Mounting device and mounting method

Abstract

To provide a mounting device and a mounting method which can achieve highly accurate mounting.SOLUTION: A mounting device 1 according to an embodiment includes a bonding head 10 for holding an object Ma to be bonded, a bonding stage 20 for holding an object Mb to be bonded, a vertical double-field optical system 30 which is inserted between the object Ma to be bonded and the object Mb to be bonded and simultaneously images the object Ma to be bonded and the object Mb to be bonded, wherein the vertical double-field optical system 30 has one image sensor 35 for acquiring an image obtained by simultaneously imaging a first alignment mark formed on the object Ma to be bonded and a second alignment mark formed on the object Mb to be bonded, and at least any one of the bonding head 10 and the bonding stage 20 adjusts a relative position between the object Ma to be bonded and the object Mb to be bonded on the basis of the image, and bonds the object Ma to be bonded and the object Mb to be bonded.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a mounting device and a mounting method.

Background Art

[0002] In order to achieve low power consumption and high driving speed, the multilayerization of semiconductor devices is progressing. In the process of stacking semiconductor chips (such as CoC (Chip on Chip) and CoW (Chip on Wafer)) or chip bonding, which is the process of mounting a semiconductor package, the connection method between contacts has changed from the conventional wire bonding method to a connection method using flip chip or through-silicon via (TSV). In the existing connection method between contacts via wire bonding, a bonding accuracy of several tens of μm was sufficient, but in the flip chip where direct contact between the bump and the pad is performed, several μm is required, and particularly in the chip bonding using through-silicon vias, sub-μm accuracy is required. Also, since metals are directly joined, high temperature and high pressure are required during joining. In a high-precision chip bonding device, minute changes in the mechanical and thermal structures become factors that impede accuracy.

[0003] Patent Document 1 describes a mounting device for the purpose of high-precision chip bonding. The device of Patent Document 1 recognizes alignment marks on the bonding surface of the lower object to be joined held on the bonding stage and on the bonding surface of the upper object to be joined held on the bonding head by an upper and lower two-field optical system inserted between the lower object to be joined and the upper object to be joined.

[0004] The dual-field optical system integrates a camera for recognizing the upper and lower surfaces, and has a drive axis at least in the horizontal plane so that it can enter from the side into the gap between the lower and upper objects to be joined just before joining. Based on the recognition results, the objects to be joined are aligned and joined. The dual-field optical system, which had been retracted for joining, is then reinserted, and the alignment marks on the upper surface of the upper object to be joined after joining are recognized. The positional deviation after mounting is calculated from the recognition results before and after joining, and when joining the next layer, the target position is set after subtracting that deviation. This is intended to prevent the accumulation of mounting errors.

[0005] However, in the form of the device described in Patent Document 1, the following challenges remain regarding high-precision bonding. Specifically, since the upper and lower two-field optical system deforms over time due to thermal and mechanical stress, using the same optical parameters for recognition before and after mounting becomes a source of error.

[0006] As a technology to solve this problem, for example, the apparatus described in Patent Document 2 has a reference mark on the bonding stage. The apparatus in Patent Document 2 recognizes the reference mark before recognizing the mounting result, thereby grasping the deformation (mainly due to thermal expansion) of the upper and lower two-field optical system and offsetting it when recognizing the mounting result. This suppresses errors due to changes in the optical system over time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5876000 [Patent Document 2] Patent No. 6478939 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, to achieve even higher precision, the measures taken by the apparatus described in Patent Document 2 are insufficient, and countermeasures must be taken against the following error factors.

[0009] 1. In a two-field optical system (upper and lower), if there are separate image sensors for upper and lower field recognition (e.g., CCD or CMOS), the accumulation of individual variation errors from each image sensor becomes an error factor that hinders high accuracy.

[0010] 2. Image sensors used in vertically and horizontally focused optical systems are susceptible to positional shifts due to thermal and mechanical factors. In the apparatus described in Patent Document 2, the temporal changes within the optical system are corrected by image recognition of a reference mark placed on the stage before mounting the next layer. However, the correction time interval is too long, making it insufficient to suppress errors. For example, when the wafer size is 12 inches and the die size is 10 mm square, it takes several tens of minutes to complete mounting one layer across the entire wafer. It has also been proposed to monitor the temperature inside the vertically and horizontally focused optical system and store the relationship between temperature and error to estimate the error based on temperature. However, deformation due to thermal stress is accompanied by a time delay and hysteresis according to the history of temperature changes, so there are limitations to the accuracy of the correction. It is desirable to perform verification using the reference mark every time immediately before image recognition of the workpiece. It is necessary to devise a way to perform verification of the reference mark at a sufficient frequency without reducing throughput.

[0011] 3. When simultaneously recognizing upper and lower alignment marks with a two-field optical system, a slight tilt in the orientation of the two-field optical system will introduce a significant error in the recognition of the alignment marks. If the distance between the upper and lower joined objects is h [mm] and the orientation error of the two-field optical system is θ [rad], the recognition error Δ [mm] is given by the following equation (1).

[0012] Δ=htanθ (1)

[0013] For example, when h=20[mm] and θ=2.5μ[rad], Δ=50[nm]. Therefore, this error cannot be ignored when aiming for recognition accuracy of a few [nm]. The upper and lower two-field optical system has a drive axis in at least the horizontal plane in order to move in and out between the joined objects in order to perform image recognition. Reducing the pitching and rolling of the drive axis to a few μ[rad] leads to an increase in equipment cost, so a method is needed to grasp and correct the attitude of the upper and lower two-field optical system in a simple way.

[0014] 4. If the orientation of the upper and lower workpieces is tilted from parallel, not only will errors be added to the image recognition results, but at the moment of mounting, a part of the chip will come into contact with the wafer, causing lateral displacement due to a phenomenon that differs from the target mounting position (uneven contact). Even if the bonding stage holding the bottom workpiece and the bonding head holding the upper workpiece are parallel with sufficient precision, they may be deviated from parallel due to the warping of the wafer itself or the accumulation of thickness variations of the workpieces due to multi-layer mounting. Therefore, the parallelism between the two upper and lower surfaces to be mounted must be determined and corrected immediately before mounting.

