JP2863131B2 - Method of manufacturing photomask blanks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photomask blank used for manufacturing a semiconductor integrated circuit or the like.

[0002]

2. Description of the Related Art In the manufacture of semiconductors such as semiconductor devices, ICs and LSIs, a process for manufacturing a photomask used when a fine pattern is transferred onto a semiconductor wafer is usually performed by precision polishing of quartz glass or the like to obtain a light-transmitting material. Polishing process to obtain a substrate,
A film forming step of forming a chromium film (light-shielding film) on one main surface of a light-transmitting substrate by sputtering or the like; a resist coating step of applying a resist film on the chromium film by spin coating or the like; a master having a predetermined pattern The exposure is performed through an exposure step of selectively exposing the resist film through a mask, an etching step of developing the exposed resist film with a predetermined developer, performing etching, and obtaining a predetermined chromium pattern. In this case, the substrate obtained in the film forming step is generally called a photomask blank.

Here, the conventional film forming process will be described in more detail with reference to FIGS. 10 and 12, as follows. First, the translucent substrate 1 is placed on its opposing main surface 10A,
After precision polishing so that 10B is parallel and mirror-finished, chamfering is performed. Next, the precision-polished translucent substrate 1 is mounted on the holder 2.

[0004] The holder 2 comprises three light-transmitting substrates 1 for each hole.
Is formed by a rectangular plate in which four long holes 3 capable of accommodating the holes are arranged side by side. Each of the four corners 5 of each long hole 3 and the middle between the long side inner wall surfaces 6A and 6B are respectively transparent. A total of eight holding parts 4A and 4B for supporting the corner lower surface of the substrate 1 are provided integrally. Each of the holding portions 4A and 4B is formed in a flat plate shape having a triangular shape in a plan view and having a uniform thickness, and in particular, two holding portions 4B provided in the middle of both long side inner wall surfaces 6A and 6B of the long hole 3.
Is protrudingly provided at a position that divides the long side inner wall surface into three equal parts,
Corner portions 1A of two adjacent translucent substrates 1 are commonly supported.

[0005] When the translucent substrate 1 is mounted, the holder 2 is set in a sputtering apparatus. The inside of the sputtering apparatus is evacuated and filled with an inert gas such as argon. Further, a target made of chromium is provided inside the sputtering apparatus, and when a high DC voltage is applied between the target and the holder 2, plasma is generated between the two and thereby ionized. Argon sputters the target to repel chromium particles 7. The chromium particles 7 are repelled toward the translucent substrate 1 and adhere to one main surface 10A below the translucent substrate 1 to form a chromium film 8 having a predetermined thickness.

[0006]

As described above, in the conventional film forming process, each corner 1A of one main surface 10A of the translucent substrate 1 is held by the holding portions 4A and 4B of the jig 2. The chromium film 8 was formed as a light shielding film on the main surface 10A. Therefore, as shown in FIG. 12, the main surface 10 excluding the corners 1A that are in close contact with the holding portions 4A, 4B of the jig 2
The chromium film 8 is formed not only on the whole A, but also on the chamfered portion 11 and a part of the end face 12 by the gap d1 between the long hole 3 and the light transmitting substrate 1 (see FIG. 11). Would. However, the chamfered portion 11 and the end surface 12 are
Unlike A and 10B, there are many cases of a semi-mirror surface or a rough surface, so that the chromium film 8 attached to these surfaces is easily peeled or dropped. In particular, the end face 12 receives the
When it is abutted against the inner wall surface, it is easily peeled off, and when it is washed in the next washing step, it is peeled off by the pressure of the washing liquid. Also,
Even if the chamfered portion 11 and the end face 12 are mirror-polished, the translucent substrate 1 is gripped during transportation, so that the chromium film 8 may peel or fall off. If the dropped chromium film 8 adheres to the main surfaces 10A and 10B, it becomes an obstacle in a pattern forming process by electron beam drawing, so that a desired pattern cannot be formed and the yield is poor. .

Therefore, as a method for solving such a problem, as shown in FIG.
A photomask blank 15 in which the chromium film 8 is formed not in the entire area of A but in the area excluding the peripheral portion 14 so that the chromium film 8 is not attached to the chamfered portion 11 and the end face 12
(Eg, JP-A-59-3437,
Japanese Utility Model Publication No. 60-39047).

