WO2022004456A1 - Mask blank manufacturing method, mask blank, photomask manufacturing method, and photomask - Google Patents

Abstract

The purpose of the present invention is to solve problems of accuracy deterioration in the shape of a formed pattern which is caused by an increase in pattern thickness resulting from increase in thickness of an oxide layer formed on a surface layer of a mask layer including molybdenum when a laser is applied thereonto in an exposure step, and occurrence of a case where a mask layer of desired film characteristics cannot be obtained if a sputter target of high specific resistance is used, and to further increase the etching speed of the mask layer in a pattern forming step.　A mask blank manufacturing method according to the present invention involves forming a mask layer containing silicon on a transparent substrate through sputtering using a target that includes a dopant for reducing specific resistance (S12).

Description

Manufacturing method of mask blanks, mask blanks, manufacturing method of photomask, and photomask

The present invention relates to a method for manufacturing a mask blank, a mask blank, a method for manufacturing a photomask, and a photomask. In particular, the present invention relates to techniques suitable for use in photomask blanks with a mask layer containing silicon.
This application claims priority based on Japanese Patent Application No. 2020-113378 filed in Japan on June 30, 2020, the contents of which are incorporated herein by reference.

Photomask blanks (mask blanks) are used to form FPDs (flat panel displays) and photomasks used in photolithography processes in semiconductor device manufacturing and the like. The mask blanks have a structure in which a mask layer is laminated on one main surface of a transparent substrate such as a glass substrate.

In the manufacture of mask blanks, a film that is a mask layer having predetermined optical characteristics, such as a light-shielding layer, is formed on a transparent substrate. The mask layer may be a single layer or a plurality of layers. A photomask is manufactured by forming a resist pattern on a mask layer, using this resist pattern as a mask, and selectively etching and removing the mask layer to form a predetermined mask pattern.

As the mask layer formed on the mask blanks, a film containing silicon, a mask layer composed of a film containing silicon and molybdenum, and the like are known (Patent Documents 1 to 3).
Further, in recent years, there has been a demand for mask blanks used in a photolithography process capable of high-definition patterning.

Japanese Patent Application Laid-Open No. 2015-11246 Japanese Patent No. 6418035 Gazette Japanese Patent No. 6579219

However, if the mask layer contains molybdenum, the film thickness of the oxide layer formed on the surface layer becomes thicker and the pattern becomes thicker when the laser is applied in the exposure process, that is, the accuracy of the shape of the formed pattern becomes higher. There was a problem of deterioration.
Further, in order to realize high-definition patterning, there is a demand to increase the etching rate of the mask layer in the pattern forming step.

In addition, when sputtering is used to form the mask layer, a target containing silicon, which is a film forming material, is used, but the high resistivity hinders plasma generation and has desired film characteristics. There was a problem that the mask layer may not be obtained.
Furthermore, when RF sputtering is used with a high resistance target when forming the mask layer, the plasma generation state fluctuates due to the decrease in the anode, and the mask layer having the desired film characteristics cannot be obtained. There was a problem.

The present invention has been made in view of the above circumstances, and achieves the following objects.
1. 1. To be able to provide mask blanks used in a photolithography process capable of high-definition patterning.
2. 2. To be able to provide mask blanks capable of accurate patterning.
3. 3. To increase the etching rate in the mask layer.
4. To enable the stabilization of plasma and the formation of a mask layer having desired film characteristics.

The method for manufacturing a mask blank according to one aspect of the present invention is a method for manufacturing a mask blank in which a mask layer containing silicon is laminated on a transparent substrate, and the mask layer is made by using a target containing a dopant that reduces resistivity. Is formed by sputtering.
In the method for producing mask blanks according to one aspect of the present invention, the specific resistance of the target may be 0.001 Ωcm to 0.1 Ωcm.
In the method for producing mask blanks according to one aspect of the present invention, the dopant may be one or more selected from the group consisting of boron, phosphorus, and arsenic.
In the method for producing mask blanks according to one aspect of the present invention, in the target, the dopant is boron and the dopant concentration is within the range of ^{1 × 10 18} atm / cm ³ to 1 × 10 ²⁰ atm / cm ^3. May be.
In the method for producing mask blanks according to one aspect of the present invention, the target may be a silicon single crystal or a silicon polycrystal.
In the method for producing mask blanks according to one aspect of the present invention, the atmospheric gas used for the sputtering may contain nitrogen.
In the method for producing mask blanks according to one aspect of the present invention, the atmospheric gas used for the sputtering may contain oxygen.
In the method for producing mask blanks according to one aspect of the present invention, the sputtering may be DC sputtering.
The mask blanks according to one aspect of the present invention are mask blanks manufactured by the above-mentioned method for producing mask blanks, in which the mask layer contains boron as the dopant and the dopant concentration of the mask layer is 1 × 10. It is within the range of ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ^3.
In the mask blanks according to one aspect of the present invention, the etching rate of the mask layer in dry etching is 1.05 to 1.5 times the etching rate of the layer formed by using a non-doped target. It is also good.
In the mask blanks according to one aspect of the present invention, the mask layer may contain nitrogen or oxygen.
In the mask blanks according to one aspect of the present invention, the composition ratio of nitrogen or oxygen in the mask layer may change in the film thickness direction.
In the mask blanks according to one aspect of the present invention, the mask layer may include a phase shift layer.
The method for manufacturing a photomask according to one aspect of the present invention is a method for manufacturing a photomask from the above-mentioned mask blanks, in which a resist pattern is formed on the surface of the mask layer (resist pattern forming step), and the resist pattern is formed. Is used as a mask to form a mask pattern by patterning the mask layer (mask pattern forming step), and when forming the mask pattern (in the mask pattern forming step), the mask layer is dry-etched. ..
The photomask according to one aspect of the present invention is manufactured by the above-mentioned photomask manufacturing method.

The method for manufacturing a mask blank according to one aspect of the present invention is a method for manufacturing a mask blank in which a mask layer containing silicon is laminated on a transparent substrate, and the mask layer is made by using a target containing a dopant that reduces resistivity. Is formed by sputtering.
As a result, when the mask layer is formed by sputtering, the specific resistance at the target is reduced, so that the electric power for forming the plasma is stabilized, the plasma in the film-forming state is stabilized, and the mask layer is formed. Is possible. As a result, it is possible to prevent the occurrence of an abnormal discharge phenomenon such as an arc during sputtering, reduce the characteristics of the thin film and the factors that cause defects, and improve the film forming characteristics. Further, the dopant can be contained in the mask layer, and the film characteristics in the mask layer can be improved.
Here, the film characteristics of the mask layer that can be improved are specifically the endpoints for determining the end of etching by the light emission monitor as the selection ratio of the mask layer to the substrate increases as the etching rate increases. Judgment becomes easy. Therefore, it means that the depth at which the transparent substrate is excessively etched can be minimized. By improving the film characteristics in this way, it is possible to provide mask blanks capable of improving the accuracy of the shape of the mask layer at the time of pattern formation and realizing high-definition patterning.

In the method for producing mask blanks according to one aspect of the present invention, the specific resistance of the target may be 0.001 Ωcm to 0.1 Ωcm.
As a result, the electric power for forming the plasma is stabilized, the plasma in the film-forming state is stabilized, and the mask layer can be formed. As a result, the film forming characteristics can be improved.

