JP2010212484A - Reflection type photomask blank and reflection type photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type photomask blank and reflection type photomask, wherein a fine pattern can be formed without causing surface roughness of a capping film or change in film quality due to dry etching. <P>SOLUTION: The reflection type photomask blank includes a substrate, a multilayer reflective film formed on the substrate and reflecting exposure light, the capping film formed on the multilayer reflective film and protecting the multilayer reflective film, a dry etching stopper film formed on the capping film and having resistance to dry etching, an absorption film formed on the dry etching stopper film and absorbing the exposure light, and an antireflective film formed on the absorption film and preventing inspection light from being reflected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflective photomask blank and a reflective photomask. In particular, in a manufacturing process of a semiconductor integrated circuit or the like, a reflective photomask blank used when transferring an ultrafine circuit pattern performed using extreme ultraviolet light in the soft X-ray region, that is, EUV (Extreme Ultra Violet) light, and The present invention relates to a reflective photomask.

  Lithography technology is used for nano-level microfabrication such as LSI circuit patterns. In recent years, with higher integration, a technique for producing a finer pattern is required, and the wavelength of an exposure light source is being shortened. For example, the exposure light source has been shifted to a KrF excimer laser (wavelength 248 nm) and an ArF excimer laser (wavelength 193 nm). In addition, developments have been made in which soft X-rays having a shorter wavelength (wavelength: 13.5 nm) are used as an exposure light source.

  Lithography using soft X-rays as an exposure light source is called EUV (Extreme Ultra Violet) lithography. In EUV lithography, since the refractive index of a substance in the wavelength region of the exposure light source is slightly smaller than 1, a conventionally used refractive optical system cannot be used, and pattern transfer can be performed by using a reflective optical system. carry out. Since EUV light is absorbed by most substances, a conventional transmissive photomask cannot be used, and a reflective photomask is used.

  The reflection type photomask uses a blank in which a multilayer reflection film capable of reflecting EUV light is formed on a substrate having a low coefficient of thermal expansion, and an absorption film is formed of a material having a high absorption rate for EUV light on the substrate. Can be obtained by processing into a desired pattern.

  In many cases, a film called a capping film is provided between the multilayer reflective film and the absorbing film in order to prevent a reduction in reflectance due to pattern defect correction or oxidation. Since the capping film becomes the outermost surface of the EUV light reflecting portion when processed into a reflective photomask, the extinction coefficient for EUV light is small, and the difference between the refractive index of the capping film and the refractive index of the vacuum is large. It is necessary to use a material that is difficult to oxidize.

  On the other hand, Patent Document 1 discloses a reflective photomask blank having a capping film containing Ru (ruthenium) as a main component. When a reflective photomask is manufactured by processing this reflective photomask blank, the absorption film formed on the capping film is processed by dry etching using chlorine gas or the like.

  Ruthenium is a material that serves as an etching stopper for dry etching of the absorption film, but it does not mean that the surface of ruthenium is not damaged at all. Due to the physical impact of dry etching, a decrease in film thickness as described in Patent Document 1, a change in surface quality, or a change in film quality due to mixing with Si, which is the uppermost layer material of the multilayer reflective film, occurs. . If only the film thickness is reduced, it can be considered that the film thickness can be coped with by adding a decrease in advance during film formation. However, if the surface roughness or film quality change occurs in the reflective photomask, the reflected light of the EUV light becomes uneven, and the transfer pattern cannot be formed accurately.

JP 2006-13280 A

  The present invention is a reflective type in which a dry etching stopper film capable of wet etching with chemicals is provided between an absorption film and a capping film in order to form a fine pattern without causing surface roughness or film quality change by dry etching. It is to provide a photomask blank and a reflective photomask.

  The invention according to claim 1 of the present invention includes a substrate, a multilayer reflective film that is formed on the substrate and reflects exposure light, a capping film that is formed on the multilayer reflective film and protects the multilayer reflective film, and a capping film. A dry etching stopper film which is formed on the dry etching stopper film and is formed on the dry etching stopper film to absorb exposure light, and is formed on the absorption film to prevent reflection of inspection light. And a reflection type photomask blank characterized by comprising an antireflection film.

  The invention according to claim 2 of the present invention is characterized in that the antireflection film is made of Ta, Si, and O, and the ratio of Ta contained is larger than that of the dry etching stopper film. This is a reflection type photomask blank described.

  The invention according to claim 3 of the present invention is characterized in that the dry etching stopper film is made of Ta, Si and O, or Si and O, and the ratio of Ta contained is smaller than that of the antireflection film. The reflective photomask blank according to claim 1 or 2 is used.

  The invention according to claim 4 of the present invention is the reflective photomask blank according to claim 1, wherein the capping film is made of a material resistant to basic chemicals.

