JP2006283054A - Sputtering target, manufacturing method for substrate with multi-layered reflecting film, manufacturing method for reflection type mask blank, and manufacturing method for reflection type mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target, a manufacturing method for a substrate with a multi-layered reflecting film, a manufacturing method for a reflection type mask blank, and a manufacturing method for a reflection type mask, respectively. <P>SOLUTION: The sputtering target consists of ruthenium compound containing ruthenium (Ru) and at least one selected from niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), silicon (Si), boron (B), and yttrium (Y). The sintering density is ≥ 95%, the content of oxygen (O) is ≤ 2,000 ppm, and the content of carbon (C) is ≤ 200 ppm. A substrate 30 with a multi-layered reflecting film is obtained by depositing a ruthenium compound protective film 6 on a multi-layered reflecting film 2 on a substrate 1 by using the target. A reflection type mask blank is obtained by forming an absorbing medium on the ruthenium compound protective film 6 of the substrate 30 with the multi-layered reflecting film. Further, a reflection type mask is obtained by forming a pattern on the absorbing medium of the reflection type mask blank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a sputtering target used for sputtering deposition of a ruthenium compound film that contributes to reflection with respect to exposure light, a method for manufacturing a substrate with a multilayer reflective film having a deposition process using the sputtering target, and the substrate. The present invention relates to a reflective mask blank and a method of manufacturing a reflective mask.

In recent years, in the semiconductor industry, with the miniaturization of semiconductor devices, EUV lithography (EUVL), which is an exposure technique using extreme ultra violet (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, an exposure reflective mask as described in JP-A-8-213303 has been proposed.
Such a reflective mask has a structure in which a multilayer reflective film that reflects EUV light is provided on a substrate, and an absorber film that absorbs EUV light is provided in a pattern on the multilayer reflective film. . In an exposure machine (pattern transfer device) equipped with such a reflective mask, the exposure light incident on the reflective mask is absorbed in a portion where the absorber film pattern is present, and a multilayer reflective film in a portion where the absorber film pattern is absent. The light image reflected by is transferred onto the semiconductor substrate (silicon wafer with resist) through the reflection optical system.

As the multilayer reflective film, a multilayer film in which a substance having a relatively high refractive index and a substance having a relatively low refractive index are alternately laminated on the order of several nm is usually used. For example, a multilayer film in which thin films of Si and Mo are alternately stacked is known as one having a high reflectivity for 13 to 14 nm EUV light. On the multilayer reflective film, a protective film made of, for example, ruthenium (Ru) is formed as a protective film for the multilayer reflective film.
The multilayer reflective film can be formed on the substrate by, for example, sputtering. When Mo and Si are included, sputtering is performed alternately using the Si target and the Mo target, the layers are stacked for 30 to 60 cycles, preferably 40 cycles, and finally a Si film is formed as the uppermost layer of the multilayer film. A ruthenium film that is a protective film on the multilayer reflective film can also be formed by a similar method.

  Patent Document 1 discloses a sputtering target used for forming electrodes and wirings used in semiconductor devices and the like by sputtering, and includes at least one refractory metal of W, Mo, Nb, Ta, Ru. A sputtering target contained as a main component is disclosed. Patent Document 2 discloses a high-purity ruthenium target having a forged structure in which both oxygen and nitrogen are 10 wtppm or less, which is used when a ruthenium thin film is formed as a ferroelectric electrode or the like of a device. .

JP 2001-295035 A JP 2002-327265 A

  By the way, when particles are generated during such film formation, defects in a product (a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask) increase, and a high-quality product cannot be obtained. In the case of pattern transfer using a conventional transmissive mask for exposure, the wavelength of exposure light is relatively long in the ultraviolet region (about 150 to 248 nm). For this reason, conventionally, in the field of exposure masks, the generation of particles during film formation has not been particularly recognized as a problem. However, when light having a short wavelength such as EUV light is used as exposure light, even if there are fine irregularities on the mask surface, the influence on the transferred image is increased, so generation of particles cannot be ignored. In such a reflective mask that uses EUV light as exposure light, for example, a phase defect that affects the transferred image even if there is a convex defect of several nm to several tens of nm on the surface of the multilayer reflective film. Can be.

According to the study of the present inventor, it has been found that the generation of particles during film formation by a normal sputtering method occurs, for example, due to abnormal discharge of the target. In the ion beam sputtering (IBD) film formation process, sputtering is performed with electrically neutral particles, so no particles are generated due to abnormal discharge, but the target quality is still generated. Also found to be involved in. In particular, when a ruthenium protective film is provided on a multilayer reflective film, if there is a defect on the surface of this ruthenium protective film, it can cause a phase defect that affects the transferred image, so particles are generated during the formation of the ruthenium protective film. It is necessary to suppress as much as possible. In addition, if particles generated during film formation are embedded in the film, the film often peels off during the cleaning process after film formation, which not only causes additional particles but also introduces new particles. Causes irregular defects. In particular, in the case of ruthenium, since the stress is large, the film is likely to peel off from the ruthenium protective film after film formation. Further, the ruthenium film once adhered to the inner side wall of the film forming apparatus is also peeled off by stress relaxation. This is likely to occur and both increase the number of particles.
Therefore, in a reflective mask blank and a reflective mask that use light of a short wavelength such as EUV light as exposure light, very high precision particle control is required, but this has not been recognized as a problem in the past. For this reason, the actual situation is that the countermeasures have not been fully examined.

