JP2966369B2 - 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 phase shift mask capable of improving the resolution of a transfer pattern by giving a phase difference between exposure lights transmitted through the mask, a phase shift mask blank as its material, and a phase shift mask blank. More particularly, the present invention relates to a halftone phase shift mask, a phase shift mask blank, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, two important characteristics required for photolithography, high resolution and securing a depth of focus, are in conflicting relations.
It has been clarified that the practical resolution cannot be improved only by shortening the wavelength (Semiconductor World 1990.12, Monthly Applied Physics, Vol. 60, November, 1991).

Under such circumstances, phase shift lithography has attracted attention as a next-generation photolithography technology. Phase shift lithography is a method of improving the resolution of optical lithography by changing only the mask without changing the optical system, and by providing a phase difference between the exposure light transmitted through the photomask, interference between transmitted light The resolution can be dramatically improved by utilizing the above.

A phase shift mask is a mask having both light intensity information and phase information.
Various types such as a die, an auxiliary pattern type, and a self-aligned type (edge enhancement type) are known. These phase shift masks have a complicated structure and require a high level of technology for manufacturing as compared with a conventional photomask having only light intensity information.

As one of the phase shift masks, a phase shift mask called a so-called halftone type phase shift mask has recently been developed.

In this halftone type phase shift mask, the light semi-transmissive portion has two functions of a light blocking function of substantially blocking exposure light and a phase shift function of shifting (normally inverting) the phase of light. Therefore, there is no need to separately form the light-shielding film pattern and the phase shift film pattern, and the feature is that the configuration is simple and the manufacturing is easy.

As shown in FIG. 1, a halftone type phase shift mask is formed by forming a mask pattern formed on a transparent substrate 1 into a light transmitting portion (transparent substrate exposed portion) for transmitting light having an intensity substantially contributing to exposure. 2) and a light semi-transmissive portion (light-shielding portion and phase shifter portion) 3 that transmits light having an intensity that does not substantially contribute to exposure (FIG. 3A). By shifting the phase of the light transmitted through the light transmissive portion so that the phase of the light transmitted through the light transmissive portion is substantially inverted with respect to the phase of the light transmitted through the light transmissive portion (FIG. (B), the lights passing through the vicinity of the boundary between the light transmissive part and the light transmissive part and sneaking into the other region by the diffraction phenomenon cancel each other out, and the light intensity at the boundary is made substantially zero, and Improve the contrast or resolution of the part Than it (Fig. (C)).

Incidentally, the light semi-transmissive portion in the above-described halftone type phase shift mask needs to have required optimum values for both the light transmittance and the phase shift amount.

The applicant of the present invention has previously filed an application for a phase shift mask capable of realizing the required optimum value with a single-layer semi-transmissive portion (Japanese Patent Laid-Open No. Hei 6-332152).
No.).

In this phase shift mask, the light semi-transmissive portion is
It is composed of a thin film made of a material mainly composed of metal such as molybdenum, silicon and oxygen.
This substance is molybdenum silicide, specifically, oxidized molybdenum and silicon (abbreviated as MoSiO-based material) or oxynitrided molybdenum and silicon (abbreviated as MoSiON-based material).

According to this, the transmittance can be controlled by selecting the oxygen content or the content of oxygen and nitrogen, and the phase shift amount can be controlled by the thickness of the thin film. Further, by configuring the light semi-transmissive portion with such a substance, the light semi-transmissive portion can be composed of a single-layer film made of one kind of material, and may be composed of a multi-layer film composed of different materials. In comparison, since the film forming process can be simplified and a single etching medium can be used,
The manufacturing process can be simplified.

[0012]

However, the above-described conventional halftone type phase shift mask and its manufacturing method have the following problems.

That is, the molybdenum oxide silicide film or the molybdenum oxynitride silicide film, which is a component of the light translucent portion of the phase shift mask, is used as a pretreatment such as cleaning in a mask manufacturing process and cleaning when a mask is used, or as a cleaning liquid. In particular, when the values of the transmittance and the phase difference of the light semi-transmission part are set for KrF excimer laser light (248 nm), the extinction coefficient (K) needs to be reduced. As a measure, the degree of oxidation or the degree of oxynitridation must be sufficiently increased, but there is a problem that the acid resistance is remarkably reduced and the set transmittance and phase difference are shifted.

In addition, when the phase shift mask blank is formed, as the degree of oxidation or the degree of oxynitridation increases, oxides are deposited on the target surface (particularly in the non-erosion region) and the discharge becomes unstable. In addition, the controllability of the transmittance and the film thickness is deteriorated, and there is a problem that defects and the like are easily generated in the blank.

Further, since the relationship between the film composition and film characteristics such as acid resistance, light resistance, conductivity, refractive index (film thickness), transmittance and etching selectivity has not been elucidated, the light transmittance and phase Even if the blank has the optimum values required for both of the shift amounts, it is not the optimum film characteristic taking the manufacturing process and the like into consideration. There has been a problem that a shift has occurred and an optimal phase shift mask cannot be obtained.

The present invention has been made in view of the above problems, and has been made in consideration of film characteristics such as acid resistance, light resistance, conductivity, refractive index (film thickness), transmittance, phase shift amount, and etching selectivity. An object of the present invention is to provide a phase shift mask and a phase shift mask blank having an excellent light translucent portion.

