Joining device and joining method

Abstract

A joining device (41) according to one embodiment of the present disclosure joins a first substrate (W1) and a second substrate (W2). The joining device comprises a first holding unit (230), a second holding unit (231), imaging units (235, 236), and a control unit (71). The first holding unit holds the first substrate. The second holding unit holds the second substrate. The imaging units capture images of the first substrate that is held by the first holding unit or the second substrate that is held by the second holding unit. The control unit selects, from an image (A) captured by the imaging units, a target region (B) that includes an alignment mark (M) provided on at least one of the first substrate and the second substrate. Then, the control unit sets a gamma value that is used for gamma correction of the image, on the basis of grayscale value information related to the grayscale value of the selected target region.

Description

Bonding device and bonding method

[0001] The present disclosure relates to a bonding apparatus and a bonding method.

[0002] 2. Description of the Related Art Conventionally, a bonding apparatus has been known that aligns substrates such as semiconductor wafers and bonds the aligned substrates together (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-194865

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

[0005] A bonding device according to one aspect of the present disclosure bonds a first substrate and a second substrate. The bonding device includes a first holding unit, a second holding unit, an imaging unit, and a control unit. The first holding unit holds the first substrate. The second holding unit holds the second substrate. The imaging unit images the first substrate held by the first holding unit or the second substrate held by the second holding unit. The control unit selects a target area including an alignment mark provided on at least one of the first substrate and the second substrate from the image captured by the imaging unit. The control unit then sets a gamma value used for gamma correction of the image based on grayscale value information regarding the grayscale value of the selected target area.

[0006] According to the present disclosure, it is possible to improve the alignment accuracy when bonding substrates.

[0007] FIG. 1 is a schematic plan view showing the configuration of a bonding system according to the first embodiment. FIG. 2 is a schematic view showing a state before bonding of a first substrate and a second substrate according to the first embodiment. FIG. 3 is a schematic plan view showing the configuration of a bonding apparatus according to the first embodiment. FIG. 4 is a schematic side view showing the configuration of the bonding apparatus according to the first embodiment. FIG. 5 is a schematic view showing an upper chuck and a lower chuck according to the first embodiment. FIG. 6 is a block diagram showing the configuration of a control device according to the first embodiment. FIG. 7 is a flowchart showing the procedure of a process executed by the bonding system according to the first embodiment. FIG. 8 is a flowchart showing an example of a specific procedure for aligning a first substrate and a second substrate. FIG. 9 is a schematic diagram showing an example of operation of the bonding system according to the first embodiment. FIG. 10 is a schematic diagram showing an example of operation of the bonding system according to the first embodiment. FIG. 11 is a schematic diagram showing an example of operation of the bonding system according to the first embodiment. FIG. 12 is a schematic diagram showing an example of operation of the bonding system according to the first embodiment. FIG. 13 is a schematic explanatory diagram for explaining gamma correction. FIG. 14 is a flowchart showing the procedure of a gamma value setting process according to the first embodiment. FIG. 15 is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 16 is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 17A is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 17B is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 17C is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 18 is an explanatory diagram illustrating the gamma value setting process according to the first embodiment. FIG. 19 is a flowchart showing the processing procedure for the gamma value setting process according to the second embodiment. FIG. 20A is an explanatory diagram illustrating the gamma value setting process according to the second embodiment. FIG. 20B is an explanatory diagram illustrating the gamma value setting process according to the second embodiment. FIG. 21 is a flowchart showing the processing procedure for the gamma value setting process according to the third embodiment. FIG. 22 is an explanatory diagram illustrating the gamma value setting process according to the third embodiment. FIG. 23 is a flowchart showing the processing procedure for the gamma value setting process according to the fourth embodiment.Fig. 24 is an explanatory diagram for explaining the gamma value setting process according to the fourth embodiment. Fig. 25 is an explanatory diagram for explaining the gamma value setting process according to the fourth embodiment.

[0008] Hereinafter, a detailed description will be given of a bonding apparatus and a bonding method according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments are designated by the same reference numerals, and redundant description will be omitted.

[0009] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0010] In the drawings referred to below, for ease of understanding, the X-axis, Y-axis, and Z-axis directions are defined as being orthogonal to each other, and an orthogonal coordinate system is shown in which the positive Z-axis direction is the vertically upward direction. The rotation direction around the vertical axis is also referred to as the θ direction.

[0011] In recent years, semiconductor devices have become increasingly highly integrated, and three-dimensional integration techniques for stacking semiconductor devices in three dimensions have been proposed. In these three-dimensional integration techniques, two semiconductor wafers (hereinafter referred to as "substrates") are bonded together using, for example, a bonding device. The bonding device bonds the first substrate and the second substrate together while holding the first substrate using a first holding part and the second substrate using a second holding part provided below the first holding part.

[0012] In the bonding apparatus, the first substrate and the second substrate are aligned (positioned) before being bonded together. The bonding apparatus according to the embodiment is configured to improve the accuracy of alignment when bonding the first substrate and the second substrate together.

[0013] First Embodiment <Configuration of Bonding System> First, the configuration of a bonding system including a bonding device according to a first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic plan view showing the configuration of the bonding system according to the first embodiment. Fig. 2 is a schematic view showing a state before bonding of a first substrate and a second substrate according to the first embodiment.

[0014] The bonding system 1 shown in FIG. 1 forms a laminated substrate T by bonding a first substrate W1 and a second substrate W2 together (see FIG. 2).

[0015] The first substrate W1 and the second substrate W2 are single crystal silicon wafers having a plurality of electronic circuits formed on their surfaces. The first substrate W1 and the second substrate W2 have approximately the same diameter. Note that one of the first substrate W1 and the second substrate W2 may be a substrate on which no electronic circuits are formed.

[0016] 2, of the surfaces of the first substrate W1, the surface that is bonded to the second substrate W2 will be referred to as a "bonding surface W1j," and the surface opposite the bonding surface W1j will be referred to as a "non-bonding surface W1n." Also, of the surfaces of the second substrate W2, the surface that is bonded to the first substrate W1 will be referred to as a "bonding surface W2j," and the surface opposite the bonding surface W2j will be referred to as a "non-bonding surface W2n."

[0017] 1, the bonding system 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are arranged in this order along the positive direction of the X-axis. The loading / unloading station 2 and the processing station 3 are also integrally connected.

[0018] The loading / unloading station 2 includes a mounting table 10 and a transport area 20. The mounting table 10 includes a plurality of mounting plates 11. Each mounting plate 11 is mounted with cassettes C1 to C4, each of which stores a plurality of substrates (e.g., 25 substrates) in a horizontal position. Cassette C1 can store a plurality of first substrates W1, cassette C2 can store a plurality of second substrates W2, and cassette C3 can store a plurality of superimposed substrates T. Cassette C4 is, for example, a cassette for recovering substrates that have developed defects. Note that the number of cassettes C1 to C4 placed on the mounting plate 11 is not limited to that shown in the figure.

[0019] The transport region 20 is disposed adjacent to the mounting table 10 on the positive side of the X axis. The transport region 20 is provided with a transport path 21 extending in the Y axis direction and a transport device 22 that is movable along the transport path 21. The transport device 22 is movable not only in the Y axis direction but also in the X axis direction and is rotatable around the Z axis. The transport device 22 transports the first substrate W1, the second substrate W2, and the laminated substrate T between the cassettes C1 to C4 placed on the mounting plate 11 and a third processing block G3 of the processing station 3, which will be described later.

[0020] Processing station 3 is provided with multiple processing blocks, e.g., three processing blocks G1, G2, and G3, each equipped with various devices. For example, a first processing block G1 is provided on the front side (negative Y-axis side in FIG. 1 ) of processing station 3, and a second processing block G2 is provided on the rear side (positive Y-axis side in FIG. 1 ) of processing station 3. Furthermore, a third processing block G3 is provided on the load / unload station 2 side of processing station 3 (negative X-axis side in FIG. 1 ).

