Bonding strength evaluation method, bonding strength evaluation device, and method for driving bonding strength evaluation device

Abstract

The embodiment of the invention provides a bonding strength evaluation method, a bonding strength evaluation device and a driving method thereof. The bonding strength evaluation method may include: preparing a bonded wafer; separating the bonded wafers by applying a force to one surface of the bonded wafers in a direction perpendicular to the one surface of the bonded wafers; measuring at least one of a force applied to one surface of the bonded wafers, a time when the force is applied, a separation distance between the bonded wafers, and a length of a region where the bonded wafers are separated; and determining a bonding strength based on at least one of the force, a time during which the force is applied, a separation distance between the bonded wafers, and a length of a region in which the bonded wafers are separated.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Application No. 10-2024-0102604, filed on August 1, 2024, and Korean Application No. 10-2024-0193598, filed on December 23, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of this disclosure relate to a method for evaluating joint strength, a device for evaluating joint strength, and a driving method thereof. Background Technology

[0004] As semiconductor devices become more highly integrated, wafer bonding processes are being introduced. However, if the bonding strength at the bonding interface of the bonded wafers (i.e., wafer bond strength) is insufficient, defects may occur in the bonded wafers during various processes performed after the wafer bonding process. Since defects in the bonded wafers reduce manufacturing yield, it is necessary to measure and manage wafer bond strength.

[0005] There are several known methods for measuring wafer bonding strength. Among them, the Masszara test or the double cantilever beam (DCB) test is widely used. The Masszara test measures the length of the crack that occurs when the bonded wafers are separated by a blade and thus determines the bonding strength. The DCB test measures the bonding strength based on the separation distance of the bonding interface when forces are repeatedly applied to and removed from the bonded wafers.

[0006] However, because the measurement is performed at some point during the propagation of the stripper wave after the edges of the bonded wafers have been separated, the Maszara test suffers from reduced accuracy and precision due to many factors that affect the strength of the wafer bond. The DCB test also suffers from reduced accuracy due to stress-induced erosion and other effects when stress is repeatedly applied to the wafer. Summary of the Invention

[0007] The embodiments of this disclosure provide a method for evaluating joint strength, a device for evaluating joint strength, and a driving method thereof, which can improve the accuracy of joint strength evaluation.

[0008] Embodiments of this disclosure may provide a method for evaluating bonding strength, the method comprising: preparing bonded wafers; separating the bonded wafers by applying a force to one surface of the bonded wafers in a direction perpendicular to one surface of the bonded wafers; measuring at least one of the force applied to one surface of the bonded wafers, the time during which the force is applied, the separation distance between the bonded wafers, and the length of the separated region of the bonded wafers; and determining the bonding strength based on at least one of the force, the time during which the force is applied, the separation distance between the bonded wafers, and the length of the separated region of the bonded wafers.

[0009] Embodiments of this disclosure may provide a bonding strength evaluation apparatus, comprising: a wafer holder configured to hold bonded wafers; and a determination module configured to determine the bonding strength of the bonded wafers. The determination module includes: a driver configured to separate the bonded wafers by applying a force to the bonded wafers in a direction perpendicular to one surface of the bonded wafers; and a sensor configured to measure at least one of the force applied to one surface of the bonded wafers, the time during which the force is applied, a separation distance between the bonded wafers, and the length of the separated region of the bonded wafers.

[0010] Embodiments of this disclosure may provide a driving method for a bonding strength evaluation apparatus, the driving method comprising: securing bonded wafers to a wafer holder; and separating the bonded wafers by applying a force to one wafer in a direction perpendicular to a surface of one of the bonded wafers, while measuring at least one of the force applied to one wafer, the time during which the force is applied, the separation distance between the bonded wafers, and the length of the region where the bonded wafers are separated.

[0011] According to embodiments of this disclosure, the accuracy of the bonding strength assessment method can be improved. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating a method for evaluating bonding strength according to an embodiment of the present disclosure; Figure 2 This demonstrates the implementation. Figure 1 A view of the separation operation; Figure 3 It is shown Figure 1 A view of the separation operation; Figure 4 This is a view illustrating a bonding strength evaluation apparatus according to an embodiment of the present disclosure; Figures 5 to 8 This is a view illustrating a driving method of a bonding strength evaluation apparatus according to an embodiment of the present disclosure; and Figure 9 This is a view showing data measured during driving of a joint strength evaluation apparatus according to an embodiment of the present disclosure. Detailed Implementation

[0013] In the following, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. When assigning reference numerals to components in each figure, the same reference numerals may be assigned to the same components, even if these same components are shown in different figures. Details of known techniques or functions may be skipped when the subject matter of the disclosure is determined to be unclear. As used herein, when a component “comprises”, “has”, or “is composed of” another component, that component may include other components, unless the term “only” is used in conjunction with “comprises other components, has other components, or is composed of other components.” As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” are intended to also include the plural forms.