  The above-mentioned Patent Document 1 describes the reduction of particles generated from a target when sputtering a refractory metal film that forms electrodes and wirings used in semiconductor devices and the like. It is described that there are problems with particles in reflective mask blanks and reflective masks that use such short-wavelength light as exposure light, and that there are other particle generation factors besides particles generated from the target during film formation. Absent. In addition, the sputtering target disclosed in Patent Document 2 improves electrical characteristics such as noise prevention in an electrode or the like by improving purity, but uses light having a short wavelength such as EUV light as exposure light. Patent Document 2 does not describe the problem caused by the generation of particles in the reflective mask blank and the reflective mask and the cause of the generation of particles during film formation.

  Accordingly, the object of the present invention is to suppress particles generated from a target during film formation, and to prevent particles generated by film peeling from a film after film formation or film peeling from the inside of a film forming apparatus. It is to provide a sputtering target capable of suppressing generation. Second, abnormal discharge of the target, rupenium compound protective film peeling after film formation, film peeling from inside the film forming apparatus, etc. The third object of the present invention is to provide a method for manufacturing a high-quality reflective mask blank for exposure with a small number of surface defects. Fourth, it is to provide a method for manufacturing a high-quality reflective mask for exposure without pattern defects.

In order to solve the above problems, the present invention has the following configuration.
(Configuration 1) From ruthenium (Ru), niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), silicon (Si), boron (B), yttrium (Y) It is composed of a ruthenium compound containing at least one selected, has a sintered density of 95% or more, an oxygen (O) content of 2000 ppm or less, and a carbon (C) content of 200 ppm or less. This is a ruthenium compound film-forming sputtering target that contributes to reflection with respect to exposure light.
According to Configuration 1, the sputtering target is configured with ruthenium (Ru), niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), silicon (Si), boron ( B), a ruthenium compound containing at least one selected from yttrium (Y), a sintered density of 95% or more, an oxygen (O) content of 2000 ppm or less, and a carbon (C) content of By setting it to 200 ppm or less, the generation of particles when the ruthenium compound film is formed by sputtering using this sputtering target can be remarkably reduced. Furthermore, since the ruthenium compound is less than ruthenium alone, stress relaxation due to lattice relaxation occurs when the film is formed and the film stress can be reduced, so film peeling from the ruthenium compound film formed using this target, Generation of particles due to film peeling from a ruthenium compound film adhering to the inside of the film forming apparatus can be suppressed.
The purity of the sputtering target is preferably 3N (99.9% by weight) or higher. It is possible to suppress a decrease in reflectance with respect to EUV light due to impurities mixing and generation of particles due to abnormal discharge during sputtering film formation due to impurity aggregation at crystal grain boundaries.

(Configuration 2) A ruthenium compound film-forming sputtering target that contributes to reflection with respect to exposure light according to Configuration 1, wherein the average crystal grain size is 5 nm or more and 1000 nm or less.
According to Configuration 2, since the average crystal grain size in the sputtering target is controlled to be 5 nm or more and 1000 nm or less, generation of particles when the ruthenium compound film is formed by sputtering using the sputtering target can be suitably suppressed. I can do it.
(Structure 3) A sputtering target for forming a ruthenium compound film that contributes to reflection with respect to exposure light according to Structure 1 or 2, wherein the sputtering target is used in a thin film forming process by an ion beam sputtering film forming method. It is.
During film formation by the normal sputtering method, for example, particles are generated due to abnormal discharge of the target. In the case of ion beam sputtering film formation (IBD), sputtering is performed with electrically neutral particles. Although no particles are produced, the quality of the target affects the generation of particles. Since the sputtering target of this invention can suppress generation | occurrence | production of a particle even if it uses it for the film-forming process by IBD method like the structure 3, this invention is especially suitable.

(Configuration 4) A method of manufacturing a substrate with a multilayer reflective film having a multilayer reflective film that reflects exposure light on the substrate, wherein the multilayer reflection is performed using the sputtering target according to any one of Configurations 1 to 3. A method for producing a substrate with a multilayer reflective film, comprising a step of forming a protective film made of a ruthenium compound on a film.
According to Configuration 4, a substrate with a multilayer reflective film is manufactured by forming a protective film made of a ruthenium compound on the multilayer reflective film using the sputtering target according to any one of Configurations 1 to 3. It is possible to suppress the generation of particles due to abnormal discharge of the target, ruthenium compound film adhering to the inside of the film formation apparatus, film peeling of the ruthenium compound protective film after film formation, etc., resulting in surface defects due to particles Can be obtained.

(Configuration 5) A step of forming an absorber film that absorbs exposure light on the protective film made of the ruthenium compound of the substrate with a multilayer reflection film obtained by the method for manufacturing a substrate with a multilayer reflection film according to Configuration 4. It is a manufacturing method of the reflective mask blank characterized by having.
According to Configuration 5, the substrate with a multilayer reflective film obtained by the method for manufacturing a substrate with a multilayer reflective film according to Configuration 4 is used, and an absorber film that absorbs exposure light is formed on the protective film made of the ruthenium compound. Since the reflective mask blank is manufactured by forming the reflective mask blank, it is possible to obtain a reflective mask blank with extremely few surface defects due to particles on the surface of the protective film made of a ruthenium compound which finally becomes the reflective surface of the mask.
Note that a buffer film having an etching stopper function for protecting the multilayer reflective film at the time of pattern formation on the absorber film can be provided between the absorber film and the protective film made of a ruthenium compound.

