JP6573806B2 - Mask blank, phase shift mask, method for manufacturing phase shift mask, and method for manufacturing semiconductor device - Google Patents

Description

  The present invention relates to a mask blank, a phase shift mask manufactured using the mask blank, and a manufacturing method thereof. The present invention also relates to a method of manufacturing a semiconductor device using the phase shift mask.

In recent years, with the miniaturization of patterns used in semiconductor devices, the miniaturization of mask patterns formed on transfer masks has progressed.
A halftone phase shift mask is known as a kind of transfer mask. This phase shift mask is provided with a phase shift pattern on a translucent substrate. This phase shift film transmits light at an intensity that does not substantially contribute to exposure, and causes the light transmitted through the phase shift film to have a predetermined phase difference with respect to light that has passed through the air by the same distance. It has a function, and this causes a so-called phase shift effect.

  In general, the outer peripheral region of the region where the phase shift pattern is formed in the phase shift mask is affected by the exposure light transmitted through the outer peripheral region when the resist film is exposed and transferred to the resist film on the semiconductor wafer using an exposure apparatus. It is required to ensure an optical density (OD: Optical Density) equal to or higher than a predetermined value so as not to be received. Usually, in the outer peripheral region of the phase shift mask, it is desirable that the OD is 3 or more, and at least about 2.8 is required. However, the phase shift film of the phase shift mask has a function of transmitting the exposure light with a predetermined transmittance, and the optical density required for the outer peripheral region of the phase shift mask is ensured with this phase shift film alone. It is difficult to do. For this reason, like a mask blank disclosed in Patent Document 1, light is shielded on a translucent film (phase shift film) that has a predetermined transmittance with respect to exposure light and generates a predetermined phase difference. A film (light-shielding film) is laminated, and a predetermined optical density is secured by a laminated structure of a translucent film and a light-shielding film.

  On the other hand, as disclosed in Patent Document 2, there is a phase shift mask blank in which a light shielding film provided on a phase shift film is formed of a material containing a transition metal and silicon. In this phase shift mask blank, a material containing a transition metal and silicon is applied to the material for forming the phase shift film as in the case of the halftone phase shift masks so far. For this reason, it is difficult to ensure etching selectivity for dry etching between the phase shift film and the light shielding film. In the phase shift mask blank of Patent Document 2, an etching stopper film made of a material containing chromium is provided between the phase shift film and the light shielding film. Further, an etching mask film made of a material containing chromium is further provided on the light shielding film.

On the other hand, Patent Document 3 discloses a transparent conductive film made of alumina (Al ₂ O ₃ ), a transparent phase shift film made of silicon dioxide (SiO ₂ ), and chromium (Cr) on a transparent substrate made of quartz. A light shielding film as a main component is formed in this order, a pattern of the main light transmitting portion and the auxiliary light transmitting portion is formed on the light shielding film, and either the main light transmitting portion or the auxiliary light transmitting portion adjacent thereto is a phase shift film A phase shift mask obtained by etching is shown and its manufacturing method. Here, the alumina (Al ₂ O ₃ ) film has a function as an etching stopper during the etching.

JP 2007-033469 A JP 2007-2441065 A JP 2006-084507 A

In general, since a mask blank for manufacturing a phase shift mask is provided with a light shielding film on the phase shift film, dry etching using a resist pattern having a phase shift pattern to be formed on the phase shift film as a mask, It cannot be performed directly on the phase shift film.
In the phase shift mask, the phase shift film is provided with a fine pattern, and the light shielding film is provided with a light shielding pattern for forming a light shielding band or the like satisfying a predetermined optical density in a laminated structure with the phase shift film. It is common. That is, in the phase shift mask, different patterns are generally formed between the phase shift film and the light shielding film. For this reason, in a mask blank having a laminated structure in which a light shielding film is provided in direct contact with the phase shift film, materials having different etching characteristics are used for the phase shift film and the light shielding film. The phase shift film needs to have not only a function of transmitting at a predetermined transmittance but also a function of controlling the phase of light transmitted through the phase shift film. A material containing silicon is often used as a material for a phase shift film because it easily obtains optical characteristics required for such a phase shift film.

  A thin film made of a material containing silicon is generally patterned by dry etching using a fluorine-based gas. As a material having etching resistance to dry etching using a fluorine-based gas, there is a material containing chromium. A thin film made of a material containing chromium can be patterned by dry etching using a mixed gas of chlorine-based gas and oxygen gas (hereinafter referred to as “oxygen-containing chlorine-based gas”). A thin film made of a material containing silicon is resistant to dry etching using an oxygen-containing chlorine-based gas. A thin film made of a material containing chromium and a thin film made of a material containing silicon are a combination that can provide sufficient etching selectivity.

  When a phase shift mask is manufactured from such a mask blank, dry etching using a resist pattern having a transfer pattern to be formed on the phase shift film as a mask is performed on the light shielding film to form the phase shift film. A transfer pattern is first formed on the light shielding film. Then, by performing dry etching on the phase shift film using the light shielding film on which the transfer pattern is formed as a mask, a transfer pattern (phase shift pattern) is formed on the phase shift film. However, dry etching using an oxygen-containing chlorine-based gas, which is performed on a light-shielding film made of a chromium-containing material, is isotropic etching because the etching gas contains radical oxygen-containing plasma. It has a tendency and it is difficult to increase the anisotropy of etching.

  In general, a resist film formed of an organic material to be used has significantly lower resistance to plasma of oxygen gas than that of other gases. For this reason, when the light shielding film of the chromium-based material is dry-etched with the oxygen-containing chlorine-based gas, the consumption amount of the resist film, that is, the reduction amount of the resist film generated during etching increases. In order to form a fine pattern on the light shielding film with high accuracy by dry etching, the resist film needs to remain with a predetermined thickness or more upon completion of patterning of the light shielding film. However, if the thickness of the resist film that forms the pattern first is increased, the cross-sectional aspect ratio of the resist pattern (the ratio of the film thickness to the pattern line width) becomes too large, so the phenomenon that the resist pattern collapses easily occurs. Become. Although it is possible to solve these problems by significantly reducing the thickness of the light shielding film, since the light shielding film requires a predetermined optical density with respect to exposure light, the thickness of the light shielding film does not hinder etching. It is difficult to make it easy.

  As described above, a fine transfer pattern (phase shift film) with high pattern shape accuracy and high in-plane CD (Critical Dimension) uniformity should be formed on the light shielding film by dry etching using an oxygen-containing chlorine-based gas. It is difficult to form a fine transfer pattern.

  Dry etching using a fluorine-based gas having a high anisotropic etching tendency is applied to dry etching performed when forming a transfer pattern on the phase shift film. However, it is difficult to form a fine transfer pattern on the phase shift film because it is necessary to use a light-shielding film, which is difficult to form a fine transfer pattern with high accuracy, as an etching mask during the dry etching. Therefore, in a mask blank having a light-shielding film between the phase shift film and the organic material resist film, a thin resist pattern capable of forming a fine transfer pattern to be formed on the phase shift film (light semi-transmissive film) Finally, it has been a problem to form the transfer pattern on the phase shift film with high accuracy.

  The mask blank disclosed in Patent Document 2 has been conceived as a means for solving the problems of the above-described mask blank. In this mask blank, a transition metal silicide-based material that can be dry-etched with a fluorine-based gas is applied to a light-shielding film that requires a predetermined thickness or more so that a fine pattern can be formed on the light-shielding film with high accuracy. Since this light shielding film has low etching selectivity with the phase shift film, an etching stopper film of a chromium-based material is provided between the phase shift film and the light shielding film. The etching stopper film is basically not restricted by the optical density. The etching stopper film only needs to have a thickness that can function as an etching mask in dry etching using a fluorine-based gas performed when a fine transfer pattern is formed on the phase shift film. Compared to a conventional chromium-based light shielding film Drastically reduce the film thickness. For this reason, the etching stopper film is formed of a chromium-based material having a tendency of isotropic etching, but it is possible to form a fine pattern with high accuracy.

  However, a thin film of a chromium-based material has a characteristic that the etching progresses in the direction of the side wall of the pattern when patterning by dry etching is relatively fast (the side etching amount is large). For this reason, the pattern formed on the resist film is designed in consideration of the etching amount (etching bias) in the side wall direction when patterning the thin film of the chromium-based material. In the case of the mask blank of Patent Document 2, it is necessary to pattern an etching mask film, an etching stopper film, and two chromium-based thin films before patterning of the phase shift film, and the etching bias becomes relatively large. There is a problem.

Therefore, the present inventor applied an etching stopper film made of Al ₂ O ₃ disclosed in Patent Document 3 in place of the chromium-based material etching stopper film of the mask blank having the structure disclosed in Patent Document 2. Thought to do. However, it has been found that an etching stopper film made of Al ₂ O ₃ tends to have low resistance to chemical cleaning. In the process of manufacturing a phase shift mask from a mask blank, cleaning with a chemical solution is performed many times. Also, the completed phase shift mask is periodically cleaned with a chemical solution. In these cleanings, ammonia overwater or TMAH (tetramethylammonium hydroxide) aqueous solution is often used as the cleaning liquid, but the etching stopper film made of Al ₂ O ₃ has low resistance to these cleaning liquids.

  For example, when the mask blank after patterning the light shielding film and the etching stopper film is cleaned with ammonia overwater, the area where the light shielding film does not exist and the surface of the etching stopper film is exposed. The etching stopper film gradually dissolves from the surface, and proceeds to a state where the surface of the phase shift film is exposed. When further cleaning is performed, the etching stopper film immediately below the light shielding pattern portion made of the light shielding film is also dissolved from the side wall side to the inner side of the light shielding film. Since the phenomenon that the etching stopper film is dissolved proceeds from both side walls of the light shielding pattern, the width of the etching stopper film remaining without being dissolved is smaller than the width of the light shielding pattern. In such a state, a phenomenon that the light-shielding pattern falls off easily occurs.

  The light-shielding pattern made of a silicon-containing material cannot function as an etching mask when patterning the phase shift film because it does not have resistance to dry etching with a fluorine-based gas when patterning the phase shift film. Therefore, the etching stopper film must function as an etching mask (hard mask) when patterning the phase shift film. If the pattern width of the etching stopper film is narrowed by dissolution with the cleaning liquid, there is a problem that the phase shift film pattern formed after the phase shift film is dry-etched becomes narrower than the design line width.

In order to solve the above problems, the present invention has the following configuration.
(Configuration 1)
A mask blank provided with a phase shift film and a light shielding film on the main surface of a translucent substrate,
The phase shift film has a structure in which a lower layer and an upper layer are laminated in this order from the translucent substrate side,
The lower layer is made of a material containing silicon and nitrogen,
The upper layer is made of a material containing silicon, aluminum and oxygen,
The light shielding film is made of a material containing one or more elements selected from silicon and tantalum,
The mask blank, wherein the light shielding film is formed in contact with the surface of the upper layer.

