Surface shape measuring device

Abstract

The surface shape measuring device according to the embodiment comprises a phase-shift interferometer, a slit illumination optical system, an image detector, and an image processing device. The phase-shift interferometer has an imaging function and simultaneously generates interference fringes of three or more different phases. The slit illumination optical system emits illumination light through a slit located at the image plane position of the phase-shift interferometer. The image detector is positioned where the surface of the object is illuminated in a slit shape by the slit illumination optical system and the phase-shift interferometer, and the reflected light forms a slit-shaped image through the phase-shift interferometer. The image detector converts the light intensity of each point in the slit-shaped image into photoelectric data. The image processing device has a one-dimensional processing function that obtains one-dimensional surface shape data from a slit-shaped image obtained by the image detector, where each point has interference fringe signals of three or more different phases, and a two-dimensional processing function that obtains two-dimensional surface shape data from the newly obtained one-dimensional surface shape data in synchronization with the movement of the object moving platform.

Description

Technical Field

[0001] Embodiments according to the present invention relate to a surface shape measuring device.

Background Art

[0002] The bonding of semiconductor chips has been shifting from bump bonding to hybrid bonding (HB: Hybrid Bonding). The bonding technology has been evolving with the miniaturization of the pitch of bumps. Solder balls have been used up to a pitch of the 60-μm class mounted on a package substrate used for FC-BGA (Flip Chip-Ball Grid Array) packages such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), but below that pitch, μ-bumps with lead-free solder on copper pillars have become mainstream. Further, for semiconductor chips with a fine pitch of less than 10 μm class, it is considered that hybrid bonding that directly bonds copper electrodes on the semiconductor chips without bumps will be adopted. This is because if bump bonding is attempted in the case of a fine pitch, the risk of being joined to adjacent bumps during solder melting increases.

[0003] Hybrid bonding joins opposing insulating films and opposing electrodes. First, the insulating films are joined, and then the electrodes are expanded by heating to join the electrodes. Considering the expansion of the electrodes in the subsequent process, the design of the step (depression) of the electrodes with respect to the surface of the insulating film is important, and the accuracy of its measurement is also important.

[0004] What is important in the measurement of each step of the electrodes is (1) the lateral resolution (planar resolution) close to the resolution limit of optical imaging and (2) the resolution in the step direction on the order of angstroms. In the measurement of electrode arrangements with a narrow pitch, higher resolution is required, but hybrid bonding with a submicron electrode pitch (for example, 0.4 μm) has already been reported.

[0005] Currently, electrode step heights are measured using an AFM (Atomic Force Microscope) (for example, Patent Document 1). Although AFMs have very high resolution in both the lateral and step height directions, enabling highly accurate measurements, they require a long measurement time, making it impossible to measure the step height of all electrodes on the entire wafer.

[0006] Since AFM requires long measurement times, we will consider optical measurement, which is advantageous for high-speed measurement. As mentioned above, the important factors in measuring each step height of an electrode are (1) lateral resolution (planar resolution) close to the resolution limit of optical imaging, and (2) step height resolution on the order of angstroms. To achieve (1) and (2) with optical measurement, one method is to use phase-shift interferometry with a high NA objective lens. In this case, light is shone on the insulating film that serves as the reference for the step height and the electrode corresponding to the bottom, and the light is reflected from the insulating film surface and the electrode surface. The reflectivity of the insulating film surface is around 5%, so most of the illumination light passes through the insulating film and is reflected by the highly reflective circuit pattern beneath the insulating film, and as a result, it is not possible to accurately measure the step height of the electrode. By using low-coherent light with a wide bandwidth as illumination light, it is possible to suppress the generation of interference signals on the circuit pattern beneath the insulating film. However, since it is not possible to eliminate the reflected light itself, a large offset signal is superimposed on the interference signal on the insulating film surface, making high-precision measurement difficult. [Prior art documents] [Patent Documents]

[0007] [Non-Patent Document 1] Japanese Patent Publication No. 2025-093912 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] One of the problems that this embodiment aims to solve is to measure the surface of electrodes across the entire wafer (for example, steps) at high speed and with high accuracy using optical measurement. [Means for solving the problem]

