Method for optimizing overlay measurement conditions and overlay measurement method using overlay measurement conditions

Abstract

A method of optimizing overlap measurement conditions includes: for each of a plurality of overlap measurement conditions, measuring an overlap of a plurality of locations of a substrate; calculating, for each of the plurality of overlap measurement conditions, a key parameter index (KPI) based on the measured overlap; for each of the plurality of overlapping measurement conditions, converting the KPI into a KPF-based key parameter function (KPF) value, where each of the KPFs has a same dimensional representation; for each of the plurality of overlapping measurement conditions, integrating the KPF values to generate an integrated KPF value; and selecting an optimized overlap measurement condition from among the plurality of overlap measurement conditions based on the integrated KPF value associated with each of the plurality of overlap measurement conditions.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims the benefit of priority of Korean Patent Application No. 10-2023-0085988 filed in the Korean Intellectual Property Office on July 3, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to an overlay measurement method, and more particularly, to a method for optimizing overlay measurement conditions and an overlay measurement method using the optimized overlay measurement conditions. Background Art

[0004] A semiconductor device or a semiconductor wafer including the semiconductor device includes patterns of adjacent layers that must be accurately aligned. Therefore, overlay measurement may be performed to align the patterns. More specifically, overlay may refer to the degree of misalignment between two layers when an exposure process is performed on a previous layer of a semiconductor substrate and another exposure process is performed again on a next layer or a current layer after performing several processes. In addition, correcting the relative position between layers is referred to as overlay correction, and overlay measurement may be performed for overlay correction. Overlay measurement includes measuring the degree of misalignment between layers, i.e., overlay misalignment or overlay error. Summary of the invention

[0005] The present disclosure provides a method of optimizing overlay measurement conditions for accurately measuring overlay and an overlay measurement method using the measurement conditions.

[0006] According to one aspect of the present disclosure, a method for optimizing an overlay measurement condition includes: executing, by a processor, instructions stored in a non-transitory storage medium to perform operations, the operations including: for each of a plurality of overlay measurement conditions, measuring the overlay of a plurality of positions of a substrate; for each of the plurality of overlay measurement conditions, calculating a key parameter index (KPI) based on the measured overlay; for each of the plurality of overlay measurement conditions, converting the KPI into a key parameter function (KPF) value based on a KPF, wherein each of the KPFs has the same dimensional representation; for each of the plurality of overlay measurement conditions, integrating the KPF values ​​to generate an integrated KPF value; and selecting an optimized overlay measurement condition from the plurality of overlay measurement conditions based on the integrated KPF value associated with each of the plurality of overlay measurement conditions.

[0007] According to another aspect of the present disclosure, an overlay measurement method includes: executing instructions stored in a non-transitory storage medium by a processor to perform operations, the operations including: identifying optimized overlay measurement conditions; setting an overlay measurement recipe based on the optimized overlay measurement conditions; and measuring overlay according to the overlay measurement recipe, wherein identifying the optimized overlay measurement conditions includes: for each of a plurality of overlay measurement conditions, measuring sample overlay at a plurality of positions of a substrate; for each of the plurality of overlay measurement conditions, calculating a key parameter index (KPI) based on the measured sample overlay; for each of the plurality of overlay measurement conditions, converting the KPI into a key parameter function (KPF) value based on a KPF, wherein each of the KPFs has the same dimensional representation; for each of the plurality of overlay measurement conditions, integrating the KPF values ​​to generate an integrated KPF value; and selecting the optimized overlay measurement condition from the plurality of overlay measurement conditions based on the integrated KPF value associated with each of the plurality of overlay measurement conditions.

[0008] According to another aspect of the present disclosure, a method for optimizing an overlay measurement condition includes: executing, by a processor, instructions stored in a non-temporary storage medium to perform operations, the operations including: for each of a plurality of overlay measurement conditions, measuring the overlay of a plurality of locations on a substrate; for each of the plurality of overlay measurement conditions, calculating a key parameter index (KPI) based on the measured overlay; for each of the plurality of overlay measurement conditions, converting the KPI into a key parameter function (KPF) value by removing a dimensional representation of the KPI; for each of the plurality of overlay measurement conditions, integrating the KPF values ​​by adding the KPF values ​​to each other to generate an integrated KPF value; and selecting, from among the plurality of overlay measurement conditions, an overlay measurement condition associated with a maximum integrated KPF value among the integrated KPF values. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments will be more clearly understood through the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a block diagram illustrating an overlay measurement system according to an embodiment;

