Wafer alignment method, wafer bonding method, wafer alignment device, and wafer bonding device

Abstract

To provide a wafer alignment method, a wafer bonding method, a wafer alignment device, and a wafer bonding device, which can improve alignment accuracy by accurately recognizing a wafer with an imaging unit, and also improve wafer bonding accuracy. [Solution] A wafer alignment method that uses a single imaging unit 18 to adjust the alignment when bonding two wafers W1 and W2 that are located at different distances from the imaging unit 18, in which the alignment mark of one wafer W1, which is located a short distance from the imaging unit 18, is imaged without the light of the imaging unit 18 passing through glass, and with the positions of the imaging unit 18 and one wafer W1 fixed, the alignment mark of the other wafer W2, which is located a long distance from the imaging unit 18, is imaged by passing the light of the imaging unit 18 through glass 22.

Description

[Technical Field]

[0001] The present invention relates to a method for aligning a wafer such as a semiconductor wafer, a method for bonding a wafer, a wafer alignment apparatus, and a wafer bonding apparatus. [Background technology]

[0002] Conventionally, techniques for bonding substrates such as semiconductor wafers and glass substrates have been known. For example, a bonding device includes a first holding unit, a second holding unit, a stage, an imaging unit, a light source, a horizontal position adjustment unit, and a control unit. The first holding unit adsorbs and holds a first substrate. The second holding unit adsorbs and holds a second substrate to be bonded to the first substrate. The imaging unit is disposed outside the stage and captures images of alignment marks provided on the first and second substrates from outside the stage through through holes formed in the stage and the first holding unit. The light source is disposed outside and inside the stage and irradiates light from outside the stage through through holes formed in the stage and the second holding unit. The control unit causes the imaging unit to perform an imaging process to capture images of the alignment marks on the first and second substrates from inside the stage, and then causes the horizontal position adjustment unit to perform an adjustment process to adjust the horizontal position of the first holding unit based on the image capture results from the imaging unit (Patent Document 1).

[0003] Also, a method for bonding a first substrate and a second substrate includes a first substrate pre-alignment step of pre-aligning the first substrate by using an imaging unit to capture an image of an alignment mark of the first substrate while the first substrate is within a depth of focus of the imaging unit and the second substrate is outside the depth of focus of the imaging unit and a light source is turned on; a second substrate pre-alignment step of pre-aligning the second substrate by capturing an image of an alignment mark of the second substrate while using a second imaging unit to capture an image of an alignment mark of the second substrate while the first substrate is outside the depth of focus of the imaging unit and the second substrate is within the depth of focus of the imaging unit and a second light source is turned on; a simultaneous imaging step of simultaneously imaging the alignment marks of the first substrate and the second substrate with the imaging unit while the first substrate and the second substrate are both in close proximity to each other within the range of the focal depth of the imaging unit and while the light source is turned on; and a bonding step of bonding the first substrate and the second substrate with the first substrate and the second substrate in close proximity to each other and while the light source is turned on (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-134459 [Patent Document 2] Patent No. 7125190 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in all of the above conventional technologies, the imaging unit is configured to move at least in the Z-axis direction, or the imaging unit is fixed and the two wafers (substrates) must be moved to adjust the focal length, which tends to reduce imaging accuracy as the imaging unit moves, resulting in a technical problem of reduced bonding accuracy between substrates.

[0006] Therefore, in order to solve the above problems, an object of the present invention is to provide a wafer alignment method, a wafer bonding method, a wafer alignment device, and a wafer bonding device that improve alignment accuracy by accurately recognizing the wafer with an imaging unit. [Means for solving the problem]

[0007] A first invention is a wafer alignment method for adjusting alignment during bonding of two wafers that are different in distance from a single imaging unit, using the single imaging unit, A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; The light from the imaging unit is directed to an alignment mark on one of the wafers located at a short distance from the imaging unit. The aforementioned Capture images without passing them through glass, With the positions of the imaging unit and one of the wafers fixed, light from the imaging unit is passed through the glass to capture an image of an alignment mark on the other wafer located at a distance from the imaging unit.

[0008] A second invention is a wafer alignment method for adjusting alignment during bonding of two wafers that are different in distance from a single imaging unit, using the single imaging unit, comprising: A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; The light from the imaging unit is directed to an alignment mark on one of the wafers located at a distance from the imaging unit. The aforementioned Shooting through glass, With the positions of the imaging unit and one of the wafers fixed, an image of the alignment mark of the other wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass.

[0009] A third invention is a wafer bonding method for bonding two wafers at different distances from a single imaging unit using the imaging unit, A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; The light from the imaging unit is directed to an alignment mark on one of the wafers located at a short distance from the imaging unit. The aforementioned Capture images without passing them through glass, With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a distance from the imaging unit is captured by illuminating the light of the imaging unit through the glass; Only one of the two wafers is moved so that the alignment marks overlap each other, and the wafers are bonded together.

