JPH1096808A - Formation of fine pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form metallic patterns including fine patterns with a printing technique of pressing a mold with good reproducibility by directly pressing and pressurizing this mold to a metallic layer. SOLUTION: An object 21 having patterned ruggedness including the fine patterns of <=1μm is brought into tight contact directly with a working object having the metallic layer on the surface and is pressurized thereto in order to form the patterned ruggedness including the fine patterns of <=1μm on the metal surface. Namely, the object 21 to be formed as the mold,i is first subjected to fine processing by electron beam lithography and dry etching, by which the patterned ruggedness is formed on the surface and the mold 22 is obtd. This mold is then brought into tight contact with the surface of the metal having the smoothed surface and is pressurized thereto, by which the relatively soft metallic is deformed and the ruggedness reverse from the ruggedness of the mold 22 is formed on the surface. The rugged patterns 24 of the metal are completed by removing the mold 22 thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a fine pattern which can be applied to manufacturing devices such as optical elements such as a diffraction grating and a polarizer.

[0002]

2. Description of the Related Art As a method of forming pattern-like irregularities on the surface of an object, molding using a mold, a pressing technique, a printing technique, and the like are widely used. However, the resolution of these technologies is several μm due to factors such as mold manufacturing accuracy and durability.
Lithography technology is used to form a so-called submicron region pattern of 1 μm or less required for optical elements and semiconductor elements. This involves irradiating a photosensitive material called a resist, which is a resist coated on the surface to be processed, with a short-wavelength exposure source such as ultraviolet rays, X-rays, or an electron beam in a pattern to form a latent image in the resist and developing it. Using this pattern-like resist as a mask,
This is for processing the surface to be processed. Although such a lithography process is generally used for manufacturing a semiconductor device such as a large-scale integrated circuit, the manufacturing process is complicated and requires a large capital investment. In addition, a high-resolution electron beam exposure apparatus is required to form nanometer-sized irregularities of 0.1 μm or less, and furthermore, if a high-density nanometer pattern is to be drawn on a large area using this apparatus, it takes a long time. Exposure is required.

[0003] As a means of overcoming such problems,
Recently, a method has been proposed in which a mold having nanometer-sized unevenness is pressed against a resist on a surface to be processed, and the unevenness is transferred onto the resist (Stephen Y. Chou, Pete).
r R. Krauss and Preston J. Renstrom; "Imprint
of sub 25nm vias and trenches in polymers ”, A
pplied Physics Letters, Vol. 67 (21), 20
November 1995 pp 3114-3116).

The above technique will be described with reference to FIGS. 3 and 4. Note that FIGS. 3 and 4 show steps in succession, and continue from (1-4) in FIG. 3 to (1-5) in FIG. First, a silicon substrate 11 serving as a mold substrate is thermally oxidized to form a silicon oxide layer 12 on the surface.
1). A pattern of a minimum of 25 nm is formed on this substrate by high-resolution electron beam lithography, the silicon oxide 13 having a depth of 250 nm is etched, and the resist is removed to complete a mold (1-2). Next, a silicon substrate 14 was similarly used as a substrate to be processed, and a PMM having a thickness of 55 nm was formed thereon.
A (polymethyl methacrylate) resist 15 is spin-coated, and a mold (11 + 13) is adhered thereon (1-3). And the glass transition temperature of PMMA of 105
After raising the temperature to 200 ° C, which is higher than
(1-4). Thereafter, the mold is cooled down to room temperature, and the mold is carefully removed, so that irregularities are formed on the PMMA 16 (1-5). To perform the subsequent processing, in the case of a metal, PMMA remaining in the concave portion is removed by oxygen plasma (1-6). Next, a metal 18 is vapor-deposited thereon (1-7), and PMMA remaining in the solvent is removed together with the metal thereon to obtain a metal pattern 19 (1-8).

In this method, if a mold is formed by using high-resolution electron beam lithography, then (1-
It has been reported that there is an advantage that a metal pattern of a nanometer size can be obtained without repeating electron beam lithography by repeating the steps 3) to (1-8). However, in this method, even if the step of electron beam lithography is omitted, the steps are still complicated, and considerable time is required for temperature rise and cooling. Also, the most problematic point is that silicon oxide having a fine uneven structure is easily broken at the time of pressurization or removal, and it is difficult to use repeatedly.

[0006]

SUMMARY OF THE INVENTION In view of the above prior art, an object of the present invention is to provide a technique capable of easily and reproducibly forming a metal pattern of 1 μm or less by a printing technique of pressing a mold. I have.

