JP2006190900A - Reflective photomask blank, reflective photomask, and semiconductor device manufacturing method using the same - Google Patents

Abstract

Reflection type capable of obtaining not only EUV light exposure reflectivity but also sufficiently low DUV light exposure reflectivity in pattern inspection, sufficient reflectivity contrast, high-precision inspection and high-precision mask pattern transfer Get a photomask.
A multilayer reflective film and a light absorption layer having a light absorption film containing at least indium are stacked on a substrate.
[Selection] Figure 2

Description

  The present invention relates to a method of manufacturing a semiconductor device using a photolithographic method using extreme ultraviolet light, that is, EUV (Extreme Ultra Violet) light, particularly light having a wavelength in the soft X-ray region, a reflective photomask therefor, and a method used for the same The present invention relates to a reflective photomask blank.

  With the recent high integration in semiconductor devices, the required pattern transfer onto a Si substrate by photolithography has been miniaturized.

  Since the shortening of the wavelength of the light source in the photolithography method using a conventional lamp light source (wavelength 365 nm) or excimer laser light source (wavelength 248 nm, 193 nm) has approached the exposure limit, it enables particularly fine processing of 100 nm or less. The establishment of a new photolithography method has become an urgent task.

  For this reason, development of a photolithographic method using F2 laser light (wavelength 157 nm), which is an excimer laser light in a shorter wavelength region, is in progress, but normally the half-wave size of the exposure wavelength is a substantial development limit. For this reason, about 70 nm was the limit in this case as well.

  Therefore, in recent years, EUV lithography methods using EUV light (wavelength 13 nm) having a wavelength of 10 to 15 nm, which is one digit or more shorter than F2 laser light, as a light source have been developed.

  Since the refractive index of the substance in the wavelength region of EUV light is slightly smaller than 1, this EUV lithography method cannot use a refractive optical system as used in a conventional exposure source, and exposure by a reflective optical system. Is used. In addition, since most substances have high light absorption in the EUV light wavelength region, a reflective photomask is used as a pattern transfer photomask instead of an existing transmissive photomask. As described above, in the EUV lithography method, the optical system and the photomask used for exposure are significantly different from the conventional exposure technique.

  This reflective photomask for EUV lithography is provided with a mirror (reflecting mirror) having a high reflectivity in the EUV wavelength region on a flat Si substrate or synthetic quartz substrate, and further has a particularly absorbing property for EUV light. A light absorption layer made of a high heavy metal is formed by patterning according to a desired exposure pattern.

  A mirror (reflecting mirror) for EUV light is composed of a multilayer reflective film made of a combination of materials having greatly different refractive indexes. In the reflection type photomask, the exposure pattern is determined by the contrast of the EUV exposure reflectivity between the absorption region where the multilayer reflection film surface is covered with the light absorption layer pattern and the reflection region where there is no light absorption layer and the multilayer reflection film surface is exposed. Perform pattern transfer.

  Usually, the pattern formed on the light absorption layer is inspected by making DUV (far ultraviolet) light having a wavelength of about 190 nm to 260 nm incident on the mask surface, detecting the reflected light, and examining the contrast of the reflectance. Is called.

  Specifically, before patterning of the light absorption layer, the buffer layer surface arbitrarily provided immediately below the light absorption layer as a protective layer of the multilayer reflection film becomes a reflection region, and the absorption region is composed of the patterned light absorption layer surface First, an inspection of whether or not the light absorption layer has been patterned as designed is first performed. In this case, a portion (black defect) where the light absorption layer that should be etched is left on the buffer layer without being etched, or a part of the light absorption layer that should be left on the buffer layer without being etched is etched. Detected spot (white defect). The buffer layer is formed for the purpose of preventing the reflectance from being reduced by damaging the multilayer film when the light absorption layer is processed by dry etching and when the pattern defect of the light absorption layer is corrected. . The buffer layer is required to have high resistance to dry etching of the light absorption layer, high resistance in the correction process, and little damage to the light absorption layer when removing unnecessary buffer films. (For example, refer to Patent Document 1).

