Large-size wafer morphology measuring device and measuring method

Abstract

According to the large-size wafer morphology measurement device and measurement method provided by the invention, the light source whose wavelength can be switched between the first wavelength and the second wavelength is set, the first wavelength is greater than the second wavelength, and the control unit can control the light source to emit the first wavelength light beam and / or the second wavelength light beam according to the warping amount or the warping range of the measured wafer. Therefore, surface morphology data of the wafer is determined, and the measurement precision and yield of the morphology of the large-size wafer are improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a large-size wafer morphology measurement device and a measurement method. Background Art

[0002] In the semiconductor process, wafer morphology inspection is a very important part of the semiconductor manufacturing process, and effective inspection is directly related to the quality and performance of the wafer.

[0003] At present, there are generally two commonly used detection methods for large-size wafer morphology. One is to use the white light interference method, which has the advantage of high detection accuracy and the disadvantage of small field of view. It requires multiple fields of view to test and then splice the results. There is a low splicing error yield, and only single-sided testing can be performed; the other is to use the detection equipment based on the principle of double Fizeau interference, which can simultaneously detect the surface morphology of both sides of the wafer, and obtain the various morphological size information of the entire wafer through a one-time test. However, the principle of Fizeau interferometer determines that the test accuracy is inversely proportional to the test wavelength used. The shorter the wavelength used, the higher the vertical accuracy, but the smaller the maximum warpage range of the wafer that can be tested at one time. For wafers whose warpage range exceeds the warpage range that can be tested at one time, it is usually necessary to tilt the silicon wafer so that the tilt range of the local area is within the warpage range that can be tested by the system. Finally, many test results are spliced ​​to obtain the information of the entire wafer. The larger the warpage, the more areas need to be spliced, and the longer the test time. Summary of the invention

[0004] In view of this, the present invention provides a large-size wafer morphology measurement device and a measurement method to improve the measurement accuracy and yield of the large-size wafer morphology.

[0005] To solve the above problems, this application adopts the following technical solutions:

[0006] One of the purposes of the present application is to provide a large-size wafer topography measurement device, comprising:

[0007] A light source, wherein the wavelength of the laser beam emitted by the light source is switchable between a first wavelength and a second wavelength, and the first wavelength is greater than the second wavelength;

[0008] A first interference system, wherein the first interference system comprises a beam splitter, a collimator, a reference reflector, a relay mirror and a detector; and

[0009] A control unit, the control unit is used to control the wavelength of the laser beam emitted by the light source to switch between a first wavelength and a second wavelength; wherein:

[0010] At least a portion of the laser beam emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after passing through the collimator is incident on the reference reflector, and the reference reflector reflects and transmits the incident light beam to form reflected light and transmitted light;

[0011] The reflected light is reflected into the collimator, and the transmitted light is reflected by the surface of one side of the wafer to be measured and then enters the collimator. The collimator converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture through the beam splitter and then converged to the detector by the relay mirror. The detector generates an interference fringe image.

[0012] The control unit determines the warping amount or warping range of the wafer under test based on the interference fringe image obtained by the first detection, and switches the light source to emit the first wavelength light beam and / or the second wavelength light beam for a second detection based on the warping amount, and then determines the wafer surface morphology data based on the interference fringe image generated by the second detection.

[0013] In some of the embodiments, the warpage of the wafer under test is greater than 300 um, and the control unit controls the light source to emit a light beam of a first wavelength.

[0014] In some embodiments, the warpage of the wafer under test is ≤300 um, and the control unit controls the light source to emit a light beam of a second wavelength.

[0015] In some of the embodiments, the control unit switches the light source to emit a first wavelength light beam to obtain the warping amount of each sub-area of ​​the wafer under test; divides N test areas according to the warping amount, and makes the warping amount of each test area within the test range of the second wavelength light beam, where N is a natural number greater than or equal to 2; the control unit switches the light source to emit a second wavelength light beam, and performs morphology measurement on the N test areas in turn.

[0016] Some of the embodiments further include a wafer stage, on which the wafer to be measured is fixed, and can drive the wafer to be measured to deflect. The wafer stage is driven to deflect by a controller to make the wafer to be measured reach a tilt angle within a preset range. The warping amount of the test area of ​​the wafer to be measured within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0017] In some of the embodiments, the wafer stage deflection angle is determined based on a warpage amount measured by a first wavelength light beam.

[0018] In some of the embodiments, the measuring device further includes a second interference system, which has the same optical path structure as the first interference system and is symmetrically arranged on two sides of the wafer to be measured.

[0019] In some embodiments, the light source is a single light source and is formed into two laser beams through a beam splitter, and the two laser beams are used as incident light for the first interference system and the second interference system respectively.

[0020] In some embodiments, the light source includes two light sources, which serve as incident light for the first interference system and the second interference system respectively.

[0021] In some embodiments, the first wavelength is an infrared wavelength, and the second wavelength is a visible light wavelength or an ultraviolet light wavelength.

