JP2004104118A - Reflection mask blank and manufacturing method for reflection mask - Google Patents

Reflection mask blank and manufacturing method for reflection mask Download PDF

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JP2004104118A
JP2004104118A JP2003298691A JP2003298691A JP2004104118A JP 2004104118 A JP2004104118 A JP 2004104118A JP 2003298691 A JP2003298691 A JP 2003298691A JP 2003298691 A JP2003298691 A JP 2003298691A JP 2004104118 A JP2004104118 A JP 2004104118A
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film
stress
multilayer
multilayer reflective
heat treatment
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JP3681381B2 (en
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Tsutomu Shiyouki
笑喜 勉
Morio Hosoya
細谷 守男
Takeshi Kinoshita
木下 健
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Hoya Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection mask blank and a manufacturing method for a reflection mask, wherein the influence of stress of a multilayered reflection film is moderated, and it is highly flat. <P>SOLUTION: In the manufacturing method for a reflection mask blank 100, including a multilayered reflection film 13 provided on a substrate 11 for reflecting exposure light, and further including a buffer layer 14 and an absorber layer 15 for absorbing exposed light provided on the multilayer reflection film 13. In the manufacturing method, it comprises a process for forming a stress correction film 12, having smaller film stress than the absolute value of film stress of the multilayer reflection film 13 in the opposite direction to the film stress of the multilayer reflection film 13 between the substrate 11 and the multilayer reflection film 13, and a process for heating the multilayer reflection film 13. The reflection mask 101 is manufactured by forming a pattern on the absorber layer 15. <P>COPYRIGHT: (C)2004,JPO

Description

 本発明は、半導体のパターン転写などに用いられる露光用反射型マスクブランク及び反射型マスクの製造方法に関する。 {Circle over (1)} The present invention relates to a reflective mask blank for exposure and a method of manufacturing a reflective mask used for pattern transfer of a semiconductor or the like.

 近年、半導体産業において、半導体デバイスの微細化に伴い、極端紫外(Extreme Ultra Violet)光(以下、EUV光と称す)を用いた露光技術であるEUVリソグラフィーが有望視されている。なお、ここで、EUV光とは、軟X線領域又は真空紫外線領域の波長帯の光を指し、具体的には波長が0.2〜100nm程度の光のことである。このEUVリソグラフィーにおいて用いられるマスクとしては、例えば特開平8-213303号公報に記載されたような露光用反射型マスクが提案されている。
 このような反射型マスクは、基板上にEUV光を反射する多層反射膜を有し、更に、多層反射膜上に、EUV光を吸収する吸収体層がパターン状に設けられた構造をしている。
反射型マスクを搭載した露光機(パターン転写装置)において、反射型マスクに入射した光は、吸収体層のある部分では吸収され、吸収体層のない部分では多層反射膜により反射された像が反射光学系を通して半導体基板(シリコンウエハ)上に転写される。
しかし、このような多層反射膜を用いた反射型マスクにおいては、短波長の光で高反射率を得るために多層膜の各層の膜密度を高くする必要がある。すると、必然的に多層反射膜は高い圧縮応力を有することになる。多層反射膜としては、例えば、13〜14nmのEUV光に対する反射率の高いものとして、数10nmオーダーのSiとMo薄膜を交互に積層したものが用いられるが、この場合、緻密な多層膜とすると、一般に圧縮応力は450〜600MPa程度の大きさになる。
In recent years, with the miniaturization of semiconductor devices in the semiconductor industry, EUV lithography, which is an exposure technique using extreme ultraviolet (Extreme Ultra Violet) light (hereinafter, referred to as EUV light), holds great promise. Here, the EUV light refers to light in a wavelength band in a soft X-ray region or a vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm. As a mask used in this EUV lithography, for example, a reflective mask for exposure as described in JP-A-8-213303 has been proposed.
Such a reflective mask has a structure in which a multilayer reflective film that reflects EUV light is provided on a substrate, and an absorber layer that absorbs EUV light is provided in a pattern on the multilayer reflective film. I have.
In an exposure machine (pattern transfer device) equipped with a reflection type mask, light incident on the reflection type mask is absorbed in a portion having an absorber layer, and an image reflected by a multilayer reflection film is formed in a portion without an absorber layer. The light is transferred onto a semiconductor substrate (silicon wafer) through a reflection optical system.
However, in a reflective mask using such a multilayer reflective film, it is necessary to increase the film density of each layer of the multilayer film in order to obtain a high reflectance with light of a short wavelength. Then, the multilayer reflective film inevitably has a high compressive stress. As the multilayer reflective film, for example, a film in which Si and Mo thin films of several tens of nm order are alternately laminated is used as a material having a high reflectance to EUV light of 13 to 14 nm. In this case, if a dense multilayer film is used, In general, the compressive stress is about 450 to 600 MPa.

 この高い圧縮応力のため、基板は、凸面に大きく反って(変形)してしまう。この結果、EUV光の反射面である多層反射膜の表面にも反りが生じてしまう。
 例えば、65nmルールのデバイス作製においては、100nm以下の平坦度が必要とされる。例えば、6インチ角、6.35mm厚の石英ガラス基板上の0.3μm厚の多層膜に対して、200MPaの圧縮応力がかかった場合、140mm角エリアにおいて、500nm程度の反り(変形)が生じる。従って、これを100nmの変形に抑えるためには、およそ50MPa以下の応力にする必要がある。
 このように、多層反射膜の圧縮応力が大きいと、多層反射膜表面の反りが原因となって、ウエハへの転写時に転写精度の低下(位置ずれ)が起こり、高精度の転写ができないという問題がある。この問題に対しては、多層反射膜の応力の影響の低減を図ることが試みられている。
 このような応力低減の方法として、基板上に多層反射膜を形成後、これを加熱処理することによって、多層反射膜自身の応力を低減する方法が知られている(米国特許6309705号公報)。
 一方、基板と多層反射膜の間に、多層反射膜の圧縮応力と同等の大きさの引っ張り応力を有する応力補正膜を形成することにより、多層反射膜の応力を相殺する方法が知られている(特開2002−15981号公報)。
特開2002−15981号公報 米国特許第6309705号明細書
Due to the high compressive stress, the substrate is largely warped (deformed) to the convex surface. As a result, the surface of the multilayer reflective film, which is the reflective surface for EUV light, is also warped.
For example, in fabricating a device according to the 65 nm rule, a flatness of 100 nm or less is required. For example, when a compressive stress of 200 MPa is applied to a 0.3 μm thick multilayer film on a 6 inch square, 6.35 mm thick quartz glass substrate, warpage (deformation) of about 500 nm occurs in a 140 mm square area. . Therefore, in order to suppress the deformation to 100 nm, it is necessary to reduce the stress to about 50 MPa or less.
As described above, when the compressive stress of the multilayer reflective film is large, the transfer accuracy is degraded (positional displacement) at the time of transfer to the wafer due to the warpage of the multilayer reflective film surface, so that high-accuracy transfer cannot be performed. There is. To solve this problem, attempts have been made to reduce the influence of the stress of the multilayer reflective film.
As a method of reducing such stress, a method is known in which a multilayer reflective film is formed on a substrate and then subjected to a heat treatment to reduce the stress of the multilayer reflective film itself (US Pat. No. 6,309,705).
On the other hand, a method of offsetting the stress of the multilayer reflective film by forming a stress correction film having a tensile stress equivalent to the compressive stress of the multilayer reflective film between the substrate and the multilayer reflective film is known. (JP 2002-15981 A).
JP-A-2002-15981 US Pat. No. 6,309,705

 しかしながら、上述した多層反射膜を加熱処理する方法では、例えば、約600MPaの圧縮応力を0(ゼロ)に近づけるためには、300℃程度以上の高温での加熱処理が必要になる。しかし、多層反射膜をこのような高温で加熱すると、多層反射膜の反射率が低下してしまい好ましくない。これは、多層反射膜の各層の界面での拡散が起こるためと思われる。
 一方、基板と多層反射膜の間に応力補正膜を形成する方法では、多層反射膜の応力を相殺するために、応力補正膜を多層反射膜と反対の高い引っ張り応力(上述の場合約600MPa)を有するように形成する必要がある。一般に、高い引っ張り応力を有する膜は、表面粗さが大きくなる。この荒れた膜上に多層反射膜を形成すると、多層反射膜が表面荒れを引き継いで形成されるため、EUV光に対する反射率の低下を引き起こすとともに、多層反射膜上に形成される吸収体パターンにおいても、エッジラフネスが大きくなる等して形状精度にも悪影響を及ぼす。例えば、0.29μmで+600MPaのSi膜は、0.45nmRmsの粗さを有し、このSi膜上に形成した多層反射膜上では0.55nmRmsの粗さとなり、3%程度の反射率低下を引き起こす。このため、基板と多層反射膜の間に、高い引っ張り応力を有する膜を形成するのは、実用的には好ましくない。
 本発明は上述の課題を解決するために案出されたものであり、多層反射膜の応力の影響を緩和し、平坦度の高い反射型マスクブランク及び反射型マスクの製造方法を提供することを目的とする。
However, in the above-described method of heat-treating the multilayer reflective film, for example, a heat treatment at a high temperature of about 300 ° C. or more is required to make the compressive stress of about 600 MPa close to 0 (zero). However, heating the multilayer reflective film at such a high temperature is not preferable because the reflectance of the multilayer reflective film is reduced. This is presumably because diffusion occurs at the interface between the layers of the multilayer reflective film.
On the other hand, in the method of forming the stress compensation film between the substrate and the multilayer reflection film, in order to cancel the stress of the multilayer reflection film, the stress compensation film is formed with a high tensile stress opposite to that of the multilayer reflection film (about 600 MPa in the above case). It must be formed to have Generally, a film having a high tensile stress has a large surface roughness. When a multilayer reflective film is formed on this rough film, the multilayer reflective film is formed by taking over the surface roughness, so that the reflectivity to EUV light is reduced and the absorber pattern formed on the multilayer reflective film is reduced. In addition, the shape accuracy is adversely affected by, for example, an increase in edge roughness. For example, a Si film of 0.29 μm and +600 MPa has a roughness of 0.45 nmRms, and a multilayer reflective film formed on this Si film has a roughness of 0.55 nmRms, which reduces the reflectance by about 3%. cause. For this reason, it is not practically preferable to form a film having a high tensile stress between the substrate and the multilayer reflective film.
The present invention has been devised to solve the above-described problems, and it is an object of the present invention to provide a reflective mask blank having a high flatness and a method of manufacturing the reflective mask, which alleviates the influence of the stress of the multilayer reflective film. Aim.

