Mask alignment system of photoetching machine

Abstract

The invention relates to the technical field of photoetching machines, and particularly provides a mask alignment system of a photoetching machine. The mask alignment system of the photoetching machine comprises a front reflecting mirror group, a fixed lens group, a high-power and low-power switching lens group and a rear reflecting mirror group which are sequentially arranged from an objective lens to a camera, and each of the front reflecting mirror group and the rear reflecting mirror group comprises one or more reflecting mirrors; the high-power and low-power switching lens group comprises a low-power lens group with a low-power amplification factor and a high-power lens group with a high-power amplification factor, the low-power amplification factor is used for a coarse alignment system, and the high-power amplification factor is used for a fine alignment system. In this way, alignment is carried out based on the common object plane and image plane and the common light source and camera during coarse alignment and fine alignment by using the high-power and low-power switching lens group, and the alignment precision is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photolithography machines, and more specifically, to a mask alignment system for a photolithography machine. Background Art

[0002] The photolithography machine is an important equipment in the semiconductor manufacturing process. Its function is to accurately transfer the circuit pattern in the mask (also called the photomask) to the silicon wafer or other substrate according to the predetermined size and position through the exposure process.

[0003] The Reticle Alignment (RA) system is responsible for aligning the pattern on the mask with the existing pattern on the wafer in the lithography machine to ensure accurate overlay between the patterns after exposure. The alignment of the mask alignment system is a step before lithography, so the accuracy of this step of calibration directly affects the overlay accuracy.

[0004] Therefore, it is desirable to provide an improved reticle alignment solution for a photolithography machine. Summary of the invention

[0005] An embodiment of the present application provides a photolithography mask alignment system, which increases alignment accuracy by using a high-power and low-power switching lens group to perform alignment based on a common object plane and image plane and a common light source and camera during coarse alignment and fine alignment.

[0006] According to one aspect of the present application, a photolithography machine mask alignment system is provided, comprising a front reflector group, a fixed lens group, a high-power and low-power switching lens group and a rear reflector group arranged in sequence from an objective lens to a camera, wherein the front reflector group and the rear reflector group each include one or more reflectors, and the high-power and low-power switching lens group includes a switchable low-power lens group with a low-power magnification and a high-power lens group with a high-power magnification, and the low-power magnification is used for a coarse alignment system and the high-power magnification is used for a fine alignment system.

[0007] In the above-mentioned lithography machine mask alignment system, the optical axes of the low-power lens group and the high-power lens group are arranged on the same horizontal plane and are parallel to each other.

[0008] In the above-mentioned lithography machine mask alignment system, the low-magnification lens group and the high-magnification lens group are fixed together by a fixed shell, the bottom of the fixed shell is fixed on a sliding mechanism, a guide rail is arranged under the sliding mechanism, and a driver pushes the sliding mechanism to move through a connecting rod at its shaft end to switch the optical axes of the low-magnification lens group and the high-magnification lens group to overlap with the fixed lens group.

[0009] In the above-mentioned lithography machine mask alignment system, when the light wavelength is 365nm, the low-power magnification is 5 times, and the high-power magnification is 25 times, the low-power lens group includes a first lens and a second lens, and the high-power lens group includes a third lens and a fourth lens.

[0010] In the above-mentioned lithography machine mask alignment system, the first lens and the second lens are arranged from the image plane to the object plane, the surface of the first lens facing the image plane is a spherical surface, with a curvature radius of 32.159, a thickness of 21.446 mm, a refractive index of 1.4745, and an dispersion coefficient of 67.82; the surface of the first lens facing the object plane is a spherical surface, with a curvature radius of 20.476, and a thickness of 11.452 mm; the surface of the second lens facing the image plane is a spherical surface, with a curvature radius of 25.608, a thickness of 15.330 mm, a refractive index of 1.5194, and an dispersion coefficient of 63.29; the surface of the first lens facing the object plane is a spherical surface, with a curvature radius of 33.846, and a thickness of 20.000 mm.

