JPH0727198B2 - Multi-layer reflective mask - Google Patents

Description

The present invention relates to a multilayer film reflection type mask for exposure to soft X-rays / vacuum ultraviolet rays used for lithography.

[Conventional technology]

Conventionally, a single crystal plate has been used as the X-ray reflection portion of a reflection type mask for X-ray exposure (Japanese Patent Application No. 52-54126). However, since this reflection mask for X-ray exposure utilizes Bragg diffraction of a single crystal, X-ray incidence must be oblique incidence. As a result, the mask area becomes very large, and since it is large, it is difficult to uniformly manufacture it with good planarity.

In view of the above-mentioned problems of the conventional example, the present invention provides a multilayer film reflection type mask for soft X-rays / vacuum ultraviolet rays, which can be used with positive incidence on soft X-rays / vacuum ultraviolet rays and is smaller than the conventional one. With the goal. It is another object of the present invention to provide a low distortion multi-layer film reflective mask by making the absorber have a low coefficient of thermal expansion and high thermal conductivity.

[Means for solving problems]

The above-mentioned object of the present invention is a laminated body in which a patterned absorber that absorbs soft X-rays / vacuum ultraviolet rays is arranged on a reflector that reflects soft X-axis / vacuum ultraviolet rays. This is achieved by a multilayer film reflective mask for soft X-ray / vacuum ultraviolet exposure, which is a multilayer laminated plate in which two types of layers having different constants are alternately laminated.

FIG. 1 is a schematic cross-sectional view of an example of a multilayer film reflective mask for soft X-ray / vacuum ultraviolet exposure of the present invention. In this multilayer film reflection type mask, as shown in the drawing, first substrate layers 2, 4 ... And second substrate layers 3, 5 ... Is formed, and an absorber A for soft X-ray / vacuum ultraviolet light, which is patterned into a desired shape, is arranged on the uppermost layer.

The film thickness d ₁ , d ₂ ... of each layer is 10 Å or more, and even if the film thicknesses are alternately equal (d ₁ = d ₃ = ..., d ₂ = d ₄ = ...) It may be changed, but considering both the reduction in amplitude due to absorption of soft X-rays and vacuum ultraviolet rays in each layer and the strengthening of reflected light due to the overlapping of the phases of reflected light at the interface of each layer, It is preferable that the thickness of the entire reflecting mirror be such that the highest reflectance is obtained. When the thickness of each layer is less than 10Å, it is not preferable because a high reflectance cannot be obtained as a reflecting mirror due to the effect of diffusion of two substances at the interface. The reflectance increases as the number of layers increases, but on the other hand, manufacturing difficulties arise. Therefore, the number of laminated layers is preferably 200 or less.

The absorber absorbs soft X-rays and vacuum ultraviolet rays, and has high thermal conductivity,
Any material may be used as long as it has a low thermal expansion property. Specifically, the linear expansion coefficient is 5 × 10 ⁻⁵ / deg or less and the thermal conductivity is 0.1 J.
/ cm · s · deg or more is preferable. If the coefficient of linear expansion and the thermal conductivity are larger than the above values, the problem that the absorber and the reflecting mirror having the multilayer structure are displaced or separated easily occurs.
As a substance forming such an absorber, for example, metals such as gold, tantalum, and tungsten, semiconductors such as silicon, and insulators such as silicon nitride, silicon carbide, and tantalum nitride are preferably used.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention.

Example 1 As shown in FIG. 2 (a), a silicon single crystal plate polished to have a surface roughness of 10 Å or less as an rms value was used as a substrate 1 to form first layers 2, 4 ... Ruthenium (R
u), silicon carbide (Si) as the material forming the second layers 3, 5 ...
C), after reaching an ultra-high vacuum of 1 × 10 ^-6 Pa or less, the argon pressure was maintained at 5 × 10 ^-1 Pa and the film thickness was 29.8Å and 33.9Å by 41 layers (Ru Layer 21 Layer, Si
C: 20 layers), and further 10 C of carbon (C) was laminated thereon as a protective film B to obtain a multilayer laminated plate. In this case, the first
Layer has a small real part of the refractive index, and the second layer has a large real part of the refractive index.

Next, as shown in FIG. 2 (b), a PMMA layer as a resist was formed on this multilayer laminated plate to a thickness of 0.5 μm, and 1.75 μm lines and spaces were patterned by EB drawing. On the patterned resist C, the soft X-ray absorber gold (linear expansion coefficient 1.42 × 10 ⁻⁵ / deg, thermal conductivity 3.
16 J / cm.S.deg) was formed by EB vapor deposition to a thickness of 0.1 μm. Next, PMMA was peeled off to obtain a gold pattern A on the multilayer film (FIG. 2 (c)).

Next, soft X-ray exposure was performed using the created multilayer reflective mask.

FIG. 3 is an optical path diagram of the projection optical system, in which soft X-ray reflection mirrors M ₁ , M ₂ , and M ₃ are concave mirrors, convex mirrors, and concave mirrors, respectively.
W indicates an exposure substrate. M ₀ is the multilayer reflective mask. The position is shown in the figure. The soft X-rays generated from the divergent X-ray source and incident on the mask M ₀ at an angle of 1.7 ° (normal incidence) enter the projection optical system through the reflecting portion of the mask M ₀ , and have a concave mirror M ₁ and a convex mirror M ₂ , The concave mirror M ₃ is reflected in this order, and the image of the mask M ₀ is formed on the exposure substrate W. The specifications of this projection optical system are a projection magnification of 1/5, an effective F number of 13, an image plane size of 28 × 14 mm ² , an image height of 20 to 37 mm, and a resolution of 0.35 μm.

