JPH0627633A - Phase shift mask - Google Patents

Abstract

PURPOSE:To provide the phase shift mask which can effectively utilize the advantages of a phase shift technology for both of isolated patterns and island- shaped patterns. CONSTITUTION:Second apertures 22a,... provided adjacently to the first aperture 22 on a transparent substrate 1 provided with light shielding parts are so constituted as to have phase shift parts 21a,... having specific light transmittance, by which the resolution of the isolated patterns is improved. The peripheral parts in the light shielding parts of the apertures on the transparent substrate are provided with the phase shift parts having the specific light transmittance or the light shielding parts are formed of the phase shift parts having the specific light transmittance, by which the advantages of the phase shift technique are effectively exhibited for the island-shaped patterns as well.

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, for example, in a semiconductor device manufacturing process, not only a repetitive pattern such as a line-and-space pattern, but especially a center hole or the like is used. It can also be used for forming an isolated pattern such as an isolated hole pattern or an isolated line pattern, and can also be used as a mask for forming an island-shaped resist pattern or the like in which a plurality of patterns exist in the vicinity. It can be used as a phase shift photomask.

[0002]

2. Description of the Related Art What is formed using a photomask,
For example, semiconductor devices and the like tend to have finer processing dimensions 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 give a phase difference to light passing through a mask, thereby improving a light intensity profile. Is in the limelight.

Regarding the conventional phase shift technique, Japanese Patent Laid-Open No. 173744/1983 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 ”magazine Vol.ED-31, No.6, JU
NE1984, P753-763.

Further, Japanese Patent Publication No. 62-50811 has a predetermined pattern formed of transparent portions and opaque portions,
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.

The 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, as shown in FIG. 5A, an ordinary conventional mask is a transparent substrate 1 such as a quartz substrate on which Cr (chromium) or other metal or metal oxide is oxidized. The light-shielding portion 10 is formed by using a light-shielding material such as an object, and thereby a line-and-space repeating pattern is formed to form an exposure mask. The intensity distribution of the light transmitted through this exposure mask is shown in FIG.
Ideally, as shown by the symbol A1 in FIG.
However, it is zero at the other parts (transmissive parts 12a, 12
It is transparent in b). Considering one transmission part 12a, the transmitted light given to the exposed material has a light intensity distribution having a peak-like maximum on both sides as shown by A2 in FIG. Become. The transmitted light A2 ′ toward the transmission part 12b is shown by the alternate long and short dash line. Each transmission part 12a, 12
When the lights from b are combined, the light intensity distribution loses sharpness as shown in A3, and the image is blurred due to the diffraction of light.
After all, sharp exposure cannot be achieved. On the other hand, the light transmitting portions 12a and 12b of the repeating pattern
If every other one of them is provided with a phase shifter 11a (called a shifter; a material such as SiO ₂ or a resist is used) as shown in FIG. 5B, an image is blurred due to diffraction of light. Is canceled by phase inversion, a sharp image is transferred, and resolution and focus latitude are improved. That is, as shown in FIG. 5B, when the phase shift portion 11a is formed on one of the transmission portions 12a, if it gives a phase shift of, for example, 180 °, it passes through the phase shift portion 11a. The light is inverted as indicated by the symbol B1. Light from the adjacent transmissive portion 12b does not pass through the phase shift portion 11a, so such inversion does not occur. As for the light given to the exposed material, the mutually reversed lights cancel each other out 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. 5 (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, The phase shift portion 11a is provided 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]

One of the problems of the above-mentioned phase shift technique, particularly the spatial frequency modulation type phase shift method, is the formation of the pattern in which three (or more) island-shaped patterns are formed. That is, it is fundamentally impossible to shift the phase of the irradiation light to adjacent patterns by 180 °, which is a feature of the phase shift method. That is, when three or more patterns A, B, and C are arranged as shown in FIG. 6, the phase shift is changed between A and B and B, respectively.
It is not possible to change 180 ° between -C and all between C-A. That is, 180 ° shift between A and B
If 180 ° is also shifted between −C, 0 ° will be shifted between B and C. Therefore, the shift cannot be performed between B and C, and the effect of the phase shift cannot be obtained. This is A-C- in the figure
The same relationship applies between B'and CB'-A '. Therefore, in the pattern formation in which the three (or more) patterns are arranged and formed in the island pattern as shown in FIG. 6 as described above, the phase of the irradiation light to the adjacent patterns is 180 ° for all the patterns. There was a fundamental problem that it could not be shifted.

Further, in forming an isolated pattern such as an isolated hole or an isolated line, as shown in FIGS. 4 (a) and 4 (b),
Around the target patterns 32a, 32b, phase shift auxiliary patterns 33a, 33a ', 33 that are not resolved by themselves
There has been proposed a method of arranging b, 33b ', 33b ", 33b"' to increase the resolution of the target isolated patterns 32a, 32b. It needs to be made thin, this width is E
Since it is close to the performance limit of the B drawing machine, there is a problem in that the accuracy of forming the auxiliary pattern having a narrow width is poor and it is difficult to achieve the desired target accuracy.

