KR20100074434A - Pattern transfer method of nanoimprint lithography using shadow evaportation and nanotransfer printing - Google Patents

Abstract

PURPOSE: A method for transferring a pattern of a nano imprint lithography is provided to implement an engraving nano structure of various shapes with one nano embossed stamp of high resolution by using the imprinted resist removed in a lift-off process as a printing mold. CONSTITUTION: A metal thin film is masked on the upper side of an imprinted resist through a shadow deposition(S15). An undercut is formed by removing the remaining layer of the resist of a first substrate by using an oxygen plasma etching(S16). A gold thin film to be patterned is formed on the metal thin film by using an electron beam evaporator(S17). The gold thin film on the first substrate is nano-transfer printed on a second substrate coated with thiol ink(S19). A first substrate is separated from a second substrate after a nano transfer printing(S20). The embossed or engraved pattern is formed by lifting off the separated substrate(S21).

Description

Pattern transfer method of nanoimprint lithography using shadow evaportation and nanotransfer printing

The present invention relates to a pattern transfer method of nanoimprint lithography, and more particularly, two types of nano-patterns having opposite shapes of high-density nanoimprinted patterns using shadow evaportation and nanotransfer printing. The present invention relates to a method of pattern transfer in nanoimprint lithography using shadow deposition and nanotransfer printing capable of transferring to a substrate without wingtips as a structure.

In general, nanoimprint lithography is a technique for transferring a nanopattern engraved on the surface of a stamp by applying a polymer material on a substrate and then contacting a stamp. It is gaining attention as the next generation of lithography technology because it can be implemented, the process is simple, and can be operated in large areas.

Such a technique is classified into an ultraviolet (UV) method and a thermal (Thermal) method according to the curing method of the polymer material.

The thermal nanoimprint process was first developed by Professor Chou of Princeton University in 1996, and the nanopattern stamp produced by electron beam lithography was brought into contact with a substrate coated with polymethylmethacrylate (PMMA) polymer material. It is a method of pressurizing and patterning by high temperature and high pressure.

The UV nanoimprint process was first proposed in 1999 by Professor Sreenivasan of the University of Texas, Austin, USA, and applied to UV-curable polymer material on a substrate. It is a way.

Both methods require a process of transferring the imprinted polymer nanopattern onto a substrate.

In general, the transfer process is performed by anisotropic etching (RIE, Reactive Ion Etching) to remove the polymer residual layer, depositing a metal thin film and lift-off (transfer).

Here, the problem that occurs in the pattern transfer process of nanoimprint lithography is largely due to two factors.

The first is that the angle between the top surface and the wall surface of the imprinted resist pattern is more than 90 °, and the second is the residual layer. In the former, the metal thin film is deposited on the pattern wall during the deposition process. In addition, the latter may cause a failure of the lift-off, and the latter may reduce the height of the pattern due to the anisotropic dry etching during the removal of the residual layer, and may cause damage to the edges of the pattern, a change in the shape of the pattern, or damage the substrate.

This problem is particularly aggravated in high density nanopatterns, which leads to difficulty in pattern transfer.

The above problem occurs in both the nano-embossed pattern and the nano-engraved pattern, but also has an additional problem in the case of the nano-embossed pattern.

For example, when manufacturing a nanohole pattern, a nanohole stamp is required, which is manufactured by patterning with a positive-tone electron beam resist or by patterning with a negative-tone electron beam resist and then replicating with Ni electroplating. Sometimes.

However, current positive tone resists (PMMA, ZEP) have a lower resolution than negative tone resists (HSQ) and thus are limited in nano pattern fabrication. In the case of Ni electroplating, the pattern dimension is changed due to the loss of the seed layer. Cause.

In addition, the nano-hole pattern has a problem that is vulnerable to the thermal deformation of the resist generated during the imprinting process and the instability of the imprinting pressure.

An object of the present invention for solving the above problems, by introducing shadow deposition and nanotransfer printing method in the nanoimprint lithography process of the nanoimprint lithography using shadow deposition and nanotransfer printing to simultaneously produce embossed and intaglio nanostructures It is to provide a pattern transfer method.

Pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to an embodiment of the present invention for achieving the object as described above comprises the steps of preparing to form a nano-pattern of a glass material nanoimprint stamp; Applying an imprint resist onto a first substrate of glass material on which nanostructures of the same shape as the stamp are to be prepared; Contacting the stamp with an upper surface of the resist to apply a predetermined pressure, and then irradiating ultraviolet light or applying heat to transfer the nanostructure and to cure the resist; After the resist is cured, separating the stamp from the patterned resist; Masking the metal thin film on the upper surface of the imprinted resist through shadow deposition; Removing the residual layer of resist of the first substrate using an oxygen plasma etch and forming an undercut; Depositing a gold thin film to be patterned on the metal thin film using an electron beam evaporator; Treating a thiol ink (SAM, Self-Assembled Monolayer) on the upper surface of the second substrate; Nanotransferring the gold thin film on the first substrate onto the second substrate coated with the thiol ink; Separating the first substrate from the second substrate after nanotransfer printing; And dipping the separated first substrate in acetone to perform lift-off to obtain an embossed or intaglio pattern of the gold thin film.

Using the pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing as described above, the following effects can be obtained.

first. The nanoimprint lithography process enables pattern transfer of high-density nanostructures and reduces wingtips that commonly occur during lift-off processes.

Second, using nanoimprint lithography, a printing mold having a uniform thickness can be manufactured, and nanotransfer printing using the nanoimprinted resist as a printing mold enables nanostructures of opposite shapes to nanoimprint stamps.

third. In shadow deposition, controlling the type and thickness of deposition material, the angle, direction, and number of depositions allows nanostructures of various shapes and sizes to be fabricated.

fourth. In general, the imprinted resist removed during the lift-off process can be used as a printing mold to realize various types of intaglio nanostructures with a single high-resolution nano-embossed stamp. To be.

Hereinafter, a preferred embodiment of a pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention will be described with reference to the accompanying drawings.

1 is a flow chart showing a pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention, Figures 2a to 2c is a pattern of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention It is a cross-sectional view showing the transfer method.

First, the technical principle of the pattern transfer method of nanoimprint lithography according to the present invention for solving the conventional problems is briefly as follows.

The present invention solved the problem that occurs during the lift-off process during the pattern transfer process of the nanoimprint lithography process by shadow deposition and oxygen plasma etching, in the case of nano-engraved pattern was prepared by applying nano-transfer printing, At this time, a nanoimprinted resist pattern was used as a printing mold.

The shadow deposition protects the thickness of the imprinted resist and the edges of the pattern even during the etching process, and easily removes the residual layer even by isotropic dry etching (oxygen plasma etching) and facilitates lift-off. You can create an undercut pattern. Here, the isotropic dry etching also has the advantage of less damage to the substrate than the anisotropic dry etching.

In the case of the nano-negative pattern, the nano-negative resist pattern generated after imprinting with a nano-embossed stamp capable of high resolution was used as a printing mold of a nanotransfer printing process.

By manufacturing a printing mold using nanoimprint, it is possible to easily produce a printing nanomold having a uniform thickness and to reduce the crack of a pattern frequently occurring in nanotransfer printing.

In addition, when the nanoprinting process is performed using the imprinted resist pattern 21 as a printing mold, a pattern having the same shape as that of the nanoimprint stamp and a pattern having the opposite shape may be simultaneously manufactured.

In addition, shadow deposition enables 3D-shaped nanopatterns to be implemented.

Therefore, the above method is to obtain the embossed and intaglio nanostructures at the same time by performing a nanoimprint operation with a high-resolution nano-embossed stamp.

The pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention according to the above technical principle will be described in detail with reference to the drawings.

As shown in the drawing, the pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention includes preparing a stamp 10 (S11), and forming a resist 21 on the first substrate 20. Applying step (S12), transferring the nanostructure and curing the resist 21 (S13), separating the stamp 10 from the resist 21 (S14), and depositing the resist 21 through shadow deposition. Masking the metal thin film 23 on the upper surface (S15), removing the residual layer 22 by using oxygen plasma etching, and forming an undercut 24 (S16), using the electron beam evaporator, the gold thin film (25) depositing (S17), treating a thiol ink (SAM) on the upper surface of the second substrate 30 (S18), and a gold thin film on the first substrate 20 Nano-printing 25 on the second substrate 30 to which the thiol ink 31 is applied (S19), the second consists of the first substrate 20 to the step (S20), and the gold thin film 27. Step (S21) to obtain a relief or intaglio pattern of separating from the second substrate 30.

