阅读说明：本技术 相移掩模坯料、其制造方法以及相移掩模 (Phase shift mask blank, method for manufacturing the same, 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、其制造方法以及相移掩模。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,曝光光为KrF准分子激光,该相移膜由单层或多层构成,单层或多层的每一层具有对于曝光光2.5以上的折射率n、0.4至1的消光系数k,相移膜具有对于曝光光170至190°的相移和4至8％的透射率,并且具有85nm以下的厚度。(The invention provides a phase shift mask blank, a method of manufacturing the same, and a phase shift mask. The phase shift mask blank includes 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 exposure light being KrF excimer laser, the phase shift film being composed of a single layer or a plurality of layers, each of the single layer or the plurality of layers having a refractive index n of 2.5 or more, an extinction coefficient k of 0.4 to 1 with respect to the exposure light, the phase shift film having a phase shift of 170 to 190 DEG and a transmittance of 4 to 8% with respect to the exposure light, and having a thickness of 85nm 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 exposure light is a KrF excimer laser,

the phase shift film is composed of a single layer or a plurality of layers each having a refractive index n of 2.5 or more and an extinction coefficient k of 0.4 to 1 with respect to exposure light, and

the phase shift film has a phase shift of 170 to 190 ° and a transmittance of 4 to 8% with respect to exposure light, and has a thickness of 85nm or less.

2. The phase shift mask blank of claim 1, wherein each layer of the single or multiple layers has a content ratio N/(Si + N) in the range of 0.43 to 0.53, the ratio N/(Si + N) representing the nitrogen content (at%) relative to the sum of silicon and nitrogen content (at%).

3. 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 exposure light is a KrF excimer laser,

the phase shift film is composed of a single layer or a plurality of layers, at least a part of the single layer or at least a part of the plurality of layers having a content ratio N/(Si + N) in the range of 0.43 to 0.53, the ratio N/(Si + N) representing a nitrogen content (at%) with respect to a sum (at%) of silicon and nitrogen contents, and

the phase shift film has a phase shift of 170 to 190 ° with respect to the exposure light.

4. The method of manufacturing a phase shift mask blank according to any one of claims 1 to 3, comprising the steps of:

forming a phase shift film by reactive sputtering using a silicon-containing target and nitrogen gas, wherein

In the forming step, the flow rate of nitrogen gas is set to a value which is-20% to + 20% of the flow rate of the highest refractive index n to which the phase shift film is given to the exposure light, and which is kept constant or continuously changed or stepwise changed, the flow rate of the highest refractive index n being obtained by changing the flow rate from a low flow rate to a high flow rate.

5. The method according to claim 4, wherein in the forming step, a flow rate of nitrogen gas is set to a flow rate that gives the phase shift film the highest refractive index n for the exposure light and is kept constant.

6. The method of claim 4, wherein the sputtering is magnetron sputtering and the silicon-containing target is a silicon target.

7. A phase shift mask manufactured by using the phase shift mask blank according to any one of claims 1 to 3.

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, and a method of manufacturing the phase shift mask blank.

Background

In the photolithography technique used for the semiconductor technology, a phase shift method is used as one of resolution enhancement techniques. For example, the phase shift method is a method using a photomask in which a phase shift film is formed on a substrate, and 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 using 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 light. Heretofore, as a phase shift film for a phase shift mask, a film containing molybdenum and silicon has been mainly used (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

In the case where the exposure light is a KrF excimer laser (wavelength 248nm), a phase shift film having a transmittance of 6%, a phase shift of about 180 ° and a thickness of about 100nm is generally used in a phase shift mask employing a film containing molybdenum and silicon. 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 a 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 KrF excimer laser is used as exposure light in the case of silicon nitride, it is necessary to adjust the content ratio of nitrogen to silicon in accordance with the wavelength thereof in order to form a film satisfying a predetermined phase shift and a predetermined transmittance in the case of KrF excimer. Further, in consideration of the inclination of the pattern and the cross-sectional shape of the pattern in the process of processing into a phase shift mask, a thin film having a uniform composition is desired. When the exposure light is ArF excimer laser, silicon nitride containing more nitrogen has a higher refractive index n and a smaller extinction coefficient k. Therefore, phase shift films with as high a nitrogen content as possible have been proposed.

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. Further, another object of the present invention is to provide a method of manufacturing a phase shift mask blank.

