KR102738956B1 - Overlay measurement method and system - Google Patents

Abstract

The present invention is a method for measuring overlay, and according to one embodiment of the present invention, an overlay measuring method is provided. The overlay measuring method may include: (a) a step of obtaining a plurality of element-specific images measured according to changes in major elements for any target among a plurality of targets formed on a wafer; (b) a step of analyzing characteristics of the plurality of element-specific images to derive a plurality of measurement values; (c) a step of configuring an image map showing that the plurality of element-specific images change according to changes in the major elements; (d) a step of derive an optimal candidate group of measurement values composed of elements that become optimal values of an overlay measurement recipe; and (e) a step of extracting conditions of each of the major elements for the measurement values of the optimal candidate group, and derive an optimal recipe by measuring and comparing the plurality of targets with the extracted conditions.

Description

{Overlay measurement method and system}

The present invention relates to a wafer overlay measurement method, and more particularly, to an overlay measurement method and an overlay measurement system using an overlay measurement device.

In general, as technology advances, the size of semiconductor devices is shrinking and the density of integrated circuits is increasing. In order to form these integrated circuits on a wafer, many manufacturing processes must be performed so that the desired circuit structures and elements are formed sequentially at specific locations. These manufacturing processes sequentially create patterned layers on the wafer.

Through these repeated stacking processes, electrically active patterns are created within the integrated circuit. If each structure is not aligned within the tolerance allowed by the production process, interference between electrically active patterns may occur, which may cause problems in the performance and reliability of the manufactured circuit.

Accordingly, the pattern alignment error between layers is measured and verified through a measuring device, and the focus position is found through the brightness or phase difference in the target image for the wafer for measurement and verification. At this time, after the wafer is placed on the stage to measure the pattern formed on each layer of the wafer, the patterns formed at various locations on the top of the wafer are detected.

In order to maximize the productivity of the manufacturing process, an automatic measurement program (ARO, Auto Recipe Optimization) is used to automatically find the optimal process variables and recipe. The above automatic measurement program selects and measures options such as wafer characteristics, filters, apertures, focuses, and pinholes, and performs these measurements repeatedly to determine the optimal option. However, the conventional automatic measurement program has a problem in that it takes a long time from selecting the option combination to setting up the recipe, which lengthens the process time.

In particular, conventional automatic measurement programs simply search for the optimized recipe in the order of filter, aperture, focus, and pinhole. However, there is a problem that cross-checking is impossible because filter information for aperture and filter information for focus cannot be found.

The present invention is intended to solve various problems including the above-mentioned problems, and aims to provide an overlay measurement method and an overlay measurement system that perform measurements on all options to prevent missing option combinations, conduct preliminary analysis to combine options by considering interactions between option combinations, thereby disclosing an optimized recipe for an overlay measurement device, thereby reducing errors of the overlay measurement device and improving measurement accuracy. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

According to one embodiment of the present invention, an overlay measurement method is provided. The overlay measurement method may include: (a) a step of acquiring a plurality of element-specific images measured according to changes in major elements for any target among a plurality of targets formed on a wafer; (b) a step of analyzing characteristics of the plurality of element-specific images in the plurality of element-specific images to derive a plurality of measurement values for the plurality of element-specific images; (c) a step of using the plurality of measurement values to construct an image map showing that the plurality of element-specific images change according to changes in the major elements; (d) a step of deriving measurement values composed of elements that become optimal values of an overlay measurement recipe from the image map as an optimal candidate group; and (e) a step of extracting conditions of each of the major elements for the measurement values of the optimal candidate group, and deriving an optimal recipe by measuring and comparing the plurality of targets with the extracted conditions.

According to one embodiment of the present invention, the step (a) may include: (a-1) a step of changing a condition of at least one element among the main elements; (a-2) a step of measuring an image for each changed condition of the main elements for the arbitrary targets; and (a-3) a step of storing the measured image as a plurality of element-specific images.

According to one embodiment of the present invention, in the step (a), the main elements may include at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated to the plurality of targets.

According to one embodiment of the present invention, in the step (b), the characteristic value may include at least one of the clarity of each layer formed on the wafer, periodicity, repeatability, and symmetry of the grating area.

According to one embodiment of the present invention, in the step (b), the plurality of measurement values can be calculated by normalizing each of the measurement values calculated from the plurality of element-specific images.

According to one embodiment of the present invention, in the step (d), the optimal candidate group among the plurality of measurement values can be derived through response surface modeling using the plurality of measurement values as variables.

According to one embodiment of the present invention, the step (e) may include: (e-1) a step of measuring an overlay for the plurality of targets by applying conditions of the main elements extracted from the measurement values of the optimal candidate group respectively; and (e-2) a step of modeling a plurality of overlay measurement values measured with conditions of each of the optimal candidate groups for the plurality of targets to obtain an optimal recipe.