[0011] Figure 2 is a plan view of a substrate having a multilayer structure formed thereon according to an embodiment;

[0012] Figure 3A is a plan view showing an image-based overlay (IBO) marker for an overlay measurement method, Figure 3B is a plan view showing a fringe-based overlay (FBO) marker for an overlay measurement method;

[0013] Figure 4is a schematic flow chart showing a method for optimizing overlapping measurement conditions according to an embodiment;

[0014] Figure 5 is a schematic flow chart showing an overlay measurement method using optimized overlay measurement conditions according to an embodiment;

[0015] Fig. 6A , Figure 6B and Figure 6C is a graph showing overlay performance according to an overlay measurement method of a comparative example; and

[0016] Figure 7 is a graph showing overlay performance of an overlay measurement method according to an embodiment. DETAILED DESCRIPTION

[0017] In order to clarify the present disclosure, parts not connected to the specification will be omitted, and the same elements or equivalents are represented by the same reference numerals throughout the specification. In addition, since the sizes and thicknesses of the constituent members shown in the drawings are arbitrarily given for better understanding and ease of description, the present disclosure is not limited to the sizes and thicknesses shown. In the drawings, the thicknesses of layers, films, panels, regions, etc. are exaggerated for clarity. In the drawings, the thicknesses of some layers and regions are excessively displayed for better understanding and ease of description.

[0018] It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element, or there can be intervening elements. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements. In addition, for ease of description, spatially relative terms such as "below," "below," "under," "above," "above," etc. may be used herein to describe the relationship between an element or feature and another element or feature, as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation shown in the figure. For example, if the device in the figure is flipped, the elements of other elements or features described as "below" or "below" will be oriented as other elements or features "above." Therefore, the term "below" may include directions above and below. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0019] In addition, unless explicitly described to the contrary, the word "include" and variations such as "comprising" will be understood to include the elements, but not to exclude any other elements. As used herein, the phrase "at least one of A, B, and C" refers to the logic (A OR B OR C) using a non-exclusive logical OR, and should not be interpreted as "at least one A, at least one B, and at least one C". As used herein, unless the context clearly indicates otherwise, the singular forms "one", "one", and "the" should also include plural forms. It should be further understood that the terms "include" and / or "comprising" when used herein specify the presence of the features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The term "and / or" includes any and all combinations of one or more related listed items. The term "connection" may be used herein to refer to physical and / or electrical connections, and may also refer to direct or indirect physical and / or electrical connections.

[0020] The present disclosure is described herein with reference to flowcharts and / or block diagrams of methods, systems, and devices according to exemplary embodiments of the present disclosure. It should be understood that each block of the flowchart and / or block diagram illustration and the combination of blocks in the flowchart and / or block diagram illustration can be implemented by computer program instructions and / or hardware operations. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, so that instructions executed by a processor of a computer or other programmable data processing device create a device for implementing the functions specified in the flowchart and / or block diagram block.

[0021] These computer program instructions may also be stored in a non-transitory computer-usable or computer-readable memory, which can direct a computer or other programmable data processing device to work in a specific manner so that the instructions stored in the computer-usable or computer-readable memory produce a product including instructions for implementing the functions specified in the flowchart and / or block diagram blocks.

[0022] Computer program instructions may also be loaded onto a computer or other programmable data processing apparatus so that a series of operational steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart and / or block diagram blocks.

[0023] Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are used for the same components, and redundant descriptions thereof are omitted.

[0024] Figure 1 is a block diagram illustrating an overlay measurement system 100 according to an embodiment. Figure 2is a plan view of a substrate W having a multilayer structure formed thereon according to an embodiment.

[0025] refer to Figure 1 The overlay measurement system 100 may include an electro-optical system 110 that emits an electron beam onto a substrate (such as a semiconductor substrate) on which a multilayer structure is formed, and detects the emitted electrons. The overlay measurement system 100 may include a processor 130 that acquires an image from the electrons detected by the electro-optical system 110 and analyzes the image to calculate the overlay between the upper and lower layers of the multilayer structure.

[0026] In an embodiment, the overlay measurement system 100 may be used to measure an overlay between a previously patterned first layer and a currently patterned second layer in a non-destructive manner during a semiconductor manufacturing process for manufacturing semiconductor devices such as dynamic random access memory (DRAM) and vertical NAND (VNAND).

