Projection objective lens distortion measurement system and method, photolithography machine

Abstract

The present invention provides a projection objective lens distortion measurement system and method, and a photolithography machine. The method is to move the mask plate according to a set path, and after the movement, obtain the projection objective lens distortion value by using the distortion values ​​of multiple field of view points obtained by the spatial image distance error between the field of view points corresponding to the adjacent alignment marks. It can be seen that the switching of the test field of view points is realized by moving the mask plate according to the set path; and under the unique design of the alignment mark, the spatial image distance error between the field of view points corresponding to the adjacent alignment marks is obtained, and the distortion value of the field of view point is characterized by this to obtain an accurate distortion value. During the measurement process, the mask plate is always in a thermally stable state to fix its deformation amount to avoid affecting the distortion value due to the change of the deformation amount. The mask plate and the light move synchronously to avoid the influence of the light on the distortion value, improve the accuracy of the distortion value, and realize absolute distortion measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography machine manufacturing, and in particular to a projection objective lens distortion measurement system and method, and a photolithography machine. Background Art

[0002] A photolithography machine is a type of equipment used in integrated circuit manufacturing, which is mainly divided into contact photolithography machines, proximity photolithography machines, and projection photolithography machines. Among them, in a projection photolithography machine, the distortion of the projection objective lens will directly affect the imaging quality of the photolithography machine, and it is easy to cause imaging deformation and cause overlay errors. For this reason, it is necessary to accurately measure the distortion of the projection objective lens. The distortion measurement of the projection objective lens generally uses mask alignment technology to achieve the spatial image position measurement of each field of view point to be measured. Then, according to the projection magnification of the objective lens and the field of view area to be measured, the layout of the mask mark on the mask plate is designed, and the mask mark on the mask plate is illuminated by an illumination beam. After passing through the projection objective lens, the image is formed at the detector end, and then the detector performs spatial image light intensity collection and position calculation. However, the accuracy of the existing projection objective lens distortion measurement method is limited and cannot meet the needs of high-precision imaging.

[0003] Therefore, a new method for measuring the distortion of projection objective lenses is urgently needed to improve the measurement accuracy of the distortion of projection objective lenses. Summary of the invention

[0004] The object of the present invention is to provide a projection objective lens distortion measurement system and method, and a photolithography machine, so as to solve the problem of how to improve the measurement accuracy of projection objective lens distortion.

[0005] In order to solve the above technical problems, the present invention provides a method for measuring the distortion of a projection objective lens, comprising:

[0006] Providing a mask having a plurality of alignment marks disposed thereon;

[0007] The mask is moved in sequence along a set path, and after the movement, the distortion values ​​of a plurality of viewing points obtained by using the spatial image distance error between the viewing points corresponding to the adjacent alignment marks are used to obtain the distortion value of the projection objective lens.

[0008] Optionally, in the projection objective lens distortion measurement method, the plurality of alignment marks are symmetrically arranged along a first direction and / or a second direction; wherein the first direction and the second direction are perpendicular to each other.

[0009] Optionally, in the projection objective lens distortion measurement method, the plurality of alignment marks are distributed at equal intervals along the first direction and / or the second direction.

[0010] Optionally, in the projection objective lens distortion measurement method, the moving direction of the mask includes the direction of a line connecting any two adjacent alignment marks.

[0011] Optionally, in the projection objective lens distortion measurement method, the distance that the mask moves each time is the spacing between two adjacent alignment marks in the current moving direction, or several times of the spacing.

[0012] Optionally, in the projection objective lens distortion measurement method, five alignment marks are provided on the mask plate, and the five alignment marks are distributed in a cross shape.

[0013] Optionally, in the projection objective lens distortion measurement method, before sequentially moving the mask plate along a set path, the projection objective lens distortion measurement method further includes:

[0014] Adjusting the temperature of the mask plate to keep the mask plate in a thermally stable state;

[0015] The deformation errors between adjacent alignment marks are measured.

[0016] Optionally, in the projection objective lens distortion measurement method, after obtaining the deformation error, the spatial image distance error is compensated according to the deformation error, and the projection objective lens distortion value is obtained by using the distortion values ​​of multiple field of view points obtained by the compensated spatial image distance error.

[0017] Optionally, in the projection objective lens distortion measurement method, in the process of moving the mask plate in sequence along a set path, the light used to illuminate the mask plate moves synchronously with the mask plate so that the optical axis of the light after movement passes through the same position of the mask plate.

[0018] Optionally, in the projection objective distortion measurement method, before moving the mask, an alignment sensor on the image plane of the projection objective is used to align the mask; and after the mask moves a distance d, the alignment sensor moves with the mask a distance d / m; wherein m is the magnification of the projection objective.

