JP2012009537A - Reflection type mask blank, reflection type mask, method of manufacturing reflection type mask blank, and method of manufacturing reflection type mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type mask blank which achieves high pattern transfer precision by preventing the reflection type mask from being distorted even when foreign matter is pinched between an electrostatic chuck and a reflection type mask, and can prevent both the electrostatic chuck and the reflection type mask from being damaged, and also to provide the reflection type mask, a method of manufacturing the reflection type mask blank, and the method of manufacturing the reflection type mask.SOLUTION: A conductive layer made of a soft material against the foreign matter is formed on the rear face of the reflection type mask to take the foreign matter in the inside of the conductive layer during absorbed to the electrostatic chuck.

Description

  The present invention relates to a reflective mask for EUV exposure for transferring a mask pattern onto a wafer using extreme ultra violet light (hereinafter referred to as EUV).

  In recent years, with the miniaturization of semiconductor devices in the semiconductor industry, EUV lithography, which is an exposure technique using 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, light having a wavelength of about 0.2 to 100 nm. As a mask used in this EUV lithography, for example, a reflective mask for exposure described in Patent Document 1 has been proposed.

  Such a reflective mask has at least a reflective layer made of a multilayer film that reflects EUV light on the substrate, and partially removes the absorbing layer that absorbs EUV light formed on the reflective layer. By doing so, an absorber pattern is formed. The EUV light incident on the reflective mask mounted on the EUV exposure machine is absorbed in a part where the absorber is present, and is reflected by the reflective layer in a part where there is no absorber, and the optical image is reflected on the transfer target through the reflective optical system. Transcribed.

  Since the inside of the EUV exposure machine is vacuum, when mounting the reflective mask on the EUV exposure machine, the surface (back surface) opposite to the surface on which the absorber pattern of the reflective mask is formed is electrostatic chuck. Generally, a method of electrostatically adsorbing is used.

  Therefore, as shown in FIG. 4, the conventional reflective mask 50 is usually provided with a conductive layer 57 on the surface (back surface) opposite to the surface on which the absorber pattern 51 is formed. This is because when the reflective mask is removed from the electrostatic chuck, the charge on the back surface of the reflective mask is removed (Patent Document 2).

  The conductive layer 57 is a thin film such as a metal or metal nitride exhibiting conductivity, and is made of, for example, Cr (chromium) or CrN (chromium nitride) and has a thickness of about 20 nm to 150 nm. Yes.

JP-A-63-201656 JP 2010-122304 A

  When pattern transfer is performed on a transfer target (generally, a resist-coated Si wafer) using a reflection mask as described above, the pattern is transferred onto the transfer target if the surface shape of the reflection mask is not flat. There is a problem that the pattern is distorted and a position shift occurs. Therefore, high flatness is required for the reflective mask.

  However, for example, as shown in FIG. 5, when the foreign matter 62 is sandwiched between the electrostatic chuck 61 and the reflective mask 50, the conventional reflective mask 50 having a hard thin conductive layer is distorted. Therefore, if pattern transfer is performed by EUV exposure as it is, the pattern transferred onto the transfer target is distorted and misaligned.

  Furthermore, once the foreign matter 62 is sandwiched between the electrostatic chuck 61 and the reflective mask 50, both the electrostatic chuck 61 and the reflective mask 50 are damaged, and there is a possibility that further foreign matter is generated. .

  The present invention has been made in view of the above problems, and the object of the present invention is to distort a reflective mask even when a foreign object is sandwiched between the electrostatic chuck and the reflective mask. Reflective mask blanks, reflective masks, and reflective mask blanks manufacturing method that can achieve high pattern transfer accuracy and prevent damage to both the electrostatic chuck and the reflective mask And a method of manufacturing a reflective mask.

  As a result of various researches, the present inventor has formed a conductive layer having a thickness on the back surface of the reflective mask and formed a material that is soft against foreign matters. The present invention has been completed by finding that the above-mentioned problems can be solved by incorporating into the above.

  That is, the invention according to claim 1 of the present invention includes a substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, and the capping layer. A reflective mask blank for EUV exposure having at least an absorption layer formed on the substrate and a conductive layer formed on the other surface of the substrate, wherein the material constituting the conductive layer is gold It is a reflective mask blank characterized by including.

  In the invention according to claim 2 of the present invention, the conductive layer is composed of a plurality of layers of different materials, and the material constituting the outermost layer of the plurality of layers includes gold. This is a reflective mask blank.

  Moreover, the invention according to claim 3 of the present invention is the reflective mask blank according to any one of claims 1 and 2, wherein the conductive layer has a thickness of 600 nm to 1 μm.