[0021] The first processing block G1 is provided with a surface modification device 30 that modifies the bonding surfaces W1j, W2j of the first substrate W1 and the second substrate W2. The surface modification device 30 modifies the bonding surfaces W1j, W2j of the first substrate W1 and the second substrate W2 by breaking SiO bonds on the bonding surfaces W1j, W2j of the first substrate W1 and the second substrate W2 to form single-bonded SiO, thereby modifying the bonding surfaces W1j, W2j so that they are more easily hydrophilized thereafter.

[0022] The first processing block G1 also includes a surface hydrophilization device 40. The surface hydrophilization device 40 hydrophilizes the bonding surfaces W1j, W2j of the first substrate W1 and the second substrate W2 using, for example, pure water, and cleans the bonding surfaces W1j, W2j. Specifically, the surface hydrophilization device 40 supplies pure water onto the first substrate W1 or the second substrate W2 while rotating the first substrate W1 or the second substrate W2 held by, for example, a spin chuck. As a result, the pure water supplied onto the first substrate W1 or the second substrate W2 spreads over the bonding surfaces W1j, W2j of the first substrate W1 or the second substrate W2, thereby hydrophilizing the bonding surfaces W1j, W2j.

[0023] Here, an example is shown in which the surface modification device 30 and the surface hydrophilization device 40 are arranged side by side, but the surface hydrophilization device 40 may be stacked above or below the surface modification device 30.

[0024] The second processing block G2 also includes a bonding device 41. The bonding device 41 bonds the hydrophilized first substrate W1 and second substrate W2 together using intermolecular forces. Details of the bonding device 41 will be described later.

[0025] The third processing block G3 is provided with a transition (TRS) device (not shown) for the first substrate W1, the second substrate W2, and the overlapped substrate T. The third processing block G3 may also be provided with a platform for temporarily placing the first substrate W1 or the second substrate W2. The platform may be capable of placing multiple wafers (first substrate W1 or second substrate W2) on it.

[0026] 1 , a transfer region 60 is formed in an area surrounded by the first processing block G1, the second processing block G2, and the third processing block G3. A transfer device 61 is disposed in the transfer region 60. The transfer device 61 has a transfer arm that is movable, for example, vertically, horizontally, and about a vertical axis. The transfer device 61 moves within the transfer region 60 and transfers the first substrate W1, the second substrate W2, and the overlapped substrate T to given devices in the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the transfer region 60.

[0027] The bonding system 1 also includes a control device 70. The control device 70 controls the operation of the bonding system 1. The control device 70 is, for example, a computer, and includes a control unit 71 and a storage unit 72. The storage unit 71 includes a microcomputer having a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), input / output ports, and various circuits. The CPU of the microcomputer realizes the control described below by reading and executing a program stored in the ROM. The storage unit 72 is, for example, realized by a semiconductor memory element such as RAM or flash memory, or a storage device such as a hard disk or optical disk.

[0028] The program may be recorded on a computer-readable recording medium and installed from the recording medium into the storage unit 72 of the control device 70. Examples of computer-readable recording media include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnetic optical disk (MO), and a memory card.

[0029] <Configuration of joining device> Next, the configuration of the joining device 41 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic plan view showing the configuration of the joining device 41 according to the first embodiment. Fig. 4 is a schematic side view showing the configuration of the joining device 41 according to the first embodiment.

[0030] 3, the bonding apparatus 41 has a processing container 190 whose interior can be sealed. A loading / unloading port 191 for the first substrate W1, the second substrate W2, and the laminated substrate T is formed on a side surface of the processing container 190 on the transfer region 60 side, and an opening / closing shutter 192 is provided at the loading / unloading port 191.

[0031] The interior of the processing vessel 190 is partitioned into a transfer region T1 and a processing region T2 by an inner wall 193. The above-mentioned loading / unloading port 191 is formed on a side surface of the processing vessel 190 in the transfer region T1. In addition, a loading / unloading port 194 for the first substrate W1, the second substrate W2, and the laminated substrate T is also formed in the inner wall 193.

[0032] In the transfer region T1, a transition 200, a substrate transfer mechanism 201, a reversing mechanism 220, and a position adjustment mechanism 210 are arranged, for example, in this order from the loading / unloading port 191 side.

[0033] The transition 200 temporarily places the first substrate W1, the second substrate W2, and the overlapped substrate T. The transition 200 is formed, for example, in two stages, and can simultaneously place any two of the first substrate W1, the second substrate W2, and the overlapped substrate T.

[0034] The substrate transport mechanism 201 has a transport arm that is movable, for example, in the vertical direction (Z-axis direction), horizontal directions (Y-axis direction and X-axis direction), and directions around the vertical axis (θ direction). The substrate transport mechanism 201 is capable of transporting the first substrate W1, the second substrate W2, and the laminated substrate T within the transport region T1 or between the transport region T1 and the processing region T2.

[0035] The position adjustment mechanism 210 adjusts the horizontal orientation of the first substrate W1 and the second substrate W2. Specifically, the position adjustment mechanism 210 has a base 211 equipped with a holder (not shown) that holds and rotates the first substrate W1 and the second substrate W2, and a detector 212 that detects the positions of the notches in the first substrate W1 and the second substrate W2. The position adjustment mechanism 210 adjusts the positions of the notches by detecting the positions of the notches in the first substrate W1 and the second substrate W2 using the detector 212 while rotating the first substrate W1 and the second substrate W2 held on the base 211. This adjusts the horizontal orientation of the first substrate W1 and the second substrate W2.

[0036] The inversion mechanism 220 inverts the first substrate W1. Specifically, the inversion mechanism 220 has a holding arm 221 that holds the first substrate W1. The holding arm 221 extends in the horizontal direction (X-axis direction). In addition, the holding arm 221 is provided with holding members 222 that hold the first substrate W1 at, for example, four locations.

[0037] The holding arm 221 is supported by a drive unit 223 that includes, for example, a motor. The drive unit 223 allows the holding arm 221 to rotate about a horizontal axis. The holding arm 221 is also rotatable around the drive unit 223 and is also movable in the horizontal direction (X-axis direction). Another drive unit (not shown) that includes, for example, a motor is provided below the drive unit 223. This other drive unit allows the drive unit 223 to move vertically along a support column 224 that extends vertically.

[0038] In this way, the first substrate W1 held by the holding member 222 can be rotated around the horizontal axis and moved in the vertical and horizontal directions by the drive unit 223. Furthermore, the first substrate W1 held by the holding member 222 can rotate around the drive unit 223 and move between the position adjustment mechanism 210 and the upper chuck 230, which will be described later.

[0039] The processing region T2 is provided with an upper chuck 230 that suction-holds the upper surface (non-bonding surface W1n) of the first substrate W1 from above, and a lower chuck 231 that suction-holds the lower surface (non-bonding surface W2n) of the second substrate W2 from below. The lower chuck 231 is provided below the upper chuck 230 and is configured to be able to be positioned opposite the upper chuck 230. The upper chuck 230 and the lower chuck 231 are, for example, vacuum chucks. The upper chuck 230 is an example of a first holding unit that holds the first substrate W1, and the lower chuck 231 is an example of a second holding unit that holds the second substrate W2. The processing region T2 is an example of a region that accommodates the first holding unit, the second holding unit, imaging units (an upper imaging unit 235 and a lower imaging unit 236, described below), and an adjustment unit 256, described below.

[0040] 4, the upper chuck 230 is supported by a support member 270 provided above the upper chuck 230. The support member 270 is fixed to the ceiling surface of the processing vessel 190 via a plurality of support columns 271, for example.

[0041] An upper imaging unit 235 is provided on the side of the upper chuck 230 to capture an image of the upper surface (bonding surface W2j) of the second substrate W2 held by the lower chuck 231. A CCD camera, for example, is used for the upper imaging unit 235. The upper imaging unit 235 is an example of an imaging unit.

[0042] The lower chuck 231 is supported by a first moving unit 250 provided below the lower chuck 231. The first moving unit 250 moves the lower chuck 231 in the horizontal direction (X-axis direction), as will be described later. The first moving unit 250 is configured to be able to move the lower chuck 231 vertically and to rotate it around a vertical axis.