[0019] Based on the same inventive concept, the present invention also provides a projection objective lens distortion measurement system, comprising: a mask and a projection objective lens distortion measurement device;

[0020] The mask is provided with a plurality of alignment marks;

[0021] The projection objective lens distortion measurement device comprises a light emitter, a mask stage, a projection objective lens, a workpiece stage and a processor; the light emitted by the light emitter passes through the mask stage and the projection objective lens in sequence and is irradiated onto the workpiece stage; wherein the mask plate is arranged on the mask stage and can be moved in sequence along a set path with the mask stage; the processor is used for obtaining the projection objective lens distortion value by using the distortion values ​​of multiple field of view points obtained by using the spatial image distance error between the field of view points corresponding to adjacent alignment marks after the mask plate moves.

[0022] Optionally, in the projection objective distortion measurement system, the plurality of alignment marks are symmetrically arranged along a first direction and / or a second direction; wherein the first direction and the second direction are perpendicular to each other.

[0023] Optionally, in the projection objective lens distortion measurement system, the plurality of alignment marks are distributed at equal intervals along the first direction and / or the second direction.

[0024] Optionally, in the projection objective lens distortion measurement system, the moving direction of the mask includes the direction of a line connecting any two adjacent alignment marks.

[0025] Optionally, in the projection objective lens distortion measurement system, the distance that the mask moves each time is the spacing between two adjacent alignment marks in the current moving direction, or several times of the spacing.

[0026] Optionally, in the projection objective lens distortion measurement system, five alignment marks are provided on the mask plate, and the five alignment marks are distributed in a cross shape.

[0027] Optionally, in the projection objective lens distortion measurement system, the projection objective lens distortion measurement device further includes a temperature control module for adjusting the temperature of the mask plate to keep the mask plate in a thermally stable state.

[0028] Optionally, in the projection objective lens distortion measurement system, the processor is also used to obtain the deformation error between the adjacent alignment marks in the thermally stable state; and to compensate the spatial image distance error based on the deformation error; and to obtain the projection objective lens distortion value using the distortion values ​​of multiple field points obtained by the compensated spatial image distance error.

[0029] Optionally, in the projection objective distortion measurement system, the light emitter can move synchronously with the mask stage; or, the light emitter has a variable window so that the light emitted through the variable window moves synchronously with the mask stage; and the optical axis of the light after movement passes through the same position of the mask plate.

[0030] Optionally, in the projection objective lens distortion measurement system, an alignment sensor is provided on the workpiece stage, and the workpiece stage can drive the alignment sensor to move; and after the mask plate moves a distance d with the mask stage, the alignment sensor moves synchronously with the workpiece stage a distance d / m; wherein m is the magnification of the projection objective lens.

[0031] Based on the same inventive concept, the present invention also provides a lithography machine for executing the projection objective lens distortion measurement method.

[0032] In summary, the present invention provides a projection objective lens distortion measurement system and method, and a lithography machine. The method is to move the mask plate according to a set path, and after the movement, obtain the projection objective lens distortion value by using the distortion values ​​of multiple field of view points obtained by the spatial image distance error between the field of view points corresponding to the adjacent alignment marks. It can be seen that moving the mask plate according to the set path can enable the alignment mark to switch between different field of view points during the measurement process, and under the unique design of the alignment mark, the spatial image distance error between the field of view points corresponding to the adjacent alignment marks can be obtained, and the distortion value of each field of view point can be characterized by this, and then a more accurate distortion value of the projection objective lens can be calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0034] Figure 1 4 is a flow chart of a method for measuring projection objective lens distortion in an embodiment of the present invention.

[0035] Figure 2 Schematic diagram of the structure of the mask in the embodiment of the present invention.

[0036] Figure 3 It is a structural schematic diagram of a projection objective lens distortion measurement device in an embodiment of the present invention.

[0037] Figure 4 Schematic diagram of the distribution of alignment marks in an embodiment of the present invention.

[0038] Figure 5 It is a schematic diagram of a preset path in an embodiment of the present invention.

[0039] Figure 6 Schematic diagram of the mask in the initial position according to the embodiment of the present invention.

[0040] Figure 7 Schematic diagram of the mask after the first movement in the embodiment of the present invention.

[0041] Figure 8It is a schematic diagram of a preset path in an embodiment of the present invention.

[0042] Fig. 9 It is a structural schematic diagram of a projection objective lens distortion measurement device in an embodiment of the present invention.

