Centering mechanism and scanning electron microscope having the same

Abstract

The application relates to a centering mechanism and a scanning electron microscope with the same, which comprises an electron gun cavity and a mounting cavity which are detachably connected in sequence; a first through hole is formed in the electron gun cavity; a first boss is arranged on the side of the electron gun cavity facing the mounting cavity, and the first boss is in an annular structure arranged around the first through hole; a mounting groove is formed in the side of the mounting cavity facing the electron gun cavity; the first boss is placed in the mounting groove; a distance is arranged between the outer side wall of the first boss and the inner side wall of the mounting groove; a mounting hole is formed in the groove bottom of the mounting groove and penetrates through the mounting cavity; a stigmator is mounted at the mounting hole; a first adjusting piece is movably mounted on the side wall of the mounting cavity at the mounting groove; the first adjusting piece penetrates through the side wall of the mounting cavity; a plurality of first adjusting pieces are arranged in a circumferential interval along the mounting groove. The electric field center of the stigmator is coincided with the optical axis center, so that the centering of the stigmator is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductors, and in particular to a centering mechanism and a scanning electron microscope having the same. BACKGROUND

[0002] With the development of semiconductor technology and the progress of process technology, integrated circuit line width is increasingly developed to be fine, and higher and more difficult requirements are put forward for the production process technology of the circuit. Not only submicron lines are etched, but also line defects are controlled within a certain range to ensure the function and yield of the chip. Research shows that when the size of the defect is more than one-third of the feature line width, it becomes a fatal defect that leads to device failure. As the size of the device continues to shrink, the size of the fatal defect becomes smaller and smaller, and the detection of the defect becomes more difficult. Optical detection equipment cannot meet the needs, and electron beam detection equipment overcomes the limitation of optical wavelength, improves the resolution to the nanometer field, and can detect extremely small defects. The core of the electron beam detection equipment is a scanning electron microscope. Among them, the stigmator is an important device in the scanning electron microscope. As the name implies, its function is to eliminate stigmation. The stigmator has a magnetic stigmator and an electrostatic stigmator. Among them, the uniformity of the electrostatic field of the electrostatic stigmator is more difficult to control, and the centering of the stigmator and the optical axis is difficult to grasp. SUMMARY

[0003] Therefore, the present application provides a centering mechanism and a scanning electron microscope having the same, which can make the center of the electric field of the stigmator coincide with the center of the optical axis, thereby realizing the centering of the stigmator.

[0004] According to an aspect of the present application, a centering mechanism is provided for adjusting the relative relationship between the center of the electric field of the stigmator and the center of the optical axis in a scanning electron microscope, comprising an electron gun cavity and a mounting cavity connected in turn.

[0005] A first through hole is formed on the electron gun cavity, and a first boss is arranged on the side of the electron gun cavity facing the mounting cavity. The first boss is in the form of an annular structure arranged around the first through hole.

[0006] A mounting groove is formed on the side of the mounting cavity facing the electron gun cavity. The first boss is placed inside the mounting groove, and a distance is provided between the outer sidewall of the first boss and the inner sidewall of the mounting groove.

[0007] A mounting hole is formed at the groove bottom of the mounting groove, and the mounting hole penetrates through the mounting cavity. The mounting hole is suitable for mounting the stigmator.

[0008] A first adjusting member is movably mounted on the side wall of the mounting cavity where the mounting groove is opened. The first adjusting member is disposed through the side wall of the mounting cavity and is used to push the first boss to move within the mounting groove.

[0009] The first adjusting member is provided in multiple parts, and the multiple first adjusting members are distributed at intervals along the circumference of the mounting groove.

[0010] In one possible implementation, the first boss includes a beveled portion, the sidewalls of which are beveled, the beveled portion is disposed adjacent to the bottom of the mounting groove, and the distance between the beveled portion and the inner sidewall of the mounting groove gradually decreases along a first direction.

[0011] Wherein, the first direction is the direction in which the electron gun cavity points to the mounting cavity;

[0012] All of the first adjusting members abut against the inclined surface.

[0013] In one possible implementation, the first adjusting member is rod-shaped, and the rod of the first adjusting member has external threads.

[0014] The mounting cavity has a first internal threaded hole on the side wall where the mounting groove is opened. The number of the first internal threaded holes is the same as the number of the first adjusting members. The first adjusting members are screwed into the first internal threaded holes one by one.

