WO2009123167A1

WO2009123167A1 - Photomask blank and method for manufacturing the same

Info

Publication number: WO2009123167A1
Application number: PCT/JP2009/056604
Authority: WO
Inventors: 浩之岩下; 博明宍戸; 淳志小湊; 雅広橋本
Original assignee: Hoya株式会社
Priority date: 2008-03-31
Filing date: 2009-03-31
Publication date: 2009-10-08
Also published as: TW200949430A; JPWO2009123167A1; KR20100127864A

Abstract

Disclosed is a photomask blank having a multiple-layered light-shield film atop a translucent substrate, the outermost surface layer of said light-shield film comprising CrO, CrON, CrN, CrOC or CrOCN, and the surface of the light-shield film having an atomic density of 9x10²²atms/cm³ to 14x10²²atms/cm³.

Description

Photomask blank and manufacturing method thereof

The present invention relates to a photomask blank, a photomask, and a method for manufacturing a photomask blank.

In general, in the manufacturing process of high-density semiconductor integrated circuits such as LSI, color filters for CCD (Charge Coupled Device) and LCD (Liquid Crystal Display), magnetic heads, etc., microfabrication is performed using photolithography technology using a photomask. Has been done.
For this microfabrication, light shielding of a photomask blank in which a light shielding film generally made of a metal thin film such as a chromium film is formed on a light transmitting substrate such as quartz glass or aluminosilicate glass by sputtering or vacuum evaporation. A photomask in which a film is formed in a predetermined pattern is used.

In the photomask using this photomask blank, an exposure process in which a desired pattern exposure is performed on a resist film formed on the photomask blank, and a desired pattern exposure is performed on the resist film formed on the photomask blank. After the application, the developer is supplied to dissolve the resist film soluble part of the developer, forming a resist pattern, and using the resulting resist pattern as a mask, mixing cerium ammonium nitrate and perchloric acid Etching such as wet etching using an aqueous etchant or dry etching using chlorine gas removes the exposed portion of the light-shielding film on which the resist pattern is not formed, and places a predetermined mask pattern on the translucent substrate. Etching process to be formed and stripping off remaining resist pattern It is manufactured through a peeling removal process.

Generally, this light shielding film made of a chromium film or the like has a high light reflectivity, and light reflected by a semiconductor substrate as an object to be exposed is reflected by a photomask through a projection lens and returns to the semiconductor substrate again. Occurs. As a result, the exposure light is irradiated to an unplanned part. In order to prevent such a phenomenon, an antireflection layer is usually formed on the surface of the light shielding film of the photomask blank.

∙ Photomasks are cleaned during production or use. In the washing, an acid such as sulfuric acid is often used (for example, JP-A-2003-248298 (Patent Document 1)). However, when the photomask is washed with sulfuric acid, sulfuric acid or sulfate ions remaining after washing react with the high-energy exposure light and precipitate as ammonium sulfide, which causes fogging of the photomask. In recent years, the shortening of the wavelength from the KrF excimer laser (wavelength 248 nm) to the ArF excimer laser (wavelength 193 nm) has progressed, and the exposure light has increased in energy. The problem of occurrence has become prominent.

Therefore, in order to prevent fogging due to such acid cleaning, ozone cleaning with ozone water or UV ozone has recently started to be used at the time of manufacturing a photomask blank or after pattern formation.

However, ozone cleaning may dissolve or degrade the light shielding film, thereby changing the optical characteristics (reflectance, etc.) of the light shielding film or the antireflection film.
JP 2003-248298 A

Under the above-described circumstances, for example, photomask blanks and photomasks whose optical characteristics (reflectance, etc.) and pattern line width are hardly changed by ozone cleaning are required.

The present inventors have found a light-shielding film that has a small amount of change in reflectance even when contacted with ozone water, and have completed the present invention based on this finding. The present invention provides the following photomask blank, photomask and the like.

[1] A photomask blank having a light-shielding film on a light-transmitting substrate,
A photomask blank, in which the amount of change in reflectance with exposure light of 193 nm to 257 nm is less than 2.5% when indirectly liquid in 50 ppm ozone water for 60 minutes.
[2] A photomask blank having a light shielding film on a translucent substrate,
A photomask blank in which the amount of change in reflectance with exposure light of 257 nm to 488 nm is 8% or less when indirectly liquid in 50 ppm ozone water for 60 minutes.
[3] The photomask blank according to [1] or [2], wherein the amount of change in film thickness when the liquid is indirectly liquid in 50 ppm ozone water for 60 minutes is 5 nm or less.
[4] The photomask blank according to any one of [1] to [3], wherein the amount of change in reflectance with exposure light of 193 nm to 200 nm is 2% or less when indirect liquid is applied to 50 ppm ozone water for 60 minutes. .
[5] The photomask blank according to any one of [1] to [4], wherein the amount of change in reflectance in exposure light of 257 nm to 488 nm when indirect liquid is applied to 50 ppm ozone water for 60 minutes is 6% or less. .
[6] The photomask blank according to any one of [1] to [5], wherein the amount of change in the film thickness when the liquid is indirectly liquid in 50 ppm ozone water for 60 minutes is 1 nm or less.
[7] The photomask blank according to any one of [1] to [6], wherein the light shielding film is composed of a plurality of layers.
[8] The photomask blank according to [7], wherein the thickness of the surface layer provided on the most surface side among the plurality of layers is 3 to 30 nm.
Further, the surface roughness Ra of the surface layer is preferably 0.5 nm or less.
[9] The photomask blank according to [8], wherein the surface layer is made of CrO, CrON, CrOC, CrN, or CrOCN.

