Integrated Wafer Warpage Measurement

Abstract

In some examples, a wafer warpage measurement system includes a measurement unit, the measurement unit including: a wafer support assembly for transmitting rotational motion to a wafer under test supported in the measurement unit; an optical sensor; a calibration standard for calibrating the optical sensor; a linear stage actuator for transmitting a linear motion direction to the optical sensor; a wafer centering sensor for determining the centering of the wafer under test supported in the measurement unit; and a wafer alignment sensor for determining the alignment of the wafer under test supported in the measurement unit.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Patent Application No. 62 / 796,963, filed on January 25, 2019 by Arora et al., entitled “Integrated WaferBow Measurements,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The subject matter disclosed herein relates to devices used in semiconductor and related industries. More specifically, the present disclosure relates to integrated wafer warpage measurement, and in one example to wafer warpage measurement using optical sensors. Background Art

[0004] The background description provided here is for the purpose of generally presenting the context of the present disclosure. The work of the presently designated inventors is neither explicitly nor implicitly admitted to be prior art against the present disclosure to the extent that it is described in this background section and in aspects of the specification that were not determined to be prior art at the time the application was filed.

[0005] Advances in plasma processing have facilitated the development of the semiconductor industry. Typically, multiple semiconductor devices can be produced from dies cut from a single processed wafer (i.e., substrate). Since most recipes for processing wafers assume that the wafer is planar, non-planar wafers (e.g., wafers with warpage) can result in variations that can result in defective semiconductor devices.

[0006] The degree of wafer warpage generally indicates the degree of wafer stress. Highly warped wafers may cause chuck failure during photolithography. Ideally, the wafer is perfectly flat. However, most wafers tend to have slight warpage and / or protrusions, resulting in a non-planar wafer. The non-planarity of the wafer may be due to the original shape of the wafer and / or may be due to stress (e.g., mechanical stress) of a film that may have been deposited onto the wafer during one or more deposition steps. In some cases, if the wafer is too non-flat, the wafer may be considered unusable and may be discarded.

[0007] In certain processing steps, such as etching or deposition, knowing the configuration of the wafer may be important to accurately determine the amount of etching and to prevent electrodes within the processing chamber from accidentally contacting the wafer, thereby causing damage to the wafer and / or damage to the electrodes. This is particularly true for processing chambers that may be sensitive to wafer warpage. In one example, a bevel etcher may be particularly sensitive to wafer warpage because the upper electrode may be very close to the wafer in order to etch along the edge (e.g., bevel) of the wafer.

[0008] In a bevel etcher, the gap between the upper electrode and the wafer may be about 0.35 mm. However, wafer warpage may be as large as 0.25 mm. Therefore, if wafer warpage is not correctly identified, the upper electrode may accidentally contact the wafer, resulting in damage to the wafer and / or the upper electrode. Furthermore, since the amount of plasma that can be introduced into the process module may also depend on knowing the actual gap, failure to accurately identify the gap may result in variations in processing.

[0009] Therefore, before etching can be performed on a wafer, measurements may have to be performed to determine the extent of wafer warpage. However, online measurements are not typically performed during the deposition process. Therefore, it may not be possible to input measurement data into the etching process to determine the extent of wafer warpage. Instead, an independent metrology tool may be employed to determine measurements of wafer warpage. However, independent metrology tools are typically used to perform characteristic measurements. In other words, each wafer is not measured to determine the wafer warpage of the wafer. Instead, a sample may be taken to determine the type of wafer warpage that can characterize a group of wafers. Furthermore, since the independent metrology tool is not in situ or even online, the format of the measurement data is typically not such that the data can be easily fed to another tool, such as a bevel etcher.

[0010] One method for achieving in-situ measurement is to include a metrology tool within the process module to measure wafer warpage. In one example, the measurement of wafer warpage can be performed while the wafer is on an electrostatic chuck within the process module while waiting for the etching process to begin. One method of performing the measurement includes shining a light beam across the wafer and measuring the light brightness level while lowering an upper electrode of the process module to reduce the gap between the upper electrode and the wafer. When a predetermined amount of light is no longer detected, the lowering of the upper electrode is stopped. At this point, the upper electrode is determined to be very close to the wafer but not yet in contact with the wafer.

