Wafer alignment device and wafer alignment method

Abstract

The invention provides a wafer alignment device and a wafer alignment method, relates to the technical field of semiconductor manufacturing, and aims to solve the problem of poor wafer alignment stability. The wafer alignment device comprises an illumination module used for providing near-infrared light; the first spectroscope is used for reflecting the near-infrared light provided by the illumination module and transmitting the light; the focal plane of the microscope objective is configured to coincide with the surface where the first alignment mark is located; the first wafer motion platform is used for driving the second wafer to move; the focal plane sensor is used for receiving imaging information of the first alignment mark and the second alignment mark; the imaging compensation mechanism is used for imaging the first reflected light and the second reflected light to the focal plane sensor; the first light is reflected by the first alignment mark and then sequentially passes through the microscope objective and the first spectroscope, and the second light is reflected by the second alignment mark and then sequentially passes through the microscope objective and the first spectroscope. The stability of wafer alignment can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a wafer alignment device and a wafer alignment method. Background Art

[0002] During the wafer bonding process, wafer alignment is a key step to ensure that the subsequent bonding process can be carried out accurately. Existing methods often have problems such as limited alignment accuracy, long alignment time, and susceptibility to environmental interference. Especially in advanced bonding processes, the accuracy requirements for wafer alignment are increasing, and traditional alignment technology can no longer meet the needs.

[0003] The currently common visible light alignment method is that visible light cannot penetrate silicon wafers. Therefore, when photographing the alignment mark of one wafer, the other wafer must be moved horizontally a certain distance, and repeated displacement leads to deviations.

[0004] The common near-infrared light alignment method currently uses the characteristic that the infrared band can penetrate silicon wafers. After the position of one wafer is determined, the alignment mark of the other wafer can be photographed without moving it, thereby completing the alignment of the two wafers. However, due to the different imaging distances of the two wafers, the infrared camera needs to focus and shoot the alignment marks of the upper and lower wafers in turn. The existing focusing methods are: objective lens movement focusing, the objective lens is installed on a precision displacement mechanism, and the position of the objective lens is adjusted by controlling the precision displacement mechanism to achieve separate focusing of the upper and lower wafers; the overall movement focusing of the visual system, the visual system is installed on a precision displacement mechanism as a whole, and the position of the visual system is adjusted by controlling the precision displacement mechanism to achieve separate focusing of the upper and lower wafers; inserting a liquid lens in the optical path, and adjusting the diopter of the liquid lens by electronic control to achieve separate focusing of the upper and lower wafers. The above-mentioned focusing methods will introduce deviations in the xy direction during the z-direction focusing process, and there will be a certain drift during the focusing interval.

[0005] To solve the above problems, CN118471878A (publication date 20240809) "A wafer alignment device and alignment method" mentions a method of using a dichroic prism to focus the upper and lower wafers on the focal planes of two cameras. However, this technology introduces a transmission error between the two cameras, and the single-sided alignment mark requires two cameras to shoot, which increases the cost of the alignment unit. In addition, this solution adjusts the Z-position of the second camera to adapt to different wafer gaps, and the movement of the camera will bring additional errors.

[0006] Traditional wafer alignment marks usually use patterns such as "cross-square" or "male-female figures", and positioning is achieved by identifying the center of the pattern through visual algorithms. This method is simple and direct, but its accuracy is limited by the resolution of the optical system, the processing accuracy of the alignment marks, and the accuracy of the algorithm.

[0007] Moiré fringes are generated by the superposition of two periodic patterns. Their variation is closely related to the relative position of the patterns. They have the function of amplifying tiny displacements and are widely used in the fields of precision measurement and positioning. The moiré fringes generated by the superposition of two-dimensional gratings of different periods embedded in the bonding surfaces of the upper and lower wafers can distinguish the slight misalignment between wafers and improve the alignment accuracy. In addition, the processing error of a single grating fringe will be averaged by the grating as a whole, reducing the deviation caused by defects in the alignment mark processing.

[0008] CN113314451A (published on 20210827) "A wafer bonding alignment and method based on moiré fringes" mentions a solution of photographing the grating marks of the upper and lower wafers separately, and then superimposing them through post-processing to generate moiré fringes for alignment. This solution cannot photograph the upper and lower wafers at the same time, and the repeated displacement of the upper and lower wafers leads to the introduction of deviations.

[0009] The journal paper Moiré-Based Alignment Using Centrosymmetric Grating Marks for High-Precision Wafer Bonding (micromachines; 2019; 10; 339) mentions using an infrared camera to simultaneously photograph the two-dimensional grating marks of the upper and lower wafers, and directly measuring the moiré fringe signals generated by their superposition to achieve alignment. However, it does not mention how to focus the upper and lower wafers at the same time. Summary of the invention

[0010] The first aspect of the present invention aims to provide a wafer alignment device to solve the technical problem of poor stability of existing wafer alignment.

[0011] The first aspect of the present invention provides a wafer alignment device, comprising:

[0012] An illumination module for providing near infrared light;

[0013] A first beam splitter, used to reflect the near-infrared light provided by the lighting module and transmit the light;

[0014] A microscope objective lens, wherein a focal plane of the microscope objective lens is configured to coincide with a surface where a first alignment mark of the first wafer is located;

[0015] The first wafer motion platform is used to drive the second wafer to move;

[0016] A focal plane sensor, configured to receive imaging information of the first alignment mark and a second alignment mark of the second wafer;

[0017] An imaging compensation mechanism is used to image a first light ray and a second light ray onto the focal plane sensor; the first light ray is the light ray that passes through the microscope objective lens and the first beam splitter in sequence after being reflected by the first alignment mark, and the second light ray is the light ray that passes through the microscope objective lens and the first beam splitter in sequence after being reflected by the second alignment mark on the second wafer.

