Dipolar deflection magnet

Abstract

The utility model discloses a dipolar deflection magnet which comprises a coil and a magnet yoke sleeved on the periphery of the coil, the coil is composed of 2n saddle-shaped windings, the windings are symmetrically stacked up and down in an independent area of two intersected circles or ellipses, the outline of the whole cross section is in a double-crescent shape, the current directions of the windings in the two crescent shapes are opposite, and the current directions of the windings in the two crescent shapes are opposite. And the current density distribution is uniform. The magnet provided by the utility model can provide a magnetic field with a large magnetic gap and uniform height, meets the deflection requirement of a strip-shaped ion beam, is simple in structure, can maintain a narrower width while forming a magnetic gap with a larger height, and can be used for the transmission of the strip-shaped ion beam compared with a conventional dipolar deflection magnet with a circular or rectangular magnetic gap, thereby improving the transmission efficiency of the strip-shaped ion beam. The magnet width can be reduced, the magnet volume is reduced, and the magnetic field utilization rate is improved.

Description

Technical Field

[0001] The utility model relates to a mass analysis magnet used in the field of ion implantation for removing impurity ions in a ribbon ion beam drawn from an ion source, and in particular to a dipole deflection magnet which provides a suitable and uniform deflection magnetic field within the entire envelope of the ribbon ion beam and separates ions by utilizing the difference in mass-to-charge ratios of ions so as to filter out the impurity ions contained in the ion beam. Background Art

[0002] Ion implantation is a key process before integrated circuit manufacturing. The use of large-sized ribbon ion beam implantation can significantly improve its implantation efficiency. For large-sized, large-divergence ribbon ion beams drawn from an ion source, a dipole deflection magnet is usually used to provide a suitable and uniform deflection magnetic field within the entire envelope of the ribbon ion beam, so as to separate the ions by using their different mass-to-charge ratios and filter out the impurity ions contained in the ion beam. On the one hand, the pole gap of the dipole deflection magnet is required to be sufficient to accommodate a large-sized ribbon ion beam, and on the other hand, it is required to provide a suitable and uniform magnetic field within the entire size range of the ribbon ion beam. These two conditions are contradictory for traditional magnets, and the solution is to make the magnet very wide and large. Utility Model Content

[0003] In view of the above technical problems, the purpose of the utility model is to disclose a dipole deflection magnet that can meet the deflection requirements of a large-size, large-divergence-angle ribbon ion beam drawn out by an ion source, provide a large magnetic gap and a highly uniform magnetic field, and has the characteristics of simple structure, small size, and high magnetic field utilization.

[0004] The technical solution adopted by the utility model is: a two-pole deflection magnet, including a coil and a magnetic yoke sleeved on the periphery of the coil, characterized in that the coil is composed of 2n saddle-shaped windings, and these windings are symmetrically stacked up and down in independent areas of two intersecting circles or ellipses, and the overall cross-sectional profile is a double crescent shape, the winding current directions in the two crescents (crescents) are opposite, and the current density is evenly distributed.

[0005] Different from the general magnet structure, the magnetic field distribution of the two-pole deflection magnet of the utility model depends on the distribution of the conductor, such as Figure 1 As shown, two cylindrical conductors with opposite currents generate a pure dipole magnetic field B in the intersection area. y , its magnetic field distribution is:

[0006]

[0007]

[0008] In the above formula, μ0 is the magnetic permeability of vacuum, J0 is the current density, R is the radius of the cylindrical conductor, r1 and r2 are the distances between a point in the intersection area and the centers of the two cylindrical conductors, θ1 and θ2 are the angles formed by the line connecting a point in the intersection area and the centers of the two cylindrical conductors and the x-axis, and s is the distance between the centers of the two intersecting cylindrical conductors.

[0009] Based on the above idea, the magnet coil adopts 2n windings symmetrically stacked in a stacked manner to achieve a conductor cross-section that is approximately "crescent-shaped". The magnet cross-section is as follows: Figure 3 As shown, a highly uniform deflection magnetic field is formed in the magnet gap to meet the deflection requirements of the ribbon ion beam. Due to the magnet structure, a relatively large gap can be formed while maintaining a relatively narrow width, which is very suitable for the transmission of the ribbon ion beam of the utility model. Compared with the traditional two-pole deflection magnet with a circular or rectangular magnetic gap, the utility model can reduce the magnet width and improve the magnetic field utilization.

