JP2017034284A - Method for manufacturing template for nanoimprint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a template for nanoimprint, by which a fine template having a 1X nm-class half pitch can be manufactured without elongating a pattern drawing time.SOLUTION: The method for manufacturing a template for nanoimprint includes steps of: forming a metal thin film and a resist pattern on a light-transmitting substrate; slimming the resist pattern; forming a coating film to cover the resist pattern and the metal thin film; subjecting the coating film to back-etching to expose the resist pattern and the metal thin film while leaving the coating film on a side face of the resist pattern as a side wall mask; removing the resist pattern; etching the metal thin film by using the side wall mask to form a metal thin film pattern; removing the side wall mask; etching the light-transmitting substrate by using the metal thin film pattern as a mask to form a concavo-convex pattern; and removing the metal thin film pattern.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a template used in a nanoimprint method for forming a fine uneven pattern.

  In recent years, particularly in semiconductor devices, high speed operation and low power consumption operation are required due to further progress in miniaturization, and high technology such as integration of functions called system LSIs is required. Under such circumstances, the lithography technology, which is essential for producing semiconductor device patterns, has pointed out the limitations of the photolithographic method due to the problem of the exposure wavelength as the device pattern becomes finer. It's getting expensive.

  In recent years, the nanoimprint lithography (NIL) method using a fine concavo-convex pattern has attracted attention as an alternative. The nanoimprint method proposed by Chou et al. In Princeton University in 1995 is expected as a technique capable of forming a fine pattern having a high resolution of about 10 nm while the apparatus price and materials used are inexpensive.

  In the nanoimprint method, a template with a nanometer-sized uneven pattern formed on the surface in advance is pressed against a transfer material such as a resin applied and formed on the surface of the substrate to be mechanically deformed to precisely transfer the uneven pattern, This is a technique for processing a substrate to be processed using a patterned nanoimprint material as a resist mask. Once the template is made, the nanostructure can be easily and repeatedly molded, so that high throughput is obtained and it is economical, and since it is a nano-processing technology with less harmful waste, not only semiconductor devices in recent years, Applications in various fields are being promoted.

  Templates used in the nanoimprint method are required to have pattern dimension stability, chemical resistance, processing characteristics, and the like. In the nanoimprint method, the pattern shape of the template must be faithfully transferred to a transfer material such as a resin. For example, in the case of the optical nanoimprint method, quartz glass that generally transmits ultraviolet light used for photocuring is used. A substrate is used as a template base material.

  Conventionally, a method for manufacturing a template for nanoimprinting is performed by etching a substrate such as quartz glass and forming an uneven pattern on the surface of the substrate (see, for example, Patent Document 1). FIG. 3 is a process cross-sectional schematic diagram showing an example of a conventional template manufacturing method.

  First, as shown in FIG. 3A, a metal thin film 32 such as chromium (Cr) is formed on a substrate 31 such as quartz glass as a template as a mask material during substrate etching, and an electron beam resist is formed thereon. The resist pattern 33 is formed by performing exposure, development and the like using an electron beam (EB) lithography technique. A method of directly forming a resist pattern on a substrate is not preferable because adhesion of the resist to the substrate and resist etching resistance are insufficient.

  Next, as shown in FIG. 3B, the resist pattern 33 is subjected to slimming treatment with oxygen plasma to reduce the thickness and width of the resist pattern. This slimming process is not an indispensable process, and it may be determined whether or not to perform according to the target resist pattern line width.

  Next, as shown in FIG. 3C, the metal thin film 32 is etched using the slimmed resist pattern 33a as a mask to form the metal thin film pattern 32a. Next, the substrate 31 is etched using the metal thin film pattern 32a as a mask, so that the substrate 31 is formed with a recess 36 as shown in FIG. Next, as shown in FIG. 3E, the resist pattern 33a is peeled and removed. The resist pattern 33a may be removed before the substrate 31 is etched.

  Next, as shown in FIG. 3F, a method is used in which the metal thin film pattern 32 a is removed by etching, and a template 30 in which a concavo-convex pattern 37 is provided on a substrate 31 is produced.

