Overlay error compensation method

Abstract

The present disclosure provides an overlay error compensation method, device and electronic device. The overlay error compensation method includes: obtaining the first coordinate of the first overlay mark of the target wafer in the current layer and the second coordinate in the previous layer; obtaining the measured overlay error corresponding to the first overlay mark according to the first coordinate and the second coordinate; determining the estimated overlay error of the second overlay mark according to the measured overlay errors of multiple first overlay marks, wherein the second overlay mark is located between multiple first overlay marks; determining the overlay error compensation value of the target wafer in the next layer according to the estimated overlay errors of multiple second overlay marks and the measured overlay errors of multiple first overlay marks. The embodiments of the present disclosure can improve wafer manufacturing efficiency.

Description

Technical Field

[0001] The present disclosure relates to the field of integrated circuit manufacturing, and in particular to an overlay error compensation method. Background Art

[0002] Overlay error compensation is a positioning method used to correct the processing position during wafer processing.

[0003] Overlay error refers to the position offset between the current processing layer of the wafer (referred to as the current layer) and the previous processing layer (referred to as the front layer), which is determined based on the overlay marks set at the same relative position on each layer. Different processing layers of the wafer are provided with overlay marks with the same relative position in the corresponding layer, and each layer has multiple overlay marks. After completing the processing of one layer (the current layer), by calculating the position deviation between a certain overlay mark of the current layer and the overlay mark of the front layer, that is, the overlay error of the overlay mark, the processing positioning can be corrected so that the overlay mark of the next layer can be more aligned with the overlay mark of the front layer during processing, thereby aligning the layers of the wafer. In order to improve the correction accuracy, the manufacturing positioning of the next layer is usually determined by the overlay error of all overlay marks set on the wafer. This process is called overlay error compensation.

[0004] In related technologies, after processing each layer, the position of each overlay mark is typically measured, and the overlay error of each mark in that layer is calculated. Due to the large number of overlay marks and the large number of wafer layers processed, the overlay error compensation process has a significant impact on wafer processing efficiency.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0006] The purpose of the present disclosure is to provide an overlay error compensation method for reducing the duration of the overlay error compensation process and improving wafer processing efficiency.

[0007] According to a first aspect of an embodiment of the present disclosure, a method for compensating for overlay errors is provided, including: obtaining a first coordinate of a first overlay mark of a target wafer in a current layer and a second coordinate of a first overlay mark in a previous layer; obtaining a measured overlay error corresponding to the first overlay mark according to the first coordinate and the second coordinate; determining an estimated overlay error of a second overlay mark according to the measured overlay errors of a plurality of the first overlay marks, the second overlay mark being located between a plurality of the first overlay marks; and determining an overlay error compensation value of the target wafer in a next layer according to the estimated overlay errors of a plurality of second overlay marks and the measured overlay errors of a plurality of the first overlay marks.

[0008] In an exemplary embodiment of the present disclosure, the measured overlay error includes a first direction value and a second direction value, the estimated overlay error includes the first direction value and the second direction value, and determining the estimated overlay error of a second overlay mark based on the measured overlay errors of the plurality of first overlay marks includes:

[0009] determining a plurality of target first overlay marks corresponding to one of the second overlay marks, wherein the plurality of target first overlay marks surround the second overlay mark;

[0010] Substituting the first direction value and the second direction value of the measured overlay error of the plurality of target first overlay marks into a preset model to obtain the first direction value and the second direction value of the estimated overlay error of the second overlay mark;

[0011] The preset model is trained based on the measured overlay errors of the plurality of first overlay marks and the measured overlay errors of the second overlay marks in the process history data.

[0012] In an exemplary embodiment of the present disclosure, the training process of the preset model includes:

[0013] Establishing a first direction value association equation and a second direction value association equation between each second overlay mark and its corresponding plurality of target first overlay marks, wherein the first direction value association equation includes a first calculation coefficient matrix between the first direction value of the second overlay mark and the plurality of first direction values ​​of the plurality of target first overlay marks, and the second direction value association equation includes a second calculation coefficient matrix between the second direction value of the second overlay mark and the plurality of second direction values ​​of the plurality of target first overlay marks;

[0014] Acquire process history data corresponding to historically processed wafers, and determine, in the process history data, measured overlay errors corresponding to a plurality of the first overlay marks and measured overlay errors corresponding to a plurality of the second overlay marks;

[0015] According to the process history data, numerically filling the first direction value association equation and the second direction value association equation of each second overlay mark to determine the first calculation coefficient matrix and the second calculation coefficient matrix;

[0016] The first direction value association equation and the second direction value association equation are fixed according to the first calculation coefficient matrix and the second calculation coefficient matrix determined after the training is completed.

[0017] In an exemplary embodiment of the present disclosure, numerically filling in the first direction value association equation and the second direction value association equation of each second overlay mark based on the process history data to determine the first calculation coefficient matrix and the second calculation coefficient matrix includes: determining the first calculation coefficient matrix and the second calculation coefficient matrix according to a fitting method.

[0018] In an exemplary embodiment of the present disclosure, bringing the first direction value and the second direction value of the measured overlay errors of the plurality of first overlay marks into a preset model includes:

[0019] Performing an N-order Zernike expansion on the first direction values ​​of the plurality of target first set engraved marks to obtain N Zernike coefficients of the first direction values ​​of the plurality of target first set engraved marks;

[0020] Substituting N Zernike coefficients of the first direction values ​​of the plurality of target first overlay marks into the preset model to obtain N Zernike coefficients of the first direction values ​​of the second overlay marks;

[0021] Substituting the N Zernike coefficients of the first direction value of the second set of engraved marks into a Zernike expansion formula to obtain the first direction value of the second set of engraved marks;

[0022] Performing an N-order Zernike expansion on the second direction values ​​of the plurality of target first set engraved marks to obtain N Zernike coefficients of the second direction values ​​of the plurality of target first set engraved marks;

[0023] Substituting N Zernike coefficients of the second direction values ​​of the plurality of target first overlay marks into the preset model to obtain N Zernike coefficients of the second direction values ​​of the second overlay marks;

[0024] The N Zernike coefficients of the second direction value of the second overlay mark are substituted into a Zernike expansion formula to obtain the first direction value of the second overlay mark.