(Configuration 2)
2. The mask blank according to Configuration 1, wherein the upper layer has an oxygen content of 60 atomic% or more.

(Configuration 3)
The mask blank according to Configuration 1 or 2, wherein the upper layer has a ratio by atomic% of the silicon content to the total content of the silicon and the aluminum of 4/5 or less.

(Configuration 4)
4. The mask blank according to any one of configurations 1 to 3, wherein the upper layer is made of silicon, aluminum, and oxygen.

(Configuration 5)
5. The mask blank according to any one of configurations 1 to 4, wherein the upper layer has a thickness of 3 nm or more.

(Configuration 6)
The mask blank according to any one of configurations 1 to 5, wherein the lower layer is made of a material containing a transition metal, silicon, and nitrogen.

(Configuration 7)
The phase shift film has a function of transmitting exposure light with a transmittance of 1% or more, and the exposure light transmitted through the phase shift film passes through the air by the same distance as the thickness of the phase shift film. The mask blank according to any one of Configurations 1 to 6, wherein the mask blank has a function of causing a phase difference of not less than 150 degrees and not more than 180 degrees with exposure light.

(Configuration 8)
The mask blank according to any one of Structures 1 to 7, wherein the light shielding film is made of a material containing a transition metal and silicon.

(Configuration 9)
9. The mask blank according to any one of Structures 1 to 8, wherein an etching stopper film is formed in contact with the main surface of the translucent substrate.

(Configuration 10)
10. The mask blank according to Configuration 9, wherein the etching stopper film has an oxygen content of 60 atomic% or more.

(Configuration 11)
11. The mask blank according to claim 9, wherein the etching stopper film has a ratio by atomic percent of the silicon content to the total content of the silicon and the aluminum of 4/5 or less.

(Configuration 12)
The mask blank according to any one of Structures 9 to 11, wherein the etching stopper film is made of silicon, aluminum, and oxygen.

(Configuration 13)
The mask blank according to any one of Structures 9 to 12, wherein the etching stopper film has a thickness of 3 nm or more.

(Configuration 14)
The mask blank according to any one of Structures 1 to 13, further comprising a hard mask film made of a material containing chromium on the light shielding film.

(Configuration 15)
A phase shift mask, wherein a phase shift pattern is formed on the phase shift film of the mask blank according to any one of Structures 1 to 13, and a light shielding pattern is formed on the light shielding film.

(Configuration 16)
A method of manufacturing a phase shift mask using the mask blank according to any one of configurations 1 to 14,
Forming a phase shift pattern on the light shielding film by dry etching;
Forming a phase shift pattern in the upper layer by dry etching using an etching gas containing boron chloride gas using the light shielding film having the phase shift pattern as a mask;
Forming a phase shift pattern in the lower layer by dry etching using an etching gas containing a fluorine-based gas using the light-shielding film having the phase shift pattern as a mask;
And 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 using the phase shift mask according to Structure 15 and exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate.

(Configuration 18)
A method for manufacturing a semiconductor device, comprising: a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the phase shift mask manufactured by the method for manufacturing a phase shift mask according to Configuration 16.

  The mask blank of the present invention is a mask blank provided with a phase shift film and a light shielding film on the main surface of a translucent substrate, and the phase shift film includes a lower layer containing silicon and nitrogen, silicon, aluminum, and oxygen. The light-shielding film formed in contact with the phase shift film is made of a material containing one or more elements selected from silicon and tantalum.

  By adopting this structure for the mask blank, the laminated phase shift film composed of the upper layer and the lower layer becomes a phase shift film that gives a predetermined phase difference and transmittance. The upper layer is a film having sufficient chemical cleaning resistance, and functions sufficiently as an etching stopper for dry etching using a fluorine-based gas when forming a pattern on the light-shielding film, and uses a fluorine-based gas. A film having a function as a hard mask when a pattern is formed in the lower layer by dry etching. By this etching stopper function and hard mask function of the upper layer, it becomes possible to form a fine and highly accurate phase shift pattern.

  For this reason, this mask blank is a mask blank suitable for producing a phase shift mask having a fine and high-accuracy phase shift pattern, a predetermined phase difference and transmittance, and high resistance to chemical cleaning. Moreover, the phase shift mask manufactured using this mask blank becomes a phase shift mask having a fine and highly accurate phase shift pattern, a predetermined phase difference and transmittance, and high resistance to chemical cleaning. Furthermore, when exposure transfer is performed using this phase shift mask, a fine and highly accurate pattern can be formed with low defects, so that a semiconductor device having a fine and highly accurate circuit pattern can be manufactured with a high yield. Become.

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 phase shift mask in the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing process of the phase shift 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 intensively studied to solve the technical problems of the Al ₂ O ₃ film. The Al ₂ O ₃ film has high resistance to dry etching with a fluorine-based gas, but low resistance to a cleaning liquid used for cleaning the phase shift mask. After repeated trial and error, we examined dry etching characteristics and chemical resistance with a mixture of Al ₂ O ₃ and SiO ₂ , which are materials containing silicon, aluminum and oxygen. It has been found that it is possible to form a film that has sufficient resistance in practical use and that has higher resistance to cleaning liquid (ammonia peroxide, TMAH, etc.) than Al ₂ O ₃ film. It was also found that a film made of Al ₂ O ₃ and SiO ₂ has an appropriate refractive index n and extinction coefficient k as a part of the phase shift film.

A film formed of a material in which Al ₂ O ₃ and SiO ₂ are mixed is not removed by dry etching with a fluorine-based gas when patterning the phase shift film, and the film thickness is slightly reduced. Even after dry etching with a fluorine-based gas when a pattern including a light-shielding band is patterned on a light-shielding film in a later process, it remains without being removed, and the film thickness is slightly reduced. Therefore, this film can be used as an upper layer constituting a part of the phase shift film. That is, the phase shift film has a laminated structure of a lower layer and an upper layer, the lower layer is made of a material used for a conventional phase shift film, and the upper layer is made of a material in which Al ₂ O ₃ and SiO ₂ are mixed. Then, the optical characteristics and thicknesses of the lower layer and the upper layer are adjusted so that the phase shift film having the laminated structure of the lower layer and the upper layer has a predetermined transmittance and a predetermined phase difference with respect to the exposure light. The mask blank of the present invention has been made as a result of the above research, and is a mask blank provided with a phase shift film and a light shielding film on the main surface of a translucent substrate, wherein the phase shift film comprises silicon and A light-shielding film formed on and in contact with the phase shift film is a laminated film composed of a lower layer containing nitrogen and an upper layer containing silicon, aluminum and oxygen. Silicon and tantalum suitable for high-precision fine pattern formation It consists of a material containing 1 or more elements chosen from these.
Hereinafter, 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 used for manufacturing a phase shift mask (transfer mask). FIG. 1 shows the configuration of the mask blank of the first embodiment. The mask blank 101 according to the first embodiment includes a lower layer 31, an upper layer 32, and a light shielding film 4 on the main surface of the translucent substrate 1, and a laminated film composed of the lower layer 31 and the upper layer 32 is A phase shift film (pattern forming thin film) 3 is formed which gives a predetermined transmittance and phase difference to the transmitted exposure light. Although not shown in FIG. 1, it is preferable to provide the hard mask film 5 on the light shielding film 4 in order to form a fine and highly accurate phase shift pattern (see FIG. 3).

  The translucent substrate 1 is not particularly limited as long as it has a high transmittance for exposure light and has sufficient rigidity for preventing deformation. In the present invention, a synthetic quartz glass substrate and other various glass substrates (for example, soda lime glass, aluminosilicate glass, etc.) can be used. Among these substrates, the synthetic quartz glass substrate, in particular, has a high transmittance in an ArF excimer laser (wavelength: 193 nm) or shorter wavelength region, so the mask blank substrate of the present invention used for forming a high-definition transfer pattern. It is suitable as.

  The lower layer 31 formed on and in contact with the translucent substrate 1 is made of a material containing silicon and nitrogen, and the upper layer 32 made of a material containing silicon, aluminum, and oxygen formed on the lower layer 31. Together with these, the phase shift film 3 is formed. The phase shift film 3 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 pattern portion that is a portion where the phase shift film 3 remains and a translucent portion that is a portion where the phase shift film 3 is not formed are formed. A relationship in which the phase of light (light having a strength that does not substantially contribute to exposure) transmitted through the pattern portion of the phase shift film 3 is substantially reversed with respect to light transmitted through the light transmitting portion (ArF excimer laser exposure light). (Predetermined phase difference). By doing so, the light intensity at the boundary is made almost zero so that the light that has entered the other region due to the diffraction phenomenon cancels each other out, thereby improving the contrast of the boundary, that is, the resolution.

  The phase shift film 3 has a function of transmitting exposure light with a transmittance of 1% or more (transmittance), and the exposure light transmitted through the phase shift film 3 is air by the same distance as the thickness of the phase shift film 3. It is preferable to have a function of causing a phase difference of not less than 150 degrees and not more than 180 degrees with the exposure light passing through the inside. 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 phase shift mask is set on a mask stage of an exposure apparatus and exposed and transferred onto an object to be transferred (such as a resist film on a semiconductor wafer), the pattern line width of the phase shift pattern (particularly, line and There is a problem that the difference in the best focus of 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 is preferably set to 170 degrees or less.

  The film thickness of the phase shift film 3 composed of the lower layer 31 and the upper layer 32 is preferably 80 nm or less, and more preferably 70 nm or less. In order to reduce the variation range of the best focus due to the pattern line width of the phase shift pattern, the thickness of the phase shift film 3 is particularly preferably 65 nm or less. The thickness of the phase shift film 3 is preferably 50 nm or more. This is because 50 nm or more is necessary to make the phase shift of the phase shift film 3 150 ° or more while forming the phase shift film 3 with an amorphous material. Here, the material of the amorphous structure generally has a small surface roughness of the film surface, and the side surface of the pattern formed by etching from the film made of the material has a small roughness, in other words, a small LER (Line Edge Roughness) is preferable. It will be a thing.

  In order to satisfy the optical properties and film thickness conditions of the entire phase shift film 3, the refractive index n (hereinafter simply referred to as “refractive index n”) at the wavelength (193 nm) of the exposure light of the ArF excimer laser of the lower layer 31 is satisfied. Is preferably 2.02 or more, and more preferably 2.17 or more. The refractive index n of the lower layer 31 is preferably 2.68 or less, and more preferably 2.51 or less. The extinction coefficient k (hereinafter simply referred to as “extinction coefficient k”) at the wavelength (193 nm) of the exposure light of the ArF excimer laser of the lower layer 31 is preferably 0.30 or more, and is 0.35 or more. More preferred. The extinction coefficient k of the lower layer 31 is preferably 1.00 or less, and more preferably 0.90 or less.

  On the other hand, the refractive index n of the upper layer 32 is preferably 1.57 or more, and more preferably 1.58 or more. The refractive index n of the upper layer 32 is preferably 1.73 or less, and more preferably 1.72 or less. The extinction coefficient k of the upper layer 32 is required to be 0.00 or more, and is preferably 0.005 or more. The extinction coefficient k of the upper layer 32 is preferably 0.04 or less.

