JP6165577B2 - Mask blank manufacturing method and transfer mask manufacturing method - Google Patents

Description

  The present invention relates to a mask blank manufacturing method and a transfer mask manufacturing method.

  The mask blank has an inorganic thin film formed by sputtering on the translucent glass substrate surface. Many of the inorganic thin films are compound layers, and many of the compound layers are formed by sputtering.

As the target used for sputtering, a material corresponding to the composition of the thin film to be formed is selected. The target is generally manufactured by a sintering method obtained by preparing and sintering a powder material, a melting method obtained by preparing a material, vacuum melting and casting, and the like. The melting method is excellent in that the surface of the obtained target is smooth and fine grain boundaries cannot be formed. However, the melting method has drawbacks in that it cannot be applied to materials made of substances that do not dissolve in each other or a material having a high melting point, and that it requires a large facility for vacuum melting and casting. The sintering method is excellent in that it can be easily manufactured without using a large-scale facility, and a target made of a composite material made of substances that do not melt together can be manufactured. As a target for forming a metal silicide-based thin film of a mask blank, a sintered compact target obtained by mixing and sintering metal, silicon, and metal silicide powder having a stable composition is used.
However, the sintering method is not universal. This is because even when a powder containing a plurality of substances and being chemically stable to each other is subjected to pressure sintering, an interface is formed between the particles of the powder.
Since the interface between the powder particles is a brittle point, when high-energy charged particles collide during sputtering, relatively large particles may fall off the target due to the impact. When relatively large particles adhere to the film formation surface, they become foreign matters. Since the mask blank is a substrate for forming a fine pattern on the surface of a semiconductor or the like, it is not allowed to attach fine foreign matters. For this reason, the technique for suppressing generation | occurrence | production of the foreign material resulting from a target is examined.

For example, a technique described in Patent Literature 1 can be cited as a technique for reducing the foreign matter caused by the target. The technique of Patent Document 1 is a technique for suppressing the generation of foreign matter by optimizing the state of a target that is a source of foreign matter.
In Patent Document 1, when a target composed of silicon-rich metal silicide is manufactured by mixing and sintering a metal silicide powder that is stoichiometrically stable and a silicon powder, the average particle size and the particle size of the metal silicide and silicon are produced. By adjusting the distribution and the surface roughness of the target after sintering, the target is in a state where foreign matter is hardly generated.

As another example, a technique related to the target described in Patent Document 2 can be cited.
The technique described in Patent Document 2 is a technique in which the hardness of the target surface is increased so that the material itself does not fall off from the target.

JP 2005-200688 A JP 2010-20335 A

The demand for defect quality of mask blanks is increasing year by year. This is due to the miniaturization of the semiconductor integrated circuit, and the defect quality of the mask blank has become unacceptable even for extremely fine foreign matter defects of the order of 0.1 μm. Even when the target described in Patent Document 1 is used, foreign matter of the order of 0.1 μm is generated. Even the technique described in Patent Document 2 cannot be suppressed as in Patent Document 1.
Moreover, when forming a thin film by reactive sputtering, the surface of the target may be modified by reacting with a reactive gas near the surface. If charged particles, which are rare gas ions, strongly collide with the modified surface, the modified material will fall off the target surface.

The present inventors have studied a method that can suppress the generation of fine foreign matters caused by the target other than the modification of the target. The inventors have focused on efficiently suppressing the generation of foreign matter by indirectly controlling the energy of charged particles that collide with the target.
SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a mask blank manufacturing method and a transfer mask manufacturing method capable of manufacturing a mask blank with few defects due to foreign substances and excellent in thin film quality stability.

The main configuration for solving the above problems will be described below.
(Configuration 1)
The present invention relates to a method for manufacturing a transfer mask blank, and is characterized by a step of forming a thin film by a sputtering method.
In the step of forming the thin film, the sputtered particles (sputtering particles) fly from the target provided in the vacuum chamber toward the film formation surface of the substrate, and film formation is performed by sputtering.
In the configuration of the present invention, the target is made of a sintered body containing metal silicide, and the rare gas component contained in the sputtering gas (sputtering atmosphere gas) is neon, helium, or a mixed gas of neon and helium. Features. In the present invention, noble gas components having a molecular weight higher than that of argon, such as argon, krypton, and xenon, are not included in the sputtering gas.

