Feature size measuring method and device

Abstract

The invention provides a feature size measuring method and device, and the method mainly comprises the steps: carrying out the pre-alignment of a wafer according to a first mark under a production environment condition; performing optical microscope alignment on the wafer according to the first mark and the second mark under the production environment condition; obtaining an alignment result of optical microscope alignment, wherein the alignment result is microscopic alignment success and microscopic alignment failure; stopping measuring the wafer which fails in microscopic alignment, or transferring the wafer which succeeds in microscopic alignment to a vacuum chamber; and under the condition that the vacuum chamber is in the first vacuum condition, performing scanning electron microscope alignment on the wafer which is successfully microscopically aligned according to the first mark, the second mark and the third mark, and measuring the feature size of the wafer which is successfully microscopically aligned. According to the application, the optical microscopic alignment step during the CDSEM measurement can be transferred to the outside of the CDSEM vacuum chamber for execution, the measurement throughput of the CDSEM is improved, and the use efficiency of the vacuum chamber is improved, so that the HVM benefit is improved and the HVM cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, and in particular, to a feature size measurement method and device. BACKGROUND

[0002] With the continuous reduction of semiconductor feature size (Critical Dimension, CD), the feature size has a greater and greater impact on the performance of semiconductor chips, and therefore the accuracy requirement of the process on the feature size is higher and higher. Generally, a feature size scanning electron microscope (Critical Dimension Scanning Electron Microscope, CDSEM) can be used to detect the feature size of a semiconductor.

[0003] Specifically, in the CDSEM, an electron gun emits an electron beam to scan the surface of a measurement object (wafer), the electron beam interacts with the atoms on the surface of the measurement object, and the electron signal (including secondary electrons, reflected electrons, backscattered electrons, X-rays, and Auger electrons, etc.) excited by the measurement object is collected to generate a two-dimensional image representing the surface topography of the measurement object. Based on the two-dimensional image, the feature size of the measurement object, such as line width, aperture, sidewall size, etc., can be extracted to measure the important geometric parameters of the process quality. It should be noted that in a vacuum environment, the electron beam will not be scattered by air molecules, so that the surface of the measurement object can be scanned more accurately and a higher quality image can be obtained.

[0004] In the related art, before the electron gun emits the electron beam, the measurement object is first transferred to the electron microscope chamber of the CDSEM; then the gas inside the electron microscope chamber is pumped out so that the electron microscope chamber is in a vacuum environment; next, the measurement object is aligned by an optical microscope (Optical Microscope, OM) according to an optical mark pattern; next, the measurement object is aligned by a scanning electron microscope (Scanning Electron Microscope, SEM) according to an electron microscope mark pattern; next, the SEM scans the measurement object to generate a two-dimensional image representing the surface topography of the measurement object, and the CD of the measurement object is extracted based on the two-dimensional image; finally, the measurement object is removed from the electron microscope chamber.

[0005] However, before the SEM scans the measurement object, a time-consuming preparation operation (including vacuum pumping, OM alignment, and SEM alignment) is required, which reduces the measurement speed of the CD of the measurement object, reduces the measurement throughput of the CDSEM, and in turn reduces the benefits of high volume manufacturing (High Volume Manufacturing, HVM). SUMMARY

[0006] The application provides a feature size measurement method and device, which can solve the problem of low measurement throughput of CDSEM in the prior art.

[0007] To solve the above technical problem, the application provides a feature size measurement method, which comprises the following steps: pre-aligning a wafer according to a first mark in a production environment condition; performing optical microscope alignment on the wafer according to the first mark and a second mark in the production environment condition; obtaining an alignment result of the optical microscope alignment, wherein the alignment result is microscopic alignment success or microscopic alignment failure; stopping measurement of the wafer with the microscopic alignment failure, or transferring the wafer with the microscopic alignment success to a vacuum chamber; performing scanning electron microscope alignment on the wafer with the microscopic alignment success according to the first mark, the second mark and a third mark in the case that the vacuum chamber is in a first vacuum condition, and measuring a feature size of the wafer with the microscopic alignment success; wherein a surface image of the wafer comprises the first mark, the second mark and the third mark.

[0008] In some embodiments of the application, the step of performing optical microscope alignment on the wafer according to the first mark and the second mark in the production environment condition comprises the following steps: obtaining a wafer map of the wafer, wherein the wafer map comprises a first positioning position and a second positioning position, the first positioning position on the wafer map corresponds to the first mark on the wafer, and the second positioning position on the wafer map corresponds to the second mark on the wafer; adjusting a physical position of the wafer according to the first mark and a relative position relationship between the first positioning position and the second positioning position in the production environment condition, so that the second mark is in a field of view of an optical microscope, and then performing optical microscope alignment on the wafer.

[0009] In some embodiments of the application, the wafer map comprises a third positioning position, the third positioning position on the wafer map corresponds to the third mark on the wafer; and the step of performing scanning electron microscope alignment on the wafer according to the first mark, the second mark and the third mark in the case that the vacuum chamber is in the first vacuum condition, and measuring a feature size of the wafer comprises the following steps: adjusting a physical position of the wafer according to the second mark and a relative position relationship between the second positioning position and the third positioning position in the case that the vacuum chamber is in the first vacuum condition, so that the third mark is in a field of view of a scanning electron microscope, and then performing scanning electron microscope alignment on the wafer and measuring a feature size of the wafer.

