JP3351892B2 - Halftone phase shift photomask and blank for halftone phase shift photomask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used for manufacturing high-density integrated circuits such as LSIs and VLSIs, and a photomask blank for manufacturing the photomask. The present invention relates to a halftone phase shift photomask obtained, and a blank for a halftone phase shift photomask for manufacturing the phase shift photomask.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are manufactured by repeating a so-called lithography process using a photomask. Use of a phase shift photomask as disclosed in Japanese Patent Publication No. 173744, Japanese Patent Publication No. 62-59296, and the like has been studied. Various types of phase shift photomasks have been proposed. Among them, for example, US Pat.
A so-called halftone phase shift photomask as shown in JP-A Nos. 90,309 and the like has attracted attention from the viewpoint of early practical use.
Some proposals have been made for a configuration and a material capable of improving the yield by reducing the number of manufacturing steps, reducing the cost, and the like, as described in Japanese Patent No. 7361 and the like.

Here, a halftone phase shift photomask will be briefly described with reference to the drawings. FIG. 5 is a diagram showing the principle of halftone phase shift lithography, and FIG. 6 is a diagram showing a conventional method. 5A and 6A are cross-sectional views of a photomask, FIGS. 5B and 6B are amplitudes of light on the photomask, and FIGS. 5 (d) and 6 (d) show the amplitude of light on the wafer, respectively, the light intensity on the wafer, 101 and 201 are substrates, 202 is a 100% light shielding film, and 102 is the phase of incident light. 180 degrees, and the transmittance is 1 to 50
%, And 103 and 203 are incident light.
In the conventional method, as shown in FIG. 6A, a 100%
Only the light-shielding film 202 is formed to form a light transmitting portion having a desired pattern, and the light intensity distribution on the wafer spreads as shown in FIG. 6D, resulting in poor resolution. On the other hand, in halftone phase shift lithography, the phase of the light transmitted through the translucent film 102 and the phase of the light transmitted through the opening thereof are substantially inverted.
As shown in (d), the light intensity at the pattern boundary on the wafer becomes 0, the spread of the skirt can be suppressed, and the resolution can be improved.

Here, it should be noted that in the phase shift lithography of a type other than the halftone, since the light-shielding film and the phase shifter film have different patterns, at least 2
In contrast, halftone phase shift lithography requires only one pattern, whereas halftone phase shift lithography requires only one pattern. It is a great advantage.

Incidentally, the semitransparent film 102 of the halftone phase shift photomask is required to have two functions of phase inversion and transmittance adjustment. Among them, the phase inversion function may be such that the phase is substantially inverted between the exposure light transmitted through the halftone phase shift unit and the exposure light transmitted through the opening. Here, the halftone phase shift layer 102 is, for example, Born,
E. FIG. Wolf, "Principles of Opt
ics "on pages 628 to 632, the multiple interference can be ignored, so that the phase change φ of the vertically transmitted light is When φ is in the range of nπ ± π / 3 (n is an odd number), the above-described phase shift effect is obtained. In Equation (1), φ is a phase change received by light that vertically transmits through a photomask in which a (m−2) -layer multilayer film is formed on a substrate, and χ ^{k, k + 1} is k Layer and (k + 1)
The phase change occurring at the interface with the k-th layer, u _k and d _k are the refractive index and thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. Here, the layer where k = 1 is the substrate, and k = m
Layer shall be air.

On the other hand, the exposure light transmittance of the halftone phase shift portion for obtaining the halftone phase shift effect is determined by the dimensions, area, arrangement, shape, etc. of the transfer pattern, and differs depending on the pattern. Substantially, in order to obtain the above-described effect, the exposure light transmittance of the halftone phase shift unit must be within the range of the optimum transmittance ± several% around the optimum transmittance determined by the pattern. Must. Usually, this optimum transmittance is 1 to 5 depending on the transfer pattern when the opening is 100%.
It fluctuates greatly within a wide range of 0%. That is, a halftone phase shift photomask having various transmittances is required to correspond to all patterns.

Actually, the phase inversion function and the transmittance adjustment function are the complex refractive index (refractive index) of the substrate material and the material constituting the halftone phase shift film (each material constituting each layer in the case of a multilayer). And extinction coefficient) and thickness. That is, the thickness of the halftone phase shift film is adjusted, and the phase difference φ obtained by the above equation (1) is nπ ± π / 3.
(N is an odd number) A material whose exposure light transmittance is included in the range of 1 to 50% when the film is formed on the substrate so as to be included in the range of the halftone phase shift of the halftone phase shift photomask. Can be used as a layer. As such a material, for example, a film mainly composed of a chromium compound disclosed in JP-A-5-127361 is known.

