JP2007273668A - Reflecttion type phototmask blank, method of manufacturing same, reflection type phototmask, method of manufacturing same and exposure method of extreme ultraviolet light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type photo mask blank which prevents the reflectivity from lowering in etching of an absorptive layer to form an exposure transfer pattern, and its manufacturing method, to provide a reflection type photo mask, and its manufacturing method, and to provide an exposure method with an extreme UV light. <P>SOLUTION: The photo mask blank 10 comprises a substrate 1, a multilayer reflective layer 2 forming a high reflective part to an exposure light on the substrate 1, a protective film 3 on the multilayer reflective film 2 for protecting the film 2, an absorber layer 5 for absorbing the exposure light as a low reflective part to the exposure light on the protective film 3, and a buffer film 4 between the absorber layer 5 and the protective film 3, having a resistance against etching for forming an exposure transfer pattern of the absorber layer 5. The protective film 3 is a thin film containing carbon as a main component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflective photomask blank used for manufacturing a semiconductor device or the like in a photolithography method and a manufacturing method thereof, a reflective photomask and a manufacturing method thereof, and an extreme ultraviolet light exposure method.

  The miniaturization of semiconductor integrated circuits is progressing year by year, and accordingly, the irradiation light used in the photolithography technology is also being shortened. In recent times, the KrF excimer laser (wavelength 248 nm), which has been used as a light source, has been shifted to an ArF excimer laser (wavelength 193 nm). In recent years, research on immersion exposure using an ArF excimer laser has been actively conducted in order to enable a line width of 50 nm or less in accordance with the demand for further miniaturization, but it has still been put into practical use. Not in.

  Against such a background, research and development of extreme ultraviolet lithography using extreme ultraviolet light, that is, EUV (Extreme Ultra Violet) light, whose wavelength is one or more orders of magnitude shorter than that of excimer lasers (ie, ultra-violet light) is being advanced. Since extreme ultraviolet light has a short wavelength, the refractive index in the substance is close to the value of vacuum, and the difference in light absorption between materials is small. For this reason, in extreme ultraviolet lithography, it is difficult to assemble a transmissive refractive optical system that has been widely used in photolithography so far, and a reflective type photomask is used.

As a reflective photomask in such an EUV lithography method, a multilayer reflective film capable of reflecting EUV light on a substrate, and an absorber layer formed on the multilayer reflective film and having a high EUV light absorption rate, The thing using the reflection type photomask blank comprised by these is proposed (for example, refer patent document 1). More specifically, the multilayer reflective film has a structure in which two or more kinds of material layers whose refractive indexes with respect to the wavelength of EUV light are significantly different from each other are periodically stacked. The absorber layer has a laminated structure of a film containing tantalum nitride and a film containing tantalum. Then, by etching the absorber layer with a predetermined pattern, the EUV light is reflected on the multilayer reflective film with the predetermined pattern, and the pattern can be transferred onto the Si substrate.
JP 2001-237174 A

  However, in the reflection type photomask blank of Patent Document 1, the surface portion of the multilayer reflective film under the absorber layer is damaged by the etching performed when the exposure transfer pattern of the absorber layer is formed. There was a problem that the rate decreased.

  The present invention has been made in view of the above-described circumstances, and is a reflective photomask blank capable of preventing a decrease in reflectivity when an absorber layer is etched to form an exposure transfer pattern, and its manufacture The present invention also provides a reflection type photomask, a manufacturing method thereof, and an extreme ultraviolet light exposure method.

In order to solve the above problems, the present invention proposes the following means.
The reflective photomask blank of the present invention includes a substrate, a multilayer reflective film that is formed on the substrate and serves as a high reflection portion of exposure light, and a protection that is formed on the multilayer reflective film and protects the multilayer reflective film. A film, an absorber layer that absorbs the exposure light as a low reflection portion of the exposure light on the protective film, and an exposure transfer of the absorber layer formed between the absorber layer and the protective film. And a buffer film resistant to etching performed during pattern formation, wherein the protective film is a thin film mainly composed of carbon.

The reflective photomask blank of the present invention is a substrate, a multilayer reflective film formed on the substrate and serving as a high reflection part of exposure light, and formed on the multilayer reflective film to protect the multilayer reflective film. A protective film that absorbs the exposure light as a low reflection part of the exposure light on the protective film,
A buffer film that is formed between the absorber layer and the protective film and that is resistant to etching performed when forming an exposure transfer pattern of the absorber layer, and the buffer film mainly includes carbon. It is characterized by being a thin film as a component.

