A projection photolithography machine alignment sensing system based on integration of gratings and lens groups

Abstract

The application discloses a projection photolithography machine alignment sensing system based on integration of a grating and a lens group. The system comprises a light source group, a detection grating, a lens group and a detector. The light source group comprises a first light source pair and a second light source pair. The first light source pair and the second light source pair both emit light beams. The angle between the incident direction of the light beams on a silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the angle between the first-order diffraction light and zero-order light of the silicon wafer alignment mark after diffraction. The horizontal plane of the detection grating and the horizontal plane of the detector are conjugated with respect to the lens group. The detection grating is on the object plane of the lens group, and the detector is on the image plane of the lens group. The projection photolithography machine alignment sensing system has a simple structure and can realize sub-nanometer and deep sub-nanometer precision photolithography machine alignment mark position detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoetching machine, and particularly relates to a projection photoetching machine alignment sensing system based on integration of grating and lens group. BACKGROUND

[0002] In the process of manufacturing integrated circuits by using a projection photoetching machine, mask patterns carrying integrated circuit layout information are transferred to the photoresist on a wafer by an imaging projection objective lens. Integrated circuit manufacturing needs to go through dozens or even hundreds of photoetching exposure processes to accurately transfer different mask patterns to the corresponding positions on the wafer layer by layer.

[0003] Therefore, the photoetching machine needs high overlay accuracy. Overlay accuracy is a core performance indicator of the photoetching machine, and improving overlay accuracy is an important factor driving the continuous development of integrated circuit manufacturing technology. The improvement of the alignment accuracy of the photoetching machine is a key factor in improving the overlay accuracy.

[0004] Photoetching machine alignment is achieved by an alignment system. In order to accurately transfer each layer of patterns to the correct position on the wafer and make the position error of the layer relative to the previous layer within the tolerance range, the position of the wafer and the position of the mask need to be detected before exposure, and the alignment between the wafer and the mask is achieved by calculating the position relationship between the wafer and the mask.

[0005] The accurate detection of the wafer position is completed by the alignment sensing system. The accurate sensing of the wafer position is a prerequisite for high-precision alignment of the photoetching machine, so the detection accuracy of the alignment sensing system determines the alignment accuracy of the photoetching machine to a great extent, and can be said to determine the level of overlay accuracy to a great extent.

[0006] Currently, the main manufacturers of projection photoetching machines for advanced node integrated circuit manufacturing are ASML Company in the Netherlands and NIKON Company in Japan. The alignment accuracy of the photoetching machines for advanced node integrated circuit manufacturing has reached sub-nanometer and deep sub-nanometer, and the detection accuracy of the corresponding alignment sensing system has been very high.

[0007] The FIA (Field Image Alignment) technology of NIKON can clearly detect the alignment mark by introducing the phase contrast microscopy technology, and obtain the alignment mark image with high contrast, and calculate the position average of the image intensity variation to obtain the alignment mark position information. The information processing of the alignment technology is relatively simple, and high-precision alignment can be realized. However, due to the light absorption of the photoresist and other materials on the surface of the silicon wafer, the alignment accuracy is easily affected by the variation of the alignment signal strength, and the system components are relatively more and the structure is relatively complex. The SMASH and ORION technologies of ASML are based on the phase grating alignment (PGA) principle, and the silicon wafer alignment mark position is calculated through the interference signals between different diffraction orders at different wavelengths, which has high alignment accuracy and process stability. Since the system is composed of self-referencing interferometer, optical lens and other optical devices, the structure is relatively complex, and the processing and adjustment are difficult.

[0008] The nanoimprint lithography tool of CANON in Japan adopts the TTM (through-the-mask) Moire fringe alignment technology to realize the alignment between the mask and the silicon wafer. The characteristics of the alignment technology are as follows: phase gratings are respectively processed on the mask and the silicon wafer as alignment marks, the illumination light is diffracted by the silicon wafer alignment mark and the mask alignment mark to obtain positive and negative first-order diffraction light, and the Moire fringe is formed by the interference between the positive and negative first-order diffraction light, and the position offset between the silicon wafer and the mask is obtained by measuring and calculating the Moire fringe, and the alignment accuracy can reach sub-nanometer. However, the TTM Moire fringe alignment technology is only suitable for the alignment under the condition that the gap between the mask and the silicon wafer is small, and cannot be used for the alignment of the projection lithography machine with a certain distance between the mask and the silicon wafer. SUMMARY

[0009] Therefore, the present application provides a projection lithography machine alignment sensing system based on the integration of gratings and lens groups, which can solve the above technical problems.

[0010] In order to solve the above technical problems, the present application is implemented as follows.

[0011] A projection lithography machine alignment sensing system based on the integration of gratings and lens groups, comprising:

[0012] a light source group, a detection grating, a lens group and a detector.

[0013] The light source group comprises a first light source group, the first light source group comprises a first light source pair and a second light source pair for illuminating in x and y directions respectively; the two light sources in each light source pair are of the same parameter and type; the light sources in the first light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; the light sources in the second light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane;

[0014] The first light source pair and the second light source pair both emit light beams, the angle between the incident direction of the light beam on the silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the angle between the first-order diffraction light and the zero-order light after the silicon wafer alignment mark is diffracted by the light beam;

[0015] The x and y directions are the horizontal and vertical directions of the horizontal plane in the global coordinate system of the projection lithography machine, and the z direction is the direction of the xy plane perpendicular to the x and y directions;

[0016] The horizontal plane where the detection grating is located and the horizontal plane where the detector is located are in conjugate relationship with respect to the object image formed by the lens group; the detection grating is on the object plane of the lens group, and the detector is on the image plane of the lens group; the lens group is an afocal optical system.

