Bonding device, bonding system, and bonding method

Abstract

The present disclosure relates to a bonding apparatus, a bonding system, and a bonding method, which improve bonding accuracy between substrates. The first holding portion holds a first substrate. The second holding portion holds a second substrate. The moving unit causes one of the first holding unit and the second holding unit to approach the other. The optical system irradiates the first substrate and the second substrate with light, and images the alignment marks provided on the first substrate and the second substrate with reflected light or transmitted light. The adjusting part is arranged on an optical path of the optical system and used for adjusting the focus depth of the optical system. The control unit executes proximity processing and imaging processing. In the approaching process, the moving unit is controlled so that one of the first holding unit and the second holding unit approaches the other. In the imaging process, in the approaching process, after the first substrate and the second substrate are positioned within the focal depth of the optical system by adjusting the focal depth of the optical system by controlling the adjusting part, the alignment marks of the first substrate and the second substrate are imaged using the optical system.

Description

Technical Field

[0001] This disclosure relates to a joining device, a joining system, and a joining method. Background Technology

[0002] Previously, there was a known bonding device for bonding substrates such as semiconductor wafers to each other (see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2018 / 088094 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a technique that can improve the bonding accuracy between substrates.

[0008] Solution for solving the problem

[0009] One aspect of the bonding apparatus disclosed herein includes a first holding portion, a second holding portion, a moving portion, an optical system, an adjustment portion, and a control portion. The first holding portion holds a first substrate. The second holding portion holds a second substrate bonded to the first substrate. The moving portion moves one of the first and second holding portions closer to the other. The optical system illuminates the first substrate held in the first holding portion and the second substrate held in the second holding portion with light, and uses reflected or transmitted light to capture alignment marks provided on the first and second substrates. The adjustment portion is disposed in the optical path of the optical system and is used to adjust the focal depth of the optical system. The control portion performs proximity processing and image capture processing. In proximity processing, the moving portion is controlled to move one of the first and second holding portions closer to the other. In image capture processing, during proximity processing, after the focal depth of the optical system is adjusted by the control adjustment portion to position the first and second substrates within the focal depth of the optical system, the optical system is used to capture the alignment marks on the first and second substrates.

[0010] The effects of the invention

[0011] According to this disclosure, the bonding accuracy between substrates can be improved. Attached Figure Description

[0012] Figure 1 This is a schematic top view illustrating the structure of the coupling system involved in the embodiment.

[0013] Figure 2 This is a schematic side view of the upper and lower wafers involved in the implementation method.

[0014] Figure 3This is a schematic top view showing the structure of the coupling device involved in the embodiment.

[0015] Figure 4 This is a schematic side view illustrating the structure of the coupling device involved in the embodiment.

[0016] Figure 5 This is a schematic diagram illustrating the upper and lower holding plates involved in the embodiment.

[0017] Figure 6 This is a diagram showing the structure of the alignment mark camera unit according to the embodiment.

[0018] Figure 7 This is a diagram showing an example of alignment marks set on the upper wafer.

[0019] Figure 8 This is a diagram showing an example of alignment marks set on the lower wafer.

[0020] Figure 9 This is a diagram showing an example of the configuration of the alignment mark and the alignment mark camera unit.

[0021] Figure 10 This is a flowchart illustrating the process performed by the coupling system according to the embodiment.

[0022] Figure 11 This is a flowchart illustrating an example of the specific process of the alignment procedure in step S110.

[0023] Figure 12 This is a diagram illustrating an example of camera processing actions.

[0024] Figure 13 This is a diagram illustrating an example of camera processing actions.

[0025] Figure 14 This is a diagram showing the structure of the alignment mark camera unit according to a variation of embodiment 1.

[0026] Figure 15 This is a diagram showing the structure of the alignment mark camera unit according to a modified example 2 of the embodiment. Detailed Implementation

[0027] Hereinafter, with reference to the accompanying drawings, a detailed description will be provided of the methods (hereinafter referred to as "Embodiments") for implementing the present disclosure, including the joining device, joining system, and joining method. However, the present disclosure is not limited to these embodiments. Furthermore, the various embodiments can be appropriately combined without contradicting the processing content. In the following embodiments, the same reference numerals are used for the same parts, and repeated descriptions are omitted.

[0028] Furthermore, in the embodiments shown below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" are sometimes used, but these expressions do not need to be strictly "constant," "orthogonal," "perpendicular," or "parallel." That is, the above-mentioned expressions, for example, allow for errors and tolerances in manufacturing precision, setting precision, etc.

[0029] Furthermore, in the accompanying figures below, to facilitate understanding, an orthogonal coordinate system is sometimes shown, defining mutually orthogonal X-axis, Y-axis, and Z-axis directions, with the positive Z-axis direction set as the vertically upward direction. Additionally, the direction of rotation about the vertical axis is sometimes referred to as the θ direction.

[0030] (Implementation Method)

[0031] <Structure of the Joining System>

[0032] First, refer to Figure 1 , Figure 2 The structure of the coupling system 1 involved in the implementation method will be explained. Figure 1 This is a schematic top view showing the structure of the coupling system 1 according to the embodiment. Figure 2 This is a schematic side view of the upper wafer W1 and the lower wafer W2 involved in the implementation method.

[0033] Figure 1 The bonding system 1 shown forms an overlapped wafer T by bonding a first substrate W1 to a second substrate W2.

[0034] The first substrate W1 and the second substrate W2 are, for example, 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 are, for example, circular plates with a diameter of approximately 300 mm.

[0035] Hereinafter, the first substrate W1 will be referred to as "upper wafer W1", and the second substrate W2 will be referred to as "lower wafer W2". That is, upper wafer W1 is an example of the first substrate, and lower wafer W2 is an example of the second substrate. In addition, sometimes when upper wafer W1 and lower wafer W2 are referred to collectively, they are referred to as "wafer W".

[0036] Additionally, below, such as Figure 2 As shown, the side of the upper wafer W1 that is bonded to the lower wafer W2 is designated as "bonding surface W1j", and the side opposite to the bonding surface W1j is designated as "non-bonding surface W1n". Similarly, the side of the lower wafer W2 that is bonded to the upper wafer W1 is designated as "bonding surface W2j", and the side opposite to the bonding surface W2j is designated as "non-bonding surface W2n".

