Calibration method and calibration system

Abstract

The application relates to a calibration method and a calibration system. The calibration method comprises the following steps: obtaining a first correction value of a test wafer in a pre-alignment station based on a pre-alignment coordinate system; obtaining a second correction value of the test wafer in a workpiece table station based on a workpiece table coordinate system; obtaining a manipulator correction value of a manipulator in the pre-alignment station and the workpiece table station based on a manipulator coordinate system according to the first correction value and the second correction value; and correcting a point position setting value of the manipulator according to the manipulator correction value. The calibration method provided by the application converts the correction values of the test wafer in the pre-alignment station and the workpiece table station to the manipulator, so that the point position of the manipulator can be automatically adjusted, and the adjustment efficiency and the point position debugging precision are improved.

Description

Technical Field

[0001] This application relates to the field of photolithography, specifically to a calibration method and calibration system. Background Technology

[0002] In semiconductor and other manufacturing fields, wafers in lithography machines rely on robotic arms to move between several fixed points to complete production. Typically, these robotic arm movement points include the wafer cassette, pre-aligner, and wafer stage. The wafer's position at each point within the machine is primarily adjusted manually by assembly engineers, which is inefficient and its accuracy is affected by human error. Inaccurate positioning at these points affects the relative position of the wafer to the wafer stage after it is mounted, thus impacting the exposure area layout and alignment calculations in subsequent production processes. Summary of the Invention

[0003] The main technical problem addressed in this application is to provide a calibration method and calibration system to improve calibration accuracy.

[0004] This application provides a calibration method, including: Obtain the first correction value of the test wafer at the pre-alignment station based on the pre-alignment coordinate system; Obtain the second correction value of the test wafer at the workpiece stage station based on the workpiece stage coordinate system; Based on the first correction value and the second correction value, the robot correction values ​​of the robot at the pre-alignment station and the workpiece table station are obtained according to the robot coordinate system. The position setting value of the robot arm is adjusted according to the robot arm correction value.

[0005] According to an embodiment of this application, the step of obtaining the robot correction values ​​based on the robot coordinate system at the pre-alignment station and the workpiece table station according to the first correction value and the second correction value includes: The first correction value is converted into a third correction value of the robot at the pre-alignment station based on the robot coordinate system; The second and third correction values ​​are converted into a fourth correction value for the robot at the workpiece station based on the robot's coordinate system.

[0006] According to an embodiment of this application, the conversion formula for converting the first correction value to the third correction value includes:

[0007] in, The first correction value, The third correction value, Let be the first rotation matrix of the pre-aligned coordinate system relative to the robot's coordinate system.

[0008] According to an embodiment of this application, the conversion formula for converting the second correction value and the third correction value into the fourth correction value includes:

[0009] in, The second correction value, The third correction value, The fourth correction value, Let be the second rotation matrix of the workpiece stage coordinate system relative to the robot arm coordinate system. This is the third rotation matrix corresponding to the angle at which the robot arm rotates the test wafer as it moves from the pre-alignment station to the workpiece stage station.

[0010] According to an embodiment of this application, the step of obtaining the second correction value of the test wafer at the workpiece stage station based on the workpiece stage coordinate system includes: Obtain the center coordinates of the test wafer; Obtain the coordinates of the rotation center of the workpiece stage; The second correction value is obtained based on the difference between the coordinates of the rotation center and the coordinates of the circle center.

[0011] According to an embodiment of this application, the step of obtaining the rotation center coordinates of the workpiece stage includes: The workpiece stage is rotated to the positive limit position, and multiple alignment marks on the test wafer are aligned respectively. The first plane coordinates of the workpiece stage corresponding to each alignment mark when aligned are recorded. Rotate the workpiece stage to the negative limit position, align the plurality of alignment marks respectively, and record the second plane coordinates of the workpiece stage corresponding to each alignment mark when it is aligned; Obtain the normal to the line connecting the first plane coordinate and the second plane coordinate corresponding to the same alignment mark, wherein the plurality of alignment marks correspond to the plurality of normals; The coordinates of the rotation center are obtained from the intersection points between the multiple normals.