[0017] Preferably, the light source group further comprises a second light source group different from the first light source group in wavelength, the second light source group comprises a third light source pair and a fourth light source pair; the two light sources in each light source pair are of the same parameter and type; the two light sources in the third light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; the two light sources in the fourth light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane;

[0018] The third light source pair and the fourth light source pair both emit light beams, the angle between the incident direction of the light beam on the silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the angle between the first-order diffraction light and the zero-order light after the silicon wafer alignment mark is diffracted by the light beam.

[0019] Preferably, the first light source group and the second light source group belong to visible light sources and near-infrared light sources respectively.

[0020] Preferably, the light source group further comprises a plurality of light source groups different from the first light source group and the second light source group in wavelength, each light source group comprises two light source pairs, and the two light sources in each light source pair are of the same parameter and type; the layout mode of each light source group is that the two light sources in one light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane, and the two light sources in the other light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane;

[0021] The two light source pairs of each light source group emit light beams, and the included angle between the incident direction of the light beams on the silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the included angle between the first-order diffraction light and the zero-order light after the light beams irradiate the silicon wafer alignment mark to generate diffraction.

[0022] Preferably, the silicon wafer alignment mark is composed of a first grating with a period P1, a second grating with a period P2, a third grating with a period P1 and a fourth grating with a period P2, and the numerical difference between P1 and P2 is less than a first preset threshold; the first grating and the second grating are used for detecting the position deviation of the silicon wafer to be aligned in the x direction, and the third grating and the fourth grating are used for detecting the position deviation of the silicon wafer to be aligned in the y direction; the first grating and the second grating are arranged adjacent to each other in the y direction, and the grating lines of the first grating and the second grating are both along the y direction, and the x coordinates of the center positions of the first grating and the second grating are the same; the third grating and the fourth grating are arranged adjacent to each other in the x direction, and the grating lines of the third grating and the fourth grating are both along the x direction, and the y coordinates of the center positions of the third grating and the fourth grating are the same.

[0023] The detection grating is composed of a fifth grating with a period P2, a sixth grating with a period P1, a seventh grating with a period P2 and an eighth grating with a period P1; the fifth grating and the sixth grating are used for detecting the position deviation of the silicon wafer to be aligned in the x direction, and the seventh grating and the eighth grating are used for detecting the position deviation of the silicon wafer to be aligned in the y direction; the fifth grating and the sixth grating are arranged adjacent to each other in the y direction, and the grating lines of the fifth grating and the sixth grating are both along the y direction, and the x coordinates of the center positions of the fifth grating and the sixth grating are the same; the relative positions of the first grating and the second grating on the silicon wafer alignment mark in the y direction are the same as the relative positions of the fifth grating and the sixth grating on the detection grating in the y direction; the relative positions of the third grating and the fourth grating on the silicon wafer alignment mark in the x direction are the same as the relative positions of the seventh grating and the eighth grating on the detection grating in the x direction.

[0024] A detection method of an alignment sensing system of a projection photolithography machine based on integration of gratings and lens groups, based on the alignment sensing system of the projection photolithography machine based on integration of gratings and lens groups as described above, the method comprises:

[0025] Step S1: determining the detection direction of the silicon wafer alignment mark 3, based on the light beams emitted by part or all of the light source pairs in the illumination direction; the silicon wafer alignment mark 3 generates negative first-order diffraction light and positive first-order diffraction light after being irradiated by the light beams; the negative first-order diffraction light and the positive first-order diffraction light generate negative first-order diffraction light and positive first-order diffraction light again after passing through the detection grating 4; the negative first-order diffraction light and the positive first-order diffraction light interfere on the detection surface of the detector 6 after passing through the lens group 5, generating a plurality of groups of interference fringes; wherein the detection direction is the x direction or the y direction.

[0026] Step S2: In the plurality of groups of interference fringes, two groups of Moire fringes are obtained, and phase information of each group of Moire fringes is obtained based on a fringe unwrapping manner; the Moire fringes are interference fringes with a period greater than a set threshold value;

[0027] Step S3: determining a phase deviation based on the two groups of Moire fringes, and determining a position deviation of the silicon wafer alignment mark 3 in the detection direction.

[0028] Preferably, when the detection direction is the x direction, the position deviation Δx in the x direction is:

[0029]

[0030] wherein P1 and P2 are the period sizes of the first grating and the second grating of the silicon wafer alignment mark 3 respectively, and Δ is the phase deviation determined based on the two groups of Moire fringes when the detection direction is the x direction.

[0031] Preferably, when the detection direction is the y direction, the position deviation Δy in the y direction is:

[0032]

[0033] wherein P1 and P2 are the period sizes of the first grating and the second grating of the silicon wafer alignment mark 3 respectively, and Δ is the phase deviation determined based on the two groups of Moire fringes when the detection direction is the y direction.