[0043] In the attached figure:

[0044] 10-mask; 101-alignment mark; 101a-first alignment mark; 101b-second alignment mark; 101c-third alignment mark; 101d-fourth alignment mark; 101e-fifth alignment mark; 101a'-first alignment mark after moving; 101b'-second alignment mark after moving; 101c'-third alignment mark after moving; 101d'-fourth alignment mark after moving; 101e'-fifth alignment mark after moving;

[0045] 20-projection objective lens distortion measuring device; 201-illuminator; 201a-variable window; 202-mask stage; 203-projection objective lens; 204-workpiece stage; 205-first interferometer; 206-second interferometer; 207-alignment sensor;

[0046] F11-first position; F12-second position; F13-third position; F21-fourth position; F22-fifth position; F23-sixth position; F31-seventh position; F213-eighth position; F413-ninth position. DETAILED DESCRIPTION

[0047] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different proportions are used. It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to represent the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0048] See also Figure 1 and Figure 2 This embodiment provides a method for measuring projection objective lens distortion, comprising:

[0049] Step 1 S1: providing a mask plate 10, wherein a plurality of alignment marks 101 are arranged on the mask plate 10;

[0050] Step 2 S2: Move the mask 10 in sequence according to the set path, and after the movement, obtain the distortion value of the projection objective lens by using the distortion values ​​of multiple field of view points obtained by the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101.

[0051] It can be seen that in the method, moving the mask 10 according to the set path can enable the alignment mark 101 to switch between different field of view points during the measurement process, and under the unique design of the alignment mark 101, the spatial image distance error between the field of view points corresponding to adjacent alignment marks 101 can be obtained, and the distortion value of each field of view point can be characterized thereby, and further a more accurate distortion value of the projection objective lens can be calculated.

[0052] The following combination Figures 1 to 9 The projection objective lens distortion measurement method provided in this embodiment is specifically described.

[0053] Step 1 S1: Please refer to Figure 2 , a mask plate 10 is provided, and a plurality of alignment marks 101 are arranged on the mask plate 10.

[0054] The alignment pattern on the mask 10 provided in this embodiment is a symmetrical structure, and is composed of a plurality of alignment marks 101. Each of the alignment marks 101 is the same, and can be as follows: Figure 2 The rectangle shown may also be a triangle, a circle, etc., which is not specifically limited in this embodiment. Preferably, the plurality of alignment marks 101 are symmetrical about the first direction X axis; or, the plurality of alignment marks 101 are symmetrical about the second direction Y axis; or, the plurality of alignment marks 101 are centrally symmetrical, symmetrical about the first direction X axis and symmetrical about the second direction Y axis. Wherein, the first direction X and the second direction Y are perpendicular to each other. Exemplarily, five alignment marks 101 are provided on the mask 10, and the five alignment marks 101 are distributed in a "cross" shape, then the five alignment marks 101 are symmetrical about the first direction X axis and symmetrical about the second direction Y axis. In other embodiments, the plurality of alignment marks 101 may also be distributed in a "rice" shape, a "well" shape, or a "field" shape, etc.

[0055] Further, the plurality of alignment marks 101 are evenly spaced in the first direction X; or, the plurality of alignment marks 101 are evenly spaced in the second direction Y; or, the plurality of alignment marks 101 are evenly spaced in both the first direction X and the second direction Y. Figure 2In the five pairs of preparation marks 101 shown, the spacings between the alignment marks 101 adjacent to each other in the first direction X are all equal, and the spacings between the alignment marks 101 adjacent to each other in the second direction Y are all equal.

[0056] Step 2 S2: Please refer to Figures 2 to 9 The mask 10 is moved in sequence along a set path, and after the movement, the distortion values ​​of the projection objective lens are obtained by using the distortion values ​​of multiple field of view points obtained by using the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101.

[0057] See also Figure 3 In order to perform the projection objective lens distortion measurement method provided in this embodiment, a projection objective lens distortion measurement device 20 or a projection lithography machine (not shown) is required. Based on this, this embodiment also provides a projection objective lens distortion measurement device 20. The projection objective lens distortion measurement device 20 at least includes a light emitter 201, a mask stage 202, a projection objective lens 203 and a workpiece stage 204. The light emitter 201 is used to emit light, and the light passes through the mask stage 202 and the projection objective lens 203 in sequence and irradiates the workpiece stage 204. Among them, the mask plate 10 is arranged on the mask stage 202 and can move in sequence along the set path with the mask stage 202. Further, the projection objective lens distortion measurement device 20 also includes a first interferometer 205, a second interferometer 206 and an alignment sensor 207. The first interferometer 205 is used to measure the position of the mask stage 202. The second interferometer 206 is used to measure the position of the alignment sensor 207. The alignment sensor 207 is located on the workpiece stage 204, and under the movement of the workpiece stage 204, the alignment sensor 207 can move with the movement of the mask stage 202. The alignment sensor 207 is used to align the multiple alignment marks 101 on the mask plate 10, and obtain the imaging of the corresponding alignment mark 101 at the field of view point. In other words, the alignment sensor 207 can collect the light intensity information of the spatial image corresponding to the mask plate 10, and obtain the corresponding spatial image position of the alignment mark 101 according to the light intensity information. Preferably, the distribution of each acquisition point in the alignment sensor 207 corresponds to the alignment mark 101 on the mask plate 10, so that each acquisition point corresponds to the acquisition of an image of the alignment mark 101. In addition, under the zooming action of the projection objective 203, the distance that the alignment sensor 207 moves with the mask stage 202 satisfies the following formula:

[0058]

[0059] Wherein, D is the distance that the alignment sensor 207 moves each time; d is the distance that the mask stage 202 moves each time; and m is the magnification of the projection objective lens 203. Further, the direction in which the alignment sensor 207 moves each time is the same as the direction in which the mask stage 202 moves each time, so as to ensure that the acquisition point in the alignment sensor 207 can be aligned with the corresponding alignment mark 101 after each movement, and obtain the corresponding image.