[0010] In some embodiments of the present application, after the transferring the wafer with the successful micro-alignment to the vacuum chamber, the method further comprises: adjusting the internal environment of the vacuum chamber until the internal environment of the vacuum chamber meets the first vacuum condition, wherein the first vacuum condition is a vacuum degree ranging from 5x10 -6 to 5x10 -7 .

[0011] In some embodiments of the present application, the adjusting the internal environment of the vacuum chamber until the internal environment of the vacuum chamber meets the first vacuum condition comprises: determining a first vacuum adjustment parameter according to a first preset adjustment time, the internal environment of the vacuum chamber and the first vacuum condition; and adjusting the internal environment of the vacuum chamber according to the first vacuum adjustment parameter until the internal environment of the vacuum chamber meets the first vacuum condition.

[0012] In some embodiments of the present application, after the scanning electron microscope alignment of the wafer and the measurement of the feature size of the wafer according to the first mark, the second mark and the third mark under the condition that the vacuum chamber meets the first vacuum condition, the method further comprises: adjusting the internal environment of the vacuum chamber until the internal environment of the vacuum chamber meets the production environment condition.

[0013] In some embodiments of the present application, the adjusting the internal environment of the vacuum chamber until the internal environment of the vacuum chamber meets the production environment condition comprises: determining a second vacuum adjustment parameter according to a second preset adjustment time, the internal environment of the vacuum chamber and the production environment condition; and adjusting the internal environment of the vacuum chamber according to the second vacuum adjustment parameter until the internal environment of the vacuum chamber meets the production environment condition.

[0014] In some embodiments of the present application, the vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

[0015] To solve the above technical problems, the application further provides a feature size measuring device, comprising: a first alignment module, a second alignment module, an acquisition module, a processing module and an alignment and measurement module; the first alignment module is used for pre-aligning a wafer according to a first mark under a production environment condition; the second alignment module is used for optically microscopically aligning the wafer according to the first mark and a second mark under the production environment condition; the acquisition module is used for acquiring an alignment result of the optical microscopic alignment, the alignment result being microscopic alignment success or microscopic alignment failure; the processing module is used for stopping measuring the wafer with the microscopic alignment failure, or transferring the wafer with the microscopic alignment success to a vacuum chamber; and the alignment and measurement module is used for scanning electron microscope aligning the wafer with the microscopic alignment success according to the first mark, the second mark and a third mark, and measuring a feature size of the wafer with the microscopic alignment success under a condition that the vacuum chamber is in a first vacuum condition; wherein a surface image of the wafer comprises the first mark, the second mark and the third mark.

[0016] In some embodiments of the application, the second alignment module is configured to: acquire a wafer map of the wafer, the wafer map comprising a first positioning position and a second positioning position, the first positioning position on the wafer map corresponding to the first mark on the wafer, and the second positioning position on the wafer map corresponding to the second mark on the wafer; and adjust a physical position of the wafer under the production environment condition according to the first mark and a relative position relationship between the first positioning position and the second positioning position, so that the second mark is in a field of view of an optical microscope, and the wafer is optically microscopically aligned.

[0017] In some embodiments of the application, the wafer map comprises a third positioning position, the third positioning position on the wafer map corresponding to the third mark on the wafer; and the alignment and measurement module is configured to: adjust a physical position of the wafer under a condition that the vacuum chamber is in a first vacuum condition according to the second mark and a relative position relationship between the second positioning position and the third positioning position, so that the third mark is in a field of view of a scanning electron microscope, the wafer is scanning electron microscopically aligned, and a feature size of the wafer is measured.

[0018] In some embodiments of the application, the device further comprises a first adjustment module; and the first adjustment module is configured to adjust an internal environment of the vacuum chamber after the wafer with the microscopic alignment success is transferred to the vacuum chamber, until the internal environment of the vacuum chamber meets the first vacuum condition, the vacuum degree of the first vacuum condition being in a range of 5x10 -6 ~ 5x10 -7 .

[0019] In some embodiments of the present application, the first adjusting module is configured to: determine a first vacuum adjusting parameter according to the first preset adjusting time, the chamber internal environment, and the first vacuum condition; and adjust the chamber internal environment in the vacuum chamber according to the first vacuum adjusting parameter until the chamber internal environment meets the first vacuum condition.

[0020] In some embodiments of the present application, the device further comprises a second adjusting module, which is configured to, in the case that the vacuum chamber is in the first vacuum condition, after performing scanning electron microscope alignment on the wafer according to the first mark, the second mark, and the third mark and measuring the feature size of the wafer, adjust the chamber internal environment in the vacuum chamber until the chamber internal environment meets the production environment condition.

[0021] In some embodiments of the present application, the second adjusting module is configured to: determine a second vacuum adjusting parameter according to the second preset adjusting time, the chamber internal environment, and the production environment condition; and adjust the chamber internal environment in the vacuum chamber according to the second vacuum adjusting parameter until the chamber internal environment meets the production environment condition.