[0043] The first moving part 250 is provided with a lower imaging part 236 that images the lower surface (bonding surface W1j) of the first substrate W1 held by the upper chuck 230. The lower imaging part 236 is, for example, a CCD camera. The lower imaging part 236 is an example of an imaging part.

[0044] The first moving part 250 is attached to a pair of rails 252, 252. The pair of rails 252, 252 are provided on the underside of the first moving part 250 and extend in the horizontal direction (X-axis direction). The first moving part 250 is configured to be movable along the rails 252.

[0045] The pair of rails 252, 252 are disposed on a second moving part 253. The second moving part 253 is attached to a pair of rails 254, 254. The pair of rails 254, 254 are disposed on the lower surface of the second moving part 253 and extend in the horizontal direction (Y-axis direction). The second moving part 253 is configured to be movable in the horizontal direction (Y-axis direction) along the rails 254. The pair of rails 254, 254 are disposed on a mounting table 255 provided on the bottom surface of the processing vessel 190.

[0046] The first mover 250, the second mover 253, etc. constitute an adjustment unit 256. The adjustment unit 256 adjusts the horizontal position of the second substrate W2 held by the lower chuck 231 by moving the lower chuck 231 in the X-axis direction, the Y-axis direction, and the θ direction. The bonding device 41 uses the adjustment unit 256 to adjust the horizontal positions of the first substrate W1 held by the upper chuck 230 and the second substrate W2 held by the lower chuck 231.

[0047] In addition, the adjustment unit 256 adjusts the vertical positions of the first substrate W1 held by the upper chuck 230 and the second substrate W2 held by the lower chuck 231 by moving the lower chuck 231 in the Z-axis direction.

[0048] Although the lower chuck 231 is moved in the X-axis direction, the Y-axis direction, and the θ-direction here, the adjustment unit 256 may, for example, move the lower chuck 231 in the X-axis direction and the Y-axis direction, and move the upper chuck 230 in the θ-direction. Also, although the lower chuck 231 is moved in the Z-axis direction here, the adjustment unit 256 may, for example, move the upper chuck 230 in the Z-axis direction.

[0049] Next, the configuration of the upper chuck 230 and the lower chuck 231 will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing the upper chuck 230 and the lower chuck 231 according to the first embodiment.

[0050] 5 , the upper chuck 230 has a main body 260. The main body 260 is supported by a support member 270. A through hole 266 is formed in the support member 270 and the main body 260, passing through the support member 270 and the main body 260 in the vertical direction. The position of the through hole 266 corresponds to the center of the first substrate W1 held by suction on the upper chuck 230. A pressing pin 281 of a striker 280 is inserted into the through hole 266.

[0051] The striker 280 is disposed on the upper surface of the support member 270, and includes a pressing pin 281, an actuator unit 282, and a linear motion mechanism 283. The pressing pin 281 is a cylindrical member that extends in the vertical direction, and is supported by the actuator unit 282.

[0052] The actuator unit 282 generates a constant pressure in a certain direction (vertically downward in this case) using air supplied from, for example, an electropneumatic regulator (not shown). The actuator unit 282 contacts the center of the first substrate W1 using the air supplied from the electropneumatic regulator, and is able to control the pressure load applied to the center of the first substrate W1. Furthermore, the tip of the actuator unit 282 is able to move up and down vertically by passing through the through-hole 266 using the air from the electropneumatic regulator.

[0053] The actuator section 282 is supported by a linear motion mechanism 283. The linear motion mechanism 283 moves the actuator section 282 in the vertical direction by means of a drive section incorporating a motor, for example.

[0054] The striker 280 is configured as described above, and controls the movement of the actuator part 282 by the linear motion mechanism 283, and controls the pressing load on the first substrate W1 by the pressing pin 281 by the actuator part 282. In this way, the striker 280 presses the center of the first substrate W1 held by suction on the upper chuck 230, bringing it into contact with the second substrate W2.

[0055] A plurality of pins 261 that come into contact with the upper surface (non-bonding surface W1n) of the first substrate W1 are provided on the lower surface of the main body 260. The pins 261 have a diameter of, for example, 0.1 mm to 1 mm and a height of several tens of μm to several hundreds of μm. The pins 261 are evenly arranged at intervals of, for example, 2 mm.

[0056] The upper chuck 230 has a plurality of suction portions for suctioning the first substrate W1 in a portion of the region where the plurality of pins 261 are provided. Specifically, a plurality of outer suction portions 262 and a plurality of inner suction portions 263 for suctioning and holding the first substrate W1 are provided on the lower surface of the main body portion 260 of the upper chuck 230. The plurality of outer suction portions 262 and the plurality of inner suction portions 263 have suction regions that are arc-shaped or annular in plan view. The plurality of outer suction portions 262 and the plurality of inner suction portions 263 have the same height as the pins 261.

[0057] The plurality of outer suction portions 262 are arranged on the outer periphery of the main body portion 260. The plurality of outer suction portions 262 are connected to a suction device (not shown) such as a vacuum pump, and suck and hold the outer periphery of the first substrate W1.

[0058] The multiple inner suction portions 263 are arranged side by side in the circumferential direction, radially inward of the main body portion 260 from the multiple outer suction portions 262. The multiple inner suction portions 263 are connected to suction devices (not shown), such as multiple vacuum pumps, and suck and hold the region between the outer periphery and center of the first substrate W1.

[0059] The lower chuck 231 has a main body 290 having a diameter equal to or larger than that of the second substrate W2. Here, the lower chuck 231 having a diameter larger than that of the second substrate W2 is shown. The upper surface of the main body 290 is an opposing surface that faces the lower surface (non-bonding surface W2n) of the second substrate W2.

[0060] A plurality of pins 291 that come into contact with the lower surface (non-bonding surface W2n) of the second substrate W2 are provided on the upper surface of the main body 290. The pins 291 have a diameter of, for example, 0.1 mm to 1 mm and a height of several tens of μm to several hundreds of μm. The pins 291 are evenly arranged at intervals of, for example, 2 mm.

[0061] Furthermore, a lower rib 292 is provided in an annular shape on the upper surface of the main body 290, outside the multiple pins 291. The lower rib 292 is formed in an annular shape near the outer circumferential edge of the second substrate W2, and supports the outer periphery of the second substrate W2 over the entire periphery.

[0062] The main body 290 also has a plurality of lower suction ports 293. The plurality of lower suction ports 293 are provided in a suction region surrounded by the lower ribs 292. The plurality of lower suction ports 293 are connected to a suction device (not shown), such as a vacuum pump, via a suction pipe (not shown).

[0063] The lower chuck 231 depressurizes the suction region surrounded by the lower ribs 292 by sucking the suction region through the plurality of lower suction ports 293. As a result, the second substrate W2 placed in the suction region is sucked and held by the lower chuck 231.

[0064] Because the lower ribs 292 support the entire outer periphery of the lower surface of the second substrate W2, the second substrate W2 is properly sucked up to near the outer periphery. This allows the entire surface of the second substrate W2 to be suction-held. Furthermore, because the lower surface of the second substrate W2 is supported by multiple pins 291, the second substrate W2 can be easily peeled off from the lower chuck 231 when the suction of the second substrate W2 is released.

[0065] <Configuration of Control Device> Next, the configuration of the control device 70 according to the first embodiment will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the configuration of the control device 70 according to the first embodiment. As shown in Fig. 6, the control device 70 includes a control unit 71 and a storage unit 72. The control device 70 is communicably connected to an upper imaging unit 235, a lower imaging unit 236, an adjustment unit 256, and the like.

[0066] In addition to the functional units shown in FIG. 6, the control device 70 may also have various functional units that known computers have, such as various input devices and audio output devices.

[0067] The control unit 71 is realized by, for example, a CPU, an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), or the like executing a program stored in the storage unit 72 using the RAM as a working area.

[0068] The control unit 71 may also be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0069] The control unit 71 includes an image capture processing unit 71a, an adjustment processing unit 71b, and a setting unit 71c. The image capture processing unit 71a, the adjustment processing unit 71b, and the setting unit 71c will be described later.

