JPH09142996A - Reflection type mask substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a mask substrate almost independent of the environment at the time of producing a mask and thermal and chemical changes in an exposure system and to enhance the precision of exposure by forming a specified SiC film on a sintered SiC sheet as a substrate. SOLUTION: A thin SiC film 2 is formed on a sintered SiC substrate 1 and the surface of the film 2 is mirror-polished to obtain the objective mask substrate. The film 2 is a (220) face oriented thin SiC film having a β-crystal structure and excellent in workability and polishability. In the X-ray diffraction of the film, the diffraction peak of the (220) face has the max. intensity. In the case of an X-ray diffraction peak ratio of >=99, the mask substrate enables the transfer of a precision pattern for exposure to the top of a wafer. Since both the substrate 1 and the film 2 are made of SiC having a low coefft. of thermal expansion, inter-facial peeling is hardly caused and a mask pattern on the specular surface 3 of the film is not deformed by the thermal strain of the substrate in the environment at the time of producing a mask and causes no trouble to the top of a wafer to which the pattern is transferred.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to vacuum ultraviolet rays and X-rays.
The present invention provides a substrate material and a substrate suitable for a reflective mask for exposure used in lithography or the like in which a line is used as an exposure light source.

[0002]

2. Description of the Related Art As the field of information processing technology advances and expands, the improvement of semiconductor technology, which is the basis of the technology, is remarkable. In particular, personalization of equipment by downsizing and price reduction has led to a rapid expansion of the market. One of the causes of this functional improvement is high-density integration of semiconductors. According to the semiconductor processing rule, an integrated circuit with a DRAM 16 Mbit capacity and a line width of 0.5 μm has already been put into practical use. At the research level, the challenge of 1 Gbit capacity is advancing. This inevitably involves updating and improving semiconductor processing rules. If the line width is 0.8 to 0.5 μm or more, integrated circuit patterning could be easily performed with a laser beam in the visible wavelength region. However, processing of a line / space width of 0.1 μm or less is extremely difficult as long as an exposure light source of visible region wavelength light is used. Therefore, there is an ongoing challenge to use the wavelength of the soft X-ray region having a shorter wavelength from the vacuum ultraviolet region having a shorter wavelength than the visible region.

Transmission type and reflection type masks have been developed for lithography masks utilizing vacuum ultraviolet rays or soft X-ray wavelength regions. The transmissive type is a method in which a wafer to be processed is positioned and installed on one surface side of a transmissive mask, and an exposure light beam is irradiated from the opposite surface side. Therefore, the circuit pattern to be transferred is drawn on the mask surface as a pattern composed of the transmitting portion and the absorbing portion of the exposure light beam. On the other hand, in the reflection type, the light beam for exposure is reflected and absorbed by the surface of the mask, and the light beam reflected by the reflecting portion spatially transfers the circuit pattern on the mask and reaches the wafer.

As the mask substrate, a silicon single crystal plate is often used. On this substrate, an absorption and reflection thin film is surface-processed into a fine pattern in a reflection type mask.
As the absorption thin film, for example, a metal such as gold, tantalum, or tungsten is used, a semiconductor such as silicon, an insulator such as silicon nitride, silicon carbide, or tantalum nitride is preferably used. As the reflective thin film, a plurality of thin film materials may be laminated in multiple layers to improve the reflective performance. On the other hand, the transmissive type has the same structure of the absorbing part thin film, but the transmissive part often uses silicon nitride, silicon carbide, boron carbide, boron-added silicon, or carbon.

The silicon single crystal substrate material is fixed to a silicon support frame. In the transmission type, the silicon support frame must be removed by etching in order to secure the passage of the irradiation X-ray.

[0006]

The function of the reflective mask is to generate a pattern on the surface of the mask by selectively reflecting and selectively absorbing the irradiation light, and spatially transferring the pattern. Therefore, the deformation of the mask surface that produces the pattern is severely limited. Conventionally, single crystal silicon is used as a mask substrate material, but in the present invention, a silicon carbide material having a small coefficient of thermal expansion and excellent heat resistance is used as a substrate material, an environment at the time of mask production, or exposure. (EN) Provided is a mask substrate excellent in exposure accuracy which is hardly affected by thermal and chemical changes in the apparatus.

In addition, the reflective mask has an absorbing portion that selectively absorbs irradiation light and a reflecting portion that selectively reflects irradiation light.
It is necessary to perform high-precision surface processing of two kinds of functional material thin films, respectively. It is an object of the present invention to provide a substrate material and a substrate in which the substrate itself constitutes an absorbing portion by making the substrate material of the mask substrate an absorbing functional material, and a reflective mask can be easily manufactured.

