JP2010143042A - Method of detecting coating state of releasing agent for nanoprint mold and pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting coating state of releasing agent for nanoprint mold capable of quickly and conveniently determining whether a mold surface including the bottom surface of recessed part pattern of a fine rugged pattern is uniformly covered with a releasing agent having such a sufficient amount as to impart an releasing operation to the mold surface, with respect to the method of microscopically detecting the coating state of the releasing agent formed on the nanoprint mold surface, and to provide a pattern forming method using the method of detecting coating state of releasing agent for nanoprint mold. <P>SOLUTION: In the method of detecting coating state of releasing agent for a nanoprint mold which has the rugged pattern on the surface thereof and is formed by applying the releasing agent on the rugged pattern, an adhesive force between an probe and the releasing agent on the rugged pattern surface is measured from a curve of the force operating between the probe tip of a cantilever and the rugged pattern formed by applying the releasing agent in a measurement area of the rugged pattern formed by applying the releasing agent by using the cantilever of a scanning type probe microscope and the coating state of the releasing agent is estimated by the adhesive force. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for inspecting a mold release agent application state of a mold for nanoimprint and an application state of the mold release agent on the surface of the mold for nanoimprint. The present invention relates to a pattern forming method having an inspection process to be evaluated.

  In recent years, especially for 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 that is necessary for producing the pattern of the semiconductor device has become very expensive as the exposure apparatus and the like as the pattern becomes finer, and the price of the mask used therefor also becomes expensive. Yes.

  On the other hand, the nanoimprint method proposed by Chou et al. At Princeton University in 1995 is attracting attention as a fine pattern forming technology having a high resolution of about 10 nm, although the apparatus price and materials used are low (non-patent) Reference 1 and Patent Reference 1).

  In the nanoimprint method, a fine pattern is formed by pressing a mold (also called a template, stamper, or mold) with a nanometer-size uneven pattern on the surface in advance against the resin that is formed on the surface of the workpiece. Is a technique for processing a workpiece using a resin with a pattern formed as a resist mask. Once the mold is made, the nanostructure can be easily and repeatedly molded, resulting in high throughput and economics, and because it is a nano-processing technology with little harmful waste, not only semiconductor devices in recent years, Application to various fields is expected.

  In such a nanoimprint method, a thermal nanoimprint method in which a concavo-convex pattern is transferred by heat using a thermoplastic resin, or a photo nanoimprint method in which a concavo-convex pattern is transferred by light using a photocurable resin (see, for example, Patent Document 2) ) Etc. are known.

  Molds used in the nanoimprint method are required to have pattern dimension stability, chemical resistance, processing characteristics, and the like. Taking the case of the optical nanoimprint method as an example, quartz glass is generally used. However, a mold made of quartz glass or the like has low releasability from the resin that is the pattern transfer material, and the resin adheres to the mold side when the mold is peeled off from the resin on which the transfer pattern is formed. There was a problem that the pattern accuracy was liable to be reduced. For this reason, as a method for improving the releasability, a method of applying and forming a thin film of a release agent such as a fluororesin on the surface of the concavo-convex pattern of the mold has been proposed.

  However, when imprinting using a mold continuously, the applied release agent is gradually lost from the surface of the concavo-convex pattern, and as a result, the resin adheres to the mold during transfer, and accurate pattern transfer cannot be performed. was there. If the application state of the release agent is not good, it is necessary to re-apply the release agent.