[0022] The second object of the present application is to provide a method for measuring the morphology of a large-size curved wafer, comprising the following steps:

[0023] At least a portion of the laser beam emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after the collimator is incident on the reference reflector, and the reference reflector reflects and transmits the incident light beam to form reflected light and transmitted light;

[0024] The reflected light is reflected into the collimator, and the transmitted light is reflected by the surface of one side of the wafer to be measured and then enters the collimator. The collimator converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture through the beam splitter and then converged to the detector by the relay mirror. The detector generates an interference fringe image.

[0025] Based on the interference fringe image obtained by the first detection, the warping amount or warping range of the wafer under test is determined, and based on the warping amount or warping range, the light source is controlled to emit the first wavelength light beam and / or the second wavelength light beam for a second detection, and then the wafer surface morphology data is determined based on the interference fringe image generated by the second detection.

[0026] In some of the embodiments, the warpage of the wafer under test is greater than 300um, and the light source is controlled to emit a light beam of a first wavelength.

[0027] In some of the embodiments, the warpage of the wafer under test is ≤300um, and the light source is controlled to emit a light beam of a second wavelength.

[0028] In some of the embodiments, the light source is controlled to emit a first wavelength light beam to obtain the warpage amount of each sub-area of ​​the wafer under test; N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the second wavelength light beam, where N is a natural number greater than or equal to 2; the light source is switched to emit a second wavelength light beam, and the morphology measurement of the N test areas is performed in turn.

[0029] In some of the embodiments, the wafer to be tested is driven to deflect so that the wafer to be tested reaches a preset range of tilt angles, and the warpage of the wafer to be tested within the preset range of tilt angles falls within a wavelength test range of the corresponding light beam.

[0030] In some of the embodiments, the wafer stage deflection angle is determined based on a warpage amount measured by a first wavelength light beam.

[0031] This application adopts the above technical solution, and its beneficial effects are as follows:

[0032] In the first aspect, the large-size wafer morphology measurement device and measurement method provided by the present application are provided with a light source whose wavelength can be switched between a first wavelength and a second wavelength and the first wavelength is greater than the second wavelength. The control unit can switch the light source to emit the first wavelength light beam and / or the second wavelength light beam according to the warping amount or warping range of the measured wafer to determine the wafer surface morphology data, thereby improving the measurement accuracy and yield of the large-size wafer morphology.

[0033] On the second aspect, the large-size wafer morphology measurement device and measurement method provided by the present application can control the light source to emit a first wavelength light beam to improve the measurement yield when there is no requirement for the large-size wafer morphology; when there is a higher nano-morphology accuracy requirement, the light source is controlled to emit a second wavelength light beam to improve the measurement accuracy; when the wafer warping range exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to measure the overall morphology, and the test area is divided according to the warping amount of each area of ​​the wafer and the warping amount of each test area is within the test range of the second wavelength light beam, and then the light source is controlled to emit the second wavelength light beam to perform morphology measurement on each test area in turn to achieve high-precision measurement of the wafer morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic diagram of the structure of a large-size wafer morphology measurement device provided in an embodiment of the present application.

[0036] Figure 2 It is a schematic diagram of generating the interference fringe image provided in the embodiment of the present application.

[0037] Figure 3 It is a flow chart of the steps of a large-size wafer morphology measurement method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0039] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0042] See also Figure 1 , is a schematic diagram of the structure of a large-size wafer profile measurement device provided in an embodiment of the present application, including a light source 100, a first interference system 200 and a control unit (not shown). The technical solution implemented is described in detail below.

[0043] The light source 100 is used to emit a laser beam. The wavelength of the laser beam emitted by the light source can be switched between a first wavelength and a second wavelength, and the first wavelength is greater than the second wavelength.

[0044] It is understandable that the specific structure of the light source 100 is not limited, and it may be a single light source or multiple light sources. The light beams emitted by the light source 100 are split or combined to meet the light path requirements, thereby ensuring the flexibility of the entire system.

[0045] The first interference system 200 includes a beam splitter 210, a collimator 220, a reference reflector 230, a relay mirror 240, and a detector 250. The detector 250 may be a charge coupled device (CCD).

[0046] It can be understood that the first interference system 200 is not limited to the above-mentioned optical structure. For example, a quarter wave plate 260 may be arranged between the beam splitter 210 and the collimator, or an aperture 270 may be arranged between the relay lens 240 and the detector 250, or other optical components may be arranged to fine-tune the optical path. All of these are within the protection scope of this embodiment as long as the main optical functions are met.

[0047] The control unit is used to control the wavelength of the laser beam emitted by the light source 100 to switch between a first wavelength and a second wavelength.

[0048] The working method of the large-size wafer profile measurement device provided in the above embodiment of the present application is as follows:

[0049] At least a portion of the laser beam emitted by the light source 100 enters the collimator 220 through the beam splitter 210, and the parallel light formed after passing through the collimator 220 is incident on the reference reflector 230, and the reference reflector 230 reflects and transmits the incident light beam to form reflected light and transmitted light.

