Overlay Measurement Apparatus and Overlay Measurement Method

Abstract

To provide an overlay measurement apparatus and method for a wafer.SOLUTION: An apparatus includes: a lens unit 200 comprising an objective lens 210 and a lens focus actuator 220, where the objective lens concentrates light at a measurement position of any point in an overlay measurement target T in which a first filling unit 11 and a second filling unit 21 are positioned, the first filling unit being formed in a first layer 10 of a wafer W, and the second filling unit being formed in a second layer 20 laminated to an upper or lower portion of the first layer, and where the lens focus actuator controls a distance between the objective lens and the overlay measurement target; a detection unit 300 acquiring a focus image at the measurement position through a beam reflected from the measurement position; and a control unit 400 aligning the sample image measured by the detection unit and a prestored setting model image, measuring a plurality of images by controlling the lens unit with a focus determined according to CI information of the aligned sample image and the setting model image, and calculating an overlay with a difference value by comparing center points of the plurality of images.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to overlay measurement of wafers, and to an overlay measurement apparatus and an overlay measurement method.

Background Art

[0002] Generally, as technology develops, the size of semiconductor devices becomes smaller, and the density of integrated circuits on a wafer is increasing. In order to form an integrated circuit on a wafer, many manufacturing processes must be performed so that a desired circuit structure and elements are sequentially formed at specific positions. Such manufacturing processes are to sequentially generate patterned layers on the wafer.

[0003] Through such repeated stacking processes, an electrically activated pattern is generated in the integrated circuit. At this time, if each structure is not aligned within the error range allowed in the manufacturing process, interference occurs between the electrically activated patterns, and problems may occur in the performance and reliability of the circuits manufactured by this phenomenon.

[0004] Therefore, in order to measure and verify the alignment error between layers, the alignment degree between the pattern of the upper layer and the pattern of the lower layer is detected using an overlay measurement pattern on the wafer. Recently, semiconductor devices including TSV (Through Silicon Via) are widely used in semiconductor packages, and TSV can be used for alignment measurement between layers in such semiconductor devices.

[0005] TSV is formed by forming a hole penetrating a silicon substrate and filling it with a conductor such as copper, and can be used to electrically connect the upper and lower sides of the silicon substrate during chip stacking to transmit signals and power between chips. However, when measuring TSV in a wafer, a problem occurs that images from each layer cannot be clearly seen.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention is for solving various problems including the above-mentioned problems, capable of confirming misalignment and connection of TSVs, and measuring the overlay of layers stacked on a wafer through TSV measurement. Also, an object of the present invention is to provide an overlay measurement apparatus and an overlay measurement method capable of determining an optimal focus and performing measurement even when the shape of the TSV is peculiar. However, such problems are exemplary and do not limit the scope of the present invention.

Means for Solving the Problems

[0007] According to an embodiment of the present invention, an overlay measurement apparatus is provided. The overlay measurement apparatus includes a light source unit configured to direct illumination toward an overlay measurement target where a first filling portion formed in a first layer and a second filling portion formed in a second layer stacked above or below the first layer are located; an objective lens configured to condense the illumination at a measurement position at any point of the overlay measurement target; a lens unit in which a lens focus actuator for adjusting a distance between the objective lens and the overlay measurement target is formed; a detection unit configured to acquire a focus image at the measurement position via a beam reflected from the measurement position; and a control unit configured to align a sample image measured by the detection unit with a preset set model image, acquire CI information of the aligned sample image and the set model image, control the lens unit at a focus determined according to the CI information to measure a plurality of images, and calculate an overlay with a difference value by comparing center points of the plurality of images.

[0008] According to an embodiment of the present invention, the control unit selects the set model image through information of a wafer on which the first layer and the second layer are formed, aligns them so that the center points of the set model image and the sample image are the same, obtains an X-axis contrast value graph and a Y-axis contrast value graph, calculates a first focus in a region having the lowest CI value in the X-axis contrast value graph and the Y-axis contrast value graph, controls to measure a first image which is one of the plurality of images with the first focus, calculates a second focus in a region having the highest CI value in the X-axis contrast value graph and the Y-axis contrast value graph, and can control to measure a second image which is another one of the plurality of images with the second focus.