For this reason, obtaining information on the application state of the release agent, such as whether the release agent sufficiently covers the mold surface, affects the quality, yield, and productivity of the imprinted product. Very important. Several methods have been proposed as an inspection method for evaluating the application state of the release agent present on the mold surface. In general, there are a method based on surface analysis and a method for measuring the contact angle of the release agent coating surface. In addition, there is a method in which a release agent is made to contain a labeling substance such as a fluorescent substance and the release agent concentration is measured by a predetermined detection method (see Patent Document 3 and Patent Document 4).
S. Y. Chou et. al. , Science, vol. 272, p. 85-87, April, 1996. JP-T-2004-504718 JP 2002-93748 A JP 2007-69217 A JP 2007-296823 A

  However, the surface analysis method has a problem that a generally used surface analysis apparatus is large and expensive, requires a lot of time for measurement analysis, and is not suitable for use in a normal manufacturing process. The method of measuring the contact angle has a problem in that it cannot produce water droplets of micrometer or less due to the vapor pressure of water, and the contact angle cannot be measured in a nanoimprint pattern region of micrometer or less. The method of measuring the release agent concentration using a labeling substance is, for example, in the measurement of emission intensity by visible light irradiation, the wavelength of visible light is larger than the pattern dimension, and the pattern to be measured is in the order of several tens of nm. On the other hand, there is a problem in that there is no resolution, and there has been a risk that the release agent and the substance that becomes the label itself may undergo chemical reaction and change in quality when irradiated with ultraviolet rays or even shorter wavelengths. In addition, since the pattern is fine, the thickness of the release agent is limited to about several nanometers in order to control the pattern dimension (CD: Critical Design), and the emission intensity becomes weaker with a release agent having a thickness of several nanometers. There was a problem that the light emission detection sensitivity was lowered.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is a method of microscopically inspecting the application state of a release agent formed on the surface of a nanoimprint mold, and the mold surface including a bottom surface of a concave portion of a fine uneven pattern has a releasing action. To provide an inspection method capable of quickly and easily knowing whether or not a uniform amount of a release agent is uniformly coated and a pattern formation method having an inspection step for evaluating the application state of the release agent It is.

  In order to solve the above problems, the method for inspecting the application state of the mold release agent of the nanoimprint mold according to the invention of claim 1 has a concavo-convex pattern on the surface, and the mold release agent is applied and formed on the concavo-convex pattern. A method for inspecting the applied state of a release agent of a mold for nanoimprinting, wherein the cantilever probe is used in a measurement region of a concavo-convex pattern in which the release agent is applied and formed using a cantilever of a scanning probe microscope. The adhesion force between the probe and the mold release agent on the surface of the concavo-convex pattern is measured from a force curve that acts between the tip and the concavo-convex pattern on which the mold release agent is applied, and the mold release is determined from the adhesion force. The application state of the agent is evaluated.

  The method for inspecting the application state of the mold release agent of the nanoimprint mold according to the invention of claim 2 has a concavo-convex pattern on the surface, and the mold release agent for the nanoimprint mold in which the mold release agent is applied and formed on the concavo-convex pattern. The cantilever probe tip and the release agent are applied and formed in the measurement region of the concavo-convex pattern where the release agent is applied and formed using a cantilever of a scanning probe microscope. The adhesion force and the friction force between the probe and the release agent on the surface of the uneven pattern are measured from a force curve that acts between the uneven pattern and the release agent is applied from the adhesion force and the friction force. It is characterized by evaluating the state.

  The method for inspecting the application state of the release agent for the nanoimprint mold according to the invention of claim 3 is the method for inspecting the application state of the release agent for the mold for nanoimprint according to claim 1 or 2, wherein The diameter of the concave / convex pattern is smaller than the concave dimension of the concave / convex pattern, the probe has a shape reaching the bottom of the concave section, and the concave / convex pattern of the concave / convex pattern is on the order of several tens of nanometers.

  According to a fourth aspect of the present invention, there is provided a pattern forming method comprising: pressing a nanoimprint mold having a concavo-convex pattern on a surface thereof and having a release agent applied and formed on the concavo-convex pattern against the transfer target; A pattern forming method for transferring to a transfer body, wherein the application state of a release agent on the surface of the nanoimprint mold is evaluated by the inspection method according to claim 1 or 2 before transferring the concavo-convex pattern. It has an inspection process.

