Wafer surface type measuring equipment and measuring method

Abstract

According to the wafer surface type measurement device and measurement method provided by the invention, the first interferometer obtains the first cavity interference image of the measurement cavity in the cavity state, the first cavity interference image determines the first cavity detection result, the first interferometer and the second interferometer emit light at the same time, and the first cavity detection result is determined by the second cavity interference image. The first interferometer obtains a first interference image in a state in which the first sample is fixed in the measuring cavity, determines a first interference detection result according to the first interference image, and adjusts the position of the first sample in the measuring cavity; when the first interference detection result is detected, a cavity ring area of the first interference detection result is made to be close to a corresponding area of the first cavity detection result, at the moment, the position of the first sample in the measuring cavity is marked as a standard station, and surface type measurement of the first sample is executed at the standard station. According to the method and the device, the crosstalk influence during cavity measurement is eliminated, and the standard station for wafer measurement is determined on the basis, so that the crosstalk influence on the circuit is effectively avoided when wafer measurement is carried out at the standard station, and the measurement precision is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor detection, in particular to a wafer surface type measuring device and a measuring method. BACKGROUND

[0002] As a high-precision wafer surface type measuring device, the Fizeau interferometer needs high system stability and illumination stability in order to meet the repeatability index within the nanometer level. During the detection process of the measuring device, environmental vibration and internal driving vibration will affect the measurement results. In order to reduce the influence of vibration on the measurement of both sides of the wafer, the interference measurement of both sides of the wafer needs to be carried out synchronously, and one of the core challenges is to suppress the signal crosstalk of the opposite interferometer light path.

[0003] In the prior art, optical isolation devices such as mechanical baffles, roller shutters, and polarization isolators are mainly used to block stray light disturbance in order to avoid crosstalk of the measurement signal of the interferometer system. However, in the actual optical element processing and optical-mechanical integration process, optical device extinction quality problems and uncontrollable factors in the adjustment process will inevitably occur, which will lead to the problem that the crosstalk of the opposite path cannot be completely intercepted, thereby affecting the measurement accuracy. SUMMARY

[0004] Therefore, the present application provides a wafer surface type measuring device and a measuring method, which can reduce the crosstalk of the opposite path while ensuring the measurement accuracy.

[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 measuring device, comprising:

[0007] The measuring device comprises a measuring cavity and a first interferometer and a second interferometer located on both sides of the measuring cavity;

[0008] The method comprises:

[0009] The first interferometer acquires a first cavity interference image under the cavity state of the measuring cavity, and determines a first cavity detection result according to the first cavity interference image;

[0010] The first sample is fixed in the measuring cavity, the first interferometer and the second interferometer emit light at the same time, a first interference image under the state of fixing the first sample in the measuring cavity is acquired, a first interference detection result is determined according to the first interference image, and the first interference detection result includes a sample region and a cavity ring region;

[0011] adjusting a position of the first sample in the measurement cavity to make a cavity ring region of the first interference detection result close to a corresponding region of the first cavity detection result, and the position of the first sample in the measurement cavity is recorded as a first standard position;

[0012] performing a surface profile measurement of the first sample at the first standard position.

[0013] In some embodiments, the first cavity detection result is a first cavity profile, and the first interference detection result is a first measurement profile.

[0014] The making of the cavity ring region of the first interference detection result close to the corresponding region of the first cavity detection result is specifically making a cavity ring region of the first measurement profile close to a corresponding region of the first cavity profile.

[0015] In some embodiments, the first sample is adjusted to the first standard position, and the surface profile measurement of all samples is sequentially completed by using a phase shifting technique.

[0016] In some embodiments, the measurement device further comprises:

[0017] The second interferometer acquires a second cavity interference image of the measurement cavity in a cavity state.

[0018] In some embodiments, the measurement device is further configured to perform a thickness distribution measurement of the first sample, and the thickness distribution of the first sample is a difference between a profile of the first cavity interference image and a sum of a profile of the first interference image and a profile of the second interference image.

[0019] In some embodiments, the measurement device further comprises:

[0020] determining a second cavity detection result according to the second cavity interference image;

[0021] acquiring a second interference image of the measurement cavity with the first sample in the first sample state, determining a second interference detection result according to the second interference image, and the second interference detection result comprises a sample region and a cavity ring region;

[0022] adjusting a position of the first sample in the measurement cavity to make a cavity ring region of the second interference detection result close to a corresponding region of the second cavity detection result, and the position of the first sample in the measurement cavity is recorded as a second standard position;

[0023] correcting the first standard position according to the second standard position.

[0024] In some embodiments, a second sample is fixed in the measurement cavity and adjusted to the first standard station, and a surface profile measurement of the second sample is performed at the first standard station.

[0025] In some embodiments, the method further comprises the following steps:

[0026] A topography distribution of a first insensitive region formed when the first sample is fixed at the first standard station is calculated, the first insensitive region being a region formed when the cavity ring region of the first interference detection result approaches the corresponding region of the first cavity detection result;

[0027] A topography distribution of a second insensitive region formed when the second sample is fixed at the first standard station is calculated, and when the second sample is adjusted to the first standard station, the first interferometer and the second interferometer simultaneously acquire a third interference image and a fourth interference image of the measurement cavity with the second sample fixed therein, and a third interference detection result and a fourth interference detection result are determined according to the third interference image and the fourth interference image respectively, the third interference detection result and the fourth interference detection result both including a sample region and a cavity ring region, and the region in the cavity ring region of the third interference detection result and / or the fourth interference detection result corresponding to the position of the first insensitive region being the second insensitive region;

[0028] All or part of the topography difference between the second insensitive region and the first insensitive region is compensated into the first cavity interference image to obtain a new cavity interference image.

[0029] In some embodiments, a change amount is obtained according to the topography difference between the second insensitive region and the first insensitive region, a change coefficient is obtained by least square fitting the distribution of the change amount, and the change coefficient is compensated into the first cavity interference image to obtain the new cavity interference image.

[0030] In some embodiments, the measurement device is further configured to perform a thickness distribution measurement of the second sample, the thickness distribution of the second sample being a difference between a surface profile of the new cavity interference image and a sum of a surface profile of the third interference image and a surface profile of the fourth interference image.

[0031] In some embodiments, the sample is adjusted to the first standard station, and a surface profile measurement of all samples is sequentially completed using a phase shifting technique.

[0032] The second object of the present application also provides a wafer surface profile measurement device, comprising:

[0033] a measurement cavity in which a first sample is fixed;

[0034] The first interferometer and the second interferometer are located on both sides of the measuring cavity; wherein:

[0035] The first interferometer is used to obtain a first cavity interference image in a cavity state of the measuring cavity, and the first cavity interference image is used to determine a first cavity detection result;

[0036] The first interferometer and the second interferometer simultaneously emit light to obtain a first interference image of the first sample in the first sample state in the measuring cavity, and a first interference detection result is determined according to the first interference image, wherein the first interference detection result includes a sample region and a cavity ring region;

[0037] The position of the first sample in the measuring cavity is adjusted so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result, and the position of the first sample in the measuring cavity is recorded as a first standard station at this time;

[0038] The surface profile measurement of the first sample is performed at the first standard station.

[0039] In some embodiments, an illumination unit and a control unit are further included, the illumination unit is used to output first polarized light and second polarized light, the first interferometer includes a first interference module, the second interferometer includes a second interference module, and the control unit is used to control the illumination unit to output the first polarized light and / or the second polarized light and control the first interference module and / or the second interference module to work;

[0040] The illumination unit outputs the first polarized light, the first polarized light is incident to the upper surface of the measuring cavity in a cavity state through the first interference module, the light beam reflected by the upper surface of the measuring cavity is imaged through the first interference module to form a first cavity interference image, and the first cavity interference image determines a first cavity detection result; or the illumination unit outputs the second polarized light, the second polarized light is incident to the lower surface of the measuring cavity in a cavity state through the second interference module, the light beam reflected by the lower surface of the measuring cavity is imaged through the second interference module to form a second cavity interference image, and the second cavity interference image determines a second cavity detection result;

[0041] The illumination unit simultaneously outputs the first polarized light and the second polarized light, the first polarized light is incident to the upper surface of the measurement cavity with the first sample state fixed through the first interference module, the light beam reflected by the upper surface of the measurement cavity is imaged through the first interference module to form a first interference image, the first interference image determines a first interference detection result, and the first interference detection result includes a sample region and a cavity ring region; or the second polarized light is incident to the lower surface of the measurement cavity with the first sample state fixed through the second interference module, the light beam reflected by the lower surface of the measurement cavity is imaged through the second interference module to form a second interference image, the second interference image determines a second interference detection result, and the second interference detection result includes a sample region and a cavity ring region.