[0018] The beneficial effects brought by the wafer alignment device of the present invention are:

[0019] An imaging compensation mechanism is used to image both the first light and the second light onto the focal plane sensor, thereby realizing real-time measurement of the upper and lower wafers using the same microscope objective lens and focal plane sensor, effectively reducing environmental interference caused by repeated focusing processes, eliminating the impact of deviations between different objective lenses and different focal plane sensors, and improving the stability of the wafer alignment process. Simultaneous focusing of two wafers can be achieved using only a single set of microscope objective lenses and focal plane sensors, which can reduce production costs. Moreover, an imaging compensation mechanism is used to finally image both the first alignment mark and the second alignment mark on the focal plane sensor, and real-time alignment is performed to avoid focusing errors, which significantly improves the alignment accuracy of the wafers and meets the needs of advanced semiconductor manufacturing. Moreover, real-time measurement and feedback can reduce the adjustment time for repeated focusing and improve production efficiency.

[0020] In an optional technical solution, the imaging compensation mechanism includes:

[0021] a second beam splitter, the second beam splitter being used to transmit or reflect the light;

[0022] A second reflector, used for reflecting the second light to the second beam splitter;

[0023] A translation stage, used for driving the second reflector to compensate for the imaging distance;

[0024] a first reflector, used for reflecting the first light back to the second beam splitter;

[0025] The compensating mirror is arranged between the second reflecting mirror and the second beam splitter.

[0026] In an optional technical solution, the imaging compensation mechanism further includes a tube lens, and the tube lens is arranged between the second beam splitter and the first beam splitter.

[0027] In an optional technical solution, the imaging compensation mechanism further includes an angle adjustment component, a second shutter and a first shutter, the angle adjustment component is used to drive the first reflector to rotate, and the angle adjustment component drives the first reflector to rotate so that the axis of rotation is perpendicular to the optical axis direction of the first reflector; the second shutter is arranged between the second reflector and the first beam splitter, and the first shutter is arranged between the first reflector and the second beam splitter;

[0028] The microscope objective lens is connected to an objective lens positioning assembly, and the objective lens positioning assembly is used to adjust the position of the microscope objective lens on the optical axis.

[0029] In an optional technical solution, the wafer alignment device further includes a second wafer motion platform, and the second wafer motion platform is used to drive the first wafer to translate in a direction perpendicular to the optical axis and to rotate about the optical axis as a rotation axis.

[0030] In an optional technical solution, the lighting module includes a near-infrared light source and a lighting component, the near-infrared light source is used to emit a continuous near-infrared incoherent light beam; the lighting component is used to collimate, homogenize and expand the near-infrared incoherent light beam.

[0031] The second aspect of the present invention aims to provide a wafer alignment method to solve the technical problem of poor wafer alignment stability.

[0032] A wafer alignment method provided in a second aspect of the present invention is applied to any of the above-mentioned wafer alignment devices, and the wafer alignment method comprises:

[0033] Controlling the translation stage to move the position of the second reflector according to a preset gap value between the first wafer and the second wafer and a magnification of the microscope objective lens;

[0034] driving the second wafer by the first wafer motion platform so that the preset gap value is maintained between the second wafer and the first wafer;

[0035] Turning on the near-infrared light source so that the first alignment mark and the second alignment mark are clearly imaged within the field of view of the focal plane sensor;

[0036] The focal plane sensor converts the optical image formed by the first alignment mark and the second alignment mark into an electrical signal and provides the electrical signal to the signal processing system;

[0037] The signal processing system obtains the relative position deviation between the first alignment mark and the second alignment mark, and feeds back the relative position deviation to the first wafer motion platform, and the first wafer motion platform adjusts the second wafer to align the first alignment mark with the second alignment mark.

[0038] The beneficial effects brought by the wafer alignment device of the present invention are:

[0039] By adopting such a wafer alignment method to eliminate the relative position deviation between the first wafer and the second wafer, the first wafer and the second wafer can be aligned to improve the position accuracy of the second wafer.

[0040] In an optional technical solution, two first alignment marks are set on the first wafer, and two second alignment marks are set on the second wafer, and the two second alignment marks correspond to the first alignment marks respectively;

[0041] The relative position deviation includes coordinate differences between the first alignment mark and the second alignment mark in two vertical dimensions on a plane perpendicular to the optical axis direction, and an angular deviation between the first wafer and the second wafer;

[0042] The coordinate difference value includes an average value of the coordinate difference between each pair of corresponding first alignment marks and second alignment marks in each dimension;

[0043] The angular deviation between the first wafer and the second wafer includes: the difference between the angles between the coordinate lines of each pair of corresponding first alignment marks and second alignment marks and two vertical dimensions.

[0044] In an optional technical solution, applied to the above-mentioned wafer alignment device, the wafer alignment method also includes a calibration process:

[0045] The calibration process includes:

[0046] Adjust the objective lens positioning assembly so that the first alignment mark is clearly imaged on the focal plane sensor;

[0047] Adjusting the translation stage so that the distance between the first reflector and the second beam splitter is the same as the distance between the second reflector and the second beam splitter;

[0048] closing the first shutter, and obtaining a first coordinate, which is a center coordinate of the first alignment mark on the focal plane sensor;

[0049] Opening the first shutter, closing the second shutter, and obtaining a coordinate of the first alignment mark on the focal plane sensor—a second coordinate;

[0050] Adjusting the angle adjustment component so that when the first shutter is opened and the second shutter is closed, the coordinates of the first alignment mark on the focal plane sensor are the first coordinates;

[0051] Open the second shutter.