[0009] According to an embodiment of the present invention, the control unit includes: a storage unit for storing the sample image acquired by the detection unit, model information of layers stacked on the wafer, and the plurality of images measured with a focus determined according to the CI information; an alignment unit for comparing and aligning the center points of any one of the set model images in the model information and the sample image; a CI acquisition unit for acquiring the CI information indicating changes in the X-axis contrast value and the Y-axis contrast value of the set model image and the sample image whose center points coincide; a focus calculation unit for calculating a first focus at a point having the lowest CI value among the CI information and calculating a second focus at a point having the highest CI value among the CI information; and an overlay calculation unit for calculating a difference by comparing the center points of the plurality of images.

[0010] According to an embodiment of the present invention, the set model image may be formed in any one of a rectangle, a rectangle with corners having a predetermined curvature, a circle, and an ellipse according to the thicknesses of the pre-stored first layer and second layer or the sample image.

[0011] According to an embodiment of the present invention, the control unit may include a lens operation unit that controls the operation of the lens focus actuator to acquire images of the first layer and the second layer separately by depth according to the focus.

[0012] According to an embodiment of the present invention, the first filling portion and the second filling portion may be TSVs (Through Silicon Vias) filled with a conductor in a hole portion penetrating the first layer and the second layer, and electrically connecting patterns formed in the first layer and the second layer.

[0013] According to an embodiment of the present invention, an overlay measurement method is provided. The overlay measurement method includes a setting model comparison step of aligning a sample image measured at a measurement position of any point of an overlay measurement target where a first filling portion formed in a first layer and a second filling portion formed in a second layer laminated above or below the first layer are located, with a preset setting model image; a CI information acquisition step of acquiring CI information of the aligned sample image and the setting model image; an image measurement step of controlling the lens unit with a focus determined according to the CI information to measure a plurality of images; and an overlay calculation step of comparing the center points of the plurality of images and calculating an overlay with a difference value.

[0014] According to an embodiment of the present invention, the setting model comparison step may include a sample image measurement step of measuring and storing the sample image with a detection unit; a model selection step of selecting the setting model image through information of a wafer on which the first layer and the second layer are formed; and a comparison step of aligning the setting model image and the sample image so that their center points are the same.

[0015] According to an embodiment of the present invention, in the CI information acquisition step, the CI information representing the change in the X-axis contrast value and the change in the Y-axis contrast value of the set model image and the sample image aligned so that the center points are the same can be acquired.

[0016] According to an embodiment of the present invention, the image measurement step may include: a focus calculation step of calculating a first focus at a point having the lowest CI value among the CI information and calculating a second focus at a point having the highest CI value among the CI information; and a measurement step of measuring a first image with the first focus determined according to the CI information and measuring a second image with the second focus.

Advantages of the Invention

[0017] According to some embodiments of the present invention configured as described above, a focus for measuring an overlay from a wafer including two or more layers is calculated, the overlay of the TSV is measured according to the calculated focus, misalignment and connection of the TSV can be confirmed, and the overlay value of the layer stacked on the wafer can be calculated through TSV measurement. Further, even if the shape of the TSV is peculiar, it has an effect that an optimal focus can be determined through the overlay measurement apparatus of the present invention to calculate the overlay value. Of course, the scope of the present invention is not limited by such effects.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0019] Hereinafter, several preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] Embodiments of the present invention are provided to more fully explain the present invention to those having ordinary knowledge in the art. The following embodiments can be modified into various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to make this disclosure more faithful and complete and to fully convey the spirit of the present invention to those skilled in the art. Note that the thickness and size of each layer in the drawings are exaggerated for the convenience of explanation and clarity.

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the drawings, for example, deformations of the illustrated shapes can be expected depending on manufacturing techniques and / or tolerances. Therefore, embodiments of the inventive concept should not be construed as being limited to the specific shapes of the regions shown herein, but should include, for example, shape changes occurring during manufacturing.

[0022] FIG. 1 schematically shows an overlay measurement apparatus according to an embodiment of the present invention, FIG. 2 shows a control unit 400 of the overlay measurement apparatus of the present invention, and FIG. 3 is an exemplary diagram showing obtaining CI information by aligning a sample image S and a set model image M according to an embodiment of the present invention.