[0070] The storage unit 72 stores information used in processing by the control unit 71. For example, the storage unit 72 stores various information such as region information 72a, gray value information 72b, and gamma value information 72c. Details of the region information 72a, gray value information 72b, and gamma value information 72c will be described later.

[0071] <Specific Operation of Bonding System> Next, specific operation of the bonding system 1 according to the first embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the procedure of processing executed by the bonding system 1 according to the first embodiment. The various processes shown in Fig. 7 are executed based on control by the control device 70.

[0072] First, a cassette C1 containing a plurality of first substrates W1, a cassette C2 containing a plurality of second substrates W2, and an empty cassette C3 are placed on a predetermined loading plate 11 in the load / unload station 2. Then, the first substrates W1 in the cassette C1 are removed by the transport device 22 and transported to a transition device arranged in the third processing block G3.

[0073] Next, the first substrate W1 is transported by the transport device 61 to the surface modification device 30 in the first processing block G1. In the surface modification device 30, oxygen gas, which is a processing gas, is excited into plasma and ionized in a predetermined reduced-pressure atmosphere. The oxygen ions are irradiated onto the bonding surface of the first substrate W1, and the bonding surface is plasma-processed. This modifies the bonding surface of the first substrate W1 (step S101).

[0074] Next, the first substrate W1 is transported by the transport device 61 to the surface hydrophilization device 40 in the first processing block G1. In the surface hydrophilization device 40, pure water is supplied onto the first substrate W1 while the first substrate W1 held by the spin chuck is being rotated. This makes the bonding surface W1j of the first substrate W1 hydrophilic. The bonding surface W1j of the first substrate W1 is also cleaned with the pure water (step S102).

[0075] Next, the first substrate W1 is transported to the bonding device 41 in the second processing block G2 by the transport device 61. After being loaded into the bonding device 41, the first substrate W1 is transported to the position adjustment mechanism 210 via the transition 200, and its horizontal orientation is adjusted by the position adjustment mechanism 210 (step S103).

[0076] Thereafter, the first substrate W1 is transferred from the position adjustment mechanism 210 to the inversion mechanism 220, and the front and back surfaces of the first substrate W1 are inverted by the inversion mechanism 220 (step S104). Specifically, the bonding surface W1j of the first substrate W1 faces downward. Next, the first substrate W1 is transferred from the inversion mechanism 220 to the upper chuck 230, and the first substrate W1 is held by suction by the upper chuck 230 (step S105).

[0077] The processing of the second substrate W2 overlaps with the processing of steps S101 to S105 for the first substrate W1. First, the transport device 22 removes the second substrate W2 from the cassette C2 and transports it to the transition device arranged in the third processing block G3.

[0078] Next, the second substrate W2 is transported by the transport device 61 to the surface modification device 30, where the bonding surface W2j of the second substrate W2 is modified (step S106). Thereafter, the second substrate W2 is transported by the transport device 61 to the surface hydrophilization device 40, where the bonding surface W2j of the second substrate W2 is hydrophilized and cleaned (step S107).

[0079] Thereafter, the second substrate W2 is transported by the transport device 61 to the bonding device 41. The second substrate W2 that has been carried into the bonding device 41 is transported to the position adjustment mechanism 210 via the transition 200. Then, the horizontal orientation of the second substrate W2 is adjusted by the position adjustment mechanism 210 (step S108).

[0080] Thereafter, the second substrate W2 is transported to the lower chuck 231 and is sucked and held by the lower chuck 231 with the notch facing in a predetermined direction (step S109).

[0081] Next, the first substrate W1 held by the upper chuck 230 and the second substrate W2 held by the lower chuck 231 are aligned in the horizontal direction (step S110). That is, the first substrate W1 and the second substrate W2 are aligned. The details of step S110 will be described later.

[0082] Thereafter, the second substrate W2 is raised using the first moving part 250, and the first substrate W1 and the second substrate W2 are bonded together (step S111). Specifically, after the second substrate W2 is raised, the center of the first substrate W1 is pressed downward using the pressing pin 281 of the striker 280 to bring it into contact with the center of the second substrate W2, thereby bonding the first substrate W1 and the second substrate W2. More specifically, because the bonding surface W1j of the first substrate W1 and the bonding surface W2j of the second substrate W2 have been modified, van der Waals forces (intermolecular forces) are first generated between the bonding surfaces W1j and W2j, and the bonding surfaces W1j and W2j are bonded together. Furthermore, since the bonding surface W1j of the first substrate W1 and the bonding surface W2j of the second substrate W2 are hydrophilized, hydrophilic groups between the bonding surfaces W1j and W2j form hydrogen bonds, thereby firmly bonding the bonding surfaces W1j and W2j together. By bonding the bonding surface W1j of the first substrate W1 and the bonding surface W2j of the second substrate W2 in this manner, a laminated substrate T is formed.

[0083] Next, an example of a specific procedure for aligning the first substrate W1 and the second substrate W2 in the horizontal direction in step S110 will be described with reference to Figures 8 to 12. Figure 8 is a flowchart showing an example of a specific procedure for the process shown in step S110, i.e., the process for aligning the first substrate W1 and the second substrate W2. Figures 9 to 12 are schematic diagrams showing an example of the operation of the bonding system 1 according to the first embodiment.

[0084] 8, the control unit 71 functions as an imaging processing unit 71a and performs imaging processing (step S201). In the imaging processing, the control unit 71 uses the upper imaging unit 235 and the lower imaging unit 236 to capture images of the first substrate W1 and the second substrate W2.

[0085] 9 , the control unit 71 first causes the first moving unit 250 and the second moving unit 253 to move the lower chuck 231 in the horizontal direction so that the lower imaging unit 236 is positioned substantially below the upper imaging unit 235. Then, the control unit 71 confirms a target X common to the upper imaging unit 235 and the lower imaging unit 236, and adjusts the horizontal position of the lower imaging unit 236 so that the horizontal positions of the origins of the upper imaging unit 235 and the lower imaging unit 236 coincide. This allows the control unit 71 to confirm the origin positions of the upper imaging unit 235 and the lower imaging unit 236.

[0086] 10 , the control unit 71 moves the lower chuck 231 vertically upward using the first moving unit 250, and then moves the lower chuck 231 horizontally using the first moving unit 250 and the second moving unit 253. Then, the control unit 71 uses the upper imaging unit 235 to capture an image of the second substrate W2 held by the lower chuck 231. For example, the control unit 71 captures an image of the alignment mark M2 provided at the center position of the second substrate W2 and the vicinity of the alignment mark M2.

[0087] The alignment mark M2 may be any mark formed on the second substrate W2 and may be set arbitrarily. For example, the alignment mark M2 may be a characteristic portion of a scribe line (for example, a portion where the scribe lines intersect (a cross portion)) when dividing the laminated substrate T including the second substrate W2 into chips, or may be an alignment mark provided on the second substrate W2. The position at which the alignment mark M2 is provided is merely an example and is not limited thereto. Although an example in which there is one alignment mark M2 is shown in FIG. 10 and other figures, the present invention is not limited thereto and there may be multiple alignment marks M2.

[0088] The upper imaging unit 235 is provided with an upper illumination unit 235a that irradiates illumination light toward the second substrate W2 when imaging the second substrate W2. The upper illumination unit 235a irradiates white light as illumination light. Therefore, the upper imaging unit 235 images the second substrate W2 irradiated with white light.

[0089] 11 , the control unit 71 uses the lower imaging unit 236 to capture an image of the first substrate W1 held by the upper chuck 230. For example, the control unit 71 captures an image of the alignment mark M1 provided at the center position of the first substrate W1 and the vicinity of the alignment mark M1.

[0090] The alignment mark M1 may be any mark formed on the first substrate W1 and may be set arbitrarily. For example, the alignment mark M1 may be a characteristic portion of a scribe line (for example, a portion where the scribe lines intersect (a cross portion)) when dividing the laminated substrate T including the first substrate W1 into chips, or may be an alignment mark provided on the first substrate W1. The position at which the alignment mark M1 is provided is merely an example and is not limited thereto. Although an example in which there is one alignment mark M1 is shown in FIG. 11 and other figures, the present invention is not limited thereto and there may be multiple alignment marks M1.

