JP2007210275A - Mold for imprint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which makes the transfer of a pattern in a high aspect ratio possible and prevents the destruction of the resin pattern in an imprint method and a method for manufacturing the mold. <P>SOLUTION: The mold for an imprint in which the uneven pattern is formed, and at least the corners of the projections of the pattern are rounded is provided. The material of the uneven pattern forming part of the mold is silicon, quartz, glass, diamond, a silicon compound, a metal, a metallic compound, or a ceramic substance. The rounding of the corners of the projections can be carried out by dry etching, wet etching, or annealing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an imprint method for manufacturing semiconductor devices, optical components such as optical waveguides and diffraction gratings, recording devices such as hard disks and DVDs, biochips such as DNA analysis, and displays such as diffusion plates and light guide plates. The present invention relates to the pattern forming method used.

  Up to now, patterns that require microfabrication, such as semiconductor device manufacturing processes, are transferred to a semiconductor substrate by reducing exposure with laser light using an original plate called a photomask on which a transfer pattern is formed. A so-called photolithography method is used.

  By the way, in this photolithography method, the size and shape of the pattern to be formed greatly depend on the wavelength of light to be exposed. For example, in recent manufacture of advanced semiconductor devices, the exposure wavelength is 150 nm or more, while the minimum line width is 65 nm or less, reaching the resolution limit due to the light diffraction phenomenon. In order to increase the resolution of resist, super-resolution technology such as proximity effect correction (OPC), phase shift mask, and modified illumination is used, but the mask pattern is faithfully transferred onto the semiconductor substrate. Has become difficult.

  Further, in the case of reduced projection exposure, since alignment accuracy is required not only in the horizontal direction of the substrate but also in the vertical direction, precise stage control (X, Y, Z, θ) of a photomask and a semiconductor substrate is required. Therefore, there has been a drawback that the cost of the apparatus becomes high.

  The problem of device cost that requires pattern blur due to the diffraction phenomenon of light and complicated mechanisms is not only in the manufacture of semiconductor devices, but also in the formation of various patterns such as displays, recording media, biochips, optical devices, and hot embossing. Has the same problem because it uses the photolithography method.

  Against this background, a technique called an imprint method (or nanoimprint method) that is very simple but suitable for mass production and capable of faithfully transferring a fine pattern has been proposed. Here, there is no strict distinction between the imprint method and the nanoimprint method, but the nanometer order method used for manufacturing semiconductor devices and diffraction gratings is called the nanoimprint method, and other micrometer order methods are used. In many cases, this method is called a printing method, but here it is called an imprinting method.

  In the imprint method, a mold called a mold in which a pattern corresponding to a negative / positive reversal image of a pattern to be finally transferred is formed on a resist, and in that state, the resist is cured by heat or ultraviolet rays. Pattern transfer is performed. A method based on thermal curing is called a thermal imprint method (see, for example, Non-Patent Document 1 and Non-Patent Document 2), and a method based on ultraviolet curing is called an optical imprint method. (For example, see Patent Document 1.)

  In these imprint methods, releasability between the mold and a resin pattern such as a resist formed on the substrate is extremely important. In the imprint, after pressing (FIG. 5 (a)), when the mold and the resin are separated, all the resin is peeled off together with the mold due to adhesion and friction between the mold and the resin (FIG. 5 (b)). In some cases, the resin peels off (FIG. 5C) or the resin partially deforms (FIG. 5D). This is because the surface energy of the mold or resin is large.

  In order to avoid such separation of the substrate and the resin, it is necessary to form a fluoropolymer having a small surface energy on the mold surface as a release agent to improve the releasability between the mold and the resin on the substrate. As a general release agent, a silane coupling agent is allowed to act on the OH group of the silicon oxide film on the mold surface, so that a film having a small surface energy (= strongly hydrophobic = a large contact angle) (this is a release layer) Is formed on the mold surface. This release layer can reduce the adhesion between the mold and the resin. (For example, see Non-Patent Document 2.)