[0023] First, an overlay measurement apparatus according to an embodiment of the present invention may generally include a light source unit 100, a lens unit 200, a detection unit 300, and a control unit 400.

[0024] As shown in FIG. 1, illumination can be directed from at least one illumination source to an overlay measurement target T. Specifically, the light source unit 100 may be configured to direct illumination to an overlay measurement target T where a first filling portion 11 formed in a first layer 10 and a second filling portion 21 formed in a second layer 20 laminated above or below the first layer 10 are located.

[0025] For example, the light source unit 100 can 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 thereto.

[0026] An overlay measurement apparatus according to an embodiment of the present invention may include a diaphragm 110, a spectral filter 120, a polarization filter 130, and a beam splitter 140.

[0027] The diaphragm 110 may be formed of an opaque plate having an aperture through which light passes, and the beam irradiated from the light source unit 100 can be changed into a form suitable for photographing the first filling portion 11 and the second filling portion 21.

[0028] The diaphragm 110 may include one or more of an aperture stop for adjusting the amount of light and a field stop for adjusting the range where an image is formed. As shown in FIG. 1, it can be formed between the light source unit 100 and the beam splitter 140. Although not shown, it may also be formed between the beam splitter 140 and the lens unit 200.

[0029] The spectral filter 120 can adjust the central wavelength and bandwidth of the beam irradiated from the light source unit 100 to be suitable for image acquisition of the first layer 10 and the second layer 20 formed on the overlay measurement target T. For example, the spectral filter 120 may be formed of at least one or more of a filter wheel, a linear translation device, a flipper device, and combinations thereof.

[0030] The beam splitter 140 transmits a part of the beam that has passed through the diaphragm 110 after exiting the light source unit 100 and reflects a part thereof, separating the beam emitted from the light source unit 100 into two beams.

[0031] As shown in FIG. 1, the lens unit 200 may include an objective lens 210 that condenses the illumination to a measurement position at any point on the overlay measurement target T, and a lens focus actuator 220 that adjusts the distance between the objective lens 210 and the overlay measurement target T.

[0032] The objective lens 210 can condense the beam reflected from the beam splitter 140 at the measurement position where the first layer 10 and the second layer 20 of the wafer W are formed, and collect the reflected beam.

[0033] The objective lens 210 may be installed on a lens focus actuator 220.

[0034] The lens focus actuator 220 can adjust the distance between the objective lens 200 and the wafer W so that the focal plane is located on the first layer 10 or the second layer 20.

[0035] The lens focus actuator 220 can adjust the focal length by vertically moving the objective lens 200 in the direction of the wafer W under the control of the control unit 400.

[0036] At this time, the measurement position is at least one point of the overlay measurement target T, and is the position where the first filling portion 11 and the second filling portion 21 formed in the first layer 10 or the second layer 20 are formed.

[0037] Here, the first filling portion 11 and the second filling portion 21 are structures in which holes penetrating the first layer 10 and the second layer 20 are filled with a conductor such as copper, and when the first layer 10 and the second layer 20 are laminated, the first layer 10 and the second layer 20 may include TSVs that electrically connect the first layer 10 and the second layer 20 to transmit signals and power between chips.

[0038] For example, the first filling portion 11 may be formed in the first layer 10 which is the lower layer of the wafer W, and the second filling portion 21 may be formed in the second layer 10 which is the upper layer of the wafer W. At this time, in the image measured by the lens portion 200 formed above the wafer W, the first filling portion 11 can be measured to be smaller than the second filling portion 21.

[0039] Also, although not shown, the TSVs may have a truncated reverse conical shape, may be formed in different sizes from each other, or may be formed in an irregular shape.

[0040] The measurement positions may include all of the step-by-step depths measured at respective positions in response to the driving of the lens focus actuator 220.

[0041] As shown in FIG. 1, the detection unit 300 can acquire a focus image at the measurement position via a beam reflected from the measurement position.

[0042] The detection unit 300 can capture a beam that exits through the beam splitter 140 after being reflected from the overlay measurement target T, and acquire images of the first layer 10 and the second layer 20.

[0043] The detection unit 300 may include an optical detector capable of measuring a beam reflected from the overlay measurement target T. For example, the optical detector may include a charge-coupled device (CCD) that converts light into charge and extracts an image, a complementary metal-oxide-semiconductor (CMOS) sensor which is one type of integrated circuit, a photomultiplier tube (PMT) that measures light, an avalanche photodiode (APD) array as a photodetector, or various sensors that generate or capture an image.

