JP2014130976A - Method of manufacturing substrate with multilayer reflection film, method of manufacturing reflective mask blank, and method of manufacturing reflective mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a substrate with a multilayer reflection film, in which the in-plane distribution of reflectance in the multilayer reflection film can be suppressed.SOLUTION: A multilayer reflection film is formed by laminating about 40 periods of the deposition of a low refractive index layer (e.g., a silicon layer) and a high refractive index layer (e.g., a molybdenum layer) in this order on a substrate, while rotating the substrate about the central axis thereof. When depositing at least the upper layer (about 10 periods, for example) of the multilayer reflection film, azimuth of the substrate is changed by 90 degrees at the start of deposition of each layer (low refractive index layer, high refractive index layer).

Description

  The present invention relates to a method for manufacturing a substrate with a multilayer reflective film, a method for manufacturing a reflective mask blank, and a method for manufacturing a reflective mask, which are original plates for manufacturing an exposure mask used in semiconductor device manufacturing and the like. is there.

With the further demand for higher density and higher precision of VLSI devices in recent years, EUV lithography, which is an exposure technique using extreme ultraviolet (hereinafter referred to as EUV) light, is promising. Here, EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, and specifically refers to light having a wavelength of about 0.2 to 100 nm. As a mask used in this EUV lithography, for example, an exposure reflective mask described in Patent Document 1 below has been proposed.

In such a reflective mask, a multilayer reflective film that reflects exposure light is formed on a substrate, and an absorber film that absorbs exposure light is formed in a pattern on the multilayer reflective film. Light incident on a reflective mask mounted on an exposure machine (pattern transfer device) is absorbed in a part where the absorber film is present, and a light image reflected by the multilayer reflective film is reflected in a part where there is no absorber film. And transferred onto the semiconductor substrate.

In order to achieve higher density and higher accuracy of semiconductor devices using such a reflective mask, the reflective region (surface of the multilayer reflective film) in the reflective mask is higher than the EUV light that is the exposure light. It is necessary to have reflectivity. Moreover, it can be said that having a high reflectance is essential in order to obtain a sufficient amount of light at the time of exposure and to suppress an increase in the blanks temperature due to absorption of EUV light.
The multilayer reflective film is a multilayer film in which elements having different refractive indexes are periodically laminated. Generally, a thin film of a heavy element or a compound thereof and a thin film of a light element or a compound thereof are alternately 40 to 40 A multilayer film laminated for about 60 cycles is used. For example, as a multilayer reflective film for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 cycles is preferably used.

The EUV light reflectance of the multilayer reflective film depends on, for example, a diffusion layer formed between Mo / Si layers. In order to suppress the formation of the diffusion layer as much as possible and increase the reflectance, for example, the incident angle of the sputtered particles with respect to the normal direction of the substrate is increased to prevent the sputtered particles from entering the formed layer. It is effective to suppress.
Patent Document 2 discloses that a multilayer reflective film made of a Mo / Si periodic laminated film is formed by using an ion beam sputtering method, and in detail, ensuring the film thickness uniformity of the multilayer reflective film. From the viewpoint of the above, while rotating the substrate at a rotation speed of 1 to 60 rpm, the angle formed by the normal of the substrate and the sputtered particles incident on the substrate is maintained at 35 degrees or more and 80 degrees or less from the viewpoint of reducing defects on the substrate surface. The film formation is described.

JP 2002-122981 A Japanese Patent No. 4858539

  The diffusion layer is generated mainly depending on the incident angle of the sputtered particles deposited on the substrate and the film forming speed. The incident angle of the sputtered particles and the film forming speed differ within the substrate surface, and the incident characteristics of the sputtered particles within the substrate surface change with time due to the rotation of the substrate during film formation. For this reason, in-plane distribution depending on the film formation start position (the azimuth angle of the substrate at the time of film formation start) occurs in the diffusion layer. In the conventional ion beam sputtering apparatus, this film formation start position is not controlled, and the in-plane distribution of the diffusion layer as described above is generated. If the deposition start position of each layer is biased when the multilayer reflective film is formed, the in-plane distribution of the diffusion layer between the layers accumulates, and the in-plane distribution of the reflectance of the formed multilayer reflective film is greatly biased. become. The formation of the diffusion layer not only reduces the reflectivity, but also causes an in-plane distribution of reflectivity, so that when pattern transfer is performed using a finally formed reflective mask, unacceptable pattern defects are generated. May occur. Recently, a predetermined standard (for example, 0.2% or less in the SEMI standard) has been required for the in-plane distribution of the reflectance of the reflective mask blank.

