JPH06267830A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE:To provide a forming method of an X-ray mask wherein the fine working of an X-ray absorber pattern is easily possible. CONSTITUTION:Resist solution wherein 1.0g of linear poly(siloxane) which has C-O-Si bond for each monometric unit and 10mg of triphenyl trifluoro methanesulfonate are dissolved is spin-coated on a W film 34 of 1.0mum in thickness which is formed on a BN film 30 via a Ti film 36. A resist film 38 of 0.3mum in thickness is formed by baking at 80 deg.C for 1 minute, and selectively irradiated with an electron beam, under the condition that the acceleration voltage is 20kV and the dose is 5mum/cm<2>. After baking at 120 deg.C for 2 minutes, development is performed. Thus an oxide film pattern 40 is formed. Next SF6 is introduced, and the W mask 34 is etched by applying the oxide film pattern 40 to an etching mask. Thereby an X-ray absorber pattern 42 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray mask manufacturing method. In particular, it relates to a method of etching a metal film for an X-ray absorber.

[0002]

2. Description of the Related Art Conventionally, with the progress of higher integration of semiconductor devices such as LSI, the resolution of photolithography used in the manufacture of semiconductor devices has become finer, for example, from sub-half micron to quarter micron. Has been needed. However, it is difficult to achieve such a fine resolution while securing a practical process margin.

Therefore, as a method for renewing the existing lithography method, a unity-exposure method using synchrotron radiation (SOR) has been proposed. The synchrotron radiation used for lithography is a soft X-ray with extremely good parallelism and, in addition, has a higher intensity than that obtained by another method, for example, an X-ray obtained from a xenon lamp.

In the equal-magnification exposure method using synchrotron radiation, an X-ray absorber pattern having the same size as the substrate processing size is required. Therefore, high-precision processing of the X-ray absorber pattern of the X-ray mask is one of the most important techniques in the same-magnification exposure method using SOR.

When an X-ray absorber pattern is formed using a conventional resist as an etching pattern, the resist and X
Since the etching selection ratio with respect to the line absorber cannot be made large, it is necessary to increase the thickness of the photoresist. As a result, the aspect ratio of the resist pattern becomes high.

Moreover, since X-rays have a strong substance penetrating power,
In order to increase the contrast of the line mask, it is necessary to make the X-ray absorber thick. The X-ray absorber currently has a thickness of about 0.5 to 1.0 μm, although it depends on the material. On the other hand, the pattern resolution required in the 1 × exposure method reaches the level of 0.2 μm. For this reason,
The aspect ratio of the X-ray mask becomes extremely high.

Therefore, according to the conventional method of using a photoresist as an etching mask as in the conventional example, a photoresist pattern having a high aspect ratio is formed, and the photoresist pattern is further used as an etching mask. The aspect ratio X-ray absorber pattern must be formed by etching. For this reason, it is difficult to form a finer wiring pattern on the submicron level or on the half submicron level.

Therefore, one example of a method of manufacturing an X-ray mask using an oxide film pattern as an etching mask, which can have a large etching selection ratio with respect to the X-ray absorber, is described in a document: "Extended Abstracts of the 16th (1984). internat
ional) Conference on Devices and Materials, Kobe, 198
4, pp.23-26 ”.

A conventional example of a method for manufacturing an X-ray mask using an oxide film pattern as an etching mask will be briefly described below with reference to the drawings.

FIGS. 3A to 3D are process diagrams for explaining a conventional example of a method for manufacturing an X-ray mask.

First, a tantalum (Ta) film 14, an oxide film 16 and a resist film 18 are sequentially laminated on a SiN film 12 which transmits X-rays and is formed on a Si substrate 10 (FIG. 3A).

Next, the resist film 18 is coated with EB (electron beam).
Pattern) by using lithography to form a resist pattern 20 (FIG. 3B).

Next, the oxide film 16 is etched using the resist pattern 20 as an etching mask,
An oxide film pattern 22 is formed (FIG. 3C).

Next, the Ta film 14 is etched by using the oxide film pattern 22 as an etching mask to form a tantalum X-ray absorber pattern 24 (FIG. 3D).

After forming the X-ray absorber pattern 24, S
The i-substrate 10 is back-etched to form an X-ray mask.
In this way, the oxide film pattern 22 is used as Ta that becomes an X-ray absorber.
When used as an etching mask for the film 14, the aspect ratio of the etching mask can be made smaller than that when a resist is used as an etching mask.

[0016]

However, in the conventional method using the oxide film pattern as an etching mask, it is necessary to transfer the resist pattern to the oxide film by etching. This not only increases the number of steps, but also
Due to the superposition of the dimension conversion error at the time of transfer, the etching accuracy may decrease.