[0008]

The present invention is intended to solve the above-mentioned problems in the substrate material and the substrate in the reflection type mask.

The supporting substrate is made of a sintered silicon carbide plate as a substrate material which is not easily influenced by the environment at the time of making the mask or the environment inside the exposure apparatus. A reflection mask substrate is formed by forming a silicon carbide thin film on a sintered silicon carbide supporting substrate by a CVD method and polishing the surface to a mirror surface.

The present invention will be described below with reference to the drawings. FIG.
As shown in, a substrate is formed by forming a thin film 2 of the same material composition on the sintered silicon carbide supporting substrate 1, and the thin film surface thus formed is mirror-polished to form a mask substrate. The thin film 2 formed by the CVD technique is a crystal-grown thin film suitable for ultra-smooth mirror polishing. The crystal structure of the thin film is a β-type crystal structure, and the diffraction peak of the (220) plane shows the highest intensity in the X-ray diffraction of the crystal film.
Has excellent workability and polishability. Crystal orientation (220)
A substrate on which a silicon carbide thin film having (111) and (200) orientation planes is vapor-deposited on a sintered silicon carbide supporting substrate, and a (220) plane oriented crystal component is X relative to the orientation component.
Comparing the abradability with the substrate on which a thin film having a linear diffraction peak ratio of 99 or more was compared, the difference between the two silicon carbide films was remarkable.
As shown in FIG. 5, when the X-ray diffraction peak ratio is 99 or more, a sufficient surface roughness of about rms 1.5Å can be obtained, so that there is almost no diffuse reflection of irradiation light from the substrate surface. It becomes possible to Therefore, a mask substrate capable of transferring a precise exposure pattern onto a wafer is provided.

Since the carbon silicon supporting substrate material 1 and the thin film material 2 are composed of the same material composition and have a small coefficient of thermal expansion, they are different materials against the thermal cyclic strain due to the repeated irradiation of the irradiation light energy for exposure. Compared to the composite, there is less damage due to delamination. In addition, due to the environment at the time of manufacturing the mask, that is, the pattern accuracy error caused by the change in the peripheral environment of the substrate such as the pattern drawing by EB, the cleaning, or the influence of the temperature fluctuation in the exposure apparatus, the thermal distortion of the substrate causes a mirror surface. The mask pattern on No. 3 is not deformed and does not hinder the patterning of the electron beam resist on the transferred wafer. The carbon silicon material has a large thermal conductivity, and the temperature can be precisely controlled according to the change in the mask dimension due to cooling and heating. A substrate that can exhibit stable functions is provided due to such materials and material configurations.

For a reflective mask structure which does not require surface treatment of the VUV absorber on the substrate, the substrate material is made of a VUV absorber material. The surface of the substrate material is polished to form an ultraviolet absorbing surface. Because of the absorbing surface, it is not necessary to polish it to a super smooth surface as much as the irradiation light reflecting mirror. A protective film is formed on the polished substrate surface to protect the surface and improve the adhesion of the thin film in the next step. The reflection part that reflects the irradiation light and forms a transfer pattern on the reflection light is formed by applying an electron beam resist on the surface of the protective film, performing an EB drawing process on the fine pattern, and then removing the thin film of the reflection material from the resist. It is formed by vapor deposition on the fine pattern portion. Therefore, an irradiation light reflection fine pattern is formed on the irradiation light absorption surface of the substrate surface through the protective film, and the irradiation light is reflected and transferred in a pattern. Unlike the conventional reflective mask formation, it is not necessary to form a thin film for absorbing irradiation light on the substrate, and a substrate that facilitates the production of a vacuum ultraviolet reflective mask by the substrate material surface performing the absorbing function. provide.

FIG. 2 is a part of the process of producing an exposure mask using a substrate material having a vacuum ultraviolet ray absorbing property. Glassy carbon is used as the substrate material 6.
Glassy carbon is a perfect absorber of vacuum ultraviolet light.
Further, it has workability sufficient for polishing the surface. That is, the surface is directly polished without performing thin film processing on the substrate material. However, in order to improve the abrasion resistance of the surface of the glassy carbon and the adhesiveness with the reflective film formed on the surface, the protective film 7 having no reflective property to the ultraviolet wavelength is used.
Is vapor-deposited on the entire surface. A vacuum ultraviolet ray reflective thin film is patterned and deposited on the protective film 7 by the above method.

[0014]

In the reflective mask substrate, the silicon carbide thin film made of the same material as the supporting substrate material is formed on the sintered silicon carbide supporting substrate by the CVD method. The surface is mirror-polished to form a mask substrate. Due to the unique thermal and chemical characteristics of silicon carbide materials, a stable reflective mask substrate and substrate with little thermal or chemical changes due to changes in the working environment during mask fabrication or environmental changes in the exposure equipment It becomes a material.

