JP2007271661A - Mask blank and halftone phase shift mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress degradation in a cross-sectional form of a light shielding film upon etching a glass substrate. <P>SOLUTION: A mask blank 10 for manufacturing a halftone phase shift mask for exposure to light at a wavelength of 200 nm or shorter is disclosed which comprises a light transmitting glass substrate 12, a halftone film 14, and a light shielding film 16. The halftone film 14 shows a transmittance of 10% to 40% at the exposure light wavelength and consists of a film comprising a metal, silicon (Si) and nitrogen (N) as main structural elements with a film thickness giving a phase shift of 140 or less for the transmitted light. The light shielding film 16 includes at least a layer containing nitrogen and chromium. The process of manufacturing a halftone phase shift mask includes etching a part to become a light transmitting part 22 of the glass substrate 12 to give about 180° phase difference between the transmitting light in the light transmitting part 22 and the transmitting light in a semitransmitting part 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mask blank and a halftone phase shift mask.

Conventionally, a method for forming a halftone phase shift mask by digging a predetermined amount of a glass substrate is known (see, for example, Patent Documents 1 and 2). In Patent Documents 1 and 2, as the material of the halftone film, a chromium-based material that can easily ensure an etching selectivity with a glass substrate is used. Conventionally, a method for forming a halftone phase shift mask by forming a halftone film with a MoSiON film and further digging a predetermined amount of a glass substrate is known (for example, see Patent Document 3). In recent years, due to the demand for higher resolution, it has been required to increase the transmittance of the halftone film to, for example, 10% to 40%. A configuration in which the transmittance of the halftone film is increased is disclosed in Patent Document 4, for example.
JP-A-4-136854 JP 7-152142 A US Patent USP5789116 JP 2003-280168 A

In recent years, with the miniaturization of LSI patterns, the wavelength of exposure light source (exposure light wavelength) has been shortened from KrF excimer laser (248 nm) to ArF excimer laser (193 nm), F ₂ excimer laser (157 nm), and the like. It is out. Therefore, the range of selection of the halftone film material that satisfies the predetermined transmittance and phase shift amount with respect to the exposure light having a shorter wavelength is narrowing. In particular, when the transmittance is 10% or more and 40% or less, selection of a halftone film material becomes more difficult.

  Therefore, an object of the present invention is to provide a mask blank and a halftone phase shift mask that can solve the above-described problems.

  The inventor of the present application uses a film material suitable for setting the transmittance to 10% or more and 40% or less of a mask blank halftone film for manufacturing a halftone phase shift mask for exposure light having a wavelength of 200 nm or less. We conducted intensive research. The inventor of the present application first considered that the transmittance should be 10% or more and 40% or less by reducing the film thickness of the halftone film as compared with a conventional halftone film having a transmittance of about 6%. However, in this case, it is difficult to set the phase shift amount to about 180 ° with only the halftone film. Therefore, it was considered that the entire phase shift amount is set to about 180 ° by digging a predetermined amount of the glass substrate that becomes a light transmitting portion when the halftone phase shift mask is manufactured.

  However, unlike the case where the glass substrate is dug to the extent that the phase shift amount is adjusted, for example, in the above case, the amount of dug the glass substrate becomes large. Therefore, a new problem accompanying an increase in the etching amount may occur. For example, when a light shielding film is formed on a halftone film in a mask blank for a halftone phase shift mask of a tritone type, the cross-sectional shape of the light shielding film is deteriorated due to an increase in etching time of the glass substrate. There is a risk that changes in optical characteristics (reflectance, etc.) may occur. In particular, when the halftone film and the glass substrate are continuously etched, if it takes a long time to etch the halftone film, the cross-sectional shape of the light-shielding film is deteriorated, and the risk of changes in optical characteristics (reflectance, etc.) increases. There is a fear.

  Furthermore, the halftone film and the glass substrate may be etched using the patterned light-shielding film as an etching mask. In this case, when the halftone film and the glass substrate are etched, the surface of the light shielding film is damaged by the etchant of the halftone film and the glass substrate, and the optical characteristics (reflectance, etc.) change. This may affect mask pattern inspection and pattern transfer, and may deteriorate pattern transfer characteristics.

  Therefore, the inventor of the present application has further studied earnestly and found a configuration that can suppress the deterioration of the cross-sectional shape of the light shielding film and the fluctuation of the optical characteristics of the light shielding film as described above. The present invention has the following configuration.