[0008]

The above-mentioned films mainly composed of chromium compounds are chromium oxides, nitrides, oxynitrides, oxycarbides, oxycarbonitrides and the like. Transmittance varies greatly with wavelength. For example,
FIG. 9 shows a spectral transmittance curve of a chromium oxide film formed on a synthetic quartz substrate by a sputtering method. here,
The thickness of the chromium oxide film is about 100 nm. As is clear from FIG. 9, the transmittance of the chromium oxide film is low in the ultraviolet region and increases as it goes to the visible and infrared regions. This tendency is the same for a chromium nitride film, a chromium oxynitride film, a chromium oxycarbide film, a chromium oxycarbonitride film, and the like.

Generally, exposure light of a halftone phase shift photomask is i-line (365 nm) of a high-pressure mercury lamp,
Although it is short-wavelength light such as g-line (436 nm), the spectral characteristics of the transmittance of the chromium compound have the above-mentioned tendency. Has a very high transmittance. For example, when the above-described compound mainly composed of chromium oxide is used for a halftone phase shifter of a halftone phase shift photomask for i-line, when the transmittance of 365 nm light is 10%, the wavelength around 500 to 600 nm is obtained. Transmittance is about 50%
It will be around.

[0010] By the way, the photomask is subjected to a defect inspection after plate making and, if necessary, to correct the confirmed defect.
This defect inspection is usually performed optically using transmitted light.
At this time, the higher the transmittance difference (contrast) between the pattern portion and the non-pattern portion, the higher the sensitivity of the inspection. Here, in a conventional photomask that does not use a phase shifter made of a pattern of chromium metal, its transmittance is almost 0% regardless of the wavelength, so that the wavelength of the inspection light is not necessarily the same as the wavelength of the exposure light. Optical systems often utilize the advantageous visible light range. Also, using visible light,
There is an advantage that the inspection status can be directly observed. In particular,
Inspection devices most widely used for inspecting fine patterns at present are those using a mercury lamp e-line (545 nm), an argon laser (488 nm) or the like as a light source. In the case of a halftone phase shift photomask, in order to perform inspection at the same level as a conventional photomask using these inspection devices, the inspection light transmittance of the pattern portion (halftone phase shifter portion) is lowered, It is necessary to increase the above-mentioned contrast. In the case of a halftone phase shift photomask, since the pattern portion is translucent at the exposure wavelength as described above, the transmittance at the inspection wavelength cannot be 0%, but a transmittance as low as at least the exposure wavelength is required. You.

However, as described above, in a halftone phase shift photomask using a chromium compound as a material for the halftone phase shift layer, when the wavelength transmittance of the exposure light is adjusted to a desired value, the wavelength of the inspection light is reduced. This significantly increases the transmittance of the photomask, making it difficult to perform inspection using the same method as that of the conventional photomask.

The present invention has been made in view of such a situation, and an object of the present invention is to adjust the exposure light transmittance of a semi-transmissive portion arbitrarily, and to adjust the transmittance from the transfer wavelength range to the inspection wavelength range. An object of the present invention is to provide a high quality halftone phase shift photomask having substantially constant transmittance and high inspection sensitivity, and blanks therefor.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has been described in view of the following points.
As a result of research to develop a halftone phase shift layer material that not only has a desired transmittance in exposure light but also has a transmittance that can be inspected even in the above-described visible wavelength inspection light, it has been completed. Things.

That is, the present invention relates to a halftone phase shift photomask including at least one layer mainly composed of a hafnium compound as a halftone phase shift layer, and a blank for the halftone phase shift photomask. Unlike a film mainly composed of a chromium compound as described above, a film mainly composed of a hafnium compound has a substantially constant transmittance from an exposure light region having a short wavelength to an inspection light region having a long wavelength. When the transmittance is set to a desired transmittance, the inspection can be performed with almost the same sensitivity using the same inspection apparatus and inspection method as those of the conventional photomask.