  After correcting the defect detected in the first stage inspection, the buffer layer is further removed to expose the surface of the multilayer reflective film immediately below the buffer layer, and then the second pattern with respect to the pattern formed in the light absorption layer. The final inspection at the stage is performed. This inspection is performed by observing the contrast of the reflectance between the absorption region formed of the light absorption layer surface and the reflection region formed of the multilayer reflective film surface. In some cases, it is not necessary to remove the buffer layer. However, if there is a coating film of the buffer layer on the surface of the multilayer reflective film, the reflectance of the multilayer reflective film tends to be reduced, so the buffer layer is not removed. There are many cases.

  In the inspection of the light absorption layer pattern by the DUV inspection light in the first stage and the second stage described above, the surface of the buffer layer from which the light absorption layer has been removed and the light absorption layer remain without being removed. This is performed by observing the DUV light reflectance contrast between the surface of the light absorbing layer and the surface of the multilayer reflective film from which the buffer layer has been removed and the surface of the light absorbing layer. Therefore, in order to further improve the inspection accuracy, the buffer layer surface and the light absorption layer surface in the first stage inspection, and the multilayer reflective film surface and the light absorption layer surface in the second stage inspection, respectively. It is desirable that the difference in reflectance at the DUV inspection wavelength is large.

  In response to such demands, a multilayer light absorption layer in which chromium or tantalum oxide or nitride is provided on the light absorption layer, as in the case of a conventionally used transmission type low reflection chromium mask blank. (For example, refer to Patent Document 2).

  However, although the oxide layer and nitride layer of chromium and tantalum have higher reflectivity with DUV inspection light, the absorption coefficient with EUV light is smaller than that of a single chromium layer or tantalum layer. The film thickness required for the absorption layer has to be increased to 70 nm or more.

In addition, since exposure by a reflective optical system is used at the EUV light wavelength, the light incident on the mask is not perpendicular to the substrate but is incident obliquely at an incident angle of, for example, 5 to 6 degrees. Due to this influence, for example, the aerial image is likely to be asymmetric or an XY direction difference is likely to occur. For this reason, it is desired that the thickness of the light absorption layer be as thin as possible.
JP-A-7-333829 JP 2004-39884 A

  The present invention has been obtained in view of the above circumstances, and not only the EUV light exposure reflectance at the time of transfer of the exposure pattern, but also the DUV light exposure reflectance in the pattern inspection of the light absorbing layer is sufficiently low, On the other hand, it is an object of the present invention to provide a reflective photomask having a light absorption layer capable of obtaining a sufficient reflectance contrast and capable of highly accurate inspection and highly accurate mask pattern transfer.

  Further, according to the present invention, not only the EUV light exposure reflectance at the time of mask pattern transfer but also the DUV light exposure reflectance in the light absorption layer pattern inspection is sufficiently low, and a sufficient reflectance contrast can be obtained for the reflection region. An object of the present invention is to provide a reflective photomask blank having a light absorption layer and capable of processing a reflective photomask capable of pattern transfer with high accuracy by high accuracy inspection.

  Furthermore, according to the present invention, not only the EUV light exposure reflectance at the time of mask pattern transfer but also the DUV light exposure reflectance in the light absorption layer pattern inspection is sufficiently low, and a sufficient reflectance contrast can be obtained for the reflection region. It is an object of the present invention to provide a reflective photomask having a light absorbing layer and capable of pattern transfer with high accuracy by high accuracy inspection and a method of manufacturing a reflective photomask blank capable of processing the same.

  The reflective photomask blank of the present invention comprises a substrate, a multilayer reflective film provided on the substrate, and a light absorption layer provided on the multilayer reflective film and having a light absorption film containing indium. It is characterized by that.

  In the reflective photomask blank of the present invention, the light absorption layer preferably further includes an antireflection film containing tantalum formed on the light absorption film.

  In the reflection type photomask blank of the present invention, it is preferable that the antireflection film containing tantalum further contains at least one element selected from the group consisting of oxygen, nitrogen, carbon, and silicon.

  The reflective photomask blank of the present invention preferably further includes an antireflection film containing chromium on the light absorption film.

  In the reflective photomask blank of the present invention, it is preferable that the chromium-containing antireflection film further contains at least one element selected from the group consisting of oxygen, nitrogen, and carbon.

  The reflective photomask blank of the present invention preferably further includes a buffer layer containing carbon as a main component between the multilayer reflective film and the light absorbing layer.

  The reflective photomask blank of the present invention preferably further includes an etching stopper layer containing at least one of tantalum and chromium as a main component between the buffer layer and the multilayer reflective film.

