JP6698438B2 - Mask blank, transfer mask, mask blank manufacturing method, transfer mask manufacturing method, and semiconductor device manufacturing method - Google Patents

Description

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

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

  Types of transfer masks include halftone phase shift masks as well as conventional binary masks having a light-shielding pattern made of a chromium-based material on a transparent substrate. As disclosed in Patent Document 1, molybdenum silicide (MoSi)-based materials are widely used for the phase shift film of the halftone type phase shift mask. Further, as disclosed in Patent Document 2, there is also known a phase shift mask including a phase shift film which is a molybdenum silicide material and has a relatively high transmittance of 9% or more for exposure light. ..

In Patent Document 3, a defect in which a black defect portion is etched and removed by irradiating the black defect portion of the light-shielding film with an electron beam while supplying xenon difluoride (XeF ₂ ) gas. A correction technique (hereinafter, such defect correction performed by irradiating charged particles such as an electron beam is simply referred to as EB defect correction) is disclosed. This EB defect repair was originally used to repair black defects in the absorber film of a reflective mask for EUV lithography (Extreme Ultraviolet Lithography), but in recent years it has also been used to repair black defects in MoSi halftone masks. There is.

In a phase shift mask using a molybdenum silicide-based material and a silicon-based material as the phase shift film, the phase shift pattern is generally formed by dry etching using a fluorine-based gas as an etching gas. However, the phase shift film of these materials does not have very high etching selectivity in dry etching with a fluorine-based gas with respect to a substrate made of a glass material. In Patent Document 4, an etching stopper film made of Al ₂ O ₃ or the like, which is a material having high resistance to dry etching of fluorine-based gas, is interposed between the substrate and the phase shift film. With such a structure, it is possible to prevent the surface of the substrate from being dug when the phase shift pattern is formed on the phase shift film by dry etching using a fluorine-based gas.

JP, 2002-162726, A JP, 2010-9038, A Japanese Patent Publication No. 2004-537758 JP, 2005-208660, A

The etching stopper film made of Al ₂ O ₃ has excellent resistance to dry etching with a fluorine-based gas, and has an advantage that it is possible to prevent substrate digging when a phase shift film made of a silicon-containing material is dry-etched. In addition, the etching stopper film made of Al ₂ O ₃ has high resistance to etching that occurs when the EB defect is repaired, and suppresses damage to the substrate that tends to occur when the EB defect is repaired with respect to the black defect portion of the phase shift film. Is also possible. However, the etching stopper film made of Al ₂ O ₃ tends to have low resistance to chemical cleaning. During the process of manufacturing a phase shift mask (transfer mask) from a mask blank, cleaning with a chemical solution is performed many times. Further, the completed phase shift mask is also regularly cleaned with a chemical solution. In these cleanings, ammonia-hydrogen peroxide solution or TMAH (tetramethylammonium hydroxide) aqueous solution is often used as the cleaning liquid, and the etching stopper film made of Al ₂ O ₃ has low resistance to these cleaning liquids.

For example, when a phase shift mask including an etching stopper film made of Al ₂ O ₃ and a phase shift film having a phase shift pattern formed on a transparent substrate made of glass is washed with ammonia-hydrogen peroxide, This is a region where the phase shift film does not exist in the shift mask, and the etching stopper film gradually dissolves from the surface in the light transmitting portion where the surface of the etching stopper film is exposed. When this cleaning is continued, the main surface of the substrate is exposed at the light-transmitting portion, and when the cleaning is further continued, the etching stopper film immediately below the pattern portion where the phase shift film is present also moves from the side wall side to the inside of the phase shift film. It melts toward you. Since the phenomenon that the etching stopper film dissolves progresses from both side walls of the phase shift film pattern, the width of the etching stopper film that remains undissolved is smaller than the pattern width of the phase shift film. It gets smaller. In such a state, the phenomenon that the pattern of the phase shift film falls off is likely to occur.

  Further, when the phase shift mask is set in the exposure device and exposed and transferred to the transfer target (resist film on the semiconductor wafer), the exposure light is provided with the phase shift pattern of the transparent substrate of the phase shift mask. The light enters from the main surface side opposite to the existing main surface and enters the phase shift pattern through the etching stopper film. The pattern formed on the phase shift film of the phase shift mask is designed on the assumption that an etching stopper film exists between the translucent substrate and the phase shift film. Therefore, in a state where the etching stopper film of the phase shift mask is dissolved, there is a possibility that the optical characteristics expected at the time of designing the phase shift pattern may not be sufficiently obtained.

  If the etching stopper film is dissolved near the side wall of the phase shift pattern that requires the phase shift effect, it becomes difficult to obtain a sufficient phase shift effect. In the case of a high-transmittance type phase shift mask such as disclosed in Patent Document 2, in which the transmittance of the phase shift film for exposure light is increased in order to obtain a higher phase shift effect, the phase shift effect does not decrease. More likely to be noticeable.

The etching stopper film made of Al ₂ O ₃ has a problem in that it has a lower transmittance for exposure light than synthetic quartz glass used as a material for a transparent substrate of a phase shift mask. In the case of the phase shift mask in which ArF excimer laser is applied to the exposure light, the tendency is more remarkable. The etching stopper film made of Al ₂ O ₃ is also left in the light transmitting portion at the stage when the phase shift mask is completed. A decrease in the transmittance of the exposure light in the light transmitting portion of the phase shift mask leads to a decrease in the phase shift effect of the phase shift mask.

  On the other hand, also in a mask blank for manufacturing a binary transfer mask having a pattern of a light shielding film having a high optical density on a light transmitting substrate, a transition metal silicide-based material is used as the material of the light shielding film. .. Dry etching with fluorine gas is also used when forming a pattern on the light-shielding film of the transition metal silicide-based material. The transition metal silicide-based material of the light-shielding film may be required to have a high optical density, and thus the nitriding degree and the oxidation degree generally tend to be lower than those of the transition metal silicide-based material of the phase shift film. Therefore, the etching selectivity between the light-shielding film and the transparent substrate for dry etching with a fluorine-based gas is likely to be higher than the selectivity between the phase shift film and the transparent substrate. However, since the etching selectivity may not be sufficient to suppress the etching of the transparent substrate, it is desired to provide an etching stopper film between the transparent substrate and the light shielding film.

  Further, when manufacturing a transfer mask from a mask blank having a light-shielding film of this transition metal silicide-based material, EB defect correction is performed even when a black defect portion is found in the pattern of the light-shielding film. Providing an etching stopper film is effective in suppressing damage to the substrate during EB defect repair. Also in the case of the etching stopper film in this binary type transfer mask, as in the case of the phase shift mask, it is necessary that the material has high resistance to chemical cleaning, and is a material having a high transmittance for exposure light. Is also desired.

  The present invention has been made to solve the above conventional problems, and a mask blank provided with a pattern forming thin film made of a material containing silicon such as a phase shift film or a light shielding film on a transparent substrate. In the case where the etching stopper film is interposed between the translucent substrate and the pattern forming thin film, the resistance to dry etching by the fluorine-based gas used in patterning the pattern forming thin film is high, and the chemical cleaning is performed. An object of the present invention is to provide a mask blank provided with an etching stopper film having high resistance and high transmittance for exposure light, and a method for manufacturing the mask blank. Moreover, it aims at providing the transfer mask manufactured using this mask blank. Further, it is an object to provide a method for manufacturing such a transfer mask. The present invention has an object to provide a method for manufacturing a semiconductor device using such a transfer mask.

In order to achieve the above-mentioned subject, the present invention has the following configurations.
(Structure 1)
A mask blank having a structure in which an etching stopper film and a pattern forming thin film are laminated in this order on a main surface of a transparent substrate,
The pattern forming thin film is provided in contact with the surface of the etching stopper film,
The pattern forming thin film contains silicon,
The etching stopper film contains silicon, aluminum and oxygen, and the ratio of the silicon content to the total content of the silicon and the aluminum in atomic% of the pattern forming thin film side is higher than that of the transparent substrate side. Mask blank characterized by high price.

(Structure 2)
The etching stopper film is a composition gradient film in which the ratio of the silicon content to the total content of the silicon and the aluminum in atomic% increases from the transparent substrate side toward the pattern forming thin film side. 2. The mask blank according to the structure 1, characterized in that

(Structure 3)
3. The mask blank according to Structure 1 or 2, wherein the etching stopper film is made of silicon, aluminum and oxygen.

(Structure 4)
The mask blank according to any one of configurations 1 to 3, wherein the etching stopper film has an oxygen content of 50 atomic% or more.

(Structure 5)
In the etching stopper film on the side of the thin film for pattern formation, the ratio of the content of the silicon to the total content of the silicon and the aluminum in atomic% is ⅕ or more. The mask blank according to any one.

(Structure 6)
In the etching stopper film on the thin film side for pattern formation, the ratio of the content of the silicon to the total content of the silicon and the aluminum in atomic% is 4/5 or less. The mask blank according to any one.

(Structure 7)
7. The mask blank according to any one of Configurations 1 to 6, wherein the etching stopper film has at least one of an amorphous structure and a microcrystalline structure.

(Structure 8)
8. The mask blank according to any one of configurations 1 to 7, wherein the etching stopper film has a thickness of 3 nm or more.

(Configuration 9)
9. The mask blank according to any one of Configurations 1 to 8, wherein the pattern forming thin film contains silicon and nitrogen.

(Configuration 10)
The pattern forming thin film is a phase shift film,
The phase shift film has a function of transmitting exposure light with a transmittance of 1% or more, and the phase shift film passes through the air by the same distance as the thickness of the phase shift film with respect to the exposure light transmitted through the phase shift film. 10. The mask blank according to any one of configurations 1 to 9, which has a function of producing a phase difference of 150 degrees or more and 200 degrees or less with exposure light.

(Configuration 11)
11. The mask blank according to Structure 10, further comprising a light-shielding film on the phase shift film.

(Configuration 12)
11. The transfer mask, wherein the pattern forming thin film of the mask blank according to any one of configurations 1 to 10 is provided with a transfer pattern.

(Configuration 13)
A transfer mask, wherein a transfer pattern is provided on the phase shift film of the mask blank according to structure 11, and a pattern including a light-shielding band is provided on the light-shielding film.

(Configuration 14)
A method for manufacturing the mask blank according to any one of configurations 1 to 11,
Forming a step of forming the etching stopper film containing aluminum and oxygen on the transparent substrate;
Forming a pattern forming thin film containing silicon in contact with the etching stopper film;
Performing a heat treatment at a temperature of 400° C. or higher on the translucent substrate on which the etching stopper film and the pattern forming thin film have been formed;
A method of manufacturing a mask blank, comprising:

(Configuration 15)
15. The method of manufacturing a mask blank according to Structure 14, wherein the step of forming the etching stopper film is a step of forming an etching stopper film having an oxygen content of less than 60 atom %.

(Configuration 16)
A method of manufacturing a transfer mask using the mask blank according to structure 11,
A step of forming a transfer pattern on the light-shielding film by dry etching,
Forming a transfer pattern on the phase shift film by dry etching using a fluorine-based gas using the light-shielding film having the transfer pattern as a mask;
A step of forming a pattern including a light-shielding band on the light-shielding film by dry etching.

(Configuration 17)
A method of 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 the structure 12 or 13.

(Structure 18)
A method of manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask manufactured by the method of manufacturing a transfer mask according to structure 16.

  The mask blank of the present invention is a mask blank having a structure in which an etching stopper film and a pattern forming thin film are laminated in this order on the main surface of a transparent substrate, and the pattern forming thin film is the etching stopper film. Provided in contact with the surface, the thin film for pattern formation contains silicon, the etching stopper film contains silicon, aluminum and oxygen, and the thin film side for pattern formation contains silicon and aluminum more than the transparent substrate side. It is characterized by a high atomic% ratio of the silicon content to the quantity. By using the mask blank having such a structure, the etching stopper film has a higher resistance to dry etching by a fluorine-based gas when forming a pattern on the pattern forming thin film than the translucent substrate, and the chemical cleaning It is possible to simultaneously satisfy the three characteristics of high resistance to exposure light and high transmittance to exposure light.

It is sectional drawing which shows the structure of the mask blank in the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the phase shift mask in the 1st Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing process of the phase shift mask in the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the mask blank in the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the transfer mask in the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing process of the transfer mask in the 2nd Embodiment of this invention.

First, the background to the completion of the present invention will be described. The inventors of the present invention have conducted extensive studies to solve the technical problem of the etching stopper film made of Al ₂ O ₃ . Al ₂ O _3, which is the material of the etching stopper film, has high resistance to dry etching with a fluorine-based gas, but its transmittance to the exposure light of an ArF excimer laser (wavelength: about 193 nm) is not so high that it is used as a transfer mask. It also has low resistance to the cleaning liquid used for cleaning. On the other hand, SiO ₂ which is the main material of the transparent substrate has a high transmittance for the exposure light of the ArF excimer laser and a high resistance to the cleaning liquid used for cleaning the transfer mask. It is also a material that is easily etched against etching. As a result of earnest studies, the present inventors have found that the etching stopper film is formed of a material in which SiO ₂ and Al ₂ O ₃ are mixed, whereby the resistance to dry etching by a fluorine-based gas and the exposure light of an ArF excimer laser are high. It has been found that it is possible to satisfy all three conditions of the transmittance and the resistance to the chemical solution used for cleaning the transfer mask.