[0022] In some embodiments of the present application, the vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

[0023] Compared with the prior art, the technical scheme of the present application sets an auxiliary optical microscope under the production environment condition, and the auxiliary optical microscope is used for optical microscopic alignment, i.e., the optical microscopic alignment step during CDSEM measurement is performed outside the CDSEM vacuum chamber. Before the scanning electron microscope scans the wafer, a time-consuming preparation operation (including vacuum pumping and scanning electron microscope alignment) needs to be performed, so as to reduce the optical microscopic alignment preparation operation, i.e., to reduce the preparation time that limits the measurement throughput of the CDSEM, to improve the measurement throughput of the CDSEM, to improve the use efficiency of the vacuum chamber, and thus to improve the HVM benefit and to reduce the HVM cost. In particular, for the case of continuously measuring the feature size of the wafer, the continuous measurement speed can be improved, the use efficiency of the vacuum chamber can be improved, the influence of the wafer with failed microscopic alignment on the continuous measurement speed can be reduced, the HVM benefit can be improved, and the HVM cost can be reduced. Moreover, the auxiliary optical microscope is arranged outside the CDSEM, which is easy to maintain. BRIEF DESCRIPTION OF DRAWINGS

[0024] The following drawings set forth illustrative embodiments of the application disclosed herein. Identical reference numerals in the drawings represent similar structures throughout the several views. Those skilled in the art will appreciate that the embodiments described herein are non-limiting, exemplary embodiments, and that the drawings are for purposes of illustration and description only and are not intended to limit the scope of the application as set forth in the appended claims. It is to be understood that the drawings are not to scale.

[0025] Figure 1 is a flow chart of a method of measuring feature size according to some embodiments of the application;

[0026] Figure 2 is a schematic diagram of a pre-alignment process according to some embodiments of the application;

[0027] Figure 3 is a block diagram of a measuring device of feature size according to some embodiments of the application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0029] It should be noted that the terms "first", "second", and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0030] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or server comprising a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] In the related art, in order to measure the characteristic size of a wafer, first, pre-alignment is performed according to a notch mark on the wafer. Then, when the CDSEM is idle, the wafer is transferred into the electron microscope chamber of the CDSEM, the gas inside the electron microscope chamber is pumped out, so that the electron microscope chamber is in a vacuum environment. Next, OM alignment of the measurement object is performed according to an optical mark pattern; next, SEM alignment of the measurement object is performed according to an electron microscope mark pattern; next, SEM scanning measurement of the measurement object is started, a two-dimensional image representing the surface topography of the measurement object is generated, and the CD of the measurement object is extracted based on the two-dimensional image; and finally, the wafer is removed from the electron microscope chamber.

[0032] The CDSEM is an instrument used to measure the critical dimension of a pattern on a wafer substrate in a semiconductor process. Its working principle is that the electron beam emitted from the electron gun is converged through the condenser lens, passes through the aperture to the pattern of the measurement object, the secondary electrons emitted are captured by the detector and converted into an electrical signal, a two-dimensional CDSEM image is obtained, and a corresponding CDSEM characteristic curve is generated. Based on the CDSEM image and the corresponding CDSEM characteristic curve, the critical dimension of the measurement object is measured with high precision.

[0033] However, before the SEM scans the wafer, a long time-consuming preparation operation (including vacuum pumping, OM alignment and SEM alignment) needs to be performed, and after the measurement is completed, the wafer also needs to be removed from the electron microscope chamber, which reduces the measurement speed of the CD of the measurement object, reduces the measurement throughput of the CDSEM, limits the measurement yield of the CDSEM, and thus reduces the benefits of high volume manufacturing (HVM).

[0034] To solve the above technical problems, the application concept of the present application is to provide an auxiliary optical microscope in a production environment, which is used for OM alignment, i.e. to transfer the OM alignment step during CDSEM measurement to outside the electron microscope chamber of the CDSEM. Before the SEM scans the wafer, a long time-consuming preparation operation (including vacuum pumping and SEM alignment) needs to be performed, which reduces the OM alignment preparation operation, i.e. reduces the preparation time that limits the measurement throughput of the CDSEM, improves the measurement throughput of the CDSEM, improves the utilization efficiency of the electron microscope chamber, and thus improves the benefits and reduces the cost of HVM.

[0035] In practical applications, the characteristic size measurement method provided by the embodiments of the present application is applied to a CDSEM device. The characteristic size measurement method provided by the embodiments of the present application will be exemplarily described below with reference to the accompanying drawings, taking a characteristic size measurement device as an example.

[0036] As shown in FIG. 1, the characteristic size measurement device includes a CDSEM device 1 and an auxiliary optical microscope 2. Figure 1As shown, the feature size measurement method provided by the embodiments of the present application can include steps S101 to S105.

[0037] Step S101, under the production environment condition, pre-aligning the wafer according to the first mark.

[0038] The surface image of the wafer includes the first mark. For example, the first mark can be a notch mark. The first mark can be distinguished by naked eyes, and the size of the first mark can be greater than 0.2 mm.

[0039] In the embodiments of the present application, the production environment condition refers to the space environment for processing the wafer, including the current atmospheric pressure.

[0040] Generally, the feature size of the wafer is measured, that is, the fine pattern in the feature area of the surface image of the wafer, such as the line width, line spacing and line profile of the photoresist line, etc.

[0041] In the embodiments of the present application, before measuring the feature size of the wafer, the wafer needs to be pre-aligned according to the first mark, that is, the physical position of the wafer is determined, so as to compare the wafer image with the surface image of the wafer, and then determine whether the measured feature size is consistent with the size set in the wafer image.

[0042] For example, as shown in (a) of FIG. 1, under the production environment condition, a carrier table and a first wafer (wafer to be aligned) for pre-alignment are set, and the surface image of the first wafer includes a notch mark. As shown in (b) of FIG. 1, the first wafer is placed on the carrier table. As shown in (c) of FIG. 1, the first wafer is rotated so that the notch mark of the wafer to be aligned is aligned with the pre-set position, and the pre-alignment of the first wafer is realized. Figure 2 Figure 2 Figure 2

[0043] Step S102, under the production environment condition, optically microscopically aligning the wafer according to the first mark and the second mark.