[0015] In one possible implementation, the first boss further includes a connecting portion;

[0016] The connecting portion is arranged in a ring shape and is arranged circumferentially around the first through hole;

[0017] The bottom end face of the connecting part is provided with an outer chamfer;

[0018] The inclined surface is fixed to the

[0019] On one side of the bottom end face of the connector, the top end face of the beveled portion matches the bottom end face of the connector;

[0020] The bottom of the connecting part is the side of the connecting part adjacent to the bottom of the mounting groove.

[0021] In one possible implementation, a first sealing ring is also included;

[0022] A first sealing groove is provided at the bottom of the mounting groove. The first sealing groove is arranged in a ring shape and is arranged opposite to the first boss. The first sealing groove is arranged around the first through hole in a circumferential direction.

[0023] The first sealing ring is arranged in the first sealing groove and used for sealing the electron gun cavity and the mounting cavity.

[0024] In a possible implementation, a gap is arranged between a side of the first boss facing the bottom of the mounting groove and the bottom of the mounting groove.

[0025] The first sealing ring is in abutment with the first boss.

[0026] In a possible implementation, the objective lens cavity is detachably arranged on a side of the mounting cavity away from the electron gun cavity.

[0027] A second through hole coaxially arranged with the first through hole is arranged on the objective lens cavity, and a placing groove is arranged on an end of the objective lens cavity facing the mounting cavity.

[0028] A second boss is arranged on a side of the mounting cavity facing the placing groove, the second boss is arranged in the placing groove, and a distance is arranged between an outer side wall of the second boss and an inner side wall of the placing groove.

[0029] A second adjusting member is movably arranged on a side wall of the objective lens cavity at the placing groove, and a plurality of second adjusting members are arranged.

[0030] The plurality of second adjusting members are arranged through the side wall of the placing groove and used for pushing the second boss to move in the placing groove.

[0031] In a possible implementation, a second sealing ring is further arranged.

[0032] A second sealing groove is arranged at the bottom of the placing groove, the second sealing groove is annularly arranged, the second sealing groove is oppositely arranged with the second boss, and the second sealing groove is circumferentially arranged around the second through hole.

[0033] The second sealing ring is arranged in the second sealing groove and used for sealing the mounting cavity and the objective lens cavity.

[0034] In a possible implementation, a gap is arranged between a side of the second boss facing the placing groove and the placing groove.

[0035] The second sealing ring is in abutment with the second boss.

[0036] The second boss has the same structure as the first boss.

[0037] In a possible implementation, the mounting hole is a stepped hole, and a hole diameter of a top of the mounting hole is greater than a hole diameter of a bottom of the mounting hole.

[0038] According to another aspect of the present application, there is provided a scanning electron microscope comprising an astigmatism corrector and the centering mechanism of any one of the above;

[0039] The astigmatism corrector is fixedly installed on the mounting hole of the centering mechanism.

[0040] The centering mechanism of the embodiment of the present application is divided into an electron gun cavity and a mounting cavity, wherein the mounting cavity is detachably mounted at the bottom of the electron gun cavity, and the mounting cavity is provided with a mounting hole for mounting the astigmatism corrector. After the electron gun cavity, the mounting cavity and the astigmatism corrector are assembled, at this time, the first boss at the bottom of the electron gun cavity is located in the mounting groove. When the astigmatism corrector is centered with the optical axis, the plurality of first adjusting members on the mounting cavity are adjusted, and the length of the first adjusting members extending into the mounting groove changes, so the movement of the first adjusting members pushes the first boss to move in the mounting groove, thereby driving the entire electron gun cavity to move and adjust. Since the first adjusting members are arranged in multiple directions along the circumference of the mounting groove, the first adjusting members can adjust the position of the electron gun cavity in various directions until the astigmatism corrector on the mounting cavity is centered with the optical axis. In summary, the centering mechanism of the embodiment of the present application adjusts the first adjusting members to fine-tune the electron gun cavity in the mounting groove, so that the center of the electric field of the astigmatism corrector coincides with the center of the optical axis, thereby realizing the centering of the astigmatism corrector. Thus, the best state of the scanning electron microscope is achieved, and the influence of the optical axis deviation on the resolution and the key parameter index of the machine is reduced.

[0041] Other features and aspects of the present application will become apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the present application and serve to explain the principles of the present application.