[0012] According to one embodiment of this application, the calibration method further includes: Obtain the first rotation angle of the test wafer at the workpiece stage station; The angle correction value of the test wafer at the pre-alignment station is obtained based on the first rotation angle; The pre-alignment station corrects the wafer's angle according to the angle correction value.

[0013] According to one embodiment of this application, the calibration method further includes: Determine whether the calibration correction value is less than a preset value, wherein the calibration correction value includes the robot arm correction value and the angle correction value; If the calibration correction value is greater than or equal to the preset value, then the first correction value, the second correction value, and the calibration correction value are obtained again, and the point setting value and the correction angle are corrected according to the calibration correction value.

[0014] According to one embodiment of this application, the calibration method further includes: The wafer under test is exposed according to the exposure center setting value to obtain the exposure area; The actual exposure center coordinates are calculated based on the arrangement of the off-axis marks in the exposure area; The exposure center correction value is obtained by subtracting the rotation center coordinates of the workpiece stage from the actual exposure center coordinates. The exposure center setting value is adjusted according to the exposure center correction value.

[0015] This application also provides a calibration system, which uses the calibration method described in the above embodiments for calibration.

[0016] The calibration method and calibration system provided in this application convert the correction values ​​of the test wafer at the pre-alignment station and the workpiece stage station to the robot arm to automatically adjust the robot arm position, which helps to improve assembly efficiency and position adjustment accuracy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of an embodiment of the calibration method of this application; Figure 2 yes Figure 1 A flowchart illustrating an embodiment of step S300 of the calibration method shown; Figure 3 yes Figure 1 A flowchart illustrating an embodiment of step S200 of the calibration method shown; Figure 4 This is a flowchart illustrating another embodiment of the calibration method of this application; Figure 5 This is a flowchart illustrating yet another embodiment of the calibration method of this application; Figure 6 This is a flowchart illustrating another embodiment of the calibration method of this application; Figure 7 This is a schematic diagram of an embodiment of the calibration system of this application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0020] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] This application provides a calibration method, such as... Figure 1 and Figure 7 As shown, the calibration method includes: Step S100: Obtain the first correction value of the test wafer based on the pre-alignment coordinate system at the pre-alignment station.

[0023] Step S200: Obtain the second correction value of the test wafer at the workpiece stage station based on the workpiece stage coordinate system.

[0024] Step S300: Obtain the robot correction values ​​of the robot arm 110 at the pre-alignment station and the workpiece table station based on the robot arm coordinate system according to the first correction value and the second correction value.

[0025] Step S400: Adjust the position setting value of robot arm 110 according to the robot arm correction value.

[0026] In related technologies, engineers can pre-set the positions of the robot arm 110 at the pre-alignment station and the workpiece stage. When the robot arm 110 moves to the corresponding position, it can perform operations such as picking up and placing wafers. The pre-alignment station and the workpiece stage have built-in position measurement schemes that can calibrate the wafer positions. This application, by repeatedly testing the wafer transfer process, converts the first correction value of the test wafer position at the pre-alignment station and the second correction value of the position at the workpiece stage into robot arm correction values, achieving automatic calibration. This makes the position of the robot arm 110 placing the wafer on the pre-alignment stage 120 and the workpiece stage 130 more accurate during actual production, reducing the need for engineers to manually adjust the positions and minimizing the interference of human factors on equipment accuracy.

[0027] In some embodiments, in step S100, each time the robot arm 110 transfers the test wafer to the pre-alignment stage 120, the planar coordinates of the test wafer in the pre-alignment coordinate system are recorded. , After performing test wafer pre-alignment, record the planar coordinates again. , ], thus obtaining the first correction value of the pre-aligned point on the plane. , ]=[ , ]-[ , ].

[0028] In some embodiments, such as Figure 2 and Figure 7 As shown, step S300 includes: Step S310: Convert the first correction value into a third correction value based on the robot coordinate system at the pre-alignment station of the robot arm 110.