[0044] In the embodiments of the present application, the surface image of the wafer includes the second mark. The second mark can be composed of a metal line etched on the semiconductor substrate. The second mark can be a special pattern such as a cross-shaped pattern, a circular pattern, a meter-shaped pattern, etc., and the second mark can also be a special pattern designed on the wafer image which can be distinguished from other surface patterns.

[0045] In the embodiments of the present application, optical microscopy can use a magnifying glass to view a small area sample under visible light with a high magnification, for example, the surface image of the wafer, the cross-sectional structure of the element and the oxidation difference, etc. The image of the small area sample viewed in the optical microscopy process is displayed on an electronic screen. ​​​

[0046] It can be understood that the imaging principle of the optical microscope is to form different contrasts by using visible light to irradiate on the surface of the sample to cause local scattering or reflection, which can theoretically be magnified by 1000 times and present a large system field of view.

[0047] Therefore, the wafer can be optically microaligned under the production environment condition so that the second mark is in the field of view of the optical microscope.

[0048] In some embodiments of the present application, the above step S102 is implemented by the following step S1021 and step S1022.

[0049] Step S1021, obtaining a wafer map of the wafer.

[0050] The wafer map includes a first positioning position and a second positioning position, the first positioning position on the wafer map corresponds to the first mark on the wafer, and the second positioning position on the wafer map corresponds to the second mark on the wafer.

[0051] It can be understood that the relative position relationship between the first positioning position and the first mark can be that the first positioning position is at the center of the first mark, or the first positioning position is at any side (left side, right side, upper side, lower side, left upper side, left lower side, right upper side, or right lower side) endpoint of the first mark. Similarly, the relative position relationship between the second positioning position and the second mark can be that the second positioning position is at the center of the second mark, or the second positioning position is at any side (left side, right side, upper side, lower side, left upper side, left lower side, right upper side, or right lower side) endpoint of the second mark.

[0052] In the embodiments of the present application, the wafer map is also a wafer design map, that is, a plan view of the wafer surface pattern.

[0053] In the embodiments of the present application, the surface pattern of a certain region in the wafer map can have high pattern complexity, high etching difficulty, or high importance, and therefore, the position corresponding to the region can be set as the second positioning position, so as to facilitate measuring the feature size of the region according to the second positioning position.

[0054] In the embodiments of the present application, after the wafer is processed according to the wafer map, the first mark can be found at the first positioning position, and the second mark can be found at the second positioning position.

[0055] Step S1022, under the production environment condition, adjusting the physical position of the wafer according to the first mark and the relative position relationship between the first positioning position and the second positioning position, so that the second mark is in the field of view of the optical microscope, and optically microaligning the wafer.

[0056] In the embodiment of the present application, the physical position of the wafer is adjusted according to the relative position relationship between the first positioning position and the second positioning position in the wafer map and the position of the first mark on the wafer, so that the second mark is in the field of view of the optical microscope, i.e., the second mark on the wafer is displayed on the electronic screen, and the optical microscopic alignment is achieved.

[0057] In this way, the approximate position of the second mark can be located by the first positioning position and the second positioning position on the wafer map and the first mark, and the speed of the optical microscopic alignment can be improved by combining the scale of the wafer map and the size of the electronic screen to align the wafer by the optical microscope.

[0058] In step S103, the alignment result of the optical microscopic alignment is obtained.

[0059] The alignment result is microscopic alignment success or microscopic alignment failure.

[0060] It can be understood that if the second mark is not etched on the wafer or the etching of the second mark fails, the alignment result of the optical microscopic alignment can be microscopic alignment failure.

[0061] In addition, if the relative position relationship between the first positioning position and the second positioning position in the wafer map deviates greatly from the relative position relationship between the first mark and the second mark, the microscopic alignment can also fail. At this time, the second mark can be brought into the field of view of the optical microscope by enlarging the amplitude of adjusting the physical position of the wafer and repeatedly adjusting the physical position of the wafer, i.e., the second mark on the wafer is displayed on the electronic screen, and the optical microscopic alignment is achieved.

[0062] It should be noted that the adjustment direction, adjustment amplitude and adjustment times of the physical position of the wafer are not limited.

[0063] In step S104, the wafer with the microscopic alignment failure is stopped from being measured, or the wafer with the microscopic alignment success is transferred to a vacuum chamber.

[0064] In the embodiment of the present application, the wafer with the microscopic alignment failure is stopped from being measured, so that the number of wafers subjected to electron microscope scanning can be reduced. When a large number of wafers are subjected to feature size measurement, the invalid measurement time can be reduced, the CDSEM throughput can be improved, the use efficiency of the electron microscope chamber can be improved, and thus the HVM benefit can be improved and the HVM cost can be reduced.

[0065] In some embodiments of the present application, after the wafer with the microscopic alignment success is transferred to the vacuum chamber in step S104, step S1041 is further included.

[0066] Step S1041, adjusting the chamber internal environment in the vacuum chamber until the chamber internal environment meets the first vacuum condition, wherein the vacuum degree of the first vacuum condition ranges from 5x10 -6 to 5x10 -7 .

[0067] Specifically, the step S1041 comprises: determining a first vacuum adjustment parameter according to the first preset adjustment time, the chamber internal environment and the first vacuum condition; and adjusting the chamber internal environment in the vacuum chamber according to the first vacuum adjustment parameter until the chamber internal environment meets the first vacuum condition.

