JP2615741C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reflection type mask, an exposure apparatus and an exposure method using the same, and more particularly to a soft X-ray or a wavelength of about 5 to 300 ° used in lithography. 300 Å ~ 2000
A reflective mask using a pattern consisting of a reflective portion and a non-reflective portion having a predetermined reflectance with respect to about Å vacuum ultraviolet rays (hereinafter referred to as "soft X-rays"), an exposure apparatus and an exposure method using the same It is about. (Prior Art) Conventionally, as a mask for exposure in a semiconductor manufacturing apparatus using soft X-rays or the like, gold (Au), gold (Au), or the like on a substrate surface as a transmission material such as silicon nitride (SiNx) or silicon carbide (SiC) is used. There have been proposed various transmission masks having an opaque pattern formed of an absorbing material such as tantalum (Ta). On the other hand, Japanese Patent Application Laid-Open No. 53-139469 discloses that a substrate made of a single crystal or a completely amorphous material is used on a substrate surface made of a single crystal or a completely amorphous material by utilizing Bragg diffraction conditions. There has been proposed a reflective mask for X-ray lithography having a pattern formed thereon. In the conventional reflection type mask, due to the nature of reflection, soft X-rays and the like must be obliquely incident on the substrate surface. As a result, the mask area increases, and polishing of the substrate and flatness of the mask surface are improved. Difficult to maintain. In addition, it is difficult to support the mask with high accuracy, and there is a problem that the entire apparatus becomes larger. Further, in actually exposing the X-ray mask, it is desired to increase the irradiation energy density on the wafer surface and shorten the exposure time in order to improve the printing accuracy and the throughput. For this reason, synchrotron radiation from an electron storage ring having a large radiant energy intensity is often used as a light source at present. However, when such intense soft X-rays or the like are irradiated, the substrate or absorber of the X-ray mask absorbs a large amount of radiant energy, the temperature increases, thermal expansion occurs, and the pattern on the mask surface is deformed, resulting in displacement. Come. Such pattern deformation and misregistration are serious problems in a high-precision exposure apparatus for printing a submicron pattern. (Problems to be Solved by the Invention) According to the present invention, by appropriately setting the material of the substrate, it is possible to increase the reflectance to radiation such as X-rays or vacuum ultraviolet rays, and to achieve low thermal expansion and high thermal conductivity. It is an object of the present invention to provide a reflection type mask which is excellent in heat resistance and can obtain low distortion and high contrast. It is another object of the present invention to provide an exposure apparatus and an exposure method using the reflective mask. (Means for Solving the Problems) (1-1) The reflective mask of the present invention has at least two reflective optical masks having different optical constants.
A reflective mask having a structure in which a multilayer film reflecting portion in which different types of substances are alternately laminated, and a pattern of a non-reflecting portion formed by an absorber is formed on the multilayer film reflecting portion, wherein the material of the substrate is linearly expanded. The coefficient of thermal conductivity is 1 × 10 ⁻⁵ K ⁻¹ or less, the thermal conductivity is 20 w / m · K or more, and the material of the absorber is substantially equal to the linear expansion coefficient of the substrate and larger than the thermal conductivity of the base. It is characterized by that. (1-2) The exposure apparatus using the reflection type mask of the present invention irradiates the mask surface of the reflection type mask with radiation including X-rays or vacuum ultraviolet rays, and applies the pattern formed on the mask surface to a predetermined surface. An exposure apparatus for exposing and transferring light, wherein the reflective mask is provided on a substrate with a multilayer reflective portion in which at least two types of substances having different optical constants are alternately laminated, and the reflective mask is absorbed on the multilayer reflective portion. It has a structure in which a pattern of a non-reflective portion is formed by a body, and the material of the substrate is made of a material having a linear expansion coefficient of 1 × 10 ⁻⁵ K ⁻¹ or less and a thermal conductivity of 20 w / m · K
As described above, the material of the absorber is substantially equal to the coefficient of linear expansion of the substrate and larger than the thermal conductivity of the substrate. (1-3) In the exposure method using the reflective mask of the present invention, the mask surface of the reflective mask is irradiated with radiation including X-rays or vacuum ultraviolet rays, and the pattern formed on the mask surface is exposed on a predetermined surface. A reflective mask, wherein the reflective mask is provided on a substrate with a multilayer reflective portion in which at least two types of substances having different optical constants are alternately laminated, and the reflective mask is absorbed on the multilayer reflective portion. The substrate has a structure in which a pattern of a non-reflection portion is formed, and the material of the substrate has a linear expansion coefficient of 1 × 10 ⁻⁵ K ⁻¹ or less, a thermal conductivity of 20 w / m · K or more, and The material is substantially equal to the coefficient of linear expansion of the substrate and larger than the thermal conductivity of the substrate. (Embodiment) FIG. 1 is a schematic sectional view of one embodiment of the reflection type mask of the present invention. In the figure, reference numeral 10 denotes a reflecting portion formed of a multilayer laminated film for soft X-rays and the like. The reflecting portion 10 is formed on the planar substrate 1 having the above-described coefficient of linear expansion and thermal conductivity. Reference numeral 16 denotes a non-reflection portion made of an absorber for soft X-rays and the like, which is provided on the surface of the reflection portion 10 and forms a pattern having a predetermined shape. .. And the second substance 3, having different optical constants.
