Overlay measurement device and overlay measurement method
By measuring and correcting the alignment error between the platform and the wafer in the wafer in the wafer incision measurement device, the problem of difficult to monitor the alignment error and offset in the incision measurement is solved, and the measurement accuracy and efficiency are improved.
Patent Information
- Application Number
- CN202410562914.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-06-09
- Filing Date
- 2024-05-08
- Publication Date
- 2024-12-10
AI Technical Summary
During the wafer incision measurement process, the platform alignment error and offset are difficult to effectively monitor and correct, resulting in long measurement time, low accuracy, and difficulty in alignment between the optical device and the platform.
A over-engraved measurement device is designed, including a light source, a lens unit, a detector and a controller, and the correction values are calculated by measuring the deviation coordinates of multiple over-engraved targets, and applied these correction values when the platform moves to reduce errors and improve the Accurate accuracy.
By continuously measuring and correcting the alignment error between the platform and wafer, the accuracy and efficiency of measurements are significantly improved, the workload of the operator is reduced, and the platform movement time is saved.
Smart Images
Figure CN119105241A_ABST
Abstract
Description
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0074412, filed on Jun. 9, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field
[0003] The present disclosure relates to wafer overlay measurement, and in particular to an overlay measurement device and an overlay measurement method. Background Art
[0004] Generally speaking, as technology develops, the size of semiconductor devices becomes smaller and the density of integrated circuits on wafers increases. In order to form integrated circuits on a wafer, many manufacturing processes need to be performed to sequentially form the required circuit structures and components at specific locations. This manufacturing process allows patterned layers to be sequentially formed on the wafer.
[0005] Through these repeated stacking processes, electrically active patterns are generated within the integrated circuit. In this case, when the individual structures are not aligned within the tolerance allowed in the production process, interference occurs between the electrically active patterns, which may lead to deterioration in the performance and reliability of the manufactured circuit. In order to measure and verify the alignment errors between these layers, an overlay measurement device is used to find the focus position based on the contrast or phase difference of the image of the wafer.
[0006] In this case, in order to measure the patterns formed on the respective layers of the wafer, the wafer is placed on a stage, and then the patterns formed at the respective positions on the upper surface of the wafer are detected.
[0007] However, the wafer may not be placed at the correct position on the stage, and may be placed on the stage in a partially misaligned or rotationally misaligned state. In this case, there is a problem that it takes a long time to move the stage to detect the pattern.
[0008] Furthermore, in order to detect the pattern formed at each position on the top of the wafer, the stage is moved to each position. In this case, due to the quality of the lens used for stage leveling, due to the vibration generated when the stage is moved, and due to the error generated during the movement, the optical device and the stage cannot be well aligned vertically, or the alignment operation of the pattern with the center of the field of view (FOV) of the optical device must be performed every time the stage is moved for optical alignment of the optical device. Summary of the invention
[0009] The present disclosure aims to solve the above problems. Therefore, its purpose is to provide an overlay measurement device and an overlay measurement method, wherein during the overlay measurement process, the alignment error between the wafer and the platform and the offset occurring each time the platform moves are continuously measured and corrected to improve the accuracy of the correction.
[0010] The purpose of the present disclosure is not limited to the above-mentioned purpose. Other purposes and advantages not mentioned in the present disclosure can be understood based on the following description, and can be more clearly understood based on the embodiments of the present disclosure. In addition, it is easy to understand that the means described in the claims and their combinations can be used to achieve the purposes and advantages of the present disclosure.
[0011] A first aspect of the present disclosure provides an overlay measurement device, comprising: a light source, which is configured to direct light to a plurality of overlay targets formed on a wafer; a lens unit, comprising: an objective lens, which is configured to focus the light onto a measurement position of one of the plurality of overlay targets; and a lens focusing driver, which is configured to adjust the distance between the objective lens and the surface of the wafer at the measurement position; a detector, which is configured to acquire a focused image at the measurement position based on a light beam reflected from the measurement position; a platform for placing the wafer; and a controller, which is configured to: control the lens unit, the detector and the platform to measure a preset overlay target for collection among the plurality of overlay targets; collect target coordinates of the overlay target for collection that deviate from the center of the field of view FOV of the lens unit; calculate a correction value based on the target coordinates; move the platform while applying the correction value; and control the lens unit, the detector and the platform to measure at least one overlay target for application among the plurality of overlay targets.
[0012] In one embodiment of the overlay measurement device, the controller includes: a platform driver configured to control the movement of the platform; a memory for storing therein images of the overlay target for collection and images of the overlay target for application acquired using the detector; an offset calculator configured to calculate the distance between the target coordinates of the overlay target for collection and the center of the field of view of the lens unit; and a correction value calculator configured to calculate the correction value based on the target coordinates.
[0013] In one embodiment of the overlay measurement device, during the measurement of the overlay target for collection, the platform driver is configured to control the platform so that the overlay targets for collection are measured sequentially, the sequence being from the overlay target for collection formed at a position closest to the center of the wafer to the overlay target for collection formed at a position farthest from the center of the wafer.
[0014] In one embodiment of the overlay measurement device, the correction value calculator is configured to calculate an average value of distances between a plurality of target coordinates repeatedly measured by the detector and the center of the field of view of the lens unit as the correction value.
[0015] In one embodiment of the overlay measurement device, the offset calculator is further configured to calculate a distance between target coordinates of the overlay target for application and a center of the field of view of the lens unit.