[0037] like Figure 1As shown, the joining system 1 includes an inbound / outbound station 2 and a processing station 3. The inbound / outbound station 2 and the processing station 3 are arranged in the order of inbound / outbound station 2 and processing station 3 along the positive X-axis. In addition, the inbound / outbound station 2 and the processing station 3 are integrally connected.

[0038] The loading / unloading station 2 includes a loading platform 10 and a transport area 20. The loading platform 10 includes multiple loading plates 11. Each loading plate 11 has boxes C1, C2, and C3 that hold multiple (e.g., 25) substrates in a horizontal position. For example, box C1 holds the upper wafer W1, box C2 holds the lower wafer W2, and box C3 holds the overlapping wafer T.

[0039] The transport area 20 is arranged adjacent to the positive X-axis side of the platform 10. The transport area 20 is provided with a transport path 21 extending in the Y-axis direction and a transport device 22 that can move along the transport path 21.

[0040] The conveying device 22 can move not only in the Y-axis direction, but also in the X-axis direction and can rotate around the Z-axis. Moreover, the conveying device 22 conveys the upper wafer W1, the lower wafer W2 and the overlapping wafer T between the boxes C1 to C3 placed on the mounting plate 11 and the third processing block G3 of the processing station 3 described later.

[0041] Furthermore, the number of boxes C1 to C3 placed on the mounting plate 11 is not limited to the number shown in the figure. In addition, besides boxes C1, C2, and C3, boxes for recycling defective substrates can also be placed on the mounting plate 11.

[0042] Processing station 3 is equipped with multiple processing blocks, such as three processing blocks G1, G2, and G3, each equipped with various devices. For example, on the back side of processing station 3 ( Figure 1 The first processing block G1 is set on the positive Y-axis side of the processing station 3. Figure 1 A second processing block G2 is installed on the negative Y-axis side. Additionally, on the inlet / outlet side of processing station 3 ( Figure 1 Set the third processing block G3 on the negative X-axis side.

[0043] A surface modification device 30 is configured in the first processing block G1 to modify the bonding surfaces W1j and W2j of the first substrate W1 and the second substrate W2. The surface modification device 30 modifies the bonding surfaces W1j and W2j by breaking the bonds of SiO2 in the bonding surfaces W1j and W2j of the first substrate W1 and the second substrate W2 to form single-bonded SiO, so that they are easier to hydrophilize later.

[0044] Additionally, a surface hydrophilization device 40 is configured in the first processing block G1. The surface hydrophilization device 40 uses, for example, pure water to hydrophilize the bonding surfaces W1j and W2j of the upper wafer W1 and the lower wafer W2, and cleans the bonding surfaces W1j and W2j.

[0045] In the surface hydrophilization apparatus 40, for example, while rotating the upper wafer W1 or the lower wafer W2 held on the rotating holding disk, pure water is supplied to the upper wafer W1 or the lower wafer W2. As a result, the pure water supplied to the upper wafer W1 or the lower wafer W2 diffuses on the bonding surfaces W1j and W2j of the upper wafer W1 or the lower wafer W2, making the bonding surfaces W1j and W2j hydrophilic.

[0046] Here, an example of a transverse arrangement of the surface modification device 30 and the surface hydrophilization device 40 is shown, but the surface hydrophilization device 40 may also be stacked above or below the surface modification device 30.

[0047] Additionally, a bonding device 41 is provided in the second processing block G2. The bonding device 41 bonds the hydrophilized upper wafer W1 to the lower wafer W2 using intermolecular forces. Details of the bonding device 41 will be described later.

[0048] A transfer unit (TRS) device (not shown) for the upper wafer W1, lower wafer W2, and overlapping wafer T is provided in the third processing block G3. Alternatively, a mounting unit for temporarily holding the upper wafer W1 or the lower wafer W2 may be provided in the third processing block G3. The mounting unit may also be capable of holding multiple wafers (upper wafer W1 or lower wafer W2).

[0049] In addition, such as Figure 1 As shown, a transport area 60 is formed in the region surrounded by the first processing block G1, the second processing block G2, and the third processing block G3. A transport device 61 is disposed in the transport area 60. The transport device 61 has, for example, a transport arm that can move freely in the vertical direction, the horizontal direction, and about the vertical axis.

[0050] The conveying device 61 moves within the conveying area 60 to convey the upper wafer W1, the lower wafer W2, and the overlapping wafer T to a given device in the first processing block G1, the second processing block G2, and the third processing block G3 adjacent to the conveying area 60.

[0051] In addition, the engagement system 1 includes a control device 70. The control device 70 controls the operation of the engagement system 1. The control device 70 controls the operation of the engagement system 1 based on signals from switches, various sensors, etc.

[0052] The control device 70 is, for example, a computer, comprising a control unit 71 and a storage unit 72. The control unit 71 includes a microcomputer with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input / output ports, and various circuits. The CPU of this microcomputer implements the control described later by reading and executing a program stored in the ROM. The storage unit 72 is implemented, for example, using semiconductor memory elements such as RAM and flash memory, or storage devices such as hard disks and optical disks.

[0053] Furthermore, the program can also be recorded on a computer-readable recording medium and installed from that medium into the storage unit 72 of the control device 70. Examples of computer-readable recording media include hard disks (HD), floppy disks (FD), optical disks (CD), magneto-optical disks (MO), and memory cards.

[0054] <Structure of the Joining Device>

[0055] Next, refer to Figure 3 and Figure 4 The structure of the coupling device 41 will be described. Figure 3 This is a schematic top view showing the structure of the coupling device 41 according to the embodiment. Figure 4 This is a schematic side view showing the structure of the coupling device 41 according to the embodiment.

[0056] like Figure 3 As shown, the bonding device 41 has a processing container 190 capable of sealing its interior. An inlet / outlet 191 for the upper wafer W1, lower wafer W2, and overlapping wafer T is formed on the side of the processing container 190 near the transport area 60, and an opening / closing gate 192 is provided at the inlet / outlet 191.

