Recipe generation method and overlay measurement apparatus with recipe generation function

Abstract

The present invention relates to a recipe generation method of an overlay measurement device, and more particularly to a recipe generation method including a reference alignment mark image. The present invention provides a recipe generation method that automatically generates a recipe of an overlay measurement device, the recipe generation method including: a step of obtaining an optimal parameter candidate group; a step of setting the overlay measurement device with an existing parameter group; a step of locating an alignment mark within a measurement range of the overlay measurement device set with the existing parameter group using an existing reference alignment mark image; a step of setting the overlay measurement device with the optimal parameter candidate group; a step of obtaining a new reference alignment mark image corresponding to the optimal parameter candidate group by photographing the alignment mark using the overlay measurement device set with the optimal parameter candidate group; and a step of generating an optimal candidate recipe including the optimal parameter candidate group and the new reference alignment mark image.

Description

Technical Field

[0001] This invention relates to a recipe generation method for an overlay measuring device, and more specifically to a recipe generation method including a reference alignment mark image. Background Technology

[0002] Multiple patterned layers are sequentially formed on a semiconductor substrate. Furthermore, through techniques such as double patterning, the circuitry of a single layer can be formed by dividing it into two patterns. Only when these patterned layers, or multiple patterns within a single layer, are precisely formed at predetermined locations can the desired semiconductor device be manufactured.

[0003] Therefore, in order to confirm whether the pattern layer is accurately aligned, alignment marks formed at the same time as the pattern layer are used, namely overlay marks.

[0004] The method for measuring overlay using overlay marks is as follows: First, on a patterned layer formed in a previous process, such as an etching process, a structure as part of the overlay mark is formed simultaneously with the formation of the patterned layer. Then, in a subsequent process, such as a photolithography process, the remaining structure of the overlay mark is formed on the photoresist.

[0005] Then, an overlay measurement device is used to acquire images of the overlay structure of the patterned layer formed in the previous process (images obtained through the photoresist layer) and the overlay structure of the photoresist layer. The overlay measurement device measures the offset between the centers of these images to measure the overlay error (alignment error) value.

[0006] Figure 1 This is a plan view of an example of an engraved mark. Figure 1 The overlay mark 1 shown has four working zones 0, groups 4, 5, 6, and 7. Each working zone group 4, 5, 6, and 7 includes two working zones diagonally distributed to each other. Each working zone group 4, 5, 6, and 7 is used to measure the overlay error of the pattern layer formed together with that working zone group in the X-axis or Y-axis direction. To prevent interference, the structure 2 formed with the first pattern layer and the structure 3 formed with the second pattern layer are configured to not overlap.

[0007] Each working area includes strips arranged at constant intervals from the center of overlay mark 1 to its outer contour. Therefore, using the overlay measuring device, measurements can be obtained from the two working areas belonging to working area groups 4, 5, 6, and 7, respectively. Figure 2 The periodic signal shown. Figure 2 For example, charts can be obtained through... Figure 1 The selected region 8 is obtained by projecting along the Y-axis. That is, by adding the grayscale values ​​of pixels with the same X-value, the result can be obtained as shown below. Figure 2 The chart shown.

[0008] exist Figure 2 In the graph, the peak appears in the section with the arranged bars. Since the bars in the previous overlay marker 1 were arranged periodically, the acquired signal also exhibits periodicity. Then, the overlay error was measured by correlation analysis of the two periodic signals acquired from the two selected regions 8 and 8'.

[0009] The overlay measuring device used in such overlay error measurement has high requirements for accuracy and reliability, which requires the appropriate setting of complex measurement conditions and multiple variables.

[0010] For example, it is necessary to optimize parameters such as the wavelength band, numerical aperture (NA), focal position, and pinhole size of the illumination of the overlay measurement device.

[0011] Previously, the method used was to optimize these parameters sequentially. For example, other parameters could be fixed, and overlay marking images could be acquired and measured according to the specified wavelength band. The quality of the overlay marking images and / or the performance of the overlay measurement device could be evaluated using various quality metrics to select the optimal illumination wavelength band.

