JPH1073913A - Sputter target, phase shift mask blank using this sputter target, and manufacture of phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase shift mask having a light semi-transmitting part excellent in film characteristics such as acidic resistance and transmissivity by containing silicon and a metal in a sputter target, and setting the composition of the sputter so as to contain silicon in a quantity larger than a stoichiometrically stable composition. SOLUTION: This sputter target contains silicon and a metal, and the composition of the sputter target is set so as to contain silicon in a quantity larger than a stoichiometrically stable composition. Thus, the extinction coefficient can be relatively easily minimized. A light semi-transmitting film 3a formed of a thin film of nitrided molybdenum and silicon is formed on the surface of a transparent base board 1 by use of this sputter target to provide a phase shift mask blank for KrF excimer laser, and the light semi-transmitting film 3a is patterned to provide a phase shift mask. The film formed by sputtering by use of such a sputter target is a thin film suitable as a light semi- transmitting part ensured in high transmissivity and acidic resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sputter target,
And a method of manufacturing a phase shift mask blank and a phase shift mask using the sputter target.

[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 (phase shift layer) in the above-described halftone type phase shift mask needs to have required optimum values for both the light transmittance and the amount of phase shift. .

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 oxynitridation increases, the surface of the sputter target (especially in the non-erosion area) increases.
Oxide accumulates on the surface and the discharge becomes unstable, so that the controllability of the transmittance and the film thickness is deteriorated, and there is also a problem that defects and the like are easily generated in the blank.

Furthermore, since the relationship between the composition of the sputter target and the composition of the sputtering gas and the film properties such as acid resistance and transmittance has not been elucidated, a phase shift mask excellent in film properties such as acid resistance and transmittance has been obtained. I couldn't.

The present invention has been made in view of the above-described problems, and is intended to provide a phase shift mask and a phase shift mask blank having a light semi-transmissive portion having excellent film characteristics such as acid resistance and transmittance. A first object is to provide a sputter target used in a film forming step of the light semi-transmissive portion.

Another object of the present invention is to provide a phase shift mask blank having a light semi-transmissive portion having excellent film characteristics and a method for manufacturing a phase shift mask by a sputtering method using the above sputtering target. I do.

[0018]

In order to achieve the above object, a sputter target according to the present invention is a sputter target used for forming a light translucent portion (phase shift layer) of a phase shift mask, The sputter target contains silicon and a metal, and the composition of the sputter target is larger than the stoichiometrically stable composition.

The sputter target of the present invention is the sputter target of the present invention, wherein the content of silicon in the sputter target is 70 to 95 mol.
%, Or the metal is at least one metal selected from molybdenum, titanium, tantalum, tungsten, and chromium.

Further, the method for manufacturing a phase shift mask blank of the present invention uses a sputter target containing silicon and metal, and containing a larger amount of silicon than a stoichiometrically stable composition, in an atmosphere containing nitrogen. By sputtering, a light semi-transmissive film (phase shift film) containing nitrogen, metal and silicon is formed.

Further, according to the method of manufacturing a phase shift mask blank of the present invention, in the manufacturing method of the present invention, the silicon content in the sputter target is 70 to 95.
mol%, the metal is at least one metal selected from molybdenum, titanium, tantalum, tungsten, and chromium, and the method of manufacturing a phase shift mask blank in which the wavelength of the exposure light source used is 248 nm. A configuration in which the amount of nitrogen contained in the sputtering atmosphere is 25 to 100%, or a method of manufacturing a phase shift mask blank in which the wavelength of the exposure light source used is 365 nm. The amount is 38 to 48%.

Further, a method of manufacturing a phase shift mask of the present invention is configured to manufacture using a phase shift mask blank obtained by the above-described manufacturing method of the present invention.

[0023]

The sputter target of the present invention contains silicon and a metal, and the composition of the sputter target has a composition in which the amount of silicon is larger than that of a stoichiometrically stable composition, so that it can be relatively easily formed. The extinction coefficient (K) can be reduced, and a film formed by a sputtering method using this sputter target is suitable as a light translucent portion (phase shift layer) ensuring high transmittance, acid resistance, and the like. Thin film.

In consideration of the discharge stability at the time of film formation, it is specifically preferable that the content of silicon in the sputter target is 70 to 95 mol%. This is because the sputter target has a silicon content of 95 m
ol%, in DC sputtering,
Since it becomes difficult to apply a voltage on the surface of the sputter target (erosion portion) (it becomes difficult for electricity to pass), the discharge becomes unstable (difficult), and if the silicon content in the sputter target is less than 70 mol%, This is because not only cannot a thin film constituting the light transmissive portion having high transmittance be obtained, but also a film having good acid resistance cannot be obtained. In addition, 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.