In addition, the present invention is a method for manufacturing a reflective photomask blank comprising a substrate, a multilayer reflective film that reflects exposure light, and an absorber layer that absorbs the exposure light, the method comprising: A multilayer reflective film forming step for forming a multilayer reflective film, a protective film forming step for forming a protective film for protecting the multilayer reflective film on the multilayer reflective film, and the absorber layer on the protective film A buffer film forming step of forming a buffer film having resistance to etching performed when forming an exposure transfer pattern of
An absorber layer forming step of forming the absorber layer on the buffer film, and at least one of the protective film forming step and the buffer film forming step uses a source gas containing methane. The method is characterized by being a step of forming a thin film containing carbon as a main component by plasma CVD.

  According to the reflective photomask blanks according to these inventions, the buffer film or the protective film is formed of a thin film mainly composed of carbon. Since the thin film containing carbon as a main component has high selectivity to etching, it can function as an etching stopper when the absorber layer is etched to form an exposure transfer pattern. For this reason, the buffer film can prevent damage to the protective film and the multilayer reflective film located in the lower layer, and the protective film can prevent damage to the multilayer reflective film located in the lower layer. Furthermore, a thin film containing carbon as a main component can be easily formed by plasma CVD or the like.

  In addition, a thin film containing carbon as a main component can control stress depending on film forming conditions, and is excellent in workability. For this reason, in the buffer film, when removing the exposed portion where the absorber layer is patterned, a pattern having a desired aspect ratio can be easily obtained with high accuracy without causing a change in position accuracy or peeling due to stress. Is possible. Furthermore, a thin film mainly composed of carbon has a high transmittance for extreme ultraviolet light. For this reason, in the protective film, the multilayer reflective film can be protected, and the irradiated extreme ultraviolet light can be reflected on the multilayer reflective film without being absorbed, so that a decrease in reflectance can be prevented.

  In the reflective photomask blank, the protective film and the buffer film are formed as a single-layer dual-purpose film that also serves as the protective film and the buffer film, and the dual-purpose film is mainly made of carbon. A thin film as a component is more preferable.

  In addition, the present invention is a method for manufacturing a reflective photomask blank comprising a substrate, a multilayer reflective film that reflects exposure light, and an absorber layer that absorbs the exposure light, the method comprising: A multilayer reflective film forming step for forming a multilayer reflective film; and the multilayer reflective film is protected on the multilayer reflective film and resistant to etching performed when forming an exposure transfer pattern of the absorber layer. A dual-use film forming step for forming the dual-use film, and an absorber layer forming step for forming the absorber layer on the dual-use film, wherein the dual-use film forming step uses a source gas containing methane The method is characterized by being a step of forming a thin film containing carbon as a main component by plasma CVD.

  According to the reflective photomask blanks according to these inventions, the multi-layer reflection at the time of etching the absorber layer is formed because the dual-purpose film serving as the protective film and the buffer film is formed of a thin film mainly composed of carbon. Film damage can be prevented. Furthermore, since it can be a single-layer film that also serves as a protective film and a buffer film, the film formation process can be simplified and the film thickness can be reduced.

In the reflective photomask blank, the thin film containing carbon as a main component is more preferably 0.001 μm or more and 0.1 μm or less.
According to the reflective photomask blanks according to these inventions, the thickness of the thin film mainly composed of carbon is set to 0.001 μm or more, so that the lower layer is etched when the absorber layer is etched or corrected. The multilayer reflective film can be reliably prevented from being damaged. Moreover, when the film thickness is 0.1 μm or less, the processing accuracy can be ensured when the exposed portion is removed according to the pattern of the absorber layer.

In the reflective photomask blank, it is more preferable that the surface of the thin film containing carbon as a main component is terminated with an electron donating group.
According to the reflective photomask blank according to the present invention, the surface of the thin film containing carbon as a main component is terminated with an electron donating group, whereby conductivity can be imparted to the surface of the thin film. For this reason, it is possible to prevent charge-up, which works advantageously during dry etching.

  In the reflective photomask blank, the thin film containing carbon as a main component is more preferably a diamond thin film.

  The diamond thin film is more preferably a non-single crystal diamond thin film.

  Further, the non-single crystal diamond thin film is more preferably a polycrystalline diamond thin film.

  According to the reflective photomask blanks according to these inventions, the selectivity to etching can be further improved, and when the absorber layer is etched, damage to the multilayer reflective film located in the lower layer can be more reliably prevented. .

  In the reflective photomask blank, the thin film containing carbon as a main component may be a diamond-like carbon thin film.

  According to the reflective photomask blank according to the present invention, similarly, the selectivity to etching is further improved, and when the absorber layer is etched, damage to the multilayer reflective film located in the lower layer is more reliably prevented. Can do.

In the reflective photomask blank, the diamond-like carbon thin film is more preferably doped with impurities.
According to the reflective photomask blank according to the present invention, since the impurity is doped in the thin film, it is possible to impart characteristics according to the physical properties of the impurity, such as improvement in conductivity, to the thin film.

  Furthermore, it is more preferable that the impurity is at least one selected from the group consisting of nitrogen, boron, sulfur and silicon.

