KR20130082224A

KR20130082224A - Method for controlling size of three-dimensional polydimethylsiloxane molds/stamps using thermal shrinkage process

Info

Publication number: KR20130082224A
Application number: KR1020120003296A
Authority: KR
Inventors: 정옥찬
Original assignee: 인제대학교 산학협력단
Priority date: 2012-01-11
Filing date: 2012-01-11
Publication date: 2013-07-19

Abstract

PURPOSE: A method for controlling a size of three-dimensional polydimethyl siloxane (PDMS) molds/stamps using a thermal shrinkage process is provided to allow various PDMS structures having other sizes, and to manufacture with various sizes by using a multi-phase thermal shrinkage process of a three dimension PDMS mold / stamp. CONSTITUTION: A method for controlling a size of three-dimensional polydimethyl siloxane molds/stamps comprises the following steps: a polydimethylsiloxane (PDMS) reproduction mold is formed by performing a hardening treatment by injecting a PDMS solution into a silicon mold having a pattern of an embossment; the PDMS reproduction mold is contracted by cooling at a room temperature after the PDMS reproduction mold is heat-treated at 250-350°C; a PDMS stamp is manufactured by injecting the PDMS solution on a contracted PDMS reproduction mold and performing a hardening treatment; and the PDMS stamp is peeled from the PDMS reproduction mold.

Description

Method for controlling size of three-dimensional polydimethylsiloxane molds / stamps using thermal shrinkage process}

The present invention relates to a method of controlling the size of a three-dimensional polydimethylsiloxane (hereinafter referred to as PDMS) mold / stamp, and more particularly, to a replica of a three-dimensional PDMS mold / stamp that can be replicated using a stepwise shrinkage effect in a heat treatment process. To adjust the size.

The ability to form patterns or structures of desired shapes on specific materials or substrates is an essential requirement for modern technology, from biotechnology to electronics. Commonly known as lithography, this technology has conventionally produced patterns based on photolithography. However, as the required line width of circuits in the semiconductor industry has become smaller than 100 nm in recent years, and the exclusivity between various organic materials and biomaterials and the chemical process of photolithography method has been increased, conventional photolithography technology has been developed at a cost and technical level. The limit has been reached. Therefore, the need for a new form of non-traditional lithography technology to replace this has been increasing.

To this end, new forms of pattern formation using physical contact have been developed since the mid-1990s. Compared to the conventional photolithography process, a non-contact pattern forming method of irradiating a mask having a desired pattern shape with a UV or X-ray light source and forming a pattern by using a difference in chemical reaction generated at this time, In the proposed technique, a pattern called a mold is brought into direct physical contact with a substrate, and the final pattern is formed by using a chemical bond or a difference in physical shape. Typical examples thereof include nano-imprint lithography and soft lithography.

The nanoimprint lithography technology forms a pattern of a desired shape on a polymer thin film by contacting a mold having a hard material pattern with a thin film of a thermoplastic polymer, and applying a high pressure while applying fluidity to the polymer thin film at conditions above the glass transition temperature of the polymer. It is a technique to do. Developed by Chou faculty at Princeton University, the technology has excellent patterning capability, capable of forming patterns down to several nm, but requires extremely high pressure and ensures flatness of the substrate for uniform distribution of applied pressure. It has a disadvantage.

In contrast, the soft lithography technology developed by Whitesides faculty at Harvard University, USA, uses a PDMS (polidimethylsiloxane) mold, which is not a hard material, as a stamp, to transfer chemicals of desired composition onto a substrate to form a pattern of a desired shape. It is a technique to do. Unlike rigid materials, flexible PDMS molds have the advantage of being able to transfer patterns while forming spontaneous conformal contacts without additional pressure on the substrate.

In general, PDMS molds / stamps have been produced in three-dimensional patterns through replication of polymers using a sequential curing process of polymers from a fixed silicon master (Y. Xia and GM Whitesides, Annu. Rev. Mater. Sci., Vol. 28 , pp. 153-184, 1998; BD Gates, Materials Today, Vol. 8, No. 2, pp. 44-49, 2005). Repeating this replication process produces many PDMS molds / stamps from each master, and multiple copies are made from the PDMS molds / stamps.