  However, even if a release layer is formed on the mold surface as described above to reduce the adhesion with the resin, the adhesion does not become completely zero. Therefore, in a pattern having a high aspect ratio (pattern depth / pattern width is large), the contact area between the mold groove and the resin filled therein becomes large, and if the adhesive force exceeds the fracture stress of the resin, Pattern destruction occurs. For example, as shown in FIG. 6 (a), when imprinted with a mold having a pattern with a different aspect ratio, the higher the aspect ratio pattern as shown in FIG. The mold groove is left behind. This phenomenon is a phenomenon that can be seen in both optical imprinting and thermal imprinting, but becomes prominent when the aspect ratio is approximately 3 or more.

  In addition, as shown in FIG. 7, when the mold is released, the resin pattern is destroyed by stress concentration near the corner inside the resin pattern during the release (stress concentration point 400), from which the resin pattern is destroyed. What happens is known from numerical simulations and experimental results. (See Non-Patent Document 4.)

  Such a resin pattern destruction becomes a defect of the transfer pattern, and a transfer pattern faithful to the mold pattern cannot be obtained. Moreover, since the mold with the resin filled in the pattern groove becomes a defect in the mold pattern, there is a problem that it cannot be repeatedly used for imprinting thereafter.

JP 2000-194142 A Appl. Phys. Lett. , Vol. 67, 1995, P3314 "Thorough explanation of nanoimprint technology", Electric Journal, November 22, 2004, P20-38 Y. Hirai, et al. J. et al. Vac. Sci. Technol. , B 21 (6), Nov / Dec 2003

  The present invention has been made to solve the above-described problems, and provides a mold capable of transferring a pattern with a high aspect ratio and reducing resin pattern destruction in an imprint method, and a method for manufacturing the same. is there.

  In order to achieve the above object in the present invention, first, in claim 1, an imprint mold in which a concavo-convex pattern is formed, wherein at least the corners of the convex portions of the pattern are rounded. It is the mold for imprint characterized.

  Further, in claim 2, the concave-convex pattern forming portion material of the mold is any one of silicon, quartz, glass, diamond, silicon compound, metal, metal compound, and ceramic. This is an imprint mold.

  According to a third aspect of the present invention, in the imprint mold according to the first or second aspect, the round shape of the convex portion corner is performed by any one of dry etching, wet etching, and annealing.

  According to the present invention, in an imprint method, pattern transfer with a high aspect ratio is possible, and resin pattern destruction can be reduced. Therefore, it is possible to reduce transfer pattern defects and extend the life of the mold, and it can be expected that a good transfer pattern can be formed and the cost can be greatly reduced in the imprint method.

  The imprint mold of the present invention has a round shape as shown in FIG. By doing so, stress concentration in the resin can be relaxed at the time of mold release in imprinting, so that it is possible to reduce resin pattern destruction.

  A method for producing a mold used in this imprint method will be described with reference to FIG. First, in the case of a Si mold for thermal imprinting, a resist 2 is coated on a Si substrate as a mold forming substrate 1 (FIG. 2B), and a resist pattern is formed by EB lithography or photolithography technology ( FIG. 2 (c)). Next, dry etching of Si is performed using the patterned resist as an etching mask to form a Si pattern (FIG. 2D). Next, the resist 10 is peeled off by oxygen plasma ashing or substrate cleaning to form a mold 10 (FIG. 2E). Finally, dry etching is performed to make the corners of the convex portions of the pattern round, thereby completing the Si mold 100. (FIG. 2 (f)). In addition, wet etching or annealing can be used to obtain a round shape.

  A quartz mold made of quartz is used for optical imprinting, but a pattern can be formed by the same manufacturing method as that for the Si mold. However, since the material to be processed by dry etching is quartz, it is necessary to change the etching gas and etching conditions. Here, the reason why dry etching is used instead of wet etching for processing the mold material is that vertical processing of nano-level patterns is possible, and if not necessary, for example, sandblasting can be used.

  Examples of dry etching for forming a round shape include an ICP type dry etching apparatus, an RIE type dry etching apparatus, an ECR type dry etching apparatus, a microwave type dry etching apparatus, a parallel plate type dry etching apparatus, and a helicon type dry etching apparatus. The dry etching apparatus can be used.

  In addition, the wet etching solution for forming a round shape uses an alkaline solution such as potassium hydroxide or hydrofluoric acid if the mold material is silicon, hydrofluoric acid if it is quartz or SiO2, and nitric acid or nitric acid if it is nickel. If acetic acid or chromic acid is used, a mixed solution of nitric acid and hydrofluoric acid can be used for tantalum, and iron chloride can be used for copper.