[0060] Furthermore, the projection objective lens distortion measuring device 20 also includes a temperature control module (not shown) for adjusting the temperature of the mask plate 10, heating or cooling the mask plate 10, so that the mask plate 10 always remains in a thermally stable state during the measurement process. It should be noted that the material of the mask plate 10 generally includes metal chromium, and during the exposure process, the metal chromium easily causes the temperature of the entire mask plate 10 to rise after absorbing the laser, and the mask plate 10 will be deformed due to the high temperature. Therefore, the setting of the temperature control module can control the mask plate 10 to be in a constant temperature state, avoiding the change of the deformation amount of the mask plate 10 due to the influence of temperature. In other words, the temperature control module controls the deformation amount of the mask plate 10 to be maintained within a relatively fixed range through temperature adjustment, so that the deformation amount of the mask plate 10 remains basically unchanged during the entire measurement process.

[0061] Based on this, in one embodiment, before executing the step 2 S2, it is necessary to calibrate the deformation amount of the mask plate 10 in the thermally stable state. Specifically, the position information of each alignment mark 101 in the mask plate 10 before temperature adjustment is obtained by the alignment sensor 207, and then the temperature of the mask plate 10 is adjusted by the temperature control module so that the mask plate 10 is in the thermally stable state. The alignment sensor 207 is then used to measure the position information of each alignment mark 101 on the mask plate 10 in the thermally stable state. Based on this, the deformation amount between any two adjacent alignment marks 101 can be obtained. Figure 4 Taking the mask plate 10 shown as an example, the mask plate 10 is provided with a first alignment mark 101a, a second alignment mark 101b, a third alignment mark 101c, a fourth alignment mark 101d and a fifth alignment mark 101e. The first alignment mark 101a, the second alignment mark 101b and the third alignment mark 101c are arranged at equal intervals in the X direction, and the interval is d; the fourth alignment mark 101d, the first alignment mark 101a and the fifth alignment mark 101e are also arranged at equal intervals in the Y direction, and the interval is also d. By using the alignment sensor 207 and the temperature control module, the deformation of the mask plate 10 in the thermally stable state is calibrated, and the following deformation difference can be obtained: x lm 、xmr 、x mu and x dm Among them, x lm is the difference in deformation between the first alignment mark 101a and the second alignment mark 101b; x mr is the difference in deformation between the first alignment mark 101a and the third alignment mark 101c; x mu is the difference in deformation between the first alignment mark 101a and the fourth alignment mark 101d; x dm is the difference in deformation between the first alignment mark 101a and the fifth alignment mark 101e.

[0062] After obtaining the difference in deformation amount under the thermally stable state, the step 2 S2 is performed. That is, the mask 10 is moved in sequence according to the set path, and after the movement, the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101 is obtained; and the spatial image distance error is used to characterize the distortion value of each field of view point. Optionally, the spatial image distance error is obtained after each movement, or the spatial image distance error is obtained after several movements, which is not specifically limited in this embodiment. Exemplarily, each time the position of the mask 10 is moved, the spatial image distance error between the image plane of the field of view points corresponding to the second alignment mark 101b, the third alignment mark 101c, the fourth alignment mark 101d and the fifth alignment mark 101e and the image plane of the field of view points corresponding to the first alignment mark 101a are obtained respectively. Therefore, after moving N times, N groups of spatial image distance error data can be obtained; wherein N is a positive integer. After obtaining all groups of the aerial image distance error data, all the aerial image distance errors in each group are compensated using the deformation difference between all adjacent field points obtained by previous offline calibration to remove the influence of the thermal deformation of the mask 10 on the distortion value.

[0063] Exemplarily, the mask 10 is Figure 5 The mask plate 10 moves in sequence along the path shown. It can be understood that the mask plate 10 can first move in sequence along the positive semi-axis direction of X, then move once along the negative semi-axis direction of Y, and then move in sequence along the negative semi-axis direction of X, and then move repeatedly in this way, so that the path is serpentine. Of course, the mask plate 10 can also first move in sequence along the negative semi-axis direction of Y, move once along the positive semi-axis direction of X, and then move in sequence along the positive semi-axis of Y, and then repeat this to form a serpentine path. If the mark on the mask plate 10 is in the shape of a "M", the mask plate 10 can also move in the direction of the straight line where Y=X and Y=-X are located. Therefore, the moving direction of the mask plate 10 can be the direction of the line connecting any two adjacent alignment marks 101, and this embodiment does not make specific limitations on this.