A target molded by the powder sintering method has a grain boundary between powder particles. The grain boundary becomes a brittle point. When high-energy charged particles collide with the grain boundaries during sputtering, the impact causes the cluster-like lump to be peeled off from the target, and if the peeled material adheres to the film-forming surface of the substrate, it becomes a foreign substance defect.
In the configuration of the present invention, a rare gas composed of helium and / or neon is used as the material before cationization of charged particles. Since helium and neon are lightweight elements, little energy is applied even when the charged ionized particles collide with the target. Even in the case of a brittle metal silicide-based sintered target, an excessive impact is not applied to the target, so that the separation of the target material can be suppressed while flying the sputtering particles.
Moreover, according to the structure of this invention, since the impact which a charged particle applies to a target at the time of sputtering is few, the particle | grains which fly are also hard to become a cluster form. Since the flying particles are not clustered, the thin film formed on the substrate has an effect of becoming dense. Furthermore, since the flying particles do not form a cluster, the reactive gas existing near the substrate reacts easily with the flying particles.

  Therefore, according to the manufacturing method of this configuration, it is possible to manufacture a mask blank having a thin film with high density, high quality, and few foreign matter defects.

(Configuration 2)
The present invention is preferably applied to a mask blank manufacturing method in which sputtering is performed using a sintered target composed of a mixed powder of a metal silicide powder having a stoichiometrically stable ratio of metal to silicon and a silicon powder. Can do.
That is, the present invention is suitable for a mask blank manufacturing method having a silicon-rich metal silicide layer and a compound layer such as a silicon-rich metal silicide oxide or nitride rather than the stoichiometry.
A stoichiometrically stable mixture of metal silicide and silicon tends to form a clear grain boundary between them even by high temperature sintering. When such a target is used, the foreign substance consisting of silicon and the foreign substance consisting of metal silicide starting from the above-mentioned grain boundary are likely to be a foreign substance derived from the target and easily cause a defect in the mask blank.
According to the method of the present invention, the destruction of the target surface due to the collision of charged particles can be suppressed, so that even if a sintered target as described above is used, it is possible to manufacture a mask blank with extremely few foreign matter defects derived from the target. it can.

(Configuration 3)
The manufacturing method of the present invention is also suitable for a mask blank manufacturing method in which a thin film is formed by reactive sputtering.
Reactive sputtering in which a rare gas and a reactive gas are introduced into a chamber can deposit a reaction product of a target material and a reactive gas on a substrate, so that a thin film such as an oxide or nitride is formed. This is a useful technique. On the other hand, when the reactive gas comes into contact with the target, there is a problem that the target surface reacts with the reactive gas to cause a composition change. If the composition is different between the surface of the target and the inside (bulk), the surface portion is easily peeled off, which causes foreign matter.
According to this configuration, even when reactive sputtering that tends to cause a composition change on the target surface is performed, the charged particles that collide with the target surface are lightweight, so there is little impact on the target surface. Accordingly, since the target material whose composition has changed from the target surface at the stage of thin film formation is difficult to peel off, a mask blank with few foreign matter defects can be manufactured.

(Configuration 4)
In this manufacturing method, it is preferable that neon is contained in the rare gas.
When the rare gas is composed of only helium, the kinetic energy of the plasma applied to the target is too low even when the charged particles collide with the target, so that the efficiency of the sputtering particles flying from the target is deteriorated. Moreover, when it is comprised only with helium, high energy is required for ionization of helium.
Neon is heavier than helium, has a lower ionization energy, and has a feature that it is more easily charged than helium. Further, since neon is approximately five times the weight of helium, it is possible to secure the kinetic energy required for the sputtering particles to fly.