[0068] In the embodiment of the present application, in order to measure the feature size of the wafer, the wafer needs to be measured in a vacuum environment. However, during the wafer transfer process, the vacuum chamber is exposed to the production environment. Therefore, after the wafer with successful micro-alignment is transferred to the vacuum chamber, the vacuum chamber needs to be vacuumed again so that the chamber internal environment meets the first vacuum condition.

[0069] In the embodiment of the present application, the first preset adjustment time can be determined according to the difference between the chamber internal environment and the first vacuum condition. The first vacuum adjustment parameter can include the pumping speed, the flux, the number of times, etc.

[0070] It should be noted that each parameter in the first vacuum condition parameter has a corresponding preset range. The first vacuum adjustment parameter determined according to the first preset adjustment time, the chamber internal environment and the first vacuum condition all belong to the preset range of the respective parameter.

[0071] Step S105, under the condition that the vacuum chamber is in the first vacuum condition, performing scanning electron microscope alignment on the wafer with successful micro-alignment according to the first mark, the second mark and the third mark, and measuring the feature size of the wafer with successful micro-alignment.

[0072] The surface image of the wafer includes the first mark, the second mark and the third mark. The vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

[0073] In the embodiment of the present application, the third mark can be composed of a metal line etched on a semiconductor substrate. The third mark can be a special pattern such as a cross-shaped pattern, a circular pattern, a rice-shaped pattern, etc. The third mark can also be a special pattern designed on the wafer map which can be distinguished from other surface patterns.

[0074] In the embodiments of the present application, the vacuum environment can reduce the interaction between the electron beam and the wafer, help to protect the wafer and the scanning electron microscope, and help to improve the accuracy of the measured feature size. Therefore, before scanning the wafer by the electron microscope, the gas inside the vacuum chamber needs to be pumped out to establish the required vacuum environment. This process is called vacuum pumping. Vacuum pumping is usually done by a professional vacuum pump. Depending on the specific scanning electron microscope model and operating requirements, different levels of vacuum may be required. During the vacuum pumping process, attention should be paid to prevent excessive pumping to prevent damage to the sample or unnecessary pressure on the instrument.

[0075] In the embodiments of the present application, the scanning electron microscope is a microtopography observation means between a transmission electron microscope and an optical microscope, which can directly use the material properties of the sample (such as a wafer) surface material for micro imaging. The main principle of the scanning electron microscope is to use a very fine high-energy electron beam to scan on the sample (such as a wafer) to excite various physical information. By receiving, amplifying and displaying the imaging of this information, the feature size of the sample (such as a wafer) surface topography is obtained. Among them, the CDSEM can be used to measure the size of the fine pattern formed on the semiconductor wafer.

[0076] In some embodiments of the present application, the wafer map includes a third positioning position, and the third positioning position on the wafer map corresponds to the third mark on the wafer. The above step S105 specifically includes: adjusting the physical position of the wafer so that the third mark is in the field of view of the scanning electron microscope under the condition that the vacuum chamber is in the first vacuum condition, according to the second mark and the relative positional relationship between the second positioning position and the third positioning position, performing scanning electron microscope alignment on the wafer, and measuring the feature size of the wafer.

[0077] In some embodiments of the present application, the wafer map includes a third positioning position, and the third positioning position on the wafer map corresponds to the third mark on the wafer. The above step S105 specifically includes: adjusting the physical position of the wafer so that the third mark is in the field of view of the scanning electron microscope under the condition that the vacuum chamber is in the first vacuum condition, according to the second mark and the relative positional relationship between the second positioning position and the third positioning position, performing scanning electron microscope alignment on the wafer, and measuring the feature size of the wafer.

[0078] It can be understood that the relative positional relationship between the third positioning position and the third mark can be that the third positioning position is at the center of the third mark, or the third positioning position is at any side (left side, right side, upper side, lower side, left upper side, left lower side, right upper side or right lower side) endpoint of the third mark.

[0079] In an embodiment of the present application, the surface pattern of a certain area in the wafer image may have high pattern complexity, high etching difficulty or high importance. Therefore, the position corresponding to the area can be set as the third positioning position to facilitate measuring the characteristic size of the area according to the third positioning position.

[0080] In an embodiment of the present application, after the wafer is processed according to the wafer map, a first mark can be found at the first positioning position, a second mark can be found at the second positioning position, and a third mark can be found at the third positioning position.

[0081] In an embodiment of the present application, the physical position of the wafer is adjusted based on the relative positional relationship between the second positioning position and the third positioning position in the wafer image, and the position of the second mark on the wafer, so that the third mark is in the field of view of the scanning electron microscope, that is, the third mark on the wafer is displayed on the electronic screen, thereby realizing optical microscopic alignment.

[0082] In this way, the approximate position of the third mark can be located through the second positioning position and the third positioning position on the wafer map, and the second mark. Combined with the scale of the wafer map and the size of the electronic screen, the wafer can be aligned with the scanning electron microscope, which can improve the speed of scanning electron microscope alignment.

[0083] In an embodiment of the present application, after the wafer is aligned with a scanning electron microscope, the characteristic dimensions of the wafer are measured. When measuring the characteristic dimensions of the wafer, the electron gun in the CDSEM emits an electron beam to scan the surface of the measurement object (semiconductor), and the electron beam interacts with the atoms on the surface of the measurement object, collects the electron signals excited by the measurement object (including secondary electrons, reflected electrons, backscattered electrons, X-rays and Auger electrons, etc.), and generates a two-dimensional image for representing the surface morphology of the measurement object. Based on the two-dimensional image, the CD of the measurement object can be extracted, such as line width, aperture, sidewall size, and other important geometric parameters for measuring process quality.