  According to a fourth aspect of the present invention, there is provided a substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, and the capping layer. A reflective mask for EUV exposure having at least an absorber pattern formed on the substrate and a conductive layer formed on the other surface of the substrate, wherein the material constituting the conductive layer is gold It is a reflective mask characterized by including.

  In the invention according to claim 5 of the present invention, the conductive layer is composed of a plurality of layers of different materials, and the material constituting the outermost layer of the plurality of layers includes gold. This is a reflective mask.

  The invention according to claim 6 of the present invention is the reflective mask according to any one of claims 4 to 5, wherein the conductive layer has a thickness of 600 nm to 1 μm.

According to a seventh aspect of the present invention, there is provided a substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, and the capping layer. A reflective mask blank for EUV exposure comprising at least an absorption layer formed on the substrate and a conductive layer formed on the other surface of the substrate,
A method of manufacturing a reflective mask blank, wherein the conductive layer includes at least a first conductive layer formed by a vacuum film forming method and a second conductive layer formed by an electrolytic plating method. .

  The invention according to claim 8 of the present invention is the method of manufacturing a reflective mask blank according to claim 7, wherein the material of the second conductive layer contains gold.

  According to a ninth aspect of the present invention, there is provided a substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, and the capping layer. A reflective mask for EUV exposure having at least an absorber pattern formed on the substrate and a conductive layer formed on the other surface of the substrate, wherein the conductive layer is at least a vacuum A reflective mask manufacturing method comprising a first conductive layer formed by a film forming method and a second conductive layer formed by an electrolytic plating method.

  The invention according to claim 10 of the present invention is the method for manufacturing a reflective mask according to claim 9, wherein the material of the second conductive layer contains gold.

  According to the present invention, when the reflective mask is attracted to the electrostatic chuck, the foreign matter adhering to the electrostatic chuck and / or the back surface of the reflective mask is put inside the conductive layer formed on the back surface of the reflective mask. By taking in, it is possible to prevent the reflective mask from being distorted and to realize high pattern transfer accuracy. Further, damage to both the electrostatic chuck and the reflective mask can be prevented.

It is a schematic sectional drawing which shows the example of the reflection type mask blanks which concern on this invention. It is a schematic sectional drawing which shows the example of the reflection type mask which concerns on this invention. It is explanatory drawing which shows the state which made the reflective mask which concerns on this invention adsorb | suck to an electrostatic chuck. It is a schematic sectional drawing which shows the example of the conventional reflective mask. It is explanatory drawing which shows the state which made the conventional reflective mask adsorb | suck to an electrostatic chuck.

  Hereinafter, a reflective mask blank, a reflective mask, a method of manufacturing a reflective mask blank, and a method of manufacturing a reflective mask according to the present invention will be described.

  FIG. 1 is a schematic cross-sectional view showing an example of a reflective mask blank according to the present invention. Here, FIG. 1A shows an example in which the conductive layer is made of a single layer of the same material, and FIG. 1B shows an example in which the conductive layer is made of a plurality of layers having different materials.

  A reflective mask blank 1 shown in FIG. 1A has a reflective layer 3 that reflects EUV light in a multilayer film structure on one surface of a substrate 2, and an anti-oxidation and mask for the reflective layer 3 on the reflective layer 3. A capping layer 4 that acts as a protective layer for protection during cleaning is provided, and then a buffer layer 5 that acts as an etching stop layer during mask pattern formation is provided, and an absorption layer 6 that absorbs EUV light thereon. The conductive layer 7 is provided on the other surface of the substrate 2.

  On the other hand, the reflective mask blank 1 shown in FIG. 1B includes a first conductive layer 8 in which the conductive layer 7 in FIG. 1A is formed on the surface of the substrate 2 and the first conductive layer 8. The second conductive layer 9 is formed in a two-layer structure.

  FIG. 2 is a schematic sectional view showing an example of a reflective mask according to the present invention. Here, FIG. 2A shows an example in which the conductive layer is made of a single layer of the same material, and FIG. 2B shows an example in which the conductive layer is made of a plurality of layers having different materials.

  The reflective mask 20 can be manufactured, for example, by processing the absorption layer 6 and the buffer layer 5 of the reflective mask blank 1 into a pattern.

  In addition, a conventional reflective mask blank having no conductive layer according to the present invention is prepared, the conductive layer according to the present invention is formed on the back side thereof, and the absorption layer and the buffer layer are processed into a pattern. Thus, the reflective mask according to the present invention may be manufactured. Further, the conductive layer according to the present invention may be formed after processing the absorption layer and the buffer layer into a pattern.

