JP2003043668A - Sputtering target, phase shift mask blank using the sputtering target and method of manufacturing phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target which is used for forming photosemipermeable sections of a phase shift mask and contains at least metal and borosilicate glass. SOLUTION: In manufacturing a phase shift film by a sputtering method, the sputtering target containing the borosilicate glass is used as the sputtering target, by which the phase shift mask blank and phase shift mask having the photosemitransmissive film (phase shift film) surpassed in chemical resistance are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for forming a phase shift mask blank used in a manufacturing process of semiconductor integrated circuits, high density integrated circuits, etc., and a light semitransmissive film constituting the phase shift mask by sputtering. Sputtering target, and a phase shift mask blank for forming a light semi-transmissive film using this target,
The present invention relates to a method for manufacturing a phase shift mask.

[0002]

2. Description of the Related Art Photolithography using a photomask for fine processing of high density semiconductor integrated circuits such as LSI and VLSI, color filters for CCD (charge coupled device), LCD (liquid crystal display device) and magnetic head. Technology has been used and photomask blanks have been used to make this photomask.

As this photomask blank, one having a light-shielding film made of chromium provided on a transparent substrate such as quartz glass is usually used.

However, phase shift lithography has been attracting attention as a technique to meet the recent demand for further miniaturization of patterns. Phase shift lithography is one of the techniques to increase the resolution of photolithography, and by providing a phase difference between the exposure light that passes through a photomask, it is possible to dramatically improve the resolution by utilizing the interference of transmitted light. It was done.

Known types of phase shift masks include Levenson type, auxiliary pattern type, and self-alignment type, which have been actively developed in recent years. One of the phase shift masks is so-called halftone. There is a phase shift mask called “type phase shift mask”, and it is the phase shift mask with the highest possibility of practical use at present.

This phase shift mask (halftone type phase shift mask) is formed by patterning a phase shift film 2 on a substrate 1 as shown in FIGS. 4A and 4B, for example. , The substrate exposed portion (first light transmitting portion) 1a where the phase shift film does not exist and the phase shifter portion (second light transmitting portion) 2a forming the pattern portion on the mask By setting the phase difference of the incoming light to 180 degrees as shown in FIG. 4B, 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 is improved. Is something that can be done. In addition, 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 exposure pattern made of a chromium 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 phase shift mask blank shown in FIG. 1 has a halftone phase shift film 2 formed on a substrate 1 which is transparent to exposure light. In the halftone type phase shift mask shown in FIG. 2, the shift film 2 is patterned to form a pattern portion on the mask, and a halftone type phase shifter portion 2a and a substrate exposed portion where the phase shift film does not exist. 1a
Is formed.

Here, the exposure light transmitted through the phase shifter portion 2a is phase-shifted with respect to the exposure light transmitted through the substrate exposure portion 1a (see FIGS. 4A and 4B). In addition, the exposure light transmitted through the phase shifter portion 2a has such a light intensity that it is not exposed to the resist on the transfer substrate.
The transmittance of the phase shifter portion 2a is set. Therefore, the phase shifter portion 2a has a 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).

As a method of producing such a phase shift mask, a method of forming a pattern on a phase shift mask blank by a lithography method is used. In this lithography method, a resist is applied on a phase shift mask blank, and a desired portion of the resist is exposed to an electron beam or ultraviolet rays and then developed to expose the surface of the phase shift film, and then the patterned resist film is used as a mask. The substrate is exposed by etching the desired portion of the phase shift film. After that, the resist film is peeled off to obtain the phase shift mask.

[0012]

The phase shift mask as described above is subjected to pretreatment such as cleaning in the manufacturing process and cleaning when the mask is used, or sulfuric acid, sulfuric acid / hydrogen peroxide (sulfuric acid / hydrogen peroxide) which is generally used as a cleaning liquid. Since the chemical resistance to acids such as mixed solution of sulfuric acid and hydrogen peroxide solution) is low, the film quality of the light semi-transmissive part changes and there is a problem that the required transmittance and phase difference cannot be obtained after cleaning. It was

In order to cope with low chemical resistance, treatments such as acid treatment and formation of a protective film have been carried out before use as a mask, but all of them have sufficient chemical resistance required. However, there is a problem in that the cost and time are increased due to the increased number of steps.