[0010] A fourth invention is a wafer bonding method for bonding two wafers at different distances from a single imaging unit using the imaging unit, A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; The light from the imaging unit is directed to an alignment mark on one of the wafers located at a distance from the imaging unit. The aforementioned Shooting through glass, With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass; Only one of the two wafers is moved so that the alignment marks overlap each other, and the wafers are bonded together.

[0011] A fifth invention is a wafer alignment method for adjusting alignment during bonding of a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; Changing the focal length of the imaging unit relative to the wafer The aforementioneda first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using a focus changing unit; and a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one of the wafers are fixed.

[0012] A sixth aspect of the present invention is a wafer alignment method for adjusting alignment during bonding of a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; Changing the focal length of the imaging unit relative to the wafer The aforementioned a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via a focus changing unit; and a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer that is located relatively close to the imaging unit with the imaging unit without using the focus changing unit, while the positions of the imaging unit and the one of the wafers are fixed.

[0013] A seventh invention is a wafer bonding method for bonding a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; Changing the focal length of the imaging unit relative to the wafer The aforementioned a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using a focus changing unit; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed; and a bonding step of bonding the first wafer and the second wafer that have undergone the alignment adjustment.

[0014] An eighth invention is a wafer bonding method for bonding a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; Changing the focal length of the imaging unit relative to the wafer The aforementioned a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via a focus changing unit; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using the focus changing unit, while the positions of the imaging unit and the one wafer are fixed; and a bonding step of bonding the first wafer and the second wafer that have undergone the alignment adjustment.

[0015] A ninth aspect of the present invention is a wafer alignment device that adjusts alignment during bonding of a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and Changing the focal length of the imaging unit relative to the wafer The aforementionedadjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using a focus changing unit; With the positions of the imaging unit and one of the wafers fixed, the other of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, is imaged by the imaging unit via the focus changing unit, thereby adjusting alignment.

[0016] A tenth aspect of the present invention is a wafer alignment device that adjusts alignment during bonding of a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and Changing the focal length of the imaging unit relative to the wafer The aforementioned adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via a focus changing unit; With the positions of the imaging unit and one of the wafers fixed, alignment is adjusted by imaging the other of the first and second wafers, which is located relatively close to the imaging unit, with the imaging unit without using the focus changing unit.

[0017] An eleventh invention is a wafer bonding apparatus for bonding a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and Changing the focal length of the imaging unit relative to the wafer The aforementioned adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using a focus changing unit; adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed; the first holding unit and the second holding unit are brought close to each other, and the first wafer and the second wafer that have undergone the alignment adjustment are bonded together; Wafer bonding equipment.

[0018] A twelfth invention is a wafer bonding apparatus for bonding a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and Changing the focal length of the imaging unit relative to the wafer The aforementioned adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via a focus changing unit; With the positions of the imaging unit and the one of the wafers fixed, alignment is adjusted by imaging the other of the first wafer and the second wafer, which is located at a relatively short distance to the imaging unit, with the imaging unit without using the focus changing unit; The first holding part and the second holding part are brought close to each other, and the first wafer and the second wafer that have undergone the alignment adjustment are bonded together. [Effects of the Invention]

[0019] According to the present invention, the alignment accuracy can be improved by accurately recognizing the wafer with the imaging unit, and the wafer bonding accuracy can also be improved. [Brief explanation of the drawings]

[0020] [Figure 1] 10 is a diagram showing a state in which the lower stage of the bonding apparatus of the present invention is retracted from the position facing the upper stage and is relatively displaced. FIG. [Figure 2] FIG. 10 is a view showing a state in which the lower stage of the bonding apparatus of the present invention is positioned opposite the upper stage. [Figure 3] 10 is a diagram showing a mounting portion formed on the upper stage of the bonding apparatus of the present invention for accommodating a focus changing portion. FIG. [Figure 4] 1 is a diagram showing the positional relationship between an imaging unit of a bonding apparatus of the present invention, a first wafer positioned above, and a second wafer positioned below. [Figure 5] 10 is a diagram showing a change in the distance to the focal point when a focus changing unit is interposed between the imaging unit of the bonding apparatus of the present invention and the first wafer positioned above. FIG. [Figure 6] 10 is a plan view showing an example of a focus changing unit holder that holds a plurality of focus changing units having different plate thicknesses. FIG. [Figure 7] FIG. 10 is a conceptual diagram in which the imaging unit of the bonding apparatus of the present invention focuses on the first wafer located above without using a focus changing unit. [Figure 8] FIG. 10 is a conceptual diagram in which the imaging unit of the bonding apparatus of the present invention focuses on a second wafer located below via a focus changing unit. [Figure 9] 3 is a flowchart showing a wafer alignment adjustment process and a wafer bonding process according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] A wafer alignment method, a wafer bonding method, a wafer alignment apparatus, and a wafer bonding apparatus according to one embodiment of the present invention will be described.

[0022] The wafer bonding method of the present invention is an invention that utilizes the wafer alignment method of the present invention. Also, the wafer bonding apparatus of the present invention is an invention that utilizes the wafer alignment apparatus of the present invention.

