JP2002280291A - Reflection-type mask blank for euv exposure, and reflection-type mask for euv exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the contrast of an EUV light absorbing pattern without increasing the thickness of an EUV light absorbing layer which is formed on an EUV light reflecting multilayered film and into which the pattern is engraved in a reflection type mask for EUV exposure used for pattern transfer at manufacturing of a semiconductor, etc. SOLUTION: The contrast of the pattern can be raised by lowering the EUV light reflectance of the EUV light absorbent layer M1 , using the effect of interference between an EUV light (1) reflected by the surface of the layer M1 and another EUV light (2), which is reflected by the multilayered film M2 , after passing through the absorbing layer M1 and again passes through the film M2 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film for reflecting EUV light, which is a main component of a reflection type mask for EUV exposure used in the manufacture of semiconductors and the like. Absorber layer that absorbs EUV light (hereinafter referred to as “EUV light absorber layer” in this specification), a method for producing the same, and the method described above. The present invention relates to a reflective mask for EUV exposure using an EUV light absorber layer, and the like. The EUV (Extreme Ultra Violet) described in the present invention
The light refers to light in a wavelength range of a soft X-ray region or a vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, photolithography using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming a semiconductor device such as an integrated circuit having a fine pattern on a Si substrate or the like. Law has been used. However, while miniaturization of semiconductor devices is accelerating, shortening the wavelength of conventional light exposure is approaching the exposure limit. In the case of light exposure, the resolution limit of the pattern is said to be の of the exposure wavelength, and an F ₂ laser (157 nm)
It is expected that about 70 nm is the limit even if is used. So 7
EUV lithography (hereinafter, referred to as “EUVL”), which is an exposure technique using EUV light (13 nm) having a shorter wavelength than the F ₂ laser, is expected as an exposure technique at 0 nm or later.

The principle of EUVL image formation is the same as that of photolithography. However, since EUV light absorbs a large amount of all substances and has a refractive index close to 1, refractive optical systems such as light exposure cannot be used. , All use a reflective optical system. As a mask used at that time, a transmission type mask using a membrane has been proposed.
There is a problem that the exposure time becomes long because the membrane absorbs a large amount of UV light, and the throughput cannot be secured. Therefore, at present, a reflective mask for exposure is generally used.

Here, EUVL is described with reference to FIGS.
This will be described with reference to FIG. In FIGS. 17 and 18 and FIG. 1 to be described later, corresponding parts are denoted by the same reference numerals. FIG. 17 is a diagram schematically illustrating a reflective mask for EUV exposure used for EUVL, FIG. 18 is a diagram schematically illustrating a reflective mask blank for EUV exposure, and FIG. 19 is a diagram illustrating, for example, using a manufactured EUV mask on a Si wafer. It is a conceptual diagram which performs exposure transfer of a pattern. As shown in FIG. 17, the main constituent elements of the reflective mask for exposure for EUV light are a substrate S, an EUV light reflective multilayer film M ₂ , and a lithographically patterned EUV absorber pattern M _1P . Incidentally, as shown in FIG. 18, the reflective mask blank for exposure has a form of the EUV light absorber layer M ₁ before the lithography patterning is performed on the EUV light absorber pattern M _1P .

Next, pattern transfer onto a semiconductor substrate using a reflective mask for EUV exposure will be described with reference to FIG. As shown in FIG. 19, the laser plasma X-ray source 1
The EUV light (soft X-ray) obtained from 1 is incident on the EUV mask 12, and the light reflected here is transferred to, for example, a Si wafer substrate 14 through a reduction optical system 13. Here, an X-ray reflection mirror can be used as the reduction optical system 13. The pattern reflected by the EUV mask 12 by the reduction optical system is usually reduced to about 1/4. For example, the transfer of the pattern to the Si wafer 14
This can be performed by exposing a pattern to the resist layer formed thereon and developing the pattern. When a wavelength band of 13 to 14 nm is used as the exposure wavelength, the transfer is usually performed such that the optical path is in a vacuum. By forming a pattern on, for example, a Si wafer by EUVL in this manner, it is possible to manufacture a semiconductor device such as a highly integrated LSI, for example.

[0006]

In order to raise the resolution limit of the above-mentioned light exposure pattern, it has become important to increase the contrast of the pattern after patterning. To increase the contrast, the EUV light reflective multilayer film simultaneously with the high reflectivity of M _2, said EUV light absorbing layer M ₁ in the absorption rate is high is demanded. Here, since the EUV light absorber layer M ₁ is a thin film of an element having a high absorption coefficient for EUV light such as TaB, for example, the EUV light incident on the EUV light absorber layer M ₁ is of course. most of the light is absorbed in the EUV light absorbing layer M ₁ without being reflected. However, since the EUV light absorbing layer M ₁ is a thin film, the portion of absorbed EUV light reaches the EUV light reflective multilayer film M ₂ of the lower layer, where the further portion of the reflected EUV light back to the outside through the thin film of the EUV light absorbing layer M ₁ again, as a result, a problem that the contrast of the pattern is reduced has been found. The most straightforward solution to this problem, it is conceivable to increase the thickness of the EUV light absorbing layer M _1.