[0027] The electro-optical system 110 of the overlay measurement system 100 may include a scanning electron microscope (SEM) for capturing an image of the substrate W as a multilayer. For example, the electro-optical system 110 may be a high acceleration SEM. The electro-optical system 110 may include a microscope stage 111 supporting the substrate W, an electron gun 112 generating a primary electron beam, a focusing lens 114 for emitting the primary electron beam on the substrate W by controlling the direction and width of the primary electron beam, a deflector 115, an objective lens 116, and a detector 120 for detecting a detection signal such as electrons emitted from the substrate W.

[0028] The processor 130 may control the operation of the overlay measurement system 100. The processor 130 may execute an operating system, an application, etc. The processor 130 may implement the functions of a central processing unit (CPU). For example, the processor 130 may control the operation of the image acquirer 132, the image processor 136, the data storage 134, and the output unit 138.

[0029] Reference Figure 2, the substrate W may include a semiconductor wafer, and a multilayer structure is formed on the semiconductor wafer. In addition, the substrate W may include a semiconductor wafer, including a plurality of chips 201. In an embodiment, the memory device may be formed in a plurality of chips 201. In an embodiment, the plurality of chips 201 may include a non-volatile memory device. In an embodiment, each of the non-volatile memory devices may include a non-volatile NAND flash memory (NAND-type flash memory). In an embodiment, each of the non-volatile memory devices may be any one of a phase change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (ReRAM), a ferroelectric RAM (FRAM), and a NOR flash memory. In other embodiments, volatile memory devices such as DRAM and static RAM (SRAM) may also be formed in a plurality of chips 201, which lose data when the power is disconnected.

[0030] In an embodiment, any one of a logic chip, a measuring device, a communication device, a digital signal processor (DSP), and a system on chip (SoC) may also be formed in each of the plurality of chips 201 .

[0031] although Figure 2 Each of the plurality of chips 201 is shown to have a substantially square outline, but the present disclosure is not limited thereto. For example, the plurality of chips 201 may include a driver integrated circuit (IC) chip, and in this case, one pair of edges of the plurality of chips 201 may be longer than the other pair of edges.

[0032] The substrate W may include a plurality of chips 201, a plurality of horizontal scribing lines 203, a plurality of vertical scribing lines 205, and a plurality of alignment marks 207. The plurality of alignment marks 207 may include, for example Figure 3A Image-based Overlay (IBO) marking as shown in or Figure 3B The stripe-based overlay (FBO) mark is shown in FIG. The substrate W may have a multi-layer structure in which an upper pattern and a lower pattern overlapped with each other are formed. The layers of the substrate W may include, for example, a photoresist, a dielectric material, and a conductive material, but are not limited thereto.

[0033] The electron gun 112 of the overlay measurement system 100 may emit an electron beam into an intra-cell region of the multilayer substrate W. Here, the intra-cell region refers to each of the plurality of chips 201, and the intra-cell region may refer to a region where an actual electronic component or an actual pattern is formed. Therefore, the intra-cell region may refer to a region isolated from the scribe lines 203 and 205 and excluding the alignment mark 207.

[0034] In an embodiment, the depth of penetration of the electron beam into the substrate W can be adjusted by adjusting the acceleration voltage of the electron beam generated by the electron gun 112 to a lower voltage or a higher voltage. For example, the electron gun 112 can generate an electron beam with an acceleration voltage of about 10 kV or higher. The higher the acceleration voltage of the electron beam, the greater the depth of penetration of the electron beam into the substrate W, and therefore, the amount of electrons emitted from the lower layer of the substrate W increases, and the electrons including the lower structure information can be detected.

[0035] Therefore, when an electron beam of a high landing voltage of about 10 kV or more is emitted onto the substrate W, backscattered electrons, spiral electrons, etc. may be emitted from the substrate W together with secondary electrons.

[0036] In addition, the electro-optical system 110 may include a detector 120 that detects electrons emitted from the substrate W. The detector 120 may include a first detector 122 that detects secondary electrons and a second detector 124 that detects backscattered electrons. For example, the first detector 122 may include an in-lens detector that detects secondary electrons that include upper structural information of the substrate W. The second detector 124 may include a backscattered electron detector that is adjacent to the objective lens 116 and includes lower substructure information. The detected electrons may be used to generate an actual image of the substrate W, as described below.

