Phase shift mask blank and phase shift mask
阅读说明：本技术 相移掩模坯料和相移掩模 (Phase shift mask blank and phase shift mask ) 是由 高坂卓郎 于 2020-03-27 设计创作，主要内容包括：本发明提供一种相移掩模坯料和相移掩模。该相移掩模坯料包括衬底和其上的相移膜,该相移膜由含有硅和氮且不含过渡金属的材料组成,该相移膜包括至少一个组成渐变层,该组成渐变层具有在厚度方向上连续变化的组成,以及在厚度方向上变化的对于曝光光的折射指数n和消光系数k,该曝光光是KrF准分子激光,该组成渐变层的最大折射指数n(H)与最小折射指数n(L)之间的差为0.40以下,最大消光系数k(H)与最小消光系数k(L)之间的差为1.5以下。(The invention provides a phase shift mask blank and a phase shift mask. The phase shift mask blank comprises a substrate and a phase shift film thereon, the phase shift film being composed of a material containing silicon and nitrogen and containing no transition metal, the phase shift film comprising at least one compositionally graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k for exposure light varying in the thickness direction, the exposure light being KrF excimer laser light, the compositionally graded layer having a difference between a maximum refractive index n (H) and a minimum refractive index n (L) of 0.40 or less, and a difference between a maximum extinction coefficient k (H) and a minimum extinction coefficient k (L) of 1.5 or less.)
1. A phase shift mask blank comprising a substrate and thereon a phase shift film composed of a material containing silicon and nitrogen and free of transition metals, wherein
The phase shift film comprises at least one composition-graded layer having a composition continuously varying in a thickness direction and a refractive index n and an extinction coefficient k for exposure light varying in the thickness direction, the exposure light being KrF excimer laser light,
the difference between the maximum refractive index n (H) and the minimum refractive index n (L) of the compositionally-graded layer is 0.40 or less, and the difference between the maximum extinction coefficient k (H) and the minimum extinction coefficient k (L) is 1.5 or less.
2. The phase shift mask blank according to claim 1, wherein said compositionally graded layer has a minimum refractive index n (l) of 2.3 or more and a maximum extinction coefficient k (h) of 2 or less, said compositionally graded layer comprising a region satisfying a refractive index n of 2.55 or more and an extinction coefficient k of 1.0 or less, said region having a thickness of 5 to 30 nm.
3. The phase shift mask blank according to claim 1, wherein the composition graded layer has a region in which a content ratio N/(Si + N), which represents a nitrogen content (at%) with respect to a sum of silicon and nitrogen contents (at%), continuously changes in a thickness direction within a range of 0.2 to 0.57.
4. The phase shift mask blank of claim 1, wherein a difference between a maximum silicon content (at%) and a minimum silicon content (at%) of the composition graded layer is 30 or less.
5. The phase shift mask blank of claim 1, wherein the phase shift film has a phase shift of 170 to 190 ° and a transmission of 4 to 8%,
in the phase shift film, a ratio of a difference between a maximum phase shift and a minimum phase shift to an average phase shift in a plane is 3% or less, a ratio of a difference between a maximum transmittance and a minimum transmittance to an average transmittance in a plane is 5% or less, and
the phase shift film has a thickness of 90nm or less.
6. The phase shift mask blank according to claim 1, wherein the material containing silicon and nitrogen and free of transition metals is a material composed of silicon and nitrogen.
7. The phase shift mask blank of claim 1, further comprising a second layer comprised of a single layer or multiple layers on the phase shift film, the second layer comprised of a chromium containing material.
8. A phase shift mask fabricated by using the phase shift mask blank of claim 1.
Technical Field
The present invention relates to a phase shift mask blank and a phase shift mask generally used for manufacturing a semiconductor integrated circuit.
Background
In the photolithography technique used for the semiconductor technology, a phase shift method is used as one of resolution enhancement techniques. The phase shift method is a contrast enhancement method by forming a phase shift film pattern provided on a transparent substrate transparent to exposure light as a photomask substrate and utilizing light interference. The phase shift film pattern has a phase shift of about 180 °, which is a difference between a phase passing through the phase shift film and a phase passing through a portion where the phase shift film is not formed, in other words, a phase passing through air having the same length as the thickness of the phase shift film. A halftone phase shift mask is one type of photomask that employs this method. The halftone phase shift mask includes a transparent substrate made of quartz or the like transparent to exposure light, and a mask pattern formed on the transparent substrate and having a phase shift of about 180 ° for a phase passing through a portion where the phase shift film is not formed and a transmittance substantially insufficient to contribute to exposure. As a phase shift film for a halftone phase shift mask, a film containing molybdenum and silicon is mainly used. As such a film, a halftone phase shift film composed of molybdenum silicon oxide or molybdenum silicon oxynitride is known (JP-A H07-140635 (patent document 1)).
