Illumination optical system for wafer bonding and wafer bonding alignment system

Abstract

The invention provides an illumination optical system for wafer bonding and a wafer bonding alignment system, and relates to the technical field of semiconductor processing, the illumination optical system comprises a first near-infrared light source, a second near-infrared light source, a third near-infrared light source and a fourth near-infrared light source, the light outlet of each near-infrared light source is provided with an optical filter; a light outlet of the first near-infrared light source and a light outlet of the second near-infrared light source are coupled through a two-in-one optical fiber and then connected to the lighting system, and a light outlet of the third near-infrared light source and a light outlet of the fourth near-infrared light source are coupled through a two-in-one optical fiber and then connected to the lighting system. And four beams of monochromatic light with set wavelengths, which are obtained after being filtered by the optical filter, are connected into an illumination system, and two pairs of parallel light beams with corresponding angles are generated and are incident into an entrance pupil of the large-view-field near-infrared dispersion microscope objective. According to the invention, the light spots can be formed only in the shooting area, the energy utilization rate of the light source is greatly improved, and the illumination requirement of high-precision bonding of the chip and the wafer is ensured.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and more specifically to an illumination optical system and a wafer bonding alignment system for wafer bonding. Background Technology

[0002] Alignment accuracy is the most critical factor in ensuring wafer bonding quality in wafer bonding equipment, and the vision system plays a decisive role. The latest high-precision bonding equipment uses near-infrared optical systems, which can penetrate the semiconductor wafer to directly observe the marking points. A major application of bonding is wafer-to-wafer bonding (W2W). In wafer-to-wafer bonding, marking points are made on the edges of each wafer, and then two vision systems are used to bond these marking points separately. During the bonding process, the infrared system first observes the marking points on the lower surface of the upper wafer. Then, a piezoelectric ceramic actuator moves the entire optical system downwards to observe the marking points on the upper surface of the lower wafer. The positions of the marking points on both wafers are recorded. Finally, a high-precision displacement platform adjusts the position of the lower wafer to move the lower wafer marking points to the upper wafer marking points. In this process, because the infrared system can observe the marking point positions, bonding accuracy is significantly improved.

[0003] Another important application of bonding is die-to-wafer bonding (D2W), which involves bonding a chip to a wafer. D2W typically requires the simultaneous alignment of two marker points—two marker points on the wafer and two marker points on the chip. Unlike W2W, chips are usually very small, requiring markers with an alignment interval of several millimeters to tens of millimeters. In most samples, the distance between the two marker points is in the range of 6–11 mm. Conventional high-magnification microscopes (with a very small object-side field of view, only 0.8 mm with a 10X infrared camera and optical system) cannot cover both marker points within this range, and the spacing between the two marker points cannot accommodate two separate systems. Therefore, using conventional objectives cannot simultaneously align two marker points spaced only a few millimeters apart.

[0004] To simultaneously image four markers on a chip and a wafer using a single vision system, a large-field-of-view dispersive microscope objective is required. However, using a large-field-of-view dispersive microscope objective places very high demands on the illumination system, requiring the energy of the light source to be distributed across the entire objective's field of view. In reality, only a very small portion of the objective's field of view is imaged, so only a small portion of the energy is utilized. Furthermore, due to the use of a light source with very high monochromaticity, the illumination energy utilization rate is very low, resulting in a very serious waste of energy, and it may even fail to meet the imaging requirements. Summary of the Invention

[0005] In view of this, embodiments of this application provide an illumination optical system and a wafer bonding alignment system for wafer bonding. The illumination system enables the formation of light spots only in the imaging area, greatly improving the energy utilization of the light source and ensuring high-precision bonding between the chip and the wafer.