[0015] 5. The optical properties of the optical components in a two-field optical system (upper and lower) change over time, so periodic detection is required.

[0016] The present invention has been made to solve at least one of these problems and provides an assembly device and assembly method that can achieve high-precision assembly. [Means for solving the problem]

[0017] An assembly apparatus according to one embodiment includes a bonding head for holding a first member, a bonding stage for holding a second member, and an upper and lower two-field optical system inserted between the first member and the second member to simultaneously photograph the first member and the second member. The upper and lower two-field optical system has one image sensor that acquires an image of a first alignment mark formed on the first member and a second alignment mark formed on the second member simultaneously. At least one of the bonding head and the bonding stage adjusts the relative positions of the first member and the second member based on the image to bond the first member and the second member.

[0018] In the above-described implementation device, the upper and lower two-field optical system may further include a plurality of optical members that project images of the first alignment mark and the second alignment mark onto the image sensor, a housing for fixing the optical members, a reference mark fixed to the housing, and a switch means for causing the image sensor to acquire the image of the reference mark at a predetermined time.

[0019] The above-described implementation device further includes a tilt sensor for detecting the tilt of the upper and lower two-field optical system, and the upper and lower two-field optical system may further include a first drive mechanism for adjusting the tilt.

[0020] The above-described mounting apparatus further includes a tilt sensor for detecting the parallelism between a first bonding surface in the first member and a second bonding surface in the second member, and at least one of the bonding head and the bonding stage may have a second drive mechanism for adjusting the relative position and the parallelism to bond the first member and the second member.

[0021] In the above-described implementation device, the upper and lower two-field optical system further comprises a plurality of optical members that image the first alignment mark formed on the first bonding surface and the second alignment mark formed on the second bonding surface onto the image sensor, and the tilt sensor may be an autocollimator that uses detection light transmitted through at least one of the optical members.

[0022] In the above mounting device, the illumination light used for imaging the first alignment mark and the second alignment mark includes wavelengths different from those of the detection light, and the optical member may include a dichroic mirror that combines and separates the illumination light and the detection light.

[0023] The above mounting device further includes a calibration block that serves as a reference for the optical characteristics of the optical members in the upper and lower two-field optical systems, and the upper and lower two-field optical systems may detect changes over time in the optical characteristics using the calibration block at predetermined time intervals.

[0024] In the above mounting device, the calibration block has a pair of calibration patterns formed on opposite upper and lower planes, and the distance, parallelism between the upper and lower planes, and the relative positions of the calibration patterns may be set in advance.

[0025] In the above mounting device, the calibration block is fixed to the bonding stage or the base, and the upper and lower two-field optical systems may detect the change over time using the calibration block while the bonding head holds the first member.

[0026] In the above mounting device, the upper and lower two-field optical systems may be set such that the first direction of the first alignment mark as viewed from the upper and lower two-field optical system side and the second direction of the second alignment mark as viewed from the upper and lower two-field optical system side are the same as the first direction and the second direction on the image sensor.

[0027] An implementation method of one embodiment includes the steps of: holding a first member with a bonding head; holding a second member with a bonding stage; inserting an upper and lower two-field optical system between the first member and the second member; acquiring an image of a first alignment mark formed on the first member and a second alignment mark formed on the second member simultaneously captured by one image sensor in the upper and lower two-field optical system; adjusting the relative positions of the first member and the second member in at least one of the bonding head and the bonding stage based on the image; and joining the first member and the second member.

[0028] In the above implementation method, in the step of inserting the upper and lower two-field optical system, the upper and lower two-field optical system may further include a step of having the image of the reference mark acquired by the image sensor at a predetermined time, before the step of acquiring the image.

[0029] The above implementation method may further include the steps of detecting the inclination of the upper and lower two-field optical system using a tilt sensor, and adjusting the detected inclination using a first drive mechanism in the upper and lower two-field optical system.

[0030] The above implementation method further includes the steps of detecting the degree of parallelism between a first joining surface of the first member and a second joining surface of the second member using a tilt sensor, and adjusting the degree of parallelism using a second drive mechanism of at least one of the bonding head and the bonding stage, wherein in the step of adjusting the relative position, the relative position may be adjusted by the second drive mechanism, and in the step of joining, the joining may be performed by the second drive mechanism.

[0031] In the above implementation method, in the step of inserting the upper and lower two-field optical system, the upper and lower two-field optical system has a plurality of optical members that image the first alignment mark formed on the first bonding surface and the second alignment mark formed on the second bonding surface onto the image sensor, and in the step of detection by the tilt sensor, the tilt sensor may be an autocollimator that uses detection light transmitted through at least one of the optical members.

[0032] In the above implementation method, in the step of acquiring the image, the illumination light used to image the first alignment mark and the second alignment mark includes a different wavelength from the detection light, and in the step of detection by the tilt sensor, the illumination light and the detection light may be combined and separated by a dichroic mirror in the optical member.

[0033] The above implementation method may further include a step of detecting changes in the optical properties over time at predetermined time intervals using a calibration block that serves as a reference for the optical properties of the optical elements in the upper and lower two-field optical system.

[0034] In the above implementation method, in the step of detecting the change over time, the calibration block has a pair of calibration patterns formed on an opposing upper plane and a lower plane, and the distance between the upper plane and the lower plane, the degree of parallelism, and the relative positions of the calibration patterns may be set in advance.

[0035] In the above implementation method, in the step of detecting the change over time, the calibration block may be fixed to the bonding stage or base, and the upper and lower two-field optical system may detect the change over time using the calibration block at the same time that the bonding head holds the first member.