[0037] Therefore, by using a highly accelerated electron beam to detect not only secondary electrons but also backscattered electrons, a unit image showing the upper and lower structures can be acquired. That is, an actual image showing the structure of the lower layer of the multilayer structure and the structure of the upper layer of the multilayer structure can be acquired. For example, an actual image showing a hole pattern, such as a contact hole of a lower structure with a high aspect ratio and a hole pattern can be acquired.

[0038] The overlay measurement system 100 may include an image acquirer 132 that receives a detection signal from the detector 120 and forms an image. The image acquirer 132 may receive detection signals from the first detector 122 and the second detector 124, and acquire a unit image simultaneously showing an upper structure and a lower structure of the substrate W. In addition, the image acquirer 32 may be operably connected to various components of the electro-optical system 110, including the electron gun 112, the focusing lens 114, the deflector 115, and may control the operation of the various components.

[0039] The processor 130 may control the electro-optical system 110 so that the image acquirer 132 acquires information about the upper structure and the lower structure of the substrate W. For example, the image acquirer 132 may control the acceleration voltage (high voltage and low voltage) of the electron gun 112, and the electro-optical system 110 emits an electron beam of the controlled acceleration voltage to penetrate the multi-layer substrate W at different depths, thereby detecting electrons including structural information of each layer of the substrate W. The image acquirer 132 may acquire a unit image from the detected electrons.

[0040] In an embodiment, the image acquirer 132 may divide the acquired unit image into sub-images showing different layers. For example, only a specific distribution of gray levels may be selected to divide the unit image into a first image showing an upper layer and a second image showing a lower layer. The gray level may be selected by considering the thickness and material of the upper and lower layers, the amount of detected electrons, etc. In addition, the unit image, the first image, and the second image may be selectively stored in the data storage 134.

[0041] In an embodiment, the image processor 136 may receive data of the first image and the second image from the data storage 134. In other embodiments, the image processor 136 may receive the first image and the second image directly from the image acquirer 132.

[0042] In an embodiment, the image processor 136 may calculate representative positions of the upper pattern and the lower pattern based on the first image and the second image, and calculate the deviation of the representative position of the second image relative to the first image. The image processor 136 may calculate the representative position of the upper pattern of the first image and the representative position of the lower pattern of the second image. For example, the image processor 136 may calculate the center position of the upper pattern of the first image, and calculate the center position of the lower pattern of the second image.

[0043] The image processor 136 may match the first image with the second image and calculate the overlap of the lower pattern of the second image relative to the upper pattern of the first image. For example, the first image may match the second image by using methods such as image edge matching and image contrast matching.

[0044] The image processor 136 may be operably connected to an output unit 138. The overlap result value and the image from the image processor 136 may be sent to the output unit 138. The output unit 138 may output the overlap result value on a display device.

[0045] Figure 1 At least one of the image acquisition device 132, the image processor 136, the data storage device 134, and the output unit 138 shown may be implemented by a single computer or processor 130 or a separate module, or may be implemented as a separate module using a data transmission or interface device. In addition, the image acquisition device 132, the image processor 136, and the output unit 138 may be combined with some controllers of the semiconductor manufacturing line. Hereinafter, the plurality of alignment marks 207 and the overlay measurement using the plurality of alignment marks 207 are described in more detail.

[0046] Figure 3A is a plan view showing an IBO mark used for the overlay measurement method.

[0047] Reference Figure 3A , substrate W (see Figure 2 ) may be an IBO mark. For example, the alignment mark 207 may be an advanced image metrology (AIM) overlap mark. The alignment mark 207 may include a main pattern MP1 that forms an outer dark pattern on a lower layer and a vernier pattern VP1 that forms an inner bright pattern on a current layer. The main pattern MP1 and the vernier pattern VP1 may be named as an outer pattern and an inner pattern, respectively, based on the positions of the patterns. When the alignment mark 207 is an IBO mark, the overlap may be measured by signal processing an optical / camera image of the alignment mark 207. For example, the overlap may be measured by calculating the relative position between the main pattern MP1 and the vernier pattern VP1 by signal processing an image of the main pattern MP1 of the alignment mark 207 and the vernier pattern VP1 of the alignment mark 207.

[0048] Figure 3B is a plan view showing the FBO marking used for the overlay measurement method.

