JP3196903B2 - Phase shift mask and phase shift mask blank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in a projection exposure apparatus, and more particularly to a phase shift mask capable of transferring a high-resolution pattern by giving a phase difference to exposure light passing through a pattern. The present invention relates to a phase shift mask blank as a material.

[0002]

2. Description of the Related Art A phase shift mask is used as one of photomasks, which is a mask for transferring a fine pattern, when manufacturing an LSI.

[0003] This phase shift mask provides a predetermined phase difference to the exposure light passing through the fine pattern, thereby expanding the exposure limit due to the interference of the exposure light caused by the miniaturization of the pattern and enabling high-resolution transfer. Or a photomask that enables fine pattern exposure by interference by positively utilizing an interference phenomenon by controlling a phase difference of exposure light.

The phase shift mask is provided with a phase shift portion for giving a phase difference to exposure light passing through the fine pattern. The phase shift portion has a transmittance of a predetermined value or more to exposure light when the thickness is set to give a predetermined phase shift amount, and the thickness is set to give a predetermined phase shift amount. It must be capable of being accurately formed to a thickness. That is, for example, in the case where i-line (wavelength: 365 nm) is used as exposure light at the time of high resolution transfer, the material constituting the phase shift portion is at least 90% or more of the i-line as much as possible. It must have high transmittance. Further, when manufacturing a phase shift mask, an etching step is indispensable to form a fine pattern, but the phase shift portion or the substrate or the like formed to a predetermined thickness is excessively etched by this etching step. In addition, the amount of phase shift by the phase shift unit must not be such that the predetermined value cannot be maintained.

[0005] As a material constituting the phase shift portion,
Conventionally, SiO ₂ , MgF ₂ or the like has been used. Si
O ₂ has a sufficient transmittance with respect to exposure light, but is made of the same material as a material of a light-transmitting substrate that is usually used, so that it is difficult to distinguish both at the time of etching. Therefore, there is a possibility that the substrate may be excessively etched during the etching of the phase shift portion, so that a predetermined amount of phase shift may not be maintained. On the other hand, MgF ₂ has attracted attention as a preferable material because it has a different composition from the substrate material, so that it can be easily etched separately from the substrate material and has a higher transmittance than SiO ₂ . In addition, as a material of the phase shift portion, for example, S
Although i ₃ N ₄ , SiC and the like are conceivable, they are unsuitable as a material of the phase shift portion for the i-line because of their low transmittance to the i-line.

[0006] A phase shift mask blank is a material which is formed at a stage during the manufacture of the phase shift mask and on which a fine pattern or the like is not formed yet. This phase shift mask blank is formed by forming at least a phase shift layer serving as a phase shift portion on a translucent substrate, and is often treated as an independent product as a phase shift mask blank.

[0007]

By the way, when manufacturing a phase shift mask, there is a step of removing and cleaning a resist film used for etching. In the step of removing and cleaning, HF, H ₂ SO ₄ , An acid such as HNO ₃ is used.
Therefore, the material constituting the phase shift portion needs to have sufficient resistance to these acids.

However, MgF ₂ does not always have sufficient resistance to these stripping and cleaning acids, and therefore, in some cases, a part of the film is dissolved in the acid during resist stripping or cleaning, and the film may be removed. There is a problem that the thickness is reduced, and a predetermined amount of phase shift may not be secured.

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned background, and has a phase shift mask having a phase shift portion having high transmittance and excellent acid resistance, and a phase shift mask as a material of the phase shift mask. It is intended to provide a shift mask blank.

[0010]

In order to solve the above-mentioned problems, a phase shift mask according to the present invention provides (1) a phase difference to exposure light passing through a fine pattern formed on a light transmitting substrate. In a phase shift mask having a phase shift portion, the phase shift portion is made of aluminum fluoride.

Further, the phase shift mask blank according to the present invention is: (2) a phase shift mask blank as a material of the phase shift mask formed in the course of manufacturing the phase shift mask of Configuration 1, In a phase shift mask blank in which at least a phase shift layer serving as a phase shift portion is formed on an optical substrate, the phase shift layer is made of aluminum fluoride.