CITATION LIST
Patent document 1: JP-A H07-140635
Patent document 2: JP-A2007-Asca 33469
Patent document 3: JP-A2007-233179
Patent document 4: JP-A-2007-241065
Disclosure of Invention
As a phase shift film for exposure light of KrF excimer laser light (wavelength 248nm), a phase shift film composed of a material containing molybdenum and silicon, which has a phase shift of 180 ° and a transmittance of about 6%, is generally used. In this case, the phase shift film has a thickness of about 100 nm. Recently, for a phase shift film using ArF excimer laser light (wavelength 193nm) as exposure light, a phase shift film of silicon nitride has been used for the purpose of minimizing the film thickness and enhancing the washing fastness and light fastness. Although not entirely as well as the ArF excimer laser light is used as the exposure light, when KrF excimer laser light is used as the exposure light, a phase shift film having high washing fastness and high light fastness and hardly generating haze is also required.
When a phase shift film used with KrF excimer laser light as exposure light is made of silicon nitride, if the phase shift film is formed as a single layer having a single composition (uniform composition in the thickness direction) of refractive index n and extinction coefficient k corresponding to a phase shift of 170 to 190 ° and a transmittance of 4 to 8%, the film is formed under film formation conditions employing an unstable region (so-called transition mode region) in reactive sputtering, and therefore, the film has a problem that in-plane uniformity of optical characteristics becomes poor.
Meanwhile, in order to obtain a film having high in-plane uniformity of optical characteristics, it is conceivable that a phase shift film composed of silicon nitride is configured as a multilayer composed of layers having a single composition (uniform composition in the thickness direction), and is formed by reactive sputtering under film formation conditions of a stable region (so-called metal mode or reaction mode). However, the refractive index n of the film that can be formed under this region is lower than that of the film formed under the transition mode region, and therefore, the film needs to be formed thick. In photolithography, a thin phase shift film is advantageous in forming a finer pattern, and further, a three-dimensional effect can be reduced. However, such a thick film composed of multiple layers is disadvantageous. Further, in the case of a multilayer composed of layers formed under film formation conditions in a stable region, the layer composition of each layer is significantly different. Therefore, there is a fear that the sectional shape of the pattern is deteriorated due to the difference in etching rate when the film is processed.
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a phase shift mask blank and a phase shift mask, which include a thin phase shift film that satisfies the requirement of pattern miniaturization even when exposure light is KrF excimer laser light having a wavelength of 248nm, and is advantageous in terms of patterning and reduction of three-dimensional effects in the case of satisfying the phase shift and transmittance necessary for the phase shift film.
The inventors have found that, when the phase shift film is composed of a material containing silicon and nitrogen and containing no transition metal and includes a composition-graded layer having a composition continuously varying in the thickness direction and having an optical constant for exposure light varying in the thickness direction, a film having a phase shift amount (phase shift) of 170 to 190 ° and a transmittance of 4 to 8% can be formed without thickening the film of the phase shift mask blank for exposure light of KrF excimer laser (wavelength 248nm), thereby obtaining a phase shift mask blank and a phase shift mask including a phase shift film having high in-plane uniformity of optical characteristics.
In one aspect, the present invention provides a phase shift mask blank comprising a substrate and thereon a phase shift film composed of a material containing silicon and nitrogen and not containing a transition metal, wherein
The phase shift film includes at least one composition-graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k for exposure light which is KrF excimer laser light varying in the thickness direction,
the difference between the maximum refractive index n (H) and the minimum refractive index n (L) constituting the graded layer is 0.40 or less, and the difference between the maximum extinction coefficient k (H) and the minimum extinction coefficient k (L) is 1.5 or less.
Preferably, the composition-graded layer has a minimum refractive index n (l) of 2.3 or more and a maximum extinction coefficient k (h) of 2 or less, and the composition-graded layer includes a region satisfying the refractive index n of 2.55 or more and the extinction coefficient k of 1.0 or less, the region having a thickness of 5 to 30 nm.
Preferably, the composition-graded layer has a region in which a content ratio N/(Si + N), which represents a nitrogen content (at%) with respect to a sum (at%) of silicon and nitrogen contents, continuously changes in a range of 0.2 to 0.57 in a thickness direction.
Preferably, the difference between the maximum silicon content (at%) and the minimum silicon content (at%) of the composition-graded layer is 30 or less.
