Joining device and joining method

Abstract

This invention provides a technique for improving positioning accuracy before joining. The bonding device of the present invention bonds a first substrate having a first positioning mark to a second substrate having a second positioning mark. When the first imaging unit photographs the second positioning mark, the first irradiation unit irradiates white light into the imaging area of ​​the first imaging unit. When the second imaging unit photographs the first positioning mark, the second irradiation unit irradiates white light into the imaging area of ​​the second imaging unit. The control unit detects the positions of the first and second positioning marks by processing the images captured by the first and second imaging units. The control unit corrects the detected position of the first positioning mark based on the relationship between the wavelength and intensity of the reflected light reflected from the first substrate. The control unit controls the moving unit based on the corrected position of the first positioning mark.

Description

Technical Field

[0001] The present invention relates to a bonding device and a bonding method. Prior Art

[0002] The bonding device described in Patent Document 1 bonds a first substrate having a first positioning mark to a second substrate having a second positioning mark. The bonding device comprises a first holding portion, a second holding portion, a first imaging portion, a first illuminating portion, a second imaging portion, a second illuminating portion, and a control portion. The first holding portion holds the first substrate. The second holding portion holds the second substrate. When the first imaging portion photographs the second positioning mark, the first illuminating portion irradiates white light onto the imaging area of ​​the first imaging portion. When the second imaging portion photographs the first positioning mark, the second illuminating portion irradiates white light onto the imaging area of ​​the second imaging portion. The control portion detects the positions of the first and second positioning marks by processing the images captured by the first and second imaging portions, and then performs positioning of the first and second substrates. [Prior Art Literature] [Patent Document]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2020-194865 Summary of the Invention

[0004] [Problems to be solved by the invention]

[0005] One aspect of the present invention provides a technique for improving positioning accuracy before bonding. [Methods for solving the problem]

[0006] According to one aspect of the present invention, a bonding device bonds a first substrate including a first positioning mark to a second substrate including a second positioning mark. The bonding device comprises a first holding portion, a second holding portion, a first imaging portion, a first illuminating portion, a second imaging portion, a second illuminating portion, a moving portion, and a control portion. The first holding portion holds the first substrate. The second holding portion holds the second substrate. The first imaging portion is disposed on the first holding portion and images the second substrate held by the second holding portion. The first illuminating portion illuminates a photographic area of ​​the first imaging portion with white light while the first imaging portion images the second positioning mark. The second imaging portion is disposed on the second holding portion and images the first substrate held by the first holding portion. The second illuminating portion illuminates a photographic area of ​​the second imaging portion with white light while the second imaging portion images the first positioning mark. The moving unit moves the first holding unit and the second holding unit relative to each other. The control unit controls the moving unit. The control unit detects the positions of the first and second positioning marks by processing images captured by the first and second imaging units, corrects the detected position of the first positioning mark based on the relationship between the wavelength and intensity of reflected light reflected from the first substrate, and controls the moving unit based on the corrected position of the first positioning mark. [Effects of the Invention]

[0007] Through one aspect of the present invention, the positioning accuracy before joining can be improved. Simple diagram description

[0008] FIG1 is a top view showing a bonding system according to one embodiment. FIG. 2 is a cross-sectional view showing an example of a superimposed wafer obtained by bonding a lower wafer and an upper wafer. FIG3 is a flow chart showing a bonding method according to one embodiment. FIG4 is a cross-sectional view showing an example of a bonding apparatus. FIG5 is a flow chart showing an example of step S105. FIG6(A) is a side view showing an example of the operation of step S112, FIG6(B) is a side view showing the operation following FIG6(A), and FIG6(C) is a side view showing the operation following FIG6(B). FIG7(A) is a cross-sectional view showing an example of the operation of step S113, FIG7(B) is a cross-sectional view showing an example of the operation of step S114, and FIG7(C) is a cross-sectional view showing the operation following FIG7(B). FIG8 is a cross-sectional view showing an example of the upper photographing section, the upper illuminating section and the upper beam splitter. FIG9 is a diagram showing an example of an image taken of the lower positioning mark. FIG10 is a diagram showing an example of a reflection spectrum. FIG11 is a diagram showing an example of components of a control unit using functional blocks. FIG12 is a cross-sectional view showing a first modified example of the upper photographing section and the upper illuminating section. FIG13 is a cross-sectional view showing a second modified example of the upper photographing section and the upper illuminating section. FIG14 is a cross-sectional view showing a third modified example of the upper photographing section and the upper illuminating section. Implementation Method

[0009] The following describes embodiments of the present invention with reference to the drawings. Identical or corresponding components are denoted by the same reference numerals throughout the drawings, and their descriptions are omitted. The X-axis, Y-axis, and Z-axis directions are perpendicular to each other; the X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical.

[0010] Referring to FIG1 , a bonding system 1 according to one embodiment is described. The bonding system 1 bonds a first substrate and a second substrate to produce a superimposed substrate. As shown in FIG2 , the substrate positioned on the lower side during bonding is referred to as the lower wafer W1, and the substrate positioned on the upper side during bonding is referred to as the upper wafer W2. The lower wafer W1 corresponds to the first substrate, and the upper wafer W2 corresponds to the second substrate. However, this combination can also be reversed, with the lower wafer W1 corresponding to the second substrate and the upper wafer W2 corresponding to the first substrate.

[0011] By bonding the lower wafer W1 and the upper wafer W2, a superimposed wafer T is obtained. Of the surfaces of the lower wafer W1, the surface that is bonded to the upper wafer W2 is designated as "bonding surface W1j," and the surface opposite to bonding surface W1j is designated as "non-bonding surface W1n." Furthermore, of the surfaces of the upper wafer W2, the surface that is bonded to the lower wafer W1 is designated as "bonding surface W2j," and the surface opposite to bonding surface W2j is designated as "non-bonding surface W2n."

[0012] The lower wafer W1 comprises a semiconductor substrate W1a, such as a silicon wafer, and a film W1b formed on the semiconductor substrate W1a. A glass substrate may also be used as an alternative to the semiconductor substrate W1a. The film W1b comprises, for example, a device layer and a bonding layer. The device layer includes a plurality of electronic circuits. The bonding layer is formed on the device layer. Examples of the bonding layer include a silicon oxide film, a silicon nitride film, or a silicon carbonitride film.