  By simply setting the deposition conditions for increasing the conventional reflectance, the in-plane distribution of the diffusion layer between the layers as described above is accumulated, and the occurrence of the in-plane distribution of the reflectance in the multilayer reflective film is sufficiently suppressed. It is not possible. In addition, in the film formation condition setting from the viewpoint of ensuring the film thickness uniformity of the multilayer reflective film and reducing the defects on the substrate surface as disclosed in Patent Document 2, the in-plane of the diffusion layer between the layers as described above It cannot be suppressed that the distribution is accumulated and the in-plane distribution of the reflectance in the multilayer reflective film is generated.

  Therefore, recent reflective mask blanks are required not only to have high reflectivity but also to have a small in-plane distribution of reflectivity. However, it has been difficult to satisfy all of these requirements under the conventional conditions for forming a multilayer reflective film.

Accordingly, an object of the present invention is to firstly provide a method for producing a high-quality multilayer reflective film-coated substrate capable of suppressing the in-plane distribution of reflectivity with a high reflectivity, and secondly, as described above. It is providing the manufacturing method of a reflective mask blank using the board | substrate with a multilayer reflective film and a manufacturing method of a reflective mask.

The present inventor has completed the present invention as a result of intensive studies to solve the above problems.
That is, in order to solve the above problems, the present invention has the following configuration.
(Configuration 1)
A method of manufacturing a substrate with a multilayer reflective film comprising a multilayer reflective film that reflects exposure light on the substrate, wherein the multilayer reflective film is formed on the substrate while rotating the substrate about its central axis, A structure in which a refractive index layer and a high refractive index layer are sputter-deposited in this order are stacked in a plurality of periods, and the substrate of the substrate at the start of film formation in the low refractive index layer and the high refractive index layer is formed. A method for producing a substrate with a multilayer reflective film, wherein the film is formed with different azimuth angles.

As in Configuration 1, when a multilayer reflective film is formed by laminating a plurality of periods with a low refractive index layer and a high refractive index layer sputter-deposited in this order on the substrate as one period, the multilayer reflective film is configured. Each layer (low refractive index layer, high refractive index layer) is formed by forming the low refractive index layer and the high refractive index layer with different azimuth angles (deposition start positions) of the substrate at the start of film formation. It is possible to suppress accumulation of the in-plane distribution of the diffusion layers between the respective layers by dispersing the film start positions. As a result, the in-plane distribution of the diffusion layer is made uniform, the in-plane distribution of the reflectance of the formed multilayer reflective film can be suppressed, and a high reflectance can be obtained.

(Configuration 2)
The configuration 1 is characterized in that when forming at least the upper layer of the multilayer reflective film, the low refractive index layer and the high refractive index layer are formed with different azimuth angles of the substrate at the start of film formation. Manufacturing method of a substrate with a multilayer reflective film.
As in Configuration 2, it is effective to make the film formation start position different for each layer, particularly when forming the upper layer of the multilayer reflective film, where the in-plane distribution of the diffusion layers between the layers is likely to occur.

(Configuration 3)
The substrate with a multilayer reflective film according to Configuration 1 or 2, wherein the azimuth of the substrate is formed by shifting the azimuth angle by one or more revolutions of the number of layers of the low refractive index layer and the high refractive index layer. Manufacturing method.
As in Configuration 3, in particular, the azimuth angle of the substrate is shifted by one or more revolutions of the number of layers of the low-refractive index layer and the high-refractive index layer, so that the in-plane distribution of the diffusion layer between the layers is increased. Accumulation can be effectively suppressed, and the in-plane distribution of the diffusion layer can be made uniform, so that the in-plane distribution of the reflectance of the multilayer reflective film can be suppressed.

(Configuration 4)
4. The method for manufacturing a substrate with a multilayer reflective film according to any one of Structures 1 to 3, wherein the low refractive index layer is a silicon layer, and the high refractive index layer is a molybdenum layer.
The present invention provides a substrate with a multilayer reflective film composed of a Mo / Si periodic laminated film in which silicon layers and molybdenum layers, which are preferably used as a multilayer reflective film for EUV light having a wavelength of 13 to 14 nm, for example, are alternately laminated, as in Configuration 4. Suitable for manufacturing.