[0036] In the above implementation method, in the step of inserting the upper and lower two-field optical system, the upper and lower two-field optical system may be set so that the first orientation of the first alignment mark as seen from the upper and lower two-field optical system side and the second orientation of the second alignment mark as seen from the upper and lower two-field optical system side are the same as the first orientation and the second orientation on the image sensor. [Effects of the Invention]

[0037] The present invention provides a mounting device and mounting method that can achieve high-precision mounting. [Brief explanation of the drawing]

[0038] [Figure 1] This is a configuration diagram illustrating an implementation device according to Embodiment 1. [Figure 2] This is a diagram illustrating the optical section of the upper and lower two-field optical system in the implementation device according to Embodiment 1. [Figure 3] This figure illustrates an image formed by an image sensor in the mounting device according to Embodiment 1. [Figure 4] This figure illustrates an image formed by an image sensor in the mounting device according to Embodiment 1. [Figure 5] This figure illustrates an image formed by an image sensor in the mounting device according to Embodiment 1. [Figure 6] This figure illustrates the reference marks of the upper and lower two-field optical system in the mounting device according to Embodiment 1. [Figure 7] This figure illustrates a reference mark that is imaged onto an image sensor in the mounting device according to Embodiment 1. [Figure 8] This is a flowchart illustrating an example of the implementation method according to Embodiment 1. [Modes for carrying out the invention]

[0039] For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. Furthermore, the same elements are denoted by the same reference numerals in each drawing, and redundant explanations have been omitted where necessary.

[0040] (Embodiment 1) A mounting apparatus according to Embodiment 1 will now be described. The mounting apparatus of this embodiment is a three-dimensional mounting apparatus that aligns and mounts the upper and lower objects to be bonded using an upper and lower two-field optical system. Figure 1 is a configuration diagram illustrating the mounting apparatus according to Embodiment 1. As shown in Figure 1, the mounting apparatus 1 includes a bonding head 10, a bonding stage 20, an upper and lower two-field optical system 30, a tilt sensor 40, a calibration block 50, and tilt sensors 60a and 60b.

[0041] Each component of the mounting device 1 may be arranged on the base frame 70. The base frame 70 is the basic structure of the mounting device 1. The base frame 70 is, for example, a rectangular parallelepiped having a base 71, an upper frame 72, and side frames 73. The side frames 73 support the upper frame 72 on the base 71. The base frame 70 may have other shapes as long as it can accommodate the components of the mounting device 1.

[0042] Here, for the sake of convenience in explaining the mounting device 1, we introduce the XYZ Cartesian coordinate system. For example, the direction perpendicular to the upper surface of the base 71 is defined as the Z-axis direction, and the two perpendicular directions in the plane parallel to the upper surface of the base 71 are defined as the X-axis direction and the Y-axis direction. The +Z-axis direction is defined as upward, and the -Z-axis direction is defined as downward. Note that upward and downward are for the sake of convenience in explaining the mounting device 1 and do not limit the direction in which the mounting device 1 is actually placed when it is used. The various components of the mounting device 1 will be explained below.

[0043] <Bonding head> The bonding head 10 holds the workpiece Ma. The workpiece Ma is a component to be bonded onto the workpiece Mb. The workpiece Ma is, for example, a die. However, the workpiece Ma is not limited to a die; it may also be a wafer, chip, interposer, or other component. The bonding head 10 has a head 11 and a drive mechanism 12.

[0044] The head 11 holds the object to be bonded Ma. For example, the head 11 may grip the object to be bonded Ma by suction. The drive mechanism 12 is fixed to the upper frame 72. The drive mechanism 12 moves the head 11 in the X-axis, Y-axis, and Z-axis directions. In addition, the drive mechanism 12 may rotate the head 11 around a rotation axis that rotates around the X-axis, Y-axis, and Z-axis. In this way, the bonding head 10 may function as a bonding tool.

[0045] Specifically, the drive mechanism 12 may have, as a function of the bonding tool, a translation axis that moves the head 11 in the X, Y, and Z axes, as well as rotation axes Tx, Ty, and Tz that rotate the head 11 around each axis. This allows the bonding head 10 to adjust the relative position and parallelism of the upper workpiece Ma and the lower workpiece Mb. The bonding head 10 can also bond the workpieces Ma and Mb.

[0046] <Bonding Stage> The bonding stage 20 holds the material to be bonded Mb. The material to be bonded Mb is, for example, a wafer or other component. However, the material to be bonded Mb is not limited to a wafer; it may also be a chip, die, interposer, or other component. The material to be bonded Mb may also be the bottom layer component in a laminate. The bonding stage 20 includes a stage 21 and a drive mechanism 22.

[0047] The stage 21 holds the material to be bonded Mb. For example, the stage 21 may adsorb the material to be bonded Mb. The drive mechanism 22 is fixed to the base 71. The drive mechanism 22 moves the stage 21 in parallel in the X-axis direction and the Y-axis direction. This allows the bonding stage 20 to move the material to be bonded Mb in the X-axis direction and the Y-axis direction. The drive mechanism 22 may also move the stage 21 in parallel in the Z-axis direction, or it may rotate around a rotation axis that rotates around the X-axis, Y-axis, and Z-axis.

[0048] The bonding stage 20 may have, in place of or in addition to the bonding head 10, rotation axes Tx, Ty, and Tz that rotate the stage 21 around each axis, as well as translation axes that move the stage 21 in the X, Y, and Z axes, respectively, as a bonding tool. This allows the bonding stage 20 to adjust the relative position and parallelism of the upper workpiece Ma and the lower workpiece Mb. The bonding stage 20 can also bond the workpieces Ma and Mb.

[0049] <Upper and lower 2-field optical system> The vertical two-field optical system 30 is inserted between the objects to be bonded Ma and Mb, and simultaneously images both objects to be bonded Ma and Mb. However, the vertical two-field optical system 30 is not limited to being inserted between the upper object to be bonded Ma and the lower object to be bonded Mb and simultaneously imaging both objects; for example, it may be inserted between the left object to be bonded Ma and the right object to be bonded Mb and simultaneously imaging both objects to the left and right. In other words, the vertical two-field optical system 30 may simultaneously image two opposite directions, such as left and right, not just vertically. In this sense, the vertical two-field optical system 30 may simply be called a two-field optical system.

[0050] The vertical two-field optical system 30 includes an optical unit 31 and a drive mechanism 32. The drive mechanism 32 is fixed to the base frame 70. The drive mechanism 32 is fixed to, for example, the upper frame 72. The drive mechanism 32 moves the optical unit 31 in parallel in the X, Y, and Z axes. The drive mechanism 32 may also rotate the optical unit 31 using a rotation axis that rotates around the X, Y, and Z axes. The drive mechanism 32 moves the optical unit 31 between a plurality of alignment marks. The drive mechanism 32 also moves the optical unit 31 in the Z-axis direction to adjust the focus of the optical unit 31. The drive mechanism 32 may also adjust the inclination of the vertical two-field optical system 30.

