Substrate bonding apparatus and substrate bonding method

Abstract

To provide a substrate bonding apparatus and a substrate bonding method.SOLUTION: A substrate bonding apparatus forms a contact area where a first substrate 211 and a second substrate 213 come into contact at the center of the first substrate 211 and the second substrate 213, and bonds the first substrate 211 and the second substrate 213 together such that the contact area expands from the center, using the contact area formed at the center as the starting point for bonding. A bonding portion 300 includes an upper stage 322 and a lower stage 332 which are holding portions which hold at least one of the first substrate 211 and the second substrate, an observation portion 344 which is a detection portion which detects that a contact area has been formed at the center, and a control portion 150 which releases the holding of at least one of the first substrate 211 and the second substrate by the holding portions in response to the detection portion detecting that a contact area has been formed at the center.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a substrate bonding apparatus and a substrate bonding method. [Background technology]

[0002] There is an apparatus that activates the surfaces of two substrates and brings the activated surfaces into contact with each other to bond the two substrates together (see, for example, Patent Document 1). Patent Document 1: JP 2013-258377 A

[0003] The time required from the start to the completion of bonding may vary depending on the conditions of the two substrates to be bonded. For this reason, if bonding is deemed to be completed when a certain time has elapsed from the start of bonding, the certain time is set longer to absorb the variation in bonding time. As a result, when bonding substrates whose actual bonding time is shorter than the set time, a waiting time occurs between the completion of bonding and the start of the next process, and this waiting time is wasted. Summary of the Invention

[0004] In a first aspect of the present invention, there is provided a substrate bonding apparatus that forms a contact area where a first substrate and a second substrate come into contact at a center of the first substrate and the second substrate, and bonds the first substrate and the second substrate together so that the contact area expands from the center, using the contact area formed at the center as a starting point for bonding. The substrate bonding apparatus includes a holding unit that holds at least one of the first substrate and the second substrate, a detection unit that detects that the contact area has been formed at the center, and a control unit that releases the holding of at least one of the first substrate and the second substrate by the holding unit in response to the detection unit detecting that the contact area has been formed at the center.

[0005] In a second aspect of the present invention, there is provided a substrate bonding apparatus that forms a contact area where a first substrate and a second substrate come into contact at a center of the first substrate and the second substrate, and bonds the first substrate and the second substrate together so that the contact area expands from the center using the contact area formed at the center as a starting point for bonding, the substrate bonding apparatus including a detection unit that detects that the contact area has been formed at the center, and the detection unit detects that the contact area has been formed at the center by detecting information regarding a change in electrical characteristics of at least one of the first substrate and the second substrate.

[0006] In a third aspect of the present invention, there is provided a substrate bonding apparatus that forms a contact area where a first substrate and a second substrate come into contact at a center of the first substrate and the second substrate, and bonds the first substrate and the second substrate together so that the contact area expands from the center, using the contact area formed at the center as a starting point for bonding, the substrate bonding apparatus including a detection unit that detects that the contact area has been formed at the center, and the detection unit detects that the contact area has been formed at the center by detecting vibrations generated on one side of the first substrate and the second substrate on the other side of the first substrate and the second substrate.

[0007] In a fourth aspect of the present invention, there is provided a substrate bonding apparatus that forms a contact area where a first substrate and a second substrate come into contact at a center of the first substrate and the second substrate, and bonds the first substrate and the second substrate together so that the contact area expands from the center using the contact area formed at the center as a starting point for bonding, the substrate bonding apparatus comprising: a holding unit that holds at least one of the first substrate and the second substrate; a judgment unit that judges whether a predetermined bonding force has been secured in the contact area; and a control unit that releases the holding of at least one of the first substrate and the second substrate by the holding unit in response to the judgment unit determining that the bonding force has been secured.

[0008] In a fifth aspect of the present invention, there is provided a substrate bonding method in which a contact area where a first substrate and a second substrate come into contact is formed in the center of the first substrate and the second substrate, and the first substrate and the second substrate are bonded together so that the contact area expands from the center using the contact area formed in the center as a starting point for bonding, the substrate bonding method including a detection step of detecting that the contact area has been formed in the center, and a release step of releasing the holding of at least one of the first substrate and the second substrate in response to detecting that the contact area has been formed in the center in the detection step.

[0009] In a sixth aspect of the present invention, there is provided a substrate bonding method in which a contact area where a first substrate and a second substrate come into contact is formed in the center of the first substrate and the second substrate, and the first substrate and the second substrate are bonded together so that the contact area expands from the center using the contact area formed in the center as a starting point for bonding, the substrate bonding method including a detection step of detecting that the contact area has been formed in the center, in which the detection step detects that the contact area has been formed in the center by detecting information regarding a change in electrical characteristics of at least one of the first substrate and the second substrate.

[0010] In a seventh aspect of the present invention, there is provided a substrate bonding method in which a contact area where a first substrate and a second substrate come into contact is formed in the center of the first substrate and the second substrate, and the first substrate and the second substrate are bonded together so that the contact area expands from the center using the contact area formed in the center as a starting point for bonding, the substrate bonding method including a detection step of detecting that the contact area has been formed in the center, in which the detection step detects that the contact area has been formed in the center by detecting vibrations generated on one side of the first substrate and the second substrate on the other side of the first substrate and the second substrate.

[0011] In an eighth aspect of the present invention, there is provided a substrate bonding method in which a contact area where a first substrate and a second substrate come into contact is formed in the center of the first substrate and the second substrate, and the first substrate and the second substrate are bonded together so that the contact area expands from the center using the contact area formed in the center as a starting point for bonding, the substrate bonding method including a judgment step of judging whether a predetermined bonding force has been secured in the contact area, and a release step of releasing the holding of at least one of the first substrate and the second substrate in response to determining in the judgment step that the bonding force has been secured.

[0012] The above summary of the invention does not list all the features of the invention. Subcombinations of these features may also be inventions. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a substrate bonding apparatus 100. [Diagram 2] 2 is a schematic plan view of a substrate 210. FIG. [Diagram 3] 2 is a flow chart showing a procedure for overlapping substrates 210. [Figure 4] 2 is a schematic cross-sectional view of a substrate holder 221 holding a substrate 211. FIG. [Diagram 5] 2 is a schematic cross-sectional view of a substrate holder 223 holding a substrate 213. FIG. [Figure 6] FIG. 2 is a schematic cross-sectional view of a bonding portion 300. [Figure 7] FIG. 2 is a schematic cross-sectional view of a bonding portion 300. [Figure 8] FIG. 2 is a schematic cross-sectional view of a bonding portion 300. [Figure 9] FIG. 2 is a schematic cross-sectional view of a bonding portion 300. [Figure 10] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 11] FIG. 2 is a schematic cross-sectional view of a bonding portion 300. [Figure 12] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 13] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 14] 13 is a schematic diagram illustrating the operation of a detector 341. FIG. [Figure 15] 13 is a schematic diagram illustrating the operation of a detector 341. FIG. [Figure 16] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 17] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 18] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 19] 2 is a schematic diagram showing the state of substrates 211 and 213 during the bonding process. [Figure 20] 13 is a schematic diagram illustrating another structure of the detector 341. FIG. [Figure 21] 13 is a schematic diagram illustrating the operation of a detector 341. FIG. [Figure 22] 13 is a schematic diagram illustrating the operation of a detector 341. FIG. [Diagram 23] 13 is a schematic diagram illustrating the structure of an observation unit 345. FIG. [Figure 24] 13 is a schematic diagram illustrating another structure of the detector 343. FIG. [Diagram 25] 13 is a schematic diagram illustrating the operation of a detector 343. FIG. [Figure 26] 13 is a schematic diagram illustrating the structure of an observation section 346. FIG. [Figure 27] 13 is a schematic diagram illustrating the operation of the observation unit 346. FIG. [Figure 28] 13 is a schematic diagram illustrating the structure of an observation unit 347. FIG. [Figure 29] 13 is a schematic diagram illustrating the structure of an observation unit 348. FIG. [Diagram 30] 13 is a schematic diagram illustrating the structure of an observation unit 349. FIG. [Diagram 31] 6 is a schematic diagram illustrating the structure of an observation unit 610. FIG. [Diagram 32] 13 is a schematic diagram illustrating the structure of an observation unit 620. FIG. [Diagram 33] 2 is a schematic cross-sectional view showing a structure of a part of a bonding portion 300. FIG. [Diagram 34] 11 is a flowchart showing a part of the operation procedure of the bonding unit 300. [Diagram 35] 11A to 11C are diagrams illustrating the operation of the bonding unit 300. [Diagram 36] 11A to 11C are diagrams illustrating the operation of the bonding unit 300. [Figure 37] 11A to 11C are diagrams illustrating the operation of the bonding unit 300. [Figure 38] 11A to 11C are diagrams illustrating the operation of the bonding unit 300. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described below through the embodiments of the invention. The following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0015] 1 is a schematic plan view of a substrate bonding apparatus 100. The substrate bonding apparatus 100 includes a housing 110, substrate cassettes 120, 130 and a control unit 150 arranged outside the housing 110, and a transport unit 140, a bonding unit 300, a holder stocker 400 and a pre-aligner 500 arranged inside the housing 110. The inside of the housing 110 is temperature-controlled and is kept at, for example, room temperature.

[0016] One substrate cassette 120 accommodates a plurality of substrates 210 to be superimposed. The other substrate cassette 130 can accommodate a plurality of bonded substrates 230 produced by superimposing the substrates 210. The substrate cassettes 120, 130 can be individually attached to and detached from the housing 110. In this manner, by using the substrate cassette 120, a plurality of substrates 210 can be loaded collectively into the substrate bonding apparatus 100. Furthermore, by using the substrate cassette 130, a plurality of bonded substrates 230 can be unloaded collectively from the substrate bonding apparatus 100.

[0017] The transport section 140 performs a transport function within the housing 110. The transport section 140 transports a single substrate 210, a substrate holder 220, a substrate holder 220 holding a substrate 210, a bonded substrate 230 formed by stacking substrates 210, and the like.

[0018] The control unit 150 comprehensively controls each unit of the substrate bonding apparatus 100 by making them cooperate with each other. The control unit 150 also receives instructions from an external user and sets manufacturing conditions for manufacturing the bonded substrate 230. Furthermore, the control unit 150 also has a user interface that displays the operating state of the substrate bonding apparatus 100 to the outside.

[0019] The bonding section 300 has a pair of stages facing each other and each holding a substrate 210. Under the control of the control section 150, the two substrates 210 held on the stages are aligned with each other, and then the substrates 210 are brought into contact with each other and bonded together. As a result, the substrates 210 form a bonded substrate 230. Note that bonding includes a state in which the terminals provided on the two substrates 210 are electrically connected to each other between the substrates 210, and a state in which the insulating films formed on the surfaces of the two substrates 210 are bonded to each other and the substrates 210 are not electrically connected to each other, and in either state, it includes both a state in which the two substrates 210 can be separated and a state in which the two substrates 210 cannot be separated. When the state in which the two substrates 210 are bonded together is a separable state, it is preferable to carry the substrates 210 into a heating device such as an annealing furnace and heat them after bonding the two substrates 210 together.

[0020] The holder stocker 400 houses a plurality of substrate holders 220. The substrate holders 220 are formed of a hard material such as alumina ceramics, and have a holding portion that adsorbs the substrate 210, and an edge portion disposed on the outside of the holding portion. Inside the substrate bonding apparatus 100, the substrate holders 220 individually hold the substrates 210, and are handled integrally with the substrates 210. This ensures flatness of the substrates 210 that may be warped or bent.

