Large-size wafer topography measurement device and measurement method

Abstract

The large-size wafer topography measuring device and the measuring method provided by the application set a light source with a wavelength switchable between a first wavelength and a second wavelength, the first wavelength is greater than the second wavelength, and a control unit can control the light source to emit a first wavelength light beam and / or a second wavelength light beam according to the warping amount or warping range of the measured wafer, so as to determine wafer surface topography data and improve the measurement accuracy and yield of the large-size wafer topography.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a large-size wafer topography measuring device and a measuring method. BACKGROUND

[0002] In a semiconductor process, wafer topography detection is a very important link in the semiconductor manufacturing process, and effective detection is directly related to the quality and performance of the wafer.

[0003] At present, the commonly used detection means for large-size wafer topography generally includes two kinds. One is to use a white light interference method, which has the advantages of high detection precision, but has the disadvantages of small field of view, the need for multi-field testing and then result splicing, the existence of splicing error, low yield, and can only perform single-side testing. The other is a detection device using the principle of double-Fizeau interference, which can simultaneously detect the topography of both sides of the wafer, and obtain the topography size information of the entire wafer through one-time testing. However, the principle of Fizeau interferometer determines that the testing precision is inversely proportional to the testing wavelength. The shorter the wavelength used, the higher the vertical precision, but the maximum warping range of the wafer that can be tested at one time is smaller. For wafers with a warping range exceeding the warping range that can be tested at one time, the silicon wafer usually needs to be tilted to adjust the local area to be within the warping range that can be tested by the system. Finally, the results of many tests are spliced to obtain the information of the entire wafer. The larger the warping, the more the number of areas that need to be spliced, and the longer the testing time. SUMMARY

[0004] Therefore, the present application provides a large-size wafer topography measuring device and a measuring method to improve the measurement precision and yield of large-size wafer topography.

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

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

[0007] a light source, the wavelength of the laser beam emitted by the light source can be switched between a first wavelength and a second wavelength, the first wavelength being greater than the second wavelength;

[0008] a first interference system, the first interference system comprising a beam splitter, a collimating mirror, a reference mirror, a relay lens, and a detector; and

[0009] a control unit, the control unit being configured to control the wavelength of the laser beam emitted by the light source to be switched between the first wavelength and the second wavelength; wherein:

[0010] At least part of the laser beams emitted by the light source enters the collimator through the beam splitter, and the parallel light formed after the collimator is incident to the reference mirror, which 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 enters the collimator after being reflected by the surface on one side of the wafer under test. The collimator converges the incident reflected light and transmitted light to form a combined beam, which is converged to the center of the diaphragm and then to the detector by the relay lens. The detector generates an interference fringe image;

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

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

[0014] In some embodiments, the warping amount of the wafer under test is less than or equal to 300 um, and the control unit controls the light source to emit a second wavelength beam.

[0015] In some embodiments, the control unit controls the light source to emit a first wavelength beam to obtain the warping amount of each sub-region of the wafer under test; divides N test regions according to the warping amount, and makes the warping amount of each test region within the test range of the second wavelength beam, N being a natural number greater than or equal to 2; and the control unit switches the light source to emit a second wavelength beam and sequentially measures the topography of the N test regions.

[0016] In some embodiments, the measurement device further comprises a wafer stage, which is fixed with the wafer under test and can drive the wafer under test to deflect. The controller drives the wafer stage to deflect to make the wafer under test reach a preset range of tilt angle, and the warping amount of the test region within the preset range of tilt angle falls within the wavelength test range of the corresponding light beam.

[0017] In some embodiments, the tilt angle of the wafer stage is determined according to the warping amount measured by the first wavelength beam.

[0018] In some embodiments, the measurement device further comprises a second interference system, which has the same optical path structure as the first interference system and is symmetrically arranged on both sides of the wafer under test.

[0019] In some embodiments, the light source is a single light source and forms two laser beams through a beam splitter, and the two laser beams are incident light of the first and second interference systems, respectively.

[0020] In some embodiments, the light source includes two light sources, and the two light sources are incident light of the first and second interference systems, respectively.