[0023] In this specification, the term "wafer" refers to a semiconductor wafer (silicon wafer) or other material used in the manufacture of semiconductors. A semiconductor substrate is referred to as a wafer. Wafers are generally thin, disk-shaped plates made by slicing single-crystal pillars of silicon (Si) or gallium arsenide (GaAs), and are an essential material for the manufacture of semiconductors. Their surfaces are mirror-finished to remove minute irregularities and particles before use.

[0024] [Wafer alignment and bonding equipment] First, a wafer alignment device and a wafer bonding device will be described. A wafer alignment device is the same as a wafer bonding device, but is a device that extracts a wafer alignment adjustment function from a wafer bonding device. A wafer bonding device is the same as a wafer alignment device, but is a device that includes a wafer bonding function for bonding wafers together in addition to the wafer alignment adjustment function. In the following explanation, it will be described as a wafer bonding device.

[0025] 1, 2, 3, 7, and 8, a wafer bonding apparatus 10 includes a housing 12, a first holder 14 that holds a first wafer W1, a second holder 16 that holds a second wafer W2, a single imaging unit 18 that images the first wafer W1 and the second wafer W2, and a focus changing unit 20 that adjusts the focal length of the imaging unit 18 with respect to each of the wafers W1 and W2. The wafer bonding apparatus 10 is also called a wafer alignment apparatus 11.

[0026] The first holding unit 14 is attached to the housing 12. The first holding unit 14 is fixed so as not to move in the vertical direction (also called the height direction, defined as the Z direction). The first holding unit 14 is also fixed so as not to move in the horizontal direction (defined as the X direction and Y direction). The first holding unit 14 is attached to a first shaft (not shown). The first shaft is attached to the housing 12 so as to be rotatable around the axis. Therefore, the first holding unit 14 is configured to be rotatable around the axis of the first shaft (in the Θ direction) together with the rotation of the first shaft. Note that the first holding unit 14 may be fixed and not rotate around the axis of the first shaft (in the Θ direction). The first holding unit 14 may also be referred to as a first stage.

[0027] The first holding portion 14 is located, for example, on the upper side in the vertical direction.

[0028] The principle by which the first holder 14 holds the first wafer W1 is the same as the principle by which a substrate is attracted to a substrate in a conventional bonding apparatus.

[0029] Specifically, the first holding unit 14 includes, for example, an electrostatic chuck, a heating unit, a cooling unit (all not shown), etc. The electrostatic chuck has an internal electrode and a dielectric, and attracts the first wafer W1 using electrostatic force generated by applying a voltage to the internal electrode.

[0030] The heating unit is a heater such as a ceramic heater, and is built into the electrostatic chuck. The heating unit heats the electrostatic chuck, thereby heating the first wafer W1 held on the electrostatic chuck.

[0031] The cooling unit is an existing unit, and after the first wafer W1 and the second wafer W2 are bonded together, cools the laminated wafer produced by bonding the first wafer W1 and the second wafer W2 together.

[0032] The second holding unit 16 is placed on the housing 12 so as to be movable in the vertical direction (also called the height direction, defined as the Z direction) and the horizontal direction (defined as the X direction and Y direction). For example, rails may be arranged on the housing 12, and the second holding unit 16 may slide on the rails to move in the horizontal direction. The second holding unit 16 does not rotate around the second axis (theta direction). The second holding unit 16 may be supported by a second axis (not shown) and attached so as to be rotatable around the second axis. The second holding unit 16 may also be referred to as a second stage.

[0033] The second holding portion 16 is located, for example, on the lower side in the vertical direction.

[0034] The principle of holding the second wafer W2 by the second holder 16 is the same as the principle of suction of a substrate in a conventional bonding apparatus.

[0035] Specifically, the second holding unit 16 includes, for example, an electrostatic chuck, a heating unit, a cooling unit (all not shown), etc. The electrostatic chuck has an internal electrode and a dielectric, and attracts the second wafer W2 by using electrostatic force generated by applying a voltage to the internal electrode.

[0036] The heating unit is a heater such as a ceramic heater, and is built into the electrostatic chuck. The heating unit heats the electrostatic chuck, thereby heating the second wafer W2 held on the electrostatic chuck.

[0037] The cooling unit is an existing unit, and after the first wafer W1 and the second wafer W2 are bonded together, cools the laminated wafer produced by bonding the first wafer W1 and the second wafer W2 together.

[0038] The imaging unit 18 captures images of the alignment marks of the first wafer W1 and the second wafer W2. The imaging results are stored in a memory unit of the imaging unit 18 as image data of the first wafer W1 and the second wafer W2. The imaging unit 18 is attached to the first holding unit 14. This fixes the position of the imaging unit 18 relative to the first holding unit 14. When the first holding unit 14 moves in the vertical direction, the imaging unit 18 moves in the vertical direction together with the first holding unit 14.