(Configuration 5)
This manufacturing method can be preferably applied even when the target is made of molybdenum silicide and the silicon element ratio in the target is larger than 2 with respect to molybdenum 1.
Molybdenum silicide has a stoichiometrically stable element ratio of molybdenum: silicon = 1: 2. It is difficult to introduce silicon exceeding the stoichiometric ratio into the structure of molybdenum silicide, and the sputtering target of molybdenum silicide having a large amount of silicon component has an excessive amount of MoSi ₂ powder and silicon having a stoichiometrically stable structure. What sintered and mixed the silicon powder for quantity is used. Since MoSi ₂ and Si cannot be bonded, the particles between the two particles cannot be fused and a grain boundary is formed. Since it is difficult to fully integrate even if pressure-sintering powder mixed with Si powder in addition to MoSi ₂ powder, when charged particles collide with strong impact during sputtering, the above-mentioned grain boundary will trigger the material from the target. May leave. According to the present invention, even if a silicon-rich molybdenum silicide target having a silicon component larger than the constituent element ratio of molybdenum silicide having a stable molybdenum ratio is used, the charged particles are lightweight and do not collide strongly with the target. The state in which the target material is difficult to peel off is maintained.

(Configuration 6)
This manufacturing method can be preferably applied also when the element ratio of silicon contained in the target made of molybdenum silicide is 6 or more and less than 25 with respect to molybdenum 1.

(Configuration 7)
Another configuration described in this specification is a method for manufacturing a transfer mask.
This configuration is characterized in that a transfer pattern is formed by patterning the thin film of the mask blank obtained by the method for manufacturing a mask blank according to any one of Configurations 1 to 6.

  According to this manufacturing method, it is possible to manufacture a mask blank having a good quality thin film with few defects due to adhesion of foreign substances.

It is explanatory drawing explaining the apparatus used in the Example.

Before describing the embodiments of the present invention, characteristic technical forms will be described below.
(Form 1)
The mask blank manufactured in the example is a binary mask blank having a light shielding film containing a molybdenum silicide compound.
In the embodiment, an example in which a target made of molybdenum silicide is used is shown, but the present invention can also be applied to a target made of another sintered body of transition metal silicide. Examples of other transition metals include tantalum, hafnium, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, and rhodium.
In the embodiments, a binary mask having a molybdenum silicide-based light shielding film having a two-layer structure is taken as an example. However, the present invention can also be applied to a single-layer structure including a metal silicide compound or a structure having three or more layers. .

(Form 2)
The mask blank manufactured in the example is a half-type phase shift mask blank having a light semi-transmissive film containing a molybdenum silicide compound.
In the embodiment, an example in which a target made of molybdenum silicide is used is shown, but the present invention can also be applied to a target made of another sintered body of transition metal silicide. Examples of other transition metals include tantalum, hafnium, tungsten, titanium, hafnium, nickel, vanadium, zirconium, niobium, palladium, ruthenium, and rhodium.

(Form 3)
The sputtering apparatus used in the examples is provided with a substrate holder below, and an evacuation means for adjusting the pressure in the vacuum chamber is also provided on the lower side of the vacuum chamber.
When the exhaust unit is located below, the gas in the atmosphere around the deposition target substrate located below can be made cleaner. If there are few rare gas elements around the deposition substrate, the frequency with which the sputtered particles collide with the rare gas element and scatter or decelerate due to the collision can be reduced, so that the sputtered particles are dense on the substrate. accumulate. That is, a dense thin film can be formed by disposing the exhaust means below.

(Form 4)
The layers formed in the examples include a layer formed by reactive sputtering. In the embodiment, oxygen and nitrogen are used as reactive gases. Other gases can also be used as the reactive gas. For example, in addition to nitrogen, oxygen, NO ₂ , NO, O ₂ , CO, CO ₂ , CH _{4 and the} like can be mentioned. By using these reactive gases and, for example, a molybdenum silicide target, a thin film having a composition of MoSiO, MoSiN, MoSiON, MoSiCO, MoSiCN, and MoSiCON can be formed.
By changing the element ratio contained in the composition of the thin film, the extinction coefficient and refractive index of the thin film change. The element ratio of the thin film can be changed by adjusting the amount of reactive gas introduced. Therefore, by performing reactive sputtering, a thin film having an extinction coefficient and a refractive index corresponding to the application can be formed.