When an etching stopper film was manufactured by using a material in which SiO ₂ and Al ₂ O ₃ are mixed as described above and verified, it was confirmed that the etching stopper film made of only Al ₂ O ₃ was resistant to dry etching by a fluorine-based gas. It was found to be sufficiently higher than the film, but sufficiently functioning as an etching stopper film. Regarding the transmittance of ArF excimer laser for exposure light, it was found that the transmittance was inferior to that of the material composed of only SiO ₂ but was significantly higher than that of the etching stopper film composed of only Al ₂ O ₃ . Further, it has been found that the resistance to chemicals (ammonia hydrogen peroxide, TMAH, etc.) is inferior to that of the material composed of only SiO _2, but is much higher than that of the etching stopper film composed of only Al ₂ O ₃ . In addition, a process of irradiating an x-ray (xeF ₂ ) gas with EB defect correction while irradiating the part with an electron beam is applied to an etching stopper film made of a mixture of SiO ₂ and Al ₂ O _3. As a result, it was found that it is inferior to the etching stopper film made of Al ₂ O ₃ only, but has sufficiently high resistance and is difficult to be etched as compared with the material made of SiO ₂ only.

On the other hand, in dry etching with a fluorine-based gas when forming a pattern on a thin film (a thin film for pattern formation) of a mask blank, various conditions such as a gas species to be used, a gas flow rate in the etching chamber, and a bias voltage are used. The etching stopper film is desired to have sufficient resistance to these various etching conditions. On the other hand, the cleaning conditions for the cleaning performed when manufacturing a transfer mask from a mask blank and the cleaning performed for the transfer mask after manufacturing also depend on various conditions such as the chemical solution used, the concentration, and the cleaning time. Used. In the etching stopper film made of a material in which SiO ₂ and Al ₂ O ₃ are mixed, as the content of SiO ₂ decreases, the etching resistance of the fluorine-based gas increases, but the chemical resistance during cleaning decreases. There is a trade-off relationship of going.

  The present inventors further researched an etching stopper film which can be widely applied to various etching conditions and various chemical cleaning conditions. As a result, it was conceived that the content ratio of silicon and aluminum in the etching stopper film should not be uniform in the film thickness direction, but the content ratio of silicon and aluminum should be different in the film thickness direction. Further, the inventors have come up with the idea that the pattern forming thin film side of the etching stopper film has a high chemical resistance, and the transparent substrate side of the etching stopper film has a high fluorine gas etching resistance. In order to satisfy these conditions, the ratio of the silicon content [atomic%] to the total silicon and aluminum content [atomic%] on the pattern forming thin film side of the etching stopper film is set to the translucent substrate side. It was concluded that the ratio should be higher than the ratio of the silicon content [atomic %] to the total silicon and aluminum content [atomic %] of.

  That is, the mask blank of the present invention is a mask blank having a structure in which an etching stopper film and a pattern forming thin film are laminated in this order on the main surface of a transparent substrate, and the pattern forming thin film is the etching stopper. The pattern forming thin film provided in contact with the surface of the film contains silicon, the etching stopper film contains silicon, aluminum and oxygen, and the pattern forming thin film side is formed of silicon (Si) rather than the transparent substrate side. And the ratio of the content of silicon (Si) to the total content of aluminum (Al) in atomic% (hereinafter, referred to as “Si/[Si+Al] ratio”) is high. Next, each embodiment of the present invention will be described.

<First Embodiment>
[Mask blank and its manufacture]
The mask blank according to the first embodiment of the present invention is one in which the pattern forming thin film is a phase shift film that is a film that imparts a predetermined transmittance and a phase difference to the exposure light. It is used for manufacturing a transfer mask). FIG. 1 shows the structure of the mask blank of the first embodiment. The mask blank 100 according to the first embodiment includes an etching stopper film 2, a phase shift film (pattern forming thin film) 3, a light shielding film 4, and a hard mask film 5 on a main surface of a transparent substrate 1. ing.

  The transparent substrate 1 is not particularly limited as long as it has a high transmittance for exposure light. In the present invention, a synthetic quartz glass substrate and various other glass substrates (for example, soda lime glass, aluminosilicate glass, etc.) can be used. Among these substrates, the synthetic quartz glass substrate is particularly preferable as the substrate of the mask blank of the present invention used for forming a high-definition transfer pattern because it has a high transmittance in the ArF excimer laser or a wavelength region shorter than that. .. However, all of these glass substrates are materials that are easily etched by dry etching with a fluorine-based gas. Therefore, it is significant to provide the etching stopper film 2 on the transparent substrate 1.

  The etching stopper film 2 is formed of a material containing silicon, aluminum and oxygen, and the Si/[Si+Al] ratio on the phase shift film 3 side is higher than the Si/[Si+Al] ratio on the transparent substrate 1 side. Is becoming The etching stopper film 2 is left unremoved at least on the entire surface of the transfer pattern forming region when the phase shift mask 200 is completed (see FIG. 2). That is, the etching stopper film 2 remains in the light-transmitting portion, which is a region where the phase shift film 3 of the phase shift pattern does not exist. Therefore, it is preferable that the etching stopper film 2 is formed in contact with the transparent substrate 1 without any other film interposed between the etching stopper film 2 and the transparent substrate 1.

  When the etching stopper film 2 is dissolved (etched) by chemical cleaning, it tends to be isotropic, whereas when the etching stopper film 2 is etched by dry etching, it tends to be anisotropic. In the case of isotropic etching, not only the etching stopper film 2 in the region where the pattern of the phase shift film 3 is not etched is etched from the surface, but also the etching stopper film 2 in the region where the phase shift film 3 is present is removed. Since the etching is performed from the pattern side wall side toward the inner side, the pattern of the phase shift film 3 may be detached. Even if the pattern of the phase shift film 3 does not fall off, if the etching stopper film 2 near the side wall of the pattern is missing, the optical characteristics of the phase shift mask change significantly, which is not preferable.

  On the other hand, in the case of anisotropic dry etching, only the surface of the etching stopper film 2 in the region where the phase shift film 3 is removed is etched. In consideration of these matters, the etching stopper film 2 has a high Si/[Si+Al] ratio so that the phase shift film 3 side has high chemical resistance. However, as will be described later, the Si/[Si+Al] ratio of the etching stopper film 2 on the phase shift film 3 side is between the phase shift film 3 and the phase shift film 3 where the etching stopper film 2 is not removed during the dry etching of the phase shift film 3. The etching rate is limited to a level that can be secured.

  The etching stopper film 2 is required to have at least a Si/[Si+Al] ratio on the phase shift film 3 side higher than a Si/[Si+Al] ratio on the transparent substrate 1 side. The etching stopper film 2 may have either a composition gradient film or a multilayer film of two or more layers. When the etching stopper film 2 is a composition gradient film, the Si/[Si+Al] ratio in the region on the phase shift film 3 side is set higher than the Si/[Si+Al] ratio in the region on the transparent substrate 1 side. In the case of this composition gradient film, the Si/[Si+Al] ratio of the region sandwiched between the region on the phase shift film 3 side of the etching stopper film 2 and the region on the transparent substrate 1 side is higher than that of the region on the phase shift film 3 side. May be higher or lower than the region on the transparent substrate 1 side.

  The etching stopper film 2 is a ratio of the silicon content to the total content of silicon and aluminum in atomic% from the transparent substrate 1 side toward the phase shift film (pattern forming thin film) 3 side (Si/[Si+Al]). It is more preferable that the composition gradient film has a high ratio (in this case, the Si/[Si+Al] ratio of the region sandwiched between the region on the side of the phase shift film 3 and the region on the side of the transparent substrate 1 is in both regions). In the middle of the range.). The etching stopper film 2 having this structure remains on the translucent substrate 1 even if dry etching with a fluorine-based gas is performed under various conditions when forming a pattern on the phase shift film 3, and the translucent substrate 1 has a translucent property. It suppresses that the surface of the substrate 1 is etched. Further, the etching stopper film 2 having this structure remains on the transparent substrate 1 even if chemical cleaning is performed after the pattern is formed on the phase shift film 3, and the pattern of the phase shift film 3 is on the transparent substrate. 1 Detach from above.

  On the other hand, when the etching stopper film 2 is a multilayer film, the Si/[Si+Al] ratio of the layer on the phase shift film 3 side is set higher than the Si/[Si+Al] ratio of the layer on the transparent substrate 1 side. When the etching stopper film 2 is a multi-layered film having three or more layers, the Si/[Si+Al] ratio of the layer sandwiched between the phase shift film 3 side layer and the transparent substrate 1 side layer is the phase shift film 3 side. It may be higher than the layer on the transparent substrate 1 side, or may be lower than the layer on the transparent substrate 1 side. When the etching stopper film 2 is a multi-layered film having three or more layers, the Si/[Si+Al] ratio of the layer sandwiched between the layer on the side of the phase shift film 3 and the layer on the side of the transparent substrate 1 is equal to the phase shift film 3 It is more preferable to be in the range between the layer on the side and the layer on the side of the transparent substrate 1. The etching stopper film 2 having this structure remains on the translucent substrate 1 even if dry etching with a fluorine-based gas is performed under various conditions when forming a pattern on the phase shift film 3, and the translucent substrate 1 has a translucent property. It suppresses that the surface of the substrate 1 is etched. Further, the etching stopper film 2 having this structure remains on the transparent substrate 1 even if chemical cleaning is performed after the pattern is formed on the phase shift film 3, and the pattern of the phase shift film 3 is on the transparent substrate. 1 Detach from above.

  It is preferable that the etching stopper film 2 has a higher transmittance with respect to the exposure light, but the etching stopper film 2 is required to have a sufficient etching selectivity with respect to the fluorine-based gas with the transparent substrate 1 at the same time. It is difficult to make the transmittance the same as that of the transparent substrate 1 (that is, the transmittance of the etching stopper film 2 when the transmittance of the transparent substrate 1 (synthetic quartz glass) for exposure light is 100%). Is less than 100%). The transmittance of the etching stopper film 2 when the transmittance of the transparent substrate 1 to the exposure light is 100% is preferably 94% or more, more preferably 95% or more, and more preferably 96% or more. And more preferable.

  The content of the metal other than aluminum in the etching stopper film 2 is preferably 2 atomic% or less, more preferably 1 atomic% or less, and is not more than the lower limit of detection when the composition analysis by X-ray photoelectron spectroscopy is performed. It is more preferable to have. This is because if the etching stopper film 2 contains a metal other than aluminum, the transmittance of the exposure light is reduced. The etching stopper film 2 preferably has a total content of elements other than silicon, aluminum and oxygen of 5 atomic% or less, more preferably 3 atomic% or less.

  The etching stopper film 2 may be formed of a material composed of silicon, aluminum and oxygen. In addition to these constituent elements, the material consisting of silicon, aluminum, and oxygen includes elements (helium (He), neon (Ne), A material containing only noble gases such as argon (Ar), krypton (Kr) and xenon (Xe), hydrogen (H) and carbon (C). By minimizing the presence of other elements that bond with silicon or aluminum in the etching stopper film 2, it is possible to significantly increase the ratio of the bonding between silicon and oxygen and the bonding between aluminum and oxygen in the etching stopper film 2. .. As a result, the etching resistance of dry etching with a fluorine-based gas can be further increased, the resistance to chemical cleaning can be further increased, and the transmittance for exposure light can be further increased.

  The etching stopper film 2 preferably has an oxygen content of 50 atomic% or more, and more preferably 55 atomic% or more. This is because it is required that the etching stopper film 2 contain a large amount of oxygen in order to make the transmittance for exposure light equal to or higher than the above-mentioned numerical value. In addition, silicon bonded to oxygen tends to have higher resistance to chemical cleaning (in particular, alkaline cleaning such as ammonia-hydrogen peroxide mixture or TMAH) than silicon that is not bonded to oxygen. It is preferable to increase the ratio of all the silicon existing in the above in the state of being bound to oxygen. On the other hand, the etching stopper film 2 is preferably an incomplete oxide film that is not a completely oxidized film. This is because mutual diffusion easily occurs with the phase shift film 3 formed of a material containing silicon, and the adhesion between the pattern of the phase shift film 3 and the etching stopper film 2 is improved. The etching stopper film 2 preferably has an oxygen content of 66 atomic% or less, and more preferably less than 66 atomic %.

The etching stopper film 2 on the phase shift film 3 side has a ratio (Si/[Si+Al] ratio of the content [atomic %] of silicon (Si) to the total content [atomic %] of silicon (Si) and aluminum (Al)). ) Is preferably 1/5 or more. By setting the Si/[Si+Al] ratio of the etching stopper film 2 on the phase shift film 3 side to 1/5 or more, the resistance to chemical cleaning can be sufficiently increased. Further, the transmittance of the etching stopper film 2 can be made higher than that in the case where it is formed of Al ₂ O ₃ . The Si/[Si+Al] ratio in the etching stopper film 2 on the phase shift film 3 side is more preferably 1/3 or more.

  The Si/[Si+Al] ratio of the etching stopper film 2 on the phase shift film 3 side is preferably 4/5 or less. By setting the Si/[Si+Al] ratio of the etching stopper film 2 on the phase shift film 3 side to 4/5 or less, the etching rate of the etching stopper film 2 on the phase shift film 3 side with respect to dry etching with a fluorine-based gas is transmitted. It can be set to 1/3 or less of the etching rate of the transparent substrate 1 (an etching selection ratio of 3 times or more can be obtained between the transparent substrate 1 and the etching stopper film 2 on the side of the phase shift film 3).