[0011] In the above-mentioned lithography machine mask alignment system, the third lens and the fourth lens are arranged from the image plane to the object plane, the surface of the third lens facing the image plane is a spherical surface, with a curvature radius of -29.445, a thickness of 4.000 mm, a refractive index of 1.5194, and an dispersion coefficient of 63.29; the surface of the third lens facing the object plane is a spherical surface, with a curvature radius of 8.000, and a thickness of 31.200 mm; the surface of the fourth lens facing the image plane is a spherical surface, with a curvature radius of 61.553, a thickness of 15.000 mm, a refractive index of 1.4745, and an dispersion coefficient of 67.82; the surface of the fourth lens facing the object plane is a spherical surface, with a curvature radius of -35.182, and a thickness of 8.901 mm.

[0012] In the above-mentioned lithography machine mask alignment system, when the magnification difference between the low magnification and the high magnification is greater than a predetermined magnification difference threshold, or the low magnification and the high magnification are both less than a predetermined low magnification threshold or greater than a predetermined high magnification threshold, the number of lenses in the low magnification lens group and the high magnification lens group is greater than two.

[0013] In the above-mentioned mask alignment system for a photolithography machine, the number and optical parameters of the lenses in the fixed lens group are set so that the light between the fixed lens group and the high-power and low-power switching lens group is parallel light.

[0014] In the above-mentioned lithography mask alignment system, the distance between the fixed lens group and the mask is greater than the predetermined microscope system working distance.

[0015] In the above-mentioned lithography machine mask alignment system, when the numerical aperture in the mask direction is less than 0.13, the distance between the fixed lens group and the mask is 59.35 mm.

[0016] In the above-mentioned lithography machine mask alignment system, the high-power and low-power switching lens group includes one or more additional lens groups that can be switched with the low-power lens group and the high-power lens group and have a magnification different from the low-power magnification and the high-power magnification.

[0017] The lithography machine mask alignment system provided in the embodiment of the present application can increase the alignment accuracy by using a high-magnification and low-magnification switching lens group to align based on a common object plane and image plane as well as a common light source and camera during coarse alignment and fine alignment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present application will become clear to those of ordinary skill in the art. The drawings in the specification are only used for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0019] Figure 1 The figure shows a schematic structural diagram of a mask alignment system for a lithography machine according to an embodiment of the present application.

[0020] Figure 2 The diagram illustrates a coarse alignment principle diagram of a mask alignment system for a lithography machine according to an embodiment of the present application.

[0021] Figure 3 The diagram illustrates a fine alignment principle diagram of a mask alignment system for a lithography machine according to an embodiment of the present application.

[0022] Figure 4 A schematic top view of a structural implementation example of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0023] Figure 5 The diagram shows Figure 4 The structure of the fixed lens barrel and the high-power and low-power switching lens barrel in the mask alignment system of the lithography machine is shown in a top view.

[0024] Figure 6 A schematic diagram of a first embodiment of a lens group of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0025] Fig. 7A and Figure 7B The MTF diagrams of the lens group of the first embodiment of the reticle alignment system of the lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated.

[0026] Fig. 8A and Figure 8B The point diagrams of the lens group of the first embodiment of the mask alignment system of the lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated.

[0027] Fig. 9 A schematic diagram of a second embodiment of a lens group of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0028] Fig. 10A and Fig. 10B The MTF diagrams of the lens group of the second embodiment of the mask alignment system for a lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated.

[0029] Fig.11A and Fig. 11B The point diagrams of the lens group of the second embodiment of the mask alignment system for a lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated.

[0030] Fig.12 A schematic diagram of a third embodiment of a lens assembly of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0031] Fig.13A and Fig. 13B The MTF diagrams of the lens group of the third embodiment of the reticle alignment system for a lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated.

[0032] Fig.14A and Fig. 14B The point diagrams of the lens group of the third embodiment of the mask alignment system for a lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. DETAILED DESCRIPTION

[0033] Below, the exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the exemplary embodiments described here.

[0034] Figure 1 FIG. 1 is a schematic diagram of the structure of a mask alignment system for a photolithography machine according to an embodiment of the present application. Figure 1As shown, in the mask alignment system of the lithography machine according to the embodiment of the present application, the light from the objective lens passes through the front reflector system, the fixed lens barrel, the high-power and low-power switching lens barrel and the rear reflector system in sequence, and finally reaches the camera. The high-power and low-power switching lens barrel includes two corresponding magnifications that can be switched, wherein the low magnification is used for the rough alignment system, and the high magnification is used for the fine alignment system.

