Bonding device, bonding system, and bonding method

Abstract

Improves the accuracy of joining substrates together. [Solution] The bonding device includes a first holding unit, a second holding unit, a moving unit, an optical system, an adjustment unit, and a control unit. The first holding unit holds a first substrate. The second holding unit holds a second substrate. The moving unit moves one of the first holding unit and the second holding unit closer to the other. The optical system irradiates light onto the first substrate and the second substrate and captures images of alignment marks on the first substrate and the second substrate using reflected or transmitted light. The adjustment unit is located on the optical path of the optical system and adjusts the focal depth of the optical system. The control unit executes an approaching process and an imaging process. The approaching process controls the moving unit to bring one of the first holding unit and the second holding unit closer to the other. The imaging process controls the adjustment unit to adjust the focal depth of the optical system during the approaching process to position the first substrate and the second substrate within the focal depth of the optical system, and then images the alignment marks on the first substrate and the second substrate using the optical system.

Description

[Technical Field]

[0001] The present disclosure relates to a bonding device, a bonding system, and a bonding method. [Background technology]

[0002] BACKGROUND ART A bonding apparatus for bonding substrates such as semiconductor wafers together is known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 088094 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can improve the bonding accuracy between substrates. [Means for solving the problem]

[0005] A bonding device according to one aspect of the present disclosure includes a first holding unit, a second holding unit, a moving unit, an optical system, an adjusting unit, and a control unit. The first holding unit holds a first substrate. The second holding unit holds a second substrate to be bonded to the first substrate. The moving unit moves one of the first holding unit and the second holding unit closer to the other. The optical system irradiates light onto the first substrate held by the first holding unit and the second substrate held by the second holding unit, and captures images of alignment marks on the first substrate and the second substrate using reflected or transmitted light. The adjusting unit is located on the optical path of the optical system and adjusts the focal depth of the optical system. The control unit executes an approaching process and an imaging process. The approaching process controls the moving unit to move one of the first holding unit and the second holding unit closer to the other. During the approach process, the imaging process controls the adjustment unit to adjust the focal depth of the optical system to position the first substrate and the second substrate within the focal depth of the optical system, and then images the alignment marks on the first substrate and the second substrate using the optical system. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to improve the bonding accuracy between substrates. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view showing the configuration of a bonding system according to an embodiment. [Figure 2] FIG. 2 is a schematic side view of the upper wafer and the lower wafer according to the embodiment. [Figure 3] FIG. 3 is a schematic plan view showing the configuration of the joining device according to the embodiment. [Figure 4] FIG. 4 is a schematic side view showing the configuration of the joining device according to the embodiment. [Figure 5] FIG. 5 is a schematic diagram showing an upper chuck and a lower chuck according to the embodiment. [Figure 6] FIG. 6 is a diagram showing the configuration of an alignment mark imaging unit according to the embodiment. [Figure 7] FIG. 7 is a diagram showing an example of alignment marks provided on the upper wafer. [Figure 8] FIG. 8 is a diagram showing an example of alignment marks provided on the lower wafer. [Figure 9] FIG. 9 is a diagram showing an example of the arrangement of alignment marks and alignment mark imaging units. [Figure 10] FIG. 10 is a flowchart illustrating a procedure of a process executed by the joint system according to the embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of a specific procedure for the alignment process in step S110. [Figure 12] FIG. 12 is a diagram illustrating an example of the operation of the imaging process. [Figure 13] FIG. 13 is a diagram illustrating an example of the operation of the imaging process. [Figure 14] FIG. 14 is a diagram showing the configuration of an alignment mark imaging unit according to the first modification of the embodiment. [Figure 15] FIG. 15 is a diagram showing the configuration of an alignment mark imaging unit according to the second modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a detailed description will be given of a bonding apparatus, a bonding system, and a bonding method (hereinafter referred to as "embodiments") according to the present disclosure, with reference to the drawings. Note that the present disclosure is not limited to these embodiments. 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 errors and tolerances, such as manufacturing accuracy and installation accuracy.

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

[0011] (Embodiment) <Configuration of the joining system> First, the configuration of a bonding system 1 according to an 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 1 according to an embodiment. Fig. 2 is a schematic side view of an upper wafer W1 and a lower wafer W2 according to an embodiment.

[0012] The bonding system 1 shown in FIG. 1 forms a laminated wafer T by bonding a first substrate W1 and a second substrate W2 together.

[0013] The first substrate W1 and the second substrate W2 are semiconductor substrates such as silicon wafers or compound semiconductor wafers. The first substrate W1 and the second substrate W2 have approximately the same diameter. The first substrate W1 and the second substrate W2 have a disk shape with a diameter of approximately 300 mm, for example.

[0014] Hereinafter, the first substrate W1 will be referred to as the "upper wafer W1," and the second substrate W2 will be referred to as the "lower wafer W2." That is, the upper wafer W1 is an example of the first substrate, and the lower wafer W2 is an example of the second substrate. Furthermore, the upper wafer W1 and the lower wafer W2 may be collectively referred to as "wafer W."

[0015] 2, of the surfaces of the upper wafer W1, the surface that is bonded to the lower wafer 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 lower wafer W2, the surface that is bonded to the upper wafer 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."

[0016] 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 the positive direction of the X-axis in this order. The loading / unloading station 2 and the processing station 3 are also integrally connected.

