JP4692984B2 - REFLECTIVE MASK BLANK, REFLECTIVE MASK, MULTILAYER REFLECTOR AND MANUFACTURING METHOD THEREOF - Google Patents

Description

  The present invention relates to a reflective mask used in EUV lithography using EUV light (soft X-ray) as exposure light, a reflective mask blank for producing the reflective mask, and the EUV lithography, X-ray microscope, and X-ray telescope. The present invention relates to a multilayer reflector used in an X-ray analyzer or the like.

  In general, in EUV lithography using EUV light (soft X-rays) as exposure light, exposure is performed using a reflective optical system. The mask pattern transferred to the wafer as the transfer target is formed on the absorber film formed on the multilayer reflective film of the reflective mask. The portion where the absorber film is present has little EUV light reflection, and the portion where the absorber film is not present is highly reflected by the exposed multilayer reflective film, and a contrast is obtained in the transferred pattern.

  The multilayer reflective film is generally a multilayer film in which molybdenum (Mo) and silicon (Si) are periodically stacked. This is also used in a multilayer mirror for an EUV exposure apparatus. A reflective mask blank used in EUV lithography generally has a configuration in which a multilayer reflective film, a buffer film, an absorber film, and a resist film are sequentially formed on a substrate.

  The production process of the reflective mask from the reflective mask blank is performed as follows. First, a resist pattern is formed on the resist film by developing after drawing with an electron beam or the like. Next, the absorber film pattern is formed on the absorber film by dry etching using the resist pattern as a mask. After the formation of the absorber film pattern, the remaining resist is removed by acid cleaning or the like, and then the mask pattern is inspected for defects and dimensions. At that time, if necessary, correction is performed using a laser beam, a focused ion beam, a minute needle or the like. In this way, a reflective mask is produced.

  In the reflective mask blank, the multilayer reflective film undergoes a plurality of heating steps as compared with an optical multilayer reflector used in an exposure apparatus or the like. For example, a multilayer reflective film of a reflective mask blank is heated to about 100 ° C. to 200 ° C. by baking after resist coating in the formation of a resist film, and in dry etching when forming an absorber film pattern, etc. In addition, it may be exposed to heat equivalent to 100 ° C. to 200 ° C. by ion bombardment, and may also receive heat in a mask inspection using a laser beam or a correction process using a laser beam or a focused ion beam.

  In addition, the multilayer reflective film of the reflective mask produced from the reflective mask blank can emit EUV light at the time of exposure, as in the case of the multilayer reflective mirror used in the exposure apparatus etc. Heated to collect light. The heat at the time of exposure depends on the power of EUV light, but considering the throughput, it is better that the power of EUV light is higher. Therefore, the multilayer reflective film of the reflective mask is required to have high heat resistance.

  By the way, in a reflective mask, a reflective mask blank, or a multilayer mirror, when a multilayer reflective film formed by laminating a molybdenum (Mo) layer and a silicon (Si) layer is heated, one set of Mo layer and Si layer is formed. The period length corresponding to the minute changes, and the reflectance at each wavelength of the EUV light changes. The fluctuation of the periodic length of the multilayer reflective film occurs when adjacent Mo layers and Si layers diffuse to each other. Interdiffusion between the Mo layer and the Si layer occurs even when the Mo layer and the Si layer are not heated immediately after the film formation. However, the mutual diffusion further proceeds by heating after the film formation, and the periodic length of the multilayer reflective film varies. In many cases, the periodic length of the multilayer reflective film is adjusted so as to obtain the maximum reflectance when used in a predetermined wavelength range in an EUV exposure apparatus. In addition, since the center wavelength or the like shifts to the short wavelength side, it has an unfavorable effect on the transfer to the wafer that is the transfer target. In addition, the throughput at the time of transfer to the wafer is reduced.

Conventionally, in a multilayer reflective film of a multilayer reflective mirror, an intermediate layer made of carbon is interposed at the interface between the molybdenum layer and the silicon layer of the multilayer reflective film in order to prevent the above-described mutual diffusion between the molybdenum layer and the silicon layer. What has been proposed is proposed (Patent Document 1).
Japanese Patent Laid-Open No. 9-230098

  However, when the multilayer reflective film in the multilayer reflective mirror described in Patent Document 1 is applied to a reflective mask blank and a reflective mask that are greatly affected by heat even in the manufacturing process, the above-described diffusion prevention of the multilayer reflective film. The effect is not always sufficient, and there is a risk that the reflectivity will decrease due to the influence of heat.

An object of the present invention is to provide a reflective mask blank capable of improving the thermal stability of reflectance, in consideration of the above-described circumstances.
Another object of the present invention is to provide a reflective mask having improved thermal stability of reflectance.
It is a further object of the present invention to provide a multilayer reflector that can improve the thermal stability of reflectance.

A first aspect of the present invention is a reflection having a substrate, a multilayer reflective film that is formed on the substrate and reflects exposure light, and an absorber film that is formed on the multilayer reflective film and absorbs exposure light. The multilayer reflective film has a structure in which a plurality of periods are formed from the substrate side in the order of silicon layer / diffusion prevention layer / molybdenum layer as one period. The total film thickness of the molybdenum layer and the diffusion prevention layer in the period is 3.0 nm or more, and the diffusion prevention layer is made of a material containing molybdenum and carbon.

According to a second aspect of the present invention, in the invention according to the first aspect, the content of carbon contained in the diffusion preventing layer is 5 to 75 at%.

According to a third aspect of the present invention, an absorber film pattern serving as a transfer pattern for a transfer target is formed on the absorber film of the reflective mask blank according to the first aspect or the second aspect of the present invention. It is a reflective mask characterized by being.