JP 2005-345737 A

  However, in the above conventional template manufacturing method, an organic resist is used as an etching mask for a metal thin film such as chromium, and the resist thickness has to be reduced in order to increase resolution with the miniaturization of the pattern. When forming a fine pattern by etching, there is a problem that it is difficult to ensure the etching resistance of the resist. Further, there is a limit to the resolution of a fine pattern that can be stably formed with the current EB lithography technology. For example, a pattern with a half pitch of about 22 nm is the resolution limit, and means a half pitch of 1 × nm (half pitch of 10 nm or more and less than 20 nm). ) There was a problem that it was difficult to form a fine pattern of the class. In addition, with the miniaturization of the pattern, there is a problem that the electron beam drawing time of the template becomes very long.

  Therefore, the present invention has been made in view of the above problems. That is, the object of the present invention is to improve the etching resistance of an etching mask at the time of pattern etching of a metal thin film in the method of manufacturing a template for nanoimprinting, and to produce a fine template of half pitch 1 × nm class using the current EB lithography technology. It is an object of the present invention to provide a template manufacturing method capable of reducing the drawing time even in fine pattern drawing.

  In order to solve the above problems, a method for producing a nanoimprint template according to the invention described in claim 1 of the present invention is a method for producing a nanoimprint template in which an uneven pattern is formed on a light-transmitting substrate, Preparing a substrate having a metal thin film formed on the light transmissive substrate, forming a resist pattern on the metal thin film, slimming the resist pattern, and the slimmed resist pattern Forming a coating film so as to cover the side surface and the upper surface of the metal film and the upper surface of the metal thin film; and etching back the coating film to expose the resist pattern and the metal thin film; Leaving the side of the resist pattern as a sidewall mask, removing the resist pattern, Etching the metal thin film using a sidewall mask to form a metal thin film pattern; removing the sidewall mask; and etching the light transmissive substrate using the metal thin film pattern as a mask Forming a pattern and removing the metal thin film pattern, and the coating film is formed by an ALD method using a material having higher etching resistance than the metal thin film when the metal thin film is etched. It is characterized by being formed.

  The method for producing a nanoimprint template according to claim 2 of the present invention is the method for producing a nanoimprint template according to claim 1, wherein the step of removing the resist pattern is a dry treatment with an oxygen-based gas. Is selectively performed.

  The method for producing a template for nanoimprint according to claim 3 of the present invention is the method for producing a template for nanoimprint according to claim 1 or 2, wherein the step of removing the sidewall mask uses water. It is characterized by being performed by wet cleaning.

  The method for producing a nanoimprint template according to claim 4 of the present invention is the method for producing a nanoimprint template according to any one of claims 1 to 3, wherein the light-transmitting property is obtained. The substrate is a quartz glass substrate.

  The method for producing a nanoimprint template according to claim 5 of the present invention is the method for producing a nanoimprint template according to any one of claims 1 to 4, wherein the sidewall mask is It is composed of a compound containing silicon.

  The method for producing a nanoimprint template according to claim 6 of the present invention is the method for producing a nanoimprint template according to any one of claims 1 to 5, wherein the metal thin film is , Chromium or a compound containing chromium.

  According to the method for manufacturing a template for nanoimprinting of the present invention, by using a sidewall mask for etching a metal thin film, the etching resistance of the mask during the metal thin film etching is improved, and the half pitch is 1X nm (10 nm or more and less than 20 nm) class. A fine template can be produced. In addition, in the fine pattern writing using an electron beam, a 1X nm-class side wall mask can be produced with the current half pitch 2X nm (20 nm or more and less than 30 nm) class writing time, and the writing time can be shortened.

It is a process cross-sectional schematic diagram which shows one Embodiment of the manufacturing method of the template for nanoimprint of this invention. It is process cross-sectional schematic diagram which shows one Embodiment of the manufacturing method of the template for nanoimprints of this invention following FIG. It is a process cross-sectional schematic diagram which shows the manufacturing method of the conventional template for nanoimprint.

  Hereinafter, based on drawings, the manufacturing method of the template for nanoimprinting concerning the embodiment of the present invention is explained in detail.

  FIG. 1 and subsequent FIG. 2 are process cross-sectional views illustrating an embodiment of a method for producing a nanoimprint template of the present invention.