(Structure 6) A reflective mask characterized in that an absorber film pattern serving as a transfer pattern is formed on the absorber film of the reflective mask blank obtained by the method of manufacturing a reflective mask blank described in Structure 5. It is a manufacturing method.
According to the configuration 6, since the reflective mask blank described in the configuration 5 is used and a pattern is formed on the absorber film to manufacture the reflective mask, a pattern caused by a surface defect on the reflective surface of the mask in particular. A reflection type mask without defects can be obtained.

According to the present invention, particles generated from a target during film formation can be suppressed, and generation of particles due to film peeling from a film after film formation or film peeling from the inside of a film forming apparatus can be suppressed. A ruthenium compound film-forming sputtering target that contributes to reflection with respect to possible exposure light can be provided. In particular, it is possible to provide a sputtering target capable of suitably suppressing the generation of particles even when used in a film forming process by the IBD method.
In addition, according to the present invention, a protective film made of a ruthenium compound is formed on the multilayer reflective film by using the sputtering target according to the present invention, so that abnormal discharge of the target and ruthenium compound protection after the film formation can be achieved. Generation of particles due to film peeling from the film, film peeling from the inside of the film forming apparatus, and the like can be suppressed, and a substrate with a multilayer reflective film with very few surface defects due to particles can be provided.
Further, according to the present invention, the ruthenium compound protective film which becomes the reflective surface of the mask in particular by forming an absorber film that absorbs exposure light on the ruthenium compound protective film using the above-mentioned substrate with a multilayer reflective film. It is possible to provide a high-quality reflective mask blank with extremely few surface defects due to particles on the surface.
Furthermore, according to the present invention, by using the above-described reflective mask blank, an absorber film pattern serving as a transfer pattern is formed on the absorber film, so that a pattern caused by a surface defect particularly on the reflective surface of the mask. A high-quality reflective mask free from defects can be provided.

Hereinafter, the present invention will be described in detail with reference to embodiments.
One embodiment of a sputtering target (hereinafter simply referred to as a target) of the present invention includes ruthenium (Ru), niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La ), Silicon (Si), boron (B), yttrium (Y), and a ruthenium compound containing at least one selected from the group consisting of a ruthenium compound having a sintered density of 95% or more and an oxygen (O) content of 2000 ppm or less. The carbon (C) content is 200 ppm or less.
In the present invention, since the target is configured as described above, the generation of particles when the ruthenium compound film is formed by sputtering using this sputtering target can be remarkably reduced. In addition, since the ruthenium compound can reduce the film stress as compared with ruthenium alone, the film is peeled off from the ruthenium compound film formed using this target, or the ruthenium compound film adhered to the inside of the film forming apparatus. Generation of particles due to film peeling or the like can be suppressed.

Here, in the ruthenium compound, ruthenium (Ru), niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), silicon (Si), boron (B), yttrium The composition of at least one selected from (Y) is niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), and silicon (Si). Is preferably in the range of 3 to 75 atomic%, and particularly preferably in the range of 40 to 75 atomic% from the viewpoint of improving chemical resistance. Further, since boron (B) and yttrium (Y) are easily oxidized metals, if the content of these metals is large, an oxide layer is formed on the surface of the formed ruthenium compound film, and optical characteristics (for example, EUV) The light reflectance) may be deteriorated, so that the content in the compound is preferably in the range of 3 to 50 atomic%.
Among the impurities, the target of the present invention has an oxygen (O) content of 2000 ppm or less and a carbon (C) content of 200 ppm or less. When both the contents of oxygen (O) and carbon (C) are low, particles generated from the target during film formation can be reduced.

The target of the present invention has a sintered density of 95% or more. The target of the present invention can be obtained by, for example, a method in which the ruthenium compound raw material powder is once purified by melting with an electron beam or the like, and a high-purity raw material powder is molded and sintered by various methods to obtain a target. When the sintered density of the obtained target is 95% or more, particles generated from the target during film formation can be reduced. In the present invention, the sintered density is more preferably 99% or more. In the present invention, the sintering density of the target is a value calculated from the volume and weight of the target and the composition obtained from X-ray photoelectron spectroscopy (XPS).
Further, in order to reduce oxygen (O) and carbon (C) among impurities contained in the target, for example, hydrogen reduction or plasma treatment is performed after the target is manufactured or when the pellet is manufactured before the target is manufactured. Thus, it is preferable to reduce the concentration of these impurities.

  In the target of the present invention, the average crystal grain size is preferably 5 nm or more and 1000 nm or less. By controlling the average crystal grain size in the target to be 5 nm or more and 1000 nm or less, the generation of particles when the ruthenium compound film is formed by sputtering using this target can be suitably suppressed. From the viewpoint of reducing particle generation, it is desirable that the crystal grain size is as small as possible. However, if the average crystal grain size is less than 5 nm, the target manufacturing cost increases, and the powder sintering method requires less than 5 nm. It is difficult to obtain a crystal grain size of. In the present invention, the average crystal grain size is more preferably in the range of 5 to 200 nm.