(Configuration 5)
The method for manufacturing a substrate with a multilayer reflective film according to any one of Structures 1 to 4, wherein the multilayer reflective film is formed using an ion beam sputtering method.
As in Configuration 5, the present invention is suitable for manufacturing a substrate with a multilayer reflective film using an ion beam sputtering method.

(Configuration 6)
Manufacturing of a reflective mask blank, characterized in that an absorber film that absorbs exposure light is formed on the multilayer reflective film in the multilayer reflective film-coated substrate obtained by the manufacturing method according to any one of configurations 1 to 5. Method.
By manufacturing a reflective mask blank using a substrate with a multilayer reflective film that has a high reflectivity and suppresses in-plane distribution of reflectivity obtained by the present invention, a high-quality reflective mask with good reflectivity characteristics A blank is obtained.

(Configuration 7)
A reflective mask manufacturing method, wherein the absorber film in a reflective mask blank obtained by the manufacturing method according to Structure 6 is patterned.
By manufacturing a reflective mask using a high-quality reflective mask blank having good reflectance characteristics according to the present invention, a high-quality reflective mask with few pattern defects can be obtained during pattern transfer using EUV light. .

ADVANTAGE OF THE INVENTION According to this invention, the board | substrate with a high quality multilayer reflection film which can suppress the in-plane distribution of a reflectance with a high reflectance can be obtained.
Further, according to the present invention, a high-quality reflective mask blank having good reflectance characteristics can be obtained by using such a substrate with a multilayer reflective film.
Furthermore, by manufacturing a reflective mask using such a reflective mask blank of the present invention, a high-quality reflective mask with few pattern defects can be obtained during pattern transfer using EUV light.

It is sectional drawing which shows the layer structure of a board | substrate with a multilayer reflective film. It is sectional drawing which shows the layer structure of a reflection type mask blank. It is sectional drawing which shows the layer structure of a reflection type mask. It is sectional drawing which shows the detailed layer structure of a board | substrate with a multilayer reflective film. It is a schematic diagram which shows the structure of the ion beam sputtering apparatus used for this invention.

Hereinafter, the present invention will be described in detail by embodiments.
[Substrate with multilayer reflective film]
First, the multilayer reflective film-coated substrate according to the present invention will be described.
FIG. 1 is a cross-sectional view showing a layer structure of a substrate with a multilayer reflective film according to the present invention. The multilayer reflective film has a multilayer reflective film 2 that reflects EUV light as exposure light on the substrate 1. The attached substrate 10 is shown.
In the case of EUV exposure, the substrate 1 is in the range of 0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably 0 ± 0.3 × 10 ⁻ in order to prevent pattern distortion due to heat during exposure. Those having a low thermal expansion coefficient in the range of ⁷ / ° C. are preferably used, and as a material having a low thermal expansion coefficient in this range, for example, SiO ₂ —TiO ₂ glass, multicomponent glass ceramics, or the like is used. I can do it.

  The main surface of the substrate 1 on which the transfer pattern is formed is subjected to surface processing so as to have high flatness from the viewpoint of obtaining at least pattern transfer accuracy and position accuracy. For example, in the case of EUV exposure, the flatness is preferably 0.1 μm or less, particularly preferably 0.05 μm or less, in the region of the main surface 142 mm × 142 mm on the side where the transfer pattern of the substrate is formed. The main surface opposite to the side on which the transfer pattern is formed is a surface that is electrostatically chucked when being set in the exposure apparatus, and has a flatness of 1 μm or less, preferably 0.8 mm in a 142 mm × 142 mm region. 5 μm or less.

In the case of EUV exposure, the surface smoothness required for the substrate 1 is such that the surface roughness of the main surface on the side where the transfer pattern of the substrate is formed is 0.2 nm or less in terms of root mean square roughness (RMS). It is preferable that

The multilayer reflective film 2 is a multilayer film in which elements having different refractive indexes are periodically laminated, and generally, a thin film (low refractive index layer) of a heavy element or a compound thereof, which is a low refractive index material, A multilayer film in which thin films (high refractive index layers) of light elements which are high refractive index materials or compounds thereof are alternately stacked for about 40 to 60 cycles is used. The multilayer film may be formed by laminating a plurality of periods with a laminated structure in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate side, or a low refractive index layer and a high refractive index layer from the substrate side. A plurality of layers may be stacked with a stacked structure sequentially stacked as one cycle. As the low refractive index material, an element selected from Mo, Ru, Rh, or Pt or an alloy thereof is used, and as the high refractive index material, Si or a Si compound is used. For example, as the multilayer reflective film for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 periods is preferably used.
In addition, as a multilayer reflective film used in the EUV light region, Ru / Si periodic multilayer film, Mo / Be periodic multilayer film, Mo compound / Si compound periodic multilayer film, Si / Nb periodic multilayer film, Si / Mo / Examples include Ru periodic multilayer films, Si / Mo / Ru / Mo periodic multilayer films, and Si / Ru / Mo / Ru periodic multilayer films. The material may be appropriately selected depending on the exposure wavelength.