The present invention solves the above-mentioned problems, and also in the formation of a pattern in which island patterns are formed,
Further, it is an object of the present invention to provide a phase shift mask that can effectively use a phase shift technique in both formation of an isolated pattern and therefore can take advantage of the phase shift technique in such pattern formation. And

[0011]

According to the invention of claim 1 of the present application, a phase shift portion is formed by a material that changes the phase of light transmitted through a transparent substrate with respect to the phase of incident light. In the mask, the light transmittance of the phase shift portion is a specific transmittance. With this configuration, the above object is achieved.

According to the invention of claim 2 of the present application, a light-shielding portion is provided on a transparent substrate, a first opening is formed by partially removing the light-shielding portion, and a first opening is provided adjacent to the first opening. In a phase shift mask having a second opening and the second opening having a phase shift part for changing the phase of transmitted light, the light transmittance of the phase shift part is a specific light transmittance. It is characterized by. With this configuration, the above object is achieved.

According to a third aspect of the present invention, there is provided a phase shift mask having a light-shielding portion formed by patterning on a transparent substrate and a phase-shifting portion for providing a phase change to transmitted light in a peripheral portion of the light-shielding portion, The light transmittance of the phase shift portion is a specific transmittance. With this configuration, the above object is achieved.

In each invention of the present application, the phase shift portion means a portion that transmits the exposure light at different phases with respect to the exposure light transmitted by the light transmitting portion. The light-shielding portion shields the exposure light used.

As the material of the light-shielding portion, chromium, other chromium oxide, or refractory metal (W, Mo, Be, etc.) is used.
General materials and oxides thereof can be used.

As the transparent substrate, quartz, ordinary glass,
It is possible to use glass containing various components as appropriate and other appropriate ones.

In each invention of the present application, the phase shift portion can be obtained by patterning a material forming the phase shift portion on a substrate or the like. Examples of the material of the phase shift film include the following.

That is, various organic substances that can be used as a photoresist can be used. For example, an EB resist (negative or positive resist) can be used to serve also as a resist function in an EB drawing apparatus. Specifically, SOG, for example, C manufactured by Tokyo Ohka Co., Ltd.
ODtype2 and other organic materials, for example, materials having a large refractive index such as polyimide resin, which are strong, and which can be easily formed (formed) and processed can be used.

Alternatively, for inorganic materials, SiO, SiO ₂ ,
A silicon nitride film (Si ₃ N ₄ film or the like) can be used. In this case, it is desirable to form at low temperature.

However, since it is sufficient for the phase shift portion to achieve a desired phase shift, it is possible to change the refractive index in a pattern in a part of the light transmitting portion (substrate) without forming it on the substrate. The substance may be doped to cause the phase shift. Depending on the case, by changing the film thickness of the light transmission part (substrate) or the light shielding part material,
It is also possible to form a phase shift part. As described above, the means for forming the phase shift portion can be arbitrarily selected, and the portions having the phase shift function are collectively referred to as the phase shift portion in this specification.

The light transmittance of the phase shift portion of the present invention has a specific light transmittance in order to exert the effect of the present invention, but it is generally preferable that the light transmittance is low.
For example, it is preferably about 40% to about 60% when used in combination with the light shielding portion, and when the phase shift portion itself also serves as the light shielding portion, the amplitude is 0.6 to 0.1 (the light intensity is 0.36). ~
0.01) is preferable. The phase shift amount is not limited to 180 °, and can be set to an optimum value as appropriate.

[0022]

According to the present invention, not only the isolated pattern but also the island-shaped pattern can exert the phase shift effect satisfactorily, and the patterning with good resolution can be realized.

That is, the EB drawing accuracy can be improved by expanding the width of the auxiliary pattern when forming the isolated pattern. However, if the width is widened, the amount of exposure light transmitted increases and the auxiliary pattern portion is transferred. As a countermeasure against this, if a material having low transmittance is used for the phase shift portion of the auxiliary pattern, the amount of transmission can be reduced. As a result, it is possible to improve only the resolution of the target isolated pattern without resolving the auxiliary pattern using the wide auxiliary pattern with high EB drawing accuracy.

For example, when forming an island pattern, the light-shielding portion has a low transmittance, for example, a transmittance of 10%.
By changing to a phase shift part that gives a phase shift of 180 °, the light with the phase inverted by 180 ° is slightly transmitted also in the light-shielding part, and the transmitted light with the phase reversed transmits the light below the phase shift part by diffraction. It is possible to cancel the light that has entered from the portion, and as a result, a sharp pattern (optical profile) can be obtained, and therefore, the improvement of the resolution of the island-shaped pattern, which was impossible with the conventional simple phase shift portion, can be achieved. Conventionally, the edge of the light shielding portion 10 has a tail of the light amplitude, and as shown in FIG. 7 (a), a sharp resolution cannot be obtained, whereas the light resolution is as shown in FIG. 7 (b). When the phase shift section 11 made of a semitransparent film is provided on the optical axis and also functions as a light shielding section, the light amplitude becomes sharp as shown in FIG. Reference numeral 12 represents a light transmitting portion.