[0084] In some embodiments of the present application, after the above step S105, the method further includes: adjusting the internal environment of the vacuum chamber until the internal environment of the chamber meets the production environment conditions.

[0085] It is understandable that the current atmospheric pressure may change due to factors such as altitude, room humidity, room temperature, and whether dust removal is performed. Before determining whether the internal environment of the chamber meets the production environment conditions, it is necessary to obtain the current production environment conditions.

[0086] In some embodiments of the present application, the chamber internal environment in the vacuum chamber is adjusted, specifically comprising: determining a second vacuum adjustment parameter according to the second preset adjustment time, the chamber internal environment and the production environment condition; and adjusting the chamber internal environment in the vacuum chamber according to the second vacuum adjustment parameter until the chamber internal environment meets the production environment condition.

[0087] In the embodiments of the present application, in order to make the pressure difference between the inside and outside of the vacuum chamber smaller when the wafer with the measured feature size is transferred out of the vacuum chamber, so as to avoid the wafer from being damaged or broken, the vacuum chamber needs to be inflated before the wafer with the measured feature size is transferred out of the vacuum chamber, so that the chamber internal environment meets the production environment condition.

[0088] In the embodiments of the present application, the second preset adjustment time can be determined according to the difference between the chamber internal environment and the first vacuum condition. The second vacuum adjustment parameter can include the pumping speed, the flux, the number of times, etc.

[0089] It should be noted that each parameter in the second vacuum condition parameter has a corresponding preset range. The second vacuum adjustment parameter determined according to the second preset adjustment time, the chamber internal environment and the first vacuum condition all belong to the preset range of the respective parameter.

[0090] In this way, when the wafer with the measured feature size is transferred out of the vacuum chamber, the pressure difference between the inside and outside of the vacuum chamber is smaller, so as to avoid the wafer from being damaged or broken, and reduce the wafer loss caused by the measured feature size.

[0091] It should be noted that in order to measure the feature size of the wafer, the alignment process comprises: adjusting the physical position and angle of the wafer according to the first positioning position on the wafer map and the first mark on the wafer, so that the wafer can be observed; adjusting the wafer position according to the first positioning position and the second positioning position on the wafer map and the first mark on the wafer, so that the second mark is in the optical microscopic field of view; adjusting the wafer position according to the first positioning position, the second positioning position and the third positioning position on the wafer map and the second mark on the wafer, so that the third mark is in the scanning electron microscope field of view.

[0092] The beneficial effects brought by the embodiments of the present application include but are not limited to: setting an auxiliary optical microscope in a production environment, the auxiliary optical microscope is used for optical microscopic alignment, i.e. shifting the optical microscopic alignment step during CDSEM measurement to be performed outside the CDSEM vacuum chamber. Before scanning the wafer by the scanning electron microscope, a time-consuming preparation operation (including vacuum pumping and scanning electron microscope alignment) is needed, so as to reduce the optical microscopic alignment preparation operation, i.e. reducing the preparation time which limits the measurement throughput of the CDSEM, improving the measurement throughput of the CDSEM, improving the utilization efficiency of the vacuum chamber, thereby improving the HVM benefit and reducing the HVM cost. Especially, for the case of continuously measuring the feature size, the continuous measurement speed can be improved, the utilization efficiency of the vacuum chamber can be improved, the influence of the wafer with failed microscopic alignment on the continuous measurement speed can be reduced, the HVM benefit can be improved and the HVM cost can be reduced. Moreover, the auxiliary optical microscope is set outside the CDSEM, which is easy to maintain.

[0093] The above mainly introduces the scheme of the embodiments of the present application from the perspective of method. It can be understood that, in combination with various examples described in the embodiments of the present application, those skilled in the art should easily realize that the present application can be realized by hardware, computer software or combination of hardware and computer software. In order to realize the above functions, the feature size measurement device comprises at least one of the hardware structure and the software module for executing the corresponding functions. Whether a certain function is realized by hardware or computer software driven hardware depends on the specific application and design constraints of the technical scheme. Those skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0094] The embodiments of the present application can divide the functional units of the feature size measurement device according to the above method examples. For example, each functional unit can be divided according to each function, or two or more functions can be integrated in one processing unit. The integrated unit can be realized in the form of hardware or software functional unit. It should be noted that the division of units in the embodiments of the present application is illustrative, and is only a logical function division. When actually implemented, there can be another division manner.

[0095] As shown in Figure 3 The feature size measurement device can comprise a first alignment module 31, a second alignment module 32, an acquisition module 33, a processing module 34 and an alignment and measurement module 35.

[0096] The first alignment module 31 is used for pre-aligning the wafer according to the first mark in a production environment; for example, as shown in Figure 1As shown, the first alignment module 31 can be configured to perform step S101.

[0097] The second alignment module 32 is configured to perform optical microscope alignment on the wafer according to the first mark and the second mark under the production environment condition; for example, as shown in Figure 1 As shown, the second alignment module 32 can be configured to perform step S102.

[0098] The acquisition module 33 is configured to acquire an alignment result of the optical microscope alignment, the alignment result being a successful microscope alignment or a failed microscope alignment; for example, as shown in Figure 1 As shown, the acquisition module 33 can be configured to perform step S103.

