JP6440996B2 - REFLECTIVE MASK BLANK AND ITS MANUFACTURING METHOD, REFLECTIVE MASK MANUFACTURING METHOD, AND SEMICONDUCTOR DEVICE MANUFACTURING METHOD - Google Patents

Description

  The present invention relates to a reflective mask blank which is an original for manufacturing an exposure mask used for manufacturing a semiconductor device, a manufacturing method thereof, and a manufacturing method of a reflective mask manufactured using the reflective mask blank. And a method for manufacturing a semiconductor device.

  The types of light sources used in exposure apparatus in semiconductor manufacturing have evolved while gradually shortening the wavelength, such as g-line with a wavelength of 436 nm, i-line with 365 nm, KrF laser with 248 nm, and ArF laser with 193 nm. EUV lithography using extreme ultraviolet (EUV: Extreme Ultra Violet) having a wavelength of around 13.5 nm has been developed in order to realize simple pattern transfer. In EUV lithography, a reflective mask is used because there are few materials transparent to EUV light. In this reflective mask, a multilayer reflective film that reflects exposure light is formed on a low thermal expansion substrate, and a mask structure in which a desired transfer pattern is formed on a protective film for protecting the multilayer reflective film. Basic structure. Also, from the configuration of the transfer pattern, as a typical example, a binary-type reflective mask composed of a relatively thick absorber pattern that sufficiently absorbs EUV light, a light that attenuates EUV light by light absorption, and a multilayer reflective film There is a phase shift type reflection mask (halftone phase shift type reflection mask) composed of a relatively thin dimmer pattern that generates reflected light whose phase is substantially reversed (about 180 ° phase inversion). This phase shift type reflection mask (halftone phase shift type reflection mask), like the transmission type optical phase shift mask, has a high transfer optical image contrast due to the phase shift effect, and has an effect of improving resolution, and is also dimming. Since the thickness of the body pattern (phase shift pattern) is thin, a fine phase shift pattern can be formed with high accuracy.

  In EUV lithography, a projection optical system including a large number of reflecting mirrors is used because of light transmittance. Then, EUV light is incident obliquely on the reflective mask so that the plurality of reflecting mirrors do not block the projection light (exposure light). At present, the incident angle is mainly set to 6 ° with respect to the vertical plane of the reflective mask substrate. However, as the numerical aperture (NA) of the projection optical system is improved, the incident angle becomes a more oblique angle of about 8 °. Is under consideration.

  In EUV lithography, since exposure light is incident obliquely, there is an inherent problem called a shadowing effect. The shadowing effect is a phenomenon in which exposure light is incident on a phase shift pattern having a three-dimensional structure from an oblique direction so that a shadow is formed and the size and position of the pattern to be transferred are changed. The three-dimensional structure of the phase shift pattern becomes a wall and a shadow is formed on the shade side, and the size and position of the pattern to be transferred are changed. For example, there is a difference in the size and position of the transfer patterns between the case where the direction of the arranged phase shift pattern is parallel to the direction of the oblique incident light and the case where it is perpendicular to the direction of the oblique incident light, thereby reducing the transfer accuracy.

  Patent Documents 1 to 5 disclose a technique related to such a reflective mask for EUV lithography and a mask blank for producing the same. Patent Document 1 and Patent Document 2 also disclose the shadowing effect. Conventionally, by using a phase shift reflective mask as a reflective mask for EUV lithography, the film thickness of the phase shift pattern is made relatively thinner than in the case of a binary reflective mask, and transfer accuracy due to the shadowing effect is improved. We are trying to control the decline.

JP 2010-080659 A JP 2009-212220 A JP 2005-268750 A JP 2004-39884 A Japanese Patent No. 5009649

  However, as the pattern becomes finer and the accuracy of the pattern dimension and pattern position increases, the electrical characteristic performance of the semiconductor device increases, and the degree of integration can be improved and the chip size can be reduced. There is a demand for high-precision fine dimension pattern transfer performance. At present, ultra fine high-precision pattern formation corresponding to the hp16 nm (half pitch 16 nm) generation is required. In order to meet this requirement, it is necessary to increase the resolution by using the phase shift effect and to further improve the transfer accuracy by further reducing the shadowing effect as compared with the current phase shift mask. In addition, in order to prevent deterioration and instability of the electrical characteristics of the semiconductor device to be manufactured, it is necessary to form a fine phase shift pattern with high dimensional accuracy on the mask with little sidewall roughness and in-plane dimensional variation. There is.

  In view of the above points, the present invention further reduces the shadowing effect of a reflective phase shift mask for EUV lithography, and a reflective mask blank capable of forming a fine and high-accuracy phase shift pattern with less sidewall roughness, and a manufacturing method therefor An object of the present invention is to provide a reflective mask and a method for manufacturing a semiconductor device.

  In order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
A reflective mask blank in which a multilayer reflective film, a protective film, and a phase shift film for shifting the phase of EUV light are formed in this order on a substrate,
The phase shift film has a tantalum material layer containing tantalum and nitrogen, and a chromium material layer containing chromium and oxygen on the tantalum material layer,
The ratio of tantalum and nitrogen (Ta: N) in the tantalum-based material layer is 1: 0.05 to 1: 0.3, and the ratio of chromium to oxygen (Cr: O) in the chromium-based material layer is 1: 0.2 to 1: 0.6,
A reflective mask blank, wherein the chromium-based material layer has a thickness of 5 nm to 25 nm.

(Configuration 2)
The reflective mask blank according to Configuration 1, wherein the chromium-based material layer contains carbon.

(Configuration 3)
The reflective mask blank according to Configuration 1 or 2, wherein the protective film is made of a material containing ruthenium.

(Configuration 4)
4. The reflective mask blank according to Configuration 3, wherein the protective film contains titanium.

(Configuration 5)
The reflective mask blank according to any one of Structures 1 to 4, wherein an etching mask film is formed on the phase shift film.

(Configuration 6)
A resist pattern is formed on the phase shift film of the reflective mask blank according to any one of Structures 1 to 4, and the resist pattern is used as a mask, and a dry etching gas containing chlorine gas that does not substantially contain oxygen A method of manufacturing a reflective mask, wherein the phase shift film is patterned by dry etching to form a phase shift film pattern.

(Configuration 7)
A resist pattern is formed on the etching mask film of the reflective mask blank according to Configuration 5, and the etching mask film pattern is formed by patterning the etching mask film with a dry etching gas containing fluorine gas using the resist pattern as a mask. And, further, using the etching mask film pattern as a mask, the phase shift film is patterned by dry etching with a dry etching gas containing a chlorine gas containing substantially no oxygen to form a phase shift film pattern. A reflective mask manufacturing method.

(Configuration 8)
8. The method of manufacturing a reflective mask according to Configuration 7, wherein the etching mask film pattern is peeled after the phase shift film pattern is formed.

(Configuration 9)
A reflective mask obtained by the reflective mask manufacturing method according to any one of Structures 6 to 8 is set in an exposure apparatus having an exposure light source that emits EUV light, and is formed on a substrate to be transferred. A method of manufacturing a semiconductor device, comprising a step of transferring a transfer pattern to a resist film.

  According to the reflective mask blank of the present invention (the reflective mask produced thereby), etching is performed by forming a lower layer as a tantalum-based material layer containing tantalum and nitrogen on the protective film surface on the multilayer reflective film. Workability is high, sidewall roughness after etching can be made relatively small, and the upper layer is made of a chromium-based material layer containing chromium and oxygen. In addition, a phase shift film having a two-layer structure that can improve etching processability can be formed. Further, the ratio of tantalum and nitrogen in the tantalum material layer is 1: 0.05 to 1: 0.3, and the ratio of chromium and oxygen in the chromium material layer is 1: 0.2 to 1: 0. And the film thickness of the chromium-based material layer is specified to be 5 nm or more and 25 nm or less. As a result, the phase shift film thickness can be reduced, the shadowing effect can be reduced, and a fine and highly accurate phase shift pattern can be formed with a stable cross-sectional shape with little sidewall roughness. Therefore, the reflection type phase shift mask manufactured using the reflection type mask blank of this structure can form the phase shift pattern itself formed on the mask finely and with high accuracy, and the accuracy during transfer due to shadowing is reduced. Can be prevented. Further, by performing EUV lithography using this reflective phase shift mask, it is possible to provide a method for manufacturing a fine and highly accurate semiconductor device.