[0011] The purpose of identifying the point at which the upper electrode can come close to contacting the wafer is to determine the minimum distance between the electrode and the wafer, thereby identifying the height of the wafer. Unfortunately, the measurement performed is limited to a single point. Therefore, the measured value may not be the actual height of the water.

[0012] Current standalone technologies are either limited by TpT (wafer point-by-point measurement) or have a measurement range of <300 microns, making them unsuitable for process control. In addition, standalone systems are not designed to measure hot wafers and are therefore not suitable for real-time measurements. For example, in some cases, wafer warpage compensation can be performed by using a deposition tool to deposit a film on the back side of a warped wafer, but this does not provide adequate warpage compensation in real time for high-volume manufacturing. Summary of the invention

[0013] In some examples, an optical sensor, such as a laser triangulation based distance sensor, is integrated into the front end of a substrate (e.g., wafer) processing tool, such as a deposition tool. Using a combination of linear and rotary stages, the optical sensor scans the wafer surface in a desired manner and measures the wafer warpage. Real-time wafer warpage measurements from the integrated optical sensor are used to establish process monitoring and control on the deposition tool.

[0014] In some examples, a wafer warpage measurement system includes a measurement unit, the measurement unit including: a wafer support assembly for transmitting rotational motion to a wafer under test supported in the measurement unit; an optical sensor; a calibration standard for calibrating the optical sensor; a linear stage actuator for transmitting a linear motion direction to the optical sensor; a wafer centering sensor for determining the centering of the wafer under test supported in the measurement unit; and a wafer alignment sensor for determining the alignment of the wafer under test supported in the measurement unit.

[0015] In some examples, the wafer centering sensor includes an actuator for actively centering a wafer under test supported in the measurement unit.

[0016] In some examples, the wafer support assembly includes a wafer alignment chuck.

[0017] In some examples, the wafer warpage measurement system further includes a reference wafer unit.

[0018] In some examples, the reference wafer unit includes a plurality of slots to accommodate a series of different reference wafers.

[0019] In some examples, the series of different reference wafers provides a series of measurement control references for the wafer under test supported in the measurement cell.

[0020] In some examples, the wafer warpage measurement system further includes a plurality of measurement units and at least one reference wafer unit.

[0021] In some examples, the wafer warpage measurement system is integrated with a wafer processing tool.

[0022] In some examples, the calibration standard includes at least one pre-measured feature or facet that can be scanned by the optical sensor to detect stray wafer bow measurements over time.

[0023] In some examples, the scannable features or facets include wedge-shaped silvered diffuse optical flats to serve as a proxy for wafer thickness.

[0024] In some examples, the calibration standard includes a plurality of steps that can be scanned by the optical sensor to detect spurious wafer bow measurements over time.

[0025] In some examples, the wafer warpage measurement system further includes a temperature sensor or a humidity sensor, and wherein the selection of a reference wafer in the series of different reference wafers is based on data derived from the temperature sensor or the humidity sensor.

[0026] In some examples, the wafer warpage measurement system further includes a vibration isolation mechanism or mount.

[0027] Some examples include a method for measuring wafer warpage of a wafer in a wafer processing flow including a wafer processing module, the method comprising: integrating a wafer warpage measurement system with the wafer processing module; extracting a wafer from the wafer processing flow for wafer warpage measurement by the wafer warpage measurement system; adjusting parameters of the wafer processing flow based on the wafer warpage measurement derived by the wafer warpage measurement system; and placing the measured wafer back into the wafer processing flow.

[0028] In some examples, the wafer warpage measurement system used in the exemplary method includes a measurement unit, which includes: a wafer support assembly, which is used to transmit rotational motion to a wafer under test supported in the measurement unit; an optical sensor; a calibration standard for calibrating the optical sensor; a linear stage actuator, which is used to transmit a linear motion direction to the optical sensor; a wafer centering sensor, which is used to determine the centering of the wafer under test supported in the measurement unit; and a wafer alignment sensor, which is used to determine the alignment of the wafer under test supported in the measurement unit.

[0029] Further scope of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the figures of the accompanying drawings, some embodiments are shown by way of example and not limitation:

[0031] Figure 1 A schematic array of different types of wafer warpage is shown according to exemplary embodiments.

[0032] Figure 2-3 A diagram and a side view are respectively shown of an exemplary measurement unit for a wafer warpage measurement system according to an exemplary embodiment.

[0033] Figure 4A schematic diagram of a reference wafer unit according to an exemplary embodiment is shown.

