JP5594106B2 - Reflective mask and method of manufacturing the same - Google Patents

Description

  The present invention relates to a reflective mask used in extreme ultraviolet (EUV) lithography.

  As a reflective mask for EUV lithography (hereinafter sometimes referred to as an EUV mask) used for manufacturing semiconductor elements, a multilayer film is generally formed on a substrate, and an absorption layer is formed in a pattern on the multilayer film. (For example, refer to Patent Document 1).

  In the process of manufacturing an EUV mask, a pattern defect is usually inspected after a pattern is formed by etching the absorption layer. If a defect is found, the defect is corrected. Here, the portion where the pattern is missing is called a white defect.

As a method for correcting a white defect in a photomask for manufacturing a semiconductor element (hereinafter sometimes referred to as a photomask), a chemical using a focused ion beam (FIB) or an electron beam (EB) is used. A method of forming a deposited film on a white defect portion by a vapor deposition method (CVD: Chemical Vapor Deposition) is known.
Even in the case of an EUV mask, white defect correction by forming a deposited film is effective. For example, Patent Document 2 discloses a CVD method using FIB and EB as a white defect correction method for an EUV mask.

JP 2002-319542 A JP 2003-133206 A

  In EUV lithography, a reflective optical system is used. Further, since the EUV mask is also a reflective mask, exposure light at the time of EUV exposure is incident obliquely on the mask. In general, an optical system in which the incident angle of exposure light is inclined by about 6 to 8 degrees with respect to the mask surface normal is the mainstream. In the manufacture of semiconductor elements, the mask pattern is transferred by projecting exposure light onto a resist on the wafer. The exposure light incident obliquely on the mask is a so-called shadow affected by the three-dimensional structure of the mask pattern. The projected image is transferred to the resist on the wafer. The shadow effect depends on the exposure light incident angle at the time of EUV exposure, the film thickness of the mask pattern, and the like. Therefore, when correcting a white defect by forming a deposited film in an EUV mask, the film thickness of the deposited film affects the transfer dimension, and therefore it is necessary to consider the shadow effect during EUV exposure.

  Here, a material that absorbs exposure light with high efficiency is used for the absorption layer, and a film thickness of about 40 nm to 90 nm is sufficient to obtain satisfactory lithography characteristics. On the other hand, in the deposited film, it is necessary to satisfy the requirement that the source gas of the CVD method can be supplied to a fine white defect portion and can form a highly accurate deposited film with charged particles such as FIB and EB. For this reason, there are limitations on selectable gas types. Therefore, generally, the deposited film has a lower absorption ability of exposure light than the absorption layer. Therefore, in order to obtain EUV light shielding characteristics equivalent to those of the absorption layer, it is necessary to form the deposited film thicker than the absorption layer. However, when a deposited film thicker than the absorbing layer is formed in the white defect portion, there arises a problem that the transfer size is different between the deposited film formation portion and the normal portion due to the shadow effect during EUV exposure.

As a source gas for the CVD method, a hydrocarbon-based gas such as phenanthrene, a metal-containing gas such as tungsten carbonyl (W (CO) ₆ ), or a silicon-containing gas such as tetraethoxysilane (TEOS) can be used. When the deposited film contains a metal, the absorption capability of exposure light is relatively high. Therefore, when a metal-containing gas is used, the desired light-shielding property can be obtained even if the deposited film is relatively thin. It is thought that the change in the transfer dimension due to the film can be suppressed, but the shape controllability of the deposited film is poor, and when the deposited film is formed in the normal part, it is very difficult to remove the deposited film. is there. On the other hand, when a hydrocarbon-based gas or a silicon-containing gas is used, the shape of the deposited film can be easily controlled, and the deposited film can be easily removed even when the deposited film is formed in the normal part. However, since the deposited film containing carbon or silicon has a low ability to absorb exposure light, as described above, it is necessary to form the deposited film to be quite thick in order to obtain a sufficient light-shielding property. There is a problem that is remarkable.

  Although methods for correcting white defects in EUV masks have been studied, there is currently no study on the problem of deterioration in transfer characteristics due to the shadow effect after white defect correction by deposit film formation.

  In the case of a photomask, the optical system is a transmission optical system in which exposure light (DUV: Deep Ultra Violet (DUV) region) having a wavelength of about 193 nm to 248 nm is perpendicularly incident on the mask. The image is transferred to resist on the wafer. Therefore, when correcting a white defect by forming a deposited film in a photomask, it is not necessary to consider the shadow effect at the time of EUV exposure, and there is no problem of variation in transfer dimensions due to the shadow effect in the first place.

  The present invention has been made in view of the above problems, and provides a reflective mask in which white defects are corrected by forming a deposited film, and has a good transfer characteristic, and a method of manufacturing the same. Is the main purpose.

  In order to achieve the above object, the present invention is a reflective mask comprising a substrate, a multilayer film formed on the substrate, and an absorber formed in a pattern on the multilayer film, The absorber has an absorption layer and a white defect portion caused by the absence of the absorption layer, and has a deposited film thicker than the absorption layer, the deposited film contains a nonmetallic material, and the deposited A straight line connecting a position of a third thickness and a position of a third thickness from the top of the deposited film on a side surface of the deposited film, the thickness of the film being in a range of 125 nm to 500 nm, and the substrate Provided is a reflective mask characterized in that an angle formed by a line perpendicular to the surface is in a range of 6 to 40 degrees.

  In the present invention, since the deposited film contains a non-metallic material, the thickness of the deposited film is within the above range in order to obtain EUV light shielding characteristics equivalent to the absorption layer at the deposited film formation location. The deposited film is formed to be considerably thicker than the absorbing layer, and a straight line connecting the position of the third thickness and the position of the third thickness from the top of the deposited film on the side surface of the deposited film, Since the angle formed by the line perpendicular to the surface is within a predetermined range, the shadow effect can be reduced even if the deposited film is thick, and the transfer dimension deviation between the normal part and the deposited film forming position is reduced. Therefore, it is possible to realize good transfer characteristics.

