Overlay measurement device and overlay measurement method

Abstract

To provide an overlay measurement device and an overlay measurement method that improve measurement accuracy and reduce man-hours of an operator.SOLUTION: An overlay measurement device includes: a light source unit 100 that directs light toward a plurality of overlay targets T formed on a wafer W; a lens unit 200 that is formed with an objective lens 210 that focuses light at a measurement position and a lens focus actuator 220 that adjusts a distance between the objective lens and a surface of the wafer at the measurement position; a detection unit 300 that obtains a focused image at the measurement position; a stage 500 on which the wafer is placed; and a control unit 400. The control unit is configured to: control the lens unit, the detection unit, and the stage so as to measure a preset collection-purposed overlay target; collect target coordinates separated away from a center of a field of view of the lens unit; calculate a correction value on the basis of the target coordinates; and apply the correction value and causes the stage to move, and measure at least one application-purposed overlay target.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to wafer overlay measurement, and to an overlay measurement apparatus and an overlay measurement method. [Background technology]

[0002] Generally, as technology advances, the size of semiconductor devices decreases and the density of integrated circuits on wafers increases. To form integrated circuits on a wafer, many manufacturing processes must be performed to sequentially form desired circuit structures and elements at specific locations. These manufacturing processes sequentially create patterned layers on the wafer.

[0003] Through these repeated stacking processes, electrically activated patterns are created within the integrated circuit. If the respective structures are not aligned within the tolerance range allowed by the production process, interference occurs between the electrically activated patterns, which can cause problems in the performance and reliability of the manufactured circuit. To measure and verify such inter-layer alignment errors, an overlay metrology tool is used to find the focus position based on the brightness or phase difference in the image of the wafer.

[0004] At this time, in order to measure the patterns formed on each layer of the wafer, the wafer is placed on a stage, and then patterns formed at various positions on the wafer are detected.

[0005] However, the wafer may not be placed at a fixed position on the stage, but may be placed on the stage in a partially shifted or rotated state. In this case, there is a problem that it takes a long time to move the stage to search for the pattern in order to detect it.

[0006] In addition, in order to detect patterns formed at various positions on the wafer, the stage must be moved to each position. At this time, there is a problem that the pattern must be aligned to the center of the field of view every time the stage is moved due to problems such as a lack of precise vertical alignment between the optical device and the stage, or problems with the optics alignment, lens quality, stage leveling, vibrations that occur during stage movement, and errors that occur during movement. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve various problems, including those described above, and aims to provide an overlay measurement apparatus and an overlay measurement method that can improve the accuracy of correction by continuously measuring and correcting misalignment between a wafer and a stage and offset amounts that occur each time the stage moves during overlay measurement. However, these problems are merely examples, and the scope of the present invention is not limited thereto. [Means for solving the problem]

[0008] According to one embodiment of the present invention, there is provided an overlay measurement apparatus that includes a light source unit configured to direct illumination onto a plurality of overlay targets formed on a wafer, a lens unit including an objective lens that focuses the illumination onto a measurement position at one of the plurality of overlay targets and a lens focus actuator that adjusts the distance between the objective lens and the measurement position and the surface of the wafer, a detector unit that acquires a focused image at the measurement position using a beam reflected at the measurement position, a stage on which the wafer is placed, and a controller that controls the lens unit, the detector, and the stage to measure a predetermined collection-type overlay target among the plurality of overlay targets, collects target coordinates spaced from a center of a field of view of the lens unit, calculates a correction value based on the target coordinates, and moves the stage by applying the correction value to measure at least one adaptive overlay target among the plurality of overlay targets.

[0009] According to one embodiment of the present invention, the control unit may include a stage operation unit that controls movement of the stage; a storage unit that stores images of the collection type overlay target and the application type overlay target acquired by the detection unit; an offset calculation unit that calculates the distance of a target coordinate where the collection type overlay target is spaced from the center of the field of view of the lens unit; and a correction value calculation unit that calculates the correction value based on the target coordinate.

[0010] According to one embodiment of the present invention, when measuring the collection-type overlay target, the stage operating unit may control the stage so that measurements can be performed sequentially from the collection-type overlay target formed at a site closest to the center of the wafer to the collection-type overlay target formed at a site farthest from the center of the wafer.

[0011] According to one embodiment of the present invention, the correction value calculation unit can calculate the average of the distance between the target coordinates repeatedly measured by the detection unit and the center of the field of view of the lens unit as the correction value.

[0012] According to an embodiment of the present invention, the offset calculation unit may calculate a distance of an additional target coordinate at which the adaptive overlay target is spaced from the center of the field of view of the lens unit.

[0013] According to one embodiment of the present invention, the lens unit and the detection unit may measure a global mark formed on the wafer, and the control unit may calculate a reference coordinate of the wafer through the global mark and calculate the correction value by applying the reference coordinate so as to correct misalignment between the stage and the wafer.

[0014] According to one embodiment of the present invention, there is provided an overlay measurement method, which may include: a collection-type overlay measurement step of measuring at least one collection-type overlay target among a plurality of overlay targets with a lens unit and a detector unit by moving a stage on which a wafer is placed, collecting target coordinates of the collection-type overlay target spaced apart from a center of a field of view of the lens unit, and measuring overlay values ​​of the collection-type overlay target; a correction value calculation step of calculating a correction value based on the target coordinates to correct for errors occurring during movement of the stage; and an adaptive overlay measurement step of applying the correction value to move the stage, measuring at least one adaptive overlay target among the plurality of overlay targets with the lens unit and the detector unit, and measuring overlay values ​​of the adaptive overlay target.

