JPH0630336B2 - Charged particle device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle device, and more specifically, it accelerates and accumulates charged particles such as an electron beam and outputs them from a deflection unit. The present invention relates to a charged particle device that uses a generated radiation beam (also called synchrotron radiation light, SOR).

[Conventional technology]

FIG. 5 is a plan view showing an example of a conventional charged particle apparatus used for exposing a semiconductor. In the figure, (1) is a storage ring that stores charged particles for a long time. In this example, the charged particles incident from the incident part (2) will be described as being accelerated to a predetermined energy, but the incident particles are incident at a lower energy than a predetermined energy, and after the incident, The same applies to the case of accelerating and accumulating. (3) is a deflecting electromagnet for deflecting charged particles to form an equilibrium orbit (4). (5) is a synchrotron radiation beam line for extracting and utilizing the synchrotron radiation generated when the charged particles are deflected. In the figure, the synchrotron radiation beam line (5) is shown as a single one, but it is usually composed of a plurality of synchrotron radiation beam lines. Further, here, for convenience of description, the case where the number of synchrotron radiation beam lines is one is shown. (6) is an exposure unit for performing fine lithography of a semiconductor using a synchrotron radiation beam line (5), the exposure unit (6), a mask (7) and a wafer coated with a resist on the surface (8) Are arranged close to or close to each other. (9) is a focusing quadrupole electromagnet for preventing divergence of charged particles. (10) shows a vacuum donut which is a passage of charged particles. (11) is a high-frequency cavity for compensating for the energy loss of the particles caused by the emission of the synchrotron radiation beam line and for accelerating or maintaining the energy at a predetermined level. In this figure, other devices such as a vacuum exhaust device and various electromagnets for beam control adjustment are omitted.

Next, the operation will be described. First, the charged particles that have been made incident from the incident part (2) enter the equilibrium orbit (4) defined by the arrangement of the electromagnet in the ring in advance, that is, the deflection electromagnet (3) and the focusing quadrupole electromagnet (9), And this equilibrium orbit (4)
Continue to rotate for a long time along. Charged particles are deflection electromagnets
When deflected by the magnetic field of (3), the electromagnetic waves are radiated in the orbit tangential direction (this is the radiated light) by the normal radiation. The spatial distribution of the synchrotron radiation beam line is shown in the schematic diagram of FIG. As shown in FIG. 6, the longitudinal spread (δ) of the synchrotron radiation beam with respect to the orbital plane (5) is expressed by the following equation.

δ (radian) 2 / γ (where ^{γ = 1/1-β 2} , β = v / c) where, v is the velocity of the particles, c is the speed of light. Normal,
In a charged particle device utilizing a synchrotron radiation beamline, v
The fast particles of c are used. Then, substituting the typical parameters for lithographic applications into the above equation, the value of γ is almost
It will be in the range of 1,000 to 2,000. That is, the spread of the emitted light beam in the vertical direction is 1 to 2 (m radian). Therefore, the emitted light beam generated from the conventional charged particle device is
It can be said that it is sufficiently wide in the lateral direction along the orbital surface, but extremely narrow in the longitudinal direction. The lateral spread is limited only by the width of the radiated light beam line (5) in FIG. 6, and if the lateral width is wide, the usable lateral width of the radiated light can be freely selected.

[Problems to be solved by the invention]

Now, one of the major problems in applying the synchrotron radiation to semiconductor lithography is that the irradiation area in the vertical direction is extremely small. In order to solve this, several methods have been conventionally proposed. FIG. 7 shows a conventional apparatus for enlarging the vertical irradiation area introduced by Mr. Feng in “Applied Physics”, Vol. 53, No. 1 (1984, pp17-25) under the title of “Synchrotron radiation lithography”. It is a schematic diagram. In FIG. 7, (12) is a swingable total reflection mirror installed on the upstream side of the synchrotron radiation beam line (5). As a result, the emitted light beam line is swung in the vertical direction to expand the irradiation area on the wafer. In this method, the control mechanism for swinging the total reflection mirror (12) in the vacuum synchrotron radiation beam line with extremely high precision becomes complicated, and the total reflection mirror (12) is damaged by the synchrotron radiation beam. There were two major problems. Furthermore, optimization of optical characteristics such as reflection, absorption, and transmission of the material of the total reflection mirror (12) is also a technical issue, and in addition,
An essential disadvantage of the conventional method of reflecting the emitted light beam with a reflector is that it impairs the parallelism of the emitted light beam. Originally, one of the major advantages as a light source when applying a synchrotron radiation beam line to semiconductor lithography was the high parallelism of the synchrotron radiation beam. In the method of FIG. 7, it is equivalent to generating a synchrotron radiation beam line in the vertical direction centering on the reflecting mirror (12),
The width of the vibration is extremely limited from the viewpoint of parallelism.