  The lower layer 31 is made of a material containing silicon and nitrogen. However, when the material containing silicon contains nitrogen, the refractive index n can be increased as compared with the case where no nitrogen is contained, and a large retardation is obtained with a thinner thickness. Is obtained. Moreover, since the extinction coefficient k can be reduced, the transmittance can be increased. For this reason, optical characteristics preferable as a phase shift film can be obtained.

  The lower layer 31 is formed of a material composed of silicon and nitrogen, a material composed of silicon and nitrogen, and a material containing one or more elements selected from nonmetallic elements and metalloid elements excluding oxygen (hereinafter referred to as SiN-based materials). can do. Among metalloid elements, the inclusion of one or more elements selected from boron, germanium, antimony, and tellurium is preferable because it can be expected to increase the conductivity of silicon used as a sputtering target.

  The lower layer 31 of the SiN-based material may contain a nonmetallic element other than oxygen. Among these nonmetallic elements, it is preferable to contain one or more elements selected from nitrogen, carbon, fluorine and hydrogen. This nonmetallic element also includes rare gases such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe). The lower layer 31 of the SiN-based material does not actively contain oxygen (below the lower limit of detection when composition analysis is performed by X-ray photoelectron spectroscopy or the like). When oxygen is contained in the material forming the lower layer 31 of the SiN-based material, both the refractive index n and the extinction coefficient k of the lower layer 31 are lowered, so that the entire thickness of the phase shift film 3 needs to be increased. As the nitrogen content in the material forming the lower layer 31 of the SiN-based material increases, the refractive index n increases and the extinction coefficient k decreases. The nitrogen content in the material forming the lower layer 31 of the SiN material is preferably 48 atomic% or more, and more preferably 50 atomic% or more. On the other hand, the nitrogen content in the material forming the lower layer 31 is preferably 57 atomic% or more, and more preferably 55 atomic% or less.

  On the other hand, the lower layer 31 can be formed of a material containing a transition metal, silicon, and nitrogen (hereinafter referred to as an MSiN-based material). Transition metals in this case include 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), etc., any one or more metals or alloys of these metals can be given. The material of the lower layer 31 of the MSiN-based material may include elements such as nitrogen (N), oxygen (O), carbon (C), and hydrogen (H) in addition to the above elements. In addition, the material of the lower layer 31 of the MSiN-based material may contain an inert gas such as helium (He), argon (Ar), krypton (Kr), and xenon (Xe).

  The lower layer 31 may be composed of a single layer or may be composed of a multilayer film having a plurality of layers. It is possible to form the lower layer 31 that is a single layer film of SiN-based material and has optical characteristics that transmit ArF excimer laser light with a transmittance of 10% or less and cause a predetermined phase difference. . However, when the lower layer 31 of the SiN-based material having such optical characteristics is formed by sputtering, a film with high uniformity of optical characteristics or a film with low defects may be stably formed depending on the method. Difficult film formation conditions may occur. In consideration of these matters, the lower layer 31 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 stacked. In this case, the low transmission layer may be a SiN-based material nitride film formed by metal mode sputtering, and the high transmission layer may be a SiN-based material nitride film formed by reaction mode (poison mode) sputtering. . By doing in this way, the lower layer 31 which satisfy | fills the conditions of desired transmittance | permeability and desired phase difference can be formed, without using sputtering in the transition mode in which film-forming conditions are difficult to determine.

  The upper layer 32 is made of a material containing silicon, aluminum, and oxygen, and functions as an etching stopper when the light-shielding film 4 formed on the film is dry-etched, and the lower layer 31 formed below the film is dried. It has a hard mask function when etching, and also has an etching selectivity for dry etching when the hard mask film 5 formed on the light shielding film 4 is removed. The phase shift film 3 needs to have a predetermined phase difference and transmittance. Elements for achieving the phase shift film 3 are a refractive index, an extinction coefficient, and a film thickness.

  The upper layer 32 preferably has an oxygen content of 60 atomic% or more. In addition, silicon bonded to oxygen is more resistant to chemical cleaning (especially alkaline cleaning such as ammonia perwater and TMAH) than oxygen unbonded silicon, and is present in the upper layer 32. It is preferable to increase the proportion of all silicon that is bonded to oxygen. On the other hand, the upper layer 32 preferably has an oxygen content of 66 atomic% or less, and more preferably 65 atomic% or less.

  The upper layer 32 has a ratio of silicon (Si) content [atomic%] to silicon (Si) and aluminum (Al) total content [atomic%] (hereinafter referred to as “Si / [Si + Al] ratio”). It is preferable that it is 4/5 or less. By setting the Si / [Si + Al] ratio of the etching stopper film 2 to 4/5 or less, the etching rate of the upper layer 32 with respect to dry etching with a fluorine-based gas is 0.2 or less of the etching rate with the light shielding film 4 or the lower layer 31. It can be. That is, an etching selection ratio of 5 times or more is obtained between the upper layer 32 and the light shielding film 4 or the lower layer 31.

  Moreover, the Si / [Si + Al] ratio in the upper layer 32 is preferably 3/4 or less, and more preferably 2/3 or less. When the Si / [Si + Al] ratio is 2/3 or less, the etching rate of the upper layer 32 for dry etching with a fluorine-based gas can be 0.16 or less of the etching rate of the light shielding film 4 or the lower layer 31. That is, an etching selectivity of 7 times or more is obtained between the upper layer 32 and the light shielding film 4 or the lower layer 31.

  The upper layer 32 preferably has a Si / [Si + Al] ratio of silicon (Si) and aluminum (Al) of 1/5 or more. By setting the Si / [Si + Al] ratio of the upper layer 32 to 1/5 or more, resistance to chemical cleaning can be increased. The Si / [Si + Al] ratio of the upper layer 32 is more preferably 1/3 or more. When the Si / [Si + Al] ratio is 1/3 or more, the resistance to chemical cleaning can be further increased.

  The upper layer 32 preferably has a content of a metal other than aluminum of 2 atomic% or less, more preferably 1 atomic% or less, and is less than or equal to the lower limit of detection when composition analysis is performed by X-ray photoelectron spectroscopy. Further preferred. The upper layer 32 preferably has a total content of elements other than silicon, aluminum, and oxygen of 5 atomic% or less, and more preferably 3 atomic% or less.

  The upper layer 32 may be formed of a material made of silicon, aluminum, and oxygen. In addition to these constituent elements, the material composed of silicon, aluminum, and oxygen is an element inevitably contained in the upper layer 32 (helium (He), neon (Ne), argon ( Ar), a material containing only rare gas such as krypton (Kr) and xenon (Xe), hydrogen (H), carbon (C) and the like). By minimizing the presence of other elements that bind to silicon or aluminum in the upper layer 32, the ratio of silicon and oxygen bonds to aluminum and oxygen bonds in the upper layer 32 can be greatly increased. Thereby, the etching tolerance of the dry etching by fluorine-type gas can be made higher, and the tolerance with respect to chemical | medical solution cleaning can be raised more. The upper layer 32 preferably has an amorphous structure. More specifically, it is preferable that the upper layer 32 has an amorphous structure including a bond of silicon and oxygen and a bond of aluminum and oxygen since the surface roughness of the upper layer 32 can be reduced.

  The upper layer 32 preferably has a thickness of 3 nm or more. By forming the upper layer 32 of a material containing silicon, aluminum, and oxygen, even if the etching rate with respect to the fluorine-based gas is significantly reduced, it is not necessarily not etched at all. Further, even when the upper layer 32 is cleaned with a chemical solution, the film does not decrease at all. Considering the influence of dry etching with a fluorine-based gas performed from the mask blank to the manufacture of the phase shift mask and the influence of chemical cleaning, the film thickness of the upper layer 32 is desirably 3 nm or more. The thickness of the upper layer is preferably 4 nm or more, and more preferably 5 nm or more.

  The upper layer 32 is more difficult to process by dry etching than the lower layer 31 containing silicon and nitrogen that can be dry etched with a fluorine-based gas, and is difficult to dry etch with a vertical cross-sectional shape and side etching suppressed. . For this reason, an etching stopper function becomes a sufficient etching stopper when the light-shielding film 4 is dry-etched to form a light-shielding pattern, and becomes a sufficient hard mask when the lower layer 31 is dry-etched to form a lower-layer pattern. It is preferable that the thickness of the upper layer 32 is as thin as possible. From this, the upper layer 32 is desired to be 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less.

  The upper layer 32 preferably has high composition uniformity in the film thickness direction, and the difference in the content of each constituent element in the film thickness direction is preferably within a fluctuation range of 5 atomic% or less. On the other hand, the upper layer 32 may have a film structure having a composition gradient in the film thickness direction. In this case, it is preferable that the composition gradient be such that the Si / [Si + Al] ratio on the lower layer 31 side of the upper layer 32 is higher than the Si / [Si + Al] ratio on the light shielding film 4 side. This is because the upper layer 32 is desired to have high resistance to dry etching with a fluorine-based gas on the light shielding film 4 side and high chemical resistance.

Regarding the method for forming the upper layer 32, 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 and the upper layer 32 is formed on the lower layer 31. Specifically, the translucent substrate 1 in which the lower layer 31 is formed is disposed on the substrate stage in the film formation chamber, and is mixed with a rare gas atmosphere such as argon gas, or oxygen gas or a gas containing oxygen. A predetermined voltage is applied to each of the two targets under a gas atmosphere. In this case, the power source to be applied is preferably an RF power source. As a result, the plasmad rare gas particles collide with the two targets to cause sputtering, respectively, and the upper layer 32 containing silicon, aluminum, and oxygen is formed on the surface of the translucent substrate 1. Incidentally, more preferable to apply the SiO ₂ target and _Al 2 _{O 3} target two targets in this case.

In addition, the upper layer 32 may be formed only with a mixed target of silicon, aluminum and oxygen (preferably, a mixed target of SiO ₂ and Al ₂ O ₃ , the same applies hereinafter), and a mixed target of silicon, aluminum and oxygen The upper layer 32 may be formed by simultaneously discharging a silicon target or two targets of an aluminum and oxygen mixed target and an aluminum target.

  The refractive index n and 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 crystal state of the thin film are factors that influence the refractive index n and the extinction coefficient k. For this reason, various conditions when forming 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 in the range of the above-mentioned refractive index n and extinction coefficient k, a mixed gas of a rare gas and a reactive gas (oxygen gas, nitrogen gas, etc.) is formed during reactive sputtering. Although it is effective to adjust the ratio, it is not limited to that. Other factors include various factors such as the pressure in the film formation chamber during film formation by reactive sputtering, the power applied to the sputtering target, and the positional relationship such as the distance between the target and the light-transmitting substrate 1. These film forming conditions are unique 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.