In general, a metal hafnium film is a light-shielding film that does not transmit light regardless of wavelength in the wavelength range from the ultraviolet region to the visible region. On the other hand, hafnium dioxide, which is a common oxide of hafnium, becomes an almost transparent film in the above-mentioned wavelength range. FIG. 7 shows a spectral transmittance curve (broken line) when hafnium dioxide is formed to a thickness of about 100 nm on a synthetic quartz for a photomask by a sputtering method. Compared with the spectral transmittance (solid line) of the synthetic quartz as the substrate, it can be seen that this hafnium dioxide is a transparent film in almost the entire wavelength range, although the transmittance is slightly lowered in the short wavelength range.

Here, if the degree of oxidation of hafnium oxide is adjusted between the above-mentioned light-shielding film and transparent film, a film that can be used as a halftone phase shift layer can be obtained. FIG. 8 shows the transmittance of hafnium oxide (HfO _x ; 0 <x <2) formed with a thickness of 100 nm on a synthetic quartz for a photomask by a sputtering method by adjusting the degree of oxidation. It can be seen that this hafnium oxide exhibits a substantially constant transmittance from the above-described transfer exposure wavelength range to the mask inspection wavelength range.

Although the oxide has been described above, the same applies to compounds such as fluorides, silicides, borides, carbides and nitrides of hafnium, as well as composite compounds such as oxyfluorides and oxycarbonitrides. By controlling the composition ratio, a film suitable for the halftone phase shift layer can be obtained. Further, these hafnium compound films can be obtained not only by a sputtering method but also by any ordinary thin film forming method such as a vacuum evaporation method and an ion plating method.

In order to form a single-layer halftone phase shift photomask blank of a hafnium compound by a sputtering method, an ordinary reactive sputtering method using a metal hafnium as a target can be used. In this case, when an argon gas is used as a discharge gas, a metal hafnium film serving as a light-shielding film is formed, and a reactive gas such as an oxygen gas, a carbon dioxide gas, a carbon tetrafluoride gas, and a nitrous oxide gas is used as a discharge gas. Then, a hafnium compound film such as hafnium dioxide which is a transparent film is formed. At this time, if a mixture gas of a reactive gas and an argon gas is used and the mixture ratio is adjusted, a film whose degree of oxidation is adjusted can be obtained, and a transmittance region required for a halftone phase shift photomask can be obtained. A film can be formed. Here, the transmittance is lower as the ratio of the argon gas is higher, and conversely, the transmittance is higher as the ratio of the reactive gas is higher, but actually, the relationship between the gas mixture ratio and the transmittance is It depends on the type, film formation conditions, device factors such as the method of introducing gas into the sputtering device, and the like. Therefore, the optical constants of various hafnium compound films formed by changing the gas mixture ratio are determined by, for example, ellipsometry, and the film in which the phase of the exposure light is inverted by 180 degrees by the above-described equation (1) for each film. It is necessary to calculate the thickness and obtain the transmittance when the film is formed on the synthetic quartz substrate for a photomask by this thickness. For example, in the case of hafnium oxide, the mixing ratio for obtaining a transmittance of 1 to 50% generally required for a halftone phase shift photomask is such that the proportion of oxygen gas is 1 to 70%.
%.

Of course, a desired hafnium compound film can also be obtained by a sputtering method using a mixture target previously adjusted to a desired mixing ratio. Also in the vacuum deposition method, a film can be formed by so-called reactive deposition using metal hafnium as an evaporation source. Here, oxygen gas, carbon dioxide gas, carbon tetrafluoride gas and the like are used as reactive gases, and by adjusting the introduction amounts of these,
A desired hafnium compound is obtained in the same manner as in the above-described sputtering method. Further, the same applies to the ion plating method.

Next, in making a plate of these hafnium compound films, a conventional lithography technique may be used to selectively etch hafnium oxide with hydrofluoric acid diluted to about 1 to 2%. Here, the etching selectivity between the synthetic quartz and the hafnium compound of the substrate is practically sufficient. Further, it is also possible to form a pattern by a so-called lift-off method. In any case, the hafnium compound is not affected by the cerium nitrate-based solution which is an etching solution for chromium, and thus chromium can be used as a mask.

Although the case where the halftone phase shift layer is a single layer of a hafnium compound has been described above, a multilayer film may be formed by laminating a hafnium compound film having a different composition or a metal hafnium thin film as necessary. . Also,
It is also possible to laminate with a film containing no hafnium.
In particular, in the case where the patterning of the halftone phase shift layer is performed by electron beam lithography, if a conductive film is included therein, there is an advantage that charge-up during electron beam writing can be prevented. Further, for fine adjustment of the transmittance, it is possible to include a thin layer which is less affected by the phase shift due to the film thickness and has a large absorption, and adjusts the transmittance by the thickness of this layer.