In the method for producing mask blanks according to one aspect of the present invention, the dopant may be one or more selected from the group consisting of boron, phosphorus, and arsenic.
This makes it possible to realize the above-mentioned resistivity range in the target, stabilize the power for forming the plasma, stabilize the plasma in the film-forming state, and form the mask layer. As a result, it is possible to prevent the occurrence of an abnormal discharge phenomenon such as an arc during sputtering, reduce the characteristics of the thin film and the factors that cause defects, and improve the film forming characteristics.
Here, when boron is used as the dopant, it is possible to form a p-type semiconductor, and when phosphorus or arsenic is used as the dopant, it is possible to form an n-type semiconductor, which is a target. It is possible to reduce the specific resistance.

In the method for producing mask blanks according to one aspect of the present invention, in the target, the dopant is boron and the dopant concentration is within the range of ^{1 × 10 18} atm / cm ³ to 1 × 10 ²⁰ atm / cm ^3. May be.
As a result, the range of the specific resistance of the target described above is realized, the power for forming the plasma is stabilized, the plasma in the film-forming state is stabilized, and the mask layer can be formed. As a result, it is possible to prevent the occurrence of an abnormal discharge phenomenon such as an arc during sputtering, reduce the characteristics of the thin film and the factors that cause defects, and improve the film forming characteristics. In particular, by reducing the specific resistance of the target, it is possible to reduce the discharge impedance, which makes it possible to stabilize the plasma.
Here, plasma stabilization specifically means that the reproducibility of the cathode current value is high when the cathode current value during film formation fluctuates and when film formation is performed multiple times under the same conditions. That is, it means that the film thickness reproducibility is high when the film is formed by time control.
Further, it is possible to make the film film uniform in the film-formed mask layer and the film characteristics at a plurality of different positions on the surface of the film-formed mask layer, and reduce the CD distribution when the wafer is exposed. ..
Further, it is possible to improve the dry etching rate in the formed mask layer, thereby improving the cross-sectional shape.

In the method for producing mask blanks according to one aspect of the present invention, the target may be a silicon single crystal or a silicon polycrystal.
As a result, the uniformity of the dopant content in the target can be maintained, the uniformity of the dopant concentration can be maintained even in the atmosphere where plasma is generated, and the uniformity of the dopant concentration in the film-formed mask layer can be maintained. can.
The target can be formed by the FZ method, the CZ method or the cast growth method.

In the method for producing mask blanks according to one aspect of the present invention, the atmospheric gas used for the sputtering may contain nitrogen.
As a result, a nitrided silicon film such as SiN or SiON can be formed as a mask layer. Alternatively, a silicon film can be formed as a part of the mask layer.

In the method for producing mask blanks according to one aspect of the present invention, the atmospheric gas used for the sputtering may contain oxygen.
As a result, an oxidized silicon film such as SiON or SiO can be formed as a mask layer. Alternatively, a silicon film can be formed as a part of the mask layer.

In the method for producing mask blanks according to one aspect of the present invention, the sputtering may be DC sputtering.
As a result, the reproducibility of the film thickness, the film characteristics, and the characteristic distribution can be improved as compared with the case where the mask layer is formed by RF sputtering.

The mask blanks according to one aspect of the present invention are mask blanks manufactured by the above-mentioned method for producing mask blanks, in which the mask layer contains boron as the dopant and the dopant concentration of the mask layer is 1 × 10. It is within the range of ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ^3.
As a result, the etching rate for the mask layer can be increased, and the etching time at the time of pattern formation for the mask layer can be reduced. As a result, the selection ratio of the mask layer with respect to the transparent substrate is increased, and it becomes easy to determine the endpoint for determining the end of etching by the light emission monitor. Therefore, the depth at which the transparent substrate is excessively etched can be minimized. Further, since side etching on the mask layer can be suppressed, the cross-sectional shape can be further improved.

In the mask blanks according to one aspect of the present invention, the etching rate of the mask layer in dry etching is 1.05 to 1.5 times the etching rate of the layer formed by using a non-doped target. It is also good.
As a result, the etching time is shortened due to the faster etching rate, the shape accuracy in patterning is improved, and even higher-definition patterning is performed, as compared with the mask layer formed by using a silicon target containing no dopant. Can be realized.

In the mask blanks according to one aspect of the present invention, the mask layer may contain nitrogen or oxygen.
As a result, a nitrided or oxidized silicon film such as SiN, SiON, and SiO can be formed as a mask layer. Alternatively, a silicon film can be formed as part of the mask layer. As a result, it is possible to obtain mask blanks having predetermined optical characteristics such as controlled transmittance and low reflectance.

In the mask blanks according to one aspect of the present invention, the composition ratio of nitrogen or oxygen in the mask layer may change in the film thickness direction.
As a result, the fluctuations in the transmittance and the reflectance with respect to the wavelength of the transmitted light are small, and the fluctuations in the etching rate at the layer interface become gentle. Therefore, mask blanks having a good cross-sectional shape can be obtained.

In the mask blanks according to one aspect of the present invention, the mask layer may include a phase shift layer.
This makes it possible to obtain mask blanks capable of manufacturing a phase shift mask capable of high-definition patterning.

The method for manufacturing a photomask according to one aspect of the present invention is a method for manufacturing a photomask from the above-mentioned mask blanks, in which a resist pattern is formed on the surface of the mask layer (resist pattern forming step), and the resist pattern is formed. Is used as a mask to form a mask pattern by patterning the mask layer (mask pattern forming step), and when forming the mask pattern (in the mask pattern forming step), the mask layer is dry-etched. ..
As a result, the selection ratio of the mask layer to the transparent substrate increases as the etching rate increases, and it becomes easy to determine the endpoint by the light emission monitor for determining the end of etching. Therefore, the depth at which the transparent substrate is excessively etched can be minimized. Further, the resist layer can be made thin, and the working time required for the resist pattern forming step can be shortened. The etching rate for the mask layer can be increased to reduce the etching time during pattern formation for the mask layer. Damage to the resist layer can be suppressed and the accuracy of the shape in etching can be maintained. It is possible to manufacture a photomask that can be applied to high-definition patterning.

The photomask according to one aspect of the present invention is manufactured by the above-mentioned photomask manufacturing method. This makes it possible to realize high-definition patterning.

According to the present invention, it is possible to provide mask blanks capable of producing a phase shift mask applicable to high-definition patterning.

It is a flowchart which shows the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is a schematic diagram which shows the film-forming apparatus in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is a schematic diagram which shows the vacuum chamber of the film forming apparatus in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is a schematic diagram which shows the vacuum chamber of the film forming apparatus in the manufacturing method of the mask blanks which concerns on embodiment of this invention. It is a flowchart which shows the manufacturing method of the photomask using the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the photomask using the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the photomask using the mask blanks which concerns on embodiment of this invention. It is sectional drawing for demonstrating the process in the manufacturing method of the photomask using the mask blanks which concerns on embodiment of this invention. It is a graph which shows the mask blanks which concerns on embodiment of this invention. It is an image which shows the mask blanks which concerns on embodiment of this invention. It is an image which shows the mask blanks which concerns on embodiment of this invention.

Hereinafter, embodiments of a mask blank, a phase shift mask (photomask), and a method for manufacturing the same according to the embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing a method for manufacturing mask blanks in the present embodiment. 2 to 5 are cross-sectional views for explaining a process in the method for manufacturing a mask blank in the present embodiment. In FIGS. 1 to 5, reference numerals 10A and 10B are mask blanks.