[0034] Beneficial effects:

[0035] (1) The projection lithography machine alignment sensing system proposed in the present application has a simple structure and can realize sub-nanometer, deep sub-nanometer precision position detection of the alignment mark of the lithography machine.

[0036] (2) The light source of the present application is in an oblique incidence manner, by controlling the angle between the incident direction of the light beam on the silicon wafer alignment mark and the center line of the alignment mark, so that it is equal to the angle between the first-order light and zero-order light after the diffraction of the light beam on the alignment mark, so that the distance between the silicon wafer alignment mark and the alignment sensing system in the z direction of the projection lithography machine is increased. Compared with the CANON alignment technology, the projection lithography machine alignment sensing system proposed in the present application is only used for nanoimprint technology with small gap between the mask and the silicon wafer, and is suitable for position detection of the alignment mark of the projection lithography machine.

[0037] (3) The present application sets two sets of light sources with different wavelengths, so that the silicon wafer alignment mark can be illuminated by two wavelengths of light, solving the problem of weakening of the illumination light caused by process factors in the silicon wafer position detection process, and enhancing the signal stability of the alignment process. Overcome the influence on the precision of the silicon wafer position detection caused by the interference cancellation of the grating alignment mark on the silicon wafer when the optical depth is equal to one half of the wavelength of the incident light, and also overcome the influence on the precision of the silicon wafer position detection caused by the absorption of the photoresist on the surface of the silicon wafer to the visible light in the advanced node lithography exposure process.

[0038] (4) The alignment sensing system of the projection lithography machine provided by the present application has fewer optical elements and simpler light path compared with the alignment sensing systems of ASML and NIKON, and the machining difficulty of the core optical element and the debugging difficulty of the optical system are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The alignment sensing system light path 1 for integrating the grating and the lens group for x-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0040] Figure 2(A) is a schematic diagram of the grating distribution on the silicon wafer alignment mark in the present application;

[0041] Figure 2(B) is a schematic diagram of the grating distribution on the detection grating in the present application;

[0042] Figure 3 The alignment sensing system light path 2 for integrating the grating and the lens group for x-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0043] Figure 4 The alignment sensing system light path 3 for integrating the grating and the lens group for y-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0044] Figure 5 The alignment sensing system light path 4 for integrating the grating and the lens group for y-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0045] Figure 6 The alignment sensing system light path for double-wavelength integration for x-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0046] Figure 7 The alignment sensing system light path for double-wavelength integration for y-direction position detection of the silicon wafer provided by the present application is shown in the figure;

[0047] Figure 8 The interference fringe schematic diagram of the silicon wafer alignment mark and the detection grating in the misaligned state obtained by the detector in the present application is shown in the figure;

[0048] Figure 9 Schematic diagram of interference fringes between the silicon wafer alignment mark and the detection grating obtained on the detection surface of the detector in the present invention in an aligned state;

[0049] Reference numerals:

[0050] 1, first light source group; 2, second light source group; 3, silicon wafer alignment mark; 4, detection grating; 5, lens group; 6, detector; 7, silicon wafer to be aligned;

[0051] 31, first grating; 32, second grating; 33, third grating; 34, fourth grating; 41, fifth grating; 42, sixth grating; 43, seventh grating; 44, eighth grating; 61, 62, 63, 64 are moiré fringes on the detector surface;

[0052] 111, 112, 113, 114 are light sources in the first light source group; 211, 212, 213, 214 are light sources in the second light source group;

[0053] 811, first reflector; 812, second reflector; 813, third reflector; 814, fourth reflector; 821, fifth reflector; 822, sixth reflector; 823, seventh reflector; 824, eighth reflector. DETAILED DESCRIPTION

[0054] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0055] like Figure 1 and Figure 4 As shown, the present invention proposes a projection lithography machine alignment sensing system based on the integration of grating and lens group, the system comprising:

[0056] Light source group, detection grating 4, lens group 5 and detector 6;

[0057] The light source group includes a first light source group 1, which includes a first light source pair and a second light source pair for respectively illuminating in the x-direction and the y-direction; the two light sources in each light source pair have the same parameters and types; the light sources in the first light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; and the light sources in the second light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane.

[0058] The first light source pair and the second light source pair both emit light beams, and the angle between the incident direction of the light beams on the silicon wafer alignment mark 3 and the center line of the silicon wafer alignment mark 3 is equal to the angle between the first-order diffracted light and the zero-order light after the light beams are diffracted when irradiating the silicon wafer alignment mark 3;

[0059] The x-direction and the y-direction are respectively the horizontal direction and the vertical direction of the horizontal plane in the global coordinate system of the projection lithography machine, and the z-direction is the direction of the xy plane determined by the x-direction and the y-direction;

[0060] The horizontal plane where the detection grating 4 is located and the horizontal plane where the detector 6 is located form an object-image conjugate relationship with respect to the lens group 5; the detection grating 4 is on the object plane of the lens group 5, and the detector 6 is on the image plane of the lens group 5; the lens group 5 is an afocal optical system.