[0017]

In order to achieve the above object, a phase shift mask according to the present invention is a mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is substantially exposed. A light transmitting portion that transmits light having an intensity that contributes to the light, and a light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and adjusts the phase of the light transmitted through the light semi-transmitting portion. By shifting the phase of light transmitted through the light transmissive part and the phase of light transmitted through the light transmissive part to be different from each other, the light transited near the boundary between the light semitransmissive part and the light transmissive part. A phase shift mask for improving the contrast of a boundary portion so that light cancels each other, wherein the light semi-transmissive portion is formed of a thin film made of a material having nitrogen, metal, and silicon as main components. Thin The content of components serving silicon material constituting the certain a configuration in which a 34 to 60 atomic%.

Further, the phase shift mask of the present invention is a mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmission method that transmits light having an intensity substantially contributing to exposure. And a light semi-transmitting portion that transmits light of an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion to transmit the light through the light semi-transmitting portion. By making the phase of the transmitted light different from the phase of the light transmitted through the light transmitting portion, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other, and the boundary portion A phase shift mask for improving contrast, wherein the light semi-transmissive portion is
It is composed of a thin film made of a substance mainly composed of nitrogen, metal and silicon, and the metal is made of molybdenum or titanium, and has a silicon content of 30 to 60 atoms as a constituent element of the substance constituting the thin film. %.

Further, the phase shift mask of the present invention is a mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmission method that transmits light having an intensity substantially contributing to exposure. And a light semi-transmissive part that transmits light of an intensity that does not substantially contribute to exposure,
Further, by shifting the phase of the light transmitted through the light semi-transmissive part to make the phase of the light transmitted through the light semi-transmissive part different from the phase of the light transmitted through the light transmissive part, the light half is transmitted. A phase shift mask that improves the contrast of the boundary portion so that light passing near the boundary between the transmission portion and the light transmission portion cancels each other, wherein the light semi-transmission portion is
It is composed of a thin film composed of a substance mainly composed of nitrogen, metal and silicon, and the metal is composed of molybdenum or titanium. The sheet resistance of the substrate on which the thin film is formed is 1 kΩ / □ to 1.5 MΩ / □. There is a configuration.

Further, in the phase shift mask according to the present invention, in the phase shift mask according to the present invention, a ratio of an atomic% of metal and silicon as constituent elements of the material constituting the thin film is 1: 1. 5 to 6.0.

Further, the phase shift mask of the present invention is a mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmission method that transmits light having an intensity substantially contributing to exposure. And a light semi-transmitting portion that transmits light of an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion to transmit the light through the light semi-transmitting portion. By making the phase of the transmitted light different from the phase of the light transmitted through the light transmitting portion, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other, and the boundary portion A phase shift mask for improving contrast, wherein the light semi-transmissive portion is
It is composed of a thin film composed of a substance mainly composed of nitrogen, metal and silicon, and the metal is composed of molybdenum or titanium, and the content of nitrogen, which is a constituent element of the substance constituting the thin film, is 30 to 60 atoms. %.

Further, in the phase shift mask according to the present invention, in the phase shift mask according to the present invention, the content of silicon as a constituent element of the substance constituting the thin film is 30 to 60.
Atomic%, the content of nitrogen, which is a constituent element of the substance constituting the thin film, is 30 to 60 atomic%, and the content of nitrogen is higher than the content of silicon.

Further, the phase shift mask blank of the present invention is a phase shift mask blank used as a material of the above phase shift mask of the present invention, wherein nitrogen, metal and silicon are main components on a transparent substrate. It has a configuration in which a thin film made of a substance is formed.

[0024]

In the phase shift mask of the present invention, the light semi-transmissive portion is formed of a thin film made of a substance mainly composed of nitrogen, metal and silicon, and the content (atomic%) of each component in the thin film. By specifying the ratio and the acid resistance,
It has a light semi-transmissive part with excellent film properties such as light resistance, conductivity, refractive index (film thickness), transmittance and etching selectivity, and enables highly accurate optical characteristics (light transmittance and phase shift amount). Satisfaction and few defects.

Since the phase shift mask blank of the present invention has the optimum film characteristics in consideration of the manufacturing process and the like, the phase shift mask blank satisfies the optical characteristics with high accuracy, and has a light semi-transmissive portion with few defects. Shift masks can be easily and inexpensively manufactured with high yield. Furthermore, in the present invention, by using a target having a specific composition, a phase shift mask blank having a light semi-transmissive portion having excellent film characteristics can be manufactured stably and without defects.

Hereinafter, the present invention will be described in detail.

In the present invention, the light semi-transmissive portion of the halftone type phase shift mask is formed of a thin film made of a material mainly composed of metal, silicon and nitrogen.
By forming the light semi-transmissive portion with a thin film containing no oxygen as described above, the acid resistance is improved and the discharge is stabilized as compared with the case containing oxygen, but this alone cannot be said to be sufficient.

Here, examples of the metal include molybdenum, tantalum, tungsten, titanium, chromium, and the like. Molybdenum or titanium is preferable in consideration of film characteristics and the like.

The bonding state of the substances constituting the light semi-transmissive portion is complicated and cannot be said unconditionally. This is because, for example, in the case of molybdenum and silicon nitride, SiN, MoSiN, Mo
This is because N and the like are complicatedly related, and it is not appropriate to use a simple chemical formula. Also, the ratio of the components is complicated because the component ratio varies in the depth direction and the like, and cannot be said unconditionally.