  In the above invention, the position of the thickness of one third from the top of the deposited film and the thickness of the two thirds on the side surface of the deposited film facing the reflective region where the absorber is not formed on the multilayer film. It is preferable that an angle formed by a straight line connecting the positions of the line and a line perpendicular to the substrate surface is in a range of 6 degrees to 40 degrees. On the side surface of the deposited film, there are a side surface facing the reflection region where the absorber is not formed on the multilayer film and a side surface facing the absorption region where the absorption layer is formed on the multilayer film. Among these side surfaces of the deposited film, a straight line connecting the position of the thickness of 1/3 and the position of the thickness of 2/3 from the top of the deposited film on the side surface facing the reflection region is perpendicular to the substrate surface. The angle formed with the line has a great influence on the transfer characteristics. Therefore, in the present invention, a straight line connecting a position of the thickness of one third and a position of the thickness of two thirds from the top of the deposited film on the side surface of the deposited film facing the reflection region is perpendicular to the substrate surface. It is preferable that the angle formed with the line is within a predetermined range.

  Moreover, in the said invention, it is preferable that the said nonmetallic material contains a silicon | silicone. It is because it can be set as a deposited film with favorable workability and weather resistance.

  The present invention also provides an absorption layer forming step of forming an absorption layer in a pattern on a substrate on which a multilayer film is formed, and supplying a non-metallic source gas to a white defect portion resulting from the absence of the absorption layer. A correction step of irradiating an energy beam to form a deposited film, and in the correction step, the total energy amount at the center of the white defect portion is larger than the total energy amount at the end portion of the white defect portion. The present invention provides a method for manufacturing a reflective mask, which is characterized by irradiating an energy beam so as to increase the number.

  In the present invention, a deposited film is formed using a non-metallic source gas. Therefore, in order to obtain EUV light shielding characteristics equivalent to those of the absorbing layer at the deposited film forming position, the deposited film is formed to be considerably thicker than the absorbing layer. In the correction process, the energy beam is irradiated so that the total energy amount at the center of the white defect portion is larger than the total energy amount at the edge of the white defect portion. The thickness of the deposited film at the edge of the defective portion is thinner than the thickness of the deposited film at the central portion of the white defective portion, and the deposited film can be adjusted to a predetermined film thickness and cross-sectional shape. The effect can be reduced, and the deviation of the transfer dimension between the normal portion and the deposited film formation portion can be reduced, and good transfer characteristics can be realized.

  In the said invention, it is preferable to irradiate an energy beam in the said correction process so that the frequency | count of irradiation in the center part of the said white defect part may become larger than the frequency | count of irradiation in the edge part of the said white defect part. This is because the film thickness and cross-sectional shape of the deposited film can be controlled under simple irradiation conditions.

  In the above invention, the energy beam is preferably a focused ion beam or an electron beam. This is because the focused ion beam and the electron beam can be subjected to high-level fine processing and can cope with a fine white defect portion.

  In the present invention, an angle formed by a straight line connecting a position of the thickness of one third and a position of the thickness of two thirds from the top of the deposited film on the side surface of the deposited film and a line perpendicular to the substrate surface Is within the predetermined range, it is possible to reduce the shadow effect and to obtain an excellent transfer characteristic.

It is the schematic plan view and sectional drawing which show an example of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show the other example of the reflective mask of this invention. It is a schematic sectional drawing which shows the other example of the reflective mask of this invention. It is a schematic sectional drawing which shows the other example of the reflective mask of this invention. It is process drawing which shows an example of the manufacturing method of the reflective mask of this invention. It is a schematic diagram which shows an example of the correction process in the manufacturing method of the reflective mask of this invention. 6 is a graph showing the relationship between the thickness of a deposited film and EUV light shielding characteristics in Experimental Example 1. 6 is a graph showing the relationship between the thickness of a deposited film and EUV light shielding characteristics in Experimental Example 1. 6 is a graph showing the relationship between the thickness of a deposited film and EUV light shielding characteristics in Experimental Example 1. It is the schematic plan view and sectional drawing which show the pattern of the absorption layer in Experiment 2, and a white defect part. It is the schematic plan view and sectional drawing which show the reflective mask in Experimental example 2. 6 is a graph showing a relationship between an inclination angle θ and a transfer dimension in Example 1. 3 is a graph showing a cross-sectional shape of a deposited film in Example 1.

  Hereinafter, the reflective mask of the present invention and the manufacturing method thereof will be described in detail.

A. Reflective Mask The reflective mask of the present invention is a reflective mask having a substrate, a multilayer film formed on the substrate, and an absorber formed in a pattern on the multilayer film, and the absorption mask. A body having an absorption layer and a white film formed in a white defect caused by the absence of the absorption layer, and a deposited film thicker than the absorption layer, the deposited film containing a nonmetallic material, and the deposited film A straight line connecting a position of a third thickness and a position of a third thickness from the top of the deposited film on the side surface of the deposited film, and the substrate surface The angle formed by a line perpendicular to the angle (hereinafter sometimes referred to as an inclination angle) is in the range of 6 degrees to 40 degrees.

The reflective mask of the present invention will be described with reference to the drawings.
1A is a schematic plan view showing an example of the reflective mask of the present invention, FIG. 1B is a cross-sectional view taken along the line AA of FIG. 1A, and FIG. It is BB sectional drawing of a). As illustrated in FIGS. 1A to 1C, the reflective mask 1 includes a substrate 2, a multilayer film 3 formed on the substrate 2, a capping layer 4 formed on the multilayer film 3, and And an absorber 5 formed in a pattern on the capping layer 4. The absorber 5 includes an absorption layer 6 and a deposited film 7 that is formed in the white defect portion 10 resulting from the absence of the absorption layer 6 and is thicker than the absorption layer 6. The deposited film 7 has a predetermined thickness and has a trapezoidal cross section. The deposited film 7 has a side surface facing the reflection region 31 where the absorber 5 is not formed on the multilayer film 3 and a side surface facing the absorption region 32 where the absorption layer 6 is formed on the multilayer film 3. Have. In FIG. 1B, a straight line L1 connecting a position a having a thickness of 1/3 and a position b having a thickness of 2/3 from the top T of the deposited film 7 on the side surface of the deposited film 7 facing the reflective region 31. And the angle (inclination angle) θ1 formed by the line L2 perpendicular to the surface of the substrate 2 is within a predetermined range. Further, in FIG. 1C, the position a having a thickness of 1/3 and the position b having a thickness of 2/3 are connected to the top T of the deposited film 7 on the side surface of the deposited film 7 facing the absorption region 32. An angle (tilt angle) θ2 formed by the straight line L1 and a line L2 perpendicular to the surface of the substrate 2 is an arbitrary angle.
In FIG. 1A, the multilayer film and the capping layer are omitted.