[0064] Further, in Figure 5 In the path shown, the distance that the mask 10 moves each time is equal to the distance between two adjacent alignment marks 101 in the mask 10 in the direction of the movement. For example, when moving along the X direction, the distance that the mask 10 moves each time is equal to the distance between two adjacent alignment marks 101 in the X direction. When moving along the Y direction, the distance that the mask 10 moves each time is equal to the distance between two adjacent alignment marks 101 in the Y direction. Based on this, Figure 6 As shown, when the mask 10 is located at the first position F11, the first alignment mark 101a is located at the first position F11, the third alignment mark 101c is located at the second position F12, and the fifth alignment mark 101e is located at the fourth position F21. The second alignment mark 101b and the fourth alignment mark 101d do not have corresponding field of view positions. According to the alignment sensor 207, the position information and image plane information of the corresponding field of view points of the first alignment mark 101a, the third alignment mark 101c, and the fifth alignment mark 101e are obtained.

[0065] When the mask 10 moves along the X direction by d, as shown in FIG. Figure 7 As shown, the first alignment mark 101a moves from the first position F11 to the second position F12, becoming the first alignment mark 101a' after the movement. The second alignment mark 101b moves to the first position F11, becoming the second alignment mark 101b' after the movement. The third alignment mark 101c moves from the second position F12 to the third position F13, becoming the third alignment mark 101c' after the movement. The fourth alignment mark 101d moves a distance d along the X direction, and there is no corresponding position. The fifth alignment mark 101e moves from the fourth position F21 to the fifth position F22, becoming the fifth alignment mark 101e' after the movement. Then, according to the alignment sensor 207, the position information and image plane information of the corresponding field of view points of the first alignment mark 101a' after the movement, the second alignment mark 101b' after the movement, the third alignment mark 101c' after the movement, and the fifth alignment mark 101e' after the movement are obtained. This process is repeated to obtain the position information and image plane information of the corresponding field of view points of each alignment mark 101 after each movement.

[0066] After obtaining the position information and image plane information of the field of view points corresponding to each alignment mark 101 after movement, the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101 after movement is calculated. The spatial image distance error refers to the difference between the imaging distance of two adjacent alignment marks 101 at the corresponding field of view points and the nominal spacing. Since this embodiment takes the equal spacing d of each alignment mark 101 as an example, and the row spacing and column spacing of each field of view point are both d, the nominal spacing is d / m or 0, and m is the magnification of the projection objective 203. After obtaining the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101 after all movements, the deformation difference previously calibrated offline is used to compensate for all the spatial image distance errors, thereby removing the influence of the deformation of the mask 10 on the distortion measurement. The deformation compensation calculation process is as follows:

[0067]

[0068]

[0069] Among them, DT i,j is the distortion value corresponding to the field of view point at the i-th row and j-th column; is the difference between the spatial image spacing of the alignment mark 101 corresponding to the field of view points at the i-th row, j-th column and the i-th row, (j+1)-th column and the nominal spacing, that is, the spatial image distance error; n is the number of field of view points in each row, and in this embodiment Figure 5 Where n is 13.

[0070] From the above, we can see that DT 1,1 DT is the distortion value of the imaging of the alignment mark 101 corresponding to the first row and first column of the field of view, that is, the distortion value of the imaging of the alignment mark 101 corresponding to the first position F11. 1,2 is the distortion value of the alignment mark 101 imaged at the first row and second column field of view point, that is, the distortion value of the alignment mark 101 imaged at the second position F12. Therefore, when the first alignment mark 101a moves from the first position F11 to the second position F12, the other alignment marks 101 also move synchronously, and the moved second alignment mark 101b' is located at the first position F11, the moved third alignment mark 101c' is located at the third position F13, and the moved fifth alignment mark 101e' is located at the fifth position F22. And the distortion value of the second alignment mark 101b' after moving is DT 1,1 The distortion value of the first alignment mark 101a' after the movement is DT 1,2 The distortion value of the moved third alignment mark 101c' is DT 1,3 , and the distortion value of the fifth alignment mark 101e' after the movement is DT2,2 Given x lm is the difference in deformation between the first alignment mark 101a and the second alignment mark 101b; x mr is the difference in deformation between the first alignment mark 101a and the third alignment mark 101c; x dm is the difference in deformation between the first alignment mark 101a and the fifth alignment mark 101e. lm To compensate for the spatial image distance error between the first alignment mark 101a' and the second alignment mark 101b' after the movement but Using x mr To compensate for the spatial image distance error between the first alignment mark 101a' and the third alignment mark 101c' after the movement but And, using x dm To compensate for the spatial image distance error between the first alignment mark 101a' after the movement and the fifth alignment mark 101e' after the movement but By analogy, the spatial image distance error between the alignment marks 101 corresponding to the adjacent view points after each movement can be compensated. In this embodiment, the distortion value of the first view point is zero as a reference for calculation. That is, DT 1,1 =0.