It is principal part sectional block diagram for demonstrating schematic structure of the 1st reflective mask blank for EUV lithography which concerns on this invention. It is principal part sectional block diagram for demonstrating schematic structure of the 2nd reflective mask blank for EUV lithography which concerns on this invention. FIG. 3 is a process diagram illustrating a process of producing a reflective mask for EUV lithography from a reflective mask blank for EUV lithography according to the first embodiment in a cross-sectional view of the main part. FIG. 10 is a process diagram illustrating a process of producing a reflective mask for EUV lithography from a reflective mask blank for EUV lithography according to a second embodiment in cross-sectional view. 4A and 4B are diagrams for explaining the shadowing effect of Example 1, where FIG. 5A is a mask pattern layout diagram (plan view) when the mask is viewed from above, and FIG. 5B is a resist pattern when the transferred resist pattern is viewed from above. It is a top view.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In addition, the following embodiment is one form at the time of actualizing this invention, Comprising: This invention is not limited within the range. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.

<Structure of reflective mask blank and manufacturing method thereof>
FIG. 1 is a cross-sectional view of an essential part for explaining the configuration of a first reflective mask blank for EUV lithography according to the present invention. As shown in the figure, a reflective mask blank 100 includes a substrate 1, a multilayer reflective film 2 that reflects EUV light that is exposure light formed on the first main surface (front surface) side, and the multilayer reflective film. 2, an etchant used for patterning a phase shift film 4 to be described later, a protective film 3 formed of a material resistant to a cleaning liquid, and a part of which absorbs EUV light and absorbs EUV light. A phase shift film 4 for reflecting the EUV light and shifting the phase thereof, which are laminated in this order. The phase shift film 4 is composed of a two-layer film composed of a lower layer phase shift film 41 and an upper layer phase shift film 42. The lower phase shift film 41 has a high etching processability and a tantalum-based material containing tantalum and nitrogen having a relatively small sidewall roughness after etching, and the upper phase shift film 42 has a relatively large refractive index difference from a vacuum even though it is a thin film. It consists of chromium that produces a large phase difference and a chromium-based material in which oxygen is contained in chromium in order to improve etching processability. On the second main surface (back surface) side of the substrate 1, a back surface conductive film 5 for electrostatic chuck is usually formed.

FIG. 2 is a cross-sectional view of an essential part for explaining the configuration of a second reflective mask blank for EUV lithography according to the present invention. The difference from the configuration of the first reflective mask blank for EUV lithography is that the etching mask film (etching hard mask film ) 12 is formed on the phase shift film 4 in the second configuration. The configuration is the same as that of the first reflective mask blank. In the second reflective mask blank 101 for EUV lithography, the use of the etching mask film 12 can reduce the thickness of the resist pattern when forming the phase shift pattern, thereby increasing the resolution of the resist pattern. In addition, there is a feature that it is possible to prevent yield reduction and defect generation due to resist pattern collapse.

  Hereinafter, each layer will be described.

<< Board >>
A substrate 1 having a low thermal expansion coefficient within a range of 0 ± 5 ppb / ° C. is preferably used in order to prevent distortion of the absorber film pattern due to heat during exposure with EUV light. As a material having a low thermal expansion coefficient in this range, for example, SiO ₂ —TiO ₂ glass, multicomponent glass ceramics, or the like can be used.

  The first main surface of the substrate 1 on which a transfer pattern (a phase shift film described later constitutes this) is formed is subjected to surface processing so as to have high flatness from the viewpoint of obtaining at least pattern transfer accuracy and position accuracy. ing. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, particularly preferably in a 132 mm × 132 mm region on the main surface on the side where the transfer pattern of the substrate 1 is formed. 0.03 μm or less. The second main surface opposite to the side on which the phase shift film is formed is a surface that is electrostatically chucked when set in the exposure apparatus, and has a flatness of 0.1 μm in a 132 mm × 132 mm region. Or less, more preferably 0.05 μm or less, and particularly preferably 0.03 μm or less. The flatness on the second main surface side in the reflective mask blank 100 is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm in a 142 mm × 142 mm region. It is as follows.

  The surface smoothness of the substrate 1 is also an extremely important item, and the surface roughness of the first main surface on which the phase shift pattern for transfer is formed is 0.1 nm or less in terms of root mean square roughness (RMS). It is preferable that The surface smoothness can be measured with an atomic force microscope.

  Furthermore, the substrate 1 preferably has high rigidity in order to prevent deformation due to film stress of a film (such as the multilayer reflective film 2) formed thereon. In particular, those having a high Young's modulus of 65 GPa or more are preferable.

<< Multilayer Reflective Film >>
The multilayer reflective film 2 provides a function of reflecting EUV light in a reflective mask for EUV lithography, and has a multilayer film structure in which layers mainly composed of elements having different refractive indexes are periodically laminated. It has become.

  In general, a thin film (high refractive index layer) of a light element or a compound thereof, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or a compound thereof, which is a low refractive index material, are alternately 40 A multilayer film laminated for about 60 cycles is used as the multilayer reflective film 2. The multilayer film may be laminated in a plurality of periods, with a laminated structure of a high refractive index layer / low refractive index layer in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 1 side as one cycle. Alternatively, a low-refractive index layer and a high-refractive index layer in which the low-refractive index layer and the high-refractive index layer are stacked in this order may be stacked in a plurality of periods. The outermost layer of the multilayer reflective film 2, that is, the surface layer opposite to the substrate 1 of the multilayer reflective film 2, is preferably a high refractive index layer. In the multilayer film described above, when the high refractive index layer / low refractive index layer laminated in this order from the substrate 1 is laminated in a plurality of periods, the uppermost layer has a low refractive index. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 2, it is easily oxidized and the reflectance of the reflective mask is reduced. It is preferable to form a multilayer reflective film 2 by further forming a high refractive index layer. On the other hand, in the multilayer film described above, when the low-refractive index layer / high-refractive index layer stack structure in which the low-refractive index layer and the high-refractive index layer are stacked in this order from the substrate 1 side is a plurality of periods, Since the upper layer is a high refractive index layer, it can be left as it is.

  In the present embodiment, a layer containing silicon (Si) is employed as the high refractive index layer. As a material containing Si, in addition to Si alone, a Si compound containing boron (B), carbon (C), nitrogen (N), and oxygen (O) in addition to Si may be used. By using a layer containing Si as the high refractive index layer, a reflective mask for EUV lithography having excellent EUV light reflectivity can be obtained. Moreover, since a glass substrate is preferably used as the substrate 1 in the present embodiment, Si is excellent in adhesion to it. As the low refractive index layer, a single metal selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof is used. For example, as the multilayer reflective film 2 for EUV light having a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 periods is preferably used. Note that a silicon oxide containing silicon and oxygen is formed between the uppermost layer (Si) and the Ru-based protective film 3 by forming a high refractive index layer, which is the uppermost layer of the multilayer reflective film 2, with silicon (Si). A layer may be formed. Thereby, mask cleaning tolerance can be improved.

  The reflectance of the multilayer reflective film 2 alone is usually 65% or more, and the upper limit is usually 73%. The thickness and period of each constituent layer of the multilayer reflective film 2 may be appropriately selected depending on the exposure wavelength, and are selected so as to satisfy the Bragg reflection law. In the multilayer reflective film 2, there are a plurality of high refractive index layers and low refractive index layers, but the thicknesses of the high refractive index layers and the low refractive index layers may not be the same. Further, the film thickness of the outermost Si layer of the multilayer reflective film 2 can be adjusted within a range in which the reflectance is not lowered. The film thickness of the outermost surface Si (high refractive index layer) can be 3 nm to 10 nm.

  The method for forming the multilayer reflective film 2 is known in the art, but can be formed by depositing each layer by, for example, ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, an Si film having a thickness of about 4 nm is first formed on the substrate 1 using an Si target, for example, by ion beam sputtering, and then about 3 nm in thickness using a Mo target. The Mo film is formed, and this is set as one period, and is laminated for 40 to 60 periods to form the multilayer reflective film 2 (the outermost layer is a Si layer).