  The reflective mask blanks according to the present invention or the conductive layer formed as the outermost layer on the back surface of the reflective mask is made of a material soft against foreign matters adhering to the electrostatic chuck or the like, and is sufficient to take in the foreign matters. Have a certain thickness.

  Therefore, as shown in FIG. 3, even if the foreign matter 32 is sandwiched between the electrostatic chuck 31 and the reflective mask 20, the foreign matter 32 is taken into the conductive layer 7 and reflected. It is possible to prevent the mask from being distorted.

  Further, since the foreign matter 32 is taken into the conductive layer 7, damage to both the electrostatic chuck 31 and the reflective mask 20 can be prevented.

  More specifically, for example, the foreign matter 32 is attached on the electrostatic chuck 31 before the reflective mask 20 is attracted, and the reflective mask 20 is electrostatically attracted to the electrostatic chuck 31 in this state. In this case, the conductive layer 7 on the back surface of the reflective mask 20 comes into close contact with the electrostatic chuck 31 due to the electrostatic adsorption force. Due to this close contact force, the foreign matter 32 is pushed into the soft conductive layer 7, and finally, the foreign matter 32 is taken into the conductive layer 7 as shown in FIG. 3. For this reason, the reflective mask 20 is not distorted unlike the conventional reflective mask 50 shown in FIG. 5, and high pattern transfer accuracy can be realized.

  Further, since the foreign matter 32 is taken into the conductive layer 7, the electrostatic chuck 31 is not damaged and the substrate 2 of the reflective mask 20 is not damaged.

  When the EUV exposure is completed and the reflective mask 20 is removed, the foreign matter 32 is taken away from the electrostatic chuck 31 together with the reflective mask 20.

  As a material constituting the conductive layer 7 having the above effects, for example, gold (Au) can be cited.

  In addition, the thickness of the conductive layer 7 needs to take in a foreign substance, so that a thickness of a certain level or more is necessary. However, if the thickness is too large, the reflective mask may be distorted due to film stress. This thickness should be kept to the minimum necessary because of fear. As a result of various investigations, the maximum size of foreign matter adhering to the back surface of the reflective mask is approximately 500 nm or less in mask handling in an environment in which foreign matter is sufficiently considered. For example, it was confirmed that foreign matter adhered during handling did not affect pattern transfer.

  Therefore, in accordance with the current technology, the thickness of the conductive layer 7 is preferably in the range of 600 nm to 1 μm. This is because the above-described adverse effects due to the adhesion of foreign matters can be effectively removed. In the future, if the handling technology is improved and the size of the adhered foreign matter is reduced, the size of the foreign matter that must be taken in is also reduced. Therefore, the thickness of the conductive film 7 can be further reduced.

  In order to form the conductive layer 7 containing gold (Au) on the back side of the reflective mask blank or the reflective mask, for example, a vacuum film forming method such as a sputtering method can be used.

  Alternatively, the conductive layer 7 containing gold (Au) may be formed using an electrolytic plating method. If the electroplating method is used, it is easy to obtain a conductive layer that is thicker than the conductive layer that has been used in conventional reflective masks.

  For example, as in the reflective mask blanks of FIG. 1B or the reflective mask of FIG. 2B, first, a first layer made of Cr (chromium), CrN (chromium nitride), or the like is formed on the substrate 2. The second conductive layer 9 containing gold (Au) is formed by electroplating using the first conductive layer 8 as a seed layer for gold (Au) plating. Can be formed.

  Further, in order to improve the flatness, the second conductive layer 9 may be formed thicker than a desired thickness, and then processed to a desired thickness by polishing.