  The reflective photomask of the present invention is characterized in that the light absorption layer of the reflective photomask blank is patterned.

  A method for producing a reflective photomask includes forming a photoresist layer on a light absorption layer of the reflective photomask blank, exposing and developing the photoresist layer partially according to a predetermined pattern. Removing the exposed portion of the light absorption layer, and patterning the light absorption layer by dry etching the light absorption layer through the photoresist layer. And

  According to the present invention, the light absorption layer used in the reflective photomask blank and the reflective photomask contains indium, so that not only during pattern transfer exposure by EUV light exposure but also during inspection exposure by DUV light. However, a favorable reflectance contrast is obtained for the reflective region, and the inspection accuracy of the reflective photomask and the pattern transfer accuracy thereof are improved. Further, by performing EUV light exposure using this reflective photomask, a semiconductor device can be manufactured with a fine pattern with high accuracy.

  The reflective photomask blank of the present invention has a substrate, a multilayer reflective film provided on the substrate, and a light absorption layer provided on the multilayer reflective film, and the light absorption layer contains indium. .

  The reflection type photomask blank is a product before processing the reflection type photomask, and the light absorption layer is not subjected to pattern processing according to the exposure pattern to be transferred.

  FIG. 1 is a schematic cross-sectional view illustrating an exemplary configuration of a reflective photomask blank according to the present invention, and FIG. 2 is a schematic cross-sectional view illustrating an exemplary configuration of a reflective photomask according to the present invention.

  As shown in FIG. 1, the reflective photomask blank 10 of the present invention has a structure in which a multilayer reflective film 2, a buffer layer 3, and a light absorption film 4 are sequentially laminated on a substrate 1. The buffer layer 3 can be arbitrarily provided. Further, although the multilayer reflective film 2 is multilayered, it is simply shown as a single layer.

  The reflective photomask of the present invention has the same configuration as that of the reflective photomask blank except that the light absorption layer is patterned.

As shown in FIG. 2, the reflective photomask 20 of the present invention includes a patterned light absorption film 4 a instead of the light absorption film 4, and a pattern instead of the buffer layer 3. The structure is the same as that shown in FIG. 1 except that a processed buffer layer 3a is provided. In the reflection type photomask 20, the light absorption film 4 is partially removed by this pattern processing, and the part where the surface of the multilayer reflection film 2 is partially exposed is the reflection region B, and the light absorption layer 4 remaining without being removed. The surface constitutes the absorption region A. According to the present invention, the light absorption layer used has the light absorption film containing indium, whereby the absorption coefficient of the light absorption layer can be increased. Thereby, the film thickness of the light absorption layer can be reduced. When the thickness of the light absorption layer is reduced, a pattern can be formed with good dimensional control.

  Moreover, the manufacturing method of the reflective photomask of the present invention is an example of a method for obtaining the reflective photomask using the reflective photomask blank, on the light absorption layer of the reflective photomask blank. Forming a photoresist layer, exposing and developing, partially removing the photoresist layer according to a predetermined pattern, exposing a part of the light absorption layer, and through the photoresist layer. The light absorption layer is subjected to pattern processing by dry etching the light absorption layer.

  3 to 12 are views for explaining an example of the manufacturing process of the reflective photomask of the present invention.

As the substrate, a material having a small coefficient of thermal expansion and good flatness and a material having a small surface roughness are preferable. For example, as shown in FIG. 3, SiO ₂ —TiO ₂ glass is flatly polished to clean the surface. A glass substrate 1 is prepared.

  Next, about 2.8 cycles of Mo2.8 nm and Si4.2 nm are alternately laminated on the substrate 1 by DC magnetron sputtering, and the reflectivity with respect to EUV light in the wavelength region of 13 to 14 nm is obtained as shown in FIG. The multilayer reflective film 2 that maximizes the thickness can be produced. Although this multilayer reflective film 2 is a multilayer film, it is shown as a single layer in the figure for simplicity.

  Thereafter, as shown in FIG. 5, for example, a buffer layer 3 of carbon or the like can be formed on the multilayer reflective film 2 by, for example, 15 nm by DC magnetron sputtering.

  Further, as shown in FIG. 6, as the light absorbing film 4 containing indium, for example, an indium oxide film having a thickness of, for example, 27 nm is formed on the buffer layer 3 by DC magnetron sputtering using an indium target in an atmosphere containing argon and oxygen. be able to. Alternatively, indium oxide can be deposited to a thickness of, for example, 27 nm in a mixed atmosphere of argon and oxygen using indium oxide as a target.