[0025] In an exemplary embodiment of the present disclosure, performing an N-order Zernike expansion on the first direction values ​​of the plurality of target first overlay marks includes: expressing the first direction values ​​of the plurality of target first overlay marks as a sum of N-order Zernike terms, where each Zernike term includes a Zernike coefficient of a corresponding order, an angle value, and a radian value of the first direction value;

[0026] The performing an N-order Zernike expansion on the second direction values ​​of the multiple target first set marks includes: expressing the second direction values ​​of the multiple target first set marks as the sum of N-order Zernike terms, each order Zernike term includes a Zernike coefficient of a corresponding order, an angle value, and a radian value of the second direction value.

[0027] In an exemplary embodiment of the present disclosure, the training process of the preset model includes:

[0028] Acquire process history data corresponding to historically processed wafers, and determine, in the process history data, measured overlay errors corresponding to a plurality of the first overlay marks and measured overlay errors corresponding to a plurality of the second overlay marks;

[0029] Determining a first direction value and a second direction value of each of the measured overlay errors, as well as an angular value and a radian value of the first direction value, and an angular value and a radian value of the second direction value;

[0030] performing an N-order Zernike expansion on the first direction value according to each first direction value and the angle value and the radian value of the first direction value to obtain N Zernike coefficients of the first direction value;

[0031] performing an N-order Zernike expansion on the second direction value according to each second direction value and the angle value and the radian value of the second direction value to obtain N Zernike coefficients of the second direction value;

[0032] Establishing a first conversion equation between N Zernike coefficients of the first direction value of the measured overlay error of the second overlay mark and N Zernike coefficients of the first direction value of the measured overlay error of multiple target first overlay marks corresponding to the second overlay mark, and training the first conversion equation based on the multiple measured overlay errors corresponding to the second overlay mark and the multiple measured overlay errors of the multiple target first overlay marks corresponding to the second overlay mark in the process history data to determine coefficients of the first conversion equation;

[0033] Establishing a second conversion equation between N Zernike coefficients of the second direction value of the measured overlay error of the second overlay mark and N Zernike coefficients of the second direction value of the measured overlay error of multiple target first overlay marks corresponding to the second overlay mark, and training the second conversion equation based on the multiple measured overlay errors corresponding to the second overlay mark and the multiple measured overlay errors of the multiple target first overlay marks corresponding to the second overlay mark in the process history data to determine the coefficients of the second conversion equation;

[0034] According to the above two steps, the first conversion equation and the second conversion equation corresponding to each second overlay mark are determined.

[0035] In an exemplary embodiment of the present disclosure, determining the coefficients of the first conversion equation includes: determining the coefficients of the first conversion equation by fitting; and determining the coefficients of the second conversion equation includes: determining the coefficients of the second conversion equation by fitting.

[0036] In an exemplary embodiment of the present disclosure, determining the estimated overlay error of the second overlay mark based on the measured overlay errors of the plurality of first overlay marks includes:

[0037] An estimated overlay error of the second overlay mark is determined according to M target first overlay marks closest to the second overlay mark, with no other overlay marks between each target first overlay mark and the second overlay mark.

[0038] In an exemplary embodiment of the present disclosure, the target wafer includes a plurality of overlay marks arranged in an array, and the plurality of overlay marks arranged in an array include a plurality of the first overlay marks and a plurality of the second overlay marks, M=8, and the target first overlay mark of one second overlay mark and the second overlay mark are respectively located in adjacent rows or adjacent columns.

[0039] In an exemplary embodiment of the present disclosure, the target wafer includes a plurality of overlay marks arranged in an array, and the plurality of overlay marks arranged in an array include a plurality of the first overlay marks and a plurality of the second overlay marks, M=4, and the target first overlay mark and the second overlay mark of one second overlay mark are respectively located in the same row or the same column.

[0040] The disclosed embodiment calculates the estimated overlay error of the second overlay mark by using the measured overlay error of the first overlay mark located around the second overlay mark. By measuring only a small amount of overlay error, the entire overlay error of the target wafer in the current layer can be obtained, and then the overlay error compensation value of the target wafer in the next layer can be determined, thereby improving the efficiency of overlay error compensation in each layer and thereby improving wafer manufacturing efficiency.

[0041] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0043] Figure 1 is a flow chart of an overlay error compensation method in an exemplary embodiment of the present disclosure.

[0044] Figure 2 Schematic diagram of an overlay mark in a target wafer according to one embodiment of the present disclosure.

[0045] Figure 3A and Figure 3B Schematic diagram of the measured overlay error in the embodiment of the present disclosure.

[0046] Figure 4A and Figure 4B Schematic diagrams of the first set of engraved marks and the second set of engraved marks in two embodiments of the present disclosure.

[0047] Figure 5 It is a sub-flowchart of step S3 in one embodiment of the present disclosure.

[0048] Figure 6 It is a sub-flowchart of step S32 in one embodiment of the present disclosure. DETAILED DESCRIPTION

[0049] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present disclosure will be more comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or that other methods, components, devices, steps, etc. may be employed. In other cases, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0050] The accompanying drawings are merely schematic illustrations of the present disclosure. Identical reference numerals in the drawings denote identical or similar components, and thus their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities that do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0051] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0052] Figure 1 is a flow chart of an overlay error compensation method in an exemplary embodiment of the present disclosure.