[0039] The imaging unit 18 is preferably, for example, an optical camera. In particular, an infrared camera (IR camera) is used as the imaging unit 18. The focal depth of the imaging unit 18 is, for example, ±1.25 μm. The imaging unit 18 may also be configured to incorporate a control unit that can perform alignment processing or bonding processing based on imaging data, etc. The imaging unit 18 may also be configured to transmit imaging data to an external control system, so that the external control system can perform wafer alignment processing or bonding processing.

[0040] The imaging unit 18 includes a light source (not shown) that emits, for example, infrared light. The light source is turned on at least during alignment of the first wafer W1, enabling imaging. In this way, the imaging unit 18 is capable of coaxial illumination.

[0041] The light source may be a conventionally known infrared LED element or halogen lamp. The light source may emit light with a wavelength of, for example, 1000 to 1200 nanometers (nm). The light source used may be one that can emit light with a wavelength that can pass through a substrate such as a semiconductor wafer including a silicon wafer.

[0042] The focus changing unit 20 is attached to the first holding unit 14. More specifically, a mounting portion 26 is formed in the first holding unit 14 so as to have a recessed shape. The focus changing unit 20 is attached to the mounting portion 26. The focus changing unit 20 is also positioned so as to be located on the optical axis L of the light irradiated from the imaging unit 18. As a result, the light irradiated from the imaging unit 18 enters the focus changing unit 20, passes through the inside of the focus changing unit 20, and irradiates the second wafer W2.

[0043] The imaging unit 18 and the focus changing unit 20 may be attached to the second holding unit 16 instead of the first holding unit 14.

[0044] The focus change unit 20 changes the focal length of the light from the imaging unit 18 to the wafers W1 and W2. The focus change unit 20 is made of, for example, glass. Quartz glass is particularly preferable as glass. The focus change unit 20 has the function of changing the focal length of the light depending on the refractive index (material) of the light and the plate thickness. Furthermore, since the focal length of the light varies depending on the refractive index (material) of the light and the plate thickness, by preparing multiple focus change units 20 with different refractive indices (materials) or plate thicknesses, the focal length of the light from the imaging unit 18 to the wafers W1 and W2 can be changed to multiple distances, and the optimal focal length can be selected to improve imaging accuracy.

[0045] Regarding the refractive index of light, light has the property of refracting when passing through different media. When light passes through air and then enters, for example, glass, the speed of light slows down inside the glass because the refractive index of the glass is higher than that of air. Therefore, even if the physical distance is the same, the optical distance (the path the light travels) when light passes through glass tends to become shorter. In other words, the theoretical focal length becomes shorter.

[0046] The focal length of the imaging unit 18 relative to the wafers W1 and W2 varies depending on the thickness of the focus changing unit 20. For example, when glass is used, the optical focal position becomes closer to the imaging unit 18. In detail, if the thickness of the glass is t and the refractive index of the glass is n, the amount of change in the focal position (amount of shortening of the optical path) Δ is calculated as follows: Δ=t(1-1 / n). For example, if the refractive index of glass is 1.5 and the thickness of the glass is 1 mm, Δ=1mm×(1-1 / 1.5)=0.33mm. This causes the focal position to move by 0.33 mm. In this way, the thicker the glass plate, the greater the distance the focal position must move.

[0047] For the above reasons, when light passes through glass, a phenomenon occurs in which the so-called travel distance changes depending on the refractive index of the light and the thickness of the glass. Therefore, when imaging a wafer by passing light from the imaging unit 18 through glass, by varying the thickness of the glass depending on the distance from the imaging unit 18 to the wafer, it is possible to focus the imaging unit 18 on the wafer while keeping the position of the imaging unit 18 fixed. As a result, it is possible to avoid positional shifts and focus shifts of the imaging unit 18, improving the accuracy of imaging the wafer.

[0048] Here, as shown in Figures 4, 5, and 7, when the imaging unit 18 images the first wafer W1, which is located relatively closer than the second wafer W2, the light from the imaging unit 18 is irradiated onto the first wafer W1 without passing through the focus changing unit 20.

[0049] On the other hand, as shown in Figures 4, 5, and 8, when the imaging unit 18 images a second wafer W2 that is located at a relatively farther distance than the first wafer W1, the light from the imaging unit 18 passes through the focus changing unit 20 and irradiates the second wafer W2.

[0050] For this reason, it is preferable to have a focus change unit moving mechanism (not shown) for moving the focus change unit 20 so that when the imaging unit 18 images the first wafer W1, the focus change unit 20 is retracted from the optical axis L of the light emitted from the imaging unit 18, and when the imaging unit 18 images the second wafer W2, the focus change unit 20 is positioned on the optical axis L of the light emitted from the imaging unit 18.

[0051] Alternatively, the imaging unit 18 may be provided with multiple light sources and multiple camera lenses, and the focus changing unit 20 may be arranged not on the optical axis L of the light emitted from one light source but on the optical axis L of the light emitted from the other light source. In this configuration, the light emitted from one light source irradiates the first wafer W1 without passing through the focus changing unit, and the light emitted from the other light source passes through the focus changing unit and irradiates the second wafer W2. This eliminates the need for a focus changing unit movement mechanism.