[0015] According to one embodiment of the present invention, the collection-type overlay measurement step may include: a first stage moving step of moving a stage on which the wafer is placed so that the lens unit is positioned above a site where the collection-type overlay target is formed; a first pattern measuring step of measuring the collection-type overlay target using the lens unit and the detection unit; and an offset calculation step of calculating a target coordinate distance from the collection-type overlay target based on the center of the field of view.

[0016] According to one embodiment of the present invention, the collecting overlay measurement step may be performed by repeatedly measuring the first collecting overlay target, the second collecting overlay target to the nth collecting overlay target among the plurality of overlay targets, so as to collect the first target coordinates, the second target coordinates to the nth target coordinates at which each collecting overlay target is spaced from the center of the field of view of the lens unit.

[0017] According to one embodiment of the present invention, in the collection-type overlay measurement step, the first collection-type overlay target, the second collection-type overlay target, to the nth collection-type overlay target may be set in order from a site closest to the center of the wafer to a site farther from the center of the wafer, and the stage may move to a position where the first collection-type overlay target located at a site closest to the center of the wafer is formed to measure the first collection-type overlay target, and the stage may move to a position where the second collection-type overlay target located at a site second closest to the center of the wafer is formed to measure the second collection-type overlay target.

[0018] According to one embodiment of the present invention, the correction value calculation step may calculate the average of the distances between the center of the field of view of the lens unit and a plurality of target coordinates repeatedly measured in the collection-type overlay measurement step as the correction value.

[0019] According to one embodiment of the present invention, the adaptive overlay measurement step may include: a second stage movement step of applying the correction value to move the stage when moving the stage so that the lens unit is positioned above the site where the adaptive overlay target is formed; and a second pattern measurement step of measuring the adaptive overlay target using the lens unit and the detection unit.

[0020] According to one embodiment of the present invention, the adaptive overlay measurement step is repeatedly performed to measure a first adaptive overlay target, a second adaptive overlay target to an n-th adaptive overlay target among the plurality of overlay targets, and the correction value can be applied when the stage moves to measure the first adaptive overlay target, the second adaptive overlay target to the n-th adaptive overlay target.

[0021] According to one embodiment of the present invention, after the adaptive overlay measurement step, the correction value calculation step is repeated, and in the adaptive overlay measurement step, the distance of an additional target coordinate spaced from the center of the field of view by the adaptive overlay target is calculated, and in the correction value calculation step, the additional target coordinate is applied to calculate the correction value.

[0022] According to one embodiment of the present invention, the method may further include, before the collection-type overlay measurement step, a wafer coordinate calculation step of measuring a global mark formed on the wafer using the lens unit and the detection unit to calculate reference coordinates of the wafer, and in the correction value calculation step, the reference coordinates may be applied to the correction value to correct misalignment between the stage and the wafer. [Effects of the Invention]

[0023] According to some embodiments of the present invention, an offset value from a measurement position of a preset overlay target is calculated and applied as a correction value to other overlay targets, thereby correcting errors that occur with each movement of the stage and reducing errors that occur with each measurement. It is also possible to reduce the time required to move to the measurement position, thereby improving measurement accuracy and reducing the number of steps required by an operator. Of course, the scope of the present invention is not limited to these effects. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram illustrating an overlay measurement apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a control unit of the overlay measurement apparatus according to the present invention. [Figure 3] 1 illustrates an overlay metrology method according to various embodiments of the present invention. [Figure 4] 1 illustrates an overlay metrology method according to various embodiments of the present invention. [Figure 5] 1 illustrates an overlay metrology method according to various embodiments of the present invention. [Figure 6] 1 illustrates an overlay metrology method according to various embodiments of the present invention. [Figure 7] 1 is a top view showing a wafer on which a global mark and a plurality of overlay targets are formed according to an embodiment of the present invention is placed on a stage. FIG. [Figure 8] 1 is a top view illustrating a collection-based overlay metrology step according to one embodiment of the present invention. [Figure 9] 1 is a top view illustrating a collection-based overlay metrology step according to one embodiment of the present invention. [Figure 10] 1 is a top view illustrating adaptive overlay metrology steps according to one embodiment of the present invention. [Figure 11] 1 is a top view illustrating adaptive overlay metrology steps according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Various preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] The examples of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples can be modified into various other forms, and the scope of the present invention is not limited to the following examples. Rather, these examples are provided to make the present disclosure more complete and complete, and to fully convey the concept 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.

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings that schematically illustrate ideal embodiments of the present invention. In the drawings, variations in the illustrated shapes can be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the concept of the present invention should not be interpreted as being limited to the specific shapes of regions illustrated in this specification, and should include, for example, variations in shapes that occur during manufacturing.

[0028] The overlay measurement system is a system that measures the error between a first overlay key and a second overlay key formed on different layers of the wafer W, respectively.

[0029] For example, the first overlay key may be an overlay mark formed in a previous layer, and the second overlay key may be an overlay mark formed in a current layer. The overlay marks are formed in scribe lines simultaneously with the formation of layers for forming semiconductor devices in the die region. 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 is hidden by a photoresist layer. The first overlay key may be made of an oxide having optical properties different from those of the second overlay key made of the photoresist material.

