Wafer alignment mark selection method

Abstract

This application relates to the field of semiconductor integrated circuit manufacturing technology, specifically to a method for selecting wafer alignment marks. The method includes the following steps: selecting a set of front-layer alignment marks corresponding to each front layer of the wafer, each set including multiple front-layer alignment marks; traversing all detection light sources in a set of detection light sources, such that each detection light source detects each front-layer alignment mark in each set of front-layer alignment marks to determine the optimal alignment combination corresponding to different front layers; a pair of optimal alignment combinations includes a combination of an optimal alignment mark and a detection light source; integrating optimal alignment combinations corresponding to the same detection light source to form an optimal alignment set, each optimal alignment set including optimal alignment marks located in different front layers; and setting the optimal allocation quantity of various optimal alignment marks in each optimal alignment set based on the target number of alignment marks.

Description

Technical Field

[0001] This application relates to the field of semiconductor integrated circuit manufacturing technology, and specifically to a method for selecting wafer alignment marks. Background Technology

[0002] Wafer alignment is one of the core processes in semiconductor manufacturing technology. Before the wafer is transferred to the processing stage for exposure, the relative positions of the wafer and the photomask are adjusted to ensure that the pattern on the wafer is aligned with the pattern on the photomask. The alignment accuracy directly affects the efficiency and yield of the entire semiconductor manufacturing process.

[0003] Related technologies typically use only the alignment marks of the previous layer for alignment operations. However, when the alignment marks in the same previous layer are damaged due to manufacturing processes, using only the alignment marks in the previous layer for subsequent alignment operations will lead to the failure of subsequent alignment operations, resulting in a low fault tolerance rate. Summary of the Invention

[0004] This application provides a wafer alignment mark selection method, which can solve the problem of low fault tolerance in related technologies.

[0005] To address the technical problems described in the background art, this application provides a wafer alignment mark selection method, which includes the following steps:

[0006] Select a set of front-layer alignment marks corresponding to each front layer of the wafer, wherein each set of front-layer alignment marks includes multiple front-layer alignment marks;

[0007] Traverse all detection light sources in the detection light source set, such that each detection light source detects each front layer alignment mark in all front layer alignment mark sets, and determines the optimal alignment combination for different front layers; a pair of optimal alignment combinations includes a combination of an optimal alignment mark and a detection light source.

[0008] The best alignment combinations corresponding to the same detection light source are integrated to form an optimal alignment set, and each of the optimal alignment sets includes the best alignment marks located in different front layers;

[0009] Based on the number of target alignment marks, the optimal allocation number of various optimal alignment marks is set in each optimal alignment set.

[0010] Optionally, the step of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination corresponding to different front layers, includes:

[0011] Step S21: Determine a detection light source from the set of detection light sources;

[0012] Step S22: Determine the set of alignment marks corresponding to the previous layer;

[0013] Step S23: Based on the detection results of the detection light source on each front-layer alignment mark in the front-layer alignment mark set, select the best alignment mark from the front-layer alignment mark set;

[0014] Step S26: One of the optimal alignment marks forms a pair of optimal alignment combinations with the detection light source.

[0015] Optionally, the step of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination corresponding to different front layers, further includes:

[0016] Step S24: Determine the set of alignment marks for the other preceding layers, and repeat step S23 until the best alignment mark is selected from all the sets of alignment marks for the preceding layers.

[0017] Optionally, the step of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination corresponding to different front layers, further includes:

[0018] Step S25: Determine other detection light sources from the set of detection light sources, and repeat steps S22 to S24 until all detection light sources in the set of detection light sources are traversed, so that the best alignment mark is selected from all the sets of previous layer alignment marks by any one of the detection light sources.

[0019] Optionally, step S23: selecting the best alignment mark from the set of front-layer alignment marks based on the detection result of the detection light source detecting each front-layer alignment mark in the set of front-layer alignment marks, includes:

[0020] Step S231: Use the detection light source to detect a front-layer alignment mark in the front-layer alignment mark set to obtain an alignment signal;

[0021] Step S232: Determine the signal fitting degree, signal strength, and alignment residual value of the alignment signal as the detection result;

[0022] Step S233: When the signal fitting degree, signal strength and alignment residual of the alignment signal are all greater than the preset threshold, the front layer alignment mark is determined to be the best alignment mark.

[0023] Step S235: Select all the best alignment marks corresponding to the previous layer alignment mark set.

[0024] Optionally, step S23: selecting the best alignment mark from the set of front-layer alignment marks based on the detection result of the detection light source detecting each front-layer alignment mark in the set of front-layer alignment marks, further includes:

[0025] Step S234: Repeat steps S231 to S233 above to determine whether all the previous alignment marks in the previous alignment mark set are the best alignment marks.