[0006] This application provides the following technical solution: an illumination optical system for wafer bonding, comprising:

[0007] A first light source system, comprising a first near-infrared light source and a second near-infrared light source, wherein filters are respectively provided at the light outlets of the first near-infrared light source and the second near-infrared light source;

[0008] The second light source system includes a third near-infrared light source and a fourth near-infrared light source, and the light outlets of the third near-infrared light source and the fourth near-infrared light source are respectively provided with filters;

[0009] The illumination system comprises the light-emitting ports of the first and second near-infrared light sources, which are connected to the illumination system via a two-in-one optical fiber coupling. The light-emitting ports of the third and fourth near-infrared light sources are also connected to the illumination system via a two-in-one optical fiber coupling. This allows four monochromatic light beams of a set wavelength, obtained after being filtered by the filter, to enter the illumination system. After passing through the illumination system, two pairs of parallel beams at corresponding angles are generated and incident on the entrance pupil of the large field-of-view near-infrared dispersive microscope objective.

[0010] The large field-of-view near-infrared dispersive microscope objective operates in the wavelength range of 1.1–1.3 μm. The optical lenses of the illumination system adopt a telecentric optical path design. The optical lenses, from the incident side to the exit side, include: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The focal length of the optical lenses is f = 350 mm, and the aperture D of the first lens is ≥ 100 mm.

[0011] According to one embodiment of this application, the first lens is a biconvex positive lens, the second lens is a meniscus positive lens, the third lens is a biconcave negative lens, the fourth lens is a meniscus negative lens, and the fifth lens is a biconvex positive lens; wherein, the first lens, the second lens, the fourth lens, and the fifth lens are made of K9 glass.

[0012] According to one embodiment of this application, the end face diameter of the two-in-one optical fiber is 8 mm.

[0013] According to one embodiment of this application, the radius of curvature of the first surface of the first lens is r1, the radius of curvature of the second surface of the first lens is r2, the radius of curvature of the first surface of the second lens is r3, the radius of curvature of the second surface of the second lens is r4, the radius of curvature of the first surface of the third lens is r5, the radius of curvature of the second surface of the third lens is r6, the radius of curvature of the first surface of the fourth lens is r7, the radius of curvature of the second surface of the fourth lens is r8, and the radius of curvature of the first surface of the fifth lens is r9, the radius of curvature of the second surface of the fifth lens is r 10 And satisfying the following conditions: 70mm < r1 < 100mm, 1200mm < r2 < 1600mm, 80mm < r3 < 100mm, 2300mm < r4 < 2900mm, 140mm < r5 < 190mm, 50mm < r6 < 80mm, 40mm < r7 < 60mm, 60mm < r8 < 90mm, 260mm < r9 < 320mm, 180mm < r 10 <240mm.

[0014] According to one embodiment of this application, the thickness of the first lens is d1, the thickness of the second lens is d2, the thickness of the third lens is d3, the thickness of the fourth lens is d4, and the thickness of the fifth lens is d5, and satisfies the following conditions: 27mm < d1 < 33mm, 18mm < d2 < 22mm, 7mm < d3 < 9mm, 9mm < d4 < 11mm, and 18mm < d5 < 22mm.

[0015] According to one embodiment of this application, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, and the refractive index of the fifth lens is n5, and they satisfy the following relationship:

[0016] 1.35≤n1≤1.70;

[0017] 1.37≤n²≤1.67;

[0018] 1.50≤n3≤1.85;

[0019] 1.37≤n4≤1.67;

[0020] 1.37≤n5≤1.67.

[0021] According to one embodiment of this application, the filter is a narrowband filter with a bandwidth of 1 to 4 nm.

[0022] According to one embodiment of this application, the first near-infrared light source, the second near-infrared light source, the third near-infrared light source, and the fourth near-infrared light source are each equipped with a near-infrared light box, which is used to emit near-infrared bands with a set center wavelength.

[0023] This application also provides a wafer bonding alignment system, including:

[0024] Such as the illumination optics system used for wafer bonding described above;

[0025] A reflector and a beam splitter are arranged in parallel. The reflector is located at the light outlet of the illumination system and is used to reflect four beams of monochromatic light of a set wavelength to the beam splitter.