[0035] Usually, the mask alignment system of the lithography machine includes a coarse alignment system and a fine alignment system. The coarse alignment system is used to align when the high- and low-magnification switching lens barrel is at a low magnification. The light source is below the base plate (Foudation Mark: FM). At this time, through the transparent area on the base plate, only the coarse alignment mark on the mask is visible on the camera. The deviation between the center of the mark on the mask and the center of the target surface of the alignment camera is calculated, such as Figure 2 shown. Figure 2 The diagram shows a rough alignment principle diagram of a mask alignment system for a lithography machine according to an embodiment of the present application. Here, the lower surface of the mask is the imaging object plane of the mask alignment system for the lithography machine, and the camera is the imaging image plane, wherein the light source can be a critical illumination system.

[0036] In the fine alignment system, the light source is also below the base plate, and parallel light with a predetermined numerical aperture is irradiated onto the base plate. The light is then magnified or reduced by a certain factor through the projection objective lens and reaches the mark on the mask. The predetermined numerical aperture describes the angular range of light that can be collected, and each optical imaging system will have a corresponding numerical aperture (NA) value. In an embodiment of the present application, the main objective lens (i.e., the projection objective lens) is an imaging system, and the mask alignment system above is an imaging system corresponding to one of the switching lenses, and another imaging system corresponding to the other switching lens. Generally speaking, in a lithography machine, the NA value of the mask alignment system is larger than that of the main objective lens. Here, since the projection objective lens is a conjugate system, the marks on the mask and the marks on the base plate will be imaged together onto the camera of the mask alignment system through the fine alignment system. The offset of the two stages is determined by the center points of the two marks, such as Figure 3 shown. Figure 3 The diagram illustrates a fine alignment principle diagram of a mask alignment system for a lithography machine according to an embodiment of the present application.

[0037] That is, in the mask alignment system of the lithography machine according to the embodiment of the present application, the coarse alignment and fine alignment optical paths are switched by the high-power and low-power switching lens barrel, and other structures except the high-power and low-power switching lens barrel are fixedly set, which can improve the alignment accuracy while saving the internal space of the lithography machine. That is, if both the coarse alignment and fine alignment systems include two cameras, there may even be two light sources, so that more lenses and reflectors will appear in the middle, and it will be difficult to adjust the optical path, and multiple light sources, multiple cameras, and multiple lenses will lead to a decrease in space utilization.

[0038] In the lithography machine mask alignment system according to the embodiment of the present application, although motors and other control components are added, redundant lenses, cameras, light sources, etc. can be reduced, and the motor control accuracy will be higher than the manual optical path adjustment accuracy.

[0039] Therefore, according to an embodiment of the present application, a mask alignment system for a lithography machine includes a front mirror group, a fixed lens group, a high-power and low-power switching lens group, and a rear mirror group arranged in sequence from an objective lens to a camera, wherein the front mirror group and the rear mirror group each include one or more mirrors, and the high-power and low-power switching lens group includes a switchable low-power lens group with a low-power magnification and a high-power lens group with a high-power magnification, and the low-power magnification is used for a coarse alignment system and the high-power magnification is used for a fine alignment system.

[0040] Figure 4 FIG. 1 is a schematic top view of a structural implementation example of a mask alignment system for a lithography machine according to an embodiment of the present application. Figure 4 As shown, in the lithography machine mask alignment system, the light from the objective lens passes through the first reflecting prism, the fixed lens barrel, the high- and low-power switching lens barrel, the second reflecting prism and the third reflecting prism in sequence, and finally reaches the camera. That is, after the light path is determined, the first reflecting mirror, the fixed lens barrel, the second reflecting mirror, the third reflecting mirror and the camera are all fixed, and the two lenses at the high- and low-power switching lens barrel are switched according to business needs, generally high magnification first and then low magnification. For example, the high- and low-power lenses are connected through the outermost lens barrel, and the entire lens barrel falls on the guide rail. The motor drives the guide rail, and the high- and low-power switching is achieved through the linear reciprocating motion of the guide rail, such as Figure 5 shown. Figure 5 The diagram shows Figure 4 The structure of the fixed lens barrel and the high-power and low-power switching lens barrel in the mask alignment system of the lithography machine is shown in a top view.