 本発明者は、上述の課題を解決するべく鋭意検討の結果、多層反射膜と逆向きの応力を有する応力補正膜を、基板と多層反射膜の間、或いは、多層反射膜上、或いは、基板と多層反射膜の間及び多層反射膜上の両方に設け、多層反射膜と応力補正膜とを加熱処理することで、上述した課題が解決できることを見い出し、本発明を成すに到ったものである。
 すなわち、本発明に係る反射型マスクブランクスの製造方法は、基板上に、露光光を反射する多層反射膜を形成し、該多層反射膜上に露光光を吸収する吸収体層を形成する反射型マスクブランクの製造方法であって、前記基板と多層反射膜の間、或いは、多層反射膜上、或いは、基板と多層反射膜の間及び多層反射膜上の両方に、多層反射膜の膜応力と逆向きで、多層反射膜の膜応力の絶対値より小さい膜応力を有する応力補正膜を形成する工程と、前記応力補正膜を加熱処理する工程と、前記多層反射膜を加熱処理する工程と、を有する。加熱処理後において、応力補正膜の有する膜応力と多層反射膜の有する膜応力とが、向きが反対で大きさが同等となって釣り合い、応力は相殺される。従って、成膜時において、応力補正膜に多層反射膜の有する膜応力を相殺するための大きな応力を与える必要がなく、応力補正膜の表面粗さが大きくなることはない。
 なお、本発明における応力補正膜の膜応力は、特に断りのない限り、多層反射膜の膜厚と同一の膜厚換算の値である。即ち、応力補正膜の有する単位膜厚当たりの応力をA、応力補正膜と多層反射膜の膜厚の比(応力補正膜膜厚/多層反射膜の膜厚)をBとした時、多層膜反射膜の膜厚と同一の膜厚換算の値は、A×Bで表される。
The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems, and as a result, has found that a stress correction film having a stress opposite to that of the multilayer reflective film is provided between the substrate and the multilayer reflective film, or on the multilayer reflective film, or on the substrate. It is found that the above-mentioned problem can be solved by performing a heat treatment on the multilayer reflective film and the stress correction film, both provided between and on the multilayer reflective film and on the multilayer reflective film, and reached the present invention. is there.
That is, the method of manufacturing a reflective mask blank according to the present invention includes forming a reflective reflective film on a substrate by forming a multilayer reflective film that reflects exposure light, and forming an absorber layer that absorbs the exposure light on the multilayer reflective film. A method of manufacturing a mask blank, wherein between the substrate and the multilayer reflective film, or on the multilayer reflective film, or between the substrate and the multilayer reflective film and on the multilayer reflective film, the film stress of the multilayer reflective film, In the opposite direction, a step of forming a stress correction film having a film stress smaller than the absolute value of the film stress of the multilayer reflection film, a step of heat-treating the stress correction film, and a step of heat-treating the multilayer reflection film, Having. After the heat treatment, the film stress of the stress compensation film and the film stress of the multilayer reflective film are opposite in direction and equal in magnitude, and the stresses are offset. Therefore, at the time of film formation, it is not necessary to apply a large stress for canceling the film stress of the multilayer reflection film to the stress correction film, and the surface roughness of the stress correction film does not increase.
The film stress of the stress correction film in the present invention is the same film thickness value as that of the multilayer reflection film unless otherwise specified. That is, when the stress per unit film thickness of the stress correction film is A and the ratio of the film thickness of the stress correction film to the multilayer reflection film (the stress correction film thickness / the film thickness of the multilayer reflection film) is B, the multilayer film A value equivalent to the film thickness of the reflection film in terms of the film thickness is represented by A × B.

 前記応力補正膜を加熱処理する工程と、前記多層反射膜を加熱処理する工程とを同時に行うことができる。
 また、基板と多層反射膜の間に応力補正膜を形成する場合、基板上に応力補正膜を形成し、該応力補正膜を加熱処理した後、該応力補正膜上に前記多層反射膜を形成し、該多層反射膜の加熱処理を行ってもよい。この場合、加熱工程は二工程で行うことになる。
 前記加熱処理は応力補正膜の成膜時の温度よりも高く200℃以下の基板加熱温度で行うことが好ましい。本発明では、高温での加熱処理は必要がなく、多層反射膜の反射率低下を防止できる。
 本発明では、加熱処理後において、応力補正膜の有する膜応力と、多層反射膜が有する膜応力が、向きが反対で大きさが同等となる必要がある。従って、多層反射膜及び応力補正膜の加熱処理による膜応力の変化分を考慮して、加熱前の応力補正膜に与える応力を決定することになるが、加熱処理前の応力補正膜の膜応力は、0〜+300MPaの範囲内であることが望ましい。尚、膜応力の+(プラス)は引張応力を示し、−(マイナス)は圧縮応力を示す。
 本発明では、加熱処理後において、応力補正膜の有する膜応力と多層反射膜が有する膜応力とが相殺しあうわけであるが、上記応力補正膜は加熱処理により、その応力の絶対値が増大する、つまり応力が引っ張り方向へシフトするような材料を用いることが出来る。
 前記応力補正膜は、金属又は合金からなるアモルファス材料で構成されることが好ましい。このような材料は、平滑性の良好な膜が得られ、かつ応力補正膜に与える初期応力の値を容易に調整できる。
また、上述の本発明に係る反射型マスクブランクの製造方法により製造された反射型マスクブランクの吸収体層にパターンを形成することにより、反射型マスクを製造することができる。本発明に係る反射型マスクの製造方法によれば、多層反射膜の応力の影響を低減し、平坦度の高い反射型マスクが得られる。
The step of heating the stress correction film and the step of heating the multilayer reflective film can be performed simultaneously.
When a stress correction film is formed between the substrate and the multilayer reflection film, a stress correction film is formed on the substrate, and the stress correction film is subjected to a heat treatment, and then the multilayer reflection film is formed on the stress correction film. Then, heat treatment of the multilayer reflective film may be performed. In this case, the heating step is performed in two steps.
The heat treatment is preferably performed at a substrate heating temperature higher than the temperature at the time of forming the stress compensation film and 200 ° C. or less. In the present invention, heat treatment at a high temperature is not required, and a decrease in the reflectance of the multilayer reflective film can be prevented.
In the present invention, after the heat treatment, the film stress of the stress correction film and the film stress of the multilayer reflective film need to be opposite in direction and equal in magnitude. Therefore, the stress applied to the stress correction film before heating is determined in consideration of the change in the film stress due to the heat treatment of the multilayer reflective film and the stress correction film. Is preferably in the range of 0 to +300 MPa. In addition, + (plus) of the film stress indicates a tensile stress, and-(minus) indicates a compressive stress.
In the present invention, after the heat treatment, the film stress of the stress correction film and the film stress of the multilayer reflective film cancel each other, but the heat treatment increases the absolute value of the stress in the stress correction film. That is, a material whose stress is shifted in the tensile direction can be used.
It is preferable that the stress correction film is made of an amorphous material made of a metal or an alloy. With such a material, a film having good smoothness can be obtained, and the value of the initial stress applied to the stress correction film can be easily adjusted.
Further, a reflective mask can be manufactured by forming a pattern on the absorber layer of the reflective mask blank manufactured by the above-described method for manufacturing a reflective mask blank according to the present invention. ADVANTAGE OF THE INVENTION According to the manufacturing method of the reflective mask which concerns on this invention, the influence of the stress of a multilayer reflective film is reduced, and the reflective mask with high flatness is obtained.

 次に、本発明の実施の形態について説明する。
 本発明において平滑性を示す単位Rmsは、二乗平均平方根粗さであり、原子間力顕微鏡で測定することができる。又本発明における平坦度は、TIR(total indicated reading)で示される表面の反り(変形量)を示す値である。これは、基板表面を元に最小二乗法で定められる平面を焦平面としたとき、この焦平面より上にある基板表面の最も高い位置と、焦平面より下にある最も低い位置の高低差の絶対値である。
 本発明の方法で製造される反射型マスクブランクは、基板上に、露光光であるEUV光を反射する多層反射膜を有し、該多層反射膜上に露光光であるEUV光を吸収する吸収体層を有している。そして、上記基板と多層反射膜の間、或いは、多層反射膜上、或いは、基板と多層反射膜の間及び多層反射膜上の両方に、応力補正膜を有している。必要に応じて、多層反射膜と吸収体層の間に、吸収体層へのパターン形成時のエッチング環境に耐性を有し、多層反射膜を保護するためのバッファ層を有していてもよい。又、本発明の方法で製造される反射型マスクは、この反射型マスクブランクの吸収体層にパターンが形成されたものである。
Next, an embodiment of the present invention will be described.
In the present invention, the unit Rms indicating the smoothness is a root mean square roughness, and can be measured by an atomic force microscope. In addition, the flatness in the present invention is a value indicating a surface warpage (amount of deformation) indicated by TIR (total indicated reading). This is the difference in elevation between the highest position on the substrate surface above the focal plane and the lowest position below the focal plane, when the plane determined by the least squares method based on the substrate surface is the focal plane. It is an absolute value.
The reflective mask blank manufactured by the method of the present invention has, on a substrate, a multilayer reflective film that reflects EUV light that is exposure light, and an absorption layer that absorbs EUV light that is exposure light on the multilayer reflective film. It has a body layer. A stress correction film is provided between the substrate and the multilayer reflective film, on the multilayer reflective film, or between the substrate and the multilayer reflective film and on the multilayer reflective film. If necessary, a buffer layer for protecting the multilayer reflective film may be provided between the multilayer reflective film and the absorber layer, which is resistant to an etching environment when a pattern is formed on the absorber layer. . The reflective mask manufactured by the method of the present invention has a pattern formed on the absorber layer of the reflective mask blank.

 本発明の反射型マスクブランクの製造方法について上記バッファ層を有する場合を例にとり説明する。
 まず基板を準備し、基板上に順次、所定の膜応力を有する応力補正膜、多層反射膜を形成する。この応力補正膜及び多層反射膜を形成した基板を加熱処理することにより、多層反射膜の有する膜応力と、応力補正膜の有する膜応力の大きさが互いに向きが逆向きで大きさが等しくなるようにする。
 加熱処理後、多層反射膜上に、順次バッファ層及び吸収体層を形成して、本実施の形態に係る反射型マスクブランクが得られる。
 次に、各製造工程について説明する。
The method of manufacturing the reflective mask blank of the present invention will be described with reference to an example having the above-mentioned buffer layer.
First, a substrate is prepared, and a stress correction film having a predetermined film stress and a multilayer reflection film are sequentially formed on the substrate. By heat-treating the substrate on which the stress correction film and the multilayer reflection film are formed, the magnitude of the film stress of the multilayer reflection film and the magnitude of the film stress of the stress correction film are opposite to each other and equal in magnitude. To do.
After the heat treatment, a buffer layer and an absorber layer are sequentially formed on the multilayer reflective film to obtain the reflective mask blank according to the present embodiment.
Next, each manufacturing process will be described.

 まず、基板の準備について説明する。
 本発明に用いる基板としては、露光時の熱によるパターンの歪みを防止するため、0±1.0×10−7/℃の範囲内、より好ましくは0±0.3×10−7/℃の範囲内の低熱膨張係数を有するものが好ましい。この範囲の低熱膨張係数を有する素材としては、アモルファスガラス、セラミック、金属の何れでも使用できる。例えばアモルファスガラスであればSiO−TiO系ガラス、石英ガラス、結晶化ガラスであればβ石英固溶体を析出した結晶化ガラス、などを用いることができる。金属としては、インバー合金(Fe-Ni系合金)等を用いることができる。
 又、基板は、高い反射率及び転写精度を得るために、高い平滑性と平坦性を備えた基板が好ましい。特に、0.2nmRms以下の平滑性(10μm角エリアでの平滑性)、100nm以下の平坦度(142mm角エリアでの平坦度)を有していることが好ましい。
 又、基板は、その上に形成される膜の膜応力による変形を防止するために、高い剛性を有しているものが好ましい。特に、65GPa以上の高いヤング率を有しているものが好ましい。以上のような点を考慮して、基板を選択し、準備する。
First, the preparation of the substrate will be described.
The substrate used in the present invention is preferably in the range of 0 ± 1.0 × 10 −7 / ° C., more preferably 0 ± 0.3 × 10 −7 / ° C., in order to prevent pattern distortion due to heat during exposure. Those having a low coefficient of thermal expansion in the range of are preferred. As a material having a low coefficient of thermal expansion in this range, any of amorphous glass, ceramic, and metal can be used. For example, amorphous glass may be SiO 2 —TiO 2 glass, quartz glass, and crystallized glass may be crystallized glass obtained by depositing a β-quartz solid solution. As the metal, an invar alloy (Fe-Ni alloy) or the like can be used.
Further, the substrate is preferably a substrate having high smoothness and flatness in order to obtain high reflectance and transfer accuracy. In particular, it is preferable to have a smoothness of 0.2 nmRms or less (smoothness in a 10 μm square area) and a flatness of 100 nm or less (flatness in a 142 mm square area).
Further, the substrate preferably has high rigidity in order to prevent deformation of the film formed thereon due to film stress. In particular, those having a high Young's modulus of 65 GPa or more are preferable. A substrate is selected and prepared in consideration of the above points.

