Surface Profile Measurement System, Overlay Measuring Device Equipped with the Same, and Surface Profile Measurement Method

Abstract

The present invention relates to a surface shape measurement system used in an optical measuring device, an overlay measuring device equipped with the same, and a surface shape measurement method. The present invention provides a surface shape measurement system comprising: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; and a light splitting device disposed on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively, wherein the light splitting device splits the reflected light such that when the surface of the measurement target is orthogonal to the optical axis of the illumination light, the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other.

Description

Technology Field

[0001] The present invention relates to a surface shape measuring system used in an optical measuring device, an overlay measuring device equipped with the same, and a surface shape measuring method. Background Technology

[0002] With technological advancements, there is a growing demand for smaller semiconductor devices and increased integrated circuit density. Meeting these requirements necessitates satisfying various conditions, among which overlay tolerance is a key indicator.

[0003] Semiconductor devices are manufactured through numerous processes. To form integrated circuits on a wafer, many manufacturing steps must be performed to ensure that desired circuit structures and elements are sequentially formed at specific locations. The manufacturing process generates patterned layers sequentially on the wafer. Through these repetitive stacking processes, electrically active patterns are created within the integrated circuit. At this stage, if the individual structures are not aligned within the error range allowed by the production process, interference occurs between the electrically active patterns, which can lead to problems with the performance and reliability of the manufactured circuit. Overlay measurement tools are used to measure and verify these inter-layer alignment errors.

[0004] General overlay measurement and methods measure and verify whether the alignment between two layers is within the tolerance. One such method involves forming a structure called an overlay mark at a specific location on a substrate and capturing this structure using an optical image acquisition device to measure the overlay. The structure for measurement is designed to measure the overlay in at least one of the X and Y directions for each layer. Each structure is designed as a symmetrical structure, and the center value between structures arranged in the symmetrical direction is calculated and used as the representative value of that layer. The overlay error is derived by calculating the relative difference between the representative values ​​of each layer.

[0005] To derive an accurate overlay error, a clear overlay mark image must be acquired. To acquire a clear overlay mark image, the image must be obtained while the overlay mark is in focus.

[0006] To focus on the overlay mark, autofocus devices are used that measure the height of the overlay mark and automatically focus.

[0007] For example, Korean Published Patent No. 10-2007-0111685 discloses an autofocusing system comprising: a light source emitting laser light; a beam splitter transmitting the laser light toward the wafer and reflecting reflected light from the wafer; a converging lens converting the reflected light into a converging form; a converging light spot generator forming the converted converging light into a converging light spot and emitting it in a diverging form; and a plurality of light receivers for detecting the time difference of the diverging light.

[0008] The chopper wheel used here as an intermittent optical spot generator rotates by a drive motor. This rotation of the chopper wheel causes vibrations that can affect the camera and receiver, and fine particles generated by the rotation can also be a problem. Additionally, there is the disadvantage of requiring space to install the chopper wheel and the drive motor. Furthermore, the aforementioned autofocusing system has the disadvantage that it is difficult to measure the inclination angle of the wafer's target surface. Prior art literature

[0009] Korean Published Patent No. 10-2007-0111685 (2007.11.22) The problem to be solved

[0010] The present invention aims to solve the aforementioned problems by providing a surface shape measuring system that can solve vibration and fine particle problems by not using a chopper wheel and a drive motor, and can measure not only the height but also the inclination angle of a surface to be measured, an overlay measuring device equipped with the same, and a surface shape measuring method. means of solving the problem

[0011] To achieve the above-mentioned objective, the present invention provides a surface shape measurement system comprising: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; and a light splitting device disposed on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively, wherein the light splitting device splits the reflected light such that when the surface of the measurement target is orthogonal to the optical axis of the illumination light, the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other.

[0012] In addition, a surface shape measuring system is provided that further includes a controller that calculates the inclination angle of the surface of the measurement target with respect to the optical axis of the irradiated light based on the difference between the signal detected by the first sensing unit and the signal detected by the second sensing unit.