[0034] Figure 5 A schematic diagram showing components of a wafer warpage measurement system according to an exemplary embodiment is shown.

[0035] Figure 6 An example wafer warpage measurement system according to an exemplary embodiment is shown.

[0036] Figure 7 Pairs of measuring units according to exemplary embodiments are shown.

[0037] Figure 8 A measurement system according to an exemplary embodiment is shown.

[0038] Figure 9-10 Schematic illustrations and cross-sectional views of a calibration standard according to an exemplary embodiment are shown.

[0039] Fig.11 A schematic diagram representing operations in a noise subtraction operation is shown in accordance with an exemplary embodiment.

[0040] Figure 12-13 Schematic pictures and cross-sectional views showing some internal components of a reference wafer unit according to an exemplary embodiment.

[0041] Figure 14-15 A schematic diagram of a measuring unit according to an exemplary embodiment is shown.

[0042] Fig.16 Exemplary graphical results of a wafer warpage measurement method according to an exemplary embodiment are shown.

[0043] Fig.17 Operations in a wafer warpage measurement method according to an exemplary embodiment are shown.

[0044] Fig.18 Schematic illustrations and cross-sectional views of aspects of multi-step and multi-interface calibration standards according to exemplary embodiments are shown.

[0045] Fig.19 Aspects of exemplary operations in a sampling method according to exemplary embodiments are shown.

[0046] Fig. 20 An arrangement or configuration of a wafer warpage measurement system according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0047] The following description includes systems, methods, techniques, instruction sequences, and computing machine program products that embody illustrative embodiments of the present invention. In the following description, for the purpose of explanation, numerous specific details are set forth to provide a thorough understanding of the exemplary embodiments. However, it will be apparent to those skilled in the art that the present embodiments may be practiced without these specific details.

[0048] A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by any person of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to any data as described below and in the drawings that form a part of this document: Copyright Owner LAM Research Corporation, 2018. All Rights Reserved.

[0049] As a general background, semiconductors typically start as wafer slices of purified semiconductor material. Typically these wafers are produced by heating the material, shaping it, and processing it to cut and grind it into small, smooth wafers.

[0050] During the deposition phase, the prepared wafer is cleaned, heated and exposed to pure oxygen in a diffusion furnace. This results in a reaction that produces a uniform silicon dioxide film on the wafer surface.

[0051] In the masking stage (also called photolithography or photomasking), the process protects one area of ​​the wafer while processing another area. After a photosensitive film is applied to a portion of the wafer, a strong light is then projected onto it through the mask, exposing the film with the mask pattern.

[0052] During the etching phase, manufacturers bake the wafer to harden the remaining film pattern, then expose it to a chemical solution to etch the areas not covered by the hardened film. After this step, the film is removed, and the wafer is inspected to ensure proper image transfer. Doping, deposition, and plating phases can occur during semiconductor manufacturing.

[0053] In some examples, the wafer warpage measurement system includes an optical distance sensor (e.g., a laser triangulation sensor with a large measurement range in the ±2000 μm region) integrated with a wafer aligner and mounted at the front end of a wafer deposition tool. Other integrated arrangements are also possible. Using a combination of linear and rotary stages, the sensor measures the relative distance relative to the wafer surface and calculates or derives the wafer shape or warpage. In some examples that allow real-time applicability, the total measurement time may take less than 2 seconds. Real-time wafer warpage measurements from an integrated wafer warpage measurement system can be used to establish process monitoring and control on wafer deposition or warpage compensation tools. In some examples, the method can be applied to other wafer processing tools, such as etching, stripping and cleaning, and metrology modules.

[0054] An example wafer warpage measurement system may include a measurement unit including the following elements: an optical distance sensor that measures the relative distance to the wafer, the linear and rotational motion axes (or the path traveled by the sensor) in order to scan the wafer in a desired manner; a set of sensors for monitoring the wafer and its environmental conditions (e.g., wafer temperature, ambient temperature, ambient humidity sensors, accelerometers, sensor temperature measurements, or wafer fiducial (notch) alignment sensors). Other environmental sensors or measurements are also possible. Environmental compensation factors may be applied based on the measurements made by the environmental sensors.

