CN115527823A

CN115527823A - Objective lens and environmental scanning electron microscope

Info

Publication number: CN115527823A
Application number: CN202211347606.3A
Authority: CN
Inventors: 王鹏飞; 史丽娜; 赵伟霞; 刘俊标; 殷伯华; 王岩; 董增雅; 韩立
Original assignee: Institute of Electrical Engineering of CAS
Current assignee: Institute of Electrical Engineering of CAS
Priority date: 2022-10-31
Filing date: 2022-10-31
Publication date: 2022-12-27

Abstract

The invention relates to the technical field of electron microscopic imaging, and provides an objective lens and an environmental scanning electron microscope, wherein the objective lens at least comprises: the upper pole shoe is provided with a connecting part and a working part, and the working part is provided with a hollow accommodating cavity and is suitable for forming an electron beam channel; the lower pole shoe is connected with the connecting part, the working part is at least partially inserted into the lower pole shoe, and a transition vacuum area is formed in an area between the inner side wall of the lower pole shoe and the outer side wall of the working part; the side wall of the lower pole shoe is provided with a first air exhaust hole which is suitable for vacuumizing the transition vacuum area; the sealing structure is arranged at one end of the lower pole shoe, which is far away from the upper pole shoe, so as to separate the electron beam channel from the transition vacuum area and separate the transition vacuum area from the external environment; the sealing structure is provided with a gas channel and a first through hole for enabling the electron beam to pass through, and the gas channel is communicated with the first through hole and the transition vacuum area. The objective lens can maintain the high vacuum degree of the electron beam channel more easily in the scanning process, thereby improving the scanning effect.

Description

Objective lens and environmental scanning electron microscope

Technical Field

The invention relates to the technical field of electron microscopic imaging, in particular to an objective lens and an environmental scanning electron microscope.

Background

Scanning Electron Microscopy (SEM) is a high-resolution Microscopy instrument used for the characterization and analysis of sample microstructures and is becoming an important tool in many fields of technical research and development. The objective lens is the core focusing element in the SEM and is generally composed of an excitation current coil, an iron shell and a pole piece, where the iron shell and the pole piece are collectively referred to as a magnetic circuit. The objective lens generates a strong magnetic field through the exciting current coil, and the distribution of the strong magnetic field is adjusted through the magnetic circuit structure. The pole shoe structure of the objective lens can enable a strong magnetic field to be intensively distributed near the pole shoe, so that final focusing of the electron beam is realized, the electron beam is reduced and focused on the surface of a sample with a short working distance, and according to the imaging characteristics of the objective lens, the SEM imaging resolution can be effectively improved by reducing the working distance of the objective lens (the distance from the pole shoe under the objective lens to the sample).

The objective lens is a key component for realizing high-resolution imaging of the SEM, and in order to meet the requirement of transmission of electron beams and maintain the performance of the electron beams, the objective lens has higher resolution, and generally higher vacuum degree (generally better than 10) is required in an electron beam channel at a pole shoe of the objective lens ^- ³ Pa) is added. However, when the observed sample contains more liquid, such as hydrate material, biological tissue, plant material, etc., the pressure in the working chamber is too low to change the properties of the sample, and therefore, in order to ensure the scanning effect, the pressure in the working chamber needs to be controlled to be greater than 610Pa (saturated water vapor partial pressure at 0 ℃). However, in this case, the difference in vacuum degree between the electron beam path and the working chamber may be large, and in this case, it is difficult for the SEM to maintain the electron beam path highThe vacuum degree can seriously affect the scanning imaging of the electron beam. Thus, in order to apply the scanning electron microscopy technology more generally to a wide variety of samples, it is necessary to keep the vacuum in the working chamber low enough to maintain the properties and morphological characteristics of the samples to be observed, such as hydrate materials, biological tissues, and plant materials, while maintaining the inside of the objective lens in a high vacuum environment to ensure that the gas molecules do not interfere too much with the quality of the electron beam.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is that when the working chamber environment pressure of the common SEM in the prior art is greater than 610Pa, the electron beam channel is in a low vacuum state, so that high-resolution sample observation cannot be realized, and an objective lens and an environment scanning electron microscope are provided.

In order to solve the technical problems, the technical scheme of the invention is as follows:

an objective lens comprising at least: the upper pole shoe is provided with a connecting part and a working part, and the working part is provided with a hollow accommodating cavity and is suitable for forming an electron beam channel; the lower pole shoe is connected with the connecting part, at least part of the working part is inserted into the lower pole shoe, and a transitional vacuum area is formed in an area between the inner side wall of the lower pole shoe and the outer side wall of the working part; a first air exhaust hole is formed in the side wall of the lower pole shoe and is suitable for vacuumizing the transition vacuum area through the first air exhaust hole; a sealing structure disposed at an end of the lower pole piece remote from the upper pole piece to isolate the electron beam passage from the transitional vacuum region and the transitional vacuum region from an external environment; the sealing structure is provided with a gas channel and a first through hole for enabling electron beams to pass through, and the gas channel is communicated with the first through hole and the transitional vacuum area.