[0009] The surface shape measuring device according to the embodiment comprises a real-time phase-shift interferometer, a slit illumination optical system, a one-dimensional or two-dimensional image detector, and an image processing device. The real-time phase-shift interferometer has an imaging function and simultaneously generates interference fringes of three or more different phases. The slit illumination optical system has a slit at the image plane position of the real-time phase-shift interferometer and emits illumination light through the slit. The image detector is positioned where the surface of the object is illuminated in a slit shape by the slit illumination optical system and the real-time phase-shift interferometer, and the reflected light forms a slit-shaped image through the real-time phase-shift interferometer. The image detector converts the light intensity of each point in the slit-shaped image into photoelectric data. The image processing device has a one-dimensional processing function that analyzes the slit-shaped image obtained by the image detector, where each point has interference fringe signals of three or more different phases, and converts it into one-dimensional surface shape data, and a two-dimensional processing function that combines the newly obtained one-dimensional surface shape data in synchronization with the movement of the object moving platform to form two-dimensional surface shape data. [Brief explanation of the drawing]

[0010] [Figure 1] A cross-sectional view showing semiconductor chips in a wafer that are joined together in a surface shape measuring device according to the first to fourth embodiments. [Figure 2] A schematic diagram showing an example configuration of a surface shape measuring device according to the first embodiment. [Figure 3] A top view showing the slit plate and pinhole plate in the surface shape measuring device according to the first to fourth embodiments. [Figure 4] A schematic diagram showing an example configuration of a surface shape measuring device according to the second embodiment. [Figure 5] A schematic diagram showing an example configuration of a surface shape measuring device according to the third embodiment. [Figure 6] A schematic diagram showing an example configuration of a surface shape measuring device according to the fourth embodiment. Embodiment

[0011] The following describes in detail an embodiment of the surface shape measuring device with reference to the drawings.

[0012] Figure 1 is a cross-sectional view showing semiconductor chips in a wafer being joined together in a surface shape measuring device according to an embodiment. Hybrid bonding is also called direct bonding or copper-copper direct bonding (Cu-Cu direct bonding). As mentioned above, when the electrode pitch is as small as 5 to 10 μm, it is thought that hybrid bonding, which directly joins the opposing electrodes of semiconductor chips without bumps, will be adopted.

[0013] Figure 1(A) shows a first semiconductor chip 80 in a wafer and a second semiconductor chip 90 that is hybrid-bonded to it. The first semiconductor chip 80 comprises a substrate (e.g., Si), an insulating film 82 on its surface (e.g., an oxide film such as SiO2 or SiN), and a plurality of electrodes 83 arranged in the planar direction on the insulating film 82 (e.g., copper electrodes, silver electrodes). The second semiconductor chip 90 also comprises a substrate 91, an insulating film 92 on its surface (e.g., an oxide film such as SiO2), and a plurality of electrodes 93 arranged in the planar direction on the insulating film 92 (e.g., copper electrodes). The plurality of electrodes 83 and the plurality of electrodes 93 are positioned opposite each other.

[0014] The surfaces of the insulating film 82 with multiple electrodes 83 embedded and the insulating film 92 with multiple electrodes 93 embedded are planarized by CMP (chemical mechanical polishing). Since electrodes 83 and 93 are softer than insulating films 82 and 92, when insulating films 82 and 92 are planarized, the surfaces of electrodes 83 and 93 become concave (dishing), resulting in dish-shaped recesses (as shown in Figure 1(B)).

[0015] Subsequently, the surfaces of the insulating films 82 and 92 are etched, and then the surfaces of the insulating films 82 and 92 are pre-treated with an ammonia-based gas such as NH4OH. When the surfaces of insulating film 82 and insulating film 92 are brought into contact with each other, the activated insulating films 82 and 92 form a covalent bond, creating a permanent bond (as shown in Figure 1(C)).

[0016] Since the electrodes 83 and 93 have recesses, when the insulating films 82 and 92 are joined, as shown in Fig. 1(C), a gap occurs between the electrode 83 and the electrode 93. Therefore, when heat treatment is performed while the insulating films 82 and 92 are being pressure-bonded, the opposing electrodes 83 and 93 expand and come into contact, forming a bond of the copper wiring by mutual diffusion.

[0017] Considering the expansion of the electrodes 83 and 93 in the subsequent process, the design of the step d (shown in Fig. 1(D)) of the electrode with respect to the surface of the insulating film, that is, the depth of the recess, is important, and the accuracy of its measurement is also important. For example, the step d is the distance from the surface of the insulating films 82 and 92 to the center position (or the maximum depth position) of the surface of the electrode with a recess. Hereinafter, a surface shape measuring apparatus related to the step d of the electrode will be described. For example, the surface shape measuring apparatuses 1 to 4 described later have a structure as a Linnik interferometer, and make the shape of the surface of the object visible in the interferometer output by interference fringes in the object image in relation to the shape of the reference mirror.

