Wafer measurement equipment

Abstract

An embodiment of the present application provides a wafer measurement device. The wafer measurement device includes an air-floating chuck for generating an air cushion so that the wafer to be measured can be suspended on the top surface of the air-floating chuck; an interferometer, arranged on the side of the wafer away from the air-floating chuck, for obtaining an interference fringe image of the front side of the wafer to perform shape measurement and / or flatness measurement on the wafer based on the interference fringe image, wherein the front side of the wafer is the surface of the wafer away from the air-floating chuck. The embodiment of the present application utilizes the air-floating chuck to generate an air cushion so that the wafer to be measured can be suspended on the top surface of the air-floating chuck, thereby avoiding damage or contamination of the original shape of the wafer by the clamping tool, thereby reducing measurement errors.

Description

Technical Field

[0001] The present application relates to the field of wafer measurement technology, and in particular to a wafer measurement device. Background Art

[0002] Wafer geometric parameters, such as shape and thickness, play a crucial role in wafer quality. Therefore, measuring these parameters is crucial for assessing wafer quality. Wafer measurement equipment with a measurement optical path is typically used to measure these parameters. The wafer must be clamped to hold the wafer vertically within the measurement optical path.

[0003] However, the above-mentioned method of fixing the wafer has certain defects. For example, the clamping force is too strong, which can easily change the original shape of the wafer. In addition, since the cleanliness of the clamping tool is difficult to guarantee, it is easy to generate debris particles or other contaminants on the wafer, which in turn causes large measurement errors. Summary of the Invention

[0004] In view of this, an embodiment of the present application provides a wafer measurement device, thereby preventing the clamping tool from damaging or contaminating the original shape of the wafer and reducing measurement errors.

[0005] An embodiment of the present application provides a wafer measurement device. The wafer measurement device includes: an air-floating chuck for generating an air cushion to enable a wafer to be measured to float on the top surface of the air-floating chuck; and an interferometer disposed on a side of the wafer away from the air-floating chuck, for acquiring an interference fringe image of the front surface of the wafer, so as to perform shape measurement and / or flatness measurement on the wafer based on the interference fringe image. The front surface of the wafer is the surface of the wafer away from the air-floating chuck.

[0006] In one embodiment of the present application, the air flotation chuck includes multiple supporting force nozzles, and the air flotation chuck uses the first gas ejected from the multiple supporting force nozzles to suspend the wafer at a first predetermined distance above the top surface of the air flotation chuck to perform shape measurement on the wafer.

[0007] In one embodiment of the present application, the air flotation chuck also includes a plurality of suction nozzles arranged alternately with the plurality of supporting force nozzles. The air flotation chuck utilizes the second gas sucked in from the plurality of suction nozzles and the first gas ejected from the plurality of supporting force nozzles to suspend the wafer at a second predetermined distance above the top surface of the air flotation chuck, and forces the shape of the back side of the wafer to match the shape of the top surface of the air flotation chuck to measure the flatness of the wafer. The back side of the wafer is the surface of the wafer close to the air flotation chuck.

[0008] In an embodiment of the present application, when the wafer measurement device is used to measure the shape of a wafer, the first predetermined distance is 60 μm-1500 μm.

[0009] In an embodiment of the present application, when the wafer measurement device is used to measure the flatness of a wafer, the second predetermined distance is 0 μm-50 μm.

[0010] In one embodiment of the present application, the wafer measuring device also includes a capacitance sensor, which is arranged in the middle of the air-floating chuck, and is used to measure the position information corresponding to at least one position point on the back of the wafer to obtain the capacitance sensor reading CPn, or to monitor whether there is a wafer on the air-floating chuck based on the capacitance sensor reading CPn, or to monitor a first predetermined distance based on the capacitance sensor reading CPn, wherein the back of the wafer is the surface of the wafer close to the air-floating chuck.

[0011] In one embodiment of the present application, the wafer measurement device further includes a laser, located on the upper side of the top surface of the air-floating chuck, for emitting a first laser toward the front surface of the wafer; a position sensor, located on the upper side of the top surface of the air-floating chuck, and on the side opposite to the laser, for receiving a second laser after the first laser is reflected from the front surface of the wafer and measuring position information corresponding to a first position point on the front surface of the wafer based on the second laser to obtain a position sensor reading Vx, wherein the capacitance sensor is further used to measure position information corresponding to a second position point on the back surface of the wafer to obtain a capacitance sensor reading CPn, the first position point and the second position point being two relative position points in the wafer representing thickness; a first standard wafer; and a processor, connected to the position sensor and the capacitance sensor, to obtain a position sensor reading Vx and a capacitance sensor reading CPn, and substitute the position sensor reading Vx and the capacitance sensor reading CPn into formula T 晶圆 =T0+(CP0-CPn)+S*(Vx–V0) to obtain the thickness T of the wafer 晶圆 , where T0 in the formula is the thickness of the first standard wafer, CP0 is the reference capacitance sensor reading when the first standard wafer is at the reference predetermined distance, V0 is the reference position sensor reading when the first standard wafer is at the reference predetermined distance, S is the horizontal axis representing the position sensor reading Vx when the first standard wafer is at different predetermined distances, and the vertical axis represents the slope of the straight line in the relationship graph of the difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0 when the first standard wafer is at different predetermined distances.

[0012] In one embodiment of the present application, the air floating chuck is also used to suspend the first standard wafer at different predetermined distances above the top surface of the air floating chuck, and the position sensor is also used to measure the position information of a third position point on the first surface of the first standard wafer at different predetermined distances to obtain a position sensor reading Vx. The first surface of the first standard wafer is the surface of the first standard wafer away from the air floating chuck. The capacitance sensor is also used to measure the position information of a fourth position point on the second surface of the first standard wafer at different predetermined distances to obtain a capacitance sensor reading CPn. The second surface of the first standard wafer is the surface of the first standard wafer close to the air floating chuck. The fourth position point and the third position point are two relative position points on the first standard wafer that characterize the thickness. The different predetermined distances include a reference predetermined distance. The reference capacitance sensor reading of the first standard wafer at the reference predetermined distance is CP0 and the reference position sensor reading is V0. The processor is also used to construct a relationship graph with the horizontal axis being the position sensor reading Vx and the vertical axis being the difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0, so as to determine the slope S of the straight line from the straight line in the relationship graph.

[0013] In one embodiment of the present application, the wafer measurement device further includes a quality sensor for measuring the quality of the wafer to obtain an average thickness of the wafer.

[0014] In one embodiment of the present application, the diameter of the air floating chuck is larger than the diameter of the wafer.

[0015] In one embodiment of the present application, when the diameter of the wafer is 200 mm, the diameter range of the air floating chuck is 210 mm-220 mm; or when the diameter of the wafer is 300 mm, the diameter range of the air floating chuck is 310 mm-330 mm.

[0016] In one embodiment of the present application, the wafer measuring device also includes at least one tilting platform located below the air-floating chuck, which is used to offset and / or tilt the air-floating chuck to align the air-floating chuck with the interferometer, or offset and / or tilt the air-floating chuck to adjust the distance between the air-floating chuck and the interferometer to achieve mechanical phase shift, or offset and / or tilt the air-floating chuck to drive the offset and / or tilt of the wafer to measure the warpage of the front side of the wafer.

[0017] In one embodiment of the present application, at least one tilting platform is a two-dimensional tilting platform, and the two-dimensional tilting platform includes two goniometer frames stacked in a 90° intersecting manner.

[0018] In one embodiment of the present application, the wafer measurement apparatus further includes a plurality of lifting pins located around the air-floating chuck for lifting the wafer from the top surface of the air-floating chuck.

[0019] In one embodiment of the present application, the interferometer includes a Fizeau interferometer or a shearing interferometer.

[0020] In one embodiment of the present application, when the interferometer is a Fizeau interferometer, the interferometer includes a standard mirror close to the air-floating chuck, and the wafer measurement device further includes: a second standard wafer with a known flatness of TTV0, which is used to calibrate the top surface of the air-floating chuck and the surface opposite to the standard mirror and the air-floating chuck, wherein, when the wafer measurement device is used to measure the flatness of the wafer, the interferometer is also used to measure a first distance change ΔS1 between the relative surfaces of the air-floating chuck and the standard mirror when the second standard wafer is not loaded, and to measure a second distance change ΔS2 between the relative surfaces of the second standard wafer and the standard mirror when the second standard wafer is loaded, and the interferometer is also used to obtain a mismatch item S between the relative surfaces of the wafer and the air-floating chuck by subtracting ΔS2 and TTV0 from ΔS1. N.C. To calibrate the top surface of the air bearing chuck and the surface of the standard mirror opposite to the air bearing chuck.