Preferably, the phase shift film has a phase shift of 170 to 190 ° and a transmittance of 4 to 8%, in which a ratio of a difference between a maximum phase shift and a minimum phase shift to an average phase shift in a plane is 3% or less, a ratio of a difference between a maximum transmittance and a minimum transmittance to an average transmittance in a plane is 5% or less, and the phase shift film has a thickness of 90nm or less.
Preferably, the material containing silicon and nitrogen and not containing a transition metal is a material composed of silicon and nitrogen.
In general, the phase shift mask blank may include a second layer of a single layer or multiple layers on the phase shift film, the second layer being comprised of a chromium containing material.
In another aspect, the present invention provides a phase shift mask fabricated by using the phase shift mask blank.
Advantageous effects of the invention
According to the present invention, there are provided a phase shift mask blank and a phase shift mask having a relatively thin phase shift film, which are advantageous in terms of patterning and exposure and have high in-plane uniformity of optical characteristics while satisfying the phase shift and transmittance necessary for the phase shift film of exposure light for KrF excimer laser light.
Drawings
FIGS. 1A and 1B are cross-sectional views illustrating exemplary phase shift mask blanks and phase shift masks of the present invention.
Fig. 2A-2C are cross-sectional views illustrating other embodiments of phase shift mask blanks of the present invention.
Detailed Description
The phase shift mask blank of the present invention includes a transparent substrate such as a quartz substrate, and a phase shift film provided on the transparent substrate. The phase shift mask of the present invention includes a transparent substrate such as a quartz substrate, and a mask pattern (photomask pattern) of a phase shift film provided on the transparent substrate.
The transparent substrate in the present invention is preferably a 6 inch square, 0.25 inch thick transparent substrate, referred to as a 6025 substrate as specified by the SEMI standard, which is generally represented by a 6.35mm thick transparent substrate that is 152mm square according to the SI unit system.
FIG. 1A is a cross-sectional view illustrating an exemplary phase shift mask blank of the present invention. In this embodiment, the phase shift mask blank 100 includes a
The phase shift film in the present invention having a prescribed thickness has a predetermined amount of phase shift (phase shift) and a predetermined transmittance with respect to the exposure light of KrF excimer laser light (wavelength: 248 nm). The phase shift film of the present invention is composed of a material containing silicon and nitrogen and not containing a transition metal. In order to improve the washing fastness of the film, it is effective to add oxygen to the phase shift film. Therefore, a material containing silicon and nitrogen and not containing a transition metal may contain oxygen in addition to silicon and nitrogen. However, when oxygen is added, the refractive index n of the film decreases, and therefore, the thickness of the film tends to increase. Therefore, as the material containing silicon and nitrogen and not containing a transition metal, a material substantially composed of silicon and nitrogen (a material composed of two elements and unavoidable impurities) is preferable.
The phase shift film is preferably composed of a single layer designed to satisfy the phase shift and transmittance necessary for the phase shift film. The phase shift film may be composed of multiple layers designed to satisfy the necessary phase shift and transmittance of the entire phase shift film. In each case of a single layer and a multilayer, the phase shift film is configured such that the film includes at least one composition-graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k for exposure light varying in the thickness direction. In the case of multiple layers, although the film may be composed of a plurality of compositionally-graded layers or a combination of a compositionally-graded layer and a single composition layer (a layer that is constant in the thickness direction), the total thickness of the compositionally-graded layers is preferably 30% or more, more preferably 50% or more, and most preferably 100% of the total thickness of the phase shift film.
In the composition-graded layer, the difference between the maximum refractive index n (h) and the minimum refractive index n (l) is preferably 0.40 or less, more preferably 0.25 or less, and is preferably 0.1 or more, more preferably 0.15 or more. In the composition-graded layer, the difference between the maximum extinction coefficient k (h) and the minimum extinction coefficient k (l) is 1.5 or less, more preferably 1.2 or less, and preferably 0.3 or more, more preferably 0.6 or more. The minimum refractive index n (l) in the compositionally-graded layer is preferably 2.3 or more, more preferably 2.4 or more, and the maximum extinction coefficient k (h) is preferably 2 or less, more preferably 1.5 or less. In particular, in the composition-graded layer, the thickness of the region satisfying the refractive index n of 2.55 or more and the extinction coefficient k of 1.0 or less is preferably 5nm or more and 30nm or less.
In the composition-graded layer of the present invention (in the entire composition-graded layer when the phase-shift film is composed of a single layer; in each layer when the phase-shift film is composed of a plurality of composition-graded layers), the composition-graded range of the silicon content is preferably in the range of 40 at% or more, particularly 45 at% or more, and 70 at% or less, and particularly 60 at% or less, and the composition-graded range of the nitrogen content is preferably in the range of 30 at% or more, particularly 40 at% or more, and 60 at% or less, particularly 55 at% or less.
