Large-size wafer morphology measuring device

Abstract

According to the large-size wafer morphology measuring device provided by the invention, the parallel light beams emitted by the light source are split to form the reference light and the test light, the reference light enters the beam combiner after being reflected by the reference reflector, and the test light enters the beam combiner after being reflected by the surface of one side of the measured wafer; the beam combiner combines the incident reference light and test light and then converges the light to the detector to generate an interference fringe image, and the control unit controls the movement of the tested wafer and / or the reference reflector to change the optical path difference between the tested wafer and the reference reflector so as to determine the surface topography of the wafer. And the test yield and precision of the large warping sheet 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. 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] The commonly used detection method for large-size wafer morphology is to use white light interference method. The advantage is high detection accuracy, but the disadvantage is small field of view. It requires multiple field of view tests and then splicing of the results. There is a low yield of splicing errors. At the same time, only single-sided testing can be performed. Another is to use detection equipment based on the principle of double Fizeau interference, which can simultaneously detect the surface morphology of both sides of the wafer. A one-time test obtains various morphological size information of the entire wafer. However, the principle of Fizeau interferometer determines that the interference cavity length between the test surface and the reference surface must be small, otherwise the system accuracy will be reduced. At the same time, the vertical incidence of the test light results in a smaller maximum warping range of the wafer tested at one time. Summary of the invention

[0004] In view of this, the present invention provides a large-size wafer morphology measurement device 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 and large-warpage wafer morphology measurement device, comprising:

[0007] A light source, the light source is used to emit a parallel light beam;

[0008] A first interference system, the first interference system comprising a beam splitter, a reference reflector, a beam combiner and a detector; and

[0009] A control unit, the control unit is used to control the movement of the wafer under test and control the wafer under test to deflect to a preset range of tilt angles; wherein:

[0010] The parallel light beam emitted by the light source is split by the beam splitter to form reference light and test light;

[0011] The reference light enters the beam combiner after being reflected by the reference reflector, and the test light enters the beam combiner after being reflected by the surface of one side of the wafer under test;

[0012] The beam combiner combines the incident reference light and the test light and then converges them to the detector, and the detector generates an interference fringe image;

[0013] The control unit changes the optical path difference between the wafer under test and the reference reflector by controlling the movement of the wafer under test and / or the reference reflector, and determines the surface morphology of the wafer according to the generated interference fringe image.

[0014] In some of the embodiments, the testing device further comprises a stress-free clamping device for vertically clamping the wafer under test, and the control unit can control the movement of the stress-free clamping device to drive the wafer under test to translate and / or deflect.

[0015] In some of the embodiments, the testing device further comprises a wafer stage, on which the wafer to be tested is fixed, and the control unit can control the movement of the wafer stage to drive the wafer to be tested to translate and / or deflect.

[0016] In some of the embodiments, one of the wafer under test and the reference mirror moves toward or away from the other.

[0017] 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.

[0018] In some of the embodiments, the wafer under test is moved in a horizontal direction in a direction of a line connecting two reference mirrors.

[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 is two light sources, and they serve as incident light for the first interference system and the second interference system respectively.

[0021] In some embodiments, the incident angle of the test light incident on the wafer under test ranges from 20° to 60°.

[0022] In some of the embodiments, the wavelength of the parallel light 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.

[0023] In some embodiments, the first wavelength is an infrared wavelength, and the second wavelength is a visible light or an ultraviolet light wavelength.

[0024] In some of the embodiments, the control unit controls the light source 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 control unit switches the light source to emit a second wavelength light beam, and performs morphology measurement on the N test areas in turn.

[0025] In some of the embodiments, the warpage amount of the test area of ​​the wafer under test within a preset tilt angle range falls within a wavelength test range of the corresponding light beam.

[0026] In some of the embodiments, the wafer stage deflection angle is determined based on a warpage amount measured by a first wavelength light beam.