  An antireflection film (not shown) can be formed on the light absorption film 4. As the antireflection film, for example, tantalum oxynitride can be formed to a thickness of, for example, 15 nm by sputtering. In this case, the light absorption film 4 and the antireflection film can function as a light absorption layer.

  Thereafter, the light absorption film 4 and an optional antireflection film can be patterned by, for example, an electron beam lithography technique.

  First, as shown in FIG. 7, an electron beam exposure resist coating solution is applied on the light absorption film 4 or an arbitrary antireflection film, and baking is performed to form the electron beam exposure resist layer 5. .

  Next, a desired pattern is drawn on the resist layer 5 by an electron beam drawing apparatus, and is developed with a developer such as a 2.38 at% tetramethylammonium hydroxide aqueous solution. As shown in FIG. A resist pattern 5a serving as a mask for etching the film 4 and an optional antireflection film can be formed.

  When the antireflection film is provided, first, the antireflection film can be etched by dry etching using the resist pattern 5a as a mask. For example, when a film containing tantalum and one or more elements selected from nitrogen, oxygen, carbon, and silicon is used as an antireflection film, etching can be performed in a gas atmosphere containing chlorine. In addition, when a film containing chromium and one or more elements selected from nitrogen, oxygen, and carbon is used as an antireflection film, etching can be performed in a gas atmosphere containing chlorine and oxygen.

  When dry etching is performed in an atmosphere containing chlorine, the etching of the antireflection film proceeds, and the etching rate rapidly decreases when reaching the lower layer containing indium. Although a film containing indium is etched even in a chlorine atmosphere, since the vapor pressure of indium chloride, which is a reaction product, is very low, the etching rate is very low at a substrate temperature of 150 ° C. or lower. By heating the substrate, the layer containing indium can be etched in a chlorine gas atmosphere. However, heating causes atomic diffusion between the layers of the reflective multilayer film to change the reflectivity. It is not preferable to etch the containing absorption film in a chlorine gas atmosphere. On the other hand, group III elements such as indium can be dry etched in a gas atmosphere containing methane. Since elements that generate volatile substances by reaction with methane plasma are almost limited to group 12 to 15 elements, the anti-reflection film, or the etching stopper layer arbitrarily provided between the buffer layer and the light absorption film, Very high selectivity is obtained.

  For example, after etching the antireflection film, dry etching is performed in an atmosphere containing methane, so that a light absorption film containing indium is formed as shown in FIG. It can be etched. However, in an atmosphere containing methane, the methane decomposed by the plasma is polymerized, so that the deposition of the polymer proceeds except at the portion where the indium is exposed. This polymer can be easily removed by an oxygen gas atmosphere process. Further, plasma containing methane and plasma containing oxygen can be alternately performed.

  Further, as shown in FIG. 10, the resist layer 5a remaining after the dry etching and the generated deposit can be removed by, for example, oxygen plasma or a resist remover.

  As shown in FIG. 11, the EUV mask after removing the resist is inspected by irradiating it with DUV light, inspecting whether the pattern of the formed light absorption layer is formed as designed, and correcting if necessary. Can do.

  After the correction process is completed, the buffer film 3 of the mask can be removed by etching to form a patterned buffer film 3a. Etching of the buffer film 3 may be dry etching or wet etching. Since the etching rate of indium by chlorine-based or fluorine-based dry etching is very low, the dimensional variation due to the etching of the absorption film by this process is very small. In this way, a reflective photomask 30 according to the present invention is obtained as shown in FIG. Here, when the buffer film 3 of the mask is not removed by etching, a reflective photomask having the same configuration as that shown in FIG. 2 is obtained.

  As the multilayer reflective film used in the present invention, a film in which materials having different refractive indexes are laminated in multiple layers can be used in order to have a high reflectance at the wavelength of EUV light. When EUV light having a wavelength of around 13 nm is used, a combination of a Mo layer and a Si layer can be used. In order to obtain a high reflectance, it is desirable that the refractive index changes sharply at the interface between the layers. The uppermost layer of the multilayer film can have higher reflectance than Mo, but since the oxide film formed on the surface is unstable, Si can be formed on the uppermost layer.

  The light absorption layer used in the present invention has at least one light absorption film.