The mask blanks 10B according to the present embodiment are used for light having a wavelength of 200 nm or less, particularly exposure light of ArF excimer laser light (wavelength 193 nm) used in photolithography using a phase shift mask.
Alternatively, the mask blanks 10B according to the present embodiment are used as a phase shift mask (photomask) used in the range where the wavelength of the exposure light is in the range of about 248 nm to 436 nm.
As shown in FIG. 5, the mask blanks 10B according to the present embodiment are a glass substrate (transparent substrate) 11 and a mask layer (phase shift layer 12, antireflection) formed on the glass substrate 11 and having predetermined optical characteristics. It is composed of a layer 13) and a resist layer 15 formed on the mask layer.

The mask layer has a phase shift layer 12 formed on the glass substrate 11 and an antireflection layer 13 formed on the phase shift layer 12. That is, the antireflection layer 13 is provided at a position farther from the glass substrate 11 than the phase shift layer 12.
The phase shift layer 12 and the antireflection layer 13 have a refractive index, an extinction coefficient, a transmittance, a reflectance, a film thickness, etc. set to predetermined values as optical characteristics required for a photomask, and the phase shift is performed. It constitutes a mask layer that is a film.

As a configuration of the mask blanks 10B according to the present embodiment, a resist layer (photoresist layer) 15 is formed in advance on the mask layer in which the phase shift layer 12 and the antireflection layer 13 are laminated, as shown in FIG. A filmed configuration can also be adopted. As the mask blanks 10B according to the present embodiment, a configuration in which the antireflection layer 13 is not laminated can be adopted.

In the mask blanks 10B according to the present embodiment, in addition to the mask layer composed of the phase shift layer 12 and the antireflection layer 13, an adhesion layer, a chemical resistant layer, a protective layer, a light shielding layer, an etching stopper layer, and the like are laminated. The configuration may be adopted. As the material of the light-shielding layer, various materials can be applied, but it is preferable to use a film made of a chromium-based material that can also be used as an auxiliary film for etching processing.
Further, as shown in FIG. 5, a resist layer 15 may be formed on the above-mentioned laminated film.

As the glass substrate 11, a material having excellent transparency and optical isotropic properties is used, and for example, a quartz glass substrate can be used. The size of the glass substrate 11 is not particularly limited, and can be used as a substrate to be exposed using the mask (for example, a semiconductor, an LCD (liquid crystal display), a plasma display, an FPD substrate such as an organic EL (electroluminescence) display, etc.). It will be selected as appropriate.

In the present embodiment, as the glass substrate 11, a rectangular substrate having a side length of about 100 mm or a rectangular substrate having a side length of 250 mm or more can be applied. Further, a substrate having a thickness of 1 mm or less, a substrate having a thickness of several mm, and a substrate having a thickness of 10 mm or more can also be used.

Further, the flatness of the glass substrate 11 may be reduced by polishing the surface of the glass substrate 11. The flatness of the glass substrate 11 can be, for example, 5 μm or less. As a result, the depth of focus of the mask becomes deeper, and it becomes possible to greatly contribute to the formation of a fine and highly accurate pattern. Further, the flatness is preferably a small value such as 0.5 μm or less.

The phase shift layer 12 contains Si (silicon) as a main component. The phase shift layer 12 contains a predetermined dopant. The phase shift layer 12 can further include O (oxygen) and N (nitrogen), C (carbon).
As the type of dopant, a material (element) whose specific resistance is reduced by doping is selected in a state where the composition ratio (atm%) of Si, N, O or the like does not change. Specifically, one or more kinds of materials selected from the group consisting of B (boron), P (phosphorus), As (arsenic) and the like are adopted.

Further, in the phase shift layer 12, it is possible to adopt a structure in which the composition of the phase shift layer 12 changes in the thickness direction. In this case, as the configuration of the phase shift layer 12, one or 2 selected from the group consisting of Si alone and Si oxides, nitrides, carbides, oxide nitrides, carbides and oxide carbides. It is also possible to stack seeds or more.
As will be described later, the phase shift layer 12 has a thickness of the phase shift layer 12 and a composition ratio (atm%) of Si, N, O, etc. so that predetermined optical characteristics, etching rate, resistivity, etc. can be obtained. And the content rate (atm%) of the dopant are set.

The film thickness of the phase shift layer 12 is set by the optical characteristics required for the phase shift layer 12, and changes depending on the composition ratio of Si, N, O, or the like. The film thickness of the phase shift layer 12 can be 40 nm to 150 nm.

Further, the phase shift layer 12 may be composed of a single layer so as to satisfy the phase difference and the transmittance required for the phase shift film. For example, the phase shift layer 12 may include a layer having antireflection functionality in order to satisfy a predetermined surface reflectance. The phase shift layer 12 may be composed of multiple layers so as to satisfy the phase difference and transmittance required for the phase shift film in the entire phase shift layer 12.

Even when the phase shift layer 12 is composed of a single layer or when the phase shift layer 12 is composed of multiple layers, the composition ratio of each layer constituting the phase shift layer 12 is in the thickness direction. The phase shift layer 12 may be formed so as to continuously change to. Further, when the phase shift layer 12 is composed of multiple layers, the phase shift layer 12 may be formed by a combination of two or more layers selected from a layer having different constituent elements and a layer having the same constituent elements but different composition ratios. When the phase shift layer 12 is configured to have three or more multilayer films, the phase shift layer 12 may be formed by a combination including the same layer, as long as the same layers are not arranged so as to be adjacent to each other.

The phase shift layer 12 has a predetermined phase shift amount (phase difference) with respect to light having a wavelength of 200 nm or less, particularly exposure light of ArF excima laser light (wavelength 193 nm) used in photolithography using a phase shift mask. , A film that provides a predetermined permeability.

For example, it is preferable that the phase shift layer 12 is configured so that a portion made of a silicon-based material represented by SiN and SiON is provided in the thickness direction of the phase shift layer 12. As a result, it has a predetermined transmittance while ensuring a predetermined phase difference, and the chemical resistance is also improved.

Regarding the phase difference of the phase shift layer 12, the phase difference of the phase shift layer 12 is about 150 to 200 ° or about 180 ± 10 ° at the boundary between the region where the phase shift film exists and the region where the phase shift film does not exist. It may be 175 to 185 °.
For example, the transmittance of the phase shift layer 12 with respect to the exposure light is preferably in the range of 3% to 40%, and can be further in the range of 5% to 10%.

The thickness of the phase shift layer 12 is 40 nm to 70 nm and 50 nm to 65 nm. The phase shift layer 12 can reduce the three-dimensional effect as the thickness of the pattern of the mask layer increases. Further, the thickness of the phase shift layer 12 is set within a thickness range in which predetermined optical characteristics can be obtained for light having a wavelength of 200 nm or less. The thinner the phase shift layer 12, the easier it is to form a fine pattern.

The phase shift layer 12 is made of a silicon-based material as described above. Specifically, the phase shift layer 12 is SiN (silicon nitride) or SiON (silicon oxynitride). The phase shift layer 12 may contain other elements. In this case, the dopant as an impurity is contained in the phase shift layer 12.