According to a fourth aspect of the present invention, there is provided a multilayer film reflecting mirror having a substrate and a multilayer reflection film that is formed on the substrate and reflects exposure light, wherein the multilayer reflection film is formed of silicon from the substrate side. A layer / diffusion prevention layer / molybdenum layer laminated in this order is formed into a plurality of periods, and the total thickness of the molybdenum layer and the diffusion prevention layer in one period of the multilayer reflective film is 3.0 nm or more. The diffusion preventing layer is made of a material containing molybdenum and carbon.

A fifth aspect of the present invention is a reflection comprising a substrate, a multilayer reflective film that is formed on the substrate and reflects exposure light, and an absorber film that is formed on the multilayer reflective film and absorbs exposure light. A method of manufacturing a type mask blank, wherein the multilayer reflective film has a structure in which a plurality of layers are formed in the order of a silicon layer / diffusion prevention layer / molybdenum layer from the substrate side , and the multilayer reflective film is formed as one cycle. The step of forming a film includes a step of forming a silicon layer on the substrate, and forming a diffusion prevention layer made of a compound of molybdenum and carbon in a mixed gas atmosphere of argon gas and hydrocarbon gas on the surface of the silicon layer. And a step of forming a molybdenum layer on the surface of the diffusion preventing layer.
Further, a sixth aspect of the present invention includes a substrate, a manufacturing method of a multilayer mirror having a multilayer reflective film for reflecting exposure light is formed on the substrate, the multilayer reflective film, the A structure in which a silicon layer / diffusion prevention layer / molybdenum layer are laminated in order from the substrate side is formed in a plurality of periods, and the step of forming the multilayer reflective film forms a silicon layer on the substrate. Forming a diffusion prevention layer made of a compound of molybdenum and carbon in a mixed gas atmosphere of argon gas and hydrocarbon gas on the surface of the silicon layer; and forming a molybdenum layer on the surface of the diffusion prevention layer. And a process.

According to the first aspect of the present invention, in the multilayer reflective film, the diffusion made of a material containing molybdenum (Mo) and carbon (C) between the molybdenum (Mo) layer and the silicon (Si) layer. Since the prevention layer is formed, mutual diffusion between the Mo layer and the Si layer of the multilayer reflective film is also effective by heat treatment such as baking after resist film formation on the absorber film and heat curing during mask pattern formation. Can be prevented. For this reason, since the amount of decrease in the periodic length of the multilayer reflective film can be suppressed, the fluctuation of the center wavelength of the reflectance spectrum in the reflective mask blank can be suppressed to 0.1 nm or less, and the reflectance of the reflective mask blank is reduced. Can be prevented and its thermal stability can be improved.

  Further, in the multilayer reflective film, the surface roughness of the surface of the multilayer reflective film is obtained by interposing a material containing molybdenum (Mo) and carbon (C) between the molybdenum (Mo) layer and the silicon (Si) layer. Therefore, the reflectance of the reflective mask blank can be prevented from being lowered, and the shape of the absorber film pattern formed thereon can be improved.

According to the 2nd aspect of this invention, the improvement of thermal stability and a high reflectance are obtained by making content of carbon (C) contained in a diffusion prevention layer into 5 to 75%.

According to the first aspect of the present invention, the multilayer reflective film has a combination of molybdenum layer / diffusion prevention layer / silicon layer, or silicon layer / diffusion prevention layer / molybdenum layer, or molybdenum layer / diffusion prevention layer / There is a mode in which a plurality of periods are formed with a silicon layer / diffusion prevention layer as a set, but the latter (molybdenum layer / diffusion prevention layer / silicon layer / diffusion prevention layer) is more effective in interdiffusion between the Mo layer and the Si layer. Since it can prevent effectively, it is preferable at the point of thermal stability of reflectance.

According to the third aspect of the present invention, since the reflective mask is manufactured using the reflective mask blank described in the first aspect or the second aspect of the present invention, the thermal stability of the reflectance is obtained. Thus, a reflective mask having a high reflectivity and a good shape of the absorber film pattern can be obtained.

According to the fourth aspect of the present invention, in the multilayer reflective film, a diffusion made of a material containing molybdenum (Mo) and carbon (C) between the molybdenum (Mo) layer and the silicon (Si) layer. Since the prevention layer is formed, mutual diffusion between the Mo layer and the Si layer of the multilayer reflective film can be effectively prevented even if the temperature rises due to irradiation with EUV light (soft X-rays) or the like. For this reason, since the amount of decrease in the periodic length of the multilayer reflecting film can be suppressed, the fluctuation of the center wavelength of the reflectance spectrum in the multilayer reflecting mirror can be suppressed to 0.1 nm or less, and the reflectance heat of the multilayer reflecting mirror can be suppressed. Stability can be improved.

  Further, in the multilayer reflective film, the surface roughness of the surface of the multilayer reflective film is obtained by interposing a material containing molybdenum (Mo) and carbon (C) between the molybdenum (Mo) layer and the silicon (Si) layer. Therefore, it is possible to prevent a decrease in the reflectance of the multilayer film reflecting mirror.

  In addition, improvement of thermal stability and a high reflectance are obtained by making content of carbon (C) contained in the said diffusion prevention layer into 5-75 at%.

  In the multilayer reflective film, molybdenum layer / diffusion prevention layer / silicon layer, or silicon layer / diffusion prevention layer / molybdenum layer is combined, or molybdenum layer / diffusion prevention layer / silicon layer / diffusion prevention layer is combined. There is a mode in which a plurality of periods are formed as a set, but the latter (in the case of molybdenum layer / diffusion prevention layer / silicon layer / diffusion prevention layer) can effectively prevent mutual diffusion of the Mo layer and the Si layer. From the viewpoint of thermal stability of rate.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing one embodiment of a reflective mask blank according to the present invention and a process for manufacturing one embodiment of a reflective mask according to the present invention using the mask blank.