[0029] Step S320: Convert the second and third correction values ​​into a fourth correction value based on the robot coordinate system at the workpiece table station of the robot 110.

[0030] The correction values ​​for the robotic arm include the third correction value and the fourth correction value.

[0031] In some embodiments, when designing the overall frame, the robot coordinate system, the pre-alignment coordinate system, and the workpiece table coordinate system can be unified (for example, all coordinate systems are Cartesian coordinate systems), and mutual transformation relationships can be established so that the horizontal relative displacement measured on the workpiece table coordinate system and the pre-alignment coordinate system can be transformed to the robot coordinate system, so as to facilitate the correction of the position by the robot 110.

[0032] In some embodiments, the conversion formula for converting the first correction value to the third correction value includes:

[0033] in, The first correction value, This is the third correction value. This is the first rotation matrix of the pre-aligned coordinate system (PA) relative to the robot coordinate system (RB).

[0034] In some embodiments, the first correction value is the displacement correction value of the test wafer at the pre-alignment station based on the pre-alignment coordinate system, and the third correction value is the displacement correction value of the robot arm 110 at the pre-alignment station based on the robot arm coordinate system. By converting the first correction value into the third correction value, the corrections required for the wafer at the pre-alignment stage 120 can be completed by the robot arm 110 during wafer transfer, thereby improving debugging efficiency and accuracy.

[0035] In some embodiments, the conversion formula for converting the second and third correction values ​​to the fourth correction value includes:

[0036] in, This is the second correction value. This is the third correction value. This is the fourth correction value. Let be the second rotation matrix of the workpiece stage coordinate system (WS) relative to the robot arm coordinate system (RB). This is the third rotation matrix corresponding to the angle at which the robot arm 110 rotates the test wafer as it moves from the pre-alignment station to the workpiece stage station. By converting the second and third correction values ​​into a fourth correction value, the corrections required for the wafer on the workpiece stage 130 can be completed by the robot arm 110 during wafer transfer, thereby improving debugging efficiency and accuracy.

[0037] In some embodiments, [ , The fourth correction value includes the component of the correction value of the robot arm 110 at the pre-alignment stage 120 position transmitted to the workpiece stage 130 position. The robot arm 110 picks up and places the test wafer at the same point in the pre-alignment station. The displacement of the test wafer before and after pre-alignment in the pre-alignment station will change, thus affecting the relative position of the robot arm 110's toothed fork and the test wafer when moving from the pre-alignment station to the workpiece stage station. Even if the position of the robot arm 110 at the workpiece stage station remains unchanged, it will still affect the relative position of the test wafer and the workpiece stage 130 when the wafer is placed onto the workpiece stage 130. Therefore, the fourth correction value includes the correction value of the robot arm 110 at the pre-alignment station transmitted to the workpiece stage station.

[0038] In some embodiments, such as Figure 3 As shown, step S200 includes: Step S210: Obtain the center coordinates of the test wafer.

[0039] Step S220: Obtain the rotation center coordinates of the workpiece stage 130.

[0040] Step S230: Obtain the second correction value based on the difference between the coordinates of the rotation center and the coordinates of the circle center.

[0041] In some embodiments, the robot arm 110 can place the test wafer onto the chuck of the workpiece stage 130, the rotation center of the workpiece stage 130 being the rotation center of the chuck. During the photolithography process, by calibrating the wafer at the workpiece stage station, the center of the wafer can be aligned with the rotation center of the workpiece stage 130, facilitating subsequent photolithography processes.

[0042] In some embodiments, the step of obtaining the center coordinates of the test wafer includes: Obtain the edge coordinates of the test wafer.

[0043] The center coordinates of the test wafer are calculated based on the edge coordinates.

[0044] In some embodiments, the number of edge coordinates of the test wafer can be three or more, and the edge coordinates are not selected from the flat edge positions of the test wafer. The center coordinates of the test wafer can be obtained through a geometric algorithm of three points defining a circle. , ].