[0014] Reference numerals such as "first", "second", "A", "B", "(a)" and "(b)" may be used to describe components of embodiments of this disclosure. These reference numerals are provided merely to distinguish one component from another, and the nature, order, or number of components is not limited by the reference numerals.

[0015] When describing the positional relationship between components, when two or more components are described as “connected,” “coupled,” or “linked,” these two or more components may be directly “connected,” “coupled,” or “linked,” or another component may be interposed therebetween. Here, the other component may be included in one or more of the two or more components that are “connected,” “coupled,” or “linked” to each other.

[0016] When terms such as “after,” “immediately following,” and “before” are used to describe time flow relationships related to components, operating methods, and manufacturing methods, time flow relationships may include discontinuous relationships unless the terms “immediately” or “directly” are used.

[0017] When a component is specified using a numerical value or its corresponding information (e.g., a grade), that numerical value or corresponding information can be interpreted as including tolerances due to various factors (e.g., process factors, internal or external influences, or noise).

[0018] Various embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0019] In the accompanying drawings, two directions parallel to the upper surface of the wafer are defined as the first direction FD and the second direction SD, respectively, and a direction projecting vertically from the upper surface of the wafer is defined as the third direction VD. The first direction FD and the second direction SD may be substantially perpendicular to each other. The third direction VD is a direction perpendicular to the first direction FD and the second direction SD. In the following detailed description, "vertical" or "vertical direction" will be used to have substantially the same meaning as the third direction VD. The directions indicated by arrows in the accompanying drawings and their opposite directions represent the same direction.

[0020] Figure 1 This is a flowchart illustrating a bonding strength evaluation method 100 according to an embodiment of the present disclosure. Figure 2 This demonstrates the implementation. Figure 1 The view of the separation operation. Figure 3 It is shown Figure 1 The view of the separation operation.

[0021] refer to Figure 1 The bonding strength assessment method 100 may include wafer fabrication operation 110, separation operation 120, measurement operation 130, and bonding strength determination operation 140.

[0022] In wafer fabrication operation 110, bonded wafers are fabricated. Each wafer may include a wafer body and an integrated circuit disposed on the wafer body. The wafer body may include silicon or a semiconductor such as silicon-on-insulator (SOI). The wafer body may include a group III-V semiconductor, such as a compound semiconductor such as GaAs. The wafer body may include monocrystalline silicon, polycrystalline silicon, amorphous silicon, monocrystalline silicon-germanium, polycrystalline silicon-germanium, carbon-doped silicon, or combinations thereof. In embodiments, the integrated circuit may be formed by a front-end process (FEOL) and a back-end process (BEOL).

[0023] In an embodiment, the bonded wafer may include a unit wafer and a peripheral wafer. The unit wafer has memory cells containing memory devices, and the peripheral wafer has peripheral circuitry for transmitting various signals and voltages to the memory cells to drive them. The bonded wafer may be one in which the unit wafer and the peripheral wafer are bonded using a hybrid bonding process.

[0024] In one embodiment, the bonded wafers may consist only of unit wafers. In this case, one unit wafer is bonded to another unit wafer to form the bonded wafers. A structure in which memory cells are vertically stacked can be implemented using bonded wafers.

[0025] In separation operation 120, a force may be applied to one surface of the bonded wafers to separate them. The force may be applied in a direction perpendicular to one surface of the bonded wafers. In an embodiment, the force may be tension pulling the bonded wafers apart in a direction perpendicular to one surface of the wafers.

[0026] refer to Figure 2 With the first wafer 210 of the joined wafers 210 and 220 fixed, force can be applied to only one surface of the second wafer 220 to separate the joined wafers 210 and 220 from each other.

[0027] In one embodiment, to secure the first wafer 210, a device for placing the first wafer 210 on a mounting stage and evacuating the space between the first wafer 210 and the mounting stage can be used. However, this is not a limitation, and the first wafer 210 can be secured in various ways.

[0028] In an embodiment, to apply force to the second wafer 220, a drive device can be used to provide an upward pulling force on the second wafer 220 upon contact with its upper surface. The drive device can apply force to the second wafer 220 while maintaining a space between the drive device and the second wafer 220 in a vacuum, moving in a direction perpendicular to the upper surface of the wafer, while in contact with its upper surface. However, this is not a limitation; various methods capable of applying force in a direction perpendicular to one surface of the second wafer 220 can be used.

[0029] A force can be applied from the edge of one surface of the second wafer 220 to separate the joined wafers 210 and 220.