[0010] For ribbon ion beams of larger size and larger aspect ratio, such as 1000mmx30mm ion beams, analogous to two cylindrical conductors with opposite currents generating a pure dipole magnetic field in the intersection area, two elliptical conductors with opposite currents can also obtain a highly uniform magnetic field in the intersection area. Similarly, 2n windings with upper and lower symmetry are stacked to achieve a conductor cross-section that is approximately "crescent-shaped". The magnet cross-section is as follows: Figure 6 As shown, the requirements for transmission and implantation of ribbon ion beams with larger size and larger aspect ratio can be met.

[0011] In order to further improve the uniformity of the magnetic field in the pores, the magnetic field is further optimized by perforating the yoke surface corresponding to the top and bottom of the two crescents on the outer side of the coil. Figure 2 , generating a sextupole field, producing Figure 4 The shape and size of the through hole can be adjusted according to the ion beam incident parameters and the ion beam spot distribution after passing through the deflection magnet.

[0012] The cross-sectional profile of the magnetic yoke is hexagonal, and is formed by splicing a plurality of pipe sections end to end, and each section is welded by 6 sheet-like plates, and the magnetic yoke surfaces corresponding to the top and bottom of the two crescents are both flat.

[0013] Preferably, a hexagonal ion beam transmission vacuum box is arranged in the gap area of ​​the magnet. The hexagonal transmission pipeline can reduce the problem of excessive temperature rise caused by the collision between ions and the side wall of the pipeline.

[0014] The winding is preferably a pancake-type double-layer winding.

[0015] The winding coils are connected in series.

[0016] Beneficial effects:

[0017] The magnet of the utility model can provide a large magnetic gap and a highly uniform magnetic field to meet the deflection requirements of a ribbon ion beam, and the magnet has a simple structure and can maintain a narrow width while forming a magnetic gap of a relatively large height. When used for the transmission of a ribbon ion beam, compared with a traditional dipole deflection magnet with a circular or rectangular magnetic gap, the magnet width can be reduced, the magnet volume can be reduced, and the utilization rate of the magnetic field can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the pure dipole magnetic field generated by two cylindrical conductors with opposite currents in the intersection area;

[0019] Figure 2 It is a schematic diagram of the three-dimensional structure of the two-pole deflection magnet (the upper left part of the yoke is omitted);

[0020] Figure 3 yes Figure 2 Schematic diagram of the Ⅰ-Ⅰ cross section of the middle two-pole deflection magnet;

[0021] Figure 4 Schematic diagram of the ion beam cross section with no holes in the yoke (a) and with holes in the yoke (b);

[0022] Figure 5 The transport path of the ion beam passing through the two-pole deflection magnet of the present embodiment is shown;

[0023] Figure 6 The beam spot distribution at the focal plane after the ion beam passes through the two-pole deflection magnet of this embodiment is shown;

[0024] Figure 7 It is a schematic diagram of the structure of a dipole deflection magnet based on a larger ion beam. DETAILED DESCRIPTION

[0025] The two-pole deflection magnet of this embodiment is as follows Figure 2 , 3 As shown, it mainly includes a coil 1 and a yoke 2 mounted on the outer periphery of the coil 1. The coil 1 is composed of 14 saddle-shaped winding turns 5-18, and these winding turns 5-18 are symmetrically stacked in an upper and lower area in an independent area of ​​two intersecting circles, as shown in FIG. Figure 3 As shown, the overall cross-sectional profile is a double crescent shape, and the winding currents in the two crescents are in opposite directions. Figure 3 The current direction of the winding in the left crescent, i.e. 5b-18b, is perpendicular to the paper surface and outward, while the current direction of the winding in the right crescent, i.e. 5a-18a, is perpendicular to the paper surface and inward.