[0091] The lower imaging unit 236 is provided with a lower illumination unit 236a that irradiates illumination light toward the first substrate W1 when imaging the first substrate W1. The lower illumination unit 236a irradiates white light as illumination light. Therefore, the lower imaging unit 236 images the first substrate W1 irradiated with white light.

[0092] Next, the control unit 71 functions as the imaging processing unit 71a and performs a correction process (step S202). The correction process is a process of performing gamma correction on the images captured by the upper imaging unit 235 and the lower imaging unit 236 to convert the captured images into images with high contrast. Such gamma correction is performed by the upper imaging unit 235 and the lower imaging unit 236, respectively, in response to a correction control command from the control unit 71, but is not limited to this. In other words, the control unit 71 may be configured to acquire the images captured by the upper imaging unit 235 and the lower imaging unit 236 and perform gamma correction on the acquired images. Details of gamma correction will be described later.

[0093] Next, the control unit 71 functions as an adjustment processing unit 71b and performs an adjustment process (step S203). In the adjustment process, the control unit 71 analyzes the images (more precisely, the images after gamma correction) captured by the upper imaging unit 235 and the lower imaging unit 236 to detect the alignment mark M1 on the first substrate W1 and the alignment mark M2 on the second substrate W2. Then, as shown in FIG. 12 , the control unit 71 adjusts the horizontal position of the second substrate W2 so that the detected alignment mark M1 on the first substrate W1 coincides with the alignment mark M2 on the second substrate W2. In other words, the control unit 71 controls the adjustment unit 256 to adjust the horizontal position of the second substrate W2 to a bonding position where the first substrate W1 and the second substrate W2 are bonded. This completes the alignment (positioning) of the first substrate W1 and the second substrate W2, and the first substrate W1 and the second substrate W2 are bonded together.

[0094] <Regarding Gamma Correction> Details of gamma correction will now be described with reference to FIG. 13. FIG. 13 is a schematic diagram illustrating gamma correction. In FIG. 13, an image A captured by the imaging unit (upper imaging unit 235 or lower imaging unit 236) is shown on the left, and a gamma-corrected image A1 is shown on the right. Note that, hereinafter, alignment marks M1 and M2 will be referred to collectively without distinction as "alignment mark M." Furthermore, the first substrate W1 and the second substrate W2 will be referred to collectively without distinction as "substrate W."

[0095] 13, image A captured by the imaging unit includes a substrate W provided with an alignment mark M. Such image A may have a relatively low contrast (for example, the difference between light and dark) depending on various conditions, such as the shooting conditions, such as ambient brightness, the performance of the imaging unit, and the color and shape of the alignment mark M. If the contrast of image A is low, for example, the boundary between the alignment mark M and parts other than the alignment mark M tends to become unclear, and as a result, it becomes difficult to detect the alignment mark M during image analysis.

[0096] Therefore, the control unit 71 according to this embodiment performs gamma correction on image A, converting it into image A1 with a relatively high contrast, as shown on the right side of Fig. 13. Increasing the contrast of image A1 in this way makes it easier to distinguish the boundary between the alignment mark M and the area other than the alignment mark M, and as a result, makes it easier to detect the alignment mark M during image analysis. Note that, for ease of understanding, Fig. 13 shows a state in which the contrast is low by adding dots of the same density to image A, and a state in which the contrast is high by adding dots of different densities to image A1.

[0097] Gamma correction is performed using the following equation (1): Output value = 255 × (input value / 255) ^ (γ) (1)

[0098] The "input value" in equation (1) is the grayscale value of the captured image A, in other words, the grayscale value before gamma correction. The "output value" in equation (1) is the grayscale value of image A1, in other words, the grayscale value after gamma correction. The grayscale value is a value that indicates a range from white to black, specifically, a value that indicates a range of shades of intermediate colors (gray colors) with white being 255 and black being 0. Hereinafter, the grayscale value may be referred to as a "gray value."

[0099] In equation (1), "γ" is a gamma value. The gamma value can be set to a value between 0.25 and 4, for example. When this gamma value changes, the output value in gamma correction changes (see FIGS. 17A to 17C , described later), and the contrast in image A1 also changes. Therefore, in order to make image A1 have as high a contrast as possible, it is necessary to set an appropriate gamma value according to the captured image A and perform gamma correction on image A using the set gamma value. In this embodiment, it is possible to set an appropriate gamma value according to the captured image A, and by performing gamma correction using this gamma value, the contrast in image A1 after gamma correction is made as high as possible. Therefore, in this embodiment, it becomes easier to detect alignment marks M during image analysis of image A1, and as a result, the accuracy of alignment (positioning) when bonding substrates W can be improved.

[0100] Here, the setting of the gamma value in the first embodiment will be described in detail with reference to Fig. 14 to Fig. 18. Fig. 14 is a flowchart showing the processing procedure for setting the gamma value according to the first embodiment. Fig. 15 to Fig. 18 are explanatory diagrams for explaining the processing for setting the gamma value according to the first embodiment.

[0101] The gamma value setting process is performed once, for example, when a certain type of substrate W is bonded for the first time (more precisely, when it is aligned for the first time). The control device 70 according to the first embodiment stores the set gamma value, and when the same type of substrate W is bonded after the substrate W has been bonded, that is, when the same type of substrate W is bonded for the second or subsequent time, the control device 70 performs gamma correction using the previously set and stored gamma value. The timing at which the gamma value setting process is performed is not limited to the above, and the gamma value setting process may be performed, for example, every time a substrate W is bonded (every time it is aligned).

[0102] The control unit 71 according to the first embodiment functions as a setting unit 71c (see FIG. 6) and performs a gamma value setting process. Specifically, as shown in FIG. 14, the control unit 71 selects a target region from an image A captured by the imaging unit (step S300). Specifically, as shown in FIG. 15, the control unit 71 acquires the image A captured by the imaging unit, and selects a target region B from the acquired image A that includes an alignment mark M provided on the substrate W.

[0103] More specifically, a template image indicating the shape of the alignment mark M included in the target area B is stored in advance in the area information 72a (see FIG. 6) of the storage unit 72. The control unit 71 reads out the template image from the area information 72a of the storage unit 72, and performs template matching processing using the image A captured by the imaging unit and the template image to select the target area B including the alignment mark M from the image A. Note that, although an example in which the target area B is selected by template matching processing has been shown above, the present invention is not limited to this, and the target area B may be selected by any other processing, or may be selected by a user instruction.

[0104] Next, the control unit 71 generates a histogram of gray values ​​in the selected target region B (step S301) and stores the generated histogram of gray values ​​as gray value information 72b (see FIG. 6 ) in the storage unit 72. Note that the histogram of gray values ​​is an example of gray value information (grayscale value information) regarding the gray values ​​of the target region B.

[0105] 16 is an explanatory diagram illustrating a gray value histogram. In FIG. 16, the histogram generated in step S301 before gamma correction is shown on the left, and the histogram after gamma correction using the set gamma value is shown on the right. In the gray value histogram, the horizontal axis represents the gray value (0 to 255) in the target region B, and the vertical axis represents the number of pixels having the corresponding gray value. In other words, the gray value histogram is a graph showing the distribution of gray values ​​in the target region B.

[0106] Next, the control unit 71 reads out a histogram of gray values ​​from the gray value information 72b in the storage unit 72, and calculates the most frequent gray value C in the histogram (step S302). In other words, the control unit 71 calculates the gray value with the largest number of pixels in the histogram as the most frequent gray value C.

[0107] Next, the control unit 71 sets a gamma value based on the calculated mode C (step S303). More specifically, the control unit 71 sets a gamma value that maximizes the slope of the output value relative to the input value in gamma correction for the calculated mode C. This gamma value setting process will be described with reference to FIGS. 17A to 17C.

