIG. 1; FIG. 6 is a cross-sectional view showing an example of an upper chuck and a lower chuck; FIG. 7 is a flowchart showing details of step S109 of FIG. 4; FIG. 9(A) is a side view showing an example of an operation in step S112 of FIG. 8; FIG. 9(B) is a side view showing an operation subsequent to FIG. 9(A); FIG. 9(C) is a side view showing an operation subsequent to FIG. 9(B); FIG. 10(A) is a cross-sectional view showing an example of an operation in step S113 of FIG. 8; FIG. 10(B) is a cross-sectional view showing an example of an operation in step S114 of FIG. 8; FIG. 10(C) is a cross-sectional view showing an operation subsequent to FIG. 10(B); FIG. 12(A) is a plan view showing an example of an adsorption surface of a lower chuck according to the first embodiment; FIG. 13(A) is an explanatory view showing a convexly warped lower wafer. FIG. 12(B) is an explanatory diagram showing a concavely warped lower wafer. FIG. 13(A) is a plan view showing the suction surface when the lower wafer is suctioned onto the lower chuck. FIG. 13(B) is a side cross-sectional view showing the case where the suction surface is deformed by suctioning the lower wafer onto the lower chuck. FIG. 13(C) is a plan view showing the state of the lower wafer and the lower chuck after the suction surface is deformed. FIG. 15(A) is a perspective view showing another example of warping of the lower wafer. FIG. 15(B) is a plan view showing the deviation of the reference point due to warping of the lower wafer. FIG. 15(C) is a plan view showing the application of negative and positive pressure to the suction surface of the lower chuck. FIG. 16(A) is a first diagram showing the operation of the substrate mounting method according to the second embodiment. FIG. 16(B) is a second diagram showing the operation of the substrate mounting method subsequent to FIG. 16(A). FIG. 16(C) is a third diagram showing the operation of the substrate mounting method subsequent to FIG. 16(B). Fig. 16(D) is a fourth diagram showing the operation of the substrate mounting method following Fig. 16(C). Fig. 17(A) is a first diagram showing the operation of the substrate mounting method according to the third embodiment. Fig. 17(B) is a second diagram showing the operation of the substrate mounting method following Fig. 17(A). Fig. 17(C) is a third diagram showing the operation of the substrate mounting method following Fig. 17(B).Fig. 17(D) is a fourth diagram showing the operation of the substrate mounting method following Fig. 17(C) Fig. 17(D) is a diagram showing the relationship between the bonding device and the warpage measuring device according to the fourth embodiment.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] A bonding apparatus 1 shown in FIGS. 1 and 2 will be described as a representative substrate processing apparatus according to the present disclosure. The substrate processing apparatus according to the present disclosure is not limited to the bonding apparatus 1, but may be any apparatus that includes a holder for holding a substrate and processes the substrate held by the holder. Examples of other substrate processing apparatus include an exposure apparatus and a temperature adjustment apparatus. An exposure apparatus is an apparatus that holds a substrate by a holder and transfers a mask pattern onto the substrate. A temperature adjustment apparatus is an apparatus that holds a substrate by a holder and adjusts the temperature of the substrate.

[0010] 3, 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.

[0011] The first substrate W1 and the second substrate W2 are formed as circular plates of approximately the same shape (same diameter). The bonding apparatus 1 bonds the first substrate W1 and the second substrate W2 by placing the second substrate W2 on the negative Z-axis side (vertically below) of the first substrate W1. Hereinafter, the first substrate W1, which is one of the substrates, may be referred to as the "upper wafer W1," the second substrate W2, which is the other of the substrates, may be referred to as the "lower wafer W2," and the bonded substrate T may be referred to as the "bonded wafer T." Hereinafter, the surface of the upper wafer W1 that is bonded to the lower wafer W2 may be referred to as the "bonding surface W1j," and the surface opposite the bonding surface W1j may be referred to as the "non-bonding surface W1n." Hereinafter, the surface of the lower wafer W2 that is bonded to the upper wafer W1 may be referred to as the "bonding surface W2j," and the surface opposite the bonding surface W2j may be referred to as the "non-bonding surface W2n."

[0012] 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 connected in the X-axis direction and integrated.

[0013] The loading / unloading station 2 includes a mounting table 10 and a transfer area 20. The mounting table 10 includes a plurality of mounting plates 11. Each mounting plate 11 is loaded with a cassette 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.

[0014] 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 around 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.

[0015] 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 ).

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 CPU, a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a circuit made up of a plurality of discrete semiconductors, and the like. The memory 92 includes a main storage device made up of a semiconductor memory or the like, and an auxiliary storage device made up of a disk, a drive, a semiconductor memory, and the like. The processor 91 executes and processes a program stored in the memory 92.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Then, the bonding apparatus 1 causes the surface hydrophilization device 34 to hydrophilize the bonding surface W1j of the upper wafer W1 (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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 6, an upper chuck (upper holding portion) 230 and a lower chuck (holding portion) 231 are provided inside the processing vessel 210. The upper chuck 230 holds the upper wafer W1 from above with the bonding surface W1j of the upper wafer W1 facing downward. The lower chuck 231 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.

[0039] The upper chuck 230 is supported by a support member 280 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.

[0040] As will be described later, the first lower chuck moving part 291 moves the lower chuck 231 in the horizontal direction (Y-axis direction). The first lower chuck moving part 291 is configured to be able to move the lower chuck 231 in the vertical direction and to rotate the lower chuck 231 around a vertical axis.

[0041] 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.

[0042] 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 table 298 provided on the bottom surface of the processing vessel 210.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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. Furthermore, the moving mechanism 290 may rotate the upper chuck 230 or the lower chuck 231 around a vertical axis.

[0048] 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.

[0049] 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.

[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 has a through-hole 243 at its center that passes through the upper chuck 230 in the vertical direction, and also has a pushing unit 250 around the through-hole 243. The pushing unit 250 pushes down the center of the upper wafer W1, which is disposed at an interval 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] On the other hand, the lower chuck 231 also has a suction surface 300 that suctions the lower wafer W2 and has a plurality of partitioned regions. Annular ribs 301, 302, and 303 and radial ribs 305 (see FIG. 11 ) are provided on the upper surface of the lower chuck 231. The suction surface 300 is defined by the upper ends of the ribs 301, 302, and 305. The configuration of the suction surface 300 of the lower chuck 231 will be described in detail later.

