JP2018205769A - Mask blank, transfer mask, and semiconductor device manufacturing method - Google Patents

Abstract

Provided is a mask blank in which a light shielding film composed of a single layer film formed of a silicon nitride material has high light shielding performance against ArF exposure light and can reduce EMF bias of a pattern of the light shielding film. To do. A mask blank includes a light-shielding film on a light-transmitting substrate. The light shielding film has an optical density of 3.0 or more with respect to ArF exposure light. The refractive index n and the extinction coefficient k for ArF exposure light of the light shielding film satisfy the relationship defined by the following formulas (1), (2), and (3) simultaneously. n ≦ 0.0733 × k2 + 0.4069 × k + 1.0083 Formula (1) n ≧ 0.0637 × k2−0.1096 × k + 0.9585 Formula (2) n ≧ 0.7929 × k2− 2.1606 × k + 2.1448 Formula (3) [Selection] FIG.

Description

  The present invention relates to a mask blank, a transfer mask manufactured using the mask blank, and a semiconductor device manufacturing method using the transfer mask.

  Generally, in a semiconductor device manufacturing process, a fine pattern is formed using a photolithography method. Also, a number of transfer masks are usually used for forming this fine pattern. When miniaturizing a semiconductor device pattern, it is necessary to shorten the wavelength of an exposure light source used in photolithography in addition to miniaturization of a mask pattern formed on a transfer mask. In recent years, the exposure light source used in the manufacture of semiconductor devices has been shortened from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm).

  One type of transfer mask is a halftone phase shift mask. A molybdenum silicide (MoSi) -based material is widely used for the phase shift film of the halftone phase shift mask. However, as disclosed in Patent Document 1, it has recently been found that the MoSi-based film has low resistance to ArF excimer laser exposure light (hereinafter referred to as ArF exposure light) (so-called ArF light resistance). . In Patent Document 1, plasma treatment, UV irradiation treatment, or heat treatment is performed on the MoSi-based film after the pattern is formed, and a passive film is formed on the surface of the MoSi-based film pattern. Sexuality is enhanced.

  On the other hand, Patent Document 2 discloses a phase shift mask including a phase shift film made of SiN, and Patent Document 3 describes that it has been confirmed that a phase shift film made of SiN has high ArF light resistance. Has been.

JP 2010-217514 A JP-A-7-159981 JP 2014-137388 A

  The problem of ArF light resistance in a transfer mask is not limited to a phase shift mask, but also occurs in a binary mask. In recent years, miniaturization of a light shielding pattern of a binary mask has been advanced. The light-shielding film of chromium-based material that has been widely used in the past can be subjected to patterning by dry etching with a relatively low anisotropy etching gas (a mixed gas of chlorine-based gas and oxygen gas), and can meet the demand for miniaturization. It's getting harder. Therefore, in recent years, molybdenum silicide-based materials have begun to be used for light shielding films of mask blanks for manufacturing binary masks. However, as described above, the transition metal silicide-based material thin film has a problem of low ArF light resistance. To solve this problem, as in the case of the phase shift film, the simplest approach is to apply a silicon nitride-based material to the light shielding film of the binary mask. The light shielding film of the binary mask is required to have high light shielding performance against ArF exposure light (for example, an optical density (OD) of 3.0 or more with respect to ArF exposure light). Further, the light shielding film of the binary mask has a surface reflectance (reflectance of the surface opposite to the substrate of the light shielding film) and a back surface reflectance (surface of the light shielding film on the substrate side) with respect to ArF exposure light as compared with the phase shift film. (Reflectance) tends to be high. In the case of a conventional chromium-based material or transition metal silicide-based material light-shielding film, the light-shielding film has a laminated structure of a light-shielding layer and an antireflection layer to reduce the surface reflectance and back surface reflectance for ArF exposure light. Yes. Silicon nitride-based materials have lower light shielding performance against ArF exposure light than chromium-based materials and transition metal silicide-based materials.

  In recent binary masks, when the pattern thickness of the light shielding film is large, a bias (a correction amount of a pattern line width or the like, hereinafter referred to as an EMF bias) due to an electromagnetic field (EMF) effect is large. The problem of becoming. In order to reduce the EMF bias of the pattern of the light shielding film, the thickness of the light shielding film is reduced and the phase difference of the light shielding film (exposure light passing through the light shielding film is transmitted through the air by the same distance as the thickness of the light shielding film). It is effective to reduce the phase difference between the exposure light and the exposure light.

  When the light shielding film is formed of a silicon nitride material having a relatively low light shielding performance, it is necessary to increase the thickness of the light shielding film in order to ensure high light shielding performance. For this reason, it is not easy to reduce the EMF bias of the pattern of the light shielding film, which has been a problem.

  The EMF bias greatly affects the CD accuracy of the transfer pattern line width to the resist on the wafer. For this reason, it is necessary to perform a simulation of an electromagnetic field effect and to correct a transfer pattern produced on a transfer mask for suppressing the influence of an EMF bias. This transfer pattern correction calculation becomes more complicated as the EMF bias increases. Further, the corrected transfer pattern becomes more complicated as the EMF bias is larger, and a larger load is imposed on the production of the transfer mask.

  Therefore, the present invention has been made to solve the conventional problems, and is composed of a single layer film made of a silicon nitride material in a mask blank provided with a light shielding film on a light transmitting substrate. Another object of the present invention is to provide a mask blank in which the light shielding film has high light shielding performance against ArF exposure light and can reduce the EMF bias of the pattern of the light shielding film. Another object of the present invention is to provide a transfer mask manufactured using the mask blank. Furthermore, an object of the present invention is to provide a method of manufacturing a semiconductor device using such a transfer mask.

  In order to achieve the above object, the present invention has the following configuration.

(Configuration 1)
A mask blank provided with a light shielding film on a translucent substrate,
The light-shielding film is a single layer film formed of a material consisting of silicon and nitrogen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and nitrogen,
The light shielding film has an optical density of 3.0 or more with respect to the exposure light of the ArF excimer laser,
A mask blank, wherein a refractive index n and an extinction coefficient k of the light shielding film with respect to the exposure light simultaneously satisfy a relationship defined by the following formulas (1) and (2).
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)

(Configuration 2)
The mask blank according to Configuration 1, wherein the light shielding film has an extinction coefficient k of 2.6 or less.

(Configuration 3)
The mask blank according to Configuration 1 or 2, wherein the light shielding film has a refractive index n of 0.8 or more.

(Configuration 4)
4. The mask blank according to claim 1, wherein the refractive index n and the extinction coefficient k of the light shielding film further satisfy a relationship defined by the following formula (3).
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)

(Configuration 5)
The variation of the nitrogen content in the thickness direction in the region excluding the surface layer on the translucent substrate side and the surface layer on the opposite side of the translucent substrate is within 5 atomic% of the light shielding film. The mask blank according to any one of configurations 1 to 4.

(Configuration 6)
The mask blank according to any one of configurations 1 to 5, further comprising a hard mask film made of a material containing chromium on the light shielding film.

(Configuration 7)
A transfer mask provided with a light-shielding film having a transfer pattern on a translucent substrate,
The light-shielding film is a single layer film formed of a material consisting of silicon and nitrogen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and nitrogen,
The light shielding film has an optical density of 3.0 or more with respect to the exposure light of the ArF excimer laser,
The transfer mask, wherein a refractive index n and an extinction coefficient k of the light shielding film with respect to the exposure light simultaneously satisfy a relationship defined by the following formulas (1) and (2).
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)

(Configuration 8)
8. The transfer mask according to Configuration 7, wherein the light shielding film has an extinction coefficient k of 2.6 or less.

(Configuration 9)
9. The transfer mask according to Configuration 7 or 8, wherein the light shielding film has a refractive index n of 0.8 or more.

(Configuration 10)
The transfer mask according to any one of Structures 7 to 9, wherein the refractive index n and the extinction coefficient k of the light shielding film further satisfy a relationship defined by the following formula (3).
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)

(Configuration 11)
The variation of the nitrogen content in the thickness direction in the region excluding the surface layer on the translucent substrate side and the surface layer on the opposite side of the translucent substrate is within 5 atomic% of the light shielding film. The transfer mask according to any one of configurations 7 to 10.