The halftone phase shift photomask containing these hafnium compounds is not limited to the above-described i-line and g-line exposure of mercury and the like, but can be excimer such as krypton fluoride (248 nm) which can perform higher resolution lithography. Laser exposure and exposure to mercury and the like in a shorter wavelength range than i-ray (365 nm) are also possible.

As described above, the halftone phase shift photomask of the present invention is characterized in that the halftone phase shift layer on the transparent substrate includes at least one layer mainly composed of a hafnium compound. is there.

In this case, the hafnium compound may be a compound containing at least one of an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom and a nitrogen atom in addition to the hafnium atom. Furthermore, the hafnium compound, the oxygen atom, the fluorine atom, the silicon atom, the boron atom, and the carbon atom are in a range in which the layer mainly composed of the hafnium compound does not change the refractive index determined by the ellipsometry with the exposure light by 0.1 or more. And an impurity atom other than a nitrogen atom. Further, it is desirable that the halftone phase shift layer is formed on the transparent substrate such that the phase difference φ determined by the following equation is in the range of nπ ± π / 3 radians (n is an odd number). Here, φ is a phase change received by light vertically transmitted through a photomask in which a (m−2) -layer multilayer film is formed on a transparent substrate, and χ ^{k, k + 1} are the k-th layer and the The phase change occurring at the interface with the (k + 1) -th layer, u _k and d _k are the refractive index and the film thickness of the material forming the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is a transparent substrate, and k = m
Layer shall be air.

When the transmittance of the halftone phase shift layer to the exposure light is 100% when the transmittance of the opening of the halftone phase shift layer to the exposure light is 100%.
It is desirable to be 50% to 50%.

Further, the blank for a halftone phase shift photomask of the present invention is characterized in that the halftone phase shift layer on the transparent substrate includes at least one layer mainly composed of a hafnium compound.

In this case, the hafnium compound may be a compound containing at least one of an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom and a nitrogen atom in addition to the hafnium atom. Furthermore, the hafnium compound, the oxygen atom, the fluorine atom, the silicon atom, the boron atom, and the carbon atom are in a range in which the layer mainly composed of the hafnium compound does not change the refractive index determined by the ellipsometry with the exposure light by 0.1 or more. And an impurity atom other than a nitrogen atom. Further, it is desirable that the halftone phase shift layer is formed on the transparent substrate such that the phase difference φ determined by the following equation is in the range of nπ ± π / 3 radians (n is an odd number). Here, φ is a phase change received by light that vertically transmits through a photomask blank in which a (m−2) -layer multilayer film is formed on a transparent substrate, and χ ^{k, k + 1} are the k-th layer and the k-th layer. Phase change occurring at the interface with the (k + 1) th layer, u
_k and d _k are the refractive index and the film thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is a transparent substrate, and the layer where k = m is air.

The half-tone phase shift layer is formed on the transparent substrate with a thickness such that the transmittance of the transparent substrate to the exposure light is 1 to 50% when the transmittance of the transparent substrate to the exposure light is 100%. It is desirable to be formed in.

[0029]

According to the halftone phase shift photomask and the blank for a halftone phase shift photomask of the present invention, a layer containing at least one layer mainly composed of a hafnium compound is used as a halftone phase shift layer. Arbitrary exposure light transmittance can be obtained by adjusting the composition of the conventional chromium compound halftone, and conductivity can be imparted by forming a laminated structure, and fine adjustment of the transmittance can be simplified. In addition to the advantages of the phase shift layer material, in addition to this, the halftone phase shift layer has a substantially constant transmittance from the transfer wavelength range to the test wavelength range. As a result, the inspection sensitivity is improved, and a high-quality halftone phase shift photomask can be manufactured.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a halftone phase shift photomask and a blank for a halftone phase shift photomask according to the present invention will be described below. Embodiment 1 An embodiment of a blank for a halftone phase shift photomask for i-line exposure of a mercury lamp according to the present invention will be described with reference to FIG. As shown in FIG. 3A, a hafnium oxide film 602 is formed on a mirror-polished silicon wafer 601 to a thickness of about 30 nm by a sputtering method under the conditions shown below. 603
I got

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: metal hafnium gas and flow rate: argon gas 70 sccm + oxygen gas 30 sscm Sputter pressure: 3 mTorr Sputter current: 4.5 amps Next, a commercially available spectroscopic ellipsometer (Sopra Corporation) ES-
4G), the mercury lamp i-line wavelength (36
When the refractive index u and the extinction coefficient k at 5 nm were measured, they were u = 2.096 and k = 0.280, respectively. This is referred to as M. Born, E .; Wolf, Pr
includes of Optics "628-63
Treated as a metal film shown on page 2, and formed on high-purity synthetic quartz used as a substrate for photomasks, 3
When the film thickness required to shift the phase of the transmitted light having a wavelength of 65 nm by 180 degrees was calculated, it was 166.5 nm.

