JPH0441487B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a soft X-ray plate making system, a mask structure used in soft X-ray lithography, and particularly a mask structure for use in soft X-ray lithography, in which an image pattern made of a soft X-ray absorbing material is The present invention relates to a mask structure embedded in a resin film transparent to visible light, which enables mask alignment (alignment and positioning of the mask with respect to a plate material) using visible light, and which has excellent reproducibility of submicron images.

[Conventional technology]

Because soft X-ray lithography inherently has high resolution, it is expected that it will be widely used in the manufacture of electronic circuit elements that require the reproduction of submicron images, and in fact, several proposals have been made. (For example, Special Publication No. 51-41551, Special Publication No. 51-42469)
However, in order to put soft X-ray lithography into practical use, there are two important problems that must be solved. One of them is how to perform mask alignment, and what kind of soft X-ray mask to use.
That's what it means.

Conventionally, such soft X-ray masks have been made by forming soft X-ray absorptive image patterns such as A _u and P _t on a soft X-ray transparent support film fixed to a support frame or support member. It has been used. Known materials for this support film include thin films of inorganic materials such as Si and Si ₃ N ₄ or polymer films such as polyethylene terephthalate (Mylar, a registered trademark of DuPont) and polyamide.

[Problem that the invention seeks to solve]

Among the above supporting films, the Si film has advantages such as thermal stability of the structure, easy availability of high-quality materials, and good processability, but it has poor transparency to visible light, so it is difficult to mask It is also necessary to use soft X-rays for alignment. However, the requirement for soft X-rays for mask alignment also makes the entire soft X-ray lithography system complex and the equipment expensive, which ultimately increases the ability to improve submicron images, which is a major advantage of soft X-ray lithography. This reduces the characteristics of being able to transfer with high precision and with a simple system. That is, the Si film has the disadvantage that mask alignment cannot be performed optically using simple visible light.

Furthermore, although the Si ₃ N ₄ film is transparent to visible light, it is extremely brittle and has the disadvantage that it is difficult to obtain a taut and strong film.

On the other hand, resin films made of Mylar film, polyamide film, etc. have the advantage of being relatively strong and transparent to visible light. However, the prior art has the disadvantage that it is difficult to secure the required thin film (for example, about 2 to 3 μm) to the support frame under tension.

In addition, in conventional masks, whether a thin film of an inorganic material as described above or a thin resin film is used as a support film, an image pattern of Au, Pt, etc. is formed after forming such a support film. Since these image patterns protrude above the support film, these image patterns are easily damaged by scratches, etc., and dust adheres around the image patterns, which reduces the reproducibility of submicron images.

[Means for solving problems]

The present invention solves the above problems, and consists of a taut resin film that is transparent to soft X-rays and visible light, a supporting member that supports the resin film, and a soft resin film that is embedded in one surface of the resin film. The resin film includes an image pattern made of a thin film of an X-ray absorbing material and an alignment pattern made of a visible light absorbing material, and a layer of an inorganic material transparent to soft X-rays is provided on the resin film except for a portion where the alignment pattern is present. A soft X-ray mask structure characterized by being laminated.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows the mask structure of the present invention, in which one surface of a taut resin film 1 transparent to soft X-rays and visible light is provided with an image pattern consisting of a thin film of a soft X-ray absorbing substance, i.e., a soft X-ray absorbing A pattern 2 and an alignment pattern 3 made of a visible light absorbing material are embedded, and the resin film 1 also has its soft X
A part of the surface where the line absorption pattern 2 and the like are embedded is fixed to supporting members 4 or 5 (in this example, 4 is silicon and 5 is silicon oxide), which is usually frame-shaped. Then, a thin film 6 made of a soft X-ray transparent material (silicon in this example) is attached to the surface of the resin film 1 on which the soft X-ray absorption pattern 2 and the alignment pattern 3 are provided, except for the portion where the alignment pattern 3 is present. There is.

The method for manufacturing the soft X-ray mask structure of the present invention and the materials of each part will be described below.

For example, the mask structure shown in FIG. 1 can be obtained as follows.

As shown in FIG. 2, a substrate 4 (in the specific example shown, a thermally oxidized silicon oxide film 5
Au, Pt,
Soft X-ray absorption pattern 2 such as Ta, Cr, Ni,
An alignment pattern 3 made of a visible light absorbing material such as Au, Pt or Ta is formed to a thickness of 0.3 to 1.0 .mu.m according to a conventional method such as an electron beam plate making system, dry etching or lift-off method. Next, as shown in FIG. 3, a resin film 1 is coated or heated to cover the soft X-ray absorption pattern 2, etc., preferably by coating and drying a solution of a thermoplastic resin or a precursor solution of a thermosetting resin. If necessary, a resin film having a thickness of, for example, 0.5 to 5.0 μm is uniformly formed by a method of curing on the substrate 4. Although the drawings show that the surface of the resin film is uneven, this is not necessarily necessary, and the surface may of course be smooth. The properties required of the resin used are as follows.

(a) Transparent to soft X-rays and visible light; (b) Heat resistance (for example, no deterioration or deformation of the resin film at temperatures up to 200°C) and chemical resistance (alkali resistance or acid resistance). Excellent (c) Able to form a taut thin film.

Particularly suitable resins having such properties include polyimide, polyethylene terephthalate, and the like.