[0013] In addition, the controller provides a surface shape measurement system that calculates the height of the surface of the measurement target based on the magnitude of the signal detected from the first sensing unit and the magnitude of the signal detected from the second sensing unit.

[0014] Additionally, the light splitting device provides a surface shape measuring system comprising a condensing lens that concentrates the reflected light to the detector, and a mask disposed between the condensing lens and the detector, which blocks the center of the reflected light passing through the condensing lens to split the reflected light passing through the condensing lens into reflected light directed toward the first detection unit and reflected light directed toward the second detection unit.

[0015] Additionally, when the optical axis of the above-mentioned irradiated light and the surface of the measurement target are orthogonal, the optical axis of the reflected light passing through the condensing lens is located at the boundary of the first sensing part and the second sensing part, thereby providing a surface shape measuring system.

[0016] In addition, the light splitting device provides a surface shape measuring system comprising a first condensing lens that concentrates a portion of the reflected light to a first sensing unit and a second condensing lens that concentrates a portion of the reflected light to a second sensing unit.

[0017] In addition, the first and second sensing units provide a surface shape measuring system that is a PSD sensor.

[0018] In addition, the first and second sensing units are photodiodes, and the surface shape measuring system is provided.

[0019] In addition, the above photodetector provides a surface shape measurement system that is a bicell photodiode.

[0020] In addition, the present invention provides a method for measuring a surface shape, comprising the steps of: illuminating a measurement target with an irradiating light; collecting reflected light from the surface of the measurement target, dividing it, and concentrating it on a first sensing part and a second sensing part respectively, which are arranged side by side on a plane orthogonal to the optical axis of the reflected light; and calculating the inclination angle of the surface of the measurement target with respect to the optical axis of the irradiating light based on the difference between the signal detected by the first sensing part and the signal detected by the second sensing part.

[0021] In addition, a surface shape measurement method is provided that further includes the step of calculating the height of the surface of the measurement target based on the magnitude of the signal detected from the first sensing unit and the magnitude of the signal detected from the second sensing unit.

[0022] In addition, the present invention provides an overlay measuring device for measuring an error between a pair of first overlay marks and a second overlay mark formed on different layers formed on a wafer, comprising an image acquisition device configured to acquire alignment images of the pair of first overlay marks and the second overlay mark at a plurality of focal positions, and a surface shape measuring system for obtaining information to adjust the focus of the image acquisition device, wherein the surface shape measuring system provides an overlay measuring device which is the surface shape measuring system described above. Effects of the invention

[0023] The surface shape measuring system according to the present invention does not use a chopper wheel and a drive motor, thereby solving problems related to vibration and fine particles. In addition, it can measure not only the height of the surface to be measured but also the angle of inclination. Brief explanation of the drawing

[0024] FIG. 1 is a conceptual diagram of an overlay measuring device according to an embodiment of the present invention. Figures 2 and 3 show signals from a one-dimensional photodetector. Figure 4 shows the signal from the two-dimensional photodetector. Figure 5 is a flowchart illustrating the operation of an overlay measuring device. FIG. 6 is a conceptual diagram of an overlay measuring device according to another embodiment of the present invention. Specific details for implementing the invention

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, embodiments of the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art. Accordingly, the shapes of elements in the drawings are exaggerated to emphasize clearer explanations, and elements indicated by the same reference numeral in the drawings represent the same elements.

[0026] FIG. 1 is a conceptual diagram of an overlay measuring device according to an embodiment of the present invention. The overlay measuring device is a device for measuring an error between a first overlay mark (OM1) and a second overlay mark (OM2) formed on different layers formed on a wafer (w).

[0027] The first overlay mark (OM1) may be an overlay mark formed on a previous layer, and the second overlay mark (OM2) may be an overlay mark formed on a current layer. The overlay marks are formed on a scribe lane while simultaneously forming a layer for forming a semiconductor device in a die region. For example, the first overlay mark (OM1) may be formed together with an insulating film pattern, and the second overlay mark (OM2) may be formed together with a photoresist pattern formed on the insulating film pattern.