  Further, in the above-described reflective photomask blank manufacturing method, the source gas further includes at least one selected from the group consisting of nitrogen, ammonia, diborane, hydrogen sulfide, and silane, and by plasma CVD, It is more preferable to form a thin film mainly composed of carbon containing at least one selected from the group consisting of nitrogen, boron, sulfur, and silicon.

  According to the reflective photomask blanks according to these inventions, any impurity contributes to stress adjustment and low resistance, but nitrogen, boron and sulfur are particularly effective in reducing resistance, and silicon has a great effect in stress adjustment. It is done.

  Moreover, the reflective photomask of the present invention is characterized in that an exposure transfer pattern is formed by etching the absorber layer of the reflective photomask blank.

  Moreover, the manufacturing method of the reflection type photomask of the present invention includes an absorber layer pattern preparation step of forming an exposure transfer pattern on the absorber layer of the reflection type photomask blank manufactured as described above, and among the buffer film, And a buffer film removing step of etching a portion exposed by forming the exposure transfer pattern on the absorber layer.

  Or the manufacturing method of the reflection type photomask of this invention is equipped with the absorber layer pattern preparation process of patterning the said absorber layer of the reflection type photomask blank manufactured by the above.

  According to the reflection type photomasks according to these inventions, a reflection region having a good reflectance is formed in a portion where the absorber layer is etched. For this reason, the pattern transfer excellent in reflection contrast can be performed by irradiating exposure light by this reflection area | region and an absorber layer.

  In the above-described reflective photomask blank manufacturing method, the buffer film removing step is more preferably performed by dry etching with an etching gas containing an oxygen gas or an oxidizing gas.

  Further, it is more preferable that the etching gas further contains a halogen-based gas.

  According to the manufacturing method of the reflective photomask according to these inventions, the carbon-containing thin film can be more effectively etched and removed in the buffer film process.

  In the extreme ultraviolet light exposure method of the present invention, the reflective photomask is irradiated with extreme ultraviolet light as exposure light, and the reflected light reflected on the multilayer reflective film of the reflective photomask is exposed. And a step of projecting an exposure transfer pattern of the absorber layer of the reflective photomask.

  Further, the extreme ultraviolet light exposure method of the present invention irradiates the reflection type photomask manufactured by the above-described reflection type photomask manufacturing method with extreme ultraviolet light as exposure light, and the multilayer reflection of the reflection type photomask. It is characterized by comprising a step of projecting an exposure transfer pattern of the absorber layer of the reflective photomask by exposing the reflected light reflected on the film.

  According to these extreme ultraviolet light exposure methods, a pattern can be transferred with excellent reflection contrast by irradiating the above-mentioned reflective photomask with extreme ultraviolet light as exposure light. Further, by irradiating extreme ultraviolet light, it is possible to perform patterning with a fine line width corresponding to the wavelength of extreme ultraviolet light.

According to the reflective photomask blank and the method of manufacturing the reflective photomask blank of the present invention, the buffer film or the protective film is formed of a thin film mainly composed of carbon, and thus has high selectivity to etching. When the absorber layer is etched, it is possible to prevent a decrease in the reflectance of the multilayer reflective film.
In addition, according to the reflective photomask of the present invention, it is possible to transfer a pattern having excellent contrast by preventing damage to the multilayer reflective film and obtaining good reflectance.
Further, according to the extreme ultraviolet light exposure method of the present invention, by irradiating the above-mentioned reflective photomask with extreme ultraviolet light and exposing the reflected light to a resist formed on the sample substrate, with high accuracy, In addition, it is possible to transfer a pattern with a fine line width corresponding to the wavelength of extreme ultraviolet light. Further, it is possible to manufacture a pattern of a semiconductor device or the like with a higher yield.

(First embodiment)
1 and 2 show an embodiment according to the present invention. As shown in FIG. 1, the reflective photomask blank 10 of this embodiment includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, a protective film 3 formed on the multilayer reflective film 2, A buffer layer 4 formed on the protective film 3 and an absorber layer 5 formed on the buffer layer 4 are provided. More specifically, the substrate 1 is a Si substrate, a synthetic quartz substrate, or the like. The multilayer reflective film 2 functions as a high reflection portion of EUV light (extreme ultraviolet light) that is exposure light, and is composed of a multilayer film made of a combination of materials having significantly different refractive indexes with respect to EUV light. For example, the multilayer reflective film 2 is formed by repeatedly laminating a combination of Mo and Si or Mo and Be for about 40 cycles.

  Further, the absorber layer 5 absorbs EUV light irradiated as a low reflection portion when it is dry-etched and formed into a predetermined exposure transfer pattern as will be described later, and Ta and Si, or It is formed with Ta, Si and N as main components.