[0021] According to the technical solution provided in the embodiment of the present application, an air cushion is generated by using an air floating chuck to enable the wafer to be measured to float on the top surface of the air floating chuck, thereby avoiding damage or contamination of the original shape of the wafer by the clamping tool, thereby reducing measurement errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a A schematic structural diagram of a device based on a double Fizeau interferometer is shown;

[0023] Figure 1b A schematic structural diagram of a device based on a shearing interferometer is shown;

[0024] Figure 1c A schematic structural diagram of a wafer measurement device is shown;

[0025] Figure 1d A schematic diagram showing calibration of a position sensor;

[0026] Figure 1e A schematic diagram showing the relationship between the position sensor reading Vx and the capacitance sensor reading CPn during the calibration process of the position sensor is shown;

[0027] Figure 1f A schematic diagram showing the positions of a position sensor and a capacitive sensor relative to a wafer is shown;

[0028] Figure 2a-2b A schematic diagram of a method for measuring wafer shape is shown;

[0029] Figure 3a-3b A schematic diagram of a wafer flatness TTV measurement method is shown;

[0030] Figure 4A schematic structural diagram of an exemplary goniometer stand for measuring a wafer tilt platform with a designed pattern according to an embodiment of the present application is shown;

[0031] Figure 5 A schematic diagram showing that a wafer in a vertical position is susceptible to deformation when the wafer is tilted;

[0032] Figure 6a A schematic cross-sectional view of an air flotation chuck provided according to an embodiment of the present application is shown;

[0033] Figure 6b A schematic cross-sectional view of an air flotation chuck provided according to another embodiment of the present application is shown;

[0034] Figure 7a A schematic top view of an air flotation chuck provided according to an embodiment of the present application is shown;

[0035] Figure 7b FIG2 shows a schematic top view of an air flotation chuck provided according to another embodiment of the present application;

[0036] Figure 7c A schematic diagram showing the connection layer of the pressure nozzle and vacuum nozzle of an air flotation chuck is shown;

[0037] Figure 7d A schematic side view of a stacking structure of air-floating chucks provided according to an embodiment of the present application is shown;

[0038] Figure 7e A schematic side view of a stacking structure of air-floating chucks provided according to another embodiment of the present application is shown;

[0039] Figure 7f Shown Figure 7e A schematic diagram of the top surface of the top plate of the stacked structure;

[0040] Figure 7g Shown Figure 7e A schematic diagram of the bottom surface of the top plate of the stacked structure;

[0041] Figure 7h Shown Figure 7e A top view of an exemplary manifold in a stacked structure;

[0042] Figure 7i Shown Figure 7e A bottom view of an exemplary manifold in a stacked structure;

[0043] Figure 7j Shown Figure 7e A top view of the rear cover plate of the stacked structure;

[0044] Figure 7k Shown Figure 7e Bottom view of the rear cover plate of the middle stacking structure;

[0045] Figure 8a and Figure 8b A schematic structural diagram of an exemplary diversion chamber provided according to an embodiment of the present application is shown.

[0046] Figure 9a Schematic diagram showing chuck marks / artifacts as a wafer is vacuumed down onto a vacuum chuck;

[0047] Figure 9b Schematic diagram showing a wafer suspended above an air-bearing chuck, with no visible chuck marks / artifacts on the wafer;

[0048] Figures 10a-10c A schematic diagram shows a method for distinguishing real features from chuck marks / artifacts on the surface of a wafer. DETAILED DESCRIPTION

[0049] The following will combine the drawings required for use in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the drawings described below are only part of the embodiments of this application, not all of the embodiments.

[0050] It should be noted that, based on the embodiments in this application, all relevant embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0051] In this article, "wafer geometry" can refer to wafer shape parameters or local flatness parameters (also known as local flatness parameters, such as local flatness (SFQR), site flatness back ideal range (SBIR), global flatness (GBIR)). Wafer flatness is also called total thickness variation (TTV) and can refer to high-density raw data (≥4M pixels / wafer) that can be used to derive SFQR, GBIR and many other related parameters. Flatness data is usually associated with the front and back side information of the wafer. For example, wafer shape parameters can be derived from a height map of a single surface, which can be the front or back side of the wafer, or the intermediate surface between the two surfaces (wafer shape defined by Semiconductor Equipment and Materials International (SEMI)). For advanced 300mm wafers, the difference between the front and back side shapes, or the intermediate values of only the front side or only the back side is very small. This is because wafer shape is measured on the order of several microns to hundreds of microns, while TTV or GBIR is measured on the order of tens or hundreds of nanometers. Wafer geometry parameter measurement equipment with designed patterns can calculate wafer shape from either the front or back side, depending on the vendor.

[0052] Wafer Geometry Tool (WGT), also known as wafer measurement equipment, is a type of measurement equipment that can be used in silicon wafer manufacturing plants to characterize the flatness, nanotopography, and shape (bow and warp) of wafers. It can also be used in glass wafer factories. Typically, each wafer must be certified by a WGT-type device before being shipped to customers. There are several existing devices that can achieve this purpose. For example, wafer geometry measurement equipment based on capacitive sensors is widely used in 200mm wafer factories. Figure 1a A schematic diagram of the structure of a device based on a double Fizeau interferometer is shown. This device can be used to measure the wafer geometric parameters of 300mm wafers. Interferometer-based wafer geometric parameter measurement equipment has advantages in both accuracy and throughput. Despite the fact that 300mm wafers are more prone to vibration than 200mm wafers, the accuracy of interferometer-based wafer geometric parameter measurement equipment is approximately one to two orders of magnitude higher than that of capacitance sensor-based equipment. However, interferometer-based 200mm wafer geometric parameter measurement equipment has not yet appeared on the market. Capacitive sensor-based wafer geometric parameter measurement equipment is designed for 250nm, 180nm, and 130nm node processes. Capacitive sensor equipment cannot meet the accuracy and throughput requirements of design nodes less than 130nm.

[0053] Figure 1b The schematic diagram of a device based on a shearing interferometer is shown. The shearing interferometer can also work together with the air-floating chuck in the present application to measure geometric parameters such as the shape and flatness of the wafer.

[0054] WGT Architecture

[0055] Figure 1c 1 shows a schematic structural diagram of a wafer measurement device 100 , which can also be called a wafer geometric parameter measurement architecture. Figure 1c The interferometer used in the wafer measurement device 100 is a Fizeau interferometer as an example. It should be understood that the architecture is not limited to the use of the Fizeau interferometer, and other types of vertical incidence interferometers can also be used, such as a shearing interferometer based on a grating structure. Figure 1c As shown, the wafer measurement device 100 includes: an air-floating chuck 110, which is used to generate an air cushion so that the wafer 1 to be measured can be suspended on the top surface of the air-floating chuck 110; an interferometer 120, which is arranged on the side of the wafer 1 away from the air-floating chuck 110, and is used to obtain the front surface S of the wafer 1. 正面 The interference fringe image is used to perform shape measurement and / or flatness measurement on the wafer 1 based on the interference fringe image. The front side of the wafer 1 is the surface of the wafer away from the air floating chuck 110.

[0056] It should be understood that when the interferometer 120 is a Fizeau interferometer, it may include a camera 121, a relay lens 122, a polarization beam splitter (PBSC) 123, a light source 124 (e.g., an illuminator), a collimator 125, and a standard mirror 126 (Transmission Flat, TF). All of these components of the single interferometer can be shown in the figure. The operation of the interferometer is well known and will not be described in detail here. In this architecture, the single interferometer 120 is configured to measure the shape of the wafer 1. The standard mirror 126 may also be referred to as a test flat, a transmission flat, etc. The wafer measurement device 100 is not limited to the use of a Fizeau interferometer. Other interferometers, such as a shearing interferometer, may also be used in the wafer measurement device using a reflective air-floating chuck of the present application. The air-floating chuck 110 may be any structure capable of generating an air cushion to suspend the wafer 1 to be measured on the top surface of the air-floating chuck 110. The embodiments of the present application do not limit the specific structure of the air-floating chuck 110. The wafer measurement device 100 can also be used to measure substrates, thin films, etc., which is not specifically limited in this application.

[0057] The present application relates to a wafer measurement device for measuring wafer flatness and wafer shape on various types of wafers, such as 200mm wafers, which may also be referred to as a semiconductor device architecture or WGT architecture. Compared to scanning devices based on capacitive sensors or optical sensors, the wafer measurement device can have better accuracy and higher throughput. Embodiments of the wafer measurement device of the present application can also be used to measure the geometric parameters of 300mm and 450mm wafers. In addition to measuring wafer geometric parameters, the wafer measurement device of the present application can also be used to measure the geometry of wafers with designed patterns (Patterned Wafer Geometry, PWG). An air-floating chuck uses an air cushion to support the wafer during the wafer shape measurement process. The air-floating chuck's air-floating membrane or air cushion has very low rigidity. The air-floating membrane or air cushion exerts a small force to support the wafer without deforming the wafer, which is ideal for wafer shape measurement. In this wafer measurement device 100, the wafer 1 under test can be loaded directly from the operator's terminal actuator into the measurement chamber.

[0058] According to the technical solutions provided in the embodiments of the present application, the wafer measurement device utilizes an air-floating chuck to generate an air cushion that allows the wafer to be measured to suspend on the top surface of the air-floating chuck, thereby preventing the clamping tool from damaging or contaminating the wafer's original shape and thus reducing measurement errors. Furthermore, the wafer measurement device can perform the same measurements as a double-Fizeau device, but at a fraction of the cost. Using this wafer measurement device for wafer geometry measurements, such as wafer shape or flatness, offers numerous advantages over existing double-Fizeau devices. For example, the air-floating chuck provides effective gas damping for the wafer positioned on the chuck. This gas damping not only makes interferometer measurements more accurate but also reduces costs by eliminating the need for expensive active vibration isolation systems and heavy acoustic vibration isolation devices. By simplifying the wafer loading process, this gas damping also reduces the cost of wafer transfer within the wafer measurement device, for example, by loading the wafer horizontally beneath a single interferometer. Compared to the double-Fizeau interferometer, the single interferometer architecture saves costs by eliminating one interferometer and its associated optical components. Similarly, the mechanism required by the double Fizeau interferometer architecture to rotate the wafer 90° from horizontal to vertical is not required. The wafer measurement device also does not require the soundproofing box used in the double Fizeau architecture. In addition, the air cushion provides gas damping. The entire wafer measurement device has fewer moving parts, making it more reliable than the double Fizeau architecture. Wafers can be loaded directly onto an air-bearing chuck, reducing the wafer transfer time required when using equipment based on a double Fizeau interferometer. This wafer measurement device has a greater advantage for 300mm or 450mm wafers, where vibration can be a major source of noise, making it difficult to achieve high accuracy in flatness measurement. For 300mm or 450mm equipment, the optical components, collimators, standard mirrors, and folding mirrors are all large and expensive. The wafer measurement device of the present application eliminates an interferometer, a vertical wafer loading system, a soundproofing box, and a data acquisition system channel, significantly reducing costs for original equipment manufacturers (OEMs) and their customers. Furthermore, compared to a dual-Fizeau interferometer architecture, the wafer measurement device of the present application has better accuracy, better matching, and lower cost. The wafer measurement device can use a grating-based shearing interferometer instead of a Fizeau interferometer and an air-floating chuck instead of three supporting lift pins, thereby improving the accuracy of the shearing interferometer measurement and increasing the measured warpage dynamic range by tilting the wafer.