[0042] The position of the first sample in the measurement cavity is adjusted so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result, at this time the position of the first sample in the measurement cavity is recorded as a first standard station, and the surface profile measurement of the first sample is performed at the first standard station; or the position of the first sample in the measurement cavity is adjusted so that the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result, at this time the position of the first sample in the measurement cavity is recorded as a second standard station, and the surface profile measurement of the first sample is performed at the second standard station.

[0043] In some embodiments, the first interferometer further includes a first PBS beam splitter, a first quarter wave plate, a first relay lens and a first detector, and the first interference module includes a first collimating mirror and a first reference mirror; the second Fizeau interferometer further includes a second PBS beam splitter, a second quarter wave plate, a second relay lens and a second detector, and the second interference module includes a second collimating mirror and a second reference mirror.

[0044] The first polarized light is reflected by the first PBS beam splitter, enters the first quarter wave plate, and then is incident to the upper surface of the measurement cavity in the cavity state through the first collimating mirror and the first reference mirror in sequence, the light beam reflected by the upper surface of the measurement cavity enters the first PBS beam splitter through the first reference mirror, the first collimating mirror and the first quarter wave plate in sequence, is transmitted by the first PBS beam splitter, and is imaged on the first detector by the first relay lens to form the cavity interference image;

[0045] The first polarized light is reflected by the first PBS beam splitter prism and enters the first quarter-wave plate, and then is incident on the upper surface of the measurement cavity in which the first sample is fixed, via the first collimating mirror and the first reference mirror in sequence, and is reflected by the upper surface of the measurement cavity, and then enters the first PBS beam splitter prism via the first reference mirror, the first collimating mirror and the first quarter-wave plate in sequence, and is transmitted by the first PBS beam splitter prism and then imaged on the first detector by the first relay lens to form the first interference image.

[0046] The second polarized light is reflected by the second PBS beam splitter prism and enters the second quarter-wave plate, and then is incident on the lower surface of the measurement cavity in which the first sample is fixed, via the second collimating mirror and the second reference mirror in sequence, and is reflected by the lower surface of the measurement cavity, and then enters the second PBS beam splitter prism via the second reference mirror, the second collimating mirror and the second quarter-wave plate in sequence, and is transmitted by the second PBS beam splitter prism and then imaged on the second detector by the second relay lens to form the second interference image.

[0047] In some embodiments, the method further comprises adjusting the position of the first sample in the measurement cavity to make the cavity ring region of the first interference detection result close to the corresponding region of the first cavity detection result or to make the cavity ring region of the second interference detection result close to the corresponding region of the second cavity detection result.

[0048] The technical scheme disclosed in the present application has the following beneficial effects:

[0049] The wafer surface measurement device and the measurement method provided by the present application have the following advantages: the first interferometer acquires a cavity interference image in a cavity state of the measurement cavity, a first cavity detection result is determined based on the first cavity interference image, the first interferometer and the second interferometer emit light at the same time, a first interference image is acquired by the first interferometer in a state in which the first sample is fixed in the measurement cavity, a first interference detection result is determined based on the first interference image, the position of the first sample in the measurement cavity is adjusted to make the cavity ring region of the first interference detection result close to the corresponding region of the first cavity detection result, at this time, the position of the first sample in the measurement cavity is recorded as a standard station, and surface measurement of the first sample is performed at the standard station, the present application eliminates the crosstalk effect during cavity measurement through specific synchronization control during cavity acquisition, and determines a standard station for wafer measurement on this basis, so that the influence of crosstalk on the wafer measurement at the standard station is effectively avoided, and the measurement accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments of the present application or the prior art will be briefly introduced. Obviously, the drawings described below only represent some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0051] Figure 1 The step flow chart of the measurement method provided for Embodiment 1 of the present application.

[0052] Figure 2 The first interferometer provided for Embodiment 1 of the present application acquires the cavity interference image under the cavity state of the measurement cavity and the first interference image under the state that the first sample is fixed in the measurement cavity.

[0053] Figure 3 The structural schematic diagram of the measurement device provided for Embodiment 2 of the present application.

[0054] Figure 4 The optical path structural schematic diagram of the measurement device provided for Embodiment 2 of the present application.

[0055] Figure 5 The acquisition control principle diagram of the phase shift under the cavity state provided for Embodiment 2 of the present application. DETAILED DESCRIPTION

[0056] The embodiments of the present application will be described in detail below, and examples of the embodiments 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.

[0057] In the description of the present application, it should 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 devices or elements indicated 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.

[0058] 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 indicated. 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.

[0059] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments.

[0060] The sample provided by the present application can include a wafer, and can also be other films / plates / substrates with similar properties. For the convenience of description, the technical scheme provided by the present application will be described in detail below with the wafer as the measured object.

[0061] Embodiment 1

[0062] Please refer to Figure 1 The wafer surface shape measurement method provided by the present embodiment has a step flow chart, and the wafer surface shape measurement method provided by the present embodiment is based on a measurement device including a measurement cavity and first and second interferometers on both sides of the measurement cavity. The measurement method specifically includes the following steps S10 to S40, and the implementation mode of each step will be described in detail below.

[0063] Step S10: The first interferometer acquires a cavity interference image in a cavity state of the measurement cavity, and determines a first cavity detection result according to the first cavity interference image.

[0064] It should be noted that the cavity state of the measurement cavity refers to a reference state when the interferometer optical path does not place the measured sample. When the measured sample is not placed, the light beam is irradiated to the bottom of the measurement cavity, i.e., a cavity region is formed, and an ideal interference cavity is formed between the interferometer reference surface and the bottom surface. This state is used to calibrate the system inherent error, which is a key link to achieve nanometer level precision. The cavity state is a "zero reference" of the interference measurement, and its precision directly determines the system measurement capability. The bottom of the measurement cavity is the reference mirror or the fixed structure of the reference mirror of the opposite interferometer.

[0065] Please refer to Figure 2 (b) is the first cavity interference image acquired by the first interferometer in the cavity state of the measurement cavity provided by the present embodiment, wherein the cavity region is the cavity region shown by 401.

[0066] It can be understood that when the measured sample is not placed, only the reference mirror surface and the bottom of the measurement cavity exist in the interferometer optical path. At this time, the reference surface and the cavity bottom form an ideal parallel or confocal interference cavity, and the first cavity interference image is generated, and the first cavity detection result is obtained after calculation.

[0067] In the present embodiment, when the cavity is measured, the first interferometer acquires the cavity interference image of the measurement cavity in the cavity state, and at this time the second interferometer is controlled to be in the closed state, so as to ensure that the light beam in the optical path of the second interferometer will not enter the opposite interference optical path, so as to avoid the cross talk of the opposite.

[0068] Step S20: fixing the first sample in the measurement cavity, the first interferometer and the second interferometer emitting light at the same time, the first interferometer acquiring a first interference image of the first sample fixed in the measurement cavity, the first interference image determining a first interference detection result, the first interference detection result containing a sample region and a cavity ring region.

[0069] It can be understood that when the wafer is measured, the area blocked by the wafer body will not be affected by the on-target crosstalk due to the presence of the wafer in the measurement cavity. At the same time, in order to eliminate the influence of vibration on wafer measurement, the two interferometers must be synchronized.

[0070] It can be understood that when the sample is measured by the double interferometer, the sample needs to be fixed in the measurement cavity, the first interferometer and the second interferometer emitting light at the same time, the first interferometer acquiring a first interference image of the first sample fixed in the measurement cavity. During the above interference image acquisition process, part of the light beam irradiates the sample surface, and after reflection, it interferes with the reference light, thereby forming the interference of the sample region. Another part of the light beam irradiates the bottom of the measurement cavity (i.e. the area not covered by the sample, that is, the cavity ring region). By analyzing and extracting the interference fringe information of the first interference image, the first interference detection result is determined, and the first interference detection result contains the sample region and the cavity ring region.

