JP2003066587A - Sputter target, and phase shift mask blank and phase shift mask manufacturing method using the sputter target - Google Patents

Abstract

(57) Abstract: A sputter target used for forming a light translucent portion of a phase shift mask, wherein the sputter target contains at least a metal and boron-doped silicon as main components. A sputter target characterized in that: According to the present invention, when a phase shift film is produced by sputtering, a very high chemical resistance is obtained by using a target composed mainly of metal and boron-doped silicon as a sputter target. A phase shift mask blank and a phase shift mask can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for forming, by sputtering, a photomask blank used in a manufacturing process of semiconductor integrated circuits, high-density integrated circuits and the like, and an optical semitransparent thin film constituting a photomask. The present invention relates to a sputter target, a phase shift mask blank using the sputter target, and a method for manufacturing a phase shift mask.

[0002]

PRIOR ART AND PROBLEM TO BE SOLVED BY THE INVENTION LS
Photolithography technology using a photomask is used for microfabrication of high-density semiconductor integrated circuits such as I and VLSI, color filters for CCD (charge coupled device), LCD (liquid crystal display device), and magnetic head. A photomask blank is used to produce 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. Phase shift lithography is one of the techniques to increase the resolution of photolithography, and it is possible to dramatically improve the resolution by using the mutual interference of transmitted light by giving a phase difference between the exposure light transmitted through the photomask. It is a thing.

Known types of phase shift masks are the Levenson type, auxiliary pattern type, self-aligned type and the like, which have been actively developed in recent years. One of the phase shift masks is the so-called halftone type. There is a phase shift mask called a phase shift mask, which is currently the most practically applicable phase shift mask.

This phase shift mask (halftone type phase shift mask) is formed by patterning a phase shift film 2 on a transparent substrate 1 as shown in FIGS. 4A and 4B, for example. Then, the transparent 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) 2 forming the pattern portion on the mask 2
Fig. 4 shows the phase difference between the light passing through both a and a.
By setting the angle to 180 degrees as shown in (B), the light intensity at the interference portion becomes zero due to the light interference at the pattern boundary portion, and the contrast of the transferred image can be improved. 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 transparent 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 transparent substrate exposed without a phase shift film are exposed. The part 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 transparent substrate exposed portion 1a (see FIGS. 4A and 4B). Also,
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 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, a desired portion of the resist is exposed by an electron beam or an ultraviolet ray, and then developed to expose the phase shift film surface, 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.

However, the phase shift mask as described above has low acid resistance to pretreatments such as cleaning in the manufacturing process and cleaning when the mask is used, and acids such as sulfuric acid and sulfuric acid / hydrogen peroxide which are generally used as a cleaning liquid. However, there is a problem that the film quality of the light semi-transmissive part is changed and the required transmittance and phase difference cannot be obtained after cleaning.

In order to cope with such low acid resistance,
Although treatment with acid before use as a mask, formation of a protective film, etc. have been performed, none of them have sufficient acid resistance required, and the number of steps increases, cost is increased. There was a problem that it took time.

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-semitransmissive portion having excellent acid resistance, the formation of the light-semitransmissive portion. A sputter target used in a film process, and a method for manufacturing a phase shift mask blank having a light-semitransmissive portion having excellent acid resistance and a method for manufacturing a phase shift mask by sputtering using the sputter target. To aim.

[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. A sputtering target containing a metal and boron-doped silicon as a main component 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 phase. In addition to satisfying the light-shielding function and the phase-shifting function required for the shift mask, it has been found that a phase-shifting mask blank and a phase-shifting mask excellent in 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. A sputter target used for forming a light-semitransmissive portion of a phase shift mask, wherein the sputter target is mainly composed of at least a metal and boron-doped silicon. target. Claim 2: The composition ratio of the metal in the sputter target to the boron-doped silicon is 1: 0.5 to a molar ratio.
The sputter target according to claim 1, which is 1: 9. 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, wherein silicon and / or metal silicide is further added to the sputter target. [Claim 5] A light-semitransmissive film is formed by performing sputtering in an inert gas atmosphere using the sputtering target according to any one of claims 1 to 4, thereby forming a phase shift mask blank. Production method. [6] The phase shift mask blank according to [5], wherein the semi-transmissive 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 for manufacturing a phase shift mask, which comprises pattern-forming a phase shift mask blank obtained by the manufacturing method 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 silicon doped with metal and boron, or silicon and / or metal silicide added thereto. The chemical property of boron is similar to that of silicon, and silicate glass to which boron is added is widely and generally used as a glass for physics and chemistry, which has excellent chemical resistance and heat resistance. For example, in order to manufacture a target, powders of silicon doped with metal and boron are mixed so as to have a predetermined composition and sintered. Further, silicon powder doped with metal, silicon and boron; silicon powder doped with metal, boron and metal silicide; or silicon powder doped with metal, boron, silicon and metal silicide are mixed so as to have a predetermined composition, It may be produced by sintering with a hot press or HIP.

As the metal in the sputter target, molybdenum, titanium, tantalum, tungsten, chromium, zirconium, germanium and the like can be mentioned, but molybdenum, titanium and zirconium are particularly preferable.

As the metal silicide, a silicide of the above metal is preferably used.

The composition ratio of the metal in the target to the silicon doped with boron is 1: 0.5 to 1: 1 by molar ratio.
It is preferable that the ratio is 9, particularly 1: 2 to 1: 8, and more preferably 1: 3 to 1: 7. 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: 9, the discharge becomes unstable in DC sputtering. However, there is a problem that a film defect occurs or the conductivity of the formed film decreases.