  The multilayer reflective film 2 can be formed by depositing each layer by ion beam sputtering. In the case of the above-described Mo / Si periodic multilayer film, for example, by an ion beam sputtering method, a Si film having a thickness of about several nanometers is first formed using a Si target, and then a Mo film having a thickness of about several nanometers is formed using a Mo target. A film is formed, and this is set as one period, and after 40 to 60 periods are stacked, finally, a Si film is formed.

Here, an ion beam sputtering method that is preferably used as a method for forming the multilayer reflective film 2 of the present invention will be described.
FIG. 5 is a schematic diagram showing a configuration of an ion beam sputtering apparatus.
An ion beam sputtering apparatus 50 shown in FIG. 5 includes an ion beam generator 51, a target holder 53, a substrate stage 58, and the like. Two kinds of sputtering targets 54 and 55 are attached to the target holder 53. In the present embodiment, one of them is a high refractive index material target (for example, Si target), and the other is a low refractive index material target. (For example, Mo target). By rotation of the target holder 53, one of the high refractive index material target and the low refractive index material target is directed to the film formation surface of the substrate 1. The substrate 1 is fixed on the substrate stage 58 by an electrostatic chuck or a mechanical chuck that mechanically holds the substrate, and is rotated in a predetermined direction by a driving device (motor 59). The rotation of the substrate 1 is detected by an optical sensor 62 installed in the vicinity of the rotation axis of the substrate stage 58. The output of the optical sensor 62 is input to a PC (personal computer) 61, and the substrate rotation control means 60 connected to the PC 61 controls the driving of the motor 59 to control the substrate rotation.

  In the ion beam sputtering apparatus 50 having such a configuration, the incident angle θ of the sputtered particles 56 generated when the ion beam 52 emitted from the ion beam generating apparatus 51 enters the sputtering target 54 (or 55) (the method of the substrate). The multilayer reflective film 2 is formed by ion beam sputtering while adjusting the position of the sputtering target 54 (or 55) so that the incident angle with respect to the line 57 becomes a predetermined angle and rotating the substrate 1. .

The present invention is a method for manufacturing a substrate with a multilayer reflective film comprising a multilayer reflective film that reflects exposure light on the substrate as in the above configuration 1, wherein the multilayer reflective film is formed on the substrate, Is formed by laminating a plurality of low-refractive-index layers and high-refractive-index layers in this order as a single cycle, and the low-refractive-index layer and the high-refractive-index layer. The film formation is performed by varying the azimuth angle of the substrate at the start of film formation in the rate layer. In other words, the low refractive index layer and the high refractive index layer are formed with different film formation start positions.

FIG. 4 is a cross-sectional view showing a detailed layer structure of a substrate with a multilayer reflective film.
As shown in FIG. 4, the multilayer reflective film-coated substrate 10 according to this embodiment includes a multilayer reflective film 2 in which silicon (Si) layers 21 and molybdenum (Mo) layers 22 are alternately stacked on a substrate 1. It has.

A characteristic of the present invention is that the layers (low refractive index layer, high refractive index layer) constituting the multilayer reflective film 2 are formed with different substrate azimuth angles at the start of film formation.
When forming a multilayer reflective film, each layer (low refractive index layer, high refractive index layer) constituting the multilayer reflective film is formed by varying the azimuth angle of the substrate at the start of film formation. It is possible to suppress the accumulation of the in-plane distribution of the diffusion layer between the respective layers by dispersing the starting position. As a result, the in-plane distribution of the diffusion layer is made uniform, the in-plane distribution of the reflectance of the formed multilayer reflective film can be suppressed, and a high reflectance can be obtained.