[0071] Specifically, the interference fringes formed by the reference light and the sample reflection light are the sample region, which carries the sample surface topography information; since the interference fringes of the reference light and the measurement cavity bottom reflection light are the cavity interference image, that is, the cavity ring region, which is characterized as an area not covered by the sample, and in an ideal case, its interference fringes should be consistent with the corresponding area in the cavity interference image. Please refer to Figure 2 Wherein (a) is the first interference image acquired by the first interferometer provided in this embodiment under the condition that the first sample is fixed in the measurement cavity, wherein 403 represents the sample (wafer) region, and 401 represents the cavity region.

[0072] Step S30: adjusting the position of the first sample in the measurement cavity so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result, which is the region 405 not sensitive to crosstalk. At this time, the position of the first sample in the measurement cavity is recorded as the first standard station 404.

[0073] It can be understood that by adjusting the position of the first sample in the measurement cavity (which can include translation, inclination or rotation), the interference fringes of the cavity ring region in the sample measurement image are close to the corresponding region of the cavity interference image (i.e. the phase difference is close to zero). When adjusted to the above state, the position of the sample is defined as the standard station, and the reference position of the sample relative to the measurement cavity is accurately determined, and the subsequent measurement can be taken as the reference.

[0074] In the embodiment, the first cavity detection result is a first cavity surface shape, and the first interference detection result is a first measurement surface shape; and the approaching of the cavity ring region of the first interference detection result to the corresponding region of the first cavity detection result specifically refers to the approaching of the cavity ring region of the first measurement surface shape to the corresponding region of the first cavity surface shape.

[0075] It can be understood that the first cavity detection result is a background surface shape of the measurement cavity without a sample (pure reference light and cavity bottom reflected light interference), denoted as a first cavity surface shape; and the first interference detection result is an interference result of the measurement cavity with a sample (sample region + cavity ring region), the overall topography of which is denoted as a first measurement surface shape. The region in the cavity ring region that is not covered by the sample (ring region) is denoted as a cavity ring region.

[0076] In the embodiment, a first reference surface shape is obtained by scanning the measurement cavity of the first interferometer without a sample, at this time the entire field of view is "cavity" without a sample region, and the result reflects the inherent error of the measurement system (such as reference mirror unevenness, optical distortion, etc.).

[0077] In the embodiment, a first interference image is collected by fixing the first sample using the first interferometer, and a first measurement surface shape is obtained by solving, which includes two sub-regions: the sample region contains sample topography information, and the cavity ring region should only contain system error; the cavity ring region data is segmented from the first measurement surface shape, the same position data is extracted from the first cavity surface shape, and a conventional fitting method is used to approach the cavity ring region of the first measurement surface shape to the corresponding region of the first cavity surface shape. Please refer to Figure 2 , the cavity ring region of the first measurement surface shape is approached to the corresponding region of the first cavity surface shape by adjusting the position of the first sample in the measurement cavity, that is, Figure 2 the region shown in the region 405 which is insensitive to crosstalk, at this time the position of the first sample in the measurement cavity is denoted as a standard station, corresponding to Figure 2 the region of the first standard station 404 in

[0078] It should be noted that the form (or distribution) of the interference fringes directly represents the optical path difference distribution of the sample surface, the surface topography (height change pattern) of the regions with similar fringe deformation patterns must also be similar, therefore, similar interference fringe forms represent similar surface height change distributions, that is, similar relative topography characteristics. Therefore, the embodiment is not limited to comparing the first interference detection result to approach the cavity ring region of the first measurement surface shape to the corresponding region of the first cavity surface shape, but also can compare the first interference image with the first cavity surface shape to approach the corresponding regions.

[0079] Step S40: performing surface profile measurement of the first sample at the standard station.

[0080] The wafer surface type measurement method provided by the above embodiment of the present application eliminates the crosstalk influence during cavity measurement through specific synchronization control during cavity acquisition, and determines the standard station for wafer measurement on this basis, so that the influence of on-way crosstalk is effectively avoided during wafer measurement at the standard station, and the measurement precision is improved.

[0081] It should be noted that, in actual semiconductor production and detection process, cavity measurement is generally performed once before the first wafer of mass production or one-day mass production is tested for the reason of yield, and cavity measurement is not performed separately before each wafer is tested. In the present embodiment, during the first wafer measurement, the position of the wafer in the cavity is adjusted through the horizontal and vertical adjustment mechanisms, so that the area of the first interference image changes, the cavity ring area is processed through an algorithm, the data acquired under the cavity condition is compared with the result calculated by using the same cavity ring position, and a substantially consistent ring area of the whole cavity ring area or part of the cavity ring area is selected, such as Figure 2 as shown in 405 in the middle, the position may be the whole ring area or part of the whole ring area, and the position of the first wafer in the measurement cavity under this condition is the first standard station 404, and then during the measurement of each subsequent wafer, the measurement station of each wafer is ensured to be consistent with the position of the first standard station 404.

[0082] Similar to the foregoing description, the first interferometer and the second interferometer simultaneously emit light, the second interferometer acquires a second interference image of the first sample under the measurement cavity, and during the acquisition of the above interference image, part of the light beam irradiates to the other surface of the sample, and after reflection, interferes with the reference light, thereby forming the interference of the sample area, and the other part of the light beam irradiates to the bottom of the measurement cavity (that is, the area not covered by the sample, that is, the cavity ring area), and the second interference detection result is determined by analyzing and extracting the interference fringe information of the second interference image, and the second interference detection result includes the sample area and the cavity ring area.

[0083] Further, the measurement device used in the above measurement method is also used to perform the measurement of the thickness distribution of the first sample, and the thickness distribution of the first sample is the difference between the surface shape of the first cavity interference image and the sum of the surface shape of the first interference image and the surface shape of the second interference image.

[0084] It can be understood that the cavity data used when calculating the thickness distribution of the first sample wafer is also selected according to the effective area of the first standard station 404 of the wafer station, and further ensures that there is no influence of on-way crosstalk in the processing of the result.

[0085] In the present embodiment, the following step is further included: the second interferometer acquires a second cavity interference image under the cavity state of the measurement cavity.

[0086] Further comprising the following steps:

[0087] Determine a second cavity detection result according to the second cavity interference image.

[0088] In this embodiment, when measuring the cavity, the second interferometer acquires the cavity interference image of the measuring cavity in the cavity state, and at this time the first interferometer is controlled to be in the closed state to ensure that the light beam in the light path of the first interferometer does not enter the interference light path, thereby avoiding cross-talk.

[0089] Acquire the second interference image of the measuring cavity with the first sample state fixed therein, and determine a second interference detection result according to the second interference image, wherein the second interference detection result contains the sample region and the cavity ring region.

[0090] Similarly, when measuring the sample by using the double interferometer, the sample needs to be fixed in the measuring cavity, and the first interferometer and the second interferometer emit light at the same time. The second interferometer acquires the second interference image of the measuring cavity in the first sample state. During the acquisition of the above interference image, part of the light beam irradiates the sample surface, and after reflection, it interferes with the reference light, thereby forming the interference of the sample region. Another part of the light beam irradiates the bottom of the measuring cavity (i.e., the region not covered by the sample, that is, the cavity ring region). The second interference detection result is determined by analyzing and extracting the interference fringe information of the second interference image, and the second interference detection result contains the sample region and the cavity ring region.

[0091] Adjust the position of the first sample in the measuring cavity so that the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result. At this time, the position of the first sample in the measuring cavity is recorded as the second standard station.

[0092] It can be understood that by adjusting the position of the first sample in the measuring cavity (which can include translation, tilting or rotation), the interference fringes of the cavity ring region in the sample measurement image are close to (i.e., the phase difference is close to zero) the corresponding region of the cavity interference image. This means that the position adjustment of the sample compensates for the tilt or defocus introduced by the sample, so that the optical path difference in the cavity ring region is the same as that in the cavity state.

[0093] Correct the first standard station according to the second standard station.

[0094] It can be understood that the first standard station may be determined under different environmental conditions, or due to system drift, the first standard station may not be accurate enough. After obtaining the second standard station, it is used to correct the previously determined first standard station to improve the accuracy of subsequent measurement.