[10] The light shielding film includes a surface layer and a light shielding layer,
The surface layer has a Cr content of 50% or less, an O / Cr atomic ratio O / Cr of 0.5 or more, a C / Cr atomic ratio C / Cr of 0.1 or more, N and The atomic ratio N / Cr with Cr is 0.3 or more,
The photomask blank according to any one of [7] to [9], wherein the light shielding layer has a Cr content of 50% or more.
[11] The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of [7] to [10], wherein the light shielding layer is made of CrO, CrON, CrC, CrCN, CrOC, CrN, or CrOCN.
[12] The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of [7] to [9], wherein the light shielding layer contains a transition metal and Si.
[13] The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of [7] to [9], wherein the light shielding layer contains Ta.
[14] The photomask blank according to any one of [1] to [13], further including a phase shifter film between the translucent substrate and the light shielding film.
[15] The photomask blank according to any one of [1] to [14], which is used for a photomask to be treated with ozone.

[16] The photomask blank according to any one of [1] to [15], wherein an atomic number density of a surface portion of the light shielding film is 9 × 10 ²² to 14 × 10 ²² atms / cm ³ .
In the present specification, the “surface portion” means a portion within 30 nm (preferably within 5 nm) from the surface.
[17] The photomask blank according to any one of [1] to [15], wherein the surface portion has an atomic number density of 10 × 10 ²² to 13 × 10 ²² atms / cm ³ .
[18] A photomask obtained by patterning the photomask blank according to any one of [1] to [17] by a lithography method.

The optical characteristics (reflectance, etc.) of the photomask blank and the photomask light-shielding film according to a preferred embodiment of the present invention are not easily changed by ozone cleaning when the photomask is manufactured or used. The photomask blank and the light shielding film of the photomask according to a preferred embodiment of the present invention are less likely to decrease in film thickness by ozone cleaning during manufacturing or use of the photomask. In addition, the photomask blank and the antireflection layer of the photomask according to a preferred embodiment of the present invention have strong chemical resistance against ozone.

It is a schematic diagram of the photomask blank which has a light shielding film of a multilayer structure. 1 is a schematic diagram of a photomask blank manufactured in Example 1. FIG. 6 is a schematic diagram of a photomask blank manufactured in Example 2. FIG. It is a reflection spectrum in Example 1 before and after the ozone water contact. It is a reflection spectrum in Example 2 before and after the ozone water contact. It is a reflection spectrum in Example 3 before and behind ozone water contact.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface layer 2 Light-shielding layer 3 Back surface antireflection layer 4 Surface antireflection layer 5 Phase shifter film 10 Translucent substrate

1 Photomask Blank In the photomask blank of the present invention, the light shielding film may be provided directly on the light transmissive substrate, or another film such as a phase shifter film is provided between the light shielding film and the light transmissive substrate. May be. The photomask blank of the present invention includes a photomask blank on which a resist film is formed and a photomask blank on which no resist film is formed.

1.1 Translucent substrate The translucent substrate is not particularly limited as long as it is a translucent substrate. However, a quartz glass substrate, an aluminosilicate glass substrate, a calcium fluoride substrate, a magnesium fluoride substrate, or the like can be used. . Among these, a quartz glass substrate is preferable because it has high flatness and smoothness, and when pattern transfer onto a semiconductor substrate using a photomask is performed, transfer pattern distortion hardly occurs and high-precision pattern transfer can be performed.

1.2 Light-shielding film The light-shielding film of the photomask blank of the present invention may have a multilayer structure composed of a plurality of layers or a single-layer structure composed of one layer.

1.2.1 Multilayer Light-shielding Film As a photomask blank having a multilayer light-shielding film, an example in which the light-shielding film is composed of three layers as shown in FIG. When the light-shielding film is composed of three layers, in this specification, the surface layer 1, the light-shielding layer 2, and the back-surface antireflection layer 3 are sequentially formed from the layer formed on the most surface side in the light-shielding film. Here, in the photomask blank in which the light shielding film shown in FIG. 1 is composed of three layers, the surface layer 1 preferably has an antireflection function.
As shown in (2) of FIG. 1, the light shielding film is composed of four layers, and in order from the outermost surface, the surface layer 1, the front surface antireflection layer 2, the light shielding layer 3, and the back surface antireflection layer 4 are another embodiment. It can also be a photomask blank.
In this case, the surface layer 1 may have an etching mask function. For example, when the front-surface antireflection layer 2, the light-shielding layer 3, and the back-surface antireflection layer 4 are films made of a Cr-based material, the etching mask layer containing a Si-based material that is resistant to chlorine-based etching of the surface layer 1 It is preferable that When the front-surface antireflection layer 2, the light-shielding layer 3, and the back-surface antireflection layer 4 are films containing a Si-based material, the surface layer 1 is an etching mask layer made of a Cr-based material having resistance to fluorine-based etching It is preferable that
Moreover, in (1) and (2) of FIG. 1, the back surface antireflection layer 3 may not be provided.