[0041] Return to reference Figure 2 and Figure 3 , Figure 4 The figure shows a mask support table, in the middle of which a hollow window area for mask alignment and exposure is provided. Figure 2 and Figure 3 The mask is aligned with the object plane, and a set of mask alignment systems are arranged on the left and right sides of the hollow window area respectively. The two sets of mask alignment systems are used to align the two alignment marks on the mask respectively. The alignment process includes coarse alignment and fine alignment, and the two sets of mask alignment systems are set to act synchronously.

[0042] As Figure 4Taking the mask alignment system on the right side as an example, it includes a first reflector arranged above one side of the hollow alignment area, a fixed lens barrel arranged on one side of the first reflector, a high-power and low-power switching lens barrel arranged on one side of the fixed lens barrel away from the first reflector, and the high-power and low-power switching lens barrel is driven by an electric cylinder, for example, and includes a coarse alignment lens barrel (low power) and a fine alignment lens barrel (high power). Among them, the configuration mode of the optical elements inside the coarse alignment lens barrel is to magnify low power, for example, 5 times, and the configuration mode of the optical elements inside the fine alignment lens barrel is to magnify high power, for example, 25 times, and the optical axes of the coarse alignment lens barrel and the fine alignment lens barrel are arranged on the same horizontal plane and parallel to each other, the coarse alignment lens barrel and the fine alignment lens barrel are fixed together by a fixed housing, such as a ferrule, and the bottom is fixed on a sliding mechanism, such as a slide seat, and a guide rail is arranged below the slide seat, and a driver, such as an electric cylinder, pushes the slide seat to move through the connecting rod at its shaft end, thereby switching the coarse alignment lens barrel or the fine alignment lens barrel to overlap the optical axis of the fixed lens barrel, so that the detected alignment mark is switched from coarse alignment with low power magnification to fine alignment with high power magnification. In actual application, the two electric cylinders on the left and right sides of the mask plate move synchronously. In addition, a second reflector and a third reflector are arranged on the side of the slide away from the fixed lens barrel, and the image collected from the first reflector passes through the fixed lens barrel, the coarse alignment lens barrel / fine alignment lens barrel, the second reflector, and the third reflector in sequence before entering the camera. Here, the fixed lens barrel can be implemented as a microscope system, and the emitted light is parallel light in each field of view, and an aperture can be set between the fixed lens barrel and the high-power and low-power switching lens barrel.

[0043] Therefore, in the mask alignment system of the lithography machine according to the embodiment of the present application, the optical axes of the low-power lens group and the high-power lens group are arranged on the same horizontal plane and are parallel to each other.

[0044] Furthermore, in the above-mentioned lithography machine mask alignment system, the low-magnification lens group and the high-magnification lens group are fixed together by a fixed shell, the bottom of the fixed shell is fixed on a sliding mechanism, a guide rail is provided under the sliding mechanism, and a driver pushes the sliding mechanism to move through a connecting rod at its shaft end to switch the optical axes of the low-magnification lens group and the high-magnification lens group to overlap with the fixed lens group.

[0045] Below, specific implementation embodiments of the lens group in the mask alignment system of the lithography machine according to the embodiments of the present application will be described respectively.

[0046] In the first embodiment, the wavelength of light is 365nm, the low magnification, i.e., the rough alignment magnification, in the mask alignment system of the lithography machine is 5 times, and the high magnification, i.e., the fine alignment magnification is 25 times. The low magnification lens group includes a first lens and a second lens in sequence from the image plane, i.e., the camera, to the object plane, i.e., the mask plane, and the fixed lens group includes a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The eighth lens is a mask, and an aperture is provided between the low magnification lens group and the fixed lens group, such as Figure 6 Here, Figure 6 A schematic diagram of a first embodiment of a lens group of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0047] Furthermore, in the order from the image plane to the object plane, that is, the surface S1 of the first lens faces the image plane, and the surface S2 faces the object plane, the optical parameters of the first lens to the eighth lens are shown in the following Table 1:

[0048]

Table 1

[0049]

[0050] Furthermore, in the first embodiment, the high-power lens group includes a first lens and a second lens in sequence from the image plane to the object plane. Similarly, the third lens to the seventh lens are fixed lens groups, and a stop is provided between the high-power lens group and the fixed lens group. The optical parameters of the first lens to the eighth lens are as shown in the following Table 2:

[0051]

Table 2

[0052]

[0053] Therefore, in the mask alignment system of the lithography machine according to the embodiment of the present application, when the light wavelength is 365nm, the low magnification is 5 times, and the high magnification is 25 times, the low magnification lens group includes a first lens and a second lens, and the high magnification lens group includes a third lens and a fourth lens.

[0054] Moreover, in the above-mentioned lithography machine mask alignment system, the surface of the first lens facing the image plane is a spherical surface with a curvature radius of 32.159, a thickness of 21.446 mm, a refractive index of 1.4745, and a dispersion coefficient of 67.82; the surface of the first lens facing the object plane is a spherical surface with a curvature radius of 20.476 and a thickness of 11.452 mm; the surface of the second lens facing the image plane is a spherical surface with a curvature radius of 25.608, a thickness of 15.330 mm, a refractive index of 1.5194, and a dispersion coefficient of 63.29; the surface of the first lens facing the object plane is a spherical surface with a curvature radius of 33.846 and a thickness of 20.000 mm.

[0055] In addition, in the above-mentioned lithography machine mask alignment system, the surface of the third lens facing the image plane is a spherical surface, with a curvature radius of -29.445, a thickness of 4.000 mm, a refractive index of 1.5194, and a dispersion coefficient of 63.29; the surface of the third lens facing the object plane is a spherical surface, with a curvature radius of 8.000, and a thickness of 31.200 mm; the surface of the fourth lens facing the image plane is a spherical surface, with a curvature radius of 61.553, a thickness of 15.000 mm, a refractive index of 1.4745, and a dispersion coefficient of 67.82; the surface of the fourth lens facing the object plane is a spherical surface, with a curvature radius of -35.182, and a thickness of 8.901 mm.

[0056] Fig. 7A and Figure 7B The MTF diagrams of the lens group of the first embodiment of the reticle alignment system of the lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig. 7A FIG. 1 illustrates an MTF diagram of a lens group of a first embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during rough alignment, and Figure 7B FIG. 1 shows an MTF diagram of a lens group of a first embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during fine alignment. Fig. 7A and Figure 7B As shown, the black line represents the diffraction limit. One is the meridional diffraction limit, and the other is the sagittal diffraction limit. The remaining lines are the MTFs of various fields of view and wavelengths. It can be seen that they reach near the meridional and sagittal diffraction limit lines. Here, the closer to the meridional and sagittal diffraction limit lines, the closer the system is to the ideal optical system. In other words, the closer to the meridional and sagittal diffraction limit lines, the better the optical performance of the system.

[0057] Fig. 8A and Figure 8B The point diagrams of the lens group of the first embodiment of the reticle alignment system of the photolithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig. 8A FIG. 1 shows a spot diagram of a lens group of a first embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during rough alignment, and Figure 8B The figure shows a spot diagram of the lens group of the first embodiment of the lithography mask alignment system according to the embodiment of the present application during fine alignment. The distribution of points in the spot diagram can approximately represent the energy distribution of the image points. The density of these points can be used to measure the imaging quality of the system. The denser the point, the better the imaging. In addition, the shape of the spot diagram distribution figure can also be used to judge and understand the influence of various geometric aberrations of the system. For example, if the shape deviates seriously from the circle, it indicates the existence of other aberrations. Fig. 8A and Figure 8BAs shown, the spot diagrams are basically circular and the spots are small, indicating that the aberrations are small and the optical performance required for alignment can be achieved. Here, the spot size mainly depends on the RMS radius shown in the figure, which is less than 1.5μm.