[0061] In the present invention, the first light source pair includes light source 111 and light source 112, and the second light source pair includes light source 113 and light source 114. Light sources 111 and 112 have the same parameters and types, and are symmetrically distributed on either side of the central optical axis of the alignment sensing system in the xz plane, and are used to illuminate the silicon wafer alignment mark 3 in the x-direction position detection. Light sources 113 and 114 have the same parameters and types, and are symmetrically distributed on either side of the central optical axis of the alignment sensing system in the yz plane, and are used to illuminate the silicon wafer alignment mark 3 in the y-direction position detection.

[0062] Light source 111 and light source 112 emit light beams, and the angle between the incident direction of the light beams on the silicon wafer alignment mark 3 and the center line of the silicon wafer alignment mark 3 is equal to the angle between the first-order diffracted light and the zero-order light after the light beams are diffracted when irradiating the silicon wafer alignment mark 3; light source 113 and light source 114 emit light beams, and the angle between the incident direction of the light beams on the silicon wafer alignment mark 3 and the center line of the silicon wafer alignment mark 3 is equal to the angle between the first-order diffracted light and the zero-order light after the light beams are diffracted when irradiating the silicon wafer alignment mark 3.

[0063] like Figure 2(A)-Figure 2(B) As shown, the silicon wafer alignment mark 3 is composed of a first grating 31 with a period P1, a second grating 32 with a period P2, a third grating 33 with a period P1, and a fourth grating 34 with a period P2. The difference between the values ​​of P1 and P2 is less than a first preset threshold value. The first grating 31 and the second grating 32 are used to detect the position deviation of the silicon wafer 7 to be aligned in the x direction, and the third grating 33 and the fourth grating 34 are used to detect the position deviation of the silicon wafer 7 to be aligned in the y direction. The first grating 31 and the second grating 32 are arranged adjacent to each other in the y direction, and the grating directions of the first grating 31 and the second grating 32 are both along the y direction. The center position of the first grating 31 and the center position of the second grating 32 have the same x coordinate. The third grating 33 and the fourth grating 34 are arranged adjacent to each other in the x direction, and the grating directions of the third grating 33 and the fourth grating 34 are both along the x direction. The center position of the third grating 33 and the center position of the fourth grating 34 have the same y coordinate.

[0064] The detection grating 4 is composed of a fifth grating 41 with a period P2, a sixth grating 42 with a period P1, a seventh grating 43 with a period P2 and an eighth grating 44 with a period P1; the fifth grating 41 and the sixth grating 42 are used for detecting the position deviation of the silicon wafer 7 in the x direction, and the seventh grating 43 and the eighth grating 44 are used for detecting the position deviation of the silicon wafer 7 in the y direction; the fifth grating 41 and the sixth grating 42 are arranged adjacently in the y direction, and the grating lines of the fifth grating 41 and the sixth grating 42 are both along the y direction, and the x coordinates of the center positions of the fifth grating 41 and the sixth grating 42 are the same; the relative positions of the first grating 31 and the second grating 32 on the silicon wafer alignment mark 3 in the y direction are the same as the relative positions of the fifth grating 41 and the sixth grating 42 on the detection grating in the y direction; and the relative positions of the third grating 33 and the fourth grating 34 on the silicon wafer alignment mark in the x direction are the same as the relative positions of the seventh grating 43 and the eighth grating 44 on the detection grating in the x direction.

[0065] In the present application, when detecting the x direction position of the silicon wafer alignment mark 3, the silicon wafer alignment mark 3 on the silicon wafer 7 is illuminated by the light source 111 and the light source 112. The angle between the incident direction of the light beam on the silicon wafer alignment mark 3 and the center line of the silicon wafer alignment mark 3 is equal to the angle between the first order light and the zero order light after the light beam illuminating the silicon wafer alignment mark 3 is diffracted. When the positive first order diffracted light generated after the silicon wafer alignment mark 3 is illuminated by the light source 111 and the negative first order diffracted light generated after the silicon wafer alignment mark 3 is illuminated by the light source 112 propagate upward, they pass through the detection grating 4. The positive and negative first order diffracted light generated by the further diffraction of the detection grating 4 is converged on the detection surface of the detector 6 after passing through the lens group 5, wherein there are two groups of interference fringes with periods greater than a set threshold, and the phase difference between the two groups of amplified interference fringes is used to calculate the position deviation Δx between the silicon wafer alignment mark 3 and the detection grating 4 in the x direction. The position deviation Δx between the silicon wafer alignment mark 3 and the detection grating 4 in the x direction can be calculated.

[0066] The present application is an alignment sensing system with simple structure and sub-nanometer, deep sub-nanometer precision. The present application can achieve the alignment precision of the photolithography machines of ASML, NIKON and CANON. Compared with the alignment sensing systems of ASML and NIKON, the present application has a simple structure, and compared with the alignment technology of CANON which can only be used in the nanoimprint technology with small gap between the mask and the silicon wafer, the alignment sensing system proposed in the present application is suitable for the position detection of the alignment mark of the projection photolithography machine.

[0067] In the present application, the light source, the detection grating 4, the lens group 5 and the detector 6 constituting the alignment sensing system of the projection photolithography machine are integrated to form an integrated alignment sensing system of the projection photolithography machine.