The light shielding film 4 is required to have light shielding properties, workability, film surface smoothness, mass productivity, and low defectivity.
Examples of the material having such characteristics include a material containing nitrogen in silicon and a material containing transition metal, silicon and nitrogen. The material containing transition metal, silicon and nitrogen has higher light shielding performance than the material containing silicon and nitrogen not containing a transition metal, and the thickness of the light shielding film 4 can be reduced. As transition metals to be contained in the light shielding film 4, molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V) , Zirconium (Zr), ruthenium (Ru), rhodium (Rh), niobium (Nb), palladium (Pd), or any other metal or an alloy of these metals. Moreover, when forming the light shielding film 4 with the material containing silicon, you may contain metals (tin (Sn) indium (In), gallium (Ga), etc.) other than a transition metal.

  The light shielding film 4 may be formed of a material containing tantalum. In this case, the silicon content of the light-shielding film 4 is preferably 5 atomic% or less, more preferably 3 atomic% or less, and even more preferably substantially not contained. These materials containing tantalum are materials that can form a transfer pattern by dry etching with a fluorine-based gas. Examples of the material containing tantalum in this case include a material in which tantalum contains one or more elements selected from nitrogen, oxygen, boron, and carbon in addition to tantalum metal. Examples thereof include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, TaBOCN, and the like.

  The material for forming the light-shielding film 4 is one or more selected from oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H) as long as the optical density is not significantly reduced. These elements may be contained. In particular, a tantalum nitride film (TaN film) containing nitrogen tends to improve the smoothness of the light shielding film and improve the roughness of the light shielding pattern. Further, since Ta metal is easily oxidized in the atmosphere, there is a problem that the line width changes with time if the pattern side wall made of Ta metal alone is exposed after the light shielding pattern is formed. When nitrogen is added to Ta metal, it becomes difficult to oxidize. Therefore, when tantalum is used for the light shielding film 4, it is preferable to contain nitrogen. In order to further improve the smoothness of the tantalum nitride film, boron, carbon, or the like may be added to the tantalum nitride film. Since these elements deteriorate the light shielding performance or etching performance of Ta metal, the addition amount is preferably 30 atomic% or less. Specifically, when boron or carbon is added, the light shielding performance is lowered. When carbon is added, the etching rate decreases.

  The light shielding film 4 may be formed of a material containing chromium. The light shielding film 4 is more preferably formed of a material containing one or more elements selected from nitrogen, oxygen, carbon, hydrogen and boron in addition to chromium. The light-shielding film 4 includes at least one metal element selected from indium (In), tin (Sn), and molybdenum (Mo) (hereinafter referred to as “metal element such as indium”). It may be formed of a material containing “. When the light shielding film 4 is formed of a material containing chromium, a material containing silicon and oxygen or a material containing tantalum and oxygen is applied to the hard mask film 5 described later.

  The light shielding film 4 can be applied to either 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 two or more layers has a composition gradient in the thickness direction of the layer even if the layers have substantially the same composition in the film thickness direction. It may be a configuration. In order to reduce the reflectance with respect to the exposure light on the surface of the light shielding film 4 opposite to the light transmissive substrate 1, the surface layer on the side opposite to the light transmissive substrate 1, that is, a two-layer structure of a lower layer and an upper layer May contain a large amount of oxygen or nitrogen in the upper layer.

  The light shielding film 4 forms a light shielding band or the like with a laminated structure with the phase shift film 3 after completion of the phase shift mask. For this reason, the light-shielding film 4 is required to ensure an optical density (OD) of 2.8 or higher with respect to exposure light (wavelength 193 nm) in a laminated structure with the phase shift film 3, It is more preferable that there is OD.

  In the first embodiment, the hard mask film 5 laminated on the light shielding film 4 is formed of a material having etching selectivity with respect to an etching gas used when the light shielding film 4 is etched (see FIG. 3). . As a result, as described below, the thickness of the resist film can be made much thinner than when the resist film is directly used as a mask for the light shielding film 4.

  As described above, the light-shielding film 4 needs to have a sufficient light-shielding function while ensuring a predetermined optical density. On the other hand, it is sufficient for the hard mask film 5 to have a film thickness that can function as an etching mask until dry etching for forming a pattern on the light shielding film 4 immediately below is completed. Not subject to restrictions. For this reason, the thickness of the hard mask film 5 can be made much thinner than the thickness of the light shielding film 4. The resist film of the organic material only needs to have a film thickness sufficient to function as an etching mask until the dry etching for forming a pattern on the hard mask film 5 is completed. The film thickness of the resist film can be made much thinner than when it is directly used as the mask 4. Since the resist film can be thinned in this way, the resist resolution can be improved and the formed pattern can be prevented from collapsing.

  For this reason, the mask blank of the first embodiment includes a hard mask film 5 on the light shielding film 4. When the light shielding film 4 is made of a material containing silicon or tantalum, the hard mask film 5 is preferably made of a material containing chromium. The hard mask film 5 is more preferably formed of a material containing one or more elements selected from nitrogen, oxygen, carbon, hydrogen and boron in addition to chromium. The hard mask film 5 may be formed of a material containing a metal element such as indium in the material containing chromium.

  In the mask blank 101, it is preferable that a resist film of an organic material is formed with a thickness of 100 nm or less in contact with the surface of the hard mask film 5. In the case of a fine pattern corresponding to the DRAM hp32 nm generation, a transfer pattern (phase shift pattern) to be formed on the hard mask film 5 may be provided with SRAF (Sub-Resolution Assist Feature) having a line width of 40 nm. Even in such a case, since the cross-sectional aspect ratio of the resist pattern is as low as 1: 2.5, it is possible to suppress the resist pattern from collapsing or detaching during development or rinsing of the resist film. In addition, it is more preferable that the film thickness of the resist film is 80 nm or less because collapse and detachment of the resist pattern are further suppressed.

  As described above, it is preferable to form the hard mask film 5 laminated on the light shielding film 4 with the above-described material, but the present invention is not limited to this embodiment, and the mask blank 101 Alternatively, 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.

  The lower layer 31, the upper layer 32, 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. In the case of using a target with low conductivity, 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 formation rate.

[Phase shift mask and its manufacture]
In the phase shift mask 201 (see FIG. 2) according to the first embodiment, a phase shift pattern 3 a as a transfer pattern is formed on the phase shift film 3 composed of the lower layer 31 and the upper layer 32, and the light shielding film 4 A light-shielding pattern 4b (light-shielding band, light-shielding patch, etc.) that is a pattern including the light-shielding band is formed. In the case where the hard mask film 5 is provided on the mask blank 101, the hard mask film 5 is removed during the manufacturing process of the phase shift mask 201.

The manufacturing method of the phase shift mask according to the first embodiment uses the mask blank 101, and includes a step of forming a transfer pattern on the light shielding film 4 by dry etching, and the light shielding film 4 having the transfer pattern or Using the hard mask film 5 as an etching mask, a transfer pattern is formed on the lower layer 31 by a step of forming a transfer pattern on the upper layer 32 using an etching gas containing boron chloride (BCl ₃ ) gas, and dry etching using a fluorine-based gas. And a step of forming a pattern including a light shielding band (light shielding band, light shielding patch, etc.) on the light shielding film 4 by dry etching. Hereinafter, the manufacturing method of the phase shift mask 201 according to the first embodiment will be described according to the manufacturing process shown in FIG. Here, a manufacturing method of the phase shift mask 201 using the mask blank 101 in which the hard mask film 5 is laminated on the light shielding film 4 will be described with reference to FIG. Further, a case where a material containing a transition metal and silicon is applied to the light shielding film 4 and a material containing chromium is applied to the hard mask film 5 will be described.

  First, a resist film is formed by spin coating in contact with the hard mask film 5 in the mask blank 101. Next, 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 form a first resist pattern 6a. (See FIG. 3A). Subsequently, dry etching using a mixed gas of chlorine-based gas and oxygen gas is performed using the first resist pattern 6a as a mask to form a first hard mask pattern 5a on the hard mask film 5 (FIG. 3B). )reference).

Next, after removing the first resist pattern 6a, dry etching using a fluorine-based gas is performed using the first hard mask pattern 5a as a mask to form the first light-shielding pattern 4a on the light-shielding film 4. (See FIG. 3C). Thereafter, using the first hard mask pattern 5a as a mask, an upper layer pattern 32a is formed on the upper layer 32 by dry etching using a mixed gas of boron chloride (BCl ₃ ) gas and chlorine (Cl ₂ ) gas (FIG. 3D )).

Next, a resist film is formed by a spin coating method, a light shielding pattern including a light shielding band (light shielding band, light shielding patch, etc.) is drawn on the resist film with an electron beam, and a predetermined process such as a development process is performed. Then, a second resist pattern 7b is formed (see FIG. 3E). Here, when the second pattern is composed only of a relatively large pattern, exposure drawing using a laser beam by a high-throughput laser drawing apparatus may be used instead of drawing using an electron beam. Is possible.
Thereafter, dry etching using a mixed gas of chlorine-based gas and oxygen gas is performed using the second resist pattern 7b as an etching mask to form a second hard mask pattern 5b on the hard mask film 5 (FIG. 3F). )reference).

  After removing the second resist pattern 7b, dry etching using a fluorine-based gas is performed to form a first pattern (phase shift pattern 31a) in the lower layer 31 (see FIG. 3G). At this time, the light shielding pattern becomes the light shielding pattern 4b in which only the portion protected by the second hard mask pattern 5b including the light shielding band and the like remains, and the light shielding film 4 in other portions is removed. In the dry etching of the lower layer 31, the light-shielding film is further formed as an upper layer pattern so that the phase shift pattern 3a has a nearly vertical cross-sectional shape and in-plane CD (Critical Dimension) uniformity of the phase shift pattern 3a. A predetermined over-etching is performed so that the light shielding film remaining on the surface of 32a is completely removed and the surface 700 of the upper layer pattern 32a is exposed. At this time, the surface 701 of the portion where the translucent substrate 1 is exposed due to the influence is slightly dug. On the other hand, the exposed surface 700 of the upper layer pattern 32a is hardly etched because the upper layer 32 has high etching resistance (etching stopper function) against dry etching of a fluorine-based gas.

  Thereafter, the second hard mask pattern 5b 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 the phase shift mask 201 (FIG. 3 (h) )reference).

  From the above, the optical conditions (refraction of the phase shift pattern 3a) in consideration of the digging amount of the surface 701 of the portion where the translucent substrate 1 is exposed (in consideration of a minute phase change with respect to the exposure light). If the ratio n, extinction coefficient k, and film thickness) are designed, the phase shift pattern 3a can control the phase difference with sufficiently high accuracy, and is a phase shift pattern suitable for highly accurate and fine pattern transfer. Become.

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. The fluorine-based gas used in the dry etching is not particularly limited as long as fluorine (F) is contained. For example, CHF ₃ , CF ₄ , C ₂ F ₆ , C ₄ F ₈ , SF ₆ etc. are mentioned.