However, in the method of manufacturing the photomask blanks 15 as described above, since the periphery of one main surface of the translucent substrate is held by the holder, the periphery of the chrome film contacts the holder. I will. Therefore, there is a problem that the chromium film 8 is damaged or peeled off when the translucent substrate is removed from the holder.

[0009] Further, a problem is caused when the resist film is coated on the chromium film 8 and then the electron beam is irradiated in accordance with a desired pattern. That is, since the width W0 of the peripheral portion 14 of the main surface 10A where the chromium film 8 is not formed and the non-light-shielding film portion is formed is large, electric charges are accumulated in the peripheral portion 14a and the photomask blanks 15 are accurately aligned. You can't do that. Therefore, when manufacturing such a photomask blank 15, it is necessary to solve the above problem by providing a transparent conductive film between the chromium film 8 and the translucent substrate 1. Therefore, this type of photomask blank has a problem that the manufacturing process is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. An object of the present invention is to prevent a light-shielding film from peeling off when detached from a holder after film formation, and to provide a light-transmitting substrate. It is an object of the present invention to provide a method of manufacturing a photomask blank in which charge accumulation can be prevented without providing a transparent conductive film between the photomask blank and the light-shielding film.

[0011]

In order to achieve the above object, the present invention provides an oblique support surface for supporting four corners of one of the opposing main surfaces of a light-transmitting substrate; By placing the translucent substrate on a photomask blank holder having a mask surface that is close to and opposed to the peripheral edge other than the corners, by attaching a light-shielding film from below the holder. A light-shielding film is formed on substantially the entire area of the one main surface of the light-transmitting substrate except for the corners and the peripheral edge.

In the present invention, when the translucent substrate is placed on the holder, the corners are supported by the inclined support surface, and the peripheral edge is in close proximity to the mask surface. For this reason, the light-shielding film is not formed on the corners and the periphery of the light-transmitting substrate. Further, since the periphery of the formed light-shielding film is only in line contact with the inclined support surface and not in contact with the mask surface, the light-shielding film does not peel off or fall off when the light-transmitting substrate is removed from the holder.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view of a photomask blank manufactured by the manufacturing method according to the present invention, and FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. The same components as those shown in the section of the prior art are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. First, a photomask blank manufactured by the manufacturing method according to the present invention will be described. The translucent substrate 1 on which the photomask blanks 20 are formed has a side length L of 126.6 ± 0.4 mm and a plate thickness T of 2.3 ± 0.1.
mm are formed in the shape of a square, and the peripheral surfaces are main surfaces 10A and 10B.
In addition, a chamfered portion 11 that is inclined at an angle of 45 ° with respect to the end surface 12 is formed. The length 1 of the chamfer 11 is 0.4 ± 0.2 mm. One main surface 10A of such a translucent substrate 1 is covered with a chromium film 8 that forms a light-shielding film portion over substantially the entire area excluding corners and peripheral edges. The width of the non-light-shielding film portion 14, that is, the dimension W from the chamfered portion 11 to the chromium film 8 is 1.0 mm or less, and usually 0.6 mm or less.
mm.

Next, a holder for a photomask blank used in manufacturing the photomask blank 20 having the above structure will be described in detail with reference to FIGS. 3 is a plan view of the holder, FIG. 4 is a side view, FIG. 5 is an enlarged sectional view taken along line VV of FIG. 3, FIG. 6 is an enlarged perspective view of a portion A of FIG. 3, and FIG. FIG. 8 is a sectional view taken along a line VII-VII in FIG.
FIG. 9 is a perspective view of a portion B in FIG. In these figures, a holder 30 for photomask blanks (hereinafter referred to as a holder) has a side length L0 = 587 m.
m, thickness T0 = 4 mm, and a rectangular plate 31 with chamfered corners. The plate 31 has a total of 12 substrate holes 32 formed in a 4 × 3 matrix.
have. The substrate holes 32 are all of the same size and are formed in a square slightly larger than the translucent substrate 1, and the length L1 of one side thereof is 129 mm. On the inner surface of the lower end side opening end of the substrate hole 32, an overhang portion 33 is integrally protruded inward over the entire periphery except for the four corners, and the upper surface thereof is formed on the mask surface of the translucent substrate 1. 34 are formed. The projecting dimension L2 of the overhang portion 33 is set to 2 mm to 1.8 mm.