Examples of the substance mainly composed of metal, silicon, and nitrogen constituting the light semi-transmissive portion include:
For example, nitrided molybdenum and silicon (MoSi
N-based material), nitrided tantalum and silicon (TaSiN-based material), nitrided tungsten and silicon (WSiN-based material), nitrided titanium and silicon (TiSiN-based material), nitrided Chromium and silicon (abbreviated as CrSiN-based material). In addition, as long as these substances do not impair the function as a light semi-transmissive part, carbon, hydrogen, and the like, as a compound of these substances or a mixture with these substances,
A small amount or an appropriate amount of fluorine, helium, or the like may be contained.

In the present invention, for example, a nitride of molybdenum silicide, a nitride of tantalum silicide, a nitride of tungsten silicide, a nitride of titanium silicide, or a mixture of at least one of these substances with silicon nitride and / or metal nitride And the like are also included as a material constituting the light semi-transmissive portion.

In the present invention, for example, molybdenum nitride silicide (MoSiN), tantalum silicide (TaSiN), tungsten nitride silicide (WS)
Conventionally generally described substances such as iN) and titanium nitride silicide (TiSiN) are also included as substances constituting the light semi-transmissive portion.

The light semi-transmissive portion has two functions, that is, a light blocking function of substantially blocking exposure light and a phase shifting function of shifting the phase of light.

Since the values of these functions differ depending on the exposure light source and its wavelength when the mask is used, it is necessary to design and select the values according to the exposure light source to be used and its wavelength. As the exposure light source and its wavelength, for example, an i-line of a mercury lamp (wavelength λ = 365 nm), a g-line of a mercury lamp (wavelength λ = 436 nm), a KrF excimer laser (wavelength λ = 248 nm), an ArF excimer laser (wavelength λ) = 193 nm).

The amount of phase shift of the light semi-transmissive portion depends on the film composition (nitrogen content (at.%), Silicon content (at.%), Metal content (at.%)) Of the film constituting the light semi-transmissive portion. It is controlled by adjusting a refractive index (including an attenuation coefficient) and a film thickness determined accordingly.

Assuming that the phase shift amount is φ, the wavelength of the exposure light is λ, and the refractive index of the light semi-transmissive portion is n, the film thickness d of the light semi-transmissive portion can be determined by the following equation (1).

D = (φ / 360) × [λ / (n−1)] (1)

The amount of phase shift φ in equation (1) is 18
Although 0 ° is most desirable from the viewpoint of improving the resolution, it may be practically about 160 ° to 200 °.

The light transmittance (light-shielding performance) of the semi-transmissive portion to exposure light depends on the sensitivity of the resist used in forming a pattern of a semiconductor element or the like, but is generally preferably about 2 to 20%. Within this range, the higher the light transmittance, the higher the transmittance, the higher the phase effect.
However, in the case of line & space, it is preferable that the transmittance is low, and in the case of a hole-based pattern, the transmittance is preferably high.

The light transmittance of the semi-transmissive portion mainly adjusts the nitrogen content (atomic%), silicon content (atomic%), and metal content (atomic%) in the film constituting the light semi-transmissive portion. Can be controlled by

In the present invention, nitrogen constituting the light semi-transmissive portion,
It is characterized in that the content (atomic%) and the ratio of each component in a thin film made of a substance mainly composed of metal and silicon are specified.

This is an absolute condition required for the light semi-transmissive portion to simultaneously satisfy the optimum values for both the light transmittance and the phase shift amount φ with a single-layer film, but this alone is not sufficient. However, it is necessary to determine the composition of the thin film forming the light semi-transmissive portion in consideration of the manufacturing process and the like.

Specifically, for example, it is resistant to an acid such as sulfuric acid used as a pretreatment or a cleaning solution such as cleaning in a mask manufacturing process and cleaning when a mask is used, and deviates in transmittance and phase difference set by the acid cleaning. It is necessary to have a film composition that does not cause the generation of the film.

Further, in order to ensure stability during film formation and prevent charge-up during mask processing, it is necessary to make the film composition excellent in conductivity. Specifically, during the deposition of the phase shift mask blank, the compound (oxide) is deposited on the target surface (particularly, the non-erosion region), and the discharge becomes unstable. Deterioration easily causes defects and the like in the blank. In addition, if the conductivity of the mask blank is poor, charge-up at the time of mask processing tends to cause a failure in drawing or a decrease in drawing accuracy or a defect in the mask.

Further, it is necessary to have a film composition which has a relatively high refractive index and can reduce the film thickness for inverting the phase. This is because, by reducing the film thickness, not only the productivity is improved, but also the step of the mask pattern is reduced, so that pattern destruction during cleaning (such as scrub cleaning) due to mechanical friction or the like can be reduced. is there.

Further, the film composition must be such that the etching selectivity with a quartz substrate or the like is improved. This is for minimizing the etching amount of the quartz substrate or the like and avoiding the fluctuation of the phase shift amount φ.

In the present invention, the content (atomic%) and ratio of each component in the thin film constituting the light semi-transmissive portion are specified from the above viewpoints. At this time, the film composition in a region (surface layer) at a certain depth from the surface of the light semi-transmissive portion is important because it affects the cleaning property and the conductivity.

In the present invention, nitrogen constituting the light semi-transmissive portion,
The content of silicon in a thin film made of a substance mainly composed of metal and silicon is 30 to 60 atomic%.