[0108] 17A to 17C are graphs showing the relationship between input values ​​and output values ​​in gamma correction where the gamma values ​​shown in the figures are set. As an example, Fig. 17A is a graph of gamma correction where the gamma value is set to "4," Fig. 17B is a graph of gamma correction where the gamma value is set to "1," and Fig. 17C is a graph of gamma correction where the gamma value is set to "0.25." In the graphs shown in Fig. 17A to 17C, the horizontal axis represents the input gray value before gamma correction, and the vertical axis represents the output gray value after gamma correction.

[0109] As shown in FIGS. 17A to 17C, the slope of the output value relative to the input value at the most frequent gray value C is greatest in the gamma correction graph where the gamma value is set to "4" (see FIG. 17A). For this reason, the control unit 71 sets the gamma value used in the gamma correction to "4." More specifically, the control unit 71 calculates the slope at the most frequent gray value C for each predetermined value (in increments of the predetermined value) within the range of possible gamma values ​​(0.25 to 4). The predetermined value is set to an arbitrary value, such as 0.1 or 0.05. FIG. 18 is a graph showing the relationship between the gamma value and the calculated slope. Here, as shown in FIG. 18, the slope D of the output value relative to the input value in the gamma correction is greatest when the gamma value is 4, and therefore the control unit 71 sets the gamma value used in the gamma correction to "4."

[0110] The control unit 71 stores the gamma value set as described above as gamma value information 72c (see FIG. 6) in the storage unit 72. When performing gamma correction, the control unit 71 reads the gamma value from the gamma value information 72c in the storage unit 72, and performs gamma correction using the read gamma value (here, "4").

[0111] The histogram on the right side of Fig. 16 is a histogram after gamma correction using the gamma value "4" set as described above. In the histogram shown on the right side of Fig. 16, the grayscale values ​​output after gamma correction are distributed over a wider range than the histogram before gamma correction (see the left side of Fig. 16). More specifically, gray values ​​near the mode C before gamma correction are output as gray values ​​over a wider range through gamma correction using a gamma value of "4." This distribution (output) of gray values ​​over a wider range after gamma correction indicates that the contrast in image A1 after gamma correction is higher than that in image A before gamma correction (see Fig. 13).

[0112] In this way, the control unit 71 can set a gamma value that maximizes the slope of the output value relative to the input value in gamma correction at the most frequent gray value C, thereby setting an appropriate gamma value according to the captured image A. Furthermore, by setting an appropriate gamma value, the control unit 71 can make the post-gamma-correction image A1 an image with as high a contrast as possible.

[0113] As described above, the bonding apparatus 41 according to the first embodiment includes the upper chuck 230, the lower chuck 231, imaging units (the upper imaging unit 235 and the lower imaging unit 236), and the control unit 71. The upper chuck 230 holds the first substrate W1. The lower chuck 231 holds the second substrate W2. The imaging unit images the first substrate W1 held by the upper chuck 230 or the second substrate W2 held by the lower chuck 231. The control unit 71 selects a target region B from the image A captured by the imaging unit, the target region B including an alignment mark M provided on at least one of the first substrate W1 and the second substrate W2. The control unit 71 then sets a gamma value used for gamma correction for the image A based on grayscale value information related to the grayscale value of the selected target region B.

[0114] As a result, in the first embodiment, it is possible to set an appropriate gamma value according to the captured image A, and by performing gamma correction using such a gamma value, it is possible to make the contrast in the corrected image A1 as high as possible. Therefore, in the first embodiment, it becomes easier to detect the alignment mark M during image analysis of the image A1, and as a result, it is possible to improve the accuracy of alignment (positioning) when bonding the substrates W.

[0115] Furthermore, the control unit 71 according to the first embodiment generates a histogram of the grayscale values ​​in the target region B as grayscale value information, and sets a gamma value based on the generated histogram. More specifically, the control unit 71 according to the first embodiment calculates the most frequent value C of the grayscale values ​​in the histogram, and sets a gamma value at the calculated most frequent value C such that the slope of the output value relative to the input value in gamma correction is maximized.

[0116] As a result, in the first embodiment, it is possible to set a more appropriate gamma value according to the captured image A. Furthermore, in the first embodiment, gray values ​​near the mode C before gamma correction can be output as gray values ​​over a wide range by gamma correction using an appropriately set gamma value. Therefore, in the first embodiment, it is possible to reliably increase the contrast in the gamma-corrected image A1 compared to the image A before gamma correction.

[0117] The imaging units (upper imaging unit 235 and lower imaging unit 236) capture an image of the first substrate W1 or the second substrate W2 irradiated with white light, thereby enabling the imaging units to capture, as the image A before gamma correction, an image with higher contrast than when imaging the first substrate W1 or the second substrate W2 irradiated with another color.

[0118] More specifically, the illumination light irradiated onto the substrate W may be white light, red light, blue light, or the like. These white light, red light, and blue light have different wavelength ranges. Specifically, among white light, red light, and blue light, white light has the widest wavelength range. On the other hand, a transparent film such as an oxide film is formed on the substrate W. When the illumination light is irradiated onto such a transparent film, optical interference occurs, and depending on the degree of the influence of the optical interference, the contrast of the image A captured by the imaging unit may be reduced. In this embodiment, the substrate W is imaged by irradiating it with white light, which has the widest wavelength range. This allows the influence of optical interference on the transparent film to be averaged compared to when other colors such as red light and blue light are irradiated. In other words, the influence of optical interference can be suppressed. Because the influence of optical interference is suppressed in this way, the imaging unit can capture an image A before gamma correction with higher contrast than when imaging a substrate W irradiated with other colors (e.g., red light or blue light).

[0119] In the above, an example is shown in which white light is irradiated onto the first substrate W1 or the second substrate W2, but this is not limited to this, and other colors (for example, red light, blue light, etc.) may also be irradiated.

[0120] Second Embodiment Next, a description will be given of a joining device 41 according to a second embodiment. In the second embodiment, the gamma value is set by a method different from that in the first embodiment.

[0121] Here, the setting of the gamma value in the second embodiment will be described in detail with reference to Fig. 19, Fig. 20A, and Fig. 20B. Fig. 19 is a flowchart showing the processing procedure for setting the gamma value according to the second embodiment. Fig. 20A and Fig. 20B are explanatory diagrams for explaining the processing for setting the gamma value according to the second embodiment.

[0122] 19, the control unit 71 according to the second embodiment selects a target area from an image A captured by the imaging unit (step S400). The process of step S400 is the same as step S300, and therefore a detailed description thereof will be omitted.

[0123] Next, the control unit 71 selects a gamma value to be used in the current process from the range of possible gamma values ​​(0.25 to 4) (step S401). In step S401, the control unit 71 sequentially selects a gamma value for each predetermined value (in increments of a predetermined value) within the range of possible gamma values ​​(0.25 to 4). Note that the predetermined value is set to an arbitrary value, such as 0.1 or 0.05. As an example, if the control unit 71 selects "0.25" as the gamma value in the current process of step S401, it will select "0.3" as the gamma value in the next process of step S401.

[0124] Next, the control unit 71 performs gamma correction on image A using the selected gamma value, and generates a histogram of gray values ​​in the target region B of the gamma-corrected image A1 (step S402). The control unit 71 stores the generated histogram of gray values ​​in the storage unit 72 as gray value information 72b (see FIG. 6).

[0125] 20A and 20B are explanatory diagrams illustrating histograms of gray values ​​according to the second embodiment. Each of Fig. 20A and Fig. 20B shows a histogram of gray values ​​in a target region B of an image A1 that has undergone gamma correction using the gamma values ​​shown in the figures. As an example, Fig. 20A shows a histogram of gray values ​​when a gamma value of "0.8" is selected, and Fig. 20B shows a histogram of gray values ​​when a gamma value of "4" is selected.

[0126] Next, the control unit 71 reads the gray value histogram from the gray value information 72b in the storage unit 72 and calculates first gray values ​​(first grayscale values) C1a and C1b and second gray values ​​(second grayscale values) C2a and C2b (step S403). Specifically, the control unit 71 calculates the first gray values ​​C1a and C1b such that the cumulative frequency from the low gray value (i.e., 0) in the gray value histogram is a predetermined percentage. The control unit 71 also calculates the second gray values ​​C2a and C2b such that the cumulative frequency from the high gray value (i.e., 255) in the gray value histogram is a predetermined percentage. The predetermined percentage can be set to any value, e.g., 30%. The predetermined percentages used to calculate the first gray values ​​C1a and C1b and the predetermined percentages used to calculate the second gray values ​​C2a and C2b are the same, but are not limited to this and may be different values.