(1) Surface layer The surface layer of the present invention is a layer provided on the side (surface side) farthest from the translucent substrate among the layers forming the light shielding film, and is a layer having ozone resistance. It is preferable.
The surface layer preferably has a uniform composition and atomic number density. Accordingly, the atomic number density of the surface layer including the surface portion of the light shielding film (the portion within 30 nm, preferably within 5 nm from the surface of the light shielding film) is 9 to 14 × 10 ²² atms / cm ³ , and is 10 to 13 × 10. More preferably, it is ²² atms / cm ³ . By having such an atomic number density, it is possible to suppress changes in optical characteristics in ozone cleaning of a photomask or photomask blank.
When the atomic number density is less than 9 × 10 ²² atms / cm ³ , the amount of change in optical characteristics due to ozone cleaning tends to increase. On the other hand, when the atom number density exceeds 14 × 10 ²² atms / cm ³ , it is not preferable because it is difficult to control the film forming conditions.

The composition of the surface layer includes one or more selected from the group consisting of O, C, and N and a metal.

When the surface layer contains Cr, the surface layer is made of CrO (chromium oxide), CrON (chromium oxynitride), CrOC (chromium oxycarbide), CrN (chromium nitride) or CrOCN (chromium oxynitride carbide). Is preferred.
Note that when the surface layer contains O, the transmittance tends to increase, thereby increasing the antireflection function. In addition, when the antireflection function of the surface layer is enhanced, the reflectance at the exposure wavelength can be made low, and when the mask pattern is transferred to the transfer object, multiple reflections with the projection exposure surface Can be suppressed, and deterioration of imaging characteristics can be suppressed.
The surface layer is made of a Cr-based compound film (particularly CrOCN or CrOC) with a Cr content of 50% or less, the atomic ratio of O and Cr is 0.5 or more, and the atomic ratio of C and Cr It is preferable that C / Cr is 0.1 or more and the atomic ratio N / Cr of N and Cr is 0.3 or more.
When the atomic ratio O / Cr is less than 0.5, the atomic ratio C / Cr is less than 0.1, and the atomic ratio N / Cr is less than 0.3, the etching rate is maintained while maintaining the antireflection function. It becomes difficult to perform control, optical density control and conductivity control.
Further, the preferred thickness of the surface layer depends on the composition and the like, but is preferably 3 to 30 nm, more preferably 10 to 20 nm. If the thickness is less than 3 nm, it is difficult to form a uniform film, which may lower the ozone resistance. If the thickness exceeds 30 nm, the film thickness becomes too thick, making it difficult to reduce the thickness of the resist. There is a possibility that it becomes impossible to cope with pattern miniaturization.

Moreover, when a surface layer contains Mo, it is preferable that the said surface layer is a layer which consists of MoSi, MoSiO, MoSiN, or MoSiON. Moreover, you may include C or H in these.
The surface layer may be a layer made of SiO ₂ or SiON.

The surface layer preferably has an amorphous structure with a grain size of 2 nm or less. An amorphous structure is easily formed when a film is formed at a low pressure. For example, when the gas pressure during discharge in DC sputtering is 0.2 Pa or less, a surface layer having a grain size of 2 nm or less can be formed.

When the surface layer is an etching mask layer, the etching mask layer has an amorphous structure, so that the etching rate of the etching mask layer can be increased and the etching time of the etching mask layer can be shortened. Therefore, it is preferable.
For example, a case will be described in which a photomask blank is used in which a backside antireflection layer made of MoSi-based material, a light-shielding layer and a front-surface antireflection layer light-shielding film, and an etching mask layer made of a Cr-based material are provided in this order on a substrate. . In this case, by using a Cr-based etching mask layer having a small thickness, the burden on the resist is reduced, and the reduction in resolution when the mask pattern is transferred to the Cr-based etching mask layer is improved.
This configuration makes it possible to reduce the thickness of the resist film. However, if the resist film thickness is set to 150 nm or even 100 nm or less, the pattern shape deteriorates, and the LER when the mask pattern is transferred to the etching mask layer. (Line Edge Roughness) may deteriorate. Therefore, it is preferable to shorten the etching time of the etching mask layer.

It is preferable that the surface layer has a reflectance of 25% or less at the exposure light wavelength because it effectively reduces the influence of standing waves when using a photomask.
Further, in the surface layer, the in-plane distribution of reflectance and the inter-plate distribution with respect to wavelengths used for defect inspection of photomask blanks and photomasks (for example, 198 nm, 257 nm, 364 nm, 488 nm, etc.) should be 2% or less. It is desirable for detecting with high accuracy.

(2) Surface antireflection layer The surface antireflection layer of the present invention is a layer arbitrarily provided between the surface layer and the light shielding layer among the layers forming the light shielding film, and mainly has an antireflection function. Is a layer.

The composition of the surface antireflection layer includes one or more selected from the group consisting of O, C, and N and a metal.

When the surface antireflection layer contains Cr, the surface antireflection layer is CrO (chromium oxide), CrON (chromium oxynitride), CrOC (chromium oxycarbide), CrN (chromium nitride) or CrOCN (chromium oxynitride carbide). ).
The surface antireflection layer is made of a Cr-based compound film (particularly CrOCN or CrOC) with a Cr content of 50% or less, an atomic ratio O / Cr of O to Cr of 0.5 or more, and an atom of C and Cr The number ratio C / Cr is preferably 0.1 or more, and the N / Cr atomic number ratio N / Cr is preferably 0.3 or more.

