JP5292747B2 - Reflective photomask for extreme ultraviolet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective photomask that eliminates the need to use an expensive rare material by using a Ti oxide, a Zr alloy, a Zr oxide, or a Zr nitride as a material for a surface coating film while reducing effects caused by changes in material properties by oxidization, and a semiconductor device manufacturing method. <P>SOLUTION: The reflective photomask has a substrate, a multilayer reflection film formed on the substrate, a protective film formed on the multilayer reflection film, a buffering film formed on the protective film, an absorbing film formed on the buffering film while having a multilayer structure, and a coating film that covers the whole face, on which an exposure transfer pattern obtained by patterning the buffering film and the absorbing film exists, and at least the side faces of the protective film and the multilayer reflection film. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a reflection photomask for extreme ultraviolet light and a method for manufacturing a semiconductor element. In particular, the present invention relates to a reflective photomask used for manufacturing a semiconductor element and the like and a method for manufacturing the semiconductor element in a photolithography method using extreme ultraviolet light in the soft X-ray region, that is, EUV (Extreme Ultra Violet) light.

  Conventionally, in semiconductor device manufacturing, when a necessary pattern is transferred onto a Si substrate by photolithography, a lamp light source (wavelength 365 nm) or an excimer laser light source (KrF: wavelength 248 nm, ArF: wavelength 193 nm) is used as a light source. Have been used. Further, as the next generation technology, immersion exposure technology using an ArF excimer laser is used. However, even with immersion exposure using an ArF excimer laser, it is not easy to produce a device having a line width of 32 nm or less that will be required in the future. In addition, there is a problem of an exposure apparatus and a resist to apply immersion exposure using an ArF excimer laser as a lithography technique for manufacturing a device having a line width of 32 nm or less. For this reason, development of a photolithography method using EUV light (wavelength of about 13 nm) having a wavelength shorter by one digit or more than excimer laser light as a light source is desired.

  In the EUV lithography method using EUV light, exposure by a reflective optical system is used. This is because the refractive index of the substance in the wavelength region of EUV light is slightly smaller than 1, and a refracting optical system used in a conventional exposure source cannot be used. In addition, a transmissive photomask is used for conventional pattern transfer, but a reflective photomask is used because most substances have high light absorption in the wavelength region of EUV light.

  As a reflection type photomask in such an EUV lithography method, a multilayer reflection film capable of reflecting EUV light on a substrate and an absorption film made of a material having a high EUV light absorption rate formed on the multilayer reflection film are used. The thing using the comprised reflection type photomask blank is proposed. 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 absorption film has a laminated structure of an alloy, oxide, nitride, or oxynitride containing Ta as a main component. Then, by etching the absorption film 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.

  In addition, when the material on the outermost surface of the mask is prevented from being repeatedly used due to repeated use, or a coating film for protecting the mask surface is formed of a material that absorbs less EUV light in order to suppress damage due to cleaning. (For example, refer to Patent Document 1).

However, the material of the coating film on the mask surface used in the reflective photomask blank of Patent Document 1 is centered on Ru (ruthenium), but Ru is a rare material and expensive, and changes in properties due to oxidation. The impact has not been elucidated. Furthermore, since the outer peripheral side surface of the substrate is not covered, mask deterioration and particles are generated due to side surface damage and the like.
JP 2003-318104 A

  The present invention uses a Ti oxide, a Zr alloy, a Zr oxide, or a nitride as the material of the surface coating film, and does not use a high-priced rare material. Provided are a reflective photomask and a method for manufacturing a semiconductor device, which can reduce the influence.

