JPS60128449A - Photomask and its manufacture - Google Patents

Abstract

PURPOSE:To prevent dropout of photomask patterns by coating the plane of a pattern side with a photoresist substantially same as the photoresist applied to the substrate to be transferred. CONSTITUTION:The pattern 6 of a light intercepting thin film made of metallic Cr or the like is formed on a transparent base 1 made of soda lime glass or the like, and then, the surface on the side of the pattern 6 is coated with a photoresist 10 same in material as a photoresist applied to the substrate to be transferred by the spin-coating method or the like. The film thickness of this photoresist 10 is usually controlled to several hundred nm from the viewpoint of preventing pinholes. The photoresist 10 is treated at high temp. in a dry atm. of dry N2 gas or the like with an electric oven or an IR dryer in a so-called prebaking stage in order to remove an org. solvent remaining in the photoresist 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to semiconductor integrated circuits and high-density r! 1. This invention relates to a photomask used in the manufacturing process of integrated circuits and the like, and a method of manufacturing the same, and particularly to an improvement of a photomask and the manufacturing method of the same used in the process of contact exposure to a transfer target substrate.

This photomask is basically manufactured by the tl' process shown in FIG. That is, a light-shielding thin film 2 of metallic chromium or the like is deposited by sputtering or the like on a transparent substrate 1 of soda lime glass or the like whose surface has been precisely polished and cleaned.
A photoresist 3 is coated on the light-shielding thin film 2 to produce a photomask blank 4 (FIG. 1(a)). Next, the photoresist 3 is coated on the light-shielding thin film 2 to obtain a predetermined pattern. After exposure, development is performed to form a resist pattern 5 on the light-shielding thin film 2 (FIG. 2(b)), and then,
Using this resist pattern 5 as a mask, the light-shielding thin film 2
The exposed portion of the resist pattern 5 is removed by etching to form a light-shielding RQ R'A pattern 6 under the resist pattern 5 (FIG. 2(C)), and the resist pattern 5 is removed using a stripping solution to form a transparent substrate. A photomask 7 having a predetermined pattern 6 formed thereon is manufactured.

Such masks 1 to 7 are used for pattern transfer by closely exposing a semiconductor substrate with a photoresist as a transfer target substrate. Furthermore, since this photomask 7 is a consumable item, it is also used when producing a photomask for master or submaster as a transfer substrate by closely exposing the photomask blank 4 described above.In this case, A photomask for master, master, or submaster is used as a photomask for pattern transfer to the aforementioned photoresist-coated semiconductor substrate. Further, as the photomask for transfer or to be transferred, a so-called emulsion mask using a silver emulsion film as a light-shielding thin film is sometimes used due to cost considerations.

However, when such a photomask 7 is closely exposed to a transfer substrate such as a semiconductor substrate with photoresist to transfer a pattern, static electricity is generated due to mutual contact, and
~A discharge phenomenon occurred in 6 patterns of mask 7, especially,
When the pattern 6 is formed in the form of an island, the pattern 6 is missing at its periphery. Such omission of the pattern 6 causes a loss of function as a transfer photomask, which becomes a fatal defect.

As a means to eliminate such defects, as shown in FIG. 2, a transparent conductive film 8 made of tin oxide or the like is deposited on the exposed surface of the transparent substrate 1 and on the pattern 6 to a thickness of about 50 mm. A photomask 9 is proposed.

However, although the photomask 9 according to this proposal can prevent static electricity charging due to the above-mentioned drawback, the thickness of the transparent conductive film 8 is relatively thin in order to ensure light transmission, and the surface of the photomask 9 is relatively thin. Because the shape is uneven,
When this is closely exposed to a transfer substrate such as a semiconductor substrate with photoresist, a part of the transparent conductive film 8 may peel off and adhere to the photoresist of the transfer substrate. The photoresist of the substrate had a drawback that made it impossible to transfer a predetermined pattern.