[0026] A large field-of-view near-infrared dispersive microscope objective is provided below the beam splitter, so that monochromatic light after passing through the beam splitter enters the large field-of-view near-infrared dispersive microscope objective.

[0027] A wafer and a chip are positioned on the object side of a large field-of-view near-infrared dispersive microscope objective, with the wafer and chip placed face-to-face. Two wafer alignment marks are provided on the lower surface of the wafer, and two chip alignment marks are provided on the upper surface of the chip. When four beams of monochromatic light of a set wavelength enter the large field-of-view near-infrared dispersive microscope objective, they simultaneously form focal points in the imaging areas of the two wafer alignment marks and the two chip alignment marks, respectively.

[0028] A wide-field telescope and an imaging device are arranged sequentially above the beam splitter. The imaging device includes a first infrared camera and a second infrared camera arranged side by side. After the four focal points on the wafer alignment mark and the chip alignment mark form four reflected images, the reflected waves pass through the beam splitter and the wide-field telescope in sequence, and finally form clear images in the fields of view of the first infrared camera and the second infrared camera, respectively.

[0029] According to one embodiment of this application, the focal length of the large field-of-view near-infrared dispersive microscope objective is f = 40 mm, and the incident angle is 6.6–7.9° when the maximum field of view is 4.7–5.5 mm; the entrance pupil of the large field-of-view near-infrared dispersive microscope objective is 28 mm.

[0030] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: using the illumination optical system and wafer bonding alignment system in the embodiments of this invention, adjacent mark points of the chip and wafer to be bonded can be observed simultaneously during the bonding process. With a large NA and a large field of view, adjacent mark points on the same layer can be observed very clearly at the same time using a single system. Due to the adoption of a special illumination system, the illumination source can be projected only onto the actual imaging area of ​​the objective lens, and by adjusting the position of the two optical fibers, corresponding illumination can be formed in different areas within the field of view of the objective lens. While greatly improving the energy utilization rate, it can also be applied to samples with different interval marks, thereby facilitating image acquisition and improving the bonding accuracy, efficiency and versatility of the system. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall structure of the illumination optical system and alignment system for wafer bonding according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the illumination optical system for wafer bonding according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the illumination optical system structure for wafer bonding according to an embodiment of the present invention;

[0035] Among them, 1-first near-infrared light box, 2-second near-infrared light box, 3-third near-infrared light box, 4-fourth near-infrared light box, 5-first narrowband filter, 6-second narrowband filter, 7-third narrowband filter, 8-fourth narrowband filter, 9-two-in-one optical fiber, 10-illumination system, 11-reflector, 12-beam splitter, 13-large field-of-view near-infrared dispersive microscope objective, 14-stage, 15-wafer, 16-chip, 17-first wafer alignment mark, 18-second wafer alignment mark, 19-first chip alignment mark, 20-second chip alignment mark, 21-large field-of-view tube lens, 22-first infrared camera, 23-second infrared camera, 24-optical fiber end face, 25-microscope objective entrance pupil, 26-sample imaging area. Detailed Implementation

[0036] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0037] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] like Figure 1 As shown, an embodiment of the present invention provides an illumination optical system for wafer bonding, comprising:

[0039] A first light source system, comprising a first near-infrared light source and a second near-infrared light source, wherein filters are respectively provided at the light outlets of the first near-infrared light source and the second near-infrared light source;

[0040] The second light source system includes a third near-infrared light source and a fourth near-infrared light source, and the light outlets of the third near-infrared light source and the fourth near-infrared light source are respectively provided with filters;

[0041] The illumination system 10 has the light output ports of the first and second near-infrared light sources connected to it via a two-in-one optical fiber 9. The light output ports of the third and fourth near-infrared light sources are also connected to the illumination system 10 via a two-in-one optical fiber 9. This allows four beams of monochromatic light of a set wavelength obtained after being filtered by the filter to enter the illumination system 10. After passing through the illumination system 10, two pairs of parallel beams at corresponding angles are generated and incident on the entrance pupil of the large field-of-view near-infrared dispersive microscope objective 13.