In particular, the composition-graded layer preferably includes a region in which a content ratio N/(Si + N), which represents a nitrogen content (at%) with respect to a sum (at%) of silicon and nitrogen contents, is continuously changed, is within a range of preferably 0.2 or more, more preferably 0.3 or more, and preferably 0.57 or less, more preferably 0.55 or less. The difference between the maximum silicon content (at%) and the minimum silicon content (at%) in the composition-graded layer is preferably 30 or less, and more preferably 15 or less. When the composition-graded layer contains oxygen, the oxygen content is preferably 30 at% or less, more preferably 10 at% or less, and most preferably 5 at% or less.
As a result of the phase shift due to interference of the exposure light passing through the respective regions, the phase shift of the exposure light passing through the phase shift film in the present invention may be sufficient to be able to increase the contrast at the boundary between the region with the phase shift film (phase shift region) and the region without the phase shift film. The phase shift may be 170 ° or more and 190 ° or less. Meanwhile, the transmittance of the phase shift film in the present invention with respect to exposure light may be 4% or more and 8% or less. The phase shift film in the present invention can have a phase shift and a transmittance for KrF excimer laser light (wavelength: 248nm) controlled within the above-mentioned ranges.
The phase shift film is configured to include at least one composition-graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k for exposure light varying in the thickness direction. According to the phase shift film of the present invention, the variation range of the phase shift, which is the ratio of the difference between the maximum and minimum phase shifts in the plane of the phase shift film (for example, in the area of 135mm square in the center of the substrate surface of the 6025 substrate) to the average phase shift, may be 3% or less, particularly 1% or less, and the variation range of the transmittance, which is the ratio of the difference between the maximum and minimum transmittances in the plane of the phase shift film to the average transmittance, may be 5% or less, particularly 3% or less.
When the entire thickness of the phase shift film is thin, a fine pattern can be easily formed. Therefore, the entire thickness of the phase shift film in the present invention is 90nm or less, preferably 85nm or less. Meanwhile, the lower limit of the thickness of the phase shift film may be set as long as the desired optical characteristics can be obtained for the exposure light, and is generally 50nm or more, but is not limited thereto.
The phase shift film in the present invention can be formed by a known film forming method. The phase shift film is preferably formed by sputtering, a highly homogeneous film can be easily obtained by forming the phase shift film by sputtering, and sputtering may be DC sputtering or RF sputtering. The target and the sputtering gas are appropriately selected depending on the kind and composition of the layer to be formed. Examples of targets include silicon targets, silicon nitride targets, and targets containing both silicon and silicon nitride. These targets may contain oxygen. The nitrogen content and the oxygen content can be controlled by reactive sputtering using any of reactive gases as a sputtering gas with the supply amount appropriately controlled, such as a nitrogen-containing gas, an oxygen-containing gas, and a nitrogen-and-oxygen-containing gas. In particular, nitrogen (N) may be added2Gas), oxygen (O)2Gas) and nitrogen oxide gas (N)2O gas, NO gas and NO2Gas) is used as the reactive gas. Rare gases such as helium, neon, and argon may also be used as the sputtering gas.
In order to suppress the variation in the properties of the phase shift film, the phase shift film composed of multiple layers may include a surface oxide layer formed as the outermost layer on the top surface (on the side away from the transparent substrate). The surface oxide layer may have an oxygen content of 20 at% or more, preferably 50 at% or more. Examples of the method for forming the surface oxide layer specifically include atmospheric oxidation (natural oxidation); a forced oxidation treatment such as a sputtering film treatment with ozone gas or ozone water, or heating in an oxygen-containing atmosphere such as an oxygen atmosphere at 300 ℃ or more by heating in an oven, lamp annealing, or laser heating. The surface oxide layer preferably has a thickness of 10nm or less, more preferably 5nm or less, most preferably 3nm or less. The effect of the surface oxide layer is generally obtained at a thickness of 1nm or more. Although the surface oxidation layer may be formed by sputtering under an increased amount of oxygen, the surface oxidation layer is more preferably formed by the aforementioned atmospheric oxidation or oxidation treatment as far as a layer having fewer defects is obtained.
The phase shift mask blank of the present invention may include a second layer, consisting of a single layer or multiple layers, formed over the phase shift film. A second layer is typically disposed adjacent to the phase shift film. The second layer is specifically exemplified by a light-shielding film, a combination of a light-shielding film and an antireflection film, and a processing auxiliary film that functions as a hard mask in patterning the phase shift film. In the case where the third layer is employed as described below, the second layer may serve as a processing auxiliary film that functions as an etching stopper (etching stopper film) in patterning the third layer. The material of the second layer is preferably a chromium containing material.