[0052] In an optional technical solution, applied to the above-mentioned wafer alignment device, the wafer alignment method further includes:

[0053] After completing the calibration process and controlling the translation stage to move the position of the second reflector, closing the second shutter and adjusting the second wafer motion platform so that the center of the first alignment mark coincides with the center of the field of view of the focal plane sensor;

[0054] closing the first shutter, opening the second shutter, and adjusting the first wafer motion platform so that the center of the second alignment mark coincides with the center of the field of view of the focal plane sensor;

[0055] The first shutter is opened, and the first wafer motion platform is adjusted again so that the center of the second alignment mark coincides with the center of the first alignment mark. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background technology, the drawings required for use in the embodiments or the background technology description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0057] Figure 1 This is a schematic structural diagram of a wafer alignment device provided in Embodiment 1 of the present invention.

[0058] Figure 2 A structural schematic diagram of an implementation form of the first alignment mark and the second alignment mark in the wafer alignment device provided in the first embodiment of the present invention.

[0059] Figure 3 A schematic structural diagram of another implementation form of the first alignment mark and the second alignment mark in the wafer alignment device provided in the first embodiment of the present invention.

[0060] Figure 4 This is a schematic structural diagram of implementation method B in the wafer alignment device provided in embodiment 1 of the present invention.

[0061] Figure 5 This is a schematic structural diagram of implementation method C in the wafer alignment device provided in embodiment 1 of the present invention.

[0062] Figure 6 This is a schematic structural diagram of implementation method D in the wafer alignment device provided in embodiment 1 of the present invention.

[0063] Figure 7 The present invention is a flowchart of a wafer alignment method of a wafer alignment device provided in accordance with the first embodiment of the present invention.

[0064] Figure 8 This is a schematic structural diagram of a wafer alignment device provided in Embodiment 2 of the present invention.

[0065] Fig. 9 It is a flow chart of the calibration process in the wafer alignment method of the wafer alignment device provided in the second embodiment of the present invention.

[0066] Fig.10 This is a schematic diagram of the structure of a wafer alignment device provided in Embodiment 3 of the present invention.

[0067] Fig.11 It is a flow chart of a wafer alignment method based on the wafer alignment device provided in the third embodiment of the present invention.

[0068] Description of reference numerals:

[0069] 1-near-infrared light source; 2-illumination assembly; 3-first beam splitter; 4-microscope objective lens; 5-first wafer; 6-second wafer; 7-first wafer motion platform; 8-tube lens; 9-second beam splitter; 10-first reflector; 11-focal plane sensor; 12-compensation mirror; 13-second reflector; 14-translation stage; 15-first alignment mark; 16-second alignment mark; 17-second wafer motion platform; 18-angle adjustment assembly; 19-objective lens positioning assembly; 20-first shutter; 21-second shutter. DETAILED DESCRIPTION

[0070] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0071] Embodiment 1:

[0072] Figure 1 This is a schematic diagram of the structure of a wafer alignment device provided in Embodiment 1 of the present invention. Figure 1As shown, the wafer alignment device provided in the first embodiment of the present invention comprises an illumination module, a first beam splitter 3, a microscope objective 4, a first wafer motion platform 7 and an imaging compensation mechanism. The illumination module is used to provide near-infrared light; the first beam splitter 3 is used to reflect the near-infrared light provided by the illumination module and transmit the light; the focal plane of the microscope objective 4 is configured to coincide with the surface where the first alignment mark 15 of the first wafer 5 is located; the first wafer motion platform 7 is used to drive the second wafer 6 to move; the focal plane sensor 11 is used to receive imaging information of the first alignment mark 15 and the second alignment mark 16 of the second wafer 6; the imaging compensation mechanism is used to image the first light and the second light onto the focal plane sensor 11; the first light is the light that passes through the microscope objective 4 and the first beam splitter 3 in sequence after being reflected by the first alignment mark 15, and the second light is the light that passes through the microscope objective 4 and the first beam splitter 3 in sequence after being reflected by the second alignment mark 16 on the second wafer 6.

[0073] An imaging compensation mechanism is used to image both the first light and the second light to the focal plane sensor 11, so that the upper and lower wafers - the first wafer 5 and the second wafer 6 - can be measured in real time using the same microscope objective lens 4 and the focal plane sensor 11, effectively reducing the environmental interference caused by the repeated focusing process, eliminating the influence of the deviation between different objective lenses and different focal plane sensors 11, and improving the stability of the wafer alignment process. Simultaneous focusing of two wafers can be achieved using only a single set of microscope objective lenses 4 and focal plane sensors 11, which can reduce production costs. Moreover, an imaging compensation mechanism is used to finally image the first alignment mark 15 and the second alignment mark 16 on the focal plane sensor 11, and real-time alignment is performed to avoid focusing errors, which significantly improves the alignment accuracy of the wafers and meets the needs of advanced semiconductor manufacturing. Moreover, real-time measurement and feedback can reduce the adjustment time of repeated focusing and improve production efficiency.

[0074] Specifically, the focal plane sensor 11 in this embodiment can use a relatively low-cost photodiode array as the focal plane sensor 11, thereby reducing the production cost.

[0075] Among them, in this embodiment, the first beam splitter 3, the microscope objective 4 and the first wafer 5, the second wafer 6 and the imaging compensation mechanism can be arranged on the first optical axis. The first beam splitter 3 is arranged at a 45° angle to the first optical axis. The first beam splitter 3 can reflect the infrared light provided by the illumination module into the microscope objective 4, and the microscope objective 4 evenly illuminates the first alignment mark 15 on the first wafer 5 and the second alignment mark 16 on the second wafer 6. Since near-infrared light can pass through the wafer, one of the first wafer 5 and the second wafer 6 is located between the other and the microscope objective 4, but it will not block the infrared light from irradiating the other one that is farther away from the microscope objective 4.

[0076] Specifically, in this embodiment, the first wafer motion platform 7 can drive the second wafer 6 to move in the direction of the first optical axis and in two directions orthogonal to the first optical axis and perpendicular to each other, and can also drive the second wafer 6 to rotate with the above three directions as rotation axes.