[0028] In this case, the second overlay mark (OM2) is exposed to the outside, but the first overlay mark (OM1) is covered by a photoresist layer and is made of an oxide with optical properties different from those of the second overlay mark (OM2), which is made of photoresist material. Additionally, the first overlay mark (OM1) and the second overlay mark (OM2) have different heights.

[0029] For overlay marks, various types of currently used overlay marks, such as box-in-box and AIM (advanced imaging metrology) overlay marks, can be used.

[0030] As illustrated in FIG. 1, an overlay measuring device (1) according to one embodiment of the present invention includes an imaging system (10) and a controller (20) that is communicably coupled to the imaging system (10).

[0031] The imaging system (10) mainly includes an image acquisition device (100) and a surface shape measurement system (200).

[0032] The image acquisition device (100) is responsible for acquiring an image (hereinafter referred to as an "aligned image") in which a first overlay mark (OM1) and a second overlay mark (OM2) are displayed together at multiple focal points.

[0033] An image acquisition device (100) is equipped with an image acquisition light source (111), a first beam splitter (113), a stage (114), an objective lens (115), and an actuator (117) to irradiate an image acquisition light onto a measurement area of ​​a wafer (W). The measurement area is an area where a first overlay mark (OM1) and a second overlay mark (OM2) are formed in the scribe lane of the wafer (W). A plurality of measurement areas exist on a single wafer (W). An overlay measurement device (1) measures overlay errors in a plurality of measurement areas.

[0034] A halogen lamp, a xenon lamp, a light-emitting diode, a supercontinuum laser, etc., can be used as the light source (111) for image acquisition. The light source (111) for image acquisition can generate light for image acquisition in the visible light region.

[0035] The first beam splitter (113) serves to reflect a portion of the image acquisition illumination light that comes out of the image acquisition light source (111) and passes through the lens (112), and guides it toward the objective lens (115). It also transmits a portion of the reflected light collected by the objective lens (115).

[0036] The stage (114) serves to support the wafer (W). The stage (114) can move the wafer (W) on a plane and adjust the tilt of the wafer (W).

[0037] The objective lens (115) focuses the beam reflected from the first beam splitter (113) into a measurement area of ​​the wafer (W) and collects the reflected light from the measurement area. The objective lens (115) is installed in an actuator (117).

[0038] The actuator (117) adjusts the distance between the objective lens (115) and the wafer (W) to adjust the focal position of the image acquisition device (100).

[0039] Additionally, the image acquisition device (100) is equipped with a hot mirror (121), a tube lens (123), and an image detector (130) to collect reflected light from a measurement area of ​​a wafer (W) to obtain an alignment image.

[0040] The tube lens (123) serves to collect reflected light that has passed through the first beam splitter (113) and the hot mirror (121) into the image detector (130).

[0041] The hot mirror (121) reflects light with a longer wavelength than the reference wavelength and transmits light with a shorter wavelength than the reference wavelength. For example, the hot mirror (121) can reflect infrared light and transmit visible light, or reflect infrared light with a relatively long wavelength and transmit infrared light with a relatively short wavelength. The hot mirror (121) can prevent long-wavelength light used in the surface shape measurement system (200) from being incident on the image detector (130).

[0042] The image detector (130) may be a two-dimensional detector including a CCD or CMOS camera. The image acquisition device (100) acquires an alignment image using an electrical signal from the image detector (130). Then, by analyzing this alignment image, an overlay error can be measured.

[0043] The surface shape measuring system (200) serves to generate a signal based on the height of the wafer (W). This signal can be used to control the actuator (117) to focus.

[0044] Additionally, the surface shape measurement system (200) also serves to generate a signal based on the angle of inclination between the surface of the wafer (W) and the optical axis. This signal can be used to adjust the angle of inclination of the stage (114) that supports the wafer (W).