[0018] (First Embodiment) Fig. 2 is a schematic diagram showing a configuration example of a surface shape measuring apparatus according to the first embodiment. Fig. 2 shows a surface shape measuring apparatus 1 according to the first embodiment. The surface shape measuring apparatus 1 includes an illumination optical system 10, a slit plate 11, a mirror 12, an unpolarized beam splitter (B / S) 13, an objective lens 14 (a first objective lens 141 and a second objective lens 142), a reference mirror 15, an imaging slit plate 16, a line sensor 17 (a part of an area sensor, including the use of, for example, 1 line to several lines), a mirror moving stage 51, an object moving stage 52, and an image processing apparatus 70, and irradiates light onto the surface of an object S, that is, the surfaces of the electrodes 83 and 93 and the insulating films 82 and 92 to measure the surface.

[0019] The non-polarizing beam splitter 13, the objective lens 14, the reference mirror 15, and the mirror stage 51 constitute a non-real-time phase shift interferometer, which has an imaging function by the objective lens 14 which is an imaging lens, and sequentially generates interference fringes with three or more different phases. The illumination optical system 10, the slit plate 11, and the mirror 12 constitute a slit illumination optical system, and form a slit-shaped illumination pattern on the object plane of the non-real-time phase shift interferometer. The line sensor 17 constitutes a one-dimensional image detector, and is arranged at a position where the surface of the object S is illuminated in a slit shape by the slit illumination optical system and the non-real-time phase shift interferometer, and the reflected light forms a slit-shaped image through the non-real-time phase shift interferometer, and photoelectrically converts the light intensity of each point of the slit-shaped image.

[0020] For example, the non-real-time phase shift interferometer is a Linnik type interferometer. In that case, the imaging function of the non-real-time phase shift interferometer is realized by arranging two objective lenses 14 having the same performance in the optical path of the reference light from the reference mirror 15 and the optical path of the object light from the object S, respectively.

[0021] The image processing device 70 includes at least a processor and a memory, and has a one-dimensional processing function and a two-dimensional processing function. The one-dimensional processing function is a function of analyzing a slit-shaped image having interference fringe signals with three or more different phases at each point, obtained by the line sensor 17 which is a one-dimensional image detector, and converting it into one-dimensional surface shape data. The two-dimensional processing function is a function of connecting newly obtained one-dimensional surface shape data in synchronization with the movement of the object stage 52 to form two-dimensional surface shape data.

[0022] The illumination optical system 10 comprises a light source 10a and an illumination lens 10b, and emits light. For example, an LED or a laser can be used as the light source 10a. The slit plate 11 extends in the Y direction, and the illumination optical system 10 illuminates the slit plate 11 from behind, thus forming a slit illumination system. The unpolarized beam splitter 13 is an example of a beam splitter and splits the illumination light that has passed through the slit of the slit plate 11. Two objective lenses 141 and 142 are provided on the two exit sides of the illumination light split by the unpolarized beam splitter 13, respectively, and form images of the slit plate 11.

[0023] The object S and the reference mirror 15 are optically positioned in the same location relative to the slit plate 11 via the unpolarized beam splitter 13, and both are illuminated by line illumination when images of the slit plate 11 are formed on them by the objective lenses 141 and 142. The light reflected from each is superimposed and interferes again by the unpolarized beam splitter 13, forming interference fringes on the imaging slit plate 16. The imaging slit plate 16 is optically positioned in the same location as the slit plate 11 via the unpolarized beam splitter 13, so the image of the slit plate 11 is again imaged on the imaging slit plate 16. The line sensor 17 is positioned in the same location as the imaging slit plate 16 and converts the intensity of the interference fringes into an electrical signal, which is transmitted to the image processing device 70.

[0024] This arrangement of the slit plate 11 and the imaging slit plate 16 is called a slit-type confocal optical system. The slit plate 11 and the imaging slit plate 16 together form a confocal slit. Although the imaging slit plate 16 is provided to clearly indicate that it is a slit-type confocal optical system, it is not necessary in practical use. The pixels of the line sensor 17 serve as the slits.

[0025] The mirror moving platform 51 functions as a phase shift mechanism that moves the reference mirror 15 in the X direction to change its position relative to the second objective lens 142. The object moving platform 52 moves the object S placed on it in steps in the X direction. The surface shape measuring device 1 then combines the movement of the object S by the object moving platform 52 with the movement of the reference mirror 15 by the mirror moving platform 51 to realize the phase shift method, and acquires a phase-shifted image using the phase shift method. A phase shift method that involves a change in the position of the reference mirror 15 relative to the second objective lens 142 is described as a non-real-time phase shift method.