[0059] In one embodiment of the present application, the wafer measurement device 100 further includes a capacitance sensor 130 disposed in the middle of the air-floating chuck 110 for measuring the back surface S of the wafer 1. 背面The position information corresponding to at least one position point on the upper surface is used to obtain the capacitance sensor reading CPn, or, based on the capacitance sensor reading CPn, the presence of wafer 1 on the air floating chuck 110 is monitored, or, based on the capacitance sensor reading CPn, the first predetermined distance is monitored, wherein the back side of wafer 1 is the surface of wafer 1 close to the air floating chuck 110.

[0060] In the embodiment of the present application, a capacitive sensor is placed in the middle of the air-floating chuck and the back surface S of the wafer is measured by the capacitive sensor. 背面 The position information corresponding to at least one position point on the capacitive sensor is specifically displayed as a capacitive sensor reading CPn. Based on the change of the capacitive sensor reading CPn, it can be known whether there is a wafer on the air floating chuck 110, and the specific value of the first predetermined distance can also be known. The capacitive sensor reading CPn can also be combined with the position sensor reading Vx to obtain the thickness of the wafer.

[0061] In one embodiment of the present application, the wafer measurement device 100 further includes a laser 140, which is located on the upper side of the top surface of the air-floating chuck 110 and is used to 正面 position sensor 150, located above the side of the top surface of the air-floating chuck 110 and opposite to the laser 140, for receiving the first laser via S 正面 The second laser reflected from the upper side and S is measured based on the second laser 正面 The position information corresponding to the first position point on the wafer 1 is obtained to obtain the position sensor reading Vx, wherein the capacitance sensor 130 is also used to measure the back side S of the wafer 1. 背面 The position information corresponding to the second position point is used to obtain the capacitance sensor reading CPn. The first position point and the second position point are two relative positions in the wafer that characterize the thickness; the first standard wafer 161; (reference Figure 1d ); a processor (not shown), connected to the position sensor 150 and the capacitance sensor 130, to obtain the position sensor reading Vx and the capacitance sensor reading CPn, and substitute the position sensor reading Vx and the capacitance sensor reading CPn into the formula T 晶圆 =T0+(CP0-CPn)+S*(Vx–V0) to obtain the thickness T of the wafer 晶圆 , where T0 in the formula is the thickness of the first standard wafer 161, CP0 is the reference capacitance sensor reading when the first standard wafer 161 is at the reference predetermined distance, V0 is the reference position sensor reading when the first standard wafer 161 is at the reference predetermined distance, S is the horizontal axis representing the position sensor reading Vx when the first standard wafer 161 is at different predetermined distances, and the vertical axis represents the slope of the straight line in the relationship graph of the difference hx between CPn and CP0 when the first standard wafer 161 is at different predetermined distances.

[0062] It should be understood that the processor can be set at any position in the wafer measurement device 100, as long as it is connected to the position sensor 150 and the capacitance sensor 130. This application does not make any specific restrictions on this. The values of T0, V0, and S can be known values stored after calibration of the wafer measurement device 100 before leaving the factory, or they can be values obtained after calibration using the first standard wafer 161 when the wafer measurement device 100 is in operation. This application does not make any specific restrictions on this. The reference predetermined distance can be greater than or equal to 0. For example, the reference predetermined distance can be the distance between the first standard wafer 161 and the air-floating chuck when the first standard wafer 161 is adsorbed on the top surface of the air-floating chuck using the suction provided by the air-floating chuck 110, or it can be the distance between the first standard wafer 161 and the air-floating chuck when the air-floating chuck 110 is used to suspend the first standard wafer 161 at any distance above the top surface of the air-floating chuck 110. This application does not make any specific restrictions on the value of the reference predetermined distance.

[0063] In an embodiment of the present application, a wafer measurement device is incorporated with a capacitive sensor on the bottom of the wafer (e.g., embedded in an air-bearing chuck) and one or more optical position sensors (bi-cell or PSD) on the top of the wafer, along with a laser, to measure wafer thickness. This interferometer tool can be used to calibrate both the capacitive sensor and the optical (bi-cell or PSD) position sensor. Both the capacitive sensor and the optical (bi-cell) position sensor can sense air-bearing stability, but only the optical (bi-cell) sensor can sense chuck assembly vibration. Optical (bi-cell) sensors are particularly useful when vibration sources need to be isolated. Furthermore, the bi-cell or PSD position sensor on the top of the wafer offers an additional advantage: the position sensor reading can be directly correlated to wafer thickness. The position sensor reading on the top of the wafer can also distinguish relative motion / vibration between the first standard wafer and the reference standard mirror. Vibration of the first standard wafer may be caused by the air-bearing chuck, flange, or support mechanism, which is not detected by the capacitive sensor because the capacitive sensor moves integrally with the unit comprising the first standard wafer and the air-bearing chuck.

[0064] Figure 1d Schematic diagram showing calibration of a position sensor. Figure 1e FIG. 1 shows a schematic diagram of the relationship between the position sensor reading Vx and the capacitance sensor reading CPn during the calibration process of the position sensor. Figure 1d and Figure 1eThe air-floating chuck 110 is further configured to suspend the first standard wafer 161 at different predetermined distances above the top surface of the air-floating chuck 110. The position sensor 150 is further configured to measure position information of a third position point on the first surface of the first standard wafer 161 at different predetermined distances to obtain a position sensor reading Vx. The first surface of the first standard wafer 161 is a surface of the first standard wafer away from the air-floating chuck. The capacitance sensor 130 is further configured to measure position information of a fourth position point on the second surface of the first standard wafer 161 at different predetermined distances to obtain a capacitance sensor reading CPn. The second surface of the first standard wafer 161 is the surface of the first standard wafer 161 close to the air floating chuck 110. The fourth position point and the third position point are two relative position points on the first standard wafer 161 that characterize the thickness. The different predetermined distances include a reference predetermined distance. The reference capacitance sensor reading of the first standard wafer at the reference predetermined distance is CP0 and the reference position sensor reading is V0. The processor is also used to construct a relationship graph with the horizontal axis being the position sensor reading Vx and the vertical axis being the difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0, so as to determine the slope S of the straight line from the straight line in the relationship graph. Figure 1d The elliptical structure in FIG. 1 represents a light spot formed when the laser is irradiated on the surface of the standard wafer 1011 .

[0065] It should be understood that the position sensor reading Vx can be calibrated using a wafer of known thickness, namely, first standard wafer 161. The position of the position sensor can be correlated with the height of the wafer top surface. Capacitive sensor 130 can measure the position of the wafer bottom surface. The combined information of the top and bottom surface positions can be used to accurately determine the thickness of wafer 1.

[0066] For example, if Figure 1dAs shown, in order to calibrate the position sensor 150, the first standard wafer 161 can be adjusted up and down at various positions. In this example, although each wafer is slightly different, the thickness T0 of the first standard wafer 161 can be set to 725μm, or other thickness values such as 775μm, etc., which is not specifically limited in this application. The thickness of the first standard wafer 161 can be measured by a coordinate measuring machine (CMM) or other thickness measuring tool. When the first standard wafer 161 is at position A0, it is at the reference predetermined distance (also known as zero suspension height). Position A0 can be the position of the first standard wafer 161 when the first standard wafer 161 is vacuumed onto the air-floating chuck, or it can be the position of the first standard wafer 161 when the first standard wafer 161 is suspended above the top surface of the air-floating chuck at a reference predetermined distance. The reference predetermined distance is greater than or equal to 0, which is not specifically limited in this application. And when the first standard wafer 161 is at position A0, the reading read by the reference capacitance sensor is CP0, and CP0 can be when CPn is set to 0. The reference position sensor reading (V0 (±10V)) from position sensor 150 can then be read. The vacuum and pressure can then be adjusted to suspend first standard wafer 161 at position A1. The capacitance sensor reading at position A1 is CP1, where CP1 minus CP0 equals 20 μm (or approximately 20 μm). The position sensor reading V1 when CP1-CP0 equals 20 μm is also recorded.

[0067] Next, the vacuum and pressure can be adjusted again until the first standard wafer 161 is suspended at position A2. The capacitance sensor reading at position A2 is CP2, where CP2 minus CP0 is approximately 30 μm. The position sensor reading V2 when CP2 minus CP0 is approximately 30 μm is also recorded. The above steps can be repeated for capacitance sensor readings CP3, CP4, CP5, and so on, at positions of 40 μm, 50 μm, 60 μm, and so on.