[0045] The surface shape measurement system (200) includes a light source (211) for irradiating irradiation light onto a measurement area of ​​a wafer (W), a light detector (230), and a light splitting device (220).

[0046] Additionally, it is equipped with an optical lens (212) that refracts irradiated light from a light source (211), a second beam splitter (213), and a cylinder lens (219). Furthermore, the hot mirror (121), the first beam splitter (113), and the objective lens (115) of the image acquisition device (100) are also used as part of the surface shape measurement system (200).

[0047] A laser diode or a light-emitting diode may be used as the light source (211). The light source (211) may, for example, generate irradiation light in the infrared region. The irradiation light is refracted by an optical lens (212), then passes through a second beam splitter (213) and a cylinder lens (215), and is reflected by a hot mirror (121).

[0048] A plano-convex lens may be used as the optical lens (212). When a laser is used as the irradiation light, it is preferable to use a polarizing beam splitter as the second beam splitter (213). This is because the reduction in light intensity during the reflection and transmission process can be minimized.

[0049] As for the cylinder lens (215), various shapes such as rectangular, square, circular, and elliptical cylinder lenses (215) can be used. The cylinder lens (215) is a lens that focuses light on a line rather than a point. The cylinder lens (215) serves to form a line beam. Using a line beam has the advantage of increasing sensitivity due to optical aberrations (astigmatism), thereby enabling more precise measurements. It is desirable that the line beam be formed so as not to be parallel to the lines forming the overlay mark. Additionally, it is desirable that the line beam not extend beyond the overlay mark. This is because if the line beam extends beyond the overlay mark, it may be affected by structures located outside the overlay mark, such as adjacent other overlay marks.

[0050] Then, the irradiating light reflected from the hot mirror (121) passes through the first beam splitter (113) and then enters the objective lens (115).

[0051] The objective lens (115) serves to concentrate the illumination light into the measurement area of ​​the wafer (W) and to collect the reflected light from the measurement area. The present invention can concentrate the illumination light and the illumination light for image acquisition using a single objective lens (115), and collect the reflected light of the illumination light and the illumination light.

[0052] In the present invention, infrared light with a wavelength band different from the illumination light for image acquisition is used as the irradiation light, and a hot mirror (121) is used to separate the reflected light from each other, thereby preventing the reflected light of the irradiation light from being incident on the image detector (130).

[0053] The reflected light of the illumination light collected from the objective lens (115) passes through the first beam splitter (113) and is then reflected by the hot mirror (121). Since infrared light cannot pass through the hot mirror (121), the reflected light in the infrared region does not enter the image detector (130).

[0054] The reflected light from the hot mirror (121) is reflected from the second beam splitter (213) toward the photodetector (230).

[0055] The photodetector (230) is configured to receive divided reflected light and generate at least two distinct electrical signals. The photodetector (230) includes at least one pair of sensing elements (231, 233) arranged side by side on a plane orthogonal to the optical axis.

[0056] The light detector (230) illustrated in FIG. 1 includes a first detection unit (231) and a second detection unit (233). The first detection unit (231) and the second detection unit (233) generate electrical signals independently of each other. It is preferable that the first detection unit (231) and the second detection unit (233) generate the same electrical signal when the same light is incident.

[0057] The photodetector (230) may be, for example, a bicell photodiode. In this case, the two cells of the bicell photodiode may become the first detection unit (231) and the second detection unit (233). The first detection unit (231) and the second detection unit (233) may each generate an electrical signal proportional to the intensity of the reflected light incident on them. Additionally, instead of a bicell photodiode, a pair of photodiodes may be used as the first detection unit (231) and the second detection unit (233).

[0058] Additionally, the photodetector (230) may include two Position Sensitive Device (PSD) sensors. A one-dimensional PSD sensor or a two-dimensional PSD sensor may be used as the PSD sensor. In this case, the PSD sensors may serve as the first detection unit (231) and the second detection unit (233). A one-dimensional PSD sensor can generate data that changes according to coordinates in a uniaxial direction.