[0068] As shown in FIG. 1, the present application is an alignment sensing system of a projection photolithography machine. Figure 6 , Figure 7As shown, further, the light source group further comprises a second light source group 2 different from the first light source group 1 in wavelength, the second light source group 2 comprising a third light source pair and a fourth light source pair; the two light sources in each light source pair are the same in parameter and kind; the two light sources in the third light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; the two light sources in the fourth light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane;

[0069] The third light source pair and the fourth light source pair both emit light beams, the angle between the incident direction of the light beam on the silicon wafer alignment mark 3 and the center line of the silicon wafer alignment mark 3 is equal to the angle between the first-order diffraction light and the zero-order light after the silicon wafer alignment mark 3 is diffracted by the light beam.

[0070] Further, the first light source group 1 and the second light source group 2 respectively belong to visible light sources and near-infrared light sources.

[0071] In the present application, the light source group further comprises a second light source group 2 different from the first light source group 1 in wavelength, the second light source group 2 comprising a light source 211, a light source 212, a light source 213, and a light source 214; the light source 211 and the light source 212 are the same in parameter and kind, and the light source 213 and the light source 214 are the same in parameter and kind.

[0072] Further, the light source group further comprises several light source groups different from the first light source group 1 and the second light source group 2 in wavelength, each light source group comprising two light source pairs, the two light sources in each light source pair being the same in parameter and kind; the layout mode of each light source group is that the two light sources in one light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane, and the two light sources in the other light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane.

[0073] Before the silicon wafer is subjected to photolithography exposure, it needs to be subjected to chemical mechanical polishing and other processes, which will change the grating alignment mark morphology on the silicon wafer, for example, change the groove depth of the grating, that is, the optical depth. When the optical depth of the grating is one-half of the wavelength of the incident light, the first-order light intensity diffracted by the grating is zero, so that alignment cannot be performed. At the same time, in the photolithography exposure process of advanced nodes, the photoresist on the surface of the silicon wafer has an absorption effect on visible light, thereby causing the illumination light to weaken. To solve the problems in the alignment process caused by these process factors, the present application can use multiple wavelength (equal to or greater than 2 wavelengths) light sources to detect the position of the silicon wafer. Therefore, the present application configures the light sources into multiple groups, so that the multiple groups of light sources can provide two or more wavelengths. The reason for selecting near-infrared light sources is that near-infrared light cannot be absorbed in photoresist, which can ensure the intensity of the signal light source.

[0074] Further, the projection lithography aligning sensing system comprises a mirror corresponding to each light source, which is used to adjust the incident direction of the light beam emitted by the light source on the silicon wafer alignment mark 3, so that the incident direction of the light beam on the silicon wafer alignment mark 3 is equal to the angle between the first-order diffraction light and the zero-order light after the light beam irradiates the alignment mark 3.

[0075] As shown in Figure 6-Figure 7 The first mirror 811, the second mirror 812, the third mirror 813, the fourth mirror 814, the fifth mirror 821, the sixth mirror 822, the seventh mirror 823 and the eighth mirror 824 correspond to each light source respectively, so as to adjust the incident direction of the light beam emitted by the light source on the silicon wafer alignment mark 3.

[0076] The application further provides a method for detecting the position of a silicon wafer alignment mark based on the projection lithography aligning sensing system integrated with a grating and a lens group, which is based on the projection lithography aligning sensing system integrated with a grating and a lens group as described above, and the method comprises the following steps:

[0077] Step S1: determining the detection direction of the silicon wafer alignment mark 3 based on the light beam emitted by the partial or whole light source in the illumination direction; the silicon wafer alignment mark 3 generates negative first-order diffraction light and positive first-order diffraction light after being irradiated by the light beam; the negative first-order diffraction light and the positive first-order diffraction light generate negative first-order diffraction light and positive first-order diffraction light again after passing through the detection grating 4; the negative first-order diffraction light and the positive first-order diffraction light interfere on the detection surface of the detector 6 after passing through the lens group 5, and generate a plurality of groups of interference fringes; wherein the detection direction is the x direction or the y direction;

[0078] Step S2: obtaining two groups of Moire fringes in the plurality of groups of interference fringes, and obtaining the phase information of each group of Moire fringes based on the de-fringe method; the Moire fringes are interference fringes with a period greater than a set threshold;

[0079] Step S3: determining the phase deviation based on the two groups of Moire fringes, and determining the position deviation of the silicon wafer alignment mark 3 in the detection direction.

[0080] When the detection direction is the x direction, the position deviation Δx in the x direction is:

[0081]

[0082] Wherein, is the phase deviation determined based on the two groups of Moire fringes when the detection direction is the x direction.

[0083] When the detection direction is the y direction, the position deviation Δy in the y direction is:

[0084]

[0085] wherein, is the phase deviation determined based on two sets of moire fringes when the detection direction is the y direction.

[0086] In the present application, the detector with small pixel size, the lens group with high amplification, and the grating with small difference between the period P1 and the period P2 (i.e. the first set threshold is small) can effectively increase the period of the moire fringes on the detector surface, thereby increasing the detection sensitivity of the silicon wafer alignment mark position and improving the detection precision of the silicon wafer alignment mark position.

[0087] The effectiveness of the calculation of the position deviation of the present application is explained in the x direction.