[0045] In some embodiments, the rotation axis of the rotatable stage 130 is used to rotate the stage 130 to the coordinates of the wafer pick-up position (usually the zero point of the rotation axis). The wafer pick-up position is an external interface for the stage 130 to complete the wafer handover task. The four edges of the test wafer are aligned off-axis (top, bottom, left, right). Flat edges can be removed, and the off-axis alignment coordinates of three edges are obtained. The center coordinates of the test wafer when aligned off-axis are then calculated. , ].

[0046] In some embodiments, the step of obtaining the rotation center coordinates of the workpiece stage 130 includes: Rotate the workpiece stage 130 to the positive limit position, align multiple alignment marks on the test wafer, and record the first plane coordinates of the workpiece stage 130 corresponding to each alignment mark when aligned.

[0047] Rotate the workpiece stage 130 to the negative limit position, align multiple alignment marks respectively, and record the second plane coordinates of the workpiece stage 130 corresponding to each alignment mark when aligned.

[0048] Obtain the normal to the line connecting the first and second plane coordinates corresponding to the same alignment mark; multiple alignment marks correspond to multiple normals.

[0049] The coordinates of the rotation center are obtained from the intersection points between multiple normals.

[0050] In some embodiments, the number of alignment marks on the test wafer can be 2, 3, 4, 6, etc. When there are multiple intersection points of the multiple normals, the average value can be taken as the rotation center coordinate.

[0051] In some embodiments, the alignment of the alignment marks on the test wafer can be off-axis alignment. The stage 130 is movable so that multiple alignment marks fall sequentially into the center of the field of view of the off-axis camera, and when the off-axis camera captures a clear signal, it records the precise coordinates of the stage 130.

[0052] In some embodiments, after the robot arm 110 transfers the test wafer to the chuck disk of the stage 130, it can rotate the vertical rotation axis of the stage 130 to the negative limit position, select four off-axis marks symmetrical about the center of the test wafer for alignment (off-axis camera visual alignment), and ensure that the lines connecting the marks to the center of the test wafer are as perpendicular as possible to each other, and record the first plane coordinates of the stage 130 plane when each off-axis mark is aligned. , Then rotate the axis to the positive limit position and record the second plane coordinates of the workpiece stage 130 plane when each mark is aligned. , ] Calculate the normal to the line connecting the two recording points, then calculate the intersection of the normals. The average of multiple intersection points is the coordinate of the rotation center of the workpiece stage 130. , ].

[0053] In some embodiments, the rotation center coordinates can also be optimized using other geometric methods or modeling, and the rotation center coordinates [ , This refers to the off-axis alignment of the Chuck disk's rotation center.

[0054] In some embodiments, the rotation center coordinates of the workpiece stage 130 are obtained. , ] and the center coordinates of the test wafer [ , After that, the second correction value for the test wafer at the workpiece stage can be obtained. , ]=[ , ]-[ , ].

[0055] In some embodiments, in the step of correcting the position setting value of the robot arm 110 according to the robot arm correction value, the correction process may be to add the robot arm correction value to the position setting value.

[0056] In some embodiments, the calibration method further includes: Step S2: Correct the calibration angle of the pre-alignment station.

[0057] In some embodiments, step S2 includes: Obtain the first rotation angle of the test wafer at the workpiece stage.

[0058] The angle correction value of the test wafer at the pre-alignment station is obtained based on the first rotation angle.

[0059] The pre-alignment station corrects the wafer's angle based on the angle correction value.

[0060] In some embodiments, the first rotation angle of the wafer coordinate system relative to the workpiece stage coordinate system is calculated by aligning the two ends of the flat edge of the test wafer off-axis. This refers to the deviation angle of the test wafer on the workpiece stage 130. The angle correction value for the rotation axis of the pre-alignment station is then determined. By using angle correction values ​​to adjust the rotation angle of the pre-alignment station, the wafer can be rotated and aligned at the pre-alignment station without needing to be aligned at the workpiece stage. The adjustment of angle correction values ​​makes the alignment angle more convenient and helps to improve calibration efficiency.