  The protective layer 3 protects the multilayer reflective film 2, and the buffer layer 4 has resistance to etching performed when forming the exposure transfer pattern of the absorber layer 5. This prevents damage to the lower layer. For this reason, the protective film 3 and the buffer film 4 need to have high selectivity with respect to etching. That is, when the absorber layer 5 is etched under a predetermined gas condition, the absorber layer 5 is easily etched, but the protective film 3 and the buffer film 4 located under the absorber layer 5 are selected so as not to be etched. . Further, since the buffer film 4 needs to be etched into the pattern shape after the absorber layer 5 is etched, it can be etched under a gas condition different from the gas condition when the absorber layer 5 is etched. It must be possible.

  And the thin film which has carbon as a main component is selected for at least one of the protective layer 3 and the buffer layer 4 from the above conditions. Moreover, as such a carbon-based thin film, a diamond thin film or a diamond-like carbon thin film is suitable. As the diamond thin film, a non-single-crystal diamond thin film, particularly a polycrystalline diamond thin film is desirable, and the selectivity to etching can be further improved. The diamond-like carbon thin film is preferably doped with at least one selected from the group consisting of impurities such as nitrogen, boron, sulfur and silicon. Note that nitrogen, ammonia, diborane, hydrogen sulfide, silane, or the like can be used as a source gas for these impurities. Thus, by doping impurities, it is possible to impart characteristics according to the physical properties of each impurity, such as improvement of conductivity. When nitrogen, boron, sulfur, or silicon is doped as an impurity, any impurity contributes to stress adjustment and low resistance. In particular, nitrogen, boron, and sulfur reduce resistance, and silicon adjusts stress. A great effect can be obtained.

  Further, it is more desirable that the thin film containing carbon as a main component is terminated with an electron donating group. Conductivity can be imparted to the surface of the thin film because the surface of the thin film containing carbon as a main component is terminated with an electron donating group. For this reason, it is possible to prevent charge-up, which works advantageously during dry etching. Examples of such an electron donating group include an H group and an OR group (R is H or an alkyl group).

  The film thickness of the thin film mainly composed of carbon is desirably 0.001 μm or more and 0.1 μm or less. If the film thickness becomes thinner than 0.001 μm, it may reach a multilayer film when etching or correction is performed, and if it becomes thicker than 0.1 μm, it is exposed according to the pattern of the absorber layer. There is a risk that the processing accuracy cannot be ensured when removing the damaged portion.

  Although not shown, an antireflection film may be further provided on the absorber layer 5 for the purpose of obtaining contrast with the inspection light. The antireflection film is a transparent thin film formed by magnetron sputtering or the like, and by adding oxygen or nitrogen to the sputtering gas, the transparent thin film is formed by a reaction product with these gases. The optical properties of the film can be controlled by controlling the sputtering output of the target and the flow rates of oxygen and nitrogen.

Then, as the absorber layer pattern forming step, the absorber layer 5 of the reflective photomask blank 10 is etched so as to form a predetermined transfer pattern. Further, as the buffer film removing step, the absorber layer 5 is etched. By removing the exposed buffer film 4, the reflective photomask 20 is produced. In the buffer film removing step, when the buffer film 4 is formed of a thin film containing carbon, it is performed by dry etching with an etching gas containing oxygen gas or oxidizing gas. Examples of such an etching gas that can be selected include oxygen (O ₂ ), ozone (O ₃ ), nitrous oxide (N ₂ O), and the like.

Furthermore, at least one selected from the group consisting of halogen-based gases such as carbon fluoride, sulfur fluoride, nitrogen fluoride, and chlorine may be selected and included. Of these halogen-based gases, carbon fluoride (CF ₄ ) is particularly desirable. The addition amount of such a halogen-based gas is preferably 0.05% or more and 10% or less, more preferably 0.5% or more and 5% or less. If the addition amount of the halogen-based gas is too small, The effect of adding a system gas is difficult to obtain. Examples of the dry etching apparatus include a dry etching apparatus using a discharge method such as RIE, magnetron RIE, ECR, ICP, microwave, helicon wave, and NLD.

  Hereinafter, based on Example 1 and Example 2, the details of the reflective photomask blank 10 of this embodiment and the manufacturing method thereof, and the reflective photomask 20 and the details of manufacturing thereof will be described.

In this embodiment, a case where a diamond-like carbon thin film is formed as the protective film 3 will be described.
In the reflective photomask blank 101 shown in FIG. 1, synthetic quartz having a 6-inch square outer shape and a thickness of 0.25 inch was used as the substrate 1 by polishing the surface to obtain a flat surface. First, as the multilayer reflective film forming step, the multilayer reflective film 2 was formed. That is, using a DC magnetron sputtering apparatus, Mo and Si targets are alternately used to form a Mo layer having a thickness of 2.8 nm and an Si layer having a thickness of 4.2 nm in an Ar atmosphere. By stacking 40 cycles as a cycle, a thickness of 280 nm was formed. The uppermost layer of the multilayer reflective film 2 is Si. The reflectance of the multilayer reflective film 2 at a wavelength of 257 nm was 63%.