[0017] 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 C1, C2, or C3, which stores a plurality of substrates (e.g., 25 substrates) in a horizontal position. For example, the cassette C1 stores an upper wafer W1, the cassette C2 stores a lower wafer W2, and the cassette C3 stores a laminated wafer T.

[0018] The transport area 20 is disposed adjacent to the mounting table 10 on the positive side of the X-axis. The transport area 20 is provided with a transport path 21 extending in the Y-axis direction and a transport device 22 movable along the transport path 21.

[0019] The transfer device 22 is movable not only in the Y-axis direction but also in the X-axis direction and rotatable around the Z-axis. The transfer device 22 transfers the upper wafer W1, the lower wafer W2, and the overlapped wafer T between the cassettes C1 to C3 placed on the mounting plate 11 and the third processing block G3 of the processing station 3, which will be described later.

[0020] The number of cassettes C1 to C3 placed on the placement plate 11 is not limited to that shown in the figure. In addition to the cassettes C1, C2, and C3, the placement plate 11 may also be placed with a cassette for recovering defective substrates.

[0021] Processing station 3 is provided with multiple processing blocks equipped with various devices, for example, three processing blocks G1, G2, and G3. For example, a first processing block G1 is provided on the front side of processing station 3 (the positive Y-axis side in FIG. 1), and a second processing block G2 is provided on the back side of processing station 3 (the negative Y-axis side in FIG. 1). Furthermore, a third processing block G3 is provided on the load / unload station 2 side of processing station 3 (the negative X-axis side in FIG. 1).

[0022] 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 breaks the SiO2 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.

[0023] 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 upper wafer W1 and the lower wafer W2 using, for example, pure water, and cleans the bonding surfaces W1j, W2j.

[0024] In the surface hydrophilization device 40, pure water is supplied onto the upper wafer W1 or the lower wafer W2 while the upper wafer W1 or the lower wafer W2 held by, for example, a spin chuck is rotated. As a result, the pure water supplied onto the upper wafer W1 or the lower wafer W2 spreads over the bonding surfaces W1j, W2j of the upper wafer W1 or the lower wafer W2, thereby making the bonding surfaces W1j, W2j hydrophilic.

[0025] 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.

[0026] The second processing block G2 also includes a bonding device 41. The bonding device 41 bonds the hydrophilized upper wafer W1 and lower wafer W2 together by intermolecular force. The bonding device 41 will be described in detail later.

[0027] The third processing block G3 is provided with a transition (TRS) device (not shown) for the upper wafer W1, the lower wafer W2, and the overlapped wafer T. The third processing block G3 may also be provided with a mounting section for temporarily mounting the upper wafer W1 or the lower wafer W2. The mounting section may be capable of mounting multiple wafers (upper wafer W1 or lower wafer W2).

[0028] 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 around a vertical axis.

[0029] The transfer device 61 moves within the transfer region 60 and transfers the upper wafer W1, the lower wafer W2, and the overlapped wafer T to given devices within the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the transfer region 60.

[0030] The joint system 1 also includes a control device 70. The control device 70 controls the operation of the joint system 1. The control device 70 controls the operation of the joint system 1 based on signals from switches, various sensors, and the like.

[0031] The control device 70 is, for example, a computer, and includes a control unit 71 and a storage unit 72. The control unit 71 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, and various other circuits. The CPU of the microcomputer reads and executes programs stored in the ROM to perform the control described below. 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.

[0032] Such a 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.

[0033] <Configuration of the 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 embodiment, and Fig. 4 is a schematic side view showing the configuration of the joining device 41 according to the embodiment.

[0034] 3, the bonding apparatus 41 has a processing container 190 whose interior can be sealed. A loading / unloading port 191 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T is formed on the side 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.

[0035] The interior of the processing vessel 190 is divided 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 the side surface of the processing vessel 190 in the transfer region T1. In addition, loading / unloading ports 194 for the upper wafer W1, the lower wafer W2, and the overlapped wafer T are also formed in the inner wall 193.

[0036] 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, from the loading / unloading port 191 side in this order.

[0037] The transition 200 temporarily holds the upper wafer W1, the lower wafer W2, and the overlapped wafer T. The transition 200 is formed, for example, in two stages, and any two of the upper wafer W1, the lower wafer W2, and the overlapped wafer T can be held thereon at the same time.

[0038] The substrate transfer mechanism 201 has a transfer arm that is movable, for example, in the vertical direction (Z-axis direction), horizontal directions (Y-axis direction, X-axis direction), and directions around the vertical axis (θ direction). The substrate transfer mechanism 201 can transfer the upper wafer W1, the lower wafer W2, and the overlapped wafer T within the transfer region T1 or between the transfer region T1 and the processing region T2.

[0039] The position adjustment mechanism 210 adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2. Specifically, the position adjustment mechanism 210 has a base 211 equipped with a holder (not shown) that holds and rotates the upper wafer W1 and the lower wafer W2, and a detector 212 that detects the positions of the notches of the upper wafer W1 and the lower wafer W2. The position adjustment mechanism 210 adjusts the positions of the notches by detecting the positions of the notches of the upper wafer W1 and the lower wafer W2 using the detector 212 while rotating the upper wafer W1 and the lower wafer W2 held on the base 211. This adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2.

[0040] The reversing mechanism 220 reverses the upper wafer W1. Specifically, the reversing mechanism 220 has a holding arm 221 that holds the upper wafer W1. The holding arm 221 extends in the horizontal direction (X-axis direction). The holding arm 221 is provided with holding members 222 that hold the upper wafer W1 at, for example, four locations.

