JP2508841Y2 - Holder for photo mask blanks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a holder for a photomask blank used when a photomask blank is manufactured by coating a light-shielding film on one main surface of a transparent substrate. It is a thing.

[Prior Art] In the manufacturing of semiconductors such as semiconductor devices, ICs, LSIs, etc., the manufacturing process of a photomask used when transferring a fine pattern to a semiconductor wafer is usually performed by precision polishing quartz glass etc. A polishing step for obtaining a substrate, a film forming step for forming a chromium film (light-shielding film) on the main surface of a transparent substrate by sputtering or the like, a resist applying step for applying a resist film on the chromium film by a spin coating method or the like, Through an exposure step of selectively exposing the resist film through a master mask having a predetermined pattern, an etching step of developing the exposed resist film with a predetermined developing solution and etching to obtain a predetermined chrome pattern. Be seen.
In this case, the substrate obtained in the film forming process is generally called a photomask blank.

Here, the conventional film forming process will be described in more detail as follows.

First, the translucent substrate is precisely polished so that its opposing main surfaces are parallel and mirror-finished, and then chamfered. Next, the precision-polished transparent substrate 1 is attached to a holding portion 2 as shown in FIG.
Attach to.

The holder 2 is composed of a rectangular plate in which four long holes 3 capable of accommodating three translucent substrates 1 are arranged side by side in each hole, and the four corners 5 of each long hole 3 and In the middle of the side inner walls 6A and 6B, a total of eight holders 4A and 4B for supporting the lower surface of the corners of the respective transparent substrates 1 are integrally provided.
Each of the holding portions 4A and 4B is formed in a flat plate shape with a uniform plate thickness of a triangular shape in plan view, and in particular, the two holding portions 4B provided between the inner wall surfaces 6A and 6B on the long side of the long hole 3 have the long sides. Are provided in a pair so as to be divided into three equal parts, and the corner portions 1A of two adjacent transparent substrates 1 are commonly supported.

When the transparent substrate 1 is mounted, the holder 2 is installed in the sputtering device. The inside of the sputtering apparatus is evacuated to vacuum and an inert gas such as argon is filled therein, and the transparent substrate 1 is arranged together with the holder 2 above a target made of chromium. When a direct current high voltage is applied between the holder 2 and the target, plasma is generated between the two, and ionized argon sputters the target to repel the chromium particles 7. The chromium particles 7 are repelled toward the translucent substrate 1 and adhere to one main surface 10A (see FIG. 11) below the substrate 1 to form a chromium film 8 having a predetermined thickness. Is formed.

[Problems to be Solved by the Invention] By the way, in such a conventional film forming process,
As shown in FIG. 12, a corner portion where the holding portion 4 of the transparent substrate 1 hits
Not only the chromium film 8 is formed on the entire main surface 10A except 1A, but the gap d ₁ between the long hole 3 and the translucent substrate ₁ (11th
As a result, a film is also formed on the chamfered portion 11 and a part of the end surface 12. However, unlike the main surfaces 10A and 10B, the chamfered portion 11 and the end surface 12 are often semi-mirror surfaces or rough surfaces, so that the chromium film 8 adhered to these surfaces is easily peeled or dropped. In particular, the end face 12
Is likely to hit the inner wall surface of the long hole 3, or the chromium film 8 is likely to fall off during cleaning in the next step. Also, the chamfer 11
Even if the end surface 12 is mirror-polished, since these surfaces are gripped when the substrate is carried, the chromium film is likely to fall off. The chromium film 8 that has fallen off in this way is
If it adheres to 0B, there is a problem in that the electron beam is blocked during the electron beam writing in the next step, thereby hindering the formation of a desired pattern.

Therefore, as a method of solving such a problem, as shown in FIG. 13, the chrome film 8 is formed not in the entire main surface 10A of the transparent substrate 1 but in the area excluding the peripheral edge portion 14 and chamfered. A photomask blank 15 has been proposed in which the chromium film 8 is prevented from adhering to the portion 11 and the end face 12.