[0012]

According to the above configuration 1, since the phase shift portion is made of aluminum fluoride, the thickness of the phase shift portion that gives a predetermined amount of phase shift accurately without attenuating the exposure light is maintained. This facilitates the formation of a mask and makes it possible to easily obtain a phase shift mask for high-resolution transfer.

That is, according to the study of the present inventor, for example, when the exposure light is i-line and aluminum fluoride is formed to a thickness to obtain the necessary amount of phase shift, the transmittance is higher than that of MgF _2. It has been found that they have excellent resistance to resist stripping and cleaning acids. Therefore, when a phase shift mask in which the phase shift portion was made of aluminum fluoride was manufactured, the thickness did not decrease even in the resist stripping and cleaning steps, and the thickness that accurately gave a predetermined phase shift amount was maintained. Thus, a phase shift mask having the above-described phase shift portion can be easily obtained.

According to the second aspect, the phase shift mask blank as the phase shift mask material of the first aspect can be obtained.

[0015]

EXAMPLE 1 FIG. 1 is a sectional view of a phase shift mask according to a first embodiment of the present invention, FIG. 2 is a sectional view of a phase shift mask blank in Example 1 of the present invention.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to these drawings. Hereinafter, first, the configuration of the phase shift mask blank will be described with reference to FIG.
Next, the configuration of the phase shift mask will be described with reference to FIG. 1, and thereafter, the manufacturing method thereof will be described.

(Configuration of Phase Shift Mask Blank of Example 1) In FIG. 2, the phase shift mask blank 1 has a light-shielding film pattern 3 made of chromium formed on a transparent substrate 2 made of quartz glass. A phase shift layer 4 made of aluminum fluoride (AlF ₃ ) is formed on a light shielding film pattern 3.

(Structure of Phase Shift Mask of Example 1) In FIG. 1, a phase shift mask 5 is manufactured using the phase shift mask blank 1 of FIG. 2 as a material, and is made of a light-transmitting quartz glass. A light-shielding film pattern 3 made of chromium is formed on the transparent substrate 2, and among the light-transmitting portions 6 formed on both sides of the light-shielding film pattern 3, one of the light-transmitting portions 6 a is a gap, and the other is a gap. Side light-transmitting portion 6b
Has a phase shift portion 7 made of aluminum fluoride.

With this configuration, the exposure light L1 passing through the light transmitting portion 6a where the phase shift portion 7 is not formed and the exposure light L2 passing through the light transmitting portion 6b where the phase shift portion 7 is formed.
Is shifted by, for example, λ / 2 (= 180 °), so that the exposure light that has reached the region of the light-shielding film pattern 3 due to the diffraction action interferes and is canceled out. In this case, λ /
The thickness required to produce a phase difference of 2 is as follows (1)
It can be obtained by an equation.

D = λ / {2 (n-1)} (1) In the equation (1), d is the thickness of the phase shift unit 7, n is the refractive index of the phase shift unit 7, and λ is the exposure. It is the wavelength of light.

According to this embodiment, since the phase shift portion 7 is made of aluminum fluoride, its transmittance is high. According to the actual measurement, the transmittance when the phase shift amount of λ / 2 is obtained by the i-line is 9% in the phase shift unit using MgF _2.
In contrast to 1-92%, it was 95% or more in the phase shift portion using aluminum fluoride.

The phase shift section 7 has sufficient resistance to a stripping solution or a cleaning solution used for stripping the resist pattern. According to the experiment, the thickness of the conventional phase shift portion using MgF ₂ was reduced in the resist stripping step, but the reduction in the thickness was completely reduced in the phase shift portion of the present embodiment using aluminum fluoride. I was not able to admit. Also,
In the phase shift mask 5 of this embodiment, since the material of the phase shift portion 7 and the material of the light transmissive substrate 2 are different, the light transmissive substrate 2 is simultaneously formed during the etching for forming the phase shift portion 7. The risk of etching can be easily removed.

(Method of Manufacturing Phase Shift Mask Blank of Example 1) The phase shift mask blank 1 was manufactured by the following procedure.