When the surface antireflection layer contains Mo, the surface antireflection layer is preferably a layer made of MoSi, MoSiO, MoSiN, or MoSiON. Moreover, you may include C or H in these.
The surface antireflection layer may be made of SiO ₂ or SiON.

The surface antireflection layer is preferable when the reflectance at the exposure light wavelength is suppressed to 25% or less because the influence of the standing wave when using the photomask is effectively reduced.
Further, in the surface antireflection layer, the in-plane distribution of the reflectance and the inter-plate distribution with respect to the wavelength (for example, 198 nm, 257 nm, 364 nm, 488 nm, etc.) used for photomask blank or photomask defect inspection may be 2% or less. It is desirable for detecting defects with high accuracy.

(3) Light-shielding layer The light-shielding layer of the present invention is a layer provided under the surface layer or optionally provided under the surface antireflection layer among the layers forming the light-shielding film. The light shielding layer constituting the light shielding film is a layer having the highest light shielding property in the multilayer film. The light shielding layer preferably contains one or more selected from the group consisting of O, C, and N and a metal. The metal contained in the light shielding layer is preferably a transition metal, and among these, Cr, Mo or Ta is preferable.

When the light shielding layer contains Cr, the light shielding layer includes CrO (chromium oxide), CrON (chromium oxynitride), CrOC (chromium oxide carbide), CrC (chromium carbide), CrCN (chromium carbonitride), CrN (nitriding). It is preferably made of chromium) or CrOCN (chromium oxynitride carbide).

The light shielding layer is preferably made of a Cr-based metal film (particularly CrN, CrON) having a Cr content of 50% or more. In this case, it is possible to easily give the surface layer an antireflection function by using the interference between the reflection at the light shielding layer and the reflection at the surface layer.

When the light shielding layer constituting the light shielding film of the photomask blank of the present invention contains Mo, the light shielding layer is preferably a layer of MoSi, MoSiO, MoSiN or MoSiON. Further, these layers may further contain C or H.

The light shielding layer constituting the light shielding film of the photomask blank of the present invention may be a light shielding layer containing Ta.

(4) Back surface antireflection layer The back surface antireflection layer of the present invention is a layer provided below the light shielding layer among the layers forming the light shielding film. The composition of the antireflection layer includes one or more selected from the group consisting of O, C, and N and a metal.
When the antireflection layer contains Cr, the antireflection layer is preferably made of CrO, CrON, CrOC, or CrOCN. The antireflection layer preferably contains O because the antireflection function is enhanced.
In the case of a three-layer structure, it is preferable that the antireflection layer has the same composition as the surface layer. In this case, it is only necessary to change the gas conditions of the film forming gas and change the gas conditions of the antireflection layer and the surface layer, thereby facilitating the film forming process.
The antireflection layer is composed of CrOCN or CrOC, the atomic ratio O / Cr of O and Cr is 0.5 or more, the atomic ratio C / Cr of C and Cr is 0.1 or more, and The atomic ratio N / Cr between N and Cr is preferably 0.1 or more. The preferred thickness of such an antireflection layer depends on the composition and the like, but is usually about 5 to 30 nm, and preferably 10 to 20 nm.
Further, if the back surface reflectance is too low in the wavelength range of about 600 nm to 800 nm, it may not be recognized by a substrate recognition sensor or the like. Therefore, it is preferable to adjust so that a reflectance of 5% or more can be secured.

In the above (1) to (4), when the surface layer, the surface antireflection layer or the surface antireflection layer is made of CrOCN, a mode in which a Cr—Cr bond component and a CrO _x N _y component are mixed is preferable. Further, when the light shielding layer is made of CrN, a mode in which the Cr—Cr bond component is the main component and the CrO _x N _y component is small is preferable. By increasing the CrO _x N _y component, the etching rate can be increased.
When the surface layer, the surface antireflection layer or the surface antireflection layer is made of CrOCN, the carbon is mainly composed of chromium carbide (Cr—C), and other components C—C, C—O, and C—N are mixed. It is preferable that it is in the state.

1.2.2 Light-shielding film having a single-layer structure As a photomask blank having a light-shielding film having a single-layer structure, the entire light-shielding film may have a uniform composition, but the composition changes depending on the depth direction of the light-shielding film. A configuration is preferred.
In the present invention, the surface portion of the light shielding film means a portion within 30 nm (preferably within 5 nm) from the surface of the light shielding film, but even in a light shielding film having a single layer structure, the atomic number density of the surface portion is 9 × 10 ²² to 14 × 10 ²² atms / cm ³ , preferably 10 × 10 ²² to 13 × 10 ²² atms / cm ³ . By having such an atomic number density, a decrease in film thickness due to ozone water can be prevented, and a change in optical characteristics in ozone cleaning of a photomask or photomask blank can be suppressed.

1.3 Phase Shifter Film In the photomask blank of the present invention, a phase shifter film may be provided between the light shielding film and the translucent substrate.
The phase shifter film is a film having a function of shifting the phase of exposure light and a function of transmitting exposure light by 2 to 40%, and a known phase shifter film can be used in the photomask blank of the present invention.
Thus, in the photomask blank of the present invention, a halftone phase shift mask blank can be provided by providing the phase shifter film between the light shielding film and the translucent substrate.

2 Photomask Blank Manufacturing Method The photomask blank of the present invention can be obtained by, for example, forming a light-shielding film and an optional phase shifter film on a translucent substrate by reactive sputtering.