(Configuration 12)
A method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the transfer mask according to any one of Structures 7 to 11.

The mask blank of the present invention is provided with a light-shielding film on a translucent substrate, the light-shielding film is a single layer film formed of a silicon nitride material, and has an optical density of 3.0 or more with respect to ArF exposure light. And the refractive index n and the extinction coefficient k of the light-shielding film with respect to ArF exposure light simultaneously satisfy the relationship defined by the following expressions (1) and (2). With such a configuration of the light shielding film, the optical density of the light shielding film with respect to ArF exposure light is 3.0 or more, and the refractive index n and the extinction coefficient k of the light shielding film with respect to ArF exposure light are expressed by the following equations: Since the relationship defined by (1) and Equation (2) is satisfied at the same time, the light shielding film has high light shielding performance against ArF exposure light, and the EMF bias of the pattern of the light shielding film can be reduced.
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)

  The transfer mask of the present invention is characterized in that the light shielding film having a transfer pattern has the same configuration as the light shielding film of the mask blank of the present invention. By using such a transfer mask, the EMF bias of the pattern of the light shielding film is reduced, so that it can be manufactured without applying a large load.

It is a figure which shows the relationship between the refractive index n and the extinction coefficient k, the film thickness d, phase difference (phi), and surface reflectance Rf derived | led-out from the simulation result. It is a figure which shows the relationship between the refractive index n and the extinction coefficient k and the surface reflectance Rf and back surface reflectance Rb which were derived | led-out from the simulation result. It is sectional drawing which shows the structure of the mask blank in embodiment of this invention. It is sectional drawing which shows the manufacturing process of the transfer mask in embodiment of this invention.

  First, the background to the completion of the present invention will be described.

  When a light-shielding film is formed of a silicon-based material that does not contain oxygen or nitrogen (for example, a material made of silicon) that causes the light-shielding performance to deteriorate, a predetermined optical density (for example, optical density (OD) with respect to ArF exposure light) 3.0 or more) can be formed with a thinner film thickness. However, silicon atoms that are not bonded to other elements tend to bond with oxygen in the air. When a mask blank having a light-shielding film made of silicon is manufactured on a light-transmitting substrate, oxidation proceeds when left in the air after the manufacture, and this is largely due to the initial optical characteristics (especially the light-shielding performance) formed by the light-shielding film. The problem of changing.

On the other hand, in the process of manufacturing a transfer mask from a recent mask blank, when a black defect is detected as a result of performing a mask inspection on the pattern of the light shielding film, the black defect is corrected by an EB defect correction technique. Is widely practiced. In this EB defect correction, a black defect is removed by irradiating the black defect portion with an electron beam while supplying a non-excited fluorine-based gas such as XeF ₂ gas around the black defect. This EB defect correction is performed by etching the non-excited fluorine-based gas of the portion of the light-shielding film (black defect portion) excited by the electron beam irradiation and the non-excited fluorine-based portion of the non-excited light-shielding film. By sufficiently ensuring an etching rate difference from the etching rate with respect to the gas, only the black defect portion can be removed. A silicon-based material that does not contain oxygen or nitrogen has low resistance to this non-excited fluorine-based gas, and etching (this is called spontaneous etching) even in a state where it is not irradiated with an electron beam (not excited). ) Is easy to progress. For this reason, the light-shielding film made of a silicon-based material that does not contain oxygen or nitrogen has a problem that, when EB defect correction is performed, spontaneous etching of the pattern side walls of the light-shielding film other than black defects is likely to proceed.

  Because of the above two problems, it is necessary to apply a material containing silicon or nitrogen or oxygen as a material for forming the light shielding film. A material in which oxygen is contained in silicon has a remarkable decrease in light shielding performance as compared with a material in which nitrogen is contained in silicon. Considering these matters, it can be said that when the light shielding film is formed of a silicon-based material, it is preferable to apply a material containing silicon in nitrogen (silicon nitride-based material). The light-shielding film made of a silicon nitride-based material, as the nitrogen content in the film increases, the extinction coefficient k (hereinafter simply referred to as the extinction coefficient k) of the light-shielding film with respect to ArF exposure light decreases. There is a characteristic that the refractive index n (hereinafter simply referred to as refractive index n) for ArF exposure light increases. As the extinction coefficient k of the light shielding film decreases, the optical density of the light shielding film decreases, so that it is necessary to increase the thickness of the light shielding film in order to ensure a predetermined optical density in the light shielding film. Further, as the refractive index n of the light shielding film increases, the phase difference of the light shielding film increases. Both an increase in the refractive index n and a decrease in the extinction coefficient k of the light shielding film lead to an increase in the EMF bias of the light shielding film. For this reason, it is necessary to control the refractive index n and extinction coefficient k of the light-shielding film made of the silicon nitride-based material to be in a predetermined range.

  Here, the inventors say that the EMF bias is sufficiently reduced while the light shielding film of the mask blank for manufacturing the binary mask has a predetermined optical density (OD = 3.0 or more). Intensive research was conducted on the relationship between the refractive index n and the extinction coefficient k of a light-shielding film that can simultaneously satisfy two conditions. As a result, with the light shielding film having the structure shown below, it was concluded that a predetermined optical density with respect to ArF exposure light could be secured, and that the EMF bias of the light shielding film could be sufficiently reduced, and the present invention was completed.

  In completing the present invention, first, an optical simulation of a light shielding film was performed. In the optical simulation, it is assumed that the exposure light is an ArF excimer laser, the light-shielding film is a single-layered thin film made of an optically uniform material, the refractive index n is in the range of 0.8 to 2.6, and the extinction coefficient k. In the range of 1.0 to 2.6, the phase difference φ and the surface in the film thickness d when the optical density (OD) is 3.0 while changing the respective values of the refractive index n and the extinction coefficient k. The reflectance Rf and the back surface reflectance Rb were obtained.

  Thereafter, based on the simulation results, the relationship between the refractive index n and the extinction coefficient k and the phase difference φ, the relationship between the refractive index n and the extinction coefficient k and the film thickness d, the refractive index n and the extinction coefficient k, The relationship with the surface reflectance Rf and the relationship between the refractive index n, the extinction coefficient k, and the back surface reflectance Rb were arranged. Based on the organized relationship, the relationship between the refractive index n and the extinction coefficient k in each of the cases where the phase difference φ is 90 degrees, 80 degrees, 0 degrees, and −20 degrees (FIG. 1), and the film thickness d is Relationship between refractive index n and extinction coefficient k in each case of 80 nm, 70 nm and 60 nm (FIG. 1), refractive index n and extinction in each case where surface reflectance Rf is 50%, 45% and 40% The relationship with the coefficient k (FIGS. 1 and 2) and the relationship between the refractive index n and the extinction coefficient k (FIG. 2) when the back surface reflectance Rb is 50%, 45%, and 40%, respectively, are obtained. It was. FIG. 1 and FIG. 2 are plots of the relationship thus obtained.

  FIG. 1 is a diagram showing the relationship between the refractive index n and the extinction coefficient k, the film thickness d, the phase difference φ, and the surface reflectance Rf derived from the simulation results. FIG. 2 is a diagram showing the relationship between the refractive index n and the extinction coefficient k, the surface reflectance Rf, and the back surface reflectance Rb, which are derived from the simulation results. 1 and 2 also show approximate curves obtained from the respective relationships. In addition, the data used in order to obtain the approximate curves of the following formulas (a) to (m) are data plotted in FIGS. 1 and 2. Each approximate curve below varies somewhat depending on the calculation method. However, the variation in the range of the refractive index n and the extinction coefficient k caused by the variation of the approximate expression has little influence on the phase difference, film thickness, front surface reflectance, and rear surface reflectance of the light shielding film, and is within an allowable range. is there.