[0051] <Tilt Sensor> The tilt sensor 40 detects the tilt of the upper and lower two-field optical system 30. The tilt sensor 40 includes, for example, a measuring unit 41 and a target 42. The measuring unit 41 is fixed to the upper frame 72 of the base frame 70. The target 42 is fixed to the optical section 31 of the upper and lower two-field optical system 30. The tilt sensor 40 measures the attitude of the upper and lower two-field optical system 30 relative to the base frame 70 by measuring the target 42 with the measuring unit 41.

[0052] The measuring unit 41 is, for example, a laser autocollimator, and the target 42 is, for example, a planar mirror. Alternatively, the tilt sensor 40 may include a measuring unit 41 with three or more distance sensors and a target 42, and measure the tilt angle from the distances between the three points.

[0053] <Calibration Block> The calibration block 50 serves as a reference for the optical properties of the optical components in the upper and lower two-field optical system 30. The calibration block 50 may be fixed to the bonding stage 20 or the base 71. The calibration block 50 has an upper plane 51, a lower plane 52, and a support portion 53. The support portion 53 supports the upper plane 51. The upper plane 51 and the lower plane 52 face each other.

[0054] <Calibration Pattern> The calibration block 50 has a pair of calibration patterns formed on an opposing upper plane 51 and lower plane 52. The distance between the upper plane 51 and the lower plane 52, the parallelism, and the relative positions of the calibration patterns are predetermined. For example, the distance between the upper plane 51 and the lower plane 52 is set to the distance between the bonding surfaces of the objects to be bonded Ma and Mb, and these two planes are set to be parallel. The upper and lower two-field optical system 30 can be inserted between the upper plane 51 and the lower plane 52. In this case, the relative positions of the calibration patterns on the upper plane 51 and the lower plane 52 are set to face the upper and lower fields of view of the upper and lower two-field optical system 30, respectively.

[0055] The upper and lower dual-field optical system 30 can calibrate the parameters of the optical section 31 of the upper and lower dual-field optical system 30, such as optical magnification, the relative relationship between the centers of the upper and lower fields of view, lens distortion, the mounting error of the target of the tilt sensor 40, and the position of the upper and lower dual-field optical system 30 itself within the mounting device 1, by recognizing each calibration pattern on each plane of the calibration block 50. The upper and lower dual-field optical system 30 uses the calibration block 50 at predetermined time intervals to detect changes in the optical characteristics of the optical section 31 over time. By devising the arrangement of the calibration block 50, periodic checks can be performed simultaneously during the process of picking up the upper workpiece Ma. For example, in the process of picking up the upper workpiece Ma, the bonding stage 20 or base 71 to which the calibration block 50 is fixed can be arranged to move near the upper and lower dual-field optical system 30. As a result, the upper and lower two-field optical system 30 allows the bonding head 10 to hold the workpiece Ma, while simultaneously detecting changes in the optical component over time using the calibration block 50.

[0056] <Department of Optical Science: Dual-Field Optical Systems> Figure 2 is a diagram illustrating the optical section 31 of the upper and lower two-field optical system 30 in the mounting device 1 according to Embodiment 1. As shown in Figure 2, the optical section 31 of the upper and lower two-field optical system 30 includes a plurality of optical elements, one image sensor 35, a reference mark 36, a backlight BL, a housing (not shown), and a light source (not shown). The plurality of optical elements include, for example, an objective lens 33a, an objective lens 33b, an imaging lens (Tube Lens) 34a, and an imaging lens 34b. The image of the upper object to be joined Ma is formed on the image sensor 35 via the objective lens 33a and the imaging lens 34a. The image of the lower object to be joined Mb is formed on the image sensor 35 via the objective lens 33b and the imaging lens 34b.

[0057] For example, the image sensor 35 acquires an image of the first alignment mark formed on the workpiece Ma and the second alignment mark formed on the workpiece Mb simultaneously. Multiple optical elements project images of each alignment mark onto the image sensor 35. Alternatively, a configuration in which the upper workpiece Ma is imaged onto the image sensor 35 and a configuration in which the lower workpiece Mb is imaged onto the image sensor 35 may be configured using a common objective lens and a common imaging lens.

[0058] In Figure 2, the objects to be joined, Ma and Mb, are shown as being on the left, but in reality, as shown in Figure 1, the objects to be joined, Ma and Mb, are positioned opposite each other with the optical unit 31 in between. Therefore, some optical components are omitted in Figure 2. For example, in Figure 2, the bending of the optical path is minimized to illustrate the upper and lower two-field optical system 30, but in reality, it may be bent with a planar mirror as appropriate in order to incorporate it into a compact housing. The housing fixes the multiple optical components of the optical unit 31.

[0059] Figures 3 to 5 illustrate images formed on the image sensor 35 in the mounting device 1 according to Embodiment 1. As shown in Figures 3 and 4, it is desirable to align the orientation of the coordinates in the images of the objects to be joined Ma and Mb formed on the image sensor 35. That is, by devising the number of reflections in the optical unit 31, the orientation of the images of the objects to be joined Ma and Mb as seen from the upper and lower two-field optical system 30 side is aligned with the orientation of the image on the image sensor 35, so that the orientation of the images of the objects to be joined Ma and Mb and the orientation of the image on the image sensor 35 are not opposite.

[0060] For example, the vertical two-field optical system 30 is set so that the first orientation (e.g., -Z axis direction) of the first alignment mark as viewed from the vertical two-field optical system 30 and the second orientation (e.g., -Z axis direction) of the second alignment mark as viewed from the vertical two-field optical system 30 are the same as the first and second orientations on the image sensor 35. This eliminates the error factor of the parallel translation component of the image sensor 35. As a result, further improvements in accuracy can be achieved.

[0061] On the other hand, as shown in Figure 5, if the coordinate orientations of the images of the joined objects Ma and Mb formed on the image sensor 35 are misaligned, the temporal positional change of the image sensor 35 may result in recognition errors. In such cases, it is desirable to periodically perform correction using a fiducial mark, as described later.