  The target of the present invention preferably has a purity of 3N or higher. By setting the target purity to 3N (99.9 wt%) level or higher, the reflectance of EUV light is reduced due to impurities, and the generation of particles due to abnormal discharge during sputter deposition due to impurity aggregation at the crystal grain boundaries. Can be suppressed. The purity of the target can be controlled in the process of forming the target, dissolving the ruthenium raw material powder before sintering, and purifying.

The target of the present invention is used in a thin film deposition process by a normal sputtering method, but is particularly suitable for use in a thin film deposition process by an ion beam sputtering deposition (IBD) method.
Film formation by a normal sputtering method is performed as follows.
That is, inert gas ions are extracted from the ion source for sputtering and irradiated onto the target. Then, atoms constituting the target are knocked out by collision of ions, and a target material is generated. The target material adheres onto the substrate placed at a position facing the target to form a thin film layer. Therefore, in the film forming process by the normal sputtering method, for example, particles are generated due to abnormal discharge of the target. By using the target of the present invention, particles generated by such abnormal discharge of the target can be reduced. I can do it.

  On the other hand, in the case of the ion beam sputtering film formation (IBD) method, since sputtering is performed with electrically neutral particles, particles due to abnormal discharge of the target do not occur. The target material (Ru) adhering to the chamber wall surface may be peeled off by the film stress, and it may be scattered and deposited on the substrate to become particles. As in the present invention, it has been found that the quality of a target obtained by alloying Ru and stress-relaxing affects the generation of particles, and the conventional Ru target cannot reduce the generation of particles. The target of the present invention is particularly suitable because the generation of particles can be effectively suppressed even when used in the film forming process by the IBD method.

Next, the manufacturing method of the board | substrate with a multilayer reflective film of this invention is demonstrated.
FIG. 1 is a cross-sectional view of a substrate with a multilayer reflective film. According to this, a substrate 30 with a multilayer reflective film is provided on a substrate 1 and a multilayer reflective film 2 that reflects exposure light on the substrate 1. And a protective film (hereinafter referred to as a ruthenium compound protective film) 6 made of a ruthenium compound. According to the method for manufacturing a substrate with a multilayer reflective film of the present invention, such a substrate with multilayer reflective film 30 is formed by forming the ruthenium compound protective film 6 on the multilayer reflective film 2 using the target of the present invention. Can be obtained.
That is, since the ruthenium compound protective film 6 is formed on the multilayer reflective film 2 by using the target of the present invention, abnormal discharge of the target, ruthenium compound film adhering to the inside of the film forming apparatus, Generation of particles due to film peeling or the like of the ruthenium compound protective film 6 after film formation can be suppressed, and a substrate with a multilayer reflective film with very few surface defects due to particles can be obtained.

As a material of the substrate 1, a glass substrate can be preferably used. A glass substrate has good smoothness and flatness, and is particularly suitable as a mask substrate. Examples of the glass substrate material include amorphous glass having a low thermal expansion coefficient (for example, SiO ₂ —TiO ₂ glass), quartz glass, crystallized glass on which β quartz solid solution is deposited, and the like. The substrate preferably has a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less in order to obtain high reflectivity and transfer accuracy. In the present invention, the unit Rms indicating smoothness is the root mean square roughness, and can be measured with an atomic force microscope. Further, the flatness in the present invention is a value indicating the surface warpage (deformation amount) indicated by TIR (total indicated reading). This is the difference in height between the highest position of 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. Absolute value. Smoothness is indicated by smoothness in a 10 μm square area, and flatness is indicated by flatness in a 142 mm square area.

  The multilayer reflective film 2 formed on the substrate 1 has a structure in which materials having different refractive indexes are alternately stacked, and can reflect light of a specific wavelength. For example, a Mo / Si multilayer reflective film in which Mo and Si are alternately stacked for about 40 cycles, which has a high reflectivity for EUV light of 13 to 14 nm, can be mentioned. Examples of other multilayer reflective films used in the EUV light region include Ru / Si periodic multilayer reflective films, Mo / Be periodic multilayer reflective films, Mo compound / Si compound periodic multilayer reflective films, and Si / Nb periodic multilayer reflective films. Examples thereof include a film, a Si / Mo / Ru periodic multilayer reflective film, a Si / Mo / Ru / Mo periodic multilayer reflective film, and a Si / Ru / Mo / Ru periodic multilayer reflective film. The multilayer reflective film 2 can be formed on the substrate 1 by, for example, an ordinary sputtering method.

As described above, the ruthenium compound protective film 6 on the multilayer reflective film 2 is formed by a normal sputtering method or IBD method using the target of the present invention. In this case, the film thickness of the ruthenium compound protective film 6 is appropriately selected within the range of 1.0 to 4.0 nm from the viewpoint of reflectance. More preferably, the film thickness is such that the reflectance of light reflected on the protective film in the reflective region is maximized. However, in the manufacturing process of the reflective mask, it is necessary to consider physical film reduction due to, for example, etching of the buffer film or the absorber film on the protective film 6, and the reflectance is reduced when such film reduction occurs. It is desirable to select the maximum film thickness.
A substrate with a multilayer reflective film in which such a multilayer reflective film and a ruthenium compound protective film are formed on a substrate is, for example, a substrate with a multilayer reflective film in an EUV reflective mask blank or an EUV reflective mask, or a multilayer reflective film in an EUV lithography system. Used as a mirror.