 次に、基板上への応力補正膜の形成について説明する。
 本発明における応力補正膜は、形成される多層反射膜の有する応力と逆向きの応力を有するものから選択される。一般に多層反射膜は緻密に形成され、圧縮応力を有するので、応力補正膜は、引っ張り応力を有する膜から選択されることになる。
そして例えば、加熱処理により応力補正膜の応力の大きさ(絶対値)が大きくなるものを選択する。具体的には、応力がより引っ張り応力側にシフトするものである。
更に、応力補正膜は、平滑な膜である事が好ましいため、アモルファス材料であることが好ましい。応力補正膜の表面の平滑性は、0.2nmRms以下であることが好ましく、更に好ましくは0.15nmRms以下である。
又、応力制御が容易な膜を用いると、応力補正膜に与える初期応力の値が容易に調整出来るため好ましい。このような応力補正膜としては、タンタル(Ta)を主成分とした材料が好ましい。
 Taを主成分とした材料としては、例えば、Ta合金等が挙げられる。更には、Taを主成分としたアモルファス材料が好ましい。このような材料としては、タンタルとホウ素を含む合金、例えば、タンタルホウ素合金(TaB)、タンタルホウ素合金の窒化物(TaBN)等が挙げられる。
Next, formation of the stress correction film on the substrate will be described.
The stress correction film in the present invention is selected from those having a stress opposite to the stress of the multilayer reflective film to be formed. Generally, since the multilayer reflective film is formed densely and has a compressive stress, the stress correction film is selected from films having a tensile stress.
Then, for example, one that increases the magnitude (absolute value) of the stress of the stress correction film by the heat treatment is selected. Specifically, the stress shifts to the tensile stress side.
Further, since the stress correction film is preferably a smooth film, it is preferably an amorphous material. The smoothness of the surface of the stress compensation film is preferably not more than 0.2 nmRms, more preferably not more than 0.15 nmRms.
Further, it is preferable to use a film whose stress can be easily controlled, because the value of the initial stress applied to the stress correction film can be easily adjusted. As such a stress correction film, a material mainly containing tantalum (Ta) is preferable.
Examples of the material containing Ta as a main component include a Ta alloy and the like. Further, an amorphous material containing Ta as a main component is preferable. Examples of such a material include an alloy containing tantalum and boron, for example, a tantalum boron alloy (TaB), a nitride of a tantalum boron alloy (TaBN), and the like.

 例えば、タンタルホウ素合金の場合、DCマグネトロンスパッタ法を用いて、室温、Arガス雰囲気で基板上に形成することが好ましい。この場合、ガス圧を上げるに伴い、圧縮応力側から引っ張り応力側へ応力が変化するため、投入パワー一定の下でスパッタガス圧を変化させることにより、応力制御を微調整することが可能である。
 TaとBを含む合金膜は、良好なアモルファス状態を得るために、Bの含有量が10〜30at%であるのが好ましい。TaとBとNを含む合金膜の場合、Nが5〜30at%であり、N以外の成分を100at%とした時、Bが10〜30at%であるのが好ましい。
 応力補正膜としては、その他にSiを主成分とした材料を用いることも出来る。具体的には、Si単体や、Siに添加物をドープしたものである。この場合の添加物としては、窒素や酸素が挙げられる。このSiを主成分とする材料もアモルファス状態のものが好ましく用いられる。
 更には、応力補正膜としてCrを含む材料を用いることも出来る。例えば、クロムと窒素を含む材料、これに更に酸素及び/又は炭素を含む材料が挙げられる。これらのCrを含む材料は、平滑性、耐洗浄性に優れており、応力の制御性も良好である。CrN膜の場合、Nは10〜50at%、好ましくは20〜50at%が望ましい。
 その他の応力補正膜としては、TaとGeの合金,TaとGeの合金の窒化物,TaとSiの合金、TaとSiの合金の窒化物,WとNの合金等も挙げられる。
For example, in the case of a tantalum boron alloy, it is preferable to form it on a substrate at room temperature and in an Ar gas atmosphere using a DC magnetron sputtering method. In this case, since the stress changes from the compressive stress side to the tensile stress side as the gas pressure increases, it is possible to fine-tune the stress control by changing the sputter gas pressure under a constant input power. .
The alloy film containing Ta and B preferably has a B content of 10 to 30 at% in order to obtain a favorable amorphous state. In the case of an alloy film containing Ta, B, and N, it is preferable that N is 5 to 30 at%, and when components other than N are 100 at%, B is 10 to 30 at%.
As the stress correction film, a material containing Si as a main component can be used. Specifically, it is a simple substance of Si or a substance obtained by doping an additive to Si. In this case, the additives include nitrogen and oxygen. The material containing Si as a main component is also preferably used in an amorphous state.
Further, a material containing Cr can be used as the stress correction film. For example, a material containing chromium and nitrogen, and a material further containing oxygen and / or carbon can be used. These Cr-containing materials have excellent smoothness and washing resistance, and also have good stress controllability. In the case of a CrN film, N is desirably 10 to 50 at%, preferably 20 to 50 at%.
Other examples of the stress correction film include an alloy of Ta and Ge, a nitride of an alloy of Ta and Ge, an alloy of Ta and Si, a nitride of an alloy of Ta and Si, and an alloy of W and N.

 これらの応力補正膜は、成膜方法や成膜条件を適宜制御することによって、初期応力の値を所望の応力値に調整することができ、又、加熱により、応力の値が引っ張り方向へ変化する性質を有している。成膜方法としては、前述のDCマグネトロンスパッタリング法等を用いて基板上に形成することができる。
 ところで、本発明の目的を達成するため、基板上への応力補正膜の形成は、次のような点を考慮して行うことが肝要である。即ち、後工程で行われる加熱処理後において、応力補正膜の有する膜応力と、多層反射膜が有する膜応力とが、向きが反対で大きさが同等となる必要がある。従って、多層反射膜及び応力補正膜の加熱処理による膜応力の変化分を考慮して、加熱処理前の応力補正膜に与える初期応力及び膜厚を決定する。
 例えば、多層反射膜の構成が予め決定している場合、まず、加熱処理温度と加熱処理後の多層反射膜の膜応力の変化との関係を求める。更に、所定の応力補正膜材料において、加熱処理温度と膜厚と加熱処理後の膜応力の変化との関係を求める。これらの情報を参照して、加熱処理後の多層反射膜の膜応力と、加熱処理後の応力補正膜の膜応力が互いに逆向きで大きさがほぼ等しくなるように、両方の膜応力の変化分を見込んで、加熱処理温度、応力補正膜に最初に与える応力及び応力補正膜の膜厚を決定すればよい。
 但し、前述のように、応力補正膜に与える初期の応力が非常に高いと、表面粗さが大きくなるため、応力補正膜に与える膜応力は、0〜+300MPa程度(多層反射膜と同じ膜厚に換算した値)とするのがよい。
In these stress compensation films, the initial stress value can be adjusted to a desired stress value by appropriately controlling the film forming method and film forming conditions, and the stress value changes in the tensile direction by heating. Have the property of As a film formation method, the film can be formed on a substrate by using the above-described DC magnetron sputtering method or the like.
By the way, in order to achieve the object of the present invention, it is important to form a stress compensation film on a substrate in consideration of the following points. That is, it is necessary that the film stress of the stress correction film and the film stress of the multilayer reflection film have opposite directions and the same size after the heat treatment performed in the subsequent step. Therefore, the initial stress and the film thickness applied to the stress correction film before the heat treatment are determined in consideration of the change in the film stress due to the heat treatment of the multilayer reflection film and the stress correction film.
For example, when the configuration of the multilayer reflective film is determined in advance, first, the relationship between the heat treatment temperature and the change in the film stress of the multilayer reflective film after the heat treatment is determined. Further, the relationship between the heat treatment temperature, the film thickness, and the change in the film stress after the heat treatment in a predetermined stress correction film material is obtained. With reference to this information, change in both film stresses so that the film stress of the multilayer reflective film after the heat treatment and the film stress of the stress correction film after the heat treatment are opposite to each other and are almost equal in magnitude. The heat treatment temperature, the stress initially applied to the stress correction film, and the thickness of the stress correction film may be determined in consideration of the amount.
However, as described above, if the initial stress applied to the stress correction film is extremely high, the surface roughness increases, so that the film stress applied to the stress correction film is about 0 to +300 MPa (the same film thickness as the multilayer reflective film). Value).

 又、応力補正膜の膜厚は、表面粗さを増大させないために、必要な膜応力が得られる範囲で小さい方がよい。好ましくは、10〜300nm程度の厚さである。
 本実施の形態では、後工程で行う加熱処理により、応力補正膜と多層反射膜の膜応力が相殺しあうので、応力補正膜として最初から高い応力の膜を形成する必要がなく、表面粗さが小さくてすむ。
 なお、加熱処理後の多層反射膜を形成した基板の好ましい平坦度は、100nm以下である。本発明においては、加熱処理後、応力補正膜と多層反射膜の膜応力の絶対値が全く等しくはならなくとも、所定の平坦度を得るのに十分となる程度に、応力補正膜と多層反射膜の膜応力が相殺しあうようにすればよい。
又、本実施の形態のように、応力補正膜は、基板と多層反射膜の間に形成されてもよいが、多層反射膜上に形成してもよい。この場合も、材料及び成膜、応力補正膜の設計の考え方は、上述した実施形態の場合と同様である。
Further, the film thickness of the stress correction film is preferably as small as possible within a range where a necessary film stress can be obtained so as not to increase the surface roughness. Preferably, the thickness is about 10 to 300 nm.
In the present embodiment, since the film stress of the stress correction film and the multilayer reflection film cancel each other out due to the heat treatment performed in a later step, it is not necessary to form a high stress film as a stress correction film from the beginning, and the surface roughness is reduced. Is small.
Note that a preferable flatness of the substrate on which the multilayer reflective film is formed after the heat treatment is 100 nm or less. In the present invention, after the heat treatment, even if the absolute values of the film stresses of the stress correction film and the multilayer reflection film are not completely equal, the stress correction film and the multilayer reflection film are sufficiently large to obtain a predetermined flatness. What is necessary is just to make the film stress of the film cancel each other.
Further, as in the present embodiment, the stress correction film may be formed between the substrate and the multilayer reflection film, or may be formed on the multilayer reflection film. Also in this case, the concept of the material, the film formation, and the design of the stress compensation film are the same as those in the above-described embodiment.