However, the silicon master mold is fixed in size, so that all PDMS molds / stamps and replicas thereof produced therefrom have the same size as the silicon mold master pattern. Therefore, if the mold pattern size should be changed slightly, there is a problem that a new mold master having a slight change in the pattern must be manufactured again.

In addition, conventional fine mold structures, such as SU8 structures, on silicon wafer substrates tend to break well. Thus, if the height of the mold exceeds 30 μm, the mold structure may break during the peeling process of the cured PDMS film. Therefore, there is a need for a method that can easily adjust the size of the PDMS mold.

However, as a technique related to the conventional PDMS mold, Dow-Corning's Sylgard 184 PDMS (hereinafter referred to as s-PDMS) is mainly used as a pattern forming mold, or component correction is performed on a portion where a pattern is formed. Double-layered mold structure (Macromolecules 2000, 33, using h-PDMS ("hard" PDMS)) to improve the rigidity, and to support the relatively thin s-PDMS layer by forming a relatively thick s-PDMS layer thereon 3042).

In recent years, a mold with a modulus between s-PDMS and h-PDMS has been introduced using PDMS cured by light (J. Am. Chem. Soc. 2003, 125, 4060). In addition, Korean Patent Registration No. 551622 discloses a method of manufacturing a pattern forming mold that can correspond to a pattern having a line width of several nm to several tens nm and an aspect ratio of 1 or more by controlling the viscosity of a mold material for making a pattern forming mold. have.

However, a technique for easily adjusting the size of the 3D PDMS mold / stamp pattern has not been reported yet.

Thus, the inventors of the present invention while studying how to easily control the size change of the three-dimensional PDMS mold / stamp pattern or the size of the fine structure, by performing a heat treatment process at a specific temperature it is broken even in the fine structure by using a stepwise shrinkage effect It has been found that the size of the 3D PDMS mold / stamp can be easily adjusted without loss or distortion, and the present invention has been completed.

Accordingly, it is an object of the present invention to provide a method for easily controlling the size of a three-dimensional polydimethylsiloxane mold / stamp without breaking or warping.

In order to achieve the above object, the present invention provides a method of controlling the size of the replicable three-dimensional PDMS mold / stamp using a stepwise shrinkage effect by repeating the heat treatment process on the three-dimensional PDMS mold / stamp.

Therefore, the present invention comprises the steps of injecting and curing the PDMS solution into a silicon mold having an embossed pattern to form a PDMS replication mold; Heat-treating the PDMS replication mold at 250-350 ° C. and then cooling it to room temperature to shrink the PDMS replication mold; Preparing a PDMS stamp by injecting and curing a PDMS solution onto the contracted PDMS replication mold; And peeling the PDMS stamp from the PDMS replication mold.

In another aspect, the present invention comprises the steps of injecting and curing the PDMS solution into a silicon mold having an embossed pattern to form a PDMS replication mold; Heat-treating the PDMS replication mold at 250-350 ° C. and then cooling it to room temperature to shrink the PDMS replication mold; Preparing a PDMS stamp by injecting and curing a PDMS solution onto the contracted PDMS replication mold; Peeling the PDMS stamp from a PDMS replica mold; And repeating the steps (b) to (d) the desired number of times to provide a method of controlling the size of the three-dimensional polydimethylsiloxane mold or stamp comprising the step of adjusting the size of the PDMS mold.

In one embodiment of the present invention, the pattern of the silicon mold of step (a) may be square, rectangular, circular, channel or chamber form.

In one embodiment of the present invention, the step (b) may be heat treatment at 300 ℃.

In addition, the present invention provides a three-dimensional polydimethylsiloxane mold adjusted in the above method.

In addition, the present invention provides a three-dimensional polydimethylsiloxane stamp sized by the above method.

According to the present invention, three-dimensional PDMS molds / stamps can be produced in a variety of sizes using a multi-step heat shrink process, and such repeated size reductions can be made in a variety of PDMSs with different sizes that can be derived from existing structures with fixed sizes. Allow structure. In addition, the method according to the present invention can be produced in a fine structure without breaking by using a multi-stage heat shrink process, it can be usefully used in the art that PDMS mold / stamp is used.