[0059] For example, as illustrated in FIGS. 2 and 3, a one-dimensional graph can be generated that represents the change in intensity of reflected light according to the distance from the boundary of the first detection unit (231) and the second detection unit (233). (a) of FIGS. 2 and 3 may be a signal from the first detection unit (231), and (b) may be a signal from the second detection unit (233). In FIG. 2, the signal from the first detection unit (231) and the signal from the second detection unit (233) match each other, so the one-dimensional graphs are symmetrical to each other, whereas in FIG. 3, the signal from the first detection unit (231) and the signal from the second detection unit (233) do not match each other, so the one-dimensional graphs are not symmetrical to each other.

[0060] As illustrated in FIG. 4, using a 2D PSD sensor can generate a 2D map showing the change in intensity of reflected light according to position on a plane. The circles in FIG. 4 connect points where the intensity of reflected light is the same. FIG. 4 (a) may be a signal from the first detection unit (231), and (b) may be a signal from the second detection unit (233). In FIG. 4, the signal from the first detection unit (231) and the signal from the second detection unit (233) do not match each other, so the 2D maps are not symmetrical to each other.

[0061] Additionally, two CCD (Charge-Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensors may be used as the photodetector (230). Additionally, two separate sections of a single CCD or CMOS sensor may be used as the first detection section (231) and the second detection section (233).

[0062] Additionally, the photodetector (230) may include two or more pairs of sensing elements. For example, a photodetector (230) in which two pairs of photodiodes or one-dimensional PSD sensors are arranged in a cross shape may be used. In this case, one pair may be used for measuring the tilt in the X-axis direction, and the other pair may be used for measuring the tilt in the Y-axis direction.

[0063] The light splitting device (220) is positioned on the light path of the reflected light (5). In this embodiment, the light splitting device (220) is positioned between the second beam splitter (213) and the light detector (230).

[0064] The light splitting device (220) serves to split the reflected light (5) and concentrate it on the first detection unit (231) and the second detection unit (233), respectively. When the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light (3), the light splitting device (220) is configured to split the reflected light (5) equally so that the signal detected from the first detection unit (231) and the signal detected from the second detection unit (233) are identical to each other, as shown in FIG. 2.

[0065] If the surface of the wafer (W) is not orthogonal to the optical axis of the irradiation light (3), the signals are different, as shown in FIG. 3. And the difference in these signals can serve as a basis for calculating the angle of inclination of the surface of the wafer (W) with respect to the optical axis of the irradiation light. That is, if the surface of the wafer (W) is orthogonal to the optical axis of the irradiation light (3), the intensity, position, size, etc. of the first reflected light (7) and the second reflected light (8) divided by the light splitting device (220) match each other, and if not, they do not match each other.

[0066] For example, if a bicell diode is used as the photodetector (230), it can be determined that the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light (3) if the magnitudes of the electrical signals from the two cells match. And if the photodetector (230) includes two 1D PSD sensors, it can be determined that the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light (3) if the shapes of the 1D graphs (see FIG. 2) obtained using the signals from the 1D PSD sensors match. And if the photodetector (230) includes two 2D PSD sensors, a CCD sensor, and a CMOS sensor, it can be determined that the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light (3) if the shapes of the 2D maps (see FIG. 4) match.

[0067] As shown in FIG. 1, the light splitting device (220) may include a condensing lens (221) and a mask (223).

[0068] The condensing lens (221) serves to concentrate the reflected light (5) reflected from the second beam splitter (213) onto the detector (230). When the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light, the optical axis of the reflected light (5) passing through the condensing lens (221) is located at the boundary between the first detection unit (231) and the second detection unit (233).