By increasing the content of nitrogen contained in the phase shift layer 12 as much as possible, the transmittance is increased. The shortage of transmittance is supplemented by adding the minimum necessary oxygen to the phase shift layer 12, and by suppressing the oxygen content to a low level, the phase shift layer 12 can be made thinner. Therefore, the oxygen content in the silicon-based material is preferably 1/3 (composition ratio) or less, particularly 1/5 (composition ratio) or less of the nitrogen content.

The phase shift layer 12 may include a layer composed of Si and N. Further, the phase shift layer 12 may be formed of two or more layers having different composition ratios of Si and N. Further, the phase shift layer 12 may be formed so that the composition ratio of Si and N changes stepwise or continuously in the thickness direction of the phase shift layer 12.

The phase shift layer 12 contains a predetermined dopant, specifically, one selected from the group consisting of B (boron), P (phosphorus), As (arsenic) and the like.
The dopant contained in the phase shift layer 12 is boron, and the dopant concentration is in the range of 1 × 10 ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ³ .

The antireflection layer 13 contains Cr (chromium) and O (oxygen) as main components. Further, the phase shift layer 12 contains C (carbon) and N (nitrogen).
In this case, as the antireflection layer 13, one or two or more selected from the group consisting of oxides, nitrides, carbides, oxide nitrides, carbides and oxide carbides of Cr are laminated. It can also be configured. Further, in the antireflection layer 13, it is possible to adopt a structure in which the composition of the antireflection layer 13 changes in the thickness direction. As will be described later, the thickness of the antireflection layer 13 and the composition ratio of Cr, N, C, O, Si, etc. (atm%) so that predetermined adhesion (hydrophobicity) and predetermined optical characteristics can be obtained. Is set.

In the antireflection layer 13, the oxygen content (oxygen concentration) is set in the range of 6.7 atm% to 63.2 atm%, and the nitrogen content (nitrogen concentration) is set in the range of 4.6 atm% to 39.3 atm%. Can be set in.
By setting the nitrogen concentration and the oxygen concentration of the antireflection layer 13, it is possible to lower the values of the refractive index and the extinction coefficient of the antireflection layer 13. In particular, by increasing the oxygen concentration of the antireflection layer 13, the values of the refractive index and the extinction coefficient of the antireflection layer 13 are greatly reduced.

Further, by setting the film thickness of the antireflection layer 13 in the range of 30 nm to 60 nm, it is possible to obtain light having a wavelength of 200 nm or less, particularly ArF excimer laser light (wavelength 193 nm) used in photolithography using a phase shift mask. The reflectance in the exposure light can be reduced. The composition ratio of the materials constituting the antireflection layer 13 is not limited to the above values. The composition ratio described above shows an example of the present invention.

As shown in FIG. 1, the method for manufacturing a mask blank in the present embodiment includes a substrate preparation step S11, a mask layer forming step S12, and a resist forming step S13.

In the substrate preparation step S11 shown in FIG. 1, as shown in FIG. 2, for example, a glass substrate 11 made of quartz glass having a predetermined dimension is prepared.
In the substrate preparation step S11, the glass substrate 11 having excellent transparency and optical isotropic properties can be subjected to surface treatment such as polishing and HF cleaning.

In the mask layer forming step S12 shown in FIG. 1, a phase shift layer 12 and an antireflection layer 13 constituting the mask layer are sequentially formed on the glass substrate 11.

FIG. 6 is a schematic view showing a mask blank manufacturing apparatus according to the present embodiment.
In the mask layer forming step S12 in the present embodiment, the phase shift layer 12 and the antireflection layer 13 in the mask blanks 10A are manufactured by the manufacturing apparatus 100 shown in FIG.

The manufacturing apparatus 100 is a single-wafer DC sputtering apparatus.
As shown in FIG. 6, the manufacturing apparatus 100 includes a load chamber 101a, an unload chamber 101b, a transport chamber 101c connected to the load chamber 101a and the unload chamber 101b via a sealing mechanism, and a vacuum chamber (first). It has a vacuum chamber (first vacuum processing chamber) 102 and a vacuum chamber (second vacuum chamber, second vacuum processing chamber) 103. The vacuum chambers 102 and 103 have a film forming mechanism corresponding to two film forming processes. The vacuum chambers 102 and 103 are film forming chambers connected to the transport chamber 101c.

The transport chamber 101c includes a transport mechanism 101d that transports the glass substrate 11 carried in from the outside of the manufacturing apparatus 100 via the load chamber 101a to the vacuum tank 102 and the vacuum tank 103, and a rotary pump that reduces the pressure inside the transport chamber 101c. , Equipped with an exhaust mechanism such as a turbo molecular pump.

FIG. 7 is a schematic view showing a vacuum chamber in the mask blank manufacturing apparatus according to the present embodiment. FIG. 8 is a schematic view showing a vacuum chamber in the mask blank manufacturing apparatus according to the present embodiment.
The vacuum chamber 102 forms a material film for a mask blank by using a long slow sputtering (LTS) method.

As shown in FIG. 7, the vacuum chamber 102 has a film forming space 102K. The reaction gas introduction port 114a and the inert gas introduction port 114b are connected to the film forming space 102K. Further, a vacuum exhaust port 114d and a vacuum exhaust port 114e are connected to the film forming space 102K. Further, the vacuum chamber 102 has a cathode electrode (backing plate) 105A (105) and a substrate holder 107.

The board holder 107 is provided with a board holding mechanism. The substrate holder 107 is configured to hold the glass substrate 11 by facing the glass substrate 11 conveyed to the vacuum chamber 102 by the conveying mechanism 101d so as to be inclined toward the target 104A during film formation. A heater 111 is provided inside the substrate holder 107.

The film forming space 102K is provided with a target 104A that functions as the first-stage film forming mechanism of the two-stage film forming mechanism and supplies the film forming material.
The film forming mechanism of the vacuum chamber 102 includes a target 104A, a cathode electrode 105A for holding the target 104A, and a power supply 112A for applying a negative potential sputtering voltage to the cathode electrode 105A. The power supply 112A can apply a high frequency voltage or a DC voltage.

The surface of the cathode electrode 105A is provided with a flat plate-shaped target 104A that serves as a base material for the material film. The cathode electrode 105A is arranged along the dome-shaped ceiling 102a constituting the vacuum chamber 102. That is, the vacuum chamber 102 has a configuration in which the flat plate-shaped target 104A, which is the base material of the material film, is inclined and arranged in a single film formation space 102K.
In the vacuum chamber 102, the target 104A corresponding to the formation of the phase shift layer (mask layer) 12 is used.

In the vacuum chamber 102, the sputtering particles flying from the target 104A face the rotating (R: rotation direction) surface of the rectangular glass substrate 11. Tilt formed by the vertical direction T11 (dotted arrow) of the target 104A with respect to the sputtering surface 104As and the line segment TSA (TS: solid arrow) connecting the center of the sputtering surface 104As of the target 104A and the center of the surface to be processed of the glass substrate 11. The angle ΔA (Δ) is different from the vertical direction T11. Here, the line segment TSA (TS) is a so-called distance between the target 104A and the glass substrate 11.

A vacuum pump (not shown) is connected to the vacuum exhaust port 114d and the vacuum exhaust port 114e. On the back surface of the cathode electrode 105A, a magnet plate 109A (109) having magnets 110A (110) arranged in double concentric circles is provided. A sputtering power supply (power supply) 112A (112) is electrically connected to the cathode electrode 105A.

