CN110491764B

CN110491764B - Magnetic yoke assembly of sputtering ion pump

Info

Publication number: CN110491764B
Application number: CN201910822526.0A
Authority: CN
Inventors: 窦仁超; 崔寓淏; 闫荣鑫; 孙立臣; 孟冬辉; 喻新发; 洪晓鹏; 窦威; 周雪茜
Original assignee: Beijing Institute of Spacecraft Environment Engineering
Current assignee: Beijing Institute of Spacecraft Environment Engineering
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2022-03-29
Anticipated expiration: 2039-09-02
Also published as: CN110491764A

Abstract

The invention discloses a magnetic yoke assembly of a sputtering ion pump, which comprises magnetic steels, yokes and stainless steel positioning plates, wherein the magnetic steels are divided into two groups, 3 layers of magnetic steels are respectively arranged between the two yokes, the two layers are arranged in the middle, and the upper layer and the lower layer are respectively arranged.

Description

Magnetic yoke assembly of sputtering ion pump

Technical Field

The invention belongs to the technical field of accessories of sputtering ion pumps, and particularly relates to a novel magnetic yoke assembly which provides a uniform, stable and high-strength magnetic field for a two-pole sputtering ion pump or a three-pole sputtering ion pump.

Background

The sputtering ion pump has the advantages of cleanness and no oil, and is a vacuum obtaining device for obtaining the mainstream of ultrahigh vacuum and ultrahigh vacuum at home and abroad at present. At present, the development of moon exploration engineering and subsequent deep space exploration tasks in China puts forward new requirements on the simulation of the ultrahigh vacuum environment, and the high-sensitivity mass spectrometry technology also depends on the ultrahigh vacuum environment. In addition, with the continuous enhancement of comprehensive national power in China, the demands of the fields of high-energy physics, nuclear industry, analytical instruments, medical equipment and the like on the sputtering ion pump are rapidly increased. Although there are mature sputtering ion pump products at home and abroad, the problem of poor pumping speed of inert gas and hydrogen of the ion pump is not solved, and the performance index of the home-made ion pump has a great gap with the international high-end brand.

The sputtering ion pump is manufactured according to the penning discharge principle, the internal structure of the sputtering ion pump is generally provided with two titanium cathode plates, a plurality of anodes arranged into a honeycomb cylinder shape are arranged between the cathode plates, when a power supply supplies power to the ion pump, a higher electric field is generated between the cathodes and the anodes which are very close to each other, electrons in the space are accelerated and bombard neutral gas molecules, and the neutral gas molecules are ionized to generate positive ions and new electrons. The positive ions are accelerated and bombard the titanium cathode plate, titanium atoms are sputtered out, and fresh titanium atoms have very strong binding capacity and can physically adsorb and chemically react with gas molecules in the space. Meanwhile, titanium atoms can form a layer of titanium film on the surface of the wall of the device, and the continuously regenerated titanium film can bury the gas molecules adsorbed on the surface of the wall of the device. So that the gas molecules in the space are continuously reduced, and the purpose of evacuation is further realized. The magnetic field applied at both ends of the cathode is to increase the electron movement path, so that there is more chance of collision with neutral gas molecules. In order to reduce the loss of magnetic lines of force, it is generally necessary to mount an annular yoke, generally pure iron, on the two magnetic steels.

The performance of the sputtering ion pump is mainly determined by the pump body structure, the magnetic yoke structure, the selected materials, the process treatment in the production process, the power supply control system and the like of the ion pump. The magnetic yoke structure can directly influence the uniformity of a magnetic field between two titanium cathodes, the intensity of the magnetic field, the electron collision efficiency, the weight of the ion pump, the pumping speed mass ratio of the ion pump, the processing production cost and other important parameters. The conventional ring yoke has a significant disadvantage: the annular yoke greatly increases the weight of the ion pump, and also increases the production cost; the magnetic field in the air extraction area is uneven, only the magnetic field at the central position can maintain penning discharge capability, and the marginal magnetic field intensity of the air extraction unit is seriously attenuated and is not enough to maintain penning discharge, so that the air extraction capability of the ion pump is seriously reduced, and the performance index of the ion pump is further reduced. Therefore, it is highly desirable to provide a yoke assembly that is stable and has a high magnetic field strength.

Disclosure of Invention

The invention aims to provide a magnetic yoke assembly of a sputtering ion pump, which provides a stable and high-strength magnetic field for a two-pole/three-pole type sputtering ion pump.

