JP2721530B2 - X-ray mask structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus, particularly to an X-ray mask structure used in an exposure apparatus for performing X-ray exposure.

(Prior Art) In recent years, with the increase in density and speed of semiconductor integrated circuits,
The pattern line width of integrated circuits tends to be reduced to 70% in about three years.

With the further integration of large-capacity memory elements (for example, 4MDRAM), devices with a 16-Mbit capacity and the like have been designed with a 0.5 μm rule. For this reason, even higher performance is required for printing equipment, and the minimum transferable line width is 0.5μ.
The high performance of less than m is beginning to be required. Therefore, a stepper using light in the X-ray region (7 to 14 °) as an exposure light source wavelength is being developed.

As shown in FIG. 1A, the mask structure used in these X-ray exposure apparatuses includes an X-ray transmitting film 2 made of an X-ray transmitting material and a holding frame 3 for holding the film in tension. On the X-ray transmission film 2, X-ray absorbers 1 arranged with a desired geometric arrangement such as alignment marks are formed.

The method of forming the X-ray transmission film 2 is roughly classified depending on whether the material used is an organic thin film or an inorganic thin film. For the former, a material that has high X-ray transmittance and is transparent to visible light is selected, and films such as polyimide, polyamide, and mylar are preferably used because of their Young's modulus, coefficient of thermal expansion, surface roughness, etc. Can be These X-ray permeable films 2 are held in tension on a holding frame 3 by an adhesive 4, and these X-ray permeable films 2 are fixed in a form having a sufficient flatness.

On the other hand, when an organic material is used for the X-ray transmission film 2,
As shown in FIG. 2, a film 2 of a silicon compound of about 2 μm, in particular, silicon nitride, silicon nitride, etc. is formed on a silicon wafer 6 by a chemical vapor deposition method or the like so as to have a slight tensile stress. Next, the silicon wafer 6 on which the film 2 is deposited is removed from the back surface only by etching in a necessary region (a region for transmitting X-rays), and the mask blank with the inorganic thin film 2 held in tension on the silicon wafer 6 is removed. Is obtained. However, since the substrate 6 is thin in this state,
Since the strength is so small that it is inconvenient for handling and practical use, it is usual to use an annular reinforcing body (holding frame) 3 bonded with an adhesive 4.

In any of the above cases, it is desirable that the holding frame or the reinforcing body be sufficiently strong, thermally stable and light. Conventionally, quartz glass, borosilicate glass (Pyrex), stainless steel, and the like have been used, but recently, ceramics sintered bodies have come to be used to satisfy the above conditions well.

In particular, a sintered body composed of aluminum nitride and boron nitride (AI
N-BN) or a sintered body composed of silicon nitride and boron nitride (Si ₃ N ₄
Ceramics such as -BN) are preferred because they are easy to cut.

(Problems to be Solved by the Invention) However, in the ceramic materials as described above, fine powders such as aluminum nitride, silicon nitride, and boron nitride, which are raw materials before sintering, remain in a fine state after sintering. Also, even after cutting or polishing, the fine powder falls off or peels off, becomes the most unfavorable source of dust in the semiconductor process, and does not necessarily take advantage of its characteristic superiority.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to generate dust even when a sintered body of ceramics such as the above-mentioned aluminum nitride, boron nitride, silicon nitride, silicon carbide, etc. is used as a holding frame or a reinforcing body. An object of the present invention is to provide an excellent X-ray mask structure free from the problem described above.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention provides an X-ray mask structure comprising an X-ray absorber having a desired pattern, an X-ray transmitting film for holding the absorber, and a holding frame for holding the X-ray transmitting film. Is an X-ray mask structure characterized by having a ceramics sintered body whose surface has been subjected to a dust-prevention treatment by coating, impregnating, or coating and impregnating with an organic or inorganic binder.

(Operation) According to the present invention, an X-ray mask structure excellent in dust generation prevention properties can be provided by performing a dust generation prevention treatment on a holding frame or a reinforcing body made of ceramics.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

X used in the construction of the X-ray mask structure of the present invention
The light transmitting film 2 is made of an inorganic substance such as a simple substance such as beryllium (Be), titanium (Ti), silicon (Si), or boron (B) or a compound thereof, an organic substance such as polyimide, polyamide, polyester, or parylene, or a composite thereof. Any film conventionally used as an X-ray permeable film, such as a film, can be used in the present invention, and these X-ray permeable films are made of inorganic film in order to maximize the amount of X-ray transmission. 0.5 in case
The thickness is preferably from 5 to 5 μm, and in the case of an organic substance, from 1 to 20 μm.