[0030] In one embodiment, a first force F1 and a second force F2 can be applied to one surface of the second wafer 220. The first force F1 can initially act on one edge of the second wafer 220 to pull the second wafer 220 apart in the vertical direction. If the second wafer 220 begins to separate from the first wafer 210 by the first force F1, the second force F2 can be applied. The second force F2 can act on the other edge of the second wafer 220 to pull the second wafer 220 apart in the vertical direction. The second wafer 220 can be completely separated from the first wafer 210 by the first force F1 and the second force F2.

[0031] The first force F1 and the second force F2 can be provided from any driving device, and the first force F1 and the second force F2 can be provided independently of each other.

[0032] For ease of description, Figure 2It is shown that force is applied only to one side and the other side of the edge of the second wafer 220, but it is not limited to this, and various methods can be used to separate the joined wafers 210 and 220 from one edge. For example, force can be applied sequentially to one side of the edge of the second wafer 220, the center of the second wafer 220, and the other side of the edge of the second wafer 220.

[0033] refer to Figure 3 In separation operation 120, only portions of the bonded wafers 210 and 220 can be separated. For example... Figure 2 As shown, since a force is applied to separate the joined wafers 210 and 220 from the edge of one surface of the joined wafers 210 and 220, at a specific moment in the separation operation 120, portions of the joined wafers 210 and 220 may be separated while other portions may remain joined.

[0034] For example, the first wafer 210 may include a region SR2 bonded to the second wafer 220 and a region SR1 that separates from the second wafer 220 at the moment when the maximum force Fmax is applied to the second wafer 220 during the separation operation 120.

[0035] The separation distance d1 between the bonded wafers 210 and 220 can be defined as: the maximum distance in the vertical direction from the edge of one surface of the second wafer 220 to the upper surface of the first wafer 210 when the maximum force is applied to the bonded wafers 210 and 220. Furthermore, the length d2 of the separated region of the bonded wafers 210 and 220 can be defined as: the maximum distance from the edge of the first wafer 210 to the bonded region SR2 of the bonded wafers 210 and 220 when the maximum force is applied to the bonded wafers 210 and 220.

[0036] In measurement operation 130, the force applied to a surface of the bonded wafer or the time during which the force is applied is measured. This force can be as referenced above. Figure 2 The first force F1 applied to the second wafer 220.

[0037] In addition, during measurement operation 130, the separation distance between the bonded wafers or the length of the area where the bonded wafers are separated is measured.

[0038] In an embodiment, during measurement operation 130, at least one of the following is measured: the force applied to a surface of the bonded wafers, the time during which the force is applied, the separation distance between the bonded wafers, or the length of the region where the bonded wafers are separated.

[0039] From the moment the force is applied to the wafer to the moment the bonded wafers are completely separated, the force applied to one surface of the bonded wafers and the time during which the force is applied are measured.

[0040] In the bonding strength determination operation 140, the bonding strength is determined based on the force applied to one surface of the bonding wafer or the time during which the force is applied.

[0041] Furthermore, in the bonding strength determination operation 140, the bonding strength is determined based on the separation distance between the bonded wafers or the length of the separated area of ​​the bonded wafers.

[0042] In an embodiment, in the bonding strength determination operation 140, the bonding strength is determined based on the force applied to a surface of the bonding wafers, the time during which the force is applied to a surface of the bonding wafers, the separation distance between the bonding wafers, the length of the separated area of ​​the bonding wafers, or a combination thereof.

[0043] In an embodiment, when determining the bonding strength based on the forces applied to one surface of the bonded wafers, the bonding strength can be determined as the maximum force among the forces applied to one surface of the bonded wafers. Since the maximum force among the forces applied to one surface of the bonded wafers is directly measured in measurement operation 130, the bonding strength of the bonded wafers can be directly measured as a numerical value. That is, when wafers are bonded in different ways, the bonding strength can be absolutely evaluated by measuring the maximum force applied to one surface of the bonded wafers.

[0044] Alternatively, in one configuration, when determining the bonding strength based on the time during which a force is applied to one surface of the bonded wafers, the bonding strength can be determined based on the time during which the maximum force is maintained within the force applied to one surface of the bonded wafers.

[0045] As described above, in separation operation 120, the bonded wafers begin to separate from their edges. Typically, wafers are manufactured in a circular shape, so when the wafers separate from their edges, the bonding area is small at the start of separation, allowing for separation with relatively small force. As the bonded wafers are separated, the bonding area increases as the separation region approaches the center of the wafer, thus requiring greater force to separate them. When the separation region passes the center of the wafer, the bonding area decreases again, thus reducing the force required to separate the bonded wafers.

