JP2002156739A - Phase shift mask blank and phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase shift mask and a phase shift mask blank, having superior light transmission properties over a wide wavelength region and superior controllability for phase difference. SOLUTION: The phase shift mask blank 10 is obtained by forming a shifter layer 2 of 1,069 Å film thickness, consisting of a ZrSiO film and having 1.781 for refractive index n and 0.0148 extinction coefficient k at 193 nm wavelength of the exposure light through reactive sputtering, which uses argon and oxygen on a transparent substrate 1 consisting of a synthetic quartz substrate and by depositing a light-shielding layer 3 consisting of a chromium film with 1,000 Åfilm thickness. Further, the light-shielding layer 3 is patterned to form a light-shielding pattern 3a, and the shifter layer 2 is subjected to dry etching with chlorine, using ICP(inductively coupled plasma) type dry etching apparatus, to form a phase shift pattern 2a for obtaining shift mask 100 of the invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask for exposing and transferring when forming a highly accurate fine pattern in a photolithography step in a semiconductor manufacturing process, and a phase shift blank for manufacturing the phase shift mask. About.

[0002]

2. Description of the Related Art In a conventional photomask, when a fine pattern is projected and exposed, light that has passed through a light transmitting portion of the mask is diffracted and interferes with an adjacent pattern.
Since the photoresist is exposed to light by strengthening the light intensity at the pattern boundary, there has been a problem that the pattern transferred onto the wafer is not separated and resolved. This phenomenon is more likely to occur for finer patterns closer to the exposure wavelength. In principle, it was impossible to resolve a fine pattern having a wavelength equal to or less than the wavelength of light using a conventional photomask and a conventional exposure optical system.

Therefore, a phase shift mask using a phase shift technique has been proposed, in which a phase difference is provided between exposure lights transmitting adjacent patterns to improve resolution of a fine pattern by utilizing interference between transmitted lights. Is being developed.

The phase shift method has a structure in which the phase of transmitted light is shifted by 180 degrees by providing a phase shift region in a part of a mask pattern. Since the phase is inverted when the transmitted light is diffracted and interferes with each other, the light intensity at the boundary is weakened, and as a result, the transfer pattern is separated and resolved. Since this relationship is established before and after the focal point, even if the focal point is slightly shifted, the resolution is improved as compared with the conventional method, and the focus latitude is improved. The thickness d of the shifter may be set to be expressed as d = λ / (2 (n−1)), where λ is the wavelength of light used for pattern transfer and n is the refractive index of the shifter material.

As the phase shift mask, a Levenson type, an auxiliary pattern type, a self-alignment type (edge emphasis type), and the like have been proposed in order to cope with various shapes of patterns in an actual LSI pattern. Above all, the Levenson type and the halftone type have been widely used at present.

The Levenson-type phase shift mask is a typical mask structure proposed by Levenson et al. Of IBM. When a pattern having the same shape is repeatedly arranged, a shifter is arranged in every other pattern. is there. JP-A-58-173744 and JP-B-62-2-5
No. 0811. When the pattern is formed of a light-shielding layer, a phase shift portion is provided on one side of the opening portion adjacent to the light-shielding pattern to reverse the phase, but the light-shielding layer does not have complete light-shielding properties, and Even when the phase is inverted, a similar resolution improving effect is obtained, and in this case, it is particularly effective for improving the resolution of an isolated pattern.

[0007] In the Levenson-type phase shift mask of the shifter placement type or the shifter placement type, there is a problem of controlling the etching in the depth direction of the shifter layer. That is, if the timing of stopping the etching of the shifter layer is too early, a desired phase difference cannot be obtained, and if the etching is continued even after the etching of the shifter layer is completed, the glass as the substrate is etched. The phase difference is 18
Since the angle is larger than 0 degrees, there is a problem that resolution and accurate transferability at the time of wafer transfer cannot be obtained.

For the etching of the shifter layer, it is necessary to perform anisotropic etching from the viewpoint of processing accuracy and the like, and therefore, dry etching is used. In addition, RIE (Reactive I / O) using a fluorine-based gas such as CHF ₃ , CF ₄ , SF ₆ , C ₂ F ₆ or a mixed gas thereof is used for etching.
On etching is common, but in particular, when a conventional SiO ₂ shifter layer is etched using this fluorine-based gas, it is difficult to control the phase difference by etching because the shifter layer is made of the same material as the quartz substrate. There is.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a phase shift mask and a phase shift mask which are excellent in light transmittance over a wide wavelength range and excellent in phase difference controllability. The purpose is to provide a blank.

[0010]

According to the present invention, there is provided a phase shift mask blank having a shifter layer and a light shielding layer on a transparent substrate, wherein the exposure of the shifter layer is performed. The refractive index n and the extinction coefficient k at the wavelength (193 nm) are n <2.2 and k <, respectively.
This is a phase shift mask blank characterized by being 0.015.

According to a second aspect of the present invention, the shifter layer is formed of a compound thin film made of a substance containing metal-silicon-oxygen or metal-silicon-oxygen-nitrogen. It is a phase shift mask blank described.