The silicon content mainly affects the transmittance. If the silicon content is less than 30 at%, it is difficult to obtain a high transmittance, and if it exceeds 60 at%, the etching selectivity with respect to a quartz substrate or the like is reduced. In this respect, the silicon content is more preferably set to 40 to 50 atomic%.

In the present invention, nitrogen constituting the light semi-transmissive portion,
It is preferable that the ratio of the atomic% of metal and silicon in the thin film composed of a substance mainly composed of metal and silicon is metal: silicon = 1: 1.5 to 6.0.

The ratio of metal and silicon mainly affects acid resistance and light resistance. If the ratio of metal and silicon is less than 1.8, the acid resistance will be poor, and if it exceeds 6.0, the resistance will be high. From this viewpoint, the ratio of metal and silicon is more preferably metal: silicon = 1: 2.0 to 5.0.

In the present invention, nitrogen constituting the light semi-transmissive portion,
It is preferable that the content of nitrogen in the thin film composed of a substance mainly composed of metal and silicon is 30 to 60 atomic%.

The nitrogen content mainly affects the transmittance and the etching characteristics like silicon. If the nitrogen content is less than 30 atomic%, it is difficult to obtain a high transmittance, and if the nitrogen content is more than 60 atomic%, the etching rate becomes extremely high, so that CD control becomes difficult.

In the present invention, nitrogen constituting the light semi-transmissive portion,
By specifying the content (atomic%) and ratio of each component in a thin film composed of a substance mainly composed of metal and silicon, the conductivity of the thin film and the sheet resistance of the substrate (blank) on which the thin film is formed can be determined. It is preferable to be about 1 kΩ / □ to 1.5 MΩ / □.

The conductivity (sheet resistance) mainly affects the stability of target discharge during film formation and the ability to prevent charge-up during mask processing. Sheet resistance is 1.5MΩ
/ □ or less, particularly preferably 1 MΩ / □ or less for obtaining discharge stability during film formation, and 0.5 MΩ / □ for preventing charge-up during mask processing. The following is preferred.

In order to obtain a thin film having the above composition while maintaining discharge stability during film formation, a target containing 70 to 95 mol% of silicon and a metal is sputtered in an atmosphere containing nitrogen. Thereby, it is preferable to form a phase shift layer containing nitrogen, a metal, and silicon to manufacture a phase shift mask blank.

This is because when the silicon content in the target is more than 95 mol%, it becomes difficult to apply a voltage on the surface of the target (erosion portion) in DC sputtering (it becomes difficult for electricity to pass), and discharge is unstable. When the content is less than 70 mol%, a film constituting a light transmissive portion having a high light transmittance cannot be obtained.

The discharge stability at the time of film formation also affects the film quality. If the discharge stability is excellent, a light semi-transmissive portion having good film quality can be obtained.

As shown in FIG. 2, the present invention includes a phase shift mask blank in which a light translucent film 3a having the above specific composition is formed on a transparent substrate 1.

In the above-described phase shift mask and the method of manufacturing the same, the transparent substrate is not particularly limited as long as it is transparent to the exposure wavelength to be used. Examples of the transparent substrate include a quartz substrate, fluorite, and various other glass substrates (for example, soda lime glass, aluminosilicate glass, aluminoborosilicate glass, and the like).

The pattern formation processing (patterning and mask processing) includes a series of well-known lithography (photo, electron beam) steps (resist coating, exposure, development,
Etching, resist stripping, washing, etc.), and is not particularly limited.

[0062]

The present invention will be described below in more detail with reference to examples.

Example 1 Manufacture of Blank A light-transmissive film made of a thin film of nitrided molybdenum and silicon (MoSiN-based material) is formed on the surface of a transparent substrate, and a phase shift mask blank for a KrF excimer laser (wavelength: 248 nm) is formed. I got

More specifically, a mixed target (Mo: Si = Si) of molybdenum (Mo) and silicon (Si: silicon)
20:80 mol%) and a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 10%, N ₂ : 90).
%, Pressure: 1.5 × 10 ⁻³ Torr) to form a nitrided molybdenum and silicon (MoSiN) thin film (film thickness 931 Å) on a transparent substrate by reactive sputtering.

FIG. 3 shows the ESC of the light translucent film obtained above.
A shows the results of the analysis.

As shown in FIG. 3, the film composition of the light semi-transmissive film (average value of Mo) was 12.5 atomic% of Mo, 40.2 atomic% of Si, and 47.3 atomic% of N. According to the ESCA analysis result, O was detected on the quartz substrate side and the surface side of the light semi-transmissive film. The surface side of the light semi-transmissive film is oxidized after film formation, and the substrate side is one in which O of SiO ₂ is detected at the interface. When oxidized in this manner, the content of nitrogen in the oxidized portion is preferably within a range of 30 to
It will be lower than 60 atomic%. The value of each composition characterized in the present invention is considered for the main part of the film except for the surface side and the substrate side in the film direction. For example, the thickness of the main portion of the semi-transmissive film not containing O occupies about 87.5% of the whole, whereas the thickness of the quartz substrate side containing O is about 8.0% of the whole. % Or less, and the thickness of the surface side containing O is about 4.5% or less of the whole. For reference, FIG.
Molybdenum and silicon (MoSiO
10 shows the results of ESCA analysis of the light semi-transmissive film made of N).