[0058] In the second embodiment, the wavelength of light is 365nm, the low magnification, i.e., the rough alignment magnification, in the mask alignment system of the lithography machine is 5 times, and the high magnification, i.e., the fine alignment magnification is 25 times. The low magnification lens group includes a first lens, a second lens, and a third lens in sequence from the image plane, i.e., the camera, to the object plane, i.e., the mask plane, and the fixed lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The ninth lens is a mask, and an aperture is provided between the low magnification lens group and the fixed lens group, as shown in FIG. Fig. 9 Here, Fig. 9 A schematic diagram of a second embodiment of a lens group of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0059] The optical parameters of the first lens to the ninth lens are shown in Table 3 below:

[0060]

Table 3

[0061]

[0062] Furthermore, in the second embodiment, the high-power lens group includes a first lens, a second lens, and a third lens in sequence from the image plane to the object plane. Similarly, the fourth lens to the eighth lens are fixed lens groups, and a stop is provided between the high-power lens group and the fixed lens group. The optical parameters of the first lens to the ninth lens are as shown in the following Table 4:

[0063]

Table 4

[0064]

[0065] Fig. 10A and Fig. 10B The MTF diagrams of the lens group of the second embodiment of the reticle alignment system of the lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig. 10A The figure shows the MTF diagram of the lens group of the second embodiment of the reticle alignment system of the lithography machine according to the embodiment of the present application during the rough alignment, and Fig. 10B FIG. 1 shows an MTF diagram of a lens group of a second embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during fine alignment. Fig. 10A and Fig. 10BAs shown, when the low-magnification lens group and the high-magnification lens group include three lenses, their MTF also reaches the diffraction limit, but is very close to the MTF of two lenses, indicating that both three and two lenses have reached the diffraction limit. This also shows that two lenses are enough, and adding more lenses will not improve the optical performance too much, and it will also increase unnecessary space.

[0066] Fig.11A and Fig. 11B The point diagrams of the lens group of the second embodiment of the reticle alignment system of the photolithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig.11A FIG. 1 illustrates a spot diagram of a lens group of a second embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during rough alignment, and Fig. 11B FIG. 1 is a point diagram of a lens group of a second embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during fine alignment. Fig.11A and Fig. 11B As shown, when the low-power lens group and the high-power lens group include three lenses, the point diagrams are small, and the RMS radius is less than 1μm, which is smaller than when the number of lenses is two, but not much smaller, indicating that a bottleneck has been reached.

[0067] In the third embodiment, the wavelength of light is 365nm, the low magnification in the mask alignment system of the lithography machine, that is, the rough alignment magnification is 5 times, and the high magnification, that is, the fine alignment magnification is 25 times. The low magnification lens group includes a first lens, and the fixed lens group includes a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from the image plane, that is, the camera, to the object plane, that is, the mask. The seventh lens is a mask, and an aperture is provided between the low magnification lens group and the fixed lens group, such as Fig.12 Here, Fig.12 A schematic diagram of a third embodiment of a lens assembly of a mask alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0068] The optical parameters of the first lens to the seventh lens are shown in the following Table 5:

[0069]

Table 5

[0070]

[0071] Furthermore, in the third embodiment, the high-power lens group includes a first lens. Similarly, the second lens to the sixth lens in order from the image plane to the object plane are a fixed lens group, and an aperture is provided between the high-power lens group and the fixed lens group, and the optical parameters of the first lens to the seventh lens are as shown in the following Table 6:

[0072]

Table 6

[0073]

[0074] Fig.13A and Fig. 13B The MTF diagrams of the lens group of the third embodiment of the reticle alignment system of the lithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig.13A FIG. 1 illustrates an MTF diagram of a lens group of a third embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during rough alignment, and Fig. 13B FIG. 1 shows an MTF diagram of a lens group of a third embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during fine alignment. Fig.13A and Fig. 13B As shown, when the low-magnification lens group and the high-magnification lens group include only one lens, the diffraction limit of black is not reached. Therefore, in the 5x and 25x lithography machine mask alignment system, it is more difficult to achieve the alignment requirement by replacing only one lens.