  As shown in FIG. 1A, a reflective mask blank 10 used for manufacturing the reflective mask of FIG. 1 is sequentially formed on a substrate 1 with a multilayer reflective film 2, a buffer film 3, and an absorber film 4. Is the structure formed. By forming a predetermined mask pattern on the absorber film 4 and the buffer film 3 of the reflective mask blank 10, the reflective mask 20 (FIG. 1 (d)) is obtained.

First, the reflective mask blank 10 shown in FIG.
As described above, the reflective mask blank 10 is obtained by sequentially forming the multilayer reflective film 2, the buffer film 3, and the absorber film 4 on the substrate 1. The multilayer reflection film 2 reflects exposure light, the absorber film 4 absorbs exposure light, and the buffer film 3 protects the multilayer reflection film 2 when a pattern is formed on the absorber film 4.

  The multilayer reflective film 2 is generally formed into a multilayer film by alternately and periodically laminating materials having a relatively high refractive index with respect to exposure light and materials having a relatively low refractive index. When the exposure light is EUV light (soft X-ray) having a wavelength of 13 to 14 nm, molybdenum (Mo) is preferably used as a material having a relatively high refractive index, and silicon (Si) is preferably used as a material having a relatively low refractive index. It is done. Further, as shown in FIG. 2, the multilayer reflective film 2 has a diffusion prevention layer 8 formed between the molybdenum (Mo) layer 6 and the silicon (Si) layer 7 which are alternately laminated.

The diffusion prevention layer 8 prevents molybdenum (Mo) and silicon (Si) from diffusing at the atomic level at the interface between the molybdenum layer 6 and the silicon layer 7, and is an oxide of molybdenum or silicon. , Nitrides, borides and oxides are preferred. However, since oxygen, nitrogen and boron have a large EUV light absorption coefficient and lower the reflectance of the multilayer reflective film 2, molybdenum or silicon carbide is preferable, and molybdenum carbide, particularly molybdenum and carbon are included. Material is preferred. Specifically, the content of carbon (C) contained in the diffusion preventing layer 8 is preferably 5 to 75 at% from the viewpoint of improvement in thermal stability and high reflectance. Here, the above at% means atomic%.
When the carbon content in the diffusion preventing layer is less than 5 at%, the diffusion preventing effect is weakened and the thermal stability is lowered, which is not preferable. When it exceeds 75 at%, the effect of the multilayer reflective film can be sufficiently exerted. Therefore, the decrease in reflectivity becomes remarkable, and a high reflectivity cannot be obtained. Preferably, the carbon (C) content is 10 to 60 at%.

  The periodic structure of the multilayer reflective film 2 including the diffusion prevention layer 8 is formed by laminating a plurality of periods (for example, 30 to 60 periods), with the silicon layer 7 / diffusion prevention layer 8 / molybdenum layer 6 as one set (one period). 9 is formed, or molybdenum layer 6 / diffusion prevention layer 8 / silicon layer 7 is laminated as a set (one period) to form a plurality of periods (for example, 30 to 60 periods) to form periodic layer 9, or molybdenum layer 6 / Diffusion prevention layer 8 / silicon layer 7 / diffusion prevention layer 8 is laminated as a set (one period) to form a plurality of periods (for example, 30 to 60 periods) to form a period laminate 9, and the top layer of these period laminates 9 is A cap layer 9 for protecting the periodic laminate 9 is formed.

  The multilayer reflective film 2 is formed using a sputtering apparatus, for example, a magnetron sputtering apparatus 11 shown in FIG. The magnetron sputtering apparatus 11 includes a substrate holder 13, sputtering cathodes 14 </ b> A and 14 </ b> B, and a shutter 15 in a vacuum chamber 12. The substrate holder 13 is rotatably provided and places the substrate 1 thereon. Further, different types of targets are mounted on the sputtering cathodes 14A and 14B, respectively. Further, the shutter 15 can shield either the sputtering cathode 14A or the sputtering cathode 14B, opens the sputtering cathode 14A or 14B on which the target to be deposited on the substrate 1 is mounted, and closes the other sputtering cathode. The target to be formed is sputtered and attached to the substrate 1 to form a film.

  For example, when the multilayer reflection film 2 having a periodic structure of silicon layer 7 / diffusion prevention layer 8 (molybdenum carbide layer) / molybdenum layer 6 is formed using this magnetron sputtering apparatus 11, first, the substrate holder The substrate 1 is mounted on 13, the silicon target is mounted on the sputtering cathode 14A, and the molybdenum target is mounted on the sputtering cathode 14B. Then, the inside of the vacuum chamber 12 is made an argon gas atmosphere, the sputtering cathode 14B is covered with the shutter 15, and the silicon target of the sputtering cathode 14A is sputtered to form the silicon layer 7 on the substrate 1. Next, the inside of the magnetron sputtering apparatus 11 is set to a mixed gas atmosphere of argon gas and hydrocarbon gas (for example, methane gas), the sputtering cathode 14A is covered with the shutter 15, the molybdenum target of the sputtering cathode 14B is sputtered, and the silicon of the substrate 1 On the layer 7, a diffusion preventing layer 8 made of a compound of molybdenum and carbon is formed. Next, the inside of the vacuum chamber 12 is set to an argon gas atmosphere, and a molybdenum target is similarly sputtered to form the molybdenum layer 6 on the diffusion prevention layer 8 of the substrate 1.

  The silicon layer 7, the diffusion prevention layer 8 (molybdenum carbide layer), and the molybdenum layer 6 are stacked as a set (one cycle) for 40 cycles (120 layers), and the periodic stack 9 is formed on the substrate 1. Finally, the inside of the vacuum chamber 12 is set to an argon gas atmosphere, the sputtering cathode 14B is covered by the shutter 15 and the silicon target of the sputtering cathode 14A is sputtered to form the cap layer 5 made of a silicon layer on the uppermost layer of the periodic stack 9. Then, the multilayer reflective film 2 is formed.