[0016] In one embodiment of the overlay measurement device, the lens unit and the detector are configured to measure a global mark formed on the wafer; wherein the controller is further configured to: calculate a reference coordinate of the wafer based on the global mark; and apply the reference coordinate to calculate the correction value, wherein the alignment error between the platform and the wafer is corrected based on the correction value.
[0017] A second aspect of the present disclosure provides an overlay measurement method, comprising: a measurement step for an overlay target for collection, including: moving a platform for placing a wafer; using a lens unit and a detector to measure at least one overlay target for collection among a plurality of overlay targets; collecting target coordinates of the overlay target for collection that deviate from the center of the field of view of the lens unit; and measuring the overlay value of the overlay target for collection; a correction value calculation step of calculating a correction value based on the target coordinates, wherein an error caused by the movement of the platform is corrected based on the correction value; and a measurement step for an overlay target for application, including: moving the platform while applying the correction value; using the lens unit and the detector to measure at least one overlay target for application among the plurality of overlay targets; and measuring the overlay value of the overlay target for application.
[0018] In one embodiment of the overlay measurement method, the step of measuring the overlay target for collection includes: a first platform movement step of moving the platform for placing the wafer so that the lens unit is located above a position where the overlay target for collection is formed; a first pattern measurement step of measuring the overlay target for collection using the lens unit and the detector; and an offset calculation step of calculating the distance between the target coordinates of the overlay target for collection and the center of the field of view of the lens unit.
[0019] In one embodiment of the overlay measurement method, the step of measuring the overlay targets for collection includes: measuring the first overlay target for collection, the second overlay target for collection to the nth overlay target for collection among the multiple overlay targets; and collecting the first target coordinates of the first overlay target for collection that deviates from the center of the field of view of the lens unit, the second target coordinates of the second overlay target for collection that deviates from the center of the field of view of the lens unit to the nth target coordinates of the nth overlay target for collection that deviates from the center of the field of view of the lens unit.
[0020] In one embodiment of the overlay measurement method, the first overlay target for collection, the second overlay target for collection to the nth overlay target for collection are arranged in increasing order of the distance between them and the center of the wafer; wherein the measurement step of the overlay target for collection includes: moving the platform to a position where the first overlay target for collection is formed at a position closest to the center of the wafer, and measuring the first overlay target for collection; and moving the platform to a position where the second overlay target for collection is formed at a position second closest to the center of the wafer, and measuring the second overlay target for collection.
[0021] In one embodiment of the overlay measurement method, in the correction value calculation step, the average value of the distances between multiple target coordinates repeatedly measured in the measurement step for collecting overlay targets and the center of the field of view of the lens unit is calculated as the correction value.
[0022] In one embodiment of the overlay measurement method, the measuring step of the overlay target for application includes: a second platform moving step of applying the correction value to move the platform so that the lens unit is located above a position where the overlay target for application is formed; and a second pattern measuring step of measuring the overlay target for application using the lens unit and the detector.
[0023] In one embodiment of the overlay measurement method, the step of measuring the overlay target for the application includes: measuring a first overlay target for the application, a second overlay target for the application to an nth overlay target for the application among the multiple overlay targets; and applying the correction value to moving the platform in order to measure the first overlay target for the application, the second overlay target for the application to the nth overlay target for the application.
[0024] In one embodiment of the overlay measurement method, the method further includes: after the measurement step of the overlay target for application, repeating the correction value calculation step; wherein the measurement step of the overlay target for application includes calculating the distance between the additional target coordinates of the overlay target for application and the center of the field of view; wherein the correction value calculation step includes further calculating the correction value based on the additional target coordinates.
[0025] In one embodiment of the overlay measurement method, the method further includes: a wafer coordinate calculation step of calculating the reference coordinates of the wafer based on the measurement results of the global mark formed on the wafer using the lens unit and the detector before the measurement step of the overlay target for collection; wherein the correction value calculation step includes applying the reference coordinates to the calculation of the correction value to correct the alignment error between the platform and the wafer.
[0026] According to some embodiments of the present disclosure as described above, the overlay measurement device and method according to the present disclosure can calculate the offset value from the measurement position of some preset overlay targets for collection among multiple overlay targets formed on the wafer, and can apply the offset value as a correction value to the remaining overlay targets for application among the multiple overlay targets, thereby correcting the error generated each time the platform moves, reducing the error generated each time the measurement is performed, and saving the travel time consumed by the platform to move to the measurement position. The result is that the accuracy of the measurement can be improved, and the workload of the operator can be reduced.
[0027] The effects of the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned above will be clearly understood by those skilled in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is a schematic diagram showing an overlay measurement device according to an embodiment of the present disclosure.
[0029] Figure 2 is a schematic diagram showing a controller of the overlay measurement device of the present disclosure.
[0030] Figures 3 to 6is a flow chart illustrating an overlay measurement method according to various embodiments of the present disclosure.
[0031] Figure 7 is a top view showing a state in which a wafer on which a global mark and a plurality of overlay targets according to an embodiment of the present disclosure are formed is located on a stage.
[0032] Figure 8 and Fig. 9 is a top view showing a measurement step for collecting an overlay target according to an embodiment of the present disclosure.
[0033] Fig.10 and Fig.11 is a top view showing a measurement step of an overlay target for application according to an embodiment of the present disclosure. DETAILED DESCRIPTION
[0034] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.
[0035] Embodiments of the present disclosure are provided to more completely describe the present disclosure for those skilled in the art. The following embodiments may be modified in various forms, and the scope of the present disclosure is not limited to the following embodiments. On the contrary, these embodiments are provided to make the present disclosure comprehensive and complete, and these embodiments are provided to fully convey the spirit of the present disclosure to those skilled in the art. In addition, for convenience and clarity of description, the thickness or size of each layer in the drawings is exaggeratedly depicted. The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings describing the embodiments of the present disclosure are exemplary, and the present disclosure is not limited thereto. The same reference numerals herein refer to the same elements.