[0127] More specifically, if "0.8" is selected as the gamma value in the process of step S401, the control unit 71 calculates a first gray value C1a and a second gray value C2a in the histogram of gray values ​​when "0.8" is selected as the gamma value, as shown in Fig. 20A. Similarly, if "4" is selected as the gamma value in the process of step S401, the control unit 71 calculates a first gray value C1b and a second gray value C2b in the histogram of gray values ​​when "4" is selected as the gamma value, as shown in Fig. 20B.

[0128] Next, the control unit 71 calculates the differences Ea and Eb between the calculated first gray values ​​C1a and C1b and the second gray values ​​C2a and C2b (step S404). More specifically, if "0.8" is selected as the gamma value in the process of step S401, the control unit 71 calculates the difference Ea between the first gray value C1a and the second gray value C2a (see FIG. 20A). Similarly, if "4" is selected as the gamma value in the process of step S401, the control unit 71 calculates the difference Eb between the first gray value C1b and the second gray value C2b (see FIG. 20B).

[0129] Next, the control unit 71 determines whether or not all gamma values ​​have been selected (step S405). Specifically, the control unit 71 determines whether or not all possible gamma values ​​within the range (0.25 to 4) have been selected in the process of step S401. If the control unit 71 determines that all gamma values ​​have not been selected (No at step S405), the control unit 71 returns to the process of step S401.

[0130] On the other hand, if it is determined that all gamma values ​​have been selected (Yes at step S405), the control unit 71 sets a gamma value based on the difference between the first gray value and the second gray value calculated at step S404 (step S406). More specifically, the control unit 71 sets a gamma value that maximizes the difference between the calculated first gray value and the second gray value.

[0131] 20A and 20B, the difference Eb when the gamma value "4" is selected is larger than the difference Ea when the gamma value "0.8" is selected. Also, if the difference Eb when the gamma value "4" is selected is larger than the differences when other gamma values ​​are selected, i.e., is the largest, the control unit 71 sets the gamma value used for gamma correction to "4."

[0132] In the histogram after gamma correction using the gamma value "4" set as described above, as shown in Fig. 20B, the grayscale values ​​output after gamma correction are distributed over a wider range than in the histogram after gamma correction using a gamma value other than "4" (see Fig. 20A). The fact that the gray values ​​after gamma correction are distributed (output) over a wider range indicates that the contrast in the gamma-corrected image A1 is higher than that in the gamma-corrected image A1 using other gamma values.

[0133] In this way, the control unit 71 according to the second embodiment generates a histogram of gray values ​​in the target region B as grayscale value information, and sets a gamma value based on the generated histogram. In more detail, the control unit 71 according to the second embodiment calculates a first gray value in the histogram where the cumulative frequency from the low gray value side is a predetermined percentage, and a second gray value where the cumulative frequency from the high gray value side is a predetermined percentage, and sets a gamma value that maximizes the difference between the calculated first gray value and second gray value.

[0134] As a result, in the second embodiment, it is possible to set an appropriate gamma value according to the captured image A. Furthermore, by setting an appropriate gamma value, the control unit 71 can make the gamma-corrected image A1 an image with as high a contrast as possible. Therefore, in the second embodiment, it becomes easier to detect the alignment mark M during image analysis of the image A1, and as a result, it is possible to improve the accuracy of alignment (positioning) when bonding substrates W.

[0135] Third Embodiment Next, a joining device 41 according to a third embodiment will be described. In the third embodiment, the gamma value is set by a method different from that of the first and second embodiments.

[0136] Here, the setting of the gamma value in the third embodiment will be described in detail with reference to Fig. 21 and Fig. 22. Fig. 21 is a flowchart showing the processing procedure for setting the gamma value according to the third embodiment. Fig. 22 is an explanatory diagram for explaining the processing for setting the gamma value according to the third embodiment.

[0137] As shown in FIG. 21 , the control unit 71 according to the third embodiment selects a target region and other regions from image A captured by the imaging unit (step S500). Specifically, as shown in FIG. 22 , the control unit 71 selects a target region B1 including the alignment mark M and other regions B2 other than the alignment mark M from image A captured by the imaging unit. Note that in the processing of step S500, template images of the target region B1 and other regions B2 may be stored in advance in the region information 72a (see FIG. 6 ) of the storage unit 72, and the target region B1 and other regions B2 may be selected from image A by template matching processing, or the target region B1 and other regions B2 may be selected by a user instruction. Furthermore, the target region B1 and other regions B2 may be selected by processing other than template matching processing.

[0138] Next, the control unit 71 selects a gamma value to be used in this process from the range of possible gamma values ​​(0.25 to 4) (step S501). The process of step S501 is the same as step S401, so a description thereof will be omitted here.

[0139] Next, the control unit 71 performs gamma correction on image A using the selected gamma value and calculates gray values ​​of the target region B1 and other regions B2 of the gamma-corrected image A1 (step S502). Specifically, the control unit 71 calculates the average gray values ​​of the target region B1 and the other regions B2. The control unit 71 stores the calculated average gray values ​​of the target region B1 and the other regions B2 in the storage unit 72 as gray value information 72b (see FIG. 6 ). Note that, although the above example illustrates the control unit 71 calculating the average gray values ​​of the target region B1 and the other regions B2, the present invention is not limited to this. That is, the control unit 71 may calculate other values, such as the mode or median of the gray values, as the gray values ​​of the target region B1 and the other regions B2.

[0140] Next, the control unit 71 reads out the average gray values ​​of the target area B1 and the other area B2 from the gray value information 72b in the memory unit 72, and calculates the difference between the gray value of the target area B1 (more precisely, the average gray value) and the gray value of the other area B2 (more precisely, the average gray value) (step S503).

[0141] Next, the control unit 71 determines whether or not all gamma values ​​have been selected (step S504). Specifically, the control unit 71 determines whether or not all possible gamma values ​​within the range (0.25 to 4) have been selected in the processing of step S501. If the control unit 71 determines that all gamma values ​​have not been selected (step S504, No), the control unit 71 returns to the processing of step S501.

[0142] On the other hand, if it is determined that all gamma values ​​have been selected (step S504, Yes), the control unit 71 sets a gamma value based on the difference between the gray values ​​of the target region B1 and the gray values ​​of the other region B2 calculated in step S503 (step S505). Specifically, the control unit 71 sets a gamma value that maximizes the difference between the calculated gray values ​​of the target region B1 and the gray values ​​of the other region B2. Here, it is assumed that the difference between the gray values ​​of the target region B1 and the gray values ​​of the other region B2 is maximized in the gamma-corrected image A1 when a gamma value of "4" is selected. In this case, the control unit 71 sets the gamma value used for gamma correction to "4."

[0143] In image A1 after gamma correction using the gamma value "4" set as described above, the difference between the gray value of target area B1 and the gray value of other area B2 is the largest, so the contrast between alignment mark M and parts other than alignment mark M can be made higher than in image A1 after gamma correction using other gamma values.

[0144] In this way, the control unit 71 according to the third embodiment selects the target region B1 including the alignment mark M and the other region B2 other than the alignment mark M. The control unit 71 calculates the gray values ​​of the target region B1 and the other region B2 as grayscale value information. The control unit 71 then sets a gamma value that maximizes the difference between the calculated gray values ​​of the target region B1 and the other region B2.

[0145] As a result, in the third embodiment, it is possible to set an appropriate gamma value according to the captured image A. Furthermore, by setting an appropriate gamma value, the control unit 71 can make the gamma-corrected image A1 an image with as high a contrast as possible. Therefore, in the third embodiment, it becomes easier to detect the alignment mark M during image analysis of the image A1, and as a result, it is possible to improve the accuracy of alignment (positioning) when bonding substrates W.