As a sputtering method, a method using a direct current (DC) power source or a method using a radio frequency (RF) power source may be used, and a magnetron sputtering method or a conventional method may be used.
Further, although either an in-line type or a single-wafer type can be used as the film forming apparatus, it is preferable to use a single-wafer type film forming apparatus in order to form a light shielding layer having a high atomic number density.

When forming a surface layer, a light shielding layer, or an antireflection layer (a front surface antireflection layer and a back surface antireflection layer) containing Cr, chromium is used as a target. Further, the composition of the sputtering gas is prepared according to the composition contained in addition to Cr.

Specifically, when a CrOC surface layer, a light shielding layer, or an antireflection layer is formed by reactive sputtering, a gas containing C such as CH ₄ , CO ₂ , CO, and the like as a sputtering gas and CO ₂ , O _2, etc. One or more gases each containing O are introduced. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.
Further, it is preferable to use CO ₂ or a mixed gas of CO ₂ and an inert gas as the sputtering gas because the atomic number density of the formed CrCO film is improved.

When a CrOCN surface layer, a light shielding layer, or an antireflection layer is formed by reactive sputtering, a gas containing C such as CH ₄ , CO ₂ , or CO as a sputtering gas and a gas containing O such as CO ₂ or O ₂ One or more kinds of N-containing gases such as N ₂ , NO, and N ₂ O are introduced. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.
Thus also, a mixed gas of CO ₂ and N ₂ as a sputtering gas, or CO ₂ and N ₂ and the use of mixed gas of an inert gas is safe, CO ₂ gas is less reactive than O _2, etc. It is preferable from the point that the gas can be uniformly introduced over a wide range in the chamber and the film quality of the CrCON film to be formed becomes uniform.

When a CrN light-shielding layer is formed by reactive sputtering, a gas containing N such as N ₂ is introduced as a sputtering gas. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.

When a CrON surface layer, a light shielding layer, or an antireflection layer is formed by reactive sputtering, a gas containing O such as NO and O ₂ and a gas containing N such as N ₂ , NO, and N ₂ O are used as sputtering gases. Introduce one or more of each. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.

When forming a CrOC surface layer, a light shielding layer, or an antireflection layer by reactive sputtering, a gas containing C such as CH ₄ , CO ₂ , or CO and a gas containing O such as CO ₂ or O ₂ are used as sputtering gases. Introduce one or more of each. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.

When a CrO surface layer, a light shielding layer or an antireflection layer is formed by reactive sputtering, a gas containing O such as O ₂ is introduced as a sputtering gas. Moreover, inert gas, such as Ar and He, can also be added to these. These gases may be introduced separately into the chamber or mixed and introduced in advance.

When forming a light-shielding layer containing Mo and Si, a target containing Mo and Si may be used, or both a Mo target and a Si target may be used. The composition ratio of Mo and Si in the light shielding layer is adjusted by adjusting the sputtering area of the target and the power applied to the target. Further, in the case where C is contained in addition to Mo and Si in the light shielding layer, CH ₄ , CO ₂ , CO or the like is contained as a gas containing C. When N is contained, N is contained as a gas containing N. ₂ , NO, N ₂ O, etc., when O is contained, CO ₂ , O _2, etc. can be used as a sputtering gas as a gas containing O.

When a light shielding layer containing Ta is formed, a target containing Ta is used as in the case of forming a light shielding layer containing Mo and Si. Further, the sputtering gas used when the light shielding layer further contains C, O, N, or the like in addition to Ta is the same as that when the light shielding layer containing Mo and Si is formed.

3 Photomask and Method for Manufacturing the Photomask A photomask obtained from the photomask blank of the present invention and a method for manufacturing the photomask will be described.

First, a resist is applied to a photomask blank on which a light shielding film is formed, and dried to obtain a resist film. It is necessary to select an appropriate resist depending on the drawing apparatus to be used. For EB drawing that is usually used, a positive type or negative type resist having an aromatic skeleton in a polymer, For the production of a photomask for a fine pattern in which the invention is particularly effectively used, it is preferable to use a chemically amplified resist.

The resist film thickness needs to be in a range where a good pattern shape can be obtained and can function as an etching mask. Especially when a fine pattern is to be formed as an ArF exposure mask, The thickness is preferably 200 nm or less, and more preferably 150 nm or less. In addition, a two-layer resist method using a combination of a resist using a silicon resin and a lower layer film using an aromatic resin, or a surface imaging method using a combination of an aromatic chemically amplified resist and a silicon surface treatment agent was used. In some cases, the film thickness can be further reduced. As for the coating conditions and the drying method, a method suitable for each resist to be used is appropriately selected.

Note that a resin layer may be formed on the surface of the photomask blank before applying the resist in order to reduce the occurrence of problems such as peeling of the fine resist pattern and falling down. Further, instead of forming the resin layer, surface treatment for reducing the surface energy of the surface of the substrate (photomask blank) may be performed before applying the resist. Examples of the surface treatment method include a method in which the surface is alkylsilylated with HMDS or other organosilicon surface treatment agents commonly used in semiconductor manufacturing processes.

Next, drawing on a resist in a photomask blank on which a resist film is formed includes a method using EB irradiation and a method using light irradiation. Generally, in order to form a fine pattern by a method using EB irradiation. This is the preferred method. When a chemically amplified resist is used, drawing is usually performed with energy in the range of 3 to 40 μC / cm ² , and after the drawing, heat treatment is performed, and then the resist film is developed to obtain a resist pattern.