According to one embodiment of the present invention, after step (e), the method may include a step (f) of performing overlay measurement on the plurality of targets by applying the optimal recipe.

According to one embodiment of the present invention, an overlay measurement method is provided. The overlay measurement system may include an element-specific image measurement unit that acquires a plurality of element-specific images according to changes in major elements for any target among a plurality of targets formed on a wafer; a measurement value calculation unit that analyzes characteristics of the plurality of element-specific images in the plurality of element-specific images to calculate a plurality of measurement values; a matrix construction unit that uses the plurality of measurement values to construct an image map that shows that the plurality of element-specific images change according to changes in the major elements; a candidate group calculation unit that calculates measurement values composed of elements that become optimal values of an overlay measurement recipe in the image map as an optimal candidate group; and a recipe calculation unit that extracts conditions of each of the major elements for the measurement values of the optimal candidate group, measures and compares the plurality of targets with the extracted conditions, and calculates an optimal recipe.

According to one embodiment of the present invention, the element-specific image measurement unit may include a condition change unit that changes a condition of at least one element among the main elements; a change measurement unit that measures an image for each changed condition of the main elements for the arbitrary targets; and a storage unit that stores the measured image as the plurality of element-specific images.

According to one embodiment of the present invention, the main elements may include at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated to the plurality of targets.

According to one embodiment of the present invention, the characteristic value may include at least one of the sharpness of each layer formed on the wafer, periodicity, repeatability, and symmetry of the grating area.

According to one embodiment of the present invention, the measurement value calculation unit can calculate the plurality of measurement values by normalizing each of the measurement values calculated from the plurality of element-specific images.

According to one embodiment of the present invention, the candidate group generating unit can generate the optimal candidate group among the plurality of measurement values through response surface modeling using the plurality of measurement values as variables.

According to one embodiment of the present invention, the recipe generating unit may include an overlay measuring unit that measures overlay for the plurality of targets by applying conditions of the main elements extracted from the measurement values of the optimal candidate group respectively; and a modeling unit that models the plurality of overlay measurement values measured with conditions of each of the optimal candidate groups for the plurality of targets to obtain an optimal recipe.

According to one embodiment of the present invention, the present invention may include an overlay measurement unit that performs overlay measurement on the plurality of targets by applying the optimal recipe.

According to some embodiments of the present invention as described above, the measuring device can automatically perform an optimization process for measurement options of a wafer, and the time for performing pre-image measurement to derive an optimal recipe can be reduced, thereby reducing the process time.

In addition, since the interaction of all option combinations is verified, redundant elements between options can be eliminated, thereby having the effect of selecting an accurate candidate group and producing an optimal recipe. Of course, the scope of the present invention is not limited by this effect.

FIG. 1 is a drawing schematically illustrating an overlay measuring device according to one embodiment of the present invention.
Fig. 2 is a drawing showing the control unit of the overlay measuring device of Fig. 1.
FIGS. 3 to 6 are drawings showing an overlay measurement method according to one embodiment of the present invention.
FIGS. 7 and 8 are drawings showing some examples of an overlay measurement method according to one embodiment of the present invention.
FIG. 9 is a flowchart illustrating an overlay measurement system according to one embodiment of the present invention.

Hereinafter, various preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following embodiments can be modified in various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely convey the idea of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

Hereinafter, embodiments of the present invention will be described with reference to drawings that schematically illustrate ideal embodiments of the present invention. In the drawings, for example, variations in the shapes depicted may be expected depending on manufacturing techniques and/or tolerances. Accordingly, embodiments of the present invention should not be construed as being limited to the specific shapes of the regions depicted in this specification, but should include, for example, variations in shapes resulting from manufacturing.

FIG. 1 is a schematic drawing of an overlay measurement device (1000) according to one embodiment of the present invention, and FIG. 2 is a top view showing a plurality of targets of a wafer mounted on a stage (500) of the overlay measurement device (1000) of FIG. 1.

As illustrated in FIGS. 1 and 2, the overlay measurement device (1000) is a device that detects a plurality of targets (T) formed on a wafer (W) and measures alignment errors for two layers. At this time, the plurality of targets (T) may include a first overlay key and a second overlay key formed on different layers, respectively.

For example, the first overlay key may be an overlay mark formed on a previous layer, and the second overlay key may be an overlay mark formed on a current layer. The overlay mark is formed on a scribe line at the same time as forming a layer for forming a semiconductor device in a die area. For example, the first overlay key may be formed together with an insulating film pattern, and the second overlay key may be formed together with a photoresist pattern formed on the insulating film pattern. In this case, the second overlay key is exposed to the outside, but the first overlay key is covered by the photoresist layer, and may be formed of an oxide having different optical properties from the second overlay key made of a photoresist material.

Additionally, although the physical locations of the first overlay key and the second overlay key are different, their focal planes may be the same or different.

The first overlay key and the second overlay key can be formed in various shapes, and preferably, the first overlay key and the second overlay key can be formed rotationally symmetrically about the origin.