2A is a schematic plan view showing another example of the reflective mask of the present invention, FIG. 2B is a cross-sectional view taken along the line CC of FIG. 2A, and FIG. It is the DD sectional view taken on the line 2 (a). The reflective mask illustrated in FIGS. 2A to 2C is different from the reflective mask illustrated in FIGS. 1A to 1C in the position of the white defect portion. 2A to 2C, the deposited film 7 has only a side surface facing the absorption region 32. As shown in FIG. 2B, among the side surfaces of the deposited film 7, the position a having a thickness of 1/3 from the top T of the deposited film 7 on the side surface of the deposited film 7 having the closest distance to the reflective region 31 and An angle (inclination angle) θ1 formed by a straight line L1 connecting the position b having a thickness of two-thirds and a line L2 perpendicular to the surface of the substrate 2 is within a predetermined range. Further, as shown in FIG. 2C, the thickness of the side surface of the deposited film 7 is one third from the top T of the deposited film 7 on the side surface of the deposited film 7 that intersects the longitudinal direction of the pattern of the absorption layer 6. An angle (inclination angle) θ2 formed by a straight line L1 connecting the position a and the position b having a thickness of 2/3 and a line L2 perpendicular to the surface of the substrate 2 is an arbitrary angle.
In FIG. 2A, the multilayer film and the capping layer are omitted.

  In the present invention, since the deposited film contains a non-metallic material, the thickness of the deposited film is within the above range in order to obtain EUV light shielding characteristics equivalent to that of the absorbing layer at the deposited film formation location. The deposited film needs to be formed much thicker than the absorbing layer. For this reason, when a pattern is transferred onto a wafer using the reflective mask of the present invention, there is a concern about a change in transfer dimension due to a shadow effect during EUV exposure. However, according to the present invention, since at least one inclination angle is within the predetermined range, the shadow effect can be reduced, and the deviation of the transfer dimension between the normal portion and the deposited film formation portion is reduced, which is favorable. Transfer characteristics can be realized.

  Hereinafter, each structure in the reflective mask of this invention is demonstrated.

1. Absorber The absorber in the present invention is formed in a pattern on a multilayer film, and has an absorption layer and a deposited film thicker than the absorption layer, formed in a white defect due to the absence of the absorption layer. In the EUV lithography using the reflective mask of the present invention, EUV is absorbed. Hereinafter, the deposited film and the absorption layer will be described.

(1) Deposited film The deposited film constituting the absorber in the present invention is formed in the white defect portion and is thicker than the absorbing layer, and absorbs EUV in EUV lithography using the reflective mask of the present invention. It is.

  In the present invention, the deposited film contains a non-metallic material. The “non-metallic material” in the present invention includes those containing a metal element at 10 at% or less. For example, in the case where a deposited film is formed by irradiating FIB while supplying a source gas, a metal that serves as an FIB ion source may be contained in the deposited film. Specifically, as the metal serving as the FIB ion source, titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), Gallium (Ga), germanium (Ge), zirconium (Zr), silver (Ag), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), platinum (Pt), Examples thereof include gold (Au), lead (Pb), and bismuth (Bi).

The non-metallic material contained in the deposited film is not particularly limited as long as it can absorb EUV, and differs depending on the type of source gas used when forming the deposited film. . Examples of the material include carbon (C) as a main component, silicon (Si) as a main component, carbon (C) and silicon (Si) as a main component. Among these, it is preferable that the nonmetallic material contains silicon. It is because it can be set as a deposited film with favorable workability and weather resistance.
The source gas used for forming the deposited film is not particularly limited as long as a deposited film containing a nonmetallic material can be formed, and is generally used when a CVD method using FIB or EB is applied. The gas used in the above can be used. For example, hydrocarbon gases such as phenanthrene, naphthalene, pyrene, silicon such as tetraethoxysilane (TEOS), 1,3,5,7-tetramethylcyclotetrasiloxane (1,3,5,7-Tetramethylcyclotetra-siloxane) A contained gas can be used.

Further, the deposited film only needs to contain a nonmetallic material. For example, as shown in FIGS. 1B and 3, the deposited film may be a single layer containing a nonmetallic material, As shown in FIG. 4, even if it has the nonmetallic material layer 7a containing a nonmetallic material and the metallic layer 7b formed so as to cover the nonmetallic material layer 7a and containing a metal. Good.
Examples of the metal contained in the metal layer include titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and gallium (Ga). , Germanium (Ge), zirconium (Zr), silver (Ag), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), platinum (Pt), gold (Au) , Lead (Pb), bismuth (Bi), and the like.

In the present invention, the deposited film is thicker than the absorbing layer, and the deposited film has a thickness in the range of 125 nm to 500 nm, preferably in the range of 125 nm to 300 nm, and more preferably in the range of 125 nm to 200 nm. If the deposited film is thinner than the above range, it is difficult to obtain a desired EUV absorption rate. If the deposited film is thicker than the above range, the transfer dimension may change due to the shadow effect. It is because it requires.
The thickness of the deposited film refers to the thickness of the top of the deposited film.
The thickness of the deposited film can be measured, for example, by observing with an atomic force microscope (AFM).