The present invention has been made to solve the above-mentioned problems, and relates to the manufacture of a phase shift mask blank and a phase shift mask having a light semi-transmissive portion excellent in chemical resistance. Provided are a sputter target used in a film forming step, and a method for manufacturing a phase shift mask blank having a light-semitransmissive portion having excellent chemical resistance and a method for manufacturing the phase shift mask by sputtering using the sputter target. The purpose is to

[0015]

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 semitransmissive film for a phase shift mask is formed by a sputtering method. As a sputtering target, one containing metal and borosilicate glass is used, and sputtering is performed in an inert gas atmosphere or in an atmosphere in which a gas containing a nitrogen element and / or an oxygen element is added to the sputtering target. In addition to satisfying the light-shielding function and the phase-shifting function, it was found that a semi-transparent film of a phase-shifting mask blank and a phase-shifting mask having excellent chemical resistance, which has been a problem so far, can be obtained, and the present invention is made. I arrived.

That is, the present invention provides the following sputter target, a phase shift mask blank using the sputter target, and a method for manufacturing a phase shift mask.

Claim 1: A sputter target used for forming a light-semitransmissive portion of a phase shift mask, wherein the sputter target contains at least a metal and borosilicate glass. [2] The sputtering according to [1], wherein the composition ratio of the metal in the sputter target and the borosilicate glass is 1: 0.5 to 1: 4 in terms of the molar ratio of the silicon content in the metal and the borosilicate glass. target. Claim 3: The sputter target according to claim 1 or 2, wherein the metal is one or more metals selected from molybdenum, titanium, tantalum, tungsten, chromium, zirconium, and germanium. Claim 4: The sputter target according to any one of claims 1 to 3, further comprising silicon and / or metal silicide. [Claim 5] A phase shift mask blank, comprising forming a light semi-transmissive film by sputtering in an inert gas atmosphere using the sputtering target according to any one of claims 1 to 4. Method. [6] The phase shift mask blank according to [5], wherein the light semitransmissive film is formed by sputtering in an atmosphere in which a gas containing a nitrogen element and / or an oxygen element is added to the inert gas as a reactive gas. Production method. (7) A method of manufacturing a phase shift mask, which comprises pattern-forming the phase shift mask blank according to (5) or (6) by a lithography method.

The present invention will be described in more detail below.

The sputter target of the present invention is composed of a metal and borosilicate glass, or a material obtained by adding silicon or metal silicide to this. The composition of borosilicate glass is mainly composed of metal, boron oxide, silicon oxide, alumina, etc., and is widely and generally used as a physics and chemistry glass (Pyrex (registered trademark)) having excellent chemical resistance and heat resistance. . For example, to make a target,
(I) A metal and borosilicate glass powder are mixed and sintered so as to have a predetermined composition. In addition, (ii) metal, borosilicate glass powder and silicon, (iii) metal, borosilicate glass powder and metal silicide, or (iv) metal,
Borosilicate glass powder, silicon and metal silicide are mixed so as to have a predetermined composition, and hot-pressed or HI is mixed.
It may be produced by sintering with P.

Examples of the metal in the sputter target include molybdenum, titanium, tantalum, tungsten, chromium, zirconium, germanium, etc.
In particular, molybdenum, titanium and zirconium are preferable.

Examples of the metal silicide include the above-mentioned metal silicide compounds, and molybdenum silicide, titanium silicide, and zirconium silicide are particularly preferable.

The composition ratio of the metal to the borosilicate glass in the target is such that the molar ratio of the metal to the silicon in the borosilicate glass is 1: 0.5 to 1: 4, particularly 1: 2 to 1: 3.
It is preferably 5. When the molar ratio is less than 1: 0.5, the formed film cannot secure the transmittance for functioning as a phase shift film, and when it exceeds 1: 4, DC is not generated.
There are problems that the discharge becomes unstable during sputtering, defects occur in the film, and the conductivity of the formed film decreases.

In a target containing metal, borosilicate glass, silicon and metal silicide, the molar ratio of total metal to total silicon in the target is 1: 2 to 1: 1.
It is preferably set to 5, particularly 1: 2 to 1: 4.