As the silicon carbide thin film, a silicon carbide thin film structure which is easily mirror-polished, that is, a thin film structure in which crystals are aligned in the (220) plane direction is used. The mask substrate having the thin film structure film is a substrate for a mask that is easy to polish and has excellent exposure accuracy.

In the vacuum ultraviolet ray reflection type mask substrate, the substrate material is made of a vacuum ultraviolet ray absorbing material, and the substrate itself constitutes a vacuum ultraviolet ray absorbing portion by polishing the surface of the substrate. It becomes a substrate for a reflective mask and a substrate material which does not require vapor deposition and treatment of a vacuum ultraviolet ray absorbing film on the substrate material.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 The support base shown in FIG. 1 uses a silicon carbide plate obtained by mixing silicon carbide powder with boric acid carbide and a phenol resin as a carbon source, and firing the powder into a plate-like shape 1. The thin film 2 is formed by chemical vapor deposition (CVD-SiC) of a pure β-type silicon carbide film on the surface of the support substrate. Chemical vapor deposition exhibits various surface morphologies by adjusting vapor deposition conditions and can be detected by an X-ray diffraction pattern.

In this example, the vapor deposition was performed in a non-oxidizing atmosphere, and the vapor deposition temperature was 1350 ° C. X-ray diffraction pattern diagram (CuKa: 30KVx) of the vapor-deposited silicon carbide film shown in FIG.
30mA, full scale: 50KCPS, slit: 1
−1-0.3, 2θ: 2 _o / min, chart: 20 m
As is clear from m / min and main peak intensity: 27 KCPS, the X-ray diffraction intensity ratio of the oriented plane (220) to the (111) plane and other planes is 99 or more at the peak intensity. That is, the crystal in the silicon carbide vapor deposition layer is oriented in the plane direction (220).

The chemical vapor deposition (CVD-SiC) surface is polished to a super smooth surface (RMS 10 Å or less) to form an X-ray reflecting surface. The vapor-deposited silicon carbide surface having a structure in which the orientation plane is oriented in the (220) direction has remarkable properties in terms of grindability. The labor such as polishing energy and polishing time required for polishing to a predetermined smoothness (RMS 10 Å or less)
Compared to the vapor-deposited film containing a crystal structure component other than the (220) plane orientation as shown in FIG. 4, the amount of polishing energy is extremely small, and the polishing surface shows almost no damage. It is suitable as a reflecting surface. Since the supporting sintered substrate and the thin film material are the same material, the adhesion between the two materials is extremely strong, and the bond boundaries are not damaged by the high-density energy light, and peeling due to thermal or mechanical strain does not occur.

The silicon carbide sintered support substrate 1, the silicon carbide chemical vapor deposition film 2 and the polishing mirror surface 3 shown in FIG. 1 (a) have already constituted the reflection mirror surface of the reflection type X-ray mask. It is possible to easily form a reflection type X-ray mask substrate and an X-ray reflection surface without the need to perform a special thin film processing treatment for X-ray reflection on the substrate material unlike the conventional reflection surface manufacturing technique. .

Next, an electron beam resist 4 was applied to the obtained mask substrate, and the X-ray absorber pattern line portion was irradiated with EB, exposed to light and removed by an EB drawing method. Silicon (linear expansion coefficient thermal conductivity J / cm-s-deg), which is the X-ray absorber 5, was formed thereon by EB vapor deposition to a thickness of 0.1 μm, and then the resist film was peeled off to remove the X-ray of the silicon carbide thin film. A silicon pattern 5 was obtained on the reflecting surface. It should be noted that, for the above mask production, X
Although the silicon film is used as the line absorber, a metal such as Ta, Au, or W, or an insulator such as silicon nitride or tantalum nitride may be used instead of silicon.

Embodiment 2 FIG. 2 shows a vacuum ultraviolet reflection type mask substrate. Glassy carbon is used as the substrate material. Glassy carbon is one of carbon on glass that exists in various chemical structures. Shows strong durability against acid, alkali metal,
The compatibility with 35 kinds of metals such as Bi, Te, B, Nb, Zr, Ta and W, and 7 kinds of dissolved halides has been investigated, but there is no difference with graphite for reactor. Ga
It does not react with III-V group compound semiconductors such as As and GaP, Te compounds, MgF ₂ , Al and nichrome at high temperatures. Therefore, the substrate made of glassy carbon can be processed without contaminating the area around the mask, such as during the mask manufacturing operation or in the exposure apparatus. These characteristics are suitable as a material for semiconductor processing for the purpose of cleanliness.

