JPH0728224A - Halftone phase shift photomask and blanks for halftone phase shift photomask - Google Patents

Abstract

(57) [Abstract] [Purpose] A halftone phase shift photo mask and blanks for it, which has a simple structure, can shorten the plate making process, can reduce the cost and can improve the yield, and can be used as it is in the conventional production line. . A halftone phase shift layer 806 on a transparent substrate 803 has at least one layer containing a chromium compound as a main component.
Halftone phase shift photomask 809 including more layers
The composition ratio of chromium atoms and oxygen atoms in the layer mainly containing a chromium compound is 1 by X-ray photoelectron spectroscopy.
It is characterized in that it is included in the range of 00: 100 to 300.

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 LSI and VLSI, 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 IC, LSI and VLSI are manufactured by repeating a so-called lithographic process using a photomask. The use of a phase shift photomask as shown in Japanese Patent No. 173744, Japanese Patent Publication No. 62-59296, etc. 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 Japanese Patent Application Laid-Open No. 90,309 has received attention from the viewpoint of early commercialization, and is disclosed in Japanese Patent Laid-Open Nos. 5-2259 and 5-12.
As in Japanese Patent No. 7361, several proposals have been made regarding a structure and a material capable of improving the yield by reducing the number of manufacturing steps and reducing the cost.

Here, a halftone phase shift photomask will be briefly described with reference to the drawings. FIG. 3 is a diagram showing the principle of halftone phase shift lithography, and FIG. 4 is a diagram showing a conventional method. 3A and 4A are cross-sectional views of the photomask, FIGS. 3B and 4B are amplitudes of light on the photomask, and FIGS. 3C and 4C are 3 (d) and 4 (d) show the light amplitude on the wafer, respectively, and 101 and 201 are the substrate, 202 is a 100% light-shielding film, and 102 is the phase of the incident light. Shifted by 180 degrees and the transmittance is 1 to 50
% Of semi-transparent film, and 103 and 203 are incident light.
In the conventional method, as shown in FIG. 4A, 100% of chromium or the like is formed on the substrate 201 of quartz glass or the like.
Only the light-shielding film 202 is formed and the light-transmitting portion having a desired pattern is formed, and the light intensity distribution on the wafer has a widened bottom as shown in FIG. 4D, resulting in poor resolution. On the other hand, in the halftone phase shift lithography, the phase of the light transmitted through the semitransparent film 102 and the light transmitted through the opening thereof are substantially inverted.
As shown in (d), the light intensity at the pattern boundary portion on the wafer becomes 0, and the skirt spread can be suppressed, so that the resolution can be improved.

Here, a point to be noted is that in phase shift lithography of types other than halftone, the light-shielding film and the phase shifter film have different patterns, so that at least 2 is required.
In contrast to half-tone phase-shift lithography, half-tone phase-shift lithography requires only one plate-making process because it requires only one plate-making process. It is a great advantage.

By the way, the semitransparent film 102 of the halftone phase shift photomask is required to have two functions of phase inversion and transmittance adjustment. As a film structure for realizing this, a single layer film that performs both functions in one layer,
It can be considered as a multilayer film in which two layers have different functions. In the former case, the plate-making process is performed once, and the advantage of the halftone phase shift lithography described above can be utilized, but in the latter case, for example, spin-on / sputtering is performed as a phase inversion layer.
As is clear from the case of using the glass (SOG) phase shifter layer and the chrome light shielding layer as the layer for adjusting the transmittance, even when the same pattern is formed, two plate making steps are required due to the difference in material. Have to go through,
This has led to higher costs and lower yields. Therefore, even if the semi-transparent film 102 has a single-layer structure or a multi-layer structure, a combination of a phase shifter layer material and a light-shielding layer material capable of performing one plate-making process was required.

[0006]

However, there is no known material for the semitransparent film which satisfies the above conditions and is practically problem-free from the viewpoint of the photomask manufacturing process, and the material selection is extremely difficult. There was a problem that was difficult. Only, there was a possibility that the film mainly composed of a chromium compound proposed in JP-A-5-127361 could satisfy the above-mentioned conditions. However, the chromium compound has a great difference in optical characteristics depending on its composition, and in many cases, it cannot be practically used as a semitransparent film of a halftone phase shift photomask.