Using the resist pattern obtained above as an etching mask, the light shielding film or the light shielding film and another film (phase shifter film, etc.) are etched. Etching can be performed using known chlorine-based or fluorine-based dry etching depending on the composition of the light-shielding film (surface layer, light-shielding layer, antireflection layer, etc.) and other films.

After obtaining the light-shielding pattern by etching, the resist is peeled off with a predetermined stripping solution to obtain a photomask on which the light-shielding film pattern is formed.

4 Pattern Transfer The photomask of the present invention is a pattern transfer for forming a fine pattern having a DRAM half pitch (hp) of 45 nm or more in a semiconductor design rule using an exposure method having a numerical aperture of NA> 1 and an exposure light wavelength of 200 nm or less. It is particularly useful as a mask used in the method.

The photomask blank of the present invention is particularly effective when it is used for forming a resist pattern having a line width of less than 100 nm on the photomask blank. An example of such a photomask blank is a mask having an OPC structure. In this OPC mask, since the width of the auxiliary pattern provided around the main pattern is the narrowest for the purpose of improving the resolution of the main pattern, it is particularly useful for pattern transfer using a photomask having these patterns. .

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1]
In this example, a halftone phase shift mask blank in which a phase shifter film 5 and a three-layer light-shielding film were provided on a translucent substrate 10 was manufactured (see FIG. 2).

First, on a translucent substrate 10 made of quartz glass having a size of 6 inches square and 0.25 inches in thickness, it is composed of a single layer using Mo, Si and N as main components using a single wafer sputtering apparatus. A halftone phase shifter film 5 for ArF excimer laser (wavelength 193 nm) was formed (film thickness 69 nm).
As shown in Table 1, the sputtering (DC sputtering) conditions were as follows.

Sputter target: mixed target of Mo and Si (Mo: Si = 8: 92 mol%)
Sputtering gas: Mixed gas atmosphere of Ar, N ₂ and He (Ar: 9 sccm, N2: 81 sccm, He: 76 sccm)
Gas pressure during discharge: 0.3 Pa
Applied power: 2.8 kW

In an ArF excimer laser (wavelength 193 nm), the transmittance of the obtained phase shifter film 5 was 5.5% and the phase shift amount was approximately 180 °.

Next, a back surface antireflection layer 3 made of CrOCN was formed (film thickness: 30 nm) using the same sputtering apparatus as the apparatus for forming the phase shifter film 5. The conditions for sputtering (DC sputtering) were as shown in Table 1.

Thereafter, a light-shielding layer 2 made of CrN was formed (film thickness: 4 nm) using the same sputtering apparatus as the apparatus for forming the back surface antireflection layer 3. The conditions for sputtering (DC sputtering) were as shown in Table 1.

Furthermore, a surface layer 1 made of CrOCN was formed (film thickness: 14 nm) using a sputtering apparatus similar to the apparatus in which the light shielding layer 2 was formed. The conditions for sputtering (DC sputtering) were as shown in Table 1.

Thus, a photomask blank was obtained in which the phase shifter film 5, the back surface antireflection layer 3, the light shielding layer 2, and the surface layer 1 were laminated in this order on a light transmitting substrate made of quartz glass. The optical density (OD) of light having a wavelength of 193.4 nm in the light-shielding film comprising the back-surface antireflection layer 3, the light-shielding layer 2 and the surface layer 1 was 1.9.

Moreover, the composition and atomic number density of the surface layer 1 and back surface antireflection layer 3 of the obtained photomask blank were analyzed by RBS (Rutherford Backscattering Spectrometry). RBS is a technique for analyzing the surface composition with respect to the surface density (atms / cm ² ) in the depth direction. If the film thickness for each layer is known, the atomic number density (atms / cm ³ ) can be calculated from the following equation: Can be calculated.
Atomic number density = surface density / film thickness The atomic number density of the surface layer 1 was calculated by the above method.

As a result, the film composition of the surface layer 1 (film thickness: 14 nm) was 34 atom% for Cr, 11 atom% for C, 39 atom% for O, and 16 atom% for N. The chromium ratio of the surface layer 1 was 0.3 for C / Cr, 1.2 for O / Cr, and 0.5 for N / Cr. Furthermore, the atom number density of the surface layer 1 was 10.5 × 10 ²² atms / cm ³ .

The film composition of the light shielding layer 2 (film thickness 4 nm) was such that Cr was at least 64 atom% or more and N was at least 8 atom% or more.

The film composition of the back surface antireflection layer 3 (thickness 30 nm) was 36 atom% for Cr, 15 atom% for C, 39 atom% for O, and 9 atom% for N. The chromium ratio of the back surface antireflection layer 3 was 0.4 for C / Cr, 1.1 for O / Cr, and 0.3 for N / Cr.

Further, when the cross section of the obtained photomask blank was observed with a TEM (transmission electron microscope) and an X-ray diffractometer (XRD), the surface layer 1 had an amorphous structure with a grain size of 1 to 2 nm. When the surface roughness was measured using an atomic force microscope (AFM), Ra = 0.45 nm.

Next, ozone water having a concentration of 50 ppm is supplied to the photomask blank obtained in this example at the flow rate of 1.4 L / min for 60 minutes while swinging with a swing arm, and the light shielding film is turned into ozone water. The chemical resistance was evaluated by measuring changes in the film thickness, surface reflectance, and optical density of the light-shielding film due to liquid contact.