[0053] refer to Figure 1 , the overlay error compensation method 100 may include:

[0054] Step S1, obtaining the first coordinate of the first set mark of the target wafer in the current layer and the second coordinate of the previous layer;

[0055] Step S2, obtaining a measured overlay error corresponding to the first overlay mark according to the first coordinate and the second coordinate;

[0056] Step S3, determining an estimated overlay error of a second overlay mark based on the measured overlay errors of the plurality of first overlay marks, where the second overlay mark is located between the plurality of first overlay marks;

[0057] Step S4 , determining an overlay error compensation value of the target wafer in the next layer according to the estimated overlay errors of the plurality of second overlay marks and the measured overlay errors of the plurality of first overlay marks.

[0058] The disclosed embodiment calculates the estimated overlay error of the second overlay mark by using the measured overlay error of the first overlay mark located around the second overlay mark. By measuring only a small amount of overlay error, the entire overlay error of the target wafer in the current layer can be obtained, and then the overlay error compensation value of the target wafer in the next layer can be determined, thereby improving the efficiency of overlay error compensation in each layer and thereby improving wafer manufacturing efficiency.

[0059] Next, each step of the overlay error compensation method 100 is described in detail.

[0060] In step S1 , a first coordinate of a first overlay mark of a target wafer in a current layer and a second coordinate of a first overlay mark in a previous layer are obtained.

[0061] Figure 2 Schematic diagram of an overlay mark in a target wafer according to one embodiment of the present disclosure.

[0062] refer to Figure 2 , in the target wafer 100, there are multiple overlay marks 1. Figure 2 In the embodiment shown, a plurality of overlay marks 1 are arranged in an array and set on a dicing lane (DL) in a wafer for position calibration during wafer processing. In the embodiment disclosed herein, the plurality of overlay marks 1 are composed of a first overlay mark (not shown) for actually measuring the overlay error. Figure 2 ) and a second overlay mark (not shown) for estimating overlay error Figure 2 shown) composition.

[0063] Figure 2 The left side is a top view of the target wafer 100. Figure 2 The right side is a side view of the target wafer 100. For an overlay mark 1, it has a first coordinate A on the current layer 10 and a second coordinate B on the previous layer 20. The first coordinate A and the second coordinate B are positioned based on the same reference coordinate system XOY.

[0064] At the same time, the relative position coordinates of the first coordinate A on the current layer 10 and the relative position coordinates of the second coordinate B on the front layer 20 are exactly the same. Therefore, by calculating the deviation between the first coordinate A and the second coordinate B, the deviation of the absolute positions of the current layer 10 and the front layer 20 in the same reference coordinate system XOY can be calculated.

[0065] In some embodiments, the reference coordinate system XOY can be represented by a first direction (X-axis direction) and a second direction (Y-axis direction). At the same time, the first coordinate A or the second coordinate B of the overlay mark 1 can be represented by the first direction value and the second direction value of the overlay mark 1 in the reference coordinate system XOY. For example, the first coordinate A is A(X1, Y1), and the second coordinate B is B(X2, Y2), where X1 and Y1 are respectively the first direction value and the second direction value of the overlay mark 1 measured in the current layer 10 based on the reference coordinate system XOY, and X2 and Y2 are respectively the first direction value and the second direction value of the overlay mark 1 measured in the previous layer 20 based on the reference coordinate system XOY. The above-mentioned first coordinate A and second coordinate B are both absolute values ​​based on the reference coordinate system XOY.

[0066] In step S2, a measured overlay error corresponding to the first overlay mark is obtained according to the first coordinate and the second coordinate.

[0067] Figure 3A and Figure 3B Schematic diagram of the measured overlay error in the embodiment of the present disclosure.

[0068] refer to Figure 3A The measured overlay error OVL1 of each overlay mark 1 can be obtained by subtracting the first coordinate A of the overlay mark 1 in the current layer 10 from the second coordinate B of the previous layer 20. Therefore, the measured overlay error OVL1 is a vector with direction and length.

[0069] like Figure 3A As shown, the first coordinate A is A(X1, Y1), the second coordinate B is B(X2, Y2), and the measured overlay error OVL1 is obtained according to AB, that is, OLV1 = (X1-X2, Y1-Y2).

[0070] For ease of expression, the measured overlay error OVL1 is expressed as OVL1(Xt, Yt), where Xt = X1-X2 and Yt = Y1-Y2. That is, the measured overlay error OVL1 can be expressed by a first direction value and a second direction value. The first direction value of the measured overlay error OVL1 is Xt, and the second direction value is Yt.

[0071] refer to Figure 3B , in computer graphics, this can be achieved by Figure 3BThe vector 31 shown in FIG. 31 represents the measured overlay error in the target wafer. The length of the vector 31 corresponding to the measured overlay error OVL1 can be determined based on the The smaller the measured overlay error, the smaller the absolute position deviation between the current layer and the previous layer, and the more accurate the processing positioning. The larger the measured overlay error, the larger the absolute position deviation between the current layer and the previous layer, and the larger the processing positioning, requiring timely adjustment to improve wafer yield.

[0072] In practical applications, different vectors 31 can be marked with different colors according to the length of the vector 31. For example, a vector 31 with a length greater than the first preset length is marked in red to indicate that the offset of the layer at the position corresponding to the overlay mark is large; a vector 31 with a length between the first preset length and the second preset length is marked in orange to indicate that the degree of offset of the layer at the position corresponding to the overlay mark should be paid attention to; a vector 31 with a length less than the second preset length is marked in green to indicate that the offset of the layer at the position corresponding to the overlay mark is small.

[0073] Due to the different effects of processing technology at different locations, the length and direction of the measured overlay error between overlay marks at different locations on the same wafer are correlated and mutually influenced, but not necessarily the same. The farther the distance between overlay marks, the greater the difference in length and direction of the measured overlay error. Figure 3B Therefore, it is necessary to actually measure the overlay errors of the overlay marks located in different areas of the wafer to comprehensively determine the offset direction and offset value for the processing position calibration of the next layer, that is, the overlay error compensation value.