  In the above phase shift mask manufacturing method, the upper layer pattern 32a is formed by dry etching using the hard mask pattern 5a as a mask. However, the present invention is not limited to this procedure. For example, after the light shielding pattern 4a is formed, the hard mask pattern 5b is formed by performing dry etching using the second resist pattern 7b as a mask, and then the upper layer pattern is formed by performing dry etching using the light shielding pattern 4a as a mask. The phase shift mask 201 can also be manufactured by the procedure for forming 32a.

  As described above, the mask blank 101 according to the first embodiment includes the phase shift film 3 that is a laminated phase shift film including the lower layer 31 containing silicon and nitrogen and the upper layer 32 containing silicon, aluminum, and oxygen. 3 and the light-shielding film 4 is a film made of a material containing silicon or tantalum that has excellent workability by dry etching and can form a highly accurate fine pattern.

  Both the light shielding film 4 and the lower layer 31 form the light shielding pattern 4b and the lower layer pattern 31a by etching using a fluorine-based gas. At this time, since the material of the upper layer 32 is a material containing silicon, aluminum, and oxygen, the upper layer 32 Takes a function as an etching stopper and a hard mask sufficient for the etching. Even in the formation process of the light shielding pattern 4b, the film thickness change of the upper layer 32 is small, and the phase controllability of the phase shift pattern 3a composed of the lower layer pattern 31a and the upper layer pattern 32a is high. Since the fluorine gas-based dry etching with high anisotropic etching property and sufficient over-etching can be performed, the perpendicularity of the side wall of the phase shift pattern 3a is high and the in-plane CD uniformity is also high. Further, all materials used for the mask blank 101 including the upper layer 32 have sufficient cleaning resistance against the cleaning liquid used from the mask blank to the mask manufacturing. For this reason, the phase shift mask 201 manufactured using this mask blank 101 has a highly accurate fine pattern, and becomes a phase shift film having high phase controllability and chemical cleaning resistance.

[Manufacture of semiconductor devices]
The semiconductor device manufacturing method of the first embodiment uses the phase shift mask 201 manufactured using the phase shift mask 201 of the first embodiment or the mask blank 101 of the first embodiment, and forms a resist film on the semiconductor substrate. The phase shift pattern (transfer pattern) 3a is exposed and transferred. The phase shift mask 201 of the first embodiment has high side wall perpendicularity of the phase shift pattern 3a and high CD uniformity within the surface of the phase shift pattern 3a. In addition, since sufficient chemical cleaning can be performed, there are few mask defects. For this reason, when the phase shift mask 201 of Embodiment 1 is used for exposure transfer to a resist film on a semiconductor device, a pattern can be formed on the resist film on the semiconductor device with a high yield with sufficient accuracy to satisfy the design specifications. it can.

<Second Embodiment>
[Mask blank and its manufacture]
The mask blank according to the second embodiment of the present invention is characterized in that the etching stopper film 2 is formed in contact with the main surface of the translucent substrate 1. This etching stopper film 2 is the same material containing silicon, aluminum and oxygen as used for the upper layer 32 in the first embodiment, and the manufacturing method is also the same. FIG. 4 shows the configuration of the mask blank 102 of the second embodiment. The mask blank 102 according to the second embodiment has a structure in which an etching stopper film 2, a phase shift film 3, and a light shielding film 4 are sequentially laminated on a translucent substrate 1. 5 can be laminated. The phase shift film 3 includes a lower layer 31 and an upper layer 32. The mask blank 102 of the second embodiment is different from the mask blank 101 of the first embodiment in that an etching stopper film 2 is further provided. Along with this, as will be described in detail later, the film thickness of the lower layer 31 is also changed. In addition, about the structure similar to the mask blank 101 of 1st Embodiment, the same code | symbol is used and description is abbreviate | omitted suitably.

  The etching stopper film 2 is formed on the entire main surface of the translucent substrate 1 and remains on the entire main surface of the translucent substrate 1 even when the phase shift mask is completed. The etching stopper film 2 remains in the light-transmitting portion that is a non-existing region (see FIG. 5). For this reason, it is preferable that the etching stopper film 2 is formed in contact with the translucent substrate 1 without interposing any other film with the translucent substrate 1.

Moreover, since the etching stopper film 2 affects the transmittance of the light transmitting portion of the phase shift mask with respect to the exposure light, a high transmittance for the exposure light (ArF excimer laser light with a wavelength of 193 nm) is required. When the transmittance is low, a larger exposure amount (dose amount) is required at the time of exposure transfer, and the exposure time is extended, thereby reducing the throughput of semiconductor device manufacturing.
On the other hand, since the etching stopper film 2 is required to have a high transmittance and a sufficient etching selectivity with respect to the fluorine-based gas with the translucent substrate 1 at the same time, the transmissivity with respect to the exposure light is reduced to It is difficult to achieve the same transmittance. That is, the transmittance of the etching stopper film 2 is less than 100% when the transmittance of the translucent substrate 1 (synthetic quartz glass) with respect to the exposure light is 100%. The transmittance of the etching stopper film 2 is preferably 95% or more, more preferably 96% or more, and 97% or more when the transmittance of the translucent substrate 1 with respect to exposure light is 100%. And more preferred.

  The etching stopper film 2 preferably has an oxygen content of 60 atomic% or more. This is because the etching stopper film 2 is required to contain a large amount of oxygen in order to set the transmittance for exposure light to the above numerical value or more. As will be described later, the etching stopper film 2 needs to have high resistance to chemical cleaning, because it is preferable that the abundance ratio of oxygen, unbonded silicon and aluminum in the etching stopper film 2 is small.

  The etching stopper film 2 preferably has a Si / [Si + Al] ratio of silicon (Si) and aluminum (Al) of 1/5 or more. By setting the Si / [Si + Al] ratio of the etching stopper film 2 to 1/5 or more, the transmittance of the etching stopper film 2 when the transmittance of the translucent substrate 1 (synthetic quartz glass) with respect to the exposure light is 100%. The rate can be 95% or more. At the same time, resistance to chemical cleaning can be increased. The Si / [Si + Al] ratio in the etching stopper film 2 is more preferably 1/3 or more. When the Si / [Si + Al] ratio is 1/3 or more, the transmittance of the etching stopper film 2 is 97% or more when the transmittance of the translucent substrate (synthetic quartz glass) 1 with respect to exposure light is 100%. be able to.

  The Si / [Si + Al] ratio of the etching stopper film 2 is preferably 4/5 or less. By setting the Si / [Si + Al] ratio of the etching stopper film 2 to 4/5 or less, the etching rate of the etching stopper film 2 with respect to the dry etching with the fluorine-based gas is set to 1/3 or less of the etching rate of the translucent substrate 1. can do. That is, a difference in etching amount of 3 times or more is obtained between the translucent substrate 1 and the etching stopper film 2. Further, the Si / [Si + Al] ratio in the etching stopper film 2 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 with respect to dry etching with a fluorine-based gas can be set to 1/5 or less of the etching rate of the translucent substrate 1. That is, an etching amount difference of 5 times or more is obtained between the translucent substrate 1 and the etching stopper film 2.

  The etching stopper film 2 preferably has a film thickness of 3 nm or more. Similar to the upper layer 32, the etching stopper film 2 is not completely etched at the time of dry etching with respect to the fluorine-based gas. Further, even when the etching stopper film 2 is washed with a chemical solution, the film does not decrease at all. In consideration of the effect of dry etching with a fluorine-based gas performed from the mask blank to the manufacture of the phase shift mask and the effect of chemical cleaning, the thickness of the etching mask film is desirably 3 nm or more. The thickness of the etching mask film is preferably 4 nm or more, and more preferably 5 nm or more. On the other hand, from the viewpoint of the transmittance for exposure light, the thickness of 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.

  The etching stopper film 2 is preferably formed of a material made of silicon, aluminum, and oxygen. In addition to these constituent elements, the material composed of silicon, aluminum, and oxygen is an element inevitably contained in the etching stopper film 2 (rare gas, hydrogen (H), carbon ( C) and the like. As described in the first embodiment, by forming the etching stopper film 2 with these materials, the etching resistance of the dry etching with the fluorine-based gas is higher and the resistance to chemical cleaning is higher than the conventional one. In addition, the transmittance for exposure light can be further increased.

  In the first embodiment, the film thickness of the lower layer 31 is set to a film thickness that obtains a predetermined phase difference, considering that the surface 701 of the portion where the translucent substrate 1 is exposed is slightly dug. It was. On the other hand, in the second embodiment, the surface 702 where the etching stopper film 2 is exposed is hardly etched when the lower layer 31 is dry-etched, so that it is not necessary to consider the digging of the surface 702. Accordingly, the film thickness of the lower layer 31 is set so that the phase shift film 3 combined with the upper layer 32 has a predetermined phase difference and a predetermined transmittance with respect to the exposure light.

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

  A mask blank having a structure in which a phase shift film (both single-layer film and multilayer film) 3 of a silicon-based material is provided in contact with the main surface of a transparent substrate 1 made of a glass material has a phase shift film 3 of silicon and nitrogen. Is the most component, whereas the translucent substrate 1 is mostly composed of silicon and oxygen, and the difference between them is substantially only oxygen and nitrogen. For this reason, it was a combination in which it was difficult to detect etching correction for EB defect correction. On the other hand, in the configuration in which the phase shift film 3 is provided in contact with the surface of the etching stopper film 2, the phase shift film 3 is mostly composed of silicon and nitrogen, whereas the etching stopper film 2 is composed of silicon. Contains aluminum in addition to oxygen. For this reason, in etching correction for EB defect correction, detection of aluminum may be used as a guideline, and end point detection becomes relatively easy. On the other hand, when the phase shift film 3 is formed of a material containing a transition metal, silicon and nitrogen, the phase shift film 3 contains aluminum in consideration of detection of the etching end point of EB defect correction. Preferably not.

[Phase shift mask and its manufacture]
In the phase shift mask 202 (see FIG. 5) according to the second embodiment, the etching stopper film 2 of the mask blank 102 is left on the entire main surface of the translucent substrate 1, and the phase shift film 3 and the light shielding film are left. 4 is characterized in that a phase shift pattern 3a and a light shielding pattern 4b necessary for pattern exposure transfer are formed.

  The manufacturing method of the phase shift mask according to the second embodiment uses the mask blank 102, and, as shown in FIG. 6, from the formation of the first resist pattern 6a, the hard mask pattern. The same steps as those in Embodiment 1 are provided until 5b is removed and cleaning with a chemical solution is performed to obtain the phase shift mask 202. The difference from the first embodiment is that when the lower layer 31 is dry-etched using a fluorine-based gas to form the lower layer pattern 31a, the surface 702 from which the etching stopper film 2 is exposed is hardly etched (FIG. 6 (g)). For this reason, in the dry etching when forming the lower layer pattern 31a, sufficient over-etching can be performed, and the mask in-plane CD uniformity of the lower layer pattern 31a and the perpendicularity of the pattern cross section can be further improved. Further, even in this state, since the upper layer pattern 32a is a hard mask having a sufficient etching stopper function, the phase accuracy of the lower layer pattern 31a is high. In addition, all materials constituting the phase shift mask 202 including the etching stopper film 2 have high chemical cleaning resistance. For this reason, there are few mask defects since sufficient mask cleaning can be performed. Thus, the phase shift mask 202 is a phase shift mask suitable for fine and high-precision pattern transfer.