[0099] The processing module 34 is configured to stop measuring the wafer with the failed microscope alignment, or transfer the wafer with the successful microscope alignment to a vacuum chamber; for example, as shown in Figure 1 As shown, the processing module 34 can be configured to perform step S104.

[0100] The alignment and measurement module 35 is configured to perform scanning electron microscope alignment on the wafer with the successful microscope alignment according to the first mark, the second mark and a third mark, and measure a feature size of the wafer with the successful microscope alignment, when the vacuum chamber is in a first vacuum condition; for example, as shown in Figure 1 As shown, the alignment and measurement module 35 can be configured to perform step S105.

[0101] The surface image of the wafer includes the first mark, the second mark and the third mark.

[0102] In some embodiments, the second alignment module 32 is configured to: acquire a wafer map of the wafer, the wafer map including a first positioning position and a second positioning position, the first positioning position on the wafer map corresponding to the first mark on the wafer, and the second positioning position on the wafer map corresponding to the second mark on the wafer; adjust a physical position of the wafer under the production environment condition, so that the second mark is in a field of view of an optical microscope, according to the first mark and a relative positional relationship between the first positioning position and the second positioning position, to perform optical microscope alignment on the wafer.

[0103] In some embodiments, the wafer map includes a third positioning position, the third positioning position on the wafer map corresponds to the third mark on the wafer; the alignment and measurement module 35 is configured to: when the vacuum chamber is in the first vacuum condition, adjust the physical position of the wafer according to the second mark and the relative positional relationship between the second positioning position and the third positioning position, so that the third mark is in the field of view of a scanning electron microscope, perform scanning electron microscope alignment on the wafer, and measure the feature size of the wafer.

[0104] In some embodiments, as shown in FIG. 1, the device further includes a first adjustment module 36. Figure 3

[0105] The first adjustment module 36 is configured to, after the wafer on which the microscopic alignment is successful is transferred to the vacuum chamber, adjust the chamber internal environment in the vacuum chamber until the chamber internal environment meets the first vacuum condition, and the vacuum degree of the first vacuum condition ranges from 5x10 -6 to 5x10 -7 torr.

[0106] In some embodiments, the first adjustment module is configured to: determine a first vacuum adjustment parameter according to a first preset adjustment time, the chamber internal environment and the first vacuum condition; and adjust the chamber internal environment in the vacuum chamber according to the first vacuum adjustment parameter until the chamber internal environment meets the first vacuum condition.

[0107] In some embodiments, as shown in FIG. 1, the device further includes a second adjustment module 37. Figure 3 The second adjustment module 37 is configured to, after the wafer is aligned by the scanning electron microscope and the feature size of the wafer is measured according to the first mark, the second mark and the third mark when the vacuum chamber is in the first vacuum condition, adjust the chamber internal environment in the vacuum chamber until the chamber internal environment meets the production environment condition.

[0108] In some embodiments, the second adjustment module 37 is configured to: determine a second vacuum adjustment parameter according to a second preset adjustment time, the chamber internal environment and the production environment condition; and adjust the chamber internal environment in the vacuum chamber according to the second vacuum adjustment parameter until the chamber internal environment meets the production environment condition.

[0109] In some embodiments, the vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

[0110] ​With respect to the devices in the above-described embodiments, in which the specific manner in which the various units perform operations has been described in detail in the embodiments relating to the methods, a detailed explanation will not be given here.

[0111] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0112] It is to be understood that the application is not limited to the precise structures hereinabove described and shown in the drawings, for purposes of illustration and description, specific details are set forth in this regard in order to provide a more explicit understanding of the application. The scope of the application is limited only by the claims that follow.

Claims

1. A method of measuring a feature size, characterized by, The method comprises: pre-aligning the wafer according to the first mark under a production environment condition; optical microscope aligning the wafer according to the first mark and the second mark under the production environment condition; obtaining an alignment result of the optical microscope aligning, the alignment result being a successful microscopic alignment and a failed microscopic alignment; stopping measuring the wafer with the failed microscopic alignment, or transferring the wafer with the successful microscopic alignment to a vacuum chamber; under a condition that the vacuum chamber is in a first vacuum condition, scanning electron microscope aligning the wafer with the successful microscopic alignment according to the first mark, the second mark and a third mark, and measuring a feature size of the wafer with the successful microscopic alignment; wherein a surface image of the wafer comprises the first mark, the second mark and the third mark.

2. The method of measuring a feature size according to claim 1, wherein, The optical microscope aligning the wafer according to the first mark and the second mark under the production environment condition comprises: obtaining a wafer map of the wafer, the wafer map comprising a first positioning position and a second positioning position, the first positioning position on the wafer map corresponding to the first mark on the wafer, and the second positioning position on the wafer map corresponding to the second mark on the wafer; under the production environment condition, adjusting a physical position of the wafer according to the first mark, and a relative position relationship between the first positioning position and the second positioning position, so that the second mark is in a field of view of an optical microscope, and the wafer is optically microscope aligned.

3. The method of measuring a feature size according to claim 2, wherein, The wafer map comprises a third positioning position, the third positioning position on the wafer map corresponding to the third mark on the wafer; and the scanning electron microscope aligning the wafer according to the first mark, the second mark and the third mark under the condition that the vacuum chamber is in the first vacuum condition, and measuring the feature size of the wafer comprises: under the condition that the vacuum chamber is in the first vacuum condition, adjusting the physical position of the wafer according to the second mark, and a relative position relationship between the second positioning position and the third positioning position, so that the third mark is in a field of view of a scanning electron microscope, and the wafer is scanning electron microscope aligned and the feature size of the wafer is measured.