The relative density of the target material (the ratio of the specific gravity of the target material actually used when the calculated value of the specific gravity of the target material of the present invention is 100) is 90% or more, preferably 95% or more. More preferably, it is preferably 98% or more. By increasing the relative density of the target material, the number of pores (cavities) of the target is reduced, so that the discharge is stabilized and generation of particles due to abnormal discharge can be prevented. If the relative density of the target material is less than 90%, it is not preferable because particles are more likely to be present in the film obtained by film formation, and pinholes are generated in the film due to the particles.

The metal in the sputter target includes molybdenum, titanium, tantalum, tungsten, chromium and the like.

In the method of manufacturing a phase shift mask blank of the present invention, a light translucent film (phase) containing nitrogen, metal, and silicon is sputtered using the above-described sputter target of the present invention in an atmosphere containing nitrogen. Shift film), the amount of nitrogen contained in the sputtering atmosphere is determined by adjusting the wavelength of the exposure light source used to 24.
25 to 100% when the wavelength is 8 nm, and 38 to 48% when the wavelength of the exposure light source to be used is 365 nm.
By doing so, it is possible to obtain a thin film constituting a light transmissive portion with high transmittance, and to inspect the optical characteristics and pattern of the phase shift mask blank and the phase shift mask obtained by patterning this phase shift mask blank. When performing the inspection, the inspection can be performed easily and reliably. This is because the wavelength of the exposure light source used is 248 nm, 3
If the thickness is 65 nm and the amount of nitrogen contained in the sputtering atmosphere is less than 25% and 38%, respectively, a phase shift layer with high transmittance cannot be obtained, and the wavelength 3
If the amount of nitrogen exceeds 65% at 65 nm,
It is not preferable because the transmittance of the phase shift layer becomes too high, which makes it difficult to inspect the optical characteristics and pattern of the phase shift layer with a transmission type inspection device.

Further, according to the method for manufacturing a phase shift mask blank of the present invention, by specifying the composition of a sputter target, the phase shift mask blank having a light semi-transmissive portion having excellent film characteristics can be obtained. It can be manufactured stably and without defects.

[0029]

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

Examples 1 to 4 and Comparative Examples 1 to 2 Production of Blanks A light semi-transmissive film 3a made of a thin film of nitrided molybdenum and silicon (MoSiN) is formed on the surface of a transparent substrate 1, and a KrF excimer laser (wavelength 248 nm), and the light transflective film was patterned to obtain a phase shift mask (FIG. 2).

Specifically, a mixed target in which the ratio of molybdenum (Mo) to silicon (Si: silicon) was changed [(Mo: Si = 30: 70 mol%) (Example 1)
(Mo: Si = 20: 80 mol%) (Example 2),
(Mo: Si = 10: 90 mol%) (Example 3),
(Mo: Si = 5: 95 mol%) (Example 4), (M
o: Si = 33: 67 mol% = stoichiometrically stable composition) (Comparative Example 1), (Mo: Si = 4: 96 mol%)
(Comparative Example 2)], using a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 10%, N ₂ O: 9).
0%, pressure: 1.5 × 10 ⁻³ Torr), a thin film of molybdenum and silicon (MoSiN) nitrided on a transparent substrate by reactive sputtering (film thickness 855 nm,
925 nm, 969 nm, 1008 nm, 795 nm,
1025 nm) to obtain a phase shift mask blank.

Mask Processing A resist film was formed on a thin film 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.

FIG. 3 shows the transmittance, acid resistance, and discharge stability when the composition of the target material was changed.

The light transmittance is measured by a spectrophotometer (Hitachi, Ltd.)
The product was measured using a model 340) and the acid resistance was evaluated as “O” when no change was observed after immersion in hot concentrated sulfuric acid (H ₂ SO ₄ ) at 120 ° C. for 2 hours. Those within the permissible range were marked with “Δ”, and those with large changes outside the permissible range were marked with “x”.