  In the present invention, there are no particular restrictions on how the azimuth angle of the substrate at the start of film formation in each layer (low refractive index layer, high refractive index layer) constituting the multilayer reflective film 2 is different. From the viewpoint of effectively dispersing the film start position, the azimuth angle of the substrate at the start of film formation of each layer is at least an angle of one rotation or more of the number of layers of each of the low refractive index layer and the high refractive index layer. It is preferable to form the films while shifting them. For example, when the number of layers of each of the low refractive index layer and the high refractive index layer is 40, the film is formed by shifting the azimuth angle of the substrate at the start of film formation by 360 degrees / 40 layers, that is, each layer 9 degrees or more. Is preferred. For controlling the film formation conditions, for example, it is preferable to change the azimuth angle of the substrate at the start of film formation for each layer by 90 degrees. In this way, by changing the azimuth angle of the substrate at the start of film formation of each layer by 90 degrees, it is possible to effectively suppress the accumulation of the in-plane distribution of the diffusion layer between the respective layers. The in-plane distribution of the multilayer reflection film can be made uniform, and the in-plane distribution of the reflectance of the multilayer reflective film can be suppressed.

As a specific method for forming the film by changing the azimuth angle of the substrate at the start of film formation of each layer by 90 degrees, for example, the following method can be given.
In the ion beam sputtering apparatus 50 described above, the output of the optical sensor 62 that detects the substrate rotation (one rotation) is input to the PC 61, and the driving of the motor 59 is controlled by the substrate rotation control means 60 connected to the PC 61. To control. By controlling the substrate rotation and film formation timing for each layer, the azimuth angle of the substrate at the start of film formation for each layer can be set, for example, by the film formation of each immediately preceding layer (low refractive index layer, high refractive index layer). It changes by 90 degrees with respect to the azimuth angle of the substrate at the time.

Note that the above 90 degrees is merely an example, and the present invention is not limited to this, and can be set as appropriate within a range that does not impair the effects of the present invention. Further, the film formation start position of each layer is not necessarily changed regularly (such as 90 degrees), and may be changed irregularly within a range not impairing the effects of the present invention.

Further, in the present invention, in all the layers constituting the multilayer reflective film 2, the layers (low refractive index layer, high refractive index layer) are formed with different azimuth angles of the substrate at the start of film formation. However, in-plane distribution of the diffusion layers between the layers is likely to occur. Particularly, when the upper layer of the multilayer reflective film 2 is formed, it is advantageous to form the film by changing the azimuth angle of the substrate at the start of film formation of each layer. Is. In this case, for example, when the multilayer reflective film 2 is formed by laminating about 40 to 60 periods with the Si layer 21 and the Mo layer 22 as one period, the upper layer is composed of 10 periods (Si and Mo) It is preferable to have about 10 layers each.

As described above, the present invention provides a substrate with a multilayer reflective film composed of a Mo / Si periodic multilayer film in which silicon layers and molybdenum layers, which are preferably used as a multilayer reflective film for EUV light with a wavelength of 13 to 14 nm, for example, are alternately laminated. Is preferred.
In addition, the present invention is suitable because the effect is better exhibited in the production of a substrate with a multilayer reflective film using an ion beam sputtering method.

Further, the incident angles of the sputtered particles during the formation of the silicon layer 21 and the molybdenum layer 22 can be appropriately set. For example, it is desirable to set as follows from the viewpoint of ensuring high reflectance.
When the silicon layer 21 is formed, the incident angle θ of the sputtered particles with respect to the normal of the main surface of the substrate 1 is preferably in the range of, for example, 25 to 35 degrees, and more preferably about 30 degrees. It is. Further, when the molybdenum layer 22 is formed, the incident angle θ of the sputtered particles with respect to the normal of the main surface of the substrate 1 is preferably in the range of, for example, 45 degrees to 55 degrees, and more preferably about 50 degrees. It is to be.

As described above, when the multilayer reflective film 2 is formed by laminating a plurality of periods, for example, by forming a silicon layer 21 and a molybdenum layer 22 in this order on the substrate 1 as one period, the multilayer reflective film 2 is configured. The azimuth angle of the substrate at the start of film formation of each layer is changed, for example, the azimuth angle at the start of film formation of each layer is changed by 90 degrees with respect to the azimuth angle of the substrate at the start of film formation of each immediately preceding layer. By forming the film, it is possible to suppress accumulation of the in-plane distribution of the diffusion layer between the respective layers by dispersing the film formation start positions of the respective layers. Thereby, the in-plane distribution of the diffusion layer is made uniform, the in-plane distribution of the reflectance in the formed multilayer reflective film can be suppressed, and a high reflectance can be obtained.