FIG. 8 is a schematic diagram showing another method of the conventionally known longitudinal irradiation area enlarging method. This is because the equilibrium orbit (4) of charged particles is vertically oscillated with the (a) part of the ring as a node by the electromagnet for transverse magnetic field generation provided in the (b) part in the storage ring, and the radiation generated by it is generated. The light beam is swung in the vertical direction. In this method, it is possible to oscillate the synchrotron radiation beam line in the vertical direction while maintaining the parallelism, but the oscillation width of this equilibrium orbit cannot be so large due to the limitation due to the instability of the synchrotron radiation beam. There was a drawback. Furthermore, as an essential problem,
There is a drawback that only the radiation beams having different swing widths can be obtained from the plurality of radiation beam lines. Furthermore, the beam control of charged particles itself is extremely complicated and theoretically difficult to predict, which is a drawback.

As still another enlargement method, the mask (7) in the exposure unit (6) shown in FIG. 7 and the resist-coated wafer (8) can be integrated vertically without changing the relative positional relationship. A method of moving it is possible. That is, this is a method in which large-area exposure is considered on the sample side without changing the irradiation area by the radiation beam line from the charged particle device. However, it is pointed out that this method causes a problem in the divided exposure method. That is, since it is necessary to take a sufficient area without moving the sample during the exposure of one step, this method of moving the sample cannot perform divided exposure. This is because the lithographic method using the synchrotron radiation beam line is intended for a line width of 0.1 micron class, and a slight error in the relative positional relationship when moving the mask and the wafer together is not allowed. There are circumstances. Therefore, the mechanism for moving the mask and the sample wafer together becomes extremely complicated.

Even if the divided exposure method is not used, the mask (7) and the wafer (8) may be slightly exposed (for example, 1/10 of the line width to be exposed).
Even so, about 0.01 micron) does not allow relative deviation,
The mechanism for moving them together becomes very complicated and also has difficulty in reliability.

[Means for solving problems]

The charged particle device according to the present invention is capable of irradiating a large area by moving the equilibrium orbit of the charged particles in parallel in the vertical direction to expand the irradiation range of the generated synchrotron radiation beam line in the vertical direction. . That is, in order to move the equilibrium trajectories of the charged particles up and down in parallel, the storage ring can be moved in parallel and up and down.

[Action]

In the charged particle device according to the present invention, since the storage ring is movable in parallel in the vertical direction, the irradiation area of the radiation light beam line can be expanded without impairing the characteristics of the radiation light beam. That is, since the storage ring is repeatedly moved in parallel in the vertical direction while the synchrotron radiation beam line is generated, the irradiation area in the vertical direction of the synchrotron radiation beam line, that is, the exposure area is larger than that of the conventional one. It can be expanded from several times to several tens of times. In addition, it is possible without making the synchrotron radiation beam line, the storage ring, or the exposure unit complicated. In addition, the advantage of parallelism of radiated light can be fully utilized.

Example of Invention

An apparatus according to an embodiment of the present invention will be described below with reference to the front view of FIG. (13) is a mount for fixing the storage ring (1), (14) is a movable mechanism represented by a hydraulic cylinder for moving the mount (13) in the vertical direction of the arrow (m), and (15) is this charged particle. Floor to install the device, (16) is the synchrotron radiation beam line
It is a vacuum bellows inserted in part of (5).

Next, the operation will be described. First, the storage ring (1)
After accumulating the predetermined charged particles on the storage ring, the storage ring is moved up and down according to the operation curve preset by the movable mechanism (14). Here, the movement of the storage ring (1) in the vertical direction is to utilize the parallelism of the emitted light beam lines. The above movement requires the deflection electromagnet (3), the quadrupole electromagnet (9), and the other orbital electromagnets, which are the components of the storage ring (1), to move in parallel without changing their relative positions. . For this purpose, as shown in FIG. 1, it is the simplest to fix the storage ring (1) on a common mount (13) and to vibrate the mount (13) in the vertical direction by hydraulic control. And it is highly accurate. The gantry (13)
It is obvious that the vibration of (1) is not limited to the hydraulic control, but may be air or a mechanical movable mechanism. Further, in FIG. 1, a system using a plurality of hydraulic cylinders is shown, but this may be a single system.