The invention according to claim 1 of the present invention includes a substrate, a multilayer reflective film formed on the substrate, a protective film formed on the multilayer reflective film, a buffer film formed on the protective film, and a buffer film An absorption film having a multilayer structure formed thereon, and the buffer film functions as an etching stopper for preventing damage to the protective film when the absorption film is patterned by etching. It functions as an etching stopper to prevent damage to the multilayer reflective film when the film is removed by etching, and further, the entire surface on which the exposure transfer pattern obtained by patterning the buffer film and the absorption film exists and a reflection type photomask which have a coating film covering at least the side surface of the protective film and the multilayer reflective film, the coating film, the O ₂ gas to the Ar gas an alloy or Ti of ZrSi targeting In a mixed gas atmosphere, the ZrSi target or Ti target and the reflective photomask are placed in a positional relationship shifted from the front, and the reflective photomask is sputtered while rotating the reflective photomask. The reflective photomask is an oxide of ZrSi or Ti having a thickness of 2 to 2.2 nm formed on the mask pattern surface of the mask and the entire mask side surface of the reflective photomask .

Invention is formed by a reflection type photomask according to claim 1, characterized in that back-surface conductive film is formed on the surface the multilayer reflective film of the substrate is not formed according to the second aspect of the present invention is there.

  According to the present invention, the use of Ti oxides, Zr alloys, oxides, and nitrides as the material of the surface coating film makes it possible to use high-priced rare materials without changing the properties of the materials due to oxidation. It is possible to provide a reflective photomask and a method for manufacturing a semiconductor element that can reduce the influence.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  As shown in FIGS. 1 and 2, the reflective photomasks 10 and 20 according to the embodiment of the present invention are provided on a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a multilayer reflective film 2. The formed protective film 3, the buffer film pattern 4 formed from the buffer film formed on the protective film 3, the absorption film lower layer pattern 5a formed on the buffer film pattern 4, and the absorption film lower layer pattern 5a The upper layer is provided with an absorption film upper layer pattern 5b. Furthermore, it has a coating film 7 and a coating film 8 for protecting the entire formed mask pattern surface.

  Examples of the substrate 1 according to the embodiment of the present invention include a Si substrate and a low thermal expansion glass substrate, but the present invention is not limited to these.

  The multilayer reflective film 2 according to the embodiment of the present invention reflects 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 can be formed by repeatedly laminating a combination of Mo (molybdenum) and Si (silicon) or Mo (molybdenum) and Be (beryllium) for about 40 cycles.

  The absorption film lower layer pattern 5a according to the embodiment of the present invention absorbs irradiated EUV light when it is formed into a predetermined exposure transfer pattern by dry etching as will be described later, that is, EUV. It is selected from heavy metals having a high absorption for light. As such a heavy metal, an alloy containing Ta (tantalum) as a main component can be preferably used, but the present invention is not limited thereto.

  Further, the crystalline state of the absorber film lower layer pattern 5a is preferably amorphous because an absorber layer surface having high smoothness is obtained or anisotropic etching of the absorber film is performed by dry etching. For example, in the case of Ta, amorphization can be performed by using an alloy containing an appropriate amount of Si (hereinafter referred to as “TaSi-based absorber”).

  The buffer film 4 according to the embodiment of the present invention is formed of a material having resistance to dry etching performed when forming the absorption film lower layer pattern 5a and the absorption film upper layer pattern 5b. It functions as an etching stopper for preventing damage to the protective film 3 when etching 5a, and can be formed of CrN or the like, but the present invention is not limited thereto.

  The back surface conductive film 100 according to the embodiment of the present invention is a film for fixing the reflection type photomask 10 and the reflection type photomask 20 using the principle of an electrostatic chuck when the reflection type photomask 10 and the reflection type photomask 20 are installed in an exposure machine.

  The protective film 3 according to the embodiment of the present invention is for protecting the multilayer reflective film 2 and functions as an etching stopper for preventing damage to the multilayer reflective film 2 when the buffer film is removed by etching. To do. The protective film 3 can be formed of Si, Ru (ruthenium) or the like, but is not limited to these in the present invention.

