JP4952009B2 - Method for producing imprint mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein the pattern size of a fine pattern changes in a boundary region of the fine pattern and deviates from a designed size, when forming the fine pattern of a nano-imprinting mold, without having to conduct calculations. <P>SOLUTION: When forming an objective fine pattern on a resist film using electron beam lithography, an auxiliary pattern, with due consideration to a pattern density, is formed simultaneously in the periphery of the objective fine pattern to suppress the change in the size of the fine pattern near the boundary thereof. In addition, after transferring the resist pattern onto a protective film by etching, a resist film is reapplied and a pattern is formed, thereby transferring only the objective fine pattern onto a substrate, while preventing the transfer of the auxiliary pattern. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for forming a fine pattern with good dimensional accuracy in a mold used for nanoimprinting, which is one of fine pattern transfer techniques.

  S. Y. The nanoimprint method proposed by Chou et al. Mechanically forms a pattern by pressing an original mold (also called a mold, template, etc.) on which a pattern such as fine grooves and holes is formed, against the material to be transferred. This is a transfer method (for example, see Non-Patent Document 1).

  Currently, photolithography using a photomask, which is commonly used as a method for transferring submicron-level fine patterns, projects a mask pattern, which is an original, onto a photoresist on a transfer substrate with light, and is irradiated. The pattern is transferred by causing the resist to react with the light. On the other hand, in nanoimprinting, a pattern is transferred by pressing a mold as an original plate against a resin or the like on a substrate to be transferred and mechanically deforming it. That is, photolithography is an indirect and two-dimensional pattern transfer technique, whereas nanoimprint is a direct and three-dimensional pattern transfer technique.

  In this way, the principle of nanoimprint is relatively simple, but in recent years, it has been demonstrated that ultra-fine patterns of several tens to several nanometers can be transferred, and the next generation that requires patterns of 50 nm or less. It is attracting attention as one of the candidates for lithography technology. In addition, taking advantage of the characteristics of the three-dimensional transfer method, a technology for transferring a pattern with a high aspect structure and a complicated shape such as a curved surface or a step shape has been put into practical use.

  Since nanoimprinting has very high transfer fidelity, if there is a defect such as a dimensional deviation or a defect in the mold pattern, it is transferred as it is. This fact means that the size and shape of the mold are very important, and the tolerance for defects becomes very narrow.

  Furthermore, in the nanoimprint that is direct transfer, it is also a great feature that a very fine pattern having the same dimensions as the finally required fine pattern is required on the mold. In photolithography, which is an indirect transfer technique, exposure is generally performed by reducing the pattern of a photomask to about a quarter by using a reduction optical system. For this reason, since the pattern of the photomask is four times larger, the fineness of the mask pattern is relatively low. As a result, the nanoimprint mold has a relatively high difficulty in pattern production.

  As described above, in the nanoimprint mold, it is necessary to form a pattern several times finer than the conventional photomask pattern formation, and the tolerance for defects such as dimensional deviation is extremely large. There is a big problem of being narrow. Needless to say, in order to solve this problem, it is necessary to improve process technologies such as electron beam lithography and etching necessary for forming a fine mold pattern, and to pursue higher precision than ever. At the same time, it is necessary to work on improving the accuracy based on a different idea from the conventional method by reviewing the entire process and contriving the combination of each process.

  In order to form a fine pattern of 100 nm or less, which is required for a mold for nanoimprinting, there is a method of forming a pattern on a resist film using electron beam lithography and transferring it to a mold substrate by dry etching or the like. It is common.

  In electron beam lithography, the electrons scattered by the resist film or the base material may affect the periphery of the irradiated portion, resulting in a problem that the pattern formed as a result spreads more than the design. In particular, when the pattern density is high or in the vicinity of a large area pattern, the electron dose to be irradiated becomes large, and this influence is great.

  Therefore, before actually irradiating the electron beam, the ratio of the pattern per unit area (unit area 1) considering the range in which the electron beam is scattered is calculated, and a unit smaller than the unit area 1 according to the value is calculated. In general, a correction for increasing or decreasing the irradiation electron dose applied to the area (unit area 2) is added. This is called “proximity effect correction” (for example, see Non-Patent Document 2).

