Off-axis alignment device, off-axis alignment method and photoetching equipment

Abstract

The invention discloses an off-axis alignment device, an off-axis alignment method and photoetching equipment. The device comprises a light source module used for providing a first light source signal for a silicon wafer, the silicon wafer is provided with a coarse alignment mark and a fine alignment mark, and the coarse alignment mark and the fine alignment mark feed back a first reflection light signal and a second reflection light signal respectively based on the first light source signal; the automatic focusing module is used for forming a first focusing mark on the surface of the silicon wafer and acquiring a third reflected light signal fed back based on the first focusing mark, and the third reflected light signal is used for performing focal plane compensation on the silicon wafer; the first detection module is used for acquiring first deviation information based on the first reflected light signal so as to perform first compensation on the position of the silicon wafer; and the second detection module is used for obtaining second deviation information based on the second reflected light signal after the first compensation so as to carry out second compensation. According to the scheme, the defocusing condition of the silicon wafer can be judged and compensated in real time, and the alignment efficiency and the overlay precision are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical detection technology, in particular to an off-axis alignment device, an off-axis alignment method and a lithography apparatus. BACKGROUND

[0002] In IC (Integrated Circuit) manufacturing, lithography technology is widely used in the preparation of various device structures, including semiconductor devices, optoelectronic devices, MEMS (Micro-Electro-Mechanical Systems), etc. Among them, the overlay accuracy of the lithography machine directly affects the transfer accuracy of the pattern, which is a key parameter to determine the performance, function reliability and manufacturing yield of the device.

[0003] For a projection lithography machine, its overlay accuracy is mainly determined by the performance of the alignment system. As one of the key paths to improve alignment accuracy, off-axis alignment technology has an independent optical module and can achieve nanometer-level alignment accuracy by fusing diffraction interference, multi-wavelength illumination, multi-level signal acquisition and image processing, etc. It is suitable for high-precision overlay requirements under complex process conditions.

[0004] However, the existing off-axis alignment device cannot real-time perceive and compensate for the defocusing of the silicon wafer (which causes the imaging contrast to decrease) and affects the alignment accuracy. In order to obtain reliable positioning, it has to rely on multiple image acquisition and iterative calculation, which greatly increases the single alignment time. Its inefficiency cannot match the high-speed step scanning demand, which has become a key bottleneck restricting the improvement of the overall machine yield. SUMMARY

[0005] In view of the above defects of the prior art, the technical scheme of the present application can real-time judge and compensate for the defocusing of the silicon wafer, accurately obtain the full-field displacement compensation amount of the silicon wafer during the exposure process, and improve the alignment efficiency and overlay accuracy.

[0006] To solve at least one of the above technical problems, the present application discloses an off-axis alignment device, an off-axis alignment method and a lithography apparatus.

[0007] According to a first aspect of the present application, an off-axis alignment device is provided, comprising:

[0008] a light source module configured to provide a first light source signal to a silicon wafer, the silicon wafer having a coarse alignment mark and a fine alignment mark, the coarse alignment mark configured to feed back a first reflected light signal based on the first light source signal, and the fine alignment mark configured to feed back a second reflected light signal based on the first light source signal;

[0009] The automatic focusing module is configured to project a first focus mark on the surface of the silicon wafer and obtain a third reflected light signal based on the feedback of the first focus mark, and the third reflected light signal is used for focus plane compensation of the silicon wafer.

[0010] The first detection module is configured to obtain first deviation information based on the first reflected light signal, and the first deviation information is used for first compensation of the position of the silicon wafer.

[0011] The second detection module is configured to obtain second deviation information based on the second reflected light signal after the first compensation of the position of the silicon wafer, and the second deviation information is used for second compensation of the position of the silicon wafer.

[0012] Optionally, the third reflected light signal is used for obtaining focus plane compensation information,

[0013] The focus plane compensation information is used for focus plane compensation of the silicon wafer, and the focus plane compensation information includes a focus plane offset of the silicon wafer and a defocus direction of the silicon wafer.

[0014] Optionally, the automatic focusing module comprises:

[0015] The focus mark plate is configured to project a first focus mark on the surface of the silicon wafer.

[0016] The focus light source is configured to provide a second light source signal to the focus mark plate to project the first focus mark on the surface of the silicon wafer, and the second light source signal feeds back the third reflected light signal based on the first focus mark.

[0017] The illumination imaging lens group is configured to homogenize the second light source signal.

[0018] The first alignment imaging lens group is configured to collect the third reflected light signal.

[0019] The light blocking structure is configured to block part of the third reflected light signal to determine the defocus direction of the silicon wafer.

[0020] The first image acquisition module is configured to acquire a second focus mark, and the second focus mark is formed based on the conversion of the third reflected light signal by the first alignment imaging lens group and the light blocking structure.

[0021] The light blocking structure is arranged between the first alignment imaging lens group and the first image acquisition module.

[0022] Optionally, the mark image of the focus mark plate is a two-dimensional mark.

[0023] Optionally, the wave band corresponding to the second light source signal is independent of the wave band corresponding to the first light source signal.

[0024] Optionally, the first detection module comprises:

[0025] The first reference mark forms a first calibration light signal after the first reflected light signal passes through the first reference mark;

[0026] The second image acquisition module acquires a first alignment image based on the first reflected light signal and acquires a first reference mark image based on the first calibration light signal, the first alignment image being used to determine first deviation information;

[0027] The second alignment imaging lens group is located between the first reference mark and the second image acquisition module, so that the first reflected light signal and the first calibration light signal are transmitted from the first reference mark to the second image acquisition module.