[0043] Figure 1 An exploded view of the centering mechanism of the embodiment of the present application is shown;

[0044] Figure 2 A partial enlarged view of the centering mechanism of the embodiment of the present application is shown;

[0045] Figure 3 A partial enlarged view of the centering mechanism of the embodiment of the present application is shown;

[0046] Figure 4 A sectional view of the centering mechanism of the embodiment of the present application is shown;

[0047] Figure 5A partial enlarged view of an assembly drawing of an electron gun cavity, a mounting cavity and an objective lens cavity of the centering mechanism of the embodiment of the present application is shown. DETAILED DESCRIPTION

[0048] Various exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numbers in different drawings represent the same or similar elements. Although various aspects of the embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0049] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate relative or positional relationships based on the orientation or position shown in the drawings, and are used only for convenience of description or simplification of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be construed as limiting the present application.

[0050] In addition, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance or an indicated number of technical features. 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 "a plurality of" is two or more, unless otherwise specifically limited.

[0051] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0052] In addition, in order to better illustrate the present application, numerous specific details are given in the following detailed description. Those skilled in the art should understand that the present application can also be implemented without some specific details. In some examples, methods, means, elements and circuits well known to those skilled in the art are not described in detail in order to highlight the main idea of the present application.

[0053] Figure 1 An exploded view of the centering mechanism of the embodiment of the present application is shown. As Figure 1As shown, the centering mechanism is used for installation in a scanning electron microscope, and adjusts the relative position relationship between the electric field center of the stigmator 400 and the optical axis center in the scanning electron microscope, and the centering mechanism comprises: an electron gun cavity 100 and a mounting cavity 200 which are sequentially detachably connected, wherein the electron gun cavity 100 is capable of mounting components such as an electron gun and a condenser lens. The electron gun cavity 100 is provided with a first through hole, and the side of the electron gun cavity 100 facing the mounting cavity 200 is provided with a first boss 110, the first boss 110 is in a ring structure, and the first boss 110 is circumferentially arranged around the first through hole. The side of the mounting cavity 200 facing the electron gun cavity 100 is provided with a mounting groove, when the electron gun cavity 100 and the mounting cavity 200 are assembled, the first boss 110 is located inside the mounting groove, and a distance is provided between the outer side wall of the first boss 110 and the inner side wall of the mounting groove (and the first boss 110 and the mounting groove can be gap-fitted). The bottom of the mounting groove is provided with a mounting hole, the mounting hole penetrates through the mounting cavity 200 and is provided at the mounting hole for mounting the stigmator 400. The side wall of the mounting cavity 200 at the position where the mounting groove is provided is movably provided with a first adjusting piece 300, a plurality of first adjusting pieces 300 are provided, the plurality of first adjusting pieces 300 are spaced apart along the circumference of the mounting groove, and each first adjusting piece 300 penetrates through the side wall of the mounting cavity 200 and is provided for pushing the first boss 110 (and the electron gun cavity 100) to move in the mounting groove.

[0054] The centering mechanism of the embodiment of the present application is divided into two parts of the electron gun cavity 100 and the mounting cavity 200, wherein the mounting cavity 200 is detachably mounted at the bottom of the electron gun cavity 100, and the mounting cavity 200 is provided with a mounting hole for mounting the stigmator 400. After the electron gun cavity 100, the mounting cavity 200 and the stigmator 400 are assembled, at this time, the first boss 110 at the bottom of the electron gun cavity 100 is located in the mounting groove. When the stigmator 400 is centered with the optical axis, the plurality of first adjusting pieces 300 on the mounting cavity 200 are adjusted, the length of the first adjusting piece 300 extending into the mounting groove changes, so the movement of the first adjusting piece 300 pushes the first boss 110 to move in the mounting groove, thereby driving the entire electron gun cavity 100 to move and adjust. Since a plurality of first adjusting pieces 300 are arranged along the circumference of the mounting groove, the first adjusting piece 300 can adjust the position of the electron gun cavity 100 in each direction until the stigmator 400 on the mounting cavity 200 is centered with the optical axis. In summary, the centering mechanism of the embodiment of the present application adjusts the first adjusting piece 300 to drive the electron gun cavity 100 to fine-tune in the mounting groove, so that the electric field center of the stigmator 400 coincides with the optical axis center, thereby realizing the centering of the stigmator 400, and achieving the best state of the scanning electron microscope, and reducing the influence of the optical axis deviation on the resolution and the key parameter index of the machine.