A soft X-ray of 124 Å is used as the light source, and PMMA 1
μm was applied. When soft X-rays were generated and the PMMA resist on the exposure substrate W was exposed and developed by a projection exposure system, 0.35 μm lines and spaces were resolved.

Example 2 Tantalum nitride (TaN) was used as the material forming the first layers 2, 4 ... On the silicon single crystal plate 1 polished in the same manner as in Example 1, and the material forming the second layers 3, 5 ... 1 using silicon (Si)
After reaching an ultra-high vacuum of 10 ^-6 Pa or less, the argon pressure is set to 5 x.
The film thickness is maintained at 10 ^-1 Pa and the film thickness is 2 by sputter deposition.
41 layers (TaN: 21 layers, Si: 20 layers) were laminated as 0.3Å and 40.6Å, and further 10Å of carbon (C) was laminated thereon as a protective film B. In this case, the first layer has a small real part of the refractive index and the second layer has a large real part of the refractive index.

Next, PMMA 0.5 μm was formed on the obtained multi-layer laminate and patterned by EB drawing. Tantalum (Ta), which is a soft X-ray absorber, has a linear expansion coefficient of 6.3 × 10 on this PMMA pattern.
^-6 / deg, thermal conductivity 0.575J / cm.s.deg) 0.1 by EB evaporation
After forming to a thickness of μm, PMMA was peeled off to obtain a tantalum pattern A on the multilayer film.

Using the mask produced here, the PMMA on the exposed substrate W was exposed by the reduction optical system shown in Example 1. As a result, 0.35 μm line and space was resolved.

Example 3 On a silicon single crystal plate polished in the same manner as in Example 1, the first
(Pd) is used as the material forming the layers 2, 4 ... Of the above, and silicon (Si) is used as the material forming the second layers 3, 5 ...
41 layers (Pd: 21 layers, Si: 20 layers) with the film thickness of 21.1Å and 40.3Å respectively by EB vapor deposition in an ultra high vacuum of ^-6 Pa or less.
Layer), and carbon (C) as a protective film on top of it
Å Stacked. In this case, the first layer has a small real part of the refractive index and the second layer has a large real part of the refractive index.

Next, PMMA 0.5 μm was formed on the obtained multi-layer laminate and patterned by EB drawing. Silicon (Si), which is a soft X-ray absorber, has a linear expansion coefficient of 2.6 × 10 ^-6 / on this PMMA pattern.
deg, thermal conductivity 1.49 J / cm.s.deg) 0.1 μm by EB evaporation
After thickly forming, PMMA was peeled off to obtain a silicon pattern A on the multilayer film.

Using the mask produced here, the PMMA on the exposed substrate W was exposed by the reduction optical system shown in Example 1. As a result, 0.35 μm line and space was resolved.

In the embodiment of the present invention, 1 / of the configuration shown in FIG.
A 5 × reduction optical system (0.35 μm resolution) is assumed, but it is of course possible to use an exposure optical system having other specifications and configurations.

Further, in the examples, the EB vapor deposition method and the sputtering method were used in the formation of the multilayer film, but the method is not limited thereto, and other methods such as resistance heating, CVD, and reactive sputtering may be used to form various thin films. Can be used. Further, although a Si single crystal plate was used as the substrate, it is not limited to this, and any substrate such as glass, fused silica, silicon carbide, etc., whose surface is sufficiently smooth compared to the wavelength used, can be used. Good.

〔The invention's effect〕

As described above, according to the multilayer reflective mask of the present invention, since the reflective layer having the multilayer structure in which two types of layers having different optical constants are alternately laminated is used as the reflecting portion, the amplitude due to the absorption of radiation is increased. Of the conventional single crystal plate, because a high reflectance can be obtained due to the reduction of the intensity and the strengthening of the reflected light due to the overlapping of the phases of the reflected light at the interface of each layer.
Unlike the reflector using agg diffraction, it is not necessary to obliquely enter the radiation from the horizontal direction, and the radiation can be normally incident. As a result, it is possible to provide a reflective mask capable of highly accurate and highly efficient exposure.

[Brief description of drawings]

FIG. 1 is a basic sectional view of a multilayer film reflective mask for soft X-ray / vacuum ultraviolet exposure of the present invention. FIG. 2 is a process drawing of the multilayer-film reflective mask of the present invention. FIG. 3 is an optical path diagram of a projection optical system using the multilayer-film reflective mask of the present invention. 1 …… Si substrate 2,4 …… First material layer 3,5 …… Second material layer A …… Soft X-ray / vacuum ultraviolet absorber (gold, tantalum, silicon) B …… Protective film C …… Resist (PMMA) M ₀ …… Multilayer film reflective mask for soft X-ray / vacuum UV exposure M ₁ …… Concave X-ray mirror M ₂ …… Convex X-ray mirror M ₃ …… Concave X-ray mirror W …… Exposure substrate d _{1 to} d ₄ …… Thickness of each layer

Claims (3)

[Claims] 1. A reflective layer having a multilayer film structure in which two types of layers having different optical constants are alternately laminated, and an absorber that absorbs soft X-rays or vacuum ultraviolet rays forming a pattern are provided on a substrate. A multi-layered reflective mask. 2. The reflective mask according to claim 1, wherein the linear expansion coefficient of the absorber is 5 × 10 ⁻⁵ / deg or less. 3. The thermal conductivity of the absorber is 0.1 J / cm · s · deg.
The reflective mask according to claim 1, which is as described above.