Are alternately laminated. The thickness d ₁ , d _2, ... Of the respective material layers of the reflection section 10 shown in the same figure is 10 ° or more, and are alternately equal in thickness (d ₁ = d ₃ =..., D ₂ = d _4). =) May also be configured with all film thicknesses changed. However, the decrease in amplitude due to the absorption of soft X-rays and vacuum ultraviolet rays in each layer,
In consideration of both the enhancement of the reflected light due to the overlapping of the phases of the reflected light at the interfaces of the respective layers, it is preferable that the thickness be such that the highest reflectance is obtained as the entire reflecting portion. If the thickness of each layer is less than 10 °, it is not preferable because a high reflectance cannot be obtained as a reflection portion due to the effect of diffusion of the two substances at the interface. As the number of layers increases, the reflectivity increases, but on the other hand, manufacturing difficulties arise. Therefore, the number of layers is preferably within 200 layers. Further, the non-reflection part 16 is an absorber for the reflection part 10. The reflection type mask preferably has a ratio of the intensity of soft X-rays or the like reflected by the reflection portion 10 and the non-reflection portion 16 to 2: 1, preferably 10: 1 or more. As described above, the reflection type mask is often used by using a strong X-ray source (for example, a light source using synchrotron radiation or the like), and the temperature rise of the mask due to absorption of irradiation energy becomes a problem. . In particular, misalignment and distortion occur in the pattern on the mask surface due to thermal expansion due to a temperature rise, and as a result, this is an important problem in forming a submicron size pattern. For this reason, in a reflective mask using soft X-rays or the like, it is necessary to suppress an increase in the temperature of the reflective mask. The reflective mask in this embodiment uses a material having a high thermal conductivity and a low linear expansion coefficient of the above-described values for the substrate to effectively radiate heat, prevent a temperature rise, and deform and position the pattern due to the temperature rise. The occurrence of displacement and distortion is minimized. Examples of the substrate material satisfying the above conditions include ceramic silicon nitride, aluminum nitride, and silicon carbide. In particular, silicon carbide is a suitable material having a remarkably large thermal conductivity (100 w / m · K). In this embodiment, when the non-reflective portion is made of an absorber, the absorber is made of a material having substantially the same coefficient of linear expansion as the substrate and having a high thermal conductivity in order to prevent a rise in the temperature of the absorber. Preferred. Examples of such a material include metals such as gold, tantalum, tungsten, molybdenum, and rhodium. When silicon carbide (SiC) is used for the substrate, it is preferable to use tungsten having a coefficient of linear expansion close to that of the substrate. For example, the linear expansion coefficient of silicon carbide is ~ 4.5 × 10 ^-6, tungsten is ~ 4.5 × 10 ^-6. Also, if molybdenum is used as the reflecting portion, the linear expansion coefficient of molybdenum is ~ 4 × 10
^Since it is ^-6 , it is preferable to configure it by combining these materials as an X-ray mask. Next, a first embodiment of a method for manufacturing a reflective mask according to the present invention will be described with reference to FIG. First, as shown in FIG. 2 (A), a substrate 1 made of vapor-grown silicon carbide (SiC) polished so as to have a surface roughness of 10 ° or less in rms value as a substrate 1 was used.
(Ru) as a material forming the layers 2, 4, 6,.
1 × 10 ⁻⁶ Pa (Pascal) using silicon carbide (SiC) as the substance forming
After reaching the following ultra-high vacuum, the argon pressure was kept at 5 × 10 ⁻¹ Pa, and the thicknesses of the first layer (Ru) and the second layer (SiC) were 29.8 ° and 33.9 ° by sputter deposition. Thus, 41 layers (21 layers of Ru layers and 20 layers of SiC layers) were laminated to form the reflection unit 10. Then, carbon (C) was laminated as a protective film A on the reflecting portion 10 to a thickness of 10 °. In this case, the first layer (Ru) has a small real part of the refractive index and the second layer (Si)
C) is selected such that the real part of the refractive index is large. Next, as shown in FIG. 2 (B), PMMA as a resist is
A layer of B (polymethyl methacrylate) was formed to a thickness of 0.5 μm, and patterning of a 1.75 μm line and space was performed by EB (electron beam) drawing. This PM
A patterned resist B made of MA was formed. Tungsten (linear expansion coefficient: 4.5 × 10 ⁻⁶ K ⁻¹ , thermal conductivity: 177 w / mK), which is an absorber for soft X-rays, is formed on the patterned resist B made of PMMA to a thickness of 0.25 μm by RF sputtering. Then, a film was formed to manufacture an X-ray mask (FIG. 2 (C)). In the figure, reference numeral 31 denotes a non-reflection portion, and 32 denotes a reflection portion. Next, soft X-ray exposure was performed using a reflective mask composed of a multilayer film formed by the method shown in FIG. 2 as an exposure apparatus. FIG. 3 is a schematic diagram showing an optical path of the projection optical system used at this time. In the drawing, soft X-ray reflecting mirrors M ₁ , M ₂ , and M ₃ are a concave mirror, a convex mirror, and a concave mirror, respectively, and W indicates an exposure substrate. M ₀ is a reflective mask composed of the above-mentioned multilayer film. The position is shown in the figure. The light enters the projection optical system via the reflection portion of the soft X-ray reflection type mask M ₀ generated from the divergent X-ray source and incident on the reflection type mask M ₀ at an angle of 1.7 ° (normal incidence), and enters the concave mirror M ₁ , The light is reflected by the convex mirror M ₂ and the concave mirror M ₃ in this order, and forms an image of the reflective mask M ₀ 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, and an image plane size of 28 × 1
4 mm ² , image height is 20 to 37 mm, and resolution is 0.35 μm. The exposure substrate W was coated with 1 μm of PMMA by using soft X-rays of 124 ° as a light source. When a soft X-ray was generated and the PMMA resist on the exposure substrate W was exposed and developed by the projection exposure system, a resolution of 0.35 μm line & space was obtained. In each embodiment of the present invention, a 1 / 5-fold reduction optical system (0.