[0055] It should be pointed out here that, in a possible implementation, the electron gun cavity 100 is cylindrical, and the axis of the first through hole is arranged coincidentally with the axis of the electron gun cavity 100. Thus, further facilitating the centering of the stigmator 400 with the optical axis, and optimizing the structure of the embodiment of the application.

[0056] It should be further pointed out here that, in a possible implementation, the mounting cavity 200 is cylindrical, and after the mounting cavity 200 is assembled with the electron gun cavity 100, the outer side wall of the mounting cavity 200 is arranged flush with the outer side wall of the electron gun cavity 100. The mounting slot is circular slot-shaped, and the axis of the mounting slot is arranged coincidentally with the axis of the first through hole, and the axis of the mounting hole is arranged coincidentally with the axis of the first through hole. Thus, the stigmator 400 is more easily centered with the optical axis, and the centering is more accurate.

[0057] It should be further pointed out here that, in a possible implementation, the top end face of the mounting cavity 200 is arranged parallel to the bottom end face of the electron gun cavity 100, and after the electron gun cavity 100 is assembled with the mounting cavity 200, the bottom flat end face of the electron gun cavity 100 is arranged abuttingly with the top end face of the mounting cavity 200. The mounting hole includes a first hole and a second hole arranged in sequence in a stepped hole shape, wherein the first hole is arranged adjacent to the electron gun cavity 100, and the hole bottom end face of the first hole is arranged parallel to the top end face of the mounting cavity 200. Thus, the parallelism of the contact surface of the electron gun cavity 100 and the mounting cavity 200 is improved, and the parallelism of the contact surface of the mounting cavity 200 and the stigmator 400 is also improved, reducing the form and position tolerances, preventing the optical axis from deviating, and reducing the installation error.

[0058] As shown in Figure 1 , Figure 2 or Figure 4 , in a possible implementation, the first boss 110 includes a beveled portion 112, the side wall of the beveled portion 112 is arranged in a bevel, the beveled portion 112 is arranged adjacent to the slot bottom of the mounting slot, and the distance between the beveled portion 112 and the inner side wall of the mounting slot gradually decreases along a first direction. Wherein the first direction is the direction in which the electron gun cavity points to the mounting cavity 200, and each first adjusting piece 300 abuts against the beveled portion 112. Since the first adjusting piece 300 abuts against the first boss 110, and the force receiving portion of the first boss 110 is the beveled portion 112, the first adjusting piece 300 will exert a downward component force on the beveled portion 112 when it acts, so that the beveled portion 112 will not be tilted up when it moves, ensuring the sealing effect.

[0059] Further, in a possible implementation, the first boss 110 further comprises a connecting portion 111, wherein the connecting portion 111 is annularly arranged, the connecting portion 111 is arranged circumferentially around the first through hole, and the bottom end surface of the connecting portion 111 is provided with an outer chamfer. The inclined surface portion 112 is fixed on one side of the bottom end surface of the connecting portion 111, and the top end surface of the inclined surface portion 112 matches the bottom end surface of the connecting portion 111. The bottom of the connecting portion 111 is the side of the connecting portion 111 adjacent to the bottom of the mounting groove. Thus, the structure of the first boss 110 is matched with the structure of the first adjusting member 300, and the warping of the first boss 110 during movement is further prevented.

[0060] Here, it should be pointed out that, in a possible implementation, the connecting portion 111, the inclined surface portion 112, and the electron gun cavity 100 can be integrally formed. Thus, the manufacturing of the electron gun cavity 100 is facilitated.

[0061] In a possible implementation, a first sealing ring 500 is further included, and a first sealing groove is formed at the bottom of the mounting groove, the first sealing groove is annular, and the first sealing groove is arranged opposite to the first boss 110 and circumferentially around the first through hole. The first sealing ring 500 is installed in the first sealing groove, and the first sealing ring 500 is used to seal the electron gun cavity 100 and the mounting cavity 200. Thus, the sealing performance of the electron gun cavity 100 and the mounting cavity 200 is increased.

[0062] Further, in a possible implementation, after the electron gun cavity 100 and the mounting cavity 200 are assembled, a gap is provided between the first boss 110 and the bottom of the mounting groove, and the first sealing ring 500 abuts against the first boss 110. Thus, without affecting the sealing effect, the first boss 110 and the bottom of the mounting groove are avoided as the contact surface, the tolerance uncertainty of the sealing ring itself is avoided, the optical axis offset is further prevented, and the installation error is reduced.