[0069] The mask (223) is placed between the condensing lens (221) and the detector (230). The mask (223) serves to block the center of the reflected light (5) passing through the condensing lens (221), thereby dividing the reflected light (5) passing through the condensing lens (221) into a first reflected light (7) directed toward the first detection unit (231) and a second reflected light (8) directed toward the second detection unit (233). The mask (223) absorbs or reflects the reflected light. The surface of the mask (223) is black anodized, 10 -6 A reflection coefficient of less than 100 can be achieved. If two pairs of sensing parts are included, the mask may divide the reflected light (5) into four parts.

[0070] The controller (20) is coupled to the imaging system (10) so as to communicate via wired or wireless means. The controller (20) includes hardware such as a processor, memory, fixed memory (ROM), and storage devices such as a hard disk or SSD, and programs such as firmware or software installed on storage media such as memory, fixed memory, and storage devices. A computing device such as a Micro controller unit (MCU), a desktop computer, a laptop computer, a smartphone, or a smart pad may be used as the controller (20).

[0071] The controller (20) is configured to calculate the inclination angle of the wafer (W) surface and the height of the wafer (W) surface based on signals from the photodetector (230). Based on these, the actuator (117) and the stage (114) can be controlled.

[0072] The controller (20) can calculate the angle of inclination of the wafer (W) surface with respect to the optical axis of the irradiated light based on the difference between the signal detected by the first detection unit (231) and the signal detected by the second detection unit (233). That is, if the signal detected by the first detection unit (231) and the signal detected by the second detection unit (233) are the same, it is determined that the optical axis of the irradiated light and the wafer (W) surface are orthogonal, and if the signal detected by the first detection unit (231) and the signal detected by the second detection unit (233) are different, the angle of inclination of the wafer (W) surface with respect to the optical axis of the irradiated light is calculated based on the difference between the signals. If a bicell diode is used as the photodetector (230), the angle of inclination is greater as the difference between the signals increases, and the direction of inclination can be determined according to the sign of the difference value between the signals. If a one-dimensional PSD sensor is used as the photodetector (230), the difference in the position of the peaks of the graph can also be used to calculate the slope angle. Additionally, if a two-dimensional PSD sensor, CMOS sensor, CCD sensor, etc. are used, the difference in the position of the peaks of the map can be used to calculate the slope angle and the slope direction.

[0073] The controller (20) can control the stage (114) using the calculated inclination angle so that the optical axis of the irradiated light and the surface of the wafer (W) are perpendicular.

[0074] Additionally, the controller (20) can calculate the height of the wafer (W) surface (distance to the detector) based on the magnitude of the signal detected from the first detection unit (231) and the magnitude of the signal detected from the second detection unit (233), and determine whether the light reflected from the wafer (W) surface is underfocus or overfocus. First, the height of the wafer (W) surface may be calculated after ensuring that the optical axis of the irradiated light and the wafer (W) surface are perpendicular.

[0075] The controller (20) can determine whether the height of the wafer (W) surface is higher or lower than the height when the focus is correct by comparing the size of the reference signal, which is the size of the signal from the first detection unit (231) and the second detection unit (233) when the focus is correct, the size of the signal detected from the first detection unit (231), and the size of the signal detected from the second detection unit (233). (It can determine whether it is under-focus or over-focus.) Through this, the controller (20) can adjust the height of the objective lens (115) so that the focus is correct at the measurement position on the wafer (W) surface.

[0076] Hereinafter, with reference to FIG. 5, the operation of the overlay measuring device described above will be explained.

[0077] First, an illumination light is shone on the object to be measured (S1).

[0078] When the surface shape measurement system (200) is operated using an input device connected to the controller (20), the light source (211) is turned on, and the irradiating light illuminates the wafer (W).

[0079] Next, reflected light from the surface of the object to be measured is collected, divided, and focused on the first sensing part and the second sensing part, respectively (S2).