[0050] The reflected light is reflected into the collimator 220, and the transmitted light is reflected by the surface of one side of the wafer 300 to be measured and then enters the collimator 220. The collimator 220 converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture 260 through the beam splitter 210 and then converged to the detector 250 by the relay lens 240. The detector 250 generates an interference fringe image.

[0051] The control unit determines the warpage amount or warpage range of the wafer 300 under test according to the interference fringe image obtained by the first detection, and controls the light source 100 to emit the first wavelength light beam and / or the second wavelength light beam for the second detection according to the warpage amount or the warpage range, and then determines the surface morphology data of the wafer according to the interference fringe image obtained by the second detection. Among them, for the warpage range, if the second wavelength light beam is emitted by the light source for the first detection, it may be impossible to obtain the actual warpage amount of the wafer with a large warpage, and only the warpage range of the wafer can be obtained, that is, the warpage amount is greater than a certain test result.

[0052] The sampling amount of the first detection and the second detection may be the same, so that the wafer surface morphology data can be obtained according to the detection results of either the first detection or the second detection. In other embodiments, the sampling amount of the first detection and the second detection may be different, and the data collection amount of the first detection is less than the data collection amount of the second detection, so that the warpage amount or warpage range can be quickly obtained during the first detection, and the wafer surface morphology data can be determined according to the detection results of the second detection.

[0053] See also Figure 2, which is a schematic diagram of generating an interference fringe image provided by this embodiment. According to the Fizeau interference principle, the difference in the morphology of the surface of the wafer 300 under test and the reference reflector 230 under test will introduce an optical path difference into the two coherent light beams. After the two light beams are combined, interference will occur, and the detector 250 will receive an interference fringe image. By switching the wavelength and phase shifting to obtain a set of interference patterns, the surface morphology data of the wafer under test can be obtained.

[0054] It can be understood that when the resolution of the detector 250 is fixed, the sensitivity of the wafer vertical topography test is inversely proportional to the wavelength. In addition, under the same detector resolution, the vertical range that can be tested increases with the increase of wavelength, and the maximum warpage of the wafer that can be tested at one time increases with the increase of wavelength.

[0055] In practical applications, in order to increase the test range of the maximum warpage of the system without losing vertical sensitivity, this embodiment is designed to use two or more test wavelengths, the first wavelength is an infrared light wavelength, and the second wavelength is a visible light or ultraviolet light wavelength. According to the actual application scenario, for example, according to the warpage range or measurement accuracy, it can be divided into a small warpage measurement mode, a high-yield measurement mode, a high-precision measurement mode and an intelligent mode. The above four modes are described in detail below.

[0056] For small warp wafers with a predetermined warp amount less than or equal to 300um, a small warp mode control unit can be used to control the light source 100 to emit a second wavelength light beam to directly obtain the surface morphology of the wafer 300 under test, thereby achieving rapid measurement of high-precision morphological data of small warp wafers.

[0057] For a large warped wafer with a predetermined warpage greater than 300um, a high-yield mode control unit can be used to control the light source 100 to emit a first wavelength light beam to directly obtain the surface morphology of the wafer 300 under test, thereby achieving high-yield measurement of high-precision morphological data of large warped wafers.

[0058] In production processes that require higher wafer surface morphology accuracy, a high-precision measurement mode can be used. The control unit controls the light source 100 to emit a first wavelength light beam to obtain the warpage amount of the measured wafer 300 based on the interference fringe image obtained by the first detection, and then controls the light source 100 to emit a second wavelength light beam to determine the wafer surface morphology data based on the interference fringe image obtained by the second detection, thereby achieving rapid measurement of the high-precision morphology data of the wafer.

[0059] It should be noted that: in actual applications, the control unit can first control the light source 100 to emit a first wavelength light beam and then control the light source 100 to emit a second wavelength light beam, thereby realizing rapid measurement of high-precision morphological data of the wafer. However, if the overall warpage of the wafer exceeds the test range of the second wavelength light beam, then the partitioning form can be adopted at this time, as follows:

[0060] First, the control unit controls the light source 100 to emit a light beam of the first wavelength to obtain the warpage amount of each sub-area of ​​the wafer 300 under test; then, N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the second wavelength light beam, where N is a natural number greater than or equal to 2; the light source is controlled to emit a light beam of the second wavelength, and the N test areas are measured in sequence to obtain the warpage amount of each test area, thereby realizing rapid measurement of high-precision morphological data of the wafer. The smaller the test area is divided, the higher the test accuracy that can be achieved.

[0061] Furthermore, in the test using the high-precision measurement mode, after dividing the N test areas according to the warpage, the path is planned, the light source is controlled to emit the second wavelength beam, and the N test areas are measured in turn. By dividing the areas and then measuring the paths, high-precision wafer measurement is achieved more scientifically, effectively improving the yield and measurement accuracy.

[0062] It can be understood that in the measurements of the above three measurement modes, the warpage of the wafer under test within the preset tilt angle range all falls within the wavelength test range of the corresponding light beam, thereby ensuring the accuracy of the measurement.