The present invention has been made in view of such a situation, and its purpose is not only to have a simple structure, to shorten the plate making process, to reduce the cost and to improve the yield, but It is an object of the present invention to provide a halftone phase shift photomask that can be used as it is for most of the chrome photomask manufacturing line and a blank for a halftone phase shift photomask for manufacturing the phase shift photomask.

[0008]

In view of the above problems, the present invention has been studied to develop a halftone phase shift photomask which is practical, accurate, and easy to manufacture. By adopting a structure including a film containing a chromium compound as a main component, a semi-transparent film of a halftone phase shift photomask that performs both phase inversion and transmittance adjustment can be patterned in a single layer or in a single plate making process. The present invention has been completed based on the finding that a possible multilayer film can be formed.

That is, according to the present invention, a halftone composed of a transparent substrate and a single layer film of a layer mainly composed of a chromium compound having a limited composition range provided thereon, or a multilayer film including this layer. The present invention relates to a blank for a phase shift photomask and a halftone phase shift photomask obtained by patterning a semitransparent film of the blank.

As described above, the characteristics required for the semitransparent film of the halftone phase shift photomask include the characteristics of inverting the phase of the exposure light and the characteristics of adjusting the transmittance. , Is determined by the complex refractive index (refractive index and extinction coefficient) of the substance forming the semitransparent film (each substance forming each layer in the case of a multilayer) and the film thickness. The semi-transparent film is, for example, M. Born, E .; Wolf "Pr
inciples of Optics "628-63
When treated as the absorption film shown on page 2, multiple interference can be ignored, so the phase change φ of the vertically transmitted light is calculated as follows.

[0011] Here, φ is a phase change that light vertically transmitted through a photomask in which a multilayer film of (m−2) layers is formed on the substrate, and χ ^{k, k + 1} is the kth layer and ( 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 kth layer, and λ is the wavelength of the exposure light. However, the layer of k = 1 is the substrate, and the layer of k = m is air.

Generally, a halftone phase shift photomask is required to have a transmittance of 1 to 50% with respect to exposure light, but it is transparent with a film thickness obtained by the calculation of the above formula (1). If the semitransparent film formed on the substrate has a transmittance within this range, it can be used as it is for a single-layer halftone phase shift photomask. In addition, if the transmittance is outside the permissible range (when more exposure light is transmitted), a light-shielding layer composed of a metal chrome thin film that adjusts the transmittance should be used in addition to this semi-transparent film. By providing and providing a laminated structure, it is possible to keep the transmittance within the above range in the form of the above-mentioned multilayer halftone phase shift photomask.

One of the features of the film containing a chromium compound as a main component of the present invention is that once a plate containing metal chromium as the light-shielding layer is used, the plate can be produced only once as shown in Examples described later. The semi-transparent film can be patterned by, the number of steps can be reduced, and the cost can be reduced and the yield can be improved. Of course, it is possible to adjust the transmittance by laminating two or more layers mainly composed of chromium compounds having different compositions.
Phase inversion can also be performed, and at this time, the composition of each layer does not necessarily have to change discontinuously at the interface, and the composition can be continuously changed without substantially having the interface. Is also possible. However, in this case, the amount of phase change is slightly deviated from the simulation of the above-mentioned formula (1). Furthermore, one layer does not necessarily have to be a uniform material in the film thickness direction, and may have a distribution in composition, structure, and the like. When a translucent film is formed by laminating two or more layers of a film containing a chromium compound as a main component and a film containing metal chromium as a main component, the composition, the structure, and the film forming conditions of them are mutually different. It is possible to adjust the transmittance spectrum distribution and to improve the etching processability by making the difference between the above and the above.

The chromium compound of the present invention is chromium oxide,
Chromium oxycarbide, chromium oxynitride, chromium oxycarbonitride, and these compounds containing argon, it has been found that the film mainly composed of these has greatly different optical properties depending on the composition. The refractive index and extinction coefficient of the formed film were measured, and the transmittance at the film thickness at which the phase was inverted as described above was measured. As a result, a semi-transparent single-layer or multi-layer halftone phase shift photomask was obtained. It has been found that there is a composition range that can be used well as a layer. The grounds for determining the composition range will be specifically described below.