This embodiment is specifically illustrated as a phase shift mask blank illustrated in fig. 2A. FIG. 2A is a cross-sectional view illustrating an exemplary phase shift mask blank of the present invention. In this embodiment, the phase shift mask blank 100 includes a
The phase shift mask blank of the present invention may include a light-shielding film as a second layer disposed over the phase shift film or an etching mask film functioning as a hard mask when forming a pattern on the phase shift film. Alternatively, the light-shielding film may be combined with an antireflection film to form a second layer. The second layer including the light-shielding film may provide a region that completely blocks exposure light in the phase shift mask. The light-shielding film and the antireflection film can also be used as processing auxiliary films in etching. There are many reports on film structures and materials of light-shielding films and antireflection films (for example, JP-a2007-33469 (patent document 2), JP-a 2007-233179 (patent document 3)). A preferable film structure in which a light-shielding film and an antireflection film are combined is exemplified as a structure in which a light-shielding film composed of a chromium-containing material is provided and an antireflection film composed of a chromium-containing material is further provided, the antireflection film serving to reduce reflection from the light-shielding film. The light-shielding film and the antireflection film may be formed of a single layer or a plurality of layers. Examples of the chromium-containing material of the light-shielding film and the antireflection film include chromium (simple substance) and chromium compounds such as chromium oxide (CrO), chromium nitride (CrN), chromium carbide (CrC), chromium oxynitride (CrON), chromium oxycarbide (CrOC), chromium carbonitride (CrNC), and chromium oxycarbonitride (CrONC). Note that the chemical formula representing the chromium-containing material represents only the constituent elements, not the compositional ratio of the constituent elements (the same applies to the chromium-containing material hereinafter).
For the second layer which is the light-shielding film or the combination of the light-shielding film and the antireflection film, the chromium content of the chromium compound in the light-shielding film is preferably 40 at% or more, more preferably 60 at% or more, and preferably less than 100 at%, more preferably 99 at% or less, most preferably 90 at% or less. The oxygen content is preferably 60 at% or less, more preferably 40 at% or less, and preferably 1 at% or more. The nitrogen content is preferably 50 at% or less, more preferably 40 at% or less, and preferably 1 at% or more. The carbon content is preferably 20 at% or less, more preferably 10 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. In this case, the total content of chromium, oxygen, nitrogen and carbon is preferably 95 at% or more, more preferably 99 at% or more, and most preferably 100 at%.
For the second layer which is a combination of the light-shielding film and the antireflection film, the antireflection film is preferably composed of a chromium compound, and the chromium content of the chromium compound is preferably 30 at% or more, more preferably 35 at% or more, and 70 at% or less, more preferably 50 at% or less. The oxygen content is preferably 60 at% or less, and is preferably 1 at% or more, more preferably 20 at% or more. The nitrogen content is preferably 50 at% or less, more preferably 30 at% or less, and is preferably 1 at% or more, more preferably 3 at% or more. The carbon content is preferably 20 at% or less, more preferably 5 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. In this case, the total content of chromium, oxygen, nitrogen and carbon is preferably 95 at% or more, more preferably 99 at% or more, and most preferably 100 at%.
For the second layer as a light-shielding film or a combination of a light-shielding film and an antireflection film, the second layer has a thickness of usually 20 to 100nm, preferably 40 to 70 nm. The total optical density of the phase shift film and the second layer with respect to the exposure light is preferably 2.0 or more, more preferably 2.5 or more, and most preferably 3.0 or more.
Above the second layer of the phase shift mask blank of the present invention, a third layer consisting of a single layer or a plurality of layers may be provided. The third layer is typically disposed adjacent to the second layer. The third layer is specifically exemplified by a processing auxiliary film functioning as a hard mask during patterning of the second layer, a light-shielding film, and a combination of the light-shielding film and an antireflection film. The material constituting the third layer is preferably a silicon-containing material, in particular a chromium-free silicon-containing material.
This embodiment is specifically illustrated as a phase shift mask blank illustrated in fig. 2B. FIG. 2B is a cross-sectional view illustrating an exemplary phase shift mask blank of the present invention. In this embodiment, the phase shift mask blank 100 includes a
For the second layer which is a light-shielding film or a combination of a light-shielding film and an antireflection film, a processing auxiliary film (etching mask film) which functions as a hard mask in patterning the second layer may be provided as the third layer. In the case where the fourth layer is employed as described below, the third layer can be used as a processing auxiliary film that functions as an etching stopper (etching stopper film) in patterning the fourth layer. The process auxiliary film is preferably composed of a material different from the second layer in etching characteristics, such as a material resistant to chlorine-based dry etching of a chromium-containing material, particularly a material which can be etched by a fluorine-containing gas such as SF6And CF4An etched silicon-containing material. Examples of the silicon-containing material include silicon (elemental substance) and silicon compounds such as a material containing silicon and either or both of nitrogen and oxygen, a material containing silicon and a transition metal, a material containing silicon and either or both of nitrogen and oxygen and a transition metal. Examples of transition metals include molybdenum, tantalum, and zirconium.