[0063] Furthermore, in practical applications, when no specific mode is specified, the measurement device provided in this embodiment defaults to the intelligent mode, that is, at least two different wavelengths are configured, including the first beam wavelength or the second beam wavelength used in the high-yield measurement mode, and may also include the first beam wavelength and the second wavelength used in the high-precision measurement mode. At the same time, the control system can also be configured to adjust the intelligent mode, for example, the long wave can be used for measurement first to obtain the warpage result, and if it is within the maximum warpage range that can be tested by the short wave, it is switched to the short wavelength for measurement to perform morphology measurement; similarly, the short wave can be used for morphology measurement first, and the control unit controls the light source 100 to emit the second wavelength beam to obtain the warpage amount or warpage range of the measured wafer 300 according to the interference fringe image obtained by the second detection. When the short wave test shows that the warpage exceeds the limit, that is, there is an area where the wafer morphology cannot be detected, it automatically switches to the first wavelength beam for morphology measurement, further improving the measurement yield and test accuracy.

[0064] Furthermore, in the measurement of the above four measurement modes, it is not limited to the form of using the first wavelength, the second wavelength, or first using the first wavelength and then switching to the second wavelength. New wavelengths can also be added according to application needs. For example, in the high-precision measurement mode, the first wavelength can be used to obtain the warpage result, and then the light source can be controlled to switch to the second wavelength or the third wavelength or switch to more wavelengths according to the warpage range. For example, the first wavelength is an infrared wavelength, the second wavelength is a visible light wavelength, and the third wavelength is an ultraviolet wavelength. The smaller the wafer warpage, the smaller the wavelength can be used, so as to select a suitable wavelength according to the degree of warpage of the wafer. For another example, the wavelength can be selected according to the test requirements. The higher the test accuracy requirement, the larger the wavelength can be used. The first wavelength is used to obtain the warpage result, and then N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the wavelength beam required for the test.

[0065] It should be noted that in the process of using the above four modes of testing, the choice of wavelength should also take into account the material and process characteristics of the wafer. For example, when the reflectivity of the wafer material to certain wavelengths is very low, the wavelength light in this band cannot be used for testing.

[0066] In some embodiments, a wafer stage (not shown) is also included. The wafer stage is fixed with a wafer to be measured and can drive the wafer to be measured to deflect. The wafer stage can be driven to deflect by a controller (not shown) to make the wafer to be measured reach a tilt angle within a preset range, so that the warping amount of the wafer to be measured within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0067] Specifically, in the high-yield measurement mode or the small warp mode, the control unit drives the wafer stage to deflect so that the wafer to be tested reaches a preset range of tilt angles. The warping amount of the wafer to be tested within the preset range of tilt angles falls within the wavelength test range of the first wavelength or the second wavelength, and then the first wavelength or the second wavelength light beam is used for measurement. At this time, the tilt angle of the wafer to be tested is between 0 degrees and 2 degrees.

[0068] Specifically, in the high-precision measurement mode, the control unit drives the wafer stage to deflect so that the wafer to be tested reaches a preset range of tilt angles. After the warping amounts of the wafer to be tested within the preset range of tilt angles fall within the first wavelength test range, a light beam of the first wavelength is used for measurement, and then a light beam at the second wavelength is used to perform morphology measurement on the corresponding test area.

[0069] Furthermore, in the high-precision measurement mode, there is another situation. When the warping amount exceeds the maximum range of a single test of the second wavelength, the control unit drives the wafer stage to deflect so that the test area of ​​the wafer to be tested reaches a preset tilt angle, so that the warping amount of each test area is within the test range of the second wavelength light beam, and the second wavelength light beam is used to perform morphology measurement on the corresponding test area.

[0070] Specifically, the wafer stage is driven to deflect so that the wafer to be tested reaches the tilt angle corresponding to the first test area, and the second wavelength light beam is used for morphology measurement; the wafer stage is driven to deflect so that the wafer to be tested reaches the tilt angle corresponding to the second test area, and the second wavelength light beam is used for morphology measurement; the wafer stage is driven to deflect so that the wafer to be tested reaches the tilt angle corresponding to the Nth test area, and the second wavelength light beam is used for morphology measurement, thereby realizing partitioned measurement of the wafer to be tested and effectively improving the detection accuracy.

[0071] For example, during the partition measurement process, path planning is performed according to the warpage amount. First, N test areas are divided according to the warpage amount and marked as 1, 2...N; then the control unit drives the wafer stage to deflect so that the N test areas of the wafer to be tested reach the preset tilt angle, and the tilt angles corresponding to the N test areas are marked as A1, A2...A in sequence. N The control unit tilts the first test area of ​​the wafer to a tilt angle of A1, and then uses the second wavelength to perform morphology measurement; the control unit tilts the second test area of ​​the wafer to a tilt angle of A2, and then uses the second wavelength to perform morphology measurement; all test areas are completed in sequence according to the path planning, thereby completing the overall measurement of the wafer to be tested.