Next, the manufacturing method of the reflective mask blank of this invention is demonstrated.
A reflective mask blank for exposure is obtained by forming an absorber film that absorbs exposure light on the ruthenium compound protective film of the substrate with a multilayer reflective film according to the present invention described above. If necessary, a buffer film is provided between the ruthenium compound protective film and the absorber film, which has resistance to the etching environment during pattern formation on the absorber film, and protects the multilayer reflective film. Also good. Since the reflective mask blank is manufactured by forming the absorber film on the ruthenium compound protective film by using the substrate with the multilayer reflective film according to the present invention, the surface of the ruthenium compound protective film which becomes the reflective surface of the mask in particular. Thus, it is possible to obtain a reflective mask blank with extremely few surface defects due to particles.
FIG. 2A is a cross-sectional view of an embodiment of a reflective mask blank obtained by the present invention. According to this, the reflective mask blank 10 is configured to have the buffer film 3 and the absorber film 4 in this order on the ruthenium compound protective film 6 of the substrate with a multilayer reflective film described above.

  The material of the absorber film 4 is a film having a high absorptivity of exposure light and located below the absorber film (in this embodiment, it is a buffer film, but in a configuration in which no buffer film is provided, a ruthenium compound protective film And those having a sufficiently large etching selection ratio are selected. For example, a material having Ta as a main metal component is preferable. In this case, if a material containing Cr as a main component is used for the buffer film, the etching selectivity can be increased (10 or more). A material having Ta as a main metal element is usually a metal or an alloy. Further, those having an amorphous or microcrystalline structure are preferable from the viewpoint of smoothness and flatness. Materials containing Ta as a main metal element include materials containing Ta and B, materials containing Ta and N, materials containing Ta, B and O, materials containing Ta, B and N, and materials containing Ta and Si A material containing Ta, 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. In addition, when N or O is added to Ta, resistance to oxidation is improved, so that an effect of improving stability over time can be obtained.

Other absorber film materials include Cr-based materials (chromium, chromium nitride, etc.), tungsten-based materials (tungsten nitride, etc.), and titanium-based materials (titanium, titanium nitride). ) Etc. can be used.
These absorber films can be formed by a normal sputtering method. The thickness of the absorber film may be a thickness that can sufficiently absorb, for example, EUV light as exposure light, but is usually about 30 to 100 nm.
The buffer film 3 has a function of protecting the lower multilayer reflective film as an etching stop layer when forming a transfer pattern on the absorber film 4. In this embodiment, the ruthenium compound on the multilayer reflective film is used. It is formed between the protective film and the absorber film. Note that the buffer film may be provided as necessary.
As the material of the buffer film, a material having a high etching selectivity with the absorber film is selected. The etching selectivity between the buffer film and the absorber film is 5 or more, preferably 10 or more, more preferably 20 or more. Furthermore, a material having low stress and excellent smoothness is preferable, and in particular, it has a smoothness of 0.3 nmRms or less. From such a viewpoint, it is preferable that the material for forming the buffer film has a microcrystalline or amorphous structure.

In general, Ta, Ta alloy, or the like is often used as a material for the absorber film. When a Ta-based material is used as the material of the absorber film, it is preferable to use a material containing Cr as the buffer film. For example, Cr alone or a material in which at least one element of nitrogen, oxygen, and carbon is added to Cr can be used. Specifically, chromium nitride (CrN) or the like is used.
On the other hand, when Cr alone or a material mainly containing Cr is used as the absorber film, the buffer film is made of a material mainly containing Ta, for example, a material containing Ta and B, or Ta and B. A material containing N and N can be used.
This buffer film may be removed in a pattern according to the pattern formed on the absorber film in order to prevent a reduction in the reflectance of the mask when the reflective mask is formed. If a large material can be used and the film thickness can be made sufficiently thin, the ruthenium compound protective film may be left to cover without being removed in a pattern. The buffer film can be formed by a film forming method such as a normal sputtering method (DC sputtering, RF sputtering) or IBD method. The thickness of the buffer film is preferably about 20 to 60 nm when correcting the absorber film pattern using the focused ion beam (FIB), but 5 to 15 nm when the FIB is not used. It is good also as a grade.

A reflective mask for exposure can be obtained by forming a predetermined transfer pattern on the absorber film of the reflective mask blank obtained as described above.
The pattern formation on the absorber film can be formed using a lithography technique. Referring to FIG. 2, first, the reflection type obtained by forming the buffer film 3 and the absorber film 4 on the ruthenium compound protective film 6 of the substrate 30 with a multilayer reflective film (see FIG. 1) according to the present invention. A mask blank 10 (see FIG. 2A) is prepared. Next, a resist layer is provided on the absorber film 4 of the reflective mask blank 10, and a predetermined resist pattern 5a is formed by drawing and developing a pattern on the resist layer (see FIG. 2B). Next, using the resist pattern 5a as a mask, the pattern 4a is formed on the absorber film 4 by a technique such as etching. For example, in the case of an absorber film containing Ta as a main component, dry etching containing chlorine gas or trifluoromethane can be applied.