[0095] For example, the first standard position can be updated to the second standard position (i.e., the old position is replaced by the new position), so that the subsequent measurements use this updated position. Alternatively, if such corrections are made multiple times, an average or weighted average can be taken to improve long-term stability.

[0096] It can be understood that, by twice sample-free measurement (to obtain two cavity surface shapes) and twice sample measurement (to obtain two measured surface shapes), the sample position is adjusted during the second measurement to match the cavity ring region, so that a more accurate sample placement position (second standard position) is obtained, and it is used to correct the previous standard position, which improves the accuracy of the sample surface shape measurement.

[0097] In this embodiment, the method further includes the following steps: fixing a second sample in the measurement cavity and adjusting it to the standard position, and performing a surface shape measurement of the second sample at the standard position.

[0098] It can be understood that, when measuring a wafer, a specific first standard position 404 needs to be specified, and the first standard position 404 is confirmed when measuring the first wafer or the first wafer, so that the measurement calculation data of the cavity ring monitoring data and the cavity measurement condition of the cavity ring position are consistent during the wafer measurement process. Then, before the subsequent multiple wafer measurement processes, each wafer needs to be measured in the first standard position 404 region, so that the actual use data region of the cavity data and the wafer measurement region remain consistent, thereby avoiding crosstalk.

[0099] It should be noted that: considering that the interval of cavity calibration will be relatively long, calibration before each wafer measurement will affect the test efficiency, therefore, usually after calibration once, multiple wafers are measured. There can be a situation of cavity tilt change between wafer and wafer measurement, so that the cavity interference image deviates. To avoid this situation, the technical solution is further optimized.

[0100] In this embodiment, the wafer surface shape measurement method provided by the present application further includes the following steps:

[0101] Step S50: Calculate the topographic distribution of the first insensitive region formed when the first sample is fixed at the first standard position, and the first insensitive region is the region formed when the cavity ring region of the first interference detection result and the corresponding region of the first cavity detection result are close.

[0102] Please refer to Figure 2In the first wafer measurement, the position of the wafer in the cavity is adjusted by the horizontal and vertical adjustment mechanisms, so that the first interference detection result is formed when the cavity ring region is close to the corresponding region of the first cavity detection result, and is compared with the result calculated by the same cavity ring position of the data collected under the cavity condition, and the substantially consistent ring region of the entire cavity ring region or part of the cavity ring region is selected, that is, the region 405 position not sensitive to crosstalk is selected, and is recorded as the first insensitive region. The first insensitive region can be the entire ring region, or part of the entire ring region.

[0103] Step S60: Calculate the topography distribution of the second insensitive region formed when the second sample is fixed in the first standard station. When the second sample is adjusted to the first standard station, the first interferometer and the second interferometer simultaneously acquire the third interference image and the fourth interference image in the measurement cavity with the second sample fixed therein. The third interference image and the fourth interference image are used to determine the third interference detection result and the fourth interference detection result, respectively. Both the third interference detection result and the fourth interference detection result include a sample region and a cavity ring region. The region in the cavity ring region of the third interference detection result and / or the fourth interference detection result corresponding to the position of the first insensitive region is the second insensitive region.

[0104] It can be understood that in the measurement of the second wafer, the wafer is adjusted to the standard station by the horizontal and vertical adjustment mechanisms, the first interferometer and the second interferometer simultaneously acquire the third interference image and the fourth interference image in the measurement cavity with the second sample fixed therein, and the third interference image and the fourth interference image are used to determine the third interference detection result and the fourth interference detection result. Both the third interference detection result and the fourth interference detection result include a sample region and a cavity ring region. The region in the cavity ring region of the third interference detection result and / or the fourth interference detection result corresponding to the position of the first insensitive region is the second insensitive region.

[0105] Step S70: Compensate all or part of the topography difference between the second insensitive region and the first insensitive region to the cavity interference image to obtain a new cavity interference image.

[0106] It can be understood that the embodiment compensates the topography difference between the second insensitive region and the first insensitive region to the cavity interference image, estimates and corrects the system error in the measurement system by using this difference, and improves the measurement accuracy. The compensation can be applied to the entire field of view, or part of the region is compensated by fitting to generate a full-field compensation amount based on the local difference. The final goal is to obtain a new interference image (phase / stripe image) or a measured surface topography map that can more truly reflect the topography of the measured surface.

[0107] Further, a variation quantity is obtained according to the topographic difference between the second insensitive area and the first insensitive area, and a least square fitting is performed on the distribution of the variation quantity to obtain a variation coefficient, and the variation coefficient is compensated into the cavity interference image to obtain a new cavity interference image.

[0108] It should be noted that the above selection and compensation of the sensitive area are for one side, and in actual measurement, there can be insensitive areas on both sides, which can be compensated respectively, and also within the protection scope of the present application, which will not be repeated here.

[0109] Further, the measurement device used in the above measurement method is also used to perform the measurement of the thickness distribution of the second sample, and the thickness distribution of the second sample is the difference between the surface shape of the new cavity interference image and the sum of the surface shape of the third interference image and the surface shape of the fourth interference image.

[0110] It can be understood that the cavity data used in the calculation of the thickness distribution of the second sample wafer is selected according to the standard station, which further ensures that there is no influence of any cross talk in the processing of the result, and at the same time, considering that the interval of the cavity calibration is relatively long, there can be a change in the cavity tilt between the measurement of the wafer and the wafer, the cavity interference image is compensated, the system error in the measurement system is corrected, and the measurement precision is improved.

[0111] It should be noted that: theoretically, the cavity ring and the corresponding area profile may not be the same, and in practice, any area can be used for correction, and the insensitive area can not be determined. The application calculates the profile distribution of the irregular area 402 (all areas or the area of the insensitive area 405 to crosstalk) during the first wafer measurement (phase extraction using the interference fringes of the irregular area 402, and the profile distribution of the area is obtained by phase unwrapping), and uses it as the initial reference of this area, so as to obtain the profile t_402ref(x,y) of the irregular area 402. Further, during the measurement of each wafer, the profile t402i(x,y) of the irregular area 402 under the current condition is calculated; the profile difference between the reference value of the first measurement and the subsequent each wafer measurement is calculated, and the profile difference is t402i(x,y)-t402ref(x,y), and the relative change coefficient is obtained according to the profile difference; then the change coefficient is compensated into the initial cavity distribution t(x,y) to obtain a new cavity interference image, and is used in the calculation of the thickness distribution of each wafer. The compensation method is as follows: calculate the profile difference of the irregular area 402, obtain the distribution of the change amount, and perform least squares fitting on the distribution of the change amount to obtain the change coefficient Δxy, and compensate it into the original cavity distribution t(x,y) to obtain a new t'(x,y) = t(x,y) + Δxy.

[0112] Further, the first interferometer further comprises: the second interferometer acquires the cavity interference image of the measurement cavity in the cavity state; the first sample is fixed in the measurement cavity; the first interferometer and the second interferometer simultaneously acquire the first interference image and the second interference image of the first sample in the measurement cavity; the first interference image and the second interference image both contain the sample area and the cavity ring area; the position of the first sample in the measurement cavity is adjusted, so that the cavity ring area of the first interference image and / or the second interference image is close to the corresponding area of the cavity interference image; at this time, the position of the first sample in the measurement cavity is recorded as the standard station; and the surface profile measurement of the first sample is performed at the standard station.

[0113] It can be understood that when the second interferometer is used for cavity measurement, the second interferometer acquires the cavity interference image of the measurement cavity in the cavity state, and at this time the first interferometer is in the closed state to ensure that the light beam in the light path of the first interferometer does not enter the interference light path, so as to avoid the crosstalk of the light path.

[0114] It can be understood that when the cavity is measured, shutter control (or attenuation adjustment) can be added in the light path of the first interferometer and the second interferometer, and the main purpose is to separately control the first interferometer and the second interferometer of each path to work respectively, that is, when the first interferometer works, the light in the light path of the second interferometer does not enter the opposite interferometer, and vice versa, to avoid crosstalk.