[0049] Reference Figure 3B , substrate W (see Figure 2 ) may be a FBO mark. The alignment mark 207 may include a lower pattern FBO1 formed on a lower layer and an upper pattern FBOu formed on an upper layer. At least a portion of the lower pattern FBO1 may overlap at least a portion of the upper pattern FBOu in a vertical direction. In this case, at least a portion of the lower pattern FBO1 and at least a portion of the upper pattern FBOu that overlap each other in a vertical direction may form a moiré pattern FBOm. Due to interference between the lower pattern FBO1 and the upper pattern FBOu, the moiré pattern FBOm may have a moiré period different from that of the lower pattern FBO1 and the upper pattern FBOu. The alignment mark 207 may include a plurality of different moiré patterns. For example, the alignment mark 207 may have a first moiré pattern (not shown) in a partial region, and may have a second moiré pattern (not shown) in other regions except the partial region. In this case, the first moiré pattern and the second moiré pattern may have different moiré periods. When the alignment mark 207 is a FBO mark, the overlay may be measured by signal processing an optical / camera image of the alignment mark 207. For example, the overlay may be measured by signal processing an image of a first moiré pattern and a second moiré pattern of the alignment mark 207 and calculating a relative position between the first moiré pattern and the second moiré pattern.

[0050] Figure 4 is a schematic flow chart illustrating a method for optimizing overlap measurement conditions according to an embodiment.

[0051] Reference Figure 4, while changing the measurement conditions, the overlap of multiple positions of the substrate may be first measured (P110). The measurement conditions may include the wavelength of the light source used for the overlap measurement, the focus of the light source, the relative position of the light source with respect to the substrate, environmental factors such as temperature and humidity, and the design of the alignment mark on the substrate. For example, when the measurement condition is the wavelength of the light source used for the overlap measurement, the overlap may be measured at multiple positions on the substrate while changing the wavelength of the light source in operation P110.

[0052] Multiple locations on the substrate where measurements overlap can be arranged Figure 2 The number of positions of the plurality of alignment marks 207 shown in . The number of positions on the substrate at which overlap is measured may be from hundreds to thousands. For example, the number of positions on the substrate at which overlap is measured may be 100 or 200. The number of positions on the substrate may vary based on the type of measurement conditions. For example, the number of positions on the substrate at which overlap is measured when the measurement condition is the focus of the light source is different from the number of positions on the substrate at which overlap is measured when the measurement condition is the relative position of the light source.

[0053] In an embodiment, overlay measurement at multiple positions on the substrate may be performed multiple times under different measurement conditions. For example, in operation P110, overlay measurement may be performed at multiple positions on the substrate while changing the wavelength of the light source, and then overlay measurement may be performed at multiple positions on the substrate while changing the focus of the light source. In this case, the number of positions on the substrate measured when the wavelength of the light source is changed may be different from the number of positions on the substrate measured when the focus of the light source is changed.

[0054] In one embodiment, operation P110 may be performed on multiple substrates instead of one substrate. For example, operation P110 may be performed on two substrates.

[0055] After performing operation P110, a key parameter index (KPI) (P120) can be calculated based on the measured overlap. KPI refers to an overlap performance index, which reflects the overlap performance according to the overlap measurement conditions. For example, when the overlap measurement is performed by using the wavelength of the light source as the measurement condition, the KPI refers to an overlap performance index in which the overlap performance according to the wavelength of the light source is reflected. In this case, the overlap performance index may refer to, for example, the quality of the overlapped image measured according to the wavelength change of the light source. Here, the quality of the overlapped image may include, for example, the brightness of the overlapped image, etc. In another example, the overlap performance index may also be the degree of defect of the alignment mark, etc. As the overlap measurement conditions change, the KPI calculated based on the measured overlap may also change. For example, when the overlap measurement condition is the wavelength of the light source, the calculated KPI may also change with the change of the overlap measurement conditions, i.e., the wavelength of the light source.

[0056] In an embodiment, operation P120 may be performed multiple times. For example, when overlay measurement is performed under two types of overlay measurement conditions in operation P110, operation P120 may be performed twice based on overlay measurement according to each overlay measurement condition, and two KPIs may be calculated.

[0057] In an embodiment, the method of calculating a KPI may be changed according to the overlapping measurement conditions or overlapping performance indicators defined by the KPI. For example, when two KPIs are calculated as described above, each KPI may be calculated in a different manner according to the overlapping measurement conditions or overlapping performance indicators defined by each KPI.

[0058] The interpretation of the KPI may vary depending on the type of overlap measurement condition. For example, it may be interpreted that when a first KPI according to a first overlap measurement condition is small, the overlap performance is acceptable, and when a second KPI according to a second overlap measurement condition is large, the overlap performance is acceptable.