Note that, as in the above-described form 3, the sputtering apparatus used in the examples has an exhaust unit provided below. The reactive gas exemplified above has a heavier specific gravity than neon and helium, and thus tends to be distributed downward. Distributing the reactive gas downward is preferable because sputtering particles can be reacted efficiently with the reactive gas before reaching the substrate.
In addition, since the reactive gas is heavier than the rare gas and easily flows toward the exhaust means, the reactive gas hardly flows into the target side above. As a result, the composition change of the target surface is suppressed. Accordingly, since the target material whose composition has changed from the target surface at the stage of thin film formation is difficult to peel off, a mask blank with fewer foreign object defects can be manufactured.

(Form 5)
In this manufacturing method, the substrate is placed horizontally so that the film formation surface faces upward, and the target is placed so that the target surface faces the film formation surface of the substrate without completely overlapping the substrate in the vertical direction. It is installed in an inclined state at the top.
When the substrate and the target are located at positions that overlap in the vertical direction, foreign matter generated from the target surface falls on the substrate surface and is easily fixed. According to this configuration, since the foreign matter generated on the target surface is unlikely to fall on the substrate, a mask blank with fewer foreign matter defects can be manufactured.

  Examples will be shown below, and the method for producing a mask blank of the present invention will be specifically described. Of course, the present invention is not limited to the following examples.

The reactive sputtering apparatus 1 used with the manufacturing method of an Example is demonstrated using FIG.
FIG. 1 is a schematic view of a reactive sputtering apparatus 1 used in the manufacturing method of the embodiment.
A rough configuration of the reactive sputtering apparatus 1 (hereinafter referred to as a sputtering apparatus 1) includes a vacuum chamber 2, a target holder 24 that holds the target 20, a substrate holder 32 that holds the substrate 30, and an exhaust that reduces the pressure in the chamber. Means 54 and a sputtering gas supply 46 for introducing a sputtering gas into the vacuum chamber 2. Each component will be described sequentially.

Inside the vacuum chamber 2, a target holder 24 is installed obliquely above, and the target 20 is mounted on the target holder 24 via a backing plate 22. The mounted target 20 is positioned obliquely above the substrate 30. The surface of the target 20 is diagonally opposed to the substrate 30 at an angle of 15 °.
A target holder 24 that holds the target 20 is connected to a DC power source 26. When a voltage is applied to the target 20 from the DC power source 26, discharge starts, and particles knocked out of the target 20 fly toward the substrate.
In this embodiment, a DC power source is used as a power source, but an RF power source may be used.

The target holder 24 is installed in a state insulated from the vacuum chamber 2. The target 20 has conductivity, and functions as an electrode (cathode) when power is applied from the power supply 26. The target holder 24 is provided with a cooler (not shown) so as not to overheat due to an increase in target temperature accompanying plasma generation.
Further, the backing plate 22 between the target 20 and the target holder 24 is made of metal and plays a role of fixing the target 20 to the target holder 24.
The material of the target 24 is selected according to the thin film to be formed. In the manufacturing example described later, a target made of molybdenum and silicon is used, but the present invention is not limited to this.

  The vacuum chamber 2 has a shield 31 inside so that sputtering particles are not deposited on the inner wall of the vacuum chamber 2. The shield 31 is provided in a region that does not inhibit the flying particles from the target 20 from being deposited on the substrate 30. The shield 31 is removable from the vacuum chamber 2 and can be replaced periodically. The space formed by the shield 31 is not a closed space, but a gap is formed at an important point. The pressure in the vacuum chamber 2 can be controlled by a pressure measuring device outside the shield 31, and the gas in the vacuum chamber 2 can be exhausted by the exhaust means 54.

A substrate holder 32 for placing the substrate 30 is provided in the space formed by the shield 31. In the vicinity of the substrate holder 32, a piping 44 for introducing a sputtering gas is provided.
The substrate holder 32 is provided with a member (not shown) for fixing the substrate 30 on the substrate holding surface so that the substrate 30 does not move from the holding surface of the substrate holder 32.
The substrate holder 32 is connected to the drive mechanism 36 via the shaft member 34.
The drive mechanism controls the height adjustment of the substrate holder 32 and the horizontal rotation of the substrate holder 32. The distance between the substrate 30 and the target 20 during sputtering can be adjusted by adjusting the height of the drive mechanism 36. Further, the driving mechanism 36 horizontally rotates the substrate holder 32 at an appropriate speed, whereby the film thickness of the thin film formed on the substrate 30 can be made uniform.