[0046] As the duration during which the maximum force applied to one surface of the bonded wafers is held increases, the bond strength of the bonded wafers increases. Therefore, if wafers are bonded in different ways, the bond strength of the bonded wafers can be relatively evaluated by measuring the duration during which the maximum force applied to one surface of the bonded wafers is held. In an embodiment, when evaluating bond strength based on the duration of the maximum force holding, the bond strength is evaluated based on the region with the largest bonding area. Therefore, the bond strength evaluated by the above method best represents the total bond strength of the bonded wafers. Furthermore, since it is not necessary to measure the time taken for the bonded wafers to completely separate, the measurement time can be shortened.

[0047] In an embodiment, when determining the bonding strength based on the time during which a force is applied to one surface of the bonded wafers, the bonding strength can be determined based on the time elapsed from the moment the force is applied to the bonded wafers to the moment the bonded wafers are completely separated, or the time elapsed from the moment the bonded wafers begin to separate to the moment the bonded wafers are completely separated.

[0048] The bonding strength of the joined wafers increases as the time elapsed from the moment force is applied to the joined wafers until the time when the joined wafers are completely separated, or from the moment the joined wafers begin to separate until the time when the joined wafers are completely separated. Therefore, when wafers are joined in different ways, the bonding strength of the joined wafers can be relatively assessed by measuring the time elapsed from the moment force is applied to the joined wafers until the time when the joined wafers are completely separated, or from the moment the joined wafers begin to separate until the time when the joined wafers are completely separated.

[0049] In an embodiment, when assessing the bonding strength based on the time taken from the moment a force is applied to the bonded wafers to the moment the bonded wafers are completely separated, or from the moment the bonded wafers begin to separate to the moment the bonded wafers are completely separated, the bonding strength is assessed based on the bonding strength over the entire area of ​​the bonded wafers, thereby allowing for the most accurate measurement of the bonding strength of the bonded wafers.

[0050] In an embodiment, when determining the bonding strength based on the time during which a force is applied to one surface of the bonded wafers, the bonding strength can be determined based on the product of the maximum force applied to one surface of the bonded wafers and the time during which the maximum force is held.

[0051] As described above, the bond strength of the bonded wafers increases as the maximum force applied to one surface of the bonded wafers increases and as the time during which the maximum force is held increases. Therefore, when wafers are bonded in different ways, the bond strength of the bonded wafers can be relatively evaluated by measuring the maximum force applied to one surface of the bonded wafers and the time during which that maximum force is held. In this embodiment, since the applied force and time are considered when determining the bond strength of the bonded wafers, the bond strength of the bonded wafers can be evaluated more accurately.

[0052] In an embodiment, when determining the bonding strength based on the separation distance between the bonded wafers, the bonding strength can be determined based on the separation distance between the bonded wafers when the force applied to one surface of the bonded wafer is at its maximum.

[0053] When the force applied to one surface of the bonded wafers is at its maximum, the bond strength increases as the separation distance between the bonded wafers decreases. Therefore, the bond strength between the wafers can be evaluated by measuring the separation distance between the bonded wafers at the moment when the force applied to one surface of the bonded wafers is at its maximum.

[0054] In an embodiment, when determining the bonding strength based on the length of the separated region of the bonded wafers, the bonding strength can be determined based on the length of the separated region of the bonded wafers when the force applied to one surface of the bonded wafers is at its maximum.

[0055] As described above, when the force applied to one surface of the bonded wafers is at its maximum, the bond strength increases as the length of the separated region of the bonded wafers decreases. Therefore, the bond strength can be determined based on the length of the separated region of the bonded wafers at the moment when the force applied to one surface of the bonded wafers is at its maximum.

[0056] In an embodiment, when determining the bonding strength based on the product of the separation distance between the bonded wafers and the length of the separated region of the bonded wafers, the bonding strength can be determined based on the product of the separation distance between the bonded wafers and the length of the separated region of the bonded wafers when the force applied to one surface of the bonded wafers is at its maximum.

[0057] Although a method for evaluating the bonding strength of bonded wafers has been described above, the bonding strength evaluation method 100 described above can be used not only to evaluate the bonding strength between bonded wafers, but also to evaluate the bonding strength between memory chips and wafers, or the bonding strength between memory chips. Furthermore, the bonding strength evaluation method 100 described above can also be used to evaluate the bonding strength of materials bonded by various bonding processes used in the manufacturing process of memory devices.

[0058] In the following description, an apparatus and its driving method for implementing the above-described bonding strength evaluation method 100 will be used as an example.

[0059] Figure 4 This is a view showing a bonding strength evaluation apparatus 400 according to an embodiment of the present disclosure.

[0060] refer to Figure 4 The bonding strength assessment device 400 may include a motor 410, a first support 420, a second support 430, a wafer holder 440, a determination module 450, and a blade 480.