[0041] The holding arm 221 is supported by a drive unit 223 equipped with, for example, a motor. The holding arm 221 is rotatable about a horizontal axis by the drive unit 223. The holding arm 221 is rotatable about the drive unit 223 and is also movable in the horizontal direction (X-axis direction). Below the drive unit 223, another drive unit (not shown) equipped with, for example, a motor is provided. This other drive unit allows the drive unit 223 to move in the vertical direction along a support column 224 extending in the vertical direction.

[0042] In this way, the upper wafer W1 held by the holding member 222 can be rotated around the horizontal axis and moved in the vertical and horizontal directions by the driving unit 223. Furthermore, the upper wafer W1 held by the holding member 222 can rotate around the driving unit 223 and move between the position adjustment mechanism 210 and the upper chuck 230, which will be described later.

[0043] The processing region T2 is provided with an upper chuck 230 that suction-holds the upper surface (non-bonding surface W1n) of the upper wafer W1 from above, and a lower chuck 231 that suction-holds the lower surface (non-bonding surface W2n) of the lower wafer W2 from below. The lower chuck 231 is provided below the upper chuck 230 and is configured to be able to be arranged 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 part that holds the upper wafer W1, and the lower chuck 231 is an example of a second holding part that holds the lower wafer W2.

[0044] 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.

[0045] An alignment mark imaging unit 300, which is an optical system that images the lower surface (bonding surface W1j) of the upper wafer W1 held by the upper chuck 230 and the upper surface (bonding surface W2j) of the lower wafer W2 held by the lower chuck 231, is provided above the upper chuck 230. Specifically, the alignment mark imaging unit 300 images the alignment marks provided on the upper wafer W1 and the lower wafer W2.

[0046] The alignment mark imaging unit 300 includes a light source 301 (see FIG. 6) and an imaging unit 302 (see FIG. 6) that are provided above the upper chuck 230. The light source 301 is provided above the upper chuck 230 and irradiates light onto the upper wafer W1 and the lower wafer W2 through through-holes 312 (see FIG. 6) formed in the upper chuck 230. The light irradiated from the light source 301 is infrared light. The imaging unit 302 is provided above the upper chuck 230 and images the alignment marks provided on the upper wafer W1 and the lower wafer W2 through the through-holes 312 formed in the upper chuck 230. The imaging unit 302 is, for example, a CCD (Charge Coupled Device) camera and includes an infrared imaging element having a sensitivity region in the infrared region. The imaging result by the imaging unit 302 is output to the control device 70. A more specific configuration of the alignment mark imaging unit 300 will be described later with reference to FIG. 6, etc.

[0047] 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.

[0048] The first moving section 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 section 250 and extend in the horizontal direction (X-axis direction). The first moving section 250 is configured to be movable along the rails 252.

[0049] The pair of rails 252, 252 are disposed on a second moving section 253. The second moving section 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 section 253 and extend in the horizontal direction (Y-axis direction). The second moving section 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.

[0050] The first moving unit 250, the second moving unit 253, etc. constitute a moving unit 256. The moving unit 256 adjusts the horizontal position of the lower chuck 231 relative to the upper chuck 230 by moving the lower chuck 231 in the X-axis direction, the Y-axis direction, and the θ direction. The horizontal position refers to the position and orientation in the horizontal direction (the X-axis direction, the Y-axis direction, and the θ direction).

[0051] Furthermore, the moving unit 256 moves the lower chuck 231 in the Z-axis direction to adjust the vertical positions of the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231. That is, the moving unit 256 moves the lower chuck 231 closer to the upper chuck 230 to adjust the vertical positions of the upper wafer W1 and the lower wafer W2.

[0052] Although the lower chuck 231 is moved in the X-axis direction, the Y-axis direction, and the θ-direction here, the moving 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 moving unit 256 may, for example, move the upper chuck 230 in the Z-axis direction.

[0053] 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 embodiment.

[0054] 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 upper wafer W1 held by suction on the upper chuck 230. A pressing pin 281 of a striker 280 is inserted into the through-hole 266.

[0055] Striker 280 is disposed on the upper surface of support member 270, and includes a pressing pin 281, an actuator unit 282, and a linear motion mechanism 283. Pressing pin 281 is a cylindrical member extending along the vertical direction, and is supported by actuator unit 282.

[0056] 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 upper wafer W1 using air supplied from the electropneumatic regulator, and is able to control the pressure load applied to the center of the upper wafer W1. In addition, the tip of the actuator unit 282 is movable up and down in the vertical direction through the through-hole 266 using air from the electropneumatic regulator.

[0057] 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.

[0058] The striker 280 is configured as described above, and controls the movement of the actuator unit 282 by the linear motion mechanism 283, and controls the pressing load on the upper wafer W1 by the pressing pin 281 by the actuator unit 282. As a result, the striker 280 presses the center of the upper wafer W1, which is held by suction on the upper chuck 230, to bring it into contact with the lower wafer W2.

[0059] A plurality of pins 261 that come into contact with the upper surface (non-bonding surface W1n) of the upper wafer W1 are provided on the lower surface of the main body 260. The pins 261 each have a diameter of 0.1 mm to 1 mm and a height of several tens to several hundreds of μm. The pins 261 are evenly spaced, for example, at intervals of 2 mm.