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

[0022] The second object of the present application also provides a large-size curved wafer topography measurement method, comprising the following steps:

[0023] At least part of the laser beam emitted by the light source enters the collimating mirror through the beam splitter, and the parallel light formed after the collimating mirror is incident to the reference mirror. The reference mirror reflects and transmits the incident light beam to form reflected light and transmitted light;

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

[0025] According to the interference fringe image obtained by the first detection, the warping amount or warping range of the measured wafer is determined, and the light source is controlled to emit a first wavelength light beam and / or a second wavelength light beam for the second detection according to the warping amount or warping range. The wafer surface topography data is determined according to the interference fringe image generated by the second detection.

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

[0027] In some embodiments, the warping amount of the measured wafer is less than or equal to 300 um, and the light source is controlled to emit a second wavelength light beam.

[0028] In some embodiments, the light source is controlled to emit a first wavelength light beam to obtain the warping amount of each sub-region of the measured wafer. According to the warping amount, N test regions are divided, and the warping amount of each test region is within the test range of the second wavelength light beam. 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 topography of the N test regions is measured in turn.

[0029] In some embodiments, the wafer under test is deflected to reach 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 corresponding light beam.

[0030] In some embodiments, the wafer stage deflection angle is determined according to the warping amount measured by the first wavelength light beam.

[0031] The technical solutions of the present application have the following beneficial effects:

[0032] In a first aspect, the present application provides a large-size wafer topography measurement device and a measurement method. A light source with a wavelength switchable between a first wavelength and a second wavelength is provided, and the first wavelength is greater than the second wavelength. A control unit can switch the light source to emit a first wavelength light beam and / or a second wavelength light beam according to the warping amount or warping range of the wafer under test, to determine the wafer surface topography data, and improve the measurement accuracy and yield of the large-size wafer topography.

[0033] In a second aspect, the present application provides a large-size wafer topography measurement device and a measurement method. When there is no requirement for the large-size wafer topography, the light source can be controlled to emit a first wavelength light beam to improve the measurement yield. When there is a higher nanometer topography accuracy requirement, the light source can be controlled to emit a second wavelength light beam to improve the measurement accuracy. When the warping range of the wafer exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to perform overall topography measurement, and the wafer is divided into test regions according to the warping amount of each region, and the warping amount of each test region is within the test range of the second wavelength light beam. Then, the light source is controlled to emit the second wavelength light beam, and the topography of each test region is measured in sequence, to realize high-precision measurement of the wafer topography. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application or the prior art description. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The structure schematic diagram of the large-size wafer topography measurement device provided by the embodiments of the present application.

[0036] Figure 2 The generation schematic diagram of the interference fringe image provided by the embodiments of the present application.

[0037] Figure 3 The step flowchart of the large-size wafer topography measurement method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0038] The embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0039] In the description of the present application, it is to be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0040] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0041] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples.

[0042] Please refer to Figure 1 The structural schematic diagram of the large-size wafer topography measurement device provided by the embodiments of the present application includes a light source 100, a first interference system 200 and a control unit (not shown in the figure). The technical scheme realized 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 can be understood that the specific structure of the light source 100 is not limited, and can be a single light source or multiple light sources. The light beam emitted by the light source 100 is split or combined to meet the light path requirement, so as to ensure the flexibility of the entire system.

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

[0046] It can be understood that the first interference system 200 is not limited to the optical structure described above, for example, a 1 / 4 wave plate 260 can also be arranged between the beam splitter 210 and the collimator 220, or an aperture 270 is arranged between the relay lens 240 and the detector 250, or other optical components are arranged to fine-tune the light path, as long as the main optical functions are met, which are within the protection scope of the embodiment.

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

[0048] The working mode of the large-size wafer topography measurement device provided in the above embodiment is as follows:

[0049] At least part 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 the collimator 220 is incident to the reference mirror 230. The reference mirror 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 the measured wafer 300 and then enters the collimator 220. The collimator 220 converges the incident reflected light and transmitted light to form a combined beam. The combined beam is converged to the center of the aperture 260 by the relay lens 240 and then converged to the detector 250. The detector 250 generates an interference fringe image.