[0057] The interior of the processing container 190 is divided into a transport area T1 and a processing area T2 by an inner wall 193. The aforementioned inlet and outlet ports 191 are formed on the side of the processing container 190 in the transport area T1. In addition, inlet and outlet ports 194 for the upper wafer W1, the lower wafer W2, and the overlapping wafer T are also formed on the inner wall 193.

[0058] In the transport area T1, the conveying unit 200, the substrate transport mechanism 201, the flipping mechanism 220, and the position adjustment mechanism 210 are arranged sequentially, for example, from the transport inlet / outlet side 191.

[0059] The transport unit 200 temporarily holds the upper wafer W1, the lower wafer W2, and the overlapping wafer T. For example, the transport unit 200 is formed as two layers, capable of simultaneously holding any two of the upper wafer W1, the lower wafer W2, and the overlapping wafer T.

[0060] The substrate transport mechanism 201, for example, has a transport arm that can move freely in the vertical direction (Z-axis direction), the horizontal direction (Y-axis direction, X-axis direction), and the direction about the vertical axis (θ direction). The substrate transport mechanism 201 can transport the upper wafer W1, the lower wafer W2, and the overlapping wafer T within the transport area T1 or between the transport area T1 and the processing area T2.

[0061] 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 includes: a base 211, which has a holding portion (not shown) for holding and rotating the upper wafer W1 and the lower wafer W2; and a detection portion 212 for detecting the position of the cut portions of the upper wafer W1 and the lower wafer W2. The position adjustment mechanism 210 rotates the upper wafer W1 and the lower wafer W2 held on the base 211 while using the detection portion 212 to detect the position of the cut portions of the upper wafer W1 and the lower wafer W2, thereby adjusting the position of the cut portions. This adjusts the horizontal orientation of the upper wafer W1 and the lower wafer W2.

[0062] The flipping mechanism 220 flips the face of the upper wafer W1. Specifically, the flipping mechanism 220 has a holding arm 221 for holding the upper wafer W1. The holding arm 221 extends in the horizontal direction (X-axis direction). In addition, holding members 222 for holding the upper wafer W1 are provided at, for example, four locations on the holding arm 221.

[0063] The retaining arm 221 is supported on a drive unit 223, such as one equipped with a motor. The retaining arm 221 is rotatable about a horizontal axis via this drive unit 223. Furthermore, the retaining arm 221 is rotatable about the drive unit 223 and can move freely in the horizontal direction (X-axis direction). Another drive unit (not shown), such as one equipped with 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 extending vertically.

[0064] In this way, the upper wafer W1 held in the holding member 222 can rotate about the horizontal axis via the drive unit 223, and can move in both the vertical and horizontal directions. In addition, the upper wafer W1 held in the holding member 222 can rotate about the drive unit 223 and move between the position adjustment mechanism 210 and the upper holding disk 230 described later.

[0065] In the processing area T2, an upper holding disk 230 is provided to hold the upper surface (non-bonding surface W1n) of the upper wafer W1 from above, and a lower holding disk 231 is provided to hold the lower surface (non-bonding surface W2n) of the lower wafer W2 from below. The lower holding disk 231 is located below the upper holding disk 230 and is configured to face the upper holding disk 230. The upper holding disk 230 and the lower holding disk 231 are, for example, vacuum holding disks. The upper holding disk 230 is an example of a first holding portion for holding the upper wafer W1, and the lower holding disk 231 is an example of a second holding portion for holding the lower wafer W2.

[0066] like Figure 4 As shown, the upper holding plate 230 is supported by a support member 270 disposed above the upper holding plate 230. The support member 270 is fixed to the top surface of the processing container 190, for example, via a plurality of support columns 271.

[0067] An alignment mark imaging unit 300 is provided above the upper holding disk 230. This alignment mark imaging unit 300 is an optical system for capturing images of the lower surface (joint surface W1j) of the upper wafer W1 held on the upper holding disk 230 and the upper surface (joint surface W2j) of the lower wafer W2 held on the lower holding disk 231. Specifically, the alignment mark imaging unit 300 captures images of the alignment marks set on the upper wafer W1 and the lower wafer W2.

[0068] The alignment mark camera unit 300 includes a light source 301 (see reference) disposed above the upper holding plate 230. Figure 6 ) and camera unit 302 (see reference) Figure 6 The light source 301 is positioned above the upper retaining plate 230, via a through hole 312 formed in the upper retaining plate 230 (see reference). Figure 6 Light is irradiated onto the upper wafer W1 and the lower wafer W2. The light irradiated from the light source 301 is infrared light. An imaging unit 302 is disposed above the upper holding disk 230 and captures images of alignment marks set on the upper wafer W1 and the lower wafer W2 via a through-hole 312 formed in the upper holding disk 230. The imaging unit 302 is, for example, a CCD (Charge Coupled Device) camera, equipped with an infrared imaging element having a sensitivity region in the infrared region. The imaging results of the imaging unit 302 are output to the control device 70. A more specific structure of the alignment mark imaging unit 300 is described below. Figure 6 More details will follow later.

[0069] The lower retaining plate 231 is supported by a first moving part 250 disposed below the lower retaining plate 231. The first moving part 250 moves the lower retaining plate 231 in the horizontal direction (X-axis direction) as described later. In addition, the first moving part 250 is configured to allow the lower retaining plate 231 to move freely in the vertical direction and to rotate about the vertical axis.

[0070] The first movable part 250 is mounted on a pair of guide rails 252, 252. The pair of guide rails 252, 252 are disposed on the lower surface side of the first movable part 250 and extend in the horizontal direction (X-axis direction). The first movable part 250 is configured to move freely along the guide rails 252.

[0071] A pair of guide rails 252, 252 are disposed on the second movable part 253. The second movable part 253 is mounted on a pair of guide rails 254, 254. The pair of guide rails 254, 254 are provided on the lower surface side of the second movable part 253 and extend in the horizontal direction (Y-axis direction). The second movable part 253 is configured to move freely in the horizontal direction (Y-axis direction) along the guide rails 254. In addition, the pair of guide rails 254, 254 are disposed on a mounting platform 255 provided on the bottom surface of the processing container 190.

[0072] The moving part 256 is composed of a first moving part 250 and a second moving part 253, etc. The moving part 256 adjusts the horizontal position of the lower holding plate 231 relative to the upper holding plate 230 by moving the lower holding plate 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 (X-axis direction, Y-axis direction, and θ direction).