Furthermore, a gap is reserved between one end, far away from the connecting part, of the working part and the inner wall of the lower pole shoe so as to communicate the transition vacuum area with the gas channel.

Further, the sealing structure comprises a sealing ring and a plugging piece; one end of the sealing ring is inserted into the accommodating cavity, the other end of the sealing ring is abutted against the inner bottom wall of the lower pole shoe, and the gas channel is arranged on the sealing ring; a second through hole is formed in the bottom of the lower pole shoe, a groove is formed in the end face, facing the second through hole, of the sealing ring, and the groove penetrates through the other end face of the sealing ring in the height direction of the sealing ring; the plugging piece is inserted into the groove through the second through hole, and the first through hole is formed in the plugging piece.

Further, the plugging piece comprises a cap body and an inserting part which are connected; the first through hole penetrates through the cap body and the inserting part in sequence along the height direction of the plugging piece; the inserting part is inserted into the groove through the second through hole; the cap body is positioned outside the lower pole shoe and is propped against the outer bottom wall of the lower pole shoe.

Further, a first sealing ring is arranged between the cap body and the outer bottom wall of the lower pole piece.

Further, a second sealing ring is arranged between the outer side wall of the sealing ring and the inner side wall of the containing cavity.

Furthermore, the objective lens also comprises an electron beam tube which is inserted into the accommodating cavity, the end part of the electron beam tube in the accommodating cavity extends into the groove, and the tube cavity of the electron beam tube forms the electron beam channel; the tube cavity of the electron beam tube is arranged in line with the first through hole along the irradiation direction of the electron beam.

Further, a third sealing ring is arranged between the outer side wall of the electron beam tube and the groove wall of the groove.

Further, the objective lens also comprises a sleeve and a vacuum pipeline; the sleeve is sleeved outside the lower pole shoe, and the edge of an opening of the sleeve is connected with the edge of the opening of the lower pole shoe through a bolt; and a second air exhaust hole is formed in the position, corresponding to the first air exhaust hole, on the side wall of the sleeve, one end of the vacuum pipeline is connected with the second air exhaust hole, and the other end of the vacuum pipeline is suitable for being connected with an external vacuum pump.

Furthermore, a fourth sealing ring and a fifth sealing ring are arranged between the inner side wall of the sleeve and the outer side wall of the lower pole piece, and the fourth sealing ring and the fifth sealing ring are respectively located on different sides of the second air suction hole along the height direction of the sleeve.

Further, the objective lens also comprises a bracket, a framework and a coil; the bracket is of an annular structure and is sleeved on the working part; the inner ring of the bracket abuts against the outer side wall of the working part, the outer ring of the bracket abuts against the inner side wall of the lower pole shoe, and the transition vacuum area is formed in an area among one surface of the bracket facing the sealing structure, the inner side wall of the lower pole shoe and the outer side wall of the working part; the framework is sleeved on the working part, and the framework abuts against one surface of the support, which is back to the sealing structure; the coil is arranged on the framework along the circumferential direction of the framework.

Furthermore, a sixth sealing ring is arranged between the inner ring of the bracket and the outer side wall of the working part; and a seventh sealing ring is arranged between the outer ring of the bracket and the inner side wall of the lower pole shoe.

Furthermore, the objective lens also comprises a water cooling structure which comprises an adapter, a water inlet pipe and a water outlet pipe; one end of the water inlet pipe is connected with the water inlet of the framework, and the other end of the water inlet pipe is connected with an external cooling water source through the adapter; one end of the water outlet pipe is connected with the water outlet of the framework, and the other end of the water outlet pipe is connected with an external cooling water source through the adapter.

An environment scanning electron microscope at least comprises the objective lens.

Further, the environmental scanning electron microscope at least further comprises: the side wall of the working chamber is provided with a third air exhaust hole and a fourth air exhaust hole; the objective lens at least partially extends into the working chamber, and a vacuum pipeline on the objective lens is communicated with the fourth air suction hole through a pipeline; and the workbench is arranged in the working chamber and is positioned below the objective lens.