  (Configuration 1) An exposure with a wavelength of 200 nm or less, comprising a light transmission part that transmits exposure light, a semi-transmission part that transmits a part of the exposure light and simultaneously shifts the phase of the transmission light by a predetermined amount, and a light shielding part. A mask blank for manufacturing a halftone phase shift mask for light, which is a translucent glass substrate, a halftone film formed on the glass substrate, and a light shielding film formed on the halftone film The halftone film has a film thickness such that the transmittance at the exposure wavelength is 10% or more and 40% or less, and the phase shift amount of transmitted light is 140 ° or less. Metal, silicon (Si), and nitrogen (N) The light shielding film has at least a layer containing nitrogen and chromium, and in the halftone phase shift mask manufacturing process, the light shielding portion is formed by patterning the light shielding film. The semi-transmission part is formed by patterning the halftone film, and the light transmission part is formed by removing the halftone film and the light-shielding film. The portion that becomes the light transmitting portion in the glass substrate is etched so that the phase difference from the transmitted light of the portion is approximately 180 °.

  The phase difference between the transmitted light of the light transmitting portion and the transmitted light of the semi-transmissive portion is, for example, a phase difference at the time when the exposure light is transmitted through the entire halftone phase shift mask. The phase difference of approximately 180 ° means that, for example, the phase difference falls within a range of 180 ° ± 5 °. This glass substrate is, for example, a synthetic quartz glass substrate. The halftone film and the glass substrate are dry-etched using, for example, a fluorine-based etching gas.

  A film containing metal, silicon (Si), and nitrogen (N) as main components (hereinafter referred to as a metal silicide nitride film) has a thin film thickness for obtaining, for example, chemical resistance and a desired phase difference. It has characteristics preferable as a halftone film in that it can be converted into a halftone film. Moreover, it has translucency with respect to exposure light having a wavelength of 200 nm or less, and it is easy to form a film with a high quality even if the film thickness ensures a transmittance of 10% to 40%. Furthermore, the metal silicide nitride-based film can easily ensure an etching selectivity with respect to the light-shielding film including a layer containing nitrogen and chromium. Therefore, the light shielding film can be appropriately patterned.

  For example, when a fluorine-based etching gas is used, a metal silicide nitride-based film (MoSiN film or the like) is etched as compared with a metal silicide-based film (MoSiO film, MoSiON film, or the like) containing 20 atomic% or more of oxygen, for example. The speed is fast. Therefore, the time required for etching the halftone film and the glass substrate can be shortened. Therefore, if comprised in this way, the deterioration of the cross-sectional shape of the light shielding film at the time of etching of a glass substrate can be suppressed. Furthermore, the layer containing nitrogen and chromium is highly resistant to an etching gas for etching the glass substrate. Therefore, with this configuration, it is possible to more appropriately suppress the deterioration of the cross-sectional shape of the light shielding film and the fluctuation of the optical characteristics (reflectance, etc.).

  (Configuration 2) In the manufacturing process of the halftone phase shift mask, the halftone film and the glass substrate are etched by dry etching using a fluorine-based etching gas using the patterned light-shielding film as an etching mask. If comprised in this way, a halftone film and a glass substrate can be appropriately patterned with high precision. After the etching of the halftone film and the glass substrate, the light shielding film is further patterned, for example, to become a light shielding portion of a tritone type halftone phase shift mask.

  (Configuration 3) The halftone film is made of a material containing 2 to 10 atomic% of metal, 25 to 45 atomic% of silicon, and 45 to 70 atomic% of nitrogen. If comprised in this way, the halftone film | membrane of a metal silicide nitride-type film | membrane can be formed appropriately. The halftone film may contain a small amount of other elements as long as the film is substantially made of metal, silicon, and nitrogen. The content of elements other than metal, silicon, and nitrogen in the halftone film is preferably 3 atomic% or less, for example.