[0036] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, the singular constructions "a" and "an" are intended to also include plural constructions unless the context clearly indicates otherwise. It should be further understood that when the terms "comprise" and "include" are used in this specification, the presence of the features, integers, operations, elements and / or parts is specified, but the presence or addition of one or more other features, integers, operations, elements, parts and / or parts thereof is not excluded.
[0037] Embodiments of the present disclosure will be described below with reference to the accompanying drawings that schematically illustrate ideal embodiments of the present disclosure. In the accompanying drawings, variations in the shapes depicted may be expected, for example, depending on manufacturing techniques and / or tolerances. Therefore, embodiments of the present disclosure should not be construed as limited to the specific shapes of the regions shown herein, and should include, for example, variations in shape caused during the manufacturing process.
[0038] The overlay measurement system is a system that measures an error between a first overlay key and a second overlay key formed on different layers formed on a wafer W, respectively.
[0039] For example, the first set of engraving keys may be an overlay mark formed on a previous layer, and the second set of engraving keys may be an overlay mark formed on a current layer. When a layer for molding a semiconductor device is formed in a mold region, the overlay mark is formed on a scribe line. For example, the first set of engraving keys may be formed together with an insulating film pattern, and the second set of engraving keys may be formed together with a photoresist pattern formed on the insulating film pattern. In this case, the second set of engraving keys is exposed to the outside, but the first set of engraving keys is covered by a photoresist layer, and the first set of engraving keys may be made of an oxide having optical properties different from those of the second set of engraving keys made of a photoresist material.
[0040] Furthermore, the physical positions of the first set of engraving keys and the second set of engraving keys are different from each other, while their focal planes may be the same as or different from each other.
[0041] Figure 1 is a schematic diagram showing an overlay measurement device according to an embodiment of the present disclosure. Figure 2 is a schematic diagram showing a controller 400 of the overlay measurement device of the present disclosure.
[0042] First, the overlay measurement device according to an embodiment of the present disclosure may mainly include a light source 100 , a lens unit 200 , a detector 300 , a controller 400 , and a platform 500 .
[0043] like Figure 1 As shown, the light source 100 can irradiate light onto a plurality of overlay targets T formed on the wafer W. Specifically, the light source 100 can be configured to irradiate light onto the overlay targets T where a first overlay key formed on a first layer stacked on the wafer W and a second overlay key formed on a second layer stacked above the first layer are located.
[0044] For example, the light source 100 may be composed of a halogen lamp, a xenon lamp, a supercontinuum laser, a light emitting diode, a laser sensor lamp, etc., and may irradiate light of various wavelengths, such as ultraviolet (UV) light, visible light or infrared (IR) light, etc. However, the present disclosure is not limited thereto.
[0045] The overlay measurement apparatus according to an embodiment of the present disclosure may further include an aperture 110 , a spectral filter 120 , a polarization filter (not shown), and a beam splitter 140 .
[0046] The stop 110 may be formed as an opaque plate having an opening through which light passes, and the light beam emitted from the light source 100 may thereby be converted into a form suitable for photographing the plurality of overlay targets T.
[0047] The aperture 110 may include one or more aperture apertures for controlling the amount of light, and a field of view aperture for adjusting the focus range of an image. Figure 1 As shown, a stop may be formed between the light source 100 and the beam splitter 140. Although not shown, a stop may also be formed between the beam splitter 140 and the lens unit 200.
[0048] The spectral filter 120 can adjust the central wavelength and bandwidth of the light beam emitted from the light source 100 so as to be suitable for acquiring images of the first overlay key and the second overlay key formed in the plurality of overlay targets T. For example, the spectral filter 120 can be composed of at least one of a filter wheel, a linear translation filter device, a flip filter device, and a combination thereof.
[0049] The beam splitter 140 transmits a portion of the light beam from the light source 100 and transmitted through the aperture 110 and reflects another portion of the light beam, thereby splitting the light beam from the light source 100 into two sub-beams.
[0050] like Figure 1 As shown, the lens unit 200 may include an objective lens 210 that focuses light onto a measurement position of one of a plurality of overlay targets T, and a lens focus driver 220 that adjusts a distance between the objective lens 210 and the plurality of overlay targets T.
[0051] The objective lens 210 may focus the light beam reflected from the beam splitter 140 onto a measurement position where the first set of engraved keys and the second set of engraved keys of the wafer W are formed, and collect the light beam reflected from the position.
[0052] The objective lens 210 may be installed in the lens focusing driver 220 .
[0053] The lens focusing driver 220 can adjust the distance between the objective lens 200 and the wafer W so that the focal planes are located at the plurality of overlay targets T, respectively.
[0054] The lens focus driver 220 may adjust the focal length by vertically moving the objective lens 200 toward the wafer W under the control of the controller 400 .
[0055] When measuring the wafer W using the lens unit 200, the area where the image is captured changes as the objective lens 210 is controlled. In this case, the area where the wafer W can be captured by the objective lens 210 is the FOV (field of view). That is, the FOV (field of view) can be adjusted by the objective lens 210, and the focal length can be adjusted by the lens focus driver 220.
[0056] Furthermore, the lens unit 200 may measure the global mark GM to check the correct position of the wafer W.
[0057] like Figure 1As shown, the detector 300 can acquire a focused image at the measurement position by means of a light beam reflected from the measurement position.