[0071] It should be noted that, during the compensation calculation process, the spatial image distance error compensation between the alignment marks 101 corresponding to the adjacent field of view points will be calculated multiple times. For example, when performing the spatial image distance error compensation calculation after the first movement, the second position F12 corresponds to the first alignment mark 101a, and the third position F13 corresponds to the third alignment mark 101c, then x is used. mr To compensate for the spatial image distance error between the alignment marks 101 corresponding to the second position F12 and the third position F13. After the second movement, the first alignment mark 101a moves from the second position F12 to the third position F13, and the second alignment mark 101b moves from the first position F11 to the second position F12. The second position F12 corresponds to the second alignment mark 101b, and the third position F13 corresponds to the first alignment mark 101a. Then, x is used. lmTo compensate for the spatial image distance error between the second position F12 and the alignment mark 101 corresponding to the third position F13. It can be seen that the spatial image distance error between the second position F12 and the alignment mark 101 corresponding to the third position F13 is compensated twice, and multiple calculations will also occur at other positions, thereby obtaining more compensated data to enhance the robustness of the data, thereby improving the accuracy of the distortion value obtained subsequently.

[0072] However, repeated measurements and calculations will affect the efficiency of obtaining the distortion value of the projection lens 203. In other embodiments, in order to improve the measurement efficiency, the number of times the mask 10 is moved can be reduced while ensuring the amount of data. Figure 8 Move along the path shown. Specifically, the initial position of the first alignment mark 101a is the fourth position F21; correspondingly, the third alignment mark 101c is located at the fifth position F22, the fourth alignment mark 101d is located at the first position F11, and the fifth alignment mark 101e is located at the seventh position F31. When the mask plate 10 moves sequentially along the X positive semi-axis direction to the last position of the second row (named the eighth position F213 in this embodiment), the spacing of each movement of the mask plate 10 is d. When the first alignment mark 101a is located at the eighth position F213 and moves again, the first alignment mark 101a moves a distance of 2d to the last position of the fourth row (named the ninth position F413 in this embodiment), and then moves sequentially along the Y negative semi-axis direction to the first position of the fourth row. Compared to Figure 5 The path shown, Figure 8 The path shown reduces two row movements and two longitudinal movements, reduces the measurement time and the amount of calculation, and improves the efficiency of obtaining the distortion value. In this embodiment, the specific movement spacing and number of times of the mask 10 are not limited. Preferably, the distance of each movement of the mask 10 is the spacing d between two adjacent alignment marks 101 in the current movement direction, or several times of the spacing d.

[0073] Furthermore, the distortion value of each of the field of view points represented by the spatial image distance error can be obtained by arranging the above deformation compensation calculation formula:

[0074]

[0075] in, is the difference between the compensated spatial image spacing of the alignment marks 101 corresponding to the field points at the i-th row, j-th column and the i-th row, (j+1)-th column and the nominal spacing, that is, the compensated spatial image distance error.

[0076] Furthermore, in other embodiments, the offline calibration of the deformation difference of the mask plate 10 can be omitted. That is, after the mask plate 10 is in a thermally stable state, the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101 on the mask plate 10 after each movement is directly measured. According to the above-arranged formula, the distortion value of each field of view point characterized by the uncompensated spatial image distance error can be obtained:

[0077]

[0078] Because the above data are measured by the same mask 10, and the mask is always in a thermally stable state, the deformation of the mask 10 is fixed. And the applicant has calculated that the influence of the mask 10 on the distortion value is mainly a first-order quantity. Then, by removing the first-order quantity in the subsequent steps, the influence of the thermal deformation of the mask 10 on the distortion value can be directly alleviated. Therefore, the deformation calibration process can be omitted. Exemplarily, the first-order influence of the deformation on the distortion value is:

[0079]

[0080] Where n is the number of view points in each row, and m is the number of rows of all view points.