Next, the reflective mask blank according to the present invention or other elements constituting the reflective mask will be described.
(substrate)
The reflective mask blank of the present invention or the substrate 2 constituting the reflective mask has a low thermal expansion coefficient to maintain high pattern position accuracy, and smoothness to obtain high reflectivity and transfer accuracy. , high flatness is preferably excellent in resistance to washing liquid to be used for such cleaning of a mask manufacturing process, quartz glass, low thermal expansion glass of SiO ₂ -TiO ₂ system, such as crystallized glass obtained by precipitating β-quartz solid solution A glass substrate or even silicon can be used. As the flatness of the mask blank, for example, 50 nm or less is required in the pattern region.
(Reflective layer)
The reflective layer 3 is made of a material that reflects EUV light used for EUV exposure with high reflectivity, and a multilayer film composed of a Mo (molybdenum) layer and a Si (silicon) layer is often used. Examples include a reflective layer made of a multilayer film in which 40 layers each of a Mo layer having a thickness and a Si layer having a thickness of 4.2 nm are stacked. Other than that, as a material capable of obtaining a high reflectance in a specific wavelength range, Ru / Si, Mo / Be, Mo compound / Si compound, Si / Nb periodic multilayer film, Si / Mo / Ru periodic multilayer film, Si / Mo / Ru / Mo periodic multilayer film and Si / Ru / Mo / Ru periodic multilayer film can also be used. However, the optimum film thickness varies depending on the material. In the case of a multilayer film composed of a Mo layer and a Si layer, a Si layer is first formed in an Ar gas atmosphere using a Si target by a DC magnetron sputtering method, and then a Mo target is used in an Ar gas atmosphere. A Mo layer is formed, and this is defined as one period, and is laminated for 30 to 60 periods, preferably 40 periods, to obtain a multilayer reflective layer. As described above, in order to reflect EUV light with high reflectivity, the reflectivity of the reflective layer 3 when 13.5 nm EUV light is incident at an incident angle of 6.0 degrees usually indicates 60% or more. Is set to
(Capping layer)
In order to increase the reflectivity of the reflective layer 3, it is preferable to use the Mo layer having a large refractive index as the uppermost layer. However, Mo is easily oxidized in the atmosphere and the reflectivity is lowered. As a protective layer, Si or Ru (ruthenium) is formed by sputtering or the like, and a capping layer 4 is provided. For example, when Si is used as the capping layer 4, the uppermost layer of the reflective layer 3 is provided with a thickness of 11 nm.
(Buffer layer)
In order to prevent damage to the lower reflective layer 3 when pattern-etching the absorbing layer 6 that absorbs EUV light used for EUV exposure by a method such as dry etching, the reflective layer 3 and the absorbing layer are usually used. 6 is provided with a buffer layer 5. As the material of the buffer layer _{5 SiO 2, Al 2 O 3} , Cr, etc. CrN is used. When CrN is used, it is preferable to form a CrN film with a film thickness of about 5 nm to 15 nm on the reflective layer in a N ₂ gas atmosphere using a Cr target by RF magnetron sputtering.
(Absorption layer)
The material of the absorption layer 6 that forms a mask pattern and absorbs EUV light is at least selected from Ta, TaB, TaBN, and other materials containing Ta as the main component, Cr, Cr as the main component, N, O, and C. A material containing one component is used in a thickness range of about 20 nm to 100 nm.
(Hard mask layer)
A hard mask layer may be provided on the absorption layer 6 as an etching mask for the absorption layer. As a material for the hard mask layer, it is necessary to use a material that is resistant to etching of the absorption layer 6 and is suitable for fine processing according to the transfer pattern of the reflective mask. For example, chromium (Cr), zirconium (Zr), hafnium (Hf), and nitrides and oxides thereof.

  The material of the hard mask layer is preferably the same material as that of the buffer layer 5. In this case, after the absorption layer 6 is etched, the hard mask layer and the buffer layer 5 can be removed in the same process.

  The thickness of the hard mask layer is, for example, 5 nm to 15 nm, although it depends on the etching resistance of the material and the processing accuracy according to the size of the transfer pattern.

  As the hard mask layer, for example, a hard mask layer made of CrN can be provided by sputtering Cr in a mixed gas atmosphere of Ar and nitrogen.

  The reflective mask blanks, the reflective mask, the reflective mask blank manufacturing method, and the reflective mask manufacturing method according to the present invention have been described above, but the present invention is not limited to the above embodiment. . The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
As the substrate 2, an optically polished 6 inch square (0.25 inch thick) synthetic quartz substrate is used, and a Si target is formed on one main surface (surface) by ion beam sputtering. A Si film is formed to 4.2 nm, then a Mo film is formed to 2.8 nm using a Mo target, and this is set as one period, and 40 periods are laminated to form a reflective layer 3 composed of a multilayer film of Mo and Si. After that, a capping layer 4 was formed by forming a Si film with a thickness of 11 nm on the outermost Mo film.

Next, on the Si film, a CrN film is formed to a thickness of 10 nm as a buffer layer 5 in a N ₂ atmosphere using a Cr target by RF magnetron sputtering, and then the CrN film is formed. On top, a TaBN film is formed with a thickness of 80 nm in a mixed gas atmosphere of Ar and nitrogen using a target containing Ta and B by DC magnetron sputtering, and an absorption layer 6 that absorbs EUV light is formed. did.

  Next, a conductive layer 7 made of gold (Au) is formed to a thickness of 700 nm on the opposite surface (back surface) of the substrate 2 by a DC magnetron sputtering method in an Ar gas atmosphere using a gold (Au) target. The reflective mask blanks according to the present invention were obtained.