  The light absorbing film used here refers to a film that is patterned on a mask to form a region having a low light intensity in an exposure process. As the light absorbing film, a material having a high ability to absorb light having an EUV wavelength can be used. The absorption capability is determined by the optical constant at the wavelength of light used for exposure.

  In the present invention, the light absorption film used contains indium.

  When the light absorption film contains indium, there is an advantage that the extinction coefficient (imaginary part of the optical constant) of the film is increased, and a film having a small thickness and a large absorption can be obtained.

  When a film of indium is formed by sputtering, crystal grains tend to grow, pattern roughness (Line edge roughness) increases, stress changes with time, and stress control tends to be difficult. Further, indium alone has a very low melting point and is not sufficiently resistant in the process of forming a mask pattern. Therefore, in addition to indium, at least one component selected from the group consisting of oxygen, tin, zinc, nitrogen, phosphorus, and antimony can be added to the light absorption layer of the present invention. For example, tin, zinc, etc. have a large absorption coefficient, and the vapor pressure of methyl compounds is high. Therefore, when these elements are added, selective etching tends to occur when dry etching at the time of pattern processing is performed with a methane-containing gas. There are advantages. Further, for example, nitrogen, phosphorus, antimony, and the like have a high vapor pressure of a hydrogen compound. Therefore, when these elements are added, there is an advantage that the speed of plasma etching using methane is high and the dimensions can be easily controlled.

  The light absorption film used in the present invention preferably has a reflectance with respect to EUV light of less than 0.6%. The smaller the reflectance, the better the contrast and the better the mask image can be obtained. If it exceeds 0.6%, the contrast becomes insufficient and the resolution tends to be adversely affected in the exposure process.

  Moreover, it is preferable that the reflectance with respect to DUV light is less than 10%. The lower the reflectivity, the greater the contrast at the time of inspection, which tends to be advantageous for the detection of minute defects. When the reflectance exceeds 10%, the contrast decreases and the defect detection limit decreases. Tend to.

  For example, when an antimony indium film is used, the light reflectance at a wavelength of 257 nm is 52%.

  The film thickness of the light absorption layer is preferably 20 nm to 100 nm. When the film thickness is within this range, a pattern with better dimension control can be formed. If it is less than 20 nm, the exposure reflectivity by EUV light and DUV light tends not to be sufficiently low, and if it exceeds 100 nm, the amount of dimensional fluctuation during pattern formation is large, and it tends to be difficult to obtain an accurate pattern. In addition, when used as a mask for exposure, the influence of shadows caused by oblique incidence tends to increase.

  The light absorption layer used in the present invention may include a light absorption film and an antireflection film arbitrarily provided on the light absorption film.

  The antireflection film used in the present invention refers to a film having a low reflectance at the wavelength of light used for defect inspection after the pattern of the light absorption film is formed on the pattern of the light absorption film. By providing this, the contrast in the defect inspection using the DUV light wavelength can be increased.

  As a material for the antireflection film, a material that can be dry-etched in an atmosphere containing fluorine or chlorine can be suitably used. For example, a film containing tantalum and one or more elements selected from nitrogen, oxygen, carbon, and silicon, and a film containing chrome and one or more elements selected from nitrogen, oxygen, and carbon Etc. The antireflection film usable in the present invention is not limited to the above, and a film having a low reflectance can be selected from the optical characteristics at the DUV light wavelength for inspection.

  As the antireflection film, a film containing at least one of tantalum and chromium as a main component can be preferably used.

  The antireflection film containing tantalum has a reflectivity for EUV light as low as 0.08% to 0.4% and a reflectivity for DUV light as low as 1% to 8% by selecting appropriate film forming conditions. In addition, when etching the light absorbing film containing indium, it can function as an etching mask, and pattern processing of the light absorbing film can be formed with high dimensional accuracy.

  The antireflection film containing chromium has a low reflectance of 0.1% to 0.6% for EUV light and a reflectance of 2% to 8% for DUV light, and etches a light absorbing film containing indium. In this case, it can function as an etching mask, and the pattern processing of the light absorption film can be formed with high dimensional accuracy.

  This main component is preferably contained in the antireflection film at 10 at% to 60 at%. If it is less than 10 at%, the absorption of light at the EUV wavelength is small, and the effect of reducing the film thickness tends to be small. If it exceeds 60 at%, the metal property is high and the reflectivity at the DUV wavelength tends to be high. There is.