[0058] The detector 300 may capture light beams reflected from the plurality of overlay targets T and then passing through the beam splitter 140 , and acquire images of the first overlay key and the second overlay key based on the captured light beams.
[0059] The detector 300 may include an optical detector capable of measuring light beams reflected from a plurality of overlay targets T. For example, the optical detector may include a charge-coupled device (CCD) that extracts an image by converting light into electric charge, a complementary metal-oxide-semiconductor (CMOS) sensor as one of integrated circuits, a photomultiplier tube (PMT) for measuring light, an avalanche photodiode (APD) array as a photodetector, or various sensors for generating or capturing images.
[0060] The detector 300 may include filters, polarizers, and beam blocks, and may further include any optical collection components (not shown) for collecting light collected by the objective lens 210 .
[0061] Furthermore, the detector 300 may measure the global mark GM to check the correct position of the wafer W.
[0062] The platform 500 may be configured to place and fix the wafer W thereon, and may be configured to be horizontally movable and rotatable so that the fixed lens unit 200 thereon may measure a plurality of overlay targets T of the wafer W.
[0063] like Figure 1 As shown, the controller 400 can control the direction of light emitted from the light source 100. The controller can control the lens unit 200 to focus the light onto a plurality of overlay targets T and collect reflected light beams therefrom. The controller can control the detector 300 to obtain a focused image measured by the reflected light beams collected by the lens unit 200, and can control the platform 500 to move so that the overlay targets are located below the lens unit 200.
[0064] In addition, the controller 400 can control the lens unit 200, the detector 300, and the platform 500 to measure a preset overlay target A for collection among the multiple overlay targets T. The controller 400 can collect the target coordinates of the overlay target deviating from the center C of the FOV of the lens unit 200, calculate the correction value through the target coordinates, apply the correction value to move the platform 500, and control the lens unit 200, the detector 300, and the platform 500 to measure at least one overlay target B for application among the multiple overlay targets T.
[0065] Specifically, the controller 400 may include a light source driver 410 , a lens driver 420 , a stage driver 430 , a memory 440 , an offset calculator 450 , a correction value calculator 460 , and an overlay measurement unit 470 .
[0066] like Figure 2 As shown, the light source driver 410 may control the direction of light emitted from the light source 100, and the lens driver 420 may control the operation of the lens focus driver 220, thereby focusing the light on a plurality of overlay targets T and obtaining a focused image.
[0067] like Figure 2 As shown, the platform driver 430 can control the movement of the platform 500 so that the overlay target is located below the lens unit 200. Specifically, the platform driver 430 can control the movement and rotation of the wafer W so that the positions of the multiple global marks GM and the multiple overlay targets T formed on the wafer W can be measured through the lens unit 200.
[0068] Specifically, the stage driver 430 may control the movement of the stage 500 so as to detect an overlay target A for collection for collecting offset data in overlay measurement, and detect an overlay target B for application to which the offset data is applied in overlay measurement, among the plurality of overlay targets T. For example, according to the preset classification of the plurality of overlay targets T, the stage driver 430 may move the stage 500 to a set position of the overlay target A for collection, but may also apply a correction value described later to the determination of the set position to move the stage 500 to the overlay target B for application.
[0069] In this regard, among the plurality of overlay targets T, the overlay target A for collection and the overlay target B for application may be preset and may vary with different wafers W.
[0070] Moreover, the platform driver 430 can control the platform 500 to move to a preset measurement position of the overlay target A for collection and the overlay target B for application. In this regard, the preset measurement position can move around the center of the overlay target. However, in actual movement, due to errors occurring during the movement, the center C of the FOV (field of view) may deviate from the center of the overlay target. Therefore, the correction value to be described later may be applied to control the movement of the platform 500.
[0071] When measuring the overlay target A for collection, the platform driver 430 can control the platform 500 so that measurement can be performed sequentially in order from the overlay target A for collection formed at the position closest to the center of the wafer W to the overlay target A for collection formed at the position farthest from the center of the wafer W.
[0072] In addition, when measuring the overlay target B for the application, the platform driver 430 can control the platform 500 so that measurement can be performed sequentially in order from the overlay target B for the application formed at the position closest to the center of the wafer W to the overlay target B for the application formed at the position farthest from the center of the wafer W.
[0073] like Figure 2 As shown, the memory 440 may store therein the image of the overlay target A for collection and the image of the overlay target B for application acquired by the detector 300 .
[0074] For example, the stage driver 430 may control the stage so that a plurality of overlay targets T formed on the wafer W are placed below the lens unit 200. Accordingly, the lens driver 420 may control the objective lens 210 and the lens focus driver 220 to obtain images of the plurality of overlay targets T measured at each position and store the images in the memory 440.
[0075] In this regard, the images of the plurality of overlay targets T stored in the memory 440 may be classified into images of the overlay target A for collection and images of the overlay target B for application.
[0076] The image of the overlay target A for collection refers to an image measured without applying the correction value calculated by the correction value calculator 460 , and the image of the overlay target B for application refers to an image measured applying the correction value calculated by the correction value calculator 460 .
[0077] The offset calculator 450 may calculate a distance between a position of an overlay target image obtained by measuring a plurality of overlay targets T using the lens unit 200 and a center C of a FOV (Field of View) and a rotation direction of the position relative to the center C.
[0078] Specifically, the offset calculator 450 may calculate the distance between the target coordinates for the collected overlay target A and the center C of the FOV of the lens unit 200. For example, the offset calculator 450 may set the center C of the FOV (field of view) to the center origin coordinates (0, 0), and may calculate the distance between the target coordinates (x and y) of the measured image for the collected overlay target A and the center origin coordinates (0, 0).