[Manufacture of semiconductor devices]
The semiconductor device manufacturing method of the second embodiment uses a phase shift mask 202 manufactured by using the phase shift mask 202 of the second embodiment or the mask blank 102 of the second embodiment, and forms a resist film on the semiconductor substrate. The transfer pattern is exposed and transferred. The phase shift mask 202 of the second embodiment has high verticality of the side wall of the phase shift pattern 3a and high CD uniformity within the mask surface. Furthermore, it has high phase controllability. For this reason, when the phase shift mask 202 of Embodiment 2 is used for exposure 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 satisfy the design specifications.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
Example 1
[Manufacture of mask blanks]
A translucent substrate 1 made of synthetic quartz glass having a main surface dimension of about 152 mm × about 152 mm and a thickness of about 6.35 mm was prepared. The translucent substrate 1 has its end face and main surface 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 process and drying process. It is.

Next, a lower layer (MoSiN film) 31 made of molybdenum, silicon, and nitrogen was formed in a thickness of 67.4 nm in contact with the main surface of the translucent substrate 1. Specifically, the translucent substrate 1 is installed in a single-wafer DC sputtering apparatus, and a mixed sintered target (Mo: Si = 12: 88 (atomic% ratio)) of molybdenum (Mo) and silicon (Si). ) And using argon (Ar), nitrogen (N ₂ ) and helium (He) mixed gas (flow ratio Ar: N ₂ : He = 8: 72: 100, pressure = 0.2 Pa) as a sputtering gas The lower layer 31 was formed by reactive sputtering (DC sputtering). As a result of analyzing the phase shift film formed on another light-transmitting substrate under the same conditions by X-ray photoelectron spectroscopy, the material composition ratio was Mo: Si: N = 4.1 to 35.6. : 60.3 (atomic% ratio).

  The lower layer 31 is formed on another translucent substrate under the same conditions, and the refractive index and the extinction coefficient of the lower layer 31 after heat treatment are measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). The refractive index n was 2.415 and the extinction coefficient k was 0.596 in the light having a wavelength of 193 nm.

Thereafter, an upper layer 32 (AlSiO film) made of aluminum, silicon and oxygen was formed in a thickness of 5 nm in contact with the surface of the lower layer 31. Specifically, the translucent substrate 1 in which the lower layer 31 is formed is installed in a single wafer RF sputtering apparatus, the Al ₂ O ₃ target and the SiO ₂ target are discharged simultaneously, and argon (Ar) gas is sputtered. The upper layer 32 was formed by sputtering (RF sputtering). As a result of analyzing the etching stopper film formed on another light-transmitting substrate under the same conditions by X-ray photoelectron spectroscopy, the material composition ratio was Al: Si: O = 21: 19: 60 (atom % Ratio). That is, Si / [Si + Al] of the upper layer 32 is 0.475. 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).

  An upper layer 32 (AlSiO film) is formed on another translucent substrate under the same conditions, and the refractive index and extinction coefficient of the upper layer 32 are measured using the above-described spectroscopic ellipsometer. The rate n was 1.625, and the extinction coefficient k was 0.000 (measurement lower limit).

  For the laminated phase shift film 3 composed of the lower layer 31 and the upper layer 32 formed on the translucent substrate 1 by the above method, the wavelength of ArF excimer laser (193 nm) is measured with a phase shift amount measuring device MPM193 (manufactured by Lasertec). ) And the phase shift amount were measured, the transmittance was 6.4% and the phase shift amount was 177.1 degrees.

Next, the light shielding film 4 was formed on the upper layer 32. The light-shielding film 4 used in Example 1 is a two-layer film made of molybdenum, silicon, and nitrogen (MoSiN). The lower layer MoSiN is formed with a thickness of 27 nm, and the upper layer MoSiON is formed with a thickness of 13 nm. . Specifically, the translucent substrate 1 after the upper layer 32 is formed is installed in a single-wafer DC sputtering apparatus, and a mixed sintered target (Mo: Si =) of molybdenum (Mo) and silicon (Si). 13:87 (atomic% ratio)), the lower layer and the upper layer of the light-shielding film 4 were formed by reactive sputtering (DC sputtering) using a mixed gas of argon (Ar) and nitrogen (N ₂ ) as a sputtering gas.

  Next, the translucent substrate 1 provided with the light shielding film 4 was subjected to a heat treatment at 450 ° C. for 30 minutes to reduce the film stress of the light shielding film 4. In addition, the analysis by X-ray photoelectron spectroscopy was performed with respect to the light-shielding film 4 formed on another translucent substrate 1 in the same procedure and subjected to the annealing treatment. As a result, the lower layer of the light shielding film 4 is Mo: Si: N = 8: 62: 30 (atomic% ratio), and the upper layer near the lower layer side is Mo: Si: N: O = 6: 54: 37: 3 (atomic% ratio) was confirmed. Moreover, it was 3.0 when the optical density (OD) of the light shielding film 4 was measured using the said spectroscopic ellipsometer.

Next, a hard mask film 5 (CrN film) made of chromium and nitrogen was formed to a thickness of 5 nm in contact with the surface of the upper layer of the light shielding film 4. Specifically, the translucent substrate 1 provided with the light-shielding film 4 is installed in a single wafer DC sputtering apparatus, and a mixed gas of argon (Ar) and nitrogen (N ₂ ) is sputtered using a chromium (Cr) target. The hard mask film 5 was formed by reactive sputtering (DC sputtering) using gas. As a result of analyzing by X-ray photoelectron spectroscopy with respect to the hard mask film | membrane formed on another translucent board | substrate on the same conditions, it was Cr: N = 72: 28 (atomic% ratio). The mask blank of Example 1 was manufactured by the above procedure.

  When the etching rate was measured by immersing another translucent substrate on which the upper layer 32 was formed in ammonia water having a concentration of 0.5%, it was 0.1 nm / min. From this result, it was confirmed that the upper layer 32 of Example 1 has sufficient resistance to chemical cleaning performed in the process of manufacturing the phase shift mask 201 from the mask blank 101.

Dry etching using a mixed gas of SF ₆ and He as an etching gas for the translucent substrate, the upper layer formed on another translucent substrate, and the lower layer formed on another translucent substrate Was performed under the same conditions. Then, each etching rate was calculated, and an etching selectivity between the three was calculated. The etching selectivity of the upper layer 32 with respect to the translucent substrate 1 was 0.1, and the etching selectivity of the lower layer 31 with respect to the translucent substrate 1 was 2.38. The etching selectivity of the lower layer 31 with respect to the upper layer 32 was 23.8.

[Manufacture and evaluation of phase shift mask]
Next, using the mask blank 101 of Example 1, the phase shift mask 201 of Example 1 was produced according to the following procedure. First, a resist film made of a chemically amplified resist for electron beam drawing was formed to a thickness of 80 nm in contact with the surface of the hard mask film 5 by spin coating. Next, a pattern for transfer exposure was drawn on the resist film with an electron beam, and a predetermined development process was performed to form a first resist pattern 6a (see FIG. 3A).

Next, dry etching using a mixed gas of chlorine and oxygen (gas flow ratio Cl ₂ : O ₂ = 4: 1) is performed using the first resist pattern 6 a as a mask, and the hard mask film 5 is subjected to the first hard pattern. A mask pattern 5a was formed (see FIG. 3B).

Next, the first resist pattern 6a was removed by TMAH. Subsequently, using the first hard mask pattern 5a as a mask, dry etching using a fluorine-based gas (mixed gas of SF ₆ gas and He gas) is performed to form the first light shielding pattern 4a on the light shielding film 4 ( (Refer FIG.3 (c)). In this dry etching with a fluorine-based gas, in addition to the just etching time which is the etching time from the start of etching of the light shielding film 4 until the etching proceeds in the film thickness direction of the light shielding film 4 and the surface of the upper layer 32 begins to be exposed, Additional etching, that is, overetching, was performed for 20% of the just etching time. Note that this dry etching with a fluorine-based gas is biased with a power of 10 W, and was performed under so-called high bias etching conditions.

Next, using the first hard mask pattern 5a as a mask, dry etching using a mixed gas of boron chloride (BCl ₂ ) and chlorine (Cl ₂ ) was performed to form an upper layer pattern 32a on the upper layer 32 (FIG. 3 ( d)).

Next, a second resist pattern 7b having a light-shielding band and a patch pattern for exposure transfer is formed by electron beam drawing (see FIG. 3E). Subsequently, chlorine is formed using the second resist pattern 7b as a mask. And dry etching using a mixed gas of oxygen and oxygen (gas flow ratio Cl ₂ : O ₂ = 10: 1) to form a second hard mask pattern 5b on the hard mask film 5 (see FIG. 3F) .

Next, the second resist pattern 7b was removed. Subsequently, using the second hard mask pattern 5b as a mask, dry etching using a fluorine-based gas (mixed gas of SF ₆ gas and He gas) is performed to form the second light shielding pattern 4b on the light shielding film 4. The lower layer 31 was also etched to form a lower layer pattern 31a (see FIG. 3G). In this dry etching using a fluorine-based gas, overetching was performed for 20% of the time in addition to the just etching time for the lower layer 31. Note that this dry etching with a fluorine-based gas is biased with a power of 10 W, and was performed under so-called high bias etching conditions. At this time, the surface 701 where the translucent substrate 1 was exposed was etched by about 3 nm. On the other hand, the upper layer pattern 32a has a sufficient function as an etching stopper, and its film thickness hardly changed before and after this etching.

Thereafter, the remaining second hard mask pattern 5b is removed by dry etching using a mixed gas of chlorine-based gas and oxygen gas (gas flow ratio Cl ₂ : O ₂ = 4: 1), washed with ammonia overwater, etc. Through the predetermined process, a phase shift mask 201 was obtained (see FIG. 3H).

When the CD uniformity in the mask surface of the phase shift pattern 3a of the manufactured phase shift mask 201 was inspected, it was a satisfactory result. Further, when the cross section of the phase shift pattern 3a was observed with a STEM, the side wall of the phase shift pattern 3a had high verticality, and problems such as pattern peeling and pattern shape defects associated with cleaning were not observed.
As described above, the phase shift amount of the phase shift film 3 was 177.1 degrees only with the phase shift film 3 of the mask blank. However, when the lower layer pattern 31a is formed by dry etching, the translucency is obtained. Since the exposed surface 701 of the substrate 1 is dug slightly, the phase shift amount of the phase shift pattern 3a at the stage of becoming the phase shift mask 201 is estimated to be 180 degrees.