[0061] In some embodiments, the error in the horizontal translation of the wafer can be corrected by the robot arm 110 changing the position setting value. The position setting value of the robot arm 110 can be corrected according to the robot arm correction value. Since the robot arm 110 does not have the degree of freedom to adjust the wafer rotation or the angle of the robot arm 110 entering and leaving different positions is a fixed value, the robot arm 110 cannot correct the rotation angle. The correction of the wafer rotation angle is completed by the pre-alignment station.

[0062] In some other embodiments, the robot arm 110 may also be equipped with a rotating structure to correct the rotation angle of the wafer. Both the horizontal translation and rotation angle of the wafer can be calibrated by the robot arm 110.

[0063] In some embodiments, the calibration method further includes: Determine whether the calibration correction value is less than the preset value. The calibration correction value includes the robot correction value and the angle correction value.

[0064] If the calibration correction value is greater than or equal to the preset value, the first correction value, the second correction value, and the calibration correction value are obtained again, and the point setting value and the correction angle are corrected according to the calibration correction value.

[0065] In some embodiments, a prepared test wafer can be used to run the wafer transfer process multiple times. Each transfer process corrects the position setting value and correction angle obtained in the previous transfer process to gradually reduce the calibration correction value so that the calibration correction value is less than the preset value, and the final position setting value and correction angle are more accurate and stable.

[0066] In some embodiments, if the calibration correction value is less than the preset value, the final position setting value and correction angle can be applied to the wafer transfer process in the actual production process, which can reduce the requirement for manual position adjustment and improve transfer accuracy and efficiency.

[0067] In some embodiments, if the calibration correction value is greater than or equal to the preset value, the wafer transfer process needs to be re-tested, the point setting value and the correction angle need to be corrected, and the process is repeated until the calibration correction value is less than the preset value.

[0068] In some embodiments, there are multiple preset values. The robot correction value can correspond to a first preset value, and the angle correction value can correspond to a second preset value. When the robot correction value is greater than or equal to the first preset value, and the angle correction value is less than the second preset value, the robot correction value can be obtained cyclically to correct the point setting value, while the angle correction value is set to 0 to avoid over-calibration. When the robot correction value is less than the first preset value, and the angle correction value is greater than or equal to the second preset value, the robot correction value can be set to 0, and the angle correction value can be obtained cyclically to correct the calibration angle.

[0069] In some embodiments, considering measurement errors and coordinate transformation errors, a correction step size coefficient of 0 < α ≤ 1 can be set. The correction value obtained after each process is completed is multiplied by this coefficient α before being compensated to the point setting value and angle correction value. This can suppress errors and prevent divergence during multiple corrections.

[0070] In some embodiments, the correction step size coefficient α can be set to a decreasing value. As the number of process loops increases, the value of the correction step size coefficient α gradually decreases. The decreasing α can better suppress measurement noise while speeding up the convergence speed.

[0071] In some embodiments, such as Figure 4 and Figure 7 As shown, the calibration method includes: Step S1: Correct the position settings of the robotic arm 110.

[0072] Step S2: Correct the calibration angle of the pre-alignment station.

[0073] Step S3: Correct the exposure center setting value of the workpiece stage station.

[0074] Step S1 includes steps S100, S200, S300 and S400.

[0075] In some embodiments, step S3 includes: The exposed area is obtained by exposing the test wafer according to the exposure center setting value.

[0076] The actual exposure center coordinates are calculated based on the arrangement of the off-axis markers in the exposure area.

[0077] The exposure center correction value is obtained by subtracting the rotation center coordinates of the workpiece stage 130 from the actual exposure center coordinates.

[0078] Adjust the exposure center setting value based on the exposure center correction value.

[0079] In some embodiments, since there is an initial deviation between the exposure center setting value and the rotation center coordinate of the workpiece stage 130, the exposure area obtained by exposing according to the exposure center setting value will also have a deviation. However, an off-axis mark can be exposed. Based on the off-axis mark, the center of the actual exposure area and the actual exposure center coordinates can be calculated, and then the exposure center setting value can be corrected.