<< Protective film >>
The protective film 3 is formed on the multilayer reflective film 2 in order to protect the multilayer reflective film 2 from dry etching and cleaning in a manufacturing process of a reflective mask for EUV lithography described later. Further, it also protects the multilayer reflective film 2 when correcting black defects in the phase shift pattern using an electron beam (EB). Here, FIG. 1 and FIG. 2 show the case where the protective film 3 is a single layer, but it has a laminated structure of three or more layers. For example, the lowermost layer and the uppermost layer are layers made of a substance containing Ru. A metal other than Ru or an alloy may be interposed between the lowermost layer and the uppermost layer. For example, the protective film 3 is made of a material containing ruthenium as a main component, and may be a simple Ru metal, or Ru may be titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y ), Boron (B), lanthanum (La), cobalt (Co), rhenium (Re), and other Ru alloys may be included, and nitrogen may be included. Among these, in particular, when a Ru-based protective film containing Ti is used, the diffusion of silicon, which is a constituent element of the multilayer reflective film, from the surface of the multilayer reflective film to the Ru-based protective film is reduced, so that the surface roughness during mask cleaning is small. In addition, there is a feature that the film is less likely to be peeled off. The reduction in surface roughness is directly linked to the prevention of a decrease in reflectance for EUV exposure light, and is therefore important for improving the exposure efficiency and throughput of EUV exposure. Further, in the case of the reflection type mask (phase shift mask) of the present invention, the reflectance is hardly changed between the multilayer reflective film surface and the phase shift pattern forming surface due to the mask cleaning, so that a stable phase shift effect can be obtained. .

  The Ru content ratio of this Ru alloy is 50 atomic percent or more and less than 100 atomic percent, preferably 80 atomic percent or more and less than 100 atomic percent, and more preferably 95 atomic percent or more and less than 100 atomic percent. In particular, if it is 95 atomic% or more and less than 100 atomic%, etching of the phase-shift film is resistant to mask cleaning while ensuring sufficient reflectivity of EUV light while suppressing diffusion of the multilayer reflective film constituent element (silicon) into the protective film. It becomes possible to have both an etching stopper function when processed and a protective film function for preventing the multilayer reflective film from changing with time.

  In EUV lithography, since there are few substances that are transparent to exposure light, EUV pellicles that prevent foreign matter from adhering to the mask pattern surface are not technically simple. For this reason, pellicleless operation without using a pellicle has become the mainstream. Also, in EUV lithography, exposure contamination such as the deposition of a carbon film on the mask or the growth of an oxide film occurs due to EUV exposure. Therefore, the mask is often washed at the stage where the mask is used for manufacturing a semiconductor device. It is necessary to remove foreign matter and contamination on the top. For this reason, EUV reflective masks are required to have orders of magnitude greater mask cleaning resistance than transmissive masks for photolithography. When a Ru-based protective film containing Ti is used, cleaning resistance to cleaning liquids such as sulfuric acid, sulfuric acid / hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water or ozone water having a concentration of 10 ppm or less is particularly good. It is high and it becomes possible to satisfy the requirement for mask cleaning resistance.

  The thickness of the protective film 3 composed of such Ru or an alloy thereof is not particularly limited as long as it can function as the protective film, but from the viewpoint of the reflectivity of EUV light, preferably 1. The thickness is from 0 nm to 8.0 nm, more preferably from 1.5 nm to 6.0 nm.

As a method for forming the protective film 3, a method similar to a known film forming method can be employed without any particular limitation. Specific examples include a sputtering method and an ion beam sputtering method.
<< Phase shift film >>

A phase shift film 4 having a two-layer structure including a lower layer film 41 and an upper layer film 42 is formed on the protective film 3. The phase shift film 4 absorbs EUV light and reflects a part thereof to shift the phase. That is, the phase shift film 4 is in the pattern over training has been reflective mask, a portion where the phase shift film 4 is formed, in part at the level of having no adverse effect on the pattern transfer with reduced light by absorbing the EUV light The light is reflected to form a desired phase difference from the reflected light from the field part reflected from the multilayer reflective film 2 via the protective film 3. The phase shift film 4 is formed so that the phase difference between the reflected light from the phase shift film 4 and the reflected light from the multilayer reflective film 2 is 170 ° to 190 °. Image contrast of the projection optical image is improved because light beams having inverted phase differences in the vicinity of 180 ° interfere with each other at the pattern edge portion. As the image contrast is improved, the resolution is increased, and various exposure tolerances such as exposure tolerance and focus tolerance are expanded. Although it depends on the pattern and exposure conditions, in general, the standard of the reflectivity for sufficiently obtaining this phase shift effect is 1% or more in absolute reflectivity, and 2 in reflectivity ratio with respect to a multilayer reflective film (with a protective film). % Or more.

  In the present invention, the lower layer film 41 is made of tantalum (Ta) having a large absorption coefficient of EUV light, high oxidation resistance, high stability over time, high etching processability, and relatively low sidewall roughness after etching. And a tantalum-based material layer containing nitrogen (N), and the upper layer film 42 has a relatively large refractive index difference from vacuum and produces a large phase difference even in a thin film. A chromium-based material layer containing oxygen (O) for improving the tantalum-based material, the ratio of tantalum and nitrogen in the tantalum-based material layer, the ratio of chromium and oxygen in the chromium-based material layer, and the film of the chromium-based material layer The thickness is specified in the following range.

The ratio of tantalum to nitrogen (Ta: N) of the lower layer film 41 is 1: 0.05 to 1: 0.3, preferably 1: 0.08 to 1: 0.25, more preferably 1: 0. 1 to 1: 0.2. By making nitrogen with respect to tantalum equal to or greater than the lower limit ratio, the size of the amorphous or microcrystalline grains of the compound containing at least tantalum and nitrogen was suppressed, and a phase shift pattern was formed by etching. Side wall roughness of the phase shift pattern can be suppressed. The side wall roughness of the phase shift pattern is related to the line edge roughness (LER) when pattern transfer is performed on the semiconductor wafer, and the LER increases as the side wall roughness increases. If the LER is large, the electrical characteristics of the semiconductor device to be manufactured deteriorate or become unstable. Therefore, the reduction of the sidewall roughness of the phase shift pattern is also important in this respect. Moreover, the shape stability of the pattern cross section after etching can be maintained by making nitrogen with respect to tantalum be equal to or greater than the lower limit ratio.
On the other hand, by making nitrogen with respect to tantalum be equal to or less than the ratio on the upper limit side, the etching rate when dry etching the lower layer film 41 with chlorine gas is increased, the manufacturing efficiency is increased, and the fine pattern is highly accurate. It becomes possible to form.

The ratio of chromium to oxygen (Cr: O) in the upper layer film 42 is 1: 0.2 to 1: 0.6, preferably 1: 0.25 to 1: 0.55, and more preferably 1: 0. 3 to 1: 0.5. By making the oxygen to chromium equal to or greater than the lower limit ratio, the etching rate when the upper layer film 42 is dry-etched with chlorine gas is increased, the manufacturing efficiency is increased, and a fine pattern is formed with high accuracy. It becomes possible to do.
On the other hand, charges the oxygen to chromium is made to be less than the ratio of these upper side is insulative lower layer film 4 1 inhibition may occur when or mask mask drawing when examined by electron beam (EB) Can be prevented, and mask drawing defects and mask inspection sensitivity decline can be prevented. Further, the adhesion of foreign matter and the increase in defects can be suppressed.

The lower layer film 41 may contain, for example, boron (B) in addition to tantalum and nitrogen, and the upper layer film 42 may contain, for example, carbon (C) in addition to chromium and oxygen. . As other additive elements, such as silicon for the lower layer film 41 (Si), germanium (Ge), carbon-containing for the upper film 42 (C), hydrogen (H), platinum (Pt), palladium (Pd), silver (Ag), molybdenum (Mo), etc. are mentioned. In particular, when carbon is contained in the upper layer film 42, resistance to the cleaning liquid increases, and the film thickness hardly changes even after repeated cleaning. Specifically, CrCON, CrCO, CrCOH, and CrCONH are more preferable. Since the change in the thickness of the phase shift film is directly linked to the change in the amount of phase shift, it is very important for the phase shift mask that no change in film thickness occurs due to cleaning. Here, examples of the cleaning liquid include sulfuric acid, sulfuric acid / hydrogen peroxide (SPM), ammonia, ammonia hydrogen peroxide (APM), OH radical cleaning water, or ozone water having a concentration of 10 ppm or less.