For the third layer as the processing auxiliary film, the processing auxiliary film is preferably composed of a silicon compound. The silicon content of the silicon compound is preferably 20 at% or more, more preferably 33 at% or more, and preferably 95 at% or less, more preferably 80 at% or less. The nitrogen content is preferably 50 at% or less, more preferably 30 at% or less, and preferably 1 at% or more. The oxygen content is preferably 70 at% or less, more preferably 66 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more, more preferably 20 at% or more. The third layer may or may not contain a transition metal. When the transition metal is contained, the content of the transition metal is preferably 35 at% or less, more preferably 20 at% or less. In this case, the total content of silicon, oxygen, nitrogen and transition metal is preferably 95 at% or more, more preferably 99 at% or more, and most preferably 100 at%.
The second layer has a thickness of usually 20 to 100nm, and preferably 40 to 70nm, for the second layer as a light-shielding film or a combination of a light-shielding film and an antireflection film, and the third layer as a processing auxiliary film, and the third layer has a thickness of usually 1 to 30nm, and preferably 2 to 15 nm. The total optical density of the phase shift film and the second layer with respect to the exposure light is preferably 2.0 or more, more preferably 2.5 or more, and most preferably 3.0 or more.
For the second layer as the processing auxiliary film, a light-shielding film may be provided as a third layer. The light-shielding film in combination with the antireflection film may be provided as a third layer. In this case, the second layer can be used as a process auxiliary film (etching mask film) which functions as a hard mask in patterning the phase shift film and a process auxiliary film (etching stopper film) in patterning the third layer. The processing auxiliary film is exemplified by ｃA film composed of ｃA chromium-containing material, such as disclosed in JP-A-2007-241065 (patent document 4). The processing aid film may be composed of a single layer or multiple layers. Examples of the chromium-containing material of the processing aid film include chromium (elemental) and chromium compounds such as chromium oxide (CrO), chromium nitride (CrN), chromium carbide (CrC), chromium oxynitride (CrON), chromium oxycarbide (CrOC), chromium carbonitride (CrNC), and chromium oxycarbonitride (CrONC).
With respect to the second layer as the processing aid film, the chromium content of the chromium compound in the second layer is preferably 40 at% or more, more preferably 50 at% or more, and preferably 100 at% or less, more preferably 99 at% or less, most preferably 90 at% or less. The oxygen content is preferably 60 at% or less, more preferably 55 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. The nitrogen content is preferably 50 at% or less, more preferably 40 at% or less, and preferably 1 at% or more. The carbon content is preferably 20 at% or less, more preferably 10 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. In this case, the total content of chromium, oxygen, nitrogen and carbon is preferably 95 at% or more, particularly 99 at% or more, and most preferably 100 at%.
The light-shielding film and the antireflection film as the third layer are preferably composed of a material different from the second layer in etching characteristics, such as a chlorine-based dry-etching-resistant material to a chromium-containing material, particularly a material that can be etched by a fluorine-containing gas such as SF6And CF4An etched silicon-containing material. Examples of the silicon-containing material include silicon (elemental substance) and silicon compounds such as a material containing silicon and either or both of nitrogen and oxygen, a material containing silicon and a transition metal, a material containing silicon and either or both of nitrogen and oxygen and a transition metal. Examples of transition metals include molybdenum, tantalum, and zirconium.
For the third layer which is the light-shielding film or the combination of the light-shielding film and the antireflection film, the light-shielding film and the antireflection film are preferably composed of a silicon compound. The silicon content of the silicon compound is preferably 10 at% or more, more preferably 30 at% or more, and preferably less than 100 at%, more preferably 95 at% or less. The nitrogen content is preferably 50 at% or less, preferably 40 at% or less, most preferably 20 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. The oxygen content is preferably 60 at% or less, more preferably 30 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. The transition metal content is preferably 35 at% or less, preferably 20 at% or less, and preferably 1 at% or more. In this case, the total content of silicon, oxygen, nitrogen and transition metal is preferably 95 at% or more, more preferably 99 at% or more, and most preferably 100 at%.