[0026] Figure 3 is a top view showing the slit plate 11 (left) and the pinhole plate 11A (right) shown in the surface shape measuring device 1. In a confocal optical system, only reflected light from the focal point (the position where the image of the pinhole or slit is formed) reaches the detector, and other light is strongly suppressed. Theoretically, the range over which a signal can be obtained at the focal point (the distance between the first positions where reflected light becomes zero before and after the focal point) W is expressed by the following equation (A). Here, "λ" is the wavelength and "NA" is the numerical aperture of the objective lens. W = 2λ / NA 2 …(A)

[0027] In equation (A) above, using an objective lens with a large NA reduces the width W, thereby suppressing reflected light from the underlying pattern. It is preferable that the "NA" is relatively large, 0.8 or higher. For example, if the "NA" is 0.8 and "λ" is 450 nm, the width W becomes 1.4 μm, and the influence of the underlying pattern can be almost completely suppressed.

[0028] In confocal optical systems, the pinhole plate 11A shown on the right side of Figure 3 is generally used. In this case, obtaining two-dimensional data (image) requires scanning the object S in two dimensions (XY direction), which significantly increases measurement time. If a slit plate 11 is used instead of the pinhole plate 11A, the slit plate 11 can obtain data equivalent to one line in the Y direction of a normal image, while the slit plate 11 can also provide a confocal effect (the effect of blocking light from outside the focal position), although it is inferior to that of the pinhole plate 11A.

[0029] By simultaneously acquiring data on the imaging slit of the imaging slit plate 16 using a line sensor 17 (shown in Figure 2) (including the use of a portion of an area sensor (1 to several lines)), and scanning the object S in the X direction perpendicular to the imaging slit extending in the Y direction of the imaging slit plate 16, high-speed data acquisition becomes possible while obtaining the effect of confocal imaging.

[0030] Furthermore, the structure and operation of the imaging slit plate 16, as well as the effects of using the imaging slit plate 16, are the same for the imaging slit plate 26 (shown in Figure 4), which will be described later, and also for the imaging slit plate 46 (shown in Figure 6), which has three rows of imaging slits.

[0031] As shown in Figure 2, by using a confocal structure with a confocal slit consisting of a slit plate 11 and an imaging slit plate 16, as in the surface shape measurement device 1, it is possible to achieve measurement by phase shift that suppresses the influence of the underlying layer pattern due to the confocal effect. As a result, with the surface shape measurement device 1, surface measurement of the entire wafer can be performed at high speed compared to surface measurement by AFM by optical measurement of the step height of the electrodes.

[0032] On the other hand, in this case, in order to measure by phase shift of a single line image using an image detector, the mirror moving platform 51 on which the reference mirror 15 is placed must be moved in the X direction, the reference mirror 15 must be moved in the X direction at least twice to acquire line images of three or more lines, and at each position, the object S must be moved in the X direction in steps to perform surface measurement. If such a non-real-time phase shift method is adopted, high-speed measurement is not easy, and there is a risk that vibrations will be generated due to the acceleration and deceleration of the step movement, which may affect the measurement accuracy.

[0033] To address these challenges, the surface shape measuring devices according to the second to fourth embodiments are described below. The surface shape measuring devices according to the second to fourth embodiments acquire a phase-shifted image necessary for the phase-shift method without physically changing the position of the reference mirror 15 relative to one of the two objective lenses 141, 142, which is on the reference mirror 15 side. Hereinafter, the phase-shift method that does not involve a change in the position of the reference mirror 15 relative to the second objective lens 142 will be referred to as the real-time phase-shift method.

[0034] (Second Embodiment) Figure 4 is a schematic diagram showing an example of the configuration of a surface shape measuring device according to the second embodiment. Figure 4 shows a surface shape measuring device 2 according to the second embodiment. Similar to the surface shape measuring device 1 shown in Figure 2, the surface shape measuring device 2 comprises an illumination optical system 10, a slit plate 11, a mirror 12, an objective lens 14 (first objective lens 141 and second objective lens 142), a reference mirror 15, and an image processing device 70, as well as a non-polarizing beam splitter 23 (first non-polarizing beam splitter 231 and second non-polarizing beam splitter 232) and an imaging slit plate 26 (first imaging slit plate 261 to third imaging slit plate 261). The system comprises a plate 263, line sensors 27 (first line sensors 271 to third line sensors 273), a polarizing beam splitter 23', phase difference plates 28 which are λ / 4 phase difference plates (object light phase difference plate 281, reference light phase difference plate 282, and interference light phase difference plate 283), polarizing plates 29 (first polarizing plates 291 to third polarizing plates 293), and an object moving platform 53, and measures the surface of the object S, that is, the surface of electrodes 83, 93 and insulating films 82, 92, by irradiating them with light.

