Overlay precision error measuring method

Abstract

The invention discloses an overlay precision error measurement method. The method comprises the following steps: step 1, designing a set of 2D OVL identifier group comprising 2D OVL identifiers of a previous layer and a current layer; step 2, establishing an OCD model, which comprises the following steps: step 21, after a current-layer photoetching process is completed on the first wafer, measuring by adopting an OCD measuring method and acquiring first spectral data; step 22, a second OVL measurement method is adopted for measurement, and a first OVL result is obtained; the second OVL measurement method comprises a BSE OVL measurement method. And step 23, using the first OVL result as a reference and carrying out modeling based on the first spectral data to obtain an OCD model. And step 3, after the current-layer photoetching process is completed on the second wafer, performing measurement by adopting an OCD measurement method, obtaining second spectral data, matching the second spectral data with the first spectral data of the OCD model, and obtaining a second OVL result. According to the invention, the OVL measurement of the 2D OVL identification graph can be realized by adopting OCD measurement, and the measurement speed and the measurement accuracy can be improved at the same time.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and in particular to a method for measuring overlay accuracy error (OVL). Background Art

[0002] Overlay error, or OVL (Overlay Visibility) (OVL) measurement, is one of the most important inspection methods in the photolithography process. OVL refers to the alignment requirement between the current layer pattern and the previous layer pattern. Only by ensuring layer-by-layer alignment can the functionality of the previous-stage device be accurately transmitted through the wiring process. Otherwise, the device will not function, resulting in direct yield loss. Most OVL measurement methods are based on optical means, specifically image-based overlay (IBO) and diffraction-based overlay (DBO). However, from the perspective of physical optics, both methods require obtaining high-order diffraction light signals from the measurement mark. The former is used to improve image quality, while the latter directly uses the relative intensity of the + / -1st order light to calculate the OVL. Since the diffraction angle of the high-order diffraction light signal is directly determined by the spatial period of the pattern, the smaller the period, the larger the diffraction angle. Therefore, to collect at least + / -1st order diffraction light, the OVL mark period is approximately 1 to 2 microns. With advancements in integrated circuit manufacturing technology, the critical dimension (CD) of semiconductor devices continues to shrink. The minimum pattern period of key photolithography layers at advanced nodes is even less than 100nm. Traditional OVL measurement cannot be used for OVL mark designs that are comparable in size to device pattern periods. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an overlay accuracy error measurement method, which can realize OVL measurement of 2D OVL logo graphics using optical critical dimension measurement (OCD), thereby improving not only the measurement speed but also the measurement accuracy.

[0004] To solve the above technical problems, the present invention provides a method for measuring overlay accuracy error, comprising the following steps:

[0005] Step 1: Design a set of 2D OVL logo groups, including a front layer 2D OVL logo and a current layer 2D OVL logo.

[0006] Step 2: Establish an OCD model, including:

[0007] Step 21: After completing the current layer photolithography process on the first wafer, use an OCD measurement method to measure the 2D OVL mark group on the first wafer and obtain first spectrum data.

[0008] Step 22: Use a second OVL measurement method to measure the 2D OVL mark group on the first wafer and obtain a first OVL result; the second OVL measurement method includes a BSE OVL measurement method.

[0009] Step 23: Use the first OVL result as a reference and perform modeling based on the first spectral data to obtain the OCD model.

[0010] Step 3: After completing the current layer lithography process on the second wafer, use the OCD measurement method to measure the 2D OVL mark group on the second wafer and obtain second spectral data, match the second spectral data with the first spectral data of the OCD model and obtain a second OVL result.

[0011] A further improvement is that the front layer 2D OVL logo is designed based on the front layer process requirements, and the front layer 2D OVL logo adopts a 2D grating structure.

[0012] The length of each side of the front layer 2D OVL mark is greater than the longest axis of the incident light spot.

[0013] The 2D grating structure of the front layer 2D OVL marker is formed by a two-dimensional arrangement of first block structures; the two-dimensional arrangement of the first block structures is a periodic arrangement or a non-periodic arrangement.

[0014] A further improvement is that the current-layer 2D OVL mark is designed based on the current-layer process requirements, and the current-layer 2D OVL mark adopts a 2D grating structure.