  First, as shown in FIG. 1A, a substrate in which a metal thin film 12 is formed by a vacuum film formation method such as a sputtering method on a light-transmitting substrate 11 that is a template material is prepared. Next, a resist pattern 13 is formed on the metal thin film 12 by electron beam drawing. As the resist, an electron beam sensitive resin film, a photosensitive resin film, or the like can be used.

  As the light-transmitting substrate 11, the positional accuracy of the concave / convex pattern is maintained at a high level, the smoothness and flatness are high in order to obtain the transfer accuracy, and the resistance to the cleaning liquid used for cleaning in the template manufacturing process is excellent. In general, a synthetic quartz glass substrate or the like is used.

  As the metal thin film 12, a material having an etching resistance that can take a sufficient etching selectivity with the light transmissive substrate 11 such as a quartz glass substrate when the light transmissive substrate 11 is etched is used. The larger the etching selectivity, the better. In the present invention, the metal thin film 12 includes not only a simple metal but also a metal compound such as a metal oxide, nitride, oxynitride and the like. Examples of materials include metals such as chromium (Cr), titanium (Ti), tantalum (Ta), silicon (Si), and aluminum (Al), or chromium nitride (CrN), chromium oxide (CrO), and chromium oxynitride. Chromium-based compounds such as (CrNO), tantalum oxide (TaO), tantalum oxynitride (TaNO), tantalum boride (TaBO), tantalum oxynitride (TaBNO) and other tantalum compounds, titanium nitride (TiN), A metal compound such as silicon nitride (SiN) or silicon oxynitride (SiON) is used in a thickness range of several nm to 10 nm. Among these, chrome-based materials have strong resistance to fluorine-based gas plasma used for dry etching of quartz glass substrates, and are easy to wet-etch, so that high-quality and high-precision pattern formation of photomasks is possible. It has been used as a material and is a preferred material.

  If the etching selectivity is ensured, the metal thin film 12 may be a multilayer film of two or more layers, for example, a two-layer film of chromium and silicon, or a two-layer film of chromium and silicon oxide. .

  Next, the resist pattern 13 is processed by oxygen plasma and slimmed to form a slimmed resist pattern 13a as shown in FIG. In the present invention, slimming is to reduce the pattern film thickness by thinning the pattern width by wet etching or dry etching (including oxygen plasma treatment). For example, the pattern width and pattern film thickness of about ½ can be obtained without changing the pitch of the resist pattern formed first by slimming by oxygen plasma treatment.

  Next, as shown in FIG. 1C, the coating film 14 is formed by a CVD (Chemical Vapor Deposition) method or an ALD (Atomic Layer) so as to cover the side surface and the upper surface of the slimmed resist pattern 13 a and the upper surface of the metal thin film 12. It is formed by a low-temperature vacuum film formation method such as a deposition method. The resist pattern 13a becomes a core (core material) in forming the coating film 14.

The coating film 14 can be formed at a low temperature without damaging the resist pattern 13a, and a material having a high etching selectivity with the metal thin film 12 when the metal thin film 12 is etched is preferable. Examples of the material include silicon-based materials such as silicon oxide (SiO ₂ ), silicon nitride (SiN), and silicon oxynitride (SiON), aluminum-based materials such as aluminum oxide (Al ₂ O ₃ ), and hafnium oxide (HfO). Examples thereof include titanium-based materials such as hafnium-based and titanium nitride (TiN). The film thickness of the coating film 14 is basically preferably a film thickness corresponding to the half-pitch design of the target pattern, and is used in the range of several nm to 50 nm. The temperature at which the coating film 14 is formed is in a temperature range that does not damage the resist pattern 13a, is not higher than the glass transition temperature of the resist that constitutes the resist pattern, is preferably 100 ° C. or lower, and is about 20 at room temperature. More preferably, the temperature is from 25 to 25 ° C. The ALD method is a more preferable film forming method because a coating film having a uniform film thickness can be formed at a low temperature with good controllability without damaging the resist pattern.