[0021] When the bonded substrate stack 230 is removed from the substrate bonding apparatus 100, the substrate holder 220 is separated from the bonded substrate stack 230 and stored again in the holder stocker 400. This allows a small number of substrate holders 220 to be used repeatedly. Therefore, the substrate holder 220 can be considered to be a part of the substrate bonding apparatus 100.

[0022] The pre-aligner 500 cooperates with the transport unit 140 to hold the substrate 210 carried into the substrate bonding apparatus 100 on the substrate holder 220. The pre-aligner 500 may also be used when separating the bonded substrate 230 carried out from the bonding unit 300 from the substrate holder 220.

[0023] The substrate bonding apparatus 100 can bond unprocessed silicon wafers, compound semiconductor wafers, glass substrates, etc., in addition to the substrate 210 on which elements, circuits, terminals, etc. are formed. It can also bond a circuit board on which a circuit is formed to an unprocessed substrate, or bond substrates of the same type, such as two circuit boards or two unprocessed substrates. Furthermore, the substrate 210 to be bonded may itself be a bonded substrate 230 already formed by stacking a plurality of substrates.

[0024] 2 is a schematic plan view of a substrate 210 that can be bonded in the substrate bonding apparatus 100. The substrate 210 has a notch 214, a plurality of circuit regions 216, and a plurality of alignment marks 218.

[0025] The notch 214 is formed on the periphery of the substrate 210, which is generally circular as a whole, and serves as an indicator of the crystal orientation of the substrate 210. Furthermore, when handling the substrate 210, the arrangement direction of the circuit regions 216 in the substrate 210 can be known by detecting the position of the notch 214. Furthermore, when circuit regions 216 including different circuits are formed on one substrate 210, the circuit regions 216 can be distinguished based on the notch 214.

[0026] The circuit regions 216 are periodically arranged on the surface of the substrate 210 in the surface direction of the substrate 210. Each of the circuit regions 216 is provided with a semiconductor device, wiring, a protective film, etc., formed by photolithography technology or the like. Pads, bumps, etc., which serve as connection terminals when electrically connecting the substrate 210 to another substrate 210, a lead frame, etc., are also arranged in the circuit region 216.

[0027] The alignment marks 218 are arranged, for example, overlapping the scribe lines 212 arranged between the circuit regions 216, and are used as indicators when aligning the substrate 210 with another substrate 210 to be laminated. The scribe lines 212 are areas that will eventually disappear due to dicing, so providing the alignment marks 218 does not reduce the area of ​​the circuit regions 216. The alignment marks 218 may be arranged inside the circuit regions 216, or a part of a structure formed in the circuit regions 216 may be used as the alignment marks 218.

[0028] 3 is a flow chart showing the procedure for producing a bonded substrate 230 by bonding substrates 210 in the substrate bonding apparatus 100. In the substrate bonding apparatus 100, a control unit 150 controls the operation of each unit. The control unit 150 also operates as a determination unit that determines whether or not bonding of the substrates 210 has been completed.

[0029] Inside the substrate bonding apparatus 100, the substrates 210 are operated in a state in which they are held one by one by the substrate holder 220. Therefore, the control unit 150 first causes the pre-aligner 500 to hold the substrates 210 taken out of the substrate cassette 120 one by one by the substrate holder 220. Next, the control unit 150 causes the multiple substrates 210 to be bonded together to be carried into the bonding unit 300 together with the substrate holder 220 (step S101).

[0030] Next, the control unit 150 detects the alignment marks 218 provided on each of the substrates 210 carried into the bonding unit 300 (step S102). Furthermore, the control unit 150 detects the relative positions of the substrates 210 to be bonded together based on the positions of the detected alignment marks 218 (step S103).

[0031] Next, the control unit 150 activates the surface of the substrate 210 (step S104). The substrate 210 can be activated, for example, by exposing the surface of the substrate 210 to plasma for cleaning. As a result, when the substrate 210 is brought into contact with another substrate 210, the substrates 210 are bonded to each other and integrated. The substrate 210 can also be activated by a mechanical process such as polishing, or a chemical process such as cleaning. A plurality of types of activation methods may be used in combination.

[0032] Next, the control unit 150 starts adjusting the temperature of the substrates 210 to be bonded together (step S105). The temperature adjustment performed here is, for example, temperature adjustment for performing correction to compensate for the magnification difference with respect to the design specifications of the substrates 210. In addition, deformation such as warping of the substrates 210 may be corrected by a method other than temperature adjustment, for example, in combination with a correction method using an actuator to be described later. This allows the multiple substrates 210 to be aligned with high precision even if each substrate 210 has its own inherent distortion.

[0033] Next, the control unit 150 aligns the multiple substrates 210 to be bonded together (step S106). The alignment is performed by moving one substrate 210 relative to the other substrate 210 based on the relative positions of the substrates 210 detected in step S103.

[0034] Next, the control unit 150 brings parts of the overlapped substrates 210 into contact with each other to form a starting point of bonding on a part of the substrates 210 (step S107). The parts in contact with each other are contact areas where the substrates 210 are in contact with each other, and are contact areas formed when bonding starts. The starting point may be an area having an area. The starting point of bonding in a pair of substrates 210 to be bonded together is formed when a part of one substrate 210 is pressed against a part of the other substrate 210, and the atmosphere or the like sandwiched between the substrates 210 is pushed out, causing the substrates 210 to come into direct contact with each other. This contact causes the contact areas of the two activated substrates 210 to bond together through chemical bonds such as hydrogen bonds. After the two substrates 210 are partially brought into contact with each other, the two substrates 210 are maintained in contact with each other. At this time, the substrates 210 may be pressed against each other to increase the area of ​​the contacted portions, thereby widening the contact area. When a predetermined time has elapsed while maintaining the contact state, a bonding force large enough to prevent misalignment between the substrates 210 during the bonding process is secured between the two substrates 210. As a result, a bonding starting point is formed at the contacted portions of the substrates 210.

[0035] In addition, when starting points for bonding are formed at multiple locations in the surface direction of the substrates 210, air bubbles remaining in the region between the multiple starting points cannot be discharged during the bonding process, and voids may occur in the finally completed bonded substrate 230. Therefore, when bonding two substrates 210 together, it is preferable to form a starting point for bonding at one location on the substrates 210 and bond the entire substrates 210 together by expanding the contact region, which is the region where the substrates 210 are bonded together, from the starting point for bonding.

[0036] Therefore, when bonding the substrates 210 in the bonding unit 300, for example, a protruding portion is formed on one of the substrates 210 to be bonded, and the protruding portion is brought into contact with the other substrate 210 to form a bonding starting point at a predetermined position. When forming a bonding starting point, it is preferable to continue to maintain the shape of the protruding portion of the substrates until the bonding starting point is formed, in order to prevent starting points from being formed at multiple locations.

[0037] Next, the control unit 150 checks whether or not a contact area of ​​the substrates 210 is formed in the substrates 210 whose parts are pressed against each other, and whether or not the above-mentioned predetermined magnitude of bonding force is secured between the two substrates 210 (step S108). When detecting that the substrates 210 are bonded at this stage, it checks whether or not a starting point of bonding that triggers the start of bonding of the substrates 210 is formed. Therefore, in step S108, it checks whether or not a region that serves as a starting point of bonding has been formed in the region where the parts of the substrates 210 were pressed against each other in step S107 or in a position close to that region.

[0038] When it is determined that a bonding starting point is formed on the substrate 210 (step S108: YES), that is, when the control unit 150 determines that the above-mentioned predetermined magnitude of bonding force is secured between the contacting parts of the two substrates 210, the control unit 150 releases at least one of the substrates 210 by releasing the substrate 210 (step S109) and allows the two substrates 210 to be bonded together by adsorbing each other by expanding the contact area of ​​the two substrates 210. That is, the bonding unit 300 constitutes a contact unit. Note that, when it is not determined in step S108 that a bonding starting point is formed on the substrate 210 (step S108: NO), the control unit 150 continues to hold both substrates 210 and continues to press a part of the substrate 210 to form a bonding starting point.

[0039] Next, the control unit 150 checks whether or not the contact area of ​​the substrate 210 has expanded from the starting point of bonding formed on the substrate 210 (step S110). Whether or not the contact area of ​​the substrate 210 has expanded can be confirmed, for example, by checking whether or not the contact area has been formed in an area different from the area where the starting point of bonding was formed.

[0040] In step S110, if it is not confirmed that the contact area of ​​the substrate 210 is expanding (step S110: NO), the control unit 150 determines that the bonding of the substrates 210 is hindered for some reason. Then, after taking measures such as stopping the operation of the bonding unit 300, issuing an alarm to the outside, and removing the substrates 210 being bonded from the bonding unit 300 (step S111), the control is returned to step S101 to start bonding the next substrate 210.

[0041] In step S110, if it is confirmed that the contact area of ​​the substrate 210 is expanding (step S110: YES), the control unit 150 determines that the bonding of the substrates 210 is progressing, and advances control to the next step. Next, the control unit 150 checks whether the bonding of the substrates 210 is complete (step S112). Completion of the bonding may be determined, for example, by checking whether the contact area of ​​the substrate 210 is formed on the outer edge of the substrate 210. In this way, the control unit 150 can reliably confirm the completion of bonding even when the time required for bonding varies for each substrate 210.

[0042] When the control unit 150 confirms in step S112 that the bonding of the substrates is completed (step S112: YES), it ends the temperature control and the like for the substrates 211, 213, and causes the conveying unit 140 to carry the bonded substrate 230 out of the bonding unit 300 (step S113). The substrate 210 carried out of the bonding unit 300 is separated into the bonded substrate 230 and the substrate holder 220, and then housed in the substrate cassette 130.

[0043] Furthermore, if the control unit 150 is unable to confirm that the bonding of the substrates 210 has been completed in step S112 (step S112: NO), the control unit 150 may repeatedly check whether the bonding of the substrates 210 has been completed until the completion of the bonding of the substrates 210 is confirmed, but if the completion of the bonding of the substrates 210 cannot be confirmed even after a predetermined threshold time has elapsed, the control unit 150 may stop bonding the substrates 210, as in the case of step S110: NO.

[0044] When the control unit 150 confirms that the contact area of ​​the substrate 210 has expanded in step S110, the control unit 150 may also detect the speed at which the contact area of ​​the substrate 210 expands, thereby predicting the time at which the bonding of the substrate 210 is completed. The speed at which the contact area of ​​the substrate 210 expands may be calculated by the control unit, for example, by measuring the time from when a part of the substrate 210 is pressed in step S107 to when it is detected in step S110 that the substrate 210 has been bonded in an area different from the starting point of bonding.

[0045] Furthermore, when a starting point for bonding is formed in a part of the substrate 210, the relative positions of the substrates 210 to be bonded together are fixed in the surface direction of the substrates 210, and even if the holding of at least one of the substrates 210 to be bonded together is released, the substrates 210 are not displaced, and one substrate 210 does not become misaligned with respect to the other substrate 210. Therefore, the control unit 150 may carry out the two substrates 210 from the bonding unit 300 before bonding of the substrates 210 is completed up to the periphery.

[0046] 4 is a schematic cross-sectional view showing a state in which one substrate 211, which is carried into the bonding section 300 in step S101, is held by the substrate holder 221. The substrate holder 221 has an electrostatic chuck, a vacuum chuck, or the like, and adsorbs and holds the substrate 211 on a holding surface 222.

[0047] The holding surface 222 of the substrate holder 221 has a curved shape with the center being higher and the periphery being lower. Therefore, the substrate 211 attracted to the holding surface 222 is also curved with the center being protruding. Furthermore, while the substrate holder 221 continues to hold the substrate 211, the convex shape of the substrate 210 is maintained. The shape of the holding surface 222 of the substrate holder 221 may be a spherical surface, a parabolic surface, a cylindrical surface, or the like.