[0012] Quality metrics used to evaluate image quality include, for example, Modulation Transfer Function (MTF), Mean Squared Error (MSE), and Root Mean Square (RMS). Furthermore, quality metrics that can be used to evaluate the performance of overlay measurement devices include, for example, Final Residual 3 Sigma, Tool Induced Shift (TIS) 3 Sigma, Registration 3 Sigma, Total Measurement Uncertainty (TMU), and Move and Measure (MAM) time.

[0013] After selecting the optimal illumination wavelength band and fixing it to this optimal wavelength band, the optimal numerical aperture value can be selected through quality assessment corresponding to the numerical aperture value. Using the same method, the optimal focal position, optimal pinhole size, and other parameters can also be selected sequentially.

[0014] However, this method does not take into account the interaction between parameters, so it is difficult to regard the parameters selected by this method as the optimal set of parameters.

[0015] Therefore, instead of sequentially optimizing the parameters, a method for evaluation and optimization based on parameter sets is proposed.

[0016] To optimize the parameters using this method, candidate parameter groups need to be selected, each candidate parameter group is applied to the overlay measurement device, overlay mark images are acquired, and the quality of the acquired overlay mark images and / or the performance of the overlay measurement device are evaluated.

[0017] To acquire an image of the overlay marks, the overlay measuring device needs to identify the position of the overlay marks. For this, a reference alignment mark image corresponding to the candidate parameter set is required. The overlay measuring device identifies the portion in the captured image that matches the reference alignment mark image. Thus, the position of the overlay mark being measured can be sensed.

[0018] Each candidate parameter group requires its own corresponding reference alignment mark image. If other reference alignment mark images are used, errors may occur during the acquisition of the overlay mark images.

[0019] [Existing Technical Documents]

[0020] 1. Korean Patent Publication No. 10-2024-0089163

[0021] 2. Korean Patent Publication No. 10-2024-0067834

[0022] 3. Korean Patent Publication No. 10-2546552

[0023] 4. Korean Patent Publication No. 10-2519813 Summary of the Invention

[0024] Technical issues

[0025] The purpose of this invention is to provide a method for generating a recipe that includes various parameter values ​​and a reference alignment mark image, as well as an overlay measuring device capable of generating such a recipe.

[0026] Technical solution

[0027] To achieve the above objectives, the present invention provides a recipe generation method that automatically generates a recipe for an overlay measuring device. The recipe generation method includes: obtaining an optimal parameter candidate set; setting the overlay measuring device with an existing parameter set; using an existing reference alignment mark image to place the alignment mark within the measurement range of the overlay measuring device set with the existing parameter set; setting the overlay measuring device with the optimal parameter candidate set; photographing the alignment mark using the overlay measuring device set with the optimal parameter candidate set to obtain a new reference alignment mark image corresponding to the optimal parameter candidate set; and generating an optimal candidate recipe including the optimal parameter candidate set and the new reference alignment mark image.

[0028] Furthermore, in the provided formula generation method, the above step a) includes: a-1) selecting at least one measurement target site; a-2) while changing the parameter values ​​of the overlay measurement device, taking pictures of the overlay marks located at the measurement target site to obtain overlay mark images of each parameter group; a-3) analyzing the overlay mark images to calculate the quality index values ​​of each parameter group; a-4) selecting at least one of the optimal parameter candidate groups based on the quality index values ​​of each parameter group.

[0029] Furthermore, in the provided formula generation method, the quality index values ​​include at least one of the following: the clarity of the structure of each layer included in the overlay mark image, the periodicity, repeatability, and symmetry of the crystal lattice.

[0030] Furthermore, in the provided recipe generation method, step a-4) above is the step of selecting the optimal parameter candidate group by means of response surface methodology.

[0031] Furthermore, in the provided recipe generation method, the alignment marks are either global alignment marks for wafer alignment or overlay marks for alignment between patterned layers formed on the wafer.

