JPH0763038B2 - Bending electromagnet with correction coil - 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).

On the other hand, recently, SOR light emitted when electrons or positrons orbit is used for surface analysis such as photoelectron spectroscopy or semiconductor L
Attention has been paid to its use as a light source for X-ray lithography when manufacturing SI. In this semiconductor industry this SO
The introduction of the R light source requires a storage ring that is smaller and designed specifically than before. For this reason, attempts are being made worldwide to reduce the size of storage rings.

One effective direction for downsizing is to make the deflection electromagnet superconducting and deflect one electron by 180 degrees so that the orbit radius of the electron is 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) ”. However, a specific magnet structure has not yet been realized which secures the required magnetic field homogeneity in a wide area of a plane perpendicular to the orbital axis through which electrons pass.

On the other hand, in an attempt to miniaturize the storage ring, there is an attempt to deflect electrons 360 degrees in a circular ring. This is described in, for example, “Takahashi, Japan Society for the Promotion of Science, Crystal Processing and Evaluation Technology 145th Committee, B Subcommittee (using synchrotron radiation), 9th Research Group Material, page 17”. However, in this example, there are many technical problems to be solved due to the circular structure.

[Problems to be solved by the invention]

In a 180-degree bending magnet, the COD (design center of the electron's equilibrium orbit) generated by the fringe magnetic field at the end of the magnet Deviation from orbit)
The problem that is large is important. The above burger (A.
In Heuberger's 180 degree deflection type, the distance between the inner coil and the outer coil is as narrow as about 10 cm. Therefore, the effect of the crossover coil on the fringe magnetic field is small, and it is so large.
Although COD does not occur, if the gap between the inner coil and the outer coil is widened in order to secure a uniform and large area of the magnetic field, the influence of the coil in the transition area will increase and the droop of the fringe magnetic field will increase. There is.

The correction coil in the conventional bending electromagnet is arranged along the coil inside the main bending electromagnet in order to correct the homogeneity inside the bending electromagnet or to correct the variation in the size of the magnetic field due to the individual difference of the individual bending electromagnets. It is usually placed parallel to it, shaping the fringe magnetic field itself, C.
No correction coil was placed in the fringe field to correct the OD.

From the above, 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]

The present invention relates to a main deflection electromagnet including a pair of upper and lower exciting coils that sandwich a charged particle orbit to generate a deflection magnetic field, and a correction coil that corrects a pair of deflection magnetic fields provided between the upper and lower exciting coils. In the deflection electromagnet with a correction coil, the main deflection electromagnet is characterized in that the vertical gap of the outer coil along the charge particle orbit of the exciting coil is larger than the vertical gap of the inner coil, and The correction coil is a deflection magnetic field formed on the charged particle orbit inside the main deflection electromagnet near the fringe magnetic field of the main deflection electromagnet. And are arranged so as to generate a magnetic field in the opposite direction.

[Action]

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

〔Example〕

First, the features of the present invention will be described. The present invention deflects the electrons 180 degrees in total by the main deflection electromagnet and the correction coil. That is, the pair of main deflection electromagnets deflects electrons approximately 180 degrees, and by adding one or more correction coils near the fringe magnetic field, the fringe magnetic field formed by the main deflection electromagnet itself is shaped into a steep stepwise distribution. Then, the B1 product (the amount obtained by integrating the magnitude B of the magnetic field along the electron orbit axis) is adjusted to a certain constant value, so that the total 18
Deflect the electrons by 0 degrees.

In this way, the COD with only the main bending magnet is very large.
The most important feature is that the location where is generated is suppressed small by the correction coil, and at the same time, the homogeneity of the magnetic field near the fringe inside the main deflection electromagnet is improved.