  That is, in the case of using the ALD method, the deposition of the coating film 14 on the side surface of the resist pattern 13a is more uniform than in the case of using a generally used CVD method (thermal CVD, plasma CVD, etc.). Highly, it is possible to deposit the coating film 14 more uniformly on the side surface and the upper surface of the resist pattern 13a. Therefore, the side wall mask can be formed in a more vertical shape in the formation of the side wall mask described later. Furthermore, when an organic resist is used as the core material, the resist pattern 13a is not damaged because the film can be formed at a low temperature, and the resist mask shape is easily maintained, and the sidewall mask shape is improved. In a general CVD method, it is difficult to achieve both a low temperature process that does not damage the shape of the organic resist pattern and a uniform coverage on the side and top surfaces of the resist pattern. Coverability is achieved.

  When the ALD method is used as described above, the pattern of the sidewall mask becomes uniform and has a more vertical shape. In particular, in the process of pattern transfer using the sidewall mask as an etching mask (hereinafter also referred to as a sidewall process), The dimensional controllability of a fine pattern is greatly improved. As a result, it becomes possible to manufacture a template that becomes a mold of a transfer master on a semiconductor substrate or the like with high accuracy.

  Here, the difference between the ALD method and the general CVD method in forming the coating film 14 of the present invention will be described in more detail.

  In the template manufacturing process of the present invention using the side wall mask, which will be described later, the variation in the thickness of the coating film 14 is directly linked to the variation in the pattern CD (critical dimension). The uniformity of the film thickness, particularly the uniformity of the coating film on the side surface of the resist pattern 13a is important. Since the ALD method is an atomic layer deposition method using a saturated surface reaction, it is possible to deposit atomic layers one by one. Since the film formation amount by the ALD method is about 0.1 nm to 0.2 nm / cycle, the controllable film formation amount is about the same.

  On the other hand, in the CVD method, the surface reaction proceeds continuously by a chemical reaction, so the film thickness controllability is inferior to that of the ALD method, and the uniformity of the coating film on the side wall when the film forming speed changes according to the apparatus condition Is also damaged. In particular, when the film thickness is small, the deviation from the film thickness target value becomes significant. In addition, in the film formation by the CVD method, the coverage property (shape following property) is inferior to that of the ALD method, and is particularly remarkable in the pattern side wall portion. For example, in the CVD method, it is easy to express the convex part that is easy to touch the film forming gas and it is difficult to form the film in the concave part. Usually, the CVD method adjusts this point according to the film forming condition. In particular, the ALD method is more advantageous.

  When a material other than a resist, for example, an inorganic compound is used as the core material when forming the coating film 14, if the core material is over-etched in the core material formation (patterning) step, the metal thin film 12 under the core material 12. In the process of etching the light-transmitting substrate 11 thereafter, pattern dimension variation and pattern formation failure are caused. A resist core material is more preferable because there is no damage to the metal thin film 12 when the resist pattern is formed. Further, as will be described later, if the core material is a resist, it is possible to remove the core material while minimizing damage to the sidewall mask by using weak ashing conditions.

  As described above, in the manufacture of a template having a fine pattern, it is desirable to use a resist as a core material. In order to perform a side wall process with a resist core material, it is more necessary to form a coating film at a low temperature by the ALD method. preferable. Hereinafter, description will be continued based on the drawings.

  Next, as shown in FIG. 1D, the coating film 14 is etched back to expose the resist pattern 13a and the metal thin film 12, while leaving the coating film 14 on the side surface of the resist pattern 13a to form a sidewall mask. 15 is assumed.

  In the present invention, the side wall mask 15 means a mask in which a side wall pattern is formed on a side wall of a dummy pattern made of a resist pattern 13a serving as a core (core material) with a coating film, and this side wall pattern is used as an etching mask. In other words, it becomes possible to form a line and space pattern with a pitch that is half the pitch of the dummy pattern.

The etch back is performed using an appropriate etching gas depending on the material of the coating film 14. For example, when the coating film 14 is formed of silicon oxide (SiO2), a fluorine-based gas such as CF ₄ , CHF ₃ , C ₂ F ₆ , or a mixed gas thereof is used as an etching gas.

  Next, as shown in FIG. 1 (e), the resist pattern 13 a is removed to form a light transmissive substrate 11 in which a sidewall mask 15 is formed on the metal thin film 12.

  In the present invention, since the coating film 14 is etched back to expose the upper surface of the resist pattern 13a, the resist pattern 13a can be easily removed.