However, when the thickness of the EUV light absorber layer M ₁ is increased, the following problems are newly generated. 1. Deformation of the mask happened since the film stress of the EUV light absorbing layer M ₁ itself increases with the film thickness, a result, the resolution limit of the optical exposure pattern can not rise. 2. EUV light absorbing layer M ₁ is, for example Ta, B, because it is formed by using a costly raw material etc., that increasing the thickness leads to immediate increase in manufacturing cost. 3. Certain incident angle EUV light that, for passing the EUV light absorbing layer M ₁ having the emission angle, the thickness of the EUV light absorbing layer M ₁ becomes thicker, EU is the portion of the edge
Since the distance V light passes through the EUV light absorbing layer M ₁ is greatly changed, a problem that the light exposure pattern blurring becomes significant. The present invention has been made under the above background, in the EUV light absorbing layer M _1, by lowering the EUV light reflectivity without increasing the film thickness, intended to increase the contrast of the pattern And

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, a first invention made by the present inventors is an EU having an EUV light absorber layer formed on an EUV light reflecting multilayer film.
A reflective mask blank for V-exposure, wherein the EUV light reflected on the surface of the EUV absorber layer and the EUV passing through the EUV absorber layer and below the EUV absorber layer.
By utilizing the interference effect between the EUV light reflected by the UV light reflecting multilayer film and the EUV light that has passed through the EUV absorber layer again,
A reflective mask blank for EUV exposure, characterized in that the thickness of the EUV absorber layer is set so that the reflectance of EUV light in the UV absorber layer is reduced.

A second invention is a reflective mask blank for EUV exposure having an EUV light absorbing layer formed on an EUV light reflecting multilayer film, wherein the reflective mask blank is reflected on the surface of the EUV light absorbing layer. Between EUV light that has passed through the EUV light absorber layer and EUV light that has been reflected by the EUV light reflecting multilayer film below the EUV light absorber layer and has passed through the EUV light absorber layer again Is simulated, and the result of the simulation of the reflectance is shown in a graph with the film thickness on the horizontal axis and the reflectance on the vertical axis. In the graph, the maximum value of the reflectance is given to the film thickness. A curve connecting the points is obtained, and when a film thickness value at which the film thickness is determined to be unsuitable for use from the viewpoint of the film stress is defined as a limit film thickness, a reflectance corresponding to the limit film thickness is obtained from the curve, When defined as reflectance, From the simulation result of the reflectance, a film thickness that gives a minimum value of the reflectance with respect to the film thickness is obtained, and the film thickness is defined as a minimum value film thickness. In forming the EUV light absorber layer, the minimum value film is formed. A reflective mask blank for EUV exposure, characterized by using a film thickness capable of obtaining a reflectivity lower than the limiting reflectivity even in anticipation of an unavoidable film thickness variation occurring when aiming for a thickness.

A third invention is a reflective mask blank for EUV exposure having an EUV light absorber layer formed on an EUV light reflective multilayer film, wherein the reflective mask blank is reflected on the surface of the EUV light absorber layer. Between EUV light that has passed through the EUV light absorber layer and EUV light that has been reflected by the EUV light reflecting multilayer film below the EUV light absorber layer and has passed through the EUV light absorber layer again In the structure for reducing the reflectivity of EUV light in the EUV light absorber layer, the conditions under which the interference effect occurs are formulated as a function of the thickness of the EUV light absorber layer, and the EUV light reflection multilayer is further formulated. By performing an approximation using the multilayer reflection on the film as the reflection on the surface, an approximate expression of an expression representing the condition under which the interference effect occurs as a function of the film thickness of the EUV light absorber layer was obtained, and the approximate expression was calculated. film A EUV exposure reflective mask blank and having an EUV light absorbing layer having a.

A fourth invention is directed to the EUV according to the third invention.
The reflective mask blank for exposure, the value of the film thickness d calculated by the above approximate expression,

(Equation 3) and

(Equation 4) Is within the range satisfying both of the above expressions, the reflectivity of EUV light is reduced using the interference effect.
It is a reflective mask blank for UV exposure. Here, λ ₀ is the wavelength of EUV light in vacuum, n ₀ is the refractive index in vacuum, n ₁
Is the refractive index of the absorber layer, θ ₀ is the angle of incidence of the EUV light on the EUV light absorber layer, k ₁ is a positive real number, T ₀₁ is the vacuum and EUV
R ₀₁ is the reflectance at the interface between the vacuum and the EUV light absorber layer, R ₁₂ is the reflectance at the interface between the EUV light absorber layer and the EUV light reflection multilayer film, m is a positive integer,
φ is the phase shift.

According to a fifth aspect of the present invention, there is provided the reflective mask blank for EUV exposure according to any one of the first to fourth aspects, wherein the EUV light reflecting multilayer film is formed by alternately stacking the first film and the second film. A first film, a transition metal, a transition metal carbide, a transition metal nitride, a transition metal silicide,
And at least one component selected from borides of transition metals, and the second film is made of B and / or Be and / or C and / or Si, B and / or
Or at least one component selected from oxides of Be and / or C and / or Si, nitrides of B and / or Be and / or C and / or Si, and the EUV absorber layer comprises: This EUV contains at least one component selected from Cr, Cr carbide, Cr nitride, Cr silicide and Cr boride.
A reflective mask blank for EUV exposure, wherein the thickness of the absorber layer is 70 nm to 100 nm.