[0051] The control unit determines the warping amount or warping range of the measured wafer 300 according to the interference fringe image obtained by the first detection, and controls the light source 100 to emit the first wavelength beam and / or the second wavelength beam for the second detection according to the warping amount or warping range. The wafer surface topography data is determined according to the interference fringe image obtained by the second detection. For the warping range, if the second wavelength beam is emitted by the light source for the first detection, the actual warping amount of the large warping wafer may not be obtained, and only the warping range of the wafer can be obtained, i.e., the warping amount is greater than a certain test result.

[0052] The sampling amount of the first detection and the second detection can be the same, so that the wafer surface topography data can be obtained according to the detection result of any one of the first detection and the second detection. In other embodiments, the sampling amount of the first detection and the second detection can be different, and the data acquisition amount of the first detection is less than that of the second detection, so that the warping amount or warping range is quickly obtained in the first detection, and the wafer surface topography data is determined according to the detection result of the second detection.

[0053] Please refer to Figure 2Fig. 1 is a schematic diagram of generating an interference fringe image according to the present embodiment. The present embodiment is based on the Fizeau interference principle. The difference in topography between the measured wafer 300 and the reference mirror 230 will introduce a path difference to the two coherent light beams. After the two light beams are combined, interference will occur, and the interference fringe image will be received on the detector 250. A set of interference images can be obtained by phase shifting with different wavelengths, and the topography data of the measured wafer can be obtained.

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

[0055] In practical applications, in order to not lose the vertical sensitivity and improve the test range of the maximum warpage of the system, the present 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 scene, for example, according to the warpage range or the measurement accuracy, the small warpage measurement mode, the high yield measurement mode, the high precision measurement mode, and the intelligent mode can be divided. The following will be described in detail.

[0056] For a small warpage wafer with a predetermined warpage less than or equal to 300 um, a small warpage mode control unit can be used to control the light source 100 to emit a second wavelength light beam, so as to directly obtain the surface topography of the measured wafer 300, and to realize the fast measurement of the high-precision topography data of the small warpage wafer.

[0057] For a large warpage wafer with a predetermined warpage greater than 300 um, a high yield mode control unit can be used to control the light source 100 to emit a first wavelength light beam, so as to directly obtain the surface topography of the measured wafer 300, and to realize the high yield measurement of the high-precision topography data of the large warpage wafer.

[0058] In a production process with high requirements for wafer surface topography precision, a high precision measurement mode can be used. The control unit controls the light source 100 to emit a first wavelength light beam, so as to obtain the warpage of the measured wafer 300 according to the interference fringe image obtained by the first detection, and then controls the light source 100 to emit a second wavelength light beam. Then, the wafer surface topography data is determined according to the interference fringe image obtained by the second detection, so as to realize the fast measurement of the high-precision topography data of the wafer.

[0059] It should be noted that, in practical 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, so as to realize the fast measurement of the high-precision topography data of the wafer. However, if the overall warpage of the wafer exceeds the test range of the second wavelength light beam, a partitioned form can be used, as follows.

[0060] First, the control unit controls the light source 100 to emit a first wavelength beam to obtain the warping amount of each sub-region of the measured wafer 300; then, according to the warping amount, N test regions are divided, and the warping amount of each test region is within the test range of a second wavelength beam, N is a natural number greater than or equal to 2; the light source is controlled to emit a second wavelength beam, and N test regions are measured in turn to obtain the warping amount of each test region, thereby realizing fast measurement of high-precision topographic data of the wafer. The smaller the test region is divided, the higher the test precision it can achieve.

[0061] Further, in the test using the high-precision measurement mode, after dividing N test regions according to the warping amount, the path is planned, the light source is controlled to emit a second wavelength beam, and the topography of N test regions is measured in turn. By dividing the region and then measuring the path, the high-precision measurement of the wafer is more scientifically realized, and the yield and measurement accuracy are effectively improved.

[0062] It can be understood that in the measurement of the above three measurement modes, the warping amount of the measured wafer within the preset range of the inclination angle falls within the wavelength test range of the corresponding beam, thereby ensuring the accuracy of the measurement.