[0027] This application adopts the above technical solution, and its beneficial effects are as follows:

[0028] The large-size wafer morphology measuring device provided by the present application, the parallel light beam emitted by the light source is split to form reference light and test light, the reference light is reflected by the reference reflector and then enters the beam combiner, the test light is reflected by the surface of one side of the measured wafer and then enters the beam combiner, the beam combiner combines the incident reference light and test light and then converges them to the detector to generate an interference fringe image, the control unit controls the movement of the measured wafer and / or the reference reflector to change the optical path difference between the measured wafer and the reference reflector to determine the wafer surface morphology, thereby improving the test yield and accuracy of large warped wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 A schematic diagram of the structure of a large-size wafer morphology measurement device provided in an embodiment of the present application.

[0031] Figure 2 It is a schematic diagram of generating an interference fringe image provided in an embodiment of the present application.

[0032] Figure 3 It is a schematic diagram of the relationship between the incident angle of light on the wafer under test and the optical path difference provided in an embodiment of the present application.

[0033] Figure 4 It is a step flow chart of the large-size wafer morphology measurement method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The light source 100 is used to emit a parallel light beam.

[0040] 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.

[0041] The first interference system 200 includes a beam splitter 210, a reference reflector 220, a beam combiner 230, and a detector 240. The detector 240 may be a charge coupled device (CCD) or a camera.

[0042] It can be understood that the first interference system 200 is not limited to the above-mentioned optical structure. For example, a reflector 250 may be arranged between the light source 100 and the beam combiner 230, a relay mirror 260 may be arranged between the beam combiner 230 and the detector 240, 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.

[0043] The control unit is used to control the movement of the wafer 400 under test and control the deflection of the wafer under test to a preset range of tilt angles, and the warping amount of the wafer under test within the preset range of tilt angles falls within the wavelength test range of the parallel light beam emitted by the light source.

[0044] The working method of the large-size wafer profile measurement device provided in the above embodiment of the present application is as follows:

[0045] The parallel light beam emitted by the light source 110 is split by the beam splitter 210 to form the reference light and the test light;

[0046] The reference light enters the beam combiner 230 after being reflected by the reference reflector 220 , and the test light enters the beam combiner 230 after being reflected by the surface of one side of the wafer 400 under test;

[0047] The beam combiner 230 combines the incident reference light and the test light and then converges them to the detector 240, and the detector 240 generates an interference fringe image;

[0048] The control unit controls the movement of the wafer 400 under test and / or the reference reflector 220 to change the optical path difference between the wafer 400 under test and the reference reflector 220 , and determines the wafer surface morphology according to the generated interference fringe image.

[0049] See also Figure 2 , which is a schematic diagram of generating an interference fringe image provided by this embodiment. According to the Mach-Zehnder interference principle, the morphological difference between the surface of the wafer 400 under test and the surface of the reference reflector 220 in this embodiment will introduce an optical path difference to the reference optical path and the test optical path. The two light beams will interfere after being combined, and the interference fringe image will be received on the detector 240. The control unit controls the movement of the wafer 400 under test and / or the reference reflector 220 to change the optical path difference between the wafer 400 under test and the reference reflector 220, and the interference pattern will produce a phase shift change, and a set of interference patterns will be obtained, and the surface morphology of the silicon wafer under test can be obtained.

[0050] See also Figure 3 When the incident angle of the light on the wafer 400 under test is θ, there is an angle reflection so that the surface shape of the wafer 400 under test is reflected in the optical path difference, which needs to be multiplied by cosθ. The vertical range that can be tested under the same CCD resolution and wavelength conditions is increased, and the maximum warpage range of the wafer that can be tested at one time is increased.

[0051] For example: When the incident angle θ is 45°, a 300mm silicon wafer is tested using a 7000X7000 camera with a 633nm test wavelength. The maximum wafer value that can be tested without tilting the system is 0.783mm. The maximum wafer range that can be measured by vertical incidence interferometers such as Fizeau or Talman Green, which also use a 633nm wavelength and camera conditions, is 0.554mm. The single warpage test range has increased by 41%. The larger the incident angle, the larger the warpage range that can be tested. Considering the vertical accuracy and spatial layout, the ideal range of the incident angle is between 20° and 60°.