  The Si/[Si+Al] ratio in the etching stopper film 2 on the phase shift film 3 side is more preferably 3/4 or less, and further preferably 2/3 or less. When the Si/[Si+Al] ratio is 2/3 or less, the etching rate of the etching stopper film 2 on the side of the phase shift film 3 against dry etching with a fluorine-based gas is set to 1/5 or less of the etching rate of the transparent substrate 1. (It is possible to obtain an etching selection ratio of 5 times or more between the transparent substrate 1 and the etching stopper film 2 on the side of the phase shift film 3).

  The Si/[Si+Al] ratio in the etching stopper film 2 on the transparent substrate 1 side is not particularly limited as long as it is within the above-specified range. The etching stopper film 2 on the side of the transparent substrate 1 may have a Si/[Si+Al] ratio of zero (does not contain silicon). It is more preferable that the etching stopper film 2 on the transparent substrate 1 side has a Si/[Si+Al] ratio of 1/5 or more. This is to secure the resistance of the etching stopper film on the transparent substrate 1 side to the chemical cleaning and to increase the transmittance of the etching stopper film 2 for the exposure light.

  The etching stopper film 2 preferably has at least one of an amorphous structure and a microcrystalline structure. With this structure, the surface roughness of the etching stopper film 2 can be suppressed and the transmittance of the exposure light can be increased. Specifically, the etching stopper film 2 preferably has at least one of an amorphous structure and a microcrystalline structure in a state containing a bond of silicon and oxygen and a bond of aluminum and oxygen. It is more preferable that the etching stopper film 2 has an amorphous structure in a state including a bond of silicon and oxygen and a bond of aluminum and oxygen.

  The etching stopper film 2 preferably has a thickness of 3 nm or more. By forming the etching stopper film 2 with a material containing silicon, aluminum and oxygen, the etching rate for the fluorine-based gas is significantly reduced, but it is not completely unetched. Further, even when the etching stopper film 2 is cleaned with a chemical solution, the film is not completely reduced. Considering the effect of dry etching with a fluorine-based gas and the effect of chemical cleaning performed from the mask blank to the manufacturing of the transfer mask, the etching stopper film 2 is desired to have a thickness of 3 nm or more. The thickness of the etching stopper film 2 is preferably 4 nm or more, more preferably 5 nm or more.

  The etching stopper film 2 is a material having a relatively high transmittance for exposure light, but the transmittance decreases as the thickness increases. Further, the etching stopper film 2 has a higher refractive index than the material forming the translucent substrate 1, and the thicker the etching stopper film 2 is, the more mask pattern (Bias correction or bias correction) actually formed on the phase shift film 3 is formed. The influence exerted when designing a pattern to which OPC, SRAF, etc. are added becomes large. Considering these points, the etching stopper film 2 is desired to be 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less.

Since the composition of the etching stopper film 2 in the film thickness direction is not uniform, the refractive index and the extinction coefficient easily change in the film thickness direction. However, even in the case of such an etching stopper film 2, it is desirable that the numerical values when the refractive index and the extinction coefficient are represented by average values in the film thickness direction are within a predetermined range. When the average refractive index and extinction coefficient in the film thickness direction are the average refractive index n _ave and the average extinction coefficient k _ave , the etching stopper film 2 is refracted with respect to the exposure light of the ArF excimer laser. The index n _ave (hereinafter, simply referred to as the refractive index n _ave ) is preferably 1.79 or less, and more preferably 1.72 or less. This is to reduce the influence on the design of the mask pattern actually formed on the phase shift film 3. Since the etching stopper film 2 is formed of a material containing aluminum, it cannot have the same refractive index n as the translucent substrate 1. The etching stopper film 2 is formed with a refractive index n _ave of 1.57 or more. On the other hand, the etching stopper film 2 preferably has an extinction coefficient k _ave (hereinafter, simply referred to as extinction coefficient k _ave ) of 0.04 or less with respect to the exposure light of the ArF excimer laser. This is to increase the transmittance of the etching stopper film 2 for exposure light. The etching stopper film 2 is made of a material having an extinction coefficient k _ave of 0.000 or more.

  Another film may be interposed between the transparent substrate 1 and the etching stopper film 2. In this case, for the other films, it is required to use a material having a higher transmittance for the exposure light and a smaller refractive index n than the etching stopper film 2. When the phase shift mask is manufactured from the mask blank, a laminated structure of the other film and the etching stopper film 2 is present in the transparent portion of the phase shift mask in the region where the pattern of the phase shift film 3 is not present. become. This is because the translucent portion is required to have a high transmittance for the exposure light, and it is necessary to increase the transmittance for the exposure light in the entire laminated structure. Examples of the material of the other film include a material composed of silicon and oxygen, or a material containing one or more elements selected from hafnium, zirconium, titanium, vanadium and boron.

  The phase shift film 3 is made of a silicon-containing material, transmits light having an intensity that does not substantially contribute to exposure, and has a predetermined phase difference. Specifically, by patterning the phase shift film 3, a portion where the phase shift film 3 remains and a portion where the phase shift film 3 does not remain are formed, and light transmitted through the portion where the phase shift film 3 is not present (ArF excimer laser exposure light) On the other hand, the phase of light transmitted through the phase shift film 3 (light having an intensity that does not substantially contribute to exposure) is substantially inverted (a predetermined phase difference). By doing so, the lights that have sneak into each other due to the diffraction phenomenon cancel each other, and the light intensity at the boundary is made substantially zero, and the contrast at the boundary, that is, the resolution is improved.

  The phase shift film 3 has a function of transmitting exposure light with a transmittance of 1% or more, and the exposure light that has passed through the air by the same distance as the thickness of the phase shift film with respect to the exposure light transmitted through the phase shift film. It is preferable to have a function of causing a phase difference of 150 degrees or more and 200 degrees or less with light. The transmittance of the phase shift film 3 is more preferably 2% or more. The transmittance of the phase shift film 3 is preferably 30% or less, and more preferably 20% or less.

  In recent years, when a halftone type phase shift mask is set on a mask stage of an exposure apparatus and transferred by exposure to an object to be transferred (a resist film on a semiconductor wafer), the pattern line width of the phase shift pattern (especially line and The problem is that the difference in the best focus of the exposure transfer due to the pattern pitch of the space pattern) is large. In order to reduce the fluctuation range of the best focus due to the pattern line width of the phase shift pattern, the predetermined phase difference in the phase shift film 3 may be 170 degrees or less.

  The thickness of the phase shift film 3 is preferably 80 nm or less, and more preferably 70 nm or less. Further, in order to reduce the fluctuation range of the best focus due to the pattern line width of the above-mentioned phase shift pattern, it is particularly preferable that the thickness of the phase shift film 3 is 65 nm or less. The thickness of the phase shift film 3 is preferably 50 nm or more. This is because it is necessary to set 50 nm or more in order to make the phase difference of the phase shift film 3 150 degrees or more while forming the phase shift film 3 with an amorphous material.

  In the phase shift film 3, the above-mentioned optical characteristics and various conditions relating to the film thickness are satisfied, so that the refractive index n of the phase shift film with respect to the exposure light (ArF exposure light) is preferably 1.9 or more. It is more preferably at least 0.0. Further, the refractive index n of the phase shift film 3 is preferably 3.1 or less, more preferably 2.7 or less. The extinction coefficient k of the phase shift film 3 with respect to ArF exposure light is preferably 0.26 or more, and more preferably 0.29 or more. The extinction coefficient k of the phase shift film 3 is preferably 0.62 or less, more preferably 0.54 or less.

  On the other hand, as will be described later, one set of a low transmission layer made of the phase shift film 3 made of a material having a relatively low exposure light transmittance and a high transmission layer made of a material having a relatively high exposure light transmittance are provided. In some cases, the above-described laminated structure is adopted. In this case, the low transmission layer has a refractive index n with respect to ArF exposure light of less than 2.5 (preferably 2.4 or less, more preferably 2.2 or less, further preferably 2.0 or less), and has an extinction coefficient. The coefficient k is preferably 1.0 or more (preferably 1.1 or more, more preferably 1.4 or more, still more preferably 1.6 or more). Further, the high transmission layer has a refractive index n for ArF exposure light of 2.5 or more (preferably 2.6 or more) and an extinction coefficient k of less than 1.0 (preferably 0.9 or less, more preferably 0.7 or less, and more preferably 0.4 or less).

  The refractive index n and the extinction coefficient k of the thin film including the phase shift film 3 are not determined only by the composition of the thin film. The film density and crystalline state of the thin film are also factors that influence the refractive index n and the extinction coefficient k. Therefore, various conditions for forming a thin film by reactive sputtering are adjusted so that the thin film has a desired refractive index n and extinction coefficient k. In order to make the phase shift film 3 within the above range of the refractive index n and the extinction coefficient k, a mixed gas of a noble gas and a reactive gas (oxygen gas, nitrogen gas, etc.) at the time of film formation by reactive sputtering. Adjusting the ratio of is effective, but not limited to. The pressure in the film forming chamber during film formation by reactive sputtering, the electric power applied to the sputtering target, and the positional relationship such as the distance between the target and the transparent substrate 1 are wide-ranging. Further, these film forming conditions are peculiar to the film forming apparatus and are appropriately adjusted so that the formed phase shift film 3 has a desired refractive index n and extinction coefficient k.

Generally, the phase shift film 3 made of a material containing silicon is patterned by dry etching with a fluorine-based gas. The transparent substrate 1 made of a glass material is easily etched by dry etching with a fluorine-based gas, and has low resistance to a fluorine-based gas containing carbon. Therefore, when patterning the phase shift film 3, dry etching using a fluorine-based gas (SF ₆ or the like) containing no carbon as an etching gas is often applied. In the case of dry etching using a fluorine-based gas, the etching anisotropy is relatively easy to increase. However, when the phase shift film 3 is patterned by dry etching using a fluorine-based gas using an etching mask pattern such as a resist pattern as a mask, the stage where the dry etching first reaches the lower end of the phase shift film 3 (this is called just etching) If the time required from the start of etching to the stage of just etching is called just etching time.), the verticality of the side wall of the phase shift pattern becomes low and the exposure transfer performance as a phase shift mask is affected. Occurs. Further, the pattern formed on the phase shift film 3 has a difference in density within the plane of the mask blank, and the progress of dry etching is slow in a portion where the pattern is relatively dense, so that an etching residue easily occurs in that portion. ..

  Due to these circumstances, during the dry etching of the phase shift film 3, even if it reaches the stage of just etching, additional etching is further continued (overetching) to increase the verticality of the side wall of the phase shift pattern, and thereby, in-plane The CD uniformity of the phase shift pattern is increased (the time from the end of just etching to the end of overetching is called overetching time). When the etching stopper film 2 is not provided between the light-transmissive substrate 1 and the phase shift film 3, if the phase shift film 3 is over-etched, the pattern side wall of the phase shift film 3 is etched and the light is transmitted at the same time. Since the etching of the surface of the transparent substrate 1 progresses, overetching cannot be performed for a very long time (the translucent substrate is stopped by about 4 nm from the surface), and the phase shift pattern is perpendicular. It was difficult to improve sex.

  The bias voltage applied during the dry etching of the phase shift film 3 is made higher than before (hereinafter, referred to as “high bias etching”) for the purpose of further improving the verticality of the side wall of the phase shift pattern. .. In this high bias etching, there is a problem in that the translucent substrate 1 near the side wall of the phase shift pattern is locally etched by etching, that is, a so-called micro trench is generated. The generation of the micro-trench occurs because the ionized etching gas wraps around to the side wall of the phase shift pattern having a lower resistance value than the transparent substrate 1 due to the charge-up generated by applying a bias voltage to the transparent substrate 1. It is believed that the cause is.

On the other hand, when an etching stopper film made of Al ₂ O ₃ is provided between the transparent substrate 1 and the phase shift film 3, the etching stopper film is etched even if the phase shift film 3 is over-etched. Since the amount is minute, the phase shift pattern can be formed with high accuracy, and the micro trenches that are likely to be generated by high bias etching can be suppressed. However, by performing the chemical cleaning after that, the phenomenon that the etching stopper film is dissolved and the phase shift pattern falls off easily occurs. Since the etching stopper film 2 of the first embodiment is formed of a material containing silicon, aluminum and oxygen, the etching stopper film 2 remains even if the phase shift film 3 is over-etched. Therefore, it is possible to suppress the micro-trench which is likely to occur in the high bias etching, the resistance to the chemical cleaning performed thereafter is also sufficiently high, and the phenomenon that the phase shift pattern is dropped is also suppressed.

  The phase shift film 3 can be formed of a material containing silicon and nitrogen. By including nitrogen in silicon, the refractive index n is made larger (a larger phase difference can be obtained at a thinner thickness) and the extinction coefficient k is made smaller (increased transmittance) than a material made of only silicon. It is possible to obtain the desired optical characteristics as a phase shift film.

  The phase shift film 3 is made of a material composed of silicon and nitrogen, or a material composed of a material composed of silicon and nitrogen and containing at least one element selected from a semi-metal element, a non-metal element and a noble gas (hereinafter, these materials are collectively referred to as “materials”). And referred to as “silicon-based material”). The phase shift film 3 made of a silicon material does not contain a transition metal that may cause a decrease in light resistance to ArF exposure light. Further, metal elements other than transition metals are not included because it is undeniable that they may be a factor that reduces the light resistance to ArF exposure light. The phase shift film 3 made of a silicon-based material may contain any metalloid element. Among these metalloid elements, when one or more elements selected from boron, germanium, antimony and tellurium are contained, the conductivity of silicon used as a target when the phase shift film 3 is formed by the sputtering method can be increased. It is preferable because it can be expected.