[0062] <Tilt Sensor> As shown in Figure 2, the tilt sensors 60a and 60b measure the angle of the bonding surfaces of the bonded objects Ma and Mb with respect to the upper and lower two-field optical system 30 by using the optical elements of the upper and lower two-field optical system 30. Specifically, the tilt sensors 60a and 60b detect the parallelism between the first bonding surface of the bonded object Ma and the second bonding surface of the bonded object Mb. The tilt sensors 60a and 60b are, for example, autocollimators that use laser light as detection light. The autocollimator includes a detection light emitter and a light receiver. The autocollimator uses detection light transmitted through at least one optical element of the upper and lower two-field optical system 30. For example, the autocollimator uses detection light transmitted through objective lenses 33a and 33b. The tilt sensors 60a and 60b may also be electronic types that detect the amount of lateral displacement of the reticle image.

[0063] Multiple optical elements of the upper and lower two-field optical system 30 cause images of the first alignment mark formed on the first bonding surface and the second alignment mark formed on the second bonding surface to be projected onto the image sensor 35. The illumination light used to image the first and second alignment marks includes wavelengths different from the detection light of the autocollimator.

[0064] In the optical unit 31, it is desirable that the tilt sensors 60a and 60b use detection light that passes through a common optical path with the optical elements of the imaging system. Therefore, when green light is used as the illumination light for image recognition of the alignment marks, the tilt sensors 60a and 60b use red light as the detection light for the autocollimator. The optical elements include dichroic mirrors 61a and 61b that combine and separate the illumination light and the detection light.

[0065] For example, the detection light reflected from the workpiece Ma passes through the objective lens 33a, is reflected by the dichroic mirror 61a, and is detected by the tilt sensor 60a via lens 62a. Similarly, the detection light reflected from the workpiece Mb passes through the objective lens 33b, is reflected by the dichroic mirror 61b, and is detected by the tilt sensor 60b via lens 62b.

[0066] To make the laser autocollimator used in tilt sensors 60a and 60b small, fast, and highly accurate, it is desirable to use a 4PD or PSD as the photodetector. However, in the case of a 4PD or PSD, the quality of the intensity distribution of the detected laser spot is important, so measures must be taken to prevent stray light and ghosts (false spots caused by partial reflection from the transmission surface) from occurring in the return optical path.

[0067] Instead of 4PDs and PSDs, two-dimensional image sensors such as CMOS can also be used. In this case, although the device size will be larger and the speed will be slower, stray light and ghosting can be removed through image processing. Therefore, the burden on optical design can be reduced.

[0068] In this embodiment, in order to match the image recognition range with the parallelism measurement range, the optical paths of the imaging systems of the joined objects Ma and Mb and the optical paths of the tilt sensors 60a and 60b are arranged in a coaxial structure. However, if design limitations arise due to sharing optical paths, a layout in which the optical paths of the tilt sensors 60a and 60b are placed next to the optical path of the imaging system, without using a coaxial configuration, can also be considered. In that case, movement is required only by the offset between the image recognition center and the measurement position center of the tilt sensors 60a and 60. Therefore, throughput decreases due to the added movement time, and errors due to the movement are added. However, the detection method can be expanded to include methods using three or more distance sensors or interferometers.

[0069] <Standard Mark> Figure 6 is a diagram illustrating the reference marks of the upper and lower two-field optical system 30 in the mounting device 1 according to Embodiment 1. As shown in Figures 2 and 6, the reference marks 36 are fixed to a housing (not shown) of the upper and lower two-field optical system 30. The reference marks 36 have a reference mark 36a for the upper field of view and a reference mark 36b for the lower field of view. The reference marks 36a and 36b are positioned in an optically conjugate relationship with the image sensor 35. The reference marks 36a and 36b are, for example, made by forming slits or reticles in a light-shielding plate. By using the reference marks 36, the effect of changes in the position of the image sensor 35 over time can be corrected.

[0070] Figure 7 is a diagram illustrating reference marks imaged onto the image sensor 35 in the mounting device 1 according to Embodiment 1. As shown in Figures 2 and 7, the reference mark 36 is imaged by the image sensor 35. The reference mark 36a is imaged onto the image sensor 35 by the imaging lens 34a via the objective lens 37a, mirrors 38a and 39a. The reference mark 36b is imaged onto the image sensor 35 by the imaging lens 34b via the objective lens 37b, mirrors 38b and 39b. The objective lenses 37a and 37b are dedicated to the reference marks 36a and 36b, while the imaging lenses 34a and 34b are shared with the imaging of the objects to be bonded Ma and Mb.

[0071] Reference marks 36a and 36b are fixed to the housing, for example, in a manner that prevents displacement or expansion / contraction due to heat or mechanical stress. When images of reference marks 36a and 36b are to be acquired by the image sensor 35, a dedicated backlight BL for reference marks 36a and 36b is turned on, and the transmitted light from reference marks 36a and 36b is captured. By turning off the backlight BL, the images of reference marks 36a and 36b are no longer captured.

[0072] Thus, the upper and lower two-field optical system 30 has a backlight BL as a switch means to cause the image sensor 35 to acquire an image of the reference mark 36 at a predetermined time. Note that the switch means for causing the image sensor 35 to acquire an image of the reference mark 36 is not limited to turning the backlight BL on or off, but may also be the movement of optical elements such as mirrors 38a, 38b, 39a, 39b. The switch means can suppress interference when imaging the images of the objects to be joined Ma and Mb. Furthermore, the predetermined time for the image sensor 35 to acquire the reference mark 36 is preferably, for example, after the upper and lower two-field optical system 30 has been inserted between the objects to be joined Ma and Mb and immediately before the image sensor 35 acquires the alignment mark, but it is not limited to this.