The exhaust port 50 is provided on the wall surface below the vacuum chamber 2. The exhaust port 50 is connected to a turbo molecular pump (exhaust means) 54 via a main valve 52.
In the present embodiment, an example in which one exhaust port 50 is provided is illustrated, but other exhaust means may be provided in addition to this.

The piping 44 for introducing the sputtering gas is installed so that the sputtering gas introduction port 42 at the front end is at a height near the surface of the substrate 30.
The pipe 44 is connected to a sputtering gas supply source 46. The sputtering gas supply source 46 has a cylinder of a reactive gas and a rare gas. Although not shown, the sputtering gas supply path is provided with a flow controller for controlling the flow rates of the reactive gas and the rare gas, a valve for switching the gas flow, a filter, and the like.
In the embodiment, an apparatus having one sputtering gas introduction system is shown, but two gas introduction systems, that is, a system for introducing a reactive gas and a system for introducing a rare gas may be used.

<Example 1: Production of two-layer structure light-shielding film_binary mask blank>
In this example, a binary mask blank having a molybdenum silicide two-layer light shielding film was manufactured by using the sputtering apparatus 1.
In this embodiment, a synthetic quartz glass substrate having a size of 6 inches square and a thickness of 0.25 inches is used as a light-transmitting substrate, and two layers of molybdenum nitride silicide having different degrees of nitridation are formed on the light-transmitting substrate as a light shielding film. A layer was formed.

(First layer deposition)
First, a mixed target of Mo and Si (Mo: Si = 13 at%: 87 at%) was placed on the target holder of the sputtering apparatus. The target is manufactured by compression sintering by mixing MoSi ₂ powder having a particle size of 0.5 μm or less and Si powder at a mass ratio of MoSi ₂ : Si = 15: 13.
Next, the translucent substrate was placed on the substrate holder.
Next, neon (Ne), which is a rare gas, was introduced from the sputtering gas inlet, and the inside of the vacuum chamber was made a rare gas atmosphere. Then, after the inside of the vacuum chamber was stabilized in a high vacuum state and the target was conditioned, nitrogen (N ₂ ) as a reactive gas was introduced. The introduction ratio of the sputtering gas was 50:50.
Sputtering conditions were as follows: the pressure in the vacuum chamber was 0.2 Pa, the power of the DC power source was 5 kW, and a 47 nm thick molybdenum nitride silicide layer (Mo: 10 at%, Si: 66 at%, N: 24 at%) was formed.

(Second layer deposition)
Next, a second molybdenum nitride silicide layer was formed using the same target as the first layer. First, a mixed gas of Ne and He (gas flow ratio Ne: He = 40: 10) was introduced into the vacuum chamber, and the inside of the vacuum chamber was made a rare gas atmosphere. Then, the inside of the vacuum chamber was stabilized in a high vacuum state, and after conditioning the target, nitrogen gas was introduced. The gas flow rate ratio is Ne: He: N ₂ = 40: 10: 50.
Subsequently, reactive sputtering was performed by applying power to the target. The sputtering conditions are a pressure in the vacuum chamber of 0.2 Pa and a DC power supply of 5 kW. A film made of molybdenum, silicon, and nitrogen (Mo: 7.5 at%, Si: 50 at%, N: 42 at%) was formed to a thickness of 13 nm.
As described above, a light shielding film having a two-layer structure having a thickness of 60 nm was formed.

<Example 2: Production of three-layer structure light-shielding film_binary mask blank>
In this example, a binary mask blank having a light-shielding film having a three-layer structure of molybdenum silicide was manufactured by using the sputtering apparatus 1.
In this example, a synthetic quartz glass substrate having a size of 6 inches square and a thickness of 0.25 inches is used as a light transmitting substrate, and a MoSiON film (back antireflection layer), MoSi is used as a light shielding film on the light transmitting substrate. A film (light shielding layer) and a MoSiON film (surface antireflection layer) were formed.