The invention adopts the following technical scheme:

the magnetic yoke assembly of the sputtering ion pump comprises an even number of magnetic steels, two yokes, a positioning piece and a middle layer fixing piece, wherein the magnetic steels have the same size and magnetic energy product, the left side and the right side of a pump shell of the well-shaped sputtering ion pump are respectively provided with a vertical yoke, the yokes respectively form a space which is used for containing the magnetic steels and is in vertical axial symmetry with one side of the well shape, a concave part in the middle of the well shape is in a central space which is used for containing a plurality of magnetic steels in an up-and-down axial symmetry mode, the magnetic steels are respectively arranged in the space at the two sides and the central space in the up-and-down direction, the magnetic steels are respectively contained at the two sides, the central space contains a plurality of magnetic steels, the magnetic yokes at the left side and the right side of the pump shell are in a symmetrical structure, parts are completely consistent in composition, and all the magnetic steels and the magnetic yokes form a closed magnetic line loop along the axial direction outside the pump shell.

The magnetic yoke on one side of the pump shell is formed by an upper magnetic steel, a lower magnetic steel, a yoke and two positioning plates, the magnetic poles of the two magnetic steels which are horizontally placed on the yoke are opposite in direction, the magnetic steels are tightly adsorbed on the yoke by virtue of magnetic attraction, the fastening or the limitation of the magnetic steels on the flat plate of the yoke in the horizontal direction is completed through the positioning plates, and the positioning plates are screwed on the plane of the yoke through screws.

Furthermore, the magnetic poles of the two pieces of magnetic steel on the yoke iron flat plate in the direction vertical to the horizontal plane are opposite to each other, namely one piece is an N pole, and the other piece is an S pole.

And the magnetic yoke structure on the other side of the pump shell is completely consistent with the magnetic yoke structure on the left side.

The magnetic yoke of the concave part in the middle of the well-shaped pump shell is positioned in the middle inner space of the pump shell, the magnetic yoke of the middle layer is composed of even number of pieces of magnetic steel and middle layer fixing pieces with corresponding quantity, the magnetic yoke of the middle layer is divided into an upper group and a lower group, each group is formed by overlapping half of the even number of pieces of magnetic steel, and the middle layer fixing pieces with corresponding quantity are fastened in the concave middle space of the pump shell.

Wherein, one or more groups of air extraction units are arranged in the adjacent protruding spaces at two sides of the upper and lower concave middle space of the pump shell.

Further, the pumping unit may be a two-pole pumping unit or a three-pole pumping unit.

The material of the pump shell must be non-magnetic steel or low-magnetic steel, such as 316L stainless steel.

Preferably, a plurality of blocks of magnetic steel are eight blocks of magnetic steel, and the installation order of magnetic poles of magnetic steel should satisfy: the directions of the magnetic lines of the upper concave type and the lower concave type of the pump shell are opposite. For example: magnetic lines of force are supposed to be emitted from the N pole of the magnetic steel below the left magnetic yoke and penetrate through the pump shell to reach the two pieces of magnetic steel below the middle magnetic yoke; then the magnetic steel is sent out from the N pole of the magnetic steel in the middle layer, penetrates through the pump shell and reaches the S pole of the magnetic steel below the magnetic yoke on the right side; magnetic force lines of the magnetic steel below the right magnetic yoke are conducted to the magnetic steel above the right magnetic yoke from the yoke iron; the magnetic steel above the right magnetic yoke emits magnetic force lines from the N pole to successively reach the upper magnetic steel of the middle magnetic yoke and the upper magnetic steel of the left magnetic yoke, and then is conducted to the lower magnetic steel of the left magnetic yoke through the yoke iron of the left magnetic yoke; eight pieces of magnetic steel and two pieces of yoke iron on the magnetic yoke component form a closed loop of magnetic force lines in a shape of Chinese character kou.

The magnetic steel can be selected from ferrite, cobalt, rubidium, iron and boron, the positioning plate is made of 316L stainless steel, and the yoke is made of pure iron, such as DT 4.

The magnetic yoke assembly can improve the pumping speed weight ratio of the ion pump, simplify the structure of the pump, facilitate processing, and improve the magnetic field intensity of the air pumping unit and make the magnetic field more uniform.