The technical scheme of the invention has the following advantages:

according to the objective lens provided by the invention, the transition vacuum area is formed between the upper pole shoe and the lower pole shoe, the electron beam channel is separated from the transition vacuum area through the sealing structure, and the transition vacuum area is separated from the external environment; and the transitional vacuum region is communicated with the electron beam channel through the gas channel. When the electron beam pumping device is used, the vacuum degree of the transitional vacuum area is kept in a proper range through the first air exhaust holes, so that the vacuum degree of the transitional vacuum area is between the electron beam channel and the working chamber; by the arrangement, a buffer area with the vacuum degree between the electron beam channel with the higher vacuum degree and the working chamber with the lower vacuum degree is established, and the difference of the vacuum degrees between the electron beam channel and the transition vacuum area is smaller, so that the high vacuum degree of the electron beam channel can be maintained more easily in the scanning process even if the environmental pressure of the working chamber is greater than 610Pa, high-resolution sample observation is realized, and the scanning effect is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic view of the overall structure of an objective lens in an embodiment of the present invention;

FIG. 2 is a cross-sectional view of FIG. 1;

FIG. 3 is an enlarged view of a portion of FIG. 2;

FIG. 4 is a schematic view of the upper pole piece of the objective lens at one viewing angle in an embodiment of the invention;

FIG. 5 is a schematic view of the upper pole piece of the objective lens at yet another viewing angle in an embodiment of the invention;

FIG. 6 is a schematic view of the lower pole piece of the objective lens in an embodiment of the present invention;

FIG. 7 is a schematic diagram of an electron beam tube in an objective lens in an embodiment of the invention;

FIG. 8 is a schematic view of a kit in an objective lens in an embodiment of the invention;

FIG. 9 is a schematic view of a seal ring in an objective lens in an embodiment of the present invention;

FIG. 10 is a schematic view of a block piece in an objective lens in an embodiment of the present invention;

FIG. 11 is a schematic view of the cross-sectional view of FIG. 10;

FIG. 12 is a schematic view of a holder in an objective lens in an embodiment of the present invention;

FIG. 13 is a schematic diagram of a coil and a bobbin in an objective lens according to an embodiment of the present invention;

fig. 14 is a schematic view of a cooling structure in an objective lens in an embodiment of the present invention;

FIG. 15 is a schematic view of a partial structure of an environmental scanning electron microscope in an embodiment of the invention;

fig. 16 is a schematic diagram of the upper and lower pole pieces in an environmental sem according to an embodiment of the present invention.

1. An objective lens; 2. An upper pole shoe; 3. A lower pole shoe;

4. a kit; 5. An electron beam tube; 6. A water-cooling structure;

7. a sealing structure; 8. A support; 9. A framework;

10. a coil; 11. An electron beam channel; 12. A transitional vacuum zone;

13. an accommodating chamber; 14. A vacuum line; 15. A first air extraction hole;

16. a second air extraction hole; 17. A third air extraction hole; 18. A fourth air extraction hole;

19. a first through hole; 20. A second through hole; 21. A connecting portion;

22. a working part; 23. A seal ring; 24. A blocking member;

25. a first seal ring; 26. A second seal ring; 27. A third seal ring;

28. a fourth seal ring; 29. A fifth seal ring; 30. A sixth seal ring;

31. a seventh seal ring; 32. A water inlet; 33. A water outlet;

34. a water inlet pipe; 35. A water outlet pipe; 36. An adapter;

37. a plug-in part; 38. An airflow aperture; 39. A groove;

40. a gas channel; 41. A working chamber; 42. A work table;

43. a notch; 44. A first diaphragm; 45. A second diaphragm;

46. a third via.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a schematic view of the overall structure of an objective lens in an embodiment of the present invention; FIG. 2 is a cross-sectional view of FIG. 1; FIG. 3 is an enlarged view of a portion of FIG. 2; FIG. 4 is a schematic view of the upper pole piece of the objective lens at one view angle in an embodiment of the invention; FIG. 5 is a schematic view of the upper pole piece of the objective lens at yet another viewing angle in an embodiment of the invention; as shown in fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5, the present embodiment provides an objective lens 1, at least including: an upper pole piece 2 having a connection portion 21 and a working portion 22, the working portion 22 having a hollow accommodating cavity 13 adapted to form an electron beam channel 11; for example, the upper pole piece 2 may have a concentric sleeve-like structure, with the inner sleeve serving as the working portion 22 and the outer sleeve serving as the connecting portion 21. Also, the length of the working part 22 may be greater than that of the connecting part 21, and the distal end of the working part 22 may be tapered.

FIG. 6 is a schematic view of the lower pole piece of the objective lens in an embodiment of the present invention; as shown in fig. 6, the lower pole piece 3 is connected to the connecting portion 21, for example, the lower pole piece 3 may have a funnel shape, an open edge of the lower pole piece 3 may be connected to the upper pole piece 2 by a screw thread, and a sealing ring may be used to seal a contact surface between the two. Wherein the working portion 22 is at least partially inserted within the lower pole piece 3, the region between the inner sidewall of the lower pole piece 3 and the outer sidewall of the working portion 22 forming the transitional vacuum zone 12.