  In the present invention, an angle formed by a straight line connecting a position of the thickness of the third and a position of the thickness of the third from the top of the deposited film on the side surface of the deposited film and a line perpendicular to the substrate surface ( (Tilt angle) is in the range of 6 degrees to 40 degrees, preferably in the range of 10 degrees to 30 degrees, more preferably in the range of 20 degrees to 30 degrees. If the tilt angle is smaller than the above range, the transfer size may change due to the shadow effect. If the tilt angle is larger than the above range, the thickness of the deposited film edge becomes thin, and a desired EUV absorption rate can be obtained. This is because it becomes difficult to obtain sufficient transfer characteristics.

The side surface of the deposited film means a surface other than the lower bottom surface and the upper bottom surface when the deposited film has a lower bottom surface and an upper bottom surface, and when the deposited film has a lower bottom surface and does not have an upper bottom surface. A surface other than the bottom surface.
The top of the deposited film refers to the thickest (highest) portion of the deposited film. In addition, when there are a plurality of white defect portions and a deposited film is formed on each white defect portion, it means the top of each deposited film.
The straight line connecting the position of the thickness of 1/3 from the top of the deposited film on the side surface of the deposited film and the position of the thickness of 2/3 is shown in FIGS. 1 (b), 1 (c), 2 (b), ( As exemplified in c), it can be determined by observing a longitudinal section (a plane perpendicular to the substrate surface) including the top T of the deposited film 7.

Further, as illustrated in FIGS. 1B and 1C and FIGS. 2B and 2C, when the inclination angle differs according to the longitudinal section including the top T of the deposited film 7, at least One inclination angle shall be in the said range.
Here, on the side surface of the deposited film, on the side surface facing the reflective region where the absorber (absorbing layer and deposited film) is not formed on the multilayer film, or on the absorbing region where the absorber layer is formed on the multilayer film. There are facing sides. Of these side surfaces of the deposited film, for example, as shown in FIGS. 1A and 1B, the inclination angle on the side surface of the deposited film 7 facing the reflective region 31 has a great influence on the transfer characteristics. Therefore, the straight line connecting the position of the thickness of 1/3 and the position of the thickness of 2/3 from the top of the deposited film on the side surface of the deposited film facing the reflective region is a line perpendicular to the substrate surface. The angle (tilt angle) is preferably within the above range.
In the case where the reflective mask has a white defect portion, the present invention is useful because it is generally considered that the white defect portion often faces the reflection region.

  In addition, the tilt angle on the side surface of the deposited film facing the absorption region may affect the transfer characteristics. For example, as shown in FIGS. 2A and 2B, when the distance between the side surface of the deposited film 7 facing the absorption region 32 and the reflective region 31 is short, the deposited film facing such an absorption region The inclination angle on the side surface can also greatly affect the transfer characteristics. Therefore, when the distance between the side surface of the deposited film facing the absorption region and the reflective region is short, the position of the thickness of one third from the top of the deposited film on the side surface of the deposited film facing such an absorption region and It is preferable that an angle (inclination angle) formed by a straight line connecting the two-third thickness positions and a line perpendicular to the substrate surface is within the above range.

  On the other hand, among the side surfaces of the deposited film facing the absorption region, for example, as shown in FIGS. 1A to 1C and FIGS. 2A to 2C, the deposited film 7 is far from the reflective region 31. The inclination angle can be an arbitrary angle on the side surfaces of the deposited film 7 intersecting with the longitudinal direction of the pattern of the absorption layer 6.

  Note that the side surface of the deposited film facing the reflective region refers to the side surface of the deposited film in contact with the reflective region. Further, the side surface of the deposited film facing the absorption region means the side surface of the deposited film in contact with the absorption region. The reflective region is a region where an absorber (absorbing layer and deposited film) is not formed on the multilayer film. The absorption region is a region where an absorption layer is formed on the multilayer film.

  The tilt angle can be measured by observing with an atomic force microscope (AFM).

  The cross-sectional shape of the deposited film is not particularly limited as long as the angle of inclination is within the above range, but normally, the cross-sectional shape from the top of the deposited film to the bottom surface (horizontal with respect to the substrate surface). The shape is such that the cross-sectional area at the surface is large. For example, a trapezoidal shape as shown in FIGS. 1B and 1C, a Gaussian distribution shape as shown in FIG. 3, and similar shapes can be mentioned. Among these, a trapezoidal shape and a Gaussian distribution shape are preferable. This is because such a cross-sectional shape can effectively suppress variation in the transfer dimension due to the shadow effect.

  As a method for forming the deposited film, a CVD method using FIB or EB is used.

(2) Absorbing layer The absorbing layer in the present invention is formed in a pattern on the multilayer film, and absorbs EUV in EUV lithography using the reflective mask of the present invention.

  The material of the absorption layer is not particularly limited as long as it can absorb EUV. A material containing one component is used. Furthermore, TaSi, TaSiN, TaGe, TaGeN, WN, TiN, etc. can be used.

  As a method for forming the absorption layer, for example, a magnetron sputtering method, an ion beam sputtering method, a CVD method, a vapor deposition method, or the like is used.

2. Multilayer film The multilayer film used in the present invention is formed on a substrate.

  As a material for the multilayer film, a material generally used for a multilayer film of a reflective mask can be used, and among them, a material having a very high reflectance with respect to EUV is preferably used. This is because the contrast can be increased when the reflective mask is used. For example, as the multilayer film that reflects EUV, a Mo / Si periodic multilayer film is usually used. In addition, as a multilayer film having a high reflectance in a specific wavelength range, for example, a Ru / Si periodic multilayer film, a Mo / Be periodic multilayer film, a Mo compound / Si compound periodic multilayer film, and a Si / Nb period A multilayer film, a periodic multilayer film of Si / Mo / Ru, a periodic multilayer film of Si / Mo / Ru / Mo, a periodic multilayer film of Si / Ru / Mo / Ru, and the like can also be used.

  The thickness of each layer constituting the multilayer film and the number of stacked layers are different depending on the material to be used and are appropriately adjusted. For example, as the Mo / Si periodic multilayer film, a multilayer film in which a Mo film and a Si film having a thickness of about several nm are stacked by 40 to 60 layers can be used.