[0068] Next, Δ(CPn-CP0) can be calculated, such as CP1-CP0, CP2-CP0, etc. Table 1 shows exemplary results of the calculation.

[0069] Table 1

[0070]

[0071] Based on the above data, a hx vs Vx diagram can be drawn, and a linear fit can be performed on the hx vs Vx diagram to obtain the slope Sμm / V (see Figure 1e). Where hx is the difference between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0, i.e., the relative wafer surface height. Calibration data includes: 1) slope, Sμm / V; 2) wafer thickness T0 = 725μm; 3) reference position sensor reading: V0; and 4) reference capacitance sensor reading: CP0. Calibration data can be saved, and software implementation of calibration can be performed using the following formula:

[0072] T 晶圆 =T0+(CP0-CPn)+S*(Vx–V0)

[0073] Here, CPn is the reading of the capacitance sensor when the first standard wafer 161 is at a predetermined distance or levitation height.

[0074] CP0 may be a reading of the capacitance sensor when the first standard wafer 161 is vacuum-sucked onto the air-floating chuck.

[0075] Vx is the reading of the position sensor in volts.

[0076] The capacitance sensor reading in μm can be calculated based on the factory calibration constant C, where C = Δh / ΔV, μm / volt and the capacitance sensor reading in μm CPn = C*ΔVcp.

[0077] According to the technical solution provided in the embodiment of the present application, by using a first standard wafer with a known thickness T0 and a reference standard mirror, the position sensor can be calibrated at any time, thereby reducing the measurement error of the wafer measurement device.

[0078] In one embodiment, a method of determining an optimal angle for a laser and / or position sensor is disclosed. Figure 1f A schematic diagram showing the positions of a position sensor and a capacitive sensor relative to a wafer is shown. Figure 1f The elliptical structure in FIG represents the light spot formed when the laser is irradiated on the surface of the first standard wafer 161. Figure 1f To obtain the best Z-axis resolution, the position sensor 150 is preferably located at a position permitted by its size and at a maximum angle β with the first standard wafer 161. If Δh is the Z-axis resolution (or z-sensitivity), the angle β is dominant.

[0079] Δh=ΔL*Cosβ / (2Cosα)

[0080] Here, ΔL is the minimum displacement detectable by the position sensor 150 . The position sensor 150 may be a commercially available sensor. For example, the minimum displacement of the sensor may be approximately 0.75 μm.

[0081] Δh=ΔL / M

[0082] Among them, M=[Cosβ / (2Cos(α))]^-1.

[0083] Due to the influence of the grazing angle α, Cos(α) is approximately equal to 1, and α is the light source (such as a laser ( Figure 1f The angle between the first standard wafer 161 and the position sensor 150 is not shown in the figure and is typically set to 10-15°. As β increases, based on the above formula, it can be seen that M will also increase, which means that the sensitivity of the position sensor 150 will also increase. However, due to the potential amplification effect on the spot size on the detector in the position sensor (for example, the size of the spot cannot be larger than the size that the detector can detect), β may not be too large. There may also be physical limitations related to how far the position sensor can be placed in the device. For example, at this grazing angle, the spot size of the laser on the sensor surface can be increased by 1 / Sin(90°-β)=1 / Sin30°=2 times. Table 2 below lists various PSD resolutions based on different angles α and β, in nm.

[0084] Table 2

[0085]

[0086] Figure 2a-2b A schematic diagram of a shape measurement method is shown. Figure 2a To measure the shape, first, a reference standard mirror TF162 (TF-ref) is placed on the surface of the air bearing chuck 110 to calibrate the TF 126 in the device. Cal = S TF –S TF-ref The reference TF flatness (in nm) can be much better than the wafer shape flatness (in μm). Therefore, S TF-ref This is a translation term and can be eliminated. If TF 126 is thick and has minimal TF concavity, the cavity calibration step can be skipped. During this step, no wafer is on the chuck. This calibration can be performed at the factory. Assuming the TF shape remains unchanged, tilt correction can be performed only at measurement time.

[0087] refer to Figure 2b In the next step, wafer 1 is placed on the top surface of air-floating chuck 110. To measure the wafer shape, wafer 1 is suspended at a relatively large air gap (e.g., 60 μm-1500 μm, preferably 60 μm-300 μm). The design and operation of the air-floating chuck ensure that pressure balances gravity, eliminating any additional forces that could deform the wafer. Therefore, at these relatively large air gaps, wafer 1 maintains its natural shape while being supported by the air cushion.

[0088] SWFR=(S TF –S正面 )

[0089] Next, get Cal and S 正面 The difference in measurements is used to calculate the wafer shape:

[0090] Wafer shape = Cal–SWFR = (S TF –S TF-ref )–(S TF –S 正面 )=S 正面 –S TF-ref =S 正面

[0091] Since the reference TF has a high flatness, S TF-ref Can be equivalent to a constant, S 正面 –S TF-ref With S 正面 All of these measures reflect the wafer shape, specifically the frontal shape of the wafer. Shape measurement performed through these steps is precise and requires no correction as long as the air gap is set correctly. This may be an ideal device architecture for patterned wafer geometry (PWG) equipment.

[0092] In an embodiment of the present application, the wafer measurement device 100 further includes a quality sensor (not shown) for measuring the quality of the wafer to obtain an average thickness of the wafer.

[0093] It should be understood that the position sensor and capacitance sensor in the above embodiments can be replaced by a mass sensor to obtain the thickness of the wafer, or by other wafer thickness measuring devices such as a coordinate measuring machine to obtain the thickness of the wafer. The thickness of the wafer can be the thickness corresponding to a certain position on the wafer, or it can be the average thickness of the wafer. This application does not make specific limitations on this.

[0094] In an embodiment of the present application, a mass sensor is set in the wafer measuring device, so that the mass of the wafer is measured by the mass sensor, and the average thickness of the wafer is obtained based on the mass of the wafer. At the same time, it is beneficial to obtain the flatness of the wafer in combination with the measurement results of the wafer shape measurement.

[0095] In an embodiment of the present application, the wafer measurement apparatus 100 further includes a plurality of lift pins 170 located around the air floating chuck 110 for lifting the wafer from the top surface of the air floating chuck 110 .

[0096] It should be understood that the number of the plurality of lifting pins 170 may be two, three, or even more, and this application does not impose any specific limitation on this.

[0097] In an embodiment of the present application, by setting lifting pins in the wafer measuring device, and setting the lifting pins around the air-floating chuck, when the wafer is placed into or taken out of the chuck, the lifting pins are used to lift the wafer, and then the robot arm can be used to reach under the wafer to take and place the wafer.

[0098] In one embodiment of the present application, when the interferometer is a Fizeau interferometer, the interferometer includes a standard mirror close to the air-floating chuck, and the wafer measurement device 100 further includes: a second standard wafer (not shown) with a known flatness of TTV0, which is used to calibrate the top surface of the air-floating chuck and the surface opposite to the standard mirror and the air-floating chuck, wherein, when the wafer measurement device is used to measure the flatness of the wafer, the interferometer is also used to measure a first distance change ΔS1 between the relative surfaces of the air-floating chuck and the standard mirror when the second standard wafer is not loaded, and to measure a second distance change ΔS2 between the relative surfaces of the second standard wafer and the standard mirror when the second standard wafer is loaded, and the interferometer is also used to obtain a mismatch item S between the relative surfaces of the wafer and the air-floating chuck by subtracting ΔS0 and TTV0 from ΔS1. N.C. To calibrate the top surface of the air bearing chuck and the surface of the standard mirror opposite to the air bearing chuck.

[0099] It should be understood that the second standard wafer can be an accessory independent of the wafer measurement device 100 , or can be an accessory that can be detachably placed in the wafer measurement device 100 , and this application does not make any specific limitation on this.

[0100] For example, Figure 3a-3b A schematic diagram of a wafer flatness TTV measurement method is shown. First, refer to Figure 3a , measuring the optical cavity formed by the standard mirror TF126 and the reflective air-bearing chuck 110. In other words, the first distance between the opposing surfaces of the standard mirror TF126 and the air-bearing chuck 110 changes by ΔS1. The TF126 may sag in the middle due to gravity. Figure 3a and 3b As shown, the surface of the air-floating chuck 110 may not be completely flat. These defects need to be calibrated in order to make the wafer flatness measurement accurate. The calibration of the cavity is to measure the change in the thickness of the cavity, or it can refer to measuring the first distance change ΔS1 between the relative surface of the air-floating chuck and the standard mirror when the wafer is not loaded. Mathematically speaking, the first distance change ΔS1 (or the change in the thickness of the cavity) is the change in the surface of the standard mirror S TF (x,y) and the chuck surface S CK The difference between (x, y): ΔS1 = S TF -S CK During this step, the wafer is not on the chuck.

[0101] refer to Figure 3bAfter calibration, the wafer 1 is placed on the top surface of the air-floating chuck 110. In order to measure the flatness of the wafer 1, the wafer 1 is suspended at a small air gap (e.g., 0 μm-50 μm, preferably 5 μm-30 μm) from the top of the air-floating chuck 110. The small air gap is generated by the air-floating chuck 110. At these small air gaps, the air-floating chuck 110 is designed to flatten the back surface of the wafer 1 or to flatten the back surface of the wafer 1. 背面 With the top surface S of the air bearing chuck CK Matched with great suction, the back side of the wafer S 背面 The front side S of the wafer 1 is close to the air-floating chuck 110. 正面 The position information is only the top surface S of the air bearing chuck. CK The sum of the position information and the total thickness variation TTV of the wafer, S 正面 =S CK +TTV, where S 正面 The surface of the wafer 1 away from the air-floating chuck 110 can also be called the top surface of the wafer. However, the back of the wafer does not completely match the top surface of the air-floating chuck. In practice, in order to accurately determine the position information of the front of the wafer, it is necessary to add a mismatch item (S N.C. ):S 正面 =(S CK +TTV+S N.C. ).