However, even in such a photomask blank 15, since the holder is in close contact with the peripheral portion of the main surface 1A, when the photomask blank 15 is removed from the holder after film formation, when the photomask blank 15 is moved, There is a problem that the chromium film 8 is damaged or peeled off by the holder. Further, after coating the chromium film 8 with a resist film,
This causes a problem when irradiating the electron beam with a desired pattern. That is, the width W _{0 of} the peripheral portion 14 of the main surface 10A where the chromium film 8 is not formed and forms the non-light-shielding film portion.
Is large, charges accumulate on the peripheral edge 14a, making it impossible to accurately align the photomask blanks 15. Therefore, when forming such a photomask blank 15, it was necessary to solve the above problem by providing a transparent conductive film between the chromium film 8 and the substrate 1.

Therefore, there is a problem that the manufacturing process becomes complicated in this type of photomask blank.

The present invention has been made in view of the conventional problems as described above, and the purpose thereof is to be able to coat the light shielding film only on the main surface, and when removing the photomask blanks from the holder, It is an object of the present invention to provide a holder for a photomask blank suitable for obtaining a photomask blank that does not damage or peel off the light-shielding film and does not cause charge accumulation.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an inclined support surface for supporting a corner portion of one main surface of a transparent substrate and a peripheral portion other than the corner portion. And a mask surface facing each other is provided.

[Operation] In the present invention, the inclined support surface of the holder for photomask blanks reduces the contact area with the transparent substrate. The mask surface covers the peripheral portion, the chamfered portion and the end surface of the main surface of the transparent substrate so that the light shielding film is not formed on these portions.

[Embodiment] Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

1 to 7 show an embodiment of a holder for photomask blanks according to the present invention. FIG. 1 is a plan view of the holder, FIG. 2 is a side view, and FIG. 3 is FIG. III-III line enlarged sectional view of FIG. 4, FIG. 4 is an enlarged perspective view of FIG. 1A part, FIG. 5 is a VV sectional view of FIG. 4, and FIG. 6 is a plan view of FIG. 1A part ,
FIG. 7 is a perspective view of part B in FIG. 1, FIG. 8 is a plan view showing an example of a photomask blank manufactured using the holder, and FIG. 9 is an enlarged cross section taken along line IX-IX in FIG. It is a figure. The same components and parts as those in FIGS. 10 to 13 are designated by the same reference numerals, and the description thereof will be omitted.

First, the structure of a photomask blank manufactured by the holder for a photomask blank according to the present invention will be described with reference to FIGS. 8 and 9. In these figures, the transparent substrate 1 forming the photomask blanks 20 has a side length L of 126.6 ± 0.4 mm and a plate thickness T of 2.3 ± 0.1.
The chamfered portion 11 is formed in a rectangular shape of mm and is inclined at an angle of 45 ° with respect to the main surfaces 10A and 10B and the end surface 12 at the peripheral edge. The length 1 of the chamfered portion 11 is 0.4 ± 0.2 mm. On one main surface 10A of the translucent substrate 1 as described above, a chromium film 8 forming a light shielding film portion is covered over substantially the entire area.

Here, the substantially entire area includes the case where the entire main surface 10A is included,
This includes both the case where the peripheral portion 14 is provided with a non-light-shielding film portion of a minute width in which the chromium film 8 is not formed. The width of the non-light-shielding film portion 14, that is, the dimension W from the chamfered portion 11 to the light-shielding film portion 8 is 1.0 mm or less, usually about 0.6 mm.

Next, one embodiment of the holder for photomask blanks according to the present invention, which is used when manufacturing the photomask blanks 20 having the above structure, will be described in detail with reference to FIGS. 1 to 7. In these drawings, a holder for photomask blanks (hereinafter referred to as a holder) 30 includes a rectangular plate 31 having one side length L ₀ = 587 mm, thickness T ₀ = 4 mm, and chamfered at four corners. There is. The plate 31 has a total of 12 substrate holes 32 opened in a 4 × 3 matrix. All the substrate holes 32 have the same size and are formed in a rectangular shape slightly larger than the translucent substrate 1, and the length L _{1 of} one side thereof.
Is 129 mm. On the inner surface of the opening at the lower end of the substrate hole 32, an overhanging portion 33 is integrally provided so as to project inward over the entire circumference except for the four corners, and the upper surface thereof is the mask of the transparent substrate 1. Forming surface 34. The protruding dimension L ₂ of the overhang 33 is 2 mm
~ 1.8mm.