[0042] The large field-of-view near-infrared dispersive microscope objective operates in the wavelength range of 1.1–1.3 μm. The optical lenses of the illumination system 10 adopt a telecentric optical path design. The optical lenses, from the incident side to the exit side, include: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The focal length of the optical lenses is f = 350 mm, and the aperture D of the first lens is ≥ 100 mm.

[0043] Traditional chip-wafer bonding alignment systems use only one light source system to provide full illumination on the object side. This light source itself has very little energy after filtering, but the illumination range is very large, while only a small area is needed for imaging. This results in significant energy waste. In this invention, to ensure that the illumination source projects only onto the actual imaging area of ​​the objective lens and generates two illumination areas in the object side field of view, two light source systems are used. The optical structure of the illumination system is specifically designed so that it illuminates only the actual imaging area, rather than completely covering the objective lens field of view. This greatly improves energy utilization, thereby facilitating image acquisition and enhancing the bonding accuracy and efficiency of the system.

[0044] In one embodiment, the first lens of the lighting system 10 is a biconvex positive lens, the second lens is a meniscus positive lens, the third lens is a biconcave negative lens, the fourth lens is a meniscus negative lens, and the fifth lens is a biconvex positive lens; wherein the first lens, the second lens, the fourth lens, and the fifth lens are made of K9 glass.

[0045] In one embodiment, the end face diameter of the two-in-one optical fiber 9 is 8 mm, and the focal length of the optical lens of the illumination system 10 is f = 350 mm. The few millimeters of fiber end face 24 can produce parallel light with a small field of view. Two identical light source systems are used to illuminate the two marked areas of the objective lens. The illumination system has a large aperture (lens D ≥ 100 mm facing the optical fiber) and the position of the optical fiber can be adjusted (the optical fiber has a large adjustable range), thereby achieving illumination in different areas of the object.

[0046] like Figure 2 As shown, the fiber end face 24 is connected to the illumination system 10. In a specific implementation, two combined optical fibers 9 are used, each fiber corresponding to one field of view of the objective lens, i.e., one sample imaging area 26. The optical system in the illumination system 10 is similar to a tube lens, adopting a telecentric optical path design. The optical system design matches the objective lens, and the optical parameters of the illumination system are obtained according to the imaging angle of the objective lens and the diameter of the illumination fiber. That is, after the fiber passes through the illumination optical system, it generates parallel light at a corresponding angle that enters the entrance pupil 25 of the microscope objective lens.

[0047] In one embodiment, the radius of curvature of the first surface of the first lens is r1, the radius of curvature of the second surface of the first lens is r2, the radius of curvature of the first surface of the second lens is r3, the radius of curvature of the second surface of the second lens is r4, the radius of curvature of the first surface of the third lens is r5, the radius of curvature of the second surface of the third lens is r6, the radius of curvature of the first surface of the fourth lens is r7, the radius of curvature of the second surface of the fourth lens is r8, and the radius of curvature of the first surface of the fifth lens is r9, the radius of curvature of the second surface of the fifth lens is r 10And satisfying the following conditions: 70mm < r1 < 100mm, 1200mm < r2 < 1600mm, 80mm < r3 < 100mm, 2300mm < r4 < 2900mm, 140mm < r5 < 190mm, 50mm < r6 < 80mm, 40mm < r7 < 60mm, 60mm < r8 < 90mm, 260mm < r9 < 320mm, 180mm < r 10 <240mm.