[0035] The objective lens 14, reference mirror 15, polarizing beam splitter 23', and phase difference plate 28 constitute a real-time phase-shift interferometer, and the objective lens 14 has an imaging function, and in combination with the unpolarized beam splitter 23 and polarizer 29 it simultaneously generates interference fringes of three or more different phases. The illumination optical system 10, slit plate 11, and mirror 12 constitute a slit illumination optical system, and form a slit-shaped illumination pattern on the object surface of the real-time phase-shift interferometer. The line sensor 27 constitutes a one-dimensional image detector, and is positioned to form a slit-shaped image through the real-time phase-shift interferometer when the surface of the object S is illuminated in a slit shape by the slit illumination optical system and the real-time phase-shift interferometer, and converts the light intensity of each point of the slit-shaped image into photoelectricity.

[0036] For example, a real-time phase-shift interferometer is a Linic interferometer. In this case, the imaging function of the real-time phase-shift interferometer is achieved by placing two objective lenses 14 with the same performance in the optical path of the reference light from the reference mirror 15 and in the optical path of the object light from the object S.

[0037] The main components of the real-time phase-shift interferometer are described below. The object light λ / 4 phase difference plate 281 is inserted into the optical path of the object light from the object S and converts linearly polarized light to circularly polarized light. The reference light λ / 4 phase difference plate 282 is inserted into the optical path of the reference light from the reference mirror 15 and converts linearly polarized light to circularly polarized light. The reference mirror 15 reflects the reference light. The interference light λ / 4 phase difference plate 283 is inserted into the optical path where the reference light and object light are reflected by the reference mirror 15 and the object S respectively, and then re-entered into the polarizing beam splitter 23' before being emitted.

[0038] The surface shape measuring device 2 further includes three line sensors (or several lines of area sensors) 27 as image detectors, a non-polarizing beam splitter 23, and polarizing plates 29. The non-polarizing beam splitter 23 comprises a first non-polarizing beam splitter 231 and a second non-polarizing beam splitter 232, and is capable of splitting the light beam emitted from the real-time phase-shift interferometer in the direction in which the three line sensors 27 are located. The polarizing plates 26 comprises a first polarizing plate 291 to a third polarizing plate 293, and are positioned between the three line sensors and the non-polarizing beam splitter 23, allowing only linearly polarized light in a different direction to pass through each of the three line sensors. Interference fringes of different phases detected by the three line sensors 27 are photoelectrically converted and sent to the image processing device 70.

[0039] In the surface shape measuring device 2 shown in Figure 4, the same reference numerals are used for components identical to those in the surface shape measuring device 1 shown in Figure 2, and their descriptions are omitted.

[0040] Illumination light from the illumination optical system 10 passes through a row of slits in the slit plate 11, is reflected by the mirror 12, and reaches the polarizing beam splitter 23'. The polarizing beam splitter 23' splits the incident illumination light into two orthogonal (90-degree apart) directions and converts each of the split illumination lights into orthogonal linearly polarized beams. Phase difference plates 281 and 282 are inserted in each optical path, converting the respective illumination light into circularly polarized beams and illuminating the object S and the reference mirror 15. The reflected light passes through the phase difference plates 281 and 282 again, reaching the polarizing beam splitter 23' in a linearly polarized state with a polarization direction changed by 90 degrees (λ / 2) from the outward path. Since the polarization direction of each light has changed by 90 degrees from the outward path, the light reflected and split by the polarizing beam splitter 23' is transmitted, and the transmitted light is reflected, so that both are emitted from the polarizing beam splitter 23' on the side of the polarizing beam splitter 23' that is 90 degrees apart from the incident surface, in a state of mutually orthogonal linear polarization.

[0041] Furthermore, as the reflected light passes through the third phase difference plate 283, one portion of the light is converted to left-handed circular polarization and the other to right-handed circular polarization. Subsequently, the light is split into three directions by two unpolarized beam splitters 231 and 232 and incident on three line sensors 271 to 273 for detection. In this case, polarizing plates 291 to 293 are placed on the inlet side of each line sensor 271 to 273, and are arranged so that they have transmission axes in different directions, for example, 45 degrees apart.

[0042] Polarizing plates 291-293 are arranged because light waves with different polarization directions do not interfere with each other (left-handed circularly polarized light and right-handed circularly polarized light do not interfere). Therefore, the polarization directions are aligned by passing the light through the polarizing plates to cause interference. Since left-handed circularly polarized light and right-handed circularly polarized light have different timings for specific polarization components, a difference in the phase difference between the respective linearly polarized light occurs when the polarizing plates are oriented differently (for example, if the circularly polarized light is oriented in the same direction, the phase difference between the two linearly polarized light waves does not change regardless of the direction to which they are converted). As a result, the phase difference between the reference light (light reflected by the reference mirror 15) and the object light (light reflected by the object S) that have passed through polarizing plates 291-293, each with a different polarization direction, is not the same but differs. This generates interference fringes with different phases simultaneously for each of the three line sensors 271-273, enabling a real-time phase shift method. As a result, with the surface shape measuring device 2, it is no longer necessary to mechanically perform a phase shift for each line, as explained using the surface shape measuring device 1 shown in Figure 2, and the object S can be moved continuously without the need for step movements.