The layer containing a chromium compound as a main component is formed on a transparent substrate by a conventional thin film forming method such as a vacuum vapor deposition method, a sputtering method and an ion plating method. For example, in the case of a sputtering method, which is an example of a manufacturing method, it is possible to form a film by a reactive sputtering method of a metal chromium target. At this time, a reactive gas which can be incorporated into the film by the reaction on the target surface, the substrate surface, or in the sputtering space to supply the element that forms the chromium compound, and a conventional sputtering gas are mixed if necessary. Then, a chromium compound is formed on the substrate. Of course, both the reactive gas and the sputtering gas can be mixed gas of a plurality of gases. This method has a great advantage in that the sputtering apparatus used for producing blanks of ordinary chromium photomasks can be used as it is. Here, the chromium compounds having various compositions can be formed by changing the kind of gas and the mixing ratio.

In such a film forming method, in general, reactive gases such as oxygen, carbon dioxide, carbon monoxide, water vapor,
Among gases that can be an oxygen source such as nitrogen oxides and nitrous oxide gas, one kind or a mixed gas of two or more kinds, and if necessary,
Among the commonly used sputter gases such as argon, nitrogen, neon, helium, and xenon, one kind or a mixed gas of two or more kinds is used. Therefore, as an example, a carbon dioxide gas is used as an oxygen source and a nitrogen gas is used as a sputtering gas, and the refractive index of a film formed by changing the flow rate ratio of carbon dioxide gas / nitrogen gas on a well-cleaned silicon wafer, The extinction coefficient is measured with a commercially available spectroscopic ellipsometer, the exposure wavelength is a high pressure mercury lamp i-line (365 nm), the substrate is synthetic quartz, and the film thickness when the phase of the exposure light is shifted by 180 degrees is calculated, and the substrate for the photomask is calculated. FIG. 5 shows the result of obtaining the transmittance of the film formed by the above film thickness. Here, the film forming apparatus is an ordinary planar type DC magnetron sputtering apparatus, the film forming conditions are a gas pressure of 3.0 mTorr, a gas flow rate of 100 sccm in total of carbon dioxide gas and nitrogen gas, and a sputtering current density of 0. It is 01 amps / square centimeter. As is clear from FIG. 5, the film formed in the region where the ratio of the carbon dioxide gas flow rate is more than several% is favorably used as the semitransparent film for the halftone phase shift photomask in relation to the transmittance.

Further, a carbon dioxide gas / nitrogen gas ratio of 0/100, 10/9 was formed on these silicon wafers.
The relationship between the composition ratio of chromium, oxygen, carbon and nitrogen atoms and the carbon dioxide gas / nitrogen gas flow rate ratio by X-ray photoelectron spectroscopy (XPS) of 0, 20/80, 70/30, 100/0 films was obtained. The results are shown in FIG. Here, 100 chromium atoms
Is the number of oxygen, carbon, and nitrogen atoms present. The composition analysis by X-ray photoelectron spectroscopy is performed under the conditions described below. As can be seen from FIG. 6, the relationship between the carbon dioxide / nitrogen gas flow rate ratio and the film composition has a clear inflection point, as indicated by point a in the figure. That is, in a region where the carbon dioxide gas flow rate ratio is smaller than the point a, the composition greatly depends on the flow rate ratio, and as the carbon dioxide gas flow rate is increased from 0 to 20%, the number of oxygen atoms when the chromium amount is 100 is set. Rapidly changes from about 50 to about 200 or more and the number of nitrogen atoms from 100 or more to 20 or less. The oxygen atom and the nitrogen atom are in a complementary relationship with each other, and the total amount of them is always about 200 to 300 with respect to 100 chromium atoms. On the other hand, the total number of carbon atoms does not change so much. Here, by comparing FIG. 5 with FIG. 6, the composition range of chromium atoms, oxygen atoms, and nitrogen atoms becomes clear.

The same film formation was carried out by using a carbon dioxide gas / argon gas system instead of general argon as a sputtering gas. As a result, the same result as that of the above carbon dioxide gas / nitrogen gas system was obtained. Therefore, it was found that the same composition range as described above is also effective for a halftone phase shift photomask for chromium atoms, oxygen atoms, and argon atoms.