[0048] According to one embodiment of this application, the thickness of the first lens is d1, the thickness of the second lens is d2, the thickness of the third lens is d3, the thickness of the fourth lens is d4, and the thickness of the fifth lens is d5, and satisfies the following conditions: 27mm < d1 < 33mm, 18mm < d2 < 22mm, 7mm < d3 < 9mm, 9mm < d4 < 11mm, and 18mm < d5 < 22mm.

[0049] According to one embodiment of this application, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, and the refractive index of the fifth lens is n5, and they satisfy the following relationship:

[0050] 1.35≤n1≤1.70;1.37≤n2≤1.67;1.50≤n3≤1.85;1.37≤n4≤1.67;1.37≤n5≤1.67;

[0051] In a further embodiment, n1 = n2 = n4 = n5.

[0052] Table 1 shows the optical lens design data for the lighting system 10 according to an embodiment of the present invention.

[0053] Table 1 Design data for the lighting system

[0054]

[0055] In this embodiment, the illumination system generates two relatively small illumination areas, corresponding to the shooting ranges of the two cameras in the wafer bonding alignment system. This significantly improves energy utilization, thereby facilitating image acquisition and enhancing the bonding accuracy and efficiency of the system. Furthermore, the two optical fibers can be symmetrically arranged to create corresponding illumination areas for shooting. When it is necessary to shoot other areas of the object, the positions of the optical fibers can be adjusted. Figure 3 As shown, this lighting system is compatible with markings at different intervals.

[0056] In this embodiment, the filter is a narrowband filter with a bandwidth of 1-4 nm. Specifically, the first and second near-infrared light sources are respectively a first near-infrared light box 1 and a second near-infrared light box 2, and the third and fourth near-infrared light sources are respectively a third near-infrared light box 3 and a fourth near-infrared light box 4, used to emit near-infrared wavelengths. The light outlet of the first near-infrared light box 1 is equipped with a first narrowband filter 5, the light outlet of the second near-infrared light box 2 is equipped with a second narrowband filter 6, the light outlet of the third near-infrared light box 3 is equipped with a third narrowband filter 7, and the light outlet of the fourth near-infrared light box 4 is equipped with a fourth narrowband filter 8. The optical fiber is a two-in-one optical fiber 9, through which two beams of monochromatic light of different wavelengths are coupled and connected to the lighting system 10.

[0057] To ensure clear imaging of the markers on chip 16 and wafer 15 simultaneously and to eliminate crosstalk from other wavelengths, four near-infrared lamp boxes are used. Narrowband filters are placed at the lamp box interfaces. These narrowband filters can achieve ±1nm bandwidth. To further improve monochromaticity, multiple narrowband filters can be placed, such as those with adjacent center wavelengths (e.g., 1199.5nm / 1200nm / 1201.5nm; since they all have ±1nm bandwidth, their superposition can produce a relatively pure 1200nm band). Each of the four lamp boxes contains a different filter, allowing for the emission of four preset wavelengths. A two-in-one fiber optic cable 9 is used to couple the light emitted from the four lamp boxes into a single fiber.

[0058] This application also provides a wafer bonding alignment system, including:

[0059] Such as the illumination optics system used for wafer bonding described above;

[0060] A reflector 11 and a beam splitter 12 are arranged in parallel. The reflector 11 is located at the light outlet of the illumination system 10 and is used to reflect four beams of monochromatic light of a set wavelength to the beam splitter 12.

[0061] A large field-of-view near-infrared dispersive microscope objective 13 is disposed below the beam splitter 12, so that monochromatic light after passing through the beam splitter 12 enters the large field-of-view near-infrared dispersive microscope objective 13.

[0062] A wafer 15 and a chip 16 are positioned below the large field-of-view near-infrared dispersive microscope objective 13, facing each other vertically. Two wafer alignment marks are respectively provided on the lower surface of the wafer 15, and two chip alignment marks are respectively provided on the upper surface of the chip 16. When four beams of monochromatic light of a set wavelength enter the large field-of-view near-infrared dispersive microscope objective 13, they simultaneously form focal points in the imaging areas of the two wafer alignment marks and the two chip alignment marks, respectively.