 次に、多層反射膜の形成について説明する。
 本発明における多層反射膜は、屈折率の異なる物質を周期的に積層させた構造をしており、特定の波長の光を反射するように構成されている。例えば、約13nmの波長の露光光(EUV光)に対しては、MoとSiを交互に40周期程度積層した多層反射膜が通常用いられる。Mo/Si多層反射膜の場合、相対的に屈折率の大きい層がMo、相対的に屈折率の小さい(屈折率がより1に近い)層がSiである。多層反射膜を形成する材料は使用する露光光の波長に応じて、適宜選択すればよい。EUV光の領域で使用されるその他の多層反射膜の例としては、Ru/Si周期多層反射膜、Mo/Be周期多層反射膜、Mo化合物/Si化合物周期多層反射膜、Si/Nb周期多層反射膜、Si/Mo/Ru周期多層反射膜、Si/Mo/Ru/Mo周期多層反射膜、及びSi/Ru/Mo/Ru多層反射膜などが挙げられる。
 多層反射膜は、基板上、或いは、応力補正膜上に例えば、DCマグネトロンスパッタ法により形成できる。Mo/Si多層反射膜の場合、Arガス雰囲気下で、SiターゲットとMoターゲットを交互に用いて、30〜60周期、好ましくは40周期程度積層し、最後にSi膜を成膜すればよい。他の成膜方法としては、IBD(イオン・ビーム・デポディション)法等が使用できる。
Next, formation of the multilayer reflective film will be described.
The multilayer reflective film according to the present invention has a structure in which substances having different refractive indices are periodically laminated, and is configured to reflect light of a specific wavelength. For example, for exposure light (EUV light) having a wavelength of about 13 nm, a multilayer reflective film in which Mo and Si are alternately stacked for about 40 periods is usually used. In the case of the Mo / Si multilayer reflective film, a layer having a relatively large refractive index is Mo, and a layer having a relatively small refractive index (the refractive index is closer to 1) is Si. The material for forming the multilayer reflective film may be appropriately selected according to the wavelength of the exposure light used. Examples of other multilayer reflective films used in the EUV light region include Ru / Si periodic multilayer reflective films, Mo / Be periodic multilayer reflective films, Mo compound / Si compound periodic multilayer reflective films, and Si / Nb periodic multilayer reflective films. Film, Si / Mo / Ru periodic multilayer reflective film, Si / Mo / Ru / Mo periodic multilayer reflective film, and Si / Ru / Mo / Ru multilayer reflective film.
The multilayer reflection film can be formed on the substrate or the stress correction film by, for example, a DC magnetron sputtering method. In the case of the Mo / Si multilayer reflective film, an Si target and an Mo target are alternately used in an Ar gas atmosphere, and the Si target may be stacked for about 30 to 60 cycles, preferably about 40 cycles, and finally form the Si film. As another film formation method, an IBD (ion beam deposition) method or the like can be used.

 前述したように、多層反射膜及び応力補正膜の設計において、加熱処理後の多層反射膜の膜応力の変化分を予め考慮しておく必要がある。
 次に、加熱処理について説明する。
 本実施の形態における、基板上に形成された応力補正膜及び多層反射膜の加熱処理は、応力補正膜の有する膜応力と、多層反射膜の有する膜応力とを互いに逆向きで大きさ(絶対値)を略等しくし、膜応力が相殺し合うようにする作用を有する。
 膜の有する力は、単位膜厚当たりの膜応力と、膜厚との積で表される力であるから、加熱処理により、多層反射膜の有する力と、応力補正膜の有する力がつりあうようにすればよい。このためには、前述の多層反射膜の膜厚換算で示される応力補正膜の膜応力と、多層反射膜の単位膜厚あたりの膜応力が互いに逆向きで大きさ(絶対値)がほぼ等しくなるようにすればよい。
 一般に、大きな圧縮応力を有する多層反射膜は、加熱処理により、その応力が緩和される(引っ張り応力方向に変化し、ゼロに近づく方向になる)傾向にある。従って、加熱処理により、多層反射膜の有する膜応力の大きさの絶対値は小さくなる。
As described above, in designing the multilayer reflective film and the stress correction film, it is necessary to consider in advance the change in the film stress of the multilayer reflective film after the heat treatment.
Next, the heat treatment will be described.
In the heat treatment of the stress correction film and the multilayer reflective film formed on the substrate in the present embodiment, the film stress of the stress correction film and the film stress of the multilayer reflective film are reversed in magnitude (absolute direction). Values) are substantially equal, and have the effect of offsetting the film stresses.
Since the force of the film is a force expressed by the product of the film stress per unit film thickness and the film thickness, the heat treatment causes the force of the multilayer reflective film to balance with the force of the stress correction film. What should I do? To this end, the film stress of the stress correction film expressed in terms of the film thickness of the multilayer reflective film and the film stress per unit film thickness of the multilayer reflective film are opposite to each other and have substantially the same magnitude (absolute value). What should be done is.
Generally, in a multilayer reflective film having a large compressive stress, the stress tends to be reduced (changes in the direction of tensile stress and approaches zero) by heat treatment. Therefore, the absolute value of the magnitude of the film stress of the multilayer reflective film is reduced by the heat treatment.

 一方、本実施の形態では、応力補正膜は、加熱処理することにより、その応力の絶対値が大きくなる材料を用いることができる。即ち、応力補正膜には、ゼロ応力あるいは多層反射膜と逆向きの応力である引っ張り応力を有する膜を使用し、加熱処理をすることにより、応力補正膜の応力は更に、引っ張り応力が増大する方向に変化する。
 従って、加熱処理前には、多層反射膜の有する膜応力(圧縮応力)の大きさ(絶対値)は、応力補正膜の有する膜応力(引っ張り応力)の大きさ(絶対値)より大きく、これらは互いにつりあっていないが、加熱処理することにより、多層反射膜の膜応力(圧縮応力)の大きさ(絶対値)が小さくなると共に、応力補正膜の膜応力(引っ張り応力)の大きさ(絶対値)が大きくなり、これらがつりあい、相殺されるようになる。
 このように、多層反射膜の膜応力を相殺するためには、前述したように、予め加熱処理による多層反射膜及び応力補正膜の膜応力のそれぞれの変化分を考慮して、加熱処理温度、多層反射膜の初期応力や膜厚、応力補正膜の初期応力や膜厚を設計すればよい。
 高温で加熱処理を行うと、多層反射膜の反射率低下を招くため、加熱処理は、応力補正膜の成膜時の温度よりも高く200℃以下の基板加熱温度、更には、150℃以下で行うのが好ましい。また、十分な応力変化を得るためには、90℃以上の温度が好ましい。また、加熱処理時間は、加熱処理による応力補正膜と多層反射膜の膜応力の変化が達成されるのに十分な時間であればよく、通常は1時間程度である。
On the other hand, in this embodiment, a material whose absolute value of the stress increases by heat treatment can be used for the stress correction film. In other words, a film having a tensile stress that is zero stress or a stress in the opposite direction to the multilayer reflective film is used as the stress correction film, and the stress of the stress correction film further increases by performing the heat treatment. Change in direction.
Therefore, before the heat treatment, the magnitude (absolute value) of the film stress (compressive stress) of the multilayer reflective film is larger than the magnitude (absolute value) of the film stress (tensile stress) of the stress correction film. Are not balanced with each other, but by performing the heat treatment, the magnitude (absolute value) of the film stress (compressive stress) of the multilayer reflective film is reduced, and the magnitude (absolute value) of the film stress (tensile stress) of the stress correction film is reduced. Value), which are balanced and offset.
As described above, in order to cancel the film stress of the multilayer reflective film, as described above, in consideration of the respective changes in the film stress of the multilayer reflective film and the stress correction film due to the heat treatment, the heat treatment temperature, The initial stress and the film thickness of the multilayer reflective film and the initial stress and the film thickness of the stress correction film may be designed.
When the heat treatment is performed at a high temperature, the reflectance of the multilayer reflective film is reduced. It is preferred to do so. In order to obtain a sufficient stress change, a temperature of 90 ° C. or more is preferable. Further, the heat treatment time may be a time sufficient to achieve a change in the film stress of the stress correction film and the multilayer reflective film due to the heat treatment, and is usually about one hour.

 加熱処理は、応力補正膜及び多層反射膜を同時に加熱処理する場合は、基板上に応力補正膜及び多層反射膜が形成された後に行うのであれば、製造工程中のどの工程で行ってもよい。他の層への影響等が少ない点から、基板上に応力補正膜と多層反射膜を形成後、バッファ層や吸収体層等の他層の形成の前に行うのが好ましい。
 以上の実施形態では、基板上に応力補正膜及び多層反射膜を形成後、これらを同時に加熱処理する形態を説明したが、基板と多層反射膜の間に応力補正膜を形成する場合には、まず基板上に応力補正膜を形成し、多層反射膜を形成する前に、応力補正膜の加熱処理を行って、応力補正膜の応力を引っ張り応力側に変化させた後、多層反射膜を形成し、多層反射膜の加熱処理を行ってもよい。このようにすると、加熱工程は二工程で行うことになるが、多層反射膜形成前に応力補正膜の加熱処理による応力変化を行うことで、多層反射膜の特性に影響を及ぼすような比較的高温での加熱処理が可能であるため、応力補正膜の応力の変化量を大きくとることが出来るようになる。
 本発明では、加熱処理による多層反射膜及び応力補正膜の膜応力の相殺を利用しているため、成膜時において、応力補正膜に多層反射膜の有する膜応力を相殺するための大きな応力を与える必要がない。従って、応力補正膜の表面粗さが大きくなることがない。又、本発明では、多層反射膜の加熱処理による応力緩和と、応力補正膜による多層反射膜の膜応力の相殺を同時に利用しているため、多層反射膜自身の有する膜応力を加熱処理だけでゼロに近づける必要がないため、高温での加熱処理は必要なく、多層反射膜の反射率低下を招くことがない。
 なお、加熱処理による応力補正膜の応力の変化量は、応力補正膜の成膜条件(成膜温度等)によっても変化する。従って、応力補正膜の応力の変化量は、成膜条件を調整することでコントロールすることが可能である。
 上述の実施の形態では、加熱処理により応力の絶対値が増大するような材料を用いた応力補正膜を例に説明したが、本発明はこれに限られない。必要な表面粗さ(平滑性)が得られ、且つ、多層反射膜の反射率に影響しない程度の加熱処理によって多層反射膜との応力の釣り合いがとれるのであれば、加熱処理によりその応力が変化しない、或いは僅かに減少するような材料を用いた応力補正膜であってもよい。応力補正膜が加熱処理によって、その応力が変化しない或いは僅かに減少するものであっても、加熱処理後に多層反射膜の応力と相殺しあうことで、上述の応力補正膜の表面粗さと多層反射膜の反射率低下を解決できる。
In the case where the heat treatment is performed simultaneously on the stress correction film and the multilayer reflection film, the heat treatment may be performed at any step in the manufacturing process as long as the heat treatment is performed after the stress correction film and the multilayer reflection film are formed on the substrate. . It is preferable to perform this step after forming the stress correction film and the multilayer reflective film on the substrate and before forming other layers such as the buffer layer and the absorber layer, because the influence on other layers is small.
In the above embodiment, the form in which the stress correction film and the multilayer reflection film are formed on the substrate and then heat-treated at the same time has been described, but when the stress correction film is formed between the substrate and the multilayer reflection film, First, a stress compensation film is formed on the substrate, and before forming the multilayer reflection film, a heat treatment is performed on the stress compensation film to change the stress of the stress compensation film to the tensile stress side, and then a multilayer reflection film is formed. Then, heat treatment of the multilayer reflective film may be performed. In this case, the heating step is performed in two steps. However, by performing a stress change due to the heat treatment of the stress correction film before forming the multilayer reflective film, a relatively large influence on the characteristics of the multilayer reflective film can be obtained. Since the heat treatment at a high temperature is possible, the amount of change in the stress of the stress correction film can be increased.
In the present invention, since the offset of the film stress of the multilayer reflective film and the stress correction film due to the heat treatment is used, a large stress for offsetting the film stress of the multilayer reflective film in the stress correction film during film formation is used. No need to give. Therefore, the surface roughness of the stress correction film does not increase. Further, in the present invention, since the stress relaxation by the heat treatment of the multilayer reflective film and the offset of the film stress of the multilayer reflective film by the stress correction film are simultaneously used, the film stress of the multilayer reflective film itself can be obtained only by the heat treatment. Since it is not necessary to approach zero, heat treatment at a high temperature is not necessary, and the reflectance of the multilayer reflective film does not decrease.
The amount of change in the stress of the stress correction film due to the heat treatment also changes depending on the film formation conditions (such as the film formation temperature) of the stress correction film. Therefore, the amount of change in the stress of the stress correction film can be controlled by adjusting the film forming conditions.
In the above-described embodiment, the stress correction film using a material whose absolute value of stress increases by the heat treatment is described as an example, but the present invention is not limited to this. If the required surface roughness (smoothness) is obtained and the stress with the multilayer reflective film is balanced by the heat treatment that does not affect the reflectance of the multilayer reflective film, the heat treatment changes the stress. A stress correction film using a material that does not or slightly reduces the stress may be used. Even if the stress correction film does not change or slightly reduces its stress due to the heat treatment, the stress correction film cancels out the stress of the multilayer reflection film after the heat treatment, so that the surface roughness of the stress correction film and the multilayer reflection are reduced. A reduction in the reflectance of the film can be solved.