In the present invention, when an attempt is made to produce a thin film of nitrided molybdenum and silicon (MoSiN), O may be contained on the quartz substrate side and the surface side of the light semi-transmissive film as described above (always including O). For example, it cannot be said that there is no case where the main portion of the MoSiN film not containing O and the film on the surface side containing O exert some kind of interaction. In that sense, the nitrided molybdenum and silicon (MoSiN) thin film according to the present invention includes such an aspect including O near the surface as one aspect.

In the above ESCA analysis results, O was hardly detected in the main portion of the light semi-transmissive film, but O may be contained in an amount that does not substantially affect the film characteristics. . Specifically, the amount of O
₂ may be contained in the light translucent film.

FIG. 5 shows the film composition (average value of the whole) and the film characteristics (transmittance, film thickness, and refractive index at a wavelength of 248 nm). FIG. 6 is a graph showing the wavelength dependence of the light transmittance of the phase shift mask blank obtained above.

The light transmittance of the obtained phase shift mask blank at a wavelength of 248 nm was 5%, the light transmittance at a wavelength of 365 nm was 19%, and the light transmittance at a wavelength of 488 nm was 40%. The phase shift amount (phase angle) φ of this phase shift mask blank was 181 ° and the refractive index was 2.34. The light transmittance was measured using a spectrophotometer (manufactured by Hitachi, Ltd .: model 340), and the phase angle was measured using a phase difference measuring instrument (manufactured by Lasertec, Inc .: MPM-).
248).

Comparative Example 1 Fabrication of Blank A light-semitransmissive film composed of a thin film of oxynitrided molybdenum and silicon (MoSiON) was formed on the surface of a transparent substrate to provide a phase shift mask blank for a KrF excimer laser (wavelength: 248 nm). Obtained.

Specifically, a mixed target (Mo: Si = Mo: Si) of molybdenum (Mo) and silicon (Si: silicon)
33: 67 mol%) using a mixed gas atmosphere of argon (Ar) and nitrous oxide (N ₂ O) (Ar: 84%,
N ₂ O: 16%, pressure: 1.5 × 10 ⁻³ Torr)
A thin film of molybdenum and silicon (MoSiON) oxynitrided (thickness: 1378 angstroms) was formed on a transparent substrate by reactive sputtering.

FIG. 5 shows the film composition (average value of the whole) and film characteristics (transmittance, film thickness, refractive index at a wavelength of 248 nm). Wavelength 248 of the obtained phase shift mask blank
Light transmittance at 2 nm is 2%, phase shift amount (phase angle)
φ was 180 ° and the refractive index was 1.90.

As is apparent from Example 1 and Comparative Example 1 and FIG. 5, nitrided molybdenum and silicon (Mo)
Since a thin film made of SiN) has a larger refractive index than a thin film made of oxynitrided molybdenum and silicon (MoSiON), it is possible to reduce the film thickness for making the phase difference 180 °.

Next, the acid resistance, light resistance, and conductivity when the film composition and the film composition ratio were changed were examined.

Example 2 Fabrication of Blank A light-transmissive film made of a thin film of nitrided molybdenum and silicon (MoSiN-based material) is formed on the surface of a transparent substrate, and a phase shift mask blank for a KrF excimer laser (wavelength: 248 nm) is formed. I got

More specifically, a mixed target of molybdenum (Mo) and silicon (Si: silicon) (Mo: Si =
30:70 mol%) and a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 10%, N ₂ : 90).
%, Pressure: 1.5 × 10 ⁻³ Torr), a thin film of molybdenum and silicon (MoSiN) nitrided (film thickness: 855 Å) was formed on the transparent substrate by reactive sputtering.

The light transmittance (at a wavelength of 248 nm) of the obtained phase shift mask blank was 2%, and the amount of phase shift (phase angle) φ was approximately 180 °. The light transmittance was measured by a spectrophotometer (Model 340, manufactured by Hitachi, Ltd.).
And the phase angle was measured using a phase difference measuring machine (manufactured by Lasertec Corporation: MPM-248).

FIG. 7 shows the film composition (average value of the whole) (including the composition ratio) and the film characteristics (transmittance, film thickness, refractive index, acid resistance, conductivity). Regarding the acid resistance, “○” indicates that no change was observed after immersion in hot concentrated sulfuric acid (H ₂ SO ₄ ) at 120 ° C. for 2 hours, “△” indicates that the change was small and within the allowable range, Those having a large change and outside the allowable range were marked as “x”.

Mask Processing A resist film was formed on the thin film made of nitrided molybdenum and silicon (MoSiN) of the phase shift mask blank, and a resist pattern was formed by pattern exposure and development. Next, the exposed portion of the thin film composed of nitrided molybdenum and silicon is removed by etching (dry etching with CF ₄ + O ₂ gas) to obtain a pattern (holes, dots, etc.) of the thin film composed of nitrided molybdenum and silicon. Was. After removing the resist, 100
It was immersed in 98% sulfuric acid (H ₂ SO ₄ ) at 15 ° C. for 15 minutes, washed with sulfuric acid, and rinsed with pure water or the like to obtain a phase shift mask for a KrF excimer laser.

Example 3 Molybdenum and silicon (MoSiN) nitrided on a transparent substrate using a mixed target (Mo: Si = 20: 80 mol%) in which the ratio of molybdenum and silicon was changed
A phase shift mask blank and a phase shift mask were obtained in the same manner as in Example 2 except that a thin film having a thickness of 925 angstroms was formed.

FIG. 7 shows the film composition and film characteristics.