[0055] The lower chuck 231 is provided with a plurality of (e.g., three) lift pins 265 that can be raised and lowered in the vertical direction. As the plurality of lift pins 265 rise, they protrude from an adsorption surface 300 of the lower chuck 231. Each lift pin 265 receives the lower wafer W2 by rising toward the lower wafer W2 carried in by the transfer device 61. After the transfer device 61 leaves, each lift pin 265 lowers to place the lower wafer W2 on the adsorption surface 300. Note that the plurality of lift pins 265 may vacuum-adsorb the lower wafer W2 when receiving the lower wafer W2.

[0056] The lower chuck 231 according to the embodiment has a deformable suction surface 300. The lower chuck 231 includes, for example, a base portion 232 and a suction portion 233. The suction portion 233 is provided above the base portion 232 and suction-holds the lower wafer W2 from below. The suction portion 233 is formed in a perfect circle shape with a diameter larger than the diameter of the lower wafer W2 in a plan view, and is fixed to the base portion 232 by a fixing ring 234 provided on the periphery. The suction portion 233 is made of a ceramic material such as alumina or silicon carbide.

[0057] The lower chuck 231 has a pressure variable space 235 between the upper surface of the base portion 232 and the lower surface of the suction portion 233, and also has a deformation adjustment portion 236 that elastically deforms the suction portion 233 by changing the pressure in the pressure variable space 235. In other words, the suction portion 233, the pressure variable space 235, and the deformation adjustment portion 236 constitute a deformation portion that deforms the lower chuck 231.

[0058] The deformation adjustment unit 236 includes a vacuum pump 236a, a pressure pump 236b, and a switching valve 236c. The vacuum pump 236a depressurizes the pressure variable space 235 by discharging gas from the pressure variable space 235. By depressurizing the pressure variable space 235, the upper surface of the suction unit 233 becomes a horizontal surface or a curved surface with a concave center. Meanwhile, the pressure pump 236b pressurizes the pressure variable space 235 by supplying gas to the pressure variable space 235. By pressurizing the pressure variable space 235, the suction surface 300 becomes a curved surface with a convex center. The deformation amount of the suction surface 300 can be adjusted by the pressure in the pressure variable space 235. The switching valve 236c switches the pressure variable space 235 between a state where it is connected to the vacuum pump 236a and a state where it is connected to the pressure pump 236b.

[0059] The base part 232 has a measurement part 237 that measures the amount of protrusion of the central region A of the adsorption surface 300. A measurement target 237a of the measurement part 237 moves up and down together with the central part of the adsorption part 233. The measurement part 237 is, for example, a capacitance sensor, and measures the amount of protrusion by detecting capacitance that changes depending on the distance from the measurement target 237a.

[0060] 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.

[0061] 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.

[0062] 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 electronic circuit patterns, electrode pads, or the like. The number of reference points can be set arbitrarily.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The first displacement meter S3 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 measures the thickness of the lower wafer W2, for example, by irradiating light onto the lower wafer W2 held by the lower chuck 231 and receiving light reflected from both the upper and lower surfaces of the lower wafer W2. The 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 a confocal method, a spectral interference method, a triangulation method, or the like. An LED or a laser can be used as the light source of the first displacement meter S3.

[0069] On the other hand, the second displacement meter S4 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 measures the thickness of the upper wafer W1, for example, by irradiating light onto the upper wafer W1 held by the upper chuck 230 and receiving light reflected from both the upper and lower surfaces of the upper wafer W1. The 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. An LED or a laser can be used as the light source of the second displacement meter S4.

[0070] Each of the first displacement gauges S3 and each of the second displacement gauges S4 transmits the measured measurement information to the control device 90. The control device 90 controls the moving mechanism 290 based on the measurement information measured by each of the first displacement gauges S3 and the measurement information measured by each of the second displacement gauges S4, and adjusts the vertical position of the lower chuck 231 so that the gap G becomes a set value.

[0071] After adjusting the gap G between the upper wafer W1 and the lower wafer W2, 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 is lowered 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 central portions of the upper wafer W1 and the lower wafer W2 are bonded together.

[0072] 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.

[0073] 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).

[0074] 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.

[0075] 8 , after the bonded wafer T is formed, the control device 90 uses 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.

[0076] 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 its hold on the bonded wafer T. Next, the multiple lift pins 265 rise and transfer the bonded wafer T to the transfer device 61. Thereafter, the multiple lift pins 265 descend to their original positions. This allows the bonding apparatus 1 to transfer the bonded wafer T out of the bonded wafer T using the transfer device 61 and transfer the bonded wafer T to the cassette CS3.

[0077] In the above-described bonding apparatus 1, when bonding is performed in a state where the upper wafer W1 and / or the lower wafer W2 are warped, misalignment between the upper wafer W1 and the lower wafer W2 is likely to occur. For this reason, the bonding apparatus 1 according to the present disclosure is configured to reduce misalignment by controlling the placement state of the lower wafer W2 by the lower chuck 231.

[0078] First Embodiment The configuration of the suction surface 300 of the lower chuck 231 according to the first embodiment will be described below with reference to Fig. 11 to Fig. 15. As shown in Fig. 11, the suction surface 300 of the lower chuck 231 has a plurality of regions that individually generate pressure along the radial direction.

[0079] For example, the suction surface 300 is partitioned by annular ribs 301 and 303 into a circular (perfectly circular) central region A and an annular outer region B. Furthermore, the outer region B is partitioned by annular rib 302 into an annular first outer region B1 adjacent to the outside of the central region A and an annular second outer region B2 adjacent to the outside of the first outer region B1. That is, the central region A, the first outer region B1, and the second outer region B2 are concentrically arranged in this order from the center of the suction surface 300 toward the outside in the radial direction. The suction surface 300 may be configured such that the central region A and one outer region B are aligned radially outward, rather than being divided into the first outer region B1 and the second outer region B2. Conversely, the outer region B of the suction surface 300 may include three or more annular regions.