[0102] Interferometer measurement can measure the distance between wafer 1 and standard mirror 126: ΔS WFR =(S TF –S 正面 )=(S TF –S CK –TTV–S N.C. ).

[0103] Next, the difference between the cavity and the wafer surface (ΔS1–ΔS WFR ) to calculate TTV. Then, the total thickness change can be calculated using the following formula: TTV actual = (ΔS1 – ΔS WFR –S N.C. ), where ΔS1 and ΔS WFR Can be achieved through Figure 1c The WGT interferometer shown is used to measure S N.C. Can be obtained based on calibration. N.C. It can be obtained by using a wafer with known TTV (such as a double-sided polished 200 mm wafer, which can also be called a second standard wafer), and measuring the second distance change ΔS2 between the second standard wafer and the opposite surface of the standard mirror using an interferometer, then S N.C. =(ΔS1–ΔS2–TTVknown ).

[0104] S N.C.E May drift over time and require frequent calibration. N.C. It is a function of wafer thickness, temperature, air bearing height FH and chuck flatness. All of these parameters can be measured simultaneously with the interferometer data and can also be used for correction.

[0105] In addition, for double-polished wafers, such as some 200mm and 300mm wafers, the backside shape can be determined by flipping the wafer over and measuring it with the backside facing up. Combined with the front-side measurement and the thickness gauge results, TTV can be calculated.

[0106] According to the technical solution provided in the embodiment of the present application, by adding a second standard wafer to the wafer measurement device, the second standard wafer is used to calibrate the top surface of the air floating chuck and the surface of the standard mirror opposite to the air floating chuck, thereby avoiding defects caused by the surface of the air floating chuck may not be completely flat, which is conducive to accurate measurement of the flatness of the wafer.

[0107] In one embodiment of the present application, the wafer measurement device 100 also includes at least one tilting platform 180 located below the air-floating chuck 110, which is used to offset and / or tilt the air-floating chuck 110 to align the air-floating chuck with the interferometer, or offset and / or tilt the air-floating chuck 110 to adjust the distance between the air-floating chuck and the interferometer to achieve mechanical phase shift, or offset and / or tilt the air-floating chuck 110 to drive the offset and / or tilt of the wafer 1 to measure the warpage of the front side of the wafer 1.

[0108] It should be understood that the at least one tilting platform 180 may be a Z-shaped tilting platform or other tilting platform, as long as it can cause the air-floating chuck to deflect and / or tilt, and this application does not impose any specific limitation on this.

[0109] In an embodiment of the present application, at least one tilting platform is provided in the wafer measuring device, so that the air-floating chuck is offset and / or tilted by adjusting the tilt angle of at least one tilting platform, thereby aligning the air-floating chuck and the interferometer. The distance between the air-floating chuck and the interferometer can also be adjusted to achieve mechanical phase shift. The offset and / or tilt of the air-floating chuck can also be used to drive the offset and / or tilt of the wafer to measure the warpage of the front side of the wafer.

[0110] In one embodiment of the present application, at least one tilting platform 180 is a two-dimensional tilting platform, which includes two goniometer frames stacked in a 90° intersecting manner.

[0111] For example, Figure 4The schematic diagram of the structure of an exemplary goniometer frame for measuring a wafer tilt platform with a design pattern according to an embodiment of the present application is shown. The steps shown include two stacked goniometer frames 200, which are used to increase the dynamic range and throughput of wafer warpage. When tilting the wafer, the wafer focus can be maintained. It should be noted that the X and Y platforms 210 and 220 intersect at 90 degrees, and Figure 4 The X and Y platforms 210 and 220 are drawn on the same plane for the purpose of illustrating a common rotation center.

[0112] In the embodiment of the present application, for a wafer with a large warpage, the two-dimensional tilting platform can overcome the Figure 1c Dynamic range limitations of the interferometer in the architecture shown.

[0113] When the wafer is tilted, the shape of the wafer 1 in a horizontal position can be better maintained than that of the same wafer 1' in a vertical position. Figure 5 As shown, with the same wafer 1 ′ in a vertical position, gravity can change the shape of the wafer 1 ′ if the wafer 1 ′ is not completely vertical.

[0114] Specifically, Figure 5 The schematic diagram shows that a wafer 1' in a vertical position is prone to deformation when the wafer is tilted. This is because when the vertically clamped wafer 1' tilts, a torque T is applied to the wafer 1'. This torque will change the shape of the wafer. This limits the measurement accuracy of the traditional double Fizeau interferometer device. In contrast, Figure 5 As shown in the horizontal setting, the architecture of the present application supports the wafer 1 on a thin air cushion, which helps to maintain the natural shape of the wafer 1 even if the wafer 1 is at a small tilt angle (typically less than a fraction of a degree).

[0115] The architecture of the present application can be used to measure the warpage of thin wafers, wherein, when the wafer is tilted in a vertical position, the wafer is too thin to be placed in a vertical position or too thin to maintain its shape. For some thin wafers, it may be too thin to form support at two points on the edge of the wafer. In this architecture, the wafer is in a horizontal position and supported by an air cushion, that is, the wafer can be placed horizontally on the air cushion generated by the top surface of the air-floating chuck. When the wafer is tilted, a very small radial force is applied to the wafer to maintain the position of the wafer. Under appropriate suspension height and vacuum / air pressure settings, the warpage of thin wafers can be measured.

[0116] Therefore, the use of the above-mentioned wafer geometry measurement equipment and the wafer geometry measurement equipment with designed patterns can achieve high accuracy and throughput, but at half the price compared to the dual-Fizeau architecture. This method is a cost-effective and high-precision solution for wafer flatness, nanotopography, and shape measurement equipment for any wafer size, such as 200mm, 300mm, and 450mm.

[0117] Figure 6a FIG. 1 shows a cross-sectional schematic diagram of an air flotation chuck provided according to an embodiment of the present application. Figure 6a As shown, the air floating chuck 110 includes multiple supporting force nozzles 111. The air floating chuck uses the first gas 10 ejected from the multiple supporting force nozzles 111 to suspend the wafer 1 at a first predetermined distance D1 above the top surface of the air floating chuck to perform shape measurement on the wafer 1.

[0118] It should be understood that the shapes of the multiple supporting force nozzles 111 can be regular or irregular shapes such as circles, rectangles, squares, pentagons, etc., and the arrangement of the multiple supporting force nozzles 111 on the air flotation chuck 110 can be arranged on concentric rings around the center of the air flotation chuck, or can be arranged on multiple parallel lines, or can be arranged on multiple straight lines or wavy lines pointing to the center of the air flotation chuck. As long as the first gas 10 ejected from the multiple supporting force nozzles 111 can suspend the wafer 1 at a first predetermined distance above the top surface of the air flotation chuck, the embodiment of the present application does not make specific restrictions on this. The multiple supporting force nozzles 111 can cover the entire top surface of the air flotation chuck so that the supporting force on the supporting object such as the wafer supported by the air cushion is balanced, which is conducive to maintaining the original shape of the wafer.

[0119] According to the technical solution provided in the embodiments of the present application, multiple support force nozzles are provided on the air flotation chuck, and a first gas ejected from the multiple support force nozzles is used to stably suspend a support object, such as a wafer, above the top surface of the air flotation chuck. Because wafer measurement eliminates the need for a clamping tool to hold the wafer and affect its shape, wafer measurement errors are reduced.

[0120] In an embodiment of the present application, when the wafer measurement device 100 is used to measure the shape of the wafer 1 , the first predetermined distance is 60 μm-1500 μm.

[0121] It should be understood that the first predetermined distance D1 may be 60 μm, 300 μm, 350 μm, 1000 μm, 1500 μm, etc., and this embodiment of the present application does not specifically limit this.

[0122] In an embodiment of the present application, by setting the first predetermined distance D1 to a range of 60μm-1500μm, the shape change of the wafer caused by external force is reduced when the air floating chuck is used to support the wafer, thereby effectively maintaining the original state of the wafer, which is beneficial to the accuracy of measurement when the air floating chuck is used for shape measurement.

[0123] Figure 6b A cross-sectional schematic diagram of an air flotation chuck provided in another embodiment of the present application is shown. Figure 6b The embodiment shown is Figure 6a A variation of the embodiment shown. Figure 6b As shown, Figure 6a The difference of the embodiment shown is that the air flotation chuck 110 further includes a plurality of suction nozzles 112 arranged alternately with the plurality of support nozzles 111, and the air flotation chuck 110 uses the second gas 20 sucked from the plurality of suction nozzles 112 to force the back side S of the wafer 1 to 背面 The shape of the wafer 1 matches the shape of the top surface of the air flotation chuck 110. Alternatively, the wafer 1 may be placed on the top surface of the air flotation chuck first, and then the second gas 20 sucked from the plurality of suction nozzles 112 may be used to force the back surface S of the wafer 1 to 背面 The shape of the wafer 1 is matched with the shape of the top surface of the air-floating chuck 110, and then the first gas 10 ejected from the multiple supporting force nozzles 111 is used to suspend the wafer 1 at a second predetermined distance D2 above the top surface of the air-floating chuck 110. This application does not make specific restrictions on this. The air-floating chuck 110 can also use the second gas 20 sucked in from the multiple suction nozzles 112 and the first gas 10 ejected from the multiple supporting force nozzles 111 to suspend the wafer at a first predetermined distance D1 above the top surface of the air-floating chuck 110. This application does not make specific restrictions on this. The air-floating chuck 110 can also include a plurality of alternating pressure channels and vacuum channels for forming and maintaining an air cushion on the top surface of the air-floating chuck 110.