A sixth invention is a reflective mask blank for EUV exposure according to any one of the first to fourth inventions, wherein the EUV light reflecting multilayer film is composed of a first film and a second film alternately laminated. A first film, a transition metal, a transition metal carbide, a transition metal nitride, a transition metal silicide,
And at least one component selected from borides of transition metals, and the second film is made of B and / or Be and / or C and / or Si, B and / or
Or at least one component selected from oxides of Be and / or C and / or Si, nitrides of B and / or Be and / or C and / or Si, and the EUV absorber layer comprises: The EU contains at least one or more components selected from Ta, a carbide of Ta, a nitride of Ta, a silicide of Ta, and a boride of Ta.
The reflective mask blank for EUV exposure, wherein the thickness of the V absorber layer is 70 nm to 110 nm.

A seventh invention is the reflective mask blank for EUV exposure according to the fifth or sixth invention, wherein the transition metal is W, Ta, Mo, Rh, Ru, Au, H
A reflective mask blank for EUV exposure, characterized by being at least one metal selected from f, Ni, Cr, and Re.

According to an eighth aspect of the present invention, there is provided a reflective mask for EUV exposure, wherein the reflective mask blank for EUV exposure according to any one of the first to seventh aspects is used.

The ninth invention is directed to the EUV according to the eighth invention.
EUV on semiconductor wafer using reflective mask for exposure
A method for manufacturing a semiconductor, wherein a pattern is transferred by light.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, EUV light and EUV light is reflected by the absorber layer M ₁ in the surface, the EUV light below the EUV light absorbing layer M ₁ through an EUV light absorbing layer M ₁ and the EUV light that has passed through the EUV light absorbing layer M ₁ again is reflected by the reflective multilayer film M ₂ is, by using the interference effect which occurs when certain conditions, the conditions that can obtain a sufficient contrast for EUVL It will be described in detail.

FIG. 1 schematically shows an EUV light reflecting multilayer film M ₂ , an EUV light absorber layer M ₁ formed thereon, and a vacuum M ₀ , each having an angle θ _0. EU
FIG. 5 is a diagram illustrating an optical path when V light enters from vacuum M ₀ with intensity I ₀ . Of the EUV light entered, E what is reflected by the surface of the EUV light absorbing layer M ₁
UV light, EUV light EUV light that has passed through the EUV light reflective multilayer film M ₂ EUV light absorbing layer M ₁ again is reflected by the bottom of the EUV light absorbing layer through the M ₁ EUV light absorbing layer M ₁ And Here, the conditions to be satisfied in order to cause the interference effect are 1) that the phase difference with the EUV light is substantially π shifted, and 2) that the intensity with the EUV light is substantially equal. That EUV light and transgressions the one under the control of the EUV light absorbing layer M _1), satisfies the condition of 2), EU without depending thickening of the EUV light absorbing layer M ₁
A sufficient contrast can be obtained for VL.

The conditions under which EUV light satisfies the above conditions 1) and 2) will be described with reference to FIG. However, _R01 is M in vacuum
₀ and the reflectance at the interface between the EUV light absorber layer M _1. R ₁₂
Is the reflectivity of the interface between the EUV light absorber layer M ₁ and the EUV light reflective multilayer film M _2. T ₀₁ is the transmittance at the interface between the vacuum M ₀ and the EUV light absorber layer M ₁ . α is the incoming EU
It is the absorption coefficient of EUV light absorbing layer M ₁ for V light.
2Z is the distance EUV light entered proceeds EUV light absorbing layer M ₁ medium. Then, the EUV light absorber layer M ₁
The intensity I ₁ of the EUV light reflected on the surface of the above equation is expressed by the following equation (1): I ₁ = I ₀ R ₀₁ (1)

On the other hand, the intensity I _{2 of the} EUV light is given by the following equation (2): I ₂ = I ₀ T ₀₁ exp [−αZ] · R ₁₂ exp [−αZ] T ₀₁ = I ₀ T ₀₁ ² R ₁₂ exp [−2αZ ] ... (2) Here, α is the equation (3) α = 2ω ₀ k ₁ / c (3) Here, ω ₀ is the angular velocity of light at M ₀ in vacuum,
k ₁ is the extinction coefficient of EUV light of the EUV light absorber layer M ₁ , and c is the speed of light. Then, ω ₀ is given by the following equation (4): ω ₀ = 2πν ₀ = 2πc / λ ₀ (4) Here, ν ₀ is the frequency of light in a vacuum, and λ ₀ is the wavelength in a vacuum. Then, Expression (5) is derived from Expression (3) and Expression (4). α = 4πk ₁ / λ ₀ (5) Further, the relationship between the optical path length z and the film thickness d in the EUV light absorber layer M ₁ is shown in Expression (6). z = d / cos θ ₁ (6) Here, θ ₁ is in the relationship of the incident angle θ ₀ and the equation (7). Here, n ₀ is the refractive index in a vacuum, and n ₁ is the refractive index of the absorber layer. n ₀ sin θ ₀ = n ₁ sin θ ₁ (7) Then, Expression (8) is derived from Expressions (6) and (7).

(Equation 5) ・ ・ ・ ・ ・ (8)

Finally, substituting equations (5) and (8) into the condition of I ₁ = I ₂ , ie, equation (1) = equation (2), gives:
Equation (9) indicating the optimum film thickness d that satisfies the condition 1) is derived. I ₀ R ₀₁ = I ₀ (T ₀₁ ) ² R ₁₂ exp [-2αz] -2αz = ln [R ₀₁ / (T ₀₁ )
² R ₁₂ ]

(Equation 6) (9) Next, a film thickness d satisfying the condition 2) will be examined. EU
The optical path difference from the V light is 2z. This is the (integer +
At 0.5) times, the phase with EUV light is shifted by π. Therefore, when trying to find this optical path difference, EUV
Since the light reflecting multilayer film M ₂ is composed of several tens of multilayer films, an optical simulation calculation for obtaining interference conditions is performed, and from this result, an EUV light absorber capable of obtaining a sufficient contrast in EUVL it is possible to obtain the thickness of the layer M _1.