[0080] The first outer region B1 is partitioned into eight arc-shaped zones by a plurality of radial ribs 305. Similarly, the second outer region B2 is partitioned into eight arc-shaped zones by the ribs 305. The number of zones in the first outer region B1 and the second outer region B2 is not limited to eight and may be designed as desired. Furthermore, the number of zones in the first outer region B1 and the number of zones in the second outer region B2 may be different from each other, or the circumferential positions of the zones may be shifted from each other.

[0081] The central region A, the multiple zones in the first outer region B1, and the multiple zones in the second outer region B2 are configured to be able to individually suck the lower wafer W2. However, the lower chuck 231 according to the embodiment has 10 adjustment mechanisms 311 connected to a total of 17 zones, and the suction surface 300 is sucked in 10-channel zones. In other words, the suction surface 300 has zones among the total of 17 zones that are suctioned by the same adjustment mechanism 311. Note that in FIG. 11 , each zone where suction is performed (negative pressure is generated) is indicated by single hatching. Each zone has multiple holes (not shown) inside the surrounding ribs (on the upper surface of the suction portion 233) that communicate with the respective adjustment mechanisms 311.

[0082] Specifically, the central region A has one zone (ch1). The first outer region B1 has three zones (ch2 to ch4). The two zones adjacent to the central region A in the X-axis direction (left and right in FIG. 11 ) are ch2. The two zones adjacent to the central region A in the Y-axis direction (top and bottom in FIG. 11 ) are ch3. The four zones in the diagonal direction in the outer region B sandwiched between the ch2 and ch3 zones are ch4. The second outer region B2 has six zones (ch5 to ch10). The zone adjacent to the first outer region B1 in the positive X-axis direction (left in FIG. 11 ) is ch5. The zone adjacent to the first outer region B1 in the negative X-axis direction (right in FIG. 11 ) is ch6. The zone adjacent to the first outer region B1 in the negative Y-axis direction (top in FIG. 11 ) is ch7. The zone 1 adjacent to the first outer region B1 in the positive Y-axis direction (bottom in FIG. 11 ) is ch 8. In the second outer region B2, the zone sandwiched between the zones ch 5 and ch 7 and the zone sandwiched between the zones ch 6 and ch 7 are ch 9. Similarly, in the second outer region B2, the zone sandwiched between the zones ch 5 and ch 8 and the zone sandwiched between the zones ch 6 and ch 8 are ch 10.

[0083] On the X-axis line (first axis) passing through the center of the suction surface 300, the zones ch5, ch2, ch1, ch2, and ch6 are arranged in this order from the positive direction of the X-axis to the negative direction of the X-axis. On the Y-axis line (second axis) passing through the center of the suction surface 300, the zones ch7, ch3, ch1, ch3, and ch8 are arranged in this order from the negative direction of the Y-axis to the positive direction of the X-axis. Of course, the suction surface 300 can be freely designed with regard to the number and locations of channels in each zone.

[0084] A pressure generating unit 310 is connected to the lower chuck 231 and performs suction (application of negative pressure) and gas discharge (application of positive pressure) for each zone of the suction surface 300 (see also FIG. 7 ). Specifically, the pressure generating unit 310 includes ten adjustment mechanisms 311 connected to the ten channels, respectively, a negative pressure generating source 312 provided upstream of each adjustment mechanism 311, and a positive pressure generating source 313 provided upstream of each adjustment mechanism 311. The pressure generating unit 310 is also communicatively connected to the control device 90 and independently operates each adjustment mechanism 311 under the control of the control device 90.

[0085] Each adjustment mechanism 311 has a main line 311a connected to each zone of the lower chuck 231, a negative pressure line 311b connecting the main line 311a and a negative pressure source 312, and a positive pressure line 311c connecting the main line 311a and a positive pressure source 313.

[0086] The main line 311a is equipped with a pressure sensor 314 and a switching valve 315. The pressure sensor 314 detects the pressure (negative pressure, positive pressure) in the flow path of the main line 311a. The switching valve 315 is provided at the branch point of the main line 311a, the negative pressure line 311b, and the positive pressure line 311c. Based on the control of the control device 90, the switching valve 315 switches between a negative pressure application pattern in which the main line 311a and the negative pressure line 311b are connected to each other, and a positive pressure application pattern in which the main line 311a and the positive pressure line 311c are connected to each other.

[0087] The negative pressure line 311b extends from the switching valve 315 to the negative pressure source 312. The negative pressure source 312 may be, for example, a turbomolecular pump or a vacuum pump capable of sucking gas. The negative pressure source 312 generates negative pressure in the zone of the suction surface 300 that is connected via the negative pressure line 311b and the main line 311a under the control of the control device 90. An electropneumatic regulator 316 and an on-off valve 317 are provided midway along the negative pressure line 311b. The electropneumatic regulator 316 adjusts the pressure of the negative pressure line 311b (in other words, the negative pressure applied to the connected zone of the suction surface 300) under the control of the control device 90 while the negative pressure source 312 is connected to the zone. The on-off valve 317 opens and closes the flow path of the negative pressure line 311b under the control of the control device 90.

[0088] Meanwhile, the positive pressure line 311c extends from the switching valve 315 to the positive pressure source 313. The positive pressure source 313 may be, for example, a compressor capable of pressurizing a gas (such as air). The positive pressure source 313 generates positive pressure (e.g., air discharge) in a zone of the suction surface 300 that is connected via the positive pressure line 311c and the main line 311a under the control of the control device 90. An electropneumatic regulator 318 and a filter 319 are provided midway along the positive pressure line 311c. The electropneumatic regulator 318 adjusts the pressure of the positive pressure line 311c (in other words, the positive pressure applied to the connected zone of the suction surface 300) under the control of the control device 90 while the positive pressure source 313 is connected to the zone. The filter 319 removes foreign matter (such as dust and particles) contained in the air pressurized and fed from the positive pressure source 313.