[0013] The bonding layer is formed by methods such as thermal oxidation, CVD (Chemical Vapor Deposition), or ALD (Atomic Layer Deposition). When a silicon oxide film is formed by CVD as the bonding layer, for example, TEOS (Tetra Ethoxy Silane) is used as the raw material for the silicon oxide film.

[0014] The lower wafer W1 has lower alignment marks M11-M13. These marks are used to horizontally align the lower wafer W1 with the upper wafer W2 before bonding. For example, the lower alignment marks M11-M13 are formed between the semiconductor substrate W1a and the film W1b. The placement and number of the lower alignment marks M11-M13 are not limited to those shown.

[0015] Similarly, the upper wafer W2 comprises a semiconductor substrate W2a, such as a silicon wafer, and a film W2b formed on the semiconductor substrate W2a. A glass substrate may also be used as an alternative to the semiconductor substrate W2a. The film W2b comprises, for example, a device layer and a bonding layer. The device layer includes a plurality of electronic circuits. The bonding layer is formed on the device layer. Examples of the bonding layer include a silicon oxide film, a silicon nitride film, or a silicon carbonitride film.

[0016] The upper wafer W2 has upper alignment marks M21-M23. These marks are used to horizontally align the lower wafer W1 and upper wafer W2 before bonding. For example, the upper alignment marks M21-M23 are formed between the semiconductor substrate W2a and the film W2b. The placement and number of the upper alignment marks M21-M23 are not limited to those shown.

[0017] The lower positioning marks M11~M13 are equivalent to the first positioning marks, and the upper positioning marks M21~M23 are equivalent to the second positioning marks, but the combination can also be reversed, that is, the lower positioning marks M11~M13 are equivalent to the second positioning marks, and the upper positioning marks M21~M23 are equivalent to the first positioning marks.

[0018] Furthermore, one of the lower wafer W1 and the upper wafer W2 may not have a device layer.

[0019] As shown in Figure 1, the bonding system 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are arranged in this order along the positive X-axis. Furthermore, the loading / unloading station 2 and the processing station 3 are integrally connected.

[0020] The loading and unloading station 2 includes a loading platform 10 and a transport area 20. The loading platform 10 includes a plurality of loading plates 11. Cassettes C1, C2, and C3, which store a plurality of substrates (e.g., 25) in a horizontal position, are placed on each loading plate 11. Cassette C1 stores the lower wafer W1, cassette C2 stores the upper wafer W2, and cassette C3 stores the overlapped wafer T. In cassettes C1 and C2, the lower wafer W1 and the upper wafer W2 are stored facing each other, with their bonding surfaces W1j and W2j facing upwards, respectively.

[0021] The transport area 20 is located adjacent to the mounting table 10 on the positive X-axis side. The transport area 20 includes a transport path 21 extending in the Y-axis direction and a transport device 22 that is movable along the transport path 21. The transport device 22 includes a transport arm that holds and transports the lower wafer W1, upper wafer W2, or overlapped wafer T. The transport arm is movable horizontally and vertically and can rotate about a vertical axis. There may be multiple transport arms. The transport arm transports the upper wafer W2, lower wafer W1, or overlapped wafer T to a predetermined device adjacent to the transport area 20.

[0022] Furthermore, the number of cassettes C1 to C3 placed on the mounting table 10 is not limited to that shown in the figure. In addition, in addition to the cassettes C1, C2, and C3, a cassette for recovering defective substrates can also be placed on the mounting table 10.

[0023] The processing station 3 is provided with three processing blocks, G1, G2, and G3, for example. For example, the first processing block G1 is provided on the back side of the processing station 3 (on the positive Y-axis side in FIG1 ), and the second processing block G2 is provided on the front side of the processing station 3 (on the negative Y-axis side in FIG1 ). Furthermore, the third processing block G3 is provided on the loading / unloading station 2 side of the processing station 3 (on the negative X-axis side in FIG1 ).

[0024] Furthermore, a transfer area 60 is formed within the area surrounded by the first through third processing blocks G1 through G3. A transfer device 61 is located within the transfer area 60. The transfer device 61 includes a transfer arm that holds and transfers the lower wafer W1, upper wafer W2, or overlapped wafer T. The transfer arm is movable horizontally and vertically, and can rotate about a vertical axis. There may be multiple transfer arms. The transfer arm transfers the lower wafer W1, upper wafer W2, or overlapped wafer T to a predetermined device adjacent to the transfer area 60.

[0025] The first processing block G1 is equipped with, for example, a surface modification device 33 and a surface hydrophilization device 34. The surface modification device 33 uses plasma to modify the bonding surface W1j of the lower wafer W1 or the bonding surface W2j of the upper wafer W2. The surface hydrophilization device 34 hydrophilizes the modified bonding surface W1j of the lower wafer W1 or the modified bonding surface W2j of the upper wafer W2. The locations of the surface modification device 33 and the surface hydrophilization device 34 are not limited to those shown. The number of surface modification devices 33 and surface hydrophilization devices 34 may also be multiple.

[0026] The surface modification device 33, for example, breaks SiO2 bonds on the bonding surfaces W1j and W2j, forming dangling Si bonds, which facilitate subsequent hydrophilization. In the surface modification device 33, for example, oxygen gas, a processing gas, is excited under a reduced pressure environment to plasma and ionize. Then, by irradiating the bonding surfaces W1j and W2j with oxygen ions, the bonding surfaces W1j and W2j are subjected to plasma treatment and modified. The processing gas is not limited to oxygen; nitrogen, for example, may also be used.

[0027] The surface hydrophilization device 34 imparts OH groups to the bonding surfaces W1j and W2j, for example. For example, while rotating the lower wafer W1 or the upper wafer W2 held on the spin chuck, the surface hydrophilization device 34 supplies pure water onto the lower wafer W1 or the upper wafer W2. The pure water diffuses over the bonding surfaces W1j and W2j, imparting OH groups to the dangling bonds of Si, thereby hydrophilizing the bonding surfaces W1j and W2j. The surface hydrophilization device 34 also cleans the bonding surfaces W1j and W2j.

