JP2008006639A - Imprinting mold and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imprinting mold capable of obtaining a pattern shape of a sol-gel material obtained by transfer as a desired pattern shape. <P>SOLUTION: This manufacturing method of the imprinting mold for transferring a pattern to the sol-gel material includes a process for measuring the deformation quantity due to the curing shrinkage of the sol-gel material, a process for performing the simulation of the pattern shape of the material transferred from the mold using the measured deformation quantity and a process for forming the pattern shape of the mold calculated by simulation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imprint mold and an imprint mold manufacturing method, and particularly to an imprint mold using a sol-gel material as a transfer material.

<Photolithography>
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 largely 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 the resist, super-resolution techniques such as optical proximity correction (OPC), phase shift mask, and modified illumination are 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.

<Imprint>
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 the other micrometer order methods are used. Often referred to as the printing method. Here, they are all called imprint methods.

  In the imprint method, a mold called a mold on which a pattern corresponding to a negative / positive reversal image of a pattern to be finally transferred is formed is impressed on a material to be patterned such as a resist, and in that state by heat or ultraviolet rays. Pattern transfer is performed by curing the material. 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.)

<Sol-gel imprint>
Various types of imprinting methods have been proposed. One of them is the sol-gel imprinting method. (For example, refer nonpatent literature 3 and patent literature 2.) The method is demonstrated using FIG.

  First, a silicon alkoxide is mixed with a solution containing ethanol, water, and a catalyst, and the mixture is stirred at room temperature, whereby a hydrolysis reaction and a polycondensation reaction proceed to prepare a sol-gel solution. A gel-like thin film is formed on the substrate by spin coating (a), and the mold is imprinted (pressed) in a vacuum (b). Thereafter, the mold is released (c), the substrate is cured by heat treatment (sintering / drying) at about 350 ° C., and the mold pattern is transferred to the sol-gel material (d).

Thus, since it is a method combining the sol-gel method and the imprint method, it is recently called the sol-gel imprint method. In contrast to the normal imprint method described above, which transfers a pattern to an organic material such as a resin, the pattern transferred to a sol-gel inorganic material such as glass in this method is characterized by excellent heat resistance. is there.
JP 2000-194142 A JP 11-314927 A Appl. Phys. Lett. , Vol. 67, 1995, P3314 "Thorough explanation of nanoimprint technology", Electric Journal, November 22, 2004, P20-38 M.M. Taniyama, et. al Fabrication of high reliable diffractive gratings by the sol-gel method, 9th Microsics Conference (MOC'03) Technical Digest,

  However, in the sol-gel imprint method, the final heat treatment (sintering / drying) volatilizes excess moisture and solvent in the gel material, resulting in a cured sol-gel material pattern. Due to this, volume shrinkage occurs. Although the shrinkage rate varies depending on the amounts of water and solvent contained in the sol-gel solution, a very large curing shrinkage of about 10 to 30% in one axis direction is observed. Therefore, there is a problem that the pattern shape of the sol-gel material obtained by the transfer does not completely match the mold pattern shape, and a desired shape pattern cannot be obtained.

  For example, even if the sol-gel imprint method is performed using a mold having a vertical concavo-convex pattern, the transferred sol-gel material pattern is a forward tapered shape as shown in FIG. turn into.

  For example, FIG. 3 shows the result of calculating the transfer pattern shape by finite element method simulation when the aspect ratio of the mold pattern is 0.5 and the shrinkage rate in one axis direction of the sol-gel material is 30%. Although the taper angle of the mold pattern is vertical, the transfer pattern is a forward taper with a taper angle of 67 °, and the height is also reduced by 30%.

  For example, when the sol-gel imprint is performed with a mold pattern having a triangle inclined at 45 degrees, the height of the triangle is reduced by about 30% when the shrinkage in one axis direction of the sol-gel material by heat treatment is 30%, and the horizontal Since the inclination angle from the direction is also 32 degrees (FIGS. 4 and 5), the actually obtained transfer pattern is different from the mold pattern.

  Accordingly, the present invention has been made to solve the above-described problems, and provides an imprint mold in which a pattern shape of a sol-gel material obtained by transfer can be obtained in a desired pattern. Objective.

  The present invention according to claim 1 is an imprint mold manufacturing method for transferring a pattern to a sol-gel material, the step of measuring a deformation amount due to cure shrinkage of the sol-gel material, and the measured deformation amount, An imprint mold manufacturing method comprising performing a process of simulating a pattern shape of a material transferred from a mold and a process of forming a pattern shape of the mold calculated from the simulation.