[0089] For example, each adjustment mechanism 311 generates negative pressure in the zone of the connected suction surface 300 by using the switching valve 315 to connect the main line 311a and the negative pressure line 311b, opening the on-off valve 317, and operating the negative pressure generation source 312. The magnitude of the negative pressure is controlled by the electropneumatic regulator 316. Also, for example, each adjustment mechanism 311 generates positive pressure in the zone of the connected suction surface 300 by using the switching valve 315 to connect the main line 311a and the positive pressure line 311c and operating the positive pressure generation source 313.

[0090] Here, the upper wafer W1 and / or the lower wafer W2 bonded by the bonding apparatus 1 may be warped overall, as shown in FIG. 12A . The warping of the upper wafer W1 and the lower wafer W2 occurs, for example, when multiple films are stacked on a semiconductor substrate such as a silicon wafer. Each film is formed by a method such as a chemical vapor deposition (CVD) method, an atomic layer deposition (ALD) method, or a spin-on method. Stress is applied to the upper wafer W1 and the lower wafer W2 due to a difference in thermal expansion during film formation, causing warping of the upper wafer W1 and the lower wafer W2.

[0091] The upper wafer W1 and the lower wafer W2 are often warped symmetrically across two orthogonal radial lines, i.e., line-symmetrically. This is because the Young's modulus, Poisson's ratio, and shear modulus of a semiconductor substrate such as a silicon wafer change in a 90° cycle. The two orthogonal radial lines extend in a specific crystal orientation of the semiconductor substrate when viewed from the direction orthogonal to the chucking surface 300 (the Z-axis direction).

[0092] The warpage of the upper wafer W1 and the lower wafer W2 is measured, for example, by a warpage measuring device 5 (see FIG. 1 ) provided separately from the bonding apparatus 1. When the control device 90 acquires information on the warpage state of the lower wafer W2 measured by the warpage measuring device 5, the control device 90 stores the information on the warpage state in a memory 92 during processing of the upper wafer W1 and the lower wafer W2. The warpage measuring device 5 may be provided as part of the bonding apparatus 1. The bonding apparatus 1 may be configured to measure the warpage when the upper wafer W1 and the lower wafer W2 are loaded using a plurality of displacement meters (not shown) provided in the bonding module 41. The warpage is measured in a state where no external force (e.g., suction pressure) other than gravity and its reaction force is acting, and is measured, for example, with the wafer placed on a flat surface of a stage or on a plurality of (e.g., three) pins.

[0093] Then, based on the information on the warpage state of the upper wafer W1, the bonding apparatus 1 transfers the upper wafer W1 from the transfer device 61 to the upper chuck 230 so that two orthogonal radial lines, on which the upper wafer W1 has large warpage, are aligned along the X-axis direction and the Y-axis direction of the upper chuck 230. For example, the posture of the upper wafer W1 is adjusted by the above-described first position adjustment device 51 (see FIG. 2 ). Furthermore, based on the information on the warpage state of the lower wafer W2, the bonding apparatus 1 transfers the lower wafer W2 from the transfer device 61 to the lower chuck 231 so that two orthogonal radial lines, on which the lower wafer W2 has large warpage, are aligned along the X-axis direction and the Y-axis direction of the lower chuck 231. For example, the posture of the lower wafer W2 is adjusted by the above-described second position adjustment device 52 (see FIG. 2 ).

[0094] The warpage of the upper wafer W1 and the lower wafer W2 can be categorized into two types: one in which the outer edges at symmetrical positions are warped in a direction closer to the suction surface 300 than the center, and the other in which the outer edges at symmetrical positions are warped in a direction away from the suction surface 300 than the center. Hereinafter, the warpage of the outer edges in a direction closer to the suction surface 300 when the lower wafer W2 is placed on the suction surface 300 and before suction is also referred to as convex warpage. Furthermore, the warpage of the outer edges in a direction away from the suction surface 300 when the lower wafer W2 is placed on the suction surface 300 and before suction is also referred to as concave warpage.

[0095] When convex warpage occurs in the lower wafer W2, as shown in the X-X cross section and the Y-Y cross section in Figure 12 (A), the outer edges at both ends of the X-axis (first axis) and the outer edges at both ends of the Y-axis (second axis) are curved in a direction approaching the suction surface 300 (vertically downward) from the center. However, the amount of warpage along the X-axis and the amount of warpage along the Y-axis do not necessarily coincide. In this specification, the "amount of warpage" refers to the length between the height position of the center and the height position of the outer edge when the plate thickness of the lower wafer W2 (or the upper wafer W1) is aligned in the vertical direction.

[0096] 12(A), the amount of warpage along the X-axis is large, while the amount of warpage along the Y-axis is small. As a result, a large stress is applied to the X-axis of the upper surface (bonding surface W2j) of the lower wafer W2, causing a large radially outward stretch, and each reference point P2x on the X-axis of the upper surface moves significantly radially outward. On the other hand, a small stress is applied to the Y-axis of the upper surface of the lower wafer W2, causing a small radially outward stretch, and each reference point P2y on the Y-axis of the upper surface moves slightly radially outward.

[0097] Furthermore, when concave warpage occurs in the lower wafer W2, as shown in the X-X cross section and the Y-Y cross section in FIG. 12(B), the outer edges at both ends of the X-axis and the outer edges at both ends of the Y-axis are curved in a direction away from the suction surface 300 (vertically upward) relative to the center. In the example of FIG. 12(B), the amount of warpage along the X-axis is large, while the amount of warpage along the Y-axis is small. As a result, a large radially inward contraction stress is applied to the X-axis on the top surface of the lower wafer W2, causing each reference point P2x on the X-axis on the top surface to move significantly radially inward. Meanwhile, a small radially inward contraction stress is applied to the Y-axis on the top surface of the lower wafer W2, causing each reference point P2y on the Y-axis on the top surface to move slightly radially inward.