[0044] The detection unit 300 may include a filter, a polarizing plate, and a beam block, and may further include any collection optical component (not shown) for collecting the illumination collected by the objective lens 210.

[0045] As shown in FIG. 1, the control unit 400 can control the direction of illumination irradiated from the light source unit 100, collect the illumination on the overlay measurement target T, and control the lens unit 200 so that the reflected beam can be collected, and can control the detection unit 300 so that a focus image measured through the reflected beam collected from the lens unit 200 can be obtained.

[0046] The control unit 400 may include an ARO (Auto Recipe Optimization) program that automatically optimizes the overlay measurement recipe via filter optimization information, aperture optimization information, focus optimization information, and pinhole optimization information.

[0047] The control unit 400 aligns the sample image S measured by the detection unit 300 with the preset setting model image M to obtain CI information, controls the lens unit 200 at a focus determined according to the CI information of the aligned and superimposed sample image S and setting model image M to measure a plurality of images, and can calculate the overlay with a difference value by comparing the center points of the plurality of images.

[0048] Specifically, the control unit 400 may include a light source operation unit 410, a lens operation unit 420, a storage unit 430, an alignment unit 440, a CI acquisition unit 450, a focus calculation unit 460, and an overlay calculation unit 470.

[0049] As shown in FIG. 2, the light source operation unit 410 can control the direction of illumination irradiated from the light source unit 100, and the lens operation unit 420 can control the operation of the lens focus actuator 220 so that the illumination is collected on the overlay measurement target T and images of the first layer 10 and the second layer 20 are obtained for each depth according to the focus.

[0050] The storage unit 430 can store the sample image S acquired by the detection unit 300, the model information of the layers stacked on the wafer W, and the plurality of images measured at the focus determined according to the CI information.

[0051] Specifically, the storage unit 430 can store the image measured by the detection unit 300 in the storage unit 430 as the sample image S. At this time, the sample image S can be measured by controlling the focus at a temporary focus via the wafer W information including the thicknesses of the previously stored first layer 10 and second layer 20.

[0052] The storage unit 430 may include a plurality of model information. At this time, the model information may include a set model image M formed of, for example, a square, a square having corners with a predetermined curvature, a circle, and an ellipse. For example, the set model image M may include an image at a virtual focus adjusted to either the first layer 10 or the second layer 20 via the previously stored wafer W information. Also, among the model information of various shapes, an image corresponding to the shape of the sample image S, for example, an image similar to the sample image S may be selected as the set model image M.

[0053] Also, the user may directly set the size of the circle or the curvature of the corners of the rectangle, etc. for the set model image M.

[0054] For example, the sample image S may be an image corresponding to the second layer 20 as a temporary focus, and the set model image M may be an image corresponding to the first layer 10 set by the previously stored wafer W information.

[0055] The storage unit 430 can store the first image I1 and the second image I2 detected through the first focus and the second focus, which will be described later, in order to measure the overlay between the first layer 10 and the second layer 20.

[0056] The alignment unit 440 can align by comparing the center points of any one of the setting model images M of the model information and the sample image S.

[0057] For example, as shown in FIGS. 3(a) and 3(b), the alignment unit 440 can align so that the setting model image M is coaxial with the central axis of the sample image S. Although not shown, the setting model image M may be formed outside the sample image S. In the case of an ellipse, it may be aligned so that the major axes are the same, or in the case of an irregular shape, it may be converted into a circle or an ellipse and aligned so that they are coaxial or the major axes are the same.

[0058] The CI acquisition unit 450 can acquire CI information indicating changes in the X-axis contrast value and the Y-axis contrast value of the setting model image M and the sample image S whose center points coincide.

[0059] The CI information is data including the contrast values of the setting model image M and the sample image S. For example, as shown in FIG. 3(a), the change in the contrast value can be graphically shown from the cross-section in the X-axis direction based on the central part or the horizontal central region of the setting model image M and the sample image S. As shown in FIG. 3(b), the change in the contrast value can be represented by a CI graph from the cross-section in the Y-axis direction based on the central part or the vertical central region of the setting model image M and the sample image S.

