JPS624318A - Adjustment of forming beam rotation in charged beam exposure apparatus - Google Patents

Abstract

PURPOSE:To facilitate adjustment of a forming beam rotation by a method wherein fine heavy metal particles are scanned with the edge of the forming beam and the inclination against the scanning direction of the forming beam is detected from a reflected electronic signal profile from the heavy metal particles. CONSTITUTION:A beam is so controlled as to have the predetermined beam size by a forming deflector 21 and the forming beam is made to scan with a scanning deflector 19 in such a manner that the edge of the forming beam 51 scans over fine particles 52 of a heavy metal such as gold. When the forming beam 51 passes on the heavy metal particle 52, reflected electron intensity becomes large. If the forming beam 51 has an inclination against the scanning direction, the reflected electron profile obtained by that reflection becomes an inclined beam profile and, if the forming beam 51 does not have an inclination, the reflected electron profile becomes uniform. Therefor,e if a beam density distribution at the beam edge part is known, the rotation (inclination) of the forming beam 51 can be obtained from that inclination. The inclination of the forming beam can be avoided by rotating aperture masks 13 and 15 corresponding to the edge by that rotation (inclination).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for adjusting the rotation of a shaped beam in a charged beam exposure apparatus using a shaped beam.

(Technical background of the invention and its problems) In recent years, various electron beam exposure apparatuses have been used to form desired patterns on samples such as semiconductor wafers and mask substrates. A variable-shaped beam type electron beam exposure apparatus that can vary the dimensions of a rectangular beam has also been researched and developed.A variable-size beam type electron beam exposure apparatus uses a first aperture mask having a rectangular aperture to which an electron beam is aligned. The beam that passes through the aperture of this mask is imaged onto a second aperture mask having a rectangular aperture, and the optical shape of the aperture is changed by deflecting the beam between each of the seven aperture masks. The dimensions are variable.

By the way, the pattern formed on the sample has a thickness of 0.5 μm.
] is required, and the beam shape can be up to about 10 [μm] in order to shorten sample exposure processing time, limit the uniformity of beam density, and reduce blur due to beam space charge effect.

Therefore, a rectangular shaped beam of 0.5[μTri,]×10[μTri,] is formed. The rotational accuracy of this shaped beam around the optical axis requires an accuracy of 1/20 of the minimum pattern dimension at the connection in order to smooth the connection between exposure positions by the shaped beam. In other words, 10 [μT
rL] for a beam of 0.5 [μm] Xi/20
In other words, the rotational adjustment of the shaped beam must be performed with a rotational accuracy of 2.5 [1 rad].

However, it is difficult to achieve such accuracy by incorporating an aperture mask, so the only way to find out the amount of rotation of the shaped beam is by assembling the aperture mask and then observing a sample that has been experimentally exposed. The only observation means available is an SEM (scanning electron microscope), which requires a large amount of measurement time and also requires skill in adjusting the rotation of the aperture mask.

Note that the above problem is not limited to the variable shaped beam method, but applies to all electron beam exposure apparatuses that use shaped beams. Furthermore, not only electron beam exposure apparatuses but also ion beam exposure apparatuses have similar problems.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a charged beam exposure apparatus that can easily and quickly adjust the rotation of a shaped beam and that can improve the operating rate. An object of the present invention is to provide a shaping beam rotation adjustment method.

[Summary of the invention]

The gist of the present invention is to detect the inclination of a shaped beam from the reflected electron or secondary electron signal profile when a minute heavy metal particle is scanned at the edge of the shaped beam.

That is, the present invention provides a charged beam exposure method in which a charged beam emitted from a charged beam source is irradiated onto an aperture mask, and the shaped beam that has passed through the aperture of the aperture mask is imaged onto a sample surface by a reduction lens system. In the apparatus, the edge of the shaped beam scans a minute area of a material that has a different intensity of reflected electrons or secondary electrons from the sample surface, and the slope of the reflected electron signal profile or secondary electron signal profile of the edge of the shaped beam obtained by this scanning. from,
This method detects the rotation angle of the shaped beam with respect to the scanning direction, and adjusts the rotation of the shaped beam based on this detected angle.