  The phase shift film 3 made of a silicon-based material may contain a noble gas such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). The phase shift film 3 made of a silicon-based material preferably has an oxygen content of 10 atomic% or less, more preferably 5 atomic% or less, and does not actively contain oxygen (X-ray photoelectron It is more preferable that the result of the composition analysis by the spectroscopy is less than or equal to the lower limit of detection). This is because when the silicon-based material contains oxygen, the extinction coefficient k tends to be significantly reduced, and the overall thickness of the phase shift film 3 increases.

  The phase shift film 3 made of a silicon-based material may be composed of a single layer or may be composed of a laminate of a plurality of layers except for a surface layer (oxidized layer) in which oxidation is unavoidable. A phase shift film 3 which is a single-layer film (including a surface oxide layer) made of a silicon-based material and which has optical characteristics of transmitting ArF exposure light with a predetermined transmittance and generating a predetermined phase difference. It is possible to form. However, when the phase shift film 3 made of a material having such optical characteristics is formed by a sputtering method, depending on the method, a film having high uniformity of optical characteristics or a film having low defects can be stably formed. The film forming conditions may be difficult. Considering these points, the phase shift film 3 made of a silicon-based material may have a structure in which a low transmission layer having a relatively low nitrogen content and a high transmission layer having a relatively high nitrogen content are laminated.

  It is preferable that the low transmission layer and the high transmission layer in the phase shift film 3 made of a silicon-based material have a structure in which the low transmission layer and the high transmission layer are in direct contact with each other without interposing another film. Further, it is preferable that the low permeable layer and the high permeable layer have a film structure in which a film made of a material containing a metal element is not in contact. This is because, if heat treatment or irradiation with ArF exposure light is performed in a state where the film containing a metal element is in contact with the film containing silicon, the metal element tends to diffuse into the film containing silicon.

  The low transmission layer and the high transmission layer in the phase shift film 3 made of a silicon-based material are preferably made of the same constituent elements. When one of the low transmission layer and the high transmission layer contains different constituent elements, and when heat treatment or irradiation with ArF exposure light is performed in a state where these layers are in contact with each other, the different constituent elements are There is a possibility that it may move to the layer on the side not containing the constituent element and diffuse. Then, the optical characteristics of the low transmission layer and the high transmission layer may change significantly from the beginning of film formation. The low permeable layer and the high permeable layer of the phase shift film 3 may be stacked in any order from the etching stopper film 2 side.

  The phase shift film 3 made of a silicon-based material preferably has two or more sets of a single layered structure including one low transmission layer and one high transmission layer. Further, it is preferable that any one of the low transmission layer and the high transmission layer has a thickness of 20 nm or less.

The phase shift film 3 made of a silicon-based material is at a position farthest from the transparent substrate 1 and is made of a material composed of silicon, nitrogen and oxygen, or one or more selected from a semi-metal element, a non-metal element and a noble gas. Has a top layer formed of a material containing the element. The uppermost layer formed of a material composed of silicon, nitrogen and oxygen, or a material containing one or more elements selected from a semi-metal element, a non-metal element and a noble gas in the material is almost the same in the thickness direction of the layer. In addition to the composition, the composition has a composition gradient in the layer thickness direction, that is, a composition having a composition gradient in which the oxygen content in the layer increases as the uppermost layer moves away from the transparent substrate 1. Be done. Suitable materials for the uppermost layer having a composition having substantially the same composition in the thickness direction of the layer include SiO ₂ and SiON. As the uppermost layer having a composition gradient in the layer thickness direction, the transparent substrate 1 side is SiN, the oxygen content increases as the distance from the transparent substrate 1 increases, and the surface layer is SiO ₂ or SiON. A certain configuration is preferable.

  The low transmission layer, the high transmission layer and the uppermost layer in the phase shift film 3 made of a silicon-based material are formed by sputtering, but any sputtering such as DC sputtering, RF sputtering and ion beam sputtering can be applied. When using a target having low conductivity, such as a silicon target or a silicon compound target that does not contain a metalloid element or has a small content, it is preferable to apply RF sputtering or ion beam sputtering. Then, it is more preferable to apply RF sputtering.

  The etching end point detection for EB defect correction is at least one of Auger electron, secondary electron, characteristic X-ray, and backscattered electron emitted from the irradiated portion when an electron beam is irradiated to the black defect. Is done by detecting. For example, in the case of detecting Auger electrons emitted from a portion irradiated with an electron beam, a change in material composition is mainly observed by Auger electron spectroscopy (AES). When detecting secondary electrons, changes in the surface shape are mainly observed from the SEM image. Furthermore, when detecting characteristic X-rays, changes in material composition are mainly observed by energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX). When detecting backscattered electrons, changes in material composition and crystalline state are mainly observed by electron backscatter diffraction (EBSD).

  A mask blank having a structure in which a phase shift film (both a single layer film and a multilayer film) made of a silicon-based material is provided in contact with the main surface of a light-transmitting substrate 1 made of a glass material has a phase shift film 3 made of silicon and nitrogen. Is most of the components, whereas the transparent substrate 1 has most of the components of silicon and oxygen, and the difference between the two is substantially only oxygen and nitrogen. Therefore, it is a combination in which it is difficult to detect the etching correction of the EB defect correction. On the other hand, in the case where the phase shift film 3 is provided in contact with the surface of the etching stopper film 2, the phase shift film 3 contains silicon and nitrogen as most components, whereas the etching stopper film 2 contains silicon. Contains aluminum in addition to oxygen. Therefore, in the etching correction for the EB defect correction, the detection of aluminum may be used as a guide, and the end point detection becomes relatively easy.

  On the other hand, the phase shift film 3 can be formed of a material containing a transition metal, silicon and nitrogen. In this case, the transition metal includes molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V), zirconium ( Zr), ruthenium (Ru), rhodium (Rh), zinc (Zn), niobium (Nb), palladium (Pd), or any one or more metals thereof or alloys of these metals can be used. The material of the phase shift film 3 may include elements such as nitrogen (N), oxygen (O), carbon (C), hydrogen (H), and boron (B) in addition to the above elements. Further, the material of the phase shift film 3 may include an inert gas such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe). Considering detection of the etching end point for EB defect correction, it is preferable that the phase shift film 3 does not contain aluminum.

The phase shift film 3 has a ratio ((atomic %) calculated by dividing the content [atomic %] of the transition metal (M) in the film by the total content [atomic %] of the transition metal (M) and silicon (Si)). Hereinafter, the M/[M+Si] ratio is required to be 0.15 or less. As the content of the transition metal increases, the phase shift film 3 has a higher etching rate for dry etching with a fluorine-based gas (SF ₆ or the like) that does not contain carbon, so that the etching with the transparent substrate 1 is performed. Selectivity is easily obtained, but it is not enough. Further, if the M/[M+Si] ratio of the phase shift film 3 is higher than this, it is necessary to add a large amount of oxygen in order to obtain a desired transmittance, which may increase the thickness of the phase shift film 3. , Not preferable.

  When it is necessary to increase the resistance to the irradiation of ArF exposure light, the M/[M+Si] ratio of the phase shift film 3 is preferably less than 0.04. The M/[M+Si] ratio in the phase shift film 3 is more preferably 0.03 or less, and further preferably 0.02 or less.

On the other hand, the M/(M+Si) ratio in the phase shift film 3 is preferably 0.01 or more. When producing a phase shift mask from a mask blank, when applying electron beam irradiation and defect correction with a non-excited gas such as XeF ₂ to black defects existing in the pattern of the phase shift film 3, This is because the sheet resistance is preferably low.

  The light-shielding film 4 may have a single-layer structure or a laminated structure of two or more layers. In addition, each layer of the light-shielding film having a single-layer structure and the light-shielding film having a laminated structure of two or more layers has a compositional gradient in the thickness direction of the layer even if the composition is almost the same in the thickness direction of the film or layer. It may be configured.

  The mask blank 100 shown in FIG. 1 has a structure in which a light shielding film 4 is laminated on a phase shift film 3 without interposing another film. For the light-shielding film 4 in this configuration, it is necessary to apply a material having sufficient etching selectivity with respect to the etching gas used when forming the pattern on the phase shift film 3.

  In this case, the light shielding film 4 is preferably made of a material containing chromium. The material containing chromium forming the light-shielding film 4 is selected from chromium (Cr), oxygen (O), nitrogen (N), carbon (C), boron (B), and fluorine (F) in addition to chromium metal. Materials containing one or more of the elements mentioned above. Generally, a chromium-based material is etched with a mixed gas of chlorine-based gas and oxygen gas. The material for forming the light-shielding film 4 is preferably a material containing chromium and one or more elements selected from oxygen, nitrogen, carbon, boron and fluorine. Further, the chromium-containing material forming the light-shielding film 4 may contain one or more elements of molybdenum (Mo), indium (In), and tin (Sn).

  The mask blank of the present invention is not limited to the one shown in FIG. 1, and is configured such that another film (etching mask/stopper film) is interposed between the phase shift film 3 and the light shielding film 4. May be. In this case, it is preferable that the etching mask/stopper film is formed of the material containing chromium and the light shielding film 4 is formed of the material containing silicon.

  The material containing silicon forming the light-shielding film 4 may contain a transition metal or a metal element other than the transition metal. The transition metal contained in the light shielding film 4 is molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V). Examples thereof include any one metal of zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), and alloys of these metals.

  After the completion of the phase shift mask, the light shielding film 4 forms a light shielding band or the like in a laminated structure with the phase shift film 3. Therefore, the light-shielding film 4 is required to secure an optical density (OD) larger than 2.0 in the laminated structure with the phase shift film 3, and it is preferable that the OD is 2.8 or more. It is more preferable that the OD is 0 or more.

  In the present embodiment, the hard mask film 5 laminated on the light shielding film 4 is formed of a material having etching selectivity with respect to the etching gas used when the light shielding film 4 is etched. Thereby, as described below, the thickness of the resist film can be significantly reduced as compared with the case where the resist film is directly used as a mask of the light shielding film 4. In the mask blank 100, a resist pattern may be directly formed on the light shielding film 4 without forming the hard mask film 5, and the light shielding film 4 may be directly etched using the resist pattern as a mask.

When the light-shielding film 4 is made of a material containing chromium, the hard mask film 5 is preferably made of the above-mentioned material containing silicon. Here, since the hard mask film 5 in this case tends to have low adhesiveness with the resist film of an organic material, the surface of the hard mask film 5 is subjected to HMDS (Hexamethyldisilazane) treatment to obtain the adhesiveness of the surface. Is preferably improved. The hard mask film 5 in this case is more preferably formed of SiO ₂ , SiN, SiON, or the like.

  When the light-shielding film 4 is made of a material containing chromium, a material containing tantalum can be used as the material of the hard mask film 5. Examples of the material containing tantalum in this case include tantalum metal and materials containing tantalum containing one or more elements selected from nitrogen, oxygen, boron and carbon. When the light-shielding film 4 is made of a material containing silicon, the hard mask film 5 is preferably made of the above-mentioned material containing chromium.

  The etching stopper film 2, the phase shift film 3, the light shielding film 4, and the hard mask film 5 are formed by sputtering, but any sputtering such as DC sputtering, RF sputtering and ion beam sputtering can be applied. When a target having low conductivity is used, it is preferable to apply RF sputtering or ion beam sputtering, but it is more preferable to apply RF sputtering in consideration of the film forming rate.

As a method of forming the etching stopper film 2, it is possible to apply a sputtering method in which the composition is selected in advance from the above range of Si/[Si+Al] and oxygen content. In this case, it is preferable that two targets, a mixed target of silicon and oxygen and a mixed target of aluminum and oxygen, are arranged in the film forming chamber to form the etching stopper film 2 on the transparent substrate 1. Specifically, the translucent substrate 1 is placed on the substrate stage in the film forming chamber, and is placed under a noble gas atmosphere such as argon gas (or a mixed gas atmosphere with oxygen gas or a gas containing oxygen). A predetermined voltage is applied to each of the two targets (in this case, an RF power source is preferable). As a result, the noble gas particles turned into plasma collide with the two targets to cause a sputtering phenomenon, and the etching stopper film 2 containing silicon, aluminum and oxygen is formed on the surface of the transparent substrate 1. During the formation of the etching stopper film 2, the voltage between the two targets is adjusted to adjust the amount of sputtered particles scattered from each target. As a result, the etching stopper film 2 can be configured as described above. It is more preferable to apply a SiO ₂ target and an Al ₂ O ₃ target to the _two targets in these cases.

  On the other hand, as a method for forming the etching stopper film 2, first, an etching stopper film 2 containing aluminum and oxygen is formed by a sputtering method, and then a phase shift film containing silicon (for pattern formation) is formed in contact with the etching stopper film 2. The thin film) 3 is formed, and the translucent substrate 1 on which the etching stopper film 2 and the phase shift film 3 have been formed is subjected to heat treatment at a temperature of 400° C. or higher to etch the above composition gradient film. A method of forming the stopper film 2 can also be applied.