  According to the method for inspecting the application state of the mold release agent of the nanoimprint mold according to the present invention, the adhesion force is measured by a force curve using a scanning probe microscope equipped with a probe having a fine tip diameter. It is possible to microscopically inspect the application state of the release agent formed on the surface of the nanoimprint mold having an order uneven pattern. In addition, by measuring the adhesive force using a probe with a smaller diameter than the pattern size, the application state such as the strength of the microscopic adhesive force of the release agent and the uniformity of application can be quantified up to the bottom of the concave pattern. Can be evaluated and inspected. According to the inspection method of the present invention, the life of the release agent applied to the mold surface can be monitored, process management is facilitated, and the transfer quality in nanoimprinting is improved. In addition, it is possible to quantitatively evaluate and inspect the application state when the mold with the transfer resin residue or foreign matter attached is washed and the release agent is applied again.

  According to the pattern forming method of the present invention, the application state of the release agent is provided by using the above-described inspection method for evaluating the application state of the release agent on the nanoimprint mold surface before transferring the uneven pattern. Can improve the quality, yield, and productivity of imprinted products.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings.

In the present invention, the adhesive force is measured using a cantilever of a scanning probe microscope, thereby inspecting the application state of a release agent provided in a fine pattern region that cannot be measured by a conventional inspection method. is there.
FIG. 1 is a schematic diagram for explanation showing the principle of measurement of adhesion force according to the present invention.

(Force curve and adhesion)
As shown in FIG. 1, the sample surface and a small probe having a cantilever structure are gradually brought closer (A to B in FIG. 1), and the distance between the probe and the sample approaches several nanometers to several tens of nanometers. Then, inter-surface forces such as van der Waals force act between them, attractive force acts first, and then repulsive force acts. When the cantilever is further pushed up and deflected upward (C in FIG. 1), when it is released in the opposite direction, the attractive force acts to cause downward deflection (D in FIG. 1). When the force due to the deflection exceeds the adsorption force (E in FIG. 1), the cantilever returns to the horizontal position (F in FIG. 1).

  The deflection of the cantilever is detected by an optical sensor based on a change in the reflection angle of the laser beam applied to the back surface of the cantilever, and the amount of deflection of the cantilever is measured. Control of the distance between the sample and the probe (Z direction) is performed by a piezo scanner. From the cantilever deflection and the cantilever spring constant, the hook force F = kx (k is the cantilever spring constant [N / m], x is the cantilever deflection [m]) and the adhesion force F is obtained. In FIG. 1, the horizontal axis represents the distance between the sample and the probe (Distance), and the vertical axis represents the force acting between the surfaces (Force: F). The cantilever deflection is shown as a force curve (also called a force distance curve). 1 is plotted (solid line in FIG. 1). The adhesive force can be read from the force curve.

  As described above, the scanning probe microscope is provided with a sharply pointed probe at the free end of a 100 μm to 2000 μm long cantilever made of an elastic body having a predetermined spring constant, and the probe is brought close to the sample. In this device, an attractive force such as van der Waals force is applied between the probe tip and the sample surface, and the local shape and physical properties of the sample are measured from the displacement of the cantilever.

  In the present invention, as a scanning probe microscope used for measuring the adhesion force, the surface of the sample is scanned with a probe called a cantilever provided with a probe at one end of the cantilever, and the size and shape of the pattern on the sample surface are measured. A microscope is used, and an atomic force microscope (hereinafter referred to as AFM) is most preferable. In the following description, the inspection method and pattern formation method of the present invention will be described by taking the case of using AFM as an example.

  As the material and shape of the cantilever probe used in the present invention, conventionally used materials and shapes can be applied. That is, silicon, silicon nitride, silicon oxide, silicon carbide, or the like is used as the probe material. Moreover, what modified the methyl group etc. on the surface of said material can also be used. Further, in order to impart conductivity to the material surface, for example, a material coated with a metal such as gold or titanium, or carbon is used. As the shape of the probe, a shape having a sharpened tip such as a pyramid-shaped quadrangular pyramid or cone is used. For example, in the case of a quadrangular pyramid, the apex angle of the tip is about 70 degrees and the radius of curvature is about several tens of nm. It is. Furthermore, in the present invention, as shown in FIG. 2, when measuring the application state of the release agent 22 applied and formed on the bottom surface of a concave portion of a fine concavo-convex pattern such as a quartz mold 21, the probe 23 is high. It can be measured by using a long and narrow probe having a diameter of several nanometers and smaller than the concave pattern dimension (CD) and a length of several hundred nanometers.