  Next, as a protective film forming step, the protective film 3 which is a diamond-like carbon thin film was formed using a parallel plate type plasma CVD apparatus. The conditions for plasma CVD are as follows. That is, as the source gas, a gas containing methane (flow rate: 20 sccm) as a main component and nitrogen (concentration: 1 to 50%) as a dope gas was used. Instead of nitrogen, ammonia may be included at a concentration of 1 to 50%. Further, the reaction pressure was set to 0.03 Torr and the self-bias voltage 0 to 1500 V, thereby forming the protective film 3 having a thickness of 10 nm.

Next, as a buffer film forming step, the buffer film 4 was formed by DC magnetron sputtering. That is, in an atmosphere of Ar gas / O ₂ gas flow rate of 36/4 (sccm), a sputtering target of Ta and Si is used, and a power ratio of Ta: Si = 100: 200 is set to 15 nm of Ta and Si. A buffer film 4 having a film thickness was formed.

  Next, as the absorber layer forming step, the absorber layer 5 was formed by DC magnetron sputtering. That is, in an atmosphere of Ar gas gas flow rate 40 (sccm), a Ta and Si sputtering target is used, and a power ratio Ta: Si = 260: 40, and an absorber layer having a thickness of 75 nm made of Ta and Si. 5 was formed, and a reflective photomask blank 101 could be obtained.

  Next, the reflective photomask 201 is manufactured from the reflective photomask blank 101. As the absorber layer pattern forming step, the absorber layer 5 is patterned with a predetermined exposure transfer pattern. First, an electron beam resist FEP171 (manufactured by Fuji Film Electronics Materials) is spin-coated on the reflective photomask blank 101 to a thickness of 300 nm, and baked at 120 ° C. for 10 minutes on a hot plate to form a resist layer. did.

Next, a pattern was drawn with a dose of 8 μC / cm ² using an electron beam drawing apparatus. The reflective photomask blank 101 after drawing was baked on a hot plate at 110 ° C. for 10 minutes, and developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for 90 seconds. Then, after rinsing with pure water, spin drying was performed to obtain a predetermined resist pattern. Further, by using an ICP etching apparatus, Cl ₂ gas and He gas are mixed at 4: 6, and dry etching is performed in an atmosphere with a gas pressure of 5 mPa, so that the absorber layer 5 is formed through the resist pattern. A predetermined exposure transfer pattern was formed.

Next, after the resist is peeled and the inspection correction process is performed, as the buffer film removing process, the portion 4a exposed by etching the absorber layer 5 in the buffer layer 4 is removed. That is, by using an ICP etching apparatus, C ₂ F ₆ gas and He gas are mixed at 1: 8, and dry etching is performed in an atmosphere with a gas pressure of 3 mPa, through the pattern of the absorber layer 5, The exposed portion 4a of the buffer film 4 was removed so that the pattern similar to that of the absorption film was obtained, whereby the reflective photomask 201 could be obtained.

  In this embodiment, a case where a diamond-like carbon thin film is formed as the buffer film 4 will be described. Note that the substrate 1, the multilayer reflective film 2, and the absorber layer 5 are the same as those in the first embodiment, and are omitted.

In the reflective photomask blank 102 shown in FIG. 1, after forming the multilayer reflective film 2 on the substrate 1 as a multilayer reflective film forming step, the protective film 3 was formed by reactive DC sputtering as the protective film forming step. That is, a protective layer 3 having a thickness of 10 nm made of Zr and Si was formed using a ZrSi ₃ sputtering target at an Ar gas gas flow rate of 40 (sccm) at a power of 300 W.

  Next, as a buffer film forming step, the buffer film 4 which is a diamond-like carbon thin film was formed using a parallel plate type plasma CVD apparatus. The conditions for plasma CVD are as follows. That is, as the source gas, a gas containing methane (flow rate: 20 sccm) as a main component and nitrogen (concentration: 1 to 50%) as a dope gas was used. Instead of nitrogen, ammonia may be included at a concentration of 1 to 50%. Further, the reaction pressure was set to 0.03 Torr and the self-bias voltage 0 to 1500 V, thereby forming a buffer film 4 having a thickness of 10 nm. Finally, as the absorber layer forming step, the reflective photomask blank 102 could be obtained by forming the absorber layer 5.

  Next, the reflective photomask 202 is manufactured from the reflective photomask blank 102. As the absorber layer pattern forming step, the absorber layer 5 is patterned with a predetermined exposure transfer pattern. Since the patterning of the absorber layer 5 is the same as that of the first embodiment, its details are omitted.