[0043] As described above, the surface shape measuring device 2 employs a confocal optical system using a slit, and since there is no need to change the position of the reference mirror, the object moving platform 53 can be moved continuously, enabling high-speed measurement. Furthermore, because it is a continuous movement, there is no need to accelerate or decelerate during movement, so low-vibration measurement is possible, which is advantageous in terms of accuracy. In addition, in the real-time phase shift method, interference fringes with different phases can be obtained at the same time, so the amount of phase shift does not vary due to vibration as in the non-real-time phase shift method, thus enabling more accurate measurement. In other words, the surface shape measuring device 2 can measure the surface of the object S (for example, steps) at high speed and with high accuracy.

[0044] Further advantages of continuous movement measurement of the object moving platform 53 using the real-time phase shift method with line sensors 271-273 (including the use of one to several lines of area sensors) include the ability to reduce random noise and improve accuracy by slowing down the continuous movement speed to acquire more detailed data and integrating the excess resolution data when higher measurement accuracy is required.

[0045] For example, if an objective lens with an NA of 0.8 is used, the optical resolution is approximately 0.34 μm at an illumination wavelength of 450 nm. If the system is designed to acquire images with a pixel resolution of 0.2 μm, line images will be acquired at 0.2 μm intervals while the object moving platform 53 moves continuously. However, if the movement speed of the object moving platform 53 is set to, for example, 1 / 10 of that speed, it becomes possible to acquire images at 0.02 μm intervals.

[0046] While data with a pixel resolution of 0.02 μm spacing is clearly excessive for an optical resolution of 0.34 μm, if we integrate every 10 pixels, for example, we get data with a resolution of 0.2 μm, which is close to the integration input processing in image processing techniques (a process that acquires the same image multiple times and integrates it pixel by pixel), and the random noise component is averaged out to 1 / 10. 1 / 2 This allows for leveling and improves measurement accuracy.

[0047] (Third embodiment) In addition to the method of the surface shape measurement device 2 shown in Figure 4, the real-time phase shift method can also be implemented by using a polarizing line camera (including the use of one to several lines of an area camera). Figure 5 is a schematic diagram showing an example configuration of the surface shape measurement device according to the third embodiment.

[0048] Figure 5 shows a surface shape measuring device 3 according to the third embodiment. Similar to the surface shape measuring device 1 shown in Figure 2, the surface shape measuring device 3 includes an illumination optical system 10, a slit plate 11, a mirror 12, an objective lens 14 (first objective lens 141 and second objective lens 142), a reference mirror 15, and an imaging slit plate 16, as well as a polarizing beam splitter 23', a polarizing line camera 37, and a phase difference plate 28 (object light phase difference plate 281, reference light phase difference plate 282, and interference light phase difference plate 283), and measures the surface by irradiating light onto the surface of the target object S, that is, the surface of electrodes 83, 93 and insulating films 82, 92.

[0049] The objective lens 14, reference mirror 15, polarizing beam splitter 23', and phase difference plate 28 constitute a real-time phase-shift interferometer, and the objective lens 14 has an imaging function, and in combination with the micro-polarizer in the polarization line sensor 37 it simultaneously generates interference fringes of three or more different phases. The illumination optical system 10, slit plate 11, and mirror 12 constitute a slit illumination optical system, and form a slit-shaped illumination pattern on the object surface of the real-time phase-shift interferometer. The polarization line sensor 37 constitutes a one-dimensional image detector, and is positioned to form a slit-shaped image through the real-time phase-shift interferometer when the surface of the object S is illuminated in a slit shape by the slit illumination optical system and the real-time phase-shift interferometer using the reflected light, and converts the light intensity of each point of the slit-shaped image into photoelectricity.

[0050] The image detector is a single polarizing camera 37. Each pixel is arranged in an N × N (where N is an integer greater than or equal to 2) array. 2 It is composed of individual elements, and each element is different N 2 Since it has the function of detecting the intensity of linearly polarized light in a given direction, the polarization line camera 37 measures N for each pixel. 2Four interference fringe signals with different phases are photoelectrically converted and sent to the image processing device 70. For example, when N=2, each pixel is composed of four elements arranged in a 2x2 grid, and each element has the function of detecting the light intensity of linearly polarized light in four different directions. Therefore, the polarization line camera 37 photoelectrically converts four interference fringe signals with four different phases for each pixel and sends them to the image processing device 70.