[0077] Figure 2 A structural schematic diagram of an implementation form of the first alignment mark and the second alignment mark in the wafer alignment device provided in the first embodiment of the present invention. Figure 3 A schematic diagram of another implementation form of the first alignment mark and the second alignment mark in the wafer alignment device provided in the first embodiment of the present invention. In addition, in this embodiment, the first alignment mark 15 and the second alignment mark 16 can be as follows: Figure 2 The grating shape shown can also be Figure 3 The cross shown.

[0078] The first light reflected by the first alignment mark 15 and the second light reflected by the second alignment mark 16 can pass through the first beam splitter 3 and enter the imaging compensation mechanism after passing through the microscope objective 4. Since the focal plane of the microscope objective 4 coincides with the surface where the first alignment mark 15 is located, the first alignment mark 15 can be directly and clearly imaged in the focal plane sensor 11. However, the surface where the second alignment mark 16 is located does not coincide with the focal plane of the microscope objective 4, so the second light reflected by the second alignment mark 16 cannot be imaged on the focal plane sensor 11 without compensation by the imaging compensation mechanism. After compensation by the imaging compensation mechanism, an image can be formed on the focal plane sensor 11. Therefore, the imaging of the first light and the second light on the focal plane sensor 11 can be compared to control the position of the second wafer 6 so that the second wafer 6 is aligned with the first wafer 5.

[0079] like Figure 1 As shown, optionally, the imaging compensation mechanism includes:

[0080] A second beam splitter 9, the second beam splitter 9 is used to transmit or reflect the light;

[0081] A second reflector 13, used for reflecting the second light to the second beam splitter 9;

[0082] A translation stage 14, used for driving the second reflecting mirror 13 to compensate for the imaging distance;

[0083] A first reflector 10, used for reflecting the first light back to the second beam splitter 9;

[0084] The compensation mirror 12 is disposed between the second reflecting mirror 13 and the second beam splitter 9 .

[0085] By setting the second beam splitter 9, the first light can be reflected or transmitted to the first reflector 10 and the first light reflected from the first reflector 10 can be transmitted or reflected to the focal plane sensor 11; and the second light can be transmitted or reflected to the second reflector 13 and the second light reflected from the second reflector 13 can be reflected or projected to the focal plane sensor 11. Moreover, the second reflector 13 can be driven to move by the displacement stage 14 to drive the second reflector 13 to move, so as to change the optical path length of the second light to match the imaging distance difference of the two wafers, so that the second light reflected by the second alignment mark 16 can be clearly imaged on the focal plane sensor 11, ensuring stable imaging and accurate measurement of wafers of different thicknesses, and improving the flexibility and versatility of alignment. By setting the compensation mirror 12, the second light can be subjected to wavefront correction after passing through the second beam splitter 9, so as to realize compensation of the magnification and image quality of the imaging of the second alignment mark 16.

[0086] Among them, in this embodiment, the angle of the second beam splitter 9 is 45° with the first optical axis. The second beam splitter 9 can reflect half of the light from the microscope objective lens 4 and transmit half. The light emitted by the microscope objective lens 4 to the second beam splitter 9 includes the first light and the second light. Similarly, the second beam splitter 9 can reflect half of the second light reflected by the second reflector 13 and transmit half. If the second reflector 13 and the focal plane sensor 11 are on the same side of the second beam splitter 9, the second beam splitter 9 reflects the second light reflected by the second reflector 13 into the focal plane sensor 11; if the second reflector 13 and the focal plane sensor 11 are respectively located on the opposite sides of the second beam splitter 9, the second beam splitter 9 transmits the second light reflected by the second reflector 13 into the focal plane sensor 11. Similarly, the second beam splitter 9 can reflect half of the first light reflected by the first reflector 10 and transmit half. If the first reflector 10 and the focal plane sensor 11 are on the same side of the second beam splitter 9, the second beam splitter 9 reflects the first light reflected by the second reflector 13 into the focal plane sensor 11; if the first reflector 10 and the focal plane sensor 11 are respectively located on the opposite sides of the second beam splitter 9, the second beam splitter 9 transmits the first light reflected by the first reflector 10 into the focal plane sensor 11.

[0087] In the present application, the second reflector 13 refers to the reflector connected to the displacement stage 14, and the only belt can drive the second reflector 13 to move one dimensionally on the optical path of the second reflector 13. The first reflector 10 is the reflector that is not driven by the displacement stage 14 among the two reflectors.

[0088] Optionally, the imaging compensation mechanism further includes a tube lens 8 , which is disposed between the second beam splitter 9 and the first beam splitter 3 .

[0089] By providing the tube lens 8, the object magnified by the microscope objective lens 4 can be clearly imaged on the image plane.

[0090] like Figure 1 As shown, optionally, the lighting module includes a near-infrared light source 1 and a lighting component 2, wherein the near-infrared light source 1 is used to emit a continuous near-infrared incoherent light beam; and the lighting component 2 is used to collimate, homogenize and expand the near-infrared incoherent light beam.

[0091] The near-infrared light source 1 is used to emit a continuous near-infrared incoherent light beam, which is beneficial for the light to pass through the first wafer 5 or the second wafer 6, and reflect the images of the first alignment mark 15 and the second alignment mark 16 to the microscope objective 4. The illumination component 2 is used to collimate, homogenize and expand the near-infrared incoherent light beam, so as to irradiate the light on the first alignment mark 15 and the second alignment mark 16 more evenly.

[0092] Among them, this embodiment can be implemented in the following manner:

[0093] Implementation method A:

[0094] like Figure 1 As shown, the first wafer 5 is located between the second wafer 6 driven by the first wafer motion platform 7 and the microscope objective lens 4, and the line connecting the second reflector 13 driven by the translation stage 14 and the focal plane sensor 11 is perpendicular to the first optical axis, that is, along the first optical axis, the first wafer motion platform 7, the second wafer 6, the first wafer 5, the microscope objective lens 4, the first beam splitter 3, the tube lens 8, the second beam splitter 9, the first reflector 10, and the translation stage 14 are arranged in sequence.