[0074] In step S3, an estimated overlay error of a second overlay mark is determined based on the measured overlay errors of the plurality of first overlay marks, where the second overlay mark is located between the plurality of first overlay marks.

[0075] Figure 4A and Figure 4B Schematic diagrams of the first set of engraved marks and the second set of engraved marks in two embodiments of the present disclosure.

[0076] refer to Figure 4A and Figure 4B In the embodiment of the present disclosure, the first set of engraved marks 41 is used for actual detection, and the second set of engraved marks 42 is used for estimation. The number of the first set of engraved marks 41 can be less than the number of the second set of engraved marks 42, or can be equal to the number of the second set of engraved marks 42, or can be greater than the number of the second set of engraved marks 42, depending on the setting method.

[0077] In one embodiment of the present disclosure, the first overlay mark 41 used to calculate the overlay error of the second overlay mark 42 is called the target first overlay mark of the second overlay mark 42. One second overlay mark 42 corresponds to multiple target first overlay marks. The multiple target first overlay marks should surround or semi-surround the second overlay mark to improve the accuracy of calculating the overlay error of the second overlay mark through numerical feedback from multiple angles.

[0078] In one embodiment, the M first overlay marks closest to the second overlay mark 42 can be set as the M target first overlay marks of the second overlay mark 42, and there is no other overlay mark between each target first overlay mark and the second overlay mark, such as Figure 4A and Figure 4B shown.

[0079] exist Figure 4A and Figure 4B In the illustrated embodiment, a plurality of overlay marks 1 are arranged in an array, that is, the plurality of overlay marks are arranged in multiple rows and columns, and the intersection of a row and a column is an overlay mark.

[0080] exist Figure 4A In the illustrated embodiment, M can be set to 8, meaning that the target first overlay mark 410 for a second overlay mark 42 is located in adjacent rows or columns with the second overlay mark 42. This calculation method uses the measured overlay errors from multiple angles to calculate the overlay error of the second overlay mark 42, resulting in a more accurate calculation. However, this method requires setting more first overlay marks 41 and performing actual measurements on each of the first overlay marks 41.

[0081] exist Figure 4B In the illustrated embodiment, M can be set to 4, meaning that the target first overlay mark 410 for a second overlay mark 42 is located in the same row or column as the second overlay mark 42. In this calculation method, only a small amount of overlay error is used to calculate the overlay error of the second overlay mark 42. This method reduces the number of first overlay marks 41 set and the number of measured overlay marks, resulting in higher efficiency. It also allows for the calculation of the overlay error of the second overlay mark 42 from different directions.

[0082] In practical applications, the multiple overlay marks 1 can also be arranged in other ways, for example, based on the actual circuitry of each chip on the wafer, to positions that do not affect chip operation. This disclosure does not limit the arrangement of the overlay marks 1. However, regardless of how the multiple overlay marks 1 are arranged, the multiple target first overlay marks 410 used to calculate the second overlay mark 42 must all belong to the first overlay mark 41 used for actual detection, and must all be located at two or more different positions around the second overlay mark 42 to provide a calculation basis for multiple angles.

[0083] In some embodiments, the plurality of target first overlay marks 410 completely surround the second overlay mark 42. That is, a line connecting two adjacent target first overlay marks 410 in the plurality of target first overlay marks 410 forms a closed figure, and the second overlay mark 42 is located within the closed figure. The closed figure can be a circle, a triangle, a quadrilateral, a polygon, an irregular figure, etc. Those skilled in the art can determine the target first overlay mark 410 corresponding to each second overlay mark 42 based on the actual arrangement of the overlay marks 1.

[0084] Different second overlay marks 42 may have the same target first overlay mark 410. The collection of all target first overlay marks 410 corresponding to all second overlay marks 42 can be recorded as the collection of first overlay marks 41, and the overlay marks in this collection can be measured. Furthermore, other important overlay marks that must be measured but are not involved in calculating the overlay error of the second overlay marks 42 can be added to the collection of first overlay marks 41. In this case, the resulting collection of first overlay marks 41 is larger than the collection of all target first overlay marks 410 corresponding to all second overlay marks 42.

[0085] In one embodiment of the present disclosure, a calculation model (preset model) can be pre-trained based on the wafer manufacturing history data corresponding to the current production line to determine the numerical correlation between the overlay error of the second overlay mark 42 and the overlay errors of multiple target first overlay marks 410. Subsequently, the overlay errors of multiple target first overlay marks 410 can be directly input into the preset model to obtain the calculated value of the second overlay mark 42, that is, the estimated overlay error of the second overlay mark 42.

[0086] Figure 5 It is a sub-flowchart of step S3 in one embodiment of the present disclosure.

[0087] refer to Figure 5 In one embodiment, step S3 may include:

[0088] Step S31, determining a plurality of target first set engraved marks corresponding to a second set engraved mark, wherein the plurality of target first set engraved marks surround the second set engraved mark;

[0089] Step S32, bringing the first direction value and the second direction value of the measured overlay error of the plurality of target first overlay marks into a preset model to obtain the first direction value and the second direction value of the estimated overlay error of the second overlay mark;

[0090] The preset model is trained based on a plurality of measured overlay errors of the first set of engraved marks and a plurality of measured overlay errors of the second set of engraved marks in the process history data.

[0091] In one embodiment, the first direction value and the second direction value of the estimated overlay error can be directly calculated using the first direction value and the second direction value of the measured overlay error. At this time, the training process of the preset model can include first establishing a first direction value association equation and a second direction value association equation for each second overlay mark and its corresponding multiple target first overlay marks.