[0048] When the substrate 211 is attracted to the holding surface 222, the surface of the substrate 211 is deformed to expand in the planar direction at the upper surface of the substrate 211 in the figure, compared to the center line A in the thickness direction of the substrate 211 shown by the dashed line in the figure, in the curved substrate 211. Also, the surface of the substrate 211 is deformed to contract in the planar direction at the lower surface of the substrate 211 in the figure.

[0049] Therefore, by holding the substrate 211 in the substrate holder 221, the in-plane magnification of the circuit region 216 formed on the surface of the substrate 211 with respect to the design specifications is also enlarged. Therefore, a plurality of substrate holders 221 having different curvatures of the holding surface 222 may be prepared, and the amount of deformation of the substrate 211 may be changed to adjust the amount of magnification correction of the substrate 211.

[0050] The substrate holder 221 also has a plurality of observation holes 227, 228, 229 penetrating in the thickness direction. One observation hole 227 is disposed in a region including the central axis X in the radial direction of the substrate holder 221. Another observation hole 229 is disposed in a region including the periphery of the substrate 211 held by the substrate holder 221. Still another observation hole 228 is disposed at a position intermediate the other observation holes 227, 228. Each of the observation holes 227, 228, 229 is filled with a material transparent to the wavelength of the illumination light used when observing the substrate 211, and the holding surface 222 of the substrate holder 221 forms a smoothly curved surface.

[0051] 5 is a schematic cross-sectional view showing a state in which another substrate 213 is held by the substrate holder 223. The substrate holder 223 has a flat holding surface 224 and a function of adsorbing the substrate 213, such as an electrostatic chuck or a vacuum chuck. The substrate 213 adsorbed and held by the substrate holder 223 is in close contact with the holding surface 224 and becomes flat following the shape of the holding surface 224.

[0052] Therefore, in the bonding section 300, when the substrate 211 held by the substrate holder 221 shown in Fig. 4 and deformed into a convex shape is pressed against the substrate 213 held in a flat state by the substrate holder 223 shown in Fig. 5, the substrates 211 and 213 are pressed strongly against each other at one point in the center. Also, while the substrate holders 221 and 223 are holding the substrates 211 and 213, respectively, the peripheral regions of the substrates 211 and 213 remain separated from each other.

[0053] In the above example, a combination of the substrate 211 deformed into a convex shape and the flat substrate 213 is taken as an example. However, even if, for example, the substrates 211 and 213 are both deformed into a convex shape, the substrates 211 and 213 are deformed into a convex shape and a concave shape with different curvatures, or the substrates 211 and 213 are deformed into a cylindrical shape with an unbalanced central axis, the substrates 211 and 213 can be brought into contact at one point in the bonding section 300.

[0054] Fig. 6 is a schematic cross-sectional view showing the structure of bonding unit 300. Fig. 6 also shows the state of bonding unit 300 immediately after substrates 211, 213 and substrate holders 221, 223 are carried in. Bonding unit 300 includes a frame 310, an upper stage 322, and a lower stage 332.

[0055] The frame 310 has a bottom plate 312 and a top plate 316 that are parallel to a horizontal floor surface, and a plurality of support columns 314 that are perpendicular to the floor plate. The bottom plate 312, the support columns 314, and the top plate 316 form the rectangular frame 310 that houses other members of the bonding unit 300.

[0056] Upper stage 322 is fixed facing downward to the lower surface of top plate 316 in the figure. Upper stage 322 has a holding function such as a vacuum chuck or an electrostatic chuck, and forms a holding portion that holds substrate holder 221. In the state shown in the figure, upper stage 322 already holds substrate holder 221 that holds substrate 211.

[0057] Furthermore, the upper stage 322 has a plurality of observation windows 327, 328, 329 provided corresponding to the positions of the observation holes 227, 228, 229 of the held substrate holder 221. Each of the observation windows 327, 328, 329 is filled with a material that is transparent to the wavelength of the illumination light used when observing the substrate 211, and the lower surface of the upper stage 322 forms a flat surface including the areas where the observation windows 327, 328, 329 are arranged.

[0058] The bonding section 300 has a plurality of detectors 341, 342, 343 provided to penetrate the top plate 316 of the frame 310 in the thickness direction at positions corresponding to the observation windows 327, 328, 329 provided in the upper stage 322. The detectors 341, 342, 343 form an observation section 344 for observing the bonding state of the substrates 211, 213 in the bonding section 300 through the observation windows 327, 328, 329 optically communicating with the lower surface of the upper stage 322 and the observation holes 227, 228, 229 of the substrate holder 221.

[0059] The detectors 341, 342, and 343 can be formed using, for example, a light receiving unit such as a photodiode and an irradiation light source. In this case, when the substrate holder 221 holding the substrate 211 is held on the upper stage 322, the light intensity of the reflected light from the substrates 211, 213, etc. can be observed by the detectors 341, 342, and 343 through the observation windows 327, 328, and 329 and the observation holes 227, 228, and 229.

[0060] Furthermore, the detectors 341, 342, and 343 can be formed using, for example, an imaging element such as a CCD or CMOS sensor and an illumination light source. In this case, when the substrate holder 221 holding the substrate 211 is held on the upper stage 322, an image of the substrate 211 on the upper stage 322 can be captured and observed by the detectors 341, 342, and 343 through the observation windows 327, 328, and 329 and the observation holes 227, 228, and 229. Furthermore, when the substrates 211 and 213 overlap in the bonding section 300, images of the substrates 211 and 213 can be captured together.

[0061] Furthermore, the detectors 341, 342, 343 use long wavelength light such as infrared light as an irradiation light source or illumination light source, which transmits through the substrate 211 held on the upper stage 322 and allows observation of the substrate 213 bonded to the substrate 211. The outputs of the detectors 341, 342, 343 are processed in, for example, the control unit 150, and the bonding of the substrates 211 and 213 is detected based on the observation results of the detectors 341, 342, 343. When infrared light is used as the illumination light source, a change in the position of the boundary between the contact area and the non-contact area of ​​the substrates 211, 213 may be observed by photographing an area including the center of the substrates 211, 213. In this case, the shape of the contact area is detected at the time when the starting point of bonding is formed or in the process of the contact area expanding. The shape of the contact area is one piece of information regarding the state of the expansion of the contact area. That is, the observation unit 344 constitutes a detection unit that detects information regarding the expansion of the contact area. The information regarding the expansion of the contact area is information that changes according to the progress of the expansion of the contact area. When the control unit 150 determines that the shape of the contact area satisfies a predetermined condition, it may determine that the contact state of the contact area is a state in which bonding will be appropriately performed thereafter, and may carry out the substrates 211, 213 from the lower stage 332. The predetermined condition is, for example, that the shape of the contact area is approximately a perfect circle. The shape of the contact area that satisfies the predetermined condition is stored in advance. In addition, if the shape of the contact area has a unique shape for each type of wafer, each lot, each wafer manufacturing process, etc., the expanding shape of each contact area may be stored in advance in a memory unit and compared with the shape stored at the time of actual bonding. Furthermore, when infrared light is used as the illumination light source, the observation area may be an area extending radially from at least the center toward the periphery of the substrates 211, 213. In this case, by continuously capturing a plurality of images, for example, every 500 msec, during the process in which the contact area expands, and comparing an image of the contact area captured at a certain point in time with an image of the contact area captured at an earlier point in time, the direction and speed of the contact area as it expands can be estimated.

[0062] The lower stage 332 is disposed opposite the upper stage 322, and is mounted on the upper surface in the figure of a Y-direction driving unit 333 which is superimposed on an X-direction driving unit 331 disposed on the upper surface of the bottom plate 312. The lower stage 332 faces the substrate 211 held by the upper stage 322, and forms a holding unit which holds the substrate 213. In the state shown in the figure, the lower stage 332 already holds the substrate holder 223 which holds the substrate 213.

[0063] In the illustrated state, the substrate holder 221 having the curved holding surface 222 is held by the upper stage 322 located at the top of the figure, and the substrate 213 held by the substrate holder 223 having the flat holding surface 224 is held by the lower stage 332 located at the bottom of the figure. However, the combination of the upper stage 322 and the lower stage 332 with the substrate holders 221 and 223 is not limited to this. In addition, the flat substrate holder 223 or the curved substrate holder 221 may be carried into both the upper stage 322 and the lower stage 332.

[0064] In the bonding section 300, the X-direction driver 331 moves in the direction indicated by the arrow X in the figure, parallel to the bottom plate 312. The Y-direction driver 333 moves in the direction indicated by the arrow Y in the figure, parallel to the bottom plate 312, on the X-direction driver 331. By combining the operations of the X-direction driver 331 and the Y-direction driver 333, the lower stage 332 moves two-dimensionally, parallel to the bottom plate 312. This allows the substrate 213 mounted on the lower stage 332 to be aligned with the substrate 211 held by the upper stage 322.

[0065] Further, the lower stage 332 is supported by an elevation drive unit 338 that moves up and down in the direction indicated by the arrow Z perpendicular to the bottom plate 312. The lower stage 332 can move up and down relative to the Y direction drive unit 333. As a result, the elevation drive unit 338 forms a pressing unit that presses the substrate 213 mounted on the lower stage 332 against the substrate 211 held by the upper stage 322.

[0066] The amount of movement of the lower stage 332 by the X-direction drive unit 331, the Y-direction drive unit 333, and the elevation drive unit 338 is precisely measured using an interferometer or the like. The X-direction drive unit 331 and the Y-direction drive unit 333 may also be configured in two stages, a coarse movement unit and a fine movement unit. This allows both highly accurate alignment and high throughput, and allows the substrate 213 mounted on the lower stage 332 to be bonded at high speed without reducing control accuracy.

[0067] A microscope 334 and an activation device 336 are further mounted on the Y-direction driving unit 333, respectively, on the sides of the lower stage 332. The microscope 334 can observe the lower surface of the downward-facing substrate 211 held on the upper stage 322. The activation device 336 generates plasma that cleans the lower surface of the substrate 211 held on the upper stage 322.

[0068] The bonding section 300 may further include a rotation drive section that rotates the lower stage 332 around a rotation axis perpendicular to the bottom plate 312, and a swing drive section that swings the lower stage 332. This makes it possible to make the lower stage 332 parallel to the upper stage 322 and to rotate the substrate 213 held by the lower stage 332, thereby improving the alignment accuracy of the substrates 211, 213.

[0069] Furthermore, the bonding section 300 has a pair of microscopes 324, 334 and a pair of activation devices 326, 336. One of the microscopes 324 and the activation device 326 is fixed to the side of the upper stage 322 on the lower surface of the top plate 316. The microscope 324 can observe the upper surface of the substrate 213 held on the lower stage 332. The activation device 326 generates plasma that cleans the upper surface of the substrate 213 held on the lower stage 332.

[0070] The other microscope 334 and the activation device 336 are mounted on the side of the lower stage 332 in the Y-direction driving unit 333. The microscope 334 can observe the lower surface of the substrate 211 held on the upper stage 322. The activation device 336 generates plasma that cleans the lower surface of the substrate 211 held on the upper stage 322.

[0071] The microscopes 324, 334 can be used in step S102 in the following procedure: The control unit 150 calibrates the relative positions of the microscopes 324, 334 by adjusting the focal points of the microscopes 324, 334 relative to each other, as shown in FIG.