[0028] Optionally, the first deviation information includes a first offset and a rotation amount.

[0029] Optionally, the second detection module includes:

[0030] The second reference mark forms a second calibration light signal after the second reflected light signal passes through the second reference mark;

[0031] The third image acquisition module acquires a second alignment image based on the second reflected light signal and acquires a second reference mark image based on the second calibration light signal, the second alignment image being used to determine second deviation information;

[0032] The third alignment imaging lens group is used to collect the second reflected light signal.

[0033] Optionally, the second deviation information includes a second offset.

[0034] Optionally, the light source module includes:

[0035] The illumination light source is used to provide a first light source signal to the silicon wafer;

[0036] The diaphragm switching structure is used to switch the illumination mode;

[0037] The illumination lens group is used to collect and homogenize the first light source signal.

[0038] Optionally, the device further includes:

[0039] The optical lens structure includes at least one of a plurality of mirrors, a plurality of lenses, and a plurality of prisms;

[0040] The optical lens structure is used to transmit each light source signal and / or each reflected light signal between the light source module, the auto-focusing module, the first detection module, and the second detection module.

[0041] According to a second aspect of the present application, an off-axis alignment method is also provided, including the following steps:

[0042] a first light source signal is provided to the silicon wafer so that the first light source signal is perpendicularly irradiated on the surface of the silicon wafer and forms a first reflected light signal and a second reflected light signal;

[0043] first deviation information is obtained based on the first reflected light signal, and the first deviation information is used to perform first compensation on the position of the silicon wafer;

[0044] second deviation information is obtained based on the second reflected light signal, and the second deviation information is used to perform second compensation on the position of the silicon wafer;

[0045] and a first focus mark is projected on the surface of the silicon wafer, and a third reflected light signal is obtained based on the feedback of the first focus mark, and the third reflected light signal is used to perform focus plane compensation on the silicon wafer.

[0046] According to a third aspect of the present application, there is also provided a photolithography device, comprising:

[0047] a photolithography illumination system for providing a third light source signal for an exposure process;

[0048] a mask table on which a mask plate is placed on a side surface close to the photolithography illumination system;

[0049] an exposure objective for reducing and imaging a pattern on the surface of the mask plate;

[0050] an off-axis alignment device according to any one of the above, which is used to compensate for the deviation of the silicon wafer;

[0051] a silicon wafer table on which a silicon wafer is placed on a side surface close to the exposure objective.

[0052] The present application provides an off-axis alignment device, which comprises a light source module, an automatic focusing module, a first detection module and a second detection module. In the off-axis alignment process, the light source module provides a first light source signal for illumination to the surface of the silicon wafer. The automatic focusing module can obtain the defocus amount and defocus direction of the silicon wafer in real time, and accordingly perform real-time focus plane compensation to ensure that the imaging is always in the best focus plane. Based on the detection result of the first detection module, the silicon wafer is moved by the silicon wafer table for displacement compensation so that the silicon wafer is within the best detection range of the second detection module; based on the detection result of the second detection module, an algorithm is used to realize the full-field (global) displacement compensation of the silicon wafer in the exposure stage. In addition, since no additional focus sensor is needed to effectively compensate for the focus plane deviation caused by factors such as silicon wafer warping and deformation, the process of frequent calibration and adjustment in the prior art is avoided, and the alignment efficiency and overall exposure yield are significantly improved.

[0053] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0055] Figure 1 is a structural schematic diagram of an off-axis alignment device provided by some embodiments of the present application Figure 1 ;

[0056] Figure 2 is a structural schematic diagram of an off-axis alignment device provided by some embodiments of the present application Figure 2 ;

[0057] Figure 3a is a structural schematic diagram of a silicon wafer provided by some embodiments of the present application

[0058] Figure 3b is a schematic diagram corresponding to a distribution of surface marks of a silicon wafer provided by some embodiments of the present application

[0059] Figure 3c is a schematic diagram corresponding to a coarse alignment mark provided by some embodiments of the present application

[0060] Figure 3d is a schematic diagram corresponding to a fine alignment mark provided by some embodiments of the present application

[0061] Figure 4 is a structural schematic diagram corresponding to a diaphragm switching structure provided by some embodiments of the present application

[0062] Figure 5 is a schematic diagram corresponding to a focus mark plate provided by some embodiments of the present application

[0063] Figure 6 is a structural schematic diagram corresponding to a light shielding structure provided by some embodiments of the present application

[0064] Figure 7 is a flowchart of an off-axis alignment method provided by some embodiments of the present application

[0065] Figure 8 is a structural schematic diagram of a lithographic apparatus provided by some embodiments of the present application Figure 1 ;

[0066] Figure 9 is a structural schematic diagram of a lithographic apparatus provided by some embodiments of the present application Figure 2 .

[0067] Explanation of reference signs:

[0068] 1-off-axis alignment device, 2-lithography apparatus, 2a-ruling track, 3-lithography illumination system, 4-mask table, 5-exposure objective, 6-silicon wafer table, 7-mask system, 8-interferometer, 9-host computer;

[0069] 10-silicon wafer, 11-coarse alignment mark, 12-fine alignment mark;

[0070] 20-light source module, 21-illumination light source, 22-diaphragm switching structure, 23-motor, 24-diaphragm mark sheet, 25-illumination lens group, 26-first illumination lens, 27-first illumination mirror;

[0071] 30-autofocus module, 31-focusing mark board, 32-focusing light source, 33-illumination imaging lens group, 34-first alignment imaging lens group, 35-light blocking structure, 36-first image acquisition module;

[0072] 40-first detection module, 41-first reference mark, 42-second image acquisition module, 43-second alignment imaging lens group;

[0073] 50-second detection module, 51-second reference mark, 52-third image acquisition module, 53-third alignment imaging lens group;

[0074] 60-optical lens group structure, 61-first prism, 62-second prism, 63-third prism, 64-fourth prism, 65-fifth prism, 66-sixth prism, 67-seventh prism, 68-first mirror, 69-second mirror, 70-third mirror, 71-first lens, 72-second lens, 73-third lens;

[0075] 80-mercury lamp, 81-illumination prism, 82-second illumination mirror, 83-third illumination mirror, 84-second illumination lens, 85-third illumination lens. DETAILED DESCRIPTION

[0076] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0077] In the description of the application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0078] "A and / or B" includes the following three combinations: only A, only B, and a combination of A and B.