According to a third aspect of the present invention, there is provided the phase shift mask blank according to the first or second aspect, wherein the metal constituting the shifter layer is made of zirconium.

According to a fourth aspect of the present invention, there is provided a phase shift mask having a phase shift pattern and a light-shielding pattern on a transparent substrate.
The light-shielding layer and the shifter layer are patterned by using the phase-shift mask blank described in the paragraph to form a light-shielding pattern and a phase-shift pattern, respectively.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a structural sectional view showing one embodiment of the phase shift mask blank and the phase shift mask of the present invention, and FIG.
FIG. 3 is a sectional view showing the configuration of another embodiment of the phase shift mask of the present invention. The phase shift mask blank of the present invention is a metal substrate in which the refractive index n and the extinction coefficient k at the exposure wavelength are n <2.2 and k <0.015, respectively, as a shifter layer on a transparent substrate such as a quartz substrate. Silicon-
A compound thin film made of oxygen, for example, a ZrSiO film, or a metal-silicon film having a refractive index n and an extinction coefficient k of n <2.2 and k <0.015 at an exposure wavelength, respectively.
It is a compound thin film made of oxygen-nitrogen, for example, a ZrSiON film, and further provided with a light shielding layer made of chromium or the like.

The phase shift mask of the present invention is obtained by patterning a shifter layer and a light shielding layer formed on a transparent substrate such as a quartz substrate to form a phase shift pattern and a light shielding pattern.

FIG. 5 shows the extinction coefficient k of the shifter layer as k = 0.
It shows a change in the transmittance T with respect to the refractive index n at a wavelength of 193 nm when set to 01. As can be seen from FIG. 5, when the refractive index n is 2.2 or less, the transmittance T is 84% or more, which satisfies the right of claim 1 and confirms that the shifter layer has sufficient transparency.

FIG. 6 shows that the refractive index n of the shifter layer is n = 2.0.
The change of the transmittance T with respect to the extinction coefficient k at the wavelength of 193 nm when the value is set to is shown in FIG. As can be seen from FIG. 6, the transmittance T is 80 when the extinction coefficient k is 0.015 or less.
% Or more, satisfying the scope of claim 1 and confirming that the shifter layer has sufficient transparency.

FIG. 7 shows the extinction coefficient k of the shifter layer as k = 0.
It shows a change in the transmittance T with respect to the refractive index n at a wavelength of 157 nm when set to 01. As can be seen from FIG. 7, when the refractive index n is 2.2 or less, the transmittance T is 80% or more, which satisfies the right of claim 1 and confirms that the shifter layer has sufficient transparency.

FIG. 8 shows that the refractive index n of the shifter layer is n = 2.0.
The change of the transmittance T with respect to the extinction coefficient k at a wavelength of 157 nm when the value is set to is shown in FIG. As can be seen from FIG. 8, the transmittance T is 80 when the extinction coefficient k is 0.015 or less.
% Or more, satisfying the scope of claim 1 and confirming that the shifter layer has sufficient transparency.

[0020]

The present invention will be described in detail with reference to the following examples.
3A to 3E and FIGS. 4A to 4F are cross-sectional views of the configuration of a phase shift mask showing an example of the method for manufacturing the phase shift mask according to the present invention. <Example 1> First, Ar was formed on a transparent substrate 1 made of a synthetic quartz substrate by reactive sputtering using argon and oxygen.
Refractive index n at exposure wavelength of 193 nm for F lithography
And the extinction coefficient k are respectively n = 1.781, k = 0.0
A ZrSiO film having a thickness of 148 was formed to a thickness of 1069 ° to form a shifter layer 2. Further, a light-shielding layer 3 made of a chromium film having a thickness of 1000 ° is formed by sputtering,
A phase shift mask blank 10 was manufactured (FIG. 3A)
reference).

Next, an electron beam resist is applied on the phase shift mask blank 10 by a spinner or the like and dried to form a photosensitive layer, and a series of patterning processes such as electron beam exposure and development are performed to form a resist pattern 4. Formed (Fig. 3
(B)).

Next, using the resist pattern 4 as a mask, the light shielding layer 3 is formed by dry etching using chlorine and oxygen.
Was etched to remove the resist pattern 4, thereby forming a light-shielding pattern 3a (see FIG. 3C).

Next, the shifter layer 2 and the light shielding pattern 3a
An electron beam resist was applied thereon by a spinner or the like and dried to form a photosensitive layer, and a series of patterning processes such as electron beam exposure and development were performed to form a resist pattern 5 (see FIG. 3D).

Next, using the resist pattern 5 as a mask, the shifter layer 2 is etched by dry etching with chlorine using an ICP (dielectrically coupled plasma) type dry etching apparatus, the resist pattern 5 is peeled off, and the phase shift is performed. The pattern 2a was formed, and the phase shift mask 100 of the present invention was obtained (see FIG. 3E).

193 nm of the phase shift mask 100
Was measured, and a good result of 180.5 degrees was obtained.