[0055] An exemplary wafer warpage measurement system may also include a reference wafer unit that accommodates different reference wafers. A specific reference wafer measurement value may be subtracted (or accounted for) from the original wafer measurement value. In some examples, the reference wafer measurement may enable compensation or reduction of mechanical component noise and the effects of gravity-related wafer sag or wafer aligner fingerprints. The wafer warpage measurement system may also include an integrated calibration standard to check sensor accuracy and status. In some examples, the calibration standard is mounted next to the wafer in the measurement unit and may be measured during wafer scanning or at periodic intervals for calibration purposes. In some examples, the wafer warpage measurement system includes a controller that can communicate with the environment and optical sensors and calculate or derive the wafer warpage.

[0056] In an exemplary process flow, in pre-processing and / or post-processing, the wafer is transferred to a warpage metrology station of a measurement unit, which is used for notch alignment and wafer warpage measurement. This measurement can be used to establish process monitoring and control in the wafer deposition tool. Some process examples can be "feedforward" based, where the pre-processed wafer warpage value is fed forward to the process module of the deposition tool to control the incoming wafer warpage variation. Other process examples are "feedback" based, where the pre-processing and post-measurement data can be used for operations such as process module quality assessment, wafer excursion detection (or non-compliance with specifications), compensation for process module drift over time, chamber accumulation, etc. If the target warpage value is not achieved, the wafer can be rerouted back to the process module to achieve the desired warpage compensation.

[0057] In some examples, instead of using an optical triangulation sensor, a chromatic confocal, confocal or interferometric based sensor, or an inductive or capacitive sensor may be used for wafer warpage measurement. A combination of multiple sensors may also be used.

[0058] refer to Figure 1 , an array 100 of different types of wafer warpage is depicted. Element 102 depicts positive warpage, element 104 depicts negative warpage, and element 106 depicts a saddle shape. Different measurement schemes 108 including combinations of linear and rotational motions may be employed to measure the types of warpage depicted in the array 100. An optical sensor in a measurement unit discussed further below may employ one of a plurality of measurement schemes 108 to measure or derive wafer warpage. Measurement scheme 110 may include a one-dimensional (1-D) wafer scan. Measurement scheme 112 may include a two-dimensional (2-D) wafer scan including, for example, a one-dimensional scan performed by an optical sensor along multiple linear axes. For example, a single linear scan may be followed by a 90° rotational motion of the scanned wafer and then a second linear scan. Measurement scheme 114 may include a 2-D spiral scan, for example including a continuous rotational motion of the wafer by the measurement unit coupled to a linear motion of the optical sensor. The measurement scheme 116 may include 2-D concentric wafer scanning, for example including a rotational motion of scanning the wafer combined with spaced or intermittent linear motion of an optical sensor to produce the illustrated concentric rings of wafer bow measurement.

[0059] An exemplary method for providing metrology for substrate processing (e.g., bow-type wafer warpage measurement) includes providing an optical metrology station including a plurality of optical sensors to measure spectra from a plurality of measurement locations on a substrate, measuring at least one of a mass or a mass change of the substrate, generating thickness values ​​at the plurality of measurement locations of the substrate based on the spectra from the plurality of measurement locations and a learned model, and generating a spatial thickness distribution model of the substrate based on the thickness values ​​at the plurality of measurement locations and at least one of the mass or the mass change. In this regard, reference is made to commonly owned U.S. Patent Application 15 / 696,768, entitled “Systems and Methods for Combining Optical Metrology with Mass Metrology,” which is incorporated herein in its entirety.

[0060] Figure 2-3 A diagram and a side view of an exemplary measurement unit 200 for a wafer warpage measurement system are depicted, respectively. The measurement unit 200 includes a housing or supporting optical sensor 1, a calibration standard 2, a wafer 3 (which is used for wafer warpage measurement), a linear stage actuator that imparts a linear motion direction 4 to the optical sensor 1, a wafer centering sensor (e.g., an active wafer centering (AWC) sensor 5, which includes an actuator for active wafer centering), a wafer alignment sensor 6, and a wafer support assembly (e.g., a rotating stage (aligner) chuck 7 ( Figure 3 )). The linear stage can apply linear motion 4 to the optical sensor 1, and the rotary stage 7 can apply rotary motion to the wafer 3 to adopt Figure 1 The wafer warpage measurement of wafer 3 is derived using one or more of the measurement schemes 108 depicted in FIG.