In order to determine the thickness of the EUV light absorber layer M _{1 by} the above-described method, for example, the following operation is performed. First, EUV reflected on the surface of the EUV light absorber layer
The interference effect between light and EUV light that has passed through the EUV light absorber layer, has been reflected by the EUV light reflection multilayer film below the EUV light absorber layer, and has again passed through the EUV light absorber layer has been added. Simulated reflectance. However, the simulation method will be described later. The results of the simulation of the reflectance are shown in the graphs shown in FIGS. 3, 6, 10 and 13 in which the horizontal axis represents the film thickness and the vertical axis represents the reflectance. Find the curve connecting. On the other hand, if the film thickness is too large, the film stress of the film itself increases, which causes distortion of the film. Therefore, from the viewpoint of film stress, when a film thickness value that is determined to be unsuitable for use as a film thickness value larger than this is set as a limit film thickness, the reflectance corresponding to the limit film thickness is obtained from the curve, Defined as rate. Here, from the simulation result of the reflectance, the EUV light reflected on the surface of the EUV light absorber layer and the EUV light reflection multilayer film passing through the EUV light absorber layer and under the EUV light absorber layer are shown. And reflected again by the EU
A point where the reflectance becomes minimal due to the interference effect between the EUV light passing through the V light absorber layer and the EUV light periodically appears. A film thickness that gives the minimum value of the reflectance to this film thickness is determined, and the film thickness is defined as the minimum value film thickness. Here, if the film thickness of the EUV light absorber layer is set to a value near the film thickness at which the reflectivity is minimized,
The reflectance at the UV light absorber layer can be reduced. Further, it is more preferable to set a value near the film thickness that gives the minimum minimum value among the minimum values of the reflectance. On the other hand, here, in the film formation of the EUV light absorber layer, even if the film formation is performed aiming at the minimum value film thickness, a change in the film thickness is inevitable in an actual film formation process. However, even in anticipation of unavoidable film thickness fluctuations that occur, if a film thickness that can obtain a reflectance lower than the critical reflectance is used, a thin film is formed by aiming at this film thickness. High contrast can be obtained even though it is.

However, when trying to find this optical path difference,
Since optical simulation calculation by a large-scale computer is required and cost and time are required, it is a more preferable configuration if the optical simulation calculation is not performed every time the film thickness is calculated. Here the present inventors, when the EUV light reflective multilayer film M ₂ assuming a uniform medium, using the integer m, and the reflection of EUV light is approximated to occur only at the interface of the M ₁ M _2, and the EUV light It has been found that the conditional expression (10) to be satisfied by the optical path difference 2z can be derived. 2z = (m + 0.5) λ ₁ / n ₁ = (m + 0.5) λ ₀ / n ₁ (10)

On the other hand, a decrease in accuracy due to this approximation will be described later, but by introducing a phase shift φ with respect to the wave reflected from the EUV light reflection multilayer film M _2, it can be reduced to a practically acceptable level. Was confirmed. When the phase shift φ is introduced, the equation (10) is modified as in the equation (10 ′) (the unit of the phase shift φ is radian). The method of calculating the phase shift φ will be described later. 2z = (m + 0.5 + φ / 2π) λ ₀ / n ₁ (10 ′) From the above, Expression (7) and Expression (11) for obtaining the film thickness d from Expression (10 ′) are derived. You.

(Equation 7) ..... (11) Therefore, the thickness of the EUV light absorbing layer M _1, and the film thickness d obtained from the equation (9), is both the thickness d obtained from the equation (11) coincides If it is set to a value, a high contrast of the pattern in EUVL can be realized by interference with EUV light.

The EUV light obtained by optical simulation based on the thickness of the EUV light absorber layer M ₁ calculated based on the above formula and the data of the EUV light reflective multilayer film M ₂ actually formed. It was compared in the thickness absorber layer M _1. However,
The optical simulation used here is described in “Optical Thin Film” (Optical Technology Series 11), edited by Shiro Fujiwara, Chapters 1 to 62,
It is based on a general multilayer optical calculation method described in Kyoritsu Shuppan. B. L. Henken et al., "L
OW ENERGY X-RAY INTERACTI
ON COEFFISIENTTS PHOTOABSOR
PTION, SCATTERING AND REFL
ECTION ATE = 50 to 30,000 eV, Z
= 1-92 ”(ATOMIC DATA AND NU
CLEAR DATA TABLE 54,181-3
42 (1993)), the refractive index and the extinction coefficient were determined.

Here, a method of calculating the phase shift φ will be described. The phase shift φ is caused by the phase of light reflected on the multilayer film surface and the light returning to the vacuum due to multiple scattering in the multilayer film when the EUV light reflecting multilayer film M ₂ is installed in a vacuum. , Are obtained as a phase difference. Therefore,
As a calculation method, the same calculation as in the above-described optical simulation is performed.