[0007]

In the method for forming a fine pattern according to the first aspect of the present invention, in order to form a pattern-like unevenness including a fine pattern of 1 μm or less on a metal surface by a simple process, a mold is formed. It is characterized by directly pressing against the metal layer and pressing.

Furthermore, in the method for forming a fine pattern according to the second aspect of the present invention, the mold is excellent in both hardness and strength so that even if the mold is pressed directly against the metal layer, the fine irregularities formed in the mold are not destroyed. It is characterized by being formed from a diamond plate or a silicon carbide plate.

In the fine pattern forming method according to the third aspect of the present invention, at least the surface of the mold is formed of diamond, diamond-like carbon, or silicon carbide in order to cope with various application fields. It is characterized by.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in order to form a pattern-like unevenness including a fine pattern of 1 μm or less on a metal surface, an object having a pattern-like unevenness including a fine pattern of 1 μm or less is formed on a metal surface. It is characterized in that it is brought into direct contact with a workpiece having a layer on the surface and is pressed. This method will be described with reference to FIG.

FIG. 1 is a sectional view showing the steps of the first embodiment of the present invention. First, the object 21 serving as a mold is subjected to fine processing by electron beam lithography and dry etching,
A pattern 22 is formed on the surface to form a mold 22 (2-
1). Next, this is brought into close contact with the surface of the metal 23 whose surface has been smoothed (2-2), and when pressurized, the relatively soft metal is deformed and irregularities opposite to the mold are formed on the surface (2).
-3). Thereafter, the metal pattern 24 is completed by removing the mold (2-4).

In this method, the process can be greatly simplified as compared with a conventional method in which a mold is pressed against a resist and a metal pattern is formed based on the unevenness of the resist. On this occasion,
The problem is that the applied pressure needs to be higher than when transferring the mold to the softened polymer.
Even in relatively soft metals such as aluminum,
A high pressure of about 30 MPa or more is required. This is more than twice as large as that of the polymer, and when the unevenness is made of silicon or silicon oxide, the minute unevenness is easily broken or the mold substrate itself is easily damaged. On the other hand, it has been found that when a mold having fine irregularities is made of metal, the mold is extremely resistant to destruction, but has a problem that the mold is easily deformed by pressure.

Based on the above findings, the inventors of the present invention have proposed that the mold be made of a diamond plate or a silicon carbide plate having excellent strength and hardness, good surface smoothness, and easy formation of fine irregularities. The inventors have found that all of the above problems can be overcome, and have completed the present invention. In the case of a diamond substrate, no damage or destruction was observed even at a pressure of 60 MPa for the fine irregularities and the substrate, and even for a silicon carbide plate,
It was found that the pressure of 50 MPa is durable, and that a fine unevenness of a mold can be printed on an object having a metal layer on the surface.

It is not necessary that the object having fine pattern irregularities is a diamond plate or a silicon carbide plate itself. If the surface of the object having appropriate strength is diamond or diamond-like carbon or silicon carbide, And transfer to a metal layer is possible. That is, a diamond film, a diamond-like carbon film, and a silicon carbide film are formed on the surface of an object such as stainless steel by means such as deposition and attachment, and are finely processed to form a mold. Furthermore, a method of attaching diamond, diamond-like carbon, or silicon carbide having irregularities is also possible.

In order to form fine irregularities of 1 μm or less on a smooth surface of a mold object, photolithography, ultraviolet two-beam interferometry, electron beam lithography, X-ray lithography, ion beam lithography, etc. are used to form a pattern or a pattern. They can be used properly depending on the situation. In the present invention, electron beam lithography which can handle most patterns is used, but it is needless to say that the present invention is not limited to this means.

[0016] In addition, the process of imparting irregularities with high resolution to the surface of diamond or diamond-like carbon is performed by using a silicon-containing resist, silicon oxide, silicon nitride or metal having excellent oxygen plasma resistance as a mask to remove oxygen as an etching gas. Can be easily performed by reactive ion etching. On the other hand, the silicon carbide surface can be processed by dry etching using a resist or metal as a mask and using a fluorocarbon-based etching gas.

