JPS61135121A - Aperture mask for beam formation - Google Patents

Abstract

PURPOSE:To contrive the improvement of machining accuracy and heat resistance by making a coated conductive film on the surface of a knife edge of one side extended externally from a supporter made of a metal plate and one of diamond, sapphire or ruby. CONSTITUTION:A supporter 10 made of a metal plate is a half of circular disk, a recession 11 is provided at the center and a knife edge from 20 made of 100mum thick diamond is attached on the upper surface of the center of the recession 11 of the supporter 10. The form 20 has two surfaces 22, 23 to form a knife edge 21 which are polished to a mirror surface of lambda/10 or less and the surface of the form 20 is coated with a high melting point metal such as tungsten or molybdenum. The form 20 is attached on the upper surface of the supporter 10 brazed at an oblique area 30. Since the knife edge 21 which constitutes each side of an aperture 50 is made of diamond, machining accuracy can be made extremely high and exposure accuracy can be improved since the area irradiated by a beam is highly heat-resistant diamond.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in beam shaping aperture masks used in charged beam exposure apparatuses and the like.

[Technical background of the invention and its problems]

In recent years, various electron beam exposure apparatuses have been developed to form desired patterns on samples such as semiconductor wafers and mask substrates. In this type of electron beam exposure equipment,
Requirements for higher throughput and higher precision include: ■ Increasing the beam current; ■ Improving the dimensional accuracy of the shaped beam; and driving the optical lens barrel with a smaller drive power source.

One way to simultaneously meet these requirements is to improve the precision and heat resistance of the aperture mask for beam shaping, and to irradiate the aperture mask with a small diameter of 7 vertices with a beam of high current density. One possible method is to make the reduction ratio relatively small. That is, by increasing the current density that irradiates the aperture mask, a large current density can be obtained even if the reduction ratio in the subsequent optical system is not very high. Furthermore, if the aperture is small, 1-aB
Even if an electron gun with a small beam radiation angle, such as a five-electron gun, is used, the aperture mask can be illuminated without greatly expanding the beam. Moreover, if the reduction ratio is small, the lens system will be small, and the distance from the electron gun to the target can be shortened, and the space charge effect can be kept small, so even if the current is large, the beam resolution will not deteriorate. Further, since the aperture is small, the amount of deflection of the beam when changing the beam size is small, and the beam size can be changed with a small driving voltage.

However, conventional aperture masks for beam shaping have insufficient heat resistance and cannot be used for illumination with a beam having a large beam current density as described above. Furthermore, the machining accuracy was insufficient, and it was not possible to form the above-mentioned small-diameter apertures with high precision. Here, as the diameter of the aperture becomes smaller, the reduction ratio in the optical system becomes smaller, so higher processing accuracy is required.

[Purpose of the invention]

An object of the present invention is to provide an aperture mask for beam shaping that can improve processing accuracy and heat resistance, and can contribute to increasing the throughput of an electron beam exposure apparatus and improving exposure accuracy.

[Key points of the invention]

The gist of the present invention is to form the knife edge of the aperture and the surface to which the beam is irradiated from a single crystal with a high melting point and high hardness, such as diamond, sapphire, or ruby.

Crystals with high hardness can generally be polished with high precision,
Especially for diamond, the surface roughness is λ/10-0.06
It is also easy to make it less than [μTrL]. Therefore, λ
If a knife edge is made of two surfaces with a surface roughness of λ/10, the edge roughness can be reduced to λ/10 or less. A large diamond plate is expensive, so if only the part where the beam enters is made of diamond and the surrounding area is attached to a metal plate, it can be realized at a relatively low cost.

The present invention has focused on such points, and provides an aperture mask for beam shaping in which a plurality of mask bodies are combined to form an aperture of a predetermined shape. , a knife forming body made of at least one of sapphire and ruby, and attached to the support so that one side thereof projects outward from one side of the support to form a knife surface; It is constructed of a coated conductive NW 4.

〔Effect of the invention〕

According to the present invention, since the knife edge and the surface to which the beam is irradiated are shaped with a high-melting-point, high-hardness single crystal such as diamond, the knife edge can be processed with high precision, and the part that is irradiated with the beam can be processed with high precision. Heat resistance can be significantly improved. Therefore, the beam shaping aperture according to the present invention can be irradiated with a beam having a high beam current density. Therefore, when applied to an electron beam exposure apparatus, for example, it is possible to increase exposure throughput and improve exposure accuracy. Further, in the conventional apparatus, a beam reduction ratio of 1/40 to 1/200 was used to reach the target, but the present invention allows the diameter of the aperture to be made small, so that the beam reduction ratio can be reduced to about 1/10. As a result, the optical cylinder length can be set to 172), and the driving power supply voltage can be halved without changing the beam dimensions.