1 is a basic conceptual diagram for the generation and duplication of PDMS stamps and / or molds using a repeated heat treatment process according to the present invention, where W ₀ and H ₀ are the width and depth of the structure before the heat treatment process, respectively, and V _p. And V _T are the pattern before the heat treatment process and the total PDMS film volume, respectively, W ₁ and H ₁ are the width and depth of the structure after the heat treatment process, respectively).
2 is a view showing the shape and shrinkage ratio of the PDMS structure after the heat treatment process at an inert nitrogen gas and various maximum temperatures in one embodiment according to the present invention.
3 is a view showing the heat shrink after the heat treatment process of the microchannel structure having various sizes in an embodiment according to the present invention.
FIG. 4 is a graph showing shrinkage ratios of microchannel structures having various sizes after an annealing process at various maximum temperatures with inert nitrogen gas according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating successful creation and replication of PDMS molds / stamps of various sizes after a three step heat treatment process of PDMS molds / stamps of various shapes in accordance with an embodiment of the present invention.
FIG. 6 is a graph illustrating shrinkage ratios of microchannel structures after a three-step heat treatment process of various shapes of PDMS molds / stamps according to the present invention.

The present invention comprises the steps of (a) injecting a PDMS (polydimethylsiloxane) solution into the silicon mold having an embossed pattern and curing to form a PDMS replication mold; (b) heat treating the PDMS replica mold under inert gas and then cooling to room temperature to shrink the PDMS replica mold; (c) injecting and curing the PDMS solution onto the contracted PDMS replica mold to produce a PDMS stamp; And (d) peeling the PDMS stamp from the PDMS replica mold.

In addition, the present invention comprises the steps of (a) injecting and curing the PDMS solution into a silicon mold having an embossed pattern to form a PDMS replication mold; (b) heat treating the PDMS replica mold under inert gas and then cooling to room temperature to shrink the PDMS replica mold; (c) injecting and curing the PDMS solution onto the contracted PDMS replica mold to produce a PDMS stamp; (d) peeling the PDMS stamp from a PDMS replica mold; And (e) repeating steps (b) to (d) as many times as desired to further control the size of the PDMS mold.

First, step (a) is a step of forming a PDMS replication mold by injecting and curing the PDMS solution into a silicon mold having an embossed pattern.

In the present invention, a silicon mold is used as a basic mold for forming a fine pattern, and the silicon mold is manufactured through an electron beam process or photo lithography. Here, the electron beam process is a process of obtaining a high resolution through direct etching using an organic material resist thin film, the photolithography process is a property that changes the properties by causing a chemical reaction when a certain chemical (Photo Resist, PR) receives light It is a process of forming the same pattern as the pattern of a mask by selectively irradiating light to PR using the mask of the pattern to obtain using the principle.

The pattern of the silicon mold may use a variety of shapes, such as square, rectangular, circular, channel, chamber shape, but is not limited thereto.

In the present invention, a PDMS replication mold is used as a mold for a pattern of a silicon mold, and the PDMS replication mold refers to a mold in which the pattern of the silicon mold is imitated by spin coating and curing the PDMS solution on the silicon mold. In order to accurately reproduce and maintain the shape of the silicon mold, a rigid PDMS layer is required, and thus, a rigid PDMS using a composite mold of soft PDMS and hard PDMS, or additionally hardening the soft PDMS. Molds can be used. In this case, the composite mold of the flexible PDMS and the rigid PDMS, after spin-coating a mixed solution of a polymer monomer, a catalyst, an initiator and the like to form a hard PDMS on the silicone mold, and then poured by curing the mixed solution of the soft PDMS monomer and initiator, and then cured It can manufacture by separating from the said silicone mold. The PDMS mold thus prepared may be continuously formed and newly formed on a silicon mold, and the PDMS mold manufactured once may be repeatedly used more than several times.

Next, step (b) is a step of shrinking the PDMS replication mold by heat-treating the PDMS replication mold prepared in step (a) under an inert gas and then cooled to room temperature.

The inventors have found that heat shrinkage occurs when the PDMS film is heat treated at a high temperature. Specifically, before and after the hardened PDMS film is subjected to a heat treatment process at 300, 500 or 700 ° C. in an inert nitrogen gas, the laser beam microscope (VK-8510, resolution: 0.01 μm, Keyence, Osaka, Japan) and as a result of measuring the shrinkage ratio of the PDMS film, as shown in Figure 2, the PDMS structure was found to shrink the depth and width.