As illustrated in FIG. 1, the overlay measuring device (1000) may include a light source unit (100), a lens unit (200), a detection unit (300), and a control unit (400).

The light source unit (100) can direct illumination to a plurality of targets (T) formed on a wafer (W). Specifically, the light source unit (100) can be configured to direct illumination to a plurality of targets (T) where a first overlay key formed on a first layer laminated on the wafer (W) and a second overlay key formed on a second layer laminated above the first layer are positioned.

The light source unit (100) may include a light source (110), a spectrum filter (120), a polarizing filter, an aperture (130), and a beam splitter (140).

The light source (110) may be formed by a halogen lamp, a xenon lamp, a supercontinuum laser, a light-emitting diode, a laser induced lamp, etc., and may include various wavelengths such as ultraviolet (UV), visible light, or infrared (IR), but is not limited thereto.

The spectral filter (120) can adjust the center wavelength and bandwidth of the beam irradiated from the light source (110) to be suitable for image acquisition of the first overlay key and the second overlay key formed on the plurality of targets (T). For example, the spectral filter (120) can be formed of at least one or more of a filter wheel, a linear translation device, a flipper device, and a combination thereof.

The aperture (130) is formed of an opaque layer having a hole on top of a transparent substrate such as a glass substrate, so that light incident on the hole can pass through it. At this time, the hole is formed in multiple pieces, so that it can be used selectively depending on the size or shape of the hole.

Specifically, the aperture (130) may be formed as an opaque plate having an opening formed through which light passes, and a beam irradiated from a light source (110) may be changed into a form suitable for photographing an overlay target (T). For example, the aperture (130) may be formed with a plurality of holes through which light passes, and each hole may be formed with a different size so as to be able to control the amount of light. Accordingly, the amount of light may be controlled by selectively using the plurality of holes.

The aperture (130) can move in all directions based on the light source, that is, can control the position through which light passes by moving in the X-axis and Y-axis in a plane perpendicular to the light source.

The aperture (130) may include at least one of an aperture stop that controls the amount of light and a field stop that controls the range of the image formed.

The aperture (130) may be an aperture of the light source unit (100), and may be configured as a pinhole separate from the aperture. According to some embodiments, as shown in FIG. 1, the aperture (130) may be formed between the light source (110) and the beam splitter (140), and in other embodiments, the aperture (130) may be formed between the beam splitter (140) and the lens unit (200). In addition, the aperture (130) may be selectively formed on a path through which a beam passes.

The beam splitter (140) separates the beam from the light source (110) into two beams by transmitting part of the beam that has passed through the aperture (130) from the light source (110) and reflecting part of the beam.

As illustrated in FIG. 1, the lens unit (200) may be formed with an objective lens (210) that focuses the light onto a measurement position of one point among a plurality of targets (T), and a lens focus actuator (220) that adjusts the distance between the objective lens (210) and the plurality of targets (T) at the measurement position.

The objective lens (210) can focus the beam reflected from the beam splitter (140) onto the measurement position where the first overlay key and the second overlay key of the wafer (W) are formed and collect the reflected beam.

The objective lens (210) can be installed in a lens focus actuator (220).

The lens focus actuator (220) can adjust the distance between the objective lens (200) and the wafer (W) so that the focal plane is positioned at a plurality of targets (T).

The lens focus actuator (220) can adjust the focal length by vertically moving the objective lens (200) in the direction of the wafer (W) under the control of the control unit (400).

When measuring a wafer (W) using a lens unit (200), the area where the image is captured changes as the objective lens (210) is controlled, and at this time, the area where the wafer (W) can be captured by the objective lens (210) is the field of view. That is, the field of view (FOV) can be adjusted by the objective lens (210), and the focus can be adjusted by the lens focus actuator (220).

As illustrated in Fig. 1, the detection unit (300) can obtain a focus image at the measurement position through a beam reflected at the measurement position.

The detection unit (300) can capture the beam reflected from multiple targets (T) and passing through the beam splitter (140) to obtain images of the first overlay key and the second overlay key.

The detection unit (300) may include an optical detector capable of measuring a beam reflected from a plurality of targets (T), and for example, the optical detector may include a charge-coupled device (CCD) that converts light into charges to extract an image, a complementary metal-oxide-semiconductor (CMOS) sensor, which is one type of integrated circuit, a photomultiplier tube (PMT) that measures light, an avalanche photodiode (APD) array as a photodetector, or various sensors that generate or capture images.

The detection unit (300) may include a filter, a polarizing plate, a beam block, and may further include any collecting optical component (not shown) for collecting the illumination collected by the objective lens (210).

Additionally, the detection unit (300) can measure a global mark to confirm the correct position of the wafer (W).

A wafer (W) is placed on the upper part of the stage (500), the wafer (W) is fixed on the upper part of the stage (500), and the stage (500) can move and rotate horizontally so that a plurality of targets (T) of the wafer (W) can be measured from the upper lens unit (200).