[0115] Further, the sample is adjusted to a first standard station, and the surface profile measurement of all samples is sequentially completed by using the phase shifting technique. Specifically, when a single sample is measured, the sample profile can be calculated only by phase shifting. When the cavity is tested, the first and second interferometers cannot work at the same time, so the test and phase shifting are alternated, and the next round of phase shifting and control exposure process is performed after the first interferometer works and the light in the light path of the second interferometer does not enter the opposite interferometer, and then the second interferometer works and the light in the light path of the first interferometer does not enter the opposite interferometer. The phase shifting mode can be mechanical phase shifting, wavelength phase shifting, spatial phase shifting, etc., which is not limited here.

[0116] It should be noted that a standard position is determined by adjustment and correction, and when the sample is at this position, the system error of the interference measurement has been minimized (by cavity ring matching or free area correction). The phase change is introduced by changing the laser wavelength, and then a plurality of interference images are obtained for phase demodulation to obtain high-precision surface profile information.

[0117] The measurement method provided in the application comprises the following steps: the first interferometer obtains a first cavity interference image in a cavity state of a measurement cavity; the first cavity interference image determines a first cavity detection result; the first interferometer and the second interferometer emit light at the same time; the first interferometer obtains a first interference image in a first sample state of the measurement cavity; a first interference detection result is determined according to the first interference image; the position of the first sample in the measurement cavity is adjusted so that the cavity ring area of the first interference detection result is close to the corresponding area of the first cavity detection result; at this time, the position of the first sample in the measurement cavity is recorded as a standard station, and the surface profile measurement of the first sample is performed at the standard station. The cavity is collected by specific synchronous control to eliminate the influence of crosstalk during cavity measurement, and the standard station for wafer measurement is determined on this basis, so that the influence of crosstalk on the wafer measurement at the standard station is effectively avoided, and the measurement accuracy is improved.

[0118] Embodiment 2

[0119] Please refer to Figure 3Figure 2 is a schematic diagram of a measuring device according to an embodiment of the present application, which is applied to the measuring method according to any one of the embodiments described above, and includes a measuring cavity 10, a first interferometer 20, and a second interferometer 30. The first sample is fixed in the measuring cavity 10, and the first and second interferometers 20 and 30 are located on two sides of the measuring cavity 10. The implementation of each component is described in detail below.

[0120] The first interferometer 20 is used to obtain a cavity interference image in the cavity state of the measuring cavity.

[0121] In this embodiment, the cavity state of the measuring cavity refers to a reference state when no sample is placed in the optical path of the interferometer. When no sample is placed, the light beam is irradiated to the bottom of the measuring cavity, i.e., a cavity ring region is formed, and an ideal interference cavity is formed between the reference surface of the interferometer and the theoretical measurement surface. This state is used to calibrate the inherent error of the system and is a key link to achieve nanometer-level precision. The cavity state is a "zero reference" for interference measurement, and its precision directly determines the measurement capability of the system.

[0122] Referring back to Figure 2 , (b) the first interferometer 20 according to this embodiment obtains a cavity interference image in the cavity state of the measuring cavity 10, wherein the cavity region is the cavity region 401.

[0123] It can be understood that when no sample is placed, only the reference mirror surface and the bottom of the measuring cavity exist in the optical path of the interferometer. At this time, the reference surface and the bottom of the cavity form an ideal parallel or confocal interference cavity, a first cavity interference image is generated, and a first cavity detection result is obtained after calculation.

[0124] In this embodiment, when the cavity is measured, the first interferometer 20 obtains a cavity interference image in the cavity state of the measuring cavity, and at this time, the second interferometer 30 is controlled to be in a closed state to ensure that the light beam in the optical path of the second interferometer does not enter the interference optical path, so as to avoid cross-talk.

[0125] The first and second interferometers 10 and 20 simultaneously emit light to obtain a first interference image in the state that the first sample is fixed in the measuring cavity 30, determine a first interference detection result according to the first interference image, and the first interference detection result includes a sample region and a cavity ring region.

[0126] It can be understood that when the wafer is measured, the wafer body shields the region that is not affected by the cross-talk of the two-way interference. In order to eliminate the influence of vibration on the measurement of the wafer, the two-way interferometers must be synchronized.

[0127] It can be understood that when the sample is measured by using the dual-interferometer, the sample needs to be fixed in the measurement cavity, and the first interferometer and the second interferometer emit light at the same time, the first interferometer obtains a first interference image of the first sample in the measurement cavity, and in the process of obtaining the interference image, part of the light beam irradiates the surface of the sample, and after being reflected, interferes with the reference light, thereby forming the interference of the sample region, and the other part of the light beam irradiates the bottom of the measurement cavity (that is, the region not covered by the sample, that is, the cavity ring region). By analyzing the first interference image and extracting the interference fringe information, the first interference detection result is determined, and the first interference detection result includes the sample region and the cavity ring region.

[0128] Specifically, the interference fringes formed under the action of the reference light and the sample reflected light are the sample region, which carries the sample surface topography information; the interference fringes formed under the action of the reference light should be the cavity ring region, that is, the region not covered by the sample, and due to the interference of the reference light and the reflected light from the bottom of the measurement cavity, the interference fringes should be consistent with the corresponding region in the cavity interference image in an ideal case.

[0129] Please refer to Figure 2 , (a) is the first interference image obtained by the first interferometer provided in the embodiment, wherein 403 represents the sample region, and 401 represents the cavity region.

[0130] By adjusting the position of the first sample in the measurement cavity 10, the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result, and at this time, the position of the first sample in the measurement cavity is recorded as the first standard station.

[0131] It can be understood that by adjusting the position of the first sample in the measurement cavity 10 (which can include translation, tilting or rotation), the interference fringes of the cavity ring region in the sample measurement image are close to (that is, the phase difference is close to zero) the corresponding region of the cavity interference image. This means that the position adjustment of the sample compensates for the tilt or defocus and other aberrations introduced by the sample, so that the optical path difference in the cavity ring region is the same as that in the cavity state. When adjusted to the above state, the position of the sample is defined as the standard station, and at this time, the reference position of the sample relative to the measurement cavity is accurately determined, and the subsequent measurement can be taken as the reference.

[0132] In the embodiment, the first cavity detection result is a first cavity surface profile, and the first interference detection result is a first measurement surface profile; and the step of making the cavity ring region of the first interference detection result close to the corresponding region of the first cavity detection result specifically includes: making the cavity ring region of the first measurement surface profile close to the corresponding region of the first cavity surface profile.

[0133] It can be understood that the first cavity detection result is the background surface shape of the measurement cavity when there is no sample (pure reference light and cavity bottom reflected light interference form), denoted as the first cavity surface shape; the first interference detection result is the interference result of the measurement cavity when there is a sample (sample region + cavity ring region), and the overall appearance is denoted as the first measurement surface shape. The region in the cavity ring region that is not covered by the sample (ring region) is denoted as the cavity ring region.

[0134] In this embodiment, the first reference surface shape is obtained by scanning the measurement cavity of the first interferometer when there is no sample, at this time the entire field of view is "cavity ring" without sample region, and the result reflects the inherent error of the measurement system (such as reference mirror unevenness, optical distortion, etc.).

[0135] In this embodiment, the first interference image is collected by fixing the first sample using the first interferometer, and the first measurement surface shape is obtained after calculation, which includes two sub-regions: the sample region contains sample topography information, and the cavity ring region should only contain system error; the cavity ring region data is segmented from the first measurement surface shape, the same position data is extracted from the first cavity surface shape, and the cavity ring region of the first measurement surface shape is close to the corresponding region of the first cavity surface shape by using a conventional fitting method.

[0136] Please refer to Figure 2 , by adjusting the position of the first sample in the measurement cavity 10 to make the cavity ring region of the first measurement surface shape close to the corresponding region of the first cavity surface shape, that is, Figure 2 the region shown by the region 405 which is not sensitive to crosstalk, at this time the position of the first sample in the measurement cavity is denoted as the standard station, which corresponds to Figure 2 the region of the first standard station 404 in

[0137] It should be noted that the form (or distribution) of the interference fringes directly represents the optical path difference distribution of the sample surface, the surface topography (height variation pattern) of the regions with similar fringe deformation patterns must also be similar, therefore, similar interference fringe patterns represent similar surface height variation distributions, that is, similar relative topography features. Therefore, this embodiment is not limited to comparing the first interference detection result to make the cavity ring region of the first measurement surface shape close to the corresponding region of the first cavity surface shape, but also can compare the first interference image with the first cavity surface shape to make the corresponding regions close.