[0060] The upper chuck 230 has a plurality of suction portions that suction-hold the upper wafer W1 in a portion of the region where the plurality of pins 261 are provided. Specifically, a plurality of outer suction portions 391 and a plurality of inner suction portions 392 that suction-hold the upper wafer W1 by suction are provided on the lower surface of the main body 260 of the upper chuck 230. The plurality of outer suction portions 391 and the plurality of inner suction portions 392 have suction regions that are arc-shaped or annular in plan view. The plurality of outer suction portions 391 and the plurality of inner suction portions 392 have the same height as the pins 261.

[0061] The plurality of outer suction portions 391 are arranged on the outer periphery of the main body portion 260. The plurality of outer suction portions 391 are connected to a suction device (not shown) such as a vacuum pump, and suck and hold the outer periphery of the upper wafer W1.

[0062] The inner suction portions 392 are arranged side by side in the circumferential direction, radially inward of the main body portion 260 relative to the outer suction portions 391. The inner suction portions 392 are connected to suction devices (not shown), such as vacuum pumps, and suck and hold the region between the outer periphery and center of the upper wafer W1.

[0063] The lower chuck 231 has a main body 290 having a diameter equal to or larger than that of the lower wafer W2. Here, the lower chuck 231 having a diameter larger than that of the lower wafer 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 lower wafer W2.

[0064] A plurality of pins 291 that come into contact with the lower surface (non-bonding surface W2n) of the lower wafer W2 are provided on the upper surface of the main body 290. The pins 291 each 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 spaced, for example, at intervals of 2 mm.

[0065] 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 peripheral edge of the lower wafer W2, and supports the outer peripheral portion of the lower wafer W2 over the entire periphery.

[0066] 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).

[0067] The lower chuck 231 reduces the pressure in 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 lower wafer W2 placed in the suction region is sucked and held by the lower chuck 231.

[0068] Because the lower ribs 292 support the entire outer periphery of the lower surface of the lower wafer W2, the lower wafer W2 is properly sucked up to near the outer periphery. This allows the entire surface of the lower wafer W2 to be suction-held. In addition, because the lower surface of the lower wafer W2 is supported by the multiple pins 291, the lower wafer W2 is easily peeled off from the lower chuck 231 when the suction of the lower wafer W2 is released.

[0069] <Configuration of alignment mark imaging unit> Next, the configuration of the alignment mark imaging unit 300 will be described in more detail with reference to Fig. 6 to Fig. 9. Fig. 6 is a diagram showing the configuration of the alignment mark imaging unit 300 according to an embodiment. Fig. 7 is a diagram showing an example of an alignment mark M1 provided on the upper wafer W1, and Fig. 8 is a diagram showing an example of an alignment mark M2 provided on the lower wafer W2.

[0070] As shown in Fig. 6, alignment marks M1 and M2 are formed in advance on the upper wafer W1 and the lower wafer W2. The alignment mark M1 has a ring shape, for example, as shown in Fig. 7. The alignment mark M2 has a ring shape with a larger diameter than the alignment mark M1, for example, as shown in Fig. 8. In a horizontal position adjustment process described later, the horizontal position of the lower chuck 231 is adjusted using the moving unit 256, thereby aligning the center position of the ring shape of the alignment mark M1 with the center position of the ring shape of the alignment mark M2.

[0071] The alignment mark imaging unit 300 includes a light source 301 , collimator lenses 303 and 306 , a reflecting mirror 304 , a condenser lens 305 , a half mirror 307 , an objective lens 308 , a relay lens 309 , an imaging diaphragm 310 , an imaging lens 311 , and an imaging unit 302 .

[0072] Light source 301 generates infrared light. Collimator lens 303 collimates the light emitted from light source 301. Reflector 304 changes the path of light incident vertically upward from collimator lens 303 to a horizontal direction, causing the light to enter condenser lens 305. Collector lens 305 collects the light incident from reflector 304 and causes it to enter collimator lens 306. Collimator lens 306 collimates the light incident from condenser lens 305 and causes it to enter half mirror 307. Half mirror 307 reflects the light incident from collimator lens 306 toward through-hole 312, and transmits light incident from the through-hole 312 side.

[0073] The objective lens 308 collects light incident from the half mirror 307 via the relay lens 309 toward the through-hole 312. The objective lens 308 also collects light incident from the through-hole 312 and makes it incident on the relay lens 309. The relay lens 309 relays the light incident from the objective lens 308 to the imaging lens 311 via the half mirror 307. The imaging diaphragm 310 is disposed between the half mirror 307 and the imaging lens 311, and adjusts the amount of light relayed from the half mirror 307 to the imaging lens 311. The imaging lens 311 collects the light incident from the half mirror 307 toward the imaging unit 302.

[0074] With this configuration, the light source 301 of the alignment mark imaging unit 300 emits light above the upper chuck 230. As indicated by the dashed arrows in FIG. 6 , the light emitted from the light source 301 is incident on the upper wafer W1 and the lower wafer W2 via the collimator lens 303, the reflecting mirror 304, the condenser lens 305, the collimator lens 306, the half mirror 307, the relay lens 309, the objective lens 308, and the through-hole 312. Thereafter, as indicated by the dashed-dotted arrows in FIG. 6 , the light reflected from the upper wafer W1 and the lower wafer W2 reaches the imaging unit 302 via the through-hole 312, the objective lens 308, the relay lens 309, the half mirror 307, the imaging diaphragm 310, and the imaging lens 311. That is, the imaging unit 302 captures images of the alignment marks M1 and M2 using the reflected light via the through-hole 312.