[0098] Although not shown, the upper wafer W1 held by suction on the upper chuck 230 may also have convex or concave warpage. The convexly warped upper wafer W1, when facing the upper chuck 230 and before being suctioned, exhibits a shape in which the outer edge is warped in a direction closer to the suction surface of the upper chuck 230 (vertically upward) than the center. Even if the upper chuck 230 suctions the convexly warped upper wafer W1 onto its flat suction surface, the convexly warped upper wafer W1 potentially contains stress that stretches it radially outward along the X-axis or Y-axis of its lower surface (bonding surface W1j). On the other hand, the concavely warped upper wafer W1, when facing the upper chuck 230 and before being suctioned, exhibits a shape in which the outer edge is warped in a direction farther away from the suction surface of the upper chuck 230 than the center (vertically downward). Even if the concavely warped upper wafer W1 is adsorbed onto the flat adsorption surface of the upper chuck 230, the concavely warped upper wafer W1 potentially has stress that causes it to shrink radially inward along the X-axis or Y-axis of the lower surface (bonding surface W1j).

[0099] Therefore, the bonding apparatus 1 according to the first embodiment is configured to move the reference points P2x and P2y of the lower wafer W2 based on the warpage of the upper wafer W1 and / or the warpage of the lower wafer W2 when the lower wafer W2 is placed on the lower chuck 231. Specifically, the bonding apparatus 1 performs an operation to stretch the bonding surface W2j of the lower wafer W2 by deforming the suction surface 300 of the lower chuck 231 while fixing the lower wafer W2. Furthermore, the bonding apparatus 1 simultaneously generates negative pressure zones and positive pressure zones among the zones (1ch to 10ch) of the suction surface 300 when fixing the lower wafer W2 and deforming the suction surface 300 based on the warpage of the upper wafer W1 and / or the warpage of the lower wafer W2.

[0100] An example of the operation of the lower chuck 231 when suctioning the lower wafer W2 will be described below with reference to Figures 13(A) to 13(C). Note that in each zone in Figures 13(A) and 13(C), as well as Figures 15(C), 16(A) to 16(D), and 17(A) to 17(D), single hatching indicates a state in which negative pressure is applied, and cross hatching indicates a state in which positive pressure is applied. Therefore, Figures 13(A) to 13(C) show an example in which negative pressure is applied in the X-axis zone of the lower chuck 231, and positive pressure is applied in other zones (Y-axis and part of the diagonal direction).

[0101] Before deforming the suction surface 300 of the lower chuck 231, the control device 90 places the lower wafer W2 on the suction surface 300 and partially suctions the lower wafer W2. The control device 90 sets zones to which negative pressure and positive pressure are applied by the lower chuck 231 and also sets the deformation amount of the suction surface 300, based on, for example, the warpage state (warpage direction and warpage amount) of the lower wafer W2 measured by the warpage measurement device 5.

[0102] For example, the control device 90 calculates a zone of the suction surface 300 at a location on the bonding surface W2j of the lower wafer W2 that is to be significantly stretched, and applies negative pressure to that zone. As an example, if the lower wafer W2 has a convex warp and the amount of warp along the X-axis is smaller than the amount of warp along the Y-axis, the X-axis of the lower wafer W2 is the location that should be significantly stretched. For this reason, in Figures 13(A) and 13(B), in order to suction the X-axis of the lower wafer W2, the control device 90 applies negative pressure to the central region A (1ch) and the 2ch, 5ch, and 6ch zones that are part of the circumferential direction of the outer region B using the pressure generating unit 310.

[0103] The 1ch, 2ch, 5ch, and 6ch zones suction the lower surface (non-bonding surface W2n) of the lower wafer W2 by negative pressure. As a result, as shown in FIG. 13B , the lower chuck 231 firmly holds the X-axis of the lower wafer W2 on the suction surface 300 before the suction surface 300 deforms. Then, while holding the X-axis of the lower wafer W2, the control device 90 deforms the central region A of the suction surface 300 so that it rises relative to the outer edge of the suction surface 300. Following the deformation of the suction surface 300 of the lower chuck 231, the lower wafer W2 also deforms into a shape in which the center is elevated relative to the outer edge. During the deformation of the suction surface 300, the lower wafer W2 held in the 1ch, 2ch, 5ch, and 6ch zones of the X-axis of the lower chuck 231 has the bonding surface W2j at the suction point of the lower wafer W2 significantly elongated along the X-axis.

[0104] 13A and 13B, the control device 90, with the lower wafer W2 held by suction along the X-axis, applies positive pressure to the 3ch (i.e., Y-axis) and 4ch (i.e., diagonal) zones, which are another part of the circumferential direction of the outer region B, by the pressure generating unit 310. In the 3ch and 4ch zones, the positive pressure separates the suction surface 300 (ribs 301 to 304) of the lower chuck 231 from the underside of the lower wafer W2. The air discharged into 3ch and 4ch moves to escape through 7ch to 10ch. As a result, as shown in FIG. 13B, the frictional force of the lower wafer W2 in the Y-axis and diagonal directions of the lower chuck 231 is weakened before the suction surface 300 of the lower chuck 231 deforms.

[0105] Then, in a state in which the frictional forces of the lower wafer W2 in the Y-axis and diagonal directions are weakened, the control device 90 controls the deformation unit to deform the central region A of the suction surface 300 so as to rise relative to the outer edge of the suction surface 300. In the deformation of the suction surface 300, the frictional forces of the lower wafer W2 in the Y-axis and diagonal directions are weakened, and the bonding surface W2j of the lower wafer W2 is restricted to an extent that it slightly elongates along the Y-axis.

[0106] 13(C), on the lower wafer W2 after the suction surface 300 is deformed, each reference point P2x on the X-axis line moves significantly outward in the radial direction, while each reference point P2y on the Y-axis line moves slightly outward in the radial direction. Note that in FIG. 13(C), the movement amounts of each reference point P2x and each reference point P2y are exaggerated by the lengths of the arrows, but the actual movement of each reference point P2x and each reference point P2y is very small, on the order of several μm to several mm.

[0107] In particular, the lower chuck 231 applies positive pressure to the portion where the lower wafer W2 is not being chucked, thereby weakening the frictional force of the lower wafer W2 at that portion, thereby preventing the amount of elongation at the portion where the lower wafer W2 is not being chucked from irregularly changing due to friction. As a result, the amount of elongation at both ends of the X-axis and the amount of elongation at both ends of the Y-axis are made uniform, and it is possible to obtain reproducibility such that the distribution of elongation amounts is approximately the same even after multiple bonding operations.