[0079] The use of "adapted for" or "configured for" in this application means open and inclusive language that does not exclude devices adapted for or configured to perform additional tasks or steps. In addition, the use of "based on" means open and inclusive, as the process, step, calculation or other action "based on" one or more stated conditions or values can in practice be based on additional conditions or values beyond those stated.

[0080] In this application, the word "exemplary" is used to mean "serving as an example, instance, or illustration." Any implementation described as "exemplary" in this application is not necessarily to be construed as preferred or advantageous over other implementations. The following description is presented to enable any person skilled in the art to make and use the application. In the following description, for the purposes of explanation, details are set forth in order to provide a thorough understanding of the application. It should be apparent to those skilled in the art that the application can be practiced without the specific details presented below. In other instances, well-known structures and processes are not described in detail in order to avoid obscuring the application. Thus, the present application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0081] Figure 1 is a structural schematic diagram of an off-axis alignment device 1 provided by some embodiments of the application. The off-axis alignment device 1 can be applied to a lithography apparatus 2. As shown in Figure 1 An off-axis alignment device 1, including a light source module 20, an automatic focusing module 30, a first detection module 40 and a second detection module 50. As shown in Figure 2As shown, the off-axis alignment device 1 can further include an optical mirror structure 60. Through the cooperation between the various modules and structures, the off-axis alignment device 1 compensates for the focal plane compensation and the position offset of the silicon wafer 10, improves the imaging quality, improves the alignment efficiency and alignment accuracy, and further improves the overlay accuracy and yield of the lithography process.

[0082] The various modules and structures will be described in detail below.

[0083] The optical mirror structure 60 is used to transfer the various light source signals and / or the various reflected light signals between the light source module 20, the autofocus module 30, the first detection module 40, and the second detection module 50 and the surface of the silicon wafer 10. The optical mirror structure 60 includes mirror groups shared by the various modules, thereby reducing the cost and size of the off-axis alignment device 1.

[0084] The optical mirror structure 60 includes at least one of a plurality of mirrors, a plurality of lenses, and a plurality of prisms. Please refer to Figure 2 The optical mirror structure 60 can include at least a first prism 61, a second prism 62, a third prism 63, a fourth prism 64, a fifth prism 65, a sixth prism 66, a seventh prism 67, a first mirror 68, a second mirror 69, a third mirror 70, a first lens 71, a second lens 72, and a third lens 73. For the optical mirror structure 60, the light path transmission relationship between each prism, mirror, and lens and each module will be described in detail below in conjunction with each module.

[0085] Please continue to refer to Figure 1 and Figure 2 The light source module 20 includes an illumination light source 21, an aperture switching structure 22, and an illumination mirror group 25. The light source module 20 is used to provide a first light source signal to the silicon wafer 10. The surface of the silicon wafer 10 has a coarse alignment mark 11 and a fine alignment mark 12, the coarse alignment mark 11 feeds back a first reflected light signal based on the first light source signal, and the fine alignment mark 12 feeds back a second reflected light signal based on the first light source signal.

[0086] In some embodiments, as shown in Figure 3a The silicon wafer 10 is placed on the wafer table 6. The silicon wafer 10 can include a plurality of scribe lanes 2a, which can be arranged in a vertical cross array to separate the surface of the silicon wafer 10 so that the silicon wafer 10 is divided into a plurality of carriers that can be applied to different IC manufacturing processes.

[0087] A coarse alignment mark 11 is disposed on the surface of the silicon wafer 10 for coarse alignment of the silicon wafer 10 to make a first compensation for the position of the silicon wafer 10. Meanwhile, a fine alignment mark 12 is also disposed on the surface of the silicon wafer 10 for fine alignment of the silicon wafer 10 to make a second compensation for the position of the silicon wafer 10. As shown in Figure 3b the surface of the silicon wafer 10, the coarse alignment mark 11 and the fine alignment mark 12 can be disposed in the scribe lane 2a. Since the scribe lane 2a is used for cutting the silicon wafer 10 after the device is manufactured, disposing the coarse alignment mark 11 and the fine alignment mark 12 in the scribe lane 2a can improve the utilization of the silicon wafer 10.

[0088] As shown in Figure 3c the coarse alignment mark 11 can have at least two types of mark images, such as a one-dimensional mark (not shown) and a two-dimensional mark. When the two-dimensional mark is used, the deviation in the two-dimensional direction can be calculated by one-time shooting, which directly accelerates the coarse alignment rate and is beneficial to improve the yield. The one-dimensional mark has a small volume and can be placed in a smaller scribe lane 2a, which improves the utilization of the silicon wafer 10. In actual application, the type of mark image of the coarse alignment mark 11 can be adjusted according to different actual lithography needs. In addition, the line width of the coarse alignment mark 11 needs to be considered in terms of the optical resolution of the lens to achieve the expected alignment effect.