The approximate curve shown in FIG. 1 when the phase difference φ is 90 degrees is expressed by the following equation (a), and the approximate curve when the phase difference φ is 80 degrees is expressed by the following equation (b): The approximate curve when the phase difference φ is −20 degrees is expressed by the following formula (c), and the approximate curve when the phase difference φ is 0 degrees is expressed by the following formula (d). Represented.
n = 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (a)
n = 0.0966 × k ² + 0.3660 × k + 0.9956 Formula (b)
n = 0.0637 × k ² −0.1096 × k + 0.9585 (formula (c))
n = 0.0636 × k ² −0.0147 × k + 0.9613 Expression (d)

The approximate curve when the film thickness d is 80 nm shown in FIG. 1 is expressed by the following formula (e), and the approximate curve when the film thickness d is 70 nm is expressed by the following formula (f). The approximate curve when the film thickness d is 60 nm is expressed by the following equation (g).
n = 29.316 × k ² −92.292 × k + 72.671 Formula (e)
n = 23.107 × k ² −82.037 × k + 73.115 Formula (f)
n = 12.717 × k ² −54.382 × k + 58.228 Expression (g)

The approximate curve when the surface reflectance Rf is 50% shown in FIG. 1 and FIG. 2 is represented by the following formula (h), and the approximate curve when the surface reflectance Rf is 45% is The approximate curve when the surface reflectance Rf is 40% is expressed by the following formula (j). In obtaining an approximate curve of formula (i), data of two points plotted with a refractive index n from about 2.4 to about 2.6 is not used. Further, in obtaining the approximate curve of the formula (j), one point of data in which the refractive index n is plotted from around 2.4 to around 2.6 is not used.
n = 0.7929 × k ² −2.1606 × k + 2.1448 Formula (h)
n = 1.71717 * k < ³ > -9.1446 * k < ² +> + 16.519 * k-9.5626 ... Formula (i)
n = 15.539 × k ⁴ −103.999 × k ³ + 260.83 × k ² −289.22 × k + 120.12 Formula (j)

The approximate curve when the back surface reflectance Rb is 50% shown in FIG. 2 is expressed by the following equation (k), and the approximate curve when the back surface reflectance Rb is 45% is the following equation ( The approximate curve when the back surface reflectance Rb is 40% is expressed by the following equation (m).
n = 0.6198 × k ² −2.17996 × k + 2.6451 Formula (k)
n = 0.2357 × k ² −0.2976 × k + 0.5410 Formula (l)
n = 0.3457 × k ² −0.5539 × k + 0.8005 Formula (m)

The following formula (1) shows conditions necessary for setting the phase difference φ of the light shielding film (OD = 3.0) in ArF exposure light to 90 degrees or less. The following formula (2) shows the conditions necessary to make the thickness of the light shielding film (OD = 3.0) 80 nm or less. The following formula (3) shows the conditions necessary to make the surface reflectance of the light shielding film (OD = 3.0) with respect to ArF exposure light 50% or less.
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)

  When simultaneously satisfying the relationship of Expression (1) and Expression (2), the thickness of the light shielding film having an OD of 3.0 can be made 80 nm or less, and the phase difference φ of the light shielding film can be made 90 degrees or less. Therefore, the EMF bias of the pattern of the light shielding film is reduced, and the load when manufacturing the transfer mask from the mask blank having the light shielding film is also reduced. Furthermore, when the relationship of the expression (3) is satisfied, the surface reflectance of the light shielding film having an OD of 3.0 can be reduced to 50% or less, so that it is easy to suppress the deterioration of the projected optical image at the time of transfer exposure. As shown in FIG. 2, when the surface reflectance is 50% or less, the back surface reflectance is also 50% or less. Therefore, when the relationship of Expression (3) is satisfied, the transfer exposure due to the back surface reflection of the light shielding film. It is easy to suppress the deterioration of the projection optical image at the time.

The following formula (4) shows conditions necessary for setting the phase difference φ of the light shielding film (OD = 3.0) in ArF exposure light to 80 degrees or less. The following formula (5) shows conditions necessary for setting the phase difference φ of the light-shielding film (OD = 3.0) in ArF exposure light to −20 degrees or more, and the following formula (6) is ArF exposure. Conditions necessary for setting the phase difference φ of the light-shielding film (OD = 3.0) in light to 0 ° or more are shown.
n ≦ 0.0966 × k ² + 0.3660 × k + 0.9956 Expression (4)
n ≧ 0.0637 × k ² −0.1096 × k + 0.9585 (5)
n ≧ 0.0636 × k ² −0.0147 × k + 0.9613 (6)

When satisfying the relationship of Expression (4), the phase difference φ of the light shielding film having an OD of 3.0 can be set to 80 degrees or less, so that the EMF bias of the pattern of the light shielding film is further reduced. The load at the time of manufacturing a transfer mask from the mask blank is also reduced.
When satisfying the relationship of Expression (5), the phase difference φ of the light shielding film having an OD of 3.0 can be set to −20 degrees or more, and when satisfying the relationship of Expression (6), the OD is 3.0. The phase difference φ of a certain light shielding film can be set to 0 degree or more.

The following formula (7) shows the conditions necessary to make the film thickness of the light shielding film (OD = 3.0) 70 nm or less, and the following formula (8) is the light shielding film (OD = 3. The conditions necessary to make the film thickness of 0) 60 nm or less are shown.
n ≧ 23.107 × k ² −82.037 × k + 73.115 (7)
n ≧ 12.717 × k ² −54.382 × k + 58.228 (8)

  When the relationship of Expression (7) is satisfied, since the film thickness of the light shielding film having an OD of 3.0 can be made 70 nm or less, the EMF bias of the pattern of the light shielding film is further reduced, and Expression (8) When the above relationship is satisfied, the thickness of the light shielding film having an OD of 3.0 can be reduced to 60 nm or less, so that the EMF bias of the pattern of the light shielding film is further reduced.

The following formula (9) shows the conditions necessary to make the surface reflectance of the light-shielding film (OD = 3.0) with respect to ArF exposure light 45% or less, and the following formula (10) is ArF exposure light. The conditions necessary to make the surface reflectance of the light-shielding film (OD = 3.0) to 40% or less are shown.
n ≧ 1.7717 × k ³ −9.1446 × k ² + 16.519 × k−9.5626 Expression (9)
n ≧ 15.539 × k ⁴ −103.99 × k ³ + 260.83 × k ² −289.22 × k + 120.12 Formula (10)

  When the relationship of formula (9) is satisfied, the surface reflectance of the light-shielding film having an OD of 3.0 can be reduced to 45% or less, so that it is easier to suppress deterioration of the projected optical image during transfer exposure. When satisfying the relationship of the formula (10), the surface reflectance of the light shielding film having an OD of 3.0 can be made 40% or less, so that the deterioration of the projected optical image at the time of transfer exposure can be further suppressed. As shown in FIG. 2, when the surface reflectance is 45% or less, the back surface reflectance is also 45% or less. Therefore, when the relationship of the formula (9) is satisfied, the transfer exposure due to the back surface reflection is performed. It is easier to suppress the deterioration of the projected optical image, and when the surface reflectance is 40% or less, the back surface reflectance is also 40% or less. Therefore, when satisfying the relationship of Expression (10), transfer exposure caused by back surface reflection It is easier to suppress the deterioration of the projection optical image at the time.

Next, each embodiment of the present invention will be described.
FIG. 3 is a cross-sectional view showing the configuration of the mask blank 100 according to the embodiment of the present invention.
A mask blank 100 shown in FIG. 3 has a structure in which a light-shielding film 2 and a hard mask film 3 are laminated in this order on a translucent substrate 1.

[[Translucent substrate]]
The translucent substrate 1 is made of a material containing silicon and oxygen, and is formed of a glass material such as synthetic quartz glass, quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass or the like). can do. Among these, synthetic quartz glass has a high transmittance with respect to ArF exposure light, and is particularly preferable as a material for forming a light-transmitting substrate of a mask blank.

[[Light shielding film]]
The light shielding film 2 is a single layer film formed of a silicon nitride material. The silicon nitride-based material in the present invention is a material composed of silicon and nitrogen, or a material composed of silicon and nitrogen, one or more elements selected from metalloid elements and nonmetallic elements. In addition, by using a single layer film, the number of manufacturing steps is reduced, the production efficiency is increased, and manufacturing quality control including defects is facilitated. Moreover, since the light shielding film 2 is formed of a silicon nitride material, it has high ArF light resistance.

  The light shielding film 2 may contain any metalloid element in addition to silicon. Among these metalloid elements, it is preferable to include one or more elements selected from boron, germanium, antimony, and tellurium, because the conductivity of silicon used as a sputtering target can be expected to be increased.

