JP2003255515A - Photomask blank and method for reducing generation of particle in photomask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask blank reduced in the amount of the particles to be generated and a method for reducing the generation of the particles in the photomask blank. <P>SOLUTION: The photomask blank comprises forming a light shielding film or phase shift film on a substrate transparent to exposure light, in which the maximum film thickness of the film deposited on the flanks of the photomask blank is ≤1/20 the average film thickness of the light shielding film or the phase shift film. Accordingly, the film thickness on the flanks of the photomask blank is thin, making it possible to obtain the high-quality photomask blank reduced in film peeling by conveyance, etc., and as a result, decreasing pattern defects during mask fabrication. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor integrated circuit,
The present invention relates to a photomask blank used for microfabrication such as a CCD (charge coupled device), an LCD (liquid crystal display) color filter, and a magnetic head.

[0002]

2. Description of the Related Art Photomasks used in a wide range of applications including the manufacture of semiconductor integrated circuits such as ICs and LSIs are basically composed of chromium on a transparent substrate. The light-shielding film containing as a main component is formed in a predetermined pattern. These light shielding films may have an antireflection film such as CrO in order to reduce the reflectance. In recent years, pattern miniaturization has rapidly progressed in response to market demands such as higher integration of semiconductor integrated circuits, which has been addressed by shortening the exposure wavelength.

However, while shortening the exposure wavelength improves the resolution, it causes a decrease in the depth of focus, which lowers the process stability and adversely affects the yield of products.

As one of the pattern transfer methods effective for such a problem, there is a phase shift method, and a phase shift mask is used as a mask for transferring a fine pattern.

This phase shift mask (halftone type phase shift mask) is formed by patterning a phase shifter portion 2a on a substrate 1 as shown in FIGS. 3A and 3B, for example. , The light that passes through both the substrate exposed portion (first light transmitting portion) 1a where the phase shift film is not present and the phase shifter portion (second light transmitting portion) 2a forming the pattern portion on the mask As shown in FIG. 3B, when the phase difference between the two is 180 °, the light intensity at the interfering portion becomes zero due to the interference of the light at the pattern boundary portion, and the contrast of the transferred image can be improved. It is a thing. Also, by using the phase shift method, it is possible to increase the depth of focus when obtaining the required resolution, compared to the case of using a normal mask having a general light shielding pattern made of a chrome film, It is possible to improve the resolution and the margin of the exposure process.

The above-mentioned phase shift mask can be roughly divided into a complete transmission type phase shift mask and a halftone type phase shift mask in practical use, depending on the light transmission characteristics of the phase shifter portion. The complete transmission type phase shift mask is a mask in which the light transmittance of the phase shifter portion is equivalent to that of the substrate and which is transparent to the exposure wavelength. On the other hand, in the halftone type phase shift mask, the light transmittance of the phase shifter portion is about several percent to several tens percent of the exposed portion of the substrate.

FIG. 1 shows the basic structure of a halftone type phase shift mask blank, and FIG. 2 shows the basic structure of a halftone type phase shift mask. The halftone type phase shift mask blank of FIG. 1 has a halftone phase shift film 2 formed on a substrate 1 which is transparent to exposure light.
In the halftone phase shift mask shown in FIG. 2, the phase shift film 2 is patterned to form a pattern portion on the mask, and a halftone phase shifter portion 2a and a substrate where the phase shift film does not exist are exposed. The part 1a is formed.

Here, the light transmitted through the phase shifter portion 2a is phase-shifted with respect to the light transmitted through the exposed substrate portion 1a (see FIGS. 3A and 3B). The transmittance of the phase shifter portion 2a is set so that the exposure light transmitted through the phase shifter portion 2a has a light intensity that does not expose the resist on the transfer substrate. Therefore, the phase shifter portion 2a has a light blocking function of substantially blocking the exposure light.

As the halftone type phase shift mask, a single layer type halftone type phase shift mask having a simple structure has been proposed. As such a single layer type halftone type phase shift mask, molybdenum silicide is used. A device having a phase shift film made of oxide (MoSiO) or molybdenum silicide oxynitride (MoSiON) has been proposed (JP-A-7-140635).

In any photomask blank having a light-shielding film or a phase shift film, particles (foreign matter on the film surface) may cause pattern defects during pattern formation, and therefore it is required to reduce it as much as possible. Usually, a vapor deposition method, a sputtering method, or the like is often used to form a light shielding film or a phase shift film. For example, in the sputtering method, the sputtering particles irradiated on the substrate are not only the surface on which the film is formed but also the side surface. If the film adheres to the side surface, the film on the side surface is easily peeled off, and in particular, the side surface is often supported during the transportation of the photomask blank. There is a problem of becoming.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a photomask blank in which the amount of particles generated is reduced and a method of reducing the generation of particles in the photomask blank.