A simulation of a transfer image was performed on this phase shift mask 201 when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications were satisfied.
When the produced phase shift mask 201 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, a fine circuit pattern could be formed with a predetermined accuracy.

(Example 2)
[Manufacture of mask blanks]
The mask blank of Example 2 is the same as the mask blank of Example 1 except that the lower layer 31 is changed to a two-layer structure of a silicon nitride film (SiN film) and the composition of the upper layer 32 is changed from that of Example 1. It was manufactured in the same way. Therefore, the structure of the mask blank in which the lower layer 31, the upper layer 32, the light shielding film 4 and the hard mask film 5 are laminated in this order in contact with the light transmissive substrate 1, and the light transmissive substrate 1, the light shielding film 4 and the hard mask film 5. The materials and the manufacturing method are the same as those in Example 1. Hereinafter, the difference from the mask blank of Example 1 will be described.

The lower layer 31 of the second embodiment has a structure in which a low transmission layer and a high transmission layer are laminated in contact with the main surface of the translucent substrate 1. A specific film forming process is as follows. A translucent substrate 1 is installed in a single-wafer RF sputtering apparatus, a silicon (Si) target is used, and a mixed gas of argon (Ar) and nitrogen (N ₂ ) (flow rate ratio Ar: N ₂ = 2: 3). The pressure of 0.035 Pa) is a sputtering gas, the power of the RF power source is 2.8 kW, and the main surface of the translucent substrate 1 is contacted by reactive sputtering (RF sputtering) in the metal mode region, and silicon and A low transmission layer made of nitrogen (Si: N = 59: 41 (atomic% ratio)) was formed to a thickness of 11.9 nm. When only the low transmission layer was formed under the same conditions on the main surface of another translucent substrate, and the optical characteristics of the low transmission layer were measured using the spectroscopic ellipsometer, the refractive index n at a wavelength of 193 nm was obtained. Was 1.85 and the extinction coefficient k was 1.70.

Next, the translucent substrate 1 on which the low transmission layer is laminated is installed in a single wafer RF sputtering apparatus, and a mixed gas of argon (Ar) and nitrogen (N ₂ ) using a silicon (Si) target ( The flow ratio Ar: N ₂ = 1: 3, pressure = 0.09 Pa) is used as the sputtering gas, the power of the RF power source is set to 2.8 kW, and the reactive sputtering (RF sputtering) in the region of the reaction mode (poison mode) is performed. On the low transmission layer, a high transmission layer (Si: N = 46: 54 (atomic% ratio)) made of silicon and nitrogen was formed with a thickness of 58.5 nm. When only the high transmission layer was formed under the same conditions on the main surface of another translucent substrate and the optical characteristics of the high transmission layer were measured using the spectroscopic ellipsometer, the refractive index n at a wavelength of 193 nm was obtained. Was 2.52 and the extinction coefficient k was 0.39.

The upper layer 32 of Example 2 is obtained by simultaneously discharging an Al ₂ O ₃ target and a SiO ₂ target using a single wafer RF sputtering apparatus and performing sputtering (RF sputtering) using argon (Ar) gas as a sputtering gas. It is an AlSiO film to be formed, and its element ratio is Al: Si: O = 13: 26: 61 (atomic% ratio). Therefore, Si / [Si + Al] of this etching stopper film 2 is 0.67. The upper layer 32 was formed in contact with the surface of the lower layer 31 to a thickness of 5 nm. The refractive index n of this film at a wavelength of 193 nm was 1.600, and the extinction coefficient k was 0.0000 (lower measurement limit). The etching rate with 0.5% ammonia water is 0.1 nm / min, and the upper layer 32 is sufficiently resistant to chemical cleaning performed in the process of manufacturing the phase shift mask 201 from the mask blank 101. It was confirmed that the

Further, when the selection ratio of dry etching using a mixed gas of SF ₆ and He as an etching gas was compared in the same manner as in Example 1, etching of the upper layer 32 of Example 2 with respect to the translucent substrate 1 was performed. The selectivity was 0.2, and the etching selectivity of the lower layer 31 of Example 2 with respect to the translucent substrate 1 was 2.03. Moreover, the etching selectivity of the lower layer 31 of Example 2 with respect to the upper layer 32 of Example 2 was 10.2.

  With respect to the phase shift film 3 composed of the lower transmission layer, the lower transmission layer 31 and the upper transmission layer 32, the transmittance and the phase difference at the wavelength of the ArF excimer laser light (about 193 nm) are measured with the above-described phase shift amount measuring device. When measured, the transmittance was 6.1% and the phase difference was 177.2 degrees.

[Manufacture of phase shift mask]
Using the mask blank 101 of Example 2, the phase shift mask 201 of Example 2 was fabricated in the same process as in Example 1.
When the CD uniformity in the mask surface of the phase shift pattern 3a of the manufactured phase shift mask 201 was inspected, it was a satisfactory result. Further, when the cross section of the phase shift pattern 3a was observed with a STEM, the perpendicularity of the side wall of the phase shift pattern 3a was high, and problems such as pattern peeling due to cleaning were not observed.
As described above, the phase shift amount of the phase shift film 3 was 177.2 degrees only with the phase shift film 3 of the mask blank. However, when the lower layer pattern 31a is formed by dry etching, the light transmissive property is obtained. Since the exposed surface 701 of the substrate 1 is dug slightly, the phase shift amount of the phase shift pattern 3a at the stage of becoming the phase shift mask 201 is estimated to be 180 degrees.

A simulation of a transfer image was performed on this phase shift mask 201 when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications were satisfied.
When the produced phase shift mask 201 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, a fine circuit pattern could be formed with a predetermined accuracy.

(Example 3)
[Manufacture of mask blanks]
The mask blank of Example 3 is manufactured in the same manner as the mask blank of Example 1 except for the lower layer 31 and the upper layer 32. The lower layer 31 of Example 3 was the same as Example 1 except that the film thickness was changed to 67.5 nm. On the other hand, an AlSiO film (Al: Si: O = 7: 28: 65 (atomic% ratio)) made of aluminum, silicon, and oxygen is applied to the upper layer 32 of Example 3 and is in contact with the surface of the lower layer 31. The film was formed with a thickness of 5 nm. That is, Si / [Si + Al] of the etching stopper film 2 is 0.8. The manufacturing method of the upper layer 32 was the same as that in Example 1, and the composition was adjusted as described above under different conditions. The refractive index n of this film at a wavelength of 193 nm was 1.589, and the extinction coefficient k was 0.0000 (measurement lower limit). The etching rate with 0.5% ammonia water is 0.1 nm / min, and the upper layer 32 is sufficiently resistant to chemical cleaning performed in the process of manufacturing the phase shift mask 201 from the mask blank 101. It was confirmed that the

Further, when the selectivity of dry etching using a mixed gas of SF ₆ and He as an etching gas was compared in the same manner as in Example 1, etching of the upper layer 32 of Example 3 with respect to the translucent substrate 1 was performed. The selectivity was 0.34, and the etching selectivity of the lower layer 31 of Example 3 with respect to the translucent substrate 1 was 2.38. Further, the etching selectivity of the lower layer 31 of Example 3 to the upper layer 32 of Example 3 was 7.0.

  With respect to the phase shift film 3 composed of the lower layer 31 and the upper layer 32, the transmittance and the phase difference at the wavelength of the ArF excimer laser light (about 193 nm) were measured with the above-described phase shift amount measuring apparatus. The phase difference was 47.0% and 177.0 degrees.

[Manufacture of phase shift mask]
Using the mask blank 101 of Example 3, the phase shift mask 201 of Example 3 was fabricated in the same process as in Example 1.
When the CD uniformity in the mask surface of the phase shift pattern 3a of the manufactured phase shift mask 201 was inspected, it was a satisfactory result. Further, when the cross section of the phase shift pattern 3a was observed with a STEM, the perpendicularity of the side wall of the phase shift pattern 3a was high, and problems such as pattern peeling due to cleaning were not observed.
As described above, the phase shift amount of the phase shift film 3 was 177.0 degrees only with the phase shift film 3 of the mask blank. However, when the lower layer pattern 31a is formed by dry etching, it is light transmissive. Since the exposed surface 701 of the substrate 1 is dug slightly, the phase shift amount of the phase shift pattern 3a at the stage of becoming the phase shift mask 201 is estimated to be 180 degrees.

A simulation of a transfer image was performed on this phase shift mask 201 when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications were satisfied.
When the produced phase shift mask 201 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, a fine circuit pattern could be formed with a predetermined accuracy.

Example 4
[Manufacture of mask blanks]
The mask blank of Example 4 is manufactured in the same manner as the mask blank of Example 1 except for the lower layer 31 and the upper layer 32. The lower layer 31 of Example 4 was the same as Example 1 except that the film thickness was changed to 67 nm. On the other hand, an AlSiO film (Al: Si: O = 31: 8: 61 (atomic% ratio)) made of aluminum, silicon, and oxygen is applied to the upper layer 32 of Example 4 and is in contact with the surface of the lower layer 31. The film was formed with a thickness of 5 nm. That is, Si / [Si + Al] of this etching stopper film 2 is 0.205. The manufacturing method of the upper layer 32 was the same as that in Example 1, and the composition was adjusted as described above under different conditions. The refractive index n of this film at a wavelength of 193 nm was 1.720, and the extinction coefficient k was 0.0328. The etching rate with 0.5% ammonia water is 0.2 nm / min, and the upper layer 32 has practical resistance to chemical cleaning performed in the process of manufacturing a phase shift mask from a mask blank. It was confirmed that it had.

Further, when the selection ratio of dry etching using a mixed gas of SF ₆ and He as an etching gas was compared in the same manner as in Example 1, etching of the upper layer 32 of Example 4 with respect to the translucent substrate 1 was performed. The selectivity was 0.04, and the etching selectivity of the lower layer 31 of Example 4 with respect to the translucent substrate 1 was 2.38. Moreover, the etching selectivity of the lower layer 31 of Example 4 with respect to the upper layer 32 of Example 4 was as extremely high as 56.5.

  With respect to the phase shift film 3 composed of the lower layer 31 and the upper layer 32, the transmittance and the phase difference at the wavelength of the ArF excimer laser light (about 193 nm) were measured with the above-described phase shift amount measuring apparatus. The phase difference was 57.0% and 177.0 degrees.

[Manufacture of phase shift mask]
Using the mask blank 101 of Example 4, the phase shift mask 201 of Example 4 was produced in the same process as Example 1.
When the CD uniformity in the mask surface of the phase shift pattern 3a of the manufactured phase shift mask 201 was inspected, it was a satisfactory result. Further, when the cross section of the phase shift pattern 3a was observed with a STEM, the perpendicularity of the side wall of the phase shift pattern 3a was high, and problems such as pattern peeling due to cleaning were not observed.
As described above, the phase shift amount of the phase shift film 3 was 177.0 degrees only with the phase shift film 3 of the mask blank. However, when the lower layer pattern 31a is formed by dry etching, it is light transmissive. Since the exposed surface 701 of the substrate 1 is dug slightly, the phase shift amount of the phase shift pattern 3a at the stage of becoming the phase shift mask 201 is estimated to be 180 degrees.