FIG. 2 is a waveform diagram showing the moving position of the storage ring in the vertical direction. It should be noted that the essence of the present invention does not change even if the moving operation is performed smoothly as shown in FIG. 2 (A) or in a stepwise manner as shown in FIG. 2 (B). The effect of the present invention can be further enhanced by making the amount of movement, the moving speed, the number of repetitions, and the like of the vertical movement operation programmable according to the conditions on the exposure side.

Further, not only is this operation waveform preset, but also the light quantity of the radiated light beam is monitored, and the time integrated value of the light quantity irradiated by the monitor signal is always constant at different positions on the wafer. It is also possible to provide a control system for controlling the vertical movement speed of the storage ring (1) or the number of repetitions thereof.

FIG. 3 is a waveform diagram showing the pattern of changes in the moving speed set by the control system as described above. In the figure, in the case of FIG. 3 (B), the light quantity per unit of the emitted light beam is shown in FIG. 3 (A).
It corresponds to the state that it is reduced to about 1/2 compared to the case of. This indicates that the amount of charged beam in the storage ring (1) usually decreases with time. The light quantity of the emitted light beam per unit time is proportional to the charged beam quantity. Even in such a state, the exposure depth of the pattern transferred to the wafer (8) is determined by the product of the irradiation time of the radiant light beam and the light amount per unit time (strictly, the integrated value of time), In order to obtain a constant pattern depth, increase the number of repetitions of the emitted light in the vertical direction (when the movement speed is constant) or increase the time for one repetition (when the number of repetitions is constant). Will be needed. Fig. 3
(B) is an example in which this is compensated by slowing the moving speed.

The present invention has an advantage that uniform exposure can be obtained because the above control can be easily performed. Incidentally, the monitor of the light amount of the radiated light beam includes a device for directly photoelectrically converting the radiated light, but it can be substituted by monitoring the charged beam amount in the storage ring, that is, the beam intensity. it is obvious. Next, description will be given of the principle that when the storage ring is moved up and down, the emitted light also moves up and down accordingly. First, the equilibrium orbit and betatron oscillation of an accelerator that generally accelerates or accumulates particles to high energy will be briefly described. Here, the equilibrium orbit is a closed orbit through which the center of a charged particle or a group of charged particles passes. The actual charged particle revolves in the storage ring, that is, in the high vacuum donut (10) while slightly oscillating around the equilibrium orbit. This slight vibration is called betatron vibration. Both of these equilibrium orbits and betatron oscillations are uniquely determined by the arrangement of the electromagnets that make up the storage ring. In other words, if the position of the electromagnet is changed slightly, the equilibrium trajectory will shift to a position corresponding to it. Of course, if the electromagnet groups are moved independently, the closed orbit itself may disappear, or the beam may become unstable and be lost. After consideration at the design stage, it is usually fixed on the floor with the installation error minimized.

By the way, in the present invention, since the entire electromagnet group is moved up and down without changing the mutual positional relationship, the shape of the equilibrium orbit is unchanged and the position in the height direction is simply shifted up and down.
On the other hand, the charged particle beam, which has orbited the original equilibrium orbit in advance, moves to a new equilibrium orbit as the equilibrium orbit moves. The movement of this charged particle (beam) is explained by the following mechanism when viewed microscopically.

Now, the new equilibrium orbit of charged particles is
It is assumed that it has moved by (δ) mm in a short time. The charged particles that were in the original orbit here start betatron oscillation with an initial amplitude value of (δ) mm, and this betatron oscillation is vertical oscillation. It should be noted that this vibration is attenuated in an extremely short time due to radiation braking due to the emission of the radiation beam line. The time constant of this decay is usually several milliseconds in the storage ring for utilizing synchrotron radiation, and looking at this macroscopically, there is no problem even if the charged particles are instantaneously transferred to a new equilibrium orbit. Therefore, since the synchrotron radiation beam line is generated from the charged particle position, the synchrotron radiation also moves in the vertical direction. However, if you move a large distance that deviates from the gap distance of the electromagnet within a few milliseconds, a situation occurs in which particles hit the magnetic poles of the electromagnet faster than the amplitude decays, so the speed of movement is such. Don't be super fast. Of course, the movement of the storage ring in the present invention does not need to be performed at such an ultrahigh speed, so there is no problem at all. The vacuum bellows (16) of FIG. 1 is used to absorb the vertical displacement of the exposure part (6) and the storage ring (1).