  When the antireflection film contains tantalum as a main component, it can further contain at least one element selected from the group consisting of oxygen, nitrogen, carbon, and silicon as a subcomponent.

  In addition to the function as an etching mask, the antireflection film containing these subcomponents can obtain good contrast in pattern defect inspection using light in the DUV wavelength region.

  The content of these subcomponents is preferably 40 at% to 90 at% in the antireflection film. If it is less than 40 at%, the content of tantalum is too large, so that the antireflection effect tends to be small. If it exceeds 90 at%, the chemical stability of the film tends to be reduced, and the effect of reducing the film thickness tends to be low due to the low tantalum content.

  When the antireflection film contains chromium as a main component, it can further contain at least one element selected from the group consisting of oxygen, nitrogen, and carbon as a subcomponent.

  In addition to the function as an etching mask, the antireflection film containing these subcomponents can obtain good contrast in pattern defect inspection using light in the DUV wavelength region.

  The content of these subcomponents is preferably 50 at% to 80 at% in the antireflection film. If it is less than 50 at%, the antireflection effect tends to be low because of the high chromium content. If it exceeds 80 at%, the chemical stability of the film is lowered, and the absorption capacity is lowered, so that the effect of reducing the film thickness tends to be reduced.

  As a more preferable antireflection film, tantalum nitride formed by DC sputtering in an atmosphere of argon, oxygen, and nitrogen gas by targeting tantalum silicide can be suitably used.

  In the present invention, a buffer layer can be further provided between the light absorption layer and the antireflection film. The buffer layer is made of a material that has high resistance to dry etching of the light absorption layer, high resistance in the correction process, and little damage to the light absorption layer when the buffer film is removed after the correction process. obtain. Further, after the dry etching of the light absorption layer, the portion where the buffer film is exposed on the surface can increase the contrast at the time of inspection when the reflectance is higher. When a material having a large absorption coefficient is used as the material of the buffer film, this exposed portion can be removed by etching. On the other hand, when a material having a small absorption coefficient is used as the material of the buffer film, it can be left without being removed, and can function as a film that prevents a change in reflectance due to a change in the surface state of the reflective multilayer film over time.

  Examples of the material for the buffer layer include chromium, chromium oxide, nitride, carbide and a mixture thereof, silicon oxide, and carbon.

  More preferably, a buffer layer containing carbon as a main component can be used.

  Since the buffer layer containing carbon as a main component can be removed by oxygen plasma, the antireflection film tends to be less damaged.

  The carbon content in the buffer layer is preferably 70 at% to 100 at%. If it is less than 70 at%, chemical stability is insufficient and the film thickness tends to fluctuate during cleaning.

  An etching stopper layer containing at least one of tantalum and chromium as a main component can be further provided between the buffer layer containing carbon as a main component and the multilayer reflective film.

  When the etching stopper layer is provided, it is possible to prevent the buffer film from being damaged when the resist and reaction products remaining on the surface of the light absorption layer are removed by oxygen plasma after the light absorption layer is etched. .

  As a material for the etching stopper layer, it is desirable to select a material having a high etching selectivity with respect to the antireflection film. When a film containing tantalum is used as the antireflection film, chromium nitride can be suitably used.

  Note that when the present invention is used, pattern transfer with high accuracy is possible in EUV lithography in a method for manufacturing a semiconductor device, so that a semiconductor device having a miniaturized pattern can be manufactured.

  EXAMPLES Hereinafter, an Example is shown and this invention is demonstrated in detail.

Example 1
A manufacturing process of the reflective photomask of Example 1 will be described with reference to FIGS.

  As the substrate 11, a synthetic quartz glass substrate having a size of 6 inches × 6 inches × 0.25 inches was prepared as shown in FIG.

  As shown in FIG. 14, Mo and Si targets are alternately used on a substrate 11 by using a DC magnetron sputtering apparatus, and a Mo layer having a film thickness of 2.8 nm in an argon atmosphere at a substrate temperature of 25 ° C. And the Si layer having a film thickness of 4.2 nm was laminated for 40 periods to form a multilayer reflective film 12 having a thickness of 280 nm. The uppermost layer of the multilayer reflective film 12 is made of Si. The multilayer reflective film 12 had a light reflectance of 63% at a wavelength of 257 nm.