[0075] The alignment marks M1 and M2 are provided at multiple positions on the upper wafer W1 and the lower wafer W2 in a one-to-one correspondence with the alignment mark imaging units 300. For example, as shown in FIG. 9, the alignment marks M1 and M2 are provided at at least two locations, one end and the other end, of the upper wafer W1 and the lower wafer W2. FIG. 9 is a diagram showing an example of the arrangement of the alignment marks M1 and M2 and the alignment mark imaging units 300. The bonding apparatus 41 also includes multiple (here, two) alignment mark imaging units 300 corresponding to the multiple alignment marks M1 and M2 provided on the upper wafer W1 and the lower wafer W2. For example, one alignment mark imaging unit 300 is provided at each of the one end and the other end of the upper wafer W1 and the lower wafer W2. The multiple alignment mark imaging units 300 capture images of the multiple alignment marks M1 and M2, respectively.

[0076] The alignment mark imaging unit 300 may be configured to be movable in the horizontal direction according to the positions of the alignment marks M1, M2 provided on the upper wafer W1 and the lower wafer W2. For example, the alignment mark imaging unit 300 may be connected to a moving mechanism 315 and configured to be movable in the horizontal direction (X-axis direction and Y-axis direction) by the moving mechanism 315. The moving mechanism 315 may be, for example, a rail and a stage movable on the rail.

[0077] Returning to FIG. 6 , the description of the alignment mark imaging unit 300 will be continued. An adjustment unit 400 that adjusts the focal depth of the alignment mark imaging unit 300 is provided on the optical path of the alignment mark imaging unit 300. The adjustment unit 400 is provided between the condenser lens 305 and the collimator lens 306. The adjustment unit 400 is a diaphragm having an aperture, and changes the aperture width to change the numerical aperture (NA) of the alignment mark imaging unit 300. The adjustment unit 400 adjusts the focal depth of the alignment mark imaging unit 300 by changing the numerical aperture of the alignment mark imaging unit 300. For example, the adjustment unit 400 can decrease the focal depth of the alignment mark imaging unit 300 by increasing the numerical aperture.

[0078] <Specific operation of the joining system> Next, a specific operation of the joint system 1 according to the embodiment will be described with reference to Fig. 10. Fig. 10 is a flowchart showing the procedure of processing executed by the joint system 1 according to the embodiment. The various processing shown in Fig. 10 is executed based on the control of the control device 70.

[0079] First, a cassette C1 containing a plurality of upper wafers W1, a cassette C2 containing a plurality of lower wafers W2, and an empty cassette C3 are placed on a predetermined loading plate 11 in the load / unload station 2. Then, the upper wafer W1 in the cassette C1 is removed by the transfer device 22 and transferred to a transition device arranged in the third processing block G3.

[0080] Next, the upper wafer W1 is transferred by the transfer 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 to form plasma and ionized in a predetermined reduced-pressure atmosphere. The oxygen ions are irradiated onto the bonding surface of the upper wafer W1, and the bonding surface is subjected to plasma processing. As a result, the bonding surface of the upper wafer W1 is modified (step S101).

[0081] Next, the upper wafer W1 is transferred by the transfer 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 upper wafer W1 while the upper wafer W1 held by the spin chuck is being rotated. This makes the bonding surface of the upper wafer W1 hydrophilic. The bonding surface of the upper wafer W1 is also cleaned with the pure water (step S102).

[0082] Next, the upper wafer W1 is transferred to the bonding device 41 in the second processing block G2 by the transfer device 61. After being transferred into the bonding device 41, the upper wafer W1 is transferred to the position adjustment mechanism 210 via the transition 200, and its horizontal orientation is adjusted by the position adjustment mechanism 210 (step S103).

[0083] Thereafter, the upper wafer W1 is transferred from the position adjustment mechanism 210 to the reversing mechanism 220, and the upper and rear surfaces of the upper wafer W1 are reversed by the reversing mechanism 220 (step S104). Specifically, the bonding surface W1j of the upper wafer W1 faces downward. Next, the upper wafer W1 is transferred from the reversing mechanism 220 to the upper chuck 230, and the upper wafer W1 is held by suction by the upper chuck 230 (step S105).

[0084] The processing of the lower wafer W2 overlaps with the processing of steps S101 to S105 for the upper wafer W1. First, the transfer device 22 removes the lower wafer W2 from the cassette C2 and transfers it to the transition device arranged in the third processing block G3.

[0085] Next, the lower wafer W2 is transferred by the transfer device 61 to the surface modification device 30, where the bonding surface W2j of the lower wafer W2 is modified (step S106). Thereafter, the lower wafer W2 is transferred by the transfer device 61 to the surface hydrophilization device 40, where the bonding surface W2j of the lower wafer W2 is hydrophilized and the bonding surface is cleaned (step S107).

[0086] Thereafter, the lower wafer W2 is transferred to the bonding device 41 by the transfer device 61. The lower wafer W2 transferred into the bonding device 41 is transferred to the position adjustment mechanism 210 via the transition 200. Then, the horizontal orientation of the lower wafer W2 is adjusted by the position adjustment mechanism 210 (step S108).

[0087] Thereafter, the lower wafer W2 is transferred to the lower chuck 231 and is held by suction on the lower chuck 231 with the notch facing in a predetermined direction (step S109).