[0059] After performing operation P120 , the calculated KPI may be converted into a key performance function (KPF) value ( P130 ).

[0060] Here, KPF is a function using the KPI calculated in operation P120 as a variable, and is a function for balancing the various KPIs calculated in operation P120. KPF can be defined so that the dimensional representation of KPI can be balanced based on the overlapping performance indicators defined by KPI. When the KPF value converted from each KPI according to KPF is large, the overlapping performance can be interpreted as acceptable. In this case, for example, when the first KPI value is relatively small, when the overlapping performance is interpreted as acceptable, because due to the inverse relationship between the first KPI value and the KPF value, the first KPF value can be converted to have a larger value. In addition, when the second KPI value is relatively large, when the overlapping performance is interpreted as acceptable, because due to the proportional relationship between the second KPI value and the KPF value, the second KPF value can be converted to have a larger value.

[0061] In an embodiment, the KPF may vary based on the type of KPI calculated in operation P120. For example, when two KPIs are calculated in operation P120, a first KPF that converts the first KPI may be different from a second KPF that converts the second KPI.

[0062] In an embodiment, the KPF may be a function for de-dimensionalizing (e.g., completely removing the dimensional representation or partially removing the dimensional representation and corresponding appropriate replacement of the dimensional representation) the KPI calculated in operation P120. For example, when the KPI value has nanometer units, the KPF value converted from the KPI value by the corresponding KPF may be a dimensionless value offset from the nanometer units.

[0063] In an embodiment, operation P130 may be performed multiple times. For example, when multiple KPIs are calculated by performing operation P120 multiple times, operation P130 may be performed multiple times on the multiple KPIs, and accordingly, the multiple KPIs may be converted into corresponding KPF values.

[0064] After performing operation P130 , the KPF values ​​may be integrated to generate an integrated KPF value ( P140 ).

[0065] Here, the integrated KPF value may refer to a KPF including a KPF value calculated according to operation P130 and may be referred to as “KPFt” unless specifically defined below. KPFt may be obtained by the following formula (1).

[0066] Formula (1): F(KPI 1 ,KPI 2 ,KPI 3 ,…,KPI n )=w 1 *f 1 (KPI 1 )+w 2 *f 2 (KPI 2 )+w 3 *f 3 (KPI 3 )+…+f n *fn(KPI n )

[0067] In the above formula, F(KPI 1 ,KPI 2 ,KPI 3 ,...,KPI n ) refers to the integrated KPF, namely KPFt; f1(KPI 1 ), …, and fn(KPI n ) refers to the KPF value calculated in operation P130; and w 1 ,…,w n Refers to the weighted value of KPF. That is, the operation of integrating each KPF value into one KPF can be performed by assigning a weighted value to each KPF value and adding all KPF values ​​assigned with the weighted value. In this case, the weighted value can be set differently based on the alignment mark of the substrate and / or the measuring device. As described above in operation P130, each KPF value is obtained by balancing the dimensional representation of each KPI value (e.g., dimensionless value). Therefore, unlike KPIs that may have different dimensional representations, all KPF values ​​have the same dimensional representation and can be converted into an integrated KPF value.

[0068] After performing operation P140, an optimized overlap measurement condition can be selected based on the integrated KPF (P150). Operation P150 can be performed by determining the overlap measurement condition where the integrated KPF value (i.e., KPFt) is maximized and setting the integrated KPF value as the actual overlap measurement condition. This is because, as described above, each KPF value is converted from a KPI value to have a larger value when interpreted as having acceptable overlap performance.

[0069] Conventionally, multiple KPI values ​​represented by different dimensions cannot be integrated with each other, and therefore, multiple KPI values ​​are considered independently to optimize overlapping measurement conditions. However, in this case, since the measurement conditions are optimized by considering multiple overlapping performance indicators individually, the optimization time is increased. In addition, the optimization also has limitations because multiple overlapping performance indicators that affect overlapping performance may not be considered simultaneously.

[0070] In addition, the method for optimizing overlay measurement conditions according to the embodiment can simultaneously consider multiple overlay performance indicators through an integrated KPF, thereby reducing the optimization time and performing optimization for improvement of overlay measurement conditions.

[0071] Figure 5 is a schematic flow chart illustrating an overlay measurement method using optimized overlay measurement conditions according to an embodiment.