The thickness of the multilayer film can be, for example, about 280 nm to 420 nm.
As a method for forming the multilayer film, for example, an ion beam sputtering method, a magnetron sputtering method, or the like is used.

3. Capping layer In the present invention, a capping layer may be formed between the multilayer film and the absorption layer. The capping layer is provided to prevent oxidation of the multilayer film and to protect the reflective mask during cleaning. By forming the capping layer, when the outermost surface of the multilayer film is a Si film or a Ru film, the Si film or the Ru film can be prevented from being oxidized. If the Si film or the Ru film is oxidized, the reflectance of the multilayer film may be reduced.
In the present invention, when a buffer layer described later is formed on the multilayer film, the capping layer and the buffer layer are usually stacked in this order on the multilayer film.

The material for the capping layer is not particularly limited as long as it exhibits the above functions, and examples thereof include Si and Ru.
Moreover, as thickness of a capping layer, it can be set as about 2 nm-15 nm, for example.
Examples of the method for forming the capping layer include a sputtering method.

4). Buffer Layer In the present invention, a buffer layer may be formed between the multilayer film and the absorption layer. The buffer layer is provided to prevent damage to the lower multilayer film. By forming the buffer layer, it is possible to prevent the underlying multilayer film from being damaged when the absorption layer is subjected to pattern etching by a method such as dry etching.

As the material of the buffer layer, any material having high etching resistance may be used, and a material having a different etching characteristic from that of the absorption layer, that is, a material having a high etching selectivity with the absorption layer is usually used. The etching selectivity of the buffer layer and the absorption layer is preferably 5 or more, more preferably 10 or more, and still more preferably 20 or more. Furthermore, the material for the buffer layer is preferably a material having low stress and excellent smoothness. In particular, the smoothness of the buffer layer is preferably 0.3 nmRms or less. From such a viewpoint, it is preferable that the material of the buffer layer has a microcrystalline or amorphous structure.
Examples of such a buffer layer material include SiO ₂ , Al ₂ O ₃ , Cr, and CrN.

Further, the thickness of the buffer layer can be, for example, about 2 nm to 25 nm.
Examples of the method for forming the buffer layer include a magnetron sputtering method and an ion beam sputtering method. When SiO ₂ is used, it is preferable to form SiO ₂ on the multilayer film in an Ar gas atmosphere using an SiO ₂ target by RF magnetron sputtering.
As a method for removing the buffer layer after correcting the white defect, a general method for removing the buffer layer can be used, and examples thereof include dry etching.

5. Substrate As the substrate used in the present invention, a substrate generally used for a reflective mask substrate can be used, and for example, a glass substrate or a metal substrate can be used. Among these, a glass substrate is preferably used. A glass substrate is particularly suitable as a substrate for a reflective mask because good smoothness and flatness can be obtained. Examples of the material of the glass substrate include quartz glass, amorphous glass having a low thermal expansion coefficient (for example, SiO ₂ —TiO ₂ glass), crystallized glass on which β quartz solid solution is precipitated, and the like. Examples of the material for the metal substrate include silicon and Fe-Ni-based invar alloys.

  The substrate preferably has a smoothness of 0.2 nmRms or less and a flatness of 100 nm or less in order to obtain a high reflectance and transfer accuracy of a reflective mask. In addition, unit Rms which shows smoothness is a root mean square roughness, and can be measured using an atomic force microscope. The flatness is a value indicating the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). This value is the difference in height between the highest position on the substrate surface above the focal plane and the lowest position below the focal plane when the plane defined by the least square method based on the substrate surface is the focal plane. Is the absolute value of. The smoothness is smoothness in a 10 μm square area, and the flatness is flatness in a 142 mm square area.

  Moreover, as thickness of a board | substrate, it can be set as about 6 mm-7 mm, for example.

B. Manufacturing method of reflective mask The manufacturing method of the reflective mask according to the present invention includes an absorption layer forming step of forming an absorption layer in a pattern on a substrate on which a multilayer film is formed, and a white defect caused by the absence of the absorption layer. A correction step of irradiating an energy beam while supplying a non-metallic source gas to the portion to form a deposited film, and in the correction step, the total energy amount at the central portion of the white defect portion is The energy beam is irradiated so as to be larger than the total energy amount at the end of the white defect portion.

  5A to 5B are process diagrams showing an example of the reflective mask manufacturing method of the present invention. First, as shown in FIG. 5A, the absorption layer 6 is formed in a pattern on the substrate 2 on which the multilayer film 3 and the capping layer 4 are sequentially laminated (absorption layer forming step). The intermediate product 11 has a white defect portion 10 caused by the lack of the absorption layer 6. In order to correct the white defect portion 10, as shown in FIGS. 5 (a) and 5 (b), while the non-metallic source gas 14 is blown from the source gas gas gun 13 to the white defect portion 10, FIB Alternatively, the deposited film 7 is formed by irradiating EB12 (correcting step). At this time, the FIB or EB 12 is irradiated so that the total energy amount at the central portion 21 of the white defect portion 10 is larger than the total energy amount at the end portion 22 of the white defect portion 10. Thereby, it is possible to form the deposited film 7 in which the film thickness at the end 22 of the white defect portion 10 is thinner than the film thickness at the central portion 21 of the white defect portion 10. In this way, the reflective mask 1 is obtained.

In the present invention, a deposited film is formed using a non-metallic source gas. Therefore, in order to obtain EUV light shielding characteristics equivalent to that of the absorbing layer at the position where the deposited film is formed, the deposited film is formed much thicker than the absorbing layer. You may have to. Therefore, when a pattern is transferred onto a wafer using a reflective mask manufactured according to the present invention, there is a concern about a change in transfer dimension due to a shadow effect during EUV exposure.
Here, the thickness of the deposited film is proportional to the amount of energy. Therefore, the film thickness and cross-sectional shape of the deposited film can be controlled by appropriately adjusting the energy amount.
According to the present invention, in the correction process, the energy beam is irradiated so that the total energy amount at the center portion of the white defect portion is larger than the total energy amount at the end portion of the white defect portion. The thickness of the deposited film at the end becomes thinner than the thickness of the deposited film at the center of the white defect portion, and the deposited film can be adjusted to a predetermined film thickness and cross-sectional shape. As a result, it is possible to reduce the shadow effect, to reduce the deviation of the transfer dimension between the normal portion and the deposited film formation location, and to realize good transfer characteristics.