The absorption film lower layer pattern 5a and the absorption film upper layer pattern 5b according to the embodiment of the present invention form a resist pattern by coating an electron beam resist on the absorption film upper layer and performing electron beam drawing. The resist pattern is transferred to the absorption film by dry etching. The dry etching is performed in an etching atmosphere mainly composed of F-based gas or Cl ₂ -based gas. Then, after the remaining resist is removed for inspection and correction, the buffer film is etched. The buffer film pattern 4 can be formed, for example, in an etching atmosphere in which O ₂ is added to Cl ₂ gas in the case of a Cr-based buffer film.

Further, after performing mask cleaning, for example, sputtering can be performed in an atmosphere in which O ₂ is added to Ar using ZrSi as a target to form the coating film 7 and the coating film 8.

In order to form the coating film 7 on the reflection pattern photomask 30 shown in FIG. 3 on the mask pattern surface and the side surfaces of the protective film 3 and the multilayer reflection film 2, for example, in an atmosphere in which O ₂ is added to Ar using ZrSi as a target. The coating film 7 is formed by sputtering while rotating the formed mask. When sputtering, the target film is disposed on the front surface of the reflective photomask 30 so that the coating film 7 can be formed on the side surface including the mask pattern surface of the reflective photomask 30 and the multilayer reflective film 2.

In order to form the coating film 8 on the mask pattern surface and the side surface of the substrate 1 on the reflective photomask 30 shown in FIG. 3, for example, the reflective photomask 30 formed in an atmosphere in which O ₂ is added to Ar using ZrSi as a target. The coating film 8 can be formed by sputtering while rotating. When sputtering, the coating film 8 can be formed on the mask pattern surface and the entire mask side surface of the reflective photomask 30 by disposing the target in a positional relationship where the reflective photomask 30 is displaced from the front. .

  Thereafter, the reflective photomask 10 or the reflective photomask 20 can be manufactured by performing cleaning as necessary.

  The coating film 7 and the coating film 8 are made of Ti oxide, Zr alloy, oxide, or nitride as the material of the mask pattern, the protective film and the side of the multilayer reflective film, and the side of the substrate. By forming the coating film 8, it is possible to reduce the influence of the property change of the material due to oxidation, and it is possible to prevent the deterioration of the mask and the generation of particles due to the damage of the side surface.

  The semiconductor device manufacturing method using the reflective photomasks 10 and 20 according to the present invention selectively irradiates the extreme ultraviolet light reflected through the reflective photomasks 10 and 20.

  Next, the reflected light reflected by the multilayer reflective film 2 of the reflective photomasks 10 and 20 is exposed to a resist layer provided on the semiconductor substrate to form a pattern, and then the reflective photomask 10 and It can pattern by transferring the pattern of 20 absorber layers to a semiconductor substrate.

  Hereinafter, the details of the production of the reflective photomasks 10 and 20 according to the embodiment of the present invention will be described with reference to FIG. 3, but the present invention is not limited to this example.

  As shown in FIG. 3, using a low thermal expansion glass as the substrate 1, the film thickness of one cycle made of Mo and Si on the substrate 1 is 7 nm, of which the film thickness of Mo is 2.8 nm and the film thickness of Si. Is formed by laminating 4.2 nm alternately for 40 periods to form a multilayer reflective film 2 for reflecting EUV light, and forming a protective film 3 made of Si on the multilayer reflective film 2. A buffer film pattern 4 made of Cr nitride is formed on the film, an absorption film lower layer pattern 5a of an alloy mainly composed of Ta is formed on the buffer film pattern 4, and an absorption film upper layer pattern is formed on the absorption film lower layer pattern 5a. 5b, and a reflective photomask 30 in which a back conductive film 100 made of CrN is formed on the back surface of the substrate 1 can be obtained.

A sputtering film was formed on the reflective photomask 30 while rotating the mask in a gas atmosphere in which O ₂ gas was mixed with Ar gas using a ZrSi alloy as a target. In this case, the ZrSi oxide coating film 7 having a thickness of 2 nm could be formed by placing the ZrSi target so as to be in front of the reflective photomask 30. Thus, the reflective photomask 10 was obtained.