[0072] refer to Figure 5 , you can first optimize the overlap measurement conditions (P210). The operation of optimizing the overlap measurement conditions (P210) can be combined with the reference Figure 4 The method for optimizing the overlay measurement conditions described is substantially the same. That is, the operation of optimizing the overlay measurement conditions (P210) may include the operation of measuring the overlay of multiple locations on the substrate while changing the measurement conditions (P110), the operation of calculating the KPI based on the measured overlay (P120), the operation of converting the KPI into a KPF (P130), the operation of converting each KPF into an integrated KPF (P140), and the operation of selecting an optimized overlay measurement condition based on the integrated KPF (P150).

[0073] After performing operation P210, an overlay measurement recipe may be set according to the optimized overlay measurement conditions (P220). The overlay measurement recipe may refer to setting values ​​of various overlay measurement conditions used during overlay measurement. For example, the overlay measurement recipe may include the wavelength of the light source used for measurement, the focus of the light source, the measurement position, the measurement time, etc. Here, the setting of the overlay measurement recipe may refer to the setting of the overlay measurement conditions for performing the overlay measurement. Figure 1 The setup of the overlay measurement system 100 is shown.

[0074] After performing operation P220, overlay may be measured based on the set overlay measurement recipe (P230). Here, overlay measurement may refer to, for example, overlay measurement of an alignment mark on a substrate used for overlay measurement.

[0075] In an embodiment, the overlay measurement method may further include an operation of feeding back the overlay measurement condition based on the overlay obtained by performing operation P230 .

[0076] The overlay measurement method according to the embodiment can optimize the overlay measurement conditions based on the integrated KPF, set the overlay measurement recipe according to the optimized overlay measurement conditions, and measure the overlay based on the set overlay measurement recipe. Therefore, fast and improved overlay measurement can be performed. Figure 6A-6C and Figure 7 , the overlap measurement method according to the comparative example is compared with Figure 5 The overlap measurement method shown in is compared.

[0077] Figure 6A-6C is a graph showing overlay performance according to an overlay measurement method of a comparative example, and Figure 7 is a graph showing the overlay performance of the overlay measurement method according to the embodiment. Specifically, Figure 6A-6C showing the overlay performance of the overlay measurement method based on the overlay measurement conditions optimized by using the KPI value, and Figure 7 The overlay performance of the overlay measurement method according to the overlay measurement condition optimized by using an integrated KPF value is shown. Fig. 6A , Figure 6B and Figure 6C The KPI values ​​of the brightness of the pattern included in the alignment mark, the KPI values ​​of the defects in the alignment mark, and the KPI values ​​of the periodic signal of the pattern are respectively shown, and FIG. 6A to FIG. 7 , the closer the R2 value is to 1, the more the overlap measurement condition related to the overlap performance according to the KPI value or the KPF value is optimized.

[0078] It can be seen that referring to FIG. 6A to FIG. 6C , R2 values ​​were 0.173, 0.235 and 06736 respectively, and refer to Figure 7 , the R2 value is 0.8513. That is, the reference FIG. 6A to FIG. 7 , it can be seen that according to FIG. 6A to FIG. 6C The overlap measurement conditions optimized for each KPI value in the above example have relatively little correlation with the overlap performance. Figure 7 The overlap measurement condition optimized by an integrated KPF value in the embodiment has a relatively large correlation with the overlap performance. That is, it can be seen that when the overlap measurement condition is selected according to an integrated KPF value, the overlap performance can be further improved.

[0079] As described above, embodiments are disclosed in the drawings and the specification. In this specification, embodiments are described by using certain terms, but these terms are only used for the purpose of describing the present disclosure and are not used to limit the meaning or scope of the present disclosure described in the claims. Therefore, those skilled in the art to which the present disclosure belongs will understand that various modifications and other equivalent embodiments can be derived therefrom. Therefore, the true technical protection scope of the present disclosure should be determined by the technical ideas of the attached claims.

[0080] While the present disclosure has been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A method for optimizing overlapping measurement conditions, the method comprising: The processor executes instructions stored in the non-transitory storage medium to perform operations, the operations comprising: for each overlay measurement condition of a plurality of overlay measurement conditions, measuring overlay at a plurality of locations of the substrate; For each of the plurality of overlap measurement conditions, calculating a key parameter index (KPI) based on the measured overlap; For each of the plurality of overlapping measurement conditions, converting the KPI into a key parameter function (KPF) value based on the KPF, wherein each of the KPFs has the same dimensional representation; For each of the plurality of overlapping measurement conditions, integrating the KPF values ​​to generate an integrated KPF value; and An optimized overlay measurement condition is selected from the plurality of overlay measurement conditions based on the integrated KPF value associated with each of the plurality of overlay measurement conditions.