As illustrated in FIG. 2, the control unit (400) may include a light source operation unit (410), a lens operation unit (420), a stage operation unit (430), a storage unit (440), a condition change unit (450), a measurement value calculation unit (460), an image mapping unit (470), a candidate group calculation unit (480), and a recipe calculation unit (490).

The light source operating unit (410) can control the direction of the light irradiated from the light source unit (100), the lens operating unit (420) can control the lens unit (200) to focus the light on a plurality of targets (T) and collect the reflected beams, and control the operation of the lens focus actuator (220) so that the light is focused on the plurality of targets (T) and a focus image is obtained, the stage operating unit (430) can control the X-axis or Y-axis movement of the stage (500) so that the overlay target is positioned below the lens unit (200), and the storage unit (440) can obtain and store the focus image measured through the reflected beams collected by the detection unit (300).

The condition change unit (450), measurement value calculation unit (460), image mapping unit (470), candidate group calculation unit (480), and recipe calculation unit (490) are described later in the image measurement unit (10), measurement value calculation unit (20), matrix composition unit (30), candidate group calculation unit (40), and recipe calculation unit (50) of the overlay measurement system.

In addition, although not shown, a series of processes performed in the control unit (400) may include a display unit (not shown) for the user to monitor and an input unit (not shown) for the user to directly control.

That is, through the display unit, data, images, graphs, etc. measured by the lens unit (200) and the detection unit (300) and produced through this can be confirmed, and through the input unit, the user can directly control the light source unit (100), the lens unit (200), the detection unit (300), and the stage (500), or directly select, change, and produce images, correction values, etc. of multiple targets (T).

In addition, the overlay measuring device (1000) may include a memory that stores commands, programs, logic, etc. that control the operation of each component of the overlay measuring device by the control unit (400), and components may be added, changed, or deleted as needed.

Additionally, the overlay measurement device (1000) may include a controller configured to be communicatively coupled and may include a controller including one or more processors configured to execute program instructions.

The controller may be configured to direct the overlay measurement device to generate overlay signals based on one or more selected recipes. Alternatively, the controller may be configured to receive data comprising overlay signals from the overlay measurement device. Additionally, the controller may be configured to determine an overlay associated with an overlay target based on the acquired overlay signals.

For example, the controller may include a workstation, a terminal, a personal computer, a laptop, a tablet, a mobile device, and the like.

FIGS. 3 to 6 are drawings showing an overlay measurement method according to one embodiment of the present invention, and FIGS. 7 and 8 are drawings showing some examples of an overlay measurement method according to one embodiment of the present invention.

According to one embodiment of the present invention, an overlay measurement method may include, as illustrated in FIG. 3, (a) a step of measuring a plurality of element-specific images, (b) a step of calculating a plurality of measurement values (am), (c) a step of configuring an image map (M), (d) a step of calculating an optimal candidate group (C), and (e) a step of calculating an optimal recipe.

As illustrated in FIG. 3, step (a) is a step of acquiring multiple element-specific images measured according to changes in major elements for any of multiple targets (T) formed on a wafer (W).

Specifically, the step (a) above is a step of obtaining images of a plurality of targets (T) formed on a wafer (W). At this time, the amount of change in each of the main elements for obtaining the plurality of targets (T) is set, and all images of the plurality of targets (T) can be measured according to all changes in the main elements.

At this time, the plurality of targets (T) may include three or more arbitrary targets formed on the wafer (W), and may include all targets formed on the wafer (W). In addition, the plurality of targets (T) may include targets at positions pre-stored in an automatic measurement program (ARO, Auto Recipe Optimization).

For example, as illustrated in FIG. 4, step (a) may include (a-1) a step of changing conditions of main elements, (a-2) a step of measuring images for each condition, and (a-3) a step of storing images for each element.

Specifically, the step (a-1) is a step of changing a condition of at least one of the main elements.

For example, as illustrated in FIG. 7, the main elements may include main element 1, main element 2, main element 3, ..., main element n, and each main element may include individually selectable options.

To give a more specific example, among the above main elements, main element 1 can be set to three conditions, and main element 2 can be set to two conditions.

The above main elements may include at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated with a plurality of targets (T). That is, the wavelength of the light source, the aperture, the pinhole, the focal depth, the focus, and the filter may each include various conditions, and in the step (a-1), each condition for the main elements is changed one by one.

At this time, the above main elements may also include the target's site.

The step (a-2) above is a step of measuring images for each changed condition of the main elements for the arbitrary targets. Specifically, the step (a-2) can measure images for multiple targets (T) each time the conditions for each of the main elements in the step (a-1) are changed one by one.

For example, as shown in Fig. 7, the overlay can be measured by changing the conditions of main element 1, main element 2, main element 3, ..., main element n. At this time, if main element 1 has three conditions and main element 2 has two conditions, a total of six images, all of which have different conditions of the main elements, can be measured.