[0061] Figure 4 A schematic diagram of a reference wafer unit 400 described further below is depicted. The reference wafer unit 400 may include multiple slots (not shown) to accommodate a range of different reference wafers, such as different wafer thicknesses, wafer warpage, stress, rigidity / flexibility, and crystal orientations to provide a range of measurement control references for different types of wafers 3 under test.

[0062] Figure 5 A schematic diagram of components of a wafer warpage measurement system 500 is depicted. In this example, the system 500 includes two stacked measurement units 200 and a reference wafer unit 400. Figure 6-8 In some exemplary embodiments, the wafer warpage measurement system 500 may be integrated with or mounted to a deposition tool or module 600. Figure 6, an exemplary wafer warpage measurement system 500 is shown mounted near a side port 602 of an exemplary deposition module 600. The measurement system 500 may include one or more measurement units 200 and, if desired, a reference wafer unit 400. A series of one or more wafer boat loaders 604 may be used to introduce wafers into the interior of the deposition module 600 where the wafers may be accessed (or pre-measured) for wafer warpage measurement by the warpage measurement unit 200.

[0063] Other installation positions of the measuring system 500 or the measuring unit 200 are possible. Figure 7 , a pair of measurement cells 200 are shown mounted at designated integrated metrology module (IMM) ports 702 of a deposition module 600. Figure 8 In FIG. 5 , the measurement system 500 is installed at the wafer boat loader position.

[0064] Return to reference Figure 2 And in some example measurement units and systems, a calibration standard 2 is provided. A schematic diagram and a cross-sectional view of an exemplary calibration standard 902 are shown in Figure 9-10 The illustrated calibration standard 902 has a structure that can be detected by an optical sensor (e.g. Figure 2 The calibration standard 902 here comprises a wedge-shaped silvered diffuse optical flat surface which may be placed in close proximity to a wafer (e.g., Figure 2 3) Positioning of the wafer in the Fig.10 , the exemplary optical plane 902 is generally tilted downward from left to right in the view to a drop or depth 1002. Other configurations or tilts of the calibration standard 2 or optical plane 902 are possible. In some examples, the pre-measured (or known) optical depth 1002 of the optical standard 2 or optical plane 902 can serve as a proxy for the verticality of the wafer thickness or wafer warpage and be used to calibrate or check that the optical sensor reports such values ​​accordingly. The calibration standard 2 or optical plane 902 can be scanned during the wafer scanning operation or can be scanned at other times (e.g., when the deposition module 600 or measurement unit 200 is available). The above exemplary calibration operations seek to ensure that the measurement unit 200 performs within the desired measurement specifications.

[0065] refer to Fig.18, in some examples, a multi-step standard 1802 is provided. As shown, the standard 1804 can include multiple flat steps instead of a wedge shape. Another example standard 1806 includes multiple interfaces. In some examples of this nature, the standard can be made of an optically transparent material that includes multiple interfaces. The light from the sensor is reflected at each interface and focused at a different point on the detector, so the thickness of each interface can be measured in one operation. This can be used for sensor calibration. In addition, the interfaces can have anti-reflection coatings to avoid multiple re-reflections between interfaces.

[0066] In some cases, wafer warpage measurements may be affected by noise or environmental conditions at a particular time. These factors may negatively impact making accurate wafer warpage measurements. Some examples herein seek to subtract or compensate for such noise or environmental conditions. For example, wafer warpage at any given time may depend on how the wafer is held on the aligner lift pins in an electrostatic chuck (ESC). A "reference" wafer measurement may be obtained by comparing the wafer to a reference wafer unit (e.g., Figure 4 The reference wafer is typically subject to the same noise as the processed wafer, so once the noise to which the reference wafer is subject can be determined, its size or effect can be subtracted from the corresponding measurements obtained from the same type of processed wafer. In the present example, such wafer referencing operation can filter out or minimize two sources of potential measurement uncertainty, namely the deformation effects of the lift pins and the effects of gravity causing the wafer to sag in the central region not supported by the pins. In further examples, systematic z-axis noise from moving mechanical components such as the linear stage 4, the rotary stage 7, etc. can be eliminated in a similar manner. One or more reference wafers, each having specific characteristics suitable for the corresponding processed wafer, can be stored in the reference wafer unit 400 in association with the measurement unit 200, for example as Figure 5 shown.