The film forming mechanism of the vacuum chamber 102 includes an inert gas introduction port 114b, a reaction gas introduction port 114a, a vacuum exhaust port 114d, and a vacuum exhaust port 114e. The inert gas introduction port 114b is connected to a gas introduction mechanism that introduces gas into the space near the cathode electrode 105A in the film formation space 102K. The reaction gas introduction port 114a introduces the reaction gas into the space near the glass substrate 11. The vacuum exhaust port 114d is connected to a high vacuum exhaust mechanism such as a turbo molecular pump that reduces the pressure in the film formation space 102K so that a high vacuum can be obtained. The vacuum exhaust port 114d exhausts the gas in the film formation space 102K from a position near the cathode electrode 105A. The vacuum exhaust port 114e exhausts the gas in the film formation space 102K from a position near the glass substrate 11.

Further, the vacuum chamber 103, which is a film forming chamber separate from the vacuum chamber 102, has a film forming mechanism for supplying the film forming material of the second stage among the two-stage film forming mechanisms. The vacuum chamber 103 has a mechanism substantially equivalent to the film forming mechanism of the vacuum chamber 102.
The vacuum chamber 103 has almost the same configuration as the vacuum chamber 102. The vacuum chamber 103 forms a material film for a mask blank by using a long slow sputtering (LTS) method.

As shown in FIG. 8, the vacuum chamber 103 has a film forming space 103K. The reaction gas introduction port 114a and the inert gas introduction port 114b are connected to the film forming space 103K. Further, a vacuum exhaust port 114d and a vacuum exhaust port 114e are connected to the film forming space 103K. Further, the vacuum chamber 103 has a cathode electrode (backing plate) 105B (105) and a substrate holder 107.

The board holder 107 is provided with a board holding mechanism. The substrate holder 107 is configured to hold the glass substrate 11 by facing the glass substrate 11 conveyed to the vacuum chamber 103 by the conveying mechanism 101d so as to be inclined toward the target 104B during film formation. A heater 111 is provided inside the substrate holder 107.

The film forming space 103K is provided with a target 104B that functions as the second-stage film forming mechanism of the two-stage film forming mechanism and supplies the film forming material.
The film forming mechanism of the vacuum chamber 103 includes a target 104B, a cathode electrode 105B for holding the target 104B, and a power supply 112B for applying a negative potential sputtering voltage to the cathode electrode 105B. The power supply 112B can apply a high frequency voltage or a DC voltage.

The surface of the cathode electrode 105B is provided with a flat plate-shaped target 104B which is a base material of the material film. The cathode electrode 105B is arranged along the dome-shaped ceiling 103a constituting the vacuum chamber 103. That is, the vacuum chamber 103 has a configuration in which the flat plate-shaped target 104B, which is the base material of the material film, is inclined and arranged in the single film forming space 103K.
In the vacuum chamber 103, the target 104B corresponding to the formation of the antireflection layer (mask layer) 13 is used.

In the vacuum chamber 103, the sputtering particles flying from the target 104B face the rotating (R: rotation direction) surface of the rectangular glass substrate 11. Tilt formed by the vertical direction T11 (dotted arrow) of the target 104B with respect to the sputtering surface 104Bs and the line segment TSB (TS: solid arrow) connecting the center of the sputtering surface 104Bs of the target 104B and the center of the surface to be processed of the glass substrate 11. The angle ΔB (Δ) is different from the vertical direction T11. Here, the line segment TSB (TS) is a so-called distance between the target 104B and the glass substrate 11.

A vacuum pump (not shown) is connected to the vacuum exhaust port 114d and the vacuum exhaust port 114e. On the back surface of the cathode electrode 105B, a magnet plate 109B (109) having double concentric magnets 110B (110) is provided. A sputtering power supply (power supply) 112B (112) is electrically connected to the cathode electrode 105B.

The film forming mechanism of the vacuum chamber 103 includes an inert gas introduction port 114b, a reaction gas introduction port 114a, a vacuum exhaust port 114d, and a vacuum exhaust port 114e. The inert gas introduction port 114b is connected to a gas introduction mechanism that introduces gas into the space near the cathode electrode 105B in the film formation space 103K. The reaction gas introduction port 114a introduces the reaction gas into the space near the glass substrate 11. The vacuum exhaust port 114d is connected to a high vacuum exhaust mechanism such as a turbo molecular pump that reduces the pressure in the film formation space 103K so that a high vacuum can be obtained. The vacuum exhaust port 114d exhausts the gas in the film formation space 103K from a position near the cathode electrode 105B. The vacuum exhaust port 114e exhausts the gas in the film forming space 103K from a position near the glass substrate 11.

The above-mentioned two-stage film forming mechanism is controlled so that the composition and film forming conditions necessary for forming the phase shift layer 12 and the antireflection layer 13 on the glass substrate 11 in order can be obtained.
In the present embodiment, the first-stage film forming mechanism in the vacuum chamber 102 corresponds to the film formation of the phase shift layer 12, and the second-stage film forming mechanism in the vacuum chamber 103 corresponds to the film formation of the antireflection layer 13. It corresponds.

Specifically, in the first-stage film forming mechanism in the vacuum chamber 102, the target 104A contains silicon and a predetermined dopant as a composition necessary for forming the phase shift layer 12 on the glass substrate 11. Is formed of.

Target 104A contains a dopant in silicon that reduces resistivity. The dopant at target 104A is boron. The dopant concentration in the target 104A is in the range of 1 × 10 ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ³ .
The specific resistance of the target 104A is 0.001 Ωcm to 0.1 Ωcm.

The resistivity at the target 104A is reduced by the addition of the dopant. As a result, the electric power for forming the plasma is stabilized, the plasma in the film-forming state is stabilized, and the phase shift layer 12 can be formed. As a result, it is possible to prevent the occurrence of an abnormal discharge phenomenon such as an arc during sputtering, reduce the characteristics of the thin film and the factors that cause defects, and improve the film forming characteristics. Further, the dopant can be contained in the phase shift layer 12, and the film characteristics in the mask layer including the phase shift layer 12 can be improved.

Further, the etching rate for the mask layer can be increased, and the etching time at the time of pattern formation for the mask layer can be reduced. As a result, the resist film thickness can be reduced.

The target 104A is a silicon single crystal or polycrystal, and is formed by the FZ method, the CZ method, or the cast growth method. The target 104A maintains the uniformity of the dopant content inside the target 104A, maintains the uniformity of the dopant concentration even in the atmosphere where plasma is generated, and maintains the uniformity of the dopant concentration in the film-formed mask layer. can do.

Here, the film properties of the mask layer that can be improved specifically mean an increase in the etching rate and the like. By improving the film characteristics in this way, the accuracy of the shape of the mask layer at the time of forming the mask pattern is improved, and the mask blanks 10B capable of realizing high-definition patterning can be obtained.

Further, in the first-stage vacuum tank 102, exhaust from the vacuum exhaust port 114d connected to the high vacuum exhaust mechanism and exhaust from the vacuum exhaust port 114e are performed according to the film forming conditions.
Further, in the first-stage film forming mechanism in the vacuum chamber 102, the sputtering voltage applied from the power supply 112A to the cathode electrode 105A is set corresponding to the film forming of the phase shift layer 12.

Further, in the second-stage film forming mechanism in the vacuum chamber 103, the target 104B is formed of, for example, a material containing chromium as a composition necessary for forming the antireflection layer 13 on the phase shift layer 12. Has been done.