[0026] Optionally, in the step of selecting a set of front-layer alignment marks corresponding to each front layer of the wafer, wherein each set of front-layer alignment marks includes multiple front-layer alignment marks,

[0027] Each front layer alignment mark in each front layer includes multiple marks.

[0028] The technical solution of this application has at least the following advantages: First, the optimal alignment mark in each front layer is determined by a specific detection light source. Then, under different detection light sources, the optimal alignment marks located in different front layers and with different allocation numbers are selected as the alignment marks for the corresponding detection light source. This avoids the problem of alignment operation failure due to selecting alignment marks only in one front layer during use, thus improving the alignment error tolerance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 A flowchart of a wafer alignment mark selection method provided in an embodiment of this application is shown;

[0031] Figure 2a This diagram illustrates the selection of the corresponding front layer alignment mark set for each front layer.

[0032] Figure 2b A schematic diagram of the detection light source assembly is shown;

[0033] Figure 2c A schematic diagram of an embodiment is shown, illustrating the selection of the optimal alignment mark from each set of alignment marks in the preceding layers using a first detection light source LS1.

[0034] Figure 2dA schematic diagram of an embodiment is shown, illustrating the selection of the optimal alignment mark from each set of alignment marks in the preceding layers using a second detection light source LS2. Detailed Implementation

[0035] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection between two components; and they can refer to wireless connections or wired connections. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0039] Figure 1 The flowchart of a wafer alignment mark selection method according to an embodiment of the present application is shown. Typically, a wafer includes several front layers, and each front layer is provided with alignment marks.

[0040] from Figure 1 As can be seen from this, the wafer alignment mark selection method includes the following steps S1 to S4:

[0041] Step S1: Select a set of front-layer alignment marks corresponding to each front layer of the wafer, wherein each set of front-layer alignment marks includes multiple front-layer alignment marks.

[0042] It should be noted that there are multiple front-layer alignment marks in one of the front layers of the wafer.

[0043] Reference Figure 2a It shows a schematic diagram of selecting the corresponding front layer alignment mark set for each front layer, from Figure 2a As can be seen from the data, the chip includes a first front layer L1, a second front layer L2, a third front layer L3... and an Mth front layer LM. Multiple front layer alignment marks are selected from each front layer to form a set of front layer alignment marks corresponding to that front layer.

[0044] For example, multiple alignment marks selected from the first front layer L1 form a front layer alignment mark set A = {A1, A2, A3…An}, multiple alignment marks selected from the second front layer L2 form a front layer alignment mark set B = {B1, B2, B3…Bn}, multiple alignment marks selected from the second front layer L2 form a front layer alignment mark set C = {C1, C2, B3…Bn}, and multiple alignment marks selected from the Mth front layer LM form a front layer alignment mark set M = {M1, M2, M3…Mn}.

[0045] Step S2: Traverse all detection light sources in the detection light source set, such that each detection light source detects each front layer alignment mark in all front layer alignment mark sets, and determines the best alignment combination for different front layers. A pair of the best alignment combinations is a combination of an best alignment mark and an best light source.

[0046] It should be noted that this set of detection light sources includes a variety of detection light sources.

[0047] Reference Figure 2b It shows a schematic diagram of the detection light source set, from Figure 2b As can be seen from the above, the set of detection light sources LS in this embodiment is a collection of multiple detection light sources, including the first detection light source LS1, the second detection light source LS2, the third detection light source LS3, ... the xth detection light source LSx.

[0048] Step S2: Traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination for different front layers, includes steps S21 to S26:

[0049] Step S21: Determine a detection light source from the set of detection light sources.

[0050] Step S22: Determine the set of alignment marks corresponding to the previous layer.

[0051] Step S23: Based on the detection results of the detection light source on each front-layer alignment mark in the front-layer alignment mark set, select the best alignment mark from the front-layer alignment mark set.

[0052] Determining whether an alignment mark is the optimal alignment mark requires assessing whether the mark is damaged or otherwise defective.

[0053] For example, step S23 includes steps S231 to S235, wherein:

[0054] Step S231: Use the detection light source to detect one of the front layer alignment marks in the front layer alignment mark set to obtain an alignment signal.

[0055] Step S232: Determine the signal fitting degree, signal strength, and alignment residual value of the alignment signal as the detection results.

[0056] Step S233: When the signal fitting degree, signal strength and alignment residual of the alignment signal are all greater than the preset threshold, the front layer alignment mark is determined to be the best alignment mark.

[0057] Step S234: Repeat steps S231 to S233 above to determine whether all the previous alignment marks in the previous alignment mark set are the best alignment marks.

[0058] Step S235: Select all the best alignment marks corresponding to the previous layer alignment mark set.