[0026] A pure dipole magnetic field is generated in the intersection area by two cylindrical conductors with opposite currents. It can be seen that a highly uniform deflection magnetic field can be formed in the common area of ​​the two intersecting circles, which meets the requirements of the ribbon ion beam for a large magnetic gap and a highly uniform magnetic field. At the same time, the magnet has a simple structure and can maintain a narrow width while forming a large magnetic gap. Compared with traditional dipole deflection magnets with circular or rectangular magnetic gaps, the magnet width and volume can be reduced, and its magnetic field utilization rate can be improved.

[0027] Each winding coil 5-18 is connected in series, and a pancake-shaped double-layer winding is used. In the crescent, the arrangement of the windings should be adapted to the crescent shape as much as possible. On this basis, the magnetic field at some positions can be compensated by adjusting the number of turns of individual windings. Figure 3 In the upper part, five pairs are 2x7 turns, and two pairs, 9 and 10, are 2x6 turns.

[0028] As a further improvement, openings 21 capable of generating a sextupole field are provided on the yoke surfaces corresponding to the top and bottom of the two crescents. Figure 2 As shown, the purpose is to play a role in de-dispersion at both ends of the ribbon ion beam. The effect is shown in Figure 4 As shown. Figure 4 It can be seen that the opening can correct the upper and lower edge ion beam trajectories.

[0029] In this embodiment, the cross-sectional profile of the magnetic yoke 2 is hexagonal, and is formed by splicing a plurality of pipe sections 22 end to end. Figure 2 , 3 As shown, each section is welded by 6 sheets of sheet material, and the opening 21 is set on the yoke plane 2a, 2b corresponding to the top and bottom of the two crescents. The yoke 2 of this structure can not only fit the coil 1 well, but also has low processing difficulty. The gap between each winding turn 5-18 in the coil 1 can be filled with interlayer pads during installation and fixed to the inner side of the yoke 2 by tooling.

[0030] Figure 3 The middle structure 3 is a hexagonal ion beam transmission vacuum box arranged in the gap of the magnet, which is made of stainless steel. Compared with the usual rectangular shape, the hexagonal shape can reduce the problem of excessive temperature rise caused by the collision between ions and the side wall of the vacuum box.

[0031] In this embodiment, each winding of the two-pole deflection magnet is wound with oxygen-free copper wire, the yoke is made of DT4 material, and the deflection angle is between 45 degrees and 180 degrees. Figure 5 The transmission trajectory of the ion beam from entering the two-pole deflection magnet of this embodiment to passing out is shown. Figure 6 The cross-sectional distribution of the ion beam after it comes out of the two-pole deflection magnet of this embodiment is shown. It can be seen that the ion beam is relatively uniform as a whole and is still rectangular. After passing through the rectangular analysis slit, not too many target ions are lost.

[0032] For larger ion beam sizes, the Figure 7 The structure shown, and Figure 3 The biggest difference between the two-pole deflection magnet is that the winding turns of its coil are arranged in independent areas of two intersecting ellipses. Its principle can be compared to Figure 3 , two elliptical conductors with opposite currents can also obtain a highly uniform magnetic field in the intersection area, which can meet the transmission and injection requirements of larger-sized ribbon ion beams.

Claims

1. A two-pole deflection magnet, comprising a coil and a yoke mounted on the periphery of the coil, characterized in that: The coil is composed of 2n saddle-shaped windings, which are symmetrically stacked in two independent areas of two intersecting circles or ellipses, and the overall cross-sectional profile is a double crescent shape, the winding currents in the two crescents are in opposite directions, and the current density is evenly distributed; Openings capable of generating a sextupole field are arranged on the yoke surfaces corresponding to the top and bottom of the two crescents.

2. The two-pole deflection magnet according to claim 1, characterized in that: The cross-sectional profile of the magnetic yoke is hexagonal, and is formed by splicing a plurality of pipe sections end to end, and each section is welded by 6 sheet-like plates, and the magnetic yoke surfaces corresponding to the top and bottom of the two crescents are both flat.

3. The two-pole deflection magnet according to claim 2, characterized in that: A hexagonal ion beam transmission vacuum box is arranged in the gap area of ​​the magnet.

4. The two-pole deflection magnet according to claim 1, characterized in that: The winding is a pancake-type double-layer winding.

5. The two-pole deflection magnet according to claim 1, characterized in that: The windings are connected in series.

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