[0072] 7, the control unit 150 operates the X-direction driving unit 331 and the Y-direction driving unit 333 to cause the microscopes 324, 334 to detect the alignment marks 218 provided on the substrates 211, 213 (step S102 in FIG. 3). The control unit 150 grasps the amount of movement of the lower stage 332 by the X-direction driving unit 331 and the Y-direction driving unit 333 until the alignment mark 218 is detected.

[0073] In this way, the relative positions of the substrates 211 and 213 are determined by detecting the positions of the alignment marks 218 of the substrates 211 and 213 with the microscopes 324 and 334, whose relative positions are known (step S103 in FIG. 3). As a result, when aligning the overlapping substrates 211 and 213, it is sufficient to calculate the relative movement amount including the relative movement amount and rotation amount of the substrates 211 and 213 so as to match the positions of the detected alignment marks 218.

[0074] However, distortion may occur individually in each of the substrates 211, 213 that form the bonded substrate 230. Distortion occurring in the substrates 211, 213 includes distortion that has a certain tendency throughout the substrates 211, 213, such as warping or bending of the substrates 211, 213, and nonlinear distortion occurring in the surface direction or radial direction of the substrates.

[0075] These distortions are caused by stress generated by the process of forming the circuit region 216 in the substrates 211, 213, anisotropy caused by the crystal orientation of the substrates 211, 213, and periodic changes in rigidity caused by the arrangement of the scribe lines 212, the circuit region 216, etc. Even if the substrates 211, 213 alone do not have distortion, the substrates 211, 213 may deform and generate distortion during the bonding process at the boundary between the contact region, which is the region already bonded, and the non-contact region, which is the region not yet bonded.

[0076] When the substrates 211 and 213 have different distortions, even if the relative movement amount is calculated in step S106, it may not be possible to calculate a value that matches the position of the alignment mark 218. Therefore, the distortion of at least one of the substrates 211 and 213 is corrected by temperature adjustment (step S105), thereby improving the alignment accuracy of the substrates 211 and 213.

[0077] For example, distortion caused by a difference in magnification of the circuit region 216 in the substrates 211, 213 with respect to the design specifications can be corrected by adjusting the temperature of at least one of the substrates 211, 213 to change the overall size of the substrates 211, 213. Also, as already described, distortion of the substrate 211 can be corrected by holding the substrate 211 in the substrate holder 221 whose holding surface 222 is curved or bent.

[0078] Furthermore, in the bonding unit 300, at least one of the upper stage 322 and the lower stage 332 on which the substrates 211 and 213 are mounted may be provided with an actuator that mechanically deforms the substrates 211 and 213, so that at least one of the substrates 211 and 213 may be deformed for correction. This allows the bonding unit 300 to correct distortion of the substrates 211 and 213, whether linear or nonlinear.

[0079] 8 shows the operation of the bonding unit 300 to activate the substrates 211, 213 (step S104 in FIG. 3). The control unit 150 resets the position of the lower stage 332 to the initial position, and then moves it horizontally, and causes the surfaces of the substrates 211, 213 to be scanned with plasma generated by the activation devices 326, 336. This cleans the surfaces of the substrates 211, 213, respectively, and increases their chemical activity. Therefore, the substrates 211, 213 autonomously adsorb and bond to each other simply by approaching each other.

[0080] The activation devices 326, 336 radiate the plasma P in a direction away from the microscopes 324, 334. This prevents the microscope 324 from being contaminated by fragments generated from the substrates 211, 213 irradiated with the plasma.

[0081] In addition, the bonding section 300 is equipped with activation devices 326, 326 that activate the substrates 211, 213. However, it is also possible to omit the activation device 326 of the bonding section 300 by transporting the substrates 211, 213 that have been activated in advance using activation devices 326, 326 provided separately from the bonding section 300 into the bonding section 300.

[0082] Furthermore, the substrates 211, 213 can be activated by sputter etching using an inert gas, an ion beam, a high-speed atomic beam, or the like, in addition to the method of exposing them to plasma. When an ion beam or a high-speed atomic beam is used, the bonding portion 300 can be generated under reduced pressure. Furthermore, the substrates 211, 213 can be activated by ultraviolet irradiation, an ozone asher, or the like. Furthermore, the substrates 211, 213 may be activated by chemically cleaning the surfaces thereof using, for example, a liquid or gaseous etchant.

[0083] The order of step S104 of activating at least one of the substrates 211 and 213 and step S105 of adjusting the temperature of one of the substrates 211 and 213 may be reversed. That is, as described above, the substrates 211 and 213 may be activated (step S104) and then the temperature of at least one of the substrates 211 and 213 may be adjusted (step S105), or the substrates 211 and 213 may be activated (step S104) after the temperature of at least one of the substrates 211 and 213 is adjusted (step S105).

[0084] 9 shows the operation (step S106 in FIG. 3) of the bonding unit 300 to align the substrates 211, 213. The control unit 150 first moves the lower stage 332 based on the relative positions of the microscopes 324, 334 detected initially and the positions of the alignment marks 218 of the substrates 211, 213 detected in step S102, so that the amount of misalignment between the substrates 211, 213 becomes smaller than a predetermined value.

[0085] Fig. 10 is a diagram showing a schematic view of the substrates 211, 213 in the state of step S106 shown in Fig. 9. As shown in the figure, the substrates 211, 213, which are held by the upper stage 322 and the lower stage 332 via the substrate holders 221, 223, respectively, face each other in an aligned state.

[0086] As already explained, the substrate holder 221 held by the upper stage 322 holds the substrate 211 on the holding surface 222 which is raised in the center, so that the substrate 211 also has a raised center. On the other hand, the substrate holder 223 held by the lower stage 332 has a flat holding surface 224, so that the substrate 213 is held in a flat state. Therefore, the distance between the opposing substrates 211, 213 in the bonding section 300 is close at the center and becomes larger as they approach the periphery.

[0087] 11 shows an operation (step S107 in FIG. 3) in which the bonding unit 300 brings the substrate 213 held on the lower stage 332 into contact with the substrate 211 held on the upper stage 322. The control unit 150 operates the elevation drive unit 338 to raise the lower stage 332, thereby bringing the substrates 211 and 213 into contact with each other.

[0088] Fig. 12 is a diagram showing a schematic view of the state of the substrates 211, 213 from step S107 to step S108 shown in Fig. 10. As shown in the figure, the central portion of the substrate 211 held by the upper stage 322 is raised, so that when the lower stage 332 approaches the upper stage 322, the central portions of the substrates 211, 213 first come into contact with each other. Furthermore, as the control unit 150 continues to operate the elevation driving unit 338, the central portions of the substrates 211, 213 come into contact with each other, and a starting point for bonding is formed on the substrates 211, 213.

[0089] At this time, the substrate 211 is still held by the curved holding surface 222 of the substrate holder 221. Therefore, when the central portion of the substrate 211 abuts against the flat substrate 213, the peripheral portion of the substrate 211 is held by the substrate holder 221 and is separated from the substrate 213. In other words, the substrate holder 221 continues to hold the substrate 211 so that portions of the substrates 211, 213 other than their central portions do not come into contact with each other.

[0090] It is preferable to correct the substrates 211 and 213 by forming a temperature difference by temperature adjustment or the like before forming the starting point of the bonding described above. This makes it possible to manufacture a bonded substrate 230 in which the positional deviation of the central portions of the substrates 211 and 213 is reduced.

[0091] Fig. 13 is a diagram showing the state of the substrates 211, 213 in the period following step S107 shown in Fig. 3. In step S107, the substrates 211, 213 are pressed against each other at a part of the center in the surface direction. As a result, a bonding starting point 231 where the substrates 211, 213 are partially bonded together is formed near the center of the substrates 211, 213. However, as described with reference to Fig. 12, the substrate 211 is still held by the substrate holder 221, and therefore the regions of the substrates 211, 213 that are out of the center have not yet been bonded together.

[0092] 14 is a partially enlarged view showing a state immediately before the substrates 211 and 213 come into contact with each other during execution of step S107 (see FIG. 3). The region shown in FIG. 14 corresponds to the region indicated by the dotted line B in FIG.

[0093] In the illustrated state, a gap G remains between the substrates 211 and 213. The gap G is formed when the atmosphere inside the bonding unit 300 is sandwiched between the substrates 211 and 213. The atmosphere sandwiched between the substrates is pushed out by the bonding unit 300 continuously pressing the substrates 211 and 213, and eventually the substrates 211 and 213 are bonded together in close contact with each other, but the time required for the substrates 211 and 213 to be bonded together may differ depending on the density of the atmosphere, etc.

[0094] In the bonding unit 300, even when the substrates 211, 213 are sandwiched between the upper stage 322 and the lower stage 332, a part near the center of the substrates 211, 213 optically communicates with the detector 341 through the observation window 327 and the observation hole 227. In the illustrated example, the detector 341 has a light source 351 and a light receiving unit 352.

[0095] The light source 351 generates irradiation light having a wavelength at least a part of which is transmitted through the substrate 211. The irradiation light generated by the light source 351 is irradiated toward the substrate 211 through the observation window 327 and the observation hole 227. The light receiving unit 352 has an opto-electrical conversion element such as a photodiode, receives the irradiation light reflected by the substrates 211, 213, etc., and generates an electrical signal according to the intensity of the reflected light. The electrical signal generated by the light receiving unit 352 is input to the control unit 150.

[0096] As indicated by the dashed line in the figure, a reflecting surface is formed at the boundary between media with different refractive indices between upper stage 322 and lower stage 332. In the illustrated example, reflecting surfaces P, Q, R, and S are formed at the boundary between observation hole 227 and substrate 213, the boundary between substrate 213 and gap G, the boundary between gap G and substrate 213, and the boundary between substrate 213 and substrate holder 221, respectively. Thus, irradiation light irradiated from light source 351 of detector 341 through observation window 327 and observation hole 227 is reflected by each of reflecting surfaces P, Q, R, and S, and the intensity of the reflected light is detected by light receiving unit 352 of detector 341.

[0097] FIG. 15 shows the state after step S107, from the same perspective as FIG. 14, where the centers of the substrates 211 and 213 are bonded together. When the substrates 211 and 213 are bonded together and in close contact with each other, the pair of reflective surfaces R and Q formed between the substrates 211 and 213 and the gap G disappears. This reduces the number of reflective surfaces that reflect the irradiated light of the detector 341, and the reflected light intensity detected by the detector 341 changes. That is, the overall reflectance from the substrates 211 and 213 changes depending on the size of the gap G; for example, the reflectance increases as the size of the gap G increases. The reflected light intensity is one piece of information regarding the state of expansion of the contact area, and is expressed as the luminance (cd / m 2), or may be the luminous intensity (lm·s) of the reflected light. Thus, upon receiving the output of detector 341, control unit 150 can determine that the contact portion of substrates 211, 213, i.e., starting point 231 of bonding, has been formed on substrates 211, 213 by detecting that the reflected light intensity has become constant or that the rate of change of the reflected light intensity has become smaller than a predetermined value. That is, control unit 150 determines that the contact state of the contact area is a state in which starting point 231 has been formed. Thus, control unit 150 can form a determination unit that determines whether substrates 211, 213 have been bonded together.

[0098] The control unit 150 may release the holding of the substrate 211 (step S109 in FIG. 3) in response to determining that the bonding starting point 231 has been formed. Through this series of controls, the bonding starting point 231 is reliably formed on the substrates 211 and 213, and the holding of the substrate 211 can be released without wasting time after the bonding starting point 231 has been formed. Therefore, the yield is improved and the throughput is shortened in the manufacture of the bonded substrate 230.