[0028] The second processing block G2 is equipped with, for example, a bonding apparatus 41. The bonding apparatus 41 flips the upper wafer W2 upside down, orienting its bonding surface W2j downward. The bonding apparatus 41 then bonds the hydrophilized lower wafer W1 to the upper wafer W2 to form a superposed wafer T. While the device for flipping the upper wafer W2 upside down is provided as part of the bonding apparatus 41 in this embodiment, it may also be provided separately from the bonding apparatus 41.

[0029] The third processing block G3 is provided with, for example, a transfer device 51. The transfer device 51 temporarily stores the lower wafer W1, the upper wafer W2, or the overlapped wafer T. The number of transfer devices 51 may be plural.

[0030] The joining system 1 includes a control device 90. The control device 90 is, for example, a computer and includes a CPU (Central Processing Unit) 91 and a storage medium 92, such as a memory. The storage medium 92 stores programs for controlling various processes performed in the joining system 1. The control device 90 controls the operation of the joining system 1 by causing the CPU 91 to execute the programs stored in the storage medium 92.

[0031] Next, referring to FIG3 , the bonding method of this embodiment will be described. The bonding method, for example, includes steps S101 to S105. Steps S101 to S105 are performed under the control of the control device 90. The bonding method need not include all steps S101 to S105; it is sufficient to include at least step S105. Furthermore, the bonding method may include processing other than step S105.

[0032] First, the cassette C1 storing the plurality of lower wafers W1 , the cassette C2 storing the plurality of upper wafers W2 , and an empty cassette C3 are placed on the mounting table 10 of the loading / unloading station 2 .

[0033] Next, the transport device 22 removes the lower wafer W1 from the cassette C1 and transports it to the transfer device 51 . The transport device 61 then removes the lower wafer W1 from the transfer device 51 and transports it to the surface modification device 33 .

[0034] Next, the surface modification device 33 modifies the bonding surface W1j of the lower wafer W1 (step S101). The modification of the bonding surface W1j is performed with the bonding surface W1j facing upward. The transport device 61 then removes the lower wafer W1 from the surface modification device 33 and transports it to the surface hydrophilization device 34.

[0035] Next, the surface hydrophilization device 34 hydrophilizes the bonding surface W1j of the lower wafer W1 (step S102). This hydrophilization is performed with the bonding surface W1j facing upward. The transport device 61 then removes the lower wafer W1 from the surface hydrophilization device 34 and transports it to the bonding device 41.

[0036] In parallel with the above-described processing of the lower wafer W1, the following processing is performed on the upper wafer W2. First, the transport device 22 removes the upper wafer W2 from the cassette C2 and transports it to the transfer device 51. Then, the transport device 61 removes the upper wafer W2 from the transfer device 51 and transports it to the surface modification device 33.

[0037] Next, the surface modification device 33 modifies the bonding surface W2j of the upper wafer W2 (step S103). The modification of the bonding surface W2j is performed with the bonding surface W2j facing upward. The transport device 61 then removes the upper wafer W2 from the surface modification device 33 and transports it to the surface hydrophilization device 34.

[0038] Next, the surface hydrophilization device 34 hydrophilizes the bonding surface W2j of the upper wafer W2 (step S104). The hydrophilization of the bonding surface W2j is performed with the bonding surface W2j facing upward. The transport device 61 then removes the upper wafer W2 from the surface hydrophilization device 34 and transports it to the bonding device 41.

[0039] Next, the bonding device 41 flips the upper wafer W2 upside down, with the bonding surface W2j of the upper wafer W2 facing downward. The bonding device 41 then bonds the lower wafer W1 to the upper wafer W2, producing a superposed wafer T (step S105). The transport device 61 then removes the superposed wafer T from the bonding device 41 and transports it to the transfer device 51.

[0040] Finally, the transport device 22 takes out the overlapped wafer T from the transfer device 51 and transports it to the cassette C3 on the mounting table 10. This completes a series of processes.

[0041] 4 , an example of a bonding apparatus 41 will be described. The bonding apparatus 41 includes a lower holding portion 110, an upper holding portion 120, a lower imaging portion 130, an upper imaging portion 150, a moving portion 170, and a control portion 200.

[0042] The lower holding portion 110 holds the lower wafer W1 from below, with its bonding surface W1j facing upward. The upper holding portion 120 holds the upper wafer W2 from above, with its bonding surface W2j facing downward. The lower holding portion 110 serves as the first holding portion, and the upper holding portion 120 serves as the second holding portion, although the combination can also be reversed.

[0043] The lower imaging unit 130 is provided on the lower holding unit 110 and photographs the wafer W held on the upper holding unit 120. The upper imaging unit 150 is provided on the upper holding unit 120 and photographs the wafer W1 held below the lower holding unit 110. The lower imaging unit 130 corresponds to the first imaging unit, and the upper imaging unit 150 corresponds to the second imaging unit, but this combination can also be reversed.

[0044] The moving portion 170 moves the lower holding portion 110 and the upper holding portion 120 relative to each other in the horizontal and vertical directions. In this embodiment, the moving portion 170 moves the lower holding portion 110, but it can also move the upper holding portion 120. The moving portion 170 can also rotate the lower holding portion 110 or the upper holding portion 120 around the vertical axis.

[0045] The control unit 200 controls the operation of the bonding device 41. The control unit 200 is, for example, a computer and has the same structure as the control device 90. The control unit 200 may also be a part of the control device 90.

[0046] The lower retaining portion 110 is divided into a plurality (e.g., two) of regions 110a and 110b. These regions 110a and 110b are arranged in this order from the center to the periphery of the lower retaining portion 110. Region 110a has a circular shape when viewed from above, while region 110b has an annular shape when viewed from above.

[0047] Each region 110a, 110b is independently provided with a suction pipe 111a, 111b. Each suction pipe 111a, 111b is connected to a different vacuum pump 112a, 112b. The lower holding portion 110 can vacuum-absorb the lower wafer W1 in each region 110a, 110b.