[0079] In addition, the offset calculator 450 can calculate an angle that represents the angle of rotational offset of the measured target coordinates (x and y) of the overlay target A for collection relative to the center C of the FOV. For example, the rotational offset angle can be obtained by calculating the angle between the X-axis symmetry line of the overlay target A for collection and the X-axis of the FOV (field of view).
[0080] In addition, the offset calculator 450 may calculate the distance between the target coordinates for the applied overlay target B and the center C of the FOV of the lens unit 200. For example, the offset calculator 450 may set the center C of the FOV (field of view) to the center origin coordinates (0, 0), and may calculate the distance between the target coordinates (x and y) of the measured image of the applied overlay target B and the center origin coordinates (0, 0).
[0081] In addition, the offset calculator 450 can calculate an angle that represents the angle of rotational offset of the measured target coordinates (x and y) of the overlay target B for application relative to the center C of the FOV. For example, the rotational offset angle can be obtained by calculating the angle between the X-axis symmetry line of the overlay target B for application and the X-axis of the FOV (field of view).
[0082] The correction value calculator 460 may calculate the correction value based on the target coordinates. For example, when the offset calculator 450 calculates the target coordinates as (x and y), the correction value calculator 460 may calculate (-x and -y) as the correction value.
[0083] Furthermore, when a plurality of overlay targets T are detected, the correction value calculator 460 may calculate an average value of distances between a plurality of target coordinates repeatedly measured by the detector 300 and the center C of the FOV of the lens unit as a correction value.
[0084] The controller 400 may calculate reference coordinates of the wafer W based on the global mark GM and calculate correction values using the reference coordinates. An alignment error between the stage 500 and the wafer W is corrected based on the correction values.
[0085] Specifically, the state of the wafer W on the platform 500 may be checked based on the global mark GM measured by the lens unit 200 and the detector 300. For example, when the wafer W is located on the upper surface of the platform 500 in a partially misaligned manner or in a rotationally biased manner, the measurement result of the global mark GM measured by the lens unit 200 may be partially misaligned or rotationally biased.
[0086] Based on the global mark GM, the distance and angle of the deviation of the wafer W relative to the platform 500 can be calculated, and a reference value that can be used to correct the deviation can be calculated. When the platform 500 is moved to measure multiple overlay targets T, the reference value can be applied to ensure that the overlay target of the wafer W is located at the center C of the field of view (FOV) of the lens unit 200.
[0087] The overlay measurement unit 470 may collect offset values and measure overlay values of all targets based on images of a plurality of overlay targets T including an overlay target A for collection for measuring overlay and an overlay target B for application for measuring overlay after applying a correction value.
[0088] Furthermore, the overlay measurement apparatus may include a display unit (not shown) so that the user can monitor a series of processes performed in the controller 400. The overlay measurement apparatus may include an input unit (not shown) through which the user can directly control the series of processes.
[0089] That is, on the display unit, the memory 440, the offset calculator 450, the correction value calculator 460 and the overlay measurement unit 470, as well as the data and images calculated thereby can be checked by the user. Through the input unit, the user can directly control the light source driver 410, the lens driver 420, the stage driver 430, or directly select, change, and calculate the images and correction values of the plurality of overlay targets T.
[0090] Furthermore, the overlay measurement device may include a memory storing therein instructions, programs, logic, etc. so that the operation of each component of the overlay measurement device is controlled by the controller 400. Certain components may be added, modified, or deleted as needed.
[0091] In other words, the overlay measurement device according to the present disclosure can calculate the offset value from the measurement positions of some preset overlay targets A for collection among the multiple overlay targets T formed on the wafer W, and can apply the offset value as a correction value to the remaining overlay targets B for application among the multiple overlay targets T, thereby correcting the error generated each time the platform 500 moves, reducing the error generated each time measurement is performed, and saving the travel time consumed by the platform to move to the measurement position.
[0092] In particular, the value of the offset may be calculated from the overlay target A for collection without applying a correction. Therefore, the average offset value may be calculated according to the movement of the platform 500. The measurement time may be reduced by applying the correction value only to the overlay target B for application.
[0093] Figures 3 to 6 is a flow chart illustrating an overlay measurement method according to various embodiments of the present disclosure. Figure 7 1 is a plan view showing a state in which a wafer W having a global mark GM and a plurality of overlay targets T formed thereon is located on a stage 500 . Figure 8 and Fig. 9 is a top view showing a measurement step S100 for collecting an overlay target according to an embodiment of the present disclosure. Fig.10 and Fig.11 is a top view showing a measurement step S300 of an overlay target for application according to an embodiment of the present disclosure.
[0094] The overlay measurement method according to an embodiment of the present disclosure may include a measurement step S100 for a collected overlay target, a correction value calculation step S200, and a measurement step S300 for an applied overlay target.
[0095] like Figure 3 As shown, the measurement step S100 for collecting the overlay target includes moving the platform 500 for placing the wafer W; using the lens unit 200 and the detector 300 to measure at least one overlay target A for collecting among multiple overlay targets T; collecting the target coordinates of the overlay target A for collecting that deviates from the center C of the field of view of the lens unit 200; and measuring the overlay value of the overlay target A for collecting.
[0096] Specifically, Figure 4 As shown, the measurement step S100 for the collected overlay target may include a first stage moving step S110 , a first pattern measuring step S120 , and an offset calculating step S130 .