As a result, the film thickness of the light shielding film was not changed by the spraying of ozone water. Further, the surface reflectance changed by + 0.82% for light having a wavelength of 193 nm. The optical density of the light shielding film changed by -0.04.

Further, the same layer as the surface layer 1 of this embodiment is directly formed on the glass substrate by sputtering, and ozone water having a concentration of 50 ppm is sprayed on the surface layer 1 for 60 minutes, so that the light shielding film is in contact with the ozone water. The amount of change in reflectivity due to was measured. In the measurement in this example, the reflection spectrum was measured before and after the wetted ozone solution with a spectrophotometer (Hitachi High Technology: U-4100).
The result was as shown in FIG. Specifically, + 0.7% (23.6% → 24.3%) for light with a wavelength of 193 nm, + 1.5% (20.7% → 22.2%) for light at 257 nm, and +2. It changed by + 1.2% (39.5% → 40.7%) at 488 nm at 0% (29.5% → 31.5%). In this specification, “+” represents an increase in reflectance, and “−” represents a decrease in reflectance.
Thus, it was confirmed that the light shielding film of the present Example has high chemical resistance against ozone treatment.

[Example 2]
In this example, a binary mask blank was manufactured in which a light-shielding film composed of three layers was provided on a light-transmitting substrate 10 (see FIG. 3).
That is, reactive sputtering was performed under the same conditions as in Example 1 except that the sputtering conditions were set as shown in Table 1.
In this manner, a photomask blank as shown in FIG. 3 in which the back surface antireflection layer 3, the light shielding layer 2, and the surface layer 1 were laminated in this order on the light transmitting substrate 10 made of quartz glass was obtained. The optical density (OD) of light with a wavelength of 193.4 nm in the light-shielding film comprising the back surface antireflection layer 3, the light-shielding layer 2, and the surface layer 1 was 3.

Next, in the same manner as in Example 1, the composition of the obtained surface layer 1, light-shielding layer 2, and back surface antireflection layer 3 and the atomic number density of the surface layer 1 were analyzed by RBS.
As a result, the film composition of the surface layer 1 (film thickness: 14 nm) was 32 atom% for Cr, 16 atom% for C, 37 atom% for O, and 16 atom% for N. The chromium ratio of the surface layer 1 was 0.5 for C / Cr, 1.2 for O / Cr, and 0.5 for N / Cr. Furthermore, the atomic number density of the surface layer 1 was 11.0 × 10 ²² atms / cm ³ .

The film composition of the light-shielding layer 2 (film thickness 25 nm) was 87 atom% for Cr, 9 atom% for O, and 4 atom% for N. The chromium ratio of the light shielding layer 2 was 0.1 for O / Cr and 0.05 for N / Cr.
The film composition of the back surface antireflection layer 3 (thickness 25 nm) was 49 atom% for Cr, 11 atom% for C, 26 atom% for O, and 14 atom% for N. The chromium ratio of the back surface antireflection layer 3 was 0.2 for C / Cr, 0.5 for O / Cr, and 0.3 for N / Cr.

Further, when the cross section of the obtained photomask blank was observed with a TEM (transmission electron microscope) and an X-ray diffractometer (XRD), the surface layer 1 had an amorphous structure with a grain size of 1 to 2 nm. When the surface roughness was measured using an atomic force microscope (AFM), Ra = 0.28 nm.

Further, ozone water having a concentration of 50 ppm was supplied to the substrate surface while swinging with a swing arm at a flow rate of 1.4 L / min for 60 minutes on the photomask blank obtained in this example, and the light shielding film was in contact with the ozone water. The chemical resistance was evaluated by measuring the change in the film thickness, surface reflectance, and optical density of the light-shielding film due to liquid.
As a result, the film thickness of the light shielding film was not changed by the spraying of ozone water. In addition, the surface reflectance changed by −0.02% for light having a wavelength of 193 nm. The optical density of the light shielding film changed by -0.06.

In addition, the same layer as the surface layer 1 of this example was directly formed on the glass substrate by sputtering, and ozone water having a concentration of 50 ppm was sprayed on the surface layer 1 for 60 minutes by the same measurement method as in Example 1. The amount of change in reflectance caused by contacting the light shielding film with ozone water was measured.
The result was as shown in FIG. Specifically, + 0.5% (18.8% → 19.3%) for light with a wavelength of 193 nm, + 2.1% (14.0% → 16.1%) for light with 257 nm, and +5. It changed by 3% (22.4% → 27.7%) and + 4.6% (38.47% → 43.03%) at 488 nm.
Thus, it was confirmed that the light shielding film of the present Example has high chemical resistance against ozone treatment.

[Comparative Example 1]
In this comparative example, a halftone phase shift mask blank having a light shielding film composed of two layers was manufactured.
Specifically, a light shielding layer was formed on the same phase shifter film as in Example 1 using an in-line type sputtering apparatus. As shown in Table 1, the sputtering (DC sputtering) conditions were as follows.

Sputter target: Cr
Sputtering gas: Mixed gas atmosphere of Ar, N ₂ and He (Ar: 30 sccm, N ₂ : 30 sccm, He: 40 sccm)
Gas pressure during discharge: 0.2 Pa
Applied power: 0.8 kW

Thereafter, a surface layer was formed on the light shielding layer. As shown in Table 1, the sputtering (DC sputtering) conditions were as follows.