[0095] After the near-infrared incoherent light beam emitted by the near-infrared light source 1 is reflected from the lighting component 2 by the first beam splitter 3, a portion of the illumination light passes through the microscope objective 4 and through the first wafer 5, uniformly illuminating the first alignment mark 15 on the lower surface of the first wafer 5 and the second alignment mark 16 on the upper surface of the second wafer 6.

[0096] The first light reflected by the first alignment mark 15 returns from the original path, is magnified by the microscope objective 4, and a portion of the light passes through the first beam splitter 3 and passes through the tube lens 8. A portion of the light is reflected by the second beam splitter 9, is reflected by the first reflection mirror 10, and then passes through the second beam splitter 9 again. A portion of the light transmitted by the second beam splitter 9 images the first alignment mark 15 on the focal plane sensor 11.

[0097] The second light reflected by the second alignment mark 16 returns from the original path, is magnified by the microscope objective 4, and a portion of the light passes through the first beam splitter 3, passes through the tube lens 8, and a portion of the light is transmitted by the second beam splitter 9, passes through the compensation mirror 12, is reflected by the second reflection mirror 13, and then passes through the compensation mirror 12 and the second beam splitter 9 again. A portion of the light reflected by the second beam splitter 9 images the second alignment mark 16 on the focal plane sensor 11.

[0098] Implementation method B:

[0099] Figure 4 This is a schematic diagram of the structure of the implementation method B in the wafer alignment device provided in the first embodiment of the present invention. Figure 4 As shown, implementation mode B is different from implementation mode A in that, in implementation mode B, the first reflector 10 is not on the first optical axis, while the second reflector 13 is located on the first optical axis, that is, the line connecting the first reflector 10 and the focal plane sensor 11 is perpendicular to the first optical axis. Correspondingly, the compensation mirror 12 is also not on the first optical axis, and the compensation mirror 12 is located between the first reflector 10 and the second beam splitter 9.

[0100] That is, on the first optical axis, the first wafer moving platform 7, the second wafer 6, the first wafer 5, the microscope objective 4, the first beam splitter 3, the tube lens 8, the second beam splitter 9 and the first reflecting mirror 10 are arranged in sequence.

[0101] After the first light passes through the tube lens 8 , a portion of the light transmitted by the second beam splitter 9 is reflected by the first reflector and then passes through the second beam splitter 9 again. A portion of the light reflected by the second beam splitter 9 images the first alignment mark 15 on the focal plane sensor 11 .

[0102] When the second light passes through the tube lens 8, a part of the light transmitted by the second beam splitter 9 passes through the compensation mirror 12, is reflected by the second reflector 13, and then passes through the compensation mirror 12 and the second beam splitter 9 again. A part of the light reflected by the second beam splitter 9 images the second alignment mark 16 on the focal plane sensor 11.

[0103] Implementation method C:

[0104] Figure 5 This is a schematic diagram of the structure of the implementation method C in the wafer alignment device provided in the first embodiment of the present invention. Figure 5 As shown, the difference between implementation mode C and implementation mode A is that in implementation mode C, the second wafer 6 is located between the first wafer 5 and the microscope objective lens 4, that is, the second alignment mark 16 is located on the lower surface of the second wafer 6, and the first alignment mark 15 is located on the upper surface of the first wafer 5. On the first wafer motion platform 7, a light-transmitting hole is provided to ensure the passage of light.

[0105] As for the propagation paths of the first light ray and the second light ray, they are the same as those in Implementation Method A and will not be described in detail.

[0106] Implementation method D:

[0107] Figure 6 FIG. 1 is a schematic diagram of the structure of the implementation method D in the wafer alignment device provided in the first embodiment of the present invention. Figure 6As shown, the difference between implementation mode D and implementation mode B is that in implementation mode D, the second wafer 6 is located between the first wafer 5 and the microscope objective lens 4, that is, the second alignment mark 16 is located on the lower surface of the second wafer 6, and the first alignment mark 15 is located on the upper surface of the first wafer 5. On the first wafer motion platform 7, a light-transmitting hole is provided to ensure the passage of light.

[0108] As for the propagation paths of the first light ray and the second light ray, they are the same as those in implementation method B and will not be described in detail.

[0109] Figure 7 FIG. 1 is a flow chart of a wafer alignment method of a wafer alignment device provided in Embodiment 1 of the present invention. Figure 7 As shown, based on the above-mentioned wafer alignment device, the wafer alignment method includes:

[0110] According to the preset gap value between the first wafer 5 and the second wafer 6 and the magnification of the microscope objective lens 4, the translation stage 14 is controlled to move the position of the second reflector 13;

[0111] The gap value g between the relative surfaces of the first wafer 5 and the second wafer 6 is set to 40 μm, that is, the gap between the first alignment mark 15 and the second alignment mark 16 is 40 μm. According to the gap value g and the magnification of the microscope objective 4, the spacing between the first reflector 10 and the second beam splitter 9 can be calculated, and the difference between the spacing between the second reflector 13 and the second beam splitter 9 is Δd=g*x 2 / 2=8mm.

[0112] The second wafer 6 is driven by the first wafer motion platform 7 so that a preset gap value is maintained between the second wafer 6 and the first wafer 5;

[0113] Turn on the near-infrared light source 1 so that the first alignment mark 15 and the second alignment mark 16 are clearly imaged within the field of view of the focal plane sensor 11;

[0114] The focal plane sensor 11 converts the optical image formed by the first alignment mark 15 and the second alignment mark 16 into an electrical signal and provides it to the signal processing system;

[0115] The signal processing system obtains the relative position deviation of the first alignment mark 15 and the second alignment mark 16 , and feeds back the relative position deviation to the first wafer motion platform 7 , and the first wafer motion platform 7 adjusts the second wafer 6 to align the first alignment mark 15 with the second alignment mark 16 .