〔Effect of the invention〕

According to the present invention, it is not necessary to once testly expose a sample, and there is no need to use an expensive SEM, and it is possible to easily adjust the rotation of a shaped beam. Then, the rotational adjustment of the forming beam, which previously took approximately one day for a skilled worker, was completed.
Even an unskilled person can easily do it in about 10 minutes. Therefore, the operating rate of the charged beam exposure apparatus can be significantly improved.

[Embodiments of the invention]

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

FIG. 1 is a schematic diagram showing the structure of an electron beam exposure apparatus used in a method according to an embodiment of the present invention. An electron beam emitted from an electron gun (charged beam source) 11 is uniformly irradiated onto a first aperture mask 13 by a focusing lens 12 .

The beam that has passed through the aperture 13a of the aperture mask 13 is imaged onto the second aperture mask 15 by the projection lens 14. The beam that is shaped after passing through the aperture 15a of the aperture mask 15 is transmitted through the reduction lens 1
6 and an objective lens 17 onto a sample surface 18 .

A scanning deflector 19 is arranged between the lenses 16 and 17, and the beam position on the sample surface 18 is changed by this deflector 19. A blanking deflector 20 and a shaping deflector 21 are arranged between the aperture mask 13 and the lens 14. Then, the timing of beam irradiation is controlled by the blanking deflector 20. Furthermore, by changing the position of the beam imaged onto the aperture mask 15 by the shaping deflector 21, the dimensions of the shaped beam can be varied.

A predetermined deflection signal is supplied to the deflectors 19, 20, 21 from a computer (CPU) 30 via an interface 32. That is, each deflection voltage is controlled by the CPLJ 30 according to the pattern data in the memory 31, and a predetermined deflection voltage is applied to each deflector 19, 20, 21, respectively.

On the other hand, above the sample surface 18, a backscattered electron detector 41 for detecting backscattered electrons is arranged. The detection signal of this detector 41 is supplied to a monitor 43 via an amplifier 42 and also to the CPU 30 via an A/D converter 44. The monitor 43 displays the profile of the reflected electron signal.

Further, each aperture mask 13.15 is driven by a drive mechanism 4.
5.46, it has a rotatable structure. and,
By providing beam inclination information to the CPU 30 in accordance with display information on the monitor 43, or by the CPU 30, the beam inclination is determined based on the backscattered electron signal, and the rotation of the aperture mask 13, 15 is controlled in accordance with this inclination. It has become a thing.

Next, a method for adjusting the rotation of the shaped beam using the above device will be explained.

First, the beam size is controlled to a predetermined size by the shaping deflector 21, and the scanning deflector is adjusted so that the edge portion of the shaped beam 51 passes over minute heavy metal particles 52 such as gold, as shown in FIG. 19 to scan the shaped beam. Here, since the heavy metal particles 52 have a larger reflected electron coefficient than the sample surface 18, for example, a silicon or carbon surface, the intensity of reflected electrons increases when the shaped beam 51 passes over the heavy metal particles 52 once. . The backscattered electron profile (displayed on the monitor 43) obtained when scanning with the edge portion of the shaped beam 51 is the third
The result will be as shown in the figure. That is, when the shaped beam 51 has an inclination with respect to the scanning direction, it becomes an inclined beam profile as shown in FIGS. 3(a) and (C), and when there is no inclination, it becomes a uniform beam profile as shown in FIG. Become something. Therefore, if the beam density distribution at the beam edge portion is known, the amount of rotation (inclination) of the shaped beam 51 can be determined from this inclination.