The side wall of the lower pole piece 3 is provided with a first air exhaust hole 15, the transitional vacuum area 12 can be vacuumized through the first air exhaust hole 15, for example, the pressure value in the transitional vacuum area 12 can be controlled at 10 ^-2 Pa-10 ^-1 Pa。

A sealing structure 7 arranged at one end of the lower pole piece 3 far away from the upper pole piece 2 to separate the electron beam channel 11 from the transition vacuum region 12 and simultaneously separate the transition vacuum region 12 from the external environment; the sealing structure 7 has a gas passage 40 and a first through hole 19 for passing the electron beam, and the gas passage 40 communicates the first through hole 19 with the transitional vacuum region 12. In use, the degree of vacuum of the transitional vacuum region 12 is maintained between the degree of vacuum of the electron beam passage 11 and the degree of vacuum of the working chamber 41 through the first pumping holes 15, so that the degree of vacuum of the electron beam passage 11 can be maintained in a higher range more easily without changing the degree of vacuum of the working chamber 41.

In the objective lens 1 provided in this embodiment, a transition vacuum region 12 is formed between the upper pole piece 2 and the lower pole piece 3, the electron beam channel 11 is separated from the transition vacuum region 12 by the sealing structure 7, and the transition vacuum region 12 is separated from the external environment; and the transitional vacuum region 12 is communicated with the electron beam passage 11 through the gas passage 40. When in use, the vacuum degree of the transitional vacuum area 12 is kept in a proper range through the first air extraction holes 15, so that the vacuum degree of the transitional vacuum area 12 is between the electron beam channel 11 and the working chamber 41; with the arrangement, a buffer area with the vacuum degree between the high vacuum degree electron beam channel 11 and the low vacuum degree working chamber 41 is established between the high vacuum degree electron beam channel 11 and the low vacuum degree working chamber 41, and the required pressure difference can be realized by adjusting the diaphragm through the vacuum degree between the electron beam channel 11 and the transitional vacuum area 12 and the vacuum degree between the transitional vacuum area and the working chamber, so that the high vacuum degree of the electron beam channel 11 can be maintained more easily in the scanning process even if the environmental pressure of the working chamber is greater than 610Pa, high-resolution sample observation is realized, and the scanning effect is improved.

A gap 43 is left between one end of the working part 22 far away from the connecting part 21 and the inner wall of the lower pole piece 3 to communicate the transitional vacuum region 12 with the gas channel 40. Further, in order to control the air flow rate in the transient vacuum region 12 and the electron beam passage 11, an air blocking diaphragm may be placed in the gas passage 40 to change the air blocking of the gas passage 40.

FIG. 9 is a schematic view of a seal ring in an objective lens in an embodiment of the present invention; FIG. 10 is a schematic view of a block-out in an objective lens in an embodiment of the invention; as shown in fig. 9 and 10, the sealing structure 7 includes a sealing ring 23 and a blocking piece 24; one end of the sealing ring 23 is inserted in the accommodating cavity 13, and the other end abuts against the inner bottom wall of the lower pole piece 3, for example, the outer side wall of the sealing ring 23 can be fitted to the inner side wall of the accommodating cavity 13 as much as possible, so as to improve the sealing performance.

Wherein the gas passages 40 are provided on the seal ring 23, for example, the gas passages 40 may be provided in a radial direction of the seal ring 23, and the number of the gas passages 40 is not limited to one.

The bottom of the lower pole shoe 3 is provided with a second through hole 20, the end surface of the sealing ring 23 facing the second through hole 20 is provided with a groove 39, and the groove 39 penetrates through the other end surface of the sealing ring 23 along the height direction of the sealing ring 23; the closure 24 is inserted into the groove 39 through the second through hole 20, for example, the outer side wall of the closure 24 fits as closely as possible to the inner side wall of the groove 39 to improve the sealing.

Wherein the first through hole 19 is provided on the block piece 24, for example, the first through hole 19 is provided in the irradiation direction of the electron beam, that is, the gas passage 40 and the pore passage of the first through hole 19 may be provided perpendicularly.

Wherein, the plugging piece 24 comprises a cap body and a plug-in part 37 which are connected; for example, the cap may have a circular plate-like structure, and the insertion portion 37 may have a columnar structure. Wherein, the first through hole 19 sequentially penetrates through the cap body and the plug part 37 along the height direction of the plugging piece 24; the insertion part 37 is inserted into the groove 39 through the second through hole 20; the cap body is located outside the lower pole shoe 3 and is abutted against the outer bottom wall of the lower pole shoe 3, for example, the cap body and the lower pole shoe 3 can be fixed by screws.