At this time, it is preferable that the said heat processing temperature is 250-350 degreeC, and it is more preferable that it is 300 degreeC. If the heat treatment temperature is less than 250 ℃ PDMS shrinkage phenomenon is very small, if it exceeds 350 ℃ because the surface of the pattern is rough, warped and locally cracked.

Next, step (c) is a step of preparing a PDMS stamp by injecting and curing the PDMS solution on the PDMS replication mold shrinkage in the step (b).

Preparation of the PDMS stamp of step (c) may be carried out in the same manner as the PDMS replica molding of step (a).

Next, step (d) is a step of peeling the PDMS stamp prepared in step (c) from the PDMS replication mold.

Through the above steps, the PDMS stamp having a smaller width of the pattern than the first PDMS stamp may be manufactured.

In addition, in the case where the width of the pattern is large, after the above step, steps (b) to (d) may be additionally repeated to prepare a PDMS stamp / mold having a desired size.

By the method according to the present invention it is possible to adjust the size of the three-dimensional PDMS mold / stamp from one fixed size to various sizes. In addition, the method according to the present invention can be produced in a fine structure without breaking by using a multi-stage heat shrink process, it can be usefully used in the art that PDMS mold / stamp is used.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are only the preferred embodiments of the present invention, and the present invention is not limited by the following Examples.

< Example 1>

Various sizes using multi-step heat treatment process PDMS Mold Manufacture of stamps

In the manner as shown in FIG. 1, PDMS molds / stamps having various sizes were prepared by repeating the thermal process.

First, the 10: 1 PDMS mixture was spin coated and cured at 75 ° C. for 30 minutes. The cured PDMS was heated stepwise to 300 ° C., held for 3 hours and then cooled to room temperature. Thereafter, the liquid PDMS mixture was poured onto the first retracted mold to make the first stamp, and after curing, the new stamp was peeled off from the first mold.

Second and third mold structures with shrinked sizes were prepared by repeating the thermal process under the same thermal process conditions for structural shrinkage.

< Comparative example >

PDMS mold structure was prepared in the same manner as in Example, except that the maximum heating temperature of PDMS was heated to 500 or 700 ° C instead of 300 ° C.

< Experimental Example 1>

PDMS Influence of temperature of contraction

In the PDMS mold / stamp according to the present invention, the following experiment was performed to investigate the effect of PDMS shrinkage with temperature.

As starting material, a 10: 1 PDMS mixture was spin coated onto a SU-8 pattern on a silicon wafer and cured at 75 ° C. for 30 minutes. The soft cured PDMS film was stripped from the SU-8 pattern on a silicon wafer and cured again at 120 ° C. for 1 hour to form a hard cured PDMS film.

Rectangles, channels and circles were used as the pattern. The total thickness of the PDMS film was 1 mm, and the laser beam microscope (VK-8510, resolution: 0.01) was used to scan the pattern size and three-dimensional shape of the PDMS structure before and after performing a heat treatment process at 300, 500, or 700 ° C. in an inert nitrogen gas. μm, Keyence, Osaka, Japan) and the shrinkage ratio of the PDMS film was measured.

The measurement results are shown in FIG. At this time, dH represents the shrinkage ratio of the depth of the PDMS film, dW represents the shrinkage ratio of the width of the PDMS film.

As shown in FIG. 2, the shrinkage ratio of the PDMS sample treated at 300 ° C. was the smallest, and the surface roughness of the pattern was also better than that of the sample treated at 500 and 700 ° C. FIG.

Therefore, in controlling the size of the PDMS mold / stamp according to the present invention, in terms of fine size control and minimization of surface roughness, the heat treatment process temperature for shrinking the PDMS is preferably 300 ° C.

< Experimental Example 2>

PDMS According to size PDMS Heat shrink

In the PDMS mold / stamp according to the present invention, the following experiment was performed to determine the effect of PDMS shrinkage according to the PDMS size.

As starting material, a 10: 1 PDMS mixture was spin coated onto five SU-8 channel patterns of different widths and depths on a silicon wafer and cured at 75 ° C. for 30 minutes. The soft cured PDMS film was stripped from the SU-8 pattern on a silicon wafer and cured again at 120 ° C. for 1 hour to form a hard cured PDMS film.