Any of these methods of forming the X-ray permeable film itself may be a conventionally known method. For example, when the X-ray permeable film 2 is an organic substance such as polyimide, an organic film may be used. It is formed in such a suitable holding frame 3 by a method of fixing it with an adhesive 4 using an adhesive 4 (see FIG. 1). If the X-ray transmitting film 2 is made of an inorganic material, the strength of the membrane 2 is insufficient. For example, the X-ray transmitting film 2 is formed on a silicon wafer (holding frame) 6, and then an etching protective film (not shown) (polyimide, silicon nitride film or the like) is provided on the back surface thereof, and etched with a 30% aqueous solution of potassium hydroxide. By doing so, the inorganic membrane 2 supported on the wafer 6 can be formed. In this case, since the strength of the silicon wafer 6 is insufficient, it is common to provide a reinforcing member 3 of metal, ceramics, glass or the like (see FIG. 2). The X-ray absorber 1 formed on the X-ray transmitting film 2 is generally a thin film of a substance having a high density, for example, gold, platinum, tungsten, tantalum, copper, nickel or a compound containing them (for example, 0.5 to 1 μm). X-ray absorbers used in conventional X-ray mask structures (such as thickness of the order) can be used in the present invention, and are not particularly limited.

Such an X-ray absorber 1 is, for example,
Provide a plating electrode layer on it, and pattern a single-layer or multilayer resist on it by electron beam drawing,
For example, gold is plated to form the entire pattern of the X-ray absorber. It is also possible to form an X-ray absorber by forming W or Ta on the X-ray transmission film, forming a single-layer or multilayer resist by electron beam lithography, and then plasma-etching the W or Ta layer. I can do it. Further, the X-ray absorber may be formed before back etching of the silicon wafer.

The bonding between the X-ray permeable film and the holding frame or the bonding between the silicon wafer and the reinforcing member is performed by an adhesive having a small shrinkage upon curing, for example,
It is preferable to use an adhesive such as a thermosetting type, a photocuring type, or a solvent type such as an epoxy type, a rubber type, an acrylic type, and a polyimide type.

According to the present invention, in the configuration of the X-ray mask structure as described above, a holding frame (including a reinforcing member) to be used is formed by molding and sintering from ceramics, and the molded body is dusted after cutting or polishing. It is characterized by performing prevention processing.

The ceramic used as a holding frame or a reinforcing body of the X-ray mask structure of the present invention is, for example, alumina (Al
₂ O ₃ ), zirconia (ZrO ₂ ), cordierite (2MgO · 2
Al ₂ O ₃ .5SiO ₂ ), Sialon (Si.Al.ON), silicon carbide (SiC), aluminum nitride (AlN), silicon nitride (Si
₃ N _4), other _{SiC-ZrB 2, Al 2 O} 3 -TiC and the like.
In addition, as a ceramic sintered body that can be cut, AlN
-BN type, Si ₃ N ₄ BN type, silicon carbide type (SiC) and the like.

Among the above ceramics, those particularly preferred for the present invention are ceramics having a Young's modulus of 100 GPa or more. More preferably, a ceramic having a linear expansion coefficient of 1 × 10 ⁻⁵ K ⁻¹ or less is used to prevent distortion due to heat generated by X-ray irradiation.

In the present invention, the values of the Young's modulus and the coefficient of linear expansion of the preferable ceramic material are exemplified below.

The present invention is not limited to the ceramics exemplified above, and any ceramics having similar physical properties can be used in the present invention.

The above ceramics can be formed and sintered into a predetermined shape according to a conventional method to obtain a desired shape. In addition, ceramics sintered bodies that can be cut (for example, AIN-BN, S
According to i ₃ N ₄ —BN, SiC), it can be formed and fired into a predetermined shape according to a conventional method, and then can have desired dimensional accuracy by cutting or the like.

The shape of the holding frame and the reinforcing member used in the present invention may be the same as conventionally known shapes, such as a ring shape, and the surface or the inside of the mask holding frame or the reinforcing member may be provided to provide magnetic chucking properties. A magnetic material can be fixed to the surface.

Dust prevention processing after cutting or polishing processing will be described.

A preferred method of the dust prevention treatment is a method of applying, impregnating, or applying and impregnating the organic or inorganic binder 5, and for example, as shown schematically in FIG. A method of applying, impregnating, or applying and impregnating an organic binder or an inorganic binder to the surface of the ceramic sintered body 3 thus obtained. When the binder has a relatively low viscosity or a relatively large amount, the binder 5 impregnates a part of the void 7 inside the ceramic sintered body. On the other hand, when the binder has a relatively high viscosity or a relatively small amount of coating, the binder is not impregnated to the inside but remains on the surface to form the coating 5. It is preferable that the binder forms a continuous film on the surface of the sintered body (FIGS. 1B and 1C), but this is not essential, and for example, as shown in FIG. As long as the coating 5 is discontinuous.