[0124] According to the technical solution provided in the embodiments of the present application, multiple supporting nozzles and multiple suction nozzles are alternately arranged on the air flotation chuck to stably suspend the wafer above the top surface of the air flotation chuck. Since there is no need to use a clamping tool to clamp the wafer during wafer measurement, which would affect the wafer's shape, wafer measurement errors are reduced.

[0125] In an embodiment of the present application, when the wafer measurement device is used to measure the flatness of a wafer, the second predetermined distance is 0 μm-50 μm.

[0126] It should be understood that the predetermined distance may be 0 μm, 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, etc., and the embodiments of the present application do not specifically limit this.

[0127] In an embodiment of the present application, by setting the range of the predetermined distance D to 0μm-50μm, it is beneficial to keep the flatness of the back side of the wafer almost as flat as the chuck surface under the action of suction when using an air floating chuck to support the wafer, which is beneficial to apply the surface shape of the air floating chuck to wafer flatness measurement after calibration.

[0128] Air flotation chuck

[0129] In another aspect of the present application, Figure 7a FIG. 1 shows a schematic top view of an air flotation chuck provided according to an embodiment of the present application. Figure 7a As shown, an air flotation chuck 110 has an array of pressure and vacuum nozzles on the chuck surface, with alternating pressure nozzles 111 and vacuum nozzles 112 arranged in each equally spaced concentric nozzle ring.

[0130] The vacuum suction and pressure support forces can keep the wafer suspended on an air cushion of a few microns to hundreds of microns on the air float chuck 110. The thinner the air cushion and the greater the air flow, the stiffer the air float. Under appropriate vacuum and pressure flow rates, the air float can be very stiff (e.g., >1N / μm). For an air gap of about 20μm, the air float will also have a significant ability to flatten the wafer. However, the stiffness of a 100μm thick air float can be as low as one-tenth of 1N / μm, where the force that deforms the shape of the wafer is very small.

[0131] To measure wafer flatness or TTV from the front side of the wafer, the back side of the wafer can be flattened and matched to the chuck surface by the air floatation chuck 110. When the air floatation gap is set at an appropriate height (e.g., 15 μm to 20 μm), no artifacts are detected on the air floatation chuck 110. To measure the shape of the wafer, the wafer is suspended on the surface of the air floatation chuck 110 with the air floatation gap set to approximately 60 μm-300 μm, where the wafer is supported by the air cushion generated by the air floatation chuck 110, and since the suction force under the large air gap is very small, the wafer is able to maintain its original shape.

[0132] In order to meet the WGT requirements for wafer flatness and shape measurement, the air bearing chuck 110 may have the following features, such as Figure 7a shown.

[0133] (1) Axisymmetrical, alternating pressure and vacuum nozzles 111, 112 arranged in concentric rings.

[0134] (2) The radius of the nozzle ring farthest from the center of the circle is smaller than the radius of the wafer. Nozzles such as vacuum nozzles or pressure nozzles extend outward from the center of the circle to approximately the last 0-20 mm, preferably 2-4 mm, of the radius of the air-floating chuck 110, thereby supporting the wafer. For example, for a 200 mm chuck, nozzles such as pressure nozzles 111 or vacuum nozzles 112 extend radially so that the center of the last set of nozzles is located at a position on the air-floating chuck with a diameter of 199 mm, 198 mm, 196 mm, 190 mm or 180 mm. In this embodiment, the surface of the air-floating chuck 110 is preferably larger than the surface of the wafer, so that the wafer does not extend beyond the edge of the air-floating chuck 110 when suspended in the air.

[0135] (3) As the radius increases, preferably, six nozzles are added to each nozzle ring, while the tangential spacing between the nozzles remains constant. To achieve this, the following formula N = 6*n is used. Here, n is the nth concentric nozzle ring, and N is the number of nozzles per nozzle ring, with n = 0 being the first "nozzle ring" at the center of wafer 1. The number "6" is preferably used so that the displacement between the nozzles in the radial and tangential directions is also approximately the same.

[0136] The number "6" is chosen based on the following method. The tangential spacing ΔT between the vacuum nozzle 112 and the pressure nozzle 111 can be the same across the entire air flotation chuck 110. Adjacent nozzle rings are spaced a constant distance ΔR. For a given ΔR, ΔT can be calculated using the following method.

[0137] Assume that for each adjacent nozzle ring, the number of nozzles increases by an even integer m as the radius increases (the even integer is because the vacuum and pressure nozzles are paired):

[0138] N=m*n

[0139] Where "N" is the number of nozzles per nozzle ring;

[0140] “n” is the nth nozzle ring; each nozzle ring is separated by ΔR, and the radius of the nth nozzle ring is Rn=n*ΔR.

[0141] Since the number of nozzles increases in pairs, "m" is an even integer (eg, 2, 4, 6, 8, 10).

[0142] ΔT=2p*n*ΔR / N=2p*ΔR / m=(2p / 6)*ΔR

[0143] Where p is the circumference constant π. When m=6, based on the above formula, ΔR and ΔT have almost the same value.

[0144] (4) The chuck flatness of the WGT 200 (wafer geometric parameter measurement equipment for measuring 200mm wafers) is preferably less than or equal to 1.5μm. The chuck flatness of the WGT 300 (wafer geometric parameter measurement equipment for measuring 300mm wafers) is preferably less than or equal to 2μm.

[0145] (5) The chuck surface needs to meet the standard of mirror polished chuck surface>N4 (according to ISO standard).

[0146] (6) In one embodiment of the present application, the diameter of the air-floating chuck is larger than the diameter of the wafer.

[0147] It should be understood that the diameter of the air floating chuck can be 1mm, 2mm, 5mm, 10mm, or even 50mm larger than the diameter of the wafer. Preferably, the diameter of the air floating chuck is 10mm larger than the diameter of the wafer. This application does not make any specific limitation on this.

[0148] In an embodiment of the present application, the diameter of the air floating chuck is set to be larger than the diameter of the wafer, which facilitates the wafer to be stably suspended on the top surface of the air floating chuck, and the area of the air floating chuck that is larger than the wafer can be used for calibration during wafer measurement because it is not blocked by the wafer during measurement.

[0149] In one embodiment of the present application, when the diameter of the wafer is 200 mm, the diameter range of the air floating chuck is 210 mm-220 mm; or when the diameter of the wafer is 300 mm, the diameter range of the air floating chuck is 310 mm-330 mm.

[0150] In an embodiment of the present application, by setting the diameter of the wafer to 200mm, the diameter range of the air floating chuck is 210mm-220mm; or when the diameter of the wafer is 300mm, the diameter range of the air floating chuck is 310mm-330mm, which is conducive to the wafer being stably suspended on the top surface of the air floating chuck.

[0151] (7) Three wafer clamps 708, two fixing parts (90 degrees apart, used to fix any two wafer clamps 708), and a driving clamp at the center of the wafer. The force on the wafer can be adjusted (e.g., 0.05 lb-1 lb).

[0152] (8) The four lifting pins 170 can lift the wafer a certain distance from the top surface of the air-floating chuck 110 in a stable manner to facilitate the removal of the wafer from the chuck.

[0153] Figure 7b FIG. 1 shows a top view of an air-floating chuck according to another embodiment of the present application. Figure 7bAs shown, air flotation chuck 110 has a vacuum nozzle 112 and a pressure nozzle 111. Vacuum nozzle 112 and pressure nozzle 111 are arranged at ΔR and ΔT, as shown in the figure. ΔR = 11.0 mm, ΔT = 9.0 mm. Since the difference between ΔR and ΔT is only 2 mm, ΔR and ΔT can be considered to be roughly the same.

[0154] Figure 7c A schematic diagram of the connection layer of the pressure nozzle 111 and the vacuum nozzle 112 of an air flotation chuck is shown. Figure 7c A top view of the stacked layers of the air flotation chuck 110 is provided. The stacked layers include a vacuum diverter layer 732, a pressure diverter layer 733, and a top chuck layer 734. The vacuum diverter layer 732 includes vacuum channels 735, which connect all vacuum channels 735 to a vacuum supply. The pressure diverter layer 733 includes pressure channels 736, which connect all pressure channels 736 to a pressure supply. The top chuck layer 734 includes a plurality of through holes, which are used to connect the vacuum channels 735 in the vacuum diverter layer 732 to the vacuum nozzles on the top surface of the top chuck layer 734. The top chuck layer 734 also includes additional through holes, which are used to connect the pressure channels 736 in the pressure diverter layer 733 to the pressure nozzles on the top surface of the top chuck layer 734. The through holes for vacuum and pressure are connected to Figure 7a and 7b The vacuum and pressure nozzle arrangements shown correspond to those arranged in an alternating fashion.

[0155] Figure 7d The figure shows a side view of a stacked structure of an air flotation chuck 110 provided according to an embodiment of the present application. The air flotation chuck 110 includes a top chuck layer 734', a vacuum diverter layer 732', and a pressure diverter layer 733'. Alternating through holes 740, 742 connect the vacuum channel 735' and the pressure channel 736' to the vacuum nozzle 112 and the pressure nozzle 111 on the top surface of the air flotation chuck 110, respectively. Figure 7d As shown in the side view of the air flotation chuck, the spacing ΔT between the alternating vacuum nozzles and pressure nozzles can be substantially the same.