[0080] In some embodiments, the stage coordinates corresponding to each exposure area (shot) during the first layer exposure of the wafer are determined by two parameters: one is the nominal coordinate of the stage 130 when the projection center of the overall mask pattern on the wafer (not the center of a specific shot) coincides with the rotation center of the Chuck disk. [ ], abbreviated as exposure center setting value, but in reality there is error, and the two centers may not coincide; secondly, the relative displacement of each shot with respect to the wafer center. ].

[0081] In some embodiments, after the robot arm 110, pre-alignment stage 120, and workpiece stage 130 are fixed at their junction positions, n exposure areas (shots) of the prepared coated test wafer are exposed using a mask with off-axis markings. The workpiece stage coordinates during exposure are […]. ]=[ ]+[ After development, the wafer is loaded, and the loading angle error is corrected. An off-axis camera is used to align with the off-axis marks of n shots on the test wafer. Based on the designed position of the off-axis marks on the mask, the workpiece stage coordinates for off-axis alignment of the n shot centers are calculated. Then calculate the workpiece stage coordinates when the center point of the actual overall mask pattern projection on the wafer is aligned off-axis. ]=[ ]-[ (The average of the results from n shots can be taken), and this average is compared with the coordinates of the rotation center of the workpiece stage 130. , The workpiece stage coordinate correction value at the exposure center position is obtained by comparison, i.e., the exposure center correction value. ]=[ , ]-[ Update to the exposure center settings. ]=[ ]+ [ ].

[0082] In some embodiments, such as Figure 5 and Figure 7 As shown, the calibration method can be applied to the wafer transport system of a lithography machine. The calibration method includes: Step S10: Perform manual coarse adjustments to the positions of the robot arm 110, the pre-alignment stage 120, and the workpiece stage 130 to ensure that the wafer transport system can operate normally, the wafer off-axis mark can be found, and the lithography machine can perform clear exposure.

[0083] Before assembly, prepare a test wafer with multiple off-axis marks, an exposed wafer coated with adhesive, and a test mask with off-axis mark patterns. Set the position (6 degrees of freedom) to which the workpiece stage 130 will move during wafer loading and unloading, i.e., the wafer pick-up position of the workpiece stage 130.

[0084] During assembly and adjustment, engineers first manually adjust the positions of the robotic arm 110, the pre-alignment stage 120, and the workpiece stage 130 to ensure that the wafer transfer system can transfer the wafer normally according to the production process, that the off-axis marks on the wafer can be found smoothly, and that the lithography machine can perform clear exposure.

[0085] Step S11: Transfer the wafer from the basket to the wafer pre-alignment station and record the xy horizontal coordinates of the wafer in the pre-alignment coordinate system before and after pre-alignment. , ]、[ , Subtracting these values ​​yields the horizontal correction value in the pre-aligned coordinate system. , ]=[ , ]-[ , ].

[0086] Step S12: The wafer is transferred from the pre-alignment stage 120 to the workpiece stage 130.

[0087] Step S13: Determine whether the Chuck disk adsorption pressure of the workpiece stage 130 is normal.

[0088] If the Chuck disk adsorption pressure on the workpiece stage 130 is abnormal, return to step S10 for debugging.

[0089] Step S14: If the Chuck disk adsorption pressure of the workpiece stage 130 is normal, rotate the workpiece stage 130 to the coaxial alignment position, align it off-axis with the three edges of the wafer (excluding the flat edge), and calculate the horizontal coordinates of the workpiece stage when the wafer center is off-axis aligned. , ].

[0090] Step S15: Rotate the workpiece stage 130° to the coaxial alignment position, align the two ends of the wafer's flat edge off-axis, and calculate the rotation angle of the wafer relative to the workpiece stage coordinate system. .

[0091] In some embodiments, the workpiece stage 130 can rotate about the z-axis to achieve coaxial alignment on a horizontal plane.