In the figure, the upstream side of the charged particle incident part (2) is omitted, but if a similar vacuum bellows is also arranged in a part of this incident line, the height with the injector omitted in the figure is omitted. It is possible to absorb the displacement of the same as in the case of the synchrotron radiation beam line (5).

FIG. 4 is a front view showing an apparatus according to another embodiment of the present invention, in which the deflection electromagnet (3) of the storage ring (1) is a superconducting electromagnet. Since this superconducting electromagnet can increase the strength of the magnetic field, it has the features that the amount of radiated light can be increased, or the storage ring can be made compact and lightweight overall. Further, as another embodiment, it is of course possible to apply the present invention to a small-sized storage ring using a weakly converging electromagnet.

In the above embodiment, the vacuum donut (10) is also an electromagnet.
Although it is configured to move together with (3) and the like, as described in the above-mentioned operation principle, even if only the electromagnet group is uniformly moved in the vertical direction, the effect does not change at all.

〔The invention's effect〕

As described above, according to the embodiment of the present invention, the storage ring
Since (1) is configured to move in parallel to the floor surface (15) in the vertical direction, it is possible to perform large-area irradiation with high performance, which is unprecedented and has excellent parallelism with a simple and inexpensive structure. effective.

[Brief description of drawings]

FIG. 1 is a front view showing a charged particle device according to an embodiment of the present invention, FIGS. 2 (A) and (B) and FIGS. 3 (A) and (B) are operating characteristic diagrams in the present invention, respectively. 4 is a front view showing a charged particle device according to another embodiment of the present invention, FIG. 5 is a front view showing a conventional charged particle device, and FIG. 6 is a schematic view showing a spatial distribution of a conventional synchrotron radiation beam line. , FIG. 7 and FIG. 8 are schematic views showing a conventional method of enlarging a synchrotron radiation beam line. In the figure, (1) is a storage ring, (2) is an incident part, (3) is a bending electromagnet, (4) is a balanced orbit, (5) is a synchrotron radiation beam line, (6) is an exposure part, (7) Is a mask, (8) is a wafer, (9) is a quadrupole electromagnet, (10) is a vacuum donut, (11) is a high frequency cavity, (12) is a reflecting mirror, (13) is a mount, (14) is a movable mechanism, (15) is the floor, (16)
Is a vacuum bellows. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (10)

[Claims] 1. A charged particle apparatus for generating and utilizing a synchrotron radiation beam, wherein an equilibrium orbit of the charged particles is moved in parallel in the vertical direction to expand the vertical irradiation range of the generated synchrotron radiation beam line. , A charged particle device characterized by being capable of irradiating a large area. 2. The charged particle device according to claim 1, wherein a storage ring composed of a plurality of electromagnets and a vacuum donut is movable in parallel in the vertical direction together with a common mount. 3. A storage ring composed of a plurality of electromagnets and a vacuum donut, wherein the plurality of electromagnets are independent of each other or divided into a plurality of groups while keeping their relative positional relationship parallel to each other and are parallel to each other in the vertical direction. The charged particle device according to claim 1, wherein the charged particle device is movable to the inside. 4. The charged particle device according to claim 2, wherein the vertical movement is performed by hydraulic or pneumatic control. 5. The upstream side of the synchrotron radiation beam line moves vertically along with the equilibrium orbit, the downstream side is fixed at a constant height with respect to the floor surface, and the upstream side and the downstream side are made flexible by a vacuum bellows. Charged particle device according to claim 1, characterized in that it is coupled. 6. The charged particle device according to claim 1, wherein the storage ring includes a bending electromagnet composed of a superconducting electromagnet. 7. The charged particle device according to claim 2 or 3, wherein the vertical movement amount, the movement speed, and the number of repetitions are programmable. 8. A control system is provided so that, with respect to either or both of the vertical movement speed and the number of repetitions, the time integrated value of the amount of light emitted by the signal from the synchrotron radiation monitor is always constant. The charged particle device according to claims 2 and 3. 9. The charged particle device according to claim 8, wherein a charged beam intensity monitor of a storage ring is used as the emitted light intensity monitor. 10. The downstream side (storage ring side) of the charged particle incident line moves in the vertical direction together with the equilibrium orbit, and the upstream side.
The charging device according to claim 1, wherein the (injector side) is fixed at a constant height with respect to the floor surface, and the upstream side and the downstream side are flexibly connected by a vacuum pellows. Particle device.