[0063] A wide-field telescope 21 and an imaging device are sequentially arranged above the beam splitter 12. The imaging device includes a first infrared camera 22 and a second infrared camera 23 arranged side by side. After the four focal points on the wafer alignment mark and the chip alignment mark form four reflected images, the reflected waves pass through the beam splitter 12 and the wide-field telescope 21 in sequence, and finally form clear images in the fields of view of the first infrared camera 22 and the second infrared camera 23 respectively.

[0064] In specific implementation, the lower surface of the wafer 15 is respectively provided with a first wafer alignment mark 17 and a second wafer alignment mark 18, and the upper surface of the chip 16 is respectively provided with a first chip alignment mark 19 and a second chip alignment mark 20 corresponding to the first wafer alignment mark 17 and the second wafer alignment mark 18. The wafer 15 is placed on a stage 14, and the chip 16 is picked up by a chip holder. The stage 14 is a transparent stage, and the alignment system is located below the stage 14, simultaneously observing two adjacent markers on the chip 16 and the wafer 15 through the stage 14. The chip holder adjusts its position according to feedback from the vision system, aligning the two markers on the chip 16 with the two markers on the wafer 15 before bonding.

[0065] In specific implementation, the position coordinates of the four focal points in the first infrared camera 22 and the second infrared camera 23 are read respectively. Based on the position coordinates, the compensation value of the wafer 15 and the chip 16 is calculated. The position of the chip 16 is adjusted according to the compensation value, and the chip 16 and the wafer 15 are aligned and corrected.

[0066] In practical implementation, the first near-infrared light box 1, the second near-infrared light box 2, the third near-infrared light box 3, and the fourth near-infrared light box 4 emit near-infrared bands. After being filtered by narrow-band filters in front of the light boxes, four wavelengths with very high monochromaticity are obtained (monochromatic light of a set wavelength can be obtained through the filters). The four light boxes enter the illumination system 10 through the two-in-one optical fiber 9, and then enter the large field-of-view near-infrared dispersive microscope objective 13 through the reflector 11 and the beam splitter 12. The dispersive microscope objective focuses the light onto the mark on the lower surface of the chip and the mark on the upper surface of the wafer, forming four focal points. Four reflected images are formed and returned to the vision system. The image reflected waves pass through the beam splitter 12 and the large field-of-view tube lens 21. Finally, two infrared cameras receive the alignment images of the adjacent marks on the wafer and the chip, which greatly improves the bonding accuracy.

[0067] Therefore, using the illumination optical system and alignment system for wafer bonding according to the embodiments of the present invention, adjacent mark points of the chip and wafer to be bonded can be observed simultaneously in real time during the bonding process. With a large NA and a large field of view, adjacent mark points on the same layer can be observed very clearly at the same time using a single system. Due to the special illumination system, the illumination source can be projected only onto the imaging area of ​​the objective lens, which greatly improves the energy utilization rate, thereby facilitating image acquisition and improving the bonding accuracy and efficiency of the system.

[0068] In practical implementation, the focal length of the large field-of-view near-infrared dispersive microscope objective is f = 40mm, the maximum field of view is 11mm, the corresponding half-field of view is 5.5mm, and the maximum range of the object receiving area for each camera is 4.7–5.5mm. The incident angle when the maximum field of view is 4.7–5.5mm is 6.6–7.9°; the entrance pupil of the large field-of-view near-infrared dispersive microscope objective is 28mm, which corresponds to the generation of a 28mm parallel beam. In practical implementation, different illumination areas can be formed by changing the position of the light source (i.e., the position of the optical fiber) to generate parallel light at different angles, depending on the actual situation.