[0092] Step S16: Rotate the workpiece stage 130 to the positive limit position, locate the four off-axis marks on the wafer, perform off-axis alignment respectively, and record the horizontal coordinates of the workpiece stage when the four off-axis marks are aligned. , ].

[0093] Step S17: Rotate the workpiece stage 130 to the negative limit, perform off-axis alignment on the four identical off-axis marks respectively, and record the horizontal coordinates of the workpiece stage when the four off-axis marks are aligned. , ].

[0094] Step S18: Based on the two measurements of the four off-axis marks [ , ]and[ , The horizontal coordinates of the workpiece stage 130 when the Chuck disk rotation center is aligned off-axis are calculated using geometric or least squares methods. , ].

[0095] Step S19: Calculate the correction value of the workpiece stage position in the workpiece stage coordinate system. , ]=[ , ]-[ , ].

[0096] Step S20: The wafer is transferred from the workpiece stage 130 to the return basket.

[0097] Step S21: Using the coordinate system transformation formula, convert the measurement and calculation results into compensation values ​​for the robot arm at the pre-alignment point and the workpiece stage point, and compensation values ​​for the rotation axis during wafer pre-alignment; apply the compensation values ​​to the point settings.

[0098] Step S22: Determine whether each compensation value is less than the preset value. If the compensation value is not less than the preset value, return to step S11.

[0099] In some embodiments, such as Figure 6 As shown, the calibration method can calibrate the exposure center setting value. The calibration method includes: Step S30: Based on the exposure center setting value [ Expose the first layer pattern with off-axis markings, develop n shots, reload the film, and correct the film loading angle error.

[0100] Step S31: Locate and align the off-axis camera with the off-axis mark, and calculate the workpiece stage coordinates when the center of each shot is aligned off-axis. ].

[0101] Step S32: Calculate the workpiece stage coordinates when the center point of the actual overall mask pattern projected onto the wafer is aligned off-axis based on the shot arrangement. ].

[0102] Step S33: Subtract the workpiece stage coordinates when the Chuck disk rotation center is aligned off-axis from the workpiece stage coordinates when the actual overall mask pattern's projection center point on the wafer is aligned off-axis to obtain the correction value for the exposure center setting. ]=[ , ]-[ ].

[0103] Step S34: Compensate the correction value to the exposure center setting value. ]superior.

[0104] Step S35: Determine whether the correction value is less than the preset error value. If the correction value is not less than the preset error value, return to step S30.

[0105] This application also provides a calibration system 10, such as... Figure 7 As shown, the calibration system 10 is calibrated using the calibration method described in the above embodiments.

[0106] In some embodiments, the calibration system 10 includes a robot arm 110, a pre-alignment stage 120, and a workpiece stage 130, wherein the robot arm 110 can transport test wafers to the pre-alignment stage 120 and the workpiece stage 130.

[0107] In some embodiments, the calibration system 10 further includes a control module 140, which can be used to obtain robot correction values ​​and angle correction values, correct the position setting values ​​of robot 110 according to the robot correction values, and correct the correction angle of pre-alignment stage 120 according to the angle correction values.

[0108] In some embodiments, the calibration system 10 further includes a coaxial camera and an off-axis camera, the coaxial camera being used for coaxial alignment and the off-axis camera being used for off-axis alignment.

[0109] This application embodiment also provides a lithography apparatus, which includes a calibration system 10, and the lithography apparatus can calibrate each working point through the calibration system 10.

[0110] The calibration method and calibration system 10 provided in this application can automatically adjust the positions of the robot arm 110 and the exposure positions of the workpiece stage 130, improving assembly efficiency, position adjustment accuracy, and exposure position accuracy. The calibration method utilizes and integrates measurement modules of different components of the whole machine, automating the adjustment of different components. It can more accurately and automatically adjust the positions of the upper and lower parts of the robot arm 110, the pre-alignment positions, and the exposure center coordinates of the workpiece stage 130, reducing the requirement for engineers to manually adjust the positions and minimizing the interference of human factors on the accuracy of the equipment. When the positions drift due to long-term operation of the equipment, it can also automatically and quickly correct the positions, improving the stability and accuracy of the lithography equipment.