  The light shielding film 2 may contain any nonmetallic element in addition to nitrogen. The nonmetallic element in the present invention refers to a substance containing a nonmetallic element (nitrogen, carbon, oxygen, phosphorus, sulfur, selenium, hydrogen), halogen (fluorine, chlorine, bromine, iodine, etc.) and a noble gas in a narrow sense. Among these nonmetallic elements, it is preferable to contain one or more elements selected from carbon, fluorine and hydrogen. The light-shielding film 2 preferably has an oxygen content of 5 atomic% or less, except for a surface layer on the side of the light-transmitting substrate 1 described later and a surface layer opposite to the light-transmitting substrate 1. More preferably, it is more preferable not to actively contain oxygen (below the lower limit of detection when composition analysis is performed by X-ray photoelectron spectroscopy or the like). When oxygen is contained in the silicon nitride-based material, the extinction coefficient k decreases, and it becomes difficult to obtain sufficient light shielding performance. The translucent substrate 1 is generally formed of a material mainly composed of silicon oxide such as synthetic quartz glass. When the light-shielding film 2 is disposed in contact with the surface of the light-transmitting substrate 1, when the light-shielding film 2 contains oxygen, the difference between the composition of the silicon nitride-based material film containing oxygen and the composition of the light-transmitting substrate is small. Thus, in dry etching using a fluorine-based gas performed when forming a pattern on the light-shielding film 2, it is difficult to obtain etching selectivity between the light-shielding film 2 in contact with the light-transmissive substrate 1 and the light-transmissive substrate 1. Sometimes. In addition, when the oxygen content of the light shielding film 2 is large, the correction rate when the EB defect is corrected is greatly reduced.

  The noble gas is an element that can increase the deposition rate and improve the productivity by being present in the deposition chamber when the light shielding film 2 is deposited by reactive sputtering. When this noble gas is turned into plasma and collides with the target, the target constituent element jumps out of the target, and the light shielding film 2 is formed on the light-transmitting substrate 1 while taking in the reactive gas in the middle. The noble gas in the film forming chamber is slightly taken in until the target constituent element jumps out of the target and adheres to the translucent substrate 1. Preferable noble gases required for this reactive sputtering include argon, krypton, and xenon. Moreover, in order to relieve the stress of the light shielding film 2, helium and neon having a small atomic weight may be actively incorporated into the light shielding film 2.

  The light shielding film 2 is preferably formed of a material composed of silicon and nitrogen. As described above, the noble gas is slightly taken in when the light shielding film 2 is formed by reactive sputtering. However, the noble gas can be detected even if the thin film is subjected to composition analysis such as Rutherford Backscattering Spectroscopy (RBS) or X-ray Photoelectron Spectroscopy (XPS). Is an element that is not easy. For this reason, it can be considered that the material composed of silicon and nitrogen includes a material containing a noble gas.

  The light shielding film 2 has a variation in the nitrogen content in the thickness direction in a region excluding the surface layer on the side of the light-transmitting substrate 1 and the surface layer on the side opposite to the light-transmitting substrate 1 (hereinafter referred to as a bulk region). It is preferably within atomic%, more preferably within 3 atomic%. If the variation is within 5 atomic%, it can be said that the composition is uniform. On the other hand, when the composition analysis by RBS or XPS is performed on the light-shielding film 2, the analysis result of the surface layer on the translucent substrate 1 side is affected by the translucent substrate 1, and therefore is the same as the bulk region. It is hard to become composition. In addition, the surface layer opposite to the light-transmitting substrate 1 is unlikely to have the same composition as the bulk region because natural oxidation occurs. Further, when the surface layer on the side opposite to the light-transmitting substrate 1 is positively incorporated with oxygen, the characteristics of the light-shielding film 2 change such as the change in surface reflectance with respect to ArF exposure light by mask cleaning or storage in the air. Can be suppressed. As a method of positively containing oxygen in the surface layer on the side opposite to the light-transmitting substrate 1, after the light shielding film 2 is formed by sputtering, heat treatment in a gas containing oxygen such as in the atmosphere, Examples include a method of adding a post-treatment such as a light irradiation treatment such as a flash lamp in a gas containing oxygen, such as a treatment of bringing ozone or oxygen plasma into contact with the surface of the light-shielding film. The surface layer on the light-transmitting substrate 1 side of the light-shielding film 2 refers to a region extending from the interface with the light-transmitting substrate 1 of the light-shielding film 2 to a depth of 5 nm from the opposite surface layer side. . Further, the surface layer of the light shielding film 2 on the side opposite to the light transmissive substrate 1 is from the surface opposite to the light transmissive substrate 1 of the light shielding film 2 to a depth of 5 nm toward the light transmissive substrate 1 side. An area that covers a range.

  The nitrogen content of the light shielding film 2 is preferably 50 atomic percent or less, and more preferably 45 atomic percent or less. When the nitrogen content exceeds 50 atomic%, the extinction coefficient k with respect to ArF exposure light becomes small, and it becomes difficult to obtain sufficient light shielding performance. Further, the nitrogen content of the light shielding film 2 is preferably 25 atomic% or more, and more preferably 30 atomic% or more. When the nitrogen content is less than 25 atomic%, the washing resistance tends to be insufficient, oxidation tends to occur, and the aging stability of the film tends to be impaired. Furthermore, when EB defect correction is performed on the light shielding film 2, spontaneous etching is likely to occur.

  The silicon content of the light shielding film 2 is preferably 50 atomic% or more, and more preferably 55 atomic% or more. When the silicon content is less than 50 atomic%, the extinction coefficient k with respect to ArF exposure light becomes small, and it becomes difficult to obtain sufficient light shielding performance. Further, the silicon content of the light shielding film 2 is preferably 75 atomic% or less, and more preferably 70 atomic% or less. When the nitrogen content exceeds 75 atomic%, the washing resistance tends to be insufficient, oxidation tends to occur, and the aging stability of the film tends to be impaired.

  The thickness of the light-shielding film 2 is 80 nm or less, preferably 70 nm or less, and more preferably 60 nm or less. When the thickness is 80 nm or less, it becomes easy to form a fine light-shielding film pattern, the EMF bias of the light-shielding film pattern is reduced, and a load when manufacturing a transfer mask from a mask blank having this light-shielding film Is also reduced. Further, the thickness of the light shielding film 2 is preferably 40 nm or more, and more preferably 45 nm or more. When the thickness is less than 40 nm, it is difficult to obtain sufficient light shielding performance for ArF exposure light.

  The optical density of the light shielding film 2 with respect to ArF exposure light is preferably 3.0 or more. When the optical density is 3.0 or more, sufficient light shielding performance can be obtained. For this reason, when exposure is performed using a transfer mask manufactured using this mask blank, a sufficient contrast of the projection optical image (transfer image) is easily obtained. Further, the optical density of the light shielding film 2 with respect to ArF exposure light is preferably 4.0 or less, and more preferably 3.5 or less. When the optical density exceeds 4.0, the thickness of the light-shielding film 2 becomes thick, and it becomes difficult to form a fine light-shielding film pattern.

  The surface reflectance of the light-shielding film 2 with respect to ArF exposure light (the reflectance on the surface opposite to the translucent substrate 1) is preferably 50% or less, more preferably 45% or less, and 40% or less. More preferably. If the surface reflectance exceeds 50%, the reflection of ArF exposure light becomes too large, and the projected optical image at the time of transfer exposure tends to deteriorate. The surface reflectance of the light shielding film 2 with respect to ArF exposure light is preferably 20% or more. When the surface reflectance is less than 20%, the pattern inspection sensitivity when performing mask pattern inspection using light having a wavelength of 193 nm or a wavelength in the vicinity thereof is lowered.

  The back surface reflectance of the light shielding film 2 with respect to ArF exposure light (the reflectance of the surface on the translucent substrate 1 side) is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less. preferable. If the back surface reflectance exceeds 50%, the reflection of the exposure light becomes too large, and the projection optical image at the time of transfer exposure tends to deteriorate.