Appl. Phys. Lett. , Vol. 67, 1995, p. 3314 Edited by Japan Society of Applied Physics, “Ultra-fine processing technology”, 1997, p. 120-129

  However, since the pattern for the nanoimprint mold is a haploid pattern unlike a tetraploid photomask, the pattern area is 1/16, while the area affected by the scattered electron beam is the pattern. Constant regardless of magnification. For this reason, it is desirable that the unit area 2 is 1/16 without changing the unit area 1 as compared with the case of the photomask. However, in this case, there is a problem that the calculation amount and the electron beam irradiation time are significantly increased. Newly occurs.

  If the unit area 2 includes a fine pattern 132 of a line & space pattern with a pattern density of 50% and a 0% region where no pattern exists, as shown in FIG. 3, for example, these regions are included. Since the pattern density changes abruptly at the boundary of, the influence of the scattered electron beam changes from the boundary line toward the inside of the region of the fine pattern 132, but the corrected dose is unit area 2 Inside it is constant. As a result, among the fine patterns 132 to be formed, there is a problem that the pattern 32b near the boundary has a smaller opening dimension than the central pattern 32a.

  Such a problem that the pattern size to be formed changes in the boundary region where the pattern density rapidly changes is inevitable as long as the calculation is performed by averaging over a unit area larger than the pattern size. On the other hand, the unit areas 1 and 2 of the calculation are made sufficiently small with respect to the pattern dimensions, or the influence of individual patterns such as one line and one polygon is considered without considering a finite unit area. This algorithm can be solved by employing an algorithm that calculates all patterns and calculates the correction to be applied to each pattern based on the sum of the influences. However, on the other hand, there is a problem that the amount of calculation required is enormous.

  In nanoimprint using a haploid pattern, the tolerance for very small dimensional deviation caused by such improper proximity effect correction is narrow, and its influence is relative to that of a tetraploid photomask. It becomes a bigger problem than before.

  The present invention has been made to solve such problems more easily, and an object of the present invention is to reduce a dimensional shift of a fine pattern in a nanoimprint mold without performing complicated calculation.

In order to achieve the above object, a first invention according to the present invention is a method for producing an imprint mold for transferring a concavo-convex shape provided on a mold onto a transfer object, wherein the substrate is provided with a protective film and an electron beam. Preparing a mold forming substrate provided with a first resist for lithography in this order;
Forming a mold pattern and an auxiliary pattern on the first resist, and forming a first resist pattern;
Using the first resist pattern as a mask, forming a mold pattern and an auxiliary pattern on the protective film, and forming a protective film pattern;
Removing the first resist;
Said second resist on the protective film is provided to form an opening pattern corresponding portions to the mold pattern portion formed in the protective film in the resist of the second, forming a second resist pattern ,
The protective layer pattern and the second resist pattern as a mask to form a mold pattern on the substrate itself,
Removing the protective film and the second resist,
It is a manufacturing method of the mold for concave imprint characterized by having.

The second invention is a method for producing an imprint mold for transferring a concavo-convex shape provided on a mold to a transfer object, wherein a protective film and a first resist for electron beam lithography are applied to a substrate in this order. A step of preparing the provided mold forming substrate, a step of forming a mold pattern and an auxiliary pattern on the first resist to form a first resist pattern, and a protection using the first resist pattern as a mask Forming a mold pattern and an auxiliary pattern on the film, forming a protective film pattern, removing the first resist, and providing a second resist on the protective film; the opening pattern is formed on a portion corresponding to the auxiliary pattern part formed on the protective film, and forming a second resist pattern, the second register Forming and removing the protective film pattern is exposed from the pattern, removing the second resist, the mold pattern of the remaining said protective film pattern as a mask, the mold pattern on the substrate itself And a process for removing the protective film. The method for producing a convex imprint mold is characterized by comprising the steps of:
In the present invention, the protective film is made of chromium. The method for producing an imprint mold according to claim 1 or 2, wherein the protective film is chromium.

  In the mold pattern forming method according to the present invention, as shown in FIG. 4, the resist pattern is formed by providing the auxiliary pattern 33 around the fine mold pattern 32 formed on the resist. It is characterized by improving the dimensional uniformity of the mold pattern 32 on the resist.

  However, if the protective film 21 and the substrate 11 are etched as they are, the auxiliary pattern 33 is also transferred at the same time as the fine mold pattern 32 on the target resist. Therefore, after the resist fine mold pattern 32 and the auxiliary pattern 33 are transferred to the protective film 21 serving as an etching mask for the base material 11, the base material 11 is not etched as it is, but a resist is applied again, and the fine mold pattern is used. The substrate 11 is etched after forming an opening pattern of only the pattern portion.