As a result, the film thickness d obtained from the equation (9)
Was slightly larger than the optimum film thickness obtained by the optical simulation. This is attributed to the influence of multiple scattering occurs in the EUV light reflective multilayer film M ₂ and the EUV light absorbing layer M _1. Here, it is desired that the reflective mask for EUV exposure has a contrast of 1000 or more. Therefore, the reflectivity is preferably 0.001, but from the simulation results so far, it has been found that a sufficient contrast can be obtained at film thickness values of about -20% and + 10% before and after the optimum film thickness. The range of the film thickness d that satisfies the condition 1) is as follows.

(Equation 8) ............ (12)

On the other hand, the film thickness d obtained from the equation (11) is
It was found that the film thickness almost coincided with the optimum film thickness obtained by the optical simulation. It was also found that the film thickness slightly deviated from the optimum film thickness, and as a result, an interference effect occurred even if the phase difference from EUV light deviated from π.
It has been found that the interference effect can be used in the range of / 2.
From the above, the range of the film thickness d satisfying the condition 2) is as follows.

(Equation 9) ............ (13)

[0029] In the reflective mask blank and EUV exposure reflective mask for EUV exposure, to between the EUV light absorber layer M ₁ and the EUV light reflective multilayer film M ₂ shown in FIG. 18, the EUV light absorber to effect when the layers M ₁ processing to suppress the spans EUV light reflective multilayer film M _2, which may etch link stopper layer is introduced. In such a case, by assuming an integral EUV light reflective multilayer film and an EUV light reflective multilayer film M ₂ and etch tank stopper layer, it is possible to derive the equation for obtaining the optimum film thickness d. That is, R ₁₂ in FIG. 1 is defined as EUV light absorber layer M ₁ and EU.
Integral membrane V light reflective multilayer film M ₂ and etch tank stopper layer, the reflectivity of the interface. Furthermore, the phase shift φ
Returning in case of installing an integral film of the EUV light reflective multilayer film M ₂ and etch link stopper layer in a vacuum, and the phase of light reflected by the etching stopper layer surface, in a vacuum occurs multiple scattering in multilayer film Can be obtained as a phase difference between the incident light and the incident light.

Here, the EUV light reflecting multilayer film M
Between ₂ and EUV light absorbing layer M _1, as a component contained in each layer are described below for preferred. Although initially the EUV light reflective multilayer film M ₂ has a first and second films laminated alternately, it is: Preferred examples of membrane components. That is, as the first film,
Transition metals, carbides of transition metals, nitrides of transition metals, silicides of transition metals, and borides of transition metals, preferably those containing at least one component selected from the group consisting of
Ta, Mo, Rh, Ru, Au, Hf, Ni, Cr, R
e, etc. and their alloys are more preferred. As the second film, B, Be, C, Si, etc. or a compound thereof,
And oxides and nitrides thereof. Meanwhile, as the EUV light absorbing layer M _1, Cr, carbide Cr, C
r, at least one component selected from a nitride of Cr, a silicide of Cr, and a boride of Cr; or at least one component selected from Ta, a carbide of Ta, a nitride of Ta, a silicide of Ta, and a boride of Ta One or more components are preferred. The thickness of the EUV absorber layer is 70 nm to 100 n.
It is preferable that m be within the range of m and both the expressions (12) and (13) should be satisfied.

[0031] From the above facts, when the thickness d of the EUV light absorbing layer M ₁ is in the range that satisfies both the equation (12) and Equation (13), an EUV light absorbing layer M ₁ is due to interference effects Sufficient contrast can be exhibited, and the film thickness can be reduced at the same time. As a result, the EUV light absorber layer M
It is possible to reduce the _first generation to film stress, since it also reduced distortion of the substrate and the EUV light reflective multilayer film M ₂ from this film stress, less EUV mask and EU distortion
A V mask blank was obtained. In addition, EUV
By the thickness of the light absorbing layer M ₁ becomes thinner, it was also solved a problem that the light exposure pattern is blurred at the portion of that edge. As shown in FIG. 19, using this EUV mask, a pattern of a semiconductor device such as an VLSI was exposed and transferred onto a semiconductor wafer such as Si.
As compared with the case where a mask was used, the resolution limit of light exposure could be greatly increased.

(Example 1) SiO _{2-having a} thickness of 600 nm
As a EUV light reflection multilayer film M ₂ on a TiO ₂ glass substrate,
Forty cycles of the Mo / Si multilayer film were laminated. The Mo / Si multilayer film forms one cycle with 4.2 nm of Si and 2.8 nm of Mo, and 40 cycles of this are stacked. On the other hand, EUV light absorbing layer M ₁ was Cr. And the wavelength of EUV light is 1
Equation (9) and Equation (1) are set to 3.5 nm, the incident angle is set to 2.05 deg, and the refractive index and absorption coefficient of each material are set to the values in FIG.
The optimum film thickness was calculated according to 1). Theoretical reflectivity of EUV light reflective multilayer film M ₂ in the absence of Cr layer was 71.7%. The phase difference of the wave reflected by M ₂ was 0.19808 rad with respect to the incident wave. FIG. 3 shows a calculation result by an optical simulation taking into account multiple scattering at M ₂ . Based on this, FIG. 4 shows a comparison between the film thickness with increased interference obtained from the equation (11) and the film thickness with increased interference obtained by calculation of the optical simulation.
On the other hand, the optimum film thickness obtained from the equation (9) is 89.86 nm.
Met. The above results are shown in FIG. According to this, it has been found that the optimum film thickness value obtained by the equation (9) is slightly thicker than the peak position based on the calculation result by the optical simulation, but can be predicted almost exactly.