[0060] Here, CI is the Contrast Index, which means the overall degree of contrast of the image pixel values, and the image may be a value indicating the difference in color and brightness. For example, as shown in FIG. 3(a), the line of the setting model image M is set to be very bright, and the contrast value is represented as the highest at the part corresponding to the line of the setting model image M in the CI graph. The brightness of the outer line of the sample image S is detected as bright, which is lower than that of the setting model image M but higher than that of the peripheral part. The inner line of the sample image S is detected as very dark, and the contrast value is represented as the lowest.

[0061] The focus calculation unit 460 can calculate the first focus at the point having the lowest CI value among the CI information, and calculate the second focus at the point having the highest CI value among the CI information.

[0062] For example, the focus calculation unit 460 calculates the first focus so as to be able to focus on a shape having a diameter equal to the lowest value of the contrast value in the CI graph, and calculates the second focus so as to be able to focus on a shape having a diameter equal to the highest value of the contrast value in the CI graph. At this time, in the CI graph, the value with the highest contrast value may be the CI information of the set model image M. Also, since the sample image S is out of focus and the thickness and contrast are not certain, the second focus can be calculated with the value having the lowest contrast value.

[0063] Therefore, in the lens operation unit 420, the first image I1 can be measured with the first focus, and the second image I2 can be measured with the second focus. By measuring the images with the first focus and the second focus, more accurate first image I1 and second image I2, that is, images of the first filling portion 11 and the second filling portion 21 can be obtained.

[0064] The overlay calculation unit 470 can calculate the difference by comparing the center points of the plurality of images. For example, the overlay calculation unit 470 can superimpose the first image I1 and the second image I2 and calculate the gap between the center portion C1 of the first image I1 and the center portion C2 of the second image I2 and measure it as an overlay value.

[0065] Specifically, a graph of the CI values of the X-axis and Y-axis can be obtained from the first image I1, and the center C1 of the first image I1 can be calculated using the midpoint value of the two positions with the largest CI values. Similarly, the center C2 of the second image I2 can be calculated. Therefore, the difference between the center C1 of the first image I1 and the center C2 of the second image I2 can be measured as the overlay value.

[0066] In addition, the series of processes performed by the control unit 400 may include a display unit (not shown) so that the user can monitor, and may also include an input unit (not shown) that the user can directly control.

[0067] That is, the storage unit 430, the alignment unit 440, the CI acquisition unit 450, the focus calculation unit 460, the overlay calculation unit 470, the set model image M, the sample image S, and the CI graph can be confirmed via the display unit, and the user can directly control the light source operation unit 410 and the lens operation unit 420 via the input unit, or directly select, change, and calculate the set model image M, the sample image S, the CI graph, the first focus, the second focus, etc.

[0068] In addition, the overlay measurement device may include a memory or the like that stores instruction words, programs, logics, etc. for controlling the operations of the respective components of the overlay measurement device by the control unit 400, and components may be added, changed, or deleted as necessary.

[0069] That is, the overlay measurement device of the present invention can calculate the focus for measuring the overlay on a wafer including two or more layers, measure the overlay of the TSV by the calculated focus, and confirm the connection of the TSV, and can accurately determine the overlay between the first layer and the second layer.

[0070] FIG. 4 to FIG. 6 are diagrams showing an overlay measurement method according to an embodiment of the present invention, FIG. 7 is a diagram showing a setting model comparison step S100 of the overlay measurement method, FIG. 8 is a diagram showing a CI information acquisition step S200, FIGS. 9 and 10 are diagrams showing measurement of a first image I1 and a second image I2 in an image measurement step S300, and FIG. 11 is a diagram showing an overlay calculation step S400 of the present invention.

[0071] As shown in FIG. 4, the overlay measurement method according to an embodiment of the present invention may include a setting model comparison step S100, a CI information acquisition step S200, an image measurement step S300, and an overlay calculation step S400.

[0072] The setting model comparison step S100 is a step of aligning a sample image S measured at a measurement position of any point of an overlay measurement target T where a first filling portion 11 formed in a first layer 10 and a second filling portion 21 formed in a second layer 20 laminated above or below the first layer 10 are located, and a setting model image M stored in advance.