Evaluation As can be seen from FIG. 3, the composition of the target material was formed using a sputter target having a composition in which the amount of silicon was larger than that of a stoichiometrically stable composition (Mo: Si = 33: 67 mol%). When the film is formed (Examples 1 to 4), the light transmittance,
A light translucent part having excellent acid resistance can be obtained. On the other hand, when a film was formed using a sputter target having a stoichiometrically stable composition (Mo: Si = 33: 67 mol%) (Comparative Example 1)
In addition, not only a high transmittance was not obtained, but also the acid resistance was poor. When the silicon content exceeds 95 mol% (Comparative Example 2), the discharge during film formation becomes unstable,
A light semi-transmissive part with good film quality could not be obtained.

Examples 5 to 8 and Comparative Examples 3 to 4 A light semi-transmissive film composed of a thin film of nitrided molybdenum and silicon (MoSiN) was formed on the surface of a transparent substrate.
A phase shift mask blank for lines (wavelength 365 nm) was obtained, and the light translucent film was patterned to obtain a phase shift mask.

More specifically, a mixed target (Mo: Si = Si: Si) of molybdenum (Mo) and silicon (Si: silicon)
20:80 mol%), the nitrogen content in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ )
38% (Example 5), 40% (Example 6), 45% (Example 7), 48% (Example 8), 37% (Comparative Example 3),
The pressure was changed to 50% (Comparative Example 4) and the pressure was changed to 1.
Adjusted in the range of 2 to 1.7 × 10 ⁻³ Torr, the same as in the above embodiment except that a thin film of nitrided molybdenum and silicon (MoSiN) was formed on a transparent substrate by reactive sputtering. Thus, a phase shift mask blank and a phase shift mask were obtained. The thickness of the light transmissive portion was adjusted such that the phase shift amount was 180 °.

FIG. 4 shows the light transmittance when the nitrogen content in the mixed gas atmosphere is changed. The light transmittance was measured using a spectrophotometer (Model 340, manufactured by Hitachi, Ltd.).

Evaluation As can be seen from FIG. 4, Mo: Si = 20: 80 mol.
% Mixed target, i-line (wavelength 365 n
When manufacturing the phase shift mask blank and the phase shift mask for m), if the amount of nitrogen in the mixed gas atmosphere at the time of film formation is smaller than 38%, a phase shift layer with high transmittance cannot be obtained. When the amount of nitrogen is more than 48%, the transmittance of the phase shift layer becomes too high, and when the optical characteristics and pattern of the phase shift layer are inspected by a transmission type inspection machine. , It is not preferable because the inspection becomes difficult.

Examples 9 to 11 and Comparative Example 5 A light semi-transmissive film made of a thin film of nitrided molybdenum and silicon (MoSiN) was formed on the surface of a transparent substrate.
A phase shift mask blank for an rF excimer laser (wavelength: 248 nm) was obtained, and the light translucent film was patterned to obtain a phase shift mask.

More specifically, a mixed target (Mo: Si = Si) of molybdenum (Mo) and silicon (Si: silicon)
20:80 mol%), the nitrogen content in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ )
80% (Example 9), 90% (Example 10), 100%
Example 11 was changed to 79% (Comparative Example 5), and the pressure was adjusted in the range of 1.2 to 1.7 × 10 ⁻³ Torr, and nitrided on a transparent substrate by reactive sputtering. A phase shift mask blank and a phase shift mask were obtained in the same manner as in the above example, except that a thin film of molybdenum and silicon (MoSiN) was formed. The thickness of the light transmissive portion was adjusted such that the phase shift amount was 180 °.

FIG. 5 shows the light transmittance when the nitrogen content in the mixed gas atmosphere is changed. The light transmittance was measured using a spectrophotometer (Model 340, manufactured by Hitachi, Ltd.).

Evaluation As can be seen from FIG. 5, Mo: Si = 20: 80 mol
% Of a mixed gas atmosphere during film formation when manufacturing a phase shift mask blank and a phase shift mask for a KrF excimer laser (wavelength: 248 nm) using a mixed target of 80% In this case, a phase shift layer having a high transmittance cannot be obtained, which is not preferable.

The relative densities of the target materials having the compositions of Examples 1 to 11 are all 90% or more, and it is possible that pinholes are not generated in the film due to the low relative density of the target materials. Did not.

Examples 12 and 13 and Comparative Example 6 A light semi-transmissive film composed of a thin film of nitrided molybdenum and silicon (MoSiN) was formed on the surface of a transparent substrate, and K
A phase shift mask blank for an rF excimer laser (wavelength: 248 nm) was obtained, and the light translucent film was patterned to obtain a phase shift mask.