In this case, as shown in FIGS. 3 and 9, the substrate holes 32 in each row are separated by ribs 35, which are twice as wide as the overhanging portions 33 (2L2). ), The upper surface of which forms a common mask surface 35A for each of the translucent substrates 1 disposed adjacent to each other in front and rear. The mask surface 34 of the overhang portion 33 and the rib 35
Forms the same plane.

The ribs 35 of the holding portions provided at the four corners of the substrate hole 32 for holding the corners of the translucent substrate 1 are provided.
As shown in FIGS. 6 to 8, the holding portion 40 provided at a corner (other than the side corner) (a portion in FIG. 3A) is a substantially isosceles triangle having an apex in a plan view and a cross section. It is formed in a plate-like body having a wedge shape. In addition, the upper surface of the holding portion 40 has a longitudinal central portion 4 of an inner edge 43 that intersects each side of the plate 31 at an angle of 45 ° from the outer edge 42.
An inclined surface (inclined support surface) 44 inclined in a mortar shape so that the plate thickness gradually decreases toward 3a. Inclined surface 44
Is 2 to 3 degrees, the outer end surface portion 42 is higher than the mask surface 34 of the overhang portion 33, and the height of the inner end edge portion 43 at the lowest central portion 43a is the same as that of the mask surface 34. It is higher than or approximately equal to 34.

Therefore, when each corner 1A of the light-transmitting substrate 1 is placed on the holding portion 40, each corner 1A is in line contact with the upper edge of the outer edge 42 as shown in FIG. It is supported, and an appropriate gap is set between the overhang portion 33 and the rib 35 (FIG. 3), and is not supported by the mask surfaces 34 and 35A. Outside the holding portion 40, support wall surfaces 45a and 45b for supporting both end surfaces of the corner 1A of the translucent substrate 1 and a processing relief portion 46 are formed. The machining relief 46 is provided between the support walls 45a and 45b. Further, both ends 43 b of the inner edge 43 of the holding portion 40 are located substantially at the center in the width direction of the side end of the overhanging portion 33. Accordingly, the end surface 12 of the light-transmitting 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 at the rib 35 side. The other end face portions do not come into contact with the inner wall surface of the substrate hole 32 only because they can come into contact with each other.

The holding portion 50 provided at the corner portion on the side of the rib 35 is formed substantially in the same manner as the holding portion 40 as shown in FIG. A plate-like body 5 having a substantially isosceles triangle shape and a wedge-shaped cross section.
1, a mortar-shaped inclined surface (inclined support surface)
52 are formed.

The upper surface of the rib 35, that is, the mask surface 35A
The two light-transmitting substrates 1 disposed adjacent to each other
A partition 53 for preventing the interference of the two is integrally provided. A portion corresponding to the holding portion 50 on the inner wall surface of the substrate hole 32 and the side surface of the partition 53 form support wall surfaces 54 and 55 for supporting the end surface of the corner 1A of the translucent substrate 1. In addition,
The other configuration is substantially the same as that of the holding unit 40, and thus the description 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 1 A of the holder 30 and the outer edges 4 of the upper surfaces of the holding portions 40 and 50 are formed.
2 and 57 are supported in line contact with each other, and both end surfaces near the corner 1A are supported at the corners of the substrate hole 31 at the support wall surfaces 45a and 45a.
45b, 54 and the support wall 55 of the partition 53 are positioned in contact with each other.

FIG. 5 shows a state in which the translucent substrate 1 is mounted in the substrate hole 32. In this state, the gap Δd between the lower surface of the translucent substrate 1 and the mask surface 34 of the overhang 33 is 0.2 m.
m, and the mask dimension l2 covered by the overhang 33 is L = 126.8 mm, L2 = 2 mm, = 0.4
mm, l2 = 0.5 mm (l2 = L2 -l-l
3) Here, l3 is (L1 -L) / 2. The mask dimension l2 is at most 0.6 mm even in the translucent substrate 1 having the maximum value of L (127 mm), and does not exceed 1 mm.