[0061] Motor 410 can control the vertical movement of the first support 420 and the second support 430. The first support 420 can move upward by passing through the wafer holder 440 in the vertical direction, and can be a reference for setting the position of the wafer on a plane defined in the first direction FD and the second direction SD. The second support 430 can be used to support the wafer holder 440.

[0062] The bonded wafers can be mounted on a wafer holder 440. The wafer holder 440 can hold the bonded wafers in place. In an embodiment, to hold the bonded wafers on the wafer holder 440, the space between the wafer holder 440 and the bonded wafers can be made into a vacuum.

[0063] The determination module 450 may include a driver 460 and a sensor 470.

[0064] A driver 460 can apply a force in a direction perpendicular to the joined wafers to separate the joined wafers. The driver 460 may include a first driver 461 and a second driver 462. Each of the first driver 461 and the second driver 462 may contact the upper surface of one of the joined wafers to apply a force to that upper surface. In an embodiment, the first driver 461 and the second driver 462 may contact one edge and the other edge of the upper surface of one wafer, respectively. In an embodiment, the force applied to the upper surface of a wafer may be a tension pulling the wafer upwards.

[0065] In an embodiment, the first driver 461 and the second driver 462 can be driven independently. For example, after the first driver 461 and the second driver 462 contact the upper surface of a wafer, only the first driver 461 can apply force to the upper surface of a wafer before the bonded wafers are separated. After the bonded wafers are separated, both the first driver 461 and the second driver 462 can apply force to the upper surface of a wafer. (Refer to below...) Figure 7 and Figure 8The detailed driving methods of the first driver 461 and the second driver 462 are described.

[0066] Sensor 470 can be attached to the first driver 461 and the blade 480. Sensor 470 can measure the force applied to a wafer by the first driver 461 and the time during which the force is applied. Sensor 470 can measure the force applied to a wafer and the time during which the force is applied from the moment the first driver 461 applies a force to a wafer to the moment the joined wafers are completely separated.

[0067] Sensor 470 can also measure the separation distance between the bonded wafers 210 and 220 and the length of the separated area of ​​the bonded wafers 210 and 220. When the force applied to a wafer by the first driver 461 is at its maximum, sensor 470 can measure the separation distance between the bonded wafers 210 and 220 and the length of the separated area of ​​the bonded wafers 210 and 220.

[0068] In an embodiment, sensor 470 may measure at least one of the force applied to a wafer, the time during which the force is applied, the separation distance between the joined wafers 210 and 220, or the length of the region where the joined wafers 210 and 220 are separated.

[0069] The blade 480 can be connected to a support platform included in the bonding strength measuring device 400, or positioned outside the bonding strength measuring device 400. The blade 480 can be inserted between the bonding interfaces of the bonded wafers to apply force to the bonding interfaces to separate the bonded wafers. The blade 480 can be a component separate from the determining module 450. Although Figure 3 The bonding strength assessment device 400 shown may include a blade 480, but the embodiments are not limited thereto, and the bonding strength assessment device 400 may not include a blade 480.

[0070] The determination module 450 can determine the bonding strength of the bonded wafers based on the results measured by the sensor 470.

[0071] In an embodiment, the determining module 450 may determine the bonding strength of the bonded wafers based on the force applied to a wafer, the time for which the force is applied to a wafer, the separation distance between the bonded wafers, the length of the separated region of the bonded wafers, or a combination thereof.

[0072] In an embodiment, if the sensor 470 measures the force applied to a wafer by the first driver 461, the determination module 450 can determine the maximum force among the forces as the bonding strength.

[0073] In an embodiment, if the sensor 470 measures the force applied to a wafer by the first driver 461, the determining module 450 can determine the bonding strength based on the time during which the maximum force is held, the time from the moment the force is applied to a wafer to the moment the bonded wafers are completely separated, or the time from the moment the bonded wafers begin to separate to the moment the bonded wafers are completely separated.

[0074] In an embodiment, when the sensor 470 measures the force applied to a wafer and the time during which the force is applied, the determination module 450 can determine the bonding strength based on the product of the maximum force among the forces applied to a surface of a wafer and the time during which the maximum force is held.

[0075] In an embodiment, when sensor 470 can measure the separation distance between the bonded wafers and the length of the separated region of the bonded wafers, determination module 450 can determine the bonding strength based on the separation distance between the bonded wafers or the length of the separated region of the bonded wafers when maximum force is applied to one surface of a wafer. For example, determination module 450 can determine the bonding strength based on the product of the separation distance between the bonded wafers and the length of the separated region of the bonded wafers when maximum force is applied to one surface of a wafer.

[0076] Figures 5 to 8 This is a view illustrating a driving method of a bonding strength evaluation apparatus according to an embodiment of the present disclosure.