  Further, it is preferable to use the upper layer film 42 as a chromium compound and the lower layer film 41 as a tantalum compound because the upper layer chromium compound functions as an antioxidant film for the lower layer tantalum compound. When the surface layer portion of the tantalum compound is oxidized, the etching rate during dry etching is partially reduced, and it becomes difficult to process a fine pattern with high accuracy. Also, the film thickness of the chromium-based compound as the upper layer film 42 should be 5 nm or more and 25 nm or less in consideration of the above-mentioned antioxidant function, washing resistance function, thinning due to its refractive index, and etching processability. Is preferred.

  The phase shift film 4 composed of the lower layer film 41 and the upper layer film 42 can be formed by a known method such as a sputtering method such as DC sputtering or RF sputtering. When forming the two-layer film, it is preferable to continuously form the film from the start of film formation to the end of film formation without exposure to the atmosphere. By doing in this way, it can prevent that an oxide layer (tantalum oxide layer) is formed in the surface of the tantalum-type material layer which is the lower layer film 41, and does not require the process for removing a tantalum oxide layer.

<< back conductive film >>
In general, a back surface conductive film 5 for an electrostatic chuck is formed on the second main surface (back surface) side of the substrate 1 (opposite the surface on which the multilayer reflective film 2 is formed). The electrical characteristics required for the back surface conductive film 5 for the electrostatic chuck are usually 100Ω / sq or less. The back surface conductive film 5 can be formed, for example, by magnetron sputtering or ion beam sputtering using a metal or alloy target such as chromium or tantalum. A typical material is CrN or Cr often used in manufacturing a mask blank such as a light transmission type mask blank. The thickness of the back surface conductive film 5 is not particularly limited as long as it satisfies the function for an electrostatic chuck, but is usually 10 nm to 200 nm. The back surface conductive film 5 also has a stress adjustment on the second main surface side of the mask blank 100, and is a flat reflective mask that balances the stress from various films formed on the first main surface side. It is adjusted to obtain a blank.

<< Etching mask >>
As the reflective mask blank, an etching mask film (etching hard mask film) 12 or a resist film may be provided on the phase shift film 4. Typical materials for the etching mask film include silicon (Si) and materials obtained by adding oxygen (O), nitrogen (N), carbon (C), and hydrogen (H) to silicon. Specific examples include SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON. As will be described later, by forming an etching mask film, the thickness of the resist film can be reduced, which is advantageous for pattern miniaturization.

<Reflective mask and manufacturing method thereof>
Using the reflective phase shift mask blanks 100 and 101 of the present embodiment, a reflective phase shift mask is manufactured. Here, only an outline description will be given, and a detailed description will be given later in the embodiment with reference to the drawings.

  A reflective mask blank 100 or 101 is prepared, and a resist film is formed on the outermost surface of the first main surface (on the phase shift film 4 or the etching mask film 12 as described in the following embodiments). (Not required if a resist film is provided as the reflective mask blank 100 or 101), a desired pattern is drawn (exposed) on the resist film, and further developed and rinsed to form a predetermined resist pattern.

For the reflective mask blank 100, using the resist pattern as a mask to dry etch the phase shift film 4 consisting of an upper layer 4 2 and the lower layer 4 1 of the two-layer film is etched, the phase shift A pattern is formed. Etching gas includes chlorine gas such as Cl ₂ , SiCl ₄ , CHCl ₃ , CCl ₄ , mixed gas containing chlorine gas and O ₂ in a predetermined ratio, chlorine gas and He in a predetermined ratio. Or a mixed gas containing a chlorine-based gas and Ar in a predetermined ratio. The etching of the upper layer film 42 and the etching of the lower layer film 41 can be performed simultaneously with the same gas, or the etching can be performed in two stages by switching the gas between the etching of the upper layer film 42 and the etching of the lower layer film 41. Here, if the etching gas contains oxygen at the final stage of etching, the surface of the Ru-based protective film is roughened. Therefore, it is preferable that the etching gas does not substantially contain oxygen at the final stage of etching. Therefore, it is preferable to perform dry etching with a dry etching gas containing a chlorine gas substantially not containing oxygen at least when etching the lower layer film. Examples of the gas substantially free of oxygen include those having an oxygen content of at least 20 atomic% or less, and preferably those containing 5 atomic% or less.
Thereafter, the resist pattern is removed by ashing or resist stripping solution, and finally, wet cleaning using an acidic or alkaline aqueous solution is performed.

In the case of the reflective mask blank 101, the etching mask film 12 is etched using this resist pattern as a mask to form a hard mask pattern (etching mask film pattern), and the resist pattern is removed by ashing or resist stripping solution. by dry etching using the hard mask pattern as a mask, the phase shift film 4 consisting of an upper layer 4 2 and the lower layer 4 1 of the two-layer film is etched, the phase shift pattern is formed. Thereafter, the hard mask pattern is removed by wet etching or dry etching. Here, as an etching gas for the etching mask film 12, for example, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , CH ₃ F, C A fluorine-based gas such as ₃ F ₈ , SF ₆ , or F ₂ , a mixed gas containing these fluorine-based gas and O ₂ at a predetermined ratio, or the like is used. Etching of the phase shift film 4 is the same as that of the reflective mask blank 100. Thereafter, wet cleaning using an acidic or alkaline aqueous solution is performed. Incidentally, immediately after the hard mask pattern formed without removing the resist pattern, there is a method of etching the phase shift film 4 consisting of an upper layer 4 2 and the lower layer 4 1 of the two-layer film with the resist pattern with a hard mask pattern. In this case, the resist pattern is automatically removed when etching the phase shift film 4 consisting of an upper layer 4 2 and the lower layer 4 1 of the two-layer film is characterized in that process can be simplified. On the other hand, in the method of etching the phase shift film 4 consisting of an upper layer 4 2 and the lower layer 4 1 of the two-layer film using the hard mask pattern the resist pattern is removed to the mask, the organic product from the resist disappears during etching There is a feature that stable etching can be performed without any change in an object (outgas).

  Through the above steps, a reflective mask (reflective phase shift mask for EUV lithography) having a highly accurate fine pattern with little shadowing effect and little sidewall roughness can be obtained.

<Method for Manufacturing Semiconductor Device>
By performing EUV exposure using the reflective mask (reflective phase shift mask) of the present embodiment, a desired transfer pattern based on the phase shift pattern on the reflective mask is formed on the semiconductor substrate by the shadowing effect. It can be formed while suppressing a decrease in transfer dimensional accuracy. Further, since the phase shift pattern is a fine and highly accurate pattern with little sidewall roughness, a desired pattern can be formed on the semiconductor substrate with high dimensional accuracy. In addition to this lithography process, a semiconductor device in which a desired electronic circuit is formed can be manufactured through various processes such as etching of a film to be processed, formation of an insulating film, conductive film, introduction of a dopant, or annealing. it can.

  More specifically, the EUV exposure apparatus includes a laser plasma light source that generates EUV light, an illumination optical system, a mask stage system, a reduction projection optical system, a wafer stage system, and a vacuum facility. The light source is provided with a debris trap function, a cut filter that cuts light of a long wavelength other than exposure light, and equipment for vacuum differential evacuation. The illumination optical system and the reduction projection system are composed of reflective mirrors. The reflective mask for EUV exposure is electrostatically attracted by the conductive film formed on the second main surface thereof and placed on the mask stage.