[0156] Figure 7e FIG2 shows a side view of a stacking structure of an air flotation chuck 110 according to another embodiment of the present application. In this embodiment, the stacking structure may include a top plate 790, a rear cover plate 792, and a diverter plate 794 sandwiched between the top plate 790 and the rear cover plate 792. The top plate 790 may be made of aluminum, ceramic, glass, or microcrystalline silicon, and the preferred thickness of the top plate 790 is in the range of 10-60 mm. Figure 7d In the embodiment, the through holes 780 and 782 alternately provided in the top plate 790 provide pressure support force and vacuum suction force respectively to keep the wafer suspended ( Figure 7d The diameter of the through holes 780 and 782 can be 1.25-1.5 mm.

[0157] The top surface and the bottom surface of the diverter plate 794 may each have one or more grooves, and the vacuum channel 796 and the pressure channel 798 may be located in the grooves, respectively. Figure 7e In the illustrated example, the grooves on the top surface of the manifold 794 can be embedded in vacuum channels 796, which connect the vacuum nozzles on the top plate 790 of the stack structure to vacuum outlets 797 on the bottom plate of the stack structure via through-holes 780. Similarly, the grooves on the bottom surface of the manifold 794 can be embedded in pressure channels 798, which connect the pressure nozzles on the top plate 790 of the stack structure to pressure outlets 799 on the bottom plate of the stack structure via through-holes 782. The grooves on the top and bottom surfaces of the manifold can be configured according to the configuration of the vacuum and pressure channels, respectively, and can be several millimeters wide and several millimeters deep, preferably 2 mm wide and 2 mm deep.

[0158] Figure 7f Shown Figure 7e Schematic diagram of the top surface 790A of the top plate 790 of the stacked structure. The top surface includes pressure and vacuum nozzles (or holes) 111, 112 with equal or unequal spacing, for example, radial and tangential spacing of 5-25 mm, preferably 8-12 mm. The diameter of the vacuum nozzle 112 can be several millimeters, for example 1.5 mm. The diameter of the pressure nozzle 111 can be several millimeters, for example 1.25 mm. Both the vacuum nozzle 112 and the pressure nozzle 111 can have chamfers.

[0159] Figure 7g Shown Figure 7e A schematic diagram of the bottom surface 790B of the top plate of the stack shows the same pattern of pressure and vacuum nozzles 111 and 112. Bottom surface 790B may also include M3.5 or M4 threaded holes 712 for fastening the plates of the stack together and sealing the vacuum and pressure channels. Alternatively, glue can be used to secure the plates together, which can improve the flatness of the top surface. If glue is used, there is no need for any M3.5, M4, or any other threaded holes in the plates.

[0160] Figure 7h Shown Figure 7e A top view of the diverter plate 794 in the stacked structure. Figure 7h All vacuum nozzles (not shown) are connected to corresponding vacuum holes 720 in the top surface 794A of the manifold 794. In contrast, the vacuum nozzles from the top plate ( Figure 7hAll pressure nozzles (not shown) are connected to the corresponding pressure holes 722 in the manifold plate 794, forming a straight hole (such as Figure 7e As shown), the pressure nozzle on the top plate is connected to the pressure channel embedded in the bottom groove of the diverter plate 794 (as shown). Figure 7i In one embodiment, the vacuum channel 720A on the top surface of the diverter plate 794 may be Figure 7h The channels are aligned with the vacuum nozzles on the top plate and are connected by external circular channels 724 along the edge of the manifold 794. Figure 7h Also shown are M3.5 or M4 threaded holes 712' for securing the stacked panels together.

[0161] Figure 7i Shown Figure 7e FIG2 is a bottom view of an exemplary manifold plate 794 in a stacked configuration. In this embodiment, pressure channels / grooves 730 may be arranged in an inner annular pattern (“pressure supply ring”) that connect pressure ports through the manifold plate 794. Due to the increased cross-section of the pressure supply ring, the pressure supply ring presents less resistance. Figure 7i The bottom view also shows the Figure 7h 5 or M4 threaded holes 712' are visible in the top view of the embodiment. Although the bottom view also shows the superimposed vacuum channel 720', it should be understood that this is for illustration purposes only. Figure 7h As shown, the actual vacuum channel 720 ′ is located in a groove on the top surface of the diverter plate 794 .

[0162] Figure 7j Shown Figure 7e A top view of the rear cover plate 792 of the stacked structure. Figure 7k Shown Figure 7e A bottom view of the rear cover plate 792 of the stacked structure. Figure 7j As shown, the top surface of the rear cover plate 792 can be polished to seal the bottom surface of the manifold with the pressure groove embedded in it. In this embodiment, there are three openings 1j for connecting the pressure channel from the bottom surface of the manifold 792 to the pressure fitting ( Figure 7j In addition, there are three other openings 2j for connecting the vacuum channel from the top surface of the manifold to the vacuum fittings ( Figure 7j Not shown in ). Figure 7k The same pressure and vacuum openings 1k, 2k are also shown on the bottom view of the rear cover plate 792 in FIG. Figure 7j The top view of the rear cover 792 is shown and Figure 7kThe bottom view of the rear cover plate 792 is also shown showing M3.5 or M4 threaded holes 712'" that are used to fasten the rear cover plate to other plates in the stack.

[0163] although Figures 7e-7k A stacking structure of an air flotation chuck is shown, which has pressure channels and vacuum channels, which are respectively located in grooves on the bottom surface and the top surface of the diverter layer, but it should be understood that these channels can also be embedded in the grooves of other layers. For example, the vacuum channel can be located in a groove on the bottom layer of the top plate, while the pressure channel can be located in a groove on the top layer of the rear cover plate. In addition, it should be understood that in other embodiments, the arrangement of the vacuum channel and the pressure channel can be interchanged. In various embodiments, different numbers of vacuum and / or pressure nozzles can be included. The paths of the vacuum and pressure channels can be adjusted according to the number and position of the nozzles. The number of vacuum fittings and pressure fittings at the bottom of the stacking structure is not limited, for example, it can be 3 or more.

[0164] Figure 8a and 8b FIG. 8 is a schematic structural diagram of an exemplary diversion chamber 800 provided according to an embodiment of the present application. The diversion chamber 800 is used to separate the pressure nozzle from the vacuum nozzle. Figure 8a and 8b The manifold chamber 800 includes a pressure manifold chamber 804 and a vacuum manifold chamber 802. All vacuum nozzles are connected to the vacuum manifold chamber 802, and all pressure nozzles directly pass through the vacuum manifold chamber 802 to reach the pressure manifold chamber 804 located below the vacuum manifold chamber. Computational fluid dynamics (CFD) simulations show that this manifold chamber greatly improves the uniformity of the vacuum and pressure nozzles. The manifold chamber can provide a uniform gas volume and maximize the optimization of the increased channel size. In addition, the chamber height can be adjusted to minimize the change in the orifice flow rate.

[0165] The air cushion used to support the wafer also has gas damping, which effectively isolates the ground vibration and acoustic vibration, while eliminating or reducing the need for sound insulation boxes and active vibration isolation systems.

[0166] There are other advantages to using the air-floating chuck in the above embodiment. For example, the accuracy of the thickness measurement of the mask layer applied on the wafer can be improved. In the three-dimensional flash memory (3D NAND) process, the thickness measurement of highly opaque hard mask (or film) has not met the demand, because traditional optical methods cannot be well applied to opaque films. The characteristics of WGT wafer thickness measurement can be used to measure the thickness of the hard mask, such as performing two measurements on the wafer thickness, one is "pre-mask, Tpre ) thickness measurement, one is the thickness measurement of "behind the mask" (T post )). T pre =T0+E_RTE_pre

[0167] T post =T1+E_RTE-post

[0168] T0 and T1 are the thickness measurements before and after mask deposition, respectively. E_RTE_pre and E_RTE-post are the ray tracing errors (RTE) before and after the mask on the wafer, respectively.

[0169] Therefore, the thickness of the mask ΔT = T post –T pre =(T1-T0)+(E_RTE-post-E_RTE_pre)

[0170] Because the wafer can warp dramatically after the mask is applied, RTE (ie, E_RTE-post-E_RTE_pre) can significantly affect T pre and T post According to the embodiments disclosed herein, after the mask is applied to the surface of the wafer, the suction force generated by the air chuck can make the wafer substantially flat so that the wafer shape before and after the mask is substantially the same, thereby minimizing RTE (i.e., E_RTE-post-E_RTE_pre 0), and increase the accuracy of thickness measurement.

[0171] Air-floating chucks can be used to reduce or eliminate interferometer ray-tracing errors by forcing highly warped wafers to align with the top surface of the air-floating chuck. Alternatively, they can be used to reduce wafer warpage after thin-film deposition, ensuring that the pre-film shape matches the post-film shape. Ray-tracing errors are ultimately eliminated when the film thickness difference is calculated by subtracting the pre-film thickness from the post-film thickness. This method can significantly reduce ray-tracing errors caused by highly warped wafers when applied to thickness measurements of opaque hardmask layers.