[0073] For example, as shown in FIG. 7, the setting model comparison step S100 is a step of aligning a sample image S measured by controlling the focus at a virtual focus via wafer W information including the thicknesses of the first layer 10 and the second layer 20 stored in advance, and a setting model image M which is an image with a virtual focus adjusted to either the first layer 10 or the second layer 20 via the wafer W information.

[0074] Specifically, the setting model comparison step S100 may include a sample image measurement step S110 of measuring and storing the sample image S by a detection unit 300, a model selection step S120 of selecting the setting model image M via information of a wafer W on which the first layer 10 and the second layer 20 are formed, and a comparison step S130 of aligning the setting model image M and the sample image S so that their center points are the same.

[0075] The CI information acquisition step S200 is a step of acquiring the CI information indicating the change in the X-axis contrast value and the change in the Y-axis contrast value of the set model image M and the sample image S aligned so that the center points are the same.

[0076] In the CI information acquisition step S200, the CI information is data including the contrast values of the set model image M and the sample image S. For example, as shown in FIG. 8, in the CI information acquisition step S200, based on the centers of the set model image M and the sample image S, the change in the contrast value can be represented by a CI graph from the cross-sections of the X-axis and the Y-axis.

[0077] The image measurement step S300 is a step of controlling the lens unit 200 with the focus determined according to the CI information to measure a plurality of images.

[0078] The image measurement step S300 may include a focus calculation step S310 and a measurement step S320.

[0079] The focus calculation step S310 is a step of calculating a first focus at a point having the lowest CI value among the CI information and calculating a second focus at a point having the highest CI value among the CI information. The measurement step S320 is a step of measuring a first image I1 with the first focus determined by the CI information and measuring a second image I2 with the second focus.

[0080] For example, as shown in FIG. 9, in the focus calculation step S310, the first focus is calculated so that the focus can be adjusted to a shape having a value with the lowest contrast value of the CI graph as the diameter. In the measurement step S320, the first image I1 can be measured with the first focus. Therefore, the image can be measured by readjusting with the first focus, and a more accurate first image I1 than the sample image S, that is, an image of the first filling portion 11 can be obtained.

[0081] Also, as shown in FIG. 10, in the focus calculation step S310, a second focus is calculated so that the focus can be adjusted to a shape having a value with the highest contrast value in the CI graph as the diameter, and in the measurement step S320, a second image I2 can be measured with the second focus. At this time, the second image I2 is an image obtained by measuring the second filling portion 21 of the second layer 20, and can be formed at a position different from the set model image M. That is, the set model image M is for calculating the second focus, and can be different from the second image I2 measured with the second focus.

[0082] The measurement step S320 may further include an illumination directing step S110 of directing illumination from the light source unit 100 to the overlay measurement target T where the first layer 10 and the second layer 20 are located, and adjusting the lens focus actuator 220 that adjusts the distance between the objective lens 210 and the overlay measurement target T, so that the illumination is collected at the measurement position of any one point of the overlay measurement target T via the lens unit 200.

[0083] The overlay calculation step S400 is a step of calculating an overlay with a difference value by comparing the center points of the plurality of images. For example, as shown in FIG. 11, in the overlay calculation step S400, the first image I1 and the second image I2 are compared, and the gap between the center portion C1 of the first image I1 and the center portion C2 of the second image I2 is calculated and measured as the overlay OVL.

[0084] That is, by the overlay measurement method of the present invention, a focus for measuring an overlay is calculated from a wafer including two or more layers, the overlay of the TSV is measured according to the calculated focus, misalignment and connection of the TSV can be confirmed, and an overlay value between the first layer and the second layer can be calculated through the TSV measurement.

[0085] In particular, even if the shape of the TSV is peculiar, overlay values via the TSV can be calculated through the overlay measurement apparatus and method of the present invention by setting various shapes and curvatures.

[0086] The present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and it is understood that those with ordinary knowledge in the art can make various modifications and equivalent other embodiments from now on. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the appended claims.