[0108] It should be noted that the zones to apply negative pressure to the lower wafer W2 and the zones to apply positive pressure to the lower wafer W2 before deformation of the chucking surface 300 are not limited to the above. For example, the control device 90 may apply positive pressure to all other zones (ch3, ch4, ch7 to ch10) while applying negative pressure along the X-axis. Alternatively, when it is desired to extend the Y-axis, the control device 90 may apply positive pressure to the zones along the X-axis and the diagonal direction while chucking the non-bonding surface W2n of the lower wafer W2 using the Y-axis zones (ch1, ch7, ch8) of the lower chuck 231.

[0109] In the above description, the case where the lower wafer W2 has a convex warp and the amount of warpage along the X-axis is smaller than the amount of warpage along the Y-axis has been described. However, even when the lower wafer W2 has a concave warp, the zones to which negative pressure and positive pressure are applied may be set according to the amount of warpage along the X-axis and the amount of warpage along the Y-axis. For example, the lower chuck 231 may apply negative pressure to a zone facing a portion that has shrunk significantly inward due to the concave warp, and apply positive pressure to a zone facing a portion that has shrunk slightly inward due to the concave warp.

[0110] The bonding apparatus 1 may also change the amount of deformation of the suction surface 300 depending on the amount of warpage of the lower wafer W2 (or the upper wafer W1). For example, if the amount of warpage of the lower wafer W2 is small, the amount of deformation of the suction surface 300 may be reduced, whereas if the amount of warpage of the lower wafer W2 is large, the amount of deformation of the suction surface 300 may be increased. Furthermore, the bonding apparatus 1 may change the zone to which negative pressure is applied and the zone to which positive pressure is applied depending on the amount of warpage of the lower wafer W2 (or the upper wafer W1). For example, if the amount of warpage of the lower wafer W2 is small, negative pressure may be applied to a zone closer to the central region A (e.g., ch2) and not to a zone closer to the outer edge. Furthermore, if the amount of warpage of the lower wafer W2 is large, only the zones on the outer edge (e.g., ch5 and ch6) may be suctioned. In this case, the control device 90 may or may not apply positive pressure to ch1 and ch2. By applying positive pressure, it is expected that the frictional force in the central region A will be weakened and the amount of elongation on the outer edge side will be increased. Furthermore, the bonding apparatus 1 may change the negative pressure and / or the positive pressure depending on the amount of warpage of the lower wafer W2 (or the upper wafer W1).

[0111] The lower chuck 231 according to the first embodiment is basically configured as described above, and its operation (a bonding method including a substrate mounting method) will be described below with reference to the flowchart in Fig. 14. In bonding the upper wafer W1 and the lower wafer W2, the control device 90 sequentially executes, for example, steps S121 to S125 in Fig. 14.

[0112] In detail, in accordance with the execution of step S111 shown in FIG. 8, the bonding apparatus 1 places the lower wafer W2 before bonding on the lower chuck 231 in the bonding module 41 (step S121: process (A)).

[0113] After the lower wafer W2 is placed (after step (A)), the lower chuck 231 applies negative pressure to a part of the lower wafer W2 while applying positive pressure to another part of the lower wafer W2 (step S122: step (B)). That is, the pressure generating unit 310 first suctions the lower wafer W2 in each zone of the suction surface 300 for which negative pressure has been selected. Then, after suctioning the lower wafer W2, the pressure generating unit 310 ejects air onto the lower wafer W2 in each zone of the suction surface 300 for which positive pressure has been selected.

[0114] Then, while applying both negative and positive pressure to the lower wafer W2, the control device 90 deforms the lower chuck 231 so as to protrude (make the central region A of the suction surface 300 convex upward) (step 123). As a result, the bonding surface W2j of the lower wafer W2 at the suctioned portion is stretched significantly, and the bonding surface W2j of the lower wafer W2 at the portion where air is ejected is stretched less. Furthermore, the influence of friction between the lower wafer W2 and the lower chuck 231 is minimized, allowing the lower wafer W2 to be stretched with good reproducibility.

[0115] When the deformation of the lower chuck 231 is completed, the control device 90 stops applying the positive pressure from the lower chuck 231 to the lower wafer W2 and then applies a negative pressure to the entire surface of the chucking surface 300 (in other words, the entire lower wafer W2) (step S124). This allows the lower chuck 231 to fix the lower wafer W2, which is in an appropriately stretched state in the above process flow, to the chucking surface 300.

[0116] The bonding module 41 bonds the upper wafer W1 and the lower wafer W2 while the entire lower wafer W2 is fixed (step S125). Specifically, the control device 90 performs step S113 and subsequent steps in FIG. 8 to bond the upper wafer W1 to the deformed lower wafer W2. The bonding surface W2j of the lower wafer W2 is uniformly stretched by the application of negative and positive pressure by the lower chuck 231 as described above. As a result, the reference points of the lower wafer W2 and the upper wafer W1 overlap with high precision. Therefore, the bonding apparatus 1 can produce bonded wafers T that are bonded with high precision with a high yield.

[0117] As described above, the bonding apparatus 1 and the substrate mounting method apply positive pressure while applying negative pressure using the pressure generating unit 310, thereby reducing friction between the lower wafer W2 and the chucking surface 300 and moving the lower wafer W2 with good reproducibility. As a result, the lower chuck 231 improves the stress distribution on the lower wafer W2 and properly holds the lower wafer W2. In particular, when applying negative pressure along the X-axis, applying positive pressure along the orthogonal Y-axis can properly stretch the lower wafer W2 in accordance with the Young's modulus, Poisson's ratio, and shear modulus, which change in 90-degree cycles. Furthermore, by setting zones to which negative pressure and positive pressure are applied according to the amount of warpage of the upper wafer W1 or the lower wafer W2, the position of the reference point can be adjusted with high precision. Furthermore, by applying positive pressure to the diagonal zone, the bonding apparatus 1 and the substrate mounting method smoothly transmit the elongation force of the axis to which negative pressure is applied to the other axis.