[0138] Further, it further includes an illumination unit 40. The illumination unit 40 is used to output first polarized light 41 and second polarized light 42. The first interferometer 20 includes a first interference module 21, and the second interferometer 30 includes a second interference module 31.

[0139] In the embodiment, the illumination unit 40 outputs the first polarized light 41, which is incident to the upper surface of the measurement cavity 10 in the cavity state through the first interference module 21, and the light beam reflected by the upper surface of the measurement cavity 10 is imaged through the first interference module 21 to form a cavity interference image; the illumination unit 40 simultaneously outputs the first polarized light 41 and the second polarized light 42, the first polarized light 41 is incident to the upper surface of the measurement cavity 10 in the first sample state through the first interference module 21, and the light beam reflected by the upper surface of the measurement cavity 10 is imaged through the first interference module 21 to form a first interference image, which contains a sample region and a cavity ring region; the second polarized light 42 is incident to the lower surface of the measurement cavity 10 in the first sample state through the second interference module 22, and the light beam reflected by the lower surface of the measurement cavity 10 is imaged through the second interference module 21 to form a second interference image, which contains a sample region and a cavity ring region.

[0140] Further, the adjustment unit 50 is further included. The adjustment unit 50 adjusts the position of the first sample in the measurement cavity 10, so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result or the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result.

[0141] It can be understood that the adjustment unit 50 can adjust the position of the first sample in the measurement cavity 10 in the manner of translation, tilting or rotation, etc.

[0142] Please refer to Figure 4 The first interferometer 20 further includes a first PBS beam splitter 22, a first quarter wave plate 23, a first relay lens 24 and a first detector 25, and the first interference module 21 includes a first collimating mirror 211 and a first reference mirror 212; the second Fizeau interferometer 30 further includes a second PBS beam splitter 32, a second quarter wave plate 33, a second relay lens 34 and a second detector 35, and the second interference module 31 includes a second collimating mirror 311 and a second reference mirror 312.

[0143] Specifically, the first polarized light 41 is reflected by the first PBS beam splitter 22 and then enters the first quarter wave plate 23, and then enters the first collimating mirror 211 and the first reference mirror 212 in sequence to be incident to the upper surface of the measurement cavity 10 in the cavity state, and the light beam reflected by the upper surface of the measurement cavity is sequentially reflected by the first reference mirror 212, the first collimating mirror 211 and the first quarter wave plate 23, and then enters the first PBS beam splitter 22, and then is transmitted by the first PBS beam splitter 22 and is imaged by the first relay lens 24 onto the first detector 25 to form a cavity interference image.

[0144] Specifically, the first polarized light 41 is reflected by the first PBS 22, enters the first quarter wave plate 23, and then is incident on the upper surface of the measuring cavity in the first sample state through the first collimating mirror 211 and the first reference mirror 212. The light reflected by the upper surface of the measuring cavity enters the first PBS 22 through the first reference mirror 212, the first collimating mirror 211 and the first quarter wave plate 23, and then is transmitted by the first PBS 22 and imaged on the first detector 25 by the first relay lens 24 to form a first interference image.

[0145] Specifically, the second polarized light 42 is reflected by the second PBS 32, enters the second quarter wave plate 33, and then is incident on the lower surface of the measuring cavity in the first sample state through the second collimating mirror 311 and the second reference mirror 312. The light reflected by the lower surface of the measuring cavity enters the second PBS 32 through the second reference mirror 312, the second collimating mirror 311 and the second quarter wave plate 33, and then is transmitted by the second PBS 32 and imaged on the second detector 35 by the second relay lens 34 to form a second interference image.

[0146] In this embodiment, a control unit 60 is further included, which is configured to control the illumination unit 40 to output the first polarized light 41 and / or the second polarized light 42, and to control the first detector 25 and / or the second detector 35 to be exposed.

[0147] The measurement device provided by the embodiment is used for cavity measurement. The control unit 60 controls the illumination unit 40 to output the first polarized light 41 alone. The first polarized light 41 is reflected by the first PBS 22, and then passes through the first quarter-wave plate 23 to become collimated light. The collimated light passes through the first reference mirror 212 and is vertically incident on the upper surface of the measurement cavity in the cavity state. The reflected light of the upper surface of the measurement cavity interferes with the reflected light of the reference surface of the first reference mirror 212, and then returns to the first quarter-wave plate 23 again. The reflected light of the first quarter-wave plate 23 becomes p light and enters the first PBS 22. The p light is transmitted by the first PBS 22, and then is imaged on the first detector 25 by the first relay lens 24 to form a cavity interference image.

[0148] The wafer surface type measurement device provided by the above-mentioned embodiment of the present application is used for cavity acquisition and is synchronously controlled to eliminate the crosstalk influence in cavity measurement. The standard position of wafer measurement is determined on this basis. The influence of on-way crosstalk is effectively avoided in wafer measurement at the standard position, and the measurement precision is improved.

[0149] It should be noted that, in actual semiconductor production and detection process, considering the yield, the cavity measurement is generally performed once before each wafer or the first wafer of the day's mass production, and a cavity measurement is not performed separately before each wafer. In this embodiment, when the first wafer is measured, the position of the wafer in the cavity is adjusted by the horizontal and vertical adjustment mechanisms, so that the area of the first interference image changes, the cavity ring area is processed by an algorithm, and the data collected under the cavity condition is compared with the results calculated by the same cavity ring position, and the substantially consistent ring area of the entire cavity ring area or part of the cavity ring area is selected, such as Figure 2 and Figure 3 The position may be the entire ring area or a part of the entire ring area, and the position of the first wafer in the measurement cavity under this condition is the first standard position 404, and then in the measurement of each subsequent wafer, the measurement position of each wafer is ensured to be consistent with the first standard position 404.

[0150] Further, the measurement device used in the above measurement method is also used to perform the measurement of the thickness distribution of the first sample, which is the difference between the surface shape of the first cavity interference image and the sum of the surface shape of the first interference image and the surface shape of the second interference image.

[0151] It can be understood that when calculating the cavity data used in the calculation of the thickness distribution of the first sample wafer, the effective area selection is also performed according to the mask1 area of the wafer position, which further ensures that there is no influence of any cross-talk in the processing of the results.

[0152] In this embodiment, the above measurement device further comprises: fixing the second sample to the measurement cavity and adjusting to the standard position, and performing the surface shape measurement of the second sample at the standard position.

[0153] It can be understood that a specific first standard position 404 needs to be specified during wafer measurement, and the first standard position 404 is confirmed during the first wafer or first wafer measurement, so as to ensure that the cavity ring monitoring data outside the mask1 area and the measurement calculation data of the same cavity ring position under the cavity measurement condition are consistent during the wafer measurement process. Then, before the measurement of the subsequent multiple wafers, each wafer needs to be measured in the first standard position 404 area, so that the actual use data area of the cavity data and the area of the wafer measurement are consistent, thereby avoiding the generation of cross-talk.

[0154] It should be noted that: considering that the interval of cavity calibration may be relatively long, there may be a change in the inclination of the cavity between the measurement of the wafers and the wafers, so that the cavity interference image deviates. In order to avoid this situation, the present application further optimizes the above technical solution.

[0155] In the embodiment, the wafer surface type measuring device provided by the application further comprises a calculation unit, which can execute the following procedures:

[0156] Calculate the topography distribution of the first insensitive region formed when the first sample is fixed at the first standard station. The first insensitive region is the region formed when the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result.

[0157] Please refer to Figure 2 When measuring the first wafer, the position of the wafer in the cavity is adjusted by the horizontal and vertical adjustment mechanisms, so that the region formed when the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result is compared with the result calculated by the same cavity ring position of the data collected under the cavity condition, and the substantially consistent ring region of the entire cavity ring region or part of the cavity ring region is selected, that is, the selected region 405 insensitive to crosstalk, and is recorded as the first insensitive region. The first insensitive region may be the entire ring region or a part of the entire ring region.