Next, in order to investigate the role of carbon atoms, similar film formation was carried out in an oxygen gas / argon gas system using oxygen gas instead of carbon dioxide as an oxygen source. At this time as well, the same result as the above was obtained, but the result was obtained that the chemical resistance of the film was inferior to the films in the carbon dioxide / nitrogen gas system and the carbon dioxide / argon gas system. For example, FIG. 7 shows the amount of film loss after immersion in a mixed acid of concentrated sulfuric acid: concentrated nitric acid = 10: 1 (volume) heated to 80 ° C. and used for cleaning a photomask for 30 minutes. From this, it can be seen that the film formed using carbon dioxide gas has better resistance to the mixed acid used for cleaning than the film formed using oxygen gas. This property is the same for other chemicals (acid, alkali, organic solvent, etc.) used in the mask process. Further, FIG. 8 shows the composition of the film formed in the oxygen gas / argon gas system, which was obtained by X-ray photoelectron spectroscopy. Comparing FIG. 8 and FIG. 6, it can be seen that the amount of carbon contained in the film is different. Therefore, it is considered that the above chemical resistance is due to the inclusion of carbon atoms. Note that quantitative analysis of carbon atoms is generally difficult, and in FIGS. 6 and 8, carbon atoms are confirmed in the film even when the gas serving as the carbon source is not positively introduced. , It is considered that there is some back ground in these results. Therefore, as a result of studying various film forming environments and analysis environments, the inventors have found that the above-mentioned effect is exhibited when carbon atoms are contained in an amount of 0.5% or more with respect to chromium atoms. Further, FIG. 9 shows a profile in the depth direction of the composition obtained by X-ray photoelectron spectroscopy. In many cases, many carbon atoms are distributed in the surface region. The film containing a large amount of carbon atoms in the surface region has improved resistance to immersion in a chemical solution.

From the above results, a film containing a chromium compound as a main component, which can be used as a semitransparent film of a halftone phase shift photomask, falls within one of the following composition ranges by X-ray photoelectron spectroscopy. It is considered limited. Note that, so far, the reactive sputtering method of the chromium target has been described as an example of the manufacturing method, but this is only an example, and in any manufacturing method,
It is considered that the same characteristics are exhibited when included in any of the composition ranges shown below.

The composition ratio of chromium atoms and oxygen atoms is 1
00 to 100 to 300.

And at least 0.5% of carbon atoms with respect to chromium atoms.

And a depth of 3 from the film surface.
The surface region within 0Å contains more carbon atoms than other regions.

And contains 10 chromium atoms.
When set to 0, the total of nitrogen atoms and oxygen atoms is 350.
Nitrogen atoms are contained in the following proportions.

And contains 10 chromium atoms.
When set to 0, the total of argon and oxygen atoms is 3
Argon atoms are contained at a ratio of 50 or less.

Impurity atoms other than chromium, oxygen, carbon, nitrogen, and argon atoms are contained in any of the following items and within a range that does not change the refractive index of the exposure light obtained by the polarization analysis method by 0.1 or more. contains.

In the present invention, X-ray photoelectron spectroscopy analysis was performed as follows. X-ray photoelectron spectroscopy analyzer is ESCASCOPE manufactured by UK VG SCIENTIFIC
Was used. The electron energy analyzer of ESCASCOPE was a 180 ° concentric hemisphere type analyzer, and the X-ray photoelectron spectrum was measured using a 6-channel tron detector.

The data processing unit is a DEC Micro P
DP11 / 53, VGS DATA SYSTEM
Quantitative calculation etc. were performed using the software of VGS5250 Version Jan 1992. The ANALYSER WORK FUNCTION of this device was 4.51 eV.

The basic performance of this apparatus is as shown in the following table when the MgKα (1253.60 eV) is used as the excitation X-ray source and the Ag peak is 3d5 / 2 when measured at 400 W.