  The invention according to claim 5 of the present invention is the reflective photomask blank according to claim 4, wherein the capping film is composed mainly of Ru.

  According to a sixth aspect of the present invention, there is provided a substrate, a multilayer reflective film that is formed on the substrate and reflects exposure light, a capping film that is formed on the multilayer reflective film and protects the multilayer reflective film, and a capping film. Formed on the dry etching stopper film having resistance to the patterned dry etching, formed on the dry etching stopper film, absorbing the patterned exposure light, formed on the absorption film, A reflection type photomask comprising an antireflection film for preventing reflection of patterned inspection light.

  The invention according to claim 7 of the present invention is characterized in that the antireflection film is composed of Ta, Si, and O, and the ratio of Ta contained is larger than that of the dry etching stopper film. The reflection type photomask is described.

  The invention according to claim 8 of the present invention is characterized in that the dry etching stopper film is made of Ta, Si and O, or Si and O, and the ratio of Ta contained is smaller than that of the antireflection film. The reflective photomask according to claim 6 or 7 is used.

  The invention according to claim 9 of the present invention is the reflective photomask according to claim 6, wherein the capping film is made of a material resistant to basic chemicals.

  The invention according to claim 10 of the present invention is the reflective photomask according to claim 9, wherein the capping film is composed mainly of Ru.

  According to an eleventh aspect of the present invention, the reflection photomask according to any one of the sixth to tenth aspects is irradiated with extreme ultraviolet light, and the reflected light reflected on the multilayer reflective film of the reflection type photomask is reflected on the semiconductor substrate. A method for manufacturing a semiconductor device comprising a step of exposing a resist layer for extreme ultraviolet light provided thereon and transferring a pattern of an absorption film of a reflective photomask to the resist layer for extreme ultraviolet light It is.

  According to the present invention, a dry etching stopper film capable of wet etching with chemicals is provided between the absorption film and the capping film in order to form a fine pattern without causing surface roughness or film quality change due to dry etching. A reflective photomask blank and a reflective photomask can be provided.

It is a schematic block diagram which shows the reflection type photomask blank which concerns on embodiment of this invention. It is a schematic block diagram which shows the reflection type photomask which concerns on embodiment of this invention.

  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.

  FIG. 1 is a schematic configuration diagram showing a reflective photomask blank 10 according to an embodiment of the present invention. As shown in FIG. 1, a reflective photomask blank 10 according to an embodiment of the present invention includes a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a capping formed on the multilayer reflective film 2. A film 3, a dry etching stopper film 4 formed on the capping film 3, an absorption film 5 formed on the dry etching stopper film 4, and an antireflection film 6 formed on the absorption film 5. The

  The substrate 1 of the reflective photomask blank 10 according to the embodiment of the present invention may be any material as long as the multilayer reflective film 2 can be uniformly formed on the substrate 1 with good adhesion and has a low coefficient of thermal expansion. . Examples include low thermal expansion glass to which Ti is added, but the present invention is not limited thereto.

  The multilayer reflective film 2 of the reflective photomask blank 10 according to the embodiment of the present invention reflects EUV light (extreme ultraviolet light) that is exposure light, and is based on a combination of materials having significantly different refractive indexes with respect to EUV light. It is configured. 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 example, the multilayer reflective film 2 is made of Mo having a film thickness of 2.8 nm and Si having a film thickness of 4.2 nm. The multilayer reflective film 2 is laminated with 30 to 50 periods and has maximum reflection with respect to EUV light having a wavelength of 13 to 14 nm. It forms so that it may become a rate.

  The main role of the capping film 3 of the reflective photomask blank 10 according to the embodiment of the present invention is to prevent a decrease in reflectance due to surface oxidation of the multilayer reflective film 2. Further, since the capping film 3 becomes the outermost surface of the reflection part 7 of the EUV light when processed into the reflective photomask 20 (FIG. 2), the extinction coefficient with respect to the EUV light is small, and the refractive index of the capping film 3 It is necessary to use a material that has a large difference from the refractive index of vacuum and is difficult to oxidize.

  Further, since the dry etching stopper film 4 is wet-etched with a chemical when the reflective photomask 20 is processed, the capping film 3 must have resistance to the chemical. As an example of the chemical solution used for wet etching, ammonia overwater, which is a basic chemical used for cleaning a photomask, is given as an example.

  Ru is a material known as a measure for suppressing oxidation of the optical mirror, and has resistance to ammonia overwater, so that Ru can be selected as the material of the capping film 3. The film thickness of the capping film 3 needs to be designed so that the reflectance of EUV light does not decrease as much as possible, and is usually preferably about 1 nm to 2.5 nm.