[0059] Step S24: Determine the set of alignment marks for the other preceding layers, and repeat step S23 until the best alignment mark is selected from all the sets of alignment marks for the preceding layers.

[0060] Reference Figure 2c It illustrates a schematic diagram of an embodiment where the optimal alignment mark is selected from the sets of alignment marks in each preceding layer using a first detection light source LS1. Figure 2c As can be seen from the above, in this embodiment, a first detection light source LS1 is determined from the detection light source set LS, and the first detection light source LS1 is used to detect the front layer alignment mark set of each front layer to determine the best alignment mark in each front layer alignment mark set.

[0061] The first detection light source LS1 detects the front layer alignment mark set A = {A1, A2, A3...An} of the first front layer L1, and determines that the optimal alignment marks of the front layer alignment mark set A = {A1, A2, A3...An} under the first detection light source LS1 are the front layer alignment mark A1 and the front layer alignment mark A3.

[0062] The first detection light source LS1 detects the front layer alignment mark set B = {B1, B2, B3...Bn} of the second front layer L2, and determines that under the first detection light source LS1, the optimal alignment marks of the front layer alignment mark set B = {B1, B2, B3...Bn} include front layer alignment mark B1 and front layer alignment mark Bn.

[0063] The first detection light source LS1 is used to detect the front layer alignment mark set C = {C1, C2, B3...Bn} of the third front layer L3. It is determined that under the first detection light source LS1, the best alignment mark of the front layer alignment mark set C = {C1, C2, B3...Bn} is the front layer alignment mark C1.

[0064] The first detection light source LS1 is used to detect the set of alignment marks M = {M1, M2, M3...Mn} of the previous layer LM. It is determined that under the first detection light source LS1, there is no optimal alignment mark in the set of alignment marks M = {M1, M2, M3...Mn} of the previous layer.

[0065] Step S25: Determine other detection light sources from the set of detection light sources, and repeat steps S22 to S24 until all detection light sources in the set of detection light sources are traversed, so that the best alignment mark is selected from all the sets of previous layer alignment marks by any one of the detection light sources.

[0066] Reference Figure 2d It shows a schematic diagram of an embodiment in which the best alignment mark is selected from the set of alignment marks of each front layer by means of a second detection light source LS2.

[0067] from Figure 2d As can be seen from the above, in this embodiment, a second detection light source LS2 is determined from the detection light source set LS, and the second detection light source LS2 is used to detect the front layer alignment mark set of each front layer to determine the best alignment mark in each front layer alignment mark set.

[0068] according to Figure 2c and Figure 2d The steps shown, after traversing all the detection light sources in the detection light source set LS, can determine the optimal alignment mark for each detection light source, corresponding to different front layers.

[0069] Step S26: One of the optimal alignment marks forms a pair of optimal alignment combinations with the detection light source.

[0070] by Figure 2cFor example, since the optimal alignment marks for the previous layer alignment mark set A = {A1, A2, A3…An} determined by the first detection light source LS1 are the previous layer alignment marks A1 and A3, the optimal alignment marks for the previous layer alignment mark set B = {B1, B2, B3…Bn} include the previous layer alignment marks B1 and Bn, and the optimal alignment mark for the previous layer alignment mark set C = {C1, C2, B3…Bn} is the previous layer alignment mark C1, thus… Figure 2c The optimal alignment combinations include optimal alignment combination A1LS1, optimal alignment combination A3LS1, optimal alignment combination B1LS1, optimal alignment combination BnLS1, and optimal alignment combination C1LS1.

[0071] by Figure 2d For example, since the optimal alignment mark for the previous layer alignment mark set A = {A1, A2, A3…An} determined by the second detection light source LS2 is the previous layer alignment mark A2, the optimal alignment marks for the previous layer alignment mark set B = {B1, B2, B3…Bn} are the previous layer alignment marks B1 and B2, the optimal alignment marks for the previous layer alignment mark set C = {C1, C2, B3…Bn} are the previous layer alignment marks C1 and C3, and the optimal alignment mark for the previous layer alignment mark set M = {M1, M2, M3…Mn} is the previous layer alignment mark M1, thus… Figure 2d The optimal alignment combinations include A2LS2, B1LS2, B2LS2, C2LS2, C3LS2, and M1LS2.

[0072] Step S3: Integrate the best alignment combinations corresponding to the same detection light source to form the best alignment set, and each of the best alignment sets includes the best alignment marks located in different front layers.

[0073] by Figure 2c For example, the best alignment combination corresponding to the first detection light source LS1 is integrated to form the first best alignment set GLS1, which is G1LS1 = {A2, A3, B1, Bn, C1...}.