  Further, when the mold pattern has a concave shape and a convex shape, the steps for realizing the above-mentioned characteristics are partially different, and therefore, an optimum step is determined for each.

  According to the imprint mold manufacturing method of the present invention, it becomes possible to improve the dimensional uniformity of the desired fine resist pattern, and as a result, improve the dimensional uniformity of the finally obtained fine mold pattern. I can do it.

  The auxiliary pattern added at the pattern design stage is designed to be the same pattern or the same pattern density as the target fine mold pattern, and it is necessary to generate special and complicated patterns by calculation. Therefore, it is possible to design and arrange easily.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 5 and 6 are schematic views showing a cross section of the nanoimprint mold according to the present invention, in which a concave fine mold pattern 12 and a convex fine mold pattern 13 are formed on the surface of the substrate 11, respectively. FIG. 5 shows a concave mold having a shape in which a fine pattern is dug down with respect to the reference surface, and FIG. 6 shows a convex mold having a shape in which the fine pattern protrudes from the reference surface. 1 and 2 are process diagrams of a method for forming a fine pattern of a nanoimprint mold according to the present invention. FIG. 1 corresponds to the process of the concave mold of FIG. 5, and FIG. 2 corresponds to the process of the convex mold of FIG.

<Recessed mold>
Hereinafter, the process of the concave mold which is 1st Embodiment is demonstrated using FIG. In FIG. 1A, a protective film 21 serving as a mask for etching the substrate 11 is formed on the substrate 11, and a first resist 31 serving as a mask for patterning the protective film 21 is further formed thereon. Is formed. The material of the protective film 21 is selected so that it has a sufficiently high resistance when etching the base material 11 and can be selectively removed from the base material 11.

  Next, as shown in FIG. 1B, the first resist 31 is patterned by electron beam lithography, and a fine mold pattern 32 and an auxiliary pattern 33 are simultaneously formed to form a first resist pattern. . The fine mold pattern 32 has the same shape as the concave fine mold pattern 12 or a shape obtained by adding a very small dimensional correction thereto. The position where the auxiliary pattern 33 is arranged is determined in consideration of the shape of the fine mold pattern 32, the point of interest of the concave fine mold pattern 12, and the like. In FIG. .

  The auxiliary pattern 33 is designed so that the pattern density is equal to that of the fine mold pattern 32. Thereby, it is possible to avoid a sharp change in the pattern density in the vicinity of the end portion of the fine mold pattern 32, and as a result, it is possible to suppress a change in the opening width in the vicinity of the end portion of the fine mold pattern 32. It is desirable that the range in which the auxiliary pattern 33 is arranged be sufficiently wide in consideration of the range in which the electron beam is scattered. However, even if a sufficiently wide range cannot be ensured due to other pattern arrangements, an allowable range is provided. A certain effect can be expected by arranging with.

  Next, as shown in FIG. 1C, the protective film 21 is etched using the first resist pattern as a mask, the first resist pattern is transferred to the protective film 21, and the fine protective film pattern that hits the mold pattern 22 and an auxiliary protective film pattern 23 corresponding to the auxiliary pattern are formed. When transferring a fine pattern as in the present invention, it is common to adopt a dry etching method using plasma, but if possible, use other etching methods such as wet etching using a chemical solution. It doesn't matter.

  Next, after removing the first resist 31 as shown in FIG. 1D, a second resist 41 is newly applied as shown in FIG. The second resist 41 is applied so as to completely cover the step between the fine protective film pattern 22 and the auxiliary protective film pattern 23.

  Next, as shown in FIG. 1F, an opening pattern 42 is formed in the second resist 41 using electron beam lithography or photolithography. The opening pattern 42 opens only on the fine protective film pattern 22 and the auxiliary protective film pattern 23 remains covered with the second resist 41.

  Since the opening pattern 42 is larger than the first resist pattern formed in FIG. 1B, it is not always necessary to use electron beam lithography, and it may be formed by photolithography. However, in any lithography, it is necessary to align the fine protective film pattern 22 and the opening pattern 42 with sufficiently high accuracy so that only the fine protective film pattern 22 is exposed.