[0052] In this embodiment, the test device further includes a stress-free clamping device 500 vertically clamping the wafer 400 under test, and the control unit can control the stress-free clamping device to move to drive the wafer 400 under test to translate and / or deflect. In this embodiment, the test device further includes a wafer stage (not shown), the wafer stage is fixed with the wafer 400 under test, and the control unit can control the wafer stage to move to drive the wafer 400 under test to translate and / or deflect.

[0053] It can be understood that the control unit controls the movement of the stress-free clamping device and / or the movement of the wafer stage to drive the measured wafer 400 to translate, so that one of the measured wafer 400 and the reference reflector 220 moves toward or away from the other, thereby changing the optical path difference between the measured wafer 400 and the reference reflector 220, and determining the surface morphology of the wafer according to the generated interference fringe image. The measured wafer 400 translates, thereby changing the optical path difference between the measured wafer 400 and the reference reflector 220. It can be understood that in this embodiment, the control unit controls the movement of the stress-free clamping device and / or the movement of the wafer stage, so that the stress-free clamping device and the transmission and the wafer stage have more movement space, expands the placement space of the measured wafer 400, removes the distance limit between the measured wafer 400 and the reference reflector 220, and makes the adjustment range of the optical path difference between the measured wafer 400 and the reference reflector 220 wider, the test range is larger, and the use scenario is more extensive.

[0054] It can be understood that the wafer 400 under test is deflected to control the wafer under test to deflect to a preset range of tilt angles, so that the warping amount of the wafer 400 under test within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam, thereby improving the detection accuracy.

[0055] In this embodiment, the wavelength of the parallel light beam emitted by the light source 110 can be switched between a first wavelength and a second wavelength, and the first wavelength is greater than the second wavelength. For example, the first wavelength is an infrared wavelength, and the second wavelength is a visible light or ultraviolet wavelength.

[0056] It can be understood that 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, and the control unit is used to control the wavelength of the laser beam emitted by the light source to switch between the first wavelength and the second wavelength. The control unit also determines the warpage amount 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 beam and / or the second wavelength beam for the second detection according to the warpage amount, and then determines the surface morphology data of the wafer based on the interference fringe image obtained by the second detection. According to the actual application scenario, for example, it can be divided into a small warpage measurement mode, a high-yield measurement mode, a high-precision measurement mode and an intelligent mode according to the warpage range or measurement accuracy. The above four modes are described in detail below.

[0057] For small warp wafers with a predetermined warp amount less than or equal to 600um, 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 400 under test, thereby achieving rapid measurement of high-precision morphological data of small warp wafers.

[0058] For a large warped wafer with a predetermined warpage greater than 600um, 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 400 under test, thereby achieving high-yield measurement of high-precision morphological data of large warped wafers.

[0059] In the production process that requires 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 400 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 realizing rapid measurement of the high-precision morphology data of the wafer.

[0060] 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:

[0061] First, the control unit controls the light source 100 to emit a first wavelength light beam to obtain the warpage amount of each sub-area of ​​the wafer 400 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 second wavelength light beam, 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 division, the higher the test accuracy that can be achieved.

[0062] 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.

[0063] It can be understood that in the measurements of the above three measurement modes, the warpage of the wafer 400 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.

[0064] 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 400 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.

[0065] 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.

[0066] 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.

[0067] Furthermore, the control unit can control the wafer stage to deflect so that the wafer to be tested reaches a preset range of tilt angles, so that the warpage of the wafer 400 to be tested within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0068] 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 400 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 and 2 degrees.

[0069] 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 400 within the preset range of tilt angles fall within the first wavelength test range, they are 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] It should be noted that the traditional Fizeau interferometer system mostly uses vertical reflection to calculate the optical path difference between the silicon wafer surface and the reference mirror surface. In order to improve the vertical ranging accuracy of the system and reduce the error, a smaller interference cavity length is required, that is, the original optical path difference of the two paths of light in theory. However, the distance of the interference cavity is too small, and the tight structural space is not convenient for the placement of the wafer to be measured, especially for the measurement of large warped wafers, it is necessary to cooperate with the wafer tilt adjustment to perform regional measurement and then splice the measurement results; the control unit of this embodiment controls the deflection of the wafer stage or the stress-free clamping device, so that the wafer stage or the stress-free clamping device has more movement space, expands the placement space of the wafer to be measured, and further increases the warpage measurement range of the wafer to be measured; for the wafer to be measured with the same warpage amount, compared with the vertical incidence interferometer tilt measurement such as Fizeau or Talman Green, the placement space of the wafer to be measured is larger and the activity is more flexible, which effectively reduces the number of times that the wafer to be measured needs to cooperate with the wafer tilt adjustment to perform regional measurement and then splice the measurement results, and the detection accuracy and efficiency are higher.