[0073] <Alignment Marks> The objects to be bonded, Ma and Mb, have matching alignment marks formed on them, one above the other. If the objects to be bonded, Ma and Mb, are large relative to the field of view, the bonding head 10 and / or bonding stage 20, which function as a bonding tool, move to multiple locations on the objects M1 and M2 to recognize the matching alignment marks at each location. To minimize misalignment of the alignment marks at all positions, the bonding head 10 and / or bonding stage 20 adjust the relative position and parallelism of the upper object to be bonded Ma and the lower object to be bonded Mb based on the image acquired by the image sensor 35, thereby bonding the objects to be bonded Ma and Mb.

[0074] In addition to implementing the above-mentioned measures to suppress mounting errors, a test mounting is performed in advance to eliminate any remaining bonding errors. For the test mounting, for example, a glass dummy chip is used. Since the alignment marks can be observed from both the front and back surfaces of the dummy chip, after the test mounting, the alignment marks of the joined objects Ma and Mb are simultaneously recognized from above the upper dummy chip using the lower field of view of the upper and lower two-field optical system 30. The deviation between each alignment mark is stored as the residual mounting error, and during the actual mounting, the value obtained by subtracting the residual mounting error is used as the target value.

[0075] <Implementation Method> Next, we will explain the mounting method using the mounting device 1. Figure 8 is a flowchart illustrating the mounting method according to Embodiment 1.

[0076] As shown in step S11 of Figure 8, the lower workpiece Mb is held by the bonding stage 20.

[0077] Next, as shown in step S12, the upper workpiece Ma is held by the bonding head 10. Specifically, a member supply unit such as a die lifter is positioned on the bonding stage 20. Therefore, by moving the bonding stage 20, the die lifter is positioned below the bonding head 10. This allows the head 11 of the bonding head 10 to grip the upper workpiece Ma from the die lifter.

[0078] If the calibration block 50 is fixed to the bonding stage 20 or base 71, the upper and lower two-field optical system 30 may use the calibration block 50 to detect changes in optical properties over time while the bonding head 10 holds the workpiece Ma. Alternatively, by using the calibration block to detect changes over time at predetermined time intervals, the upper and lower two-field optical system 30 may be periodically checked, and the parameters of the optical components of the optical unit 31 may be corrected.

[0079] Next, as shown in step S13, the assembly area is moved. Specifically, the bonding stage 20 is moved to move the assembly area of ​​the lower workpiece Mb below the bonding head 10.

[0080] Next, as shown in step S14, the upper and lower two-field optical system 30 is inserted between the upper object to be joined Ma and the lower object to be joined Mb. Then, the upper and lower two-field optical system 30 is used to simultaneously image the objects to be joined Ma and Mb. Specifically, the alignment marks are captured within the field of view of the upper and lower two-field optical system 30 that has been inserted between the objects to be joined Ma and Mb.

[0081] Next, as shown in step S15, the parallelism of the objects to be joined Ma and Mb is detected by the tilt sensors 60a and 60b. Specifically, the parallelism between the first joining surface of the object to be joined Ma and the second joining surface of the object to be joined Mb is detected by the tilt sensors 60a and 60b. Alternatively, the inclination of the upper and lower two-field optical system 30 may be detected by the tilt sensor 40.

[0082] Next, as shown in step S16, the detected parallelism is adjusted. Specifically, the detected parallelism is adjusted by at least one of the bonding tools on the bonding head 10 and the bonding stage 20. Alternatively, the tilt detected by the tilt sensor 40 may be adjusted by the drive mechanism 32 of the upper and lower two-field optical system 30.

[0083] Next, as shown in step S17, the image sensor 35 is used to detect misalignment of the upper and lower alignment marks. Specifically, for example, an image is acquired by simultaneously capturing the first alignment mark formed on the workpiece Ma and the second alignment mark formed on the workpiece Mb using one image sensor 35 in the upper and lower two-field optical system 30.

[0084] Before acquiring images of each alignment mark simultaneously captured by the image sensor 35, the image sensor 35 may, if necessary, be allowed to acquire an image of the reference mark 36. For example, when joining objects Ma and Mb, the image sensor 35 may be allowed to acquire an image of the reference mark 36 each time to adjust for positional misalignment. This can be used to correct for changes in the image sensor 35 over time. The amount of positional misalignment of the alignment marks is calculated by considering the information from the acquired images and the attitude information of the upper and lower two-field optical system 30 itself, measured by the tilt sensor 40.

[0085] Next, the misalignment is adjusted as shown in step S18. Specifically, the relative positions of the workpieces Ma and Mb are adjusted in at least one of the bonding head 10 and bonding stage 20 based on the alignment mark image acquired by the image sensor 35.

[0086] Next, as shown in step S19, the upper workpiece Ma and the lower workpiece Mb are joined together. Specifically, for example, the bonding head 10, which acts as a bonding tool, is lowered and the upper workpiece Ma is pressed and joined to the lower workpiece Mb.

[0087] Next, as shown in step S20, it is determined whether all sections have been mounted. If the answer is NO (not mounted in all sections), the process returns to step S12, moves to an un-mounted section in the lower workpiece Mb, and repeats steps S12 to S20. In step S20, if the answer is YES (all sections have been mounted), it is determined as shown in step S21 whether the predetermined number of layers has been reached. If the answer is NO (not reached), the process returns to step S12 and repeats steps S12 to S21. In step S21, if the answer is YES (the predetermined number of layers has been reached), the process ends. In this way, semiconductor devices including workpieces Ma and Mb can be mounted.

[0088] Next, the effects of this embodiment will be explained. The implementation device 1 of this embodiment can achieve high-precision implementation by at least one of the following: simultaneously acquiring images of the upper and lower joined objects Ma and Mb with a single image sensor 35; the upper and lower two-field optical system 30 having a built-in reference mark 36; the upper and lower two-field optical system 30 having built-in tilt sensors 60a and 60b; correcting the attitude changes of the upper and lower two-field optical system 30 itself; and using a calibration block 50 to grasp and correct the temporal changes of the upper and lower two-field optical system 30. A detailed explanation follows below.

[0089] 1. The upper and lower dual-field optical system 30 can simultaneously image the upper and lower joined objects Ma and Mb with a single image sensor 35. The image sensor 35 undergoes positional displacement over time due to thermal and mechanical factors. The amount of positional displacement is added directly as an error in the recognition position of the joined objects Ma and Mb. In addition, points of interest on the image fluctuate over time due to minute mechanical vibrations, etc. Optical magnification tends to be increased to improve the accuracy of image recognition, but the higher the magnification, the more the effects of minute vibrations are amplified and captured. Therefore, if the images of the upper and lower joined objects Ma and Mb are not captured at the same time, errors due to fluctuations will be added.