(35 μm resolution) is assumed, but of course, an exposure optical system having other specifications and configurations may be used. In addition, although the EB vapor deposition method and the sputtering method were used in forming the multilayer film, the present invention is not limited thereto, and other methods of forming various thin films such as resistance heating, CVD, and reactive sputtering can be used. . (Effect of the Invention) According to the present invention, by forming the substrate of the reflection type mask from the material having the above-described characteristics, the heat is sufficiently released from the substrate, so that the temperature rise is low and the coefficient of linear expansion is small. Therefore, it is possible to achieve a highly accurate reflection type mask for lithography, which is extremely stable thermally and with little distortion, and an exposure apparatus and an exposure method using the same. In addition, a reflection type mask having a simple configuration capable of normal incidence of soft X-rays and the like is provided by forming a reflection portion provided on the substrate surface from a multilayer laminated structure in which two substances having different optical constants are alternately laminated. An exposure apparatus and an exposure method using the same can be achieved. Also, if a material having substantially the same thermal properties as the substrate is used for the absorber provided on the reflecting portion, a pattern-type mask and an exposure apparatus and an exposure method using the same can minimize distortion and displacement of the pattern. Can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of one embodiment of a reflective mask of the present invention, FIG. 2 is an explanatory diagram of a first embodiment showing a method of manufacturing a reflective mask of the present invention, and FIG. FIG. 3 is a schematic optical path diagram of lithography using the reflective mask of the present invention. In the figure, 1 is a substrate, 10 is a reflecting portion having a multilayer laminated structure, 2, 4... Is a first substance, 3, 5,... Is a second substance, M ₀ is a reflective mask, W is an exposure substrate, 16 Is the absorber,
B is a resist, and A is a protective film.

Claims (1)

Claims: (1) On a substrate, there is provided a multilayer reflection part in which at least two kinds of substances having different optical constants are alternately laminated, and a pattern of a non-reflection part by an absorber is provided on the multilayer reflection part. Wherein the material of the substrate has a linear expansion coefficient of 1 × 10 ⁻⁵ K ^−1.
An X-ray or a heat source, wherein the thermal conductivity is 20 w / m · K or more, and the material of the absorber is substantially equal to the linear expansion coefficient of the substrate and larger than the thermal conductivity of the substrate. Reflective mask for vacuum ultraviolet rays. (2) An exposure apparatus that irradiates a radiation including X-rays or vacuum ultraviolet rays onto a mask surface of a reflective mask and exposes and transfers a pattern formed on the mask surface onto a predetermined surface. Having a structure in which at least two types of substances having different optical constants are alternately laminated on a substrate, and a pattern of a non-reflection part by an absorber is formed on the multilayer reflection part, The material of the substrate has a coefficient of linear expansion of 1 × 10 ⁻⁵ K ⁻¹ or less, a thermal conductivity of 20 w / m · K or more, and the material of the absorber is substantially equal to the coefficient of linear expansion of the substrate. An exposure apparatus for X-rays or vacuum ultraviolet rays, wherein the exposure apparatus has a higher thermal conductivity. (3) An exposure method for irradiating radiation including X-rays or vacuum ultraviolet rays onto a mask surface of a reflective mask, and exposing and transferring a pattern formed on the mask surface onto a predetermined surface. Having a structure in which at least two types of substances having different optical constants are alternately laminated on a substrate, and a pattern of a non-reflection part by an absorber is formed on the multilayer reflection part, The material of the substrate has a linear expansion coefficient of 1 ×.
10 ^-5 K ^-1 or less, the thermal conductivity is 20 w / m · K or more, and the material of the absorber is substantially equal to the linear expansion coefficient of the substrate and larger than the thermal conductivity of the substrate. Characteristic exposure method for X-rays or vacuum ultraviolet rays.