As described above, the process for the method according to an embodiment of the present invention begins with preparing a nanoimprint stamp 10 (see FIG. 2A (a)) (step S11).

The stamp 10 is preferably manufactured by electron beam lithography, and may also be manufactured using other lithography.

The electron beam lithography resist includes positive-tone and negative-tone, and when dry etching is used, a negative stamp is used as a negative tone resist and a negative stamp is used as a positive tone resist. Can be.

Among commercially available electron beam resists, HSQ, a negative tone resist, can produce the highest resolution high density pattern, thereby enabling the implementation of high density embossed nano stamps.

The material of the stamp 10 may be a glass material such as silicon or quartz.

Next, the imprint resist 21 is applied to the first substrate 20 on which the nanostructure having the same shape as the nanoimprint stamp 10 is to be fabricated (see (a) of FIG. 2A) (step S12).

In this case, the resist 21 may be a thermosetting polymer material or an ultraviolet curable polymer material, and the first substrate 20 may be a silicon wafer or a glass wafer.

The stamp 10 having an arbitrary nanopattern formed thereon is brought into contact with the resist 21 on the first substrate 20 to apply a predetermined pressure, and then irradiated with ultraviolet rays or heated (see FIG. 2A (b)). (Step S13).

At this time, the heat curable resist 21 is melted at a glass transition temperature or higher, and then patterned and cured when cooled to a glass transition temperature or lower. The UV curable resist 21 is formed of a flexible resist by ultraviolet rays. Allow to cure.

After the resist 21 is cured, the stamp 10 is separated from the resist 21 of the patterned first substrate 20 (see (c) of FIG. 2A) (step S14).

Next, the upper surface of the imprinted resist 21 on the first substrate 20 is masked with the metal thin film 23 through shadow deposition (see (d) of FIG. 2A) (step S15).

In the shadow deposition, the first substrate 20 of the imprinted resist 21 is inclined from 45 ° to 80 ° according to the aspect ratio of the pattern, and the metal thin film 23 is deposited by e-beam evaporation. .

It is also possible to determine the direction of the inclination according to the shape of the pattern and to perform shadow deposition several times in different directions.

For example, in the case of nanorods having a long length in the vertical direction, shadow deposition is performed twice in the left and right directions, and in the case of nanodots, the shadow deposition is performed in the vertical, four directions.

As the shadow-deposited metal thin film 23, chromium (Cr) or titanium (Ti) used as an adhesion layer may be used, and an imprint resist (at step S19) will be described later. An oxide such as SiO ₂ having a weak bonding force with the gold thin film 25 may be used to facilitate the separation of the gold thin film 25 from 21.

Oxygen plasma etching is used to remove the residual layer 22 of the resist 21 on the first substrate 20 (see (e) of FIG. 2B) (step S16).

Since the resist 21 masked with the metal thin film 23 is protected from oxygen plasma etching, the thickness of the resist 21 can be maintained and the remaining layer 22 of the unmasked resist 21 is removed by oxygen plasma etching. .

Oxygen plasma etching, which is an isotropic dry etching, does not damage the first substrate 20, unlike reactive ion etching (RIE), which causes the undercut 24 to be lifted off. off).

In general, the undercut 24 facilitates the lift-off by preventing the metal thin film deposited on the wall surface of the pattern during metal deposition, and serves to prevent wingtips commonly occurring during the lift-off process.

Next, a gold thin film 25 to be patterned is deposited using an electron beam evaporator (see (f) of FIG. 2B) (step S17).

The shape of the deposited gold thin film 25 is determined according to the shape of the shadow deposited metal thin film 23. When the metal deposited is thick, the length of x (see (f) of FIG. 2B) becomes long. Since the pattern of the gold thin film 25 of the upper surface becomes large, the pattern of the gold thin film 27 of the lower surface becomes small.

In this case, in order to increase adhesion to the first substrate 20, chromium (Cr) or titanium (Ti) may be deposited first and then the gold thin film 25 may be deposited.