[0118] The bonding apparatus 1 and the substrate mounting method can easily move the reference point of the lower wafer W2 by applying negative and positive pressure to the suction surface 300 and deforming the suction surface 300 using the deformation unit. After deforming the suction surface 300, the pressure generating unit 310 applies negative pressure to all of the multiple zones to suction the lower wafer W2 onto the suction surface 300, thereby enabling stable substrate processing (bonding with the upper wafer W1).

[0119] The bonding apparatus 1 and the substrate mounting method are not limited to the above-described embodiment and may take various modifications. For example, in the above-described substrate mounting method, an example has been described in which the negative and positive pressures of the lower chuck 231 and the deformation of the suction surface 300 are controlled in accordance with the warpage state of the lower wafer W2. However, the bonding apparatus 1 may control the negative and positive pressures of the lower chuck 231 and the deformation of the suction surface 300 based on the warpage state of the upper wafer W1 (and / or both the warpage states of the upper wafer W1 and the lower wafer W2).

[0120] Furthermore, for example, the bonding apparatus 1 may bond a lower wafer W2 (or an upper wafer W1) having a saddle-shaped curved surface, as shown in FIG. 15A. The bonding surface W2j of the lower wafer W2, which is a saddle-shaped curved surface, is extended outward along the Y-axis, while being contracted inward along the X-axis, as shown in FIG. 15B. In this case, the lower chuck 231 also applies negative pressure to the lower wafer W2 along the X-axis, while applying positive pressure to the lower wafer W2 along the Y-axis, as shown in FIG. 15C. This significantly extends the inwardly contracted X-axis of the lower wafer W2, while suppressing the outwardly extended Y-axis. Moreover, the lower chuck 231 can reproducibly extend the lower wafer W2 by applying positive pressure, thereby enabling accurate bonding to the upper wafer W1.

[0121] <Second Embodiment> As shown in Figures 16(A) to 16(D), the substrate mounting method according to the second embodiment differs from the substrate mounting method according to the first embodiment in that the timing of applying negative pressure and positive pressure to the lower wafer W2 and the timing of deforming the lower chuck 231 are made different.

[0122] 16A , the control device 90 of the bonding apparatus 1 slightly deforms the suction surface 300 of the lower chuck 231 as a first step before placing the lower wafer W2. Hereinafter, the shape of the lower chuck 231 deformed before placement is referred to as a first-stage deformation pattern. At the timing when this first-stage deformation pattern is performed, the lower wafer W2 has not been placed, and therefore the pressure generating unit 310 is not applying negative pressure or positive pressure.

[0123] 16(B), the control device 90 places the lower wafer W2 on the suction surface 300 of the lower chuck 231 of the first-stage deformation pattern. Then, the control device 90 applies negative pressure to an appropriate zone (X-axis in FIG. 16) based on the warpage of the lower wafer W2, and then applies positive pressure to other zones (Y-axis and diagonal directions in FIG. 16). As a result, the lower wafer W2 is held on the suction surface 300 of the first-stage deformation pattern with only the X-axis slightly stretched.

[0124] As shown in FIG. 16C , the control device 90 further deforms the suction surface 300 of the lower chuck 231 in the second stage. Hereinafter, the shape of the lower chuck 231 deformed after the lower wafer W2 is placed thereon is referred to as the second-stage deformation pattern. When the second-stage deformation pattern is performed, the lower chuck 231 continues to apply negative and positive pressure. As a result, the lower wafer W2 expands more in the X-axis direction and less in the Y-axis direction. However, the amount of expansion can be reduced when the lower wafer W2 is transformed from the first-stage deformation pattern to the second-stage deformation pattern compared to when the lower wafer W2 is transformed to the second-stage deformation pattern in one step. Therefore, the lower chuck 231 can easily adjust the amount of expansion at the desired location on the lower wafer W2.

[0125] 16(D), the control device 90 fixes the entire lower wafer W2 by applying negative pressure to the lower wafer W2 in all of the zones of the suction surface 300 while continuing the second-stage deformation pattern. Then, in this state, the bonding device 1 bonds the upper wafer W1 and the lower wafer W2, thereby enabling the reference point of the upper wafer W1 and the reference point of the lower wafer W2 to be accurately aligned.

[0126] In this way, in the second embodiment, the movement amount of the reference point of the lower wafer W2 can be controlled with greater precision by gradually deforming the lower chuck 231. Therefore, the bonding apparatus 1 and the substrate mounting method can bond the upper wafer W1 and the lower wafer W2 while sufficiently suppressing misalignment between them.

[0127] 17(A) to 17(D), a bonding apparatus 1A and a substrate mounting method according to a third embodiment differ from the bonding apparatus 1 and the substrate mounting method described above in that both negative pressure and positive pressure are applied to the lower wafer W2 without deforming the chucking surface 300 of the lower chuck 231. For example, when the bonding surface W2j of the lower wafer W2 is significantly elongated in the X-axis direction (large amount of warpage), the bonding apparatus 1 holds the lower wafer W2 in the procedure shown in FIGS.

[0128] Specifically, after the lower wafer W2 is placed, the control device 90 controls the pressure generating unit 310 to apply negative pressure only to ch1 (central region A) to suction the vicinity of the center of the lower wafer W2, as shown in FIG. 17A. Thereafter, the pressure generating unit 310 applies positive pressure to ch2, ch5, and ch6, which are the X-axis. As a result, the lower wafer W2 is slightly lifted from the suction surface 300 along the X-axis that sandwiches the vicinity of the center. An inward contracting force is applied to the X-axis of the bonding surface W2j of the lower wafer W2.

[0129] 17B, ​​the pressure generating unit 310 applies negative pressure to ch3. At this time, stress is applied to the bonding surface W2j of the lower wafer W2 in a direction that expands the Y-axis side due to a contracting force on the X-axis side, and the bonding surface W2j is attracted while expanding along the Y-axis.

[0130] 17C, the pressure generating unit 310 applies negative pressure to ch7 and ch8. As a result, the bonding surface W2j of the lower wafer W2 is attracted to the wafer W2 while being stretched further on the outer edge side of the Y-axis.