[0048] The lower holding portion 110 is provided with a plurality of holding pins 115 that can be freely raised and lowered in the vertical direction. The lower wafer W1 is placed on the top of the plurality of holding pins 115. Alternatively, the lower wafer W1 can be vacuum-adsorbed on the top of the plurality of holding pins 115.

[0049] The plurality of holding pins 115 rise and protrude from the holding surface of the lower holding portion 110. In this state, the plurality of holding pins 115 receive the lower wafer W1 from the transport device 61. The plurality of holding pins 115 then descend, bringing the lower wafer W1 into contact with the holding surface of the lower holding portion 110. Subsequently, the lower holding portion 110 operates the vacuum pumps 112a and 112b to horizontally vacuum-absorb the lower wafer W1 in each of the areas 110a and 110b.

[0050] The upper retaining portion 120 is divided into a plurality (e.g., three) of regions 120a, 120b, and 120c. These regions 120a, 120b, and 120c are arranged in this order from the center to the periphery of the upper retaining portion 120. Region 120a has a circular shape when viewed from above, while regions 120b and 120c have an annular shape when viewed from above.

[0051] Suction pipes 121a, 121b, and 121c are independently installed in each region 120a, 120b, and 120c. Vacuum pumps 122a, 122b, and 122c are connected to each suction pipe 121a, 121b, and 121c. The upper holding portion 120 can vacuum-absorb the wafer W2 in each region 120a, 120b, and 120c.

[0052] The upper holding portion 120 is provided with a plurality of holding pins 125 that can be raised and lowered vertically. These pins 125 are connected to a vacuum pump 126, which operates to vacuum-absorb the upper wafer W2. The upper wafer W2 is vacuum-absorbed against the bottom ends of the holding pins 125. Ring-shaped suction pads can also be used in place of the holding pins 125.

[0053] The plurality of holding pins 125 descend and protrude from the holding surface of the upper holding portion 120. In this state, the plurality of holding pins 125 vacuum-hold the upper wafer W2 and remove it from the transport device 61. The plurality of holding pins 125 then ascend, bringing the upper wafer W2 into contact with the holding surface of the upper holding portion 120. Subsequently, the upper holding portion 120 vacuum-holds the upper wafer W2 horizontally in each of the areas 120a, 120b, and 120c through the operation of the vacuum pumps 122a, 122b, and 122c.

[0054] A through hole 123 is formed in the center of the upper holding portion 120, extending vertically through the upper holding portion 120. A pressing member 190, described below, is inserted into the through hole 123. The pressing member 190 pushes the center of the upper wafer W2, which is spaced apart from the lower wafer W1, downward, bringing it into contact with the lower wafer W1.

[0055] The pressing portion 190 includes a pressing pin 191 and an outer cylinder 192, which serves as a guide for raising and lowering the pressing pin 191. The pressing pin 191 is inserted into the through hole 123, for example, via a drive unit (not shown) with a built-in motor, and protrudes from the holding surface of the upper holding portion 120, thereby pressing the center of the upper wafer W2 downward.

[0056] Next, an example of the operation of the bonding apparatus 41 will be described with reference to Figures 5 to 7. First, the transport device 61 loads the lower wafer W1 and the upper wafer W2 into the bonding apparatus 41 (step S111). The lower holding unit 110 holds the lower wafer W1 from below, with its bonding surface W1j facing upward. The upper holding unit 120 holds the upper wafer W2 from above, with its bonding surface W2j facing downward.

[0057] Next, the moving unit 170 moves the lower holding unit 110 and the upper holding unit 120 relative to each other to align the lower wafer W1 and the upper wafer W2 (step S112). This alignment is performed using the lower photographing unit 130 and the upper photographing unit 150, as shown in FIG6 . The upper photographing unit 150 is fixed to the upper holding unit 120 and photographs the bonding surface W1j of the wafer W1 held below the lower holding unit 110. Meanwhile, the lower photographing unit 130 is fixed to the lower holding unit 110 and photographs the bonding surface W2j of the wafer W2 held above the upper holding unit 120.

[0058] First, as shown in Figure 6(A), the moving unit 170 horizontally positions the lower photographic unit 130 and the upper photographic unit 150. Specifically, the moving unit 170 horizontally moves the lower holding unit 110 so that the lower photographic unit 130 is approximately directly below the upper photographic unit 150. Then, while the upper and lower photographic units 150, 130 photograph a common target X, the moving unit 170 fine-tunes the horizontal position of the lower photographic unit 130 to align their horizontal positions. This completes the horizontal positioning of the upper and lower photographic units 150, 130.

[0059] Next, as shown in FIG6(B), the moving unit 170 moves the lower holding unit 110 vertically upward, and then horizontally aligns the lower holding unit 110 and the upper holding unit 120. Specifically, while the moving unit 170 moves the lower holding unit 110 horizontally, the upper photographing unit 150 sequentially photographs the lower positioning marks M11 to M13, and the lower photographing unit 130 sequentially photographs the upper positioning marks M21 to M23. FIG6(B) shows the upper photographing unit 150 photographing the lower positioning mark M11 and the lower photographing unit 130 photographing the upper positioning mark M23.

[0060] The lower camera 130 and the upper camera 150 transmit the captured image data to the control unit 200. The control unit 200 detects the positions of the lower positioning marks M11-M13 and the upper positioning marks M21-M23 by processing the images captured by the lower camera 130 and the upper camera 150. The control unit 200 controls the moving unit 170 so that the lower positioning marks M11-M13 and the upper positioning marks M21-M23 overlap in the vertical direction.

[0061] Next, as shown in FIG6(C), the moving unit 170 moves the lower holding unit 110 vertically upward. As a result, the gap G (see FIG4) between the bonding surface W1j of the lower wafer W1 and the bonding surface W2j of the upper wafer W2 becomes a predetermined distance, for example, 80 μm to 200 μm.