The advantages of the invention include the following aspects:

1. the magnetic field intensity of the air extraction unit installed in four blank areas formed by the eight pieces of magnetic steel in the horizontal direction is large, the magnetic field is more uniform relative to a magnetic field area formed by the two pieces of magnetic steel, and the pumping speed of the ion pump can be increased;

2. two groups of magnetic steels in opposite directions and two DT4 soft irons can be combined into a closed magnetic circuit, thereby reducing the leakage of magnetic energy, reducing the usage amount of yoke irons, increasing the pumping space of the pump, being capable of placing more pumping units and further increasing the pumping speed;

3. compared with the common annular yoke, the two yokes can well reduce the weight of the ion pump and improve the ratio of the pumping speed to the pump weight.

Drawings

Fig. 1 is a schematic view of an overall structure of a yoke assembly according to an embodiment of the present invention.

Wherein: 1. a yoke; 2. a pump housing; 3. fixing the nut hole; 4. a screw; 5. magnetic lines of force; 6. an air extraction unit; 7. magnetic steel; 8. magnetic steel; 9. magnetic steel; 10. magnetic steel; 11. magnetic steel, 12, magnetic steel; 13. magnetic steel; 14. and (5) magnetic steel.

Fig. 2 is a schematic structural view of a left yoke of a pump case according to an embodiment of the present invention.

Wherein: 15. positioning plates; 16. and (7) installing holes.

Fig. 3 is a three-dimensional structure diagram of a yoke assembly according to an embodiment of the present invention.

Wherein: 17. is a middle layer magnetic steel positioning plate.

Fig. 4 is a schematic diagram of a reference line in the simulation of the magnetic yoke according to the present invention.

Wherein: 18. the X axis is vertical to the horizontal plane direction; 19. the Y axis is in the vertical direction.

FIG. 5 is a diagram of the magnetic field strength variation in the broadside X-axis direction between two pieces of magnetic steel for installing the air extraction unit.

FIG. 6 is a diagram showing the variation of magnetic field intensity in the Y-axis direction of the long side between two pieces of magnetic steel according to the present invention.

Detailed Description

The following is a description of the present invention, which is further illustrated by the following embodiments. The following detailed description, of course, is merely illustrative of various aspects of the invention and is not to be construed as limiting the scope of the invention.

Generally, a yoke used in a sputter ion pump has a ring shape, and two pieces of magnetic steel are contained inside the ring. The blank area in the middle of two magnet steels is installed and is bled the unit. In a specific embodiment of the invention, eight pieces of magnetic steel are arranged between two yokes and divided into three layers. Eight pieces of magnetic steel can form four groups of ion pump pumping units.

Referring to fig. 1, fig. 1 is a schematic view of an overall structure of a yoke assembly according to an embodiment of the present invention. Wherein, the magnetic yoke assembly of the sputter ion pump, including eight rubidium iron

boron magnet steel

7, 8, 9, 10 and 11, 12, 13, 14, two DT4 yoke 1, spacer and intermediate layer stator, wherein rubidium iron

boron magnet steel

7, 8, 9, 10 and 11, 12, 13, 14 have the same size and magnetic energy product, wherein, the pump case 2 left and right sides of the well-shaped sputter ion pump set up a vertical yoke 1 respectively, yoke 1 forms the space of a magnet steel of upper and lower shaft symmetry with one side of the well-shaped respectively, the well-shaped middle concave part is upper and lower shaft symmetry to form the central space to hold four magnet steels, wherein, a plurality of magnet steels are installed in the space of both sides and central space of the vertical direction respectively, both sides hold a magnet steel respectively, two magnet steels are held respectively above and below the central space, the magnet yokes of the left and right sides of the pump case 2 are the same symmetrical structure, the part composition is completely identical, wherein, all magnet steels and magnet yokes form a closed magnetic line loop along the outside axial direction of the pump shell.

In the above embodiment, the yoke assembly is mainly composed of two yokes 1 and eight

magnetic steels

7, 8, 9, 10 and 11, 12, 13, 14. Two magnetic steels are uniformly arranged on the plane of each yoke 1, and two magnetic steels 7 and two magnetic steels 11 are arranged on the yoke 1 by taking a left magnetic yoke of a pump shell made of 316L stainless steel as an example. The magnetic pole directions of the magnetic steel 7 and the magnetic steel 11 are opposite, and if the magnetic pole of the magnetic steel 7 horizontally towards the right side is the S pole, the magnetic pole direction of the magnetic steel 11 horizontally towards the right side is the N pole.