[0158] Calculate the topography distribution of the second insensitive region formed when the second sample is fixed at the first standard station. When the second sample is adjusted to the first standard station, the first interferometer and the second interferometer simultaneously acquire the third interference image and the fourth interference image of the second sample under the condition that the second sample is fixed in the measurement cavity. The third interference image and the fourth interference image are used to determine the third interference detection result and the fourth interference detection result, respectively. The third interference detection result and the fourth interference detection result both contain a sample region and a cavity ring region. The region in the cavity ring region of the third interference detection result and / or the fourth interference detection result corresponding to the position of the first insensitive region is the second insensitive region.

[0159] It can be understood that when measuring the second wafer, the wafer is adjusted to the standard station by the horizontal and vertical adjustment mechanisms, the first interferometer and the second interferometer simultaneously acquire the third interference image and the fourth interference image of the second sample under the condition that the second sample is fixed in the measurement cavity, and the third interference image and the fourth interference image are used to determine the third interference detection result and the fourth interference detection result. The third interference detection result and the fourth interference detection result both contain a sample region and a cavity ring region. The region in the cavity ring region of the third interference detection result and / or the fourth interference detection result corresponding to the position of the first insensitive region is the second insensitive region.

[0160] Compensate all or part of the topographic difference between the second insensitive area and the first insensitive area into the cavity interference image to obtain a new cavity interference image.

[0161] It can be understood that the embodiment compensates the topographic difference between the second insensitive area and the first insensitive area into the cavity interference image, estimates and corrects the system error in the measurement system by using the difference, and improves the measurement accuracy. The compensation can be applied to the entire field of view, or partial area compensation is performed by fitting to generate a full-field compensation amount based on the local difference. The ultimate goal is to obtain a new interference image (phase / stripe image) or a measured surface topography graph that can more truly reflect the measured surface topography.

[0162] Further, the variation is obtained according to the topographic difference between the second insensitive area and the first insensitive area, and the distribution of the variation is least square fitted to obtain a variation coefficient, and the variation coefficient is compensated into the cavity interference image to obtain a new cavity interference image.

[0163] It should be noted that the above selection and compensation of the sensitive area are for one side, and in actual measurement, there can be insensitive areas on both sides, which can be compensated respectively, and also within the protection scope of the present application, which will not be repeated here.

[0164] Further, the above measurement device is also used to perform the measurement of the thickness distribution of the second sample, and the thickness distribution of the second sample is the difference between the surface shape of the new cavity interference image and the sum of the surface shape of the third interference image and the surface shape of the fourth interference image.

[0165] It can be understood that the cavity data used in the calculation of the thickness distribution of the second sample wafer is selected according to the standard station, which further ensures that there is no influence of any cross talk in the processing of the result, and at the same time, considering that the interval of the cavity calibration is relatively long, there can be a change in the cavity tilt between the measurement of the wafer and the wafer, the cavity interference image is compensated, the system error in the measurement system is corrected, and the measurement accuracy is improved.

[0166] The present application calculates the topography distribution of the irregular area 402 (phase extraction using interference fringes of the irregular area 402, and phase unwrapping to obtain the topography distribution of the area) as the initial reference of the area of the irregular area 402 during the first wafer measurement, and obtains the topography t_402ref(x, y) of the irregular area 402. Further, the topography t402i(x, y) of the irregular area 402 under the current condition is calculated during each wafer measurement. Then, the topography difference between the reference value during the first measurement and each subsequent wafer measurement is calculated, and the relative change coefficient is obtained according to the topography difference. Then, the change coefficient is compensated into the initial cavity distribution t(x, y) to obtain a new cavity interference image, and participates in the calculation of the thickness distribution of each wafer. The compensation method is as follows: the topography difference of the irregular area 402 is calculated to obtain the distribution of the change amount, the least square fitting is performed on the distribution of the change amount to obtain the change coefficient Δxy, and the original cavity distribution t(x, y) is compensated to obtain a new t'(x, y) = t(x, y) + Δxy.

[0167] Further, the first interferometer 20 obtains the cavity interference image of the measurement cavity 10 in the cavity state, and the second interferometer 30 obtains the cavity interference image of the measurement cavity in the cavity state. The first sample is fixed in the measurement cavity, and the first interferometer 20 and the second interferometer 30 simultaneously obtain the first interference image and the second interference image of the first sample in the state of being fixed in the measurement cavity 10. The first interference image and the second interference image both contain the sample area and the cavity ring area. The position of the first sample in the measurement cavity 10 is adjusted so that the cavity ring area of the first interference image and / or the second interference image is close to the corresponding area of the cavity interference image. At this time, the position of the first sample in the measurement cavity is recorded as the standard station. The surface profile measurement of the first sample is performed at the standard station.

[0168] It can be understood that when the second interferometer 20 is used for cavity measurement, the second interferometer 30 obtains the cavity interference image of the measurement cavity in the cavity state, and at this time the first interferometer 20 is in the closed state to ensure that the light beam in the light path of the first interferometer does not enter the interference light path to avoid cross-talk.

[0169] Further, the sample is adjusted to the first standard station, and the surface profile measurement of all samples is sequentially completed by using the phase shift technique.

[0170] Specifically, when measuring a single sample, phase shifting is required to calculate the sample's morphology. During cavity testing, since the first and second interferometers cannot work simultaneously, alternating interferometry-phase shifting-alternating testing-phase shifting is necessary. After a single phase shift, the process involves first controlling the first interferometer to prevent light from entering the opposing interferometer from the optical path of the second interferometer, then controlling the second interferometer to prevent light from entering the opposing interferometer from the optical path of the first interferometer, and then proceeding to the next phase shifting and exposure control process until the test is completed.

[0171] It should be noted that a standard position was previously determined through adjustment and calibration. When the sample is in this position, the systematic error of its interferometry has been minimized (through cavity ring matching or free region correction). By changing the laser wavelength to introduce phase change, multiple interferograms are obtained for phase demodulation, resulting in high-precision surface shape information.

[0172] like Figure 5 As shown, during cavity measurement, shutter control (or attenuation adjustment) can be added to the illumination optical path. The main purpose is to control each beam and detector individually. For example, control unit 60 controls illumination unit 40 to emit first polarized light 41. The first polarized light 41 is transmitted to the first interferometer for operation and simultaneously controls the first detector to expose, thereby obtaining the first interference image. At this time, control unit 60 controls illumination unit 40 to prevent the output of second polarized light 42. The second polarized light 42 will not enter the opposing interferometer, and vice versa, thus avoiding crosstalk. After a single phase shift, the process can be repeated as follows: first, control the shutter to open to emit the first polarized light 41 (at this time, control the shutter to close the second polarized light) and control the first detector to expose (at this time, control the second detector to close), then control the shutter to open to emit the second polarized light 42 and control the second detector to expose (at this time, control the shutter to close the first polarized light), and then proceed to the next round of phase shifting and exposure control until all wafers in the sequence have been inspected.

[0173] The wafer surface measurement equipment provided in the above embodiments of this application eliminates crosstalk during cavity measurement through specific synchronous control during cavity acquisition, and determines a standard station for wafer measurement based on this, so that the influence of crosstalk is effectively avoided when performing wafer measurement at the standard station, thereby improving measurement accuracy.

[0174] The above merely describes preferred embodiments of the present application, and only specifically describes the technical principles of the present application, and these descriptions are only for explaining the principles of the present application, and cannot be explained as limitations on the protection scope of the present application in any way. Based on the explanations here, any modifications, equivalent replacements and improvements made within the spirit and principles of the present application, and other specific embodiments of the present application that can be 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 method for measuring wafer surface shape, characterized in that, The measuring equipment includes a measuring cavity and a first interferometer and a second interferometer located on both sides of the measuring cavity; The method includes: The first interferometer acquires a first cavity interference image in the cavity state of the measurement cavity, and determines the first cavity detection result based on the first cavity interference image; A first sample is fixed in the measurement cavity. The first interferometer and the second interferometer emit light simultaneously. The first interferometer acquires a first interference image in the measurement cavity with the first sample fixed in it. A first interference detection result is determined based on the first interference image. The first interference detection result includes the sample area and the cavity ring area. The position of the first sample in the measurement cavity is adjusted so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result. At this time, the position of the first sample in the measurement cavity is recorded as the first standard position. The surface shape measurement of the first sample is performed at the first standard workstation.