[0088] As shown in Figure 1 , the light beam a emitted by the light source 111 is irradiated to the first grating 31 with a period P1, generating a negative first-order diffraction light a1 -1 propagating upward through the third grating 41 with a period P2 on the detection grating 4. The light beam b emitted by the light source 112 is irradiated to the first grating 31 with a period P1, generating a positive first-order diffraction light b1 +1 propagating upward through the third grating 41 with a period P2 on the detection grating 4.

[0089] The complex amplitude of the diffraction light a1 -1 is:

[0090]

[0091] wherein A0 is the amplitude of the light beam a, is the initial phase of the light beam a, and x w is the x direction position of the first grating 31 with a period P1 on the silicon wafer alignment mark 3.

[0092] The complex amplitude of the diffraction light b1 +1 is:

[0093]

[0094] As shown in Figure 3 , the light beams a and b are diffracted after being illuminated by the second grating 32 with a period P2, generating diffraction lights a2 -1 and b2 +1 , and the complex amplitudes are respectively:

[0095]

[0096] The diffraction lights a1 -1 , b1 +1 , a2 -1 , and b2+1 Diffract on the probe grating 4.

[0097] Wherein:

[0098] First grating 31 with period P1 produces diffracted light a1 -1 and b1 +1 Diffract on the third grating 41 with period P2, diffracted light a1 -1 After diffracting through the third grating 41 with period P2, produce positive first-order light a1 -1,+1 and negative first-order light a1 -1,-1 , diffracted light b1 +1 After diffracting through the third grating 41 with period P2, produce positive first-order light b1 +1,+1 and negative first-order light b1 +1,-1 . By interference of diffracted light a1 -1,+1 and b1 +1,-1 Moiré fringes can be formed.

[0099] a1 -1,+1 and b1 +1,-1 Complex amplitudes are respectively:

[0100]

[0101] Wherein, A1 is the amplitude of positive and negative first-order diffracted light after diffracting of diffracted light a1 -1 and b1 +1 through the probe grating 4, x p is the x-direction position of the probe grating 4.

[0102] Second grating 32 with period P2 produces diffracted light a2 -1 and b2 +1 Diffract at grating 42, diffracted light a2 -1 After diffracting through the fourth grating 42 with period P1, produce positive first-order light a2 -1,+1 and negative first-order light a2 -1,-1 , diffracted light b2 +1 After diffracting through the fourth grating 42 with period P1, produce positive first-order light b2 +1,+1 and negative first-order light b2 +1,-1 . By interference of diffracted light a2 -1,+1 and b2 +1,-1 Moiré fringes can be formed.

[0103] Diffracted light a2 -1,+1 and b2 +1,-1 Complex amplitudes are respectively:

[0104]

[0105] Diffracted light a1-1,+1 , a1 -1,-1 , b1 +1,-1 , b1 +1,+1 , a2 -1,+1 , a2 -1,-1 , b2 +1,-1 , b2 +1,+1 After passing through the lens group 5, the interference occurs on the detector 6. Among them, the diffracted light a1 -1,+1 interferes with the diffracted light b1 +1,-1 to form Moire fringes, the diffracted light a2 -1,+1 interferes with the diffracted light b2 +1,-1 to form Moire fringes, as shown in Figure 8 .

[0106] In theory, a1 -1,+1 , a1 -1,-1 , b1 +1,-1 , b1 +1,+1 These four beams of light will interfere with each other on the detector 6. But in addition to a1 -1,+1 and b1 +1,-1 interference to form Moire fringes, the period of other interference fringes is much smaller than the pixel size of the detector, and the background interference light formed can be removed by post-processing, for example, it can be filtered out in the frequency domain by Fourier transform. Similarly, light beams a2 -1,+1 , a2 -1,-1 , b2 +1,-1 , b2 +1,+1 will also interfere with each other, and the influence of the background interference light formed can also be removed.

[0107] The diffracted light a1 -1,+1 interferes with b1 +1,-1 , and the light intensity distribution of the interference fringes 61 formed is:

[0108]

[0109] The diffracted light a2 -1,+1 interferes with b2 +1,-1 , and the light intensity distribution of the interference fringes 62 formed is:

[0110]

[0111] When the detection grating 4 and the silicon wafer alignment mark 3 have a positional deviation Δx in the x direction, let x p =x w +Δx, the light intensity distributions of the interference fringes 61 and the interference fringes 62 are respectively:

[0112]

[0113] When Δx is not zero, the interference fringes 61 and 62 on the detector 6 are not aligned, as shown in FIG. Figure 8 When the position deviation Δx is zero, the interference fringes 61 and 62 are aligned, as shown in FIG. Figure 9 shown.

[0114] When Δx is not zero, there is a phase difference between the two sets of fringes. Phase difference The relationship with the position deviation Δx can be expressed as:

[0115]

[0116] Therefore, the position deviation Δx in the x-direction between the silicon wafer alignment mark 3 and the detection grating 4 that the alignment sensing system needs to detect is:

[0117]

[0118] when When it is greater than 2π, it exceeds the detection range, so the detection range x of the alignment sensor system range for:

[0119]

[0120] The above-mentioned Δx is the positional deviation in the x-direction between the detection grating 4 and the silicon wafer alignment mark 3. After light sources 111 and 112 illuminate the first grating 31 with a period P1 and the second grating 32 with a period P2 on the silicon wafer alignment mark 3, the resulting diffracted light is diffracted by the third grating 41 with a period P2 and the fourth grating 42 with a period P1 on the detection grating. The diffracted light is then focused by lens assembly 5 onto detector 6. The moiré fringes on detector 6 are processed to obtain the positional deviation Δx, thereby determining the x-direction position of the silicon wafer alignment mark 3.