  The phase difference of the light shielding film 2 with respect to ArF exposure light is 90 degrees or less, and preferably 80 degrees or less. When the phase difference is 90 degrees or less, the EMF bias of the pattern of the light shielding film 2 is reduced, and the load when manufacturing a transfer mask from the mask blank having the light shielding film is also reduced. Moreover, the phase difference of the light shielding film 2 with respect to ArF exposure light is preferably −20 degrees or more, and more preferably 0 degrees or more.

The refractive index n and extinction coefficient k of the light-shielding film 2 with respect to ArF exposure light satisfy the relationship defined by the following formulas (1) and (2). When the relationship of the formula (1) is satisfied, the phase difference of the light shielding film 2 with respect to the ArF exposure light can be 90 degrees or less, and when the relationship of the formula (2) is satisfied, the thickness of the light shielding film is set to 80 nm or less. be able to. For this reason, if the relationship of Formula (1) and Formula (2) is satisfied, the EMF bias of the pattern of the light shielding film 2 is reduced, and the load when manufacturing a transfer mask from the mask blank having the light shielding film is also reduced. The Moreover, it is preferable that the refractive index n and the extinction coefficient k with respect to ArF exposure light satisfy | fill the relationship prescribed | regulated to the following formula | equation (3). When the relationship of formula (3) is satisfied, the surface reflectance of the light shielding film 2 can be reduced to 50% or less, and as described above, the back surface reflectance of the light shielding film 2 can also be decreased to 50% or less. . For this reason, when the relationship of the expression (3) is satisfied, it becomes easy to suppress the deterioration of the projection optical image during the transfer exposure.
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)

It is preferable that the refractive index n and the extinction coefficient k of the light shielding film 2 with respect to ArF exposure light satisfy the relationship of the following formula (4). When the relationship of formula (4) is satisfied, the phase difference of the light shielding film 2 with respect to ArF exposure light can be made 80 degrees or less, the EMF bias of the pattern of the light shielding film 2 is further reduced, and the mask blank having this light shielding film Therefore, the load when manufacturing the transfer mask from the above is further reduced. Moreover, it is preferable that the refractive index n and the extinction coefficient k with respect to ArF exposure light satisfy | fill the relationship of the following formula | equation (5), and it is more preferable to satisfy | fill the relationship of the following formula | equation (6). When the relationship of the formula (5) is satisfied, the phase difference of the light shielding film 2 with respect to the ArF exposure light can be set to −20 degrees or more, and when the relationship of the formula (6) is satisfied, the level of the light shielding film 2 with respect to the ArF exposure light. The phase difference can be 0 degree or more.
n ≦ 0.0966 × k ² + 0.3660 × k + 0.9956 Expression (4)
n ≧ 0.0637 × k ² −0.1096 × k + 0.9585 (5)
n ≧ 0.0636 × k ² −0.0147 × k + 0.9613 (6)

The refractive index n and extinction coefficient k of the light-shielding film 2 with respect to ArF exposure light preferably satisfy the relationship of the following equation (7), and more preferably satisfy the relationship of the following equation (8). When the relationship of Expression (7) is satisfied, the thickness of the light shielding film can be reduced to 70 nm or less, the EMF bias of the pattern of the light shielding film 2 is further reduced, and a transfer mask is manufactured from the mask blank having the light shielding film. The load when doing so is also reduced. If the relationship of the following formula (8) is satisfied, the thickness of the light shielding film can be reduced to 60 nm or less, the EMF bias of the pattern of the light shielding film 2 is further reduced, and transfer from the mask blank having the light shielding film is performed. The load when manufacturing a mask for the use is further reduced.
n ≧ 23.107 × k ² −82.037 × k + 73.115 (7)
n ≧ 12.717 × k ² −54.382 × k + 58.228 (8)

The refractive index n and extinction coefficient k of the light-shielding film 2 with respect to ArF exposure light preferably satisfy the relationship of the following formula (9), and more preferably satisfy the relationship of the following formula (10). When the relationship of formula (9) is satisfied, the surface reflectance of the light shielding film 2 can be reduced to 45% or less, and as described above, the back surface reflectance of the light shielding film 2 can also be decreased to 45% or less. Further, it becomes easier to suppress the deterioration of the projection optical image during the transfer exposure. Further, when the relationship of the formula (10) is satisfied, the surface reflectance of the light shielding film 2 can be made 40% or less, and as described above, the back surface reflectance of the light shielding film 2 is made 40% or less. This makes it easier to suppress deterioration of the projected optical image during transfer exposure.
n ≧ 1.7717 × k ³ −9.1446 × k ² + 16.519 × k−9.5626 Expression (9)
n ≧ 15.539 × k ⁴ −103.99 × k ³ + 260.83 × k ² −289.22 × k + 120.12 Formula (10)

  The refractive index n of the light-shielding film 2 with respect to ArF exposure light is preferably 0.8 or more, more preferably 0.9 or more, and further preferably 1.0 or more. In order to make the refractive index n less than 0.8, it is necessary to significantly reduce the nitrogen content of the light shielding film 2. For this reason, if the refractive index is less than 0.8, spontaneous etching tends to occur when EB defect correction is performed.

  The extinction coefficient k of the light shielding film 2 with respect to ArF exposure light is preferably 2.6 or less, more preferably 2.5 or less, and even more preferably 2.4 or less. In order to make the extinction coefficient k exceed 2.6, it is necessary to significantly reduce the nitrogen content of the light shielding film 2. For this reason, if the extinction coefficient k exceeds 2.6, spontaneous etching tends to occur when EB defect correction is performed.

  In the light shielding film 2, oxidation of the surface layer on the side opposite to the translucent substrate 1 proceeds. For this reason, the surface layer of the light shielding film 2 is different in composition from the other regions of the light shielding film 2, and the optical characteristics are also different. However, in this specification, the light shielding film 2 is treated as a single layer film having uniform optical characteristics in the film thickness direction. Therefore, in this specification, the refractive index n and the extinction coefficient k of the light shielding film 2 refer to the refractive index n and the extinction coefficient k of the entire light shielding film 2 including the surface layer.

  The refractive index n and extinction coefficient k of a thin film are not determined only by the composition of the thin film. The film density and crystal state of the thin film are factors that influence the refractive index n and the extinction coefficient k. For this reason, various conditions when forming the light shielding film 2 by reactive sputtering are adjusted so that the light shielding film 2 has a desired refractive index n and extinction coefficient k, and the optical density and surface reflection with respect to ArF exposure light. The film is formed so that the ratio, the back surface reflectance, and the phase difference are within the prescribed values. In order to make the light-shielding film 2 within the ranges of the above-mentioned refractive index n and extinction coefficient k, it is only necessary to adjust the ratio of the mixed gas of noble gas and reactive gas when forming the film by reactive sputtering. I can't. There are a variety of positional relationships such as the pressure in the film formation chamber during reactive sputtering, the power applied to the target, and the distance between the target and the translucent substrate. These film forming conditions are unique to the film forming apparatus, and are appropriately adjusted so that the formed light shielding film 2 has a desired refractive index n and extinction coefficient k.

  The light shielding film 2 is formed by sputtering. Any sputtering such as DC sputtering, RF sputtering and ion beam sputtering is applicable. In the case of using a target with low conductivity (such as a silicon target or a silicon compound target that does not contain a metalloid element or has a low content), it is preferable to apply RF sputtering or ion beam sputtering, but the film formation rate is considered. Then, it is more preferable to apply RF sputtering.

  The light shielding film 2 is a reactive sputtering in a sputtering gas containing a nitrogen-based gas and a noble gas, using a silicon target or a target made of silicon and containing at least one element selected from a metalloid element and a non-metal element. Is formed by.

As the nitrogen-based gas used as the sputtering gas when forming the light-shielding film 2, any gas can be used as long as it contains nitrogen. As described above, since the light shielding film 2 preferably has a low oxygen content except for its surface layer, it is preferable to apply a nitrogen-based gas that does not contain oxygen, and to apply nitrogen gas (N ₂ gas). Is more preferable. Moreover, although there is no restriction | limiting in the kind of noble gas used as sputtering gas when forming the light shielding film 2, It is preferable to use argon, krypton, and a xenon. Further, in order to relieve the stress of the light shielding film 2, helium and neon having a small atomic weight can be actively taken into the light shielding film 2.