More specifically, a mixed target (Mo: Si = Si) of molybdenum (Mo) and silicon (Si: silicon)
5:95 mol%), and the content of nitrogen in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ )
25% (Example 12), 35% (Example 13), 24%
(Comparative Example 6) while changing the pressure to 1.2 to
The phase was adjusted in the range of 1.7 × 10 ⁻³ Torr, and the phase was adjusted in the same manner as in the above example except that a thin film of molybdenum and silicon (MoSiN) was formed on a transparent substrate by reactive sputtering. A shift mask blank and a phase shift mask were obtained. The thickness of the light transmissive portion was adjusted such that the phase shift amount was 180 °.

FIG. 6 shows the light transmittance when the content of nitrogen in the mixed gas atmosphere is changed. The light transmittance was measured using a spectrophotometer (Model 340, manufactured by Hitachi, Ltd.).

Evaluation As shown in FIG. 6, Mo: Si = 5: 95 mol%
When manufacturing a phase shift mask blank and a phase shift mask for a KrF excimer laser (wavelength 248 nm) using the mixed target described above, when the amount of nitrogen occupying in the mixed gas atmosphere during film formation is less than 25% Is not preferable because a phase shift layer having a high transmittance cannot be obtained.

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, as reactive sputtering, D
A thin film of the light semi-transmissive portion can be formed by C sputtering, RF sputtering, or the like. It should be noted that DC sputtering is more effective.

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).

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

Further, although only the nitrided metal and silicon thin films are described in the examples, the target of the present invention is an oxidized metal and silicon thin film as described in JP-A-6-332152. It is also useful for forming a thin film such as an oxynitrided metal or silicon thin film.

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

In the embodiment, an example is shown in which the target of the present invention is used as a target for forming a light semi-transmissive portion of a phase shift mask. However, the present invention is not limited to this. It can also be used as a target for forming a light shielding film, a low reflection film, and the like in a mask or the like.

[0056]

As described above, according to the present invention, it is possible to provide a phase shift mask and a phase shift mask blank having a light semi-transmissive portion having excellent film characteristics such as acid resistance and transmittance.

Further, a light semi-transmissive portion having excellent film stability and excellent film quality can be obtained.

Further, when inspecting the optical characteristics and patterns of the phase shift mask blank and the phase shift mask, the inspection can be performed easily and reliably.

[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 the relationship between the composition of a target material and transmittance, acid resistance, and discharge stability.

FIG. 4 is a diagram showing a relationship between a composition of a target material, a nitrogen content in a mixed gas atmosphere, and transmittance.

FIG. 5 is a diagram showing the relationship between the composition of a target material, the nitrogen content in a mixed gas atmosphere, and transmittance.

FIG. 6 is a diagram showing the relationship between the composition of a target material, the nitrogen content in a mixed gas atmosphere, and the transmittance.

[Explanation of symbols]

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

Claims (9)

[Claims] 1. A sputter target used for forming a light transmissive portion of a phase shift mask, wherein the sputter target contains silicon and a metal, and the composition of the sputter target is stoichiometric. A sputter target characterized by having a larger amount of silicon than a stable composition. 2. The sputter target according to claim 1, wherein the content of silicon in the sputter target is 70 to 95 mol%. 3. The sputter target according to claim 1, wherein the metal is at least one metal selected from molybdenum, titanium, tantalum, tungsten, and chromium. 4. Use of a sputter target containing silicon and a metal and containing a larger amount of silicon than a stoichiometrically stable composition, and performing sputtering in an atmosphere containing nitrogen to obtain nitrogen, metal and silicon. A method for producing a phase shift mask blank, comprising forming a light translucent film containing: 5. The method according to claim 4, wherein the content of silicon in the sputter target is 70 to 95 mol%. 6. The method for manufacturing a phase shift mask blank according to claim 4, wherein the metal is at least one metal selected from molybdenum, titanium, tantalum, tungsten, and chromium. 7. A method for manufacturing a phase shift mask blank in which the wavelength of an exposure light source used is 248 nm, wherein the amount of nitrogen contained in a sputtering atmosphere is 25 to
7. The method for manufacturing a phase shift mask blank according to claim 4, wherein the phase shift mask blank is set to 100%. 8. A method for manufacturing a phase shift mask blank in which the wavelength of an exposure light source used is 365 nm, wherein the amount of nitrogen contained in a sputtering atmosphere is 38 to
7. The method for producing a phase shift mask blank according to claim 4, wherein the ratio is set to 48%. 9. A method for manufacturing a phase shift mask, comprising using the phase shift mask blank obtained by the method for manufacturing a phase shift mask blank according to claim 4.