[0030] The measurement conditions are as follows. X-ray source is AlKα ray 14
It measured at 500 W using the excitation line of 86.60 eV.
The incident angle of X-ray is 60 ° from the sample normal, and the detector is arranged on the normal to the sample. The degree of vacuum is measured by MIL
LENIA SERIES IPGC1 was used. The degree of vacuum was not less than 5 × 10 ⁻¹⁰ mbar and not more than 1 × 10 ⁻⁶ mbar. The exhaust system is a Varian ion pump St.
arCell power unit 929-017
2 (220 l / s) and VGSPS7 SUBLIMA
By a titanium sublimation pump by TION PUMP CONTROLLER. Analysis area is about 1m
The area below mφ was measured. The XPS spectrum was measured separately for each binding energy. In wide scan,
1000 eV to 0 eV (BE), Cr 2p is 62
0 eV to 570 eV (BE), O 1s is 560 e
V-520 eV (BE), C 1s is 320 eV-
270 eV (BE), N 1s is 430 eV to 38.
It was measured at 0 eV (BE). For each measurement, measure in CAE mode, and use Pass E for wide scan.
energy 60eV, 1eV STEP, Scan is 2 times, otherwise, Pass Energy
y 50 eV, 0.1 eV STEP, Scan number of times was measured 5 times. The channel time was 100 ms in all cases. These measurement conditions were adopted in this measurement, but this is only an example, and in a general device, it is possible to perform measurement within a practically sufficient range in consideration of the charge amount and without significantly impairing resolution and sensitivity.

The elemental composition quantitative calculation procedure is as follows.
The background deduction is S in the software
Using the hillley type, to determine the background,
Careful consideration was given to the most natural peak shape so as not to be affected by satellites of the main peak. For the quantitative calculation, the composition ratio of each element was calculated from the peak area obtained by the measurement divided by the relative sensitivity coefficient based on the relative sensitivity coefficient of Scofield in the software.

As the composition ratio of the constituent elements, a value when the calculated composition ratio becomes substantially constant regardless of the etching time is adopted. The relative sensitivity coefficient of Scofield is 1.00 for carbon, 2.85 for oxygen, 7.60 for chromium, 1.77 for nitrogen, and 3.13 for argon.

The etching conditions are as follows. Ion gun EX05 Electron impact type ion gun with differential exhaust type two-stage electrostatic lens, 400XGUN as controller
Using the SUPPLY unit, PHYSICAL IM
A magnification of AGE UNIT was used as 1. 626 SAMPLE CURRENT M
ETER was used. Vacuum degree is 1 × 10 ^-7 mbar to 1 ×
In the range of 10 ⁻⁶ mbar, the sample current is −0.5 μA to −
Etching was performed in the range of about 1.0 μA. FILA
MENT current is 2.2A, EMISIONCURRENT
T is 5 to 10 mA, Source ENERGY is 3 to
It was 5 KV. Ar or Ne as etching gas
Was used. The etching time varied depending on the etching rate of the substrate, and etching and XPS spectrum measurement were alternately performed until the abundance ratio of the detected element was considered to be almost constant. Charge correction using an electron gun was not performed.

The above measurement conditions and etching conditions in the present invention are only one example, and generally, measurement can be performed with equivalent spectral quality as long as sensitivity and resolution are not impaired.

As described above, in the halftone phase shift photomask and the blank for a halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate has at least one layer containing a chromium compound as a main component. In the halftone phase shift photomask including the above, the composition ratio of chromium atoms and oxygen atoms in the layer mainly containing the chromium compound is in the range of 100: 100 to 300 by X-ray photoelectron spectroscopy. It is characterized by.

In this case, it is preferable that the layer containing a chromium compound as a main component contains carbon atoms in an amount of 0.5% or more with respect to the chromium atoms. At that time, it is desirable that the surface region within a depth of 30 Å from the film surface of the layer mainly containing a chromium compound contains more carbon atoms than other regions.

Further, in the layer containing a chromium compound as a main component, when the number of chromium atoms is 100, the total number of nitrogen atoms and oxygen atoms is 350 or less, the nitrogen atoms are contained, or the argon atoms and oxygen are contained. It is preferable that argon atoms are contained in a ratio of 350 or less in total with the atoms.

In the above, the layer containing a chromium compound as a main component does not change the refractive index obtained by the polarization analysis method with exposure light by 0.1 or more, and chromium, oxygen,
It may contain impurity atoms other than carbon, nitrogen and argon atoms.

Further, the layers constituting the halftone phase shift layer are formed on the transparent substrate so that the phase difference φ obtained by the following equation is nπ ± π / 3 radians (n is an odd number). Is desirable. Here, φ is a phase change that 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} is the k-th layer. The phase change occurring at the interface with the (k + 1) th layer, u _k and d _k are the refractive index and film thickness of the material forming the kth layer, and λ is the wavelength of the exposure light. However, the layer of k = 1 is a transparent substrate and k = m
The layer is air.