[0077] refer to Figure 5 The bonded wafers 510 and 520 can be loaded onto the wafer holder 440. The bonded wafers 510 and 520 can be connected to a reference... Figure 1 and Figure 2 The wafers 210 and 220 described are the same wafers.

[0078] The bonded wafers 510 and 520 can be secured to the wafer holder 440. In an embodiment, the bonded wafers 510 and 520 can be secured to the wafer holder 440 by evacuating the space between the bonded wafers 510 and 520 and the wafer holder 440.

[0079] After the joined wafers 510 and 520 are secured, a blade 480 can be inserted into the interface between the joined wafers 510 and 520. In an embodiment, the process of inserting the blade 480 into the interface between the joined wafers 510 and 520 can be omitted.

[0080] refer to Figure 6The first driver 461 and the second driver 462 can move downward to contact the upper surface of the second wafer 520. The first driver 461 and the second driver 462 can contact the upper surface of the second wafer 520 at different positions. The first driver 461 can contact at least one of the first positions 610 on the second wafer 520. Figure 6 The first position 610 shown is exemplary, and the position where the first driver 461 contacts the second wafer 520 is not limited to this. The second driver 462 contacts the edge of the upper surface of the second wafer 520 at a position other than the first position 610. In an embodiment, the first driver 461 and the second driver 462 may be symmetrically positioned relative to the center of the second wafer 520.

[0081] After the first driver 461 and the second driver 462 make contact with the upper surface of the second wafer 520, the driver 460 can evacuate the space between the first driver 461 and the second wafer 520 and the space between the second driver 462 and the second wafer 520. Because the space between the first driver 461 and the second wafer 520 and the space between the second driver 462 and the second wafer 520 becomes a vacuum, the first driver 461 and the second driver 462 can make close contact with the second wafer 520.

[0082] refer to Figure 7 With the first driver 461 and the second driver 462 in close contact with the second wafer 520, the first driver 461 can move in the vertical direction. In an embodiment, the first driver 461 can move at a constant speed. With the second driver 462 in close contact with the second wafer 520, the bonded wafers 510 and 520 can separate from their edges solely due to the movement of the first driver 461.

[0083] Sensor 470 can measure the time from when the first driver 461 applies a force to the second wafer 520 until the joined wafers 510 and 520 are completely separated, as well as the force applied to the second wafer 520 during that time.

[0084] refer to Figure 8 After the joined wafers 510 and 520 begin to separate, the first actuator 461 and the second actuator 462 can move together in the vertical direction. In this embodiment, the first actuator 461 and the second actuator 462 can move at a constant speed. As the first actuator 461 and the second actuator 462 move in the vertical direction, the joined wafers 510 and 520 are completely separated. With the joined wafers 510 and 520 completely separated, the sensor 470 can terminate the measurement.

[0085] Figure 9This is a view showing data measured during driving of a joint strength evaluation apparatus according to an embodiment of the present disclosure.

[0086] refer to Figure 9 It can identify the change in the force applied to the second wafer 520 over time when the joined wafers 510 and 520 are separated.

[0087] At time t0, the first driver 461 and the second driver 462 can contact the upper surface of the second wafer 520.

[0088] During the time period from time t0 to time t1, the first driver 461 and the second driver 462 can be in close contact with the upper surface of the second wafer 520. In an embodiment, during the time period from time t0 to time t1, the space between the first driver 461 and the second wafer 520 and the space between the second driver 462 and the second wafer 520 can be evacuated. When applying force to one surface of the second wafer 520 using an alternative method without evacuating the space between the first driver 461 and the second wafer 520, the time period from time t0 to time t1 can be omitted.

[0089] At time t1, the first actuator 461 begins to move upward, simultaneously pulling the second wafer 520 apart. In an embodiment, the sensor 470 can measure the force applied to the second wafer 520 from time t1 onwards and the time during which the force is applied.

[0090] At time t2, the joined wafers 510 and 520 begin to separate from one edge.

[0091] During the time interval from time t2 to time t3, there may be a period during which the force applied to the second wafer 520 increases. As described above, when the bonded wafers separate from the edge, the bonding area increases towards the center of the wafer, thus requiring increasingly larger forces to separate the bonded wafers. Therefore, after the bonded wafers are separated, the force applied to the second wafer 520 may increase.

[0092] At time t3, the joined wafers 510 and 520 can be separated to near the center of the wafer. The force applied to the second wafer 520 at time t3 can be expressed as Fmax.

[0093] During the time period from time t3 to time t4, the force applied to the second wafer 520 can be maintained. The force applied to the second wafer 520 during the time period from time t3 to time t4 can be a force that acts to separate the bonded wafers 510 and 520 near the center of the wafer.

[0094] At time t4, the joined wafers 510 and 520 can be separated by passing through the center of the wafer.