[0099] 14 and 15, the illumination light is shown as if it were obliquely irradiated with respect to the substrates 211 and 213 in order to easily distinguish between the illumination light and the reflected light. However, even if the illumination light is irradiated perpendicularly to the substrates 211 and 213, an optical system for detecting the reflected light intensity can be formed by using an optical device such as a half mirror. Also, the detector 341 may use an image sensor such as a CCD or CMOS sensor instead of the light receiving unit 352. Also, the above structure of the detector 341 can be applied to the other detectors 342 and 343 shown in FIG. 6 and the like.

[0100] Fig. 16 is a schematic plan view showing the state of the substrates 211, 213 in the period following step S109 (see Fig. 3), and Fig. 17 is a schematic vertical cross-sectional view of the substrates 211, 213 in the state shown in Fig. 16.

[0101] In step S109, the substrate 211 is released from the substrate holder 221 held by the upper stage 322. Since the surfaces of at least one of the substrates 211 and 213 are activated, a part of the substrates 211 and 213 comes into contact with each other to form a bonding starting point, and when one of the substrates 211 and 213 is released from the substrate holders 221 and 223, adjacent regions of the substrates 211 and 213 are autonomously attracted to each other and bonded together due to the intermolecular force between the substrates 211 and 213. The contact region of the substrates 211 and 213 gradually expands to adjacent regions over time.

[0102] As a result, the bonding wave 232, which is the boundary between the contact area, where the substrates 211 and 213 are bonded, and the non-contact area, where the substrates are not yet bonded, moves in each radial direction from the inside to the outside of the substrates 211 and 213, and the bonding of the substrates 211 and 213 progresses. That is, the movement of the bonding wave expands the contact area. However, in the area outside the area surrounded by the bonding wave 232, the substrates 211 and 213 are not yet bonded.

[0103] As already described, the substrate holder 221 held by the upper stage 322 of the bonding unit 300 also has an observation hole 228 at a midpoint between the center and the periphery of the substrate 211 it holds. The upper stage of the bonding unit 300 also has an observation window 328 and a detector 342 at a position corresponding to the observation hole 228 when the substrate holder 221 is held.

[0104] Therefore, when the substrates 211 and 213 are bonded together in the bonding section 300, it can be determined whether the substrates 211 and 213 are bonded together even at the position of the observation hole 228. The detector 342 may have the same structure as the detector 341 disposed in the center of the substrates 211 and 213, but is not limited to this.

[0105] In step S108, after it is detected that the bonding starting point 231 is formed at the center of the substrates 211 and 213, if bonding of the substrates 211 and 213 is detected through the observation hole 228, the control unit 150 can determine in step S110 that the contact area of ​​the substrates 211 and 213 has expanded to the middle between the center and the periphery of the substrates 211 and 213 (step S110: YES). That is, it is determined that the bonding wave has reached the middle position, which is a predetermined position. The position of the bonding wave is one piece of information regarding the state of expansion of the contact area. This allows the control unit 150 to proceed with the control procedure to step S112.

[0106] Furthermore, the substrate holder 221 also has an observation hole 229 on the periphery of the substrate 211 that it holds. Also, the upper stage of the bonding unit 300 has an observation window 329 and a detector 343 at a position that corresponds to the observation hole 229 when the substrate holder 221 is held. Therefore, when the substrates 211 and 213 are bonded in the bonding unit 300, it can be determined whether the substrates 211 and 213 have been bonded, even at the position of the observation hole 229.

[0107] 16 and 17, the substrates 211, 213 are bonded together at the position of the observation hole 228, but are not yet bonded together at the position of the observation hole 229. Therefore, the control unit 150 can determine that although the bonding wave 232 is expanding and the bonding of the substrates 211, 213 is progressing, the entire substrates 211, 213 are not yet bonded together.

[0108] Fig. 18 is a schematic plan view showing the state of the substrates 211, 213 at the time when the control unit 150 determines in step S112 (see Fig. 3) that the bonding of the substrates 211, 213 is completed (step S112: YES). Fig. 19 is a schematic vertical cross-sectional view of the substrates 211, 213 in the state shown in Fig. 18.

[0109] In step S110, the control unit 150 confirms that the bonding of the substrates 211, 213 is progressing through the observation hole 228, the observation window 328, and the detector 342. When the bonding of the substrates 211, 213 progresses further and the bonding wave 232 reaches the periphery of the substrates 211, 213, the contact area reaches the entire substrates 211, 213. As a result, the substrates 211, 213 are bonded to each other to form a bonded substrate 230.

[0110] As already explained, the substrate holder 221 held by the upper stage 322 of the bonding unit 300 also has an observation hole 229 at the peripheral position of the substrate 211 it holds. The upper stage of the bonding unit 300 also has an observation window 329 and a detector 343 at a position corresponding to the observation hole 229 when the substrate holder 221 is held. Therefore, when the substrates 211 and 213 are bonded together in the bonding unit 300, it can be determined whether the substrates 211 and 213 have been bonded together even at the position of the observation hole 229.

[0111] In the bonding section 300, after the expansion of the contact area of ​​the substrates 211 and 213 surrounded by the bonding wave 232, which is the boundary between the contact area and the non-contact area, is detected in step S110 (step S110: YES), it can be detected through the observation hole 229 whether the bonding wave has reached the outer edge of the substrates 211 and 213, that is, whether the bonding has been completed (step S112). The detector 342 can have the same structure as the detector 341 arranged in the center of the substrates 211 and 213, but is not limited to this. In particular, the peripheral portion of the substrates 211 and 213 is exposed to the outside even after the substrates 211 and 213 are bonded together. Therefore, the detector 343 that detects the bonding at the peripheral portion of the substrates 211 and 213 can have a structure different from that of the other detectors 341 and 342.

[0112] Thus, in the bonding section 300, the contact area of ​​the substrates 211, 213 expands from the center toward the outer edge of the substrates 211, 213. Therefore, the atmosphere, for example, air, that was sandwiched between the substrates 211, 213 before bonding is pushed out from the inside to the outside of the substrates 211, 213 in the process of the area of ​​the contact area of ​​the substrates 211, 213 expanding, and air bubbles are prevented from remaining between the bonded substrates 211, 213.

[0113] In order to smoothly push out air bubbles and the like from between the substrates 211 and 213 in the process of overlapping the substrates 211 and 213, it is preferable that a gap having a width that does not prevent the movement of air bubbles and a continuous gap is formed between the substrates 211 and 213 at the time when the contact between the substrates 211 and 213 starts. Therefore, it is preferable to select a deformation procedure that leaves a certain degree of curvature when the substrate 211 is deformed by adsorbing the substrate holder 221 with the curved holding surface 222 at the stage of contacting the substrate 213 in step S107 (FIG. 3). In addition, when it is expected that the curvature of the substrate 211 will decrease at the overlapping stage, a substrate holder 223 with a curved holding surface 224 like the substrate holder 221 may be used as the substrate holder 223 that holds the substrate 213 held by the lower stage 332 in order to ensure a gap through which air bubbles can pass.

[0114] In the above example, in step S109, the substrate 211 held by the upper stage 322 is released. However, in the same step, the substrate 211 held by the lower stage 332 may be released, or the substrates 211, 213 may be released from both stages.

[0115] However, the released substrate 211 also releases the correction of distortion caused by suction by the substrate holder 221. Therefore, when releasing the substrate in step S109, it is preferable to release the substrate 211, 213 which has relatively less deformation and has a smaller amount of correction.

[0116] 20 is a schematic diagram illustrating another structure of the detector 341 in the bonding portion 300. FIG 20 is drawn from the same perspective as FIG 14 and FIG 15.

[0117] In the bonding section 300, the detector 341 shown in the figure has a displacement meter 353. The displacement meter 353 itself is fixed in position relative to the upper stage 322, and detects the displacement of the substrates 211, 213, etc., as the measurement target, from a change in optical characteristics. Various types of optical displacement meter 353 can be used, and examples of the optical displacement meter 353 include a triangulation type, a laser focus type, and a spectroscopic interference type.

[0118] The illustrated detector 341 continuously measures the relative distance H1 between the top surface of the upper substrate 211 in the figure and the top surface of the lower substrate 213 in the figure, while moving the substrates 211 and 213 closer to each other in step S107 (see FIG. 3) and eventually pressing them together. In this process, when the value of the distance H1 becomes equal to the known thickness T1 of the upper substrate 211, it is detected that the substrates 211 and 213 are in contact with each other without any gaps and are bonded together. In this way, by using the displacement meter 353 as the detector 341, the control unit 150 can continuously observe the bonding of the substrates 211 and 213 and reflect the results in the control of the bonding unit 300. The value of the distance H1 is one piece of information regarding the state of expansion of the contact area.

[0119] 21 has the same structure as the bonding unit 300 shown in FIG. 20, but the measurement target of the displacement meter 353 as the detector 341 is different. In the bonding unit 300 shown in the figure, the displacement meter 353 measures the distance H2 between the position of the upper surface of the substrate 211 on the upper side in the figure and the position of the lower surface of the substrate 213 on the lower side in the figure, or the position of the upper surface of the substrate holder 221 on the lower side. Then, in step S107 (see FIG. 3), the substrates 211 and 213 are brought close to each other and then pressed together. In this process, when the value of the distance H2 becomes equal to the sum of the known thickness T1 of the substrate 211 and the thickness T2 of the substrate 213, it can be detected that the substrates 211 and 213 are in contact with each other without any gaps and are bonded together.

[0120] 22 has the same structure as the bonding section 300 shown in FIGS. 20 and 21, but the measurement target of the displacement meter 353 serving as the detector 341 is different. In the bonding section 300 shown in the figure, the displacement meter 353 measures the thickness T3 of the gap G between the substrates 211 and 213 based on the position of the bottom surface of the substrate 211 on the upper side in the figure and the position of the top surface of the substrate 213 on the lower side in the figure. Then, in step S107 (see FIG. 3), the substrates 211 and 213 are brought close to each other and then pressed together. In this process, when the value of the thickness T3 becomes zero, it can be detected that the substrates 211 and 213 are in contact with each other without any gaps and are bonded together. Like detectors 341, 342, and 343, displacement meters 353 may be arranged at the center, intermediate portion, and peripheral portion of substrates 211 and 213, respectively, to detect the position of the boundary of the contact area at each position. In this case, control unit 150 determines that formation of starting point 231 is complete by detecting contact at the center, and determines that bonding is complete by detecting contact at the peripheral portion.

[0121] 20, 21, and 22, there are a plurality of measurement targets of the displacement meter 353 as the detector 341 in the observation unit 344. Therefore, the detection accuracy of the detector 341 may be improved by selecting two or more of the plurality of detection targets, for example, the detection targets shown in FIGS.

[0122] In the above example, the case where an optical displacement meter is used has been described, but there are several known types of displacement meters, such as eddy current type, ultrasonic type, and contact type. Of course, displacement meters using other types may be used. In addition, the multiple detectors 341, 342, and 343 forming the observation unit 344 may be a mixture of displacement meters of different types. In addition, the displacement meter 353 may measure the amount of displacement of the upper surface of the substrate 213 while the contact area is expanding based on the state in which the upper substrate 213 is held by the substrate holder 223, that is, the distance between the upper surface of the substrate 213 and the holding surface of the substrate holder 223. The value of this distance is one piece of information regarding the state of the expansion of the contact area. In this case, the control unit 150 may determine that the bonding is completed when the displacement of the upper surface of the substrate 213 becomes 0 and the amount of displacement becomes constant, or when the amount of change becomes smaller than a predetermined value.

[0123] Fig. 23 is a schematic diagram of an observation section 345 having another structure. In the bonding section 300 having the observation section 345, similar to the observation section 344 shown in Fig. 22 and up, observation windows 327, 328, and 329 are provided in the upper stage 322, and observation holes 227, 228, and 229 are provided in the substrate holder 221 held by the upper stage.