  When the metal content is less than 2 atomic%, or when the silicon content exceeds 45 atomic%, the etching selectivity with the glass substrate is deteriorated, which is not preferable. When the silicon content is less than 25 atomic% or the metal content is more than 10 atomic%, it is difficult to obtain a high transmittance of 10% to 40% as the transmittance at the exposure wavelength. In order to increase the transmittance, it is necessary to reduce the film thickness. In this case, however, the phase difference becomes small, so it is necessary to dig deep into the glass substrate when creating a halftone phase shift mask. . In order to dig deep into the glass substrate, the etching time increases, which is not preferable because the optical characteristics change due to damage to the surface of the light-shielding film by the etchant of the glass substrate. When the nitrogen content is more than 70 atomic%, the etching rate becomes extremely fast and it is difficult to control the pattern line width, which is not preferable. When the nitrogen content is less than 45%, the phase difference in the halftone film becomes small. Therefore, it is necessary to dig deep into the glass substrate when creating a halftone phase shift mask. In order to dig deep into the glass substrate, the etching time increases, which is not preferable because the optical characteristics change due to damage to the surface of the light-shielding film by the etchant of the glass substrate.

  (Configuration 4) The metal includes at least one of molybdenum (Mo), zirconium (Zr), tungsten (W), titanium (Ti), and nickel (Ni). If comprised in this way, the phase difference of the transmitted light of a light transmissive part and the transmitted light of a semi-transmissive part can be appropriately made into about 180 degrees.

  (Structure 5) A halftone phase shift mask manufactured using the mask blank according to any one of Structures 1 to 4, wherein a light-shielding portion formed by patterning the light-shielding film, and a halftone film A semi-transparent portion formed by patterning and a light transmissive portion formed by etching the glass substrate in a region where the halftone film and the light-shielding film are removed. If comprised in this way, the effect similar to the structures 1-4 can be acquired.

  According to the present invention, it is possible to appropriately suppress the deterioration of the cross-sectional shape of the light shielding film and the fluctuation of the optical characteristics of the light shielding film when the glass substrate is etched.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 shows an example of the configuration of a mask blank 10 according to an embodiment of the present invention. The mask blank 10 is a mask blank for a tritone type halftone phase shift mask. The mask blank 10 is used for manufacturing a halftone phase shift mask for exposure light having a wavelength of 200 nm or less (for example, 140 to 200 nm). The exposure light having a wavelength of 200 nm or less is exposure light such as ArF excimer laser (193 nm) and F ₂ excimer laser (157 nm). The mask blank 10 includes a glass substrate 12, a halftone film 14, a light shielding film 16, and a resist film 18. The glass substrate 12 is translucent and is made of, for example, synthetic quartz.

  The halftone film 14 is a metal silicide nitride film. For example, the metal (at least one of Mo, Zr, W, Ti, and Ni) is about 2 to 10 atomic%, and silicon (Si) is about 25 to 45. It is made of a material containing about 45% to 70% by atom of nitrogen (N). Further, the halftone film 14 is formed to have a film thickness with a transmittance of 10% to 40% and a phase shift amount of transmitted light of 140 ° or less. The film thickness of the halftone film 14 is, for example, about 150 to 600 angstroms. If the film thickness of the halftone film 14 is thin, the defect inspection accuracy tends to decrease, and if the film thickness of the halftone film 14 is thick, the etching time tends to increase, and the optical characteristics of the light shielding film vary. More preferably, the thickness is about 250 to 450 angstroms.

  The content of each element in the halftone film 14 is a value measured by Rutherford backscattering analysis (RBS) method, for example. The phase shift amount of the halftone film 14 is, for example, 15 to 140 °, more preferably 30 to 140 °.

  The light shielding film 16 is a chromium-based film having at least a layer containing nitrogen and chromium. For example, a chromium nitride layer (CrN layer), a chromium carbonitride layer (CrCN layer), and a chromium oxynitride layer (CrON layer) are included. The structure is formed on the halftone film 14 in this order. In this case, for example, the chromium nitride layer improves adhesion to the halftone film. The chromium carbonitride layer enhances the light shielding property of the light shielding film. The chromium oxynitride layer has an antireflection function. The film thickness of the light shielding film 16 is set to a film thickness of 3 or more in optical density in combination with the halftone film 14, and is, for example, about 400 to 1200 angstroms, and more preferably about 500 to 800 angstroms. Each layer constituting the light shielding film 16 may be a composition gradient film. Further, the resist film 18 is formed on the light shielding film 16, and serves as an etching mask for patterning the light shielding film 16 in the manufacturing process of the halftone phase shift mask.