And the structure of stainless steel pump case right side yoke is unanimous with left side yoke structure, but requires that the magnet steel 10 of right side yoke and the magnet steel 7 subtend magnetic pole of left side yoke are different each other, if magnet steel 7 level is the S utmost point towards the magnet on right side, then magnet steel 10 level is the N utmost point to the magnet on left side. Similarly, the opposite magnetic poles of the magnetic steel 11 and the magnetic steel 14 are different from each other.

The 316L stainless steel pump casing 2 is a "-shaped structure consisting of two upper and lower" concave "shapes. And

magnetic steels

8, 9, 12 and 13 are respectively arranged at the concave notches. Wherein, the magnetic steel 8 and the magnetic steel 9 are overlapped together, and the magnetic steel 12 and the magnetic steel 13 are overlapped together.

The magnetic steel 7, the magnetic steel 8, the magnetic steel 9 and the magnetic steel 10 are consistent in the direction of the magnetic force line 5 or the magnetic poles are consistent in the horizontal direction. The magnetic steel 11, the magnetic steel 12, the magnetic steel 13 and the magnetic steel 14 have the same direction of the magnetic lines of force 5 or the same magnetic poles in the horizontal direction.

Because the pump shell 2 is made of nonmagnetic materials and the yoke 1 is made of magnetic conductive materials, the magnetic force lines 5 can form a closed loop between the eight pieces of magnetic steel and the two yokes. Four separated spaces are formed on the closed loop of the magnetic lines of force 5, and one group or a plurality of groups of air extraction units 6 can be placed in each separated space.

The mounting mode of left side yoke does: a yoke 1 with two

magnetic steels

7 and 11 is arranged in a fixed nut hole 3 on a pump shell 2 through a screw 4. The mounting mode of the right magnetic yoke is similar to that of the left magnetic yoke.

Referring to fig. 2, fig. 2 is a schematic structural view of a left yoke of a pump case according to an embodiment of the present invention. The magnetic steel 7 and the magnetic steel 11 are fixed on the yoke 1 by magnetic attraction and the positioning sheet 15. Strong attraction force exists between the

magnetic steels

7 and 11 and the yoke 1, and the

magnetic steels

7 and 11 can be ensured not to fall off in the direction vertical to the horizontal plane of the yoke. And meanwhile, a positioning piece 15 is arranged on the horizontal plane of the yoke so as to limit the movement limitation of the

magnetic steels

7 and 11 on the horizontal plane of the yoke 1. The positioning piece 15 is arranged at the bottom of the

magnetic steels

7 and 11 in the gravity direction.

The structure and the installation mode of the magnetic yoke on the right side of the pump shell are consistent with those of the magnetic yoke on the left side.

Fig. 3 is a schematic three-dimensional structure of a yoke assembly according to an embodiment of the present invention. Wherein, the magnetic steel 8 and the magnetic steel 9 are overlapped together and are tightly wrapped and fixed on the pump shell 2 through two positioning sheets 17. Similarly, the magnetic steel 12 and the magnetic steel 13 are overlapped together and are tightly wrapped and fixed on the pump shell 2 through two positioning sheets 17. The

magnetic steels

8, 9 and the

magnetic steels

12, 13 constitute an intermediate layer yoke.

Referring to fig. 4, a schematic diagram of a reference line in a yoke simulation is shown. An air extraction unit space on a magnetic line closed loop is selected, and software is adopted to simulate the magnetic field intensity change between two pieces of magnetic steel on an X axis 18 vertical to the horizontal plane direction and a Y axis 19 vertical to the horizontal plane direction.

FIG. 5 shows the result of simulation calculation of the magnetic field intensity variation in the central region of the air extraction unit perpendicular to the horizontal plane between two pieces of magnetic steel. It can be seen from the figure that the whole air extraction unit has higher magnetic field strength in the X-axis direction, the whole magnetic field strength curve is flattened and has better uniformity, and the magnetic field at the edge of the air extraction unit still has higher magnetic field, so that the air extraction unit can be ensured to have higher pumping speed.

FIG. 6 shows the result of simulation calculation of the magnetic field intensity variation in the vertical direction in the central region of the installation pumping unit between two magnetic steels. It can be seen from the figure that the whole air extraction unit has higher magnetic field strength in the Y-axis direction, the whole magnetic field strength curve is flattened and has better uniformity, and the magnetic field at the edge of the air extraction unit still has higher magnetic field, so that the air extraction unit can be ensured to have higher pumping speed.