[0124] Furthermore, in the bonding unit 300 having the observation unit 345, the lower stage 332 is also provided with observation windows 327, 328, and 329. The flat substrate holder 223 held by the lower stage 332 is also provided with observation holes 227, 228, and 229.

[0125] Furthermore, in the observation unit 345, the light source 351 irradiates the substrates 211 and 213 with irradiation light through the observation windows 327, 328, and 329 of the upper stage 322 and the observation holes 227, 228, and 229 of the substrate holder 221 on the upper side in the figure, while the light receiving unit 352 receives the irradiation light through the observation windows 327, 328, and 329 of the lower stage 332 and the observation holes 227, 228, and 229 of the substrate holder 223 on the lower side in the figure. With this structure, the light receiving unit 352 may observe the bonding state of the substrates 211 and 213 based on the amount of irradiation light transmitted through the substrates 211 and 213. The amount of irradiation light is one piece of information regarding the state of expansion of the contact area. By experimentally determining in advance the amount of light when the formation of the starting point 231 is completed and the amount of light when the bonding is completed, the control unit 150 determines that the formation of the starting point 231 and the bonding are completed based on the amount detected by the observation unit 345 reaching the predetermined value. In the examples shown in Figures 4 to 23, the bonding wave propagation speed, i.e., the expansion speed of the contact area, may be predicted based on the time from when detector 341 detects that the formation of the starting point is completed to when detector 342 detects the boundary of the contact area, or the time from when detector 342 detects the boundary to when detector 343 detects the boundary, and the time when bonding is completed may be predicted. In addition, although an example in which three detectors 341, 342, and 343 are arranged at the center, intermediate portion, and peripheral portion of the substrates 211 and 213 has been shown, instead of or in addition to this, multiple detectors may be arranged so as to be able to observe the peripheral portion of the substrate that is fixed without being released from the stage during bonding of the two substrates 211 and 213. In this case, when the peripheral portion of the released substrate is detected by all of the multiple detectors, it is determined that bonding is completed. In addition, the progress of the bonding wave can be grasped based on the detection timing of the peripheral portion of the substrate by the multiple detectors. That is, when the detection timing by one detector is different from the detection timing by the other detector, it is found that the progress of the bonding wave is slow in the region including the peripheral portion with the slow detection timing. In this case, the control unit 150 feeds back to the device to promote the progress of the region where the progress of the bonding wave is slow.

[0126] 24 is a schematic diagram showing another structure of the detector 343 in the bonding portion 300. As already described, the peripheral portions of the substrates 211 and 213 are exposed to the outside even after the substrates 211 and 213 are bonded together. Therefore, the detector 343 that detects the bonding at the peripheral portions of the substrates 211 and 213 may have a structure different from that of the other detectors 341 and 342.

[0127] The illustrated detector 343 has a light source 351, a light receiving unit 352, and an optical fiber 354. The light source 351 irradiates irradiation light toward the peripheral edges of the substrates 211 and 213 through the observation window 329 and the observation hole 229. One end of the optical fiber 354 is disposed near the edge of the substrate 213 held by the lower stage 332. As a result, the irradiation light scattered by the peripheral edge of the substrate 213 is incident on the optical fiber 354.

[0128] The other end of the optical fiber 354 is disposed facing the light receiving unit 352. As a result, the irradiated light incident on the optical fiber 354 is incident on the light receiving unit 352. The light receiving unit 352 receives the irradiated light, generates an electrical signal, and inputs it to the control unit 150. The electrical signal input from the light receiving unit 352 to the control unit 150 is one piece of information relating to the state of the expansion of the contact area.

[0129] Fig. 25 is a schematic diagram for explaining the operation of the detector 343 shown in Fig. 24. When the substrates 211 and 213 are bonded to the peripheral edge in the bonding section 300, the irradiated light irradiated from the light source 351 is irradiated to the substrate 211 instead of the substrate 213 and scattered. Therefore, the irradiated light is no longer incident on the optical fiber 354 arranged on the side of the substrate 213. This changes the electrical signal input from the light receiving section 352 to the control section 150, so that the control section 150 can determine that the substrate 211 has been bonded to the substrate 213 up to the peripheral edge.

[0130] 26 is a schematic diagram of an observation section 346 having another structure. The observation section 346 has a plurality of light sources 361, 362, and 363 and light receiving sections 371, 372, and 373, respectively.

[0131] The light receiving units 371, 372, and 373 are disposed facing the light sources 361, 362, and 363 with the substrates 211 and 213 interposed therebetween in the surface direction of the substrates 211 and 213. One light receiving unit 371 is disposed at a position facing one light source 361 with the center of the substrates 211 and 213 in between. The other light receiving unit 373 is disposed at a position facing another light source 363 with a region including the periphery of the substrates 211 and 213 in between. The other light receiving unit 372 is disposed at a position facing the light source 362 disposed between the light sources 361 and 362.

[0132] Fig. 27 is a schematic diagram for explaining the operation of the observation unit 346 shown in Fig. 26. Fig. 27 shows the substrates 211, 213 observed by the observation unit 346 as viewed from the light receiving units 371, 372, 373 on the sides in the surface direction.

[0133] In the illustrated substrates 211 and 213, the upper substrate 211 has been released from the upper stage 322 (step S109 in FIG. 3), and the bonding has already progressed to the state shown in FIG. 17. Therefore, when viewed from the light receiving units 371 and 372 side, the width of the light flux of the irradiated light irradiated by the light sources 361 and 362 onto the substrates becomes narrower because it is blocked by the substrates 211 and 213 bonded to each other. Therefore, the light receiving units 371 and 372 input an electric signal when they receive a small amount of irradiated light to the control unit 150. The electric signal input from the light receiving units 371 and 372 to the control unit 150 is one piece of information regarding the state of the expansion of the contact area. By detecting the change in the amount of received light by the light receiving unit 371 before the two substrates 211 and 213 come into contact with each other, it may be determined that the starting point has been formed when the rate of change becomes 0 and the value of the amount of light remains constant until a predetermined time has passed, or when the rate of change becomes smaller than a predetermined value. The light receiving portion 372 may also detect a change in the amount of received light, and when the rate of change becomes 0 and the value of the amount of light remains constant until a predetermined time has elapsed, or when the rate of change becomes smaller than a predetermined value, it may be determined that the bonding wave spreading from the starting point 231 of bonding has reached the midpoint between the center and the peripheral portion of the substrates 211, 213.

[0134] In contrast, in the illustrated state, the peripheries of the substrates 211 and 213 have not yet been bonded together. Therefore, the light irradiated by the light source 363 onto the substrates 211 and 213 passes between the substrates 211 and 213 and is received by the light receiving unit 372 with a wide beam width. Therefore, an electrical signal is input from the light receiving units 371 and 372 to the control unit 150 when strong irradiated light is received.

[0135] In this way, the observation unit 346 can detect, from the output of the light receiving unit 371, that the starting point 231 of bonding is formed at the center of the substrates 211, 213. Also, the observation unit 346 can detect, from the output of the light receiving unit 372, that the bonding of the substrates 211, 213 is spreading from the center toward the periphery. Furthermore, the observation unit 346 can determine that the bonding of the substrates 211, 213 has been completed up to the periphery by detecting, from the output of the light receiving unit 373, that the rate of change becomes 0 and the value of the light quantity remains constant until a predetermined time has elapsed, or that the rate of change has become smaller than a predetermined value.

[0136] The surfaces of the substrates 211 and 213 are not necessarily flat due to the circuit region 216 and the like. The substrates 211 and 213 themselves may be warped or otherwise deformed in the process of forming the circuit region 216. Furthermore, in the bonding unit 300, the substrates 211 and 213 to be bonded may be deformed to correct the magnification, distortion, and the like of the substrates 211 and 213. For this reason, there may be no gap formed between the substrates 211 and 213 through which light can travel straight from the light sources 361, 362, and 363 to the light receiving units 371, 372, and 373.

[0137] However, if the gap between the substrates 211 and 213 is continuous from the light sources 361, 362, and 363 to the light receiving units 371, 372, and 373, a part of the irradiated light reaches the light receiving units 371, 372, and 373. Therefore, even if the gap between the substrates 211 and 213 is such that the light sources 361, 362, and 363 cannot be seen from the light receiving units 371, 372, and 373, the observation unit 346 can detect whether the substrates 211 and 213 are bonded together.

[0138] Furthermore, the irradiated light generated by the light sources 351, 361, 362, and 363 in the observation units 344, 345, and 346 may be modulated at a predetermined frequency, and the irradiated light may be locked-in detected in the light receiving units 352, 371, 372, and 373. This makes it possible to eliminate the influence of background light and accurately detect weak irradiated light.

[0139] 28 is a schematic diagram of an observation unit 347 having another structure. The observation unit 347 has a light source 361, an image capturing unit 374, and a background plate 364.

[0140] The light source 361 and the imaging unit 374 are disposed laterally of the substrates 211, 213 in the surface direction of the substrates 211, 213, on the same side with respect to the substrates 211, 213. Illumination light generated by the light source 361 is irradiated toward the substrates 211, 213 from the same side as the imaging unit 374, and illuminates the imaging field of view of the imaging unit 374.

[0141] The background plate 364 is disposed on the opposite side of the substrates 211 and 213 with respect to the light source 361 and the imaging unit 374. In this way, when the imaging unit 374 captures images of the substrates 211 and 213, the background plate 364 forms the background of the substrates 211 and 213. The background plate 364 has a color and brightness that have a strong contrast with the images of the substrates 211 and 213 captured by the imaging unit 374.

[0142] In the observation section 347, the imaging field of the imaging section 374 extends from the center to the periphery of the substrates 211 and 213 as indicated by the dotted lines in the figure. As a result, in the observation section 347, the imaging section 374 collectively plays the role of the light receiving sections 371, 372, and 373 of the observation section 346 shown in Figures 26 and 27. The video captured by the imaging section 374 is acquired by the control section 150 and subjected to image processing.

[0143] In the bonding section 300, when the upper stage 322 and the lower stage 332, which respectively hold the substrates 211 and 213, face each other, the imaging section 374 captures an image of the background plate 364 seen between the substrates 211 and 213. When the substrates 211 and 213 form the bonding starting point 231 in step S108 (see FIG. 3), a part of the image of the background plate 364 is blocked and divided by the substrates 211 and 213 in the image captured by the imaging section 374. This enables the control section 150 to detect that the bonding starting point 231 has been formed.

[0144] Next, in step S110, the imaging unit 374 can continuously monitor the expansion of the contact area of ​​the substrates 211, 213. Furthermore, in step S112, the imaging unit 374 can detect that the contact area of ​​the substrates 211, 213 has reached the periphery of the substrates and bonding has been completed. In this way, the observation unit 347 can directly image the bonding of the substrates 211, 213 and continuously detect the bonding based on the distance between the substrates 211, 213 on the captured image.

[0145] In the above example, the imaging unit 374 is disposed on the side of the substrates 211, 213 in the surface direction to detect bonding. However, for example, the imaging unit 374 may be disposed on the side of the substrates 211, 213 in the thickness direction to detect bonding, using the imaging unit 374 sensitive to a wavelength that passes through at least one of the upper stage 322 and the lower stage 332 and the substrate holders 221, 223 held on the stage.

[0146] Furthermore, the images acquired by the imaging unit 374 are not limited to images directly capturing the shapes of the substrates 211 and 213. For example, the state of bonding of the substrates 211 and 213 may be detected based on a change in an interference fringe image caused by an optical phenomenon such as interference between the substrates 211 and 213.