[0088] Next, the upper wafer W1 held by the upper chuck 230 and the lower wafer W2 held by the lower chuck 231 are aligned in the horizontal and vertical directions (step S110). Details of step S110 will be described later.

[0089] At the end of the alignment process, the distance between the bonding surface W2j of the lower wafer W2 and the bonding surface W1j of the upper wafer W1 is a predetermined distance, for example, 80 μm to 100 μm.

[0090] Thereafter, a bonding process is performed to bond the upper wafer W1 and the lower wafer W2 together (step S111). Specifically, the center of the upper wafer W1 is pressed downward using the pressing pin 281 of the striker 280 to bring the center of the upper wafer W1 into contact with the center of the lower wafer W2, thereby bonding the upper wafer W1 and the lower wafer W2 together.

[0091] Thereafter, the pressing pin 281 is raised to the upper chuck 230. Also, the evacuation of the lower wafer W2 in the lower chuck 231 is stopped, and the lower wafer W2 is released from suction and holding by the lower chuck 231. This completes the bonding process in the bonding device 41.

[0092] Next, an example of a specific procedure for aligning the upper wafer W1 and the lower wafer W2 in step S110 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of a specific procedure for the alignment process in step S110. Figs. 12 and 13 are diagrams showing an example of the operation of the imaging process.

[0093] 11, the control device 70 starts an approaching process for bringing the upper chuck 230 and the lower chuck 231 closer to each other (step S201). In the approaching process, first, the control device 70 starts raising the lower chuck 231 using the first moving part 250 of the moving part 256.

[0094] Next, the control device 70 performs an imaging process to capture images of the alignment marks M1 and M2 provided on the upper wafer W1 and the lower wafer W2 (step S202).

[0095] In the imaging process, first, as shown in FIG. 12, the control device 70 controls the adjustment unit 400 to adjust the focal depth of the alignment mark imaging unit 300, thereby positioning the upper wafer W1 and the lower wafer W2 within the focal depth D of the alignment mark imaging unit 300. In this state, the control device 70 uses the alignment mark imaging unit 300 to image the alignment marks M1 and M2 provided on the upper wafer W1 and the lower wafer W2. This results in an image in which both alignment marks M1 and M2 are in focus. Image data of this image is output to the control device 70. The control device 70 detects the alignment marks M1 and M2 by performing edge detection on the acquired image data.

[0096] In this way, in the bonding system 1 according to this embodiment, the alignment marks M1 and M2 are imaged using the alignment mark imaging unit 300 while the upper wafer W1 and the lower wafer W2 are positioned within the focal depth D of the alignment mark imaging unit 300.

[0097] As a result, during the approach process, the alignment marks M1 and M2 for adjusting the horizontal position of the lower chuck 231 relative to the upper chuck 230 can be detected with high accuracy using an image in which both the alignment marks M1 and M2 are in focus. Therefore, the accuracy of adjusting the horizontal position of the lower chuck 231 based on the detection results of the alignment marks M1 and M2 can be improved, and as a result, the accuracy of bonding substrates together can be improved.

[0098] Furthermore, the control device 70 positions the upper wafer W1 and the lower wafer W2 within the focal depth D of the alignment mark imaging unit 300 by decreasing the focal depth D of the alignment mark imaging unit 300 as the distance between the upper chuck 230 and the lower chuck 231 decreases. For example, as shown in FIG. 13 , the control device 70 can decrease the focal depth D of the alignment mark imaging unit 300 by increasing the aperture width AW of the adjustment unit 400 to increase the numerical aperture. This allows images in focus of both alignment marks M1 and M2 to be obtained in real time when the upper chuck 230 and the lower chuck 231 are brought closer to each other, thereby enabling more accurate detection of the alignment marks M1 and M2. This can further improve the accuracy of adjusting the horizontal position of the lower chuck 231 based on the detection results of the alignment marks M1 and M2, thereby resulting in more accurate bonding of substrates.

[0099] Thereafter, the control device 70 controls the moving unit 256 based on the detection results (imaging results) of the alignment marks M1 and M2 to adjust the horizontal position of the lower chuck 231 relative to the upper chuck 230. Specifically, the control device 70 controls the moving unit 256 to adjust the horizontal position of the lower chuck 231 relative to the upper chuck 230 so that the center position of the ring shape of the alignment mark M2 (see FIG. 8) coincides with the center position of the ring shape of the alignment mark M1 (see FIG. 7).

[0100] This makes it possible to adjust the horizontal position of the lower chuck 231 with high precision based on the highly accurate detection results of the alignment marks M1 and M2, thereby improving the bonding precision between the substrates.

[0101] Next, the control device 70 determines whether the upper chuck 230 and the lower chuck 231 have approached each other to a predetermined distance (step S204).

[0102] If the upper chuck 230 and the lower chuck 231 have not approached each other to the predetermined distance (step S204, No), the control device 70 returns the process to step S202 and executes the image capturing process (step S202) and the horizontal position adjusting process (step S203) again. That is, the control device 70 executes the image capturing process and the horizontal position adjusting process multiple times during the approaching process.

[0103] This makes it possible to obtain images in focus on both the alignment marks M1 and M2 in real time until just before bonding the upper wafer W1 and the lower wafer W2, thereby enabling more accurate detection of the alignment marks M1 and M2. This further improves the accuracy of adjusting the horizontal position of the lower chuck 231 based on the detection results of the alignment marks M1 and M2, thereby resulting in more accurate bonding of the substrates.