Example 4 Molybdenum and silicon (MoSiN) nitrided on a transparent substrate using a mixed target (Mo: Si = 10: 90 mol%) in which the ratio of molybdenum and silicon was changed
A phase shift mask blank and a phase shift mask were obtained in the same manner as in Example 2 except that a thin film having a thickness of 969 Å was formed.

FIG. 7 shows the film composition and film characteristics.

Comparative Example 2 Production of Blank A light-transmissive film made of a thin film of oxynitrided molybdenum and silicon (MoSiON) was formed on the surface of a transparent substrate to obtain a phase shift mask blank for a KrF excimer laser (wavelength: 248 nm). Obtained.

More specifically, a mixed target (Mo: Si = Si) of molybdenum (Mo) and silicon (Si: silicon)
33: 67 mol%) using a mixed gas atmosphere of argon (Ar) and nitrous oxide (N ₂ O) (Ar: 76%,
N ₂ O: 24%, pressure: 1.5 × 10 ⁻³ Torr)
A phase shift mask blank and a phase shift mask were prepared in the same manner as in Example 2 except that a thin film (film thickness: 1278 Å) of oxynitrided molybdenum and silicon (MoSiON) was formed on a transparent substrate by reactive sputtering. Obtained.

FIG. 7 shows the film composition and film characteristics.

Examples 5 to 7 Production of Blanks A light semi-transmissive film made of a thin film of nitrided molybdenum and silicon (MoSiN) is formed on the surface of a transparent substrate, and i
A phase shift mask blank for a line (wavelength 365 nm) was obtained.

More specifically, a mixed target of molybdenum (Mo) and silicon (Si: silicon) (Mo: Si =
20:80 mol%) and a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 62 to 52%,
N ₂ : 38 to 48%, pressure: 1.2 to 1.7 × 10 ⁻³ T
orr), a phase shift mask blank was formed in the same manner as in Example 2 except that a thin film of nitrided molybdenum and silicon (MoSiN) (film thickness: 1106 to 1177 Å) was formed on a transparent substrate by reactive sputtering. And a phase shift mask.

FIG. 8 shows the film composition and film characteristics. The light transmittance was measured by a spectrophotometer (Model 340, manufactured by Hitachi, Ltd.).
And the phase angle was measured using a phase difference measuring device (MPM-100 manufactured by Lasertec Co., Ltd.).

Comparative Examples 3 to 5 Production of Blanks A light-transmissive film made of a thin film of oxynitrided molybdenum and silicon (MoSiON) is formed on the surface of a transparent substrate, and a phase shift mask blank for i-line (wavelength 365 nm) I got

More specifically, a mixed target (Mo: Si = Si) of molybdenum (Mo) and silicon (Si: silicon)
33: 67 mol%) and a mixed gas atmosphere of argon (Ar) and nitrous oxide (N ₂ O) [(Ar: 86
%, N ₂ O: 14%, pressure: 1.5 × 10 ⁻⁶ Torr)
(Comparative Example 3), (Ar: 85%, N ₂ O: 15%, pressure: 1.5 × 10 ⁻⁶ Torr) (Comparative Example 4), (Ar:
83%, N ₂ O: 17%, pressure: 1.5 × 10 ⁻⁶ Torr
r) (Comparative Example 5)]
A phase shift mask blank and a phase shift mask were obtained in the same manner as in Examples 5 to 7, except that a thin film of molybdenum and silicon (MoSiON) oxynitrided was formed on a transparent substrate.

FIG. 8 shows the film characteristics.

Evaluation

[0095] As can be seen from the membrane composition and film characteristics diagram 7, Si is reduced and the transmittance of the film is deteriorated, tends to decrease even acid resistance. Conversely, it can be seen that the transmittance and acid resistance tend to increase as the Si content in the film increases. For this reason, the Si content (atomic%) in the film is preferably 30% or more, and more preferably 40% or more in consideration of acid resistance. Also, it can be seen that when the Si content in the film is too large, the resistance value tends to increase. For this reason, the Si content (atomic%) in the film is preferably 60% or less.

As can be seen from FIGS. 7 and 8, it is understood that the refractive index and the film thickness can be controlled by adjusting the composition in the film.

Since the refractive index is relatively high and the film thickness for inverting the phase can be made extremely thin, not only the productivity is improved, but also because the pattern step of the mask is reduced, mechanical rubbing and the like are performed. Since the pattern destruction at the time of cleaning due to the above-mentioned method is reduced and the etching rate can be extremely increased, it has been found that the etching selectivity with respect to a quartz substrate or the like is good.

Conductivity Further, as can be seen from FIGS. 7 and 8, it is understood that the conductivity (sheet resistance) can be controlled by adjusting the composition in the film.

The sheet resistance is preferably 1.5 MΩ / □ or less, particularly preferably 1 MΩ / □ or less in order to obtain discharge stability during film formation. 0.5MΩ / □ to prevent
The following is preferred.

As can be seen from FIGS. 7 and 8, Comparative Example 2
In the case of (1), since the conductivity of the film itself is poor, oxynitride is deposited on the non-erosion portion of the MoSi target during the film formation, whereby the discharge becomes unstable. Therefore, the controllability of the transmittance and the film thickness is poor, and the film sometimes has defects.

On the other hand, in the case of Examples 2 to 7, since the film itself has good conductivity, the discharge does not become unstable during the film formation. The film had good properties, and no defects or the like occurred in the film. In addition, because the conductivity of the phase shift pattern is good,
When using a mask, the pattern is not destroyed by static electricity.