The metal species of the metal silicide is selected from the above-mentioned metals and need not be the same metal species as the metal to be blended.

Since the target containing the borosilicate glass and the metal is electrically conductive, the discharge is stable during DC sputtering, and the formed light semi-transmissive film (phase shift film) is uniform and resistant to chemicals. Has very excellent properties,
Furthermore, since it also has conductivity, it is possible to prevent charge-up during EB exposure and to perform good drawing.

A light semi-transmissive film (phase shift film) is formed by sputtering in an inert gas atmosphere using a sputter target containing the selected metal and borosilicate glass. The refractive index of the formed light semi-transmissive film is often lower than the refractive index required from the film thickness. In that case, a thin film can be obtained by sputtering in a mixed gas atmosphere containing an inert gas and nitrogen as a reactive gas, using a sputter target in which an appropriate amount of silicon and / or metal silicide is added to the sputter target. Since the silicon nitride component is contained in the composition, the refractive index is improved, and the desired refractive index can be adjusted.

As the sputtering method, direct current (DC) is used.
A power source may be used, a high frequency (RF) power source may be used, and a magnetron sputtering method or a conventional method may be used. In addition,
The film forming apparatus may be a passage type or a single wafer type.

The phase shift film according to the present invention is formed on a transparent substrate by a sputtering method using a target containing a metal and borosilicate glass as a sputtering target, and has a transmittance of exposure light of several% to several tens. % (Especially 3
%), And the phase of light transmitted through the phase shifter portion has a phase difference of 180 ± 5 degrees with respect to light transmitted through only the transparent substrate.
The transparent substrate is not particularly limited as long as it is a substrate transparent to the exposure wavelength used. Examples of the transparent substrate include a quartz substrate, fluorite, and various other glass substrates (eg, soda lime glass, aluminosilicate glass, etc.).

The composition of the sputtering gas used for forming the phase shift film is a gas containing carbon such as oxygen gas, nitrogen gas, various nitric oxide gases, various carbon oxide gases, etc. in an inert gas such as argon. The phase shift film to be formed may be appropriately added so that it has a desired composition. Note that when it is desired to increase the transmittance of the formed phase shift film, the amount of gas containing oxygen or nitrogen added to the sputtering gas can be adjusted so that a large amount of oxygen and nitrogen is incorporated into the film. .

Next, when manufacturing the phase shift mask as shown in FIG. 2 using the phase shift mask blank of the present invention, as shown in FIG. 3 (A), the phase shift is performed on the transparent substrate 1. After forming the film 2, a resist film 3 is formed on the phase shift film 2, the resist film 3 is patterned as shown in FIG. 3 (B), and further, as shown in FIG. 3 (C). , FIG. 3D after etching the phase shift film 2.
As shown in, the method of peeling the resist film 3 can be adopted. In this case, application of the resist film, patterning (exposure, development), and removal of the resist film can be performed by known methods.

The phase shift film thus obtained is
Not only does it have a function as a phase shift film (optical characteristics such as transmittance and refractive index), but also has excellent chemical resistance, which has been a problem so far. Further, since it has conductivity, good EB drawing can be performed.

[0032]

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.

Example 1 Powders of molybdenum and Pyrex (registered trademark) were used, and the molar ratio of Mo: Si was 1: 2.3.
The mixture thus obtained was sintered to prepare a sputter target, which was used to form a light semi-transmissive film.

Specifically, the above sputtering target is used on a 6 "square quartz substrate, a mixed gas having a flow ratio of argon and nitrogen of 1: 5 is used as a sputtering gas, and the gas pressure during discharge is 0. 2 Pa, 200 W, film forming temperature 1
Phase shift film (film thickness 1
21 nm) was obtained. The film thickness was adjusted so that the phase difference was 180 degrees.

An electron beam resist film is formed on the above thin film,
A resist film was formed by pattern exposure and development. Next, the thin film portion was removed by dry etching using a fluorine-based gas to obtain an L & S pattern of the phase shift thin film. After peeling the resist film, it was immersed in concentrated sulfuric acid at 80 ° C. for 15 minutes for cleaning, and rinsed with pure water to obtain a phase shift mask. In addition, the charge-up at the time of electron beam drawing was not a problem.