[0025]

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 described below.

Embodiment-1 This embodiment is the invention of claim 1 of the present application, and particularly claim 2
The present invention is applied to the manufacture of a semiconductor device, and the width of an auxiliary line for improving the resolution of isolated holes is EB according to the present invention.
It is possible to expand to a size that is well within the performance range of the drawing machine.

In the present embodiment, the light shielding portion 20 is provided on the transparent quartz substrate 1 by the Cr light shielding portion, and the 0.35 μm square first opening portion 22 is formed by partially removing the light shielding portion 20. (See FIG. 1A), the first opening 22
1B to 1D, a second opening 22a, 22b, 22c, 22d is formed (0.5 μm from the center to the center) as shown in FIGS. SOG 21a, 21b, 21c, 21d with 90% conventional transmittance
(FIG. 1B), 60% resists 21a ', 21
b ', 21c', 21d '[SAL60 from Shipley Co., Ltd.
1. Thick film 1800Å) (FIG. 1 (c)], 40% resists 21a ″, 21b ″, 21c ″, 21d ″ (specifically in this example, SEL-N552 manufactured by Somar) (FIG. 1)
A phase shift mask having a 180 ° phase shift part of (d)] was provided.

As a result, the width of the auxiliary pattern which does not cause resolution is EB in the conventional phase shift mask having a light transmittance of 90%.
The value was 0.15 μm (W in the figure), which was close to the performance limit of the drawing machine, whereas it was 0.25 μm (W 'in the figure) and 40% in the phase shift mask with a transmittance of 60%. Then, the auxiliary pattern could be formed with sufficient accuracy by expanding to 0.35 μm (W ″ in the figure).

Embodiment 2 This embodiment is an embodiment of the invention of claim 1 of the present application, in which the phase shift technique is applied to improve the resolution in line and space pattern formation. It has been confirmed that it is effective to increase the light transmittance a little when using the phase shift technique for the line and space pattern formation. Therefore, the amplitude of the light transmission is 0.6 ( A phase shift part having a light intensity of 0.36) was used. Cr was used as the comparative light-shielding portion.

Excimer laser light (KrF25) is used as a light source.
0 nm) [Fig. 2 (a)-(b)] and i-line [Fig. 3 (a)]
~ (B)] was used, but both of them completely shielded from light
Compared with the above, in the case of the present embodiment using the phase shift mask that transmits the light whose phase is slightly inverted, the effect of canceling the light that has entered due to the diffraction appears, and the phase shift mask has a sharp shape. And the line and space pattern of 0.24 μm could be resolved.

[0031]

As described in detail above, the phase shift mask of the present invention has a specific light transmittance, so that in forming an isolated pattern, the auxiliary pattern arranged around it has a performance limit of an EB drawing machine. Therefore, it is possible to draw and create with high accuracy by providing a width that can be formed with sufficient accuracy, and to prevent the portion from being resolved. Further, instead of the conventional light shield portion or by providing a phase shift portion having a specific light transmittance in the periphery of the light shield portion, an island pattern, which could not take advantage of the conventional phase shift technology, is arranged. Also for the pattern formation, the phase shift technology is effectively used to exhibit the effect of improving the resolution.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a relationship between a light intensity and an auxiliary pattern width according to a first embodiment of the present invention.

FIG. 2 is a comparison diagram with a chrome light-shielding portion having a light intensity when an excimer laser beam is used as a light source in Example-2 of the present invention.

FIG. 3 is a comparison diagram of light intensity when a i-line is used as a light source in Example-2 of the present invention with a chrome light shielding portion.

FIG. 4 is a reticle pattern for forming isolated lines and isolated holes using a phase shift technique.

FIG. 5 is a diagram illustrating the principle of a phase shift mask.

FIG. 6 is a diagram showing a problem.

FIG. 7 is an explanatory view of the operation of the present invention.

[Explanation of symbols]

 10 ... Shading part 11 ... Phase shift part 21 ... 1st opening part 22a-22d ... 2nd opening part

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[Submission date] June 22, 1993

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Claims (3)

[Claims] 1. A phase shift mask comprising a phase shift portion formed of a material that changes the phase of light transmitted through a transparent substrate with respect to the phase of incident light, wherein the light transmittance of the phase shift portion is specific. A phase shift mask having a light transmittance. 2. A light-shielding portion is provided on a transparent substrate, a first opening is formed by partially removing the light-shielding portion, and a second opening is formed adjacent to the first opening. A phase shift mask having a phase shift portion in which the second opening portion changes a phase of transmitted light, wherein the light transmittance of the phase shift portion is a specific light transmittance. 3. A phase shift mask having a light-shielding portion patterned on a transparent substrate and a phase-shifting portion for changing the phase of transmitted light in a peripheral portion of the light-shielding portion, the light transmittance of the phase-shifting portion. Is a specific transmittance, a phase shift mask.