JPH0763037B2 - Air core type bending magnet - Google Patents

Description

The present invention relates to a storage ring as a charged particle accelerating storage device for rotating or accelerating or storing charged particles on a closed orbit, that is, a structure of a deflection electromagnet of a SOR exposure apparatus. It is about.

[Conventional technology]

Conventional synchrotrons and storage rings are manufactured for high-energy physics experiments (mainly experiments for interaction of elementary particles and collisions of electrons and positrons, protons and antiprotons, and discovery of new particles). And was generally large (tens of meters to tens of kilometers in diameter).

As described above, the conventional storage ring is large and is composed of a large number of deflection electromagnets. Since each deflection electromagnet has a substantially linear structure, the magnetic field that is a condition necessary for the electrons to orbit for a long time is A two-dimensional magnetic field analysis was sufficient for optimizing the magnetic pole structure to ensure the uniformity.

On the other hand, recently, attention has been paid to the use of SOR light emitted when electrons or positrons circulate as a light source for X-ray lithography in surface analysis such as photoelectron spectroscopy or in manufacturing a semiconductor LSI. The introduction of this SOR light source into these semiconductor industries will require smaller and more specifically designed storage rings than before. For this reason, attempts are being made worldwide to reduce the size of storage rings.

One important direction for miniaturization is to make the deflection electromagnet superconducting and deflect electrons by 180 degrees with one deflection electromagnet to make the orbital radius of the electron on the order of several tens of centimeters. This is described, for example, in “Heuberga, Solid State Engineering, p. 93, 1986, February (A. Heuberger, Solid State Technology, p. 93, February.
1986) ”.

[Problems to be solved by the invention]

Therefore, the conventional two-dimensional analysis is insufficient, and the handling of the three-dimensional analysis is indispensable. However, the required homogeneity of the magnetic field is ensured in a wide area of a plane perpendicular to the orbital axis through which the electrons pass. Magnetic structure has not been realized yet.

Moreover, the conventional superconducting bending electromagnet is manufactured for the above elementary particle experiment, and the structure is linear and has a so-called cos θ winding coil structure with no space for SOR light extraction. A uniform area of the magnetic field was secured in the axis and in the plane perpendicular to it.
It cannot be used as an electromagnet for SOR light utilization equipment.

That is, the conventional problem is that the miniaturization of the storage ring and the uniform magnetic field distribution along the electron orbit have not been realized.

The present invention has been made in view of such a point, and an object of the present invention is to downsize a SOR for the semiconductor industry.
It is to provide a deflection electromagnet for an exposure apparatus.

[Means for solving problems]

In order to achieve such an object, the present invention provides an air-core type deflection electromagnet for generating a deflection magnetic field in the vacuum duct of a charged particle accelerating and accumulating device having a horizontal cross section of the vacuum duct having a substantially fan shape. There is a pair of upper and lower parts sandwiching the coil, and there is an exciting coil that forms a loop so that currents in opposite directions flow inside and outside along the vacuum duct, and this exciting coil is an outside coil along the vacuum duct. The vertical gap is larger than the vertical gap of the inner coil, and the coil at the connecting portion connecting the outer coil and the inner coil is arranged so as to bounce outward at an angle of 30 ± 15 degrees.

[Action]

In the present invention, it is possible to realize a uniform storage field and a uniform magnetic field distribution along the electron orbit.

〔Example〕

First, the features of the present invention will be described. The most main feature of the present invention is that a single deflection electromagnet deflects electrons by 180 degrees and a uniform magnetic field is realized in a wide area in a plane perpendicular to the orbital axis of the electron and the electron.

We also clarified a three-dimensional coil structure with an orbital radius as small as several tens of cm by making it superconducting while ensuring a region for extracting SOR light.

Furthermore, since it is based on the air-core type coil structure, the same magnetomotive force (the product of the current flowing through the coil and the number of turns of the coil is obtained by reducing and expanding the arrangement of the obtained coils to a similar shape, It is a factor that determines the capacity of the power supply), and electrons of the same energy can be circulated. That is, since the orbital radius changes with the same energy, light having an arbitrary wavelength can be provided with a structure that simply expands and contracts in a similar shape.

It should be noted that this time, a three-dimensional magnetic field analysis was performed, and a coil arrangement that facilitated SOR light extraction was realized. The coil arrangement will be described below.

FIG. 1 to FIG. 4 are layout diagrams showing an embodiment of an air-core coil as an air-core type deflection electromagnet according to the present invention viewed from various angles, 1 is an inner coil, 2 is an outer coil, and 3 is a crossover. The coils 4 and 4 are vacuum ducts. 1 to 4, (a) shows the outer shape of the actual coil winding, and (b) shows the center line of the coil and the outer shape of the vacuum duct. With the coil arrangement structure shown in the figure, the orbital radius of electrons is set to several tens of cm (52.38 cm in this example, which corresponds to the orbital radius of 3.5 T, 550 MeV). In this embodiment,
The outer coil 2 is made higher than the inner coil 1 in order to secure a uniform region along the orbital axis through which the electrons pass, and the coil 3 at the connecting portion connecting the two coils 1 and 2 is placed outside. It has a structure that jumps up by a certain angle. Further, in the actual magnetic field calculation, there is sufficient accuracy only by calculating the line current model.