In the meantime, the inventor of the present application, in the document: Japanese Patent Application No. 4-017588, discloses a silicone resin in which an alkoxy group is bonded to the side chain of Si (silicon) of polysiloxane and acid generation. A radiation-sensitive resin composition comprising an agent is proposed. In this resin composition, when a functional group having a C—O bond such as t-butoxy group is bonded to Si as shown in the following formula (3),
The C-O bond is cleaved by the acid to remove the carbon component from the polymer. Therefore, the inventor of this application continued the tests and studies and found that by utilizing the reaction of breaking the C—O bond, the etching selection with the X-ray absorber was performed without transferring from the resist. It was concluded that a high ratio etching pattern can be formed.

[0018]

[Chemical 2]

Therefore, an object of the present invention is to provide a method of forming an X-ray mask which enables easy fine processing of an X-ray absorber pattern.

[0020]

To achieve this object, according to the pattern forming method of the present invention, an X-ray permeable membrane and an X-ray absorbing metal provided on the membrane are provided. In forming a patterned X-ray mask having a body as a part of the structure, X is formed on the membrane.
A step of forming a metal film for a line absorber, and a silicon or linear silicone having a C--O--Si bond for each monomer unit on the metal film. A step of forming a thin film of a radiation-sensitive resin composition containing a resin and an acid generator that decomposes to generate an acid by the action of radiation, a step of selectively irradiating the thin film with an electron beam, and an electron beam After heating the thin film irradiated with rays, the thin film is developed to form an oxide film pattern, and the oxide film pattern is used as an etching mask to etch the metal film. To do.

Preferably, the linear poly (siloxane) is represented by the following formula (1), and the ladder-shaped poly (siloxane) is represented by the following formula (2): ) And the functional group R in the formula (2) is hydrogen, tert-butyl, 1-
At least one functional group selected from the functional group group of phenethyl, 1-methyl-1-phenethyl, cyclohexen-2-yl, and t-butoxycarbonyl is preferable.

[0022]

[Chemical 1]

Preferably, the acid generator is an aromatic compound having at least one trichloromethyl group,
It is preferable to use one kind of acid generator selected from the group of sulfonium salts, iodonium salts or p-toluenesulfonic acid esters.

The heating temperature is preferably 60 ° C. or higher. This is because the heating time can be shortened.

[0025]

[Function] It is obvious that the oxide film itself has no photosensitivity, but if a radiation-sensitive composition that can be converted into an oxide film by photolithography is used, etching by transfer can be performed with only one photolithography. An etching pattern of an oxide film having a large etching selection ratio with respect to the X-ray absorber can be easily formed without fear of deterioration of accuracy. As such a radiation-sensitive composition, the inventor of the present application discloses a silicone resin represented by the following formulas (1) and (2) in the document: "Japanese Patent Application No. 4-017588". A radiation-sensitive resin composition (hereinafter also referred to as a composition) comprising a trace amount of an acid generator that decomposes to generate an acid by the action of light, an electron beam, an X-ray or an ion beam is proposed. When this composition is irradiated with an electron beam and then heat-treated, an elimination reaction for cleaving the C—O bond occurs as shown in the following formula (3). In the film formed in this manner, a trace amount of decomposed products of the acid generator remains as an organic component, but it can be considered that the film used in etching is substantially an oxide film.

[0026]

[Chemical 1]

[0027]

[Chemical 2]

[0028]

Embodiments of the method of manufacturing an X-ray mask according to the present invention will be described below with reference to the drawings. Materials used and their amounts mentioned in the following description, processing time, processing temperature,
Numerical conditions such as film thickness are only suitable examples within the scope of the present invention. Therefore, it is obvious that the present invention is not limited to the following examples. Further, the drawings referred to below only schematically show the sizes, shapes and arrangement relationships of the respective constituents to the extent that the present invention can be understood. Therefore, it is obvious that the present invention is not limited to this embodiment.

First Embodiment FIGS. 1A to 1D are process drawings for explaining a first embodiment of the method for manufacturing an X-ray mask of the present invention. The figure is
The hatching and the like showing the cross section are partially omitted.

First, a BN (boron nitride) film 30 is formed as a membrane that transmits X-rays. The double-sided polished (100) Si substrate 32 is placed in the molding reaction chamber of the LPCVD method and heated to a temperature of 400 ° C. Next, B ₂ H ₆ (diluted with 6% H ₂ ) and NH ₃ were introduced into the chamber, the pressure was 360 Torr, the partial pressure of NH ₃ /
The BN film 30 is formed under the condition that the partial pressure of B ₂ H ₆ is 0.6. When the film thickness of the BN film 30 was measured by an ellipsometer, it was 5 μm.