[0147] Fig. 29 is a schematic diagram of a bonding unit 300 equipped with an observation unit 348 having another structure. The bonding unit 300 shown in the figure has the same structure as the bonding unit 300 shown in Fig. 6 and the like, except for the parts described below. Therefore, the same reference numbers are used for the common components, and duplicated explanations will be omitted.

[0148] 6 in that it has an observation unit 348 having a load cell 380 instead of the observation unit 344 that optically observes the bonding state. The load cell 380 is disposed between the top plate 316 of the frame 310 and the upper stage 322.

[0149] As a result, the observation unit 348 can continuously detect the reaction force that the upper stage 322 receives from the substrates 211, 213 when the substrates 211, 213 are pressed against each other by raising the lower stage 332 with the lifting / lowering drive unit 338, using the load cell 380. That is, the load cell 380 first detects an increase in the reaction force when the substrates 211, 213 pressed against each other in step S107 (see FIG. 3) come into contact with each other to form the bonding starting point 231. The reaction force detected by the load cell 380 is one piece of information regarding the state of the expansion of the contact area, and is transmitted to the control unit 150. When the reaction force reaches a predetermined value, or when the predetermined value is maintained for a threshold time or more, the control unit 150 can determine that the bonding starting point 231 has been formed on the substrates 211, 213 (step S108: YES). Furthermore, when forming the starting point 231, a part of the substrate 213 is pressed against a part of the substrate 211 via the atmosphere or the like sandwiched between the substrates 211 and 213, and after the atmosphere or the like is pushed out, the substrates 211 and 213 come into direct contact with each other. For this reason, the reaction force detected by the load cell 380 becomes temporarily small when the atmosphere is pushed out. The control unit 150 may determine that the bonding starting point 231 has been formed on the substrates 211 and 213 by detecting that the value of the load cell 380 has temporarily decreased, or by detecting that the value of the load cell 380 has increased again after becoming temporarily small and exceeded a predetermined value.

[0150] Thereafter, when the entire substrates 211, 213 are bonded together, the force with which the lifting drive unit 338 lifts the lower stage 332 is directly applied to the load cell 380. Therefore, the control unit 150 can determine that the entire substrates 211, 213 are bonded together by the increase in the reaction force detected by the load cell 380 of the observation unit 348.

[0151] In this way, the bonding state of the substrates 211 and 213 can also be detected by a change in mechanical characteristics. The structure of the observation unit 348 that detects based on mechanical characteristics is not limited to the above. The reaction force of the substrates 211 and 213 may be detected based on a change in driving power corresponding to a change in the driving load on the lifting / lowering drive unit 338, a pressure change of the working fluid, or the like. When the completion of bonding is determined by detecting the driving load of the lifting / lowering drive unit 338, as in the illustrated example, when the upper substrate 211 is stacked on the lower substrate 213, the load of the substrate 211 is applied to the lower stage 332 as the contact area of ​​the substrates 211 and 213 expands, so that the thrust of the lifting / lowering drive unit 338 increases. The control unit 150 detects that the change in the thrust disappears, the load value becomes constant, and the constant load value is maintained for a threshold time, or the rate of change in the thrust becomes smaller than a predetermined value, and determines that bonding is completed.

[0152] In addition, the observation area 348 can also be formed using a mechanical displacement meter having a contactor that comes into contact when the peripheral portion of the substrate 211, which has been released from the upper stage 322 in step S109, is displaced to a position in contact with the fixed substrate 213.

[0153] Fig. 30 is a schematic diagram of a bonding unit 300 equipped with an observation unit 349 having another structure. The bonding unit 300 shown in the figure has the same structure as the bonding unit 300 shown in Fig. 6 and the like, except for the parts described below. Therefore, the same reference numbers are used for the common components, and duplicated explanations will be omitted.

[0154] 6 in that it has an observation unit 349 having a microphone 390 instead of the observation unit 344 that optically detects the bonding state. The microphone 390 is suspended from the top plate 316 of the frame 310, and detects elastic waves generated between the upper stage 322 and the lower stage 332.

[0155] In the bonding section 300, the substrates 211 and 213 generate elastic waves during the bonding process. For example, until the substrate 211 held by the upper stage 322 is released in step S109 (see FIG. 3), the substrate 211 is in a warped state due to being held by the substrate holder 221 having the curved holding surface 222. On the other hand, when the substrate 211 is released from step S109, the substrate 211 is deformed into a shape following the shape of the other substrate 213 as the bonding process progresses.

[0156] As the substrate 211 deforms, it generates minute elastic waves. Therefore, by acquiring an electrical signal based on the sound detected by the microphone 390, the control unit 150 can determine that the bonding of the substrates 211 and 213 is progressing.

[0157] Furthermore, in the process of bonding the substrates 211 and 213, the atmosphere that was initially sandwiched between the substrates 211 and 213 is pushed out from between the substrates 211 and 213. The vibrations generated by the atmosphere accompanying this movement can also be detected as acoustic elastic waves. Therefore, by detecting the elastic waves generated in the atmosphere by the microphone 390, the continuation and end of bonding can be detected.

[0158] Furthermore, when the bonding of the substrates 211 and 213 reaches the periphery of the substrates 211 and 213, the periphery of one substrate 211 abuts against the other substrate 213, and the continuing displacement of the substrate 211 is suddenly stopped. As a result, a collision sound is generated between the substrates 211 and 213. Therefore, by acquiring an electrical signal generated by the microphone 390 that detects the collision sound, the control unit 150 can determine that the bonding of the substrates 211 and 213 has reached the periphery and is complete.

[0159] The elastic waves generated by the substrate 211 do not necessarily have frequencies in the audible band. Therefore, it is preferable that the microphone 390 used in the observation unit 349 has sensitivity outside the audible band.

[0160] Fig. 31 is a schematic diagram of a bonding unit 300 equipped with an observation unit 610 having another structure. The bonding unit 300 shown in the figure has the same structure as the bonding unit 300 shown in Fig. 30, except for the parts described below. Therefore, the same reference numbers are used for the common components, and duplicated explanations will be omitted.

[0161] In the illustrated bonding unit 300, the observation unit 610 has a vibration generating unit 391 and a vibration detecting unit 392 instead of the microphone 390. The vibration generating unit 391 is disposed on the upper stage 322, and generates vibrations of a predetermined frequency. When the vibration generating unit 391 generates vibrations, the generated vibrations are transmitted to the substrate 211 via the upper stage 322 and the substrate holder 221. The vibration generating unit 391 can be formed of a piezoelectric element or the like.

[0162] Vibration detection unit 392 is disposed on lower stage 332 and detects vibrations transmitted from substrate 211 to lower stage 332 via substrate 213 and substrate holder 221. Therefore, even if vibration generation unit 391 generates vibrations, vibration detection unit 392 does not detect the vibrations until substrates 211, 213 are pressed against each other in step S107 (see FIG. 3). However, when substrates 211, 213 come into contact with each other in step S107, vibration detection unit 392 can detect the vibrations generated by vibration generation unit 391.

[0163] Furthermore, even after the substrates 211, 213 come into contact with each other in step S107, the acoustic impedance of the vibration system formed by the upper stage 322, the substrate holders 221, 223, the substrates 211, 213, and the lower stage 332 changes according to the change in the contact state of the substrates 211, 213. Therefore, the detection result by the vibration detection unit 392 when the vibration generation unit 391 generates vibration also changes. This allows the vibration detection unit 392 to detect the progress and completion of bonding of the substrates 211, 213.

[0164] Fig. 32 is a schematic diagram of a bonding unit 300 equipped with an observation unit 620 having another structure. The bonding unit 300 shown in the figure has the same structure as the bonding unit 300 shown in Fig. 6 and the like, except for the parts described below. Therefore, the same reference numbers are used for the common components, and duplicated explanations will be omitted.

[0165] In the illustrated bonding section 300, the observation section 620 has a capacitance detection section 621. The capacitance detection section 621 applies a periodically changing electric signal to an LC resonant circuit formed by including the capacitance between the substrates 211 and 213 to be measured and a standard inductor. At this time, the capacitance detection section 621 superimposes an AC voltage on a DC voltage applied to the electrodes of the two substrate holders 221 and 223 having the function of an electrostatic chuck, and detects the AC component of the electric signal that changes according to the change in the capacitance in the substrates 211 and 213. The capacitance value and the change rate value detected by the capacitance detection section 621 are one piece of information regarding the state of the expansion of the contact area.

[0166] The total capacitance between the two substrate holders 221, 232 is the combination of the capacitance between the electrode of the substrate holder 221 and the substrate 211, the capacitance between the silicon layer of the substrate 211 and the surface oxide layer, the capacitance between the two substrates 211, 213, the capacitance between the silicon layer and the oxide layer of the substrate 213, and the capacitance between the electrode of the substrate holder 223 and the substrate 213. The capacitance between the substrates 211 and 213 increases as the gap between the substrates 211 and 213 narrows, and reaches a maximum when the substrates 211 and 213 are partially in contact with each other, and the total capacitance also reaches a maximum. That is, the maximum value is reached when a starting point is formed between the substrates 211 and 213. Thereafter, as the bonding wave progresses, the gap between the substrate 211 and the electrode of the substrate holder 221 increases, and the total capacitance decreases.

[0167] In this way, the capacitance changes in response to changes in the bonding state of the substrates 211 and 213. By detecting this change, the bonding state of the substrates 211 and 213 is electrically detected.

[0168] The control unit 150 detects that the capacitance value has exceeded a threshold value or reached a value previously determined as a maximum value, and determines that a starting point has been formed between the substrates 211 and 213. Alternatively, the control unit 150 may detect that a predetermined time has elapsed after the capacitance value has exceeded a threshold value or reached a value previously determined as a maximum value, and determine that a starting point has been formed. The predetermined time is determined according to the bonding strength between the contacting parts of the substrates 211 and 213, and is set, for example, based on the activation conditions of the substrates 211 and 213. Alternatively, the control unit 150 may detect that the contact area of ​​the contacting parts of the substrates 211 and 213 has reached a predetermined size, and determine that a starting point has been formed. The size of the predetermined area is determined according to the bonding strength between the parts of the substrates 211 and 213, and may be experimentally obtained in advance. The size of the area can be detected by a change in capacitance when the contact area expands minutely after the substrates 211 and 213 come into contact at one point, or by taking an image from outside using a means such as that shown in FIG. 28.

[0169] The control unit 150 determines that the bonding is complete when it detects that the capacitance value becomes constant and a constant load value is maintained for a threshold time, or that the rate of change in capacitance becomes smaller than a predetermined value. Alternatively, the control unit 150 may determine that the bonding is complete when it detects that the total capacitance value has returned to the value before the substrates 211 and 213 came into contact.

[0170] As described above, in the bonding section 300, a change in the bonding state can be detected based on changes in various characteristics, such as optical characteristics, mechanical characteristics, and electrical characteristics, of the substrates 211 and 213. Furthermore, the bonding section 300 may be formed by combining a plurality of the various observation sections 344, 345, 346, 347, 348, 349, 610, and 620 described above.

[0171] Fig. 33 is a partially enlarged schematic cross-sectional view showing a modified example of the bonding unit 300. The illustrated bonding unit 300 has the same structure as the bonding unit 300 shown in Fig. 10, except for the parts described below. Therefore, the same reference numbers are used for common elements, and duplicated explanations will be omitted.

[0172] In the illustrated bonding unit 300, the upper stage 322 has a plurality of vent holes 325 penetrating in the thickness direction. The lower end of each of the vent holes 325 in the figure opens to the lower surface of the upper stage 322. The upper end of each of the vent holes 325 in the figure is connected via a valve 632 to a tank 631 arranged outside the bonding unit 300.