At the same time, in the second-stage film forming mechanism in the vacuum chamber 103, the gas supplied into the film forming space 103 from the inert gas introduction port 114b and the reaction gas introduction port 114a corresponds to the film formation of the antireflection layer 13. Is set. Such gases include process gases and sputtering gases. The process gas contains nitrogen, oxygen and the like. The sputtering gas contains argon, nitrogen gas and the like. The gas including the process gas and the sputtering gas is set so that a predetermined gas partial pressure can be obtained.
_{Here, He, Ar, Ne, N 2} , NO, NO ₂ , O ₂ , CO ₂ , and CH ₄ can be applied as the atmospheric gas in the film formation of the antireflection layer 13.

Further, in the second-stage vacuum tank 103, exhaust from the vacuum exhaust port 114d connected to the high vacuum exhaust mechanism and exhaust from the vacuum exhaust port 114e are performed according to the film forming conditions.
Further, in the second-stage film forming mechanism in the vacuum chamber 103, the sputtering voltage applied from the power supply 112B to the cathode electrode 105B is set corresponding to the film forming of the antireflection layer 13.

In the manufacturing apparatus 100 shown in FIG. 6, the glass substrate 11 carried into the transport chamber 101c from the load chamber 101a is carried into the vacuum chamber 102 by the transport mechanism 101d. Then, the first-stage sputtering film formation is performed on the glass substrate 11 in the vacuum chamber 102. After that, the glass substrate 11 is carried from the vacuum tank 102 to the vacuum tank 103 via the transport chamber 101c by the transport mechanism 101d. After that, a second-stage sputtering film formation is performed in the vacuum chamber 103. After that, the glass substrate 11 having been film-formed is carried out by the transport mechanism 101d to the unload chamber 101b via the transport chamber 101c, and further carried out from the unload chamber 101b to the outside of the manufacturing apparatus 100.

In the phase shift layer forming step, in the first-stage film forming mechanism in the vacuum chamber 102, the sputtering gas is supplied as a supply gas from the inert gas introduction port 114b to the space near the backing plate 105A of the vacuum chamber 102. Further, the reaction gas is supplied as a supply gas from the reaction gas introduction port 114a to the space near the backing plate 105A of the vacuum chamber 102. In this state, a sputtering voltage is applied from the power supply 112A to the cathode electrode 105A. Further, a predetermined magnetic field may be formed on the target 104A by the magnetron magnetic circuit of the magnet plate 109A.

The ions of the sputtering gas excited by the plasma generated in the space near the cathode electrode 105A in the vacuum chamber 102 collide with the target 104A of the cathode electrode 105A and eject the particles of the film-forming material. Then, after the ejected particles and the reaction gas are combined, they adhere to the glass substrate 11. As a result, as shown in FIG. 3, a phase shift layer 12 having a predetermined composition is formed on the surface of the glass substrate 11.

At this time, in the film formation of the phase shift layer 12, the reactive gas containing nitrogen gas, oxygen-containing gas, etc. and having a predetermined partial pressure is contained in the vacuum chamber 102 from the inert gas introduction port 114b and the reaction gas introduction port 114a. Is supplied to. The operation of the gas introduction mechanism is switched so as to control the partial pressure, and the composition of the phase shift layer 12 is set within the set range.

Here, as the reactive gas, nitrogen gas (N ₂ gas), oxygen gas (O ₂ gas), nitrogen oxide gas (N ₂ O gas, NO gas, NO ₂ gas), carbon dioxide gas (CO ₂ ) Etc. can be used. As the sputtering gas, helium gas, neon gas, argon gas or the like can also be used as the rare gas.

Similarly, in the antireflection layer forming step, in the second stage film forming mechanism in the vacuum chamber 103, the sputtering gas is supplied as a supply gas from the inert gas introduction port 114b to the space near the cathode electrode 105B of the vacuum chamber 103. Will be done. Further, the reaction gas is supplied as a supply gas from the reaction gas introduction port 114a to the space near the backing plate 105B of the vacuum chamber 103. In this state, a sputtering voltage is applied from the power supply 112B to the cathode electrode 105B. Further, a predetermined magnetic field may be formed on the target 104B by the magnetron magnetic circuit of the magnet plate 109B.

The ions of the sputtering gas excited by the plasma generated in the space near the cathode electrode 105B in the vacuum chamber 103 collide with the target 104B of the cathode electrode 105B and eject the particles of the film-forming material. Then, after the ejected particles and the reaction gas are combined, they adhere to the glass substrate 11. As a result, the antireflection layer 13 having a predetermined composition is formed on the surface of the glass substrate 11.

Further, in the film formation of the antireflection layer 13, nitrogen gas, oxygen-containing gas and the like are supplied into the vacuum chamber 103 from the inert gas introduction port 114b and the reaction gas introduction port 114a so that a predetermined partial pressure can be obtained. .. The operation of the gas introduction mechanism is switched so as to control the partial pressure, and the composition of the antireflection layer 13 is set within the set range.

Here, examples of the oxygen-containing gas include CO ₂ (carbon dioxide), O ₂ (oxygen), N ₂ O (nitric oxide), NO (nitric oxide), CO (carbon monoxide) and the like. can.
Examples of the carbon-containing gas include CO ₂ (carbon dioxide), CH ₄ (methane), C ₂ H ₆ (ethane), and CO (carbon monoxide).

Further, in addition to the film formation of the phase shift layer 12 and the antireflection layer 13 described above, another film may be laminated on the mask layer. In this case, for example, a method of preparing a target corresponding to another film material and forming a film by sputtering based on sputtering conditions such as gas is adopted. Further, the mask blanks 10A without the resist layer 15 may be manufactured by laminating the film on the mask layer by a film forming method other than sputtering. In addition, instead of the manufacturing apparatus 100 for forming a single-wafer film, an interback type or an in-line type film forming apparatus can be used.

In the resist forming step S13 shown in FIG. 1, the resist layer 15 is formed on the outermost surface of the mask blanks 10A on which the mask layer is formed. The resist layer 15 may be a positive type or a negative type. As the resist layer 15, a resist layer capable of etching a so-called chromium-based material and etching a silicon-based material is adopted. A liquid resist is used as the resist layer 15. As the resist liquid, a chemically amplified resist may be used.

In the resist forming step S13 in the present embodiment, the resist layer 15 is applied to the mask blanks 10A by using a known application device such as a spin coater. The coating device can be used in the production of a mask blank with a photoresist film, and a resist solution is applied to the mask blanks 10A.

In the resist forming step S13, the resist layer 15 is applied to the outermost surface of the mask blanks 10A to form the resist layer 15, and then a bake treatment or the like is applied to complete the resist forming step S13. As shown in FIG. 5, the mask blanks 10B are manufactured. Will be done.

In the method for manufacturing mask blanks, in addition to the phase shift layer 12, the antireflection layer 13, and the resist layer 15, as a mask layer, an adhesion layer, a protective layer, a light-shielding layer, a chemical resistant layer, an etching stopper layer, and the like are provided on a glass substrate. It may be laminated on 11. In this case, it is possible to have a step of laminating these layers on the glass substrate 11 before forming the resist layer 15.

