JPS6276621A - Aperture mask for charged beam restriction - Google Patents

Abstract

PURPOSE:To improve the machining accuracy of an aperture by a method wherein two openings differing in diameter are used for aperture to make the thickness of a mask substrate sufficient thickness for heat conduction, and the depth of the opening is made thin to the degree where required machining accuracy can be obtained so as to prevent the thermal deformation of the aper ture and melting losses with favorable heat conduction. CONSTITUTION:The trancated corn-shaped second opening 12 is formed until it reaches from the back of the mask substrate 10 to the surface. Then, the first opening section 11 whose diameter is smaller than the largest diameter of the second opening section 12 and is larger than the smallest diameter of the second one is formed from the surface of the substrate 10 parallel to it. For forming the first opening section 11, it is convenient to use the substrate with higher machining accuracy such as panching. When the first opening section 11 is formed, the depth h of the first opening section 11 is sufficiently shallower than the thickness of the substrate 10. Moreover, it is possible to change the depth h beforehand in accordance with conditions such as the size of the second opening 12 and its taper angle suitably and also possible to sufficiently make it thin until the required machining accuraly is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a charged beam limiting aperture mask used in a charged beam device.

(Technical background of the invention and its problems) In a charged beam exposure device such as an electron beam exposure device or an ion beam exposure device, a predetermined size and shape is used for the purpose of defining the beam shape and checking the alignment state. A charged beam limiting aperture mask with seven apertures is used.

As shown in FIG. 5, this aperture mask is generally formed by drilling parallel holes 51 as apertures in a high melting point metal plate 50 as a mask substrate. In addition, 5 in the figure
Reference numeral 3 indicates a holder for holding an aperture mask, 54 indicates an electron beam irradiated to the aperture mask, and 55 indicates an electron beam passing through the aperture mask.

However, this type of aperture mask has the following problems. That is, due to limitations in the method of forming an aperture hole, a highly accurate hole can only be formed to a depth of about 10 [μm] at most.

Therefore, the thickness of the substrate must also be the same size. On the other hand, when the electron beam hits the aperture mask,
Part of that energy is converted into heat, and due to the lack of heat conduction due to the thinness of the aperture mask, the temperature of the aperture mask increases, causing problems such as thermal deformation and melting of the aperture shape. .

In particular, as shown in Figure 6, when the aperture shape seen from the top is not round, in the case of a so-called shaped aperture mask, the area around the aperture will be locally heated, resulting in thermal deformation and melting of the aperture. Losses are likely to occur. Moreover, in order to avoid this, there is a disadvantage that the energy of the electron beam must be lowered.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to improve heat conduction, prevent thermal deformation and melting damage of the aperture, and improve the machining accuracy of the aperture. An object of the present invention is to provide an aperture mask for limiting a charged beam.

[Summary of the invention]

The gist of the present invention is to use two openings with different diameters as apertures, so that the thickness of the mask substrate is sufficient for heat conduction, and the depth of the opening limits the passage of the vI electric beam. The process consists of thinning the material until the required processing accuracy is obtained.

In a charged beam device, the difference between the amount of the beam that irradiates the aperture mask and the amount of the beam that passes through the aperture mask, that is, the amount of the beam that hits the aperture mask, is the heat source, which is mainly present near the aperture. There is. This heat is transmitted through the aperture mask member and radiated to the aperture mask holder and the like. Once the material of the aperture mask is determined, the thermal conductivity is uniquely determined, so as is well known in heat transfer optics, the total amount of heat flowing from the high temperature area to the low temperature area is proportional to the thickness of the aperture mask. do. From this relationship, the thickness required for heat transfer can be determined, and this thickness is sometimes required to be about 1 [M].

On the other hand, regarding the depth of the aperture, for example, when etching molybdenum, it is possible to precisely process the aperture to only about 50 [μm]. Furthermore, if the aperture shape seen from the top is not round, the etching process tends to round the corners, making it unsuitable for use as a shaping aperture mask. In this case, if the punching process is performed using a punch finished with the desired aperture outline shape,
This is desirable because the shape and precision of the punch can be directly transferred to the aperture mask. Even with this punching process,
The thickness that can be processed with high accuracy is limited to several hundred [μ77L].

Therefore, in the present invention, the necessary thickness of the high melting point metal plate is first determined from the viewpoint of heat conduction, and the first step is to limit the passage of the charged beam.
A second aperture having a larger diameter than the aperture is provided so that the depth of the aperture falls within an allowable range for machining accuracy. In addition, in order to form the difference between the thickness required for heat transfer and the depth that can be machined with high precision, that is, the second hole, the precision is not very high, but the dimension is sufficient, such as electrical discharge machining or coining. Just use whatever method you can.

The present invention focuses on such points, and provides an aperture mask for limiting a charged beam in which an aperture is formed in a mask substrate that blocks a charged beam. It is formed by a first aperture that restricts the passage of the beam, and a second aperture that is opened from the opposite side of the substrate until it reaches the aperture and has a larger diameter than the aperture. It was designed to do so.