<Example 2> First, a normal chrome mask blank 20 in which a light shielding layer 12 made of a chromium film was formed on a transparent substrate 11 made of a quartz substrate or the like was manufactured.
(A)).

Next, an electron beam resist is applied on the chromium mask blank 20 by a spinner or the like and dried to form a photosensitive layer, and a series of patterning processes such as electron beam exposure and development are performed to form a resist pattern 13. (Fig. 4
(B)).

Next, the light-shielding layer 12 is etched by dry etching using chlorine and oxygen using the resist pattern 13 as a mask, and the resist pattern 13 is peeled off to form a light-shielding pattern 12a (FIG. 4 (c)). )reference).

Next, the exposure wavelength of ArF lithography is set to 1 by reactive sputtering using argon, oxygen and nitrogen.
The refractive index n and the extinction coefficient k at 93 nm are n
A ZrSiON film in which = 1.909 and k = 0.0096 was formed to a thickness of 919 ° to form a shifter layer 14 (see FIG. 4D).

Next, an electron beam resist is applied on the shifter layer 14 by a spinner or the like and dried to form a photosensitive layer.
A series of patterning processes such as electron beam exposure and development were performed to form a resist pattern 15 (see FIG. 4E).

Next, the shifter layer 14 is etched by dry etching with chlorine using an ICP (dielectrically coupled plasma) type dry etching apparatus, the resist pattern 15 is peeled off, and the phase shift pattern 14 is removed.
was formed to obtain the phase shift mask 200 of the present invention (see FIG. 4F).

193 nm of the phase shift mask 100
Was measured, and a good result of 180.5 degrees was obtained.

[0033]

The shifter layer of the phase shift mask blank of the present invention has a refractive index n and an extinction coefficient k at an exposure wavelength of 193 nm of n <2.2 and k <0.015, respectively, and is made of ZrSiO or ZrSiON. Since it is formed of a compound thin film, transparency comparable to that of a conventional shifter layer can be obtained, and the selectivity to a quartz substrate in dry etching is significantly improved. further,
The phase shift mask of the present invention having high phase difference controllability and small in-plane variation in the phase difference can be obtained.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a configuration of an embodiment of a phase shift mask blank of the present invention. FIG. 2B is a sectional view showing the configuration of an embodiment of the phase shift mask of the present invention.

FIG. 2 is a structural sectional view showing another embodiment of the phase shift mask of the present invention.

FIGS. 3A to 3E are cross-sectional views showing an embodiment of a method for manufacturing a phase shift mask according to the present invention.

FIGS. 4A to 4F are sectional views showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 5 is an explanatory diagram showing a change in the transmittance T with respect to the refractive index n at a wavelength of 193 nm when the extinction coefficient k of the shifter layer is set to k = 0.01.

FIG. 6 shows a transmittance T with respect to an extinction coefficient k at a wavelength of 193 nm when the refractive index n of the shifter layer is set to n = 2.0.
FIG. 4 is an explanatory diagram showing a change in the state.

FIG. 7 is an explanatory diagram showing a change in the transmittance T with respect to the refractive index n at a wavelength of 157 nm when the extinction coefficient k of the shifter layer is set to k = 0.01.

FIG. 8 shows the transmittance T with respect to the extinction coefficient k at a wavelength of 157 nm when the refractive index n of the shifter layer is set to n = 2.0.
FIG. 4 is an explanatory diagram showing a change in the state.

[Explanation of symbols]

 1, 11 transparent substrate 2, 14 shifter layer 2a, 14a phase shift pattern 3, 12 light shielding layer 3a, 12a light shielding pattern 4, 5, 13, 15 resist pattern 10 Chrome mask blank 20: Phase shift mask blank of the present invention 100, 200 ... Phase shift mask of the present invention

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichiro Kanayama 1-5-1, Taito, Taito-ku, Tokyo Letterpress Printing Co., Ltd. (72) Inventor Tsukasa Yamazaki 1-15-1 Taito, Taito-ku, Tokyo Letterpress F-term (reference) in Printing Co., Ltd. 2H095 BB03

Claims (4)

[Claims] 1. A phase shift mask blank having a shifter layer and a light-shielding layer on a transparent substrate, wherein a refractive index n and an extinction coefficient k of the shifter layer at an exposure wavelength (193 nm) are respectively n <2.2. A phase shift mask blank, wherein k <0.015. 2. The phase shift mask according to claim 1, wherein said shifter layer is formed of a compound thin film made of a material containing metal-silicon-oxygen or metal-silicon-oxygen-nitrogen. blank. 3. The phase shift mask blank according to claim 1, wherein the metal constituting the shifter layer is made of zirconium. 4. A phase shift mask having a phase shift pattern and a light-shielding pattern on a transparent substrate, wherein
A phase shift mask, wherein the light shielding layer and the shifter layer are patterned by using the phase shift mask blank according to any one of claims 3 to 3, thereby forming a light shielding pattern and a phase shift pattern, respectively.