FIGS. 1 to 4 show an arrangement structure of a deflection electromagnet with a correction coil according to the present invention, wherein 1 is an outer coil of the main deflection electromagnet, 2 is a correction coil, 3 is a coil of a transition portion of the main deflection electromagnet, 5 Is the inner coil of the main bending magnet. Large banana-shaped main bending electromagnets 1, 3, 5 in the figure
On the other hand, the correction coil 2 whose magnetic field direction is opposite to that of the main deflection electromagnets 1, 3 and 5 is provided on both the left and right sides in the vicinity of the electron orbit axis near the fringe portion (which deflects electrons by approximately 180 degrees). There are 3 pairs each. FIG. 2 shows the current paths P1 and P2, P in the main deflection electromagnet 1 and the correction coil 2.
The direction of 3 is indicated by an arrow. The correction coil 2 generates a magnetic field in the opposite direction to the deflection magnetic field inside the deflection electromagnet. In this embodiment, the vertical gap of the outer coil 1 is made larger than the vertical gap of the inner coil 5 in order to secure a uniform region along the orbital axis through which the electrons pass, and the two coils 1, 5 are It has a structure in which the coil 3 at the connecting portion connecting the two is flipped up to the outside.

FIG. 5 to FIG. 7 are layout diagrams showing examples of the truncated shape of the main deflection electromagnet 1. The correction coil 2 is installed in the fringe portion of these main deflection electromagnets 1. Two major effects of the correction coil 2 will be described in detail with reference to the embodiment shown in FIGS.

First, the effect of reducing the B1 product will be described. FIG. 8 is along the electron orbit axis of only the banana type main deflection electromagnet 1 −
The distribution of the z-direction component of the magnetic field within the range of 50 cm ≦ y ≦ 0 cm is shown. Further, FIG. 9 shows the distribution of the z-direction component of the magnetic field formed by the main deflection electromagnet and the correction coil group in the same region as in FIG. 8 and the positions A1 to A3 of the three pairs of correction coils.

As is clear from FIG. 8, with only the main bending electromagnet, the drooping of the magnetic field (fringe magnetic field) in the vicinity of the end of the bending electromagnet is remarkable, and a very large COD is generated. In order to reduce this, the coil 3 at the connecting portion connecting the inner coil and the outer coil of the banana type main bending electromagnet 1 is translated in the + y direction to be truncated, or rotated in the positive direction around the z axis. The so-called B1 product of the magnetic field must be reduced by devising the above (see FIGS. 5 to 7).

However, even if COD can be reduced by doing so,
It is easily expected that the homogeneity of the magnetic field inside the deflecting electromagnet will deteriorate. Therefore, the correction coil 2 as shown in FIGS. 1 to 4 is arranged near the fringe portion. As a result, as shown in FIG. 9, it was possible to sharply reduce the fringe magnetic field droop and obtain a magnetic field distribution that changes substantially stepwise. Further, as can be seen from FIG. 9, in order to compensate for a slight amount of sag to the outside of the deflection electromagnet, a correction coil is arranged so as to intentionally form an undershoot as shown by the curve S1 and return to 0 thereafter. Optimized.

Next, the effect of improving the magnetic field homogeneity inside the main bending electromagnet will be described. In addition to the effect of reducing the B1 product, the homogeneity of the magnetic field in the vicinity of the fringe portion inside the main deflection electromagnet was also significantly improved by this correction coil 2. This is shown in Figs. 10 and 11.

Figure 10 shows a banana-shaped main deflection electromagnet 1 without a correction coil.
Fig. 11 shows the homogeneity of the magnetic field in the presence of only the magnetic field, and Fig. 11 shows the homogeneity of the magnetic field inside the deflection electromagnet in the presence of the correction coil. These figures show from 0 degree (x axis) to 90 degree (y axis) along the electron orbit axis in the θx direction from the top.
Magnetic field homogeneity (Uniformit
y, hereinafter abbreviated as “U”) (see FIG. 6A for θx). The horizontal axis in the figure represents the uniformity U,
The vertical axis shows the position in the radial direction when the cross section perpendicular to the orbital axis of the electron is taken (in cm). The solid line, the chain line, the one-dot chain line, and the two-dot chain line are the height z = 0c in the direction perpendicular to the electron orbit axis.
The uniformity U for the position parameters of m, 1 cm, 2 cm and 3 cm is shown. Here, the homogeneity U is defined by the following equation from the value of the z component BZ of the magnetic field at the position determined by the vertical axis and the parameter, and the value of BZ corresponding to the position of the electron's equilibrium orbit at z = 0 cm. Amount.