[[Hard mask film]]
In the mask blank 100 including the light shielding film 2, a hard mask film 3 formed of a material having etching selectivity with respect to an etching gas used when etching the light shielding film 2 is further laminated on the light shielding film 2. A configuration is preferable. Since the light-shielding film 2 needs to ensure a predetermined optical density, there is a limit in reducing the thickness thereof. It is sufficient that the hard mask film 3 has a film thickness that can function as an etching mask until dry etching for forming a pattern on the light shielding film 2 immediately below the hard mask film 3 is completed. Not subject to restrictions. For this reason, the thickness of the hard mask film 3 can be made much thinner than the thickness of the light shielding film 2. The resist film made of an organic material is sufficient to have a thickness sufficient to function as an etching mask until dry etching for forming a pattern on the hard mask film 3 is completed. The thickness of the resist film can be greatly reduced. For this reason, problems such as resist pattern collapse can be suppressed.

The hard mask film 3 is preferably formed of a material containing chromium (Cr). The material containing chromium has particularly high dry etching resistance against dry etching using a fluorine-based gas such as SF ₆ . A thin film made of a material containing chromium is generally patterned by dry etching using a mixed gas of chlorine-based gas and oxygen gas. However, since this dry etching has not so high anisotropy, etching (side etching) in the side wall direction of the pattern is likely to proceed during dry etching when patterning a thin film made of a material containing chromium.
When a material containing chromium is used for the light-shielding film, the thickness of the light-shielding film 2 is relatively large, so that a problem of side etching occurs during dry etching of the light-shielding film 2. In the case of using a material containing, since the hard mask film 3 is relatively thin, problems caused by side etching hardly occur.

  Examples of the material containing chromium include a material containing one or more elements selected from oxygen, nitrogen, carbon, boron and fluorine in addition to chromium metal, such as CrN, CrC, CrON, CrCO, and CrCON. . When these elements are added to chromium metal, the film tends to be a film having an amorphous structure, and the surface roughness of the film and the line edge roughness when the light-shielding film 2 is dry-etched are preferably suppressed.

Further, also from the viewpoint of dry etching of the hard mask film 3, as a material for forming the hard mask film 3, a material containing one or more elements selected from oxygen, nitrogen, carbon, boron and fluorine in chromium is used. Is preferred.
A chromium-based material is etched with a mixed gas of a chlorine-based gas and an oxygen gas, but chromium metal does not have a very high etching rate with respect to this etching gas. By including one or more elements selected from oxygen, nitrogen, carbon, boron and fluorine in chromium, it becomes possible to increase the etching rate of the mixed gas of chlorine-based gas and oxygen gas with respect to the etching gas.

  Note that the hard mask film 3 made of CrCO does not contain nitrogen that tends to be large in side etching with respect to dry etching using a mixed gas of chlorine-based gas and oxygen gas, contains carbon that suppresses side etching, and further etches. It is particularly preferable because it contains oxygen that improves the rate. Further, the chromium-containing material forming the hard mask film 3 may contain one or more elements of indium, molybdenum and tin. By including one or more elements of indium, molybdenum and tin, the etching rate with respect to the mixed gas of chlorine gas and oxygen gas can be further increased.

  As a material for forming the hard mask film 3 other than a material containing chromium, a material containing a metal such as tantalum can be used in addition to a metal such as tantalum (Ta) or tungsten (W). For example, the material containing tantalum in this case includes a material in which tantalum contains one or more elements selected from nitrogen, boron and carbon in addition to tantalum metal. Specific examples thereof include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like.

  In the mask blank 100, it is preferable that a resist film made of an organic material is formed with a thickness of 100 nm or less in contact with the surface of the hard mask film 3. In the case of a fine pattern corresponding to the DRAM hp 32 nm generation, a transfer pattern to be formed on the hard mask film 3 may be provided with SRAF (Sub-Resolution Assist Feature) having a line width of 40 nm. However, even in this case, since the cross-sectional aspect ratio of the resist pattern can be reduced to 1: 2.5, it is possible to prevent the resist pattern from collapsing or detaching during development or rinsing of the resist film. be able to. The resist film is more preferably 80 nm or less in thickness.

  It is also possible to directly form a resist film in contact with the light shielding film 2 without providing the hard mask film 3 in the mask blank 100. In this case, since the structure is simple and dry etching of the hard mask film 3 is not required even when a transfer mask is manufactured, the number of manufacturing steps can be reduced. In this case, it is preferable to form the resist film after performing a surface treatment such as HMDS (hexyldisilazane) on the light shielding film 2.

  Further, as described below, the mask blank of the present invention is a mask blank suitable for a binary mask application, but is not limited to a binary mask, but is a mask blank for a Levenson type phase shift mask, or CPL (Chromeless). It can also be used as a mask blank for Phase Lithography) masks.

[Transfer mask]
In FIG. 4, the cross-sectional schematic diagram of the process of manufacturing the transfer mask (binary mask) 200 from the mask blank 100 which is embodiment of this invention is shown.

  The manufacturing method of the transfer mask 200 shown in FIG. 4 uses the mask blank 100 described above, and includes a step of forming a transfer pattern on the hard mask film 3 by dry etching, and a hard mask film 3 ( The method includes a step of forming a transfer pattern on the light shielding film 2 by dry etching using the hard mask pattern 3a) as a mask, and a step of removing the hard mask pattern 3a.

  Hereinafter, according to the manufacturing process shown in FIG. 4, an example of a method for manufacturing the transfer mask 200 will be described. In this example, a material containing silicon and nitrogen is applied to the light shielding film 2, and a material containing chromium is applied to the hard mask film 3.

  First, a mask blank 100 (see FIG. 4A) is prepared, and a resist film is formed by spin coating in contact with the hard mask film 3. Next, a transfer pattern to be formed on the light shielding film 2 is exposed and drawn on the resist film, and a predetermined process such as a development process is performed to form a resist pattern 4a (see FIG. 4B).

Subsequently, using the resist pattern 4a as a mask, dry etching using a chlorine-based gas such as a mixed gas of chlorine and oxygen is performed to form a pattern (hard mask pattern 3a) on the hard mask film 3 (FIG. 4C). )reference). The chlorine-based gas is not particularly limited as long as it contains Cl, and examples thereof include Cl ₂ , SiCl ₂ , CHCl ₃ , CH ₂ Cl ₂ , and BCl ₃ . In the case of using a mixed gas of chlorine and oxygen, for example, the gas flow rate ratio may be Cl ₂ : O ₂ = 4: 1.
Next, the resist pattern 4a is removed using ashing or a resist stripping solution (see FIG. 4D).

Subsequently, using the hard mask pattern 3a as a mask, dry etching using a fluorine-based gas is performed to form a pattern (the light shielding film pattern 2a) on the light shielding film 2 (see FIG. 4E). As the fluorine-based gas, any gas containing F can be used, but SF ₆ is preferable. In addition to SF ₆ , for example, CHF ₃ , CF ₄ , C ₂ F ₆ , C ₄ F _{8, and the} like can be given. However, the fluorine-based gas containing C has an etching rate with respect to the transparent substrate 1 made of a glass material. Relatively high. SF ₆ is preferable because damage to the translucent substrate 1 is small. Incidentally, more preferable the addition of such He as SF _6.

  Thereafter, the hard mask pattern 3a is removed using a chrome etching solution, and a transfer mask 200 is obtained through a predetermined process such as cleaning (see FIG. 4F). The step of removing the hard mask pattern 3a may be performed by dry etching using a mixed gas of chlorine and oxygen. Here, as a chromium etching liquid, the mixture containing ceric ammonium nitrate and perchloric acid can be mentioned.

A transfer mask 200 manufactured by the manufacturing method shown in FIG. 4 is a binary mask provided with a light-shielding film 2 (light-shielding film pattern 2 a) having a transfer pattern on a light-transmitting substrate 1. The light shielding film 2 is a single layer film formed of a material containing silicon and nitrogen, and has an optical density of 3.0 or more with respect to ArF exposure light, and the refractive index n and extinction of the light shielding film 2 with respect to ArF exposure light. The coefficient k satisfies the relationship defined in the following expressions (1) and (2) at the same time.
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 29.316 × k ² −92.292 × k + 72.671 Formula (2)

  The matters relating to the translucent substrate 1 and the light shielding film 2 in the transfer mask 200 have the same technical features as the matters relating to the translucent substrate 1 and the light shielding film 2 of the mask blank 100.