  The dry etching stopper film 4 of the reflective photomask blank 10 according to the embodiment of the present invention has etching resistance to the extent that it functions as an etching stopper when the absorption film 5 is dry-etched, and is basic due to ammonia overwater or the like. It is formed of a material that can be processed by wet etching using chemicals. Examples of such a material include a material composed of Ta, Si, and O.

  At this time, the Ta content of Si in the dry etching stopper film 4 needs to be lower than the Ta content of Si in the antireflection film 6 (Ta / (Ta + Si)), and is about 0% to 40%. This is because the dry etching stopper film 4 is wet-etched with a basic chemical, but it is known that the lower the Ta content relative to Si, the easier it is to etch with ammonia overwater, which is a basic chemical. As for the film thickness, any film thickness may be used as long as the selective ratio can be sufficiently obtained during dry etching of the absorption film 5, but it is preferably about 2 nm to 10 nm.

  The absorption film 5 of the reflective photomask blank 10 according to the embodiment of the present invention absorbs the irradiated EUV light when it is dry-etched and formed into a predetermined exposure transfer pattern. It is selected from heavy metals having high absorbency. As such a heavy metal, an alloy containing Ta as a main component is preferably used. The film thickness of the absorption film 5 is determined by adjusting the entire film constituting the reflective photomask blank 10 in order to consider optical characteristics with respect to EUV light and DUV (Deep Ultra Violet) light used for defect inspection. About 80 nm.

  The antireflection film 6 of the reflective photomask blank 10 according to the embodiment of the present invention is a material that is antireflective with respect to DUV light used for defect inspection, and is a material that can be processed by etching. Examples of such a material include a material composed of Ta, Si, and O. The film thickness is determined by adjusting the entire film constituting the reflective photomask blank 10 in order to consider optical characteristics with respect to EUV light and DUV light used for defect inspection, but may be about 5 nm to 30 nm.

  The Ta content of Si in the antireflection film 6 needs to be higher than the Ta content of Si in the dry etching stopper film 4. Further, considering that the film thickness is about 5 nm to 30 nm and the reflectivity for DUV light used for defect inspection is 10% or less, the Ta content for Si is appropriately about 60% to 80%.

  The multilayer reflective film 2, the capping film 3, the dry etching stopper film 4, the lower layer absorbing film 5, and the upper layer absorbing film 6 formed on the substrate 1 constituting the reflective photomask blank 10 are formed by sputtering, chemical vapor deposition, It can be manufactured using a vacuum deposition method or the like. Among these, since the kinetic energy of the target atom is large, it is preferable to use a sputtering method that can form a strong and difficult-to-peel film.

  Next, a manufacturing method of the reflective photomask 20 according to the embodiment of the present invention will be described with reference to FIG.

  The reflective photomask 20 according to the embodiment of the present invention is manufactured by forming a desired pattern using the reflective photomask blank 10.

  First, a resist (not shown) is applied to the pattern forming surface side of the reflective photomask blank 10, and a desired resist pattern is formed by drawing and developing with an electron beam drawing apparatus.

  Next, using the resist pattern as a mask, the antireflection film 6 and the absorption film 5 are processed by dry etching. Thereafter, a resist stripping process and a particle removing process are performed to complete a reflective photomask 20 as shown in FIG.

  When the reflective photomask blank 10 according to the embodiment of the present invention is used, the dry etching stopper film 4 on the capping film 3 can be processed by wet etching when the reflective photomask 20 is processed. A fine pattern can be formed without causing surface roughness or film quality change of the film 3.

  Next, a method for manufacturing a semiconductor device using the reflective photomask 20 according to the embodiment of the present invention will be described. The method for manufacturing a semiconductor device using the reflective photomask 20 according to the embodiment of the present invention selectively irradiates the extreme ultraviolet light reflected through the reflective photomask 20.

  Next, the reflected light reflected by the multilayer reflective film 2 of the reflective photomask 20 is exposed to an extreme ultraviolet light resist layer (not shown) provided on the semiconductor substrate to form a pattern, and then the extreme ultraviolet light is formed. The pattern of the absorption film 4 of the reflective photomask 20 is transferred to the semiconductor substrate onto the resist layer for light, so that the reflective photomask 20 can be faithfully patterned.

  An example of the reflective photomask blank 10 and the reflective photomask 20 of the present invention is shown below. However, the present invention is not limited to the examples.

  A 6-inch square low thermal expansion glass was prepared as the substrate 1 as a base. Next, the multilayer reflective film 2 was formed by laminating Mo with a thickness of 2.8 nm and Si with a thickness of 4.2 nm on the substrate 1 in 40 cycles.