First, chromium was formed to a thickness of 1000 angstroms by a sputtering method on a translucent substrate 2 made of quartz glass whose front and back surfaces (main surfaces) were mirror-polished to form a light-shielding film made of chromium.

Next, an electron beam resist (manufactured by Toray Industries, Inc .:
EBR-9HS31) is spin-coated to a thickness of 5
A resist film was formed by applying the resist film to a thickness of 2,000 angstroms, and the resist film was selectively irradiated with light and developed to form a resist pattern.

Next, ceric ammonium nitrate 16
5 g, 42 ml of perchloric acid (70%) and 10 ml of pure water
After forming the light-shielding film pattern 3 by etching the light-shielding film along the resist pattern using an etching solution made up to 00 ml, the resist pattern is peeled off using a predetermined stripping solution (for example, concentrated sulfuric acid) and washed. did.

Next, a phase shift layer 4 was formed on the light shielding film pattern 3 by depositing aluminum fluoride to a thickness of 5200 angstroms by a vacuum evaporation method.

(Method of Manufacturing Phase Shift Mask) The phase shift mask 5 was manufactured according to the following procedure.

First, the phase shift mask blank 1 manufactured by the method for manufacturing the phase shift mask blank described above.
An electron beam resist (ZEP-520, manufactured by Zeon Corporation) is applied on the phase shift layer 4 of FIG. 2 by spin coating so as to have a film thickness of 8000 angstroms, and baked at 180 ° C. for 30 minutes. Forming a resist film,
The resist film was selectively irradiated with an electron beam, developed, and baked at 130 ° C. for 30 minutes to form a resist pattern.

Next, CF ₄ and O are formed along the resist pattern.
_The phase shift portion 7 was formed by plasma etching using the mixed gas of No. ₂ .

Thereafter, the resist pattern was stripped off using a predetermined stripping solution (for example, concentrated sulfuric acid) and washed to obtain a phase shift mask 5.

Embodiment 2 Next, Embodiment 2 of the present invention will be described.

FIG. 3 is a sectional view of a phase shift mask blank according to the second embodiment of the present invention, and FIG. 4 is a sectional view of a phase shift mask according to the second embodiment of the present invention. Below, first,
The structure of the phase shift mask blank will be described with reference to FIG. 3, and then the structure of the phase shift mask will be described with reference to FIG.

(Structure of Phase Shift Mask Blank of Example 2) In FIG. 3, a phase shift mask blank 10 has a phase shift layer 4 made of aluminum fluoride formed on a transparent substrate 2 made of quartz glass. The light-shielding film 11 made of chromium is formed on the phase shift layer 4.

(Configuration of the Phase Shift Mask of the Second Embodiment) In FIG. 4, the phase shift mask 12 is manufactured using the phase shift mask blank 10 of FIG. 3 as a material, and is made of a light-transmitting quartz glass. Phase shift layer 7 made of aluminum fluoride is formed on conductive substrate 2, and has a width wider than that of phase shift layer 7 so that peripheral portion 13 of the surface of phase shift layer 7 is exposed on phase shift layer 7. The light shielding film pattern 3 of narrow chrome is formed.

With this configuration, the phase of the exposure light L1 passing through the light transmitting portion 6 where the phase is shifted and on which no layer is formed, and the phase of the exposure light L2 passing through the exposed peripheral portion 13 of the phase shift layer are, for example, By shifting by ２ (= 180 °), the exposure light that has reached the region of the phase shift layer 7 and the light-shielding film pattern 3 due to the diffraction action interferes with each other and cancels out. In this case, the thickness necessary for causing the phase shift layer 7 to generate a phase difference of λ / 2 can be obtained by the equation (1), as in the first embodiment.

In this embodiment, the same advantages as in the first embodiment can be obtained.

(Method of Manufacturing Phase Shift Mask Blank of Example 2) The phase shift mask blank 10 was manufactured by the following procedure.

First, aluminum fluoride was deposited to a thickness of 5200 Å on a translucent substrate 2 made of quartz glass whose front and back surfaces (main surfaces) were mirror-polished by a vacuum deposition method. Was formed.