[0146] Fourth Embodiment Next, a joining device 41 according to a fourth embodiment will be described. In the fourth embodiment, the gamma value setting method in the first to third embodiments can be selected, and the gamma value is set using the selected setting method. Note that, hereinafter, the gamma value setting method according to the first embodiment may be referred to as the "first setting method," the gamma value setting method according to the second embodiment as the "second setting method," and the gamma value setting method according to the third embodiment as the "third setting method."

[0147] Here, the setting of the gamma value in the fourth embodiment will be described in detail with reference to Fig. 23 to Fig. 25. Fig. 23 is a flowchart showing the processing procedure for setting the gamma value according to the fourth embodiment. Fig. 24 and Fig. 25 are explanatory diagrams for explaining the processing for setting the gamma value according to the fourth embodiment.

[0148] As shown in FIG. 23 , the control unit 71 according to the fourth embodiment selects a setting method from among the first to third setting methods (step S600). As an example of the process of selecting a setting method, the control unit 71 first generates a gamma-corrected image A1 using the gamma values ​​set by each of the first to third setting methods. That is, the control unit 71 generates a gamma-corrected image A1 using the first setting method, a gamma-corrected image A1 using the second setting method, and a gamma-corrected image A1 using the third setting method. The control unit 71 then displays and provides the three generated images A1 to the user, and selects the setting method corresponding to the image A1 that the user determines has the highest contrast as the setting method.

[0149] As another example of the process for selecting the setting method, the control unit 71 may analyze the distribution state of a histogram of gray values ​​in the target region B of the captured image A and select the setting method based on the analysis results. For example, as shown in Fig. 24, in the histogram of gray values, there may be a case where a gray value Fx different from the range F1 to F2 in which a wide distribution of gray values ​​is desired by gamma correction becomes the mode value. In such a case, the first setting method using the mode value cannot distribute the gray values ​​in the range F1 to F2 over a wide range by gamma correction, and therefore the control unit 71 selects the second setting method (or the third setting method) as the setting method.

[0150] 25, there may be cases where the gray values ​​are distributed evenly over a wide range G in a gray value histogram. In such cases, the second setting method using the difference between the first gray value and the second gray value may not be able to distribute the vicinity of the desired gray value over a wide range. Therefore, the control unit 71 selects the first setting method (or the third setting method) using the mode H as the setting method.

[0151] Although the above describes the process of selecting a setting method from the first to third setting methods, these are merely examples and are not limiting, and the setting method may be selected using any method.

[0152] Next, the control unit 71 sets the gamma value using the selected setting method (step S601). As a result, in the fourth embodiment, it is possible to set an appropriate gamma value using the setting method selected from the first to third setting methods.

[0153] In the fourth embodiment described above, an example has been shown in which a gamma value setting method is selected from among the first to third setting methods, but the present invention is not limited to this. That is, in the fourth embodiment, a setting method may be selected from among the first and second setting methods, or from among the first and third setting methods, or from among the second and third setting methods.

[0154] Although the above describes an example in which the alignment marks M are provided on both the first substrate W1 and the second substrate W2, the present invention is not limited to this, and the alignment marks M may be provided on one of the first substrate W1 and the second substrate W2. In other words, it is sufficient that the alignment marks M are provided on at least one of the first substrate W1 and the second substrate W2.

[0155] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0156] The present disclosure may also be configured as follows: (1) A bonding device for bonding a first substrate and a second substrate, comprising: a first holding unit that holds the first substrate; a second holding unit that holds the second substrate; an imaging unit that images the first substrate held by the first holding unit or the second substrate held by the second holding unit; and a control unit that selects a target area including an alignment mark provided on at least one of the first substrate and the second substrate from an image captured by the imaging unit, and sets a gamma value used for gamma correction of the image based on grayscale value information regarding the grayscale value of the selected target area. (2) The bonding device described in (1), wherein the control unit generates a histogram of the grayscale values ​​in the target area as the grayscale value information, and sets the gamma value based on the generated histogram. (3) The joining device according to (2), wherein the control unit calculates a mode of the grayscale values ​​in the histogram and sets the gamma value such that a gradient of an output value relative to an input value in the gamma correction is maximized at the calculated mode. (4) The joining device according to (2) or (3), wherein the control unit calculates a first grayscale value in the histogram at which a cumulative frequency from a low side of the grayscale values ​​is a predetermined percentage and a second grayscale value in the histogram at which a cumulative frequency from a high side of the grayscale values ​​is a predetermined percentage, and sets the gamma value such that a difference between the calculated first grayscale value and the second grayscale value is maximized. (5) The bonding device described in any one of (1) to (4), wherein the control unit selects the target area including the alignment mark and other areas other than the alignment mark from the image captured by the imaging unit, calculates the grayscale values ​​of the target area and the other areas as the grayscale value information, and sets the gamma value such that the difference between the calculated grayscale value of the target area and the grayscale value of the other areas is maximized.(6) The bonding device according to any one of (1) to (5), wherein the imaging unit images the first substrate or the second substrate irradiated with white light. (7) A bonding method for bonding a first substrate and a second substrate, comprising: a step of holding the first substrate using a first holding unit; a step of holding the second substrate using a second holding unit; a step of imaging the first substrate held by the first holding unit or the second substrate held by the second holding unit, using an imaging unit; and a control step of selecting a target area including an alignment mark provided on at least one of the first substrate and the second substrate from the image captured by the imaging unit, and setting a gamma value used for gamma correction for the image based on grayscale value information regarding the grayscale value of the selected target area.

[0157] REFERENCE SIGNS LIST 1 Bonding system 41 Bonding device 70 Control device 71 Control unit 71a Imaging processing unit 71b Adjustment processing unit 71c Setting unit 72 Memory unit 72a Area information 72b Gray value information 72c Gamma value information 230 Upper chuck 231 Lower chuck 235 Upper imaging unit 235a Upper irradiation unit 236 Lower imaging unit 236a Lower irradiation unit M, M1, M2 Alignment mark T Superposed substrate W1 First substrate W2 Second substrate

Claims

1. A bonding device for bonding a first substrate and a second substrate, comprising: a first holding unit that holds the first substrate; a second holding unit that holds the second substrate; an imaging unit that images the first substrate held by the first holding unit or the second substrate held by the second holding unit; and a control unit that selects a target area including an alignment mark provided on at least one of the first substrate and the second substrate from an image captured by the imaging unit, and sets a gamma value to be used for gamma correction of the image based on grayscale value information regarding the grayscale value of the selected target area.

2. The joining device according to claim 1, wherein the control unit generates a histogram of the grayscale values ​​in the target area as the grayscale value information, and sets the gamma value based on the generated histogram.

3. The joining device according to claim 2, wherein the control unit calculates the most frequent value of the grayscale values ​​in the histogram, and sets the gamma value at the calculated most frequent value such that the slope of the output value relative to the input value in the gamma correction is maximized.

4. The joining device according to claim 2, wherein the control unit calculates a first grayscale value in the histogram at which the cumulative frequency from the low side of the grayscale value is a predetermined percentage, and a second grayscale value at which the cumulative frequency from the high side of the grayscale value is a predetermined percentage, and sets the gamma value such that the difference between the calculated first grayscale value and the calculated second grayscale value is maximized.

5. The joining device of claim 1, wherein the control unit selects the target area including the alignment mark and other areas other than the alignment mark from the image captured by the imaging unit, calculates the grayscale values ​​of the target area and the other areas as the grayscale value information, and sets the gamma value such that the difference between the calculated grayscale value of the target area and the grayscale value of the other areas is maximized.

6. The bonding device according to claim 1, wherein the imaging unit captures an image of the first substrate or the second substrate irradiated with white light.

7. A method for bonding a first substrate and a second substrate, comprising: a step of holding the first substrate using a first holding unit; a step of holding the second substrate using a second holding unit; a step of capturing an image of the first substrate held by the first holding unit or the second substrate held by the second holding unit using an imaging unit; and a control step of selecting a target area including an alignment mark provided on at least one of the first substrate and the second substrate from the image captured by the imaging unit, and setting a gamma value used for gamma correction for the image based on grayscale value information regarding the grayscale value of the selected target area.

Images