 次に、バッファ層の形成について説明する。
 バッファ層は、吸収体層に転写パターンを形成する際に、エッチング停止層として下層の多層反射膜を保護する機能を有し、通常は多層反射膜と吸収体層との間に形成される。なお、バッファ層は必要に応じて設ければよい。
 バッファ層の材料としては、吸収体層とのエッチング選択比が大きい材料が選択される。バッファ層と吸収体層のエッチング選択比は5以上、好ましくは10以上、さらに好ましくは20以上である。更に、低応力で、平滑性に優れた材料が好ましく、とくに0.3nmRms以下の平滑性を有していることが好ましい。このような観点から、バッファ層を形成する材料は、微結晶あるいはアモルファス構造であることが好ましい。
 一般に、吸収体層の材料には、TaやTa合金等が良く用いられている。吸収体層の材料にTa系の材料を用いた場合、バッファ層としては、Crを含む材料を用いるのが好ましい。例えば、Cr単体や、Crに窒素、酸素、炭素の少なくとも1つの元素が添加された材料が挙げられる。具体的には、窒化クロム(CrN)等である。
一方、吸収体層として、Cr単体や、Crを主成分とする材料を用いる場合には、バッファ層には、Taを主成分とする材料、例えば、TaとBを含む材料や、TaとBとNを含む材料等を用いることができる。
Next, formation of the buffer layer will be described.
The buffer layer has a function of protecting the lower multilayer reflective film as an etching stop layer when forming a transfer pattern on the absorber layer, and is usually formed between the multilayer reflective film and the absorber layer. Note that the buffer layer may be provided as needed.
As the material of the buffer layer, a material having a high etching selectivity with respect to the absorber layer is selected. The etching selectivity between the buffer layer and the absorber layer is 5 or more, preferably 10 or more, and more preferably 20 or more. Further, a material having low stress and excellent in smoothness is preferable, and it is particularly preferable to have a smoothness of 0.3 nmRms or less. From such a viewpoint, the material forming the buffer layer preferably has a microcrystalline or amorphous structure.
Generally, Ta, Ta alloy, or the like is often used as a material for the absorber layer. When a Ta-based material is used for the material of the absorber layer, it is preferable to use a material containing Cr for the buffer layer. For example, Cr alone or a material in which at least one element of nitrogen, oxygen, and carbon is added to Cr may be used. Specifically, it is chromium nitride (CrN) or the like.
On the other hand, when Cr alone or a material containing Cr as a main component is used for the absorber layer, a material containing Ta as a main component, for example, a material containing Ta and B, or a material containing Ta and B is used for the buffer layer. And a material containing N can be used.

 このバッファ層は、反射型マスク形成時には、マスクの反射率低下を防止するために、通常、吸収体層に形成されたパターンに従って、パターン状に除去される。しかし、バッファ層に露光光であるEUV光の透過率の大きい材料を用い、膜厚を十分薄くすることが出来れば、パターン状に除去せずに、多層反射膜を覆うように残しておいてもよい。
バッファ層は、例えば、DCスパッタ、RFスパッタ、イオンビームスパッタ等のスパッタ法で形成することができる。
 バッファ層の有する膜応力はゼロであることが好ましいが、このバッファ層の膜応力がゼロ又はそれに近い値ではなく、かつ反射型マスクとして用いられる際に、バッファ層にパターンが形成されない場合には、バッファ層の有する膜応力も考慮して、バッファ層、多層反射膜、応力補正膜の応力がつりあうように設計すればよい。
 バッファ層以外のパターンが形成されない層を更に有する場合にも同様な考え方で設計を行えばよい。
This buffer layer is usually removed in a pattern according to the pattern formed on the absorber layer in order to prevent a decrease in the reflectance of the mask when the reflective mask is formed. However, if a material having a high transmittance of EUV light as exposure light is used for the buffer layer and the film thickness can be made sufficiently small, it is not removed in a pattern but left to cover the multilayer reflective film. Is also good.
The buffer layer can be formed by, for example, a sputtering method such as DC sputtering, RF sputtering, or ion beam sputtering.
It is preferable that the film stress of the buffer layer is zero.However, when the film stress of the buffer layer is not zero or a value close thereto and when a pattern is not formed in the buffer layer when used as a reflective mask, The design may be made such that the stresses of the buffer layer, the multilayer reflective film, and the stress correction film are balanced in consideration of the film stress of the buffer layer.
The design may be performed based on the same concept even when a layer other than the buffer layer, on which a pattern is not formed, is further provided.

 次に、吸収体層の形成について説明する。
 本発明における吸収体層の材料としては、露光光の吸収率が高く、吸収体層の下側に位置する層(通常バッファ層或いは多層反射膜)とのエッチング選択比が十分大きいものが選択される。例えば、Taを主要な金属成分とする材料が好ましい。この場合、バッファ層にCrを主成分とする材料を用いれば、エッチング選択比を大きく(10以上)取ることができる。ここで、Taを主要な金属元素とする材料とは、成分中の金属元素のうち、もっとも組成比の大きい金属がTaであるという意味である。この吸収体層に用いられるTaを主要な金属元素とする材料は、通常金属または合金である。また、平滑性、平坦性の点から、アモルファス状または微結晶の構造を有しているものが好ましい。Taを主要な金属元素とする材料としては、TaとBを含む材料、TaとNを含む材料、TaとBとOを含む材料、TaとBとNを含む材料、TaとSiを含む材料、TaとSiとNを含む材料、TaとGeを含む材料、TaとGeとNを含む材料等を用いることができる。TaにBやSi,Ge等を加えることにより、アモルファス状の材料が容易に得られ、平滑性を向上させることができる。また、TaにNやOを加えれば、酸化に対する耐性が向上するため、経時的な安定性を向上させることができるという効果が得られる。
Next, formation of the absorber layer will be described.
As the material of the absorber layer in the present invention, a material having a high absorptance of exposure light and a sufficiently large etching selectivity with a layer (usually a buffer layer or a multilayer reflective film) located below the absorber layer is selected. You. For example, a material containing Ta as a main metal component is preferable. In this case, if a material containing Cr as a main component is used for the buffer layer, a large etching selectivity (10 or more) can be obtained. Here, the material having Ta as a main metal element means that the metal having the largest composition ratio among the metal elements in the component is Ta. The material containing Ta as the main metal element used for the absorber layer is usually a metal or an alloy. Further, those having an amorphous or microcrystalline structure are preferable from the viewpoint of smoothness and flatness. Materials containing Ta as a main metal element include materials containing Ta and B, materials containing Ta and N, materials containing Ta, B and O, materials containing Ta, B and N, and materials containing Ta and Si. For example, a material containing Ta, Si, and N, a material containing Ta and Ge, a material containing Ta, Ge, and N can be used. By adding B, Si, Ge or the like to Ta, an amorphous material can be easily obtained, and the smoothness can be improved. Further, if N or O is added to Ta, the resistance to oxidation is improved, and thus the effect of improving the stability over time can be obtained.

 他の吸収体層の材料としては、Crを主成分とする材料(クロム、窒化クロム等)、タングステンを主成分とする材料(窒化タングステン等)、チタンを主成分とする材料(チタン、窒化チタン)等を用いることができる。
 これらの吸収体層は、通常のスパッタ法で形成する事が出来る。なお、パターン形成後のパターンの形状精度、位置精度を高く保つために、吸収体層は応力が小さくなるように形成するのが好ましい。
 以上のようにして、本実施の形態の反射型マスクブランクが得られる。
 なお、本実施の形態の反射型マスクブランクは必要に応じて更に別の層を有していてもよい。
As a material of another absorber layer, a material containing Cr as a main component (chromium, chromium nitride, etc.), a material containing tungsten as a main component (tungsten nitride, etc.), a material containing titanium as a main component (titanium, titanium nitride, etc.) ) Etc. can be used.
These absorber layers can be formed by a normal sputtering method. It is preferable that the absorber layer is formed so as to reduce the stress in order to keep the shape accuracy and the position accuracy of the pattern after the pattern formation high.
As described above, the reflective mask blank of the present embodiment is obtained.
Note that the reflective mask blank of the present embodiment may have another layer as needed.

 次に、反射型マスクの製造方法について説明する。
 反射型マスクは、上述した反射型マスクブランクの吸収体層にパターンを形成することで製造できる。
 吸収体層へのパターン形成は次のようにして行う。上記反射型マスクブランク上に電子線描画用レジスト層を形成し、電子線描画及び現像によりレジストパターンを形成する。次いで、このレジストパターンをマスクとして、吸収体層をドライエッチングなどの方法でエッチングする。吸収体層がTaを主要な金属成分とする材料の場合、バッファ層を多層反射膜の保護層として、塩素を用いたドライエッチングでパターンを形成することができる。吸収体層のパターン形成後、吸収体層のパターン上に残ったレジスト層を除去する。更に、必要に応じて、バッファ層を吸収体層のパターンに従って、パターン状に除去する。例えば、バッファ層にCrを主成分とする膜を使用している場合には、塩素と酸素の混合ガスを用いたドライエッチングでバッファ層を除去することができる。
以上のようにして、反射型マスクが得られる。
Next, a method for manufacturing a reflective mask will be described.
The reflective mask can be manufactured by forming a pattern on the absorber layer of the reflective mask blank described above.
The pattern formation on the absorber layer is performed as follows. A resist layer for electron beam lithography is formed on the reflective mask blank, and a resist pattern is formed by electron beam lithography and development. Next, using the resist pattern as a mask, the absorber layer is etched by a method such as dry etching. When the absorber layer is made of a material containing Ta as a main metal component, a pattern can be formed by dry etching using chlorine using the buffer layer as a protective layer of the multilayer reflective film. After forming the pattern of the absorber layer, the resist layer remaining on the pattern of the absorber layer is removed. Further, if necessary, the buffer layer is removed in a pattern according to the pattern of the absorber layer. For example, when a film mainly containing Cr is used for the buffer layer, the buffer layer can be removed by dry etching using a mixed gas of chlorine and oxygen.
As described above, a reflection type mask is obtained.