Sputter target: Chrome (Cr)
Sputtering gas: mixed gas of argon (Ar) and methane (CH ₄ ) (CH4: 3.5% by volume), gas in which NO and He are mixed (Ar + CH ₄ : 65 sccm, NO: 3 sccm, He: 40 sccm)
Gas pressure during discharge: 0.3 Pa
Applied power: 0.3 kW

Thus, a photomask blank having a light-shielding film thickness of 48 nm was obtained in which a phase shifter film, a light-shielding layer, and a surface layer were sequentially laminated on a light-transmitting substrate made of quartz glass. The optical density (OD) of light having a wavelength of 193.4 nm in the light shielding film comprising the light shielding layer and the surface layer was 1.9.

Next, in the same manner as in Example 1, the composition and atomic number density of the obtained surface layer 1 were analyzed by RBS.
As a result, the film composition of the surface layer (film thickness: 24 nm) was 34 atom% for Cr, 32 atom% for O, and 23 atom% for N. The chromium ratio of the surface layer was 0.9 for O / Cr and 0.7 for N / Cr. Furthermore, the atomic number density of the surface layer was 7.4 × 10 ²² atms / cm ³ .

Further, when the cross section of the obtained photomask blank was observed with a TEM (transmission electron microscope) and an X-ray diffractometer (XRD), the surface layer had a low-density porous columnar structure. When the surface roughness was measured using an atomic force microscope (AFM), Ra = 0.70 nm.

Furthermore, as in Example 1, the chemical resistance of the photomask blank obtained in this comparative example was evaluated.
As a result, the film thickness of the light shielding film was reduced by 5.8 nm by the spraying of ozone water. Further, the surface reflectance changed by + 2.72% with light having a wavelength of 193 nm. The optical density of the light shielding film changed by −0.38.

In addition, the same layer as the surface layer of this comparative example was directly formed on the glass substrate by sputtering, and ozone water having a concentration of 50 ppm was sprayed on the surface layer for 60 minutes by the same measurement method as in Example 1. The amount of change in reflectance due to contact with ozone water was measured.
The result was as shown in FIG. Specifically, + 2.5% (19.8% → 22.3%) for light with a wavelength of 193 nm, + 9.1% (16.4% → 25.5%) for light with 257 nm, and +13. 9% (19.9% → 33.8%), 488 nm changed + 11.0% (29.9% → 40.9%).
Thereby, it was confirmed that the light-shielding film of this comparative example has low chemical resistance with respect to the ozone treatment as compared with Examples 1 and 2.

As a method of utilizing the present invention, for example, fine processing such as a photomask, a photomask blank, and a semiconductor integrated circuit using them can be cited.

Claims

A photomask blank having a light shielding film on a translucent substrate,
A photomask blank, in which the amount of change in reflectance with exposure light of 193 nm to 257 nm is less than 2.5% when indirectly liquid in 50 ppm ozone water for 60 minutes.
A photomask blank having a light shielding film on a translucent substrate,
A photomask blank in which the amount of change in reflectance with exposure light of 257 nm to 488 nm is 8% or less when indirectly liquid in 50 ppm ozone water for 60 minutes.
The photomask blank according to claim 1 or 2, wherein the amount of change in film thickness is 5 nm or less when the liquid is indirectly liquid in 50 ppm ozone water for 60 minutes.
The photomask blank according to any one of claims 1 to 3, wherein the amount of change in reflectance with exposure light of 193 nm to 200 nm is 2% or less when indirect liquid is applied to 50 ppm ozone water for 60 minutes.
The photomask blank according to any one of claims 1 to 4, wherein the amount of change in reflectance with exposure light of 257 nm to 488 nm when indirect liquid is applied to 50 ppm ozone water for 60 minutes is 6% or less.
6. The photomask blank according to any one of claims 1 to 5, wherein the amount of change in film thickness is 1 nm or less when indirect liquid is applied to 50 ppm ozone water for 60 minutes.
The photomask blank according to any one of claims 1 to 6, wherein the light shielding film comprises a plurality of layers.
The photomask blank according to claim 7, wherein the thickness of the surface layer provided on the most surface side among the plurality of layers is 3 to 30 nm.
The photomask blank according to claim 8, wherein the surface layer is made of CrO, CrON, CrOC, CrN or CrOCN.
The light shielding film includes a surface layer and a light shielding layer,
The surface layer has a Cr content of 50% or less, an O / Cr atomic ratio O / Cr of 0.5 or more, a C / Cr atomic ratio C / Cr of 0.1 or more, N and The atomic ratio N / Cr with Cr is 0.3 or more,
The photomask blank according to any one of claims 7 to 9, wherein the light shielding layer has a Cr content of 50% or more.
The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of claims 7 to 10, wherein the light shielding layer is made of CrO, CrON, CrC, CrCN, CrOC, CrN, or CrOCN.
The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of claims 7 to 9, wherein the light shielding layer contains a transition metal and Si.
The light shielding film includes a surface layer and a light shielding layer,
The photomask blank according to any one of claims 7 to 9, wherein the light shielding layer contains Ta.
The photomask blank according to any one of claims 1 to 13, further comprising a phase shifter film between the translucent substrate and the light shielding film.
15. The photomask blank according to any one of claims 1 to 14, which is used for a photomask to be treated with ozone.
A photomask obtained by patterning the photomask blank according to any one of claims 1 to 15 by a lithography method.