[0072] It can be understood that in practice, the test path can also be planned according to demand, and some of the test areas can be measured. For example, in N test areas, some areas can be tested in high-throughput mode, while other areas can be measured in high-precision mode. When measuring in high-precision mode, the second wavelength can be directly used for measurement, or the measurement can be performed according to the partitioned planned path. The specific measurement mode can be found in the above description, which will not be repeated here.

[0073] It can be understood that during the test process, the overall wafer result obtained by the long-wave test can be used as the input of the overall wafer tilt angle during the short-wave local test.

[0074] In some embodiments, the measuring device further includes a second interference system 300 . The second interference system 300 has the same optical path structure as the first interference system 200 , and is symmetrically disposed on both sides of the wafer 300 to be measured.

[0075] It can be understood that when the optical paths on both sides of the wafer 300 under test are measured simultaneously, the overall morphological characteristics of the silicon wafer can be obtained based on the coordinate information calibrated by the optical system, including but not limited to parameters such as warpage, distortion, flatness, thickness, edge roll, and nanomorphology.

[0076] In some embodiments, the light source 100 is a single light source and forms two laser beams through a beam splitter, which serve as incident light for the first interference system 200 and the second interference system 400 respectively; or the light source 100 includes two separate sub-light sources, which serve as incident light for the first interference system 200 and the second interference system 400 respectively.

[0077] The large-size wafer morphology measuring device provided in the above embodiment of the present application is provided with a light source 100 whose wavelength can be switched between a first wavelength and a second wavelength and the first wavelength is greater than the second wavelength. The control unit can control the light source to emit a first wavelength light beam and / or a second wavelength light beam according to the warpage amount or warpage range of the measured wafer to determine the wafer surface morphology data, thereby improving the measurement accuracy and yield of the large-size wafer morphology. The first wavelength light beam and the second wavelength light beam can be emitted by two sub-light sources with different wavelengths, or emitted by a wide spectrum light source and obtained by filtering and modulation.

[0078] When there is no requirement for the morphology of large-size wafers, the light source 100 can be controlled to emit a first wavelength light beam to improve the measurement yield; when there is a requirement for higher nano-morphology accuracy, the light source 100 is switched to emit a second wavelength light beam to improve the measurement accuracy; when the wafer warpage range exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to measure the overall morphology, and the test area is divided according to the warpage amount of each area of ​​the wafer so that the warpage amount of each test area is within the test range of the second wavelength light beam, and then the light source is controlled to emit the second wavelength light beam to perform morphology measurement on each test area in turn to achieve high-precision measurement of the wafer morphology.

[0079] The present application also provides a large-size wafer morphology measurement method, which is applied to the large-size wafer morphology measurement device provided in any of the above embodiments, such as Figure 3 As shown, the large-size wafer topography measurement method includes the following steps:

[0080] Step S110: At least a portion of the laser beam emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after the collimator is incident on the reference reflector, which reflects and transmits the incident light beam to form reflected light and transmitted light.

[0081] Step S120: The reflected light is reflected into the collimator, and the transmitted light is reflected by the surface of one side of the wafer to be measured and then enters the collimator. The collimator converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture through the beam splitter and then converged to the detector by the relay mirror. The detector generates an interference fringe image.

[0082] Step S130: Determine the warpage amount or warpage range of the wafer under test based on the interference fringe image obtained by the first detection, and control the light source to emit the first wavelength beam and / or the second wavelength beam based on the warpage amount or the warpage range, and then determine the wafer surface morphology data based on the interference fringe image obtained by the second detection.

[0083] Among them, for the warp range, if the light source emits a second wavelength beam for the first detection, it may be impossible to obtain the actual warp amount of the large warp wafer, and only the warp range of the wafer can be obtained, that is, the warp amount is greater than a certain test result.

[0084] The sampling amount of the first detection and the second detection may be the same, so that the wafer surface morphology data can be obtained according to the detection results of either the first detection or the second detection. In other embodiments, the sampling amount of the first detection and the second detection may be different, and the data collection amount of the first detection is less than the data collection amount of the second detection, so that the warpage amount or warpage range can be quickly obtained during the first detection, and the wafer surface morphology data can be determined according to the detection results of the second detection.

[0085] It can be understood that the above-mentioned embodiments of the present application are based on the Fizeau interference principle. The morphological difference between the surface of the measured wafer 300 and the reference reflector 230 will introduce an optical path difference to the two coherent light beams. The two light beams will interfere after being combined, and the interference fringe image will be received on the detector 250. By switching the wavelength and phase shifting to obtain a set of interference patterns, the surface morphology data of the measured wafer can be obtained.

[0086] It can be understood that when the resolution of the detector 250 is fixed, the sensitivity of the wafer vertical topography test is inversely proportional to the wavelength. In addition, under the same detector resolution, the vertical range that can be tested increases with the increase of wavelength, and the maximum warpage of the wafer that can be tested at one time increases with the increase of wavelength.