[0097] The first stage moving step S110 is a step of moving the stage 500 on which the wafer W is placed so as to position the lens unit 200 above a position where the overlay target A for collection is formed. The first pattern measuring step S120 is a step of measuring the overlay target A for collection using the lens unit 200 and the detector 300.
[0098] The offset calculation step S130 is a step of calculating the distance between the center C and the target coordinates of the collected overlay target A that are offset from the center C.
[0099] For example, in the first platform moving step S110, the platform may be moved so that the first overlay target A-1 for collection is located at the center C of the FOV of the lens unit 200. In this regard, the movement of the platform 500 may be controlled so that the center of the first overlay target A-1 for collection coincides with the center C of the FOV (field of view). However, in practice, due to errors generated during the movement, the center C of the FOV (field of view) may not coincide with the center of the overlay target.
[0100] Therefore, the error can be measured in the first pattern measuring step S120 and calculated in the offset calculating step S130. Figure 8 As shown, the measured first overlay target A-1 for collection may deviate from the center C of the FOV (field of view) of the lens unit. At this time, the target coordinates of the first overlay target A-1 for collection can be calculated as (x and y).
[0101] In this regard, the measurement step S100 for collecting overlay targets can measure the first overlay target A-1 for collection, the second overlay target A-2 for collection to the nth overlay target An for collection among multiple overlay targets T, and can collect the first target coordinates of the first overlay target A-1 for collection that deviates from the center of the field of view of the lens unit 200, the second target coordinates of the second overlay target A-2 for collection that deviates from the center of the field of view of the lens unit 200 to the nth target coordinates of the nth overlay target An for collection that deviates from the center of the field of view of the lens unit 200.
[0102] The step S100 of measuring the collected overlay target may be repeated to measure a plurality of collected overlay targets A. For example, Figure 8 As shown, in the first platform moving step S110, the platform 500 may be moved so that the first overlay target A-1 for collection is located below the lens unit 200. In the first pattern measuring step S120, the first overlay target A-1 for collection may be measured. Then, in the offset calculating step S130, the distance between the center C of the FOV and the first target coordinates of the first overlay target A-1 for collection that deviates from the center C may be calculated.
[0103] The first target coordinates calculated in this way can be stored in a memory, and the second overlay target A-2 for collection formed at a position different from the first overlay target A-1 for collection can be measured in the same way, such as Fig. 9 Therefore, the second target coordinates of the second overlay target A-2 for collection can be calculated and stored in the memory.
[0104] In this regard, the overlay target A for collection among the plurality of overlay targets T may be preset, and the preset may vary from wafer to wafer.
[0105] Furthermore, the measurement order of the overlay targets A for collection may preferably be preset to be along a direction from the center of the wafer W to the edge thereof.
[0106] For example, in the measurement step S100 of the collected overlay targets, the first collected overlay target A-1, the second collected overlay target A-2 to the nth collected overlay target An can be sorted in increasing order of the distance between them and the center of the wafer W.
[0107] For example, Figure 8 As shown, the overlay target T formed at the center of the wafer W is set as the first overlay target A-1 for collection. Fig. 9 As shown, the overlay target T closest to the first overlay target A-1 for collection may be set as the second overlay target A-2 for collection.
[0108] Therefore, the first overlay target A-1 for collection and the second overlay target A-2 for collection may be measured, and then the third overlay target A-3 for collection and the fourth overlay target A-4 and the fifth overlay target A-5 for collection may be measured.
[0109] That is, in the measurement step S100 of the overlay target for collection, the platform 500 moves to a position where a first overlay target A-1 for collection is formed at a position closest to the center of the wafer W, and the first overlay target A-1 for collection can be measured. Then, the platform 500 moves to a position where a second overlay target A-2 for collection is formed at a position second closest to the center of the wafer W, and the second overlay target A-1 for collection can be measured. Accordingly, the first target coordinates and the second target coordinates having different measurement values due to errors generated during initial placement of the wafer on the platform and errors generated when the platform 500 is moved can be calculated.
[0110] like Figure 3 As shown, the correction value calculation step S200 is a step of calculating a correction value based on the target coordinates to correct the error generated when the platform 500 moves.
[0111] In the process of repeatedly measuring multiple overlay targets A for collection, the correction value calculation step S200 may include calculating the average value of the distances between the multiple target coordinates repeatedly measured in the measurement step S100 for collecting overlay targets and the center C of the field of view of the lens unit 200 as the correction value.
[0112] In other words, the correction value can be calculated by six-parameter modeling of the repeatedly measured pattern recognition (PR) offset for the collected overlay target A. For example, using the PR offset on the wafer, the translation, rotation and scaling components of its change can be calculated.
[0113] That is, the average values of the first target coordinate, the second target coordinate to the nth target coordinate may be calculated as the correction value, which may then be applied to the measurement step S300 of the overlay target for application, which step will be described later.
[0114] like Figure 3 As shown, the measuring step S300 of the overlay target for application may include applying a correction value to move the platform 500; measuring at least one overlay target B for application among multiple overlay targets T using the lens unit 200 and the detector 300; and measuring the overlay value of the overlay target B for application.
[0115] Specifically, Figure 4 As shown, the measuring step S300 for the applied overlay target may include a second stage moving step S310 and a second pattern measuring step S320.
[0116] The second stage moving step S310 is a step of moving the stage 500 by applying the correction value so that the lens unit 200 is located above a position where the overlay target B for application is formed. The second pattern measuring step S320 is a step of measuring the overlay target B for application using the lens unit 200 and the detector 300.