2. The method according to claim 1, wherein: KPF is based on multiple overlapping measurements.

3. The method according to claim 1, wherein: KPF transforms the corresponding dimensional representations of KPIs into the same dimensional representation based on multiple overlapping measurement conditions.

4. The method according to claim 1, wherein: Integrating the KPF values ​​to generate an integrated KPF value also includes adding each of the KPF values ​​to each other.

5. The method according to claim 1, wherein: Aggregating the KPF values ​​to generate an aggregate KPF value also includes assigning a weighted value to each KPF value.

6. The method according to claim 1, wherein: Selecting the optimized overlay measurement condition further includes identifying, from among the plurality of overlay measurement conditions, an overlay measurement condition associated with a maximum integrated KPF value among the integrated KPF values.

7. The method according to claim 1, wherein: The plurality of locations are associated with alignment marks of the substrate, and wherein the alignment marks include at least one of an image-based overlay (IBO) and a fringe-based overlay (FBO).

8. The method according to claim 7, wherein: The plurality of overlay measurement conditions include at least one of a wavelength of the light source, a focus of the light source, and a design of the alignment mark.

9. The method according to claim 1, further comprising: Measure overlay on multiple substrates.

10. The method according to claim 1, wherein: The number of multiple positions is based on multiple overlapping measurement conditions.

11. An overlap measurement method, comprising: The processor executes instructions stored in the non-transitory storage medium to perform operations, the operations comprising: Identify optimized overlap measurement conditions; setting an overlay measurement recipe based on the optimized overlay measurement conditions; and Measuring overlap based on the overlap measurement recipe, Among them, identifying optimized overlapping measurement conditions includes: for each of a plurality of overlay measurement conditions, measuring sample overlay at a plurality of locations of the substrate, For each of the plurality of overlap measurement conditions, a key parameter index (KPI) is calculated based on the measured sample overlap, For each of the plurality of overlapping measurement conditions, converting the KPI into a key parameter function (KPF) value based on the KPF, wherein each of the KPFs has the same dimensional representation; For each of the plurality of overlapping measurement conditions, integrating the KPF values ​​to generate an integrated KPF value; and An optimized overlay measurement condition is selected from among the plurality of overlay measurement conditions based on the integrated KPF value associated with each of the plurality of overlay measurement conditions.

12. The overlay measurement method according to claim 11, wherein: KPF is based on multiple overlapping measurements.

13. The overlay measurement method according to claim 11, wherein: KPF transforms the corresponding dimensional representations of KPIs into the same dimensional representation based on multiple overlapping measurement conditions.

14. The overlay measurement method according to claim 11, wherein: Aggregating the KPF values ​​to generate an aggregate KPF value further includes assigning weighted values ​​to the KPF values ​​and adding each of the weighted KPF values ​​to one another.

15. The overlay measurement method according to claim 14, wherein: The optimized overlap measurement condition is associated with the maximum integrated KPF value among the integrated KPF values.

16. The overlay measurement method according to claim 11, further comprising: Sample overlays of a plurality of substrates are measured, and the number of the plurality of locations is based on a plurality of overlay measurement conditions.

17. The overlay measurement method according to claim 11, further comprising: Overlap measurement conditions associated with the overlap measured based on the overlap measurement recipe are fed back.

18. A method for optimizing overlapping measurement conditions, the method comprising: The processor executes instructions stored in the non-transitory storage medium to perform operations, the operations comprising: for each overlay measurement condition of a plurality of overlay measurement conditions, measuring overlay at a plurality of locations on the substrate; For each of the plurality of overlap measurement conditions, calculating a key parameter index (KPI) based on the measured overlap; For each of the multiple overlapping measurement conditions, converting the KPI into a key parameter function (KPF) value by removing the dimensional representation of the KPI; for each of the plurality of overlapping measurement conditions, integrating the KPF values ​​to generate an integrated KPF value by adding the KPF values ​​to each other; and The overlap measurement condition associated with the maximum integrated KPF value among the integrated KPF values ​​is selected from among the plurality of overlap measurement conditions.

19. The method according to claim 18, wherein: KPIs have different dimensional representations.

20. The method according to claim 18, wherein: Aggregating the KPF values ​​to generate an aggregate KPF value also includes assigning a weighted value to each KPF value.

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