  Furthermore, in the present invention, since the material that becomes the core when forming the sidewall mask is an organic resist, the resist pattern 13a can be selectively removed by dry treatment using an oxygen-based gas. For example, dry etching such as dry etching using oxygen plasma or ozone treatment can be used. In the conventional method of wet etching using an inorganic compound as the core material, the side mask pattern may collapse or deform due to the surface tension of the etchant generated by wet etching when the core material is removed. The method of using the dry treatment for removing the resist pattern of the present invention can provide an effect that the side mask pattern can be prevented from collapsing and deforming. Since the method of the present invention using an organic resist as a core material does not require etching resistance to the resist, the controllability of resist pattern dimensions and pattern edge roughness is good, and compared with a method using an inorganic compound as a core material. The number of material processing steps can be reduced, and a high-quality sidewall mask can be obtained.

  Next, as shown in FIG. 2F, the metal thin film 12 is etched using the sidewall mask 15 to form a metal thin film pattern 12a.

For example, when quartz glass is used for the light-transmitting substrate 11 and silicon oxide (SiO ₂ ) is used for the sidewall mask 15 and the metal thin film 12 is made of chromium or a compound containing chromium, a mixed gas of oxygen and chlorine is used as an etching gas. Thus, by dry etching the metal thin film 12, the etching selectivity can be increased, and the metal thin film pattern 12a can be formed without damaging the sidewall mask 15 and the light transmissive substrate 11.

  Next, after the sidewall mask 15 is removed, the light transmissive substrate 11 is etched using the metal thin film pattern 12a as an etching mask to form a recess 16 in the light transmissive substrate 11 as shown in FIG. . For example, when the light-transmitting substrate 11 is quartz glass, the etching selectivity can be increased by dry-etching the light-transmitting substrate 11 with a fluorine-based gas using chromium or a compound containing chromium as the material of the metal thin film pattern 12a. A large pattern can be formed on the light transmissive substrate 11.

  The method for removing the sidewall mask 15 varies depending on the characteristics of the material of the coating film 14 used for the sidewall mask and the adhesion to the metal thin film pattern 12a, but is optimal from wet etching, dry etching, cleaning with liquid, etc. Can be used.

For example, when the sidewall mask 15 is silicon oxide (SiO ₂ ) and the metal thin film pattern 12a is chromium (Cr), the adhesion between the two is low, so the sidewall mask 15 made of silicon oxide is removed by wet cleaning using water. There is an advantage that the manufacturing process can be simplified.

  Examples of water used for wet cleaning include pure water, ozone water, and functional water that does not affect the template. The water to be used may be heated in a range that does not affect the template such as damage. Further, physical cleaning such as ultrasonic waves may be added as long as the metal thin film pattern and the light transmissive substrate are not affected by damage or the like.

  Further, in the present invention, the light-transmitting substrate 11 is a quartz glass substrate, the sidewall mask 15 is made of a compound containing silicon such as silicon oxide, and in the step of removing the sidewall mask 15, if the sidewall mask is If it remains, it is possible to remove the remaining side wall mask 15 at the same time in the step of forming a concave / convex pattern by dry etching the light-transmitting substrate 11 described below, and the template manufacturing process becomes easier. There are advantages.

  Next, the metal thin film pattern 12a is removed, and as shown in FIG. 2H, the nanoimprint template 10 in which the concave and convex pattern 17 is formed on the light transmissive substrate 11 is obtained.

  The metal thin film pattern 12a is removed by either wet etching or dry etching. For example, when the metal thin film pattern 12a is chromium (Cr) or a compound containing chromium, it can be easily removed by wet etching with a ceric ammonium nitrate aqueous solution.

  As described above, the nanoimprint template manufacturing method of the present invention uses a sidewall mask to convert a metal thin film etching mask such as chromium from an organic resist to an inorganic hard mask, and improves etching resistance as a mask. A fine hard mask pattern of half pitch 1X nm (10 nm or more and less than 20 nm) class can be formed. By using a sidewall mask and a hard mask made of a metal thin film, it is possible to form a fine pattern of half pitch 1X nm class, which is difficult with the current EB lithography technology. In addition, by using the sidewall mask, a sidewall mask of 1X nm class can be manufactured with a half pitch 2X nm (20 nm or more and less than 30 nm) class drawing time, and the writing time can be shortened.