Next, a part of the substrate 4 of the structure shown in FIG. 3 is left as a support member, and a soft X-ray transparent material, for example, about 0.5
The substrate 4 is coated along the resin film 1 as a thin film of ~5 μm.
The parts of the substrate 4 corresponding to the soft X-ray absorption pattern 2 and the alignment pattern 3 are left so as to leave a part of the
The structure shown in FIG. 1 is obtained by removing the . As the corrosive liquid, one that corrodes and dissolves the inorganic material of the substrate but does not corrode the soft X-ray absorption pattern, alignment pattern, and resin film is used. As such a corrosive liquid, for example, a solution of hydrofluoric acid, nitric acid, ethylenediamine, pyrocatechol/water mixture, caustic soda, caustic potash, etc. is heated as necessary. At this time, in order to effectively control the thickness of such an inorganic thin film (for example, silicon), it is necessary to It is certain that elements (e.g., boron, arsenic, gallium, antimony, aluminum, etc.) that have a covalent radius different from that of the constituent elements of the inorganic material (e.g., Si) on the substrate surface are diffused to the required thickness. Yes, it is preferable.
In this case, particularly preferred as the corrosive liquid are ethylenediamine, pyrocatechol, and water.

The thus obtained laminated film of the inorganic thin film 6 and the resin film 2 becomes transparent to soft X-rays. For example, a laminated film of a 1 μm thick polyamide film and a 2 μm thick silicon film can be exposed to soft X-rays (for example, AIKα).
It has a transmittance of approximately 65% for

In the mask structure shown in FIG. 1 obtained as described above, the part provided with the soft X-ray absorption pattern, which occupies the main part of the support film, is a laminated film.
It has the advantage of being structurally sound.

[Effect]

The resin film functions as a supporting film for the image pattern and the alignment pattern, and is transparent to visible light, so alignment is easy.
Further, the resin film has the function of protecting the image pattern and the alignment pattern, and preventing the absorbing pattern from being scratched or dusted.

Further, a layer of an inorganic material that is locally laminated on the resin film and is transparent to soft X-rays serves to reinforce the resin film.

〔Example〕

As shown in Fig. 2, high concentration boron was deposited on a 280 μm thick silicon wafer 2 with a 0.3 μm thick silicon oxide film 5 on the back surface by the volatilization diffusion method at 1100°C for 3 hours. Do a diffusion process,
On the boron diffusion surface, gold was deposited to a thickness of 0.35 μm using a conventional vacuum deposition method. Subsequently, patterning was performed using an ordinary electron beam plate making system and dry etching method to provide a soft X-ray absorption pattern 2 and an alignment pattern 3. Next, a polyimide resin precursor liquid is applied onto the silicon wafer by a spin coating method, covering the soft X-ray absorption pattern 2, etc.
A polyimide resin film with a thickness of 1 μm was obtained by holding the temperature at 300°C for 1 hour while gradually heating it to obtain a polyimide resin film with a thickness of 1 μm.
figure).

Next, only the portions corresponding to patterns 2 and 3 of the silicon oxide film are removed using a normal buffer HF solution to open a window, and the remaining silicon oxide film is used as a resist film to cover the silicon in the portions corresponding to patterns 2 and 3 on the back side. When corrosion was removed using a 1:5:2 mixture of ethylenediamine, pyrocatechol, and water at 110°C, the corrosion stopped at the boron diffusion layer, leaving a 2 μm thick silicon film 6 as shown in Figure 4. I got a structure.

Next, the portion of the silicon film 4 in the structure shown in FIG. 4 that was in contact with the alignment pattern 3 was removed using a etchant containing nitric acid:hydrofluoric acid=5:1. Alignment pattern 3 was transferred to the polyimide resin film.
As a result, a mask structure having excellent strength as shown in FIG. 1 in which the polyimide film portion having the absorption pattern 2 was reinforced with a silicon thin film was obtained.

The visible light (e-ray) transmittance of the polyamide resin film single layer portion of the obtained mask structure was approximately 85%,
In addition, the transmittance of soft X-rays (AIKα rays) in the laminated portion with the silicon film was approximately 65%.

The thus obtained mask structure was used in a soft X-ray plate making system as schematically shown in FIG. That is, as shown in FIG. 5, a mask structure is placed on a silicon element substrate 9 having a soft X-ray resist film 7 of polymethyl methacrylate and an alignment pattern 8, so that the surface having the resin film 1 faces the mask structure. The alignment pattern 8 of the element substrate and the alignment pattern 3 of the mask were optically aligned using visible light 10. After fixing the position via a spacer (not shown), a resist image was obtained by irradiating with soft X-rays (AIKα rays: 8.34A) 11.

〔Effect of the invention〕

As detailed above, the mask for soft X-ray lithography of the present invention enables mask alignment using visible light, has excellent strength, and allows the soft X-ray absorption pattern to be formed on an inorganic substrate in advance. , Sputter etching and other dry etching techniques enable highly accurate processing, with excellent positional and dimensional accuracy.Also, since the soft X-ray absorbing pattern does not protrude above the support film, there is no possibility of scratches or adhesion of dust. It has the advantage of having excellent image reproducibility with almost no fear of such problems.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the soft X-ray mask structure of the present invention, FIGS. The figure is an explanatory diagram of a soft X-ray plate making system using the soft X-ray mask structure of the present invention. 1... Resin film, 2... Soft X-ray absorption pattern, 3
...Alignment pattern, 4...Mask substrate or support member, 6...Inorganic thin film, 9...Element substrate, 10...Visible light, 11...Soft X-ray.

Claims (1)

[Claims] 1 An image pattern made of a thin film of soft X-ray absorbing material and an alignment pattern made of visible light absorbing material are embedded in one side of a tensile resin film with a thickness of 0.5 to 5.0 μm that is transparent to soft X-rays and visible light. an inorganic material layer transparent to soft X-rays is disposed on the surface side of the resin film in which the pattern is embedded, except for the portion where the alignment pattern is present, and the inorganic material layer is transparent to soft X-rays; The support member made of an inorganic substance integrated with the
A soft X-ray mask structure, characterized in that it protrudes on a side opposite to the resin layer.