[0075] Fig.14A and Fig. 14B The point diagrams of the lens group of the third embodiment of the reticle alignment system of the photolithography machine according to the embodiment of the present application at low magnification and high magnification are respectively illustrated. Fig.14A FIG. 1 illustrates a spot diagram of a lens group of a third embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during rough alignment, and Fig. 14B FIG. 1 is a point diagram of a lens group of a third embodiment of a mask alignment system for a lithography machine according to an embodiment of the present application during fine alignment. Fig.14A and Fig. 14B As shown, when the low-power lens group and the high-power lens group include only one lens, the spot diagrams are both relatively large, and the RMS radius is larger than that of the first embodiment and the second embodiment. In addition, the RMS radius obtained between the central field of view (0,0) and the edge field of view is quite different, and the spot diagram of the edge field of view presents an ellipse with a large spot radius, indicating that there is a large aberration and the optical performance required for alignment is not met.

[0076] However, in other embodiments, the more replaceable lenses the low-power lens group and the high-power lens group include, the more possibilities for imaging magnification can be provided. That is, in the above embodiment, the magnification is 5 times and 25 times. If the magnification is 5 times and 30 times, or 1 times and 50 times, etc., the difference in magnification is large, or the low-power magnification and the high-power magnification are both large or both small, more lenses are needed to achieve the index.

[0077] That is, in the mask alignment system of the lithography machine according to the embodiment of the present application, when the magnification difference between the low magnification and the high magnification is greater than a predetermined magnification difference threshold, or when the low magnification and the high magnification are both less than a predetermined low magnification threshold or greater than a predetermined high magnification threshold, the number of lenses of the low magnification lens group and the high magnification lens group is greater than two.

[0078] In addition, in the above first to third embodiments, the fixed lens group includes five lenses, but in the embodiments of the present application, the number and optical parameters of the lenses in the fixed lens group are not limited. It is only necessary to ensure that the light between the fixed lens group and the high-magnification and low-magnification switching lens group is parallel light.

[0079] That is, in the mask alignment system of the lithography machine according to the embodiment of the present application, the number and optical parameters of the lenses in the fixed lens group are set so that the light between the fixed lens group and the high-power and low-power switching lens group is parallel light.

[0080] In addition, in the embodiment of the present application, the distance between the fixed lens group and the mask is appropriately increased, that is, the working distance of the fixed lens group (microscope system) is greater than the working distance of a normal microscope. Specifically, in the first to third embodiments, the working distance of the fixed lens group is 10+20+23+6.35=59.35mm. This is because in the embodiment of the present application, the numerical aperture in the mask alignment system of the lithography machine is relatively small. For example, in the first to third embodiments, the numerical aperture in the mask direction is less than 0.13.

[0081] That is, in the lithography machine mask alignment system according to the embodiment of the present application, the distance between the fixed lens group and the mask is greater than the predetermined microscope system working distance.

[0082] Furthermore, in the above-mentioned lithography machine mask alignment system, when the numerical aperture in the mask direction is less than 0.13, the distance between the fixed lens group and the mask is 59.35 mm.

[0083] Therefore, the mask alignment system of the lithography machine according to the embodiment of the present application uses the common object plane and image plane, common light source and camera for the coarse alignment and fine alignment, thereby sharing a mark on the mask, and increasing the alignment accuracy by reducing the second displacement. In addition, the mask alignment system of the lithography machine according to the embodiment of the present application uses a fixed lens group to partially overlap the coarse alignment and fine alignment entities, thereby reducing space and improving the space utilization rate of the lithography machine.

[0084] Furthermore, in the mask alignment system of the lithography machine according to the embodiment of the present application, the low-magnification imaging and high-magnification imaging of the low-magnification lens group and the high-magnification lens group are combined, wherein the low-magnification field of view can reach the millimeter level, and the high-magnification field of view can reach the micron level.

[0085] It is worth noting that although in the above description, the high-power and low-power switching lens group of the lithography machine mask alignment system according to the embodiment of the present application includes a switchable low-power lens group with a low magnification and a high-power lens group with a high magnification, the high-power and low-power switching lens group may include more lens groups.

[0086] That is, in the lithography machine mask alignment system according to the embodiment of the present application, the high-power and low-power switching lens group includes one or more additional lens groups that can be switched with the low-power lens group and the high-power lens group, and have a magnification different from the low-power magnification and the high-power magnification.

[0087] In addition, in the lithography machine mask alignment system according to the embodiment of the present application, the low-magnification lens group and the high-magnification lens group can be either a coaxial lens group or an off-axis lens group.