The remaining resist pattern 5a is removed to obtain a mask 11 on which a predetermined absorber film pattern 4a is formed as shown in FIG.
After the pattern 4a is formed on the absorber film 4, the buffer film 3 is removed according to the absorber film pattern 4a, and the ruthenium compound protective film 6 on the multilayer reflective film is exposed in the region without the absorber film pattern 4a. A mold mask 20 is obtained (see FIG. 2D). Here, for example, in the case of a buffer film made of a Cr-based material, dry etching using a mixed gas containing chlorine and oxygen can be used. At this time, the ruthenium compound protective film 6 protects the multilayer reflective film 2 against dry etching of the buffer film 3. If the necessary reflectance can be obtained without removing the buffer film 3, the buffer film 3 is not processed into the same pattern as the absorber film as shown in FIG. It can also be left on the multilayer reflective film 2 comprising
According to the present invention, since the reflective mask blank is used as a reflective mask, it is possible to obtain a reflective mask free of pattern defects caused by surface defects on the reflective surface of the mask.

Next, the embodiment of the present invention will be described more specifically with reference to examples. Hereinafter, sintering density, average crystal grain size, oxygen (O), carbon (C), niobium (Nb), zirconium (Zr), molybdenum (Mo), and other metals contained in the examples and comparative examples The amount is determined by appropriately adjusting the raw material powder material and purity, the raw material powder grinding conditions (grinding time), sintering temperature, pressure during sintering, etc., and the ruthenium compound target sintering density and average crystal grain size to be used. , Targets with different contents of oxygen (O) and carbon (C) were prepared.
Example 1
A low-expansion SiO ₂ —TiO ₂ glass substrate having an outer shape of 152 mm square and a thickness of 6.3 mm was prepared as the substrate. This glass substrate has a smooth surface of 0.12 nmRms and a flatness of 100 nm or less by mechanical polishing.
Next, an alternate laminated film made of Mo and Si suitable as a reflective film in an exposure wavelength region of 13 to 14 nm was formed as a multilayer reflective film on the substrate. Film formation was performed using an ion beam sputtering apparatus. First, using a Si target, a Si film was formed to a thickness of 4.2 nm. After that, using a Mo target, a Mo film was formed to a thickness of 2.8 nm. Was deposited to 4 nm. The total film thickness is 284 nm.
When the number of particles on the surface of the multilayer reflective film of the substrate with the multilayer reflective film obtained as described above was measured, it was 12 for the entire substrate. The particles were measured with a defect inspection apparatus (MAGICS M-1320 manufactured by Lasertec Corporation) having a size of 150 nm or more.

  Next, a RuNb protective film was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained above. Film formation was performed using an ion beam sputtering apparatus. The RuNb target used at that time had a target sintered density of 99.5% and an average crystal grain size of 76 nm. The average crystal grain size was measured by observation with a scanning electron microscope (SEM).

Further, when the composition of the obtained target was analyzed by X-ray photoelectron spectroscopy (XPS), it contained 79 atomic% ruthenium (Ru) and 21 atomic% niobium (Nb), and oxygen (O) as an impurity. The carbon (C) content was 2000 ppm or less, and the carbon (C) content was 200 ppm or less.
The film thickness of the RuNb protective film formed using the RuNb target was 4 nm.
After the RuNb protective film was formed, the number of particles on the surface of the protective film of the substrate with the multilayer reflective film was measured using the defect inspection apparatus. As a result, the number of increase was very small and increased by 2 over the entire substrate. .

Next, a buffer film made of chromium nitride (CrN: N = 10 at%) was formed on the RuNb protective film of the substrate with the multilayer reflective film. Film formation was performed with a DC magnetron sputtering apparatus, and the film thickness was 20 nm.
Next, a film containing Ta as a main component and containing B and N was formed on the buffer film as an absorber film for exposure light having a wavelength of 13 to 14 nm. The film forming method was performed by a DC magnetron sputtering apparatus using a target containing Ta and B, adding 10% nitrogen to Ar. The film thickness was set to 70 nm as a thickness capable of sufficiently absorbing exposure light. The composition ratio of the formed TaBN film was 0.8 for Ta, 0.1 for B, and 0.1 for N.
As described above, the reflective mask blank of this example was obtained.

Next, using the reflective mask blank, a pattern was formed on the absorber film, and a reflective mask having a pattern for 16 Gbit-DRAM having a design rule of 0.07 μm was produced.
First, an EB resist was applied on the reflective mask blank, and a predetermined resist pattern was formed by EB drawing and development. Next, using this resist pattern as a mask, the TaBN film as the absorber film was dry-etched using chlorine to form an absorber film pattern.
Next, using the pattern formed on the absorber film as a mask, the CrN film as the buffer film is dry-etched using a mixed gas of chlorine and oxygen (mixing ratio is 1: 1 by volume), and the absorber film It was removed in a pattern according to the pattern formed.