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

FIG. 1 is a perspective view showing a schematic configuration of a mask body, for explaining an aperture mask for beam shaping according to an embodiment of the present invention. In the figure, 10 is a support made of a metal plate, and this support 10 is formed by dividing a disk into 1/2 and providing a recess 11 in the center. A knife forming body 20 made of diamond and having a thickness of 100 μm is attached to the upper surface of the central portion of the recess 11 of the support 10 .

This formed body 2o is formed by a knife 21 as shown in FIG.
The two surfaces 22 and 23 forming the surface are polished to a mirror surface of λ/10 or less.

Further, although not shown in the figure, the surface of the formed body 20 is coated with a film of a high melting point metal such as tungsten or molybdenum. The formed body 20 has a hatched portion 30 shown in the figure.
is attached to the upper surface of the support body 10 by brazing.

In addition, 40 in the figure is a dowel hole provided in the support body 10, and this hole 40 is formed by positioning while looking at the knife 21.

To make an aperture mask having, for example, a rectangular aperture using the mask body configured as described above, four mask bodies are combined and adjacent knifes 21 (211, 212) are formed as shown in FIG.

213, 214) are orthogonal to each other.

At this time, if the thickness of the mask body is 200 [μm],
The thickness of the aperture is (number of sheets - 1) x 200 [μTrL], and for four sheets, it is 600 [μm]. However, 1/
In an optical system with a reduction ratio of 10, the depth of focus is 100 times the depth of focus on the target, so for a depth of focus on the target of ±5 [μm:l, a depth of focus of 1 [Im] is the aperture. Therefore, 600 [μm] does not pose any problem.

In the beam shaping aperture mask configured in this way, the knife edges 2 forming each side of the aperture 50 are
Since aperture 1 is made of diamond, aperture 5
0 processing accuracy can be made extremely high. Therefore, even a small-diameter 7-vertia can be formed with sufficient accuracy. In general, since the portion irradiated by the beam is made of highly heat-resistant diamond, a beam with a high beam current density can be used. Therefore, when applied to, for example, an electron beam exposure apparatus, it is possible to illuminate seven beams with a small diameter with a beam having a large beam current density, and it is possible to improve exposure throughput and exposure accuracy.

Note that the present invention is not limited to the embodiments described above. For example, the member forming the knife formation body is not limited to diamond, but sapphire, ruby, etc., which are single crystals with a high melting point and high hardness, can also be used. Further, the shape of the aperture is not limited to a rectangle, and can be changed as appropriate. In addition, two beam shaping apertures are used, and the aperture 501 as shown in FIG.
When forming a rectangular variable dimension beam using an overlap of 502 degrees, each side of the aperture 501 is 61 degrees to 64 degrees.
and each side 71. of the aperture 502. ~
, 74, only the two sides 71 and 72 may be formed of knife blades made of diamond or the like. In addition, attachment of the knife formation body to the support body is not limited to brazing,
It is possible to use screws or other methods. Furthermore, the present invention is applicable not only to electron beam exposure apparatuses but also to ion beam exposure apparatuses and other various apparatuses that require beam shaping. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic structure of the mask body for explaining an aperture mask for beam shaping according to an embodiment of the present invention, FIG. 2 is a plan view showing an enlarged knife portion, and FIG. The figure is a schematic diagram showing an example in which seven rectangular virtuaries are created by combining mask bodies, and FIG. 4 is a schematic diagram for explaining a modified example. DESCRIPTION OF SYMBOLS 10... Support body, 11... Recessed part, 20,201. ~
. 204... Naifetsuji formation, 21,211. ~. 214... knife hole, 22.23... knife forming surface, 30... brazing part, 40... dowel hole, 50.50s, 502... aperture. Applicant's agent Patent attorney Takehiko Suzue Plagiarism Figure 2 Figure 3

Claims (3)

[Claims] (1) In a beam shaping aperture mask formed by combining a plurality of mask bodies to form an aperture of a predetermined shape, each mask body is made of a support body made of a metal plate and at least one of diamond, sapphire, and ruby. and a knife edge forming body attached to the support such that one side thereof projects outward from one side of the support to form a knife edge, and a conductive film coated on the surface of the forming body. An aperture mask for beam shaping that is characterized by (2) The aperture mask for beam shaping according to claim 1, wherein the aperture is formed in a rectangular shape. (3) The aperture mask for beam shaping according to claim 1, wherein the knife edge forming body is brazed to the support body.