[0063] Further, in actual application, when no specific mode is specified, the measurement device provided by the embodiment defaults to an 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, or including 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 warping result, and if the maximum warping range that can be tested by the short wave is within the range, the short wave is switched to perform measurement to perform topographic measurement. Similarly, the short wave can be used for topographic measurement first, the control unit controls the light source 100 to emit a second wavelength beam to obtain the warping amount or warping range of the measured wafer 300 according to the interference fringe image obtained by the second detection, and when the warping exceeds the limit of the short wave test, that is, there is a region where the wafer topography cannot be detected, the first wavelength beam is automatically switched to perform topographic measurement, thereby further improving the measurement yield and test accuracy.

[0064] Further, in the measurement of the above four measurement modes, the first wavelength, the second wavelength or the first wavelength and then the second wavelength are not limited, and new wavelengths can be added according to the application needs. For example, in the high-precision measurement mode, the first wavelength can be used to obtain the warping result, and then the light source can be switched to the second wavelength or the third wavelength or more wavelengths according to the warping range. For example, the first wavelength is an infrared wavelength, the second wavelength is a visible wavelength, and the third wavelength is an ultraviolet wavelength. The smaller the wafer warping is, the smaller the wavelength can be used to select the appropriate wavelength according to the wafer warping degree. For another example, the wavelength can be selected according to the test requirements. The higher the test accuracy requirement is, the greater the wavelength can be used. The first wavelength is used to obtain the warping result, and then the warping amount is divided into N test areas, and the warping amount of each test area is within the test range of the wavelength beam.

[0065] It should be noted that in the above four mode test process, the selection of the wavelength should also consider the material and process characteristics of the wafer. For example, when the material of the wafer has low reflectivity to some wavelengths, the wavelength light of the wavelength band cannot be used for testing.

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

[0067] Specifically, in the high-yield measurement mode or the small warping mode, the control unit drives the wafer carrier to deflect to make the wafer to be measured reach a preset range of tilt angle, and the warping amount of the wafer to be measured within the preset range of tilt angle falls within the wavelength test range of the first wavelength or the second wavelength. Then, the light beam of the first wavelength or the second wavelength is used for measurement, and the tilt angle of the wafer to be measured is 0-2 degrees.

[0068] Specifically, in the high-precision measurement mode, the control unit drives the wafer carrier to deflect to make the wafer to be measured reach a preset range of tilt angle, and the warping amount of the wafer to be measured within the preset range of tilt angle falls within the wavelength test range of the first wavelength. Then, the light beam of the first wavelength is used for measurement, and the light beam of the second wavelength is used for topography measurement of the corresponding test area.

[0069] Further, in the high-precision measurement mode, there is another case when the warping amount exceeds the maximum range of the 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 measured reaches the preset tilt angle, so that the warping amount of each test area is within the test range of the second wavelength beam, and the corresponding test area is measured by the second wavelength beam.

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

[0071] For example, during the partition measurement process, the path is planned according to the warping amount. First, N test areas are divided according to the warping 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 measured reach the preset tilt angle, and the tilt angles corresponding to the N test areas are sequentially marked as A1, A2, …, AN; the control unit tilts the first test area of the wafer to the state of the tilt angle A1, and then uses the second wavelength for topography measurement; the control unit tilts the second test area of the wafer to the state of the tilt angle A2, and then uses the second wavelength for topography measurement; all test areas are sequentially completed according to the path planning, thereby completing the overall measurement of the wafer to be measured. N

[0072] It can be understood that in practice, the test path can also be planned according to the needs, and some test areas can be measured, for example, in N test areas, some areas can be tested in the high-yield mode, and some areas can be measured in the high-precision mode; in the high-precision measurement mode, the second wavelength can be directly used for measurement, or the measurement can be performed according to the partition planning path. The specific measurement mode can be referred to the above description, which will not be repeated here.

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

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

[0075] ​It can be understood that when the light paths on both sides of the wafer 300 under test are measured at the same time, the overall topography of the silicon wafer can be obtained according to the coordinate information calibrated by the optical system, including but not limited to warping, twisting, flatness, thickness, edge roll-off, nanotopography and other parameters.

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

[0077] The large-size wafer topography measurement device provided by the above-mentioned embodiments 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 warping amount or warping range of the wafer under test, so as to determine the wafer surface topography data, thereby improving the measurement accuracy and yield of the large-size wafer topography. The first wavelength light beam and the second wavelength light beam can be emitted by two sub-sources with different wavelengths, or can be emitted by a wide-spectrum light source and obtained through filtering and modulation.