〔Effect of the invention〕

According to the present invention, since the mask substrate has a thickness sufficient for heat transfer, there are no problems such as deformation of the aperture shape or melting. Furthermore, since the depth of the first opening that restricts the passage of the beam can be made sufficiently thinner than the thickness of the substrate, processing accuracy can be improved. Therefore, it is possible to avoid the situation where the beam energy is lowered to prevent thermal deformation of the aperture, resulting in a reduction in throughput, and it is also possible to avoid replacing the aperture mask due to melting damage.
Effects such as the elimination of lost time due to evacuation, etc. can be obtained.

[Embodiments of the invention]

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

FIG. 1 is a sectional view showing a schematic structure of an aperture mask according to an embodiment of the present invention. In the figure, 10 is a mask substrate made of a high melting point metal such as molybdenum.
A circular first aperture 11 and a truncated conical second aperture 12 are formed in the center. Further, 13 is a holder that holds an aperture mask, 14 is an electron beam irradiated to the aperture mask, and 15 is an electron beam that has passed through the aperture mask and has been shaped.

FIGS. 2(a) and 2(b) are cross-sectional views showing the manufacturing process of the aperture mask. First, as shown in FIG. 2(a), a truncated conical second opening 12 is formed from the back side of the mask substrate 10 to the front side. This second opening 1
2 does not require high machining accuracy, so electrical discharge machining or the like may be used. Next, as shown in FIG. 2(b), from the surface side of the substrate 10, a first opening 1 is formed which is smaller than the maximum diameter of the second opening 12 and larger than the minimum diameter.
1 are formed in parallel. The first opening 11 may be formed using a highly accurate process such as punching. Here, when forming the first opening 11, the first
The depth h of the opening 11 is sufficiently thinner than the thickness of the substrate 10.

Further, this depth h can be changed as appropriate depending on conditions such as the size of the second opening 12 formed in advance and its Taber angle, and it is possible to make it sufficiently thin until the required processing accuracy is achieved.

Thus, according to this embodiment, by forming the second openings 12 in advance, the first openings 11 can be formed with high processing accuracy regardless of the thickness of the substrate 10.

Therefore, an aperture mask with high aperture processing accuracy and good heat dissipation properties can be realized, and its usefulness is extremely high.

FIGS. 3(a) and 3(b) are process sectional views for explaining another embodiment.

This embodiment differs from the previously described embodiments in that a polygonal opening is provided as a beam-limiting aperture. That is, in this embodiment, first, as shown in FIG. 3(a), a truncated cone-shaped second flowering portion 22 is formed such that the distance from the back side of the mask substrate 2o to the substrate surface is h. This flowering part 22 does not require high processing precision as before. Next, as shown in FIG. 3(b), a first opening 21 that acts as an aperture for beam restriction is formed by punching or the like. The shape of this first opening 21 is as follows:
As shown in FIG. 4, two rectangles are combined.

In this embodiment, when forming the first opening 21,
Since it is only necessary to process at the thickness of the board, sufficient processing accuracy (
This means that you will be able to do this. Furthermore, the thickness of the substrate 20 can be set to a sufficient thickness necessary for heat transfer compared to the above-mentioned plate thickness. Therefore, the same effects as in the previous embodiment can be obtained.

Note that the present invention is not limited to the embodiments described above. For example, the mask substrate is not limited to molybdenum, but may also be tungsten or tantalum.

Other high melting point metals can be used. Furthermore, the shape of the first and second apertures is such that the entire first aperture is the same as the second aperture.
It can be changed as appropriate as long as it fits within the opening.

Further, the first opening may be formed by any method other than punching, as long as it can provide high processing accuracy. moreover,
Forming the second opening does not require high machining accuracy, but any method can be used as long as it allows sufficient dimensional machining. Furthermore, it goes without saying that the present invention can be applied not only to electron beams but also to aperture masks that restrict the passage of ion 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 sectional view showing a schematic structure of an aperture mask according to an embodiment of the present invention, FIGS. 2(a) and 2(b) are sectional views showing the manufacturing process of the aperture mask of the above embodiment,
a) and (b) are process cross-sectional views for explaining other embodiments,
FIG. 4 is a plan view showing the shape of the opening in the above-mentioned embodiment, FIG. 5 is a sectional view showing the schematic structure of a conventional aperture mask, and FIG. FIG. 10.20... Mask substrate, 11.21... First opening, 12.22... Second opening, 13... Holder, 14... Electron beam, 15. ...Shaped beam. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) In a charged beam limiting aperture mask in which an aperture through which the charged beam passes is formed in a substrate that blocks the charged beam, the aperture is opened in parallel halfway from one main surface side of the substrate to prevent the charged beam from passing through. It consists of a limiting first aperture and a second aperture that is opened from the opposite side of the substrate until it reaches the aperture and has a larger diameter than the aperture. Aperture mask for limiting charged beams. (2) The first aperture is formed by punching after the second aperture is formed. Aperture mask for charged beam restriction. (3) The opening depth of the first opening portion is within a range that allows for machining accuracy.
Aperture mask for limiting charged beam as described in .