In this case, as shown in FIGS. 1 and 7, the substrate holes 32 in each row are partitioned by ribs 35, which are twice the width (2L ₂ ), The upper surface of which forms a common mask surface 35A for the transparent substrates 1 and 1 which are arranged adjacently in the front and rear. The mask surface 34 of the overhanging portion 33 and the mask surface 35A of the rib 35 form the same plane.

Of the holding portions that are provided at the four corners of the substrate hole 32 and that hold the corners of the translucent substrate 1, the holders that are provided at the corners other than the ribs 35 side corners (A in FIG. 1). As shown in FIGS. 4 to 6, the portion 40 is a substantially isosceles triangle whose top view is arcuate in a plan view, and is formed into a plate-like body having a wedge-shaped cross section, and its upper surface is an outer end. From the edge 42 to each side of the plate 31
The inclined surface 44 is inclined like a mortar so that the plate thickness gradually decreases toward the central portion 43a in the longitudinal direction of the inner edge portion 43 intersecting at an angle of 45 °. The inclination angle Θ of the inclined surface 44 is 2
At -3 °, the outer end surface portion 42 is higher than the mask surface 34 of the overhang portion 33, and even at the lowest central portion 43a of the inner end edge portion 43, the height is higher than or substantially equal to the mask surface 34. .

Therefore, when the corner portion 1A of the translucent substrate 1 is placed on the holding portion 40, the corner portion 1A has the outer edge portion 42 as shown in FIG.
Is supported in a state of being in line contact with the upper edge of the above, and an appropriate gap is set between the overhanging portion 33 and the rib 35 (FIG. 1), and is supported in contact with these mask surfaces 34, 35A. There is no.

Outside the holding portion 40, support wall surfaces 45a and 45b that support both end surfaces of the corner portion 1A of the translucent substrate 1 and a processing relief portion 46 are formed. The processing relief portion 46 is connected to the outer edge 42. Further, both ends 43b of the inner end edge portion 43 of the holding portion 40
Are in contact with each other at substantially the center of the lateral end of the overhanging portion 33 in the width direction.
Therefore, the end surface 12 of the transparent substrate 1 is formed on the inner wall surface of the substrate hole 32 at each corner 1A supported by the holding portion 40 and the holding portion 50 provided at the corner portion on the rib 35 side. Only the contact can be made, and the other end face portions do not contact the inner wall surface of the substrate hole 32.

The holding portion 50 provided at the corner portion on the rib 35 side,
As shown in FIG. 7, it is formed in substantially the same manner as the holding portion 40, and is composed of a plate-like body 51 having a substantially isosceles triangle whose plan view has an arcuate top and a wedge-shaped cross section. The upper surface forms a mortar-shaped inclined surface 52.

In this case, a partition 53 for preventing the interference of the two translucent substrates 1 arranged adjacent to each other is integrally provided on the upper surface of the rib 35, that is, the base end portion of the mask surface 35A. Board hole 32
The portion of the inner wall surface corresponding to the holding portion 50 and the side surface of the partition 53 form support wall surfaces 54 and 55 for supporting the end surfaces of the corners 1A of the transparent substrate 1.

The rest of the configuration is substantially the same as that of the holding section 40, and therefore its explanation is omitted.

In the holder 30 having such a structure, when the translucent substrate 1 is inserted into each of the substrate holes 32, the corners 1A thereof are held.
40 and 50 are supported in line contact with the upper outer edge portions 42 and 57 of the upper surface, and both end surfaces in the vicinity of the corner 1A support the wall surfaces 45a, 45b, 54 and the partition 53 at the corners of the board hole 31. Positioned by abutting against the wall surface 55.