  Next, the adhesion force acting between the cantilever probe and the mold will be further described. FIG. 3 shows a cantilever probe in which Optool DSX (manufactured by Daikin Industries), which is a fluorine-containing silane compound that is commercially available as an example of a mold release agent, is applied to the surface of a quartz mold having a fine uneven pattern. It is a figure which shows the force curve which measures the adhesive force which acts between the front-end | tip and the mold which apply | coated the mold release agent. The horizontal axis in FIG. 3 indicates the distance (nm) between the mold and the probe, and the vertical axis indicates the force (nN) acting between the mold and the probe. In the force curve in FIG. 3, the dotted line indicates the state in which the probe approaches the mold (Approach), the solid line indicates the state in which the probe is separated from the mold (Retract), and the value indicated by the arrow is in the mold to which the release agent is applied. Adhesive strength.

  On the other hand, for comparison, FIG. 4 shows a force curve for measuring the adhesion force acting between the tip of the cantilever probe tip and the mold in a quartz mold in which a release agent is not applied to the surface. In the force curve in FIG. 4, as in FIG. 3, the dotted line indicates the state in which the probe approaches the mold (Approach), the solid line indicates the state in which the probe is released (Retract), and the value indicated by the arrow indicates that the release agent is applied. It is the adhesive force in the mold. Compared to the case where the release agent shown in FIG. 3 is applied, the adhesive force when the release agent shown in FIG. 4 is not applied is about five times as high. Higher adhesion indicates that when imprinting is performed using a mold, the resin is in close contact with the mold and defects such as chipping are likely to occur in the uneven pattern of the resin.

(Method of applying release agent)
In the present invention, as the release agent, a conventionally known release agent such as a hydrophobic fluororesin having a small surface energy can be applied in order to improve the release property of the resin.
Next, the difference in adhesive force depending on the application method of the release agent will be described. As a method for applying the release agent in the present invention, a conventionally known method is used. The release agent is dissolved in a predetermined solvent to form a release agent solution, and the mold is immersed in the solution, and then dried and released. A method of forming a mold on the mold surface, a method of applying and forming a release agent solution on the mold by spin coating, a mold that is placed in a sealed container and put in a gas phase state on the mold A vapor deposition method for forming a film is used. In the present invention, any of the above methods can be used, and the above methods for forming a release agent thin film on a mold are collectively referred to as a release agent coating method.

  FIG. 5 shows the case where the release agent OPTOOL DSX is applied and formed on the quartz mold surface by spin coating (FIG. 5B), the case where it is applied by vapor deposition (FIG. 5C), and a comparison. 6 is a diagram showing the upper limit value / lower limit value of adhesive force, variation (dots), and average value (long line in the x direction) in the case of a quartz mold not provided with a release agent (FIG. 5A). As shown in FIG. 4, the adhesive force of the quartz mold without the release agent (FIG. 5A) exceeds 15 nN on average, whereas the mold (FIG. 5) is formed by applying the release agent. 5 (b) and FIG. 5 (c)) both show a low value of 5 nN or less.

  Furthermore, compared to the case where the release agent is applied and formed by spin coating (FIG. 5B), the adhesive force when applied by vapor deposition (FIG. 5C) is about ½ of the former. (2.5 nN), which indicates that a minute difference due to a difference in the release layer forming method can be measured.

(Frictional force)
In the method for inspecting the application state of the mold release agent of the nanoimprint mold of the present invention, the friction force is also measured in addition to the adhesion force acting between the tip of the cantilever probe and the uneven pattern on which the mold release agent is applied and formed. It is also a preferable form to evaluate the application state of the release agent from the adhesive force and the frictional force.