[0089] As shown in Figure 3d the fine alignment mark 12 can have at least two types of mark images, such as a one-dimensional mark and a two-dimensional mark. When the two-dimensional mark is used, the deviation in the two-dimensional direction can be calculated by one-time shooting with the cooperation of a corresponding image processing algorithm, which simplifies the steps and optical path structure required by the alignment process, is beneficial to reduce the cost of the off-axis alignment device 1, directly accelerates the coarse alignment rate and improves the yield. The one-dimensional mark has a small volume and can be placed in a smaller scribe lane 2a, which improves the utilization of the silicon wafer 10. The line width of the fine alignment mark 12 can be adjusted according to actual needs. A larger line width mark is beneficial to alignment, and a smaller line width mark is beneficial to improve the utilization of the silicon wafer 10.

[0090] For the illumination light source 21, a halogen light source such as a halogen lamp can be selected. The illumination light source 21 can be used to provide a first light source signal to the silicon wafer 10 and can serve as the light source signal of the first detection module 40 and the second detection module 50.

[0091] In addition, the adaptability of matching different processes can be set. The wavelength range of the illumination light source 21 can be switched to other wavelengths through a fiber coupler to obtain the most ideal pattern quality. At the same time, in order to achieve nanoscale alignment accuracy, the residual vibration of the overall optical system should be as small as possible.

[0092] For the diaphragm switching structure 22, it is used to switch the illumination mode, for example, to switch the annular illumination with different σ according to different process requirements, so as to enhance the pattern contrast and solve the problem of large alignment error caused by low mark contrast.

[0093] As shown in Figure 4 , the diaphragm switching structure 22 can include a motor 23 and a diaphragm mark sheet 24. Among them, the motor 23 can be a high-precision linear motor 23. Two kinds of illumination diaphragm marks can be plated on the diaphragm mark sheet 24, which are traditional illumination and annular illumination with different σ. When it is necessary to switch the illumination mode or switch the illumination parameter, the motor 23 receives the issued instruction to drive the diaphragm mark sheet 24 to move with high precision, thereby realizing the switching function of the illumination. It needs to be further explained that the diaphragm mark sheet 24 can be designed with different diaphragm marks according to the actual situation to achieve the purpose of enhancing the image quality.

[0094] Through the setting of the diaphragm switching structure 22, the diaphragm switching and diaphragm maintenance can be realized in real time and quickly under the driving of the motor 23, without manual plugging operation. Different σ factor illumination modes can be selected according to different working conditions.

[0095] For the illumination lens group 25, it is used to collect and homogenize the first light source signal, and change the propagation direction of the first light source signal, so that the first light source signal can be projected to the surface of the silicon wafer 10. As shown in Figure 2 , the illumination lens group 25 can include a first illumination lens 26 for collecting and homogenizing the first light source signal, and a first illumination mirror 27 for changing the propagation direction of the first light source signal.

[0096] Specifically, as shown in Figure 2 , the first light source signal emitted by the illumination light source 21 reaches the diaphragm switching structure 22, passes through the first illumination mirror 27 and the first illumination lens 26 after the diaphragm, and cooperates with the first prism 61, the second prism 62, the third lens 73, the third prism 63, the second mirror 69, the first mirror 68, the fourth prism 64, the first lens 71 and the fifth prism 65 in the optical lens group structure 60, and is vertically projected to the surface of the silicon wafer 10.

[0097] Please continue to refer to Figure 1 and Figure 2 , the automatic focusing module 30 includes a focusing mark board 31, a focusing light source 32, an illumination imaging lens group 33, a first alignment imaging lens group 34, a light blocking structure 35 and a first image acquisition module 36. The automatic focusing module 30 is used to project a first focusing mark corresponding to the focusing mark board 31 on the surface of the silicon wafer 10, and is also used to acquire a third reflected light signal based on the feedback of the first focusing mark. Among them, the silicon wafer 10 is focus plane compensated based on the third reflected light signal.

[0098] The focusing mark board 31 is used to project a first focusing mark on the surface of the silicon wafer 10. Since the mark of the focusing mark board 31 needs to reflect the change of the defocus direction, the mark image type should be selected as a two-dimensional mark. As shown in Figure 5 Figure 5 Three exemplary two-dimensional marks are given in the above table, and other two-dimensional marks can also be selected.

[0099] The focusing light source 32 is used to provide a second light source signal to the focusing mark board 31, so that the focusing mark board 31 projects a first focusing mark on the surface of the silicon wafer 10, and the second light source signal is used to feedback a third reflected light signal based on the first focusing mark. The third reflected light signal is used to obtain focus plane compensation information, and the focus plane compensation information is used to compensate the focus plane of the silicon wafer 10. The focus plane compensation information includes the focus plane offset of the silicon wafer 10 and the defocus direction of the silicon wafer 10.

[0100] The waveband corresponding to the second light source signal is independent of the waveband corresponding to the first light source signal. That is, the focusing light source 32 can select a visible light waveband independent of the halogen light source waveband, so as to prevent stray light crosstalk between the first light source signal and the second light source signal under normal working conditions.

[0101] Based on the projection of the second light source signal, the focusing mark board 31 forms a first focusing mark on the surface of the silicon wafer 10, and its reflected light is used as the third reflected light signal.

[0102] The illumination imaging lens group 33 is used to homogenize the second light source signal, so that the second light source signal irradiates the focusing mark board 31 through the illumination imaging lens group 33 and projects it onto the surface of the silicon wafer 10, thereby realizing the wafer mark free function of the auto-focusing module 30, i.e. without setting another mark for focusing on the silicon wafer 10, which can simplify the structural design of the silicon wafer 10. The illumination imaging lens group 33 can be selected as a lens.