The translucent substrate 1 is placed on the holder 30 having such a structure, and chromium is sputtered from below onto one main surface 10A of the translucent substrate 1 by a sputtering apparatus.
When the chromium film 8 was formed, a photomask blank 20 having a non-light-shielding film portion 14 having a peripheral portion of 1 mm or less as shown in FIGS. 1 and 2 was obtained. A resist is applied on the light-shielding film 8 of the obtained photomask blank 20, and then electron beam drawing is performed. In the case of electron beam writing, the width of the non-light-shielding film portion 14 is at most about 1 mm. It was confirmed that there was no adverse effect on

It is not preferable that the thickness be 1 mm or more, since charge accumulation occurs and adversely affects alignment. Next, after performing electron beam writing, development is performed, and the chromium film 8 is selectively removed using the developed resist as a mask, whereby a photomask can be obtained.

As described above, the manufacturing method according to the present invention is characterized in that the light shielding film 8 is formed using a special holder having an inclined support surface and a mask surface. For this reason,
In the present invention, the substrate does not contact the mask surfaces 34 and 35A, and is supported only by the inclined support surface. As a result, the contact area with the holder 30 can be made extremely small, and after the light shielding film 8 is formed, the light shielding film 8 may be damaged or peeled off when the light shielding film 8 is removed from the holder 30. Absent. Further, since the peripheral portion of the main surface 10A can be formed as the non-light-shielding film portion 14 having a desired width, when electron beam drawing is performed, no charge is accumulated, and alignment of the photomask blanks can be performed well.

In this embodiment, the inclined surface 44 is used.
Is formed on a flat surface, but may be formed on a concave curved surface. Also,
The light shielding film 8 may have a layer structure in which a chromium film is formed on a chromium oxide film.

[0026]

As described above, the method of manufacturing a photomask blank according to the present invention comprises the inclined support surface for supporting the four corners of any one of the opposing main surfaces of the translucent substrate. Placing the light-transmitting substrate on a photomask blank holder having a mask surface that is close to and opposed to a peripheral portion other than the corners, and attaches a light-shielding film from below the holder. Thereby, since the light-shielding film is formed in substantially the entire area of the one main surface of the light-transmitting substrate except for the corners and the peripheral edge, the contact area with the holder is extremely small, and the light-shielding film is formed. After removal from the holder, the light-shielding film is not damaged or peeled off. Also, even if a transparent conductive film is not interposed between the light-transmitting substrate and the light-shielding film portion, no charge is accumulated during electron beam writing,
The alignment of the photomask blanks can be performed favorably. Further, since the light-shielding film portion is not formed up to the end face and the chamfered portion, there is no possibility that the light-shielding film portion falls off.

[Brief description of the drawings]

FIG. 1 is a plan view of a photomask blank manufactured by a manufacturing method according to the present invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is a plan view of a holder for photomask blanks.

FIG. 4 is a side view.

FIG. 5 is an enlarged sectional view taken along line VV of FIG. 3;

FIG. 6 is an enlarged perspective view of a portion A in FIG. 3;

7 is a sectional view taken along line VII-VII of FIG. 6;

FIG. 8 is a plan view of a part A in FIG. 3;

FIG. 9 is a perspective view of a portion B in FIG. 3;

FIG. 10 is a perspective view of a conventional holder for photomask blanks.

FIG. 11 is an enlarged sectional view of a main part.

FIG. 12 is a plan view of a photomask blank.

FIG. 13 is a view showing another example of a conventional photomask blank.

[Explanation of symbols]

1: Translucent substrate, 8: Chromium film (light shielding film), 10A, 1
0B: Main surface, 11: chamfered portion, 12: end surface, 14: peripheral portion (non-light-shielding film portion), 15, 20: photomask blanks, 33: overhanging portion, 34: mask surface, 35: rib, 3
5A: mask surface, 40: holding portion, 44: inclined surface, 50:
Holder, 52: inclined surface.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03F 1/08 G03F 1/14 H01L 21/30

Claims (1)

(57) [Claims] An inclined support surface that supports four corners of one of the main surfaces of the opposing main surface of the light-transmitting substrate; and a mask surface that is close to and opposed to a peripheral edge other than the corners. The light-transmissive substrate is placed on a holder for a photomask blank provided with a light-shielding film, and a light-shielding film is attached from below the holder, whereby the corner of the one main surface of the light-transmissive substrate is provided. A method for manufacturing a photomask blank, comprising: forming a light-shielding film over substantially the entire area except a part and a peripheral part.