[0032] Furthermore, the present invention provides an overlay measurement apparatus, including an imaging system configured to acquire an image of an alignment mark, and a controller communicatively integrated with the imaging system. In the overlay measurement apparatus, the controller includes: at least one memory including instructions, and a processor configured to execute the instructions included in the at least one memory, the processor executing the instructions to perform the following steps: a) acquiring an optimal parameter candidate set; b) setting the overlay measurement apparatus with an existing parameter set; c) using an existing reference alignment mark image to place an alignment mark within the measurement range of the overlay measurement apparatus set with the existing parameter set; d) setting the overlay measurement apparatus with the optimal parameter candidate set; e) capturing the alignment mark with the overlay measurement apparatus set with the optimal parameter candidate set to acquire a new reference alignment mark image corresponding to the optimal parameter candidate set; and f) generating an optimal candidate formula including the optimal parameter candidate set and the new reference alignment mark image.

[0033] The effects of the invention

[0034] According to the present invention, recipes including various parameter values ​​and reference alignment mark images can be automatically generated, thereby minimizing errors caused by manual operations and improving efficiency.

[0035] Furthermore, unlike existing methods that sequentially optimize parameters, deriving an optimal set of candidate parameters that considers the interactions between parameters can improve the accuracy and reliability of overlay measurements. Attached Figure Description

[0036] Figure 1 This is a plan view of an example of an engraved mark.

[0037] Figure 2 Showing from Figure 1 The signal acquired in one working area of ​​the overprinted mark shown.

[0038] Figure 3 This is a schematic diagram of an overlay measuring device according to an embodiment of the present invention.

[0039] Figure 4 This is a sequence diagram of a recipe generation method according to an embodiment of the present invention.

[0040] Figure 5 This is a sequence diagram of an example of the steps to obtain the optimal parameter candidate group.

[0041] Figure 6 It is a diagram that marks the measurement points on a semiconductor wafer with dots. Detailed Implementation

[0042] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention can be modified in many different forms, and the scope of the present invention should not be construed as limited to the embodiments detailed below. The embodiments of the present invention are provided to provide a more complete explanation of the invention to those skilled in the art. Therefore, the shapes of elements in the figures are exaggerated for clarity, and elements indicated by the same symbols in the figures refer to the same elements.

[0043] Figure 3 This is a schematic diagram of an overlay measuring device according to an embodiment of the present invention.

[0044] like Figure 3 As shown, the overlay measurement apparatus 10 includes: an imaging system 100 configured to acquire an alignment mark image including an overlay mark image and a global alignment mark image; and a controller 200. The overlay measurement apparatus 10 captures images of a semiconductor wafer W on which global alignment marks and overlay marks are formed to acquire images. The acquired alignment mark images are then analyzed to measure the overlay error between patterned layers formed on the wafer W.

[0045] The imaging system 100 of the overlay measurement apparatus 10 includes: an illumination optical system 110 for illuminating alignment marks on a semiconductor wafer W, an imaging optical system 120 for focusing reflected light from the alignment marks and imaging the alignment marks, an image detector 130 for acquiring the alignment mark image imaged by the imaging optical system 120, and a stage 140 for placing the semiconductor wafer W.

[0046] The illumination optical system 110 can be constructed using a variety of optical elements. For example, the illumination optical system 110 may include an illumination source 111, a pinhole 115, a beam splitter 116, and an objective lens 118. In addition, it may also include a lens 113 disposed between the pinhole 115 and the illumination source 111.

[0047] The illumination source 111 may include a light source capable of generating light with a wide wavelength band, and a variable optical filter capable of adjusting the wavelength band of the transmitted light.

[0048] The beam splitter 116 is positioned between the illumination source 111 and the objective lens 118, and serves to transmit the illumination from the illumination source 111 to the objective lens 118.

[0049] Objective lens 118 serves to focus illumination onto the measurement position on the surface of semiconductor wafer W and collect reflected light from the measurement position. Objective lens 118 is mounted on lens focusing driver 119. Lens focusing driver 119 is used to adjust the distance between objective lens 118 and semiconductor wafer W.

[0050] The imaging optical system 120 can be constructed using a variety of optical elements. For example, the imaging optical system 120 may include a barrel lens 123. In addition, the imaging optical system 120 may use the objective lens 118 and beam splitter 116 of the illumination optical system 110.