  Hereafter, each process in the manufacturing method of the reflective mask of this invention is demonstrated.

1. Absorption layer formation process The absorption layer formation process in this invention is a process of forming an absorption layer in pattern shape on the board | substrate with which the multilayer film was formed.

  As a method for forming the absorption layer in a pattern, a photolithography method is usually used. Specifically, an absorption layer is formed on a substrate on which a multilayer film is formed, a resist layer is formed on the absorption layer, the resist layer is patterned, and the absorption layer is etched using the resist pattern as a mask to remain. The resist pattern is removed to form an absorption layer in a pattern. As the photolithography method, a general method can be used.

  Since the substrate, the multilayer film and the film forming method thereof, the absorption layer and the film forming method thereof, and other points are described in the above section “A. Reflective mask”, description thereof is omitted here.

2. Correction Step The correction step in the present invention is a step of forming a deposited film by irradiating an energy beam while supplying a non-metallic source gas to a white defect portion caused by a lack of an absorption layer, the white defect This is a step of irradiating the energy beam so that the total energy amount at the center of the portion is larger than the total energy amount at the end of the white defect portion.

  The source gas is not particularly limited as long as it is a non-metallic source gas, and a gas generally used when a CVD method using FIB or EB is applied can be used. For example, hydrocarbon gases such as phenanthrene, naphthalene, pyrene, silicon such as tetraethoxysilane (TEOS), 1,3,5,7-tetramethylcyclotetrasiloxane (1,3,5,7-Tetramethylcyclotetra-siloxane) A contained gas can be used.

  The energy beam is not particularly limited as long as a deposited film can be locally formed in the white defect portion, but FIB or EB is preferably used. This is because advanced microfabrication is possible and it is possible to deal with fine white defect portions.

In the present invention, the energy beam is irradiated so that the total energy amount at the center of the white defect portion is larger than the total energy amount at the end of the white defect portion. As a result, the thickness of the deposited film at the edge of the white defect portion becomes thinner than the thickness of the deposited film at the central portion of the white defect portion, and the deposited film can be controlled to a predetermined film thickness and cross-sectional shape. Become.
Examples of the method for adjusting the total energy amount include a method of adjusting the intensity of the energy beam, the number of irradiations, the irradiation time, and the like. Specifically, a method of making the intensity at the center of the white defect portion greater than the intensity at the end of the white defect portion, and the number of irradiations at the center of the white defect portion to irradiate at the end of the white defect portion Examples include a method of increasing the number of times more than the number of times, a method of making the irradiation time at the center of the white defect portion longer than the irradiation time at the end of the white defect portion, and the like. These methods may be combined. In particular, since the irradiation conditions of the energy beam can be simplified, it is preferable to irradiate the energy beam so that the number of times of irradiation at the center portion of the white defect portion is larger than the number of times of irradiation at the end portion of the white defect portion.

  In general, when a deposited film is formed by irradiating an energy beam while supplying a raw material gas to a white defect portion, for example, as shown by an arrow in FIG. There is a tendency to irradiate the energy beam and repeat this several times. In such a case, when adjusting the number of times of irradiation of the energy beam, for example, a method of adjusting the irradiation interval of the energy beam, or the first irradiation of the energy beam to the end portion and the center portion of the white defect portion. And the method of irradiating an energy beam only to the center part of a white defect part etc. can be used for the 2nd time.

The EUV reflectance is substantially proportional to the thickness of the deposited film, and the EUV reflectance becomes lower as the deposited film becomes thicker. In EUV lithography using a reflective mask manufactured according to the present invention, the EUV reflectance at which the deposited film formation portion is not transferred onto the wafer has a threshold value depending on the size and shape of the white defect portion and the wafer transfer conditions. Exists. For example, when the reflectance in the absorption region where the absorption layer is formed on the multilayer film is 2%, the reflectance on the deposited film formation site must be reduced to the same level as the reflectance in the absorption region. In some cases, it may not be transferred onto the wafer if it is reduced to 10% even if the reflectance at the deposited film forming portion is not reduced to 2%. Specifically, when the white defect portion is a fine pinhole defect, it is possible to prevent the deposited film formation portion from being transferred onto the wafer simply by forming the deposited film thinly. Thus, the necessary thickness of the deposited film depends on the white defect portion to be corrected. Therefore, in the method for manufacturing a reflective mask according to the present invention, the thickness of the deposited film may be a thickness that can obtain transfer characteristics equivalent to those of the absorption layer, and specifically, may be in the range of 50 nm to 500 nm. Preferably, in the range of 100 nm to 300 nm, more preferably in the range of 100 nm to 200 nm. If the deposited film is thinner than the above range, it is difficult to obtain a desired EUV absorption rate. If the deposited film is thicker than the above range, the transfer dimension may change due to the shadow effect. It is because it requires.
The thickness of the deposited film refers to the thickness of the top of the deposited film.
The thickness of the deposited film can be measured, for example, by observing with an atomic force microscope (AFM).

  Since the other points of the deposited film can be the same as those described in the above section “A. Reflective mask”, description thereof is omitted here.

3. Capping layer forming step In the present invention, a capping layer forming step of forming a capping layer on the multilayer film may be performed before the absorbing layer forming step. By forming the capping layer, when the outermost surface of the multilayer film is a Si film or a Ru film, the Si film or the Ru film can be prevented from being oxidized, and the reflective mask can be protected during cleaning. Can do.

  The film forming method of the capping layer and other points are described in the above section “A. Reflective mask”, and thus the description thereof is omitted here.