[0063] In a possible implementation, the first adjusting rod member is rod-shaped, and the rod body of the first adjusting member 300 is provided with external threads. The side wall of the mounting cavity 200 at the mounting groove is provided with first internal thread holes, the number of the first internal thread holes is the same as the number of the first adjusting members 300, and the first adjusting members 300 are threadedly connected with the first internal thread holes one by one. Thus, the position of the electron gun cavity 100 can be adjusted by rotating the first adjusting member 300, and the centering of the stigmator 400 and the optical axis is more convenient.

[0064] As Figure 1 , Figure 2 , Figure 3 or Figure 4As shown, further, in a possible implementation, the objective lens cavity 600 is detachably mounted on the side of the mounting cavity 200 away from the electron gun cavity 100. The objective lens cavity 600 is provided with a second through hole coaxially arranged with the first through hole, and an end of the objective lens cavity 600 facing the mounting cavity 200 is provided with a placement groove. The side of the mounting cavity 200 facing the placement groove is provided with a second boss 210, the second boss 210 is placed in the placement groove, and a distance is provided between the outer side wall of the second boss 210 and the inner side wall of the placement groove. The side wall of the objective lens cavity 600 at the placement groove is movably provided with a second adjusting member 700, and the second adjusting member 700 is provided in plurality, and the plurality of second adjusting members 700 are distributed along the circumference of the placement groove. The plurality of second adjusting members 700 are arranged through the side wall of the placement groove, and the end of the plurality of second adjusting members 700 facing the second boss 210 is connected with the second boss 210, for pushing the mounting cavity 200 to move in the placement groove. Through the above structure, the second adjusting member 700 is adjusted to drive the second boss 210 to move in the placement groove, so that the position of the mounting cavity 200 can be adjusted, and the stigmator 400 on the mounting cavity 200 is centered with the objective lens.

[0065] Here, it should be pointed out that, in a possible implementation, the second through hole is coaxially arranged with the first through hole, the objective lens cavity 600 is cylindrical, the outer wall of the objective lens cavity 600 is flush with the outer wall of the mounting cavity 200, and the aperture of the second through hole is the same as the aperture of the first through hole. Thus, the structure of the embodiment of the application is further optimized.

[0066] Here, it should be further pointed out that, in a possible implementation, the side wall of the second boss 210 is parallelly arranged with the side wall of the first boss 110. The top end face of the objective lens cavity 600 is parallelly arranged with the bottom end face of the mounting cavity 200, and after the objective lens cavity 600 and the mounting cavity 200 are assembled, the top end face of the objective lens cavity 600 is coincidentally arranged with the bottom end face of the mounting cavity 200. The top end face of the objective lens cavity 600 is parallelly arranged with the groove bottom of the mounting groove of the mounting cavity 200. Thus, the form and position tolerances are further eliminated.

[0067] It should be pointed out here that, in a possible implementation, a plurality of first bolt holes are formed on the electron gun cavity 100, the plurality of first bolt holes are all arranged through the electron gun cavity 100, and the plurality of first bolt holes are distributed around the axis of the electron gun cavity 100, and the plurality of first bolt holes are all arranged adjacent to the edge position of the electron gun cavity 100. A plurality of second bolt holes are formed on the mounting cavity 200, the number of the second bolt holes is the same as that of the first bolt holes, and the second bolt holes are arranged one by one corresponding to the first bolt holes, and the second bolt holes are all arranged through the mounting cavity 200. A plurality of third bolt holes are formed on the objective lens cavity 600, the number of the third bolt holes is the same as that of the first bolt holes, and the third bolt holes are arranged one by one corresponding to the first bolt holes. The electron cavity, the mounting cavity 200 and the objective lens cavity 600 are connected by bolts (the bolts are screwed with the first bolt holes, the second bolt holes and the third bolt holes in turn). Thus, after the electron gun cavity 100 and the mounting cavity 200 are adjusted, the bolts can be used for locking to prevent movement and ensure that the relative position does not change.

[0068] Further, a second sealing ring 800 is further included, a second sealing groove is formed at the groove bottom of the placement groove, the second sealing groove is arranged in a ring shape, the second sealing groove is arranged opposite to the second prime number boss 210, and the second sealing groove is arranged circumferentially around the second through hole. The second sealing ring 800 is installed in the second sealing groove and is used for sealing the mounting cavity 200 and the objective lens cavity 600.