[0062] Next, as shown in FIG7(A), vacuum pump 122a is stopped to release the vacuum suction on upper wafer W2 in region 120a. Then, pressing pins 191 of pressing unit 190 descend, pushing the center of upper wafer W2 downward, bringing it into contact with lower wafer W1 (step S113). As a result, the centers of lower wafer W1 and upper wafer W2 are bonded to each other.

[0063] The bonding surface W1j of the lower wafer W1 and the bonding surface W2j of the upper wafer W2 are modified to generate van der Waals forces (intermolecular forces) between the bonding surfaces W1j and W2j, bonding them together. Furthermore, the bonding surfaces W1j and W2j are hydrophilized, so the hydrophilic groups (e.g., OH groups) form hydrogen bonds, strongly and securely bonding the bonding surfaces W1j and W2j together.

[0064] Next, as shown in FIG7(B), the vacuum pump 122b is stopped to release the vacuum suction of the upper wafer W2 in the region 120b. Next, the vacuum pump 122c is stopped to release the vacuum suction of the upper wafer W2 in the region 120c as shown in FIG7(C).

[0065] In this manner, the vacuum holding of the upper wafer W2 is gradually released from its center toward its periphery, causing it to gradually drop and contact the lower wafer W1. Furthermore, the lower wafer W1 and upper wafer W2 are bonded sequentially from the center toward the periphery (step S114). As a result, the bonding surface W2j of the upper wafer W2 and the bonding surface W1j of the lower wafer W1 are in full contact, and the lower wafer W1 and upper wafer W2 are bonded to form a superimposed wafer T. The pressing pins 191 then rise to their original positions.

[0066] Next, the moving unit 170 lowers the lower holding unit 110, increasing the vertical distance between the lower holding unit 110 and the upper holding unit 120. The transport device 61 then removes the overlapped wafer T from the bonding device 41 (step S115). Specifically, the lower holding unit 110 first releases the overlapped wafer T. Next, the plurality of holding pins 115 rise and transfer the overlapped wafer T to the transport device 61. The plurality of holding pins 115 then descend to their original positions.

[0067] Next, referring to Figures 8 to 11 , an example of detecting the position of the lower alignment mark M12 and correcting the detected position will be described. As shown in Figure 8 , the bonding device 41 includes, for example, an upper imaging unit 150 , an upper illumination unit 160 , and an upper beam splitter 165 , to detect the position of the lower alignment mark M12 and correct the detected position.

[0068] The upper imaging unit 150 captures the lower wafer W1. The upper imaging unit 150 includes, for example, an objective lens 151, an imaging lens 152, and a light-receiving element 153. Although not shown, a plurality of light-receiving elements 153 are arranged two-dimensionally. Each light-receiving element 153 constitutes a pixel. The light-receiving element 153 receives light reflected from the lower wafer W1.

[0069] The upper camera 150 can be either a monochrome camera or a color camera, but in this embodiment, it is a monochrome camera. When the upper camera 150 is a monochrome camera, the light receiving element 153 receives light of various colors (various wavelengths) rather than a specific color (a specific wavelength), and generates an electrical signal corresponding to the intensity of the received light. The higher the received light intensity, the higher the pixel brightness.

[0070] The upper camera unit 150 may include a beam splitter 154 such as a half mirror between the objective lens 151 and the imaging lens 152. The beam splitter 154, for example, reflects the white light emitted by the upper illumination unit 160 toward the lower wafer W1, while allowing the reflected light generated by the white light reflecting off the lower wafer W1 to pass through the light receiving element 153.

[0071] The upper illuminating unit 160 is fixed to the upper holding unit 120, similarly to the upper photographing unit 150, but may not be fixed to the upper holding unit 120. When the upper photographing unit 150 photographs the lower positioning mark M12, the upper illuminating unit 160 irradiates the photographing area of ​​the upper photographing unit 150 with white light. The white light is irradiated onto the photographing area of ​​the upper photographing unit 150 via the beam splitter 154. Alternatively, the beam splitter 154 may be omitted, and the white light may be irradiated directly onto the photographing area of ​​the upper photographing unit 150.

[0072] The upper illumination unit 160 includes a white light source 161. Light source 161 is, for example, a white LED. The light-emitting method of a white LED is not particularly limited. A white LED may include a blue LED and a yellow phosphor, a red LED, a green LED, and a blue LED, or a near-ultraviolet LED, a red phosphor, a green phosphor, and a blue phosphor.

[0073] As shown in FIG9 , the upper camera unit 150 captures an image P including the lower positioning mark M12 and its surroundings. The upper camera unit 150 transmits the image P to the control unit 200. The control unit 200 includes a position detection unit 201 (see FIG11 ). The position detection unit 201 processes the image P to detect the position of the lower positioning mark M12. For example, the position detection unit 201 detects the location where the brightness change in the image P reaches a maximum value as the location of the lower positioning mark M12.

[0074] The brightness difference (contrast) between the lower alignment mark M12 and its surroundings in image P is primarily determined by the reflectivity difference between the lower alignment mark M12 and its surroundings. The greater the reflectivity difference, the greater the brightness difference. This reflectivity difference is primarily determined by the film thickness and material of the film W1b on the lower wafer W1, as well as the thickness and material of the lower alignment mark M12.

[0075] Figure 10 shows an example of the reflection spectrum of the lower alignment mark M12 and its surroundings. Because the lower alignment mark M12 and its surroundings differ in their layered structures on the lower wafer W1, their reflection spectra differ. The reflectivity difference between the lower alignment mark M12 and its surroundings increases or decreases with the wavelength of light.

[0076] Therefore, when the upper imaging unit 150 captures the lower alignment mark M12, the upper illuminating unit 160 irradiates the imaging area of ​​the upper imaging unit 150 with white light containing various wavelengths, rather than light of a specific wavelength (e.g., red light). This ensures a stable reflectivity difference between the lower alignment mark M12 and its surroundings, even if the thickness or material of the film W1b changes, and thus a stable brightness difference in the image P.