In this case, in the boron-doped silicon, the doping amount of boron is 1 × 10 ¹⁶ pieces / cm ³ -1.
It is preferably × 10 ²⁰ pieces / cm ³ , and if the amount of doped boron is too small, the electrical conductivity decreases and the discharge becomes unstable. If the boron doping amount is too large, the film becomes unstable and defects occur.

Since the target composed of the above metal and silicon doped with boron has conductivity, the discharge is stable during DC sputtering, and the formed light semi-transmissive film (phase shift film). (2) has uniform properties and is extremely excellent in chemical resistance, and also has conductivity, so that charge-up during EB exposure can be prevented and good drawing can be performed.

According to the present invention, a light semi-transmissive film (phase shift film) is formed by sputtering in an inert gas atmosphere using a sputter target composed of a selected metal and silicon doped with boron. 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 sputtering target containing at least a metal and silicon doped with boron as main components, and has a transmittance for exposure light. Is several% to several tens% (particularly preferably 3% to 40%), and the phase of light transmitted through the light semi-transmissive portion (phase shifter portion) is relative to light transmitted through only the transparent substrate. 180 ±
It is preferable to have a phase difference of 5 degrees. 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 nitrogen oxide gases, various carbon oxide gases, etc. in an inert gas such as argon. The phase shift film to be formed can be formed by adding appropriately so that it has a desired composition. Note that, when it is desired to increase the transmittance of the formed phase shift film, it is possible to adjust the amount of gas containing oxygen and nitrogen added to the sputtering gas by increasing the amount of oxygen and nitrogen so that the oxygen and nitrogen are incorporated into the film. it can.

Next, when the phase shift mask blank of the present invention is used to manufacture the phase shift mask shown in FIG. 2, the phase shift is performed on the transparent substrate 1 as shown in FIG. 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.

[0029]

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 Molybdenum and boron-doped (boron-doped amount 1 × 10 ¹⁸ pieces / cm ³ ) powders of a silicon wafer were mixed at a molar ratio of 1: 2.3 and sintered. Then, a target was produced, and a light semi-transmissive film was formed using this. Specifically, using the above target on a 6 ″ square quartz substrate, a mixed gas having a flow ratio of argon, nitrogen, and oxygen of 1: 5: 2 was caused to flow, and the gas pressure during discharge was 0.25 Pa. Mainly MoSi by DC magnetron sputtering method at 200 W, film formation temperature 120 ° C.
A phase shift film (film thickness 125 nm) made of BNO was obtained. The film thickness was adjusted so that the phase difference was 180 degrees. The film composition of this sample was analyzed by an X-ray photoelectron meter (XPS).
3 atomic%, 1 atomic% boron, 42 atomic% nitrogen, 21 oxygen
It contained atomic%. A resist film was formed on the MoSiBNO thin film, and the resist film was formed by pattern exposure and development. Next, the thin film portion is removed by dry etching using a fluorine-based gas, and MoSiB
An L & S pattern of a thin film of NO was obtained. After removing the resist, 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. The obtained phase shift mask was treated with sulfuric acid / hydrogen peroxide mixture at 80 ° C. (H ₂ SO ₄ : H ₂ O ₂ =
It was immersed in 4: 1) 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 the phase difference was 1.9 degrees, and the amount of change in the transmittance was 0.8%. The results are shown in Table 1. The retardation and the transmittance were measured with MPM-248 manufactured by Lasertec Co. at a wavelength of 248 nm.

[Comparative Example 1] A target was prepared by sintering a powder of molybdenum and silicon so that the Mo: Si molar ratio was 1: 2.3, and the same method as in Example 1 was used. Under the conditions, a phase shift film (film thickness 122 nm) made of MoSiNO was obtained. The film thickness has a phase difference of 18
Adjusted to 0 degree. As a result of analyzing the film composition in the same manner as in Example 1, molybdenum was 13 atom%, and silicon was 2
It contained 4 atom%, 42 atom% of nitrogen, and 21 atom% of oxygen. After obtaining a resist pattern in the same manner as in Example 1 above, this was peeled off to produce a phase shift mask.
The obtained phase shift mask was evaluated for chemical resistance in the same manner as in Example 1 above. The amount of change in the phase difference was 5 degrees, and the amount of change in the transmittance was 2%. The results are shown in Table 1. The phase difference and the transmittance were measured in the same manner as in Example 1 above.

[0032]

[Table 1]

[0033]

According to the present invention, when a phase shift film is manufactured by sputtering, by using a sputtering target composed mainly of metal and boron-doped silicon, the chemical resistance is greatly improved. An excellent phase shift mask blank and 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.

3A and 3B are explanatory views showing a method for manufacturing a photomask, in which (A) shows a state where a resist film is formed, (B) shows a state where the resist film is patterned, and (C) shows dry etching or wet etching. 3D is a schematic cross-sectional view in a state where the resist film is removed.

4A and 4B are diagrams illustrating the principle of a halftone type phase shift mask, and FIG. 4B is a partially 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 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 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 (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 BB03                 4K029 BD00 BD01 DC05

Claims (7)

[Claims] 1. A sputter target used for forming a light-semitransmissive portion of a phase shift mask, wherein the sputter target is mainly composed of at least a metal and boron-doped silicon. Sputter target. 2. The composition ratio of the metal in the sputter target to the boron-doped silicon is 1: 0.
The sputter target according to claim 1, having a ratio of 5 to 1: 9. 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 added to the sputter target. 5. A phase shift mask blank, comprising forming a light semitransmissive film by sputtering in an inert gas atmosphere using the sputtering target according to claim 1. Description: Manufacturing method. 6. The phase shift mask 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. Blank manufacturing method. 7. A method of manufacturing a phase shift mask, which comprises patterning a phase shift mask blank obtained by the method of claim 5 or 6 by a lithography method.