[Reflective mask blank]
The present invention also provides a method for manufacturing a reflective mask blank using a substrate with a multilayer reflective film manufactured by the above-described manufacturing method of the present invention.
FIG. 2 is a cross-sectional view showing the layer structure of the reflective mask blank. On the substrate 1, a multilayer reflective film 2 that reflects EUV light, a protective film (capping layer) 3 and a pattern for absorbing EUV light are formed. The reflective mask blank 20 in which the absorber film 4 is formed is shown. Although not shown, a back conductive film can be provided on the side of the substrate 1 opposite to the side where the multilayer reflective film or the like is formed.
The substrate with the multilayer reflective film in the state where the multilayer reflective film is formed on the substrate 1 is as described above, and the description thereof is omitted here.

Usually, the protective film 3 and the buffer film are provided between the multilayer reflective film 2 and the absorber film 4 for the purpose of protecting the multilayer reflective film 2 during patterning or pattern correction of the absorber film 4. As a material for the protective film 3, in addition to silicon, ruthenium or a ruthenium compound containing one or more elements of niobium, zirconium, and rhodium in ruthenium is used. As a material for the buffer film, a chromium-based material is mainly used. Used.
The protective film 3 and the buffer film are preferably formed by a sputtering method such as magnetron sputtering.
In the present invention, the substrate having the multilayer reflective film includes the protective film 3 formed on the multilayer reflective film 2.

The absorber film 4 has a function of absorbing exposure light such as EUV light. For example, tantalum (Ta) alone or a material mainly composed of Ta can be preferably used. The material mainly composed of Ta is usually an alloy of Ta. Such an absorber film preferably has an amorphous or microcrystalline structure in terms of smoothness and flatness.
As a material having Ta as a main component, a material containing Ta and B, a material containing Ta and N, a material containing Ta and B and further containing at least one of O and N, a material containing Ta and Si, Ta A material containing Si and N, a material containing Ta and Ge, a material containing Ta, Ge and N can be used. By adding B, Si, Ge or the like to Ta, an amorphous material can be easily obtained and the smoothness can be improved. Further, when N or O is added to Ta, resistance to oxidation is improved, so that an effect that stability with time can be improved is obtained.

Among these, as a particularly preferable material, for example, a material containing Ta and B (composition ratio Ta / B is in the range of 8.5 / 1.5 to 7.5 / 2.5), Ta, B and N are included. Materials (N is 5 to 30 atomic%, and B is 10 to 30 atomic% when the remaining components are 100). In the case of these materials, a microcrystalline or amorphous structure can be easily obtained, and good smoothness and flatness can be obtained.
Such an absorber film containing Ta alone or Ta as a main component is preferably formed by a sputtering method such as magnetron sputtering. For example, in the case of a TaBN film, a target containing tantalum and boron can be used and a film can be formed by a sputtering method using an argon gas to which nitrogen is added.

As the absorber film, materials other than materials mainly composed of Ta include materials such as WN, TiN, and Ti.
The thickness of the absorber film 4 may be a thickness that can sufficiently absorb, for example, EUV light as exposure light, but is usually about 30 to 100 nm. The absorber film 4 may have a laminated structure of a plurality of layers having different materials and compositions (for example, a laminated film of a TaBN film and a TaBO film).

Even in the case of a reflective mask that applies EUV light to exposure light, the inspection light used for pattern inspection is often light having a longer wavelength than EUV light having a wavelength of 193 nm, 257 nm, or the like. In order to deal with long-wavelength inspection light, it is necessary to reduce the surface reflection of the absorber film. In this case, the absorber film may have a structure in which an absorber layer mainly having a function of absorbing EUV light and a low reflection layer mainly having a function of reducing surface reflection with respect to inspection light are laminated from the substrate side. As the low reflection layer, when the absorber layer is a material mainly composed of Ta, a material containing O in Ta or TaB is suitable.
The reflective mask blank may be in a state where a resist film for forming a predetermined transfer pattern is formed on the absorber film.

According to the present invention, a reflective mask blank is manufactured using a substrate with a multilayer reflective film that has a high reflectance obtained by the above-described present invention and suppresses the in-plane distribution of the reflectance. A good high quality reflective mask blank is obtained.

[Reflective mask]
The present invention also provides a method for manufacturing a reflective mask using the reflective mask blank having the above-described configuration.
FIG. 3 is a cross-sectional view showing a layer structure of the reflective mask, and shows a reflective mask 30 including an absorber film pattern 4a in which the absorber film 4 in the reflective mask blank 20 of FIG. 2 is patterned.
As a method for patterning the absorber film 4 serving as a transfer pattern in the reflective mask blank, a photolithography method capable of performing high-definition patterning is most preferable.