[0078] When there is no requirement for the large-size wafer topography, the light source 100 can be controlled to emit the first wavelength light beam, so as to improve the measurement yield; when there is a higher requirement for the nanotopography accuracy, the light source 100 is switched to emit the second wavelength light beam, so as to improve the measurement accuracy; when the warping range of the wafer exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to perform overall topography measurement, and the wafer is divided into test regions according to the warping amount of each region of the wafer, and the warping amount of each test region is within the test range of the second wavelength light beam. After the light source emits the second wavelength light beam, the topography of each test region is measured in turn, so as to realize high-precision measurement of the wafer topography.

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

[0080] Step S110: At least part of the laser beam emitted by the light source enters the collimating mirror through the beam splitter, and the parallel light formed after the collimating mirror is incident to the reference mirror. The reference mirror reflects and transmits the incident light beam to form reflected light and transmitted light.

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

[0082] Step S130: According to the interference fringe image obtained by the first detection, the warping amount or the warping range of the measured wafer is determined, and the light source is controlled to emit the first wavelength light beam and / or the second wavelength light beam according to the warping amount or the warping range, and the wafer surface topography data is determined according to the interference fringe image obtained by the second detection.

[0083] For the warping range, if the second wavelength light beam is emitted by the light source to perform the first detection, the actual warping amount of the wafer with large warping may not be obtained, and only the warping range of the wafer can be obtained, that is, the warping amount is greater than a certain test result.

[0084] The sampling amount of the first detection and the second detection can be the same, so that the wafer surface topography data can be obtained according to the detection result of any one of the first detection and the second detection. In other embodiments, the data acquisition amount of the first detection is less than that of the second detection, so that the warping amount or the warping range is quickly obtained in the first detection, and the wafer surface topography data is determined according to the detection result of the second detection.

[0085] It can be understood that according to the Fizeau interference principle, the difference in topography between the measured wafer 300 and the reference mirror 230 will introduce an optical path difference to the two coherent light beams, and interference will occur after the two light beams are combined. The detector 250 will receive an interference fringe image, and a set of interference images can be obtained by switching the wavelength to phase shift, so that the measured wafer surface topography data can be obtained.

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

[0087] In practical applications, in order not to lose the vertical sensitivity and to improve the test range of the maximum warping of the system, two or more test wavelengths are designed in the embodiment, 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 scene, for example, according to the warping range or the measurement accuracy, the small warping measurement mode, the high yield measurement mode, the high precision measurement mode and the intelligent mode are divided, and the above four modes are described in detail as follows.

[0088] For a small warping wafer with a predetermined warping amount less than or equal to 300 um, the light source 100 can be controlled to emit a second wavelength beam in a small warping mode to directly obtain the surface topography of the wafer 300, thereby realizing fast measurement of high-precision topography data of the small warping wafer.

[0089] For a large warping wafer with a predetermined warping amount greater than 300 um, the light source 100 can be controlled to emit a first wavelength beam in a high yield mode to directly obtain the surface topography of the wafer 300, thereby realizing high yield measurement of high-precision topography data of the large warping wafer.

[0090] In a production process with high precision requirements for wafer surface topography, a high-precision measurement mode can be used to control the light source 100 to emit a first wavelength beam to obtain the warping amount of the wafer 300, and then control the light source 100 to emit a second wavelength beam, and then determine the wafer surface topography data according to the interference fringe image obtained by the second detection, thereby realizing fast measurement of high-precision topography data of the wafer.

[0091] It should be noted that in actual application, the light source 100 can be controlled to emit a first wavelength beam first and then emit a second wavelength beam, thereby realizing fast measurement of high-precision topography data of the wafer, but if the overall warping amount of the wafer exceeds the test range of the second wavelength beam, then a partitioned form can be used, as follows:

[0092] First, the light source 100 is controlled to emit a first wavelength beam to obtain the warping amount of each sub-region of the wafer 300; then N test regions are divided according to the warping amount, and the warping amount of each test region is within the test range of the second wavelength beam, N is a natural number greater than or equal to 2; the light source is controlled to emit a second wavelength beam, and N test regions are measured in turn to obtain the warping amount of each test region, thereby realizing fast measurement of high-precision topography data of the wafer. The smaller the test region is divided, the higher the test precision it can achieve.