Furthermore, the layer constituting the halftone phase shift layer has a transmittance of 1 for the exposure light on the transparent substrate.
It is desirable that the film is formed to have a thickness of 50% to 50%.

[0041]

The halftone phase shift photomask and the blanks therefor according to the present invention have a simple structure, can shorten the plate making process, and can achieve the reduction of cost and the improvement of the yield. Since most of the mask manufacturing line can be used as it is, practical application becomes extremely easy.

[0042]

EXAMPLES Examples of halftone phase shift photomasks and blanks for halftone phase shift photomasks of the present invention will be described below. [Embodiment 1] An embodiment of a single-layer halftone phase shift photomask will be described with reference to the drawings for explaining the manufacturing process of FIG. As shown in FIG. 1 (a), a chromium compound film 802 having a thickness of about 50 nm is formed on a mirror-polished silicon wafer 801 by a sputtering method under the conditions as shown below, and is used for polarization analysis. A sample 807 was obtained.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium gas and flow rate: Carbon dioxide gas 70 sccm + nitrogen gas 3
0 sccm spatter pressure: 3 mTorr spatter current: 6 amps Next, a commercially available spectroscopic ellipsometer (ES-made by Sopra) is used.
4G), this sample 807 was used for mercury lamp i-line wavelength (365
When the refractive index u and the extinction coefficient k in (nm) are measured,
U = 2.580 and k = 0.374, respectively. This is described in M. Born, E .; Wolf "Princ"
When treated as a metal film shown on pages 628 to 632 of “iples of optics” and formed on high-purity synthetic quartz used as a photomask substrate, the film has a thickness of 365 nm.
The film thickness required to shift the phase of the transmitted light having the wavelength of 180 degrees by 180 degrees was 118 nm.

Therefore, as shown in FIG. 1B, a chromium compound film 804 of about 120 nm is formed on the highly-purified synthetic quartz substrate 803 that has been optically polished and well washed under the above-described film forming conditions.
When the film was formed, a single layer halftone phase shift photomask blank 808 of the present invention having a transmittance of light having a wavelength of 365 nm of about 15% was obtained.

Next, as shown in FIG. 1C, a desired resist pattern 805 containing an organic material as a main component is obtained on the blanks 808 by a conventional electron beam lithography method or photolithography method, and then, , Figure 1
As shown in (d), the semitransparent film 804 exposed from the resist pattern 805 is converted into CH ₂ Cl ₂ : O ₂ = 1:
The desired semi-transparent film pattern 806 was obtained by performing dry etching selectively by exposing to high-frequency plasma under a mixed gas of 2.5 and a pressure of 0.3 torr. Finally, the remaining resist is peeled off by a conventional method, and then, as shown in FIG.
A single-layer halftone phase shift photomask 809 of the present invention as shown in FIG.

This single-layer halftone phase shift photomask can be put to practical use in terms of dimensional accuracy of the removed portion, sectional shape, film thickness distribution, transmittance distribution, adhesion of the film to the substrate, etc. Met.

[Embodiment 2] An embodiment of a multi-layer halftone phase shift photomask will be described with reference to the drawings for explaining the manufacturing process of FIG. In the same manner as in Example 1,
A polarization analysis sample was prepared in advance, the refractive index and the extinction coefficient were measured, and the film thickness necessary to shift the light having a wavelength of 365 nm by 180 degrees was calculated from the measurement, and as shown in FIG. When a chromium compound 902 having a calculated film thickness was actually formed on a high-purity synthetic quartz substrate 901 under the following conditions, the transmittance of light having a wavelength of 365 nm was about 20%.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium gas and flow rate: Carbon dioxide gas 20 sccm + Nitrogen gas 8
0 sccm Sputter pressure: 3 mTorr Sputter current: 6 ampere Next, a film of metal chromium 903 of about 10 nm was formed on this chromium compound 902 under the following conditions.
A multi-layer halftone phase shift photomask blank 906 of the present invention having a transmittance of light of nm of about 12% was obtained.