 以上のように、本発明の反射型マスクブランク及び反射型マスクの製造方法においては、加熱処理による多層反射膜の膜応力と応力補正膜の膜応力の相殺を利用して多層反射膜の膜応力の影響を低減するようにしたため、応力補正膜の表面荒れを抑え、平坦性に優れた高精度なパターン転写が可能な反射型マスクブランク及び反射型マスクが得られる。又、比較的低温での加熱処理で良いため、多層反射膜の反射率の低下を招かずに、平坦性に優れた反射型マスクブランク及び反射型マスクが得られる。
 次に、本発明の実施例により本発明を更に具体的に説明する。
As described above, in the reflective mask blank and the method of manufacturing the reflective mask of the present invention, the film stress of the multilayer reflective film is compensated by utilizing the offset between the film stress of the multilayer reflective film and the film stress of the stress correction film due to the heat treatment. Therefore, the reflection type mask blank and the reflection type mask which can suppress the surface roughness of the stress correction film and can transfer the pattern with high accuracy and excellent flatness can be obtained. In addition, since heat treatment at a relatively low temperature is sufficient, a reflective mask blank and a reflective mask excellent in flatness can be obtained without lowering the reflectance of the multilayer reflective film.
Next, the present invention will be described more specifically with reference to examples of the present invention.

 図1を参照しながら本実施例のEUV反射型マスクブランク100及びEUV反射型マスク101の製造方法を説明する。図1(a)は上記反射型マスクブランクの断面図、同(b)は上記反射型マスクの断面図である。
 基板11は、SiO2-TiO2系のガラス基板(外形6インチ角、厚さが6.3mm)である。この基板の熱膨張率は0.2×10−7/℃、ヤング率は67GPaである。そして、ガラス基板は機械研磨により、0.2nmRms以下の平滑な表面と100nm以下の平坦度に形成した。
 まず、基板11上に、応力補正膜12として、TaとBを含む膜を70nmの厚さで形成した。成膜は、Ta及びBを含むターゲットを用いて、Arガスを用いて、DCマグネトロンスパッタ法で行った。この際、スパッタ条件を制御することで応力補正膜12の有する応力は、単位膜厚当たりの+600MPaとした。Ta:Bの組成比は、4:1であり、応力補正膜12表面の表面粗さは、0.14nmRmsであった。
 この応力補正膜12の応力及び膜厚は、後工程にて行われる加熱処理における多層反射膜及び応力補正膜の膜応力の変化を考慮して決定した。後に形成する多層反射膜の膜厚(290nm)換算にすると、応力補正膜12の膜応力は+145MPaである。
A method for manufacturing the EUV reflective mask blank 100 and the EUV reflective mask 101 of the present embodiment will be described with reference to FIG. FIG. 1A is a sectional view of the reflective mask blank, and FIG. 1B is a sectional view of the reflective mask.
The substrate 11 is a SiO 2 —TiO 2 glass substrate (external size 6 inch square, thickness 6.3 mm). The thermal expansion coefficient of this substrate is 0.2 × 10 −7 / ° C., and the Young's modulus is 67 GPa. The glass substrate was formed by mechanical polishing to have a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less.
First, a film containing Ta and B was formed with a thickness of 70 nm as the stress correction film 12 on the substrate 11. The film was formed by a DC magnetron sputtering method using a target containing Ta and B and using Ar gas. At this time, the stress of the stress correction film 12 was controlled to +600 MPa per unit film thickness by controlling the sputtering conditions. The composition ratio of Ta: B was 4: 1, and the surface roughness of the surface of the stress correction film 12 was 0.14 nmRms.
The stress and the film thickness of the stress correction film 12 were determined in consideration of changes in the film stress of the multilayer reflective film and the stress correction film in a heat treatment performed in a later step. When converted to a film thickness (290 nm) of a multilayer reflective film to be formed later, the film stress of the stress correction film 12 is +145 MPa.

 次に、応力補正膜12上に、多層反射膜13を形成した。
 多層反射膜13は、13〜14nmの露光光波長帯域に適した多層反射膜を形成するために、本実施例では、Mo/Si周期多層反射膜を採用した。多層反射膜13は、MoとSiをDCマグネトロンスパッタ法により基板上に交互に積層して形成した。まず、Siターゲットを用いて、Arガス圧0.1PaでSi膜を4.2nm成膜し、その後Moターゲットを用いて、Arガス圧0.1PaでMo膜を2.8nm成膜し、これを一周期として、40周期積層した後、最後にSi膜を10nm成膜した。合計膜厚は290nmである。形成された多層反射膜の応力は、―450MPaであった。
 この多層反射膜に対し、露光波長帯域での入射角5度でのピーク反射率は65%であった。又、多層反射膜上の表面粗さは0.15nmRmsであった。多層反射膜表面の平坦度は800nmであった。
 以上のようにして、多層反射膜付き基板を得た。
Next, a multilayer reflective film 13 was formed on the stress correction film 12.
In this embodiment, the multilayer reflective film 13 is a Mo / Si periodic multilayer reflective film in order to form a multilayer reflective film suitable for the exposure light wavelength band of 13 to 14 nm. The multilayer reflective film 13 was formed by alternately laminating Mo and Si on a substrate by DC magnetron sputtering. First, using a Si target, a 4.2 nm Si film was formed at an Ar gas pressure of 0.1 Pa, and then using a Mo target, a 2.8 nm Mo film was formed at an Ar gas pressure of 0.1 Pa. After stacking for 40 cycles, a Si film was finally formed to a thickness of 10 nm. The total film thickness is 290 nm. The stress of the formed multilayer reflective film was -450 MPa.
With respect to this multilayer reflective film, the peak reflectance at an incident angle of 5 degrees in the exposure wavelength band was 65%. The surface roughness on the multilayer reflective film was 0.15 nmRms. The flatness of the multilayer reflective film surface was 800 nm.
As described above, a substrate with a multilayer reflective film was obtained.

 次に、得られた多層反射膜付き基板に加熱処理を行った。加熱処理は、150℃基板加熱温度で、1時間行った。これにより、多層反射膜13の有する応力は、引っ張り方向に変化し−300MPaとなり、応力補正膜12のTaB膜は、単位膜厚当たりの応力が+1000MPaに変化した。即ち、応力補正膜の膜応力(多層反射膜の膜厚換算の値)は+241MPaである。この加熱処理により、多層反射膜付き基板全体の応力は、−59MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は80nmと平坦度が約1/10に向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、65%と、加熱処理前と比較して反射率の低下は見られなかった。
 次に、加熱処理後の多層反射膜付き基板の多層反射膜13上にバッファ層14として、窒化クロム(CrN)膜を30nmの厚さに形成した。成膜は、Crターゲットを用いて、スパッタガスとして、窒素とArを用いてDCマグネトロンスパッタ法によって行った。成膜されたCrN膜において、Cr:Nの組成比は0.9:0.1で結晶状態は多結晶であった。又、膜応力は50nm膜厚換算で+40MPaであった。
Next, heat treatment was performed on the obtained substrate with a multilayer reflective film. The heat treatment was performed at a substrate heating temperature of 150 ° C. for one hour. As a result, the stress of the multilayer reflective film 13 changed in the tensile direction to -300 MPa, and the stress per unit film thickness of the TaB film of the stress correction film 12 changed to +1000 MPa. That is, the film stress of the stress correction film (the value converted into the film thickness of the multilayer reflective film) is +241 MPa. By this heat treatment, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to -59 MPa (value in terms of the multilayer film thickness). The flatness of the substrate with the multilayer reflective film was 80 nm, and the flatness was improved to about 1/10. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, the reflectance was found to be 65%, which was lower than that before the heat treatment. I couldn't.
Next, a chromium nitride (CrN) film having a thickness of 30 nm was formed as a buffer layer 14 on the multilayer reflection film 13 of the substrate with the multilayer reflection film after the heat treatment. The film was formed by a DC magnetron sputtering method using a Cr target and using nitrogen and Ar as sputtering gases. In the formed CrN film, the composition ratio of Cr: N was 0.9: 0.1 and the crystal state was polycrystalline. The film stress was +40 MPa in terms of a film thickness of 50 nm.

 次に、CrN膜より構成されるバッファ層14の上に、吸収体層15として、タンタルとホウ素と窒素からなる合金(TaBN膜)を50nmの厚さで形成した。成膜は、Ta及びBを含むターゲットを用いて、Arに窒素を10%添加して、DCマグネトロンスパッタ法によって行った。この際、スパッタ条件を制御することで吸収体層15の有する応力は、バッファ層である窒化クロム膜とほぼ同等の大きさで逆向きの応力である―50MPaとした。成膜されたTaBN膜において、Taは0.8Bは0.1、Nは、0.1であり、結晶状態はアモルファスであった。
 以上のようにして、本実施例の反射型マスクブランク100を得た。 
 なお、上記の応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表1に示した。
Next, an alloy (TaBN film) made of tantalum, boron and nitrogen was formed with a thickness of 50 nm as the absorber layer 15 on the buffer layer 14 composed of the CrN film. The film was formed by DC magnetron sputtering using a target containing Ta and B and adding 10% of nitrogen to Ar. At this time, by controlling the sputtering conditions, the stress of the absorber layer 15 was set to −50 MPa, which is the same as the stress of the chromium nitride film as the buffer layer and the stress in the opposite direction. In the formed TaBN film, Ta was 0.8B for 0.1, N was 0.1, and the crystalline state was amorphous.
As described above, the reflective mask blank 100 of the present example was obtained.
Table 1 below summarizes numerical values such as the film thickness, surface roughness, stress before and after the heat treatment, and flatness of the stress correction film and the multilayer reflective film.

Figure 2004104118
Figure 2004104118

 次に、このEUV反射型マスクブランク100を用いて、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを、次に記載する方法により作製した。
 まず、前記EUV反射型マスクブランク100上に電子線描画用レジストを塗布・ベークし、電子線により描画して現像を行い、レジストパターンを形成した。
 このレジストパターンをマスクとして、EUV吸収体層15を塩素を用いてドライエッチングし、EUV反射型マスクブランク上に吸収体層パターン15aを形成した。
 更に吸収体層パターン15a上に残ったレジストパターンを100℃の熱硫酸で除去した。次に、バッファ層14を塩素と酸素の混合ガスを用いて、吸収体層のパターン15aに従ってドライエッチングし、パターン状のバッファ層14aとした。
以上の様にして、本実施例の反射型マスク101が得られた。
 次に、図2を参照して、反射型マスク101を用いてレジスト付き半導体基板33にEUV光によってパターンを転写する方法を説明する。図2に示す反射型マスクを搭載したパターン転写装置50は、レーザープラズマX線源31、反射型マスク101、縮小光学系32等から概略構成される。縮小光学系32は、X線反射ミラーを用いた。縮小光学系32により、反射型マスク101で反射されたパターンは通常1/4程度に縮小される。尚、露光波長として13〜14nmの波長帯を使用するので、光路が真空中になるように予め設定した。
Next, using this EUV reflective mask blank 100, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was produced by the method described below.
First, a resist for electron beam lithography was applied and baked on the EUV reflective mask blank 100, and then drawn and developed with an electron beam to form a resist pattern.
Using this resist pattern as a mask, the EUV absorber layer 15 was dry-etched using chlorine to form an absorber layer pattern 15a on the EUV reflective mask blank.
Further, the resist pattern remaining on the absorber layer pattern 15a was removed with hot sulfuric acid at 100 ° C. Next, the buffer layer 14 was dry-etched using a mixed gas of chlorine and oxygen in accordance with the pattern 15a of the absorber layer, to obtain a patterned buffer layer 14a.
As described above, the reflective mask 101 of this example was obtained.
Next, with reference to FIG. 2, a method of transferring a pattern to the semiconductor substrate 33 with a resist by EUV light using the reflective mask 101 will be described. A pattern transfer apparatus 50 equipped with a reflection type mask shown in FIG. 2 is schematically constituted by a laser plasma X-ray source 31, a reflection type mask 101, a reduction optical system 32 and the like. As the reduction optical system 32, an X-ray reflection mirror was used. The pattern reflected by the reflective mask 101 by the reduction optical system 32 is normally reduced to about 1/4. Since a wavelength band of 13 to 14 nm is used as the exposure wavelength, it was set in advance so that the optical path was in a vacuum.