[0075] In this embodiment, 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 400 to be measured.

[0076] It can be understood that when the optical paths on both sides of the wafer 400 under test are measured simultaneously, and based on the coordinate information calibrated by the optical system, the overall morphological characteristics of the wafer 400 under test can be obtained, including but not limited to parameters such as warpage, distortion, flatness, thickness, edge roll, and nanomorphology.

[0077] It can be understood that the present embodiment uses a two-path reflection structure, and the wafer 400 under test can be moved horizontally in the direction of the line connecting the two reference reflectors, further removing the distance restriction between the wafer 400 under test and the reference reflectors, so that the stress-free clamping device or the wafer carrier has more movement space, further expanding the placement space of the wafer 400 under test, and further improving the detection accuracy and detection efficiency.

[0078] It is understood that the reference optical path and the measured optical path designed in this embodiment can be equal optical path and a specific initial optical path difference can be designed according to system requirements. The methods that can be used include but are not limited to using beam splitters or beam splitters of different thicknesses or materials, adding phase delay elements such as phase plates in the optical path, etc., all of which are within the scope of protection of this application.

[0079] 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 300 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 300 respectively.

[0080] The large-size wafer morphology measuring device provided in the present application, the parallel light beam emitted by the light source is split to form reference light and test light, the reference light is reflected by the reference reflector and then enters the beam combiner, the test light is reflected by the surface of one side of the measured wafer 400 and then enters the beam combiner, the beam combiner combines the incident reference light and test light and then converges them to the detector to generate an interference fringe image, the control unit controls the movement of the measured wafer 400 and / or the reference reflector to change the optical path difference between the measured wafer 400 and the reference reflector, so as to determine the surface morphology of the wafer, thereby improving the test yield and accuracy of large warped wafers.

[0081] See also Figure 4 , which is a flow chart of the steps of the large-size wafer morphology measurement method provided in an embodiment of the present application, is applied to the large-size wafer morphology measurement device provided in any of the above embodiments, and includes the following steps:

[0082] Step S410: the parallel light beam emitted by the light source 110 is split by the beam splitter 210 to form a reference light and a test light;

[0083] Step S420: the reference light is reflected by the reference reflector 220 and then enters the beam combiner 230 , and the test light is reflected by the surface of one side of the wafer 400 under test and then enters the beam combiner 230 ;

[0084] Step S430: The beam combiner 230 combines the incident reference light and the test light and converges them to the detector 240, which generates an interference fringe image; the control unit controls the movement of the wafer 400 under test and / or the reference reflector 220 to change the optical path difference between the wafer 400 under test and the reference reflector 220, and determines the wafer surface morphology based on the generated interference fringe image.

[0085] It can be understood that in this embodiment, based on the Mach-Zehnder interference principle, the morphological difference between the surface of the measured wafer 400 and the surface of the reference reflector 220 will introduce an optical path difference to the reference light path and the test light path. The two light beams will interfere after being combined, and an interference fringe image will be received on the detector 240. The control unit controls the movement of the measured wafer 400 and / or the reference reflector 220 to change the optical path difference between the measured wafer 400 and the reference reflector 220, and the interference pattern produces a phase shift change, and a set of interference patterns will be obtained, and the surface morphology of the measured silicon wafer can be obtained.

[0086] In this embodiment, the control unit can control the stress-free clamping device to move to drive the measured wafer 400 to translate and / or deflect. In this embodiment, the control unit can control the wafer stage and / or the wafer stage to move to drive the measured wafer 400 to translate and / or deflect.