The above step (a-3) is a step of saving the measured image as multiple element-specific images. For example, in the above step (a-3), a total of six images measured in the above step (a-2) can be saved as multiple element-specific images.

As illustrated in FIG. 3, the step (b) is a step of analyzing the characteristics of the plurality of element-specific images from the plurality of element-specific images to derive a plurality of measurement values (am) for the plurality of element-specific images.

Specifically, in the step (b), the characteristic values of each of the plurality of element-specific images measured in the step (a) can be analyzed.

The above characteristic value can be calculated by analyzing images acquired from multiple targets (T), and is a numerical value of a characteristic that can determine the reliability of overlay measurement. For example, as illustrated in Fig. 7, the characteristic value can include numerical values of information such as the clarity of each layer formed on the wafer (W), the periodicity, repeatability, symmetry, image clarity, and stability of the grating on the image.

In the step (b) above, one plurality of measurement values (am) are derived from one plurality of element-specific images, and the plurality of measurement values (am) may include all images obtained from the main elements that may affect the overlay measurement.

In addition, in the step (b), each of the measurement values derived from the plurality of element-specific images can be normalized. For example, as illustrated in FIG. 7, all of the measurement values can be normalized before analyzing the characteristic values of each of the plurality of element-specific images measured in the step (a), or after analyzing the characteristic values. That is, the plurality of measurement values (am) of the step (b) can be normalized values so as to form an image map (M).

For example, multiple measurement values (am) can have values between 0 and 1 as normalization values, and if it is 0, it can be judged to have a good measurement value.

As illustrated in FIG. 3, the step (c) is a step of constructing an image map (M) that shows how the plurality of element-specific images change according to changes in the main elements using a plurality of measurement values (am).

Specifically, the step (c) above is a step of modeling by configuring a matrix for multiple measurement values (am) that digitize all images obtained from the main elements. For example, as illustrated in Fig. 8, the modeling can be composed of an image map (M) of multiple measurement values (am).

As illustrated in Fig. 3, step (d) is a step of generating a plurality of images composed of elements that are optimal values of an overlay measurement recipe in an image map (M) as an optimal candidate group (C).

Specifically, in the step (d) above, the optimal candidate group (C) among the multiple measurement values (am) can be derived through response surface modeling using the multiple measurement values (am) as variables.

The above response surface analysis method is a statistical analysis method for the response surface formed by the change in the response when multiple variables have a complex effect and affect other variables. In other words, a change in any one of the above major elements can affect another of the above major elements, and accordingly, all conditions of each of the above major elements can be changed and measured, and through this, the optimal candidate group (C), which is the desired result value, can be derived.

For example, as illustrated in Fig. 8, the isoplethora of the image map (M) can be used to derive the target corresponding to the lowest area and the area locally lower than the surrounding area as the optimal candidate group (C).

More specifically, in the step (d), the interaction between the main factors can be confirmed through analysis of variance (ANOVA).

Specifically, the above characteristic value can be measured with a large difference depending on the optical conditions during the overlay measurement process. As described above, the characteristic value can include values that quantify information such as the clarity of each layer formed on the wafer (W), the periodicity, repeatability, symmetry, image clarity, and stability of the grating on the image, and the optical conditions can include the focal position, the wavelength of the irradiation light source, the bandwidth, and the lens numerical aperture as the above-described main elements.

At this time, the characteristics of the overlay measurement do not change consistently depending on the fixed and changed conditions among the optical conditions, and for example, when the wavelength is changed and other conditions are fixed, a phenomenon occurs in which the form of interaction changes depending on the remaining optical conditions.

That is, an interaction occurs in which the characteristics of the overlay measurement do not change consistently depending on the fixed and changed conditions among the optical conditions, and in the present invention, by changing all of the above major elements into fixed and changed conditions through statistical analysis of variance (ANOVA), multiple images for each element are acquired, and the degree to which each of the above major elements affects the above characteristic value can be calculated, and the strength of the interaction and interaction between the above major elements can be confirmed.

As illustrated in FIG. 3, the step (e) is a step of extracting conditions of each of the above main elements for the measurement values of the optimal candidate group (C), and measuring and comparing multiple targets (T) with the extracted conditions to derive an optimal recipe.

The above step (e) may include, as in FIG. 5, a step of (e-1) measuring an overlay for multiple targets (T) and a step of (e-2) obtaining an optimal recipe.

The above step (e-1) is a step of measuring an overlay for multiple targets (T) by applying the conditions of the main elements extracted from the measurement values of the optimal candidate group (C) to each target.

Specifically, the step (e-1) is a step of extracting conditions of the main elements for one of the measurement values constituting the optimal candidate group (C) and measuring an overlay for multiple targets (T) with the extracted conditions. In this way, in the step (e-1), an overlay can be measured for each of the conditions for all the measurement values constituting the optimal candidate group (C).