[0015] The length of each side of the 2D OVL mark of the layer is greater than the longest axis of the incident light spot.

[0016] The 2D grating structure of the 2D OVL mark of the current layer is formed by a two-dimensional arrangement of the second block structures; the two-dimensional arrangement of the second block structures is a periodic arrangement or a non-periodic arrangement.

[0017] A further improvement is that the top view structure of the first block structure is circular or square; the first block structure is a raised island structure or a sunken hole structure.

[0018] A further improvement is that the top view structure of the second block structure is circular or square; the second block structure is a raised island structure or a sunken hole structure.

[0019] A further improvement is that, in the current layer lithography process, a placement rule of the current layer 2D OVL mark is to make the center coordinates of the current layer 2D OVL mark coincide with the center coordinates of the previous layer 2D OVL mark.

[0020] A further improvement is that, in the 2D OVL mark group, each of the second block structures has an aligned first block structure.

[0021] Each of the first block-shaped structures has at least one aligned second block-shaped structure.

[0022] A further improvement is that when the two-dimensional arrangement of the first block structure is a periodic arrangement, in the front layer 2D OVL mark, in the X direction, the side length of the first block structure has a first side length value, and the side length and spacing of the first block structure have a first period value.

[0023] In the Y direction, the side length of the first block-shaped structure has a second side length value, and the side length and the spacing of the first block-shaped structure have a second period value.

[0024] A further improvement is that when the two-dimensional arrangement of the second block structures is a periodic arrangement, in the layer 2D OVL mark, in the X direction, the side length of the second block structure has a third side length value, and the side length and spacing of the second block structure have a third period value.

[0025] In the Y direction, the side length of the second block-shaped structure has a fourth side length value, and the side length and the spacing of the second block-shaped structure have a fourth period value.

[0026] A further improvement is that the first side length value is an integer multiple of more than 1 times the third side length value, and the first period value is an integer multiple of more than 1 times the third period value.

[0027] The second side length value is an integer multiple of at least 1 times the fourth side length value, and the second period value is an integer multiple of at least 1 times the fourth period value.

[0028] A further improvement is that the lengths of the sides of the front layer 2D OVL mark are all equal, and the lengths of the sides of the current layer 2D OVL mark are all equal and equal to the lengths of the sides of the front layer 2D OVL mark.

[0029] A further improvement is that the first side length is 1 / 2 of the first period value, and the second side length is 1 / 2 of the second period value.

[0030] The third side length is 1 / 2 of the third period value, and the fourth side length is 1 / 2 of the fourth period value.

[0031] A further improvement is that in step 2, steps 21 to 23 need to be repeated multiple times to obtain multiple sets of the first spectral data and the corresponding first OVL results.

[0032] A further improvement is that, in step 23, a rigorous coupled wave algorithm or a machine learning-based method is used for modeling.

[0033] A further improvement is that the second OVL measurement method also includes an OVL measurement method based on secondary electrons and an OVL measurement method based on TEM slices.

[0034] The overlay accuracy error of the present invention is achieved by combining a set of 2D OVL markers and OCD measurement, and is calibrated using the OVL results of a second OVL measurement method, such as the BSE OVL measurement method, wherein:

[0035] The front-layer 2D OVL mark and the current-layer 2D OVL mark in the 2D OVL mark set can achieve a minimum effective period that is closer to the device pattern period than the minimum effective period of the existing 1D OVL mark. Therefore, the 2D OVL mark set of the present invention is more likely to reflect the actual status of the device, thereby improving the accuracy of OVL measurement.

[0036] The 2D OVL marking group can obtain OVL information in the x and y directions through one pattern and one measurement, thereby saving the pattern area of ​​the OVL marking and the number of OVL measurements, and improving measurement efficiency.

[0037] OCD measurement is performed using an optical method, and the measurement speed is much higher than that of BSE OVL measurement. Therefore, the present invention can improve the measurement speed.

[0038] The present invention employs a second OVL measurement method, such as the BSE OVL measurement method, for calibration. Due to the high accuracy of the second OVL measurement method, it can improve the accuracy of the first OVL result used in modeling. Furthermore, after modeling is complete, it can improve the accuracy of the second OVL result obtained through OCD measurement, ultimately improving the accuracy of OVL measurement.