Example 2 The same SiO 2 as in Example 1 was used._Two−
TiO_TwoEUV light reflective multilayer film M using glass substrate _Twoage
Thus, a Si / Mo multilayer film was stacked for 40 periods. Other conditions are
This is similar to the first embodiment. EUV light response without Cr layer
Multilayer film M_TwoHad a theoretical reflectance of 70.8%. Ma
M_TwoThe phase difference of the wave reflected by is 2.
5,736 rad. Optical simulation similar to that of the first embodiment.
FIG. 6 shows the calculation results by the calculation. Based on this
Therefore, the film thickness of the interference obtained from the equation (11) and the optical thickness
The thickness of the interference that was obtained by the simulation
7 is shown in FIG. Here, the maximum obtained from equation (9) is obtained.
The appropriate film thickness was 89.69 nm. Combining the above results
FIG. According to this, the optimum film thickness obtained by equation (9)
The values were measured by optical simulation as in Example 1.
Although it is slightly thicker than the peak position according to the calculation result,
It turns out that it can be predicted exactly.

(Embodiment 3) The same SiO 2 as in Embodiment 1_Two−
TiO_TwoGlass substrate and EUV light reflective multilayer film M _TwoFor
No, EUV light absorber layer M₁Is TaB. And the EU
V light is the same as in Example 1, and the refractive index and absorption coefficient of each material
Is the value of FIG. 9, the optimum film is obtained by the equations (9) and (11).
Thickness calculations were performed. EUV light reflection without TaB layer
Multilayer film M_TwoHad a theoretical reflectance of 71.7%. Also,
M_TwoThe phase difference of the wave reflected by is 0.19 with respect to the incident wave.
808 rad. Optical simulation similar to that of the first embodiment.
FIG. 10 shows the results of the calculation based on the solution. Based on this
Therefore, the film thickness of the interference obtained from the equation (11) and the optical thickness
The thickness of the interference that was obtained by the simulation
Is shown in FIG. Here, the value obtained from Expression (9) is obtained.
The optimum film thickness was 95.73 nm. Combining the above results
FIG. According to this, the optimum obtained by equation (9)
The film thickness was determined by optical simulation as in Example 1.
Is slightly thicker than the peak position according to the calculation result
However, it turned out to be almost exactly predictable.

In Example 3, the case where the thickness of the EUV light absorber layer satisfies the condition 1) and the condition 2) are shown in FIG.
FIG. 16 filled in was prepared. In FIG. 17, condition 1)
The graph of the portion satisfying the condition 2 is indicated by a solid line, and the portion satisfying the condition 2) is indicated by hunting. As shown in FIG. 16, when the thickness of the EUV light absorber layer satisfies the conditions 1) and 2) at the same time, the thickness of at least 160 nm is reduced by the interference effect as compared with the case where the interference effect is not used. There was found.

Example 4 The same SiO 2 as in Example 1 was used._Two−
TiO_TwoEUV light reflective multilayer film M using glass substrate _Twoage
Thus, a Si / Mo multilayer film was stacked for 40 periods. Other conditions are
This is the same as the third embodiment. EUV light without TaB layer
Reflective multilayer film M_TwoHad a theoretical reflectance of 70.8%. Ma
M_TwoThe phase difference of the wave reflected by is 2.
5,736 rad. Optical simulation similar to that of the first embodiment.
FIG. 13 shows the calculation results by the calculation. Based on this
And the film thickness of the interference obtained from equation (11)
Film thickness of interference obtained by calculation of chemical simulation
14 is shown in FIG. Where the equation (9)
The optimum film thickness was 95.71 nm. Based on the above results
FIG. According to this, the maximum obtained by equation (9)
The optimum film thickness value is calculated by the optical simulation as in the first embodiment.
Is slightly thicker than the peak position calculated by
However, it turned out to be almost exactly predictable.

Example 5 A low-expansion SiO ₂ —TiO ₂ glass substrate having an outer shape of 6 inches square and a thickness of 6 mm was prepared as a glass substrate, and the surface smoothness was 0.2 nm or less and the flatness was 100 nm or less by mechanical polishing. And On this glass substrate, Mo and Si were laminated as an EUV light reflection multilayer film. The laminating method is as follows. First, a 4.2 nm Si film is formed in 0.1 Pa of Ar gas using a Si target by a DC magnetron sputtering method, and then a Mo film is formed in 0.1 Pa of Ar gas using a Mo target. Was formed into a film having a thickness of 2.8 nm.
An i film was formed to a thickness of 4.2 nm. Next, from the graph of FIG. 13 and the result of the table of FIG. 14, a film thickness that can be expected to have a minimum reflectance is obtained, and a TaB film having a thickness of 85 nm is formed on the EUV light reflecting multilayer film as a EUV light absorber layer by sputtering. Then, a reflective mask blank for EUV exposure was obtained. An EB resist is coated on the obtained reflective mask blank for EUV exposure, a pattern is formed by EB lithography, and the EUV light absorber layer is dried using Cl ₂ using this resist pattern as a mask. Etching was performed to form an EUV light absorption pattern, thereby producing a reflective mask for EUV exposure having a pattern of 16 Gbit-DRAM having a design rule of 70 nm. With respect to the manufactured reflective mask for EUV exposure, the incident angle on the mask was 2.05 de.
g and exposure transfer was performed using EUV light having a wavelength of 13.5 nm.
Highly accurate transfer characteristics could be obtained.