  Next, as shown in FIG. 1G, the substrate 11 is etched using the fine protective film pattern 22 and the opening pattern 42 corresponding to the second resist pattern as a mask to form the fine mold pattern 12. Subsequently, as shown in FIG. 1H, the second resist 41 and the protective film 21 are removed to complete the nanoimprint mold.

<Convex mold>
Next, a convex mold pattern forming process according to the second embodiment will be described with reference to FIG. 2 (a) to 2 (e) are the same as those in FIGS. 1 (a) to 1 (e) in forming the concave mold, and thus the description thereof is omitted. However, the shape of the fine mold pattern 32 and the auxiliary pattern 33 is a negative / positive inverted shape unlike the case of FIG.

  FIG. 2F shows a step of patterning the second resist 41 by lithography. Unlike FIG. 1F, the second resist pattern is formed by leaving the protective pattern 43 so as to protect the fine protective film pattern 22 and patterning so as to remove the periphery thereof. At this time, it is necessary to pay sufficient attention to alignment with the fine protective film pattern 22 as in the case of the concave mold.

  Next, as shown in FIG. 2G, the protective film 21 is etched again using the remaining protective pattern 43 as a mask. By this step, the auxiliary protective film pattern 23 is removed, and only the fine protective film pattern 22 is left.

  Next, as shown in FIG. 2H, the protective pattern 43 which is the second resist pattern is removed. Subsequently, as shown in FIG. 2I, the base material 11 is etched to form a desired fine mold pattern 13. Then, as shown in FIG. 2J, the protective film fine pattern 22 is removed to complete the nanoimprint mold.

  Hereinafter, the present invention will be described more specifically with reference to two examples, but the present invention is not limited to these examples.

  With reference to FIG. 1, an example of manufacturing a concave mold made of quartz will be described. First, a very thin chromium film was formed on a quartz substrate. In this case, the material of the base material 11 and the protective film 21 is quartz and chromium, respectively. Further thereon, a positive type electron beam drawing resist was applied as the first resist 31 (FIG. 1A).

  Next, exposure was performed using an electron beam exposure apparatus. Here, the fine mold pattern 32 and the auxiliary pattern 33 are assumed to be a 1: 1 line & space pattern having a pattern width of 100 nm and a pitch of 200 nm. The auxiliary pattern 33 is preferably arranged so as to have a width of, for example, about 10 to 20 μm in consideration of the electron beam scattering range. After the electron beam exposure, the first resist 31 was developed to form a fine mold pattern 32 and an auxiliary pattern 33 (FIG. 1B).

  Next, the pattern of the first resist 31 was transferred to the chromium film 21 by reactive ion etching using chlorine plasma (FIG. 1C). Further, the first resist 31 was removed by ashing with oxygen plasma or cleaning with a chemical solution (FIG. 1D).

  Subsequently, a positive electron beam resist was again applied as the second resist 41 (FIG. 1E), and electron beam exposure was performed. At this time, the alignment with the pattern on the chromium film 21 requires an accuracy within ± 50 nm at the minimum. Further, development was performed to obtain an opening pattern 42 (FIG. 1 (f)).

  Next, the quartz substrate 11 was etched by reactive ion etching using fluorine plasma to obtain a concave fine mold pattern 12. Finally, the second resist 41 and the chromium film 21 were removed, and the entire substrate was washed to complete a quartz concave mold.

  Next, an example of producing a quartz convex mold will be described. First, the point that a very thin chromium film is formed on a quartz substrate is the same as that of the first embodiment.

  Further, a first resist film 31 is applied thereon. In this embodiment, a negative type electron beam resist is used instead of a positive type. As in Example 1, it is possible to use a positive type electron beam resist. However, in this case, the ratio of the area irradiated with the electron beam is increased, and it is more susceptible to the influence of electron beam scattering. Cost.

  Next, exposure is performed using an electron beam exposure apparatus. Here, it is assumed that the fine mold pattern 32 is a pattern in which ten 1: 2 lines and spaces having a pattern width of 200 nm and a pitch of 600 nm are arranged side by side. 33 was a 1: 2 line & space pattern having a pattern width of 1 μm and a pitch of 3 μm. Both patterns were arranged so that the pattern density was about 33% at the resist pattern boundary. It is desirable to arrange the auxiliary pattern 33 so that the width of the auxiliary pattern 33 is about 10 to 20 μm as in the first embodiment. After the electron beam exposure, the first resist 31 was developed to form a pattern (FIG. 2B).