[0087] It can be understood that the control unit controls the movement of the stress-free clamping device and / or the wafer carrier to drive the deflection of the wafer 400 under test, so as to control the deflection of the wafer under test to a preset range of tilt angles, so that the warping amount of the wafer under test 400 within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0088] It can be understood that the control unit controls the movement of the stress-free clamping device and / or the wafer stage to drive the measured wafer 400 to translate, so that one of the measured wafer 400 and the reference reflector 220 moves toward or away from the other, thereby changing the optical path difference between the measured wafer 400 and the reference reflector 220, and determining the surface morphology of the wafer based on the generated interference fringe image.

[0089] It can be understood that in this embodiment, the control unit controls the movement of the stress-free clamping device and / or the wafer carrier, so that the stress-free clamping device and the transmission and wafer carrier have more movement space, the placement space of the wafer 400 under test is expanded, and the distance restriction between the wafer 400 under test and the reference reflector 220 is removed, so that the adjustment range of the optical path difference between the wafer 400 under test and the reference reflector 220 is wider, the test range is larger, and the usage scenarios are also more extensive.

[0090] In this embodiment, the wavelength of the parallel light beam emitted by the light source 110 can be switched between a first wavelength and a second wavelength, and the first wavelength is greater than the second wavelength. For example, the first wavelength is an infrared wavelength, and the second wavelength is a visible light or ultraviolet wavelength.

[0091] It can be understood that in actual 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.

[0092] For small warp wafers with a predetermined warp amount less than or equal to 600um, 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 400 under test, thereby achieving rapid measurement of high-precision morphological data of small warp wafers.

[0093] For a large warped wafer with a predetermined warpage greater than 600um, 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 400 under test, thereby achieving high-yield measurement of high-precision morphological data of large warped wafers.

[0094] In the production process that requires 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 400 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 realizing rapid measurement of the high-precision morphology data of the wafer.

[0095] 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:

[0096] First, the control unit controls the light source 100 to emit a first wavelength light beam to obtain the warpage amount of each sub-area of ​​the wafer 400 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 second wavelength light beam, 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 division, the higher the test accuracy that can be achieved.

[0097] 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.

[0098] It can be understood that in the measurements of the above three measurement modes, the warpage of the wafer 400 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.

[0099] 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 400 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.

[0100] 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.

[0101] 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.

[0102] Furthermore, the control unit can control the wafer stage to deflect so that the wafer to be tested reaches a preset range of tilt angles, so that the warpage of the wafer 400 to be tested within the preset range of tilt angles falls within the wavelength test range of the corresponding light beam.

[0103] 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 400 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 and 2 degrees.

[0104] 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 400 within the preset range of tilt angles fall within the first wavelength test range, they are 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] It should be noted that the traditional Fizeau interferometer system mostly uses vertical reflection to calculate the optical path difference between the silicon wafer surface and the reference mirror surface. In order to improve the vertical ranging accuracy of the system and reduce the error, a smaller interference cavity length is required, that is, the original optical path difference of the two paths of light in theory. However, the distance of the interference cavity is too small, and the tight structural space is not convenient for the placement of the wafer to be measured, especially for the measurement of large warped wafers, it is necessary to cooperate with the wafer tilt adjustment to perform regional measurement and then splice the measurement results; the control unit of this embodiment controls the deflection of the wafer stage or the stress-free clamping device, so that the wafer stage or the stress-free clamping device has more movement space, expands the placement space of the wafer to be measured, and further increases the warpage measurement range of the wafer to be measured; for the wafer to be measured with the same warpage amount, compared with the vertical incidence interferometer tilt measurement such as Fizeau or Talman Green, the placement space of the wafer to be measured is larger and the activity is more flexible, which effectively reduces the number of times that the wafer to be measured needs to cooperate with the wafer tilt adjustment to perform regional measurement and then splice the measurement results, and the detection accuracy and efficiency are higher.

[0110] In this embodiment, 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 400 to be measured.

[0111] It can be understood that when the optical paths on both sides of the wafer 400 under test are measured simultaneously, the overall morphological characteristics of the wafer under test 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.