  As described above, the reflective mask of this example was obtained. When pattern defects were measured with the defect inspection apparatus, it was found that there were no pattern defects due to particles. Further, using this reflective mask, pattern transfer onto a semiconductor substrate was performed by a pattern transfer apparatus 50 as shown in FIG. The pattern transfer apparatus 50 is roughly configured by a laser plasma X-ray source 31, a reduction optical system 32, and the like, and the pattern reflected by the reflective mask 20 is normally reduced to about ¼ by the reduction optical system 32. Since the wavelength band of 13 to 14 nm is used as the exposure wavelength, it was set in advance so that the optical path was in vacuum. In this state, EUV light obtained from the laser plasma X-ray source 31 is incident on the reflective mask 20, and the light reflected here passes through the reduction optical system 32 on the semiconductor substrate 33 (silicon wafer with resist layer). Transcribed to. As a result, a good transfer image was obtained on the semiconductor substrate.

(Example 2)
A RuNb protective film was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained in the same manner as in Example 1. In this example, film formation was performed using a DC magnetron sputtering apparatus. At this time, the same RuNb target as in Example 1 was used, but the sintered density was 99.3%.
After the formation of the RuNb protective film, the number of particles on the surface of the RuNb protective film of the substrate with the multilayer reflective film was measured using the defect inspection apparatus. As a result, the total number of particles increased by 8 compared to before the protective film was formed. It was.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuNb protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank.
Next, using the reflective mask blank, a pattern is formed on the absorber film as in Example 1, and a buffer film is formed in the same pattern as the absorber film. The design rule is 0.07 μm. A reflective mask having a pattern for 16 Gbit-DRAM was prepared. When pattern defects were measured for the obtained reflective mask, it was found that there were almost no pattern defects due to particles. Further, when a pattern was transferred onto a semiconductor substrate using this reflective mask, a good transfer image was obtained.

(Example 3)
In the same manner as in Example 1, a RuZr protective film was formed on the multilayer reflective film of the obtained substrate with the multilayer reflective film. In this example, film formation was performed using an ion beam sputtering apparatus. The RuZr target used at that time had a target sintered density of 99.2% and an average crystal grain size of 81 nm. Further, when the composition of the obtained target was analyzed by XPS, Ru contained 89 atomic% and Zr contained 11 atomic%, and oxygen (O) and carbon (C) were contained as impurities. The content of (O) was 2000 ppm or less, and the content of carbon (C) was 200 ppm or less.

The film thickness of the RuZr protective film formed using the RuZr target was 4 nm.
After the formation of the RuZr protective film, the number of particles on the RuZr protective film surface of the multilayer reflective film-coated substrate was measured using the defect inspection apparatus. As a result, the total number of particles increased by 7 compared to before the protective film was formed. It was.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuZr protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank.
Next, a reflective mask was produced in the same manner as in Example 1 using the reflective mask blank. When pattern defects were measured for the obtained reflective mask, it was found that there were almost no pattern defects due to particles. Further, when a pattern was transferred onto a semiconductor substrate using this reflective mask, a good transfer image was obtained.

Example 4
A RuZr protective film similar to that in Example 3 was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained in the same manner as in Example 1. The film formation in this example was performed using a DC magnetron sputtering apparatus. At this time, the same RuZr target as in Example 3 was used, but the sintered density was 99.5%.
After the formation of the RuZr protective film, the number of particles on the surface of the RuZr protective film of the multilayer reflective film substrate was measured using the defect inspection apparatus. As a result, the total number of particles increased by 12 compared to before the protective film was formed. It was.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuZr protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank.
Next, a reflective mask was produced in the same manner as in Example 1 using the reflective mask blank. When pattern defects were measured for the obtained reflective mask, it was found that there were almost no pattern defects due to particles. Further, when a pattern was transferred onto a semiconductor substrate using this reflective mask, a good transfer image was obtained.

(Example 5)
In the same manner as in Example 1, a RuMo protective film was formed on the multilayer reflective film of the obtained substrate with the multilayer reflective film. In this example, film formation was performed using an ion beam sputtering apparatus. The RuMo target used at that time had a target sintered density of 99.1% and an average crystal grain size of 58 nm. Moreover, when the composition of the obtained target was analyzed by XPS, it contained 92 atomic% Ru and 8 atomic% Mo and contained oxygen (O) and carbon (C) as impurities. The content of (O) was 2000 ppm or less, and the content of carbon (C) was 200 ppm or less.

The film thickness of the RuMo protective film formed using the RuMo target was 4 nm.
After the formation of the RuMo protective film, the number of particles on the surface of the RuMo protective film of the substrate with the multilayer reflective film was measured using the defect inspection apparatus. As a result, the total number of particles increased by 8 compared to before the protective film was formed. It was.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuMo protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank.
Next, a reflective mask was produced in the same manner as in Example 1 using the reflective mask blank. When pattern defects were measured for the obtained reflective mask, it was found that there were almost no pattern defects due to particles. Further, when a pattern was transferred onto a semiconductor substrate using this reflective mask, a good transfer image was obtained.