[0069] In a possible implementation, a gap is arranged between the side of the second boss 210 facing the placement groove and the placement groove, and the second sealing ring 800 abuts against the second boss 210. The structure of the second convex strip is the same as that of the first boss 110. Thus, the second boss 210 (and the objective lens cavity 600) can be prevented from being warped during movement, so that the sealing performance is ensured.

[0070] In a possible implementation, the mounting hole is in a stepped hole shape, and the top hole diameter of the mounting hole is greater than the bottom hole diameter of the mounting hole. By arranging the mounting hole in a stepped hole shape, a mounting position is provided for the stigmator 400, and it should be pointed out here that the stigmator 400 is completely arranged in the mounting hole.

[0071] As Figure 1 or Figure 5As shown, based on the centering mechanism of any of the above, the present disclosure also provides a scanning electron microscope. Wherein, the scanning electron microscope of the present disclosure comprises the centering mechanism of any of the above and the stigmator 400. Wherein, the stigmator 400 is fixedly installed on the mounting hole of the centering mechanism, and the centering mechanism of any of the above is installed on the scanning electron microscope, thereby facilitating the centering of the stigmator 400 and the optical axis. Wherein, the electron gun and the condenser lens can be installed on the electron gun cavity 100, and the objective aperture, the detector, the objective lens and the deflector can be installed on the objective lens cavity 600.

[0072] Here, it should be pointed out that in one possible implementation, the stigmator 400 can include a base 410 and a plurality of polar plates 420, the base 410 is hollow cylindrical, and the base 410 is used to be fixedly installed on the centering mechanism. The plurality of polar plates 420 are provided, and the plurality of polar plates 420 are arranged in sequence around the inner wall of the base 410, and the plurality of polar plates 420 are fixedly connected with the bottom plate. One end of the plurality of polar plates 420 extends out of the base 410. Thus, by providing the plurality of polar plates 420, the plurality of polar plates 420 are arranged in a ring structure around the inner wall of the base 410, thereby facilitating the centering of the stigmator 400 and the optical axis.

[0073] Here, it should be pointed out that in one possible implementation, the base 410 is cylindrical, and the base 410 is provided with a baffle plate at one side end face, and the baffle plate is circumferentially arranged around the outer wall of the base 410. A plurality of fixing holes are formed in the baffle plate for fixing the stigmator 400 to be fixedly installed on the mounting cavity.

[0074] Here, it should be pointed out that in one possible implementation, the polar plate 420 includes an extension part 412 and a fixed part 411, wherein the fixed part 411 is an arc-shaped plate matching the inner wall of the bottom plate. The fixed part 411 is arranged flush with the baffle plate adjacent to one side end face of the fixed part 411, and the extension part 412 is fixed at the end face adjacent to the baffle plate of the fixed part 411. The extension plate is arc-shaped, and the end face area of the extension part 412 is larger than the end face area of the fixed part 411, so that the extension part 412 is arranged in abutment with the baffle plate. Here, it should be pointed out that the side of the fixed part 411 facing the axis of the base 410 is flush with the side of the extension part 412 facing the axis of the base 410. Thus, the structure of the stigmator 400 of the present application is optimized.

[0075] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. It is intended that the scope of the application be defined by the scope of the patent and by the claims as allowed by the patent office, which can include adaptations based on the description, equivalents, and / or substitutions of elements individually or collectively to the entire disclosure.

Claims

1. A centering mechanism characterized in that, A device for adjusting the relative position between the electric field center of an anastigmat and the optical axis center in a scanning electron microscope, comprising an electron gun cavity and a mounting cavity connected in sequence; The top end surface of the mounting cavity is arranged in parallel with the bottom end surface of the electron gun cavity, and the bottom flat end surface of the electron gun cavity is arranged in abutment with the top end surface of the mounting cavity after the electron gun cavity and the mounting cavity are assembled; A first through hole is formed in the electron gun cavity, and a first boss is arranged on the side of the electron gun cavity facing the mounting cavity, and the first boss is in the form of a ring structure arranged around the first through hole; A mounting groove is formed in the side of the mounting cavity facing the electron gun cavity, the first boss is placed inside the mounting groove, and a distance is provided between the outer side wall of the first boss and the inner side wall of the mounting groove; An installation hole is formed in the groove bottom of the mounting groove, the installation hole penetrates through the mounting cavity, and the installation hole is suitable for mounting the anastigmat; the installation hole is in the form of a stepped hole, the hole diameter of the top of the installation hole is larger than the hole diameter of the bottom of the installation hole, and the installation hole comprises a first hole and a second hole, wherein the first hole is arranged adjacent to the electron gun cavity, and the hole bottom end surface of the first hole is arranged in parallel with the top end surface of the mounting cavity, so that the anastigmat is completely placed in the installation hole; A first adjusting member is movably arranged on the side wall of the mounting cavity where the mounting groove is formed, the first adjusting member penetrates through the side wall of the mounting cavity, and the first adjusting member is used to push the first boss to move in the mounting groove; A plurality of first adjusting members are provided, and the plurality of first adjusting members are distributed in a circumferential direction of the mounting groove.