2. The wafer surface shape measurement method as described in claim 1, characterized in that, The first cavity detection result is the first cavity surface shape, and the first interference detection result is the first measurement surface shape; Specifically, making the cavity ring region of the first interference detection result close to the corresponding region of the first cavity detection result means making the cavity ring region of the first measurement surface shape close to the corresponding region of the first cavity surface shape.

3. The wafer surface shape measurement method as described in claim 2, characterized in that, The first sample is adjusted to the first standard station, and the surface shape measurement of all samples is completed sequentially using phase-shifting technology.

4. The wafer surface shape measurement method as described in claim 1, characterized in that, Also includes: The second interferometer acquires a second cavity interference image in the cavity state of the measurement cavity.

5. The wafer surface shape measurement method as described in claim 4, characterized in that, The measuring device is also used to measure the thickness distribution of the first sample, which is the difference between the surface shape of the first cavity interference image and the sum of the surface shapes of the first interference image and the second interference image.

6. The wafer surface shape measurement method as described in claim 4, characterized in that, Also includes: The second cavity detection result is determined based on the second cavity interference image; A second interference image is acquired with the first sample fixed in the measurement cavity. A second interference detection result is determined based on the second interference image. The second interference detection result includes the sample region and the cavity ring region. The position of the first sample in the measurement cavity is adjusted so that the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result. At this time, the position of the first sample in the measurement cavity is recorded as the second standard position. The first standard workstation is modified according to the second standard workstation.

7. The wafer surface shape measurement method as described in claim 1, characterized in that, The second sample is fixed in the measuring cavity and adjusted to the first standard station, and the surface shape measurement of the second sample is performed at the first standard station.

8. The wafer surface shape measurement method as described in claim 7, characterized in that, It also includes the following steps: Calculate the morphological distribution of the first insensitive region formed when the first sample is fixed at the first standard station. The first insensitive region is the region formed when the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result. The morphological distribution of the second insensitive region formed when the second sample is fixed at the first standard station is calculated. When the second sample is adjusted to the first standard station, the first interferometer and the second interferometer simultaneously acquire the third interference image and the fourth interference image in the state where the second sample is fixed in the measurement cavity. The third interference detection result and the fourth interference detection result are determined according to the third interference image and the fourth interference image, respectively. The third interference detection result and the fourth interference detection result both include the sample region and the cavity ring region. The region in the cavity ring region of the third interference detection result and / or the fourth interference detection result that corresponds to the location of the first insensitive region is the second insensitive region. All or part of the morphological differences between the second insensitive region and the first insensitive region are compensated into the first cavity interference image to obtain a new cavity interference image.

9. The wafer surface shape measurement method as described in claim 8, characterized in that, The change amount is obtained based on the morphological difference between the second insensitive region and the first insensitive region, and the distribution of the change amount is fitted by least squares to obtain the change coefficient. The change coefficient is then compensated into the first cavity interference image to obtain the new cavity interference image.

10. The wafer surface shape measurement method as described in claim 8, characterized in that, The measuring device is also used to measure the thickness distribution of the second sample, which is the difference between the surface shape of the new cavity interference image and the sum of the surface shapes of the third interference image and the fourth interference image.

11. A wafer surface profile measuring device, characterized in that, include: A measuring chamber, in which a first sample is fixed; A first interferometer and a second interferometer are located on opposite sides of the measuring cavity; wherein: The first interferometer is used to acquire a first cavity interference image in the cavity state of the measurement cavity, and the first cavity interference image is used to determine the first cavity detection result; The first interferometer and the second interferometer simultaneously emit light to acquire a first interference image with the first sample fixed in the measurement cavity. A first interference detection result is determined based on the first interference image. The first interference detection result includes the sample region and the cavity ring region. The position of the first sample in the measurement cavity is adjusted so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result. At this time, the position of the first sample in the measurement cavity is recorded as the first standard position. The surface shape measurement of the first sample is performed at the first standard workstation.

12. The wafer surface profile measuring device as described in claim 11, characterized in that, It also includes an illumination unit and a control unit. The illumination unit is used to output first polarized light and second polarized light. The first interferometer includes a first interference module, and the second interferometer includes a second interference module. The control unit is used to control the illumination unit to output the first polarized light and / or output the second polarized light and to control the first interference module and / or the second interference module to work. The illumination unit outputs the first polarized light, which is incident on the upper surface of the measurement cavity in the cavity state via the first interference module. The light beam reflected from the upper surface of the measurement cavity is imaged by the first interference module to form a first cavity interference image, and the first cavity interference image determines the first cavity detection result; or the illumination unit outputs the second polarized light, which is incident on the lower surface of the measurement cavity in the cavity state via the second interference module. The light beam reflected from the lower surface of the measurement cavity is imaged by the second interference module to form a second cavity interference image, and the second cavity interference image determines the second cavity detection result. The illumination unit simultaneously outputs the first polarized light and the second polarized light. The first polarized light is incident on the upper surface of the measurement cavity in the state where the first sample is fixed through the first interference module. The light beam reflected by the upper surface of the measurement cavity is imaged by the first interference module to form a first interference image. The first interference image determines the first interference detection result. The first interference detection result includes the sample area and the cavity ring area. Alternatively, the second polarized light is incident on the lower surface of the measurement cavity in which the first sample is fixed via the second interference module. The light beam reflected by the lower surface of the measurement cavity is imaged by the second interference module to form a second interference image. The second interference image determines the second interference detection result, which includes the sample area and the cavity ring area. Adjust the position of the first sample in the measurement cavity so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result. At this time, the position of the first sample in the measurement cavity is recorded as the first standard station, and the surface shape measurement of the first sample is performed at the first standard station; or adjust the position of the first sample in the measurement cavity so that the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result. At this time, the position of the first sample in the measurement cavity is recorded as the second standard station, and the surface shape measurement of the first sample is performed at the second standard station.

13. The wafer surface profile measuring device as described in claim 12, characterized in that, The first interferometer further includes a first PBS beam splitter prism, a first quarter-wave plate, a first relay lens, and a first detector; the first interferometer module includes a first collimating mirror and a first reference mirror. The second Fizeau interferometer further includes a second PBS beam splitter prism, a second quarter-wave plate, a second relay lens, and a second detector; the second interferometer module includes a second collimating mirror and a second reference mirror. The first polarized light is reflected by the first PBS beam splitter and enters the first quarter-wave plate. It then passes through the first collimating lens and the first reference lens in sequence and is incident on the upper surface of the measurement cavity in the cavity state. The beam reflected by the upper surface of the measurement cavity passes through the first reference lens, the first collimating lens and the first quarter-wave plate in sequence and enters the first PBS beam splitter. After being transmitted through the first PBS beam splitter, it is imaged onto the first detector by the first relay lens to form the cavity interference image. The first polarized light is reflected by the first PBS beam splitter and enters the first quarter-wave plate. It then passes through the first collimating lens and the first reference lens in sequence and is incident on the upper surface of the measurement cavity in which the first sample is fixed. The light beam reflected by the upper surface of the measurement cavity passes through the first reference lens, the first collimating lens and the first quarter-wave plate in sequence and enters the first PBS beam splitter. After being transmitted through the first PBS beam splitter, it is imaged onto the first detector by the first relay lens to form the first interference image. The second polarized light is reflected by the second PBS beam splitter and enters the second quarter-wave plate. It then passes through the second collimating lens and the second reference lens in sequence and is incident on the lower surface of the measurement cavity in which the first sample is fixed. The light beam reflected by the lower surface of the measurement cavity passes through the second reference lens, the second collimating lens and the second quarter-wave plate in sequence and enters the second PBS beam splitter. After being transmitted through the second PBS beam splitter, it is imaged onto the second detector by the second relay lens to form the second interference image.

14. The wafer surface profile measuring device as described in claim 11, characterized in that, It also includes an adjustment unit, the modulation unit being used to adjust the position of the first sample in the measurement cavity, so that the cavity ring region of the first interference detection result is close to the corresponding region of the first cavity detection result or so that the cavity ring region of the second interference detection result is close to the corresponding region of the second cavity detection result.

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