[0090] If the image sensors 35 are separate for the upper and lower fields of view, independent errors are added to each of the upper and lower images, and the [relative position between the upper and lower joined objects Ma and Mb] calculated from the results obtained from each image accumulates errors. If the upper and lower recognition is performed simultaneously with a single image sensor 35, the [relative position between the upper and lower joined objects Ma and Mb] is calculated from a single image, so there is no accumulation of errors due to the positional shift of the image sensor 35 or errors added due to the timing difference of the image capture, and the recognition accuracy is improved. Furthermore, if the optical system is designed so that the relative orientation (direction) of the upper and lower images is equal to the relative orientation (direction) of the upper and lower objects, the effect of the positional shift (translational translation component) of the image sensor 35 can be eliminated.

[0091] 2. To understand and correct the positional displacement of the image sensor 35 over time, a reference mark 36 is always visible in the field of view. The image sensor 35 experiences positional displacement over time due to thermal and mechanical factors, and the amount of positional displacement is added directly as an error in the recognition position. A reference mark 36, such as a slit or reticle, is placed inside the upper and lower two-field optical system 30 at a position that is optically conjugate to the image sensor 35. By enabling the backlight BL to capture a transmitted image of the reference mark 36, the amount of pixel movement over time can be understood using the reference mark 35 as a reference. When the backlight BL is turned off, the image of the reference mark 36 becomes invisible, and only the upper and lower joined objects Ma and Mb are visible. By understanding the positional displacement of the image sensor 35 immediately before recognizing the upper and lower joined objects Ma and Mb, and correcting the positional displacement from the recognition result, the recognition error can be reduced. In addition, since the positional displacement can be checked using the reference mark 36 each time before mounting the joined object Ma, the recognition error can be reduced.

[0092] 3. The system has a mechanism for understanding and correcting changes in the orientation of the upper and lower dual-field optical system 30. When the upper and lower dual-field optical system 30 simultaneously recognizes the upper and lower alignment marks, if the orientation of the upper and lower dual-field optical system 30 is tilted, a large error is added to the recognition result of the alignment marks. The upper and lower dual-field optical system 30 has a drive axis in at least the horizontal plane in order to move in and out between the joined objects Ma and Mb in order to perform image recognition. Suppressing the pitching and rolling of the drive axis to a few μrad leads to an increase in equipment cost. Therefore, in this embodiment, a tilt sensor 40 is provided for measuring the pitching and rolling of the upper and lower dual-field optical system 30. Image recognition of the upper and lower joined objects Ma and Mb is performed simultaneously with understanding the orientation using the tilt sensor 40. This makes it possible to eliminate errors caused by changes in orientation when calculating the relative position between the upper and lower joined objects Ma and Mb, and improve the recognition accuracy.

[0093] 4. To grasp and correct the parallelism between the bonding surfaces of the upper and lower bonded objects Ma and Mb, coaxial tilt sensors 60a and 60b are built into the upper and lower two-field optical system 30. It is desirable that the parallelism measurement by the tilt sensors 60a and 60b be evaluated at the same location simultaneously with image recognition by the upper and lower two-field optical system 30. For this reason, the tilt sensors 60a and 60b are implemented, for example, as small laser autocollimators and built into the upper and lower two-field optical system 30. By coaxially irradiating detection light from the objective lenses 33a and 33b of the upper and lower two-field optical system 30, image recognition of alignment marks and angle detection can be performed simultaneously at the same location.

[0094] 5. To compensate for changes in the upper and lower two-field optical system 30 over time, a reference calibration block 50 is provided within the mounting device 1. The upper and lower two-field optical system 30 has its optical parameters acquired in advance in order to calculate the position of an object from the captured image. However, the optical components of the upper and lower two-field optical system 30 deform over time due to heat and mechanical stress. As a result, errors occur in the optical parameters, and errors are added to the estimated position of the object calculated. Therefore, for example, by fixing the calibration block on the bonding stage 20 and performing image recognition periodically, changes in the optical parameters can be corrected. This makes it possible to eliminate errors caused by the deformation of the upper and lower two-field optical system 30.

[0095] The present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. For example, each component of Embodiment 1 can be omitted or combined with others as appropriate. [Explanation of symbols]

[0096] 1. Mounting device 10 Bonding Heads 11 heads 12 Drive mechanism 20 Bonding Stages 21 stages 22 Drive mechanism 30 Upper and lower two-view optical system 31 Optics Department 32 Drive mechanism 33a, 33b objective lenses 34a, 34b imaging lenses 35 Image Sensors 36, 36a, 36b Reference marks 37a, 37b objective lenses 38a, 38b, 39a, 39b Miller 40 Tilt Sensor 41 Measuring part 42 Targets 50 Calibration Blocks 51 Upper plane 52 Lower plane 53 Support part 60a, 60b tilt sensor 61a, 61b Dichroic mirrors 62a, 62b lenses 70 Base Frame 71 Base 72 Upper frame 73 Side frame Ma, Mb welded material BL backlight

Claims

1. A bonding head that holds the first member, A bonding stage for holding the second member, The system includes an upper and lower two-field optical system inserted between the first member and the second member, which simultaneously photographs the first member and the second member, The aforementioned upper and lower two-field optical system is The system includes one image sensor that acquires an image of a first alignment mark formed on the first member and a second alignment mark formed on the second member simultaneously. Using illumination light, the first alignment mark image and the second alignment mark image are acquired, and the images of the first alignment mark and the second alignment mark are arranged on the image sensor so as not to overlap and formed as images. The parallelism between the first joining surface of the first member and the second joining surface of the second member is detected using detection light with a different wavelength from the illumination light. At least one of the bonding head and the bonding stage adjusts the relative position and parallelism of the first member and the second member based on the image of the first alignment mark, the image of the second alignment mark, and the parallelism, and joins the first member and the second member. Mounting device.