[0131] 17(D), the pressure generating unit 310 stops applying the positive pressure and applies a negative pressure to the entire suction surface 300 to suction the lower wafer W2. With the lower wafer W2 fixed, each reference point on the bonding surface W2j is adjusted to an appropriate position according to the extension of the Y-axis and the contraction of the X-axis. This makes it possible to precisely align the reference points on the upper wafer W1 and the lower wafer W2.

[0132] In this way, also in the third embodiment, the bonding apparatus 1 and the substrate mounting method make it possible to move the reference point of the bonding surface W2j of the lower wafer W2, thereby improving the stress distribution of the lower wafer W2 and enabling the lower wafer W2 to be held appropriately.

[0133] 18 , a bonding apparatus 1A according to a fourth embodiment differs from the above-described bonding apparatus 1 in that it measures the warpage or bonding accuracy of the bonded wafers T after bonding and feeds back the measured results. For example, a control device 90 of the bonding apparatus 1A measures the warpage of the upper wafer W1 and the lower wafer W2 before bonding using a warpage measurement device 5, predicts the amount of deviation of a reference point on the bonded wafer T, and calculates the extension direction (or contraction direction) and extension amount (or contraction amount) of the lower wafer W2. Furthermore, the control device 90 performs feedforward control to set the application of negative pressure and positive pressure by the lower chuck 231 and the deformation amount of the lower chuck 231, based on the extension direction and extension amount of the lower wafer W2.

[0134] In addition to the above feedforward control, the bonding apparatus 1A measures the warpage or bonding accuracy of the bonded wafer T and feeds back the actual amount of deviation relative to the predicted amount of deviation of the reference point. This allows the control device 90 to effectively correct the negative and positive pressures applied by the lower chuck 231 and the amount of deformation of the lower chuck 231 based on the warpage or bonding accuracy of the bonded wafer T. As a result, the bonding apparatus 1 can bond the upper wafer W1 and the lower wafer W2 with even greater accuracy.

[0135] The bonding apparatus 1 and the substrate mounting 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 spirit and scope of the appended claims. The features described in the above embodiments can be configured differently within a consistent range, and can be combined within a consistent range.

[0136] This application claims priority from Japanese Patent Application No. 2024-135086, filed on August 13, 2024, with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0137] 1 Bonding device 231 Lower chuck 300 Suction surface 310 Pressure generating section A Central region B Outer region W1 Upper wafer W2 Lower wafer

Claims

1. A substrate processing apparatus comprising a holding unit having an adsorption surface for adsorbing a substrate, the holding unit having a circular central region and an annular outer region located outside the central region, wherein the adsorption surface defines a plurality of zones in the central region and in regions obtained by dividing the outer region circumferentially, and further comprising a pressure generating unit for generating pressure in each of the plurality of zones, wherein the pressure generating unit applies positive pressure to at least one of the plurality of zones to which the negative pressure is not applied when the substrate is placed on the adsorption surface and negative pressure is applied to at least one of the plurality of zones.

2. The substrate processing apparatus of claim 1, wherein the pressure generating unit applies the negative pressure to one of the zones facing the first axis and the zones facing the second axis among the plurality of zones based on the amount of warping of the substrate along a first axis and the amount of warping of the substrate along a second axis perpendicular to the first axis, and applies the positive pressure to the zones facing the first axis and the zones facing the second axis to which the negative pressure is not applied.

3. The substrate processing apparatus of claim 2, wherein the pressure generating unit applies the negative pressure to a zone facing either the first axis or the second axis, whichever has the greater amount of warping, and applies the positive pressure to a zone facing either the first axis or the second axis, whichever has the smaller amount of warping.

4. The substrate processing apparatus according to claim 2, wherein the pressure generating unit applies the positive pressure to zones of the substrate that are diagonally opposed to each other between the first axis and the second axis.

5. A substrate processing apparatus according to any one of claims 1 to 4, wherein the pressure generating unit applies the negative pressure and the positive pressure to zones set based on the warpage state of the substrate measured by a measuring unit that detects the warpage state of the substrate.

6. A substrate processing apparatus as described in any one of claims 1 to 4, further comprising a deformation section that displaces the central region relative to the outer edge of the holding section to deform the suction surface, and the deformation section deforms the suction surface while both the negative pressure and the positive pressure are applied to the multiple zones by the pressure generating section.

7. The substrate processing apparatus according to claim 6, wherein the pressure generating unit deforms the suction surface and then applies the negative pressure to all of the plurality of zones to suction the substrate onto the suction surface.

8. The substrate processing apparatus according to claim 6, wherein the deformation unit deforms the suction surface by an amount of deformation that is set based on the warpage of the substrate measured by a measurement unit that detects the warpage of the substrate.

9. The substrate processing apparatus according to claim 6, wherein the deformation unit deforms the suction surface by a first stage before placing the substrate on the suction surface, and deforms the suction surface to a greater extent than the first stage while the pressure generating unit applies the negative pressure and the positive pressure to the substrate placed on the suction surface.

10. A substrate processing apparatus according to any one of claims 1 to 4, wherein the pressure generating unit applies the negative pressure to the central region to adsorb the substrate, while applying the positive pressure to a portion of the zone of the outer region, and then applies the negative pressure to another portion of the zone of the outer region.

11. A substrate processing apparatus as claimed in any one of claims 1 to 4, comprising an upper holding part that is provided vertically above the holding part and holds a first substrate, the holding part holds the substrate, which is a second substrate, and the pressure generating part applies the negative pressure and the positive pressure to the second substrate, and then bonds the first substrate and the second substrate together.

12. A substrate mounting method for a substrate processing apparatus having a holding part with an adsorption surface that adsorbs a substrate, the holding part having a circular central region and an annular outer region located outside the central region, wherein the adsorption surface has a plurality of zones set in regions that circumferentially divide the outer region and in the central region, the substrate mounting method comprising: (A) a step of placing the substrate on the adsorption surface; and (B) after step (A), a step of applying a positive pressure to at least one of the plurality of zones to which the negative pressure is not being applied, while applying a negative pressure to at least one of the plurality of zones by a pressure generating part.

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