  The present invention described in claim 2 is the imprint mold manufacturing method according to claim 1, characterized in that dry etching or focused ion beam (FIB) is used in the process of manufacturing the mold pattern shape. This is a method for manufacturing an imprint mold.

  The present invention described in claim 3 is an imprint mold produced by the imprint mold manufacturing method according to claim 1.

  The present invention according to claim 4 is an imprint method using the imprint mold according to claim 3.

  According to the present invention, in the imprint method to the sol-gel material, the deformation amount of the curing shrinkage after the heat treatment can be calculated in advance, and the mold shape can be controlled accordingly, so that a transfer pattern having a desired shape can be formed, High-precision shape control and dimension control are possible, and a high-quality sol-gel transfer pattern can be obtained.

  Hereinafter, the imprint mold manufacturing method of the present invention will be described.

<Process for measuring deformation due to curing shrinkage of sol-gel material>
In the sol-gel imprint method, the transferred sol-gel material undergoes volume shrinkage due to volatilization of moisture and solvent after heat curing in the imprint method described later. The shrinkage rate varies depending on the amount of water and solvent contained in the sol-gel solution. For this reason, first, for the sol-gel material to be transferred, the volume shrinkage before and after curing is obtained.

  The method for obtaining the volume shrinkage is not particularly limited. For example, a sol-gel material solution to be transferred is prepared, a gel-like thin film is coated on a suitable substrate by a spin coating method, the film thickness is measured by a contact-type step gauge, heat-treated (sintered / dried), and cured sol-gel A method of measuring the film thickness of the material in the same manner may be used. In this case, the shrinkage rate in the uniaxial direction can be measured by comparing the film thickness before heat treatment with the film thickness after heat treatment.

<Process for simulating pattern shape of sol-gel material>
Next, using the measured shrinkage rate, simulation is performed to determine a mold pattern to be formed. At this time, a finite element method is used as a simulation calculation method.

  At this time, in the sol-gel imprint method, the sol-gel material applied on the flat substrate cannot move laterally on the adhesive surface with the substrate. Since the member (polarizing plate, light guide plate, etc.) has a repetitive pattern with a simple shape, it can be carried out at a symmetrical boundary. As a result, the number of variables can be reduced, so that the time required for the simulation can be shortened.

  From the simulation, the height and taper angle of the concavo-convex mold pattern are determined as design values of the mold pattern to be formed. This is because the transfer pattern height and taper angle are determined by the curing shrinkage of the sol-gel material and the aspect ratio of the mold pattern. Here, the concavo-convex pattern is not limited to a rectangular shape, but is a pattern that periodically repeats a circular or polygonal groove. In optical members such as a display manufactured by the sol-gel imprint method (polarizing plate, light guide plate, etc.), the repeating pattern of such rectangular, circular, and polygonal grooves is almost the same, and the height of the pattern and the taper angle are Its characteristics are determined.

<Process of forming mold pattern shape calculated from simulation>
Next, an imprint mold is formed based on the calculated design value.

  The material for forming an uneven pattern of the imprint mold of the present invention is not particularly limited. For example, a metal such as nickel, chromium, iron, aluminum or a compound of these metals, silicon, quartz, glass, diamond, SiC, etc. These silicon compounds and ceramics can be used.

  The method for producing the concavo-convex pattern is not particularly limited, and an existing method can be used. However, dry etching or focused ion beam (FIB) is preferably used.

  When dry etching is used, the imprint mold of the present invention can be preferably produced in that a substrate having a large area can be processed all over.

  In the case of using a focused ion beam (FIB), the imprint mold of the present invention can be suitably produced in that each pattern can be independently formed into an arbitrary shape.

  The mold pattern is changed at any time according to the required transfer pattern. Several examples of the mold pattern of the imprint mold of the present invention are illustrated in FIG.

  Hereinafter, the sol-gel imprint method using the formed imprint mold will be described.

First, silicon alkoxide is mixed with a solution containing ethanol, water, and a catalyst and stirred. Thereby, a hydrolysis reaction and a polycondensation reaction advance, and a sol-gel solution is prepared. This is coated on a substrate to form a gel-like thin film. (Fig. 1 (a))
As the silicon alkoxide, those usually used can be used. For example, silicon methoxide (Tetramethylorthosilicate: TMOS), silicon ethoxide (Tetraethylorhosilicate: TEOS), etc. are specifically mentioned.
The sol-gel solution can be coated by spin coating, die coating, spray coating, or the like.