[0087] In practical applications, in order to increase the test range of the maximum warpage of the system without losing vertical sensitivity, this embodiment is designed to use two or more test wavelengths, the first wavelength is an infrared light wavelength, and the second wavelength is a visible light or ultraviolet light wavelength. According to the actual application scenario, for example, according to the warpage range or measurement accuracy, it can be divided into a small warpage measurement mode, a high-yield measurement mode, a high-precision measurement mode and an intelligent mode. The above four modes are described in detail below.

[0088] For a small warp wafer with a predetermined warp amount less than or equal to 300um, the small warp mode can be used to control the light source 100 to emit a second wavelength light beam to directly obtain the surface morphology of the wafer 300 under test, thereby achieving rapid measurement of high-precision morphological data of small warp wafers.

[0089] For a large warped wafer with a predetermined warpage greater than 300um, a high-yield mode can be used to control the light source 100 to emit a first wavelength light beam to directly obtain the surface morphology of the wafer 300 under test, thereby achieving high-yield measurement of high-precision morphological data of large warped wafers.

[0090] In production processes that require higher wafer surface morphology accuracy, a high-precision measurement mode can be used to control the light source 100 to emit a first wavelength light beam to obtain the warpage of the wafer 300 under test, and then control the light source 100 to emit a second wavelength light beam. The wafer surface morphology data is then determined based on the interference fringe image obtained by the second detection, thereby achieving rapid measurement of the wafer's high-precision morphology data.

[0091] It should be noted that: in practical applications, the light source 100 can be controlled to emit a first wavelength light beam and then to emit a second wavelength light beam, so as to achieve rapid measurement of high-precision morphological data of the wafer. However, if the overall warpage of the wafer exceeds the test range of the second wavelength light beam, then the partitioning method can be used, as follows:

[0092] First, the light source 100 is controlled to emit a light beam of the first wavelength to obtain the warpage amount of each sub-area of ​​the wafer 300 under test; then, N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the second wavelength light beam, where N is a natural number greater than or equal to 2; the light source is controlled to emit a light beam of the second wavelength, and the N test areas are measured in sequence to obtain the warpage amount of each test area, thereby realizing rapid measurement of high-precision morphological data of the wafer. The smaller the test area is divided, the higher the test accuracy that can be achieved.

[0093] Furthermore, in the test using the high-precision measurement mode, after dividing the N test areas according to the warpage, the path is planned, the light source is controlled to emit the second wavelength beam, and the N test areas are measured in turn. By dividing the areas and then measuring the paths, high-precision wafer measurement is achieved more scientifically, effectively improving the yield and measurement accuracy.

[0094] It can be understood that in the measurements of the above three measurement modes, the warpage of the wafer under test within the preset tilt angle range all falls within the wavelength test range of the corresponding light beam, thereby ensuring the accuracy of the measurement.

[0095] Furthermore, in practical applications, when no specific mode is specified, the measurement device provided in this embodiment defaults to the intelligent mode, that is, at least two different wavelengths are configured, including the first beam wavelength or the second beam wavelength used in the high-yield measurement mode, and may also include the first beam wavelength and the second wavelength used in the high-precision measurement mode. At the same time, the control system can also be configured to adjust the intelligent mode, for example, the long wave can be used for measurement first to obtain the warpage result, and if it is within the maximum warpage range that can be tested by the short wave, it is switched to the short wavelength for measurement to perform morphology measurement; similarly, the short wave can be used for morphology measurement first, and the control unit controls the light source 100 to emit the second wavelength beam to obtain the warpage amount or warpage range of the measured wafer 300 according to the interference fringe image obtained by the second detection. When the short wave test shows that the warpage exceeds the limit, that is, there is an area where the wafer morphology cannot be detected, it automatically switches to the first wavelength beam for morphology measurement, further improving the measurement yield and test accuracy.

[0096] Furthermore, in the measurement of the above four measurement modes, it is not limited to the form of using the first wavelength, the second wavelength, or first using the first wavelength and then switching to the second wavelength. New wavelengths can also be added according to application needs. For example, in the high-precision measurement mode, the first wavelength can be used to obtain the warpage result, and then the light source can be controlled to switch to the second wavelength or the third wavelength or switch to more wavelengths according to the warpage range. The smaller the wafer warpage, the smaller the wavelength can be used to select a suitable wavelength according to the degree of warpage of the wafer. For another example, the wavelength can be selected according to the test requirements. The higher the test accuracy requirement, the larger the wavelength can be used. The first wavelength is used to obtain the warpage result, and then N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the wavelength beam required for the test. .

[0097] It should be noted that in the process of using the above four modes of testing, the choice of wavelength should also take into account the material and process characteristics of the wafer. For example, when the reflectivity of the wafer material to certain wavelengths is very low, the wavelength light in this band cannot be used for testing.