A simulation of a transfer image was performed on this phase shift mask 201 when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications were satisfied.
When the produced phase shift mask 201 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, a fine circuit pattern could be formed with a predetermined accuracy.

(Example 5)
[Manufacture of mask blanks]
The mask blank of Example 5 corresponds to the second embodiment, and is characterized in that the etching stopper film 2 is formed on the entire main surface of the translucent substrate 1. Therefore, this mask blank is a mask blank in which the etching stopper film 2, the lower layer 31, the upper layer 32, the light shielding film 4 and the hard mask film 5 are formed on the translucent substrate 1. Here, except for the introduction of the etching stopper film 2 and the film thickness of the lower layer 31, the material and the manufacturing method are the same as those in the first embodiment.
The etching stopper film 2 is the same material as that used as the upper layer 32 in Example 1, and the manufacturing method is also the same. Therefore, it is an AlSiO film having an atomic% ratio of Al: Si: O = 21: 19: 60 and Si / [Si + Al] of 0.475, and the characteristics are the same as those of the upper layer 32 of the first embodiment. This film was formed to a thickness of 10 nm on the entire main surface of the translucent substrate 1.

When the transmittance of the etching stopper film formed on another translucent substrate 1 at the wavelength of ArF excimer laser (193 nm) was measured with the above-mentioned phase shift measuring device, the transmissivity of the translucent substrate was 100%. The transmittance was 98.3%, and the influence of the decrease in the transmittance of the mask blank caused by providing the etching stopper film 2 of Example 5 was small.
The etching stopper film 2 has an etching rate for dry etching using a mixed gas of SF ₆ and He as an etching gas, which is 1/10 of the etching rate for the translucent substrate 1. It becomes a sufficient etching stopper when the lower layer 31 is dry-etched.
Further, the etching stopper film 2 has a small etching rate of 0.1 nm / min for ammonia water having a concentration of 0.5%, and has sufficient resistance to chemical cleaning.

  The film thickness of the lower layer 31 was 68.3 nm. With respect to the phase shift film 3 composed of the lower layer 31 and the upper layer 32, the transmittance and the phase difference at the wavelength of the ArF excimer laser light (about 193 nm) were measured with the above-described phase shift amount measuring apparatus. The phase difference was 180.0 degrees.

[Manufacture of phase shift mask]
Using the mask blank 102 of Example 5, the phase shift mask 202 of Example 5 was produced in the same process as in Example 1.
When the CD uniformity in the mask surface of the phase shift pattern 3a of the manufactured phase shift mask 202 was inspected, it was a satisfactory result. Further, when the cross section of the phase shift pattern 3a was observed with a STEM, the perpendicularity of the side wall of the phase shift pattern 3a was high, the depth of the etching stopper film 2 was as small as less than 1 nm, and no microtrench was generated. . In addition, problems such as pattern peeling due to cleaning were not observed.
Note that when the lower layer pattern 31a is formed by dry etching, the exposed portion surface 702 of the etching stopper film 2 is hardly scraped. For this reason, the phase shift amount of the phase shift pattern 3a at the stage of becoming the phase shift mask 202 is almost 180 degrees, which is the same as the phase difference 180 degrees of the phase shift film 3 of the mask blank alone, and a phase shift with high phase accuracy. Mask 202 was obtained.

For this phase shift mask 202, a transfer image was simulated when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications were satisfied.
When the produced phase shift mask 202 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, a fine circuit pattern could be formed with a predetermined accuracy.

(Comparative Example 1)
[Manufacture of mask blanks]
The mask blank of Comparative Example 1 is the same as the mask blank of Example 1 except that the thickness of the lower layer 31 is changed to 66.5 nm and the upper layer 32 is formed of a material (alumina) made of aluminum and oxygen. The configuration is provided. The upper layer 32 of Comparative Example 1 was formed on the lower layer 31 with a thickness of 5 nm. Specifically, a translucent substrate 1 having a lower layer 31 made of MoSiN is placed in a single wafer RF sputtering apparatus, an Al ₂ O ₃ target is used, and sputtering using argon (Ar) gas as a sputtering gas is performed. The upper layer 32 was formed by (RF sputtering). As a result of performing the same composition analysis as described above, it was Al: O = 42: 58 (atomic% ratio). That is, Si / [Si + Al] of the upper layer 32 is zero.

  The translucent substrate 1 on which the upper layer 32 was formed was immersed in ammonia water having a concentration of 0.5% and the etching rate was measured. As a result, it was 4.0 nm / min. From this result, it can be seen that the upper layer 32 of Comparative Example 1 does not have sufficient resistance to chemical cleaning performed in the process of manufacturing the phase shift mask from the mask blank. The refractive index n of the upper layer 32 at the wavelength (193 nm) of the ArF excimer laser was 1.864, and the extinction coefficient was 0.0689.

For each of the translucent substrate, the upper layer formed on another translucent substrate, and the lower layer formed on another translucent substrate, dry etching using a mixed gas of SF ₆ and He as an etching gas is performed. The same conditions were used. Then, each etching rate was calculated, and an etching selectivity between the three was calculated. The etching selectivity of the upper layer of Comparative Example 1 with respect to the etching rate of the translucent substrate was 0.03. The etching selectivity of the lower layer of Comparative Example 1 with respect to the etching rate of the translucent substrate was 2.38. The etching selectivity of the lower layer of Comparative Example 1 relative to the etching rate of the upper layer of Comparative Example 1 was 95.0.

  With respect to the phase shift film 3 composed of the lower layer 31 and the upper layer 32 of Comparative Example 1, the transmittance and phase difference at the wavelength of light (about 193 nm) of the ArF excimer laser were measured with the above-described phase shift amount measuring device. Was 6.6% and the phase difference was 177.0 degrees.

[Manufacture of phase shift mask]
Next, using the mask blank 101 of Comparative Example 1, a phase shift mask 201 of Comparative Example 1 was produced in the same procedure as in Example 1. When the mask pattern was inspected by the mask inspection apparatus on the manufactured phase shift mask 201 of Comparative Example 1, many defects were detected.
Using another mask blank 101, the phase shift mask 201 was manufactured in the same procedure, and the cross section of the phase shift pattern 3a was observed with a STEM for the defective portion. As a result, the upper layer pattern 32a was damaged by the chemical cleaning. A number of defects that were thought to be caused were observed.

For the phase shift mask 201 of Comparative Example 1, a transferred image was simulated when AIMS 193 (manufactured by Carl Zeiss) was exposed and transferred to a resist film on a semiconductor device with exposure light having a wavelength of 193 nm. When the exposure transfer image of this simulation was verified, the design specifications could not be satisfied. Many portions were found where the phase shift pattern 3a was damaged and normal exposure transfer was not possible.
When the produced phase shift mask 202 was placed on an exposure apparatus and exposed to form a resist pattern on the wafer, transfer defects due to the mask were observed, and it was difficult to manufacture a semiconductor device with a high yield. It was.

DESCRIPTION OF SYMBOLS 1 ... Translucent substrate 1a ... Translucent substrate 2 after etching ... Etching stopper film 3 ... Phase shift film 3a ... Phase shift pattern 4 ... Light shielding film 4a, 4b ... Light shielding pattern 5 ... Hard mask film 5a, 5b ... Hard Mask pattern 6a ... 1st resist pattern 7b ... 2nd resist pattern 31 ... Lower layer 31a ... Lower layer pattern 32 ... Upper layer 32a ... Upper layer pattern 101, 102 ... Mask blank 201, 202 ... Phase shift mask 700 ... Upper layer pattern surface 701 ... Translucent substrate surface (exposed part)
702 ... Etching stopper surface (exposed part)

Claims (16)

A mask blank provided with a phase shift film and a light shielding film on the main surface of a translucent substrate,
The phase shift film has a structure in which a lower layer and an upper layer are laminated in this order from the translucent substrate side,
The lower layer is made of a material containing silicon and nitrogen,
The upper layer is made of a material containing silicon, aluminum and oxygen,
In the upper layer, the ratio by atomic% of the silicon content to the total content of the silicon and the aluminum is 1/5 or more and 4/5 or less,
The upper layer has an oxygen content of 60 atomic% or more,
The light shielding film is made of a material containing one or more elements selected from silicon and tantalum,
The mask blank, wherein the light shielding film is formed in contact with the surface of the upper layer. The upper layer of silicon, the mask blank according to claim 1, characterized in that it consists of aluminum and oxygen. The upper layer, the mask blank according to claim 1 or 2, wherein the thickness is 3nm or more. The mask blank according to any one of claims 1 to 3 , wherein the lower layer is made of a material containing a transition metal, silicon, and nitrogen. The phase shift film has a function of transmitting exposure light with a transmittance of 1% or more, and the exposure light transmitted through the phase shift film passes through the air by the same distance as the thickness of the phase shift film. The mask blank according to any one of claims 1 to 4 , which has a function of causing a phase difference of 150 degrees or more and 180 degrees or less with respect to the exposure light. Mask blank according to any one of claims 1 5, characterized in that the etching stopper film in contact with the main surface of the transparent substrate is formed. The mask blank according to claim 6 , wherein the etching stopper film has an oxygen content of 60 atomic% or more. The etching stopper film, the ratio by atomic% of the content of the silicon to the total content of the silicon and the aluminum, the mask blank according to claim 6 or 7, wherein the at 4/5 or less. The etching stopper film, a mask blank according to claim 6 8, characterized in that consisting of silicon, aluminum and oxygen. The etching stopper film, a mask blank according to any one of claims 6 9, wherein the thickness is 3nm or more. The light-shielding film, the mask blank according to any one of claims 1 to 10, characterized in that it consists of a material containing a transition metal and silicon. The mask blank according to claim 11, further comprising a hard mask film made of a material containing chromium on the light shielding film. The mask blank according to any of claims 1 to 11, the phase shift film phase shift pattern is formed on a phase shift mask, wherein a light-shielding pattern is formed on the light shielding film. A method of manufacturing a phase shift mask using the mask blank according to any one of claims 1 to 12 ,
Forming a phase shift pattern on the light shielding film by dry etching;
Forming a phase shift pattern in the upper layer by dry etching using an etching gas containing boron chloride gas using the light shielding film having the phase shift pattern as a mask;
Forming a phase shift pattern in the lower layer by dry etching using an etching gas containing a fluorine-based gas using the light-shielding film having the phase shift pattern as a mask;
And a step of forming a pattern including a light-shielding band on the light-shielding film by dry etching. 14. A method of manufacturing a semiconductor device, comprising using the phase shift mask according to claim 13 and exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate. 15. A method of manufacturing a semiconductor device, comprising: a step of exposing and transferring a transfer pattern onto a resist film on a semiconductor substrate using the phase shift mask manufactured by the method of manufacturing a phase shift mask according to claim 14 .

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