[0103] The first alignment imaging lens group 34 is used to collect the third reflected light signal, so that the third reflected light signal is projected to the first image acquisition module 36 through the first alignment imaging lens group 34 and the light blocking structure 35. The first alignment imaging lens group 34 can be selected as a lens.

[0104] The light blocking structure 35 is used to block part of the third reflected light signal to determine the defocus direction of the silicon wafer 10. The light blocking structure 35 is arranged between the first alignment imaging lens group 34 and the first image acquisition module 36. The structure of the light blocking structure 35 should be able to block half of the third reflected light signal to determine the defocus direction of the silicon wafer 10. As shown in Figure 6 Figure 6 ​​Three examples of the light blocking structure 35 are shown in the figures. The embodiments of the present application are not limited to the specific structure of the light blocking structure 35, and any element that blocks half of the light can be used as the light blocking structure 35.

[0105] For the first image acquisition module 36, a second focus mark is acquired, which is the image of the third reflected light signal after being reflected on the surface of the wafer 10 and then being formed by the first alignment imaging lens group 34 and the light blocking structure 35. The second focus mark is formed based on the conversion of the third reflected light signal by the first alignment imaging lens group 34 and the light blocking structure 35. The first image acquisition module 36 can be a CMOS (complementary metal-oxide-semiconductor) camera.

[0106] Specifically, as shown in FIG. 2, the focus light source 32 provides a second light source signal, which is uniformly lighted by the illumination imaging lens group 33, and then illuminates the focus mark plate 31. The focus mark plate 31 is imaged to the surface of the wafer 10 by the third mirror 70, the sixth prism 66, the second lens 72, the third prism 63, the second mirror 69, the first mirror 68, the fourth prism 64, the first lens 71, and the fifth prism 65 in the optical lens group structure 60, forming a first focus mark. Figure 2 Further, the reflected light of the first focus mark on the surface of the wafer 10 forms a third reflected light signal. The third reflected light signal enters the first alignment imaging lens group 34 through the fifth prism 65, the first mirror 68, the second mirror 69, the third prism 63, and the second lens 72, and then passes through the first alignment imaging lens group 34 and the light blocking structure 35. Half of the light beam is blocked by the light blocking structure 35 and projected to the first image acquisition module 36, forming a second focus mark.

[0107] According to the second focus mark, the offset of the focus mark plate 31 at this time can be determined. By comparing with the defocus database, the focus offset in the focus compensation information can be determined. In addition, the defocus direction in the focus compensation information can be determined by the light blocking structure 35. Then, based on the focus compensation information, the Z-direction (the direction perpendicular to the horizontal plane) of the wafer 10 is adjusted in real time to compensate for the focus.

[0108] Through the setting of the auto-focusing module 30, the focusing sensor of the whole machine is not needed, and the defocus amount and the defocus direction can be detected in real time during the alignment process and the focus compensation of the wafer stage 6 is performed to obtain the best imaging quality and minimize the impact of the focus offset caused by the warping and deformation of the wafer 10.

[0109] Please continue to refer to

[0110] Figure 2 ​The first detection module 40 includes a first reference mark 41, a second image acquisition module 42, and a second alignment imaging lens group 43. The first detection module 40 is used to acquire first deviation information based on a first reflected light signal, and the first deviation information is used to perform a first compensation on the position of the silicon wafer 10.

[0111] Furthermore, the portion of the first reflected light signal passing through the first reference mark 41 will form a first calibration light signal.

[0112] The second image acquisition module 42 is used to acquire a first alignment image based on a first reflected light signal and to acquire a first reference mark image based on a first calibration light signal. The first alignment image is used to determine first deviation information; the first deviation information includes a first offset and a rotation amount.

[0113] The second alignment imaging lens group 43 can be located between the first reference mark 41 and the second image acquisition module 42, so that the first reflected light signal and the first calibration light signal can be transmitted from the first reference mark 41 to the second image acquisition module 42.

[0114] In some embodiments, the first detection module 40 can be a low-magnification detection module. The low-magnification detection module can provide a large field-of-view, low-magnification search and alignment function, while also being compatible with some special application scenarios, such as back-side alignment. The first detection module 40 can collect and image the reflected light signal (first reflected light signal) of the coarse alignment mark 11 set within the scribing track 2a on the surface of the silicon wafer 10 to the second image acquisition module 42. Simultaneously, during the imaging process of the first reflected light signal to the second image acquisition module 42, it also illuminates the first reference mark 41. Therefore, in addition to the coarse alignment mark 11 corresponding to the first reflected light signal being imaged in the second image acquisition module 42 (first alignment image), the first reference mark 41 corresponding to the first calibration light signal is also simultaneously imaged in the second image acquisition module 42 (first reference mark image).

[0115] Specifically, such as Figure 2 As shown, the first reflected light signal passes through the common optical path section (fifth prism 65, first lens 71, fourth prism 64, first reflector 68, second reflector 69 and third prism 63) and enters the first detection module 40 in conjunction with the third lens 73, second prism 62, first prism 61 and seventh prism 67 in the optical lens group structure 60, and illuminates the first reference mark 41, so as to form an image of the coarse alignment mark 11 (first alignment image) and an image of the first reference mark 41 (first reference mark image) on the second image acquisition module 42.