By designing a new magnetic yoke assembly, the magnetic yoke assembly can be applied to a two-pole sputtering ion pump and a three-pole sputtering ion pump. This yoke simple structure, the magnetic field of the unit of bleeding is even, and magnetic field intensity is high, can reduce the weight of yoke subassembly, improves the specific value of ion pump size of bleeding and weight, reduces the material cost and the installation degree of difficulty in the ion pump development process.

The structure can enhance the magnetic field intensity in the pump shell, reduce the magnetic energy leakage, reduce the usage amount of the magnetic steel and the yoke iron and increase the volume of the air pumping space.

Although particular embodiments of the present invention have been described and illustrated in detail, it should be understood that various equivalent changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and that the resulting functional effects are within the scope of the invention as defined by the appended claims and drawings.

Claims

1. A magnetic yoke assembly of a sputtering ion pump comprises an even number of magnetic steels, two yokes, a positioning piece and a middle layer fixing piece, wherein the magnetic steels have the same size and magnetic energy product, the ion pump is in a # -shaped shape, a pump shell of the ion pump is a structure which is similar to a '+' -shaped structure and is formed by two concave shapes up and down, the vertical yokes are respectively arranged on the left side and the right side of the pump shell of the ion pump, the yokes respectively form a space which is axially symmetrical up and down with one side of the pump shell of the # -shaped ion pump and contains one magnetic steel, the middle concave part in the middle of the pump shell of the # -shaped ion pump is axially symmetrical up and down to form a central space containing four magnetic steels, a plurality of magnetic steels are respectively arranged in the space on the two sides and the central space in the vertical direction, two sides of the pump shell of the # -shaped ion pump respectively contain one magnetic steel, the two magnetic steels are respectively contained up and down in the central space, the magnetic poles of the two magnetic steels corresponding to the two magnetic steels on the same yoke are opposite in the magnetic pole direction, the structure of the magnetic yoke on the right side of the pump shell is consistent with that of the magnetic yoke on the left side, the magnetic steel on the yoke iron is fixed through the positioning sheet, the magnetic steel installed on the pump body is installed in a groove of the pump shell of the ion pump in a shape like a Chinese character jing and is fixed through the fixing sheet of the middle layer, and all the magnetic steel and the magnetic yoke form a closed magnetic line loop along the axial direction of the outer side of the pump shell.

2. The magnetic yoke assembly of claim 1, wherein the magnetic yoke of the pump housing side of the well-shaped ion pump is formed by upper and lower magnetic steels, a yoke and two positioning plates, the magnetic poles of the two magnetic steels lying on the yoke are opposite, the magnetic steels are tightly attached to the yoke by magnetic attraction, the fastening or restriction of the magnetic steels on the yoke in the horizontal direction is accomplished by the positioning plates, and the positioning plates are screwed on the yoke plane by screws.

3. The magnetic yoke assembly as claimed in claim 1, wherein the magnetic poles of the two magnetic steels on the yoke in the direction perpendicular to the horizontal plane are opposite to each other, one of which is an N pole and the other is an S pole.

4. The magnetic yoke assembly of claim 1, wherein the magnetic yoke of the concave portion in the middle of the pump housing of the ion pump is located in the space in the middle of the pump housing, the magnetic yoke of the middle layer is composed of an even number of magnetic steels and a corresponding number of fixing pieces of the middle layer, two pieces of yoke iron and the even number of magnetic steels are divided into two groups, and are respectively installed on the upper and lower sides of the pump housing of the ion pump, each group is composed of half of the number of magnetic steels, and are fastened in the concave middle space of the pump housing by the fixing pieces of the middle layer.

5. The magnetic yoke assembly of claim 4, wherein one or more sets of pumping units are disposed in the adjacent protruding spaces on both sides of the concave middle space of the housing of the well-shaped ion pump.

6. The magnetic yoke assembly of claim 5, wherein the pumping cell is a two-pole pumping cell or a three-pole pumping cell.

7. The magnetic yoke assembly of claim 1, wherein the pump housing of the groined ion pump is made of non-magnetic steel or low-magnetic steel.

8. The magnetic yoke assembly of claim 7, wherein the material of the pump housing of the well-shaped ion pump is 316L stainless steel.

9. The magnetic yoke assembly of claim 1, wherein the magnetic steel is selected from one of ferrite, cobalt or rubidium, iron and boron, the positioning plate is made of 316L stainless steel, and the yoke is made of pure iron.