  Next, a capping film 3 made of Ru is formed with a film thickness of 2 nm on the multilayer reflective film 2, and subsequently a dry film composed of Ta, Si, O and having a Ta content (Ta / (Ta + Si)) of 20%. The etching stopper film 4 is formed with a film thickness of 3 nm, and then the absorption film 5 made of Ta and Si is formed with a film thickness of 51.5 nm. Further, the film is composed of Ta, Si, and O, and the Ta content (Ta / (Ta + Si )) Is 80%, an antireflection film 6 having a film thickness of 15 nm is formed to obtain a reflective photomask blank 10 (see FIG. 1). A sputtering method was used to form each film.

  Next, a resist (not shown) was applied on the reflective photomask blank 10, and a resist pattern was formed by electron beam drawing. Using the obtained resist pattern as a mask, dry etching of the antireflection film 6, the absorption film 5, and the dry etching stopper film 4 was performed using chlorine gas or fluorine gas.

  Then, a resist stripping process is performed, followed by a particle removal process using ammonia overwater prepared by mixing ammonia: hydrogen peroxide water: ultra pure water at a volume ratio of 1: 2: 20, and a reflective photomask. 20 was obtained (see FIG. 2).

  At this time, since ammonia overwater is used, the dry etching stopper film 4 is wet-etched. By TEM observation, it was confirmed that the etching stopper film 4 was etched in about 10 minutes and the capping film 3 was exposed on the surface. Further, there was no surface roughness or mixing of Ru of the capping film 3 and Si of the multilayer reflective film 2, so that a good reflective photomask 10 could be produced.

  Further, a method for manufacturing a semiconductor device using the reflective photomask 20 according to the first embodiment will be described. The semiconductor device manufacturing method using the reflective photomask 20 according to the first embodiment selectively irradiates extreme ultraviolet light reflected through the reflective photomask 20.

  Next, the reflected light reflected by the multilayer reflective film 2 of the reflective photomask 20 is exposed to an extreme ultraviolet light resist layer (not shown) provided on the semiconductor substrate to form a pattern, and then the extreme ultraviolet light is formed. The pattern of the absorption film 4 of the reflective photomask 20 was transferred onto the semiconductor substrate on the resist layer for light, and the patterning could be faithfully performed on the reflective photomask 20.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Multilayer reflection film 3 ... Capping film 4 ... Dry etching stopper film 5 ... Absorption film 6 ... Antireflection film 7 ... Reflection part 8 ... Absorption part 10 ... Reflective photomask blank 20 ... Reflection type photomask

Claims (11)

A substrate,
A multilayer reflective film formed on the substrate and reflecting exposure light;
A capping film formed on the multilayer reflective film and protecting the multilayer reflective film;
A dry etching stopper film formed on the capping film and having resistance to dry etching;
An absorption film that is formed on the dry etching stopper film and absorbs exposure light;
An antireflection film that is formed on the absorption film and prevents reflection of inspection light;
A reflective photomask blank characterized by comprising:   2. The reflective photomask blank according to claim 1, wherein the antireflection film is made of Ta, Si, and O, and a ratio of Ta contained is larger than that of the dry etching stopper film.   3. The reflection according to claim 1, wherein the dry etching stopper film is made of Ta, Si, and O, or Si and O, and a ratio of Ta contained is smaller than that of the antireflection film. Type photomask blank.   The reflective photomask blank according to claim 1, wherein the capping film is made of a material resistant to basic chemicals.   The reflective photomask blank according to claim 4, wherein the capping film is composed mainly of Ru. A substrate,
A multilayer reflective film formed on the substrate and reflecting exposure light;
A capping film formed on the multilayer reflective film and protecting the multilayer reflective film;
A dry etching stopper film formed on the capping film and having resistance to patterned dry etching;
An absorption film that is formed on the dry etching stopper film and absorbs patterned exposure light;
An antireflection film that is formed on the absorption film and prevents reflection of the patterned inspection light;
A reflective photomask characterized by comprising:   7. The reflective photomask according to claim 6, wherein the antireflection film is made of Ta, Si, and O, and the ratio of Ta contained is larger than that of the dry etching stopper film.   The reflection according to claim 6 or 7, wherein the dry etching stopper film is made of Ta, Si, and O, or Si, and O, and a ratio of Ta contained is smaller than that of the antireflection film. Type photomask.   The reflective photomask according to claim 6, wherein the capping film is made of a material resistant to basic chemicals.   The reflective photomask according to claim 9, wherein the capping film includes Ru as a main component. Irradiating the reflection type photomask according to any one of claims 6 to 10 with extreme ultraviolet light,
Exposing the reflected light reflected on the multilayer reflective film of the reflective photomask to a resist layer for extreme ultraviolet light provided on a semiconductor substrate,
A method of manufacturing a semiconductor device, comprising: transferring a pattern of the absorption film of the reflective photomask to the resist layer for extreme ultraviolet light.