JPH02236549A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To suppress the etching time dependency of the dimension of a pattern by bringing an arbitrary pattern to picture drawing to an outside peripheral part, etc. of an object pattern, and adjusting an etching speed. CONSTITUTION:To an object pattern part 2 provided on a prescribed part of a substrate 1 to which a resist is applied, an object prescribed pattern is brought to picture drawing. Also, to a suitable area 3 of the outside of the object pattern part 2, an arbitrary pattern is brought to picture drawing. In such a way, by adjusting an etching area, the etching time can be adjusted, and the etching time dependency of the dimension of an object pattern can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a photomask using a dry etching method for forming a fine pattern on a photomask.

[Conventional technology] In recent years, due to demands for higher density and higher integration of semiconductor integrated circuits, line widths of 0. Formation of fine patterns of about 2 μm has become essential.

For this reason, recently, we have developed a method that has good dry etching resistance.
In addition, due in part to the development of negative resists with excellent resolution, dry etching methods have been widely adopted because they produce fewer undercuts and have better dimensional control than wet etching methods.

[Problems to be solved by the invention] However, although the dry etching method is advantageous in forming fine patterns, the etching time becomes longer in proportion to the etching area between and within the substrates (loading effect). ) There is a problem. In other words, dry etching is performed at a uniform speed regardless of the shape (
(isotropic etching), so if the etching area is large, the etching time, that is, the time required for the metal film of the substrate to penetrate, becomes longer, and there is a problem that the etching time varies between substrates and within the substrate. Ta.

In addition, a high-resolution negative resist is used as the resist, and Cr, which is commonly used as a photomask material, is used.
For example, 02
It is known that when Cr is dry etched using a mixed gas of Cr and CC Is, renost is also etched at a certain rate, and in general, resist film reduction is unavoidable during the etching process.

In addition, in order to obtain a high-resolution pattern, a substrate coated with a resist film of 4000 Å or less, which is thinner than usual, is coated with an electron beam tili! Although drawing is performed using an i-image device, the cross-sectional shape of the resist after development is not necessarily rectangular due to back scattering of electrons that occur during electron beam drawing, and is smooth as shown in Figure 4. Due to the tapered shape, there was also a problem in that the amount of dimensional lift of the resist could not be easily controlled in the etching process.

In addition, in FIG. 4, 10 is a mask substrate such as Cr;
1 indicates resist.

In particular, when patterning a fine pattern of about 0.2 μm, if the etching area of the mask is large, the etching time will be longer, and the resist will also be etched accordingly, increasing the amount of recession, resulting in a dimensional shift amount. They tend to get bigger, which is a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photomask manufacturing method that can shorten etching time and thereby reduce the amount of resist recession.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, when using a negative resist, by forming an arbitrary pattern on the outer periphery other than the intended pattern part, the etching area can be reduced. It is characterized by reducing the etching rate between patterns on the same substrate and adjusting the etching rate between patterns on different substrates.

[Function] In the present invention, an arbitrary pattern is drawn on the outer periphery of the target pattern and the etching speed is adjusted, so that variations in the etching time for each part of the pattern can be reduced. In addition, since the etching area can be reduced, the etching time can be shortened, the amount of resist recession can be reduced, and the dependence of pattern dimensions on etching time can be suppressed, making it possible to form fine patterns. This makes things easier.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention, in which a predetermined target pattern is drawn on a target pattern section 2 provided at a predetermined location on a substrate 1 coated with lenost. . Furthermore, an arbitrary pattern is drawn in an appropriate area outside the target pattern area 2, indicated by 3 in FIG. . ). In addition, in FIG. 1, the arbitrary pattern drawing section 3 is filled with electron beam, but
Any pattern may be used. Further, the area of the arbitrary pattern drawing section 3 may be adjusted as necessary.

As described above, it is possible to adjust the etching time by adjusting the etching area, and the dependence of the dimensions of the target pattern on the etching time can be reduced.

Figures 2 and 3 show the shift in resist dimensions ffi with respect to over-etching time when etching is performed by changing the area of the arbitrary pattern drawing area on a 5-inch square substrate.
The results of actual measurements are shown. Figure 2 (a), (b), (c)
In each case, the area of the target pattern part is 80 s
m x 6 0 +n, and the only difference is the area of the arbitrary pattern drawing section. Specifically, in the one shown in FIG. 2(a), the entire area outside the target pattern area is an arbitrary pattern drawing area, and in the one shown in FIG. 2(b), the target pattern area is 70 m including
The area other than the range of 90 mm x 70 + u is the arbitrary pattern drawing area, and in the case shown in FIG. ing. Accordingly, the second
The etching area of the one shown in Figure (b) is as shown in Figure 2 (a).
In the case shown in FIG. 2(C), it is 2.25 times that shown in FIG. 2(a).

Note that the range indicated by 4 in FIG. 2 is an unexposed portion, that is, a range to be etched. Also, FIGS. 2(a) and (b).
In (c), a Cr film is used as the light-shielding film of the photomask, and the same pattern is drawn on the target pattern portion of each substrate.

After creating these three types of substrates under the same conditions, the line width was 0.
Figure 3 shows the actual measurement of the dimensional shift with respect to over-etching time for a 4 μm pattern. 6. The graphs indicated by 7 are the second
Figure (a). (b) shows the case of +c.

As is clear from FIG. 3, it was confirmed that the smaller the etched area, the smaller the amount of dimensional shift for the same over-etching time. The etching method used was a parallel plate type reactive ion etching device.
02 gas, CCI. Crl by converting gas etc. into plasma state
la was removed.

[Effects of the Invention Since the over-etching time after co-dry etching greatly changes the amount of shift in resist dimensions, that is, the amount of retreat, the present invention reduces the etching area by reducing the mask area within the substrate and between the substrates. Dimensional variations can be reduced.

Furthermore, since the amount of shift in resist dimensions due to over-etching can be reduced, it is possible to easily realize fine patterns of around 0.2 μm, which have been considered difficult in the past.

Furthermore, even when the resist film is made thinner to improve resolution, it is possible to minimize the loss of resist during the mask film etching process, making it possible to produce masks with fewer defects in terms of quality. It is something.

[Brief explanation of drawings]

Figure 1 is a diagram explaining one embodiment of the present invention, Figure 2 is a diagram showing three types of substrates with different areas of arbitrary pattern drawing parts, and Figure 3 is a diagram showing over-etching of each substrate shown in Figure 2. FIG. 4 is a diagram showing the relationship between the over-etching time and the dimensional shift amount of the resist, and FIG. 4 is a diagram showing the state of the resist after conventional development. 1... Substrate coated with resist, 2... Target pattern section, 3... Arbitrary pattern drawing section. Figure 1 Applicant Dainippon Printing Co., Ltd. Agent Patent Attorney Hideo Sugai (and 5 others) 1 o Mamata 4 Figures (a) Figure (b) Figure (c) Figure O

Claims (1)

[Claims] (1) In a photomask manufacturing method using dry etching to form a fine pattern on a photomask using a high-resolution negative resist, an arbitrary pattern is formed on the outer periphery of the photomask other than the target pattern, and etching is performed. A photomask manufacturing method characterized by reducing the area.