2. The aforementioned upper and lower two-field optical system is A plurality of optical members that project images of the first alignment mark and the second alignment mark onto the image sensor, A housing for fixing the optical element, A reference mark fixed to the housing for detecting changes in the position of the image sensor over time, After inserting the upper and lower two-field optical system between the first member and the second member, and immediately before the first alignment mark and the second alignment mark are acquired by the image sensor, a switch means is provided to cause the image sensor to acquire an image of the reference mark. It further possesses, The mounting device according to claim 1.

3. A tilt sensor for detecting the tilt of the upper and lower two-field optical system, Furthermore, The aforementioned upper and lower two-field optical system further includes a first drive mechanism for adjusting the tilt. The mounting apparatus according to claim 1 or 2.

4. A tilt sensor for detecting the degree of parallelism between the first joining surface of the first member and the second joining surface of the second member, Furthermore, At least one of the bonding head and the bonding stage has a second drive mechanism for adjusting the relative position and parallelism to join the first member and the second member. The mounting apparatus according to any one of claims 1 to 3.

5. The upper and lower two-field optical system further comprises a plurality of optical members that image the first alignment mark formed on the first bonding surface and the second alignment mark formed on the second bonding surface onto the image sensor. The tilt sensor is an autocollimator that uses detection light transmitted through at least one of the optical elements. The mounting apparatus according to claim 4.

6. The optical member includes a dichroic mirror that combines and separates the illumination light and the detection light. The mounting apparatus according to claim 5.

7. A calibration block that serves as a reference for the optical characteristics of the optical elements in the upper and lower two-field optical system, Furthermore, The upper and lower two-field optical system detects the change in the optical characteristics over time using the calibration block at predetermined time intervals. The mounting apparatus according to any one of claims 1 to 6.

8. The calibration block has a pair of calibration patterns formed on opposing upper and lower planes, The distance between the upper plane and the lower plane, the parallelism, and the relative positions of the calibration patterns are predetermined. The mounting apparatus according to claim 7.

9. The calibration block is fixed to the bonding stage or base, The upper and lower two-field optical system, when the bonding head holds the first member, simultaneously uses the calibration block to detect the change over time. The mounting apparatus according to claim 7 or 8.

10. The upper and lower two-field optical system is configured such that the first orientation of the first alignment mark as viewed from the upper and lower two-field optical system side and the second orientation of the second alignment mark as viewed from the upper and lower two-field optical system side are the same as the first orientation and the second orientation on the image sensor. The mounting apparatus according to any one of claims 1 to 9.

11. The steps include: holding the first member with a bonding head, The steps include: holding the second member with a bonding stage, The step of inserting an upper and lower two-field optical system between the first member and the second member, The steps include simultaneously acquiring a first alignment mark formed on the first member and a second alignment mark formed on the second member using illumination light with one image sensor in the upper and lower two-field optical system, and arranging the images of the first alignment mark and the second alignment mark on the image sensor so as not to overlap and forming an image, A step of detecting the parallelism between the first joining surface of the first member and the second joining surface of the second member using detection light with a different wavelength from the illumination light, A step of causing at least one of the bonding head and the bonding stage to adjust the relative position and parallelism of the first member and the second member based on the aforementioned image and the parallelism, The steps of joining the first member and the second member, An implementation method that includes the following features.

12. In the step of inserting the upper and lower two-field optical system, The aforementioned upper and lower two-field optical system is A plurality of optical members that project images of the first alignment mark and the second alignment mark onto the image sensor, A housing for fixing the optical element, A reference mark fixed to the housing for detecting changes in the position of the image sensor over time, It has, Before the step of arranging the images of the first alignment mark and the second alignment mark on the image sensor so as not to overlap and forming an image, the upper and lower two-field optical system is inserted between the first member and the second member, and immediately before the image sensor acquires the first alignment mark and the second alignment mark, the image sensor acquires the image of the reference mark. Furthermore, The implementation method according to claim 11.

13. The steps include: detecting the inclination of the upper and lower two-field optical system using a tilt sensor; The steps include adjusting the detected tilt using the first drive mechanism in the upper and lower two-field optical system, Furthermore, The implementation method according to claim 11 or 12.

14. The steps include: detecting the degree of parallelism between the first joining surface of the first member and the second joining surface of the second member using a tilt sensor; The steps include adjusting the parallelism using a second drive mechanism in at least one of the bonding head and the bonding stage, Furthermore, In the step of adjusting the relative position, The second drive mechanism adjusts the relative position, In the step of joining, The second drive mechanism connects them. The implementation method according to any one of claims 11 to 13.

15. In the step of inserting the upper and lower two-field optical system, The upper and lower two-field optical system has a plurality of optical members that image the first alignment mark formed on the first bonding surface and the second alignment mark formed on the second bonding surface onto the image sensor. In the step of detecting by the tilt sensor, The tilt sensor is an autocollimator that uses detection light transmitted through at least one of the optical elements. The implementation method according to claim 14.

16. In the step of detecting by the tilt sensor, The dichroic mirror in the optical member combines and separates the illumination light and the detection light. The implementation method according to claim 15.

17. A step of detecting the change in optical characteristics over time at predetermined time intervals using a calibration block that serves as a reference for the optical characteristics of the optical elements in the upper and lower two-field optical system, Furthermore, The implementation method according to any one of claims 11 to 16.

18. In the step of detecting the change over time, The calibration block has a pair of calibration patterns formed on opposing upper and lower planes, The distance between the upper plane and the lower plane, the parallelism, and the relative positions of the calibration patterns are predetermined. The implementation method according to claim 17.

19. In the step of detecting the change over time, The calibration block is fixed to the bonding stage or base, The upper and lower two-field optical system, when the bonding head holds the first member, simultaneously uses the calibration block to detect the change over time. The implementation method according to claim 17 or 18.

20. In the step of inserting the upper and lower two-field optical system, The upper and lower two-field optical system is configured such that the first orientation of the first alignment mark as viewed from the upper and lower two-field optical system side and the second orientation of the second alignment mark as viewed from the upper and lower two-field optical system side are the same as the first orientation and the second orientation on the image sensor. The implementation method according to any one of claims 11 to 19.

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