[0117] For example, in the second stage moving step S310, the stage may be moved so that the overlay target B for application is located at the center of the FOV (field of view). In this regard, the stage 500 may be moved while applying the correction value calculated in the correction value calculating step S200, and then the second pattern measuring step S320 may be performed.
[0118] Accordingly, the first overlay target B-1 for application may be measured to be deviated from the center C of FOV. At this time, the distance that the first overlay target B-1 for application deviates from the center of FOV may be smaller than the distance that the overlay target A for collection deviates from the center C of FOV.
[0119] For example, Fig.10 The distance that the first overlay target B-1 for application to which the correction value is applied deviates from the center C of the FOV is less than Figure 8 and Fig. 9The overlay target A for collection without the correction values applied is shown offset from the center C of the FOV. This is because the first overlay target B-1 for application is measured after the correction values are applied to move the platform 500.
[0120] That is, the offset value can be calculated from the preset overlay targets A for collection in the overlay targets T, at which the multiple overlay patterns formed on the wafer W are formed, and then the offset value is applied as a correction value to the remaining overlay targets B for application in the overlay targets T. Thus, the overall overlay measurement speed on the wafer W can be accelerated, so that the processing time is reduced.
[0121] To this end, the step S300 of measuring the overlay targets for application may be repeatedly performed to measure the first overlay target for application B-1, the second overlay target for application B-2 to the nth overlay target for application Bn among the plurality of overlay targets T.
[0122] The step S300 of measuring the overlay target for application may be repeatedly performed to measure a plurality of overlay targets B for application. Figure 4 As shown, in the second platform moving step S310, the platform 500 may be moved so that the first overlay target B-1 for application is located below the lens unit 200, and in the second pattern measuring step S320, the first overlay target B-1 for application may be measured.
[0123] Then, in the second stage moving step S310, the stage 500 may be moved so that the second overlay target for application B-2 is located below the lens unit 200, and in the second pattern measuring step S320, the second overlay target for application B-2 may be measured.
[0124] In this regard, in the second platform moving step S310 , in order to measure each of the first, second, to nth overlay targets B for application, a correction value may be applied to the mobile platform 500 .
[0125] As an alternative, after the measurement step S300 of the overlay target for application, the correction value calculation step S200 may be repeatedly performed.
[0126] Specifically, the measuring step S300 for the applied overlay target may include calculating the distance between the additional target coordinates for the applied overlay target B and the center C of the field of view. The correction value calculating step 200 may include further calculating the correction value based on the additional target coordinates.
[0127] That is, the correction value may be calculated by simultaneously considering the target coordinates calculated in the measurement step S100 for the collected overlay target and the additional target coordinates calculated in the measurement step S300 for the applied overlay target.
[0128] Furthermore, after the measurement step S300 of the applied overlay target, the correction value calculation step S200 may be repeatedly performed so that the additional target coordinates are cumulatively calculated, thereby continuously updating the correction value. Therefore, as the overlay measurement continues, the additional target coordinates may gradually converge to the center C of the FOV.
[0129] For example, Fig.10 and 11 As shown, the distance between the second overlay target B-2 for application and the center C of the field of view may be smaller than the distance between the first overlay target B-1 for application and the center of the field of view.
[0130] In this regard, an overlay target B for application among a plurality of overlay targets T may be preset, and the preset may vary from wafer to wafer.
[0131] like Figure 6 As shown, the overlay measurement method according to an embodiment of the present disclosure may further include a wafer coordinate calculation step S400 before the measurement step S100 for collecting the overlay target, in which the reference coordinates of the wafer W are calculated based on the measurement results of the global mark GM formed on the wafer W using the lens unit 200 and the detector 300.
[0132] The wafer coordinate calculation step S400 is a step of checking the correct position of the wafer W after the wafer is placed on the upper surface of the platform 500 .
[0133] For example, when the wafer W is not placed in the correct position on top of the platform 500, all measurement positions of the plurality of overlay targets T subsequently measured may be misaligned. Therefore, in the wafer coordinate calculation step S400, the position of the wafer W may be checked, and if the wafer W is not in the correct position, the reference coordinates may be stored and applied to the plurality of overlay targets T subsequently measured.
[0134] That is, in the correction value calculation step S200 , a final correction value is calculated by applying the reference coordinates to the correction value to correct the alignment error between the stage 500 and the wafer W.
[0135] As described above, the overlay measurement device and overlay measurement method according to the present disclosure can measure the value of the offset according to the platform movement in the initial measurement, and apply the offset value to subsequent measurements to correct the alignment error of the wafer and the error generated when the platform moves, and reduce the error generated in each measurement, thereby improving the measurement accuracy, saving the time required to shift the site with the overlay pattern to the measurement position and shortening the moving distance therebetween, and reducing the operator's working hours. In addition, by automatically optimizing the optimization results that are greatly affected by the ability of individual workers based on data, consistent results can be obtained.
[0136] The present disclosure is described with reference to the embodiments shown in the accompanying drawings, but the embodiments are merely examples, and those skilled in the art will appreciate that various modifications and equivalent other embodiments may be made therefrom. Therefore, the true scope of the present disclosure should be determined based on the technical essence of the attached patent claims.