[0051] Objective lens 118 collects light reflected from semiconductor wafer W. The light collected by objective lens 118 passes through beam splitter 116 and is focused by lens barrel lens 123 onto image detector 130.

[0052] The image detector 130 serves to receive reflected light from the alignment mark generated by the illumination and to generate an image. The image detector 130 can be a CCD camera or a CMOS camera.

[0053] The controller 200 can be communicatively integrated with the imaging system 100 via wired or wireless means. The controller 200 may include hardware such as a processor, memory, read-only memory (ROM), a storage device such as a hard disk or solid-state drive (SSD), and wired or wireless communication devices. In addition, it may include programs such as firmware or software stored in storage media such as memory, read-only memory, and storage devices.

[0054] The controller 200 can be a microcontroller unit (MCU), desktop computer, laptop computer, smartphone, tablet computer, or other computing device.

[0055] The controller 200 of the overlay measuring device 10 can instruct the execution of the program via instructions run by the processor. Figure 4 All or some of the steps in the process. To minimize human intervention, it is preferable that all steps be executed by instruction from the controller 200.

[0056] Figure 4 This is a sequence diagram of a recipe generation method according to an embodiment of the present invention.

[0057] like Figure 4 As shown, a recipe generation method according to an embodiment of the present invention includes: obtaining an optimal parameter candidate set (S1); setting the overlay measuring device with the existing parameter set (S2); placing the alignment mark within the measurement range of the overlay measuring device (S3); setting the overlay measuring device with the optimal parameter candidate set (S4); obtaining a new reference alignment mark image (S5); and generating an optimal candidate recipe (S6).

[0058] Alignment marks can be global alignment marks used for wafer alignment or overlay marks used for alignment between patterned layers formed on the wafer.

[0059] First, the step S1 of obtaining the optimal parameter candidate group will be explained.

[0060] The parameters that constitute the candidate group of optimal parameters in step S1 may include, for example, the wavelength band of illumination, the numerical aperture value (NA), the focal position, and the size and position of the pinhole.

[0061] Figure 5 This is a sequence diagram of an example of the steps to obtain the optimal parameter candidate group.

[0062] like Figure 5 As shown, step S11 includes: selecting the measurement target site; obtaining the overlay mark image of each parameter group; calculating the quality index value of each parameter group; and selecting the optimal parameter candidate group.

[0063] First, step S11, which involves selecting at least one measurement target site, will be explained. This step S11 is the process of selecting several measurement target sites that can represent the wafer and the process.

[0064] Figure 6 This is a diagram that uses dots to mark the measurement sites on a semiconductor wafer. Each measurement site has an overlay mark formed on it. For example... Figure 6 As shown, multiple overlay marks are formed on a semiconductor wafer. The overlay marks are formed on the scribe lanes of the semiconductor wafer.

[0065] Although not illustrated, in the case of global alignment marks, they are primarily positioned near the edge of the wafer.

[0066] In this step S11, a minimum number of representative sites can be selected by analyzing existing measurement results.

[0067] Next, step S12, which involves obtaining the overlay mark images for each parameter group, will be explained.

[0068] In this step S12, firstly, a parameter group is defined. For example, parameters such as the wavelength band of illumination, numerical aperture (NA), focal position, and pinhole size can be included in the parameter group.

[0069] Next, the values ​​of the parameters included in the parameter group are changed within an adjustable range to define multiple parameter groups with different parameter values ​​from each other.

[0070] Afterwards, the overlay measuring device is set with the parameter values ​​of the parameter set, and images are taken to obtain more than one overlay mark image. This process is repeated to obtain more than one overlay mark image for each parameter set.

[0071] Next, step S13 for calculating the quality index values ​​of each parameter group will be explained.

[0072] In this step S13, the overlay mark image from the previous step S12 is analyzed. For example, the numerical values ​​of the clarity, lattice periodicity, repeatability, symmetry, etc. of the structures in each layer included in the overlay mark image can be calculated as quality index values.

[0073] An overlay marking image may include a first overlay and a second overlay, formed together with patterned layers that are different from each other. The sharpness of the first and second overlays in the overlay marking image may differ from each other. This is because there may be a height difference between the first and second overlays, and they may be composed of different materials. The periodicity, repeatability, symmetry, etc., of the lattice may also vary from layer to layer.