[0098] In some embodiments, the wafer to be tested can be driven to deflect so that the wafer to be tested reaches a preset range of tilt angles, so that the warping amount of the wafer to be tested within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0099] Specifically, in the high-yield measurement mode or the small warp mode, the wafer stage is driven to deflect so that the wafer to be tested reaches a tilt angle within a preset range. The warping amount of the wafer to be tested within the preset range of tilt angles falls within the wavelength test range of the first wavelength or the second wavelength, and then the first wavelength or the second wavelength light beam is used for measurement. At this time, the tilt angle of the wafer to be tested is between 0 degrees and 2 degrees.

[0100] Specifically, in the high-precision measurement mode, the wafer stage is driven to deflect so that the wafer to be tested reaches a tilt angle within a preset range. After the warping amount of the wafer to be tested within the preset range of tilt angles falls within the first wavelength test range, it is measured using a light beam of the first wavelength, and then a light beam at the second wavelength is used to perform morphology measurement on the corresponding test area.

[0101] Furthermore, in the high-precision measurement mode, there is another situation. When the warping amount exceeds the maximum range of a single test of the second wavelength, the wafer to be tested is controlled to be deflected so that the test area of ​​the wafer to be tested reaches a preset tilt angle, so that the warping amount of each test area is within the test range of the second wavelength light beam, and the second wavelength light beam is used to perform morphology measurement on the corresponding test area.

[0102] Specifically, the wafer to be tested is driven to deflect so that the wafer to be tested reaches the tilt angle corresponding to the first test area, and the second wavelength light beam is used to perform morphology measurement; the wafer to be tested is driven and controlled to deflect so that the wafer to be tested reaches the tilt angle corresponding to the second test area, and the second wavelength light beam is used to perform morphology measurement; the wafer to be tested is driven and controlled to deflect so that the wafer to be tested reaches the tilt angle corresponding to the Nth test area, and the second wavelength light beam is used to perform morphology measurement, thereby realizing partitioned measurement of the wafer to be tested and effectively improving the detection accuracy.

[0103] For example, during the partition measurement process, path planning is performed according to the warpage amount. First, N test areas are divided according to the warpage amount and marked as 1, 2...N; then the wafer to be tested is driven and controlled to deflect so that the N test areas of the wafer to be tested reach the preset tilt angle, and the tilt angles corresponding to the N test areas are marked as A1, A2...A in sequence. N ; Control the first test area of ​​the wafer to be tested to tilt to a state with a tilt angle of A1, and then use the second wavelength to perform morphology measurement; control the second test area of ​​the wafer to be tested to tilt to a state with a tilt angle of A2, and then use the second wavelength to perform morphology measurement; complete all test areas in sequence according to the path planning, thereby completing the overall measurement of the wafer to be tested.

[0104] It can be understood that in practice, the test path can also be planned according to demand, and some of the test areas can be measured. For example, in N test areas, some areas can be tested in high-throughput mode, while other areas can be measured in high-precision mode. When measuring in high-precision mode, the second wavelength can be directly used for measurement, or the measurement can be performed according to the partitioned planned path. The specific measurement mode can be found in the above description, which will not be repeated here.

[0105] It can be understood that during the test process, the overall wafer result obtained by the long-wave test can be used as the input of the overall wafer tilt angle during the short-wave local test.

[0106] In some embodiments, the above-mentioned measurement method also includes another identical optical path to realize the measurement of the other side of the wafer. When the optical paths on both sides of the wafer 300 to be measured are measured at the same time, and the overall morphological characteristics of the silicon wafer can be obtained according to the coordinate information calibrated by the optical system, including but not limited to warping, distortion, flatness, thickness, edge roll, nanomorphology and other flatness parameters.

[0107] The large-size wafer morphology measurement method provided by the above embodiment of the present application is provided with a light source 100 whose wavelength can be switched between a first wavelength and a second wavelength and the first wavelength is greater than the second wavelength. The light source can be controlled to emit a first wavelength light beam and / or a second wavelength light beam according to the warpage amount or warpage range of the wafer to be measured, so as to determine the surface morphology data of the wafer, and improve the measurement accuracy and yield of the large-size wafer morphology. When there is no requirement for the morphology of the large-size wafer, the light source 100 can be controlled to emit a first wavelength light beam to improve the measurement yield; when there is a requirement for higher nano-morphology accuracy, the light source 100 can be controlled to emit a second wavelength light beam to improve the measurement accuracy; when the wafer warpage range exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to measure the overall morphology, and the test area is divided according to the warpage amount of each area of ​​the wafer so that the warpage amount of each test area is within the test range of the second wavelength light beam, and then the light source is controlled to emit the second wavelength light beam to perform morphology measurement on each test area in turn, so as to achieve high-precision measurement of the wafer morphology.