[0030] Also, the first and second overlay keys may be located in different physical positions, but may have the same or different focal planes.

[0031] FIG. 1 is a diagram schematically illustrating an overlay measurement apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a control unit 400 of the overlay measurement apparatus according to the present invention.

[0032] First, the overlay measurement apparatus according to an embodiment of the present invention may broadly include a light source unit 100, a lens unit 200, a detection unit 300, a control unit 400, and a stage 500.

[0033] 1, the light source unit 100 can direct illumination to a plurality of overlay targets T formed on the wafer W. Specifically, the light source unit 100 can be configured to direct illumination to 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.

[0034] For example, the light source unit 100 may be formed of 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 to these.

[0035] The overlay metrology apparatus according to one embodiment of the present invention may include an aperture 110 , a spectral filter 120 , a polarizing filter 130 , and a beam splitter 140 .

[0036] The aperture 110 may be formed of an opaque plate having an aperture through which light passes, and may change the beam emitted from the light source unit 100 into a form suitable for photographing a plurality of overlay targets T.

[0037] The aperture 110 may include one or more of an aperture stop that adjusts the amount of light and a field stop that adjusts the range of the image, and may be formed between the light source unit 100 and the beam splitter 140 as shown in FIG. 1, or may be formed between the beam splitter 140 and the lens unit 200, although not shown.

[0038] The spectral filter 120 can adjust the center wavelength and bandwidth of the beam emitted from the light source unit 100 to be suitable for acquiring images of the first and second overlay keys formed on the multiple overlay targets T. For example, the spectral filter 120 may be formed of at least one of a filter wheel, a linear translation device, a flipper device, and combinations thereof.

[0039] The beam splitter 140 transmits a part of the beam that has left the light source unit 100 and passed through the aperture 110, and reflects the other part, thereby separating the beam that has left the light source unit 100 into two beams.

[0040] As shown in FIG. 1, the lens unit 200 may be formed with an objective lens 210 that focuses the illumination onto a measurement position at any one of the multiple overlay targets T, and a lens focus actuator 220 that adjusts the distance between the objective lens 210 and the multiple overlay targets T.

[0041] The objective lens 210 can focus the beam reflected by the beam splitter 140 at a measurement position on the wafer W where the first overlay key and the second overlay key are formed, and collect the reflected beam.

[0042] The objective lens 210 may be mounted on a lens focus actuator 220 .

[0043] 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 overlay targets T.

[0044] The lens focus actuator 220 can adjust the focal length by moving the objective lens 200 vertically toward the wafer W under the control of the control unit 400 .

[0045] When measuring the wafer W using the lens unit 200, the area where an image is captured changes by controlling the objective lens 210, and at this time, the area where the wafer W can be captured by the objective lens 210 is the field of view FOV. 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.

[0046] Furthermore, the lens unit 200 can measure a global mark GM that confirms the fixed position of the wafer W.

[0047] As shown in FIG. 1, the detector 300 can obtain a focused image at the measurement position through the beam reflected at the measurement position.

[0048] The detection unit 300 can capture the beams reflected from the multiple overlay targets T and passing through the beam splitter 140 to obtain images of the first and second overlay keys.

[0049] The detection unit 300 may include an optical detector capable of measuring beams reflected from multiple overlay targets T. For example, the optical detector may include a charge-coupled device (CCD) that converts light into electric charges to extract an image, a complementary metal-oxide-semiconductor (CMOS) sensor, which is an 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.

[0050] The detector 300 may include filters, polarizers, and beam blocks, and may further include optional collection optical components (not shown) for collecting illumination collected by the objective lens 210.

[0051] Furthermore, the detection unit 300 can measure a global mark GM that confirms the fixed position of the wafer W.

[0052] The stage 500 can be configured to have a wafer W placed on top and to fix the wafer W, and can move and rotate horizontally so that multiple overlay targets T on the wafer W can be measured with the lens unit 200 fixed above.

[0053] As shown in FIG. 1, the control unit 400 can control the direction of the illumination emitted from the light source unit 100, can control the lens unit 200 to focus the illumination on a plurality of overlay targets T and collect reflected beams, can control the detection unit 300 to obtain a measured focused image through the reflected beams collected by the lens unit 200, and can control the movement of the stage 500 so that the overlay targets are positioned below the lens unit 200.

[0054] In addition, the control unit 400 controls the lens unit 200, the detection unit 300, and the stage 500 to measure a predetermined collection-type overlay target A among the multiple overlay targets T, collects target coordinates spaced apart from the center C of the field of view of the lens unit 200, calculates a correction value based on the target coordinates, and moves the stage 500 by applying the correction value, thereby controlling the stage 500 to measure at least one application-type overlay target B among the multiple overlay targets T.

[0055] Specifically, the control unit 400 can include a light source operation unit 410 , a lens operation unit 420 , a stage operation unit 430 , a storage unit 440 , an offset calculation unit 450 , a correction value calculation unit 460 , and an overlay measurement unit 470 .

[0056] As shown in FIG. 2, the light source operating unit 410 can control the direction of the illumination emitted from the light source unit 100, and the lens operating unit 420 can control the operation of the lens focus actuator 220 so that the illumination is focused onto multiple overlay targets T to obtain a focused image.