Scan the laser beam microscope (VK-8510, resolution: 0.01 μm, Keyence, Osaka, Japan) before and after the hardened PDMS film was subjected to a heat treatment process at 300, 500 or 700 ° C. in an inert nitrogen gas. 3), and the shrinkage ratio of the PDMS film with respect to the initial channel width at each temperature was measured and shown in FIG.

As shown in Figures 3 and 4, the width of each channel pattern was found to shrink more as the temperature of the heat treatment process increases. For example, the PDMS film heated at 300 ° C. changed the shrinkage ratio of the microchannel structure from 1.7% to 3.4%, but the PDMS film heated up to 700 ° C. showed a shrinkage ratio of 7.7 compared to the unheated film. Increased from 24.5%. Thus, it can be seen that the size dependent shrinkage of the PDMS film manifests itself as the heat treatment temperature increases.

However, the surface roughness of the channel microstructures heated to 500 ° C. or 700 ° C. was very rough, causing distortion and local cracking in the channels.

< Experimental Example 3>

Various shapes and sizes using multi-step heat treatment process PDMS Mold Manufacture of stamps

For PDMS molds / stamps having various shapes, for example channel shapes, chamber shapes and circular patterns, PDMS molds / stamps having various sizes due to heat shrinkage of PDMS by a three-step heat treatment process in the method of the embodiment. 5 was shown in FIG. 5 by generating and duplicating and measuring the shrinkage ratio of the width and depth of the PDMS film according to the repeating process.

As shown in FIG. 5, in various shapes, PDMS molds / stamps having various sizes by thermal shrinkage of PDMS have been successfully manufactured by a multi-step heat treatment process, and as shown in FIG. As the width increases, the width becomes narrower and the depth deepens. This is thought to be caused by the difference in heat capacity in the embossed micropattern area, the PDMS structure, and the curing process of the original PDMS structure.

Thus, PDMS molds / stamps having a large size or volume can be continuously shrunk using elevated temperatures in inert nitrogen because of their large volume. However, as shown in FIG. 3, the micropatterns of PDMS molds / stamps with small pattern sizes cure quickly.

Accordingly, the present invention can produce three-dimensional PDMS molds / stamps in various sizes using a multi-stage heat shrink process, with repeated size reductions of various PDMS structures with different sizes that can be derived from existing structures with fixed sizes. Allow. In addition, the method according to the present invention can overcome fixed size and breakable or warp structures which are disadvantages of conventional silicone and / or polymer molds, and thus can be usefully used in the art where PDMS molds / stamps are used. have.

So far I looked at the center of the preferred embodiment for the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims

(a) injecting and curing the PDMS solution into a silicon mold having an embossed pattern to form a polydimethylsiloxane (PDMS) replica mold;
(b) heat treating the PDMS replication mold to 250-350 ° C. and then cooling to room temperature to shrink the PDMS replication mold;
(c) injecting and curing the PDMS solution onto the contracted PDMS replica mold to produce a PDMS stamp; And
(d) peeling the PDMS stamp from a PDMS replication mold, the method of controlling the size of a 3D polydimethylsiloxane mold or stamp.

(a) injecting and curing the PDMS solution into a silicon mold having an embossed pattern to form a polydimethylsiloxane (PDMS) replica mold;
(b) heat treating the PDMS replication mold to 250-350 ° C. and then cooling to room temperature to shrink the PDMS replication mold;
(c) injecting and curing the PDMS solution onto the contracted PDMS replica mold to produce a PDMS stamp;
(d) peeling the PDMS stamp from a PDMS replica mold; And
(e) adjusting the size of the PDMS mold by repeating steps (b) to (d) as many times as desired.

The method according to claim 1 or 2,
The pattern of the silicon mold of step (a) is characterized in that the square, rectangular, circular, channel or chamber shape.

The method according to claim 1 or 2,
The step (b) is characterized in that the heat treatment is 300 ℃.

A three-dimensional polydimethylsiloxane mold sized by the method of claim 1.

A three-dimensional polydimethylsiloxane stamp sized by the method of claim 1.