[0051] In the surface shape measuring device 3 shown in Figure 5, the same reference numerals are used for components identical to those in the surface shape measuring device 1 shown in Figure 2 and the surface shape measuring device 2 shown in Figure 4, and their descriptions are omitted.

[0052] The polarized line camera 37 is an example of an image detector, and it acquires line images without parallax by passing reflected light from the object S and the reference mirror 15 through polarizing plates in four directions (0 degrees, 45 degrees, 90 degrees, and 135 degrees).

[0053] The polarization line camera 37 is divided into 2x2 sections of 4 pixels, and each of the 4 pixels has a tiny polarizing plate attached to it with a different polarization direction. If the 4 pixels are positioned within the width of the short axis of the image of the imaging slit of the imaging slit plate 16 (approximately the spot diameter), then a single polarization line camera 37 can generate phase-shifted images simultaneously and in parallel without using the light splitting by the unpolarized beam splitter 23' or the three line sensors 271-273 (shown in Figure 4).

[0054] As described above, the surface shape measuring device 3, like the surface shape measuring device 2 shown in Figure 4, can measure the surface of the object S (for example, steps) at high speed and with high accuracy.

[0055] (Fourth Embodiment) Real-time phase shifting can be achieved not only by the method of the surface shape measuring device 2 shown in Figure 4 and the surface shape measuring device 3 shown in Figure 5, but also by changing the phase by providing a step in the reference mirror. Figure 6 is a schematic diagram showing an example of the configuration of the surface shape measuring device according to the fourth embodiment.

[0056] Figure 6 shows a surface shape measuring device 4 according to the fourth embodiment. Similar to the surface shape measuring device 1 shown in Figure 2, the surface shape measuring device 4 includes an illumination optical system 10, a mirror 12, a non-polarizing beam splitter 13, and objective lenses 14 (first objective lens 141 and second objective lens 142), as well as a slit plate 41, a reference mirror 45, an imaging slit plate 46, a camera 47, and an image processing device 70. It measures the surface of an object S, that is, the surface of electrodes 83, 93 and insulating films 82, 92, by irradiating them with light.

[0057] The objective lens 14, the unpolarized beam splitter 13, and the reference mirror 45 constitute a real-time phase-shift interferometer, and the objective lens 14 has an imaging function, simultaneously generating interference fringes of three or more different phases. The illumination optical system 10, the slit plate 41, and the mirror 12 constitute a slit illumination optical system, forming a slit-shaped illumination pattern on the object surface of the real-time phase-shift interferometer. The camera 47 constitutes a two-dimensional image detector and is positioned to form a slit-shaped image through the real-time phase-shift interferometer when the surface of the object S is illuminated in a slit shape by the slit illumination optical system and the real-time phase-shift interferometer, and the light intensity of each point of the slit-shaped image is photoelectrically converted.

[0058] In the surface shape measuring device 4 shown in Figure 6, the same reference numerals are used for components identical to those in the surface shape measuring device 1 shown in Figure 2 and the surface shape measuring device 2 shown in Figure 4, and their descriptions are omitted.

[0059] The slit plate 41 extends in the Y direction and has n rows of slits (where n is an integer greater than or equal to 3). The illumination optical system 10 illuminates the slit plate 41 from behind, thus forming a slit illumination system. The reference mirror 45 has n steps with differences in the direction of incidence. The imaging slit plate 46 extends in the Y direction and has n rows of imaging slits 46 into which the object S illuminated in a line by the two objective lenses 141 and 142 and the reflected light from the reference mirror 15 are imaged.

[0060] Phase shift can be achieved by using three or more (for example, three) rows of imaging slit plates 46 to create a step difference in the reference mirrors 45 for each image on the reference mirror 45, thereby changing the phase. In this case, the images obtained by the phase shift simultaneously and in parallel are of different object positions, so it is not possible to perform phase calculations using these simultaneously obtained images. However, by continuous scanning with the object moving platform 53, it is possible to obtain images with interference fringes of different phases at the same object position at different time points.

[0061] As described above, the surface shape measuring device 4, like the surface shape measuring devices 2 and 3 shown in Figures 4 and 5, can measure the surface of the object S (for example, the step d) at high speed and with high accuracy.

[0062] According to at least one embodiment described above, optical measurement can be performed quickly and accurately to measure the surface of electrodes across the entire wafer. This is particularly effective for hybrid bonding electrodes where the target object S has a pitch of 10 μm or less.