[0172] Methods for distinguishing real wafer surface features from chuck marks / artifacts

[0173] The wafer measurement device 100 according to the embodiment of the present application can also achieve artifact-free measurement. Figure 1cThe embodiment of the wafer measurement apparatus 100 shown utilizes a vertically mounted Fizeau interferometer for both flatness measurement and wafer shape measurement. However, in practice, methods for wafer flatness measurement and wafer shape measurement present many challenges. The chuck itself may not be flat, and there may be artifacts, such as grains, on the surface of the chuck. When the wafer is vacuumed onto the chuck, artifacts may appear on the top surface of the wafer. For example, Figure 9a Schematic diagram showing chuck marks / artifacts as the wafer is vacuumed down onto the vacuum chuck. Figure 9a As shown, large die 902 may appear as protrusions on wafer 1 on the top side of chuck 110 ′. According to another embodiment of the present application, these types of artifacts can be calibrated using the methods disclosed herein. Figure 9b A schematic diagram of wafer 1 suspended above air-bearing chuck 110 is shown, wherein no chuck marks / artifacts are visible on wafer 1 .

[0174] Figures 10a-10c A schematic diagram of a method for distinguishing real features 1004 from chuck marks / artifacts 1006 on the surface of a wafer 1 is shown. Figure 10a A schematic diagram of measuring wafer geometric parameters on the S1 surface is shown, where real features 1004 are mixed with chuck marks / artifacts 1006 in the interferometer measurement. Figure 10b The schematic diagram of measuring the geometric parameters of the wafer on the S2 surface is shown, where the S2 surface is the chuck surface after the chuck is rotated 180 degrees from the original position of the S1 surface measurement. When the chuck mark / artifact 1006 rotates 180 degrees with the chuck 300, the real feature 1004 remains in the same position. Therefore, by placing the wafer 1 on the chuck surface S2 after rotating 180 degrees (as shown in FIG. Figure 10b ), and the surface S2 of the wafer 1 at 180° is aligned with the surface S1 at 0° (as shown in FIG. Figure 10a By comparing the measurement results of the wafer 1000 with those of the wafer 1001 (shown in FIG. 1 ), true wafer features 1004 (those features that remain in the same position in the wafer coordinate system before and after rotation) can be identified. Conversely, when wafer 1 is rotated 180°, the position of the chuck mark / artifact 1006 will be offset by 180° in the wafer's coordinate system.

[0175] Figure 10c The S1 and S2 difference plots are provided, showing chuck artifacts as pairs 1016 and 1020. These chuck artifacts can be calibrated out if they do not move around on the chuck. If the chuck is clean and the artifacts are isolated, they also have specific characteristics that can be removed by the algorithm. When limited artifacts are on the chuck and / or wafer backside, wafer or chuck rotation can be used to isolate and remove the artifacts.

[0176] Although the embodiments of the present application have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications should be understood to be included within the scope of the embodiments of the present application as defined by the appended claims.

Claims

1. A wafer measurement device, characterized in that: include: an air-floating chuck for generating an air cushion so that the wafer to be measured can be suspended on the top surface of the air-floating chuck; an interferometer, disposed on a side of the wafer away from the air floating chuck, for acquiring an interference fringe image of the front side of the wafer, so as to perform shape measurement and / or flatness measurement on the wafer based on the interference fringe image, wherein the front side of the wafer is a surface of the wafer away from the air floating chuck; a capacitance sensor disposed in the middle of the air flotation chuck, configured to measure position information corresponding to at least one position point on the back side of the wafer to obtain a capacitance sensor reading CPn, or to monitor whether the wafer is present on the air flotation chuck based on the capacitance sensor reading CPn, or to monitor a first predetermined distance based on the capacitance sensor reading CPn, wherein the back side of the wafer is a surface of the wafer close to the air flotation chuck; a laser, located on an upper side of the top surface of the air-floating chuck, for emitting a first laser toward the front surface of the wafer; a position sensor located on the upper side of the top surface of the air-floating chuck and on the side opposite to the laser, for receiving a second laser after the first laser is reflected by the front side of the wafer and measuring position information corresponding to a first position point on the front side of the wafer based on the second laser to obtain a position sensor reading Vx, wherein the capacitance sensor is also used to measure position information corresponding to a second position point on the back side of the wafer to obtain a capacitance sensor reading CPn, wherein the first position point and the second position point are two relative position points in the wafer that represent the thickness; First standard wafer; a processor connected to the position sensor and the capacitance sensor to obtain the position sensor reading Vx and the capacitance sensor reading CPn, and substitute the position sensor reading Vx and the capacitance sensor reading CPn into a formula Twafer = T0 + (CP0-CPn) + S* (Vx–V0) to obtain the thickness Twafer of the wafer, wherein T0 in the formula is the thickness of the first standard wafer, CP0 is a reference capacitance sensor reading when the first standard wafer is at a reference predetermined distance, V0 is a reference position sensor reading when the first standard wafer is at a reference predetermined distance, S is a slope of a straight line in a relationship graph of a difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0 when the first standard wafer is at different predetermined distances, the horizontal axis being the position sensor reading Vx when the first standard wafer is at different predetermined distances, and the vertical axis being the slope of a straight line in a relationship graph of a difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0 when the first standard wafer is at different predetermined distances; A quality sensor is used to measure the quality of the wafer to obtain the average thickness of the wafer.

2. The wafer measurement device according to claim 1, wherein: The air floating chuck includes a plurality of supporting force nozzles. The air floating chuck suspends the wafer at the first predetermined distance above the top surface of the air floating chuck using a first gas ejected from the plurality of supporting force nozzles to perform shape measurement on the wafer.

3. The wafer measurement device according to claim 2, wherein: The air flotation chuck also includes a plurality of suction nozzles arranged alternately with the plurality of supporting force nozzles. The air flotation chuck utilizes the second gas sucked in from the plurality of suction nozzles and the first gas ejected from the plurality of supporting force nozzles to force the wafer to approach a second predetermined distance from the air flotation chuck, and forces the shape of the back side of the wafer to match the shape of the top surface of the air flotation chuck to perform flatness measurement on the wafer, wherein the back side of the wafer is the surface of the wafer close to the air flotation chuck.

4. The wafer measurement device according to claim 2, wherein: When the wafer measurement device is used to measure the shape of a wafer, the first predetermined distance is 60 μm-1500 μm.

5. The wafer measurement device according to claim 3, wherein: When the wafer measurement device is used to measure the flatness of the wafer, the second predetermined distance is 0 μm-50 μm.

6. The wafer measurement device according to claim 1, wherein: The air-floating chuck is further configured to suspend the first standard wafer at different predetermined distances above the top surface of the air-floating chuck. The position sensor is further configured to measure position information of a third position point on the first surface of the first standard wafer at different predetermined distances to obtain a position sensor reading Vx, wherein the first surface of the first standard wafer is a surface of the first standard wafer away from the air-floating chuck. The capacitance sensor is further used to measure position information of a fourth position point on the second surface of the first standard wafer when the first standard wafer is at different predetermined distances to obtain a capacitance sensor reading CPn, wherein the second surface of the first standard wafer is the surface of the first standard wafer close to the air-floating chuck, and the fourth position point and the third position point are two relative position points on the first standard wafer that characterize the thickness. The different predetermined distances include a reference predetermined distance, and the reference capacitance sensor reading of the first standard wafer at the reference predetermined distance is CP0 and the reference position sensor reading is V0. The processor is further configured to construct a relationship graph with the horizontal axis being the position sensor reading Vx and the vertical axis being the difference hx between the capacitance sensor reading CPn and the reference capacitance sensor reading CP0, so as to determine the slope S of the straight line from the straight line in the relationship graph.

7. The wafer measurement device according to claim 1, wherein: The diameter of the air floating chuck is larger than the diameter of the wafer.

8. The wafer measurement device according to claim 7, wherein: When the diameter of the wafer is 200 mm, the diameter range of the air floating chuck is 210 mm-220 mm; or when the diameter of the wafer is 300 mm, the diameter range of the air floating chuck is 310 mm-330 mm.

9. The wafer measurement device according to claim 1, wherein: Also includes: At least one tilting platform located below the air-floating chuck is used to offset and / or tilt the air-floating chuck to align the air-floating chuck with the interferometer, or offset and / or tilt the air-floating chuck to adjust the distance between the air-floating chuck and the interferometer to achieve mechanical phase shift, or offset and / or tilt the air-floating chuck to drive the offset and / or tilt of the wafer to measure the warpage of the front side of the wafer.

10. The wafer measurement device according to claim 9, wherein: The at least one tilting platform is a two-dimensional tilting platform, and the two-dimensional tilting platform includes two goniometer frames stacked in a 90° intersecting manner.

11. The wafer measurement device according to claim 1, wherein: Also includes: A plurality of lifting pins are located around the air-floating chuck and are used to lift the wafer from the top surface of the air-floating chuck.

12. The wafer measurement device according to any one of claims 1 to 11, wherein: The interferometer includes a Fizeau interferometer or a shearing interferometer.

13. The wafer measurement device according to claim 12, wherein: When the interferometer is the Fizeau interferometer, the interferometer includes a standard mirror close to the air-floating chuck, and the wafer measurement device further includes: A second standard wafer with a known flatness of TTV0 is used to calibrate the top surface of the air-floating chuck and the surface of the standard mirror opposite to the air-floating chuck. Wherein, when the wafer flatness is measured using the wafer measurement device, the interferometer is further used to measure the first distance change ΔS1 between the relative surface of the air-floating chuck and the standard mirror when the second standard wafer is not loaded, and to measure the second distance change ΔS2 between the relative surface of the second standard wafer and the standard mirror when the second standard wafer is loaded, and the interferometer is further used to obtain the mismatch item S between the relative surface of the wafer and the air-floating chuck by subtracting ΔS2 and TTV0 from ΔS1. N.C. The top surface of the air-floating chuck and the surface of the standard mirror opposite to the air-floating chuck are calibrated.

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