[0039] Compared to existing OVL measurement methods that combine a 2D OVL marker group and a BSE OVL measurement method, the OCD measurement method of the present invention is faster than BSE OVL measurement, thus improving measurement speed. Furthermore, the OCD measurement modeling of the present invention utilizes the first OVL result obtained by the BSE OVL measurement method for calibration, thus achieving measurement accuracy comparable to that of the BSE OVL measurement method. Therefore, the present invention can utilize OCD measurement to implement OVL measurement of 2D OVL marker patterns, thereby improving both measurement speed and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] Figure 1 is a flow chart of a method for measuring overlay accuracy error according to an embodiment of the present invention;

[0042] Figure 2A 2. It is a schematic structural diagram of a front-layer 2D OVL marker in the overlay accuracy error measurement method according to an embodiment of the present invention;

[0043] Figure 2B This is a structural diagram of a 2D OVL marker in a method for measuring overlay accuracy error according to an embodiment of the present invention;

[0044] Figure 2C 2D OVL mark of the previous layer and the current layer obtained by the BSE OVL measurement method in the overlay accuracy error measurement method according to an embodiment of the present invention;

[0045] Figure 2D The first OVL result is calculated by graphically calculating the front layer 2D OVL mark and the current layer 2D OVL mark obtained by the BSE OVL measurement method in the overlay accuracy error measurement method according to an embodiment of the present invention;

[0046] Figure 3A 2 is a schematic structural diagram of another front-layer 2D OVL marker in the overlay accuracy error measurement method according to an embodiment of the present invention;

[0047] Figure 3B This is a structural diagram of another layer 2D OVL marker in the overlay accuracy error measurement method according to an embodiment of the present invention;

[0048] Figure 3C 2 is a schematic diagram of an overlay accuracy error measurement method according to an embodiment of the present invention when an OCD measurement method is used for measurement;

[0049] Figure 4 It is a flow chart of establishing an OCD model in the overlay accuracy error measurement method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] like Figure 1 FIG. 1 is a flow chart of a method for measuring overlay accuracy error according to an embodiment of the present invention. The method for measuring overlay accuracy error according to an embodiment of the present invention comprises the following steps:

[0051] Step 1: Design a set of 2D OVL logos, including a front layer 2D OVL logo 101 and a current layer 2D OVL logo 103 .

[0052] The embodiment of the present invention, as Figure 2A As shown, the front layer 2D OVL mark 101 is designed based on the front layer process requirements, and the front layer 2D OVL mark 101 adopts a 2D grating structure.

[0053] The length of each side of the front layer 2D OVL mark 101 is greater than the longest axis of the incident light spot 105. Figure 3C . Figure 2A , the side length L1 of the front layer 2D OVL mark 101 in the X direction is shown.

[0054] The 2D grating structure of the front layer 2D OVL mark 101 is composed of a two-dimensional arrangement of first block structures 102; the two-dimensional arrangement of the first block structures 102 is a periodic arrangement. In other embodiments, the two-dimensional arrangement of the first block structures 102 can also be a non-periodic arrangement.

[0055] like Figure 2B As shown, the current layer 2D OVL mark 103 is designed based on the current layer process requirements, and the current layer 2D OVL mark 103 adopts a 2D grating structure.

[0056] The lengths of the sides of the 2D OVL mark 103 are all greater than the longest axis of the incident light spot 105 . Figure 2B , the side length L2 of the current layer 2D OVL mark 103 in the X direction is shown.

[0057] In the embodiment of the present invention, the lengths of the sides of the front layer 2D OVL mark 101 are all equal, and the lengths of the sides of the current layer 2D OVL mark 103 are all equal and equal to the lengths of the sides of the front layer 2D OVL mark 101 .

[0058] The 2D grating structure of the current layer 2D OVL mark 103 is formed by a two-dimensional arrangement of second block structures 104. The two-dimensional arrangement of the second block structures 104 is a periodic arrangement. In other embodiments, the two-dimensional arrangement of the second block structures 104 can also be a non-periodic arrangement.