  The light from the EUV light source is applied to the reflective mask through an illumination optical system at an angle of 6 ° to 8 ° with respect to the vertical surface of the reflective mask. The reflected light from the reflective mask with respect to this incident light is reflected (regular reflection) in the opposite direction to the incident angle and at the same angle as the incident angle, and is usually guided to a reflective projection optical system having a reduction ratio of 1/4. Then, the resist on the wafer (semiconductor substrate) placed on the wafer stage is exposed. During this time, at least the place where EUV light passes is evacuated. In this exposure, scanning exposure in which the mask stage and the wafer stage are scanned at a speed corresponding to the reduction ratio of the reduction projection optical system and exposure is performed through the slits is the mainstream. Then, by developing this exposed resist film, a resist pattern can be formed on the semiconductor substrate. In the present invention, a mask having a high-accuracy phase shift pattern which is a thin film with a small shadowing effect and has little sidewall roughness is used. For this reason, the resist pattern formed on the semiconductor substrate becomes a desired one having high dimensional accuracy. Then, by performing etching or the like using this resist pattern as a mask, for example, a predetermined wiring pattern can be formed on the semiconductor substrate. A semiconductor device is manufactured through such other necessary processes such as an exposure process, a processed film processing process, an insulating film or conductive film formation process, a dopant introduction process, or an annealing process.

Hereinafter, each embodiment will be described with reference to the drawings. In addition, the same code | symbol is used about the same component in each Example, and description is simplified or abbreviate | omitted.
[Example 1]

  FIG. 3 is a schematic cross-sectional view of an essential part showing a step of producing a reflective phase shift mask 200 for EUV lithography from a reflective phase shift mask blank 100 for EUV lithography.

  The reflective phase shift mask blank 100 of Example 1 is a phase shift film composed of a back conductive film 5, a substrate 1, a multilayer reflective film 2, a protective film 3, a lower film 41, and an upper film 42. 4. The lower layer film 41 is made of a tantalum material, and the upper layer film 42 is made of a chromium material. Then, as shown in FIG. 3A, the resist film 11 is formed on the upper layer film 42.

((Reflective phase shift mask blank))
First, the reflective phase shift mask blank 100 of Example 1 will be described.
(((substrate)))
A SiO ₂ —TiO ₂ glass substrate, which is a low thermal expansion glass substrate of 6025 size (about 152 mm × 152 mm × 6.35 mm) in which both the first main surface and the second main surface are polished, was prepared as substrate 1. Polishing including a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process was performed so as to obtain a flat and smooth main surface.

(((Back conductive film)))
A back conductive film 5 made of CrN was formed on the second main surface (back surface) of the SiO ₂ —TiO ₂ glass substrate 1 by a magnetron sputtering (reactive sputtering) method under the following conditions.
Back surface conductive film formation conditions: Cr target, mixed gas atmosphere of Ar and N ₂ (Ar: 90 atomic%, N: 10 atomic%), film thickness 20 nm.

(((Multilayer reflective film)))
Next, the multilayer reflective film 2 was formed on the main surface (first main surface) of the substrate 1 opposite to the side on which the back conductive film 5 was formed. The multilayer reflective film 2 formed on the substrate 1 was a periodic multilayer reflective film made of Mo and Si in order to obtain a multilayer reflective film suitable for EUV light having a wavelength of 13.5 nm. The multilayer reflective film 2 was formed by alternately stacking Mo layers and Si layers on the substrate 1 by ion beam sputtering in an Ar gas atmosphere using a Mo target and a Si target. First, a Si film was formed with a thickness of 4.2 nm, and then a Mo film was formed with a thickness of 2.8 nm. This was set as one period, and 40 periods were laminated in the same manner. Finally, a Si film was formed with a thickness of 4.0 nm, and the multilayer reflective film 2 was formed. Here, 40 cycles are used, but the present invention is not limited to this. For example, 60 cycles may be used. In the case of 60 cycles, the number of steps is increased as compared with 40 cycles, but the reflectance for EUV light can be increased.

(((Protective film)))
Subsequently, a RuTi protective film 3 having a thickness of 2.5 nm was formed by ion beam sputtering using a RuTi (Ru: 95 atomic%, Ti: 5 atomic%) target in an Ar gas atmosphere.

((((Phase shift film))))
Next, a TaN film as the lower layer film 41 and a CrCON film as the upper layer film 42 were laminated by the DC sputtering method, and the phase shift film 4 composed of this two-layer film was formed. The TaN film was formed by reactive sputtering using tantalum (Ta) as a target in a mixed gas atmosphere of Xe gas and N ₂ gas. The film thickness is 33.4 nm, and the element ratio of this film is Ta at 88 atomic% and N at 12 atomic%. The CrCON film was formed by a reactive sputtering method in a mixed gas atmosphere of Ar gas, He gas, CO ₂ gas, and N ₂ gas using chromium (Cr) as a target. The film thickness is 25 nm, and the element ratio of this film is 55 atomic% for Cr, 12 atomic% for C, 22 atomic% for O, and 11 atomic% for N. Here, the film was continuously formed without being exposed to the atmosphere from the TaN film formation to the CrCON film formation. As a result, it was possible to prevent an oxide layer (tantalum oxide layer) from being formed on the surface of the TaN film. When a tantalum-based material layer is included as a material of the phase shift film, a tantalum oxide layer is formed on the surface of the layer when exposed to the atmosphere. When an intermediate layer made of a tantalum oxide layer is formed between the lower layer film 41 and the upper layer film 42 in this way, the upper layer film and the lower layer film can be etched with a chlorine-based gas, but this intermediate layer is formed with a fluorine-based gas. Etching is not preferable because the process becomes complicated. However, according to this embodiment, the formation of an oxide layer (tantalum oxide layer) can be prevented, and the problem is avoided.

The refractive index n and extinction coefficient (refractive index imaginary part) k at a wavelength of 13.5 nm of the formed TaN film and CrCON film were as follows.
TaN: n = 0.9486, k = 0.0317
CrCON: n = 0.9393, k = 0.0288
The absolute reflectance at a wavelength of 13.5 nm of the phase shift film composed of the two layers of TaN film and CrCON film is 3.6% (the reflectance with respect to the multilayer reflective film surface with the protective film is equivalent to 5.4%). Met. The thickness of the phase shift film 4 composed of the upper layer film 42 and the lower layer film 41 is 58.4 nm, and the phase difference when patterning the phase shift film is a film thickness corresponding to 180 °. As a result, the shadowing effect could be reduced by reducing the thickness of the TaN single layer phase shift film in the comparative example described later by about 10%. Details regarding the reduction of the shadowing effect will be described in the section “Manufacturing of Semiconductor Devices”.

((Reflective phase shift mask))
Next, a reflective phase shift mask 200 was manufactured using the reflective phase shift mask blank 100.

As described above, the resist film 11 is formed to a thickness of 100 nm on the upper layer film 42 of the reflective phase shift mask blank 100 (FIG. 3A). Then, a desired pattern is drawn (exposed) on the resist film 11, and further developed and rinsed to form a predetermined resist pattern 11a (FIG. 3B). Next, dry etching of the CrCON film (upper layer film 42) is performed using Cl ₂ gas using the resist pattern 11a as a mask (FIG. 3C), and then dry etching of the TaN film (lower layer film 41) is performed using Cl ₂ gas. By using _two gases, the phase shift pattern 41a is formed (FIG. 3D). That is, a phase shift pattern composed of the upper layer film pattern 42a and the lower layer film pattern 41a is formed by collective dry etching using Cl ₂ gas with the resist pattern 11a as a mask. Since it is a batch etching, the process can be simplified, and since the oxygen gas is not used, the film thickness reduction of the resist pattern 11a during the dry etching is relatively small. Therefore, there is a feature that a resist having a relatively thin film thickness can be applied with high resolution and less occurrence of pattern collapse. Thereafter, the resist pattern 11a was removed by ashing, resist stripping solution, or the like, and wet cleaning using an acidic or alkaline aqueous solution was performed to manufacture the reflective phase shift mask 200 (FIG. 3D). If necessary, a mask defect inspection is performed after wet cleaning, and mask defect correction is performed as appropriate. Further, here, a method of collectively etching the phase shift film 4 composed of two layers with Cl ₂ gas is shown, but the chromium-based upper layer film 42 is mixed gas of Cl ₂ and O ₂ (Cl ₂ + O ₂ gas). Thus, the tantalum-based lower layer film 41 can be dry-etched in two stages using Cl ₂ gas. This method includes a step of dry etching with a gas containing oxygen. Since this step is limited to etching of the relatively thin upper layer film 42, the resist pattern 11a functions as an etching mask. Further, since the protective film 3 is not subjected to dry etching with a gas containing oxygen, the surface roughness of the protective film can be prevented.