  Specifically, first, a mixed target of aluminum and oxygen is placed in the film forming chamber, the transparent substrate 1 is placed on the substrate stage, and a noble gas atmosphere such as argon gas (or oxygen gas or oxygen A predetermined voltage is applied to the target in a mixed gas atmosphere with the contained gas) (in this case, an RF power source is preferable). As a result, the etching stopper film 2 containing aluminum and oxygen is formed on the transparent substrate 1. Next, a target containing silicon is placed in the film forming chamber, and the translucent substrate 1 having the etching stopper film 2 provided on the substrate stage is placed. Then, by applying a predetermined voltage to the target in an atmosphere of a mixed gas of a reactive gas and a noble gas (in this case, an RF power source is preferable), a phase shift containing silicon on the transparent substrate 1 is performed. The film 3 is formed.

  Next, the transparent substrate 1 in which the etching stopper film 2 and the phase shift film 3 are laminated in this order is placed in a heating furnace, and heat treatment is performed at a temperature of 400° C. or higher. When the etching stopper film 2 and the phase shift film 3 are heated at a high temperature, silicon in the phase shift film 3 diffuses from the phase shift film 3 side of the etching stopper film 2 toward the transparent substrate 1 side. Occur. As a result, the etching stopper film 2 becomes a composition gradient film in which the Si/[Si+Al] ratio on the phase shift film 3 side is higher than the Si/[Si+Al] ratio on the transparent substrate 1 side. The etching stopper film 2 formed by this method has a high adhesiveness with the phase shift film 3, and the pattern becomes more difficult to detach when the pattern is formed on the phase shift film 3.

  The heating temperature of the heat treatment for the etching stopper film 2 and the phase shift film 3 is more preferably 450° C. or higher. On the other hand, the heating temperature of the heat treatment is preferably 900° C. or lower in consideration of the influence of deformation and the like on the transparent substrate 1. The heating time of the heat treatment is preferably 10 minutes or longer, more preferably 20 minutes or longer, and further preferably 30 minutes or longer. On the other hand, the heating time of the heat treatment is preferably 120 minutes or less, and more preferably 90 minutes or less. The above heat treatment can also serve as an annealing treatment for reducing the film stress of the phase shift film 3. The phase shift film 3 may be made of any of a transition metal, a material containing silicon and nitrogen, and a material containing silicon and nitrogen.

  In the case of the etching stopper film 2 of the composition gradient film formed by the heat treatment, the etching stopper film 2 made of the material containing aluminum and oxygen when formed by the sputtering method is not completely oxidized (oxygen deficiency exists). Incomplete oxide film). In the etching stopper film 2 of the incomplete oxide film, compared with the etching stopper film of the complete oxide film, silicon is more likely to diffuse from the phase shift film 3 during the heat treatment, and the etching stopper film 2 having a composition gradient of Si/[Si+Al] ratio is formed. This is because they are easily formed. The etching stopper film made of a material containing aluminum and oxygen formed by the above sputtering method may contain silicon, but the Si/[Si+Al] ratio is 1/5 or less. preferable.

  Examples of the noble gas used when forming the etching stopper film 2 and the phase shift film 3 by the sputtering method include helium, neon, argon, krypton, and xenon. In addition, examples of the reactive gas used when forming the phase shift film 3 by the sputtering method include oxygen, nitrogen, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, methane, and ethane.

  On the other hand, as a method of forming the etching stopper film 2, first, an etching stopper film 2 containing aluminum and oxygen is formed by a sputtering method, and then a phase shift film containing silicon (for pattern formation) is formed in contact with the etching stopper film 2. Thin film) 3 is formed, and the light-transmissive substrate 1 on which the etching stopper film 2 and the phase shift film 3 have been formed is subjected to a light irradiation process to form the etching stopper film 2 of the above composition gradient film. The method of doing is also applicable. In this light irradiation processing, light (high energy rays) emitted from a flash lamp is irradiated to the transparent substrate 1 on which the etching stopper film 2 and the phase shift film 3 have been formed.

A flash lamp is a light source capable of emitting light having a continuous and wide wavelength range. As the flash lamp, for example, a lamp capable of emitting light by enclosing a gas such as xenon in a tube made of a material that transmits light such as glass and applying a high voltage in a pulsed manner to the tube is used. it can. The irradiation intensity of the flash lamp is 0.1 to 100 J/cm ² , preferably 1 to 50 J/cm ² , and more preferably 10 to 50 J/cm ² . If the irradiation intensity is higher than this range, the phase shift film 3 may be scattered or the surface may be roughened. If the irradiation intensity is smaller than this range, the silicon in the phase shift film 3 may not diffuse into the etching stopper film 2.

  The irradiation time of the light from the flash lamp is 1 second or less, preferably 0.1 second or less, more preferably 0.01 second or less. By shortening the irradiation time of the light emitted from the flash lamp, the silicon in the phase shift film 3 can be diffused into the etching stopper film 2 without heating the transparent substrate 1 too much. This can prevent the transparent substrate 1 from being damaged. The light from the flash lamp may be irradiated from the film surface or the main surface side of the translucent substrate 1 where the etching stopper film 2 is not provided.

  The atmosphere around the place where the translucent substrate 1 is placed when irradiating light with a flash lamp is an inert gas such as argon, nitrogen, oxygen, or a mixed gas of two or more of these, in vacuum, or in the atmosphere. Any atmosphere, such as inside, may be used. Other matters are the same as in the case of forming the etching stopper film 2 of the composition gradient film by the above heat treatment.

  As described above, the mask blank 100 according to the first embodiment contains silicon, aluminum and oxygen between the transparent substrate 1 and the phase shift film 3 which is a thin film for pattern formation, and the phase shift film 3 side is The etching stopper film 2 has a higher ratio of the silicon content to the total content of silicon and aluminum in atomic% than that of the transparent substrate 1 side. The etching stopper film 2 has a higher resistance to dry etching with a fluorine-based gas when forming a pattern on the phase shift film 3 than the translucent substrate 1, and has a higher resistance to chemical cleaning, so that the exposure light is exposed. It simultaneously satisfies the three characteristics of high transmittance for Accordingly, when the transfer pattern is formed on the phase shift film 3 by dry etching using a fluorine-based gas, overetching can be performed without engraving the main surface of the translucent substrate 1, and thus the verticality of the pattern sidewalls can be improved. And the CD uniformity in the plane of the pattern can be improved. Further, when the black defect of the phase shift pattern found during the manufacture of the phase shift mask is corrected by the EB defect correction, the etching end point is easily detected, so that the black defect can be accurately corrected.

[Phase shift mask and its manufacture]
In the phase shift mask 200 (see FIG. 2) according to the first embodiment, the etching stopper film 2 of the mask blank 100 is left on the entire main surface of the transparent substrate 1, and a transfer pattern is formed on the phase shift film 3. (Phase shift pattern 3a) is formed, and a pattern including a light blocking band (light blocking pattern 4b: light blocking band, light blocking patch, etc.) is formed on the light blocking film 4. In the case where the mask blank 100 is provided with the hard mask film 5, the hard mask film 5 is removed during the production of the phase shift mask 200.

  That is, the phase shift mask 200 according to the first embodiment includes the phase shift pattern 3a, which is a phase shift film having a transfer pattern on the main surface of the transparent substrate 1, and the light-shielding band is provided on the phase shift pattern 3a. A light-shielding pattern 4b which is a light-shielding film having a pattern including a pattern, and an etching stopper film 2 between the light-transmissive substrate 1 and the phase shift pattern 3a. The phase shift pattern 3a contains silicon, and the etching stopper film 2 Contains silicon, aluminum and oxygen, and the ratio of the silicon content to the total content of silicon and aluminum on the phase shift film 3 side is higher than that on the transparent substrate 1 side in terms of atomic%. is there.

  The method for manufacturing the phase shift mask according to the first embodiment uses the mask blank 100 described above, and includes a step of forming a transfer pattern on the light shielding film 4 by dry etching, and a light shielding film having the transfer pattern. 4 as a mask, a step of forming a transfer pattern on the phase shift film 3 by dry etching using a fluorine-based gas, and a pattern including a light-shielding band (light-shielding band, light-shielding patch, etc.) is formed on the light-shielding film 4 by dry etching. And a process. The method of manufacturing the phase shift mask 200 according to the first embodiment will be described below according to the manufacturing process shown in FIG. Here, a method for manufacturing the phase shift mask 200 using the mask blank 100 in which the hard mask film 5 is laminated on the light shielding film 4 will be described. Further, a case where a material containing chromium is applied to the light shielding film 4 and a material containing silicon is applied to the hard mask film 5 will be described.

  First, a resist film is formed in contact with the hard mask film 5 in the mask blank 100 by a spin coating method. Next, a first pattern which is a transfer pattern (phase shift pattern) to be formed on the phase shift film 3 is drawn on the resist film with an electron beam, and a predetermined process such as a development process is performed to perform the phase A first resist pattern 6a having a shift pattern is formed (see FIG. 3A). Then, dry etching using a fluorine-based gas is performed using the first resist pattern 6a as a mask to form a first pattern (hard mask pattern 5a) on the hard mask film 5 (see FIG. 3B). ..

  Next, after removing the resist pattern 6a, dry etching using a mixed gas of chlorine-based gas and oxygen gas is performed using the hard mask pattern 5a as a mask to form a first pattern (light-shielding pattern 4a) on the light-shielding film 4. Are formed (see FIG. 3C). Subsequently, using the light shielding pattern 4a as a mask, dry etching using a fluorine-based gas is performed to form a first pattern (phase shift pattern 3a) on the phase shift film 3 and, at the same time, remove the hard mask pattern 5a ( See FIG. 3D).

  During the dry etching of the phase shift film 3 with a fluorine-based gas, additional etching (over etching) is performed to increase the verticality of the pattern side walls of the phase shift pattern 3a and to improve the CD uniformity in the plane of the phase shift pattern 3a. Etching). Even after the over-etching, the surface of the etching stopper film 2 is slightly etched, and the surface of the transparent substrate 1 is not exposed at the transparent portion of the phase shift pattern 3a.

  Next, a resist film is formed on the mask blank 100 by a spin coating method. Thereafter, a second pattern, which is a pattern (light-shielding pattern) to be formed on the light-shielding film 4, is drawn on the resist film with an electron beam, and a predetermined process such as a developing process is further performed to form a second pattern having the light-shielding pattern. Forming a resist pattern 7b (see FIG. 3E). Here, since the second pattern is a relatively large pattern, it is possible to replace with drawing using an electron beam and perform exposure drawing using a laser beam by a laser drawing apparatus having a high throughput.

  Then, using the second resist pattern 7b as a mask, dry etching is performed using a mixed gas of chlorine-based gas and oxygen gas to form a second pattern (light-shielding pattern 4b) on the light-shielding film 4. Further, the second resist pattern 7b is removed, and predetermined processing such as cleaning is performed to obtain the phase shift mask 200 (see FIG. 3F). In the cleaning step, ammonia-hydrogen peroxide mixture was used, but the surface of the etching stopper film 2 was hardly dissolved and the surface of the transparent substrate 1 was not exposed in the transparent portion of the phase shift pattern 3a.

The chlorine-based gas used in the dry etching is not particularly limited as long as it contains chlorine (Cl). For example, Cl ₂ , SiCl ₂ , CHCl ₃ , CH ₂ Cl ₂ , BCl _{3 and the} like can be mentioned. Further, since the mask blank 100 includes the etching stopper film 2 on the transparent substrate 1, the fluorine-based gas used in the dry etching is not particularly limited as long as it contains fluorine (F). Absent. For _{example, CHF 3, CF 4, C} 2 F 6, C 4 F 8, SF 6 , and the like.

  The phase shift mask 200 according to the first embodiment is manufactured using the mask blank 100 described above. The etching stopper film 2 has higher resistance to dry etching with a fluorine-based gas when forming a pattern on the phase shift film 3 than the translucent substrate 1, has higher resistance to chemical cleaning, and has a transmittance for exposure light. It simultaneously satisfies the three characteristics of high price. Accordingly, when the phase shift pattern (transfer pattern) 3a is formed on the phase shift film 3 by dry etching using a fluorine-based gas, overetching can be performed without engraving the main surface of the translucent substrate 1. Therefore, in the phase shift mask 200 of the first embodiment, the sidewall of the phase shift pattern 3a has a high verticality, and the in-plane CD uniformity of the phase shift pattern 3a is also high. Further, during the manufacturing of the phase shift mask 200, a black defect is found in the phase shift pattern 3a, and when the black defect is corrected by the EB defect correction, the etching end point is easily detected. Therefore, the black defect is accurately corrected. can do.

[Manufacturing of semiconductor devices]
The method of manufacturing a semiconductor device according to the first embodiment uses a phase shift mask 200 manufactured by using the phase shift mask 200 according to the first embodiment or the mask blank 100 according to the first embodiment to form a resist film on a semiconductor substrate. The feature is that the transfer pattern is transferred by exposure. The phase shift mask 200 according to the first embodiment has high verticality of the side wall of the phase shift pattern 3a and high in-plane CD uniformity of the phase shift pattern 3a. Therefore, when the phase shift mask 200 according to the first embodiment is used to perform exposure and transfer onto the resist film on the semiconductor device, a pattern can be formed on the resist film on the semiconductor device with sufficient accuracy to meet design specifications.

  In addition, even when the black defect portion is exposed and transferred to the resist film on the semiconductor device using the phase shift mask in which the black defect portion is corrected by the EB defect correction during the manufacturing, the black defect is accurately corrected. It is possible to prevent the transfer failure from occurring in the resist film on the semiconductor device corresponding to the pattern portion where the black defect of 200 existed. Therefore, when a circuit pattern is formed by dry-etching a film to be processed using this resist pattern as a mask, a circuit pattern with high precision and high yield is formed without wiring short circuit or disconnection due to insufficient accuracy or transfer failure. be able to.