FIG. 5 to FIG. 7 are coil chopping layouts showing three specific coil value examples from above (± z direction) and side (± x direction), showing only the center line of the coil. It is a thing.
The center line of the coil in the space of x ≧ 0, y ≧ 0, z ≧ 0 in FIG. 6 is the arc of z = D1, x ² + y ² = R1 ² and z = D2, x ² + y ² = R2 ²
Of arc (where D1>D2> 0, R1>R2> 0) α ≦ θx ≦
This is a portion of 90 degrees (see FIG. 6 (a)). That is, the center line of the coil coincides with the circular arc within a predetermined range. here,
α and θx represent the angles of the three-dimensional cylindrical coordinates, and α is 0 ° ≦ α
It is a constant value between ≦ 90 degrees. In this example, α ≠ 0. In both FIG. 6 and FIG. 7, the inner coil 1
And the plane including the center line of the outer coil 2 therein intersects with the plane of z = 0 at an angle of 30 ° ± 15 °, and the line of intersection is y = tanα ・
It is parallel to x or y = α. FIG. 5 shows α in FIG.
= 0 or a = 0 in FIG. 7.

Hereinafter, the embodiment of FIGS. 1 to 4 will be described in detail.
Detailed coil arrangements in FIGS. 1 to 4 are as follows (see FIG. 15).

Outer coil center radius R1 = 784.9mm Outer coil center height D1 = 161.3mm Inner coil center radius R2 = 268.4mm Inner coil center height D2 = 124.8mm Jumping angle of the coil at the transition point = 30 degrees here The thickness of the coil is defined by the magnetomotive force and the maximum current density that can be passed through the coil, and depends on factors such as the characteristics of the wire, the empirical magnetic field in the coil, and the excitation speed.

FIGS. 8 (a) and 8 (b) show the homogeneity distribution of the magnetic field in the plane along the electron orbit axis and perpendicular to the axis when the coil is arranged as described above. This figure shows 0 degrees (x axis) to 40 degrees (FIG. 8 (a)) and 50 degrees to 90 degrees (y) along the electron orbit axis from above.
The magnetic field homogeneity (Uniformity, hereinafter abbreviated as "U") is shown for each cross section every 10 degrees up to the axis) (Fig. 8 (b)). In the figure, the horizontal axis represents the uniformity U, and the vertical axis represents the position in the radial direction when the cross section perpendicular to the orbital plane of the electron is taken (in cm). The solid line, the chain line, the one-dot chain line, and the two-dot chain line each have a height z = 0 cm in the direction perpendicular to the electron orbit axis,
The uniformity U for the positions of 1 cm, 2 cm and 3 cm is shown. here,
The homogeneity U is the value of the z component BZ of the magnetic field at the position determined by the vertical axis and each curve, and the value of BZ that corresponds to the position of the electron's equilibrium orbit at z = 0 cm (the position of 52 cm on the horizontal axis in the figure). It is a quantity defined by the following formula from BZ0.

U = (BZ-BZ0) / BZ0 The uniformity U on the horizontal axis in Fig. 8 is 0 at the center and ± on one scale.
It is 1 × 10 ^-3 . The thick line on the vertical axis represents ± 5 × 10 ⁻⁴ . That is, this figure shows approximately ± 5 × 10 ^{− in} a wide area of 10 cm × 6 cm (z = 3 cm × 2 = 6 cm in the height direction due to the symmetry of the system) of a plane perpendicular to the electron's orbital axis. ^Four
It shows that the homogeneity of is achieved. This value is
The value is almost equivalent to the magnetic field accuracy (uniformity) required for the bending electromagnet of the conventional electron storage ring. Thus, without adding a correction coil, a coil having a vertical gap of the outer coil 2 larger than that of the inner coil 1 and having a plane symmetric shape with respect to the plane of x = 0 is obtained. Only by arranging in plane symmetry with respect to the plane of z = 0, such a magnetic field precision is achieved in the height of the plane perpendicular to the electron orbital axis and the wide region in the radial direction. These calculations are the results of a strict three-dimensional magnetic field analysis using the Biot-Savart law, and the coil arrangements described above are also the values obtained as a result of the parameter survey by this program.

Next, with respect to the jumping-up angle of the coil 3 at the crossing portion, the setting accuracy of the angle will be clarified. 9 to 14 show that in the above optimum coil arrangement, the positions of the inner coil 1 and the outer coil 2 are the same as in FIGS. 1 to 4, and the hoisting angle of the coil 3 at the crossing portion is 15 degrees. FIG. 9 shows the state of the magnetic field homogeneity corresponding to FIG. 8 when the magnetic field is changed by 5 degrees up to 45 degrees. As is clear from these figures, with respect to the jumping-up angle of the coil 3 in the crossing portion, the uniformity is disturbed as it deviates from the optimum value of 30 degrees, especially near 0 to 20 degrees of the deflection electromagnet exit. , It can be seen that it only needs to be in the range of 30 degrees ± 15 degrees.