[0073] Furthermore, the moving part 256 adjusts the vertical position between the upper wafer W1 held on the upper wafer 230 and the lower wafer W2 held on the lower wafer 231 by moving the lower holding disk 231 in the Z-axis direction. That is, the moving part 256 adjusts the vertical position between the upper wafer W1 and the lower wafer W2 by bringing the lower holding disk 231 closer to the upper holding disk 230.

[0074] Furthermore, here it is assumed that the lower holding plate 231 is moved in the X-axis direction, Y-axis direction, and θ direction. However, the moving part 256 may also move the lower holding plate 231 in the X-axis direction and Y-axis direction, and move the upper holding plate 230 in the θ direction. Additionally, here it is assumed that the lower holding plate 231 is moved in the Z-axis direction. However, the moving part 256 may also move the upper holding plate 230 in the Z-axis direction.

[0075] Next, refer to Figure 5 To illustrate the structure of the upper holding plate 230 and the lower holding plate 231. Figure 5 This is a schematic diagram showing the upper holding plate 230 and the lower holding plate 231 involved in the embodiment.

[0076] like Figure 5As shown, the upper holding disk 230 has a main body portion 260. The main body portion 260 is supported by a support member 270. A through hole 266 is formed in the support member 270 and the main body portion 260, penetrating through the support member 270 and the main body portion 260 in the vertical direction. The position of the through hole 266 corresponds to the center of the upper wafer W1 held in the upper holding disk 230. The pressing pin 281 of the impactor 280 is inserted into the through hole 266.

[0077] The impactor 280 is disposed on the upper surface of the support member 270 and includes a pressing pin 281, an actuator part 282, and a direct-acting mechanism 283. The pressing pin 281 is a cylindrical member extending in the vertical direction and is supported by the actuator part 282.

[0078] The actuator section 282, for example, uses air supplied from an electro-pneumatic regulator (not shown) to generate a fixed pressure in a fixed direction (here, vertically downward). The actuator section 282 can use the air supplied from the electro-pneumatic regulator to control the pressing load applied to the center of the upper wafer W1 by abutting against the center of the upper wafer W1. In addition, the front end of the pressing pin 281 is inserted through the through hole 266 by air from the electro-pneumatic regulator and can move freely up and down in the vertical direction.

[0079] The actuator section 282 is supported on the direct motion mechanism 283. The direct motion mechanism 283 moves the actuator section 282 in the vertical direction via a drive section, for example, with a built-in motor.

[0080] The impactor 280 is configured as described above. The movement of the actuator section 282 is controlled by the direct-acting mechanism 283, and the pressing load of the pressing pin 281 on the upper wafer W1 is controlled by the actuator section 282. As a result, the impactor 280 presses and holds the center of the upper wafer W1 held on the upper holding disk 230 so that it contacts the lower wafer W2.

[0081] A plurality of pins 261 are provided on the lower surface of the main body 260, which contact the upper surface (non-bonding surface W1n) of the upper wafer W1. The plurality of pins 261 have, for example, a diameter of 0.1 mm to 1 mm and a height of tens of μm to hundreds of μm. The plurality of pins 261 are arranged evenly at intervals of 2 mm, for example.

[0082] The upper holding disk 230 has a plurality of adsorption portions for adsorbing the upper wafer W1 in a portion of the area where the plurality of pins 261 are provided. Specifically, a plurality of outer adsorption portions 391 and a plurality of inner adsorption portions 392 are provided on the lower surface of the main body 260 of the upper holding disk 230 for suction, adsorption and holding the upper wafer W1. The plurality of outer adsorption portions 391 and the plurality of inner adsorption portions 392 have an arc-shaped or annular adsorption area when viewed from above. The plurality of outer adsorption portions 391 and the plurality of inner adsorption portions 392 have the same height as the pins 261.

[0083] Multiple outer adsorption portions 391 are disposed on the outer periphery of the main body portion 260. The multiple outer adsorption portions 391 are connected to a suction device (not shown) such as a vacuum pump, and are used to suction and adsorb the outer periphery of the upper wafer W1.

[0084] Multiple inner adsorption portions 392 are arranged circumferentially at a position radially inward of the main body 260 compared to the multiple outer adsorption portions 391. The multiple inner adsorption portions 392 are connected to multiple suction devices (not shown) such as vacuum pumps for suction and adsorption of the area between the outer periphery and the center of the upper wafer W1.

[0085] The lower holding disk 231 has a main body portion 290, which has the same diameter as or a larger diameter than the lower wafer W2. Here, a lower holding disk 231 with a diameter larger than that of the lower wafer W2 is shown. The upper surface of the main body portion 290 is an opposing surface facing the lower surface (non-bonding surface W2n) of the lower wafer W2.

[0086] A plurality of pins 291 are provided on the upper surface of the main body 290, which contact the lower surface (non-bonding surface W2n) of the lower wafer W2. The plurality of pins 291 have, for example, a diameter of 0.1 mm to 1 mm and a height of tens of μm to hundreds of μm. The plurality of pins 291 are arranged evenly at intervals of 2 mm, for example.

[0087] Additionally, on the upper surface of the main body 290, a lower side rib 292 is provided in a ring shape on the outer side of a plurality of pins 291. The lower side rib 292 is formed in a ring shape near the outer peripheral end of the lower wafer W2, supporting the outer peripheral portion of the lower wafer W2 in a manner that covers the entire circumference.

[0088] In addition, the main body 290 has a plurality of lower suction ports 293. Multiple lower suction ports 293 are provided in an adsorption area surrounded by lower ribs 292. The multiple lower suction ports 293 are connected to a suction device (not shown) such as a vacuum pump via a suction tube (not shown).

[0089] The lower holding disk 231 depressurizes the adsorption region by suctioning the adsorption region surrounded by the lower ribs 292 from multiple lower suction ports 293. As a result, the lower wafer W2 placed in the adsorption region is adsorbed and held in the lower holding disk 231.