[0067] Fig.11A schematic diagram representing operations in an exemplary noise subtraction operation 1110 is shown in . Wafer warpage measurement data for a process wafer may include noise or background factors, which are generally shown in area 1102 of the data input graph. Noise 1102 may be caused, for example, by one or more of the elements described above. At this point, the level of any noise, or even its existence, may not yet be determined. Measurements made on a corresponding reference wafer that is subject to the same noise as the process wafer can be used to determine the presence of noise and derive the noise level. The presence of noise and its level are shown by area 1104 of the intermediate reference wafer graph. As shown, the noise level can be subtracted from the data input data to obtain an accurate data output graph. Data output graph 1106 is more representative of the actual wafer warpage measurement. Schematic diagrams and cross-sectional views depicting the internal components of an exemplary reference wafer unit 400 are shown in . Figure 12-13 . The reference wafer unit 400 may include a reference wafer slot 1202 for supporting one or more reference wafers 1302. Temperature and humidity sensors 1304 and 1306 may be included in the exemplary reference wafer unit 400. In some examples, the temperature and humidity sensors 1304 and 1306 may work with other sensors discussed further below. In some examples, noise generated by temperature and humidity may also be excluded or compensated.

[0068] In some examples, the temperature of the wafer can change the stress in the wafer film and substrate and affect the wafer warpage. To this end, in some examples, a series of non-contact optical sensors are placed under the wafer in the measurement unit 200 for wafer temperature measurement. Depending on the temperature of the wafer and the characteristics of certain deposited films and substrates, temperature compensation can be applied to the warpage measurement of the wafer. A schematic diagram of the measurement unit 200 including an exemplary temperature sensor 1402 is shown in Figure 14-15 A reference or handling wafer 1302 located above the sensor for warpage measurement is Fig.15 An example warpage measurement is shown in Fig.16 In the graph of . Relative to the chip temperature plotted on the x-axis, Fig.16 The change in wafer warpage (warpage variable) is shown on the y-axis.

[0069] Therefore, in some examples, ambient humidity and temperature compensation is provided. Ambient humidity and temperature sensors are added to the measurement unit 200 and the reference wafer unit 400. This arrangement can be used to minimize the measurement uncertainty or noise associated with these ambient conditions. In a further example, sensor temperature compensation can be provided. For example, the temperature of an optical or distance sensor can affect its linearity. A temperature sensor can therefore be mounted next to the sensor to assess the extent of linear drift. This arrangement can be used to minimize the measurement uncertainty associated with the sensor temperature.

[0070] Some examples of the measurement unit 200 and / or the reference wafer unit 400 include vibration compensation. Any vibration in these components may affect the uncertainty of the wafer warpage measurement. Exemplary vibration isolation mechanisms may include one or more of isolation mounts (e.g., to minimize floor vibrations), O-rings (e.g., to isolate front-end vibrations), accelerometers (e.g., to mark measurements during large vibrations), and anti-vibration mounts (e.g., to minimize seismic vibrations).

[0071] Other examples may include specific wafer placement in the measurement unit 200 or reference wafer unit 400. For example, eccentricity or incorrect wafer placement on the lift pins can affect the warpage measurement. An AWC mechanism may be added to the measurement unit 200 to address this source of error (or noise). AWC may ensure that the measured process or reference wafer is concentric with the lift pins.

[0072] The present disclosure also includes method embodiments. The operations in the exemplary wafer warpage measurement method 1770 are Fig.17 One or more operations included in method 1700 are shown and may be performed in the order shown or in other orders. The output of method 1700 may include action 1702, which includes an exemplary use case.

[0073] Exemplary action 1702 may include process monitoring and control. As previously described, a wafer may have positive or negative warp, or include a saddle shape. In a feed-forward process, pre-processed wafer warp values ​​(warp measurements) are fed forward to a processing module to control incoming wafer warp changes. In a feedback process, pre-processed wafer warp values ​​and post-measurement increments may be used in operations including process module quality analysis, offset detection, compensation for process module drift over time, chamber accumulation, and other operations. If a target value or specification for a process wafer is not achieved at a given processing stage, the wafer may be rerouted back to the process module to receive adjusted warp compensation to achieve the desired target or specification. Further warp measurements in a process step may provide feed-forward for process control in a subsequent process step.