Next, after the resist is peeled and the inspection correction process is performed, as the buffer film removing process, the portion 4a exposed by etching the absorber layer 5 in the buffer layer 4 is removed. That is, CF ₄ gas is mixed at a flow rate of ₂ ccm with O ₂ gas at a flow rate of 98 sccm, that is, a mixture of 2% CF ₄ is used as an etching gas, the reaction pressure is 30 mTorr, the high frequency power is 300 W, and the absorber layer 5 is By performing reactive ion etching as a hard mask, the exposed portion 4a of the buffer layer 4 was removed, whereby the reflective photomask 202 could be obtained.

  As described above, in each example, by using the reflective photomask blank 10 (101, 102) that includes the protective layer 3 and the buffer layer 4 and one of which is formed of a diamond-like carbon film, It has high selectivity for etching, and can prevent a decrease in the reflectance of the multilayer reflective film 2 when the absorber layer 5 is etched. For this reason, according to the reflective photomask 20 (201, 202) manufactured from the reflective photomask blank 10 (101, 102), it is possible to prevent damage to the multilayer reflective film and obtain a good reflectance. The pattern transfer with excellent contrast is made possible.

  In the extreme ultraviolet light exposure method using such a reflective photomask 20, the pattern can be transferred with high accuracy. That is, first, a photoresist layer is provided on a substrate on which a layer to be processed is formed. Next, the pattern of the absorber layer is transferred by irradiating the reflective photomask 20 with extreme ultraviolet light as exposure light and exposing the reflected light reflected by the multilayer reflective film 2 to the photoresist layer. Next, unnecessary portions of the photoresist layer in the development process are removed, and a pattern of the etching resist layer is formed on the substrate. Then, the layer to be processed is etched using the pattern of the etching resist layer as a mask. Finally, by removing the pattern of the etching resist layer, it is possible to transfer onto the substrate a fine pattern having a line width that is faithful to the photomask pattern and that corresponds to the wavelength of extreme ultraviolet light (10 to 15 nm).

(Second Embodiment)
3 and 4 show an embodiment according to the present invention. In this embodiment, members that are the same as those used in the above-described embodiment are assigned the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 3, the reflective photomask blank 30 of this embodiment includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, a dual-purpose film 6 formed on the multilayer reflective film 2, And an absorber layer 5 formed on the dual-purpose film 6. Since the substrate 1, the multilayer reflective film 2, and the absorber layer 5 are the same as those in the first embodiment, the configuration and the forming process and the process of forming a pattern on the absorber layer 5 of the reflective photomask blank 30 The description of the details will be omitted.

  The dual-purpose film 6 includes a protective film that protects the multilayer reflective film 2, a buffer film that is resistant to etching performed when forming an exposure transfer pattern of the absorber layer 5, and prevents damage to the lower layer. Is a single layer film. For this reason, the combined membrane 6 needs to have high selectivity. That is, when the absorber layer 5 is etched under a predetermined gas condition, the absorber layer 5 is easily etched, but the dual-purpose film 6 positioned below the absorber layer 5 is selected so as not to be etched. From such conditions, a thin film containing carbon as a main component is selected as the dual-purpose film 6, and a diamond thin film or a diamond-like carbon thin film is suitable. As the diamond thin film, a non-single-crystal diamond thin film, particularly a polycrystalline diamond thin film is desirable, and the selectivity to etching can be further improved. The diamond-like carbon thin film is preferably doped with at least one selected from the group consisting of impurities such as nitrogen, boron, sulfur and silicon. Note that nitrogen, ammonia, diborane, hydrogen sulfide, silane, or the like can be used as a source gas for these impurities. Thus, by doping impurities, it is possible to impart characteristics according to the physical properties of each impurity, such as improvement of conductivity. When nitrogen, boron, sulfur, or silicon is doped as an impurity, any impurity contributes to stress adjustment and low resistance. In particular, nitrogen, boron, and sulfur reduce resistance, and silicon adjusts stress. A great effect can be obtained.

  The thin film mainly composed of carbon used as the dual-purpose film 6 is more preferably terminated with an electron donating group as in the first embodiment, and the film thickness is 0.001 μm or more, 0 It is desirable that it is 1 μm or less.

  And as a absorber layer pattern formation process, the reflection type photomask 40 shown in FIG. 4 is produced by etching the absorber layer 5 of this reflection type photomask blank 30 so as to form a predetermined transfer pattern. In addition, since the etching method of the absorber layer 5 in the absorber layer pattern forming step is the same as that of the first embodiment, the description thereof is omitted. Hereinafter, based on Example 3, the details of the reflective photomask blank 30 and the manufacturing method thereof according to the present embodiment, and the reflective photomask 40 and the manufacturing details thereof will be described.

  In this embodiment, a case where a diamond carbon thin film is formed as the dual-purpose film 6 will be described. Since the substrate 1, the multilayer reflective film 2, and the absorber layer 5 are the same as those in the first embodiment and the second embodiment, the details thereof are omitted.