For the second layer as the processing aid film, and for the third layer as the light-shielding film or the combination of the light-shielding film and the antireflection film, the second layer has a thickness of usually 1 to 20nm, preferably 2 to 10nm, and the third layer has a thickness of usually 20 to 100nm, preferably 30 to 70 nm. The total optical density of the phase shift film, the second layer, and the third layer with respect to exposure light is preferably 2.0 or more, more preferably 2.5 or more, and most preferably 3.0 or more.
A fourth layer, which may be a single layer or a plurality of layers, may be disposed over the third layer of the phase shift mask blank of the present invention. The fourth layer is typically disposed adjacent to the third layer. The fourth layer is specifically exemplified as a process auxiliary film functioning as a hard mask in patterning the third layer. The material of the fourth layer is preferably a chromium containing material.
This embodiment is specifically illustrated as a phase shift mask blank illustrated in fig. 2C. Fig. 2C is a cross-sectional view illustrating an exemplary phase shift mask blank of the present invention. In this embodiment, the phase shift mask blank 100 includes a
For the third layer which is a light-shielding film or a combination of a light-shielding film and an antireflection film, a processing auxiliary film (etching mask film) which functions as a hard mask in patterning the third layer may be provided as the fourth layer. The process auxiliary film is preferably composed of a material different from the third layer in etching characteristics, such as a fluorine-based dry-etching-resistant material of a silicon-containing material, particularly a chromium-containing material etchable by a chlorine-based gas containing oxygen. Chromium-containing materials are exemplified by chromium (elemental) and chromium compounds such as chromium oxide (CrO), chromium nitride (CrN), chromium carbide (CrC), chromium oxynitride (CrON), chromium oxycarbide (CrOC), chromium carbonitride (CrNC), and chromium oxycarbonitride (CrONC).
The chromium content of the fourth layer as the processing aid film is preferably 40 at% or more, more preferably 50 at% or more, and preferably 100 at% or less, more preferably 99 at% or less, and most preferably 90 at% or less. The oxygen content is preferably 60 at% or less, more preferably 40 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. The nitrogen content is preferably 50 at% or less, more preferably 40 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. The carbon content is preferably 20 at% or less, more preferably 10 at% or less, and if the etching rate needs to be adjusted, preferably 1 at% or more. In this case, the total content of chromium, oxygen, nitrogen and carbon is preferably 95 at% or more, more preferably 99 at% or more, and most preferably 100 at%.
For the second layer as the processing aid film, for the third layer as the light-shielding film or the combination of the light-shielding film and the antireflection film, and for the fourth layer as the processing aid film, the second layer has a thickness of usually 1 to 20nm, preferably 2 to 10nm, the third layer has a thickness of usually 20 to 100nm, preferably 30 to 70nm, and the fourth layer has a thickness of usually 1 to 30nm, preferably 2 to 20 nm. The total optical density of the phase shift film, the second layer, and the third layer with respect to exposure light is preferably 2.0 or more, more preferably 2.5 or more, and most preferably 3.0 or more.
The film composed of a chromium-containing material for the second layer and the fourth layer can be formed by reactive sputtering using a target such as a chromium target or a chromium-containing target to which one or more elements selected from oxygen, nitrogen, and carbon are added, and using a sputtering gas containing a rare gas such as Ar, He, and Ne to which a reactive gas selected from an oxygen-containing gas, a nitrogen-containing gas, and a carbon-containing gas is appropriately added according to the composition of the film to be formed.
Meanwhile, the film composed of a material containing silicon for the third layer can be formed by reactive sputtering using a target such as a silicon target, a silicon nitride target, a target containing both silicon and silicon nitride, a transition metal target, and a composite target of silicon and transition metal, and a sputtering gas containing a rare gas such as Ar, He, and Ne to which a reactive gas selected from an oxygen-containing gas, a nitrogen-containing gas, and a carbon-containing gas is appropriately added depending on the composition of the film to be formed.
The phase shift mask of the present invention can be fabricated from a phase shift mask blank by any conventional method. Phase shift masks can generally be fabricated by the following process from an exemplary phase shift mask blank that includes a film composed of a chromium-containing material formed as a second layer over a phase shift film.
First, an electron beam resist film is formed on the second layer of the phase shift mask blank, and a pattern is drawn by an electron beam, followed by a predetermined developing operation to obtain a resist pattern. Next, the obtained resist pattern was used as an etching mask, and the resist pattern was transferred to the second layer by chlorine-based dry etching containing oxygen to obtain a second layer pattern. Next, the obtained second layer pattern was used as an etching mask, and the second layer pattern was transferred onto the phase shift film by fluorine-based dry etching to obtain a phase shift film pattern. In the case where a portion of the second layer needs to be left, another resist pattern that protects the portion to be left is formed on the second layer, and the portion of the second layer that is not protected by the resist pattern is removed by chlorine-based dry etching containing oxygen. The resist pattern is then removed by conventional methods to obtain a phase shift mask.