  Next, as in Example 1, the pattern of the first resist 31 was transferred to the chromium film 21 by reactive ion plasma etching using chlorine gas plasma (FIG. 2C). Further, the first resist 31 was removed by ashing with oxygen plasma or cleaning with a chemical solution (FIG. 2D).

  Subsequently, a second resist 41 was applied, exposure and development operations were performed, and patterning was performed so that the protective pattern 43 remained on the chromium fine pattern 22. In this embodiment, an ultraviolet photosensitive resist is used, and patterning is performed by photolithography using a laser drawing apparatus, a stepper, a contact aligner, or the like. Although it is possible to use electron beam lithography, in this case, it is necessary to sufficiently consider the influence of charging of the substrate surface by the electron beam.

  Next, the exposed chromium film was removed by etching. In this embodiment, not only dry etching using plasma but also wet etching using a diammonium cerium nitrate aqueous solution or the like may be used. Thereafter, the protective pattern 43 was removed by ashing with oxygen plasma or cleaning with a chemical solution.

  Next, the quartz substrate 11 was etched by reactive ion plasma etching using a fluorine-based gas to obtain a convex fine mold pattern 13. Finally, the chromium film 21 was removed and the entire substrate was washed to complete a quartz convex mold.

  INDUSTRIAL APPLICABILITY The present invention can be used when a mold used for imprinting, which is one of fine pattern transfer techniques, particularly when a nano-level pattern is formed with good dimensional accuracy.

It is the schematic explaining the manufacturing process of the mold for concave imprint which concerns on this invention. It is the schematic explaining the manufacturing process of the mold for convex imprint which concerns on this invention. It is the schematic which shows the problem of fine pattern formation in a prior art. It is the schematic explaining the solution means in this invention. 1 is a schematic view of a cross section of a concave nanoimprint mold according to the present invention. It is the schematic of the convex nanoimprint mold cross section which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Base material 12 ... Concave micro mold pattern 13 formed in base material ... Convex micro mold pattern 21 formed in base material ... Protective film 22 ... Fine protective film pattern 23 ... Auxiliary protective film pattern 31 ... first resist 32 ... fine mold pattern 32a formed in the first resist ... middle mold pattern 32b in which no change in opening dimension occurred The pattern 33 for the mold near the boundary where the change of the opening dimension occurs ... the auxiliary pattern 41 formed on the first resist ... the second resist 42 ... the opening pattern 43 formed on the second resist ..Protective pattern 132 formed on second resist ... fine pattern

Claims (3)

A method for manufacturing an imprint mold for transferring an uneven shape provided in a mold to a transfer object, comprising a mold forming substrate provided with a protective film and a first resist for electron beam lithography in this order on a base material And a process of
Forming a mold pattern and an auxiliary pattern on the first resist, and forming a first resist pattern;
Using the first resist pattern as a mask, forming a mold pattern and an auxiliary pattern on the protective film, and forming a protective film pattern;
Removing the first resist;
Said second resist on the protective film is provided to form an opening pattern corresponding portions to the mold pattern portion formed in the protective film in the resist of the second, forming a second resist pattern ,
The protective layer pattern and the second resist pattern as a mask to form a mold pattern on the substrate itself,
Removing the protective film and the second resist,
A method for producing a concave imprint mold, comprising: A method for manufacturing an imprint mold for transferring an uneven shape provided in a mold to a transfer object, comprising a mold forming substrate provided with a protective film and a first resist for electron beam lithography in this order on a base material And a process of
Forming a mold pattern and an auxiliary pattern on the first resist, and forming a first resist pattern;
Using the first resist pattern as a mask, forming a mold pattern and an auxiliary pattern on the protective film, and forming a protective film pattern;
Removing the first resist;
Said second resist on the protective film is provided to form an opening pattern corresponding portions to said auxiliary pattern portion formed in the protective film in the resist of the second, forming a second resist pattern ,
Removing the protective film pattern is exposed from the second resist pattern,
Removing the second resist;
The mold pattern portion of the remaining said protective film pattern as a mask to form a mold pattern on the substrate itself,
Removing the protective film;
A method for producing a convex imprint mold, comprising: The method for producing an imprint mold according to claim 1, wherein the protective film is chromium.