JPH0619115A - Mask for stepper - Google Patents

Abstract

PURPOSE:To lessen the dimensional change with the defocusing of a photoresist size stepped to a mask size, to widen a focusing allowance and to enable the formation of fine size patterns. CONSTITUTION:The size (mask size) of the mask patterns 1 for stepping to a photoresist is pet at the size obtd. by adding a mask bias size DELTAL set to minimize the change in the photoresist size by the defocusing at the time of exposure to the design pattern size L of a semiconductor device. For example, the mask bias size is set at an optimum value according to the wavelength of exposing light of the stepper, numerical aperture, coherent factor, and the pattern widths of the respective design patterns.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask for a projection exposure apparatus used for manufacturing a semiconductor device and performing pattern projection.

[0002]

2. Description of the Related Art Conventionally, a mask of this type is constructed by using the same pattern as a pattern formed on a semiconductor device as a mask pattern. This pattern is exposed on a photoresist formed on the semiconductor device and the photoresist is developed. The pattern described above is formed on the semiconductor device by etching using the remaining photoresist. Alternatively, in consideration of the proximity effect between the patterns in the exposure apparatus, a mask pattern in which the proximity effect is corrected by using the light intensity shape in on-focus and the simulation result of the photoresist shape formed by this is used. ing.

FIG. 5 shows a mask pattern when designed according to a design pattern in which line patterns are arranged at the same interval L as the line size. FIG. 6 shows the defocus dependence of the photoresist size when a negative photoresist is formed using this mask. from now on,
It can be seen that an error occurs between the design dimension and the resist dimension when the focus is on and when the focus is defocus. It can also be seen that this error is changed by the change of the exposure amount. Normally, the exposure amount is set so that the dimensions of the photoresist are formed according to the mask when on-focus.

[0004]

As described above, even if the conventional mask is formed in the same size as the designed size, if the focus of the exposure apparatus is deviated, the pattern is largely deformed in the on-focus pattern. There is a problem. This dimensional change tends to increase as the pattern size becomes finer. If this dimensional change exceeds the manufacturing size tolerance, the manufactured semiconductor device becomes defective, and there is a problem that the focus margin is narrow. . The cause of defocus is the focusing accuracy of the exposure apparatus, the warp of the semiconductor substrate, the unevenness due to the pattern on the surface of the semiconductor device, etc., and it is necessary to determine the minimum design dimension in consideration of these margins. An object of the present invention is to provide a mask for a projection exposure apparatus that reduces dimensional change due to defocus, expands focus margin, and enables formation of a fine dimensional pattern.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a mask bias dimension set so as to minimize a change in photoresist dimension due to defocus during exposure is added to a mask dimension added to a design pattern dimension of a semiconductor device. Set. For example, the mask bias dimension is set to an optimum value according to the exposure light wavelength of the projection exposure apparatus, the numerical aperture, the coherent factor, and the pattern width of each design pattern.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a mask pattern of the present invention. According to the defocus dependence between the photoresist size and the design size shown in FIG. 6, when the exposure amount is set to a pivotal point whose size is different from that of the mask by −ΔLp, the size change upon defocusing is minimized. I understand. Therefore, a mask bias is added to the design dimension so that the photoresist pattern becomes a pivotal point in the design dimension. As shown in FIG. 1, the bias dimension ΔL is added to the design value of the line dimension of the mask pattern 1. On the other hand, the dimension between the lines 1 is obtained by subtracting the bias dimension ΔL.

FIG. 2 shows the dependence of the photoresist dimension on the out-of-focus using the mask thus formed.
In this case, when the resist dimension is the design dimension, the pivotal point is where the dimension variation due to defocus is minimized. The optimum mask bias value depends on the exposure light wavelength of the exposure apparatus, the coherent factor, the numerical aperture, the pattern size, and the like.

FIG. 3 is a diagram showing a design procedure for forming the mask pattern of FIG. The mask bias value for each exposure device and each pattern dimension is obtained in advance. Next, the mask bias value obtained in accordance with the pattern dimension of the actual design pattern of the semiconductor device is selected and added to obtain the pattern dimension of the mask pattern.

Here, the mask pattern design procedure as shown in FIG. 4 may be adopted. That is, using the design pattern as a mask pattern, the dimensional change of the photoresist pattern due to defocus is obtained by a sample three-dimensional simulator or the like. Then, the mask pattern is corrected as the mask bias value at each pattern end, and the simulation is performed again. This procedure is repeated one to several times to find the optimum mask pattern. Since this method requires several times of resist pattern simulation, it requires a long time calculation by a computer as compared with the above-mentioned embodiment, but since it is calculated based on an actual design pattern, it is more accurate in optimal mask bias. There is an advantage that the value can be obtained. In particular, it is suitable for a mask of a pattern that has strict design rules and requires high dimensional accuracy.

[0010]

As described above, according to the present invention, the mask bias dimension set to minimize the change in the photoresist dimension due to the defocus during the exposure is added to the design pattern dimension of the semiconductor device. Since the defocus dependency is the pivotal point with the smallest dimensional change with respect to the defocus, the focus margin can be further expanded. This allows
There are effects such as expansion of the manufacturing margin and use of a finer dimension pattern.

[Brief description of drawings]

FIG. 1 is a mask pattern diagram showing a pattern example of a mask of the present invention.

FIG. 2 is a diagram showing the defocus dependence of the photoresist dimension by the mask pattern of FIG.

FIG. 3 is a diagram showing a procedure for designing the mask pattern of FIG.

FIG. 4 is a diagram showing another example of a design procedure.

FIG. 5 is a mask pattern diagram showing an example of a conventional mask pattern.

FIG. 6 is a diagram showing a defocus dependence of a photoresist dimension by a conventional mask pattern.

[Explanation of symbols]

 1 line (mask pattern) L line width ΔL Mask bias dimension

Claims (2)

[Claims] 1. A mask bias dimension set in a mask for performing projection exposure on a photoresist provided in a semiconductor device, wherein a mask bias dimension set so as to minimize a change in photoresist dimension due to defocus during exposure. A mask for a projection exposure apparatus, which is set to a mask size added to a design pattern size of a semiconductor device. 2. The mask for a projection exposure apparatus according to claim 1, wherein the mask bias dimension is set to an optimum value according to the exposure light wavelength of the projection exposure apparatus, the numerical aperture, the coherent factor, and the pattern width of each design pattern.