[0038]

As described in detail above, the present invention relates to EUV
EUV light reflected on the surface of the absorber layer, EUV light that has passed through the EUV absorber layer, has been reflected by the EUV light reflecting multilayer film below the EUV absorber layer, and has again passed through the EUV absorber layer The film thickness of the EUV absorber layer is set so that the EUV light reflectance in the EUV absorber layer is reduced by utilizing an interference effect with light.
This is a reflective mask blank for UV exposure. By using this mask, the thickness of the EUV light absorber layer can be increased without increasing the thickness.
The EUV light reflectance of the UV light absorber layer was reduced, and the pattern contrast was increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of M ₀ in vacuum according to an embodiment of the present invention.
Arrangement of the EUV light absorbing layer M ₁ and the EUV light reflective multilayer film M _2, and the optical path of the EUV light entering thereto is a diagram schematically showing.

FIG. 2 is a table showing the refractive indices of Cr, Si, and Mo members.

FIG. 3 is a graph showing the relationship between the reflectance of the EUV light absorber layer and the Cr film thickness according to Example 1 of the present invention, calculated by an optical simulator taking into account multiple scattering in the EUV light reflective multilayer film. FIG.

FIG. 4 is a table showing a comparison between a film thickness with increased interference obtained from Expression (11) and a film thickness with increased interference obtained by calculation of an optical simulation according to Example 1 of the present invention.

5 is a diagram in which values in the table of FIG. 4 and optimum film thickness values obtained from Expression (9) according to the first embodiment of the present invention are written in FIG. 3;

FIG. 6 is a graph showing the relationship between the reflectance of the EUV light absorber layer and the Cr film thickness according to Example 2 of the present invention, calculated by an optical simulator taking into account multiple scattering in the EUV light reflective multilayer film. FIG.

FIG. 7 is a table showing a comparison between a film thickness with increased interference obtained from Expression (11) and a film thickness with increased interference obtained by calculation of an optical simulation according to Example 2 of the present invention.

8 is a diagram in which values in the table of FIG. 7 and optimum film thickness values obtained from Expression (9) according to Example 2 of the present invention are written in FIG. 6;

FIG. 9 is a table showing the refractive index of each member of TaB, Si, and Mo.

FIG. 10 is a graph showing the relationship between the reflectance of the EUV light absorber layer and the Cr film thickness according to Example 3 of the present invention, calculated by an optical simulator taking into account multiple scattering in the EUV light reflective multilayer film. FIG.

FIG. 11 is a table showing a comparison between a film thickness with increased interference obtained from Expression (11) and a film thickness with increased interference obtained by calculation of an optical simulation according to Example 3 of the present invention.

FIG. 12 shows the values in the table of FIG. 11 and the optimum film thickness values obtained from Equation (9) according to Example 3 of the present invention (FIG. 1).
FIG.

FIG. 13 is a graph showing the relationship between the reflectance of the EUV light absorber layer and the TaB film thickness according to Example 4 of the present invention, which is calculated by an optical simulator taking into account multiple scattering in the EUV light reflective multilayer film. FIG.

FIG. 14 is a table showing a comparison between a film thickness with increased interference obtained from Expression (11) and a film thickness with increased interference obtained by calculation of an optical simulation according to Example 4 of the present invention.

FIG. 15 shows the values in the table of FIG. 14 and the optimum film thickness values obtained from Equation (9) according to Example 4 of the present invention (FIG. 1).
It is the figure entered in 3).

FIG. 16 is a diagram in which a case where the film thickness of the EUV light absorber layer satisfies the condition 1) and a case where the film thickness of the EUV light absorber layer satisfies the condition 2) according to Example 3 of the present invention are shown in FIG.

FIG. 17 is a diagram schematically illustrating a reflective mask for EUV exposure used in EUVL.

FIG. 18 is a view schematically illustrating a reflective mask blank for EUV exposure used for manufacturing a reflective mask for EUV exposure and the like.

FIG. 19 is a conceptual diagram in which a pattern is exposed and transferred onto, for example, a Si wafer using a reflective mask for EUV exposure.

[Explanation of symbols]

EUV. EUV light EUV. EUV reflected on the surface of the EUV light absorber layer
Light EUV. EUV light M ₀ which passes through the EUV light absorbing layer is reflected by the EUV light reflective multilayer film has passed the EUV light absorber layer again. Vacuum M ₁ . EUV light absorber layer M ₂ . EUV light reflection multilayer film θ ₀ . Angle of incidence of EUV light on EUV light absorber layer θ ₁ . Angle of incidence of EUV light on EUV light reflecting layer I ₀ . EUV light intensity R ₀₁ . Reflectance at interface between vacuum M ₀ and EUV light absorber layer M ₁ R ₁₂ . Reflectance T ₀₁ of the interface between the EUV light absorber layer M ₁ and the EUV light reflective multilayer film M _2. Transmittance at the interface between vacuum M ₀ and EUV light absorber layer M ₁ d. Film thickness of EUV light absorber layer M ₁ z. The optical path length in the EUV light absorbing layer M ₁

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) G03F 1/16 H01L 21/30 531M F-term (Reference) 2H048 FA05 FA07 FA09 FA18 FA24 GA07 GA46 GA51 GA60 GA61 2H095 BA00 BC04 BC13 5F046 CA08 GD01 GD16

Claims (9)