[0116] Among them, the first wafer motion platform 7 adjusts the second wafer 6 to align the first alignment mark 15 with the second alignment mark 16, which is not completely limited to the first wafer motion platform 7 driving the second wafer 6 to move into place at one time. It can include, after the first wafer motion platform 7 drives the second wafer 6 to move, re-detecting the relative position of the first alignment mark 15 and the second alignment mark 16 to determine whether the relative position deviation is within the allowable tolerance range. If it is outside the tolerance range, continue to control the movement of the first wafer motion platform 7 according to the re-detected relative position.

[0117] Optionally, two first alignment marks 15 are set on the first wafer 5, and two second alignment marks 16 are set on the second wafer 6, and the two second alignment marks 16 correspond to the first alignment marks 15 respectively; a wafer alignment device is set corresponding to each group of first alignment marks 15 and second alignment marks 16.

[0118] For example, two first alignment marks 15 may be provided on the first wafer 5 , one on the left and one on the right; correspondingly, two second alignment marks 16 may also be provided on the second wafer 6 along the left and right sides.

[0119] The relative position deviation includes the coordinate difference between the first alignment mark 15 and the second alignment mark 16 in two vertical dimensions on a plane perpendicular to the optical axis direction, and the angular deviation between the first wafer 5 and the second wafer 6;

[0120] The coordinate difference value includes an average value of the coordinate difference between each pair of corresponding first alignment marks 15 and second alignment marks 16 in each dimension;

[0121] The signal processing system converts the coordinates (Xlc1, Ylc1) and (Xlc2, Ylc2) of the first alignment mark 15 and the second alignment mark 16 photographed by the left wafer alignment device in the coordinate system of the left focal plane sensor 11 and the coordinates (Xrc1, Yrc1) and (Xrc2, Yrc2) of the first alignment mark 15 and the second alignment mark 16 photographed by the right wafer alignment device in the coordinate system of the right focal plane sensor 11 into the machine coordinate system according to the pre-calibrated conversion relationship. The coordinates in the system can be calculated from the machine coordinates (Xl1, Yl1), (Xl2, Yl2) of the first alignment mark 15 and the second alignment mark 16 on the left and the machine coordinates (Xr1, Yr1), (Xr2, Yr2) of the first alignment mark 15 and the second alignment mark 16 on the right to obtain the relative position deviation ΔX=((Xl2-Xl1)+(Xr2-Xr1)) / 2 and ΔY=((Yl2-Yl1)+(Yr2-Yr1)) / 2 of the second wafer 6 and the first wafer 5.

[0122] The angle deviation of the first wafer 5 and the second wafer 6 includes: the difference between the angles between the coordinate lines of each pair of corresponding first alignment marks 15 and second alignment marks 16 and the two vertical dimensions. That is, the angle deviation Δθ=arctan((Yr2-Yl2) / (Xr2-Xl2))-arctan(Yr1-Yl1) / (Xr1-Xl1);

[0123] Two wafer alignment devices are used to align the two pairs of first alignment marks 15 and second alignment marks 16 on the first wafer 5 and the second wafer 6 respectively, and the coordinate difference and angle deviation of the first alignment mark 15 and the second alignment mark 16 are eliminated respectively, so that the first wafer 5 and the second wafer 6 can be overlapped accordingly to align the second wafer 6.

[0124] The allowable tolerance range is that ΔX and ΔY are within ±10 nm, and Δθ is within ±50 nrad.

[0125] Embodiment 2:

[0126] Figure 8 This is a schematic diagram of the structure of a wafer alignment device provided in Embodiment 2 of the present invention. Figure 8 As shown, the difference between the second embodiment and the first embodiment is that the imaging compensation mechanism further includes an angle adjustment component 18, a first shutter 20 and a second shutter 21. The angle adjustment component 18 is used to drive the first reflector 10 to rotate. The angle adjustment component 18 drives the first reflector 10 to rotate so that the axis of rotation is perpendicular to the optical axis direction of the first reflector 10. The first shutter 20 is arranged between the first reflector 10 and the second beam splitter 9, and the second shutter 21 is arranged between the second reflector 13 and the first beam splitter 3.

[0127] The microscope objective lens 4 is connected to an objective lens positioning assembly 19 , and the objective lens positioning assembly 19 is used to adjust the position of the microscope objective lens 4 on the optical axis.

[0128] By setting an angle adjustment mechanism, the pitch and deflection of the first reflector 10 can be changed so that the second light reflected by the first reflector 10 can be aligned with the focal plane sensor 11. By setting a first shutter 20 and a second shutter 21, the light paths of the first reflector 10 and the second reflector 13 can be controlled to be on and off respectively, so as to image the light reflected by the first reflector 10 and the second reflector 13 separately. By setting an objective lens positioning assembly 19, the first alignment mark 15 can be clearly imaged on the focal plane sensor 11.