[0069] Furthermore, since the infrared camera's field of view cannot cover the large field of view of the object side (object side field of view is 11mm, 10X system image side corresponds to 110mm, while the infrared camera's diagonal field of view is only 8mm), the large field of view tube lens 21 adopts a beam splitting design, that is, using two cameras to receive two marker images through the tube lens respectively. In addition, different interval marker imaging observations can be achieved by adjusting the interval between the two cameras (adjusting the interval between the two infrared cameras corresponds to different field of view of the object side), which is compatible with the alignment requirements of different types of chips and wafer bonding markers with intervals of 6-11mm.

[0070] Furthermore, the positions of the chip and wafer differ for different bonding processes, typically between 30 and 200 μm. Therefore, the large field-of-view near-infrared dispersive microscope objective uses a wavelength range of 1.1–1.3 μm. The focusing distances at 1.1 μm and 1.3 μm differ by 200 μm. The focusing distances within this wavelength range are essentially linearly related; for example, the difference between 1.1 μm and 1.2 μm is 100 μm, and so on. Thus, for bonding processes of different natures, only the filter in front of the lamp box needs to be changed to obtain clear images of the chip and wafer at different distances. This allows for rapid adaptation to different high-precision bonding requirements. Moreover, due to the good wavelength monochromaticity, the contrast of the wafer and chip mark images can be improved (multiple wavelengths affect the low frequencies of the image, i.e., contrast; single-wavelength images have better contrast), which is beneficial for algorithm processing.

[0071] This invention employs a special illumination system that projects the illumination source only onto the actual imaging area of ​​the objective lens, greatly improving energy utilization and thus facilitating image acquisition, thereby enhancing the bonding accuracy and efficiency of the system. Simultaneously, the wafer bonding alignment system utilizing this illumination system allows for simultaneous observation of adjacent mark points on both the chip and the wafer during the bonding process. With a large field of view and a wide field of view, a single system can clearly observe adjacent mark points on the same layer simultaneously, ensuring high-precision bonding between the chip and the wafer.

[0072] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An illumination optical system for wafer bonding, characterized in that, include: A first light source system, comprising a first near-infrared light source and a second near-infrared light source, wherein filters are respectively provided at the light outlets of the first near-infrared light source and the second near-infrared light source; The second light source system includes a third near-infrared light source and a fourth near-infrared light source, and the light outlets of the third near-infrared light source and the fourth near-infrared light source are respectively provided with filters; The illumination system comprises the light-emitting ports of the first and second near-infrared light sources, which are connected to the illumination system via a two-in-one optical fiber coupling. The light-emitting ports of the third and fourth near-infrared light sources are also connected to the illumination system via a two-in-one optical fiber coupling. This allows four monochromatic light beams of a set wavelength, obtained after being filtered by the filter, to enter the illumination system. After passing through the illumination system, two pairs of parallel beams at corresponding angles are generated and incident on the entrance pupil of the large field-of-view near-infrared dispersive microscope objective. The large field-of-view near-infrared dispersive microscope objective operates in the wavelength range of 1.1–1.3 μm. The optical lenses of the illumination system adopt a telecentric optical path design. The optical lenses, from the incident side to the exit side, include: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The focal length of the optical lenses is f = 350 mm, and the aperture D of the first lens is ≥ 100 mm.

2. The illumination optical system for wafer bonding according to claim 1, characterized in that, The first lens is a biconvex positive lens, the second lens is a meniscus positive lens, the third lens is a biconcave negative lens, the fourth lens is a meniscus negative lens, and the fifth lens is a biconvex positive lens; wherein the first lens, the second lens, the fourth lens, and the fifth lens are made of K9 glass.

3. The illumination optical system for wafer bonding according to claim 1, characterized in that, The end face diameter of the two-in-one optical fiber is 8mm.