[0121] like Figure 4 and Figure 5 As shown, for detecting the position deviation Δy between the grating 4 and the silicon wafer alignment mark 3 in the y direction, the detection principle is the same as that in the x direction and will not be repeated here.

[0122] The present invention provides a specific embodiment of a detection method for a projection lithography machine alignment sensor system based on the integration of a grating and a lens group, based on the projection lithography machine alignment sensor system based on the integration of a grating and a lens group as described above.

[0123] Take the x-direction position detection of silicon wafer as an example.

[0124] The helium-neon laser LGK7665-18 of Lubang Company is used as light source 111 and light source 112, and the light beam with a wavelength of 632.8nm is emitted to illuminate the silicon wafer alignment mark 3.

[0125] The silicon wafer alignment mark 3 is composed of a grating 31 with a period of 2 μm and a grating 32 with a period of 2.05 μm. The detection grating 4 is composed of a grating 41 with a period of 2.05 μm and a grating 42 with a period of 2 μm.

[0126] The light beams a, b illuminate the silicon wafer alignment mark 3 at an incident angle of 18°.

[0127] The detector 6 is an Hikvision MV-CU200-20GM(NPOE) with a pixel size of 1.4 μm x 1.4 μm and a resolution of 5120 x 3840.

[0128] The light intensity I1 of the Moiré fringe 61 and the light intensity I2 of the Moiré fringe 62 formed at the detector 6 are expressed as follows:

[0129]

[0130] When the detection grating 4 and the silicon wafer alignment mark 3 have a positional deviation Δx in the x direction, let x p = x w + Δx, the light intensities of the two sets of Moiré fringes with the period amplified are as follows:

[0131]

[0132] When the silicon wafer alignment mark 3 and the detection grating 4 have a positional deviation Δx in the x direction, the two sets of interference fringes 61 and 62 on the detector 6 will also have a shift. Combining Figure 8 , there is a phase difference between the two sets of fringes. The relationship between the displacement deviation Δx and the phase difference

[0133]

[0134] The positional deviation Δx between the silicon wafer alignment mark 3 to be detected and the detection grating 4 is:

[0135]

[0136] The lens group 5 is an afocal system and can amplify the light beam aperture. When the amplification factor is 20 and the pixel size of the detector 6 is 1.4 μm, the minimum phase shift that can be detected is 7π / 2050, and the minimum positional deviation of the silicon wafer alignment mark 3 that can be detected is 0.86 nm. When the amplification factor of the lens group 5 is further increased and the pixel size of the detector 6 used is further reduced, the minimum positional deviation of the silicon wafer alignment mark 3 that can be detected can be further reduced when the period difference P1, P2 of the gratings on the silicon wafer alignment mark 3 is smaller.

[0137] When the dual-wavelength light is used for the silicon wafer position detection, another light source LBL-785-50mW is used, which emits near-infrared light with a wavelength of 785nm. After the adjustment of a reflecting mirror, the angle between the incident direction on the silicon wafer alignment mark and the normal of the plane where the silicon wafer alignment mark is located is 23°. After the first-order diffraction of the silicon wafer alignment mark 3, the positive and negative first-order diffraction light is formed into Moire fringes on the detector surface after the integrated alignment sensing system. The position information of the silicon wafer alignment mark 3 can be obtained according to the Moire fringes.

[0138] The above specific embodiments only describe the design principles of the present application, and the shapes and names of the components in the description can be different and are not limited. Therefore, the person skilled in the art of the present application can modify or equivalently replace the technical solutions described in the foregoing embodiments; and the modifications and replacements do not deviate from the purpose and technical solutions of the present application and should belong to the protection scope of the present application.