  Next, as shown in FIG. 15, a 10 nm thick buffer layer 13 made of an amorphous carbon film was formed on the multilayer reflective film 12 at a temperature of 150 ° C. by plasma CVD.

  Further, as shown in FIG. 16, a chromium nitride film is formed on the buffer layer 13 by DC magnetron sputtering in a gas atmosphere using chromium as a target, a temperature of 25 ° C., and a flow ratio of argon and nitrogen of 2: 1. The film was formed to a thickness of 15 nm, and an etching stopper layer 17 at the time of resist peeling was formed.

  After that, as shown in FIG. 17, a light absorption film 14 made of indium antimonide was formed on the etching stopper layer 17 to a thickness of 27 nm by DC magnetron sputtering in an argon gas atmosphere using indium and antimony as targets. .

  Furthermore, an antireflection film 15 made of tantalum oxide silicide is formed on the etching stopper layer 14 by DC magnetron sputtering using tantalum and silicon as targets in an argon and oxygen gas atmosphere, thereby forming the structure shown in FIG. As shown, a reflective mask blank 30 for EUV light was obtained.

  The mask blank 30 is spin-coated with an electron beam resist FEP171 (manufactured by Fuji Film Arch Co., Ltd.) to a thickness of 300 nm, baked on a hot plate at 110 ° C. for 10 minutes, and as shown in FIG. Formed.

Next, as shown in FIG. 20, a pattern was drawn with a dose of 10 μC / cm ² using an electron beam drawing apparatus. The blank after drawing was baked on a hot plate at 110 ° C. for 10 minutes, developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for 90 seconds, rinsed with pure water and spin-dried to obtain a resist pattern 16a. .

Subsequently, as shown in FIG. 21, the antireflection film 15 was etched by reactive ion etching using SF ₆ gas using the resist pattern 16a as an etching mask to obtain an antireflection film pattern 15a.

  Subsequently, as shown in FIG. 22, by using the resist pattern 16a and the antireflection film 15a pattern as an etching mask, reactive ion etching is performed in a gas atmosphere of methane and hydrogen, and the light absorption film 14 is subjected to pattern processing. Absorption film pattern 14a was obtained. At this time, the etching end point was detected by monitoring the emission of indium.

  Further, as shown in FIG. 23, plasma ashing was performed in an oxygen gas atmosphere to remove the remaining resist pattern 16a and a polymerization product of methane (not shown) generated during reactive ion etching.

  In this state, as shown in FIG. 24, inspection DUV light having a wavelength of 257 nm was irradiated to inspect whether the formed light absorption layer pattern was formed as designed, and correction was performed as necessary.

  The exposure reflectance of the portion of the antireflection film 15a protected by the exposure resist pattern 16a by the inspection light having a wavelength of 257 nm was 1.6%. Further, the reflectance of the surface of the etching stopper layer 17 made of chromium nitride exposed by etching was 39.7%.

  Separately, a multilayer reflective film, a buffer layer, an etching stopper layer, a light absorption layer, and a resist layer are formed on the substrate in the same manner except that the antireflection film 15 is not provided, and the etching of the light absorption layer and the resist pattern are formed. Removal was performed. In this case, the reflectance was 54.7%. By providing the antireflection film, it was confirmed that the contrast of the inspection light having a wavelength of 257 nm was improved from 16% to 92%, and a sufficient contrast for the inspection was obtained.

  After the inspection and correction, the exposed etching stopper layer 17 made of chromium nitride is removed by etching with a mixed aqueous solution of ceric ammonium nitrate and perchloric acid. As shown in FIG. 25, the photo for reflective EUV according to the present invention is removed. A mask 40 was obtained.

  The buffer layer made of amorphous carbon exposed after etching has a light reflectance of 46.8% at a wavelength of 257 nm, and a sufficient value of 63% can be obtained even in the final inspection after the antireflection film 15a is completed. It was confirmed. The light reflectance at an exposure wavelength of 13.5 nm was 0.46% at the antireflection film portion, and the reflectance at the portion where the carbon was exposed was 59.4%. Therefore, the reflection optical density at the exposure wavelength was 2.1, which is a sufficient value.

  The reflection optical density is obtained by -log {(reflectance of the antireflection film portion) / (reflectance of the buffer layer exposed portion)}.