[0074] Other actions 1702 may include wafer stress measurements. When performing wafer stress assessment, in addition to known parameters (such as Young's modulus, Poisson's ratio, etc.), three parameters are generally required: wafer thickness, wafer film thickness, and radius of curvature or warpage. Wafer thickness can be measured in any of the following ways. For example, a relative measurement is made at the aligner pin position before and after the wafer is placed, and the height increment between the two positions represents the wafer thickness. Another example includes making a relative measurement between two distance sensors mounted at the same position, one of which is above the wafer and the other is below the wafer. In some examples, a sensor based on near-infrared spectral interferometry can be used for wafer thickness measurement.

[0075] When performing thin film stress assessment, wafer warpage and thickness measurements performed by measurement unit 200 (e.g., as part of integrated wafer measurement system 500) can be combined with optical thickness measurements or mass measurements converted to thickness based on thin film properties. Some examples may include an integrated measurement system 500 where separate optical thickness metrology sensors are mounted at locations on the front side and / or underside of the wafer being measured and film thickness measurements are performed using one or more motion control axes.

[0076] For effective wafer temperature compensation, accurate wafer temperature measurement is generally required. In this regard, non-contact optical sensors generally require film and substrate emissivity calibration to accurately measure wafer temperature. For example, silicon wafers are transparent in IR, and the emissivity value varies depending on the film thickness. Alternatively, the wafer temperature can be measured using a contact-based probe embedded in the aligner pin. One advantage of this arrangement is that accurate wafer temperature measurement is provided without additional particles. The wafer temperature can also be measured using a combination of a contact probe embedded in the aligner pin and a non-contact temperature sensor (e.g., an IR camera), wherein the non-contact sensor (e.g., emissivity calibration) can be calibrated in real time based on the measurement values ​​obtained by the contact probe. Based on the calibration points, a wafer temperature non-uniformity map can be generated across the wafer. Some examples include a thermal stabilization station. A thermal stabilization station can be added to the measurement unit 200 or the system 500, which enables the process wafer or reference wafer to be thermally stabilized before measurement.

[0077] refer to Fig.19 , showing exemplary operations in sampling method 1900 in schematic outline. The exemplary operations may be included or used in conjunction with the wafer warpage, wafer measurement, or wafer alignment methods described herein. The number and location of measurement locations 1902 may be optimized by synchronous rotation, linear stage speed, sensor trigger rate during wafer scanning. For example, the measurement locations 1902 may be adjusted by the distance between points, by the number of points in a defined area, or to a suitable custom combination to minimize measurement errors. The exemplary spiral scan depicted on the left shows a variable distance between measurement locations 1902. The exemplary spiral scan on the right shows a mixture of combinations, including equal distances between measurement locations 1902 in some cases.

[0078] refer to Fig. 20, shows an arrangement or configuration 2000 of a wafer warpage measurement system. Wafer warpage measurement is performed in parallel with robot movement to minimize the impact on wafer throughput in a wafer handling module. In configuration 1, the inner diameter (ID) of the robot end effector (EE) may be larger than the outer diameter (OD) of the aligner pins. Configuration 2 includes optimized movement between the aligner pins and the robot using an existing EE, wherein during pick, the wafer is oriented so that there are no obstructions between the aligner pins and the robot EE.

[0079] In an exemplary measurement mode, the robot pick time is > 3 seconds and the wafer warpage measurement time is < 2 seconds, i.e., the duration is shorter, thereby minimizing the throughput, or at least not affecting the time aspect or interfering with the wafer pick. By synchronizing the motion, the wafer warpage measurement can be done while the robot is in motion and before the robot picks up the wafer.

[0080] In some examples, additional benefits can be provided. For example, in terms of cost, an aligner wafer lift is no longer required. The same robot can be used to place, pick up and lift the wafer. From a throughput perspective, the warpage measurement is performed in parallel with the robot movement, i.e., during the robot movement to pick up the wafer. Since the actions (including raising / lowering) are completed by the same robot, reduced wafer pick and place times can also be provided.

[0081] Some examples of wafer warpage measurement systems thus provide real-time accurate wafer warpage measurement independent of wafer and environmental conditions. Some example systems or methods may also be used or integrated in wafer thickness measurement systems, wafer alignment systems, and wafer stress. The exemplary system may be used as both a wafer aligner and a wafer warpage measurement system. Active compensation for wafer temperature, ambient temperature, and humidity (among other factors) may result in improved and more reliable metrology performance. Warpage measurement may be used for process monitoring and control (feedforward or feedback) of deposition tools. The wafer warpage measurement described herein may be combined with film thickness / quality metrology, and film stress may be measured.