[0074] Next, step S14, which involves selecting at least one candidate group of optimal parameters, will be explained.

[0075] In this step S14, at least one optimal parameter candidate group is selected based on the quality index values ​​of each parameter group obtained in the previous step S13.

[0076] This step S14 can be performed, for example, using response surface methodology (RSM). RSM is a method that optimizes multiple quality index values ​​by adjusting multiple parameters.

[0077] Multinomial regression models and similar methods can be used to model the relationship between parameters and various quality indicators mathematically, and the constructed regression model can be used to plot response surface graphs. Response surface graphs visually demonstrate how parameters interact and thus affect quality indicator values. Analyzing response surface graphs makes it easy to select the optimal parameter candidate group.

[0078] Next, step S2, which involves setting up the overlay measuring device using the existing parameter set, will be explained.

[0079] Step S2 is the process of applying a pre-set set of existing parameters to accurately measure the overlay marks on the wafer.

[0080] In this stage S2, the overlay measuring device calls up the data provided by the formula and the previously stored parameter values, and sets the wavelength band of the illumination, numerical aperture (NA) value, focal position, pinhole size and position, and other options for the overlay measuring device.

[0081] The software of the overlay measurement equipment can be used to select a recipe from the list of available recipes that matches the corresponding process stage. This recipe may include various parameters, the type of alignment mark, the position of the alignment mark, including the wavelength band of illumination, numerical aperture (NA) value, focal point position, and the size and position of the pinhole.

[0082] Next, step S3, which involves placing the alignment mark within the measurement range of the overlay measuring device, will be explained.

[0083] In this step S3, the existing reference alignment mark image stored in the existing formula is used to ensure that the alignment mark being measured is within the measurement range of the overlay measuring device set with the existing parameter group.

[0084] First, the overlay measuring device calls upon the coordinates of the alignment marks defined in the formula. The overlay measuring device then adjusts itself using these coordinates to bring the alignment marks within its measurement range.

[0085] An existing reference alignment mark image stored in the formulation is loaded into the overlay measurement device. A pattern recognition algorithm compares the reference alignment mark image with an image captured by the overlay measurement device to sense the position of the alignment mark. The wafer is moved using a stage to precisely position the alignment mark within the measurement range of the overlay measurement device.

[0086] Next, step S4 of setting up the overlay measuring device with the optimal parameter candidate group will be explained.

[0087] In step S4, the overlay measuring device is reset with the optimal parameter candidate set obtained in S1, replacing the existing parameter set.

[0088] Input the parameter values ​​of the optimal parameter candidate group into the device. This can be done manually in the software or by calling a pre-stored recipe file.

[0089] Even if the wavelength band of the illumination, numerical aperture (NA), focal position, and the size and position of the pinhole of the overlay measurement device change, the alignment mark is precisely located within the measurement range of the overlay measurement device because the wafer is not moved.

[0090] Next, step S5, which involves obtaining a new reference alignment mark image, will be explained.

[0091] In step S5, an alignment mark is captured using an overlay measuring device set with optimal parameter candidate groups. This alignment mark image becomes the reference alignment mark image for the optimal parameter candidate group. Because the parameters of the overlay measuring device have been changed, a new reference alignment mark image can be obtained that is similar in shape to the existing reference alignment mark image but has significantly different quality and characteristics.

[0092] For example, while shortening the wavelength of illumination is beneficial for sensing small patterns or fine details, it may result in a shallower depth of focus. Higher numerical aperture values ​​can improve resolution, but may also lead to a shallower depth of focus. Reducing the pinhole size increases contrast and yields a sharper image, but the image may become darker, and noise may increase.

[0093] Next, step S6, which generates the optimal candidate formulation, will be explained.

[0094] In step S6, an optimal candidate recipe is generated, which includes the optimal parameter candidate group and a new reference alignment marker image.

[0095] Specify a unique name for the optimal candidate formulation and enter additional metadata (process stage, equipment type, wafer type, alignment mark location, etc.).

