JPS62114220A - Matching method for beam axis of charged beam lithography equipment - Google Patents

Abstract

PURPOSE:To readily match a charged beam axis to an objective lens by applying a voltage for generating a quadruple pole magnetic field in a scanning deflector, and so regulating the optical path of the beam by a beam axis matching deflector as not to move the beam position on a sample even if the amplitude of the applied voltage varies. CONSTITUTION:Whether a beam axis and the center of a scanning deflector 24 are matched is decided by detecting the movement of a beam position on a sample 17 when an applied voltage V of the deflector 24 is varied, and the beam axis can be matched to the center of the deflector 24 by setting currents of alignment coils 26, 27 so that the beam position does not move. The charged beam can be readily and effectively matched to an objective lens 15 only by detecting the beam movement on the sample 17. Thus, the resolution of an electron beam on the sample 17 is improved, and the beam resolution at deflecting time can be improved to remarkably enhance a drawing accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a charged beam lithography apparatus, and more particularly to a beam alignment method for a charged beam lithography apparatus for aligning a beam to the center of an objective lens.

[Technical background of the invention and its problems]

In recent years, various electron beam lithography devices have been used as devices for forming fine and high-density patterns for VLSIs and the like. This device directly draws a desired pattern on a sample by focusing the electron beam emitted from an electron gun using various lens systems and focusing it using each positive deflection system.

Then, 0.5 [μrrL, which cannot be transferred with light.
] It is extremely effective as an LSI manufacturing device because it can directly draw a VLSI pattern with the following design rules.

Incidentally, in this type of apparatus, in order to draw a highly accurate pattern, it is necessary to align the axis of the electron beam and various lens systems, especially the objective lens.

As a method for performing axis alignment, there is a method using an aperture of an objective lens and an alignment coil as shown in FIG. In this method, a wide range of deflection is not performed, and the scanning deflector 72 is placed above the center of the objective lens 71.
．． 73 is arranged, and in order to deflect the beam using the center of the objective lens 71 as a fulcrum, a system is used in which the beam is deflected in two stages using deflectors 72 and 73 so that the beam 74 always passes through the center of the lens 71. We are hiring. Here, in order to obtain the desired resolution, the beam 74 must be
It must be adjusted with the alignment coil 75 so that it passes through the center of 1. In this case, the beam axis can be easily aligned by inserting an aperture 76 in the center of the objective lens 71 and adjusting the alignment coil 75 while observing the beam current.

However, in a so-called in-lens deflection system in which a deflector 77 is disposed within a lens 71 for the purpose of deflection over a relatively wide range as shown in FIG. It is not possible to insert an aperture for center detection inside. Therefore, in order to align the axes, the deflected beam shape is observed at each point on the sample surface, and if the axes are aligned, the aberration pattern becomes isotropic. must be used. Therefore, each time the alignment coil 75 is moved once, the aberration pattern at each point on the field is changed to 1! It took a lot of time to align the beam axes, and reproducibility could not be achieved.

Note that the above problem is not limited to electron beam lithography apparatuses, but also applies to ion beam lithography apparatuses using ion beams.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to easily align the axis of a charged beam with respect to an objective lens, and to be applicable to devices that deflect a large amount of charged beam. An object of the present invention is to provide a method for aligning the beam axis of a drawing device.

[Summary of the invention]

The gist of the present invention is to use a scanning deflector consisting of 4n electrodes (n is a positive integer), apply a voltage to each electrode of this deflector to generate a quadrupole electric field, and apply the voltage to each electrode of the deflector. The purpose is to measure the movement of the beam position on the sample when the magnitude of the voltage is changed. In other words, when the beam axis and the center of the objective lens are perfectly aligned, the beam position on the sample does not change, so the position of the charged beam is adjusted using the alignment coil so that the beam position does not change. be.

That is, the present invention provides VIN emitted from a charged beam radiation source.
An objective lens that focuses the beam onto the sample, a scanning deflector consisting of 4 n electrodes (n is a positive integer) that scans the beam on the sample, and a charged beam radiation source than the scanning deflector. In the beam axis alignment method of the charged beam lithography apparatus, the charged beam lithography apparatus includes a beam axis alignment deflector disposed on the side, the beam axis alignment method of the charged beam lithography apparatus aligning the axis of the charged beam with respect to the objective lens, the scanning deflector A voltage that generates a quadrupole electric field is applied to the device, and the optical path of the beam is adjusted using the beam axis alignment deflector so that the beam position on the sample does not shift even if the magnitude of the applied voltage is changed. This is how I did it.