[0059] In the embodiment of the present invention, Figure 2A As shown, the top view structure of the first block structure 102 is square. In some embodiments, the top view structure of the first block structure 102 can also be circular.

[0060] The first block structure 102 is a raised island structure or a sunken hole structure.

[0061] In the embodiment of the present invention, Figure 2B As shown, the top view structure of the second block structure 104 is circular. In some embodiments, the top view structure of the second block structure 104 can also be square.

[0062] The second block structure 104 is a protruding island structure or a recessed hole structure.

[0063] In the embodiment of the present invention, in the current layer lithography process, the placement rule of the current layer 2D OVL mark 103 is to make the center coordinates of the current layer 2D OVL mark 103 coincide with the center coordinates of the previous layer 2D OVL mark 101 .

[0064] In the embodiment of the present invention, in the 2D OVL marker group, each second block structure 104 has an aligned first block structure 102. Each first block structure 102 has at least one aligned second block structure 104.

[0065] like Figure 2C As shown, there is a one-to-one correspondence between the second block structure 104 and the first block structure 102 .

[0066] like Figure 2A As shown, when the two-dimensional arrangement of the first block structure 102 is a periodic arrangement, in the front layer 2D OVL mark 101, in the X direction, the side length of the first block structure 102 has a first side length value a1, and the side length and spacing of the first block structure 102 have a first period value b1.

[0067] In the Y direction, the side length of the first block-shaped structure 102 has a second side length value c1, and the side length and the interval between the first block-shaped structures 102 have a second period value d1.

[0068] like Figure 2B As shown, when the two-dimensional arrangement of the second block structure 104 is a periodic arrangement, in the layer 2D OVL mark 103, in the X direction, the side length of the second block structure 104 has a third side length value a2, and the side length and spacing of the second block structure 104 have a third period value b2.

[0069] In the Y direction, the side length of the second block-shaped structures 104 has a fourth side length value c2, and the side length and the interval between the second block-shaped structures 104 have a fourth period value d2.

[0070] In some embodiments, the first side length value a1 is 1 / 2 of the first period value b1, and the second side length value c1 is 1 / 2 of the second period value d1. Figure 2A , the first side length value a1 and the second side length value c1 are equal.

[0071] The third side length value a2 is 1 / 2 of the third period value b2, and the fourth side length value c2 is 1 / 2 of the fourth period value d2. Figure 2B , the third side length value a2 and the fourth side length value c2 are equal and are the diameter of the second block structure 104 .

[0072] In the embodiment of the present invention, the first side length value a1 is an integer multiple of at least 1 times the third side length value a2, and the first period value b1 is an integer multiple of at least 1 times the third period value b2. Figure 2A and Figure 2B In a corresponding 2DOVL identification group, the first side length value a1 is equal to the third side length value a2, and the first period value b1 is equal to the third period value b2.

[0073] The second side length value c1 is an integer multiple of at least 1 times the fourth side length value c2, and the second period value d1 is an integer multiple of at least 1 times the fourth period value d2. Figure 2A and Figure 2B In a corresponding 2D OVL marker group, the second side length value c1 is equal to the fourth side length value c2, and the second period value d1 is equal to the fourth period value d2.

[0074] The following further describes the 2D OVL identification group in the embodiment of the present invention with reference to specific numerical values:

[0075] like Figure 3A , which is a structural schematic diagram of another front-layer 2D OVL marker in the overlay accuracy error measurement method according to an embodiment of the present invention; Figure 3A The front layer process corresponding to the front layer 2D OVL mark 101a is a gate layer, namely a polysilicon gate layer (poly) process. The first block structure 102a of the front layer 2D OVL mark 101a is a polysilicon block. In some embodiments, the length of each side of the front layer 2D OVL mark is equal to 40μm.

[0076] In the X direction, the first side length is 50 nm, and the first period is 100 nm.

[0077] In the Y direction, the polysilicon line end cut (LEC) width 102b, that is, the interval between the first block structures 102a in the Y direction is 50nm, the second period value is 200nm, and the second side length value is 150nm.