[Claims] 1. An EU film formed on an EUV light reflecting multilayer film
A reflective mask blank for EUV exposure having a V light absorber layer, wherein EUV light reflected on the surface of the EUV absorber layer;
The light passes through the EUV absorber layer, is reflected by the EUV light reflecting multilayer film below the EUV absorber layer, and is again irradiated with the EUV light.
The thickness of the EUV absorber layer is set so that the EUV light reflectance of the EUV absorber layer is reduced by utilizing the interference effect between the EUV light passing through the UV absorber layer. A reflective mask blank for EUV exposure. 2. An EU film formed on an EUV light reflecting multilayer film
A reflective mask blank for EUV exposure having a V light absorber layer, wherein the EUV light reflected on the surface of the EUV light absorber layer and the EUV light absorber layer passing through the EUV light absorber layer Simulate the reflectance obtained by adding the interference effect with the EUV light reflected by the EUV light reflecting multilayer film below and passing through the EUV light absorber layer again. The horizontal axis,
The reflectance is represented in a graph with the vertical axis. In the graph, a curve connecting the points giving the maximum value of the reflectance with respect to the film thickness is obtained, and the film whose film thickness is determined to be unsuitable for use from the viewpoint of film stress When the thickness is defined as the critical film thickness, the reflectance corresponding to the critical film thickness is obtained from the curve, and defined as the critical reflectance.From the simulation result of the reflectance, the minimum value of the reflectance with respect to the film thickness is obtained. Is determined, and the film thickness is defined as a minimum value film thickness. In the film formation of the EUV light absorber layer, even if an unavoidable film thickness variation occurring when aiming for the minimum value film thickness is considered. A reflective mask blank for EUV exposure, characterized by using a film thickness capable of obtaining a reflectance lower than the limiting reflectance. 3. An EU formed on an EUV light reflecting multilayer film
A reflective mask blank for EUV exposure having a V light absorber layer, comprising: EUV light reflected on the surface of the EUV light absorber layer; and the EUV light absorber layer passing through the EUV light absorber layer. Reflected by the EUV light reflective multilayer film below
In a structure for reducing the reflectivity of EUV light in the EUV light absorber layer by using an interference effect with EUV light passing through the UV light absorber layer, the condition under which the interference effect occurs is determined by the EUV light absorber layer By formulating as a function of the film thickness of the EUV light-absorbing layer, the conditions under which the interference effect occurs are approximated by making the multilayer reflection in the EUV light-reflecting multilayer film the surface reflection. A reflective mask blank for EUV exposure, comprising: an EUV light absorber layer having a film thickness calculated by the approximate expression. 4. The reflective mask blank for EUV exposure according to claim 3, wherein a value of the film thickness d calculated by the approximate expression is: And Is within the range satisfying both of the above expressions, the reflectivity of EUV light is reduced using the interference effect.
Reflective mask blank for UV exposure. Here, λ ₀ is the wavelength of EUV light in vacuum, n ₀ is the refractive index in vacuum, n ₁ is the refractive index of the absorber layer, θ ₀ is the incident angle of EUV light to the EUV light absorber layer, k ₁ is a positive real number, T ₀₁ is the transmittance at the interface between the vacuum and the EUV light absorber layer, R ₀₁ is the reflectance at the interface between the vacuum and the EUV light absorber layer, and R ₁₂ is the EUV light absorber layer And EUV
The reflectance at the interface with the light reflection multilayer film, m is a positive integer, and φ is the phase shift. 5. The EU according to claim 1, wherein:
A reflective mask blank for V exposure, wherein the EUV light reflective multilayer film has a first film and a second film alternately laminated, wherein the first film is a transition metal, a carbide of a transition metal. , A transition metal nitride, a transition metal silicide, and a transition metal boride, and at least one component selected from the group consisting of B and / or Be and / or C and / or Or Si, B and / or Be and / or
Or an oxide of C and / or Si, a nitride of B and / or Be and / or C and / or Si,
The EUV absorber layer includes at least one component selected from Cr, Cr carbide, Cr nitride, Cr silicide, and Cr boride. The EUV absorber layer has a thickness of 70 nm to 100 nm.
Reflective mask blank for V exposure. 6. The EU according to claim 1, wherein:
A reflective mask blank for V exposure, wherein the EUV light reflective multilayer film has a first film and a second film alternately laminated, wherein the first film is a transition metal, a carbide of a transition metal. , A transition metal nitride, a transition metal silicide, and a transition metal boride, and at least one component selected from the group consisting of B and / or Be and / or C and / or Or Si, B and / or Be and / or
Or an oxide of C and / or Si, a nitride of B and / or Be and / or C and / or Si,
The EUV absorber layer contains at least one component selected from Ta, a carbide of Ta, a nitride of Ta, a silicide of Ta, and a boride of Ta. The EUV absorber layer has a thickness of 70 nm to 110 nm.
Reflective mask blank for UV exposure. 7. EUV according to claim 5 or claim 6.
A reflective mask blank for exposure, wherein the transition metal is W, Ta, Mo, Rh, Ru, Au, Hf, Ni,
A reflective mask blank for EUV exposure, comprising at least one metal selected from Cr and Re. 8. The EU according to claim 1, wherein:
A reflective mask for EUV exposure, wherein a reflective mask blank for V exposure is used. 9. A method for manufacturing a semiconductor, comprising: transferring a pattern on a semiconductor wafer by EUV light using the reflective mask for EUV exposure according to claim 8.