[0090] Since the lower rib 292 supports the outer periphery of the lower surface of the lower wafer W2 in a manner that covers the entire circumference, the lower wafer W2 is appropriately drawn to the vicinity of the outer periphery. Thus, the entire surface of the lower wafer W2 can be held and held. Furthermore, since the lower surface of the lower wafer W2 is supported by multiple pins 291, the lower wafer W2 can be easily detached from the lower holding disk 231 when the drawing of the lower wafer W2 is released.

[0091] <Structure of the alignment mark camera unit>

[0092] Next, refer to Figures 6-9 The structure of the alignment mark camera unit 300 will be explained in more detail. Figure 6 This is a diagram showing the structure of the alignment mark camera unit 300 according to the embodiment. Figure 7 This diagram shows an example of an alignment mark M1 set on the upper wafer W1. Figure 8 This is a diagram showing an example of an alignment mark M2 set on the lower wafer W2.

[0093] like Figure 6 As shown, alignment marks M1 and M2 are pre-formed on the upper wafer W1 and the lower wafer W2. Alignment mark M1 is, for example, as shown in the diagram. Figure 7 The diagram shows a ring shape. Additionally, the alignment mark M2 is, for example, as shown... Figure 8 The ring shape shown has a diameter larger than that of the alignment mark M1. In the horizontal position adjustment process described later, the horizontal position of the lower holding disk 231 is adjusted by using the moving part 256 so that the center position of the ring shape of the alignment mark M1 is aligned with the center position of the ring shape of the alignment mark M2.

[0094] The alignment mark camera unit 300 includes a light source 301, collimating lenses 303 and 306, a reflecting mirror 304, a condenser lens 305, a semi-transparent mirror 307, an objective lens 308, a relay lens 309, an imaging aperture 310, an imaging lens 311, and a camera unit 302.

[0095] Light source 301 generates infrared light. Collimating lens 303 makes the light emitted from light source 301 parallel. Reflector 304 changes the path of light incident vertically upward from collimating lens 303 to a horizontal direction, causing the light to be incident on condenser lens 305. Condenser lens 305 focuses the light incident from reflector 304 and directs it onto collimating lens 306. Collimating lens 306 makes the light incident from condenser lens 305 parallel and directs it onto semi-transparent mirror 307. Semi-transparent mirror 307 reflects the light incident from collimating lens 306 toward the through-hole 312 side and allows light incident from the through-hole 312 side to pass through.

[0096] Objective lens 308 focuses light incident from transflective mirror 307 via relay lens 309 toward through-hole 312. Additionally, objective lens 308 focuses light incident from through-hole 312 onto relay lens 309. Relay lens 309 relays light incident from objective lens 308 via transflective mirror 307 to imaging lens 311. Imaging aperture 310 is positioned between transflective mirror 307 and imaging lens 311 to adjust the amount of light relayed from transflective mirror 307 to imaging lens 311. Imaging lens 311 focuses light incident from transflective mirror 307 toward imaging unit 302.

[0097] With this structure, the light source 301 of the marker camera 300 emits light above the upper holding plate 230. For example... Figure 6 As indicated by the dashed arrow, light emitted from light source 301 passes through collimating lens 303, reflecting mirror 304, condenser lens 305, collimating lens 306, semi-transparent mirror 307, relay lens 309, objective lens 308, and through-hole 312 before entering the upper wafer W1 and lower wafer W2. Then, as... Figure 6 As indicated by the dashed arrow, light reflected from the upper wafer W1 and the lower wafer W2 reaches the imaging unit 302 via the through-hole 312, objective lens 308, relay lens 309, semi-transparent mirror 307, imaging aperture 310, and imaging lens 311. That is, the imaging unit 302 uses the reflected light through the through-hole 312 to photograph the alignment marks M1 and M2.

[0098] Alignment marks M1 and M2 are set at multiple locations on the upper wafer W1 and the lower wafer W2 in a manner that corresponds one-to-one with the alignment mark imaging unit 300. For example, Figure 9 As shown, alignment marks M1 and M2 are set at at least two locations at one end and the other end of the upper wafer W1 and the lower wafer W2. Figure 9 This diagram illustrates an example of the configuration of alignment marks M1, M2 and alignment mark imaging units 300. Furthermore, the bonding device 41 includes multiple (in this case, two) alignment mark imaging units 300 corresponding to the multiple alignment marks M1, M2 provided on the upper wafer W1 and the lower wafer W2. For example, one alignment mark imaging unit 300 is provided at one end of the upper wafer W1 and one at the other end of the lower wafer W2. The multiple alignment mark imaging units 300 respectively capture images of the multiple alignment marks M1, M2.

[0099] The alignment mark camera unit 300 can also be configured to move horizontally according to the positions of alignment marks M1 and M2 provided on the upper wafer W1 and the lower wafer W2. For example, the alignment mark camera unit 300 can also be connected to the moving mechanism 315, and configured to move horizontally (in the X-axis and Y-axis directions) via the moving mechanism 315. The moving mechanism 315 can be, for example, a guide rail and a worktable that can move on the guide rail.

[0100] return Figure 6Continuing with the description of the alignment mark camera unit 300, an adjustment unit 400 for adjusting the depth of focus of the alignment mark camera unit 300 is provided in the optical path of the alignment mark camera unit 300. The adjustment unit 400 is disposed between the condenser lens 305 and the collimating lens 306. The adjustment unit 400 is an aperture with an opening, and the numerical aperture (NA) of the alignment mark camera unit 300 is changed by changing the width of the opening. The adjustment unit 400 adjusts the depth of focus of the alignment mark camera unit 300 by changing the numerical aperture of the alignment mark camera unit 300. For example, the adjustment unit 400 can make the depth of focus of the alignment mark camera unit 300 shallower by increasing the numerical aperture.

[0101] <Specific Operations of the Joining System>

[0102] Next, refer to Figure 10 To explain the specific operation of the coupling system 1 involved in the implementation method. Figure 10 This is a flowchart illustrating the process performed by the coupling system 1 according to the embodiment. Figure 10 The various processes shown are executed based on the control of the control device 70.

[0103] First, a box C1 containing multiple upper wafers W1, a box C2 containing multiple lower wafers W2, and an empty box C3 are placed on a designated mounting plate 11 in the loading / unloading station 2. Then, the upper wafers W1 in box C1 are removed by the transport device 22 and transported to the transfer unit device located in the third processing block G3.