Next, chromium was deposited to a thickness of 1000 angstroms by sputtering, and a light-shielding film 11 made of chromium was formed to obtain a phase shift mask blank 10.

(Method of Manufacturing Phase Shift Mask of Example 2) The phase shift mask 12 was manufactured by the following procedure.

First, the phase shift mask blank 1 manufactured by the method for manufacturing the phase shift mask blank described above.
An electron beam resist (EBR-9HS31 manufactured by Toray Industries, Inc.) is applied on the light-shielding film 11 of FIG. 0 (FIG. 2) by a spin coating method so as to have a film thickness of 5000 angstroms to form a resist film. The film was selectively irradiated with light and developed to form a resist pattern.

Next, ceric ammonium nitrate 16
5 g, 42 ml of perchloric acid (70%) and 10 ml of pure water
After the light-shielding film pattern 3 is formed by etching the light-shielding film along with the resist pattern using an etching solution of 00 ml, the resist pattern is peeled off using a predetermined stripping solution (for example, concentrated sulfuric acid) and washed did.

Next, an electron beam resist (ZEP manufactured by Zeon Corporation: ZEP) is formed on the phase shift film 4 and the light shielding film pattern 3.
-520) is applied by spin coating to a thickness of 8000 angstroms, baked at 180 ° C. for 30 minutes to form a resist film, and the resist film is selectively irradiated with an electron beam and developed. The resist pattern was formed by baking at 130 ° C. for 30 minutes.

Next, the phase shift layer 7 was formed by plasma etching using a mixed gas of CF ₄ and O ₂ along the resist pattern.

Thereafter, the resist pattern was stripped off using a predetermined stripping solution (for example, concentrated sulfuric acid) and washed to obtain a phase shift mask 12.

The present invention is not limited to the above embodiment.

As the translucent substrate, other than quartz glass, soda lime glass, aluminoborosilicate glass, borosilicate glass, sapphire, or the like may be used.

The light-shielding film pattern constituting the fine pattern may be a mixture of chromium metal oxides, silicides, carbides, and fluorides in addition to chromium, or may be a transition metal or a transition metal. A metal silicide or the like may be used.

Further, the phase shift mask of the present invention includes, for example, a phase shift mask having a structure in which a phase shift layer functions as a light shielding film pattern without using a light shielding film pattern. This phase shift mask utilizes the fact that a shadow as if it has a light-shielding film pattern is formed by the light diffraction phenomenon at the upper edge of the phase shift layer. Further, the phase shift mask may have any other structure.

In the present invention, in addition to the films provided in the above-described embodiments, a conductive film or the like for preventing charge-up when exposing an electron beam may be provided.

[0052]

As described above in detail, the phase shift mask and the phase shift mask blank according to the present invention impart a phase difference to the exposure light passing through the fine pattern formed on the translucent substrate in the phase shift mask. When the phase shift portion and the phase shift mask are formed, the phase shift layer of the phase shift mask blank which becomes the phase shift portion is made of aluminum fluoride, whereby the transmittance is high, and the acid resistance is excellent. Therefore, it is possible to obtain a phase shift mask provided with a phase shift portion that does not cause a decrease in film thickness during manufacturing, and a phase shift mask blank as a material of the phase shift mask.

[Brief description of the drawings]

FIG. 1 is a sectional view of a phase shift mask according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the phase shift mask blank according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a phase shift mask blank according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a phase shift mask according to a second embodiment of the present invention.

[Explanation of symbols]

1, 10: phase shift mask blank, 2: light transmissive substrate, 3: light shielding film pattern, 4: phase shift layer, 5, 12
... A phase shift mask, 6 a translucent section, 7 a phase shift section.

Claims (2)

(57) [Claims] 1. A phase shift mask having a phase shift portion for giving a phase difference to exposure light passing through a fine pattern formed on a light transmitting substrate, wherein the phase shift portion is made of aluminum fluoride. A phase shift mask. 2. A phase shift mask blank as a material of a phase shift mask formed in the course of manufacturing the phase shift mask according to claim 1, wherein the light transmitting substrate has at least a phase shift portion. A phase shift mask blank having a phase shift layer formed thereon, wherein the phase shift layer is made of aluminum fluoride.