[0093] Further, in the high-precision measurement mode, after dividing N test regions according to the warping amount, a path is planned, the light source is controlled to emit a second wavelength beam, and the N test regions are measured in turn. By dividing and measuring the path, the high-precision measurement of the wafer is more scientifically realized, and the yield and measurement precision are effectively improved.

[0094] It can be understood that in the measurement of the above three measurement modes, the warping amount of the wafer within the preset range of the inclination angle falls within the wavelength test range of the corresponding beam, thereby ensuring the accuracy of the measurement.

[0095] Further, in actual applications, the measuring device provided by the embodiment defaults to the intelligent mode when no specific mode is specified, that is, at least two different wavelengths are configured, including the first light beam wavelength or the second light beam wavelength used in the high-yield measurement mode, or the first light beam wavelength and the second wavelength used in the high-precision measurement mode. Meanwhile, the control system can also be configured to perform intelligent mode adjustment, for example, the long wave can be used preferentially for measurement to obtain the warping result, and if the maximum warping range that can be tested by the short wave is within the range, the short wave is switched to perform measurement to perform topography measurement; similarly, the short wave can be used preferentially for topography measurement, and the control unit controls the light source 100 to emit the second wavelength light beam to obtain the warping amount or the warping range of the wafer 300 according to the interference fringe image obtained by the second detection. When the short wave test exceeds the limit, that is, there is a region where the wafer topography cannot be detected, the first wavelength light beam is automatically switched to perform topography measurement, thereby further improving the measurement yield and the test precision.

[0096] Further, in the measurement in the above four measurement modes, the first wavelength, the second wavelength, or the first wavelength and then the second wavelength are not limited to be used, and a new wavelength can also be added according to application requirements. For example, in the high-precision measurement mode, the first wavelength can be used to obtain the warping result, and then the light source can be switched to the second wavelength or the third wavelength or more wavelengths according to the warping range. The smaller the wafer warping is, the smaller the wavelength that can be used is, so that a suitable wavelength can be selected according to the wafer warping degree. For another example, the wavelength can be selected according to the test requirement. The higher the test precision requirement is, the greater the wavelength that can be used is. The first wavelength is used to obtain the warping result, and then N test regions are divided according to the warping amount, and the warping amount of each test region is within the test range of the wavelength light beam.

[0097] It should be noted that, in the test process in the above four modes, the selection of the wavelength should also consider the material and process characteristics of the wafer. For example, when the reflectivity of the wafer material to a certain wavelength is very low, the wavelength light of the wavelength band cannot be used for test.

[0098] In some embodiments, the wafer to be tested can also be driven to be deflected to make the wafer to be tested reach 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 warping mode, the wafer carrier is driven to be deflected to make the wafer to be tested reach 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 first wavelength or the second wavelength, and then the light beam of the first wavelength or the second wavelength is used for measurement. At this time, the tilt angle of the wafer to be tested is 0 degrees to 2 degrees.

[0100] Specifically, in the high-precision measurement mode, the wafer stage is driven to deflect so that the wafer to be measured reaches a preset range of tilt angles, and after the warping amount of the wafer to be measured within the preset range of tilt angles falls within the first wavelength test range, the first wavelength light beam is used for measurement, and then the second wavelength light beam is used for topography measurement of the corresponding test region.

[0101] Further, in the high-precision measurement mode, there is another case that when the warping amount exceeds the maximum range of single test of the second wavelength, the wafer to be measured is controlled to deflect so that the test region of the wafer to be measured reaches a preset tilt angle, so that the warping amount of each test region is within the test range of the second wavelength light beam, and the second wavelength light beam is used for topography measurement of the corresponding test region.