U = (BZ−BZ0) / BZ0 Uniformity U on the horizontal axis in FIGS. 10 and 11 is 0 in the middle and 1
The scale is ± 1 × 10 ^-3 . The thick line on the vertical axis is ± 5 ×
^Represents 10 ^-4 . That is, Fig. 11 shows the whole cross section except 0 degree 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) perpendicular to it along the electron's orbital axis. It shows that the uniformity of approximately ± 5 × 10 ⁻⁴ is achieved. This value is almost the same as the magnetic field accuracy (uniformity) required for the bending electromagnet of the conventional electron storage ring. On the other hand, FIG. 10 shows the uniformity without the correction coil. Figure 10 shows that a uniform area of about 10 ^-4 was achieved in a wide area of 10 cm × 6 cm in a plane perpendicular to the electron's orbital axis, except for 10 degrees and 20 degrees. It can be seen that the cross section has the same degree of uniformity as in FIG. This is the effect of making the gap of the outer coil 1 larger than the gap of the inner coil 5 and flipping up the coil 3 at the crossing portion to the outside, and it can be seen that such a magnetic field accuracy can be achieved without the correction coil. However,
In the 10 ° and 20 ° cross sections, considerable deterioration is observed, but it is clear from FIG. 11 that such deterioration is remarkably improved by providing the correction coil.

These calculations are exact 3 using the Biot-Savart law.
It is the result of the dimensional magnetic field analysis, and the above coil arrangement is also the value obtained as a result of the parameter survey by this program.

Next, a case where both the main deflection electromagnet 1 and the correction coil 2 have a return yoke will be described. FIG. 12 and FIG. 13 are layout diagrams showing a second embodiment of the deflection electromagnet with a correction coil according to the present invention, showing the case where an iron return yoke 4 is attached. In the second embodiment, the iron return yoke 4 is provided and the main deflection electromagnet 1 is arranged as shown in FIGS.
The position of the correction coil 2, the magnetomotive force (the product of the current value flowing through the coil and the number of turns), etc. are completely the same as those in the first embodiment except for the case of the first embodiment shown in FIG. Is the same as. Also in the second embodiment, as in the first embodiment, two major effects are shown below.

First, the effect of reducing the B1 product will be described. FIG. 14 shows the distribution of the z-direction component of the magnetic field along the electron orbit axis by only the banana type main bending electromagnet 1 as in the first embodiment.
Further, FIG. 15 shows the distribution of the z-direction component of the magnetic field along the electron orbit axis formed by the banana type main deflection electromagnet 1 and the correction coil 2. As is clear from FIG. 14, the fringe magnetic field droop of the deflection electromagnet is remarkable only with the main deflection electromagnet 1.
Very large COD is generated. Therefore, the correction coil 2 as shown in FIGS. 11 and 12 is arranged near the fringe portion. As a result, as shown in FIG. 15, the droop of the fringe magnetic field was sharply reduced, and a magnetic field distribution that changed in a substantially stepwise manner could be obtained. Further, as can be seen from FIG. 15, in order to compensate for a slight amount of sag to the outside of the deflection electromagnet, a correction coil is arranged to intentionally form an undershoot as shown by the curve S1 and return to 0 thereafter. Was optimized.

Next, the effect of improving the magnetic field homogeneity inside the main bending electromagnet 1 will be described. In addition to the effect of reducing the B1 product, the correction coil 2 also greatly improves the uniformity near the fringe portion inside the main deflection electromagnet 1. This is shown in Figs. 16 and 17.

The meaning of this graph is shown in FIGS. 10 and 11 in the case of the first embodiment.
It is similar to the figure. The 16th is the uniformity without the correction coil, and the uniformity is considerably deteriorated in the cross section of 10 degrees and 20 degrees. It is clear that this is remarkably improved in FIG.

These calculations are the results of three-dimensional magnetic field analysis using the Biot-Savart law and the finite element method including magnetic materials and the integration method. This is the value obtained as a result of the survey.