FIG. 9 is a flowchart showing a method of manufacturing a photomask using mask blanks in the present embodiment. 10 to 12 are cross-sectional views for explaining a process in a method for manufacturing a photomask using mask blanks in the present embodiment.
As shown in FIG. 12, the phase shift mask (photomask) 10 in the present embodiment forms an exposure pattern on a mask blank 10B having a laminated phase shift layer 12, an antireflection layer 13, and a resist layer 15. Obtained by.

Hereinafter, a manufacturing method for manufacturing the phase shift mask 10 from the mask blanks 10B of the present embodiment will be described.
As shown in FIG. 9, the method for manufacturing a photomask using mask blanks in the present embodiment includes a resist pattern forming step S21 and a mask pattern forming step S22.

In the resist pattern forming step S21 shown in FIG. 9, as shown in FIG. 10, the resist layer 15 is exposed and developed to form the resist pattern 15P on the outer side of the mask layer. The resist pattern 15P functions as an etching mask between the phase shift layer 12 and the antireflection layer 13.

In the resist pattern forming step S21, the chemically amplified resist layer 15 is selectively exposed to form a latent image. This exposure process can be performed by irradiating with active rays.
Here, a laser or an electron beam can be adopted as the active ray of the exposure process.

Next, the resist layer 15 on which the latent image is formed by light irradiation is subjected to PEB treatment. This PEB treatment is usually performed at a temperature of about 70 to 150 ° C. for 30 seconds to 150 seconds.
Next, as a developing process, the resist layer 15 heated after exposure is brought into contact with a developer for lithography to reveal a resist pattern 15P corresponding to a latent image.

The shape of the resist pattern 15P is appropriately determined according to the etching pattern of the phase shift layer 12 and the antireflection layer 13. As an example, in the phase shift region, a shape having an opening width corresponding to the opening width of the phase shift pattern to be formed is set.

Next, as the first step in the mask pattern forming step S22, an antireflection pattern forming step is performed. In this step, dry etching is performed via the resist pattern 15P, and the antireflection layer 13 is etched to form the antireflection pattern 13P.

As the etching in the antireflection pattern forming step, chlorine-based dry etching containing oxygen can be used.

Next, as the second step in the mask pattern forming step S22, a phase shift pattern forming step is performed. In this step, the phase shift layer 12 is dry-etched via the patterned antireflection pattern 13P and the resist pattern 15P. As a result, as shown in FIG. 12, the phase shift pattern 12P is formed.

Fluorine-based dry etching can be used as the etching in the phase shift pattern forming step.

In the present embodiment, the target 104A used when forming the phase shift layer 12 contains a dopant that reduces the specific resistance in silicon. By setting the boron concentration within the above range, the specific resistance at the target 104A can be set within the above range. As a result, the electric power for forming the plasma is stabilized, the plasma in the film-forming state is stabilized, and the phase shift layer 12 can be formed. As a result, the film forming characteristics can be improved. Further, the dopant can be contained in the phase shift layer 12, and the film characteristics in the mask layer including the phase shift layer 12 can be improved.

Further, the etching rate for the mask layer can be increased, and the etching time at the time of pattern formation for the mask layer can be reduced. Further, since the etching rate ratio of the mask layer to the glass substrate becomes large, the etching process can be easily controlled based on the determination of the endpoint for determining the end of etching. Therefore, the depth at which the glass substrate 11 is excessively etched can be minimized.

Further, the target 104A is a silicon single crystal or a silicon polycrystal, and is formed by an FZ method, a CZ method, or a casting method. It is possible to maintain the uniformity of the dopant content in the target 104A, maintain the uniformity of the dopant concentration even in the atmosphere where plasma is generated, and maintain the uniformity of the dopant concentration in the film-formed mask layer.

Further, in the method for manufacturing mask blanks of the present embodiment, by using DC sputtering for the sputtering in the mask layer forming step S12, the reproducibility of the film characteristics is improved as compared with the case where the mask layer is formed by RF sputtering. be able to.

As a result, in the mask blanks 10B of the present embodiment, the phase shift layer 12 represented by SiN or SiON contains, for example, B (boron). Further, the boron concentration is set to be in the range of ^{1 × 10 18} atm / cm ³ to 1 × 10 ²⁰ atm / cm ^3. As a result, the etching rate in dry etching can be improved by 1.05 to 1.5 times with respect to the etching rate of the layer formed by using the non-doped target.

This makes it possible to shorten the etching time, improve the accuracy of the shape in patterning, and apply it to even higher-definition patterning due to the faster etching rate as compared with the case where the dopant is not contained.
This reduces the etching time during pattern formation on the mask layer, suppresses damage to the surface of the resist layer 15, maintains shape accuracy in etching, and can be applied to high-definition patterning. The shift mask 10 can be manufactured.

In the present embodiment, the case where boron is used as the dopant has been described, but the etching rate can be improved even when phosphorus or arsenic is used as the dopant.

Further, the plurality of configurations described in the above embodiment can be used individually or in combination.

Hereinafter, examples of the present invention will be described.

First, a DC sputtering test will be described as a specific example of the mask blanks in the present invention.

<Experimental Example 1>
Reactive sputtering was performed using a target made of silicon doped with a dopant to form a mask layer on a transparent substrate. Further, a DC voltage was applied as a sputtering voltage supplied from the power source to the target to perform DC sputtering film formation.
At this time, the film forming conditions and the film thickness were optimized as follows.

Phase difference at wavelength 193 nm: 180 deg
Transmittance: 5.8%

The specifications in sputtering are shown.
Substrate: Quartz Sputtering power: DC 1.5kW
Target: Silicon Dopant: Boron (B)
Dopant concentration: 1 × 10 ¹⁹ atm / cm ³
Film formation gas: Ar: 10 sccm, N ₂ : 8 sccm

<Experimental Example 2>
Similar to Experimental Example 1, reactive sputtering was performed using a target made of non-doped silicon not doped with boron or the like, and a mask layer was formed on a transparent substrate.
At this time, the film forming conditions and the film thickness were optimized as follows.

Phase difference at wavelength 193 nm: 180 deg
Transmittance: 5.8%

The specifications in sputtering are shown.
Substrate: Quartz Sputtering power: DC 1.5kW
Target: Silicon Dopant: None Dopant concentration: 0 atm / cm ³
Film formation gas: Ar: 10 sccm, N ₂ : 7 sccm

<Experimental example 3>
Similar to Experimental Example 2, reactive sputtering was performed using a target made of non-doped silicon not doped with boron or the like, and a mask layer was formed on a transparent substrate.
At this time, the film forming conditions and the film thickness were optimized as follows.

Phase difference at wavelength 193 nm: 180 deg
Transmittance: 5.8%

The specifications in sputtering are shown.
Substrate: Quartz sputtering RF frequency 13.56MHz
Sputtering power: 1.5kW
Target: Silicon Dopant: None Dopant concentration: 0 atm / cm ³
Film formation gas: Ar: 10 sccm, N ₂ : 5 sccm

In Experimental Examples 1 to 3, the time required to form a film until a predetermined film thickness was obtained (deposition time), the number of defects of 0.5 μm or more observed on the film surface per unit area, and 10 The phase difference reproducibility (deg) when the film was continuously formed was measured.
Here, the phase difference reproducibility (deg) means the difference between the maximum value and the minimum value of the monitor value when the average phase difference of each substrate is used as the monitor value.
The phase difference reproducibility (deg) is an index showing the stability of the film thickness and the optical constant.
The results are shown in Table 1.