[0102] Specifically, the wafer to be measured is driven to deflect so that the wafer to be measured reaches the tilt angle corresponding to the first test region, and the second wavelength light beam is used for topography measurement; the wafer to be measured is driven to deflect so that the wafer to be measured reaches the tilt angle corresponding to the second test region, and the second wavelength light beam is used for topography measurement; the wafer to be measured is driven to deflect so that the wafer to be measured reaches the tilt angle corresponding to the Nth test region, and the second wavelength light beam is used for topography measurement, thereby realizing partition measurement of the wafer to be measured and effectively improving the detection precision.

[0103] For example, in the partition measurement process, the path is planned according to the warping amount. First, N test regions are divided according to the warping amount and marked as 1, 2, …, N; then the wafer to be measured is driven to deflect so that the N test regions of the wafer to be measured reach a preset tilt angle, and the tilt angles corresponding to the N test regions are sequentially marked as A1, A2, …, AN; the first test region of the wafer to be measured is controlled to tilt to a state with a tilt angle of A1, and then the second wavelength is used for topography measurement; the second test region of the wafer to be measured is controlled to tilt to a state with a tilt angle of A2, and then the second wavelength is used for topography measurement; all test regions are sequentially completed according to the path planning, thereby completing the overall measurement of the wafer to be measured. N

[0104] It can be understood that in practice, the test path can also be planned according to the needs, and some test regions can be measured, for example, in N test regions, some regions can be tested in the high-yield mode, and some regions can be measured in the high-precision mode; in the high-precision measurement mode, the second wavelength can be directly used for measurement, or the measurement can be performed according to the partition planning path. The specific measurement mode can be referred to the above description, which will not be repeated here.

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

[0106] In some embodiments, the above measurement method further includes another same light path to realize measurement of the other side of the wafer, and when the light paths on both sides of the wafer to be measured are simultaneously measured, the overall topography of the wafer can be obtained according to the coordinate information calibrated by the optical system, including but not limited to warping, twisting, flatness, thickness, edge roll-off, nanotopography and other flatness parameters.

[0107] The large-size wafer topography measurement method provided by the above embodiments of the present application sets the light source 100 with the wavelength switchable between the first wavelength and the second wavelength, and the first wavelength is greater than the second wavelength. The first wavelength light beam and / or the second wavelength light beam emitted by the light source can be controlled according to the warping amount or warping range of the wafer to be measured, so as to determine the wafer surface topography data, thereby improving the measurement accuracy and yield of the large-size wafer topography. When there is no requirement for the large-size wafer topography, the first wavelength light beam emitted by the light source 100 can be controlled to improve the measurement yield; when there is a higher nanotopography accuracy requirement, the second wavelength light beam emitted by the light source 100 can be controlled to improve the measurement accuracy; when the warping range of the wafer exceeds the maximum range of a single test of the second wavelength, the first wavelength light beam is controlled to measure the overall topography, and the test area is divided according to the warping amount of each region of the wafer, and the warping amount of each test area is located within the test range of the second wavelength light beam, and then the second wavelength light beam is emitted by the light source to sequentially measure the topography of each test area, so as to realize high-precision measurement of the wafer topography.

[0108] The above is only a preferred embodiment of the present application, and only the technical principle of the present application is specifically described, and these descriptions are only for explaining the principle of the present application, and cannot be explained as a limitation on the protection scope of the present application in any way. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principle of the present application, and other specific embodiments of the present application that can be easily thought of by those skilled in the art without creative labor, should be included in the protection scope of the present application.

Claims

1. A large-size wafer morphology measuring device, characterized in that, include: The light source emits a laser beam whose wavelength can be switched between a first wavelength and a second wavelength, wherein the first wavelength is greater than the second wavelength; The first interferometric system includes a beam splitter, a collimating mirror, a reference mirror, a relay mirror, and a detector. and The control unit is used to control the switching of the wavelength of the laser beam emitted by the light source between a first wavelength and a second wavelength; wherein: At least a portion of the laser beam emitted from the light source enters the collimating lens through the beam splitter, and the parallel light formed after passing through the collimating lens is incident on the reference mirror. The reference mirror reflects and transmits the incident beam to form reflected light and transmitted light. The reflected light is reflected into the collimating lens, and the transmitted light is reflected again by the surface of one side of the wafer being tested and then enters the collimating lens. The collimating lens converges the incident reflected light and transmitted light to form a combined beam. The combined beam is converged to the center of the aperture by 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 warpage amount or warpage range of the wafer under test based on the interference fringe image obtained from the first detection, and controls the light source to emit a first wavelength beam and / or a second wavelength beam for a second detection based on the warpage amount or warpage range, and then determines the wafer surface morphology data based on the interference fringe image obtained from the second detection.