[0078] like Figure 3B 2 is a structural diagram of another layer 2D OVL marker in the overlay accuracy error measurement method according to an embodiment of the present invention; Figure 3B The current layer process corresponding to the current layer 2D OVL mark 103a is a contact hole layer process. The second block structure 104a of the current layer 2D OVL mark 103a is a contact hole. In some embodiments, the length of each side of the current layer 2D OVL mark 103a is equal to 40 μm.

[0079] In the X direction, the third side length is 50 nm, and the third period is 100 nm.

[0080] In the Y direction, the fourth side length is 50 nm and the fourth period is 100 nm. It can be seen that the second period is twice the fourth period, and each first block structure 102a corresponds to two second block structures 104a.

[0081] like Figure 3C As shown, it is a schematic diagram of the overlay accuracy error measurement method according to an embodiment of the present invention when the OCD measurement method is used for measurement. For the OCD measurement method, please refer to the subsequent steps 21 and step 3. The OCD measurement method is to use an optical method for measurement. After the incident light spot 105 irradiates the 2D OVL mark group formed by the front layer 2D OVL mark 101a and the current layer 2D OVL mark 103a, the corresponding spectral data is obtained by collecting the 0-level light signals at different wavelengths.

[0082] Step 2: Establish an OCD model, including:

[0083] Step 21: After completing the current layer photolithography process on the first wafer, use an OCD measurement method to measure the 2D OVL mark group on the first wafer and obtain first spectrum data.

[0084] Step 22: Use a second OVL measurement method to measure the 2D OVL mark group on the first wafer and obtain a first OVL result; the second OVL measurement method uses a BSE OVL measurement method.

[0085] In some embodiments, the second OVL measurement method can be replaced by a secondary electron-based OVL measurement method or a TEM section-based OVL measurement method. BSE OVL measurement methods, secondary electron-based OVL measurement methods, and TEM section-based OVL measurement methods can all produce accurate first OVL results and serve as calibration data. In actual processes, one method can be selected as the second OVL measurement method as needed. BSE OVL measurement methods are more efficient and less costly.

[0086] Step 23: Use the first OVL result as a reference and perform modeling based on the first spectral data to obtain the OCD model.

[0087] In some embodiments, in step 23, a rigorous coupled wave algorithm or a machine learning-based method is used for modeling.

[0088] In the embodiment of the present invention, steps 21 to 23 need to be repeated multiple times to obtain multiple sets of the first spectral data and the corresponding first OVL results, so as to continuously optimize the OCD model.

[0089] like Figure 4 FIG. 1 is a flow chart of establishing an OCD model in the overlay accuracy error measurement method according to an embodiment of the present invention, including:

[0090] Step S101 : Acquire a plurality of first spectral data, where each first spectral data is acquired through step 21 . Figure 4 Displays n pieces of the first spectrum data, namely Spectrum1, Spectrum2, and Spectrum n .

[0091] Step S102: Acquire multiple first OVL results. Each first OVL result is obtained through step S22. Figure 4 The first n OVL results are shown, namely BSE OVL1, BSE OVL2 to BSE OVL n .

[0092] Step S103: Tuning OCD library.

[0093] Step S104: perform a linear correlation check, and then make a judgment, such as whether the slope is within 1±0.01 and the goodness of fit (R 2 ) is greater than 0.99, that is, Slope within 1±0.01&R2>0.99?

[0094] If the judgment result is negative, that is, N, the process returns to step S103 to continue adjusting the OCD database.

[0095] If the judgment result is yes, that is, Y, then:

[0096] Step S105: Output OCD library.

[0097] The above steps S103 to S105 implement step 23.

[0098] Step 3: After completing the current layer lithography process on the second wafer, use the OCD measurement method to measure the 2D OVL mark group on the second wafer and obtain second spectral data, match the second spectral data with the first spectral data of the OCD model and obtain a second OVL result.

[0099] The overlay accuracy error of the present invention is achieved by combining a set of 2D OVL markers and OCD measurement, and is calibrated using the OVL results of a second OVL measurement method, such as the BSE OVL measurement method, wherein:

[0100] The front-layer 2D OVL marker 101 and the current-layer 2D OVL marker 103 in the 2D OVL marker set can achieve a minimum effective period that is closer to the device pattern period than the minimum effective period of the existing 1D OVL marker. Therefore, the 2D OVL marker set of the present invention is more likely to reflect the actual status of the device, thereby improving the accuracy of OVL measurement.