(Example 6)
A RuMo protective film similar to that in Example 5 was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained in the same manner as in Example 1. The film formation of this example was performed using a DC magnetron sputtering apparatus. At this time, the RuMo target was the same as that of Example 5, but the sintered density was 99.5%.
After the formation of the RuMo protective film, the number of particles on the surface of the RuMo protective film of the substrate with a multilayer reflective film was measured using the defect inspection apparatus. As a result, the total number of the substrates increased by 9 compared to before the protective film was formed. It was.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuMo protective film of the substrate with the multilayer reflective film, thereby producing a reflective mask blank.
Next, a reflective mask was produced in the same manner as in Example 1 using the reflective mask blank. When pattern defects were measured for the obtained reflective mask, it was found that there were almost no pattern defects due to particles. Further, when a pattern was transferred onto a semiconductor substrate using this reflective mask, a good transfer image was obtained.
Next, the comparative example with respect to the said Example is given.

(Comparative Example 1)
A ruthenium protective film was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained in the same manner as in Example 1. The film formation was performed using an ion beam sputtering apparatus as in Example 1. The Ru target used in Comparative Example 1 had a target sintered density of 92.3% and an average crystal grain size of 10 nm. . Moreover, when the composition of the obtained target was analyzed by XPS, ruthenium (Ru) was contained in 99.9% by weight or more, but oxygen (O) and carbon (C) were contained as impurities. The oxygen content was over 200 ppm.

The thickness of the ruthenium protective film formed using the Ru target was 4 nm.
After the formation of the ruthenium protective film, the number of particles on the surface of the ruthenium protective film of the multilayer reflective film-coated substrate was measured using the defect inspection apparatus. As a result, the total number of particles increased by 1513 compared to before the protective film was formed. . It was found that when a ruthenium protective film was formed using the target of this comparative example, the generation of particles during film formation was very large. The reason is considered to be due to the abnormal discharge of the target, peeling of the ruthenium film attached to the inside of the film forming apparatus (chamber inner wall), peeling of the formed ruthenium protective film, and the like.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the ruthenium protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank. Next, a reflective mask was prepared using the reflective mask blank in the same manner as in Example 1. When pattern defects were measured for the obtained reflective mask, there were very many pattern defects due to particles.

(Comparative Example 2)
A RuMo protective film was formed on the multilayer reflective film of the substrate with the multilayer reflective film obtained in the same manner as in Example 1. The film formation of this comparative example 2 was performed using an ion beam sputtering apparatus, and the RuMo target used at this time had a sintered density of 92.3% and an average crystal grain size of 112 nm. The composition ratio of the target is that Ru is 92 atomic% and Mo is 8 atomic%, oxygen (O) and carbon (C) are included as impurities, and the oxygen (O) content is 2000 ppm. And the carbon (C) content was over 200 ppm.
After the formation of the RuMo protective film, the number of particles on the surface of the RuMo protective film of the substrate with the multilayer reflective film was measured using the defect inspection apparatus. As a result, the total number of particles increased by 63 compared to before the protective film was formed. . That is, it was found that when a RuMo protective film was formed using the target of Comparative Example 2, the generation of particles during the film formation was very large.
Next, a buffer film and an absorber film similar to those in Example 1 were formed on the RuMo protective film of the multilayer reflective film-coated substrate, thereby preparing a reflective mask blank. Next, a reflective mask was prepared using the reflective mask blank in the same manner as in Example 1. When pattern defects were measured for the obtained reflective mask, there were very many pattern defects due to particles.

It is sectional drawing of the board | substrate with a multilayer reflective film obtained by this invention. It is sectional drawing which shows the manufacturing process of the reflective mask blank by using the reflective mask blank by this invention, and this mask blank. It is a block diagram which shows schematic structure of the pattern transfer apparatus used for the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multilayer reflective film 3 Buffer film 4 Absorber film 5a Resist pattern 6 Ruthenium compound protective film 10 Reflective mask blank 20 Reflective mask 30 Substrate with multilayer reflective film 50 Pattern transfer device

Claims (6)

  Ruthenium (Ru) and at least one selected from niobium (Nb), molybdenum (Mo), zirconium (Zr), titanium (Ti), lanthanum (La), silicon (Si), boron (B), and yttrium (Y) An exposure light characterized in that the sintered density is 95% or more, the oxygen (O) content is 2000 ppm or less, and the carbon (C) content is 200 ppm or less. A ruthenium compound film sputtering target that contributes to reflection.   2. The sputtering target for forming a ruthenium compound film that contributes to reflection with respect to exposure light according to claim 1, wherein the average crystal grain size is 5 nm or more and 1000 nm or less.   The sputtering target for forming a ruthenium compound film that contributes to reflection with respect to exposure light according to claim 1, wherein the sputtering target is used for a thin film forming step by an ion beam sputtering film forming method.   A method for manufacturing a substrate with a multilayer reflective film having a multilayer reflective film that reflects exposure light on the substrate, wherein the sputtering target according to any one of claims 1 to 3 is used on the multilayer reflective film. A method for producing a substrate with a multilayer reflective film, comprising a step of forming a protective film made of a ruthenium compound.   It has the process of forming the absorber film | membrane which absorbs exposure light on the protective film which consists of the said ruthenium compound of the board | substrate with a multilayer reflective film obtained by the manufacturing method of the board | substrate with a multilayer reflective film of Claim 4. A method for producing a reflective mask blank. The manufacturing method of the reflective mask characterized by forming the absorber film pattern used as a transfer pattern in the said absorber film of the reflective mask blank obtained by the manufacturing method of the reflective mask blank of Claim 5.

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