JPH05313342A - Phase shift mask and pattern forming method - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Pattern formation is performed by taking advantage of the phase shift technology. According to the phase shift mask for forming an island-shaped pattern of the present invention, light of the same phase is transmitted in one direction of the array of mask patterns, and light of which the phase is alternately changed is transmitted in the other direction of the array. By arranging the phase shifter in the configuration, the light having the same phase is emitted in one direction of the pattern arrangement, and the light whose phase is alternately changed is emitted in the other direction of the arrangement. As a result, the phase shift technique can be effectively used even in the formation of a pattern in which island patterns are arranged, and the advantages of the phase shift technique can be utilized.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a phase shift mask. INDUSTRIAL APPLICABILITY The present invention can be used as a phase shift mask used in various pattern forming techniques and the like, and can be used as a phase shift photomask used as a mask when forming a resist pattern in a semiconductor device manufacturing process, for example.

[0002]

2. Description of the Related Art What is formed using a photomask,
For example, the processing dimensions of semiconductor devices and the like tend to become finer year by year. Against this background, in a photolithography technique for obtaining a miniaturized semiconductor device, in order to further improve the resolution, a so-called phase shift technique is applied to impart a phase difference to light passing through a mask, thereby improving a light intensity profile. Is in the limelight.

A conventional phase shift technique is disclosed in Japanese Unexamined Patent Publication No. 58-173744 and MARC D. et al. LEVE
NSON and others “Improving Resoluti
onin Photolithography wit
ha Phase-Shifting Mask "I
EEE TRANSACTIONS ON ELECT
RON DEVICES. Vol. ED-29 No.
12, DECEMBER 1982, P1828-18
36, also MARC D.M. LEVENSON and others "T
he phase-Shifting MaskII:
Imaging Simulations and S
ubmicrometer Resist Expos
ures "same magazine Vol.ED-31, No.6.
JUNE 1984, P753-763.

Japanese Patent Publication No. 62-50811 has a predetermined pattern formed of a transparent portion and an opaque portion,
Disclosed is a phase shift mask in which a phase member is provided on at least one of transparent portions on both sides of an opaque portion and a phase difference is generated between the transparent portions on both sides.

A conventionally known phase shift technique will be described below with reference to FIG. For example, in the case of performing line-and-space pattern formation, an ordinary conventional mask has a structure in which Cr (chrome) is formed on a transparent substrate 1 such as a quartz substrate as shown in FIG.
The light-shielding portion 10 is formed by using a light-shielding material such as metal, metal oxide, or the like, and a repetitive pattern of lines and spaces is formed as a mask for exposure. The intensity distribution of the light transmitted through this exposure mask is
As shown by a symbol A1 in FIG. 12A, ideally, the light-shielding portion 10 has zero, and the other portions (transmission portions 12a, 12a,
It is transparent in 12b). Considering one transmission part 12a, the transmitted light given to the exposed material has a light intensity distribution having a peak-shaped maximum on both sides as shown by A2 in FIG. Become. The transmitted light A2 ′ toward the transmissive portion 12b is shown by the alternate long and short dash line. Each transmission part 12
When the lights from a and 12b are combined, the light intensity distribution loses sharpness as shown by A3, and the image is blurred due to the diffraction of light, so that sharp exposure cannot be achieved. On the other hand, the light transmitting portions 12a of the repeating pattern described above,
If every other one of the phase shift portions 11a (referred to as a shifter; a material such as SiO ₂ or a resist is used) is provided on 12b as shown in FIG. Blurring is canceled by phase inversion, a sharp image is transferred, and resolution and focus latitude are improved.
That is, as shown in FIG. 12B, when the phase shift part 11a is formed on one of the transmissive parts 12a, it becomes, for example, 18
If it gives a phase shift of 0 °, the light passing through the phase shifter 11a is inverted as indicated by the symbol B1.
The light from the transmitting portion 12b adjacent to the phase shifter 11
Since it does not pass through a, such inversion does not occur. As for the light given to the exposed material, the mutually inverted lights cancel each other at the position shown by B2 in the figure at the bottom of the light intensity distribution, and finally the distribution of the light given to the exposed material is shown in FIG. 12 (b).
As shown by B3, the shape becomes sharp and ideal.

In the above case, it is most advantageous to invert the phase by 180 ° in order to make this effect most reliable, but for this purpose, A phase shift portion 11a is formed with a film thickness D such that (n is the refractive index of the phase shift portion and λ is the exposure wavelength).