[0092] The first direction value association equation can be expressed as:

[0093] Xt2=F1(XtA0,XtA1,...XtAM) (1)

[0094] Wherein, Xt2 is the first direction value of the second set of engraved marks 42 , XtAi (1≤i≤M) is the first direction value of the i-th target first set of engraved marks of the second set of engraved marks 42 , and the second set of engraved marks 42 has a total of M target first set of engraved marks.

[0095] As shown in formula (1), the first direction value association equation F1 includes a first calculation coefficient matrix between the first direction value of the second overlay mark and the plurality of first direction values ​​of the plurality of target first overlay marks.

[0096] The second direction value association equation can be expressed as:

[0097] Yt2=F2(YtA0, YtA1,...YtAM) (2)

[0098] Yt2 is the second direction value of the second set of engraved marks 42 , and YtAi (1≤i≤M) is the second direction value of the i-th target first set of engraved marks of the second set of engraved marks 42 . The second set of engraved marks 42 has a total of M target first set of engraved marks.

[0099] As shown in formula (2), the second direction value association equation F2 includes a second calculation coefficient matrix between the second direction value of the second overlay mark and the plurality of second direction values ​​of the plurality of target first overlay marks.

[0100] After establishing the first direction value association formula F1 and the second direction value association formula F2, the process history data corresponding to the historically processed wafer can be obtained, and the measured overlay errors corresponding to the multiple first overlay marks and the measured overlay errors corresponding to the multiple second overlay marks can be determined in the process history data. Next, according to the process history data, the first direction value association equation and the second direction value association equation of each second overlay mark are numerically filled to determine the first calculation coefficient matrix and the second calculation coefficient matrix. Finally, the first direction value association equation and the second direction value association equation are fixed according to the first calculation coefficient matrix and the second calculation coefficient matrix determined after the training is completed. In one embodiment, the first calculation coefficient matrix and the second calculation coefficient matrix can be determined according to the numerical fitting method.

[0101] In another embodiment, the measured overlay error may first be transformed and expanded to obtain the expanded coefficients of the measured overlay error corresponding to the layer. The expanded result of the estimated overlay error after the coordinate transformation is then determined based on the coefficients. A further coordinate transformation is then performed to obtain the estimated overlay error. Calculating the estimated overlay error using the expanded coefficients achieves higher accuracy than directly calculating the estimated overlay error based on numerical fitting.

[0102] Figure 6 It is a sub-flowchart of step S32 in one embodiment of the present disclosure.

[0103] refer to Figure 6 In one embodiment, step S32 may include:

[0104] Step S321, performing an N-order Zernike expansion on the first direction values ​​of the first set of target engraved marks to obtain N Zernike coefficients of the first direction values ​​of the first set of target engraved marks;

[0105] Step S322, bringing the N Zernike coefficients of the first direction values ​​of the plurality of target first set engraved marks into a preset model to obtain the N Zernike coefficients of the first direction values ​​of the second set engraved marks;

[0106] Step S323, substituting the N Zernike coefficients of the first direction values ​​of the second set of engraved marks into the Zernike expansion formula to obtain the first direction values ​​of the second set of engraved marks;

[0107] Step S324, performing an N-order Zernike expansion on the second direction values ​​of the plurality of target first set engraved marks to obtain N Zernike coefficients of the second direction values ​​of the plurality of target first set engraved marks;

[0108] Step S325 , bringing the N Zernike coefficients of the second direction values ​​of the first set of target engraved marks into a preset model to obtain the N Zernike coefficients of the second direction values ​​of the second set of engraved marks;

[0109] Step S326 , substituting the N Zernike coefficients of the second direction value of the second set of engraved marks into the Zernike expansion formula to obtain the first direction value of the second set of engraved marks.

[0110] In which, in step S321, the first direction values ​​of the first set marks of the multiple targets can be expressed as the sum of N-order Zernike terms, and each order Zernike term includes a Zernike coefficient of a corresponding order, an angle value and a radian value of the first direction value; in step S324, the second direction values ​​of the first set marks of the multiple targets can be expressed as the sum of N-order Zernike terms, and each order Zernike term includes a Zernike coefficient of a corresponding order, an angle value and a radian value of the second direction value.

[0111] exist Figure 6 In the illustrated embodiment, the training process of the preset model includes: first, obtaining process history data corresponding to historically processed wafers, and determining the measured overlay errors corresponding to multiple first overlay marks and the measured overlay errors corresponding to multiple second overlay marks in the process history data; then, determining the first direction value and the second direction value of each measured overlay error, as well as the angle value and radian value of the first direction value, and the angle value and radian value of the second direction value; next, performing an N-order Zernike expansion on the first direction value according to each first direction value and the angle value and radian value of the first direction value to obtain N Zernike coefficients of the first direction value, and performing an N-order Zernike expansion on the second direction value according to each second direction value and the angle value and radian value of the second direction value to obtain N Zernike coefficients of the second direction value.

[0112] The Zernike expansion of a first direction value Xt can be expressed as:

[0113] Xt=

[0114] (X_Z1)+

[0115] (X_Z2*2ρcos(θ))+

[0116] (X_Z3*2ρsin(θ))+

[0117] (X_Z4*sqrt(3)*(2ρ 2 -1))+

[0118] (X_Z5*sqrt(6)*ρ 2 sin(2θ))+

[0119] (X_Z6*sqrt(6)*ρ 2 cos(2θ))+

[0120] (X_Z7*sqrt(8)*(3ρ 3 -2ρ)*sin(θ))+

[0121] (X_Z8*sqrt(8)*(3ρ 3 -2ρ)*cos(θ))+

[0122] (X_Z9*sqrt(8)*ρ 3 sin(3θ))+

[0123] (X_Z10*sqrt(8)*ρ 3 cos(3θ))+

[0124] (X_Z11*sqrt(5)*(6ρ 4 -6p 2 +1))+

[0125] (X_Z12*sqrt(10)*(4ρ 4 -3p 2 )*cos(2θ))+

[0126] (X_Z13*sqrt(10)*(4ρ 4 -3p 2 )*sin(2θ))+

[0127] (X_Z14*sqrt(10)*ρ 4 cos(4θ))+

[0128] (X_Z15*sqrt(10)*ρ 4 sin(4θ))+

[0129] (X_Z16*sqrt(12)*(10p 5 -12p 3 +3ρ)*cos(θ))+

[0130] (X_Z17*sqrt(12)*(10p 5 -12p 3 +3ρ)*sin(θ))+

[0131] (X_Z18*sqrt(12)*(5ρ 5 -4p 3 )*cos(3θ))+

[0132] (X_Z19*sqrt(12)*(5ρ 5 -4p 3 )*sin(3θ))+

[0133] (X_Z20*sqrt(12)*ρ 5 cos(5θ))+

[0134] (X_Z21*sqrt(12)*ρ 5 sin(5θ)) ……(3)

[0135] Formula (3) illustrates performing a 21-order expansion on the first direction value, that is, setting N=21.

[0136] Where X_Zi (1≤i≤21) is the coefficient of the i-th order Zernike term, ρ is the radian value of the first direction value Xt after transforming from the Cartesian coordinate system to the polar coordinate system, and θ is the angle value of the first direction value Xt after transforming from the Cartesian coordinate system to the polar coordinate system. Any Xt can be expressed as

[0137] By substituting the first direction value Xt of each measured overlay error into formula (3), the expansion formula of the first direction value of each measured overlay error is determined, and the coefficient of each order Zernike term corresponding to the first direction value of each measured overlay error is obtained. Through a large number of numerical fittings, the correlation between the coefficient of each order Zernike term of the first direction value of a measured overlay error and the coefficient of each order Zernike term of the first direction values ​​of its corresponding multiple target first overlay errors under the current processing environment can be obtained. Subsequently, according to the Zernike term coefficients of the first direction values ​​of multiple target first overlay errors of a second overlay error, the coefficient of each order Zernike term of the first direction value of the second overlay error can be obtained, and then the first direction value of the second overlay error can be obtained.

[0138] Correspondingly, the Zernike expansion of a second direction value Yt can be expressed as:

[0139] Yt=

[0140] (Y_Z1)+

[0141] (Y_Z2*2ρcos(θ))+

[0142] (Y_Z3*2ρsin(θ))+

[0143] (Y_Z4*sqrt(3)*(2ρ 2 -1))+

[0144] (Y_Z5*sqrt(6)*ρ 2 sin(2θ))+

[0145] (Y_Z6*sqrt(6)*ρ 2 cos(2θ))+

[0146] (Y_Z7*sqrt(8)*(3ρ 3 -2ρ)*sin(θ))+

[0147] (Y_Z8*sqrt(8)*(3ρ 3 -2ρ)*cos(θ))+

[0148] (Y_Z9*sqrt(8)*ρ 3 sin(3θ))+

[0149] (Y_Z10*sqrt(8)*ρ 3 cos(3θ))+

[0150] (Y_Z11*sqrt(5)*(6ρ 4 -6p 2 +1))+

[0151] (Y_Z12*sqrt(10)*(4ρ 4 -3p 2 )*cos(2θ))+

[0152] (Y_Z13*sqrt(10)*(4ρ 4 -3p 2 )*sin(2θ))+

[0153] (Y_Z14*sqrt(10)*ρ 4 cos(4θ))+

[0154] (Y_Z15*sqrt(10)*ρ 4 sin(4θ))+

[0155] (Y_Z16*sqrt(12)*(10p 5 -12p 3 +3ρ)*cos(θ))+

[0156] (Y_Z17*sqrt(12)*(10p 5 -12p 3 +3ρ)*sin(θ))+

[0157] (Y_Z18*sqrt(12)*(5ρ 5 -4p 3 )*cos(3θ))+

[0158] (Y_Z19*sqrt(12)*(5ρ 5 -4p 3 )*sin(3θ))+

[0159] (Y_Z20*sqrt(12)*ρ 5 cos(5θ))+

[0160] (Y_Z21*sqrt(12)*ρ 5 sin(5θ))……(4)

[0161] Formula (4) illustrates performing a 21-order expansion on the second direction value, that is, setting N=21.

[0162] Among them, Y_Zi (1≤i≤21) is the coefficient of the i-th order Zernike term, ρ is the radian value of the second direction value Yt after transforming from the Cartesian coordinate system to the polar coordinate system, and θ is the angle value of the second direction value Yt after transforming from the Cartesian coordinate system to the polar coordinate system. Any Yt can be expressed as

[0163] By substituting the second direction value Xt of each measured overlay error into formula (4), the expansion formula of the second direction value of each measured overlay error is determined, and the coefficient of each order Zernike term corresponding to the second direction value of each measured overlay error is obtained. Through a large number of numerical fittings, the correlation relationship between the coefficient of each order Zernike term of the second direction value of a measured overlay error and the coefficient of each order Zernike term of the second direction values ​​of its corresponding multiple target first overlay errors under the current processing environment can be obtained. Subsequently, according to the Zernike term coefficients of the second direction values ​​of multiple target first overlay errors of a second overlay error, the coefficient of each order Zernike term of the second direction value of the second overlay error can be obtained, and then the second direction value of the second overlay error can be obtained.