Here, when performing reactive sputtering, it is necessary to induce a voltage on the surface of the target, so that it is necessary to reduce the resistance of the target in order to perform DC sputtering. However, in order to sputter a high resistance target such as non-doped silicon, it was necessary to apply high frequency to perform RF sputtering.
From the above results, it can be seen that by adding a dopant to Si, DC sputtering becomes possible, and the film formation time, defects, and reproducibility are improved.

In particular, when DC sputtering was performed using a high-concentration B-doped silicon target in Experimental Example 3, the phase difference was higher than that in the case of DC sputtering using a non-doped silicon target as in Experimental Example 2. It is possible to form a film with good reproducibility and with extremely few defects.
Further, in the case of DC sputtering using a high-concentration B-doped silicon target in Experimental Example 3, the reproducibility of the phase difference is as compared with the case of RF sputtering using a non-doped silicon target as in Experimental Example 1. Is extremely good, and it can be seen that there are few defects.

<Experimental Example 4>
The mask layer obtained in Experimental Example 1 and the quartz substrate on which the mask layer was formed were dry-etched, and their respective etching rates (Etching Rate) were evaluated. In addition, the selection ratio (selectivity) at that time was measured.
The result is shown in FIG.

The specifications in dry etching are shown.
Plasma source: ICP (Inductively Coupled Plasma)
Antenna power: 1.5kW
Bias power: 0-200W
Pressure of dry etching atmosphere: 1.36 Pa
Supply gas: CF ₄ : 150 sccm, O ₂ : 8 sccm

<Experimental Example 5>
Similar to Experimental Example 4, the mask layer obtained in Experimental Example 3 and the quartz substrate on which the mask layer was formed were dry-etched, and their respective etching rates (Etching Rate) were evaluated. In addition, the selection ratio (selectivity) at that time was measured.
The result is shown in FIG.

From the results shown in FIG. 13, in Experimental Example 4 in which the film was formed using the target doped with boron (B-dope), the Etching speed was faster with the same bias amount as in Experimental Example 5 without doping. I understand. It can also be seen that the selectivity is also improved in the boron-doped target.

<Experimental Example 6>
A light-shielding layer containing Cr as a main component and an antireflection layer were laminated on the mask layer obtained in Experimental Example 1, and a resist layer was further formed on the antireflection layer.
Next, these laminates were dry-etched under the same conditions as in Experimental Examples 4 and 5. After that, the cross-sectional shape of the laminated body was observed.
Here, the bias power was set to 100 W.
The SEM image in Experimental Example 6 is shown in FIG. In FIG. 14, the surface of the quartz substrate in the vicinity of the mask layer on which the pattern is formed is shown by a solid line.

<Experimental Example 7>
Similar to Experimental Example 6, a light-shielding layer containing Cr as a main component and an antireflection layer were laminated on the mask layer obtained in Experimental Example 3, and a resist layer was further formed on the antireflection layer.
Next, these laminates were dry-etched under the same conditions as in Experimental Examples 4 and 5. After that, the cross-sectional shape of the laminated body was observed.
Here, the bias power was set to 100 W.
The SEM image in Experimental Example 7 is shown in FIG. In FIG. 15, the surface of the quartz substrate in the vicinity of the mask layer on which the pattern is formed is shown by a solid line.

From the results shown in FIG. 15, it can be seen that in Experimental Example 7 in which the film was formed using a non-doped target, the overetching of the quartz substrate was large because the selection ratio was small. As a result, in Experimental Example 7, it can be seen that the optical characteristics of the photomask are deteriorated because the phase difference is deviated.

On the other hand, from the results shown in FIG. 15, in Experimental Example 6 in which the film was formed using a target doped with boron (B-dope), the selectivity was large, so that the overetch of the quartz substrate was small. You can see that. As a result, in Experimental Example 6, it can be seen that the phase difference shift is reduced and the optical characteristics of the photomask are improved.

In the method for producing mask blanks of the present invention, the DC input power was set to 0.1 to 0.2 to 4.0 kW, and the film forming pressure was set to 0.05 to 0.6 to 0.7 Pa. The sputtering may be carried out under the conditions.
This makes it possible to stabilize the discharge.

In the method for manufacturing a photomask of the present invention, the plasma forming power is set to 0.2 to 1.0 kW, the Bias power is set to 10 to 80 W, and CF _{4 is set as the dry etching conditions in the mask pattern forming step.} Can be set to 100 to 200 sccm.
This reduces the etching time during pattern formation on the mask layer, suppresses damage to the resist layer surface, maintains shape accuracy in etching, and makes a photomask that can be applied to high-definition patterning. Can be manufactured.

10 ... Phase shift mask (photomask)
10A, 10B ... Mask blanks 11 ... Glass substrate (transparent substrate)
12 ... Phase shift layer (mask layer)
12P ... Phase shift pattern (mask pattern)
13 ... Antireflection layer (mask layer)
13P ... Anti-reflection pattern (mask pattern)
15 ... Resist layer (photoresist layer)
15P ... Resist pattern 100 ... Manufacturing equipment 104A, 104B ... Target

Claims (15)

1. A method for manufacturing mask blanks in which a mask layer containing silicon is laminated on a transparent substrate.
   The mask layer is formed by sputtering using a target containing a dopant that reduces resistivity.
   Manufacturing method of mask blanks.
2. The specific resistance of the target is 0.001 Ωcm to 0.1 Ωcm.
   The method for manufacturing a mask blank according to claim 1.
3. The dopant is at least one selected from the group consisting of boron, phosphorus, and arsenic.
   The method for manufacturing a mask blank according to claim 1 or 2.
4. In the target, the dopant is boron.
   The dopant concentration is in the range of 1 × 10 ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ³ .
   The method for manufacturing a mask blank according to claim 3.
5. The target is a silicon single crystal or a silicon polycrystal.
   The method for manufacturing a mask blank according to claim 4.
6. The atmospheric gas used for the sputtering contains nitrogen,
   The method for manufacturing a mask blank according to any one of claims 1 to 5.
7. The atmospheric gas used for the sputtering contains oxygen.
   The method for manufacturing a mask blank according to any one of claims 1 to 5.
8. The sputtering is referred to as DC sputtering.
   The method for manufacturing a mask blank according to any one of claims 1 to 7.
9. A mask blank manufactured by the manufacturing method according to any one of claims 1 to 8.
   The mask layer contains boron as the dopant and
   The dopant concentration of the mask layer is in the range of 1 × 10 ¹⁸ atm / cm ³ to 1 × 10 ²⁰ atm / cm ³ .
   Mask blanks.
10. The etching rate in the dry etching of the mask layer is 1.05 to 1.5 times the etching rate of the layer formed by using the non-doped target.
    The mask blanks according to claim 9.
11. The mask layer contains nitrogen or oxygen,
    The mask blanks according to claim 9 or 10.
12. The composition ratio of nitrogen or oxygen in the mask layer changes in the film thickness direction.
    The mask blanks according to claim 11.
13. The mask layer includes a phase shift layer.
    The mask blank according to any one of claims 9 to 12.
14. A method for manufacturing a photomask from the mask blanks according to any one of claims 9 to 13.
    A resist pattern is formed on the surface of the mask layer to form a resist pattern.
    A mask pattern is formed by patterning the mask layer using the resist pattern as a mask.
    When forming the mask pattern, the mask layer is dry-etched.
    How to make a photomask.
15. A product manufactured by the production method according to claim 14.
    Photomask.

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