FIG. 3 shows a state in which the transparent substrate 1 is mounted in the substrate hole 32. At this time, the gap Δd between the lower surface of the translucent substrate 1 and the mask surface 34 of the projecting portion 33 is about 0.2 mm, and the mask dimension l ₂ covered by the projecting portion 33 is L = 126.8 mm, L ₂ = 2 mm, l
= 0.4 mm, l ₂ = 0.5 mm (l ₂ = L ₂ -l ₃ ). However, l ₃ is (L ₁ −L) / 2. This mask dimension l ₂
Is 0.6 mm even in the translucent substrate 1 having the maximum L value (127.0 mm), which does not exceed 1 mm.

Thus, using the holder 30 having such a structure, chromium is sputtered on the one main surface 10A of the translucent substrate 1 by the sputtering device to form the chromium film 8. As shown in FIG. 8 and FIG. A photomask blank 20 having the non-light-shielding film portion 14 of 1 mm or less at the peripheral portion shown was obtained. When electron beam drawing is performed after applying a resist to such a photomask blank 20, the maximum width of the non-light-shielding film portion 14 is about 1 mm. Is hardly accumulated, and photomask blanks
It was confirmed that there is no adverse effect on the alignment of 20.

It should be noted that if the thickness is 1 mm or more, charge is accumulated and the alignment is adversely affected, which is not preferable.

[Advantages of the Invention] As described above, the holder for the photomask blank according to the present invention is formed with the non-light-shielding film portion which is separated from the inclined surface supporting the corner lower surface of the transparent substrate and the main surface of the substrate. Since the mask surface is provided, the mask surface can cover the peripheral edge portion, the chamfered portion, and the end surface of the main surface, and the light-shielding film can be prevented from being formed on these surfaces.
In this case, since the main surface is mirror-polished, the light-shielding film has high adhesion and peeling and falling can be prevented. Further, the mask surface can surely form the non-light-shielding film portion having the desired width on the peripheral portion of the main surface, and since the transparent substrate comes into line contact only with the inclined surface, the contact area is remarkably small and it is not removable. Sometimes the light shielding film is not scratched or peeled off, and the area of the non-light shielding film portion supported by the light shielding film can be reduced, so that the practical effects such as the prevention of charge accumulation are great.

[Brief description of drawings]

1 to 7 show an embodiment of a holder for photomask blanks according to the present invention. FIG. 1 is a plan view of the holder, FIG. 2 is a side view, and FIG. 3 is FIG. III-III line enlarged sectional view of FIG. 4, FIG. 4 is an enlarged perspective view of FIG. 1A part, FIG. 5 is a VV sectional view of FIG. 4, and FIG. 6 is a plan view of FIG. 1A part ,
FIG. 7 is a perspective view of part B in FIG. 1, FIG. 8 is a plan view showing an example of a photomask blank manufactured using the holder, and FIG. 9 is an enlarged cross section taken along line IX-IX in FIG. FIG. 10, FIG. 10 are perspective views of a conventional holder for photomask blanks, FIG. 11 is an enlarged cross-sectional view of essential parts, FIG. 12 is a plan view of photomask blanks, and FIG. 13 is another conventional photomask blanks. It is a side sectional view showing an example of. 1 ... Transparent substrate, 8 ... Chrome film (light shielding film), 10A, 1
0B: main surface, 11: chamfered part, 12: end face, 14: peripheral part (non-light-shielding film part), 15, 20: photomask blanks, 33: overhang part, 34: masked surface , 35 …… Rib, 35A
...... Mask surface, 40 …… holding part, 44 …… sloping surface, 50 …… holding part, 52 …… sloping surface.

Claims (1)

(57) [Scope of utility model registration request] 1. A tilted support surface for supporting a corner portion of one main surface of a transparent substrate, and a mask surface provided correspondingly to a peripheral portion other than the corner portion so as to be spaced apart from each other. A holder for photomask blanks.