[0108] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A large-size wafer profile measurement device, characterized in that: include: A light source, wherein the wavelength of the laser beam emitted by the light source is switchable between a first wavelength and a second wavelength, and the first wavelength is greater than the second wavelength; A first interference system, the first interference system comprising a beam splitter, a collimator, a reference reflector, a relay mirror and a detector; and A control unit, the control unit is used to control the wavelength of the laser beam emitted by the light source to switch between a first wavelength and a second wavelength; wherein: At least a portion of the laser beam emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after passing through the collimator is incident on the reference reflector, and the reference reflector reflects and transmits the incident light beam to form reflected light and transmitted light; The reflected light is reflected into the collimator, and the transmitted light is reflected by the surface of one side of the wafer to be measured and then enters the collimator. The collimator converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture through the beam splitter and then converged to the detector by the relay mirror. The detector generates an interference fringe image. The control unit determines the warping amount or warping range of the wafer under test based on the interference fringe image obtained by the first detection, and controls the light source to emit the first wavelength light beam and / or the second wavelength light beam for a second detection based on the warping amount or warping range, and then determines the wafer surface morphology data based on the interference fringe image obtained by the second detection.

2. The large-size wafer profile measurement device according to claim 1, characterized in that: The warpage amount of the wafer under test is greater than 300um, and the control unit controls the light source to emit a light beam of a first wavelength.

3. The large-size wafer profile measurement device according to claim 1, characterized in that: The warpage amount of the wafer under test is ≤300um, and the control unit controls the light source to emit a light beam of a second wavelength.

4. The large-size wafer profile measurement device according to claim 1, characterized in that: The control unit controls the light source to emit a light beam of a first wavelength to obtain the warpage amount of each sub-area of ​​the wafer under test; divides N test areas according to the warpage amount, and makes the warpage amount of each test area within the test range of the second light beam of a wavelength, where N is a natural number greater than or equal to 2; the control unit switches the light source to emit a light beam of a second wavelength, and performs morphology measurement on the N test areas in turn.

5. The large-size wafer profile measurement device according to claim 2, 3 or 4, characterized in that: It also includes a wafer carrier, which fixes the wafer to be tested and can drive the wafer to be tested to deflect. The wafer carrier is driven to deflect by a controller so that the wafer to be tested reaches a preset range of tilt angles. The warping amount of the test area of ​​the wafer to be tested within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

6. The large-size wafer profile measurement device according to claim 5, characterized in that: The wafer stage deflection angle is determined according to the warpage amount measured by the first wavelength light beam.

7. The large-size wafer profile measurement device according to claim 1, characterized in that: The measuring device further includes a second interference system. The second interference system has the same optical path structure as the first interference system and is symmetrically arranged on two sides of the wafer to be measured.

8. The large-size wafer profile measurement device according to claim 7, characterized in that: The light source is a single light source and forms two laser beams through a beam splitter, and serves as incident light for the first interference system and the second interference system respectively.

9. The large-size wafer profile measurement device according to claim 7, characterized in that: The light source includes two sub-light sources, which serve as incident light for the first interference system and the second interference system respectively.

10. The large-size wafer profile measurement device according to claim 1, characterized in that: The first wavelength is an infrared light wavelength, and the second wavelength is a visible light or an ultraviolet light wavelength.

11. A method for measuring the morphology of a large-size curved wafer, characterized in that: The steps include: At least a portion of the laser beam emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after the collimator is incident on the reference reflector, and the reference reflector reflects and transmits the incident light beam to form reflected light and transmitted light; The reflected light is reflected into the collimator, and the transmitted light is reflected by the surface of one side of the wafer to be measured and then enters the collimator. The collimator converges the incident reflected light and the transmitted light to form a combined light beam. The combined light beam is converged to the center of the aperture through the beam splitter and then converged to the detector by the relay mirror. The detector generates an interference fringe image. Based on the interference fringe image obtained by the first detection, the warping amount or warping range of the wafer under test is determined, and based on the warping amount or warping range, the light source is controlled to emit the first wavelength light beam and / or the second wavelength light beam for a second detection, and then the wafer surface morphology data is determined based on the interference fringe image generated by the second detection.

12. The large-size wafer topography measurement method according to claim 11, characterized in that: When the warpage of the wafer under test is greater than 300um, the light source is controlled to emit a light beam of a first wavelength.

13. The large-size wafer topography measurement method according to claim 11, characterized in that: The warpage amount of the wafer under test is ≤300um, and the light source is controlled to emit a light beam of a second wavelength.

14. The large-size wafer topography measurement method according to claim 11, characterized in that: The light source is controlled to emit a light beam of a first wavelength to obtain the warpage amount of each sub-area of ​​the wafer under test; N test areas are divided according to the warpage amount, and the warpage amount of each test area is within the test range of the second light beam of a wavelength, where N is a natural number greater than or equal to 2; the light source is switched to emit a light beam of a second wavelength, and topography measurements are performed on several test areas in turn.

15. The large-size wafer topography measurement method according to claim 12, 13 or 14, characterized in that: The wafer to be tested is driven to deflect so that the wafer to be tested reaches a preset range of tilt angles, and the warpage of the wafer to be tested within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

16. The large-size wafer topography measurement method according to claim 15, characterized in that: The wafer stage deflection angle is determined according to the warpage amount measured by the first wavelength light beam.

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