Wherein, a first sealing ring 25 is arranged between the cap body and the outer bottom wall of the lower pole shoe 3. For example, an annular groove may be formed in a surface of the cap body facing the lower pole piece 3, the first sealing ring 25 is placed in the annular groove to limit the first sealing ring 25 and prevent the first sealing ring from moving back and forth and left and right, and the cap body is pressed against the lower pole piece 3 to seal a gap between the cap body and the lower pole piece 3 by the first sealing ring 25.

Wherein, a second sealing ring 26 is arranged between the outer side wall of the sealing ring 23 and the inner side wall of the accommodating cavity 13. For example, an annular groove may be provided on the outer side wall of the sealing ring 23 to place the second sealing ring 26 in the annular groove to limit the second sealing ring 26 from moving up and down.

FIG. 7 is a schematic diagram of an electron beam tube in an objective lens in an embodiment of the invention; as shown in fig. 7, the objective lens 1 further includes an electron beam tube 5 inserted into the accommodating chamber 13, and an end of the electron beam tube 5 located in the accommodating chamber 13 extends into the groove 39, and a lumen of the electron beam tube 5 forms the electron beam channel 11, for example, the groove 39 may be a stepped groove, a notch of the groove 39 on one side facing the electron beam tube 5 is larger, and a notch of the groove 39 on one side facing the blocking piece 24 is smaller, so as to prevent the electron beam tube 5 from extending from the other side of the sealing ring 23. Wherein, along the irradiation direction of the electron beam, the lumen of the electron beam tube 5 is arranged in line with the first through hole 19, ensuring that the electron beam can be emitted from the objective lens 1.

The area between the electron beam tube 5 and the receiving chamber 13 can be used for mounting a deflector, astigmatism elimination, etc. for improving the performance of the electron beam.

Wherein, a third sealing ring 27 is arranged between the outer side wall of the electron beam tube 5 and the groove wall of the groove 39. For example, an annular groove may be provided in the groove wall of the groove 39 to place the third seal ring 27 in the annular groove to limit the third seal ring 27 from moving up and down. The second sealing ring 26 and the third sealing ring 27 are arranged to effectively separate the electron beam passage 11 from the excessive vacuum region, so that the gas between the two can only flow through the flow channel formed by the first through hole 19, the gas passage 40 and the notch 43.

FIG. 8 is a schematic diagram of a kit in an objective lens in an embodiment of the invention; as shown in fig. 8, the objective lens 1 further includes a sleeve 4 and a vacuum pipe 14; for example, the sleeve 4 may have a circular truncated cone-shaped structure as a whole, and the sleeve 4 is sleeved outside the lower pole piece 3, so that the sleeve 4 is better attached to the lower pole piece 3. Wherein, the open edge of the sleeve 4 is connected with the open edge of the lower pole shoe 3 through bolts. A second air suction hole 16 is arranged on the side wall of the sleeve 4 at a position corresponding to the first air suction hole 15, one end of the vacuum pipeline 14 is connected with the second air suction hole 16, and the other end is suitable for being connected with an external vacuum pump.

A fourth sealing ring 28 and a fifth sealing ring 29 are arranged between the inner side wall of the sleeve 4 and the outer side wall of the lower pole shoe 3, and the fourth sealing ring 28 and the fifth sealing ring 29 are arranged at intervals along the height direction of the sleeve 4; for example, to improve the sealing effect, the fourth sealing ring 28 may be located above the second suction hole 16, and the fifth sealing ring 29 may be located below the second suction hole 16. Similarly, an annular groove may be provided at a corresponding position on the inner wall of the sleeve 4 for limiting the fourth sealing ring 28 and the fifth sealing ring 29.

FIG. 12 is a schematic view of a holder in an objective lens in an embodiment of the present invention; FIG. 13 is a schematic diagram of a coil and a bobbin in an objective lens according to an embodiment of the present invention; as shown in fig. 12 and 13, the objective lens 1 further includes a holder 8, a frame 9, and a coil 10; the bracket 8 is in an annular structure, and the bracket 8 is sleeved on the working part 22; the inner ring of the bracket 8 is abutted against the outer side wall of the working part 22, the outer ring of the bracket 8 is abutted against the inner side wall of the lower pole piece 3, and a transition vacuum area 12 is formed in an area among one surface of the bracket 8 facing the sealing structure 7, the inner side wall of the lower pole piece 3 and the outer side wall of the working part 22; the framework 9 is sleeved on the working part 22, and the framework 9 is abutted against one surface of the support 8, which is back to the sealing structure 7; the coil 10 is provided on the bobbin 9 in the circumferential direction of the bobbin 9.