Or it is also possible to form a metal thin film (refer to (m) of FIG. 2C) by several types of metal in multiple layers.

A nanopattern gold thin film 25 deposited on top of the resist is treated with a thiol ink (SAM) self-assembled monolayer (SAM) 31 on top of another second substrate 30 to be printed (see (g) of FIG. 2B). (Step S18).

3-mercaptopropyl trimethoxy silane (MPTMS) is typically used for the SAM material, and the material binds to the second substrate 30 of silicon and exposes a thiol group on the opposite side, thereby covalently bonding the gold thin film 25. It can also be called thiol ink 31.

The thiol ink 31 is coated with the gold thin film 25 deposited on the mold by using the nanoimprint lithography imprinted resist 21 pattern (see FIG. 2B (f)) as a mold for nanotransfer printing. The printed substrate is printed on the first substrate 30 (see (h) of FIG. 2B) (step S19).

When the printing mold is manufactured by nanoimprint lithography, a printing mold (FIG. 2B (f)) having a uniform thickness can be manufactured.

Therefore, since printing can be performed at a uniform pressure compared to a mold manufactured by a conventional molding method, it is possible to greatly improve a crack phenomenon of the gold thin film 25 that occurs frequently after printing.

After the nanotransfer printing as described above, the first substrate 20 is separated from the second substrate 30 ((i) of FIG. 2C) (step S20).

When the separated printing mold is immersed in acetone and lift-off, a gold thin film 27 pattern having the same shape as the nanoimprint stamp 10 may be obtained (see (j) of FIG. 2C) (step S21). .

Here, when the imprint stamp 10 is embossed, the gold foil films 25 and 27 patterns of the embossed parts are obtained after lift-off.

In addition, the printed second substrate 30 may obtain patterns of various types of gold thin films 25 according to the conditions of shadow deposition (see (d) of FIG. 2A).

Some examples of this are as follows:

When the pattern engraved on the nanoimprint stamp 10 is a line pattern in the vertical direction, the mask is masked to the metal thin film 23 layer of chrome through shadow deposition by giving a high angle in the left and right directions (see (d) of FIG. 2A). .

Thereafter, the metal thin film 23 layer of chromium is present on the pattern of the nano-printed gold thin film 25 through the process of steps S16 to S21 (see (k) of FIG. 2C).

In this case, if the shadow deposition of chromium is performed in either of the left direction and the right direction in step S15, the metal thin film 23 layer of chromium is printed in a different shape (see (l) of FIG. 2C).

The height y of the metal thin film 23 layer of chromium may be adjusted at an angle of shadow deposition (see (f) of FIG. 2B).

In addition, after the metal thin film 23 layer of chromium is oriented in the left and right steps at step S15, another material layer 29, such as SiO ₂ , Si, Ti, or Ni, is deposited and the gold thin film 25 is deposited. A patterned multilayer metal thin film can be prepared (see (m) of FIG. 2C).

In (l) and (m) of FIG. 2c, the metal thin film 23 layer of chromium is removed by wet etching to implement the metal patterns of (n) and (o) of FIG. 2c, respectively. If the metal thin film 23 layer is replaced with gold (Au) instead of chromium, various types of gold thin film patterns may be manufactured (see FIGS. 2C and 2).

Therefore, it is possible to implement various types of nanometal pattern through the method according to the present invention as described above.

In addition, the pattern transfer method of the nanoimprint lithography according to the embodiment of the present invention as described above is a biodevice, such as Localized Surface Plamson Resonance (LSPR) sensor, Surface Enhanced Raman Spectroscopy (SERS) sensor, Molecular Electronic Crossbar Memory (MECM) It can be applied to memory devices such as circuits, high density compact disks (CD), semiconductor devices such as organic thin-film transistors (OTFTs) and thin film solar cells, waveguide devices, optical devices such as displays, and the like.

In the above described and illustrated with respect to the preferred embodiment of the present invention, the present invention is not limited to the above-described embodiment, the technical field to which the present invention belongs without departing from the spirit of the invention claimed in the claims Anyone of ordinary skill in the art of various modifications can be made, as well as such changes are within the scope of the claims.