〔The invention's effect〕

As described above, the present invention has a structure in which the vertical gap of the outer coil of the main deflection electromagnet is made larger than the vertical gap of the inner coil, and the coil of the crossover portion is flipped up to the outside. It is possible to obtain good magnetic field homogeneity over a wide area inside the bending magnet.
Also, by installing a pair of correction coils in the vicinity of the fringe magnetic field of the main deflection electromagnet that deflects charged particles so as to generate a magnetic field in the direction opposite to the deflection magnetic field formed on the charged particle orbit inside the main deflection electromagnet, It can deflect electrons by 180 degrees, suppress the generation of COD, and improve the homogeneity of the magnetic field near the fringe, so that a small storage ring can be put to practical use and at the same time, it can be used in semiconductor LSI lithography processes. It becomes possible to form patterns,
This has the effect of enabling a small storage ring to be installed as a SOR exposure device in a semiconductor factory.

[Brief description of drawings]

1 to 4 are layout diagrams showing an embodiment of a deflection electromagnet with a correction coil according to the present invention, FIGS. 5 to 7 are layout diagrams showing a coil truncation structure, and FIG. 8 is a main deflection electromagnet. Fig. 9 is a graph showing the distribution of the fringe magnetic field along the electron orbital axis due to only the fringe magnetic field. Fig. 9 is a graph showing the distribution of the fringe magnetic field along the electron orbital axis when the magnetic field distribution is corrected by three pairs of correction coils together with the main deflection electromagnet Fig. 10 is a graph showing the homogeneity distribution of the magnetic field in a plane perpendicular to the electron orbit axis inside the deflection electromagnet when there is only a main deflection electromagnet and no correction coil, and Fig. 11 shows the main deflection electromagnet together. Graphs showing the homogeneity distribution of the magnetic field in the plane perpendicular to the electron orbit axis inside the deflecting electromagnet when the magnetic field distribution is corrected by three pairs of correction coils, FIG. 12 and FIG. With correction coil involved FIG. 14 is a layout diagram showing the second embodiment of the counter electromagnet, FIG. 14 is a graph showing the distribution of the fringe magnetic field along the electron orbit axis by only the main deflection electromagnet in the second embodiment, and FIG. 15 is the second embodiment. In the example, a graph showing the distribution of the fringe magnetic field along the electron orbit axis when the magnetic field distribution is corrected by three pairs of correction coils together with the main deflection electromagnet, and FIG. 16 is an electron orbit inside the deflection electromagnet in the embodiment of FIG. FIG. 17 is a graph showing the homogeneity distribution of the magnetic field in the plane perpendicular to the axis, and FIG. 17 shows the inside of the deflection electromagnet when the magnetic field distribution is corrected by three pairs of correction coils together with the main deflection electromagnet in the second embodiment. 6 is a graph showing the homogeneity distribution of the magnetic field in a plane along the electron orbit axis of the and of FIG. 1 ... Outer coil, 2 ... Correction coil, 3 ... Crossover coil, 5 ... Inner coil.

Claims (3)

[Claims] 1. A main deflection electromagnet comprising a pair of upper and lower exciting coils which sandwich a charged particle orbit to generate a deflecting magnetic field, and a correction which corrects the pair of deflecting magnetic fields provided between the upper and lower exciting coils. A deflection electromagnet with a correction coil including a coil, wherein the main deflection electromagnet has a vertical gap of an outer coil along the charged particle orbit of the excitation coil that is larger than a vertical gap of an inner coil, And the coil of the transition part connecting the outer coil and the inner coil is arranged so as to jump outward, the correction coil, in the vicinity of the fringe magnetic field of the main deflection electromagnet on the charged particle orbit inside the main deflection electromagnet A deflection electromagnet with a correction coil, wherein the deflection electromagnet is arranged so as to generate a magnetic field in a direction opposite to that of the deflection magnetic field formed. 2. A coil of a main bending electromagnet has three-dimensional rectangular coordinates.
When the space defined by x, y, z has a shape symmetrical with respect to the plane of x = 0 and is arranged symmetrically with respect to the plane of z = 0,
The deflection electromagnet with a correction coil according to claim 1, wherein a main portion of a pair of correction coils having the same symmetry is installed in a fringe magnetic field formed by the main deflection electromagnet. 3. The deflection electromagnet with a correction coil according to claim 1, wherein the main deflection electromagnet and the correction coil have a magnetic material.