[0129] Fig. 9 FIG. 1 is a flow chart of a calibration process in a wafer alignment method of a wafer alignment device provided in Embodiment 2 of the present invention. Fig. 9 As shown, optionally, applied to the above-mentioned wafer alignment device, the wafer alignment method also includes a calibration process:

[0130] The calibration process includes:

[0131] Adjust the objective lens positioning assembly 19 so that the first alignment mark 15 is clearly imaged on the focal plane sensor 11;

[0132] Adjust the translation stage 14 so that the distance between the first reflector 10 and the second beam splitter 9 is the same as the distance between the second reflector 13 and the second beam splitter 9;

[0133] Close the first shutter 20, and obtain the center coordinates of the first alignment mark 15 on the focal plane sensor 11 at this time, namely, the first coordinates (x0, y0); that is, at this time, the first alignment mark 15 is reflected by the second reflector 13 and imaged on the focal plane sensor 11, and the center coordinates relative to the focal plane sensor 11 are the first coordinates;

[0134] The first shutter 20 is opened, and the second shutter 21 is closed, and the coordinates of the first alignment mark 15 on the focal plane sensor 11 at this time, namely, the second coordinates (x1, y1); that is, at this time, the image of the first alignment mark 15 reflected by the first reflector 10 on the focal plane sensor 11 is the second coordinate relative to the center coordinate of the focal plane sensor 11;

[0135] The angle adjustment component 18 is adjusted so that when the first shutter 20 is opened and the second shutter 21 is closed, the coordinates of the first alignment mark 15 on the focal plane sensor 11 are the first coordinates; specifically, the method comprises: obtaining the imaging of the first alignment mark 15 on the focal plane sensor 11 through different reflectors, and the difference values ​​Δx=x1-x0 and Δy=y1-y0 in two dimensions relative to the focal plane sensor 11, and then, adjusting the angle adjustment component 18 so that when the first shutter 20 is opened and the second shutter 21 is closed, the imaging of the first alignment mark 15 on the focal plane sensor 11 through the first reflector 10, and the coordinates relative to the center of the focal plane sensor 11 are corrected to (x1-Δx, y1-Δy), i.e., the same as the coordinates when the second shutter 21 is opened and the first shutter 20 is closed, i.e., the coordinates at this time are the first coordinates.

[0136] Then, the second shutter 21 is opened.

[0137] After executing the calibration process, the relevant steps of the wafer alignment method introduced in the first embodiment are executed.

[0138] By setting the first reflecting mirror 10 so that: when the first shutter 20 is open and the second shutter 21 is closed, the coordinates of the image of the first alignment mark 15 on the focal plane sensor 11 relative to the center of the focal plane sensor 11 are the same as the coordinates when the first shutter 20 is closed and the second shutter 21 is open, it can be achieved that the image of the first alignment mark 15 reflected on the focal plane sensor 11 by the first reflecting mirror 10 is the same as the image reflected on the focal plane sensor 11 by the second reflecting mirror 13, so as to eliminate the difference caused by passing through different reflecting mirrors, so that the second alignment mark 16 is aligned with the first alignment mark 15 when it is reflected by the second reflecting mirror 13 and imaged on the focal plane sensor 11, thereby indicating that the relative positions of the first wafer 5 and the second wafer 6 are aligned.

[0139] Embodiment three:

[0140] Fig.10 This is a schematic diagram of the structure of a wafer alignment device provided in Embodiment 3 of the present invention. Fig.10 As shown, the difference between the third embodiment and the second embodiment is that the wafer alignment device further includes a second wafer motion platform 17, and the second wafer motion platform 17 is used to drive the first wafer 5 to translate in a direction perpendicular to the optical axis and to rotate around the optical axis.

[0141] By setting up a second wafer motion platform 17 to drive the first wafer 5 to move in the above-mentioned direction, the first alignment mark 15 can be moved as close as possible to the center of the field of view of the focal plane sensor 11, so that more information of the first alignment mark 15 and the second alignment mark 16 can be displayed in the field of view of the focal plane sensor 11, thereby facilitating confirmation of whether the first alignment mark 15 and the second alignment mark 16 are aligned.

[0142] Fig.11 FIG. 1 is a flow chart of a wafer alignment method of a wafer alignment device provided in Embodiment 3 of the present invention. Fig.11 As shown, the wafer alignment method applied to the above-mentioned wafer alignment device also includes:

[0143] After completing the calibration process and controlling the translation stage 14 to move the position of the second reflector 13, the second shutter 21 is closed, and the second wafer motion platform 17 is adjusted so that the center of the first alignment mark 15 coincides with the center of the field of view of the focal plane sensor 11;

[0144] The first shutter 20 is closed, the second shutter 21 is opened, and the first wafer motion platform 7 is adjusted so that the center of the second alignment mark 16 coincides with the center of the field of view of the focal plane sensor 11;

[0145] The first shutter 20 is opened, and the first wafer moving platform 7 is adjusted so that the center of the second alignment mark 16 coincides with the center of the first alignment mark 15 .

[0146] By aligning the centers of the first alignment mark 15 and the second alignment mark 16 with the center of the field of view of the focal plane sensor 11, more information about the first alignment mark 15 and the second alignment mark 16 can be reflected in the field of view of the focal plane sensor 11, so as to facilitate confirmation of whether the first alignment mark 15 and the second alignment mark 16 are aligned.

[0147] The center of the first alignment mark 15 coincides with the center of the field of view of the focal plane sensor 11, which should be understood as the center of the first alignment mark 15 trying to coincide with the center of the field of view of the focal plane sensor 11, and the two do not absolutely coincide. The center of the second alignment mark 16 coincides with the center of the first alignment mark 15, which should be understood as the center of the second alignment mark 16 trying to coincide with the center of the first alignment mark 15, and the two do not absolutely coincide.

[0148] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

[0149] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0150] In the above embodiments, the descriptions of directions such as “upper” and “lower” are all based on the drawings.

[0151] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0152] Thus, the present invention will not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wafer alignment device, characterized in that: include: An illumination module for providing near infrared light; A first beam splitter (3) is used to reflect the near-infrared light provided by the lighting module and transmit the light; A microscope objective lens (4), wherein a focal plane of the microscope objective lens (4) is configured to coincide with a surface where a first alignment mark (15) of the first wafer (5) is located; A first wafer motion platform (7) is used to drive the second wafer (6) to move; A focal plane sensor (11) for receiving imaging information of the first alignment mark (15) and a second alignment mark (16) of the second wafer (6); An imaging compensation mechanism is used to image a first light ray and a second light ray onto the focal plane sensor (11); the first light ray is the light ray that passes through the microscope objective lens (4) and the first beam splitter (3) in sequence after being reflected by the first alignment mark (15); and the second light ray is the light ray that passes through the microscope objective lens (4) and the first beam splitter (3) in sequence after being reflected by the second alignment mark (16) on the second wafer (6).