Next, a tungsten (W) film 34 is formed on the BN film 30 as a metal film for the X-ray absorber. W film 3
Prior to the formation of 4, the titanium (Ti) film 3 is used as an adhesion film.
6 is formed. First, the Si substrate 3 on which the BN film 34 is formed
2 is installed in a sputtering film forming apparatus, Ti is used as a target, Ar is used as a sputtering gas, power is 1 kW, and pressure is 3 mTo.
BN with Ti under the condition of rr and substrate bias voltage of 350V
A Ti film is formed by depositing on the film 30. The thickness of the formed Ti film 36 was 500 A ° (A ° is a symbol representing angstrom). Next, replace the target with W,
W is deposited on the Ti film under the same conditions as the film 36 to form the W film 34. The formed W film 34 has a thickness of 1.
It was 0 μm.

Then, on the W film 34, the silicone resin made of linear or ladder poly (siloxane) having a C--O--Si bond for each monomer unit is acted on by the action of radiation. A thin film of a radiation-sensitive resin composition containing an acid generator that decomposes to generate an acid is formed. In the first example, 1.0 g of poly (siloxane) represented by the following formula (3) and 10 mg of triphenyltrifluoromethanesulfonate were dissolved in 9.0 ml of methyl isobutyl ketone, and this was filtered through a 0.2 μm filter. To prepare a resist solution. Next, the adjusted resist solution is applied on the W film 34 by 250
After spin coating at 0 rpm, baking is performed at a temperature of 80 ° C. for 1 minute to form a resist film 38 having a thickness of 0.3 μm as the above-mentioned thin film ((A) of FIG. 1).

[0033]

[Chemical 3]

Next, using an electron beam exposure apparatus, the lower layer voltage 2
Under the conditions of 0 kV and an exposure amount of 5 μC / cm ² , the resist film 28 is selectively irradiated with an electron beam ((B) of FIG. 1).

Next, the resist film 28 irradiated with the electron beam was baked on a hot plate at a temperature of 120 ° C. for 2 minutes, heated, developed in isoamyl acetate for 30 seconds, and rinsed with cyclohexane for 30 seconds. The oxide film pattern.
Forming a film 40 (FIG. 1 (C)). Oxide film pattern 4
When the pattern of the sample in which 0 was formed was measured with a SEM length measuring machine, it was confirmed that a line-and-space pattern of 0.2 μm was resolved. Further, according to the characteristic curve obtained by examining the characteristics of the exposure amount and the remaining film ratio before the formation of the oxide film pattern 40 of the first embodiment, the exposure amount was 5 μC / c.
The residual film rate at m ² is 60%. Therefore, the film thickness of the oxide film pattern 40 formed in this embodiment is the same as the resist film 3
8 is 0.18 μm, which is 60% of the film thickness of 0.3 μm.

Next, in the first embodiment, the oxide film pattern 4 is used.
The sample formed with is attached to the cathode of a parallel plate type dry etcher, and the sample is cooled to -20 ° C. Then S
F ₆ gas is introduced at a flow rate of 20 SCCM and the pressure is 5 mTorr
Under the conditions of r, input power 20 W, and self-bias 150 V, the oxide film pattern 40 is used as an etching mask to etch the W film 34 to form an X-ray absorber pattern 42 (FIG. 1 (D)). This etching is
The etching was stopped when 25% was over-etched, and the cross section of the sample was observed by SEM.
The line and space pattern of the taper angle 85 °
It was confirmed that they were formed in. The remaining film thickness of the oxide film pattern used as the etching mask is 0.0
It was 8 μm, and it was found that it was etched by about 0.1 μm. Therefore, the etching selectivity is 1.0 μm.
It was found that /0.1 μm = about 10.

Second Embodiment FIGS. 2A to 2D are process drawings for explaining the first embodiment of the method for manufacturing an X-ray mask of the present invention. The figure is
The hatching and the like showing the cross section are partially omitted.

In the second embodiment, a tantalum (Ta) film 44 having a thickness difference of 1.0 μm is formed on the BN film 30 and the Ti film 36 formed on the Si substrate 32 under the same conditions as in the first embodiment. The W film 34 is formed under the same conditions as the formation. Next, a resist film 38 is formed on the Ta film 44 under the same conditions as in the first embodiment ((A) of FIG. 2).