The silicon content in the target was 9
When the content is more than 5 mol%, in DC sputtering, it becomes difficult to apply a voltage on the target surface (erosion portion) (it becomes difficult for electricity to pass), so that the discharge becomes unstable.

Acid Resistance The nitrided molybdenum and silicon of the present invention (MoSi
N) and a blank of oxynitrided molybdenum and silicon (MoSiON) of Comparative Example
In 96% sulfuric acid (H ₂ SO ₄ ).

FIG. 9 shows the result. FIG. 9 shows the light transmittance (at a wavelength of 248 nm) of the film and the amount of phase shift (at a wavelength of 365 n) with respect to the immersion time of these blanks in sulfuric acid.
(in m).

As can be seen from FIG. 9, the changes in the light transmittance and the phase shift of the nitrided molybdenum and silicon (MoSiN) of the present invention when immersed in sulfuric acid at 100 ° C. for 120 minutes are the same as those of the comparative example. The light transmittance of the oxynitrided molybdenum and silicon (MoSiON) and the change amount of the phase shift amount are approximately 1/100 respectively.
8, the phase shift amount was a small value of about 1/6.

Next, sulfuric acid (H ₂ SO ₄ ) at 100 ° C.
The alkali resistance was examined in the same manner as described above, except that the aqueous solution was replaced with a 2% aqueous ammonia solution at a temperature of 2 ° C.

FIG. 10 shows the result. FIG. 10 shows the changes in the light transmittance (at a wavelength of 248 nm) and the amount of phase shift (at a wavelength of 365 nm) of the blank of the present invention and the comparative example with respect to the immersion time in the aqueous ammonia solution.

As can be seen from FIG. 10, the changes in the light transmittance and the phase shift of the nitrided molybdenum and silicon (MoSiN) of the present invention when immersed in an aqueous ammonia solution at 20 ° C. for 120 minutes are shown in FIG. The light transmittance and the phase shift amount of the oxynitrided molybdenum and silicon (MoSiON) were as small as approximately 1/5 in the light transmittance and approximately 1/3 in the phase shift amount, respectively.

From the above results, the phase shift mask blank of the present invention was excellent in acid resistance.

Specifically, the above Examples 2 to 7 and Comparative Example 2
The results of acid resistance in are as shown in FIG. 7 and FIG.
The sum of these results is as follows.

The optical characteristics such as the light transmittance and the phase shift amount (phase difference) of the phase shift masks obtained in Examples 2 to 7 are different from the optical characteristics such as the light transmittance and the phase difference of the phase shift mask blank. The change in the optical characteristics due to the sulfuric acid cleaning in the mask processing step was very small, the deviation from the set value was small, and the acid resistance was excellent. On the other hand, the optical characteristics such as the light transmittance and the phase difference of the phase shift mask obtained in Comparative Example 2 are greatly changed by the sulfuric acid cleaning in the mask processing step, the deviation from the set value is large, and the acid resistance is poor. Was.

The light transmittances of the phase shift masks obtained in Examples 2 to 7 were all 2 or more, indicating high values.

Lightfastness The nitrided molybdenum and silicon (MoSi) of the present invention
The light fastness of the blank N) was evaluated.

As a test method, the MoSiN blank was irradiated with a KrF excimer laser beam (wavelength: 248 nm) of 3.09 mJ / cm ² and 200 Hz (cumulative irradiation energy: 53.3 kJ / cm ² ). Phase shift (wavelength 248 nm), phase shift (wavelength 36
(At 5 nm) and the change in film thickness.

The results are shown in FIG. The KrF excimer laser is manufactured by Lambda Physics, Inc .:
200 cc of LPX was used.

As can be seen from FIG. 11, the MoS of the present invention
The iN blank had a light transmittance of 0.21%, a phase shift of -0.43 [deg.], and a film thickness of only 1 nm, and was very excellent in light resistance.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.

For example, instead of DC sputtering,
A thin film of the light translucent portion may be formed by RF sputtering. It should be noted that DC sputtering is more effective.

Also, instead of reactive sputtering, metal,
A thin film of the light semi-transmissive portion may be formed by sputtering using a target containing silicon and nitrogen. Note that reactive sputtering has relatively few discharges and therefore has less particles.

In the embodiment, other inert gas such as helium, neon, xenon, etc. may be used instead of Ar gas.

Further, in the embodiment, a metal such as Ta, W, Ti, Cr or the like may be used instead of Mo.

[0122]

As described above, in the phase shift mask of the present invention, the light semi-transmissive portion is formed of a thin film made of a substance mainly composed of nitrogen, metal and silicon, and each component in this thin film is formed. By specifying the content (atomic%) and ratio of, a semi-transmissive part with excellent film properties such as acid resistance, light resistance, conductivity, refractive index (film thickness), transmittance and etching selectivity is provided. In addition, optical characteristics (light transmittance and phase shift amount, etc.) are satisfied with high accuracy, and defects are small.

Since the phase shift mask blank of the present invention has the optimum film characteristics in consideration of the manufacturing process and the like, the phase shift mask blank satisfies the optical characteristics with high precision and has the phase having the light semi-transmission part with few defects. The shift mass can be manufactured easily and inexpensively with a high yield.

Further, in the present invention, by using a target having a specific composition, a phase shift mask blank having a light semi-transmissive portion having excellent film characteristics can be manufactured stably and without defects.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a transfer principle of a halftone type phase shift mask.