Deposition apparatus: Planar type DC magnetron sputtering apparatus Target: Metal chromium gas and flow rate: Argon gas 100 sccm Sputter pressure: 3 mTorr Sputter current: 6 amps Next, as shown in FIG.
A desired resist pattern 904 containing an organic material as a main component is obtained by a conventional electron beam lithography method or a photolithography method, and then, as shown in FIG. 2C, the half exposed from the resist pattern 904. By exposing the transparent film to a high-frequency plasma under the condition of a mixed gas of CH ₂ Cl ₂ : O ₂ = 1: 2.5 and a pressure of 0.3 Torr, dry etching is selectively performed at a stroke to obtain a desired half. A transparent film pattern 905 was obtained. Finally, the remaining resist is peeled off by a conventional method, and the multilayer halftone phase shift photomask 907 of the present invention as shown in FIG.
Got

Since the layer 902 mainly containing a chromium compound and the metallic chromium film 903 have the same chromium atoms as the base material, the etching characteristics are almost the same, and therefore the pattern processing characteristics of the multilayer halftone phase shift photomask 907 are as follows. This is almost the same as the single layer halftone phase shift photomask as shown in Example 1.

This multilayer halftone phase shift photomask also has dimensional accuracy, cross-sectional shape, film thickness distribution, transmittance distribution,
The adhesion of the film to the substrate and the like were all practical.

[0052]

As is apparent from the above description, the halftone phase shift photomask and the blanks therefor according to the present invention have a simple structure, can shorten the plate making process, and can reduce the cost and improve the yield. In addition to being able to do so, most of the conventional chrome photomask manufacturing lines can be used as they are, so that practical application becomes extremely easy.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a manufacturing process of a single-layer halftone phase shift photomask according to a first embodiment of the present invention.

FIG. 2 is a drawing for explaining the manufacturing process of the multilayer halftone phase shift photomask of Example 2.

FIG. 3 is a diagram showing the principle of halftone phase shift lithography.

FIG. 4 is a diagram showing a conventional method.

FIG. 5 is a diagram showing transmittance when a chromium compound film formed by changing the flow rate ratio of carbon dioxide gas / nitrogen gas undergoes phase inversion.

FIG. 6 is a diagram showing the results of composition analysis of the film of FIG. 5 by X-ray photoelectron spectroscopy.

FIG. 7 is a diagram showing how the amount of film loss due to chemical immersion differs depending on the oxygen source gas.

FIG. 8 is a diagram showing a composition analysis result by X-ray photoelectron spectroscopy of a chromium compound film formed by changing a flow rate ratio of oxygen gas / nitrogen gas.

FIG. 9 is a view showing a profile of a composition in the depth direction, which is obtained by X-ray photoelectron spectroscopy.

[Explanation of symbols]

101, 201 ... Substrate 102 ... Phase inversion semi-transparent film 103 and 203 ... Incident light 202 ... 100% light-shielding film 801 ... Silicon wafer 802 ... Chromium compound film 803 ... High-purity synthetic quartz substrate 804 ... Chromium compound film (semi-transparent film) ) 805 ... Resist pattern 806 ... Semi-transparent film pattern 807 ... Polarization analysis sample 808 ... Single layer halftone phase shift photomask blanks 809 ... Single layer halftone phase shift photomask 901 ... High purity synthetic quartz substrate 902 ... Chromium compound 903 ... Metal chromium 904 ... Resist pattern 905 ... Semi-transparent film pattern 906 ... Multilayer halftone phase shift photomask blanks 907 ... Multilayer halftone phase shift photomask

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Mohri 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. (72) Inventor Masayasu Takahashi 1-chome, Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 Dai Nippon Printing Co., Ltd. (72) Hiroyuki Miyashita 1-chome, Ichigaya Kaga-cho, Shinjuku-ku, Tokyo 1-1 No. 1 Dai Nippon Printing Co., Ltd. (72) Inventor, Yukio Iimura Ichi-kaya Ichiya, Shinjuku-ku, Tokyo 1st-1st Dai Nippon Printing Co., Ltd.