Wherein, a sixth sealing ring 30 is arranged between the inner ring of the bracket 8 and the outer side wall of the working part 22; a seventh sealing ring 31 is arranged between the outer ring of the bracket 8 and the inner side wall of the lower pole shoe 3. For example, an annular groove may be provided at a corresponding position of the inner ring side wall of the carrier 8 for limiting the sixth seal ring 30. For example, an annular groove may be provided at a corresponding position on the outer ring side wall of the bracket 8 to limit the seventh seal ring 31.

Fig. 14 is a schematic view of a cooling structure in the objective lens in the embodiment of the present invention; as shown in fig. 14, the objective lens 1 further includes a water cooling structure 6, which includes an adapter 36, a water inlet pipe 34 and a water outlet pipe 35; one end of the water inlet pipe 34 is connected with the water inlet 32 of the framework 9, and the other end is connected with an external cooling water source through a joint 36; one end of the water outlet pipe 35 is connected with the water outlet 33 of the framework 9, and the other end is connected with an external cooling water source through a joint 36. For example, the frame 9 may be provided with a cooling channel inside, and cooling water enters the cooling channel from the water inlet 32 of the frame 9, and flows out of the cooling channel from the water outlet 33 of the frame 9 after absorbing heat. So set up, take away the heat that coil 10 produced through endless constant temperature rivers, maintain objective 1 operating temperature then to keep objective 1 job stabilization nature, reduced the external disturbance that influences the high performance work of electron beam.

Fig. 15 is a schematic view of a partial structure of an environmental sem in an embodiment of the present invention, as shown in fig. 15, another embodiment further provides an environmental sem including at least the objective lens 1.

Wherein, this environment scanning electron microscope still includes at least: the side wall of the working chamber 41 is provided with a third air suction hole 17 and a fourth air suction hole 18; for example, the working chamber 41 may be evacuated by connecting the third suction hole 17 to an external vacuum pump through a pipe.

Wherein, the objective lens 1 at least partially extends into the working chamber 41, the vacuum pipeline 14 on the objective lens 1 is communicated with the fourth pumping hole 18 through a pipeline, and the transition vacuum region 12 is pumped by a vacuum pump, for example, the pressure value in the working chamber 41 can be 133Pa-1000Pa. The transitional vacuum zone 12 has a smaller difference from the vacuum level in the working chamber 41, and thus it is easier to maintain a desired vacuum level. Similarly, the difference between the vacuum degrees in the electron beam channel 11 and the transitional vacuum region 12 is also small, and the required vacuum degree is easier to maintain, thereby being beneficial to improving the scanning effect. For example, the pressure in the electron beam channel 11 may have a value of less than 10 ^-3 Pa。

And a worktable 42 disposed in the working chamber 41 and below the objective lens 1 for placing a sample to be scanned.

In the present application, both the upper pole shoe 2 and the lower pole shoe 3 can be made of a high magnetic conductive material, for example, DT4C can be used as a material for making the upper pole shoe 2 and the lower pole shoe 3, and a similar ferromagnetic material can also be used as needed.

Wherein, the material of external member 4 can be stainless steel or other like non-magnetic material. The taper of the sleeve 4 may be the same as that of the lower pole piece 3, and in order not to affect the sealing effect, the sleeve 4 and the vacuum pipe 14 may be connected by welding.

The material of the electron beam tube 5 can be TA2 or other non-magnetic materials of the same type.

Wherein, the material of the sealing ring 23 can be oxygen-free copper or other non-magnetic materials of the same type. The outer side of the sealing ring 23 is ensured to be matched and positioned with the taper of the lower pole shoe 3, meanwhile, an internal thread can be arranged in the groove 39, and an external thread is arranged on the surface of the insertion part 37 of the plugging piece 24, so that the sealing ring 23 is in threaded connection with the plugging piece 24.

The material of the blocking piece 24 may be pure molybdenum/360, and a plurality of gas flow holes 38 may be disposed on the surface of the insertion portion 37, wherein the gas flow holes 38 communicate the gas channel 40 with the first through hole 19. Wherein, an end of the blocking piece 24 remote from the sealing ring 23 may be provided with a third through hole 46, and the third through hole 46 is communicated with the gas channel 40 through the gas flow hole 38.

For example, three first diaphragm sheets 44 may be provided in the first through hole 19. Similarly, three second diaphragm sheets 45 may be disposed in the third through hole.

Wherein the first diaphragm sheets 44 have the same size and the inner hole diameter is d ₁ Thickness t ₁ . The second diaphragm pieces 45 have the same size and the inner hole diameter is d ₂ Thickness of t ₂ 。

A plurality of first diaphragm sheets 44 are mounted in an overlapping manner in the first through hole 19 of the blocking member 24, and a plurality of second diaphragm sheets 45 are mounted in an overlapping manner in the third through hole 46 of the blocking member 24.

FIG. 11 is a schematic view of the cross-sectional view of FIG. 10; as shown in fig. 11, the number of the first diaphragm and the second diaphragm is given as an example, and the actual number can be adjusted.

