JPH1083070A - Photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deflection of a photo mask due to a pellicle frame, and to accurately arrange the pellicle frame at the specified position of a photomask by forming a metal film in a region including the adhering face of the pellicle frame on the photomask and adhering the pellicle frame with to the photomask interposing a metal film in between. SOLUTION: The metal film 4 is formed by an electron beam vapor deposition method on the region including the adhering face of a pellicle frame 32 which supports a pellicle film 2 on the photomask 1. The metal film 4 has a scale, and the pellicle frame 3 is adhered with an adhesive on the photomask 1 according to the scale. By adhering the pellicle frame 3 with the metal film 4 to the photomask 1, deflection of the photomask 1 can be reduced. Deviation of the adhesion position of the pellicle frame 3 on the photomask 1 can be easily and accurately checked by using the scale.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photomask to which a pellicle frame supporting a pellicle film is adhered.

[0002]

2. Description of the Related Art A photomask is formed by forming a pattern on a glass substrate with a light-shielding film of Cr or the like. The pattern is transferred to a resist film on a semiconductor wafer by irradiating ultraviolet rays through the photomask. for that reason,
If foreign matter such as dust adheres to the photomask, the foreign matter is transferred to the resist film and becomes a pattern defect. Therefore, in the semiconductor manufacturing process, it is necessary to perform strict control so that foreign matter does not adhere to the photomask. However, the recent increase in the diameter of the semiconductor wafer has made such control difficult. In addition, with the progress of pattern miniaturization, even fine particles of sub-micron order, which could not be ignored in the past, have caused pattern defects, making it difficult to effectively prevent pattern defects with conventional management methods. I have. Therefore, recently, a method of constantly protecting the photomask surface using a pellicle film has been used.

FIG. 2 shows a photomask on which a pellicle film is mounted. FIG. 2A is a plan view, and FIG.
It is A 'sectional drawing. The pellicle film 2 is made of an organic thin film such as nitrocellulose, and is attached to a pellicle frame 3 made of a metal such as aluminum. At the center of the photomask 1, a pattern region 5 composed of a pattern group formed of a Cr film is disposed as shown by a dotted line in the figure. 5 is adhered using an adhesive material. Thus, the pattern region 5 is protected by the pellicle film 2. Since the distance between the pellicle film 2 and the pattern region 5 is maintained at a constant value by the pellicle frame 3, even when foreign matter adheres to the pellicle film 2, the focus shifts during the irradiation of ultraviolet rays, and the pellicle film 2 remains on the semiconductor wafer. It will not be transcribed. Usually, the pellicle frame 3 supporting the pellicle film 2 is also adhered to the same position on the surface of the photomask 1 opposite to the surface on which the pattern region 5 is formed. Thus, even if foreign matter adheres to any surface of the photomask 1, the occurrence of pattern defects can be prevented.

[0004]

As described above, the method of protecting a pattern region of a photomask by a pellicle film is effective in reducing pattern defects, and is widely used. On the other hand, a pellicle film is mounted. This causes the following problem.

Conventionally, the pellicle frame supporting the pellicle film is directly bonded to the photomask. However, this causes a large stress to be applied to the photomask from the pellicle frame, causing the photomask to bend. When a pattern is transferred to a resist film on a semiconductor wafer using a bent photomask, the pattern placement accuracy is reduced as described below, which has a significant effect on the performance and manufacturing yield of semiconductor devices.

FIG. 3 is a view for explaining a shift caused in the pattern arrangement position due to the deflection of the photomask, and shows a case where the same pattern is disposed on a flat photomask and a photomask which is bent downward. . As can be seen from the figure, the arrangement position of the pattern 6 arranged at the center position of the photomask 1 hardly changes depending on the presence or absence of bending, but is arranged at a position off the center of the photomask 1. The pattern 7 is displaced due to the deflection of the photomask. The shift amount δ of the pattern arrangement position shown in the figure is proportional to the amount of deflection of the photomask and the distance from the center position of the photomask 1 to the pattern 7. Therefore, the larger the area of the photomask and the greater the amount of deflection, the greater the displacement of the pattern arrangement position.

In general, in a semiconductor manufacturing process, a target device pattern is formed on a semiconductor wafer by transferring a plurality of patterns of a plurality of photomasks having various patterns in a superimposed manner. When the transfer is performed, the arrangement position of the pattern is shifted as described above, and the overlay accuracy is reduced, resulting in a device failure. Therefore, when using a photomask, the amount of deflection is inspected, and only a photomask having an amount of deflection equal to or less than a predetermined value is used. However, it is difficult to perform an inspection when the pellicle frame is adhered to the photomask. Therefore, inspection was conventionally performed before bonding. However, as described above, the bonding of the pellicle frame causes a new deflection in the photomask. Therefore, when pattern transfer is actually performed using a photomask to which the pellicle frame is bonded, the pattern overlay accuracy is expected. There was a problem that it was lowered more than it did.

Further, the pellicle frame is adhered to the outside of the pattern region. However, in a negative type photomask used for transferring a pattern to a negative resist film, the glass surface is exposed outside the pattern region. On the other hand, in a positive-type photomask used for transferring a pattern to a positive-type resist film, a Cr film for pattern formation is left outside the pattern region. Therefore, the pellicle frame is adhered to either the glass surface or the Cr film surface according to the type of the photomask.