[0077] The light receiving element 153 of the upper imaging unit 150 receives light of various wavelengths. At this point, these wavelengths of light pass through the objective lens 151 and the imaging lens 152, causing chromatic aberration. This chromatic aberration is related to the offset of the detection position of the lower positioning mark M12. This is not a problem if the offset (magnitude and direction) of the detection position is fixed. However, if the thickness or material of the film W1b changes, the reflection spectrum changes, and the influence of chromatic aberration also changes, causing the offset of the detection position to change.

[0078] Therefore, the upper beam splitter 165 detects the reflection spectrum of the light reflected from the lower wafer W1. Like the upper imaging unit 150, the upper beam splitter 165 is fixed to the upper holding unit 120, but may not be fixed to the upper holding unit 120. For example, like the upper illumination unit 160, the upper beam splitter 165 includes a white light source (not shown). It irradiates the lower wafer W1 with white light emitted from the light source and detects the reflection spectrum of the light reflected from the lower wafer W1.

[0079] The upper beam splitter 165 mainly detects the reflection spectrum of the reflected light around the lower positioning mark M12. This is because the detection area of ​​the upper beam splitter 165 is larger than the size of the lower positioning mark M12, making it difficult to obtain the reflection spectrum of the reflected light reflected only from the lower positioning mark.

[0080] The upper spectrometer 165 transmits the detection results to the control unit 200. The control unit 200 includes a reflection characteristic analysis unit 202 (see Figure 11). The reflection characteristic analysis unit 202 calculates the relationship between the wavelength and intensity of the reflected light. The relationship to be calculated includes, for example, the intensity ratio of a first color light and a second color light of different colors. The first color light is, for example, red light, and the second color light is, for example, blue light. The relationship to be calculated may also include the intensity ratio of the first color light, the second color light, and a third color light of different colors. The third color light is, for example, green light. Changes in these intensity ratios indicate changes in the influence of color aberration and, therefore, changes in the offset of the detection position.

[0081] The control unit 200 includes a position correction unit 203. This unit corrects the position detected by the position detection unit 201 based on the relationship (e.g., the intensity ratio of the first and second colored light) determined by the reflection characteristics analysis unit 202. This allows the accurate position of the lower alignment mark M12 to be determined even if the film thickness or material of the film W1b changes, causing changes in color difference. The relationship between the intensity ratio of the first and second colored light and the correction amount (magnitude and direction) to the detected position is determined through preliminary experiments and stored in advance on the control unit 200's recording medium.

[0082] The control unit 200 includes a movement control unit 204. The movement control unit 204 controls the movement unit 170 based on the position of the lower positioning mark M12 corrected by the position correction unit 203. The movement control unit 204 controls the movement unit 170 so that the lower positioning mark M12 and the upper positioning mark M22 overlap in the vertical direction. This improves positioning accuracy before bonding.

[0083] Although not shown, the bonding apparatus 41 may also include, for example, a lower imaging unit 130, a lower illuminating unit, and a lower beam splitter to detect the position of the upper alignment mark M22 and correct the detected position. The lower illuminating unit irradiates white light onto the imaging area of ​​the lower imaging unit 130 when the lower imaging unit 130 is imaging the upper alignment mark M22. The lower illuminating unit, like the lower imaging unit 130, is fixed to the lower holding unit 110, but it may not be fixed to the lower holding unit 110. The lower beam splitter detects the reflection spectrum of the light reflected from the upper wafer W2 and transmits the detection results to the control unit 200. The lower beam splitter, like the lower imaging unit 130, is fixed to the lower holding unit 110, but it may not be fixed to the lower holding unit 110.

[0084] The reflection characteristics analysis unit 202 determines the relationship between the wavelength and intensity of the reflected light reflected from the upper wafer W2. The position correction unit 203 corrects the position of the upper alignment mark M22 detected by the position detection unit 201 based on the relationship (such as the intensity ratio of the first color light and the second color light) determined by the reflection characteristics analysis unit 202. The movement control unit 204 controls the movement unit 170 based on the position of the upper alignment mark M22 corrected by the position correction unit 203.

[0085] Next, a first modified example of the upper imaging unit 150 and the upper illuminating unit 160 will be described with reference to FIG12 . The following mainly describes the differences. As shown in FIG12 , the bonding apparatus 41 includes the upper imaging unit 150 and the upper illuminating unit 160, but does not include the upper beam splitter 165 shown in FIG8 . The reflection characteristics analysis unit 202 utilizes the upper imaging unit 150 in place of the upper beam splitter 165 to determine the relationship between the wavelength and intensity of the reflected light reflected from the lower wafer W1.

[0086] The upper camera unit 150 is a color camera. The color camera includes a first color light-receiving element 153A, a second color light-receiving element 153B, and a third color light-receiving element 153C. The first color light-receiving element 153A, the second color light-receiving element 153B, and the third color light-receiving element 153C receive light that passes through different color filters, thereby receiving light of different colors. A single pixel is composed of the first color light-receiving element 153A, the second color light-receiving element 153B, and the third color light-receiving element 153C. Although not shown, the plurality of pixels are arranged in a two-dimensional configuration.

[0087] The reflection characteristics analysis unit 202 calculates the ratio of the light intensity received by the first color light-receiving element 153A and the second color light-receiving element 153B constituting the same pixel. For example, the first color is red, and the second color is blue. The reflection characteristics analysis unit 202 can also calculate the ratio of the light intensity received by the first color light-receiving element 153A, the second color light-receiving element 153B, and the third color light-receiving element 153C constituting the same pixel. For example, the third color is green. These light intensity ratios represent the relationship between the wavelength and intensity of the reflected light.

[0088] The size of the imaging area of ​​one pixel is much smaller than the size of the lower alignment mark M12. Therefore, the light intensity ratio can be calculated for the lower alignment mark M12 and the area around the lower alignment mark M12.

[0089] The pixels for which the received light intensity ratio is calculated can be either the pixels capturing images of the area surrounding the lower alignment mark M12 or the pixels capturing images of the lower alignment mark M12, or both. Multiple pixels can also be used to calculate either of the received light intensity ratios. In other words, the received light intensity ratio can be an average value.