 このような状態で、レーザープラズマX線源31から得られたEUV光を反射型マスク101に入射し、ここで反射された光を縮小光学系32を通してレジスト付き半導体基板(Siウエハ)33上に転写した。
 反射型マスク101に入射した光は、吸収体層のパターン15aのある部分では、吸収体層に吸収されて反射されず、一方、吸収体層のパターン15aのない部分に入射した光は多層反射膜13により反射される。このようにして、反射型マスク101から反射される光により形成される像が縮小光学系32に入射する。縮小光学系32を経由した露光光は、半導体基板33上のレジスト層に転写パターンを露光する。そして、露光済レジストを現像することによってレジストパターンを形成した。以上のようにして半導体基板上へのパターン転写を行った結果、反射型マスク101の精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In such a state, EUV light obtained from the laser plasma X-ray source 31 is incident on the reflection type mask 101, and the light reflected here is passed through the reduction optical system 32 onto the semiconductor substrate with resist (Si wafer) 33. Transcribed.
Light incident on the reflective mask 101 is absorbed by the absorber layer and is not reflected at a portion where the pattern 15a of the absorber layer is provided, while light incident on a portion of the absorber layer where the pattern 15a is not provided is a multilayer reflection. The light is reflected by the film 13. Thus, an image formed by the light reflected from the reflective mask 101 enters the reduction optical system 32. The exposure light having passed through the reduction optical system 32 exposes a transfer pattern to a resist layer on the semiconductor substrate 33. Then, a resist pattern was formed by developing the exposed resist. As a result of pattern transfer onto the semiconductor substrate as described above, it was confirmed that the accuracy of the reflective mask 101 was 16 nm or less, which is the required accuracy of the 70 nm design rule.

 本実施例では、前記の応力補正膜12の成膜時の条件を変えて、最初に応力補正膜に与える膜応力を+50MPaとし、加熱処理条件を200℃60分とした以外は、実施例1と同様の方法で、反射型マスクブランクを形成した。
 本実施例における応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表2に示した。
Example 1 In this example, the conditions at the time of forming the stress correction film 12 were changed so that the film stress initially applied to the stress correction film was +50 MPa, and the heat treatment condition was 200 ° C. for 60 minutes. A reflective mask blank was formed in the same manner as described above.
Table 2 below summarizes numerical values of the film thickness, surface roughness, stress before and after heat treatment, flatness, and the like of the stress correction film and the multilayer reflective film in this example.

Figure 2004104118
Figure 2004104118

 本実施例では、加熱処理により、多層反射膜付き基板全体の応力は、+66MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は85nmに向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、加熱処理前と比較して反射率の低下は見られなかった。
 次に、この反射型マスクブランクを用いて、実施例1と同様に、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを作製した。さらに、実施例1と同様に、作製した反射型マスクを用いて、図2のパターン転写装置により、半導体基板上へのパターン転写を行った結果、本実施例の反射型マスクの精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In this example, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to +66 MPa (a value in terms of the thickness of the multilayer film) by the heat treatment. The flatness of the substrate with the multilayer reflective film was improved to 85 nm. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, no decrease in the reflectivity was observed as compared with that before the heat treatment.
Next, using this reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured in the same manner as in Example 1. Further, as in the case of Example 1, the pattern transfer onto the semiconductor substrate was performed by the pattern transfer device of FIG. 2 using the manufactured reflective mask, and as a result, the accuracy of the reflective mask of this embodiment was 70 nm. It was confirmed that the required accuracy of the rule was 16 nm or less.

 本実施例では、応力補正膜を基板と多層反射膜の間に設けるのではなく、多層反射膜上(多層反射膜とバッファ層の間)に設け、基板上に順次多層反射膜、応力補正膜が設けられた構成とした。更に、加熱処理は、200℃60分とし、多層反射膜上に応力補正膜が設けられた後に行った。応力補正膜としては、Ru膜を用い、10nmの厚さに形成した。これら以外は、実施例1と同様の方法で、反射型マスクブランクを形成した。
本実施例における応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表3に示した。
In this embodiment, the stress correction film is not provided between the substrate and the multilayer reflection film, but is provided on the multilayer reflection film (between the multilayer reflection film and the buffer layer), and the multilayer reflection film and the stress correction film are sequentially provided on the substrate. Was provided. Further, the heat treatment was performed at 200 ° C. for 60 minutes after the stress correction film was provided on the multilayer reflective film. As the stress correction film, a Ru film was used and formed to a thickness of 10 nm. Except for these, a reflective mask blank was formed in the same manner as in Example 1.
Table 3 below summarizes numerical values such as the film thickness, surface roughness, stress before and after heat treatment, and flatness of the stress correction film and the multilayer reflective film in this example.

Figure 2004104118
Figure 2004104118

 本実施例では、加熱処理により、多層反射膜付き基板全体の応力は、−62MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は80nmに向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、加熱処理前と比較して反射率の低下は見られなかった。
 次に、この反射型マスクブランクを用いて、実施例1と同様に、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを作製した。さらに、実施例1と同様に、作製した反射型マスクを用いて、図2のパターン転写装置により、半導体基板上へのパターン転写を行った結果、本実施例の反射型マスクの精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In the present example, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to -62 MPa (a value in terms of the thickness of the multilayer film) by the heat treatment. The flatness of the substrate with the multilayer reflective film was improved to 80 nm. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, no decrease in the reflectivity was observed as compared with that before the heat treatment.
Next, using this reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured in the same manner as in Example 1. Further, as in the case of Example 1, the pattern transfer onto the semiconductor substrate was performed by the pattern transfer device of FIG. 2 using the manufactured reflective mask, and as a result, the accuracy of the reflective mask of this embodiment was 70 nm. It was confirmed that the required accuracy of the rule was 16 nm or less.

 本実施例は、実施例1における応力補正膜12として、CrN膜(Cr:N=8:2)を用い、70nmの厚さに形成し、加熱処理を200℃、60分とした以外は実施例1と同様の方法で、反射型マスクブランクを形成した。
本実施例における応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表4に示した。
The present embodiment was performed except that a CrN film (Cr: N = 8: 2) was used as the stress correction film 12 in the first embodiment, the thickness was 70 nm, and the heat treatment was performed at 200 ° C. for 60 minutes. In the same manner as in Example 1, a reflective mask blank was formed.
Table 4 below summarizes numerical values of the film thickness, surface roughness, stress before and after the heat treatment, flatness, and the like of the stress correction film and the multilayer reflective film in this example.

Figure 2004104118
Figure 2004104118

 本実施例では、加熱処理により、多層反射膜付き基板全体の応力は、−40MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は40nmに向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、加熱処理前と比較して反射率の低下は見られなかった。
 次に、この反射型マスクブランクを用いて、実施例1と同様に、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを作製した。さらに、実施例1と同様に、作製した反射型マスクを用いて、図2のパターン転写装置により、半導体基板上へのパターン転写を行った結果、本実施例の反射型マスクの精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In this example, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to −40 MPa (a value in terms of the thickness of the multilayer film) by the heat treatment. The flatness of the substrate with the multilayer reflective film was improved to 40 nm. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, no decrease in the reflectivity was observed as compared with that before the heat treatment.
Next, using this reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured in the same manner as in Example 1. Further, as in the case of Example 1, the pattern transfer onto the semiconductor substrate was performed by the pattern transfer device of FIG. 2 using the manufactured reflective mask, and as a result, the accuracy of the reflective mask of this embodiment was 70 nm. It was confirmed that the required accuracy of the rule was 16 nm or less.

 本実施例は、実施例1における応力補正膜12として、Si膜を用い、50nmの膜厚に形成し、加熱処理を200℃、60分とした以外は、実施例1と同様の方法で、反射型マスクブランクを形成した。
 本実施例における応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表5に示した。
In the present embodiment, a Si film is used as the stress correction film 12 in the first embodiment, the film is formed to a thickness of 50 nm, and the heat treatment is performed at 200 ° C. for 60 minutes. A reflective mask blank was formed.
Table 5 below summarizes numerical values of the film thickness, surface roughness, stress before and after heat treatment, flatness, and the like of the stress correction film and the multilayer reflective film in this example.

Figure 2004104118
Figure 2004104118

 本実施例では、加熱処理により、多層反射膜付き基板全体の応力は、−50MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は45nmに向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、加熱処理前と比較して反射率の低下は見られなかった。
 次に、この反射型マスクブランクを用いて、実施例1と同様に、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを作製した。さらに、実施例1と同様に、作製した反射型マスクを用いて、図2のパターン転写装置により、半導体基板上へのパターン転写を行った結果、本実施例の反射型マスクの精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In this example, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to −50 MPa (a value in terms of the multilayer film thickness) by the heat treatment. The flatness of the substrate with the multilayer reflective film was improved to 45 nm. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, no decrease in the reflectivity was observed as compared with that before the heat treatment.
Next, using this reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured in the same manner as in Example 1. Further, as in the case of Example 1, the pattern transfer onto the semiconductor substrate was performed by the pattern transfer device of FIG. 2 using the manufactured reflective mask, and as a result, the accuracy of the reflective mask of this embodiment was 70 nm. It was confirmed that the required accuracy of the rule was 16 nm or less.

 本実施例は、応力補正膜として、基板と多層反射膜との間に、TaB膜(Ta:B=4:1)を70nmの膜厚に形成し、多層反射膜上に、Ru膜を5nmの膜厚に形成し、加熱処理を130℃、60分とした以外は、実施例1と同様の方法で、反射型マスクブランクを形成した。
 本実施例における応力補正膜及び多層反射膜の膜厚、表面粗さ、加熱処理前後の応力、平坦度等の数値をまとめて下記表6に示した。
In this embodiment, as a stress correction film, a TaB film (Ta: B = 4: 1) is formed to a thickness of 70 nm between the substrate and the multilayer reflective film, and a Ru film is formed on the multilayer reflective film to a thickness of 5 nm. A reflective mask blank was formed in the same manner as in Example 1 except that the heat treatment was performed at 130 ° C. for 60 minutes.
Table 6 below summarizes numerical values of the film thickness, surface roughness, stress before and after the heat treatment, flatness, and the like of the stress correction film and the multilayer reflective film in this example.

Figure 2004104118
Figure 2004104118

 本実施例では、加熱処理により、多層反射膜付き基板全体の応力は、−50MPa(多層膜の膜厚換算の値)と充分小さくなった。この多層反射膜付き基板の平坦度は45nmに向上した。又、加熱処理後の多層反射膜付き基板につき、波長13.4nm、入射角5°のEUV光により反射率を測定したところ、加熱処理前と比較して反射率の低下は見られなかった。
 次に、この反射型マスクブランクを用いて、実施例1と同様に、デザインルールが0.07μmの16Gbit−DRAM用のパターンを有するEUV反射型マスクを作製した。さらに、実施例1と同様に、作製した反射型マスクを用いて、図2のパターン転写装置により、半導体基板上へのパターン転写を行った結果、本実施例の反射型マスクの精度は70nmデザインルールの要求精度である16nm以下であることが確認できた。
In this example, the stress of the entire substrate with the multilayer reflective film was sufficiently reduced to −50 MPa (a value in terms of the multilayer film thickness) by the heat treatment. The flatness of the substrate with the multilayer reflective film was improved to 45 nm. When the reflectance of the substrate with the multilayer reflective film after the heat treatment was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 5 °, no decrease in the reflectivity was observed as compared with that before the heat treatment.
Next, using this reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit-DRAM having a design rule of 0.07 μm was manufactured in the same manner as in Example 1. Further, as in the case of Example 1, the pattern transfer onto the semiconductor substrate was performed by the pattern transfer device of FIG. 2 using the manufactured reflective mask, and as a result, the accuracy of the reflective mask of this embodiment was 70 nm. It was confirmed that the required accuracy of the rule was 16 nm or less.