[0088] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0089] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0090] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0091] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0092] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A mask alignment system for a photolithography machine, comprising a front reflector group, a fixed lens group, a high-power and low-power switching lens group and a rear reflector group arranged in sequence from an objective lens to a camera; in, The front reflector group and the rear reflector group each include one or more reflectors, and the high-power and low-power switching lens group includes a switchable low-power lens group with a low magnification and a high-power lens group with a high magnification, and the low magnification is used for a coarse alignment system and the high magnification is used for a fine alignment system.

2. The mask alignment system for a photolithography machine according to claim 1, characterized in that: The optical axes of the low-power lens group and the high-power lens group are arranged on the same horizontal plane and are parallel to each other.

3. The mask alignment system for a photolithography machine according to claim 2, characterized in that: The low-magnification lens group and the high-magnification lens group are fixed together by a fixed shell, the bottom of the fixed shell is fixed on a sliding mechanism, a guide rail is arranged below the sliding mechanism, and a driver pushes the sliding mechanism to move through a connecting rod at its shaft end to switch the optical axes of the low-magnification lens group and the high-magnification lens group to overlap with the fixed lens group.

4. The mask alignment system for a photolithography machine according to claim 1, wherein: When the wavelength of light is 365 nm, the low magnification is 5 times, and the high magnification is 25 times, the low magnification lens group includes a first lens and a second lens, and the high magnification lens group includes a third lens and a fourth lens.

5. The mask alignment system for a photolithography machine according to claim 4, characterized in that: The first lens and the second lens are arranged from the image plane to the object plane, The surface of the first lens facing the image plane is a spherical surface with a curvature radius of 32.159, a thickness of 21.446 mm, a refractive index of 1.4745, and an Abbe number of 67.82; The surface of the first lens facing the object plane is a spherical surface with a curvature radius of 20.476 and a thickness of 11.452 mm; The surface of the second lens facing the image plane is a spherical surface with a curvature radius of 25.608, a thickness of 15.330 mm, a refractive index of 1.5194, and an Abbe number of 63.29; The surface of the first lens facing the object plane is a spherical surface with a curvature radius of 33.846 and a thickness of 20.000 mm.

6. The mask alignment system for a photolithography machine according to claim 5, characterized in that: The third lens and the fourth lens are arranged from the image plane to the object plane, The surface of the third lens facing the image plane is a spherical surface, with a curvature radius of -29.445, a thickness of 4.000 mm, a refractive index of 1.5194, and an Abbe number of 63.29; The surface of the third lens facing the object plane is a spherical surface with a curvature radius of 8.000 and a thickness of 31.200 mm; The surface of the fourth lens facing the image plane is a spherical surface with a curvature radius of 61.553, a thickness of 15.000 mm, a refractive index of 1.4745, and an Abbe number of 67.82; The surface of the fourth lens facing the object plane is a spherical surface with a curvature radius of -35.182 and a thickness of 8.901 mm.

7. The mask alignment system for a photolithography machine according to claim 4, characterized in that: When the magnification difference between the low magnification and the high magnification is greater than a predetermined magnification difference threshold, or the low magnification and the high magnification are both less than a predetermined low magnification threshold or greater than a predetermined high magnification threshold, the number of lenses in the low magnification lens group and the high magnification lens group is greater than two.

8. The mask alignment system for a photolithography machine according to claim 1, characterized in that: The number and optical parameters of the lenses in the fixed lens group are set so that the light between the fixed lens group and the high-power and low-power switching lens group is parallel light.

9. The mask alignment system for a photolithography machine according to claim 1, characterized in that: The distance between the fixed lens group and the mask is greater than a predetermined working distance of the microscope system.

10. The mask alignment system for a photolithography machine according to claim 9, characterized in that: When the numerical apertures in the direction of the mask are all less than 0.13, the distance between the fixed lens group and the mask is 59.35 mm.

11. The mask alignment system for a photolithography machine according to claim 1, characterized in that: The high-low magnification switching lens group includes one or more additional lens groups switchable with the low-power lens group and the high-power lens group, and having magnifications different from the low-power magnification and the high-power magnification.

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