<Second Embodiment>
[Mask blank and its manufacture]
A mask blank according to a second embodiment of the present invention uses a thin film for pattern formation as a light-shielding film having a predetermined optical density, and includes a binary type mask (transfer mask), a recessed Levenson type phase shift mask ( It is used for manufacturing a transfer mask) or a CPL (Chromeless Phase Lithography) mask (transfer mask). FIG. 4 shows the structure of the mask blank of this second embodiment. The mask blank 110 of the second embodiment has a structure in which an etching stopper film 2, a light shielding film (pattern forming thin film) 8 and a hard mask film 9 are sequentially stacked on a transparent substrate 1. The same components as those of the mask blank of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted here.

  The light shielding film 8 is a pattern forming thin film on which a transfer pattern is formed when a binary mask is manufactured from a mask blank. In the binary mask, the pattern of the light shielding film 8 is required to have high light shielding performance. The OD with respect to the exposure light is required to be 2.8 or more only with the light shielding film 8, and the OD of 3.0 or more is more preferable. The light-shielding film 8 may have a single-layer structure or a laminated structure of two or more layers. In addition, each layer of the light-shielding film having a single-layer structure and the light-shielding film having a laminated structure of two or more layers has a compositional gradient in the thickness direction of the layer even if the composition is almost the same in the thickness direction of the film or layer. It may be configured.

  The light shielding film 8 is formed of a material capable of patterning a transfer pattern by dry etching with a fluorine-based gas. Examples of materials having such characteristics include materials containing silicon, as well as materials containing transition metals and silicon. A material containing a transition metal and silicon has higher light-shielding performance than a material containing silicon that does not contain a transition metal, and the thickness of the light-shielding film 8 can be reduced. The transition metal contained in the light shielding film 8 is molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V). Examples thereof include any one metal of zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), and alloys of these metals. Considering the detection of the etching end point for EB defect correction, it is preferable that the light shielding film 8 does not contain aluminum.

  When forming the light-shielding film 8 with a material containing silicon, a metal other than a transition metal (tin (Sn) indium (In), gallium (Ga), etc.) may be contained. However, if aluminum is contained in the material containing silicon, the etching selectivity of the dry etching with the fluorine-based gas between the material containing silicon and the etching stopper film 2 may be deteriorated. When the etching is performed, it may be difficult to detect the etching end point.

  The light-shielding film 8 can be formed of a material composed of silicon and nitrogen, or a material composed of a material composed of silicon and nitrogen and containing at least one element selected from a semi-metal element, a non-metal element and a noble gas. In this case, the light shielding film 8 may contain any metalloid element. Among these metalloid elements, if one or more elements selected from boron, germanium, antimony and tellurium are contained, it is expected that the conductivity of silicon used as a target when the light shielding film 8 is formed by the sputtering method is increased. It is possible because it is possible.

  When the light-shielding film 8 has a laminated structure including a lower layer and an upper layer, the lower layer is formed of a material made of silicon or a material containing at least one element selected from carbon, boron, germanium, antimony and tellurium in silicon, and the upper layer. Can be formed of a material containing silicon and nitrogen or a material containing one or more elements selected from a semi-metal element, a non-metal element and a noble gas in a material containing silicon and nitrogen.

  The light shielding film 8 may be formed of a material containing tantalum. In this case, the content of silicon in the light shielding film 8 is preferably 5 atom% or less, more preferably 3 atom% or less, and further preferably substantially not contained. The material containing tantalum is a material that can be patterned into a transfer pattern by dry etching with a fluorine-based gas. Examples of the material containing tantalum in this case include tantalum metal and materials containing tantalum containing one or more elements selected from nitrogen, oxygen, boron and carbon. Examples thereof include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN.

  The material forming the light-shielding film 8 may contain one or more elements selected from oxygen, nitrogen, carbon, boron, and hydrogen as long as the optical density is not significantly reduced. In order to reduce the reflectance with respect to the exposure light on the surface of the light-shielding film 8 on the side opposite to the transparent substrate 1, the surface layer on the side opposite to the transparent substrate 1 (in the case of a two-layer structure of a lower layer and an upper layer, The upper layer) may contain a large amount of oxygen and nitrogen.

  Also in the mask blank of the second embodiment, the hard mask film 9 is provided on the light shielding film 8. The hard mask film 9 needs to be formed of a material having etching selectivity with respect to the etching gas used for etching the light shielding film 8. This hard mask film 9 is preferably formed of a material containing chromium. Further, the hard mask film 9 is more preferably formed of a material containing, in addition to chromium, one or more elements selected from nitrogen, oxygen, carbon, hydrogen and boron. The hard mask film 9 is formed by using at least one metal element selected from indium (In), tin (Sn), and molybdenum (Mo) (hereinafter, these metal elements are referred to as “metals such as indium”) in addition to these chromium-containing materials. It may be formed of a material containing an element.

  As described above, in the mask blank 110 of the second embodiment, silicon, aluminum and oxygen are contained between the transparent substrate 1 and the light shielding film 8 which is a thin film for pattern formation, and the phase shift film 3 side is transparent. The etching stopper film 2 has a higher ratio of the silicon content with respect to the total silicon and aluminum content in atomic% than that of the optical substrate 1 side. The etching stopper film 2 has a higher resistance to dry etching with a fluorine-based gas when forming a pattern on the light-shielding film 8 than the translucent substrate 1, has a higher resistance to chemical cleaning, and has a higher resistance to exposure light. It simultaneously satisfies the three characteristics of high transmittance. Thereby, when the transfer pattern is formed on the light-shielding film 8 by dry etching using a fluorine-based gas, overetching can be performed without engraving the main surface of the translucent substrate 1, so that the verticality of the pattern sidewall can be improved. It is possible to enhance the CD uniformity in the plane of the pattern. Further, when the black defect of the light-shielding pattern found in the manufacturing process of the transfer mask (binary type mask) is corrected by the EB defect correction, the etching end point is easily detected, so that the black defect can be accurately corrected.

[Transfer mask and its manufacture]
In the transfer mask 210 (see FIG. 5) according to the second embodiment, the etching stopper film 2 of the mask blank 110 is left on the entire main surface of the transparent substrate 1, and the transfer pattern ( The light-shielding pattern 8a) is formed. In the case where the mask blank 110 is provided with the hard mask film 9, the hard mask film 9 is removed during the production of the transfer mask 210.

  That is, the transfer mask 210 according to the second embodiment includes the light-shielding pattern 8a, which is a light-shielding film having a transfer pattern, on the main surface of the light-transmissive substrate 1, and includes the light-transmissive substrate 1 and the light-shielding pattern 8a. An etching stopper film 2 is provided between them, the light shielding pattern 8a contains silicon, the etching stopper film 2 contains silicon, aluminum and oxygen, and the light shielding film 8 side is made of silicon and aluminum more than the light transmitting substrate 1 side. It is characterized in that the ratio of the content of silicon to the total content in atomic% is high.

  The method of manufacturing a transfer mask (binary mask) according to the second embodiment uses the mask blank 110 described above, and a transfer pattern is formed on the light-shielding film 8 by dry etching using a fluorine-based gas. It is characterized by including steps. The manufacturing method of the transfer mask 210 according to the second embodiment will be described below according to the manufacturing process shown in FIG. Here, a method of manufacturing the transfer mask 210 using the mask blank 110 in which the hard mask film 9 is laminated on the light shielding film 8 will be described. Further, a case where a material containing a transition metal and silicon is applied to the light shielding film 8 and a material containing chromium is applied to the hard mask film 9 will be described.

  First, a resist film is formed by a spin coating method in contact with the hard mask film 9 in the mask blank 110. Next, a transfer pattern (light-shielding pattern) to be formed on the light-shielding film 8 is drawn on the resist film with an electron beam, and a predetermined process such as a developing process is performed to form a resist pattern 10a having the light-shielding pattern. (See FIG. 6A). Subsequently, dry transfer using a mixed gas of chlorine gas and oxygen gas is performed using the resist pattern 10a as a mask to form a transfer pattern (hard mask pattern 9a) on the hard mask film 9 (see FIG. 6B). ).

  Next, the resist pattern 10a is removed, and then dry etching using fluorine gas is performed using the hard mask pattern 9a as a mask to form a transfer pattern (light shielding pattern 8a) on the light shielding film 8 (FIG. 6C). reference). During the dry etching of the light-shielding film 8 with a fluorine-based gas, additional etching (over-etching) is performed in order to improve the verticality of the pattern side walls of the light-shielding pattern 8a and to improve the CD uniformity in the surface of the light-shielding pattern 8a. Is going. Even after the over-etching, the surface of the etching stopper film 2 was only slightly etched, and the surface of the light-transmissive substrate 1 was not exposed even in the light-transmitting portion of the light-shielding pattern 8a.

  Further, the remaining hard mask pattern 9a is removed by dry etching using a mixed gas of chlorine-based gas and oxygen gas, and a predetermined process such as cleaning is performed to obtain a transfer mask 210 (see FIG. 6D). . In the cleaning step, ammonia-hydrogen peroxide mixture was used, but the surface of the etching stopper film 2 was hardly dissolved, and the surface of the transparent substrate 1 was not exposed at the transparent portion of the light shielding pattern 8a. The chlorine-based gas and the fluorine-based gas used in the dry etching are the same as those used in the first embodiment.

  The transfer mask 210 of the second embodiment is manufactured by using the mask blank 110 described above. The etching stopper film 2 has higher resistance to dry etching with a fluorine-based gas when forming a pattern on the light-shielding film 8 than the translucent substrate 1, has higher resistance to chemical cleaning, and has higher transmittance to exposure light. It simultaneously satisfies the three characteristics of being high. As a result, when the light shielding pattern (transfer pattern) 8a is formed on the light shielding film 8 by dry etching using a fluorine-based gas, overetching can be performed without engraving the main surface of the transparent substrate 1. Therefore, in the transfer mask 210 according to the second embodiment, the sidewall of the light shielding pattern 8a has high verticality, and the in-plane CD uniformity of the light shielding pattern 8a is also high. Further, during the manufacturing of the transfer mask 210, a black defect is found in the light shielding pattern 8a, and when the black defect is corrected by the EB defect correction, the etching end point is easily detected, so that the black defect is accurately corrected. be able to.

[Manufacturing of semiconductor devices]
The semiconductor device manufacturing method according to the second embodiment uses a transfer mask 210 manufactured according to the transfer mask 210 according to the second embodiment or the mask blank 110 according to the second embodiment to form a resist film on a semiconductor substrate. The feature is that the transfer pattern is transferred by exposure. In the transfer mask 200 according to the second embodiment, the sidewall of the light shielding pattern 8a has high verticality, and the CD uniformity in the plane of the light shielding pattern 8a is also high. Therefore, when the transfer mask 210 of the second embodiment is used to perform exposure and transfer onto a resist film on a semiconductor device, a pattern can be formed on the resist film on the semiconductor device with sufficient accuracy to meet design specifications.

Hereinafter, the embodiment of the present invention will be described more specifically by way of 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 6.35 mm was prepared. The translucent substrate 1 has its end faces and main surfaces polished to a predetermined surface roughness or less (root mean square roughness Rq of 0.2 nm or less), and then subjected to a predetermined cleaning treatment and drying treatment. Is.

Next, an etching stopper film 2 (AlO film) made of aluminum and oxygen was formed to a thickness of 10 nm in contact with the surface of the transparent substrate 1. Specifically, the translucent substrate 1 is installed in a single-wafer RF sputtering apparatus, an Al ₂ O ₃ target is discharged, and an etching stopper is formed by sputtering (RF sputtering) using argon (Ar) gas as a sputtering gas. The film 2 was formed. The etching stopper film formed under the same conditions on another transparent substrate was analyzed by X-ray photoelectron spectroscopy, and the result was Al:O=42:58 (atomic% ratio). In the analysis by X-ray photoelectron spectroscopy, numerical correction is performed based on the result of RBS analysis (analysis by Rutherford backscattering method) (the same applies to the following analysis).

Next, in contact with the surface of the etching stopper film 2, the phase shift film 3 having a structure in which a high transmission layer, a low transmission layer, a high transmission layer, a low transmission layer and an uppermost layer were laminated was formed. The specific film forming process is as follows. A light-transmissive substrate 1 having an etching stopper film 2 formed therein is set in a single-wafer RF sputtering apparatus, a silicon (Si) target is used, and krypton (Kr), helium (He), and nitrogen (N ₂ ) are mixed. Gas (flow ratio Kr:He:N ₂ =1:10:3, pressure=0.09 Pa) was used as a sputtering gas, RF power was set to 2.8 kW, and reactivity in a reaction mode (poison mode) region was set. A highly permeable layer (Si:N=44:56 (atomic% ratio)) made of silicon and nitrogen was formed in a thickness of 17 nm in contact with the surface of the etching stopper film 2 by sputtering (RF sputtering). On the main surface of another translucent substrate, only the high transmission layer was formed under the same conditions, and the optical characteristics of this high transmission layer were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). As a result of measurement, the refractive index n at a wavelength of 193 nm was 2.66 and the extinction coefficient k was 0.38.