(First layer: formation of a back surface antireflection layer)
First, a mixed target of Mo and Si (Mo: Si = 21 at%: 79 at%) was placed on the target holder of the sputtering apparatus. The target is manufactured by compression sintering by mixing MoSi ₂ powder having a particle size of 0.5 μm or less and Si powder at a mass ratio of approximately MoSi ₂ : Si = 3: 1. A translucent substrate was placed on the substrate holder.
Next, a mixed gas (gas flow ratio Ne: He = 30: 20) of neon (Ne) and helium (He) was introduced from the sputtering gas inlet, and the inside of the vacuum chamber was made a rare gas atmosphere. The pressure in the vacuum chamber was reduced to 0.2 Pa.
After conditioning the target, a mixed gas (O ₂ : N ₂ = 4: 46) of oxygen (O ₂ ) and nitrogen (N ₂ ), which is a reactive gas, was introduced from the sputtering gas inlet.
Thereafter, reactive sputtering was performed to form a back surface antireflection layer. The sputtering conditions were as follows: the pressure in the vacuum chamber was 0.2 Pa, the power of the DC power source was 5 kW, and the film of molybdenum, silicon, oxygen, and nitrogen with a film thickness of 7 nm (Mo: 12.9 at%, Si: 36.3 at%) , O: 3.1 at%, N: 47.7 at%).

(Second layer: formation of light shielding layer)
Next, a second light shielding layer was formed using the same target as the first layer.
First, Ne was introduced into the vacuum chamber, the inside of the chamber was replaced with Ne gas, and the inside of the vacuum chamber was changed to a rare gas atmosphere. Then, after the inside of the vacuum chamber was stabilized in a high vacuum state and the target was conditioned, a light shielding layer was formed by sputtering. The sputtering conditions were such that the gas pressure was 0.3 Pa, the power of the DC power source was 4.0 kW, and a film of 30 nm thick molybdenum and silicon (Mo: 21.0 at%, Si: 79 at%) was formed.

(3rd layer: formation of a surface antireflection layer)
Next, a third surface antireflection layer was formed in a vacuum chamber (specification is the same as the first and second layers) different from the first and second layers.
First, a mixed target of Mo and Si (Mo: Si = 4 at%: 96 at%) was placed on the target holder. The target is manufactured by compression sintering by mixing a MoSi ₂ powder having a particle size of 0.5 μm or less and a Si powder at a mass ratio of approximately MoSi ₂ : Si = 1: 4.
Next, the substrate formed up to the second layer was placed on a substrate holder.
Next, a mixed gas of Ne and He which is a rare gas (gas flow ratio Ne: He = 40: 10) was introduced from the sputtering gas inlet, and the inside of the vacuum chamber was made a rare gas atmosphere. Then, after the inside of the vacuum chamber is stabilized in a high vacuum state and the target is conditioned, a mixed gas of O ₂ and N ₂ that are reactive gases (gas flow ratio O ₂ : N ₂ = 12) is introduced from the sputtering gas inlet. : 25) was introduced.
Thereafter, reactive sputtering was performed to form a surface antireflection layer. The sputtering conditions were as follows: the pressure in the vacuum chamber was 0.1 Pa, the power of the DC power source was 5 kW, and the film of molybdenum, silicon, oxygen, and nitrogen with a film thickness of 15 nm (Mo: 1.6 at%, Si: 38.8 at%) , O: 18.8 at%, N: 41.1 at%).
The total thickness of the light shielding film was 52 nm. The optical density (OD) of the light-shielding film was 3.0 at a wavelength of 193 nm of ArF excimer laser exposure light.

<Example 3: Production of halftone phase shift mask blank>
In this example, a halftone phase shift mask blank having a molybdenum silicide-based light semi-transmissive film was manufactured using the sputtering apparatus 1.
In this example, a synthetic quartz glass substrate having a size of 6 inches square and a thickness of 0.25 inches was used as a light transmissive substrate, and a MoSiN film was formed as a light semi-transmissive film on the light transmissive substrate.