4). Buffer layer forming step and buffer layer peeling step In the present invention, a buffer layer forming step for forming a buffer layer on the multilayer film is performed before the absorbing layer forming step, and the exposed buffer layer is removed after the correcting step. You may perform the buffer layer peeling process to peel. By forming the buffer layer, it is possible to prevent the lower multilayer film from being damaged when the absorption layer is patterned.
In the present invention, when the capping layer forming step is performed, the buffer layer forming step is usually performed after the capping layer forming step.

  Since the buffer layer forming method, the peeling method, and other points are described in the above section “A. Reflective Mask”, the description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The following examples illustrate the present invention in more detail.

[Experimental Example 1]
The relationship between the thickness of the deposited film and the EUV light shielding characteristics was verified.

(Hydrocarbon gas)
FIG. 7 shows the calculation result of the relationship between the film thickness of the deposited film and the EUV light shielding characteristics when the deposited film is formed on the multilayer film using phenanthrene as the source gas. In addition, when the EUV light-shielding characteristic when an absorption layer (film thickness 51 nm) made of tantalum was formed on the multilayer film was calculated, the reflectance was 2%.
As is apparent from FIG. 7, the amount of decrease in EUV reflectance from the multilayer film is substantially proportional to the film thickness of the deposited film. There is a threshold value of reflectance that is not transferred onto the wafer depending on the pattern, line width, and wafer transfer conditions that are subject to defect correction, but the light-shielding characteristics equivalent to the reflectance (2%) when the absorption layer is formed It was confirmed from FIG. 7 that a film thickness of 150 nm or more thicker than the absorption layer is required to obtain a deposited film.

(Silicon-containing gas)
FIG. 8 shows a deposited film when a deposited film is formed on a multilayer film using 1,3,5,7-tetramethylcyclotetrasiloxane (1,3,5,7-tetramethylcyclotetrasiloxane) as a source gas. The result of having computed the relationship between the film thickness of this and EUV light-shielding characteristic by calculation is shown.
In order to obtain a light-shielding characteristic equivalent to the reflectance (2%) when the absorption layer is formed with the deposited film, it was confirmed from FIG. 8 that a film thickness of 125 nm or more thicker than the absorption layer is required.

(Metal-containing gas)
FIG. 9 shows the calculation result of the relationship between the film thickness of the deposited film and the EUV light shielding characteristics when the deposited film is formed on the multilayer film using tungsten carbonyl (W (CO) ₆ ) as the source gas. Show.
It was confirmed from FIG. 9 that a film thickness of about 110 nm is sufficient to obtain a light-shielding characteristic equivalent to the reflectance (2%) when the absorption layer is formed.

  As described above, when using a hydrocarbon-based gas or a silicon-containing gas, it is necessary to form a deposited film considerably thicker in order to obtain the desired light-shielding characteristics than when a metal-containing gas is used. The variation of the transfer dimension due to the shadow effect appears remarkably. Therefore, in the present invention, the deposited film contains a nonmetallic material. In addition, when the deposited film contains a non-metallic material, it is sufficient that the deposited film has a thickness of at least 125 nm or more. In the present invention, the deposited film has a thickness of 125 nm or more.

[Experiment 2]
The transfer characteristics of the deposited film formation site were verified. The simulator used was EM-Suite made by Panoramic Technology. The simulation was performed using an actual EUV mask structure and an optical system of an EUV transfer apparatus as models.

  The structure of the EUV mask is shown in FIGS. 10 (a) and 10 (b). 10A is a plan view, and FIG. 10B is a cross-sectional view taken along the line EE of FIG. 10A. As shown in FIGS. 10A and 10B, the EUV mask has a structure in which 40 pairs of molybdenum (film thickness 2.8 nm) and silicon (film thickness 4.2 nm) are formed on a substrate 2 made of silicon oxide. A multilayer film 3, a capping layer 4 (thickness 11 nm) made of silicon, and an absorption layer 6 (thickness 66 nm) made of patterned tantalum were sequentially formed. The pattern of the absorption layer 6 was a line pattern having a line width of 260 nm, and the white defect portion 10 was a disconnection defect in which a line having a width of 260 nm and a length of 520 nm disappeared. In FIG. 10A, the multilayer film and the capping layer are omitted.

  FIGS. 11A and 11B show the structure of the EUV mask after the deposited film is formed. Fig.11 (a) is a top view, FIG.11 (b) is the FF sectional view taken on the line of Fig.11 (a). In FIG. 11A, the multilayer film and the capping layer are omitted. In the simulation of the deposited film formation location, as shown in FIG. 11B, the position a having a thickness of 1/3 from the top T of the deposited film 7 on the side surface of the deposited film 7 facing the reflective region 31 and 3 minutes. The angle (inclination angle) θ between the straight line L1 connecting the position b of the thickness 2 and the line L2 perpendicular to the surface of the substrate 2 was changed in the range of 0 to 40 degrees. The transfer conditions are set in the optical system of the EUV exposure apparatus EUV1 manufactured by Nikon Corporation, and NA = 0.25 and σ = 0.8 (conventional), and the incident angle ω of the EUV 51 as shown in FIG. Was set to 6 degrees. The transfer pattern dimension was calculated from an optical image that was subjected to 1/4 reduction exposure on the wafer. The material of the deposited film was set to an optical constant of diamond-like carbon (DLC), and the film thickness was set to 150 nm calculated in FIG.

  FIG. 12 shows the relationship between the inclination angle θ and the transfer dimension. Here, the transfer size of the normal part is 65 nm. When the inclination angle θ was 0 degree, that is, when the cross-sectional shape was a rectangular shape, the transfer dimension of the deposited film formation portion was 75.9 nm, and a deviation amount of about 11 nm (17%) occurred compared to the normal part. Generally, it is required that the transfer size of the white defect correction portion is within 5% as compared with the normal portion. It was calculated that the inclination angle θ should be 6 degrees or more in order to keep it within 5%, that is, within 3.25 nm. This confirmed the effectiveness of controlling the tilt angle, that is, the cross-sectional shape of the deposited film in consideration of the shadow effect during EUV exposure.