Next, the mold produced by the above-described method is imprinted (embossed) on the gel-like thin film in vacuum (FIG. 1B).
Next, the mold is released (FIG. 1 (c)), the substrate is cured by heat treatment (sintering / drying), and the mold pattern is transferred to the sol-gel material (FIG. 1 (d)).
At this time, an oven is generally used for the heat treatment, but a hot plate may be used.

<Process for measuring deformation due to curing shrinkage of sol-gel material>
First, a solution containing ethanol and water was mixed with silicon ethoxide (Tetraethylorthosilicate: TEOS material / Yamanaka Semiconductor) and stirred at room temperature to prepare a sol-gel solution. (Mixing ratio, TEOS: ethanol: water = 1: 5: 5)
Next, the gel-like thin film was coated on the Si substrate with the sol-gel solution by a spin coating method, and the film thickness was measured with a contact step meter.
Next, heat treatment (sintering / drying) was performed at about 350 ° C., and the film thickness of the cured sol-gel material was measured in the same manner.
From the above, from the film thickness measurement before and after the heat treatment, the uniaxial cure shrinkage rate of this material was about 10%.

<Process of forming mold pattern shape calculated from simulation>
Next, using a simulation software based on a finite element method, a mold shape was obtained so that a desired pattern shape was obtained after the heat treatment. As input parameters at this time, an initial shape such as an aspect ratio and a taper angle, and a uniaxial curing shrinkage rate of 10% were input and calculated. In addition, as boundary conditions, the bottom surface was completely fixed and left-right symmetric boundary was used.
In this example, when the initial shape was calculated such that a triangular transfer pattern having a height of 100 nm, a width of 200 nm, a repetition pitch of 400 nm, and an inclination angle of 45 degrees was obtained after the heat treatment, the taper angle of the mold pattern was 50 degrees and the height was calculated. A calculation result of 111 nm was obtained.

<Process of forming mold pattern shape calculated from simulation>
A mold was produced by the following procedure so as to have the shape calculated in Example 2. First, a mold manufacturing method is shown in FIG. A 4-inch quartz substrate is prepared as a base substrate for the mold, and this substrate is coated with an electron beam resist (ZEP520 / Nippon ZEON) to a thickness of 100 nm (FIG. 6B). A remaining 60 nm line & space resist pattern was formed (FIG. 6C). The conditions at this time are a drawing dose of 100 μC / cm 2 and a development time of 2 minutes.

Next, a quartz pattern with a 50-degree taper shape having a depth of 78 nm was formed by dry etching of quartz using an ICP dry etching apparatus (FIG. 6D). The conditions for quartz etching are the following conditions with strong depot so as to be tapered: C ₄ F ₈ flow rate 20 sccm, O ₂ flow rate 10 sccm, Ar flow rate 50 sccm, pressure 2 Pa, ICP power 500 W, RIE power 150 W, etching time 23 seconds , And.
Next, the resist was stripped by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) (FIG. 6E). Next, a quartz mold pattern having a taper angle of 50 degrees, a height of 111 nm (FIG. 6F), a width of 200 nm, and a repetition pitch of 400 nm was completed by isotropic wet etching using hydrofluoric acid. The shape of the mold pattern was determined by observing the cross-sectional shape with a scanning electron microscope (SEM).

  Using the sol-gel solution prepared in Example 1 (a solution containing ethanol and water mixed with silicon alkoxide) and the quartz mold prepared in Example 3, sol-gel imprinting was performed according to the following procedure.

First, a sol-gel solution was coated on the substrate by a spin coating method to form a gel-like thin film (FIG. 7A).
Next, the quartz mold produced in Example 2 was imprinted in a vacuum (FIG. 7B), the mold was released (FIG. 7C), and the substrate was heated to about 350 ° C. The sol-gel material was cured by heat treatment (sintering / drying), and the mold pattern was transferred to the sol-gel material (FIG. 7D). When the pattern shape of the transferred sol-gel material pattern was cross-sectional observed with a scanning electron microscope (Hitachi High-Technologies Corporation), a triangular transfer pattern with an inclination angle of 45 degrees and a pattern height of 100 nm was found to be well formed. Observed.