  The ratio of tantalum and nitrogen (Ta: N) in the lower layer film 41 is 1: 0.136 because Ta is 88 atomic% and N is 12 atomic%. The ratio of chromium and oxygen in the upper layer film (Cr : O) is 1: 0.400 because Cr is 55 atomic% and O is 22 atomic%. At this elemental ratio, the lower layer film pattern 41a, that is, the TaN pattern had a small side wall roughness and had a stable cross-sectional shape.

In the reflective mask 200 of the present embodiment, the upper layer film 42 is a chromium-based material containing oxygen, so that the workability with a chlorine-based gas is good and the upper layer film pattern 42a can be formed with high accuracy. Further, since this chromium-based material does not contain excessive oxygen, mask pattern drawing and mask pattern defect inspection using EB could be performed without causing charge-up. That is, there were no problems such as pattern drawing defects, a decrease in inspection sensitivity, and generation of pseudo defects due to charge-up. In addition, since the upper layer film pattern 42a contains 12 atomic% of carbon (C), it has high resistance to mask cleaning, and problems such as a change in phase shift effect due to a decrease in film thickness even if foreign matter removal and contamination cleaning are frequently performed. Did not occur.
((Manufacture of semiconductor devices))

The reflective phase shift mask created in Example 1 was set in an EUV scanner, and EUV exposure was performed on a wafer on which a processed film and a resist film were formed on a semiconductor substrate. Then, by developing the exposed resist film, a resist pattern was formed on the semiconductor substrate on which the film to be processed was formed. In order to evaluate the shadowing effect in this exposure, the difference in the transfer dimension was measured using a pattern arranged in parallel to a pattern arranged in parallel to the exposure light incident on the mask. FIG. 5A is a plan view of the phase shift pattern arranged on the mask, and the phase shift pattern arranged in the direction perpendicular to the phase shift pattern 4 b arranged in the direction parallel to the incident exposure light 50. 4c is shown. The phase shift patterns 4b and 4c are patterns having the same shape except for the arrangement direction. Therefore, the line width L _MP of the phase shift pattern 4b and the line width L _MN of the phase shift pattern 4c have the same line width. The exposure light 50 enters the mask at an angle inclined by 6 ° with respect to the normal direction of the mask surface. FIG. 5B shows a plan view of a resist pattern formed on the wafer by exposure and development. The resist patterns 24b and 24c are formed by transfer using the phase shift patterns 4b and 4c, respectively. Line width _{L PP} and _{L PN} difference ΔL of the resist pattern transferred form ₍₌ L PN _{-L PP)} is an indicator of shadowing effects. In general, this difference is called a dimension XY difference due to a shadowing effect. When a positive resist is used due to the shadow of exposure light generated by the phase shift pattern as a wall, the line width _LPN is better. The line width L _PP becomes thicker.

  In the case of the reflection type phase shift mask created in Example 1, the dimension XY difference ΔL was 2.3 nm. As will be described again in the comparative example, when a TaN single layer phase shift film having a film thickness of 65 nm is used, the dimension XY difference ΔL is 2.6 nm. By using a mask, it was possible to improve the transfer accuracy decrease due to the shadowing effect by 10% or more. In addition, the reflection type phase shift mask created in Example 1 has less side wall roughness of the phase shift pattern and a stable cross-sectional shape, so that there is less variation in LER and dimension in-plane of the transferred resist pattern. It had high transfer accuracy. In addition, as described above, the absolute reflectivity of the phase shift surface is 3.6% (the reflectivity of 5.4% with respect to the multilayer reflective film surface with the protective film), so that a sufficient phase shift effect is obtained. As a result, it was possible to perform EUV exposure with high exposure latitude and high focus tolerance.

The resist pattern is transferred to a film to be processed by etching, and a semiconductor device having desired characteristics can be manufactured through various processes such as formation of an insulating film, a conductive film, introduction of a dopant, or annealing. did it.
[Example 2]

  Example 2 is an example in the case of using a reflective mask blank (reflective phase shift mask blank for EUV lithography) on which an etching mask film (etching hard mask film) is formed. Example 1 is the same as Example 1 except for the formation of the etching mask film, the etching of the phase shift film using the etching mask film, and the removal of the etching mask film. Here, description will be given with reference to FIG. 2 which is a cross-sectional structural diagram of the main part of the mask blank and FIG. 4 which shows a process of manufacturing a reflective mask (reflective phase shift mask for EUV lithography) based on the cross-sectional structure diagram of the main part. To do.

As shown in FIG. 2, the reflective mask blank (reflective phase shift mask blank for EUV lithography) 101 used in Example 2 has an etching mask film (etching) on the upper layer film 42 which is a part of the phase shift film. Hard mask film) 12 is formed, and is the same as the mask blank of Example 1 except for the etching mask film 12. That is, the substrate 1, the multilayer reflective film 2, the protective film 3, the two-layer structure phase shift film 4 composed of the upper layer film 42 and the lower layer film 41, and the conductive film 5 are all in the first embodiment. This is the same as the reflective mask blank. Here, a SiO ₂ film was used as the etching mask film 12 and was formed with a film thickness of 5 nm by RF sputtering.

Next, a manufacturing process of a reflective mask (a reflective phase shift mask for EUV lithography) will be described with reference to FIG. First, after the surface of the etching mask film 12 of the reflective mask blank 101 is subjected to HMDS treatment, a resist film 11 is formed with a thickness of 80 nm on the etching mask film 12 (FIG. 4A). Then, a desired pattern is drawn (exposed) on the resist film 11, and further developed and rinsed to form a predetermined resist pattern 11a (FIG. 4B). Next, using the resist pattern 11a as a mask, the SiO ₂ film is dry-etched with a fluorine-based gas (CF ₄ gas) to form an etching mask film pattern (hard mask pattern for etching) 12a (FIG. 4C). Thereafter, the resist pattern 11a is removed using ashing or a resist stripping solution (FIG. 4D). Next, using the etching mask film pattern 12a as a mask, the CrCON film (upper layer film 42) is dry-etched with a mixed gas of Cl ₂ and O ₂ (hereinafter simply referred to as “Cl ₂ + O ₂ gas”) (FIG. 4 ( e)) Thereafter, the TaN film (lower layer film 41) is dry-etched with Cl ₂ gas to form the phase shift pattern 41a (FIG. 4F). By removing the resist pattern 11a before etching the upper layer film 42, there is no change in the organic product (outgas) from the resist that disappears during the etching of the upper layer film 42 or the lower layer film 41. The film 41 can be etched stably.
Thereafter, the etching mask film pattern 12a is removed by dry etching using a fluorine-based gas (CF ₄ gas or the like) or a dilute hydrofluoric acid-based solution, and wet cleaning using an acidic or alkaline aqueous solution is performed to manufacture the reflective mask 201. (FIG. 4 (g)). Since the etching mask film absorbs EUV light, it is desirable to remove the etching mask film pattern 12a from the viewpoint of ensuring EUV reflectance. If necessary, a mask defect inspection is performed after wet cleaning, and mask defect correction is performed as appropriate.

Here, the method of etching the phase shift film 4 composed of the two-layer film in two stages using Cl ₂ + O ₂ gas and Cl ₂ gas is shown, but not limited to this, as in the first embodiment, It is also possible to perform batch etching with Cl ₂ gas. Although the resist pattern 11a is removed by a dedicated process immediately after the etching mask film pattern 12a is formed here, the upper film 42 and the lower film 41 are dry-etched while leaving the resist pattern 11a. It is also possible to do this. In this case, the resist pattern 11a is automatically removed at the time of dry etching of the phase shift film 4, and the process is shortened.