Next, using this reflective mask blank, an EB resist was applied, and EB drawing was performed to form a resist pattern. Next, the TaBN absorption layer 6 is dry-etched with Cl ₂ gas, and the CrN buffer layer 5 is dry-etched with a mixed gas of Cl ₂ and oxygen to expose the capping layer 4 and strip the resist pattern. Thus, a reflective mask according to the present invention was obtained.
(Example 2)
As the substrate 2, an optically polished 6 inch square (0.25 inch thick) synthetic quartz substrate is used, and a Si target is formed on one main surface (surface) by ion beam sputtering. A Si film is formed to 4.2 nm, then a Mo film is formed to 2.8 nm using a Mo target, and this is set as one period, and 40 periods are laminated to form a reflective layer 3 composed of a multilayer film of Mo and Si. After that, a capping layer 4 was formed by forming a Si film with a thickness of 11 nm on the outermost Mo film.

Next, on the Si film, a CrN film is formed to a thickness of 10 nm as a buffer layer 5 in a N ₂ atmosphere using a Cr target by RF magnetron sputtering, and then the CrN film is formed. On top, a TaBN film is formed with a thickness of 80 nm in a mixed gas atmosphere of Ar and nitrogen using a target containing Ta and B by DC magnetron sputtering, and an absorption layer 6 that absorbs EUV light is formed. did.

  Next, a first conductive layer 8 made of Cr is formed to a thickness of 20 nm on the opposite surface (back surface) of the substrate 2 by DC magnetron sputtering using a Cr target in an Ar gas atmosphere. The second conductive layer 9 made of gold (Au) is formed with a thickness of 700 nm by electrolytic plating using the first conductive layer 8 as a seed layer, and the reflective mask blanks according to the present invention are obtained. It was.

Next, using this reflective mask blank, an EB resist was applied, and EB drawing was performed to form a resist pattern. Next, the TaBN absorption layer 6 is dry-etched with Cl ₂ gas, and the CrN buffer layer 5 is dry-etched with a mixed gas of Cl ₂ and oxygen to expose the capping layer 4 and strip the resist pattern. Thus, a reflective mask according to the present invention was obtained.

DESCRIPTION OF SYMBOLS 1 Reflective mask blanks 2, 52 Substrate 3, 53 Reflective layer 4, 54 Capping layer 5, 55 Buffer layer 6, 56 Absorbing layer 7, 57 Conductive layer 8 First conductive layer 9 Second conductive layer 20, 50 Reflection Mold mask 21, 51 Absorber pattern 31, 61 Electrostatic chuck 32, 62 Foreign matter

Claims (10)

A substrate, a reflective layer composed of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, an absorption layer formed on the capping layer, A reflective mask blank for EUV exposure having at least a conductive layer formed on the other surface,
A reflective mask blank, wherein the material constituting the conductive layer contains gold.   The reflective mask blank according to claim 1, wherein the conductive layer includes a plurality of layers made of different materials, and a material constituting the outermost layer of the plurality of layers includes gold.   The reflective mask blank according to claim 1, wherein the conductive layer has a thickness of 600 nm to 1 μm. A substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, an absorber pattern formed on the capping layer, and the substrate A reflective mask for EUV exposure having at least a conductive layer formed on the other surface of
A reflective mask, wherein the material constituting the conductive layer contains gold.   The reflective mask according to claim 4, wherein the conductive layer includes a plurality of layers made of different materials, and a material constituting the outermost layer of the plurality of layers includes gold.   The reflective mask according to claim 4, wherein the conductive layer has a thickness of 600 nm to 1 μm. A substrate, a reflective layer composed of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, an absorption layer formed on the capping layer, A method for producing a reflective mask blank for EUV exposure comprising at least a conductive layer formed on the other surface,
The method of manufacturing a reflective mask blank, wherein the conductive layer includes at least a first conductive layer formed by a vacuum film forming method and a second conductive layer formed by an electrolytic plating method.   The method for manufacturing a reflective mask blank according to claim 7, wherein the material of the second conductive layer includes gold. A substrate, a reflective layer made of a multilayer film formed on one surface of the substrate, a capping layer formed on the reflective layer, an absorber pattern formed on the capping layer, and the substrate A reflective layer for EUV exposure having at least a conductive layer formed on the other surface of
A method for manufacturing a reflective mask, wherein the conductive layer includes at least a first conductive layer formed by a vacuum film forming method and a second conductive layer formed by an electrolytic plating method. The method for manufacturing a reflective mask according to claim 9, wherein the material of the second conductive layer includes gold.

Images