[0104] Next, the upper wafer W1 is transported by the conveying device 61 to the surface modification device 30 of the first processing block G1. In the surface modification device 30, under a specified reduced pressure atmosphere, oxygen as a processing gas is excited and plasma-ionized. The oxygen ions irradiate the bonding surface of the upper wafer W1, and the bonding surface is subjected to plasma treatment. As a result, the bonding surface of the upper wafer W1 is modified (step S101).

[0105] Next, the upper wafer W1 is transported by the conveying device 61 to the surface hydrophilization device 40 of the first processing block G1. In the surface hydrophilization device 40, while the upper wafer W1, held on a rotating holding disk, is rotated, pure water is supplied to the upper wafer W1. This hydrophilizes the bonding surfaces of the upper wafer W1. In addition, the bonding surfaces of the upper wafer W1 are cleaned with the pure water (step S102).

[0106] Next, the upper wafer W1 is transported by the transport device 61 to the bonding device 41 of the second processing block G2. The upper wafer W1, which has been transported into the bonding device 41, is transported by the transfer unit 200 to the position adjustment mechanism 210, and the horizontal orientation is adjusted by the position adjustment mechanism 210 (step S103).

[0107] Next, the upper wafer W1 is transferred from the position adjustment mechanism 210 to the flipping mechanism 220, where the flipping mechanism 220 flips the front and back surfaces of the upper wafer W1 (step S104). Specifically, the mating surface W1j of the upper wafer W1 faces downward. Then, the upper wafer W1 is transferred from the flipping mechanism 220 to the upper holding disk 230, where the upper holding disk 230 holds the upper wafer W1 (step S105).

[0108] The processing of the lower wafer W2 is repeated in the same manner as the processing of steps S101 to S105 performed on the upper wafer W1. First, the lower wafer W2 is taken out of the box C2 by the transfer device 22 and transferred to the transfer unit device arranged in the third processing block G3.

[0109] Next, the lower wafer W2 is transported by the conveying device 61 to the surface modification device 30, where the bonding surface W2j of the lower wafer W2 is modified (step S106). After that, the lower wafer W2 is transported by the conveying 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).

[0110] Next, the lower wafer W2 is transported to the bonding unit 41 by the transport device 61. The lower wafer W2, which has been transported into the bonding unit 41, is then transported to the position adjustment mechanism 210 via the transfer unit 200. Then, the horizontal orientation of the lower wafer W2 is adjusted by the position adjustment mechanism 210 (step S108).

[0111] Then, the lower wafer W2 is transferred to the lower holding disk 231, and the lower wafer W2 is held in the lower holding disk 231 with the cut portion facing a predetermined direction (step S109).

[0112] Next, alignment is performed in both the horizontal and vertical directions between the upper wafer W1 held on the upper holding disk 230 and the lower wafer W2 held on the lower holding disk 231 (step S110). Details of step S110 will be described later.

[0113] Furthermore, 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 specified distance, for example, 80μm~100μm.

[0114] Next, a bonding process is performed to bond the upper wafer W1 to the lower wafer W2 (step S111). Specifically, the pressing pin 281 of the impactor 280 is used to press the center of the upper wafer W1 from top to bottom to make it contact the center of the lower wafer W2, thereby bonding the upper wafer W1 to the lower wafer W2.

[0115] Then, the pressing pin 281 is raised to the upper holding plate 230. Meanwhile, the vacuuming of the lower wafer W2 is stopped at the lower holding plate 231, releasing the lower holding plate 231 from holding the lower wafer W2. Thus, the bonding process in the bonding apparatus 41 is completed.

[0116] Next, refer to Figure 11 This is an example illustrating the specific process of alignment between the upper wafer W1 and the lower wafer W2 in step S110. Figure 11 This is a flowchart illustrating an example of the specific process of the alignment procedure in step S110. Figure 12 and Figure 13 This is a diagram illustrating an example of camera processing actions.

[0117] like Figure 11 As shown, the control device 70 initiates a proximity process (step S201) to bring the upper holding plate 230 closer to the lower holding plate 231. In the proximity process, firstly, the control device 70 uses the first moving part 250 of the moving part 256 to initiate the rise of the lower holding plate 231.

[0118] Next, the control device 70 performs image processing to capture images of the alignment marks M1 and M2 set on the upper wafer W1 and the lower wafer W2 (step S202).

[0119] In video processing, firstly, as... Figure 12 As shown, the control device 70 adjusts the focal depth of the alignment mark imaging unit 300 via the control adjustment unit 400, so that the upper wafer W1 and the lower wafer W2 are located 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 capture images of alignment marks M1 and M2 set on the upper wafer W1 and the lower wafer W2. This obtains an image with the focal point aligned with both alignment marks M1 and M2. The 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.

[0120] Thus, in the bonding system 1 according to this embodiment, the alignment mark camera 300 is used to capture alignment marks M1 and M2 while the upper wafer W1 and the lower wafer W2 are located within the focal depth D of the alignment mark camera 300.

[0121] Therefore, during the proximity processing, the alignment marks M1 and M2, which are used to adjust the horizontal position of the lower holding disk 231 relative to the upper holding disk 230, can be detected with high precision using images focused on both alignment marks M1 and M2. Consequently, the adjustment accuracy of the horizontal position of the lower holding disk 231 based on the detection results of alignment marks M1 and M2 can be improved, and as a result, the bonding accuracy between the substrates can be improved.

[0122] 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 narrowing the gap between the upper holding disk 230 and the lower holding disk 231, thereby making the focal depth of the alignment mark imaging unit 300 shallower. For example, as Figure 13 As shown, the control device 70 can increase the numerical aperture by increasing the opening width AW of the adjustment section 400, thereby making the focal depth D of the alignment mark imaging section 300 shallower. This allows for the real-time acquisition of images with the focal point aligned with both alignment marks M1 and M2 when the upper holding plate 230 and the lower holding plate 231 are brought close together, thus enabling higher precision detection of alignment marks M1 and M2. Consequently, the adjustment accuracy of the horizontal position of the lower holding plate 231 based on the detection results of alignment marks M1 and M2 can be further improved, resulting in further improved bonding accuracy between the substrates.