[0116] Further, the first deviation information can be determined according to the first alignment image. Preferably, after the first deviation information is obtained by capturing the coarse alignment marks 11 in two symmetric fields on the silicon wafer 10, the silicon wafer 10 is moved by the wafer stage 6 to perform the first compensation of the position of the silicon wafer 10 so that the silicon wafer 10 is in the optimal detection range of the center of the field of view of the second detection module 50. The first deviation information can include a first offset and a rotation amount. The first offset ΔX1, ΔY1 and the rotation amount θ1 can be calculated according to the first alignment image including the imaging of the coarse alignment marks 11, combined with a search algorithm or an alignment algorithm.

[0117] Please continue to refer to Figure 2 The second detection module 50 includes a second reference mark 51, a third image acquisition module 52 and a third alignment imaging lens group 53. The second detection module 50 is used to obtain second deviation information based on the second reflected light signal after the first compensation of the position of the silicon wafer 10, and the second deviation information is used to perform the second compensation of the position of the silicon wafer 10.

[0118] Further, the part of the second reflected light signal passing through the second reference mark 51 forms a second calibration light signal;

[0119] The third image acquisition module 52 is used to acquire a second alignment image based on the second reflected light signal and acquire a second reference mark image based on the second calibration light signal; the second alignment image is used to determine the second deviation information; and the second deviation information includes a second offset.

[0120] The third alignment imaging lens group 53 is used to collect the second reflected light signal.

[0121] In some embodiments, the second detection module 50 can be a high-magnification detection module. The high-magnification detection module can provide a small field of view and a large magnification for fine alignment. The third alignment imaging lens group 53 needs to strictly control its wave aberration parameters to achieve the purpose of providing high-quality clear imaging. Similar to the first detection module 40, the second detection module 50 can collect the reflected light signal (second reflected light signal) of the fine alignment mark 12 of the scribe lane 2a of the silicon wafer 10 to the third image acquisition module 52. At the same time, the second reflected light signal also illuminates the second reference mark 51 during imaging to the third image acquisition module 52, so that in addition to the fine alignment mark 12 corresponding to the second reflected light signal being imaged (second alignment image) in the third image acquisition module 52, the second reference mark 51 corresponding to the second calibration light signal is also imaged (second reference mark image) in the third image acquisition module 52.

[0122] As Figure 2As shown, the second reflected light signal passes through the common optical path part (fifth prism 65, first lens 71, fourth prism 64, first mirror 68, second mirror 69 and third prism 63) and enters the second detection module 50 in cooperation with the third lens 73 and the second prism 62 in the lens group structure 60, and illuminates the second reference mark 51, so as to form the second alignment image and the second reference mark image on the third image acquisition module 52.

[0123] Further, the second deviation information can be determined according to the second alignment image. Preferably, the second deviation information (i.e. the full-field displacement compensation information of the wafer 10 during exposure) is obtained by shooting the fine alignment marks 12 in multiple fields on the wafer 10. According to the second deviation information, the wafer 10 is moved by the wafer stage 6 during exposure to compensate for the position (global position) of each exposure field of the wafer 10, so as to achieve accurate overlay between levels and improve overlay accuracy. It can be understood that the number of fine alignment marks 12 can be selected according to actual conditions, for example, 6-16. The second deviation information can include a second offset. The second offsets ΔX2 and ΔY2 can be calculated by using an alignment algorithm according to the second alignment image including the imaging of the fine alignment marks 12 and the data of the interferometer 8 corresponding to the wafer stage 6 on which the wafer 10 is placed.

[0124] In the present application, the defocus amount and defocus direction of the wafer 10 can be obtained in real time by introducing the auto-focusing module 30, and real-time focal plane compensation is performed accordingly to ensure that the imaging is always on the best focal plane. Based on the detection result of the first detection module 40, the wafer 10 is moved by the wafer stage 6 for displacement compensation, so that the wafer 10 is in the best detection range of the second detection module 50; based on the detection result of the second detection module 50, an algorithm is used to achieve full-field (global) displacement compensation of the wafer 10 during exposure. In addition, since the focal plane deviation caused by the warping and deformation of the wafer 10 and other factors can be effectively compensated without using an additional focusing sensor, the process of frequent calibration and adjustment in the related art is avoided, and the alignment efficiency and the overall exposure yield are significantly improved.

[0125] Correspondingly, the present application also discloses an off-axis alignment method, which is implemented based on the off-axis alignment device 1 in any of the above embodiments and can be applied to an exposure process. An off-axis alignment method can include:

[0126] providing a first light source signal to the wafer 10, so that the first light source signal is perpendicularly irradiated on the surface of the wafer 10;

[0127] obtaining first deviation information based on the first reflected light signal, the first deviation information being used for first compensation of the position of the wafer 10;

[0128] The second deviation information is used for second compensation of the position of the silicon wafer 10.

[0129] The first focus mark is projected on the surface of the silicon wafer 10, and a third reflected light signal is obtained based on the feedback of the first focus mark, and the third reflected light signal is used for focus plane compensation of the silicon wafer 10.

[0130] In some embodiments, when the light source module 20 provides the first light source signal, the first reflected light signal is formed by the coarse alignment mark 11 on the surface of the silicon wafer 10, and the second reflected light signal is formed by the fine alignment mark 12.

[0131] Firstly, the coarse alignment mark 11 in the two symmetrical fields on the surface of the silicon wafer 10 is photographed by the first detection module 40, the first deviation information of the silicon wafer 10 is calculated by the two coarse alignment marks 11 and a specific algorithm, and the silicon wafer table 6 drives the silicon wafer 10 to be compensated based on the first deviation information. The first deviation information can include a first offset (ΔX1, ΔY1) and a rotation amount (θ1). After the compensation, the fine alignment mark 12 can enter the center of the best detection range of the second detection module 50 to ensure that the second detection module 50 can clearly photograph the fine alignment mark 12.