According to the manufacturing method of the reflective mask (reflective phase shift mask for EUV lithography) 201 using the etching mask (etching hard mask film) of this embodiment, the etching mask film 12 is formed on the phase shift upper layer film 42. By being formed, the resist film 11 for forming the transfer pattern can be thinned, and a reflective mask having a fine pattern can be obtained. That is, when the etching mask film 12 is not provided, the resist pattern 11a is also etched during the dry etching of the phase shift film 4 by Cl ₂ + O ₂ gas or Cl ₂ gas, so the thickness of the resist film 11 is increased. Although necessary, the resolution of a thick resist film is low, and when the aspect ratio (height / line width) of the resist pattern 11a is increased, pattern collapse occurs during pattern development and rinsing. In this embodiment, since the etching mask film 12 having etching selectivity with respect to the material of the outermost surface layer of the phase shift film 4 is formed, the resist film 11 can be thinned.

Also in this example, the phase shift film is a two-layer film consisting of a TaN lower layer film and a CrCON upper layer film similar to the first example, and the film thickness is the same as that of the first example. The same effect as in Example 1 was also obtained with respect to the roughness of the side wall of the phase shift pattern and the stability of the cross-sectional shape thereof. Therefore, the dimension XY difference ΔL in manufacturing the semiconductor device is the same as that in the first embodiment.
[Example 3]

Example 3 is an example in which only the film thicknesses of the lower layer film 41 and the upper layer film 42 are changed in Example 1, and a reflective phase shift mask for EUV exposure having various reflectances for EUV light is manufactured. , Mask blank substrate, multilayer reflective film, protective film, conductive film, TaN underlayer film and CrCON film upper layer manufacturing method, composition, optical constant, resist pattern formation method and removal method, phase shift consisting of TaN underlayer film and CrCON upper layer film The film etching method and the like are all the same as in the first embodiment. Therefore, the refractive index n and the extinction coefficient (imaginary index imaginary part) k of the TaN lower layer film and the CrCON upper layer film at a wavelength of 13.5 nm were as follows.
TaN: n = 0.9486, k = 0.0317
CrCON: n = 0.9393, k = 0.0288

The film thickness combinations of the TaN lower layer film and the CrCON upper layer film, the total film thickness, and the reflectance at a wavelength of 13.5 nm at that time are as follows. In any case, the phase difference by the two-phase phase shift film is 180 °.
(1) TaN: 54.3 nm, CrCON: 5 nm, total film thickness: 59.3 nm, absolute reflectance: 2.4% (reflectance with respect to the multilayer reflective film surface with a protective film: 3.6%)
(2) TaN: 48.9nm, CrCON : 10nm, total thickness: 58.9Nm, absolute reflectance: 2.9% (reflectance with respect to the protective film with multilayer reflective film surface: 4.4%)
(3) TaN: 43.7nm, CrCON : 15nm, total thickness: 58.7Nm, absolute reflectance: 3.0% (reflectance with respect to the protective film with multilayer reflective film surface: 4.5%)
(4) TaN: 33.4nm, CrCON : 25nm, total thickness: 58.4Nm, absolute reflectance: 3.6% (reflectance with respect to the protective film with multilayer reflective film surface: 5.4%)
In addition, the conditions of Example 1 were described in (4) for easy comparison.
In this way, by changing the combination of the TaN lower layer film and the CrCON upper layer film constituting the phase shift film, the total film thickness of the phase shift pattern is less than 60 nm and the absolute reflectivity while ensuring a phase difference of 180 °. To obtain a reflective phase shift mask for EUV exposure having various reflectances ranging from 2.4% to 3.6% (reflectance with respect to a multilayer reflective film surface with a protective film is 3.6% to 5.4%) Can do. Since the total thickness of the phase shift film is less than 60 nm, it can be made about 10% thinner than the 65 nm film thickness of a TaN single-layer film phase shift film, which will be described later in the comparative example, and the shadowing effect is reduced. I was able to. Also in this example, the phase shift film is a two-layer film composed of a TaN lower layer film and a CrCON upper layer film similar to the first example, and the film thickness is the same as that of the first example. The same effect as in Example 1 was obtained with respect to the roughness of the side wall and the stability of the cross-sectional shape. Therefore, the dimension XY difference ΔL in manufacturing the semiconductor device is the same as that in the first embodiment.
[Example 4]

  Example 4 is a case where a TaBN film is used in place of the TaN film as the lower layer film 41 of the reflective mask blank (reflective phase shift mask blank for EUV lithography). Other than that, the configuration of the mask blank, the configuration of the mask, The manufacturing method and the manufacturing method of the semiconductor device are the same as those in the first embodiment.

The protective film 3 is formed on the mask blank substrate in the same manner as in Example 1, and a TaBN film as the lower film 41 and a CrCON film as the upper film 42 are laminated on the protective film 3 by DC sputtering. Thus, the phase shift film 4 made of this two-layer film was formed. The TaBN film was formed by reactive sputtering using TaB as a target in a mixed gas atmosphere of Xe gas and N ₂ gas. Its film thickness is 36.8 nm. The elemental composition is 75 atomic% Ta, 12 atomic% B and 13 atomic% N, and the element ratio of Ta and N is 1: 0.16. The CrCON film was formed by the same method as in Example 1. The film thickness is 25 nm, and the elemental composition is 55 atomic% for Cr, 12 atomic% for C, 22 atomic% for O, and 11 atomic% for N. Here, the film was continuously formed without exposure to the air from the TaBN film formation to the CrCON film formation. This prevented the formation of an oxide layer (tantalum oxide layer) on the surface of the TaBN film as in Example 1. When a tantalum-based material layer is included as a material of the phase shift film, a tantalum oxide layer is formed on the surface of the layer when exposed to the atmosphere. When an intermediate layer made of a tantalum oxide layer is formed between the lower layer film 41 and the upper layer film 42 in this way, the upper layer film and the lower layer film can be etched with a chlorine-based gas, but this intermediate layer is formed with a fluorine-based gas. Etching is not preferable because the process becomes complicated. However, according to this embodiment, the formation of an oxide layer (tantalum oxide layer) can be prevented, and the problem is avoided.

  Thereafter, the resist film 11 is formed on the upper layer film 42 in the same manner as in the first embodiment, and a desired pattern drawing (exposure), development and rinsing are performed to form a resist pattern 11a. Then, using this resist pattern 11a as a mask, the phase shift film 4 composed of the CrCON film upper layer film and the TaBN film lower layer film is dry-etched using chlorine gas in the same manner as in Example 1 to form a phase shift pattern. did. Resist pattern removal and mask cleaning were performed in the same manner as in Example 1 to manufacture a reflective mask (reflective phase shift mask for EUV lithography) 100.

The refractive index n and extinction coefficient (refractive index imaginary part) k at a wavelength of 13.5 nm of the formed TaBN film and CrCON film were as follows.
TaBN: n = 0.949, k = 0.030
CrCON: n = 0.9393, k = 0.0288
The absolute reflectance at a wavelength of 13.5 nm of the phase shift film composed of the two layers of the TaBN film and the CrCON film is 1.3% (corresponding to 2.0% with respect to the multilayer reflective film surface with the protective film). there were. The total thickness of the phase shift film 4 composed of the upper layer film 42 and the lower layer film 41 is 61.8 nm, and the phase difference when patterning the phase shift film is a film thickness corresponding to 180 °. The thickness of the TaN single layer phase shift film in the comparative example to be described later can be reduced by about 5% from the film thickness of 65 nm, and the shadowing effect can be reduced. In addition, the lower layer film pattern 41a formed of TaBN had a small sidewall roughness and a stable cross-sectional shape like the lower layer film pattern formed of TaN. As a result, the dimension XY difference ΔL when manufacturing the semiconductor device was improved by about 5% compared to a comparative example described later.