Next, using an electron beam exposure apparatus, the lower layer voltage 2
Under the conditions of 0 kV and an exposure amount of 4.5 μC / cm ² , the resist film 38 is selectively irradiated with an electron beam ((B) of FIG. 2). Next, the resist film 38 irradiated with the electron beam is heated and developed under the same conditions as in the first embodiment to form an oxide film pattern 40 ((C) in FIG. 2). Oxide film pattern
When the pattern of the sample on which the pattern 40 was formed was measured with an SEM length measuring machine, it was confirmed that a 0.2 μm line-and-space pattern was resolved. Further, according to the characteristic curve obtained by examining the characteristics of the exposure amount and the residual film ratio prior to the formation of the oxide film pattern 40 of the second embodiment, the exposure amount was 5 μC.
The residual film ratio at 60 cm ² / cm ² is 60%. Therefore, the film thickness of the oxide film pattern 40 formed in this embodiment is 0.18 μm, which is 60% of the film thickness 0.3 μm of the resist film 38.

Next, in the second embodiment, the oxide film pattern 4 is used.
The sample on which 0 is formed is mounted on the cathode of a parallel plate type dry etcher, and the sample is cooled to 0 ° C. Next, CBr
F ₃ gas is introduced at a flow rate of 15 SCCM and the pressure is 5 mTorr
Under the conditions of r, input power 20 W, and self-bias 150 V, the oxide film pattern 40 was used as an etching mask and Ta was used.
The film 44 is etched to form an X-ray absorber pattern.
Forming a film 46 ((D) of FIG. 2). In this etching, the etching was stopped when 25% was over-etched. When the cross section of the sample was observed by SEM, it was 0.
It was confirmed that a line-and-space pattern of 2 μm was formed with a taper angle of 85 °. Further, it was found that the remaining film thickness of the oxide film pattern 40 used as the etching mask was 0.06 μm, which was etched by about 0.12 μm. On the other hand, since the film thickness of the Ta film 44 was 1.0 μm, the etching selection ratio was 1.0.
It was found that μm / 0.12 μm = 8.3 or more.

In each of the above-described embodiments, the present invention has been described with reference to an example in which a specific material is used and formed under specific conditions, but the present invention can be modified and modified in many ways. For example, in the above-described embodiments, an example in which tungsten (W) or tantalum (Ta) is used as the X-ray absorber has been described, but in the present invention, for example, tungsten nitride (BN) may be used.

[0042]

According to the method of manufacturing an X-ray mask of the present invention, since a radiation-sensitive composition that can be converted into an oxide film by photolithography is used, a pattern by etching can be formed by only one photolithography. It is possible to form an etching pattern of the oxide film without performing transfer to the substrate. As a result, fine processing of the X-ray absorber pattern can be easily performed.

Further, the method of the present invention is suitable for use in, for example, an equal-magnification exposure method using SOR.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining a first embodiment of a method for manufacturing an X-ray mask of the present invention.

FIG. 2 is a process drawing for explaining a second embodiment of the X-ray mask manufacturing method of the present invention.

FIG. 3 is a process drawing for explaining a conventional method for manufacturing an X-ray mask.

[Explanation of symbols]

 10: Si substrate 12: SiN film 14: Tantalum (Ta) film 16: Oxide film 18: Resist film 20: Resist pattern 22: Oxide film pattern 24: X-ray absorber pattern 30: Boron nitride ( BN) film 32: Si substrate 34: Tungsten (W) film 36, 36a: Titanium (Ti) film 38: Resist film 40: Oxide film pattern 42: X-ray absorber pattern 44: Tantalum (Ta) film 46: X-ray absorber pattern

Claims (3)

[Claims] 1. When forming a patterned X-ray mask, which comprises an X-ray permeable membrane and an X-ray absorbing metal absorber provided thereon as a part of the structure, said membrane A step of forming a metal film for an X-ray absorber thereon, and a linear or ladder-shaped poly (siloxane) having a C—O—Si bond for each monomer unit on the metal film. A step of forming a thin film of a radiation-sensitive resin composition containing a silicone resin and an acid generator that decomposes to generate an acid by the action of radiation, and a step of selectively irradiating the thin film with an electron beam A step of heating the thin film irradiated with an electron beam and then developing it to form an oxide film pattern; and a step of etching the metal film using the oxide film pattern as an etching mask. X-rays characterized by containing Method of manufacturing a disk. 2. The X-ray mask forming method according to claim 1, wherein the linear poly (siloxane) is represented by the following formula (1), and the ladder-shaped poly (siloxane) is Of the functional group R in the formulas (1) and (2)
Is hydrogen, tert-butyl, 1-phenethyl, 1-methyl-
1-phenethyl, cyclohexen-2-yl and t-
A pattern characterized by being at least one kind of functional group selected from the group of butoxycarbonyl functional groups.
Forming method. [Chemical 1] 3. The method of manufacturing an X-ray mask according to claim 1, wherein the acid generator is an aromatic compound having at least one trichloromethyl group, a sulfonium salt, an iodonium salt, or p-toluene sulfone. A method for producing an X-ray mask, which comprises using one kind of acid generator selected from a group of acid esters.