4. The method for measuring characteristic dimensions according to claim 1, wherein: After the wafer with the successful microscopic alignment is transferred to the vacuum chamber, the method further comprises: adjusting a chamber internal environment within the vacuum chamber until the chamber internal environment meets the first vacuum condition, the first vacuum condition having a vacuum level ranging from 5 x 10 -6 to 5 x 10 -7 torr.

5. The method of measuring a feature size according to claim 4, wherein, The adjusting the chamber internal environment in the vacuum chamber until the chamber internal environment meets the first vacuum condition comprises: determining a first vacuum adjustment parameter according to a first preset adjustment time, the chamber internal environment and the first vacuum condition; adjusting the chamber internal environment in the vacuum chamber according to the first vacuum adjustment parameter until the chamber internal environment meets the first vacuum condition.

6. The method of measuring a feature size according to claim 1, wherein, After the scanning electron microscope aligning the wafer according to the first mark, the second mark and the third mark under the condition that the vacuum chamber is in the first vacuum condition, and measuring the feature size of the wafer, the method further comprises: adjusting the chamber internal environment in the vacuum chamber until the chamber internal environment meets the production environment condition.

7. The method of measuring a feature size according to claim 6, wherein, The adjusting the chamber internal environment in the vacuum chamber until the chamber internal environment meets the production environment condition comprises: determining a second vacuum adjustment parameter according to a second preset adjustment time, the chamber internal environment and the production environment condition; adjusting the chamber internal environment in the vacuum chamber according to the second vacuum adjustment parameter until the chamber internal environment meets the production environment condition.

8. The method of measuring a feature size according to any of claims 1-7, wherein, The vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

9. A device for measuring a feature size, characterized in that comprise: a first alignment module, a second alignment module, an acquisition module, a processing module and an alignment and measurement module; The first alignment module is configured to pre-align a wafer according to a first mark under a production environment condition. The second alignment module is configured to optically microscope align the wafer according to the first mark and a second mark under the production environment condition. The acquisition module is configured to acquire an alignment result of the optically microscope alignment, the alignment result being a successful microscopic alignment or a failed microscopic alignment. The processing module is configured to stop measuring the wafer with the failed microscopic alignment, or transfer the wafer with the successful microscopic alignment to a vacuum chamber. The alignment and measurement module is configured to scan electron microscope align the wafer with the successful microscopic alignment according to the first mark, the second mark and a third mark under a first vacuum condition of the vacuum chamber, and measure a feature size of the wafer with the successful microscopic alignment. The surface image of the wafer comprises the first mark, the second mark and the third mark.

10. The device for measuring a feature size as claimed in claim 9, characterized in that The second alignment module is configured to: acquire a wafer map of the wafer, the wafer map comprising a first positioning position and a second positioning position, the first positioning position on the wafer map corresponding to the first mark on the wafer, and the second positioning position on the wafer map corresponding to the second mark on the wafer; adjust a physical position of the wafer under the production environment condition according to the first mark and a relative positional relationship between the first positioning position and the second positioning position, so that the second mark is in a field of view of an optical microscope, and optically microscope align the wafer.

11. The device for measuring a feature size as claimed in claim 10, wherein The wafer map comprises a third positioning position, the third positioning position on the wafer map corresponding to the third mark on the wafer; and the alignment and measurement module is configured to: adjust a physical position of the wafer under a first vacuum condition of the vacuum chamber according to the second mark and a relative positional relationship between the second positioning position and the third positioning position, so that the third mark is in a field of view of a scanning electron microscope, scan electron microscope align the wafer, and measure a feature size of the wafer.

12. The device for measuring a feature size as claimed in claim 9, wherein, The device further comprises a first adjustment module. The first adjustment module is configured to adjust the internal environment of the vacuum chamber until the internal environment of the vacuum chamber satisfies the first vacuum condition after the wafer with the successful microscopic alignment is transferred to the vacuum chamber, wherein the first vacuum condition has a vacuum degree ranging from 5x10 -6 to 5x10 -7 torr.

13. The apparatus for measuring a feature size according to claim 12, wherein, The first adjustment module is configured to: determine a first vacuum adjustment parameter according to a first preset adjustment time, the chamber internal environment and the first vacuum condition; According to the first vacuum adjustment parameter, the chamber internal environment in the vacuum chamber is adjusted until the chamber internal environment meets the first vacuum condition.

14. The characteristic dimension measuring device according to claim 9, wherein: The device further comprises a second adjustment module. The second adjustment module is configured to, after performing the scanning electron microscope alignment on the wafer according to the first mark, the second mark and a third mark and measuring the feature size of the wafer, adjust the chamber internal environment in the vacuum chamber until the chamber internal environment meets the production environment condition when the vacuum chamber is in the first vacuum condition.

15. The device for measuring a feature size as claimed in claim 14, characterized in that The second adjustment module is configured to: determine a second vacuum adjustment parameter according to a second preset adjustment time, the chamber internal environment and the production environment condition; adjust the chamber internal environment in the vacuum chamber according to the second vacuum adjustment parameter until the chamber internal environment meets the production environment condition.

16. The apparatus for measuring feature size according to any of claims 9 to 15, wherein, The vacuum chamber is an electron microscope scanning chamber in a feature size scanning electron microscope.

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