The number of first diaphragm plates mounted in the first through-holes 19 substantially determines the pressure difference between the electron beam passage 11 and the intermediate vacuum region 12. Similarly, the number of the second diaphragm sheets 45 mounted to the third through-holes 46 substantially determines the difference between the degree of vacuum in the intermediate vacuum region 12 and the pressure of the working chamber 41.

Derived and calculated according to the formula (1),

P ₁ is the pressure value (Pa) of the high-pressure (low-vacuum) end;

P ₂ a pressure value (Pa) at a low pressure (high vacuum) end;

q is the air output (Pa.L/s) of the vacuum chamber wall;

c is pipeline conductance (L/s);

l is the air resistance length (mm);

d is the diameter (mm) of the air-blocking hole.

When the low vacuum pressure of the vacuum chamber is known, the inner hole diameter and the number of the second diaphragm sheets 45 installed in the third through hole 46 are changed, so that the vacuum degree of the transitional vacuum region 12 is higher than the vacuum degree of the working chamber 41.

Similarly, the vacuum degree of the electron beam channel 11 is higher than that of the transition vacuum region 12 by changing the inner hole aperture and the installation number of the first diaphragm sheets 44 in the first through hole 19, so as to meet the design requirement.

For example, when the number of the second diaphragm sheets 45 in the third through hole 46 is n ₂ Total length n ₂ ×t ₂ ＝L ₂ . If n is ₂ Is 4 pieces, t ₂ 0.5mm, then L ₂ 2mm, the diameter d of the inner hole of the second diaphragm 45 ₂ 1mm, according to experimental test data: when the vacuum value of the working chamber 41 is 700Pa, the corresponding vacuum value of the transition vacuum area 12 is 5Pa; when the vacuum value of the working chamber 41 is 2.7Pa, the corresponding vacuum value of the transition vacuum area 12 is 4.8e-2Pa; it is evident that: the vacuum level of the transitional vacuum zone 12 can be two orders of magnitude higher than the vacuum level of the working chamber 41.

For example, when the number of the first diaphragm sheets 44 in the first through hole 19 is n ₁ Total length n ₁ ×t ₁ ＝L ₁ . If n is ₁ Is 6 tablets, t ₁ 0.5mm, then L ₁ 3mm, the diameter d of the inner hole of the first diaphragm 44 ₂ 0.4mm, according to experimental test data: when the vacuum value of the transitional vacuum area 12 is 1.3e-1Pa, the vacuum value of the corresponding electron beam channel 11 is 9.0e-4Pa; when the vacuum value of the transition vacuum area 12 is 5Pa, the vacuum value of the corresponding electron beam channel 11 is 3.0e-2Pa; it is evident that: the vacuum level of the electron beam path 11 may be two to three orders of magnitude higher than the vacuum level of the transitional vacuum region 12.

Wherein, the electron beam is focused on the sample surface of the worktable 42 in the electron beam channel 11 through the magnetic field generated by the coil 10, the magnetic field generated by the deflection coil 10 is changed by changing the current excitation of the deflection coil 10, and the deflection motion of the electron beam is controlled, so that the electron beam is scanned on the sample surface.

FIG. 16 is a schematic diagram of the upper and lower pole pieces of an environmental scanning electron microscope according to an embodiment of the present invention, and S is a pole piece gap as shown in FIG. 16; d1 is the aperture of the upper pole shoe; d2 is the aperture of the lower pole shoe.

Relationship between working distance and resolution: and designing a pole shoe structure parameter S =4.5mm, wherein the aperture D1=24mm of the upper pole shoe and the aperture D2=5mm of the lower pole shoe. The beam spot diameter was 1.2nm when the working distance was 5mm. The beam spot diameter was 1nm when the working distance was 3 mm. The beam spot diameter was 0.86nm at a working distance of 1 mm. It can be seen that SEM imaging resolution can be effectively improved by reducing the objective lens working distance (the distance from the lower pole piece of the objective lens to the sample).

In conclusion, the objective lens 1 and the environmental scanning electron microscope provided by the application can ensure that the low vacuum or environmental vacuum working environment of the environmental scanning electron microscope is realized under the condition of high resolution performance of the objective lens 1.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the invention.

Claims

1. An objective lens, characterized in that it comprises at least:

the upper pole shoe is provided with a connecting part and a working part, and the working part is provided with a hollow accommodating cavity and is suitable for forming an electron beam channel;

the lower pole shoe is connected with the connecting part, the working part is at least partially inserted into the lower pole shoe, and a transitional vacuum area is formed in an area between the inner side wall of the lower pole shoe and the outer side wall of the working part; a first air exhaust hole is formed in the side wall of the lower pole shoe and is suitable for vacuumizing the transition vacuum area through the first air exhaust hole;

a sealing structure disposed at an end of the lower pole piece remote from the upper pole piece to isolate the electron beam passage from the transitional vacuum region and the transitional vacuum region from an external environment; the sealing structure is provided with a gas channel and a first through hole for enabling an electron beam to pass through, and the gas channel is communicated with the first through hole and the transition vacuum area.