Explanation of Reference Numerals

[0087] M ··· Setting model image S ··· Sample image T ··· Overlay measurement target W ··· Wafer 10 ··· First layer 11 ··· First filling portion 20 ··· Second layer 21 ··· Second filling portion 100 ··· Light source unit 110 ··· Diaphragm 120 ··· Spectrum filter 140 ··· Beam splitter 200 ··· Lens unit 210 ··· Objective lens 220 ··· Lens focus actuator 300 ··· Detection unit 400 ··· Control unit

Claims

1. A light source unit configured to direct illumination towards an overlay measurement target where a first filling portion formed in a first layer and a second filling portion formed in a second layer laminated above or below the first layer are located; An objective lens that condenses the illumination at a measurement position at any point of the overlay measurement target, and a lens unit in which a lens focus actuator for adjusting the distance between the objective lens and the overlay measurement target is formed; A detection unit that acquires a focus image at the measurement position through the beam reflected from the measurement position; and A control unit that aligns the sample image measured by the detection unit with a preset model image, acquires CI information of the aligned sample image and the preset model image, controls the lens unit at a focus determined according to the CI information to measure a plurality of images, compares the center points of the plurality of images, and calculates an overlay from the difference value; An overlay measurement apparatus comprising the above.

2. The control unit: Selects the preset model image through information of the wafer on which the first layer and the second layer are formed, aligns the preset model image and the sample image so that their center points are the same, and acquires an X-axis contrast value graph and a Y-axis contrast value graph; Calculates a first focus in a region having the lowest CI value from the X-axis contrast value graph and the Y-axis contrast value graph, controls to measure a first image which is one of the plurality of images at the first focus, calculates a second focus in a region having the highest CI value from the X-axis contrast value graph and the Y-axis contrast value graph, and controls to measure a second image which is another one of the plurality of images at the second focus. The overlay measurement apparatus according to Claim 1.

3. The control unit: A storage unit that stores the sample image acquired by the detection unit, model information of the layers laminated on the wafer, and the plurality of images measured at a focus determined according to the CI information; An alignment unit that compares and aligns the center points of any one of the preset model images in the model information and the sample image; A CI acquisition unit that acquires CI information indicating changes in the X-axis contrast value and the Y-axis contrast value of the set model image and the sample image whose center points coincide; A focus calculation unit that calculates a first focus at a point having the lowest CI value among the CI information and calculates a second focus at a point having the highest CI value among the CI information; and An overlay calculation unit that compares the center points of the plurality of images and calculates a difference; The overlay measurement device according to claim 1, comprising:

4. The set model image is The overlay measurement device according to claim 1, which is formed in any one of a square, a square having corners with a predetermined curvature, a circle, and an ellipse according to the thicknesses of the first layer and the second layer stored in advance or the sample image.

5. The control unit is A lens operation unit that controls the operation of the lens focus actuator so as to acquire respective images of the first layer and the second layer by depth according to the focus; The overlay measurement device according to claim 1, comprising:

6. The first filling portion and the second filling portion are The overlay measurement device according to claim 1, which is a TSV (Through Silicon Via) filled with a conductor in a hole portion penetrating the first layer and the second layer and electrically connecting patterns formed in the first layer and the second layer.

7. A set model comparison step of aligning a sample image measured at a measurement position of any one point of an overlay measurement target where a first filling portion formed in a first layer and a second filling portion formed in a second layer laminated above or below the first layer are located, and a preset set model image; A CI information acquisition step of acquiring CI information of the aligned sample image and the set model image; An image measurement step of controlling a lens unit with a focus determined according to CI information to measure a plurality of images; and An overlay calculation step of comparing the center points of the plurality of images and calculating an overlay with a difference value; An overlay measurement method, comprising:

8. The set model comparison step is A sample image measurement step of measuring and storing the sample image with a detection unit; a model selection step of selecting the set model image through information on a wafer on which the first layer and the second layer are formed, and a comparison step of aligning the set model image and the sample image so that their center points are the same, The overlay measurement method according to claim 7, comprising:

9. In the CI information acquisition step, The overlay measurement method according to claim 7, wherein CI information indicating a change in the X-axis contrast value and a change in the Y-axis contrast value of the set model image and the sample image, which are aligned so that their center points are the same, is acquired.

10. The image measurement step includes: a focus calculation step of calculating a first focus at a point having the lowest CI value among the CI information and calculating a second focus at a point having the highest CI value among the CI information, and a measurement step of measuring a first image with the first focus determined according to the CI information and measuring a second image with the second focus, The overlay measurement method according to claim 7, comprising:

Images