  In addition, the annealing method for forming a round shape can be performed in accordance with the molding material and pattern size, and thermal annealing, far-infrared annealing, laser annealing, or the like in an oven or an electric furnace can be performed.

  Further, as the material for forming the concavo-convex pattern of the mold, a metal such as nickel, chromium, iron, aluminum or a compound of these metals, a silicon compound such as silicon, quartz, glass, diamond, SiC, ceramic, or the like can be used.

In addition, the mold of the present invention performs pattern transfer to a thermal imprint method in which a pattern is transferred to a thermoplastic resin, a light imprint method in which a pattern is transferred to a photocurable resin, or HSQ (Hydrogen Silses Quioxane) that does not require heat or light. All types of imprinting methods are available, including room temperature imprinting, sol-gel imprinting for pattern transfer to gel-like glass materials, and direct imprinting for direct pattern transfer to metal and glass. Applicable to
Examples according to the present invention will be described below.

  In the present invention, the imprint method and the molding material are not limited, but in this example, a Si mold for thermal imprinting was manufactured and thermal imprinting was performed. First, a mold manufacturing method is shown in FIG. A 4-inch silicon wafer was prepared as the mold forming substrate 1 (FIG. 2 (a)). This substrate is coated with an electron beam resist 2 (ZEP520 / manufactured by Nippon Zeon Co., Ltd.) to a thickness of 500 nm (FIG. 2B). Was formed (FIG. 2C). The conditions at this time were a drawing dose of 100 μC / cm 2 and a development time of 2 minutes.

  Next, a Si pattern having a depth of 1000 nm was formed by Si dry etching using an ICP dry etching apparatus (FIG. 2D). The Si etching conditions were C4F8 flow rate 30 sccm, O2 flow rate 30 sccm, Ar flow rate 50 sccm, pressure 2 Pa, ICP power 500 W, and RIE power 130 W. Finally, the resist was peeled off by O 2 plasma ashing (conditions: O 2 flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) to form a mold 10 (FIG. 2E). Subsequently, dry etching was performed to round the corners of the Si mold pattern (FIG. 2 (f)). As the dry etching apparatus, an ICP type dry etching apparatus was used, and the Si etching conditions at this time were CF4 flow rate 10 sccm, O2 flow rate 40 sccm, Ar flow rate 60 sccm, pressure 2.5 Pa, ICP power 500 W, and RIE power 5 W. When dry etching is performed under these conditions, the electric field concentrates on the corners of the Si pattern, so that the corners are etched intensively. As a result, the corners have a round shape as shown in FIG. Became.

  Next, the Si mold was manufactured by performing the wet etching process as the step of rounding the corners of the pattern of the Si mold manufactured in Example 1. Usually, when single crystal Si is etched with a potassium hydroxide solution, the plane orientation conforms to the crystal orientation plane, but isotropic etching can be performed using hydrofluoric acid. It is necessary to select a solution in accordance with the crystallinity and crystal orientation of the Si mold. In this embodiment, since single crystal Si is used as the mold material, etching is performed with hydrofluoric acid, and the corners are rounded as shown in FIG. In the wet etching of the present embodiment, the entire pattern is isotropically etched, so the pattern bottom of the Si mold also has a round shape.

  Next, the Si mold was manufactured by annealing the step of making the corners of the pattern of the Si mold manufactured in Example 1 round. Using an excimer laser annealing apparatus (excimer laser wavelength 308 nm / apparatus LA5060J / manufactured by Nippon Steel Co., Ltd.) as the annealing apparatus, a uniform line beam having a width of 0.4 mm and a length of 100 mm is scanned and irradiated. Only annealed. At this time, the irradiation energy density was 300 nJ / cm 2. As a result, the corner portion of the Si mold had a round shape as shown in FIG. When laser annealing is used, only the outermost surface of the Si mold is heated and melted and recrystallized while the entire substrate remains at a relatively low temperature, so that only the pattern corners have a round shape. On the other hand, when thermal annealing is performed in an oven or the like, the entire substrate is heated, so that the bottom of the pattern also has a round shape as shown in FIG.

  The round shape of the mold in the present invention may be selected from the round method of the corners of the patterns of Examples 1 to 3 and the annealing method according to the requirements of the transferred pattern shape after imprinting.