[0164] Finally, the following two steps are repeated to determine the first conversion equation and the second conversion equation corresponding to each second set of engraved marks:

[0165] Establishing a first conversion equation between N Zernike coefficients of a first direction value of a measured overlay error of a second overlay mark and N Zernike coefficients of a first direction value of a measured overlay error of a plurality of target first overlay marks corresponding to the second overlay mark, and training the first conversion equation based on the plurality of measured overlay errors corresponding to the second overlay mark and the plurality of measured overlay errors of the plurality of target first overlay marks corresponding to the second overlay mark in process history data to determine coefficients of the first conversion equation;

[0166] A second conversion equation is established between N Zernike coefficients of the second direction value of the measured overlay error of the second overlay mark and the N Zernike coefficients of the second direction value of the measured overlay error of multiple target first overlay marks corresponding to the second overlay mark, and the second conversion equation is trained based on the multiple measured overlay errors corresponding to the second overlay mark and the multiple measured overlay errors of the multiple target first overlay marks corresponding to the second overlay mark in the process history data to determine the coefficients of the second conversion equation.

[0167] Wherein, determining the coefficients of the first conversion equation includes: determining the coefficients of the first conversion equation by fitting; and determining the coefficients of the second conversion equation includes: determining the coefficients of the second conversion equation by fitting.

[0168] It's important to note that due to the varying positioning methods and parameter settings of different processes, the aforementioned first and second transformation equations must be retrained and recalculated for wafers of different types and functions, even if the corresponding layers have the same number. Furthermore, different first and second transformation equations can be set for different layers of the same wafer to accommodate the varying processing techniques used for each layer.

[0169] In step S4 , an overlay error compensation value of the target wafer in the next layer is determined according to the estimated overlay errors of the plurality of second overlay marks and the measured overlay errors of the plurality of first overlay marks.

[0170] Since all overlay marks on the target wafer are set to be the measured first overlay marks or the estimated second overlay marks, after completing step S3, the overlay errors corresponding to all overlay marks on all target wafers in the current layer can be obtained. Next, according to the direction and length of the overlay errors of overlay marks at different positions, the positioning adjustment direction and positioning adjustment value when manufacturing the next layer can be determined according to the general overlay error calibration method, so that the next layer is aligned with the current layer as much as possible, thereby improving the process yield.

[0171] Since the wafer manufacturing process involves a large number of layers and a large number of overlay marks, the embodiments of the present disclosure can greatly improve wafer manufacturing efficiency by saving the time of measuring the overlay error of each layer.

[0172] In one embodiment of the present disclosure, Kernel Overlay (KOV), a data analysis software, can be used to simulate and calculate the angle and arc of sample measurement results to determine the overall wafer overlay error. KOV then automatically calculates compensation values ​​and feeds them back to the R2R (Run to Run) system. Compared to traditional compensation methods, KOV's compensation cycle is much shorter and more efficient.

[0173] Based on different process requirements, different orders of models are made for the 300 measured sampling results to obtain the global overlay error. Then, based on the global overlay error, the CPE (Correction Per Exposure, independently compensating each exposure area) model is further calculated to compensate for the R2R system. CPE refers to the use of the measured and calculated global overlay error (including the first overlay error and the second overlay error) to correct each exposure area separately.

[0174] RT model simulation: Using more than 300 sampled measurement results (i.e., the number of first-set marks is greater than 300), the sampled measurement results are calculated, the angle and arc of each first-set mark are analyzed, and the estimated overlay error of the second-set mark near each first-set mark is simulated and calculated, ultimately deriving the global overlay error.

[0175] Next, based on the global overlay error calculated by RT model simulation, KOV's Gridmapper calculation method is used to calculate the W1F1 (Wafer1step Field1step, the first-order processing area of ​​the wafer, that is, the minimum exposure unit of the processing area) model results to obtain the final compensation value required to compensate for CPE.

[0176] A new model is established in KOV to analyze and simulate the overall situation of the measurement results of product sampling, and then the CPE analysis is performed on the simulation results. In summary, the process of the embodiment of the present disclosure is to manufacture the target wafer, then measure the first overlay mark to obtain the measured overlay error, then use KOV CPE to automatically calculate and estimate the overlay error, and finally complete the overlay error compensation and manufacture the next layer of the target wafer through the R2R feedback model. This avoids the need for global measurement of overlay error, saves machine time, improves machine production capacity, and prevents human error.

[0177] It should be noted that although several modules or units of the device for action execution are mentioned in the detailed description above, this division is not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of two or more modules or units described above can be concretized in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided into multiple modules or units to be concretized.

[0178] Furthermore, the above-described figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention and are not intended to be limiting. It is readily understood that the processes illustrated in the above-described figures do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0179] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the claims.

Claims

1. A method for compensating overlay error, characterized in that: include: Obtaining a first coordinate of a first set of engraved marks on a target wafer in a current layer and a second coordinate of a previous layer; Obtaining a measured overlay error corresponding to the first overlay mark according to the first coordinate and the second coordinate; determining an estimated overlay error of a second overlay mark based on the measured overlay errors of the plurality of first overlay marks, the second overlay mark being located between the plurality of first overlay marks; determining an overlay error compensation value of the target wafer in a next layer according to the estimated overlay errors of the plurality of second overlay marks and the measured overlay errors of the plurality of first overlay marks; The measured overlay error includes a first direction value and a second direction value, the estimated overlay error includes a first direction value and a second direction value, and determining the estimated overlay error of the second overlay mark based on the measured overlay errors of the plurality of first overlay marks includes: determining a plurality of target first overlay marks corresponding to one of the second overlay marks, wherein the plurality of target first overlay marks surround the second overlay mark; Substituting the first direction value and the second direction value of the measured overlay error of the plurality of target first overlay marks into a preset model to obtain the first direction value and the second direction value of the estimated overlay error of the second overlay mark; The preset model is trained based on the measured overlay errors of the plurality of first overlay marks and the measured overlay errors of the second overlay marks in the process history data; The training process of the preset model includes: Establishing a first direction value association equation and a second direction value association equation between each second overlay mark and its corresponding plurality of target first overlay marks, wherein the first direction value association equation includes a first calculation coefficient matrix between the first direction value of the second overlay mark and the plurality of first direction values ​​of the plurality of target first overlay marks, and the second direction value association equation includes a second calculation coefficient matrix between the second direction value of the second overlay mark and the plurality of second direction values ​​of the plurality of target first overlay marks; Acquire process history data corresponding to historically processed wafers, and determine, in the process history data, measured overlay errors corresponding to a plurality of the first overlay marks and measured overlay errors corresponding to a plurality of the second overlay marks; According to the process history data, numerically filling the first direction value association equation and the second direction value association equation of each second overlay mark to determine the first calculation coefficient matrix and the second calculation coefficient matrix; The first direction value association equation and the second direction value association equation are fixed according to the first calculation coefficient matrix and the second calculation coefficient matrix determined after the training is completed.