〔Effect of the invention〕

According to the present invention, it is possible to easily and accurately align the axis of the charged beam with respect to the objective lens simply by measuring and stabilizing the beam movement on the sample surface. Therefore, it is possible to improve the resolution of charged particles on the sample, especially the beam resolution during deflection. Furthermore, since there is no need to provide an aperture for center detection within the objective lens, it can be easily applied to devices with large deflection.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing an electron beam lithography apparatus used in the first embodiment method of the present invention. In the figure, 11 is an electron gun, and the electron beam emitted from this electron iii is
Various lenses 12. . . . , 16 onto the sample surface 17. Here, 12 and 13 are condenser lenses, 14 is a projection lens, 15 is a reduction lens, and 16 is an objective lens. A first shaped aperture mask 21 is arranged between the condenser lens 13 and the projection lens 14, and a second shaped aperture mask 22 is arranged between the projection lens 14 and the reduction lens 15. Further, between the first shaped aperture mask 21 and the projection lens 14, a mask 21-. A dimension variable deflector 23 is disposed for varying the dimensions of the aperture image by varying the overlap of each of the seven groups of 22.

Further, between the reduction lens 15 and the objective lens 16, a scanning deflector 24 for scanning the beam on the sample surface 17 is provided.
is located. Here, the scanning deflector 24 is
As shown in the figure, four plate-shaped electrodes (quadrupole electrodes) 24a, ~
, 24d, and the electron beam is scanned over the sample surface 17 by applying a voltage IIJ m to each electrode 24a, . . . , 24d. Alignment coils 25 and 26 are arranged between the scanning deflector 24 and the reduction lens 15, respectively. Furthermore, an electron detector 27 for detecting anti-IJJIt particles and the like from the sample surface 17 is arranged between the objective lens 16 and the sample surface 17. In FIG. 1, P indicates an electron gun crossover image, PI, .

Next, a beam axis alignment method using the above device will be explained.

First, as shown in FIG. 2, each 1' pole 2 of the scanning deflection B24 is
A predetermined voltage for axis alignment adjustment is applied to 4a to 24d. That is, a voltage of /i5) polarity is applied to the opposing electrodes, and a voltage of opposite polarity is applied to the adjacent electrodes.
For example, +V is applied to the electrodes 24a and 24c facing each other in the X direction.
1M24b, 24 facing in the Y direction.
A voltage of -V is applied to d. With such a voltage arrangement, the deflector 24 generates an electric field represented by an electric force of 1 m29 in the figure, that is, a 4I-pole electric field.

In this state, when the electron beam passes through the center O of the deflector 24, the electron beam passes through an area where there is no electric field, so it travels straight. When the electron beam passes through a location away from the center O, for example when passing through point R in the figure, the electron beam is deflected in the direction of the arrow. The degree of this deflection depends on the distance from the center O to the point R and the voltage V applied to each electrode of the deflector 24. That is, as shown in FIG. 3, when the voltage V applied to the deflector 24 is changed, the electron beam incident on the deflector 24 with a deviation from the center O becomes 31, 32, 33 in the figure.
The beam passes through an optical path such as , and the beam position on the sample surface 17 also moves as shown at 35°36.37 in the figure. On the other hand, since the beam passing through the center of the deflector 24 as shown in FIG.

Therefore, even if the voltage V applied to the deflector 24 is changed, the beam position on the sample surface 17 is not moved.
The optical path of the electron beam incident on the alignment coil 25
．． 26 causes the electron beam to pass through the center of the objective lens 16.

Now, in order to actually align the beam axes, first align the alignment coil 25 as shown in the flowchart in FIG.
Initialize the current of 26. In this initial setting, for example, each current of the coils 25 and 26 is set to zero. Next, by varying the applied voltage (2) to the scanning deflector 24, it is detected whether or not the beam position on the sample surface 17 at this time has moved. Various methods can be considered for this detection, but for example, the beam is set to irradiate fine particles such as gold placed on the sample surface 17 at the initial value of the applied voltage V of the deflector 24, and the applied voltage It is sufficient to detect whether or not the reflected electron detection output changes when V is changed. Furthermore, the position of the probe on the sample surface 17 may be monitored using a CRT or the like based on the backscattered electron signal.

If the beam position on the sample surface 17 does not move, the beam axis is aligned with the center of the objective lens 16, so the current in the alignment coils 25, 26 is maintained at its current value. In addition, when the beam position on the sample surface 17 moves, the current I of the alignment coils 25 and 26 is reset, and the applied voltage V of the scanning deflector 16 is varied again to move the beam position on the sample surface 17. Detect movement of. Here, the current settings of the alignment coils 25 and 26 may be determined as appropriate depending on the moving direction of the beam (X direction component and Y direction component). By repeating this, a point where the beam position does not move is found, and the alignment of the beam axis is completed.