The inventors have found that: when the exposure light is KrF excimer laser, unlike ArF excimer laser, silicon nitride has the highest refractive index N at a Si/N content (at%) ratio of about 53/47; and a thin film cannot be obtained by simply increasing the nitrogen content. Further, the inventors have found that, with respect to silicon nitride for exposure light of KrF excimer laser light, in a phase shift mask blank for exposure with KrF excimer laser light having a wavelength of 248nm, a phase shift film having a composition containing silicon and nitrogen and containing no transition metal, and satisfying a predetermined refractive index n and a predetermined extinction coefficient k or having a nitrogen ratio in a predetermined range, can provide a phase shift amount (phase shift), particularly a transmittance of 4 to 8%, with respect to exposure light of 170 to 190 °, having a thickness of 85nm or less, thereby obtaining a phase shift mask blank and a phase shift mask including a thinner phase shift film.

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 exposure light is a KrF excimer laser,

the phase shift film is composed of a single layer or a plurality of layers each having a refractive index n of 2.5 or more and an extinction coefficient k of 0.4 to 1 with respect to exposure light, and

the phase shift film has a phase shift of 170 to 190 ° and a transmittance of 4 to 8% with respect to exposure light, and has a thickness of 85nm or less.

Preferably, each of the single layer or the multiple layers has a content ratio N/(Si + N) representing a nitrogen content (at%) with respect to a sum of silicon and nitrogen contents (at%) in a range of 0.43 to 0.53.

In another aspect, the present invention provides a phase shift mask blank comprising a substrate and a phase shift film thereon, the phase shift film being composed of a material containing silicon and nitrogen and not containing a transition metal, wherein,

the exposure light is a KrF excimer laser,

the phase shift film is composed of a single layer or a plurality of layers, at least a part of the single layer or at least a part of the plurality of layers having a content ratio N/(Si + N) in the range of 0.43 to 0.53, the ratio N/(Si + N) representing a nitrogen content (at%) relative to a sum (at%) of silicon and nitrogen contents, and

the phase shift film has a phase shift of 170 to 190 ° with respect to the exposure light.

In another aspect, the present invention provides a method of manufacturing the phase shift mask blank of any one of claims 1 to 3, comprising the steps of:

a phase shift film is formed by reactive sputtering using a silicon-containing target and nitrogen gas, wherein,

in the forming step, the flow rate of nitrogen gas is set to a value which is-20% to + 20% of the flow rate of the highest refractive index n to be imparted to the phase shift film with respect to the exposure light, and which is kept constant or continuously or stepwise varied, the flow rate being imparted to the highest refractive index n obtained by changing the flow rate from a low flow rate to a high flow rate.

Preferably, in the forming step, the flow rate of nitrogen gas is set to give the phase shift film the highest refractive index n with respect to the exposure light, and is kept constant.

Preferably, the sputtering is magnetron sputtering and the silicon-containing target is a silicon target.

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 while satisfying the phase shift and transmittance necessary for a phase shift film used for exposure of 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.

Fig. 3 is a graph plotting the refractive index n for the nitrogen flow rate in example 1.

Fig. 4 is a graph plotting the extinction coefficient k for the nitrogen flow rate in example 1.

Fig. 5 is a graph plotting the refractive index N for the content ratio N/(Si + N) in example 1.

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 transparent substrate 10 and a phase shift film 1 formed on the transparent substrate 10. FIG. 1B is a cross-sectional view illustrating an exemplary phase shift mask of the present invention. In this embodiment, the phase shift mask 101 includes a transparent substrate 10 and a phase shift film pattern 11 formed on the transparent substrate 10. A phase shift mask may be obtained by using a phase shift mask blank and patterning a phase shift film thereof.

The phase shift film in the present invention having a predetermined 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 may be composed of a single layer or multiple layers designed to satisfy the phase shift and transmittance necessary for the phase shift film. In each case of the single layer and the multiple layers, each layer of the single layer or the multiple layers may be a single composition layer in which the composition is constant in the thickness direction, or a composition-graded layer in which the composition is varied in the thickness direction.

In each of the single layer or the multiple layers of the phase shift film of the present invention, the refractive index n is preferably 2.5 or more, more preferably 2.55 or more. The upper limit of the refractive index n is usually 2.7 or less. In each of the single layer or the multiple layers of the phase shift film of the present invention, the extinction coefficient k is preferably 0.4 or more, more preferably 0.5 or more, and preferably 1 or less, more preferably 0.8 or less.