A phase shift mask may be generally manufactured from an exemplary phase shift mask blank including a light-shielding film composed of a chromium-containing material or a combination of a light-shielding film and an antireflection film as a second layer on a phase shift film, and a process assist film composed of a silicon-containing material as a third layer on the second layer.
First, an electron beam resist film is formed on the third layer of the phase shift mask blank, patterned by an electron beam, followed by a predetermined developing operation to obtain a resist pattern. Next, the obtained resist pattern was used as an etching mask, and the resist pattern was transferred to the third layer by fluorine-based dry etching to obtain a third layer pattern. Next, the obtained third layer pattern was used as an etching mask, and the third layer pattern was transferred to the second layer by chlorine-based dry etching containing oxygen to obtain a second layer pattern. The resist pattern is then removed, and the second layer pattern is transferred onto the phase shift film by fluorine-based dry etching using the obtained second layer pattern as an etching mask to obtain a phase shift film pattern and simultaneously remove the third layer pattern. Next, another resist pattern that protects a portion of the second layer to be left is formed on the second layer, and a portion of the second layer not protected by the resist pattern is removed by chlorine-based dry etching containing oxygen. The resist pattern is then removed by conventional methods to obtain a phase shift mask.
Meanwhile, a phase shift mask may be generally manufactured from an exemplary phase shift mask blank including a process assistance film composed of a chromium-containing material as a second layer on the phase shift film, a light-shielding film composed of a silicon-containing material as a third layer on the second layer, or a combination of the light-shielding film and an antireflection film by the following processes.
First, an electron beam resist film is formed on the third layer of the phase shift mask blank, patterned by an electron beam, followed by a predetermined developing operation to obtain a resist pattern. Next, the obtained resist pattern was used as an etching mask, and the resist pattern was transferred to the third layer by fluorine-based dry etching to obtain a third layer pattern. Next, the obtained third layer pattern is used as an etching mask, and the third layer pattern is transferred to the second layer by chlorine-based dry etching containing oxygen to obtain a second layer pattern in which the portion of the phase shift film to be removed has been removed. The resist pattern is then removed. Next, another resist pattern that protects a portion of the third layer to be left is formed on the third layer, and the second layer pattern is transferred onto the phase shift film by fluorine-based dry etching using the obtained second layer pattern as an etching mask to obtain a phase shift film pattern, and at the same time, a portion of the third layer that is not protected with the resist pattern is removed. The resist pattern is then removed by conventional methods. Further, the portion of the second layer exposed in the portion of the third layer that has been removed is then removed by chlorine-based dry etching containing oxygen to obtain a phase shift mask.
Further, a phase shift mask may be generally manufactured from an exemplary phase shift mask blank including a process auxiliary film composed of a chromium-containing material as a second layer on the phase shift film, a light-shielding film composed of a silicon-containing material or a combination of the light-shielding film and an antireflection film as a third layer on the second layer, and a process auxiliary film composed of a chromium-containing material as a fourth layer on the third layer.
First, an electron beam resist film is formed on the fourth layer of the phase shift mask blank, patterned by an electron beam, followed by a predetermined developing operation to obtain a resist pattern. Next, the obtained resist pattern was used as an etching mask, and the resist pattern was transferred to the fourth layer by chlorine-based dry etching containing oxygen to obtain a fourth layer pattern. Next, the obtained fourth layer pattern was used as an etching mask, and the fourth layer pattern was transferred to the third layer by fluorine-based dry etching to obtain a third layer pattern. The resist pattern is then removed. Next, another resist pattern for protecting a portion of the third layer to be left is formed on the fourth layer, and the obtained third layer pattern is used as an etching mask, and the third layer pattern is transferred to the second layer by chlorine-based dry etching containing oxygen to obtain a second layer pattern, and at the same time, a portion of the fourth layer not protected with the resist pattern is removed. Next, the second layer pattern was used as an etching mask, and the second layer pattern was transferred onto the phase shift film by fluorine-based dry etching to obtain a phase shift film pattern, and at the same time, the portion of the third layer not protected by the resist pattern was removed. The resist pattern is then removed by conventional methods. Further, a portion of the second layer exposed in the portion of the third layer that has been removed and a portion of the fourth layer exposed in the portion of the resist pattern that has been removed are then removed by chlorine-based dry etching containing oxygen to obtain a phase shift mask.