In general, if the adhesion of the pellicle frame to the photomask is too strong, a large force is required to separate the pellicle frame and the photomask may be damaged.
If the adhesive strength is too weak, it may peel off during use. Therefore, it is necessary to determine the bonding conditions such as the type and amount of the bonding material so as to obtain the bonding strength of a predetermined strength, but the bonding surface is different from the glass surface or the Cr film surface depending on the type of the photomask as described above. For this reason, the bonding conditions are changed accordingly, and there is a problem that the bonding operation of the pellicle frame becomes complicated.

In the case where a photomask is used for pattern transfer, as shown in FIG.
The photomask 1 to which is adhered is placed on a photomask stage 8.
However, if the bonding position of the pellicle frame 3 is displaced on the surface of the photomask 1, the pellicle frame 3 easily comes into contact with the photomask stage 8 during the fixing operation, and as a result, the pellicle frame There is a risk that the photomask 3 was peeled off from the photomask 1 or the photomask 1 was damaged. In order to avoid such a problem, the pellicle frame 3 is usually arranged at a position symmetrical with respect to the center of the photomask 1 and bonded, and further, after the bonding, the position of the pellicle frame 3 on the surface of the photomask 1 is set. Inspection is performed. However, conventionally, a mark indicating the position where the pellicle frame 3 is to be bonded is not provided on the surface of the photomask 1, so that there is a possibility that the bonding position may be shifted, and the inspection for the shift of the arrangement position may be performed accurately. Was not possible.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the deflection of a photomask caused by a pellicle frame and to enable the pellicle frame to be accurately positioned at a predetermined position on the photomask.

[0012]

The object of the present invention is to provide a photomask to which a pellicle frame supporting a pellicle film is bonded, wherein a metal film is formed on the photomask surface in a region including the bonding surface of the pellicle frame. The pellicle frame is achieved by a photomask characterized in that it is bonded to a photomask via the metal film, or the photomask characterized in that the metal film is provided with a scale. You.

When the pellicle frame is bonded to the glass surface of the photomask, a tensile stress acts on the photomask from the pellicle frame, thereby causing the photomask to bend. The present inventor has found that when a metal film is formed on the glass surface of a photomask, a compressive stress opposite to the tensile stress acts. Therefore, a metal film is formed in advance on the photomask surface in a region including the bonding surface of the pellicle frame, and the pellicle frame is bonded to the photomask via this metal film, so that the pellicle frame and the metal film are converted to the photomask. The acting stresses are canceled out and the deflection of the photomask is reduced.

Further, by bonding the pellicle frame to the photomask via the metal film, the same bonding conditions can be always used regardless of the type of the photomask, so that the bonding operation is facilitated.

Further, by providing a scale on the metal film, the position of bonding the pellicle frame to the photomask can be determined easily and accurately, so that the work of fixing the photomask to the photomask stage becomes easy.

[0016]

FIG. 1 is a sectional view showing an embodiment of the present invention, in which a photomask 1 for a negative resist is used. The photomask 1 has a pattern area 5 of about 90 × 90 mm square in the center of a 127 × 127 mm square glass substrate.
The glass surface is exposed outside the pattern region 5. The pellicle film 2 is a transparent thin film made of nitrocellulose, and the pellicle frame 3 for supporting the pellicle film 2 is made of an aluminum frame member having a width of 2 mm and a height of 2 mm. Then, Cr is selectively vapor-deposited through a metal mask by an electron beam vapor deposition method in a region including the bonding surface of the pellicle frame 3 on the surface of the photomask 1 to form a band-shaped metal film 4 having a thickness of 3000 mm and a width of 10 mm. Then, as shown in the enlarged view in FIG. 1, a scale is formed on the metal film 4 at intervals of, for example, 0.5 mm, and the pellicle frame 3 is arranged on the photomask 1 surface based on the scale, and an adhesive is applied. And glue.

By bonding the pellicle frame 3 to the photomask 1 via the metal film 4 as described above, the deflection of the photomask 1 averaging about 10 μm conventionally is 5 μm.
Could be reduced to

Further, the displacement of the bonding position of the pellicle frame on the surface of the photomask 1 can be easily and accurately checked by using the scale. Therefore, when fixing the photomask to the photomask stage, the pellicle frame is fixed. The problem that the frame comes into contact with the photomask stage and peels off is eliminated.

In the photomask for a negative resist used in the above embodiment, since the glass surface is exposed outside the pattern region, the metal films 4 are formed on both sides of the photomask. When used, the Cr film is formed outside the pattern region, so the metal film may be formed only on the surface opposite to the pattern region.

In this embodiment, the thickness and the width of the metal film 4 are set to 3000 mm and 10 mm. However, these values can be determined experimentally so as to reduce the amount of deflection. You can also.

[0021]

As described above, according to the present invention, the deflection of the photomask which occurs when the pellicle frame holding the pellicle film is bonded to the photomask can be reduced, so that the pattern overlay accuracy can be improved. In addition, since the position of the pellicle frame on the photomask can be easily and accurately determined, the handling of the photomask becomes easier than before, and the production yield of the semiconductor device is improved. It is useful.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 shows a conventional photomask.

FIG. 3 illustrates a problem of a conventional photomask (part 1).

FIG. 4 illustrates a problem of a conventional photomask (part 2).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photomask 6, 7 pattern 2 Pellicle film 8 Photomask stage 3 Pellicle frame 9 Semiconductor wafer 4 Metal film 10 Wafer stage 5 Pattern area

Claims (2)

[Claims] 1. A photomask to which a pellicle frame supporting a pellicle film is adhered, wherein a metal film is formed in a region including an adhesion surface of the pellicle frame on a photomask surface, and the pellicle frame is formed by attaching the metal film to the pellicle frame. A photomask adhered to a photomask via a photomask. 2. The photomask according to claim 1, wherein a scale is provided on the metal film.