2. The large-size wafer morphology measuring device as described in claim 1, characterized in that, The warpage of the wafer under test is >300µm, and the control unit controls the light source to emit a first wavelength beam.

3. The large-size wafer morphology measuring device as described in claim 1, characterized in that, The warpage of the wafer under test is ≤300µm, and the control unit controls the light source to emit a second wavelength beam.

4. The large-size wafer morphology measuring device as described in claim 1, characterized in that, The control unit controls the light source to emit a first wavelength beam to obtain the warpage amount of each sub-region of the wafer under test; divides the wafer into N test regions according to the warpage amount, and ensures that the warpage amount of each test region is within the test range of the second wavelength 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 beam and sequentially performs morphology measurements on the N test regions.

5. The large-size wafer morphology measuring device as described in claim 4, characterized in that, It also includes a wafer stage, on which the wafer under test is fixed and can drive the wafer under test to deflect. The wafer stage is driven to deflect by a controller so that the wafer under test reaches a preset tilt angle. Within the preset tilt angle, the warpage of the test area of ​​the wafer under test falls within the wavelength test range of the corresponding light beam.

6. The large-size wafer morphology measuring device as described in claim 5, characterized in that, The deflection angle of the wafer stage is determined based on the warpage measured by the first wavelength beam.

7. The large-size wafer morphology measuring device as described in claim 1, characterized in that, 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 both sides of the wafer under test.

8. The large-size wafer morphology measuring device as described in claim 7, characterized in that, The light source is a single light source and is split into two laser beams by a beam splitter, which are respectively used as the incident light for the first interference system and the second interference system.

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

10. The large-size wafer morphology measuring device as described in claim 1, characterized in that, The first wavelength is the infrared wavelength, and the second wavelength is the visible or ultraviolet wavelength.

11. A method for measuring the morphology of large-size wafers, characterized in that, Includes the following steps: At least a portion of the laser beam emitted from the light source enters the collimating mirror through the beam splitter, and the parallel light formed after passing through the collimating mirror is incident on the reference mirror. The reference mirror reflects and transmits the incident beam to form reflected light and transmitted light. The reflected light is reflected into the collimating lens, and the transmitted light is reflected again by the surface of one side of the wafer being tested and then enters the collimating lens. The collimating lens converges the incident reflected light and transmitted light to form a combined beam. The combined beam is converged to the center of the aperture by 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 from the first detection, the warpage amount or warpage range of the wafer under test is determined, and the light source is controlled to emit a first wavelength beam and / or a second wavelength beam for a second detection based on the warpage amount or warpage range. Then, the wafer surface morphology data is determined based on the interference fringe image generated by the second detection.

12. The method for measuring the morphology of large-size wafers as described in claim 11, characterized in that, When the warpage of the wafer under test is greater than 300µm, the light source is controlled to emit a first wavelength beam.

13. The method for measuring the morphology of large-size wafers as described in claim 11, characterized in that, The warpage of the wafer under test is ≤300µm, and the light source is controlled to emit a second wavelength beam.

14. The method for measuring the morphology of large-size wafers as described in claim 11, characterized in that, The light source is controlled to emit a first wavelength beam to obtain the warpage amount of each sub-region of the wafer under test; N test regions are divided according to the warpage amount, and the warpage amount of each test region is within the test range of the second wavelength beam, where N is a natural number greater than or equal to 2; the light source is switched to emit a second wavelength beam, and the morphology of several test regions is measured sequentially.

15. The method for measuring the morphology of large-size wafers as described in claim 12, 13, or 14, characterized in that, The wafer stage is driven to deflect so that the wafer under test reaches a preset tilt angle. The warpage of the wafer under test within the preset tilt angle falls within the wavelength test range of the corresponding light beam.

16. The method for measuring the morphology of large-size wafers as described in claim 15, characterized in that, The deflection angle of the wafer stage is determined based on the warpage measured by the first wavelength beam.

Images