  When the diffusion prevention layer 8 is formed, other hydrocarbon gas such as ethane gas or propane gas may be used in place of the mixed gas methane gas filled in the vacuum chamber 12. By adjusting the supply flow rate of the hydrocarbon such as methane, the carbon content of the diffusion preventing layer 8 in the multilayer reflective film 2 is optimized, and the diffusion preventing effect by the diffusion preventing layer 8 is improved.

The substrate 1 is in the range of 0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably in the range of 0 ± 0.3 × 10 ⁻⁷ / ° C., in order to prevent distortion of the pattern due to heat during exposure. Those having a low coefficient of thermal expansion are preferred. As a material having a low thermal expansion coefficient in this range, any of amorphous glass, ceramic, and metal can be used. For example, if the amorphous glass, it is possible to use SiO ₂ -TiO ₂ type glass, quartz glass, crystallized glass (beta-quartz solid solution was precipitated crystallized glass). Examples of metal substrates include Invar alloys (Fe—Ni alloys). A single crystal silicon substrate can also be used.

  The substrate 1 is preferably a substrate having high smoothness and flatness in order to obtain high reflectivity and high transfer accuracy. In particular, it is preferable to have a smooth surface of 0.2 nmRms or less (smoothness in a 10 μm square area) and a flatness of 100 nm or less (flatness in a 142 mm square area). In addition, the substrate 1 preferably has high rigidity in order to prevent deformation due to film stress of a film formed thereon. In particular, those having a high Young's modulus of 65 GPa or more are preferable.

  In addition, unit Rms which shows smoothness is a root mean square roughness, and can be measured with an atomic force microscope. Further, the flatness is a value representing the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading), and a plane determined by the least square method with respect to the substrate surface is a focal plane, and is above the focal plane. This is the absolute value of the height difference between the highest position on the substrate surface and the lowest position on the substrate surface below the focal plane.

  The buffer film 3 is interposed between the multilayer reflective film 2 and the absorber film 4, and protects the multilayer reflective film 2 when forming a pattern on the absorber film 4. The material of the buffer film 3 is an absorber. The film 4 is selected from those having resistance to the etching environment during pattern formation and correction. Among such materials, for example, Cr alone or a material containing Cr as a main component is preferable because of excellent film smoothness. The smoothness of the surface can be improved by making the crystal state of the material mainly composed of Cr microcrystalline or amorphous.

As a material containing Cr as a main component, a material containing at least one element selected from Cr and N, O, and C can be used. By containing nitrogen, it has excellent smoothness, dry etching resistance is improved by adding carbon, and stress of the film can be reduced by adding oxygen. Specifically, CrN, CrO, CrC, CrNC, CrNOC, etc. are mentioned. In addition to materials containing Cr as a main component, materials containing SiO ₂ , SiON, and Ru as main components, materials containing Rh as main components, materials containing Ti as main components, and the like can be given. The buffer film 3 can be formed on the multilayer reflective film 2 by a sputtering method such as ion beam sputtering other than DC sputtering and RF sputtering.

  The thickness of the buffer film 3 is preferably about 20 to 60 nm when the absorber film pattern is corrected using a focused ion beam (FIB). However, when the FIB is not used (for example, EB (electron) In the case of using (beam), the thickness may be about 5 to 15 nm.

  The absorber film 4 has a function of absorbing exposure light such as EUV light, and tantalum (Ta) alone or a material mainly composed of Ta can be preferably used. The material mainly composed of Ta is usually an alloy of Ta. The crystalline state of the absorber film 4 preferably has an amorphous or microcrystalline structure from the viewpoint of smoothness and flatness. As a material having Ta as a main component, a material containing Ta and B, a material containing Ta and N, a material containing Ta and B and further containing at least one of O and N, a material containing Ta and Si, Ta A material containing Si and N, a material containing Ta and Ge, a material containing Ta, Ge and N can be used. By adding B, Si, Ge or the like to Ta, an amorphous material can be easily obtained and the smoothness can be improved. Further, when N or O is added to Ta, resistance to oxidation is improved, so that stability over time can be improved.

  Among these, as a particularly preferable material, for example, a material containing Ta and B (composition ratio Ta / B is in the range of 8.5 / 1.5 to 7.5 / 2.5), Ta, B and N are included. Materials (N is 5 to 30 at%, and B is 10 to 30 at% when the remaining components are defined as 100). In the case of these materials, a microcrystalline or amorphous structure can be easily obtained, and good smoothness and flatness can be obtained.

  Such an absorber film 4 containing Ta alone or Ta as a main component is preferably formed by a sputtering method such as magnetron sputtering. For example, in the case of a TaBN film, a target containing tantalum and boron can be used and a film can be formed by a sputtering method using an argon gas to which nitrogen is added. When formed by the sputtering method, the internal stress can be controlled by changing the power and gas pressure supplied to the sputtering target. Further, since it can be formed at a temperature as low as room temperature, the influence of heat on the multilayer reflective film 2 and the like can be reduced. Other than materials mainly composed of Ta, for example, materials such as WN, TiN, and Ti can be used. The absorber film 4 may have a laminated structure of a plurality of layers. Although the film thickness of the absorber film 4 should just be a thickness which can fully absorb EUV light which is exposure light, it is about 30-100 nm normally.

  In the present embodiment, the reflective mask blank 10 is configured as described above and has the buffer film 3. However, depending on the method of forming a pattern on the absorber film 4 and the method of correcting the formed pattern, this buffer A configuration in which the film 3 is not provided may be employed. That is, the absorber film 4 may be directly provided on the multilayer reflective film 2.

Next, the manufacturing process of the reflective mask 20 using the reflective mask blank 10 of this Embodiment is demonstrated.
The reflective mask blank 10 (see FIG. 1A) of the present embodiment is obtained by sequentially forming each layer of the multilayer reflective film 2, the buffer film 3, and the absorber film 4 on the substrate 1. The material and the forming method are as described above.