[0052] As shown in FIG. 6, for example, a focus change unit holder 24 may be provided in which a plurality of focus change units 20, each differing in at least one of the refractive index (material) or thickness, are arranged in a planar direction. The focus change unit holder 24 is preferably detachably attached to a mounting portion 26 formed on the first holding unit 14. The focus change unit holder 24 may be configured to be rotatable around a central axis. Depending on the material or surface condition of the wafer to be imaged, the focus change unit holder 24 rotates around the central axis to select an optimal focus change unit 20. The rotation of the focus change unit holder 24 around the central axis may be performed manually by an operator or may be automatically controlled using a rotation control mechanism (not shown).

[0053] Here, for example, five pieces of glass (e.g., quartz glass) 22 of different thicknesses are arranged in the focus changing unit holder 24. For example, pieces of glass 22 with thicknesses of 3.0 mm, 1.0 mm, 0.3 mm, 0.1 mm, and 0.05 mm are arranged. Also, the portion with a thickness of 0.0 mm means that no glass is arranged and is hollow. In this way, by rotating the focus changing unit holder 24 around the central axis of the focus changing unit holder 24, each piece of glass 22 (e.g., quartz glass) with thicknesses of 3.0 mm, 1.0 mm, 0.3 mm, 0.1 mm, and 0.05 mm can be positioned on the optical axis L of the imaging unit 18, and the glass 22 (e.g., quartz glass) can be retracted from the optical axis L of the imaging unit 18.

[0054] The material (component, composition) of the glass 22 is not limited to quartz. The refractive index of light can be changed by changing the material (component, composition) of the glass 22, so for example, glass 22 of different materials but the same thickness may be arranged side by side. Also, glass 22 of different materials (component, composition) and thicknesses may be arranged side by side.

[0055] In a configuration in which a glass 22 (e.g., quartz glass) with a thickness of 3.0 mm is arranged on the optical axis L of the imaging unit 18, the focal length increases by approximately 1000 μm. Furthermore, in a configuration in which a glass 22 (e.g., quartz glass) with a thickness of 1.0 mm is arranged on the optical axis L of the imaging unit 18, the focal length increases by approximately 300 μm. Furthermore, in a configuration in which a glass 22 (e.g., quartz glass) with a thickness of 0.1 mm is arranged on the optical axis L of the imaging unit 18, the focal length increases by approximately 30 μm. Furthermore, in a configuration in which a glass 22 (e.g., quartz glass) with a thickness of 0.05 mm is arranged on the optical axis L of the imaging unit 18, the focal length increases by approximately 15 μm.

[0056] The thickness of the glass 22 (for example, quartz glass) is preferably in the range of 0.02 mm or more and 1.0 mm or less, but is not limited to these ranges.

[0057] When imaging the first wafer W1, which is 12.5 mm away from the camera lens of the imaging unit 18, glass 22 (e.g., quartz glass) (focus changing unit) is not placed on the optical axis L of the imaging unit 18, and the light from the imaging unit 18 is irradiated onto the first wafer W1 without passing through the glass 22, and the alignment mark on side A is imaged (recognized). This allows alignment adjustment of the first wafer W1 to be performed (first alignment step S100 in FIG. 9).

[0058] Next, a piece of glass 22 (e.g., quartz glass) with a thickness of 1.0 mm is placed on the optical axis L of the imaging unit 18. This extends the focal length of the imaging unit 18 relative to the wafer by approximately 300 μm. If there is a positional deviation D (see FIGS. 4 and 5) in which the second wafer W2 is located on the side away from the imaging unit 18 by approximately 300 μm compared to the first wafer W1, placing the piece of glass 22 (e.g., quartz glass) with a thickness of 1.0 mm on the optical axis L of the imaging unit 18 will cancel out the extension of the focal length and the positional deviation D (see FIGS. 4 and 5), and the camera lens will be in focus. In other words, the value of the positional deviation D (see FIGS. 4 and 5) of the second wafer W2 relative to the first wafer W1 and the value of the optical path shortening are offset (cancelled out), and with the positions (particularly the vertical positions) of the imaging unit 18 and the first wafer W1 fixed, the light from the imaging unit 18 passes through the glass 22 and is irradiated onto the second wafer W2, thereby capturing (recognizing) the alignment mark on side B. In this way, alignment adjustment of the second wafer W2 is performed (second alignment step S200 in FIG. 9).

[0059] This adjustment method can be used to adjust the focal position of the imaging unit 18 relative to the second wafer W2, for example, by using glass 22 (e.g., quartz glass) with a thickness in the range of 0.02 mm or more and 1.0 mm or less. By selecting the thickness of the glass 22 according to the positional deviation D (see FIGS. 4 and 5) between surface A on the first wafer W1 and surface B on the second wafer W2, it is possible to focus on both surface A on the first wafer W1 and surface B on the second wafer W2 using a single imaging unit 18 and a single camera lens.