(発明の効果)
 以上詳細に説明したように、本発明の反射型マスクブランクの製造方法によれば、基板と多層反射膜の間、或いは、多層反射膜上、或いは、基板と多層反射膜の間及び多層反射膜上の両方に、多層反射膜の膜応力と逆向きで、多層反射膜の膜応力の絶対値より小さい膜応力を有する応力補正膜を形成し、多層反射膜と応力補正膜を加熱処理することにより、加熱処理後において、応力補正膜の有する膜応力と多層反射膜の有する膜応力とが、向きが反対で大きさが同等となって釣り合い、応力は相殺されるので、平坦性に優れた高精度なパターン転写が可能な反射型マスクブランクが得られる。またこのように、加熱処理による多層反射膜の膜応力と応力補正膜の膜応力の相殺を利用して多層反射膜の膜応力の影響を低減するようにしたため、成膜時において応力補正膜に多層反射膜の有する膜応力を相殺するための大きな応力を与える必要がなく、応力補正膜の表面荒れを抑え、平坦性に優れた反射型マスクブランクが得られる。
 上記加熱処理は、基板上に応力補正膜及び多層反射膜が形成された後に行うのであれば、応力補正膜及び多層反射膜を同時に加熱処理することができ、加熱は一工程で行える。
また、基板と多層反射膜の間に応力補正膜を形成する場合、まず基板上に応力補正膜を形成し、応力補正膜の加熱処理を行ってから、多層反射膜を形成し、多層反射膜の加熱処理を行なうことも可能である。このようにすると、多層反射膜形成前に応力補正膜の加熱処理を行うことで、多層反射膜の特性に影響を及ぼすような比較的高温での加熱処理が可能であるため、応力補正膜の応力の変化量を大きくとることが出来る。
 また、本発明の反射型マスクブランクの製造方法によれば、多層反射膜の有する膜応力を加熱処理だけで緩和させる必要がないため、高温での加熱処理は必要がなく、前記加熱処理は応力補正膜の成膜時の温度よりも高く200℃以下の基板加熱温度で行うことができ、多層反射膜の反射率低下を防止できる。
(The invention's effect)
As described above in detail, according to the method for manufacturing a reflective mask blank of the present invention, between the substrate and the multilayer reflective film, or on the multilayer reflective film, or between the substrate and the multilayer reflective film, and between the multilayer reflective film On both of the above, forming a stress correction film having a film stress that is opposite to the film stress of the multilayer reflection film and is smaller than the absolute value of the film stress of the multilayer reflection film, and heat-treats the multilayer reflection film and the stress correction film. Thereby, after the heat treatment, the film stress of the stress correction film and the film stress of the multilayer reflective film are opposite in direction and equal in magnitude and balanced, and the stress is canceled out, so that the flatness is excellent. A reflective mask blank capable of transferring a pattern with high accuracy is obtained. Further, as described above, the influence of the film stress of the multilayer reflective film is reduced by utilizing the offset between the film stress of the multilayer reflective film and the film stress of the stress correction film due to the heat treatment. There is no need to apply a large stress for canceling the film stress of the multilayer reflective film, and the surface roughness of the stress correction film is suppressed, and a reflective mask blank excellent in flatness can be obtained.
If the heat treatment is performed after the stress correction film and the multilayer reflection film are formed on the substrate, the stress correction film and the multilayer reflection film can be heated simultaneously, and the heating can be performed in one step.
When a stress compensation film is formed between the substrate and the multilayer reflection film, a stress compensation film is first formed on the substrate, the heat treatment of the stress compensation film is performed, and then the multilayer reflection film is formed. It is also possible to carry out a heat treatment. In this case, by performing the heat treatment of the stress correction film before forming the multilayer reflection film, it is possible to perform the heat treatment at a relatively high temperature that affects the characteristics of the multilayer reflection film. The amount of change in stress can be increased.
Further, according to the method of manufacturing a reflective mask blank of the present invention, since it is not necessary to reduce the film stress of the multilayer reflective film only by heat treatment, heat treatment at high temperature is not necessary, and the heat treatment This can be performed at a substrate heating temperature higher than the temperature at the time of forming the correction film and not more than 200 ° C., and a decrease in the reflectance of the multilayer reflective film can be prevented.

 また、本発明の反射型マスクブランクの製造方法においては、加熱処理後において、応力補正膜の有する膜応力と多層反射膜が有する膜応力が向きが反対で大きさが釣り合えばよいので、加熱処理前の応力補正膜の膜応力は、0〜+300MPaの範囲内とすることができ、応力補正膜の表面粗さを小さく出来る。
 また、本発明の反射型マスクブランクの製造方法においては、前記応力補正膜を加熱処理によりその応力が引っ張り方向へ増大する材料で構成することにより、応力補正膜に与える初期応力の大きさを小さくすることが出来、応力補正膜の表面粗さを小さく出来る。
また、本発明の反射型マスクブランクの製造方法においては、前記応力補正膜を金属又は合金からなるアモルファス材料で構成することにより、平滑性の良好な膜が得られ、かつ応力補正膜に与える初期応力の値を容易に調整することができる。
 また、上述の反射型マスクブランクの製造方法により製造された反射型マスクブランクの吸収体層にパターンを形成することにより、多層反射膜の応力の影響を低減し、平坦性に優れた反射型マスクが得られる。
In the method of manufacturing a reflective mask blank according to the present invention, after the heat treatment, the film stress of the stress correction film and the film stress of the multilayer reflective film may be opposite in direction and their sizes may be balanced. The film stress of the previous stress compensation film can be in the range of 0 to +300 MPa, and the surface roughness of the stress compensation film can be reduced.
In the method of manufacturing a reflective mask blank according to the present invention, the stress correction film is made of a material whose stress increases in a tensile direction by heat treatment, thereby reducing the magnitude of the initial stress applied to the stress correction film. And the surface roughness of the stress compensation film can be reduced.
Further, in the method for manufacturing a reflective mask blank of the present invention, by forming the stress correction film from an amorphous material made of a metal or an alloy, a film having good smoothness can be obtained, and an initial value applied to the stress correction film can be obtained. The value of the stress can be easily adjusted.
Further, by forming a pattern on the absorber layer of the reflective mask blank manufactured by the above-described method for manufacturing a reflective mask blank, the influence of stress of the multilayer reflective film is reduced, and the reflective mask is excellent in flatness. Is obtained.

(a)は本発明に係る反射型マスクブランクの断面図、(b)は反射型マスクの断面図である。(A) is a sectional view of a reflective mask blank according to the present invention, and (b) is a sectional view of a reflective mask. 反射型マスクを搭載するパターン転写装置の概略構成図である。FIG. 2 is a schematic configuration diagram of a pattern transfer device equipped with a reflective mask.

符号の説明Explanation of reference numerals

 11 基板
 12 応力補正膜
 13 多層反射膜
 14 バッファ層
 15 吸収体層
 100 反射型マスクブランク
 101 反射型マスク
DESCRIPTION OF SYMBOLS 11 Substrate 12 Stress correction film 13 Multilayer reflective film 14 Buffer layer 15 Absorber layer 100 Reflective mask blank 101 Reflective mask

Claims (8)

基板上に、露光光を反射する多層反射膜を形成し、該多層反射膜上に露光光を吸収する吸収体層を形成する反射型マスクブランクの製造方法であって、前記基板と多層反射膜の間、或いは、多層反射膜上、或いは、基板と多層反射膜の間及び多層反射膜上の両方に、多層反射膜の膜応力と逆向きで、多層反射膜の膜応力の絶対値より小さい膜応力を有する応力補正膜を形成する工程と、前記応力補正膜を加熱処理する工程と、前記多層反射膜を加熱処理する工程と、を有することを特徴とする反射型マスクブランクの製造方法。 A method of manufacturing a reflective mask blank, comprising forming a multilayer reflective film for reflecting exposure light on a substrate, and forming an absorber layer for absorbing exposure light on the multilayer reflective film, wherein the substrate and the multilayer reflective film are provided. During or on the multilayer reflective film, or between the substrate and the multilayer reflective film and on the multilayer reflective film, in the opposite direction to the film stress of the multilayer reflective film and smaller than the absolute value of the film stress of the multilayer reflective film A method of manufacturing a reflective mask blank, comprising: a step of forming a stress correction film having a film stress; a step of heating the stress correction film; and a step of heating the multilayer reflective film. 前記応力補正膜を加熱処理する工程と、前記多層反射膜を加熱処理する工程とを同時に行うことを特徴とする請求項1記載の反射型マスクブランクの製造方法。 The method for manufacturing a reflective mask blank according to claim 1, wherein the step of heating the stress correction film and the step of heating the multilayer reflective film are performed simultaneously. 基板上に前記応力補正膜を形成し、該応力補正膜を加熱処理した後、該応力補正膜上に前記多層反射膜を形成し、該多層反射膜を加熱処理することを特徴とする請求項1記載の反射型マスクブランクの製造方法。 Forming the stress compensation film on a substrate, heating the stress compensation film, forming the multilayer reflection film on the stress compensation film, and heating the multilayer reflection film. 2. The method for producing a reflective mask blank according to item 1. 前記加熱処理を前記応力補正膜の成膜時の温度よりも高く200℃以下の基板加熱温度で行うことを特徴とする請求項1乃至3の何れかに記載の反射型マスクブランクの製造方法。 4. The method of manufacturing a reflective mask blank according to claim 1, wherein the heat treatment is performed at a substrate heating temperature higher than the temperature at the time of forming the stress correction film and not more than 200 ° C. 5. 前記加熱処理前の応力補正膜の膜応力が、0〜+300MPaの範囲内であることを特徴とする請求項1乃至4の何れかに記載の反射型マスクブランクの製造方法。 The method according to claim 1, wherein the stress of the stress correction film before the heat treatment is in a range of 0 to +300 MPa. 前記応力補正膜は、加熱処理によりその応力が引っ張り方向へ増大するものであることを特徴とする請求項1乃至5の何れかに記載の反射型マスクブランクの製造方法。 The method for manufacturing a reflective mask blank according to claim 1, wherein the stress of the stress correction film increases in a tensile direction by a heat treatment. 前記応力補正膜が金属又は合金からなるアモルファス材料で構成されることを特徴とする請求項1乃至6の何れかに記載の反射型マスクブランクの製造方法。 7. The method of manufacturing a reflective mask blank according to claim 1, wherein the stress correction film is made of an amorphous material made of a metal or an alloy. 請求項1乃至7の何れかに記載の反射型マスクブランクの製造方法により製造された反射型マスクブランクの吸収体層にパターンを形成することを特徴とする反射型マスクの製造方法。 A method of manufacturing a reflective mask, comprising: forming a pattern on an absorber layer of the reflective mask blank manufactured by the method of manufacturing a reflective mask blank according to claim 1.
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