  Then, an absorber film pattern 22 is formed on the absorber film 4 of the reflective mask blank 10. First, an electron beam resist is applied on the absorber film 4 and baked. Next, it draws using an electron beam drawing machine, develops this, and forms the predetermined resist pattern 21. FIG. Using the formed resist pattern 21 as a mask, the absorber film 4 is dry-etched to form the absorber film pattern 22 (see FIG. 5B). When the absorber film 4 is made of a material mainly composed of Ta, dry etching using chlorine gas can be used. The resist pattern 21 remaining on the absorber film pattern 22 is removed using hot concentrated sulfuric acid, and the mask 11 (see FIG. 10C) is manufactured.

  Usually, it is inspected here whether the absorber film pattern 22 is formed as designed. For the inspection of the absorber film pattern 22, for example, DUV light having a wavelength of about 190 nm to 260 nm is used, and this inspection light is incident on the mask 11 on which the absorber film pattern 22 is formed. Here, the inspection light reflected on the absorber film pattern 22 and the inspection light reflected on the buffer film 3 exposed by removing the absorber film 4 are detected, and the inspection is performed by observing the contrast. Do.

  Thus, for example, a pinhole defect (white defect) from which the absorber film 4 that should not be removed or a portion of the absorber film 4 remaining without being removed due to insufficient etching is left. (Black defect) is detected. If such pinhole defects or defects due to insufficient etching are detected, they are corrected. To correct the pinhole defect, for example, there is a method of depositing a carbon film or the like on the pinhole by the FIB assist deposition method. In addition, there is a method of removing an unnecessary portion by FIB irradiation to correct a defect due to insufficient etching. At this time, the buffer film 3 serves as a protective film for protecting the multilayer reflective film 2 against FIB irradiation.

  After completing the pattern inspection and correction in this way, the exposed buffer film 3 is removed according to the absorber film pattern 22, and a pattern 23 is formed on the buffer film 3 to produce the reflective mask 20 (see FIG. 4D). ). Here, in the case of the buffer film 3 made of, for example, a Cr-based material, dry etching with a mixed gas containing chlorine and oxygen can be used. In the portion where the buffer film 3 is removed, the multilayer reflective film 2 that is a reflection region of the exposure light is exposed. The exposed uppermost layer of the multilayer reflective film 2 is protected by a cap layer 5 containing Si as a main component.

  Finally, an inspection for final confirmation as to whether or not the absorber film pattern 22 is formed with dimensional accuracy as specified. Also in the case of this final confirmation inspection, the aforementioned DUV light is used. Here, inspection is performed by detecting inspection light reflected on the absorber film pattern 22 and inspection light reflected on the multilayer reflection film 2 exposed by removing the absorber film 4 and the buffer film 3. . The above-described buffer film 3 may be removed as necessary. When the necessary reflectance can be obtained without removing the buffer film 3, the buffer film 3 has the same pattern as the absorber film 4. It can be left on the multilayer reflective film 2 without being processed into a shape. The reflective mask 20 manufactured according to the present embodiment is particularly suitable when EUV light is used as exposure light, but can also be used as appropriate for light of other wavelengths.

  Next, as shown in FIG. 4, using the obtained reflective mask 20, exposure transfer by the pattern transfer device 30 is performed on the semiconductor substrate (silicon wafer 33) with EUV light. The pattern transfer apparatus 30 on which the reflective mask 20 is mounted is configured to include exposure apparatuses such as a laser plasma X-ray source 31 and a reduction optical system 32. The reduction optical system 32 uses a multilayer film reflecting mirror 34. By this reduction optical system 32, the pattern reflected by the reflective mask 20 is usually reduced to about ¼. In addition, since EUV light (soft X-ray) having a wavelength band of 13 to 14 nm is used as the exposure wavelength, the optical path is set in advance so as to be in a vacuum.

In such a state, EUV light obtained from the laser plasma X-ray source 31 is incident on the reflective mask 20, and the light reflected here passes through the multilayer mirror 34 of the reduction optical system 32 to form a silicon wafer (resist Transferred onto a layered semiconductor substrate 33.
The light incident on the reflective mask 20 is absorbed and not reflected by the absorber film 4 in the portion where the absorber film pattern 22 exists, while the light incident on the portion where the absorber film pattern 22 does not exist is multilayered. Reflected by the reflective film 2. In this way, an image formed by the light reflected from the reflective mask 20 enters the reduction optical system 32. The exposure light passing through the reduction optical system 32 exposes the transfer pattern on the resist layer on the silicon wafer 33. By developing the exposed resist layer, a resist pattern is formed on the silicon wafer 33.

With the configuration as described above, the following effects (1) to (6) are achieved according to the above embodiment.
(1) In the multilayer reflective film 2 of the reflective mask blank 10 and the reflective mask 20, molybdenum (Mo) and carbon (C) are interposed between the molybdenum (Mo) layer 6 and the silicon (Si) layer 7. Since the diffusion prevention layer 8 made of a material containing is formed, a baking process after forming a resist film on the absorber film 4 or a heat treatment such as a heat curing at the time of forming a mask pattern (absorber film pattern 22) is also possible. The mutual diffusion between the molybdenum layer 6 and the silicon layer 7 of the multilayer reflective film 2 can be effectively prevented. For this reason, since the amount of decrease in the periodic length of the multilayer reflective film 2 can be suppressed as indicated by broken lines A and B in FIG. 5 described later, the central wavelength of the reflectance spectrum in the reflective mask blank 10 and the reflective mask 20 is reduced. The fluctuation can be suppressed to 0.1 nm or less, the reduction of the reflectance of the reflective mask blank 10 and the reflective mask 20 can be prevented, and their thermal stability can be improved.