Claims (16)

[Claims] 1. A halftone phase shift photomask in which a halftone phase shift layer on a transparent substrate includes at least one layer mainly containing a chromium compound, wherein a chromium atom and an oxygen atom of the layer mainly containing the chromium compound are provided. The compositional ratio of and is 100: 10 by X-ray photoelectron spectroscopy.
A halftone phase shift photomask characterized by being included in the range of 0 to 300. 2. The layer according to claim 1, wherein the layer containing the chromium compound as a main component has 0.5 carbon atoms relative to the chromium atoms.
% Or more of the halftone phase shift photomask. 3. The halftone according to claim 2, wherein the surface region of the layer containing the chromium compound as a main component within a depth of 30 Å contains more carbon atoms than other regions. Phase shift photomask. 4. The layer according to claim 1, wherein the layer containing the chromium compound as a main component contains nitrogen atoms at a ratio of 350 or less with respect to 100 chromium atoms. A halftone phase shift photomask characterized by the following. 5. The layer according to claim 1, wherein, in the layer containing the chromium compound as a main component, when the number of chromium atoms is 100, the total of argon atoms and oxygen atoms is 350 or less,
A halftone phase shift photomask, which is characterized by containing argon atoms. 6. The method according to any one of claims 1 to 5,
The layer containing the chromium compound as a main component contains impurity atoms other than chromium, oxygen, carbon, nitrogen, and argon atoms within a range that does not change the refractive index obtained by the deflection analysis method with exposure light by 0.1 or more. A halftone phase shift photomask. 7. The method according to any one of claims 1 to 6,
A layer comprising a halftone phase shift layer is formed on a transparent substrate such that a phase difference φ obtained by the following equation is nπ ± π / 3 radians (n is an odd number). Tone phase shift photomask. Here, φ is a phase change that light vertically transmitted through a photomask in which a multilayer film of (m-2) layers is formed 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 th layer, u _k and d _k are the refractive index and film thickness of the material forming the k th layer, and λ is the wavelength of the exposure light. However, the layer of k = 1 is the transparent substrate, and the layer of k = m is air. 8. The method according to claim 1, wherein
A halftone phase shift photomask, wherein a layer constituting the halftone phase shift layer is formed on the transparent substrate with a film thickness such that the transmittance for exposure light is 1 to 50%. 9. A blank for a halftone phase shift photomask in which a halftone phase shift layer on a transparent substrate includes at least one layer mainly containing a chromium compound, and a chromium atom of the layer mainly containing the chromium compound. The composition ratio with oxygen atoms is determined by X-ray photoelectron spectroscopy.
Blanks for halftone phase shift photomasks, characterized in that they are contained in the range of 100 to 100 to 300. 10. The layer according to claim 9, wherein the layer mainly containing the chromium compound has carbon atoms of 0.
Blanks for halftone phase shift photomasks, characterized by containing 5% or more. 11. The halftone according to claim 10, wherein the surface region within a depth of 30 Å from the film surface of the layer mainly containing the chromium compound contains more carbon atoms than other regions. Blanks for phase shift photomasks. 12. The layer according to claim 9, wherein the number of chromium atoms is 100 in the layer containing the chromium compound as a main component,
A blank for a halftone phase shift photomask, wherein nitrogen atoms are contained at a ratio of 350 or less in total of nitrogen atoms and oxygen atoms. 13. The layer according to claim 9, wherein the number of chromium atoms is 100 in the layer containing the chromium compound as a main component,
A blank for a halftone phase shift photomask, comprising argon atoms in a proportion of 350 or less in total of argon atoms and oxygen atoms. 14. The chromium according to claim 9, wherein the layer containing the chromium compound as a main component does not change the refractive index obtained by a polarization analysis method with exposure light by 0.1 or more. Blanks for halftone phase shift photomasks, which contain impurity atoms other than oxygen, carbon, nitrogen and argon atoms. 15. The layer constituting the halftone phase shift layer according to claim 9, wherein the phase difference φ obtained by the following formula on a transparent substrate is nπ ± π /
A blank for a halftone phase shift photomask, which is formed so as to have 3 radians (n is an odd number). Here, φ is a phase change that light vertically transmitted through a photomask in which a multilayer film of (m-2) layers is formed 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 th layer, u _k and d _k are the refractive index and film thickness of the material forming the k th layer, and λ is the wavelength of the exposure light. However, the layer of k = 1 is the transparent substrate, and the layer of k = m is air. 16. The film forming the halftone phase shift layer according to claim 9, wherein the layer forming the halftone phase shift layer has a film thickness of 1 to 50% for exposure light on the transparent substrate. A blank for a halftone phase shift photomask, which is formed.