[0101] The 2D OVL marking group can obtain OVL information in the x and y directions through one pattern and one measurement, thereby saving the pattern area of ​​the OVL marking and the number of OVL measurements, and improving measurement efficiency.

[0102] OCD measurement is performed using an optical method, and the measurement speed is much higher than that of BSE OVL measurement. Therefore, the present invention can improve the measurement speed.

[0103] The present invention employs a second OVL measurement method, such as the BSE OVL measurement method, for calibration. Due to the high accuracy of the second OVL measurement method, it can improve the accuracy of the first OVL result used in modeling. Furthermore, after modeling is complete, it can improve the accuracy of the second OVL result obtained through OCD measurement, ultimately improving the accuracy of OVL measurement.

[0104] Compared to existing OVL measurement methods that combine a 2D OVL marker group and a BSE OVL measurement method, the OCD measurement method of the present invention is faster than BSE OVL measurement, thus improving measurement speed. Furthermore, the OCD measurement modeling of the present invention utilizes the first OVL result obtained by the BSE OVL measurement method for calibration, thus achieving measurement accuracy comparable to that of the BSE OVL measurement method. Therefore, the present invention can utilize OCD measurement to implement OVL measurement of 2D OVL marker patterns, thereby improving both measurement speed and accuracy.

[0105] Existing OVL measurement methods require a long OVL measurement mark period, which significantly deviates from the actual device size. Furthermore, the accuracy of existing OVL measurements is affected by the asymmetry of the OVL measurement mark. While BSE OVL can improve OVL measurement accuracy, it is slower.

[0106] Scatterometry-based optical critical dimension (OCD) measurement technology characterizes the signal variations of zero-order light at different wavelengths and reversely calculates the required structural information. Therefore, this technology can be applied to characterize OVL by measuring structures with smaller periods. However, two issues need to be addressed and optimized for its application. First, traditional OVL markers are all one-dimensional (1D) gratings composed of lines and grooves. The diffracted light distribution of a 1D grating is also 1D, meaning that its zero-order light signal only reflects the OVL variation in one direction. To simultaneously obtain OVL in two directions, the OCD measurement grating should be modified to a two-dimensional (2D) one. Second, OCD measurement requires calibration with other measurement data, such as CD or height information obtained from transmission electron microscopy (TEM) imaging or scanning electron microscopy (SEM) imaging. The OVL obtained by backscattered electron (BSE) imaging is not affected by optical asymmetry and is considered to be the true OVL. Therefore, choosing BSE OVL for calibration can bring the accuracy of OCD OVL to the level of BSEOVL.

[0107] Based on the above principles, an embodiment of the present invention implements a method for measuring overlay accuracy errors based on scatterometry. This method includes a set of 2D OVL markers designed for OCD measurement and utilizes BSE OVL for scatterometry OVL calibration. This method offers four advantages: First, the minimum effective period of the OVL marker is closer to the device pattern period, making it more reflective of the device's true condition; second, the 2D OVL marker can obtain OVL information in both the x and y directions using a single pattern and a single measurement; third, using BSE OVL for calibration, this method's OVL accuracy surpasses that of optical OVL measurement; and fourth, because it still uses an optical method, its measurement speed is much higher than that of BSE OVL measurement.

[0108] The present invention has been described in detail above by means of specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered as the scope of protection of the present invention.

Claims

1. A method for measuring overlay accuracy error, characterized in that: The steps include: Step 1: Design a set of 2D OVL logo groups, including a front layer 2D OVL logo and a current layer 2D OVL logo; Step 2: Establish an OCD model, including: Step 21, after completing the current layer photolithography process on the first wafer, use the OCD measurement method to measure the 2D OVL mark group on the first wafer and obtain first spectrum data; Step 22: Use a second OVL measurement method to measure the 2D OVL mark group on the first wafer and obtain a first OVL result; the second OVL measurement method includes a BSE OVL measurement method; Step 23: using the first OVL result as a reference and performing modeling based on the first spectral data to obtain the OCD model; Step three: after completing the current layer lithography process on the second wafer, use the OCD measurement method to measure the 2D OVL mark group on the second wafer and obtain second spectral data, match the second spectral data with the first spectral data of the OCD model and obtain a second OVL result.