  In the transfer mask 200, the optical density of the light-shielding film pattern 2a is 3.0 or more, and the refractive index n and the extinction coefficient k of the light-shielding film pattern 2a with respect to ArF exposure light are expressed by Equations (1) and (2). Satisfy the specified relationships at the same time. For this reason, the light shielding film pattern 2a has a high light shielding performance with respect to ArF exposure light. Moreover, since the EMF bias of the pattern of the light shielding film 2 can be reduced, the transfer mask 200 can be manufactured without applying a large load.

  Although the case where the transfer mask 200 is a binary mask has been described here, the transfer mask of the present invention is not limited to a binary mask, but can be applied to a Levenson type phase shift mask and a CPL mask. That is, in the case of the Levenson type phase shift mask, the light shielding film of the present invention can be used as the light shielding film. In the case of a CPL mask, the light shielding film of the present invention can be used mainly in a region including a light shielding band on the outer periphery.

  Furthermore, in the method for manufacturing a semiconductor device of the present invention, a pattern is exposed and transferred onto a resist film on a semiconductor substrate using the transfer mask 200 manufactured using the transfer mask 200 or the mask blank 100. It is characterized by.

  Since the transfer mask 200 and the mask blank 100 of the present invention have the effects as described above, the transfer mask 200 is set on the mask stage of an exposure apparatus using ArF excimer laser as exposure light, and a resist film on the semiconductor device. When the transfer pattern is transferred by exposure, the transfer pattern can be transferred to the resist film on the semiconductor device with high CD accuracy. For this reason, when the circuit pattern is formed by dry etching the lower layer film using this resist film pattern as a mask, a highly accurate circuit pattern free from wiring short-circuiting or disconnection due to insufficient accuracy can be formed.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
Example 1
[Manufacture of mask blanks]
A translucent substrate 1 made of synthetic quartz glass having a main surface dimension of about 152 mm × about 152 mm and a thickness of about 6.25 mm was prepared. The translucent substrate 1 had its end face and main surface polished to a predetermined surface roughness, and then subjected to a predetermined cleaning process and a drying process.

Next, the translucent substrate 1 is installed in a single wafer RF sputtering apparatus, a silicon (Si) target is used, and a mixed gas of krypton (Kr), helium (He), and nitrogen (N ₂ ) is used as a sputtering gas. The light shielding film 2 made of silicon and nitrogen was formed to a thickness of 58.8 nm on the translucent substrate 1 by reactive sputtering (RF sputtering) with the power of the RF power source set to a predetermined value.

  Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film 2 was formed was subjected to heat treatment in the atmosphere at a heating temperature of 500 ° C. and a processing time of 1 hour.

  The optical density (OD) of the light-shielding film 2 after the heat treatment at a wavelength of 193 nm was measured using a spectrophotometer (Cary 4000 manufactured by Agilent Technologies), and the value was 3.00. From this result, the mask blank of Example 1 has high light shielding performance.

  When the phase difference of the light-shielding film 2 after the heat treatment at a wavelength of 193 nm was measured using a phase shift amount measuring apparatus (MPM-193 manufactured by Lasertec Corporation), the value was 75.2 degrees.

  Using a spectrophotometer (manufactured by Hitachi, U-4100), the surface reflectance and the back surface reflectance of the light-shielding film 2 after the heat treatment at a wavelength of 193 nm were measured, and the values were 37.1% and 30.0 respectively. %Met. From this result, the transfer mask manufactured using the mask blank of Example 1 can suppress deterioration of the projection optical image during transfer exposure.

  The refractive index n and extinction coefficient k of the light-shielding film 2 after heat treatment at a wavelength of 193 nm were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). The refractive index n at a wavelength of 193 nm was 1.83, and the extinction coefficient k was 1.79. From the values of the refractive index n and the extinction coefficient k, the refractive index n and the extinction coefficient k of the light shielding film 2 are the conditions of the above formulas (4), (6), (8), and (10). And match with the respective values of the film thickness, optical density, phase difference, surface reflectance, and back surface reflectance. The refractive index n and extinction coefficient k of the light shielding film 2 satisfy the conditions of the above expressions (4), (8), and (10), so that the above expressions (1) and (2) And the condition of equation (3) is also satisfied.

  Next, an optical simulation for calculating an EMF bias was performed on the light-shielding film 2 of Example 1. In this optical simulation, the refractive index n, extinction coefficient k, and film thickness d of the light shielding film 2 obtained by the above measurement were used as input values. As a design pattern applied to the optical simulation, a line and space pattern with a DRAM half pitch (hp) of 40 nm was applied. Dipole illumination was set as the illumination condition of the exposure light applied to the optical simulation. The EMF bias was calculated by taking the difference between the bias (correction amount) calculated by the optical simulation by TMA and the bias (correction amount) calculated by the simulation considering the EMF effect. As a result, the EMF bias was 0.5 nm. From this result, it can be said that the EMF bias of the mask blank of Example 1 is sufficiently reduced. Furthermore, it can be said that the load related to the calculation correction of the design pattern when manufacturing the transfer mask from the mask blank of Example 1 is reduced, and the complexity of the pattern actually formed on the light shielding film 2 can be suppressed.

Next, the translucent substrate 1 on which the heat-shielding light-shielding film 2 is formed is placed in a single-wafer DC sputtering apparatus, and using a chromium (Cr) target, argon (Ar), nitrogen (N ₂ ), Then, reactive sputtering (DC sputtering) was performed in a mixed gas atmosphere to form a hard mask film 3 made of a CrN film having a thickness of 5 nm. The film composition ratio measured by XPS was 75 atomic% for Cr and 25 atomic% for N. Then, heat treatment was performed at a lower temperature (280 ° C.) than the heat treatment performed on the light shielding film 2 to adjust the stress of the hard mask film 3.

  With the above procedure, a mask blank 100 having a structure in which the light shielding film 2 and the hard mask film 3 were laminated on the light transmitting substrate 1 was manufactured.

[Manufacture of transfer masks]
Next, using the mask blank 100 of Example 1, a transfer mask (binary mask) 200 of Example 1 was manufactured according to the following procedure.

  First, a mask blank 100 of Example 1 (see FIG. 4A) was prepared, and a resist film made of a chemically amplified resist for electron beam drawing was formed with a thickness of 80 nm in contact with the surface of the hard mask film 3. . Next, a transfer pattern to be formed on the light shielding film 2 was drawn on the resist film with an electron beam, and predetermined development processing and cleaning processing were performed to form a resist pattern 4a (see FIG. 4B).

Next, using the resist pattern 4a as a mask, dry etching using a mixed gas of chlorine and oxygen (gas flow ratio Cl ₂ : O ₂ = 4: 1) is performed to form a pattern (hard mask pattern 3a on the hard mask film 3). ) Was formed (see FIG. 4C).

Next, the resist pattern 4a was removed (see FIG. 4D). Subsequently, using the hard mask pattern 3a as a mask, dry etching using a fluorine-based gas (a mixed gas of SF ₆ and He) is performed to form a pattern (the light shielding film pattern 2a) on the light shielding film 2 (FIG. 4E). )reference).

  Thereafter, the hard mask pattern 3a was removed using a chromium etching solution containing ceric ammonium nitrate and perchloric acid, and a transfer mask 200 was obtained through a predetermined process such as cleaning (see FIG. 4F). ).

  As a result of setting the transfer mask 200 of Example 1 on the mask stage of the exposure apparatus and performing exposure transfer on the resist film on the semiconductor device, the transfer pattern is transferred to the resist film on the semiconductor device with high CD accuracy. I was able to.

(Example 2)
[Manufacture of mask blanks]
The mask blank of Example 2 was manufactured in the same procedure as the mask blank 100 of Example 1 except that the light shielding film was changed as follows.