FIG. 2 shows an example of a manufacturing method for manufacturing the halftone phase shift mask 20 using the mask blank 10. In this manufacturing method, first, as shown in FIG. 2A, a mask blank 10 is prepared. Then, as shown in FIG. 2B, the resist film 18 is patterned by using, for example, an electron beam exposure method. As shown in FIG. 2C, the light shielding film 16 is dried using the resist film as an etching mask. The light shielding film 16 is patterned by etching. The light shielding film 16 is patterned by, for example, dry etching using a chlorine-based etching gas. The chlorine-based etching gas is, for example, Cl ₂ , BCL ₃ , HCL, a mixed gas thereof, or a gas containing O _{2 or} a rare gas (He, Ar, Xe) as an additive gas.

Next, as shown in FIG. 2D, after the resist film 18 is peeled and removed, the halftone film 14 and the glass substrate 12 are cleaned with a fluorine-based etching gas using the patterned light-shielding film 16 as an etching mask. Etching is continued by the dry etching used. Examples of the fluorine-based etching gas include CxF (CF ₄ , C ₂ F ₆ , C ₃ F _8, etc.), CHF ₃ , SF ₆ , a mixed gas thereof, or an additive gas such as O ₂ , a rare gas ( He, Ar, Xe) and the like. In this etching, the resist film 18 may be removed.

  Here, in this etching step, the etching amount of the glass substrate 12 is appropriately set according to the phase shift amount of the halftone film 14. For example, when the phase shift amount of the halftone film 14 is 100 °, the glass substrate 12 on which the halftone film 14 is not formed is removed by etching by an amount corresponding to the phase shift amount of 80 °. In this way, in the halftone phase shift mask 20, the phase difference between the transmitted light of the light transmitting portion and the transmitted light of the semi-transmitting portion can be appropriately made approximately 180 °.

  Then, after the halftone film 14 and the glass substrate 12 are etched, the resist film 18 is recoated and patterned (not shown), and the light shielding film 16 is further patterned as shown in FIG. . The portion from which the light shielding film 16 and the halftone film 14 are removed by the above process becomes the light transmission portion 22 of the tritone type halftone phase shift mask. Further, the portion where the light shielding film 16 is removed and the patterned halftone film 14 remains becomes a semi-translucent portion 24. The portion where the patterned light shielding film 16 remains is a light shielding portion 26. The light shielding part 26 is formed in a region excluding the vicinity of the boundary between the light transmission part 22 and the semi-light transmission part 24, for example. Thereby, the halftone type phase shift mask 20 including the light transmission part 22, the semi-transmission part 24, and the light shielding part 26 can be appropriately manufactured.

Example 1
In this example, a manufacturing method in the case of corresponding to ArF excimer laser exposure (wavelength 193 nm) in the halftone phase shift mask of the present invention is shown. On a synthetic quartz glass substrate, a MoSi target was used, and Ar and N ₂ were used as sputtering gases to form a MoSiN halftone film of 384 Å. The composition of the halftone film measured by Rutherford backscattering analysis (RBS) was a composition containing 4.2 atomic% molybdenum, 35.8 atomic% silicon, and 60 atomic% nitrogen. Further, the transmittance of the halftone film with respect to the exposure light (wavelength 193 nm) was 20%, and the phase shift amount was 100 °. The transmittance and the phase shift amount of the halftone film were measured with a phase shift amount measuring apparatus (MPM193: manufactured by Lasertec Corporation).

Next, using a Cr target, Ar gas and N ₂ gas are used as sputtering gas, CrN layer is 250 angstrom, then Ar gas, CH ₄ gas, and N ₂ gas are used as sputtering gas, CrCN layer is 330 angstrom, and then Ar gas is used. Then, a CrON layer was continuously formed in a thickness of 150 Å using NO gas as a sputtering gas. The surface reflectance at a wavelength of 193 nm on the surface of the light shielding film was 19%. The surface reflectance was measured with a spectrophotometer (U-4100: manufactured by Hitachi, Ltd.).

A mask blank was manufactured by forming a resist film on the light-shielding film, and then a halftone phase shift mask was manufactured by the method described with reference to FIG. Note that Cl ₂ + O ₂ was used as an etching gas for etching the light shielding film. Further, CF ₄ was used as an etching gas for etching the halftone film, and CF ₄ + O ₂ was used as an etching gas for etching the substrate. Further, the etching amount of the glass substrate 12 was set to an amount corresponding to 80 ° in terms of the phase shift amount.

  In Example 1, when the glass substrate was etched, there was no problem with deterioration of the cross-sectional shape of the light shielding film. Therefore, a halftone phase shift mask that satisfies the quality required for a mask blank for exposure light having a wavelength of 200 nm or less could be appropriately manufactured. Further, the surface reflectance at a wavelength of 193 nm on the surface of the light-shielding film hardly changed compared to the mask blank state.