Next, the influence of the positions of the center of the inner coil and the center of the outer coil will be described. FIG. 15 is a diagram showing an allowable range (hatched portion) of the positions of the center of the inner coil and the center of the outer coil. However, the relative angle θ from the inner coil 1 to the outer coil 2 is not tan θ = (D1-D2) / (R1-R2) ) = 0.0707 ± 0.0089 is required.

Next, the degree of uniformity will be shown for coil arrangements falling within these ranges.

Figure 16 shows the positional relationship of the coil centers, Table 1 shows that at the coil positions described in the embodiment shown in FIGS. 1 to 4, the positions in the radial direction are left unchanged (R1, R2,
θ is constant), and shows the degree of uniformity when the center of the inner coil and the center of the outer coil are translated in the height direction by the same length. The numerical value at the left end of the table represents the amount of translation, J,
Numerical values indicated by K and I are shown in FIGS. 8 to 14 in which the uniformity U is ± 5 × 10 ⁻⁴ , ± 1 × 10 ⁻³ , ±, respectively. It is the number of points within the range of 2 × 10 ^-3 . That is, there are 10 ways of each cross section every 10 degrees from 0 degree to 90 degrees, 11 ways showing the position every 1 cm of radial direction 47 cm to 57 cm, and further 1 cm of height direction z = 0 to 3 cm.
Each of the four positions shown in each position represents the space through which electrons inside the deflection electromagnet pass, with a total of 10 × 11 × 4 = 440 points, of which the number of points within the above range of uniformity is shown. is there. From Table 1, if the number I of points within the range of ± 2 × 10 ^-3 is about 300, that is, in the volume of 300/400 = 70% of the above space, ± 2 × 10 ^-3
The allowable range of parallel movement in the height direction was determined on the basis that it is sufficient to achieve the uniformity. As a result, as shown in FIG. 16, the range of −11.9 mm to +21.1 mm was set as the allowable value for the coil arrangement described in the embodiment of FIGS.

Similarly, in FIG. 17 and Table 2, the center position PC of the center of the inner coil and the center of the outer coil is not moved ((R1 + R2) / 2, (D1 + D
2) / 2, constant θ), and shows the degree of uniformity when the coil arrangement is moved both inside and outside in the radial direction. Further, FIG. 18 and Table 3 show the positions R1 and R2 and the height D in the radial direction.
2 is constant and indicates the degree of uniformity when the relative angle θ from the center of the inner coil to the center of the outer coil is changed. In each of these tables, the allowable value of coil arrangement was set based on the standard that the number of points within ± 2 × 10 ^-3 was about 300, and the range of allowable values shown in Fig. 15 was calculated. .

〔The invention's effect〕

As described above, according to the present invention, a pair of exciting coils having loops formed so that currents in opposite directions flow inward and outward along the vacuum duct are placed above and below the vacuum duct, and the gap between the upper and lower outer coils is set. Is larger than the gap between the top and bottom of the inner coil, and the coil at the crossover is arranged so as to bounce outward at an angle of 30 ± 15 degrees, so that a good magnetic field uniformity can be achieved over a wide area inside the deflection electromagnet. Since it is possible to obtain one time and commercialize a small storage ring, it becomes possible to form a minute pattern in the lithography process of a semiconductor LSI, and the small storage ring can be installed as a SOR exposure device in a semiconductor factory. There is an effect that it becomes possible.

[Brief description of drawings]

1 to 4 are layout drawings showing an embodiment of an air-core type bending electromagnet according to the present invention, FIGS. 5 to 7 are coil layout layout drawings, and FIG. 8 is FIGS. 1 to 4. Graphs showing the homogeneity of the magnetic field in the air-core type deflection electromagnet shown in Fig. 9, and Figs. 9 to 14 show the homogeneity when the coil hoisting angle of the transition portion connecting the inner coil and the outer coil is changed. Graph, FIG. 15 is an explanatory view showing the allowable range of the positions of the inner coil center and the outer coil center, FIG. 16 is an explanatory view corresponding to Table 1, FIG. 17 is an explanatory view corresponding to Table 2, and FIG. The figure is an explanatory diagram corresponding to Table 3. 1 ... Inner coil, 2 ... Outer coil, 3 ... Crossover coil, 4 ... Vacuum duct.

Claims (2)

[Claims] 1. An air-core type deflection electromagnet for generating a deflection magnetic field in the vacuum duct of a charged particle accelerating and accumulating device, wherein a horizontal cross section of the vacuum duct is substantially fan-shaped. And has an exciting coil that forms a loop so that currents in opposite directions flow inside and outside along the vacuum duct, and this exciting coil is a coil in which the upper and lower gaps of the outside coil along the vacuum duct are inside. The air-core type deflection electromagnet is characterized in that it is larger than the gap between the upper and lower sides of the coil, and the coil of the connecting portion connecting the outer coil and the inner coil is arranged so as to jump up to the outside at an angle of 30 ± 15 degrees. . 2. The air-core type deflection electromagnet according to claim 1, wherein the coil forming the deflection electromagnet is a superconducting coil.