Claims
1. An overlay measurement device, comprising: A light source configured to direct light to a plurality of overlay targets formed on the wafer: Lens unit, comprising: an objective lens configured to focus the light onto a measurement position of one of the plurality of overlay targets; as well as a lens focus driver configured to adjust a distance between the objective lens and a surface of the wafer at the measuring position; a detector configured to acquire a focused image at the measurement location based on the light beam reflected from the measurement location; A platform for placing the wafer: and A controller, the controller being configured to: controlling the lens unit, the detector, and the platform to measure a preset overlay target for collection among the plurality of overlay targets; Collecting target coordinates of the overlay target for collection that deviates from the center of the field of view FOV of the lens unit; Calculating a correction value based on the target coordinates; moving the platform while applying the correction value; as well as The lens unit, the detector, and the stage are controlled to measure at least one overlay target of the plurality of overlay targets for application.
2. The overlay measurement device according to claim 1, wherein the controller comprises: a platform driver configured to control movement of the platform; a memory for storing therein the image of the overlay target for collection and the image of the overlay target for application acquired using the detector; an offset calculator configured to calculate a distance between a target coordinate of the overlay target for collection and a center of a field of view of the lens unit; as well as A correction value calculator is configured to calculate the correction value based on the target coordinates.
3. The overlay measurement device as described in claim 2, wherein in the process of measuring the overlay target for collection, the platform driver is configured to control the platform so that the overlay targets for collection are measured in sequence, and the sequence is from the overlay target for collection formed at a position closest to the center of the wafer to the overlay target for collection formed at a position farthest from the center of the wafer.
4. The overlay measurement device of claim 2, wherein the correction value calculator is configured to calculate an average value of distances between a plurality of the target coordinates repeatedly measured by the detector and the center of the field of view of the lens unit as the correction value. 5 . The overlay measurement device of claim 2 , wherein the offset calculator is further configured to calculate a distance between a target coordinate of the overlay target for application and a center of a field of view of the lens unit.
6. The overlay measurement apparatus of claim 1, wherein the lens unit and the detector are configured to measure a global mark formed on the wafer; in, The controller is also configured to: calculating reference coordinates of the wafer based on the global mark; and calculating the correction value using the reference coordinates, wherein an alignment error between the platform and the wafer is corrected based on the correction value.
7. An overlay measurement method, comprising: The measurement steps for the collected overlay targets include: Moving the platform on which the wafer is placed; measuring at least one of the plurality of overlay targets for the collected overlay targets using a lens unit and a detector; collecting target coordinates of the overlay target for collection that deviates from the center of the field of view of the lens unit; and measuring an overlay value of the overlay target for collection; a correction value calculating step of calculating a correction value based on the target coordinates, wherein an error generated due to movement of the platform is corrected based on the correction value; and The measurement steps for the overlay target used for the application include: moving the platform while applying the correction value; measuring at least one overlay target of the plurality of overlay targets for application using the lens unit and the detector; and An overlay value of the overlay target for the application is measured.
8. The overlay measurement method of claim 7, wherein the step of measuring the collected overlay targets comprises: A first platform moving step of moving the platform for placing the wafer so that the lens unit is located above a position where the overlay target for collection is formed; a first pattern measurement step of measuring the overlay target for collection using the lens unit and the detector; as well as An offset calculation step is performed to calculate the distance between the target coordinates of the overlay target for collection and the center of the field of view of the lens unit.
9. The overlay measurement method of claim 7, wherein the step of measuring the collected overlay targets comprises: measuring a first overlay target for collection, a second overlay target for collection to an nth overlay target for collection among the plurality of overlay targets; as well as Collect the first target coordinates of the first overlay target for collection that deviates from the center of the field of view of the lens unit, the second target coordinates of the second overlay target for collection that deviates from the center of the field of view of the lens unit, to the nth target coordinates of the nth overlay target for collection that deviates from the center of the field of view of the lens unit.
10. The overlay measurement method according to claim 9, wherein the first overlay target for collection, the second overlay target for collection to the nth overlay target for collection are arranged in increasing order of the spacing between them and the center of the wafer; The measuring step for collecting the overlay target comprises: moving the platform to a position where the first overlay target for collection is formed at a position closest to the center of the wafer, and measuring the first overlay target for collection; as well as The stage is moved to a position where the second overlay target for collection is formed at a position second closer to the center of the wafer, and the second overlay target for collection is measured.
11. The overlay measurement method according to claim 7, wherein: In the correction value calculation step, an average value of distances between a plurality of target coordinates repeatedly measured in the measurement step for collecting overlay targets and the center of the field of view of the lens unit is calculated as the correction value.
12. The overlay measurement method according to claim 7, wherein the step of measuring the overlay target for application comprises: A second stage moving step of applying the correction value to move the stage so that the lens unit is located above a position where the overlay target for application is formed; as well as A second pattern measuring step of measuring the overlay target for application using the lens unit and the detector.
13. The overlay measurement method according to claim 7, wherein the step of measuring the overlay target for application comprises: measuring a first overlay target for application, a second overlay target for application to an nth overlay target for application among the plurality of overlay targets; as well as The correction value is applied to move the stage in order to measure the first overlay target for application, the second overlay target for application to the nth overlay target for application.
14. The overlay measurement method according to claim 7, wherein the method further comprises: After the step of measuring the overlay target for application, repeating the step of calculating the correction value; wherein the step of measuring the overlay target for application includes calculating the distance between the additional target coordinates of the overlay target for application and the center of the field of view; The correction value calculation step includes further calculating the correction value based on the additional target coordinates.
15. The overlay measurement method according to claim 7, wherein the method further comprises: a wafer coordinate calculation step of calculating reference coordinates of the wafer based on a measurement result of a global mark formed on the wafer using the lens unit and the detector before the measurement step for collecting the overlay target; The correction value calculation step includes applying the reference coordinates to the calculation of the correction value to correct the alignment error between the platform and the wafer.