[0132] Then, after the coarse alignment of the silicon wafer is performed, the reference version mark on the silicon wafer table 6 is photographed by the second detection module 50 to update the baseline of the interferometer 8. The position of the calibration interferometer 8 can reduce the temperature drift error of the interferometer 8 and ensure the measurement accuracy of the interferometer 8.

[0133] Secondly, after the baseline update of the interferometer 8 is performed, the plurality of fine alignment marks 12 on the silicon wafer 10 are photographed by the second detection module 50, and the second deviation information (i.e. full-field position displacement compensation information of the silicon wafer 10 at exposure) of the fine alignment mark 12 at this time is calculated by a fine alignment algorithm. According to the second deviation information, the silicon wafer table 6 can drive the silicon wafer 10 to move in the subsequent exposure process to compensate for the position of each exposure field (global position) of the silicon wafer 10, to achieve nanometer-level alignment of the mark on the exposure field of the silicon wafer 10 and the silicon wafer table 6, and to achieve accurate overlay between levels and improve the overlay accuracy. It can be understood that the number of fine alignment marks 12 photographed can be selected according to actual conditions, for example, it can be 6-16.

[0134] Meanwhile, during the fine alignment, the second light source signal is obtained by using the auto-focusing module 30, the second light source signal is projected onto the surface of the silicon wafer 10 by the illumination imaging lens group 33 and the focusing mark plate 31, and then the reflected image (i.e. the second focusing mark) is formed by the first alignment imaging lens group 34 and the light blocking structure 35. The defocus offset of the surface of the silicon wafer 10 at this time and the positive and negative defocus are calculated by the auto-focusing algorithm, and real-time compensation is performed, so as to avoid the defocus influence caused by the warping and deformation of the surface of the silicon wafer 10, thereby ensuring that the imaging is always in the best focal plane state, and the fine alignment precision (the precision of the second detection module 50) is ensured.

[0135] As shown in the drawings, Figure 7 In some specific embodiments, after the silicon wafer 10 is placed, the coarse alignment is first performed. The two coarse alignment marks 11 on the scribe lane 2a are photographed by using the first detection module 40 of the off-axis alignment device 1, and the first deviation information (the first offsets ΔX1 and ΔY1 and the rotation amount θ) of the silicon wafer 10 is calculated by an algorithm. After the compensation of the wafer stage 6, the off-axis baseline update is performed on the data of the interferometer 8. Then, the off-axis fine alignment is performed, the plurality of fine alignment marks 12 on the scribe lane 2a are photographed by using the second detection module 50 of the off-axis detection device, and the second deviation information (the second offsets ΔX2 and ΔY2, i.e. the displacement amount of each field of the silicon wafer 10 in the subsequent exposure process) of the marks at this time is obtained by combining the data of the interferometer 8 and the fine alignment algorithm. The number of times of photographing the fine alignment marks 12 is multiple, for example, can be 6-16 times, the global position compensation amount ΔX and ΔY of the silicon wafer 10 at this time is obtained by the EGA algorithm, and finally the fine alignment compensation is performed by the wafer stage 6. During the fine alignment, the auto-focusing alignment is simultaneously performed by using the auto-focusing module 30, the defocus offset of the silicon wafer 10 from the best focal plane and the defocus direction at this time are calculated according to the imaging of the focusing mark plate 31 on the first image acquisition module 36, and real-time compensation is performed by the wafer stage 6. After the compensation is completed and the alignment is determined, the silicon wafer 10 enters the exposure position and the exposure is started.

[0136] Correspondingly, the application also discloses a photolithography device 2. As shown in the drawings, Figure 8 The photolithography device 2 can comprise:

[0137] A photolithography illumination system 3 is used to provide a third light source signal for the exposure process;

[0138] A mask table 4 is used to place a mask on the side surface of the photolithography illumination system 3;

[0139] An exposure objective lens 5 is used to perform the reduction imaging of the pattern on the surface of the mask;

[0140] The off-axis alignment device 1 as described in any one of the above embodiments is used to compensate the deviation of the silicon wafer 10;

[0141] A silicon wafer 10 is placed on the surface of the silicon wafer stage 6, which is close to the exposure objective lens 5.

[0142] In some embodiments, such as Figure 8 As shown, the off-axis alignment device 1 is located on the side of the silicon wafer stage 6 near the exposure objective lens 5 and is positioned close to the silicon wafer stage 6.

[0143] like Figure 9 As shown, the photolithography illumination system 3 may include a mercury lamp 80, an illumination prism 81, a second illumination reflector 82, a third illumination reflector 83, a second illumination lens 84, and a third illumination lens 85. The photolithography equipment 2 may also include an interferometer 8, a mask system 7, and a host computer 9. The mask system 7 is used to control the mask stage 4 to complete mask mounting. The host computer 9 is used to obtain the compensation amounts ΔX and ΔY of the silicon wafer 10 across the entire field through a global alignment algorithm after obtaining the second deviation information after multiple alignments. Furthermore, the host computer 9 is also used to control the mercury lamp 80 for illumination exposure after off-axis alignment is completed.

[0144] The third light source signal provided by the mercury lamp 80 illuminates the mask stage 4 through the illumination prism 81, the second illumination reflector 82, the third illumination reflector 83, the second illumination lens 84, and the third illumination lens 85. The mask system 7 pre-controls the mask stage 4 to complete the mask mounting. The pattern on the mask on the mask stage 4 is transferred to the silicon wafer 10 on the silicon wafer stage 6 via the exposure objective lens 5, completing the exposure.