[0060] Once the alignment adjustment of the first wafer W1 and the second wafer W2 is completed, the first holder 14 and the second holder 16 are brought relatively close to each other, and the first wafer W1 and the second wafer W2 are bonded together (wafer bonding step S300 in FIG. 9). At this time, one of the holders (e.g., the first holder 14) of the first holder 14 or the second holder 16 is fixed in the horizontal and vertical directions, and only the other holder (e.g., the second holder 16) is moved in the horizontal and vertical directions, thereby fixing one of the two wafers, W1, and moving only the other wafer, W2, to bond the wafers W1 and W2 together. This can improve the positional accuracy during bonding.

[0061] As a result, alignment adjustment of the first wafer W1 and the second wafer W2 is completed with the position of the imaging unit 18 fixed, eliminating positional misalignment and vibration and improving alignment accuracy compared to a method of adjusting wafer alignment by moving the position of the imaging unit 18. As a result, by bonding wafers with high alignment accuracy, relative misalignment between the wafers is eliminated and wafer bonding accuracy is also improved.

[0062] In particular, by simply inserting the focus changing unit 20, two focal lengths can be achieved using only a single imaging unit 18 and one camera lens, which contributes to making the joining device 10 smaller and less expensive.

[0063] Next, the wafer alignment adjustment process and wafer bonding process using the wafer bonding apparatus 10 (alignment apparatus 11) will be described.

[0064] As shown in FIG. 9, the wafer alignment adjustment process and bonding process mainly includes a first alignment step S100, a second alignment step S200, and a wafer bonding step S300.

[0065] The following description will be given on the assumption that the first wafer W1 is held by the first holder 14 and the second wafer W2 is held by the second holder 16.

[0066] In the first alignment step S100, as shown in FIGS. 4, 5, and 7, the light source of the imaging unit 18 is turned on, and light (e.g., infrared light) is emitted from the imaging unit 18 toward the first wafer W1, which is located relatively closer than the second wafer W2, to capture an image of the alignment mark on the first wafer W1. At this time, the light emitted from the imaging unit 18 is irradiated onto the first wafer W1 without passing through the glass 22 (e.g., quartz glass) of the focus changing unit 20. The positions of the imaging unit 18 and the first wafer W1 are fixed by the first holding unit 14, so imaging accuracy is high. After the imaging unit 18 captures an image of the alignment mark on the first wafer W1, the imaging unit 18 stores the image data of the alignment mark.

[0067] In the second alignment step S200, as shown in FIGS. 4, 5, and 8, while the positions of the imaging unit 18 and the first wafer W1 are fixed, the light source of the imaging unit 18 is turned on, and light (e.g., infrared light) is emitted from the imaging unit 18 toward the second wafer W2, which is located at a relatively longer distance than the first wafer W1, to capture an image of the alignment mark on the second wafer W2. At this time, glass 22 (e.g., quartz glass) serving as the focus changing unit 20 is positioned on the optical axis L of the light emitted from the imaging unit 18. Therefore, the light emitted from the imaging unit 18 passes through the glass 22 (e.g., quartz glass) serving as the focus changing unit 20 and is irradiated onto the second wafer W2. Since the positions of the imaging unit 18 and the second wafer W2 are fixed by the second holder 16, high imaging accuracy is achieved. After the imaging unit 18 captures the image of the alignment mark on the second wafer W2, the imaging unit 18 stores the image data of the alignment mark.

[0068] The focal length of the light emitted from the imaging unit 18 increases by approximately 30% of the thickness of the glass (e.g., quartz glass) 22. For example, if glass 22 (e.g., quartz glass) with a thickness of 0.1 mm is used, the focal length of the light increases by approximately 30 μm.

[0069] Here, while the imaging unit 18 is reading the alignment marks of the second wafer W2, the second holding unit 16 is moved horizontally and in the Θ direction to overlap the alignment marks of the second wafer W2 with the alignment marks of the first wafer W1.

[0070] In the wafer bonding step S300, once the alignment marks of the first wafer W1 and the second wafer W2 are aligned, the second holder 16 moves vertically (heightwise) to approach the first holder 14, and the first wafer W1 and the second wafer W2 are bonded together. At this time, the first holder 14 and the first wafer W1 are fixed vertically, and only the second holder 16 and the second wafer W2 are moved horizontally and vertically to bond the first wafer W1 and the second wafer W2. This allows for increased positional accuracy during bonding.

[0071] In the first alignment step S100, the alignment adjustment is first performed on the first wafer W1, which is located at a relatively closer distance from the imaging unit 18 than the second wafer W2, but this is not limiting. For example, the alignment adjustment may be first performed on the second wafer W2, which is located at a relatively farther distance from the imaging unit 18 than the first wafer W1.