2. The centering mechanism of claim 1, wherein, The first boss comprises a bevel portion, the side wall of the bevel portion is arranged in the form of a bevel, the bevel portion is arranged adjacent to the groove bottom of the mounting groove, and the distance between the bevel portion and the inner side wall of the mounting groove gradually decreases in a first direction; The first direction is the direction in which the electron gun cavity points to the mounting cavity; The plurality of first adjusting members are in abutment with the bevel portion.

3. The centering mechanism of claim 1, wherein, The first adjusting member is in the form of a rod, and an external thread is formed on the rod body of the first adjusting member; A first internal thread hole is formed in the side wall of the mounting cavity where the mounting groove is formed, the number of the first internal thread holes is the same as the number of the first adjusting members, and the first adjusting members are in one-to-one correspondence with the first internal thread holes.

4. The centering mechanism of claim 2, wherein, The first boss further comprises a connecting portion; The connecting portion is arranged in the form of a ring and is arranged in a circumferential direction around the first through hole; An outer chamfer is arranged on the bottom end surface of the connecting portion; The bevel portion is fixed on one side of the bottom end surface of the connecting portion, and the top end surface of the bevel portion matches the bottom end surface of the connecting portion; The bottom of the connecting portion is on one side of the groove bottom of the mounting groove. A first sealing ring is further provided; 5. The centering mechanism of claim 1, wherein, A first sealing groove is formed in the groove bottom of the mounting groove, the first sealing groove is arranged in the form of a ring, the first sealing groove is arranged opposite to the first boss, and the first sealing groove is arranged in a circumferential direction around the first through hole; ​ The first sealing ring is arranged in the first sealing groove and used for sealing the electron gun cavity and the mounting cavity.

6. The centering mechanism of claim 5, wherein, The first protrusion is provided with a gap between one side of the first protrusion facing the bottom of the mounting groove and the bottom of the mounting groove. The first sealing ring is in abutment with the first protrusion.

7. The centering mechanism according to any one of claims 1 to 6, characterized in that An objective lens cavity is detachably arranged on one side of the mounting cavity away from the electron gun cavity. A second through hole coaxially arranged with the first through hole is arranged on the objective lens cavity. An accommodation groove is arranged on one end of the objective lens cavity facing the mounting cavity. A second protrusion is arranged on one side of the mounting cavity facing the accommodation groove. The second protrusion is arranged in the accommodation groove.

8. The centering mechanism of claim 7, wherein, An outer side wall of the second protrusion is provided with a distance from an inner side wall of the accommodation groove. Second adjusting members are movably arranged on the side wall of the objective lens cavity at the accommodation groove. The second adjusting members are provided in plurality and are distributed along the circumference of the accommodation groove.

9. The centering mechanism of claim 8, wherein, The second adjusting members are arranged through the side wall of the accommodation groove and used for pushing the second protrusion to move in the accommodation groove. A second sealing ring is further included. A second sealing groove is arranged at the bottom of the accommodation groove.

10. A scanning electron microscope characterized by, The second sealing groove is annularly arranged and oppositely arranged with the second protrusion. The second sealing groove is circumferentially arranged around the second through hole. The second sealing ring is arranged in the second sealing groove and used for sealing the mounting cavity and the objective lens cavity. The second protrusion is provided with a gap between one side of the second protrusion facing the accommodation groove and the accommodation groove. The second sealing ring is in abutment with the second protrusion. The structure of the second protrusion is the same as that of the first protrusion. The centering mechanism is further provided with an anastigmat. The anastigmat is fixedly arranged on the mounting hole of the centering mechanism.

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