[0057] 2, the stage operation unit 430 can control the movement of the stage 500 so that the overlay target is located below the lens unit 200. Specifically, the stage operation unit 430 can control the movement and rotation of the wafer W so that the positions of the global marks GM and the overlay targets T formed on the wafer W can be measured by the lens unit 200.

[0058] Specifically, the stage operation unit 430 can control the movement of the stage 500 so as to detect, among the multiple overlay targets T, a collection-type overlay target A that collects offset data during overlay measurement and an adaptive overlay target B that applies offset data during overlay measurement. For example, the stage operation unit 430 can control the stage 500 to move to a set position for the collection-type overlay target A according to the classification of the multiple overlay targets T that has been set in advance, and to move the stage 500 by applying a correction value, which will be described later, at the set position for the adaptive overlay target B, depending on the classification of the multiple overlay targets T that has been set in advance.

[0059] In this case, among the multiple overlay targets T, the collection type overlay target A and the adaptive type overlay target B may be set in advance or may be different for each wafer W.

[0060] Furthermore, the stage operation unit 430 can control the movement of the stage 500 to the collection-type overlay target A and the application-type overlay target B according to a preset measurement position. At this time, the preset measurement position moves based on the center of the overlay target, but during actual movement, an error occurs that causes the field of view center C of the field of view angle FOV to deviate from the center of the overlay target. Therefore, the movement of the stage 500 can be controlled by applying a correction value, which will be described later.

[0061] When measuring the collection type overlay target A, the stage operation unit 430 can control the stage 500 so that measurements can be made sequentially from the collection type overlay target A formed at the site closest to the center of the wafer W to the collection type overlay target A formed at the site farthest from the center of the wafer W.

[0062] In addition, when measuring adaptive overlay target B, stage operating unit 430 can control stage 500 so that measurements can be performed sequentially from adaptive overlay target A formed at the site closest to the center of wafer W to adaptive overlay target A formed at the site farthest from the center of wafer W.

[0063] As shown in FIG. 2, the storage unit 440 can store the image of the acquisition type overlay target A and the image of the application type overlay target B acquired by the detection unit 300 .

[0064] For example, the stage operation unit 430 controls multiple overlay targets T formed on the wafer W to be positioned below the lens unit 200, and the lens operation unit 420 controls the objective lens 210 and the lens focus actuator 220 to acquire images of multiple overlay targets T measured at each position and store them in the storage unit 440.

[0065] At this time, the images of the plurality of overlay targets T stored in the storage unit 440 may be classified into collection-type overlay targets A and application-type overlay targets B and stored.

[0066] The collected overlay target A is an image measured without the correction value calculated by the correction value calculation unit 460 being applied, and the adaptive overlay target B is an image measured with the correction value calculated by the correction value calculation unit 460 being applied.

[0067] The offset calculation unit 450 measures a plurality of overlay targets T using the lens unit 200, and can calculate the distance, position, and rotation direction of the measured overlay target images from the center C of the field of view FOV.

[0068] Specifically, the offset calculation unit 450 may calculate the distance of the target coordinates where the collection type overlay target A is separated from the center C of the field of view of the lens unit 200. For example, the offset calculation unit 450 may set the center C of the field of view of the field of view angle FOV as the center coordinates (0,0) and calculate the distance of the target coordinates (x, y) where the measured image is separated on the X-axis and Y-axis from the center coordinates (0,0).

[0069] The offset calculation unit 450 can also measure the collection overlay target A and calculate the angle of rotation from the field of view center C. For example, the rotation angle can be calculated by calculating the angle between the X-axis symmetry line of the collection overlay target A and the X-axis of the field of view FOV.

[0070] In addition, the offset calculation unit 450 can calculate the distance of the additional target coordinates at which the adaptive overlay target B is spaced from the center C of the field of view of the lens unit 200, and can also calculate the rotation angle of the adaptive overlay target B.

[0071] The correction value calculation unit 460 can calculate a correction value based on the target coordinates. For example, if the target coordinates are calculated as (x, y) by the offset calculation unit 450, the correction value can be calculated as (-x, -y).

[0072] In addition, when detecting multiple overlay targets T, the correction value calculation unit 460 can calculate the average of the distance between the multiple target coordinates repeatedly measured by the detection unit 300 and the center of the field of view of the lens unit as the correction value.

[0073] The control unit 400 calculates the reference coordinates of the wafer W through the global mark GM, and calculates the correction value by applying the reference coordinates so as to correct misalignment between the stage 500 and the wafer W.

[0074] Specifically, the state of the wafer W placed on the stage 500 can be confirmed through the global mark GM measured by the lens unit 200 and the detection unit 300. For example, if the wafer W is placed on the stage 500 with a partial deviation or rotation, the global mark GM measured by the lens unit 200 may be measured with a partial deviation or rotation.

[0075] By calculating the distance and angle by which the wafer W is shifted from the stage 500 using the global mark GM and calculating a reference value that can correct this, when the stage 500 is moved to measure multiple overlay targets T, the reference value can be applied so that the overlay targets of the wafer W are positioned at the center C of the field of view of the lens unit 200.

[0076] The overlay measurement unit 470 can measure the overlay values ​​for all targets through images of multiple overlay targets T, including an acquisition-type overlay target A that collects offset values ​​and measures overlay, and an adaptation-type overlay target B that applies correction values ​​and measures overlay.

[0077] In addition, the control unit 400 may include a display unit (not shown) so that a user can monitor a series of processes performed by the control unit 400, and may include an input unit (not shown) that can be directly controlled by a user.