  According to the reflection type photomask 10 as described above, the reflection type photomask 10 causes the film quality deterioration due to oxidation of the absorption film upper layer pattern 5b, the absorption film lower layer pattern 5b, and the protection film 3 due to the coating film 7 on the mask surface or due to the chemical solution. Can be prevented. The EUV light reflectivity drop by the surface coating film 7 is about 0.2%, and stable pattern transfer can be performed even when a semiconductor element is manufactured using the reflective photomask 10.

  As shown in FIG. 3, using a low thermal expansion glass as the substrate 1, the film thickness of one cycle made of Mo and Si on the substrate 1 is 7 nm, of which the film thickness of Mo is 2.8 nm and the film thickness of Si. Is formed by alternately laminating 4.2 nm for 40 periods, forming a multilayer reflective film 2 for reflecting EUV light, forming a protective film 3 made of Si thereon, and forming Cr on the protective film 3 A buffer film pattern 4 made of nitride is formed, an absorption film lower layer pattern 5a of an alloy mainly composed of Ta is formed on the multilayer reflective film 2, and an absorption film upper layer pattern 5b is formed on the absorption film lower layer pattern 5a. In addition, a reflective photomask 30 in which a back conductive film 100 made of CrN is formed on the back surface of the substrate 1 can be obtained.

A sputtering film was formed on the reflective photomask 30 while rotating the mask in a gas atmosphere in which O ₂ gas was mixed with Ar gas using a ZrSi alloy as a target. At this time, the ZrSi target and the reflective photomask 30 were placed so as to have a positional relationship shifted from the front, whereby the ZrSi oxide coating film 8 could be formed with a thickness of 2 nm. Thus, a reflective photomask 20 was obtained.

  According to the reflection type photomask 20 as described above, the reflection type photomask 20 causes the film quality deterioration due to the oxidation of the absorption film upper layer pattern 5b, the absorption film lower layer pattern 5a and the protection film 3 due to the coating film 8 on the mask surface or the chemical solution. Can be prevented. The surface coating film 8 also reduces the EUV light reflectance by about 0.2%, and stable pattern transfer can be performed even when a semiconductor element is manufactured using the reflective photomask 10.

  As shown in FIG. 3, using a low thermal expansion glass as the substrate 1, the film thickness of one cycle made of Mo and Si on the substrate 1 is 7 nm, of which the film thickness of Mo is 2.8 nm and the film thickness of Si. Is formed by laminating 4.2 nm alternately for 40 periods to form a multilayer reflective film 2 for reflecting EUV light, and forming a protective film 3 made of Ru on the multilayer reflective film 2. A buffer film pattern 4 made of Cr nitride is formed on the film, an absorption film lower layer pattern 5a of an alloy mainly composed of Ta is formed on the buffer film pattern 4, and an absorption film upper layer pattern is formed on the absorption film lower layer pattern 5a. 5b, and a reflective photomask 30 in which a back conductive film 100 made of CrN is formed on the back surface of the substrate 1 can be obtained.

Sputter film formation was performed on the reflective photomask 30 while rotating the mask in a gas atmosphere in which O ₂ gas was mixed with Ar gas using Ti as a target. At this time, the Ti oxide coating film 7 was formed to a thickness of 2.2 nm by placing the Ti target so as to be in front of the reflective photomask. Thus, the reflective photomask 10 was obtained.

  According to the reflection type photomask 10 as described above, the reflection type photomask 10 causes deterioration of the film quality due to oxidation of the absorption film upper layer pattern 5, absorption film lower layer pattern 5 and protective film 3 due to the coating film 7 on the mask surface or chemical solution. Can be prevented. The EUV light reflectivity drop by the surface coating film 7 is about 0.3%, and stable pattern transfer can be performed even when a semiconductor element is manufactured using the reflective photomask 20.