  (2) In the multilayer reflective film 2 of the reflective mask blank 10 and the reflective mask 20, the diffusion preventing layer 8 made of a material containing molybdenum (Mo) and carbon (C) is replaced with the molybdenum (Mo) layer 6 and silicon (Si). ) Since the surface roughness of the surface of the multilayer reflective film 2 can be reduced by interposing it between the layer 7 and the reflective mask blank 10 and the reflective mask 20 can be prevented from lowering the reflectivity, and on top of that, The shape of the formed absorber film pattern 22 is also improved.

  (3) In the multilayer reflective film 2 of the reflective mask blank 10 and the reflective mask 20, the diffusion prevention layer 8 made of a material containing molybdenum and carbon is formed between the molybdenum layer 6 and the silicon layer 7. The presence of the diffusion preventing layer 8 can reduce the roughness at the interface of the multilayer reflective film 2. Therefore, it is possible to prevent a halo phenomenon in which the contrast of the transfer pattern transferred onto the transfer target is lowered due to irregular reflection caused by the unevenness of the interface of the multilayer reflective film 2, and thus the contrast of the transfer pattern can be increased. .

(4) In the multilayer reflective film 2 of the reflective mask blank 10 and the reflective mask 20, the diffusion prevention layer 8 made of a material containing molybdenum and carbon is interposed between the molybdenum layer 6 and the silicon layer 7. The reflectance of the multilayer reflective film 2 can be improved as compared with the case where the diffusion preventing layer 8 is not present. Compared with molybdenum silicide (MoSi ₂ ) formed by diffusion between the molybdenum layer 6 and the silicon layer 7 in the multilayer reflective film 2 in which the diffusion prevention layer 8 does not exist, the diffusion prevention layer 8 includes Since the refractive index is close to molybdenum (Mo), the reflectivity generated between the silicon layer 7 and the diffusion prevention layer 8 is larger than the reflectivity generated between the silicon layer 7 and the molybdenum silicide layer. Thus, the reflectance of the entire multilayer reflective film 2 is improved.

(5) By making the content of carbon contained in the diffusion preventing layer 8 of the reflective mask blank 10 and the reflective mask 20 5 to 75 at%, an improvement in thermal stability and a high reflectance can be obtained.

(6) The multilayer reflective film 2 of the reflective mask blank 10 and the reflective mask 20 is a set of molybdenum layer 6 / diffusion prevention layer 8 / silicon layer 7 or silicon layer 7 / diffusion prevention layer 8 / molybdenum layer 6 ( 1 cycle), or a plurality of cycles (molybdenum layer 6 / diffusion prevention layer 8 / silicon layer 7 / diffusion prevention layer 8) are formed as one set (one cycle). In the case of a silicon layer / diffusion prevention layer), mutual diffusion between the molybdenum layer 6 and the silicon layer 7 can be effectively prevented, so that the thermal stability of the reflectance is preferable.

Next, another embodiment will be described.
In another embodiment, the present invention is applied to a multilayer film reflector 34 used in an exposure apparatus in the pattern transfer apparatus 30 shown in FIG. 4 and an optical apparatus such as an X-ray microscope, an X-ray telescope, and an X-ray analyzer. It is a thing. In other words, the multilayer-film reflective mirror 34 has a structure having the substrate 1 and the multilayer reflective film 2 in the reflective mask blank 10 shown in FIG. 1A. The multilayer reflective film 2 is the same as that of the above-described embodiment. Further, a diffusion prevention layer 8 made of a material containing molybdenum and carbon is formed between the molybdenum layer 6 and the silicon layer 7. And it is preferable that the content of carbon (C) contained in the diffusion preventing layer 8 is 5 to 75 at% in terms of improvement in thermal stability and high reflectance. Further, the multilayer reflective film 2 is composed of molybdenum layer 6 / diffusion prevention layer 8 / silicon layer 7, or silicon layer 7 / diffusion prevention layer 8 / molybdenum layer 6 as one set (one cycle), or molybdenum layer 6 / diffusion prevention. A plurality of periods are formed with the layer 8 / silicon layer 7 / diffusion prevention layer 8 as one set (one period) to form a periodic stack 9, and the cap layer 5 is formed on the uppermost layer of the periodic stack 9.

Accordingly, the effects (7) to (11) similar to the effects (1), (2), and (4) to (6) of the above-described embodiment are also achieved by the other embodiments.
(7) The multilayer reflective film 2 of the multilayer mirror 34 is made of a material containing molybdenum (Mo) and carbon (C) between the molybdenum (Mo) layer 6 and the silicon (Si) layer 7. Since the diffusion preventing layer 8 is formed, mutual diffusion between the molybdenum layer 6 and the silicon layer 7 of the multilayer reflective film 2 can be effectively prevented even if the temperature rises due to irradiation with EUV light (soft X-ray) or the like. . For this reason, since the amount of decrease in the periodic length of the multilayer reflective film 2 can be suppressed, the fluctuation of the center wavelength of the reflectance spectrum in the multilayer reflective mirror 34 can be suppressed to 0.1 nm or less, and the reflection of the multilayer reflective mirror 34 The thermal stability of the rate can be improved.

  (8) In the multilayer reflective film 2 of the multilayer reflective mirror 34, the diffusion prevention layer 8 made of a material containing molybdenum (Mo) and carbon (C) is bonded to the molybdenum (Mo) layer 6 and the silicon (Si) layer 7. By interposing them in between, the surface roughness of the surface of the multilayer reflective film 2 can be reduced, so that a decrease in the reflectance of the multilayer reflective mirror 34 can be prevented.

(9) In the multilayer reflective film 2 of the multilayer mirror 34, the diffusion prevention layer 8 made of a material containing molybdenum (Mo) and carbon (C) is interposed between the molybdenum layer 6 and the silicon layer 7. Thus, the reflectance of the multilayer reflective film 2 can be improved as compared with the case where the diffusion preventing layer 8 is not present. Compared with molybdenum silicide (MoSi ₂ ) formed by diffusion between the molybdenum layer 6 and the silicon layer 7 in the multilayer reflective film 2 in which the diffusion prevention layer 8 does not exist, the diffusion prevention layer 8 includes Since the refractive index is close to molybdenum (Mo), the reflectivity generated between the silicon layer 7 and the diffusion prevention layer 8 is larger than the reflectivity generated between the silicon layer 7 and the molybdenum silicide layer. Thus, the reflectance of the entire multilayer reflective film 2 is improved.