[0081] Furthermore, since the position and angle of the projected light have a direct impact on the imaging of the alignment mark 101 on the mask 10, the relative position of the light and the mask 10 is kept unchanged after each movement in this embodiment, so that each measurement is performed under the same lighting conditions to further ensure the accuracy of the distortion value acquisition. Preferably, during each movement of the mask 10, the light used to illuminate the mask 10 moves synchronously with the mask 10, so that the optical axis of the light passes through the same position of the mask 10 after each movement. In other words, each time the mask 10 moves along the path, the mask 10 and the light move synchronously so that the relative positions of the two remain unchanged. Among them, the optical axis refers to the central axis of the light beam emitted by the light emitter 201. Preferably, the optical axis is located at the center of the mask 10. It should be noted that, during each measurement process, the light irradiating the mask plate 10 will also have a certain impact on the temperature of the mask plate 10, but under the regulation of the temperature control module, the mask plate 10 remains in a thermally stable state, thereby ensuring that the deformation of the mask plate 10 is fixed.

[0082] In one embodiment, Figure 3 As shown, the light emitter 201 in the projection objective lens distortion measuring device 20 can move synchronously with the mask stage 202. In other embodiments, Fig. 9As shown, a variable window 201a is provided on the light emitter 201. When the mask stage 202 moves, the opening position of the variable window 201a moves synchronously therewith, so that the light emitted by the light emitter 201 maintains a relative position with the mask stage 202 after being emitted through the opening.

[0083] Furthermore, after obtaining the distortion values ​​of all the viewpoints, the distortion values ​​of all the viewpoints are array-calculated and the first-order quantities are removed, thereby obtaining the distortion value of the projection objective lens 203 .

[0084] See also Figure 3 and Fig. 9 Based on the same inventive concept, this embodiment also provides a projection objective distortion measurement system, including the above-mentioned mask 10 and the above-mentioned projection objective distortion measurement device 20. Among them, the mask 10 and the projection objective distortion measurement device 20 can refer to the above-mentioned records, and this embodiment will not be repeated here. In addition, the projection objective distortion measurement device 20 also includes a processor (not shown), which is used to obtain the projection objective distortion value by using the distortion values ​​of multiple field of view points obtained by the spatial image distance error between the field of view points corresponding to the adjacent alignment marks 101 after the mask 10 moves. That is, the spatial image distance error is used to characterize the distortion value of each field of view point; and the distortion values ​​of all the field of view points are arrayed and calculated, and the first-order quantity is removed to obtain the distortion value of the projection objective 203. Furthermore, the processor is also used to obtain the deformation error between each pair of adjacent alignment marks 101 in the thermally stable state; and to compensate all the spatial image distance errors according to the deformation error; and to use the compensated spatial image distance error to characterize the distortion value of each of the field of view points to improve the accuracy of the obtained distortion value.

[0085] Based on the same inventive concept, this embodiment also provides a lithography machine (not shown) for executing the projection objective lens distortion measurement method to obtain accurate distortion values ​​of the projection objective lens and improve the imaging quality of the lithography machine.

[0086] In summary, the projection objective lens distortion measurement system and method, and the lithography machine provided in this embodiment use the designed moving path and alignment mark 101 to realize the switching of the alignment mark 101 at different viewpoints, and characterize the distortion value of each viewpoint according to the obtained multiple spatial image distance errors, and then calculate a more accurate distortion value of the projection objective lens 203. Also, during the measurement process, the temperature of the mask 10 is adjusted by the temperature control module so that it is always kept in a thermally stable state, thereby fixing its deformation amount, avoiding the deformation amount of the mask 10 due to the change of temperature, thereby affecting the measurement accuracy of the projection objective lens distortion value. In addition, during each movement of the mask 10, the projection light also moves synchronously with the mask 10, thereby ensuring that each measurement is performed under the same lighting conditions, avoiding the influence of the light on the measurement accuracy, further improving the accuracy of the distortion value, and realizing absolute distortion measurement.

[0087] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for measuring projection objective lens distortion, characterized in that: include: Providing a mask having a plurality of alignment marks disposed thereon; The mask is moved sequentially along a set path, and after each or several movements, an alignment sensor on the projection object image plane is used to obtain the imaging of the corresponding alignment mark at the field of view point; wherein the distribution of each acquisition point in the alignment sensor corresponds to each alignment mark on the mask, and the alignment sensor can move with the movement of the mask; and, Acquire the spatial image distance error between the field of view points corresponding to the adjacent alignment marks according to the imaging of the field of view points; All the spatial image distance errors are compensated by using the deformation difference between all adjacent field of view points calibrated offline, so as to remove the distortion value error caused by the thermal deformation of the mask; and the compensated spatial image distance error is used to characterize the distortion value of each field of view point; The projection objective lens distortion value is obtained according to the distortion values ​​of the plurality of field of view points.

2. The method for measuring projection objective lens distortion according to claim 1, characterized in that: The plurality of alignment marks are symmetrically arranged along a first direction and / or a second direction; wherein the first direction and the second direction are perpendicular to each other.

3. The method for measuring projection objective lens distortion according to claim 2, characterized in that: The plurality of alignment marks are distributed at equal intervals along the first direction and / or the second direction.