[0078] That is, the storage unit 440, the offset calculation unit 450, the correction value calculation unit 460, and the overlay measurement unit 470, as well as the data and images calculated therethrough, can be checked through the display unit, and the user can directly control the light source operation unit 410, the lens operation unit 420, and the stage operation unit 430 through the input unit, or directly select, change, and calculate the images and correction values ​​of multiple overlay targets T.

[0079] In addition, the overlay measurement apparatus may include a memory for storing commands, programs, logic, etc. that allow the control unit 400 to control the operation of each component of the overlay measurement apparatus, and components may be added, modified, or deleted as needed.

[0080] In other words, the overlay measurement apparatus of the present invention calculates an offset value from the measurement position for a predetermined set of collection-type overlay targets A among the multiple overlay targets T formed on the wafer W, and applies this as a correction value to the remaining adaptive overlay targets B among the multiple overlay targets T. This corrects errors that occur each time the stage 500 moves, reduces errors that occur each time a measurement is made, and also saves the time required to move to the measurement position.

[0081] In particular, by calculating the offset value without correction using the collect-type overlay target A, an average offset value due to the movement of the stage 500 can be calculated, and by applying the correction value from the adapt-type overlay target B, the measurement time can be reduced.

[0082] 3 to 6 are diagrams showing overlay measurement methods according to various embodiments of the present invention, FIG. 7 is a top view showing a wafer W on which a global mark GM and multiple overlay targets T are formed, placed on a stage 500, FIGS. 8 and 9 are top views showing a collection-type overlay measurement step S100 according to one embodiment of the present invention, and FIGS. 10 and 11 are top views showing an adaptive overlay measurement step S300 according to one embodiment of the present invention.

[0083] The overlay measurement method according to an embodiment of the present invention may include a collection-type overlay measurement step S100, a correction value calculation step S200, and an adaptive overlay measurement step S300.

[0084] As shown in FIG. 3, the collection-type overlay measurement step S100 is a step of moving the stage 500 on which the wafer W is placed, measuring at least one collection-type overlay target A among the multiple overlay targets T using the lens unit 200 and the detection unit 300, collecting target coordinates where the collection-type overlay target A is spaced apart from the center C of the field of view of the lens unit 200, and measuring the overlay value of the collection-type overlay target A.

[0085] Specifically, as shown in FIG. 4, the collection-type overlay measurement step S100 may include a first stage moving step S110, a first pattern measuring step S120, and an offset calculation step S (not shown).

[0086] The first stage movement step S110 is a step of moving the stage 500 on which the wafer W is placed so that the lens unit 200 is positioned above the site where the collection type overlay target A is formed, and the first pattern measurement step S120 is a step of measuring the collection type overlay target A using the lens unit 200 and the detection unit 300.

[0087] The offset calculation step S130 is a step of calculating the distance of the target coordinates at which the collection type overlay target A is separated from the center C of the visual field.

[0088] For example, the first stage movement step S110 may move the first collecting overlay target A-1 so that it is positioned at the center of the field of view FOV of the lens unit 200. At this time, the movement of the stage 500 is controlled so that the center of the first collecting overlay target A-1 is positioned at the center of the field of view FOV, but in reality, due to errors that occur during movement, the field of view center C of the field of view FOV may deviate from the center of the overlay target.

[0089] Therefore, such an error can be measured in the first pattern measuring step S120 and calculated in the offset calculating step S130. For example, as shown in Fig. 9, the measured first collecting overlay target A-1 may be separated from the center C of the field of view of the field of view angle FOV, and the target coordinates of the first collecting overlay target A-1 at this time can be calculated as (x, y).

[0090] At this time, the collection type overlay measurement step S100 measures the first collection type overlay target A, the second collection type overlay target A to the nth collection type overlay target A among the multiple overlay targets T, and the measurement can be repeated so as to collect the first target coordinates, the second target coordinates to the nth target coordinates at which each collection type overlay target A is spaced from the field of view center C of the lens unit 200.

[0091] The collecting overlay measurement step S100 can repeatedly measure multiple collecting overlay targets A. For example, as shown in FIG. 8, in the first stage movement step S110, the stage 500 is moved so that the first collecting overlay target A-1 is positioned below the lens unit 200, the first collecting overlay target A-1 is measured in the first pattern measurement step S120, and the distance of the first target coordinates at which the first collecting overlay target A-1 is spaced from the center of the field of view C is calculated in the offset calculation step S130.

[0092] The first target coordinates calculated in this manner are stored, and a second collectible overlay target A-2, which is formed at a different position from the first collectible overlay target A-1, as shown in Figure 9, is measured in the same manner, and the second target coordinates can be calculated and stored.

[0093] In this case, the collection type overlay target A among the plurality of overlay targets T may be preset or may be different for each wafer.

[0094] Furthermore, the measurement sequence of the collection type overlay target A can be set in advance, and preferably can be measured in the direction from the center of the wafer W toward the edge.

[0095] For example, in the collection-type overlay measurement step S100, the first collection-type overlay target A, the second collection-type overlay target A to the n-th collection-type overlay target A may be set in order from the site closest to the center of the wafer W to the site farther from the center of the wafer W.