A mixed target of Mo and Si (Mo: Si = 10 at%: 90 at%) was placed on the target holder of the sputtering apparatus. The target is manufactured by compression sintering by mixing MoSi ₂ powder having a particle size of 0.5 μm or less and Si powder at a mass ratio of approximately MoSi ₂ : Si = 44: 56.
Next, the translucent substrate was placed on the substrate holder.
Next, neon (Ne), which is a rare gas, was introduced from the sputtering gas inlet, and the inside of the vacuum chamber was made a rare gas atmosphere, and then stabilized in a high vacuum state and the target was conditioned.
After conditioning, nitrogen (N ₂ ) gas, which is a reactive gas, was introduced from the sputtering gas inlet.
Thereafter, reactive sputtering was performed to form a back surface antireflection layer. Sputtering conditions were as follows: the sputtering gas flow ratio is Ne: N ₂ = 51: 49, the pressure in the vacuum chamber is 0.3 Pa, the power of the DC power supply is 5 kW, the phase difference is 180 degrees, and the wavelength is 193 nm. A molybdenum nitride silicide film having a designed transmittance of 6.0% for the excimer laser was formed. The film thickness was 69 nm.

<Comparative Example 1: Production of binary mask blank>
In Example 1, a mask blank was manufactured in the same manner as in Example 1 except that neon was changed to argon (Ar) and the power applied to the target during sputtering was set to 3.0 kW.

<Comparative Example 2: Three-layer structure light-shielding film_Production of binary mask blank>
In Example 2, neon and helium are changed to argon (Ar), and the power of the DC power source applied to the target during sputtering is 3.0 kW for the first layer, 2.0 kW for the second layer, and 3.0 kW for the third layer. A mask blank was manufactured in the same manner as in Example 2 except that.

<Comparative Example 3: Production of Halftone Phase Shift Mask Blank>
In Example 3, a mixed gas of argon and helium (Ar: He = 5: 46) was introduced instead of the rare gas component neon of the sputtering gas, and the power of the DC power source was changed to 3.0 kW. A mask blank was produced in the same manner as in No. 3.

<Evaluation 1: Foreign object defect evaluation>
Thin films were formed on 100 substrates, respectively, by the production methods of Examples 1 to 3 and Comparative Examples 1 to 3. Defect inspection was performed on these substrates, and elemental analysis was performed on foreign matters having a size of 0.2 μm or more using SEM-EDX. From the mask blanks manufactured in Examples 1 to 3, the average number of foreign matter in which the characteristic X-ray spectra of molybdenum and silicon derived from the target material were detected was less than 1.0 per substrate. . On the other hand, the mask blanks manufactured by the methods of Comparative Examples 1 to 3 had an average of two or more foreign substances from which characteristic X-ray spectra of molybdenum and silicon derived from the target material were detected per substrate. The results are shown in Table 1.

<Evaluation 2: Target surface evaluation>
Next, 100 mask blanks were manufactured for each of the manufacturing methods of Examples 1 to 3 and Comparative Examples 1 to 3, and then the surface roughness of the used target was measured. The results are shown in Table 2. In Table 2, ◯ indicates that the surface roughness Ra is less than 0.5 μm, Δ indicates that the surface roughness Ra is 0.5 μm or more and less than 1 μm, and × indicates that the surface roughness Ra is 1 μm or more. All targets had a surface roughness Ra before use of about 0.06 μm.

The targets used in Examples 1 to 3 were found to have a low surface roughness of the target surface even after 100 films were formed. This is presumably because the kinetic energy of the rare gas cations is small and the collision energy when colliding with the target is small, so that the sputtered particles gradually flew from the surface of the target. As a result, it is considered that reactive sputtering could be performed while maintaining the smoothness of the target. If the surface is smooth, the number of atoms exposed on the surface is kept small, so that the reaction with the reactive gas is also effectively suppressed.
In Examples 1 to 3, the rare gas components are He and Ne, and both gases are lighter than the reactive gases O ₂ and N ₂ . Therefore, the reactive gas is unlikely to contact the target provided above. Since the target surface is in a state where it is difficult to react with the reactive gas, it is considered that the composition change of the target surface could be prevented.