Similarly to Example 3, a mold was produced by the following procedure so as to have the shape calculated in Example 2. However, a focused ion beam (FIB) was used as a mold manufacturing method.
First, a 4-inch quartz substrate is used as a mold substrate, the substrate is held at an inclination angle of 50 degrees (FIGS. 8A and 8B), and a focused ion beam (FIB) having an acceleration voltage of 5 to 50 kV and a current value of 5 to 30 nA is obtained. By repeating the processing, a triangular pattern with an inclination angle of 50 degrees was formed (FIG. 8C).

Sol-gel imprinting was performed in the same manner as in Example 4. However, the mold produced in Example 5 was used.
As a result, similar to Example 4, a triangular pattern having an inclination angle of 45 degrees and a pattern height of 100 nm was formed satisfactorily.

  The imprint mold of the present invention is used in the manufacture of 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. It is useful for a pattern forming method using a sol-gel imprint method.

It is the model which shows the standard process of the sol-gel imprint method, (a) The state which coated the sol-gel material (gel form) on the board | substrate, (b) The state which imprinted the mold, (c) The mold was released It is a figure which shows a state and the state which the (d) sol-gel material hardened | cured by heat processing. It is a schematic diagram showing an example of volume shrinkage of a sol-gel material in a sol-gel imprint method (in the case of a rectangular uneven pattern), (a) a state in which a sol-gel material (gel-like) is coated on a substrate, and (b) a mold is inserted in a vacuum (C) State where mold was released (d) State where volume contraction occurred when sol-gel material was cured by heat treatment. It is a schematic diagram showing an example of volume shrinkage of a sol-gel material in a sol-gel imprint method (in the case of a rectangular uneven pattern), a simulation result when the shrinkage rate in the uniaxial direction is 30%. It is a schematic diagram showing an example of volume shrinkage of a sol-gel material in a sol-gel imprint method (in the case of a triangular pattern), (a) sol-gel material before heat treatment (immediately after imprint) (b) when the sol-gel material is cured by heat treatment It is a figure which shows the state which volume contracted. It is a schematic diagram showing an example of volume shrinkage of the sol-gel material in the sol-gel imprint method (simulation result when the shrinkage rate in one axial direction is 30% in the case of a triangular pattern). It is a schematic diagram which shows the manufacturing method of the mold of Example 3, (a) The quartz substrate used as the origin of a mold, (b) The state which coated the EB resist, (c) The state which patterned the resist by EB lithography, FIG. 4 is a diagram showing a state in which d) a dry etching process with a forward taper is performed, (e) a state in which a resist is removed by oxygen plasma ashing, and (f) a state in which an isotropic etching process is performed with hydrofluoric acid. It is a schematic diagram which shows the sol-gel imprint of Example 4, (a) The state which coated the sol-gel material (gel form) on the board | substrate, (b) The state which imprinted the quartz mold in the vacuum, (c) Quartz It is a figure which shows the state which released the mold, (d) the state which volume contracted when the sol-gel material hardened | cured by heat processing, and (e) the enlarged view (tilt angle before and behind heat processing) of a pattern part. 6 is a schematic diagram showing a method for manufacturing a mold by FIB of Example 5. FIG. The example of manufacture of the mold formed by the mold manufacturing method of this invention is shown.

Explanation of symbols

101 ... substrate 102 ... sol-gel material (gel-like thin film)
DESCRIPTION OF SYMBOLS 103 ... Mold 104 ... Vacuum chamber 105 ... Sol-gel thin film 106 ... Sol gel pattern 107 ... Shape before heat processing 108 ... Pattern shape after heat processing 110 ... Quartz substrate 111 ... Resist 112 ... Quartz mold 120 ... Ion gun 121 ... Ion beam

Claims (4)

An imprint mold manufacturing method for transferring a pattern to a sol-gel material,
Measuring the amount of deformation due to curing shrinkage of the sol-gel material;
A step of simulating the pattern shape of the material transferred from the mold from the measured deformation amount;
And a step of forming a pattern shape of the mold calculated from the simulation. The imprint mold manufacturing method according to claim 1,
A method for producing an imprint mold, wherein dry etching or focused ion beam (FIB) is used in the step of producing a mold pattern shape.   An imprint mold made by the imprint mold manufacturing method according to claim 1.   A sol-gel imprint method using the imprint mold according to claim 3.