[0096] For example, as shown in FIG. 8, the overlay target T formed at the center of the wafer W can be set as the first collection type overlay target A-1, and as shown in FIG. 9, the overlay target T formed closest to the first collection type overlay target A-1 can be set as the second collection type overlay target A-2.

[0097] Therefore, the first collecting overlay target A-1, the second collecting overlay target A-2 can be measured, and then the third collecting overlay target A-3, the fourth collecting overlay target A-4, and the fifth collecting overlay target A-5 can be measured.

[0098] That is, in the collection-type overlay measurement step S100, the stage 500 moves to a position where the first collection-type overlay target A-1, located at the site closest to the center of the wafer W, is formed, and measures the first collection-type overlay target A-1. The stage 500 then moves to a position where the second collection-type overlay target A-2, located at the site second closest to the center of the wafer W, is formed, and measures the second collection-type overlay target A-2. This allows the first target coordinates and the second target coordinates, which are measured differently due to errors that occur during initial placement and errors that occur during movement of the stage 500, to be calculated.

[0099] As shown in FIG. 3, the correction value calculation step S200 is a step of calculating a correction value based on the target coordinates in order to correct an error that occurs when the stage 500 moves.

[0100] When multiple collected overlay targets A are repeatedly measured, the correction value calculation step S200 can calculate the average distance between the multiple target coordinates repeatedly measured in the collected overlay measurement step S100 and the center of the field of view of the lens unit as the correction value.

[0101] That is, the correction value can be calculated by six-parameter modeling of the PR (pattern recognition) offset of the collected overlay target A, which has been repeatedly measured. For example, the PR offset on the wafer can be used to calculate the changed translation, rotation, and scale components.

[0102] That is, the average value of the first target coordinates and the second to n-th target coordinates can be calculated as a correction value and applied to the adaptive overlay measurement step S300 described later.

[0103] As shown in FIG. 3, the adaptive overlay measurement step S300 is a step of applying the correction value to move the stage 500, measuring at least one adaptive overlay target B among the multiple overlay targets T with the lens unit 200, and measuring the overlay value of the adaptive overlay target B.

[0104] Specifically, as shown in FIG. 4, the adaptive overlay measurement step S300 may include a second stage movement step S310 and a second pattern measurement step S320.

[0105] The second stage movement step S310 is a step of applying the correction value to move the stage 500 so that the lens unit 200 is positioned above the site where the adaptive overlay target B is formed, and the second pattern measurement step S320 is a step of measuring the adaptive overlay target B using the lens unit 200 and the detection unit 300.

[0106] For example, in the second stage movement step S310, the first adaptive overlay target B-1 may be moved to be positioned at the center of the field of view FOV. In this case, the stage 500 may be moved by applying the correction value calculated in the correction value calculation step S200, and the second pattern measurement step S320 may be performed.

[0107] Therefore, the first adaptive overlay target B-1 may be measured at a distance from the center of the field of view C. In this case, the distance at which the first adaptive overlay target B-1 is separated from the center of the field of view C may be smaller than the distance at which the collection overlay target A is separated from the center of the field of view C.

[0108] For example, when measuring an adaptive overlay target B-1 to which the correction value is applied, as in Figure 10, the correction value is applied when moving the stage 500, and therefore the measurement can be performed closer to the center of the field of view C than when measuring a collection-type overlay target A to which the correction value is not applied, as in Figures 8 and 9.

[0109] That is, by calculating an offset value from a predetermined collection-type overlay target A among the overlay targets T on which numerous overlay patterns are formed on the wafer W, and applying the offset value to the remaining application-type overlay targets B among the overlay targets T as a correction value, the overall overlay measurement speed of the wafer W can be increased and the process time can be reduced.

[0110] In this case, the adaptive overlay measurement step S300 can be repeatedly performed to measure the first adaptive overlay target B, the second adaptive overlay target B to the n-th adaptive overlay target B among the multiple overlay targets T.

[0111] The adaptive overlay measurement step S300 can repeatedly measure multiple adaptive overlay targets B. For example, as shown in FIG. 4, in the second stage movement step S310, the stage 500 is moved so that the first adaptive overlay target B-1 is positioned below the lens unit 200, and in the second pattern measurement step S320, the first adaptive overlay target B-1 can be measured.

[0112] In this case, the second stage movement step S310 can apply the correction value when moving the stage 500 for measuring the first adaptive overlay target B, the second adaptive overlay target B to the nth adaptive overlay target B.

[0113] Alternatively, the correction value calculation step S200 can be repeated after the adaptive overlay measurement step S300.

[0114] Specifically, in the adaptive overlay measurement step S300, the distance of the additional target coordinates that the adaptive overlay target B is spaced from the center of the field of view C is calculated, and in the correction value calculation step S200, the additional target coordinates can be applied to calculate the correction value.

[0115] That is, the correction value can be calculated by applying both the target coordinates calculated in the collection-type overlay measurement step S100 and the additional target coordinates calculated in the adaptive overlay measurement step S300.

[0116] Furthermore, by repeating the correction value calculation step S200 after the adaptive overlay measurement step S300, the additional target coordinates are accumulated, thereby continuously updating the correction value, and the more the overlay measurement continues, the more it can gradually converge to the center of the field of view C.

[0117] For example, as shown in Figures 10 and 11, when measuring the second adaptive overlay target B-2, the overlay target T can be positioned closer to the center of the field of view C than when measuring the first adaptive overlay target B-1.