  A reflective photomask blank 301 shown in FIG. 3 is formed in a diamond-like shape using a parallel plate type plasma CVD apparatus as a dual-layer film forming step after the multilayer reflective film 2 is formed on the substrate 1 as a multilayer reflective film forming step. A dual-purpose film 6 that is a carbon thin film was formed.

  The conditions for plasma CVD are as follows. That is, as the source gas, a gas containing methane (flow rate: 20 sccm) as a main component and nitrogen (concentration: 1 to 50%) as a dope gas was used. Instead of nitrogen, ammonia may be included at a concentration of 1 to 50%. Further, the reaction pressure was set to 0.03 Torr and the self-bias voltage 0 to 1500 V, thereby forming the dual-purpose film 6 having a thickness of 10 nm. Finally, as the absorber layer forming step, the reflective photomask blank 301 could be obtained by forming the absorber layer 5.

  Next, a reflective photomask 401 is manufactured from the reflective photomask blank 301. As the absorber layer pattern forming step, the absorber layer 5 is patterned with a predetermined exposure transfer pattern. In addition, since the patterning of the absorber layer 5 is the same as that of Example 1, the details are omitted.

  As described above, the dual-purpose film 6 formed of the diamond-like carbon film that is a carbon-containing thin film is provided, and the reflective photomask blank 30 (301) is used, so that high selectivity to etching is obtained. Further, it is possible to prevent the reflectance of the multilayer reflective film 2 from being lowered when the absorber layer 5 is etched. For this reason, according to the reflection type photomask 40 (401) manufactured from the reflection type photomask blank 30 (301), it is possible to obtain a good reflectance by preventing damage to the multilayer reflection film, thereby providing excellent contrast. It is possible to transfer a pattern having Further, according to the reflective photomask blank 30, the film for protecting the multilayer reflective film 2 and the film for protecting the absorber layer 5 against etching can be used as the single-layer film 6 as a single film. In addition, the film forming process can be simplified and the film thickness can be reduced.

  Also in the extreme ultraviolet light exposure method using such a reflective photomask 40, the pattern can be transferred with high accuracy as in the first embodiment. That is, first, a photoresist layer is provided on a substrate on which a layer to be processed is formed. Next, the pattern of the absorber layer is transferred by irradiating the reflective photomask 20 with extreme ultraviolet light as exposure light and exposing the reflected light reflected by the multilayer reflective film 2 to the photoresist layer. Next, unnecessary portions of the photoresist layer in the development process are removed, and a pattern of the etching resist layer is formed on the substrate. Then, the layer to be processed is etched using the pattern of the etching resist layer as a mask. Finally, by removing the pattern of the etching resist layer, it is possible to transfer onto the substrate a fine pattern having a line width that is faithful to the photomask pattern and that corresponds to the wavelength of extreme ultraviolet light (10 to 15 nm).

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

It is sectional drawing of the reflection type photomask blank of 1st Embodiment of this invention. It is sectional drawing of the reflection type photomask of 1st Embodiment of this invention. It is sectional drawing of the reflection type photomask blank of 2nd Embodiment of this invention. It is sectional drawing of the reflection type photomask of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multilayer reflective film 3 Protective film 4 Buffer film 5 Absorber layer 6 Combined film 10, 101, 102, 30, 301 Reflective photomask blank 20, 201, 202, 40, 401 Reflective photomask

Claims (22)