[0072] Specifically, the light source of the imaging unit 18 is turned on, and light (e.g., infrared light) is emitted from the imaging unit 18 toward the second wafer W2, which is located at a relatively longer distance than the first wafer W1, to capture an image of the alignment marks on the second wafer W2. At this time, glass 22 (e.g., quartz glass) which is the focus changing unit 20 is placed on the optical axis L of the light emitted from the imaging unit 18. Therefore, the light emitted from the imaging unit 18 passes through the glass 22 (e.g., quartz glass) which is the focus changing unit 20 and is irradiated onto the second wafer W2. After the imaging unit 18 captures the image of the alignment marks on the second wafer W2, the imaging unit 18 stores the image data of the alignment marks.

[0073] Thereafter, in a second alignment step S200, alignment is performed on the first wafer W1, which is located relatively closer to the imaging unit 18 than the second wafer W2. The light source of the imaging unit 18 is turned on, and light (e.g., infrared light) is emitted from the imaging unit 18 toward the first wafer W1, which is located closer than the second wafer W2, to capture an image of the alignment mark on the first wafer W2. At this time, the glass 22 (e.g., quartz glass) that is the focus changing unit 20 is retracted from the optical axis L of the imaging unit 18, and the light emitted from the imaging unit 18 is irradiated onto the first wafer W1 without passing through the glass 22. After the imaging unit 18 captures the image of the alignment mark on the first wafer W1, the imaging unit 18 stores the image data of the alignment mark.

[0074] Here, while the alignment marks of the first wafer W1 are read by the imaging unit 18, the second holder 16 is moved appropriately in the horizontal direction and the Θ direction to align the alignment marks of the first wafer W1 with the alignment marks of the second wafer W2. Then, the wafer bonding step S300 is executed, and the first wafer W1 and the second wafer W2 are bonded together.

[0075] As described above, according to this embodiment, after imaging the alignment marks of one wafer, the alignment marks of the other wafer are imaged while the positions of the imaging unit 18 and one wafer are fixed. This improves wafer alignment accuracy. In contrast, in the prior art, the imaging unit is moved vertically, resulting in two errors: the driving accuracy of the imaging unit and the positional accuracy of one wafer, which reduces alignment accuracy. Therefore, in this embodiment, the focal length of the imaging unit 18 can be freely adjusted by adjusting the glass material (refractive index of light) and the glass thickness, so the position of the imaging unit 18 can be fixed without needing to be moved. As a result, the alignment accuracy of the wafers W1 and W2 is improved, and ultimately the bonding accuracy of the wafers W1 and W2 is improved.

[0076] It should be noted that the present embodiment and examples illustrate one aspect of the present invention, and the present invention is not limited thereto. Differences in the degree of design changes from the present embodiment and examples are naturally included within the scope of the technical idea of ​​the present invention. [Explanation of symbols]

[0077] 10 Bonding equipment 11 Alignment device 12. Case 14 First holding unit (upper stage) 16 Second holding part (lower stage) 18 Imaging unit 20 Focus change section 22 Glass (quartz glass) 24 Focus change unit holder 26 Mounting part D. Misalignment between the first wafer and the second wafer L optical axis W1 First wafer (upper wafer) W2 Second wafer (lower wafer)

Claims

1. A wafer alignment method for adjusting alignment during bonding of two wafers at different distances from a single imaging unit, using the single imaging unit, comprising: A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; An image of an alignment mark of one wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass; With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a distance from the imaging unit is captured by illuminating light from the imaging unit through the glass. A method for aligning a wafer.

2. A wafer alignment method for adjusting alignment during bonding of two wafers at different distances from a single imaging unit, using the single imaging unit, comprising: A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; an image of an alignment mark of one wafer located at a distance from the imaging unit is captured by illuminating the light from the imaging unit through the glass; With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass. A method for aligning a wafer.

3. When the light from the imaging unit is passed through the glass to image the wafer, the thickness of the glass is varied depending on the distance from the imaging unit to the wafer.

3. The wafer alignment method according to claim 1 or 2.

4. A wafer bonding method for bonding two wafers at different distances from a single imaging unit using the imaging unit, A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; An image of an alignment mark of one wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass; With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a distance from the imaging unit is captured by illuminating the light of the imaging unit through the glass; moving only one of the two wafers so that the alignment marks overlap each other, and bonding the wafers together; Wafer bonding method.

5. A wafer bonding method for bonding two wafers at different distances from a single imaging unit using the imaging unit, A recessed mounting portion is formed in the holding portion on which the wafer is held, and glass is attached to the mounting portion; an image of an alignment mark of one wafer located at a distance from the imaging unit is captured by illuminating the light from the imaging unit through the glass; With the positions of the imaging unit and the one wafer fixed, an image of an alignment mark of the other wafer located at a short distance from the imaging unit is captured without light from the imaging unit passing through the glass; moving only one of the two wafers so that the alignment marks overlap each other, and bonding the wafers together; Wafer bonding method.

6. When the light from the imaging unit is passed through the glass to image the wafer, the thickness of the glass is varied depending on the distance from the imaging unit to the wafer.

6. The wafer bonding method according to claim 4 or 5.

7. A wafer alignment method for adjusting alignment during bonding of a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit, without using the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed, A method for aligning a wafer.