[0123] Subsequently, based on the detection results (image results) of alignment marks M1 and M2, the control device 70 controls the moving part 256 to adjust the horizontal position of the lower holding plate 231 relative to the upper holding plate 230. Specifically, the control device 70 controls the moving part 256 to adjust the horizontal position of the lower holding plate 231 relative to the upper holding plate 230 so that the ring shape of the alignment mark M2 (refer to...) Figure 8 The center position of ) and the ring shape of alignment mark M1 (refer to) Figure 7 The center position is consistent with that of the two.

[0124] Therefore, the horizontal position of the lower holding disk 231 can be adjusted with high precision based on the high-precision detection results of alignment marks M1 and M2, thereby improving the bonding accuracy between the substrates.

[0125] Next, the control device 70 determines whether the upper holding plate 230 and the lower holding plate 231 have approached the specified distance (step S204).

[0126] If the upper holding plate 230 and the lower holding plate 231 do not approach the specified distance (step S204: "No"), the control device 70 returns the process to step S202 and executes the camera processing (step S202) and the horizontal position adjustment processing (step S203) again. That is, the control device 70 executes the camera processing and the horizontal position adjustment processing multiple times during the approach process.

[0127] Therefore, until the upper wafer W1 and the lower wafer W2 are about to be joined, images with the focus aligned with both alignment marks M1 and M2 can be obtained in real time, thus enabling higher precision detection of alignment marks M1 and M2. Consequently, the adjustment accuracy of the horizontal position of the lower holding disk 231 based on the detection results of alignment marks M1 and M2 can be further improved, and as a result, the bonding accuracy between the substrates can be further improved.

[0128] In step S204, when the upper holding plate 230 and the lower holding plate 231 approach a predetermined distance (step S204: "Yes"), the control device 70 stops the approach of the upper holding plate 230 and the lower holding plate 231 (step S205). That is, the control device 70 uses the first moving part 250 of the moving part 256 to stop the rise of the lower holding plate 231. Thus, the series of alignment processes ends.

[0129] (Modified Example)

[0130] Next, refer to Figure 14 and Figure 15 Various variations of the implementation method will be described. Figure 14 This is a diagram showing the structure of the alignment mark camera unit 300 according to a modified example 1 of the embodiment.

[0131] like Figure 14 As shown, in Modified Example 1, the adjustment section 400 is disposed between the relay lens 309 and the objective lens 308. Therefore, as in the embodiment, the adjustment section 400 can increase the numerical aperture by increasing the opening width, thereby making the depth of focus of the alignment mark imaging section 300 shallower.

[0132] In addition, 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 collimating lens 306.

[0133] Figure 15 This is a diagram showing the structure of the alignment mark camera unit 300 according to a modified example 2 of the embodiment.

[0134] like Figure 15 As shown, the alignment mark camera unit 300 involved in Modification Example 2 includes a light source 301 disposed below the lower holding plate 231 and a camera unit 302 disposed above the upper holding plate 230.

[0135] Additionally, the alignment mark imaging unit 300 includes collimating lenses 303 and 306, reflecting mirrors 304a and 304b, and condenser lenses 305a and 305b disposed below the lower holding plate 231. Furthermore, the alignment mark imaging unit 300 includes an objective lens 308, a relay lens 309, an imaging aperture 310, and an imaging lens 311 disposed above the upper holding plate 230. A through hole 312 extending through the upper holding plate 230 in the thickness direction is formed therein, and a through hole 313 extending through the lower holding plate 231 in the thickness direction is formed therein.

[0136] Light source 301 generates infrared light. Collimating lens 303 makes the light emitted from light source 301 parallel. Reflector 304a changes the path of light incident vertically upward from collimating lens 303 to horizontal so that the light is incident on condenser lens 305a. Condenser lens 305a focuses the light incident from reflector 304a and directs it onto collimating lens 306. Collimating lens 306 makes the light incident from condenser lens 305a parallel and directs it onto reflector 304b. Reflector 304b changes the path of light incident horizontally from collimating lens 306 to vertical so that the light is incident on condenser lens 305b. Condenser lens 305b focuses the light incident from reflector 304b toward the through-hole 313 side.

[0137] Objective lens 308 focuses the light incident from through aperture 312 onto relay lens 309. Relay lens 309 relays the light incident from objective lens 308 to imaging lens 311. Imaging aperture 310 is positioned between relay lens 309 and imaging lens 311 to adjust the amount of light relayed from relay lens 309 to imaging lens 311. Imaging lens 311 focuses the light incident from relay lens 309 toward imaging unit 302.

[0138] With this structure, the light source 301 of the aligned marker camera 300 emits light vertically upward from below the lower holding plate 231. For example... Figure 15 As indicated by the dashed arrow, light emitted from the light source 301 passes through the collimating lens 303, reflecting mirror 304a, condenser lens 305a, collimating lens 306, reflecting mirror 304b, condenser lens 305b, and through-hole 313, and is incident on the upper wafer W1 and the lower wafer W2. Then, the light passing through the upper wafer W1 and the lower wafer W2 passes through the through-hole 312, objective lens 308, relay lens 309, imaging aperture 310, and imaging lens 311 to reach the imaging unit 302. That is, the imaging unit 302 uses transmitted light through the through-hole 312 to photograph the alignment marks M1 and M2.

[0139] In addition, the adjustment unit 400 is disposed between the condenser lens 305a and the collimating lens 306 in the same manner as in the embodiment.

[0140] Furthermore, the adjustment unit 400 may also be disposed between the relay lens 309 and the objective lens 308. Additionally, the adjustment unit 400 may also be disposed between the relay lens 309 and the objective lens 308, and between the condenser lens 305a and the collimating lens 306.

[0141] (other)

[0142] In the above embodiments, an example was described in which the first substrate W1 and the second substrate W2 are circular plates with approximately the same diameter. However, one of the first substrate W1 and the second substrate W2 may also have a shape different from that of a circular plate. For example, the second substrate W2 may also be a rectangular chip of approximately 30mm × 30mm obtained by monolithically processing a circular plate-shaped substrate with a diameter of approximately 300mm through dicing or other methods.