[0118] In this case, the adaptive overlay target B among the plurality of overlay targets T may be preset or may be different for each wafer.

[0119] As shown in FIG. 6, the overlay measurement method according to one embodiment of the present invention may further include a wafer coordinate calculation step S400 before the collection-type overlay measurement step S100, in which the lens unit 200 and the detection unit 300 measure a global mark GM formed on the wafer W and calculate reference coordinates of the wafer W.

[0120] The wafer coordinate calculation step S400 is a step for confirming the fixed position of the wafer W after the wafer W is placed on the upper part of the stage 500.

[0121] For example, if the wafer W is not placed in a fixed position on top of the stage 500, the measurement positions of the multiple overlay targets T measured thereafter may all be shifted. Therefore, the position of the wafer W is confirmed in the wafer coordinate calculation step S400, and if the wafer W is not located in a fixed position, the reference coordinates can be stored and applied to the multiple overlay targets T measured thereafter.

[0122] That is, in the correction value calculation step S200, in order to correct misalignment between the stage 500 and the wafer W, the correction value can be calculated by applying the reference coordinates to the correction value.

[0123] As described above, the overlay measurement apparatus and method of the present invention measure offset values ​​due to stage movement in an initial measurement and reflect these values ​​in subsequent measurements, thereby correcting for wafer misalignment and errors that occur during stage movement and reducing errors that occur with each measurement. This increases measurement accuracy, saves time and distance for a site where an overlay pattern is formed to move to a measurement position, and reduces operator man-hours. Furthermore, optimization results that were previously heavily influenced by the individual capabilities of operators can now be derived consistently through data-based automatic optimization.

[0124] The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will recognize that various modifications and equivalent embodiments are possible. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. [Explanation of symbols]

[0125] A. Collective Overlay Target B. Adaptive Overlay Target GM Global Mark T Multiple overlay measurement targets W wafer 100 Light source section 110 aperture 120 Spectral Filters 140 Beam Splitter 200 Lens section 210 objective lens 220 Lens focus actuator 300 Detector 400 control section 500 stages

Claims

1. a light source configured to direct illumination onto a plurality of overlay targets formed on the wafer; a lens unit including an objective lens for focusing the illumination onto a measurement position at any one of the plurality of overlay targets, and a lens focus actuator for adjusting a distance between the objective lens and the measurement position from the surface of the wafer; a detection unit that acquires a focused image at the measurement position through a beam reflected at the measurement position; a stage on which the wafer is placed; a control unit that controls the lens unit, the detection unit, and the stage to measure a predetermined collection type overlay target among the plurality of overlay targets, collects target coordinates spaced apart from a center of a field of view of the lens unit, calculates a correction value based on the target coordinates, and moves the stage by applying the correction value to measure at least one or more application type overlay targets among the plurality of overlay targets, The control unit a stage operating unit for controlling the movement of the stage; a storage unit for storing the images of the collection type overlay target and the application type overlay target acquired by the detection unit; an offset calculation unit that calculates a distance of a target coordinate of the collection type overlay target from the center of the field of view of the lens unit; a correction value calculation unit that calculates the correction value based on the target coordinates; Including, The correction value calculation unit an overlay measurement device that calculates a correction value using a distance between the plurality of target coordinates repeatedly measured by the detection unit and the center of the field of view of the lens unit.

2. The stage operating unit 2. The overlay metrology apparatus of claim 1, wherein the stage is controlled so that, when measuring the collection-type overlay targets, measurements can be performed sequentially from the collection-type overlay target formed at a site closest to the center of the wafer to the collection-type overlay target formed at a site farthest from the center of the wafer.

3. The correction value calculation unit The overlay measurement apparatus according to claim 1 , wherein the correction value is calculated as an average of the distances between the target coordinates repeatedly measured by the detection unit and the center of the field of view of the lens unit.

4. A light source unit configured to direct illumination onto a plurality of overlay targets formed on a wafer; a lens unit including an objective lens for focusing the illumination onto a measurement position at any one of the plurality of overlay targets, and a lens focus actuator for adjusting a distance between the objective lens and the measurement position from the surface of the wafer; a detection unit that acquires a focused image at the measurement position through a beam reflected at the measurement position; a stage on which the wafer is placed; a control unit that controls the lens unit, the detection unit, and the stage to measure a predetermined collection type overlay target among the plurality of overlay targets, collects target coordinates spaced apart from a center of a field of view of the lens unit, calculates a correction value based on the target coordinates, and moves the stage by applying the correction value to measure at least one or more application type overlay targets among the plurality of overlay targets, The control unit a stage operating unit for controlling the movement of the stage; a storage unit for storing the images of the collection type overlay target and the application type overlay target acquired by the detection unit; an offset calculation unit that calculates a distance of a target coordinate of the collection type overlay target from the center of the field of view of the lens unit; a correction value calculation unit that calculates the correction value based on the target coordinates; Including, The offset calculation unit The adaptive overlay target calculates the distance of an additional target coordinate away from the center of field of view of the lens portion.