When a pattern is formed by exposure, a reduced projection is called a reticle, a one-to-one projection is called a mask, or a master is called a reticle and a duplicate thereof is called a mask. However, in the present invention, masks and reticles in such various meanings are collectively referred to as masks.

[0008]

The problem of the above-mentioned phase shift technique, especially the spatial frequency modulation type phase shift method, is that three or more patterns A, B and C are arranged as shown in FIG. Phase shift between A and B, B
This means that it is not possible to make a 180 ° change between -C and all between C-A. That is, 18 between A and B
If you shift 0 ° and shift 180 ° between A and C, B
There is a 0 ° shift between -C. Therefore B-C
The phase cannot be shifted between them and the effect of the phase shift cannot be obtained. This is the same relationship between A-C-B 'and C-B'-A' in the figure. Therefore, in the pattern formation in which three (or more) island-shaped patterns are arranged in this manner, the phase of the irradiation light to the adjacent patterns is shifted by 180 °, which is a feature of the phase shift method. Can not fundamentally.

Therefore, conventionally, there has been a problem that the phase shift method of the spatial frequency modulation system is difficult to use only for the line-and-space pattern or the pattern lined up in the perfect island pattern.

The present invention solves the above-mentioned problems, and in forming a pattern in which island patterns are arranged,
It is an object of the present invention to provide a phase shift mask and a pattern forming method which can effectively use the phase shift technique and therefore can take advantage of the phase shift technique even in such pattern formation.

[0011]

A phase shift mask according to the present invention is a pattern forming phase shift mask for forming a pattern in which island patterns are arranged, and the same phase is formed in one direction of the mask pattern arrangement. Light is transmitted,
The above object is achieved by arranging the phase shifter in a configuration in which the light whose phase changes alternately is transmitted in the other direction of the array.

The pattern forming method of the present invention is a pattern forming method for forming a pattern in which island-shaped patterns are arranged. In one direction of the pattern arrangement, light of the same phase is irradiated and in the other direction of the arrangement. The above-mentioned object is achieved by adopting a structure in which light having a phase that alternates is irradiated.

In the inventions of the present application, the island-shaped pattern means a pattern other than a line-and-space pattern or a complete island-shaped lattice pattern. Says something that is difficult to apply between patterns.

The structure of the present invention will be described below with reference to FIG. That is, as shown in FIG. 1, island-shaped patterns 11 are formed in the horizontal direction and the vertical direction of the drawing.
0,120,130,21,22,31-33,41,
In the case of a pattern in which 42 is arranged, phase A and this and 1
The phases B having a phase difference of 80 ° are alternately arranged in every other column as shown in the figure. That is, in FIG. 1, the patterns 110, 120, 130 in the left-right direction all have a phase A, but the patterns 21, 22 in the next row have a phase B. Similarly, the patterns 31 to 33 of the next row are set to the phase A, and the patterns 41 and 42 of the next row are set to the phase B which is 180 ° out of phase with the patterns.

By doing so, the phase shift effect works in the Y direction, which is the vertical direction in the figure, as intended by the phase shift technique. On the other hand, the phase shift effect does not work in the X direction, which is the left-right direction in the figure. This can be dealt with, for example, by loosening the design rule. For example, this technique may be applied so that the phase shift effect works on the portion where the design size must be made smaller. For example, specifically, the island-shaped patterns to be formed are wider in the same phase direction and narrower in the direction in which the phases alternate, and the technique of the present invention can be preferably applied.

Further, the method of phase shift is described in I and J of FIG.
(J is 180 ° out of phase with I). In this case, contrary to the above, the phase shift effect works in the X direction, but does not work in the Y direction.

Further, the amount of light that goes around the light-shielding portions (C) and (D) when the phase shift is not used is calculated, and even if X = Y, the amount of light is larger, for example (D). ) Region, the above phase shifts of A and B may be used, and conversely, if (C) wraps around and there is a large amount of light,
The I and J phase shifts may be used.

Although the above description has been made on the island pattern to be formed, the phase shift mask has a mask pattern having a shape corresponding to the island pattern, and the phase shift is performed as described above. The phase shift mask of the present invention can be obtained by forming the light transmitting portion and the phase shift portion in the above.

[0019]

According to the present invention, even with respect to the island pattern, the phase shift effect can be satisfactorily exerted and the patterning with a good resolution can be realized.

The operation of the present invention will be described with reference to FIG. In FIG. 2, A and B are 180 relative to each other.
This is the case when there is a phase shift of °, but at this time, X
The light amplitude between −X ′ is as shown in FIG. In this case, the light intensity is the square of FIG. 3, and shows almost the same shape.
On the other hand, the optical amplitude between YY 'is as shown in FIG. 4 (a), which shows the phase shift effect. When the phase shift is not used, the result is as shown in FIG. These Figure 4
The light intensities of (a) and (b) are as shown in FIGS.