(Comparative Example 1)
A halftone phase shift mask according to Comparative Example 1 was manufactured in the same manner as in Example 1 except that the halftone film was formed of a MoSiON film (including O ₂ : 20 atomic% or more). The film thickness of the MoSiON film was such that the transmittance was 20% as in Example 1.

  In Comparative Example 1, since the MoSi-based film containing oxygen was used as the halftone film, the time required for etching the halftone film was longer than that in Example 1. As a result, the time during which the light shielding film was exposed to the etching gas during etching of the glass substrate was increased, and the cross-sectional shape of the light shielding film was deteriorated as compared with Example 1. Further, the surface reflectance at a wavelength of 193 nm on the surface of the light-shielding film was slightly changed as compared with the mask blank state. Therefore, in Comparative Example 1, there is a possibility that a halftone phase shift mask that satisfies the quality required for a mask blank for exposure light having a wavelength of 200 nm or less cannot be appropriately manufactured.

(Comparative Example 2)
A halftone phase shift mask according to Comparative Example 2 was manufactured in the same manner as in Example 1 except that the light shielding film was formed of a laminated film of metal chromium and chromium oxide.

  In Comparative Example 2, the resistance of the light shielding film to the etching gas for etching the substrate was weaker than that of Example 1, and the cross-sectional shape of the light shielding film was deteriorated compared to Example 1. In addition, the surface reflectance at a wavelength of 193 nm on the surface of the light-shielding film was found to change by several percent compared to the mask blank state. Therefore, in Comparative Example 2, there is a possibility that a halftone phase shift mask that satisfies the quality required for a mask blank for exposure light having a wavelength of 200 nm or less cannot be appropriately manufactured.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The present invention can be suitably used for, for example, a mask blank and a halftone type phase shift mask.

It is a figure showing an example of composition of mask blank 10 concerning one embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a manufacturing method for manufacturing a halftone phase shift mask 20 using a mask blank 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mask blank, 12 ... Glass substrate, 14 ... Halftone film, 16 ... Light-shielding film, 18 ... Resist film, 20 ... Halftone type phase shift mask, 22 ...・ Light transmission part, 24 ... Semi-transmission part, 26 ... Light-shielding part

Claims (5)

A half for exposure light having a wavelength of 200 nm or less, comprising: a light transmission part that transmits exposure light; a semi-transmission part that transmits a part of the exposure light and simultaneously shifts the phase of the transmission light; and a light shielding part. A mask blank for manufacturing a tone type phase shift mask,
A translucent glass substrate;
A halftone film formed on the glass substrate;
A light-shielding film formed on the halftone film,
The halftone film is mainly composed of metal, silicon (Si), and nitrogen (N) having a film thickness such that the transmittance at the exposure wavelength is 10% to 40% and the phase shift amount of transmitted light is 140 ° or less. A membrane as a component,
The light shielding film has at least a layer containing nitrogen and chromium,
In the manufacturing process of the halftone phase shift mask,
The light shielding part is formed by patterning the light shielding film,
The semi-translucent portion is formed by patterning the halftone film,
The light transmission part is formed by removing the halftone film and the light shielding film,
The glass substrate is etched so that the phase difference between the transmitted light of the light transmitting portion and the transmitted light of the semi-transmitting portion is approximately 180 °. Mask blank. In the manufacturing process of the halftone phase shift mask,
The mask blank according to claim 1, wherein the halftone film and the glass substrate are etched by dry etching using a fluorine-based etching gas with the patterned light-shielding film as an etching mask.   3. The mask blank according to claim 1, wherein the halftone film is made of a material containing 2 to 10 atomic% of metal, 25 to 45 atomic% of silicon, and 45 to 70 atomic% of nitrogen.   4. The metal according to claim 1, wherein the metal includes at least one of molybdenum (Mo), zirconium (Zr), tungsten (W), titanium (Ti), and nickel (Ni). Mask blank. A halftone phase shift mask manufactured using the mask blank according to any one of claims 1 to 4,
A light shielding portion formed by patterning the light shielding film;
A semi-translucent portion formed by patterning the halftone film;
A halftone phase shift mask comprising: a light transmission portion formed by etching the glass substrate in a region where the halftone film and the light shielding film are removed.

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