[0080] In this step, reflected light from the surface of the measurement target (wafer) is collected using an objective lens (115), and a light splitting device (220) is placed in the path of the reflected light (5) so that the collected reflected light (5) passes through the light splitting device (220). The light splitting device (220) splits the reflected light (5) into a first reflected light (7) and a second reflected light (8), and concentrates them on the first detection unit (231) and the second detection unit (233), respectively.

[0081] Next, the inclination angle of the surface of the measurement target is calculated based on the difference between the signal detected from the first detection unit and the signal detected from the second detection unit (S3).

[0082] If the signal from the first sensing unit (231) and the signal from the second sensing unit (233) are the same, the controller (20) determines that the surface of the measurement target and the optical axis of the irradiated light are orthogonal, and if the signals are different, it calculates the inclination angle of the surface of the measurement target based on the difference between the signals. The greater the difference between the signals, the more the surface of the measurement target can be determined to be tilted.

[0083] The controller (20) can adjust the inclination angle of the stage (114) using the calculated inclination angle so that the surface of the measurement target and the optical axis of the irradiation light are orthogonal.

[0084] Additionally, the controller (20) compares the signal from the first detection unit (231) and the signal from the second detection unit (233) with the signal when the focus is correct to determine whether the state is under focus or over focus, and accordingly, may adjust the distance between the objective lens (115) and the wafer (W) to focus.

[0085] FIG. 6 is a conceptual diagram of an overlay measuring device according to another embodiment of the present invention. In this embodiment, the overlay measuring device (2) differs from the embodiment shown in FIG. 1 only in the surface shape measuring system (300) of the imaging system (20), so only this part will be described in detail.

[0086] The surface shape measuring system (300) of the present embodiment includes a light source (311) for irradiating irradiating light onto a measuring area of ​​a wafer (W), a light detector (330), and a light splitting device (320). Additionally, it includes an optical lens (312) for refracting irradiating light from the light source (311), a second beam splitter (313), and a cylinder lens (319).

[0087] The light splitting device (320) of the present embodiment includes a first condensing lens (321) that concentrates a portion of the reflected light reflected from the second beam splitter (313) onto a first detection unit (331), and a second condensing lens (323) that concentrates a portion of the reflected light onto a second detection unit (333). The first condensing lens (321) and the second condensing lens (323) may be the same lens. The light splitting device (320) may also be a lens array comprising two lenses.

[0088] The light splitting device (320) is configured to split the reflected light (5) equally so that when the surface of the wafer (W) is orthogonal to the optical axis of the irradiated light (3), the signal detected from the first detection unit (331) and the signal detected from the second detection unit (333) are identical to each other.

[0089] The embodiments described above are merely illustrative of preferred embodiments of the present invention, and the scope of the present invention is not limited to the described embodiments. Various changes, modifications, or substitutions may be made by those skilled in the art within the technical spirit and scope of the claims of the present invention, and such embodiments should be understood to fall within the scope of the present invention. Explanation of the symbols

[0090] 1, 2: Overlay measuring device 10, 30: Imaging system 20: Controller 100: Image acquisition device 111: Light source for image acquisition 115: Objective lens 117: First actuator 121: Hot mirror 130: Image detector 200, 300: Surface shape measuring system 211, 311: Light source 212, 312: Optical lens 215, 315: Cylinder lens 220, 320: Light splitting device 230, 330: Photodetector