By manufacturing a reflective mask using the above-described high-quality reflective mask blank with good reflectance characteristics according to the present invention, a reflective mask with few pattern defects can be obtained during pattern transfer using EUV light.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
Example 1
The substrate to be used is a SiO ₂ —TiO ₂ glass substrate (6 inch square, thickness 6.35 mm).
Then, the end surface of the glass substrate is chamfered and ground, and the glass substrate that has been subjected to rough polishing with a polishing liquid containing cerium oxide abrasive grains is set on the carrier of a double-side polishing apparatus, and the colloidal silica abrasive is used as the polishing liquid. Using an alkaline aqueous solution containing grains, precise polishing was performed under predetermined polishing conditions. After precision polishing, the glass substrate was washed.
As described above, an EUV reflective mask blank glass substrate was produced. The surface roughness of the main surface of the obtained glass substrate was as good as 0.150 nm or less in terms of root mean square roughness (RMS). Moreover, it was formed with a flatness of 50 nm or less.

Next, a multilayer reflective film was formed on the reflective mask blank glass substrate as follows. As the multilayer reflective film formed on the substrate, a Mo film / Si film periodic multilayer reflective film was employed in order to obtain a multilayer reflective film suitable for an exposure light wavelength band of 13 to 14 nm.
That is, the multilayer reflective film was formed by alternately stacking on the substrate by ion beam sputtering using a Mo target and a Si target.

First, the Si target angle was adjusted so that the incident angle of sputtered particles with respect to the substrate main surface was 30 degrees, and a Si film was formed to a thickness of 4.2 nm.
Subsequently, the Mo target angle was adjusted so that the incident angle of sputtered particles with respect to the main surface of the substrate was 50 degrees, and a Mo film was formed to 2.8 nm.

As described above, a Si film having a thickness of 4.2 nm and a Mo film having a thickness of 2.8 nm were formed, and this was formed as one period, and then 40 periods were laminated. Then, an Si film was formed with an incident angle of 30 degrees.
However, in this example, for the 10 cycles of the upper layer (each 10 layers of Si and Mo), the substrate azimuth at the start of film formation of each layer is set to the substrate azimuth at the start of film formation of each immediately preceding layer. The film was formed by changing 90 degrees each.
When the reflectivity of this multilayer reflective film was measured with 13.5 nm EUV light at an incident angle of 6.0 degrees, the reflectivity was 66%. The in-plane distribution of reflectance was 0.2%. As for the in-plane distribution of reflectance, 81 points of reflectance are measured at equal intervals in a measuring area of 132 mm × 132 mm, and the difference between the maximum value and the minimum value (MAX−MIN) is calculated. Asked.
Further, in the same manner as described above, 50 multilayer reflective film-coated substrates were produced. As a result of measuring the in-plane distribution of the reflectance of the 50 substrates with the multilayer reflective film, 45 out of 50 substrates (yield 90%) had an in-plane distribution of the reflectance of 0.3% or less. The substrate that was 0.2% or less was 33 out of 50 substrates (yield was 66%).

  As described above, according to the embodiment of the present invention, good results can be obtained in both the EUV light reflectance and the in-plane distribution of reflectance, and the reflectance is high and the in-plane distribution of reflectance is suppressed. can do.

(Comparative example)
In Example 1, the azimuth angle of the substrate at the start of film formation of each layer is 90 degrees with respect to the substrate azimuth angle at the start of film formation of each immediately preceding layer for 10 periods of the upper layer (10 layers of Si and Mo). A multilayer reflective film was formed without performing the control of changing each one, thereby producing a substrate with a multilayer reflective film.
When the reflectance of this multilayer reflective film was measured with 13.5 nm EUV light at an incident angle of 6.0 degrees, the reflectance was 64%. In addition, the in-plane distribution of reflectance was as large as 0.4%.
Further, in the same manner as described above, 50 multilayer reflective film-coated substrates were produced. As a result of measuring the in-plane distribution of the reflectivity of the 50 substrates with multilayer reflective films, 20 out of 50 substrates (yield 40%) had an in-plane distribution of reflectivity of 0.3% or less. The substrate that was 0.2% or less was 0 out of 50 substrates (the yield was 0%).

  As described above, according to this comparative example, the EUV light reflectance is slightly low, and the in-plane distribution of the reflectance cannot be suppressed. Reflective mask blanks and reflective masks that do not meet the in-plane distribution standard of reflectivity (0.2% or less in SEMI standard) and that use such a substrate with a multilayer reflective film having a large in-plane distribution of reflectivity When the pattern is transferred to the transfer target with EUV light using the obtained reflective mask, there is a risk that an unacceptable pattern defect will occur.