The schematic diagram shown in FIG. 2A shows a glassy carbon substrate 6 coated with a 0.1 μm thick Ti film as a protective film 7. The glassy carbon surface is a perfect absorber of vacuum ultraviolet rays, and since it is relatively soft, surface processing is easy.

Since the mask substrate serves as an absorber instead of forming the absorption film on the substrate by thin film processing as in the prior art, one step of thin film processing can be omitted.
It provides an efficient mask manufacturing process. Further, when absorbing energetic light, one of the reasons why glassy carbon can be used is that it does not require a super-smooth surface like a reflecting surface.

FIG. 3B is a schematic view of the process of patterning the ultraviolet reflecting portion on the glassy carbon substrate 6 according to FIG. Electron beam resist 8 is applied on the mask substrate and EB
By a drawing method, the line portion of the VUV reflector pattern was exposed and removed. On top of this, Pt, which is a vacuum ultraviolet ray reflector, is added.
After forming a film having a thickness of 0.1 μm by B vapor deposition, the resist film was peeled off to obtain a Pt pattern 9 on the glassy carbon. The vacuum ultraviolet ray reflective film may be a metal such as Au or a multilayer film such as Mo / Si.

[0026]

Since the present invention is configured as described above, it has the following effects.

In the reflective mask substrate, the supporting substrate and the thin film on the supporting substrate are made of sintered silicon carbide and silicon carbide thin film, respectively, and the thin film surface is mirror-polished to form a reflective mask substrate. Due to the inherent material properties of the laminated and silicon carbide, a thermally and chemically stable reflective mask substrate material can be provided.

By aligning the crystal orientation of the silicon carbide thin film constituting the reflective mask substrate in the (220) plane direction, the reflective mask is excellent in abradability suitable for mirror-polishing and has excellent exposure accuracy. A substrate material can be provided.

In the reflective mask substrate, since the surface of the substrate material constitutes an irradiation light absorbing portion and a structure forming a reflective mask by forming an irradiation light reflecting fine pattern thin film on the surface of the absorbing portion is used. It is possible to provide a reflective mask substrate that does not require the formation of a light absorbing thin film on the substrate surface.

A reflection type mask substrate in which the irradiation light absorbing portion is composed of the substrate itself is produced by using glassy carbon as the substrate material. Since the glassy carbon is a complete absorber of the vacuum ultraviolet ray which is the irradiation light, it is possible to provide the reflective mask substrate material having the irradiation light absorbing portion.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a manufacturing process of an X-ray reflective mask. (A) A sintered silicon carbide support substrate and a mask substrate on which a silicon carbide thin film is formed. (B) It is the figure which patterned and formed the X-ray absorption film on the mask substrate. (C) It is a figure which shows a part of cross section of the X-ray reflection type mask which finished the process.

FIG. 2 is a schematic cross-sectional view of a process of manufacturing a VUV reflective mask. (A) A vacuum ultraviolet reflective mask substrate including a classy carbon substrate and a protective film. (B) It is the figure which patterned and formed the reflective film on the vacuum ultraviolet reflective mask substrate.

FIG. 3 is an X-ray diffraction pattern diagram of the surface of an X-ray reflection type mask substrate in which the plane orientation of a vapor-deposited silicon carbide film is the (220) direction.

FIG. 4 is an X-ray diffraction pattern diagram of the surface of an X-ray reflective mask substrate including crystal components other than the plane orientation of the vapor-deposited silicon carbide film in the (220) direction.

FIG. 5 is a graph showing polishing accuracy corresponding to a peak intensity ratio (220) / (111).

[Explanation of symbols]

 1 Sintered Silicon Carbide Supporting Substrate 2 Evaporated Silicon Carbide Film 3 X-Ray Reflecting Mirror 4 Patterning Resist Film 5 Patterned X-ray Absorber 6 Classy Carbon Substrate 7 Protective Film 8 Patterning Resist Film 9 Patterned Vacuum UV reflection mirror

Continuation of the front page (51) Int.Cl. ⁶ Identification code Reference number within the agency FI Technical display location G03F 1/16 C04B 35/56 101X H01L 21/027 H01L 21/30 531M

Claims (3)

[Claims] 1. A reflective mask comprising a sintered silicon carbide plate as a support substrate, and a silicon carbide film (CVD-SiC) having a crystal orientation oriented in a (220) plane formed on the support substrate. substrate. 2. A substrate for a vacuum ultraviolet reflective mask, wherein the substrate is made of a vacuum ultraviolet absorbing material, and the substrate itself constitutes a vacuum ultraviolet absorbing portion and a reflective portion is formed on the surface of the substrate. . 3. The vacuum ultraviolet reflective mask substrate according to claim 2, wherein the substrate material is glassy carbon.