5. A light source unit configured to direct illumination onto a plurality of overlay targets formed on a wafer; a lens unit including an objective lens for focusing the illumination onto a measurement position at any one of the plurality of overlay targets, and a lens focus actuator for adjusting a distance between the objective lens and the measurement position from the surface of the wafer; a detection unit that acquires a focused image at the measurement position through a beam reflected at the measurement position; a stage on which the wafer is placed; a control unit that controls the lens unit, the detection unit, and the stage to measure a predetermined collection type overlay target among the plurality of overlay targets, collects target coordinates spaced apart from a center of a field of view of the lens unit, calculates a correction value based on the target coordinates, and moves the stage by applying the correction value to measure at least one or more application type overlay targets among the plurality of overlay targets, the lens unit and the detection unit are capable of measuring a global mark formed on the wafer, The control unit calculates reference coordinates of the wafer through the global mark, and calculates the correction value by applying the reference coordinates so as to correct misalignment between the stage and the wafer.

6. A collection type overlay measurement step in which a stage on which a wafer is placed is moved, and at least one of a plurality of overlay targets is measured using a lens unit and a detection unit, and the collection type overlay target collects target coordinates at a distance from the center of the field of view of the lens unit, and measures the overlay value of the collection type overlay target; a correction value calculation step of calculating a correction value based on the target coordinates in order to correct an error that occurs when the stage moves; an adaptive overlay measurement step of applying the correction value to move the stage, measuring at least one adaptive overlay target among a plurality of overlay targets using the lens unit and the detection unit, and measuring an overlay value of the adaptive overlay target; Including, The correction value calculation step an overlay measurement method, wherein a correction value is calculated using a distance between a plurality of target coordinates repeatedly measured in the collection-type overlay measurement step and the center of the field of view of the lens unit.

7. The collection type overlay measurement step includes: a first stage moving step of moving a stage on which the wafer is placed so that the lens unit is positioned above a site where the collection type overlay target is formed; a first pattern measuring step of measuring the collection type overlay target using the lens unit and the detection unit; an offset calculation step of calculating a distance of a target coordinate at which the collection type overlay target is spaced from the center of the field of view; The overlay metrology method of claim 6 , comprising:

8. The collection type overlay measurement step includes:

7. The overlay measurement method of claim 6, wherein the first collecting overlay target, the second collecting overlay target, and the n-th collecting overlay target are measured among the plurality of overlay targets, and the measurement is repeated so that the first target coordinates, the second target coordinates, and the n-th target coordinates, each of which is spaced apart from the center of the field of view of the lens unit, can be collected.

9. In the collection type overlay measurement step, the first collection type overlay target, the second collection type overlay target to the nth collection type overlay target are set in an order from a site closest to the center of the wafer to a site farther from the center of the wafer; 9. The overlay measurement method of claim 8, wherein the stage moves to a position where a first collection-type overlay target located at a site closest to the center of the wafer is formed, and measures the first collection-type overlay target, and the stage moves to a position where a second collection-type overlay target located at a site second closest to the center of the wafer is formed, and measures the second collection-type overlay target.

10. The correction value calculation step The overlay measurement method according to claim 6 , wherein an average of the distances between the target coordinates repeatedly measured in the collection-type overlay measurement step and the center of the field of view of the lens unit is calculated as the correction value.

11. The adaptive overlay measurement step: a second stage moving step of applying the correction value to move the stage so that the lens unit is positioned above the site where the adaptive overlay target is formed; a second pattern measuring step of measuring the adaptive overlay target using the lens unit and the detection unit; The overlay metrology method of claim 6 , comprising:

12. The adaptive overlay measurement step: Repeating the measurement of the first adaptive overlay target, the second adaptive overlay target to the n-th adaptive overlay target among the plurality of overlay targets; The overlay measurement method according to claim 6 , wherein the correction value is applied when the stage moves for measuring the first adaptive overlay target, the second adaptive overlay target, and the nth adaptive overlay target.

13. A collection type overlay measurement step in which a stage on which a wafer is placed is moved, and at least one of a plurality of overlay targets is measured using a lens unit and a detection unit, and the collection type overlay target collects target coordinates at a distance from the center of the field of view of the lens unit, and measures the overlay value of the collection type overlay target; a correction value calculation step of calculating a correction value based on the target coordinates in order to correct an error that occurs when the stage moves; an adaptive overlay measurement step of applying the correction value to move the stage, measuring at least one adaptive overlay target among a plurality of overlay targets using the lens unit and the detection unit, and measuring an overlay value of the adaptive overlay target; Including, After the adaptive overlay measurement step, Repeating the correction value calculation step, In the adaptive overlay measurement step, the adaptive overlay target calculates a distance of an additional target coordinate spaced from the center of the field of view; an overlay measurement method, wherein in the correction value calculation step, the correction value is calculated by applying the additional target coordinates.

14. A collection type overlay measurement step in which a stage on which a wafer is placed is moved to measure at least one of a plurality of overlay targets using a lens unit and a detection unit, the collection type overlay target collects target coordinates at a distance from the center of the field of view of the lens unit, and the overlay value of the collection type overlay target is measured; a correction value calculation step of calculating a correction value based on the target coordinates in order to correct an error that occurs when the stage moves; an adaptive overlay measurement step of applying the correction value to move the stage, measuring at least one adaptive overlay target among a plurality of overlay targets using the lens unit and the detection unit, and measuring an overlay value of the adaptive overlay target; Including, Before the acquisition-based overlay metrology step, a wafer coordinate calculation step of measuring a global mark formed on the wafer by the lens unit and the detection unit and calculating a reference coordinate of the wafer; In the correction value calculation step, an overlay measurement method, wherein the reference coordinates are applied to the correction value to calculate the correction value in order to correct misalignment between the stage and the wafer;

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