[0074] Among them, the best alignment mark A2 and the best alignment mark A3 are located in the first front layer L1, the best alignment mark B2 and the best alignment mark Bn are located in the second front layer L2, and the best alignment mark C1 is located in the third front layer L3.

[0075] by Figure 2d For example, the optimal alignment combination corresponding to the second detection light source LS2 is integrated to form the second optimal alignment set GLS2, which is {A2, B1, B2, C2, C3, M1...}.

[0076] Among them, the best alignment mark A2 is located in the first front layer L1, the best alignment marks B1 and B2 are located in the second front layer L2, the best alignment marks C2 and C3 are located in the third front layer L3, and the best alignment mark M1 is located in the Mth front layer LM.

[0077] Step S4: Based on the number of target alignment marks, set the optimal allocation number of various optimal alignment marks in each optimal alignment set.

[0078] The number of target alignment marks can be preset as needed. For example, the number of target alignment marks is preset to 64. For the first optimal alignment set GLS1 corresponding to the first detection light source LS1, 22 alignment marks are allocated in the first front layer L1, of which 10 are optimal alignment marks A2 and 12 are optimal alignment marks A3; 22 alignment marks are allocated in the second front layer L2, of which 10 are optimal alignment marks B1 and 12 are optimal alignment marks Bn; and 20 alignment marks are allocated in the third front layer L3, of which 20 are optimal alignment marks C1.

[0079] This embodiment first determines the optimal alignment mark in each front layer using a specific detection light source. Then, under different detection light sources, it selects the optimal alignment marks located in different front layers and with different allocation numbers as the alignment marks for the corresponding detection light source. This avoids the problem of alignment operation failure caused by selecting alignment marks only in one front layer during use, thus improving the alignment error tolerance.

[0080] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for selecting wafer alignment marks, characterized in that, The wafer alignment mark selection method includes the following steps: Select a set of front-layer alignment marks corresponding to each front layer of the wafer, wherein each set of front-layer alignment marks includes multiple front-layer alignment marks; Traverse all detection light sources in the detection light source set, such that each detection light source detects each front layer alignment mark in all front layer alignment mark sets, and determines the optimal alignment combination for different front layers. The best alignment combinations corresponding to the same detection light source are integrated to form an optimal alignment set, and each of the optimal alignment sets includes the best alignment marks located in different front layers; Based on the number of target alignment marks, the optimal allocation number of various optimal alignment marks is set in each optimal alignment set; The process of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determines the optimal alignment combination corresponding to different front layers, includes: Step S21: Determine a detection light source from the set of detection light sources; Step S22: Determine the set of alignment marks corresponding to the previous layer; Step S23: Based on the detection results of the detection light source on each front-layer alignment mark in the front-layer alignment mark set, select the best alignment mark from the front-layer alignment mark set; Step S26: One of the optimal alignment marks forms a pair of the optimal alignment combinations with the detection light source; Step S23 includes: Step S231: Use the detection light source to detect a front-layer alignment mark in the front-layer alignment mark set to obtain an alignment signal; Step S232: Determine the signal fitting degree, signal strength, and alignment residual value of the alignment signal as the detection result; Step S233: When the signal fitting degree, signal strength and alignment residual of the alignment signal are all greater than the preset threshold, the previous layer alignment mark is determined to be the best alignment mark; Step S235: Select all the best alignment marks corresponding to the previous layer alignment mark set.

2. The wafer alignment mark selection method as described in claim 1, characterized in that, The step of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination corresponding to different front layers, further includes: Step S24: Determine the set of alignment marks for the other preceding layers, and repeat step S23 until the best alignment mark is selected from all the sets of alignment marks for the preceding layers.

3. The wafer alignment mark selection method as described in claim 2, characterized in that, The step of traversing all detection light sources in the detection light source set, such that each detection light source detects each front-layer alignment mark in all front-layer alignment mark sets, and determining the optimal alignment combination corresponding to different front layers, further includes: Step S25: Determine other detection light sources from the set of detection light sources, and repeat steps S22 to S24 until all detection light sources in the set of detection light sources are traversed, so that the best alignment mark is selected from all the sets of previous layer alignment marks by any one of the detection light sources.

4. The wafer alignment mark selection method as described in claim 1, characterized in that, Step S23: Based on the detection results of the detection light source on each front-layer alignment mark in the front-layer alignment mark set, selecting the best alignment mark from the front-layer alignment mark set, further includes: Step S234: Repeat steps S231 to S233 above to determine whether all the previous alignment marks in the previous alignment mark set are the best alignment marks.

5. The wafer alignment mark selection method as described in claim 1, characterized in that, In the step of selecting a set of front-layer alignment marks corresponding to each front layer of the wafer, wherein each set of front-layer alignment marks includes multiple front-layer alignment marks, each front-layer alignment mark in each front layer includes multiple types.

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