[0090] The content of this modified example is also applicable to the lower imaging unit 130 and the lower illumination unit. That is, when the lower imaging unit 130 is a color camera, the reflection characteristics analysis unit 202 can use the lower imaging unit 130 instead of the lower spectrometer to determine the relationship between the wavelength and intensity of the reflected light reflected from the upper wafer W2.

[0091] Next, a second modified embodiment of the upper imaging unit 150 and upper illuminating unit 160 will be described with reference to FIG13 . The following primarily describes the differences. Even if the upper imaging unit 150 is a monochrome camera, as long as the upper illuminating unit 160 can switch between illuminating the imaging area of ​​the upper imaging unit 150 with white light, first color light, and second color light, the upper beam splitter 165 is unnecessary. The reflection characteristics analysis unit 202 utilizes the upper imaging unit 150 in place of the upper beam splitter 165 to determine the relationship between the wavelength and intensity of the reflected light reflected from the lower wafer W1.

[0092] Upper illumination unit 160 includes, for example, a white light source 161, a first color filter 162A, and a second color filter 162B. First color filter 162A selectively transmits a first color of light within the white light. Second color filter 162B selectively transmits a second color of light within the white light. The first color of light is, for example, red light, and the second color of light is, for example, blue light.

[0093] The first color filter 162A and the second color filter 162B are movable between positions within the optical path of the white light and positions outside the optical path of the white light, respectively. Thus, the upper illumination unit 160 can switch between irradiating the imaging area of ​​the upper imaging unit 150 with white light, the first color light, and the second color light of different colors.

[0094] The upper illumination unit 160 may further include a third color filter 162C. The third color filter 162C selectively transmits a third color of light within the white light. The third color light is, for example, green light. The third color filter 162C is movable between a position within the optical path of the white light and a position outside the optical path of the white light. In this manner, the upper illumination unit 160 can switch between irradiating the imaging area of ​​the upper imaging unit 150 with different colors of white light, the first color light, the second color light, and the third color light.

[0095] The reflection characteristics analysis unit 202 calculates the ratio of the light intensity received by the same light receiving element 153 when the upper imaging unit 150's imaging area is fixed and the light is switched between the first and second color lights. For example, the first color is red, and the second color is blue. The reflection characteristics analysis unit 202 can also calculate the ratio of the light intensity received by the same light receiving element 153 when the upper imaging unit 150's imaging area is fixed and the light is switched between the first, second, and third color lights. For example, the third color is green. These light intensity ratios represent the relationship between the wavelength and intensity of the reflected light.

[0096] The size of the imaging area of ​​one pixel is much smaller than the size of the lower alignment mark M12. Therefore, the light intensity ratio can be calculated for the lower alignment mark M12 and the area around the lower alignment mark M12.

[0097] The pixels for calculating the light intensity ratio can be either the pixels capturing images of the area surrounding the lower alignment mark M12 or the pixels capturing images of the lower alignment mark M12, or both. Multiple pixels can also be used to calculate either light intensity ratio. That is, the light intensity ratio can be an average value.

[0098] The contents of this modified example can also be applied to the lower camera unit 130 and the lower illumination unit. Even if the lower camera unit 130 is a monochrome camera, as long as the lower illumination unit can switch between illuminating the imaging area of ​​the lower camera unit 130 with white light, first color light, and second color light, a lower beam splitter is not required. The lower illumination unit can include a white light source, a first color filter, and a second color filter. The lower illumination unit can also include a third color filter.

[0099] Next, a third variation of the upper imaging unit 150 and upper illumination unit 160 will be described with reference to FIG14 . The following primarily describes the differences. The white light source 161 can include a first color light source 161A, a second color light source 161B, and a third color light source 161C, allowing the imaging area of ​​the upper imaging unit 150 to be switched between irradiating white light, the first color light, the second color light, and the third color light with different colors.

[0100] The first color light is, for example, red light, the second color light is, for example, blue light, and the third color light is, for example, green light. Upper illumination unit 160 can emit white light by simultaneously emitting light from the three light sources 161A, 161B, and 161C. Alternatively, upper illumination unit 160 can emit only one of the first, second, and third color lights by emitting light from only one of the three light sources 161A, 161B, and 161C.

[0101] The white light source 161 includes a first color light source 161A, a second color light source 161B, and a third color light source 161C, but the present invention is not limited thereto. The upper illumination unit 160 may also include a white light source 161, a first color light source 161A, a second color light source 161B, and a third color light source 161C.

[0102] The content of this modified example can also be applied to the lower imaging unit 130 and the lower illumination unit. Specifically, the lower illumination unit can include a white light source, and the white light source can include a first color light source, a second color light source, and a third color light source. Furthermore, the lower illumination unit can also include a white light source, a first color light source, a second color light source, and a third color light source.

[0103] While the above describes embodiments of the bonding apparatus and bonding method according to the present invention, the present invention is not limited to the aforementioned embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Such changes are naturally within the technical scope of the present invention.

[0104] 1:Joint system 2: Moving in and out of the station 3: Processing Station 10: Loading table 11: Loading plate 20:Transportation area 21: Portage Road 22: Transport device 33: Surface modification device 34: Surface hydrophilization device 41:Jointing device 51:Transmission device 60:Transportation area 61: transport device 90: Control device 91:CPU 92: Recording Media 110: Lower holding portion (first holding portion) 110a,110b: Area 111a, 111b: Suction tube 112a, 112b: Vacuum pump 115: Retaining pin 120: Upper holding portion (second holding portion) 120a, 120b, 120c: Area 121a, 121b, 121c: Suction tube 122a, 122b, 122c: Vacuum pump 123:Through hole 125: Holding pin 126: Vacuum pump 130: Lower Photographic Section (1st Photographic Section) 150: Upper Photographic Section (Second Photographic Section) 151:Objective lens 152: Imaging lens 153: Light receiving element 153A: 1st color light receiving element 153B: Second color light receiving element 153C: 3rd color light receiving element 154: Beam splitter 160: Upper irradiation part (second irradiation part) 161: Light Source 161A: Light source 161B: Light Source 161C: Light Source 162A: 1st color filter 162B: 2nd color filter 162C: 3rd color filter 165: Upper optical splitter 170: Mobile Department 190: Pressing part 191: Press pin 192:Outer cylinder 200: Control Department 201: Position detection unit 202: Reflection characteristics analysis unit 203: Position Correction Unit 204: Mobile Control Unit W1: lower wafer (first substrate) W1a:Semiconductor substrate W1b: Membrane W1n: non-joint surface W1j: Joint surface W2: Upper wafer (second substrate) W2a: semiconductor substrate W2b: Membrane W2n: non-joint surface W2j: Joint surface T: Overlapped wafer C1~C3: Box G1: Processing block (1st processing block) G2: Processing block (2nd processing block) G3: Processing block (3rd processing block) M11~M13: Lower positioning mark M21~M23: Upper positioning mark G:Interval P: Image S101~S105: Steps S111~S115: Steps