Thus, according to the method of this embodiment, by detecting the movement of the beam position on the sample surface 17 after changing the voltage V applied to the scanning deflector 24, the beam axis and the deflector 24 can be adjusted.
By setting the 'I flow of the alignment coils 25 and 26 so that the beam position does not move, the axis of the beam can be determined to be aligned with the center of the deflector 24. can be matched. That is, simply by detecting the beam movement on the sample surface 17, the axis of the charged beam with respect to the objective lens 16 can be easily and reliably aligned. Therefore, it is possible to improve the resolution of the electron beam on the sample surface 17, especially the beam resolution during deflection, and it is possible to significantly improve the writing accuracy. Further, since there is no need to arrange an aperture for center detection at the center of the objective lens 16, the present invention can be easily applied to devices with large deflection.

FIG. 5 is a plan view showing the structure of a deflector of an electron beam lithography apparatus used in the second embodiment method of the present invention. The scanning deflector 54 of this device has eight rod-shaped electrodes 54a, .
h are arranged at equal intervals on the circumference. Also in this case, a pair of electrodes 54a facing each other with respect to the center of the circle
, 54e are applied with a voltage of +V, electrodes 54C and 54Q which are orthogonal to the electrodes 54a and 54e are applied with a voltage of +V, and the middle four electrodes 54b, 54d and 54f are applied with a voltage of +V.

By applying Ov to each of the electrodes 54h, a 41-pole electric field can be formed as shown by the lines of electric force 59 in the figure. Therefore, the electron beam can be aligned to the center of the objective lens 24 in the same way as in the previously described embodiments.

FIG. 6 is a schematic diagram showing the main structure of an electron beam lithography apparatus used in the third embodiment method of the present invention. The scanning deflector 60 of this device is composed of two stages: a main deflector 61 and a sub-deflector 62. The main deflector 61 and the sub-deflector 62 are each composed of 4-pole or 8-pole electrodes, and the voltage shown in FIG. 2 or 4 is applied to each electrode to generate a quadruple electric field. has been done.

In this embodiment, as in the first embodiment, even if the voltages applied to the main deflector 61 and the sub-deflector 62 are changed, the beam position on the sample surface 17 is prevented from moving. By adjusting the optical path of the beam using the alignment coils 25 and 26, the electron beam can be passed through the centers of the main deflector 61 and the sub deflector 62. That is, the axis of the electron beam can be aligned to the center of the objective lens 16.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the scanning deflector is not limited to one formed of four or eight electrodes, but may be formed of 4n electrodes (n is a positive integer), and can generate a quadruple contact electric field. Good to have.

Further, as a means for detecting the beam position on the sample surface, a method such as monitoring backscattered electrons may be appropriately selected. Furthermore, the electron optical lens barrel is not limited to the configuration shown in FIG. 1 or FIG. 6, but may include an objective lens,
Any device having a scanning deflector and an axis alignment deflector can be applied. Furthermore, electron beam lithography 'V
Of course, the present invention can be applied not only to Aili but also to ion beam lithography apparatuses. In addition, numerous modifications can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam drawing device used in the first embodiment method of the present invention, FIG. 2 is a plan view showing a specific configuration of a scanning deflector used in the device, and FIG. The figure is a schematic diagram for explaining the operation of the method of the above embodiment, FIG. 4 is a flowchart for explaining a specific example of the axis alignment method, and FIG. 6th plan view showing the structure of the scanning deflector of the beam writing device;
The figure is a schematic diagram showing the main structure of an electron beam lithography system used in the third embodiment method of the present invention, and FIGS. 7 and 8 are schematic diagrams for explaining the problems of the prior art, respectively. 11... Electron gun, 16... Objective lens, 17...
Sample surface, 24.54.60--Scanning deflector, 24a
. ~, 24d, 54a, ~, 54h-... Electrode, 25° 26... Alignment coil (deflector for axis alignment),
27...electronic detector. Applicant's agent Patent attorney Takehiko Suzue LUJ ~ 11 Figure 1 V Chrysanthemum 2 Figure 3 Figure 4 -■ 5th factor Figure 6 Figure 7 Figure 8

Claims (3)

[Claims] (1) an objective lens that focuses a charged beam emitted from a charged beam radiation source onto a sample, and a scanning deflector consisting of 4n electrodes (n is a positive integer) that scans the beam on the sample; A charged beam lithography apparatus is provided with a beam axis alignment deflector disposed closer to the charged beam radiation source than the scanning deflector, and in the method of aligning the axis of the charged beam to the center of the objective lens, 4 for scanning deflector
A voltage that generates a heavy pole electric field is applied, and the optical path of the beam is adjusted by the beam axis alignment deflector so that the beam position on the sample does not move even if the magnitude of the applied voltage is changed. A method for aligning the beam axis of a charged beam lithography system. (2) As the scanning deflector, a device in which the electrodes are arranged axially symmetrically is used, and the same voltage is applied to opposing electrodes. A method for aligning the beam axis of a charged beam lithography system. (3) A beam axis alignment method for a charged beam drawing apparatus according to claim 1, characterized in that the scanning deflector is arranged in two stages in the beam traveling direction.