The obtained phase shift mask was treated with sulfuric acid / hydrogen peroxide mixture at 80 ° C. (mixed solution of sulfuric acid and hydrogen peroxide solution H ₂ SO ₄ : H ₂
It was immersed in O ₂ = 1: 4 (weight ratio)) for 2 hours, the phase difference and the transmittance before and after the immersion were measured, and the chemical resistance was evaluated from the amount of change.

The amount of change in phase difference was 1.9 degrees, and the amount of change in transmittance was 0.82%. The results are shown in Table 1.

The phase difference and the transmittance are measured at the wavelength of 2
It was measured at 48 nm with MPM-248 manufactured by Lasertec.

[Comparative Example 1] Mo:
A target was prepared by sintering powder of molybdenum and silicon so that the molar ratio of Si was 1: 2.3, and argon, nitrogen, and oxygen were used as sputtering gas in the same flow rate ratio as in Example 1 above. A mixed gas of 5: 2 was used, gas pressure during discharge was 0.25 Pa, 200 W, and film formation temperature was 120.
A phase shift film made of MoSiNO (film thickness: 102
nm) was obtained. The film thickness was adjusted so that the phase difference was 180 degrees.

After obtaining a resist pattern in the same manner as in Example 1, the resist pattern was peeled off to prepare a phase shift mask. The chemical resistance of the obtained phase shift mask was evaluated in the same manner as in Example 1.

The amount of change in phase difference was 5.0 degrees, and the amount of change in transmittance was 2.11%. The results are shown in Table 1.

The phase difference and the transmittance were measured in the same manner as in Example 1.

[0043]

[Table 1]

[0044]

According to the present invention, when a phase shift film is manufactured by a sputtering method, a sputter target containing a metal and borosilicate glass is used, so that light semi-transmission with excellent chemical resistance is obtained. A phase shift mask blank having a film (phase shift film) and a phase shift mask can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a photomask blank according to an embodiment of the present invention.

FIG. 2 is a sectional view of a photomask according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining a step of manufacturing a phase shift mask from a phase shift mask blank, (A) shows a state in which a resist film is formed on the phase shift film of the phase shift mask blank, and (B) shows a resist film. Patterned state, (C) is a state where the phase shift film is patterned by dry etching or wet etching, (D)
FIG. 4 is a cross-sectional view showing a state in which the resist film is removed and a phase shift mask is formed.

4A and 4B are diagrams illustrating the principle of a halftone type phase shift mask, and FIG. 4B is an enlarged view of an X portion.

[Explanation of symbols]

1 transparent substrate 1a Transparent substrate exposed part 2 Phase shift film 2a Phase shifter section 3 Resist film

   ─────────────────────────────────────────────────── ─── Continued front page    (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 (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 Hideo Kaneko             28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture             Shin-Etsu Chemical Co., Ltd.Research on new functional materials technology             In-house (72) Inventor Masataka Watanabe             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 BB03 BB25 BC05 BC08                 4K029 BA50 BC08 BD00 CA05 DC03                       DC05

Claims (7)

[Claims] 1. A sputter target used for forming a light-semitransmissive portion of a phase shift mask, wherein the sputter target contains at least a metal and borosilicate glass. 2. The composition ratio of metal to borosilicate glass in the sputter target is 1: 0.5 to 1: 4 in terms of molar ratio of metal content to silicon content in borosilicate glass. Sputter target. 3. The metal is one or more selected from molybdenum, titanium, tantalum, tungsten, chromium, zirconium, and germanium.
Or the sputter target according to 2. 4. The sputter target according to claim 1, further comprising silicon and / or metal silicide. 5. A phase shift mask blank, comprising forming a light semi-transmissive film by sputtering in an inert gas atmosphere using the sputter target according to claim 1. Production method. 6. The phase shift mask blank according to claim 5, wherein the light semitransmissive film is formed by sputtering in an atmosphere in which a gas containing a nitrogen element and / or an oxygen element is added as a reactive gas to the inert gas. Manufacturing method. 7. A method of manufacturing a phase shift mask, which comprises pattern-forming the phase shift mask blank according to claim 5 or 6 by a lithography method.