Claims

Claim 1 A surface shape measuring system comprising: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; a light splitting device arranged on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively; and a controller that calculates the inclination angle of the surface of the measurement target with respect to the optical axis of the illumination light based on the difference between a signal detected from the first sensing unit and a signal detected from the second sensing unit, wherein the light splitting device splits the reflected light such that the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other when the surface of the measurement target is orthogonal to the optical axis of the illumination light. Claim 2 delete Claim 3 A surface shape measuring system comprising: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; a light splitting device arranged on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively; and a controller that calculates the height of the surface of the measurement target based on the magnitude of a signal detected from the first sensing unit and the magnitude of a signal detected from the second sensing unit, wherein the light splitting device splits the reflected light such that the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other when the surface of the measurement target is orthogonal to the optical axis of the illumination light. Claim 4 A surface shape measuring system according to claim 1 or 3, wherein the light splitting device comprises a condensing lens that concentrates the reflected light to the detector, and a mask disposed between the condensing lens and the detector, which blocks the center of the reflected light passing through the condensing lens to split the reflected light passing through the condensing lens into reflected light directed toward the first detection unit and reflected light directed toward the second detection unit. Claim 5 A light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; and a light splitting device disposed on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively. The light splitting device splits the reflected light such that when the surface of the measurement target is orthogonal to the optical axis of the illumination light, the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other. The light splitting device includes a condensing lens that concentrates the reflected light to the detector, and a mask disposed between the condensing lens and the detector that blocks the center of the reflected light passing through the condensing lens to split the reflected light passing through the condensing lens into reflected light directed toward the first sensing unit and reflected light directed toward the second sensing unit. The optical axis of the illumination light and the measurement A surface shape measuring system in which, when the surface of the object is orthogonal, the optical axis of the reflected light passing through the condensing lens is located at the boundary of the first sensing part and the second sensing part. Claim 6 A surface shape measuring system comprising: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; and a light splitting device disposed on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively, wherein the light splitting device splits the reflected light such that when the surface of the measurement target is orthogonal to the optical axis of the illumination light, the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other, and the light splitting device includes a first focusing lens that concentrates a portion of the reflected light to the first sensing unit and a second focusing lens that concentrates a portion of the reflected light to the second sensing unit. Claim 7 A surface shape measuring system according to any one of claims 1, 3, 5 and 6, wherein the first sensing unit and the second sensing unit are PSD sensors. Claim 8 A surface shape measuring system according to any one of claims 1, 3, 5 and 6, wherein the first sensing unit and the second sensing unit are photodiodes. Claim 9 A surface shape measuring system in any one of claims 1, 3, 5 and 6, wherein the photodetector is a bicell photodiode. Claim 10 A method for measuring a surface shape, comprising the steps of: illuminating a measurement target with an illuminating light; collecting reflected light from the surface of the measurement target, dividing it, and concentrating it on a first sensing part and a second sensing part respectively, which are arranged side by side on a plane perpendicular to the optical axis of the reflected light; and calculating the inclination angle of the surface of the measurement target with respect to the optical axis of the illuminating light based on the difference between the signal detected by the first sensing part and the signal detected by the second sensing part. Claim 11 A surface shape measurement method further comprising the steps of: illuminating a measurement target with an irradiating light; collecting reflected light from the surface of the measurement target, dividing it, and concentrating it on a first sensing part and a second sensing part respectively, which are arranged side by side on a plane orthogonal to the optical axis of the reflected light; and calculating the height of the surface of the measurement target based on the magnitude of the signal detected from the first sensing part and the magnitude of the signal detected from the second sensing part. Claim 12 An overlay measuring device for measuring an error between a pair of first overlay marks and a second overlay mark formed on different layers formed on a wafer, comprising: an image acquisition device configured to acquire alignment images of the pair of first overlay marks and the second overlay mark at a plurality of focal positions; and a surface shape measuring system for obtaining information for adjusting the focus of the image acquisition device. The surface shape measuring system comprises: a light source that generates illumination light that illuminates a measurement target; a light detector configured to receive reflected light reflected from the surface of the measurement target and having at least one pair of sensing units, wherein the sensing units include a first sensing unit and a second sensing unit arranged side by side on the same plane orthogonal to the optical axis; and a light splitting device disposed on the optical path of the reflected light and configured to split the reflected light and concentrate it on the first sensing unit and the second sensing unit, respectively. The light splitting device divides the reflected light such that when the surface of the measurement target is orthogonal to the optical axis of the illumination light, the signal detected from the first sensing unit and the signal detected from the second sensing unit match each other. Overlay measuring device, which is a measuring system.

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