On the other hand, as for the thin film formed by the method of the comparative example, the targets other than the target for forming the third layer of the comparative example 2 had a surface roughness Ra of 1 μm or more. The Ar cation contained in the rare gas has high kinetic energy and excellent flight efficiency of the sputtered particles, but also has a large damage when hitting the target surface. For this reason, it is considered that the roughening of the target surface has progressed. When the target surface is rough, the number of atoms exposed on the surface increases, so that the reaction with the reactive gas easily proceeds.
In the comparative example, since the rare gas argon is heavier than the reactive gas, the reactive gas is likely to diffuse toward the upper side of the chamber. In the manufacturing method of the comparative example, the reaction between the reactive gas and the target surface is more likely to occur than in the examples, and as a result, the progress of the roughening of the target surface and the generation of foreign matters are considered to have occurred.

<Evaluation 3: Manufacturing evaluation of transfer mask>
Next, a halftone phase shift mask was prepared using the phase shift mask blank manufactured in Examples and Comparative Examples.

  First, after scrub cleaning the phase shift mask blanks manufactured in Examples and Comparative Examples, a chemically amplified positive resist film for electron beam lithography (PRL009 manufactured by Fuji Film Electronics Materials Co., Ltd.) is used as a resist film on the mask blank. Formed. The resist film was formed by spin coating using a spinner (rotary coating apparatus).

Next, a desired pattern was drawn on the resist film formed on the mask blank using an electron beam drawing apparatus, and then developed with a predetermined developer to form a resist pattern.
Next, the halftone phase shift film was etched using the resist pattern as a mask to form a phase shift pattern. A mixed gas of SF ₆ and He was used as the dry etching gas.
Thereafter, the resist was peeled off, immersed in sulfuric acid at 100 ° C. and 98% sulfuric acid for 15 minutes and washed with sulfuric acid, and then rinsed with pure water or the like to produce a phase shift mask.

  As a result, no pattern defect was found in the transfer mask patterned with the mask blanks manufactured in Examples 1 to 3, but the transfer mask patterned with the mask blanks manufactured in Comparative Examples 1 to 3 had a pattern. Defects were confirmed. This is presumed to be a defect due to foreign particles adhering during film formation that fall out in the cleaning process.

As mentioned above, although embodiment and the Example of this invention were described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, in the above-described embodiment, the sputtering apparatus including one vacuum chamber has been described as an example. However, the sputtering apparatus including a plurality of vacuum chambers may be used. Moreover, although the example which uses the same target was described when using the target with the same composition, each layer can also be formed with a separate target.
Specific applications of the thin film include, for example, a light semi-transmissive film for a halftone phase shift mask, a light shielding film for a binary mask, a reflective film, an absorber film and a protective film for a reflective mask, an etching stopper layer, a hard mask Various uses such as a mask (etching mask layer) are exemplified.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2 .... Vacuum chamber 20 ... Target 22 ... Backing plate 24 ... Target holder 26 ... DC power supply 31 ... Shield 32 ... Substrate holder 34 ... Shaft material 40 ... Substrate 42 ... Sputtering gas inlet 44・ ・ Piping 46 ・ ・ Sputtering gas supply source 50 ・ ・ Exhaust port

Claims (7)

A mask blank manufacturing method,
A process of forming a thin film by flying sputtering particles from a target provided in a vacuum chamber toward a film formation surface of a substrate;
In the step of forming the thin film,
The target consists of a sintered body containing metal silicide,
Mask blank manufacturing method, which is a noble gas component Gane on and a mixed gas of helium containing sputtering gas.   2. The mask blank manufacturing method according to claim 1, wherein the target is a target obtained by sintering a mixed powder of a metal silicide powder and a silicon powder in which the ratio of metal to silicon is stoichiometrically stable. The method for producing a mask blank according to claim 1, wherein in the step of forming the thin film, a reactive gas is included in the sputtering gas. The method for manufacturing a mask blank according to claim 3, wherein each of the rare gas components is lighter than the reactive gas . The target is molybdenum silicide, the element ratio of silicon in the target is equal to or greater than 2 with respect to molybdenum 1, the production method of the mask blank according to any one of claims 1 to 4. The mask blank manufacturing method according to claim 5, wherein an element ratio of silicon in the target is 6 or more and 25 or less with respect to molybdenum 1.   A method for producing a transfer mask, comprising patterning the thin film of the mask blank obtained by the method for producing a mask blank according to claim 1 to form a transfer pattern.

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