[0012]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to solve the above problems, the present inventor has found that a light-shielding film or a phase shift film is formed on a substrate transparent to exposure light. In the formed photomask blank, the maximum film thickness of the film attached to the side surface of the photomask blank is set to 1/20 or less of the average film thickness of the light-shielding film or the phase shift film, so that almost no particles are generated during transportation. It was found that the present invention has been completed.

That is, the present invention provides the following photomask blank and a method for reducing generation of particles in the photomask blank. Claim 1: A photomask blank in which a light shielding film or a phase shift film is formed on a substrate transparent to exposure light,
A photomask blank, wherein the maximum film thickness of the film attached to the side surface of the photomask blank is 1/20 or less of the average film thickness of the light shielding film or the phase shift film. Claim 2: A photomask blank in which a light shielding film or a phase shift film is formed on a substrate transparent to exposure light,
The film thickness of the film attached to the central portion in the thickness direction of the side surface of the photomask blank is 1 of the average film thickness of the light shielding film or the phase shift film.
/ 20 or less, The photomask blank characterized by the above-mentioned. Claim 3: A photomask blank in which a light-shielding film or a phase shift film is formed on a substrate transparent to exposure light,
A photomask blank, wherein the film thickness of the film attached to the central portion of the side surface of the photomask blank in the thickness direction is 10 nm or less. Claim 4: A method for reducing the generation of particles on a photomask blank formed by forming a light shielding film or a phase shift film on the surface of a substrate transparent to exposure light,
Generation of particles in a photomask blank characterized by selecting and using a photomask blank in which the maximum film thickness of the film attached to the side surface of the substrate is 1/20 or less of the average film thickness of the light shielding film or the phase shift film. Reduction method. Claim 5: A method for reducing the generation of particles on a photomask blank formed by forming a light shielding film or a phase shift film on the surface of a substrate transparent to exposure light,
The film thickness of the film attached to the central portion in the thickness direction of the side surface of the substrate is
A method of reducing the generation of particles in a photomask blank, characterized in that a photomask blank having a thickness of 1/20 or less of the average thickness of the light shielding film or the phase shift film is selected and used. Claim 6: A method for reducing the generation of particles on a photomask blank formed by forming a light shielding film or a phase shift film on the surface of a substrate transparent to exposure light,
The film thickness of the film attached to the central portion in the thickness direction of the side surface of the substrate is
A method for reducing the generation of particles in a photomask blank, which comprises selecting and using a photomask blank having a size of 10 nm or less.

According to the present invention, the dust generation amount (particle amount) can be reduced by reducing the film thickness on the side surface of the photomask blank.

The present invention will be described in more detail below. The photomask blank of the present invention is one in which a light-shielding film or a phase shift film is formed on a substrate transparent to exposure light, a substrate containing synthetic quartz glass or silicon dioxide as a main component as a substrate, and fluorine Containing C, or using calcium fluoride as the main component,
r, CrO, CrN, CrON, CrC, CrCO, C
One or more layers of light-shielding film such as rCON, CrCN, MoSi,
Or MoSiO, MoSiN, MoSiON, ZrSi
ON, ZrSiO, ZrSiN, TaSiO, TaSi
At least one layer of a phase shift film such as a compound containing silicon and a metal other than silicon such as N and TaSiON or a compound containing only silicon as a metal such as SiN, SiON, and SiO, or a light-shielding film. Those in which both of the phase shift films are formed are included.

As shown in FIG. 4, the photomask blank of the present invention has a light-shielding film or a phase shift film 12 formed on the surface of a substrate 10. In this case, as shown in FIG. The surface average film thickness of the light shielding film or the phase shift film 12 formed on the surface of the substrate (the surface average film thickness of the total film thickness in the case where both the light shielding film and the phase shift film are formed) The maximum film thickness of the light shielding film or the phase shift film 12a formed on the side surface 10a of
It is set to 0 or less. If this exceeds 1/20,
The film adhering to the side surface is peeled off, which adheres to the substrate and causes particles.

In this case, it is particularly preferable that the film thickness at the central portion C in the thickness direction of the side surface 10a of the substrate 10 (indicated by a point C in FIG. 5) is 1/20 or less of the average film thickness, The film thickness at the central portion C in the thickness direction is preferably 10 nm or less.

The surface average film thickness is not particularly limited, but is usually 20 to 300 nm, especially 30 to 30 nm.
The thickness is preferably 200 nm, and the maximum film thickness is 10
It is particularly preferable that the thickness is not more than nm.

Known methods can be applied to the sputtering conditions (sputtering method, sputtering gas, film forming temperature, etc.).