(10) When the content of carbon contained in the diffusion preventing layer 8 in the multilayer reflective film 2 of the multilayer reflective mirror 34 is 5 to 75 at%, an improvement in thermal stability and a high reflectance are obtained.

  (11) The multilayer reflective film 2 of the multilayer mirror 34 is composed of molybdenum layer 6 / diffusion prevention layer 8 / silicon layer 7 or silicon layer 7 / diffusion prevention layer 8 / molybdenum layer 6 as a set, or a molybdenum layer. 6 / Diffusion prevention layer 8 / Silicon layer 7 / Diffusion prevention layer 8 has a mode of forming a plurality of periods, but the latter (in the case of molybdenum layer / diffusion prevention layer / silicon layer / diffusion prevention layer) is more Since mutual diffusion between the molybdenum layer 6 and the silicon layer 7 can be effectively prevented, it is preferable in terms of thermal stability of the reflectance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to this Example.

Example 1
A reflective mask blank, a reflective mask, in which a silicon (Si) layer / molybdenum carbide (MoC) layer / molybdenum (Mo) layer is formed as a set (one period), and a plurality of periods are formed to form a multilayer reflective film. The blank film structure is as follows: Si layer (film thickness: 4.0 nm) / molybdenum carbide layer (film thickness: 0.8 nm) / Mo layer (film thickness: 2.2 nm), period length 6.999 nm on a glass substrate. Are formed as a set (one cycle), and a cap layer (material: Si, film thickness: 11.0 nm) is formed thereon to form a multilayer reflective film. Then, an absorber film (material: TaBN, film thickness: 70.0 nm) was formed on the cap layer, which is the uppermost layer of the multilayer reflective film, to produce a reflective mask blank. Thereafter, an absorber film pattern was formed on the absorber film of the reflective mask blank to obtain a reflective mask.

  The crystal structure of the molybdenum carbide layer of the multilayer reflective film in these reflective mask blanks and reflective masks is a polycrystalline structure, and the crystallinity differs depending on the pressure and composition during film formation. This crystallinity was measured using a measuring instrument such as an X-ray diffractometer or a transmission electron microscope. Moreover, the surface roughness of the multilayer reflective film in these reflective mask blanks and reflective masks was 0.12 nmRms as measured with an atomic force microscope. Furthermore, the reflectance of the multilayer reflective film in these reflective mask blanks and reflective masks was 65.0% when irradiated with 13.4 nm EUV light at an incident angle of 6 degrees.

  Further, when the periodic length and the film thickness of each layer (molybdenum layer, silicon layer, molybdenum carbide layer) in the multilayer reflective film of the reflective mask blank or reflective mask were calculated by X-ray reflection spectrum analysis, the periodic length was 6. It was 999 nm. This multilayer reflective film was heated to 200 ° C. using a hot plate and held for 10 minutes. After cooling this sample at room temperature, the periodic length of the multilayer reflective film and the film thickness of each layer were calculated by X-ray reflection spectrum analysis. As a result, the periodic length of the multilayer reflective film was 6.976 nm. As shown in FIG. 4, the thickness was reduced by 0.023 nm compared to before heating.

(Example 2)
A reflective mask blank in which a molybdenum (Mo) layer / molybdenum carbide (MoC) layer / silicon (Si) layer / molybdenum carbide (MoC) layer is formed as one set (one cycle), and a plurality of cycles are formed to form a multilayer reflective film; Reflective Mask The film structure of this reflective mask blank is as follows: Mo layer (film thickness: 2.0 nm) / molybdenum carbide layer (film thickness: 0.8 nm) / Si layer (film thickness: 3.8 nm) ) / Molybdenum carbide layer (film thickness: 0.4 nm), 40 periods are formed with a period length of 6.999 nm as one set (one period), and a cap layer (material: Si, film thickness: 11.0 nm) is formed thereon. Then, a multilayer reflective film is formed. Then, an absorber film (material: TaBN, film thickness: 70.0 nm) was formed on the cap layer, which is the uppermost layer of the multilayer reflective film, to produce a reflective mask blank. Thereafter, an absorber film pattern was formed on the absorber film of the reflective mask blank to obtain a reflective mask.

  The crystal structure of the molybdenum carbide layer of the multilayer reflective film in these reflective mask blanks and reflective masks is a polycrystalline structure, and the crystallinity differs depending on the pressure and composition during film formation. This crystallinity was measured using a measuring instrument such as an X-ray diffractometer or a transmission electron microscope. Moreover, the surface roughness of the multilayer reflective film in these reflective mask blanks and reflective masks was 0.12 nmRms as measured with an atomic force microscope. Furthermore, the reflectance of the multilayer reflective film in these reflective mask blanks and reflective masks was 64.9% when irradiated with 13.4 nm EUV light at an incident angle of 6 degrees.

  Further, when the periodic length and the film thickness of each layer (molybdenum layer, silicon layer, molybdenum carbide layer) in the multilayer reflective film of the reflective mask blank or reflective mask were calculated by X-ray reflection spectrum analysis, the periodic length was 6. It was 999 nm. This multilayer reflective film was heated to 200 ° C. using a hot plate and held for 10 minutes. After cooling this sample at room temperature, the periodic length of the multilayer reflective film and the film thickness of each layer were calculated by X-ray reflection spectrum analysis. As a result, the periodic length of the multilayer reflective film was 6.980 nm, and the broken line B in FIG. As shown in the figure, it was decreased by 0.019 nm compared to before heating.