[0143] Furthermore, in the above embodiment, an example was described where the adjustment unit 400 adjusts the focal depth of the alignment mark camera unit 300 by changing the numerical aperture of the alignment mark camera unit 300. However, the focal depth of the alignment mark camera unit can also be adjusted using parameters different from the numerical aperture. For example, in the bonding system 1, the focal depth of the alignment mark camera unit 300 can also be adjusted by changing the wavelength of the light emitted from the light source 301.

[0144] As described above, the bonding device according to the embodiment (bonding device 41, for example) includes a first holding part (upper holding disk 230, for example), a second holding part (lower holding disk 231, for example), a moving part (moving part 256, for example), an optical system (alignment mark imaging part 300, for example), an adjustment part (adjustment part 400, for example), and a control part (control part 71, for example). The first holding part holds a first substrate (upper wafer W1, for example). The second holding part holds a second substrate bonded to the first substrate (lower wafer W2, for example). The moving part moves one of the first holding part and the second holding part closer to the other. The optical system irradiates light onto the first substrate held in the first holding part and the second substrate held in the second holding part, and uses reflected light or transmitted light to photograph the alignment marks (alignment marks M1, M2, for example) provided on the first substrate and the second substrate. The adjustment part is provided in the optical path of the optical system for adjusting the focal depth (focal depth D, for example). The control unit performs proximity processing and image processing. In proximity processing, the moving unit is controlled to bring one of the first holding unit and the second holding unit closer to the other. In image processing, during proximity processing, after the control adjustment unit adjusts the focal depth of the optical system to position the first substrate and the second substrate within the focal depth of the optical system, the optical system is used to capture the alignment marks of the first substrate and the second substrate.

[0145] Therefore, the bonding device 41 according to the embodiment can improve the bonding accuracy between substrates.

[0146] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. In fact, the above-described embodiments can be implemented in various ways. Furthermore, the above-described embodiments can be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0147] Explanation of reference numerals in the attached figures

[0148] 1: Bonding system; 30: Surface modification device; 40: Surface hydrophilization device; 41: Bonding device; 70: Control device; 71: Control unit; 72: Storage unit; 230: Upper holding disk; 231: Lower holding disk; 250: First moving part; 253: Second moving part; 256: Moving part; 300: Alignment mark imaging unit; 301: Light source; 302: Imaging unit; 400: Adjustment unit; W1: Upper wafer; W2: Lower wafer.

Claims

1. A coupling device comprising: The first holding portion holds the first substrate; The second holding portion holds the second substrate that is bonded to the first substrate; A moving part that brings one of the first holding part and the second holding part closer to the other; An optical system that irradiates light onto a first substrate held in a first holding portion and a second substrate held in a second holding portion, and uses reflected light or transmitted light to photograph alignment marks provided on the first substrate and the second substrate; An adjustment unit, disposed in the optical path of the optical system, is used to adjust the focal depth of the optical system; and Control Department in, The control unit performs the following processing: Approach processing involves controlling the moving part to bring one of the first holding part and the second holding part closer to the other. as well as In the camera processing, during the proximity processing, after adjusting the focal depth of the optical system by controlling the adjustment unit to position the first substrate and the second substrate within the focal depth of the optical system, the optical system is used to capture the alignment marks of the first substrate and the second substrate.

2. The coupling device according to claim 1, wherein, The adjustment unit adjusts the focal depth of the optical system by changing the numerical aperture of the optical system.

3. The coupling device according to claim 1, wherein, In the image processing, the control unit controls the adjustment unit. The narrower the interval between the first holding part and the second holding part, the shallower the focal depth of the optical system, thereby placing the first substrate and the second substrate within the focal depth of the optical system.

4. The coupling device according to claim 1, wherein, The moving part adjusts the 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 the horizontal direction. The control unit also performs a horizontal position adjustment process during the proximity process. In the horizontal position adjustment process, the moving unit is controlled based on the shooting results of the camera processing to adjust the horizontal position of the second holding unit relative to the first holding unit.

5. The coupling device according to claim 4, wherein, The control unit performs the camera processing and the horizontal position adjustment processing multiple times during the proximity processing.

6. The coupling device according to claim 1, wherein, Equipped with multiple of the aforementioned optical systems, Multiple alignment marks are set at multiple positions on the first substrate and the second substrate respectively captured by the multiple optical systems in a manner that corresponds one-to-one with the multiple optical systems.

7. The coupling device according to claim 1, wherein, The optical system is configured to move horizontally according to the position of alignment marks provided on the first substrate and the second substrate.

8. A joining system comprising: A surface modification apparatus for modifying the surfaces of a first substrate and a second substrate; A surface hydrophilization device that hydrophilizes the surfaces of the modified first substrate and the second substrate; as well as A bonding device that uses intermolecular forces to bond the hydrophilized first substrate to the second substrate. The joining device includes: A first holding portion holds the first substrate; The second holding portion holds the second substrate; A moving part that brings one of the first holding part and the second holding part closer to the other; An optical system that irradiates light onto a first substrate held in a first holding portion and a second substrate held in a second holding portion, and uses reflected light or transmitted light to photograph alignment marks provided on the first substrate and the second substrate; An adjustment unit, disposed in the optical path of the optical system, is used to adjust the focal depth of the optical system; and Control Department The control unit performs the following processing: Proximity processing, controlling the moving part to bring one of the first holding part and the second holding part closer to the other; and In the camera processing, during the proximity processing, after adjusting the focal depth of the optical system by controlling the adjustment unit to position the first substrate and the second substrate within the focal depth of the optical system, the optical system is used to capture the alignment marks of the first substrate and the second substrate.

9. A joining method, comprising the following steps: The first substrate is held using a first holding portion for holding the first substrate; The second substrate is held using a second holding portion for holding the second substrate in contact with the first substrate; and A moving part is used to bring one of the first holding part and the second holding part closer to the other. In the process of making the approach, after adjusting the focal depth of the optical system so that the first substrate and the second substrate are within the focal depth of the optical system, the optical system is used to photograph the alignment marks on the first substrate and the second substrate. The optical system is a system that illuminates the first substrate and the second substrate and uses reflected or transmitted light to photograph the alignment marks provided on the first substrate and the second substrate.

Images