2. The overlay error compensation method according to claim 1, wherein: The step of numerically filling the first direction value association equation and the second direction value association equation of each second overlay mark according to the process history data to determine the first calculation coefficient matrix and the second calculation coefficient matrix includes: determining the first calculation coefficient matrix and the second calculation coefficient matrix according to a fitting method.

3. The overlay error compensation method according to claim 1, wherein: The step of bringing the first direction value and the second direction value of the measured overlay errors of the plurality of first overlay marks into a preset model comprises: Performing an N-order Zernike expansion on the first direction values ​​of the plurality of target first set engraved marks to obtain N Zernike coefficients of the first direction values ​​of the plurality of target first set engraved marks; Substituting N Zernike coefficients of the first direction values ​​of the plurality of target first overlay marks into the preset model to obtain N Zernike coefficients of the first direction values ​​of the second overlay marks; Substituting the N Zernike coefficients of the first direction value of the second set of engraved marks into a Zernike expansion formula to obtain the first direction value of the second set of engraved marks; Performing an N-order Zernike expansion on the second direction values ​​of the plurality of target first set engraved marks to obtain N Zernike coefficients of the second direction values ​​of the plurality of target first set engraved marks; Substituting N Zernike coefficients of the second direction values ​​of the plurality of target first overlay marks into the preset model to obtain N Zernike coefficients of the second direction values ​​of the second overlay marks; The N Zernike coefficients of the second direction value of the second overlay mark are substituted into a Zernike expansion formula to obtain the first direction value of the second overlay mark.

4. The overlay error compensation method according to claim 3, wherein: The performing an N-order Zernike expansion on the first direction values ​​of the plurality of target first overlay marks comprises: expressing the first direction values ​​of the plurality of target first overlay marks as a sum of N-order Zernike terms, where each Zernike term includes a Zernike coefficient of a corresponding order, an angle value, and a radian value of the first direction value; The performing an N-order Zernike expansion on the second direction values ​​of the multiple target first set marks includes: expressing the second direction values ​​of the multiple target first set marks as the sum of N-order Zernike terms, each order Zernike term includes a Zernike coefficient of a corresponding order, an angle value, and a radian value of the second direction value.

5. The overlay error compensation method according to claim 3 or 4, wherein: The training process of the preset model includes: Acquire process history data corresponding to historically processed wafers, and determine, in the process history data, measured overlay errors corresponding to a plurality of the first overlay marks and measured overlay errors corresponding to a plurality of the second overlay marks; Determining a first direction value and a second direction value of each of the measured overlay errors, as well as an angular value and a radian value of the first direction value, and an angular value and a radian value of the second direction value; performing an N-order Zernike expansion on the first direction value according to each first direction value and the angle value and the radian value of the first direction value to obtain N Zernike coefficients of the first direction value; performing an N-order Zernike expansion on the second direction value according to each second direction value and the angle value and the radian value of the second direction value to obtain N Zernike coefficients of the second direction value; Establishing a first conversion equation between N Zernike coefficients of the first direction value of the measured overlay error of the second overlay mark and N Zernike coefficients of the first direction value of the measured overlay error of multiple target first overlay marks corresponding to the second overlay mark, and training the first conversion equation based on the multiple measured overlay errors corresponding to the second overlay mark and the multiple measured overlay errors of the multiple target first overlay marks corresponding to the second overlay mark in the process history data to determine coefficients of the first conversion equation; Establishing a second conversion equation between N Zernike coefficients of the second direction value of the measured overlay error of the second overlay mark and N Zernike coefficients of the second direction value of the measured overlay error of multiple target first overlay marks corresponding to the second overlay mark, and training the second conversion equation based on the multiple measured overlay errors corresponding to the second overlay mark and the multiple measured overlay errors of the multiple target first overlay marks corresponding to the second overlay mark in the process history data to determine the coefficients of the second conversion equation; According to the above two steps, the first conversion equation and the second conversion equation corresponding to each second overlay mark are determined.

6. The overlay error compensation method according to claim 5, wherein: The determining of the coefficients of the first conversion equation includes: determining the coefficients of the first conversion equation by fitting; the determining of the coefficients of the second conversion equation includes: determining the coefficients of the second conversion equation by fitting.

7. The overlay error compensation method according to claim 1, wherein: Determining the estimated overlay error of a second overlay mark according to the measured overlay errors of the plurality of first overlay marks comprises: An estimated overlay error of the second overlay mark is determined according to M target first overlay marks closest to the second overlay mark, with no other overlay marks between each target first overlay mark and the second overlay mark.

8. The overlay error compensation method according to claim 7, wherein: The target wafer includes multiple overlay marks arranged in an array, and the multiple overlay marks arranged in the array include multiple first overlay marks and multiple second overlay marks, M=8, and the target first overlay mark and the second overlay mark of one second overlay mark are respectively located in adjacent rows or adjacent columns.

9. The overlay error compensation method according to claim 7, wherein: The target wafer includes multiple overlay marks arranged in an array, and the multiple overlay marks arranged in the array include multiple first overlay marks and multiple second overlay marks, M=4, and the target first overlay mark and the second overlay mark of one second overlay mark are respectively located in the same row or the same column.

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