  In this embodiment, the Si mold has been described. However, for a mold made of SiO2, nickel, or other inorganic material, conditions such as dry etching conditions, gas types, types of wet etching solutions, etching time / temperature, annealing, etc. The corners of the mold pattern can be rounded by optimizing the method, temperature, irradiation energy, and the like.

<Comparison of imprint results>
Next, using the Si mold produced in Examples 1 to 3 above and the Si mold (comparative example) in which the corner of the mold of Example 1 was not rounded, the curvature radius of the corner was scanned with a scanning electron micrograph. Measured from Further, thermal imprinting was performed on these Si molds under the same conditions, and the aspect ratio (pattern depth / pattern opening width value) at which resin pattern destruction occurred was examined.

  Before imprinting, the surface of the Si mold was subjected to immersion treatment with a fluorine-based surface treatment agent EGC-1720 (manufactured by Sumitomo 3M Limited) as a release agent. A 4-inch silicon substrate was used as the substrate 300 to be imprinted, and a thermoplastic resin PMMA310 (polymethyl methacrylate) was coated on the silicon substrate to a thickness of 350 nm (FIG. 3B). The Si mold was heat-imprinted there (FIG. 3C), and then the mold was released (FIG. 3D). The thermal imprinting conditions at this time were a substrate and mold temperature of 110 ° C., a press pressure of 15 MPa, and a holding time of 1 minute.

  Table 1 shows the aspect ratio of the mold pattern used for imprinting and the transfer result of the resin pattern. Table 2 shows the radius of curvature of the corners of these molds and the aspect ratio at which resin pattern destruction occurs. From this result, the mold in which the corners of the mold were processed into round shapes by the processing methods of Examples 1 to 3, the radius of curvature of the corners was about 10 to 15 nm, and the aspect ratio up to about 5 was imprinted with resin. Although the pattern did not break, the mold of the comparative example that was not processed into the round shape had a corner radius of curvature of about 3 nm, and the resin pattern was broken by imprint even when the aspect ratio was about 3.

  From this, by making the corners of the mold pattern round, stress concentration in the resin can be relaxed at the time of mold release in imprinting, so that it is possible to reduce resin pattern destruction.

  A quartz mold was produced in the same manner as in Examples 1 to 3, a round shape treatment was performed at the corners of the pattern, and optical imprinting was performed. As in the case of thermal imprinting using a Si mold, the higher the curvature radius, the higher the aspect ratio. Ratio of the resin pattern could be transferred.

  As shown in FIG. 4A, the resin pattern imprinted using the mold of the present invention has a round shape formed in the resin pattern as well as the round shape of the mold pattern. If this round shape becomes a problem depending on the subsequent use or process of the transferred resin pattern, the round shape can be eliminated by O 2 RIE (oxygen reactive ion etching) (FIG. 4B).

  INDUSTRIAL APPLICABILITY The present invention can be used not only for manufacturing semiconductor devices but also for imprint molds used for forming various patterns such as displays, recording media, biochips, optical devices, and hot embossing.

It is sectional drawing explaining the mold for imprint of this invention. It is process sectional drawing which shows the manufacture process of the mold for imprint of this invention. It is process sectional drawing which shows the process of thermal imprint. It is sectional drawing which shows the resin cross section after the imprint using the mold of this invention, and the pattern shape after O2RIE process. It is sectional drawing which shows the pattern destruction at the time of mold release by the imprint method. It is sectional drawing which shows another pattern destruction at the time of mold release by the imprint method. It is sectional drawing explaining the pattern destruction at the time of mold release by the imprint method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mold formation base material 2 ... Resist 10 ... Mold 100, 200 ... Mold 300 which round pattern corner part ... Board | substrate 310 ... Resin 400 ... Stress concentration location

Claims (3)

  An imprint mold in which a concavo-convex pattern is formed, wherein the corners of at least convex portions of the pattern are rounded.   2. The mold for imprinting according to claim 1, wherein the material for forming the concavo-convex pattern of the mold is any one of silicon, quartz, glass, diamond, silicon compound, metal, metal compound, and ceramic.   3. The imprint mold according to claim 1, wherein the round shape of the convex corner is performed by any one of dry etching, wet etching, and annealing.

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