(Comparative Example 1)
A reflective mask blank, a reflective mask in which a multilayer reflective film is formed by forming a plurality of periods of silicon (Si) layer / molybdenum layer (Mo) as one set (one period), the reflective mask The film structure of this reflective mask blank is a glass substrate On top, a Si layer (film thickness: 4.4 nm) / Mo layer (film thickness: 2.6 nm), with a period length of 7.0 nm formed as one set (one period), 40 periods are formed, and a cap layer (material) : Si, film thickness: 11.0 nm) to form a multilayer reflective film. Then, an absorber film (material: TaBN, film thickness: 70.0 nm) was formed on the cap layer, which is the uppermost layer of the multilayer reflective film, to produce a reflective mask blank. Thereafter, an absorber film pattern was formed on the absorber film of the reflective mask blank to obtain a reflective mask.

  The surface roughness of the multilayer reflective film in these reflective mask blanks and reflective masks was 0.15 nmRms as measured with an atomic force microscope. Moreover, the reflectance of the multilayer reflective film in these reflective mask blanks and reflective masks was 64.9% when irradiated with 13.4 nm EUV light at an incident angle of 6 degrees.

  Further, the periodic length of the reflective mask blank or the multilayer reflective film of the reflective mask and the film thickness of each layer (molybdenum layer, silicon layer) were calculated by X-ray reflection spectrum analysis, and the periodic length was 6.999 nm. . This multilayer reflective film was heated to 200 ° C. using a hot plate and held for 10 minutes. After cooling this sample at room temperature, the periodic length of the multilayer reflective film and the film thickness of each layer were calculated by X-ray reflection spectrum analysis. As a result, the periodic length of the multilayer reflective film was 6.973 nm, and the broken line C in FIG. As shown in FIG. 4, the thickness decreased by 0.026 nm compared to before heating.

  About the multilayer reflective film of Examples 1-3, the fluctuation amount of the periodic length by heating is small compared with the multilayer reflective film of the comparative example 1, and it turns out that the heat resistance of a multilayer reflective film is improving. . In Examples 1 and 2, a layer containing molybdenum and carbon is interposed between the silicon layer and the molybdenum layer. It can be seen that the layer containing molybdenum and carbon serves as a diffusion preventing layer and suppresses fluctuations in the periodic length due to heat of the multilayer reflective film.

It is a schematic sectional drawing which shows one Embodiment of the reflective mask blank which concerns on this invention, and the process of manufacturing one Embodiment of the reflective mask which concerns on this invention using this reflective mask blank. It is a schematic sectional drawing which shows the multilayer reflective film in the reflective mask and reflective mask blank of FIG. It is a sectional side view which shows schematic structure of the magnetron sputtering apparatus for manufacturing a reflective mask blank. It is a side view which shows the structure of the pattern transfer apparatus which transfers a pattern to a wafer using the reflection type mask of FIG. It is a graph which shows the heat resistance evaluation result of the multilayer reflective film in the reflective mask and reflective mask blank of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multilayer reflective film 4 Absorber film 6 Molybdenum layer 7 Silicon layer 8 Diffusion prevention layer 10 Reflective mask blank 20 Reflective mask 22 Absorber film pattern 30 Pattern transfer device 34 Multilayer reflective mirror

Claims (6)

A reflective mask blank having a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light, and an absorber film formed on the multilayer reflective film and absorbing exposure light,
The multilayer reflective film has a structure in which a plurality of periods are formed from the substrate side, in which a silicon layer / a diffusion preventing layer / a molybdenum layer are sequentially laminated ,
The total film thickness of the molybdenum layer and the diffusion prevention layer in one cycle of the multilayer reflective film is 3.0 nm or more,
The diffusion masking layer is made of a material containing molybdenum and carbon.   The reflective mask blank according to claim 1, wherein the content of carbon contained in the diffusion preventing layer is 5 to 75 at%.   A reflective mask, wherein an absorber film pattern serving as a transfer pattern for a transfer target is formed on the absorber film of the reflective mask blank according to claim 1. A multilayer film reflecting mirror having a substrate and a multilayer reflection film formed on the substrate and reflecting exposure light,
The multilayer reflective film has a structure in which a plurality of periods are formed from the substrate side, in which a silicon layer / a diffusion preventing layer / a molybdenum layer are sequentially laminated ,
The total film thickness of the molybdenum layer and the diffusion prevention layer in one cycle of the multilayer reflective film is 3.0 nm or more,
The diffusion barrier layer is made of a material containing molybdenum and carbon. A method of manufacturing a reflective mask blank comprising a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light, and an absorber film formed on the multilayer reflective film and absorbing exposure light. ,
The multilayer reflective film has a structure in which a plurality of periods are formed from the substrate side, in which a silicon layer / a diffusion preventing layer / a molybdenum layer are sequentially laminated ,
The step of forming the multilayer reflective film includes:
Forming a silicon layer on the substrate;
Forming a diffusion barrier layer made of a compound of molybdenum and carbon in a mixed gas atmosphere of argon gas and hydrocarbon gas on the surface of the silicon layer;
Forming a molybdenum layer on the surface of the diffusion preventing layer;
A method for producing a reflective mask blank, comprising: A multilayer film reflector having a substrate and a multilayer reflection film formed on the substrate and reflecting exposure light, the method comprising:
The multilayer reflective film has a structure in which a plurality of periods are formed from the substrate side, in which a silicon layer / a diffusion preventing layer / a molybdenum layer are sequentially laminated ,
The step of forming the multilayer reflective film includes:
Forming a silicon layer on the substrate;
Forming a diffusion barrier layer made of a compound of molybdenum and carbon in a mixed gas atmosphere of argon gas and hydrocarbon gas on the surface of the silicon layer;
Forming a molybdenum layer on the surface of the diffusion preventing layer;
A method of manufacturing a multilayer-film reflective mirror, comprising:

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