[0063] While several embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, modifications, combinations of embodiments, and combinations of embodiments with one or more modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0064] 1-4... Surface shape measuring device 10…Illumination optical system 11,41…Slit plate 12…Mirror 13, 23, 231, 232… Non-polarized beam splitter 23'...Polarizing beam splitter 14, 141, 142… Objective lenses (imaging lenses) 15,45... See mirror 16, 26, 46, 261~263... Imaging slit plates 17, 27, 271~273… Line sensors 28,281~283…Retardation plate (λ / 4 retardation plate) 29,291~292...Polarizing plates 37…Polarized Line Camera 47... Camera 70…Image processing device 82,92… Insulating film 83,93...electrode

Claims

1. An object moving platform on which an object is placed and moved, A real-time phase-shift interferometer having an imaging lens and a reference mirror, having an imaging function that images the reference light reflected by the reference mirror and the object light reflected by the object, and simultaneously generating three or more interference fringes with different phases, A slit illumination optical system having a slit at the image plane position of the real-time phase-shift interferometer and emitting illumination light through the slit, The surface of the object is illuminated in a slit shape by the slit illumination optical system and the real-time phase-shift interferometer, and at least one one-dimensional or two-dimensional image detector is positioned to form a slit-shaped image through the real-time phase-shift interferometer using the reflected light, and the light intensity of each point of the slit-shaped image is photoelectrically converted. An image processing apparatus having a one-dimensional processing function that analyzes a slit-shaped image obtained by the image detector, in which each point has interference fringe signals of three or more different phases, and converts it into one-dimensional surface shape data, and a two-dimensional processing function that concatenates the newly obtained one-dimensional surface shape data in synchronization with the movement of the object moving platform to obtain two-dimensional surface shape data, A surface shape measuring device characterized by comprising the following features.

2. The aforementioned real-time phase-shift interferometer is a Linic interferometer. The surface shape measuring device according to claim 1, characterized in that the imaging function is achieved by arranging two imaging lenses having the same performance in the optical path of the reference light from the reference mirror and in the optical path of the object light from the object.

3. The aforementioned real-time phase-shift interferometer is At least one imaging lens, A polarization beam splitter converts the illumination light into two orthogonal linearly polarized beams and splits the two linearly polarized beams into two optical paths: a reference beam from a reference mirror and an object beam from the object. A reference light λ / 4 phase difference plate is inserted into the optical path of the aforementioned reference light and converts linearly polarized light into circularly polarized light, A reference mirror that reflects the aforementioned reference light, A λ / 4 phase difference plate for object light, which is inserted into the optical path of the object light and converts linearly polarized light into circularly polarized light, An interference light λ / 4 phase difference plate is inserted into the optical path into which the reference light and the object light are reflected by the reference mirror and the object, respectively, and then re-entered into the polarizing beam splitter before being emitted. Equipped with, The surface shape measuring apparatus according to claim 1 or 2, characterized in that the reference light and the object light, which are incident on the interference light λ / 4 phase difference plate as linearly polarized light orthogonal to the interference light λ / 4 phase difference plate, are emitted as circularly polarized light rotating in opposite directions.

4. The image detector consists of three line sensors or area sensors. A non-polarized beam splitter capable of splitting the light beam emitted from the real-time phase-shift interferometer in the direction in which the three sensors are arranged, Three polarizing plates are arranged between the three sensors and the non-polarizing beam splitter, allowing only linearly polarized light in a different direction to pass through each of the three sensors. Furthermore, The surface shape measuring device according to claim 3, characterized in that interference fringes with different phases detected by the three sensors are photoelectrically converted and sent to the image processing device.

5. The aforementioned image detector is a single polarization line camera. Each pixel is composed of N × N (where N is an integer greater than or equal to 2) elements, and each element is different N ２ Since it has the function of detecting the intensity of linearly polarized light in a given direction, the single polarization line camera can detect N for each pixel. ２ The surface shape measuring device according to claim 3, characterized in that it has a configuration in which interference fringes of different phases are photoelectrically converted and sent to the image processing device.

6. The aforementioned slit illumination optical system comprises n (where n is an integer of 3 or more) rows of slits, The aforementioned reference mirror has n steps with a difference in the direction of incidence, The image detector is the two-dimensional image detector. A surface shape measuring device according to claim 1 or claim 2.

7. The aforementioned object is used for surface measurement of hybrid bonding electrodes with a pitch of 10 μm or less. A surface shape measuring device according to claim 1 or claim 2.

8. The numerical aperture of the imaging lens is 0.8 or greater. A surface shape measuring device according to claim 1 or claim 2.

Images