2. The overlay error measurement method according to claim 1, characterized in that: The front layer 2D OVL logo is designed based on the front layer process requirements, and the front layer 2D OVL logo adopts a 2D grating structure; The length of each side of the front layer 2D OVL mark is greater than the longest axis of the incident light spot; The 2D grating structure of the front layer 2D OVL mark is formed by a two-dimensional arrangement of first block structures; the two-dimensional arrangement of the first block structures is a periodic arrangement or a non-periodic arrangement.

3. The overlay error measurement method according to claim 2, wherein: The current layer 2D OVL mark is designed based on the current layer process requirements, and the current layer 2D OVL mark adopts a 2D grating structure; The length of each side of the 2D OVL mark of the current layer is greater than the longest axis of the incident light spot; The 2D grating structure marked by the 2D OVL layer is formed by a two-dimensional arrangement of second block structures; the two-dimensional arrangement of the second block structures is a periodic arrangement or a non-periodic arrangement.

4. The overlay error measurement method according to claim 3, characterized in that: The top view structure of the first block structure is circular or square; the first block structure is a raised island structure or a sunken hole structure.

5. The overlay error measurement method according to claim 4, characterized in that: The top view structure of the second block structure is circular or square; the second block structure is a raised island structure or a sunken hole structure.

6. The overlay error measurement method according to claim 5, characterized in that: In the current layer lithography process, the placement rule of the current layer 2D OVL mark is to make the center coordinate of the current layer 2D OVL mark coincide with the center coordinate of the previous layer 2D OVL mark.

7. The overlay error measurement method according to claim 6, wherein: In the 2D OVL mark group, each of the second block structures has an aligned first block structure; Each of the first block-shaped structures has at least one aligned second block-shaped structure.

8. The overlay error measurement method according to claim 7, characterized in that: When the two-dimensional arrangement of the first block structure is a periodic arrangement, in the front layer 2D OVL mark, in the X direction, the side length of the first block structure has a first side length value, and the side length and the spacing of the first block structure have a first period value; In the Y direction, the side length of the first block-shaped structure has a second side length value, and the side length and the spacing of the first block-shaped structure have a second period value.

9. The overlay error measurement method according to claim 8, characterized in that: When the two-dimensional arrangement of the second block structures is a periodic arrangement, in the layer 2D OVL mark, in the X direction, the side length of the second block structure has a third side length value, and the side length and the spacing of the second block structure have a third period value; In the Y direction, the side length of the second block-shaped structure has a fourth side length value, and the side length and the spacing of the second block-shaped structure have a fourth period value.

10. The overlay error measurement method according to claim 9, characterized in that: The first side length value is an integer multiple of at least 1 times the third side length value, and the first period value is an integer multiple of at least 1 times the third period value; The second side length value is an integer multiple of at least 1 times the fourth side length value, and the second period value is an integer multiple of at least 1 times the fourth period value.

11. The overlay accuracy error measurement method according to claim 2, characterized in that: The lengths of the sides of the front-layer 2D OVL mark are all equal, and the lengths of the sides of the current-layer 2D OVL mark are all equal and equal to the lengths of the sides of the front-layer 2D OVL mark.

12. The overlay error measurement method according to claim 9, wherein: The first side length is 1 / 2 of the first period value, and the second side length is 1 / 2 of the second period value; The third side length value is 1 / 2 of the third period value, and the fourth side length value is 1 / 2 of the fourth period value.

13. The overlay error measurement method according to claim 1, wherein: In step 2, steps 21 to 23 need to be repeated multiple times to obtain multiple sets of the first spectral data and the corresponding first OVL results.

14. The overlay error measurement method according to claim 13, wherein: In step 23, a rigorous coupled wave algorithm or a machine learning-based method is used for modeling.

15. The overlay accuracy error measurement method according to claim 1, characterized in that: The second OVL measurement method also includes an OVL measurement method based on secondary electrons and an OVL measurement method based on TEM slices.

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