[0173] Tank 631 contains a fluid, such as dry air or an inert gas, at a pressure higher than atmospheric pressure, which may be mixed into the atmosphere of substrates 211 and 213. Valve 632 opens and closes under the control of control unit 150. When valve 632 is opened, the fluid supplied from tank 631 is sprayed from upper stage 322 through vent hole 325.

[0174] In addition, in the illustrated bonding unit 300, the substrate holder 221 held by the upper stage 322 also has a plurality of vent holes 225 penetrating in the thickness direction at positions corresponding to the vent holes 325 of the upper stage 322. As a result, when the valve 632 is opened under the control of the control unit 150, a fluid supplied from the tank 631, for example, an inert gas such as nitrogen or argon, is sprayed from the vent holes 225 of the substrate holder 221. As a result, for example, when the substrate 211 remains adsorbed to the substrate holder 221 even after the power supply to the electrostatic chuck or the like is cut off, the substrate 211 can be forcibly pushed away, thereby improving the throughput of the substrate bonding apparatus 100.

[0175] Fig. 34 is a flow chart showing a part of the control procedure around the stage in the above-mentioned bonding unit 300. The procedure shown in the figure may be executed in the process from step S107 to step S112 in the procedure shown in Fig. 3. Therefore, in the following description, the correspondence to the procedure shown in Fig. 3 will be shown together with the procedure shown in Fig. 34.

[0176] 3, when the substrate 211 held by the upper stage 322 and the substrate 213 held by the lower stage 332 are aligned, the control unit 150 determines whether the substrates 211 and 213 have come into contact with each other (step S202) while raising the lower stage 332 (step S201). The raising of the lower stage 332 continues until the substrates 211 and 213 come into contact with each other (step S202: NO).

[0177] When it is detected that the substrates 211, 213 approaching each other as the lower stage 332 rises and come into contact with each other (step S202: YES), the control unit 150 detects that the substrate 213 held by the lower stage 332 and the substrate 211 held by the upper stage 322 approach each other. When the lower stage 332 rises further, the substrates 211, 213 come into contact with each other as shown in FIG. 35 (step S202: YES).

[0178] Fig. 35 is a schematic cross-sectional view showing a state in which substrates 211, 213 come into contact with each other as lower stage 332 is raised. Elements common to Fig. 34 are given the same reference numerals and duplicated explanations will be omitted. As shown in the figure, substrate 211 held by upper stage 322 is held with its central portion protruding downward in the figure, so that first, the central portion is partially pressed against substrate 213 held by lower stage 332 in a flat state (step S107).

[0179] 34 again, next, the control unit 150 starts measuring the pressure that the upper stage 322 receives due to the rise of the lower stage 332, through the load cell 380 disposed between the upper stage 322 and the top plate 316 (step S203). The control unit 150 also determines whether or not a region where the substrates 211 and 213 are bonded to each other has been formed on the abutted substrates 211 and 213 (step S108), and waits for a bonding starting point to be formed on the substrates 211 and 213 (step S204: NO).

[0180] When it is detected that a bonding starting point has been formed on the substrates 211, 213 (step S204: YES), the control unit 150 sets the position of the lower stage 332 in the lifting direction at this time, i.e., position L0 in the Z direction shown in Fig. 35, as the reference position when controlling the position of the lower stage 332. Furthermore, the control unit 150 stores the pressure measured by the load cell 380 when the lower stage 332 is located at the reference position as the control reference pressure when controlling the position of the lower stage in the Z direction (step S205).

[0181] Furthermore, when it is detected that the starting points of bonding have been formed on the substrates 211 and 213 (step S204: YES), the control unit 150 releases the substrate 211 from at least the upper stage 322 side (steps S109 and S206).The control unit 150 also opens the valve 632 to blow out the fluid through the vent holes 325 and 225, thereby pushing the substrate 211 away from the substrate holder 221 held by the upper stage 322, as shown in FIG. 36 (step S07).

[0182] 36 is a schematic cross-sectional view showing a state in which the control unit 150 pushes the substrate 211 away from the upper stage 322 by ejecting a fluid after the starting point of bonding is formed between the substrates 211 and 213. When the fluid ejected from the upper stage 322 side is sprayed onto the substrate 211, the pressure of the fluid also acts on the lower stage 332 through the lower substrate 213 and the substrate holder 223 that are in contact with the substrate 211. This increases the load on the elevation drive unit 338 that drives the lower stage 332, so that the lower stage 332 is displaced downward from the reference position L0.

[0183] Here, the substrate 211 initially held by the upper stage 322 has already been partially bonded to the substrate 211 held by the lower stage 332. Therefore, when the lower stage 332 descends, the upper substrate 211 also descends. As a result, the gap between the upper substrate holder 221 held by the upper stage 322 and the substrate 211 becomes wider, and the pressure of the fluid between the substrate holder 221 and the substrate 211 decreases.

[0184] As a result, the pressure measurement value by the load cell 380 decreases (step S208: YES), so that the control unit 150 operates the lifting drive unit 338 to raise the lower stage 332 in order to bring the measurement value of the load cell 380 closer to the control reference pressure (step S209). That is, the Z position of the lower stage 332 is controlled so as to be at a position where the force that the substrate 211 receives from the fluid and the force lifting the lower stage 332 by the lifting drive unit 338 are balanced. When the substrate 211 is separated from the upper substrate holder 221 by the injection of the fluid, the space between the substrate 211 and the substrate 213 becomes large, so that the pressure of the fluid between the substrates 211 and 213 decreases, and the balance of the forces is lost. Therefore, in order to increase the pressure of the fluid, the lower stage 332 is raised to a position where the fluid pressure and the force of the lifting drive unit 338 are balanced. In this way, as shown in FIG. 37, the lower stage 332 rises and approaches the reference position L0 again.

[0185] After this, the control unit 150 detects the value of the pressure measured by the load cell 380, and continues to control the position of the lower stage 332 so that the upward force of the lower stage 332 by the lifting drive unit 338 and the pressure of the fluid ejected from the upper stage 322 are balanced, and the value of the load cell 380 is constant (step S208: YES). However, while the bonding of the substrates 211 and 213 is in progress, the state between the upper substrate holder 221 and the upper substrate 211 changes over time, so the position of the lower stage 332 in the Z direction is not stable. As the bonding wave advances and the contact area expands and the substrate 211 moves away from the upper substrate holder 221, the space between the substrate 211 and the substrate holder 221 gradually increases, and the fluid pressure gradually decreases, so that the Z position of the lower stage 332 gradually rises during the process of the contact area expanding. When the bonding is completed, the size of the space between the substrate 211 and the substrate holder 221 does not change and the fluid pressure does not change either, so the Z position of the lower stage 332 becomes constant.

[0186] 38 is a schematic cross-sectional view showing a state in which the bonding of the substrates 211 and 213 in the bonding section 300 is completed through the above-mentioned process. As shown in the figure, when the bonding of the substrates 211 and 213 is completed and the state between the upper substrate holder 221 and the substrate 211 does not change, the change in the pressure value measured by the load cell 380 converges and the position of the lower stage 332 also does not change. Therefore, a threshold time determined in advance, for example, by an experiment is set, and when the pressure measurement value by the load cell 380 or the detection value of the position detection section detecting the Z position of the lower stage 332 does not change beyond the threshold time, the control section 150 can determine that the bonding of the substrates 211 and 213 is completed (step S210).

[0187] In the above embodiment, the control unit 150 can determine that an abnormality has occurred in bonding when the progress of the bonding wave stops, or when the degree of progress is uneven in the circumferential direction of the substrates 211 and 213, etc. In this case, the control unit 150 outputs a signal to resolve the abnormality according to the cause of the abnormality.

[0188] For example, if the progress of the bonding wave is uneven due to the presence of dirt between the substrates 211 and 213, a signal is output to a cleaning device to clean the substrate holder or stage.

[0189] When the substrate is deformed by the actuator described above, if the cause of the abnormality is the amount of deformation of the substrate by the actuator, the control unit 150 outputs a control signal to the control unit that controls the drive of the actuator to adjust the drive amount of the actuator to adjust the amount of deformation.

[0190] In the examples shown in Figures 33 to 38, if the cause of the abnormality is the fluid flow rate or fluid pressure, the control unit 150 adjusts the flow rate and fluid pressure from the air vent 325 corresponding to the area where the bonding wave progresses slower or faster than other areas.

[0191] If the cause of the abnormality is at least one of the temperature and air pressure around upper stage 322 and lower stage 332, a control signal is output to a temperature regulator or pressure regulator (not shown) to change the temperature and air pressure.

[0192] When a region of the substrate 211 where the bonding wave is progressing slowly is detected, at least one of the upper stage 322 and the lower stage 332 may be tilted so that the region approaches the substrate 213 .

[0193] If the cause of the abnormality is non-uniform activation within the surface of at least one of the two substrates 211, 213, the control unit 150 outputs a control signal to the activation device to adjust the degree of activation according to the distribution of the progress of the bonding wave. If the cause of the abnormality is the deformation amount, including the warpage amount, of the substrates 211, 213, the control unit 150 outputs a control signal to a pre-processing device, such as a film forming device or an exposure device, used in the process of manufacturing the substrates 211, 213, to adjust the deformation amount occurring in the substrate. Furthermore, if it takes a long time to form the starting point, this may be due to factors such as a weak degree of activation of the substrate or a weak pressing force when the substrates 211, 213 come into contact, so the control unit 150 outputs a control signal to the activation device to adjust the degree of activation, or controls the amount of drive of the lower stage 332 when the substrates 211, 213 come into contact.

[0194] The feedback control by the control unit 150 described above may be performed in real time, or may be performed when bonding the next substrate. Also, the feedback control may be performed for each lot of substrates, or each time the recipe for the bonding process is changed, etc.

[0195] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0196] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0197] 100 substrate bonding apparatus, 110 housing, 120, 130 substrate cassette, 140 transport unit, 150 control unit, 210, 211, 213 substrate, 212 scribe line, 214 notch, 216 circuit area, 218 alignment mark, 220, 221, 223 substrate holder, 222, 224 holding surface, 225, 325 ventilation hole, 227, 228, 229 observation hole, 230 bonded substrate, 231 bonding starting point, 232 bonding wave, 300 bonding unit, 310 frame, 312 bottom plate, 314 support, 316 top plate, 322 upper stage, 324, 334 microscope, 326, 336 activation device, 327, 328, 329 Observation window, 331 X-direction drive unit, 332 Lower stage, 333 Y-direction drive unit, 338 Lifting drive unit, 341, 342, 343 Detector, 344, 345, 346, 347, 348, 349, 610, 620 Observation unit, 351, 361, 362, 363 Light source, 354 Optical fiber, 364 Background plate, 352, 371, 372, 373 Light receiving unit, 353 Displacement meter, 374 Imaging unit, 380 Load cell, 390 Microphone, 391 Vibration generating unit, 392 Vibration detecting unit, 400 Holder stocker, 500 Prealigner, 621 Capacitive detecting unit, 631 Tank, 632 Valve

Claims

[Claim 1] A substrate bonding apparatus for bonding a first substrate and a second substrate, comprising: a first holding part that holds the first substrate; a second holding part that holds the second substrate; a control unit that releases at least one of the holding of the first substrate by the first holding unit and the holding of the second substrate by the second holding unit in order to enlarge a contact area formed between a portion of the first substrate and a portion of the second substrate; a detection unit that detects information regarding a change in an electrical characteristic of at least one of the first substrate and the second substrate; a determination unit that determines an expansion state of the contact area based on a detection result of the detection unit; A substrate bonding apparatus comprising:

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