[0104] When the upper chuck 230 and the lower chuck 231 approach each other to a predetermined distance in the process of step S204 (Yes in step S204), the control device 70 stops the upper chuck 230 and the lower chuck 231 from approaching each other (step S205). That is, the control device 70 stops the lifting of the lower chuck 231 using the first moving unit 250 of the moving unit 256. This completes the series of alignment processes.

[0105] (Variation) Next, various modifications of the embodiment will be described with reference to Figures 14 and 15. Figure 14 is a diagram showing the configuration of an alignment mark imaging section 300 according to a first modification of the embodiment.

[0106] 14, in Modification 1, adjustment unit 400 is provided between relay lens 309 and objective lens 308. As a result, adjustment unit 400 can decrease the focal depth of alignment mark imaging unit 300 by increasing the aperture width and increasing the numerical aperture, as in the embodiment.

[0107] The adjustment unit 400 may be provided between the relay lens 309 and the objective lens 308 , and between the condenser lens 305 and the collimator lens 306 .

[0108] FIG. 15 is a diagram showing the configuration of an alignment mark imaging section 300 according to the second modification of the embodiment.

[0109] As shown in FIG. 15, the alignment mark imaging unit 300 according to the second modification includes a light source 301 provided below the lower chuck 231 and an imaging unit 302 provided above the upper chuck 230.

[0110] The alignment mark imaging unit 300 also includes collimator lenses 303 and 306, reflecting mirrors 304a and 304b, and condenser lenses 305a and 305b, which are provided below the lower chuck 231. The alignment mark imaging unit 300 also includes an objective lens 308, a relay lens 309, an imaging diaphragm 310, and an imaging lens 311, which are provided above the upper chuck 230. The upper chuck 230 has a through-hole 312 formed therethrough in the thickness direction, and the lower chuck 231 has a through-hole 313 formed therethrough in the thickness direction.

[0111] Light source 301 generates infrared light. Collimator lens 303 collimates the light emitted from light source 301. Reflector 304a changes the path of light incident vertically upward from collimator lens 303 to a horizontal direction and causes the light to enter condenser lens 305a. Collector lens 305a collects the light incident from reflector 304a and causes the light to enter collimator lens 306. Collimator lens 306 collimates the light incident from condenser lens 305 and causes the light to enter reflector 304b. Reflector 304b changes the path of light incident horizontally from collimator lens 306 to a vertically upward direction and causes the light to enter condenser lens 305b. Collector lens 305b collects the light incident from reflector 304b toward through-hole 313.

[0112] Objective lens 308 collects light incident from through-hole 312 and makes it incident on relay lens 309. Relay lens 309 relays the light incident from objective lens 308 to imaging lens 311. Imaging diaphragm 310 is disposed between relay lens 309 and imaging lens 311, and adjusts the amount of light relayed from relay lens 309 to imaging lens 311. Imaging lens 311 collects the light incident from relay lens 309 toward imaging unit 302.

[0113] With this configuration, the light source 301 of the alignment mark imaging unit 300 emits light vertically upward from below the lower chuck 231. As indicated by the dashed arrows in FIG. 15 , the light emitted from the light source 301 is incident on the upper wafer W1 and the lower wafer W2 via the collimator lens 303, the reflecting mirror 304a, the condenser lens 305a, the collimator lens 306, the reflecting mirror 304b, the condenser lens 305b, and the through-hole 313. Thereafter, the light transmitted through the upper wafer W1 and the lower wafer W2 reaches the imaging unit 302 via the through-hole 312, the objective lens 308, the relay lens 309, the imaging diaphragm 310, and the imaging lens 311. That is, the imaging unit 302 captures images of the alignment marks M1 and M2 using the transmitted light via the through-hole 312.

[0114] Moreover, the adjustment unit 400 is provided between the condenser lens 305 and the collimator lens 306, as in the embodiment.

[0115] The adjustment unit 400 may be provided between the relay lens 309 and the objective lens 308. The adjustment unit 400 may also be provided between the relay lens 309 and the objective lens 308, and between the condenser lens 305 and the collimator lens 306.

[0116] (others) In the above-described embodiment, the first substrate W1 and the second substrate W2 are disk-shaped and have approximately the same diameter, but one of the first substrate W1 and the second substrate W2 may have a shape other than a disk. For example, the second substrate W2 may be a rectangular chip of approximately 30 mm × 30 mm obtained by dicing a disk-shaped substrate with a diameter of approximately 300 mm.

[0117] In the above-described embodiment, an example has been described in which the adjustment unit 400 adjusts the focal depth of the alignment mark image plane by changing the numerical aperture of the alignment mark imaging unit 300. However, the focal depth of the alignment mark image plane may be adjusted using a parameter other than the numerical aperture. For example, in the bonding system 1, the light source 301 of the alignment mark imaging unit 300 may adjust the focal depth of the alignment mark imaging unit 300 by changing the wavelength of the light emitted from the light source 301.