Next, the translucent substrate 1 on which the high transmission layer is laminated is placed in a single-wafer RF sputtering apparatus, and a silicon (Si) target is used to set krypton (Kr), helium (He) and nitrogen (N ₂ ). ) Mixed gas (flow ratio Kr:He:N ₂ =1:10:1, pressure=0.035 Pa) was used as the sputtering gas, the power of the RF power source was 2.8 kW, and the reactive sputtering was performed in the metal mode region. A low transmission layer (Si:N=62:38 (atomic% ratio)) made of silicon and nitrogen was formed to a thickness of 8 nm on the high transmission layer by (RF sputtering). On the main surface of another transparent substrate, only the low transmission layer was formed under the same conditions, and the optical characteristics of this low transmission layer were measured using the above-mentioned spectroscopic ellipsometer. Was 1.69 and the extinction coefficient k was 1.87.

  Next, the translucent substrate 1 in which the high transmission layer and the low transmission layer are laminated is placed in a single-wafer type RF sputtering apparatus, and the high transmission layer 1 is formed on the low transmission layer under the same conditions as those for forming the high transmission layer. The transparent layer is formed with a thickness of 17 nm, the low transparent layer is formed with a thickness of 8 nm under the same conditions as those for forming the low transparent layer, and the uppermost layer is formed with a thickness of 17 nm under the same conditions for forming the high transparent layer. And formed in this order. The composition and optical characteristics of the formed high transmission layer and low transmission layer are the same as those of the above-mentioned high transmission layer and low transmission layer. The composition and optical characteristics of the uppermost layer 23 thus formed are similar to those of the above-mentioned high transmission layer 22. By the procedure described above, the phase shift film 3 having a structure in which the high transmission layer, the low transmission layer, the high transmission layer, the low transmission layer and the uppermost layer were laminated was formed on the translucent substrate 1 to have a total film thickness of 67 nm.

  Next, the translucent substrate 1 in which the etching stopper film 2 and the phase shift film 3 were laminated in this order was subjected to heat treatment in the atmosphere at a heating temperature of 500° C. for a treatment time of 1 hour. The phase shift film 3 after the heat treatment has an internal structure having a composition gradient that increases as the oxygen content of the uppermost layer moves away from the transparent substrate 1 side. When the transmittance and the phase difference of the phase shift film 3 at the wavelength of the light of the ArF excimer laser (about 193 nm) and the phase difference were measured with a phase shift amount measuring device, the transmittance was 5.7% and the phase difference was 175.8. It was degree.

  An etching stopper film and a phase shift film were formed on the main surface of another transparent substrate by the same procedure, and heat treatment was performed. The etching stopper film after the heat treatment was analyzed by X-ray photoelectron spectroscopy, and as a result, the composition gradient film in which the Si/[Si+Al] ratio became higher from the transparent substrate side toward the phase shift film side. It was confirmed that The composition of the etching stopper film on the transparent substrate side was Si:Al:O=8:31:61 (atomic% ratio). That is, the Si/[Si+Al] ratio of this etching stopper film on the transparent substrate side was 0.205. On the other hand, the composition of this etching stopper film on the phase shift film side was Si:Al:O=28:7:65 (atomic% ratio). That is, the Si/[Si+Al] ratio on the phase shift film side of this etching stopper film was 0.8.

Further, the optical characteristics of the etching stopper film after the heat treatment were measured using the above-mentioned spectroscopic ellipsometer. This etching stopper film has a distribution of the refractive index n and the extinction coefficient k in the film thickness direction, but when expressed as an average value obtained by taking a simple average in the film thickness direction, the refractive index at a wavelength of 193 nm is obtained. The n _ave was 1.655, and the extinction coefficient k _ave was 0.016. Further, the light-transmissive substrate on which the etching stopper film after the heat treatment was formed was immersed in aqueous ammonia having a concentration of 0.5%, and the etching rate was measured to be 0.1 nm/min. From this result, it was confirmed that the etching stopper film 2 of Example 1 had sufficient resistance to the chemical cleaning performed in the process of manufacturing the phase shift mask from the mask blank.

SF ₆ and He are added to another light-transmissive substrate, the etching stopper film formed on the other light-transmissive substrate after the heat treatment, and the phase shift film formed on the other light-transmissive substrate, respectively. Dry etching was performed under the same conditions using the mixed gas of No. 1 as an etching gas. Then, each etching rate was calculated, and the etching selection ratio among the three was calculated. The etching selection ratio of the etching stopper film to the etching rate of the transparent substrate was 0.33. The etching selection ratio of the phase shift film to the etching rate of the transparent substrate was 2.03. The etching selection ratio of the phase shift film to the etching rate of the etching stopper film was 6.16.

Next, a light-shielding film (CrOCN film) 4 made of chromium, oxygen, carbon and nitrogen was formed in a thickness of 46 nm in contact with the surface of the phase shift film 3. Specifically, the translucent substrate 1 after the heat treatment is installed in a single-wafer DC sputtering apparatus, a chromium (Cr) target is used, and argon (Ar), carbon dioxide (CO ₂ ) and nitrogen (N ₂ ) are used. ) And helium (He) as a sputtering gas, the light shielding film 4 was formed by reactive sputtering (DC sputtering). An X-ray photoelectron spectroscopy analysis of a light-shielding film formed on another transparent substrate under the same conditions showed that Cr:O:C:N=55.2:22.1:11.6: It was 11.1 (atomic% ratio). In the laminated structure of the phase shift film 3 and the light shielding film 4, the optical density at the wavelength (193 nm) of the ArF excimer laser was 2.8 or more.

  Next, a hard mask film (SiON film) 5 made of silicon, oxygen, and nitrogen was formed to a thickness of 5 nm in contact with the surface of the light shielding film 4. Specifically, the light-transmissive substrate 1 after the light-shielding film 4 is formed is set in a single-wafer DC sputtering apparatus, a silicon (Si) target is used, and argon (Ar) and nitric oxide (NO) are used. A hard mask film 5 was formed by performing reactive sputtering using a mixed gas of helium (He) and helium (flow ratio Ar:NO:He=8:29:32, pressure 0.3 Pa) as a sputtering gas. The hard mask film formed under the same conditions on another transparent substrate was analyzed by X-ray photoelectron spectroscopy, resulting in Si:O:N=37:44:19 (atomic% ratio). .. The mask blank of Example 1 was manufactured by the above procedure.

[Manufacture of phase shift mask]
Next, using the mask blank 100 of this Example 1, the phase shift mask 200 of Example 1 was manufactured by the following procedure. First, the surface of the hard mask film 5 was subjected to HMDS treatment. Subsequently, a resist film made of a chemically amplified resist for electron beam drawing having a film thickness of 80 nm was formed in contact with the surface of the hard mask film 5 by a spin coating method. Then, a first pattern, which is a phase shift pattern to be formed on the phase shift film 3, is electron beam-drawn on the resist film, and a predetermined developing process is performed to form a first resist having the first pattern. A pattern 6a was formed (see FIG. 3A). At this time, a program defect was added to the first pattern drawn by the electron beam in addition to the phase shift pattern to be originally formed so that a black defect is formed in the phase shift film.

Next, using the first resist pattern 6a as a mask, dry etching was performed using CF ₄ gas to form a first pattern (hard mask pattern 5a) on the hard mask film 5 (see FIG. 3B). .. Next, the first resist pattern 6a was removed by TMAH. Then, using the hard mask pattern 5a as a mask, dry etching is performed using a mixed gas of chlorine and oxygen (gas flow rate ratio Cl ₂ :O ₂ =4:1) to form the first pattern (the light shielding pattern) on the light shielding film 4. 4a) was formed (see FIG. 3(C)).

Next, using the light shielding pattern 4a as a mask, dry etching is performed using a fluorine-based gas (SF ₆ +He) to form a first pattern (phase shift pattern 3a) on the phase shift film 3, and at the same time, a hard mask pattern. 5a was removed (see FIG. 3(D)). In the dry etching using the fluorine-based gas, the etching time from the start of the etching of the phase shift film 3 until the etching progresses in the thickness direction of the phase shift film 3 and the surface of the etching stopper film 2 begins to be exposed (just etching time). In addition to the above), additional etching (overetching) was performed for 20% of the just etching time (overetching time). The dry etching with the fluorine-based gas was performed with a bias of 25 W.

Next, a resist film made of a chemically amplified resist for electron beam writing having a film thickness of 150 nm was formed on the light shielding pattern 4a by a spin coating method. Next, a second pattern which is a pattern (light-shielding pattern) to be formed on the light-shielding film 4 is drawn on the resist film, and a predetermined process such as a developing process is further performed to form the second resist having the light-shielding pattern. A pattern 7b was formed (see FIG. 3E). Then, using the second resist pattern 7b as a mask, dry etching is performed using a mixed gas of chlorine and oxygen (gas flow rate ratio Cl ₂ :O ₂ =4:1), and the second pattern ( A light shielding pattern 4b) was formed. Further, the second resist pattern 7b was removed by TMAH, and a predetermined process such as cleaning with ammonia-hydrogen peroxide was performed to obtain a phase shift mask 200 (see FIG. 3F).

When the mask pattern was inspected with respect to the manufactured halftone type phase shift mask 200 of Example 1 by a mask inspection apparatus, a black defect was confirmed in the phase shift pattern 3a where the program defect was arranged. .. When EB defect correction using an electron beam and XeF ₂ gas is performed on the black defect portion, the etching end point can be easily detected, and etching on the surface of the etching stopper film 2 can be minimized. did it.

  Using another mask blank, a phase shift mask was manufactured in the same procedure, and the in-plane CD uniformity of the phase shift pattern was inspected. The result was good. When the cross section of the phase shift pattern was observed by STEM, the verticality of the side wall of the phase shift pattern was high, the etching stopper film had a minute recess of about 1 nm, and no microtrench was generated.

  When the AMS 193 (manufactured by Carl Zeiss Co., Ltd.) is used to expose and transfer the halftone type phase shift mask 200 of Example 1 after the EB defect correction to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. The transfer image was simulated. When the exposure transfer image of this simulation was verified, the design specifications were sufficiently satisfied. The influence of the decrease in the transmittance of the light transmitting portion on the exposure transfer due to the provision of the etching stopper film 2 was slight. In addition, the transferred image in the portion where the EB defect was corrected was comparable to the transferred image in the other areas. From this result, even if the phase shift mask of Example 1 after the EB defect correction is set on the mask stage of the exposure apparatus and transferred by exposure to the resist film on the semiconductor device, it is finally formed on the semiconductor device. It can be said that the formed circuit pattern can be formed with high accuracy.

(Example 2)
[Manufacture of mask blanks]
The mask blank of Example 2 is for manufacturing a binary mask (transfer mask), and as shown in FIG. 4, an etching stopper film 2, a lower layer and an upper layer are formed on a transparent substrate 1. The light shielding film 8 and the hard mask film 9 each having a laminated structure are laminated. The points different from the mask blank of Example 1 will be described below.

  In the same procedure as in Example 1, a light-transmissive substrate 1 was prepared, and then an etching stopper film 2 (AlO film) made of aluminum and oxygen was formed to a thickness of 10 nm in contact with the surface of the light-transmissive substrate 1. Formed by.

Next, in contact with the surface of the etching stopper film 2, a lower layer (MoSiN film) of the light-shielding film 8 made of molybdenum, silicon and nitrogen is formed with a thickness of 47 nm, and an upper layer (MoSiN film) is formed with a thickness of 13 nm. Formed. Specifically, the translucent substrate 1 after the etching stopper film 2 is formed is installed in a single-wafer DC sputtering apparatus, and a mixed sintering target (Mo: Mo) of silicon and molybdenum (Si) (Mo: Si=13:87 (atomic% ratio)) is used to form the lower layer and the upper layer of the light shielding film 8 by reactive sputtering (DC sputtering) using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas. did. Next, the light-transmitting substrate 1 provided with the etching stopper film 2 and the light-shielding film 8 was heat-treated in the atmosphere at 450° C. for 30 minutes.

  An etching stopper film and a light-shielding film were formed on the main surface of another transparent substrate by the same procedure, and heat treatment was performed. The light-shielding film and the etching stopper film formed on another transparent substrate after the heat treatment were analyzed by X-ray photoelectron spectroscopy. As a result, the lower layer of the light-shielding film was Mo:Si:N=9.2:68.3:22.5 (atomic% ratio), and the upper layer near the lower layer side was Mo:Si:N:O=5. It was confirmed that the ratio was 0.8:64.4:27.7:2.1 (atomic% ratio). Further, in the upper surface layer of the light shielding film, nitrogen was 14.4 atom% and oxygen was 38.3 atom %. The optical density of the light-shielding film was measured using the above-mentioned spectroscopic ellipsometer and found to be 3.0.

  On the other hand, it was confirmed that the etching stopper film after the heat treatment was a composition gradient film in which the Si/[Si+Al] ratio increased from the transparent substrate side toward the light shielding film side. The composition of the etching stopper film on the transparent substrate side was Si:Al:O=5:34:61 (atomic% ratio). That is, the Si/[Si+Al] ratio of the etching stopper film on the transparent substrate side was 0.13. On the other hand, the composition of the etching stopper film on the light-shielding film side was Si:Al:O=26:13:61 (atomic% ratio). That is, the Si/[Si+Al] ratio of the etching stopper film on the light-shielding film side was 0.67.

Further, the optical characteristics of the etching stopper film after the heat treatment were measured using the above-mentioned spectroscopic ellipsometer. This etching stopper film has a distribution of the refractive index n and the extinction coefficient k in the film thickness direction, but when expressed as an average value obtained by taking a simple average in the film thickness direction, the refractive index at a wavelength of 193 nm is obtained. n _ave was 1.680 and extinction coefficient k _ave was 0.020. Further, the light-transmissive substrate on which the etching stopper film after the heat treatment was formed was immersed in aqueous ammonia having a concentration of 0.5%, and the etching rate was measured to be 0.1 nm/min. From this result, it was confirmed that the etching stopper film 2 of Example 1 had sufficient resistance to the chemical cleaning performed in the process of manufacturing the transfer mask from the mask blank.