[0082] Although an embodiment has been described with reference to a specific exemplary embodiment, it is apparent that various modifications and changes may be made to these embodiments without departing from the broader scope of the subject matter of the present invention. Therefore, the specification and the accompanying drawings are considered to be illustrative rather than restrictive. The accompanying drawings forming a part thereof show, by way of illustration and not limitation, specific embodiments in which the subject matter may be practiced. The illustrated embodiments are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom so that structural and logical replacements and changes may be made without departing from the scope of the present disclosure. Therefore, this detailed description should not be understood as limiting, and the scope of the various embodiments is limited only by the appended claims and the full scope of the equivalents given by these claims.

[0083] These embodiments of the subject matter of the present invention may be referred to herein individually and / or collectively as the term "the present invention", which is only for convenience and is not intended to voluntarily limit the scope of the present application to any single invention or inventive concept, if more than one is in fact disclosed. Therefore, although specific embodiments have been illustrated and described herein, it should be understood that any arrangement calculated to achieve the same purpose can replace the specific embodiments shown. This disclosure is intended to cover all modifications or variations of the various embodiments. After reading the above description, the combination of the above-mentioned embodiments and other embodiments not specifically described herein will be obvious to those skilled in the art.

Claims

1. A wafer warpage measurement system, comprising: A measuring unit comprising: a wafer support assembly for transmitting rotational motion to a wafer under test supported in the measurement unit; Optical sensors; a calibration standard for calibrating the optical sensor; a linear stage actuator for transmitting a linear motion direction to the optical sensor; a wafer centering sensor for determining the centering of the wafer under test supported in the measurement unit; and A wafer alignment sensor is used to determine the alignment of the wafer under test supported in the measurement unit.

2. The wafer warpage measurement system according to claim 1, wherein: The wafer centering sensor includes an actuator for actively centering the wafer under test supported in the measurement unit.

3. The wafer warpage measurement system of claim 1, wherein the wafer support assembly comprises a wafer alignment chuck. 4 . The wafer warpage measurement system according to claim 1 , further comprising a reference wafer unit. 5 . The wafer warpage measurement system of claim 4 , wherein the reference wafer unit comprises a plurality of slots to accommodate a series of different reference wafers.

6. The wafer warpage measurement system of claim 5, wherein the series of different reference wafers provide a series of measurement control references for the wafer under test supported in the measurement unit.

7. The wafer warpage measurement system of claim 4, further comprising a plurality of measurement units and at least one reference wafer unit.

8. The wafer warpage measurement system of claim 1, wherein the wafer warpage measurement system is integrated with a wafer processing tool.

9. The wafer warpage measurement system of claim 1, wherein the calibration standard includes at least one pre-measured feature or facet that can be scanned by the optical sensor to detect stray wafer warpage measurements over time.

10. The wafer warpage measurement system of claim 9, wherein the scannable features or facets include wedge-shaped silvered diffuse optical flats to serve as a proxy for wafer thickness.

11. The wafer warpage measurement system of claim 1 , wherein the calibration standard comprises a plurality of steps that can be scanned by the optical sensor to detect spurious wafer warpage measurements over time.

12. The wafer warpage measurement system of claim 5, wherein the wafer warpage measurement system further comprises a temperature sensor or a humidity sensor, and wherein the selection of a reference wafer in the series of different reference wafers is based on data derived from the temperature sensor or the humidity sensor.

13. The wafer warpage measurement system of claim 1 further comprising a vibration isolation mechanism or mount.

14. A method of measuring wafer warpage of a wafer in a wafer processing flow including a wafer processing module, the method comprising: A wafer warpage measurement system is integrated with the wafer processing module, wherein the wafer warpage measurement system comprises: A measuring unit comprising: a wafer support assembly for transmitting rotational motion to a wafer under test supported in the measurement unit; Optical sensors; a calibration standard for calibrating the optical sensor; a linear stage actuator for transmitting a linear motion direction to the optical sensor; a wafer centering sensor for determining the centering of the wafer under test supported in the measurement unit; and a wafer alignment sensor for determining an alignment of the wafer under test supported in the measurement unit; extracting a wafer from the wafer processing flow to perform wafer warpage measurement by the wafer warpage measurement system; adjusting parameters of the wafer processing flow based on wafer warpage measurements derived by the wafer warpage measurement system; and The wafer under test is placed back into the wafer processing flow.

Images