4. The illumination optical system for wafer bonding according to claim 1, characterized in that, The radius of curvature of the first surface of the first lens is r1, the radius of curvature of the second surface of the first lens is r2, the radius of curvature of the first surface of the second lens is r3, the radius of curvature of the second surface of the second lens is r4, the radius of curvature of the first surface of the third lens is r5, the radius of curvature of the second surface of the third lens is r6, the radius of curvature of the first surface of the fourth lens is r7, the radius of curvature of the second surface of the fourth lens is r8, and the radius of curvature of the first surface of the fifth lens is r9, the radius of curvature of the second surface of the fifth lens is r 10 And satisfying the following conditions: 70mm < r1 < 100mm, 1200mm < r2 < 1600mm, 80mm < r3 < 100mm, 2300mm < r4 < 2900mm, 140mm < r5 < 190mm, 50mm < r6 < 80mm, 40mm < r7 < 60mm, 60mm < r8 < 90mm, 260mm < r9 < 320mm, 180mm < r 10 <240mm.

5. The illumination optical system for wafer bonding according to claim 1, characterized in that, The thickness of the first lens is d1, the thickness of the second lens is d2, the thickness of the third lens is d3, the thickness of the fourth lens is d4, and the thickness of the fifth lens is d5, and they satisfy the following conditions: 27mm < d1 < 33mm, 18mm < d2 < 22mm, 7mm < d3 < 9mm, 9mm < d4 < 11mm, and 18mm < d5 < 22mm.

6. The illumination optical system for wafer bonding according to claim 1, characterized in that, The first lens has a refractive index of n1, the second lens has a refractive index of n2, the third lens has a refractive index of n3, the fourth lens has a refractive index of n4, and the fifth lens has a refractive index of n5, and they satisfy the following relationship: 1.35≤n1≤1.70； 1.37≤n2≤1.67； 1.50≤n3≤1.85； 1.37≤n4≤1.67； 1.37≤n5≤1.67。 7. The illumination optical system for wafer bonding according to claim 1, characterized in that, The filter is a narrowband filter with a bandwidth of 1 to 4 nm.

8. The illumination optical system for wafer bonding according to claim 1, characterized in that, The first near-infrared light source, the second near-infrared light source, the third near-infrared light source, and the fourth near-infrared light source are each equipped with a near-infrared light box to emit near-infrared wavelengths.

9. A wafer bonding alignment system, characterized in that, include: An illumination optical system for wafer bonding as described in any one of claims 1 to 8; A reflector and a beam splitter are arranged in parallel. The reflector is located at the light outlet of the illumination system and is used to reflect four beams of monochromatic light of a set wavelength to the beam splitter. A large field-of-view near-infrared dispersive microscope objective is provided below the beam splitter, so that monochromatic light after passing through the beam splitter enters the large field-of-view near-infrared dispersive microscope objective. A wafer and a chip are positioned on the object side of a large field-of-view near-infrared dispersive microscope objective, with the wafer and chip placed face-to-face. Two wafer alignment marks are provided on the lower surface of the wafer, and two chip alignment marks are provided on the upper surface of the chip. When four beams of monochromatic light of a set wavelength enter the large field-of-view near-infrared dispersive microscope objective, they simultaneously form focal points in the imaging areas of the two wafer alignment marks and the two chip alignment marks, respectively. A wide-field telescope and an imaging device are arranged sequentially above the beam splitter. The imaging device includes a first infrared camera and a second infrared camera arranged side by side. After the four focal points on the wafer alignment mark and the chip alignment mark form four reflected images, the reflected waves pass through the beam splitter and the wide-field telescope in sequence, and finally form clear images in the fields of view of the first infrared camera and the second infrared camera, respectively.

10. The wafer bonding alignment system according to claim 9, characterized in that, The large field-of-view near-infrared dispersive microscope objective has a focal length f = 40 mm and an incident angle of 6.6–7.9° when the maximum field of view is 4.7–5.5 mm; the entrance pupil of the large field-of-view near-infrared dispersive microscope objective is 28 mm.

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