[0096] The generated optimal candidate formulations are stored in the controller of the overlay measuring equipment or other database. The optimal candidate formulation includes a parameter set and a reference alignment mark image. Stored optimal candidate formulations can be shared in other equipment or process lines using the same process.

[0097] Repeating the above steps yields multiple optimal candidate formulations. Furthermore, by using these optimal candidate formulations to acquire and evaluate alignment marker images, the optimal formulation can be found.

[0098] The final optimized formula is input into the controller of the overlay measuring device and stored in the database so that it can be easily retrieved whenever needed.

[0099] If the goal is to generate an optimal formula that can be used for both global alignment and overlay error measurement, steps S3 to S5 can be performed on the global alignment mark, and then steps S3 to S5 can be performed on the overlay mark to generate an optimal candidate formula that simultaneously stores the optimal candidate formula, the reference alignment mark image for global alignment, and the reference alignment mark image for overlay error measurement.

[0100] The embodiments described above are merely illustrative of preferred embodiments of the present invention. The scope of the present invention is not limited to the described embodiments. Within the scope of the technical concept and claims of the present invention, those skilled in the art will be able to make various changes, modifications or substitutions, and such embodiments should be understood to fall within the scope of the present invention.

[0101] Figure Labels

[0102] 10: Overlay measuring device; 100: Imaging system; 110: Illumination optical system; 115: Pinhole; 120: Imaging optical system; 130: Image detector; 200: Controller.

Claims

1. A recipe generation method, the method automatically generating a recipe for an overlay measuring device, the recipe generation method being characterized by comprising: a) Steps for obtaining the candidate set of optimal parameters; b) Steps for setting up the overlay measuring device using the existing parameter set; c) The step of placing the alignment mark within the measurement range of the overlay measuring device set with the existing parameter set, using an existing reference alignment mark image; d) The step of setting the overlay measuring device using the aforementioned optimal parameter candidate set; e) The step of acquiring a new reference alignment mark image corresponding to the optimal parameter candidate set by photographing the alignment mark using an overlay measuring device configured with the optimal parameter candidate set; and f) The step of generating the optimal candidate recipe, which includes the optimal parameter candidate set and the new reference alignment mark image.

2. The formula generation method according to claim 1, characterized in that, Step a) above includes: a-1) The step of selecting at least one measurement target site; a-2) The step of changing the parameter values ​​of the overlay measuring device while taking pictures of the overlay marks located at the measurement object site to obtain overlay mark images of each parameter group; a-3) The step of analyzing the overlay mark image to calculate the quality index values ​​of each parameter group; a-4) The step of selecting at least one of the optimal parameter candidate groups based on the quality index values ​​of each parameter group.

3. The formula generation method according to claim 2, characterized in that, The quality index values ​​include at least one of the following: the sharpness of the structure of each layer included in the overlay marking image, the periodicity, repeatability, and symmetry of the crystal lattice.

4. The formula generation method according to claim 2, characterized in that, Step a-4 above is the step of selecting the candidate group of optimal parameters by means of response surface methodology.

5. The formula generation method according to claim 1, characterized in that, The alignment marks are either global alignment marks for wafer alignment or overlay marks for alignment between patterned layers formed on the wafer.

6. A scaling measurement apparatus, comprising an imaging system configured to acquire an image of alignment marks, and a controller communicatively coupled to the imaging system, characterized in that, The controller comprises: The system includes at least one memory containing instructions, and a processor configured to execute the instructions contained in the at least one memory, the processor executing the instructions to perform the following steps: a) Steps for obtaining the candidate set of optimal parameters; b) Steps for setting up the overlay measuring device using the existing parameter set; c) The step of placing the alignment mark within the measurement range of the overlay measuring device set with the existing parameter set, using an existing reference alignment mark image; d) The step of setting the overlay measuring device using the aforementioned optimal parameter candidate set; e) The step of acquiring a new reference alignment mark image corresponding to the optimal parameter candidate set by photographing the alignment mark using an overlay measuring device configured with the optimal parameter candidate set; and f) The step of generating the optimal candidate recipe, which includes the optimal parameter candidate set and the new reference alignment mark image.

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