4. The method for measuring projection objective lens distortion according to claim 1, characterized in that: The moving direction of the mask includes the direction of a line connecting any two adjacent alignment marks.

5. The method for measuring projection objective lens distortion according to claim 1, characterized in that: The distance that the mask plate moves each time is the distance between two adjacent alignment marks in the current moving direction, or several times of the distance.

6. The method for measuring projection objective lens distortion according to claim 1, characterized in that: Five alignment marks are arranged on the mask plate, and the five alignment marks are distributed in a "cross" shape.

7. The method for measuring projection objective lens distortion according to claim 1, characterized in that: The process of offline calibration of the deformation difference between all adjacent field points includes: Before sequentially moving the mask plate along a set path, adjusting the temperature of the mask plate so as to keep the mask plate in a thermally stable state; The deformation errors between adjacent alignment marks are measured.

8. The method for measuring projection objective lens distortion according to claim 7, characterized in that: The process of compensating all the aerial image distance errors by using the deformation amount differences between all adjacent field of view points calibrated offline includes: compensating the aerial image distance error according to the deformation error.

9. The method for measuring projection objective lens distortion according to claim 1, characterized in that: In the process of sequentially moving the mask plate along a set path, the light used to illuminate the mask plate moves synchronously with the mask plate, so that the optical axis of the light after movement passes through the same position of the mask plate.

10. The method for measuring projection objective lens distortion according to claim 1, characterized in that: Before moving the mask, the mask is aligned with an alignment sensor on the projection objective image plane; and after the mask moves a distance d, the alignment sensor moves with the mask a distance d / m; wherein m is the magnification of the projection objective.

11. A projection objective lens distortion measurement system, characterized in that: include: Mask and projection objective distortion measuring device; The mask is provided with a plurality of alignment marks; The projection objective lens distortion measuring device comprises a light emitter, a mask stage, a projection objective lens, a workpiece stage and a processor; the light emitted by the light emitter passes through the mask stage and the projection objective lens in sequence and is irradiated on the workpiece stage; wherein the mask is arranged on the mask stage and can move in sequence along a set path with the mask stage; an alignment sensor is arranged on the workpiece stage, and the workpiece stage can drive the alignment sensor to move along with the movement of the mask; and the alignment sensor is used to obtain the imaging of the corresponding alignment mark at the field of view point after each or several movements of the mask; and the distribution of each acquisition point in the alignment sensor corresponds to each alignment mark on the mask; The processor is used to obtain the spatial image distance error between the field of view points corresponding to the adjacent alignment marks according to the imaging of the field of view points after each or several movements of the mask; and to compensate all the spatial image distance errors using the deformation difference between all adjacent field of view points calibrated offline to remove the distortion value error caused by the thermal deformation of the mask; and the compensated spatial image distance error is used to characterize the distortion value of each field of view point; and to obtain the distortion value of the projection objective lens according to the distortion values ​​of multiple field of view points.

12. The projection objective lens distortion measurement system according to claim 11, characterized in that: The plurality of alignment marks are symmetrically arranged along a first direction and / or a second direction; wherein the first direction and the second direction are perpendicular to each other.

13. The projection objective lens distortion measurement system according to claim 12, characterized in that: The plurality of alignment marks are distributed at equal intervals along the first direction and / or the second direction.

14. The projection objective lens distortion measurement system according to claim 11, characterized in that: The moving direction of the mask includes the direction of a line connecting any two adjacent alignment marks.

15. The projection objective lens distortion measurement system according to claim 11, characterized in that: The distance that the mask plate moves each time is the distance between two adjacent alignment marks in the current moving direction, or several times of the distance.

16. The projection objective lens distortion measurement system according to claim 11, characterized in that: Five alignment marks are arranged on the mask plate, and the five alignment marks are distributed in a "cross" shape.

17. The projection objective lens distortion measurement system according to claim 11, characterized in that: The projection objective lens distortion measurement device further includes a temperature control module for adjusting the temperature of the mask plate so as to keep the mask plate in a thermally stable state.

18. The projection objective lens distortion measurement system according to claim 17, characterized in that: The processor is further configured to obtain a deformation error between adjacent alignment marks in the thermally stable state; and to compensate for the aerial image distance error according to the deformation error.

19. The projection objective lens distortion measurement system according to claim 11, characterized in that: The light emitter can move synchronously with the mask stage; or, the light emitter has a variable window, so that the light emitted through the variable window moves synchronously with the mask stage; and the optical axis of the light after movement passes through the same position of the mask plate.

20. The projection objective lens distortion measurement system according to claim 11, characterized in that: After the mask plate moves a distance d along with the mask stage, the alignment sensor moves synchronously with the workpiece stage a distance d / m; wherein m is the magnification of the projection objective lens.

21. A photolithography machine, characterized in that: The lithography machine is used to execute the projection objective lens distortion measurement method as described in any one of claims 1 to 10.

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