For example, as illustrated in Fig. 8, step (e-1) is a step of calculating five conditions of the main elements of five optimal candidate groups (C) when five optimal candidate groups (C) are calculated in step (d). That is, five candidate recipes can be calculated in step (e-1), and overlays can be measured for multiple targets (T) with the five calculated candidate recipes.

The above step (e-2) is a step of obtaining an optimal recipe by modeling multiple overlay measurement values measured under conditions of each optimal candidate group (C) for multiple targets (T).

The above step (e-2) can calculate a final evaluation value for each optimal candidate group (C) measured in the above step (e-1).

The above final evaluation value (Final Residual) can be a residual or TMU (Total Measurement Uncertainty) for each of multiple targets (T) measured as optimal candidates (C).

The final evaluation value is calculated, and the standard deviation of the calculated residual can be calculated. Then, three times the standard deviation value of the residual can be calculated as the final evaluation value, and the smaller the final evaluation value, the better the recipe can be evaluated.

In the above step (e-2), the candidate rankings can be calculated in order of the smallest final evaluation value.

In the above step (e), the optimal recipe can be stored in the automatic measurement program.

The above automatic measurement program is a program that performs steps (a) to (e) above, and can automatically optimize the main elements of the overlay measurement recipe. In addition, the automatic measurement program can include, in addition to the optimized recipe information regarding the operation of the measurement device, information about the measurement device and information about the wafer (W) introduced into the overlay measurement device (1000). Therefore, the automatic measurement program can automatically derive the optimal recipe through the optimized recipe information, the measurement device information, and the measurement target position information.

According to some embodiments of the present invention, the overlay measurement method may include, after step (e), a step (f) of performing overlay measurement, as illustrated in FIG. 6.

Specifically, the step (f) is a step of performing overlay measurement on a plurality of targets (T) by applying the optimal recipe. For example, the step (f) is a step of measuring a plurality of targets (T) formed on a wafer (W) with the optimal recipe stored in the automatic measurement program in the step (e).

FIG. 9 is a flowchart illustrating an overlay measurement system according to one embodiment of the present invention.

An overlay measurement system according to one embodiment of the present invention may include an image measurement unit (10), a measurement value calculation unit (20), a matrix configuration unit (30), a candidate group calculation unit (400), and a recipe calculation unit (50).

As illustrated in FIG. 9, the element-by-element image measurement unit (10) can measure a plurality of element-by-element images by changing the main elements for any of a plurality of targets (T) formed on a wafer (W).

Specifically, the element-by-element image measurement unit (10) is a step for measuring images of a plurality of targets (T) formed on a wafer (W). At this time, all images of the plurality of targets (T) can be measured for all measurement options of the main elements according to the change amount that can be set for the main elements measuring the plurality of targets (T).

The element-by-element image measurement unit (10) may include a condition change unit (11), a change measurement unit (12), and a storage unit (13).

The condition change unit (11) can change the condition of at least one of the above main elements. For example, the condition change unit (11) can set the wavelength of the light source, which is one of the above main elements, to three conditions including a first wavelength, a second wavelength, and a third wavelength, and set the aperture value, which is another of the above main elements, to two conditions including a first aperture value and a second aperture value.

The above main elements may include at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated to a plurality of targets (T). That is, the wavelength of the light source, the aperture, the pinhole, the focal depth, the focus, and the filter may each include various conditions, and the conditions for each of the main elements may be changed one by one in the condition changing unit (11).

The change measurement unit (12) can measure images for each changed condition of the main elements for the arbitrary targets. Specifically, the change measurement unit (12) can measure images for multiple targets (T) each time the conditions for each of the main elements are changed one by one in the condition change unit (11).

For example, the change measuring unit (12) can measure images for the plurality of targets (T) at the first wavelength among the wavelength conditions of the light source, measure images for the plurality of targets (T) at the second wavelength, and measure images for the plurality of targets (T) at the third wavelength. In addition, it can measure images at the first aperture value and the second aperture value, which are conditions of the aperture value, under each condition of the wavelength of the light source.

That is, when the wavelength of the light source has three conditions and the aperture value has two conditions, a total of six images, all with different conditions of the main elements, can be measured.

The condition change unit (11) and change measurement unit (12) can perform condition change and overlay measurement in parallel so that measurement can be performed under conditions set during overlay measurement.

The storage unit (13) can store the measured image as a plurality of element-specific images. For example, the storage unit (13) can store a total of six images measured by the change measurement unit (12) as a plurality of element-specific images.

As illustrated in Fig. 9, the measurement value calculating unit (20) can calculate a plurality of measurement values (am) by analyzing the characteristics of the plurality of element-specific images from the plurality of element-specific images. Specifically, the measurement value calculating unit (20) can analyze the characteristics of each of the plurality of element-specific images measured by the element-specific image measuring unit (10).