A substrate,
A multilayer reflective film formed on the substrate and serving as a highly reflective portion of exposure light;
A protective film formed on the multilayer reflective film and protecting the multilayer reflective film;
On the protective film, an absorber layer that absorbs the exposure light as a low reflection part of the exposure light,
A buffer film which is formed between the absorber layer and the protective film and has resistance to etching performed when forming an exposure transfer pattern of the absorber layer;
The reflective photomask blank, wherein the protective film is a thin film containing carbon as a main component. A substrate,
A multilayer reflective film formed on the substrate and serving as a highly reflective portion of exposure light;
A protective film formed on the multilayer reflective film and protecting the multilayer reflective film;
On the protective film, an absorber layer that absorbs the exposure light as a low reflection part of the exposure light,
A buffer film which is formed between the absorber layer and the protective film and has resistance to etching performed when forming an exposure transfer pattern of the absorber layer;
The reflection type photomask blank, wherein the buffer film is a thin film containing carbon as a main component. The reflective photomask blank according to claim 1 or 2,
The protective film and the buffer film are formed as a single-layer combined film that also serves as the protective film and the buffer film,
A reflective photomask blank, wherein the dual-use film is a thin film mainly composed of carbon. In the reflective photomask blank according to any one of claims 1 to 3,
A reflective photomask blank, wherein the thin film containing carbon as a main component has a thickness of 0.001 μm or more and 0.1 μm or less. In the reflective photomask blank according to any one of claims 1 to 4,
A reflective photomask blank, wherein the surface of the thin film containing carbon as a main component is terminated with an electron donating group. In the reflective photomask blank according to any one of claims 1 to 5,
A reflective photomask blank, wherein the thin film containing carbon as a main component is a diamond thin film. The reflective photomask blank according to claim 6,
A reflective photomask blank, wherein the diamond thin film is a non-single crystal diamond thin film. The reflective photomask blank according to claim 7,
The reflective photomask blank, wherein the non-single-crystal diamond thin film is a polycrystalline diamond thin film. In the reflective photomask blank according to any one of claims 1 to 5,
The reflective photomask blank, wherein the thin film containing carbon as a main component is a diamond-like carbon thin film. The reflective photomask blank according to claim 9,
A reflective photomask blank, wherein the diamond-like carbon thin film is doped with impurities. The reflective photomask blank according to claim 10,
The photomask blank is characterized in that the impurity is at least one selected from the group consisting of nitrogen, boron, sulfur and silicon.   The reflective photomask which formed the exposure transfer pattern by etching the said absorber layer of the reflective photomask blank in any one of Claims 1-11. A method of manufacturing a reflective photomask blank comprising a substrate, a multilayer reflective film that reflects exposure light, and an absorber layer that absorbs the exposure light,
A multilayer reflective film forming step of forming the multilayer reflective film on the substrate;
A protective film forming step of forming a protective film for protecting the multilayer reflective film on the multilayer reflective film;
A buffer film forming step of forming on the protective film a buffer film having resistance to etching performed in forming an exposure transfer pattern of the absorber layer;
An absorber layer forming step of forming the absorber layer on the buffer film,
At least one of the protective film forming step and the buffer film forming step is a step of forming a thin film mainly composed of carbon by a plasma CVD method using a source gas containing methane. Of manufacturing a reflective photomask blank. In the manufacturing method of the reflection type photomask blank according to claim 13,
The source gas further includes at least one selected from the group consisting of nitrogen, ammonia, diborane, hydrogen sulfide, and silane, and is selected from the group consisting of nitrogen, boron, sulfur, and silicon by a plasma CVD method. A method for producing a reflective photomask blank, comprising forming a thin film mainly containing carbon containing at least one. A method of manufacturing a reflective photomask blank comprising a substrate, a multilayer reflective film that reflects exposure light, and an absorber layer that absorbs the exposure light,
A multilayer reflective film forming step of forming the multilayer reflective film on the substrate;
A dual-layer film forming step of forming a dual-layer film on the multilayer reflective film, which protects the multilayer reflective film and is resistant to etching performed when forming an exposure transfer pattern of the absorber layer;
An absorber layer forming step of forming the absorber layer on the dual-purpose film,
The method for forming a reflective photomask blank is characterized in that the combined film forming step is a step of forming a thin film mainly composed of carbon by a plasma CVD method using a source gas containing methane. In the manufacturing method of the reflective photomask blank according to claim 15,
The source gas further includes at least one selected from the group consisting of nitrogen, ammonia, diborane, hydrogen sulfide, and silane, and is selected from the group consisting of nitrogen, boron, sulfur, and silicon by a plasma CVD method. A method for producing a reflective photomask blank, comprising forming a thin film mainly containing carbon containing at least one. An absorber layer pattern production step of forming an exposure transfer pattern on the absorber layer of the reflective photomask blank produced by the reflective photomask blank production method according to claim 13 or 14,
A method of manufacturing a reflective photomask, comprising: a buffer film removing step of etching a portion of the buffer film exposed by forming an exposure transfer pattern on the absorber layer. In the manufacturing method of the reflective photomask of Claim 17,
The method of manufacturing a reflective photomask, wherein the buffer film removing step is performed by dry etching with an etching gas containing oxygen gas or oxidizing gas. In the manufacturing method of the reflection type photomask of Claim 18,
The method of manufacturing a reflective photomask, wherein the etching gas further contains a halogen-based gas.   And an absorber layer pattern manufacturing step of patterning the absorber layer of the reflective photomask blank manufactured by the method for manufacturing a reflective photomask blank according to claim 15 or 16. Type photomask manufacturing method.   The absorption of the reflective photomask is performed by irradiating the reflective photomask according to claim 12 with extreme ultraviolet light as exposure light and exposing the reflected light reflected on the multilayer reflective film of the reflective photomask. An extreme ultraviolet light exposure method comprising a step of projecting an exposure transfer pattern of a body layer.   An extreme ultraviolet light is irradiated as exposure light to the reflective photomask manufactured by the method for manufacturing a reflective photomask according to any one of claims 17 to 20, and the multilayer reflective film of the reflective photomask is irradiated An extreme ultraviolet light exposure method, comprising: exposing the reflected transfer light to project an exposure transfer pattern of the absorber layer of the reflective photomask.

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