In the phase shift film of the present invention, when the phase shift film is composed of a single layer, the content ratio N/(Si + N) is preferably 0.43 or more, more preferably 0.45 or more, and preferably 0.53 or less, more preferably 0.5 or less, in at least a part of the single layer, particularly in the entire single layer, or when the phase shift film is composed of a plurality of layers, in at least a part of the plurality of layers, particularly in each layer (in all layers) of the plurality of layers. The ratio N/(Si + N) represents the nitrogen content (at%) relative to the sum of the silicon and nitrogen contents (at%). It is to be noted that, with the composition-graded layer, it is preferable that the composition is graded within the above-mentioned content ratio range. In the case where the single layer or each of the multiple layers 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.

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 may be 85nm or less, preferably 80nm 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, preferably magnetron 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-containing targets such as silicon targets, silicon nitride targets, and targets containing both silicon and silicon nitride. The nitrogen content can be controlled by reactive sputtering using nitrogen as a reactive gas in a sputtering gas with the supply amount appropriately controlled. Rare gases such as helium, neon, and argon may also be used as the sputtering gas.

When the phase shift film of the present invention is formed by reactive sputtering using a silicon-containing target and nitrogen gas, the phase shift film is preferably formed at a nitrogen gas flow rate set to a value of-20% to + 20% of the flow rate given to the highest refractive index n with respect to the exposure light, particularly at a nitrogen gas flow rate set to a value of the flow rate given to the highest refractive index n with respect to the exposure light. In this way, a phase shift film having a phase shift of 170 to 190 ° and a transmittance of 4 to 8% can be formed thinner. The flow rate giving the highest refractive index n can be determined in advance by confirming the change in the refractive index n of silicon nitride while the flow rate is changed from a low flow rate to a high flow rate. At this time, sputtering conditions (power applied to the target, flow rate of other sputtering gas, sputtering pressure, and the like) other than the flow rate of nitrogen gas are fixed (constant). Notably, the flow rate may be kept constant or varied continuously or in stages when the membrane is actually formed.

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), forced oxidation treatment such as 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 specifically exemplifies 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 be used as a processing auxiliary film (etching stopper film) that functions as an etching stopper in patterning the third layer. The material of the second layer is preferably a chromium containing material.

This embodiment specifically exemplifies the 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 the present embodiment, the phase shift mask blank 100 includes a transparent substrate 10, a phase shift film 1 formed on the transparent substrate 10, and a second layer 2 formed on the phase shift film 1.

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 the light-shielding film and the antireflection film are combined is exemplified by a structure in which a light-shielding film composed of a chromium-containing material is provided and an antireflection film for reducing reflection from the light-shielding film, composed of a chromium-containing material, is further provided. 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 specifically exemplifies 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 specifically exemplifies the 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 the present embodiment, the phase shift mask blank 100 includes a transparent substrate 10, a phase shift film 1 formed on the transparent substrate 10, a second layer 2 formed on the phase shift film 1, and a third layer 3 formed on the second layer.

For the second layer as a light-shielding film or a combination of a light-shielding film and an antireflection film, a processing auxiliary film (etching) functioning as a hard mask in patterning the second layer may be usedA mask film) is provided as a 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 (etching stopper film) which functions as an etching stopper in patterning the fourth layer. Preferably, the process-assisting film is composed of a material different from the second layer in etching characteristics, such as a chlorine-based dry-etched material resistant 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 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 membrane is exemplified by ｃA membrane 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 by a processing auxiliary film that functions as a hard mask in patterning the third layer. The material of the fourth layer is preferably a chromium containing material.

This embodiment specifically exemplifies the 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 the present embodiment, the phase shift mask blank 100 includes a transparent substrate 10, a phase shift film 1 formed on the transparent substrate 10, a second layer 2 formed on the phase shift film 1, a third layer 3 formed on the second layer 2, and a fourth layer 4 formed on the third layer 3.

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 of the second layer and the fourth layer composed of a chromium-containing material 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 silicon-containing material of the third layer can be formed by reactive sputtering using targets 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 a 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 may generally be fabricated from an exemplary phase shift mask blank comprising a film composed of a chromium-containing material formed as a second layer on a phase shift film by the following process.

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 by the following process.

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 a 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 process.

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 at the portion where the third layer 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 processing 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 a light-shielding film and an antireflection film as a third layer on the second layer, and a processing auxiliary film composed of a chromium-containing material as a fourth layer on the third layer by the following process.

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 at the portion where the third layer has been removed and a portion of the fourth layer exposed at the portion where the resist pattern has been removed are then removed by chlorine-based dry etching containing oxygen to obtain a phase shift mask.