[Example 1]
On a substrate made of silicon oxide, a multilayer film consisting of 40 pairs of molybdenum (film thickness 2.8 nm) and silicon (film thickness 4.2 nm), a capping layer (film thickness 11 nm) made of silicon, and patterned tantalum An absorption layer (film thickness 66 nm) made of was formed in order. The pattern of the absorption layer is a line pattern having a line width of 260 nm as shown in FIGS. 10A and 10B, and a defect in which a line having a width of 260 nm and a length of 520 nm disappeared as a white defect portion was formed. For the formation of the deposited film on the white defect portion, a photomask correcting FIB apparatus SIR7 (gallium ion, acceleration voltage 15 kV) manufactured by SII Nanotechnology Inc. was used. This was corrected by forming a deposited film using phenanthrene as a source gas in the white defect portion.

  When the cross-sectional shape of the deposited film was observed with an atomic force microscope, a trapezoidal cross-sectional shape as shown in FIG. 13 was obtained. The thickness of the deposited film was 150 nm, and the inclination angle θ on the side surface of the deposited film facing the reflection region was about 20 degrees.

  The EUV mask on which white defect correction was performed as described above was transferred to a resist applied on the wafer by one-fourth reduction using a Nikon EUV exposure apparatus EUV1. Next, a resist pattern was obtained by developing the resist. By observing this resist pattern with a SEM type size measuring machine (CG4000) manufactured by Hitachi High-Technologies Corporation, the transfer characteristics of the deposited film formation site were evaluated. When the transfer dimensions of the normal part and the deposited film formation part were compared, it was confirmed by SEM observation that a pattern equivalent to the normal pattern was formed.

[Example 2]
White defect correction was performed in the same manner as in Example 1 except that EB was used instead of FIB in the formation of the deposited film.
The apparatus was implemented with SIB nanotechnology Co., Ltd. FIB-SEM double beam apparatus XVision200. At this time, the acceleration voltage of EB was 1 keV, and the source gas was phenanthrene.

  When the cross-sectional shape of the deposited film was observed with an atomic force microscope, a trapezoidal cross-sectional shape was obtained. The thickness of the deposited film was 180 nm, and the inclination angle θ on the side surface of the deposited film facing the reflection region was about 20 degrees.

  In the same manner as in Example 1, the transfer characteristics of the deposited film formation site were evaluated. When the transfer dimensions of the normal part and the deposited film formation part were compared, it was confirmed by SEM observation that a pattern equivalent to the normal pattern was formed.

[Example 3]
Example 1 or Example 2 except that a silicon-containing gas such as TEOS (Tetraethoxysilane) or TMCTS (1,3,5,7-Tetramethylcyclotetra-siloxane) is used instead of phenanthrene as a source gas in forming the deposited film The white defect was corrected in the same manner.

  When the cross-sectional shape of the deposited film was observed with an atomic force microscope, a trapezoidal cross-sectional shape was obtained in all cases. The thickness of the deposited film was 130 nm, and the inclination angle θ on the side surface of the deposited film facing the reflection region was about 25 degrees.

  In the same manner as in Example 1, the transfer characteristics of the deposited film formation site were evaluated. When the transfer dimensions of the normal part and the deposited film formation part were compared, it was confirmed by SEM observation that a pattern equivalent to the normal pattern was formed.

DESCRIPTION OF SYMBOLS 1 ... Reflective type mask 2 ... Substrate 3 ... Multilayer film 4 ... Capping layer 5 ... Absorber 6 ... Absorbing layer 7 ... Deposited film 10 ... White defect part 21 ... Central part of white defect part 22 ... End part of white defect part 31 ... Reflection area 32 ... Absorption area a ... Position of the thickness of one third from the top of the deposited film on the side surface of the deposited film b ... Position of the thickness of two thirds from the top of the deposited film on the side face of the deposited film L1 ... a straight line connecting the position of the thickness of one-third and the position of the thickness of two-thirds from the top of the deposited film on the side surface of the deposited film L2 ... a line perpendicular to the substrate surface T ... the top of the deposited film θ, θ1, θ2... Angle formed by a straight line connecting the position of the third thickness and the position of the second thickness from the top of the deposited film on the side surface of the deposited film and a line perpendicular to the substrate surface ( Tilt angle)

Claims (5)

A reflective mask having a substrate, a multilayer film formed on the substrate, and an absorber formed in a pattern on the multilayer film,
The absorber has an absorption layer and a deposited film formed in a white defect portion due to the lack of the absorption layer, and is thicker than the absorption layer,
The deposited film contains a non-metallic material;
The deposited film has a thickness in the range of 125 nm to 500 nm;
The deposited film has a side surface facing a reflective region where the absorber is not formed on the multilayer film;
A straight line connecting the position of the third thickness and the position of the second thickness from the top of the deposited film on the side surface of the deposited film facing the reflective region, and a line perpendicular to the substrate surface And a reflection type mask characterized in that the angle formed by is within a range of 6 to 40 degrees. The reflective mask according to claim 1 , wherein the non-metallic material contains silicon. An absorption layer forming step of forming an absorption layer in a pattern on the substrate on which the multilayer film is formed;
The white defect portion due to the lack of the absorption layer is irradiated with energy beam while supplying a raw material gas of non-metallic, and a correcting step of forming a deposited film, in said modifying step, the multilayer film When forming the deposited film having a side surface facing the reflective region where the absorber is not formed , the total energy amount at the center of the white defect portion is the total energy amount at the end of the white defect portion. The thickness of the edge of the white defect portion on the side surface of the deposited film facing the reflection region is thinner than the thickness of the central portion of the white defect portion. A method of manufacturing a reflective mask, comprising forming the deposited film . 4. The energy beam irradiation is performed according to claim 3 , wherein in the correction step, the energy beam is irradiated such that the number of irradiation times at the central portion of the white defect portion is larger than the number of irradiation times at an end portion of the white defect portion. A method for manufacturing a reflective mask. Method for producing a reflective mask according to claim 3 or claim 4, wherein the energy beam is a focused ion beam or an electron beam.

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