(Example 2)
In Example 1 above, the azimuth angle of the substrate at the start of film formation for each layer for the 40 periods (40 layers of Si and Mo) of all layers constituting the multilayer reflective film is the same as that at the start of film formation of each immediately preceding layer. 50 substrates with a multilayer reflective film were produced in the same manner as in Example 1 except that the film was formed by changing the substrate azimuth by 90 degrees.
As a result, the reflectivity is 66% and the reflectivity is 66%. In addition, 50 out of 50 substrates (yield 100%) and 0.2% or less of the substrates where the in-plane distribution of reflectivity is 0.3% or less. The number of the substrates was as good as 35 out of 50 (yield 70%).

(Example 3)
On the multilayer reflective film of the multilayer reflective film-coated substrate produced in Example 1, a protective film (thickness 2.5 nm) made of RuNb was formed by DC magnetron sputtering.
When the reflectance of this protective film surface was measured with 13.5 nm EUV light at an incident angle of 6.0 degrees, the reflectance was 63%.
Next, a laminated film of a TaBN film (film thickness 56 nm) and a TaBO film (film thickness 14 nm) was formed as an absorber film on the protective film by a DC magnetron sputtering method.
Thus, a reflective mask blank was produced.

Next, using this reflective mask blank, a reflective mask for EUV exposure having a pattern of DRAM hp 20 nm generation in the semiconductor design rule was produced as follows.
First, a resist film for electron beam drawing was formed on the reflective mask blank, a predetermined pattern was drawn using an electron beam drawing machine, and after drawing, a resist pattern was formed by development.
Next, using this resist pattern as a mask, the TaBO film was dry-etched with fluorine-based gas (CF ₄ gas), and the TaBN film was dry-etched with chlorine-based gas (Cl ₂ gas) to form a transfer pattern on the absorber film.
Further, the resist pattern remaining on the absorber film pattern was removed with hot sulfuric acid to obtain a reflective mask.

When the final confirmation inspection of the obtained reflective mask was performed, it was confirmed that the DRAM hp 20 nm generation pattern in the semiconductor design rule was formed as designed.
Next, when pattern transfer by EUV light is performed on a semiconductor substrate using the obtained reflective mask of this embodiment, a semiconductor device of the semiconductor design rule DRAM hp 20 nm generation can be manufactured.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multi-layer reflective film 21 Si film 22 Mo film 3 Protective film 4 Absorber film 10 Substrate with multilayer reflective film 20 Reflective mask blank 30 Reflective mask 50 Ion beam sputtering apparatus 51 Ion beam generators 54 and 55 Sputtering target 59 Motor 60 Substrate rotation control means 61 PC
62 Optical sensor

Claims (7)

A method of manufacturing a substrate with a multilayer reflective film comprising a multilayer reflective film that reflects exposure light on the substrate,
The multilayer reflective film is formed by laminating a plurality of periods on the substrate, in which a low refractive index layer and a high refractive index layer are sputter-deposited in this order while rotating the substrate about its central axis. And
A method for producing a substrate with a multilayer reflective film, wherein the low refractive index layer and the high refractive index layer are formed with different azimuth angles at the start of film formation.   2. The film forming method according to claim 1, wherein when forming at least the upper layer of the multilayer reflective film, the low refractive index layer and the high refractive index layer are formed with different azimuth angles of the substrate at the start of film formation. The manufacturing method of the board | substrate with a multilayer reflective film of description.   3. The multilayer reflective film according to claim 1, wherein the azimuth angle of the substrate is formed by shifting the azimuth of the low refractive index layer and the high refractive index layer by one or more revolutions of the number of layers. A method for manufacturing a substrate.   4. The method for manufacturing a substrate with a multilayer reflective film according to claim 1, wherein the low refractive index layer is a silicon layer, and the high refractive index layer is a molybdenum layer.   The method for manufacturing a substrate with a multilayer reflective film according to claim 1, wherein the multilayer reflective film is formed by using an ion beam sputtering method.   6. A reflective mask blank comprising an absorber film that absorbs exposure light on the multilayer reflective film in the substrate with the multilayer reflective film obtained by the manufacturing method according to claim 1. Production method. A method for producing a reflective mask, comprising patterning the absorber film in a reflective mask blank obtained by the production method according to claim 6.

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