Further, the photomask 9 according to this proposal has a transparent conductive film 8
Even though a predetermined pattern 6 was formed before the film was deposited, high-temperature treatment at about 400 to 500° C. is usually required afterwards in order to increase the transmittance of the transparent conductive film 8 to 90% or more. However, the above-mentioned pattern 6 caused thermal deformation on the order of .mu.l, which resulted in a 1.1 defect.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, that is, (1) no defects occur in the pattern of the photomask during the close exposure process with the transfer target substrate; (2) the transfer target substrate A photomask that simultaneously satisfies the following three items: (3) transferring a predetermined pattern to photoresist reliably and precisely, and (3) eliminating the need for high-temperature treatment as a means of improving the transmittance of a transparent conductive film. The goal is to provide the following.

In order to achieve this object, the photomask according to the present invention has a photoresist that is substantially the same as the photoresist on the transfer target substrate, and is coated on the pattern side surface of the photomask.

FIG. 3 shows a photomask according to an embodiment of the present invention, in which a pattern 6 of a light-shielding thin film of metallic chromium or the like (this example: line width 2 μm) is formed on a transparent substrate 1 of soda lime glass or the like. (Up to this point, the photomask 7 shown in FIG.
is the same as ), and on the surface of this pattern 6 side, photoresist 10 (this example: positive type) No. 1 cyst (
Z-1350 (manufactured by Hipley, Inc. in the United States) is coated using a spin code method, a spray method, or the like. The film thickness of this photoresist 10 is usually several thousand (in this example: 500) in consideration of pinholes. Next, in order to remove the organic solvent remaining in the coated photoresist 10, the photoresist 10 is subjected to high temperature treatment in a dry atmosphere such as dry N2 gas using an electric oven or infrared heating in a so-called pre-baking process. This blebake temperature is normally set at around 80 to 90°C, taking into consideration the vitrification temperature, for example, for the photoresist 3 of the blank 4 shown in FIG. 10, the temperature is set lower than the normal set temperature (near 0° C. in this example).

FIG. 4 shows a contact exposure process when the photomask 11 according to the present invention is used as a transfer mask and the submaster photomask blank 4 (FIG. 1(a)) is used as a transfer target substrate. First, the close contact device of this example is composed of a transfer chamber 12 and a transfer target distiller 19. The transfer chamber 12 includes a frame 16 (made of material : steel material, etc.), a transparent sealing plate 17 (made of diquartz, etc.) installed on the exposure surface, and cushion sheets 1 to 18 (U quality: rubber, etc.) interposed between the photomask 11 and the pedestal 13. ,
The chamber 19 for transfer is 1. A frame body 22 (material: steel, etc.) having a pedestal 20 for storing and installing the blank 4, a through hole 21, a sealing plate 23 (material: red resin, etc.), and a cushion sheet 24 interposed between the blank 4 and the pedestal 20. (Material: rubber, etc.).

The mask 11 and the blank 4 are installed on the pedestals 13 and 20 via the cushion seats 1, 18 and 24, and are inserted into the respective chambers 12 and 19 through the through holes 14 and 21.
By creating a vacuum inside the device, the installation state is changed to the suction state (FIG. 4(a)). Next, each ditonba 12
After the head surfaces of the frames 16 and 22 of the frames 16 and 19 are brought into contact with each other, the space facing the blank 4 such as the mask 11 is evacuated through the through hole 15, and the interior of each chamber 12 and 19 that was previously blown is evacuated. When leaking (Figure 4 (b) → (
C)), photomask 11 etc. blank 4 is each 7
The photoresists 10 and 3 come into contact with each other and are in close contact with each other. In this close contact state, the photoresist 3 of the blank 4 is exposed to mercury lamp light 25 from the side of the transparent sealing plate 17 through the photomask 11, and the pattern 6 of the mask 11 from the pattern A1 to the mask 11 is transferred onto the blank 4. After that, the photomask 11 and the blank 4 are attached to each channel through the reverse procedure for vacuum and leakage as described above.
from the chambers 12 and 19.