Therefore, as shown in FIG. 1B, a hafnium oxide film 605 having a wavelength of 365 nm was formed on a high-purity synthetic quartz 604 which had been optically polished and washed well under the above-mentioned film forming conditions under the above-mentioned film forming conditions. Light transmittance of about 1
6% of the blank 606 for a halftone phase shift photomask of the present invention was obtained. FIG. 4 shows the spectral transmittance curve of this blank. As is clear from the figure, the transmittance of this blank is not high even in the visible light region.

[Embodiment 2] An embodiment of a halftone phase shift photomask for i-line exposure of a mercury lamp according to the present invention will be described with reference to the manufacturing process diagram of FIG. As shown in FIG. 2A, on the blanks 701 obtained in Example 1, a chromium film 702 by sputtering was formed to a thickness of about 100 nm under the following conditions.
Formed.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium Gas and flow rate: Argon gas 100 sccm Sputter pressure: 3 mTorr Sputter current: 3.5 amps Next, as shown in FIG. Membrane 702
A desired resist pattern 703 containing an organic substance as a main component was obtained by a conventional electron beam lithography method or photolithography method. Thereafter, as shown in FIG. 4C, the chromium film 7 exposed from the resist pattern 703 is formed.
02 was selectively removed by immersion in a cerium nitrate-based chromium etchant, and then the resist pattern 703 was peeled off to obtain a desired chromium pattern 704 as shown in FIG.

Next, as shown in FIG. 3E, the blanks are immersed in 1.5% hydrofluoric acid to form a hafnium oxide film 70 using the chromium pattern 704 as a mask.
5 was performed, and finally, the chromium film 704 was peeled off using the above-described chromium etching solution, thereby obtaining a desired hafnium oxide pattern 706 as shown in FIG.
The hafnium oxide pattern 706 satisfied characteristics required for a photomask, such as chemical stability, adhesion to a substrate, weather resistance, and irradiation resistance. Further, since the transmittance of this mask is almost constant from the ultraviolet region to the visible region, the inspection can be performed with the same sensitivity as that of the chrome mask using the conventional chrome mask inspection apparatus.

[Embodiment 3] Another embodiment of a halftone phase shift photomask for i-line exposure of a mercury lamp according to the present invention will be described with reference to the manufacturing process diagram of FIG. First, as shown in FIG. 3A, a chromium pattern 801 obtained by inverting a desired pattern in a negative / positive manner was formed on a synthetic quartz substrate 802 for a photomask by a normal chrome plate making technique. continue,
As shown in FIG. 7B, a 170 nm hafnium oxide film 804 was formed on the substrate 803 on which the chromium pattern was formed under the same conditions as in Example 1. Next, the substrate 805 on which the hafnium oxide film 804 is formed is immersed in a cerium nitrate-based chromium etchant, and the chromium pattern 801 is removed.
In FIG. 4C, a desired hafnium oxide pattern 80 as shown in FIG.
6 was obtained. This hafnium oxide pattern was also excellent in characteristics as a halftone phase shift photomask, like the hafnium oxide pattern obtained in Example 2.

[0037]

As is apparent from the above description, according to the halftone phase shift photomask and the blank for a halftone phase shift photomask of the present invention, the layer containing at least one layer mainly composed of a hafnium compound is used. In order to form a halftone phase shift layer, an arbitrary exposure light transmittance can be obtained by adjusting the composition of the hafnium compound, and conductivity is imparted by forming a laminated structure, and fine adjustment of the transmittance is performed. In addition to the advantages of the conventional chromium compound halftone phase shift layer material, such as simplification, the halftone phase shift layer has an almost constant transmittance from the transfer wavelength range to the inspection wavelength range. As a result, the transmittance in the inspection wavelength range is reduced, the inspection sensitivity is improved, and a high-quality halftone phase shift photomask is used. Manufacturing is possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a process of obtaining a blank for a halftone phase shift photomask according to a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a halftone phase shift photomask according to a second embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of a halftone phase shift photomask according to Embodiment 3 of the present invention.