The above characteristic value can be calculated by analyzing images acquired from multiple targets (T), and is a numerical value of a characteristic that can determine the reliability of overlay measurement. For example, as illustrated in Fig. 7, the characteristic value can include numerical values of information such as the clarity of each layer formed on the wafer (W), the periodicity, repeatability, symmetry, image clarity, and stability of the grating on the image.

The measurement value generating unit (20) generates a plurality of measurement values (am) from the plurality of element-specific images, and the plurality of measurement values (am) may include values for all images obtained from the main elements that may affect overlay measurement.

In addition, the measurement value calculating unit (20) can calculate a plurality of measurement values (am) by normalizing each of the measurement values (am) calculated from the plurality of element-specific images. For example, all of the plurality of element-specific images can be normalized before analyzing the characteristic values of each of the plurality of element-specific images measured by the measurement value calculating unit (20), or after analyzing the characteristic values.

That is, the plurality of measurement values (am) of the measurement value generating unit (20) may be normalized values so as to constitute an image map (M). For example, the plurality of measurement values (am) may have values of 0 to 1 as normalized values, and if it is 0, it may be determined to be a good measurement value.

As illustrated in FIG. 9, the matrix configuration unit (30) can configure an image map (M) that shows changes in the main elements of the plurality of element-specific images according to changes in the main elements using a plurality of measurement values (am).

Specifically, the matrix configuration unit (30) can be modeled by configuring a matrix for multiple measurement values (am) that digitize all images obtained from the above main elements. At this time, the modeling can be configured as an image map (M) of the multiple element-specific images.

As illustrated in Fig. 9, the candidate group generating unit (40) can generate measurement values composed of elements that become the optimal values of the overlay measurement recipe in the image map (M) as an optimal candidate group (C).

Specifically, in the candidate group generating unit (40), the plurality of element-specific images for the plurality of measurement values (am) can be generated as an optimal candidate group (C) through response surface modeling using the plurality of measurement values (am) as variables.

For example, the candidate group generating unit (40) can construct an image map (M) with a plurality of generated measurement values (am), determine a contour map from the image map (M), and generate a target corresponding to the lowest area and a region locally lower than the surrounding area in the contour map as an optimal candidate group (C).

As illustrated in FIG. 9, the recipe generating unit (50) can extract conditions for each of the above main elements for the measurement values of the optimal candidate group (C), and measure and compare multiple targets (T) with the extracted conditions to generate an optimal recipe.

Specifically, the recipe generation unit (50) may include an overlay measurement unit (52) and a modeling unit (53).

The overlay measurement unit (52) can measure the overlay for a plurality of measurement targets (T) by applying the conditions of the above-mentioned main elements extracted from the measurement values of the optimal candidate group (C) to each of them. For example, when four optimal candidate groups (C) are produced by the candidate group production unit (40), the overlay measurement unit (52) can produce the conditions of the four above-mentioned main elements of the four optimal candidate groups (C). That is, the overlay measurement unit (52) can produce four candidate recipes, and can measure the overlay for a plurality of targets (T) with the four produced candidate recipes.

The modeling unit (53) can obtain an optimal recipe by modeling a plurality of overlay measurement values measured under conditions of each of the optimal candidate group (C) for a plurality of targets (T). For example, the modeling unit (53) can calculate a final evaluation value for each optimal candidate group (C) measured by the overlay measurement unit (52). The final evaluation value (Final Residual) can calculate a residual for each of the plurality of targets (T) measured as the optimal candidate group (C), and the standard deviation of the calculated residual can be calculated. Then, three times the standard deviation value of the residual can be calculated as the final evaluation value, and the smaller the final evaluation value, the better the recipe can be evaluated.

The modeling unit (53) can calculate the candidate ranking in order of the smallest final evaluation value.

The optimal recipe produced by the above recipe production unit (50) can be stored in an automatic measurement program.

The above automatic measurement program can automatically optimize the above main elements of the overlay measurement recipe by including each program performing the image measurement unit (10), measurement value calculation unit (20), matrix composition unit (30), candidate group calculation unit (400) and recipe calculation unit (50).

According to some embodiments of the present invention, the overlay measurement system may include an overlay measurement unit (60), as illustrated in FIG. 9.

The overlay measurement unit (50) can perform overlay measurement on the plurality of targets (T) by applying the above optimal recipe.

For example, when measuring multiple targets (T) of a wafer (W), the overlay can be measured using the optimal recipe stored in the automatic measurement program.

As described above, the overlay metrology method and the overlay metrology system of the present invention enable a metrology device to automatically perform an optimization process for measurement options of a wafer, reduce the time for performing pre-image metrology to derive an optimal recipe, and eliminate redundant elements between options by verifying the interaction of all option combinations to derive an optimal recipe.

Accordingly, when measuring overlay for a plurality of targets (T) formed on a wafer (W), the accuracy of overlay measurement for a plurality of targets (T) can be improved by measuring with an optimal recipe.

Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the appended claims.

T: Multiple targets
W: Wafer
100: Light source
110: Light source
120: Spectral Filter
130: Aperture
140: Beam splitter
200: Lens section
210: Objective lens
220: Lens Focus Actuator
300: Detection Unit
400: Control Unit
500: Stage

Claims (16)

(a) a step of acquiring a plurality of element-specific images measured according to changes in major elements for any target among a plurality of targets formed on a wafer;
(b) a step of analyzing the characteristics of the plurality of element-specific images from the plurality of element-specific images and calculating a plurality of measurement values for the plurality of element-specific images;
(c) a step of constructing an image map using the plurality of measurement values to show that the plurality of element-specific images change according to changes in the main elements;
(d) a step of generating measurement values composed of elements that are optimal values of the overlay measurement recipe in the image map as optimal candidate groups; and
(e) a step of extracting conditions of each of the main elements for the measurement values of the optimal candidate group, and measuring and comparing the plurality of targets with the extracted conditions to derive an optimal recipe;
Including,
Step (a) above,
(a-1) a step of changing the condition of at least one of the above main elements;
(a-2) a step of measuring an image for each changed condition of the main elements for the above arbitrary targets; and
(a-3) A step of saving the measured image as images for each of the plurality of elements;
Including,
In step (a) above,
Measure all images for all changes in the above key elements,
In step (a) above, the main elements are:
An overlay measurement method comprising at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated by the plurality of targets. delete delete In paragraph 1,
In the above step (b), the characteristic value is,
An overlay metrology method, comprising at least one of the sharpness of each layer formed on the wafer, periodicity, repeatability, and symmetry of the grating area. In paragraph 1,
In step (b) above,
An overlay measurement method in which the above plurality of measurement values are calculated by normalizing each measurement value calculated from the above plurality of element-specific images. In paragraph 1,
In step (d) above,
An overlay measurement method for producing the optimal candidate group among the plurality of measurement values through response surface modeling using the plurality of measurement values as variables. In paragraph 1,
Step (e) above,
(e-1) a step of measuring the overlay for the plurality of targets by applying the conditions of the main elements extracted from the measurement values of the optimal candidate group respectively; and
(e-2) A step of obtaining an optimal recipe by modeling a plurality of overlay measurement values measured under conditions of each of the optimal candidates for the plurality of targets;
An overlay measurement method comprising: In paragraph 1,
After step (e) above,
(f) a step of performing overlay measurement on the plurality of targets by applying the above optimal recipe;
An overlay measurement method comprising: An element-by-element image measuring unit that acquires a plurality of element-by-element images according to changes in major elements for any target among a plurality of targets formed on a wafer;
A measurement value calculation unit that analyzes the characteristics of the plurality of element-specific images from the plurality of element-specific images and calculates a plurality of measurement values;
A matrix configuration unit that uses the plurality of measurement values to construct an image map showing that the plurality of element-specific images change according to changes in the main elements;
A candidate group generating unit that generates a group of optimal candidates from measurement values composed of elements that become the optimal values of the overlay measurement recipe in the image map above; and
A recipe generation unit that extracts conditions of each of the above main elements for the measurement values of the above optimal candidate group, and derives an optimal recipe by measuring and comparing the plurality of targets with the extracted conditions;
Including,
The image measurement unit for each of the above elements is:
Measure all images of the multiple targets for all measurement options of the above main elements,
The image measurement unit for each of the above elements is:
A condition changing unit for changing the condition of at least one of the above main elements; and
For the above arbitrary targets, a change measurement unit that measures images for each changed condition of the main elements;
A storage unit that stores the measured image as images for each of the plurality of elements;
Including,
The above key elements are:
An overlay measurement system comprising at least one of a wavelength, an aperture (NA), a pinhole, a focal depth, a focus, and a filter of a light source irradiated by the plurality of targets. delete delete In Article 9,
The above characteristics are,
An overlay metrology system comprising at least one of the following characteristics: sharpness of each layer formed on the wafer, periodicity, repeatability, and symmetry of the grating area. In Article 9,
The above measurement value calculation unit,
An overlay measurement system that normalizes each measurement value produced from the plurality of element-specific images to produce the plurality of measurement values. In Article 9,
The above candidate group generation section is,
An overlay measurement system that derives the optimal candidate group from among the plurality of measurement values through response surface modeling using the plurality of measurement values as variables. In Article 9,
The above recipe generation section,
An overlay measurement unit that measures overlay for the plurality of targets by applying conditions of the main elements extracted from the measurement values of the above optimal candidate group to each of the above; and
A modeling unit that obtains an optimal recipe by modeling a plurality of overlay measurement values measured under conditions of each of the above optimal candidates for the above plurality of targets;
An overlay measurement system comprising: In Article 9,
An overlay measurement unit for performing overlay measurement on the plurality of targets by applying the above optimal recipe;
An overlay measurement system comprising:

Images