  FIG. 6 is a partial cross-sectional schematic diagram for explaining the force acting when the nanoimprint mold 61 coated with the release agent 62 is pressed against the transfer material resin 64 on the substrate 63 and then separated. is there. At this time, an adhesion force P and a friction force Q act between the resin and the mold. By obtaining the frictional force, information on the side surface of the concave portion of the concave / convex pattern of the mold can be obtained indirectly, and the uniformity of the release layer can be evaluated. By measuring the frictional force in addition to the adhesive force, wider information can be obtained than in the case of the adhesive force alone.

  FIG. 7 is an explanatory diagram showing the frictional force acting on the mold surface on which a release agent is applied and formed. The origin of the frictional force is thought to be the sum of the adhesion force, that is, the intermolecular force and the condensing force of the atmospheric substance, indicating that there is a correlation between the two. FIG. 8 is a diagram showing the adhesion (white circle) and frictional force (black circle) of the release agent when the release agent is applied and formed on the surface of the quartz mold. The frictional force (mV) is shown on the left. FIG. 8 shows the case in which the release agent OPTOOL DSX is applied and formed on the surface of the quartz mold by the spin coat method and the vapor phase growth method, and in the case of only the quartz mold without the release agent as a comparison. It is a figure which shows adhesive force and frictional force. As shown in FIG. 8, the frictional force of the quartz mold without the release agent is about 20 mV on average, whereas the frictional force of the mold formed by applying the release agent is 4 mV or less. . It can also be seen that the adhesion force and the friction force are correlated.

As described above, the tip of the cantilever tip of the scanning probe microscope is extremely small, and by obtaining the adhesion force, or adhesion force and friction force from the force curve measured in the micro area of several tens of nanometers, the separation in the micro area is obtained. The mold application state can be evaluated and inspected, and the mold release agent application state of the mold can be managed by setting a predetermined adhesion force or adhesion force and friction force.
Hereinafter, the present invention will be described in detail by way of examples.

Example 1
As a sample, a nanoimprint mold made of quartz glass in which a concavo-convex pattern of lines / spaces with a half pitch of 2 μm was formed on one main surface was used. A mold release agent (OPTOOL DSX: manufactured by Daikin Industries, Ltd.) was formed on the entire pattern side of the mold by vapor phase growth, and the mold release agent was applied and formed on the mold surface.

  Next, AFM (SPA400 / SPI4000: manufactured by SII Nano Technology) is used as a scanning probe microscope, and a cantilever is made of silicon nitride and a tip having a radius of curvature of 10 nm is used as a release agent. The adhesion force acting between the cantilever probe and the release agent was measured for the convex and concave portions of the concavo-convex pattern formed by coating. The adhesion before nanoimprinting was almost the same between the convex part and the concave part, and the average was 1.2 nN.

Next, in order to evaluate the durability of the release agent applied and formed on the concavo-convex pattern of the mold by a vapor phase method, the relationship between the number of imprints and the adhesive force was determined as shown in FIG. Using a UV nanoimprint technique, PAK-01 (manufactured by Toyo Gosei Co., Ltd.) was used as a UV curable resin. The transfer area is a circle with a radius of about 2 cm. As shown in FIG. 9, the adhesive force increases according to the number of imprints up to 20 times, and becomes 1.5 nN at 20 times, and the adhesive force is 20 times from 20 times to 100 times. It showed a tendency to increase more slowly than before.
FIG. 10 shows the results of evaluating the in-plane distribution of the adhesive force when the number of UV nanoimprints is 20 times and 100 times. It can be seen that the adhesion force in the peripheral portion is lower than that in the vicinity of the center. Thus, it was possible to evaluate the position dependency of the deterioration of the releasability.

(Example 2)
In this example, AFM was used in the same manner as in Example 1, and the friction force was measured in addition to the adhesion force obtained in Example 1, and the application state of the release agent was evaluated from the adhesion force and the friction force. FIG. 11 shows the relationship between the number of imprints and the frictional force.