The formation method of the light shielding film of Example 2 is as follows.
A translucent substrate 1 is installed in a single-wafer DC sputtering apparatus, a silicon (Si) target is used, a mixed gas of krypton (Kr), helium (He), and nitrogen (N ₂ ) is used as a sputtering gas, and a DC power source The light-shielding film 2 made of silicon and nitrogen was formed to a thickness of 45.7 nm on the translucent substrate 1 by reactive sputtering (DC sputtering).

  Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film 2 was formed was subjected to heat treatment in the atmosphere at a heating temperature of 500 ° C. and a processing time of 1 hour.

  When the optical density (OD) of the light-shielding film 2 after the heat treatment was measured in the same manner as in Example 1, the value was 3.06. From this result, the mask blank of Example 2 has high light shielding performance. Moreover, although the phase difference of the light shielding film 2 after heat processing was measured similarly to Example 1, the value was not measurable. Therefore, an optical simulation was performed based on the refractive index n and extinction coefficient k of the light-shielding film 2 after the heat treatment, and the phase difference was obtained. The value was −11.7 degrees. Moreover, when the surface reflectance and the back surface reflectance of the light-shielding film 2 after the heat treatment were measured in the same manner as in Example 1, the values were 54.3% and 52.1%, respectively. Similarly to Example 1, when the refractive index n and extinction coefficient k of the light-shielding film 2 after the heat treatment were measured, the refractive index n was 1.16 and the extinction coefficient k was 2.40. From the values of the refractive index n and the extinction coefficient k, the refractive index n and the extinction coefficient k of the light-shielding film 2 after the heat treatment satisfy the conditions of the expressions (4), (5), and (8), It matches with each value of said film thickness, optical density, phase difference, surface reflectance, and back surface reflectance. The refractive index n and the extinction coefficient k of the light shielding film 2 satisfy the conditions of the above expressions (4) and (8), and therefore also satisfy the conditions of the above expressions (1) and (2).

  Similarly to Example 1, the EMF bias of the light shielding film 2 was determined to be 3.6 nm. From this result, it can be said that the mask blank of Example 2 can sufficiently reduce the EMF bias. Furthermore, it can be said that the load related to the correction calculation of the design pattern when manufacturing the transfer mask from the mask blank of Example 2 is reduced, and the complexity of the pattern actually formed on the light shielding film 2 can be suppressed.

[Manufacture of transfer masks]
Next, using the mask blank of Example 2, a transfer mask (binary mask) of Example 2 was produced in the same procedure as in Example 1. As a result of setting the transfer mask 200 of Example 2 on the mask stage of the exposure apparatus and performing exposure transfer on the resist film on the semiconductor device, the transfer pattern is transferred to the resist film on the semiconductor device with high CD accuracy. I was able to.

(Comparative Example 1)
[Manufacture of mask blanks]
The mask blank of Comparative Example 1 was manufactured in the same procedure as the mask blank 100 of Example 1 except that the light shielding film was changed as follows.

The formation method of the light shielding film of Comparative Example 1 is as follows.
A translucent substrate 1 is installed in a single wafer RF sputtering apparatus, a silicon (Si) target is used, a mixed gas of krypton (Kr), helium (He), and nitrogen (N ₂ ) is used as a sputtering gas, and an RF power source A light-shielding film made of silicon and nitrogen was formed to a thickness of 69.5 nm on the translucent substrate 1 by reactive sputtering (RF sputtering).

  Next, for the purpose of adjusting the stress of the film, the light-transmitting substrate 1 on which the light-shielding film was formed was subjected to heat treatment in the atmosphere at a heating temperature of 500 ° C. and a processing time of 1 hour.

  When the optical density (OD) of the light-shielding film after the heat treatment was measured in the same manner as in Example 1, the value was 3.01. From this result, the mask blank of Comparative Example 1 has sufficient light shielding performance. Moreover, although the phase difference of the light shielding film after heat processing was measured similarly to Example 1, the value was not measurable. Therefore, when the phase difference was obtained by simulation based on the refractive index n and extinction coefficient k of the light-shielding film after the heat treatment, the value was 129.9 degrees. Moreover, when the surface reflectance and the back surface reflectance of the light-shielding film after the heat treatment were measured in the same manner as in Example 1, the values were 29.4% and 19.6%, respectively. Similarly to Example 1, when the refractive index n and extinction coefficient k of the light-shielding film 2 after the heat treatment were measured, the refractive index n was 2.10 and the extinction coefficient k was 1.51. From the values of the refractive index n and the extinction coefficient k, the refractive index n and the extinction coefficient k of the light-shielding film after the heat treatment satisfy the expressions (7) and (10). It does not satisfy | fill, but it matches with each value of said film thickness, optical density, phase difference, surface reflectance, and back surface reflectance. Note that the refractive index n and the extinction coefficient k of the light shielding film satisfy the expressions (2) and (3) because the expressions (7) and (10) are satisfied, but the expression (1) is satisfied. Absent.

  Similarly to Example 1, the EMF bias of the light shielding film was determined to be 8.2 nm. From this result, it can be said that the mask blank of Comparative Example 1 cannot sufficiently reduce the EMF bias. Furthermore, it can be said that the load relating to the correction calculation of the design pattern when manufacturing the transfer mask from the mask blank of Comparative Example 1 is excessive, and the pattern actually formed on the light shielding film 2 is also complicated.

[Manufacture of transfer masks]
Next, using the mask blank of Comparative Example 1, a transfer mask (binary mask) of Comparative Example 1 was produced in the same procedure as in Example 1. As a result of setting the transfer mask of Comparative Example 1 on the mask stage of the exposure apparatus and performing exposure transfer on the resist film on the semiconductor device, the CD variation of the transfer pattern formed on the resist film on the semiconductor device was large.

DESCRIPTION OF SYMBOLS 1 Translucent substrate 2 Light shielding film 2a Light shielding film pattern 3 Hard mask film | membrane 3a Hard mask pattern 4a Resist pattern 100 Mask blank 200 Transfer mask (binary mask)

Claims (10)

A mask blank provided with a light shielding film on a translucent substrate,
The light-shielding film is a single layer film formed of a material consisting of silicon and nitrogen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and nitrogen,
The light shielding film has an optical density of 3.0 or more with respect to the exposure light of the ArF excimer laser,
A mask blank characterized in that the refractive index n and the extinction coefficient k of the light shielding film with respect to the exposure light simultaneously satisfy the relationships defined in the following formulas (1), (2), and (3).
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 0.0637 × k ² −0.1096 × k + 0.9585 (2)
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)   The mask blank according to claim 1, wherein the light shielding film has an extinction coefficient k of 2.6 or less.   The mask blank according to claim 1, wherein the light-shielding film has a refractive index n of 0.8 or more.   The variation of the nitrogen content in the thickness direction in the region excluding the surface layer on the translucent substrate side and the surface layer on the opposite side of the translucent substrate is within 5 atomic% of the light shielding film. The mask blank according to any one of claims 1 to 3.   The mask blank according to claim 1, further comprising a hard mask film made of a material containing chromium on the light shielding film. A transfer mask provided with a light-shielding film having a transfer pattern on a translucent substrate,
The light-shielding film is a single layer film formed of a material consisting of silicon and nitrogen, or a material consisting of one or more elements selected from metalloid elements and nonmetallic elements, and silicon and nitrogen,
The light shielding film has an optical density of 3.0 or more with respect to the exposure light of the ArF excimer laser,
The transfer mask, wherein a refractive index n and an extinction coefficient k of the light shielding film with respect to the exposure light simultaneously satisfy a relationship defined by the following formulas (1), (2), and (3):
n ≦ 0.0733 × k ² + 0.4069 × k + 1.0083 Formula (1)
n ≧ 0.0637 × k ² −0.1096 × k + 0.9585 (2)
n ≧ 0.7929 × k ² −2.1606 × k + 2.1448 Formula (3)   The transfer mask according to claim 6, wherein the light shielding film has an extinction coefficient k of 2.6 or less.   The transfer mask according to claim 6, wherein the light shielding film has a refractive index n of 0.8 or more.   The variation of the nitrogen content in the thickness direction in the region excluding the surface layer on the translucent substrate side and the surface layer on the opposite side of the translucent substrate is within 5 atomic% of the light shielding film. The transfer mask according to claim 6.   A method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the transfer mask according to claim 6.

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