Comparative Example 1
As the light absorbing film, a tantalum silicide film made of tantalum and silicon and containing tantalum in a larger amount than the above-described antireflection film is formed in place of the film made of indium antimonide by sputtering in an argon atmosphere using tantalum and silicon as a target. Except for forming a film, a reflective EUV photomask was formed in the same manner as in Example 1. As a result, the reflectance at an exposure wavelength of 13.5 nm was 2.3%, and the reflectance of the exposed portion of carbon was 59.4. %Met. Therefore, the reflection optical density at the exposure wavelength is 1.4, and a sufficient value cannot be obtained. The reflectance is changed by changing the film thickness of the light absorption film, and the film thickness at which a reflectance of 0.46% equivalent to that in Example 1 can be obtained under this film forming condition is about 48 nm. It was necessary to make it about 20 nm larger than the film thickness of the light absorption layer.

  Moreover, the light reflectance of the antireflection layer by the inspection light having a wavelength of 257 nm was 2.0%. Regarding the obtained reflective EUV photomask, the light reflectance at a wavelength of 257 nm of the buffer layer made of amorphous carbon exposed after etching is 46.8%, and the contrast is 92 even in the final inspection after the completion of the antireflection film. %, A value almost equivalent to that of the above example was obtained.

Comparative Example 2
A reflective EUV photomask was formed in the same manner as in Example 1 except that a film composed of chromium and nitrogen was formed as a light absorption film by sputtering in an atmosphere of argon and nitrogen using chromium as a target. As a result, the reflectance at 13.5 nm, which is the exposure wavelength, was 2.4%, and the reflectance of the portion where the carbon was exposed was 58.5%. Therefore, the reflection optical density at the exposure wavelength was 1.4, and a sufficient value was not obtained. By increasing the film thickness of the light absorption layer, the reflectance decreases, but the film thickness at which a reflectance of 0.52% close to that of Example 1 is obtained is about 49 nm, which is the same as in Comparative Example 1 above. In addition, the film thickness of the light absorption layer in the above example must be about 20 nm larger.

  The reflective photomask for EUV light according to the present invention can be suitably used for forming a fine pattern using a resist for EUV light in a manufacturing process of a semiconductor element, a semiconductor device, an electronic circuit device or the like.

Schematic sectional view showing an example of the configuration of a reflective photomask blank according to the present invention Schematic sectional view showing the structure of an example of a reflective photomask according to the present invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating an example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention The figure for demonstrating another example of the manufacturing process of the reflection type photomask of this invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,11 ... Board | substrate, 2,12 ... EUV reflective multilayer film, 3,13 ... Buffer layer, 4,14 ... Light absorption film, 14a ... Absorption film pattern, 15 ... Antireflection film, 15a ... Antireflection film pattern, 5 , 16 ... resist layer, 5a, 16a ... resist pattern, 17 ... etching stopper

Claims (9)

  A reflective photomask blank comprising: a substrate; a multilayer reflective film provided on the substrate; and a light absorption layer provided on the multilayer reflective film and having a light absorption film containing indium. .   The reflective photomask blank according to claim 1, wherein the light absorption layer further includes an antireflection film containing tantalum formed on the light absorption film.   3. The reflective photomask blank according to claim 2, wherein the antireflection film containing tantalum further contains at least one element selected from the group consisting of oxygen, nitrogen, carbon, and silicon. .   2. The reflective photomask blank according to claim 1, further comprising an antireflection film containing chromium on the light absorption film.   5. The reflective photomask blank according to claim 4, wherein the antireflection film containing chromium further contains at least one element selected from the group consisting of oxygen, nitrogen, and carbon.   The reflective photomask blank according to claim 1, further comprising a buffer layer containing carbon as a main component between the multilayer reflective film and the light absorption layer.   The reflective photomask blank according to claim 6, further comprising an etching stopper layer containing at least one of tantalum and chromium as a main component between the buffer layer and the multilayer reflective film.   A reflective photomask, wherein the light absorption layer of the reflective photomask blank according to claim 1 is patterned.   A photoresist layer is formed on the light absorption layer of the reflective photomask blank according to claim 1, exposed to light, and developed, so that the photoresist layer is formed according to a predetermined pattern. Partially removing and exposing a part of the light absorption layer, and patterning the light absorption layer by dry etching the light absorption layer through the photoresist layer. A method for manufacturing a reflective photomask.

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