Claims

1. A bonding device for bonding a first substrate including a first positioning mark to a second substrate including a second positioning mark, comprising: a first holding portion for holding the first substrate; a second holding portion for holding the second substrate; a first photographing portion disposed on the first holding portion for photographing the second substrate held on the second holding portion; a first irradiation portion for irradiating white light onto the photographing area of ​​the first photographing portion when the first photographing portion photographs the second positioning mark; a second photographing portion disposed on the second holding portion for photographing the first substrate held on the first holding portion; a second irradiation portion for irradiating white light onto the photographing area of ​​the second photographing portion when the second photographing portion photographs the first positioning mark; a moving portion for moving the first holding portion and the second holding portion relative to each other; and a control portion for controlling the moving portion. The control unit detects the positions of the first positioning mark and the second positioning mark by processing the images captured by the first and second imaging units, corrects the detected position of the first positioning mark based on the relationship between the wavelength and intensity of the reflected light reflected from the first substrate, and controls the moving unit based on the corrected position of the first positioning mark.

2. The coupling device as described in claim 1, wherein, The control unit corrects the position of the detected second positioning mark based on the relationship between the wavelength and intensity of the reflected light reflected from the second substrate, and controls the moving unit based on the corrected position of the second positioning mark.

3. The bonding device as described in claim 1 or 2 further comprises: a beam splitter for detecting the reflection spectrum of the reflected light reflected from the first substrate; and a control unit for correcting the position of the first positioning mark based on the detection result of the beam splitter.

4. The coupling device as described in claim 1 or 2, wherein, The second camera unit includes a color camera, which includes a first color light-receiving element and a second color light-receiving element that receive light of different colors; the control unit corrects the position of the first positioning mark based on the ratio of the light intensity of the first color light-receiving element and the second color light-receiving element constituting the same pixel.

5. The coupling device as described in claim 1 or 2, wherein, The second illumination unit illuminates the photographic area of ​​the second photographic unit with different colors of white light, first color light, and second color light. The second photographic unit includes a monochrome camera, which includes a light-receiving element. The control unit corrects the position of the first positioning mark based on the ratio of the light intensity of the same light-receiving element when the first color light and the second color light are illuminated while the photographic area of ​​the second photographic unit is fixed.

6. The coupling device as described in claim 5, wherein, The second irradiation unit further includes: a first color filter that selectively allows the first color light in the white light to pass through; and a second color filter that selectively allows the second color light in the white light to pass through.

7. The coupling device as described in claim 5, wherein, The second irradiation unit has a white light source, and the white light source includes the first color light source and the second color light source; or, the second irradiation unit has the white light source, the first color light source and the second color light source respectively.

8. A bonding method comprising the steps of bonding a first substrate including a first positioning mark and a second substrate including a second positioning mark, the bonding method comprising the following steps: holding the first substrate with a first holding portion; holding the second substrate with a second holding portion; taking a photograph of the second substrate held on the second holding portion with a first photographing portion provided on the first holding portion; irradiating white light from a first irradiation portion into the photographing area of ​​the first photographing portion while the first photographing portion is taking a photograph of the second positioning mark; taking a photograph of the first substrate held on the first holding portion with a second photographing portion provided on the second holding portion; irradiating white light from a second irradiation portion into the photographing area of ​​the second photographing portion while the second photographing portion is taking a photograph of the first positioning mark; and detecting the positions of the first positioning mark and the second positioning mark by processing the images taken by the first photographing portion and the second photographing portion. Based on the relationship between the wavelength and intensity of the reflected light reflected from the first substrate, the position of the detected first positioning mark is corrected; and based on the corrected position of the first positioning mark, the first holding part and the second holding part are moved relative to each other.

9. The bonding method as described in claim 8 further includes the following steps: correcting the position of the detected second positioning mark based on the relationship between the wavelength and intensity of the reflected light reflected from the second substrate; and moving the first holding portion relative to the second holding portion based on the corrected position of the second positioning mark.

10. The bonding method as described in claim 8 or 9 further comprises the following steps: detecting the reflection spectrum of the reflected light reflected from the first substrate using a beam splitter; and correcting the position of the first positioning mark based on the detection result of the beam splitter.

11. The joining method as described in claim 8 or 9, wherein, The second camera unit includes a color camera, which includes a first color light-receiving element and a second color light-receiving element that receive light of different colors; the joining method further includes the following steps: adjusting the position of the first positioning mark based on the ratio of the light intensity of the first color light-receiving element and the second color light-receiving element constituting the same pixel.

12. The joining method as described in claim 8 or 9, wherein, The second irradiation unit irradiates the photographic area of ​​the second photography unit with different colors of white light, first color light, and second color light; the second photography unit includes a monochrome camera, which includes a light-receiving element; the joining method further includes the following step: based on the ratio of the light intensity of the same light-receiving element when switching between irradiating the first color light and the second color light while the photographic area of ​​the second photography unit is fixed, the position of the first positioning mark is corrected.

13. The joining method as described in claim 12, wherein, The second irradiation unit further includes: a first color filter that selectively allows the first color light in the white light to pass through; and a second color filter that selectively allows the second color light in the white light to pass through.

14. The joining method as described in claim 12, wherein, The second irradiation unit has a white light source, and the white light source includes the first color light source and the second color light source; or, the second irradiation unit has the white light source, the first color light source and the second color light source respectively.

Images