[0095] During the time interval t4 to t5, the bonded wafers 510 and 520 are gradually separated to the other edge of the bonded wafers 510 and 520. As the separation proceeds, the bonding area gradually decreases, making it easier for the bonded wafers 510 and 520 to separate, and thus the force applied to the second wafer 520 gradually decreases.

[0096] At time t5, the bonded wafers 510 and 520 are completely separated. With the bonded wafers 510 and 520 completely separated, no force is applied to the second wafer 520. With the bonded wafers 510 and 520 completely separated, sensor 470 terminates the measurement.

[0097] The determining module 450 can determine the difference Fmax-F0 between the force Fmax applied to the second wafer 520 during the time period from time t3 to time t4 and the force F0 applied to the second wafer 520 at time t1 as the bonding strength of the bonded wafers 510 and 520.

[0098] Alternatively, the determining module 450 may determine the bonding strength based on the time t34 when the maximum force is applied to the second wafer 520, the time t15 from the moment the force is applied to the second wafer 520 to the moment when the bonded wafers 510 and 520 are completely separated, or the time t25 from the moment when the bonded wafers 510 and 520 begin to separate to the moment when the bonded wafers 510 and 520 are completely separated.

[0099] Alternatively, the determining module 450 may determine the bonding strength based on the product of the difference between the force Fmax applied to the second wafer 520 and the force F0 applied to the second wafer 520 at time t1 and time t34 when the maximum force is applied to the second wafer 520.

[0100] Alternatively, during the period t34 in which the maximum force is applied to the second wafer 520, the determining module 450 may determine the bonding strength based on the separation distance between the bonded wafers 210 and 220, the distance in the area where the bonded wafers 210 and 220 are separated, or a combination thereof.

[0101] According to the above-described bonding strength evaluation method, bonding strength evaluation device, and driving method, the bonding strength can be determined by measuring the time required for separation when the bonded wafers are separated or the force acting on the wafers during separation.

[0102] Traditionally known methods for determining bond strength involve either applying a crack to the wafer or measuring the crack length based on this, or measuring the separation length caused by repeatedly applying and removing force from the wafer.

[0103] However, all known conventional methods can cause stress and damage to the wafer and cannot be used to measure the bonding strength of wafers containing integrated circuits or memory cells. Furthermore, conventional methods lack consistency in measurement due to variations in wafer crack or separation lengths (e.g., variations caused by humidity or operating conditions at the measurement site).

[0104] The embodiments of this disclosure can measure the bonding strength by a peeling method without causing repeated stress or artificial cracks to the wafer, and are therefore used to measure the bonding strength in a wafer in which integrated circuits and memory cells are disposed.

[0105] Furthermore, since the force applied to the wafer or the time during which the force is applied depends only on the bonding strength of the bonded wafers, the consistency of the bonding strength determination can be ensured even when measurement conditions vary, thus providing higher accuracy in bonding strength assessment.

[0106] According to embodiments of the present disclosure, the determining module 450 can determine the maximum force among the forces applied to one surface of the bonded wafers 210 and 220 as the bond strength.

[0107] According to embodiments of the present disclosure, the determining module 450 can determine the bonding strength based on the duration during which the maximum force among the forces applied to one surface of the bonded wafers 210 and 220 is held.

[0108] According to embodiments of the present disclosure, the determining module 450 can determine the bonding strength based on the time taken from the moment a force is applied to the bonded wafers 210 and 220 to the moment the bonded wafers 210 and 220 are completely separated.

[0109] According to embodiments of the present disclosure, the determining module 450 can determine the bonding strength based on the time taken from the moment when the bonded wafers 210 and 220 begin to separate to the moment when the bonded wafers 210 and 220 are completely separated.

[0110] According to embodiments of the present disclosure, the determining module 450 can determine the bonding strength based on the product of the maximum force among the forces applied to one surface of the bonded wafers 210 and 220 and the time during which the maximum force is held.

[0111] The above embodiments are merely illustrative, and those skilled in the art should understand that various modifications can be made thereto without departing from the scope of this disclosure. Therefore, the embodiments described herein are provided for illustrative purposes and not to limit the scope of this disclosure, and it should be understood that the scope of this disclosure is not limited by these embodiments. The scope of this disclosure should be interpreted by the appended claims, and all technical spirit within their equivalents should be interpreted as falling within the scope of this disclosure. Furthermore, these embodiments can be combined to form additional embodiments.

Claims

1. A method for evaluating bond strength, comprising: Fabricating bonded wafers; The joined wafers are separated by applying a force to one surface of the joined wafers in a direction perpendicular to that surface. The force applied to one surface of the joined wafers, the time during which the force is applied, the separation distance between the joined wafers, and the length of the region where the joined wafers are separated are measured. as well as The bonding strength is determined based on at least one of the force, the time during which the force is applied, the separation distance between the bonded wafers, and the length of the region in which the bonded wafers are separated.