For each of the other transparent substrate, the etching stopper film formed on the other transparent substrate, and the light shielding film formed on the other transparent substrate, a mixed gas of SF ₆ and He is used as an etching gas. The dry etching used was performed under the same conditions. Then, each etching rate was calculated, and the etching selection ratio among the three was calculated. The etching selection ratio of the etching stopper film of Example 2 to the etching rate of the transparent substrate was 0.1. The etching selection ratio of the light-shielding film of Example 2 to the etching rate of the transparent substrate was 1.9. The etching selection ratio of the light-shielding film of Example 2 to the etching rate of the etching stopper film of Example 2 was 19.0.

Next, a hard mask film 9 (CrN film) made of chromium and nitrogen was formed in a thickness of 5 nm in contact with the surface of the upper layer of the light shielding film 8. Specifically, the translucent substrate 1 including the light-shielding film 8 after the heat treatment is installed in a single-wafer DC sputtering apparatus, a chromium (Cr) target is used, and argon (Ar) and nitrogen (N ₂ ) are used. The hard mask film 9 was formed by reactive sputtering (DC sputtering) using a mixed gas as a sputtering gas. The hard mask film formed on another transparent substrate under the same conditions was analyzed by X-ray photoelectron spectroscopy, resulting in Cr:N=72:28 (atomic% ratio). The mask blank of Example 2 was manufactured by the above procedure.

[Manufacture of transfer mask]
Next, using the mask blank 110 of Example 2, a transfer mask 210 of Example 2 was manufactured by the following procedure. First, a resist film made of a chemically amplified resist for electron beam writing having a film thickness of 80 nm was formed in contact with the surface of the hard mask film 9 by spin coating. Next, a transfer pattern to be formed on the light-shielding film 8 was electron beam-drawn on this resist film, and a predetermined developing process was performed to form a resist pattern 10a (see FIG. 6A). At this time, a program defect was added to the pattern drawn by the electron beam in addition to the transfer pattern to be originally formed so that a black defect is formed on the light shielding film 8.

Next, using the resist pattern 10a as a mask, dry etching is performed using a mixed gas of chlorine and oxygen (gas flow rate ratio Cl ₂ :O ₂ =4:1), and the hard mask film 9 is covered with a light shielding pattern (hard mask pattern 9a). ) Was formed (see FIG. 6(B)).

Next, the resist pattern 10a was removed by TMAH. Then, using the hard mask pattern 9a as a mask, dry etching was performed using a fluorine-based gas (SF ₆ +He) to form a transfer pattern (light-shielding pattern 8a) on the light-shielding film 8 (see FIG. 6C). In the dry etching using the fluorine-based gas, the etching time (just etching time) from the start of the etching of the light-shielding film 8 until the etching progresses in the thickness direction of the light-shielding film 8 and the surface of the etching stopper film 2 starts to be exposed. In addition, additional etching (overetching) was performed for 20% of the just etching time (overetching time). The dry etching with the fluorine-based gas was performed with a bias of 25 W.

Furthermore, the remaining hard mask pattern 9a is removed by dry etching using a mixed gas of chlorine-based gas and oxygen gas (gas flow rate ratio Cl ₂ :O ₂ =4:1), and a predetermined amount such as cleaning with ammonia hydrogen peroxide is performed. Through the treatment, a transfer mask 210 was obtained (see FIG. 6D).

When a mask pattern was inspected on the manufactured transfer mask 210 of Example 2 by a mask inspection apparatus, a black defect was confirmed in the light-shielding pattern 8a where the program defect was arranged. When EB defect correction using an electron beam and XeF ₂ gas is performed on the black defect portion, the etching end point can be easily detected, and etching on the surface of the etching stopper film 2 can be minimized. did it.

  Using another mask blank, a transfer mask was manufactured in the same procedure, and the CD uniformity in the plane of the light shielding pattern was inspected. As a result, a good result was obtained. When the cross section of the light shielding pattern was observed by STEM, the verticality of the side wall of the light shielding pattern was high, the digging into the etching stopper film was as small as less than 1 nm, and no micro trench was generated.

  A transfer image obtained by exposing and transferring to the resist film on the semiconductor device with exposure light having a wavelength of 193 nm by using AIMS 193 (manufactured by Carl Zeiss Co., Ltd.) on the transfer mask 210 of Example 5 after the EB defect correction. Was simulated. When the exposure transfer image of this simulation was verified, the design specifications were sufficiently satisfied. The influence of the decrease in the transmittance of the light transmitting portion on the exposure transfer due to the provision of the etching stopper film 2 was slight. In addition, the transferred image in the portion where the EB defect was corrected was comparable to the transferred image in the other areas. From this result, even if the transfer mask of Example 2 after the EB defect correction is set on the mask stage of the exposure apparatus and exposure-transferred to the resist film on the semiconductor device, it is finally formed on the semiconductor device. It can be said that the formed circuit pattern can be formed with high accuracy.

(Comparative Example 1)
[Manufacture of mask blanks]
The mask blank of Comparative Example 1 was the same as the mask blank of Example 1 except that the etching stopper film 2 was formed of a material consisting of aluminum and oxygen, and then the high temperature heat treatment was not performed under the above conditions. With configuration. As the etching stopper film 2 of Comparative Example 1, an etching stopper film 2 (AlO film) made of aluminum and oxygen was formed with a thickness of 10 nm in contact with the surface of the transparent substrate 1. Specifically, the translucent substrate 1 is installed in a single-wafer RF sputtering apparatus, an Al ₂ O ₃ target is used, and an etching stopper film is formed by sputtering (RF sputtering) using argon (Ar) gas as a sputtering gas. Formed 2. The etching stopper film formed under the same conditions on another transparent substrate was analyzed by X-ray photoelectron spectroscopy, and the result was Al:O=42:58 (atomic% ratio). That is, Si/[Si+Al] of this etching stopper film 2 is zero. The etching stopper film has a refractive index n of 1.864 and an extinction coefficient k of 0.069 for light having a wavelength of 193 nm.

  An etching stopper film was formed on another translucent substrate by the same procedure, and the translucent substrate on which the etching stopper film was formed was immersed in 0.5% ammonia water to measure the etching rate. It was 4.0 nm/min. From this result, it is understood that the etching stopper film 2 of Comparative Example 1 does not have sufficient resistance to chemical cleaning performed in the process of manufacturing a phase shift mask from a mask blank.

An etching gas containing a mixed gas of SF ₆ and He is used for each of the other transparent substrate, the etching stopper film formed on the other transparent substrate, and the phase shift film formed on the other transparent substrate. The dry etching used for the above was performed under the same conditions. Then, each etching rate was calculated, and the etching selection ratio among the three was calculated. The etching selectivity of the etching stopper film of Comparative Example 1 to the etching rate of the transparent substrate was 0.025. The etching selection ratio of the phase shift film of Comparative Example 1 to the etching rate of the transparent substrate was 2.38. The etching selection ratio of the phase shift film of Comparative Example 1 to the etching rate of the etching stopper film of Comparative Example 1 was 95.2.

[Manufacture of phase shift mask]
Next, using the mask blank 100 of Comparative Example 1, a phase shift mask 200 of Comparative Example 1 was produced in the same procedure as in Example 1. When the mask pattern inspection was performed on the manufactured halftone type phase shift mask 200 of Comparative Example 1 by a mask inspection device, many defects other than the program defects were detected. Examination of each defective portion revealed that most of the defects were due to the phase shift pattern 3a falling off. In addition, when the EB defect correction using an electron beam and XeF ₂ gas is performed on the black defect portion where the program defect is arranged, the etching end point can be easily detected and the surface of the etching stopper film 2 can be detected. It was possible to minimize the etching.

  Using another mask blank, a phase shift mask was manufactured by the same procedure, and the cross section of the phase shift pattern was observed by STEM at the part where the phase shift pattern did not fall off. As a result, the etching stopper film in the light transmitting part disappeared. (Dissolution by chemical cleaning), and it was confirmed that the etching stopper film immediately below the region where the phase shift pattern was present also proceeded to dissolve inward from the side wall side of the phase shift pattern. From this result, it can be inferred that the etching stopper film was dissolved by the chemical cleaning, which was a factor of frequent dropout of the phase shift pattern.

  When the halftone type phase shift mask 200 of Comparative Example 1 after the EB defect correction is exposed and transferred to a resist film on a semiconductor device by using an exposure light having a wavelength of 193 nm by using AIMS193 (manufactured by Carl Zeiss). The transfer image was simulated. When the exposure transfer image of this simulation was verified, the design specifications could not be satisfied. A large number of places where normal exposure and transfer could not be performed due to the falling of the phase shift pattern 3a were found. Further, even in the portion where the phase shift pattern 3a itself is formed with high accuracy, the accuracy of the transferred image, which is considered to be due to the low transmittance of the etching stopper film 2 for ArF exposure light, was observed. From this result, when the phase shift mask of Comparative Example 1 is set on the mask stage of the exposure device and transferred by exposure to the resist film on the semiconductor device, it is finally formed on the semiconductor device regardless of the presence or absence of EB defect correction. It is expected that disconnection and short circuit of the circuit pattern will frequently occur in the formed circuit pattern.

1 translucent substrate 2 etching stopper film 3 phase shift film (pattern forming thin film)
3a Phase shift pattern (transfer pattern)
4 Light-shielding films 4a, 4b Light-shielding patterns 5, 9 Hard mask films 5a, 9a Hard mask pattern 6a First resist pattern 7b Second resist pattern 8 Light-shielding film (pattern forming thin film)
8a Light-shielding pattern (transfer pattern)
10a Resist pattern 100, 110 Mask blank 200 Phase shift mask (transfer mask)
210 Transfer mask

Claims (18)

A mask blank having a structure in which an etching stopper film and a pattern forming thin film are laminated in this order on a main surface of a transparent substrate,
The pattern forming thin film is provided in contact with the surface of the etching stopper film,
The pattern forming thin film contains silicon,
The etching stopper film contains silicon, aluminum, and oxygen, and the ratio of the content of silicon to the total content of the silicon and the aluminum in atomic% of the thin film side for pattern formation is more than that of the transparent substrate side. Mask blank characterized by high price.   The etching stopper film is a composition gradient film in which the ratio of the content of silicon to the total content of silicon and aluminum in atomic% increases from the transparent substrate side toward the pattern forming thin film side. The mask blank according to claim 1, wherein:   The mask blank according to claim 1 or 2, wherein the etching stopper film is made of silicon, aluminum, and oxygen.   The mask blank according to any one of claims 1 to 3, wherein the etching stopper film has an oxygen content of 50 atomic% or more.   5. The etching stopper film on the side of the thin film for pattern formation has a ratio of the content of silicon to the total content of silicon and aluminum in atomic% of 1/5 or more. The mask blank according to any one of 1.   The etching stopper film on the side of the thin film for pattern formation has a ratio of the content of silicon to the total content of silicon and aluminum in atomic% of 4/5 or less. The mask blank according to any one of 1.   The mask blank according to any one of claims 1 to 6, wherein the etching stopper film has at least one of an amorphous structure and a microcrystalline structure.   The mask blank according to any one of claims 1 to 7, wherein the etching stopper film has a thickness of 3 nm or more.   The mask blank according to claim 1, wherein the pattern forming thin film contains silicon and nitrogen. The pattern forming thin film is a phase shift film,
The phase shift film has a function of transmitting exposure light with a transmittance of 1% or more, and the phase shift film has passed through the air by the same distance as the thickness of the phase shift film with respect to the exposure light transmitted through the phase shift film. The mask blank according to any one of claims 1 to 9, having a function of causing a phase difference of 150 degrees or more and 200 degrees or less with respect to the exposure light.   The mask blank according to claim 10, wherein a light-shielding film is provided on the phase shift film. A transfer mask, wherein a transfer pattern is provided on the pattern forming thin film of the mask blank according to any one of claims 1 to 9 .   The transfer mask according to claim 11, wherein a transfer pattern is provided on the phase shift film of the mask blank, and a pattern including a light-shielding band is provided on the light-shielding film. A method for manufacturing the mask blank according to any one of claims 1 to 11, comprising:
Forming a step of forming the etching stopper film containing aluminum and oxygen on the transparent substrate;
Forming a pattern forming thin film containing silicon in contact with the etching stopper film;
Performing a heat treatment at a temperature of 400° C. or higher on the translucent substrate on which the etching stopper film and the pattern forming thin film have been formed;
A method of manufacturing a mask blank, comprising:   15. The method of manufacturing a mask blank according to claim 14, wherein the step of forming the etching stopper film is a step of forming an etching stopper film having an oxygen content of less than 60 atomic %. A method for manufacturing a transfer mask using the mask blank according to claim 11.
A step of forming a transfer pattern on the light-shielding film by dry etching,
Forming a transfer pattern on the phase shift film by dry etching using a fluorine-based gas using the light-shielding film having the transfer pattern as a mask;
And a step of forming a pattern including a light-shielding band on the light-shielding film by dry etching.   A method for manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask according to claim 12 or 13.   A method of manufacturing a semiconductor device, comprising the step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask manufactured by the method of manufacturing a transfer mask according to claim 16.

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