1 is a flow chart showing a pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention.

2A to 2C are cross-sectional views showing a pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to the present invention.

* Brief description of symbols for the main parts of the drawings *

10: stamp 20: first substrate

21: resist 22: residual layer

23: metal thin film 24: undercut

25: gold film 27: gold film

29 material layer 30 second substrate

31: thiol ink

Claims (11)

In the method of simultaneously producing the embossed and intaglio nanostructures by introducing shadow deposition and nanotransfer printing method in the nanoimprint lithography process, Preparing a nano-pattern 10 of glass material by forming a nanopattern (S11); Applying an imprint resist (21) on the first substrate (20) of glass material in which nanostructures having the same shape as the stamp (10) are to be manufactured (S12); Contacting the stamp 10 with an upper surface of the resist 21 to apply a predetermined pressure, and then irradiating ultraviolet rays or applying heat to transfer the nanostructures and to cure the resist 21 (S13); After the resist (21) is cured, separating the stamp (10) from the patterned resist (S14); Masking the metal thin film 23 on the upper surface of the imprinted resist 21 through shadow deposition (S15);  Removing the residual layer (22) of the resist (21) of the first substrate (20) by using oxygen plasma etching and forming an undercut (S16); Depositing a gold thin film 25 to be patterned on the metal thin film 23 using an electron beam evaporator (S17); Treating a thiol ink (SAM) on an upper surface of the second substrate 30 (S18); Nanotransferring printing the gold thin film 25 on the first substrate 20 on the second substrate 30 to which the thiol ink 31 is applied (S19); Separating the first substrate 20 from the second substrate 30 after nanotransfer printing (S20); And Submerging the separated first substrate in acetone to obtain an embossed or intaglio pattern of the gold thin film 27 by performing a lift-off (S21); using shadow deposition and nanotransfer printing Pattern transfer method of nanoimprint lithography. The nanoimprint lithography using shadow deposition and nanotransfer printing according to claim 1, wherein the stamp (10) is made by electron beam lithography consisting of a positive-tone resist and a negative-tone resist. Pattern transfer method. The method of claim 1, wherein the resist (21) is formed of a thermosetting polymer material or an ultraviolet curable polymer material. The method of pattern transfer of nanoimprint lithography using shadow deposition and nanotransfer printing. The method of claim 1, wherein the shadow deposition inclines a 45 ° to 80 ° angle of the imprinted resist first substrate 20 according to the aspect ratio of the pattern, and chromium (Cr) or titanium (Ti) by electron beam evaporation. The pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing, wherein the deposition of the metal thin film 23) is performed according to the shape of the pattern, and the deposition is performed a plurality of times in different directions. . 5. The method of claim 4, wherein the shadow deposition is performed twice in left and right directions in the case of nanorods having a long length in the vertical direction, and four times in the up, down, left and right directions in the case of nanodots. Pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing. The method of claim 1, wherein the shadow deposition in the step S15 is a metal thin film of chromium by giving a high angle to the upper surface of the resist 21 in the horizontal direction when the pattern engraved on the stamp 10 is a vertical line pattern (23) A pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing, characterized by depositing a layer and depositing a gold thin film (25) on the chromium metal thin film (23) layer. The method of claim 6, wherein the thickness of the chromium thin film layer (23) is controlled by adjusting a shadow deposition angle. 10. The pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing. The method of claim 6, wherein a material layer 29, such as SiO ₂ , Si, Ti, and Ni, is deposited between the metal thin film 23 layer of chromium and the gold thin film 25 layer to produce a multilayer metal thin film. Pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing. The pattern transfer method of nanoimprint lithography using shadow deposition and nanotransfer printing according to claim 6, wherein the metal thin film layer is made of gold (Au). A method of pattern transfer in nanoimprint lithography using shadow deposition and nanotransfer printing as claimed in claim 1, characterized in that the imprinted resist pattern is a mold for nanotransfer printing. The method of claim 10, wherein when the nanoprinting process is performed using the imprinted resist 21 pattern as a printing mold, a shadow having a shape opposite to that of a nanoimprint stamp can be simultaneously produced. Pattern transfer method of nanoimprint lithography using deposition and nanotransfer printing.

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