Therefore, in the present invention, since the photoresist 10, which is the same as the resist 3, is applied to the photoresist 3 on the photoresist 1 of the blank 4 on the surface of the pattern side of the photomask 11, the photoresist 10, which is the same as the photoresist 3, is applied to the surface of the photomask 11 on the pattern side. 3.10 Comrades will come into contact, and this photoresist 3.10
Static electricity is difficult to generate, and even if static electricity is generated, it is only a small amount of charge, so the pattern 6 of the photomask 11
There is no possibility of damage due to electrical discharge. Further, even if dust 26 is present between the photomask 11 and the blank 4, this dust 26 is removed through the steps after the blank 4 is exposed, that is, the steps of development, etching, and resist stripping. Further, the photomask 11 is subjected to high temperature treatment in the pre-baking process of the photoresist 10, and the blebake temperature is usually 100'Cg.

Since the pattern 6 is below, thermal deformation on the order of μm will not occur to the pattern 6. Furthermore, when pre-baking is carried out at a temperature lower than the pre-baking temperature of blank 4 as in this example, the adhesion of photoresist 10 of photomask 11 is weaker than that of photoresist 3 of blank 4; Therefore, in the contact exposure process described above, part or all of the photoresist 1O of the photoresist 10 of the photo mask 11 is peeled off and attached to the photoresist 3 of the blank 4, but both photoresists 3 and 10 are originally the same. Since it is a substance, the deposits from photoresist A1 to photoresist i from 10 are treated in exactly the same way as photoresist 3. I!
There is no problem, and peeling of the resist 3 from A1 of the blank 4 is prevented.

Furthermore, since the mask A1 to mask 11 according to the present invention has the entire surface on the pattern 6 side covered with the 7 photoresist 10, the entire surface is protected both physically and chemically.

Note that the present invention is not limited to the above embodiments, and the transparent substrate may be made of other types of glass such as aluminoborosilicate glass or synthetic quartz, and the light-shielding thin film may be made of Ta, Ti, etc.
, W, Mo, Fe, Cr, and other oxides, nitrides, etc., for F-A1~ resist, positive type F-1~ resist of Haku type (e.g. 0FP manufactured by Tokyo Ohka Kogyo Co., Ltd.).
R-800), negative July resist (e.g. interlayer 0DO
R-120) or a photoresist formed by an X-ray exposure method.The film thicknesses of the light-shielding thin film and the photoresist are each appropriately selected. In addition to directly depositing this light-shielding thin film on the transparent substrate, one or both of a transparent conductive film and a back anti-reflection film are coated on the transparent I1g substrate side, and the surface reflection film is placed between the light-shielding thin film and the photoresist. A protective film may be applied as required. These film forming methods may include air vapor deposition, vapor phase growth, ion blating, and the like.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the manufacturing process of a conventional photomask.
FIG. 2 is a sectional view showing a conventional photomask that prevents charging, and FIG. 3 is a sectional view showing a photomask according to the present invention.
and FIG. 4 are cross-sectional views showing a contact exposure process which is an example of the use of the photomask according to the present invention. 1... Transparent substrate, 2... Light-shielding thin film, 3, 10...
・Photoresist, 4...Photomask blank, 6
...Pattern of light-shielding thin film, 11...Photomask Fig. 1

Claims (2)

[Claims] (1) In a photomask in which a light-shielding thin film pattern is formed above a transparent substrate, a photoresist that is substantially the same as the photoresist of the photoresist-coated substrate to which the pattern is transferred by contact exposure with the photomask. A photomask characterized in that a photoresist is applied to a pattern side surface of the photomask. (2) In a photomask in which a light-shielding thin film pattern is formed above a transparent substrate, a photoresist that is substantially the same as the photoresist of the photoresist-coated substrate to which the pattern is transferred by contact exposure with the photomask; A method for manufacturing a photomask, comprising applying a resist to a pattern-side surface of the photomask, and setting a pre-baking temperature of the photomask lower than a pre-baking temperature of the transfer target substrate.