[0111] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A calibration method, characterized in that, include: Obtain the first correction value of the test wafer at the pre-alignment station based on the pre-alignment coordinate system; Obtain the second correction value of the test wafer at the workpiece stage station based on the workpiece stage coordinate system; Based on the first correction value and the second correction value, the robot correction values ​​of the robot at the pre-alignment station and the workpiece table station are obtained according to the robot coordinate system. The position setting value of the robot arm is adjusted according to the robot arm correction value.

2. The calibration method according to claim 1, characterized in that, The step of obtaining the robot correction values ​​based on the robot coordinate system at the pre-alignment station and the workpiece table station according to the first correction value and the second correction value includes: The first correction value is converted into a third correction value of the robot at the pre-alignment station based on the robot coordinate system; The second and third correction values ​​are converted into a fourth correction value for the robot at the workpiece station based on the robot's coordinate system.

3. The calibration method according to claim 2, characterized in that, The conversion formula for converting the first correction value to the third correction value includes: in, The first correction value, The third correction value, Let be the first rotation matrix of the pre-aligned coordinate system relative to the robot's coordinate system.

4. The calibration method according to claim 2, characterized in that, The conversion formula for converting the second and third correction values ​​to the fourth correction value includes: in, The second correction value, The third correction value, The fourth correction value, Let be the second rotation matrix of the workpiece stage coordinate system relative to the robot arm coordinate system. This is the third rotation matrix corresponding to the angle at which the robot arm rotates the test wafer as it moves from the pre-alignment station to the workpiece stage station.

5. The calibration method according to claim 1, characterized in that, The step of obtaining the second correction value of the test wafer based on the workpiece stage coordinate system at the workpiece stage station includes: Obtain the center coordinates of the test wafer; Obtain the coordinates of the rotation center of the workpiece stage; The second correction value is obtained based on the difference between the coordinates of the rotation center and the coordinates of the circle center.

6. The calibration method according to claim 5, characterized in that, The step of obtaining the rotation center coordinates of the workpiece stage includes: The workpiece stage is rotated to the positive limit position, and multiple alignment marks on the test wafer are aligned respectively. The first plane coordinates of the workpiece stage corresponding to each alignment mark when aligned are recorded. Rotate the workpiece stage to the negative limit position, align the plurality of alignment marks respectively, and record the second plane coordinates of the workpiece stage corresponding to each alignment mark when it is aligned; Obtain the normal to the line connecting the first plane coordinate and the second plane coordinate corresponding to the same alignment mark, wherein the plurality of alignment marks correspond to the plurality of normals; The coordinates of the rotation center are obtained from the intersection points between the multiple normals.

7. The calibration method according to claim 1, characterized in that, The calibration method further includes: Obtain the first rotation angle of the test wafer at the workpiece stage station; The angle correction value of the test wafer at the pre-alignment station is obtained based on the first rotation angle; The pre-alignment station corrects the wafer's angle according to the angle correction value.

8. The calibration method according to claim 7, characterized in that, The calibration method further includes: Determine whether the calibration correction value is less than a preset value, wherein the calibration correction value includes the robot arm correction value and the angle correction value; If the calibration correction value is greater than or equal to the preset value, then the first correction value, the second correction value, and the calibration correction value are obtained again, and the point setting value and the correction angle are corrected according to the calibration correction value.

9. The calibration method according to claim 1, characterized in that, The calibration method further includes: The wafer under test is exposed according to the exposure center setting value to obtain the exposure area; The actual exposure center coordinates are calculated based on the arrangement of the off-axis marks in the exposure area; The exposure center correction value is obtained by subtracting the rotation center coordinates of the workpiece stage from the actual exposure center coordinates. The exposure center setting value is adjusted according to the exposure center correction value.

10. A calibration system, characterized in that, The calibration system is calibrated using the calibration method described in any one of claims 1-9.

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