[0145] It should be noted that the above method may include other implementation methods according to the description of the system embodiments. For specific implementation methods, please refer to the description of the relevant system embodiments, which will not be elaborated here.

[0146] The system embodiments described above are merely illustrative. In the above embodiments, the descriptions of each embodiment have different emphases; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. The above preferred embodiments are not intended to limit this application. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of this application; therefore, the scope of protection of this application is determined by the scope defined in the claims.

[0147] The foregoing has provided a detailed description of an off-axis alignment device, an off-axis alignment method, and a photolithography apparatus provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are intended to help understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there may be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An off-axis alignment device, characterized by, The device comprises: a light source module configured to provide a first light source signal to a wafer, the wafer having coarse alignment marks and fine alignment marks, the coarse alignment marks feeding back a first reflected light signal based on the first light source signal, and the fine alignment marks feeding back a second reflected light signal based on the first light source signal; an auto-focusing module configured to project a first focusing mark on a surface of the wafer, and configured to acquire a third reflected light signal fed back based on the first focusing mark, the third reflected light signal being used for focus plane compensation of the wafer; a first detection module configured to acquire first deviation information based on the first reflected light signal, the first deviation information being used for first compensation of a position of the wafer; a second detection module configured to acquire second deviation information based on the second reflected light signal after the first compensation of the position of the wafer, the second deviation information being used for second compensation of the position of the wafer.

2. The off-axis alignment device of claim 1, wherein, The third reflected light signal is used to acquire focus plane compensation information, the focus plane compensation information is used for focus plane compensation of the wafer, and the focus plane compensation information comprises a focus plane offset of the wafer and a defocus direction of the wafer.

3. The off-axis alignment device according to claim 1 or 2, characterized in that, The auto-focusing module comprises: a focusing mark plate configured to project the first focusing mark on the surface of the wafer; a focusing light source configured to provide a second light source signal to the focusing mark plate, so that the focusing mark plate projects the first focusing mark on the surface of the wafer, the second light source signal feeding back the third reflected light signal based on the first focusing mark; an illumination imaging lens group configured to homogenize the second light source signal; a first alignment imaging lens group configured to collect the third reflected light signal; a light blocking structure configured to block part of the third reflected light signal to determine the defocus direction of the wafer; a first image acquisition module configured to acquire a second focusing mark, the second focusing mark being formed based on conversion of the third reflected light signal by the first alignment imaging lens group and the light blocking structure; The light blocking structure is arranged between the first alignment imaging lens group and the first image acquisition module.

4. The off-axis alignment device of claim 3, wherein, A mark image of the focusing mark plate is a two-dimensional mark.

5. The off-axis alignment device of claim 3, wherein, A wave band corresponding to the second light source signal is independent of a wave band corresponding to the first light source signal.

6. The off-axis alignment device of claim 1, wherein, The first detection module comprises: a first reference mark, the first reflected light signal forming a first calibration light signal after passing through the first reference mark; a second image acquisition module configured to acquire a first alignment image based on the first reflected light signal and to acquire a first reference mark image based on the first calibration light signal, the first alignment image being used to determine the first deviation information; a second alignment imaging lens group arranged between the first reference mark and the second image acquisition module, so that the first reflected light signal and the first calibration light signal are transmitted from the first reference mark to the second image acquisition module.

7. The off-axis alignment device of claim 6, wherein, The first deviation information comprises a first offset and a rotation amount.

8. The off-axis alignment device of claim 1, wherein, The second detection module comprises: a second reference mark, the second reflected light signal forming a second calibration light signal after passing through the second reference mark; a third image acquisition module configured to acquire a second alignment image based on the second reflected light signal and a second reference mark image based on the second calibration light signal, wherein the second alignment image is used to determine the second deviation information; a third alignment imaging lens group configured to collect the second reflected light signal.

9. The off-axis alignment device of claim 8, wherein, The second deviation information includes a second offset.

10. The off-axis alignment device of claim 1, wherein, The light source module includes: an illumination light source configured to provide the first light source signal to the silicon wafer; a diaphragm switching structure configured to switch illumination modes; an illumination lens group configured to collect and homogenize the first light source signal.

11. The off-axis alignment device of claim 1, wherein, The device further includes: an optical lens group structure including at least one of a plurality of mirrors, a plurality of lenses, and a plurality of prisms; The optical lens group structure is used to transfer each light source signal and / or each reflected light signal between the light source module, the autofocus module, the first detection module, and the second detection module.

12. A method of off-axis alignment, applied to the off-axis alignment device according to any one of claims 1-11, characterized in that, The method includes: providing a first light source signal to a silicon wafer, so that the first light source signal is vertically irradiated on the surface of the silicon wafer, and a first reflected light signal and a second reflected light signal are formed; acquiring first deviation information based on the first reflected light signal, wherein the first deviation information is used to perform first compensation on the position of the silicon wafer; acquiring second deviation information based on the second reflected light signal, wherein the second deviation information is used to perform second compensation on the position of the silicon wafer; and projecting a first focus mark on the surface of the silicon wafer, and acquiring a third reflected light signal based on the feedback of the first focus mark, wherein the third reflected light signal is used to perform focus compensation on the silicon wafer.

13. A lithographic apparatus, characterized in that, The photolithography device includes: a photolithography illumination system configured to provide a third light source signal for an exposure process; a mask table having a mask placed on one side surface of the photolithography illumination system; an exposure objective configured to perform reduction imaging on a pattern on the surface of the mask; an off-axis alignment device according to any one of claims 1-11, wherein the off-axis alignment device is used to compensate for silicon wafer deviation; a silicon wafer table having a silicon wafer placed on one side surface of the exposure objective.

Images