[0020]

Since the photomask blank of the present invention has a thin film on the side surface of the photomask blank, it is possible to obtain a high-quality photomask blank with less peeling of the film due to transportation or the like. It is possible to reduce pattern defects at the time.

[0021]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Embodiment 1] A 6-inch square quartz substrate was used with a MoSi target and A was used as a sputtering gas.
Oxidation and nitridation of molybdenum silicide was performed by flowing r, O ₂ and N ₂ in a molar ratio of 1: 2: 2, forming a film by DC sputtering at a gas pressure of 0.3 Pa during discharge, 200 W, and a film formation temperature of 120 ° C. (MoSiON) phase shift film was formed. The average thickness of the phase shift film was 150 nm, and the maximum thickness of the film attached to the side surface was 7 nm. After this was placed in a case holding the end face and transported, the number of particles of 0.2 μm or more was examined and the result was one increase.

[Embodiment 2] As in Embodiment 1, MoSiO
An N phase shift film was formed. The average film thickness of the phase shift film was 150 nm, and the maximum film thickness of the film attached to the center of the side surface was 6 nm. After putting this in a case and transporting it,
As a result of examining the number of particles of 0.2 μm or more, there was no increase.

[Comparative Example 1] A 6-inch square quartz substrate was used, and a MoSi target was used.
A phase shift film of MoSiON was formed by a DC sputtering method at a gas pressure of 0.3 Pa during discharge, 200 W, and a film formation temperature of 120 ° C. by flowing r, O ₂ and N ₂ at a molar ratio of 1: 2: 2. .
The average thickness of the phase shift film was 150 nm, and the maximum thickness of the film attached to the side surface was 16 nm. After this was put in a case and transported, the number of particles of 0.2 μm or more was examined, and as a result, the number was increased by 42.

[Brief description of drawings]

FIG. 1 is a sectional view showing a general phase shift mask blank.

FIG. 2 is a cross-sectional view showing a general phase shift mask.

3A and 3B are diagrams illustrating the principle of a halftone type phase shift mask, and FIG. 3B is a partially enlarged view of an X portion of FIG.

FIG. 4 is a perspective view showing an example of a photomask blank of the present invention.

FIG. 5 is an enlarged partial sectional view showing another example of the photomask blank of the present invention.

[Explanation of symbols]

1 substrate 2 Phase shift film 1a Board exposed part 2a Phase shifter section 10 substrates 10a side 12 Light-shielding film or phase shift film 12a Light shielding film or phase shift film formed on the side surface C Side thickness center

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jinomi Inazuki             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house (72) Inventor Satoshi Tsukamoto             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house (72) Inventor Tamotsu Maruyama             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house (72) Inventor Tsutomu Shinagawa             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house (72) Inventor Satoshi Okazaki             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house F-term (reference) 2H095 BC26

Claims (6)

[Claims] 1. In a photomask blank having a light-shielding film or a phase shift film formed on a substrate transparent to exposure light, the maximum film thickness of the film attached to the side surface of the photomask blank is the light-shielding film or the phase shift film. 1/20 of the average film thickness
A photomask blank characterized in that: 2. In a photomask blank having a light-shielding film or a phase shift film formed on a substrate transparent to exposure light, the film thickness of the film attached to the central portion in the thickness direction of the side surface of the photomask blank is the light-shielding film. A photomask blank, which is 1/20 or less of the average film thickness of the film or the phase shift film. 3. A photomask blank in which a light-shielding film or a phase shift film is formed on a substrate transparent to exposure light, and the film thickness of the film attached to the central portion in the thickness direction of the side surface of the photomask blank is 10 nm. A photomask blank characterized in that: 4. A method for reducing the generation of particles on a photomask blank formed by forming a light-shielding film or a phase shift film on the surface of a substrate transparent to exposure light, the film being attached to the side surface of the substrate. A method of reducing particle generation in a photomask blank, wherein a photomask blank having a maximum film thickness of 1/20 or less of the average film thickness of the light-shielding film or the phase shift film is selected and used. 5. A method for reducing the generation of particles on a photomask blank formed by forming a light-shielding film or a phase shift film on the surface of a substrate transparent to exposure light, the method comprising: The film thickness of the film attached to the central portion is 1/20 of the average film thickness of the light shielding film or the phase shift film.
A method for reducing the generation of particles in a photomask blank, comprising selecting and using the following photomask blanks. 6. A method for reducing the generation of particles on a photomask blank formed by forming a light-shielding film or a phase shift film on the surface of a substrate transparent to exposure light, the method comprising: A method for reducing the generation of particles in a photomask blank, characterized in that a photomask blank having a film thickness of 10 nm or less attached to the central portion is selected and used.