As described above, by using the phase shift in the Y direction (here, the pattern interval is narrow in this direction), the light intensity ratio can be made large. In the X direction, the light intensity ratio is sufficient without using the phase shift method. For example, if the light intensity distribution is as shown in FIG. 5B without using the phase shift method, the patterns are connected to each other, but FIG.
In that case, fine patterning is possible and the effect of the present invention can be obtained.

Although the above description has been made for the phases A and B in FIG. 1, the same applies to the cases of the phases I and J, except that
The X and Y directions are opposite.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. However, as a matter of course, the present invention is not limited to the examples shown below.

Embodiment 1 In this embodiment, island patterns I to I as shown in FIG. 6 are used.
This example was applied to II. When a light intensity simulation was actually performed on such a pattern, a light intensity distribution curve as shown in FIG. 7 was obtained. Although the dimensions of the patterns I, II, and III are all the same, the pattern I and the pattern I can be seen from the contour lines of the light intensity shown in FIG.
The most wraparound of light to the portion shown in the figure between I and I. It is larger than between the patterns I and II and the pattern III. Therefore, in this embodiment, the pattern I,
A phase shift of 180 ° was applied between II. This allows
It is possible to form a good pattern in the area I without having to change all the sizes of the patterns I to III.

Example 2 In this example, the present invention was applied to pattern formation in a DRAM. The pattern 100 shown in FIG. 8 is an island pattern to which the present invention can be effectively applied. The other pattern portions are shown by broken lines.

Embodiment 3 This embodiment also applies the present invention to pattern formation in a DRAM. Three patterns 100a-shown in FIG.
100c can be preferably used in the present invention for the same reason as described in Example-1. That is, in this example, formation of the patterns 100a and 100b and formation of the pattern 100c were performed with a phase shift of 180 °. Pattern 100a, 100b and pattern 100
The distance from c and the distance between the patterns 100a and 100b are both 0.5 μm. Other patterns are indicated by broken lines.

Embodiment 4 This embodiment also applies the present invention to the pattern formation of a miniaturized DRAM. Patterns 100a-in FIG.
Reference numeral 100c denotes an island pattern to which the present invention is applied, which was performed with the same phase shift as in Example-3. Other patterns are indicated by broken lines.

Example 5 In this example, the present invention was applied to the pattern formation of an SRAM, particularly a miniaturized and integrated SRAM. FIG. 11 shows patterns (a) and (b) to which the present invention is applied. When carrying out,
In (a) and (b) of the figure, the phase software was inverted by 180 °. As a result, desired patterning could be favorably performed.

[0029]

As described above, the phase shift mask and the pattern forming method of the present invention solve the problems of the prior art and effectively use the phase shift technique for the pattern formation in which island patterns are arranged. Is something that can be done.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of the present invention.

FIG. 2 is an explanatory view of the operation of the present invention.

FIG. 3 is a diagram for explaining the operation of the present invention.

FIG. 4 is an explanatory view of the operation of the present invention.

FIG. 5 is an explanatory view of the operation of the present invention.

FIG. 6 is a diagram showing an array of patterns of Example-1.

FIG. 7 is a diagram showing contour lines of light intensity in Example-1.

FIG. 8 is a diagram showing a pattern of Example-2.

FIG. 9 is a diagram showing a pattern of Example-3.

FIG. 10 is a diagram showing a pattern of Example-4.

FIG. 11 is a diagram showing a pattern of Example-5.

FIG. 12 is a diagram illustrating the principle of a phase shift mask.

FIG. 13 is a diagram showing a problem.

[Explanation of symbols]

110,120,130,21,22,31-33,4
1,42 Island pattern I to III
Island pattern 100, 100a-100c
Island pattern (a) (b)
Island pattern

Claims (2)

[Claims] 1. A phase shift mask for pattern formation, which forms a pattern in which island-shaped patterns are arrayed, wherein light of the same phase is transmitted in one direction of the array of mask patterns and is transmitted in the other direction of the array. A phase shift mask, wherein a phase shift portion is arranged in a configuration in which light whose phase changes alternately is transmitted. 2. A pattern forming method for forming a pattern in which island-shaped patterns are arranged, wherein light of the same phase is irradiated in one direction of the pattern arrangement,
A pattern forming method, characterized in that a light whose phase changes alternately is applied to the other direction of the array.