As the organic binder to be used, for example, an organic solvent solution or a water dispersion of an organic resin such as a polyimide resin, an acrylic resin, an epoxy resin, a polyester resin, a urea resin, a melamine resin, and an alkyd resin can be used. For example, colloidal silica can be used.

The application, impregnation, or the amount of application and impregnation of the binder may be at least the state shown in FIG. 1d. For example, the object of the present invention is sufficiently achieved at a rate of 0.1 to 50 g / m ^{2 based} on solid content. I can do it.

In addition, another preferred dust-preventing treatment of the present invention includes Ti
Preference is given to coating with ceramics such as N, SiC, Si ₃ N ₄ , Al ₂ O ₃ , TiC, etc., or dust prevention treatment by metal plating such as nickel kanigen plating. With these ceramic coatings and metal plating, low temperature coating is possible and there is no pinhole, it is hard and has excellent wear resistance,
For example, a sufficient effect can be obtained with the thin film 5 having a thickness of about 0.1 to 5 μm.

(Examples) Next, the present invention will be described more specifically with reference to examples.

Embodiment 1 FIG. 1 is a diagram schematically showing a cross section (a) of an X-ray mask structure of this embodiment and enlarged views (b to d) of a holding frame 3 thereof.

In the figure, an X-ray absorber 1 is formed on one surface of an X-ray transmission film 2 in a desired pattern. Absorber 1 is about 0.7mm
Of gold. The X-ray transmission film 2 is a two-layer film of a polyimide thin film having a thickness of 12 μm and a nickel thin film having a thickness of 0.03 μm. The peripheral portion of the X-ray transmission film 2 is held on the upper end surface of the annular holding frame 3 and is bonded with the adhesive material 4 only on the inclined surface of the holding frame in order to maintain flatness. The holding frame 3 is formed of a machinable ceramic (for example, AlN-BN), and the surface thereof is impregnated with an epoxy resin at a rate of about 5 g / m ² (solid content) to form a dust prevention treatment layer 5. I have. The holding frame 3 has an annular shape with an inner diameter of 50 mm, an outer diameter of 100 mm, and a thickness of 6 mm.

Example 2 An X-ray mask structure of the present invention was obtained in the same manner as in Example 1 except that a polyimide resin was used instead of the epoxy resin in Example 1.

Example 3 An X-ray mask structure of the present invention was obtained in the same manner as in Example 1 except that a polyester resin was used instead of the epoxy resin in Example 1.

Embodiment 4 FIG. 2 is a diagram schematically showing a cross section of an X-ray mask structure according to another embodiment of the present invention.

Back etched silicon wafer (holding frame)
An X-ray transmitting film 2 made of Si ₃ N ₄ and having a thickness of 2 μm is formed on 6, and an X-ray absorber pattern 1 made of W and having a thickness of 0.8 μm is formed thereon. Reinforcement 3
To an epoxy-based adhesive (Alpha Giken Co., model number 3500) 4
And fixed.

The reinforcing body 3 is made of machinable ceramics (for example, Al
N-BN), and the surface of the reinforcing body is coated with TiN5 to a thickness of 3 μm by ion plating after depositing chromium as a base material to a thickness of 0.1 μm.

When the X-ray mask structure of the present invention was compared with the same mask structure except that the dust prevention treatment was not performed, the X-ray mask structure according to the present invention was significantly reduced in dust generation.

(Effects of the Invention) As described above, by firing the holding frame or the reinforcing member made of ceramics and then performing the dust prevention treatment, the effect of providing an X-ray mask structure having excellent dust prevention properties is provided. can get.

[Brief description of the drawings]

1 and 2 are views schematically showing a cross section of the X-ray mask structure of the present invention. 1: X-ray absorber 2: X-ray transmission film 3: Holding frame (reinforcement) 4: Adhesive 5: Dust prevention treatment layer 6: Silicon wafer 7: Void

Claims (2)

(57) [Claims] 1. An X-ray mask structure comprising an X-ray absorber having a desired pattern, an X-ray transmitting film for holding the absorber, and a holding frame for holding the X-ray transmitting film, wherein the holding frame is An X-ray mask structure comprising: a ceramic sintered body having a surface subjected to a dust-prevention treatment by applying, impregnating, or applying and impregnating an organic or inorganic binder. 2. The X according to claim 1, wherein the holding frame also includes a reinforcing body.
Line mask structure.