  As shown in FIG. 11, the frictional force increased according to the number of imprints until the number of imprints was 20, and showed a tendency to gradually increase from 20 to 100 times.

  FIG. 12 shows a result of measuring the friction force using AFM and a shape image for comparison. There is almost no difference between the convex portion and the concave portion, and it can be seen that the release layer is formed equally on the convex portion and the concave portion.

It is an explanatory schematic diagram showing the principle of the measurement of adhesion force of the present invention. It is a cross-sectional schematic diagram which shows the case where the recessed part bottom face of a fine uneven | corrugated pattern is measured with the probe of a cantilever. It is a figure which shows the force curve which acts between the probe tip of a cantilever and the mold which apply | coated the mold release agent. It is a figure which shows the force curve which acts between the probe tip of a cantilever and the mold in the quartz mold which has not applied the mold release agent. It is a figure which shows the relationship between the surface state of a mold, the application | coating method of a mold release agent, and adhesive force. It is a partial cross-sectional schematic diagram for demonstrating the force which acts when it presses and separates the mold which apply | coated and formed the mold release agent to resin. It is explanatory drawing which shows the adhesive force and frictional force which act on the mold surface which apply | coated and formed the mold release agent. It is a figure which shows the adhesive force and frictional force of a mold release agent when a mold release agent is apply | coated and formed on the quartz mold surface. It is a figure which shows the relationship between the frequency | count of imprinting, and the adhesive force of the mold which apply | coated the mold release agent. It is a figure which shows the position dependence of the adhesive force after repeated transfer in UV nanoimprint. It is a figure which shows the relationship between the frequency | count of imprint, and the frictional force of the mold which apply | coated the mold release agent. It is a figure which shows the AFM shape image for comparison with the AFM frictional force image which measured the frictional force using AFM.

Explanation of symbols

21 Quartz mold 22 Release agent 23 Cantilever probe 61 Quartz mold 62 Release agent 63 Substrate 64 Resin

Claims (4)

A method for inspecting the application state of a mold release agent of a mold for nanoimprint, which has an uneven pattern on the surface, and a release agent is applied and formed on the uneven pattern,
Using a cantilever of a scanning probe microscope, a force acting between the tip of the probe tip of the cantilever and the concavo-convex pattern on which the release agent is applied and formed in the measurement region of the concavo-convex pattern on which the release agent is applied and formed. Measure the adhesive force between the probe and the mold release agent on the surface of the concavo-convex pattern from the curve,
The method for inspecting the application state of the release agent of the nanoimprint mold, wherein the application state of the release agent is evaluated from the adhesive force. A method for inspecting the application state of a mold release agent of a mold for nanoimprint, which has an uneven pattern on the surface, and a release agent is applied and formed on the uneven pattern,
Using a cantilever of a scanning probe microscope, a force acting between the tip of the probe tip of the cantilever and the concavo-convex pattern on which the release agent is applied and formed in the measurement region of the concavo-convex pattern on which the release agent is applied and formed. Measure the adhesion force and friction force between the probe and the mold release agent on the surface of the concavo-convex pattern from the curve,
A method for inspecting the application state of the release agent of the mold for nanoimprint, wherein the application state of the release agent is evaluated from the adhesive force and the frictional force.   The diameter of the probe is smaller than the concave dimension of the concave / convex pattern, the probe has a shape reaching the bottom surface of the concave section, and the concave dimension of the concave / convex pattern is on the order of several tens of nanometers. The inspection method of the application | coating state of the mold release agent of the mold for nanoimprints of Claim 1 or Claim 2. A pattern forming method for transferring the concavo-convex pattern to the transferred body by pressing a nanoimprint mold having a concavo-convex pattern on the surface and applying a release agent on the concavo-convex pattern to the transferred body,
3. A pattern forming method comprising an inspection step of evaluating the application state of a release agent on the surface of the nanoimprint mold by the inspection method according to claim 1 or 2 before transferring the uneven pattern. .

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