On the other hand, as an object having a metal layer on the surface,
A substrate configuration suitable for the application purpose is used, such as a metal itself such as a mirror-polished metal plate, or a metal thin film deposited on a suitable substrate having a mirror surface by vapor deposition, sputtering, electroplating, or the like. However, at a high pressure of several tens MPa,
It is necessary to ensure the strength of the substrate such that it does not break even when the mold is pressed. As the type of metal to be processed, soft aluminum, gold, silver, lead, tin, and brass are suitable from the viewpoint that the pressing pressure can be reduced. As the pressurizing means, a normal press device such as a hydraulic press can be used.

In the case of a diffraction grating having only a metal surface having only irregularities, such as a reflection type diffraction grating, only the step of pressing the mold in close contact is performed. Those that need to be separated in a shape can be patterned by a process as shown in FIG.

FIG. 2 is a sectional view showing the steps of the second embodiment of the present invention. In FIG. 2, first, unevenness corresponding to a wiring pattern or a pattern on a grid used for a polarizer is formed on the surface of a substrate 31 of diamond or silicon carbide by electron beam lithography and reactive ion etching (3-1). This mold 32 is brought into close contact with a substrate 33 on which gold, aluminum or silver 34 having a thickness of several hundreds to several tens nm is deposited (3-2), and when a pressure of about 40 to 50 MPa is applied using a press device, the metal becomes Asperities 35 are formed on the thin film (3-3). After removing the mold (3-4), the metal corresponding to the thickness remaining in the concave portion is removed by ion beam sputtering using argon gas.
This is a metal pattern 36 (3-5).

As described above, in the fine pattern forming method of the present invention, compared with the steps shown in FIGS. 3 and 4 in which a conventional resist is printed and processed into a metal pattern, the steps are greatly reduced. There is an advantage that can be simplified. The fine metal pattern produced by the present invention can be used for optical elements such as diffraction gratings and polarizers, and fine metal wiring for semiconductor devices. Further, although the mold of the structure of the present invention cannot of course greatly simplify the process, it is also applicable to a technique of printing a mold on a resist in the process shown in FIGS. It is clear that the durability against repeated use can be greatly improved.

[0021]

Next, the present invention will be described more specifically with reference to examples. Example 1 An electron beam negative resist SNR-M5 (manufactured by Tosoh Corporation) was spin-coated on a diamond substrate at a thickness of 0.1 μm, and a diffraction grating pattern having a line width of 50 nm and a line width of 50 nm was formed by electron beam exposure in an area of 50 mm. After developing with xylene, the diamond was etched to a depth of 200 nm by reactive ion etching using oxygen gas. Then, the residual of the SNR resist was removed using buffered hydrofluoric acid to obtain a mold for a diffraction grating.

On the other hand, an aluminum plate having a purity of 99.99% was electropolished in a 1: 4 mixed bath of perchloric acid and ethanol to obtain an aluminum plate having a mirror surface. The mold made of the diamond plate was brought into close contact with this, and after applying a pressure of 50 MPa using a hydraulic press machine, the mold was removed. As a result, a 160 nm deep depression was formed on the aluminum plate surface with a period of 200 nm. It was formed in a lattice.
When the above printing step was repeated using this same mold, the fine irregularities of the mold did not change even after several tens of printing steps.

Example 2 A positive electron beam resist, ZEP-520, was spin-coated on a silicon carbide substrate at a thickness of 0.1 μm, and an electron beam exposure apparatus was used for a metal-semiconductor-metal (MSM) photodetector. The comb-shaped electrode pattern was exposed at a period of 0.1 μm at a width of 40 nm and developed. On this, chromium having a thickness of 50 nm was vapor-deposited by an electron beam vapor deposition apparatus, immersed in diglyme as a solvent, and ultrasonic waves were applied to remove chromium on the resist together with the resist. A periodic lattice-like chromium pattern is formed. Using this chromium as a mask, the silicon carbide substrate was etched to a depth of 160 nm by reactive dry etching using CF ₄ gas. Thereafter, chromium is removed by oxygen plasma, and the width is about 50 nm and the period is 0.1.
A mold having a lattice pattern of μm and a height of 160 nm was prepared.

On the other hand, gold is deposited on a silicon substrate having a thickness of 2 mm by an electron beam evaporation apparatus having a thickness of 100 nm.
The mold of the silicon carbide substrate is brought into close contact, and a pressure of 40 MPa is applied by a hydraulic press. After removing the mold,
The thickness of the gold was 45 nm in the concave portion and 195 nm in the convex portion, and a step of 150 nm was generated. Next, the gold of 55 nm in thickness was removed by etching with an argon ion milling device to completely remove the gold in the concave portion, thereby obtaining a gold comb-shaped electrode pattern having a width of about 50 nm, a period of 100 nm, and a height of 90 nm. Thereafter, a pad electrode and the like were formed by a normal photolithography process to complete the MSM photodetector. Even in this printing process, even if the printing process was repeatedly used, no disconnection or the like of the electrode pattern was observed, and it was found that there was sufficient resistance.