[Examples 5 to 6]
In Examples 5-6, as the lower layer film 41 of the reflective mask blank (reflective phase shift mask blank for EUV lithography), the TaN film has an element ratio of 77 atomic% Ta, 23 atomic% N, tantalum and nitrogen. The ratio of Ta (N: N) is 1: 0.299 (Example 5), the element ratio of the TaN film is 95 atomic% Ta, 5 atomic% N, and the ratio of tantalum to nitrogen (Ta: N). 1: 0.053 (Example 6) and the upper layer film 42 is a reflective phase shift mask blank and a reflective phase shift mask in the same manner as in Example 1 except that the upper layer film 42 is a CrCON film having the same film thickness as in Example 1. Produced.
The refractive index n and the extinction coefficient (imaginary refractive index part) k at a wavelength of 13.5 nm of the TaN films of Examples 5 and 6 formed above were as follows.
TaN (Example 5): n = 0.9488, k = 0.0309
TaN (Example 6): n = 0.9485, k = 0.0321
The absolute reflectance at a wavelength of 13.5 nm of the phase shift film composed of the two layers of TaN film and CrCON film is 3.7% (Example 5), 3.5% (Example 6), with a protective film It was 5.6% (Example 5) with respect to the multilayer reflective film surface, and 5.3% (Example 6) with respect to the multilayer reflective surface with a protective film. The thicknesses of the phase shift film 4 composed of the upper layer film 42 and the lower layer film 41 are 58.5 nm (Example 5) and 58.5 nm (Example 6), respectively. The film thickness corresponds to a phase difference of 180 °. As a result, the shadowing effect could be reduced by reducing the thickness of the TaN single layer phase shift film in the comparative example described later by about 10%. Also in this example, the phase shift film is a two-layer film composed of a TaN lower layer film and a CrCON upper layer film similar to the first example, and the film thickness is the same as that of the first example. The same effect as in Example 1 was obtained with respect to the roughness of the side wall and the stability of the cross-sectional shape. Therefore, the dimension XY difference ΔL in manufacturing the semiconductor device is the same as that in the first embodiment.

  The embodiments have been described above. Next, comparative examples with the above embodiments according to the present invention will be described.

(Comparative example)
In the comparative example, a reflective mask blank and a reflective mask were manufactured by the same structure and method as in Example 1 except that a single layer TaN film was used as the phase shift film 4, and the same as in Example 1 A semiconductor device was manufactured by the method.
A single-layer TaN film was formed on the protective film 3 of the mask blank structure of Example 1 in place of the two-layer film of the lower film made of TaN and the upper film made of CrCON. The method of forming this TaN film is the same as that in Example 1, and Ta was used as a target, and reactive sputtering was performed in a mixed gas atmosphere of Xe gas and N ₂ gas to form a TaN film. The thickness of the TaN film is 65 nm, and the element ratio of this film is 88 atomic% for Ta and 12 atomic% for N as in the first embodiment.

The refractive index n and the extinction coefficient (refractive index imaginary part) k at a wavelength of 13.5 nm of the TaN film formed as described above were the same as those in Example 1, and were as follows.
TaN: n = 0.9486, k = 0.0317
The phase shift film at a wavelength of 13.5 nm of the phase shift film made of the single TaN film is 180 °. The reflectance was 1.7% with respect to the multilayer reflective film surface. In the comparative example, the phase shift effect was small, and the contrast of the projection optical image could not be sufficiently improved.
Thereafter, a resist film is formed on the phase shift film made of a single TaN film by the same method as in Example 1, and a desired pattern is drawn (exposure), developed, and rinsed to form a resist pattern. Then, using this resist pattern as a mask, the phase shift film made of a TaN single layer film was dry-etched using chlorine gas in the same manner as in Example 1 to form a phase shift pattern. Resist pattern removal and mask cleaning were performed in the same manner as in Example 1 to manufacture a reflective mask (reflective phase shift mask for EUV lithography) 100.
As described in the item of the manufacturing method of the semiconductor device of Example 1, when the shadowing effect was examined using this reflection type phase shift mask, the dimension XY difference ΔL was 2.6 nm.

  In Example 1 described above, the CrCON film of the upper layer film 42 has Cr of 50 atomic%, C of 10 atomic%, O of 10 atomic%, and N of 30 atomic%, and the ratio of chromium to oxygen (Cr: O ) Is 1: 0.2, Cr is 40 atomic%, C is 11 atomic%, O is 24 atomic%, N is 25 atomic%, and the ratio of chromium to oxygen (Cr: O) is 1: Also in the reflection type phase shift mask blank and the reflection type phase shift mask in the case of 0.6, the same roughness of the phase shift pattern side wall as in Example 1 and the stability of its cross-sectional shape were obtained.

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Multilayer reflective film, 3 ... Protective film, 4 ... Phase shift film, 4b ... Phase shift pattern, 4c ... Phase shift pattern, 5 ... Conductive film, 11 ... Resist film, 11a ... Resist pattern, 12 ... etching mask film (hard mask layer for etching), 12a ... etching mask film pattern (the hard mask pattern etching), 24b ... resist pattern, 24c ... resist pattern, (under layer film for phase shift) 41 ... tantalum-based material film, 41a ... tantalum-based material film pattern (under layer film pattern for phase shift), 42 ... (on layer film for phase shift) chromium base material film, 42a ... chromium-containing material film pattern (on-layered film pattern for phase shift), 50 ... exposure light, 100 ... reflective mask blank, 101 ... reflective mask blank, 200 ... reflective mask, 201 ... reverse Type mask, L _{MP ...} phase shift pattern line width, L _{MN ...} phase shift pattern line width, L _{PP ...} resist pattern line width, L _{PN ...} resist pattern line width

Claims (9)

A reflective mask blank in which a multilayer reflective film, a protective film, and a phase shift film for shifting the phase of EUV light are formed in this order on a substrate,
The phase shift film has a tantalum material layer containing tantalum and nitrogen, and a chromium material layer containing chromium and oxygen on the tantalum material layer,
The ratio of tantalum and nitrogen (Ta: N) in the tantalum-based material layer is 1: 0.05 to 1: 0.3, and the ratio of chromium to oxygen (Cr: O) in the chromium-based material layer is 1: 0.2 to 1: 0.6,
The thickness of the chromium base material layer state, and are more 25nm or less 5 nm,
On the phase shift film, reflective mask blank according to claim Rukoto with an etching mask film containing silicon.   The reflective mask blank according to claim 1, wherein the chromium-based material layer contains carbon.   The reflective mask blank according to claim 1, wherein the protective film is made of a material containing ruthenium.   The reflective mask blank according to claim 3, wherein the protective film contains titanium. 5. The etching mask film according to claim 1, wherein the etching mask film is made of a material obtained by adding at least one of oxygen, nitrogen, carbon, and hydrogen to the silicon. 6. Reflective mask blank.   A resist pattern is formed on the phase shift film of the reflective mask blank according to any one of claims 1 to 4, and the resist pattern is used as a mask for dry etching containing chlorine gas that does not substantially contain oxygen. A method of manufacturing a reflective mask, wherein the phase shift film is patterned by dry etching with a gas to form a phase shift film pattern. A reflective mask manufacturing method manufactured using a reflective mask blank,
In the reflective mask blank, a multilayer reflective film, a protective film, and a phase shift film for shifting the phase of EUV light are formed in this order on a substrate, and the phase shift film is a tantalum-based material layer containing tantalum and nitrogen. And a chromium-based material layer containing chromium and oxygen on the tantalum-based material layer, and a tantalum-to-nitrogen ratio (Ta: N) in the tantalum-based material layer is 1: 0.05 to 1: 0. 3 and the chromium-to-oxygen ratio (Cr: O) in the chromium-based material layer is 1: 0.2 to 1: 0.6, and the thickness of the chromium-based material layer is 5 nm or more 25 nm or less, and an etching mask film is formed on the phase shift film,
Wherein forming a resist pattern on the etching mask film on the reflective mask blank, and a resist pattern as a mask, and patterning the etching mask film by dry etching gas to form an etching mask film pattern including fluorine gas, further A reflective type characterized in that the phase shift film pattern is formed by patterning the phase shift film by dry etching with a dry etching gas containing a chlorine gas containing substantially no oxygen, using the etching mask film pattern as a mask. Mask manufacturing method.   8. The method of manufacturing a reflective mask according to claim 7, wherein the etching mask film pattern is peeled after the phase shift film pattern is formed.   A reflective mask obtained by the reflective mask manufacturing method according to any one of claims 6 to 8 is set in an exposure apparatus having an exposure light source that emits EUV light, and is formed on a transfer substrate. A method for manufacturing a semiconductor device, comprising: transferring a transfer pattern to a resist film.

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