8. A wafer alignment method for adjusting alignment during bonding of a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively short distance to the imaging unit, with the imaging unit without using the focus changing unit, while the positions of the imaging unit and the one wafer are fixed, A method for aligning a wafer.

9. In the first alignment step or the second alignment step, glass is used as the focus changing unit.

9. The wafer alignment method according to claim 7 or 8.

10. The focal length of the imaging unit with respect to the wafer is adjusted by the optical refractive index or plate thickness of the glass. The wafer alignment method according to claim 9.

11. Quartz glass is used as the glass. The wafer alignment method according to claim 10.

12. A wafer bonding method for bonding a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit, without using the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed; a bonding step of bonding the first wafer and the second wafer that have undergone the alignment adjustment, Wafer alignment bonding method.

13. A wafer bonding method for bonding a first wafer and a second wafer using a single imaging unit, comprising: a recessed mounting portion is formed in the holding portion on which the wafer is held, and a focus changing portion is attached to the mounting portion; a first alignment step of adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; a second alignment step of adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit without using the focus changing unit, while the positions of the imaging unit and the one wafer are fixed; a bonding step of bonding the first wafer and the second wafer that have undergone the alignment adjustment, Wafer alignment bonding method.

14. In the first alignment step or the second alignment step, glass is used as the focus changing unit. The wafer bonding method according to claim 12 or 13.

15. The focal length of the imaging unit with respect to the wafer is adjusted by the optical refractive index or plate thickness of the glass. The wafer bonding method according to claim 14.

16. Quartz glass is used as the glass. The wafer bonding method according to claim 15.

17. A wafer alignment device that adjusts alignment when bonding a first wafer and a second wafer, a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit, without using the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; and adjusting alignment by imaging the other wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed. Wafer alignment equipment.

18. A wafer alignment device that adjusts alignment when bonding a first wafer and a second wafer, a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; and adjusting alignment by imaging the other wafer, which is located relatively close to the imaging unit, of the first wafer and the second wafer without using the focus changing unit, with the imaging unit while the positions of the imaging unit and the one wafer are fixed. Wafer alignment equipment.

19. The focus-changing portion is glass.

19. The wafer alignment apparatus according to claim 17 or 18.

20. adjusting the focal length of the imaging unit with respect to the wafer by adjusting the optical refractive index and thickness of the glass; 20. The wafer alignment apparatus according to claim 19.

21. a glass holder provided with a plurality of glasses each having a different refractive index or / and a different plate thickness; 21. The wafer alignment apparatus according to claim 20.

22. The imaging unit is attached to either the first holding unit or the second holding unit.

19. The wafer alignment apparatus according to claim 17 or 18.

23. the focus changing unit is the first holding unit or the second holding unit, and is attached on an optical axis of the imaging unit through which light of the imaging unit passes; 23. The wafer alignment apparatus according to claim 22.

24. The glass is quartz glass.

20. The wafer alignment apparatus according to claim 19.

25. A wafer bonding apparatus for bonding a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and adjusting alignment by imaging one of the first wafer and the second wafer, which is located relatively close to the imaging unit, with the imaging unit, without using the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; adjusting alignment by imaging the other wafer of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit while the positions of the imaging unit and the one wafer are fixed; the first holding unit and the second holding unit are brought close to each other, and the first wafer and the second wafer that have undergone the alignment adjustment are bonded together. Wafer bonding equipment.

26. A wafer bonding apparatus for bonding a first wafer and a second wafer, comprising: a first holding part that holds the first wafer; a second holding part that holds the second wafer; a single imaging unit that images the first wafer and the second wafer; a focus changing unit attached to a recessed attachment portion formed in the first holding portion or the second holding portion; and adjusting alignment by imaging one of the first wafer and the second wafer, which is located at a relatively long distance from the imaging unit, with the imaging unit via the focus changing unit that changes the focal length of the imaging unit with respect to the wafer; With the positions of the imaging unit and the one of the wafers fixed, alignment is adjusted by imaging the other of the first wafer and the second wafer, which is located at a relatively short distance to the imaging unit, with the imaging unit without using the focus changing unit; the first holding unit and the second holding unit are brought close to each other, and the first wafer and the second wafer that have undergone the alignment adjustment are bonded together. Wafer bonding equipment.

27. The focus-changing portion is glass.

27. The wafer bonding apparatus according to claim 25 or 26.

28. adjusting the focal length of the imaging unit with respect to the wafer by adjusting the optical refractive index and thickness of the glass; 28. The wafer bonding apparatus according to claim 27.

29. a glass holder provided with a plurality of glasses each having a different refractive index or / and a different plate thickness; The wafer bonding apparatus according to claim 28.

30. The imaging unit is attached to either the first holding unit or the second holding unit.

27. The wafer bonding apparatus according to claim 25 or 26.

31. the focus changing unit is the first holding unit or the second holding unit, and is attached on an optical axis of the imaging unit through which light of the imaging unit passes; The wafer bonding apparatus according to claim 30.

32. The glass is quartz glass.

28. The wafer bonding apparatus according to claim 27.

Images