The beam density distribution at the edge part is shown in Figure 4 (y-a
X (a is μ layer unit), and if the slope of the backscattered electron intensity profile at the edge part is (50%/10μ7FL), then the amount of beam rotation is 1 1 1 1 (ra
d) a 2 10 20a. Therefore, the aperture mask 13. corresponding to the edge by this amount. By rotating -15, the inclination of the shaped beam can be eliminated.

Thus, according to the method of this embodiment, by scanning minute heavy metal particles at the edge portion of the shaped beam, it is possible to easily detect the tilt of the shaped beam with respect to the scanning direction from the reflected electron signal profile. By rotating the aperture mask 13.degree. 15, the tilt of the shaped beam can be eliminated. Therefore, there is no need to testly expose the sample as in the past, and even 82M
There is no need for observation, and the rotational adjustment of the shaped beam can be performed very easily and in a single time. Therefore, the operation rate of the electron beam exposure apparatus can be greatly improved, and its usefulness in semiconductor manufacturing technology is enormous.

Note that the present invention is not limited to the method of the embodiment described above. For example, instead of rotating the aperture mask, the strength of the lens between the aperture mask and the sample may be changed to rotate the shaped beam. Also, can you convert the backscattered electron signal intensity profile to a digital signal and use a computer to broach it? It is also possible to automate the rotational adjustment of the shaped beam by determining the inclination of the beam and rotating the aperture mask with a motor or the like based on the amount of inclination. Furthermore, as means for detecting the inclination of the shaped beam, secondary electrons from the sample surface may be detected instead of reflected electrons. Further, the present invention is applicable not only to variable shaped beam type electron beam exposure apparatuses but also to general electron beam exposure apparatuses using shaped beams. Furthermore, the invention is not limited to electron beam exposure apparatuses, but can also be applied to ion beam exposure apparatuses that use shaped beams. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of an electron beam exposure apparatus used in a method according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the relationship between the edge position and scanning direction of a shaped beam and minute heavy metal particles. 3(a) to (C) are schematic diagrams showing the relationship between the inclination of the shaped beam and the backscattered electron signal profile, and FIG. 4 is a schematic diagram for explaining the linear approximation of the edge portion of the backscattered electron intensity profile. . 11... Electron gun (charged beam source), 12... Focusing lens, 13... First aperture mask, 13a#1
5a...Aperture, 14 river projection lens, 15...
Second 7 Virtua mask, 16... Reduction lens, 17
... Objective lens, 18... Sample surface, 19... Scanning deflector, 20... Blanking deflector, 2o... Shaping deflector, 3o... CPU, 31... Memory, 32
...interface, 41...backscattered electron detector,
43...Monitor, 45.46...Drive mechanism. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 (a) (b) (c)
Figure 3 Figure 4

Claims (2)

[Claims] (1) In a charged beam exposure device that irradiates a charged beam emitted from a charged beam source onto an aperture mask, passes through the aperture of the aperture mask, and images the shaped beam onto a sample surface using a reduction lens system. , scan a micro region of a material that has a different reflected electron intensity or secondary electron intensity from the sample surface with the edge of the shaped beam, and from the slope of the reflected electron profile or secondary electron signal profile of the shaped beam edge obtained by this scanning. A method for adjusting rotation of a shaped beam in a charged beam exposure apparatus, comprising: detecting a rotation angle of the shaped beam with respect to a scanning direction, and adjusting the rotation of the shaped beam based on the detected angle. (2) As the aperture masks, first and second aperture masks arranged apart in the beam traveling direction are used, the beam from the charged beam source is irradiated onto the first aperture mask, and the beam from the charged beam source is irradiated onto the first aperture mask. The beam that has passed through the aperture of the first aperture mask is transferred to the second aperture mask by the projection lens.
A shaped beam that is imaged or directly irradiated onto an aperture mask of the second aperture mask, and is formed by passing through an aperture of a second aperture mask is imaged onto the sample surface by the reduction lens system. 2. A shaped beam rotation adjustment method in a charged beam exposure apparatus according to item 1.