2. The wafer alignment device according to claim 1, characterized in that: The imaging compensation mechanism comprises: A second beam splitter (9), the second beam splitter (9) is used to transmit or reflect light; a first reflector (10), used for reflecting the first light back to the second beam splitter (9); A second reflector (13), used for reflecting the second light to the second beam splitter (9); A translation stage (14) for driving the second reflector (13) to compensate for the imaging distance; A compensation mirror (12) is arranged between the second reflector (13) and the second beam splitter (9).

3. The wafer alignment device according to claim 2, characterized in that: The imaging compensation mechanism further comprises a tube lens (8), wherein the tube lens (8) is arranged between the second beam splitter (9) and the first beam splitter (3).

4. The wafer alignment device according to claim 2, characterized in that: The imaging compensation mechanism further comprises an angle adjustment component (18), a first shutter (20) and a second shutter (21); the angle adjustment component (18) is used to drive the first reflector (10) to rotate; the angle adjustment component (18) drives the first reflector (10) to rotate so that the axis of rotation is perpendicular to the optical axis direction of the first reflector (10); the first shutter (20) is arranged between the first reflector (10) and the second beam splitter (9); and the second shutter (21) is arranged between the second reflector (13) and the second beam splitter (9); The microscope objective lens (4) is connected to an objective lens positioning component (19), and the objective lens positioning component (19) is used to adjust the position of the microscope objective lens (4) on the optical axis.

5. The wafer alignment device according to claim 4, characterized in that: The wafer alignment device also includes a second wafer motion platform (17), which is used to drive the first wafer (5) to move in a direction perpendicular to the optical axis and to rotate with the optical axis as the rotation axis.

6. The wafer alignment device according to any one of claims 1 to 5, characterized in that: The lighting module comprises a near-infrared light source (1) and a lighting component (2); the near-infrared light source (1) is used to emit a continuous near-infrared incoherent light beam; and the lighting component (2) is used to collimate, homogenize and expand the near-infrared incoherent light beam.

7. A wafer alignment method, characterized in that: The wafer alignment device according to any one of claims 2 to 5, wherein the wafer alignment method comprises: Controlling the translation stage (14) to move the position of the second reflector (13) according to a preset gap value between the first wafer (5) and the second wafer (6) and the magnification of the microscope objective lens (4); driving the second wafer (6) by means of the first wafer motion platform (7) so that the preset gap value is maintained between the second wafer (6) and the first wafer (5); Turning on the near-infrared light source (1) so that the first alignment mark (15) and the second alignment mark (16) are clearly imaged within the field of view of the focal plane sensor (11); The focal plane sensor (11) converts an optical image formed by the first alignment mark (15) and the second alignment mark (16) into an electrical signal and provides the electrical signal to a signal processing system; The signal processing system obtains the relative position deviation between the first alignment mark (15) and the second alignment mark (16), and feeds back the relative position deviation to the first wafer motion platform (7), and the first wafer motion platform (7) adjusts the second wafer (6) to align the first alignment mark (15) with the second alignment mark (16).

8. The wafer alignment method according to claim 7, characterized in that: Two first alignment marks (15) are arranged on the first wafer (5), and two second alignment marks (16) are arranged on the second wafer (6), and the two second alignment marks (16) correspond to the first alignment marks (15) respectively; The relative position deviation includes coordinate differences between the first alignment mark (15) and the second alignment mark (16) in two perpendicular dimensions on a plane perpendicular to the optical axis direction, and an angular deviation between the first wafer (5) and the second wafer (6); The coordinate difference value comprises an average value of the coordinate difference between each pair of corresponding first alignment marks (15) and second alignment marks (16) in each dimension; The angular deviation of the first wafer (5) and the second wafer (6) comprises: the difference between the angles between the coordinate lines of each pair of corresponding first alignment marks (15) and second alignment marks (16) and two vertical dimensions.

9. The wafer alignment method according to claim 7, characterized in that: The wafer alignment device according to claim 4, wherein the wafer alignment method further comprises a calibration process: The calibration process includes: Adjusting the objective lens positioning assembly (19) so that the first alignment mark (15) is clearly imaged on the focal plane sensor (11); adjusting the displacement stage (14) so ​​that the distance between the first reflector (10) and the second beam splitter (9) is the same as the distance between the second reflector (13) and the second beam splitter (9); Closing the first shutter (20), obtaining the center coordinate of the first alignment mark (15) on the focal plane sensor (11)—a first coordinate; Opening the first shutter (20), closing the second shutter (21), and obtaining the coordinates of the first alignment mark (15) on the focal plane sensor (11)—second coordinates; adjusting the angle adjustment component (18) so that when the first shutter (20) is opened and the second shutter (21) is closed, the coordinates of the first alignment mark (15) on the focal plane sensor (11) are the first coordinates; The second shutter (21) is opened.

10. The wafer alignment method according to claim 9, characterized in that: The wafer alignment device according to claim 5, wherein the wafer alignment method further comprises: After completing the calibration process and controlling the translation stage (14) to move the position of the second reflector (13), closing the second shutter (21) and adjusting the second wafer motion platform (17) so that the center of the first alignment mark (15) coincides with the center of the field of view of the focal plane sensor (11); Closing the first shutter (20), opening the second shutter (21), and adjusting the first wafer motion platform (7) so that the center of the second alignment mark (16) coincides with the center of the field of view of the focal plane sensor (11); The first shutter (20) is opened, and the first wafer motion platform (7) is adjusted again so that the center of the second wafer alignment mark (16) coincides with the center of the first alignment mark (15).

Images