2. The objective of claim 1,

a gap is reserved between one end, far away from the connecting part, of the working part and the inner wall of the lower pole shoe so as to communicate the transition vacuum area with the gas channel.

3. The objective lens of claim 2,

the sealing structure comprises a sealing ring and a plugging piece;

one end of the sealing ring is inserted into the accommodating cavity, the other end of the sealing ring is abutted against the inner bottom wall of the lower pole shoe, and the gas channel is arranged on the sealing ring;

a second through hole is formed in the bottom of the lower pole shoe, a groove is formed in the end face, facing the second through hole, of the sealing ring, and the groove penetrates through the other end face of the sealing ring in the height direction of the sealing ring;

the plugging piece is inserted into the groove through the second through hole, and the first through hole is formed in the plugging piece.

4. The objective of claim 3,

the plugging piece comprises a cap body and an inserting part which are connected;

the first through hole penetrates through the cap body and the inserting part in sequence along the height direction of the plugging piece;

the inserting part is inserted into the groove through the second through hole;

the cap body is positioned outside the lower pole shoe and is propped against the outer bottom wall of the lower pole shoe.

5. The objective of claim 4,

a first sealing ring is arranged between the cap body and the outer bottom wall of the lower pole shoe.

6. The objective of claim 3,

and a second sealing ring is arranged between the outer side wall of the sealing ring and the inner side wall of the accommodating cavity.

7. The objective of any one of claims 3 to 6,

the electron beam tube is inserted into the accommodating cavity, the end part of the electron beam tube, which is positioned in the accommodating cavity, extends into the groove, and a tube cavity of the electron beam tube forms the electron beam channel;

the tube cavity of the electron beam tube is arranged in line with the first through hole along the irradiation direction of the electron beam.

8. The objective of claim 7,

and a third sealing ring is arranged between the outer side wall of the electron beam tube and the groove wall of the groove.

9. The objective of any one of claims 1 to 6,

the device also comprises a kit and a vacuum pipeline;

the sleeve is sleeved outside the lower pole shoe, and the open edge of the sleeve is connected with the open edge of the lower pole shoe through a bolt;

and a second air exhaust hole is formed in the position, corresponding to the first air exhaust hole, on the side wall of the sleeve, one end of the vacuum pipeline is connected with the second air exhaust hole, and the other end of the vacuum pipeline is suitable for being connected with an external vacuum pump.

10. The objective of claim 9,

a fourth sealing ring and a fifth sealing ring are arranged between the inner side wall of the sleeve and the outer side wall of the lower pole shoe, and the fourth sealing ring and the fifth sealing ring are respectively positioned on different sides of the second air exhaust hole in the height direction of the sleeve.

11. The objective of claim 1,

the device also comprises a bracket, a framework and a coil;

the bracket is of an annular structure and is sleeved on the working part;

the inner ring of the bracket abuts against the outer side wall of the working part, the outer ring of the bracket abuts against the inner side wall of the lower pole shoe, and the transition vacuum area is formed in an area among one surface of the bracket facing the sealing structure, the inner side wall of the lower pole shoe and the outer side wall of the working part;

the framework is sleeved on the working part, and the framework abuts against one surface of the support, which is back to the sealing structure;

the coil is arranged on the framework along the circumferential direction of the framework.

12. The objective lens of claim 11,

a sixth sealing ring is arranged between the inner ring of the bracket and the outer side wall of the working part;

and a seventh sealing ring is arranged between the outer ring of the bracket and the inner side wall of the lower pole shoe.

13. The objective of claim 11,

the water cooling structure comprises an adapter, a water inlet pipe and a water outlet pipe;

one end of the water inlet pipe is connected with the water inlet of the framework, and the other end of the water inlet pipe is connected with an external cooling water source through the adapter;

one end of the water outlet pipe is connected with the water outlet of the framework, and the other end of the water outlet pipe is connected with an external cooling water source through the adapter.

14. An environmental scanning electron microscope comprising at least the objective lens of any one of claims 1 to 13.

15. The environmental scanning electron microscope of claim 14, further comprising at least:

the side wall of the working chamber is provided with a third air suction hole and a fourth air suction hole;

the objective lens at least partially extends into the working chamber, and a vacuum pipeline on the objective lens is communicated with the fourth air suction hole through a pipeline;

and the workbench is arranged in the working chamber and is positioned below the objective lens.