Claims

1. A projection lithography machine alignment sensing system based on the integration of grating and lens group, characterized in that: The system includes: Light source group, detection grating, lens group and detector; The light source group includes a first light source group, the first light source group includes a first light source pair and a second light source pair for respectively illuminating in the x-direction and the y-direction; the two light sources in each light source pair have the same parameters and type; the light sources in the first light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; and the light sources in the second light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane; The first light source pair and the second light source pair both emit light beams, and the angle between the incident direction of the light beams on the alignment mark of the silicon wafer and the center line of the alignment mark of the silicon wafer is equal to the angle between the first-order diffracted light and the zero-order light after the alignment mark of the silicon wafer is diffracted by the light beams; The x-direction and the y-direction are respectively the horizontal direction and the vertical direction of the horizontal plane in the global coordinate system of the projection lithography machine, and the z-direction is the direction of the xy plane determined by the x-direction and the y-direction; The horizontal plane where the detection grating is located and the horizontal plane where the detector is located form an object-image conjugate relationship with respect to the lens group; the detection grating is on the object plane of the lens group, and the detector is on the image plane of the lens group; the lens group is an afocal optical system; The light source group further includes a second light source group having a different wavelength from the first light source group; The silicon wafer alignment mark comprises a first grating with a period of P1, a second grating with a period of P2, a third grating with a period of P1, and a fourth grating with a period of P2, wherein the difference between the values ​​of P1 and P2 is less than a first preset threshold value; the first grating and the second grating are used to detect position deviations in the x-direction of the silicon wafer to be aligned, and the third grating and the fourth grating are used to detect position deviations in the y-direction of the silicon wafer to be aligned; the first grating and the second grating are arranged adjacent to each other in the y-direction, and the scribed lines of the first grating and the second grating are both oriented in the y-direction, and the center position of the first grating and the center position of the second grating have the same x-coordinate; the third grating and the fourth grating are arranged adjacent to each other in the x-direction, and the scribed lines of the third grating and the fourth grating are both oriented in the x-direction, and the center position of the third grating and the center position of the fourth grating have the same y-coordinate; The detection grating is composed of a fifth grating with a period of P2, a sixth grating with a period of P1, a seventh grating with a period of P2, and an eighth grating with a period of P1; the fifth grating and the sixth grating are used to detect the position deviation of the silicon wafer to be aligned in the x direction, and the seventh grating and the eighth grating are used to detect the position deviation of the silicon wafer to be aligned in the y direction; the fifth grating and the sixth grating are arranged adjacent to each other in the y direction, and the directions of the lines of the fifth grating and the sixth grating are both along the y direction, and the center position of the fifth grating has the same x coordinate as the center position of the sixth grating; The seventh grating and the eighth grating are arranged adjacent to each other in the x-direction, and the scribed lines of the seventh grating and the eighth grating are both along the x-direction. The center position of the seventh grating and the center position of the eighth grating have the same y-coordinate. The relative position of the first grating and the second grating on the silicon wafer alignment mark in the y-direction is the same as the relative position of the fifth grating and the sixth grating on the detection grating in the y-direction. The relative position of the third grating and the fourth grating on the silicon wafer alignment mark in the x-direction is the same as the relative position of the seventh grating and the eighth grating on the detection grating in the x-direction.

2. The system according to claim 1, wherein The second light source group includes a third light source pair and a fourth light source pair; the two light sources in each light source pair have the same parameters and types; the two light sources in the third light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; and the two light sources in the fourth light source pair are symmetrically distributed on both sides of the central optical axis of the alignment sensing system in the yz plane. The third light source pair and the fourth light source pair both emit light beams, and the angle between the incident direction of the emitted light beam on the silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the angle between the first-order diffracted light and the zero-order light after the emitted light beam irradiates the silicon wafer alignment mark and is diffracted.

3. The system according to claim 2, wherein: The first light source group and the second light source group are visible light sources and near-infrared light sources respectively.

4. The system according to claim 1, wherein: The light source group further includes several light source groups having wavelengths different from those of the first light source group and the second light source group, each light source group including two light source pairs, the parameters and types of the two light sources in each light source pair being identical; the layout of each light source group is such that the two light sources in one light source pair are symmetrically distributed on either side of the central optical axis of the alignment sensing system in the xz plane; and the two light sources in another light source pair are symmetrically distributed on either side of the central optical axis of the alignment sensing system in the yz plane. The two light source pairs in each light source group emit light beams, and the angle between the incident direction of the emitted light beam on the silicon wafer alignment mark and the center line of the silicon wafer alignment mark is equal to the angle between the first-order diffracted light and the zero-order light after the emitted light beam irradiates the silicon wafer alignment mark and diffracts.

5. A detection method for a projection lithography machine alignment sensor system based on an integrated grating and lens assembly, based on the projection lithography machine alignment sensor system based on an integrated grating and lens assembly as claimed in any one of claims 1 to 4, characterized in that: The method comprises: Step S1: Determine the detection direction of the silicon wafer alignment mark, and emit a light beam based on part or all of the light source illumination in the illumination direction; the silicon wafer alignment mark is illuminated by the outgoing light beam to generate negative first-order diffraction light and positive first-order diffraction light; the negative first-order diffraction light and the positive first-order diffraction light are diffracted again after passing through the detection grating to obtain negative first-order diffraction light and positive first-order diffraction light, respectively; the negative first-order diffraction light and the positive first-order diffraction light interfere with each other on the detection surface of the detector after passing through the lens group, generating multiple groups of interference fringes; wherein the detection direction is the x direction or the y direction; Step S2: obtaining two groups of moiré fringes from the plurality of groups of interference fringes, and obtaining phase information of each group of moiré fringes based on a fringe decomposition method; the moiré fringes are interference fringes with a period greater than a set threshold; Step S3: determining the phase deviation based on the two groups of moiré fringes, and determining the position deviation of the silicon wafer alignment mark in the detection direction.

6. The method according to claim 5, wherein When the detection direction is the x direction, the position deviation Δx in the x direction is: Wherein, P1 and P2 are the periods of the first grating and the second grating of the silicon wafer alignment mark, respectively, and Δφ1 is the phase deviation determined based on the two sets of moiré fringes when the detection direction is the x direction.

7. The method according to claim 5, wherein When the detection direction is the y direction, the position deviation Δy in the y direction is: Among them, P1 and P2 are the periods of the first grating and the second grating of the silicon wafer alignment mark respectively. It is the phase deviation determined based on two sets of moiré fringes when the detection direction is the y direction.

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