  Next, an example explains the present invention.

  A synthetic quartz glass substrate having an outer shape of 6 inches square and a thickness of 0.25 inches is used as a light-transmitting substrate for the template, and chromium is deposited on one main surface of the substrate by a sputtering method to have a film thickness of 5 nm. A substrate on which a chromium film was formed was prepared. Next, an electron beam resist was applied on the chromium film, and a resist pattern having a resist thickness of 60 nm composed of a line and space with a pattern width of 30 nm and a half pitch of 30 nm was formed by electron beam drawing.

  Next, the resist pattern was slimmed by dry etching with oxygen plasma to form a slimmed resist pattern having a pattern width of 15 nm.

Next, SiO ₂ was deposited by ALD so as to cover the side and top surfaces of the slimmed resist pattern and the top surface of the chromium film, thereby forming a 15 nm thick SiO ₂ coating film.

Next, the entire surface of the SiO ₂ coating film is etched back by dry etching using CF ₄ gas to expose the resist pattern and the chromium film, while leaving the SiO ₂ coating film on the side surface of the resist pattern to form a sidewall mask. Formed.

Next, the resist pattern was selectively removed by dry etching using oxygen plasma, and a substrate in which a SiO ₂ sidewall mask was formed on a chromium film was prepared. In the present embodiment, since the core material is an organic resist, the resist pattern can be easily removed, and the side mask has not collapsed or deformed. The sidewall mask of SiO ₂ was a line and space pattern having a pattern width of 15 nm, a thickness of 47 nm, and a half pitch of 15 nm.

Next, the chromium film was dry-etched using a mixed gas of oxygen and chlorine using a SiO ₂ sidewall mask to form a chromium pattern.

Next, the SiO ₂ sidewall mask was removed by wet cleaning with pure water, and then the quartz glass substrate was dry-etched using CF ₄ gas using the chromium pattern as an etching mask to form a recess in the quartz glass substrate.

  Next, the chrome pattern was removed by wet etching using a ceric ammonium nitrate aqueous solution, and a nanoimprint template in which a line-and-space uneven pattern having a pattern width of 15 nm and a half pitch of 15 nm was formed on a quartz glass substrate was produced.

DESCRIPTION OF SYMBOLS 10 Template 11 Light transmissive board | substrate 12 Metal thin film 12a Metal thin film pattern 13, 13a Resist pattern 14 Cover film 15 Side wall mask 16 Concave part 17 Concave and convex pattern 30 Template 31 Substrate 32 Metal thin film 33 and 33a Resist pattern 36 Concave part 37 Concave and convex pattern

Claims (6)

A method for producing a template for nanoimprint in which an uneven pattern is formed on a light transmissive substrate,
Preparing a substrate on which the metal thin film is formed on the light transmissive substrate;
Forming a resist pattern on the metal thin film;
Slimming the resist pattern;
Forming a coating film so as to cover a side surface and an upper surface of the slimmed resist pattern and an upper surface of the metal thin film;
Etching back the coating film to expose the resist pattern and the metal thin film, and leaving the coating film on the side surface of the resist pattern as a sidewall mask;
Removing the resist pattern;
Etching the metal thin film using the sidewall mask to form a metal thin film pattern;
Removing the sidewall mask;
Etching the light transmissive substrate using the metal thin film pattern as a mask to form the uneven pattern; and
Removing the metal thin film pattern;
Including
The method for producing a nanoimprint template, wherein the coating film is formed by an ALD method using a material having higher etching resistance than the metal thin film when the metal thin film is etched.   The method for producing a template for nanoimprinting according to claim 1, wherein the step of removing the resist pattern is selectively performed by dry treatment with an oxygen-based gas.   The method for producing a nanoimprint template according to claim 1 or 2, wherein the step of removing the sidewall mask is performed by wet cleaning using water.   The method for producing a template for nanoimprinting according to any one of claims 1 to 3, wherein the light-transmitting substrate is a quartz glass substrate.   The method for manufacturing a template for nanoimprint according to any one of claims 1 to 4, wherein the sidewall mask is made of a compound containing silicon.   The method for producing a nanoimprint template according to any one of claims 1 to 5, wherein the metal thin film is formed of chromium or a compound containing chromium.

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