2. The bonding strength evaluation method as described in claim 1, in, The steps for preparing the bonded wafers include bonding a first wafer and a second wafer, and The step of separating the joined wafers includes applying the force to a surface of the second wafer while the first wafer is fixed, so as to separate the first wafer and the second wafer.

3. The bonding strength evaluation method as described in claim 2, wherein, The step of separating the joined wafers includes applying the force from the edge of one surface of the second wafer toward the one surface.

4. The bonding strength evaluation method as described in claim 1, wherein, The step of measuring at least one of the force, the time, the separation distance, and the length includes: measuring the force and the time over a period from the moment the force is applied to the joined wafers to the moment the joined wafers are completely separated.

5. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes: determining the maximum force among the forces applied to one surface of the bonded wafers as the bonding strength.

6. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes determining the bonding strength based on the time during which the maximum force among the forces applied to the wafers being bonded is held.

7. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes: determining the bonding strength based on the time taken from the moment the force is applied to the bonded wafers to the moment the bonded wafers are completely separated.

8. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes: determining the bonding strength based on the time taken from the moment when the bonded wafers begin to separate to the moment when the bonded wafers are completely separated.

9. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes determining the bonding strength based on the product of the maximum force among the forces applied to one surface of the bonded wafer and the time during which the maximum force is held.

10. The bonding strength evaluation method as described in claim 1, wherein, The step of determining the bonding strength includes: determining the bonding strength based on at least one of the separation distance between the bonded wafers when the maximum force among the forces applied to the bonded wafers is applied to the one surface of the bonded wafers, and the length of the region in which the bonded wafers are separated when the maximum force is applied to the one surface of the bonded wafers.

11. The bonding strength evaluation method as described in claim 10, wherein, The step of determining the bonding strength includes: determining the bonding strength based on the product of the separation distance between the bonded wafers when the maximum force is applied to the one surface of the bonded wafers and the length of the region in which the bonded wafers are separated when the maximum force is applied to the one surface of the bonded wafers.

12. The bonding strength evaluation method as described in claim 1, in, The steps for preparing the bonded wafers include bonding a first wafer and a second wafer, and The separation distance between the joined wafers is the maximum distance from the edge of one surface of the second wafer to one surface of the first wafer.

13. The bonding strength evaluation method as described in claim 1, wherein, The length of the region where the joined wafers are separated is the maximum distance from the edge of one of the joined wafers to the region where the joined wafers are not separated.

14. A bonding strength evaluation device, comprising: A wafer holder that secures a wafer in place; as well as A determining module, the determining module determining the bonding strength of the bonded wafers, wherein the determining module includes: A driver that separates the joined wafers by applying a force to the joined wafers in a direction perpendicular to one surface of the joined wafers; and A sensor that measures at least one of the force applied to one surface of the joined wafers, the time during which the force is applied, the separation distance between the joined wafers, and the length of the region where the joined wafers are separated.

15. The bonding strength evaluation device as described in claim 14, in, The driver contacts one surface of one of the joined wafers and pulls the one wafer away to separate the joined wafers. The driver includes a first driver and a second driver that contact different locations on one surface of the wafer, and The first driver and the second driver independently apply the force to the surface of the wafer.

16. The bonding strength evaluation apparatus as claimed in claim 15, wherein, The first driver applies the force to the one surface of the one wafer before the joined wafers are separated, and the first driver and the second driver apply the force to the one surface of the one wafer after the moment when the joined wafers begin to separate.

17. The bonding strength evaluation apparatus of claim 14, further comprising: A blade that applies force to the boundary of the joined wafers to separate the joined wafers.

18. The bonding strength evaluation apparatus as claimed in claim 14, wherein, The sensor measures the force applied to one surface of the joined wafer and the time during which the force is applied, from the moment the force is applied to the joined wafer to the moment the joined wafer is completely separated.

19. The bonding strength evaluation apparatus as claimed in claim 14, wherein, The determining module determines the bonding strength based on at least one of the separation distance between the bonded wafers when a maximum force is applied to one surface of the bonded wafers, and the length of the region in which the bonded wafers are separated when the maximum force is applied to one surface of the bonded wafers.

20. A driving method for a bonding strength evaluation device, the driving method comprising: Secure the joined wafers to the wafer holder; as well as The bonding strength is determined by applying a force to one of the wafers in a direction perpendicular to one surface of the bonded wafers to separate the bonded wafers, and measuring at least one of the force applied to the one wafer, the time during which the force is applied, the separation distance between the bonded wafers, and the length of the region where the bonded wafers are separated.

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