Example 3 A diamond-like carbon thin film having a thickness of 0.5 μm was deposited on a silicon carbide substrate having a thickness of 400 μm by using an ECR type CVD apparatus using a mixed gas of 80% methane and 20% hydrogen. On top of this, a positive type electron beam resist ZEP-520 is coated with a thickness of 0.1 μm.
m spin-coated and 0.1 μm
A grid pattern having a cycle of 50 nm width was exposed to an area of 20 mm square and developed. On top of this, 40
The titanium on the resist is removed together with the resist by applying ultrasonic waves, and a titanium-like titanium pattern having a width of 60 nm and a period of 0.1 μm is formed. Form. Using this titanium as a mask, the silicon carbide substrate was etched to a depth of 200 nm by reactive dry etching using oxygen gas. Thereafter, the chromium is removed by oxygen plasma, and the
A silicon carbide substrate having a lattice pattern having an nm width, a period of 0.1 μm, and a height of 200 nm was manufactured. This substrate was attached to a stainless steel cylinder having a diameter of 50 mm and a length of 50 mm using an adhesive, and this was used as a mold.

On the other hand, silver is deposited on a 3 mm-thick polycarbonate substrate by an electron beam evaporation apparatus having a thickness of 120 nm, and a stainless steel + silicon carbide mold is brought into close contact therewith, and a pressure of 40 MPa is applied by a hydraulic press. afterwards,
When the mold was removed, the silver thickness was 40 nm in the concave portions and 200 nm in the convex portions, and a step of 160 nm was generated. Next, the silver having a thickness of 40 nm was removed by etching with an argon ion milling apparatus to obtain a width of about 55 nm and a period of 100 nm.
m, a silver periodic pattern having a height of 100 nm was obtained. When the polarization transmission characteristics of this sample were measured, the transmittance was 95% in the direction perpendicular to the lattice pattern, and was 3 in the direction parallel to the lattice pattern.
It turned out to be 0%, and it turned out that it acts as a polarizer. Even if this printing process was repeated 100 times or more, the mold was not damaged or deformed.

[0027]

As described above, according to the present invention,
If a mold with ultra-fine irregularities is made using a high-resolution device such as electron beam lithography, then the ultra-fine metal pattern in the sub-micron to nanometer range can be easily and repeatedly produced by a printing process. The effect of increasing the economical efficiency in the production of fine electrode patterns for semiconductor devices such as optical components such as gratings and polarizers and photodetectors is very large.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a step of forming a fine metal uneven pattern according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a step of forming a fine metal uneven pattern according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a part of the steps of a conventional fine pattern forming method.

FIG. 4 is a sectional view showing another part of the process of the conventional fine pattern forming method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Silicon substrate 12 ... Thermal silicon oxide 13 ... Thermal silicon oxide with unevenness 14 ... Silicon substrate 15 ... PMMA resist 16 ... PMMA resist on which unevenness is printed 17 ... PMMA resist which is patterned 18 ... Evaporated metal 19 ... Metal pattern 21: Object to be a mold 22: Mold with irregularities 23: Metal substrate 24: Metal substrate with irregularities printed 31: Diamond or silicon carbide substrate to be a mold 32 ... Mold with irregularities 33: Substrate 34: metal layer 35: metal layer with unevenness printed 36: metal pattern

 ──────────────────────────────────────────────────の Continuing on the front page (72) Akira Ozawa, 1-3-1 Gotenyama, Musashino City, Tokyo NTT Advanced Technology Corporation

Claims (3)

[Claims] 1. An object made of metal having a surface of 1 μm
A fine pattern forming method, characterized in that the object having pattern-shaped irregularities including the following fine pattern is brought into close contact with and pressurized to form the pattern-shaped irregularities on the metal surface. 2. The method for forming a fine pattern according to claim 1, wherein the object having fine pattern-like irregularities is a diamond plate or a silicon carbide plate. 3. The method for forming a fine pattern according to claim 1, wherein at least the surface of the object having fine pattern irregularities is diamond, diamond-like carbon, or silicon carbide.