[0118] As described above, the bonding apparatus according to the embodiment (for example, bonding apparatus 41) includes a first holding unit (for example, upper chuck 230), a second holding unit (for example, lower chuck 231), a moving unit (for example, moving unit 256), an optical system (for example, alignment mark image capturing unit 300), an adjusting unit (for example, adjusting unit 400), and a control unit (for example, control unit 71). The first holding unit holds a first substrate (for example, upper wafer W1). The second holding unit holds a second substrate (for example, lower wafer W2) to be bonded to the first substrate. The moving unit moves one of the first holding unit and the second holding unit closer to the other. The optical system irradiates light onto the first substrate held by the first holding unit and the second substrate held by the second holding unit, and captures images of alignment marks (for example, alignment marks M1 and M2) provided on the first substrate and the second substrate using reflected or transmitted light. The adjustment unit is provided on the optical path of the optical system and adjusts the focal depth (for example, focal depth D) of the optical system. The control unit executes an approaching process and an imaging process. The approaching process controls the moving unit to move one of the first holding unit and the second holding unit closer to the other. The imaging process controls the adjustment unit to adjust the focal depth of the optical system during the approaching process to position the first substrate and the second substrate within the focal depth of the optical system, and then images the alignment marks of the first substrate and the second substrate using the optical system.

[0119] Therefore, the bonding device 41 according to the embodiment can improve the bonding accuracy between the substrates.

[0120] 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. [Explanation of symbols]

[0121] 1. Joint System 30 Surface modification equipment 40 Surface hydrophilization device 41 Joining equipment 70 Control device 71 Control Unit 72 Memory section 230 Upper chuck 231 Lower zipper 250 First Mobile Section 253 Second Mobile Section 256 Mobile Unit 300 Alignment mark imaging unit 301 Light source 302 Imaging unit 400 Adjustment section W1 upper wafer W2 lower wafer

Claims

1. a first holding portion that holds a first substrate; a second holding portion that holds a second substrate to be bonded to the first substrate; a moving unit that moves one of the first holding unit and the second holding unit closer to the other; an optical system that irradiates light onto the first substrate held by the first holding unit and the second substrate held by the second holding unit, and captures images of alignment marks provided on the first substrate and the second substrate using reflected light or transmitted light; an adjustment unit provided on an optical path of the optical system and configured to adjust a focal depth of the optical system; Control unit and Equipped with The control unit an approaching process of controlling the moving unit to bring one of the first holding unit and the second holding unit closer to the other; an imaging process of imaging alignment marks of the first substrate and the second substrate using the optical system after positioning the first substrate and the second substrate within the focal depth of the optical system by controlling the adjustment unit during the approach process; and A joining device that performs the above.

2. The adjustment unit The depth of focus of the optical system is adjusted by changing the numerical aperture of the optical system. The joining device according to claim 1 .

3. The control unit In the imaging process, the adjustment unit is controlled to make the focal depth of the optical system shallower as the distance between the first holding unit and the second holding unit becomes narrower, thereby positioning the first substrate and the second substrate within the focal depth of the optical system. The joining device according to claim 1 .

4. The moving unit is adjusting a horizontal position of the second holding part relative to the first holding part by moving one of the first holding part and the second holding part in a horizontal direction; The control unit During the approach process, a horizontal position adjustment process is further performed by controlling the moving unit based on an image pickup result of the image pickup process to adjust the horizontal position of the second holding unit relative to the first holding unit. The joining device according to claim 1 .

5. The control unit During the approach process, the image capturing process and the horizontal position adjustment process are executed multiple times. The joining device according to claim 4 .

6. A plurality of the optical systems are provided, The plurality of optical systems include: A plurality of alignment marks are respectively captured at a plurality of positions on the first substrate and the second substrate, the alignment marks being provided in a one-to-one correspondence with the plurality of optical systems. The joining device according to claim 1 .

7. The optical system comprises: The first substrate and the second substrate are configured to be movable in the horizontal direction in accordance with the positions of the alignment marks provided on the first substrate and the second substrate. The joining device according to claim 1 .

8. a surface modification device for modifying the surfaces of the first substrate and the second substrate; a surface hydrophilization device for hydrophilizing the modified surfaces of the first substrate and the second substrate; a bonding device that bonds the hydrophilized first substrate and the hydrophilized second substrate together by intermolecular forces; Equipped with The joining device is a first holding portion that holds the first substrate; a second holding portion that holds the second substrate; a moving unit that moves one of the first holding unit and the second holding unit closer to the other; an optical system that irradiates light onto the first substrate held by the first holding unit and the second substrate held by the second holding unit, and captures images of alignment marks provided on the first substrate and the second substrate using reflected light or transmitted light; an adjustment unit that is provided on an optical path of the optical system and adjusts the focal depth of the optical system; Control unit and Equipped with The control unit an approaching process of controlling the moving unit to bring one of the first holding unit and the second holding unit closer to the other; an imaging process of imaging alignment marks of the first substrate and the second substrate using the optical system after positioning the first substrate and the second substrate within the focal depth of the optical system by controlling the adjustment unit during the approach process; and A joint system that performs the above.

9. holding the first substrate using a first holding part that holds the first substrate; a step of holding a second substrate using a second holding portion that holds a second substrate to be bonded to the first substrate; a step of moving one of the first holding unit and the second holding unit closer to the other by using a moving unit that moves one of the first holding unit and the second holding unit closer to the other; during the approaching step, adjusting a focal depth of an optical system that irradiates light onto the first substrate and the second substrate and captures images of alignment marks provided on the first substrate and the second substrate by reflected light or transmitted light to position the first substrate and the second substrate within the focal depth of the optical system, and then capturing images of the alignment marks on the first substrate and the second substrate using the optical system; A bonding method comprising:

Images