  As shown in FIG. 3, using a low thermal expansion glass as the substrate 1, the film thickness of one cycle made of Mo and Si on the substrate 1 is 7 nm, of which the film thickness of Mo is 2.8 nm and the film thickness of Si. Is formed by laminating 4.2 nm alternately for 40 periods to form a multilayer reflective film 2 for reflecting EUV light, and forming a protective film 3 made of Ru on the multilayer reflective film 2. A buffer film pattern 4 made of Cr nitride is formed on the film, an absorption film lower layer pattern 5a of an alloy mainly composed of Ta is formed on the buffer film pattern 4, and an absorption film upper layer pattern is formed on the absorption film lower layer pattern 5a. 5b, and a reflective photomask 30 in which a back conductive film 100 made of CrN is formed on the back surface of the substrate 1 can be obtained.

Sputter film formation was performed on the reflective photomask 30 while rotating the mask in a gas atmosphere in which O ₂ gas was mixed with Ar gas using Ti as a target. At this time, the Ti oxide coating film 8 was formed to a thickness of 2.2 nm by placing the Ti target and the reflective photomask 30 so as to have a positional relationship shifted from the front. Thus, a reflective photomask 20 was obtained.

  According to the reflection type photomask 20 as described above, the reflection type photomask 20 causes the film quality deterioration due to the oxidation of the absorption film upper layer pattern 5b, the absorption film lower layer pattern 5a and the protection film 3 due to the coating film 8 on the mask surface or the chemical solution. Can be prevented. The EUV light reflectivity drop by the surface coating film 8 is about 0.3%, and stable pattern transfer can be performed even when a semiconductor element is manufactured using the reflective photomask 20.

  According to the reflective photomasks 10 and 20 according to the present invention, by using Ti oxide, Zr alloy, oxide, or nitride as the material of the surface coating films 7 and 8, a semiconductor element, a semiconductor device, and an electron It can be suitably used for forming a fine pattern using a resist for extreme ultraviolet light in a manufacturing process of a circuit device or the like.

  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 a schematic sectional drawing of the reflection type photomask which covered the whole pattern surface and the multilayer film of the side surface concerning the embodiment of this invention with the coating film. It is a schematic sectional drawing of the reflective photomask which covered the whole pattern surface and the whole side surface which concern on embodiment of this invention with the coating film. It is a schematic sectional drawing of the reflection type photomask which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multi-layer reflective film 3 Protective film 4 Buffer film pattern 5a Absorbing film lower layer pattern 5b Absorbing film upper layer pattern 7 Surface coating film 8 on the pattern surface 8 Surface coating film 10 on the entire mask Mask pattern surface and multilayer reflective film Reflective photomask 20 having a coating film on the mask side wall including the reflective photomask 30 having a coating film on the mask pattern surface and the entire mask side wall Reflective photomask 100 Back surface conductive film

Claims (2)

A substrate,
A multilayer reflective film formed on the substrate;
A protective film formed on the multilayer reflective film;
A buffer film formed on the protective film;
An absorption film having a multilayer structure formed on the buffer film;
Have
The buffer film functions as an etching stopper for preventing damage to the protective film when the absorption film is patterned by etching,
The protective film functions as an etching stopper that prevents damage to the multilayer reflective film when the buffer film is etched away.
Furthermore, the reflection type photomask have a coating film covering the side surface of the entire surface of the buffer layer and the absorbing layer patterned to the resulting exposure transfer pattern exists and at least the protective film and the multilayer reflective film Because
The coating film is installed so that the ZrSi target or Ti target and the reflective photomask are displaced from the front in a gas atmosphere in which O ₂ gas is mixed with Ar gas using a ZrSi alloy or Ti as a target. Then, by performing sputtering film formation while rotating the reflective photomask, the thickness of 2 to 2.2 nm formed on the mask pattern surface of the reflective photomask and the entire mask side surface of the reflective photomask. A reflective photomask characterized by being an oxide of ZrSi or Ti . 2. The reflective photomask according to claim 1, wherein a back conductive film is formed on a surface of the substrate where the multilayer reflective film is not formed.

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