FIG. 4 is a diagram showing a spectral transmittance curve of a blank for a halftone phase shift photomask of Example 1.

FIG. 5 is a diagram illustrating the principle of halftone phase shift lithography.

FIG. 6 is a diagram showing a conventional method.

FIG. 7 is a diagram showing a comparison between a spectral transmittance curve of hafnium dioxide and a spectral transmittance curve of synthetic quartz.

FIG. 8 is a diagram showing a spectral transmittance curve of hafnium oxide whose degree of oxidation is adjusted.

FIG. 9 is a diagram showing a spectral transmittance curve of a chromium oxide film.

[Explanation of symbols]

 Reference numeral 601: silicon wafer 602: hafnium oxide film 603: sample for ellipsometry 604: high-purity synthetic quartz 605: hafnium oxide film 606: blanks 701: blanks 702: chromium film 703: resist pattern 704: chrome pattern 705: hafnium oxide film 706 … Hafnium oxide pattern 801 chrome pattern 802 synthetic quartz substrate 803 chromium pattern formed substrate 804 hafnium oxide film 805 substrate formed hafnium oxide film 806 hafnium oxide pattern

Continuation of front page (56) References JP-A-5-134386 (JP, A) JP-A-61-270760 (JP, A) JP-A-3-173638 (JP, A) JP-A-7-261370 (JP) , A) JP-A-7-134392 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 1/00-1/16

Claims (10)

(57) [Claims] 1. A halftone phase shift photomask, wherein the halftone phase shift layer on the transparent substrate includes at least one layer mainly composed of a hafnium compound. 2. The method according to claim 1, wherein the hafnium compound is a compound containing at least one of an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom, and a nitrogen atom in addition to a hafnium atom. A characteristic halftone phase shift photomask. 3. The method according to claim 1, wherein the layer mainly composed of the hafnium compound does not change the refractive index obtained by ellipsometry with exposure light by 0.1 or more.
A halftone phase shift photomask containing an impurity atom other than a hafnium atom, an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom, and a nitrogen atom. 4. In any one of claims 1 to 3,
A halftone phase shift layer formed on a transparent substrate such that a phase difference φ determined by the following equation is in a range of nπ ± π / 3 radians (n is an odd number). Photo mask. Here, φ is a phase change received by light vertically transmitted through a photomask having a multilayer film of (m−2) layers on the transparent substrate, and χ ^{k, k + 1} is a k-th layer. And (k + 1)
The phase change occurring at the interface with the k-th layer, u _k and d _k are the refractive index and thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is the transparent substrate, and the layer where k = m is air. 5. The method according to claim 1, wherein:
The transmittance of the halftone phase shift layer for exposure light is
A halftone phase shift photomask, wherein the transmittance of the opening of the halftone phase shift layer with respect to the exposure light is 1 to 50% when the transmittance is 100%. 6. A blank for a halftone phase shift photomask, wherein the halftone phase shift layer on the transparent substrate includes at least one layer mainly composed of a hafnium compound. 7. The method according to claim 6, wherein the hafnium compound is a compound containing at least one of an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom, and a nitrogen atom in addition to the hafnium atom. Characteristic blanks for halftone phase shift photomasks. 8. The method according to claim 6, wherein the layer mainly composed of the hafnium compound does not change the refractive index obtained by ellipsometry with exposure light by 0.1 or more.
A blank for a halftone phase shift photomask, characterized by containing an impurity atom other than a hafnium atom, an oxygen atom, a fluorine atom, a silicon atom, a boron atom, a carbon atom, and a nitrogen atom. 9. In any one of claims 6 to 8,
A halftone phase shift layer formed on a transparent substrate such that a phase difference φ determined by the following equation is in a range of nπ ± π / 3 radians (n is an odd number). Blanks for photomasks. Here, φ is a phase change received by light vertically transmitting through a photomask blank in which a (m−2) -layer multilayer film is formed on the transparent substrate, and χ ^{k, k + 1} is a k-th phase change. Phase change occurring at the interface between the (k + 1) th layer and the
u _k and d _k are the refractive index and the thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is the transparent substrate, and the layer where k = m is air. 10. The transmittance of the halftone phase shift layer for exposure light according to claim 6, wherein the transmittance of the transparent substrate for the exposure light is 100.
%. The blank for a halftone phase shift photomask, which is formed on the transparent substrate so as to have a thickness of 1 to 50% when expressed as%.