[0112] It can be understood that the present embodiment uses a two-path reflection structure, and the wafer 400 under test can be moved horizontally in the direction of the line connecting the two reference reflectors, thereby removing the distance restriction between the wafer 400 under test and the reference reflectors, allowing the stress-free clamping device or wafer carrier to have more movement space, further expanding the placement space of the wafer 400 under test, and further improving the detection accuracy and detection efficiency.

[0113] It is understood that the reference optical path and the measured optical path designed in this embodiment can be equal optical path and a specific initial optical path difference can be designed according to system requirements. The methods that can be used include but are not limited to using beam splitters or beam splitters of different thicknesses or materials, adding phase delay elements such as phase plates in the optical path, etc.

[0114] The present application provides a large-size wafer morphology measurement method, in which a parallel light beam emitted by a light source is split to form a reference light and a test light, the reference light is reflected by a reference reflector and then enters a beam combiner, the test light is reflected by a surface of one side of a wafer 400 under test and then enters a beam combiner, the beam combiner combines the incident reference light and the test light and then converges them to a detector to generate an interference fringe image, the control unit controls the movement of the wafer 400 under test and / or the reference reflector to change the optical path difference between the wafer 400 under test and the reference reflector, so as to determine the wafer surface morphology and improve the test yield and accuracy of large warped wafers.

[0115] 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 and large-warp wafer morphology measurement device, characterized in that: include: A light source, the light source is used to emit a parallel light beam; A first interference system, the first interference system comprising a beam splitter, a reference reflector, a beam combiner and a detector; and A control unit, the control unit is used to control the movement of the wafer under test and control the wafer under test to deflect to a preset range of tilt angles; wherein: The parallel light beam emitted by the light source is split by the beam splitter to form reference light and test light; The reference light enters the beam combiner after being reflected by the reference reflector, and the test light enters the beam combiner after being reflected by the surface of one side of the wafer under test; The beam combiner combines the incident reference light and the test light and then converges them to the detector, and the detector generates an interference fringe image; The control unit changes the optical path difference between the wafer under test and the reference reflector by controlling the movement of the wafer under test and / or the reference reflector, and determines the surface morphology of the wafer according to the generated interference fringe image.

2. The large-size and large-warpage wafer morphology measurement device according to claim 1, characterized in that: The testing device further comprises a stress-free clamping device for vertically clamping the wafer under test, and the control unit can control the stress-free clamping device to move so as to drive the wafer under test to translate and / or deflect.

3. The large-size wafer profile measurement device according to claim 1, characterized in that: The testing device further comprises a wafer stage, on which the wafer to be tested is fixed, and the control unit can control the movement of the wafer stage to drive the wafer to be tested to translate and / or deflect.

4. The large-size and large-warpage wafer morphology measurement device according to claim 1, 2 or 3, characterized in that: One of the wafer under test and the reference reflector moves toward or away from the other.

5. The large-size and large-warpage wafer morphology measurement device according to claim 4, 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.

6. The large-size and large-warpage wafer morphology measurement device according to claim 5, characterized in that: The wafer under test is moved in the horizontal direction in the direction of the line connecting the two reference reflectors.

7. The large-size and large-warpage wafer morphology measurement device according to claim 5, 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.

8. The large-size wafer profile measurement device according to claim 5, characterized in that: The light sources are two light sources, and serve as incident light for the first interference system and the second interference system respectively.

9. The large-size and large-warpage wafer morphology measurement device according to claim 1, characterized in that: The incident angle of the test light incident on the wafer under test ranges from 20° to 60°.

10. The large-size and large-warpage wafer morphology measurement device according to claim 1, characterized in that: The control unit controls the wavelength of the parallel light beam emitted by the light source to switch between a first wavelength and a second wavelength, wherein the first wavelength is greater than the second wavelength.

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

12. The large-size wafer profile measurement device according to claim 10, 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.

13. The large-size wafer profile measurement device according to claim 12, characterized in that: The warpage amount of the test area of ​​the wafer under test within the preset tilt angle range falls within the wavelength test range of the corresponding light beam.

14. The large-size wafer profile measurement device according to claim 13, 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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