FIG. 2 is a partial sectional view showing a halftone type phase shift mask blank.

FIG. 3 is a diagram showing an ESCA analysis result of the light semi-transmissive film in Example 1.

FIG. 4 is a diagram showing an ESCA analysis result of a light semi-transmissive film (MoSiON).

FIG. 5 is a diagram showing film composition and film characteristics.

FIG. 6 is a diagram showing the wavelength dependence of light transmittance in Example 1.

FIG. 7 is a diagram showing film composition and film characteristics.

FIG. 8 is a diagram showing film composition and film characteristics.

FIG. 9 is a view showing acid resistance of the phase shift mask blank of the present invention.

FIG. 10 is a diagram showing the alkali resistance of the phase shift mask blank of the present invention.

FIG. 11 is a diagram showing light resistance of the phase shift mask blank of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Light transmission part 3 Light semi-transmission part 3a Light semi-transmission film

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-261370 (JP, A) JP-A-6-83034 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 1/00-1/16

Claims (10)

(57) [Claims] 1. A mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmitting portion that transmits light having an intensity substantially contributing to exposure.
A light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion so that light transmitted through the light semi-transmitting portion is shifted. By making the phase and the phase of the light transmitted through the light transmitting portion different, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other to improve the contrast at the boundary portion. A phase shift mask, wherein the light semi-transmissive portion is formed of a thin film made of a substance mainly composed of nitrogen, metal and silicon, and silicon as a constituent element of the material constituting the thin film is made of 34 to 6
A phase shift mask containing 0 atomic% . 2. A mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by: a light transmitting portion that transmits light having an intensity substantially contributing to exposure;
A light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion so that light transmitted through the light semi-transmitting portion is shifted. By making the phase and the phase of the light transmitted through the light transmitting portion different, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other to improve the contrast at the boundary portion. A phase shift mask, wherein the light semi-transmissive portion is formed of a thin film made of a material having nitrogen, metal and silicon as main components, and the metal is made of molybdenum or titanium, and the thin film is made of Silicon, which is a constituent element of the material,
Phase shift mask which comprises child%. 3. A mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmitting portion that transmits light having an intensity substantially contributing to exposure.
A light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion so that light transmitted through the light semi-transmitting portion is shifted. By making the phase and the phase of the light transmitted through the light transmitting portion different, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other to improve the contrast at the boundary portion. A phase shift mask, wherein the light semi-transmissive portion is formed of a thin film made of a substance mainly composed of nitrogen, metal and silicon, and the metal is made of molybdenum or titanium, and a substrate on which the thin film is formed Wherein the sheet resistance is 1 kΩ / □ to 1.5 MΩ / □. 4. The phase shift mask according to claim 3, wherein
And the sheet resistance of the substrate is 1 kΩ / □ to 1.0 MΩ.
/ □, a phase shift mask. 5. The phase shift mask according to claim 3, wherein
And the sheet resistance of the substrate is 1 kΩ / □ to 0.5 MΩ.
/ □, a phase shift mask. 6. The phase shift mask according to claim 1, wherein the ratio of the atomic% of metal and silicon, which are constituent elements of the material constituting the thin film, is metal: silicon =
1: 1.5 to 6.0 phase shift mask. 7. A mask for exposing a fine pattern, wherein a mask pattern formed on a transparent substrate is formed by a light transmitting portion that transmits light having an intensity substantially contributing to exposure.
A light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and shifts the phase of light transmitted through the light semi-transmitting portion so that light transmitted through the light semi-transmitting portion is shifted. By making the phase and the phase of the light transmitted through the light transmitting portion different, the light passing near the boundary between the light semi-transmitting portion and the light transmitting portion cancels each other to improve the contrast at the boundary portion. A phase shift mask, wherein the light semi-transmissive portion is formed of a thin film made of a material having nitrogen, metal and silicon as main components, and the metal is made of molybdenum or titanium, and the thin film is made of 30 to 60 atomic% of nitrogen
A phase shift mask characterized by including . 8. The phase shift mask according to any of claims 1 to 7, comprising 30 to 60 atomic% of components serving the silicon material constituting the thin film, serving as a component of the material constituting the thin film 30-60 atomic% of nitrogen
It is intended to include, and a phase shift mask according to claim <br/> that nitrogen is contained more than silicon. 9. A mask for exposing a fine pattern.
The mask pattern to be formed on the transparent substrate
A light transmitting portion that transmits light having an intensity that contributes to the exposure,
Translucent light that transmits light of an intensity that does not substantially contribute to exposure
And the light transmitted through the light semi-transmission part.
The phase of the light transmitted through the semi-transmissive portion is shifted by shifting the phase.
And the phase of the light transmitted through the light transmitting portion may be different.
With this, the vicinity of the boundary between the light semi-transmission part and the light transmission part
As the transmitted light cancels each other,
A phase shift mask for improving contrast, wherein the light semi-transmissive portion is mainly composed of nitrogen, metal and silicon.
It is composed of a thin film made of the substance
The metal comprises molybdenum or titanium, and the thin film
Molybdenum or titanium as a component of the material constituting
A phase shift mass containing 8 to 18 atomic%.
H. 10. A phase shift mask blank used as a material for a phase shift mask according to claim 1, wherein a material mainly composed of nitrogen, metal and silicon is formed on a transparent substrate. A phase shift mask blank characterized by forming a thin film.